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Alexander Iheanyichukwu Opara,Casmir Zanders Akaolisa,Chigozie Osita Akakuru,Amarachi Udoka Nkwoada,Francis Chizoruo Ibe,Andrew Wirnkor Verla,Ikechukwu Chigozie Chukwuemeka 환경독성보건학회 2021 환경독성보건학회지 Vol.36 No.4
Numerous particulates are released from the dumpsites in Owerri metropolis and later dispersed to other areas in the environment where they cause adverse health challenges to the inhabitants. To analyze the PM concentrations, field measurements were carried out at seven major dumpsites in Owerri Metropolis. Estimates of the possible health risks as the result of exposure to airborne particulate matter (PM2.5, PM10, etc.) were performed using the United States Environmental Protection Agency (USEPA) human health risk assessment framework. A scenario assessment approach in which normal exposure and worst-case scenario were adopted for acute and chronic exposure periods for infants, children, and adults were carried out. The concentrations of PM2.5 which ranged from 122.30-501.76 μg/m³ at the dumpsites exceeded the WHO 24 hr annual mean maximum exposure limit. The Nigerian National Ambient Air Quality Standard allowable limit for PM10 was exceeded by most of the dumpsites. Hazard quotient > 1 was exceeded for PM 2.5 by nearly all dumpsites and is therefore likely to cause health challenges to people in the vicinity of the dumpsites. The results showed that under monthly conditions, both PM2.5 and PM10 concentration levels at the dumpsites have the potential to cause adverse health effects for infants, children, and adults on acute or chronic bases. Actions should be taken to regulate such PM exposure and to raise public awareness for the inhabitants of the affected areas. In conclusion, regular monitoring is therefore recommended to decrease the ambient particulate matter (PM) concentrations in the study area.
Hong Seong-Su,E. Zanders 여수대학교 1994 論文集 Vol.8 No.-
수질의 부영양화를 방지하기 위하여 폐수증의 질소 및 인은 반드시 제거되어야 한다. 질소의 제거는 질화 및 탈질화에 의하여 가능하며 이 두가지 공정에서 요구되는 조건은 전혀 다르지만, 만약 폐수증의 질소를 최적속도로 제거하고자 하면 이 두공정을 꼭 적용시켜야만 한다. 단속주입법은 활성슬러지법의 폭기조에서 연속적으로 질화 및 탈질화가 가능하다. 실험실적 활성슬러지 처리공정으로 질소를 60g-N/MLSSㆍd까지 주입하여 95%의 질소제거율을 얻었다. 대부분의 현재 운용되고 있는 일단하수처리공정에 단속주입법을 적용하면 상대적으로 간단한 방법에 의해 질소의 제거가 가능하였다.
Jihong Park,Seong-Lyun Kim,Zander, Jens IEEE 2016 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.15 No.6
<P>The forthcoming 5G cellular network is expected to overlay millimeter-wave (mmW) transmissions with the incumbent micro-wave (mu W) architecture. The overall mm-mu Wresource management should, therefore, harmonize with each other. This paper aims at maximizing the overall downlink (DL) rate with a minimum uplink (UL) rate constraint, and concludes: mmWtends to focus more on DL transmissions while mu W has high priority for complementing UL, under time-division duplex (TDD) mmW operations. Such UL dedication of mu W results from the limited use of mmW UL bandwidth due to excessive power consumption and/or high peak-to-average power ratio (PAPR) at mobile users. To further relieve this UL bottleneck, we propose mmW UL decoupling that allows each legacy mu Wbase station (BS) to receive mmW signals. Its impact on mm-mu W resource management is provided in a tractable way by virtue of a novel closed-form mm-mu W spectral efficiency (SE) derivation. In an ultra-dense cellular network (UDN), our derivation verifies mmW (or mu W) SE is a logarithmic function of BS-to-user density ratio. This strikingly simple yet practically valid analysis is enabled by exploiting stochastic geometry in conjunction with real three-dimensional (3-D) building blockage statistics in Seoul, South Korea.</P>
Cross-Layer Resource Allocation Model for Cellular-Relaying Network Performance Evaluation
Timus, B.,Soldati, P.,Dongwoo Kim,Zander, J. IEEE 2011 IEEE Transactions on Vehicular Technology VT Vol.60 No.6
<P>The enhancement of cellular networks with relaying technologies is expected to bring significant technoeconomic benefits at the expense of more complex resource allocation. Suitable models for solving network dimensioning problems in cellular-relaying networks must handle radio resource allocation among hundreds of links and tackle interactions between networking layers. For this purpose, we propose a novel cross-layer resource allocation model based on average interference and ideal rate adaptation for the physical layer (PHY), time shares for the medium access layer, and fluid flows for the transport and network layers. We formulate a centralized social welfare maximization problem. When the routes are selected with an a priori algorithm, we show that the resource allocation problem admits an equivalent convex formulation. We show a numerical example for how to use the proposed framework for configuring the backhaul link in a practical relaying network. The overall problem of selecting routes and allocating time shares and link rates is nonconvex. We propose an iterative suboptimal algorithm to solve the problem based on a novel approximation of PHY. We state and prove several convergence properties of the algorithm and show that it typically outperforms routing based on signal-to-noise ratio only.</P>
Pilot power adjustment for saving transmit power in pilot channel assisted DS-CDMA mobile systems
Young-Keum Song,Dongwoo Kim,Zander, J. IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.2
<P>In DS-CDMA systems coherent detection is usually adopted by adding or multiplexing redundant pilot signals with voice or data traffic. The pilot signals need additional transmit power but, at the same time, decrease the power used for traffic channel through facilitating channel estimation, which reduces the bit energy-to-noise density ratio (E<SUB>b</SUB>/N<SUB>o</SUB>) required for delivering the traffic signals. The interdependency between pilot and traffic channel powers has been analyzed in various studies, but has not yet been exploited in existing power control methods. In this letter, we provide a method of using the interdependency to adjuIn DS-CDMA systems coherent detection is usually adopted by adding or multiplexing redundant pilot signals with voice or data traffic. The pilot signals need additional transmit power but, at the same time, decrease the power used for traffic channel through facilitating channel estimation, which reduces the bit energy-to-noise density ratio (E<SUB>b</SUB>/N<SUB>o</SUB>) required for delivering the traffic signals. The interdependency between pilot and traffic channel powers has been analyzed in various studies, but has not yet been exploited in existing power control methods. In this letter, we provide a method of using the interdependency to adjust pilot power in the context of the existing power control algorithms, and prove its convergence and that it reduces the total transmit power.st pilot power in the context of the existing power control algorithms, and prove its convergence and that it reduces the total transmit power.</P>
Impact of open-loop power controlled feedback on multiuser capacity in Rayleigh fading channels
Eun-Hee Shin,Dongwoo Kim,Zander, J. IEEE 2009 IEEE communications letters Vol.13 No.12
<P>This letter investigates the impact of open-loop power control (OLPC) employed in uplink (UL) feedback channel on the multiuser downlink (DL) capacity. OLPC is used to reduce the capacity loss caused by the feedback outage. Assuming flat Rayleigh channels correlated between DL and UL, we provide probability distributions on the DL SNR that are successfully fed back through UL managed by OLPC. Numerical results are used to verify the accuracy of the analysis and to show the impact of relevant parameters of OLPC on the capacity as a function of DL-UL correlation.</P>
Temporal Spectrum Sharing Based on Primary User Activity Prediction
Ki Won Sung,Seong-Lyun Kim,Zander, Jens IEEE 2010 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.9 No.12
<P>In this paper we investigate the opportunistic spectrum access in temporal domain where a secondary user shares a radio channel with a primary user during the OFF period of the primary user. We consider practical ON/OFF traffic models whose bursty natures are not properly described by a Markovian assumption. An optimal strategy to determine the transmission power of the secondary user is proposed, which can be adapted to any source traffic model of the primary user. This strategy will maximize the spectrum utilization of the secondary user while keeping interference violations to the primary user below a threshold. Numerical results show that the transmission power of the secondary user depends on the probability distribution of the primary traffic as well as the elapsed time of the OFF period.</P>