Construction project scheduling under workspace interference

Workspace interference in construction sites usually leads to work inefficiency, rework, and risk to the workforce. In this paper, we present a study on controlling and mitigating workspace interference in construction project scheduling. In particular, we consider two types of workspace interference: unacceptable workspace interference (USI) and acceptable workspace interference (ASI). During the scheduling process, if two activities cause USI, they must be scheduled for non‐overlapping execution periods. If the two activities that cause ASI are executed concurrently, it will lead to decrease in productivity. We first establish a mathematical model for construction project scheduling subject to these two types of workspace interference. This established model is a mixed‐integer, multiobjective optimization problem. Then, a two‐stage metaheuristic algorithm is developed to solve the problem. Two construction scenarios are selected to illustrate the effectiveness of the proposed method. By comparing with traditional forward scheduling method, the two‐stage metaheuristic algorithm can achieve solutions with, on average, shorter project makespan, less total cost as well as milder resource usage variation in execution.     

Effects of Sr2+ substitution on the crystal structure,Raman spectra,bond valence and microwave dielectric properties of Ba3-xSrx(VO4)2 solid solutions

The effects of Sr²⁺ substitution for Ba²⁺ on microwave dielectric properties and crystal structure of Ba_3-xSr_x(VO₄)₂ (0 ≤ x ≤ 3, BSVO) solid solution were investigated. Such Sr²⁺ substitution contributes to significant reduction in sintering temperature from 1400 °C to 1150 °C. Both permittivity (∑_r) and quality factor (Q × f) values decreased with increasing x value, which was determined to be related with the descending values of average polarizability and packing fraction, whereas the increase in τ_f value was explained by the decreased average VO bond length, A-site bond valence. BSVO ceramics possessed encouraging dielectric performances with ∑_r = 12.2–15.6 ± 0.1, Q × f = 44,340 - 62,000 ± 800 GHz, and τ_f = 24.5–64.5 ± 0.2 ppm/°C. Low-temperature sintering was manipulated by adding B₂O₃ as sintering additive for the representative Sr₃V₂O₈ (SVO) ceramic and only 1 wt.% B₂O₃ addition successfully contributed to a 21.7% decrease in sintering temperature to 900 °C, showing good chemical compatibility with silver electrodes, which render BSVO series and SVO ceramics potential candidates in multilayer electronic devices fabrication.     

High‐Quality‐Factor Mid‐Infrared Toroidal Excitation in Folded 3D Metamaterials

With unusual electromagnetic radiation properties and great application potentials, optical toroidal moments have received increasing interest in recent years. 3D metamaterials composed of split ring resonators with specific orientations in micro‐/nanoscale are a perfect choice for toroidal moment realization in optical frequency considering the excellent magnetic confinement and quality factor, which, unfortunately, are currently beyond the reach of existing micro‐/nanofabrication techniques. Here, a 3D toroidal metamaterial operating in mid‐infrared region constructed by metal patterns and dielectric frameworks is designed, by which high‐quality‐factor toroidal resonance is observed experimentally. The toroidal dipole excitation is confirmed numerically and further demonstrated by phase analysis. Furthermore, the far‐field radiation intensity of the excited toroidal dipoles can be adjusted to be predominant among other multipoles by just tuning the incident angle. The related processing method expands the capability of focused ion beam folding technologies greatly, especially in 3D metamaterial fabrication, showing great flexibility and nanoscale controllability on structure size, position, and orientation.     

空间主颜色描述符的图像特征提取算法

分析了MPEG-7标准中推荐的主颜色描述符和颜色结构描述符各自的优缺点,并提出了一种新的空间主颜色描述符,它采用图像中少数几个代表性颜色和它们的空间分布信息来表征整幅图像。实验表明,空间主颜色描述符集合了主颜色描述符和颜色结构描述符的优点,具有检索精确高、提取速度快和存储空间小的优点.     

提升小波包和神经网络在轴承故障诊断中的应用

针对轴承故障信号的特点,采用9／7提升小波包和概率神经网络（Probabilistic Neural Networks）相结合的算法对轴承故障进行诊断。首先对原始数据进行小波变换,并对其进行特征提取。然后利用概率神经网络对得到的特征向量进行类别判定。在VB和Matlab设计的故障诊断仿真实验平台上,验证了9／7提升小波包和概率神经网络混合的故障诊断方法满足实验要求．     

装备故障仿真及评估方法

阐述了虚拟样机仿真的重要性,介绍了机械系统动力学仿真软件ADAMS,讨论了利用ADAMS建立虚拟样机的特点。首次将ADAMS的应用引入到武器装备工程应用领域,对火炮反后坐装置典型故障模式进行分析,在ADAMS环境下建立了火炮虚拟样机,运用Fortran语言结合火炮故障模式编制了故障仿真外挂程序,并对故障参数影响火炮工作性能的规律进行了研究。最后,提出了故障评判函数的概念及基于虚拟样机的故障评估方案,为火炮质量评估提供了新的途径。     

Ultra-Low Loss Microwave Dielectric Ceramic Li<Subscript>2</Subscript>Mg<Subscript>2</Subscript>TiO<Subscript>5</Subscript> and Low-Temperature Firing Via B<Subscript>2</Subscript>O<Subscript>3</Subscript> Addition

Li₂Mg₂TiO₅, a rock-salt structured ceramic fabricated by a solid-state sintering technique, was characterized at the microwave frequency band. As a result, a microwave dielectric permittivity (ε_r) of 13.4, a quality factor of 95,000 GHz (at 11.3 GHz), and a temperature coefficient of resonance frequency (τ_f) of ? 32.5 ppm/°C have been obtained at 1320°C. Li₂Mg₂TiO₅ ceramics have low permittivity, a broad processing temperature region, and a low loss, making them potential applications in millimeter-wave devices. Furthermore, B₂O₃ addition efficiently lowered the sintering temperature of Li₂Mg₂TiO₅ to 900°C, which opens up their possible applications in low-temperature co-fired ceramics (LTCC) technology.     

Low-energy envelope design of residential building in hot summer and cold winter zone in China

With the development of the economy, the demand for energy in hot summer and cold winter zone in China is increasing very fast while the energy supply is going short. Air conditioning both for cooling and heating accounts for more than 50% of the total electricity used in the residential sector. This paper used eQUEST software to analyze envelope design on energy saving of air conditioner (AC) and the effects of energy saving strategies on AC electric consumption of different orientation rooms in hot summer and cold winter zone in China, which included exterior wall thermal insulation, solar radiation absorptance of exterior wall, area ratio of window to wall, categories of glazing and kinds of shading system, and two combined strategies. The results indicate that envelope shading and exterior wall thermal insulation are the best strategies to decrease the AC electric consumption which achieved a saving of 11.31 and 11.55%. The optimization of different strategies can decrease the annual electric consumption of AC by 25.92%, and cooling and heating electric consumption is decreased by 21.08 and 34.77%, respectively.     

智能决策支持系统（IDSS）在暖通空调设计决策中的应用研究

智能决策支持系统ＩＤＳＳ是一种面向对象，运用知识、数据对人们决策过程进行支持的计算机软件系统。论述了暖通空调设计决策的意义及应用方法，讨论了建立暖通空调设计决策支持系统的几个问题，开发了一个直燃式溴化锂吸收式制冷机组的选型决策支持系统，使用表明能很好地实现对用户的选型决策支持。     

An all-metallic logic gate based on current-driven domain wall motion

The walls of magnetic domains can become trapped in a ferromagnetic metallic point contact when the thickness of the film and the width of the contact are less than their critical values. The discovery that domain walls can be moved from such constrictions by a sufficiently large current has attracted considerable attention from researchers working on both fundamental research and potential applications. Here we show that Invar nanocontacts fabricated on silica substrates exhibit a sharp drop in resistance with increasing bias voltage at room temperature in the absence of an applied magnetic field. Moreover, when two nanocontacts are combined in an all-metallic comparison circuit, it is possible to perform logical NOT operations. The use of electrical currents rather than applied magnetic fields to control the domain walls also reduces energy consumption and the risk of crosstalk in devices.