• 한국정보통신학회논문지
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• 제26권11호
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• pp.1672-1678
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• 2022

본 논문에서는 28GHz 대역의 5G 이동 통신 중계용 혼 안테나의 방사 패턴, 반사손실 등의 성능을 고려하여 중계용 안테나를 설계하였다. 안테나 소자를 위상 배열하여 5G 이동통신 중계기용 혼 Array를 설계하고 성능을 분석하였다. 밀리미터파 대역 통신에서는 기존의 WCDMA(3G), LTE(4G)와 달리 송수신 간의 높은 경로 손실이 발생한다. 5G 밀리미터파 혼 안테나 설계에서는 안테나의 이득, 대역폭뿐만 아니라, 안테나 소자 간 격리도, 이득 등의 안테나 성능을 추가로 고려해야 한다. 28GHz 대역의 단일 혼 안테나(1×1)와 배열 혼 안테나(2×4)의 안테나 이득은 각각 약 10.44dBi와 19.58dBi, 반사손실도 -18dB 이하의 특성을 되도록 설계하여 측정 결과로부터 구현의 타당함을 입증하였고, 5G 이동 통신 중계 시스템에 응용에 적합함을 보였다.

• Animal Bioscience
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• 제37권7호
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• pp.1213-1224
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• 2024

Objective: Enterotypes (ETs) are the clustering of gut microbial community structures, which could serve as indicators of growth performance and carcass traits. However, ETs have been sparsely investigated in waterfowl. The objective of this study was to identify the ileal ETs and explore the correlation of the ETs with growth performance and carcass traits in Muscovy ducks. Methods: A total of 200 Muscovy ducks were randomly selected from a population of 5,000 ducks at 70-day old, weighed and slaughtered. The growth performance and carcass traits, including body weight, dressed weight and evidenced weight, dressed percentage, percentage of apparent yield, breast muscle weight, leg muscle weight, percentage of leg muscle and percentage of breast muscle, were determined. The contents of ileum were collected for the isolation of DNA and 16S rRNA gene sequencing. The ETs were identified based on the 16S rRNA gene sequencing data and the correlation of the ETs with growth performance and carcass traits was performed by Spearman correlation analysis. Results: Three ETs (ET1, ET2, and ET3) were observed in the ileal microbiota of Muscovy ducks with significant differences in number of features and α-diversity among these ETs (p<0.05). Streptococcus, Candida Arthritis, and Bacteroidetes were the presentative genus in ET1 to ET3, respectively. Correlation analysis revealed that Lactococcus and Bradyrhizobium were significantly correlated with percentage of eviscerated yield and leg muscle weight (p<0.05) while ETs were found to have a close association with percentage of eviscerated yield, leg muscle weight, and percentage of leg muscle in Muscovy ducks. However, the growth performance of ducks with different ETs did not show significant difference (p>0.05). Lactococcus were found to be significantly correlated with leg muscle weight, dressed weight, and percentage of eviscerated yield. Conclusion: Our findings revealed a substantial variation in carcass traits associated with ETs in Muscovy ducks. It is implied that ETs might have the potential to serve as a valuable biomarker for assessing duck carcass traits. It would provide novel insights into the interaction of gut microbiota with growth performance and carcass traits of ducks.

• 한국지반공학회논문집
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• 제30권9호
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• pp.57-66
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• 2014

동토지역에서는 계절변화에 상관없이 항시 영하상태로 동결되어 있는 영구동토층과, 그 위로 동결융해가 반복되는 활동층으로 구성되어있다. 일반적으로 대기온도 변화에 따라 동결융해가 반복되는 활동층은 얼음과 물의 상변화 작용이 반복되기 때문에 지반의 융기현상과 침하현상, 그리고 영구동토층의 온도상승을 초래할 수 있다. 열사이펀이란 구조체 내부에 충전된 냉매의 자가적인 열순환을 이용하여 지반의 온도를 영하상태로 제어하는 지반 안정화 공법 중 하나이다. 열사이펀은 대기중에 냉매의 열을 방출하는 응축부와 지중에 열을 흡수하는 증발부로 구성되어 있으며 대기의 온도가 영하의 상태일 때 지반의 온도를 영하상태로 제어한다. 본 연구에서는 열사이펀의 지반 열전달성능을 분석하기 위해 모형지반에 단열재를 배치하여 열사이펀을 통한 지반동결실험을 수행하였다. 단열재의 열차단성 및 열사이펀 길이를 고려하여 단열재 및 열사이펀의 성능실험을 수행하였으며, 실험에서 얻어진 물성치를 상용수치해석 프로그램인 TEMP/W에 반영하였다. 본 연구에서 제시된 실내실험과 수치해석 방법을 통해 열사이펀의 열성능을 산정할 수 있었다.

• Journal of Microbiology and Biotechnology
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• 제3권2호
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• pp.95-98
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• 1993

This study was carried out to isolate and characterize the mutant strains of Schwanniomyces castellii NRRL Y-2477. Mutants were prepared with the treatment of ethyl methane sulfonate. 2-deoxy-D-glucose resistant mutants were isolated and two mutants were selected based on their high production of amylolytic enzymes and their ability to ferment starch. The mutants selected had higher a-amylase and glucoamylase activities than the wild type strain from several other carbon sources. Especially, it was revealed that mutant strain M-9, when cultured in the presence of glucose as a sole carbon source, shows relatively high activities of a-amylase and glucoamylase compared to those of the wild type strain. In result, this mutant strain can be considered as a constitutive producer of amylolytic enzymes. To compare the ethanol production ability of wild type strain and of mutant strains selected, an alcohol fermentation was carried out using 100 g/l soluble starch. Mutant strain M-9 did not improve the direct alcohol fermentation of starch, despite its excellent amylolytic activities performance. On the other hand, mutant strain M-6 produced 37.9 g/l (4.8%, v/v) ethanol by utilizing about 82% of substrate.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.1073-1081
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• 2008

A centrifugal turbo blower of the fuel cell electric vehicle (FCEV) operates at very high speed above 30000 rpm in order to increase the pressure of the air, which supplied to a stack of FCEV, using rotation of its impeller blades. Vibration which originated from the blower is generated by unbalance of mechanical components, rotation of bearings and rotating asymmetry that rotate at high speed. The vibration is transmitted to receiving structure through vibration isolators and it can causes serious problems in the noise, vibration and harshness(NVH) performance. Thus, the study about reducing this kind of vibration is an important task. In this paper, dynamic analysis of the blower executed by numerical simulation and experimental analysis of the blower is also performed. Then, measured and simulated results are compared in order to validate of the simulation. Finally, reducing vibration through modifying mount stiffness is the main purpose of this paper.

• 한국CDE학회논문집
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• 제17권2호
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• pp.97-110
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• 2012

High performance sensors and modern data logging technology with real-time telemetry facilitate system fault diagnosis in a very precise manner. Fault detection, isolation and identification in fault diagnosis systems are typical steps to analyze the root cause of failures. This systematic failure analysis provides not only useful clues to rectify the abnormal behaviors of a system, but also key information to redesign the current system for retrofit. The main barriers to effective failure analysis are: (i) the gathered data (event) logs are too large in general, and further (ii) they usually contain noise and redundant data that make precise analysis difficult. This paper therefore applies suitable pre-processing techniques to data reduction and feature extraction, and then converts the reduced data log into a new format of event sequence information. Finally the event sequence information is decoded to investigate the correlation between specific event patterns and various system faults. The efficiency of the developed pre-filtering procedure is examined with a terminal box data log of a marine diesel engine.

• Smart Structures and Systems
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• 제20권1호
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• pp.23-33
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• 2017

Variable Curvature Friction Pendulum (VCFP) bearing is one of the alternatives to control excessive induced responses of isolated structures subjected to near-fault ground motions. The curvature of sliding surface in this isolator is varying with displacement and its function is non-spherical. Selecting the most appropriate function for the sliding surface depends on the design objectives and ground motion characteristics. To date, few polynomial functions have been experimentally tested for VCFP however it needs comprehensive parametric study to find out which one provides the most effective behavior. Herein, seismic performance of the isolated structure mounted on VCFP is investigated with two different polynomial functions of the sliding surface (Order 4 and 6). By variation of the constants in these functions through changing design parameters, 120 cases of isolators are evaluated and the most proper function is explored to minimize floor acceleration and/or isolator displacement under different hazard levels. Beside representing the desire sliding surface with adaptive behavior, it was shown that the polynomial function with order 6 has least possible floor acceleration under seven near-field ground motions in different levels.

• Advances in aircraft and spacecraft science
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• 제4권1호
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• pp.53-64
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• 2017

Aerospace Launch Vehicles (ALV) are generally designed with high reliability to operate in complete security through fault avoidance practices. However, in spite of such precaution, fault occurring is inevitable. Hence, there is a requirement for on-board fault recovery without significant degradation in the ALV performance. The present study develops an advanced fault recovery strategy to improve the reliability of an Aerospace Launch Vehicle (ALV) navigation system. The proposed strategy contains fault detection features and can reconfigure the system against common faults in the ALV navigation system. For this purpose, fault recovery system is constructed to detect and reconfigure normal navigation faults based on the sliding mode observer (SMO) theory. In the face of pitch channel sensor failure, the original gyro faults are reconstructed using SMO theory and by correcting the faulty measurement, the pitch-rate gyroscope output is constructed to provide fault tolerant navigation solution. The novel aspect of the paper is employing SMO as an online tuning of analytical fault recovery solution against unforeseen variations due to its hardware/software property. In this regard, a nonlinear model of the ALV is simulated using specific navigation failures and the results verified the feasibility of the proposed system. Simulation results and sensitivity analysis show that the proposed techniques can produce more effective estimation results than those of the previous techniques, against sensor failures.

• 한국식품과학회지
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• 제36권4호
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• pp.643-647
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• 2004

땅콩껍질에 함유된 항미생물 활성물질의 탐색을 위해 땅콩껍질을 MeOH로 추출하고 이 MeOH 추출물을 용매분획하여 EtOAc 중성획분을 얻었다. 이 획분에 함유된 항미생물 활성물질을 silica gel adsorption column chromatography, Sephadex LH-20 column chromatography, ODS column chromatography로 정제한 다음 HPLC를 이용하여 1종의 화합물을 단리하였다. $^1H-NMR$, MS 및 NOESY 분석에 의해 땅콩껍질로부터 분리된 항미생물 활성물질은 pratensein으로 동정되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제8권2호
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• pp.221-230
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• 2004

본 논문에서는 지진하중 작용시, 점탄성 감쇠기 및 면진장치를 설치한 다층 철골 모멘트 저항 골조의 동적응답을 해석적으로 규명하였다. 본 연구의 목적은 구조해석을 수행하여 최대 층간변위 및 최대응력법에 의해 효율적인 점탄성 감쇠기의 위치를 결정하는 것이다. 또한, 효율적인 진동 제어방법을 모색하기 위하여 점탄성 감쇠기 및 납삽입고무베어링형 면진장치에 의한 제어효과를 부재력, 조합응력, 그리고 구조물의 고유주기 등을 이용하여 상호 비교 분석하였다.