检索结果-南通市图书馆

Study of the Effect of Gas Nitriding Time on Microstructure and Wear Resistance of 42CrMo4 Steel

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials Sciences and Applications 2017年第6期8卷 493-507页

作者： Mohamed Ali Terres lotfi Ammari Abdelkarim Chérif Laboratory Mechanics Materials and Processes (LMMP) ENSIT University of Tunis Tunis Tunisia

Prior studies have noted that gas nitriding has a considerable effect for wear resistance. The aim of this paper is to study the influence of gas nitriding time (12, 24, 36 and 48 h) in the wear behaviour of 42CrMo4 steel. It has been assessed by micro hardness, pin-on-disc tribosystem, and SEM through the nitrided layer for each nitriding time. The study relates to the performance of the compound layer and the diffusion layer with respect to adhesive wear. The results were analyzed in terms of the weight lost during wear, for nitrided steel with and without the compound layer, and for untreated steel. It has been observed that wear rate varies as a function of the tests conditions due to the presence of different wear mechanisms. Thus, for short tests conditions wear rate depends on two mechanisms: plastic deformation and adhesive wear, whereas for large tests conditions the mechanisms controlling wear rate are abrasive and oxidative wear. Furthermore, this study contains an analysis of the wear mechanisms of a nitrided part, founded on scanning electron microscopy (SEM) observations of the wear traces at various stages of the evolution of wear. The SEM examination of worn surfaces revealed signatures for the adhesion, abrasion, delamination and tribochemical (oxidative) modes of wear. This is an important issue for future research.

关键词： Gas Nitriding 42CrMo4 Steel Hardening Wear Rate Wear Mechanisms Adhesive Wear

Safety analysis of Sormeh underground mine to improve sublevel stoping stability

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Deep Underground Science and Engineering 2023年第2期2卷 173-187页

作者： Mostafa Hosseini Amin Azhari Rahman lotfi Alireza Baghbanan Department of Mining Engineering Isfahan University of TechnologyIsfahanIran

In underground mines,sublevel stoping is used among a variety of different methods for mining an orebody,which creates large underground *** this case,the stability of these openings is affected by a number of factors,including the geometrical characteristics of the rock and mining-induced *** this study,a sensitivity analysis was conducted with the numerical,squat pillar,and Mathews stability methods using the Taguchi technique to properly understand the influence of geometric parameters and stress on stope stability according to Sormeh underground mine *** results show a full factorial analysis is more reliable since stope stability is a complex ***,the numerical results indicate that overburden stress has the most impact on stope stability,followed by stope ***,the results obtained with Mathews and squat pillar methods show that stope height has the greatest impact,followed by overburden stress and *** appears that these methods overestimate the impact of stope ***,it is highly recommended that Mathews and squat pillar methods should not be used in high stope that is divided with several sill ***,Mathews method cannot accurately predict how the sill pillar impacts the stope *** addition,numerical analysis shows that all geometric parameters affect the roof safety factor,whereas the sill pillar has no significant influence on the safety factor of the hanging wall,which is primarily determined by the stope height–span ratio.

关键词： numerical method rib pillar stope stability sublevel stoping underground mining

Evaluating Pressure Ulcer Development in Wheelchair-Bound Population Using Sitting Posture Identification

维普期刊数据库博看期刊

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Engineering（科研） 2013年第10期5卷 132-136页

作者： Farve Daneshvar Fard Sahar Moghimi Reza lotfi Department of Electrical Engineering Biomedical Engineering Research Center Ferdowsi University of Mashhad Mashhad Iran Department of Electrical Engineering Biomedical Engineering Research Center Ferdowsi University of Mashhad Mashhad Iran

Pressure ulcers are a common complication among wheelchair-bound population. They are resulted from prolonged exposure to high pressure, which restricts blood flow and leads to tissue necrosis. In this work, a continuous pressure monitoring system is developed for pressure ulcer prevention. The system consists of 64 pressure sensors on a 40×50 cm2 sheet. Real time pressure data and corresponding maps are displayed on a computer simultaneously. Furthermore, a posture detection procedure is proposed for sitting posture identification. Having information about the patient’s postural history, caregivers are capable of a better decision about repositioning and treating the patient.

关键词： Interface Pressure Monitoring Pressure Ulcer Sitting Posture

Reduce Torque Ripple of IM by Approach Method DTC

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Intelligent Control and Automation 2011年第4期2卷 320-329页

作者： lotfi El M’Barki Moez Ayadi Rafik Neji 不详

This paper presents a new methodology for direct torque control (DTC) with improvement method control for induction motor (IM) systems. The application of approached method DTC (AMDTC), allows by using two hysteresis controllers to regulate torque and flux with the information of the angular location to address the switching table. The principal advantage of this AMDTC (optimization method of DTC) enables the minimization of the electromagnetic torque ripple and the reduction of the output current total harmonic distortion (THDI). Furthermore, it improved consumption quality of IM and it improved the lifespan of the motor. The switching characteristics of an inverter feeding an IM controlled with the AMDTC system are assessed in steady *** proposed method of AMDTC is illustrated by computer

关键词： AMDTC Minimum RMS THD Evolution of Temperature

Fluid Inclusion Investigations of the Masjed Daghi Copper-Gold Porphyry-Epithermal Mineralization, East Azerbaijan Province, NW Iran

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Geology 2017年第8期7卷 1110-1127页

作者： Solat Atalou Nima Nazafati Mohammad lotfi Mehraj Aghazadeh Department of Geology Science and Research Branch Islamic Azad University Tehran Iran Department of Geology North Tehran Branch Islamic Azad University Tehran Iran Department of Geology Payame Nour University Tehran Iran

The Masjed Daghi mineralization is located 30 km southeast of Jolfa city at the bank of Araxes River, northwest Iran. This area is situated in the Alborz-Azarbaijan structural zone of Iran. The most widespread rocks in the mineralization area are andesite and trachyandesite, while there are rock units of latite tuff, andesitic agglomerate, and hornblende porphyry basalt in eastern hills and Eocene flysch in the southern part of the area. Several intrusive bodies are present in the study area, from which the dominant intrusive rock hosting the mineralization is diorite porphyry. The mineralized rock units of the area are cut by different diorite ad mafic dikes. The most prevalent texture of mineralization is dissemination, while open space filling textures including veins and veinlets, are common as well. Diverse types of alteration including potassic, phyllic, argillic, silicification, and a little of carbonatization were recognized in the field and microscopic observations as well as by XRD. In addition to thick silica veins and stockwork zones, some silica, barite, sulfide, and calcite veins and veinlets have occurred in the Masjed Daghi mineralization area. In this research, 26 doubly polished thin sections (wafers) were prepared and investigated. Four samples were taken from surface veins, while 22 samples were chosen from core samples (of 6 boreholes) of white and grey-white silica, and silica-barite veins. The fluid inclusion studies on 105 primary fluid inclusions indicated five phases for inclusions including: 1) liquid or gas, 2) liquid and gas, 3) liquid, gas, and solid, 4) liquid, gas, halite, and solid, and 5) liquid, gas, halite, and two types of solids. The data gained from fluid inclusions approved two mineralization fluids which caused porphyry and epithermal mineralizations. The porphyry fluid inclusions were homogenized in temperatures of 122°C to 550°C with a maximum of 700°C and average salinity of 55 wt% NaCl equivalent, while the epithermal inc

关键词： Fluid Inclusion Porphyry Mineralization Epithermal Alteration Diorite Masjed Daghi Siyah Roud

Analytical Calculation of the Energy in a Permanent Magnet

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Modern Physics 2016年第16期7卷 2281-2287页

作者： Jean-Paul Yonnet Christian Chillet Hicham Allag lotfi Chouikhi Laboratoire de Génie Electrique de Grenoble G2E Lab Université Grenoble Alpes Grenoble France Laboratoire de Génie Electrique de Grenoble G2E Lab CNRS Grenoble France Laboratoire d’Electronique et d’Electrotechnique Industrielle Jijel University Jijel Algeria

The energy in permanent magnet is not a trivial problem because it exist two types of energy: the field energy and the demagnetizing energy. For parallelepiped shape, the magnet energy has been calculated by fully analytical expressions in 3D. The result has been obtained after four successive integrations of Arctangent and Logarithm functions. The analytically calculated energy corresponds to the demagnetization energy in the magnet. The analytical results have been compared with different terms of energy obtained by computation.

关键词： Analytical Calculation Energy Permanent Magnet

Effect of Dietary Lipid Levels on Fatty Acids Composition of Cultured Sparusaurata

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Life Sciences 2016年第6期10卷 312-320页

作者： Zayene Nesrine Gam Haouas Wafa Guerbej Hamadi Achour lotfi Integrative Biology and Valorisation (LR 14 ES 06) Institute of Biotechnology Monastir 5000 Tunisia National Institute of Marine Sciences and Technologies Monastir 5000 Tunisia

The aim of this study was to determine the progressive evolution of fish muscle fatty acids composition feeding by different lipid levels of farmed Mediterranean gilthead sea bream （Sparusaurata）. During twenty one weeks, Sparusaurata were hand-feed two diets with protein and lipid ratios 47/20 （Diet A） and 45/22 （Diet B） respectively. At the end of the feeding period, lipid contents of muscle, as well as fatty acids profiles of different portions of the muscles were studied. Results indicated the effects of fatty acids profiles of diets throughout the liver and white muscle fillet （dorsal, middle and ventral）. These were more noticeable when Sparusaurata was fed on the diet Athat decreased the content of monounsaturated fatty acids （MUFA）, and polyunsaturated fatty acids （PUFA） in all the muscles during the period of feeding while the saturated fatty acids （SFA） content tended to increase and it was lower than ones in the muscles of Sparusaurata fed on diet B. The highest amount of PUFA and docosahexaenoic acid, （22：6n-3 DHA） were found among the different portions of ventral muscles. In addition, the progressive evolution of different parts of muscle＇s fatty acid profiles showed significant differences in contents of SFA, PUFA and especially the n-3 PUFA. However, the content of MUFA seems to be alike in different muscles and tended to decrease in dorsal and ventral muscle from Do to Df and inversely when the fish were fed on diet A.

关键词： Fatty acids Liver Muscles cultured fish Sparusaurata.

Study of the Prevalence of Hypertension and Complications of Hypertensive Disorders in Pregnancy

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Preventive Medicine 2014年第11期4卷 860-867页

作者： Shahla Khosravi Soheila Dabiran M. lotfi Mohammad Asnavandy Reproductive Health and Community Medicine Faculty of Medical Sciences Tehran University of Medical Sciences Tehran Iran Reproductive Health and Community Medicine Faculty of Medical Sciences Tehran University of Medical Sciences Tehran Iran Department of Community Medicine Tehran University of Medical Sciences Tehran Iran Islamic Azad University of Varamin Varamin Iran

Introduction: Hypertension is one of the common problems associated with pregnancy that may be followed by eclampsia, acute renal failure, maternal death, premature delivery, intra-uterine growth restriction and other. This study was conducted to determine the results of pregnancies associated with hypertension in patients visiting in the Delivery Ward of Valiasr Hospital. Methods: A descriptive study was conducted on all the patients admitted to the aforementioned department and who possessed the inclusion criteria for hypertensive pregnancy. Results: Among the 1694 delivery cases examined, 173 cases had hypertension (9.8%). Among these, 75 (45%) had gesta-tional hypertension;24 (14.8%) had preeclampsia-eclampsia;30 (18%) had preeclampsia su-perimposed on chronic hypertension;21 (13.5%) cases had chronic hypertension;and 13 (8%) had pregnancy-aggravated chronic hypertension. Ninety-six point three percent (96.3%) had a systolic blood pressure (BP) of 140 - 190 mmHg, and 3.7% had a systolic BP greater than 190 mmHg. Whereas 61.1% of diastolic blood pressure 90 - 110 mmHg and 38.9% of the mothers had diastolic BP greater than 110 mmHg. The HELLP (Hemolysis, Elevated Liver enzymes & Low Platelet count) syndrome was present in 4.9% of cases;52.6% experienced premature delivery;7.4% had IUFD (intra uterine fetal death);9.9% had IUGR (intrauterine growth retardation);and 17.3% had LBW babies. Conclusions: Based on our results, hypertensive mothers who are younger and have lower weight babies at birth experience more perinatal complications. The unpleasant effects of hypertension in pregnancy warrant the need for training, routine prenatal care, the early detection and treatment of hypertension at younger ages of pregnancy, and follow-up after delivery.

关键词： Hypertension Pregnancy Induced Hypertension Preeclampsia Eclampsia Chronic Hypertension

Meaning in the Holy Quran： A Text Analysis of the ＂Surah Livestock＂（＂A1-An＇am＂） Within the Framework of Grice＇s Theory of Implicature

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Sino-US English Teaching 2013年第11期10卷 868-885页

作者： Ali Ebrahimi Badejani Maryam Afshari Badejani Ahmad Reza lotfi Khansar Branch-Isfahan University Isfahan Iran University of Isfahan Isfahan Iran Islamic Azad University-Khorasgan Branch Isfahan Iran

The Holy Quran （1982） is the Holy Book of the Moslems and the most understandable aspect of its eloquence. One of the most interesting aspects found in different languages is the use of implicatures or implied meaning. How and why such implicatures are generated and are discussed in pragmatics？ In this study, a list of conversations （direct and indirect） from ＂Surah Livestock＂（＂A1-An＇am＂）, the sixth Chapter of the Holy Quran, and the implicatures implied in the conversations are analyzed through a pragmatic theory： CP （Cooperative Principle）. The present study shows that in most cases, the non-observance of Grice＇s （1975） maxims is found in the maxim of Quantity and the least in Manner. Grice＇s CP and its contributory maxims have not been observed in the ＂Surah Livestock＂ in this study. All maxims of Grice have been flouted in This Surah （1982） and there is no difference among Gricean maxims as far as flouting in the Surah is concerned.

关键词： "Surah Livestock" ("A1-An'am") eloquence implicature CP (Cooperative Principle) maxims of Quality Quantity Relevance and Manner