一种手腕同步驱动码垛机械手设计

根据啤酒箱码垛系统工艺流程要求,对码垛机械手运动轨迹进行了设计,在此基础上建立码垛机械手模型;设计了一种手腕同步驱动机构,对同步驱动机构进行动力学分析并对驱动转矩参数进行优化。最后,利用ADAMS软件对该机构进行仿真分析。     

SUPERDISLOCATION DISSOCIATION IN INTERMETALLIC COMPOUND Ni 3Al

１　ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅａｎｏｍａｌｏｕｓｉｎｃｒｅａｓｅｏｆｆｌｏｗｓｔｒｅｓｓｗｉｔｈｉｎｃｒｅａｓｉｎｇｔｅｍｐｅｒａｔｕｒｅｉｎＬ１２ｏｒｄｅｒｅｄＮｉ３Ａｌｈａｓｒｅｃｅｉｖｅｄｇｒｅａｔｉｎｔｅｒｅｓｔｂｅｃａｕｓｅｏｆｉｔｓｔｈｅｏｒｅｔｉｃａｌｉｍｐｏｒｔａｎｃｅｉｎｕｎｄｅｒｓｔａｎｄｉｎｇｍｅｃｈａｎｉｃａｌｂｅｈａｖｉｏｒｓｏｆｍａｎｙｉｎｔｅｒｍｅｔａｌｌｉｃｃｏｍｐｏｕｎｄｓ．Ｕｐｔｏｎｏｗｔｈｅｒｅｈａｖｅｂｅｅｎｓｅｖｅｒａｌｍｏｄｅｌｓｐｒｏｐｏｓｅｄ…     

Void Formation in Magnesium Aluminate Spinel Heavily Irradiated with Fast Neutrons

Single crystals of magnesium aluminate spinel (MgAl₂O₄) were heavily irradiated to fission neutron fluences from ?1 × 10²⁶ to ?2×10²⁷ n/m² (E>0.1 MeV) at 658 and 1,023 K in FFTF (Fast Flux Test Facility) to investigate their microstructural evolution under heavy neutron irradiation and to confirm their previously observed resistance to void swelling. At 658 K no voids were observed up to 2.29 × 10²⁷ n/m², but 1/4[110] interstitial loops were formed. These loops changed their habit planes from (111) to (110) with increasing neutron fluence. At 1,023 K the 1/4[110] type of interstitial loops grew to form stacking fault netuorks composed of stacking faults on each of the six equivalent (110) planes. Tiny voids were also observed to form preferentially on or near stacking faults after 1.37×10²⁷ n/m². A limited number of very small cavities, contributing to a volumetric swelling of only 0.07%, were also observed in the crystal matrix after 2.17×10²⁷ n/m². The possible mechanisms of suppression of void formation in MgAl₂O₄ are discussed.     

Fuelwood as an energy source for the commercial cooking sector – An overview analysis focused in the city of São Paulo,Brazil

This paper provides an overview analysis of fuelwood utilization in the commercial cooking sector. Cultural, market and logistic factors that may weaken the explanatory power of the energy ladder hypothesis are highlighted. Additionally, gender issues and health and environmental aspects related to fuelwood use in cities are explored. The analysis is developed as from the viewpoint of the use of different fuels for cooking in urban areas, focusing on commercial establishments. Evidences were observed in the pizza market in the city of São Paulo, Brazil, demonstrating that consumer expectations, expressed by means of classical market pressure mechanisms, can markedly influence this commercial cooking niche and consist in an important driving force for its energy choice. The city has the second largest pizza market in the world, characterized by the commercialization of 40 million units of the product per month in over 5000 commercial establishments. Interviews conducted in 270 of these establishments reveal that 88% use fuelwood ovens despite its lower practicality and wide availability of modern energy options such as electricity and liquefied petroleum gas (LPG). The work validates the fuel stacking model, according to which energy diversification – and not substitution –, results from economic development, urbanization and/or a population income growth.     

Modeling motivation and habit in driving behavior under lifetime driver's license revocation

The purpose of the present study was to verify the motivational factors underlying the theory of planned behavior (TPB) predicting the driving behavior of lifetime driving license revoked offenders. Of a total of 639 drivers whose licenses had been permanently revoked, 544 offenders completed a questionnaire constructed to measure attitudes toward behaviors, subjective norms, perceived behavioral control, behavioral intentions (the key constructs of the TPB), and previous driving habit strength. The finding of the study revealed that an offenders’ driving behavior after a lifetime license revocation was significantly correlated to behavioral intention (R = 0.60, p < 0.01), perceived behavioral control (R = 0.61, p < 0.01), previous driving habit (R = 0.44, p < 0.01), and attitude (R = 0.41, p < 0.01). There was no evidence that subjective norms including road regulation, society ethics, and people important to offenders had an influence on driving behavior (R = 0.03). Low driving habit strength offenders are motivated to drive because of behavioral intention, whereas strong driving habit strength offenders are motivated to drive because of perceived behavioral control. Previous driving habit strength is a moderator in the intention–behavior relationship. The model appeared successful when previous habits were weak, but less successful when previous habits were strong.     

A spatial generalized ordered response model to examine highway crash injury severity

This paper proposes a flexible econometric structure for injury severity analysis at the level of individual crashes that recognizes the ordinal nature of injury severity categories, allows unobserved heterogeneity in the effects of contributing factors, as well as accommodates spatial dependencies in the injury severity levels experienced in crashes that occur close to one another in space. The modeling framework is applied to analyze the injury severity sustained in crashes occurring on highway road segments in Austin, Texas. The sample is drawn from the Texas Department of Transportation (TxDOT) crash incident files from 2009 and includes a variety of crash characteristics, highway design attributes, driver and vehicle characteristics, and environmental factors. The results from our analysis underscore the value of our proposed model for data fit purposes as well as to accurately estimate variable effects. The most important determinants of injury severity on highways, according to our results, are (1) whether any vehicle occupant is ejected, (2) whether collision type is head-on, (3) whether any vehicle involved in the crash overturned, (4) whether any vehicle occupant is unrestrained by a seat-belt, and (5) whether a commercial truck is involved.     

Structural characteristics of antifolate dihydrofolate reductase enzyme interactions

The ubiquitous enzyme dihydrofolate reductase (DHFR) is responsible for the reduction of 5,6-dihydrofolate to 5,6,7,8-tetrahydrofolate in an NADPH-dependent manner. It is also a key pharmacological target for the treatment of cancer, as well as bacterial and opportunistic pathogenic infections. Interest in the design of potent and selective antifolate inhibitors has made DHFR one of the most studied enzymes, in particular its structural and biochemical properties. This review surveys more than 129 DHFR solution and crystal structures currently (02/07) reported in the Protein Data Bank representing 15 species of enzyme. Comparison of these DHFR sequences shows that while there is a high sequence homology among vertebrate species (75–95%), there is only about 30% homology between vertebrate and bacterial species. Despite the highly conserved nature of the ligand and cofactor binding sites, DHFR can bind a wide range of compounds that can have a high degree of flexibility. The enzyme itself can also undergo ligand-induced conformational changes that reflect its catalytic mechanism of action. Mechanistic questions can now be addressed with the structural data available for atomic resolution enzyme complexes as well as from neutron diffraction data that have recently become available. These data provide new insight into the design of novel inhibitors that can target specific species with high selectivity of binding.     

The use of partial observations,partial models and partial residuals to improve the least-squares refinement of crystal structures

Some common misconceptions in least-squares crystal structure refinement can be resolved by recasting the usual equations in terms of partial observations, partial models and partial residuals. An observation has components that are determined by an initial calculated model and each component, including the background, is considered to be a partial observation of the total observation. The use of partial observations, partial models and partial residuals allows various misconceptions to be identified and suggests ways to improve the least-squares methodology. A fixed component of a model of peak-plus-background does not fix its contribution to the observation for each refinement step. A covariance matrix obtained from the least-squares equations enables a standard uncertainty to be estimated for any function of the structural parameters. An oversight in current refinement methods is the failure to estimate the variances of components of the calculated model of an observation and the fraction of each residual associated with the various features of a refinement. A distinction should be made between least-squares equations for model development and least-squares equations for the estimation of a variance–covariance matrix. Methods for detecting systematic errors are discussed. A proposed look-ahead option for model development includes the assessment of the ability to refine parameters. For pseudo-symmetric structures, the use of symmetrized combinations of pseudo-equivalent intensities allows the reliability of minor components of the intensities to be better evaluated. It is also shown how homometric structure solutions can result from the use of powder diffraction data or equally twinned crystals.     

L12相间有序畴界成分的微观相场研究

利用微观相场模型研究了有序畴界结构、合金成分和弹性应变能对Ni75AlxV25-x合金中L12-Ni3Al相间有序畴界成分的影响规律。结果表明:L12相间形成的3种有序畴界中,在(100)//(200)·[001]处,Ni的贫化程度最小,Al的贫化程度最大,V的偏聚程度最大;在(200)//(200)处,Ni的贫化程度最大,Al的贫化程度最小,V的偏聚程度最小。随着合金中Al浓度的增加,3种有序畴界处Ni的浓度降低,Al的浓度升高,V的浓度降低。弹性应变能使得L12相间3种有序畴界处Ni和Al的浓度升高,V浓度降低。但弹性应变能对(200)//(200)·[001]和(100)//(200)·[001]成分的影响较大,对(200)//(200)成分的影响则相对较小。     

尾矿干堆工艺技术应用分析

介绍尾矿干堆工艺特点及要求,分析尾矿干堆工艺与湿堆工艺的区别及优缺点,着重阐述尾矿干堆工艺中应特别注意的几项问题。通过介绍与分析云南地区几个尾矿干堆工程应用实例,归纳该地区尾矿干堆工艺的特点,可为区域类似工程实践提供一定的指导和参考。