Temperature cycling and its effect on mechanical behaviours of highporosity chalks

Temperature history can have a significant effect on the strength of water-saturated chalk.In this study,hydrostatic stress cycles are applied to understand the mechanical response of chalk samples exposed to temperature cycling between each stress cycle,compared to the samples tested at a constant temperature.The total accumulated strain during a stress cycle and the irreversible strain are reported.Chalk samples from Kansas(USA)and Mons(Belgium),with different degrees of induration(i.e.amount of contact cementation),were used.The samples were saturated with equilibrated water(polar)and nonpolar Isopar H oil to quantify water weakening.All samples tested during 10 stress cycles with varying temperature(i.e.temperature cycled in between each stress cycle)accumulated more strain than those tested at constant temperatures.All the stress cycles were performed at 30℃.The two chalk types behaved similarly when saturated with Isopar H oil,but differently when saturated with water.When saturated with water,the stronger Kansas chalk accumulated more total strain and more irreversible strain within each stress cycle than the weaker Mons chalk.     

Animations showing Lego manipulative tasks: Three potential moderators of effectiveness

Evidence suggests that transient visual information, such as animations, may be more challenging to learn than static visualizations. However, when a procedural-manipulative task is involved, our evolved embodied cognition seems to reverse this transitory challenge. Hence, for object manipulative tasks, instructional animations may be more suitable than statics. We investigated this argument further by comparing animations with statics using a Lego task shown to university students, by examining three potential moderators of effectiveness: (a) the environment of manipulation (virtual or physical), (b) the quality of visual information (focused or unfocused), and (c) the presence of hands (no hands or with hands). In Experiment 1 we found an advantage of animation over statics, and no differences among the environments. In Experiment 2, we again observed an animation advantage, a small advantage of focused static information compared to unfocused static information, and a positive effect of not showing the hands.     

Alkali catalyzed liquefaction of corncob in supercritical ethanol–water

Corncob liquefaction in supercritical ethanol–water was performed with and without the addition of an alkali catalyst by direct addition or biomass impregnation in a 250-cm³ batch reactor. The effects of temperature, solvent and alkali addition on the biomass conversion level and oil yield were investigated to find the optimum condition. For non-catalytic liquefaction using a 1:1 (v/v) ethanol: water ratio, a maximum oil yield and conversion level of 49.0% and 93.4%, respectively, were obtained at 340 °C. For alkali catalytic liquefaction, the oil yield with KOH addition (57.5%) was higher than that from KOH-impregnated corncob liquefaction (43.3%). The oil from liquefaction with KOH addition had higher heating value (26.7–35.3 MJ kg⁻¹) than the corncob (19.1 MJ kg⁻¹). The dominant components of the obtained oil were found by GC/MS analysis to be aldehyde, ester, phenol derivatives and aromatic compounds.     

Reducing numerical dissipation in smoke simulation

Numerical dissipation acts as artificial viscosity to make smoke viscous. Reducing numerical dissipation is able to recover visual details smeared out by the numerical dissipation. Great efforts have been devoted to suppress the numerical dissipation in smoke simulation in the past few years. In this paper we investigate methods of combating the numerical dissipation. We describe visual consequences of the numerical dissipation and explore sources that introduce the numerical dissipation into course of smoke simulation. Methods are investigated from various aspects including grid variation, high-order advection, sub-grid compensation, invariant conservation, and particle-based improvement, followed by discussion and comparison in terms of visual quality, computational overhead, ease of implementation, adaptivity, and scalability, which leads to their different applicability to various application scenarios.     

The benefit of being physically present: A survey of experimental works comparing copresent robots,telepresent robots and virtual agents

The effects of physical embodiment and physical presence were explored through a survey of 33 experimental works comparing how people interacted with physical robots and virtual agents. A qualitative assessment of the direction of quantitative effects demonstrated that robots were more persuasive and perceived more positively when physically present in a user׳s environment than when digitally-displayed on a screen either as a video feed of the same robot or as a virtual character analog; robots also led to better user performance when they were collocated as opposed to shown via video on a screen. However, participants did not respond differently to physical robots and virtual agents when both were displayed digitally on a screen – suggesting that physical presence, rather than physical embodiment, characterizes people׳s responses to social robots. Implications for understanding psychological response to physical and virtual agents and for methodological design are discussed.     

宁夏宁东供水工程主机设备形式参数选择与国际招标

宁东供水工程供水水泵共有卧式和立式离心泵2种方案可供选择,也是工程论证时争论的焦点,经综合比较及主机设备的国际招标,最终确定了奥地利安德里兹公司的卧式双吸中开式离心泵为宁东供水工程的供水水泵。     

变频调速技术在定量包装机中的应用

介绍一种基于变频调速控制的全自动定量包装机，结构简单，组态灵活，性价比高，可广泛应用于食品饲料等行业，现场运行实践证明其通用性好，准确度和可靠性高、速度快、稳定性好。并论述变频器控制系统的设计及使用中的注意问题。     

大同市水资源开发利用状况与承载能力的思考

文中分析了大同市水资源开发利用的状况，并对水资源承载能力的有关问题进行了讨论。     

基于承包商预期收益不变的不平衡报价模型

在招标实践中,通常采用最低价中标原则,使得投标人不得不压低其投标价格。基于承包商预期收益不变的不平衡报价模型,是在“工程量清单报价”的条件下,考虑到施工中工程量的变化及施工顺序的影响,体现了资金的时间价值,在保持承包商预期收益不变的前提下,通过调整各分项工程的单价,来降低工程报价,以增加中标机会而建立的。所建立的模型简单,易于操作,并配以具体的工程实例,通过计算机求得其最优解,可供承包商投标报价时参考。     

大同市节水型社会建设的探讨

大同市是全国108个比较严重缺水城市之一，人均水资源量不足全国的1/10（全国人均水资源量2231m^3），稍超过全省的1／2（全省人均水资源量388m^3），市中心城区工农业及城市生活用水近20年来靠超采地下水来支撑。文中就大同市水资源供需不平衡的现状，提出大同市节水型社会建设的必要性，及今后水资源开源和节流的措施。