检索结果-南通市图书馆

矩形微通道内蒸气冷凝过程的计算流体力学分析

在线全文

学校读者我要写书评

暂无评论

矩形微通道内蒸气冷凝过程的计算流体力学分析

作者： Hoyam mustafa Abdelrahim ibrahim 华北电力大学(北京)

学位级别：硕士

近年来,微化工技术已成为化学工程学科中一个新的发展方向和研究热点。微化工设备的主要组成部分是特征尺度为纳米到微米级的微通道,对微通道内流体的传热传质过程研究具有重要意义。水蒸气蒸发和凝结过程在许多工程应用中是很重要的,... 详细信息

近年来,微化工技术已成为化学工程学科中一个新的发展方向和研究热点。微化工设备的主要组成部分是特征尺度为纳米到微米级的微通道,对微通道内流体的传热传质过程研究具有重要意义。水蒸气蒸发和凝结过程在许多工程应用中是很重要的,例如火力发电厂、冷却系统、沸水反应堆等。本文通过使用CFD计算流体动力学软件进行数值模拟,研究了垂直矩形铜质微通道换热器中流量变化对换热器流动换热特性的影响,VOF方法是一种界面跟踪方法,适用于具有气液界面的流动,在离散网格的尺度上可以完全分辨。根据文献调研,本文是第一个研究微通道中流量变化对微通道换热器的影响的工作。本文采用计算流体动力学(CFD)方法,利用设计建模器创建几何体,并对三维几何体进行网格划分,采用VOF方法对矩形微通道换热器内的流体流动和传热行为进行了数值模拟,并对模型的瞬态响应进行了研究,得到了在流量变化下传热速率、温度、速度和压力分布等计算结果,分析了改变流道尺寸和改变入口速度对系统性能的影响。研究结果表明,减小通道的宽度和高度或减小入口速度都能增加冷凝量,从而增加总换热量。然而,可能存在的弊端为微通道会被凝结水阻塞,这将导致总传热率下降。在本文的实验中,当通道宽度为200微米,高度为100微米,长度为1厘米时,得到了最佳的换热率。

关键词：微化工技术换热器矩形微通道冷凝 CFD 多相流 VOF方法

Synthesis of some new fused coumarin derivatives

同方学位论文库评论

在线全文

同方学位论文库

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2000年第4期18卷 590-595页

作者： EL-DEEN ibrahim Mohey ibrahim H.K. MAHMOUD F.F. Faculty of Education Suez Canal University Port-Said EgyptFaculty of Science Suez Canal University Ismailia EgyptFaculty of Science (for Girls) Al-Azhar University Nasr City Egypt

2-Hydrazino-4-hydroxy-5H-[1]-benzopyrano-[4,3-d]-pyrimidin-5-one (3) was prepared via condensation of 2 with hydrazine hydrate. Treatment of 3 with methylene chloride, ethyl chloroformate, ethyl chloroacetate and benzaldehyde yielded the corresponding 2 - ( substituted ) hydrazino - 4 -hydro-xy-5H-[1]-benzopyrano-[4,3-d]-pyrimidin-5-one (4, 5, 6, and 10), followed by cyclization of 4, 5 and 6 with dimethyl formamide and fused sodium acetate under reflux, while compound 10 was cyclized with bromine and sodium acetate in acetic acid. Compound 3 reacted with β-(toloyl) acrylic acid, ethyl α-cyano-p-methoxycinnamate, diethyl malonate and acetyl chloride affording the corresponding 2-(substituted) hydrazino-4-hydroxy-5H-[1]-benzopyrano-[4,3-d]-pyrimidin-5-one (12, 13, 14, 15 and 16).

关键词： Synthesis fused coumarin derivatives cyclization

Hidden Hierarchy Based on Cipher-Text Attribute Encryption for IoT Data Privacy in Cloud

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2023年第7期76卷 939-956页

作者： Zaid Abdulsalam ibrahim Muhammad Ilyas Department of Electrical and Computer Engineering Altinbas UniversityIstanbulTurkey Department of Computer Engineering Altinbas UniversityIstanbulTurkey

Most research works nowadays deal with real-time Internetof Things (IoT) data. However, with exponential data volume increases,organizations need help storing such humongous amounts of IoT data incloud storage systems. Moreover, such systems create security issues whileefficiently using IoT and Cloud Computing technologies. Ciphertext-Policy Attribute-Based Encryption (CP-ABE) has the potential to make IoT datamore secure and reliable in various cloud storage services. Cloud-assisted IoTssuffer from two privacy issues: access policies (public) and super polynomialdecryption times (attributed mainly to complex access structures). We havedeveloped a CP-ABE scheme in alignment with a Hidden HierarchyCiphertext-Policy Attribute-Based Encryption (HH-CP-ABE) access structure embedded within two policies, i.e., public policy and sensitive *** this proposed scheme, information is only revealed when the user’sinformation is satisfactory to the public policy. Furthermore, the proposedscheme applies to resource-constrained devices already contracted tasks totrusted servers (especially encryption/decryption/searching). Implementingthe method and keywords search resulted in higher access policy privacy andincreased security. The new scheme introduces superior storage in comparisonto existing systems (CP-ABE, H-CP-ABE), while also decreasing storage costsin HH-CP-ABE. Furthermore, a reduction in time for key generation canalso be ***, the scheme proved secure, even in handling IoT datathreats in the Decisional Bilinear Diffie-Hellman (DBDH) case.

关键词： Bilinear Diffie-Hellman(DBDH) Internet of Things(IoT) Ciphertext-Policy Attribute-Based Encryption(CP-ABE) Hidden Hierarchy CP-ABE(HH-CP-ABE)

Chemical behaviours of 3-[1'-chloro-3'-(2"-phenyl-1",3"-oxazol-5"-one-4"-ylidene)propen-l'-yl]coumarin towards some nucleophilic reagents

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

Chinese Journal of Chemistry 1998年第6期16卷 533-537页

作者： EL-DEEN ibrahim Mohey Faculty of Education Suez Canal University Port-Said EgyptFaculty of Education Suez Canal University Port-Said Egypt

The chemical behaviours of 3-[1'-chloro-3'-(2'-phenyl-1',3'-oxazol-5'-one-4'-ylidene)-propen-1'-yl]coumarin towards nucleophilic reagents (such as hydrolysis,aminolysis,hydroxyl-aminolysis,methanolysis and hydrazinoly... 详细信息

关键词： Chemical behaviours coumarin derivatives nucleophiles

Cooling and lubrication techniques in grinding:A state-of-the-art review,applications,and sustainability assessment

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2023年第7期36卷 76-113页

作者： Ahmed Mohamed Mahmoud ibrahim Wei LI Abdel-Hamid ISMAIL MOURAD Mohamed A.E.OMER Fadl A.ESSA Ahmed mustafa ABD EL-NABY Mohammad S.Al SOUFI Muhammad F.EZZAT Ammar ElSHEIKH College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China Production Engineering and Mechanical Design Department Faculty of EngineeringMinia UniversityEl Minya 61519Egypt Mechanical and Aerospace Engineering Department College of EngineeringUnited Arab Emirates UniversityAl-Ain 15551United Arab Emirates Department of Production Engineering and Mechanical Design Faculty of EngineeringTanta UniversityTanta 31527Egypt Mechanical Engineering Department Faculty of EngineeringKafrelsheikh UniversityKafrelsheikh 33516Egypt Mechanical Engineering Department College of Engineering and Islamic ArchitectureUmm Al-Qura UniversityMakkah 24231Saudi Arabia Mechanical Engineering Department Faculty of EngineeringUniversity of AlbertaEdmonton T6G 2R3Canada Automotive and Tractors Engineering Department Faculty of EngineeringMinia UniversityEl Minya 61519Egypt Tokyo Institute of Technology Tokyo 152-8550Japan

Grinding technology is an essential manufacturing operation,in particular,when a component with a superfinishing and an ultra-resolution is *** the required strict quality checklist with maintaining a high level of productivity and sustainability is a substantive *** recent paper outlines the lubrication and cooling technologies and mediums that are used for ***,it provides a basis for a critical assessment of the different lubrication/cooling techniques in terms of machining outputs,environmental impact,hygiene effect,***,the paper put light on the sustainability of different cooling/lubrication *** sustainability of machining aims to get the product with the best accuracy and surface quality,minimum energy consumption,low environmental impact,reasonable economy,and minimum effect on worker’s *** paper revealed that despite some cooling/lubrication mediums like mineral oils and semisynthetic,afford sufficient lubrication or cooling,they have a significant negative impact on the environment and public *** the other hand,emulsions can overcome environmental problems but the economy and the energy consumption during grinding are still a matter of *** and vegetable oils are considered eco-friendly oils,but they suffer from a lack of thermal stability which affects their ability of efficiently *** the cooling medium with the lowest amount can achieve the goal of the economy but it may be reflected negatively on the ***,cryogenic lubrication doesn’t provide sufficient lubrication to reduce friction and hence energy *** research described in the paper is such a comprehensive compilation of knowledge regarding the machinability and machining performance under different cooling and lubrication systems that it will aid the next generation of scientists in identifying current advancements as well as potential future directions of research on ecolo

关键词： Cryogenic cooling Dry lubrication Minimum quantity lubrication Precision grinding Solid lubrication Sustainable machining Vegetable oils

New insights into astrocyte diversity from the lens of transcriptional regulation and their implications for neurodegenerative disease treatments

在线全文

学校读者我要写书评

暂无评论

Neural Regeneration Research 2024年第11期19卷 2335-2336页

作者： ibrahim Olabayode Saliu Guoyan Zhao Department of Genetics Washington University School of MedicineSt.LouisMOUSA Department of Neurology Department of Pathology and ImmunologyWashington University School of MedicineSt.LouisMOUSA

Astrocytes are a major glial cell type in the central nervous system,and they provide trophic and metabolic support to *** addition to these roles,they play crucial roles in modulating synaptic functions,development,and pruning(Brandebura et al.,2023).Astrocytes become reactive(activated)by undergoing morphological,molecular,and functional alterations in response to neuropathology such as in injuries and neurodegenerative diseases(NDs)(Escartin et al.,2021).

关键词： degenerative injuries

Keypoint Description Using Statistical Descriptor with Similarity-Invariant Regions

在线全文

学校读者我要写书评

暂无评论

Computer Systems Science & Engineering 2022年第7期42卷 407-421页

作者： ibrahim El rube Sameer Alsharif Department of Computer Engineering College of Computers and Information TechnologyTaif UniversityP.o.Box 11099Taif21944Saudi Arabia

This article presents a method for the description of key points using simple statistics for regions controlled by neighboring key points to remedy the gap in existing ***,the existent descriptors such as speeded up robust features(SURF),Kaze,binary robust invariant scalable keypoints(BRISK),features from accelerated segment test(FAST),and oriented FAST and rotated BRIEF(ORB)can competently detect,describe,and match images in the presence of some artifacts such as blur,compression,and ***,the performance and reliability of these descriptors decrease for some imaging variations such as point of view,zoom(scale),and *** intro-duced description method improves image matching in the event of such *** utilizes a contourlet-based detector to detect the strongest key points within a speciﬁed window *** selected key points and their neighbors con-trol the size and orientation of the surrounding regions,which are mapped on rec-tangular shapes using polar *** resulting rectangular matrices are subjected to two-directional statistical operations that involve calculating the mean and standard ***,the descriptor obtained is invariant(translation,rotation,and scale)because of the two methods;the extraction of the region and the polar transformation techniques used in this *** descrip-tion method introduced in this article is tested against well-established and well-known descriptors,such as SURF,Kaze,BRISK,FAST,and ORB,techniques using the standard OXFORD *** presented methodology demonstrated its ability to improve the match between distorted images compared to other descriptors in the literature.

关键词： Keypoint detection descriptors neighbor region similarity invariance

Presence of Fragmented QRS Complexes in Patients with Obstructive Sleep Apnea Syndrome

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

Chinese Medical Journal 2015年第16期128卷 2141-2146页

作者： Muhammet Rasit Sayin Murat Altuntas Ziyaeddin Aktop ibrahim I Oz Nesimi Yavuz ibrahim Akpinar Erol Sagatli Turgut Karabag mustafa Aydin Department of Cardiology School of MedicineBulent Ecevit UniversityZonguldakTurkey Department of Pulmonology Uzun Mehmet State HospitalZonguldakTurkey Department of Radiology School of MedicineBulent Ecevit UniversityZonguldakTurkey Department of Cardiology Ataturk State Hospital Zonguldak Turkey

Background：Obstructive sleep apnea syndrome （OSAS） is a disease with increasing prevalence,which is mainly characterized by increased cardiopulmonary mortality and *** is well-known that OSAS patients have increased prevalence of cardiovascular diseases including coronary heart disease,heart failure,and *** aim of this study was to evaluate the presence of prolonged and fragmented QRS complexes,which have previously been associated with cardiovascular mortality,in OSAS ***：Our study included 51 patients （mean age 41.6 ± 10.1 years） who were recently diagnosed with OSAS （apnea-hypopnea index [AHI] ≥5 events/h） and never received *** control group consisted of 34 volunteers （mean age 43.1 ± 11.6 years） in whom OSAS was excluded （AHI 〈5 events/h）.The longest QRS complexes was measured in the 12-lead electrocardiogram （ECG） and the presence of fragmentation in QRS complexes was ***：Fragmented QRS frequency was significantly higher in patients with OSAS （n =31 [61%] vs.n =12 [35%],P =0.021）.QRS and QTc durations were also significantly longer in OSAS patients than controls （99.8 ± 13.9 ms vs.84.7 ± 14.3 ms,P 〈 0.001;411.4 ± 26.9 ms vs.390.1 ± 32.2 ms,P =0.001,respectively）.Analysis of the patient and controls groups combined revealed a weak-moderate correlation between AHI and QRS duration （r =0.292,P =0.070）.OSAS group had no correlation between AHI and QRS duration （r =-0.231,P =0.203）.Conclusions：In our study fragmented QRS frequency and QRS duration were found to increase in OSAS *** parameters are related with increased cardiovascular *** the prognostic importance of ECG parameters,it may be reasonable to recommend more detailed evaluation of OSAS patients with fragmented or prolonged QRS complexes with respect to presence of cardiovascular diseases.

关键词： Electrocardiogram Fragmented QRS Obstructive Sleep Apnea QRS Duration QT Duration

Proactive Load Balancing Mechanism for Fog Computing Supported by Parked Vehicles in IoV-SDN

在线全文

学校读者我要写书评

暂无评论

China Communications 2021年第2期18卷 271-289页

作者： Ahmed Jawad Kadhim Jaber ibrahim Naser Ministry of Education General Directorate for Education in Al-QadisiyahAl-Qadisiyah 58002Iraq

Internet of Vehicles(IoV)is a new style of vehicular ad hoc network that is used to connect the sensors of each vehicle with each other and with other vehicles’sensors through the *** sensors generate different tasks that should be analyzed and processed in some given period of *** send the tasks to the cloud servers but these sending operations increase bandwidth consumption and *** computing is a simple cloud at the network edge that is used to process the jobs in a short period of time instead of sending them to cloud computing *** some situations,fog computing cannot execute some tasks due to lack of ***,in these situations it transfers them to cloud computing that leads to an increase in latency and bandwidth occupation ***,several fog servers may be fuelled while other servers are *** implies an unfair distribution of *** this research study,we shall merge the software defined network(SDN)with IoV and fog computing and use the parked vehicle as assistant fog computing *** can improve the capabilities of the fog computing layer and help in decreasing the number of migrated tasks to the cloud *** increases the ratio of time sensitive tasks that meet the *** addition,a new load balancing strategy is *** works proactively to balance the load locally and globally by the local fog managers and SDN controller,*** simulation experiments show that the proposed system is more efficient than VANET-Fog-Cloud and IoV-Fog-Cloud frameworks in terms of average response time and percentage of bandwidth consumption,meeting the deadline,and resource utilization.

关键词： IoV parked vehicles SDN fog computing load balancing