• Transactions of The Korea Fluid Power Systems Society
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• v.5 no.3
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• pp.1-8
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• 2008

The optimal design of a large-size fully hydraulic breaker is studied in this paper. Mathematical modeling of the breaker is established and verified by experiments. Through sensitivity analysis, the key design parameters of the breaker are selected, which mostly affect the performance of the breaker. Taguchi method is used to optimize the key design parameters in order to maximize the output power through simulation using AMESim. As a result, the impact energy is increased by 18.9% and the output power is increased by 12.4% compared with the current design. The pressure pulsation in the supply line is also reduced by the optimization.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.202-208
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• 2015

For a prototype turbine operating under part load conditions, the turbine output is fluctuating strongly, leading to the power station incapable of connecting to the grid. The field test of the prototype turbine shows that the main reason is the resonance between the draft tube vortex frequency and the generator natural vibration frequency. In order to reduce the fluctuation of power output, different measures including the air admission, water admission and adding flow deflectors in the draft tube are put forward. CFD method is adopted to simulate the three-dimensional unsteady flow in the Francis turbine, to calculate pressure fluctuations in draft tube under three schemes and to compare with the field test result of the prototype turbine. Calculation results show that all the three measures can reduce the pressure pulsation amplitude in the draft tube. The method of water supply and adding flow deflector both can effectively change the frequency and avoid resonance, thus solving the output fluctuation problem. However, the method of air admission could not change the pressure fluctuation frequency.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.2
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• pp.19-28
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• 2010

Generally, combustion instability is generated by the mutual coupling between the heat release and the acoustic pressure in the combustor. On the occasion, the acoustic pressure generates the oscillation of the mass flow rate of propellant injected from injector, and this oscillation again affects combustion in the combustor. So, the dynamic characteristics of the injector have been studied to control combustion instability using injector itself in Russia from 1970's. In order to study injector dynamics, a mechanical pulsator for forced pressure pulsation is produced and the method to quantify the mass flow rate of the propellant that is oscillating at the exit of the injector is developed. With the pulsator and the method, pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the exit of the simplex swirl injector are measured in real time. And phase-amplitude characteristics of each parameter are analyzed using these pulsating values acquired at the exit of the simplex swirl injector.

• The Journal of the Society of Korean Medicine Diagnostics
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• v.12 no.2
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• pp.1-7
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• 2008

Objectives: The basis research of aged people's healthcare technology is very important, because our nation goes into an aged society rapidly. Especially in traditional medicine, pulse shapes of aged people were supposed to weak and empty pulse until now, but any objective measurement and compare research do not taken. Methods and Results: Therefore in this study we design observation study to find characteristic of pulse between younger group (age $20{\sim}30$) and elder group (age $43{\sim}80$) in Busan area. We used 3-dimensional pulse analyzer '3-D MAC' (Daeyomedi Co., Ltd.). And major parameters for comparison are 1) pulse height (h1), 2) applied pressure, 3) pulse power (energy), 4) high pressure duration (w) and 5) R-AI. Conclusions: According to analysis result, elder people's pulse has more large value in pulse height, applied pressure and pulse power than younger's that. It reveals that elder people in modernized lifestyle has Yang symptoms as well Yin symptoms. Consequently we need new method to care elder people's health, and this means more important direction than old text book. From now on verification research with objective diagnosis device like 3-D MAC, must be activated to build of evidence in traditional medicine. Cause traditional medicine's spirit of care and prevention is suitable to care elder people's cardiac and cerebral vascular disease those are have close relation with elder people.

• Journal of Chest Surgery
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• v.16 no.2
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• pp.170-174
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• 1983

Aortic arch syndrome is an unusual disease entity characterized by the narrowing or obliteration of major branches of the arch of the aorta regardless of etiology. We have experienced 2 cases. One of them was 22 years old office girl with 3 months history of headache, intermittent syncope and weakness and claudication on left arm especially during her physical exercise. On physical examination, pulseless on left antecubital and radial artery and blood pressure on left arm was inable to check and coldness with weakness were noted on the same side. Aortic angiography reealed 34% narrowing of left subclavian artery as that of right. But both common carotid artery and both axillary arterial patency were relatively good. Through right supraclavicular and left axillary incision, bypass graft with Gore-tex prosthesis (I.D. 6mm, Length 25 cm) was implanted from right subclavian artery on 2cm distal to origin of right common carotid arery to left axillary artery distal to axillary fossa. End to side anastomosis with preservation of left subclavian artery was done. Postoperative state was stable with blood pressure of 110/70 mmHg on left arm and palpable antecubital and radial pulsation. Another one was 41 year old male patient with 8 months history of pain and numbness on right upper arm and shoulder. On admission, right arm blood pressure was 110/80 mmHg, left arm was 160/110 mmHg, but other physical findings had no abnormalities. Angiography revealed segmental narrowing of right axillary artery on the beginning with 2 cm in length. Operative treatment with right wupraclavicular and right axillary incision, bypass graft with great saphenous vein (Length; 15 cm) from right subclavian artery between scalenus anticus and medius to axillary artery at distal end of axillary fossa was done. The authors report two cases of Aortic arch syndrome treated with bypass graft using Autograft or Gore-tex with good result.

• Journal of Korean Academy of Nursing
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• v.14 no.2
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• pp.93-111
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• 1984

The main purpose of this study is to develop a ratio scale measuring level of pain using Korean pain terms. The specific purposes of this study are to identify the degree of pain of each pain term in each subclass: to classify each subclass in terms of dimensions of pain; and to analyze factors of the Korean pain ratio scale clustering together. One hundred an4 fifty eight pain terms which were originally identified as representative terms and their synonyms were used for data collection. Fifty eight nursing professors ana sixty one medical doctors who have contacted with patients having pain were asked to rate the weight of each pain term on a visual analogue scale. Subclasses in which ranks of pain terms were same f s findings in two previous studies were 1) thermal 3 am 2) cavity pressure, 3) single stimulating pain, 4) radiation pain. and 5) chemical pain. Subclasses in which ranks of pain terms were confused were 1) incisive pressure, and 2) cold pain. Subclasses in which one new pain term was added were 1) inflammatory-repeated pain, 2) punctuate pressure, 3) constrictive pressure, 4) fatigue-related pressure, and 5) suffering-relate4 pain. Subclasses in which two new pain terms were added were 1) traction pressure, 2) peripheral nerve pain, 3) dull pain, 4) pulsation-related pain, 5) digestion-related pain, 6) tract pain, and 7) punishment-related pain. Subclass in which 3 new pain terms were included was fear-related pain. Rating scores of 5 words in 4 subclasses were significantly different between the normal group and the extreme group of subjects in terms of subjective rating. Only one word among 6 words was that newly added to the scale. Rating scores of 12 words in 9 subclasses were significantly different between doctor group and nursing professor group. Among these 12 words, only 3 were those newly added to the scale. In comparison of these 12 words, mean scores of the nursing professors were always 7 to 16 points higher than those of the medical doctors. In the analysis of judgement of subjects in terms of dimensions of pain terms, subclasses of dull pain, cavity pressure, tract pain and cold pain were suggested to be included in the miscellaneous dimension. As a result of factor analysis of the ratings given to 96 pain words using principal components analysis without iteration and with varimax rotation limiting the number of factors to 4, factors of severe pain (factor I) mild-moderate pain (factor II) , causative pain (factor III) and temperature-related pain(factor IV) were extracted with the factor loading above 0.388. When the pain words were re-arranged on the bases of factor loading above 0.368, number of factors decreased to only first two factors. Maximum score of pain word in factor II was 46.17 and the minimum score of the factor I was 45.36. Further studies are needed to identify the validity, reliability, sensitivity and practicability of this ratio scale using patients having various sources of pain.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.175-181
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• 2019

In the case of a conventional single stage decompression regulator used for large depressurization in the hydrogen fuel cell system of a fuel cell electric vehicle (FCEV), problems can arise, such as pulsation, slow response, hydrogen brittleness, leakage, high weight, and high cost due to high decompression. Most of these problems can be overcome easily using two decompression mechanisms (two-stage structures). In addition, a wide outlet-pressure control range can be secured if an electronic solenoid is applied to the second decompression. Accordingly, it is necessary to improve the precision of the outlet pressure of a two-stage pressure-reducing regulator and develop techniques, such as leakage prevention, durability, light weight, and price reduction. Therefore, to improve the outlet pressure accuracy and prevent leakage, the structural part before and after decompression to improve the air tightness were divided and the analysis was carried out assuming that the valve part was closed (open ratio: 0%) after each initial internal pressure application.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.2
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• pp.479-491
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• 1994

Discrete vortex method was applied for simulating an active control of turbulent leading- edge separation bubble. The leading-edge separation zone was perturbed by a time-dependent sinusoidal perturbation of different frequencies and levels. In order to describe the local sinusoidal perturbation at the separation point, a source pulsation vortex technique was proposed. The present two-dimensional vortex simulations were qualitatively compared with the experimental results for a blunt circular cylinder, where perturbation was introduced along the square-cut leading edge of the cylinder $(Kiya et al.^{(6,7)}).$ It was found that the reattachment length attained a minimum point at low levels of perturbation and two minima at a moderate higher perturbation frequency. The effects of local perturbation on the evolution of leading-edge separation bubble were scrutinized by comparing the perturbed flow with the natural flow. These comparisons were made for the distributions of mean velocity and its velocity fluctuations, intermittency and wall velocity. The motions of instantaneous reattachment in the space-time domain were demonstrated, which were also compared with the experimental findings. In order to investigate the reduction mehanism of reattachment length in the separation bubble, various cross-correlations for velocity and pressure and the relevant convection velocities were evaluated. It was observed that the convection velocity was closely associated with its corresponding pulsationg frequency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3A
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• pp.279-286
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• 2010

Although seaman has made a contribution marine transportation and the marine products industry, the current status of preventing occupational disease by monitoring health danger factors is very unsatisfied. Therefore, a monitoring system regarding health condition and disease occurrence of seaman is required. In this paper, we propose a real-time sailor management system based on uniqutious healthcare, which collects various organic signals and analyzes their relation in order to confirm blood pressure, temperature and pulsation of seaman. The proposed system enables a medical doctor to manage the diseases anywhere at any time even via a PC and PDA.

• The KSFM Journal of Fluid Machinery
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• v.8 no.2 s.29
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• pp.23-30
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• 2005

The rotary compressor is widely used in the air conditioner because it is efficient and compact. Recently, the need for silent and efficient compressors is much stronger than the past. The new type muffler was invented to reduce the noise level and to improve the efficiency. The new type muffler that has two side discharge holes and dome shape resulted in much lower overall noise level, especially noise levels around 1kHz than the old type one of one center discharge hole in the acoustic spectra. Also it showed a higher efficiency of air conditioner by lowering oil discharging amount of a compressor than old type one of a rectangular shape and two side discharge holes. The noise reduction and efficiency improvement by the new type muffler were verified by tests for votary compressors and air conditioners.