VCSEL激光器抗干扰温度控制

由于VCSEL具有低功耗、小体积、高调制频率和容易集成等特征,被广泛应用于磁探测领域之中。作为一种高精密的传感器,原子磁强计在测量磁场过程中由于激光器的输出不稳定导致测量精度下降。针对环境等干扰导致激光器的输出不稳定问题,设计了一种可以抵抗环境温度变化的控制器。首先,通过带DSP内核的ADAU1401A芯片与DPSD方法实现了高分辨率温度解算;然后,通过系统辨识的方式建立温控数学模型;最后,应用干扰观测器与内模控制原理设计出抗扰动、低超调、鲁棒性的控制器。实验结果表明:在70 ℃温度下, 存在干扰的控制精度为±0.003 ℃,常温下控制精度为±0.001 5 ℃,为激光器稳定输出与高精度磁场测量奠定了基础。     

Stabilising surface-wave devices against temperature variations

Surface-elastic-wave devices can be temperature-stabilised with a feedback circuit which includes a phase comparator for a reference signal and a deposited thin-film heater. In a 50 MHz yz lithium-niobate test delay line, the phase variation corresponded to a maximum temperature change of ±0.017°C, while the ambient temperature varied from 25 to 35°C.     

A Temperature Control System for Small Biological Preparations, Displaying Relatively Fast Heating and Cooling Capability

An apparatus is described with which it is possible to warm and cool the main duct of rabbit submaxillary gland in 10cc Ringer solution between 0°C and 50°C. The apparatus can be used for any small biological preparations such as muscles, nerves, etc. The heating and cooling is performed by a peltier element together with its control unit. Temperature is measured with a Cu-Const. thermocouple-with the reference placed in melting ice. The absolute accuracy of the temperature is ±0.5°C but reproducibility is within 0.10C. Speed of warming up for a large temperature change (AT) is 0.8°C/s. Cooling is-stower, i.e., 0.4°C/s. For AT 5°C the speed of warming up is about 0.60°C/s and the cooling rate in this case varies between 0.5°C/s and 0.16°C/s depending upon starting temperature. Full details are given about the construction of the control unit and the perfusion chamber in which the main duct is mounted. Some modifications are discussed with which it is also possible to use the system for flat biological preparations. The use of the apparatus as a programmable temperature system or as a temperature function generator is also discussed.     

A Laser Stimulator for the Study of Cutaneous Thermal and Pain Sensations

A laser thermal stimulator system is described which enables the psychophysical and neurophysiological study of cutaneous thermal and pain sensations by means of a non-contact, precise stimulator. A carbon dioxide laser is used as the heat source with closed loop control of skin temperature via a sophisticated radiometer. Temperature steps of 0.1°C to 25°C have been achieved with rise rates of greater than 30°C/second. The temperature can be maintained to better than ±0.1°C over pulse durations of 0.3 seconds to 20 seconds.     

适用于AFM的数字智能反馈控制器设计

原子力显微镜(AFM)是进行纳米测量和操作的一种重要工具.近年来,纳米科技的迅速发展使得传统AFM越来越无法满足纳米测量快速和高分辨率的测试需求,而反馈控制器的速度是限制AFM成像速度和分辨率的关键因素之一.为此,本文搭建基于高速数字信号处理器(DSP)的数字反馈控制系统,将模糊控制算法与比例积分PI控制算法结合,利用模糊规则自动选择合适的比例和积分参数,改善Z向反馈系统的鲁棒性.基于自制的AFM系统,将该方法与传统PI控制算法进行对比实验,在相同的扫描条件下,该数字智能反馈控制器可在扫描范围为30μm×30μm时,将AFM的行扫描速度由3 Hz提高到40 Hz,验证了该方法能够有效改善AFM的扫描速度和成像分辨率.     

A Modular Expandable Implantable Temperature Biotelemeter

An implantable biotelemetry system is described for multisite temperature measurements with ease of expansion by use of different master circuit boards to accommodate additional channels. Modular construction of the multichannel FM-FM system allows addition or deletion of channels as the experiment requires. The radio frequency carrer osciUlator is tunable to a "quiet" frequency in the 90-105 MHz range prior to implantation. The telemeter may incorporate enclosed or remote temperature probes which allow deep body temperature measurements in the range of 30-42 °C with an available resolution of ±0.015°C. Transmitters have been utilized in monitoring ovarian and subcutaneous temperatures, and also as an aid in detection of ovulation in the Macaca mulatta.     

A Zero-Heat-Flow Transducer for Monitoring Perfusion Blood Temperature

The transducer in which the zero-heat-flow method was applied is designed for monitoring the blood temperature flowing in a tube. The circumference of the probe was heated or cooled to the same temperature as the tube-surface temperature which finally showed the blood temperature, so that the net heat flow across the probe was reduced to zero. Experiments showed that the water temperature could be measured from the surface of a vinyl-chloride tube with the accuracy of ±0.2°C between 20 and 400°C of water temperature. The measured temperature was not affected by the ambient temperature, tube thickness, tube material, and flow rate. Time delay of ramp-like change in the water temperature was around 2 min to measure on the vinyl-chloride tube. Time delay depends on the heat capacity of the metal frame, the thermal conductivity of the tube material, and the power of thermomodule. The in vivo experiment of this device appeared to be satisfactry with a high accuracy and good response time.     

High-peak-power asymmetric double-heterostructure (GaAl)As-GaAs injection laser

An asymmetric double-heterostructure pulsed-power laser is described. This laser exhibits low-temperature sensitivity of optical power in the operating temperature range of ?40 to +90°C. The threshold current is below 10 A at 90°C. The power loss at 40 A and 90°C operation is at least a factor of two less severe for this structure compared to that of the single heterostructure.     

基于MgO:PPLN晶体的中红外光参量振荡器的数值计算与分析

本文计算分析了基于准相位匹配技术的光参量振荡器的输出波长,其中振荡器所用的非线性晶体是极化周期为26-31μm(每个极化周期之间间隔为0.5μm)的MgO:PPLN晶体,晶体温度控制在40-200°C范围内,振荡器的泵浦波长为1.064μm。计算出输出波长为1.355-1.735μm(信号光范围)和2.75-4.948μm(闲频光范围),并分析了在该振荡器中极化周期、晶体温度和输出波长之间的关系。     

Low-voltage light-amplitude modulation

A 45°y cut low-voltage light-amplitude modulator is described, overcoming previously reported difficulties. The thermal dependence of retardation is discussed, and a feedback system is outlined to control the d.c. light-intensity drift to ±0.5% of its preset value.     

A Temperature Compensated Ultrasonic Sensor Operating in Air for Distance and Proximity Measurements

An ultrasonic sensor operating in air was developed to measure distance (up to 100 cm) or to operate as a proximity sensor in a presettable distance range. The error in the measured distance is about ±1 mm while the accuracy is maintained within ±1 percent of the reading in the whole temperature range from -20°C to +110°C, being the temperature dependence of the sound velocity electronically compensated. As a proximity sensor it can overcome most of the drawbacks and limitations of inductive, capacitive, optical, and Hall-effect commercial proximity sensors.     

Dual-row needle arrays under an electromagnetic thermotherapy system for bloodless liver resection surgery

Electromagnetic thermotherapy has been extensively investigated recently and may become a new surgical modality for a variety of medical applications. It applies a high-frequency alternating magnetic field to heat up magnetic materials inserted within the human body to generate tissue coagulation or cell apoptosis. Using a new procedure with dual-row needle arrays under an electromagnetic thermotherapy system with a feedback temperature control system, this study demonstrates bloodless porcine liver resection, which is challenging using existing methods. In vitro experiments showed that hollowed, stainless-steel needles could be heated up to more than 300 °C within 30 s when centered under the induction coils of the electromagnetic thermotherapy system. In order to generate a wide ablation zone and to prevent the dual-row needle arrays from sticking to the tissue after heating, a constant temperature of 120 °C was applied using a specific treatment protocol. The temperature distribution in the porcine livers was also measured to explore the effective coagulation area. Liver resection was then performed in Lan-Yu pigs. Experimental results showed that seven pigs underwent liver resection without bleeding during surgery and no complications afterward. The dual-row needle arrays combined with the electromagnetic thermotherapy system are thus shown to be promising for bloodless tissue resection.     

A radio-frequency coupling network for heating of citrate-coated gold nanoparticles for cancer therapy: design and analysis

Gold nanoparticles (GNPs) are nontoxic, can be functionalized with ligands, and preferentially accumulate in tumors. We have developed a 13.56-MHz RF-electromagnetic field (RF-EM) delivery system capable of generating high E-field strengths required for noninvasive, noncontact heating of GNPs. The bulk heating and specific heating rates were measured as a function of NP size and concentration. It was found that heating is both size and concentration dependent, with 5 nm particles producing a 50.6 ± 0.2 °C temperature rise in 30 s for 25 μg/mL gold (125 W input). The specific heating rate was also size and concentration dependent, with 5 nm particles producing a specific heating rate of 356 ± 78 kW/g gold at 16 μg/mL (125 W input). Furthermore, we demonstrate that cancer cells incubated with GNPs are killed when exposed to 13.56 MHz RF-EM fields. Compared to cells that were not incubated with GNPs, three out of four RF-treated groups showed a significant enhancement of cell death with GNPs (p<0.05). GNP-enhanced cell killing appears to require temperatures above 50 °C for the experimental parameters used in this study. Transmission electron micrographs show extensive vacuolization with the combination of GNPs and RF treatment.     

Light sensitivity of Al0.25Ga0.75As/GaAs modulation-doped structures grown by molecular beam epitaxy: effect of substrate temperature

The sensitivity of carrier concentration and mobility of Al0.25Ga0.75As/GaAs modulation-doped structures to light exposure has been studied. The light sensitivity of both parameters was found to be strongly dependent on the growth temperature of the Al0.25Ga0.75As which was varied between 580°C and 695°C. A growth temperature of about 610°C was observed to produce the least light sensitivity, while a growth temperature of 660°C resulted in the most sensitivity to light. The corresponding minimum and maximum changes in carrier concentration, measured at 10 K, were 5% and 52% of the dark values, respectively, while changes in mobility were 2% and 40%, respectively. A persistent photoconductivity effect was also observed in the samples. The minimum in this effect was found to be a 1% change in 10 K carrier concentration at a growth temperature of 610°C.     

Standing stability enhancement with an intelligent powered transfemoral prosthesis

The authors have developed a ground-adaptive standing controller for a powered knee and ankle prosthesis which is intended to enhance the standing stability of transfemoral amputees. The finite-state-based controller includes a ground-searching phase, a slope estimation phase, and a joint impedance modulation phase, which together enable the prosthesis to quickly conform to the ground and provide stabilizing assistance to the user. In order to assess the efficacy of the ground-adaptive standing controller, the control approach was implemented on a powered knee and ankle prosthesis, and experimental data were collected on an amputee subject for a variety of standing conditions. Results indicate that the controller can estimate the ground slope within ±1° over a range of ±15°, and that it can provide appropriate joint impedances for standing on slopes within this range.     

New 1.5 ?m wavelength GaInAsp/InP distributed feedback laser

A new 1.5 ?m-wavelength GalnAsP/InP distributed feedback buried-heterostructure laser was fabricated by a three-step LPE growth process. The second-order corrugation grating was formed on the waveguide layer grown on the active layer. High differential quantum efficiency of 13%/facet was obtained. Single-longitudinal-mode operation in the temperature range from ?20°C to 55°C was obtained.     

BSO/fibre-optic voltmeter with excellent temperature stability

A new BSO/fibre-optic voltmeter for measurement of AC voltage from 0 to 500 V has been successfully developed for practical use in various fields. This voltmeter has been given outstanding temperature stability of within ± 0.2% from ?10°C to 85°C by using the electro-optic effect of a 4.7 mm-thick Bi12SiO20.     

用于红外气体检测的多通池温度、压强控制系统研制

为了实现CO₂气体同位素的高性能检测,研制了高精度、高稳定性的多通池温度、压强控制系统。采用柔性PCB作为加热片包覆圆柱形多通池。考虑到温度控制系统的加热速率,外层包覆保温棉作为隔热装置,使得整个温度控制系统能实现快速加热,且能够保持温度的长时间稳定。采用铂电阻PT1000温度传感器对多通池温度进行精确采集,主控制器通过PWM信号,调控柔性PCB加热膜的发热功率,从而实现温度的闭环控制。压强控制系统方面,采用压强传感器连接于多通池前、后端,检测多通池内部气压,主控制器通过PWM信号,调控多通池前、后端比例阀导通状态,从而实现压强的闭环控制。结果表明,温度控制范围为18.48~42 ℃,温度控制精度为±0.08 ℃。多通池压强为60 Torr(1 Torr ≈ 133.322 Pa)时,控制精度为±0.04 Torr。该系统为红外CO₂气体同位素的高性能检测提供可靠保障。     

Regrowth of amorphous layers in silicon-on-insulator structures formed by the implantation of oxygen

Synthesised silicon-on-insulator structures have been formed and implanted with 1×1016 As+ cm?2 at 40 keV. The regrowth kinetics of the amorphised layer, which also contains lattice defects and excess oxygen, has been studied by Rutherford backscattering. The regrowth of the layer occurs at a mean rate of 13 ? min?1 at 500°C with an activation energy of 2.7±0.2 eV. This experiment further demonstrates the suitability of these synthesised structures as a direct replacement for bulk silicon in VLSI technology.     

后路经椎弓根椎体楔形截骨矫形治疗胸腰椎陈旧性骨折伴后凸畸形

目的：探讨后路经椎弓根椎体楔形截骨矫形治疗胸腰椎陈旧性骨折伴后凸畸形的临床疗效。方法：回顾性分析我科于2006年1月至2010年10月收治的胸腰椎陈旧性骨折伴后凸畸形患者23例,男15例,女8例;年龄23岁至88岁;胸113例,胸127例,腰19例,腰24例;胸腰段（胸10~腰2）后凸畸形Cobb角为32°至66°,平均为46°±2.4°;伤椎后凸Cobb角为16°至42°,平均30°±1.8°。术前神经损伤程度按照ASIA分级：C级3例,D级11例,E级9例;腰背痛VAS评分平均7.84±0.28。23例患者均采用经椎弓根椎体楔形截骨矫形、减压、椎弓根钉系统内固定植骨融合手术治疗。结果：术后胸腰段后凸Cobb角平均12°±1.7°,矫正率74%;伤椎Cobb角为0°至4°,平均2.8°,矫正率91%;术后随访X片,胸腰段Cobb角矫正丢失角度不明显（2°至5°）。术后神经功能ASIA分级：3例C级2例改善至E级,1例为D级;11例D级均改善至E级;腰背痛VAS评分平均为2.9±0.13;内固定物无松动或断裂,无假关节形成等并发症。结论：后路经椎弓根椎体楔形截骨矫形治疗胸腰椎陈旧性骨折伴后凸畸形可重建胸腰段矢状面生理曲度,改善临床症状。