Generalized difference simulation for coupled transport models of unsaturated soil water flow and solute

The generalized difference methods (GDM) have been successfully used in numerical simulations of unsaturated soil water flow problems. The object of this paper is to extend applications of the GDM, that is, apply GDM to numerically solve one-dimensional coupled transport models of unsaturated soil water flow and solute. The semi-discrete and fully discrete generalized difference schemes are established, and the detailed algorithm of numerical approximation schemes is provided. Moreover, some numerical examples illustrate that the generalized difference methods are feasible and efficient to find the numerical solutions of one-dimensional coupled transport models in this paper. Finally, satisfactory results and some other significant and valuable conclusions are obtained from studies.     

Atomistic modelling of deformation and failure mechanisms in nanostructured materials

<正>Over the past two decades,there has been a whirlwind of worldwide research activities on nanostructured materials,with the long-term promise to tailor-design material properties from the nanoscale and up.In this grand efort,computation is playing an increasingly important role in complementing experiments to     

Hierarchically structured porous materials: synthesis strategies and applications in energy storage

To address the growing energy demands of sustainable development, it is crucial to develop new materials that can improve the efficiency of energy storage systems. Hierarchically structured porous materials have shown their great potential for energy storage applications owing to their large accessible space, high surface area, low density, excellent accommodation capability with volume and thermal variation, variable chemical compositions and well controlled and interconnected hierarchical porosity at different length scales. Porous hierarchy benefits electron and ion transport, and mass diffusion and exchange. The electrochemical behavior of hierarchically structured porous materials varies with different pore parameters. Understanding their relationship can lead to the defined and accurate design of highly efficient hierarchically structured porous materials to enhance further their energy storage performance. In this review, we take the characteristic parameters of the hierarchical pores as the survey object to summarize the recent progress on hierarchically structured porous materials for energy storage. This is the first of this kind exclusively to survey the performance of hierarchically structured porous materials from different porous characteristics. For those who are not familiar with hierarchically structured porous materials, a series of very significant synthesis strategies of hierarchically structured porous materials are firstly and briefly reviewed. This will be beneficial for those who want to quickly obtain useful reference information about the synthesis strategies of new hierarchically structured porous materials to improve their performance in energy storage. The effect of different organizational, structural and geometric parameters of porous hierarchy on their electrochemical behavior is then deeply discussed. We outline the existing problems and development challenges of hierarchically structured porous materials that need to be addressed in renewable energy applications. We hope that this review can stimulate strong intuition into the design and application of new hierarchically structured porous materials in energy storage and other fields.     

Study on arsenic level in ground water of Delhi using hydride generator accessory coupled with atomic absorption spectrophotometer

Surveillance of drinking water is essentially a health measure intended to protect the public from water borne diseases. Hydride generator accessory coupled with atomic absorption spectrophotometer was used to analyze arsenic level in 49 ground water samples collected from different areas of Delhi. Arsenic level in ground water samples was in the range of 0.0170 to 0.100 ppm (Mean-0.0431, Standard Deviation-0.0136, Std. error of Mean-0.00194) with minimum concentration at Raney Well No. 7 (0.0170 ppm) and maximum at Kotla Mubarak Pur (0.100 ppm). Arsenic containing sediments and percolation of chemicals into soil as the result of dumping of garbage rich in chemicals into open landfills could be the possible source of arsenic in ground water of Delhi. Extensive survey and continuous monitoring is required to be made to assess the magnitude of problem and earlier intervention.     

Study on arsenic level in public water supply of Delhi using hydride generator accessory coupled with atomic absorption spectrophotometer

Exposure to arsenic has been associated with several health hazards. Worldwide the main reason for chronic human intoxication with arsenic is intake of contaminated drinking water. Air acetylene type of atomic absorption spectrophotometer in combination with hydride generator accessory was used to analyze arsenic level in 25 water samples collected from 25 booster pumping stations and 313 water samples collected from tap water supply of 62 areas of Delhi. Results were analyzed using SPSS and Barlett’s Chi Square Test. Mean arsenic level detected in water samples collected from booster pumping stations was 0.00976 ppm (Range 0.000–0.017 ppm, Standard Deviation 0.006 and Standard error of Mean 0.00118). Maximum arsenic level (0.017 ppm) was found in water samples of booster pumping stations of Mehrauli, Punjabi Bagh and Ramjas Road. Mean arsenic level detected in samples collected from tap water supply was 0.013 ppm (Range 0–0.0430 ppm, Standard Deviation 0.00911 and Standard error of Mean 0.000515). In water samples of 42 areas arsenic level detected was exceeding WHO/EPA permissible limit of 0.01 ppm (10 ppb). The mean arsenic level detected in water samples of booster pumping station was within WHO/EPA permissible limit while mean arsenic level detected in tap water samples was marginally higher. Mixing of ground water and contamination through broken or leaking channel could be the possible reason of higher arsenic level in tap water. Continuous monitoring of quality of drinking water is required particularly in view of water contamination caused by industrial waste and uncontrolled ground water extraction.     

Structural design of a double-layered porous hydrogel for effective mass transport

Mass transport in porous materials is universal in nature, and its worth attracts great attention in many engineering applications. Plant leaves, which work as natural hydraulic pumps for water uptake, have evolved to have the morphological structure for fast water transport to compensate large water loss by leaf transpiration. In this study, we tried to deduce the advantageous structural features of plant leaves for practical applications. Inspired by the tissue organization of the hydraulic pathways in plant leaves, analogous double-layered porous models were fabricated using agarose hydrogel. Solute transport through the hydrogel models with different thickness ratios of the two layers was experimentally observed. In addition, numerical simulation and theoretical analysis were carried out with varying porosity and thickness ratio to investigate the effect of structural factors on mass transport ability. A simple parametric study was also conducted to examine unveiled relations between structural factors. As a result, the porosity and thickness ratio of the two layers are found to govern the mass transport ability in double-layered porous materials. The hydrogel models with widely dispersed pores at a fixed porosity, i.e., close to a homogeneously porous structure, are mostly turned out to exhibit fast mass transport. The present results would provide a new framework for fundamental design of various porous structures for effective mass transport.     

张掖市水价改革的定量研究——基于引入水土账户的CGE模型

近几年黑河流域的水资源供需问题已经得到政府的关注,其中农业用水价格的调整是改革的重点。张掖市是黑河流域水资源的主要消耗区,本文以张掖市为例,采用引入水土账户的CGE模型模拟分析水价改革的经济影响和节水效益。结果表明：①水价改革对经济仅有微弱影响,仅带来0.091%的GDP损失;②但在节约用水方面的效益却很大,将节约9.568%的水资源使用、万元GDP耗水量下降9.384%;③节约的水资源类型主要是地下水,且全部来自用水强度高的农业;④水土资源在需求总量上减少了,并表现出从农业部门向非农业部门转移的趋势;⑤在行业产出上,仅玉米、果蔬等几个对水资源依赖程度高的农业部门受到打击,产出平均下降4.1%。综上,通过价格杠杆可以实现较好的节水效益,但要关注改革过程中对特色优势农业的冲击以及不同类型水资源之间的消费替代转移。     

太阳能热水器环保型高效保温材料的开发与应用

聚氨酯硬泡沫因导热系数较低、成型方便而作为太阳热水器水箱主要的保温材料,但其成型后收缩性较大以及环保性能有待改进等原因,使太阳能热水器保温材料聚氨酯硬泡沫的高效保温性能、环保性能、生产质量的工艺性能等成为许多生产企业的关注点。文章依据本企业的"太阳能热水器水箱发泡组合物"发明专利,介绍、分析太阳能热水器新的环保型高效保温材料生产技术的开发与应用,取得较好的效果。     

The vertical distribution of dissolved oxygen and the precipitation by salt water in certain tidal areas

It has been shown that the lower layers of certain tidal waters under investigation contain less dissolved oxygen than the upper layers. Evidence has been presented to show that this phenomenon is caused by the stratification of the water due to the specific gravity of the under-run of sea-water, which cuts off vertical circulation, and to the subsequent depletion of the oxygen in the lower layers by natural agencies. The depletion of oxygen was found to be greatest in September. The precipitation and sedimentation of matter in tidal areas by sea-water have been presented in graphic form. These data are considered to be of particular interest from the viewpoint of fish and shellfish life.     

Experimental measurement of the quantum geometric tensor using coupled qubits in diamond

Geometry and topology are fundamental concepts, which underlie a wide range of fascinating physical phenomena such as topological states of matter and topological defects. In quantum mechanics, the geometry of quantum states is fully captured by the quantum geometric tensor. Using a qubit formed by an NV center in diamond, we perform the first experimental measurement of the complete quantum geometric tensor. Our approach builds on a strong connection between coherent Rabi oscillations upon parametric modulations and the quantum geometry of the underlying states. We then apply our method to a system of two interacting qubits, by exploiting the coupling between the NV center spin and a neighboring ¹³C nuclear spin. Our results establish coherent dynamical responses as a versatile probe for quantum geometry, and they pave the way for the detection of novel topological phenomena in solid state.     

收益共享视角下的项目群工期激励的计算实验模型

已有项目群工期优化的激励机制主要从业主角度探讨总量激励策略,较少考虑承包商的收益共享偏好。为此,从项目群相关者收益共享视角,探讨项目群工期激励仿真的计算实验模型。首先,分析收益共享激励策略下的项目群工期优化机理；其次,引入激励总量和激励强度,构建收益共享视角下的项目群工期激励的计算实验模型；进而,通过激励总量、收益共享比例动态调整,构建不同情境下承包商行为、项目群工期及优化带来的业主收益的仿真方法。最后,以U项目为例,进行计算实验,结果表明：单独依靠激励总量存在激励效率边际递减效应；收益分享比例设计能够在激励总量基础上进一步提升承包商努力水平及业主收益；激励总量和收益分享比例的平衡是实现工期及业主收益最优的关键；收益共享激励策略的引入形成并强化了项目群工期优化的激励-努力程度的反馈回路。研究成果为揭示承包商行为及项目群工期演化规律、并且制定相关管理策略提供新的研究思路和分析方法。     

西藏林芝地区水资源可持续开发利用研究

介绍西藏林芝的气候、河流、冰川和湖泊等基本情况的基础上，分析指出该地区目前水资源利用现状及存在的主要问题，并对未来十年、二十年工业、农业、居民生活需水进行了基本预测，提出该地区水资源可持续开发利用的主要途径。     

Isolation of target DNA using synergistic magnetic bead transport and electrokinetic flow

The advent and dissemination of next-generation sequencing (NGS) technologies such as Illumina''s sequencing platforms has brought forth vast reductions in the cost, time, and technical difficulties associated with DNA and RNA sequencing. Despite this trend, the workflow required to generate nucleic acid libraries for sequencing remains time-consuming and laborious. The following research proposes a method for simplifying and streamlining this process by replacing the manual washing steps of the common magnetic bead-based cleanup with a novel microfluidic method by integrating magnetic separation and electrokinetic purification (MSEP). Requiring no pumps, pipette mixing, vortexing, or centrifugation, MSEP relies on selective adsorption of target DNA onto the magnetic beads with subsequent transport of beads through a microchannel undergoing an antiparallel electroosmotic flow. The synergetic flow conditions were optimized using a simple electrohydrodynamic flow model. This work demonstrates that MSEP is as effective in eliminating adapter-dimers from the post-ligation library mix as the manual method while also greatly reducing the hands-on time and amount of pipetting required. Although MSEP has been applied specifically toward NGS library preparation at this time, it has the potential to be adapted and employed for any bead-based separation scheme, namely, solid phase extraction, sequence-specific hybridization, and immunoprecipitation on a microscale.     

Effects of non-Newtonian power law rheology on mass transport of a neutral solute for electro-osmotic flow in a porous microtube

Mass transport of a neutral solute for a power law fluid in a porous microtube under electro-osmotic flow regime is characterized in this study. Combined electro-osmotic and pressure driven flow is conducted herein. An analytical solution of concentration profile within mass transfer boundary layer is derived from the first principle. The solute transport through the porous wall is also coupled with the electro-osmotic flow to predict the solute concentration in the permeate stream. The effects of non-Newtonian rheology and the operating conditions on the permeation rate and permeate solute concentration are analyzed in detail. Both cases of assisting (electro-osmotic and poiseulle flow are in same direction) and opposing flow (the individual flows are in opposite direction) cases are taken care of. Enhancement of Sherwood due to electro-osmotic flow for a non-porous conduit is also quantified. Effects if non-Newtonian rheology on Sherwood number enhancement are observed.