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Artificial ground freezing of underground mines in cold regions using thermosyphons with air insulation

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International Journal of Mining Science and Technology 2024年第5期34卷 643-654页

作者： Ahmad F.Zueter Mohammad Zolfagharroshan Navid bahrani Agus P.Sasmito Department of Civil and Resource Engineering Dalhousie UniversityHalifax B3H4R2Canada Department of Mining Engineering McGill UniversityMontreal H3A0E8Canada

Current practice of underground artificial ground freezing(AGF)typically involves huge refrigeration systems of large economic and environmental *** this study,a novel AGF technique is proposed deploying available cold wind in cold *** is achieved by a static heat transfer device called thermosyphon equipped with an air insulation layer.A refrigeration unit can be optionally integrated to meet additional cooling *** introduction of air insulation isolates the thermosyphon from ground zones where freezing is not needed,resulting in:(1)steering the cooling resources(cold wind or refrigeration)towards zones of interest;and(2)minimizing refrigeration *** design is demonstrated using well-validated mathematical models from our previous work based on two-phase enthalpy method of the ground coupled with a thermal resistance network for the *** Canadian mines are considered:the Cigar Lake Mine and the Giant *** results show that our proposed design can speed the freezing time by 30%at the Giant Mine and by two months at the Cigar Lake ***,a cooling load of 2.4 GWh can be saved at the Cigar Lake ***,this study provides mining practitioners with sustainable solutions of underground AGF.

关键词： Artificial ground freezing Underground mining Sustainable mining Thermosyphon Air insulation Cold regions

Explicit reinforcement models for fully-grouted rebar rock bolts

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第2期9卷 267-280页

作者： Navid bahrani John Hadjigeorgiou Lassonde Institute of Mining University of TorontoTorontoM5S 1A4Canada

This paper investigates the explicit use of rock reinforcement in a discontinuous stress analysis model.A series of numerical experiments was undertaken to evaluate the performance of local and global reinforcement models implemented in universal distinct element code(UDEC).This was made possible by calibrating the reinforcement models to the laboratory behavior of a fully-grouted rebar bolt tested under pure pull and pure shear loading *** model calibration focuses on matching different loading stages of the force-displacement curve including the initial elastic response,the hardening behavior and the bolt *** paper concludes with a discussion on the suitability of the different reinforcement models in UDEC including their advantages and ***,it addresses the choice of input parameters required for a realistic simulation of fully-grouted rebar bolts.

关键词： Rock reinforcement Fully-grouted rebar Distinct element method Local reinforcement Global reinforcement Pull-out test Shear test

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

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International Journal of Minerals,Metallurgy and Materials 2013年第10期20卷 953-960页

作者： Amir Momeni Shahab Kazemi Ali bahrani Materials Science and Engineering Department Hamedan University of Technology Department of Materials Engineering Faculty of EngineeringBu Ali Sina University

The hot deformation characteristics of 1.4462 duplex stainless steel （DSS） were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100~C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-HoUomon parameter （Z） increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6. x 1015 （lnZ---35.5）, a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction （EBSD） confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.

关键词： duplex stainless steel compression testing strain partitioning high temperature operations deformation

Influence of degree of interlock on confined strength of jointed hard rock masses

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1152-1170页

作者： Navid bahrani Peter K.Kaiser a Department of Civil and Resource Engineering Dalhousie UniversityHalifaxNova ScotiaCanada b Bharti School of Engineering Laurentian UniversitySudburyOntarioCanada

The strength of jointed rock mass is strongly controlled by the degree of interlock between its constituent rock *** degree of interlock constrains the kinematic freedom of individual rock blocks to rotate and slide along the block forming *** HoekeBrown(HB)failure criterion and the geological strength index(GSI)were developed based on experiences from mine slopes and tunneling projects in moderately to poorly interlocked jointed rock *** has since then been demonstrated that the approach to estimate the HB strength parameters based on the GSI strength scaling equations(called the‘GSI strength equations’)tends to underestimate the confined peak strength of highly interlocked jointed rock masses(***>65),where the rock mass is often non-persistently jointed,and the intact rock blocks are strong and *** estimation of the confined strength of such rock masses is relevant when designing mine pillars and abutments at great depths,where the confining pressure is high enough to prevent block rotation and free sliding on block *** this article,a grain-based distinct element modeling approach is used to simulate jointed rock masses of various degrees of interlock and to investigate the influences of block shape,joint persistence and joint surface condition on the confined peak *** focus is on non-persistently jointed and blocky(persistently jointed)rock masses,consisting of hard and homogeneous rock blocks devoid of any strength degrading defects such as *** results from this investigation confirm that the GSI strength equations underestimate the confined strength of highly interlocked and non-persistently jointed rock ***,the GSI strength equations are found to be valid to estimate the confined strength of persistently jointed rock masses with smooth and non-dilatant joint surfaces.

关键词： Rock mass strength Degree of interlock Non-persistently jointed rock mass Blocky rock mass Geological strength index(GSI) GSI strength equations

Enhanced Electrocatalytic Activity by RGO/MWCNTs/NiO Counter Electrode for Dye-sensitized Solar Cells

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Nano-Micro Letters 2015年第3期7卷 298-306页

作者： Majid Raissan Al-bahrani Waqar Ahmad Hadja Fatima Mehnane Ying Chen Ze Cheng Yihua Gao Center for Nanoscale Characterization & Devices Wuhan National Laboratory for Optoelectronics School of PhysicsHuazhong University of Science and Technology Faculty of Science Thi-Qar University School of Physics and Technology and Key Laboratory of Artificial Micro- and Nano-structure of Ministry of Education Wuhan University School of Physics Huazhong University of Science and Technology

We applied the reduced graphene oxide/multi-walled carbon nanotubes/nickel oxide(RGO/MWCNTs/Ni O)nanocomposite as the counter electrode(CE) in dye-sensitized solar cells(DSSCs) on fluorine-doped tin oxide substrates by blade doctor method. Power conversion efficiency(PCE) of 8.13 % was achieved for this DSSCs device, which is higher than that of DSSCs devices using Ni O, RGO, and RGO/Ni O-CE(PCE = 2.71 %, PCE = 6.77 % and PCE = 7.63 %). Also, the fill factor of the DSSCs devices using the RGO/MWCNTs/Ni O-CE was better than that of other CEs. The electron transfer measurement of cyclic voltammetry and electrochemical impedance spectroscopy showed that RGO/MWCNTs/Ni O film could provide fast electron transfer between the CE and the electrolyte, and high electrocatalytic activity for the reduction of triiodide in a CE based on RGO/MWCNTs/Ni O in a DSSC.

关键词： Graphene oxide Carbon nanotubes Nickel oxide Counter electrode Dye-sensitized solar cells

Measurement of circulating levels of VEGF-A,-C,and -D and their receptors,VEGFR-1 and -2 in gastric adenocarcinoma

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World Journal of Gastroenterology 2008年第24期14卷 3879-3883页

作者： Mansour S Al-Moundhri A Al-Shukaili M Al-Nabhani B Al-bahrani IA Burney A Rizivi SS Ganguly Medical Oncology Unit Department of MedicineCollege of Medicine and Health SciencesSultan Qaboos University Department of Microbiology and Immunology (SQU) National Cancer Institute Royal Hospital Department of Epidemiology and Medical Statistics (SQU)

AIM: To analyze the serum levels and prognostic significance of vascular endothelial growth factor (VEGF) -A,-C,and -D,and their receptors,VEGFR-1 and -2 in gastric adenocarcinomas. METHODS: The serum levels of VEGF family members were measured in 76 control subjects and 76 patients with gastric adenocarcinoma using an enzyme-linked immunosorbent assay (ELISA). These measurements were correlated with clinco-pathological features and survival rates. RESULTS: The serum levels of VEGF-A and its receptor,VEGFR-1,were signifi cantly higher in patients with gastric cancer than in healthy donors (t = 2.3,P = 0.02 and t = 4.2,P < 0.0001,respectively). In contrast,the serum levels of VEGF-D were signif icantly higher in control subjects than in patients (t = 2.9,P = 0.004). There was no significant difference in serum levels of VEGF-C and VEGFR-2 between patients and controls. VEGF-C was associated with advanced tumor stage and presence of metastasis. VEGFR-1 was associated with metastasis,advanced overall stage,tumor differentiation and survival. VEGFR-2 levels were associated with poor tumor differentiation. There was no significant prognostic value for any of the VEGF family members or their receptors except for VEGFR-1 where high levels were associated with a poor overall survival. CONCLUSION: Serum VEGF levels vary significantly in the same cohort of patients with variable clinico-pathological features and prognostic values. The simultaneous measurement of VEGF receptors levels in sera may overcome the limitations of a single biomarker assay.

关键词： Gastric cancer Serum Vascular endothelialgrowth factor Oman

Association of E-cadherin (CDH1) gene polymorphisms and gastric cancer risk

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World Journal of Gastroenterology 2010年第27期16卷 34332-3436页

作者： Mansour S Al-Moundhri Manal Al-Khanbashi Mohammed Al-Kindi Maryam Al-Nabhani Ikram A Burney Abdulaziz Al-Farsi Bassim Al-bahrani Medical Oncology Unit Department of MedicineCollege of Medicine and Health SciencesSultan Qaboos University Department of Clinical Genetics College of Medicine and Health SciencesSultan Qaboos University Department of Biochemistry College of Medicine and Health SciencesSultan Qaboos University National Oncology Center Royal Hospital

AIM:To investigate the associations between CDH1 gene polymorphisms and gastric cancer(GC) risk ***:We analyzed four CDH1 polymorphisms(+54 T>C,-160 C>A,-616 G>C,-3159 T>C) in an Omani population,by extraction of genomic DNA from the peripheral blood of 192 patients with GC and 170 control participants and performed CDH1 genotyping using DNA ***:CDH1-160-AA genotype was associated with an increased risk of GC(OR = 3.6,95% CI:1.1-11.8)(P = 0.03).There was no significant association between the other polymorphisms and GC *** haplotype analysis of +54 T>C,-160 C>A,-616 G>C,-3159 T>C genotypes revealed that the OR of CCGC and CAGC haplotypes was 1.5(95% CI:0.7-3.5) and 1.5(95% CI:0.2-3.0),but did not reach statistical ***:The current study suggests that the-160 AA genotype was associated with an increased risk of GC in Oman.

关键词： Gastric cancer Polymorphism CDH1

Expression of cell adhesion molecule CD44 in gastric adenocarcinoma and its prognostic importance

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World Journal of Gastroenterology 2008年第41期14卷 6376-6381页

作者： Kamran Ghaffarzadehgan Mostafa Jafarzadeh Hamid Reza Raziee Hamid Reza Sima Ehsan Esmaili-Shandiz Hanieh Hosseinnezhad Ali Taghizadeh Kermani Omeed Moaven Maryam bahrani Department of Pathology Mashhad University Cancer Research Center Omid Oncology Hospital Mashhad University of Medical Sciences Gastric Cancer Research Group Mashhad University of Medical Sciences Department of Radiation Oncology Mashhad University Cancer Research Center Omid Oncology Hospital Mashhad University of Medical Sciences Department of Internal Medicine Imam Reza Hospital Mashhad University of Medical Sciences Department of Medicine The Mount Sinai Medical Center New York Young Researchers' Club Medical School of Islamic Azad University of Mashhad

AIM: To evaluate the relation of cluster of differentiation 44 (CD44) expression with clinicopathological features of gastric adenocarcinoma, and also its effect on prognosis with an emphasis on the differences between intestinal and diffuse types. METHODS: From 2000 to 2006, 100 patients with gastric adenocarcinoma, who had undergone total or subtotal gastrectomy without any prior treatment, were studied. Haematoxylin & eosin (HE) staining was used for histological evaluation, including the type (Lauren's classifi cation) and grading of the tumor. The expression of CD44 in the gastric adenocarcinoma mucosa and the adjacent mucosa were determined by immunohistochemistry. The survival analysis was obtained using the Kaplan-Meier test. RESULTS: Of 100 patients, 74 (74%) patients were male. The tumors were categorized as intestinal type (78%) or diffuse type (22%). Sixty-five percent of patients were CD44-positive. CD44 expression was not detected in normal gastric mucosa. Rather, CD44 was more commonly expressed in the intestinal subtype (P = 0.002). A signifi cant relation was seen between the grade of tumor and the expression of CD44 (P = 0.014). The survival analysis showed a poor prognosis of patients with CD44-positive tumors (P = 0.008); and this was more prominent in the intestinal (P = 0.001) rather than diffuse type. CONCLUSION: Cell adhesion molecule CD44 is highly expressed in gastric adenocarcinoma. CD44 expression is correlated with a poor prognosis in patients with the intestinal type of gastric adenocarcinoma. CD44 can, therefore, be utilized as a prognostic marker for this group of patients.

关键词： Gastric cancer Cluster of differentiation 44 Survival rateImmunohistochemistry Cell adhesion molecules

NAT2 polymorphism in Omani gastric cancer patients-risk predisposition and clinicopathological associations

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World Journal of Gastroenterology 2007年第19期13卷 2697-2702页

作者： Mansour S Al-Moundhri Mohamed Al-Kindi Maryam Al-Nabhani Bassim Al-bahrani Ikram A Burney Ali Al-Madhani Shyam S Ganguly Misbah Tanira Medical Oncology Unit Department of Medicine College of Medicine and Health Sciences Sultan Qaboos University Sultanate of Oman Department of Biochemistry and Genetics Sultan Qaboos University Sultanate of Oman National Cancer Institute Royal Hospital Sultanate of Oman Department of Medicine Sohar Hospital Sultanate of Oman Department of Epidemiology and Medical Statistics Sultan Qaboos University Sultanate of Oman Department of Pharmacology Sultan Qaboos University Sultanate of Oman

AIM： To study whether N-acetyltransferase 2 （NAT2） genotypes and phenotypes are associated with increased risk factor for gastric cancer in Omani patients and to study the clinico-pathological correlations and the prognostic significance of NAT2. METHODS： Genomic DNA was extracted from peripheral blood of 100 gastric cancer patients and 100 control subjects. NAT2 genotyping was performed using DNA sequencing. The prognostic significance of NAT2 and other clinicopathological features was assessed by univariate and multivariate analyses. RESULTS： We observed no significant association between NAT2 genotypes and phenotypes and gastric cancer risk. The IVAT2 phenotype polymorphisms and gastric cancer risk predisposition were not modified by concomitant Hpylori infection and smoking. There was no significant association between NAT2 and clinicopathological features, and NAT2 had no independent prognostic significance. CONCLUSION： In the current study, NAT2 genotypes and phenotypes are not associated with gastric cancer risk predisposition. Moreover NAT2 phenotypes had no clinicopathological associations or prognostic significance.

关键词： Gastric cancer Polymorphism NAT2 Hpylori Arab Omani