卫星电源测试评估系统的初步研究

介绍了卫星电源基本体系结构以及卫星电源测试评估方法 ,建立了基于虚拟仪器概念的卫星电源测试评估系统 ,并对一个简单的非调节母线卫星电源系统模型进行测试 ,给出了结果分析 .     

Designing machine operating strategy with simulated annealing and Monte Carlo simulation

This paper describes a simulation-based parameter design (PD) approach for optimizing machine operating strategy under stochastic running conditions. The approach presents a Taguchi-based definition to the PD problem in which control factors include machine operating hours, operating pattern, scheduled shutdowns, maintenance level, and product changeovers. Random factors include machine random variables (RVs) of cycle time (CT), time-between-failure (TBF), time-to-repair (TTR), and defects rate (DR). Machine performance, as a complicated function of control and random factors, is defined in terms of net productivity (NP) based on three key performance indicators: gross throughput (GT), reliability rate (RR), and quality rate (QR). It is noticed that the resulting problem definition presents both modeling and optimization difficulties. Modeling complications result from the sensitivity of machine RVs to different settings of machine operating parameters and the difficulty to estimate machine performance in terms of NP under stochastic running conditions. Optimization complications result from the limited capability of mathematical modeling and experimental design in tackling the resulting large-in-space combinatorial optimization problem. To tackle such difficulties, therefore, the proposed approach presents a combined empirical modeling and Monte Carlo simulation (MCS) method to model the sensitive factors interdependencies and to estimate NP under stochastic running conditions. For combinatorial optimization, the approach utilizes a simulated-annealing (SA) heuristic to solve the defined PD problem and to provide optimal or near optimal settings to machine operating parameters. Approach procedure and potential benefits are illustrated through a case study example.     

Analyzing shear stress-induced alignment of actin filaments in endothelial cells with a microfluidic assay

The physiology of vascular endothelial cells is strongly affected by fluid shear stress on their surface. In this study, a microfluidic assay was employed to analyze the alignment of actin filaments in endothelial cells in response to shear stress. When cells were cultured in microfluidic channels and subjected to shear stress, the alignment of filaments in the channel direction was significantly higher than in static cultures. By adding inhibitory drugs, the roles of several signaling proteins in the process of alignment were determined. Thus, it is shown how microfluidic technology can be employed to provide a mechanistic insight into cell physiology.     

Biotinidase deficiency—Diagnosis by enzyme assay and a follow-up study

A 3 month old male child was brought to the hospital with complaints of skin rashes, developmental delay, seizures, seborrheic dermatitis, alopecia and mild, acidosis. The child was subjected to a simple metabolic screening protocol. The result of the screening and the clinical symptoms provided an index pointing towards biotinidase deficiency., a rare autosomal recessive, inherited metabolic disorder. The enzyme was then assayed by using n-biotinylp-aminobenzoate as substrate and the diagnosis confirmed. A follow-up of the case indicated the efficacy, of biotin supplementation in biotinidase deficiency.     

Design and optimization of a double-enzyme glucose assay in microfluidic lab-on-a-chip

An electrokinetic driven microfluidic lab-on-a-chip was developed for glucose quantification using double-enzyme assay. The enzymatic glucose assay involves the two-step oxidation of glucose, which was catalyzed by hexokinase and glucose-6-phosphate dehydrogenase, with the concomitant reduction of NADP⁺ to NADPH. A fluorescence microscopy setup was used to monitor the different processes (fluid flow and enzymatic reaction) in the microfluidic chip. A two-dimensional finite element model was applied to understand the different aspects of design and to improve the performance of the device without extensive prototyping. To our knowledge this is the first work to exploit numerical simulation for understanding a multisubstrate double-enzyme on-chip assay. The assay is very complex to implement in electrokinetically driven continuous system due to the involvement of many species, which has different transport velocity. With the help of numerical simulation, the design parameters, flow rate, enzyme concentration, and reactor length, were optimized. The results from the simulation were in close agreement with the experimental results. A linear relation exists for glucose concentrations from 0.01 to 0.10 g l⁻¹. The reaction time and the amount of enzymes required were drastically reduced compared to off-chip microplate analysis.     

核心能力战略危机预警系统设计原理与方法

核心能力战略的实施与运作过程中因为各种因素的扰动,难免发生偏差。设计核心能力战略危机预警系统的目的就在于及时发现和预见偏差以便实施控制,保证核心能力战略的可持续性和高效性。基于此,本文探讨了核心能力战略的危机预警系统设计原理与方法。     

Highly sensitive FET sensors for cadmium detection in one drop of human serum with a hand-held device and investigation of the sensing mechanism

As the heavy metal contamination is becoming worse, monitoring the heavy metal content in water or human body gets more and more important. In this research, a cadmium ion-selective field effect transistor (Cd-ISFET) for rapidly detecting cadmium ions has been developed and the mechanism of the sensor is also investigated in depth. Our Cd-ISFET sensor exhibits high sensitivity beyond the ideal Nernst sensitivity, wide dynamic range, low detection limit (∼10⁻¹¹M), which is comparable with inductively coupled plasma mass spectrometry, and easy operation enabling people to detect cadmium ion by themselves. From the analysis of electrical measurement results, this Cd-ISFET is preferred to operate at the bias with the maximum transconductance of the FET to enhance the sensor signal. The AC impedance measurement is carried out to directly investigate the mechanism of an ion-selective membrane (ISM). From impedance results, the real part of the total impedance, which is the resistance, was shown to dominate the sensor signal. The potential drop across the ISM is caused by the heavy metal ion in the membrane, which is employed to the gate of the FET via an extended gate electrode. Cadmium ion detection in one drop of human serum with this sensor was demonstrated. This cost-effective and highly sensitive sensor is promising and can be used by anyone and anywhere to prevent people from cadmium poisoning.     

Designing the information architecture of a complex website: A strategy based on news content and faceted classification

Information architecture (IA) is an essential component of a website, and its design significantly impacts the user experience. Within complex, large-scale organizational settings, the practice of IA must address a number of critical management issues. This paper describes a pilot action research project whose aim was to develop and test a model for designing the IAs of complex institutional websites. The resulting model is based on the strategic use of news content organized in accordance with a faceted classification approach. The model was piloted during the redevelopment of the website of the Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe), a large Italian healthcare and research organization. Based on the collected data, the proposed IA model was found to effectively manage the website and to greatly reduce the need for structural changes in the 12 months after the intervention. The model also permits the collection of web analytics data that can be useful for web content editors and organization managers. Further research will be needed to validate or improve the model.     

学科服务设计与实践的微创新研究--北京师范大学图书馆学科服务发展历程

“微创新”理念的实质是用户需求导向的创新,这一理念与学科服务发展的理念有异曲同工之妙。北京师范大学图书馆在启动新一轮的学科服务过程中,通过对学科服务的格局、模式和过程设计的微创新;通过开展全程跟踪式的学科资源支持、嵌入式信息素养教育、高端课题咨询等微创新服务;通过对技术平台应用以及营销推广方式的微创新,优化用户服务体验,快速的推动学科服务向纵深发展。     

An algorithm for modeling the sinusoidal input/steady-state response behavior of nonlinear systems over a set of frequencies and amplitudes

An algorithm for constructing a black box model of the sinusoidal input/steady-state response behavior of nonlinear time-invariant systems over a set of frequencies and amplitudes is presented. It is assumed that the steady-state response is periodic of the same fundamental frequency as the excitation, and that the Fourier coefficients are continuous functions of amplitude and square-integrable functions of frequency. The algorithm converges, in a mean-square sense, to an exact representation of the first N harmonics of the steady-state response minus its d.c. component. The model constructed by the algorithm admits a relatively simple physical realization characterized by 2NM+1 linear dynamic elements, and N(2M+1)+1 nonlinear static elements. The underlying mathematical structure of the model is an orthogonal series expansion relative to time whose coefficients are themselves truncated orthogonal expansions relative to frequency. Here M, the number of harmonics used for frequency interpolation, is determined by the algorithm. Of the N(2M+1)+1 memoryless nonlinearities which characterize the model, N of these are specified ahead of time (Tchebysheff polynomials), and 2NM+1 are parameters which mold the representation to the specific system being modeled. Each of these functions of a single variable can be obtained in a pointwise manner directly from steady-state measurements. The algorithm was implemented on a digital computer, and forced versions of the classic equations of van der Pol and Duffing were run as examples. An additional analytic example of a frequency multiplier of prescribed bandwidth was also presented.     

基于机器视觉的SMD晶振上片点胶机的设计和实现

利用机器视觉、自动控制和机械技术,设计并开发了一种高速高精度的SMD晶振点胶上片一体化机器人.系统通过标定模块建立完整的绝对坐标体系,通过图像处理和模式识别技术,系统能逻辑上判断分析晶体和晶体基座的绝对位置,并补偿机械运动的精度,完成满足工艺精度的点胶和上片动作.     

Estimation of the levels of atrial natriuretic peptide (ANP) in cardiac blood samples by a simple and indigenous enzyme linked immunosorbent assay

Levels of Atrial Natriuretic Peptide (ANP) were estimated in twenty four blood samples collected from the right and the left ventricles of the patients undergoing cardiac catheterization by an Enzyme Linked Immunosorbent Assay (ELISA) developed to the sensitivity of 5 pp/well and within 10% of interassay coeficient of variance. Simultaneously, levels of ANP in plasma samples from the systemic venous blood of seventy five normal subjects were also estimated which ranged between 25–60 pg/ml.     

运用大协调学构建高效益的和谐社会

大协调学(Macro-coordinationScience),是研究人类同自然与社会各环节大尺度交叉协调规律及其应用的科学,主要帮助人们扩大视野,在大尺度上认识和解决或预防社会经济发展与生态、环境、资源不协调的问题,是人类同自然宏观协调不可缺少的科学。大协调学涉及约140门文理工学科,主要的功能是为宏观决     

旅游者与目的地契合的概念与测量

在当前多渠道和多主体构成的旅游地服务关系网中,契合是理解和预测旅游行为的关键,是目的地进行顾客关系管理的重要策略。以消费领域（含休闲与旅游品牌领域）契合研究为基础,在回顾消费者契合的理论基础与识别多种契合概念关键特征的基础上,尝试结合旅游学理论和目的地特征,界定旅游者契合的概念,识别和验证其维度和测量指标,并以凤凰古城为研究区域收集数据,检验契合测量指标。研究界定了旅游者契合,并构建了包括认同、注意、热情、专心致志、社会互动等5个维度、25个测项的旅游者契合指标体系。同时,研究证实了旅游者契合对目的地忠诚的正向影响,表明旅游者契合测量具有良好的效标关联效度。旅游目的地领域契合的实证研究,完善了旅游市场营销学的概念体系,对目的地实施契合营销策略有一定的启示。     

Bifurcation analysis in a predator-prey system with stage-structure and harvesting

In this paper, we consider a predator-prey model with stage-structure and harvesting. This model is the same as the one developed by Kar and Pahari (2007) [9], but we make bifurcation analysis more general than their work. In particular, using the approach of Beretta and Kuang (2002) [4], we show that the positive steady state can be destabilized through a Hopf bifurcation. We also investigate the stability and direction of periodic solutions bifurcating from Hopf bifurcation by using the normal form theory and the center manifold theorem presented in Hassard et al. (1981) [8]. Numerical simulations are then carried out as supporting evidences of our analytical results.     

Asymmetry of red blood cell motions in a microchannel with a diverging and converging bifurcation

In microcirculation, red blood cells (RBCs) flowing through bifurcations may deform considerably due to combination of different phenomena that happen at the micro-scale level, such as: attraction effect, high shear, and extensional stress, all of which may influence the rheological properties and flow behavior of blood. Thus, it is important to investigate in detail the behavior of blood flow occurring at both bifurcations and confluences. In the present paper, by using a micro-PTV system, we investigated the variations of velocity profiles of two working fluids flowing through diverging and converging bifurcations, human red blood cells suspended in dextran 40 with about 14% of hematocrit level (14 Hct) and pure water seeded with fluorescent trace particles. All the measurements were performed in the center plane of rectangular microchannels using a constant flow rate of about 3.0 × 10⁻¹² m³/s. Moreover, the experimental data was compared with numerical results obtained for Newtonian incompressible fluid. The behavior of RBCs was asymmetric at the divergent and convergent side of the geometry, whereas the velocities of tracer particles suspended in pure water were symmetric and well described by numerical simulation. The formation of a red cell-depleted zone immediately downstream of the apex of the converging bifurcation was observed and its effect on velocity profiles of RBCs flow has been investigated. Conversely, a cell-depleted region was not formed around the apex of the diverging bifurcation and as a result the adhesion of RBCs to the wall surface was enhanced in this region.     

Design and implementation of a rectangular frequency invariant beamformer with a full azimuth angle coverage

A novel design of the frequency invariant beamformer based on a rectangular array is proposed with two unique features: there are no taped delay-lines (TDLs) or any other temporal processing involved and the resultant beamformer has a full 360° azimuth angle coverage. This leads to a wideband beamformer with complex-valued coefficients and its implementation is not as straightforward as the traditional ones. Depending on whether the input signal is complex-valued or real-valued, special arrangements and structures are required for its effective implementation. Several design examples are provided with a satisfactory frequency invariant property. Two sets of implementation results are given based on both simulations and data collected by a planar microphone array system.