超高层建筑高速电梯关键技术研究

高速电梯作为超高层建筑的垂直运输设备,其性能备受关注。针对超高层建筑高速电梯关键技术展开探讨、分析,希望能进一步促进高速电梯的发展和应用。     

基于FPGA的多通道高速光纤光栅解调系统

研发了一种基于波长扫描光源和嵌入式解调的多通道高速光纤布拉格光栅解调系统。该系统采用半导体光放大器(SOA)结合可调谐F-P滤波器产生频率为1 kHz的稳定波长扫描光。通过使用对称三角波技术和快速FPGA解调算法,系统最终能够同时实现16个通道以及2 kHz的解调速率,测量范围80 nm。     

Enhancing nugget size and weldable current range of ultra-high-strength steel using multi-pulse resistance spot welding

ABSTRACT

This paper presents an innovative approach that uses a pulse-profile to improve the welding quality of CP1180 steel in resistance spot welding process. Three pulses with two cooling times were used in the developed multi-pulse welding (MPW) schedule. The experimental results show that the first pulse increases the contact area between the sheets to improve the current flow pattern. The second pulse was designed to extend the sheet-to-sheet contact area and corona bond for preventing rapid nugget growth. Using these designs, the nugget size was maximised through the third pulse. The maximum nugget size using the designed MPW schedule was 18.5% greater than that of the single-pulse welding schedule and the weldable current range was extended by 130%.     

基于TOD模式的高铁站区景观设计初探——以济南西客站为调研解析案例

在我国快速城市化进程中,近年来高铁站区的建设方兴未艾,城市与站区各方面的发展需求日益迫切。TOD模式作为协调城市交通与土地利用的有效途径,是一种较为理想的高铁站区发展模式。通过典型高铁站区的实地调研与问卷访谈,分析总结经验并结合TOD发展理念,建设性地提出TOD模式下的高铁站区景观设计策略,阐述相关设计内容,希望对现阶段我国高铁站区景观设计与站区TOD健康发展思路具有良好的启示。     

Pulse-burst laser-based 10kHz Thomson scattering measurements

Thomson scattering(TS),as a popular and reliable diagnostic technique,has successfully measured electron temperatures and electron number densities of plasmas for many years.However,conventional TS techniques using Nd:YAG lasers operate only at tens of hertz.Here,we present the development of a high-repetition-rate TS instrument based on a high-speed,pulse-burst laser system to greatly increase the temporal resolution of measurements.Successful instrument prototype testing was carried out by collecting TS light from laboratory helium and argon plasmas at 10 kHz.Calibration of the instrument detection sensitivity using nitrogen/oxygen rotational Raman scattering signal is also presented.Quantitative electron number densities and electron temperatures of the plasma were acquired at 10 kHz,for stable plasma discharges as,respectively,～0.9 eV and ～5.37×10~(21)m~(-3) for the argon plasma,and ～1eV and ～6.5×1021 m~(-3) for the helium plasma.     

High-Speed Trains Automatic Operation with Protection Constraints: A Resilient Nonlinear Gain-based Feedback Control Approach

This paper addresses the control design for automatic train operation of high-speed trains with protection constraints. A new resilient nonlinear gain-based feedback control approach is proposed, which is capable of guaranteeing, under some proper non-restrictive initial conditions, the protection constraints control raised by the distance-to-go (moving authority) curve and automatic train protection in practice. A new hyperbolic tangent function-based model is presented to mimic the whole operation process of high-speed trains. The proposed feedback control methods are easily implementable and computationally inexpensive because the presence of only two feedback gains guarantee satisfactory tracking performance and closed-loop stability, no adaptations of unknown parameters, function approximation of unknown nonlinearities, and attenuation of external disturbances in the proposed control strategies. Finally, rigorous proofs and comparative simulation results are given to demonstrate the effectiveness of the proposed approaches.      

Characterization of cloud cover with a smartphone camera

A smartphone sky camera and associated image analysis algorithm has been developed and validated to determine total cloud cover and the percentage of thick and thin clouds using supervised image classification for a range of cloud types, cloud cover from 4% to 98%, and solar zenith angles between 6° and 49°. Additionally, this system provides the percentage of total, thick, and thin clouds in proximity to the solar disc. The measurement errors were comparable to those associated with values obtained by commercial sky camera systems. The benefits of increasing the availability of cloud fraction measurements include the potential to develop improved local ultraviolet indices and weather forecasts and to provide a better understanding of cloud patterns required for the generation of solar energy.     

基于FPGA的高速峰值检测

针对研发数字多道的实际需求,提出了一种基于FPGA的高速峰值检测技术,并且采用ARM+FPGA的架构实现了基于该技术的数字多道系统。通过Modelsim仿真分析了FPGA峰值检测算法的理论,该算法可精确获取高斯信号的最值并获得幅度值。最后通过CZT探测器进行~(241)Am源实测γ射线能谱,实验结果表明该峰值检测算法及数字多道系统设计可准确并且快速获得能谱图。通过合理设置峰值检测算法的高低阈值,可以测试不同基线值的前放信号。     

New trends on moving object detection in video images captured by a moving camera: A survey

This paper presents a survey on the latest methods of moving object detection in video sequences captured by a moving camera. Although many researches and excellent works have reviewed the methods of object detection and background subtraction for a fixed camera, there is no survey which presents a complete review of the existing different methods in the case of moving camera. Most methods in this field can be classified into four categories; modeling based background subtraction, trajectory classification, low rank and sparse matrix decomposition, and object tracking. We discuss in details each category and present the main methods which proposed improvements in the general concept of the techniques. We also present challenges and main concerns in this field as well as performance metrics and some benchmark databases available to evaluate the performance of different moving object detection algorithms.     

A study on sensitivity correction factor of gamma camera in whole body bone image

The aim of this study was to calculate a reasonable correction factor that could be corrected when the sensitivity of each gamma camera is measured and a whole body bone scan is performed as a follow-up examination. Seven pieces of equipment were used to analyse the sensitivity measurements of each gamma camera based on the source sensitivity measurement method recommended by the IAEA. These were BRIGHTVIEW, PRECEDENCE, ECAM, ECAM signature, ECAM Plus, SYMBIA T2 and INFINIA. The ^99mTc line source for the sensitivity measurement was generated in 4–7 kcps, which are the common values in a whole body bone scan. All the cameras were equipped with a low-energy and high-resolution parallel multi-hole collimator and set at a window width and photo peak of 15% and 140 keV, respectively. After placing the ^99mTc source as closely as possible to the collimator, the count was measured for 60 and 120 seconds to calculate correction factor. To determine if the correction factor calculated using the ^99mTc line source could be applied to a whole body bone scan of a real patient, a whole body bone scan was performed on 27 patients before applying the correction factor for comparative analysis. According to the experimental results using the ^99mTc line source, the gamma camera sensitivity was the highest for ECAM plus, followed in order by the gamma cameras, ECAM signature, SYMBIA T2, ECAM, BRIGHTVIEW, INFINIA and PRECEDENCE. When the results were used to calculate the correction factor based on the ECAM gamma camera, which had a medium-degree of sensitivity, the respective correction factors were 1·07, 1·05, 1·03, 1·00, 0·90, 0·83 and 0·72. The correction factors calculated based on the experiment using a ^99mTc line source were similar to those calculated based on the whole body bone scan. Clinical application of correction factor for measured sensitivity enables estimation of factor correction depending on difference in equipment when image is read, which improves accuracy and reliability of examination, and is expected to be used especially for continuous follow-up examination.