Disparity of a Seat Cushion and Its Influence on Postural Control

Properties of supporting surfaces of a seat have an influence on postural control. Centre of pressure (COP) displacement parameters reflect both the balance controlling process and movements of the centre of a mass of entire body. The subjects of the study were 9 healthy men. A seat cushion was examined with a 2-force platform setup. Force exertion at a seat pan and feet and COP displacement at a seat pan were measured to analyse postural control. Analysis of variance determined the differences in postural control depending on a cushion type among the subjects. Significant differences in COP displacement parameters were in COP trajectory length, medio-lateral COP displacement and COP velocity. The results of the study showed that foam cushion ensures better postural control.     

考虑油滴碰撞聚结的斜板除油过程模拟

考虑离散油滴在油田废水除油过程中发生的油滴碰撞聚结现象,模拟得出斜板除油器内全部油滴的动态信息,用于斜板除油器除油效率的计算.对矩形同向流斜板除油过程的模拟研究表明:油滴的碰撞聚结会增加斜板除油的效率;当废水的原始含油浓度增大时,斜板除油的效率会增大,碰撞聚结对除油效率提高的影响也越大;废水流动速度提高及斜板的倾斜角度增加均会使斜板的除油效率降低,但此时油滴碰撞聚结对除油效率的影响仍很明显.     

改善企业安全文化技术手段的应用研究

安全文化建设在我国企业界受到重视,但是缺乏安全文化建设明确、实用的方法.将安全文化定义为"影响企业安全业绩的核心要素",设计Likert量表、硬件设备和计算机管理系统对安全文化进行定量测量,根据测量结果设计有针对性的培训可以快速改善企业的安全文化.从实际的企业测量可知,通过三次测量、两次抽样培训,企业安全文化可以提高8%左右,说明测量和培训相结合的方法是企业安全文化改善的有效手段.     

Elevated CO2 facilitates C and N accumulation in a rice paddy ecosystem

Elevated CO2 can stimulate wetland carbon(C) and nitrogen(N) exports through gaseous and dissolved pathways, however, the consequent influences on the C and N pools are still not fully known. Therefore, we set up a free-air CO2 enrichment experiment in a paddy field in Eastern China. After five year fumigation, we studied C and N in the plant–water–soil system. The results showed:(1) elevated CO2 stimulated rice aboveground biomass and N accumulations by 19.1% and 12.5%, respectively.(2) Elevated CO2 significantly increased paddy soil TOC and TN contents by 12.5% and 15.5%, respectively in the 0–15 cm layer, and22.7% and 26.0% in the 15–30 cm soil layer.(3) Averaged across the rice growing period,elevated CO2 greatly increased TOC and TN contents in the surface water by 7.6% and 11.4%,respectively.(4) The TOC/TN ratio and natural δ15N value in the surface soil showed a decreasing trend under elevated CO2. The above results indicate that elevated CO2 can benefit C and N accumulation in paddy fields. Given the similarity between the paddies and natural wetlands, our results also suggest a great potential for long-term C and N accumulation in natural wetlands under future climate patterns.     

人口与经济发展对植被的影响研究

植被是陆地表面主要的覆盖物，也是许多地球系统过程的重要变量。人类活动对植被的影响在区域尺度上是显著的。以重庆市为例，使用滑动平均和SG滤波对SPOT/VGT NDVI时间序列数据进行了平滑处理，结合GDP和人口栅格化数据，从时间序列和空间相关场两个方面分析了植被与人类活动因子之间的时空相关性。结果表明，从1998到2005年，植被的分布和生长状况并没有随GDP和人口的持续增加而增加。在时间序列上，植被覆盖与GDP和人口之间总体上呈显著的负相关关系；在空间上，这种相关关系表现出了较强的异质性。空间相关场表明：较强的负相关主要发生在相对发达的主城区周围，反映了快速的经济发展和城市化使得植被面积和生产力降低；然而在偏远的山区，由于经济落后同时植被覆盖较少，出现了正相关。     

Quantification and valuation of ecosystem services in diverse production systems for informed decision-making

The empirical evidence of decline in ecosystem services (ES) over the last century has reinforced the call for ES quantification, monitoring and valuation. Usually, only provisioning ES are marketable and accounted for, whereas regulating, supporting and cultural ES are typically non-marketable and overlooked in connection with land-use or management decisions. The objective of this study was to quantify and value total ES (marketable and non-marketable) of diverse production systems and management intensities in Denmark to provide a basis for decisions based on economic values. The production systems were conventional wheat (Cwheat), a combined food and energy (CFE) production system and beech forest. Marketable (provisioning ES) and non-marketable ES (supporting, regulating and cultural) ES were quantified by dedicated on-site field measurements supplemented by literature data. The value of total ES was highest in CFE (US$ 3142 ha⁻¹ yr⁻¹) followed by Cwheat (US$ 2767 ha⁻¹ yr⁻¹) and beech forest (US$ 2328 ha⁻¹ yr⁻¹). As the production system shifted from Cwheat - CFE–beech, the marketable ES share decreased from 88% to 75% in CFE and 55% in beech whereas the non-marketable ES share increased to 12%, 25% and 45% of total ES in Cwheat, CFE and beech respectively, demonstrating production system and management effects on ES values. Total ES valuation, disintegrated into marketable and non-marketable share is a potential way forward to value ES and ‘tune’ our production systems for enhanced ES provision. Such monetary valuation can be used by policy makers and land managers as a tool to assess ES value and monitor the sustained flow of ES. The application of ES-based valuation for land management can enhance ES provision for maintaining the productive capacity of the land without depending on the external fossil-based fertilizer and chemical input.     

L型钢管混凝土芯柱耐火极限研究

火灾高温对结构安全有显著影响,为研究等肢L形钢管混凝土芯柱的耐火极限及其影响因素,利用ABAQUS软件建立合理的高温反应分析模型,在验证模型可靠性基础上,分析了荷载比、截面边长、长细比、荷载偏心率、含钢率等对L形钢管混凝土芯柱耐火极限的影响。研究结果表明:在一定参数范围内,荷载比和截面边长是构件耐火极限的主要影响参数,荷载比越小,截面边长越大,构件的耐火极限越高;长细比和荷载偏心率对其影响较大,长细比和荷载偏心率越小,构件的耐火极限越高;含钢率对其影响不显著。结果可为异形钢管混凝土芯柱的抗火安全设计提供参考。     

本煤层瓦斯抽采渗流模型及数值模拟

在研究煤层瓦斯抽采时,假定煤岩为具有孔隙裂隙的双重介质,在运动方程、连续性方程和辅助方程基础上,以煤岩体应变为耦合媒介建立了考虑裂隙瓦斯渗流、微孔隙吸附瓦斯解吸扩散和煤岩变形的渗流模型.借助多物理场分析软件COMSOL Multiphysics,将模型转化为偏微分方程组,结合沙曲矿24305工作面瓦斯赋存条件进行分析求解.结果表明,进行煤层瓦斯预抽时,抽采初期瓦斯压力下降较快,抽采孔间距对抽采效果影响比较显著,距离抽采孔越远瓦斯压力下降越慢,抽采时瓦斯渗流速度变化可分3个阶段.参考模拟结果现场布置孔距为6m的顺层钻孔,抽采稳定时瓦斯纯量达5～7 m3/min,抽采效果比较理想.     

黄壤表面电场作用下Cu~(2+)与Zn~(2+)的吸附/解吸动力学研究

利用静态恒流法研究了黄壤表面电场作用下Cu2+与Zn2+的吸附/解吸动力学.结果发现:考虑黄壤表面电场作用下,Cu2+和Zn2+的吸附实验呈现初期强吸附作用下的零级动力学过程和一定时间之后弱吸附作用下的一级动力学过程,与理论预期一致;在Cu2+和Zn2+的解吸实验中,只有前期出现了弱吸附作用下的一级动力学过程,实验结果与理论预期存在差别,原因在于专性吸附的Cu2+、Zn2+很难被解吸下来;在交换/吸附实验中,Cu2+的吸附速率值和平衡吸附量均大于Zn2+,且Cu2+-K+体系的表面电化学参数φ0、σ0、E0均大于Zn2+-K+体系中的对应值,证明了黄壤颗粒表面对Cu2+的吸附作用强于Zn2+;在交换/解吸实验中,Zn2+的解吸速率值和平衡解吸量均大于Cu2+,Zn2+-K+体系的表面电化学参数φ0、σ0、E0均大于Cu2+-K+体系中的对应值,证明Zn2+-K+体系中Zn2+的解吸作用比Cu2+-K+体系中的Cu2+解吸作用强.     

A fouling suppression system in submerged membrane bioreactors using dielectrophoretic forces

A novel method was developed to suppress membrane fouling in submerged membrane bioreactors. The method is based on the dielectrophoretic (DEP) motion of particles in an inhomogeneous electrical field. Using a real sample of biomass as feed, the fouling-suppression performance using DEP with different electrical field intensities (60–160 V) and different frequencies (50–1000 Hz) was investigated. The fouling-suppression performance was found to relate closely with the intensity and frequency of the electrical field. A stronger electrical field was found to better recover the filtrate flux. This is because of a stronger DEP force acting on the biomass particles close to the membrane's surface. Above an intensity and frequency value of 130 V and 1 kHz, respectively the permeate flux was reduced due to an electrothermal effect.