Multi-Schlieren CT Measurements of Supersonic Microjets from Circular and Square Micro Nozzles

Instantaneous three-dimensional (3D) density distributions of a shock-cell structure of perfectly and imperfectly expanded supersonic microjets escaping into an ambient space are measured. For the 3D observation of supersonic microjets, non-scanning 3D computerized tomography (CT) technique using a 20-directional quantitative schlieren optical system with flashlight source is employed for simultaneous schlieren photography. The 3D density distributions data of the microjets are obtained by 3D-CT reconstruction of the projection’s images using maximum likelihood-expectation maximization. Axisymmetric convergent-divergent (Laval) circular and square micro nozzles with operating nozzle pressure ratio 5.0, 4.5, 4.0, 3.67, and 3.5 have been studied. This study examines perfectly expanded, overexpanded, and underexpanded supersonic microjets issued from micro nozzles with fully expanded jet Mach numbers Mj ranging from 1.47 - 1.71, where the design Mach number is Md = 1.5. A complex phenomenon for free square microjets called axis switching is clearly observed with two types “upright” and “diagonal” of “cross-shaped”. The initial axis-switching is 45° within the first shock-cell range. In addition, from the symmetry and diagonal views of square microjets for the first shock-cells, two different patterns of shock waves are viewed. The shock-cell spacing and supersonic core length for all nozzle pressure ratios are investigated and reported.

Carrier fringe method of moire interferometry for tiny strain measurements in micro-field

In this paper, we demonstrate a new optical method for tiny strain measurements based on the principle of carrier fringes of moire interferometry. A cross-line grating with frequency of 1200 lp/mm is replicated on the specimen surface, and the strain can be deduced from the changes in carrier fringes before and after the deformation of an object. Four coherent laser beams are used to obtain the carrier fringe patterns of field U and V. Both theoretical analysis and numerical simulation indicate that the ideal accuracy of strain can be controlled within a range of ±1με. Case study of a plane extension experiment shows that the measurement accuracy of strain can be controlled within the range of ±10με. The average strain values of every row of field U and every column of field V can be obtained by using this method, and approximated strain of every pixel in the whole-field can be further acquired, and thus it is possible to measure tiny strains occurred in a micro-field. The technology in this paper can provide comprehensive information for analyzing related mechanical content in the field of MEMS.

Comparison between Double Crystals X-ray Diffraction and Micro-Raman Measurement on Composition Determination of High Ge Content Si_(1-x)Ge_(x) Layer Epitaxied on Si Substrate

It is important to acquire the composition of Si1-xGex layer, especially that with high Ge content, epitaxied on Si substrate. Two nondestructive examination methods, double crystals X-ray diffraction （DCXRD） and micro-Raman measurement, were introduced comparatively to determine x value in Si1-xGex layer, which show that while the two methods are consistent with each other when x is low, the results obtained from double crystals X-ray diffraction are not credible due to the large strain relaxation occurring in Si1-xGex layers when Ge content is higher than about 20%. Micro-Raman measurement is more appropriate for determining high Ge content than DCXRD.

Development of laser and microwave scanning technologies in the blast furnace burden profile and lining condition measurement at CSC

In order to stabilise the operation of the blast furnace and to raise its operation efficiency,research works for the application of microwave and laser scanning technologies to the measurement have been intensively carried out at China Steel Corporation(CSC).To monitor the burden profile during the operation,a microwave burden profile measuring system was developed.The system consists of a radar unit,a signal processing system, and a driving device which is capable of rotating the radar to scan the burden surface in a specified direction.A nitrogen cooling system was designed to protect the measurement system.A prototype burden profile meter was successfully tested in No.1 blast furnace in 2008,and a permanent one was installed at No.3 blast furnace.The system has provided useful information for adjusting the charging sequence in No.3 blast furnace.For another application,3 - D laser scanning technology is employed to monitor the blast furnace lining condition.To this end,a data registration method has been developed,through which two measured range images sensed at different period and locations can be fitted into the same coordinate system.In practice,the erosion of the blast furnace lining can be estimated when the current inner profile is compared with that taken before the blow-in operation. This technology is also adopted to evaluate the performance of gunning operation in the blast furnaces at CSC.

High-Precision Wideband Phase-Derived Velocity Measurement for Micro-Motion Extraction

A phase-derived velocity measurement method is proposed in a wideband coherent system,based on a precise echo model considering the inner pulse Doppler effect caused by fast moving targets.The Cramer-Rao low band of velocity measurement precision is deduced,demonstrating the high precision of the proposed method.Simulations and out-field experiments further validate the effectiveness of the proposed method in high-precision measurement and micro-motion extraction for targets with weak reflection intensity.Compared with the long-time integration approaches for velocity measurement,the phase-derived method is easy to implement and meets the requirement for high data rate,which makes it suitable for micro-motion feature extraction in wideband systems.

Generation and Display System of Measurement Matrix Based on DMD

A measurement matrix is the key to sampling and signal reconstruction during the process of compressed sensing.On the basis of digital light processing(DLP)technology,ageneration and display system of measurement matrix based on digital micro-mirror device(DMD)is proposed and well designed.In this system,the generation and controlling of measurement matrix are implemented on a PC,which reduces the hardware requirement to generate a random matrix and overcomes the difficulty of the hardware implementation for the random matrix.It can set up the display number of the measurement matrix,the mode of display and display time according to the requirements from users.The display information can be designed to complete the display of measurement matrix with a better adaptability.The system can be easily embedded into a variety of compressed sensing applications,which can be used to generate and display the corresponding measurement matrice with strong portability.In addition,the DMD of this system will be used as a spatial optical modulator to manipulate near-infrared light in a fast,accurate and efficient way in several applications such as in 3D scanning devices and spectrometers.

不同长度micro-lysimeters对测定土壤蒸发的影响

研究了 5 ,10 ,15 ,2 0 ,2 5 cm共 5种不同长度处理和内壁有孔、内外壁均有孔 2种处理由 PVC管制成的 micro- lysimeters对土壤蒸发的影响。结果表明 :降雨后 5 ,10 cm处理的土壤水分蒸发较快 ,15 ,2 0 ,2 5 cm处理的变化不明显 ,可以利用 15 cm长的 m icro- lysimeters测定土壤蒸发 ;壁上有孔处理的蒸发要高于同样长度的无孔处理。

应用Micro CT下颌磨牙“C”形根管的解剖学研究

目的应用Micro CT技术研究尚未修复或牙髓治疗的下颌第二磨牙"C"字形根管的患病率及解剖学特点。方法应用Micro CT(Skyscan1072,Antwerpen,Belgium)及cutome计算机软件分析"C"字形牙根管结构。测量下颌第二磨牙"C"形根颈部、中部、根尖部位牙体组织最小厚度及正常下颌第二磨牙的危险区域的厚度。结果 60颗牙中"C"字形根管占46.2%,舌侧融合97%。在下颌第二磨牙的"C"字形根管根颈部、中部、根尖部窝沟区的最薄牙体组织厚度与正常下颌第二磨牙的危险区域厚度的测量结果无统计学差异(P>0.05)。结论 Micro CT是一种快速、准确、不损伤样本内部结构有效的评价方法。"C"字形根管解剖结构的分析和解剖数据库的建立,将为口腔医师提供可靠的参考和依据。

DISTRIBUTED MICROBEND FIBER-OPTIC STRAIN SENSOR

The distributed strain sensor has significant application in real time measurement of strain status for large and important engineering structures such as aircraft, bridge and dam. In this paper, a quasi distributed optical fiber strain sensor system is set up using optical time domain reflect technique. The local strain sensors based on a novel microbend configuration are designed and applied to measure local strains along the optical fiber. As the result of the experimental research, the microbend sensors show high sensitivity, good linearity and repeatability in certain operation range.

用Micro-CT测量ICFT型源靶柱腔诊断孔轴线与靶杆夹角的研究

用微CT测量ICF(惯性约束聚变)T型源靶柱腔诊断孔轴线与靶杆夹角(下文以θ代替)可以有效的排除柱腔外壁所镀金层厚度的不均匀对测量结果的影响。将微CT测量的两种方法与金层厚度均匀条件下用显微镜测量的结果进行比较,得出划定诊断孔上下边界点找中心的微CT测量方法具有更高的可信度。

基于低密度粒子图像叠加的Micro-PIV速度场测量

提出了一种基于低密度粒子图像的微流体粒子图像全场测速技术。经过背景噪声去除、阈值过滤、图像增强等图像预处理过程,获得了高质量的低密度荧光示踪粒子图像。对100对图像进行图像叠加处理,得到了满足互相关算法求解二维速度场的高密度叠加粒子图像。针对宽度为250μm,深60μm的长直微通道开展了覆盖全场不同流体层平面的二维速度测量,并利用多个流体平面的二维速度场实现了微通道内全场速度的构建。研究结果表明:由于图像叠加法去除了像径大但灰度低的背景粒子图像,采用互相关分析能够准确获得分层二维速度场,所构建的全场速度场正确反映了长直微通道内流流场特征。

Approach to inter-satellite time synchronization for micro-satellite cluster

Micro-satellite cluster enables a whole new class of missions for communications, remote sensing, and scientific research for both civilian and military purposes. Synchronizing the time of the satellites in a cluster is important for both cluster sensing capabilities and its autonomous operating. However, the existing time synchronization methods are not suitable for microsatellite cluster, because it requires too many human interventions and occupies too much ground control resource. Although, data post-process may realize the equivalent time synchronization, it requires processing time and powerful computing ability on the ground, which cannot be implemented by cluster itself. In order to autonomously establish and maintain the time benchmark in a cluster, we propose a compact time difference compensation system（TDCS）, which is a kind of time control loop that dynamically adjusts the satellite reference frequency according to the time difference. Consequently, the time synchronization in the cluster can be autonomously achieved on-orbit by synchronizing the clock of other satellites to a chosen one＇s. The experimental result shows that the standard deviation of time synchronization is about 102 ps when the carrier to noise ratio（CNR） is 95 d BHz, and the standard deviation of corresponding frequency difference is approximately0.36 Hz.

Analysis and Prevention for Oscillation Failure of Capacitive Micro-accelerometers

As actuator of the force-rebalanced servo loop, the electrostatic force generator of the micro-accelerometer shows high nonlinearity while the interpole of the micro-electro-mechanical system（MEMS） sensor is far away from its balance position. The control system cannot rebalance itself with the limited bandwidth after an external long overload, because the characteristics of the force generator differ from normal case. Although for similar problems, solutions with cascading lead-lag blocks, with the anti-windup（AW） technology, or with the sliding-mode control, are widely reported, the problems such as performance loss or difficulty to synthesize a digital controller still remain. Based on existing researches, remedies are developed by analyzing the characteristic of the system not only near the balance position, but also corresponding to the whole moveable range of the interpole, and a new controller is proposed. The solution is compared with the common solutions of cascading lead-lag blocks method, AW methods, and sliding mode methods. Comparison results show that the proposed solution avoid performance loss, compared to cascading lead-lag blocks solution; the proposed solution is easily synthesized and implemented in the analog servo loop of the micro-accelerometer, compared to digital AW methods; at the same time, the proposed solution avoids suffering the chattering effect problem but just utilize it, compared to the sliding-mode control solution. Nevertheless, comparison results show the solution is lack of commonality, since the solution is only more suitable to micro electrostatic force-rebalance system. The SIMULINK models with and without the proposed solution, taking typical micro-accelerometer parameters, have been set up for simulation; corresponding experiments utilizing electrometric method are also conducted after the successful simulations. Simulation and experiment results verify that the micro-accelerometer will reliably return to normal operation after external long overload with the proposed solution. Therefore, it is expected to design the analog servo loop of high performance micro electrostatic force-rebalance system so as to ensure the rebalance after long overload without performance loss.

NEW SELF-MIXING MICRO-INTERFEROMETER BASED ON EXTERNAL PHASE MODULATION

ASeblsf-tmraicxti：n gA innteewrf esreelnf-cme ioxcincgu rms iicnr oa -liansteerrf derioodmee t（eLrD b）a sbeyd r eofnl eecxtitnergn tahl ep lhiagshet fmroomdu ala tmioinrr oisr-plirkees etanrtgedet. in front of the laser. Sinusoidal phase modulation of the beam is obtained by an electro-optic crystal （EOC） in the external cavity. The phase of the interference signal is demodulated by Fourier analysis method. The combination of the modulation and demodulation decreases the sensitivity of the instru-ment to fluctuations of the laser power and the noise induced by environment. Experimentally, the new micro-interferometer is applied to measure the micro-displacement of a high precision commer-cial PZT with an accuracy of 〈10 nm.

Development of MEMS-based micro capacitive tactile probe

In this paper, a micro capacitive sensor with nanometer resolution is presented for ultra-precision measurement of micro components, which is fabricated by the MEMS （micro electromechanical systems） non-silicon technique. Based on the sensor, a micro capacitive tactile probe is constructed by stylus assembly and packaging design for dimension metrology on micro/nano scale, in which a data acquiring system is developed with AD7747. Some measurements of the micro capacitive tactile probe are performed on a nano positioning and measuring machine （NMM）. The measurement results show good linearity and hysteresis with a range of 11.6 μm and resolution of better than 5 nm. Hence, the micro capacitive tactile probe can be integrated on NMM to realize measurement of micro structures with nanometer accuracy.

COMPACT PHASE GRATING INTERFERENCE SENSOR FOR MICRO-DISPLACEMENT

On the basis of existing techniques, a compact micro-displacement sensor of phase grating interference （PGI） is described, which adopts cylindrical hologram diffraction grating as the calibration standard. The optical principle of the sensor is explained, and the relation between the grating motion displacement and the phase shift of interference stripes is deduced. The improvement of the integral structure and the method of photoelectric signal processing are described in detail. With the software system based on the virtual instrument development platform Labwindows/CVI and other hardwares such as the precision displacement worktable, the surfaces of typical parts are measured and the characterization results are given. The sensor has wide measuring range and high resolution, its sensitivity and resolution being independent of the wavelength of the incident light. The vertical measuring range is 0-6 mm, and the vertical resolution is 0.005μm. The experimental results show that the sensor can be used to measure and characterize the surface topography parameters of the plane and curved surface.

Comparison of Multimodality Image-Based Volumes in Preclinical Tumor Models Using <i>In-Air</i>Micro-CT Image Volume as Reference Tumor Volume

Purpose: Changes in tumor volume are used for therapy response monitoring in preclinical studies. Unlike prior studies, this article introduces in-air micro-computed tomography (micro-CT) image volume as reference tumor volume in rodent tumor models. Tumor volumes determined using imaging modalities such as magnetic resonance imaging (MRI), micro-CT and ultrasound (US), and with an external caliper are compared with the reference tumor volume. Materials and Methods: In vivo MR, US and micro-CT imaging was performed 4, 6, 9, 11 and 13 days after tumor cell inoculation into nude rats. On the day of the imaging study, in vivo caliper measurements were also made. After in vivo imaging, tumors were excised followed by in-air micro-CT imaging and ex vivo caliper measurements of excised tumors. The in-air micro-CT image volume of excised tumors was determined as reference tumor volume. Then tumor volumes were calculated using formula V = (π/6) × a × b × c, where a, b and c are maximum diameters in three perpendicular dimensions determined by the three image modalities and caliper, and compared with reference tumor volume by linear regression analysis as well as Bland-Altman plots. Results: The correlation coefficients (R2) of the regression lines for in vivo tumor volumes measured by the three imaging modalities were 0.9939, 0.9669 and 0.9806 for MRI, US and micro-CT respectively. For caliper measurements, the coefficients were 0.9274 and 0.9819 for caliperin vivo and caliperex vivo respectively. In Bland-Altman plots, the average of tumor volume difference from reference tumor volume (bias) was significant for caliper and micro-CT, but not for MRI and US. Conclusion: Using the in-air micro-CT image volume as reference tumor volume, tumor volume measured by MRI was the most accurate among the three imaging modalities. In vivo caliper volume measurements showed unreliability while ex vivo caliper measurements reduced errors.

基于双层三维太赫兹超材料的多功能传感器

传感器作为集成化器件中至关重要的部分,其多功能性越来越受到重视。本文介绍了一种基于双层三维谐振结构耦合的太赫兹超材料多功能传感器。传感装置包括上下两层聚酰亚胺薄膜基底,附着在下层聚酰亚胺薄膜基底上的石墨层,以及在石墨层和上层聚酰亚胺薄膜基底之间的周期性双层三维齿形耦合谐振结构,此结构包括下层对称山形结构和上层对称凹形结构。该三维超材料结合多层结构可实现多功能测量:可通过谐振频率确定待测液体介质层的折射率变化,从而实现液体成分的高精度分辨;在一维方向的微位移传感方面,则可分别在z轴方向以及y轴方向上实现微位移的高灵敏度测量。本文所提出的三维超材料传感器能为功能集成化传感在太赫兹领域的应用提供了新的思路。