bluuebunny/crossref_metadata_2025 huggingface dataset:
Le nouvel idéal politique
Authors: Kacenelenbogen Edwige
Published: March 2011

Résumé À partir d'une enquête sur la proximité entre les fondements épistémologiques du républicanisme moderne et ceux de l'idée néolibérale, cet article interroge la cohérence de la doctrine républicaine contemporaine en tant que projet d'organisation politique et social. Sans occulter les zones de profonde divergence entre ces deux compréhensions spécifiques du politique, j'éclaire l'existence d'une proximité entre les républicanismes de Philip Pettit, David Miller et Jean-Marc Ferry, d'une part, et le paradigme néolibéral élaboré par Friedrich Hayek de l'autre. Outre la prégnance, dans les deux courants de pensée, de l'empire du droit et de la menace de l'imperium étatique, j'identifie en leur sein une même révérence pour l'autorité d'une raison collective issue d'un nexus d'individus interconnectés. Je m'attache ainsi à prouver l'existence, dans les deux courants, d'un idéal essentiellement intersubjectif et fondé en majeure partie sur le rôle des opinions. Mon enquête vise à éclairer les raisons ainsi que les enjeux de cette étrange proximité entre ces deux visions a priori très différentes du politique.
Le souci de l'élite politique chez les libéraux
Authors: Leboyer Olivia
Published: March 2011

Résumé Le phénomène de l'élite politique est une réalité et, dans le même temps, il ne cesse de susciter des jugements de valeurs, comme s'il constituait une sorte de pierre d'achoppement de la modernité. Analyser la place de l'autorité et des hiérarchies permet d'interroger les limites du libéralisme et du système représentatif. De fait, les libéraux ne manifestent pas tous le même attachement à la démocratie, ni aux principes du libéralisme.Il y a visiblement une difficulté à penser l'élite, ou la dimension élitiste du pouvoir. Est-ce une difficulté propre à la pensée libérale ?Nous étudions la conception de l'élite de trois libéraux, représentant chacun un certain type de libéralisme : Guizot un libéralisme fermement antidémocratique ; Hayek un libéralisme qui opère une distinction soigneuse entre libéralisme et démocratie, pour poser la primauté des principes libéraux ; Rawls un libéralisme qui considère que libéralisme et démocratie se conditionnent mutuellement, leurs principes se fondant harmonieusement dans la démocratie libérale.Il s'agit de mettre en lumière trois conceptions singulières des principes de liberté et d'égalité, trois modes de compréhension de la démocratie. Si le libéralisme, dans tous ses courants, témoigne d'un souci de l'élite, peut-on parler d'un élitisme libéral ? Quels principes cette appellation recouvrirait-elle ? Ces questions doivent nous aider à éclairer l'énigme de la démocratie libérale.
Réapparaître.
Authors: Claverie Élisabeth
Published: March 2011

Résumé Près de 30 000 personnes ont disparu en Bosnie-Herzégovine pendant la guerre. Les fragments de corps retrouvés, une fois identifiés, permettent de faire passer les « disparus » au statut de « victimes », et sont mobilisés comme preuves judiciaires par le Tribunal Pénal International pour l'ex-Yougoslavie. L'article analyse tout d'abord les processus de localisation, d'exhumation, d'identification et de ré-inhumation des corps. Puis il décrit un cas exemplaire, celui de Srebrenica, qui met en exergue le problème des déplacements des corps de fosses primaires vers des fosses secondaires et tertiaires. La réapparition des fragments de corps a changé la qualification du conflit, qui n'a pas été un combat opposant des combattants contre des combattants, mais un nettoyage ethnique.
Ground Zero entre chantier et charnier
Authors: Truc Gérôme
Published: March 2011

Résumé Depuis les attentats du 11-Septembre, le site de Ground Zero à New York est un vaste chantier, mais reste aussi, aux yeux de beaucoup, un charnier ayant le statut de « terre sacrée ». Près de la moitié des personnes mortes dans l'effondrement des tours du World Trade Center le 11 septembre 2001 n'ont en effet jamais été identifiées, leurs corps ayant été réduits en poussière. À partir de ce cas, cet article vise à interroger l'impact sur un lieu de mort de la pulvérisation de corps humains. Pour cela, y sont examinées tour à tour les opérations de déblaiement et de tri des gravats et d'identification des restes humains, les controverses suscitées par les découvertes de nouveaux restes humains à Ground Zero lors de sa reconstruction, la mobilisation des familles de victimes réclamant une sépulture décente pour leurs morts, et les formes de patrimonialisation de Ground Zero contribuant à en faire un lieu de mémoire plutôt que de mort.
Les morts mobiles
Authors: Esquerre Arnaud
Published: March 2011

Résumé Alors que la crémation a été autorisée à partir de 1887 en France, ce n'est qu'en 1976 que, sous la pression des associations des partisans de la crémation, les « crématistes », la libre circulation des cendres et leur dispersion dans la nature sont permises. Alors que le taux de crémation augmente fortement jusqu'à représenter environ 22 % des décès en 2005, le nombre d'urnes cinéraires remises aux proches est rapidement élevé. Voulant encadrer le devenir des cendres, les parlementaires ont, par la loi du 19 décembre 2008, interdit que celles-ci, désormais assimilées à des restes de personnes décédées, puissent se trouver dans un espace privée, et ils ont rendu obligatoire leur localisation, même en cas de dispersion, au nom du travail de deuil. Cependant ce changement alimente aussi une idée de la nation, dans laquelle les morts sont « enracinés » sur un territoire.
Enterrer, submerger, oublier
Authors: Delaplace Grégory
Published: March 2011

Résumé Cet article traite d'une réforme des pratiques funéraires conduite en Mongolie à partir du milieu des années 1950. Instituant l'obligation d'enterrer les morts, son enjeu principal est de rendre illégal le rituel pratiqué jusqu'à lors, consistant à déposer les cadavres des défunts à même le sol. Cette pratique, en effet, est jugée inconvenante et inadaptée à la vie urbaine. Le succès de la réforme est mitigé : si l'inhumation semble avoir été adoptée sans trop de difficulté par la population, les cimetières, en revanche, ne prennent pas le tour que les réformateurs avaient souhaité. Imaginés comme des espaces enclos et fleuris, où le souvenir des morts pourrait être dignement célébré, ils se présentent jusqu'à aujourd'hui comme de vastes terrains vagues, évités autant que possible, où les tombes sont livrées à l'oubli et au délabrement. Il s'agira ici de comprendre les raisons de la subversion du projet de cette réforme, en tentant de caractériser l'idéologie funéraire qui sous-tend la configuration singulière des cimetières mongols.
Nostalgie de la Mitteleuropa et engagement politique
Authors: Hirsch Yaël
Published: March 2011

Résumé À partir des trajectoires et des œuvres de trois poètes nés en Mitteleuropa et ayant du quitter l'Europe, cet article propose une analyse politique de la nostalgie. Repensée depuis l'exil, la Mitteleuropa est sublimée par ce sentiment. Ce mythe littéraire de la Mitteleuropa fonctionne comme un point de repère pour les trois poètes, qui formulent leurs visions du monde en fonction de la perte de leur patrie. La nostalgie se développe ainsi sous le signe du manque : un monde a disparu et rien ne peut le ramener. Face à ce sentiment, les individus peuvent développer deux types de comportements : soit œuvrer pour la construction d'un monde qui soit à la hauteur de ce qu'ils ont perdu, soit se replier sur leur sphère privée. Ainsi, cette nostalgie incite Czeslaw Milosz à s'engager dans ses écrits. Lus et appris dans son pays natal, les textes de Milosz ont un impact politique fort. En revanche, l'œuvre de Else Lasker Schüler montre comment l'intellectuel déraciné et nostalgique peut se figer pour se fermer au monde. Entre ces deux types de réaction, Benjamin Fondane se détourne des questions formelles pour amorcer un engagement politique dans ses derniers écrits. Mais le poète déporté à l'âge de 46 ans n'a peut-être pas eu tout à fait le temps de développer cet engagement.
Danos socioambientais originados pelas usinas eólicas nos campos de dunas do Nordeste brasileiro e critérios para definição de alternativas locacionais
Authors: Meireles Antonio Jeovah de Andrade
Published: March 2011

O potencial eólico brasileiro é uma importante alternativa para a produção de energia renovável para enfrentar as emissões de poluentes atmosféricos com a utilização de energia limpa. Uma excelente política ambiental para minimizar as consequências previstas pelo aquecimento global, perante as emissões de dióxido de carbono e poluentes relacionados com a utilização de carvão mineral e outros combustíveis fósseis. Este artigo enumerou as consequências ambientais das usinas eólicas sobre os campos de dunas através da fragmentação dos sistemas ambientais provocado pelas obras de engenharia. Ao final foi possível analisar os impactos cumulativos tomando como exemplo o litoral cearense, definir alternativas locacionais e ações adequadas para o planejamento de ambientes costeiros diante esta nova forma de geração de energia limpa.
Stratégies pour un vol virtuel : exemple de paysages brésiliens
Authors: Filho Alfredo Pereira de Queiroz
Published: March 2011

Ce travail aborde les deux principaux problèmes posés par le vol virtuel, l’orientation spatiale et la surcharge cognitive, et propose des stratégies qui facilitent la pratique de la navigation. Pour illustrer cette recherche, sont utilisés des exemples de paysages reconnus du territoire brésiliens, tels que Foz de Iguaçu (Paraná), Rio de Janeiro (État de Rio de Janeiro), Pantanal – (Mato Grosso du Sud), Salvador (Bahia), Belém (Pará), Manaus (Amazonas), et São Paulo (État de São Paulo).
Computer Simulation for Movement Law of a 4L-20/8 Piston Compressor Valve
Authors: Chen Shuang
Published: March 2011

In this paper,mathematical model of valve movement law was established after simultaneous equations (such as flow equations and differential equations of motion) .Simulation of the intake valve movement law was carried out by using Simulink in the Matlab.The valve displacement diagram ,the velocity curve and pressure ratio curve as well as volume change curves were got,which will help us to have a proper understanding on the working process and properties of valve and make the air compressor valve designs to become more theoretical and more in accord with practical.
Micro-Structure Study on Collapsibility Loess with SEM Method
Authors: Cai Jing , Dong Bing Yin
Published: March 2011

To study the micro-structure of collapsibility loess, the triaxial shear test under pressure of 10MPa to 100MPa and consolidation test under 1000kPa, 2000kPa and 4000kPa were respectively used on collapsibility loess here to imitate the working condition of dynamic compaction. Micro-images of the soil samples in above tests and undisturbed soil samples were collected by SEM at 500 enlarge. The results of images analysis are that the flocculated structure is destroyed drastically under compaction; the macrovoids and large set of grains are destroyed and recombined with tamping energy’s increase and the primary unordered sank is recombined and more dense and directional.
Application of Fractal Theory to Geotechnical Engineering
Authors: Liu Bo , Ning Ye
Published: March 2011

Fractal theory has been established for more than 20 years. Taking the fractal theory into solving geotechnical engineering problems has been gradually perfected. This paper concludes several common methods within the fractal theory research. Meanwhile, sums up the research results of the predecessors during the correlation field. At last, illustrates the application of fractal theory within the geotechnical engineering problems' research in detail, such as the microstructure fractal of soil, the fractal dimension on the joint surface, the relation between fractal dimension and rock quality coefficient(RQD), fractal damage and fractal fracture, and application of fractal theory(mechanics) to related geotechnical engineering.
Fault Diagnosis of Shearer Based on Fuzzy Inference
Authors: Gao Feng , Xiao Lin Jing , Zhong Wei Yan , Liu Wei
Published: March 2011

The purpose of this study is to provide a correct and timely diagnosis mechanism of shearer failures by knowledge acquisition through a fuzzy inference system which could approximate expert experience. Concerning a question of uncertain knowledge expression and reasoning in shearer malfunction, the fuzzy inference theory is used in shearer malfunction fault diagnosis. The fuzzy relation matrix of faults and signs is deduced based on deep research of failure mechanism and expert experience, which agrees with fault and fault symptoms non one-to-one relationship and human thinking. Fault characteristic parameter is calculated to corresponding subordinate degree, then is operated with fuzzy relation matrix and get fault fuzzy vector. Finally, the shearer malfunction fault is diagnosed according to certain diagnosis principle. The example proves that the method has less calculation, explicit conclusion and other merits.
Heat Transfer Enhancement by Using Four Kinds of Porous Structures in a Heat Exchanger
Authors: Ding Xin Rui , Lu Long Sheng , Chen Chuan , He Zhan Shu , Ou Dong Sheng
Published: March 2011

Four kinds of porous structures, copper wire mesh, metal foam, copper fiber sintered felts and cross-connected micro-channel plates were applied in a heat exchanger. Heat transfer coefficient per unit volume, pressure drop and comprehensive heat transfer effect of the heat exchanger were studied. The results show that: four kinds of porous structures can enhance the heat transfer performance obviously. The heat exchanger with copper metal foam has the largest comprehensive heat transfer coefficient which can reach 821.5W•m-3•K-1•Pa-1. And it increased about 2.5 times than that of the heat exchanger without porous structures. The comprehensive heat transfer coefficient increases with the flow rate in small case and decreases with the flow rate in large case. The coefficient reaches the largest value at the flow rate range of 6L/h-8L/h. The heat transfer coefficient per unit volume of the heat exchanger with four kinds of structures increases with the flow rate, and the increasing trend tends slowly. Metal foam of brass has the largest heat transfer coefficient per unit volume of 1266.8 W•m-3•K-1. Pressure drop increases with the flow rate, and the increasing trend tends rapidly. The 200 mesh copper wire mesh has the least pressure drop of 968.8Pa.
The Computer Modeling of Forging by Using the Overrange Collocation Method
Authors: Guo Yong Ming
Published: March 2011

In this paper, a forging problem is analyzed by using the overrange collocation method (ORCM), which is a new meshless method. By introducing some collocation points, which are located out of domain of the analyzed body, unsatisfactory issue of the positivity conditions of boundary points in collocation methods can be avoided. Because the overrange points are used only in interpolating calculation, no overconstrain occurs in partial differential equations on the solved problems.
Effect of Electrode Force on Tensile Shear and Nugget Size of Austenitic Stainless Steel Grade 304 Welds Using Resistance Spot Welding
Authors: Peasura Prachya
Published: March 2011

This research was to effect of electrode force on the tensile shear and nugget size of the resistance spot welding. The specimen was austenitic stainless steel 304 grade sheet metal 1.2 mm thickness. The electrode force are 1, 1.5, 2.0, 2.5, and 3.0 kN apply to the specimen. The replications in each treatment are 20 follow JIS Z 3136:1999 and JIS Z 3139:1978. Factor control, welding current 7 kA., time current flow 7 cycle and electrode tip diameter 6 mm. The welded specimens were tested by tensile shear testing according to JIS Z 3136: 1999, macro structure testing according to JIS Z 3139: 1978 and analysis results by using One-way ANOVA .The result showed that electrode force had affected on tensile shear and nugget size at 95% confidential (P value > 0.05). The low force induced the gab between specimen increasing then the current flow difficult to pass and both of gab between specimen and nugget seize had increase (Q=I2Rt). When the resistance increased so that fusion zone will have a high heating. It had affected to nugget size, heat affected zone and mechanical properties decreasing. The electrode forces are complete 2.5 kN. tensile shear 9.21 kN and nugget size 5.82 mm. The data can be applied to be used as process monitoring of resistance spot weld quality
Definition of Boundary Conditions and Dynamic Analysis of Rocket Sled and Turntable
Authors: Zhang Jian Hua , Jiang Shou Shan
Published: March 2011

The Dynamics Analysis & Simulation of the Rocket Sled were done based on the Multibody System Dynamics and Finite Element Analysis Theory. The most difficult work in the analysis is how to establish the boundary conditions of the rocket sled. This paper makes this kind of attempt. Then the relevant postprocessing figures and data were obtained，thereby providing the designer and manufacturer with detailed and reliable data. The conclusion is the simulation method is more effective than those before and the boundary conditions are acceptable.
Through-Hole Drilling of Glass Plate Using Electroplated Diamond Tool
Authors: Mizobuchi Akira , Ogawa Hitoshi
Published: March 2011

Hard and brittle materials such as ceramics and glass are not only difficult-to-machine but also occur easily cracks at the exit surface in through-hole drilling. This paper deals with through-hole drilling of glass plate for plasma display panel using an electroplated abrasive grain tool in order to find out drilling conditions for smaller cracks, higher drilling efficiency and longer tool life. In particular, the influence of the crack in two kinds of abrasive grain is examined. The main conclusions obtained in this study are as follows. The crack in diamond grain tool is smaller than that in CBN grain tool. Moreover, the tool life of diamond grain tool is longer than that of CBN grain tool. Adhered volume of chip increases with drilling numbers, so the crack size and the thrust force increases. The washing of tool is required in order to restrain crack and force.
Source Localization for Multiple Impacts Based on Elastodynamics and Wavelet Analysis
Authors: Lee Sang Kwon , Park Jong Ho
Published: March 2011

The aim of this paper is to present the method of identifying the impact location on the plate. This basic research has the purpose to achieve the human-interaction technology based on the signal processing, piezoelectric materials, and wave propagation. The work concerning the location identification of a single impact on the plate has been previously studied by means of the time frequency analysis applied to accelerometer signals. In this paper, a novel approach for the location identification of the discrete impact is presented to investigate the feasibility of applying to a human-interaction system. For the identification of the impact location, the major axisymmetry mode of the Lamb wave on the plate is used for this work.
RETRACTED: Tool Wear Intelligence Measure in Cutting Process Based on HMM
Authors: Kang Jing , Guan Li Na
Published: March 2011

RETRACTED PAPER: A method of tool wear intelligence measure based on Discrete Hidden Markov Models (DHMM) is proposed to monitor tool wear and to predict tool failure. FFT features are first extracted from the vibration signal and cutting force in cutting process, and then FFT vectors are presorted and converted into integers by SOM. Finally, these codes are introduced to DHMM for machine learning and 3 models for different tool wear stage are built up. Pattern of HMM is recognised by calculating probability. The results of tool wear intelligence measure and pattern recognition of tool wear experiments show that the method is effective.
Dynamic Mechanical Properties of Steel Fiber-Reinforced Concrete Subjected to Shock Loading
Authors: Jiang Fang , Tan Yue Sheng , Zhao Dong
Published: March 2011

One-stage light gas gun is used to study the dynamic mechanical properties of reinforced concrete (SFRC) subjected to shock loading. The material of projectile is the same as of the target. The stress-time curves are recorded by three manganin pressure transducers embedded in the targets beforehand. The data of experiment are analyzed by self-designed program using the path line principle of Lagrangian analysis method. With the stress records, complete histories of particle velocity, density (and thus strain) and specific internal energy can be obtained at any point within the gaged region of the material. Moreover, the numerical constitutive relations of RC are obtained and the strain rate ranges from 104 to 105 per second. The result of experiment indicates that the stress-strain curves of SFRC present stagnant-return properties. And some other dynamic properties can be gained, such as rate dependent, waveform dissipation etc.
Study of Back Analysis of Material Parameters of Mass Concrete
Authors: Lan Wen Gai , Zhao Xin Ming
Published: March 2011

The Kalman filtering theory was applied for the back analysis of mechanical parameters of mass concrete on the first time. The time-spreading equation and the observation-correcting equation were deduced. After the coupling problem of extending Kalman filtering theory and FEM was solved, the Kalman-FEM formula were deduced and the corresponding back analysis procedures were given. The results indicate that the Kalman filtering method has good characteristics of convergence and stability. The broached method can be used in other research fields such as the back analysis of creeping parameters. Many more conclusions are tested and discussed through a classic example.
3D Numerical Simulation of a New Type of Throttle Control Valve
Authors: Zhou San Pin
Published: March 2011

According to the requirements of hydraulic pressure controlling system of the State 863 Plan of China: “the development of cased hole twin packer cell”, a new type of two-way valve used in the hydraulic pressure controlling system of downhole tester was developed, which could control the direction of liquid movement. The valve has not only the sealing function of seal valve, but also the adjustment function of the rate of flow of throttle valve. It is different from the ordinary two-way valve in structure because of its particular demands of function and performance. In this paper, a study was carried out on the flow field and flow characteristics in the throttle control valve by means of hydromechanics numerical simulation and with the resulting analysis, structural optimization was performed to the throttle control valve. The result that obtained by simulation calculation can provide theoretic reference for the valve design.
Structural Analysis of Universal Shaft Based on ANSYS
Authors: Ying Fu Qiang , Wu Ling Dong , Wang Yi , Li Liang Yi
Published: March 2011

Universal shaft is widely used to transfer the torque and rotational movement from the drive shaft to the slave while position of one shaft can be changed. Crack used to appear in the fork part of the universal shaft in tests in a universal company. In order to solve this problem, in this paper, a finite element model of universal shaft was established with the application of Pro/E and ANSYS, and the static stiffness analysis, stress analysis and dynamic analysis were all applied in ANSYS. According to the results, the weak points were found and some improvements on the original structure were made.
Texturing of Multi-Crystalline Silicon Wafers Through Ionized Bubble for Solar Cell Fabrication
Authors: Wu Li Qun , Chao Yan , Shao Jian
Published: March 2011

Surface texturing of silicon can reduce the reflectance of incident light and hence increase the conversion efficiency of solar cells. Many approaches have been present in texturing silicon solar cell. As a practical method, chemical wet etching has been widely used in monocrystalline silicon and multicrystalline silicon (mc-Si), but the cost and high reflectance hamper its widely used. In this paper, a new approach is present by using ionized bubble to texture multicrystalline solar cell. The electric field and ultrasonic wave is introduced into traditional chemical wet etching. After mixed solution ionized by electrolysis and gasified by the ultrasonic wave, the ionized bubble is formed. The movement of ionized bubble is observed to study the impact on the surface of mc-Si solar cell. At last, a spectrophotometer was used to measure mc-Si surface reflectance to test the efficiency of two methods. The result express that the reflectance of mc-Si surface textured by ionized bubble is much low than that of chemical mixed acid etching.
The Method of Fault Feature Extraction from Acoustic Emission Signals Using Wigner-Ville Distribution
Authors: Bin G.F. , Liao C.J. , Li Xue Jun
Published: March 2011

Wigner-Ville distribution (WVD) has the characteristics of very high-energy accumulation and excellent time-frequency resolution. It is a good way to extract fault feature of acoustic emission (AE) signals due to mechanical component broken. The characteristics of typical AE signals initiated by damages are analyzed. Based on the extracting principle of AE signals from damaged components, the WVD analysis method of AE signal is developed. WVD method is employed to the fault diagnosis of rolling bearings with AE technique. The fault features reading from experimental data analysis are clear, accurate and intuitionistic, meantime, the validity and accuracy of WVD method proposed are nice from the experimental results. Therefore, WVD method is useful for condition monitoring and fault diagnosis in conjunction with AE technique.
Theoretical Analysis of Young’s Modulus for Unidirectional Fiber Reinforced Composites with Different Fiber Orientations
Authors: Gui Le Le , Zhou Hong Wei , Wang Huai Wen
Published: March 2011

In order to explore the effect of fiber orientation angle on the Young’s modulus of fiber reinforcement polymer (FRP) composites, from the basic theory of elastic mechanics, a procedure which can be applied to evaluate the elastic stiffness matrix of FRP composite as an analytical function of fiber orientation angle (0-90o), is developed in Mathematica environment. Results indicate that Young’s modulus of the composites strongly depends on the fiber orientation angles. A U-shaped dependency of the Young’s modulus of composites on the inclined angle of fiber is found, which agree well with the experimental results and numerical simulation. The shear modulus was found to have significant effect on the Young’s modulus.
Process Analysis for Rapid Tooling Technology Based on Rapid Prototyping
Authors: Liu Hong Pu , Su Jun , Li Xiao Jing
Published: March 2011

This paper discussed the working principle, classification, modeling process and technology features for rapid tooling based on rapid prototyping and investigated into the difference between rapid tooling with traditional modeling manufacture. Several typical rapid tooling technologies are compared and summarized from mould period, fabrication cost and production cycle. Some key problems that rapid tooling industry will face with are analyzed. The application of the rapid tooling based on rapid prototyping is prospected.
Stress Generation during Grain Boundary Interdiffusion
Authors: Klinger Leonid , Rabkin Eugen
Published: March 2011

A grain boundary interdiffusion in a semi-infinite bicrystal under the conditions of negligible bulk diffusion is considered. We show that the inequality of intrinsic grain boundary diffusion coefficients of the two components leads to plating out of additional material at the grain boundary in the form of extra material wedge, which generates an elastic stress field in the vicinity of the grain boundary. We solved a coupled diffusion/elasticity problem and determined the time-dependent stress field and concentration distribution in the vicinity of the grain boundary.
Cutting Path Optimization Using Tabu Search
Authors: Dewil Reginald , Vansteenwegen Pieter , Cattrysse Dirk
Published: March 2011

This paper deals with generating paths for cutting irregular parts nested on a metal sheet. The objective is to minimize the total non-cutting time for the cutter head starting at a known location, cutting all the required elements and returning to the known location. In contrast to most literature on this topic, a part does not have to be cut at once. If this reduces the total non-cutting time, it is possible to cut a number of elements on a given part, then cut other parts and then return later to finish cutting the given part. The problem is modeled as a generalized traveling salesperson problem with special precedence constraints. An initial feasible solution is generated and improved by local moves embedded in a tabu search framework. The proposed algorithm shows promising results in comparison with a commercial software package on a limited set of test cases.
Investigation on Incremental Sheet Forming Combined with Laser Heating and Stretch Forming for the Production of Lightweight Structures
Authors: Taleb Araghi Babak , Göttmann Alexander , Bergweiler Georg , Saeed-Akbari Alireza , Bültmann Jan , Zettler Joachim , Bambach Markus , Hirt Gerhard
Published: March 2011

Asymmetric Incremental Sheet Forming (AISF) is a process for the flexible production of sheet metal parts. In AISF, a part is obtained as the sum of localized plastic deformations produced by a simple forming tool that, in most configurations, moves under CNC control. Flexible processes with low tooling effort like AISF are suitable for sectors with small lot sizes but premium products, e.g. for the aviation and the automotive sector. Four main process limits restrict the range of application of AISF and its take-up in industry. These are: (i) material thinning, (ii) limited geometrical accuracy, (iii) the process duration and (iv) the calculation time and accuracy of process modelling. Moreover, the material spectrum of AISF for structural parts is mostly restricted to cold workable materials like steel and aluminum. This paper presents some new investigations of incremental sheet forming combined with laser heating or stretch forming as possible hybrid approaches to overcome the above mentioned limitations of AISF. These hybrid incremental sheet forming processes can increase the technological and economical potentials of AISF. A possible application is the fabrication of lightweight sheet metal parts as individual parts or small batches, e.g. for the aerospace industry. The present study provides a short overview of the state of the art of AISF, introduces the new hybrid process variations of AISF and compares the capabilities of the hybrid processes and the standard AISF process. Finally, two examples for applications are presented: (i) the production of a part used in an airplane for which the manufacturing steps consist of die manufacture, sheet metal forming by means of stretch forming combined with AISF and a final trimming operation using a single hybrid machine set-up; (ii) laser-assisted AISF for magnesium alloys.
Predicting Dimensional Accuracy of Mechanically Joined Car Body Assemblies
Authors: Neugebauer Reimund , Rössinger Markus , Wahl Martin , Schulz Frank , Eckert Alexander , Schützle W.
Published: March 2011

Mechanical joining of complex car body components is an essential part of lightweight construction concepts in the field of car body manufacturing. Besides the mechanical behavior of the joints, the influence on the dimensional accuracy is of particular interest, as joining techniques like clinching or self-piercing riveting cause distortion comparable to spot welding. In recent years, a lot of simplified models using the FE-Method to predict the distortion of assemblies caused by welding (weld seams, spot welds) were presented and commercialized. In contrast to thermal joining technologies, there are no such simplified models with practical relevance existing in the mechanical joining technology sector. In this paper, a new method to predict distortion, caused by different mechanical joining technologies, including effects from previous forming processes, and clamping conditions, is presented. The validation of the simplified model takes place due to an extensive design of expe-riments. It can be proved that the distortion of simple as well as of complex specimens can be relia-bly predicted.
Epitaxial Growth of 3C-SiC on Si Substrates by Atmospheric Hot Wall CVD Using Hexamethyledisilane[(CH3)6Si2]
Authors: Lee Tae Woo , Yeo Im Gyu , Shin Byoung Chul , Lee Won Jae , Park Mi Seon , Hwang Hyun Hee , Nishino Shigehiro
Published: March 2011

We adopted HMDS(Hexamethyledisilane) as a SiC(Silicon carbide) source material for epitaxial growth of 3C-SiC on Si substrate. Various growth profiles were investigated to optimize hetero-epitaxial growth of 3C-SiC layers. We also focused on the homogeneous film deposition of 3C-SiC on Si by employing two susceptor shapes, flat and tilted susceptors, to control a thickness of the boundary layer formed on the Si substrate. Fringe color patterns were observed on 3C-SiC layer on Si and hence it was easy to characterize the film uniformity by analyzing this color. 3C-SiC epitaxial layers were systematically analyzed by an optical microscope, a Raman spectroscopy, a SEM and an XRD.
4H-SiC Epitaxy with Very Smooth Surface and Low Basal Plane Dislocation on 4 Degree Off-Axis Wafer
Authors: Chung Gil Yong , Loboda Mark J. , Zhang Jie , Wan Jian Wei , Carlson E.P. , Toth T.J. , Stahlbush Robert E. , Skowronski Marek , Berechman R. , Sundaresan Siddarth G. , Singh Ranbir
Published: March 2011

Improvements in the quality and consistency of 4H-SiC epitaxy wafers are now starting to enable growth of commercial SiC power device applications in areas such as inverters for photo-voltaic systems and power supplies. Recent work has achieved very low epitaxy surface roughness and very low BPD (Basal plane dislocation) in the on 4 degree off-axis substrates. In this paper, we report characterization of the very low BPD epitaxy wafers and a newly observed triangular defect.
Nondestructive Evaluation of Photo-Electrical Properties of 3C-SiC (111) Homoepitaxial Layers Grown by CVD
Authors: Jegenyes Nikoletta , Manolis Georgios , Lorenzzi Jean , Soulière Véronique , Dompoint Deborah , Boulle Alexandre , Ferro Gabriel , Jarašiūnas Kęstutis
Published: March 2011

Free carrier absorption (FCA) and picosecond light-induced transient grating (LITG) techniques were applied to study the photoelectrical properties of 3C-SiC(111) homoepitaxial layers grown by CVD method on VLS (vapour-liquid-solid) grown seeds. The thickness of the CVD layers was ~10.5 µm with non-intentional type doping of n (~ 1017 cm-3) or p (<1015 cm-3). The carrier lifetime and the diffusion coefficient were measured as the function of the sample temperature, the injected excess carrier density at different growth parameters. At room temperature the ambipolar diffusion coefficient was Da=2.5-3 cm2/s, while the lifetime was in the range of 12-18 ns. The best structural and electrical properties were obtained for a CVD layer grown at high, 1600 °C temperature.
Optical Investigation of Defect Filtering Effects in Bulk 3C-SiC Crystals Grown by the CF-PVT Method Using a Necking Technique
Authors: Zoulis Georgios , Sun Jian Wu , Galben-Sandulache Irina G. , Sun Guoli L. , Juillaguet Sandrine , Ouisse Thierry , Chaussende Didier , Madar Roland , Camassel Jean
Published: March 2011

We present the results of an optical investigation performed using low temperature photomuminescence and Raman spectroscopy on bulk 3C-SiC samples grown with the Continuous-Feed Physical Vapor Transport technique, using a small diameter neck to filter the defects and improve the as-grown material.
Electrical Characterization of Nitrogen Implanted 3C-SiC by SSRM and C­TLM Measurements
Authors: Song Xi , Bazin Anne Elisabeth , Michaud Jean François , Cayrel Frédéric , Zielinski Marcin , Portail Marc , Chassagne Thierry , Collard Emmanuel , Alquier Daniel
Published: March 2011

Two electrical characterization methods were used to study 3C-SiC epilayers doped by nitrogen implantation: circular Transfer Length Method (c­TLM) which allows extracting the specific contact resistance and Scanning Spreading Resistance Microscopy (SSRM) used to measure activated doping concentration. 3C-SiC samples were implanted at room temperature with different energies (ranging from 30 to 150keV) and doses (from 1 to 5.4x1015cm-2) in order to obtain a 300nm thick box-like profile at 5x1020cm-3. To activate the dopant, the samples were then annealed from 1150°C to 1350°C for 1h to 4h. Titanium-nickel c-TLM contacts annealed at 1000°C under argon showed the best results in terms of specific contact resistance (8x10-6.cm2) after a 1350°C–1h annealing. For this annealing condition, the activation rate was assessed by SSRM around 13%. This value confirms the difficulty to activate the dopants introduced into the 3C-SiC as the temperature is limited by the silicon substrate. However, this work demonstrates that low resistance values can be achieved on 3C-SiC, using nitrogen implantation at room temperature.
Using Intrinsic Defect Spectra in 4H SiC as Imbedded Thermometers in the Temperature Range from 100°C to 1500°C
Authors: Yan Fei , Espenlaub A. , Devaty Robert P. , Ohshima Takeshi , Choyke Wolfgang J.
Published: March 2011

Low doped epitaxial films of 4H SiC irradiated at 1 MeV and electron fluences of 1×1015 cm-2, 3×1015 cm-2 and 1×1016 cm-2 have been used to measure temperatures in two temperature intervals: 580°C to 640°C and 1220°C to 1320°C. Possible accuracy of the temperature measurements is judged to be better than 10 degrees Centigrade. Similar measurements should be possible from 100°C to 1500°C.
Iron-Related Defect Centers in 3C-SiC
Authors: Tsirimpis Thanos , Beljakova S. , Zippelius Bernd , Weber Heiko B. , Pensl Gerhard , Krieger M. , Nagasawa Hiroyuki , Kawahara Takamitsu , Hatta Naoki , Yagi Kuniaki , Uchida Hidetsugu , Kobayashi Motoki , Schöner Adolf
Published: March 2011

p-type 3C-SiC samples were implanted by iron (Fe) and investigated by means of deep level transient spectroscopy (DLTS). Corresponding argon (Ar) profiles with similar implantation damage were implanted in order to distinguish between iron-related defects and defects caused by implantation damage. Two donor-like iron-related centers were identified in p-type 3C-SiC.
Formation Mechanism of Stacking Faults in PVT 4H-SiC Created by Deflection of Threading Dislocations with Burgers Vector c+a
Authors: Dudley Michael , Wang Huan Huan , Wu Fang Zhen , Byrapa Sha Yan , Raghothamachar Balaji , Choi Gloria , Sanchez Edward , Hansen Darren M. , Drachev Roman , Mueller Stephan G. , Loboda Mark J.
Published: March 2011

Synchrotron White Beam X-ray Topography studies are presented of dislocation behavior and interactions in a new generation of seventy-six millimeter diameter, 4H-SiC wafers grown using Physical Vapor Transport under specially designed low stress conditions. Such low stress growth conditions have enabled reductions of dislocation density by two or three orders of magnitude compared to the lowest previously reported levels [1]. In this paper, detailed topography analysis will be presented of the deflection of threading dislocations with Burgers vectors of c and c+a onto the basal plane leading to reductions of the density of such dislocations down to levels of ~187 cm-2. The deflection of the latter type of dislocations produces complex faulted defect configurations and models for their creation are presented and discussed.
Electrical Activity of Structural Defects in 3C-SiC
Authors: Eriksson Jens , Roccaforte Fabrizio , Weng Ming Hung , Giannazzo Filippo , Lorenzzi Jean , Raineri Vito
Published: March 2011

Defects in cubic silicon carbide (3C-SiC) epilayers, that were grown using different techniques and on different substrates, were studied in terms of electrical activity and device limiting implications. An electrical characterization by conductive atomic force microscopy (C-AFM) showed that stacking faults (SFs) are normally the predominant type of defects that are electrically active at the semiconductor surface and, therefore, the most important defects that can affect the contact properties on these epilayers. It is also shown that an ultraviolet (UV) irradiation process can be used to suppress detrimental leakage currents passing through SFs that are carbon terminated at the semiconductor surface. Indeed, current-voltage characterization of Au/3C-SiC diodes showed a subsequent improvement of the Schottky behavior.
Etch Pits on 4H-SiC Surface Produced by ClF3 Gas
Authors: Habuka Hitoshi , Furukawa Kazuchika , Tanaka Keiko , Katsumi Yusuke , Iizuka Shinji , Fukae Katsuya , Kato Tomohisa
Published: March 2011

Selective etching on the surface of single-crystalline 4H-SiC was performed using ClF3 gas at 700 K and at atmospheric pressure in a cold wall reactor. The etch pits at the Si-face and C-face 4H-SiC surface may have relationship with the threading edge and screw dislocation.
Microscopic Examination of SiO2/4H-SiC Interfaces
Authors: Hatakeyama Tetsuo , Matsuhata Hirofumi , Suzuki T. , Shinohe Takashi , Okumura Hajime
Published: March 2011

SiO2/4H-SiC interfaces are examined by high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and spatially resolved electron energy-loss spectroscopy (EELS). HRTEM and HAADF-STEM images of SiO2/4H-SiC interfaces reveal that abrupt interfaces are formed irrespective of the fabrication conditions. Transition regions around the interfaces reported by Zheleva et al. were not observed. Using EELS, profiles of the C/Si and O/Si ratios across an interface were measured. Our measurements did not reveal a C-rich region on the SiC side of the interface, which was reported by Zheleva et al.
Crystal Growth of 4H-SiC on 6H-SiC by Traveling Solvent Method
Authors: Kusunoki Kazuhiko , Kamei Kazuhito , Yashiro Nobuyoshi , Moriguchi Koji , Okada Nobuhiro
Published: March 2011

We attempted the traveling solvent method (TSM) growth of SiC on 6H-SiC(0001) substrates using Si and Si-M (M=Ti, Cr and Dy) solvents at growth temperatures of 1500-1800°C. It was confirmed that 4H-SiC polytype was extremely stabilized in the highly carbon dissolved liquid phase. 4H-SiC growth on 6H-SiC, i.e. hetropolytype epitaxial growth, was observed only from Si-Dy solvent. The Dy content above 60at% was necessary to obtain 100% 4H-SiC polytype.
Impact of Surface Morphology on the Electrical Properties of Al/Ti Ohmic Contacts on Al-Implanted 4H-SiC
Authors: Frazzetto Alessia , Roccaforte Fabrizio , Giannazzo Filippo , Lo Nigro Raffaella , Bongiorno Corrado , Di Franco Salvatore , Weng Ming Hung , Saggio Mario , Zanetti Edoardo , Raineri Vito
Published: March 2011

This paper reports on the impact of the surface morphology on the properties of Ti/Al Ohmic contacts fabricated on Al-implanted 4H-SiC. In particular, the surface roughness of the Al-implanted regions after annealing at 1700 °C was strongly reduced by the using a protective carbon capping layer during annealing (the surface roughness decreased from 9.0 nm to 1.3 nm). In this way, also the morphology and the specific contact resistance of Ti/Al Ohmic contacts formed on the implanted regions could be improved. The electrical and morphological data were correlated with the structural properties of the reacted metal layer and of the metal/SiC interfacial region.
Improved MOS Interface Properties of C-Face 4H-SiC by POCl3 Annealing
Authors: Kotake Shinya , Yano Hiroshi , Okamoto Dai , Hatayama Tomoaki , Fuyuki Takashi
Published: March 2011

Metal-oxide-semiconductor (MOS) capacitors and MOS field-effect transistors (MOSFETs) were fabricated on C-face 4H-SiC with post-oxidation annealing in phosphorus- containing atmosphere. POCl3/N2 annealing at 1000 °C, which is an effective condition for Si-face, did not bring any improvement in the interface state density (Dit) for C-face due to additional oxide growth. We have developed a new process sequence suitable for C-face MOS structures. As a result, the Dit near the conduction band edge was drastically decreased by the developed process to less than 3x1011 cm−2eV−1. The field-effect mobility of C-face 4H-SiC MOSFETs was effectively increased to 37 cm2/Vs. We found that the incorporation of phosphorus atoms into the SiO2/SiC interface can improve MOSFET performance not only for the Si-face but also for the C-face.
Comparative Study on Metallization and Passivation Materials for High Temperature Sensor Applications
Authors: Daves Walter , Krauss A. , Le-Huu Martin , Kronmüller S. , Haeublein Volker , Bauer Anton J. , Frey Lothar
Published: March 2011

We investigated the performance of different metallization/passivation systems for high temperature applications. The metallizations comprised a 150 nm sputtered Pt or a 150 nm e-beam evaporated PtRh layer on Ti/TiN underlayers, respectively. The passivation coatings consisted of amorphous PECVD SiOx, of amorphous stress-reduced PECVD SiNy, and of a SiOx/ SiNy stack. For samples with SiOx and SiOx/ SiNy passivation layers the electrical properties changed after a short high temperature anneal at 600 °C but then remained stable during further annealing. This was attributed to the formation of PtTi alloys, which stabilized the metallization stack. In samples with SiNy passivation a significant Pt out-diffusion into the passivation layer was observed. This led to a degradation of the electrical and mechanical properties. The best performance was achieved with Pt-based metallizations and SiOx or SiOx/SiNy passivations.
Toward a Better Understanding of Ni-Based Ohmic Contacts on SiC
Authors: Tanimoto Satoshi , Miyabe Masanori , Shiiyama Takamitsu , Suzuki Tatsuhiro , Yamaguchi Hiroshi , Nakashima Shinichi , Okumura Hajime
Published: March 2011

There is still little consensus regarding why low contact resistivity is achieved when Ni on n-type 4H- and 6H-SiC is annealed at temperatures of more than above 950°C. The objective of this paper is to provide an answer concerning to this question. It is has been reported that even Ni-based contacts formed in the n++ region exhibited a steep reduction of contact resistivity in an annealing temperature range > 900°C. This effect reduction cannot be explained by the carbon vacancy induced donor model (Vc model) proposed by Han and his coworkers [Appl. Phys. Lett., Vol. 79, p. 1816 (2001)]. And, it is clarified that It was observed that the surface of substrates annealed at 1000°C was not covered with not Ni2Si but with a thin layer of NiSi. Finally, a plausible model is proposed that as the result of annealing at higher temperatures, results in the formation of the a NiSi/SiC system is builtat the substrate interface, resulting in significant reduction in low causing contact resistivity to be reduced significantly.
Thinning of 2-Inch SiC Wafer by Plasma Chemical Vaporization Machining Using Cylindrical Rotary Electrode
Authors: Sano Yasuhisa , Kato Takehiro , Aida Kohei , Yamamura Kazuya , Mimura Hidekazu , Matsuyama Satoshi , Yamauchi Kazuto
Published: March 2011

To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. In this study, we attempted to thin a 2-inch 4H-SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. By controlling the scanning speed of the table and optimizing the oxygen percentage in the CF4+O2+He mixture gas, a maximum removal rate of 0.56 μm/min was obtained over the entire wafer. Furthermore, the surface roughness was improved after thinning. Therefore, PCVM can be used as an effective method for thinning SiC wafers.