Weight distribution symmetry during the sit-to-stand movement of unilateral transtibial amputees

This study characterises weight distribution symmetry between the intact and amputated limbs of unilateral transtibial amputees during a sit-to-stand movement. A total of 12 amputees and 12 age-matched, non-amputees performed the activity for two conditions – rising with and without chair arm-rest assistance. The sit-to-stand movement was divided into five events: Pre-Ascent; Ascent Initiation; Seat-Off; Deceleration; Standing. Symmetry in ground reaction forces between limbs was calculated at each event together with the rise time. Results indicate that during the course of the movement, amputees increased loading of the intact limb by approximately 27%, resulting in a significant asymmetry at seat-off and deceleration events. Non-amputees loaded the dominant limb more than the non-dominant limb throughout the activity but did not exhibit substantial weight shifts. Weight distribution symmetry was not significantly different between the two rising conditions in either population. Amputees had significantly longer rise times than non-amputees only while rising without arm-rest assistance.

Statement of Relevance: Sit-to-stand movements are performed frequently every day. Incorrect movement biomechanics caused by musculoskeletal impairments can lead to reduced functional independence and secondary co-morbidities. This study defines five events of a sit-to-stand cycle and is the first to address asymmetries of transtibial amputees, providing ergonomic insights for clinical assessment and intervention.     

Impression creep behavior of Al–1.9%Ni–1.6%Mn–1%Mg alloy

In the present study, microstructure and creep behavior of an Al–1.9%Ni–1.6%Mn–1%Mg alloy were studied at temperature ranging from 493 to 513 K and under stresses between 420 and 530 MPa. The creep test was carried out by impression creep technique in which a flat ended cylindrical indenter was impressed on the specimens. The results showed that microstructure of the alloy is composed of primary α(Al) phase covered by a mantle of α(Al)+Ni₃Al intermetallic compound. Mn segregated into Al_xMn_yNi_z or Al₆Mn phases distributed inside the matrix phase. It was found that the stress exponent, n, decreases from 5.2 to 3.6 with increasing temperature. Creep activation energies between 115 kJ/mol and 151 kJ/mol were estimated for the alloy and it decreases with rising stress. According to the stress exponent and creep activation energies, the lattice and pipe diffusion- climb controlled dislocation creep were the dominant creep mechanism.     

饱和土体固结压缩和蠕变的热力学本构理论及模型分析

岩土热力学模型（thermodynamic soil model,TSM）是基于颗粒固体的非平衡态热力学理论,建立的一种崭新的描述岩土力学问题的统一理论模型。该模型引入“颗粒熵运动”和“弹性弛豫”,对土体颗粒层次的耗散机制进行了合理地考虑,这些使得模型能够更深入描述土体的变形和能量耗散机理,从而能够在统一理论框架中描述岩土体复杂多变的物理力学行为。基于该理论模型,研究了饱和土体的固结压缩和蠕变问题,分析了加载速率、应力/应变路径和非单调荷载等因素的影响规律。模拟结果表明：模型具有描述复杂条件下的饱和土体的固结压缩和蠕变特性的能力,具有较高的理论和工程应用价值。     

Rumination activity of dairy cows in the 24 hours before and after calving

Monitoring rumination behavior serves multiple purposes in feeding and herd management of dairy cows. The process of calving is a major event for cows, and a detailed understanding of alterations in behavioral patterns of animals in the time around calving is important in calving detection. The objective of this study was to describe the short-term changes in rumination patterns in dairy cows immediately before and after parturition. In total, 17 cows were fitted with rumination sensors that were able to monitor rumination time, number of rumination boli, and number of rumination jaw movements. Rumination time was decreased in the last 4 h antepartum and in the first 8 h postpartum. Cows stopped ruminating 123 ± 58 min (mean ± standard deviation) before calving and resumed ruminating 355 ± 194 min after calving. The number of rumination jaw movements and boli per day were decreased in the 24-h period postpartum. Rumination rate, the number of rumination jaw movements per rumination minute, and the number of boli per rumination minute changed little around calving. The calving event primarily influenced the duration and frequency of various rumination characteristics but not rumination intensity. Among detected characteristics, rumination time showed the greatest potential for monitoring of calving events.     

On a rigid inclusion pressed between two elastic half spaces

A solution to the problem of a rigid cylindrical inclusion pressed between two elastic half spaces is obtained using the distributed dislocation technique. The solution is compared with previously published analytical and numerical results for a rigid cylindrical inclusion bounded by two parabolic arcs with rounded corners. A simplified solution to the problem based on the classical contact theory and well-known results for crack problems is also suggested and validated. The simplified solution agrees well with analytical results in the case when the length of the opening around inclusion is much larger than the length of the contact zone.     

Probing of human implicit intent based on eye movement and pupillary analysis for augmented cognition

The ultimate purpose of augmented cognition is to enhance human cognitive abilities, which are intrinsically limited. To enhance limited human cognitive abilities, we developed a human augmented cognition system that can offer appropriate information or services by actively responding to the user's intention. This article mainly describes a framework for probing human implicit intentions for the purpose of augmented cognition. The type of user intention, either task‐free human implicit intention or task‐oriented human implicit intention, can be predicted based on fixation count, fixation length, and pupil size variation induced by eye response. Further, these features are used to detect the transition point between task‐free human implicit intention and task‐oriented human implicit intention. Maximum a Posteriori in Naïve Bayes classification model is used for selecting relevant query keywords to search and retrieve specific information from a personalized knowledge database. The experimental results show that the proposed human intention recognition and probing models are suitable for achieving the goal of augmented cognition. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 114–126, 2013     

发射药连续化生产模型研究

为研究发射药连续化生产技术,以发射药溶塑制造工艺为背景,建立发射药连续化生产模型.利用制造发射药的物料在工序中的流动速度,研究了发射药连续化生产各工序物流匹配关系和工艺设备匹配关系,通过对发射药连续化生产工艺单元物料流速进行分析,建立了发射药连续化生产线物料流速为特征的发射药连续化生产模型,并以某种发射药制造为例研究发射药连续化生产模型在该发射药连续化生产中的应用.结果表明:该模型可用于发射药连续化生产工艺优化,解决离散工序与连续工序的连续化结合问题.     

基于空间多轨迹运动的大型机械道具设计

为提供2010年广州亚运会开幕式上《海洋之舟》在演绎中所需要的设备,设计了基于机械原理的道具帆船,展现了帆船在海洋波涛里乘风破浪和摆转倾斜的生动情景,正式运行获得了圆满成功,证实了该设计的合理性。     

High Hole Mobility of GaSb Relaxed Epilayer Grown on GaAs Substrate by MOCVD through Interfacial Misfit Dislocations Array

The structural property of GaSb epilayers grown on semi-insulator GaAs (001) substrate by metalorganic chemical vapor deposition (MOCVD) using Triethylgallium (TEGa) and trimethylantimony (TMSb),was investigated by variation of the Sb:Ga (V/III) ratio.An optimum V/III ratio of 1.4 was determined in our growth conditions.Using transmission electron microscopy (TEM),we found that there was an interfacial misfit dislocations (IMF) growth mode in our experiment,in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg.IMF array at the hetero-epitaxial interface.The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10 μm×10 μm scan from atomic force microscopy (AFM) result.The best hole density and mobility of 300 nm GaSb epilayer are 5.27×10 6 cm 3 (1.20×10 6) and 553 cm 2 ·V 1 ·s 1 (2340) at RT (77 K) from Hall measurement,respectively.These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy (MBE) technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.