• Wind and Structures
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• 제17권1호
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• pp.87-105
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• 2013

Modeling an equilibrium atmospheric boundary layer (ABL) in an empty computational domain has routinely been performed with the k-${\varepsilon}$ turbulence model. However, the research objects of structural wind engineering are bluff bodies, and the SST k-${\omega}$ turbulence model is more widely used in the numerical simulation of flow around bluff bodies than the k-${\varepsilon}$ turbulence model. Therefore, to simulate an equilibrium ABL based on the SST k-${\omega}$ turbulence model, the inlet profiles of the mean wind speed U, turbulence kinetic energy k, and specific dissipation rate ${\omega}$ are proposed, and the source terms for the U, k and ${\omega}$ are derived by satisfying their corresponding transport equations. Based on the proposed inlet profiles, numerical comparative studies with and without considering the source terms are carried out in an empty computational domain, and an actual numerical simulation with a trapezoidal hill is further conducted. It shows that when the source terms are considered, the profiles of U, k and ${\omega}$ are all maintained well along the empty computational domain and the accuracy of the actual numerical simulation is greatly improved. The present study could provide a new methodology for modeling the equilibrium ABL problem and for further CFD simulations with practical value.

• 품질경영학회지
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• 제47권1호
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• pp.97-108
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• 2019

Purpose: The purpose of this study is to propose a new Risk Priority Number(RPN) evaluation method which analyzes value of product functions by mining customer opinions in Social Network Service(SNS). Methods: A traditional RPN is measured by three evaluation standards (Severity, Occurrence, Detection) which are analyzed by manufacturing engineers and researchers. On the other hand, these standards are analyzed by customers' viewpoints through SNS opinion mining in this research. In order to extract customer feedbacks from textual data sets, the methodology in this paper implies natural language processing, hereby collecting product related data sets and analyzing the opinions automatically. An emotional polarity of an opinion indicates severity, while the number of negative opinion shows occurrence, and the entire number of customer opinion refers to detection. Results: The results of this study are as follows; As a result of the CRPN evaluation, it is confirmed that the features evaluated as risky are highly likely to be improved in the next series. Therefore, CRPN is an effective risk assessment model that reflects customer feedback. Conclusion: Reflecting customer feedback is a useful tool for risk assessment of the product as well as for developing new products and improving existing products.

• 대한화장품학회지
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• 제46권4호
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• pp.349-360
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• 2020

최근 피부 기능 개선과 관련한 다양한 가능성으로 인해 화장품 소재로서 수요가 높아지고 있는 인삼 유래 사포닌의 한 종류인 ginsenoside Rd를 위한 생물 전환 제조 기술을 확립하였다. 홍삼 사포닌(RGS)에 포함된 ginsenoside Rb1을 Rd로 전환하기 위하여 상업용 효소를 탐색하였고 그 중 Viscoflow MG가 가장 효율적인 것을 확인하였다. Ginsenoside Rd로의 전환에 영향을 주는 요인을 최적화하기 위하여 반응표면분석법(RSM)을 통하여 실험 조건을 설계하였다. 주요 독립변수는 RGS 농도, 효소 농도와 반응 시간이었고 Box-Behnken design (BBD) 모델설계법에 따라 선정된 17 가지 조건으로 ginsenoside Rd로 전환을 수행하고 최적화 조건을 분석하였다. 전환된 Ginsenoside Rd의 농도는 0.3113 g/L에서 최대 0.5277 g/L까지였고 RGS 2%, 효소 1.25%를 13.5 h 반응시킨 조건에서 가장 높은 생성량을 보였다. 결론적으로, ginsenoside Rd 생물전환의 독립변수인 RGS 농도, 효소 농도는 p-value가 0.05보다 작은 값으로 유의미한 값을 나타내었고 각 독립변수 사이의 교호작용 중에서는 효소 농도와 반응 시간 사이의 교호 작용이 가장 큰 영향력을 갖고 있음을 확인하였다.

• 한국전산구조공학회논문집
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• 제29권2호
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• pp.115-122
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• 2016

기존 건축물의 구조 안전성평가와 보수 보강 시에는 해당 건축물의 상태를 정확히 알기 위해 현장 또는 실험실에서의 실험을 수행하는 경우가 많고 최초설계 단계와 다르게 시공된 건축물의 실제 상태 등을 구조해석 모델에 반영하게 된다. 이 경우, 각종 실험값을 전통적인 통계학적 방법은 구조기술자가 지닌 경험과 지식은 구조모델링 및 해석에서 아무런 가치를 더 할 수가 없다. 본 논문은 현장 및 실험실에서 얻은 단순한 실험값을 구조기술자의 축적된 경험과 지식을 변수로 활용하여 보다 유효하게 구조해석 모델에 필요한 데이터로 개선하는 방법으로서 통계학적인 베이스 경신법을 이용한 안전성평가 방법에 대해 살펴보았다. 구조기술자의 적절한 판단이 변수로서 포함되면 적은 개수의 샘플 수로도 비교적 정확한 값의 최종 예측값을 산정할 수 있어 전통적인 통계학적 접근에 비해 보다 실제값에 근접한 예측값을 구할 수 있는 것을 확인하였다.

• 공업화학
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• 제29권5호
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• pp.565-570
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• 2018

본 연구에서는 초음파 용매추출공정을 이용하여 닥나무로부터 항산화성분을 추출하고, 중심합성계획모델을 이용하여 추출공정을 최적화하였다. 중심합성계획모델의 반응치로는 추출수율과 DPPH 라디칼소거활성을 설정하고, 독립변수인 추출시간, 주정/초순수 부피비, 초음파 조사세기에 따른 주효과도와 교호효과도를 해석하였다. 추출수율과 DPPH 라디칼소거활성 모두 계량인자의 주효과도와 교호효과도를 모두 고려하였을 때 가장 큰 영향을 미치는 인자는 주정/초순수 부피비이었다. 반응표면분석법을 이용하여 추출공정의 최적화과정을 수행한 결과 최적추출조건은 추출시간(19.92 min), 주정/초순수 부피비(54.23 vol%), 초음파 조사세기(557.65 W)로 나타났다. 이 조건으로부터 예상되는 반응치의 값은 추출수율(38.93 wt%), DPPH 라디칼소거활성(55.33%)으로 나타났다.

• Smart Structures and Systems
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• 제29권3호
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• pp.499-512
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• 2022

This work proposes a novel contactless vibration damping and thermal isolation tripod platform based on Superconducting Magnetic Levitation (SML). This prototype is suitable for cryogenic environments, where classical passive, semi active and active vibration isolation techniques may present tribological problems due to the low temperatures and/or cannot guarantee an enough thermal isolation. The levitating platform consists of a Superconducting Magnetic Levitation (SML) with inherent passive static stabilization. In addition, the use of Operational Modal Analysis (OMA) technique is proposed to characterize the transmissibility function from the baseplate to the platform. The OMA is based on the Stochastic Subspace Identification (SSI) by using the Expectation Maximization (EM) algorithm. This paper contributes to the use of SSI-EM for SML applications by proposing a step-by-step experimental methodology to process the measured data, which are obtained with different unknown excitations: ambient excitation and impulse excitation. Thus, the performance of SSI-EM for SML applications can be improved, providing a good estimation of the natural frequency and damping ratio without any controlled excitation, which is the main obstacle to use an experimental modal analysis in cryogenic environments. The dynamic response of the 510 g levitating platform has been characterized by means of OMA in a cryogenic, 77 K, and high vacuum, 1E-5 mbar, environment. The measured vertical and radial stiffness are 9872.4 N/m and 21329 N/m, respectively, whilst the measured vertical and radial damping values are 0.5278 Nm/s and 0.8938 Nm/s. The first natural frequency in vertical direction has been identified to be 27.39 Hz, whilst a value of 40.26 Hz was identified for the radial direction. The determined damping values for both modes are 0.46% and 0.53%, respectively.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.622-627
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• 2009

Business process engineering (BPE) is a top-down management approach for increasing efficiency and productivity through radical and fundamental changes to the business processes of the organization. BPE requires firms to initially develop a model of the existing business processes of the firm to distinguish functional tasks from processes used for coordinating inputs, activities and outputs. The model is used for understanding the business processes in the organization and to simulate the effect of changes to the processes. The model can also be used to justify business processes, which involves assessing whether the business process provides value to the customer in its current configuration. Justification requires a careful examination of the key business processes used by the firm to identify systemic shortcomings in the process and to create a new business process to produce greater efficiency. BPE also considers automating as many business processes as possible to increase operational efficiency and the integration of business process tasks. The construction industry has been slow to adopt BPE because of its project approach in which a major firm contracts with various functional service providers and regards each project as unique. The industry focuses on functional task efficiency rather than business process efficiency. There is no formal methodology or criteria for determining whether a business process is effective for a construction firm in its current configuration. The use of performance measures such as costs, task duration times or other metrics can be useful in evaluating the effectiveness of an existing business process and for modeling the possible outcome of a fundamental and radical change to the process.

• 한국식품과학회지
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• 제35권5호
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• pp.884-892
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• 2003

균질화 속도와 시간, 그리고 온도, 물 첨가량에 따른 감귤과피 물균질액의 제조공정시 최적조건을 찾기 위하여 물균질액의 추출효율지수를 나타내는 EI와 감귤과피 물균질액으로 코팅한 유색미의 색도를 나타내는 b value를 변수로 하여 최적화를 시도하였다. 감귤과피를 이용한 물균질액 제조시 EI는 추출온도를 제외한 균질화 속도와 시간, 물 첨가량에 크게 영향을 받았다. 수립된 회귀식에 대한 적합성 결여 분석결과 EI, b value에 대해 유의성이 없어 반응표면 모형이 통계적으로 유의하였다. 최적조건을 선정하기 위하여 비교적 영향이 적은 것으로 판단되는 균질화 시간과 온도를 중심점으로 고정하고 제한 변수를 최대로 하는(EI을 400이상, b value를 24이상) 물균질액 제조의 최적조건은 물 첨가량 42mL, 균질화 속도 8,500rpm이었다. 다음으로 첨가량과 균질화 속도를 이 조건으로 고정하고서 EI을 400이상, b value를 24이상으로 하는 감귤과피 물균질액의 제조조건으로는 물의 온도는 $53^{\circ}C$ 및 균질화 시간은 2.8분으로 결정할 수 있었다.

• International Journal of Computer Science & Network Security
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• 제21권3호
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• pp.245-256
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• 2021

Poor logistical infrastructure and agri-food supply chain management leads to significant food waste in logistic system. The concept of the sustainable value added agri-food chains requires defined approach to the analysis of the existing situation, possible improving strategies and also assessment of these changes impact on further development. The purpose of research is to provide scientific substantiation of theoretical and methodological principles and develop practical recommendations for the improvement of the agri-food logistics distribution system. A case study methodology is used in this article. The research framework is based on 4 steps: Value Stream Mapping (VSM), Gap and Process Analysis, Validation and Improvement Areas Definition and Imitation Modelling. This paper presents the appropriateness of LEAN logistics tools using, in particular, Value Stream Mapping (VSM) for minimizing logistic losses and Simulation Modeling of possible logistics distribution system improvement results. The algorithm of VSM analysis of the agri-food supply chain, which involves its optimization by implementing the principles of sustainable development at each stage, is proposed. The methodical approach to the analysis of possible ways for optimizing the operation of the logistics system of the agri-food distribution is developed. It involves the application of Value Stream Mapping, i.e. designing of stream maps of the creation of the added value in the agri-food supply chain for the current and future state based on the minimization of logistic losses. Simulation modeling of the investment project on time optimization in the agri-food supply chain and economic effect of proposed improvements in logistics product distribution system functioning at the level of the investigated agricultural enterprise has been determined. Improvement of logistics planning and coordination of operations in the supply chain and the innovative pre-cooling system proposed to be introduced have a 3-year payback period and almost 75-80% probability. Based on the conducted VSM analysis of losses in the agri-food supply chain, there have been determined the main points, where it is advisable to conduct optimization changes for the achievement of positive results and the significant economic effect from the proposed measures has been confirmed. In further studies, it is recommended to focus on identifying the synergistic effect of the agri-food supply chain optimization on the basis of sustainable development.

• 유통과학연구
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• 제18권9호
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• pp.67-75
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• 2020

Purpose: The purpose of this study is to enhance sales promotion efficiency for using solid refuse fuel facilities. Renewable energy technology using Solid Refuse Fuel (SRF) is an economic efficiency technology that recovers waste by burning various wastes. A survey on the pollutants discharged from the solid fuels facilities was investigated so that the SRF facilities could be expanded, distributed and reflected in the policy. Research design, data, and methodology: In this study, 9 business sites using SRF and Bio-SRF as main raw materials were investigated for 2 years. The characteristics of target business sites such as the type of fuel used, combustion method, combustion temperature, daily fuel consumption and environmental prevention facilities were studied. Results: The average pollution & ammonia concentration of Bio-SRF facilities was found to be 88.15% higher than that of SRF facilities. But the average acetaldehyde concentration of SRF facilities was found to be 88.15% higher than that of Bio-SRF facilities. Conclusions: The main issue is how much electric power generation using combustible materials affects air pollution. The waste recycling law provides the standard value according to the fuel property, but there is a considerable gap with the mixed fuel. Therefore, for efficient utilization of facilities using solid fuel products, additional research is needed to improve the distribution structure of exhaust pollutants is needed.