3G认证和密钥分配协议的形式化分析及改进

介绍了第三代移动通信系统所采用的认证和密钥分配(AKA)协议,网络归属位置寄存器/访问位置寄存器(HLR/VLR)对用户UE(用户设备)的认证过程和用户UE对网络HLR/VLR的认证过程分别采用了两种不同的认证方式,前者采用基于"询问-应答"式的认证过程,后者采用基于"知识证明"式的认证过程.使用BAN形式化逻辑分析方法分别对这两种认证过程进行了分析,指出在假定HLR与VLR之间系统安全的前提下,基于"知识证明"式的认证过程仍然存在安全漏洞.3GPP采取基于顺序号的补充措施;同时,文中指出了另一种改进方案.     

岩石爆破破碎块度的预测

由于爆破性质和各种地质因素的变化,要准确或如实地预测爆破效果是困难的。然而,爆破物理学的进步和计算机的发展已能令人意外地对爆破效果进行可靠的预测。本文叙述一种预测破碎质量的经验方法,它是以将V.M.Kuznetsov方程和Rasin-Rammler曲线综合考虑的结果为依据。实践证明该法在各种条件下都能得出符合实际情况的结     

溶剂对RDX热分解的影响

用布氏压力计研究不同溶剂对溶液中RDX热分解的影响。影响分为加速、抑帛和无影响三种影响三种情况：在苯、萘、异辛烷中RDX热分解速率与熔融态一臻,这类溶剂对RDX热分解无影响;脂肪族芳香化合物,醚,酯,酮及醇能加速RDX热分解,粘度较大的化合物则抑制RDX热分解。     

Adaptive speckle reduction filter for log-compressed B-scan images

A good statistical model of speckle formation is useful for designing a good adaptive filter for speckle reduction In ultrasound B-scan images. Previously, statistical models have been used, but they failed to account for the log compression of the echo envelope employed by clinical ultrasound systems. Log-compression helps in reducing the dynamic range of the B-scan Images for display on a monitor as well as enhancing weak backscatters. In this article, statistics of log-compressed echo images, using the K-distribution statistical model for the echo envelope, are used to derive a parameter that can be used to quantify the extent of speckle formation. This speckle quantification can be used with an unsharp masking filter to adaptively reduce speckle. The effectiveness of the filter is demonstrated on images of contrast detail phantoms and on in-vivo abdominal images obtained by a clinical ultrasound system with log-compression.     

Numerical 3D model of viscous turbulent flow in one stage gas turbine and its experimental validation

The paper describes 3D numerical Reynolds Averaged Navier-Stokes (RANS) model and approximate sector approach for viscous turbulent flow through flow path of one stage axial supercharge gas turbine of marine diesel engine. Computational data are tested by comparison with experimental data. The back step flow path opening and tip clearance jet are taken into account. This approach could be applied for variety of turbine theory and design tasks: for offer optimal design in order to minimize kinetic energy stage losses; for solution of partial supply problem; for analysis of flow pattern in near extraction stages; for estimation of rotational frequency variable forces on blades; for sector vane adjustment (with thin leading edges mainly), for direct flow modeling in the turbine etc. The development of this work could be seen in the direction of unsteady stage model application.     

拉伸时应变速度对关节软骨力学性质的影响

量测关节软骨的拉伸模量和破坏性质,可能是关节软骨结构性组织损坏的灵敏指标。但是,以前利用单相粘弹性模型[1]对这种生物组织所作的拉伸研究,只能描述其总的表象学性质,最近,提出了二相模型[2],并应用该模型确定了当受压缩时组织内隙间液体流动和压力以及固体基质的本征性质对组织整体粘弹性响应的影响,本文是用新的二相分析方法去描述拉伸的应力—应变试验。     

Locating blood vessels in retinal images by piecewise threshold probing of a matched filter response

We describe an automated method to locate and outline blood vessels in images of the ocular fundus. Such a tool should prove useful to eye care specialists for purposes of patient screening, treatment evaluation, and clinical study. Our method differs from previously known methods in that it uses local and global vessel features cooperatively to segment the vessel network. We evaluate our method using hand-labeled ground truth segmentations of 20 images. A plot of the operating characteristic shows that our method reduces false positives by as much as 15 times over basic thresholding of a matched filter response (MFR), at up to a 75% true positive rate. For a baseline, we also compared the ground truth against a second hand-labeling, yielding a 90% true positive and a 4% false positive detection rate, on average. These numbers suggest there is still room for a 15% true positive rate improvement, with the same false positive rate, over our method. We are making all our images and hand labelings publicly available for interested researchers to use in evaluating related methods.     

Physical properties of sprayed antimony doped tin oxide thin films:The role of thickness

Transparent conducting antimony doped tin oxide（Sb:SnO₂） thin films have been deposited onto preheated glass substrates using a spray pyrolysis technique by varying the quantity of spraying solution.The structural, morphological,X-ray photoelectron spectroscopy,optical,photoluminescence and electrical properties of these films have been studied.It is found that the films are polycrystalline in nature with a tetragonal crystal structure having orientation along the（211） and（112） planes.Polyhedrons like grains appear in the FE-SEM images. The average grain size increases with increasing spraying quantity.The compositional analysis and electronic behaviour of Sb:SnO₂ thin films were studied using X-ray photoelectron spectroscopy.The binding energy of Sn3d_5/2 for all samples shows the Sn⁴⁺ bonding state from SnO₂.An intensive violet luminescence peak near 395 nm is observed at room temperature due to oxygen vacancies or donor levels formed by Sb⁵⁺ ions.The film deposited with 20 cc solution shows 70%transmittance at 550 nm leading to the highest figure of merit(2.11×10^-3Ω^-1). The resistivity and carrier concentration vary over 1.22×10^-3 to 0.89×10^-3Ω·cm and 5.19×10²⁰ to 8.52×10²⁰ cm^-3,respectively.