RADIOGRAPHIC IMAGING OF THE CANINE INTERCONDYLAR FOSSA

The intercondylar fossa is believed to play an important role in the pathology of cranial cruciate ligament rupture and therefore has received considerable attention in the last decade. Accurate radiographic imaging of the intercondylar fossa requires that the central x-ray beam pass through the center of the intercondylar "tunnel". The anatomy of the canine intercondylar fossa is similar to humans, however, the orientations of the intercondylar fossa's differ. Consequently, the positioning techniques described for humans are not appropriate for the dog. To pass through the center of the dog, intercondylar fossa, the central x-ray beam should be 12° (S.D. 1.7°) caudal from the femoral diaphysis in the sagittal plane and obliqued caudolateral to craniomedial 7° (S.D. 0.60°) (caudo78°proximo7° lateralcraniodistomedial oblique). Cross table positioning was used with the hip flexed and the radiograph cassette placed on the cranial surface of the stifle. However, superimposition of the tuber ischii and soft tissues caudal to the femur made 15° to 20° the best angle obtainable. There was not a significant difference (p = 0.17) in the notch width index between a 12° versus 20° angle of the central x-ray beam caudal to the femoral diaphysis, both with 7° of external rotation of the stifle. The notch width index of 0.252 obtained from radiographic measurements was not significantly different from measurements obtained grossly of 0.254 (n = 26; p = 0.69). Failure to oblique the central x-ray beam caused a significant (p = 0.0008) decrease in the apparent fossa width radiographically.     

利用耳组织、血液、牛奶样品检测牛病毒性腹泻病毒的比较

牛病毒性腹泻病以发热、口腔及消化道粘膜糜烂、腹泻为主要症状,可引起怀孕母牛流产或产畸型胎儿,给养牛业造成巨大的经济损失,该病已成为当前严重危害我国养牛业的传染病之一。由于大部分感染BVDV的牛不表现特征性的临床症状和病理变化,而且引起腹泻和消化道黏膜糜烂或溃疡的疾病很多,所以确诊需进行实验室检查。目前实验室检测BVDV的主要方法是利用美国IDEXX公司ELISA诊断试剂盒,通过BVDV抗原和抗体的检测区别牛群持续感染牛。用于检测BVDV的样品种类有许多种,绝大多数是采集血液(血清)或牛奶样品进行检测。本试验对奶牛进行耳组织采样,同时采集血液和牛奶,用三种样品在相同条件下同时检测BVDV抗原,用血清和牛奶样品检测抗体,比较样品的检测结果。结果表明,这三种样品检测结果具有一致性,且耳组织采样更宜于大面积筛查。     

基于Multisim的抗干扰AM通信系统设计

分析了抗干扰AM通信系统原理和抗干扰的方法,并利用Multisim虚拟仿真软件为试验平台,设计抗干扰AM通信系统电路,利用Multisim提供的示渡器模块和频谱分析模块,分别对AM调制波和干扰抑制后的解调渡进行了波形和频谱分析.结果表明,Multisim在通信电路仿真中具有快速、准确、灵活的优点,而且所设计的自适应陷波...     

PD Online Measurement of Transformers with Wide Frequency Band System and the Noise Eliminating Method by Cascaded IIR Lattice Notch Digital Filter

The frequency band of conventional partial discharge (PD) measurement systems is selected just within several ten kilohertz. With the development of computer and digital signal processing techniques, wide frequency band (WFB) measurement systems have been used to detect PD in electrical equipment for its higher sensitivity. Nevertheless, the WFB measurement systems are easy suffered from the interference of strong field electromagnetism noises. A set of PD online monitoring system with frequency band from 50 kHz to 1 megahertz used for transformer is developed, in which pre-processing device and cascaded 2nd order IIR lattice notch digital filter are mainly used to suppress periodic narrow-band interference. With analysis of field monitored signal at a 220 kV substation, it is shown that the monitoring system not only can detect and extract the discharge pulse signal effectively, but also has the powerful capability of suppressing interference.     

Frequency tracking method and simulation for coriolismass flowmter based on a new adaptive notch filter

In order to improve the long-playing frequency tracking ability in the signal processing for coriolis mass flowmeter (CMF) , a new IIR adaptive notch filter (ANF) is developed via steiglitz-mcBride method (SMM) and applied to filter the sensor output signal whose frequency, amplitude and phase are time-varying following the random walk model. The proposed method can detect the signal frequency fleetly and track the frequency variations continuously. The tracking performances of the proposed method and the adaptive lattice notch filter (LANF) method are investigated with computer simulations. Simulations demonstrate the superiority of the proposed method and show it has advantages of fast convergence rate, insensitivity to initial phase variations, and higher long-playing tracking stability and accuracy than LANF method.     

夹具与槽口距离对胶合板强度测定结果的影响

通过试验,研究了胶合板胶合强度检测试验中夹具与试件槽口的距离对胶合板胶合强度的影响.结果表明,当夹具与槽口的距离在0～40 mm内时,距离值与胶合强度检测值呈一定的线性相关.距离在0～15 mm区间,胶合强度随距离增大呈现增加的趋势,之后则逐步减小.相距15 mm时板的胶合强度最大(1.71 MPa),距离为40 mm时胶合强度最小(1.11 MPa).方差分析的结果表明,夹具与试件槽口的距离对胶合强度检测结果有显著的影响.     

A METHOD FOR CALCULATING STRESS INTENSITY FACTORS OF CHEVRON-NOTCHED THREE-POINT BEND ROUND BAR SPECIMENS

An effective approximate method is proposed to obtain the stress intensity factors (SIF) of the chevron notched three-point bend round bar specimens, the least square principle is applied to fit the results into a polynomial for SIF,which is applied to the fracture toughness specimen suggested by the International Society for Rock Mechanics(ISRM) ,the result is satisfatory.     

AN INVESTIGATION FOR TESTING ROCK FRACTURE TOUGHNESS WTH THREE-POINT BEND ROUND BARS

Chevron-notched and straight-through-notched three-point bend round bars are used to test fracture toughness K of a Chongqing limestone. The results show that the former specimen has some advantages over the latter in the aspects of preventing overload,avoiding deviation of crack growth from notch plane and considering nonlinear correction in calculation,etc. However,the size effects of test values are to be solved.     

Signal Processing Method for Coriolis Mass Flowmeter Based on Lattice Notch Filter and DTFT

A novel signal processing method for Coriolis mass flowmeter is proposed based on time-varying signal model. First, an adaptive lattice notch filter is applied to filter the output signal, whose frequency, amplitude and phase are time-varying based on the random walk model, of Coriolis mass flowmeter to get its frequency and enhanced signal. Then, by short window intercepting, the DTFT algorithm with negative frequency contribution is introduced to calculate the real-time phase difference between two enhanced signals. With the frequency and the phase difference, the time interval between two signals is calculated. Simulation results show that the proposed method is efficient. Furthermore, the computation of algorithms is simple so that it can be applied to real-time signal processing for Coriolis mass flowmeter.