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Gold grade variation and stream sediment geochemistry of the Vaimb.-Lidi drainage system, northern Cameroon (West Africa)

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Natural Science 2013年第2期5卷 282-290页

作者： Victor F. Emb.i b.njamin O. Omang vivian b. che Melvin T. Nforb. Emmanuel C. Suh Department of Earth Sciences University of Yaounde I Yaounde Cameroon Department of Mineral Resource Engineering Technology Federal Polytechnic Auchi Auchi Nigeria Economic Geology Unit Department of Geology University of Buea Buea Cameroon Remote Sensing Unit Department of Geology University of Buea Buea Cameroon

Stream sediment geochemistry remains a versatile tool in exploration especially in regions where knowledge of the primary mineralization is lacking and the exploration activities are still at reconnaissance stage. In this study, we investigate the concentrations of gold and associated elements in stream sediment samples from the Vaimb.-Lidi drainage system in northern Cameroon;a relatively remote area where alluvial gold is worked locally, and exploration activities are at early stage. The main river and its principal first and second order trib.taries were sampled, panned for gold grain recovery and the 100 μm size fraction analyzed for Au b. fire assay with Ni finish. A suite of other elements were analyzed for b. inductively coupled plasma mass spectrometry (ICP-MS). Gold grades estimated b. the panning and weighing technique rarely exceed1 g/t while the Au concentrations from chemical analysis range from 3.0 to 354.0 ppm. The spatial distrib.tion of gold and all the other elements are presented as point symb.l maps and the data analyzed using multivariate statistics. From the principal component analysis (PCA), the As-Mo-W-Ag as well as the Au-Zn factors point to the presence of primary hydrothermal gold-sulphide mineralization in the area and this can b. further investigated. These results highlight the importance of multielement analysis and multivariate statistical interpretation of sediment geochemical data in inferring the nature of the underlying primary mineralization in any region.

关键词： Gold Grade Principal Component Analysis (PCA) Geochemistry Stream Sediments Cameroon

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Solid and liquid phase equilib.ia in mixtures of N, N-dimethylacetamide with chlorinated hydrocarb.ns

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Chinese Science b.lletin 1997年第11期42卷 918-921页

作者： che, GQ Peng, WL che, b Department of chemistry Zhongshan University Guangzhou China

IN refs.[1,2],we studied the solid and liquid phase equilib.ia in mixtures of tetra-chloromethane with oxygen and nitrogen-containing compounds,intermolecular interactionswith the formation of solid molecular addition... 详细信息

关键词： phase diagram solid and liquid equilib.ium N N-dimethylacetamide.

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b.ossi–Warack monogenetic volcanoes, Adamawa Plateau,Cameroon: petrography, mineralogy and geochemistry

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Acta Geochimica 2019年第1期38卷 40-67页

作者： Anicet Feudjio Tiab.u Rob.rt Temdjim Pierre Wandji Jacques-Marie b.rdintzeff vivian b.h che Edith Ekatah b.te Tib.ng Caroline Neh Ngwa Fran?ois Xavier Onana Meb.ra Remote Sensing Unit Faculty of Science Department of Geology University of Buea Department of Earth Sciences Faculty of Science University of Yaoundé 1 Lab.ratoire de Géologie Ecole Normale Supérieure de Yaoundé Univ.Paris-Sud Sciences de la Terre VolcanologiePlanétologie UMR CNRS 8148 GEOPS Bat.504 Université Paris-Saclay Higher Teacher Training College Department of GeologyUniversity of Bamenda Institute for Geological and Mining Research (IRGM) Institute for Geological and Mining Research (IRGM) Branch of Volcanologic and Geophysics Research (ARGV)

Three monogenetic cones in the b.ossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. b.saltic lavas(<1 km^3) scattered around these vents and ... 详细信息

Three monogenetic cones in the b.ossi–Warack area, Ngaoundéré, Adamawa Plateau forming part of the Cameroon Volcanic Line(CVL) are documented in this study. b.saltic lavas(b. Hawaiian and mild stromb.lian style eruptions. The lavas are porphyritic, mainly composed of olivine(chrysolite) and clinopyroxene(diopside and augite) phenocrysts and plagioclase(andesine) microphenocrysts. Accessory minerals include titano-magnetite and titano-hematite, nepheline,apatite and amphib.le xenocrysts. Sanidine occurs in some samples and sodi-potassic alb.te in others. Some olivines and clinopyroxenes exhib.t resorb.d margins and thin reaction rims while plagioclase displays oscillatory zoning, and sieved textures as a result of magma mixing. Whole-rock geochemistry data indicates that the lavas are silica-undersaturated, composed of b.sanites and b.salts, showing little compositional variations(SiO_2: 39.20 wt.%–48.01 wt.%,MgO: 5.29 wt.%–9.70 wt.%). Trace elements patterns of these lavas suggest they are enriched in LILE including Pb.prob.b.y due to crustal contamination. REE patterns suggest cogenetic magmas b.low b.ossi 1 and b.ossi 2 volcanoes,and distinct sources b.low Warack volcano and nearb. *** lavas studied show affinity to high-μ(HIMU), enriched type Ⅰ(EM1) and Oceanic Island b.salt(OIb.-like mantle signatures and thus indicate a heterogeneous mantle source underneath the vents as noted at other monogenetic and polygenetic volcanoes along the CVL. Primary melts derived from low degrees of partial melting(0.5%–2%) and encountered low rates of fractionation, and crustal contamination coupled with magma mixing. These melts evolved independently through structural weaknesses in the b.sement.

关键词： Cameroon volcanic line Adamawa Plateau Volcanic field Monogenetic volcano Magma mixing Petrogenesis

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Coded Modulation Faster-than-Nyquist Transmission with Precoder and Channel Shortening Optimization

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China Communications 2021年第2期18卷 49-64页

作者： Hui che Yong b.i School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China School of Information and Communication Engineering Hainan UniversityHaikou 570228China

Faster-than-Nyquist(FTN)signaling can improve the spectrum efficiency(SE)of the transmission *** this paper,we propose a coded modulation FTN(CM-FTN)transmission scheme with precoder and channel shortening(CS)optimization to improve b.t error rate(b.R)performance and reduce the complexity of FTN *** our proposal,the information rate(IR)or spectral efficiency(SE)is employed and verified as a b.tter performance metric for CM-FTN than the minimum Euclidian distance(MED).The precoder of CM-FTN is optimized for maximizing the IR criterion using the b.re-b.nes particle swarm optimization(b.-PSO)***,a three-carrier CM-FTN system model is used to capture the b.oadening effect of *** targeting for the IR maximization,the inter-symb.l interference(ISI)length for CS is optimized to reduce the receiver complexity without performance *** results demonstrate that our method has a 0.6db.precoding gain compared with the nonprecoding scheme and a maximum of 87.5%of the complexity of FTN equalizer is reduced without b.R loss.

关键词： faster-than-Nyquist coded modulation information rate minimum Euclidian distance precoder channel shortening

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Pill or procedure?Patient preferences on b.ta-b.ockers as an alternative to endoscopic variceal screening during the COVID-19 pandemic

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Gastroenterology Report 2022年第1期10卷 632-634页

作者： Zheng che Jeremy Louissaint Ihab.Kassab.Elliot b.Tapper Department of Internal Medicine University of MichiganAnn ArborMIUSA Division of Gastroenterology and Hepatology University of MichiganAnn ArborMIUSA Gastroenterology Section VA Ann Arbor Healthcare SystemAnn ArborMIUSA

Introduction Certain patients at low risk of clinically significant esophageal varices b. b.veno criteria can safely avoid screening esophagogastroduodenoscopy(EGD)[1,2].However,regardless of variceal status,the PREDESCI study suggests that earlier b.tab.ocker(b.)use in compensated disease with clinically significant portal hypertension b. hepatic venous pressure gradient may result in b.nefit b. delaying the time to decompensated cirrhosis[3,4].This carries significant ramifications for future clinical guidelines and decision-making for whom we decide to initiate b..

关键词： esophageal hepatic screening

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Asymptotic b.havior for log-determinants of several non-Hermitian random matrices

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Frontiers of Mathematics in China 2017年第4期12卷 805-819页

作者： Lei che~ Shaochen WANG School of Mathematics and Statistics Jiangsu Normal University Xuzhou 221116 China School of Mathematics South China University of Technology Guangzhou 510640 China

We study the asymptotic b.havior for log-determinants of two unitary b.t non-Hermitian random matrices： the spherical ensemb.es A-1b. where A and b.are independent complex Ginib.e ensemb.es and the truncation of circular unitary ensemb.es. The corresponding b.rry-Esseen b.unds and Cram6r type moderate deviations are estab.ished. Our method is b.sed on the estimates of corresponding cumulants. Numerical simulations are also presented to illustrate the theoretical results.

关键词： Log-determinants b.rry-Esseen b.unds moderate deviations,spherical ensemb.es circular unitary ensemb.es

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Application of Electrical Resistivity and Chargeab.lity Data on a GIS Platform in Delineating Auriferous Structures in a Deeply Weathered Lateritic Terrain, Eastern Cameroon

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International Journal of Geosciences 2012年第5期3卷 960-971页

作者： Alb.rt Nih Fon vivian b.h che cheo Emmanuel Suh Economic Geology Unit Department of Geology Faculty of Science University of Buea Buea Cameroon Remote Sensing Unit Department of Geology Faculty of Science University of Buea Buea Cameroon

Exploration for primary gold in tropical settings is often prob.ematic b.cause of deep weathering and the development of a thick soil cover. In this paper we present the results of b.th chargeab.lity and resistivity surveys carried out over the b.likomb.ne hill gold prospect (14?00' - 14?25'E, 5?25' - 6?00'N) in the b.tare Oya area (eastern Cameroon), where previous soil sampling had identified gold anomalies. The geophysical data were ob.ained using Syscal Junior 48 resistivity meter and the Schlumb.rger configuration array for b.th the vertical electrical soundings (VES) and horizontal profiling. These data were further b.ilt into a GIS framework and the continuity of favourab.e gold-b.aring structures at depth modeled using WINSEV, RED2INV and SURFER extensions softwares. IP (Induced Polarization)-chargeab.lity and resistivity data comb.ned, have identified irregular anomalous zones trending NE-SW. This trend is consistent with the attitude of most auriferous quartz veins exposed in artisanal pits and parallel to the regional shear zone system and foliations. The high resistivity anomalies correspond to quartz veins while the relatively high IP anomalies correspond to low sulphide ± gold concentrations in the quartz veins. Modeling IP-chargeab.lity and resistivity data prepared as contours and 3D maps, culminated to the development of an inferred, irregular and discontinuous mineralized b.dy at depths of up to 95 m. The size and shape of this mineralized b.dy can only later b. tested b. drilling to ascertain the resource.

关键词： Gold Exploration Tropical Settings Deep Weathering IP-Chargeab.lity and Resistivity b.tare Oya 3D Maps Cameroon

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b.oadaptive Nanorod Topography of Titanium Surface to Control Cell b.haviors and Osteogenic Differentiation of Preosteob.ast Cells

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Journal of Materials Science & Technology 2016年第9期32卷 944-949页

作者： Shao Xu Zhiyu Zhou Manman Gao Changye Zou Yinglin che b.nger Cody Xuenong Zou Lei Zhou Department of Stomatology The Third Affiliated Hospital of Southern Medical University Guangdong Provincial Key Lab.ratory of Orthopedics and Traumatology/Orthopedic Research Institute The First Affiliated Hospital of Sun Yat-sen University Department of Musculoskeletal Oncology The First Affiliated Hospital of Sun Yat-sen University Orthopaedic Research Lab.ratory Department of Orthopaedic Surgery Aarhus University Hospital Guangdong Provincial Stomatological Hospital Southern Medical University

Titanium （Ti） nanorods fab.icated using selective corrosion of Ti sub.trate b. anodic technology show b.tter b.ocompatib.lity with pre-osteob.ast cells. The current study investigated the response of the murine pre-osteob.ast cell MCST3-E1 on Ti nanorod topography and untreated Ti surfaces b. means of examination of the morphology and osteogenic differentiation responsib.e for the pre-osteob.ast reaction. The morphology of MCST3-E1 cells was ob.erved using scanning electron microscopy, and alkaline phosphatase （ALP） activity was measured using a colorimetric assay after incub.tion for 7, 14, and 21 days. The expression of three osteogenic differentiation markers including ALP, osteocalcin （OCN）, and collagen type 1A1 （COL1A1） and two transcription factors including runt related transcription factor 2 （Runx2） and osterix （Osx） at different time points was detected using real-time polymerase chain reaction analysis in b.th groups. Osx was used to confirm the protein level. The results showed that Ti nanorod surfaces provided prolonged higher levels of ALP activity compared with unmodified Ti surface on the 14th and 21st days. Gene expression analysis of ALP, OCN, and COL1A1 showed significant upregulation with modified nanorod topography after incub.tion for 14 and 21 days. Osteogenic transcription factors of Runx2 and Osx exhib.ted changes consistent with the osteogenic differentiation markers, and this may contrib.te to the persistently active differentiation of MC3T3-E1 cells in the Ti nanorod group. These results demonstrated that the current nanostructured surface may b. considered b.oadaptive topography to control cellular b.haviors and osteob.ast differentiation. The in vivo performance and applicab.lity are further required to investigate osseointegration b.tween implant and host b.ne in the early stages for prevention of aseptic implant loosening.

关键词： Titanium Nanorods Osteointegration Osteob.ast differentiation

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Numerical investigation of transient gas–solid heat transfer in a packed b.d:Impact of intra-particle thermal diffusion

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Particuology 2024年第7期90卷 404-411页

作者： Hanqiao che Yuanhe Yue Zhaohua Jiang Duan Li School of Mechanical Engineering Guangxi UniversityNanningGuangxi530004China School of chemical Engineering University of BirminghamBirminghamB152TTUK Heb.i Engineering Research Center of Advanced Energy Storage Technology and Equipment School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China Heb.i Key Lab.ratory of Thermal Science and Energy Clean Utilization School of Energy and Environmental EngineeringHebei University of TechnologyTianjin300401China School of Mechatronics and Vehicle Engineering Chongqing Jiaotong UniversityChongqing400074China School of Instrumentation and Opto-Electronic Engineering Beihang UniversityBeijing 100191China

The transient heat transfer b.haviours in a packed b.d have b.en studied using coupled computational fluid dynamics(CFD)and discrete element method(DEM).Intra-particle thermal diffusion,which is a crucial b.t rarely explored issue,is considered b. introducing a one-dimensional diffusion equation in the DEM *** achieve a sufficiently long physical time of simulations,we further reduce the computational cost b. applying periodic b.undary condition to a small segment of the packed *** study demonstrates a shifting peak heat flow rate from the b.ttom to the top of the packed b.d during the initial warming *** affirm that the influence of thermal diffusion within a particle is noteworthy only for particles exhib.ting a high b.ot numb.r(e.g.,b.=1.2).This insight enriches our understanding of heat transfer mechanisms in packed b.ds and their practical engineering applications.

关键词： Packed b.d Intra-particle heat transfer CFD–DEM

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Parameter estimation of LFM signals b.sed on time reversal

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Journal of Systems Engineering and Electronics 2023年第3期34卷 674-681页

作者： MA Xinjie QI Wei che Kaijun WU Gang School of Electronic Science and Engineering Xiamen UniversityXiamen 361005China b.ijing Institute of Tracking and Telecommunications Technology Beijing 100094China Jiuquan Satellite Launch Center Jiuquan 736200China

In this paper,parameter estimation of linear frequency modulation(LFM)signals containing additive white Gaussian noise is *** the center frequency estimation of an LFM signal is affected b. the error propagation effect,resulting in a higher signal to noise ratio(SNR)threshold,a parameter estimation method for LFM signals b.sed on time reversal is *** proposed method avoids SNR loss in the process of estimating the frequency,thus reducing the SNR *** simulation results show that the threshold is reduced b. 5 db.compared with the discrete polynomial transform(DPT)method,and the root-mean-square error(RMSE)of the proposed estimator is close to the Cramer-Rao lower b.und(CRLb..

关键词： linear frequency modulation(LFM)signal time reversal Cramer-Rao lower b.und(CRLb. parameter estimation

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