摘要：基于"螺丝-螺母"的工作原理,设计了可调的透射型三通道螺旋单元,通过调节螺丝的旋拧深度来改变声通道的长度,从而实现对透射声波相位的调节.利用有限元方法计算了单元的透射波相位差和透射系数随频率和旋拧深度的变化规律.在平面广义Snell定律基础上推导了适用于圆弧形曲面的广义Snell定律.设计了圆弧形超表面,包括弧状和圆环状两种,实现了对透射声波波前的可调控制.根据所要实现的声学功能和给定的工作频率,利用单元的透射波相位差随旋拧深度的变化规律和圆弧形表面的广义Snell定律,确定超表面上所需的相位分布梯度及每个单元的旋拧深度,并同时考虑透射系数随旋拧深度的变化规律来对单胞旋拧深度进行适当的调整,以保证超表面具有较高的透射率.利用圆弧形超表面实现了宽频范围内声波的定向折射、波束分离和声束聚焦等声学功能的转换;利用圆环形超表面则实现了三向分波、波场螺旋化及源位置虚拟移动等声学功能的转换.同时针对上述功能进行了全波场的有限元数值模拟和相应的声学实验,实验结果与有限元模拟结果吻合良好,验证了所设计超表面对声波波前调控的有效性.研究结果将为不规则非平面可调声学器件的设计提供理论指导.

摘要：In gamma camera and single-photon emission computerized tomography, the collimator removes most photons. Here, a gamma camera without collimator utilizes a specific arrangement of detectors. Instead of bending beams(like a lens) or directing beams(by parallel hole collimator), changes are created in detectors' field of view(FOV), so that each detector's FOV looks different from others. Simulation proved this theory, with 98 detectors(2 cm 9 1.41 cm) arranged in a zigzag manner for Monte Carlo simulation. A radioactive source with energy of140 ke V was situated on the detectors' faces. Sixty projections, each 3(0 –179) apart, were simulated by Monte Carlo N-Particle(MCNP) 4C code, rotating detectors around a radioactive point. The band containing the radioactive source is clearly visible in each *** obtained after simulation in different projections were reconstructed, and point source location emerged correctly. Simulation of gamma camera with zigzag arrangement of detectors and MCNP-4C code demonstrated that one could string the space and determine radioactive source by image reconstruction without using collimators, solely through these special detectors' distribution.

摘要：中行湖北分行办公楼建筑总高度为239.9m,采用钢管混凝土柱＋钢梁混合框架＋钢筋混凝土核心筒的混合结构体系,核心筒剪力墙为整体结构提供大部分的抗侧刚度,筒体与楼盖钢梁之间采用铰接,在15层、30层设置了伸臂桁架和带状桁架形成加强层。分析表明,结构体系能满足承载力、整体稳定性、抗侧力和变形的需求。结构多项指标超限,根据设定的抗震性能目标,针对不同重要性的构件采取不同的性能水准进行了分析和设计。通过罕遇地震作用下的弹塑性时程分析,找出了结构潜在的抗震薄弱部位和薄弱构件,并提出了相应的抗震加强措施。

摘要：The most common apparatus used to investigate the load-deformation parameters of homogeneous fine-grained soils is a Casagrande-type oedometer. A typical Casagrande oedometer cell has an internal diameter of 76 mm and a height of 19 ***, the dimensions of this kind of apparatus do not meet the requirements of some civil engineering applications like studying load-deformation characteristics of specimens with large-diameter particles such as granular materials or municipal solid waste materials. Therefore, it is decided to design and develop a large-scale oedometer with an internal diameter of 490 mm. The new apparatus provides the possibility to evaluate the load-deformation characteristics of soil specimens with different diameter to height ratios. The designed apparatus is able to measure the coefficient of lateral earth pressure at rest. The details and capabilities of the developed oedometer are provided and discussed. To study the performance and efficiency, a number of consolidation tests were performed on Firoozkoh No. 161 sand using the newly developed large scale oedometer made and also the 50 mm diameter Casagrande oedometer. Benchmark test results show that measured consolidation parameters by large scale oedometer are comparable to values measured by Casagrande type oedometer.

摘要：Performance-based seismic design(PBSD) aims to assess structures at different damage states. Since damage can be directly associated to displacements, seismic design with consideration of displacement seems to be logical. In this study, simple formulae to estimate the peak floor displacement patterns of eccentrically braced frames(EBFs) at different performance levels subjected to earthquake ground motions are proposed. These formulae are applicable in a PBSD and especially in direct displacement-based design(DDBD). Parametric study is conducted on a group of 30 EBFs under a set of 15 far field and near field accelerograms which they scaled to different amplitudes to adapt various performance levels. The results of thousands of nonlinear dynamic analyses of EBFs have been post-processed by nonlinear regression analysis in order to recognize the major parameters that influence the peak displacement pattern of these frames. Results show that suggested displacement patterns have relatively good agreement with those acquired by an exact nonlinear dynamic analysis.

摘要：在当今世界,电力、能源和安全是人们日常生活的基本要求。为了应对日益增长的能源需求,最终的解决办法是实施可再生能源,然后将其用于人类的安全。可再生能源需要以它们各自正确的方式实施。研究基于压电传感器片的迈步发电装置,并演示了如何利用这些能量实现建筑物疏散照明。我们在传感器的下方和顶部分别固定了木板和可移动网螺栓,利用压电传感器系统,行人可以通过迈步向发电装置施加电能,另外,将硅凝胶粘贴在位于下部木板空洞中的所有传感器顶部。当有人踩到板上时,就会自动施加压力。在木板的顶部和底部设置了一个孔,以便随时调整在底部和顶板之间安装的可移动网螺栓。烟雾传感器用于启动灯光。使用这种设备,我们实现了建筑物疏散路径上的LED灯正常运行。结果表明,这种安全发电的设计和方法具有一定的实用价值,同时也满足了全球对能源的需求。

摘要：简·威瑟斯是一位在策展艺术领域有着深厚造诣的专家,她以其独特的视角和敏锐的洞察力,在设计、可持续性和环境倡导等多个领域都取得了显著的成就。在即将到来的2024年伦敦设计节上,她将再次担任布朗普顿设计区的策展人,为观众带来一场视觉与思想的盛宴。

摘要：Cellulose is a renewable,biodegradable,ecofriendly and sustainable *** market of nanocellulose is comprehensively very high due to its *** of nanocellulose from bacteria and plant results in different morphology and size of ***,mechanical strength,biofabrication,crystallinity,high surface area per unit mass,hydrophilicity,porosity,transparency and non-toxicity of bacterial cellulose make it more *** extravagant nanoscaled three-dimensional network of cellulosic structures possess extraordinary properties for biomedical application,evidencing its usage in skin therapy,cardiovascular implants,cartilage meniscus implants,tissue engineering,bone tissue and neural implants,wound care products,drug delivery agents,tablet modification,tissue engineered urinary conduits,and synthesis of artificial *** due to potential benefits associated with nanocellulose effective and efficient techniques are required for the isolation of nanocellulose that should be economical,ecofriendly and non-toxic.

摘要：V-shape hulls are widely used in peacekeeping efforts such as demining vehicles in order to deflect the blast energy and reduce the effects of mine blast. Blast resistant design and energy absorption enhancement of V-shape plates were carried out using finite element analysis package ABAQUS. Various geometries of V-shape plates with and without interlayer of materials like Al-foams and honeycomb were employed to analyze their effects on the deformation of the plate and applied stresses and strains. The results obtained show that application of metallic foams leads to better response of the plate and consequently results in more energy dissipation, less dame to vehicle and enhances crew survivability.

摘要：An optimal layout or three-dimensional spatial distribution of stopes guarantees the maximum profitability over life span of an underground mining ***,stope optimization is one of the key areas in underground mine planning ***,the computational complexity in developing an optimal stope layout has been a reason for limited availability of the algorithms offering solution to this *** article shares a new and efficient heuristic algorithm that considers a three-dimensional ore body model as an input,maximizes the economic value,and satisfies the physical mining and geotechnical constraints for generating an optimal stope *** implementation at a copper deposit demonstrates the applicability and robustness of the algorithm.A parallel processing based modification improving the performance of the original algorithm in terms of enormous computational time saving is also presented.