• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2006년도 추계 학술대회논문집
• /
• pp.101-105
• /
• 2006

The computational fluid dynamic analysis has been conducted for the thermo-chemical flow field in an arcjet thruster with mono-propellant Hydrazine (N2H4) as a working fluid. The Reynolds Averaged Navier-Stokes (RANS) equations are modified to analyze compressible flows with the thermal radiation and electric field. The Maxwell equation, which is loosely coupled with the fluid dynamic equations through the Ohm heating and Lorentz forces, is adopted to analyze the electric field induced by the electric arc. The chemical reactions of Hydrazine were assumed to be infinitely fast due to the high temperature field inside the arcjet thruster. The chemical and the thermal radiation models for the nitrogen-hydrogen mixture and optically thick media respectively, were incorporated with the fluid dynamic equations. The results show that performance indices of the arcjet thruster with 1kW arc heating are improved by amount of 180% in thrust and 200% in specific impulse more than frozen flow. In addition to thermo-physical process inside the arcjet thruster is understood from the flow field results.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
• /
• 제52권10호
• /
• pp.501-506
• /
• 2003

A Superconducting Rotary Machine (SRM) is characterized by an air-cored machine with its rotor iron and stator iron teeth removed. For this reason, the SRM is featured by 3D magnetic flux distribution, which decreases in the direction of axis. Therefore, 3D magnetic field analysis method is required to know about characteristic of magnetic field distribution of SRM. In this paper, 3D flux distribution of SRM is calculated by analytical method. The magnetic field distribution of the field coils is calculated by Biot-Savart equation. The magnetic core is represented by magnetic surface polarities. This paper describes the combined use of above methods for the total field computation, and compares results of analytical method and 3D FEM(Finite Element Method).

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 1997년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Fall 1997
• /
• pp.128-135
• /
• 1997

The indirect boundary integral equation is formulated to analyze the behavior of a cavity in a multilayered half-plane subjected to earthquake waves. This formulation uses the fundamental solutions that are numerically calculated by the generalized transmission and reflection coefficient method. The free surface of the cavity without external excitation influences the behavior of the half-plane. Consequently this analysis adds the consideration of scattering-field into the analysis and the total motion field of the cavity is decomposed into the free-field and scattering-field motions. The free-field motion is obtained from the modification of the transmission and reflection coefficient method. The scattering-field motion is calculated is calculated by the indirect boundary value problem which has the ficticious boundaries and sources. In this study, P wave, SV wave, SH wave, and Rayleigh wave are analyzed respectively.

• Structural Engineering and Mechanics
• /
• 제4권3호
• /
• pp.227-242
• /
• 1996

An important class of problems in the field of geotechnical engineering may be analyzed with the aid of a simple integro-differential equation. Behavior of "rigid" piles(say concrete piles), "deformable" piles(say gravel piles), pile groups, pile-raft foundations, heavily reinforced earth, flow within circular silos and down drag on cylindrical structures (for example the crusher unit of a mineral processing complex) are the type of situations that can be handled by this type of equation. The equation under consideration has the form; $$\frac{{\partial}w(r,\;z)}{{\partial}z}+f(z){\int}^z_0g({\xi})(\frac{{\partial}^2w(r,\;{\xi})}{{\partial}r^2}+\frac{1}{r}\frac{{\partial}w(r,\;{\xi})}{{\partial}r})d{\xi}+h(r,\;z)=0$$ where w(r, z) is the vertical displacement of a soil particle expressed as a function of the polar cylindrical space coordinates (r, z) and the symbols f, g and h represent soil properties and the loading conditions. The merit of the analysis is its simplicity (both in concept and in application) and the ease with which it can be expressed in a computer code. In the present paper the analysis is applied to investigate the behavior of a single rigid pile to bedrock. The emphasis, however, is placed on developing the equation, the numerical techique used in its evaluation and validation of the technique, hereafter called the ID technique, against a formal program, CRISP, which uses the FEM.

• 한국농공학회논문집
• /
• 제60권4호
• /
• pp.55-62
• /
• 2018

Problems on vibration due to blasting for infrastructure development are getting important because of a civil appeal. Blasting-induced vibration is representative construction pollution, hence, it is possible that a number of environmental damages occur. In this study, borehole test blasting was conducted at Sintanjin area, Daejeon and square root equation with 95% confidence level was proposed for prediction of blasting-induced vibration. The vibration value predicted from this equation was more conservatively evaluated than the values predicted from U.S. Department of Interior, Bureau of Mines (USBM) and Nippon Oil & Fats Co., Ltd. (NOF) equations. Therefore, the proposed equation in this study seems to contribute for safety blast design. However, for optimal blast design, inducing equation for prediction of blasting-induced vibration through the identical test blasting with field construction such as rock slope blasting would be required.

• 한국농공학회지
• /
• 제24권4호
• /
• pp.99-108
• /
• 1982

This thesis aims to estimate the rainfall runoff from paddy field in a small watershed during irrigation period. When the data observed at the proposed site are not available, the Monthly Runoff Equation of Korean Rivers which was derived from data observed under the following assumptions is used to study the water balance. a. Monthly base flow was assumed as 10. 2mm even if these is no mouthly rainmfall. b. Monthly comsumption of rainfall was ranged from 100 to 2OOmm without relation to the rainfall depth. However, the small watershed which consists mainly of paddy fields encounters severe droughts and accordingly the baseflow is negligible. Under the circumstances the author has developed the following equation called "Flood Irrigation Method for Rainfall Runoff "taking account of the evapotranspiration, precipitation, seepage, less of transportation, etc. R= __ A 7000(1 +F) -5n(n+1)+ (n+1)(Pr-S-Et)] where: R: runoff (ha-m) A: catchment area (ha) F: coefficient of loss (o.o-0. 20) Pr: rainfall (mm) S: seepage Er: evapotranspiration (mm) To verify the above equation, the annual runoff ratio for 28 years was estimated using the Monthly Runoff Equation of Korean Rivers the Flood Irrigation Method and the Complex Hydrograph Method based on meteorological data observed in the Dae Eyeog project area, and comparison was made with data observed in the Han River basin. Consequently, the auther has concluded that the Flood Irrigation Method is more consi- stent with the Complex Hydrograph Method and data observed than the Monthly Runoff Equation of Korean Rivers.

• 한국지반공학회논문집
• /
• 제26권11호
• /
• pp.39-46
• /
• 2010

본 연구에서는 Strain Wedge 해석모델을 이용하여 수평하중이 작용하는 단독말뚝의 수평저항력 산출식을 제시하였고, 이를 모형실험, 현장 실험의 결과와 기존의 문헌에서 제시된 수평저항력 산정식과 비교 분석하였다. 그 결과 모형 실험의 시험 결과보다 조금 작게 나타났고, 현장 재하실험 결과와는 말뚝 두부의 변위가 작을 경우 상당히 잘 일치하고 있으나, 말뚝 두부의 변위가 증가할 수록 결과 값의 차가 조금씩 발생하였다. 그리고 기존의 산출식과 비교 검토한 결과 유한차분법과 잘 일치하였다.

• 한국안전학회지
• /
• 제39권2호
• /
• pp.22-27
• /
• 2024

The purpose of this study is to explore the trend in insulation resistance values according to temperature and overcurrent by conducting an investigation on the actual condition and experiments on the electrical wiring during the melting furnace process. In addition, the Arrhenius equation is used to determine whether temperatures in the furnace operating process can be applied to the actual field. In the investigation of the actual condition, the insulation resistance started to decrease seven years after replacement, even though cables in oil pump A were replaced in 2010. Both the experimental and theoretical values of the insulation resistance obtained using the Arrhenius equation decreased with an increase in temperature. Errors in insulation resistance (MΩ) values between tests and the Arrhenius equation ranged from ±2 to ±10, demonstrating a high similarity. Results revealed that when the insulation resistance cannot be measured in a manufacturing workplace (quarterly analysis), it can be estimated by partially applying the Arrhenius equation.

• 한국항만학회지
• /
• 제13권1호
• /
• pp.155-166
• /
• 1999

The construction of the coastal structures and reclamation work causes the circulation reduced in the semi-closed inner water area and the unbalanced sediment budget of beach results in an alteration of beach topography. Among the various fluid motions in the nearshore zone water particle motion due to wave and wave-induced currents are the most responsible for sediment movement. Therefore it is needed to predict the effect of the environmental change because of development and so the prediction of wave transformation dose. The purpose of this study is to introduce the relation between waves wave-induced currents and sediment movement. In this study we will show numerical method using energy conservation equation involving reflection diffraction and reflection and the surfzone energy dissipation term due to wave breaking is included in the basic equation. For the wave-induced current the momentum equation was combined with radiation stresses lateral mixing and friction Various information is required in the prediction of wave-induced current depending on the prediction tool. We can predict changes in wave-induced current from the distribution of wave especially near the wave breaking zone. To evaluate these quantities we have to know the local condition of waves mean sea level and so on. The results from the wave field and wave-induced current field deformation models are used as input data of the sediment transport and bottom change model. Numerical model were established by a finite difference method then were applied to the development plan of the eastern Pusan coastal zone Yeonhwa-ri and Daebyun fishing port. We represented the result with 2-D graphics and made comparison between before and after development.

• 한국균학회지
• /
• 제37권1호
• /
• pp.55-59
• /
• 2009

버섯은 생태계에서 분해자로 역할을 담당하며, 그 양은 생태계의 건전성을 나타내는 중요한 지표이다. 버섯의 생산량을 알기 위해서는 개체를 수확하여 그 무게를 측정하여야 한다. 그러나 이 방법은 버섯 개체를 수확할 때 서식지를 훼손하고, 또한 한 지역에서 버섯의 동태를 장기적으로 관찰하는데 적합하지 못하다. 따라서 본 연구에서는 자실체의 외부 형질을 측정하고 이로부터 현존량을 추정하는 비례식을 만들었다. 사용한 버섯은 표고(L. edodes), 느타리(P. ostreatus), 팽이버섯(F. velutipes)과 종버섯(C. tenera)이다. 버섯의 자실체에서 형질 변수(갓 직경, PD; 갓 면적, PA; 대 길이, SL; 대 두께, ST)를 측정하고, 이 변수로부터 건조 생물량과의 회귀관계식을 구하였다. 그 결과 버섯 4종 모두 추정한 식에서 유의한 상관성을 보임으로써(p < 0.05), 외부 형질 변수로부터 유도된 비례식을 사용하여 버섯의 현존량을 예측할 수 있음이 확인되었다.