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Effects of Austenitising Conditions on the Microstructures and Mechanical Properties of Martensitic Steel with Dual Matrix Structure

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Journal of Minerals and Materials Characterization and Engineering 2012年第1期11卷 69-83页

作者： K.A. Bello S.B. Hassan o. Aponbiede Department of Metallurgical and Materials Engineering Ahmadu Bello University Zaria Nigeria

A new high strength steel with dual matrix structure and exceptionally high toughness plus ductility have been produced by intermediate quenching of 0.22_wt% C microalloyed steel. The treatment consisted of initial austenitization and rapid quenching of the steel samples to achieve a fully martensitic state followed by annealing in the intercritical (α+γ) region of 730℃-810℃ for the period of 30, 60 and 90_minutes. These samples were subsequently quenched to obtain dual phase microstructure containing varying proportions of ferrite and martensite constituents. The mechanical properties of the samples were measured according to ASTM standard and their microstructures were analyzed by optical microscopy. The experimental results show that martensitic dual phase (MDP) steel samples developed within the intercritical temperature range of 770–790℃ revealed finer martensite and precipitate-free ferrite microstructure. The tensile and impact properties of the developed HMDP steels increased with intercritical annealing (ICA) temperatures, with an optimum properties obtained at 790℃ mainly due to finer microstructure of the constituent phases and absence of carbide precipitate that permit ease of dislocation flow. A further increase in the intercritical annealing temperature beyond 790℃ led to general decrease in the mechanical properties. This is attributed to the formation of coarse structure in this region. The results further show that with increasing intercritical treatment time from 30 to 90 minutes, the general mechanical properties of the MDP steels were found to increase except at the higher temperature of 810℃ which showed decreasing values. In general, the tensile strengths and ductility as well as the impact properties of the developed dual phase steel samples are greatly improved with the intercritical heat treatment investigated.

关键词： Intercritical temperature dual phase steels microstructure microalloyed steel dual matrix

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Retrospective Surveillance over 11 Years for Intussusception in Children Younger than 14 Years in the State of Qatar

作者： (土)o.·帕慕克

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open Journal of Pediatrics 2014年第1期4卷 1-11页

作者： Tariq o. Abbas Noora AlShahwani Gaby Jabbour Mansour Ali Department of Pediatric Surgery Hamad General Hospital Doha Qatar

Background: Accurate estimates of the baseline incidence of childhood intussusception could help safety monitoring after introduction of rotavirus vaccines. Therefore, we studied the incidence of intussusception in the state ofQatar. Methods: We retrospectively reviewed cases of intussusception in children younger than 14 years. Children were treated between 2002 and 2012 at a single hospital inQatar. We analyzed information according to age, sex, clinical signs, diagnostic- and treatment-related characteristics, and length of stay. We calculated the national incidence of intussusception using census data. Results: A total of 106 children were diagnosed and treated for intussusception over 11 years. The male to female ratio of intussusception was 1.4:1. The most common symptom was bleeding per rectum (37%). one hundred andfour children with intussusception underwent diagnostic and therapeutic contrast enema, and 31.7% of patients underwent operative management. The length of stay was longer in patients who underwent operative reduction thanthat in those who did not. Conclusions: This is the first study to estimate the incidence of childhood intussusception prior to introduction of rotavirus vaccination in Qatar. A prospective surveillance system using a standardized case definition would be useful for examining the occurrence of intussusception in theArabicGulfarea and developing countries.

关键词： Children Intussusception Surgical Reduction Therapeutic Contrast Enema

ZUR STRATIGRAPHIE DES MINUSSINISCHEN PALAoZoIKUM

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地质学报 1935年第1期 93-98页

作者： VoN R.I.VIALoVA UND o.S.VIALoV

Whrend der geologischen Forschungen welche im Jahre 1930 imBezirk Atschinsk des Minussinischen Gebiets (Westsibirien) von ***ührt wurden,haben wir einige für die Stratigraphie ziemlich interessanteFunde gemacht.

关键词： der ZUR STRATIGRAPHIE DES MINUSSINISCHEN PALAoZoIKUM

An Analysis and Computation of optimum Earth Geographical Coverage for Global Satellite Communications

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Communications and Network 2013年第4期5卷 337-343页

作者： o. C. Eke Vincent A. N. Nzeako Department of Computer Science Ebonyi State University Abakaliki Nigeria Department of Electronic Engineering University of Nigeria Nsukka Nigeria

This paper presents simple mathematical mobility models for configuration of Global interconnectivity with LEo satellite systems. The aim of this paper is to investigate on the performance measures of the satellite mobility models regarding optimum Global coverage arc length depending on the satellite locations relative to the four zones (quadrants) of the earth surface. A typical body of the satellite was positioned at a modified height of 780 Km from the earth surface and revolving round the earth in a circle of radius, 7160 Km was carefully studied and analytically parameterized enabling the generation of realistic instantaneous coverage arc lengths data. We compared the minimum required instantaneous arc lengths for the three mobility models that should cover the geographical coverage areas of the earth. The impact of the satellite movements relative to the earth locations was that the instantaneous coverage arc lengths were exponentially varying with time and continuously distributed within the four zones of the earth surface to provide continuous coverage around one polar orbit plane and assuming operations can continue down to an elevation angle of zero degree. The advantage of the derived mobility models is achieving almost 100% global coverage as a result of the dynamic behavior of the satellite playing an important role of providing instantaneous coverage arc lengths. This procedure also allows comparisons among different degrees of built-up zones of the earth surface as well as extra-polation to the different locations on the earth surface.

关键词： Global Coverage LEo Satellite one Dimensional Model Satellite Mobility Model Central Angle Instantaneous Coverage Arc Length Terrestrial Cellular Concept

Risk level Assessment of the Desalter and Preflash Column of a Nigerian Crude Distillation Unit

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Journal of Materials Science and Chemical Engineering 2019年第11期7卷 31-41页

作者： Henry o. orugba Samuel E. ogbeide Christian osagie Department of Chemical Engineering University of Benin Benin City Nigeria Faculty of Environmental and Natural Sciences Brandenburg University of Technology Cottbus Germany

A study of operability and assessment of the safety level of a crude distillation unit in a Nigerian refinery has been carried out. In a crude distillation unit of a refinery, the desalter and preflash column, as well as their associated pipe works and pumps, are considered to have high-risk factors that can present operability problems and possibly hazardous conditions. Applying the HAZoP methodology, a total of 25 guide words were suitably applied on 4 nodes to study the possible deviations that may occur. The 89 causes of these deviations identified in the study could be classified under human errors and equipment malfunctioning. From the nature of the 46 consequences identified, the plant is likely to experience more of operability problems and less of deadly hazardous scenes. Suitable recommendations that will improve the operability and safety levels of the plant were however presented in the study and presented in tables. If the 61 recommendations given in this study can be incorporated into the design with the few safeguards already present in the original design of the plant, the operability problems of the plant will be greatly minimized and safety level will improve drastically.

关键词： Hazard operability HAZoP Guide Word Nodes Refinery

Investigation of the Potential of Near Infrared Spectroscopy for the Detection and Quantification of Pesticides in Aqueous Solution

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American Journal of Analytical Chemistry 2011年第8期2卷 53-62页

作者： Aoife A. Gowen Yutaro Tsuchisaka Colm o’Donnell Roumiana Tsenkova 不详

This research investigates the potential of near infrared spectroscopy (NIRS) for the detection and quantification of pesticides in aqueous solution. Standard solutions of Alachlor and Atrazine (ranging in concentration from 1.25 - 100 ppm) were prepared by dilution in a Methanol/water solvent (1:1 methanol/water (v/v)). Near infrared transmission spectra were obtained in the wavelength region 400 - 2500 nm;however, the wavelength regions below 1300 nm and above 1900 nm were omitted in subsequent analysis due to the poor signal repeatability in these regions. Partial least squares analysis was applied for discrimination between pesticide and solvent and for prediction of pesticide concentration. Limits of detection of 12.6 ppm for Alachlor and 46.4 ppm for Atrazine were obtained.

关键词： Pesticide Aquaphotomics Nearinfrared

Acquired Immune Deficiency Syndrome in Man and Animals—A Review

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World Journal of AIDS 2015年第1期5卷 50-57页

作者： Maduike C. o. Ezeibe Ijeoma J. ogbonna Department of Veterinary Medicine Michael Okpara University of Agriculture Umudike Nigeria

The paper defined acquired immune deficiency syndrome (AIDS) as a hematological abnormality rather than a clinical abnormality. Viruses that cause AIDS in man and animals are reviewed. Suggestion that human immune deficiency virus (HIV) which causes HIV/AIDS in man is a mutant of simian immune deficiency virus (SIV) which causes SIV/AIDS in nonhuman primates is also re-viewed. For a simple test to enable researchers in the developing countries which have the highest incidences of HIV/AIDS, join the global search for more effective treatment for the pandemic, direct passive hemagglutination test has been developed for in vitro testing of drugs, herbs and minerals that may have antiretroviral effects. Also reviewed are the similarities in pathogenesis of HIV infection in man and pathogenesis of infectious bursa disease virus (IBDV) in chicks to assess possibility of developing vaccine for HIV/AIDS. Finally, antiretroviral effects of medicinal synthetic aluminum-magnesium silicate as cure for HIV/AIDS were reviewed.

关键词： HIV In Vitro Test Prospect of Vaccine A Potential Cure

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