多探测源优化布站方法

为了在给定的应用背景和任意的自然环境下形成无缝探测,提出了警戒系统的一种多探测源优化布站方法——GT算法,即在优化选择的探测源阵地网格中,根据各类探测源的性能差异而部署在不同的探测源阵地上,从而使预警系统具有反低空突防的能力.

基于突防航迹的多探测源优化布站方法

在假定的预警区域内给出了一条最优的突防航迹,同时提出了根据突防航迹和各类探测源的性能差异进行多探测源优化布站的方法———网格GT搜索算法.结果表明,该布站方案能有效地探测超低空突防的飞行器.

多探测点超声法在线钢轨检测系统研究

钢轨是铁路运输中主要组成部分,因此钢轨质量至关重要。针对传统钢轨检测方法探测点不全面、误报多、成品之后进行检测的不足,提出一种多探测点超声法在线钢轨检测系统。该系统可实现钢轨在矫正工序后的在线超声波A扫和C扫,系统具有检测迅速、缺陷定位精准的特点。多探测点超声法在线对钢轨的检测,强化了传统钢轨超声检测的应用范围,具有抗干扰能力强、检测效率高、探测品种多和参量容易调节等优点。

多探测点超声在线钢轨检测控制系统设计

根据合格成品钢轨的要求,设计了具有20个探头的多探测点超声在线钢轨检测系统。通过PLC总线与计算机通信、FPGA编程、超声分析回波信号采集钢轨A扫数据,对钢轨内部缺陷判断。经标准钢轨检测证明,多探测点超声在线钢轨检测系统能够检测钢轨内缺陷,在伤波数据采集、处理、存储及图像显示等方面满足钢轨的检测要求,应用前景较好。

多探测点超声检测在60 kg/m钢轨缺陷的波形分析

铁路铺设量日益增加,导致行车安全对钢轨的质量要求十分严格。以铺设最广的60 kg/m钢轨为例,分析了多探测点超声波钢轨在线检测系统中各个通道的钢轨缺陷A扫波形;总结了超声波在不同钢轨缺陷中传播的波形特征。结果表明,回波第1周期的波形为缺陷回波主要参考依据,并且缺陷程度越大,回波振幅越高。60 kg/m钢轨的波形分析为钢轨超声波探伤和钢轨的实际生产提供了经验指导。

多探测点超声法在线钢轨检测系统的设计研究

钢轨是铁路建设的重要组成部分,在火车满载运行时钢轨要承受火车的巨大压力。为了能使铁路安全运行,钢轨的安全检测非常关键。本文就运用多探测点超声法检测钢轨做了一系列设计研究,经设计要求布设了多探测点位机钢轨检测系统,系统内含有20个探头。运用计算机编程系统、各种检测仪器设备对钢轨内部存在缺陷进行判断评估。经过系统检测证明,多探测点超声法能够准确的探测出钢轨内部缺陷,值得广泛应用和推广。

低慢小目标多装备协同探测分配问题研究

综合运用雷达、可见光、红外、无线电等多种探测装备协同探测是解决低空慢速小目标的探测跟踪难题的主要手段.针对多探测装备协同的目标分配问题,建立了低空慢速小目标和探测装备模型,提出了一种基于粒子群的多探测装备协同目标分配算法,最后给出了实例仿真.仿真结果表明,该算法是可行的,在实际应用中能较好地满足指挥决策和实时性要求.

基于Multi-probe LSH的菊花花型相似性计算

针对海量高维菊花图像相似性计算带来的挑战,研究了基于多探测局部位置敏感哈希技术的菊花表型相似性计算方法。针对菊花图像,采用SIFT技术提取菊花图像特征,并采用BoVW模型进行建模。由于图像特征的高维性质,海量的菊花表型相似性计算效率不高,为了提高计算效率,提出采用近似相似性技术中的多探测局部位置敏感哈希技术,用此方法构建菊花图像数据的哈希数据结构,在菊花相似性查询方面提高了计算效率,并确保了计算结果的质量。在菊花数据集上进行了计算效率和查询质量两方面的测试,并与典型的方法进行了试验对比和分析。结果表明,相比线性式扫描,平均查询成功概率达到0.90以上,平均加速比为3.3~19.8。本文方法能够在查询质量和计算效率两方面通过参数设置提供灵活的优化选择,并对参数的选择提供了参考范围,可为海量菊花花型相似性计算提供参考。

基于突防航迹的预警网组网研究

为使防区内多探测源的探测效能发挥最大,并有利于探测到低空突防目标,必须满足预警网探测的连续性和严密性。文中在假定的预警区域内给出了一条最优的突防航迹,同时提出了根据突防航迹和各类探测源的性能差异进行多探测源优化组网的方案———网格GT搜索算法。结果表明,该布站方案能有效地探测超低空突防的飞行器。

预警网优化组网的网格GT算法研究

为使防区内多探测源的探测效能发挥最大,有利于探测到低空突防目标,必须满足预警网探测的连续性和严密性.在预警区域内给出了一条最优突防航迹,提出了由突防航迹和各类探测源的性能差异进行多探测源优化组网的方案———网格GT搜索算法.结果表明,该布站方案能有效探测超低空突防的飞行器.

Adjustment of lipiodol dose according to tumor blood supply during transcatheter arterial chemoembolization for large hepatocellular carcinoma by multidetector helical CT

AIM: To work out an indMdualized lipiodol dose in transcabheter arterial chemoembolization (TACE) for large hepatocellular carcinoma (HCC) according to its blood supply evaluated by CT.METHODS: One hundred patients with large HCC (more than 8 cm in diameter) were studied by multidetector helical CT. Patterns of blood supply of HCC were divided into sufficient blood supply, poor blood supply, mixed blood supply and arteriovenous (A-V) shunt. The dose of ultrafluid lipiodol was determined by diameter and blood supply type of HCC. Patients were divided into two groups (50 cases each): lipiodol perfusion group and iodized oil perfusion group according to tumor diameter and the blood supply type of tumor.RESULTS: The confirmation and effective rates were 82%,84% in the first group and 36%, 46% in the second group (P<0.01).CONCLUSION: A relatively individualized lipiodol dose may be determined according to the blood supply pattern and the tumor diameter by CT imaging.

随钻电阻率测量方法研究

在地层的物理参数中,电阻率是反映岩性和含油气性的重要参数之一,钻井过程中的侧向电阻率测井是石油勘探开发中电阻率测井的重要技术。本文对随钻电阻率测量方法进行研究。首先,研究了随钻电阻率的测量方法,包括以下几种电阻率测量方法 :基于相位差的测量方法,基于幅度比值的测量方法,基于相位差和幅度比值组合的测量方法;然后,对多探测深度方案分析。研究结果表明;改变地层的电阻率对电磁场的幅度的影响可以用来测量井眼附近的地层参数。当△Ar/△φr达到1.57的极限时,幅度比值和相位差测量精度要求是等效的。同时,幅度比值测量方法适用于低电阻率,而相位差测量方法则适合于高电阻率。幅度比值测量具有更高的探测深度,相位差测量具有更好的纵向分辨率。

Development of multi-channel observation and inversion for IP electrical sounding method

In order to improve the exploration effect of deep non-ferrous mineral resources, multi-channel observation methods for induced polarization （IP） electrical sounding data and their inversion imaging technology are studied. First of all, four multi-channel observation methods are developed based on conventional IP electrical method, namely three-electrode and four-electrode arrays of unilateral and bilateral current transmitting. Then the maximum smoothness constrained inversion method of the least squares sense for IP electrical sounding data is proposed, and the inversion software is programmed. Finally, the simulation and inversion results of geo-electrical model for the proposed observation methods are analyzed. And the comparison results show that three-electrode array of bilateral current transmitting gives the best result, but the intensity in field work is larger than others; unilateral three-electrode and four-electrode arrays give the better results. Taking detection results and convenience of field exploration work into consideration, these two methods are more suitable for practical application; bilateral observation method of four-electrode array is not suitable for the detection of the steep ore bodies.

Predictive value of multi-detector computed tomography for accurate diagnosis of serous cystadenoma:Radiologic-pathologic correlation

AIM： To identify multi-detector computed tomography （MDCT） features most predictive of serous cystadenomas （SCAs）, correlating with histopathology, and to study the impact of cyst size and MDCT technique on reader performance. METHODS： The MDCT scans of 164 patients with surgically verified pancreatic cystic lesions were reviewed by two readers to study the predictive value of various morphological features for establishing a diagnosis of SCAs. Accuracy in lesion characterization and reader confidence were correlated with lesion size （≤3 cm or 〉≥3 cm） and scanning protocols （dedicated vs routine）. RESULTS： 28/164 cysts （mean size, 39 mm; range, 8-92 mm） were diagnosed as SCA on pathology. The MDCT features predictive of diagnosis of SCA were microcystic appearance （22/28, 78.6%）, surface Iobulations （25/28, 89.3%） and central scar （9/28, 32.4%）. Stepwise logistic regression analysis showed that only microcystic appearance was significant for CT diagnosis of SCA （P = 0.0001）. The sensitivity, specificity and PPV of central scar and of combined microcystic appearance and Iobulations were 32.4%/100%/100% and 68%/100%/100%, respectively. The reader confidence was higher for lesions 〉 3 cm （P = 0.02） and for MDCT scans performed using thin collimation （1.25-2.5 mm） compared to routine 5 mm collimation exams （P 〉 0.05）. CONCLUSION： Central scar on MDCT is diagnostic of SCA but is seen in only one third of SCAs. Microcystic morphology is the most significant CT feature in diagnosis of SCA. A combination of microcystic appearance and surface Iobulations offers accuracy comparable to central scar with higher sensitivity.

Development of Method in Precise Multibeam Acoustic Bathymetry

The sound ray tracing method can achieve higher accuracy in determining depths and plan positions with multibeam echo sounding system. In data processing, actual sound speed profile must be used in the method. However, the method is too complicated. In order to overcome the shortcoming, this paper presents a new method, the position correction method. Two situations are considered in the new method, namely, change of sound velocity keeps constant gradient in whole water column (including N layers) or in different water layer.

Detection of small hepatocellular carcinoma:Comparison of dynamic enhancement magnetic resonance imaging and multiphase multirow-detector helical CT scanning

AIM: To compare the gadolinium-enhanced multiphase dynamic magnetic resonance imaging (MRI) and multiphase multirow-detector helical CT (MDCT) scanning for detection of small hepatocellular carcinoma (HCC). METHODS: MDCT scanning and baseline MRI with SE T1-WI and T2-WI sequence combined with FMPSPGR sequence were performed in 37 patients with 43 small HCCs. Receiver operating characteristic (ROC) curves were plotted to analyze the results for modality. RESULTS: The areas below ROC curve (Az) were calculated. There was no statistical difference in dynamic enhancement MDCT and MRI. The detection rate of small HCC was 97.5%-97.6% on multiphase MDCT scanning and 90.7%-94.7% on MRI, respectively. The sensitivity of detection for small HCC on MDCT scanning was higher than that on dynamic enhancement MRI. The sensitivity of detection for minute HCC (tumor diameter ≤ 1 cm) was 90.0%-95.0% on MDCT scanning and 70.0%-85.0% on MRI, respectively. CONCLUSION: MDCT scanning should be performed for early detection and effective treatment of small HCC in patients with chronic hepatitis and cirrhosis during follow-up.

Fault detection of excavator’s hydraulic system based on dynamic principal component analysis

In order to improve reliability of the excavator's hydraulic system, a fault detection approach based on dynamic principal component analysis(PCA) was proposed. Dynamic PCA is an extension of PCA, which can effectively extract the dynamic relations among process variables. With this approach, normal samples were used as training data to develop a dynamic PCA model in the first step. Secondly, the dynamic PCA model decomposed the testing data into projections to the principal component subspace(PCS) and residual subspace(RS). Thirdly, T2 statistic and Q statistic performed as indexes of fault detection in PCS and RS, respectively. Several simulated faults were introduced to validate the approach. The results show that the dynamic PCA model developed is able to detect overall faults by using T2 statistic and Q statistic. By simulation analysis, the proposed approach achieves an accuracy of 95% for 20 test sample sets, which shows that the fault detection approach can be effectively applied to the excavator's hydraulic system.

Design of dual Beam multi-wavelength UV-visible absorbance detectors based on CCD

Because the general multi-wavelength UV-Visible absorbance detector cannot avoid the noise and drift resulting from the intensity fluctuation of the light source,a dual beam multi-wavelength UV-Visible detector based on CCD was designed. The ray of light source is divided into a signal ray and a reference ray by the beam splitter after it passes through the chopper. The signal ray shines into the sample cell. The signal ray passing through the sample cell falls onto a concave mirror which focuses it onto a slot that is imaged on one portion of COD by a concave grating. The reference ray is imaged on the other portion of COD by the concave grating after the slot. The signal spectrum, the reference spectrum and the dark current of COD can be measured on the same CCD under the cooperation of the optical system and accessorial circuits. The real-time compensation for the signal spectrum by using the reference spectrum and the dark current of OCD can effectively depress the noise and drift of the detector. The short-term noise is 10^-5 AU and the drift is 10^-1 AU/h.

BLIND ADAPTIVE MULTIUSER DETECTION BASED ON A CONSTRAINED MMSE CRITERION

The proposed blind adaptive multiuser detector utilizes the signature waveform and time information of the desired user. With each received sample vector, the proposed algorithm updates the detector and gives the symbol estimate in the current time slot. Such property facilitates it to track time-varying channels.