bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimation of the Fluidelastic Instability Boundary for Steam-Generator Tubes Subjected to Two-Phase Flows
Authors: Mureithi Njuki W. , Sawadogo Teguewinde P. , Grie Affoua Amenan C.
Published: April 2011

The estimation of tube wear due to vibration-induced tube-support impacting remains an important problem for operating steam generators. For fluidelastic excitation this requires a realistic model for the excitation fluid forces. Recently the authors (Mureithi et al., 2008) have presented detailed force measurements in a rotated triangular tube bundle subjected to air-water two-phase flow. The data provides new potential to designers to estimate expected fluid dynamic loads for two-phase flow conditions. In particular, the data may be used for quantitative estimation of critical velocities for fluidelastic instability — the most important excitation mechanism for steam generator tube bundles. In the work reported here the fluid force field is employed along with the quasi-steady vibration stability model, adapted to two-phase flows, to model the two-phase flow problem and predict the critical instability velocity for a steam-generator U-tube subjected to non-uniform two-phase flow. The implication of the present model, with respect to improved estimation of tube wear is discussed in the paper.
Stress Analysis and Evaluation of Mussel Trap for Nuclear Power Plant
Authors: Tao Hongxin , Zhao Feiyun
Published: April 2011

The mussel trap is an important component used in nuclear power plant (NPP). The component belongs to RCC-P nuclear safety class 3, code and class RCC-M3, seismic category 1F and Q.A category Q2. The mussel trap is made up of screen, half-sphere, main flanges, nozzles, rotors, bolts, motor, supports and so on. The loads requirements in design conditions contain both internal loads and external loads. The loads have dead weight, pressure, nozzles loads and seismic loads. In this paper, the finite element model of the mussel trap is built with shell element using the structural analysis software-ANSYS. The stress analysis is based on linear elastic static analysis. The subspace iteration method is used for the modal analysis of the mussel trap. The static analysis is used for the mussel trap under deadweight, pressure and nozzle loads. At last, an evaluation of all loads combinations stresses against the respective stress limit for plate- and shell-type components and linear type systems is done according to the requirements of relative criteria specified in RCC-M. The evaluation result demonstrates that all loads combinations stresses of the mussel trap structure meet the requirements of RCC-M.
Mechanical Test Correlation for Microwave Based NDE Inspection of HDPE Thermal and Electro-Fusion Pipe Joints
Authors: Stakenborghs Robert , Little Jack
Published: April 2011

This paper provides a follow up to prior works [1,2,3,4] describing the theory and method associated with an innovative microwave based NDE method for inspection of HDPE thermal and electro fusion pipe joints. The method employs a first of a kind apparatus that is based on the creation of an image using electromagnetic energy in the microwave frequency range. This paper presents the results of a series of field and laboratory trials of the HDPE thermal and electro-fusion inspections and the corresponding mechanical test of the joint. A close correlation between the inspection results and the mechanical test results are shown. The data presented provides definitive evidence of the ability of the inspection method to detect numerous typical defect types in HDPE fusion joints.
Neutron Diffraction and SEM Study on CaO-Al2O3-SiO2(ZnO-BaO-Na2O) Glass-Ceramics Prepared Under Different Cooling Conditions
Authors: Guo Liping , Xie Jun , Sun Kai , Yang Zheng , Jin Shuoxue , Peng Guoliang , Fang Yami
Published: April 2011

Neutron diffraction and Scanning Electron Microscope (SEM) were employed to study complex two-phase coexistence structure and surface morphology of CaO-Al2O3-SiO2(ZnO-BaO-Na2O) glass ceramics prepared under different cooling conditions. With the rapid cooling temperature decreasing from above 850°C to 750°C and 300°C, the length of the needle-like precipitated β-wollastonite crystal decreased from 30 μm to 15 μm and 5 μm, respectively. Meanwhile, the transgranular fracture appeared and the grain boundary became indistinct in the sample rapidly cooled to 750°C, and the microcracks appeared in the samples rapidly cooled to 300°C and below. These phenomena contribute to the decrease of bending strength for the rapid cooling. Neutron diffraction revealed that the unit cell of precipitated β-wollastonite crystal elongated along its three axes and its volume increased at different cooling conditions. With the decrease of the cooling temperature, the elongation of axes and increase of volume were enhanced, implying that the tensile stress of the β-wollastonite crystal increased. At the same time, intensity of the crystal diffraction peaks increased and atomic temperature factors decreased, which revealed that defects inside a smaller size of crystal granular were less than that in larger one. Amorphous peaks at low diffraction angle did not changed with cooling temperature, showing that the middle-range-order inside residual glass phases were almost the same for all cooling conditions, while intensity of amorphous peaks at high diffraction angle increased notably for samples rapidly cooled to below 850°C, showing that rapid cooling may result in severe short-range-order in residual glass phase, which induced tensile stress of crystalline phase from around amorphous phase and therefore lead to occurrence of transgranular fracture and microcracks. This study suggests that rapid cooling to below 850°C should be avoided in order to obtain preferable mechanical properties for CaO-Al2O3-SiO2(ZnO-BaO-Na2O) glass ceramics.
Current Trends in I&C Diversity Implementation
Authors: Stiffler C. Daniel , Seaman Stephen
Published: April 2011

This paper discusses how reactor plant instrumentation and control (I&C) diversity implementation is achieved and impacted with evolving U.S. and worldwide diversity regulatory guidelines and requirements. With increased reliance on digital-based I&C architectures and risk-informed insight methods, diversity regulatory guidelines and requirements are still evolving. In some cases, the regulators are prescribing different methodologies to achieve the common goal of an adequate level of defense in depth through diversity. This paper analyzes differing diversity methodologies to compare and contrast rules as applied to actual diversity implementation on I&C systems.
Research on the Methods of Neutron Tube Ion Source Steady Flow
Authors: Qiao Shuang , Jing Shiwei
Published: April 2011

Neutron tube is a widely used small-scale accelerator-type neutron source, it is mainly made up of the storage, ion source, acceleration system, target and other parts. One of the important parameters of neutron tube is ion source current and its stability, which has a direct impact on the amount of neutron tube production and stability. Ion source current depends on storage heating current and it is hysteresis controlled object. This paper presents a kind of nonlinear PID controller and the control method is applied to ion source current control by using B&R PCC controller, the stability of current is not more than 2%, which meet the requirements of high-quality neutron tube.
Data Processing Method of Charpy Impact in the Specimen Reconstitution Technology
Authors: Wang Rongshan , Weng Likui , Wan Qiangmao
Published: April 2011

In the Specimen Reconstitution Technology, the empirical fitting equation of Boltzman function can be adopted for fitting the relationship between Charpy impact absorbed energy & percent ductile fraction and temperature, and the judgment index of goodness-of-fit is adjusted coefficient of determination (Adj.R). The t/t′ hypothesis testing can be adopted to check the identity of ductile-brittle transition temperature before & after reconstitution, and in advance, F testing should be carried out on the homogeneity of two groups of samples’ variances.
Determination of 89Zr Production Parameters via Different Reactions Using ALICE and TALYS Codes
Authors: Kakavand Tayeb , Taghilo Morteza , Sadeghi Mahdi
Published: April 2011

The 89Zr radioisotope is used in the field of tumor diagnostics, tumor therapy and the investigation of the biokinetic. The present work is investigated a suitable reaction to produce 89Zr..The Zirconium-89 excitation function via 89Y(p,n)89Zr, 89Y(d,2n)89Zr, natZr(p,pxn)89Zr, natSr(α,xn)89Zr and 90Zr(n,2n)89Zr reactions were calculated by ALICE-91 and TALYS-1.0 codes and the reaction of 89Y(p,n)89Zr has been selected. The calculated excitation function of 89Y(p,n)89Zr reaction was compared with the reported measurement and evaluations. Requisite thickness of targets was obtained by SRIM code for all above reactions except the 90Zr(n,2n)89Zr reaction. The 89Zr production yield was evaluated with attention to excitation function and stopping power for all above reactions except 90Zr(n,2n)89Zr reaction.
Depletion Calculation for a Nodal Reactor Physics Code
Authors: Alvim Antonio Carlos Marques , da Silva Fernando Carvalho , Martinez Aquilino Senra
Published: April 2011

This paper deals with an alternative numerical method for calculating depletion and production chains of the main isotopes found in a pressurized water reactor. It is based on the use of the exponentiation procedure coupled to orthogonal polynomial expansion to compute the transition matrix associated with the solution of the differential equations describing isotope concentrations in the nuclear reactor. Actually, the method was implemented in an automated nuclear reactor core design system that uses a quick and accurate 3D nodal method, the Nodal Expansion Method (NEM), aiming at solving the diffusion equation describing the spatial neutron distribution in the reactor. This computational system, besides solving the diffusion equation, also solves the depletion equations governing the gradual changes in material compositions of the core due to fuel depletion. The depletion calculation is the most time-consuming aspect of the nuclear reactor design code, and has to be done in a very precise way in order to obtain a correct evaluation of the economic performance of the nuclear reactor. In this sense, the proposed method was applied to estimate the critical boron concentration at the end of the cycle. Results were compared to measured values and confirm the effectiveness of the method for practical purposes.
Calculations of Excitation Functions to Produce 88Y via Various Nuclear Reactions by ALICE/91 and TALYS-1.0 Codes
Authors: Kakavand Tayeb , Taghilo Morteza
Published: April 2011

Excitation functions were calculated by the ALICE/91 and TALYS-1.0 codes for natRb(a,xn)88Y, natZr(p,pxn)88Y, natSr(a,xn)88Y, 89Y(p,n)88Y and 88Sr(p,n)88Y reactions. The calculated cross sections were compared with the experimental data. The suitable energy ranges for the production of 88Y for each reaction is reported. From the excitation functions, integral yields of the products were calculated. Finally the suitable reaction was selected for the production of 88Y.
The International Safety Regime of Radioactive Materials Transport
Authors: Mohamed Mohamed Ashraf Elsayed
Published: April 2011

Every day thousands of shipments of radioactive materials are transported on international and national routes. These consignments, which are carried by road, rail, sea, air and inland waterway, can range from smoke detectors and cobalt sources for medical uses to reprocessed fuel for use in electricity generation. The transport of radioactive materials worldwide is governed by stringent regulatory regime, which includes standards, codes and regulations that have been continuously revised and updated over the past four decades. The safety measures have been developed to protect the general public, transport workers, emergency response teams and the environment against the risks posed by the cargoes. These risks include the radioactivity itself and other chemical risks that the cargoes may pose, such as toxicity or corrosivity. In addition to the safety regulations, the regulatory regime addresses other, related issues such as physical protection and liability. It was recognized that these standards should provide a uniform, global regime to ensure that all parties apply the same provisions. Since 1961, the UN (United Nations) has published and periodically reviewed and updated the regulations for the safe transport of radioactive material. These regulations are used today by more than 60 countries as the basic for their national regulations. In addition, the main international modal organizations responsible for the safe transport of dangerous goods by road, rail, sea, air and inland waterways have incorporated the relevant parts of the UN regulations into their own instruments. This paper will discuss and outline the principal regulations that apply to the transport of radioactive materials such as the UN regulations for the safe transport of radioactive materials, The UN regime governing the international transport of dangerous goods, the principal modal regulations governing the transport of dangerous goods and achievement of a more harmonized regime. and the international organizations responsible for their development and implementation.
ACR-1000™ Fuel Design Verification
Authors: Wren David J. , Reid Patrick , Wright Len L.
Published: April 2011

The ACR-1000™ design is an evolutionary advancement of the proven CANDU® reactor design that delivers enhanced economic performance, safety, operability and maintainability. The fuel for the ACR-1000 design is based on the well established CANDU fuel bundle design that has over 40 years of demonstrated high performance. Building on its extensive experience in fuel design and analysis, and fuel testing, AECL has designed a CANFLEX-ACR™ fuel bundle that incorporates the latest improvements in CANDU fuel bundle design. The ACR-1000 fuel bundle also includes features that enable the ACR-1000 to achieve higher fuel burn-up and improved reactor core physics characteristics. To verify that the CANFLEX-ACR fuel bundle design will meet and exceed all design requirements, an extensive program of design analysis and testing is being carried out. This program rigorously evaluates the ability of the fuel design to meet all design and performance criteria and particularly those related to fuel failure limits. The design analyses address all of the phenomena that affect the fuel during its residence in the reactor core. Analysis is performed using a suite of computer codes that are used to evaluate the temperatures, deformations, stresses and strains experienced by the fuel bundle during its residence in the reactor core. These analyses take into account the impact of fuel power history and core residence time. Complementing the analyses, testing is performed to demonstrate the compatibility of the fuel with the reactor heat transport system and fuel handling systems, and to demonstrate the ability of the fuel to withstand the mechanical forces that it will experience during its residence in the core. The testing program includes direct measurement of prototype fuel element and fuel bundle properties and performance limits. A number of different test facilities are used including a cold test loop and a hot test loop with a full-scale ACR-1000 fuel channel that operates at reactor coolant temperatures, pressures and flows. This paper summarizes the out-reactor test program and related analysis that provide the basis for verifying that the ACR-1000 fuel design meets its requirements.
Analysis on Ex-Vessel Steam Explosion in CPR1000+ Unit
Authors: Zhang Juanhua , Lin Jiming , Zhang Shishun
Published: April 2011

Reactor Pit Flooding System (RPF) is adopted under the severe accidents situation in CPR1000+ units. It can move the heat generated from the reactor core via external reactor vessel cooling (ERVC) to keep the integrity of RPV and achieve the in-vessel corium retention (IVR). But if IVR function of RPF is failed, there is Ex-Vessel Steam Explosion (EX-SE) risk. The Ex-Vessel Steam Explosion is analyzed by MC3D software which is for fuel and cooling interaction (FCI). The physical model of CPR1000+ for Steam Explosion is built firstly and then the phenomenon of Ex-Vessel Steam Explosion under typical severe accident is analyzed. The conclusion of this study is that the impulse load of pressure on the cavity wall induced by steam explosion is about 310KPas ∼ 440KPas. Referencing the structure capacity of AP600 containment, if the structural capacity of CPR1000+ containment is equal to AP600, the impulse load of pressure is lower than it. So it could be preliminarily estimated that steam explosion will not threaten the integrality of CPR1000+ containment.
ACR-1000™ Design and Safety Performance
Authors: Yu Stephen , Bilanovic Zoran , Reid Patrick , Santamaura Paul , Soulard Mike
Published: April 2011

The ACR-1000™ design has evolved from AECL’s in depth knowledge of CANDU® systems, components and materials based on the CANDU 6 design, as well as the experience and feedback received from owners and operators of CANDU plants. The ACR® design retains the proven strengths and features of CANDU reactors, while incorporating innovations and state-of-the-art technology. It also features major improvements in inherent safety characteristics, safety margin and operational performance. The ACR design has been reviewed by domestic and international regulatory bodies, and has been given a positive regulatory opinion about its licensability in Canada and internationally. The Canadian regulator, the Canadian Nuclear Safety Commission (CNSC) completed the Phase 1 [1] and Phase 2 [2] pre-project design reviews in December 2008 and August 2009 respectively, and concluded that there are no fundamental barriers to licensing the ACR-1000 design in Canada. The generic PSAR for ACR-1000 was completed in September 2009. The PSAR contains the ACR-1000 design details, the safety and design methodology, and the safety analysis that demonstrate ACR-1000 safety case and compliance with Canadian and international regulatory requirements and expectations. The final stage of the ACR-1000 design is currently underway including documentation and additional confirmatory analysis, and the basic engineering will be completed in 2011. This paper provides an overview of the ACR-1000 design including a summary of the safety methodology used and compliance with regulatory and customer requirements, along with a demonstration of how modern expectations on safety margins and operational performance (i.e., typically characterized as Generation III+) are met. It also provides a summary of the safety analysis results (both deterministic and probabilistic) from the generic safety analysis that has been completed.
Digital Instrumentation and Control Systems Upgrades in Current Generation Nuclear Power Plants
Authors: Arndt Steven A.
Published: April 2011

Over the past 20 years, the nuclear power industry in the United States (U.S.) has been slowly replacing old, obsolete, and difficult-to-maintain analog technology for its nuclear power plant protection, control, and instrumentation systems with digital systems. The advantages of digital technology, including more accurate and stable measurements and the ability to improve diagnostics capability and system reliability, have led to an ever increasing move to complete these upgrades. Because of the difficulties with establishing digital systems safety based on analysis or tests, the safety demonstration for these systems relies heavily on establishing the quality of the design and development of the hardware and software. In the United States, the U.S. Nuclear Regulatory Commission (NRC) has established detailed guidelines for establishing and documenting an appropriate safety demonstration for digital systems in NUREG-0800, “Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants: LWR Edition,” Chapter 7, “Instrumentation and Controls,” Revision 5, issued March 2007 [1], and in a number of regulatory guides and interim staff guidance documents. However, despite the fact that the United States has a well-defined review process, a number of significant challenges associated with the design, licensing, and implementation of upgrades to digital systems for U.S. plants have emerged. Among these challenges have been problems with the quality of the systems and the supporting software verification and validation (V&V) processes, challenges with determining the optimum balance between the enhanced capabilities for the new systems and the desire to maintain system simplicity, challenges with cyber security, and challenges with developing the information needed to support the review of new systems for regulatory compliance.
Numerical Simulation of Logging-While-Drilling Azimuth Density Measurement
Authors: Wang Baosheng , Wang Lijuan , Zhang Jianmin , Yue Aizhong
Published: April 2011

A numerical simulation of logging while drilling density (LWD) is investigated by using Monte-Carlo (MC) method. The response of azimuth imaging is performed with in a highly deviated well with 60 degree slope. And then, the influence of counting rates of detectors was discussed due to characteristics of the inhomogeneous stratum. The numerical result shows that the azimuthal density image can intuitively display the characteristics of metrical stratum. Moreover, it can really display the thickness and location of the reservoir when drilling. The density image visually realized the visualization of the results and achieved application of geo-steering while drilling in theory. A further numerical study was carried out by using a Spine-and-Rib plot and the Far Detector Count Rate Compensation to analyze the influence of the standoff distances. And the numerical simulation results were analyzed with different Be-windows design parameters. The numerical result shows that the compensated density can satisfy the precision requirement with the two methods when the standoff distance is less than a predetermined value. Otherwise, just the far detector count rate can be compensated the stratum density with the cone-shape Be-windows.
Cylindrical IEC Fusion Neutron Source for Broad Area NAA
Authors: Miley George H. , Momota Hiromu , Leon Hugo , Ulmen Ben , Amadio Guilherme , Khan Atanu , Chen George , Matisiak William , Azeem Ali , Keutelian Paul
Published: April 2011

The development of a unique long cylindrical neutron source for broad area neutron activation analysis (NAA) is presented. This source uses inertial electrostatic confinement (IEC) to produce 2.54 MeV D-D or 14.1 MeV D-T fusion neutrons for applications ranging from security inspection stations to driven-subcritical research assemblies. This design uses a biased grid to initial in a unique “star” mode plasma discharge forming beam-background gas (target) fusion. In spherical geometry it routinely produces ∼108 2.54-MeV D-D fusion neutrons/s at steady-state. Pulsed operation has achieved up to 109 neutrons/sec. (equivalent to 1011 n/s using D-T fill). Indeed, a version of the spherical IEC has been produced commercially as a portable neutron source for industrial NAA applications. Recently a cylindrical (2-dimensional version) design based on the spherical unit has been developed. This provides a unique long “line-like” neutron source for use in broad area NAA. This IEC forms ion beams in the volume between the grounded wall and the concentric cylindrical grid. Those beams converge in the center, much like in the star mode spherical IEC. To date, neutron yields of up to 108 D-D neutrons/sec have been achieved with the cylindrical device. A sealed-off unit using getters for gas storage-control has been developed to simplify use in practical applications such as a luggage inspection station. Such units would be filled with deuterium at a central fueling facility, and sent out to the field. After extended operation, they would be returned to this facility for refilling.
Growth and thermal conductivity analysis of polycrystalline GaAs on chemical vapor deposition diamond for use in thermal management of high-power semiconductor lasers
Authors: Clark S. P. R. , Ahirwar P. , Jaeckel F. T. , Hains C. P. , Albrecht A. R. , Rotter T. J. , Dawson L. R. , Balakrishnan G. , Hopkins P. E. , Phinney L. M. , Hader J. , Moloney J. V.
Published: April 2011

The authors demonstrate the growth of polycrystalline GaAs thin films on polycrystalline chemical vapor deposition (CVD) diamond by low-temperature molecular beam epitaxy. The low-temperature GaAs (LT-GaAs) layer is easily polished compared to the CVD diamond, and this process results in a reduction of rms surface roughness from >50 to <5 nm. This makes the LT-GaAs on diamond layer an ideal wafer-bonding interface for high-power semiconductor devices. The samples were grown at 0.2 μm/h with a substrate temperature of 250 °C and a 1:8 III/V beam equivalent pressure ratio. The samples were analyzed by x-ray powder diffraction, atomic force microscopy for surface roughness, and in situ reflective high-energy electron diffraction during molecular beam epitaxy growth. The authors also measure the thermal conductivity of the GaAs layer on CVD diamond using pump-probe time domain thermoreflectance.
Integrated Multilevel Surveillance of the World's Infecting Microbes and Their Resistance to Antimicrobial Agents
Authors: O'Brien Thomas F. , Stelling John
Published: April 2011

Microbial surveillance systems have varied in their source of support; type of laboratory reporting (patient care or reference); inclusiveness of reports filed; extent of microbial typing; whether single hospital, multihospital, or multicountry; proportion of total medical centers participating; and types, levels, integration across levels, and automation of analyses performed. These surveillance systems variably support the diagnosis and treatment of patients, local or regional infection control, local or national policies and guidelines, laboratory capacity building, sentinel surveillance, and patient safety. Overall, however, only a small fraction of available data are under any surveillance, and very few data are fully integrated and analyzed. Advancing informatics and genomics can make microbial surveillance far more efficient and effective at preventing infections and improving their outcomes. The world's microbiology laboratories should upload their reports each day to programs that detect events, trends, and epidemics in communities, hospitals, countries, and the world.
Microbiology of Animal Bite Wound Infections
Authors: Abrahamian Fredrick M. , Goldstein Ellie J. C.
Published: April 2011

The microbiology of animal bite wound infections in humans is often polymicrobial, with a broad mixture of aerobic and anaerobic microorganisms. Bacteria recovered from infected bite wounds are most often reflective of the oral flora of the biting animal, which can also be influenced by the microbiome of their ingested prey and other foods. Bacteria may also originate from the victim's own skin or the physical environment at the time of injury. Our review has focused on bite wound infections in humans from dogs, cats, and a variety of other animals such as monkeys, bears, pigs, ferrets, horses, sheep, Tasmanian devils, snakes, Komodo dragons, monitor lizards, iguanas, alligators/crocodiles, rats, guinea pigs, hamsters, prairie dogs, swans, and sharks. The medical literature in this area has been made up mostly of small case series or case reports. Very few studies have been systematic and are often limited to dog or cat bite injuries. Limitations of studies include a lack of established or inconsistent criteria for an infected wound and a failure to utilize optimal techniques in pathogen isolation, especially for anaerobic organisms. There is also a lack of an understanding of the pathogenic significance of all cultured organisms. Gathering information and conducting research in a more systematic and methodical fashion through an organized research network, including zoos, veterinary practices, and rural clinics and hospitals, are needed to better define the microbiology of animal bite wound infections in humans.
HIV and Tuberculosis: a Deadly Human Syndemic
Authors: Kwan Candice K. , Ernst Joel D.
Published: April 2011

A syndemic is defined as the convergence of two or more diseases that act synergistically to magnify the burden of disease. The intersection and syndemic interaction between the human immunodeficiency virus (HIV) and tuberculosis (TB) epidemics have had deadly consequences around the world. Without adequate control of the TB-HIV syndemic, the long-term TB elimination target set for 2050 will not be reached. There is an urgent need for additional resources and novel approaches for the diagnosis, treatment, and prevention of both HIV and TB. Moreover, multidisciplinary approaches that consider HIV and TB together, rather than as separate problems and diseases, will be necessary to prevent further worsening of the HIV-TB syndemic. This review examines current knowledge of the state and impact of the HIV-TB syndemic and reviews the epidemiological, clinical, cellular, and molecular interactions between HIV and TB.
Epidemiology and Infectivity of Plasmodium falciparum and Plasmodium vivax Gametocytes in Relation to Malaria Control and Elimination
Authors: Bousema Teun , Drakeley Chris
Published: April 2011

Malaria remains a major cause of morbidity and mortality in the tropics, withPlasmodium falciparumresponsible for the majority of the disease burden andP. vivaxbeing the geographically most widely distributed cause of malaria. Gametocytes are the sexual-stage parasites that infectAnophelesmosquitoes and mediate the onward transmission of the disease. Gametocytes are poorly studied despite this crucial role, but with a recent resurgence of interest in malaria elimination, the study of gametocytes is in vogue. This review highlights the current state of knowledge with regard to the development and longevity ofP. falciparumandP. vivaxgametocytes in the human host and the factors influencing their distribution within endemic populations. The evidence for immune responses, antimalarial drugs, and drug resistance influencing infectiousness to mosquitoes is reviewed. We discuss how the application of molecular techniques has led to the identification of submicroscopic gametocyte carriage and to a reassessment of the human infectious reservoir. These components are drawn together to show how control measures that aim to reduce malaria transmission, such as mass drug administration and a transmission-blocking vaccine, might better be deployed.
Mucormycosis Caused by Unusual Mucormycetes, Non-Rhizopus, -Mucor, and -Lichtheimia Species
Authors: Gomes Marisa Z. R. , Lewis Russell E. , Kontoyiannis Dimitrios P.
Published: April 2011

Rhizopus,Mucor, andLichtheimia(formerlyAbsidia) species are the most common members of the order Mucorales that cause mucormycosis, accounting for 70 to 80% of all cases. In contrast,Cunninghamella,Apophysomyces,Saksenaea,Rhizomucor,Cokeromyces,Actinomucor, andSyncephalastrumspecies individually are responsible for fewer than 1 to 5% of reported cases of mucormycosis. In this review, we provide an overview of the epidemiology, clinical manifestations, diagnosis of, treatment of, and prognosis for unusual Mucormycetes infections (non-Rhizopus, -Mucor, and -Lichtheimiaspecies). The infections caused by these less frequent members of the order Mucorales frequently differ in their epidemiology, geographic distribution, and disease manifestations.Cunninghamella bertholletiaeandRhizomucor pusillusaffect primarily immunocompromised hosts, mostly resulting from spore inhalation, causing pulmonary and disseminated infections with high mortality rates.R. pusillusinfections are nosocomial or health care related in a large proportion of cases. WhileApophysomyces elegansandSaksenaea vasiformisare occasionally responsible for infections in immunocompromised individuals, most cases are encountered in immunocompetent individuals as a result of trauma, leading to soft tissue infections with relatively low mortality rates. Increased knowledge of the epidemiology and clinical presentations of these unusual Mucormycetes infections may improve early diagnosis and treatment.
Hormones and the Resistance of Women to Paracoccidioidomycosis
Authors: Shankar Jata , Restrepo Angela , Clemons Karl V. , Stevens David A.
Published: April 2011

Paracoccidioidomycosis, one of the most important endemic and systemic mycoses in Latin America, presents several clinical pictures. Epidemiological studies indicate a striking rarity of disease (but not infection) in females, but only during the reproductive years. This suggested a hormonal interaction between female hormones and the etiologic dimorphic fungus
Paracoccidioides brasiliensis
. Many fungi have been shown to use hormonal (pheromonal) fungal molecules for intercellular communication, and there are increasing numbers of examples of interactions between mammalian hormones and fungi, including the specific binding of mammalian hormones by fungal proteins, and suggestions of mammalian hormonal modulation of fungal behavior. This suggests an evolutionary conservation of hormonal receptor systems. We recount studies showing the specific hormonal binding of mammalian estrogen to proteins in
P. brasiliensis
and an action of estrogen to specifically block the transition from the saprophytic form to the invasive form of the fungus
in vitro
. This block has been demonstrated to occur
in vivo
in animal studies. These unique observations are consistent with an estrogen-fungus receptor-mediated effect on pathogenesis. The fungal genes responsive to estrogen action are under study.
Finite element formulation for shear deformable thin-walled beams
Authors: Wu Liping , Mohareb Magdi
Published: April 2011

Starting with the principle of stationary potential energy, this paper develops the governing differential equations of equilibrium and boundary conditions for shear deformable thin-walled beams with open cross-section. Unlike conventional solutions, the formulation is based on a non-orthogonal coordinate system, in which the selected origin is generally offset from the section centroid. The exact solution of the resulting coupled differential equations of equilibrium is derived and used to develop exact shape functions. A finite element based on the exact shape functions is then formulated. Through a series of examples, the adoption of non-orthogonal coordinates is shown to enable the seamless modelling of structural members with eccentric boundary conditions and (or) stepwise cross-sectional variations.
Numerical characteristics of a coupled river ice and hydrodynamic model
Authors: Nzokou François , Morse Brian , Robert Jean-Loup , Richard Martin , Tossou Edmond
Published: April 2011

Prediction of dam break surges using numerical tools has been the subject of tremendous research efforts in the past four decades. Powerful numerical tools that can model surge phenomena are readily available on the market. However, for winter conditions, when a river is covered by ice, it becomes difficult or even impossible to predict wave propagation dynamics using these traditional tools. It is therefore important to know what will happen should a dam break or an ice jam release in an ice-covered river. In this study, fully conservative form of the one-dimensional St. Venant equations are derived for water hydrodynamics in variable width trapezoidal channels having a stiff floating ice cover (that is not frozen to the river banks) in addition to the cover’s one-dimensional flexural response (as a beam on an elastic foundation) to incoming waves. A coupled numerical model (HYDROBEAM) using the Galerkin finite element method (FEM) is then developed. The coupling technique in the model uses an iterative computation process to find a simultaneous solution to both flow and ice cover models at each time step. The FEM schemes are evaluated by the simulation of progressive and regressive wave propagations and by the simulation of Stocker’s hypothetical dam break problem. For these simplified cases, analytical solutions exist and are used as references to evaluate the numerical attenuation of the model. The results of the hypothetical dam break simulations are in agreement with the theory. The effects of the spatial and temporal discretization on numerical attenuation of flow dynamics and ice cover peak stresses are evaluated and presented. When used within the recommended guidelines, HYDROBEAM’s performance is more than adequate to simulate (a) open channel flow, (b) rivers with passive (flexible) ice covers or (c) rivers with stiff ice covers that respond as a beam on an elastic foundation.
Specifications and testing of self-consolidating mortar designated for annular space grouting
Authors: Hwang Soo-Duck , Khayat Kamal H. , Morin Richard
Published: April 2011

An experimental program was undertaken to evaluate the performance of self-consolidating mortar designed for filling small annular spaces for the rehabilitation of underground water line or sewage pipelines. The study also intended to establish a testing protocol to validate the workability of repair grout. All the investigated mixtures had good filling and passing ability with adequate retention of workability over 3 h. The repair mortars exhibited high stability with bleeding lower than 0.3% compared to 3% bleeding in the case of the reference neat cement grout. The reference grout had a lower plastic viscosity and higher slump flow values than the sanded repair grouts. A V-funnel with 30 mm × 30 mm overture and a flow cone with 12.7 mm overture are recommended for mortar made with concrete sand with a 5 mm nominal size and micro mortar with fine sand with a nominal size up to 3 mm, respectively.
Effect of wind loads on the stability of conical tanks
Authors: Hafeez G. , El Ansary A.M. , El Damatty A.A.
Published: April 2011

During the past few decades, a number of conical tanks have collapsed in various locations around the globe. Previous studies attributed the reason of collapse to inadequate thickness of the conical vessel especially at the bottom part. Most of the previous studies focused on studying the stability of conical tanks under the effect of only hydrostatic pressure. The current study focuses on studying the combined effect of wind loading and hydrostatic pressure on the stability of conical tanks. The study is conducted numerically, using a three-dimensional finite element model that is developed in-house. The critical imperfection shapes leading to minimum buckling capacity of conical shells under wind load alone, and under the combined effect of wind load and hydrostatic pressure, are determined. The study shows that a non-axisymmetric imperfection shape leads to minimum buckling capacity of empty conical tanks subjected to wind loads, while an axisymmetric distribution is noticed in the case of conical tanks under the combined effect of wind loads and hydrostatic pressure. In addition, the current study assesses the adequacy of an existing design procedure, which accounts for hydrostatic pressure, when the combination of hydrostatic pressure and wind load is considered.
A fuzzy logic model for benchmarking the knowledge management performance of construction firms
Authors: Kale Serdar , Karaman Erkan A.
Published: April 2011

Knowledge management is rapidly becoming a key organizational capability for creating competitive advantage in the construction industry. The emergence of knowledge management in this capacity poses enormous challenges to executives of construction firms. This paper proposes a model for benchmarking the knowledge management performance of construction firms that can guide and assist construction business executives in meeting these challenges. The proposed model incorporates benchmarking and knowledge management concepts with fuzzy set theory to adequately handle imprecision, vagueness, and uncertainty that prevail in this process. It uses the fuzzy-weighted average (FWA) algorithm to evaluate the knowledge management performance of construction firms. It is an internal reporting model that can provide powerful diagnostic information to executives of construction firms by evaluating their firm’s knowledge management performance, identifying their firm’s strengths and weaknesses with regard to each knowledge management practice, and setting priorities for managerial actions related to knowledge management practices that need improvement. A real-world case study is presented to illustrate the implementation and utility of the proposed model.
On calculating equivalent static seismic forces in the 2005 National Building Code of Canada
Authors: Paultre Patrick , Lapointe Éric , Mousseau Sébastien , Boivin Yannick
Published: April 2011

Several major changes were introduced in the seismic design provisions of the 2005 edition of the National Building Code of Canada (NBCC). The lateral earthquake design force at the base and the lateral force distribution along the building height depend on the design spectra and on modification factors that, in most cases, require a large number of interpolations and calculations. This note presents a spreadsheet that facilitates determination of the 2005 NBCC seismic design forces from the equivalent static force procedure.
SENSITIVITY ANALYSIS OF WEAK EFFICIENCY IN MULTIPLE OBJECTIVE LINEAR PROGRAMMING
Authors: SITARZ SEBASTIAN
Published: April 2011

This paper, studies the sensitivity analysis of weakly efficient extreme solutions in multiple objective linear programming (MOLP). The aim of the paper is to compute the set of the parameters (corresponding to one coefficient) for which a given extreme point is a weakly efficient solution. We also focus on the properties of the parameters set by proving convexity and closeness of this set. Moreover, we compare the results of the sensitivity analysis of efficiency and of weak efficiency in MOLP.
THE EFFECT OF FINANCING ON A BUDGET-CONSTRAINED SUPPLY CHAIN UNDER WHOLESALE PRICE CONTRACT
Authors: CHEN XIANGFENG , WAN GUOHUA
Published: April 2011

This paper examines the impact of financing on the performance of a two-level supply chain consisting of a supplier and a budget-constrained retailer. To carry out our study, we set up a three-stage Stackelberg game under a wholesale price contract with a financial market. We show that financing from a competitive financial market can create value for both the supplier and the retailer. We also demonstrate that in a competitive financial market with symmetric information on the retailer's initial budget, the retailer's operational and financial decisions could be decoupled. We provide numerical results to shed light on additional managerial insights as well.
SINGLE MACHINE SCHEDULING WITH A LEARNING EFFECT AND A RATE-MODIFYING ACTIVITY
Authors: ZHAO CHUANLI , TANG HENGYONG
Published: April 2011

In the paper, single machine scheduling problems with a learning effect and a rate-modifying activity are considered. Under the learning effect, the processing time of a job is a decreasing function of its position in the sequence. The rate-modifying activity is an event that can change the speed of the machine, and hence the processing time of jobs after the activity. The following objective functions are considered: the makespan, the total earliness, tardiness and completion time penalty, and the total earliness, tardiness, due-window starting time and due-window size penalty. Polynomial time algorithms are proposed to optimally solve the problems.
QUARK MASSES IN QCD: A PROGRESS REPORT
Authors: DOMINGUEZ C. A.
Published: April 2011

Recent progress on QCD sum rule determinations of the light and heavy quark masses is reported. In the light quark sector a major breakthrough has been made recently in connection with the historical systematic uncertainties due to a lack of experimental information on the pseudoscalar resonance spectral functions. It is now possible to suppress this contribution to the 1% level by using suitable integration kernels in Finite Energy QCD sum rules. This allows one to determine the up-, down-, and strange-quark masses with an unprecedented precision of some 8–10%. Further reduction of this uncertainty will be possible with improved accuracy in the strong coupling, now the main source of error. In the heavy quark sector, the availability of experimental data in the vector channel, and the use of suitable multipurpose integration kernels allows one to increase the accuracy of the charm- and bottom-quarks masses to the 1% level.
THE ALIGNED K-CENTER PROBLEM
Authors: BRASS PETER , KNAUER CHRISTIAN , NA HYEON-SUK , SHIN CHAN-SU , VIGNERON ANTOINE
Published: April 2011

In this paper we study several instances of the alignedk-center problem where the goal is, given a set of points S in the plane and a parameter k ⩾ 1, to find k disks with centers on a line ℓ such that their union covers S and the maximum radius of the disks is minimized. This problem is a constrained version of the well-known k-center problem in which the centers are constrained to lie in a particular region such as a segment, a line, or a polygon.

We first consider the simplest version of the problem where the line ℓ is given in advance; we can solve this problem in time O(n log 2 n). In the case where only the direction of ℓ is fixed, we give an O(n2 log 2 n)-time algorithm. When ℓ is an arbitrary line, we give a randomized algorithm with expected running time O(n4 log 2 n).

Then we present (1+ε)-approximation algorithms for these three problems. When we denote T(k, ε) = (k/ε2+(k/ε) log k) log (1/ε), these algorithms run in O(n log k + T(k, ε)) time, O(n log k + T(k, ε)/ε) time, and O(n log k + T(k, ε)/ε2) time, respectively. For k = O(n1/3/ log n), we also give randomized algorithms with expected running times O(n + (k/ε2) log (1/ε)), O(n+(k/ε3) log (1/ε)), and O(n + (k/ε4) log (1/ε)), respectively.
A PULSE VACCINATION STRATEGY AT VARIABLE TIMES DEPENDING ON INCIDENCE
Authors: CÓRDOVA–LEPE FERNANDO , VALLE RODRIGO DEL , ROBLEDO GONZALO
Published: April 2011

This work presents a new pulse vaccination strategy for a SIS (susceptible–infective–susceptible) disease in an endemic context. Here, given a time of vaccination, the instant of the next one is not predetermined, but it is a function of the present incidence and this function allows us to obtain an epidemic threshold ensuring the convergence of infectives toward the disease-free scenario. Numerical results show that our condition is sufficient but not necessary and that the convergence is faster compared with fixed time vaccination strategies.
THE ANALYSIS OF YEAST CELL MORPHOLOGY FEATURES IN EXPONENTIAL AND STATIONARY PHASE
Authors: LIU YIHUI , AUBREY WAYNE , MARTIN KATHERINE , SPARKES ANDREW , LU CHUAN , KING ROSS D.
Published: April 2011

The use of automated microscopes, combined with digital image analysis, is an increasingly important way of high-throughput phenotype analysis of biological systems. We have developed a new method of measuring the basic morphological features of budding yeast (Saccharomyces cerevisiae) cells. Using this method we have performed investigation on four deletant strains: ΔYLR371w, ΔYDR349c, ΔYLR192c, and ΔYDR414c. These investigations demonstrate that our robotics and image analysis software provide an efficient way to automatically obtain quantitative morphology features of yeast cells. The results show that statistically significant morphological differences can be identified between strains, and that these differences vary by growth stage.