• Journal of the Society of Naval Architects of Korea
• /
• v.36 no.1
• /
• pp.30-36
• /
• 1999

A surface panel method for the analysis of ducted propellers in both uniform and non-uniform onset inflow is developed. A low order, perturbation potential based panel method with an efficient numerical Kutta condition is used. The boundary surface is discretized with hyperboloidal panels and the boundary condition is applied at the panel centroids. The unsteady analysis is based on a time-step algorithm in time domain. Numerical implementation is employed into both steady and unsteady problems. The results with the resent method are shown to have good convergence on the circumferential distribution of circulation on the duct. The effect of the propeller tip clearance on the circumferential circulation on the duct is also presented Numerical results on forces and moments of the propeller and the duct are compared with other numerical results and experimental data.

• Journal of Digital Convergence
• /
• v.16 no.6
• /
• pp.417-426
• /
• 2018

The purpose of this study is to understand the safety consciousness of high school students, disaster safety education, and the degree of first aid knowledge and to understand the relationship between safety consciousness and first aid knowledge. The subjects were 293 male students attending third grade of high school at G city and analyzed using SPSS 21.0 from March 19, 2018 to March 28, 2018. The results of the study showed that the correctness rate of first aid knowledge was 40.15% and that the relationship between safety consciousness and subcategories of first aid knowledge was significant(r=-.131, p=.025), respiratory and circulatory system(r=.213, p<.001), dressing and bandages(r=.156, p=.008). The purpose of this study is to contribute to the utilization of the basic knowledge of the curriculum to cultivate the ability to cope with safety accidents and to develop and evaluate educational programs to improve the level of first aid.

• Geophysics and Geophysical Exploration
• /
• v.18 no.3
• /
• pp.133-142
• /
• 2015

Displacement of the Earth's surface due to atmospheric loading has been recognized since a century years ago, and its accurate estimation is required in present day geodesy and surveying, particularly in space geodesy. Atmospheric load deformation in continental region can readily be calculated with the given atmospheric pressure field and the load Green's function, and, in near coastal area, approximate model is used for the calculation. The changes in the Earth's atmospheric circulation and the seasonal variation of atmospheric pressure on two hemispheres of the Earth are the each main causes of variation of the Earth's spin angular velocity and polar motion respectively. Wind and atmospheric pressure do the major role in other periodic and non-periodic perturbations of the positions in the Earth's reference frame and variations in the Earth's spin rotational state. In this reviewing study, the developments of related theories and models are summarized along with brief description of phenomena, and the geodetic perturbing effects of a hypothetical typhoon passing Korea are shown as an example. Finally related existing problems and further necessary studies are discussed in general.

• Korean Chemical Engineering Research
• /
• v.55 no.3
• /
• pp.341-352
• /
• 2017

Butyl acetate is produced from acetic acid and butanol via an esterification reaction in a reactive distillation column. Entrainer can be used for efficient removal of produced water from the reaction region, leading to significant improvement of the column performance. Batch reactive distillation has clear advantages over continuous one in terms of flexibility and adaptability in a small plant. We studied batch and semi-batch reactive distillation processes through process simulation and pilot-scale experiments. We investigated process configuration and type of entrainer for improvement of the column performance and suggested a novel cyclic operation strategy using the semi-batch reactive distillation column. The cyclic strategy was shown to give relatively high production rate and stable operation.

• Journal of Environmental Science International
• /
• v.7 no.3
• /
• pp.375-382
• /
• 1998

The characteristics of the basic statistics and steadiness of wind and the monthly normality test of surface wind distribution are investigated by using the observed wind data compiled from 10m meteorological observation tower at Seocheon district, where is located In the western coastal region of Korea. during the period from Feb. 7, 1996 to Feb. 7 1997 The northerly is appeared to be even in August and Sepember due to the influences of loccal circulation such as land and sea breeze. The correlation coefacients between two wind components are seemed to be positive during the in the period of from June to September and negative from October to April, respectively The constancy of wand Is high In shifts to lower values Increasing sampling time. It is found from monthly normality test based on the skewness and the excess of kurtosis coefficients that the distribution of zonal wind component is normal In spring and meridional one Is normal in late summer and early autumn.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.48 no.3
• /
• pp.207-215
• /
• 2020

Design of a shape transition nozzle is carried out as a part of building a lab-scale supersonic combustion experimental equipment. In order to connect directly the circular shaped vitiation air heater to the square shaped scramjet combustor, area change is evaluated by using the method of characteristics. Shape transition function is introduced to control the transition rate. Boundary layer correction was made through the three-dimensional computational fluid dynamics with the assessment on the several shape transition functions. The shape transition nozzle is proved minimizing the growth of boundary layer at the center of the rectangular nozzle surfaces that caused by the pressure gradient at the corners of the rectangular nozzle and the following recirculation regions.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.16 no.1
• /
• pp.36-44
• /
• 2012

Multi-injector rocket engine using high-concentrated hydrogen peroxide and kerosene was designed and manufactured. Design requirements of a rocket engine were determined and main geometrical parameters of rocket engine were determined on the basis of fundament. Six coaxial swirl injectors were mounted on the multi-injector engine. Flow analysis in the hydrogen peroxide manifold was performed to minimize stagnation and recirculation zones. Finally, the optimized hydrogen peroxide manifold was manufactured and cold flow test was carried out to confirm mass flow rate per uni-element, spray pattern and atomization characteristics. The results of cold flow test showed that the mixing head design process was successful and enough to use as a essential database for the development of a full-scale engine.

• Journal of the Korea Society of Computer and Information
• /
• v.17 no.5
• /
• pp.169-176
• /
• 2012

The supply chain of online digital contents industry differs much from the supply chain of offline industry which produces and supplies physical products. Portal facilitates the creation, distribution, and usage of online digital contents by providing efficient and convenient content distribution platform to contents suppliers and users, resulting in enhancing competitiveness of portal supply chain. Each portal builds it's own supply chain and various participant firms like CPs(Content Providers) and SPs(Solution Providers) are collaborating together to survive from the fierce competition. However, there is few research work on portal SCM to explain how to design and implement a Portal SCM in a successful way. So, this paper investigates the structure of Portal SCM and the differences between traditional SCM and Portal SCM. Also, this paper proposes seven research issues need to be addressed to design and implement a portal in an efficient and effective way.

• Journal of the Korean Society for Railway
• /
• v.13 no.5
• /
• pp.493-499
• /
• 2010

The next generation domestic high speed railway system is a power dispersed type and uses vector control method for motor speed control. Nowadays, inverter driven induction motor system is widely used. However, recently PMSM drives are deeply considered as a alternative candidate instead of an induction motor driven system due to their advantages in efficiency, noise reduction and maintenance. In this paper, the maximum torque control approach is presented for the IPMSM drives with reluctance torque. The applied control method uses maximum torque control per ampere technique. Simulation programs based on Matlab/Simulink are developed. Finally the designed system is verified by simulation and their characteristics are analyzed by the simulation results.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.23 no.6
• /
• pp.788-794
• /
• 1999

The swirl flame is mostly used to stabilize the flame on the burner nozzle in the industrial combustor. In the case of the weak swirl flame(S<0.4), the recirculation zone could not be formed, but in the strong swirl(S>0.6) flame, it could be formed in the center of the swirl flame. In this study, the measurement and analysis of emission species, temperature, radicals of premixed swirl flame in the combustor were performed to understand the NO formation and emission characteristics of the swirl flame of natural gas. The result of NO emission in the swirl flame is that the amount of NO emission in the strong swirl flame decreased about 60% compared with that of the weak swirl flame. The main region of NO formation of the weak swirl flame is positioned in the down stream(z=100~200mm) of the flame, but that of the strong swirl flame is positioned in the up stream(z=40mm) where the recirculation zone seems to be formed. It is supposed that the increase of flame surface and the formation of inversed flame cause the reduction of the high temperature region on the production of NO in the strong swirl flame. The result of NO-temperature relation revealed that the factor of NO formation is not only temperature but also another parameters in the weak swirl flame, but in the strong swirl flame, NO is proportional to the temperature of higher than 1200K.