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低剂量CT；CT成像；全变分；稀疏字典学习 1

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支承垫片 1

整体沉放 1

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Creep-fatigue crack growth behavior in GH4169 superalloy

Dianyin HU, Xiyuan WANG, Jianxing MAO, Rongqiao WANG

《机械工程前沿（英文）》 2019年 第14卷 第3期   页码 369-376 doi: 10.1007/s11465-018-0489-7

摘要： This study aims to examine the crack growth behavior of turbine disc GH4169 superalloy under creep-fatigue loading. Crack growth experiments were performed on compact tension specimens using trapezoidal waveform with dwell time at the maximum load at 650 °C. The crack growth rate of GH4169 superalloy significantly increased with dwell time. The grain boundaries oxidize during the dwell process, thereby inducing an intergranular creep-fatigue fracture mode. In addition, testing data under the same dwell time showed scattering at the crack growth rate. Consequently, a modified model based on the Saxena equation was proposed by introducing a distribution factor for the crack growth rate. Microstructural observation confirmed that the small grain size and high volume fraction of the d phase led to a fast creep-fatigue crack growth rate at 650 °C, thus indicating that two factors, namely, fine grain and presence of the d phase at the grain boundary, increased the amount of weakened interface at high temperature, in which intergranular cracks may form and propagate.

关键词： crack growth rate     creep-fatigue     GH4169 superalloy     CT specimen     dwell time    

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结合全变分最小化和稀疏字典学习后处理的低剂量CT重建 Article

Yong DING, Tuo HU

《信息与电子工程前沿（英文）》 2017年 第18卷 第12期   页码 2001-2008 doi: 10.1631/FITEE.1700287

摘要： 随着CT（computed tomography）中过量辐射剂量带来的健康风险日渐引发人们的担忧，低剂量CT得到了大量的关注。然而对于低剂量CT成像而言，在降低剂量的同时保证图像的高质量是一个很大的挑战。相比传统的滤波反投影算法，基于压缩感知的迭代重建法取得了良好的成像效果。但是迭代重建计算复杂度高，阻碍了其临床应用。

关键词： 低剂量CT；CT成像；全变分；稀疏字典学习    

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Simultaneous acquisition of CT angiography and whole brain CT perfusion images by using multiphase dynamic

Weiwei CHEN, Jianpin QI, Wenzhen ZHU, Wenhua HUANG, Jinmei SONG

《医学前沿（英文）》 2009年 第3卷 第2期   页码 230-235 doi: 10.1007/s11684-009-0023-8

摘要： We implemented a new protocol — multiphase dynamic helical scan to acquire CT angiography (CTA) and whole brain CT perfusion (CTP) images simultaneously with single scan on 16 multidetector CT (MDCT). A total of 90 patients who were randomly assigned into 3 groups were included in our study. Each group underwent CT scan by using the new protocol, traditional CTA and CTP protocol, respectively. The image quality of CTA, the CTP parameter values and the X-ray doses were measured and compared between the new protocol and the traditional protocols. There was no statistically significant difference in the CTA image quality between the above methods ( =0.55). For CTP parameters, the new protocol tended to overestimate the blood volume (BV) and blood flow (BF) value, and to underestimate the mean transit time (MTT) value compared with the traditional method. However, there was no statistically significant difference in BV, BF, and MTT value between the two methods except permeability surface (PS) ( >0.05). The volume CT dose index (CTDIvol) and dose length product (DLP) of our protocol were lower than the traditional one. The new protocol can obtain valuable diagnostic information in a shorter time without significant compromise in image quality. In addition, it reduces the radiation dose as well as contrast medium usage on the patient.

关键词： computed tomography angiography     computed tomography perfusion    

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Low-dose CT for lung cancer screening: opportunities and challenges

null

《医学前沿（英文）》 2018年 第12卷 第1期   页码 116-121 doi: 10.1007/s11684-017-0600-1

摘要：

Lung cancer is among the most frequently diagnosed cancers worldwide and the leading cause of cancer death in both males and females. Screening for lung cancer coupled with earlier intervention has long been studied as an approach to mortality reduction. However, minimal progress was achieved until recently, when low-dose spiral computed tomography (LDCT) screening demonstrated a 20% reduction in mortality from lung cancer in a randomized controlled trial (RCT), the National Lung Screening Trial, from the United States. On the basis of this finding, LDCT has been recommended for lung cancer screening in high-risk populations by several clinical guidelines. However, results from the following independent RCTs in Europe failed to show consistent conclusions. In addition, intractable problems gradually emerged with the progress of LDCT screening. This paper summarizes and discusses the main observations and challenges of LDCT screening for lung cancer. Before spreading implementation of LDCT screening, challenges, including high false-positive rates, overdiagnosis, enormous costs, and radiation risk, must be addressed. Complementary biomarkers and technical improvement are expected in the field of lung cancer screening in the near future.

关键词： lung cancer     low-dose computerized tomography     early detection     opportunities     challenges    

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The dynamic correction of collimation errors of CT slicing pictures

LIU Ya-xiong, Sekou Sing-are, LI Di-chen, LU Bing-heng

《机械工程前沿（英文）》 2006年 第1卷 第2期   页码 168-172 doi: 10.1007/s11465-006-0016-0

摘要： To eliminate the motion artifacts of CT images caused by patient motions and other related errors, two kinds of correctors (A type and U type) are proposed to monitor the scanning process and correct the motion artifacts of the original images via reverse geometrical transformation such as reverse scaling, moving, rotating and offsetting. The results confirm that the correction method with any of the correctors can improve the accuracy and reliability of CT images, which facilitates in eliminating or decreasing the motion artifacts and correcting other static errors and image processing errors. This provides a foundation for the 3D reconstruction and accurate fabrication of the customized implants.
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Effects of delamination in drilling glass/polyester composite

Mehdi GANJIANI, Majid SAFARABADI, Nabi MEHRI-KHANSARI, Hossein ORUJI

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 552-567 doi: 10.1007/s11709-021-0699-7

摘要： Considering failures during machinery processes such as drilling, a precautionary analysis involving delamination and the corresponding dissipated energy is required, especially for composite structures. In this context, because of the complexity of both the analysis procedure and experimental test setup, most studies prefer to represent mode I and III interlaminar crack propagation instead of that involving mode II. Therefore, in this study, the effect of mode delamination and corresponding interlaminar crack propagation was considered during the drilling process of multilayered glass/polyester composites using both numerical and experimental approaches. In the experimental procedure, the mechanical properties of the glass/polyester specimens were obtained according to ASTM D3039. In addition, the interlaminar mixed-mode (I/II) loadings were determined using an ARCAN test fixture so that the fracture toughness of glass/polyester could then be identified. The mode II critical strain energy release rate (CSERR) was then obtained using an experimental test performed using an ARCAN fixture and the virtual crack closure technique (VCCT). It was determined that the numerical approach was in accordance with the experiments, and more than 95% of crack propagation could be attributed to mode II compared to the two other modes.

关键词： delamination     VCCT     ARCAN specimen     drilling     mode II    

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Analyzing the characterization of pore structures and permeability of diesel contaminated clays under different aging conditions

《结构与土木工程前沿（英文）》   页码 1264-1280 doi: 10.1007/s11709-023-0921-x

摘要： In this study, mercury intrusion porosimetry (MIP) and X-ray micro-computed tomography (XRμCT) were used to characterize the pore structures and investigate the permeability characteristics of clay after aging and contamination with diesel. The results of the MIP tests showed that aging leads to reductions in porosity and average diameter, as well as an increase in tortuosity. The XRμCT analysis yielded consistent results; it showed that aging renders pores more spherical and isotropic and pore surfaces smoother. This weakens the pore connectivity. Micromorphological analysis revealed that aging led to the rearrangement of soil particles, tighter interparticle overlapping, and a reduction in pore space. The combination of MIP and XRμCT provided a comprehensive and reliable characterization of the soil pore structure. An increased diesel content increased the porosity and average diameter and reduced the tortuosity of the pores. Mechanistic analysis showed that aging weakens interparticle cohesion; this causes large agglomerates to break down into smaller agglomerates, resulting in a tighter arrangement and a subsequent reduction in porosity. An increase in diesel content increases the number of large agglomerates and pore spaces between agglomerates, resulting in increased porosity. Both aging and diesel content can weaken the permeation characteristics of soil.

关键词： MIP     XRμCT     aging     diesel content     pore structure     permeability characteristics    

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考虑垫片形状和尺寸效应的珊瑚混凝土劈裂抗拉性能的三维细观研究 Article

吴彰钰, 张锦华, 余红发, 方秦, 麻海燕, 陈力

《工程（英文）》 2022年 第17卷 第10期   页码 110-122 doi: 10.1016/j.eng.2021.02.024

摘要：

珊瑚混凝土（CAC）作为一种新型建筑材料，已经在岛礁工程结构建设领域引起了极大的关注。为了研究CAC的静态劈裂抗拉性能，本文提出了一种考虑骨料形状和空间分布随机性的三维（3D）随机混凝土细观模型，影响因素包括试件形状和支承垫片尺寸。我们建立了12 个不同的混凝土细观模型，按照试件形状可分为两种，即边长为150 mm的立方体和尺寸为ϕ150 mm×300 mm的圆柱体。其中，支承垫片宽度为6 mm、9 mm、12 mm、15 mm、18 mm和20 mm。本文系统分析和讨论了试件几何形状和垫片宽度对CAC劈裂抗拉性能的影响规律，研究内容包括混凝土开裂过程、最终破坏模式和劈裂抗拉强度（fst）。结果表明：本文所开发的细观模型具有很高的可靠性，并确定了适用于CAC劈裂抗拉性能模拟和预测的最优计算参数。CAC的fst值与试件形状和垫片宽度直接相关。其中，在垫片尺寸相同的情况下，立方体CAC试件的fst值要略高于圆柱体模型，表明可以采用断裂面积的差异来解释试件形状效应对CAC fst值的影响规律。此外，当垫片的相对宽度由0.04 增加到0.13 时，CAC的fst值会呈现逐渐增大的趋势。基于弹性力学理论，本文初步确定了不同垫片宽度条件下CAC fst的取值范围，这对于研究CAC的抗拉性能具有重要意义。

关键词： 珊瑚混凝土     三维细观模拟     劈拉试验     抗拉强度     试件形状     支承垫片    

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Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway stations

《结构与土木工程前沿（英文）》 2023年 第17卷 第5期   页码 763-779 doi: 10.1007/s11709-023-0917-6

摘要： A disadvantage of the conventional quasi-static test method is that it does not consider the soil restraint effect. A new method to test the seismic performance of prefabricated specimens for underground assembled structures is proposed, which can realistically reflect the strata restraint effect on the underground structure. Laboratory work combined with finite element (FE) analysis is performed in this study. Three full-scale sidewall specimens with different joint forms are designed and fabricated. Indices related to the seismic performance and damage modes are analyzed comprehensively to reveal the mechanism of the strata restraint effect on the prefabricated sidewall components. Test results show that the strata restraint effect effectively improves the energy dissipation capacity, load-bearing capacity, and the recoverability of the internal deformation of the precast sidewall components. However, the strata restraint effect reduces the ductility of the precast sidewall components and aggravates the shear and bending deformations in the core region of the connection joints. Additionally, the strata restraint effect significantly affects the seismic performance and damage mode of the prefabricated sidewall components. An FE model that can be used to conduct a seismic performance study of prefabricated specimens for underground assembled structures is proposed, and its feasibility is verified via comparison with test data.

关键词： underground structures     precast sidewall specimen     seismic test method     bearing capacity     energy dissipation capacity     plastic deformation    

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Experimental study on compaction-induced anisotropic mechanical property of rockfill material

Xiangtao ZHANG, Yizhao GAO, Yuan WANG, Yu-zhen YU, Xun SUN

《结构与土木工程前沿（英文）》 2021年 第15卷 第1期   页码 109-123 doi: 10.1007/s11709-021-0693-0

摘要： The anisotropy of rockfill materials has a significant influence on the performance of engineering structures. However, relevant research data are very limited, because of the difficulty with preparing specimens with different inclination angles using traditional methods. Furthermore, the anisotropy test of rockfill materials is complex and complicated, especially for triaxial tests, in which the major principal stress plane intersects with the compaction plane at different angles. In this study, the geometric characteristics of a typical particle fraction consisting of a specific rockfill material were statistically investigated, and the distribution characteristics of particle orientation in specimens prepared via different compaction methods were examined. For high-density rockfill materials, a set of specimen preparation devices for inclined compaction planes was developed, and a series of conventional triaxial compression tests with different principal stress direction angles were conducted. The results reveal that the principal stress direction angle has a significant effect on the modulus, shear strength, and dilatancy of the compacted rockfill materials. Analysis of the relationship between the principal stress direction angles, change in the stress state, and change in the corresponding dominant shear plane shows that the angle between the compacted surface and dominant shear plane is closely related to interlocking resistance associated with the particle orientation. In addition, different principal stress direction angles can change the extent of the particle interlocking effect, causing the specimen to exhibit different degrees of anisotropy.

关键词： rockfill     inclination of specimen preparation     anisotropy     mechanical property     mechanism    

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A pilot study on Paxlovid therapy for hemodialysis patients with severe acute respiratory syndrome coronavirus 2 infections

《医学前沿（英文）》 doi: 10.1007/s11684-023-1011-0

摘要： We aimed to investigate the safety and efficacy of nirmatrelvir/ritonavir (Paxlovid) therapy for hemodialysis-dependent patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Thirteen hemodialysis patients infected with the Omicron variant of SARS-CoV-2 from April 3 to May 30, 2022, were recruited. Laboratory parameters and chest CT (computed tomography) imaging were analyzed. The treatment group included six patients who received 150 mg/100 mg of Paxlovid orally once daily for 5 days, whereas the control group included seven patients who received basic treatment. No serious adverse reactions or safety events were recorded. Four control patients progressed to moderate disease, and none in the treatment group showed progression of chest CT findings (P < 0.05). Paxlovid therapy tended toward early viral clearance and low viral load on Day 8. Moreover, 83.3% of the patients in the treatment group and 57.1% of the patients in the control group turned negative within 22 days. In the Paxlovid treatment group, we found significantly increased levels of lymphocytes (P=0.03) and eosinophils (P=0.02) and decreased levels of D-dimer on Day 8 compared with those on Day 1. Paxlovid therapy showed a potential therapeutic effect with good tolerance in hemodialysis patients. The optimal dose and effectiveness evaluation must be further investigated in a largeer cohort.

关键词： Paxlovid     hemodialysis     SARS-CoV-2     viral load     chest CT scan    

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Comparison of CT-guided aspiration to key hole craniotomy in the surgical treatment of spontaneous putaminal

ZHAO Jizong, WANG Dejiang, WANG Shuo, YUAN Ge, KANG Shuai, JI Nan, ZHAO Yuanli, YE Xun, ZHOU Liangfu, ZHOU Dingbiao, WANG Renzhi, WANG Mei

《医学前沿（英文）》 2007年 第1卷 第2期   页码 142-146 doi: 10.1007/s11684-007-0027-1

摘要： This study was designed to compare the approaches and efficacies of two different ways of neurosurgical management for spontaneous putaminal hemorrhage (SPH): computed tomographic-guided aspiration (CTGA) and the key-hole approach (KHA). The indications of the two approaches are also explored. From September 2001 to 2003, a total of 1077 cases of SPH distributed in 135 hospitals all over the mainland of China were included for analysis. All cases had three-month follow-up data. The study was designed in a single-blinded manner to compare the efficacies of the different approaches. There were 563 cases in the CTGA group, 165 in the KHA group, and 217 cases in the conventional open craniotomy (COC) group. In the CTGA and KHA groups, the mortalities at one month after operation (M1m) were 17.9% and 18.3%, respectively, while the mortalities at three months after operation (M3m) were 19.4% and 19.4%, respectively (>0.05). The postoperative complications due to CTGA (23.7%) were not significantly different from those due to KHA (25.7%) ( = 0.420). The M3m of patients with Glasgow coma scale (GCS) "d8 was 3.45 and 4.0 times as much as those with GCS>8, respectively. The M3m of patients with complications was 3.92 times as much as those without complications. The M3m of patients with hemorrhage volume "e70 mL was 2.67 times as much as those <70 mL. The CTGA is not better than KHA in the treatment of SPH in terms of a more favorable outcome or less mor tality and morbidity, but CTGA could be the first choice for those with bleeding volumes "d50mL, while KHA is the first choice for those with bleeding volumes >50 mL.

关键词： tomographic-guided aspiration     single-blinded manner     favorable outcome     operation     Glasgow    

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Trauma-induced “Macklin effect” with pneumothorax and large pneumomediastinum, disguised by allergy

null

《医学前沿（英文）》 2013年 第7卷 第3期   页码 386-388 doi: 10.1007/s11684-013-0278-y

摘要：

A 56-year-old man presented spontaneously to the Emergency Department complaining of facial and neck oedema after assumption of nonsteroidal anti-inflammatory drugs (NSAIDS). The triage nurse assigned the patient to Accident & Emergency (A&E) doctor as probable allergic reaction to NSAIDS. Chest X-ray (CXR), ordered after 24 hours, revealed a huge subcutaneous chest and neck emphysema without clearly visible pneumothorax. Subsequent chest CT scan showed a small left pneumothorax and a large amount of air in the mediastinum. The patient was conservatively treated since he was eupnoeic and hemodynamically stable. The pathophysiology of pneumomediastinum was first described by Macklin in 1939. The Macklin effect involves alveolar ruptures with air dissection along bronchovascular sheaths to the mediastinum. In this case the patient did not report in his history a recent blunt thoracic trauma and the initial suspicion of an allergic reaction has prevented physicians to immediately achieve the correct diagnosis.

关键词： thoracic trauma     differential diagnosis     critical care     pneumothorax     pneumomediastinum     CT scan     pitfalls     lung and airways physiology    

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A study on quality evaluation for bituminous mixture using X-ray CT

Satoshi TANIGUCHI, Keiichiro OGAWA, Jun OTANI, Itaru NISHIZAKI

《结构与土木工程前沿（英文）》 2013年 第7卷 第2期   页码 89-101 doi: 10.1007/s11709-013-0197-7

摘要： The objective of this paper is to propose a new quality evaluation method for asphalt concrete mixture using X-ray CT scanner. To achieve this aim, asphalt mixtures should be subjected to the X-ray CT scanning and its characteristics should be clarified. The approach employed in this study was as follows: 1) Coarse aggregate, fine aggregate, filler and bitumen were prepared; 2) dense-graded, coarse-graded and porous asphalt mixtures were made; 3) materials and mixtures were subjected to the X-ray CT scanning; 4) frequency of CT-value, threshold value, average slice CT-value, average segment CT-value were computed. In the material examination, CT-value of aggregate becomes smaller in the order of coarse aggregate, fine aggregate and filler and CT image of bitumen was nearly homogeneous. In the mixture examination, histograms of CT-value and four segmentation images made from CT images expressed the material and mixture characterization such as particle size and the difference in bitumen content and mixture type visibly and the bitumen content varies with the threshold values. In addition, the average segment CT-value without threshold value by dividing the fine aggregate from the coarse aggregate and average CT-value of the coarse aggregate, especially is highly correlated with average CT-value of the bitumen.

关键词： asphalt concrete mixture     aggregate     bitumen     bitumen content     quality evaluation     X-ray CT    

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A miniature triaxial apparatus for investigating the micromechanics of granular soils with

Zhuang CHENG, Jianfeng WANG, Matthew Richard COOP, Guanlin YE

《结构与土木工程前沿（英文）》 2020年 第14卷 第2期   页码 357-373 doi: 10.1007/s11709-019-0599-2

摘要： The development of a miniature triaxial apparatus is presented. In conjunction with an X-ray micro-tomography (termed as X-ray μCT hereafter) facility and advanced image processing techniques, this apparatus can be used for investigation of the micro-scale mechanical behavior of granular soils under shear. The apparatus allows for triaxial testing of a miniature dry sample with a size of (diameter height). triaxial testing of a 0.4–0.8 mm Leighton Buzzard sand (LBS) under a constant confining pressure of 500 kPa is presented. The evolutions of local porosities (i.e., the porosities of regions associated with individual particles), particle kinematics (i.e., particle translation and particle rotation) of the sample during the shear are quantitatively studied using image processing and analysis techniques. Meanwhile, a novel method is presented to quantify the volumetric strain distribution of the sample based on the results of local porosities and particle tracking. It is found that the sample, with nearly homogenous initial local porosities, starts to exhibit obvious inhomogeneity of local porosities and localization of particle kinematics and volumetric strain around the peak of deviatoric stress. In the post-peak shear stage, large local porosities and volumetric dilation mainly occur in a localized band. The developed triaxial apparatus, in its combined use of X-ray μCT imaging techniques, is a powerful tool to investigate the micro-scale mechanical behavior of granular soils.

关键词： triaxial apparatus     X-ray μCT     in situ test     micro-scale mechanical behavior     granular soils    

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标题 作者 时间 类型 操作

Creep-fatigue crack growth behavior in GH4169 superalloy

Dianyin HU, Xiyuan WANG, Jianxing MAO, Rongqiao WANG

期刊论文

结合全变分最小化和稀疏字典学习后处理的低剂量CT重建

Yong DING, Tuo HU

期刊论文

Simultaneous acquisition of CT angiography and whole brain CT perfusion images by using multiphase dynamic

Weiwei CHEN, Jianpin QI, Wenzhen ZHU, Wenhua HUANG, Jinmei SONG

期刊论文

Low-dose CT for lung cancer screening: opportunities and challenges

null

期刊论文

The dynamic correction of collimation errors of CT slicing pictures

LIU Ya-xiong, Sekou Sing-are, LI Di-chen, LU Bing-heng

期刊论文

Effects of delamination in drilling glass/polyester composite

Mehdi GANJIANI, Majid SAFARABADI, Nabi MEHRI-KHANSARI, Hossein ORUJI

期刊论文

Analyzing the characterization of pore structures and permeability of diesel contaminated clays under different aging conditions

期刊论文

考虑垫片形状和尺寸效应的珊瑚混凝土劈裂抗拉性能的三维细观研究

吴彰钰, 张锦华, 余红发, 方秦, 麻海燕, 陈力

期刊论文

Effect of strata restraint on seismic performance of prefabricated sidewall joints in fabricated subway stations

期刊论文

Experimental study on compaction-induced anisotropic mechanical property of rockfill material

Xiangtao ZHANG, Yizhao GAO, Yuan WANG, Yu-zhen YU, Xun SUN

期刊论文

A pilot study on Paxlovid therapy for hemodialysis patients with severe acute respiratory syndrome coronavirus 2 infections

期刊论文

Comparison of CT-guided aspiration to key hole craniotomy in the surgical treatment of spontaneous putaminal

ZHAO Jizong, WANG Dejiang, WANG Shuo, YUAN Ge, KANG Shuai, JI Nan, ZHAO Yuanli, YE Xun, ZHOU Liangfu, ZHOU Dingbiao, WANG Renzhi, WANG Mei

期刊论文

Trauma-induced “Macklin effect” with pneumothorax and large pneumomediastinum, disguised by allergy

null

期刊论文

A study on quality evaluation for bituminous mixture using X-ray CT

Satoshi TANIGUCHI, Keiichiro OGAWA, Jun OTANI, Itaru NISHIZAKI

期刊论文

A miniature triaxial apparatus for investigating the micromechanics of granular soils with

Zhuang CHENG, Jianfeng WANG, Matthew Richard COOP, Guanlin YE

期刊论文