• 한국정밀공학회지
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• 제17권8호
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• pp.165-171
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• 2000

In this study the 4-way spool valve characteristics are clearly defined and clearly defined and proposed new type of spool valve. This paper presents governing equations of the flow through clearances between sleeve and spool as a model of orifice flow for null characteristics analysis and programmed analysis software of it. This software is possible to basically analysis that not only which case of open center closed center or critical center but _ -displacement of spool lab position boundary region and spool opening of the valve and to estimate the pressure variation in the spool and external leak flow variation. We are convinced that the scale of load pressure difference is changed as lab condition of valve and this scale is changed with boundary point on the annular clearance. It is vary useful to designer and user of spool valve with this design data and analysis software.

• Archives of Pharmacal Research
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• 제13권3호
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• pp.227-232
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• 1990

A Physiologically based pharmacokinetic model was used to describe the distribition and elimination of cefriazone in the rat. To validate the practical application of the model, the effect of cffeine on the model was also examined. The model consisted of eleven compartments representing the major sites for ceftriaxone distribution including carcass which served as a residual compartment. Elimination was represented by renal and hepatic (metabolic biliary )excretion with GI secretion and re-absorption. The drug concentrations in most of the tissues were simulated using flow limited equations while brain levels were simulated using membrane limited passive diffusion distribution. The experimental data were obtained by averaging the concentration of drug in the plasma and tissues of five rats after i. v. injection of cefriazone 100 mg/kg without and with caffeine 20 mg/kg. The data for the amount of ceftriazone excreted in urine and gut contents were used to apportion total body clearance. HPLC with UV detection was used for the assay with 0.1-0.2 $\mu$g/ml sensitivity. The great majority of drug concentrations with and without caffeine show reasonably good agreements to the simulation results within 20%. The effect of caffeine on renal and hepatic clearances was apparent with 18.8% and 18.6% increase in the model values, respectively.

• 신재생에너지
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• 제18권3호
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• pp.32-42
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• 2022

Rapid spread of intermittent renewable energy has amplified the instability and uncertainty of power systems. The Korea Power Exchange (KPX) promoted efficient management by opening the power brokerage market in 2019. By combining small-scale intermittent renewable energy with a flexible facility through the power brokerage market, the KPX aims to develop a virtual power plant system that will allow the conversion of existing intermittent renewable energy into collective power plants. However, the participation rate of renewable power owners in the power brokerage market is relatively low because other markets such as the small solar power contract market or the Korea Electric Power Corporation power purchase agreement are more profitable. In this study, we used a choice experiment to determine the attributes affecting the participation rate in the power brokerage market for 113 renewable power owners and estimate the value of the power brokerage market. According to the estimation results, a low smart meter installation cost, low profit variations, long contract periods, and few clearances increased the probability of participation. Moreover, the average value of the power brokerage market was estimated to be 2.63 million KRW per power owner.

• 대한조선학회지
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• 제19권1호
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• pp.3-14
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• 1982

In this paper, the sway added mass of a rectangular cylinder in a restricted water is considered by applying Hamilton's principle as the frequency tends to zero. The present method is an extension of Isshiki's method proposed in 1978. In the present method, it is assumed that the fluid velocity distribution in each subdomain of the fluid can be represented by higher order polynomials while Isshiki assumed linear velocity distribution. The fluid flow is assumed as a rotational motion in the present analysis. However, the results obtained from the present method show good agreement with Bai's numerical results for the case of large clearances between a canal wall and a cylinder. From Kelvin's minimum energy theorem, we can see that the value of sway added mass obtained from the present method approaches the upper bound. The approximate formula obtained in the present study takes a simple form which consists of the dimensions of the canal and the cylinder. The present formulae are derived for the cases of a rectangular cylinder swaying at the center of a narrow or wide canal relative to a cylinder, at off-center location in a canal, and in the restricted water with a single wall. From the results of numerical calculation, it is concluded that the sway added mass in restricted waters is more affected by water depth than clearance between a wall and a cylinder.

• Tribology and Lubricants
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• 제39권4호
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• pp.123-132
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• 2023

In this study, the expansion, stress, and operating clearance of bearing elements during operation are observed using the inner/outer ring temperature test data of a 3.0×10⁶ DN-class roller bearing. The operating clearance characteristics of inner-/outer-ring cooling (IORC) bearings are compared to those of inner-ring cooling (IRC) bearings. For IRC bearings, the thermal expansion of the outer ring is the most important factor in clearance variation. As a result, the operating clearance is less than the initial clearance of 61 ㎛, and the operating clearance decreases to 0.5 ㎛ at 25,500 rpm. Conversely, the temperature of the outer ring of IORC bearings is lower than that of IRC bearings, so the operating clearance is kept smaller. When the coolant flow rate to the outer ring is approximately 1.5 to 2.0 L/min, the temperature difference between the inner and outer rings is minimized and the operating clearance is maintained at a significantly lower level than IRC bearings. Small operating clearances are expected to be effective in reducing cage slip and skid damage in roller bearings. The results and analysis procedures of this study can be utilized to design of bearing clearance, lubricant flow rate, and assembled interference in the early design stage of aerospace roller bearings.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.3975-3984
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• 2022

Distributed control system architecture is adopted for I&C systems of Prototype Fast Breeder Reactor, where the geographically distributed control systems are connected to centralized servers & display stations via switched Ethernet networks. TCP/IP communication plays a significant role in the successful operations of this architecture. The communication tasks at control nodes are taken care by TCP/IP offload modules; local area switched network is realized using layer-2/3 switches, which are finally connected to network interfaces of centralized servers & display stations. Safety, security, reliability, and fault tolerance of control systems used for safety-related applications of nuclear power plants is ensured by indigenous design and qualification as per guidelines laid down by regulatory authorities. In the case of commercially available components, appropriate suitability analysis is required for getting the operation clearances from regulatory authorities. This paper details the proposed approach for the suitability analysis of TCP/IP communication nodes, including control systems at the field, network switches, and servers/display stations. Development of test platform using commercially available tools and diagnostics software engineered for control nodes/display stations are described. Each TCP link behavior with impaired packets and multiple traffic loads is described, followed by benchmarking of the network switch's routing characteristics and security features.

• Korean Chemical Engineering Research
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• 제45권2호
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• pp.124-132
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• 2007

본 논문에서는 Ti 모재에 대한 Pt 도금 특성 연구를 통하여 안정한 platinized Ti 전극의 제조 방법이 제시되었으며, Sn이 흡착된 platinized Ti 전극의 질산염 이온에 대한 전기화학적 특성이 연구되었다. 에칭된 Ti 모재 표면에 전착된 Pt 도금 층 내에 적당하게 공간적 틈을 갖도록 도금하는 것은 도금 후 표면에 잔존하는 도금 용액 오염원을 제거하는데 효과적이며, 또 용액과 접하게 되는 전극의 실제 표면적을 최대화할 수 있었다. 제작된 platinized Ti 전극을 끓이는 과정과 전해 세정 과정을 통해 안정적이며 재현성 있게 만드는 것은 Sn-modified platinized Ti 전극에서 표면의 Sn 덮힘율을 정량화하는데 있어 매우 중요하였다. 전해 세정 과정은 전극 표면에 형성된 솜털과 같은 미세한 돌기들이 없어지면서 전극 표면을 안정화된 구조로 변화시켰다. 본 연구의 경우 질산염 이온의 환원을 목적으로 하는 Sn-modified platinized Ti 전극은 약 30분 도금 시간을 통해 제조한 경우가 가장 좋았다.

• 대한조선학회논문집
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• 제37권3호
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• pp.57-68
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• 2000

이착륙 속력을 줄이기 위해 날개 밑으로 프로펠러 후류를 불어넣어 날개와 수면사이의 압력을 증가시키는 PAR(Power Augmented Ram) 효과는 해면효과익선의 성능을 크게 향상시킨다. 본 논문에서는 풍동실험을 통해 이러한 PARWIG(Wing in Ground)선의 공력특성을 연구하였으며 송풍기(blower)와 덕트(duct)를 사용한 제트분사를 프로펠러 후류로 대신하였다. 제트의 분사속도, 분사위치(수평 및 수직 방향), 분사각 및 덕트 직경 변화에 대해 20인승 PARWIG선의 1/25 축소 모형선의 지면과의 고도, 앙각 및 플랩각의 변화에 따른 양력, 항력 및 피치모멘트를 계측하여 공력특성을 비교하였다. 적절한 PAR효과의 사용은 양력을 크게 증가시키며 최대 4의 양력계수까지 얻을 수 있었다.

• 한국임상약학회지
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• 제1권1호
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• pp.31-36
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• 1991

Tobramycin is one of the most frequently selected agents for pharmacokinetic drug monitoring because of its narrow therapeutic index and essential role for the management of serious infections, especially gram-negative infections. Its pharmacokinetic parameters are dependent on race, sex, age, ideal body weight. disease states, and etc. Therefore, to schedule the dosing of tobramycin, the individual pharmacokinetic parameters such as half-life and volume of distribution are needed. However, these pharmacokinetic parameters have never been reported in Koreans. The purposes of this study were to evaluate the volume of distribution of tobramycin in cancer patients who had normal renal function, to compare the mean values of Vd reported in the literature, and to compare the measured half-life with the expected half-life based on ABW, LBW, and IBW, respectively. Venous blood samples were collected just before and thirty minutes after dosing during steady state. Serum tobramycin concentrations were determined by $TD_x$ (fluorescence immunoassay). IBW were measured by the method of Devine: and LBW were measured by the method of Hallynck. Creatinine clearances (CLcr) of the patients were estimated using the Cockcroft and Gault equation. Elimination rate constants (kel) were determined using the Welling and Craig equation. Infusion rate (ko), volume of distribution (Vd), and half-life $(t_{1/2})$ were determined using the Saw chuk and Zaske equation. The volume of distribution Was $27\%$ greater than the Schentag's study (0.26 vs 0.33 l/kg), but the half-life was similar to the Levy's study. The predicted half-lives based on IBW were the closest to actual half-lives (1.85 vs 2.01 hr).

• 한국항공우주학회지
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• 제38권9호
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• pp.943-954
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• 2010

본 연구에 적용된 터빈은 반경류형이며, 동익의 외경은 108 mm이다. 터빈은 1.4-4.1%의 낮은 부분분사율에서 작동하므로 익형은 축류형으로 설계되었으며 3단으로 구성되었다. 터빈에서 부분분사율과 팁간극 및 노즐유동각의 변화에 따른 성능의 변화를 측정하였다. 또한 터빈의 단수를 변경하면서 각 단수에서 발생되는 출력의 차이에 대한 측정이 이루어졌다. 본 연구의 터빈은 다양한 작동조건에서 운전되므로 넓은 작동범위에 따른 비교를 위하여 회전수를 변경하면서 탈설계 영역에서의 성능 평가가 이루어졌다. 뿐만 아니라 다양한 작동조건에 합당한 시스템의 평가를 위하여 총비오크가 얻어졌다. 아울러 소형터빈의 설계 및 성능예측을 위하여 유동해석을 수행하였으며 얻어진 예측의 결과는 실험으로 얻어진 결과와 잘 일치하였다.