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Design concerns of room and pillar retreat panels

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International Journal of mining Science and Technology 2017年第1期27卷 29-35页

作者： Klemetti Ted m. Sears morgan m. Tulu Ihsan B. mining Engineer Ground Control Branch NIOSH Office of Mine Safety and Health ResearchPittsburghPAUSA

Why do some room and pillar retreat panels encounter abnormal conditions? What factors deserve the most consideration during the planning and execution phases of mining and what can be done to mitigate those abnormal conditions when they are encountered? To help answer these questions, and to determine some of the relevant factors influencing the conditions of room and pillar(R & P) retreat mining entries, four consecutive R & P retreat panels were evaluated. This evaluation was intended to reinforce the influence of topographic changes, depth of cover, multiple-seam interactions, geological conditions, and mining geometry. This paper details observations were made in four consecutive R & P retreat panels and the data were collected from an instrumentation site during retreat mining. The primary focus was on the differences observed among the four panels and within the panels themselves. The instrumentation study was initially planned to evaluate the interactions between primary and secondary support, but produced rather interesting results relating to the loading encountered under the current mining conditions. In addition to the observation and instrumentation, numerical modeling was performed to evaluate the stress conditions. Both the La model 3.0 and Rocscience Phase 2 programs were used to evaluate these four panels. The results of both models indicated a drastic reduction in the vertical stresses experienced in these panels due to the full extraction mining in overlying seams when compared to the full overburden load. Both models showed a higher level of stress associated with the outside entries of the panels. These results agree quite well with the observations and instrumentation studies performed at the mine. These efforts provided two overarching conclusions concerning R & P retreat mine planning and execution. The first was that there are four areas that should not be overlooked during R & P retreat mining: topographic relief, multiple-seam stress relie

关键词：面板支柱设计仪器仪表相互作用开采条件地形变化地质条件

Synthesis, Characterization and X-ray Structure of N-(4-bromobutanoyl-N'-(2-3-and 4-methylphenyl)thiourea

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Chinese Journal of Structural Chemistry 2015年第3期34卷 379-385页

作者： Hamza m Abosadiya Siti Aishah Hasbullah Bohari m Yamin School of Chemical Sciences and Food Technology Faculty of Science and TechnologyUniversiti Kebangsaan Malaysia

N-4-（bromobutanoyl）-N＇-（o-, m- and p-tolyl）thioureas 3a, 3b and 3c respectively, were synthesized by the reaction of 4-bromobutanoylisothiocyanate with p-, m- and o-toludine. The products were characterized by IR, and NmR spectroscopic techniques. The two carbonoylthiourea isomers N-（4-bromobutanoyl）-N＇-（3-methylphenyl）thiourea （3b） and N-（4-bromobutanoyl）-N＇-（4- methylphenyl）thiourea （3c） were obtained in crystalline form by recrystallization from DmSO. X- ray crystallographic studies showed that both compounds 3b and 3c crystallize in triclinic system with space group ofPi. The molecules adopt trans-cis configuration with respect to the positions of 4-bromobutanoyl and tolyl groups respectively, against the thiono C=S bond across their C-N bonds The configuration is attributed by the intrahydrogen bond between the carbonyl oxygen and amide hydrogen atoms. Both crystal structures are stabilized by N-H…S intermolecular hydrogen bonds to form dimers and arranged along the b axis.

关键词： 4-bromobutyryl chloride, thiourea derivatives, X-ray structural study

Stability of Quark Star models

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Communications in Theoretical Physics 2016年第5期65卷 575-584页

作者： m.Azam S.A.mardan m.A.Rehman Division of Science and Technology University of Education Department of mathematics University of the Management and Technology

In this paper,we investigate the stability of quark stars with four different types of inner matter configurations;isotropic,charged isotropic,anisotropic and charged anisotropic by using the concept of *** this purpose,we have applied local density perturbations technique to the hydrostatic equilibrium equation as well as on physical parameters involved in the *** conclude that quark stars become potentially unstable when inner matter configuration is changed and electromagnetic field is applied.

关键词：夸克模型稳定性电各向异性静力平衡方程各向同性扰动技术局部密度物理参数

UV reflectance but no evidence for colour mimicry in a putative brood-deceptive orchid Corybas cheesemanii

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Current Zoology 2014年第1期60卷 104-113页

作者： m. m. KELLY A. C. GASKETT School of Biological Sciences The University of Auckland Private Bag 92019 Auckland 1142 New Zealand

Rewardless orchids attract pollinators by food, sexual, and brood-site mimicry, but other forms of sensory deception may also operate. Helmet orchids (Corybas, Nematocerasand related genera) are often assumed to be brood-site deceivers that mimic the colours and scents of mushrooms to fool female fungus gnats (mycetophilidae) into attempting oviposition and pollinating flowers. We sampled spectral reflectances and volatile odours of an endemic terrestrial New Zealand orchidCorybas cheesemanii, and co-occurring wild mushrooms. The orchid is scentless to humans and SPmE GC-mS analyses did not detect any odours, but more sensitive methods may be required. The orchids reflected strongly across all visible wavelengths (300-700nm) with peaks in the UV (~320nm), yellow-green (500-600 nm) and red regions (650-700 nm), whereas mushrooms and surrounding leaf Utter reflected predominantly red and no UV. Rather than mimicking mushrooms, these orchids may attract pollinators by exploiting insects’ strong sensory bias for UV. modelhng spectral reflectances into a categorical fly vision model and a generic tetrachromat vision model provided very different results, but neither suggest any mimicry of mushrooms. However, these models require further assessment and data on fly spectral sensitivity to red wavelengths is lacking – a problem given the predominance of red, fly-pollinated flowers worldwide.

关键词：光谱反射率紫外线欺骗性兰花模仿育雏野生蘑菇挥发性气味

Vibration suppression in multi-tool ultrasonic machining to multi-external and parametric excitations

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Acta mechanica Sinica 2009年第3期25卷 403-415页

作者： m.m.Kamel W.A.A.El-Ganaini Y.S.Hamed Department of Engineering mathematics Faculty of Electronic EngineeringMenoufiya University

Ultrasonic machining （USm） is of particular interest for the machining of non-conductive, brittle materials such as engineering ceramics. In this paper, a multi-tool technique is used in USm to reduce the vibration in the tool holder and have reasonable amplitude for the tools. This can be done via dynamic absorbers. The coupling of four nonlinear oscillators of the tool holder and tools representing ultrasonic cutting process are investigated. This leads to a four-degree-of-freedom system subjected to multi-external and multi-parametric excitation forces. The aim of this work is to control the tool holder behavior at simultaneous primary, sub-harmonic and internal resonance condition. multiple scale perturbation method is used to obtain the solution up to the second order approximations. The different resonance cases are reported and studied numerically. The stability of the system is investigated by using both phase-plane and frequency response techniques. The effects of the different parameters of the tools on the system behavior are studied numerically. Comparison with the available published work is reported.

关键词： Control Stability Ultrasonic machining (USm)

Hamstring autograft utilization in reconstructing anterior cruciate ligament:Review of harvesting techniques,graft preparation,and different fixation methods

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World Journal of Orthopedics 2022年第10期13卷 876-890页

作者： Waleed Albishi Baraa Baltow Nora Albusayes Ameer A Sayed Hamza m Alrabai Department of Orthopedic Surgery College of MedicineKing Saud UniversityRiyadh 11362Saudi Arabia Department of Orthopedic Surgery AlHada Armed Forces HospitalMinistry of DefenseAlHada 26792Saudi Arabia Department of Orthopedic Surgery King Fahad Armed Forces HospitalMinistry of DefenseJeddah 23311Saudi Arabia

Rupture of the anterior cruciate ligament(ACL)is a common orthopedic *** graft options are available for the reconstruction of ruptured *** the hamstring muscle as an autograft was first described in 1934,and it remains a commonly harvested graft for ACL *** autografts can be harvested using the traditional anteromedial approach or the newer posteromedial *** isolated semitendinosus tendon can be used or combined with the gracilis *** are numerous methods for graft fixation,such as intra-tunnel or extra-tunnel *** comprehensive review discusses the different hamstring muscle harvesting techniques and graft preparation options and fixation *** provides a comprehensive overview for choosing the optimal surgical technique when treating patients.

关键词： Anterior cruciate ligament Anterior cruciate ligament reconstruction Graft fixation Hamstring autograft Infrapatellar nerve injury Patient reported outcomes

Localized Corrosion Behavior of 6% mo Super Austenitic & 316L Stainless Steels in Low pH 3% NaCl Solution

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Journal of materials Science & Technology 2005年第4期21卷 465-469页

作者： m.m.A.Gad H.G.Salem A.m.Nasreldin H.Sabry A.A.EI-Sayed metallurgy Department Atomic Energy Authority Cairo EgyptMechanical Engineering Department AUC Cairo EgyptMetallurgy Department Atomic Energy Authority Cairo EgyptEuropean Neighbourhood and Partnership Instrument (ENPI) Cairo EgyptMetallurgy Department Atomic Energy Authority Cairo Egypt

Electrochemical techniques were applied to study the crevice corrosion resistance of two types of stainless steel alloys namely, conventional 316L and 6% mo super austenitic in acidified 3% NaCl solution at room *** results showed that 6% mo alloy possessed a remarkable resistance to crevice corrosion compared with 316L alloy when they are tested in the same solution. The breakdown potential at which passivity broke down for 316L alloy was 0.00 mV （SCE）. The corresponding value for 6% mo alloy could not reach up to the potential value of 700 mV （SCE）. 316L alloy suffered extremely from crevice corrosion at room temperature （about 25℃）, which indicates that the critical crevice corrosion temperature, below which crevice corrosion does not occur, was lower than the test temperature. For 6% mo alloy, the critical crevice corrosion temperature was higher than the testing temperature. Electrochemical parameters indicated that 6% mo alloy exhibited higher crevice corrosion resistance than 316L alloy.

关键词： Crevice corrosion 6% mo super austenitic Conventional 316L Critical crevice temperature

Peristaltic Flow of Shear Thinning Fluid via Temperature-Dependent Viscosity and Thermal Conductivity

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Communications in Theoretical Physics 2019年第4期71卷 367-376页

作者： S.Noreen A.malik m.m.Rashidi Department of mathematics COMSATS University Islamabad Shanghai Automotive Wind Tunnel Center Tongji University

In this paper Williamson ?uid is taken into account to study its peristaltic ?ow with heat effects. The study is carried out in a wave frame of reference for symmetric channel. Analysis of heat transfer is accomplished by accounting the effects of non-constant thermal conductivity and viscosity and viscous dissipation. modeling of fundamental equations is followed by the construction of closed form solutions for pressure gradient, stream function and temperature while assuming Reynold's number to be very low and wavelength to be very long. Double perturbation technique is employed, considering Weissenberg number and variable ?uid property parameter to be very small. The effects of emerging parameters on pumping, trapping, axial pressure gradient, heat transfer coe?cient, pressure rise,velocity pro?le and temperature are analyzed through the graphical representation. A direct relation is observed between temperature and thermal conductivity whereas the indirect proportionality with viscosity. The heat transfer coe?cient is lower for a ?uid with variable thermal conductivity and variable viscosity as compared to the ?uid with constant thermal conductivity and constant viscosity.

关键词： temperature-dependent viscosity temperature-dependent thermal conductivity shear thinningfluid peristalsis

Effects of surface finish and treatment on the fatigue behaviour of vibrating cylinder block using frequency response approach

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2006年第3期7卷 352-360页

作者： RAHmAN m. m. ARIFFIN A. K. Computational and Experimental mechanics Group Department of Mechanical and Materials Engineering Universiti Kebangsaan Malaysia 43600 UKM Bangi Selangor DE Malaysia

This paper presents the effects of surface finish and treatment on the high cycle fatigue behaviour of vibrating cylinder block of a new two-stroke free piston engine at complex variable amplitude loading conditions using frequency response approach. Finite element modelling and frequency response analysis was conducted using finite element analysis software Package ***/*** and fatigue life prediction was carried out using *** software. Based on the finite element results, different frequency response approach was applied to predict the cylinder block fatigue life. Results for different load histories and material combinations are also discussed. Results indicated great effects for all surface finish and treatment. It is concluded that polished and cast surface finish conditions give the highest and lowest cylinder block lives, respectively; and that Nitrided treatment leads to longest cylinder block life. The results were used to draw contour plots of fatigue life and damage in the worst or most damaging case.

关键词：有限元法疲劳寿命表面抛光表面处理频率响应方法振筒