The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Hyo Jin Seo - One of the best experts on this subject based on the ideXlab platform.
-
photoluminescence and time resolved luminescence spectroscopy of novel naba4 bo3 3 tb3 phosphor
ChemInform, 2011Co-Authors: Xinmin Zhang, Zhi Zhang, Hyo Jin SeoAbstract:The title phosphor is synthesized by solid state reaction of Na2CO3, BaCO3, H3BO3, and Tb4O7 (CO atmosphere, 700 °C, 12 h).
-
photoluminescence and time resolved luminescence spectroscopy of novel naba4 bo3 3 tb3 phosphor
Journal of Alloys and Compounds, 2011Co-Authors: Xinmin Zhang, Zhi Zhang, Hyo Jin SeoAbstract:Abstract This paper reports the photoluminescence (PL) properties of Tb 3+ in NaBa 4 (BO 3 ) 3 , as well as the time-resolved luminescence properties. The PL excitation spectrum exhibits intense f → f transition absorption; the PL emission spectrum shows the strongest 5 D 4 → 7 F 5 emission at 540 nm. The relative intensity of 5 D 3 emission is much weaker than that of 5 D 4 emission even in the samples with lower Tb 3+ concentration. The 5 D 3 → 5 D 4 cross-relaxation produces a marked increase in the 5 D 3 decay rate with increasing Tb 3+ concentrations and introduces a non-exponential component into the initial part of the decay. The dipole–dipole interaction is found to be responsible for the cross-relaxation. The decay curves of 5 D 4 → 7 F 5 transition exhibit an initial rise phenomenon. The two exponential fitting indicates that the initial slow rise is attributed to the 5 D 3 → 5 D 4 cross-relaxation process.
Vietkinh Nguyen - One of the best experts on this subject based on the ideXlab platform.
-
pairwise error probability of distributed space time coding employing alamouti scheme in wireless relays networks
International Symposium on Communications and Information Technologies, 2009Co-Authors: Trung Q Duong, Ngoctien Nguyen, Trang Hoang, Vietkinh NguyenAbstract:In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes, in which the source and the relay generate Alamouti space-time code in a distributed fashion. We restrict our attention to the space-time code construction for Protocol III in Nabar et al. (IEEE Journal on Selected Areas Communications 22(6): 1099-1109, 2004). In particular, we derive two closed-form approximations for PEP when the relay is either close to the destination or source and an upper bound for any position of the relay. Using the alternative definition of Q-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.
-
exact pairwise error probability of distributed space time coding in wireless relays networks
International Symposium on Communications and Information Technologies, 2007Co-Authors: Trung Q Duong, Ngoctien Nguyen, Vietkinh NguyenAbstract:In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes employing Alamouti scheme. We restrict our attention to the space-time code construction for Protocol III in the work of Nabar et al. (2004). In particular, we derive two exact closed-form expressions for PEP when the relay is either close to the source or destination. Using the alternative definition of Q-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.
Xinmin Zhang - One of the best experts on this subject based on the ideXlab platform.
-
photoluminescence and time resolved luminescence spectroscopy of novel naba4 bo3 3 tb3 phosphor
ChemInform, 2011Co-Authors: Xinmin Zhang, Zhi Zhang, Hyo Jin SeoAbstract:The title phosphor is synthesized by solid state reaction of Na2CO3, BaCO3, H3BO3, and Tb4O7 (CO atmosphere, 700 °C, 12 h).
-
photoluminescence and time resolved luminescence spectroscopy of novel naba4 bo3 3 tb3 phosphor
Journal of Alloys and Compounds, 2011Co-Authors: Xinmin Zhang, Zhi Zhang, Hyo Jin SeoAbstract:Abstract This paper reports the photoluminescence (PL) properties of Tb 3+ in NaBa 4 (BO 3 ) 3 , as well as the time-resolved luminescence properties. The PL excitation spectrum exhibits intense f → f transition absorption; the PL emission spectrum shows the strongest 5 D 4 → 7 F 5 emission at 540 nm. The relative intensity of 5 D 3 emission is much weaker than that of 5 D 4 emission even in the samples with lower Tb 3+ concentration. The 5 D 3 → 5 D 4 cross-relaxation produces a marked increase in the 5 D 3 decay rate with increasing Tb 3+ concentrations and introduces a non-exponential component into the initial part of the decay. The dipole–dipole interaction is found to be responsible for the cross-relaxation. The decay curves of 5 D 4 → 7 F 5 transition exhibit an initial rise phenomenon. The two exponential fitting indicates that the initial slow rise is attributed to the 5 D 3 → 5 D 4 cross-relaxation process.
Gavin Hilson - One of the best experts on this subject based on the ideXlab platform.
-
poverty traps in small scale mining communities the case of sub saharan africa
Canadian Journal of Development Studies, 2012Co-Authors: Gavin HilsonAbstract:This article critically reflects on why, in many rural stretches of sub-Saharan Africa, scores of people engage in artisanal and small-scale mining (ASM) activity – low-tech, labour-intensive mineral extraction – for lengthy periods of time. It argues that a large share of the region's ASM operators have mounting debts which prevent them from pursuing alternative, less arduous, employment. The article concludes with an analysis of findings from research carried out by the author in Talensi-Nabdam District, Northern Ghana, which captures the essence of the poverty trap now plaguing so many ASM communities in sub-Saharan Africa. Resume Ce travail reflete de facon critique sur les activites d'extraction artisanale dans les regions rurales de l'Afrique subsaharienne – de type traditionnel et rigoureux pendant des periodes de longue duree. Il est constate que la plupart de ces participants possedent une si grande dette qu'elle les entrave a poursuivre d'autres formes d'emploi moins rigoureuses. Ce travail conc...
-
can microcredit services alleviate hardship in african small scale mining communities
World Development, 2011Co-Authors: Gavin Hilson, Abigail AckahbaidooAbstract:Summary This paper critically examines the challenges with implementing microcredit services for small-scale mine operators--individuals engaged in labor-intensive mineral extraction and/or processing using low-tech methods--in sub-Saharan Africa. The region's policymakers have shied away from launching microcredit programs for small-scale mining, frustrated by the disappointing results of the past and unsure about how to proceed with implementation. Recent efforts to provide microcredit services for operators in Talensi-Nabdam District, Northern Ghana, however, illustrate how with a renewed level of commitment and the development of blueprints which adequately address the appropriate criteria, fairly robust schemes can be launched.
-
child labour in african artisanal mining communities experiences from northern ghana
Development and Change, 2010Co-Authors: Gavin HilsonAbstract:The issue of child labour in the artisanal and small-scale mining (ASM) economy is attracting significant attention worldwide. This article critically examines this ‘problem’ in the context of sub-Saharan Africa, where a lack of formal sector employment opportunities and/or the need to provide financial support to their impoverished families has led tens of thousands of children to take up work in this industry. The article begins by engaging with the main debates on child labour in an attempt to explain why young boys and girls elect to pursue arduous work in ASM camps across the region. The remainder of the article uses the Ghana experience to further articulate the challenges associated with eradicating child labour at ASM camps, drawing upon recent fieldwork undertaken in Talensi-Nabdam District, Upper East Region. Overall, the issue of child labour in African ASM communities has been diagnosed far too superficially, and until donor agencies and host governments fully come to grips with the underlying causes of the poverty responsible for its existence, it will continue to burgeon.
Trung Q Duong - One of the best experts on this subject based on the ideXlab platform.
-
pairwise error probability of distributed space time coding employing alamouti scheme in wireless relays networks
International Symposium on Communications and Information Technologies, 2009Co-Authors: Trung Q Duong, Ngoctien Nguyen, Trang Hoang, Vietkinh NguyenAbstract:In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes, in which the source and the relay generate Alamouti space-time code in a distributed fashion. We restrict our attention to the space-time code construction for Protocol III in Nabar et al. (IEEE Journal on Selected Areas Communications 22(6): 1099-1109, 2004). In particular, we derive two closed-form approximations for PEP when the relay is either close to the destination or source and an upper bound for any position of the relay. Using the alternative definition of Q-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.
-
exact pairwise error probability of distributed space time coding in wireless relays networks
International Symposium on Communications and Information Technologies, 2007Co-Authors: Trung Q Duong, Ngoctien Nguyen, Vietkinh NguyenAbstract:In this paper, we analyze the pairwise error probability (PEP) of distributed space-time codes employing Alamouti scheme. We restrict our attention to the space-time code construction for Protocol III in the work of Nabar et al. (2004). In particular, we derive two exact closed-form expressions for PEP when the relay is either close to the source or destination. Using the alternative definition of Q-function, we can express these PEPs in terms of finite integral whose integrand is composed of trigonometric functions. We further show that with only one relay assisted source-destination link, system still achieves diversity order of two, assuming single-antenna terminals. We also perform Monte-Carlo simulations to verify the analysis.
