Phase imaging with intermodulation atomic force microscopy

Intermodulation atomic force microscopy (IMAFM) is a dynamic mode of atomic force microscopy (AFM) with two-tone excitation. The oscillating AFM cantilever in close proximity to a surface experiences the nonlinear tip-sample force which mixes the drive tones and generates new frequency components in the cantilever response known as intermodulation products (IMPs). We present a procedure for extracting the phase at each IMP and demonstrate phase images made by recording this phase while scanning. Amplitude and phase images at intermodulation frequencies exhibit enhanced topographic and material contrast.     

Experimentally vibration and noise analysis of two types of washing machines with a proposed neural network predictor

Due to unpredictable noises, there are plenty of health problems on human. This paper is focused on neural networks (NNs) based prediction analyzer for two types drive schemes of washing machines that are direct drive and belt-pulley drive, for vibration and fault diagnosis of motors bearings. Furthermore, eight different cases including, during washing with direct drive and belt-pulley, squeezing during washing with direct drive and belt-pulley for noises and acceleration of the washing machines systems are investigated using the proposed algorithm of NNs. An Intelligent Data Acquisition (IDA), a microphone and PC are used to measure the system noise. For the case of different working conditions of the system, three types of NN are used to investigate the noise levels. The results show that NN with quick propagation algorithm gives superior performance for predicting and evaluating the noise of washing machine systems.     

Frequency measurement technique based on frequency conversion

To measure the signals with high freq u ency(>500 MHz),a sampling frequency down conversion method is introduced.This pa per analyzes the intermodulation signals and figures out the relationship betwee n the intermodulation signal and intermediate frequenc y signal.Based on the frequency conversion technology,an exclusion algorithm i s proposed a nd the actual implementation of the algorithm is given.The application resu lts show that the exclusion algorithm can identify the intermodulation signal exactly and eliminate the bad influence on the frequency measurement.     

1470nm大功率半导体激光溶脂仪控制系统设计

为了实现大功率激光溶脂仪安全、稳定的输出,设计了1 470nm大功率半导体激光溶脂的控制系统。对该控制系统所采用的驱动模块、温控模块、主控模块和人机交互模块等进行了研究。首先,采用FPGA实现恒流源的数字控制,功率反馈闭环实现恒功率控制,以提供1 470nm大功率激光器和弱激光红光指示的驱动,单片机负责实现RS232的协议解析。采用数字模拟PID混合控制,根据NTC的反馈对TEC进行驱动实现激光器温度控制。设计了基于ARM Cortex-M3架构的STM32F系列微处理器主控模块和人机交互模块,实现了相关数据的输出显示与存储、触摸屏驱动及响应以及各接口控制。最后,利用MDK平台编写控制软件并对整机控制系统进行联调和测试。实验结果表明:整机输出功率与设置功率的偏差小于2%,安全性能符合国家医用电气安全通用标准的要求。该系统能够满足1 470nm大功率半导体激光溶脂仪的稳定可靠、安全性高、抗干扰能力强等要求。     

基于CPLD的彩色线阵CCD在木板色选系统中的应用

针对彩色线阵光电耦合器件(CCD)在木板色选系统中驱动电路的设计问题,提出了一种基于复杂可编程逻辑器件(CPLD)的驱动电路设计方案。首先给出了该驱动的系统框图,并介绍了其工作原理,然后对其中各重要模块进行了详细的介绍。该系统采用了Altera公司的EPM240复杂可编程逻辑器件;分析了彩色线阵CCD芯片TCD2252D的驱动时序图;通过硬件描述语言(VHDL)实现了各脉冲信号的发送,并给出了各脉冲参数之间的时序关系。简要介绍了从RBG色彩空间到HSL色彩空间的转换。最后,在QUARTUS 2上进行信号的软件仿真测试,并用逻辑分析仪检测实际电路。应用及实践结果表明,该基于CPLD的驱动电路方案具有可靠性高、成本低廉、维护方便的优点、具有很强的可扩展性,适用于CCD传感器驱动电路的设计。     

新能源汽车驱动电机轴承噪声分析及改进措施

针对新能源汽车驱动电动机噪声大的问题,从新能源汽车中央电动机皮带传动结构的驱动总成形式入手,分析了不同径向载荷和转速下轴承的受力情况,采用西门子LMS便携式振动噪声分析仪对电动机噪声来源进行分析,发现电动机嘀嗒声可能由保持架与钢球碰撞产生.提出采用工程塑料保持架进行降噪处理,对使用不同材料保持架的轴承进行噪声对比,并分...     

SINO-005电解质分析仪的研制与实现

SINO-005电解质分析仪采用离子选择电极法（ISE）对样本进行测量,以单片机C8051F020和8713脉冲分配器取代传统的控制器来驱动步进电机。此种电解质分析仪能够同时测量样本中钾（K）、钠（Na）、氯（Cl）、钙（Ca）离子的浓度和pH值。该仪器具有测量参数多、分析速度快、样品用量少、测量准确等优点。     

High-energy spectrophotometer for rapid constituent analysis in the range of 0.25-2.4 mum

This publication describes a constituent analyzer which uses a concave holographic grating for high-energy throughput, a conjugate cam drive to allow up to ten spectral scans per second, a microprocessor for data gathering and system control, and a minicomputer for the complex statistical computations required in the interpretation of the spectral data gathered. The instrument was specifically developed for quantitative measurement of food constituents in food processing and quality control. However, as a general state-of-the-art spectrophotometer it was found to be a valuable tool in other disciplines such as industrial, clinical, and medical applications.     

Nonlinearity characterization of temperature sensing systems for integrated circuit testing by intermodulation products monitoring

This work presents an alternative characterization strategy to quantify the nonlinear behavior of temperature sensing systems. The proposed approach relies on measuring the temperature under thermal sinusoidal steady state and observing the intermodulation products that are generated within the sensing system itself due to its nonlinear temperature-output voltage characteristics. From such intermodulation products, second-order interception points can be calculated as a figure of merit of the measuring system nonlinear behavior. In this scenario, the present work first shows a theoretical analysis. Second, it reports the experimental results obtained with three thermal sensing techniques used in integrated circuits.     

An experimental study of the nozzle lip thickness effect on supersonic jet screech tones

It is well known that screech tones of supersonic jet are generated by a feedback loop driven by the instability waves. Near the nozzle lip where the supersonic jet mixing layer is receptive to external excitation, acoustic disturbances impinging on this area excite the instability waves. This fact implies that the nozzle lip thickness can influence the screech tones of supersonic jet. The objective of the present study is to experimentally investigate the effect of nozzle-lip thickness on screech tones of supersonic jets issuing from a convergent-divergent nozzle. A baffle plate was installed at the nozzle exit to change the nozzle-lip thickness. Detailed acoustic measurement and flow visualization were made to specify the screech tones. The results obtained obviously show that nozzle-lip thickness significantly affects the screech tones of supersonic jet, strongly depending on whether the jet at the nozzle exit is over-expanded or under-expanded.     

An Automated Sample Changer For X-Ray Fluorescence Analysis Of Bio-Medical Samples

ABSTRACT

A sample changer designed to process automatically up to 48 2 cc samples is described. Mechanical drive mechanisms, digital electronics logic, and operational flow diagrams are presented. The changer is an integral part of a system consisting of an x-ray exciting source, a turntable changer, a Si(Li) radiation detector, and a preprogrammed pulse-height analyzer. X-ray fluorescence analysis of a sample allows quantitation of selected trace elements after simple, spectral integrations are performed by an on-line microprocessor. Selection of the changer's MIX mode will cause each solution sample to be mixed just prior to analysis, thus insuring that representative tracer concentrations are determined.     

一种消除周期性毛刺相位误差的互补格雷码双 N 步相移法

互补格雷码双 N 步相移法因其具有鲁棒性好、检测精度高等特点在条纹投影轮廓术领域成为研究热点。 然而,传统互 补格雷码双 N 步相移法存在检测效率低以及未消除周期性毛刺相位误差的问题。 针对这些问题,本文对传统互补格雷码双 N 步相移法进行改进消除周期性毛刺相位误差,首先通过相机捕获形变条纹图像并计算出两组截断相位,然后利用两组截断相位 的相关性消除检测数据中的相位差、周期性毛刺相位误差,再对两组截断相位进行融合,最后通过互补格雷码相位展开法对融 合后的截断相位进行相位展开。 实验得出本文方法在检测效率不变的情况下,能有效消除周期性毛刺相位误差,得到高精度展 开相位,相比于未消除周期性毛刺相位误差的互补格雷码双 N 步相移法,本文检测方法精度提高了约 24. 57% ,相比于互补格 雷码 N 步相移法,本文检测方法精度提高了约 6. 29% 。     

新型激光旋光仪测量方法的研究与实现

旋光仪多用于制糖业中含糖量的测定,它在食品医药、生命科学、有机化工和高等院校教学实验等领域也有广泛的应用。近年来,基于光学旋光法的无创血糖检测技术也得到了不断地发展。现设计了一种新型激光旋光仪,采用曲线拟合的方法确定起偏器和检偏器的正交位置,与传统旋光仪中采用电子检测部分驱动反馈机制调整电机转角控制系统来寻找正交位置相比,理论上能提高测量精度。搭建了实验装置,采用白砂糖溶液作为样品对整个装置的效果进行了测试,并进行了性能分析。实验结果表明,所设计的新型激光旋光仪测量系统能够实现旋光度的测量。     

Multi-tone noise elimination in a space-constrained room lined with hybrid sound absorbers using a particle swarm method

High noise levels can be harmful to workers and lead to psychological and physiological ailments. A broadband noise hybridized with multiple pure tones has a high peak value and is detrimental to human hearing in an enclosed machine room. To efficiently reduce the reverberant part of the peak noise level, interest in shape optimization of a Helmholtz resonator attached to the internal wall is coming to the forefront. Research on Helmholtz resonators in dealing with a pure tone has been well-addressed. However, the development of a hybrid sound absorber used in simultaneously reducing both the pure tone and the broadband noise is rare. Therefore, we propose two kinds of hybrid sound absorbers (sound absorber A: a piece of perforate plate + a piece of sound absorbing material + air space + a Helmholtz resonator; sound absorber B: a piece of perforate plate + a piece of sound absorbing material + air space + two Helmholtz resonators) used to deal with a broadband noise hybridized with multiple tones. Here, two case studies for dealing with broadband noise hybridized with one tone and two tones will be introduced. Moreover, a numerical assessment of a sound absorption coefficient and the best optimized design for two kinds of hybrid sound absorbers under a space-constrained situation will be performed. Consequently, a successful approach in eliminating a broadband noise hybridized with multiple tones by using an optimally shaped hybrid sound absorber as well as a particle swarm method within a constrained space has been demonstrated.     

电解质分析仪校准方法

电解质分析仪是临床检验中的常用仪器,为了保证电解质分析仪检测结果的准确性和可靠性,我们通过大量实验和系统研究,初步建立了一套电解质分析仪的校准方法。文中对电解质分析仪的工作原理和校准方法进行了详细的介绍。     

A Two-Channel Power Amplifier with a Diplexer Output

To sum up the powers of two independent signals from a two-channel amplifier, a diplexer constructed with the use of small-sized directional couplers is used. The level of the intermodulation components of the output spectrum is decreased down to –60 dB. The output power of the signals is 10 and 75 W, respectively; the gain of the channel amplifiers is 40 dB; and the amplified signals are the video and audio signals of the TV channel 12.     

光散射粉尘测试仪的发展现状与趋势

光散射粉尘测试仪是一种广泛应用的粉尘浓度测试仪器。本文简要介绍了光散射粉尘测试仪的工作原理和结构特点,概述了国内外光散射粉尘测试仪的发展现状与技术特点,并指出光散射粉尘测试仪存在的问题及其将来发展的方向。     

A digital dynamic amplitude-frequency spectrum analyzer

A new method for recurrent calculations of spectral coefficients is used in the analyzer. A spectrum analyzer developed in accordance with up-to-date digital processing conceptions is based on very-large-scale-integration components, such as a high-speed field programmable gate array (FPGA) and a specialized signal microprocessor. The analyzer is based on a personal computer PCI card and operates on the Windows platform.     

A Pinhole Camera-Type Multichord Analyzer of Neutral Hydrogen Atoms

The design, operational principle, and results from the calibration of a multichord analyzer of neutral hydrogen atoms and their isotopes, based on the principle of a pinhole camera, is described. The analyzer is designed for studying the spatial distribution of fluxes of fast charge exchange atoms emitted by a high-temperature, magnetically confined plasma. The analyzer's dispersion system is based on electrostatic analysis. The stripping of hydrogen atoms can be performed in both a gas cell with hydrogen and a thin carbon film. The analyzer has seven spatial channels with a full angle of view of 42°. Its energy range is 1–50 keV. The energy resolution for the existing version of the analyzer can be varied between 3 and 12%.     

Retarding field analyzer for ion energy distribution measurements at a radio-frequency biased electrode

A retarding field energy analyzer designed to measure ion energy distributions impacting a radio-frequency biased electrode in a plasma discharge is examined. The analyzer is compact so that the need for differential pumping is avoided. The analyzer is designed to sit on the electrode surface, in place of the substrate, and the signal cables are fed out through the reactor side port. This prevents the need for modifications to the rf electrode--as is normally the case for analyzers built into such electrodes. The capabilities of the analyzer are demonstrated through experiments with various electrode bias conditions in an inductively coupled plasma reactor. The electrode is initially grounded and the measured distributions are validated with the Langmuir probe measurements of the plasma potential. Ion energy distributions are then given for various rf bias voltage levels, discharge pressures, rf bias frequencies--500 kHz to 30 MHz, and rf bias waveforms--sinusoidal, square, and dual frequency.