• The Journal of the Acoustical Society of Korea
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• 제16권1E호
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• pp.29-34
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• 1997

Numerical prediction of aerodynamic noise radiated by subsonic rotors are carried out. A computer program has been developed which incorporates both the discrete frequency noise as well as the broadband noise arising from the ingestion of turbulence. Acoustic analogy is used in conjunction with Homicz's formulation of turbulence ingestion noise. Formulation 1A of Farassat is used to enhance the numerical analysis performance of Ffowcs-Williams Hawkings equation by eliminating the numericla time differentiation. Homicz's trubulence ingestion noise prediction technique is used to understand the characteristics of broadband noise radiated by isotropic trubulence in gestion. Numerical predictions are carried out for a number of rotor configurations and compared with experimental data. Monopole consideration of transonic rotor agrees well with both the experimental data and the linear theory. Noise radiation characteristics of rotor at lifting hover are investigated utilizing simple blade loading obtained by thin wing section theory. By incorporating discrete noise prediction of steady loading with broadband spectrum, much better agreement with experimental data is obtained in the low frequency region. The contributions from different noise mechanisms can also be analyzed through this method.

• 대한치과의사협회지
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• 제48권3호
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• pp.190-195
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• 2010

Oral appliance therapy is a simple, reversible way for improving snoring and/or obstructive sleep apnea. It may be indicated for the patients who are unable to tolerate continuous positive airway pressure (CPAP) or who have potential risks for surgical intervention. Oral appliance therapy increases airway space by the providing stable anterior positioning of the mandible, pulling out tongue, lifting up soft palate, or changing the muscle activity of the genioglossus. Currently, more than 80 different types of oral appliances have been introduced for snoring and/or obstructive sleep apnea. They are classified by their characteristics such as mode of action, adjustability and material used. This article provides a detailed clinical protocol and treatment procedure for oral appliance therapy.

• 대한조선학회논문집
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• 제41권3호
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• pp.13-21
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• 2004

This paper deals with a theoretical and experimental method for the design of a biased asymmetric pre-swirl stator propulsion system which is an energy saving device by recovering a propeller rotational energy. In the case of slow-speed ships, the upward flow is generated along the afterbody hull form at the propeller plane. The generated upward flow cancels the rotating flow of the propeller at the starboard part while it increases at port part. The present biased asymmetric pre-swirl stator propulsion system consists of three blades at the port and one blade at the starboard which can recover the biased rotating flow effectively. This paper provides the design concept which gives more simple and a high degree of efficiency and the experimental results for the compound propulsion system.

• 한국철도학회논문집
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• 제15권6호
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• pp.531-536
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• 2012

판토그라프 팬헤드의 공력소음 발생의 주요 인자와 영향을 미치는 변수를 분석하였다. 팬헤드 주변의 유체 유동과 결과적인 소음 방사를 분석하기 위해, 수치해석적인 방법 중 하나인 격자볼츠만 방법으로 팬헤드 단순모델을 사용했다. 풍동실험을 통해 측정된 결과로 시뮬레이션 결과를 검증했다. 와흘림이 주요한 공력소음 발생원인이며 Strouhal수, 유체의 속도 및 판토그라프의 형상에 영향을 받았다. 이 논문에 사용된 직사각형 형상을 통해 양력의 발생을 증가시키면서 방사 소음을 줄이는 팬헤드의 설계가 가능함을 제시하였다. 또한 통로나 유선 형상을 이용해 와흘림을 최소로 줄이면, 방사 소음을 크게 저감하는 형상의 설계가 가능함을 구축된 해석모델을 이용하여 검증하였다.

• 한국산업정보학회논문지
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• 제6권3호
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• pp.79-86
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• 2001

신종 직업병 중 누적외상성질환(Cumulative Trauma Disorders)은 고도로 분업화된 현대 산업환경에서 주로 수작업을 수행하는 종사자에게 발생된다. 본 연구는 단순반복근로자의 누적외상성질환에 노출되는 정도를 EMG시스템을 이용하여 분석한 결과는 다음과 같다. AEMG에서는 작업경과에 따라 근피로도는 증가하다가 작업 완료시에는 근피로도가 내화벽돌을 들기 전보다 감소하였다. MF와 MPF에에서는 천극근, 다열근의 근피로도가 많은 것으로 나타났다. ZCR에서는 모든 내화벽돌의 무게에서 작업전과 작업후의 근피로도가 가장 낮게 나타났다. 종합적으로 작업진행이 계속됨에 따라 근육피로도는 증가하고 있었고, 단순반복운반작업시에 천극근과 다열관에 대한 근피로도가 큰 것으로 나타났다.

• 대한인간공학회지
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• 제27권4호
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• pp.27-35
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• 2008

Recently, many studies have reported the fact that an excessively accumulated psychological and physical burden induced from physical labor conducted routinely in home and industry can be one of main reasons of musculoskeletal disorders in the working population. This fact makes increase interests in studies to reduce a risk of musculoskeletal disorders through grafting ergonomic considerations on working environment. However, there are currently limited methodologies in quantitative evaluations of new ergonomic suggestions to reduce a risk of musculoskeletal disorders. The current study is therefore performed to evaluate quantitatively effects of a design of washing machine as a new ergonomic suggestion onto prevention of musculoskeletal disorders, through application of a biomechanical evaluation methodology. For this, three-dimensional motion analysis by using musculoskeletal models with Rapid Entire Body Assessment (REBA), which has been generally used for a simple evaluation of a degree of harmfulness of the human body at specific working postures to be considered, was performed. The results of REBA did not give us enough information and their results were somewhat simple and inaccurate, but the results of the three-dimensional motion analysis give us enough information such as alteration of main muscle forces and joint moments required during washing work. All results showed that the main muscle strengths and joint moments were decreased effectively for reduction of a risk of musculoskeletal disorders during the washing work with newly designed washing machine evaluated in the current study, compared with those generated during the washing work with general washing machine. From these results, it can be concluded that a risk of the musculoskeletal disorders, which may be induced by a repetitive washing work, may be reduced through using the washing machine designed ergonomically and newly. Also, it is thought that if our ergonomic design can be applied for improvement of working environment in lifting and laying works conducted repeatedly for a treatment work of goods, which have a strong resemblance to the behaviors generated frequently during the washing work, a possibility of occurrence of the musculoskeletal disorders by the lifting and laying works may be reduced highly.

• 한국실내디자인학회논문집
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• 제14권5호
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• pp.44-51
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• 2005

This study focuses 'Korean characteristics' in architectural interior design. In this study, some Korean characteristics was extracted by analysing traditional Korean spaces and as well as by considering the architectural interior spaces which are designed with Korean character since 1970. This paper started with differenciating the elements and principles that consist of space, and then classified the elements into 8 categories such as Spatial system, Enclosure system, Circulation system, Material system, Furnishing system, Light, Color, Context which are analysing frames. As a conclusion, the concepts of Korean characteristics are extracted and suggested as design concept with Korean characteristics by analysing the contents of each category. These concepts were presented with simple diagrams and supporting cases were also presented in this paper. The design concepts of 'Korean characteristics' are classified in the 25 concepts: Holonic composition, Transitional space, Hierarchy by floor level, Gradation of privacy, Changeability, Various central yards, Space with opened edges, Gray space, Continuity of space, Translucent wall, Folding-lifting wall, Skeleton, Abstract facet, Path as a message, Mild light, Multii-layered vista, Fluidity, framed scenery, Serial view, Interpenetrating Space, Harmony with nature, Organic interrelationship, Complementary Dual Structure, Temporal change of space, Hierarchical order.

• 한국해양공학회지
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• 제13권3B호
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• pp.14-21
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• 1999

As an effective means to convey crushed materials from seabed to onboard ship and to raise hazardous or abrasive liquids, air-lift pump provides a reliable mechanism due to its simple configuration and easy-to-operate principle. The present study is focused on investigation of related performance by the analysis program based on the gas-liquid two-phase flow in circular pipes. The program covers pump operating in isothermal and vertical two-phase flow with Newtonian liquids. It is summarized as important result that an optimum air mass flow rate exists for the maximum lifted liquid mass flow rate in terms of a given submergence rates. The comparison between riser performance of the conveyed liquid flow rate calculated by the computer program and measured data with large scale air lift pump system constructed in 200 meter depth vertical tank reveals similar distribution.

• 드라이브 ㆍ 컨트롤
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• 제12권4호
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• pp.35-40
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• 2015

A gas spring provides support force for lifting, positioning, lowering, and counterbalancing weights. It offers a wide range of reaction force with a flat force characteristic, simple mounting, compact size, speed controlled damping, and cushioned end motion. The most common usage is as a support on a horizontally hinged automotive tail gate. However, its versatility and ease of use has been applied in many other industrial applications ranging from office equipment to off-road vehicles. The cylinder of a gas spring is filled with compressed nitrogen gas, which is applied with equal pressure on both sides of the piston. The surface area of the rod side of the piston is smaller than the opposite side, producing a pushing force. The magnitude of the reaction force is determined by the cross-sectional area of the piston rod and the internal pressure inside the cylinder. The reaction force is influenced by many design parameters such as initial chamber volume, diameter ratio, etc. In this paper, we investigated the reaction force characteristics and carried out parameter sensitivity analysis for the design parameters of a gas spring.

• 한국작물학회:학술대회논문집
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• 한국작물학회 2004년도 추계학술발표회
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• pp.36-41
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• 2004

Postharvest handling of sweetpotatoes is inevitable procedure for the maintenance, storage, management and utilization of high fresh quality of storage roots. It ranges in degree from simple lifting of roots, carrying them from field to storage house and immediate consumption after cooking, to sophisticated methods of curing, and storage under controlled conditions followed by processing into a high quality food products. Postharvest saleability, quality and nutritional value of roots and the presence or absence in roots of bitter, toxic furanoterpenoid phytoalexins or mycotoxins depends greatly on the degree and types of treatment to which produce is subjected. Climatic and soil conditions before harvest and contamination or attack by microorganisms or insect pests in the field may initiate or enhance subsequent postharvest deterioration. Careless postharvest handling can lead to both quantitative and qualitative losses which may be extremely high in some circumstances. Research has concentrated on the improvement of preharvest conditions to increase yield and lower decrease rates. However, such efforts are wasted unless they go hand in hand with others designed to reduce the high degree of loss associated with careless postharvest handling.