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Virtual nonenhanced abdominal dual-energy MDCT:Analysis of image characteristics

World Journal of Radiology 2012年第4期4卷 167-173页

作者： Jacob Sosna Shmuel Mahgerefteh liran goshen Galit Kafri Galit Aviram Arye Blachar Department of Radiology Hadassah-Hebrew University Medical CenterJerusalem 91120Israel Department of Radiology Beth Israel Deaconess Medical CenterBostonMA 02215United States Philips Healthcare Haifa 31004Israel Department of Radiology Tel Aviv Sourasky Medical CenterSackler School of MedicineTel Aviv UniversityTel Aviv 64239Israel

AIM: To evaluate abdominal and pelvic image characteristics and artifacts on virtual nonenhanced (VNE) images generated from contrast-enhanced dual-energy multidetector computed tomography (MDCT) studies. METHODS: Hadassah-Hebrew University Medical Institutional Review Board approval was obtained; 22 patients underwent clinically-indicated abdominal and pelvic single-source dual-energy MDCT (Philips Healthcare, Cleveland, OH, USA), pre- and post-IV administration of Omnipaque 300 contrast (100 cc). Various solid and vascular structures were evaluated. VNE images were generated from the portal contrast-enhanced phase using probabilistic separation. Contrast-enhanced-, regular nonenhanced (RNE)-, and VNE images were evaluated with a total of 1494 density measurements. The ratio of iodine contrast deletion was calculated. Visualization of calcifications, urinary tract stones, and image artifacts in VNE images were assessed. RESULTS: VNE images were successfully generated in all patients. Significant portal-phase iodine contrast deletion was seen in the kidney (61.7%), adrenal gland (55.3%), iliac artery (55.0%), aorta (51.6%), and spleen (34.5%). Contrast deletion was also significant in the right atrium (RA) (51.5%) and portal vein (39.3%), but insignificant in the iliac vein and inferior vena cava (IVC). Average post contrast-to-VNE HU differences were significant (P < 0.05) in the: RA -135.3 (SD 121.8), aorta -114.1 (SD 48.5), iliac artery -104.6 (SD 53.7), kidney -30.3 (SD 34.9), spleen -9.2 (SD 8.8), and portal vein -7.7 (SD 13.2). Average VNE-to-RNE HU differences were significant in all organs but the prostate and subcutaneous fat: aorta 38.0 (SD 9.3), RA 37.8 (SD 16.1), portal vein 21.8 (SD 12.0), IVC 12.2 (SD 11.6), muscle 3.3 (SD 4.9), liver 5.7 (SD 6.4), spleen 22.3 (SD 9.8), kidney 40.5 (SD 6.8), and adrenal 20.7 (SD 13.5). On VNE images, 196/213 calcifications (92%) and 5/6 renal stones (84%) were visualized. Lytic-like artifacts in the vertebral bodies we

关键词： Abdominal computed tomography Dual-energy computed tomography Pelvic computed tomography Virtual nonenhanced computed tomography

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A review of recent advances in the effects of surface and interface properties on marine propellers

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Friction 2024年第2期12卷 185-214页

作者： Manfu ZHU liran MA State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

Marine propellers are important propulsion devices for both surface ships and underwater *** severe environmental problems have required further performance enhancement for ***,traditional methods to improve propeller performances through geometrical and structural optimizations have been extensively investigated,while the underlying mechanisms of the effects of surface and interface properties on marine propellers are still far from being fully *** paper presented a comprehensive review of recent advances in the effects of surface and interface properties,such as surface roughness and surface wettability,on marine propellers with an emphasis on the significant improvements in both hydrodynamic and cavitation performances,hoping to arouse more in-depth investigations in the field of surface/interface science and technologies on marine propellers,and also promote the state-of-the-art technologies,such as superlubricity technology,into practical applications.

关键词： marine propellers hydrodynamics cavitation surface roughness surface wettability

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L^(*)—An index for evaluating long range performance of autonomous underwater vehicles(AUVs)

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Friction 2024年第10期12卷 2205-2221页

作者： Manfu ZHU liran MA Jianbin LUO State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

Autonomous underwater vehicles(AUVs)have various applications in both military and civilian fields.A wider operation area and more complex tasks require better overall range performance of ***,until recently,there have been few unified criteria for evaluating the range performance of *** the present work,a unified range index,i.e.,L^(*),considering the cruising speed,the sailing distance,and the volume of an AUV,is proposed for the first time,which can overcome the shortcomings of previous criteria using merely one single parameter,and provide a uniform criterion for the overall range performance of various *** constructing the expression of the L^(*)index,the relevant data of 49 AUVs from 12 countries worldwide have been collected,and the characteristics of the L^(*)range index in different countries and different categories were compared and ***,by analyzing the complex factors affecting the range index,methods to enhance the L^(*)range index value,such as efficiency enhancement and drag reduction,have been introduced and *** this condition,the work proposes a unified and scientific criterion for evaluating the range performance of AUVs for the first time,provides valuable theoretical insight for the development of AUVs with higher performance,and then arouses more attention to the application of the cutting-edge superlubricity technology to the field of underwater vehicles,which might greatly help to accelerate the coming of the era of the superlubricitive engineering.

关键词： autonomous underwater vehicles(AUVs) range performance range index superlubricity drag reduction

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Photoinduced superlubricity on TiO_(2) surfaces

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Friction 2024年第3期12卷 428-438页

作者： Ke HAN liran MA Yu TIAN Jianbin LUO State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China Received:16 September 2022/Revised:28 October 2022/Accepted:27 December 2022The author(s)2022.

Superlubricity control is of great interest in both industry and scientific research,and several methods have been proposed to achieve this *** this work,ultraviolet(UV)light was introduced into titanium dioxide(TiO_(2))and silicon nitride(Si_(3)N_(4))tribosystems to accomplish photoinduced *** friction coefficients(COFs)between Si_(3)N_(4) balls and TiO_(2) plates in the mixtures of sulfuric acid(H^(2)SO_(4))solution and glycerol solution were obviously reduced,and the system entered the superlubricity region(COF<0.01)after UV illumination at a speed of 56 mm/***,the COF was much larger without UV treatment than that with UV *** formation of silica(SiO_(2))layers on the surfaces of Si_(3)N_(4) balls and the elastohydrodynamic effects were determined to be fundamental to the low friction in this experiment,and the enhancement of the combination between the TiO_(2) surface and the hydroxy group of glycerol by UV illumination was the key to the photoinduced superlubricity in this *** findings showed one method for achieving superlubricity by introducing a light field that could be further applied to special working conditions.

关键词： light control friction superlubricity glycerol titanium dioxide(TiO_(2))

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Photo-induced grease/oil switched lubricant for friction regulation

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Friction 2024年第8期12卷 1696-1706页

作者： Zheng ZHANG Shuangxi TANG liran MA Yu TIAN State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

Controllable friction regulation has drawn much interest in both scientific and industrial *** there have been many researches on friction regulation by many physical fields and chemical ***-sensitive materials are promising because it is relatively easy to change their properties compared with ***,a new kind of photo-induced grease/oil switched lubricant is designed and shows great reversibility under ultraviolet(UV)and visible(Vis)*** viscosity can change more than 50 times under different irradiation,and the coefficients of friction(COFs)obviously increase under Vis irradiation and decrease under UV irradiation,which performs better than those of the common *** to the experimental results,the phenomena are contributed to the break and reconstruction of the three-dimensional network inside the *** a switchable grease/oil state under different irradiation,this work provides a new principle for designing a smart lubricant with controllable friction regulation.

关键词： photo-induced spiropyran switched lubricant friction regulation

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Hydration lubrication modulated by water structure at TiO2–aqueous interfaces

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Friction 2024年第4期12卷 591-605页

作者： Pingsu MA Yuan LIU Ke HAN Yu TIAN liran MA State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

The nature of solid-liquid interfaces is of great significance in *** advances have been made in lubrication based on hydration ***,a detailed molecular-level understanding is still ***,we investigated water molecule behaviors at the TiO2-aqueous interfaces by the sum-frequency generation vibrational spectroscopy(SFG-VS)and atomic force microscope(AFM)to elucidate the fundamental role of solid-liquid interfaces in *** contributions of water structures and hydration effects were revealed,where water structures played the dominant role in lubrication for TiO2 surfaces of varying hydrophilicity,while hydration effects dominated with the increasing of ion *** lubrication is observed on the initial TiO2 surfaces with strongly H-bonded water molecules compared to the hydrophilic TiO2 surfaces with more disordered *** stable ordered water arrangement with strong hydrogen bonds and the shear plane occurring between the ordered water layer and subsequent water layer may play a significant role in achieving lower *** adsorbed hydrated molecules with the increasing ionic concentration perturb ordered water but lead to the enhancement of hydration effects,which is the main reason for the improved lubrication for both *** work provides more insights into the detailed molecular-level understanding of the mechanism of hydration lubrication.

关键词： hydration lubrication interfacial water structures hydration effects titanium dioxide(TiO2)

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Experiment and modelling of texture and sliding direction dependence on finger friction behavior

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Friction 2024年第9期12卷 1955-1968页

作者： Yuanzhe LI Xue ZHOU Pengpeng BAI Zhonghuan XIANG Yonggang MENG liran MA Yu TIAN State Key Laboratory of Tribology in Advanced Equipment School of Mechanical EngineeringTsinghua UniversityBeijing 100084China

Humans rely on their fingers to sense and interact with external *** the tribological behavior between finger skin and object surface is crucial for various fields,including tactile perception,product appearance design,and electronic skin *** describing finger frictional behavior is always challenging,given the complex structure of the *** this study,the texture and sliding direction dependence of finger skin friction was quantified based on explicit mathematic *** proposed double-layer model of finger skin effectively described the nonlinear elastic response of skin and predicted the scaling-law of effective elastic modulus with contact ***,the skin friction model on textured surface considering adhesion and deformation factors was *** revealed that adhesive term dominated finger friction behavior in daily life,and suggested that object texture size mainly influenced friction-induced vibrations rather than the average friction *** with digital image correlation(DIC)technique,the effect of sliding direction on finger friction was *** was found that the anisotropy in finger friction was governed by the finger’s ratchet pawl structure,which also contributes to enhanced stick-slip vibrations in the distal sliding *** proposed friction models can offer valuable insights into the underlying mechanism of skin friction under various operating conditions,and can provide quantitative guidance for effectively encoding friction into haptics.

关键词： finger friction tactile perception tribological model textured surface sliding direction

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Low friction under ultrahigh contact pressure enabled by self-assembled fluorinated azobenzene layers

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Friction 2024年第7期12卷 1434-1448页

作者： Dandan XUE Zhi XU Linyuan GUO Wendi LUO liran MA Yu TIAN Ming MA Qingdao ZENG Ke DENG Wenjing ZHANG Yichun XIA Shizhu WEN Jianbin LUO State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China National Center for Nanoscience and Technology Beijing 100190China

Extensive efforts have been made to pursue a low-friction state with promising applications in many fields,such as mechanical and biomedical *** which,the load capacity of the low-friction state has been considered to be crucial for industrial ***,we report a low friction under ultrahigh contact pressure by building a novel self-assembled fluorinated azobenzene layer on an atomically smooth highly-oriented pyrolytic graphite(HOPG)*** friction coefficients could be as low as 0.0005 or even lower under a contact pressure of up to 4 *** demonstrates that the low friction under ultrahigh contact pressure is attributed to molecular *** fluorination leads to effective and robust lubrication between the tip and the self-assembled layer and enhances tighter rigidity which can reduce the stress concentration in the substrate,which was verified by density functional theory(DFT)and molecular dynamics(MD)*** work provides a new approach to avoid the failure of ultralow friction coefficient under relatively high contact pressure,which has promising potential application value in the future.

关键词： ultrahigh contact pressure self-assembled layer fluorination robust lubrication

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重大公共卫生事件对联合国全球采购的影响及中国供应地位的变化——以新冠疫情为例

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地理与地理信息科学 2024年第5期40卷 59-66页

作者：刘晶丽蒋梅英熊理然云南师范大学地理学部云南昆明650500 云南师范大学孟加拉湾地区研究中心云南昆明650500 云南师范大学柬埔寨研究中心云南昆明650500

全球重大公共卫生事件的暴发严重危害人类生命健康,同时也对全球经济格局形成全面冲击。该文以新冠疫情为例,基于联合国全球采购数据库,综合运用数理统计、空间可视化等方法揭示重大公共卫生事件对联合国全球采购规模、结构、来源地的... 详细信息

全球重大公共卫生事件的暴发严重危害人类生命健康,同时也对全球经济格局形成全面冲击。该文以新冠疫情为例,基于联合国全球采购数据库,综合运用数理统计、空间可视化等方法揭示重大公共卫生事件对联合国全球采购规模、结构、来源地的影响以及中国供应地位的变动,结果表明:①疫情发生使联合国全球采购规模迅速扩大,采购结构发生明显变化。疫情发生前联合国采购来源地主要集中于美国、印度、阿联酋等国家,疫情发生后地域集中趋势越发明显,对部分国家的依赖程度不断加深。②联合国全球采购网络在疫情发生前后均表现出明显的层级性和空间非均衡性特征,少数大国占据网络的核心地位;疫情后不同等级的采购网络发生变化,中国跻身于一级核心网络,也门、苏丹等国处于二、三级网络,更低等级采购网络呈现“长尾”分布特征。③疫情发生前,中国在联合国全球采购中的供应地位与全球第二大经济体的地位极不匹配,这与中国企业专业投标人才短缺、竞争优势不足和联合国采购存在路径依赖等因素有关;疫情发生后,中国供应地位不断攀升,尤其在医疗卫生领域有明显突破。研究结果有助于中国政府和企业深入了解联合国全球采购的空间格局、来源结构、路径依赖和采购潜力,对疫情后中国企业主动参与联合国全球采购、拓展中国企业海外市场具有重要意义。

关键词：联合国全球采购空间网络供应地位中国新冠疫情

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改革开放前期香港地区“塔楼-裙房”模式传播对中国内地城市景观现代化的影响——以重庆为例

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广东园林 2024年第3期46卷 14-22页

作者：陈力然澳门科技大学人文艺术学院中国澳门999078 重庆大学建筑城规学院重庆400045

以重庆为例,考察香港地区“塔楼-裙房”模式对20世纪八九十年代中国内地城市景观现代化的影响。“塔楼-裙房”模式受香港地区人多地少的现实和市场化的建设机制影响,具备效率优先的特征,倾向于通过自足、独立于周边城市环境的内部环境... 详细信息

以重庆为例,考察香港地区“塔楼-裙房”模式对20世纪八九十年代中国内地城市景观现代化的影响。“塔楼-裙房”模式受香港地区人多地少的现实和市场化的建设机制影响,具备效率优先的特征,倾向于通过自足、独立于周边城市环境的内部环境来排除外部对其使用效率与商业效率的干扰,体现出孤岛化倾向。在1980年代该模式传播至重庆时,由于重庆没有地产市场,其效率优先及孤岛化倾向一度被弱化。1990年代起,随着重庆地产市场成立,“塔楼-裙房”重新出现效率优先及孤岛化倾向。“塔楼-裙房”一定程度上为重庆城市景观带来具有香港地区特质的现代性(实用主义、重视效率、世俗化、商业化),但同时,其孤岛化特征又导致城市景观现代化发展格局的碎片化与各自为政。

关键词：风景园林城市景观城市现代化塔楼裙房

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