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Modelling of Electrical Conductivity of a Silver Plasma at Low Temperature

Plasma Science and Technology 2016年第8期18卷 812-820页

作者： Pascal ANDRE William BUSSIERE Alain COULBOIS jean-louis gelet David ROCHETTE Université Clermont Auvergne LAEPT MERSEN 15 rue Jacques de Vaucanson

During the working of electrical fuses, inside the fuse element the silver ribbon first begins to melt, to vaporize and then a fuse arc appears between the two separated parts of the element. Second, the electrodes are struck and the burn-back phenomenon takes place. Usually, the silver ribbon is enclosed inside a cavity filled with silica sand. During the vaporization of the fuse element, one can consider that the volume is fixed so that the pressure increase appears to reach pressures higher than atmospheric pressure. Thus, in this paper two pressures, 1 atm and 10 atm, are considered. The electrical field inside the plasma can reach high values since the distance between the cathode surface and the anode surface varies with time. That is to say from zero cm to one cm order. So we consider various electrical fields： 102 V/m, 103 V/m, 5×103 V/m, 104 V/m at atmospheric pressure and 105 V/m at a pressure of 10 atm. This study is made in heavy species temperature range from 2,400 K to 10,000 K. To study the plasma created inside the electric fuse, we first need to determine some characteristics in order to justify some hypotheses. That is to say： are the classical approximations of the thermal plasmas physics justified？ In other words： plasma frequency, the ideality of the plasma, the Debye-Hückel approximation and the drift velocity versus thermal velocity. These characteristics and assumptions are discussed and commented on in this paper. Then, an evaluation of non-thermal equilibrium versus considered electrical fields is given. Finally, considering the high mobility of electrons, we evaluate the electrical conductivities.

关键词： electrical conductivity silver fuses non-ideal plasma Debye-Hiickelapproximation drift velocity thermal velocity thermal non-equilibrium electrical fields

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Scanning transmission electron microscopy and atom probe tomography analysis of non-stoichiometry long-period-stacking-ordered structures in Mg-Ni-Y/Sm alloys

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Journal of Magnesium and Alloys 2024年第3期12卷 954-965页

作者： Yimeng Chen Manuel Legrée jean-louis Bobet Alexander Kvit CAMECA Instruments Inc MadisonWI 53711USA ICMCB Universitéde BordeauxPessacCEDEX 33608France NIAC&Materials Science Department University of WisconsinMadisonWI 53706USA

The long-period-stacking-ordered(LPSO)structure affects the mechanical,corrosion and hydrolysis properties of Mg *** current work employs high angle annular dark field-scanning transmission electron microscopy(HAADF-STEM)and atom probe tomography(APT)to investigate the structural and local chemical information of LPSO phases formed in Mg-Ni-Y/Sm ternary alloys after extended isothermal *** on the alloying elements and their concentrations,Mg-Ni-Y/Sm develops a two-phase LPSO+α-Mg structure in which the LPSO phase contains defects,hybrid LPSO structure,and Mg ***-STEM and APT indicate non-stoichiometric LPSO with incomplete Ni_(6)(Y/Sm)_(8) *** addition,the APT quantitatively determines the local composition of LPSO and confirms the presence of Ni within the Mg bonding *** results provide insight into a better understanding of the structure and hydrolysis properties of LPSO-Mg alloys.

关键词： Magnesium alloys Long-range ordering Atom probe tomography(APT) STEM HAADF Hydrolysis properties.

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Joint Management of Shared Resources, Issues and Conflicts of the Nso and Oku Tribes in the Ngongbaa Montane Forest Area, NWR of Cameroon

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Natural Resources 2024年第6期15卷 149-172页

作者： jean-louis Tatah Elvis Kah Department of Geography Faculty of Arts Letters and Social Sciences University of Yaounde I Yaounde Cameroon School of Geology and Mining Engineering University of Ngaoundere Ngaoundere Cameroon

Wherever people live together in or near homelands that harbour joint natural resources such as forest, water, minerals, oil etc., they must collaborate, co-exist and share these resources irrespective of their genetic, social, cultural, and political peculiarities. This is not always the case when self-interest, ethnic divisions, elitist politics, economic interest and power tussle set in. The Nso and Oku people who reside in the Ngongbaa Forest area constitute an example of joint management of resources where at one period, their relationship over the management of the Oku Mountain Forest was cordial and at another, the relationship became conflictive. This study was designed to study the influence of the KIFP forest management policies on the Nso indigenous forest Management system in Ngongbaa Forest, and its implications. The data collected for the study was secured through the administration of a questionnaire to residents of 10 villages adjacent to the Ngongbaa Forest, and forest users who carried out livelihood activities there between 1963 and 2015. These forest user groups include beekeepers, rat trappers, grazers, mushroom gatherers, ground honey/tree honey harvesters, carvers, etc. The investigation also extended to the traditional leaders of Nso and Oku who are in charge of the land tenure systems. The findings show that the Oku Mountain Forest is jointly owned by the Nso and Oku people. The Nso own the eastern half of the forest known as Ngongbaa Forest while the Oku own the western half, known as the Kilum Forest. The cordial relationship that existed between these people ensured the conservation of the forest. But the conflicts that later set in, especially due to the creation of the Kilum Mountain Forest Project in 1987 later changed to the Kilum Ijim Forest Project (KIFP) in 1992 sidelined the local communities which was contrary to the dispositions of the new Cameroon forest law enacted in 1994. Thus, the indigenous conservation practices became ig

关键词： Conflict Joint Management Shared Resources Ngongbaa Kilum Conservation

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Statistical Study of the Geoeffectivity of Halo Coronal Mass Ejections Associated with X-Class Flares during Solar Cycles 23 and 24

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Open Journal of Applied Sciences 2024年第4期14卷 950-960页

作者： Younoussa Diakite Christian Zoundi M’Bi Kabore jean louis Zerbo Laboratoire de Chimie Analytique de Physique Spatiale et Energ&#233tique (L@CAPSE) Physics Department Universit&#233 Norbert Zongo Koudougou Burkina Faso Laboratoire de Maté riaux d&#8217H&#233liophysique et Environnement (LAMHE) Physics Department Universit&#233 Nazi Boni Bobo-Dioulasso Burkina Faso

By analysing a long series of data (1996-2019), we show that solar cycle 23 was more marked by violent solar flares and coronal mass ejections (CMEs) compared to solar cycle 24. In particular, the halo coronal mass ejections associated with X-class flares appear to be among the most energetic events in solar activity given the size of the flares, the speed of the CMEs and the intense geomagnetic storms they produce. Out of eighty-six (86) X-class halo CMEs, thirty-seven (37) or 43% are highly geoeffective;twenty-four (24) or approximately 28% are moderately geoeffective and twenty-five (25) or 29% are not geoeffective. Over the two solar cycles (1996 to 2019), 71% of storms were geoeffective and 29% were not. For solar cycle 23, about 78% of storms were geoeffective, while for solar cycle 24, about 56% were geoeffective. For the statistical study based on speed, 85 halo CMEs associated with X-class flares were selected because the CME of 6 December 2006 has no recorded speed value. For both solar cycles, 75.29% of the halo CMEs associated with X-class flares have a speed greater than 1000 km/s. The study showed that 42.18% of halo (X) CMEs with speeds above 1000 km/s could cause intense geomagnetic disturbances. These results show the contribution (in terms of speed) of each class of halo (X) CMEs to the perturbation of the Earth’s magnetic field. Coronal mass ejections then become one of the key indicators of solar activity, especially as they affect the Earth.

关键词： CME Halo (X) Geoeffectivity Geomagnetic Storm Solar Flare Solar Cycle

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Experimental Assessment of the Thermal Performance of Two Corrugated Metal Roofs

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Open Journal of Applied Sciences 2024年第9期14卷 2374-2392页

作者： Kouamé jean-louis Kouakou Ekoun Paul Magloire Koffi Bi Tra Désiré Zinla Prosper Gbaha Laboratoire des Procds Industriels de Synthse de lEnvironnement et des Energies Nouvelles Institut National Polytechnique Felix Houphout-Boigny Yamoussoukro Cte dIvoire

This experimental study is a contribution to the search for solutions to reduce indoor heat gain through sheet metal roofing in hot weather. It has evaluated the thermal impact of two different sheet metal roofs inside of two identical test buildings in sunny weather and cloudy weather conditions. Test building 1 has a single sheet corrugated roof and the building 2 is covered with roof made from top to bottom with corrugated sheet metal, a 12 mm thick serpentine copper tube in which water is circulated, a sheet of aluminium foil acting as a heat reflector, a 4 cm thick polystyrene panel and a 1.5 cm thick plywood. A maximum reduction of 15.1˚C in the temperature of the inner face of the test Building 2 roof was obtained comparatively to the temperature of the inner face of the test Building 1 roof consisting of a single sheet of metal at the warmest hours. In addition, the simple corrugated sheet metal roof of the test building generates high and varied temperatures inside the building. Whereas the proposed heat recovery roof favours low and relatively uniform temperatures inside the building. The proposed sheet metal roof construction technique is very effective in reducing the heat gain through the roof considerably;thus improving the thermal comfort inside sheet metal roofed dwellings. Hot water has been produced by recovering heat from the metal sheet of the roof of test building 2. The temperature of the hot water produced reached of 39˚C. This study could be also an alternative for the reduction of energy consumption due to the use of mechanical means for cooling of sheet metal roofed houses and the reduction of the use of fossil fuels for domestic hot water production.

关键词： Metal Roof Corrugated Time Lag Decrement Factor

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Interpretation of Geological and Gravity Data from the Bamiléké Plateau (West-Cameroon): Implication for the Understanding of Its Underground Lithotectonic Geometry

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Journal of Geoscience and Environment Protection 2024年第9期12卷 283-314页

作者： louis Christian Kamgang Chendjou jean Victor Kenfack Jules Tcheumenak Kouémo Fidèle Koumetio Armand Kagou Dongmo Department of Earth Sciences Faculty of Science University of Dschang Dschang Cameroon Department of Earth Sciences Faculty of Sciences University of Douala Douala Cameroon Department of Physics Faculty of Sciences University of Dschang Dschang Cameroon

The Bamiléké Plateau represents a key domain in the understanding of the geodynamics associated with the central Cameroon shear. The study aimed to highlight the subsurface architecture of the plateaus basement setting with focus on high potential areas for hydrogeological and mining development projects. To this end, geological field observations were carried out. Since the structures sought were near-surface, a separation approach based on the upward continuation method was applied to the Bouguer anomaly grid. A set of processing techniques, including vertical derivative or DZ, analytical signal or SA and categorization of gravity signatures, was applied to generate the residual map. The synthesis geological model, obtained from analysis and interpretation of the various transformed maps and 2.5D modeling of two gravity profiles P1 and P2 highlights the following features: 1) intrusions of steep-sided granitic batholiths from Dschang to Bandjoun (profile P1), increasing in width from NW (Dschang) to SE (Bandjoun);2) larger volume batholiths with moderate sides located at Bafang and Bangangté (profile P1). These plutonic massifs were weakened by brittle deformation, which favored the emplacement of phonolite or anorthosite dykes within them. The emplacement of these dykes was accompanied by compressional faults with high dip between Dschang and Bandjoun and extensional faults with medium dip between Bafang and Bangangté. These fault zones (trending N85E to N95E) are ideal for hydrogeological investigations in a basement setting, as well as a series of dyke networks that could potentially be preferred zones for the circulation and accumulation of useful substances. The resulting geological sections P1 and P2 highlight the influence of granitic intrusions in the geological system of the study area, as well as the structural control associated with the various dyke intrusions. All the models obtained can serve as fundamental references for hydrogeological and mining e

关键词： Bamiléké Plateau Gravity Measurement Gravity Anomalies Lineaments

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Lateral ring compression test applied to a small caliber steel jacket:Identification of a constitutive model

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Defence Technology（防务技术） 2024年第6期36卷 133-148页

作者： Yann Coget Yael Demarty Christophe Czarnota Anthony Bracq jean-Sebastien Brest Alexis Rusinek French-German Research Institute of Saint-louis 5 Rue Du General Cassagnou68300 Saint-LouisFrance Laboratoire d'Etude des Microstructures et de Mecanique des Materiaux(LEM3) CNRSUniversite de LorraineArts&Metiers ParisTechF-57000 MetzFrance

The evolution of threats and scenarios requires continuous performance improvements of ballistic protections for armed *** a modeling point of view,it is necessary to use sufficiently precise material behavior models to accurately describe the phenomena observed during the impact of a projectile on a protective *** this context,the goal of this paper is to characterize the behavior of a small caliber steel jacket by combining experimental and numerical *** experimental method is based on the lateral compression of ring specimens directly machined from the thin and small *** speeds and temperatures are considered in a quasi-static regime in order to reveal the strain rate and temperature dependencies of the tested *** Finite Element Updating Method(FEMU)is *** results are coupled with an inverse optimization method and a finite element numerical model in order to determine the parameters of a constitutive model representative of the jacket *** of the present model are verified against experimental results and a parametric study as well as a discussion on the identified material parameters are *** results indicate that the strain hardening parameter can be neglected and the behavior of the thin steel jacket can be described by a modeling without strain hardening sensitivity.

关键词： Full metal jacket ammunition Lateral ring compression Inverse identification Numerical simulation

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Emoti-Shing: Detecting Vishing Attacks by Learning Emotion Dynamics through Hidden Markov Models

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Journal of Intelligent Learning Systems and Applications 2024年第3期16卷 274-315页

作者： Virgile Simé Nyassi Franklin Tchakounté Blaise Omer Yenké Duplex Elvis Houpa Danga Magnuss Dufe Ngoran jean louis Kedieng Ebongue Fendji Department of Mathematics and Computer Science Faculty of Science University of Ngaoundr Ngaoundr Cameroon Department of Computer Engineering University Institute of Technology University of Ngaoundr Ngaoundr Cameroon

This study examines vishing, a form of social engineering scam using voice communication to deceive individuals into revealing sensitive information or losing money. With the rise of smartphone usage, people are more susceptible to vishing attacks. The proposed Emoti-Shing model analyzes potential victims’ emotions using Hidden Markov Models to track vishing scams by examining the emotional content of phone call audio conversations. This approach aims to detect vishing scams using biological features of humans, specifically emotions, which cannot be easily masked or spoofed. Experimental results on 30 generated emotions indicate the potential for increased vishing scam detection through this approach.

关键词： Social Engineering Hidden Markov Model Vishing Voice Mining

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Molecular Characterization of Gastrointestinal Stromal Tumors (Gist) and Contribution of Immunohistochemistry in Congolese from Kinshasa

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Open Journal of Gastroenterology 2024年第4期14卷 109-116页

作者： Rive Lukuaku Jérémie Okumadi Fabrice Bokambandja Andy Mbangama Vincent Mbatu Georges Mvumbi jean-louis Mumbere David Azako Serge Pezo Dieudonné Mvumbi Faculty of Medicine Bel Campus Technological University Kinshasa DR Congo Department of Anatomy and Pathological Cytology University Clinics of Kinshasa Kinshasa DR Congo Department of Gyneco-Obstetrics University Clinics of Kinshasa Kinshasa DR Congo Molecular Biology Department Faculty of Medicine University of Kinshasa Kinshasa DR Congo Institute of Medical Immunology Free University of Brussels Ixelles Belgium

Introduction: The differentiation of digestive tumors very often requires the use of techniques currently not widely in use in the Democratic Republic of Congo (DRC), such as immunohistochemistry. This is perfectly verified for GISTs whose precise, or at least highly certain, diagnosis can only be made using immunohistochemical markers. This underuse of these techniques due to lack of equipment and human skills explains the limited epidemiological data available to date, thus leading to untargeted and too often late treatment of patients. Research question: What contribution can immunohistochemical markers make to the diagnosis of digestive tract tumours? Objective: Discuss the contribution of immunohistochemical markers in the diagnosis of GIST and provide basic data on the epidemiology of these nosological entities in Kinshasa. Methodology: This was a retrospective study carried out at the LEBOMA private anatomy and pathological cytology centre. The main inclusion criterion was any digestive tract block or slide whose diagnosis of GIST had been requalified after review by at least 2 pathologists. An immuhistochemical study was performed using an automated technique (with a Ventana XT machine) using a panel of antibodies: CD-117 and DOG-1 which are listed in the literature as strongly correlated with the occurrence of GIST, all slides were made at Hj Hospital using an OLYMPUS BX41 co-observation microscope. Results: Of 601 cases of digestive tumors recorded during the concerned period, 32 (5.32%) concerned GIST. This prevalence was confirmed by our immunohistochemical results where the expression of CD117 and that of DOG-1 were positive in 90.6% and 100% of cases which prevalence is high compared with the worldwide prevalence according to the literature, respectively. The distribution of the patients concerned was made with a sex ratio of 1.6 women/men with a median age of 53 years. Most cases (81%) had a gastric location and were fusiform GISTs. Conclusion: Gastro

关键词： Digestive Tumors GIST Immunohistochemistry CD117 DOG-1

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Phytochemical Analysis and Antioxidant Activity of Aqueous and Hydroethanolic Extracts from Three Anticancerous Fabaceae of Northern Cameroon Pharmacopoeia

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Journal of Biosciences and Medicines 2024年第6期12卷 19-32页

作者： Halmata Mohamadou Landry Lienou Lienou Richard Simo Tagne Herve Pabamé Kada Elisee Libert Enyengue Embolo Grace Kembaou Nganwa jean louis Oyono Essame Piere Michel Dongmo Jazet Anatomy and Cytology Pathology Laboratory Institute of Medical Research and Medicinal Plants Studies (IMPM) Yaound Cameroon Department of Biochemistry Faculty of Science University of Douala Douala Cameroon Department of Biomedical Sciences University of Ngaoundere Ngaoundere Cameroon General Hospital of Garoua (HGG) Garoua Cameroon Anatomo-Cytopathology Department of Biological Sciences Faculty of Medicine and Pharmacy University of Douala Douala Cameroon

Background: Cancer continues to pose a significant threat to our society, representing one of the most pressing health concerns worldwide. This study aimed to evaluate the chemical composition and the antioxidant activity of aqueous and hydroethanolic extracts from Acacia nilotica (An), Bauhinia reticulate (Br), and Tamarindus indica (Ti) of Fabaceae family, traditionally used in Northern Cameroon for cancer treatment. Methods: The phytochemical screening of the three plants was conducted using conventional colorimetric methods, followed by the measurement of total phenol content, flavonoids, and tannins. The antiradical and antioxidant activities of both plant extracts were assessed through FRAP, ABTS, and DPPH methods. A principal components analysis was employed to correlate the quantities of the evaluated secondary metabolites with the activities. Results: Both types of extracts from the three plants contain alkaloids, saponins, flavonoids, phenolic compounds, tannins, glycosides, terpenoids, coumarins, anthocyanins, and anthraquinones. The aqueous extracts of Br and An are significantly richer (p Conclusion: The three Fabaceae plants from northern Cameroon, prepared in different solvents, can be utilized for their antiradical properties in cancer treatment.

关键词： Cancer Antioxidant Fabaceae Phenolic Compounds Aqueous Extract Hydroethanolic Extract

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