• The KSFM Journal of Fluid Machinery
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• v.5 no.4 s.17
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• pp.11-18
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• 2002

A turbopump system composed of two pumps and one turbine is considered. The turbine composed of a nozzle and a rotor is used to drive the pumps while gas passes through the nozzle and potential energy is converted to kinetic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of turbine system is investigated with some pre-determined design requirements (i.e., pressure ratio, rotational speed, required power, etc.) following Liquid Rocket Engine (L.R.E.) system specifications. For simplicity of turbine system, impulse-type rotor blades for open-type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow-rate compared to close-type system. In this study, a partial admission nozzle is adopted to maximize the efficiency of the open-type turbine system. A design methodology of turbine system was introduced. Especially, partial admission nozzle was designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design is presented for a 10 ton thrust level of L.R.E.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.12
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• pp.1833-1840
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• 2013

A golf ball collecting robot in a golf ball driving range has been recently required because it is safer and more economic than a human being. In this paper, the golf ball recognition and distance estimation system based on a neural network and OpenCV is developed for the robot. The simulation results show that the recognition ratio is over 87% for the distance of less than 120cm and accurate rate for distance estimation is over 85% for golf balls in 30-180cm from a webcam.

• Journal of Chest Surgery
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• v.25 no.9
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• pp.955-961
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• 1992

In this study, 237 cases of spontaneous pneumothorax experienced at the department of Thoracic and Cardiovascular Surgery, Kosin Medical College during from January 1986 to December 1990 were analysed retrospectively. 1. The ratio of male to female was 4.6: 1, predominent in male. The incidence of age group was highest as 36% between 21 and 40 years old. 2. The associated diseases of pneumothorax were 27 cases, in which pyothorax were 8 cases, and hydrothorax were 19 cases. 3. The site of pneumothorax was as follows: right side was 53%, left side was 45%, and both side was 2%, so right side was slight high. 4. The empolyed managements were as follows: bed rest with oxygen inhalation in 13 cases, closed thoracostomy in 155 cases, open thoracotomy in 69 cases. 5. The operative procedures of thoracotomy were as follows; simple pleurodesis in 2 cases, blebectomy & bullectomy in 38 cases, parietal pleurecttnny in 4 cases, segmentectomy in 12 cases, lobectomy in 9 cases. 6. The indication of open thoracotomy were as follows, recurrent history in 35 cases, contralateral pneumothorax history in 2 cases, continuous air leakage in 24 cases, bilateral pneumothorax in 2 cases, and visible blebs & bullaes on the chest X-ray in 6 cases. 7. The hospital duration after management was as follow, open thoracotomy in 13.2 days, closed thoracostomy in 22.4 days. The recurrent pneumothorax after closed thoracostomy was 25 cases, about 15%.

• Proceedings of the KSRS Conference
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• v.1
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• pp.495-498
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• 2006

Optical profile and spectral absorption of suspended solids in waters of Sanya bay was measured on August 8-14, 2003. Optical profile was taken by using MicroPro optical profile. Apparent optical indexes, vertical diffuse attenuation coefficient ($K_d$) and water leaving radiance (Lw), were calculated. $K_d$ at the blue end of the spectrum was greater than that at the red end of the spectrum in waters near Sanya River mouth, however, in waters near open sea, $K_d$ at the blue end of the spectrum was smaller than that at the red end of the spectrum. Distribution of water leaving radiance was relatively higher in waters near Sanya River mouth, but relatively weaker in near open sea water. Spectral absorption of suspended particulates was also measured. Results showed that the spectral absorption of chlorophyll a was greater in waters near Sanya river mouth, but relatively weaker in waters near open sea, which indicated higher concentration of phytoplankton in waters near Sanya river mouth. Except for water at the 5th sampling station, the ratio of spectral absorption of chlorophyll a to total suspended particulates in surface waters was greater than that in bottom waters at all stations.

• 유체기계공업학회:학술대회논문집
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• 2000.12a
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• pp.145-152
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• 2000

A turbopump system composed of two pumps and one turbine is considered. The turbine composed of a nozzle and a rotor is used to drive the pumps while gas passes through the nozzle, potential energy is converted to kinematic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of turbine system is investigated using compressible fluid dynamic theories with some pre-determined design requirements (i.e., pressure ratio, rotational speed, required power etc.) obtained from liquid rocket engine (L.R.E.) system design. For simplicity of turbine system, impulse-type rotor blades for open type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow rate compared to close-type system. In this study, a partial admission nozzle Is adopted to maximize the efficiency of the open-type turbine system. A design methodology of turbine system has been introduced. Especially, partial admission nozzle has been designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design for a 10 ton thrust level of L.R.E is presented.

• Journal of Environmental Health Sciences
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• v.28 no.2
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• pp.89-98
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• 2002

This study was taken in general hospital, hotel, shopping center, underground cafe, school, house, for the purpose of investigating the distribution of indoor radon concentration in urban area, by E-PERM which approved U.S. EPA, between August and November 1999. There are two sampling Places were exceed 148 ㏃/㎥(4 pCi/L; U.S EPA remedial level), difference mean is 24.0㏃/㎥ when compared with underground vs. aboveground indoor radon concentration in the same building and ratio is 1.6, so underground area is higher than aboveground (p<0.05). Influencing factors were examined. They related to the location of sampler(detector) open or near the door is lower radon concentration than inside portion, which explains probably open area has better ventilated air and dilutes indoor radon concentration. Temperature has a negative relationship (p<0.05) with indoor radon concentration and relative humidity has a positive (p<0.05) Simultaneously to investigate water radon concentration, collected piped-water and the results were very low, which is the same in piped-water concentration other countries. In conclusion, underground indoor radon concentration is higher than aboveground. Concentration was related to sampling spot, open portion is lower than inside. Higher the temperature, lower the indoor radon concentrations. On the other hand higher the relative humidity, higher the indoor radon concentrations. Indoor radon concentration is influenced by sampling point, temperature, relative humidity.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.2
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• pp.170-178
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• 2007

Most of parabolic approximation models employ a relatively limited open boundary condition in which there is no depth variation in the longshore direction outside of the computation domain so that Snell's law may be presumed to hold. Existing Kirby's condition belongs to this category and in the paper both modified Kirby's method and Dirichlet boundary condition are presented in detail and numerical results of three methods were shown. Judging from computation to wave propagations over a circular shoal in a constant depth, the method based on present Dirichlet boundary condition with fictitious numerical adjusting regions in both sides of the computation domain gives the least distorted amplitude ratio distribution.

• Current Photovoltaic Research
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• v.6 no.1
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• pp.12-16
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• 2018

The interest in perovskite solar cells has been skyrocketed owing to their rapid progress in efficiency in recent years. Here, we report the effect of non-stoichiometry in the methylammonium lead trihalide ($MAPbI_3$) precursors used in a solution process with different MAI : $PbI_2$ ratios of 1 : 0.96, 1 : 1.10, 1 : 1.15, and 1:1.20. With an increase in the $PbI_2$ content, the $PbI_2$ secondary phase was found to form at grain boundary region of perovskite thin films, as evidenced by X-ray diffraction (XRD) and scanning electron microscopy (SEM). In terms of device performance, open-circuit voltage in particular is significantly improved with increasing the molar ratio of $PbI_2$, which is possibly ascribed to the reduction in recombination sites at grain boundary of perovskite and hence the prolonged life time of light-generated carriers according to the reported. As a result, the $PbI_2-excess$ devices exhibited a higher power conversion efficiency compared to the MAI-excess ones.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.114-117
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• 2009

In this work, closing behavior of the voids generated in a casting process was investigated for various parameters such as reductions in height void size and billet rotation during hot open die forging process. The reduction in height and path schedule including the number of paths and billet rotation were chosen as key process variables to express the change of geometrical void shape and void closing behavior. On the other hand, values of die overlapping and die width ratio were set to be constant. Extend of void closure was observed and evaluated using tensile test and microscope. Based on the experimental result, it is ensured that void closure do not occur at 15% and 30% reduction in height as well as one or two rotations of a billet. The useful datum obtained from this study could be utilized to establish an optimum path schedule in the open die forging process.

• ETRI Journal
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• v.40 no.1
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• pp.51-60
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• 2018

In Long Term Evolution (LTE) cellular networks, the transmit power control (TPC) mechanism consists of two parts: the open loop (OL) and closed loop. Most cellular networks consider OL/TPC because of its simple implementation and low operation cost. The analysis of OL/TPC parameters is essential for efficient resource management from the cellular operator's viewpoint. In this work, the impact of the OL/TPC parameters is investigated for homogeneous small cells and heterogeneous small-cell/macrocell network environments. A mathematical model is derived to compute the transmit power at the user equipment, the received power at the eNodeB, the interference in the network, and the received signal-to-interference ratio. Using the analytical platform, the effects of the OL/TPC parameters on the system performance in LTE networks are investigated. Numerical results show that, in order to achieve the best performance, it is appropriate to choose ${\alpha}_{small}=1$ and $P_{o-small}=-100dBm$ in a homogenous small-cell network. Further, the selections of ${\alpha}_{small}=1$ and $P_{o-small}=-100dBm$ in the small cells and ${\alpha}_{macro}=0.8$ and $P_{o-macro}=-100dBm$ in the macrocells seem to be suitable for heterogeneous network deployment.