• The Journal of the Acoustical Society of Korea
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• 제24권1E호
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• pp.7-15
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• 2005

This paper addresses issues encountered in measuring the general, 6-degree-of-freedom motion of a human head, A complete mathematical description for measuring the head motion using the six-accelerometer configured bite-bar is suggested, The description shows that the six-axis vibration cannot be completely obtained without the roll, pitch and yaw angular velocity components, A new method of estimating the three orthogonal (roll, pitch and yaw) angular velocities from the six acceleration measurements is introduced. The estimated angular velocities are shown to enable further quantitative error analysis in measuring the translational and angular accelerations at the head. To make this point clear, experimental results are also illustrated in this paper. They show that when the effects of angular velocities are neglected in the head vibration measurement the maximum percentage errors were observed to be more than $3 \%$ for the angular acceleration of the head and to be close to $5 \%$ for its translational acceleration, respectively. It means that the inclusion of all the angular velocity dependent acceleration components gives more accurate measurement of the head vibration.

• Current Photovoltaic Research
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• 제4권2호
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• pp.59-63
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• 2016

A key point of a soldering process for photovoltaic (PV) modules is to increase an adhesive strength leading a low resistivity between ribbon and cell. In this study, we intended to optimize a heating condition for the soldering process and characterize the soldered joint via physical and chemical analysis methods. For the purpose, the heating conditions were adjusted by IR lamp power, heating time and hot plate temperature for preheating a cell. Since then the peel test for the ribbon and cell was conducted, consequently the peel strength data shows that there is some optimum soldering condition. In here, we observed that the peel strength was modified by increasing the heating condition. Such a soldering property is affected by a various factors of which the soldered joint, flux and bus bar of the cell are changed on the heating condition. Therefore, we tried to reveal causes determining the soldering property through analyzing the soldered interface.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.21-35
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• 2006

This paper examines critical successful elements related to the management of new product development process. For this, we have selected a VK-X100, slim bar type cellular phone, produced by VK mobile co., which was thought as a successful product development case and then analysed the case from a concept driven strategic product development's point of view. We have performed in-depth interviews with project managers, engineers and designers to get information on the product development process and analysed huge amount of data obtained from web-sites, global market indicators, and related firms' materials to find a changing trend of market conditions. The findings suggest that the successful new Product development and management is shaped by a number of different factors, such as the business environments, firm's technological level, firm's deep market insight capabilities, nature of the product development activities, and so on. Finally, we suggested the limitation of our research and further research subjects that would be required to support our findings.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2008년도 학술발표회 논문집
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• pp.1594-1598
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• 2008

자연하천에서의 형상은 직류하천보다는 어느 정도 만곡이 있는 사행하천이다. 이러한 만곡부가 교호적으로 나타나는 사행하천의 흐름구조는 매우 복잡하며, 이차류가 발생하는 만곡부에서 직류하천에서 예상되는 흐름분포를 왜곡시킴으로써, 유사의 이동, 횡방향의 유속분포가 다르게 나타난다. 이러한 만곡부의 흐름 특성은 만곡부 외측에 측방세굴과 수면교란, 그리고 수위를 상승시키며, 에너지 손실을 가져온다. 일반적으로 사행하천의 만곡부 외측에는 소(pool)가 발달되고, 내측에는 이차류에 의해 강턱 퇴적을 유발함으로써 점 사주(point bar)가 형성된다(우효섭, 2001). 본 연구에서는 사행하천이 비교적 발달한 섬진강 상류 덕치지구 구간에 대하여 2차원 수치모형인 RMA-2 모형을 이용하여 만곡부의 흐름특성을 분석하였다. 분석한 결과 유속의 분포는 만곡부 상류부에서 최대 흐름의 구역이 나타났으며, 만곡부에서는 흐름의 편향구역과 정체구역, 그리고 만곡부 하류부에서 에너지 손실이 일어난 후 흐름의 회복구역으로 흐름의 특성을 나타났다. 또한 수위의 분포는 상류부에서 점차적으로 수위가 감소하다가 만곡부에서 수위가 상승하였고 만곡부가 끝나는 하류부에서의 수위는 감소하였다. 만곡부에서의 횡적인 수위 분포는 만곡부의 외측이 내측보다 수위가 상승되는 것으로 나타났다. 본 연구에서 2차원 수치모형인 RMA-2 모형을 이용한 만곡부의 흐름 특성은 만곡부에서의 홍수위 상승에 대한 검토로서 하천의 바람직한 치수관리 방안에 효과적으로 이용될 수 있을 것으로 판단된다.

• 한국분무공학회지
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• 제2권4호
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• pp.7-14
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• 1997

Laser Raman scattering method has been applied to measure equivalence ratio of methane/air mixture in injected spray. We used high power KrF excimer laser$(\lambda=248nm)$ and a high gain ICCD camera to capture low intensity signal. Raman shifts and Raman scattering cross -sections of $H_2,\;O_2,\;N_2,\;CO_2,\;CH_4\;and\;C_3H_8$ are measured precisely. Our results show an excellent agreement with those of other groups. Mole fraction measurement of $O_2\;and\;N_2$ from air shows that $O_2:N_2=0.206:0.794$. We used gas injector which was operated at 1 bar. Methane is used as a fuel. Spray region is $10mm\times37mm$ and this region is divided into 80 points. In Raman signals are obtained and ensemble averaged for each point. 3-d and contour plot of distribution of equuivalence ratio is presented. Our measured results show that the equivalence ratio of methane/air mixture in methane-rich region is reasonable. However, more study is necessary for methane-lean region because background noise level is almost same as Raman intensity of methane.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1998년도 춘계학술발표회논문집(2)
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• pp.336-343
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• 1998

An iteration method has been developed for determining crack growth and fracture resistance cure (J-R curve) from the load versus load-line displacement record only. In this method, the hardening curve, the load versus displacement curve at a given crack length, is assumed to be a power-law function, where the exponent varies with the crack length. The exponent is determined by an iterative calculation method with the assumption that the exponent varies linearly with the load-line displacement. The proposed method was applied to the static J-R tests using compact tension(CT) specimens, a three-point bend (TPB) specimen, and a cracked round bar (CRB) specimen as well as it was applied to the quasi-dynamic J-R tests using CT specimens. The J-R curves determined by the proposed method were compared with those obtained by the conventional testing methodologies. The results showed that the J-R curves could be determined directly by the proposed iteration method with sufficient accuracy in the specimens from SA508, SA533, and SA516 pressure vessel steels and SA312 Type 347 stainless steel.

• 한국정밀공학회지
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• 제31권2호
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• pp.165-170
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• 2014

Reproducibility of injection molding machines are studied at the study of this time. We applied computer aided engineering program so it could generate clamping force, about 1,500 kN, to the nozzle center part of flex link in tie-bar and at this time, we made sure condition of stress distribution and transformation quantity in flex link. The result of computer aided engineering transformation quantity was confirmed that transformation of top area was 247~257 kN and bottom areas was 273~279 kN and also was confirmed that the stresses are distributed in a range of 57~750 $N/mm^2$ from top to the bottom of the surface. This time we could confirm the condition of transformation quantity and stress distribution by enforcing the previously used structure analysis of flex link. And we utilized the reference data to establish important point of section for non destructive test overhaul.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.605-607
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• 2011

A Study on the flow-structure characteristics of a 3/2 way pneumatic valve is essential for optimizing the performance of ship engines. It is important for the valve to have desirable safety factor am reduced weight from the safety and economic point of view. In this study, we capture flow-structure characteristics of 3/2 way pneumatic valve. This is optimized based on the proper design criteria. The air at a pressure of 30 bar is the working fluid which is made to fill in the tack in short time. This time is defined as the filling time. The flow and structure analysis is performed for three cases under maximum stress and safety factor. In optimum design, considering the flow-structure characteristics, we model twenty seven cases by using DOE(design of experiments) method Here, analysis for each cases is performed and then metamodels are created We obtain optimized parameters and then analysis is repeated to compare with the initial model. Finally, the feasibility of the optimum design is verified.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2011년도 학술발표회
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• pp.115-115
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• 2011

본 연구에서는 자갈사주의 식생 이입 과정을 밝히고, 식생 이입에 영향을 미치는 수리적 특성을 규명하기 위한 현지조사 방안을 제시하였다. 자갈사주의 식생이입은 조절 하천과 비조절 하천에서의 이입 과정이 다르며, 본 연구에서는 비조절 하천을 대상으로 하였다. 따라서 상류에 댐이나 저수지가 없는 자연에 가까운 하천을 고려하였으며, 장기적으로는 조절 하천의 식생이입 과정과의 비교를 위해 임하댐의 반변천과 가까운 길안천의 중류 구간을 선정하였다. 자갈사주의 식생이입 과정을 모니터링하기 위해, 자갈사주를 전구역과 세부구역으로 나누어 같은 지점에서 같은 배율로 사진을 촬영하였다. 전자는 자갈사주 전체를 대상으로 촬영하며, 이를 위한 view point 선정이 중요하고 선정에 적절한 지점을 제시하였다. 후자의 경우 식생의 이입 정도를 왕성, 보통, 미약, 없음(4단계)로 구분하기 위해 대상 지점을 matrix가 50% 이상인 지점 ; 식생이입 왕성 (2개 지점), matrix가 50% 이하인 지점 ; 식생이입 보통, 또는 미약 (2개 지점), matrix가 없는 자갈만의 지점 ; 식생이입 없음 (1개 지점)을 선정하였다. 식생이입에 영향을 미치는 변수로는 하상토의 입경과 흐름의 특성(수심, 유속, 하상 소류력 등)을 들 수 있으며, 이들 조사를 위한 방법을 제시하였다.

• 대한치과보철학회지
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• 제37권6호
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• pp.791-799
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• 1999

The purpose of this study was to investigate the displacements of cast framework by torch soldering and electric soldering techniques. Specimen had two cylinders and connecting bar that had sectioned with 0.3mm gap at mid point. 10 of total specimens were divided into two groups. In torch soldered group, soldering investment block was made and conventional torch solder-ing procedure was carried out. In electric soldered group, electric soldering was carried out on the master cast without soldering investment block by using electric soldering machine(Dentapunkt DP 7, Kulzer, Germany) After soldering procedure, three dimensional coordinates of two centroids of each cylinder were measured by three dimensional coordinate measuring machine. The intercentroidal displacement and global displacement were calculated and then, these values were compared and evaluated. The results were obtained as follows: 1. Intercentroidal distances of specimens decreased after both soldering procedures, and the decrease in intercentroidal distance was greater for torch soldered group than for electric soldered group 2. Global displacements of torch soldered group were greater than those of electric soldered group.