• The KSFM Journal of Fluid Machinery
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• v.18 no.6
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• pp.45-56
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• 2015

This paper aims to develop a submerged propeller turbine for micro hydropower plant which allows to sustain high values of efficiency in a broad range of hydrological conditions (H=2~6 m, $Q=0.15{\sim}0.39m^3/s$). The two aspects to be considered in this development are mechanical simplicity and high-efficiency operation. Unlike conventional turbines that have spiral casing and gear box, this is directing driving and no spiral casing. A 10 kW class turbine which has the most high potential of the power generation has been developed. The most important element in the design of turbine is the runner blade. The initial blade is designed using inverse design method and then the runner geometry is modified by classical hydraulic method. The design process is carried out in two steps. First, the blade shape is fix and then other components of submerged propeller turbine are designed. Computational fluid dynamics analyses based on the Navier-Stokes equations have been used to obtain overall performance data for the blade and the full turbine, respectively. The results generated by performance parameters(head, guide vane opening angle and rotational speed) variations are theoretically analysed. The evaluation criteria for the blade and the turbine performances are the pressure distribution and flow's behavior on the runner blades and turbine. The results of simulation reveals an efficiency of 91.5% and power generation of 10.5kW at the best efficiency point at the head of 4m and a discharge of $0.3m^3/s$.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.30 no.3
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• pp.443-454
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• 2020

The JavaScript engine is a module that receives JavaScript code as input and processes it, among many functions that are loaded into web browsers and display web pages. Many fuzzing test studies have been conducted as vulnerabilities in JavaScript engines could threaten the system security of end-users running JavaScript through browsers. Some of them have increased fuzzing efficiency by guiding test coverage in JavaScript engines, but no coverage guided fuzzing of optimized, dynamically generated machine code was attempted. Optimized JavaScript codes are difficult to perform sufficient iterative testing through fuzzing due to the function of runtime guards to free the code in the event of exceptional control flow. To solve these problems, this paper proposes a method of performing fuzzing tests on optimized machine code by avoiding deoptimization. In addition, we propose a method to measure the coverage of runtime-guards by the dynamic binary instrumentation and to guide increment of runtime-guard coverage. In our experiment, our method has outperformed the existing method at two measures: runtime coverage and iteration by time.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.10 no.1
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• pp.18-26
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• 1998

In order to find out hydrodynamic changes due to huge complex constructions in the Keum River Estuary, two-dimensional finite element model is applied. Model results show that gate closing of the estuary dam yields tide amplifications at Kunsan Inner Port to 17 cm and 6 cm of M$_2$ and S$_2$, while 5 cm and 3 cm of amplification at Kunsan Outer Port. Tidal currents in the main channel due to stepwise flow-guide dikes construction have been simulated and show that dynamic equilibrium bottom shear stress is 0.4 N/m$\^$2/ on this Keum River Estuary. Sedimentation rates R have correlation with maximum bottom shear stress (equation omitted), R=-0.37-0.40 ln $\tau$.

• Korean Institute of Interior Design Journal
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• v.14 no.4 s.51
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• pp.95-105
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• 2005

To plan more effective exhibitions, exhibitions should be evaluated and verified through research. This is Important in that it will present measures for improving shortcomings in exhibition goals and procedures; and it will also provide new ideas and goals for future exhibition plans. The purposes of this study are to investigate the applicability of evaluation methods by organizing related theories systematically through a literature review and to provide more practical and valuable information about the methods by applying them to actual museums. For this study, the National Science Museum was investigated since it uses various themes and exhibition methods, compared with other science museums. Exhibition structures and presentation formats were first analyzed, and then the methods of trace and observation were used to investigate how visitors use the museum. Surveys were also conducted at two different times. The results of the analyses showed that problems of exhibits, arrangement methods of exhibition space, or guide systems are more prominent than those of the presentation format itself. Based on these results, measures for improvement are suggested as follows: First, new formats of exhibition halls using new window frames or holes should be explored to stimulate visitors' curiosity and to lead viewing traffic flow in the museum. Second, in presenting representative exhibits, a gate can be installed at each exhibition area, and representative exhibits are displayed by the gate or between exhibition booths. Third, if a small space is provided at the end of each exhibition area, it can be used to give an orientation on the next exhibition or used as a resting place.

• Korean Journal of Pharmacognosy
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• v.36 no.3 s.142
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• pp.177-185
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• 2005

For the purpose of the quality control of Poria cocos, three major compounds were isolated and identified as pachymic acid (1), $3{\beta}-hydroxylanosta-7,9(11),24-trien-21-oic$ acid (2), and dehydroeburicoic acid (3). The optimal extraction conditions for the quantification of pachymic acid its analogues were the 3 hours of reflux with 15g of P. cocos in 100ml 95% ethanol. HPLC conditions were as follows: Column; ZORBAX Eclipse XDB C18 $(4.6{\times}250\;mm,\;Agillent)$, mobile phase; 1% HOAc in 70% $MeOH{\rightarrow}1%$ HOAc in 100% MeOH for 25 min, then 1% HOAc in 100% MeOH for 15 min, detector, ELSD, flow rate; 1ml/min. The mean contents of 1,2, and 3 in Poria cocos cultivated at 18 different site were $0.65{\pm}0.19,\;0.88{\pm}0.72,\;and\;0.84{\pm}0.54\;mg/g$, respectively, and values might be the guide line for the quality control of P. cocos.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5384-5391
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• 2011

The computational fluid dynamics was analyzed for the pressure distribution, stream velocity distribution, stream line field, retention time and temperature distribution which are applied to the catalyst layer in the RCO reactor to derive the optimum operating condition of the heat condensing type catalytic oxidation (RCO) reactor. The results from the computational analysis revealed that the pressure loss due to the ceramic honeycomb in the catalytic bed of the reactor which is operating currently is not significant and the stream velocity (1.8~2.7 m/s) after the ceramic filter is working in stability without big channeling. To improve the stream velocity distribution of the air stream, it is necessary to extension of the connecting range between the plenum and catalytic bed inside the facility. However, the method of attaching the air stream guide vane or the perforated plate inside the reactor was not so effective.

• Journal of the Semiconductor & Display Technology
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• v.18 no.4
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• pp.69-74
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• 2019

The aim of this work is to investigate the effect of the microtip length in a slot-die head on coating of a fine poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) stripe. To this end, we have employed a meniscus guide with a 150-㎛-wide microtip and performed roll-to-roll slot-die coatings by varying its length between 500 ㎛ and 50 ㎛. When the microtip length is 150 ㎛ or shorter, we have observed three unexpected phenomena; 1) though the solution spreads much wider than the microtip width, yet the coated stripe width is almost the same as the microtip width, 2) the stripe width decreases, but the stripe thickness is rather increased with increasing coating speed at a fixed flow rate, 3) we obtain stripes much narrower than the microtip width at high coating speeds. It is due to the fact that 1) the meniscus is not well controlled by a short microtip, 2) the main stream of solution from the outlet is very close to the substrate and thus the distributed solution along the head lip merges with the main stream, and 3) the solution is not spread over the entire microtip end at high coating speeds, causing a tiny wobble in the meniscus. Using the 150-㎛-wide and 250-㎛-long microtip, we have fabricated 153-㎛-wide and 94-nm-thick PEDOT:PSS stripe at the maximum coating speed of 13 mm/s. To demonstrate its applicability in solution-processable organic light-emitting diodes (OLEDs), we have also fabricated an OLED device with the fine PEDOT:PSS stripe and obtained strong light emission from it.

• Plant Journal
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• v.13 no.4
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• pp.48-50
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• 2017

A program for analyzing the transient behaviors of industrial gas turbines was developed. Each component (compressor, combustor, turbine and ducts)of gas turbine is modeled as a fully module to enhance the expandability of the program. We used object-oriented programing for this purpose. The mass and energy balance equations are solved numerically by Multivariable Newton Raphson method. The characteristic maps for the compressor and turbine were used for predicting the performance of a gas turbine engine. Combustion in the combustor is assumed to be complete combustion. PID control is used to maintain constant rotational speed and turbine exhaust temperature by the control of the fuel flow rate and the changing of the compressor inlet guide vane angle at the same time. It was confirmed that stable control of the gas turbine was possible, even for a rapid load change.

• Healthcare Informatics Research
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• v.24 no.4
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• pp.317-326
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• 2018

Objectives: The demand for hospice has been increasing among patients with cancer. This study examined the current hospice referral scenario for terminally ill cancer patients and created a data form to collect hospice information and a modified health information exchange (HIE) form for a more efficient referral system for terminally ill cancer patients. Methods: Surveys were conducted asking detailed information such as medical instruments and patient admission policies of hospices, and interviews were held to examine the current referral flow and any additional requirements. A task force team was organized to analyze the results of the interviews and surveys. Results: Six hospices completed the survey, and 3 physicians, 2 nurses, and 2 hospital staff from a tertiary hospital were interviewed. Seven categories were defined as essential for establishing hospice data. Ten categories and 40 data items were newly suggested for the existing HIE document form. An implementation guide for the Consolidated Clinical Document Architecture developed by Health Level 7 (HL7 CCDA) was also proposed. It is an international standard for interoperability that provides a framework for the exchange, integration, sharing, and retrieval of electronic health information. Based on these changes, a hospice referral scenario for terminally ill cancer patients was designed. Conclusions: Our findings show potential improvements that can be made to the current hospice referral system for terminally ill cancer patients. To make the referral system useful in practice, governmental efforts and investments are needed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.8
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• pp.1032-1038
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• 2021

Rate of penetration(ROP) is one of the important variables for maximizing the drilling performance. In order to maximize drilling efficiency, it is necessary to increase the drilling speed, and real-time ROP prediction is important so that the driller can identify problems during drilling. The ROP has a high correlation with the drillstring rotational speed, weight on bit, and flow rate. In this paper, the ROP was predicted using a data-driven supervised learning model trained from the drilling efficiency parameters. As a result of comparison through the performance evaluation metrics of the regression model, the root mean square error(RMSE) of the RF model was 4.20 and the mean absolute percentage error(MAPE) was 9.08%, confirming the best predictive performance. The proposed method can be used as a base model for ROP prediction when constructing a real-time drilling operation guide system.