Identifying the Magnitude and Location of a Load on a Slender Beam Using a Strain Gauge Based Force Transducer

A unique strain gauge based method is developed to identify the magnitude and location of a load on a slender beam with variable cross sections, and pinned, firm rest, soft rest, pinned‐fixed, and fixed boundary conditions. Four uniaxial strain gauges are mounted to the bottom surface of the beam, and the bending moment diagram of the beam can be constructed using measured strains on the beam. By combining individually scaled strain gauge outputs, the magnitude and location of the load can be accurately identified. The strain gauge based force transducer methodology is experimentally validated on prismatic beams with firm rest, soft rest, firm rest‐fixed, and fixed boundary conditions, and a continuously tapered beam with rest boundary conditions. The force transducer methodology is independent of the boundary conditions of the beam, and the error from strain gauge drift due to uniform thermal expansion on a prismatic beam can cancel out.     

Effects of psychosocial and individual factors on physiological risk factors for upper extremity musculoskeletal disorders while typing

Psychosocial factors are hypothesized to contribute to work-related musculoskeletal disorder (WMSD) development, although previous research has been largely epidemiological or has focused primarily on the shoulders, back and neck. The objective of this study was to quantify the effects of mental workload and time pressure on perceived workload and physiological responses of the distal upper extremity. A total of 18 typists completed nine 5-min typing sessions representing three levels of time pressure and mental workload. Levels were manipulated by adjusting typing speed and by requiring participants to perform arithmetic tasks while typing. Outcomes were measured in muscle activation levels, wrist postures and movements, key strike force and subjective assessments of workload. In general, increased time pressure increased muscle activation, key strike force and wrist deviations; and increased mental workload increased key strike force. Mental workload and time pressure mediated physical risk factors during typing to increase WMSD risk for the distal upper extremity.     

一种新型粘合力测试方法探讨及其应用

目前,漆包线行业内尚无测试?0.05 mm及以下漆包自粘线粘合力的方法。针对这一情况,本文提出了一种适用于测试微细自粘线热粘合力的方法,即扭绞法。实践证明,该方法在生产中可以快速、简便、准确地测试微细自粘线的热粘合力。     

Monitoring by Remote Sensing of Habitat Quality Changes in Xianyang City

With the accelerating process of society，economy and urbanization，land use and landscape changes have gradually become important to make effects on regional habitat quality.It is necessary to further investigate those two effects，the result of which can provide a scientific basis for regional habitat conservation and reasonable utilization of land，then will be of great importance in habitat protection and development of the region.In this paper，the study area was located in Xianyang city，Shaanxi Province，which had the frequent human activities and obvious land use changes.Based on the classification of land use data which interpreted by remote sensing，supported by ArcGIS software，the land use transfer matrix of Xianyang from 2000 to 2010 was analyzed.Landscape metrics were calculated by the Fragstats software，which represented for the landscape pattern changes and spatial characteristics.The InVEST model was selected to evaluate habitat quality in study area.The habitat quality changes was monitored.The results indicate that the integrated land use dynamics of Xianyang city is 2.34%，and the changes of land use rate is slow.The main transition from cultivated land and grassland to forest and construction land，which cause the area of first two land use types reduced，and the latter two types increased.The degree of fragmentation and the complexity of structure in landscape are higher than before.Habitat quality improved slightly，and its overall spatial pattern is that central and north areas are relatively higher than the south.Area percentage of excellent，good and poor grades increase，while the habitat quality of medium grade significantly decline.Among 14 districts and counties of habitat quality in Xianyang city，Xunyi County is the best，and the improved magnitude of Liquan county is the most significant.The main driving force of habitat quality change is the transform of land use pattern.Therefore，the relevant departments of Xianyang city should continue to implement the ecological protection measures，and increase the intensity about the protection and management of environment.Thereby to promote the coordinated sustainable development of land use and habitats.     

Woody Breast短期贮藏中肉质的变化

为研究近年来速生型肉鸡鸡胸肉硬度缺陷(woody/wooden breast,WB)俗称"木质肉"在短期贮藏中生肉肉质参数的变化。实验选取68只42日龄Cobb 500肉鸡作为研究对象,经宰杀后人工分级为低(normal,NORM)、高(severe,SEV)两组(n=34只/组)。在不同时间节点下(1、3、8 d)对所有样本测定质量、挤压力(compression force,CF)、滴水损失(drip loss,DL)、肌节长度(sarcomere length,SL)及肉破碎化指数(gravimetric fragmentation index,GFI)。对所有参数进行组间(不同WB等级间,不同时间节点)显著性分析,同时对各参数与WB等级间进行相关性分析。结果表明:SEV样本质量、CF、SL、GFI在贮藏时间节点处都显著高于NORM样本(P0.05),DL在1 d时NORM与SEV间无差异,在3~8 d时显著上升(P0.05)。CF、SL、GFI在1~3 d时,所有样本都显著减小(P0.05),3~8 d时CF无显著变化(P0.05),SL、GFI在NORM样本间无差异但在SEV样本间继续减小(P0.05)。相关性分析表明,CF、累积DL与WB等级极显著相关(P0.01),SL、GFI随时间变化与WB硬度减小存在联系。综上可知,SEV生肉肉质较NORM差,WB硬度随贮藏时间变长而减小,但其生肉品质并不会发生改变,因此对WB检测应在宰杀当天在线进行,且WB硬度由多种原因共同作用导致。     

Effects of annealing on the polymer solar cells based on CdSe-PVK electron acceptor

CdSe-poly(N-vinylcarbazole) (CdSe-PVK) nanocomposite was synthesized and utilized as the electron acceptor in the active layer of polymer solar cells. The photovoltaic properties of the polymer solar cells based on poly(3-hexylthiophene) (P3HT):CdSe-PVK as the active layer were investigated in detail. The effects of annealing temperature (100-200 °C) and time (5-60 min) on the device performance were studied. At annealing temperature of 150 °C for 30 min, the device demonstrated an optimal efficiency of 0.235% under AM 1.5 (100 mW cm⁻²) solar simulated light irradiation. The improved efficiency under the optimal conditions was confirmed by the highest light harvest in UV-vis spectra due to the increased crystallinity of P3HT after thermal annealing. Photoluminescence of these devices also exhibited that the quench effect increases with the increasing of annealing temperature, indicating that the charge separation between electron-donating (P3HT) and electron-accepting (CdSe-PVK) molecules was increased after heat treatment. Atomic force microscopy (AFM) images showed that the phase segregation and 3D interpenetrating networks of P3HT:CdSe-PVK were responsible for the enhancement of the device efficiency.     

优化和控制大型变压器铁心夹紧力降低本体噪声

讨论了优化和控制大型变压器铁心夹紧力及降低本体噪声的要求。     

桁架因高度不同而内力变化的优化设计

通过马钢股份公司三钢轧总厂全连铸工程46m长钢桁架的设计,按照桁架高度5m和6m的两种方案,分别计算出桁架因高度不同而内力变化的各项设计指标,从而选出优化设计方案.     

Cell morphology and focal adhesion location alters internal cell stress

Extracellular mechanical cues have been shown to have a profound effect on osteogenic cell behaviour. However, it is not known precisely how these cues alter intracellular mechanics to initiate changes in cell behaviour. In this study, a combination of in vitro culture of MC3T3-E1 cells and finite-element modelling was used to investigate the effects of passive differences in substrate stiffness on intracellular mechanics. Cells on collagen-based substrates were classified based on the presence of cell processes and the dimensions of various cellular features were quantified. Focal adhesion (FA) density was quantified from immunohistochemical staining, while cell and substrate stiffnesses were measured using a live-cell atomic force microscope. Computational models of cell morphologies were developed using an applied contraction of the cell body to simulate active cell contraction. The results showed that FA density is directly related to cell morphology, while the effect of substrate stiffness on internal cell tension was modulated by both cell morphology and FA density, as investigated by varying the number of adhesion sites present in each morphological model. We propose that the cells desire to achieve a homeostatic stress state may play a role in osteogenic cell differentiation in response to extracellular mechanical cues.     

Understanding interaction mechanisms between pentlandite and gangue minerals by zeta potential and surface force measurements

Understanding the interaction between valuable and gangue minerals is of both fundamental and practical importance in the field of flotation. In this study, we investigated the interactions between valuable (i.e. pentlandite) and gangue minerals (i.e. serpentine, olivine, and magnesite) in an aqueous solution by directly measuring the zeta potential distributions. In addition, interaction force measurements using an atomic force microscope (AFM) were performed between a silicon nitride tip and gangue mineral surfaces, and the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory was used to fit the interaction force between the silicon nitride tip and gangue mineral surfaces. In the case of serpentine and pentlandite mixture system at pH 10.1, only a single zeta potential distribution was obtained, as compared to two distinct distributions for the two individual minerals, indicating an attractive interaction is present between the two minerals. For olivine and pentlandite mixture system, a single distribution with two distinct spikes was obtained in the zeta potential distribution of the mixture, indicating repulsive interaction between the two minerals. Similarly, a single distribution with two distinct spikes was also observed in the zeta potential distribution of magnesite and pentlandite mixture system, indicating repulsive interaction between the two minerals. Repulsive interaction between silicon nitride tip and olivine surface, and slight attractive interaction between silicon nitride tip and magnesite surface, were observed and consistent with the DLVO model. The zeta potential and AFM force measurements show good agreement regarding the surface charge properties and interactions of the minerals, and provide complementary information and new insights into the interaction mechanism of valuable and gangue minerals.