检索结果-南通市图书馆

Elaboration and Characterization of a Composite Material Based on <i>Canarium schweinfurthii</i>Engl Cores with a Polyester Matrix

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Materials Sciences and Applications 2020年第3期11卷 204-215页

作者： Dieunedort Ndapeu francis tamwo Morino Bernard Nganou Koungang Ghislain Tchuen Nicodème R. Sikame Tagne Sophie Bistac Ebénezer Njeugna Research Unit of Industrial Systems and Environmental Engineering (URISIE) UIT-FV Bandjoun University of Dschang Bandjoun Cameroon Research Unit of Mechanics and Physical Systems Modelling (UR2MSP) Department of Physics University of Dschang Dschang Cameroon Mechanics and Adapted Materials Laboratory (LAMMA) ENSET Douala Cameroon Physics and Macromolecular Engineering Laboratory (LPIM) UHA Mulhouse France

The aim of this work was to develop and characterize a polyester matrix composite material based on Canarium schweinfurthii Engl core granule. The particle size and the mass fractions of these cores used as fillers in this composite were the two optimization parameters. The experimentation of the twelve sample areas was based on the following optimization parameters: Three particles sizes of 80 1 2 3 ·m-3, which allows us to admit that this composite belongs to the family of light materials. The maximum compressive stress at break was obtained for the formulation 40% filler of size T3. This compressive stress at maximum rupture is in the range of 199.14 MPa. From 0% to 45% of filler, the flexural Young’s modulus of the composite increases whatever the particle size. The highest value is obtained for T2 particle size, i.e. 13.11 GPa. The static friction coefficient of the composite on wood increases as the filler content varies from 0.30 to 0.42. Thus, in view of the properties obtained, this composite can be used as alternative solutions in industrial applications, for the manufacturing of shoe heel, house ceiling, floors for housing and table support.

关键词： Canarium schweinfurthii Engl Characterization Composite Polyester Filler

Model Design and Simulation of an 80 kW Capacitor Coupled Substation Derived from a 132 kV Transmission Line

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Modelling and Simulation 2025年第1期13卷 1-19页

作者： Sinqobile Wiseman Nene Bolanle Tolulope Abe Agha francis Nnachi Department of Electrical Engineering Tshwane University of Technology eMalahleni South Africa

The global rise in energy demand, particularly in remote and sparsely populated regions, necessitates innovative and cost-effective electrical distribution solutions. Traditional Rural Electrification (RE) methods, like Conventional Rural Electrification (CRE), have proven economically unfeasible in such areas due to high infrastructure costs and low electricity demand. Consequently, Unconventional Rural Electrification (URE) technologies, such as Capacitor Coupled Substations (CCS), are gaining attention as viable alternatives. This study presents the design and simulation of an 80 kW CCS system, which taps power directly from a 132 kV transmission line to supply low-voltage consumers. The critical components of the CCS, the capacitors are calculated, then a MATLAB/Simulink model with the attained results is executed. Mathematical representation and state-space representation for maintaining the desired tapped voltage area also developed. The research further explores the feasibility and operational performance of this CCS configuration, aiming to address the challenges of rural electrification by offering a sustainable and scalable solution. The results show that the desired value of the tapped voltage can be achieved at any level of High Voltage (HV) with the selection of capacitors that are correctly rated. With an adequately designed control strategy, the research also shows that tapped voltage can be attained under both steady-state and dynamic loads. By leveraging CCS technology, the study demonstrates the potential for delivering reliable electricity to underserved areas, highlighting the system’s practicality and effectiveness in overcoming the limitations of conventional distribution methods.

关键词： Capacitor-Coupled Substation Transmission Line-linked Capacitor-Coupled Substation Capacitor-Coupled Substation Simulation Microgrids Rural Electrification Power System Modeling

Morphological Characteristics of Local Chicken Populations (Gallus gallus domesticus) in Farmed Basins of the Far North Region, Cameroon

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Open Journal of Animal Sciences 2025年第1期15卷 51-68页

作者： Christophe Wang-baa Temoa Jean Massawa francis Dongmo Djiotsa Yakouba Manjely Felix Meutchieye Faculty of Agronomy and Agricultural Sciences University of Dschang Dschang Cameroon Department of Agriculture Livestock and Deriveted Product National Advanced School of Engineering University of Maroua Maroua Cameroon Institute of Agricultural Research for Development IRAD Garoua Garoua Cameroon School of Science and Veterinary Medicine University of Ngaoundere Ngaoundere Cameroon

In order to contribute to a better understanding of the biodiversity of local chicken populations, this study focused on the description of the essential qualitative parameters in the phenotypic characterization of local species. Conducted in 6 localities in the Far North Region of Cameroon (Doukoula, Yagoua, Guidiguis, Dziguilao, Maroua 3rd and Méri), a population of 240 local chickens, including 172 hens and 68 cocks were characterized in family farms. The choice of localities was made on the basis of their strong potential local chicken flocks in the region. To this end, each animal was the subject of a qualitative description based on the identification of the sex of the animal, the description of the colorations of the plumage and extremities, and the description of the types of format, plumage and crests. All observations were made with the naked eye and in daylight and then photographed. The main results show that the plumage colors are multiple and dominated by the White-Pied-Black (21.7%) and the Mille-fleur (20.8%);the wattles are dominated by the red (60%) and the pink (35.4%);the tarsi are dominated by the white (43.8%) and the black (32.08%);the white skin (92.5%) dominates over the pink skin (7.5%);the “Smooth-uniform” feather is dominant (97.08%), followed by the smooth-crested type (2.08%) and the fries type (0.82%);the medium size of the chickens is dominant (86.66%), followed by the dwarf size (9.58%) and the large size (3.75%). The results of this study demonstrate that there is a strong phenotypic diversity within the local chicken population. This diversity can serve as a basis for the development of selection, conservation and genetic potential improvement programs based on rational exploitation of the local chicken.

关键词： Morphological Characteristics Local Chicken Far North Cameroon

Predicting the Yield Loss of Winter Wheat Due to Drought in the Llano Estacado Region of the United States Based on the Cultivar-Specific Sensitivity to Drought

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Agricultural Sciences 2025年第1期16卷 13-30页

作者： Prem Woli Gerald R. Smith Charles R. Long francis M. Rouquette Jr. Texas A&M AgriLife Research Center Overton USA

In most agricultural areas in the semi-arid region of the southern United States, wheat (Triticum aestivum L.) production is a primary economic activity. This region is drought-prone and projected to have a drier climate in the future. Predicting the yield loss due to an anticipated drought is crucial for wheat growers. A reliable way for predicting the drought-induced yield loss is to use a plant physiology-based drought index, such as Agricultural Reference Index for Drought (ARID). Since different wheat cultivars exhibit varying levels of sensitivity to water stress, the impact of drought could be different on the cultivars belonging to different drought sensitivity groups. The objective of this study was to develop the cultivar drought sensitivity (CDS) group-specific, ARID-based models for predicting the drought-induced yield loss of winter wheat in the Llano Estacado region in the southern United States by accounting for the phenological phase-specific sensitivity to drought. For the study, the historical (1947-2021) winter wheat grain yield and daily weather data of two locations in the region (Bushland, TX and Clovis, NM) were used. The logical values of the drought sensitivity parameters of the yield models, especially for the moderately-sensitive and highly-sensitive CDS groups, indicated that the yield models reflected the phenomenon of water stress decreasing the winter wheat yields in this region satisfactorily. The reasonable values of the Nash-Sutcliffe Index (0.65 and 0.72), the Willmott Index (0.88 and 0.92), and the percentage error (23 and 22) for the moderately-sensitive and highly-sensitive CDS groups, respectively, indicated that the yield models for these groups performed reasonably well. These models could be useful for predicting the drought-induced yield losses and scheduling irrigation allocation based on the phenological phase-specific drought sensitivity as influenced by cultivar genotype.

关键词： ARID Cultivar Drought Model Phase Prediction Semi-Arid Stage Wheat Yield

Assessment of Optimal Use, Maintenance, Repair and Calibration of Radiation Monitoring Instruments in Nigeria

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Nuclear Science and Technology 2025年第1期15卷 1-16页

作者： Samuel Mofolorunsho Oyeyemi Olumide Olaife Akerele Sunday Ufuoma Obarhua francis Adole Agada Wasiu Kofoworola Ayuba Helen Enikpi Alakiu David Olakanmi Olaniyi Ethel Ebere Ofoegbu National Institute of Radiation Protection and Research University of Ibadan Ibadan Oyo State Nigeria Nigerian Nuclear Regulatory Authority Abuja Nigeria

The response and performance of radiation detectors for accurate measurements and effective use for radiological safety in medical, industrial, and nuclear sectors are based on the optimal use, maintenance, repair and calibration of radiation monitoring instruments in a secondary standard dosimetry laboratory. In Nigeria, the suboptimal performances of these instruments are attributed to inadequate maintenance practices, insufficient calibration, and limited awareness of proper equipment handling for optimal use. This study assesses the current practices related to the optimal use, maintenance, repair, and calibration of radiation detection equipment across Nigeria’s six geopolitical zones. Using a cross-sectional survey approach, data were collected from Ninety (90) radiation monitoring equipment operators, Radiation Safety Officers, and frontline responders to evaluate their knowledge, awareness, and practices concerning equipment usage, operation, storage, handling, and calibration. The findings reveal significant gaps in knowledge of usage (trained is 43.2%, not trained is 56.8%) and inconsistencies in maintenance practices (as indicated by the regression analysis (β = 0.51, p < 0.01), particularly regarding specialized instruments such as the PackEye, Mobile Detection System (MDS), Radionuclide Identifinder (RID), and Personal Radiation Detectors (PRD). While there is high awareness of the need for regular calibration and handling training, the lack of standardized protocols and training alignment poses challenges to the effective use of these instruments. This study underscores the importance of comprehensive training programs, standardized maintenance protocols, and enhanced awareness initiatives to optimize the usage, performance and safety of radiation monitoring instruments in Nigeria.

关键词： Radiation Monitoring Instruments Detectors Calibration Radiation Safety Officers PackEye Radionuclide Identifinder Personal Radiation Detectors

Retrospective Assessment of Calibration Behaviour, Faulty Trends and Durability of Commonly Used Radiation Survey Meters in Nigeria

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Nuclear Science and Technology 2025年第1期15卷 30-44页

作者： Olumide Olaife Akerele Samuel Mofolorunsho Oyeyemi francis Adole Agada Sunday Ufuoma Obarhua Helen Enikpi Alakiu Wasiu Kofoworola Ayuba David Olakanmi Olaniyi Ethel Ebere Ofoegbu National Institute of Radiation Protection and Research University of Ibadan Ibadan Nigeria Nigerian Nuclear Regulatory Authority Abuja Nigeria

Radiation detectors, such as survey meters, are essential for ensuring radiation safety in various sectors, including healthcare, industrial processing, emergency response, etc. However, regular calibration and proper maintenance of survey meters are important in order to ascertain their accuracy and reliability. This study provides a comprehensive retrospective assessment of the calibration behaviour, durability, and fault trends of 160 survey meters, spanning ten different models. They were calibrated at the Secondary Standard Dosimetry Laboratory (SSDL) in Nigeria over a decade (2012-2023) using an X-Ray Beam Irradiator Model X80-225K and Cs-137 irradiator (OB6) with a PTW reference spherical chamber traceable to the IAEA SSDL in Seibersdorf, Austria. The calibration stability of each model was evaluated, revealing that models like Instrument A and Instrument B demonstrated high reliability with calibration factors close to the ideal value of 1, while models like Instrument C exhibited higher variability, suggesting less consistent performance for dose rate monitoring. Fault analysis showed that the most common issues were related to the battery compartment, indicating a need for improved handling practices. Correlation analysis reveals no statistically significant correlation between calibration factor and age of survey meter across the analysed models. The study concludes that regular calibration, proper handling, and user training are crucial for maintaining the accuracy and longevity of radiation detectors.

关键词： Radiation Detectors Survey Meters Calibration Stability Fault Trends Radiation Safety Maintenance Strategies Handling Practices

Determination of contact parameters for discrete element method simulations of granular systems

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Particuology 2008年第6期6卷 521-528页

作者： Kevin francis Malone Institute of Particle Science and Engineering University of Leeds

Both linear-spring-dashpot （LSD） and non-linear Hertzian-spring-dashpot （HSD） contact models are commonly used for the calculation of contact forces in Discrete Element Method （DEM） simulations of granular systems. Despite the popularity of these models, determination of suitable values for the contact parameters of the simulated particles such as stiffness, damping coefficient, coefficient of restitution, and simulation time step, is not altogether obvious. In this work the relationships between these contact parameters for a model system where a particle impacts on a flat base are examined. Recommendations are made concerning the determination of these contact parameters for use in DEM simulations.

关键词： Discrete Element Method (DEM) Linear-spring--dashpot model Non-linear Hertzian-spring-dashpot model Contact parameters

Performance Assessment of Semiconductor Detector Used in Diagnostics and Interventional Radiology at the Nigerian Secondary Standard Dosimetry Laboratory

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

World Journal of Nuclear Science and Technology 2025年第1期15卷 17-29页

作者： Samuel Mofolorunsho Oyeyemi Olumide Olaife Akerele David Olakanmi Olaniyi francis Adole Agada Sherif Olaniyi Kelani Akinkunmi Emmanuel Ladapo Ahmed Mohammed Shiyanbade Bamidele Musbau Adeniran Latifat Ronke Owoade National Institute of Radiation Protection and Research University of Ibadan Ibadan Oyo State Nigeria

Radiation doses to patients in diagnostics and interventional radiology need to be optimized to comply with the principles of radiation protection in medical practice. This involves using specific detectors with respective diagnostic beams to carry out quality control/quality assurance tests needed to optimize patient doses in the hospital. Semiconductor detectors are used in dosimetry to verify the equipment performance and dose to patients. This work aims to assess the performance, energy dependence, and response of five commercially available semiconductor detectors in RQR, RQR-M, RQA, and RQT at Secondary Standard Dosimetry for clinical applications. The diagnostic beams were generated using Exradin A4 reference ion chamber and PTW electrometer. The ambient temperature and pressure were noted for KTP correction. The detectors designed for RQR showed good performance in RQT beams and vice versa. The detectors designed for RQR-M displayed high energy dependency in other diagnostic beams. The type of diagnostic beam quality determines the response of semiconductor detectors. Therefore, a detector should be calibrated according to the beam qualities to be measured.

关键词： Semiconductor Detectors Optimization of Protection Calibration Patient Dose Diagnostic Radiology

Neutrino astronomy： An update

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Frontiers of physics 2013年第6期8卷 759-770页

作者： francis Halzen Wisconsin IceCube Particle Astrophysics Center (WIPAC) and Department of Physics University of Wisconsin Madison WI 53706 USA

Detecting neutrinos associated with the still enigmatic sources of cosmic rays has reached a new watershed with the completion of IceCube, the first detector with sensitivity to the anticipated fluxes. In this review, we will briefly revisit the rationale for constructing kilometer-scale neutrino detectors and summarize the status of the field.

关键词： neutrinos cosmic rays astrophysics