X线诱导声学计算机断层扫描在放射检测及疾病诊断中的研究进展

X线诱导声学计算机断层扫描(XACT)是一种新兴的数字成像技术。XACT是利用单脉冲X线和超声信号的实时分析实现低辐射量和高分辨率的成像,XACT在放射检测、辐射剂量监测、肿瘤定位以及骨疾病诊断等方面具有广阔的应用前景。此外,XACT能够在单次光照时间内成像,减少辐射暴露,对临床转化具有重要意义。目前,XACT在各种医学成像领域的应用潜力已被验证,但仍需要优化成像重建算法以及提高设备临床适用性等。未来,应深入开发新的成像算法以及开展大规模临床试验,以推动其在医学成像中的广泛应用。

计算诱导短程挠率的一种新方法

为了分析线接触共轭齿面的诱导短程挠率 ,并清楚地诠释有关公式及计算推导的过程 ,运用微分几何、向量代数、线性代数等数学工具 ,寻找了一种计算诱导短程挠率的方法。推导过程中利用齿面主曲率、主方向可以使计算过程简化 。

离心泵的汽蚀和诱导轮设计

该文简述了离心泵内产生汽蚀现象的机理,介绍预防和减轻汽蚀现象的方法,以及提高离心泵抗汽蚀性能的主要途径。并介绍了设计计算前置轴流诱导轮的一种方法。

Reliability Improvements to Centrifugal Pump Performance in Conjunction with Inducers, CFD Comparative Study

In this research, centrifugal pump unit was analysed to study the effects of using inducers on its performance. Hydraulic tests were done to obtain the optimum hydraulic performance before and after using inducer. Two types of inducers were used in this work （axial, helical）. For this purpose, a test rig was specially designed with a pump system to investigate the parameters under consideration. Plots （H-Q） curves, （B.P.-Q） curves and （q-Q） curves were used to show the effect of pump performance with and without inducers. The present study introduces a simulation of centrifugal pump performance in conjunction with inducers using CFD （Computational Fluid Dynamics）, to compare it with experimentally observed values. The model investigates the impact of using inducers on the head and flow of the pump. The results of the CFD model and experimental are correlated well. Furthermore, the results help the decision makers of the pumps for future developments in pump performance assuring safe and reliable running condition of the water pumps. Also it may be used for more applications of larger head and flow pumps.

The Calculations of Propeller Induced Velocity by RANS and Momentum Theory

In order to provide instructions for the calculation of the propeller induced velocity in the study of the hull-propeller interaction using the body force approach,three methods were used to calculate the propeller induced velocity：1） Reynolds-Averaged Navier-Stokes（RANS） simulation of the self-propulsion test,2） RANS simulation of the propeller open water test,and 3） momentum theory of the propeller.The results from the first two methods were validated against experimental data to assess the accuracy of the computed flow field.The thrust identity method was adopted to obtain the advance velocity,which was then used to derive the propeller induced velocity from the total velocity field.The results computed by the first two approaches were close,while those from the momentum theory were significantly overestimated.The presented results could prove to be useful for further calculations of self-propulsion using the body force approach.

Medical treatment for a fish bone-induced ileal micro-perforation:A case report

Ingested fish bone induced intestinal perforations are seldom diagnosed preoperatively due to incomplete patient history taking and difficulties in image evidence identification.Most literature suggests early surgical intervention to prevent sepsis and complications resulting from fish bone migrations.We report the case of a 44-year-old man suffered from acute abdomen induced by a fish bone micro-perforation.The diagnosis was supported by computed tomography(CT) imaging of fish bone lodged in distal ileum and a history of fish ingestion recalled by the patient.Medical treatment was elected to manage the patient's condition instead of surgical intervention.The treatment resulted in a complete resolution of abdominal pain on hospital day number 4 without complication.Factors affecting clinical treatment decisions include the nature of microperforation,the patient's good overall health condition,and the early diagnosis before sepsis signs develop.Micro-perforation means the puncture of intestine wall without CT evidence of free air,purulent peritoneum or abscess.We subsequently reviewed the literature to support our decision to pursue medical instead of surgical intervention.

A new approach to quantifying vehicle induced turbulence for complex traffic scenarios

Traffic-related pollutants adversely affect air quality, especially in regions near major roadways. The vehicleinduced turbulence(VIT) is a significant factor that controls the initial dilution, dispersion, and ultimately the chemical and physical fate of pollutants by altering the conditions in the microenvironment. This study used a computational fluid dynamics(CFD) software FLUENT to model the vehicle-induced turbulence(VIT) generated on roadways, with a focus on impact of vehicle-vehicle interactions, traffic density and vehicle composition on turbulent kinetic energy(TKE). We show, for the first time, that the overall TKE from multiple vehicles traveling in series can be estimated by superimposing the TKE of each vehicle, without considering the distance between them while the distance is greater than one vehicle length. This finding is particularly significant since it enables a new approach to VIT simulations where the overall TKE is calculated as a function of number of vehicles. We found that the interactions between vehicles traveling next to each other in adjacent lanes are insignificant,regardless the directions of the traffic flow. Consequently, simulations of different traffic scenarios can be substantially simplified by treating two-way traffic as one-way traffic, with less than 5% difference in the overall volume-averaged TKE. We also developed equations that allow the estimation of the overall volume-averaged TKE as a function of the number and the type of vehicles.

Modeling of Earth Magnetic Field Disturbances Induced by Ferromagnetic Objects

This paper presents the methodology and results of modelling of Earth magnetic field disturbances induced by ferromagnetic objects. The modeling was carried out using the finite elements calculations, and the results were compared with the measurements. The special test stand, consisting of magnetovision scanner and Helmholtz coils, has been used. The measurement system is able to measure the distribution of planar magnetic induction vectors, and to differentiate the sources of measured disturbances.

Calculation of laser induced collisional energy transfer in the Sr-Ca system

Based on the four-state model of laser-induced collisional energy transfer,the cross section of the collisional energy transfer in the Sr-Ca system is obtained.Various factors,including field intensity,relative speed,and temperature,which influence the collisional cross section,are discussed for illustrating the features of the Sr-Ca laser-induced collisional energy transfer(LICET) process.The calculated results show that the LICET spectral profiles obviously become narrower when the laser field intensity increases.The collision cross section rises with laser intensity and tends to saturate.In the vicinity of the spectral profile center,the cross section at fixed laser detuning becomes smaller as the relative speed and system temperature increase.The results indicate that the intermediate states strongly affect the spectral profile of LICET.

Therapeutic effect of osteogenically induced adipose derived stem cells on vascular deprivation-induced osteonecrosis of the femoral head in rabbits

Objective： To explore the therapeutic ef- fect of osteogenically induced adipose-derived stem cells （ADSCs） on vascular deprivation-induced osteonecrosis of the femoral head （ONFH） in rabbit model. Methods： Vascular deprivation-induced ONFH was established by intramuscular injection of methylpre- dnisolone, and vascular occlusion of the capital femoral epiphysis by electrocoagulation in adult New Zealand white rabbits. Eight weeks afLer the establishment of vascular dep- rivation-induced ONFH, animals were randomly divided into three equal groups. In Group A （control）, no therapy was given. In Group B, core decompression was performed by drilling a hole （1.2 mm in diameter） from the outer cortex 2.5 cm distal to the proximal end of the greater trochanter. In Group C, 1 x 107 osteogenically induced ADSCs were resus- pended in 0.5 ml PBS, and then injected directly into the femoral head. Femoral head specimens were obtained at postoperative 8 weeks. The bone formation and three-di- mensional microstructure of the femoral head was evaluated by micro-computed tomography scans （u-CT）. Immunohistochemical analysis was performed to detect the expression ofosteocalcin. Angiogenesis and repair of the femoral head were observed histologically. Results： In trabecular bone at the proximal femur region, the trabecular volume was higher in Group C （130.70 mm3± 4.33 mm3） than that in Groups A （101.07 mm3±7.76 mm3） and B （107.89 mm3±8.6g mm3, P〈0.01）. Bone volume was significantly increased in Group C （40.09 mm3±6.35 mm3） than in Groups A （29.65 mm3±4.61 mm3） and B （31.80 mm3± 4.01 mm3, P〈0.01）. The trabecular number was higher in Groups C （1.58±0.25） than other two groups （1.15±0.18, 1.16± 0.21, P〈0.01）. Bone mineral density showed statistically significant difference between Groups C and A or B （375.38± 23.06） mg HA/ccm, vs （313.73 ± 19.30） mg HA/ccm and （316.09± 16.45） mg HA/ccm, P〈0.01）. Histological examination indicated that there was more new bone formation in Group C than in other groups. Conclusion： Treatment with autologous osteogenically induced ADSCs transplantation results in an enhanced osteogenesis and microstructure of the vascular deprivation-induced osteonecrosis in rabbits.

Prediction of Pressure-Induced Structural Transition and Mechanical Properties of Mg Y from First-Principles Calculations

Using the particle swarm optimization algorithm on crystal structure prediction,we first predict that Mg Y alloy undergoes a first-order phase transition from Cs Cl phase to P4/NMM phase at about 55 GPa with a small volume collapse of 2.63%.The dynamical stability of P4/NMM phase at 55 GPa is evaluated by the phonon spectrum calculation and the electronic structure is discussed.The elastic constants are calculated,after which the bulk moduli,shear moduli,Young's modui,and Debye temperature are derived.The brittleness/ductile behavior,and anisotropy of two phases under pressure are discussed in details.Our results show that external pressure can change the brittle behavior to ductile at10 GPa for Cs Cl phase and improve the ductility of Mg Y alloy.As pressure increases,the elastic anisotropy in shear of Cs Cl phase decreases,while that of P4/NMM phase remains nearly constant.The elastic anisotropic constructions of the directional dependences of reciprocals of bulk modulus and Young's modulus are also calculated and discussed.