• Environmental Engineering Research
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• 제22권4호
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• pp.339-346
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• 2017

The objective of this study is the evaluation of the performance of a large-scale respirometer (LSR) of 17.7 L in the determination of the methane generation rate constant (k) values. To achieve this objective, a comparison between anaerobic (GB21) and LSR tests was conducted. The data were modeled using a linear function, and the resulting correlation coefficient ($R^2$) of the linear regression is 0.91. This result shows that despite the aerobic conditions, the biodegradability values that were obtained from the LSR test produced results that are similar to those from the GB21 test. In this respect, the LSR test can be an indicator of the anaerobic biodegradability for landfill waste. In addition, the results show the high repeatability of the tests with an average coefficient of variance (CV) that is lower than 10%; furthermore, the CV for the LSR is lower than that of the GB21, which indicates that the LSR-test method could provide a better representation of waste samples. Therefore, the LSR method allows for both the prediction of the long-term biodegradation potential in a shorter length of time and the reduction of the sampling errors that are caused by the heterogeneity of waste samples. The k values are $0.156y^{-1}$ and $0.127y^{-1}$ for the cumulative biogas production (GB21) and the cumulative oxygen uptake for the LSR, respectively.

• Wind and Structures
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• 제20권4호
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• pp.579-607
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• 2015

A Combination Random Flow Generation (CRFG) technique for obtaining the fluctuating inflow boundary conditions for Large Eddy Simulation (LES) is proposed. The CRFG technique was developed by combining the typical RFG technique with a novel calculation of k and ${\varepsilon}$ to estimate the length- and time-scales (l, ${\tau}$) of the target fluctuating turbulence field used as the inflow boundary conditions. Through comparatively analyzing the CRFG technique and other existing numerical/experimental results, the CRFG technique was verified for the generation of turbulent wind velocity fields with prescribed turbulent statistics. Using the turbulent velocity fluctuations generated by the CRFG technique, a series of LESs were conducted to investigate the wind flow around S-, R-, L- and U-shaped building models. As the pressures of the models were also measured in wind tunnel tests, the validity of the LES, and the effectiveness of the inflow boundary generated by the CRFG techniques were evaluated through comparing the simulation results to the wind tunnel measurements. The comparison showed that the LES accurately and reliably simulates the wind-induced pressure distributions on the building surfaces, which indirectly validates the CRFG technique in generating realistic fluctuating wind velocities for use in the LES. In addition to the pressure distribution, the LES results were investigated in terms of wind velocity profiles around the building models to reveal the wind flow dynamics around bluff bodies. The LES results quantitatively showed the decay of the bluff body influence when the flow moves away from the building model.

• 한국항공우주학회지
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• 제34권6호
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• pp.59-66
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• 2006

액체 로켓엔진에서의 고주파 연소불안정 제어를 위한 수동 안정화 제어 기구로 음향공을 적용하여 감쇠 효과의 적합성을 검증하였다. 우선, 기본형 모델링 연소실에서 발생한 유해 공진주파수는 음향공의 동조를 통하여 효과적으로 감쇠될 수 있음을 확인 하였다. 또한, 음향공의 기하학적 형상에 따른 음향 감쇠 효과를 비교하기 위하여, 주요 설계 변수를 변화시킨 몇 가지 음향공 모델에 대해 유해 공진주파수 감쇠 효과를 정량적으로 비교, 분석하였다. 선형음향해석과 실험적 방법 모두 만족할만한 일치성을 나타내었으며, 오리피스 입구 면적이 가장 크거나 오리피스 길이가 가장 짧은 경우에서 감쇠 효과가 가장 크게 나타났다. 결론적으로 음향공을 이용한 최적의 음향공 제어를 위해서는 음향공 부피를 고려한 최적의 음향공 설계가 절대적으로 필요함을 입증한다.

• 한국광학회지
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• 제17권2호
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• pp.149-158
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• 2006

가우스 괄호법을 이용한 굴절능 배치 방법과 등가렌즈 설계법으로 기존에 설계한 반도체와이어 본딩 검사용 다중배치 현미경 광학계에 대한 공차 분석을 하였다. 축상 대칭 공차인 곡률과 두께에 대한 공차는 회절 한계에 의한 초점심도 내에서 후방초점거리(BFL)가 변하도록 결정하였고, 축 비대칭 공차인 decenter와 tilt에 대한 공차는 0.7 field에서 공간주파수 50 lp/mm에서의 MTF(Modulation Transfer Function) 변화가 5% 이내가 되도록 시행착오 방법으로 정하였다. 이 결과 공차분포확률에 관계없이 MTF의 감소율이 5% 미만 되는 곳에 가장 많은 확률로 공차가 분포하므로 위와 같은 방법으로 공차를 부여하면 원하는 본 광학계의 결상 성능을 만족시킬 수 있음을 확인하였다.

• 농업과학연구
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• 제45권4호
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• pp.601-614
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• 2018

Chitosan with a natural antimicrobial property has been introduced to protect horticultural crops from diseases as an environmentally friendly method. The purpose of this study was to investigate the effects of the pre-harvest application of chitosan on growth and quality during the late stage of fruit development and on the simulated marketing of the peach fruit (Prunus persica L.). The application of chitosan with calcium chloride ($100mg{\cdot}L^{-1}$) three times at one week intervals 4 weeks before the harvest significantly increased the fruit weight, changed the fruit shape, and reduced the fruit length/diameter ratio giving the peach fruits a round oblate shape. The calcium treatment contributed to enhancing or maintaining the storage potential by increasing the flesh firmness. However, at higher concentrations of $CaCl_2$, i.e., > $600mg{\cdot}L^{-1}$, the positive effects of the chitosan application were offset, and fruit growth was not affected by calcium alone. The application of the chitosan/calcium mixture delayed fruit softening; however, this effect was shortened when the storage temperature was $20^{\circ}C$ rather than $15^{\circ}C$. The internal quality of the fruit was profoundly affected by the concentration of calcium added to the chitosan, and delayed fruit maturation was observed at a higher concentration of calcium. The pre-harvest application of chitosan with calcium contributes to the enhancement of food safety by inhibiting the occurrence of diseases during postharvest handling. Considering the above results, chitosan has the potential to improve both the yield of peach fruits and their storability. Because chitosan can enhance the freshness and shelf-life of fresh produce, it is necessary to examine its effects on other horticultural crops.

• Mycobiology
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• 제50권4호
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• pp.254-257
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• 2022

Wolfiporia cocos is a wood-decay brown rot fungus belonging to the family Polyporaceae. While the fungus grows, the sclerotium body of the strain, dubbed Bokryeong in Korean, is formed around the roots of conifer trees. The dried sclerotium has been widely used as a key component of many medicinal recipes in East Asia. Wolfiporia cocos strain KMCC03342 is the reference strain registered and maintained by the Korea Seed and Variety Service for commercial uses. Here, we present the first draft genome sequence of W. cocos KMCC03342 using a hybrid assembly technique combining both short- and long-read sequences. The genome has a total length of 55.5 Mb comprised of 343 contigs with N50 of 332 kb and 95.8% BUSCO completeness. The GC ratio was 52.2%. We predicted 14,296 protein-coding gene models based on ab initio gene prediction and evidence-based annotation procedure using RNAseq data. The annotated genome was predicted to have 19 terpene biosynthesis gene clusters, which was the same number as the previously sequenced W. cocos strain MD-104 genome but higher than Chinese W. cocos strains. The genome sequence and the predicted gene clusters allow us to study biosynthetic pathways for the active ingredients of W. cocos.

• 대한토목학회논문집
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• 제26권2A호
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• pp.371-382
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• 2006

사장교는 난류에 의해 불규칙한 진동을 일으키며 이 현상을 규명하기 위하여 버페팅해석을 수행한다. 버페팅해석을 위해서 는 구조적 변수, 공기역학적 변수, 그리고 구조물-바람 상호작용 효과를 고려하기 위한 공탄성 변수의 입력값을 적절히 선정해야 한다. 본 연구에서는 버페팅해석을 수행하기 위한 입력 변수 중 대표적 변수들에 대하여 변수연구를 수행함으로써 각 변수들이 해석 결과에 미칠 수 있는 민감도를 분석해 보고자 하였다. 풍동실험 자료가 가장 잘 구축되어 있는 서해대교를 대상교량으로 선정하였다. 검토 변수로서는 정적 삼분력계수의 기울기, 난류의 공간분포 상관관계감소계수, 조도길이, 변동풍속 스펙트럼, 구조감쇠율을 선정하였다. 검토결과 각 입력변수는 버페팅 응답에 미치는 영향이 큰 것으로 확인되었기 때문에 적정한 입력변수 선정의 중요성을 강조함과 동시에 일반적 결론 도출을 위하여 추후 연구가 필요함을 제시하였다.

• Steel and Composite Structures
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• 제51권1호
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

• 생물환경조절학회지
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• 제28권3호
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• pp.218-224
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• 2019

본 연구는 우리나라 대표 수출 포도 품종인 '캠벨얼리'를 대상으로 에틸렌작용억제제인 1-methylcylopropene(1-MCP)과 에틸렌생합성 저해 효과를 지닌 salicylic acid(SA)를 단독 혹은 병행처리하여 과실의 저장 및 유통환경에서 발생하는 탈립, 갈변 및 부패 등 생리장해의 발생과 과실 품질에 미치는 영향을 에틸렌 발생물질인 에테폰과 비교하여 검토하였다. 1-MCP 1,000ppb 훈증 처리 후 SA $25{\mu}M$을 살포 처리하고 $19^{\circ}C$에서 16일간 저장한 후 조사한 과립경도 및 산함량 수준은 단용처리에 비하여 높게 나타났다. 탈립률은 $100{\mu}L{\cdot}L^{-1}$ 에테폰 처리구 41.7%, SA 처리구 40.8%, 1-MCP 처리구 38.2%로 나타났으나 1-MCP 처리 후 SA를 처리한 경우는 18.7%로 탈립방지 효과가 월등하였다. 브러쉬의 길이를 측정한 결과, 에테폰 처리구는 1mm 미만의 비율이 74.3%로 매우 높게 나타났던 반면, 1-MCP 처리 후 SA를 처리한 경우는 2-4mm의 비율이 22.8%, 4-6mm 비율이 27.9%로 브러쉬 길이가 길게 조사되었다. 과축의 무게는 에테폰 처리구에서 2.3g으로 가장 낮아 감모율의 증가에 미치는 에틸렌의 영향과 1-MCP 및 SA의 감모 억제효과를 확인할 수 있었다. 또한 1-MCP와 SA는 저장 중 '캠벨얼리' 포도의 줄기갈변 억제 및 부패 경감에 일부 효과가 있음을 확인되어 추후 수출시 품질유지를 위한 기술 적용이 가능할 것으로 판단되었다.

• Nuclear Engineering and Technology
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• 제47권3호
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• pp.293-305
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• 2015

In this paper, we suggest the conceptual design of a water-cooled reactor system for a low-pressure inherent heat sink nuclear desalination plant (LIND) that applies the safety-related design concepts of high temperature gas-cooled reactors to a water-cooled reactor for inherent and passive safety features. Through a scoping analysis, we found that the current LIND design satisfied several essential thermal-hydraulic and neutronic design requirements. In a thermal-hydraulic analysis using an analytical method based on the Wooton-Epstein correlation, we checked the possibility of safely removing decay heat through the steel containment even if all the active safety systems failed. In a neutronic analysis using the Monte Carlo N-particle transport code, we estimated a cycle length of approximately 6 years under 200 $MW_{th}$ and 4.5% enrichment. The very long cycle length and simple safety features minimize the burdens from the operation, maintenance, and spent-fuel management, with a positive impact on the economic feasibility. Finally, because a nuclear reactor should not be directly coupled to a desalination system to prevent the leakage of radioactive material into the desalinated water, three types of intermediate systems were studied: a steam producing system, a hot water system, and an organic Rankine cycle system.