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Characteristics of Crack Growth in High Performance Concrete Subjected to Fire

Journal of Materials Science & Technology 2005年第1期21卷 118-122页

作者： GaifeiPENG SammyYinNinCHAN JianhuaYAN YefengLIU QuanxinYI FacultyofCivilEngineering&Architecture BeijingJiaoTongUniversityBeijing100044China wong&chengconsultingengineersltd. HongKongChina BeijingUniversityofTechnology Beijing100022China

An experimental investigation was conducted to identify the characteristics of crack growth in high performance concrete (HPC) subjected to fire, including two parts of work, i.e. crack growth resistance determinations and cracking observations, using concrete of three strength grades 40 MPa, 70 MPa, and 110 MPa. The crack growth resistance curves (R-curves ) of HPC subjected to high temperatures were determined using notched three-point bend beam specimens of 100 mm×100 mm×300mm. The R-curve (crack growth resistance curve) flattening shows that the crack growth resistance has been significantly reduced by elevated temperature. Concrete with a higher strength grade has a steeper R-curve, with a higher fracture toughness but a shorter critical crack growth. The shorter critical crack growth means that concrete of a higher strength grade has a more brittle behavior. The concrete cracking observations reveal that the consequences of rapid heating are quite different from those of slow heating. For slow heating at a rate of 0.5℃/min, HPC suffered no obvious cracking below 600℃ even if it had a high moisture content. Explosive spalling is an extreme case of the internal cracking driven mainly by vapor pressure. All these results confirmed the vapor pressure mechanism for spading behavior which should be more significant for denser concrete. The crack growth ranges obtained from the R-curve determination results are in good agreement with those measured in the concrete cracking observations.

关键词： High performance concrete Fire resistance Explosive spoiling Crack growth Vapor pressure

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Two-dimensional CFD simulation and pilot-scale experimental verification of a downdraft gasifier: effect of reactor aspect ratios on temperature and syngas composition during gasification

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International Journal of Coal Science & Technology 2020年第3期7卷 536-550页

作者： Chootrakul Siripaiboon Prysathyrd Sarabhorn Chinnathan Areeprasert Department of Mechanical Engineering Faculty of EngineeringKasetsart University50 Ngam Wong Wan RoadLat YaoChatuchakBangkok10900Thailand

This paper focuses on a two-dimensional CFD simulation of a downdraft gasifier and a pilot-scale experiment for verification using wood pellet *** simulation work was carried out via the ANSYS-Fluent CFD software package with in-house coding via User Defined *** gasification parameters were taken into account in the simulation and validation to achieve highly accurate results;namely,fuel consumption,temperature profile,and syngas *** verification of the developed model,the effects of aspect ratios on temperature and syngas composition were *** from simulation and experimental work indicated that the fuel consumption rate during the steady state gasification experiment was 1.750±0.048 g/*** average steady state temperature of the experiment was 1240.32±14.20 *** sum,the fuel consumption and temperature profile during gasification from modeling and experimentation show an error lower than 1.3%.Concentrations of CO,CO2,H2,and CH4 were 20.42 vol%,15.09 vol%,8.02 vol%,and 2.6 vol%,respectively,which are comparable to those of the experiment:20.00 vol%,15.48 vol%,8.00 vol%,and 2.65 vol%.A high concentration of syngas is observed in the outer radial part of the reactor because of the resistive flow of the air inlet and the synthesis gas *** average temperatures during the steady state of the gasifier with aspect ratios(H/D)of 1.00,1.38(experiment),and 1.82 were 978.77±11.60,1256.46±9.90,and 1368.94±9.20 K,*** 1.82 aspect ratio reactor has the smallest diameter,therefore the radiative heat transferred from the reactor wall affects the temperature in the *** compositions are *** relationships between the aspect ratios and the syngas LHV,(4.29–4.49 MJ/N m3),cold gas efficiency(29.66%to 31.00%),and carbon conversion(79.59%to 80.87%)are observed.

关键词： CFD Simulation Gasification Downdraft gasifier Biomass Wood pellets Aspect ratio

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Effect of sample size on the response of DEM samples with a realistic grading

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Particuology 2014年第4期12卷 107-115页

作者： Xin Huang Kevin J.Hanley Catherine O'Sullivan Fiona C.Y.Kwok Skempton Building Department of Civil and Environmental EngineeringImperial College LondonLondon SW7 2AZUnited Kingdom Haking wong Building Department of Civil EngineeringThe University of Hong Kong

This paper shows that for DEM simulations of triaxial tests using samples with a grading that is repre- sentative of a real soil, the sample size significantly influences the observed material response. Four DEM samples with identical initial states were produced： three cylindrical samples bounded by rigid wails and one bounded by a cubical periodic cell, When subjected to triaxial loading, the samples with rigid boundaries were more dilative, stiffer and reached a higher peak stress ratio than the sample enclosed by periodic boundaries. For the rigid-wall samples, dilatancy increased and stiffness decreased with increasing sample size, The periodic sample was effectively homogeneous, The void ratio increased and the contact density decreased close to the rigid walls, This heterogeneity reduced with increasing sample size. The positions of the critical state lines （CSLs） of the overall response in e-log p＇ space were sensitive to the sample size, although no difference was observed between their slopes. The critical states of the interior regions of the rigid-wall-bounded samples approached that of the homogeneous periodic sample with increasing sample size. The ultimate strength of the material at the critical state is independent of sample size.

关键词： Discrete element method Sample size Rigid boundary Periodic boundary Critical state

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Long-term clinical outcomes of drug-eluting stents ***-metal stents in Chinese geriatric patients

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Journal of Geriatric Cardiology 2013年第4期10卷 330-335页

作者： Pak-Hei Chan Sha-Sha Liu Hung-Fat Tse Wing-Hing Chow Man-Hong Jim Hee-Hwa HO Chung Wah Siu Department of Medicine Li Ka Shing Faculty of Medicine The University of Hong Kong 102 Pokfulam Rd Hong Kong China Cardiac Medical Unit Grantham Hospital 125 Wong Chuk Hang Rd Aberdeen Hong Kong China

BACKGROUND & OBJECTIVE: Little is known about the relative efficacies of percutaneous coronary intervention (PCI) with drug-eluting stents (DES) and bare-metal stents (BMS) in elderly patients。 The objective of this study was to evaluate the clinical outcome for geriatric patients who received either DES or BMS。 METHODS: From January 2002 to October 2005, 199 consecutive Chinese geriatric patients (≥ 75 years old) underwent PCI with coronary DES or BMS implantation at our institution。 We analyzed the major clinical end points that included all-cause mortality, cardiovascular death, myocardial infarction, target lesion revascularization (TLR), stent thrombosis, and bleeding complications。 RESULTS: The three-year cumulative rates of all-cause mortality, cardiovascular death, and myocardial infarction were significantly lower in the DES group (6.3%,3.6%,5.4%) compared with the BMS group (16.2%,11.5%,14.9%; P <0.05)。 No significant differences were found in the three-year cumulative rate for target lesion revascularization (6.3% vs4.6%, P =0.61) or stent thrombosis (3.6% vs2.3%, P =0.70)。 Likewise, there were no statistically significant differences in the cumulative rate for intracranial hemorrhage, or major and minor hemorrhage at three years。 CONCLUSIONS: DES-based PCI was associated with a significant reduction in the three-year cumulative rate of all-cause mortality, cardiovascular death, and myocardial infarction compared with BMS, without increased risk of TLR, stent thrombosis, or bleeding complications at three years in this group of Chinese geriatric patients。

关键词： Bare-metal stents Drug-eluting stents Geriatric patients Percutaneous coronary intervention

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A New Lagrangian-Eulerian Coupling Model System

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Advances in Atmospheric Sciences 2000年第4期17卷 587-600页

作者：雷孝恩 Rudklao Manonom Prungchan wongwises Business Management Department Electricity Generating Authority of Thailand 53 Charan Sanit Wong Road. Bang Krui. Nonthaburi 11130. Thailand) King Mongkut's University of Thonburi. 91 Pracha-Utit Road Bangmod Thongkru

A new Lagrangian—Eulerian coupling model system is developed to study regional air quality. The system consists of mesoscale dynamical meteorological model (MM), Monte—Carlo model (MCM), parameterized model on planetary boundary layer (PBL) turbulent statistics, dry and wet removal model, and Eulerian nonlinear chemical model (ENCM). The physical, chemical and biological processes on air pollutants are considered comprehensively. 3—D distribution laws tor acidic gaseous pollutants (SO2 and NOx) emitted by Thai Mae Moh Power Plant and the secondary pollutants are studied in detail. The results simulated by the coupling model system are in good agreement with observational concentration data. Key words MM - MCM - ENCM - Coupling model system The authors wish to express their thanks to Prof. Zeng Q. C. for his support to this research and to Dr. Han Z. W. and Zhang M. G. for their help in programming and numerical calculation of IAP, Chinese Academy of Sciences. Thanks are also due to NSTD and EGAT in Thailand for supporting this research.

关键词： MM MCM ENCM Coupling model system

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Semi-continuous casting of magnesium alloy AZ91 using a filtered melt delivery system

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Journal of Magnesium and Alloys 2015年第4期3卷 283-301页

作者： Mainul Hasan Latifa Begum Department of Mining&Materials Engineering McGill UniversityM.H.Wong Building3610 University StreetMontrealQC H3A 0C5Canada

A 3-D numerical simulation of an industrial-sized slab caster for magnesium alloy AZ91 has been carried out for the steady state operational phase of the *** simulated model consists of an open-top melt delivery system fitted with a porous filter near the *** melt flow through the porous filter was modeled on the basis of Brinkmann-Forchimier-Extended non-Darcy model for turbulent *** in-house 3-D CFD code was modified to account for the melt flow through the porous *** are obtained for four casting speeds namely,40,60,80,and 100 mm/*** metal-mold contact region as well as the convective heat transfer coefficient at the mold wall were also *** addition to the above,the Darcy number for the porous media was also *** parametric studies were performed for a fixed inlet melt superheat of 64℃.The results are presented pictorially in the form of temperature and velocity *** sump depth,mushy region thickness,solid shell thickness at the exit of the mold and axial temperature profiles are also presented and correlated with the casting speed through regression analysis.©2015 Production and hosting by Elsevier *** behalf of Chongqing University.

关键词： Magnesium alloy AZ91 VDC casting Slab caster 3D CFD modeling Porous filter Non-Darcy model Turbulent melt flow Solidification Mushy region

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On numerical modeling of low-head direct chill ingot caster for magnesium alloy AZ31

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Journal of Magnesium and Alloys 2014年第4期2卷 275-286页

作者： Mainul Hasan Latifa Begum Department of Mining&Materials Engineering McGill UniversityM.H.Wong Building3610 University StreetMontrealQC H3A 0C5Canada

A comprehensive 3D turbulent CFD study has been carried out to simulate a Low-Head(LH)vertical Direct Chill(DC)rolling ingot caster for the common magnesium alloy *** model used in this study takes into account the coupled laminar/turbulent melt flow and solidification aspects of the process and is based on the control-volume finite-difference *** the aluminum/magnesium DC casting industrial practices,the LH mold is taken as 30 mm with a hot top of 60 *** previously verified in-house code has been modified to model the present casting *** quantitative results are obtained for four casting speeds,for three inlet melt pouring temperatures(superheats)and for three metal-mold contact heat transfer coefficients for the steady state operational phase of the *** variable cooling water temperatures reported by the industry are considered for the primary and secondary cooling zones during the ***,the temperature and velocity fields,sump depth and sump profiles,mushy region thickness,solid shell thickness at the exit of the mold and axial temperature profiles at the center and at three strategic locations at the surface of the slab are presented and discussed.

关键词： Low-head DC caster Magnesium alloy AZ31 3D CFD modeling Turbulent melt flow Solidification Mushy region thickness Sump profile

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ClinicalexperiencewiththecordiscoronarystentintheChinesepopulation

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Chinese Medical Journal 1998年第4期111卷 70-70页

作者： K. Fan W.H. Chow L. Chow A. Yip K.L. Cheung University Cardiac Medical Unit Grantham Hospital 125 Wong Chuk Hang Road Aberdeen Hong Kong

Objective To assess the safety and efficacy of the new Cordis coronary stent in the Chinese *** A total of 32 patients recieved 34 Cordis stents (target lesions of 32) from July to December 1995 in our hospital. Vessel distribution was 18 LAD (53%), 8 Lcx (23.5%) and 8 RCA (23.5%).Methods All cases were studies retrospectively. The coronary lesions were predilated with standard balloon angioplasty followed by implantation of Cordis stents. The reference diameter of the vessels and the minimal luminal diameters (both before and after stent implantation) were measured by quantitative angiography. All patients were followed up at mean peroid of 3 months with regards to their symptoms and angiographic follow-up at 6 month's time were carried out in 8 *** Delivery success was achieved in all lesions except 1 unsuccessful delivery due to failure to negotiate an acute angle of a left main vessel to LAD. Average MLD post stenting was satisfactory (0.53±0.36 mm vs 3.32±0.34 mm) compared to reference diameter of 3.13±0.4 mm. There was 1 patient with complication of subacute stent thrombosis. Another patient died 5 weeks later from non-ischaemic end stage heart failure secondary to severe aortic regurgitation. Loop seperations occurred in 2 stents (5.8%) during *** The Cordis stent implantation is efficacious with high angiographic success rate. The strong radiopacity facilitates precise positioning of the stent in the target lesions. Our experience in the Chinese population is favourable. Stent deformity was possible. For smaller stents of 3 mm, higher pressure of balloon inflation for deployment followed by adequate anticoagulation is recommended. Further studies are required to investigate the long term restenosis rate.

关键词： Chinese population stent implantation aortic regurgitation precise positioning balloon angioplasty coronary stent heart failure

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尊贵气派

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城市住宅 2007年第8期14卷 97-105页

作者： Simon wong Simon wong Design Co.Ltd

由嘉里建设有限公司策划兴建的高尚住宅——灏畋峰，座落于香港何文田山顶峰。为了充份发挥地处高峰的优势，灏畋峰70％外墙均为玻璃窗户，每一户都可俯瞰维港两岸精彩景致。

关键词：灏畋峰嘉里建设有限公司玻璃窗户外墙豪华时尚风格

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An in vitrostudy of the bioefifcacy of essential oil blends againstAedes aegypti (Linn.) andAnopheles dirus (Peyton and Harrison) by using membrane feeding apparatus

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Journal of Coastal Life Medicine 2017年第2期5卷 82-87页

作者： Nutthanun Auysawasdi Sawitri Chuntranuluck Vichien Keeratinijakal Siriporn Phasomkusolsil Silas A Davidson Department of Biotechnology Faculty of Agro-IndustryKasetsart University50 Ngam Wong Wan RoadLadyaowChatuchakBangkok 10900Thailand Department of Agronomy Faculty of AgricultureKasetsart University50 Ngam Wong Wan RoadLadyaowChatuchakBangkok 10900Thailand Department of Entomology Armed Forces Research Institute of Medical ScienceBangkok 10400Thailand

Objective:To determine the bioefficacy of plant essential oils on Aedes aegyptiandAnopheles dirus. Repellency was determined by measuring reduction in feeding and mortality. A novelin vitro bioassay apparatus was developed that had a sausage-casing membrane feeding system. Methods:Mixtures of three essential oils were evaluated: turmeric (Curcuma longa), eucalyptus (Eucalyptus globulus), and orange (Citrus aurantium). The oils were mixed in pairs or all together at equal volume for a total of 10% volume and then formulated with 90% virgin coconut oil. Completed formulations were evaluated with and without an additional 5% vanillin. The formulations were applied to the sausage casing membranes and female mosquitoes provided (expose) blood meals (0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5 and 4.0 h) to assess the percentage repellency over time. Results:The strongest repellency was at shorter exposure periods. ForAedesaegypti, the strongest feeding reduction was with the turmeric and eucalyptus combination and with the addition of vanillin (97.6%–99.6%). ForAnopheles dirus, the strongest repellency was when all three oils were combined (98.4%–99.6%). Conclusions:Vanillin increased the effects of repellency and mortality for all formulations and demonstrated an increased potential to enhance the bioefficacy of essential oil repellents. This study also demonstrated anin vitro membrane feeding system that can be used to screen essential oils.

关键词： Aedes aegypti Anopheles dirus Essential oil Repellent Membrane feeding system

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