刘启洋,外文翻译原文

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Module7Time off Unit1

We should ________________ protect the environment in Guilin immediately.
4. I've phoned my teacher ...
Verb. = call
How often do you phone your best friend?
to do what he said Li Yong told Han Hong ______________.
Don’t fight!
not to fight Jackie Chan told Li Yong _____________.
Are you from Hongkong?
Pan Changjiang asked Jackie Chan if he was from Hongkong ______________________.
1. Why is Sally phoning her teacher? A. Because she was practising too much. B. Because she wants to say that her hand and arm hurt, and can't play in the final practice. 2. What does Mrs. Styles ask Sally? A. “Are you going to play in the final practice?” B. “Are you practising too much?” 3.What does Mrs. Styles tell Sally to do? A. She tells her to get some rest. B. She tells her to practice more.

小王子第七章（中西对照）

小王子第七章（中西对照）Al quinto día,siempre gracias al cordero,me fue revelado este otro secreto de la vida del principito.Me preguntóbruscamente,y sin preámbulo,como resultado de un problema largamente meditado en silencio:-Si un cordero se come los arbustos,se comerátambién las flores¿no?-Un cordero se come todo lo que encuentra.-¿Y también las flores que tienen espinas?-Sí;también las flores que tienen espinas.-Entonces,¿para quéle sirv en las espinas?Confieso que no lo sabía.Estaba yo muy ocupado tratando de destornillar un perno demasiado apretado del motor;la avería comenzaba a parecerme cosa grave y la circunstancia de que se estuviera agotando mi provisión de agua,me hacía temer lo peor.-¿Para quésirven las espinas?El principito no permitía nunca que se dejara sin respuesta una pregunta formulada porél.Irritado por la resistencia que me oponía el perno,le respondílo primero que se me ocurrió: -Las espinas no sirven para nada;son pura maldad de las flores.-¡Oh!Y después de un silencio,me dijo con una especie de rencor: -¡No te creo!Las flores son débiles.Son ingenuas.Se defienden como pueden.Se creen terribles con sus espinas…No le respondínada;en aquel momento me estaba diciendo a mímismo:"Si este perno me resiste un poco más,lo harésaltar de un martillazo".El principito me interrumpióde nuevo mis pensamientos:-¿Túcrees que las flores…?-¡No!,!No!Yo no creo nada!Te contestécualquier cosa para que te calles.Tengo que ocuparme de cosas serias.Me miróestupefacto.-¡De cosas serias!Me miraba con mi martillo en la mano,los dedos llenos de grasa e inclinado sobre algo que le parecía muy feo.-¡Hablas como las personas grandes!Me avergonzóun poco.Peroél,implacable,añadió:-¡Lo confundes todo!…!todo lo mezclas!…Estaba verdaderamente irritado;sacudía la cabeza,agitando al viento sus cabellos dorados.-Conozco un planeta donde vive un señor muy colorado,que nunca ha olido una flor,ni ha mirado una estrella y que jamás ha querido a nadie.En toda su vida no ha hecho más que sumas y restas.Y todo el día se lo pasa repitiendo como tú:"¡Soy un hombre serio,soy un hombre serio!"…Al parecer esto le llema de orgullo.Pero no es un hombre,¡es un hongo!第五天，还是羊的事，把小王子的生活秘密向我揭开了。

美文翻译习作_优秀作文.doc

美文翻译习作_优秀作文美文翻译习作译自高一英语周报第二十七期阅读A篇译者：高一1508班刘泽南指导老师：尹旭日SUNDAYS，IWALKTOTHESUPERMARKET.MOTHERHANDSMETHEGROCERYLISTANDPUTSMONEYINMYPOCKET，HOPINGITWILLBEENOUGH.SHE'SHADAHARDDAY，ANDI'VEHADAHARDWEEK.NOTHINGOUTOFTHEORDINARYHAPPENSWHENIGETTOTHESTORE.IGRABT HEBREAD，SOMEMILK，ANDOTHERTHINGSONTHELIST.ASITURNTOHEADOUT，ISEEABEAUTIFULDRESSINTHEWINDOW.ITURNAWAY，BITTERTHATICOULDNEVEROWNSUCHADRESS. OUTSIDE，ICANNOTSTOPTHINKINGABOUTTHATPRETTYDRESS.IT'SNOTFAIRTHATICANNEVERHAVEWHATIWA NT.IWORKSOHARDTOHELPMYFAMILYANDYETIGETNOTINGINRETURN.JUSTANOTHERLISTTODO.IN MYANGER，IFAILTOREALIZETHEAPPLESAREROLLINGACROSSTHEROAD.SUDDENLY，ISEEAPAIROFHANDS，OFFERINGMEANAPPLE.LOOKINGUP，ISEETHETANNEDFACEOFTHISSTRANGER.HISCLOTHESAREMISMATCHED，BORROWEDORSTOLEN.BUTHISEYESARESOFTANDKIND.”THANKS，”ISAY.NOOTHERWORDSARESPOKENASHECONTINUESTOHELPME.ITELLHIM”THANKYOU”ONEMORETIMEANDAMONMYWAYBECAUSEIHAVEMANYOTHERTHINGSTOFINISH.SUDDENLY，HESAYS，”HAVEAGOODDAY，MA'AM.”（）ANDTHENHEGIVESMETHEBIGGESTSMILEIHAVEEVERSEEN.RIGHTTHEN，HELOOKSYEARSYOUNGER－－－－－ANDIFEELAFOOL.LOOKATME，FEELINGSORRYFORMYSELFBECAUSEIDON'TGETWHATIWANT！DOITHINKOTHERAREINTHESAMEBOAT，ORWORSE？THEREAREWORSETHINGSTHANNOTHAVINGABEAUTIFULDRESS. MYMOTHERWILLHANDMETHELISTTODAY.IWILLMAKETHESAMEJOURNEYANDPROBABLYSEESOMETH INGIWANTBUTCANNOTHAVE.BUTBEFOREISTARTTOFEELSORRYFORMYSELF，IWILLREMEMBERTHEKINDSTRANGERWITHTHEBIGSMILE，ANDIWILLGRABTHELASTITEM，ANDCHECKOUT.译文：每个周日，我都要走路去超市，妈妈给我食品清单并把钱放到我口袋里，希望这些钱够了。

英文文献

Antonio ArmillottaGiovanni MoroniDipartimento di Meccanica,Politecnico di Milano,Via La Masa1,20156Milano,ItalyWilma Polini Dipartimento di Ingegneria Industriale, Universitàdegli Studi di Cassino,Via Di Biasio43,03043Cassino(FR),Italy Quirico SemeraroDipartimento di Meccanica,Politecnico di Milano,Via La Masa1,20156Milano,Italy A Uniﬁed Approach to Kinematic and Tolerance Analysis of Locating FixturesA workholdingﬁxture should ensure a stable and precise positioning of the workpiece with respect to the machine tool.This requirement is even more important when modular ﬁxtures are used for the sake of efﬁciency and reconﬁgurability.They include standard locating elements,which set the part in a predeﬁned spatial orientation by contacting its datum surfaces.In the computer-based design of aﬁxture,the layout of locators must be tested against two main sources of problems.Kinematic analysis veriﬁes that any relative motion between the part and the worktable is constrained.Tolerance analysis evaluates the robustness of part orientation with respect to manufacturing errors on datum sur-faces.We propose a method to carry out both tests through a common set of geometric parameters of theﬁxture conﬁguration.These derive from the singular value decompo-sition of the matrix that represents positioning constraints in screw coordinates.For a poorly designedﬁxture,the decomposition allows us toﬁnd out either unconstrained degrees of freedom of the part or a possible violation of tolerance speciﬁcations on machined features due to geometric errors on datum surfaces.In such cases,the analysis provides suggestions to plan the needed corrections to the locating scheme.This paper describes the procedure for kinematic and tolerance analysis and demonstrates its sig-niﬁcance on a sample case ofﬁxture design.͓DOI:10.1115/1.3402642͔Keywords:ﬁxture design,kinematic analysis,tolerance analysis,screw theory1IntroductionModularﬁxtures are the key to exploit the inherentﬂexibility and reconﬁgurability ofﬂexible manufacturing systems.They are built from standard components that are readily mounted on a base plate and easily adapted to changing part types and sizes͓1͔. The layout ofﬁxture components is customarily designed around computer aided design͑CAD͒descriptions of workpieces with the help of3D catalogs͓2͔.Integrated software support to this task is pursued through the extraction of geometric information from CAD models in order to simulate the kinematic,static,and dy-namic behaviors ofﬁxtures͓3͔.Basically,aﬁxture constrains the relative motion between part and worktable by two different mechanisms:–deterministic positioning,which sets a spatial orientation of the part by form closure;–total restraint,which allows part orientation to be maintained by force closure during machining operationsIn this paper,we focus on deterministic positioning,with the aim of proposing a method to check the correctness of geometric constraints imposed to the workpiece.Theﬁrst requirement to be satisﬁed by the system of constraints is of a kinematic type:The part cannot be allowed to move in any way relative to theﬁxture. Possible residual degrees of freedom͑DOFs͒in part motion must be detected in order to allow new constraints to be added.The second requirements for a kinematically correctﬁxture are related to precision:Tolerances on machined features must be satisﬁed despite manufacturing errors on bothﬁxture and workpiece.In literature,a kinematic analysis ofﬁxtures has been dealt with by description models of feasible motions for constrained rigid bodies.The objective is to check whether a given layout ofﬁxture components constrains all DOFs of part motion.Some approachesderive from early research topics of geometric modeling,such assymbolic spatial relationships͓4͔and spatial occupancy represen-tations͓5,6͔.Apart from them,most studies rely upon a commondescription of motion constraints based on the screw theory ofkinematics͓7͔.We recall its basic results in Sec.2of this paper.Based on previous applications of the theory to the study ofmechanisms͓8,9͔,earlier attempts to use its basic results in thecontext ofﬁxtures have led to a compact formulation,which ismore easily applied to real cases and implemented in a CADenvironment͓10,11͔.Although not explicitly citing the screwtheory,other studies have proposed a similar description,high-lighting new properties useful for modelingﬁxture kinematics ͓12–14͔.A similar approach has been recently applied to the analysis and optimization ofﬁxturing schemes with redundantconstraints͓15,16͔.In Ref.͓17͔,a mathematical procedure is pro-posed to analyze kinematically unconstrainedﬁxtures and calcu-late residual degrees of freedom for the workpiece.Solving thelatter problem is critical to allow corrective actions to a poorlydesignedﬁxture.As treated in Sec.3,we develop a different kindof manipulation on the screw-based description to achieve thesame objective.A kinematic analysis is not sufﬁcient to ensure precise position-ing.Errors onﬁxtures and part surfaces cause uncertainty onmachine-workpiece referencing parameters,which can result inthe stack-up of manufacturing errors.To control these deviations,aﬁxture layout should be carefully chosen according to part ge-ometry and tolerances.Some studies have proposed guiding rulesand algorithms based on tolerance charting techniques to selectpositioning surfaces on the workpiece in order to control tolerancestacks on functional dimensions͓18–20͔.To compare alternative ﬁxture conﬁgurations,Ref.͓21͔investigates on precision issues related to different types ofﬁxture components and provides rules to evaluate their combined effect on positioning uncertainty.In Ref.͓22͔,the uncertainty propagation problem is addressed by introducing probabilistic terms in the calculation of workpiece-machine transformation from contact points.Calculation proce-Contributed by the Computational Metrology/Reverse Engineering Committee ofASME for publication in the J OURNAL OF C OMPUTING I NFORMATION S CIENCE AND E NGI-NEERING.Manuscript received February26,2008;ﬁnal manuscript received March11,2010;published online June8,2010.Assoc.Editor:A.Fischer.Journal of Computing and Information Science in Engineering JUNE2010,Vol.10/021009-1Copyright©2010by ASMEdures on the constraints description based on the screw theory have also been proposed to address tolerance analysis.They esti-mate either displacements in selected points on the workpiece ͓23–26͔or geometric errors on machined features ͓27–29͔as a result of ﬁxture errors.Most of these approaches also include the search for a minimum-error layout of the ﬁxture:at a lower level of computer support,guidelines for this design task have been proposed in Ref.͓30͔.In Sec.4,we demonstrate a method to detect possible conditions on the ﬁxture layout in which error propagation from ﬁxture to machined features can be critical with respect to tolerance speciﬁcations on the part.The solution we propose is based on a uniﬁed approach for the two subproblems of kinematic and tolerance analyses.It consists of a simple calculation procedure based on the description of po-sitioning constraints according to the screw theory.The output of the procedure allows us to validate the conﬁguration of a ﬁxture by detecting either a possible lack of constraints or negative ef-fects on machining accuracy due to part-ﬁxture -pared with existing approaches,we attempt to streamline the analysis of deterministic positioning by using a reduced set of parameters easily extracted by available geometric data.A discus-sion of an application example in Secs.5and 6will allow us to better clarify the types of decisions that can be supported by the method.2Description of Positioning ConstraintsA ﬁxture holds a workpiece in a given spatial conﬁguration ͑position and orientation ͒relative to the reference frame of a ma-chine tool.This task includes two different functions.–Positioning :Remove all DOFs of part motion and allow each part of a batch to assume the same conﬁguration within a given tolerance.–Clamping :Withstand forces acting on the part during the machining process without excessive deformation and vibration.In a modular ﬁxture,positioning is usually done before clamp-ing by means of highly accurate ﬁxture components called loca-tors .As shown in Fig.1,they are grouped into a limited number of functional types ͓31,32͔:–support pins and blocks with ﬂat,round,conical,or vee shape,in contact with external resting surfaces of the part –sleeved support pins and blocks,providing both vertical sup-port and side positioning–locating pins,horizontal ﬂat or vee blocks,providing only side positioning on lateral surfaces–center pins,in contact with surfaces of holes and other inter-nal featuresIn most cases,contact between locators and parts occurs on either a point,a straight line segment,or a planar surface area.Line and surface contacts constrain part movement more than point contacts do,and each of them can be replaced by two or more kinematically equivalent point contacts,as shown in Fig.2͑a ͒.However,it is not safe to rely on this property in the pres-ence of a small contact length or area,which is better approxi-mated by a simple point contact ͑Fig.2͑b ͒͒.A proper number of equivalent point contacts can align the part to the reference frame of the worktable.The completeness of such alignment is often related to the number of DOFs of part move-ment that are restricted by the ﬁxture.Since a rigid body has 6DOF ͑translations and rotations along the x ,y ,and z axes of the machine reference frame ͒and each of them can have either sense,12“bidirectional”DOFs are conventionally considered.A basic condition for a deterministic positioning test could check that a given number ͑say,nine ͒of these DOF is restricted by the loca-tors.However,such criterion would not work whenever locators restrict translations or rotations along directions not parallel to x ,y ,and z axes.A more general condition,which will be assumed throughout the paper,is the following:Provided that part is held in contact with locators,translation and rotation along any direc-tion must be restricted ͑with the only exception of rotations along axes of fully symmetric parts ͒.The screw theory provides an effective representation of geo-metrical constraints on the part due to point contacts with locators.Each contact is deﬁned by the direction of the reaction force at the locator.Any set of forces and couples is equivalent to a force f and a couple c along the same direction:They can be joined in a wrench w ,deﬁned by either f and the pitch h =c /f .The direction of f can be expressed in line coordinates by the column vector͓␸x ,␸y ,␸z ,␮x ,␮y ,␮z ͔T͑1͒where ͑␸x ,␸y ,␸z ͒and ͑␮x ,␮y ,␮z ͒are the force itself and its mo-ment about the origin of the coordinate system xyz ,and ␸x ␮x +␸y ␮y +␸z ␮z =0.Similarly,the wrench can be expressed in screw coordinates by the vectorw =͓␸x ,␸y ,␸z ,␮x −h ␸x ,␮y −h ␸y ,␮z −h ␸z ͔T͑2͒The reaction force at the i th frictionless point constraint is directed along the normal to the contact surface and can be represented by a wrench with a zero pitchw i =͓␸xi ,␸yi ,␸zi ,␮xi ,␮yi ,␮zi ͔T͑3͒where conventionally ␸xi 2+␸yi 2+␸zi 2=1.Then,the 6ϫp matrix of contact wrenchesW =͓w i ͔͑4͒represents the constraints at the p locators of the ﬁxture.ItisFig.1Types of modular locatingelementsFig.2Point contacts kinematically equivalent to line and plane contacts021009-2/Vol.10,JUNE 2010Transactions of the ASMEusually referred to as the locating matrix and can be used to check the deterministic positioning of the part.The six equations of translational and rotational equilibrium under an arbitrary set of forces are expressed by the matrix equationWF=−w E͑5͒where F=͓f1,...,f p͔T represents the constraint reactions and w E is the wrench of the resultant of external loads acting on the part. If W has rank6,Eq.͑5͒has a unique solution F,which means that any external action is balanced by a sum of reaction forces anddoes not cause any displacement of the part.If the rank of W is less than6,Eq.͑5͒has no solution whenever w E does not belong to the range of W͓10,11͔.An equivalent condition,based on the rank of the Jacobian matrix associated with the constraints,is proposed in Ref.͓12͔and applied in Ref.͓13͔:It can be shown that the Jacobian matrix is the transpose of the locating matrix as deﬁned before.As a consequence of this property of W,the sim-plest way of obtaining the deterministic positioning of a part is through six locators.Less constraints fail to locate the part,while more are redundant.A similar problem at a reduced dimension is planar determinis-tic positioning,where reaction forces at locators are parallel to the xy plane,and only planar motion of the part is allowed.The test condition is based on the3ϫp matrix deﬁned as in Eq.͑4͒,withw i=͓␸xi,␸yi,␮zi͔T͑6͒and␸xi2+␸yi2=1.Deterministic positioning is accomplished if at least three equivalent point contacts are used and W has rank3. 3Kinematic AnalysisAlthough the rank of the locating matrix is an index of deter-ministic positioning,it does not allow full kinematic characteriza-tion of aﬁxture.Speciﬁcally,–it does not explain the cause of a nondeterministic position-ing,nor does it suggest any corrective action on theﬁxture design;–even in the full-rank case,it does not guarantee that part positioning is unaffected by manufacturing errors on parts and locators.Some properties of the above description of positioning con-straints can help to fully exploit its information content.For this purpose,we propose a method based on a matrix factorization technique known as singular value decomposition͑SVD͓͒33͔. The SVD of an mϫn matrix A isA=USV T͑7͒where U is an mϫm orthogonal matrix,V is an nϫn orthogonal matrix,and S=diag͑␴1,...,␴k͒is an mϫn matrix with elements ␴iՆ0such that k=min͑m,n͒.The␴i are the singular values of A,while the columns of U and V are,in turn,the left and right singular vectors of A.The SVD is especially helpful in solving ill-conditioned sets of linear equations in the form Ax=b.The rank of A equals the number of nonzero singular values.The columns of U correspond-ing to the␴iϾ0are an orthonormal basis for the range of A, while the columns of V corresponding to the␴i=0are an ortho-normal basis for the null space of A.Low values of some␴i may denote a linear dependency among equations,which can beﬁxed by setting the low␴i to zero.These properties have suggested several uses of the SVD in the solution of linear regression problems by the least-squares method and in other matrix manipulation problems͓34,35͔,as well as in the analysis of kinematic and dynamic properties of robot manipu-lators͓36͔.In our problem,since W is the coefﬁcient matrix of the set͑Eq.͑5͒͒of equilibrium equations,the SVD is likely to be a better tool for checking deterministic positioning than simple rank inspection.Speciﬁcally,it allows us to draw additional infor-mation on motion constraints when W is rank deﬁcient.A singularity of W means that the part is not positioned in a well deﬁned spatial conﬁguration.That is,the part can translate or rotate from the desired position although keeping contact with locators.Therefore,all DOFs of the guided movement of the part need to be determined in order to make corrections to the design of the locatingﬁxture.The problem can beﬁrst solved in the xy plane,where deter-ministic positioning requires three contact points.The SVD of W provides its rank r,equal to the number of nonzero singular val-ues.If r=3͑Fig.3͑a͒͒,we have correct positioning.Otherwise, the part could either rotate about the z axis͑Fig.3͑b͒͒or translate along some direction in the plane͑Fig.3͑c͒͒.To recognize the two cases,we can build a translation subma-trix W T from theﬁrst two rows of W.W T is associated with a set of equilibrium equations similar to Eq.͑5͒,where couples and rotations are not considered.We can now apply the SVD to W T, thusﬁnding its rank r T.If r T=2,any set of external forces is balanced by the con-straints,and the part cannot translate;then,the residual DOF is a rotation about the z axis.This is the case depicted in Fig.3͑b͒, where the normals to part surfaces at the locators’contact points meet at a center of instantaneous rotation.In such a condition,the ﬁxture only allows small rotations͑arbitrarily close to zero if part boundaries are perfectly straight lines͒,yet sufﬁcient to hinder deterministic positioning.If r T=1,the residual DOF is a translation,and we canﬁnd the motion direction from the base of the range of W T,given by the left singular vector corresponding to its only nonzero singular value.In fact,the range of W T is the set of the resultants of the external forces acting in the plane that do not affect the transla-tional equilibrium of the part.In the latter case,possible resultants can have only one direction,whose unit vector is given͑regard-less of the orientation͒by the base of the range:This direction is perpendicular to the unconstrained translation.In the example of Fig.3͑c͒,the base of the range of W T is the unit vector of the y axis,resulting in a translational DOF along the x axis.In the three-dimensional case,similarly,we apply the SVD to W and,if it is rank deﬁcient,to the translational submatrix W T, including theﬁrst three rows of W.From the inspection of singu-lar values,we get the ranks r and r T of the matrices W and W T, with rՅ5and r TՅ3.With six locators,these two parameters provide information on the residual DOF of the part.–If r TϽ3,the part has3−r T translational DOF,as we can infer by a similar consideration to those applying on the2D case about the set of the translational equilibrium conditions.–If r−r TϽ3,the part has3−͑r−r T͒rotational degrees of freedom.The two above conditions can be satisﬁed simultaneously since the part could translate and rotate at the same time.However,six distinct contact points guarantee that rՆ2and r TՆ1,which means at most four total DOFs,not more than two translational. Figure4shows sample locatingﬁxtures for a prismatic work-piece,representative of all applicable combinations of r and r T. Each conﬁguration includes six locators in contact with part sur-faces͑locators denoted with“2”are in contact with parallelsur-Fig.3Examples of planar locating schemesJournal of Computing and Information Science in Engineering JUNE2010,Vol.10/021009-3faces and may have either coincident or opposite normals ͒.The ﬁrst case ͑Fig.4͑a ͒͒corresponds to a 3-2-1scheme with determin-istic positioning.In the other cases,the part is allowed one or more DOF,which are calculated from the properties of some sub-matrices of W .If r T Ͻ3,we can determine the ϱ2−r T free directions of transla-tion,as in the 2D case,from the range of W T :–If r T =2,the base of the range of W T includes two orthogonal unit vectors deﬁning a plane perpendicular to the single translation direction ͑Figs.4͑c ͒,4͑e ͒,4͑g ͒,and 4͑i ͒͒.–If r T =1,the base of the range of W T consists of a single unit vector,whose normal plane contains a set of feasible trans-lation directions ͑Figs.4͑h ͒and 4͑j ͒͒.If r −r T Ͻ3,we need to solve the problem of deterministic po-sitioning in the plane to ﬁnd the unconstrained rotation axes.For example,to detect a rotation about the x axis,we can build the submatrix W x from the rows of W associated with the equations of equilibrium to either translation along y and z and rotation about x ͑the second,the third,and the fourth one ͒.If the rank of W x is less than 3and is equal to that of its ﬁrst two rows ͑corre-sponding to translations ͒,x is a free rotation axis.In this case,we have ϱ2−͑r −r T ͒feasible rotation directions.Speciﬁcally,–if r −r T =2,there is a single rotation axis ͑Figs.4͑b ͒,4͑e ͒,and 4͑h ͒͒;–if r −r T =1,there is a set of rotation axes,deﬁned by two orthogonal directions ͑Figs.4͑d ͒,4͑g ͒,and 4͑j ͒͒;–r −r T =0,any direction is a feasible rotation axis;in this case,all the contact normals converge in a single rotation center for the part ͑Figs.4͑f ͒and 4͑i ͒͒.We can ﬁnd the unrestricted rotation axes even if they are not parallel to the x ,y ,and z axes.For a generic unit vector t ,we can apply a coordinate transformation such that t is parallel to the unit vector k of the z axis.The same transformation is also applied to the two 3ϫp submatrices of W associated with translational and rotational equilibrium equations,resulting in a new matrix W Јand in the corresponding submatrix W z Ј.If the part has a single rotational DOF,we can search for the direction t for which the submatrix W z Јis rank deﬁcient.The third singular value of W z Јis a continuous function of the angular parameters,which appear in the transformation,and has a unique global minimum of zero value in either Cartesian half-space.Therefore,we can do the search by any technique that is able to recognize and rule out possible local minima ͑direction set algorithms,simulated anneal-ing ͒.If a set of feasible rotation directions exists,we ﬁnd two distinct directions t ,which deﬁne the plane containing the free rotation axes.4Tolerance AnalysisThe second problem in the analysis of deterministic positioning consists in detecting proximity to incorrect locating conditions.As a result of all its contacts with locators,a fully constrained part may still be allowed signiﬁcant displacements from the nominal position due to form errors on datum surfaces.Although the ma-trix W carries all information required to detect such situations,a method is needed to properly recognize them.In the following,we show how the SVD can be helpful for this task.As it has been said before,low singular values of the locating matrix are related to a quasi-singularity of W ,which we associate with a possible lack of positioning accuracy.For instance,in the basic planar case of Fig.5͑a ͒,a displacement ␦of locator 2along its normal direction would force the part to rotate from its nominal conﬁguration by an angle depending on ␦/a .Such an angle,which would result in geometric errors on machined features,can be relatively high if the distance a takes a small value.It can be veriﬁed that a takes a special meaning with respect to the SVD of the locating matrix.Speciﬁcally,with the coordinate system as in Fig.5͑a ͒,it isW =΄0011100−a 0΅͑8͒Singular values of W equal the square roots of the eigenvalues of W T ·W ,which can be easily derived by solving the characteristic equation of the latter matrix.We ﬁnd that␴1=1Fig.4Examples of three-dimensional locatingschemesFig.5Quasi-singular locating conditions021009-4/Vol.10,JUNE 2010Transactions of the ASME␴2=ͱa 2+2+ͱa +42␴3=ͱa 2+2−ͱa 4+42͑9͒andP =␴1␴2␴3=a͑10͒With a proper choice of the coordinate system,Eq.͑10͒applies to the general planar case depicted in Fig.5͑b ͒.The product P equals the distance a between the contact normal of locator 3and the intersection point of the contact normals of locators 1and 2͑or the corresponding distance for any permutation of locators ͒.As in the previous case,a displacement at locator 3causes a rotation of the workpiece by an angle that is inversely propor-tional to a .Similarly,in the 3-2-1scheme of Fig.5͑c ͒,distances a ,b ,and c should be long enough to avoid undesired rotations relative to the nominal conﬁguration.Again,we have that P =␴1␴2,...,␴6equals the product abc of the critical distances.The product of singular values of W can thus provide the information we need to detect a lack of positioning “robustness.”It is difﬁcult to provide a mathematical proof for the geometric meaning of the quasi-singularity index P .In the following,how-ever,we will try to strengthen the conjecture that it is inversely related to geometric errors,which can result on machined fea-tures.Meanwhile,we will investigate on the inﬂuence of speciﬁed tolerances and geometric parameters of the ﬁxture.We will only consider planar locating schemes as in Fig.5͑a ͒,which can be regarded as approximations of three-dimensional cases where the support on a base plane ͑locators 1–3in Fig.5͑b ͒͒is more accu-rate than the side positioning on lateral datum surfaces ͑locators 4–6in the same ﬁgure ͒.We will neglect any error sources that are not related to part and ﬁxture geometry.They include uncertainties in tool positioning and workpiece set-in due to clamping and machining forces.We also assume that locators are exactly in their nominal position,which is reasonable when considering that tolerances on locating ﬁxtures are usually tighter than workpiece errors.As a result of these assumptions,worst-case position errors will be underesti-mated by an amount depending on speciﬁc machine conﬁgura-tions.Let us suppose that a hole is to be drilled on a part as in Fig.6where speciﬁed by basic dimensions x and y .A straightness tol-erance t A on the primary datum A and a perpendicularity tolerance t B on the secondary datum B are assigned,as well as a position tolerance on the hole.The locating ﬁxture for the workpiece con-sists in two locating pins on the primary datum and one pin on the secondary,spaced according to dimensions l 1,l 2,and l 3.Hole position will be checked by a functional gauge,whose datum simulators are put in contact with locating surfaces.Theoretically,contact points of locators with datum surfaces lie on the reference planes of the machine tool,which thus match exactly the datum simulators of the gauge.Under the assumption that the hole is drilled in its theoretical position relative to the machine,hole position is perfect also relative to the gauge,and there is no position error.Actually,as illustrated in Fig.7,locating surfaces do not coincide with gauge planes due to form and ori-entation errors.Therefore,contact with locators occurs in points that do not lie on datum simulators anymore.As contact points determine the geometric transformation of the part relative to the machine,the hole turns out to be displaced relative to its checking position on the gauge.The position error is equal to the distance between theoretical and actual ͑i.e.,after part-machine transfor-mation ͒hole axes.Figure 8͑a ͒shows that locators are assumed to be in their nomi-nal positions,and gauge planes are determined by geometric er-rors on locating surfaces.Point-to-point distances of part surfaces from datum simulators could be estimated by one of the available computational models of contacts between surfaces with an im-perfect form.As an example,in Ref.͓37͔,a constrained optimi-zation problem is solved to calculate the actual mating position between two imperfect planes.We prefer to simply calculate part-ﬁxture transformation from a limited number of displacements at locators,to be treated as random variables.For this purpose,as shown in Fig.8͑b ͒,we imagine locating surfaces as perfect planes determined by equivalent displacements of locators.The set of displacement at locators⌬p =͓␦1,␦2,␦3͔T͑11͒transforms the workpiece coordinate system by⌬x =͓⌬x ,⌬y ,⌬␣͔T͑12͒where ͑⌬x ,⌬y ͒is the displacement of the origin and ⌬a is the rotation angle of x and y axes.According to results of Ref.͓12͔,the above parameters are related by the following equation:⌬p =W T ⌬x͑13͒Therefore,workpiece transformation can be found from locator displacements by inverting the transpose of the locating matrix.Following the equivalence described in Fig.8,locator displace-ments can take values less than or equal to the tolerances on corresponding data.Displacement values are negative ͑i.e.,theyFig.6Reference problem in theplaneFig.7Geometric transformation between machine tool and functionalgageFig.8Transformation based on locator displacementJournal of Computing and Information Science in Engineering JUNE 2010,Vol.10/021009-5。

英语演讲稿关于孤独症

刘泽洋：（ppt第3页）He was a Dutch Post-Impressionist painter whose work had a far reaching influence on 20th century art for its vivid colors and emotional impact. today many of his pieces—including his numerous self portraits, landscapes, portraits and sunflowers—are among the world's most recognizable and expensive works of art. His depression gradually deepened. On 27 July 1890, aged 37, he walked into a field and shot himself in the chest with a revolver.（ppt第4页）The British comedymogul Lowen Atkinson (RowanAtkinson).We can never underestimate this"bean", heclaims to have 18500000 viewers in the UK but,in other regional languagesalsohaving a great reputation, carry the world before one"The British spy Johnny"strongly criticized"the criticsthat he needs time toadjust,even the money cannotmake him happy."Americancomedian Jim Carryand Italycomedian Saddo Parla"depressionhit, youwill feel very despair, can't find a solution to the problem."What is DepressionThe word 'depression' is used to describe everyday feelings of low mood which can affect us all from time to time. Feeling sad or fed up is a normal reaction to experiences that are upsetting, stressful or difficult; those feelings will usually pass.If you are affected by depression, you are not 'just' sad or upset. You have an illness which means that intense feeling of persistent sadness, helplessness and hopelessness are accompanied by physical effects such as sleeplessness, a loss of energy, or physical aches and pains.Sometimes people may not realise how depressed they are, especially if they have been feeling the same for a long time, if they have been trying to cope with their depression by keeping themselves busy, or if their depressive symptoms are more physical than emotional. Here is a list of the most common symptoms of depression. As a general rule, if you have experienced four or more of these symptoms, for most of the day nearly every day, for over two weeks, then you should seek help.o Tiredness and loss of energyo Persistent sadnesso Loss of self-confidence and self-esteemo Difficulty concentratingo Not being able to enjoy things that are usually pleasurable or interestingo Undue feelings of guilt or worthlessnesso Feelings of helplessness and hopelessnesso Sleeping problems - difficulties in getting off to sleep or waking up much earlier than usualo Avoiding other people, sometimes even your close friendso Finding it hard to function at work/college/schoolo Loss of appetiteo Loss of sex drive and/ or sexual problemso Physical aches and painso Thinking about suicide and deatho Self-harm(1--8)页杨琛伟（ppt第9-14页）：We are still not sure what causes depression but a combination of factors are thought to play a role. Major life events such as bereavement, redundancy or marital breakdown are all common triggers for depression.the cause of depressionis divided into external reasons and internal reasons.External reasons:1、环境诱因：令人感到有压力的生活事件及失落感可能诱发忧郁症，如丧偶(尤其老年丧偶，几乎八、九成的人会得此病)、离婚、丢掉工作、财务危机、失去健康等。

Unit7TheMonster课文翻译综合教程四

Unit 7The Mons‎t erDeems Taylor‎1He was an u‎n dersized little‎man, with a hea‎d too big for hi‎s body ― a sickl‎y little man. Hi‎s nerves were ba‎d. He had skin t‎r ouble. It was a‎g ony for him to ‎w ear anything ne‎x t to his skin c‎o arser than silk‎. And he had del‎u sions of grande‎u r.2He was a‎monster of conc‎e it. Never for o‎n e minute did he‎look at the wor‎l d or at people,‎except in relat‎i on to himself. ‎H e believed hims‎e lf to be one of‎the greatest dr‎a matists in the ‎w orld, one of th‎e greatest think‎e rs, and one of ‎t he greatest com‎p osers. To hear ‎h im talk, he was‎Shakespeare, an‎d Beethoven, and‎Plato, rolled i‎n to one. He was ‎o ne of the most ‎e xhausting conve‎r sationalists th‎a t ever lived.S‎o metimes he was ‎b rilliant; somet‎i mes he was madd‎e ningly tiresome‎. But whether he‎was being brill‎i ant or dull, he‎had one sole to‎p ic of conversat‎i on: himself. Wh‎a t he thought an‎d what he did.3‎He had a mani‎a for being in t‎h e right. The sl‎i ghtest hint of ‎d isagreement, fr‎o m anyone, on th‎e most trivial p‎o int, was enough‎to set him off ‎o n a harangue th‎a t might last fo‎r hours, in whic‎h he proved hims‎e lf right in so ‎m any ways, and w‎i th such exhaust‎i ng volubility, ‎t hat in the end ‎h is hearer, stun‎n ed and deafened‎, would agree wi‎t h him, for the ‎s ake of peace.4‎It never occu‎r red to him that‎he and his doin‎g were not of th‎e most intense a‎n d fascinating i‎n terest to anyon‎e with whom he c‎a me in contact. ‎H e had theories ‎a bout almost any‎subject under t‎h e sun, includin‎g vegetarianism,‎the drama, poli‎t ics, and music;‎and in support ‎o f these theorie‎s he wrote pamph‎l ets, letters, b‎o oks ...thousan‎d s upon thousand‎s of words, hund‎r eds and hundred‎s of pages. He n‎o t only wrote th‎e se things, and ‎p ublish ed them ―‎usually at some‎b ody else’s expe‎n se ― but he wou‎l d sit and read ‎t hem aloud, for ‎h ours, to his fr‎i ends, and his f‎a mily.5He ha‎d the emotional ‎s tability of a s‎i x-year-old chil‎d. When he felt ‎o ut of sorts, he‎would rave and ‎s tamp, or sink i‎n to suicidal glo‎o m and talk dark‎l y of going to t‎h e East to end h‎i s days as a Bud‎d hist monk. Ten ‎m inutes later, w‎h en something pl‎e ased him he wou‎l d rush out of d‎o ors and run aro‎u nd the garden, ‎o r jump up and d‎o wn off the sofa‎, or stand on hi‎s head. He could‎be grief-strick‎e n over the deat‎h ofa pet dog, ‎a nd could be cal‎l ous and heartle‎s s to a degree t‎h at would have m‎a de aRoman empe‎r or shudder.6‎He was almost i‎n nocent of any s‎e nse of responsi‎b ility. He was c‎o nvinced that th‎eworld owed him‎a living. In su‎p port of this be‎l ief, he borrowe‎d money from eve‎r ybody who was g‎o od for a loan ―‎men, women, fri‎e nds, or strange‎r s. He wrote beg‎g ing letters by ‎t he score, somet‎i mes groveling w‎i thout shame, at‎others loftily ‎o ffering his int‎e nded benefactor‎the privilege o‎f contributing t‎o his support, a‎n d being mortall‎y offended if th‎e recipient decl‎i ned the honor.7‎What money h‎e could lay his ‎h and on he spent‎like an Indian ‎r ajah. No one wi‎l l ever know ― c‎e rtainly he neve‎r knows ― how mu‎c h money he owed‎. We do know tha‎t his greatest b‎e nefactor gave h‎i m $6,000 to pay‎the most pressi‎n g of his debts ‎i n one city, and‎a year later ha‎d to give him $1‎6,000 to enable ‎h im to live in a‎n other city with‎o ut being thrown‎into jail for d‎e bt.8He was ‎e qually unscrupu‎l ous in other wa‎y s. An endless p‎r ocession of wom‎e n marched throu‎g h his life. His‎first wife spen‎t twenty years e‎n during and forg‎i ving his infide‎l ities. His seco‎n d wife had been‎the wife of his‎most devoted fr‎i end and admirer‎, from whom he s‎t ole her. And ev‎e n while he was ‎t rying to persua‎d e her to leave ‎h er first husban‎d he was writing‎to a friend to ‎i nquire whether ‎h e could suggest‎some wealthy wo‎m an ― any wealt h‎y woman ― whom h‎e could marry fo‎r her money.9‎He had a genius‎for making enem‎i es. He would in‎s ult a man who d‎i sagreed with hi‎m about the weat‎h er. He would pu‎l l endless wires‎in order to mee‎t some man who a‎d mired his work ‎a nd was able and‎anxious to be o‎f use to him ― a‎n d would proceed‎to make a morta‎l enemy of him w‎i th some idiotic‎and wholly unca‎l led-for exhibit‎i on of arrogance‎and bad manners‎. A character in‎one of his oper‎a s was a caricat‎u re of one of th‎e most powerful ‎m usic critics of‎his day. Not co‎n tent with burle‎s quing him, he i‎n vited the criti‎c to his house a‎n d read him the ‎l ibretto aloud i‎n front of his f‎r iends.10The ‎n ame of this mon‎s ter was Richard‎Wagner. Everyth‎i ng I have said ‎a bout him you ca‎n find on record‎― in newspapers‎, in police repo‎r ts, in the test‎i mony of people ‎w ho knew him, in‎his own letters‎, between the li‎n es of his autob‎i ography.And th‎e curious thing ‎a bout this recor‎d is that it doe‎s n’t matter in t‎h e least.11Be‎c ause this under‎s ized, sickly, d‎i sagreeable, fas‎c inating little ‎m an was right al‎l the time, the ‎j oke was on us. ‎H e was one of th‎e world’s greate‎s t dramatists; h‎e was a great th‎i nker; he was on‎e of the most st‎u pendous musical‎geniuses that, ‎u p to now, the w‎o rld has ever se‎e n. The world di‎d owe him a livi‎n g. What if he d‎i d talk about hi‎m self all the ti‎m e? If he talked‎about himself f‎o r twenty-four h‎o urs every day f‎o r the span of h‎i s life he would‎not have uttere‎d half the numbe‎r of words that ‎o thermen have s‎p oken and writte‎n about him sinc‎e his death.12‎When you consid‎e r what he wrote‎― thirteen oper‎a s and music dra‎m as, eleven of t‎h em still holdin‎g the stage, eig‎h t of them unque‎s tionably worth ‎r anking among th‎e wor ld’s great ‎m usico-dramatic ‎m asterpieces ― w‎h en you listen t‎o what he wrote,‎the debts and h‎e artaches that p‎e ople had to end‎u re from him don‎’t seem much of ‎a price.13‎W hat if he was f‎a ithless to his ‎f riends and to h‎i s wives? He had‎one mistress to‎whom he was fai‎t hful to the day‎of his death: M‎u sic. Not for a ‎s ingle moment di‎d he ever compro‎m ise with what h‎e believed, with‎what he dreamed‎. There is not a‎line of his mus‎i c that could ha‎v e been conceive‎d by a little mi‎n d. Even when he‎is dull, or dow‎n right bad, he i‎s dull in the gr‎a nd manner. List‎e ning to his mus‎i c, one does not‎forgive him for‎what he may or ‎m ay not have bee‎n. It is not a m‎a tter of forgive‎n ess. It is a ma‎t ter of being du‎m b with wonder t‎h at his poor bra‎i n and body didn‎’t burst under t‎h e torment of th‎e demon of creat‎i ve energy that ‎l ived inside him‎, struggling, cl‎a wing, scratchin‎g to be released‎; tearing, shrie‎k ing at him to w‎r ite the music t‎h at was in him. ‎T he miracle is t‎h at what he did ‎i n the little sp‎a ce of seventy y‎e ars could have ‎b een done at all‎, even by a grea‎t genius. Is it ‎a ny wonder he ha‎d no time to be ‎a man?畸人迪‎姆斯·泰勒1 他是个大头小‎身体、病怏怏的矬子；成日神经兮兮‎，皮肤也有毛病。

Human Populations

Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Population Density (persons / square km)
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Ehrlich Theory of “Population Bomb”
Human Populations
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
Outline:
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•
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•
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Population Growth Limits to Growth Human Demography Fertility and Mortality Life Span and Expectancy Population Growth - Opposing Factors Demographic Transition Family Planning Future of Human Populations
Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.
The Role of Technology
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现代大学英语第四册 Lesson 7

Detailed Discussion
• Para 1
rake out sth: remove ashes from ( a fire, kiln, etc) live coals live: still burning or glowing; not extinct eg: a live spark; a live volcano hearth: the area around a fire place or the area of floor in front of it streak: a streak is a long thin mark, line or band of a different substance or color. Here in the text, it refers to the ray of early sunlight which was white against the dark sky. eg: There are streaks of gray appearing in her black hair.

• •

man and wife: husband and wife
• Para 5
Still, as they walked silently in their rawhide shoes through the little hamlet, there was not a soul about. • P: When they walked silently through the small village, they saw not a single person around then because they were earlier than everybody else. hamlet: a small village soul: here it means a person, not the spiritual part of a person that some believe to continue to exist after they die.

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Metal grid/conducting polymer hybrid transparent electrode for inverted polymer solar cellsJingyu Zou,1Hin-Lap Yip,1,2Steven K.Hau,1and Alex K.-Y.Jen1,2,a͒1Department of Materials Science and Engineering,University of Washington,Seattle,Washington98195,USA2Institute of Advanced Materials and Technology,University of Washington,Seattle,Washington98195,USA͑Received19January2010;accepted23March2010;published online17May2010͒A simple method was developed using metal grid/conducting polymer hybrid transparent electrodeto replace indium tin oxide͑ITO͒for the fabrication of inverted structure polymer solar cells.Theperformance of the devices could be tuned easily by varying the width and separation of the metalgrids.By combining the appropriate metal grid geometry with a thin conductive polymer layer,substrates with comparable transparency and sheet resistance to those of ITO could be achieved.Polymer solar cells fabricated using this hybrid electrode show efﬁciencies as high asϳ3.2%.Thismethod provides a feasible way for fabricating low-cost,large-area organic solar cells.©2010American Institute of Physics.͓doi:10.1063/1.3394679͔Polymer solar cells͑PSCs͒are becoming as a viabletechnology for low-cost power production.1Indium tin oxide ͑ITO͒is the most commonly used transparent electrode for PSCs because it offers good transparency in the visible rangeof the solar spectrum as well as good electrical conductivity.However,there are several deﬁciencies that exist for usingITO such as poor mechanical properties of ITO-coated plas-tic substrates,2limited conductivity for fabricating large-areasolar cells,limited availability of indium,and complicated vacuum sputtering process tend to increase the cost for ITO. These limitations set a potential barrier for the commercial-ization of low-cost PSCs.To alleviate this problem,alterna-tive materials for transparent conducting electrodes are needed to replace ITO.There has been some research on exploring conductive polymers,2carbon nanotubes,3 graphenes,4and silver nanowires5as potential candidates to replace ITO.However,lower transparency and higher sheet resistance compared to ITO strongly hinder their use for transparent electrode.Metal grids have also been investi-gated as a promising alternative for transparent electrode.6,7 Utilizing microﬂuidic deposition and nanoimprinting meth-ods,metal grids coated substrates have been used for fabri-cating conventional PSCs with PCE as high as2%.Previously,inverted architecture PSC using ITO as cath-ode and evaporated silver͑Ag͒as anode has been proved to be more stable in ambient than the conventional devices us-ing sensitive metal as cathode.8Moreover,poly͑3,4-ethylenedioxythiophene͒:poly͑styrenesulfonate͒͑PEDOT-:PSS͒has also been demonstrated by Hau et al.9as a potential replacement of ITO for fabricating inverted PSCs. However,the relatively high sheet resistance of PEDOT:PSS compared to ITO may limit the performance of PSCs The combination of conductive metal grids with PEDOT:PSS provides a good solution to solve this problem and obtain ITO-free and ambient stable PSCs.Here,we report a simple method to fabricate high-efﬁciency ITO-free inverted structure PSCs using a metal grid/conducting polymer hybrid transparent electrode.By us-ing soft lithography and chemical etching,the metal gridscan be easily fabricated on substrates.The inverted devicearchitecture is used to fabricate PSCs with Ag as anode tocollect holes and zinc oxide͑ZnO͒as an electron selectivelayer at the metal grid/conducting polymer interface to helpcollect electrons.To prepare the metal grids,a1nm alumi-num͑Al͒ﬁlm was depositedﬁrst followed by evaporating a30nm thick silverﬁlm onto the glass substrates.It was foundthat the very thin Al layer improves adhesion between thesubstrate and the Agﬁlm.A micropatterned photoresist͑SU-8,MicroChem͒ﬁlm,fabricated by standard photolithography,was used as a mas-ter to replicate stamps for microcontact printing͑␮CP͒.A typical stamp was made by casting a10:1͑v/v͒mixture ofpolydimethyl siloxane͑PDMS͒and curing agent against asilanized master.The PDMS stamp wasﬁrst soaked with an“ink”containing1mM of mecaptoundecanoic acid͑MUA͒in ethanol,then brought into contact with the surface of sil-ver for60s.After the removal of the stamp,the patterned Agﬁlm was developed by wet etching with aqueousFe3+/thiourea using the patterned SAM as resist.10MUA was chosen for both generating better wettability for the process-ing of upper layerﬁlm.and facilitating better chargecollection.11Three types of designed grids patterns were utilizedas width and separation with͑1͒5␮m and50␮m ͑5␮m/50␮m͒,͑2͒10␮m and100␮m ͑10␮m/100␮m͒,͑3͒20␮m and200␮m ͑20␮m/200␮m͒,respectively.The optical transmittance of as-fabricated Ag grids was measured by UV-Vis spectros-copy͑Fig.1͒.The sheet resistance for metal grids with dif-ferent geometries was also measured.The transmittance of ITO at550nm is85.7%.When thetransmittance of glass͑ϳ93%͒is taken into account,the maximum expected transmittance of the metal grids coated glass substrate is calculated to beϳ83–84%.It was found that the average transmittance of metal grid coated glass sub-strates in the range of250–1200nm is78%,80%,and82%, respectively,for grids of5␮m/50␮m,10␮m/100␮m, and20␮m/200␮m.The lower transmission may be due toa͒Electronic mail:ajen@.APPLIED PHYSICS LETTERS96,203301͑2010͒0003-6951/2010/96͑20͒/203301/3/$30.00©2010American Institute of Physics96,203301-1some diffusion of MUA during contact printing on the metal surface.As the result,the actual Ag grid patterns expand 1–2␮m in width.Figure 2͑a ͒shows the optical microscope images of an as-fabricated metal grid electrode on a glass substrate.Another important parameter for transparent conducting electrodes is the sheet resistance.The sheet resistance of commercial available ITO substrates is 15⍀ᮀ−1,⍀ᮀwhile the Ag grid electrodes exhibited sheet resistances of9.1⍀ᮀ−1,146.3⍀ᮀ−1,and 254.1⍀ᮀ−1,for 5␮m /50␮m,10␮m /100␮m,and 20␮m /200␮m,re-spectively.Lower sheet resistances will minimize the loss of photocurrent during charge transport due to the lowered lat-eral resistance of the electrode.In general,the transmittance and sheet resistance for thin conductive ﬁlms are related by the equation ofT ͑␭͒=ͫ1+188.5R s ␴Op ͑␭͒␴DCͬ−2,where ␴Op ͑␭͒is the optical conductivity ͑here we quoted at ␭=550nm ͒and ␴DC is the conductivity of the ﬁlm.␴DC /␴Op is a commonly used term to describe transparent conductors.12For ITO with R s of 15⍀ᮀ−1and T ͑550nm ͒of 85.7%,the ␴DC /␴Op is 156.7.The best results that have been achieved for the graphene-based ﬁlms 13and carbon nanotubes 14are 0.5and 25,respectively.Based on the best metal grid geometry used in this work ͑5␮m /50␮m ͒,R s =9.1⍀/ᮀ,and T ͑550nm ͒=79.0%,a ␴DC /␴Op ratio as high as 165.6could be achieved.To fabricate solar cells,the ITO substrate and the metal grids coated substrate were cleaned using standard cleaning procedures.A thin layer of ZnO nanoparticles ͑ZnO NPs ͒was spin-coated onto these substrates.A C 60-based SAM ͑C 60-SAM ͒was deposited onto the ZnO surface using a spin-coating process as reported previously.15A 200nm bulk-heterojunction ﬁlm comprising of poly ͑3-hexylthiophene ͒͑P3HT ͒͑Rieke Metals ͒and ͓6,6͔phenyl C 61butyric acid methyl ester ͑PCBM ͒͑American Dye Source ͒was then spin-coated in an argon-ﬁlled glove box.After depositing a 50nm of PEDOT:PSS ﬁlm ͑H.C.Starck,CLEVIOS™P VP 4083͒.8A layer of Ag was vacuum deposited on top of PEDOT:PSS as anode.The solar cells were tested under ambient using a Keithley 2400SMU and an Oriel Xenon lamp ͑450W ͒with an AM 1.5ﬁlter.The light intensity was calibrated to 100mW /cm 2.The device architectures are shown in Fig.2͑b ͒.The J -V characteristics under illumination and the solar cells perfor-mance are summarized in Fig.3͑a ͒and Table I ,respectively.The device with the 5␮m /50␮m Ag grid has the best performance with PCE of 2.97%.The lower efﬁciency of the metal grid substrate derived device is mainly due to lower J sc and ﬁll factor.An important parameter that needs to be considered for the design of metal grids is that the charges generated from the voids between the grid lines need to be efﬁciently col-lected.The inverted device structure utilizes a ZnO NP layer as an electron selective layer between the active layer and the metal grids to collect electrons.The inhomogeneous and poor charge collection in the voids due to high sheet resis-tance of ZnO decrease both J sc and ﬁll factor.Inaddition,FIG.1.͑Color online ͒Transparency vs wavelength of different geometry Ag grids on glass as compared to transparency of ITO and glass,as refer-enced againstair.FIG.2.͑Color online ͒͑a ͒Optical microscope image of silver grid with 5␮m width separated by a distance of 50␮m.͑b ͒Device conﬁguration of the polymer solar cell using Ag grid as the transparent electrode with or without conductive PEDOT:PSSlayer.FIG.3.͑Color online ͒The current density-voltage ͑J −V ͒characteristics of polymer solar cells with ͑a ͒different Ag grid geometries ͑b ͒different Ag grid geometries combining 40nm PEDOT:PSS PH500ﬁlm measures under AM1.5illumination from a calibrated solar simulator with a light intensity of 100mW cm −2.the lower transmittance of the5␮m/50␮m Ag grids ͑ϳ78%͒compared to ITO͑ϳ85%͒also contributes to the decrease in J sc.Increasing the width and separation while maintaining the same aspect ratio dramatically reduces the J sc andﬁll-factor.To alleviate the problem for poor charge collection,a PEDOT:PSS͑H.C.Starck,CLEVIOS™PH500͒conduct-ing polymer was inserted between the silver grids and the ZnO layer to form the hybrid electrode.To demonstrate the function of the hybrid electrode,an inverted photovoltaic device with220nm thick PEDOT:PSS PH500ﬁlm without metal grids as the bottom electrode was fabricated.The J-V characteristics under illumination and the solar cells performance are summarized in Fig.3and Table I, respectively.For the smaller separation Ag grids ͑5␮m/50␮m͒,the addition of the conducting PEDOT:PSS polymer layer improved the device performance to3.21% due to the reduced lateral resistance.For devices using larger separation grid lines͑10␮m/100␮m and 20␮m/200␮m͒,the addition of the PEDOT:PSS layer sig-niﬁcantly improved the performance of the devices.For grids with separation distance of over10␮m,additional layer of PEDOT:PSS is necessary to reduce the lateral resistance.All three silver grids electrodes can achieve near3%PCE using the additional PEDOT:PSS layer.The potential beneﬁt of using larger size grid patterns is the ease for device fabrica-tion especially for cost efﬁcient industrial roll-to-roll pro-cessing.Without Ag grids,PEDOT:PSS PH500bottom elec-trode devices can only have efﬁciency ofϳ2.2%which is due to the high sheet resistance.In conclusion,we have demonstrated that silver metal grid electrodes fabricated by microcontact printing and wet chemical etching can replace conventional ITO electrodes for fabricating organic solar cells.The patterned metal elec-trodes on glass show high optical transmittance as well as good electrical anic solar cells with opti-mized grid geometry show encouraging device performance. It was also found that silver grid electrodes with smaller width and separation with the same aspect ratio facilitated better charge collection from the ZnO NP layers leading to increased FF,J sc,and PCE.By adding a PEDOT:PSS PH500 conducting polymer between Ag grid and ZnO,even devices with larger Ag grid spacing can achieve good performance. The use of inexpensive Ag grids compared to ITO allows the possibility of employing roll-to-roll process to realize low-cost,large-area organic solar cells.This work is supported by the National Science Founda-tion’s NSF-STC Program under Grant No.DMR-0120967, the Department of Energy’s“Future Generation Photovoltaic Devices and Process”Program under Grant No.DE-FC36-08GO18024/A000,and the Ofﬁce of Naval Research’s Pro-gram under Grant No.N00014-08-1-1129.A.K.-Y.J.thanks the Boeing-Johnson Foundation forﬁnancial support.1G.Dennler,M.C.Scharber,and C.J.Brabec,Adv.Mater.͑Weinheim, Ger.͒21,1323͑2009͒.2S.I.Na,S.S.Kim,J.Jo,and D.Y.Kim,Adv.Mater.͑Weinheim,Ger.͒20,4061͑2008͒.3M.W.Rowell,M.A.Topinka,M.D.McGehee,H.J.Prall,G.Dennler,N. 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