Analytical synthesis of voltage‐mode even/odd‐nth‐order differential difference current conveyor and fully differential current conveyor II‐grounded resistor and capacitor universal filter structures

A complete definition of an odd/even‐nth‐order notch or band‐reject filter transfer function is presented. Based on the differences between the input voltage and (i) an nth‐order high‐pass; (ii) a traditional nth‐order notch; and (iii) an nth‐order all‐pass filtering transfer function, a systematic method has been proposed to derive a universal filter structure that can realize voltage‐mode odd/even‐nth‐order low‐pass, band‐pass, high‐pass, all‐pass and traditional notch filters. The intrinsic capability of voltage‐mode addition and subtraction of the two active elements, differential difference current conveyors and fully differential current conveyors, is used to advantage in the aforementioned synthesis procedure. Based upon the definition of an nth‐order notch or band‐reject filter transfer function proposed in this paper, the aforementioned universal one has been further extended to the newly defined nth‐order band rejection filter. The voltage and current tracking errors of the two active elements are compensated by varying the resistances of the proposed filter. Filtering feasibility, stability, component sensitivities, linear and dynamic ranges, power consumption, and noise are simulated using H‐Spice with 0.35 µm process. Compared to some of the recently reported universal biquads, the new one is shown to enjoy the lowest component sensitivities and the best output accuracy for all‐pass signals. Moreover, Monte Carlo and two‐tone tests for intermodulation linearity simulations are also investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Recent Progress of Innovative Perovskite Hybrid Solar Cells

Recently, innovative perovskite hybrid solar cells have attracted great interest in solar cell research fields, such as dye-sensitized solar cells, organic photovoltaics, thin-film solar cells, and silicon solar cells, because their device efficiencies are gradually approaching those of crystalline Si solar cells, and they can be fabricated by cheap low-temperature solution processes. Here, we review the recent progress of innovative perovskite hybrid solar cells. The introduction includes the general concerns about solar cells and why we need innovative solar cells. The second part explains the structure and the material properties of hybrid perovskite materials. We focus on why the hybrid perovskite materials can exhibit excellent solar cell properties, such as high open-circuit voltage. The third part introduces recent progress in innovative perovskite hybrid solar cells, in terms of device architecture and deposition methods for dense perovskite thin films with full surface coverage. The device architecture is important in attaining high power conversion efficiency; the device operating mechanism is dependent on the device structure; and the pinhole-free dense perovskite thin films with full surface coverage are crucial for achieving high efficiency. Finally, we summarize the recent progress in perovskite hybrid solar cells, and the issues to be solved, in the summary and outlook section.     

Bridging cell multiscale modeling of fatigue crack growth in fcc crystals

The previously developed bridging cell method for modeling coupled continuum/atomistic systems at finite temperature is used to model fatigue crack growth in single crystal nickel under two crystal orientations at different temperatures. The method is expanded to implement a temperature‐dependent embedded atom method potential for finite temperature simulations avoiding time‐scale restrictions associated with small timesteps. Results for the fatigue simulation were compared with respect to deformation behavior, stress distribution, and crack length. Results showed very different crack growth mechanisms between the two crystal orientations as well as reduced resistance to crack growth with increased temperature. Copyright © 2015 John Wiley & Sons, Ltd.     

Algorithmically imposed thermodynamic compliance for material models in mechanical simulations using the AIM method

Thermodynamic irreversibility can be imposed on empirical material behaviour by using an appropriate algorithm which takes the path‐dependence of the degradation process into account. This new algorithm, Algorithmically Imposed Mechanics (AIM), for algorithmically irreversible mechanics, is described, and the convergence and unicity of the solutions obtained are proven. AIM is applicable to a range of mechanical behaviour and is demonstrated to work in conjunction with non‐local damage with rotating cracks as well as a mixed plastic and damage behaviour. Copyright © 2015 John Wiley & Sons, Ltd.     

Constrained pseudo‐transient continuation

This paper addresses the problem of finding a stationary point of a nonlinear dynamical system whose state variables are under inequality constraints. Systems of this type often arise from the discretization of PDEs that model physical phenomena (e.g., fluid dynamics) in which the state variables are under realizability constraints (e.g., positive pressure and density). We start from the popular pseudo‐transient continuation method and augment it with nonlinear inequality constraints. The constraint handling technique does not help in situations where no steady‐state solution exists, for example, because of an under‐resolved discretization of PDEs. However, an often overlooked situation is one in which the steady‐state solution exists but cannot be reached by the solver, which typically fails because of the violation of constraints, that is, a non‐physical state error during state iterations. This is the shortcoming that we address by incorporating physical realizability constraints into the solution path from the initial condition to steady state. Although we focus on the DG method applied to fluid dynamics, our technique relies only on implicit time marching and hence can be extended to other spatial discretizations and other physics problems. We analyze the sensitivity of the method to a range of input parameters and present results for compressible turbulent flows that show that the constrained method is significantly more robust than a standard unconstrained method while on par in terms of cost. Copyright © 2015 John Wiley & Sons, Ltd.     

钎焊板式热交换器验证试验设计及检验方法讨论

对钎焊板式热交换器验证性试验设计方法及耐压试验、泄漏试验、疲劳试验、爆破试验等检验方法进行了讨论,可用于指导国内钎焊板式热交换器的生产。     

Generative methods in urban design: a progress assessment

The year 2007 marked the 20‐year anniversary of A New Theory of Urban Design (1987), a slender volume by Christopher Alexander and colleagues that serves as a notable milepost within the half‐century old “design methods movement” in which Alexander himself played a seminal role. The “generative” design method of A New Theory focused less upon the specification of a final form through schematic planning, and more on the stepwise process by which a form might emerge from the evolutionary actions of a group of collaborators. In so doing, it challenged the notion of “design” as a progressive expression of schematic intentions, and argued for a conception of design as a stepwise, non‐linear evolution in response to a series of contextual urban factors. In the 20 years since, significant progress has been made to develop the insights of generativity in urban design, as in other fields. Some of Alexander’s ideas have been incorporated – notably by practitioners of The New Urbanism – and some have been challenged and dismissed, including, notably, by Alexander himself. The author assesses progress since this milepost volume – substantial, he argues – as well as setbacks and shortcomings, and significant opportunities still remaining.     

考虑随机风压场非高斯特性的大跨度膜屋盖风振响应

作用于大跨度膜屋盖结构上的随机风压场在统计意义上由高斯和非高斯区域构成。基于零记忆非线性转化法理论,提出了这种混合随机风压场的模拟方法,算例表明,生成的随机风压场样本能准确描述实验数据的各项统计特性。将生成的样本和利用传统方法生成的高斯随机风压样本作用于某膜屋盖结构,经风振时域分析后发现,高斯随机风压激励下结构部分构件的响应值比非高斯随机风压激励下的响应值低,这表明,随机风压荷载的非高斯特性不容忽视。文章还给出了结构不同构件的整体风振响应系数。     

Kernel regression for real-time building energy analysis

This study proposes a new technique for real-time building energy modelling and event detection using kernel regression. We show that this technique can exceed the performance of conventional neural network algorithms, and do so by a large margin when the available training dataset is small. Furthermore, unlike the synapse weights in a neural network, the parameters of our kernel regression models are amenable to human interpretation and can give useful information about the building being studied. We extensively test our proposed algorithms using a new dataset consisting of 1.5 years of power and environmental measurements for four buildings, in addition to benchmarking against the ASHRAE Predictor Shootout dataset. On the new dataset, our kernel regression algorithm gave the best prediction performance in three of four cases and significantly outperformed neural networks (the nearest competitor) with training sets of 1/2 a year or less.     

宜兴大酒店装修改造“设计施工一体化”应用与研究分析

本文以宜兴大酒店装修改造为例,探析了＂设计施工一体化＂如何让酒店改造重新装修旧貌换新颜,如何把原来中规中矩、缺少格局变化的旧商务大楼规划成为配套设施完善,环境宜人的宾馆区。这对设计者来说是很大的挑战,也是十分值得探索的课题。