Gasdynamic model of street canyon

合集下载

小学下册第十四次英语第1单元期中试卷

小学下册英语第1单元期中试卷英语试题一、综合题(本题有100小题，每小题1分，共100分.每小题不选、错误，均不给分)1.What do we call the planet we live on?A. MarsB. VenusC. EarthD. Jupiter答案:C2.The capital of Kenya is _______.3. A ________ (航空港) is where planes take off and land.4.________ (观赏植物) are often used in landscaping.5.What do you call a person who works with metal?A. BlacksmithB. CarpenterC. ElectricianD. Mason答案:A6. A hydrate is a compound that contains ______ molecules.7.What is 15 + 10?A. 20B. 25C. 30D. 358. A _____ (蚂蚁) works hard to gather food for winter.9.What do we call a sweet food made from cocoa?A. CandyB. ChocolateC. CakeD. Biscuit答案:B10.I can play with my ________ (玩具类型) anywhere.11. A halogen is an element found in group ______ of the periodic table.12.What do we call a person who repairs shoes?A. TailorB. CobblerC. SeamstressD. Artisan答案:B13.What is the name of the first artificial satellite launched into orbit?A. Sputnik 1B. Explorer 1C. Vanguard 1D. Luna 114.What is the season after spring?A. WinterB. SummerC. FallD. Autumn答案:B15.The ancient Sumerians are known for creating the first ________ (城市).16.I found a _______ (古老的) coin.17.Which animal has a long neck?A. ElephantB. GiraffeC. DogD. Cat答案:B18.I like to watch ________ (纪录片) about animals.19.The ice cream is ___. (melting)20.The sunset is _______ (动人的).21.She is wearing a cute ___. (outfit)22.The car is _____ (fast/slow).23. A ______ is a type of bird that can mimic sounds.24.What is 10 - 4?A. 5B. 6C. 7D. 8答案:B25.The rain is ______ on the roof. (falling)26. A _____ (草坪) is perfect for picnics in the park.27.What is the color of an orange?A. BlueB. OrangeC. PurpleD. Green28. A ________ (植物知识普及) can inspire others.29.What do you call a person who plays a musical instrument?A. PainterB. SingerC. MusicianD. Dancer答案:C30.The _______ of a solution tells us how concentrated it is. (浓度)31.What is the main ingredient in falafel?A. LentilsB. ChickpeasC. BeansD. Rice32.The hamster stores food in its ______ (脸颊).33.We enjoy visiting the ___. (aquarium)34. A shooting star is actually a _______ that burns up in the atmosphere.35. A ______ is an animal that can be found in the ocean.36.What is the name of the famous American holiday celebrated on the fourth Thursday in November?A. ThanksgivingB. ChristmasC. New Year'sD. Independence Day答案:A37.Which animal has a long trunk?A. GiraffeB. ElephantC. ZebraD. Lion答案:B38. A solution that can dissolve more solute is called a _______ solution.39.The ________ was a significant movement for women's rights.40.My mom loves to _______ on weekends.41.We have math _____ today. (class)42. A _____ (生态平衡) is essential for a healthy environment.43.The ice cream is ___. (melting)44. A baby cat is called a __________.45.How many days are in a leap year?A. 365B. 366C. 367D. 364答案:B46.What do you call the person who teaches you in school?A. DoctorB. TeacherC. ChefD. Engineer答案:B47.I enjoy planting _____ in the garden.48.Which animal is known as "man's best friend"?A. CatB. DogC. BirdD. Fish49.I can ________ a message.50.__________ are used in the construction industry for insulation.51.What is the name of the fairytale character who climbed a beanstalk?A. JackB. PeterC. HanselD. Gretel52.The __________ (历史的启发性思维) drives innovation.53.I want to ___ a great cook. (become)54.What is the term for the distance light travels in one year?A. Light-YearB. Astronomical UnitC. ParsecsD. Cosmic Yard55.What is the name of the famous volcano in Italy?A. Mount EtnaB. Mount VesuviusC. Mount FujiD. Mount St. Helens答案:B56.The __________ helps to protect the brain.57.What is the name of the fictional land where Peter Pan lives?A. NeverlandB. WonderlandC. OzD. Narnia答案:A58.What is the capital of Portugal?A. LisbonB. MadridC. RomeD. Paris答案:A59.I have a ___ (dream) to travel the world.60.Which flower is known for being red?A. TulipB. RoseC. DaisyD. Sunflower答案:B61.What is the capital of Switzerland?A. ZurichB. GenevaC. BernD. Basel答案:C62.What is the name of the famous American singer known for her powerful voice?A. AdeleB. Whitney HoustonC. Mariah CareyD. Beyoncé答案:B63.What do we call a baby cat?A. KittenB. PuppyC. CubD. Foal答案:A64.The process of making biodiesel involves _______ oils.65.What color is a ripe banana?A. GreenB. YellowC. RedD. Blue66.The dog is _____ with its favorite toy. (playing)67.The ancient Greeks held _______ to honor their gods. (运动会)68.小鱼) plays with its friends in the tank. The ___69.The ______ communicates through sounds.70.What do you call a baby platypus?A. PuggleB. KitC. CalfD. Pup答案:A71.Cleopatra was the last active ruler of the __________ (埃及) dynasty.72.The bird is singing a ______ (happy) song.73.I can ______ (坚持) my beliefs.74.Light pollution makes it difficult to see the stars in an urban _______.75.What is the name of the famous American author known for "Beloved"?A. Toni MorrisonB. Maya AngelouC. Alice WalkerD. Zora Neale Hurston答案:A76.What do you call the hot liquid inside a volcano?A. MagmaB. LavaC. AshD. Gas答案:A77.What is the sound of a sheep?A. MeowB. BarkC. BaaD. Moo答案:C78.What is the name of the famous festival held in Rio de Janeiro?A. CarnivalB. OktoberfestC. DiwaliD. Holi答案:A Carnival79.We can _______ (一起学习) for the exam.80.My best friend is my loyal _______ who always supports me.81.Cosmic rays are high-energy particles that travel through ______.82. A _____ (植物文化交流) fosters appreciation for diversity.83. (Russian) Revolution led to the establishment of the Soviet Union. The ____84.The children are ________ in the playground.85.The ice cream is _____ (cold/warm) and delicious.86.The capital of Canada is _____.87.The _____ (大象) communicates with low-frequency sounds.88.What is the capital of Sri Lanka?A. ColomboB. KandyC. GalleD. Jaffna答案:A89.My sister's name is . (我妹妹的名字是。

科学物理实验特拉斯变压器说明书

3B SCIENTIFIC ® PHYSICSInstruction Sheet06/15 LW/ALF1 Coil tap2 Ignition coil3 Base plate4 4-mm safety sockets5 Spark gap (spark plug)6 Primary coil7 Secondary coil8 Spherical electrode, short9 Spherical electrode, long∙Caution! It is essential that experiments be performed with care by trained technical staff. The experiment is to be performed by tea-chers.∙ Only to be operated indoors∙The Tesla transformer may only be operated exclusively as described in this manual using the supplied accessories.∙The Tesla transformer produces high-frequency electromagnetic waves. Due to its large bandwidth the transformer can interferewith or damage sensitive electronic equipment in close proximity toit. Such equipment should therefore be placed at least 5 meters away from the transformer.∙The frequencies emitted by the Tesla trans-former cover many radio frequency bands. The equipment may therefore be used only for brief periods for educational demonstration purposes.∙If there are people with cardiac pacemakers or other electronic control units close to the Tesla transformer, the transformer may not be put into operation. This could result in death.∙The equipment may not be used by persons to whom electrical shocks pose a serious danger (people who are ill).∙The Tesla transformer may not be used for experiments on animals or any other living creatures.∙The Tesla transformer may not come into contact with any fluid or become damp in any way.∙Do not try to repair any faults or damage to the Tesla transformer yourself.∙The Tesla transformer may not come into contact with any metal or other conductors. A safe distance of 20 cm from the high-voltage coil must be maintained at all times in order to prevent the crossing of sparks.∙Do not use in the proximity of flammable ma-terials or volatile liquids, gases or vapours.The equipment generates sparks.∙The design of the Tesla transformer involved the best compromise between performance and universality of use whilst maintaining the required safety.∙Safety equipment to prevent any contact with the high-voltage components has been de-liberately omitted so that students can see the design and operation of the device in full de-tail.∙The safety of those performing the experi-ments is thoroughly guaranteed if changes to the Tesla transformer (modifications to the number of windings in the primary coil) and the experiment setup are only made when the equipment is switched off.∙There is no need to touch parts of the trans-former or the experiment set-up while voltage is being applied during any of the experi-ments.∙The input voltage for the Tesla transformer(20 V) can be handled with no risk to safety atall. The primary current (3 A) is also safe.∙This is also true of the output voltage. The secondary voltage has a frequency between 200 kHz and 1200 kHz at a voltage of appro-ximately 100 000 V. The maximum current is about 0.08 mA.The Tesla transformer is for demonstration and study of physical laws relating to high-frequency electromagnetic waves.In detail, the Tesla transformer allows the follo-wing phenomena to be demonstrated:∙Generation of high-frequency electromagnetic oscillations in a resonant circuit with low in-ductance and capacitance∙Shielding for high-frequency electromagnetic oscillations∙Illumination of a fluorescent lamp in a high-frequency field with no electrical contact∙Corona discharge∙Spark discharge∙Wireless energy transmission via Hertz waves ∙Penetration and absorption of Hertz waves∙Standing waves in a Tesla coil2.1 Set-upThe secondary coil is inserted concentrically into the primary coil. The Tesla transformer is connec-ted to an AC supply via the connection sockets (4).2.2 How it worksA capacitor is charged by means of a half-wave of the power supply voltage via the ignition coil. The capacitor discharges via the spark gap/spark plug and the primary coil of the Tesla transformer.A damped oscillation starts in the primary winding and this transfers energy to the secondary coil where an electromagnetic oscillation is induced at a frequency between 200 and 1200 kHz.A high-frequency voltage of more than 100 kV is generated in the secondary coil. The secondary coil oscillates at the frequency of the resonant circuit.1 Tesla transformer1 Spherical electrode, short1 Spherical electrode, long1 Needle electrode withspin electrode1 Hand coil1 Secondary coil1 Fluorescent lamp with holder1 ReflectorDimensionsTransformer: 330x200x120 mm3 Secondary coil: 240 mm x 75 mm Ø Transformer weight: approx. 3 kgNo. of windingsPrimary coil: 9Secondary coil: 1150Primary coil voltage: 20 V AC Secondary coil voltage: approx. 100 kVAdditional coil 1000967 AC/DC power supply 30 V, 6 A @230V 1003593 orAC/DC power supply 30 V, 6 A @230V 1003593∙For all the experiments described in the follo-wing, a power supply with an AC voltage ad-justable between 15 and 24 V (max. 4 A) is required. To start up the equipment the power supply voltage is increased until sparks begin to discharge periodically across the spark plug.∙The equipment is not suitable for continuous operation. After 5 minutes of operation the equipment requires a cooling period of at least 15 minutes.7.1 Shielding for electromagnetic oscillations ∙The Tesla transformer is operated without its secondary coil. The hand coil is placed over the plastic ring of the secondary coil.∙The tap for the primary coil should be placed at its highest position. After starting the Tesla transformer, a voltage is induced in the hand coil (and the fluorescent lamp illuminates).∙Next the reflector is inserted between the pri-mary coil and the hand coil. The aluminium foil forms a shield that the electromagnetic oscilla-tions cannot penetrate and the lamp connected to the hand coil no longer illuminates.7.2 Thomson's equation for the oscillation∙The Tesla transformer is run with secondary coil. Needle electrode is inserted into the so-cket at the top. ∙When the voltage is applied, a corona discharge ensues from the point of the need-le. Varying the position of the tap (modifying the inductance of the primary coil) the equipment is configured so that the discharge is at its maximum level (increase in voltage at the resonant frequency).∙Next the two secondary coils are inserted one above the other and the needle electrode is inserted into the upper coil.∙Resonance now occurs with a higher number of turns in the primary coil since the pair of secondary coils now has twice the number of turns. This means the resonant frequency is lower.∙Increasing the number of windings in the re-sonant circuit reduces the resonant fre-quency.7.3 Corona discharge∙The Tesla transformer is operated with two secondary coils and the needle electrode in-serted.∙The number of turns for the coil in the reso-nant circuit is set to seven. There now ensuesa corona discharge from the tip of the needledue to the high voltage.7.4 Electrical wind∙The transformer is operated with one se-condary coil and 4 windings in the primary coil. The needle electrode is inserted into the secondary coil and the tinsel wheel placed on it.∙The ends of the S-shaped spin electrode come to a point. Due to the strong electric field electrons are emitted and attach them-selves to molecules of air. These are then re-pelled. The motion of the air molecules results in a force of reaction, which causes the electrode to spin.7.5 Spark discharge∙The transformer is operated with just one secondary coil and 4 windings on the primary coil. The needle electrode is placed on the secondary coil.∙The long spherical electrode is plugged into the second earth socket and the sphere is di-rected towards the tip of the needle.∙Now sparks several centimeters long start to leap between the tip of the needle and the sphere.7.6 Wireless transmission of energy∙The transformer is operated with one se-condary coil and the spherical electrode atta-ched.∙ A second secondary coil attached to the base with its holder for fluorescent lamp is set up about 1 m away from the Tesla transformer. ∙The earth sockets of the coil base and the Tesla transformer should be connected toge-ther via a laboratory cable.∙When the Tesla transformer is switched on with the light in the room partially dipped, it can be seen that the fluorescent tube illumi-nates. Wireless energy transfer is taking place between the coils.∙With reflector inserted between the coils, the shielding effect of the metal foil can be de-monstrated.7.7 Standing waves in a Tesla coil∙The Tesla transformer is operated with two coils connected together. The small spherical electrode is placed at the upper end. The number of primary coil windings is set to 8.∙Move the hand coil from above down over the pair of coils. The lower it gets, the brighter the lamp lights. The secondary coil oscillates as a λ/4 dipole. At the top end a current node appears and at the bottom, an antinode.∙Reduce the number of primary coil windings to three and slowly lower the hand coil from the upper end of the Tesla coil again. A cur-rent node appears at the top end and the lamp does not illuminate or only very weakly. ∙Moving further down, it is possible to detect two more antinodes and one more node in the oscillation. The Tesla coil is oscillating in the nature of a 3/4-λ dipole.∙Keep the equipment in a clean, dry and dust-free place.∙Before cleaning the equipment, disconnect it from its power supply.∙Do not clean the unit with volatile solvents or abrasive cleaners.∙Use a soft, damp cloth to clean it.∙The packaging should be disposed of at local recycling points.∙Should you need todispose of the equip-ment itself, never throwit away in normal do-mestic waste. Localregulations for the dis-posal of electricalequipment will apply.3B Scientific GmbH ▪ Rudorffweg 8 ▪ 21031 Hamburg ▪ Germany ▪ 。

达坎·赛卡姆 TS500 超音波测试设备说明书

DUKANE SEACOM, INC. SARASOTA, FLORIDA 34243 PHONE: 941-741-3200 FAX: 941-739-3201DOCUMENT NO. 03-TM-0082 © DUKANE SEACOM, INC.INTERNET: MAY 22, 2017REV ATECHNICAL MANUAL ULTRASONIC TEST SETMODEL TS500L LE DWHE N DTo buy, sell, rent or trade-in this product please click on the link below:/Dukane-Avionics-TS500-ULB-test-set.aspxThis manual should be read in its entirety priorto operation of the TS500 Test SetUNCONT ROL LE DWHE N PRI NT E DSECTION IGENERAL INFORMATION1.1. INTRODUCTION1.1.1. GENERAL. This manual contains the description, operation and maintenance of the TS500 Ultrasonic Test Set manufactured by Dukane Seacom, Inc., 7135 16th Street East, Suite 101, Sara-sota, FL 34243. See Figure 1.1.1.2. SYMBOLS AND ABBREVIATIONS. All symbols and abbreviations used in this manual are in accordance with the ANSI Y14.15 and MIL-STD-12, respectively.1.2. GENERAL DESCRIPTION1.2.1. FUNCTION. The TS500 is a battery operated heterodyne type receiver that operates at an ultrasonic frequency of 8.8 kHz and 37.5 kHz. The test set was designed primarily as a self-contained, hand held functional tester for testing the Low Frequency Underwater Acoustic Beacons 1.2.2. SPECIFICATIONS. The specifica-tions for the TS500 are given in Table 1TABLE 1. TS500ULTRASONIC TEST SET SPECIFICATIONSSize ................................ 3.3" x 6.5" x 1.2"(8.4 cm x 16.5 cm x 3.0 cm)Weight ........................... 13 ounces (368 grams)Battery*........................... 9 Volt* NEDA Type 1604AFigure 1. Ultrasonic Test Set ModelTS500(DK180) and Recorder Mounted Under-water Acoustic Beacons (DK100 Series). Utilizing the internal microphone, LED indicator and loudspeaker, the Test Set can perform an operational test on Dukane Seacom, Inc. beacons without removing the beacon from its mount. The test set can also be used to perform a voltage measurement to test the battery in a Dukane Seacom, Inc. underwater bea-con.UNCONT ROL LE DWHE N PRI NT E DSECTION II OPERATION2.1. OPERATIONA. Turn the test set ON using the small slide switch located on the left side of the housing.B. If the display reads LB, the TS500 battery voltage has fallen below the level required for op-eration of the test set and the 9 Volt battery should be replaced. See Maintenance Section 3.2.C. Testing Beacon Voltage. Choose the appropriate cable for the beacon (large clip for theDK180 (8.8 kHz) and smaller clip for the DK100 series (37.5k Hz)). Attach the test probe clip to the beacon case. See Figure 2. Place the tip of the probe in contact with the silver pad on the white dome at the end of the beacon. The display will show the battery voltage of the bea-con. Refer to the appropriate beacon manual for the acceptable range of the beacon battery voltage.D. Operational Test. Place the probes on the beacon as described above and press the red button on the TS500 (the test set display will be blank during this operation). The beacon should acti-vate and a sound will be audible from the TS500. Please note that high levels of background noise can interfere with this test. If difficulty is experienced in hearing the beacon, the operator should repeat the test in a quieter area.The TS500 LED Indicator will also illuminate when the beacon is actively pinging. The LED Indicator will illuminate "RED" for each 37.5 kHz ping and "GREEN" for each 8.8 kHz ping.Note: To accommodate timely functional and acceptance testing, the Low Frequency Underwa-ter Acoustic Beacon (DK180) is configured to generate a 10mS pulse about once per second for the first 10 minutes of operation. The pulse repetition rate reduces to about once per 10 seconds after that.Figure 2. Testing BeaconUNCONT ROL LE DWHE N PRI NT E DSECTION III MAINTENANCE3.1. BATTERY LIFE3.1.1. The test set battery should be replaced when its load voltage has dropped to 7 volts or the display reads LB when the test set is turned on.3.2. BATTERY REPLACEMENT3.2.1. Any 9 Volt battery may be used but longer service will be obtained by the use of premium batteries such as NEDA Type 1604A. The battery is accessible in the Test Set by removing the bat-tery access door on the bottom rear of the case and dropping out the old battery. A snap type con-nector facilitates change of battery and prevents reversal of polarity, but as an additional precau-tion, always turn the test set off before making the battery change.3.3. TEST SET CALIBRATION3.3.1. The TS500 Test Set is calibrated at the factory during manufacture. Under normal operat-ing conditions the test set will not require calibration for a period of 15 months. The calibration due date is shown on the back of the test set.3.3.2. For calibration procedures, please contact Dukane Seacom, Inc. or refer to the calibration procedures in the CT200 manual.UNCONT ROL LE DWHE N PRI NT E DSECTION IVWARRANTY TEST SETSDukane Seacom, Inc. warrants that the Test Set (referred to as the unit) will be free from defects in materials and workmanship, when used under normal operating conditions as determined solely by Dukane Seacom, Inc., for a period of one (1) year from the date of shipment from Dukane Sea-com, Inc.As the sole remedy for breach of the foregoing warranty, Dukane Seacom, Inc. shall repair or re-place, at Dukane Seacom, Inc.’s option, any unit, component or part thereof found defective or nonconforming within said one (1) year period from the date of shipment. Customer shall give Dukane Seacom, Inc. notice of any defect or nonconformity and, if so instructed by Dukane Sea-com, Inc., customer shall, at its expense, ship the unit, component or part to Dukane Seacom, Inc.. If Dukane Seacom, Inc. determines that the unit, component or part is actually defective or non-conforming, it shall, at its expense, ship a new or a rebuilt unit, component or part to the customer. The customer shall be responsible to perform, at its own expense, any necessary installation work related to any defective or nonworking unit, component or part. The functionality and operational aspects of the unit is determined by the unit operating within the specifications and is dependent of proper maintenance as required to be performed by the customer.Dukane Seacom, Inc. shall not be liable for any expense or damages resulting from interruptions in the operation of the unit.Dukane Seacom, Inc. shall not be liable for the cost of any repairs undertaken by the customer or any third party without Dukane Seacom, Inc. prior written authorization.Dukane Seacom, Inc. shall not be liable for any incidental, special consequential or exemplary damages arising out of the installation, use, testing, servicing or maintenance of any unit, compo-nent or part. This warranty is given in lieu of all other warranties, express or implied, included the warranties of merchantability or fitness for a particular purpose.Dukane Seacom, Inc.’s total liability under this warranty is limited to the remanufacture or re-placement of the unit, component or part .UNCONT ROL LE DWHE N PRI NT E D。

高中英语外研版选择性必修第三册Unit4AGlimpseoftheFuturePresentingi

一、根据首字母填写单词(单词拼写)1. He was so d_________ for the job to support his family that he could do anything.（根据首字母单词拼写）2. His heart sank when no further c________ was found about his missing child. (根据首字母单词拼写)3. Color is a medium for expressing different feelings, but the meaning of color is not c_____ across different cultures.二、根据汉语意思填写单词(单词拼写)4. The professor's stability theory is ________ (一致的) and complete. (根据汉语提示单词拼写)5. We now have an important ________ (线索) as to the time of the murder.(根据汉语提示单词拼写)6. The last few years has witnessed a ________ (持续的) improvement in the country’s economy. (根据汉语提示单词拼写)三、根据中英文提示填写单词(单词拼写)7. His wife left him after he lost his job, leaving him in a d________ (绝望的，拼命的) situation. (根据中英文提示填空)8. All of us are very excited because the police have found an important c________(线索) to the missing child. （根据中英文提示填空）四、完成句子9. 他的眼睛在车内搜寻可能发生的事情的线索。

EATON NZM系列模型选择指南说明书

Molded Case Circuit Breaker Utvalgsguide effektbryter NZM1Ii = elektromagnetisk utløserstrømA-type: termisk/elektromagnetisk vern3-polet NZMB1-...3-polet NZMN1-...Beskrivelse Type Elnr Type ElnrTilleggsutstyrIi = elektromagnetisk utløserstrømA-type: termisk/elektromagnetisk vern 100 % vern i nøytral100 % vern i nøytral 4-polet NZMB1-...4-polet NZMN1-...Beskrivelse Type Elnr Type ElnrChanges to the products, to the information contained in this document, and to prices are reserved; so are errors and omissions. Only order confirmations and technical documentation by Eaton is binding. Photos and pictures also do not warrant a specific layout or functionality. Their use in whatever form is subject to prior approval by Eaton. The same applies to Trademarks (especially Eaton, Moeller, and Cutler-Hammer). The Terms and Conditions of Eaton apply, as referenced on Eaton Internet pages and Eaton order confirmations.Follow us on social media to get the latest product and support information.Eaton ElectricAS Ryensvingen 5-70680 Oslo, Norge EatonEMEA Headquarters Route de la Longeraie 71110 Morges, Switzerland © 2023 EatonAll Rights ReservedPublication No. SA012023NN April 2023Eaton is a registered trademark.All other trademarks are property of their respective owners.To contact us please visit https:///us/en-us/support/international-support-contacts.htmlFor technical questions please contact your local Eaton team.Eaton’s electrical business is a global leader with deep regionalapplication expertise in power distribution and circuit protection; power quality, backup power and energy storage; control and automation; life safety and security; structural solutions; and harsh and hazardous environment solutions. Through end-to-end services, channel and an integrated digital platform & insights Eaton is powering what matters across industries and around the world, helping customers solve their most critical electrical power management challenges.For more information, visit .。

触头运动特性对直流接触器开断性能影响

第27卷㊀第11期2023年11月㊀电㊀机㊀与㊀控㊀制㊀学㊀报Electri c ㊀Machines ㊀and ㊀Control㊀Vol.27No.11Nov.2023㊀㊀㊀㊀㊀㊀触头运动特性对直流接触器开断性能影响李静1,㊀袁志曹1,㊀曹云东1,㊀刘树鑫1,㊀于龙滨2(1.沈阳工业大学特种电机与高压电器教育部重点实验室,辽宁沈阳110870;2.辽宁省电力有限公司电力科学研究院,辽宁沈阳110006)摘㊀要:为研究触头运动特性对直流接触器开断性能的影响,建立直流空气接触器电磁操动机构与灭弧系统联合仿真模型,对接触器操动机构进行运动结构电磁耦合仿真,得到操动机构动作过程中触头位移行程曲线,并与电弧磁流体模型相耦合,仿真得到了直流空气接触器从机构运动到触头打开电弧形成㊁弧根运动直至熄灭的全过程㊂讨论了接触器操动机构参数变化对开断性能的影响,并通过电弧现象背后的物理场变化分析了开断过程中重击穿现象产生的原因㊂结果表明:操动机构驱动动触头进而带动电弧完成了电弧拉伸㊁弧根转移以及被栅片切割等重要电弧演变过程;反力弹簧和触头弹簧预压力增大有利于提高触头的分断速度,加速电弧熄灭,但分断速度过高有可能导致电弧重击穿现象发生,其根本原因是栅片入口处产生的顺时针气流漩涡;通过控制触头的分断速度和灭弧室栅片区磁场分布,实现了对重击穿现象的抑制㊂关键词:直流接触器;操动机构;触头运动特性;电弧演变;重击穿现象DOI :10.15938/j.emc.2023.11.009中图分类号:TM572文献标志码:A文章编号:1007-449X(2023)11-0079-11㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀收稿日期:2022-08-16基金项目:国家自然科学基金(51977132);辽宁省重大科技专项(2020JH1/10100012);辽宁省教育厅面上项目(LJKZ0126)作者简介:李㊀静(1977 ),女,博士,副教授,研究方向为微观电器电弧理论及气体绝缘应用;袁志曹(1997 ),男,硕士研究生,研究方向为直流电弧理论及直流开断技术;曹云东(1963 ),男,教授,博士生导师,研究方向为现代电器理论及应用;刘树鑫(1982 ),男,博士,副教授,研究方向为开关设备开断㊁绝缘性能及智能化;于龙滨(1975 ),男,高级工程师,研究方向为高电压与绝缘技术㊂通信作者:袁志曹Influence of contact motion characteristics on breakingperformance of DC contactorLI Jing 1,㊀YUAN Zhicao 1,㊀CAO Yundong 1,㊀LIU Shuxin 1,㊀YU Longbin 2(1.Key Lab of Special Electric Machine and High Voltage Apparatus,Shenyang University of Technology,Shenyang 110870,China;2.Electric Power Research Institute of Liaoning Electric Power Limited Company,Shenyang 110006,China)Abstract :In order to study the influence of contact motion characteristics on the breaking performance of DC contactor,the combined simulation model of electromagnetic operating mechanism and the arc extin-guishing system of DC air contactor was established to simulate the movement,structure,and electromag-net of the contactor operating mechanism,so as to get contact displacement curves in the process of oper-ating mechanism motion,and couple with magnetohydrodynamics (MHD)model of the arc.The whole breaking process of the DC air contactor from mechanism movement to arc formation,arc root movement and arc extinction was obtained by simulation.The influence of the parameters of the contactor s operat-ing mechanism on the breaking performance was discussed,and the reason of the restriking phenomena in the process of breaking was analyzed by the variations of the physical fields behind the arc phenomenon.The results show that the operating mechanism drives the moving contact and then drives the arc to com-plete the important arc evolution processes such as arc stretching,arc root transfer and splitter plates cut-ting.The increases of the pre-pressure of the counterforce spring and contact spring are beneficial to im-prove the breaking speed of the contact and accelerate the arc extinction,but too high breaking speed may lead to the restriking phenomena of the arc,the basic cause of which is the clockwise airflow vortex generated at the splitter plates entrance.By controlling the breaking speed of the contacts and magnetic field distribution in the splitter plates area of the arc extinguishing chamber,the restriking phenomena was suppressed.Keywords:DC contactor;actuating mechanism;contact motion characteristics;arc evolution;restriking phenomena0㊀引㊀言直流空气接触器常用于频繁通断大容量控制电路以及主电路[1]㊂近年来,随着我国新能源汽车领域发展,电动机车驱动电机功率不断增大,直流接触器作为其主回路控制电器,升级发展面临着大容量㊁小型化的要求㊂直流空气接触器以空气为灭弧介质,辅以灭弧栅片提升弧压实现开断,由于其灭弧室结构复杂,实验难以观测灭弧室内部的电弧现象及电弧现象背后复杂的物理过程,因此电弧模型成为了当前研究直流空气电弧开断问题的有效手段㊂磁流体动力学(magnetohydrodynamics,MHD)模型通过一组描述电弧变化的偏微分方程组,实现了流体流动电流磁场之间的多物理场耦合,能够遵循电弧现象发生背后最根本的物理本质,成为了研究电弧问题的最有效方法㊂空气灭弧室结构复杂,MHD模型求解难度较大,早期针对直流空气电弧的MHD模型多以高度简化的平板电极为主,分析直流空气电弧开断过程中的基本物理规律[2-4],文献[5]建立了直流继电器简化极板电弧开断模型,研究了金属蒸气以及加装栅片对直流空气电弧开断的影响㊂文献[6]基于实际断路器产品结构,研究了气流场驱动作用以及栅片材料对灭弧性能的影响,但电弧演变背后的物理场变化未能体现,文献[7-8]从电弧现象发生背后物理场变化的角度揭示了电弧演变机理,包括磁场㊁气流场和温度场及场量耦合关系㊂通过栅片鞘层建立近极压降是直流灭弧的有效手段,由于近极区物理过程的复杂性,在早期MHD模型中近极过程常被忽略,文献[9]在早期MHD模型的基础上,引入鞘层有效电导率假设,建立了塑壳断路器三维MHD模型;文献[10]考虑了非线性近极鞘层产生近极压降的过程,建立了空气断路器MHD模型㊂MHD电弧模型的发展对认识直流空气电弧开断起到了较大作用,但由于其计算复杂,费时长,实现触头运动特性与MHD模型的耦合依然比较困难,所以现有MHD模型求解中常忽略复杂的机械运动,以两种方法简化计算:一是忽略触头运动过程,在仿真初始时刻假设电弧分布于上下跑弧道之间;二是忽略触头的变速运动,取动触头运动的平均速度作匀速运动假设[7,11]㊂直流接触器操动机构带动触头分断形成电弧,电弧在机构的带动下,运行进入到灭弧室中,完成弧根在跑弧道运动,进入栅片熄灭全过程㊂触头运动特性对灭弧性能的影响至关重要[12-13]㊂西安交通大学学者打破传统操动机构动力学仿真与电弧仿真的壁垒,采用链式电弧模型实现了低压断路器开断过程中复杂机械运动㊁弧根运动数学描述㊁电磁场和电路瞬态的多场域耦合,并研究了操动机构结构件参数等变量对开断性能的影响[14-16]㊂虽然这些研究有效地反映了开断过程中动触头运动特性对电弧特性的影响,但由于链式电弧模型是一个高度简化的宏观模型[17],不能精准描述开断过程中电弧现象背后的复杂物理场量变化,因此,推进操动机构动力学模型与灭弧室MHD模型耦合仿真是直流空气开关研究领域亟待解决的问题㊂综上,在前期空气电弧MHD模型研究的基础上[7],建立直流空气接触器电磁操动机构与灭弧系统联合仿真模型,将触头分断过程动力学仿真与MHD电弧模型相结合,并引入近极鞘层假设,对直流接触器电弧开断过程进行仿真,求解电弧开断全动态发展过程,探寻电弧演变机理㊂在此基础上讨论操动机构不同构件参数对直流电弧开断影响,并分析开断过程中灭弧室内多物理场的变化情况,建立触头运动特性与电弧重击穿现象发生背后物理场变化之间的联系㊂08电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀1㊀物理过程与仿真流程使用直流空气接触器样机建立操动机构灭弧系统联合仿真模型,操动机构驱动触头运动完成开断操作,开断过程产生的电弧受洛伦兹力及气流场驱动进入灭弧系统,灭弧系统将电弧熄灭,其具体过程如下:直流接触器操动机构线圈断电失去对衔铁的吸引作用,衔铁在反力弹簧和触头弹簧的作用下被弹开,动触头通过连杆被衔铁带动远离静触头,动静触头分离后,电弧形成,弧柱通道带电粒子流向阴极㊁阳极运动,机构带动触头运动,电弧被拉长,弧根向引弧片跳跃,在灭弧室内温度场㊁电磁场与气流场的共同作用下,电弧被灭弧栅片切割,建立近极压降,完成开断,其物理过程可用图1表示㊂图1㊀直流接触器开断物理过程Fig.1㊀Physical process of DC contactor breaking Manner㊀㊀针对操动机构采用多体动力学仿真,计算出动触头在开断过程中任意时刻的位移,采用移动网格技术,将动触头位移时间曲线耦合到直流接触器灭弧室MHD模型中,进行多物理场仿真求解,得到直流接触器开断过程中动静触头两端的电压电流变化趋势以及灭弧室内温度场㊁气流场的实时分布情况,实现直流接触器开断过程操动机构灭弧系统联合仿真,仿真流程如图2所示㊂图2㊀仿真流程图Fig.2㊀Simulation flow chart2㊀数学模型与假设条件2.1㊀操动机构数学模型1)刚柔体控制方程㊂直流接触器电磁操动机构中连接件㊁触头等刚体可采用拉格朗日运动方程描述:dd t K g q j()-K gq j+ðn i=1 ψi q jλi=F j;ψi=0,i=1,2, ,m㊂üþýïïï(1)式中:K g为系统动能;q j为系统广义坐标向量;F j为广义力列阵;ψi为系统的约束方程;λi为拉格朗日乘子矩阵㊂弹簧柔性体运动控制方程为Mξ㊃㊃+M㊃ξ㊃-12 M ξξ㊃[]Tξ㊃+Kξ+f g+Dξ㊃+Ψξ[]Tλ=Q㊂(2)式中:ξ为柔性体整体坐标;M为质量矩阵;K为刚度系数矩阵;f g为重力;D为模态阻尼矩阵;Ψ为约束方程;λ为拉格朗日系数;Q为柔性体受到的作用力㊂2)电磁动态特性方程㊂操动机构的电磁动态过程遵循以下方程:18第11期李㊀静等:触头运动特性对直流接触器开断性能影响▽㊃(-σ▽ϕ)=0;E =-▽ϕ- At ;J =σE ;▽ˑA =B ;▽2A =-μ0J ㊂üþýïïïïïïïï(3)式中:ϕ为电位;σ为电导率;E 为电场强度;A 为矢量磁位㊂d ψ(t )d t =U s -i (t )R ;m d 2z d 2t=F Z -F f (t )㊂üþýïïïï(4)式中:U s 为线圈电压;R 为线圈电阻;i (t )为线圈电流;ψ(t )为系统磁链;F Z 为衔铁所受磁力;F f (t )为衔铁所受反力;z 为衔铁位移;m 为衔铁质量㊂3)反力计算㊂机构的反力特性曲线可由下式及表1中弹簧参数计算得到:F k =K 1z m +F 1;F c =(K 1+K 2)z n +F 2+F k ㊂}(5)式中:F k ㊁F c 为动触头行程阶段㊁超程阶段的反力;K 1㊁K 2为反力弹簧㊁触头弹簧的刚度系数;z m 为动触头行程;z n 为超程;F 1㊁F 2为反力弹簧㊁触头弹簧装配预压力㊂弹簧的装配预压力F 1㊁F 2可由下式计算得到:F 1=K 1(L 1-L f1);F 2=K 2(L 2-L f2)㊂}(6)式中:L 1㊁L 2为弹簧的原长;L f1㊁L f2为弹簧在装配位置的长度㊂2.2㊀电弧MHD 模型与假设条件电弧模型基于MHD 方法提出,电弧等离子体被描述为流体,由于电弧物理现象复杂性,并考虑到实际研究对象的物理属性,对模型作如下假设:1)由于研究对象为低压直流接触器,开断过程中灭弧室温度并不高,在此忽略触头熔蚀以及引弧片㊁灭弧栅片材料相变形成的金属蒸汽;2)空气电弧在考虑小尺度灭弧室空间以层流为主,因此电弧等离子体视为牛顿流体;3)近极鞘层假设:在实际直流空气电弧开断过程中,由于非平衡效应的存在,使得在空气与金属栅片交界处存在高于空气电导率的近极鞘层[18],根据前人研究[19-21],通过设置空气与金属栅片交界处厚度为0.1mm 的高电导率非线性电阻区域来描述近极鞘层压降㊂电弧控制方程如下所示㊂1)动量守恒方程为:ρ V t +V ㊃▽V ()=▽㊃{-p I +μ[▽V +(▽V )T]-23μ(▽㊃V )I }+F ;F =J ˑB ㊂üþýïïïïïïï(7)式中:p 为流体微元上的压力;μ为流体的动力黏度;I 为单位矩阵;F 为洛伦兹力;J 为电流密度;B 为磁通密度㊂2)质量守恒方程为ρt+▽㊃(ρV )=0㊂(8)式中:ρ为电弧等离子体等效成流体的密度;V 为电弧等离子体的速度矢量㊂3)能量守恒方程为:(ρH )t +▽㊃(ρH V )=▽㊃λC p ▽H ()+S H ;S H =1σJ 2-S rad +S ϕ;S ϕ= T k B T 2e λC p +5()[](▽T ㊃J )㊂üþýïïïïïïï(9)式中:H 为热焓;λ为热导率;C p 为恒压比热;T 为热力学温度;S H 为等离子热源㊂等离子体热源S H 包括3项,第1项为焦耳热,第2项为总体积辐射项,第3项为电子焓传递项;k B 为波尔兹曼常数;e 为元电荷㊂电磁场方程如式(3)所示㊂在阴极和阳极,根据电子与离子的能量守恒方程,得出阴极的热边界条件如下:-n ㊃(-λ▽T )=-|J elec |ϕc +|J ion |U ion ;|J ion |=|J ㊃n |-|J elec |;|J elec |=|J R (T )|;J R (T )=A R T 2exp -eϕeff k B T()㊂üþýïïïïïï(10)式中:U ion 为等离子体电离电位;J ion 为离子电流密度;J elec 为电子流密度;ϕc 为阴极材料表面功函数;|J ㊃n |为面电流密度模;A R 为理查德森常数;ϕeff 为电极表面有效逸出功;J R (T )为电流密度㊂28电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀阳极的热边界条件为-n ㊃(-λ▽T )=|J ㊃n |ϕs ㊂(11)式中ϕs 为阳极材料表面功函数㊂3㊀几何模型与仿真参数3.1㊀电磁操动机构几何模型与仿真参数直流接触器样机操动机构如图3所示,其中触头弹簧与反力弹簧参数如表1所示,动触头开距为8mm,超程为2mm㊂电磁模型中:线圈匝数为3600匝;最大工作气隙δ为10mm;线圈加载外部电路电压为24V;线圈电阻为39Ω㊂图3㊀操动机构几何模型Fig.3㊀Model of operating mechanism 表1㊀反力弹簧和触头弹簧参数Table 1㊀Reaction spring and contact spring parameters㊀㊀㊀参数反力弹簧触头弹簧刚度系数K /(N /mm)0.632 6.16装配长度L f /mm 2513原长L /mm 3515.5行程长度x /mm1023.2㊀灭弧室二维几何模型与仿真参数参照直流接触器实物灭弧室,忽略电弧在垂直纸面方向的变化,建立如图4所示灭弧室二维几何模型㊂灭弧室由动触头㊁静触头㊁灭弧栅片㊁上下引弧片㊁强磁铁构成,在模型中:1)外部电路接440V 电压源,1Ω纯阻性负载;2)灭弧室内填充空气,设置空气气压为1atm,灭弧室右侧入口㊁栅片左侧出口为开边界;3)设置区域差异磁场,灭弧室入口区为80mT,触头区㊁栅片区为50mT,方向垂直纸面向外㊂图4㊀灭弧室二维几何模型Fig.4㊀2d geometric model of arc extinguishing chamber4㊀仿真结果分析4.1㊀接触器开断过程及电弧演变进行动力学仿真得到的接触器分断过程中动触头坐标时间曲线如图5(a)所示,线圈断电失去电磁吸力后,衔铁释放首先要经过超程,然后带动动触头使之与静触头分离,分断过程末期,衔铁返回到吸合初始位置时,动触头由于惯性的原因,会继续向前运动压缩触头弹簧,然后在触头弹簧反力的作用下,动触头最终稳定在平衡位置㊂由于分断初期衔铁进行超程运动,并未带动触头向前运动;在分断末期触头振动现象发生时电弧已经熄灭,这一现象对电弧开断没有影响,因此忽略这一现象导致的触头位移时间曲线波动,并进行坐标变换,得到分断过程中触头位移时间曲线如图5(b)所示㊂可以看出,动触头的位移时间曲线是一条微曲的曲线,动触头在运动过程中的速度变化对接触器开断性能影响不可忽视㊂将反力弹簧预压力为6.32N,触头弹簧预压力为15.4N 条件下分断过程中动触头位移时间曲线赋予到MHD 模型的动触头,仿真得到开断过程中动静触头两端弧压变化曲线如图6所示㊂如图所示开断过程中,弧压变化分为3个阶段:Ⅰ初期电弧拉长阶段㊁Ⅱ重击穿阶段㊁Ⅲ后期电弧充分切割阶段,其产生原因可由开断过程中电弧温度分布云图7来解释㊂38第11期李㊀静等:触头运动特性对直流接触器开断性能影响图5㊀触头分断位移—时间曲线Fig.5㊀Contact breaking displacements-timecurve图6㊀接触器开断过程中弧压变化曲线Fig.6㊀Arc voltage change curve of contactor duringbreaking动触头分断初期,电弧随着动静触头的分离而被拉长,电弧的弧阻随着弧长的增加而升高,而触头两端弧压随着弧阻的升高而升高,如图6所示,此过程一直持续到电压数值升高为110V 左右,在这一阶段,动触头的分断速度越高越利于接触器开断;弧压数值升高为110V 左右后,电弧演变进入第二阶段,触头运动速度继续升高,如图7所示,t =6.3ms 时电弧进入灭弧栅片,弧压迅速上升,随即灭弧室内发生了剧烈的重击穿现象,重击穿现象使得弧压迅速下降,这种现象非常不利于直流空气电弧的开断;如图7所示,t =6.8ms 阴极弧根从动触头转移到下引弧片,而后电弧演变进入第三阶段,电弧在洛伦兹力及气流场的作用下充分进入灭弧栅片,电弧被分为多段串联短弧,最终触头两端电压上升到电源电压,开断完成㊂图7㊀电弧温度分布云图Fig.7㊀Cloud diagram of arc temperature distribution4.2㊀弹簧预压力对接触器开断性能的影响改变操动机构中反力弹簧和触头弹簧的预压力即可改变接触器开断过程中动触头的运动特性㊂通常,操动机构反力曲线要和动态吸力曲线要满足一定的配合关系才能满足工作要求,因此首先进行操动机构电磁动态特性仿真以确定合理的反力设计范围[22]㊂进行电磁操动机构动态过程仿真得到操动机构吸合过程中的动态吸力曲线与反力曲线配合如图8所示㊂在吸合过程中工作气隙小于2mm 时,48电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀衔铁进入超程,此时弹簧的反力大于电磁吸力,吸反力曲线出现一段交叉面积,这样的配合可以减缓衔铁对静铁心的冲击㊂在吸合动作完成后,电磁吸力远大于弹簧反力以保障衔铁吸合的可靠性㊂图8㊀操动机构吸反力配合Fig.8㊀Coordination of suction and reaction force ofoperating mechanism最终,根据接触器操动机构的尺寸限制以及吸反力配合关系的要求,在弹簧刚度系数不变的情况下,通过改变弹簧的自由长度和弹簧装配时的压缩长度来改变弹簧的预压力,结合式(6),确定反力弹簧和触头弹簧预压力的参数取值范围如表2所示㊂选取两弹簧不同预压力组合,得到操动机构在4组不同弹簧预压力条件下的反力曲线如图9所示㊂表2㊀弹簧预压力参数取值范围Table 2㊀Parameter range of springs pre-pressure取值水平反力弹簧预压力/N触头弹簧预压力/N上限㊀ 6.3227.72中间值 5.05615.4下限㊀1.8963.08图9㊀操动机构在4组不同弹簧预压力条件下的反力曲线Fig.9㊀Reaction curves of operating mechanism underfour different springs pre-pressure conditions动力学仿真得到动触头分断位移时间曲线如图10所示,其中F 1为反力弹簧预压力,F 2为触头弹簧预压力㊂从图中可以看出,当触头弹簧预压力不变,减小反力弹簧的预压力,动触头的运动速度减慢,触头分断时间变长,减小触头弹簧的预压力导致触头的初分速度减小㊂图10㊀动触头位移—时间曲线对比Fig.10㊀Comparison of displacements-time curves ofmoving contacts将多组触头位移时间曲线赋予到灭弧室MHD 模型,仿真得到不同弹簧预压力作用下接触器开断过程弧压变化曲线如图11所示,当反力弹簧和触头弹簧的预压力都最大时,弧压在上升到一定值后发生由电弧背后的重击穿导致的弧压下降现象,当弹簧预压力减小到一定程度,电压下降现象消失,重击穿现象的发生情况与弹簧预压力的关系如表3所示,弹簧预压力增大使触头分断速度增加,分断速度增加使电弧电压上升速度加快,同时分断速度过高会使开断过程发生重击穿现象㊂图11㊀不同预压力条件下电弧电压变化Fig.11㊀Arc voltage variation at different pre-pressureconditions58第11期李㊀静等:触头运动特性对直流接触器开断性能影响表3㊀不同预压力条件下的开断特性Table3㊀Breaking characteristics under different pre-pressure conditions弹簧预压力/N 触头行程时间/ms熄弧时间/ms是否发生电弧重击穿现象F1=6.32,F2=27.728.98.4是F1=6.32,F2=15.49.89.15是F1=1.896,F2=15.411.28.65否F1=5.056,F2=3.0811.79.1否4.3㊀栅片入口处重击穿现象分析为建立重击穿现象发生原因与触头运动特性之间的联系,在4组触头位移时间曲线中选取具有对比意义的F1=6.32N㊁F2=15.4N为1号曲线㊁F1=1.896N㊁F2=15.4N为2号曲线,通过二者开断过程中气流场与温度场的变化对电弧重击穿现象的发生原因进行分析㊂1㊁2号动触头位移时间曲线如图12(a)所示,曲线作用下接触器开断过程中弧压变化趋势对比如图12(b)所示㊂在电弧演变至Ⅱ阶段,1号曲线作用下电弧发生了重击穿现象,这一现象会导致弧压剧烈下降,而2号曲线没有发生这一现象,动触头运动速度较慢的2号曲线其熄弧时间反而快于1号曲线0.5ms,由此可见重击穿现象对直流开断影响显著㊂在开断过程中,电弧受到的驱动气流由灭弧室右侧开口流向灭弧室内,动触头位于这个开口之间,驱动气流的流通路径被动触头一分为二,分别是以静触头和动触头为边界的上方通道,以及以动触头和下引弧片为边界的下方通道㊂触头分断速度不同时,由于电弧演变过程差异以及动触头位置不同导致的气流通道宽度不同,所以气流场分布也有差异㊂取电弧初期拉长阶段1号曲线和2号曲线作用下的电弧形态㊁洛伦兹力及气流场对比如图13,由于1号曲线作用下触头运动速度比较快,所以2号曲线作用下这一阶段要比1号曲线滞后0.7ms,在这两个时刻,1号曲线和2号曲线作用下动静触头间气流场分布大致相同,但正是由于0.7ms滞后时间的存在,2号曲线作用下的电弧受洛伦兹力作用时间长,因此2号曲线作用下的电弧要先于1号曲线与下引弧片充分接触,并先于1号曲线完成阴极弧根转移㊂图12㊀1㊁2号位移时间曲线及开断过程弧压对比Fig.12㊀Comparison of displacements-time curves1㊁2 and arc voltage in the breakingprocess图13㊀初期拉长阶段电弧形态㊁洛伦兹力及气流场对比Fig.13㊀Comparison of arc morphology,Lorentz force and airflow field at the initial arc stretch stage 取1号曲线和2号曲线作用下,弧柱充分挤压2㊁3号灭弧栅片阶段时的电弧形态及灭弧室内气流场对比如图14所示,由于1号曲线作用下阴极弧根未转移,由上方通道产生的逆时针气流大量涌入下方通道;不同于1号曲线,此时2号曲线作用下的阴极弧根已经转移,下方通道的气流流向由外侧流入灭弧室内,在下方通道产生气流的挤压作用下,导致2号曲线作用下的灭弧室内栅片右侧逆时针气流的68电㊀机㊀与㊀控㊀制㊀学㊀报㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀㊀第27卷㊀主要流通路径较于1号曲线整体靠上,这样的不同最终导致图15所示的上方通道气流进入2㊁3号栅片之间的气流量差异㊂图14㊀1号曲线和2号曲线作用下弧柱充分挤压2㊁3号灭弧栅片时电弧形态及气流场对比Fig.14㊀Comparison of arc and air flow field at thefunction of curve 1and 2when arc column fully squeezing splitter plates 2and3图15㊀1号曲线和2号曲线作用下电弧被2㊁3号栅片切割阶段电弧形态及气流场对比Fig.15㊀Comparison of arc and air flow field at thefunction of curve 1and 2when arc cut off by splitter plates 2and 3取1号曲线和2号曲线作用下电弧处于被2㊁3号栅片切断阶段时的电弧形态㊁灭弧室内气流场对比如图15,此时1号曲线作用下上方通道产生的气流在受到3号栅片的阻碍作用后主要流向左下方,极少部分气流流向2号栅片与3号栅片之间,而2号曲线作用下的上方通道产生的气流在受到3号栅片的阻碍作用后半数流向2号栅片与3号栅片之间,由于2号曲线作用下流入2㊁3号栅片之间的气流分量较于1号曲线流速快㊁流量大,足以保持沿2㊁3号栅片的水平流向;而1号曲线作用下,这一小部分气流由于流量小㊁流速慢,所以流向保持能力较弱,等压线对比如图16所示,在2㊁3号栅片间右侧形成气压空洞最终导致顺时针气流漩涡产生㊂图16㊀1号曲线和2号曲线作用下电弧被2㊁3号栅片切割阶段时等压线对比Fig.16㊀Comparison of isobars of at the function ofcurve 1and 2when the arc cut off by splitterplates 2and 31号曲线作用下发生重击穿现象时的电弧温度云图如图17所示,由于2㊁3号栅片间产生的顺时针气流漩涡的存在,3号栅片右上方的弧柱受到反吹作用而向下弯曲,直至t =7.1ms,弧柱在3号栅片右上侧形成新的导电通道,电弧重击穿完成㊂综上,触头分断速度不同导致灭弧室内气流场分布产生差异,使灭弧室内栅片入口处产生气压空洞并产生顺时针气流漩涡,最终导致此处电弧重击穿现象发生㊂图17㊀1号曲线作用下发生重击穿现象时的电弧温度云图Fig.17㊀Arc temperature cloudat the function of curve 1when restriking phenomena occurring4.4㊀仿真结果在实际产品优化中的应用根据前文对电弧重击穿现象的分析,可知重击穿现象由气流场㊁温度场和磁场共同作用产生,在气流场作用下栅片入口处产生气流漩涡致使电弧周围的高温气体被吹到栅片右侧,最终在此处形成新的导电通道㊂通过改进灭弧室区域磁场分布,防止栅78第11期李㊀静等:触头运动特性对直流接触器开断性能影响。

canonical_circuit_model

3. Converter must contain an effective lowpass filter characteristic • necessary to filter switching ripple • also filters ac variations
He(s) 1 : M(D) +
Fundamentals of Power Electronics
127
Chapter 7: AC equivalent circuit modeling
Steps in the development of the canonical circuit model
e(s) d(s)
He(s) 1 : M(D) + Zei(s) Effective low-pass filter – Zeo(s)
Fundamentals of Power Electronics
128
Chapter 7: AC equivalent circuit modeling
Transfer functions predicted by canonical model
e(s) d(s)
He(s) 1 : M(D) + Zei(s) Effective low-pass filter – Zeo(s)
node B
Vg – V d D
+ –
1:D
sLI d D'
L
D' : 1 + C
V + v(s)
+ –
DI d D'
Vg + vg(s)
+ –
Id
DI d D'

碳纤维轮组空气动力

碳纤维轮组空气动力英文回答：Carbon fiber wheels are the pinnacle of cycling performance, offering a unique combination of lightweight, stiffness, and aerodynamic efficiency. The use of carbon fiber in wheel construction allows for the creation of rims that are both incredibly strong and lightweight, providing riders with a significant advantage in terms of acceleration, climbing, and overall speed.Aerodynamic Benefits of Carbon Fiber Wheels:The aerodynamic benefits of carbon fiber wheels are primarily attributed to their ability to reduce drag. The shape and design of carbon fiber rims are optimized to minimize air resistance, creating a more streamlinedprofile that allows riders to cut through the wind with less effort. This reduction in drag translates into increased speed, especially at higher speeds.Furthermore, carbon fiber wheels often feature deep-section rims, which further enhance their aerodynamic properties. Deep-section rims create a more stable airflow around the wheel, reducing turbulence and improving the overall efficiency of the bike's propulsion.Additional Benefits of Carbon Fiber Wheels:In addition to their aerodynamic advantages, carbon fiber wheels offer several other benefits that contribute to their popularity among cyclists:Lightweight: Carbon fiber is an incredibly lightweight material, allowing for the creation of wheels that are significantly lighter than traditional aluminum or steel wheels. This reduction in weight results in improved acceleration, hill-climbing ability, and overall handling.Stiffness: Carbon fiber wheels are also exceptionally stiff, providing riders with a more responsive andefficient ride. The increased stiffness translates intobetter power transfer from the rider to the wheels,resulting in a more direct and controlled feel.Durability: While carbon fiber is a lightweight material, it is also highly durable and resistant to damage. Carbon fiber wheels are designed to withstand the rigors of everyday use, making them a reliable choice for both recreational and competitive cyclists.Conclusion:Carbon fiber wheels represent the cutting-edge ofcycling technology, offering riders a combination of lightweight, stiffness, and aerodynamic efficiency that cannot be matched by traditional wheel materials. Whether you're a competitive racer or a recreational rider, carbon fiber wheels can help you unlock your full cyclingpotential and achieve new levels of performance.中文回答：碳纤维轮组的空气动力学优势：碳纤维轮组的空气动力学优势主要归功于其降低阻力的能力。

基于情境意识模型的高速公路出口区域逐级限速方案研究

第21卷第2期2023年06月交通运输工程与信息学报Journal of Transportation Engineering and InformationVol.21No.2Jun.2023文章编号：1672-4747（2023）02-0066-13基于情境意识模型的高速公路出口区域逐级限速方案研究杨艳群1,2，陈铭1,2，樵婷3，郑新夷*2,4(1.福州大学，土木工程学院，福州350116；2.福州大学，交通心理与行为国际联合实验室，福州350116；3.福建工程学院，福州350118；4.福州大学，人文社会科学院，福州350116)摘要：为分析高速公路出口区域限速方案的效果，研究提出了逐级限速方案（一级限速、二级限速、三级限速），并开展不同交通流情况下的驾驶模拟实验。

引入情境意识理论（Situation Aware-ness,SA）和ACT-R认知理论从驾驶人角度对逐级限速方案进行研究，建立了道路交通驾驶人SA的定量计算模型，通过与情境意识全面评估技术（SAGAT）结果的对比，评估出SA定量计算模型的有效性。

结果表明：（1）在自由流状态下，车辆在分流鼻端的速度分别超过限速13.4km/h （一级限速）、7.4km/h（二级限速）、4.0km/h（三级限速），在不稳定流状态下则超过9.7km/h（一级限速）、6.2km/h（二级限速）、1.7km/h（三级限速）；（2）交通量一定时，随着限速次数增加，驾驶人的SA水平提高，事故的可能性下降，其中三级限速方案是考虑驾驶人SA的最佳方案；（3）瞳孔面积和平均扫视频率可作为衡量SA的眼动行为指标，分流鼻端速度可作为衡量SA的操纵绩效指标。

关键词：交通工程；逐级限速；情境意识；驾驶模拟；眼动特征中图分类号：U491.25文献标志码：A DOI:10.19961/ki.1672-4747.2022.09.019Research on the successive-stage speed limit design at freeway exit areabased on situation awareness modelYANG Yan-qun1,2,CHEN Ming1,2,QIAO Ting3,ZHENG Xin-yi*2,4(1.College of Civil Engineering,Fuzhou University,Fuzhou350116,China;2.Joint International Research Laborato-ry on Traffic Psychology&Behaviors,Fuzhou University,Fuzhou350116,China;3.Fujian University of Technolo-gy,Fuzhou350118,China;4.College of Arts and Human Science,Fuzhou University,Fuzhou350116,China)Abstract：In this study,three successive-stage speed limit designs(level-1speed limit,level-2speed limit,and level-3speed limit)were devised,and driving simulation experiments were performed un-der different traffic flows to analyze the effect of the speed limit design of a freeway exit area.The sit-uation awareness(SA)and ACT-R cognitive theory were introduced to study the successive-stage speed limit from the driver’s perspective,and a quantitative model of the driver’s SA was estab-lished.Subsequently,the effectiveness of the SA model was evaluated by comparing its results with those of the situation awareness global assessment techniques(SAGAT).The results show that(1) For free flow,the shunt nose speed exceeds the level-1speed limit of13.4km/h,level-2speed limit of7.4km/h,and level-3speed limit of4.0km/h;and for unsteady flow,it exceeds level-1speed limit收稿日期：2022-09-21录用日期：2022-11-01网络首发：2022-11-17审稿日期：2022-09-21~09-27；10-19~10-28；10-30~11-01基金项目：福建省社科基金项目（2021B062）作者简介：杨艳群（1969—），男，副教授，研究方向为交通安全、交通心理等，E-mail:******************.cn通信作者：郑新夷（1971—），女，副教授，研究方向为交通心理等,E-mail:******************.cn引文格式：杨艳群，陈铭，樵婷，等.基于情境意识模型的高速公路出口区域逐级限速方案研究[J].交通运输工程与信息学报，2023，21(2)：66-78.YANG Yan-qun,CHEN Ming,QIAO Ting,et al.Research on the successive-stage speed limit design at freeway exit area based onsituation awareness model[J].Journal of Transportation Engineering and Information，2023，21(2)：66-78.of9.7km/h,level-2speed limit of6.2km/h,and level-3speed limit of1.7km/h.(2)When the traffic volume is fixed,as the number of speed limits increases,the driver’s SA increases and the possibility of accident decreases.Therefor,the three-level speed limit design is the best design considering driv-er’s SA.(3)The pupil area and average saccade frequency can be used as eye movement behavior in-dicator,and the shunt nose speed can be used as a maneuver performance indicator when measuring the SA.Key words：traffic engineering;successive-stage speed limit;situation awareness;driving simula-tion;eye movement characteristics0引言我国是高速公路里程最长的国家之一，而作为高速公路转换行车方向的重要节点——出口匝道，其交通事故情况日益严峻。

科普教育出版社九年级上册单词背诵版

1U1 Topic12take place3volunteer4bell5Africa6disable7shut8ever9rope10narrow11various12report13keep in touch with14relative15telegram16rapidly17since18reform19reform and opening-up 20satisfy21medical22cellphone=mobile phone 23fax24machine25rapid26progress27make progress28already29succeed in30pleased31leisure32hide33hide and seek34chess35radio36spare37recent38abroad39U1 Topic240yet41probably42cinema43department store44nearby45population46billion47increase48reach50policy51Russia52measure53social54supply55natural56worse57so far58government59take measure to do sth 60thanks to sb/sth61paragraph62opportunity63newborn64percent65offer66surround67discourage68local69capital70huge71market72transportation73excellent74U1 Topic375as a matter of fact76block77artist78millions of79visitor80industry81chemistry82term83program84homeless85manage86treatment87immediately88secretary89helper90club91engineer92wound93basic94human95value96period98homelessness99earn100drug101mental102on purpose103whatever104effect105steal106suppose107phrase108according to109context110laborer111cruel112project113aid114primary115contribution116make a contribu to 117encourage118moral119development120respect121importance122continue123college124Review of unit 1 125indeed126method127teenager128hardly129plenty130plenty of131sunshine132sunbathe133beach134volleyball135culture136surf137U2 Topic1138bee139butterfly140mess141shame142several143pour144waste146destroy147cut down148pollute149goodness150breath151pain152produce153chest154awful155bear156editor157breathe158soil159harmful160be harmful to161deaf162print163hearing164loss165recently166disturb167do harm to168uncomfortable169unpleasant170sort171environmental172including173onto174sentence175coal176create177blood178high blood pressure 179planet180U2 topic2181sand182sandstorm183change into184desert185human186although187reduce188completely189user190none191rubbish192here and there193spit194wild195nobody196untidy197worst198rude199behavior200situation201punish202perhaps203everybody204nowhere205take away206oxygen207hole208ozone layer209radiation210directly211carbon dioxide 212form213blanket214escape215rise216the greenhot effect 217refer to218shortage219avoid220resource221discover222reuse223thirsty224nearly225law226U2 Topic3227protection228organization229recycle230plastic231can232nod233agreement234disagreement235hurry236give up237battery238ought to239shut off240electricity241distance242cloth243action244after all245acid rain246nuclear247biogas248technology249straw250renewable251shortage252process253require254electric255best-known256maglev train257German258per259wheel260efficient261guide262path263steel264wave265deep266source267run out268worldwide269sunlight270steam271remove272replace273dry274insect275bite276planter277Review of units 278colleague279motorbike280gasoline281anybody282examine283marry284weight285media286package287product288excessive289goods290seriously291video292allow293quality294historical295lifestyle296difference297U3 Topic1 298cartoon299character300widely301throughout302from now on 303foreigner304film-maker 305garage306be pleased with 307pack308on business 309tonight310Spanish311be similar to 312communicate 313conversation 314interpreter315explain316impossible317twin318divide319divide..into. 320dig321lay322mother tongue 323root324trader325native326speaker327foreign328base329European330kingdom331tourism332Britain333powerful334leading335position336U3 Topic2337see..off 为..338stranger339thumb340ask for a ride 341minibus342give sb. a.ride 343get on344flight345guidebook346whenever347board348bow349silence350hip351praise352research353do some research 354secret355puzzled356victory357misunderstanding 358typical359differently360negative361consider362honest363positive364at times365ancient366magical367creature368emperor369compare..to.. 370courage371underline372mistake373make mistakes 374peacock375pride376wisdom377British378kowtow379expression380spelling381elevator382pronunciation383cent384cookbook386U3 Topici3387accent388oral389dare390sleepy391final392real393retell394indirect395granddaughter396pronounce397dialog398composition399copy400notebook401diary402keep a diary403tape404aloud405object406textbook407ability408take a breath409toothpaste410preview411translate412discussion413exactly414honor415as long as416stick to (doing) to417chant418achieve419easily420download421actually422effective423imitate424Review of unit3 companyn 425bored426concentrate427pull428fold429mention430U4 Topic1431rocket432metal434spaceship 435lock436laptop437digital438bulb439airplane440hard-wearing 441Korea442invention443list444crayon445thought446brainstorm 447evaluate448detailed449redesign450balloon451gun452robot453keyboard454explorer455mark456system457man-made 458U4 Topic2 459display460screen461alien462outer space 463describe464astronaut465admire466master467dancer468realize469universe470solar system 471Roman472god473diameter474storm475gravity476weigh477generally478journey479limit480excitement481launch482beyond483U4 Topic3484prove485lunar486legend487significance488independently489spacewalk490electronic491spacesuit492telescope493entertainment494doubt495no doubt496tiny497inside498normally499brain500cancel501workplace502connect503for instance504besides505servant506certain507for certain508on one's own509warn510might model511housework512Review of unit 43163 513waitress514magazine515rooster516wife517chick518paint519struggle520palace521the Summer Palace522tower523prison524prisoner525vocabulary526a bunch of发生, 进行n.志愿者n.钟声; 钟, 铃n.非洲adj.残疾的, 残废的v.关闭, 关上adv.在任何时候, 从来n.绳子, 绳索adj.狭窄的adj.,各种各样的n.&v.通讯; 交流与.. 保持联系n.亲属, 亲戚n.电报; 电文adv.快速地, 迅速地prep.&conj.自.. 从; 既然n.改革, 改良改革开放v.使满足, 使满意adj.医学的, 医疗的移动电话n.传真, 传真机n.机器, 机械adj.迅速的, 快速的n.&v. 进步; 进展取得进步adv.已经, 早已成功地做了..adj.高兴的n.空闲, 空暇v.躲藏; 遮挡; 隐瞒捉迷藏n.国际象棋n.收音机adj.空闲的, 空余的adj.近来的, 最近的adv.在国外; 到国外adv.仍, 还adv.很可能, 大概n.电影院百货公司adj.&adv. 附近; 在附近n.人口, 人数num.十亿v.&n.(使) 增大, 增加; 增大v.实现; 达到; 够得着; 到达adv. 幸运地n.政策, 方针n. 俄罗斯n. 措施, 方法adj. 社会的; 社交的v.&n.提供; 供应量, 补给adj. 天然的; 天生的adj.&adv. 更差的; 更差到目前为止n. 政府, 内阁采取措施做..幸亏, 由于n. 段落n. 机会, 时机adj. 新生的, 初生的n. 百分之..v. 提供v. 围绕, 环绕v. 阻止; 使灰心adj. 当地的, 本地的n. 首都, 资本adj. 巨大的, 极多的n. 集市, 市场n. 运输adj. 优秀的, 杰出的事实上, 其实n. 街道; 块n. 艺术家, 画家of 大量的, 数以百万计n. 游客, 来访者, 参观者n. 行业, 工业n. 化学, 化学物质n. 学期; 词语, 措辞n. 计划, 方案, 节目adj. 无家的v. 完成; 能解决(问题)n. 治疗; 待遇adv.&conj. 立刻; 一.. 就n. 秘书n. 帮手, 助手n. 俱乐部n. 工程师n.&v. 伤口; 伤害adj. 基本的, 基础的adj.&n. 人的; 人v.&n. 重视, 珍视; 价值n. 一段时间, 时期n. 收容所; 遮蔽物n. 无家可归v. 挣钱; 赢得n.毒品; 药物, 药adj. 精神健康的; 思想的故意pron.无论什么; 任何事物n.影响, 结果; 效果v.偷, 窃取v.帮助, 支持, 援助n.短语, 词组据.. 所说, 据.. 所报道n. 上下文; 语境; 背景n. 劳工, 工人adj. 残酷的, 冷酷的n. 项目, 方案v.&n. 援助; 帮助adj. 小学教育的; 主要的; 最初的n. 贡献; 捐款为.. 做贡献v. 鼓励adj. 道德(上) 的n. 发展, 开发v. 尊敬, 尊重n. 重要性v. 持续, 继续做n.(美) 大学,(英) 学院adv. 真正地; 实际上n. 方法, 办法n. 青少年adv. 几乎不pron.&n. 大量, 众多; 充足of 大量的n. 阳光v. 晒太阳, 日光浴n. 海滩, 海滨n. 排球adj. 文化的v. 上网, 浏览n. 蜜蜂n. 蝴蝶; 蝶泳n. 肮脏, 脏乱; 困境n. 羞耻, 羞愧det.&pron. 几个, 数个v. 倒出, 倾泻; 不断流出v.&adj. 废弃的, 无用的; 浪费n. 村民v. 摧毁, 破坏砍倒v. 污染n. 天啊v. 呼吸n. 疼痛, 痛苦v. 生产, 制造n. 胸部, 胸膛adj. 很坏的, 极讨厌的v. 承受, 忍受n. 主编, 编辑n. 一次吸入的空气n. 土壤, 土地adj. 有害的对.. 有害adj. 聋的v. 印刷n. 听力, 听觉n. 丧失; 损失; 丢失adv. 不久前, 最近v. 打扰, 扰乱伤害, 损害adj. 使人不舒服的adj. 令人不快的n.&v. 种类, 品种; 整理, 把.. 分类adj. 环境的prep. 包括.. 在内prep. 向, 朝n. 句子; 审判, 判决n. 煤; 煤块v.创造n. 血高血压n. 行星n. 沙n. 沙尘暴转换成, 变成n.&v. 沙漠; 舍弃n. 人conj. 虽然, 尽管, 既使v. 减少, 减轻adv. 彻底地; 完整地n. 使用者, 用户pron. 没有一个; 毫无n. 垃圾; 废物在各处; 到处v. 吐, 唾adj. 野生的pron.&n. 没有人; 小人物adj. 不整洁的, 凌乱的adj. 最差的, 最糟的adj. 无理的, 粗鲁的n. 行为, 举止n. 状况; 形势; 局面v. 惩罚adv. 可能, 大概pron. 人人, 每个人adv. 无处; 哪里都不拿走n. 氧气n. 洞, 坑臭氧层n. 放射, 放射物adv. 直接地二氧化碳v.&n.(使) 出现; 总类; 形式n. 毛毯, 毯子v. 渗出; 逃跑; 逃出v. 上升; 起床; 逃脱温室效应提起, 涉及, 有关n. 不足; 缺少; 短缺v. 防止, 避免n. 资源, 财力v. 发现, 找到v. 再次使用; 重复使用adj. 缺水的;(渴) 的adv. 几乎, 将近n. 法律, 法令; 定律n. 保护, 防卫n. 组织, 机构, 团体n. 回收利用, 再利用adj. 塑料的n.(美) 罐子, 罐头v. 点头n. 同意, 一致, 协议n. 分歧, 争论赶快, 快点放弃n. 电池应该关掉, 关闭n. 电, 电能n. 距离n. 织物, 布料n. 行为; 行动毕竟酸雨adj. 原子核的; 核动力的n. 沼气n. 技术n. 禾秆, 稻草adj. 可更新的, 可再生的n. 不利因素; 障碍n.&v. 步骤, 过程, 加工, 处理v. 需要, 要求adj. 用电的; 电动的最知名的磁悬浮列车n. 德国人; 德语prep. 每, 每一n. 轮; 轮子adj. 效率高的, 有能力的n. 向导, 导游; 指南, 手册n. 道路, 途径n. 钢铁n.&v. 挥手; 海浪adj.&adv. 深的, 厚的; 深深地n. 来源, 出处; 源头耗尽, 用完adv. 全世界; 世界各地n. 阳光n. 水蒸气, 蒸汽v. 去除, 使消失, 移开v. 替代, 取代adj.&v. 干燥的, 雨少的; 擦干n. 昆虫v. 咬; 叮n. 种植园主n. 同事, 同僚n. 摩托车n. 汽油pron. 任何人, 无论谁v. 检查, 调查v. 嫁, 结婚n. 重量, 分量n. 传播媒介, 传播工具n.&v. 一包, 一袋; 将.. 包装好n. 产品, 制品adj. 过度的, 过分的n. 商品, 货品adv. 严重地; 严肃地n. 录像带; 录像v. 允许n. 质量; 品质adj. 历史的n. 生活方式n. 差别; 差异n. 漫画n. 角色; 汉字, 字体; 品格adv. 普遍地; 广范地prep. 遍及, 贯穿nowon 从今往后, 从现在开始n. 外国人电影制作人n. 停车库, 车库对.. 感到高兴满意v.&n. 把.. 打包; 包, 捆; 一群出差adv. 在今晚n.&adj. 西班牙语; 西班牙的与.. 相似v. 交流, 沟通n. 对话, 谈话n. 口译译员v. 解释, 说明adj. 不可能的adj.&n. 双胞胎之一的; 双胞胎之一v. 划分把.. 分成v. 掘, 凿, 挖v. 放置, 安放 , 搁母语n. 起源, 根源, 根, 词根n. 商人, 买卖人adj. 出生地的, 当地的n. 讲(某种语言) 的人, 发言人adj. 外国的n.&v. 根据; 根基; 总部; 以.. 为基础adj. 欧洲的n. 王国, 管辖范围; 领域n. 旅游业, 观光n. 英国, 不列颠adj. 强大的, 有权势的, 有影响力的adj. 最重要的, 最成功的n. 位置, 方位送行; 送别n. 陌生人n. 拇指搭乘, 搭车n. 小型公共汽车, 中巴让.. 搭便车上车n. 航班飞机; 空中航行n. 旅游手册conj. 无论何时, 在任何时候v. 上(交通工具); 住宿v. 点头, 鞠躬n.&v. 沉默; 使安静n. 臀部, 髋v.&n. 表扬, 赞扬n. 研究, 调查做调查n. 秘密adj. 困惑的n. 胜利n. 误会, 误解adj. 典型的adv. 不同地, 有差异地adj. 负面的, 消极的v. 认为, 以为; 考虑到adj. 诚实的, 坦率的adj. 正面的, 乐观的有时, 间或adj. 古代的, 古老的adj. 奇妙的, 有魔力的n. 生物; 动物n. 皇帝把.. 比作n. 勇气, 谋略v. 在.. 画线n.&v. 错误; 误解犯错误n. 雄孔雀n. 骄傲, 自豪n. 智慧, 精明adj. 英国的, 英国人的v. 磕头; 唯命是从n. 词语; 表达; 表情n. 拼写n. 电梯n. 发音n. 分n. 烹饪书adv. 完全地, 整个地n. 口音, 腔调adj. 口头的v. 敢于adj.瞌睡的adj. 最终的, 最后的adj. 真实的, 真正的v. 复述adj. 间接的, 附带的n. 外孙女v. 发音n. 对白, 对话n. 作文, 作曲; 构成v. 抄写; 复印n. 笔记本n. 日记写日记n. 磁带, 录影带adv. 大声地n. 物品, 东西; 目标n. 教科书, 课本n. 能力, 才能吸一口气n.牙膏v. 预习, 预告v. 翻译n. 讨论, 谈论, 商讨adv. 精确地, 确切地n.&v. 尊敬只要坚持做..n. 重复唱的歌词, 圣歌v. 达到, 成功adv. 容易地, 轻易地v. 下载adv. 的确, 事实上adj. 有效的v. 模仿, 仿效adj. 厌倦的, 烦闷的n. 集中(精力), 聚精会神v. 拉; 拽; 扯; 拖v. 折叠, 包v. 提到n. 火箭n.金属n. 卫星n. 太空飞船n.&v. 锁; 上锁n. 笔记本电脑adj. 数码的, 数字的n. 电灯泡n. 飞机adj.耐磨的n. 韩国, 朝鲜n. 发明, 创造v.&n. 列清单; 目录, 名单n. 彩色铅笔n. 想法, 看法, 主意v. 集思广益, 动脑筋v. 估值, 评价, 评估adj. 详细的v. 重新设计n. 气球, 热气球n. 枪, 炮n. 机器人n. 键盘n. 探险家n.&v. 标记; 做标记n. 体系, 方法, 制度adj 人造的v. 显示, 显露, 展示n. 屏幕n.&adj. 外星人; 外星的外层空间v. 描述, 形容, 把.. 称为n. 宇航员v. 钦佩, 羡慕v.&n. 掌握, 精通n. 舞蹈演员v. 意识到n. 宇宙太阳系adj. 古罗马的n. 上帝, 神n. 直径n. 风暴n. 重力, 引力v.重, 有.. 重adv. 一般地n.(长途) 旅行v.&n. 限制, 限定n. 激动, 令人激动的事v. 发射, 发起, 发行prep. 超出, 除.. 外v. 证明, 证实probe 月球探测器n. 传说, 传奇故事n. 重要性, 意义adv. 独立地n. 太空漫步adj. 电子的n. 航天服n. 望远镜n. 娱乐, 招待n.&v. 怀疑毫无疑问adj. 极小的, 微小的prep.&adv. 在.. 内; 在里面adv. 通常, 正常情况下n. 脑, 智力v. 取消, 撤销, 废止n. 工作场所v. 连接例如adv.&prep. 而且; 除.. 之外n. 仆人, 佣人adj. 确定的, 无疑的肯定, 确定独自, 单独v. 警告, 告诫v. 可以, 可能n. 家务n. 女服务员n. 杂志n. 公鸡n. 妻子n. 小鸡n.&v. 油漆; 在.. 刷油漆v. 奋斗; 努力; 争取n. 王宫, 宫殿颐和园n. 塔n. 监狱n. 囚犯, 俘虏n. 词汇; 词汇量一束; 一串。

1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。

a r X i v :c o n d -m a t /0211673v 2 [c o n d -m a t .d i s -n n ] 3 J u l 2003GASDYNAMIC MODEL OF STREET CANYON Maciej M.Duras Institute of Physics,Cracow University of Technology,ulica Podchorazych 1,PL-30-084Cracow,Poland.Proceedings of the XIV Polish Conference on Computer Methods in Mechanics (PCCMM’99),26th May 1999-28th May 1999,Rzesz´o w,Poland,85-86(1999).AD 1999,July 26th 1Abstract A general proecological urban road trafﬁc control idea for the street canyon is proposed with emphasis placed on development of advanced continuum ﬁeld gasdynamical (hydro-dynamical)control model of the street canyon.The continuum ﬁeld model of optimal con-trol of street canyon is studied.The mathematical physics approach (Eulerian approach)to vehicular movement,to pollutants’emission and to pollutants’dynamics is used.The rigorous mathematical model is presented,using gasdynamical (hydrodynamical)theory for both air constituents and vehicles,including many types of vehicles and many types of pollutant (exhaust gases)emitted from vehicles.The six optimal control problems are formulated and numerical simulations are parison with measurements are provided.General trafﬁc engineering conclusions are inferred.2Description of the modelThe vehicular ﬂow is multilane bidirectional one-level one-dimensional rectilinear and it is considered with two coordinated signalized junctions [1,2].The vehicles belong to different vehicular classes:passenger cars,trucks.The emission from vehicles are based on technical measurements and many types of pollutants are considered (carbon monoxide CO,hydrocarbons HC,nitrogen oxides NOx).The vehicular dynamics is based on hydrodynamical approach [3].The governing equations are continuity equation for number of vehicles and Greenshields’equilibrium speed-density u-k model [4].The model of dynamics of pollutants is also hydrodynamical.The model consists of a set of mutually interconnected vector nonlinear,spatially three-dimensional,temporally dependent,partial differential equations with nonzero righthand sides (sources),and of boundary and initial problem.The pollutants,oxygen,and remaining gaseous constituentsof air,are treated as mixture of noninteracting,Newtonian,viscousﬂuid(perfect or ideal gases).The model incorporates as variables the followingﬁelds:density of mixture,mass concentrations of constituents of mixture,velocity of mixture,temperature of mixture, pressure of mixture,and intrinsic(internal)energy of mixture.The energy of mixture is calculated ab initio assuming classical Grand Canonical ensemble with external gravita-tional Newtonian body force densityﬁeld of Earth.The results from classical thermody-namics are adopted to framework of thermodynamics of continuum,andﬁnally used in hydrodynamical model.The hydrodynamical model is based on assumption on local laws of balance(of conservation):of mass of mixture,of masses of constituents of mixture,of momentum of mixture,and of energy of mixture.The set of governing equations is com-plete and it is composed of the above balance equations,of state equation(Clapeyron’s law),and equations of conservation of number of vehicles of given type.The model of dynamics is solved byﬁnite difference scheme.The six optimization problems are formulated by deﬁning functionals of total travel time,of global emissions of pollutants,and of global concentrations of pollutants,both in the studied street canyon,and in its two nearest neighbour substitute canyons.The vector of control is aﬁve-tuple composed of two cycle times,two green times,and one offset time between the trafﬁc lights.The optimal control problem consists of minimization of the six functionals over admissible control domain.The model depends on hydrodynamical parameters:velocity,density,temperature, pressure of mixture,concentrations of constituents of mixture;as well as on trafﬁc pa-rameters:jam,saturation vehicular densities,freeﬂow speed.This variety of parameters produces variety of minimal(optimal)solutions.The set of minimal(optimal)solutions for a set of different hydrodynamical and trafﬁc parameters(scenarios)is presented,and discussion of results is provided.The comparison between numerical simulations and measurements is presented.Moreover,the inferences for trafﬁc engineering are given. The discussion of future development is also presented.References[1]DURAS M.M.,1998,Road Trafﬁc Control in Street Canyons,Ph.D.thesis,Univer-sity of Mining and Metallurgy,Cracow,August1998,pp.1-363[2]ADAMSKI A.and DURAS M.M.,1997,Environmental Trafﬁc Control Issues inStreet Canyons,Polish Journal of Environmental Studies,V ol.6,No1,pp.13-20 [3]MICHALOPOULOS P.G.,BESKOS D.E.,and LIN J.-K.,1984,Analysis of Inter-rupted Trafﬁc Flow by Finite Difference Methods,Transportation Research-B,V ol.18B,No4/5,pp.409-421[4]GREENSHIELDS B.D.,1934,A study of trafﬁc capacity,Proceedings of HighwayResearch Board,V ol.14,pp.448-477。