Numerical comparison of airborne particles deposition and dispersion in radiator and floor heating systems

Many studies have been shown the advantage of low-energy heating systems, such as floor heating system in comparison with high-energy consuming systems, such as radiator heating system. The adoption of these energy-efficient heating systems still requires the provision of acceptable indoor air quality. In this research, three-dimensional comparison of deposition and dispersion of airborne particles in two radiator and floor heating systems is investigated numerically by an Eulerian–Lagrangian method. In an attempt to provide such data, the deposition of solid particles ranging from 0.3 to 10 μm is calculated and the main goal is to survey the removal efficiency of these two heating systems. The model validation is performed through result comparisons with published data from literatures. The results indicate that deposition ratio of particles is higher in radiator heating system. Furthermore, the numerical results show that the floor and radiator heating systems trend to deposit the suspended particles on the ceiling and on the floor, respectively.     

Online retailer recommender systems: a competitive analysis

As thriving and fast-moving technologies, recommender systems have been widely adopted by online retailers to increase their sales recently. This has significant impacts on the stakeholders in the online supply chain. How an online retailer uses recommender systems to maximise its profit through choosing different recommendation strategies for two upstream competing manufacturers is explored in this paper. In particular, a game between one online retailer and two competitive manufacturers is constructed in which these manufacturers can be selectively and strategically recommended by the retailer. The analytical results show that as the recommendation strength of recommender systems increases, neither manufacturers nor the retailer can always enjoy higher profits, which is counterintuitive. Furthermore, this study reveals that (i) a recommended manufacturer may enjoy a higher profit through sharing the recommendation market with its rival than through monopolising this market; (ii) recommending two manufacturers in both is the most feasible way for the online retailer to benefit from controlling the supply chain. Finally, it is interesting that recommender systems are found to be good mechanisms to help to coordinate the online supply chain with one retailer and two manufacturers because the recommendation market generated by recommender systems alleviates channel conflict.     

Mixed valence and superconductivity

Mixed-valence (MV) systems are referred to here as MV-2 and MV-3 depending on whether two or three consecutive valence states are involved. MV-3 systems range from systems with Hubbard U>0, corresponding to a single stable, intermediate valence state, and U<0, corresponding to stable alternating valences differing by two units. Experiments using inelastic neutron scattering or inelastic X-ray scattering show softening of breathing phonon modes in MV systems compared with related systems with a single valence. It is hypothesized that softening is due to coupling between potential energy surfaces, corresponding to differing localizations of the electron. As predicted, softening is larger in the delocalized case. A mechanism for superconductivity is suggested.     

Analysis of bifurcations and stability properties of molecular systems

The dynamics and stability of a three-dimensional model of dissipative molecular systems are studied in detail The model considered is produced by an approximate quantum formulation, and it contains two parameters. It has been demonstrated analytically that the system exhibits 'cusp catastrophe' as in the case of potential systems; however, the non-potential nature of the dissipative model is reflected by the existence of limit cycles bifurcating from the equilibrium surface. The critical lines in the parameter plane and the family of limit cycles bifurcating from equilibria are determined analytically, and it has been shown that they are unstable     

A new approach to the definition of power components in three-phasesystems under nonsinusoidal conditions

A method has been proposed for the definition of active and nonactive power components in three-phase systems under nonsinusoidal conditions. The method is more attractive than others since it is not a mere extension of methods employed in single-phase systems, but comes from the application of a quite powerful and synthetic mathematical tool specifically studied for the representation of three-wire three-phase systems in any possible condition: the Park transformation and the Park vectors. It is proven that the application of this method leads to the definition of two quantities, the real and the imaginary power, that are measurable in a quite simpler way than those proposed by other theories. The two satisfy all properties typical of the electrical power and are directly related, under sinusoidal and balanced conditions, to the active and reactive powers. It is shown how this method fits with other proposed methods that can be regarded in terms of this more general theory     

A Review of Commercially Available Cost-Estimating Software Systems for the Construction Industry

ABSTRACT

A wide variety of estimating software systems for the construction industry is available on the market. Just as the needs of estimators vary greatly, so do the capabilities and applications of these systems. This article summarizes the results of a recent survey of commercially available cost-estimating software systems for the construction industry. The focus of this study is on the Australian market, although a few of the systems reviewed are from the United Kingdom and the United States. The study identifies a list of software features on which the systems are evaluated and summarizes these features in 17 commercially available estimating systems. The benefits of these systems are illustrated by example applications. The article then compares Australian estimating systems to U.K. and U.S. systems, based on similar studies performed by other researchers in those two countries. This article aims to assist users in identifying particular software features currently available from vendors and to provide a basis for the initial comparison of the systems reviewed. It illustrates the current level of development of commercially available computerized estimating systems found in most markets. It can help readers to become aware of the possibilities that now exist for computerized estimating.     

Differentiating customer service on the basis of delivery lead-times

This paper studies distribution systems that provide two classes of service: emergency service and non-emergency service. The two service classes are differentiated by a demand-lead-time, which is the time elapsed from a demand arrival to its fulfillment. An emergency service demand is to be filled immediately upon its arrival, while a non-emergency demand is not filled until T days later. We first analyze a single location model with the two service classes. We then extend the analysis to a two-echelon system. We study steady-state characteristics of the systems to derive various performance metrics. We then discuss managerial issues related to system design and control.     

Portable, Fiber-Based, Diffuse Reflection Spectroscopy (DRS) Systems for Estimating Tissue Optical Properties

Steady-state diffuse reflection spectroscopy is a well-studied optical technique that can provide a noninvasive and quantitative method for characterizing the absorption and scattering properties of biological tissues. Here, we compare three fiber-based diffuse reflection spectroscopy systems that were assembled to create a light-weight, portable, and robust optical spectrometer that could be easily translated for repeated and reliable use in mobile settings. The three systems were built using a broadband light source and a compact, commercially available spectrograph. We tested two different light sources and two spectrographs (manufactured by two different vendors). The assembled systems were characterized by their signal-to-noise ratios, the source-intensity drifts, and detector linearity. We quantified the performance of these instruments in extracting optical properties from diffuse reflectance spectra in tissue-mimicking liquid phantoms with well-controlled optical absorption and scattering coefficients. We show that all assembled systems were able to extract the optical absorption and scattering properties with errors less than 10%, while providing greater than ten-fold decrease in footprint and cost (relative to a previously well-characterized and widely used commercial system). Finally, we demonstrate the use of these small systems to measure optical biomarkers in vivo in a small-animal model cancer therapy study. We show that optical measurements from the simple portable system provide estimates of tumor oxygen saturation similar to those detected using the commercial system in murine tumor models of head and neck cancer.     

Premelting behavior and interfacial reaction of the Sn/Cu and Sn/Ag soldering systems during the reflow process

The early interfacial reaction and premelting characteristics of the Sn/Cu and Sn/Ag soldering systems, and the formation and morphology transition of interfacial intermetallic compounds in the two systems during the reflow soldering process were investigated by using a differential scanning calorimeter. Results show that the initial interfacial eutectic reaction arising from atomic interdiffusion in solid-state Sn/Cu and Sn/Ag systems results in the premelting at each interface of the two systems at a temperature 4.9 and 10.6?°C respectively lower than the actual melting point of pure tin, and consequently both of the Sn/Cu and Sn/Ag soldering systems exhibit morphology change of the intermetallic compound (IMC) as the solder experiences a transition from solid-state to liquid-state in a very small temperature range. The change in the interfacial energy between the solid (or liquid) Sn-rich phase and IMC phase is the essential factor leading to the morphology transition of the interfacial IMC in the Sn/Cu and Sn/Ag soldering systems.     

Related yet diverging sectoral systems: telecommunications equipment and semiconductors in China

This study examines the evolution of the telecommunications equipment and semiconductor industries in China from 1978 to 2012 using the sectoral systems framework. The article advances research on sectoral systems by examining the diverging evolution of two vertically related industries from a common starting point. In one case, system factors worked to foster global competitiveness, while in the other case, system factors slowed the formation of a competitive industry. The findings contribute to research on industrial dynamics and catching up by suggesting that the characteristics of vertically integrated industries may be seen as two sectoral systems that interact and influence the speed and direction of innovation and industrial development of each other’s industries.     

Use of equivalent mass method for free vibration analyses of a beam carrying multiple two‐dof spring–mass systems with inertia effect of the helical springs considered

This paper investigates the free vibration characteristics of a beam carrying multiple two‐degree‐of‐freedom (two‐dof) spring–mass systems (i.e. the loaded beam). Unlike the existing literature to neglect the inertia effect of the helical springs of each spring–mass system, this paper takes the last inertia effect into consideration. To this end, a technique to replace each two‐dof spring–mass system by a set of rigidly attached equivalent masses is presented, so that the free vibration characteristics of a loaded beam can be predicted from those of the same beam carrying multiple rigidly attached equivalent masses. In which, the equation of motion of the loaded beam is derived analytically by means of the expansion theorem (or the mode superposition method) incorporated with the natural frequencies and the mode shapes of the bare beam (i.e. the beam carrying nothing). In addition, the mass and stiffness matrices including the inertia effect of the helical springs of a two‐dof spring–mass system, required by the conventional finite element method (FEM), are also derived. All the numerical results obtained from the presented equivalent mass method (EMM) are compared with those obtained from FEM and satisfactory agreement is achieved. Because the equivalent masses of each two‐dof spring–mass system are dependent on the magnitudes of its lumped mass, spring constant and spring mass, the presented EMM provides an effective technique for evaluating the overall inertia effect of the two‐dof spring–mass systems attached to the beam. Furthermore, if the total number of two‐dof spring–mass systems attached to the beam is large, then the order of the overall property matrices for the equation of motion of the loaded beam in EMM is much less than that in FEM and the computer storage memory required by the former is also much less than that required by the latter. Copyright © 2005 John Wiley & Sons, Ltd.     

An overview and a contribution to the optical measurement of lineardisplacement

The present work is a contribution to the field of linear displacement measurements by optical means. For that purpose, a brief overview of some existing solutions is presented and two systems for axial linear displacement measurement based on light intensity detection are introduced. The systems have redundancy and were designed with the purpose of achieving identification and automatic correction of errors arising from inadvertent angular variations between the sensor and the light beam positions     

Estimation of biological properties by means of chromatographic systems: evaluation of the factors that contribute to the variance of biological-chromatographic correlations

The performance of chromatographic systems to emulate biological systems is evaluated in terms of the precision that can be achieved. The variance obtained when biological parameters are correlated against physicochemical ones can be decomposed in three terms: the variance of the biological data, the variance of the physicochemical data, and the variance caused by the dissimilarity between the two correlated systems (biological and physicochemical). The three terms contribute to the overall variance observed when measurements in chromatographic systems are correlated with experimental biological properties. The Abraham linear free energy relationships (LFERs) provide a very good approach to characterize biological and physicochemical systems and thus the variance of the analyzed data and the similarity/dissimilarity between them. The contribution of the three variances to the precision of the biological parameter estimated in this way is evaluated from the characterization of the biological and chromatographic systems by means of the Abraham model. The proposed method is able to estimate the goodness of chromatographic systems to predict particular biological properties. In particular, this method is illustrated by comparison of toxicity data (-log LC(50)) for the fish fathead minnow with retention data (log k) in several micellar electrokinetic chromatography (MEKC) systems and also by correlations between retention data (log k) in the sodium taurocholate (STC) MEKC system and data of several biological systems.     

Deadlock prediction and avoidance based on Petri nets for zone-control automated guided vehicle systems

Deadlock problems of zone-control uni-directional automated guided vehicle (AGV) systems are discussed in this paper. Deadlocks of two types in such AGV systems are first classified from the perspective of shared resources, i.e. guide-path zones and buffers. A special class of Petri nets, attributed Petri nets (APN), is defined and used to represent the current state and to generate future states of zone-control AGV systems. We propose an algorithmic procedure to predict in real time and to avoid deadlocks that are caused by sharing guide-path zones in zone-control AGV systems. The proposed algorithm utilizes the current system state and future predicted states to avoid deadlocks. These states are obtained and generated from the obtained APN. A modular approach is employed to facilitate the construction of APN models of zone-control AGV systems.     

基于广义置信区间的测量系统能力比较

研究了测量系统分析中对测量同一产品质量特性的两个测量系统能力的比较方法。基于广义推断法,提出了一种比较两个测量系统能力的方法。通过重复性与再现性（R&R）试验研究,利用广义推断法对两个测量系统能力的比较指数建立相应的广义置信区间,并进行计算机仿真。结果表明,基于广义置信区间的方法,可以有效地比较两个测量系统的能力。     

基于数据驱动仿真的两设备系统元模型

半导体封装测试系统等复杂制造系统的性能分析是项非常困难的任务。利用仿真模型构建两设备系统元模型,并以元模型为基石构建面向大规模复杂系统的近似解析方法是分析复杂制造系统的有效手段。为了快速准确地构建两设备系统元模型,提出了一种基于数据驱动仿真技术及人工神经网络的元模型构建方法。该方法以考虑缓存输送时间的两设备制造系统为研究对象,采用AREAN的二次开发技术实现仿真模型的自动配置、运行、统计,以生成人工神经网络所需案例,并通过比较分析BP、RBF和Chebyshev这3类典型的函数逼近神经网络确定最优的人工神经网络模型。实验结果表明径向基函数密度为120的RBF神经网络模型表现最优,其结果误差最小,能够成为大规模复杂制造系统近似解析方法的基石。     

在光DD-OFDM背靠背和传输系统中研究IQ不平衡

在直接检测光正交频分复用(DD-OFDM)系统中,同相/正交相(IQ)不平衡造成严重的性能下降.我们搭建了两个分别实现双边带(DSB)和单边带(SSB)调制的背靠背DD-OFDM系统,并依据差错向量幅度(EVM)和符号差错率(SER)分析比较了上述两系统对IQ不平衡的容忍度.结果表明,在背靠背情形下,DSB系统比SSB系统对IQ不平衡的容忍度要大.我们还搭建了两个传输距离均为40 km的DD-OFDM系统,分别实现了DSB信号和SSB信号的传输,同样依据EVM和SER分析比较了这两个系统对IQ不平衡的容忍度.结果表明,在传输距离为40 km的情况下,SSB调制比DSB调制更能增强DD-OFDM系统在传输信号时对IQ不平衡的容忍度.     

System performance evaluation of refractive surgical lasers: a mathematical approach

A study was conducted for the purpose of improving the designs of the next generation of refractive surgical laser systems. Two common refractive laser systems, variable-spot scanning (type A) and small-spot scanning (type B), are discussed by identifying sources of error that could adversely affect the capability of these lasers to accurately produce complex, customized wavefront guided ablations. A mathematical model was used to construct a laser simulator that models the two common laser systems in terms of the root-mean-square error. Error sources from ablation profile fitting, ablation registration, eye tracking, and the laser delivery system are compared, and the relative contribution of each to the overall system error is analyzed. This system-level analysis can be helpful to the improvement of both laser systems.     

Numerical study on hypervelocity acceleration of flyer plates by overdriven detonation of high explosive

In most applications of explosives to flyer acceleration, the detonation of explosives is usually regarded as a steadily progressing wave phenomenon in which the pressure of the detonation products immediately behind the wave front is characterized by the so-called Chapman-Jouguet (C-J) pressure value. This type of detonation is therefore routinely referred to as the C-J detonation behavior and the detonation products start to expand from this C-J state to accelerate the flyer plate to a high velocity status. Overdriven detonation, however, is a detonation process that can provide a higher or much higher pressure than does the C-J detonation. Taking use of the detonation products from the overdriven detonation to push the plate may lead the plate to reach a hypervelocity status not achievable by means of the usual explosive acceleration techniques. This paper presents a numerical study on two acceleration systems for hypervelocity acceleration of plates by the application of overdriven detonation of explosives. The first acceleration system is the so-called planar acceleration system, which some researchers also call as the multi-stage launcher system. The other acceleration system is the improved technique that is named as the converging tunnel acceleration system. The numerical method used for the study mainly follows the formulation of HEMP computer code. Through numerical study, it is found that both systems can give an obvious improvement on the ability to hypervelocity acceleration of plates. Moreover, the comparison of two acceleration systems shows that the converging tunnel system has more superiority over the planar acceleration system for hypervelocity acceleration of plates.     

Development of an improved calibration method for the LFB ultrasonic material characterization system

We investigated standard specimens for accurately calibrating the line-focus-beam ultrasonic material characterization (LFB-UMC) system without system dependencies. We evaluated several types of lithium tantalate (LiTaO3) substrates using two LFB-UMC systems with different device/system characteristics to measure and calibrate the propagation characteristics of the leaky surface acoustic waves (LSAWs), and analyzed the variations between the calibrated results. We concluded from this analysis that, by selecting materials with the cut surfaces and propagation directions of standard specimens that are identical to the objects to be calibrated, calibration errors resulting from different performance characteristics between the two systems could be nearly eliminated. Also, analytical errors caused by the effects of spectra with two close peaks (another propagation wave mode), one of the most common problems of characterization in the past, could be eliminated at the same time by this method.