• KEPCO Journal on Electric Power and Energy
• /
• v.3 no.2
• /
• pp.127-131
• /
• 2017

The present paper describes the slagging field data obtained with the one-dimensional process model for the 500 MW tangentially coal fired boiler in Korea. To obtain slagging field data in terms of thermal resistances [$m^2{\cdot}^{\circ}C/kW$], a number of plant data were collected and analyzed with the one-dimensional modelling software at 500 MW full load. The slagging field data for the primary superheater were obtained for six coal blends, and compared with two TMA (Thermo-Mechanical analyzer) slagging indices and the numerical slagging index, along with the conventional slagging indices which were modified with the ash loading. The advanced two TMA indices for six blended coals give a good slagging tendency when comparing them with the slagging field data, while the modified conventional slagging indices give a relatively poor agreement.

• Proceedings of the KIEE Conference
• /
• 1997.11a
• /
• pp.285-287
• /
• 1997

We have deposited hydrogen-free diamond-like carbon (DLC) films by pulsed laser deposition of graphite. Pulsed laser deposition (PLD) can be utilized to generate films with desired properties quite different from those of the starting material. Since DLC films grown by PLD using turbo pump are perpared without hydrogen, they have a higher density and a higher index of refraction than the hydrogenated DLC films. In this study, effects of the substrate temperature and laser energy density on the properties of DLC films were systematically investigated. The structure and properties of the films have been studied by scanning electron microscopy (SEM), Fourier Transform Infrared (FT-IR), X-ray diffraction (XRD), and Raman spectroscopy.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.10
• /
• pp.1400-1404
• /
• 2001

$Holstein\;{\times}\;indigenous$ multiparous dairy cows were offered diets with increasing roughage neutral detergent fiber (NDF) contents to determine the effects on intake, milk yield and compositions. Roughage NDF contents were 15, 18, 21 and 24% dry matter (DM), and concentrate NDF content was 10% DM. Experimental treatments were isonitrogenous and isocaloric diets. Maximum and minimum temperature humidity index during the experimental period were 85.9 and 76, respectively. Intakes of DM, crude protein and net energy, 4% fat corrected milk, milk protein and average daily gain decreased with increasing roughage NDF contents (p<0.05). Intakes of ether extract (p<0.01) and dietary NDF (p>0.05) and milk fat (p<0.01) increased with increasing roughage NDF contents. The results support the conclusion that higher DM intake, optimal milk yield and compositions can be maintained with lower roughage NDF diets for dairy cows under tropical conditions.

• Ocean and Polar Research
• /
• v.25 no.4
• /
• pp.437-446
• /
• 2003

Field measurements of directional waves were carried out during the summer of 2002 at two coastal sites in water of finite depth. A couple of general purpose instruments were used employing acoustic Doppler technology. The aim of the study was to investigate the spatial behavior of the directional movement of waves as they come ashore. In total,74 tests were carried out during which sea states of low to moderate intensity were recorded. A great number of these runs displayed bimodal characteristics of the spreading function at high frequencies. It was found that in general, the frequency-integrated directional width tends to broaden as the water shoals and when refraction effects are negligible. This is attributed to wave-wave interactions that become pronounced in shallow water. The same directional width showed, also, a tendency to increase with increasing peak frequency of the sea state spectrum. The behavior of the kurtosis of the spreading function was also examined. It was found that for higher frequencies this index tends to increase in wave spectra above a certain sea severity threshold.

• Architectural research
• /
• v.8 no.2
• /
• pp.37-42
• /
• 2006

Starting from the quadratic optimal control algorithm, this study obtains the relation of the performance index for constrained systems and Gauss's principle. And minimizing a function of the variation in kinetic energy at constrained and unconstrained states with respect to the velocity variation, the dynamic equation is derived and it is shown that the result compares with the generalized inverse method proposed by Udwadia and Kalaba. It is investigated that the responses of a 10-story building are constrained by the installation of a two-bar structure as an application to utilize the derived equations. The structural responses are affected by various factors like the length of each bar, damping, stiffness of the bar structure, and the junction positions of two structures. Under an assumption that the bars have the same mass density, this study determines the junction positions to minimize the total dynamic responses of the structure.

• 연구논문집
• /
• s.25
• /
• pp.105-113
• /
• 1995

Fresnel lenses are developed for flat optics with the optical characteristics close to aspherical lens such as sharp focusing and dispersion instead of spherical or aspherical surface. Usually, these fresnel lenses and diffraction gratings are machined by high-energy beam such as electron beam machining, but recently with the development of ultra precision machine tool and machining technology, 3-dimension micro machining becomes preferable. This study on the micro machining of fresnel lens is carried out to develop the basic technology of ultra precision micro machining. The machined lens mold will be used for the manufacturing of fresnel lens with 120mm focal distance using synthetic resin material with 1.49 refractive index(PMMA), and the shape of lens is 48mm diameter, $300\mum$ pitch and about $5-700\mum$depth of groove in brass.

• Journal of the Korean Institute of Navigation
• /
• v.19 no.2
• /
• pp.1-12
• /
• 1995

The final aim of our research project is a study on assessment of automatic steering system of ships in open seas. In order to achieve this aim, we need to know the characteristics of each component of the system, and also to know the characteristics of disturbance to ship dynamics. In this paper, we provide calculation method of irregular disturbance to ships in autopilot navigation in open seas, and also show calculation examples about two kinds of ship, ore carrier and fishing boat. The disturbance consists of irregular wave and random wind. The disturbance is calculated as equivalent yaw angular velocity. Each spectrum and time history of disturbance are reasonably evaluated. Further investigation concerning to performance index of autopilot system and energy loss related to automatic course keeping, will be dealt with in another paper.

• Macromolecular Research
• /
• v.13 no.3
• /
• pp.194-205
• /
• 2005

The network structure of Ni-coated carbon black (NCB) composites filled with phenolic resin was investigated by means of using scanning electron microscopy, viscosity, interfacial tension, shrinkability, Flory-Huggins interaction parameters, and swelling index. The electrical properties of the composites have been characterized by measurement of the specific conductivity as a function of temperature. Additionally, the variation of conductivity with temperature for the composites has been reported and analyzed in terms of the dilution volume fraction, relative volume expansion, and barrier heights energy. The thermal stability of phenolic-NCB composites has been also studied by means of the voltage cycle processes. The experimental data of EMI wave shielding were analyzed and compared with theoretical calculations. The mechanical properties such as tensile strength, tensile modulus, hardness and elongation at break (EB) of NCB-phenolic resin composites were also investigated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.05a
• /
• pp.146-149
• /
• 1996

Polymerization rate, transmittance, refractive index, and extinction coefficient of plasma polymerized tetramethydisiloxane (TMD) have been investigated. The rate of polymerization of TMD films increased nonlinearly with the discharge lower. The refractive indices of thin films varied from 1.40 to 1.43 and they also increased with increasing discharge power. Also, the extinction coefficient was about 0.2 and is independent of photon energy.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.29 no.3
• /
• pp.453-459
• /
• 2000

This study was performed to investigate the effect of dietary crab shell powder on lipid metabolism in diet induced hyperlippidemic rats. Sixteen male Sprague-Dawley rats were divided into two groups and fed 20% (w/w) carb shell powder supplemented diet for 4 weeks. Energy intake and weight gain were lower in experimental group than in control group. Concentrations of plasma triglyceride, total cholesterol, LDL-cholesterol, and atherogenic index (AI) were decreased and concentration of HDL-cholesterol was increased by crab shell powder supplementation. Concentrations of liver total cholesterol and triglyceride were significantly lower in experimental group. The crab shell decreased triglyceride and cholesterol concentration in plasma and liver, and increased bile acid excretion in feces. Therefore, the crab shell powder is assumed to exhibit function of chitin or chitosan that effects on lipid metabolism and cholesterol reabsorption.