Microfluidic separation of viruses from blood cells based on intrinsic transport processes

Clinical analysis of acute viral infection in blood requires the separation of viral particles from blood cells, since the cytoplasmic enzyme inhibits the subsequent viral detection. To facilitate this procedure in settings without access to a centrifuge, we present a microfluidic device to continuously purify bionanoparticles from cells based on their different intrinsic movements on the microscale. In this device, a biological sample is layered on top of a physiological buffer, and both fluids are transported horizontally at the same flow rate in a straight channel under laminar flow. While the micron sized particles such as cells sediment to the bottom layer with a predictable terminal velocity, the nanoparticles move vertically by diffusion. As their vertical travel distances have a different dependence on time, the micro- and nanoparticles can preferentially reside in the bottom and top layers respectively after certain residence time, yielding purified viruses. We first performed numerical analysis to predicate the particle separation and then tested the theory using suspensions of synthetic particles and biological samples. The experimental results using dilute synthetic particles closely matched the numerical analysis of a two layer flow system containing different sized particles. Similar purification was achieved using diluted blood spiked with human immunodeficiency virus. However, viral purification in whole blood is compromised due to extensive bioparticle collisions. With the parallelization and automation potential offered by microfluidics, this device has the potential to function as an upstream sample preparation module to continuously provide cell depleted bio-nanoparticles for downstream analysis.     

Microfluidic electrical sorting of particles based on shape in a spiral microchannel

Shape is an intrinsic marker of cell cycle, an important factor for identifying a bioparticle, and also a useful indicator of cell state for disease diagnostics. Therefore, shape can be a specific marker in label-free particle and cell separation for various chemical and biological applications. We demonstrate in this work a continuous-flow electrical sorting of spherical and peanut-shaped particles of similar volumes in an asymmetric double-spiral microchannel. It exploits curvature-induced dielectrophoresis to focus particles to a tight stream in the first spiral without any sheath flow and subsequently displace them to shape-dependent flow paths in the second spiral without any external force. We also develop a numerical model to simulate and understand this shape-based particle sorting in spiral microchannels. The predicted particle trajectories agree qualitatively with the experimental observation.     

A novel recommendation method based on social network using matrix factorization technique

The rapid development of information technology and the fast growth of Internet have facilitated an explosion of information which has accentuated the information overload problem. Recommender systems have emerged in response to this problem and helped users to find their interesting contents. With increasingly complicated social context, how to fulfill personalized needs better has become a new trend in personalized recommendation service studies. In order to alleviate the sparsity problem of recommender systems meanwhile increase their accuracy and diversity in complex contexts, we propose a novel recommendation method based on social network using matrix factorization technique. In this method, we cluster users and consider a variety of complex factors. The simulation results on two benchmark data sets and a real data set show that our method achieves superior performance to existing methods.     

基于SOPC的LED显示屏控制系统

系统地阐述了以Altera公司的Cycione芯片为核心的基于Nios Ⅱ软核的嵌入式16×16点阵的LED显示屏控制系统的设计方法;简要介绍了可编程片上系统(SOPC)技术的灵活性和优越性;详细介绍了Nios Ⅱ系统中PWM IP核和以太网控制模块等自定义模块的设计,结果表明采用SOPC的设计方法对LED显示屏性能有明显提高.     

Microfluidic rectifier based on poly(dimethylsiloxane) membrane and its application to a micropump

A microfluidic rectifier incorporating an obstructed microchannel and a PDMS membrane is proposed. During forward flow, the membrane deflects in the upward direction; thereby allowing the fluid to pass over the obstacle. Conversely, during reverse flow, the membrane seals against the obstacle, thereby closing the channel and preventing flow. It is shown that the proposed device can operate over a wide pressure range by increasing or decreasing the membrane thickness as required. A microfluidic pump is realized by integrating the rectifier with a simple stepper motor mechanism. The experimental results show that the pump can achieve a vertical left height of more than 2 m. Moreover, it is shown that a maximum flow rate of 6.3 ml/min can be obtained given a membrane thickness of 200 μm and a motor velocity of 80 rpm. In other words, the proposed microfluidic rectifier not only provides an effective means of preventing reverse flow but also permits the realization of a highly efficient microfluidic pump.     

苏州市全要素能源效率分析——基于面板数据的DEA分析

全要素能源效率指数是能源消费的目标值与实际值的比值.采用苏州市2000-2008年各个地区的面板数据,分析比较了2000-2008年苏州市各个地区的全要素能源效率.本文在构建DEA分析模型时,将能源、人力资本、固定资本投入、土地资源等作为多元投入,工业增加值作为产出,这克服了传统能源效率指标仅以能源作为单一投入的缺点.通过对结果的分析,发现张家港、昆山、常熟和吴江的全要素能源效率始终处于较高水平,而市区与太仓的全要素能源效率相对较低.     

FDI和环境污染的关系分析——基于中国省级面板数据的研究

采用面板协整理论这一最新发展起来的计量经济学方法,以2000-2006年期间中国大陆27个省市的面板数据为基础,对FDI与环境污染之间的关系进行了研究.研究结果表明:"污染避难所"假说在中国的经验验证中可能并不成立,FDI的流入不仅带来了资金同样也带来了技术,FDI的技术效应对于中国环境产生了积极的影响.     

Overcoming backstepping limitations via a novel MIMO non-affine-in-control convex optimization technique

Limitations of the standard backstepping control technique are overcome in this paper by yielding global conditions for regional ones; specifically, flexible cascade arrangements that do not require the system to be put in a pure- or strict-feedback form to ensure controllability beforehand, handling of nonlinear MIMO blocks without invertible input distribution matrices, calculation of virtual and real control laws regardless of the non-affine-in-control nature of subsystems, and systematic numerical synthesis of Lyapunov-based control laws at each step of the cascade connection via linear matrix inequalities. All these benefits derive from exploiting exact convex rewriting of nonlinear terms, splitting available and non-available signals for control implementation, and applying the direct Lyapunov method to cast conditions as a convex optimization problem. Examples of academic and practical interest illustrate the advantages of the novel methodology over former approaches.     

特征因子与其他文献计量指标关系研究——基于面板数据的估计

为了研究期刊特征因子与其他文献计量指标间的关系,克服简单相关系数和普通回归分析的缺陷,本文基于汤森路透JCR纯数学期刊数据,采用面板数据(Panel Data)研究特征因子分值(Eigenfactor Score)及论文影响分值(Article Influence Score)与其他文献计量指标的关系。研究发现:特征因子分值和论文影响分值互为高度相关。即年指标及影响因子与特征因子分值无关,但和论文影响分值正相关。被引半衰期及5年影响因子与特征因子分值负相关,与论文影响分值正相关。总被引频次及期刊论文数量与特征因子分值正相关,与论文影响分值负相关。研究认为,特征因子的推出有利于期刊重视提高学术质量而不是提高文献计量指标值,对文献计量指标的相关关系的研究方法要重新审视,对于其他学科特征因子与文献计量指标的关系有待进一步研究。     

Novel space shift keying MIMO technique based on a Steiner triple system

A novel space shift keying (SSK) multiple–input multiple–output (MIMO) technique based on Steiner triple system is proposed and analyzed in this article. SSK attracted considerable research interest in the past few years driven by the several promised inherent advantages including low error probability, low computational complexity and a very simple hardware implementation with very low cost and power consumption. Yet, the spectral efficiency of SSK increases with a base two logarithm of the number of transmit antennas and high data rates are only viable with a massive and impractical number of transmit antennas. Alternatively, generalized SSK (GSSK) scheme is considered, where a combination of antennas is activated at each time instant. GSSK promises the use of arbitrary number of transmit antennas not necessarily a power of two integer. Also, GSSK can attain high data rate with low number of transmit antennas at the cost of substantial degradation in the error performance. In this study, a Steiner triple system is utilized to propose a tailored SSK scheme with substantial reduction in the required number of transmit antennas, without compromising the error probability. It is shown that the proposed Steiner–SSK (S–SSK) MIMO system achieves almost identical error performance to a conventional SSK system but with nearly 90% reduction in the number of transmit antennas. As well, the average bit error rate (ABER) of S–SSK is shown to outperform GSSK by at least 3dB. It is also reported that a S–SSK system accomplishes significant reduction in hardware cost, power consumption, and computational complexity as compared to conventional SSK scheme. Yet, GSSK is shown to marginally outperforms S–SSK in these metrics as it requires smaller number of transmit antennas per a target spectral efficiency.     

The relationship between eigenfactor and other bibfiometric indicators based on panel data

为了研究期刊特征因子与其他文献计量指标间的关系,克服简单相关系数和普通回归分析的缺陷,本文基于汤森路透JCR纯数学期刊数据,采用面板数据（Panel Data）研究特征因子分值（Eigenfactor Score）及论文影响分值（Article InfluenceScore）与其他文献计量指标的关系。研究发现：特征因子分值和论文影响分值互为高度相关。即年指标及影响因子与特征因子分值无关,但和论文影响分值正相关。被引半衰期及5年影响因子与特征因子分值负相关,与论文影响分值正相关。总被引频次及期刊论文数量与特征因子分值正相关,与论文影响分值负相关。研究认为,特征因子的推出有利于期刊重视提高学术质量而不是提高文献计量指标值,对文献计量指标的相关关系的研究方法要重新审视,对于其他学科特征因子与文献计量指标的关系有待进一步研究。     

Modeling of a novel fish passage-way using coupled spatially varied flow

An innovative hydraulic structure was proposed for passage of fish in surface water. The structure consisted of identical ‘cells’ throughout its length and was designed to create coupled spatially varied flow for optimization of depth and velocity of water. The objective of this paper was to simulate the hydraulics of a single cell of this fish passage structure. A numerical model was developed to simulate the water surface profiles and longitudinal variation of 1-D velocity through one cell. The transition in the water surface profile between longitudinally adjacent cells (chamber) was also investigated. It was found that numerical convergence was usually achieved after three iterations with 2% discretization. The difference in depth arising from cell vs. chamber analysis was found to be small. The experimental results indicated turbulence in the water surface. The water surface profile matched the results obtained from numerical results. However, there were errors observed in estimation of flow rate. It is concluded that the mathematical approach used for the numerical simulation is reliable and can be used to analyze coupled spatially varied flow for any hydraulic structures aimed at controlling depth and velocity of water. Innovative approach to the interface between can potentially be used to achieve hydraulic goal of any structure.     

新常态下环境规制对经济增长的影响——基于2009—2013年省际面板数据

在我国生态文明建设的主题下,我国的经济增长速度出现"新常态",环境规制政策加强与否是一个重要的课题,研究环境规制与经济增长的关系是当前制定环境政策的重要依据。在研究"新常态"背景下环境规制与经济增长的关系,通过东中西区域的结果对比,提出不同的环境规制政策,采用2009-2013年数据,运用静态面板模型进行回归分析,结果发现在全国范围内环境规制对经济增长的影响为负,在东部地区影响最小,中部地区次之,西部地区最大,因此在目前的背景下,环境规制抑制经济增长,且受区域差异的影响,最后提出使环境与经济协调发展的策略。     

环境规制对中国海水养殖业绿色转型的影响——基于动态面板模型的实证检验

加快海水养殖业绿色转型对于全面推进海洋生态文明建设具有重要的现实意义,然而环境规制能否以及如何促进海水养殖业绿色转型尚无定论。本文以波特假说理论为基础,深入分析环境规制影响海水养殖业绿色转型的作用机制,以2009—2019年中国沿海地区省际面板数据为样本,采用基于系统GMM的动态面板模型和面板门限回归模型实证检验环境规制对海水养殖业绿色转型的影响。研究发现：①环境规制对海水养殖业绿色转型总体呈现先抑制后促进的“U”型非线性影响,且影响具有一定的滞后性。②不同环境规制对海水养殖业绿色转型的影响存在异质性,命令型环境规制对海水养殖业绿色转型产生先抑制后促进的“U”型非线性影响,市场型环境规制对海水养殖业绿色转型的影响在短期内不显著。③市场型环境规制对海水养殖业绿色转型的影响存在基于命令型环境规制的单门限效应,当命令型环境规制强度跨越阈值时,市场型环境规制对海水养殖业绿色转型的影响将失效。本文结论丰富了波特假说理论在海水养殖业方面的应用,为促进海洋环境治理与海水养殖业绿色转型双赢提供了有力的科学依据。     

基于面板门槛模型的环境规制对区域生态效率溢出效应研究

利用2001—2013年中国省级面板数据,基于超效率DEA模型测算各地区生态效率,结合面板门槛模型对影响环境规制的生态效率溢出效应的因素及其门槛特征进行分析,发现外商投资规模、开放化程度和研发投入具有显著的门槛特征,在越过一定的门槛值后,环境规制对于生态效率由负面作用变为正向溢出。目前我国绝大多数地区这三项指标均处在门槛值以下,应以合理引进外资、扩大对外开放以及提高研发投入等措施来改善现状,为可持续发展的路径规划提供政策借鉴。     

环境分权对中国污染减排效果的影响——基于空间动态面板模型的检验

环境分权能否助推由经济与财政分权引起的负向激励,进而影响减排治污效果,以往研究中始终没有达成共识。本文利用2001—2016年中国省级面板数据,通过测算省级环境监管权限的配置格局,结合空间动态面板模型,对分别以PM2.5浓度、人均废水排放量、人均一般工业固体废物产生量表征的大气污染、水污染、固废污染指标进行回归,以此检验环境分权的减排效果及其作用机制。结果表明：①环境分权弱化了减排效果,分权程度越高,3种污染指标的污染程度越重,其中对大气污染的作用最大,对水污染的作用最小;②大气污染与环境分权之间呈倒U型的非线性关系,水污染、固废污染与环境分权之间非线性关系不显著;③环境监测、执法与监察3项监管权限的分权程度对污染物减排效果的影响显著为负,其中环境执法的地方分权程度负效应最大,环境监察的负效应最小;④尽管环境分权弱化了减排效果,但将经济事务上的分权激励考虑进模型当中时,环境分权反而对分权激励与合谋污染有抑制作用。本文的政策启示是：要进一步提升环保政策的执行效果,提高地方政府减排的执行能力,对环保机构进行实质性的垂直管理改革势在必然;结合地区在经济发展上的分权激励,适当给予地方环保政策执行的灵活度,一定程度上也能提升减排效果。     

出口贸易方式与区域经济增长:基于中国省际面板数据的分析

出口作为中国经济增长的驱动力早已成为学者的共识,出口转型升级是中国出口持续发展的重要途径,出口贸易方式在一定程度上反映了中国出口发展潜力。通过对1998-2013年中国27个省际数据的分析,得出了出口贸易方式与区域经济增长之间的关系。分析表明:(1)总体来说,出口促进经济增长,不同贸易方式的作用存在差别。一般贸易对于经济增长的影响显著于加工贸易,中国经济增长已经不再主要依赖于加工贸易,有一定自主性,出口贸易结构优化潜力较大;(2)出口对于地区的经济增长促进作用,按东中西递减。基于理论和实证的分析,本文提出政府在东部地区应制定中长期战略,鼓励加工贸易转型升级;在中西部地区出台一系列鼓励出口的优惠政策,尤其是在丝绸之路经济带建设的带动下,为其建设发展注入强劲动力。     

基于业务流程的知识模块化分析

业务流程环节是知识的集合,不同的环节具有不同的知识构成。知识构成之间具有相关性。针对研究知识的模块化问题,首先基于业务流程提出知识节点的相关度以及知识网络的模块度,再结合复杂网络的群聚系数,提出了知识的模块化指数并以此来度量知识的模块化程度。此方法有利于研究知识模块的划分以及潜在知识模块的挖掘。