检索结果-南通市图书馆

Senographe DS数字乳腺X射线机故障维修2例

在线全文

学校读者我要写书评

暂无评论

医疗卫生装备 2024年第1期45卷 118-120页

作者：杨朔卢亮亮宋琳琳临沂市妇幼保健院医学装备科山东临沂276016 山东医学高等专科学校济南250002

介绍了Senographe DS数字乳腺X射线机的结构组成和工作原理,分析了Senographe DS数字乳腺X射线机无法曝光、图像出现伪影2例故障的原因及排除方法,为同行维修类似故障提供了参考。

关键词： Senographe DS数字乳腺X射线机故障维修故障排除

西南典型碳酸盐岩高地质背景区农田重金属化学形态、影响因素及回归模型

在线全文

学校读者我要写书评

暂无评论

环境科学 2024年第5期45卷 2995-3004页

作者：唐瑞玲徐进力刘彬杜雪苗顾雪于林松毕婧中国地质科学院地球物理地球化学勘查研究所廊坊065000 山东省物化探勘查院济南250013 山东省地质测绘院济南250014

土壤重金属化学形态是决定重金属生物活性和生物毒性的重要因素,是科学评价西南碳酸盐岩高地质背景区土壤重金属生态风险的关键.为了探明碳酸盐岩高地质背景区土壤重金属化学形态分布情况,选择贵州省典型碳酸盐岩分布区,以第二次全国土... 详细信息

土壤重金属化学形态是决定重金属生物活性和生物毒性的重要因素,是科学评价西南碳酸盐岩高地质背景区土壤重金属生态风险的关键.为了探明碳酸盐岩高地质背景区土壤重金属化学形态分布情况,选择贵州省典型碳酸盐岩分布区,以第二次全国土壤普查图斑为采样单元,在农田中采集土壤表层样品309件,利用改进的Tessier七步顺序提取法,分析了As、Cd、Cu、Hg、Ni、Pb和Zn等7种重金属的水溶态(F1)、离子交换态(F2)、碳酸盐结合态(F3)、弱有机结合态(F4)、铁锰氧化物结合态(F5)、强有机结合态(F6)和残渣态(F7)这7种化学形态.结果发现,土壤中重金属As、Cu、Hg、Ni、Pb和Zn残渣态比例均超过50%,有效组分(F1~F3)比例均小于5%,潜在生物有效组分(F4~F6)比例低于45%,活性较低,生态风险不高.Cd的有效组分和潜在生物有效组分占比分别为55.49%和29.37%,远高于其他重金属,基于土壤重金属形态的生态风险远小于基于土壤总量的生态风险.逐步回归方程可以有效建立Cd、Cu和Pb生物有效组分与影响因素之间的关系.重金属全量和pH值是影响碳酸盐岩高地质背景区土壤重金属化学形态的重要因子,受研究区长期土法炼锌活动和碳酸盐岩风化成土过程中重金属元素倾向于在残渣态中富集的影响,土壤有机质(OM)和氧化物含量对土壤重金属化学形态影响相对较小.

关键词：土壤重金属化学形态生态评价影响因素回归模型高地质背景区

Hydrogen absorption/desorption cycling performance of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2023年第4期11卷 1180-1192页

作者： Fenghai Guo Tiebang Zhang Limin Shi lin song State Key Laboratory of Solidification Processing Northwestern Polytechnical UniversityXi’an 710072China School of Materials and Chemical Engineering Xi’an Technological UniversityXi’an 710072China

Aiming to elucidate the hydrogen absorption/desorption cycling properties of Mg-based alloys with in-situ formed Mg_(2)Ni and LaH_(x)(x=2,3)nanocrystallines,the hydrogen storage cycle stability,hydriding/dehydriding cycling kinetics and thermodynamic stability of the experimental alloys have been investigated in *** results show that the Mg-Ni-La alloys exhibit improved hydrogen storage cycling properties and can remain storage hydrogen above 5.5 wt%after 200 *** the increase of cycling numbers,the dehydrogenation rates of the experimental samples increase firstly and then gradually decrease,and eventually maintain relative stable *** observation reveals that powders sintering and hydrogen decrepitation both exist during hydrogen absorption/desorption cycles due to repeated volume expansion and ***,the in-situ formed LaH_(x)(x=2,3)and Mg_(2)Ni nanocrystallines stabilize the microstructures of the particles and hinder the powders *** 200 cycles,the average particle size of the experimental samples decreases and the specific surface area apparently increases,which leads to the decomposition temperatures of MgH_(2)and Mg_(2)NiH_(4)slightly shift to lower ***,Mg_(2)Ni and LaH_(x)(x=2,3)have been proven to be stable catalysts during long-term cycling,which can still uniformly distribute within the powders after 200 cycles.

关键词： Mg-based hydrogen storage alloys Cycle stability Microstructure evolution Catalyst stability Thermodynamics

Robust Video Watermarking Using a Hybrid DCT-DWT Approach

在线全文

学校读者我要写书评

暂无评论

Journal of Electronic Science and Technology 2020年第2期18卷 179-189页

作者： Jie Sang Qi Liu Chun-lin song School of Computer Science Jiangnan UniversityWuxi 214000

In order to solve the limitations of the digital video watermarking algorithm,this paper proposes a new robust video watermarking algorithm using combining discrete cosine transform(DCT)and discrete wavelet transform(DWT)*** of all,the video frames are randomly selected and then the DCT algorithm is applied to the selected video *** that,the first column of the selected video frames is scrambled using the Arnold ***,every column with 4 direct current(DC)coefficients is reshaped and transformed into four different sub-bands using the DWT ***,the watermark is embedded into the approximation(LL)*** proposed algorithm is easy to carry out because it provides random frames with no special requirements for video *** experiment results indicate that this algorithm can resist against different kinds of watermarking attacks,such as the Gaussian filter attack and sharpen *** addition,it also illustrates that the proposed algorithm has a better result than some other watermarking algorithms.

关键词： Arnold Hybrid DCT

晚更新世以来海南岛西部河流阶地演化及其成因机制

在线全文

学校读者我要写书评

暂无评论

地球科学 2024年第8期49卷 3043-3055页

作者：陈康林姜涛胡亦潘周从艳梁晨宋霖中国地质大学海洋地质资源湖北省重点实验室湖北武汉430074

晚更新世以来,海南岛构造活动活跃且差异性构造升降特征明显.受这些构造活动影响,海南岛上各条主要河流发育了一系列河流阶地,深刻理解这些阶地的形成演化过程无疑将有助于更好地揭示海南岛不同部位的构造差异活动特征.运用光释光测年... 详细信息

晚更新世以来,海南岛构造活动活跃且差异性构造升降特征明显.受这些构造活动影响,海南岛上各条主要河流发育了一系列河流阶地,深刻理解这些阶地的形成演化过程无疑将有助于更好地揭示海南岛不同部位的构造差异活动特征.运用光释光测年技术对海南岛西部6条河流的河流阶地沉积物进行定年,结合野外地质调查与地貌学研究,系统建立了4级河流阶地年代框架:27.3~29.6 ka、2.82~3.92 ka、0.60~0.93 ka、~0.40~0.50 ka,进而结合海南岛构造活动和区域气候演化等探讨了河流阶地的成因.研究结果表明,T4阶地的形成主要受控于气候变化,它改变了径流搬运能力和沉积物通量,进而导致了河流产生堆积和侵蚀作用;T3、T2、T1阶地的形成受控于多条断裂活动,间歇性的差异性构造升降运动是这些河流阶地形成的主要驱动力,而且河流下切速率差异性表明0.60~3.92 ka海南岛中西部构造隆升速率高于西南部.

关键词：海南岛河流阶地光释光测年构造活动气候变化海洋地质

Mapping the Uniformity of Deep Level Defects Distribution by Scanning Photoluminescence

在线全文

学校读者我要写书评

暂无评论

Chinese Physics Letters 1991年第7期8卷 380-383页

作者： WENG Yumin lin song ZONG Xiangfu Institute of Materials Science Fudan UniversityShanghai 200433

Deep level defects in undoped semi-insulating GaAs were investigated by photo-luminescence technique at room *** 0.69eV band is associated with the main mid-gap level EL2,and the 0.76eV band is suggested to be caused by some native point defects related to excess As,such as As anti-site ***-dimensional and pseudo three-dimensional plots of the EL2 related band have been observed for as grown and annealed wafers.

关键词： temperature EL2 Deep

Epidural analgesia followed by epidural hydroxyethyl starch prevented post-dural puncture headache:Twenty case reports and a review of the literature

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Clinical Cases 2021年第8期9卷 1946-1952页

作者： lin-lin song Yin Zhou Zhi-Yu Geng Department of Anesthesiology Peking University First HospitalBeijing 100034China

BACKGROUND Accidental dural puncture(ADP)and subsequent post-dural puncture headache(PDPH)remain common complications of epidural procedures for obstetric anesthesia and *** clear consensus exists on the best way to prevent PDPH after *** SUMMARY We report our findings in twenty parturients who underwent an incorporated strategy of epidural analgesia followed by epidural hydroxyethyl starch(HES)to prevent PDPH after ADP with a 16-gauge Tuohy needle during epidural *** with a 16-gauge Tuohy needle occurred in nine parturients undergoing a cesarean section(CS)and in eleven parturients receiving labor *** epidural catheter was re-sited at the same or adjacent intervertebral space in all *** CS,the epidural catheter was used for postoperative pain relief over a 48-h *** delivery in eleven cases,epidural infusion was maintained for 24 ***,15 mL of 6%HES 130/0.4 was administered via the epidural catheter immediately prior to catheter *** of the parturients developed PDPH or neurologic deficits over a follow-up period of at least two months to up to one year *** An incorporated strategy of epidural analgesia followed by epidural hydroxyethyl starch may have great efficacy in preventing PDPH after ADP.

关键词： Epidural analgesia Hydroxyethyl starch Accidental dural puncture Postdural puncture headache Prophylaxis Case report

Active Authentication Protocol for IoV Environment with Distributed Servers

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2022年第12期73卷 5789-5808页

作者： Saravanan Manikandan Mosiur Rahaman Yu-lin song Department of Computer Science and Information Engineering Asia UniversityTaichungTaiwan Bioinformatics and Medical Engineering Asia UniversityTaichungTaiwan

The Internet of Vehicles(IoV)has evolved as an advancement over the conventional Vehicular Ad-hoc Networks(VANETs)in pursuing a more optimal intelligent transportation system that can provide various intelligent solutions and enable a variety of applications for vehicular *** volumes of data are produced and communicated wirelessly among the different relayed entities in these vehicular networks,which might entice adversaries and endanger the system with a wide range of security *** ensure the security of such a sensitive network,we proposed a distributed authentication mechanism for IoV based on blockchain technology as a distributed ledger with an ouroboros *** timestamp and challenge-responsemechanisms,the proposed authentication model can withstand several security attacks such asMan-in-Middle(MiM)attacks,Distributed Denial of Service(DDoS)attacks,server spoofing attacks and *** proposed method also provides a solution for single-point failure,forward secrecy,revocability,*** exhibit the security of our proposed model by using formal(mathematical)analysis and informal *** used Random Oracle Model to perform themathematical *** addition,we compared the communication cost,computation cost,and security of the proposed model with the related existing *** have verified the security of the model by using AVISPA tool *** security analysis and computation analysis show that the proposed protocol is viable.

关键词： IoV message authentication random oracle model blockchain distributed server revocability

HYDROSTATIC STRESS-DEPENDENT PERFECTLY-PLASTIC STRESS FIELDS AT A STATIONARY PLANE-STRESS CRACK-TIP

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Applied Mathematics and Mechanics(English Edition) 1992年第8期13卷 767-770页

作者： lin Bai-song Central-South University of Technology Changsha

Under the condition that all the stress components at a crack-tip are the functions ofθonly,making use of equilibrium equations and hydrostatic stress-dependent yield condition,in this paper,we derive the generally analytical expressions of the hydrostatic stress-dependent perfectly-plastic stress fields at a stationary plane-stress *** these generally analytical expressions to the concrete cracks,the analytical expressions of hydrostatic stress-dependent perfectly-plastic stress fields at the tips of mode I and mode II cracks are obtained.

关键词： hydrostatic stress-dependent perfectly-plastic stress field plane-stress crack-tip