• Nuclear Engineering and Technology
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• v.45 no.2
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• pp.265-276
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• 2013

Pressure tubes made of Zr-2.5 wt% Nb alloy are important components consisting reactor coolant pressure boundary of a pressurized heavy water reactor, in which unanticipated through-wall cracks and rupture may occur due to a delayed hydride cracking (DHC). The Canadian Standards Association has provided deterministic and probabilistic structural integrity evaluation procedures to protect pressure tubes against DHC. However, intuitive understanding and subsequent assessment of flaw behaviors are still insufficient due to complex degradation mechanisms and diverse influential parameters of DHC compared with those of stress corrosion cracking and fatigue crack growth phenomena. In the present study, a deterministic flaw assessment program was developed and applied for systematic integrity assessment of the pressure tubes. Based on the examination results dealing with effects of flaw shapes, pressure tube dimensional changes, hydrogen concentrations of pressure tubes and plant operation scenarios, a simple and rough method for effective cooldown operation was proposed to minimize DHC risks. The developed deterministic assessment program for pressure tubes can be used to derive further technical bases for probabilistic damage frequency assessment.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.666-674
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• 2007

It is very important to estimate static squeezing pressure distributions for lining material of sterntube after bearing at dry dock stage since the maximum squeezing pressure value can be one of the significant characteristics representing coming navigation performances of the propulsion system. Moderate oil film pressure between lining material and propulsion shaft is also essential for safe ship service. In this paper, Hertz contact theory is explained to derive static squeezing pressure. Reynolds equation simplified from Navier-Stokes equation is centrally differentiated to numerically obtain dynamic oil film pressures. New shaft alignment technology of nonlinear elastic multi-support bearing elements is also used in order to obtain external forces acting on lining material of bearing. For 300K DWT class VLCC with synthetic bush of sterntube after bearing, static squeezing pressures are calculated using derived external forces and Hertz contact theory. Optimum partial slope of the after bush is presented by parametric shaft alignment analyses. Dynamic oil film pressures are comparatively evaluated for partially bored and unbored after bush. Finally it is proved that the partial slope can drastically reduce oil film pressure during engine running.

• Proceedings of the KIEE Conference
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• 2005.07d
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• pp.3081-3083
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• 2005

한국형 고속전철차량의 자동제어 구현을 위해서 우선 다양한 종류의 장치들로부터 상태정보(Line Voltage-열차가선전압, Bogie Hunting, Preset Speed, PWM, Train Velocity, Brake Pressure, Reservoir Pressure)를 취득해야하며, Main Process Unit(MPU)에서의 고속 Data 처리를 위해서 취득한 Analog Data를 신속하게 Digital Data로 변환해야 한다. 또한 열차내의 특수한 조건(Noise, Vibration)에서도 안정적인 데이터의 취득을 만족시켜야한다. 이와 같은 상황을 고려한 독자적이 통합형 데이터 취득 장치 -Integrated Data Acquisition Board(IDAB)-의 설계방안을 제시하였다.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1450-1454
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• 1996

Even though digital control type high speed solenoid valve is a little inferior to analog control type servo valve and proportional control valve in performance, it is cheap and has secure performance against pollutant and simple control circuit. But high speed solenoid valve is hardly used for heavy machinery instead of servo valve or proportional control valve that is used in severe condition because the valve itself is small capacity and it shows wide dead zone during on-off control and chattering of hydraulic cylinder by chattering of pressure. It is desirable to use low-priced and strong pollutant resistant high speed solenoid valve for obtaining reliability of operation from severe working condition because it isn't necessary to acquire response characteristic of high frequency when we consider the characteristic of heavy machinery operation. In this study, PWM control algorithm for pilot pressure control of large capacity pilot operating valve will be used for precision position control of heavy machinery hydraulic cylinder. Not only cost reduction of main control valve but also high reliability of heavy machinery in severe condition can be obtained by using this pilot operating spool valve with high speed solenoid valve.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.142-149
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• 2000

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed in the scale 1:1. The model experiments were executed at a pressure smaller than in the real gas turbine. The combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure, and NOx emission were measured at partial and full load for both model and on-site testing. The comparison of these items of information, received on similar modes in the stand and field tests, has allowed the development of a method of calculation and the improvement of gas turbine combustors.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1319-1327
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• 2001

The results of stand and field testing of a combustion chamber for a heavy-duty 150 MW gas turbine are discussed. The model represented one of 14 identical segments of a tubular multican combustor constructed 1:1 scale. The model experiments were executed at a lower pressure than that in a real gas turbine. Combustion efficiency, pressure loss factor, pattern factor, liner wall temperature, flame radiation, fluctuating pressure and NOx emission were measured at partial and full loads for both model and on-site testing. The comparison of these items in the stand and field test results led to has the development of a method of calculation and the improvement of gas turbine combustors.

• Journal of Biosystems Engineering
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• v.38 no.4
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• pp.306-311
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• 2013

Purpose: With the ever-rising energy prices, thermal energy heavily consuming facilities of the agricultural sector such as commercialized greenhouses and large-scale Rice Processing Complexes (RPCs) need to cut down their energy cost if they must run profitable businesses continually. One possible way to reduce their energy cost is to utilize combustible agricultural by-products or low-price oil instead of light oil as the fuel for their boiler systems. This study aims to analyze the heavy oil combustion characteristics of a newly developed hot water boiler system that can use both rice husk and heavy oil as its fuel convertibly. Methods: Heavy oil combustion experiments were conducted in this study employing four fuel feed rates (7.6, 8.5, 9.5, 11.4 $l/h$) at a combustion furnace vacuum pressure of 500 Pa and with four combustion furnace vacuum pressures (375, 500, 625, 750 Pa) at fuel feed rates of 9.5 and 11.4 $l/h$. Temperatures at five locations inside the combustion furnace and 20 additional locations throughout the whole hot water boiler system were measured to ascertain the combustion characteristics of the heavy oil. From the temperature measurement data, the thermal efficiency of the system was calculated. Flue gas smoke density and concentrations of air-polluting components in the flue gas were also measured by a gas analyzer. Results: As the fuel feed rate or combustion furnace vacuum pressure increased, the average temperature in the combustion furnace decreased but the thermal efficiency of the system showed no distinctive change. On the other hand, the thermal efficiency of the system was inversely proportionally to the vacuum level in the furnace. For all experimental conditions, the thermal efficiency remained in the range of 80.1-89.6%. The CO concentration in the flue gas was negligibly low. The NO and $SO_2$ concentration as well as the smoke density met the legal requirements. Conclusions: Considering the combustion temperature characteristics, thermal efficiency, and flue gas composition, the optimal combustion condition of the system seemed to be either the fuel feed rate of 9.5 $l/h$ with a combustion furnace vacuum pressure of 375 Pa or a fuel feed rate of 11.4 $l/h$ with a furnace vacuum pressure between 500 Pa and 625 Pa.

• Journal of Korean Society of Water and Wastewater
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• v.18 no.4
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• pp.493-499
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• 2004

Rejection characteristics of heavy metals by nanofiltration membranes were investigated. Nanofiltration membranes rejected heavy metals much better than chloride, sulfate and TOC, of which concentration in synthetic wastewater was higher than that of heavy metals. To consider rejection characteristics of various metals by nanofiltration membranes, separation coefficient, which is the ratio of the metal permeation rate to the chloride ion or TOC permeation rate, was introduced. In spite of different materials and different nominal salt rejection of nanofiltration membrane used, the separation coefficients of metals were nearly the same. In particular, the separation coefficient of arsenic against chloride ion and TOC was larger than any other separation coefficient of heavy metals. These phenomena were observed in the relationship between the molar conductivity and the separation coefficient for heavy metals.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.414-430
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• 2013

This paper shows the study of preswirl duct as an effective energy saving devices that have been devised and reviewed to support the propeller performance, especially for the ship of VLCC with large block coefficients. From the bare hull wake measurements, typical upper/lower asymmetry of hull wake at the propeller disk was found. The 2 kinds of pre-swirl duct, Unconventional half circular duct and Conventional circular pre-swirl duct have been designed and reviewed to recover the loss of propeller running in that condition. The general function of the pre-swirl duct was set to work against this asymmetry of wake and generate pre-swirled flow into the propeller against the propeller rotating direction. The optimum self propulsion tests with various angle configurations were carried out and the best configuration was decided. Accordingly, cavitation test was carried out with best configuration of unconventional half circular duct. The blade surface and tip vortex cavitation behaved smoother when the duct was mounted. The hull pressure amplitudes reflected this difference, so the hull pressure amplitude with duct was smaller than that of without duct.

• Korean Journal of Clinical Laboratory Science
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• v.42 no.3
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• pp.129-135
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• 2010

This study was performed to determine the risk factors associated with increased body mass index (BMI) in 672 heavy industry men workers. Subjects were examined in March, 2010 to September, 2010 in Gyeongnam province. Height, weight, systolic blood pressure, and diastolic blood pressure were measured. And fasting blood glucose, total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglyceride levels were measured by Olympus AU 680, and their BMIs calculated. Age, smoking statue, and alcohol drinking of the workers were surveyed by questionnairs. The mean total cholesterol levels were $190.06{\pm}36.62mg/dL$, HDL-cholesterol $53.65{\pm}11.92mg/dL$, LDL-cholesterol $104.28{\pm}30.31mg/dL$, triglyceride $151.11{\pm}99.53mg/dL$, and fasting blood glucose $96.92{\pm}19.53mg/dL$. Mean systolic blood pressure was $126.08{\pm}13.78mmHg$, and diastolic blood pressure $71.88{\pm}10.45mmHg$. Subjects were categorized into two BMI groups, BMI ${\geq}23$ and BMI ${\leq}22.9$. The subjects with BMI of 23 or above had significantly higher levels of LDL-cholesterol, systolic blood pressure, and triglyceride, with lower levels of HDL-cholesterol. BMI showed the highest level at the age of thirties, increasing with age. BMI of smokers was higher than BMI of non-smokers, not showing a link between alcoholics and non alcoholics. In conclusion, age, systolic blood pressure, and HDL-cholesterol are mostly relevant to the increase of BMI in this study.