HealthSit: Designing Posture-Based Interaction to Promote Exercise during Fitness Breaks

This research was motivated by a desire to help office workers change their sedentary behavior because a prolonged sedentary posture increases the risks of developing musculoskeletal injuries and chronic diseases, thus threatening their physical and psychological well-being. Regular breaks involving low-effort physical activities are effective in reducing the adverse impacts of inactive behaviors. In this article, we present the design of a posture-based interactive system called HealthSit, which was developed to promote a short lower-back stretching exercise during work breaks. Through a within-subject study involving 30 office workers, the effectiveness of HealthSit in facilitating the stretching exercise was examined by making comparisons between an interaction-aided, a guided, and a self-directed exercise mode. We also used HealthSit as a research probe to investigate the interactivity of the system in enhancing user experience and the psychological benefits of the fitness breaks. Compared with the other two modes, the interaction-aided exercise mode significantly improved the quality of the stretching exercise and enhanced motivation and emotional state. These results confirm the effectiveness of HealthSit in supporting fitness breaks as a new workplace technology. Based on our study, a set of design implications have been derived for technology-assisted fitness work breaks.     

Short‐term effects in a reduced flow stretch: The case of the Antas River in South Brazil

The building of adduction channels (penstocks) that conduct water from reservoirs to turbines, which are located kilometres from the dam, is becoming common, optimizing the electricity generation in small dams. This design creates a river stretch with reduced discharge between the dam and the powerhouse. This study evaluates the short‐term impacts of the below‐dam decrease in river flow on fish assemblages. Samples were collected in the reduced flow stretch of the Castro Alves Hydropower Plant (Antas River, Rio Grande do Sul, Brazil) before the reservoir started operating (January 2008; mean discharge of 103.7 m³/s) and immediately after operation began (March 2008; mean discharge of 12.4 m³/s). Sampling was conducted in distinct habitats of the reduced flow stretch (slow waters—gillnets, sand beaches—seining nets, structured littoral—electrofishing, and fast waters—cast nets) with a strongly standardized effort. The attributes of the fish assemblages were not negatively affected by the flow reduction in any habitat sampled. However, distinct changes in the spatial structure were observed considering the different types of habitat predominantly used by the species, which represents an entire reorganization of the fish assemblages in the short term. It is fundamental that these short‐term aspects be considered in the licensing of hydropower plants in addition to the long‐term changes.     

Influence of trace Ca addition on texture and stretch formability of AM50 magnesium alloy sheet

The AM50, AM50–0.1Ca, AM50–0.3Ca and AM50–0.5Ca (wt.%) alloys were hot-rolled and their mechanical properties were determined for the purpose of investigating the effect of trace Ca addition on the texture and stretch formability of AM50 alloy. The results show that the addition of trace Ca can effectively modify the basal texture, which is characterized by the split of basal poles deviated from the normal direction (ND) after the hot rolling, while a broad spread of the basal planes toward the transverse direction (TD) after the annealing. Such change of the basal texture is related to the prior formation of massive compression twins and the decrease of the c/a ratio. Erichsen value increases from 2.25 to 4.21 mm with the increase of Ca content. The enhancement of stretch formability is ascribed to the weakened basal texture, which results in the increase of n-value and the decrease of r-value.     

对太子河流域煤田西部构造的认识

太子河流域煤田西部区（如本溪煤田和红阳煤田）为旋卷构造和伸展构造所控制；受太平洋板块对大陆边缘俯冲和大陆的仰冲先后产生旋扭和拉张形成上述两种构造类型，形成时间为晚侏罗世至早第三纪。     

后张法预应力筋理论伸长量精确计算方法探讨

对现行的JTJ041—2000公路桥涵施工技术规范预应力筋理论伸长量计算方法进行了理解与补充，并对由直线与曲线组成曲线筋张拉理论伸长量分段精确计算公式进行了推导，并提出了计算注意事项。     

护坡植物根系与岩体相互作用的力学特性

通过野外原位拉拔试验，选取灌木铁仔、黄荆、羊蹄甲和禾本科金发草等4种植物，按着生点基岩风化程度不同，测定植株的抗拔力、单根的力学特性和生物指标，研究护坡植物根系与岩体相互作用的力学特性。试验结果表明：受根系构型、受力单根的极限抗拉力及作用根系数量的影响，其单根极限抗拉力随根径的增加而增大，之间有很好的幂函数关系；随植物类型不同，单根的拉力-伸长率关系不同，且极限伸长率随着根径的不同而变化，羊蹄甲与黄荆的拉力-伸长率为线性关系，遵从胡克定律，而灌木铁仔的拉力-伸长率为对数函数关系，羊蹄甲与黄荆根系的极限伸长率表现为随根径增大而降低，铁仔根系的极限伸长率与根径的关系表现出单峰形曲线；在地茎或株高相近的情况下，灌木的抗拔力随基岩风化程度的加剧而增大，在基岩风化程度相近的情况下，抗拔力随地茎、株高及地下生物量的增加而增大，之间具有很好的指数关系；草本植物金发草生物指标与抗拔力之间无明显的数学关系，与基岩问的力学作用不明显。探明根系力学作用特性随植被与基岩类型改变而改变的特征，可为岩石边坡植被护坡工程构造设计及植被类型选择提供必要的参考。     

铝合金蓄能器壳体冷挤压成形多目标优化

以铝合金蓄能器壳体冷挤压为例,针对实际生产中筒壁存在缺陷现象,基于有限元软件DEFORM-3D和响应面法与多目标优化的NSGA-II相结合的方法对此进行多目标优化分析。首先将AA6061铝合金棒料进行室温拉伸实验获得应力应变数据,导入DEFORM-3D构建FEM模型。其次以凸模工作部分过渡圆角（X₁）、挤压速度（X₂）、摩擦系数（X₃）为优化变量建立关于挤压载荷（Y₁）和壳体零件表面损伤度（Y₂）的数学模型, 方差结果表明:模型精度较高能很好的描述2个优化目标对设计变量的响应,同时由3D响应面图可以直观分析挤压载荷与零件表面损伤度关于响应变量之间存在一定冲突性。为解决冲突,采用NAGA-II进行多目标优化,得到一组Pareto最优解;进而得到挤压成形合理的工艺参数范围: X₁为0.64~0.68 mm, X₂为5.8~6.2 mm/s,X₃=0.1。最后选用一组较优参数组合进行试验验证,结果表明工件成形性能与质量良好,仿真结果与试验结果具有较好的可靠性。      

200 MHz带宽基带信号发生器的设计与实现

介绍了基于FPGA的基带信号发生器设计方案,主要叙述了成型滤波以及任意重采样内插比等关键技术。该基带信号发生器不仅实现了标准数字调制格式的基带信号发生,而且通过FPGA内部的并行架构设计,实现了500 MHz的高速数据速率,I/Q带宽达到200 MHz。将其应用于矢量信号发生器中,既实现了PSK、ASK、FSK、MSK、QAM等标准数字调制格式的矢量信号,又实现了400 MHz矢量调制带宽。经过测试,在4 M码元速率的情况下,QPSK和512QAM调制格式的EVM分别达到0.7%和1.0%;400 MHz带宽的矢量调制信号频响小于1 dB。     

Physics‐based spectral sharpening through filter‐chart calibration

The spectral overlap of color‐sampling filters increases errors when using a diagonal matrix transform, for color correction and reduces color distinction. Spectral sharpening is a transformation of colors that was introduced to reduce color‐constancy errors when the colors are collected through spectrally overlapping filters. The earlier color‐constancy methods improved color precision when the illuminant color is changed, but they overlooked the color distinction. In this article, we introduce a new spectral sharpening technique that has a good compromise of color precision and distinction, based on real physical constraints. The spectral overlap is measured through observing a gray reference chart with a set of real and spectrally disjoint filters selected by the user. The new sharpening method enables to sharpen colors obtained by a sensor without knowing the camera response functions. Experiments with real images showed that the colors sharpened by the new method have good levels of color precision and distinction as well. The color‐constancy performance is compared with the data‐based sharpening method in terms of both precision and distinction. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 564–576, 2015