闸室基础开挖一次三台阶消聚能爆破技术

老挝南公1水电站溢洪道闸室段基础开挖为多面临空的保留岩体结构,工程实践中,多面临空岩体结构开挖成型采用爆破方式进行施工。传统的多面临空岩体结构开挖成型多采用梯段爆破的方式进行,爆破开挖成型质量差,会损伤甚至破坏保留岩体,受损伤或者破坏的保留岩体需进行加固衬砌,导致工程施工成本增加、施工进度滞后,且衬砌后的多面临空岩体结构较岩体完整的结构性能有所降低,给工程长期运行带来了安全隐患。南公1溢洪道闸室基础开挖采取“一次三台阶大孔径(120mm)浅孔(孔深3.13m)预裂爆破与消聚能联合爆破技术”尚为首例。且根据开挖程序依次进行预裂爆破能够满足多面临空岩体结构开挖成型不损伤或者破坏保留岩体的质量要求。有效提升了爆破质量,提高了开挖效率,为今后同类工程提供了有益借鉴,具有一定的推广应用前景。

南公1水电站溢洪道保护层开挖孔底消能-聚能结构优选研究

岩石基础的开挖成型质量对工程建设及运行安全有着重要影响。基于老挝南公1水电站溢洪道保护层开挖,在现场开展了不同消能-聚能结构的爆破试验,结合试验数据研究了孔底不同消能-聚能结构对开挖成型效果的影响。结果表明:相较于“铁精粉+松砂垫层”的消能-聚能结构,“铁球+松砂垫层”的消能-聚能结构能够获得更加平整的建基面;“铁精粉+松砂垫层”的消能-聚能结构则能够更有效地缓冲消耗传递至孔底的爆炸能量,更好地保护孔底岩体。综合开挖成型效果和残孔破坏分析结果,现场优选了“铁球+松砂垫层”的消能-聚能结构,并在一级消力池的保护层开挖中推广了消能-聚能联合控制爆破技术,取得了良好的开挖成型效果。

深圳赤湾停车场基坑工程场地平整控制爆破试验研究

岩石地基开挖的平整性与完整性直接影响着工程质量与进度,为了使深圳赤湾停车场基坑开挖工程同时满足开挖的经济高效性及地基的平整完整性,将垂直孔复合消能爆破技术应用到工程中。基于工程原8 m及12 m台阶爆破参数,以炮孔间排距作为主要变量设计了多组现场爆破试验。试验中不改变原爆破联网方式、单孔装药结构及炸药单耗等参数,将同一次起爆区分为常规区及消能试验区以做对比。爆破堆渣清除后,用RTK定位系统测量地基高程数据,建立了三维地表模型图;同时结合统计结果分析了垂直孔复合消能爆破技术对地基平整度的影响。结果发现:在两种不同高度的台阶爆破试验下,垂直孔复合消能爆破技术均能使爆破后地基的平整度更优;此外,孔间排距是影响爆破效果的重要因素,为使地基平整度最好,工程中8 m台阶爆破参数下最优间排距为2.0 m×2.0 m,12 m台阶爆破参数下则为4.0 m×4.5 m,为现场施工运用提供了相关依据。

A Cooperative MIMO Transmission Scheme for Cluster-based Wireless Sensor Networks

Wireless sensor network is becoming more and more popular in recent years, but energy- constrained characteristic of sensor nodes is one of the critical issues that we must consider in system design. In this paper, a cluster-based virtual VBLAST transmission scheme is proposed to achieve energy savings for energy-constrained wireless sensor networks. In the proposed scheme, instead of using cluster member as cooperative nodes, multiple cluster heads cooperate to form virtual antenna array so that V-BLAST based virtual MIMO transmission can be implemented. Based on the communication energy consumption model, a way to optimize the parameters for the scheme is given. In addition, detailed simulation is performed to evaluate the performance of the proposed scheme for both densely and sparsely deployed sensor networks. Theoretical analysis and simulation results verify the energy efficiency of the proposed scheme.

Separation of growth-stimulating peptides for Bifidobacterium from soybean conglycinin

AIM： To isolate and identify the soybean conglycinin peptides that selectively stimulates the growth of bifidobacteria in vitro, and to investigate the effect of soybean conglycinin peptides on intestinal ecosystem in vivo. METHODS： Soybean conglycinin was purified from soybean seeds by gel filtration （Sepharose-CL-6B）. These proteins were submitted to hydrolysis by pepsin. Several growth-stimulating peptides for bifidobacteria were isolated chromatographically from pepsin hydrolysis of soybean conglycinin and identified by means of matrixassisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）. Parallel to in vitro study, in vivo experiments with soybean conglycinin peptides were performed in mice. Ninety male KM mice were randomly assigned into five groups of 16 mice each, and each group was administered for 21d intragastrically with physiological saline （control）, conglycinin, pepsin-treated conglycinin （PTC）, the most active fraction which isolated from pepsin-treated conglycinin （P2-PTC） and HCl-full hydrolysis of conglycinin （HCl-FHC）, respectively. Intestinal microflora were evaluated by standard microbiologic methods and biochemical assays of cecal content samples after treatment. RESULTS： The results showed that the peptides which were isolated from soybean conglycinin could stimulate the growth of bifidobacteria in vitro, and the molecular mass of purified peptides with MALDI-TOF-MS ranged from 693.32 to 1829.55. Compared with control group, in vivo experiments showed that P2-PTC group decreased cecal pH （7.08±0.08 vs7.21±0.09, P〈0.05） and enterococcicounts （5.38±0.26 log10CFU/g vs 5.78±0.19 log10CFU/g, P〈0.05）, significantly increased sIgA level （172.08±35.40 ng/g vs 118.27±33.93 ng/g, P〈0.01） and β-galactosidase activity （1.28±0.23 U/g vs 1.82±0.58 U/g, P〈0.05） CONCLUSION： The results have shown that conglycinin is good source for enzyme-mediated production of peptides which stimulate the growth of bifidobacteria. These peptides are inactive within the sequence of the parent protein but can be released during enzymatic hydrolysis, and in vivo experiments demonstrate that conglycinin peptides may be beneficial for improving gastrointestinal health.

A Survey on the Privacy-Preserving Data Aggregation in Wireless Sensor Networks

Wireless sensor networks(WSNs)consist of a great deal of sensor nodes with limited power,computation,storage,sensing and communication capabilities.Data aggregation is a very important technique,which is designed to substantially reduce the communication overhead and energy expenditure of sensor node during the process of data collection in a WSNs.However,privacy-preservation is more challenging especially in data aggregation,where the aggregators need to perform some aggregation operations on sensing data it received.We present a state-of-the art survey of privacy-preserving data aggregation in WSNs.At first,we classify the existing privacy-preserving data aggregation schemes into different categories by the core privacy-preserving techniques used in each scheme.And then compare and contrast different algorithms on the basis of performance measures such as the privacy protection ability,communication consumption,power consumption and data accuracy etc.Furthermore,based on the existing work,we also discuss a number of open issues which may intrigue the interest of researchers for future work.

Energy Consumption in Wireless Sensor Networks

Wireless sensor networks （WSNs） can be used to collect surrounding data by multi-hop. As sensor networks have the constrained and not rechargeable energy resource, energy efficiency is an important design issue for its topology. In this paper, the energy consumption issue under the different topology is studied. We derive the exact mathematical expression of energy consumption for the fiat and clustering scheme, respectively. Then the energy consumptions of different schemes are compared. By the comparison, multi-level clustering scheme is more energy efficient in large scale networks. Simulation results demonstrate that our analysis is correct from the view of prolonging the large-scale network lifetime and achieving more power reductions.

Related factors and regional differences in energy consumption in China

This article used the Cluster analysis of statistical method to separate China＇s 30 provinces and municipalities into three categories according to their energy consumption discrepancies and characteristics from 1985 to 2007. The categories were high, moderate and low energy consumption areas and they had significant differences in energy consumption. Based on this classification, the authors analyzed the influencing factors of energy consumption in the three areas by means of panel data econometric model. The results showed that the influencing factors were obviously different. In order to support national goal of energy conservation and emission reduction, the energy measures and policies should be distinctly taken.

Life Cycle Assessment of Biodegradable Polylactic Acid(PLA)Plastic Packaging Products—Taking Tianjin,China as a Case Study

In this paper, the life cycle assessment(LCA) method is used to evaluate and quantify the energy consumption and environmental impacts of biodegradable polylactic acid(PLA) plastic packaging from the five stages of raw material acquisition, raw material transportation, product production, products use and final disposal. Seven impact categories were selected for the impact analysis: abiotic depletion potential fossil fuels(ADP), global warming potential(GWP), acidification potential(AP), eutrophication potential(EP), photochemical ozone formation potential(POCP), human toxicity potential(HTP), and terrestrial ecotoxicity potential(TETP). The results of the LCA are discussed and the results show that production of products is the highest stage of the environmental impact. Meanwhile, in the entire life cycle, the top three environmental impact categories are GWP, ADP and HTP,which account for 32.63%, 24.83% and 14.01%, respectively. The LCA results show that the environmental impact can be reduced in several ways: reducing the consumption of electricity, increasing the input of new energy, increasing the conversion rate of materials in the production process, using organic and water-soluble fertilizers instead of conventional fertilizers, using environment-friendly fuels and establishing a sound recycling system.