55,178 research outputs found
Ji-Su Kim
No full text학위논문(박사)--아주대학교 일반대학원 :전자공학과,2014. 8DoctoralThe current wireless networks with orthogonal frequency division multiple access (OFDMA) system gives us high speed wireless communication. With high speed, variety mobile services that have different traffic characteristics and requirements have been produced. However, the interference sensitivity of OFDMA system degrades performances of cell-edge users. In addition, the diversity of mobile services causes a channel quality asymmetry between a downlink and an uplink in OFDMA system. Unfortunately, conventional mobility management schemes have not taken account the channel quality asymmetry and the diversity of service traffic. Therefore, this dissertation presents advanced mobility schemes considering the channel quality asymmetry and the diversity of service traffic for improving service continuity and user-perceived performance.
The first proposed mobility scheme is a handover scheme considering downlink-uplink channel quality asymmetry. The proposed handover scheme determines an appropriate handover timing and handover direction according to an estimated uplink channel quality and a measured downlink channel quality. For exploiting an uplink channel quality in handover, an efficient uplink channel estimation method is also proposed. The proposed method estimates an uplink signal strength using the measured downlink signal strength and predicts an uplink interference on the basis of the interference-level information that is from neighbor base stations. To improve user-perceived performances, the proposed handover scheme adjusts weights of handover criteria according to service traffic pattern. Simulation results show that the proposed uplink estimation method can accurately compute the uplink channel quality of neighbor cells where the estimation error rate is less than 0.7%. The simulation results also show that the proposed handover scheme reduces handover-call-dropping probability by up to 69% compared to LTE-Advanced system and the proposed scheme outperforms previous studies in terms of throughput and mean opinion score (MOS). In addition, the end-to-end delay of the proposed scheme is better than that of LTE-Advanced system by 26%.
The second proposed mobility scheme is the user-centric mobility scheme that exploits multipath communication to support seamless mobility. For that, the service continuity management (SCM) protocol is newly designed. SCM has four functional blocks which are located between the application layer and the transport layer. SCM monitors quality of experience (QoE) and makes multiple sessions for one service using multiple radio adaptors in order to maintain QoE requirements. To improve the efficiency of the proposed multipath communication scheme, a high efficiency transport method is proposed. The proposed scheme sends identical packets over multiple paths to improve reliability; likewise, different packets are sent to improve throughput, simultaneously. The simulation results show that the user-centric mobility scheme enable a mobile device to reduce service interruptions during handover in heterogeneous networks. Numerical results indicate that the proposed transport scheme achieves the maximum transport control protocol (TCP) throughput when the proportion of same and different packets is adjusted according to link conditions
Su Youn Kim
No full text학위논문(석사)아주대학교 일반대학원 :의학과,2012. 2ABSTRACT
TABLE OF CONTENTS
LIST OF FIGURES
LIST OF TABLES
Ⅰ. INTRODUCTION
Ⅱ. STUDY POPULATION AND METHODS
A. Study Population
B. Method
1. Health Examination Survey
2. Definition of metabolic syndrome
C. Statistical analysis
Ⅲ. RESULT
A. Characteristics of the Study Population
B. AUC of Each Obesity Indicators for Metabolic
Syndrome
Ⅳ. DISCUSSION
Ⅴ. CONCLUSION
REFERENCE
국문요약MasterBackground: Recent studies have suggested that waist to height ratio (WHtR) is the better indicator to predict cardiovascular risk than body mass index (BMI) and waist circumference (WC). The aim of the study is to identify the best anthropometric index among obesity indicators that predicts metabolic syndrome (MS) in different gender and age groups.
Methods: This study is a cross-sectional survey of 6,160 subjects aged 19 years (yr) and over who participated in the Fourth Korea National Health and Nutrition Examination Surveys (KNHANES IV) between January 2008 and December 2008. To compare predictive power of anthropometric indices for MS, the areas under the receiver-operating characteristics curves (AUCs) of BMI, WC and WHtR were calculated.
Results: In entire age population, AUC of WHtR was the largest among obesity indicators to predict MS in both genders. However after adjustment for age, there was no significant difference among three obesity indicators in both men and women. When compared within three different age groups, there was no significant difference among three obesity indices for men and young aged women (19-39yr). AUC of WHtR and WC were similar with each other, but greater than AUC of BMI for middle-aged (40-60yr) and elderly (> 60yr) women.
Conclusion: There is no superiority among obesity indicators to predict MS in men and young women. BMI has less predicting power for MS in middle-aged and elderly women than WC and WHtR
Enhancement of hydrolysis efficiency and biogas production by treatment of secondary sludge with bacteriophage lysozymes
No full textAnaerobic digestion of secondary sludge from wastewater treatment plants can degrade sludge while producing methane that can be burned as bioenergy. Hydrolysis of secondary sludge is the first step in anaerobic digestion, but is the rate-limiting step. In this study, to speed hydrolysis of secondary sludge, lysozymes from bacteriophage species T4, T7 and λ were applied to batch tests. The volatile suspended solids were removed by lysozymes at efficiencies of 23.6–50.1 %. Use of the lysozymes increased the reaction coefficient of biogasification of volatile suspended solids by 0.4–1.0 d−1, regardless of the origin of sludge, or sources of lysozyme. The removal efficiency of volatile suspended solids and methane yield had significantly positive correlation (p < 0.001). Relative abundances of genera Simplicispira (10.3 → 5.2 %), Dokdonella (4.9 → 3.9 %), and Thermomonas (2.7 → 1.2 %) were high in original secondary sludge, and maintained relative abundance over other genera even after lysozyme treatment. To increase the ratio of microbes to organics, sludge samples from various sources were aerated and cultivated with 40 g/L glucose. In experiments on this cultivated sludge, Klebsiella (3.7 → 23.0 %) Kosakonia (1.8 → 19.0 %) and Dysgonomonas (0.0 → 15.3 %) sharply increased after lysozyme treatment, due to their fast growth. Treatment with bacteriophage lysozymes can significantly increase sludge reduction. © 202211Nsciescopu
Startup of Demo-Scale Anaerobic Digestion Plant Treating Food Waste Leachate: Process Instability and Recovery
No full textA demo-scale (600 m(3) working volume) anaerobic digester treating food waste leachate was monitored during its startup period. The operation strategy was adjusted twice (i.e., three distinct phases) during the operation to recover the process from instability. During the first phase, the organic loading rate (OLR) > 2.7 kg chemical oxygen demand (COD)/m(3)∙day corresponded to volatile fatty acid (VFA) accumulation along with a decreasing pH, resulting in the drop in biogas yield to 0.43 ± 0.9 m(3)/kg COD(in). During phase 2, fast recovery of this process was aimed at using a sequencing batch operation. One batch cycle (5 to 2 days) consisted of the combined drawing and feeding step (5 h), the reacting step (91 to 17 h), and the settling step (24 h). The duration of the reacting step was determined for each cycle such that (1) the biogas production ceased before the cycle end and (2) the residual VFA concentration was < 1 g/L. In total, 11 cycles were operated with a gradual increase in biogas yield to 0.55 m(3)/kg COD(in) with the absence of any sign of system disturbance. After phase 2, the digester was fed at the designed OLR of 4.1 ± 0.3 kg COD/m(3)∙day. The biogas yield was elevated to 0.58 ± 0.2 m(3)/kg COD(in) during phase 3 with the residual VFA concentration maintained at 2.2 ± 0.6 g/L. Methanogen populations, as determined by real-time PCR, did not change significantly throughout the period. These results imply that the adaptation of this process to the OLR of ca. 4 kg COD/m(3)∙day was not due to the increase in methanogen population but due to the elevation of its activity. Overall, this study suggests that the sequencing batch operation with adjustable cycle duration can be one successful recovery strategy for biogas plants under system instability
Effect of seed bacterial community and diversity on the carbohydrate degradation in anaerobic digestion
No full text1
Shift in methanogenic community in protein degradation using different inocula
No full textAnaerobic digestion (AD) of protein-rich wastes is problematic due to production of ammonia and hydrogen sulfide. In this work, eight inocula were used in batch AD of solutions of gelatin and gluten at 3 g COD substrate/ 1g VSS inoculum. AD plants from which inocula originated were treating food waste or food wastewater, wastewater sludge, or a combination of them. Inocula were evaluated by fitting methane production data using the modified Gompertz model. Sequencing of 16 s rRNA of microorganisms showed that Methanoculleus was dominant in inocula from plants that were treating food waste, and Methanosaeta was dominant in the others. The maximum methane production rate varied by a factor of three for each substrate: 2.734-7.438 mLCH4 gCOD1 d-1 for gelatin, and 1.950 to 5.532 mLCH4 gCOD-1 d-1 for gluten. This study demonstrates that inoculum must be chosen appropriately when treating proteinaceous waste by AD.11Nsciescopu
Kim In su
No full text학위논문(석사)--아주대학교 일반대학원 :건설교통공학과,2010. 2본 연구에서는 국내 램프 미터링 도입에 있어 기준을 설정하기 위한 과정중 하나로 램프 미터링 정지선의 위치 선정에 있어 변화 가능성을 검토하고자 한다. 이에 국외 지침들을 검토하여 설계지침들을 검토하고 미시적 시뮬레이션을 이용해 그 적정성을 파악하여 국내 실정에 맞춰 그 효과를 분석하였다.
시나리오를 선정하고 실험한 결과 전진 배치를 실시한 경우 하부도로의 속도가 증가하고 본선의 효과가 떨어지는 반면, 후진배치를 하는 경우에는 본선의 속도가 증가하고 하부도로의 효과가 떨어졌다. 전진 배치의 경우 문헌 고찰에서 전술하였던 대기행렬 관리 수단들과 더불어 병행 사용하게 될 시 램프미터링에 접속하는 대기행렬 차량들과 하부도로를 효과적인 관리가 가능하지만 본선에 악영향을 미치며, 후진 배치의 경우 본선 속도에 효과적인 것을 확인하였지만 하부도로에 좋지 않은 영향을 주게 된다. 이와 같이 본 연구는 국내에 없는 지침을 적용하고 정지선의 전∙후진 배치 요소를 통해 최적 레이아웃 설계가 가능하다는 것에 의의를 둘 수 있다.제 1 장 서 론
제 1 절 연구의 배경 및 목적
1.1 연구의 배경
1.2 연구의 목적
제 2 절 연구의 방법 및 범위
2.1 연구의 범위
2.2 연구의 방법
제 2 장 문헌고찰
제 1 절 램프 미터링의 개념
1.1 개념
1.2 중요성
제 2 절 국내외 관련 지침, 연구 고찰
2.1 국외 관련 지침, 연구 고찰
2.2 국내 관련 지침, 연구 고찰
2.3 램프미터링 시스템 기준 고찰
2.4 국내 램프미터링 시스템(RMS) 설치기준 제시안
2.5 문헌 검토 결과
제 3 장 미시적 시뮬레이션 분석
제 1 절 시뮬레이션 개요
1.1 개요
1.2 시뮬레이션 설정과 수행과정
제 2 절 예비 시나리오 분석
2.1 예비 시나리오 과정
2.2 예비 시나리오 결과
2.3 변수 설정
제 3 절 시나리오(1) 분석
3.1 시나리오 과정
3.2 시나리오(1) 결과
3.3 소결론
제 4 절 시나리오(2) 분석
4.1 시나리오 과정
4.2 시나리오(2) 결과
4.3 소결론
제 5 절 현장 적용 및 결과
5.1 현장 적용
5.2 적용 결과
제 4 장 결론 및 향후 연구 과제
제 1 절 결과 종합
1.1 결과 종합
1.2 의사 결정 과정의 활용
제 2 절 결론 및 향후 연구 과제
참고문헌Maste
Shift in bacterial diversity in acidogenesis of gelatin and gluten seeded with various anaerobic digester inocula
No full textThe aim of this study was to investigate divergence of bacteria degrading model proteins of food-processing wastewater. Gelatin and gluten were used as substrate to represent animal and plant proteins from food wastes, respectively. The inocula were obtained from eight full-scale anaerobic digestion reactors. Food-to-microorganism ratio was 3 g chemical oxygen demand equivalent of substrate per 1 g volatile suspended solids of inoculum. A first-order reaction model revealed reaction constants ranged 1.34 ≤ k ≤ 2.30 d−1 for gelatin and 0.63 ≤ k ≤ 1.69 d−1 for gluten. Metagenomic analysis of 16s rRNA sequences showed that dominant bacteria after gelatin degradation batch were different for each inocula. Klebsiella aerogenes, Hathewaya, Peptoclostridium, or Clostridium collagenovorans were most abundant. Klebsiella aerogenes was the most abundant species after gluten degradation for all inocula.11Nsciescopu
Monitoring microbial community structure and variations in a full-scale petroleum refinery wastewater treatment plant
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