超高频振动下材料本构关系探析

金属材料在超高频振动作用下的屈服点，硬化度和延伸率都较常规情况明显降低，因此材料的本构关系发生了重大变化。研究金属材料在超高频振动下的特殊行为，建立材料在超高频振动下的本构方程，利用所建立的本构方程解释这些特殊现象，给出了低碳钢试件的实验曲线，通过与理论分析比较证明二者完全相符。     

Disturbance Attenuation and Trajectory Tracking via a Reduced-order Output Feedback Controller for Robot Manipulators

This paper presents a solution to the problem of trajectory tracking with external disturbance attenuation in robotics systems via a reduced-order output feedback controller, without velocity measurement. The proposed control law ensures both semi-global asymptotic stability of the closed-loop system and external disturbance attenuation. The approach is based on the notion of the L₂-gain and requires to solve two algebraic Riccati inequalities. The proposed controller design is illustrated by a simulation example.     

狭长区域内120m钢筋混凝土烟囱控制爆破拆除

在狭长区域内实施高烟囱定向爆破拆除,必须解决精确定向和落地冲击问题。本文结合峨眉铝业集团120m钢筋混凝土烟囱的爆破拆除,介绍了出灰口、后坐和偏心等几个重要问题的处理,提出了控制定向精度的方法和工艺手段。文中还介绍了爆破缺口参数的计算、震动安全距离的校核以及作者的体会。     

热风式大气湍流模拟装置的哈特曼测量

大气湍流是由于大气温度、压强的随机变化引起大气折射率随机改变而产生的。遵循这一原理,热风式湍流模拟装置对传输光束周围的空气加热,用风扇抽吸热空气产生湍流,通过改变加热温度和风扇的转速,模拟不同强弱的湍流。用哈特曼传感器对该装置进行测量并采集数据,通过波前斜率处理复原波前,在此基础上从时间域和空间域等方面分析所产生湍流的特点,并与理论进行比较。结果表明,该装置能产生基本符合大气湍流统计理论的湍流。     

Nonlinearity Measurements of High-Power Laser Detectors at NIST

We briefly explain the fundamentals of detector nonlinearity applicable to both electrical and optical nonlinearity measurements. We specifically discuss the attenuation method for optical nonlinearity measurement that the NIST system is based upon, and we review the possible sources of nonlinearity inherent to thermal detectors used with high-power lasers. We also describe, in detail, the NIST nonlinearity measurement system, in which detector responsivity can be measured at wavelengths of 1.06 µm and 10.6 µm, over a power range from 1 W to 1000 W. We present the data processing method used and show measurement results depicting both positive and negative nonlinear behavior. The expanded uncertainty of a typical NIST high-power laser detector calibration including nonlinearity characterization is about 1.3 %.     

辊套材料对铸轧区磁感应强度影响的实验研究

电磁场快速铸轧技术要求辊套材料不仅具有高导热系数、高承载能力和高抗疲劳能力，而且要具有磁场控制能力，保证铸轧区足够的磁感应强度，达到细化晶粒、改善板坯组织性能的目的．本文主要从介质对电磁场的集肤效应、涡流效应、磁场衰减以及屏蔽效应的角度，研究辊套对铸轧区电磁场的影响．     

强化作用在重油催化裂化中的应用

对常渣及其添加表面活性剂后的强化油进行了催化裂化反应对比实验研究,结果表明,由于表面活性剂对催化裂化反应的强化作用,改善了原料油与催化剂的接触状况,提高了原料的转化深度。在相同反应条件下,强化油的转化率比常渣高4～6个百分点,汽油产率提高2～5个百分点,液化气产率提高3个百分点左右,液收率增加4～6个百分点,干气产率增加近2个百分点,柴油产率下降1～2个百分点,焦炭产率下降2个百分点。在近似转化率下,强化油作为原料时的产品选择性优于常渣。     

Artificial intelligence implementation in the APS process diagnostic

Thermal spray process is a technique of coating manufacturing implementing a wide variety of materials and processes. This technique is characterized by up to 150 processing parameters influencing the coating properties. The control of the coating quality is needed through the consideration of a robust methodology that takes into account the parameter interdependencies, the process variability and offers the ability to quantify the processing parameter-process response relationships. The aim of this work is to introduce a new approach based on artificial intelligence responding to these requirements. A detailed procedure is presented considering an artificial neural network (ANN) structure which encodes implicitly the physical phenomena governing the process. The implementation of such a structure was coupled to experimental results of an optic sensor controlling the powder particle fusion state before the coating formation. The optimization steps were discussed and the predicted results were compared to the experimental ones allowing the identification of the control factors.     

Axial power flow distributions of ultrasonic guided waves in viscous liquid-filled pipes

The axial power flow (APF) magnitude and attenuation distributions of ultrasonic longitudinal guided waves in viscous liquid-filled elastic pipes are investigated. The optimal location, optimal mode and its frequency-thickness product (fd) for the test of pipes filled with viscous liquid are chosen according to APF and attenuation distributions. The results show that the APF magnitude distribution is an important parameter in choosing the modes and parameters. A particular mode has weak dispersion in ranges of fd values with large group velocity, while other modes with smaller group velocity in the same fd ranges have stronger dispersion. It has been observed that, within these ranges, the chosen mode has a larger APF on the pipe's wall. Therefore, in the region of fd values where a particular mode has a large group velocity, this mode will be effective to be used in testing elastic pipes filled with viscous liquid. The results obtained from both the APF analysis and attenuation distribution are consistent.     

Comparison of land surface emissivity and radiometric temperature derived from MODIS and ASTER sensors

This study compared surface emissivity and radiometric temperature retrievals derived from data collected with the MODerate resolution Imaging Spectroradiometer (MODIS) and Advanced Spaceborne Thermal Emission Reflection Radiometer (ASTER) sensors, onboard the NASA's Earth Observation System (EOS)-TERRA satellite. Two study sites were selected: a semi-arid area located in northern Chihuahuan desert, USA, and a Savannah landscape located in central Africa. Atmospheric corrections were performed using the MODTRAN 4 atmospheric radiative transfer code along with atmospheric profiles generated by the National Center for Environmental Predictions (NCEP). Atmospheric radiative properties were derived from MODTRAN 4 calculations according to the sensor swaths, which yielded different strategies from one sensor to the other. The MODIS estimates were then computed using a designed Temperature-Independent Spectral Indices of Emissivity (TISIE) method. The ASTER estimates were derived using the Temperature Emissivity Separation (TES) algorithm. The MODIS and ASTER radiometric temperature retrievals were in good agreement when the atmospheric corrections were similar, with differences lower than 0.9 K. The emissivity estimates were compared for MODIS/ASTER matching bands at 8.5 and 11 μm. It was shown that the retrievals agreed well, with RMSD ranging from 0.005 to 0.015, and biases ranging from −0.01 to 0.005. At 8.5 μm, the ranges of emissivities from both sensors were very similar. At 11 μm, however, the ranges of MODIS values were broader than those of the ASTER estimates. The larger MODIS values were ascribed to the gray body problem of the TES algorithm, whereas the lower MODIS values were not consistent with field references. Finally, we assessed the combined effects of spatial variability and sensor resolution. It was shown that for the study areas we considered, these effects were not critical.