• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2008년도 춘계 종합학술대회 논문집
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• pp.780-783
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• 2008

본 연구는 Manning's coefficient 와 Chezy coefficient를 이용하여 양재천 하도의 조도를 산정할 수 있는 모형을 개발하였다. 계산된 등가조도는 수위-유량자료가 없는 하천에서 수위, 유량 및 조도계수를 산정하는데 이용하였다. 조도계수는 대상구간에 대해 부정류 해석을 수행하여 유량규모별로 수위를 산정하였다. 그 결과 식생이 있을 때와 없을 때의 수위차가 1.29m 이었고, 식생밀도가 증가함에 따라 흐름저항이 크게 증가함을 알 수 있었다.

• Corrosion Science and Technology
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• 제8권5호
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• pp.193-196
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• 2009

For the estimation of uncertainty in potentiodynamic polarization resistance measurement, the type A uncertainty was measured using type 316 stainless steel in an acidified NaCl solution. Sensitivity coefficients were determined for measurand such as scan rate of potential, temperature of solution, concentration of NaCl, concentration of HCl, surface roughness of specimen and flow rate of purging gas. Sensitivity coefficients were large for the measurand such as the scan rate of potential, temperature of solution and roughness of specimen. However, the sensitivity coefficients were not the major factors influencing the combined standard uncertainty of polarization resistance due to the low values of uncertainty in measurements of the measurands. A major influencing factor was the concentration of NaCl. The value of type A uncertainty was 1.1 times the value of type B uncertainty, and the combined standard uncertainty was 10.5 % of the average value of polarization resistance.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권4호
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• pp.246-248
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• 2000

Closed-form expressions for the temperature dependent breakdown voltage and the on-resistance of the Si power MOSFETs were derived by employing effective temperature dependent ionization coefficient for electrons and holes. The breakdown voltage increases by 20% and the on-resistance increases 2 times when the temperature increases from 300 K to 423 K. The analytic results normalized to the values at 300 K show good agreement with the experimental data of Motorola within 3.5% and 7% for the breakdown voltage and the on-resistance, respectively.

• 대한조선학회논문집
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• 제40권4호
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• pp.8-15
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• 2003

This paper presents the method for developing an optimum hull form with minimum wave resistance using SQP(sequential quadratic programming) as an optimization technique. The wave resistance is evaluated by a Rankine source panel method with non-linear free surface conditions and the ITTC 1957 friction line is used to predict the frictional resistance coefficient. The geometry of the hull surface is represented and modified using B-spline surface patches. The optimization method is applied to Series 60 hull and KCS(KRISO 3600 TEU Container Ship). The obtained results prove that the method is appropriate for preliminary hull form design.

• 한국농공학회논문집
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• 제47권7호
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• pp.37-45
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• 2005

In this study, R/S analysis which was proposed by Mandelbrot & Wallis (1969) was applied to evaluate the presence of the fractal property in the cone tip resistance of in-situ CPT data. Hurst exponents (H) were evaluated in the range of 0.660$\sim$0.990 and the average was 0.875. It was confirmed that a cone tip resistance data had the characteristic of fractals and it was expected that cone tip resistance data sets are well approximated by a fBm process with an Hurst exponent near 0.875. It was also observed that the boundary between layers were obviously identified as a result of R/S analysis and it will be usage in practices.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.967-973
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• 2004

Rock socketed drilled shafts transfer significant portion of structural loads at the socketed part. Therefore, a proper design of side and base resistances of a shaft at the socket is a major concern for the geotechnical engineers. In this study, we modified the Hoek-Brown criterion to estimate side resistance of rock socketed drilled shafts. Earlier method to compute side resistance of a shaft is linear or power functions of intact rock masses. However, side resistance is mobilized like shearing which influenced by the mechanical properties of concrete and rock masses, adhesion of rock/concrete interface, roughness of rock socket. Therefore, a single coefficient or power of uniaxial compressive strength of intact rock cannot provide accurate values of side resistance in a wide range of the uniaxial compressive strength. A new approach proposed in this study can consider in situ rock mass condition (frequency or discontinuities, weathering condition), and rock types thus, it has a wider applicability than the earlier models.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권6호
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• pp.613-623
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• 2017

A semi-empirical model to predict ship resistance in level ice based on Lindqvist's model is presented. This model assumes that contact between the ship and the ice is a case of symmetrical collision, and two contact cases are considered. Submersion force is calculated via Lindqvist's formula, and the crushing and breaking forces are determined by a concept of energy consideration during ship and ice impact. The effect of the contact coefficient is analyzed in the ice resistance prediction. To validate this model, the predicted results are compared with model test data of USCGC Healy and icebreaker Araon, and full-scale data of the icebreaker KV Svalbard. A relatively good agreement is achieved. As a result, the presented model is recommended for preliminary total resistance prediction in advance of the evaluation of the icebreaking performance of vessels.

• 한국전기전자재료학회논문지
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• 제30권1호
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• pp.59-62
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• 2017

CNT (carbon nanotube) resistors with low resistance and negative TCR (temperature coefficient of resistance) were fabricated with yarned CNT (carbon nanotube) fibers. The CNT fibers were prepared by yarning CNTs grown on the silicone substrate by CVD (chemical vapor deposition) method. The CNT resistors were fabricated by winding CNT fibers on the surface of ceramic rod. Both metal terminals were connected with the CNT fiber wound on the ceramic rod. We measured electrical resistance and thermal stability with the number of CNT fibers wound. The CNT resistor system shows linearly decreased resistance with the number of CNTs wound on the ceramic rod and saturated at 20 strands. The CNT resistor system has negative TCR between $-1,000{\sim}-2,000ppm/^{\circ}C$ and stable frequency properties under 100 kHz.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.152-155
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• 1996

Platinum thin films were deposited on $Al_2$O$_3$substrate by DC magnetron sputtering for RTD(Resistance Thermometer Devices) temperature sensors. We made Pt resistance pattern on $Al_2$O$_3$substrate by lift-off method and fabricated Pt-RTD temperature sensors by using W-wire, silver epoxy and SOG(spin-on-glass). In the temperature range of 25~40$0^{\circ}C$, we investigated TCR(temperature coefficient of resistance) and resistance ratio of Pt-RTD temperature sensors. TCR values were increased with increasing the annealing temperature, time and the thickness of Pt thin films. Resistance values were varied lineally within the range of measurement temperature. At annealing temperature of 100$0^{\circ}C$, annealing time of 240min and thin film thickness of 1${\mu}{\textrm}{m}$, we obtained Pt-RDT TCR value of 3825ppm/$^{\circ}C$ closed to the Pt bulk value.

• 수산해양기술연구
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• 제17권2호
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• pp.109-113
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• 1981

Most existing theories on ship waves and wave resistance are based on the perturbation of the flow field by a small pararr.eter which specifies the slenderness of the ship hull. Since however, ship hulls in practice are neither so slender nor thin enough to secure the validity of the linearized theory, the agreen:ent between the theoretical prediction and the experimental result is not generally satisfactory. The author pointed out that the contribution by the non-linear term in the free surface condition can be represented by sorr.e source distribution over the still water plane. This paper leads to a forrr.ula for the wave resistance of not slender ships at low Froude nurr.bers. and deals with the asynptotic expression. As a nurr.erical example, the wave resistance of Wigley model is calculated, and the result is compared with experimental values. It is concluded that the wave resistance coefficient varies in the rate of Fn6 at low speed limit in general. A comparison with the result derived from the linearized free surface condition shows that the non-linearity of the free surface is irr portant at low speed.