Three-dimensional finite element simulation and reconstruction of jointed rock models using CT scanning and photogrammetry

The geometry of joints has a significant influence on the mechanical properties of rocks.To simplify the curved joint shapes in rocks,the joint shape is usually treated as straight lines or planes in most laboratory experiments and numerical simulations.In this study,the computerized tomography (CT) scanning and photogrammetry were employed to obtain the internal and surface joint structures of a limestone sample,respectively.To describe the joint geometry,the edge detection algorithms and a three-dimensional (3D) matrix mapping method were applied to reconstruct CT-based and photogrammetry-based jointed rock models.For comparison tests,the numerical uniaxial compression tests were conducted on an intact rock sample and a sample with a joint simplified to a plane using the parallel computing method.The results indicate that the mechanical characteristics and failure process of jointed rocks are significantly affected by the geometry of joints.The presence of joints reduces the uniaxial compressive strength (UCS),elastic modulus,and released acoustic emission (AE) energy of rocks by 37%–67%,21%–24%,and 52%–90%,respectively.Compared to the simplified joint sample,the proposed photogrammetry-based numerical model makes the most of the limited geometry information of joints.The UCS,accumulative released AE energy,and elastic modulus of the photogrammetry-based sample were found to be very close to those of the CT-based sample.The UCS value of the simplified joint sample (i.e.38.5 MPa) is much lower than that of the CT-based sample (i.e.72.3 MPa).Additionally,the accumulative released AE energy observed in the simplified joint sample is 3.899 times lower than that observed in the CT-based sample.CT scanning provides a reliable means to visualize the joints in rocks,which can be used to verify the reliability of photogrammetry techniques.The application of the photogrammetry-based sample enables detailed analysis for estimating the mechanical properties of jointed rocks.

The Application of Impact Echo Scanning on Nondestructive Test of Pavement

A new nondestructive test method-Impact Echo Scanning was introduced. Application of this method on pavement structure test was discussed. A method to increase the measurement accuracy of the test on multi-layers was proposed, and was verified by field test. The test results show that the basic structural information can obtained rapidly and accurately by 3-D scanning of the impact echo system.

Method for visualizing the shear process of rock joints using 3D laser scanning and 3D printing techniques

This study presents a visualized approach for tracking joint surface morphology.Three-dimensional laser scanning(3DLS)and 3D printing(3DP)techniques are adopted to record progressive failure during rock joint shearing.The 3DP resin is used to create transparent specimens to reproduce the surface morphology of a natural joint precisely.The freezing method is employed to enhance the mechanical properties of the 3DP specimens to reproduce the properties of hard rock more accurately.A video camera containing a charge-coupled device(CCD)camera is utilized to record the evolution of damaged area of joint surface during the direct shear test.The optimal shooting distance and shooting angle are recommended to be 800 mm and 40?,respectively.The images captured by the CCD camera are corrected to quantitatively describe the damaged area on the joint surface.Verification indicates that this method can accurately describe the total sheared areas at different shear stages.These findings may contribute to elucidating the shear behavior of rock joints.

Research on wind erosion processes and controlling factors based on wind tunnel test and 3D laser scanning technology

The study of wind erosion processes is of great importance to the prevention and control of soil wind erosion.In this study,three structurally intact soil samples were collected from the steppe of Inner Mongolia Autonomous Region,China and placed in a wind tunnel where they were subjected to six different wind speeds(10,15,17,20,25,and 30 m/s)to simulate wind erosion in the wind tunnel.After each test,the soil surfaces were scanned by a 3D laser scanner to create a high-resolution Digital Elevation Model(DEM),and the changes in wind erosion mass and microtopography were quantified.Based on this,we performed further analysis of wind erosion-controlling factors.The study results showed that the average measurement error between the 3D laser scanning method and weighing method was 6.23%for the three undisturbed soil samples.With increasing wind speed,the microtopography on the undisturbed soil surface first became smooth,and then fine stripes and pits gradually developed.In the initial stage of wind erosion processes,the ability of the soil to resist wind erosion was mainly affected by the soil hardness.In the late stage of wind erosion processes,the degree of soil erosion was mainly affected by soil organic matter and CaCO_(3)content.The results of this study are expected to provide a theoretical basis for soil wind erosion control and promote the application of 3D laser scanners in wind erosion monitoring.

Low overhead design-for-testability for scan-based delay fault testing

An efficient design-for-testability （DFT） technique is proposed to achieve low overhead for scan-based delay fault testing. Existing techniques for delay test such as skewed-load or broadside make the test generation process complex and produce lower coverage for scan-based designs as compared with non-scan designs, whereas techniques such as enhanced-scan test can make the test easy but need an extra holding latch to add substantial hardware overhead. A new tri-state holding logic is presented to replace the common holding latch in enhanced-scan test to get a substantial low hardware overhead. This scheme can achieve low delay overhead by avoiding the holding latch on the critical timing scan path. What＇s more, this method can also keep the state and signal activity in the combinational circuit from the scan during data scan-in operation to reduce the power dissipation. Experiment results on a set of ISCAS89 benchmarks show the efficiency of the proposed scheme.

A Portable Noncontact Profile Scanning System for Aircraft Assembly

Three-dimensional(3D)profile scanning plays a crucial role in the inspection of assembled large aircraft.In this paper,to achieve noncontact automatic measurements of the high-reflective profiles of large-scale curved parts and components,an automated noncontact system and method with high accuracy and high efficiency are presented.First,a hybrid 3D coordinate measurement system based on proximity sensors and cameras is proposed to obtain noncontact measurements while avoiding the influence of high reflection on the measurement accuracy.A hybrid measurement model that combines the one-dimensional distances measured by the proximity sensors and the 3D information obtained by cameras is proposed to determine high-accuracy 3D coordinates of the measured points.Then,a profile-driven 3D automated scanning method and strategy are designed to rapidly scan and reconstruct the profile within the effective range without scratching the profile or exceeding the measurement range of the proposed system.Finally,experiments and accuracy analyses are performed in situ on an assembled tailplane panel(approximately 1760 mm×460 mm).The automated scanning process is completed in a timeframe of 208s with an average error of less than 0.121 mm for profile reconstruction.Therefore,the proposed method is promising considering both the high accuracy and high efficiency requirements of profile inspections for large aircraft.

Five modified boundary scan adaptive test generation algorithms

To study the diagnostic problem of Wire-OR （W-O） interconnect fault of PCB （Printed Circuit Board）, five modified boundary scan adaptive algorithms for interconnect test are put forward. These algorithms apply Global-diagnosis sequence algorithm to replace the equal weight algorithm of primary test, and the test time is shortened without changing the fault diagnostic capability. The descriptions of five modified adaptive test algorithms are presented, and the capability comparison between the modified algorithm and the original algorithm is made to prove the validity of these algorithms.

Corrosion of Carbon Steel under Epoxy-varnish Coating Studied by Scanning Kelvin Probe

The corrosion behavior of partly coated carbon steel was investigated by salt spray test and scanning Kelvin probe （SKP） in order to understand the long-term corrosion behavior of coated carbon steel in marine atmosphere environment. The localized corrosion was accurately characterized by SKP in both coated and uncoated regions. The SKP results showed that Volta potential varied with the test time, and the more the corrosion products, the more positive the potential. The borderline between coated and uncoated regions of partly coated steel shifted towards the coated side with the increasing of test time. The coating disbonding rate could be determined according to the shift of potential borderline measured by SKP. The corrosion mechanism of partly coated steel in NaCl salt spray was discussed according to the potential maps and corrosion morphologies.

Measurement and Analysis of Three-Dimensional Surface Topography of Sawn Timber Based on Scanning Probe Method

In order to explore the characteristics of the three-dimensional surface morphology of sawn timber,a three-dimensional wood surface morphology tester based on the scanning probe method and the principle of atomic force microscope was used to test the three-dimensional sur face morphology of three kinds of sawn timber and calculate its surface roughness.This study also analyzed the reasonable plan for the value of wood surface roughness and the advantages of the three dimensional shape tester,as well as the influence of tree species,three sections,air dry density and other factors on the surface roughness of the specimen after mechanical processing.The results have shown that it is a more appropriate method to select the calculated values of S。and Sq as the evaluation of the surface roughness of wood with random surface characteristics.The three dimensional wood surface topo-graphy tester can efficiently,conveniently and accurately display the three dimensional topography of wood at a micron-level resolution,and is characterized by high eficiency and good durability.The three dimensional surface morphology characteristics of the three sawn woods correspond to their roughness.The surface roughness of woods is arranged as follows:Sitka spruce>Larch>Beech.For the same tree species,the roughness of the corresponding section after sawing is as follows:chordwise section>crosswise section>radial section.The radial section has lower roughness than the other surfaces.The surface roughness of the wood after sawing is mainly related to its air-dry density.The above is intended to provide a useful reference for the application of measuring and evaluating the surface roughness of sawn timber using the three dimensional surface topography test method.

Localizing Test Power Consumption for Scan Testing

A two stage scan architecture is proposed to do low power and low test application cost scan testing. The first stage includes multiple scan chains, where each scan chain is driven by a primary input. Each scan flip-flop in the multiple scan chains drives a group of scan flip-flops. The scan flip-flop in the multiple scan chain and the scan flip-flop driven by it are assigned the same values for all test vectors. Scan flip-flops in the multiple scan chains and those in the second stage use separate clock signals, but the design for testability technqiue needs only one clock. The proposed scan architecture localizes test power consumption to the multiple scan chains during test application. Test signals assigned to scan flip-fiops in the multiple scan chains are applied to the scan flip-flops in the second stage after the test vector has been applied to the multiple scan chains. This technique can make test power consumption very small.

TEST OF BOARD-LEVEL BOUNDARY SCAN INTEGRITY

The IEEE Standard 1149.1 boundary scan (BS) implementation provides the internal access required for testing the digital printed circuit board (PCB). However, the integrity of the boundary scan test infrastructure should be tested first to guarantee the validation of the results of the rest functional test and diagnosis. This paper describes the fault models and test principles of the BS test access port (TAP) lines on PCBs. A test algorithm with high fault coverage and short time is then presented for the PCB on which all ICs are BS ones.

Analysis of Recent Secure Scan Test Techniques

Side channel attack may result in user key leakage as scan test techniques are applied for crypto-graphic chips. Many secure scan designs have been proposed to protect the user key. This paper meticulously selects three current scan test techniques, analyses their advantages and disadvantages and also compares them in security and area overhead. Users can choose one of them according to the requirements and further combination can be implemented to achieve better performance.

Rapid ultrasonic C-scan on image test for spot welding based interpolation

In this paper, ultrasonic C-scan test of spot welds for stainless steel has been studied. It is concluded that large scanning step length contributes to high testing efficiency, however, the low-resolution C-scan image generated cannot be used to assess spot welding quality reliably. Based on bicubic image interpolation, the C-scan image in low resolution with the large step length 1 000 ~xm is subdivided and reconstructed. By this means, the C-scan image resolution is greatly enhanced and testing results obtained are satisfactory, realizing rapid assessment of spot welds. The results of rapid ultrasonic C-scan test fit the actual metallographic measured value well. Mean value of normal distribution of error statistics is O. 006 67, and the standard deviation is O. 087 11. Rapid ultrasonic C-scan test based on image interpolation is of high accuracy and excellent stability.

A Novel Secure Scan Design Based on Delayed Physical Unclonable Function

The advanced integrated circuits have been widely used in various situations including the Internet of Things,wireless communication,etc.But its manufacturing process exists unreliability,so cryptographic chips must be rigorously tested.Due to scan testing provides high test coverage,it is applied to the testing of cryptographic integrated circuits.However,while providing good controllability and observability,it also provides attackers with a backdoor to steal keys.In the text,a novel protection scheme is put forward to resist scan-based attacks,in which we first use the responses generated by a strong physical unclonable function circuit to solidify fuseantifuse structures in a non-linear shift register(NLSR),then determine the scan input code according to the configuration of the fuse-antifuse structures and the styles of connection between the NLSR cells and the scan cells.If the key is right,the chip can be tested normally;otherwise,the data in the scan chain cannot be propagated normally,it is also impossible for illegal users to derive the desired scan data.The proposed technique not only enhances the security of cryptographic chips,but also incurs acceptable overhead.

A novel method for geometric quality assurance of rock joint replicas in direct shear testing-Part 2:Validation and mechanical replicability

Each rock joint is unique by nature which means that utilization of replicas in direct shear tests is required in experimental parameter studies.However,a method to acquire knowledge about the ability of the replicas to imitate the shear mechanical behavior of the rock joint and their dispersion in direct shear testing is lacking.In this study,a novel method is presented for geometric quality assurance of replicas.The aim is to facilitate generation of high-quality direct shear testing data as a prerequisite for reliable subsequent analyses of the results.In Part 1 of this study,two quality assurance parameters,smf and V_(Hp100),are derived and their usefulness for evaluation of geometric deviations,i.e.geometric reproducibility,is shown.In Part 2,the parameters are validated by showing a correlation between the parameters and the shear mechanical behavior,which qualifies the parameters for usage in the quality assurance method.Unique results from direct shear tests presenting comparisons between replicas and the rock joint show that replicas fulfilling proposed threshold values of σ_(mf)<0.06 mm and
|V_(Hp100)|
<0.2 mm have a narrow dispersion and imitate the shear mechanical behavior of the rock joint in all aspects apart from having a slightly lower peak shear strength.The wear in these replicas,which have similar morphology as the rock joint,is in the same areas as in the rock joint.The wear is slightly larger in the rock joint and therefore the discrepancy in peak shear strength derives from differences in material properties,possibly from differences in toughness.It is shown by application of the suggested method that the quality assured replicas manufactured following the process employed in this study phenomenologically capture the shear strength characteristics,which makes them useful in parameter studies.

Test Accuracy of CT-Scan for the Detection of Malignant Liver Mass

Background: Detection of malignant liver mass is very important for the treatment modalities. Objective: The purpose of the present study was to establish the usefulness of CT scan in the diagnosis of malignant hepatic mass. Methodology: This cross sectional study was carried out in the Department of Radiology and Imaging at Mymensingh Medical College Hospital (MMCH), Mymensingh, Banghabandhu Sheikh Mujib Medical University (BSMMU), Dhaka and Dhaka Medical College Hospital (DMCH), Dhaka during the period of 1st January 2006 to 31st December 2007. Patients admitted in the Department of Medicine and Department of Hepatobiliary of MMCH, BSMMU, and DMCH with the clinical diagnosis of fever, abdominal pain, anorexia, nausea/vomiting, loss of appetite, jaundice, weight loss and ascites were selected as study population. CT scan and histopathology were performed to all the patients. Result: A total number of 50 patients were recruited for this study. Mean age of all patients was 51.28 ± 14 years with a range of 17 year to 78 years. Among all patients 28 had multiple lesion, of them 71.4% was malignant and 28.6% was benign. On the other side 22 patients had solitary lesion, of them 36.4% was malignant and 63.6% was benign

膨胀土微结构对膨胀行为的影响

评估膨胀土的膨胀行为对于膨胀土地区的结构设计十分重要。因降雨入渗,膨胀土在垂直方向和水平方向均产生膨胀变形,当膨胀变形受抑制时将产生膨胀压力,影响其周围结构的稳定性。为揭示膨胀土在增湿膨胀过程中出现各向异性的原因,从微观角度出发,通过电镜扫描(SEM)对百色中膨胀土和枝江弱膨胀土的微观结构进行观察,并通过图像处理技术统计分析膨胀土内黏土矿物颗粒的层状排列。通过研发的二维膨胀仪和改进的试件制备方法,从宏观角度测得了侧限条件下的两向膨胀规律。研究结果表明,膨胀土的微观结构呈片状且面-面相叠;当膨胀土处于天然松散状态时,其内部的黏土矿物颗粒随机定向排列且集聚;压实后,因受各向不均等应力作用,黏土矿物颗粒开始趋向于水平层状排列;干密度越大,土样越密实,其水平层状排列越显著。侧限条件下,两向的膨胀规律表现出显著的差异,干密度越大,膨胀性越强,这种差异就越明显。然而,对黏土矿物颗粒来说,其膨胀的方向垂直于其长轴,高度的水平定向是造成膨胀土在宏观上表现出膨胀各向异性的原因,这种两向的膨胀差异受到干密度和膨胀性的影响,难以做出预测,建议在工程实践中实测两向的膨胀规律。

正弦扫描振动模拟瞬态振动环境等效性研究

使用正弦扫描振动模拟低频瞬态振动环境是航天工业的一种传统试验方法,其对产品的环境考核可能同时存在欠试验和过试验。首先对两者等效性进行分析,进而采用冲击响应谱、最大响应谱等相关理论,对等效正弦扫描振动试验条件制定中的扫描速率、阻尼系数进行了研究,并给出参数选择建议。最终提出了制定正弦扫描振动环境试验条件的步骤,为采用正弦扫描试验进行低频瞬态环境适应性考核提供借鉴。

不均匀卵石持力层桩端后注浆效果试验研究

我国东南沿海尤其是温州地区广泛存在上覆深厚软土下覆不均匀卵石的地层。该区域的钻孔灌注桩常采用后注浆技术改善其承载性能。为了评价后注浆技术对这类地层中灌注桩承载力改善效果,开展了相应的模型试验,对比了不同注浆量对桩承载力的影响程度;并结合扫描电镜(scanning electron microscope,简称SEM)试验分析了浆液分布特点,探讨了浆液在卵石层中的扩散范围,研究了浆液扩散范围与桩承载力之间的关系。结果表明:浆液能够有效地填充桩端卵石层,注浆量的增加使得填充范围扩大,填充范围为3~4倍桩径时,桩的承载力改善最显著。在不均匀卵石持力层中存在一个最优注浆量,最优归一化注浆量约为2.8,若超过该最优注浆量归一化值,桩的承载力不再显著提高。单桩模型试验确定的最优注浆量与刘金砺公式[1]的预测结果接近。扫描电镜技术有助于评价桩的后注浆技术在上覆深厚软土下覆不均匀卵石的土层中的效果。

基于激光扫描的电子档案异构时态数据检测方法

研究一种基于激光扫描的电子档案异构时态数据检测方法,该方法利用激光扫描获取数据并生成电子档案。针对电子档案中的数据实施缺失数据填补和离群数据处理。提取电子档案数据的递归率、仙农熵以及歪度三个特征。结合随机森林算法,输入递归率、仙农熵以及歪度三个特征,得出电子档案异构时态数据类型。结果表明:1处和3处边坡工程的位移处于轻微状态;2处边坡工程的位移处于严重状态;4处边坡工程的位移处于安全状态;5处边坡工程的位移处于较严重状态。所研究方法的Kappa系数达到相对最大值,说明所研究方法的检测能力更高。