• Microbiology and Biotechnology Letters
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• v.19 no.3
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• pp.265-271
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• 1991

In order to produce alcohol for the alternative energy from dried powder of Jerusalem artichoke was investigated with Kluyveromyces marxianus UCD(FST)55-82, which was reported to assimilate inulin. The optimal condition for the production of ethanol by K. marxianus was elucidated to be incubation temperature of $30^{\circ}C$, initial pH 5.44, agitation of 100 rpm, 1,000 ml of medium in a 2.5l-vessel, anaerobic state, and inoculation of 2.5%(v/v). Addition of antifoam A concentrate(si1icon polymer) of 0.01% and urea of 0.1% increased the concentration of ethanol effectively. The optimized condition showed ethanol concentration of 6.8%(v/v) in Jerusalem artichoke liquid medium, production yield of 91.91% and productivity of 2.71 g/l/hr during the first day and 0.71g ethanol/l/hr during four days of incubation.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.143-152
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• 1998

In this paper, we present the performances of a Doppler system using single channel RF(Radio Frequency) sampling. This technique consists of undersampling the ultrasonic blood backscattered RF signal on a single channel. Conventional undersampling method in Doppler imaging system have to use a minimum of two identical parallel demodulation channels to reconstruct the multigate analytic Doppler signal. However, this system suffers from hardware complexity and problem of unbalance(gain and phase) between the channels. In order to reduce these problems, we have realized a multigate pulsed Doppler system using undersampling on a single channel, It requires sampling frequency at $4f_o$(where $f_o$ is the center frequency of the transducer) and 12bits A/D converter. The proposed " single-Channel RF Sampling" method aims to decrease the required sampling frequency proportionally to $4f_o$/(2k+1). To show the influence of the factor k on the measurements, we have compared the velocity profiles obtained in vitro and in vivo for different intersequence delays time (k=0 to 10). We have used a 4MHz center frequency transducer and a Phantom Doppler system with a laminar stationary flow. The axial and volumetric velocity profiles in the vessel have been computed according to factor k and have been compared. The influence of the angle between the ultrasonic beam and the flow axis direction, and the fluid viscosity on the velocity profiles obtained for different values of k factor is presented. For experiment in vivo on the carotid, we have used a data acquisition system with a sampling frequency of 20MHz and a dynamic range of 12bits. We have compared the axial velocity profiles in systole and diastole phase obtained for single channel RF sampling factor.ng factor.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.1 s.145
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• pp.43-49
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• 2006

The hull form of icebreaking tanker depends on the trade route and ice characteristic. The hull form has to be designed for icebreaking concept if the vessel is operating in heavy ice and also the hull from has to be optimized for general tanker when the ship is operating in ice-free ocean. This paper presents comparison of ship resistance in pack ice, level ice and open water. Four ships are used to compare the resistance characteristic. One is conventional tanker and three ships are icebreaking tankers. The ice model test was carried out at the IOT (Institute for Ocean Technology, Newfoundland, Canada) and open water test was performed at 55MB (Samsung Ship Model Basin). The ice resistance of conventional tanker was predicted by Colbourne's method. The resistance of open water, pack ice and level ice are compared and discussed. The best hull form of icebreaker is not good in open water performance compare to conventional tanker. This result explains that the hull form of icebreaker and normal tanker have to compromise when the ship is operated in ice and ice-free condition. The result of this paper gives a guide for icebreaking tanker design.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.933-940
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• 2017

Draught and trim conditions are highly related to the loading condition of a vessel and are important factors in predicting ship manoeuverability. This paper estimates hydrodynamic coefficients from sea trial measurements with three different trim and draught conditions. A mathematical optimization method for system identification was applied to estimate the forces and moment acting on the hull. Also, fast time simulation software based on the Rheinmetall Defense model was applied to the whole estimation process, and a 4,500 Twenty-foot Equivalent Unit (TEU) class container carrier was chosen to collect sets of measurement data. Simulation results using both optimized coefficients and newly-calculated coefficients for validation agreed well with benchmark data. The results show mathematical optimization using sea measurement data enables hydrodynamic coefficients to be estimated more simply.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.11
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• pp.1-7
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• 2020

Recently, hydrogen has gained considerable attention as an eco-friendly fuel, which helps in reducing carbon dioxide content. Specifically, there is a growing interest in vehicles powered by a hydrogen fuel cell, which is spotlighted as an environmental-friendly alternative. A hydrogen transport system, fuel cell system, fuel supply system, power management system, and hydrogen storage system are key parts of a hydrogen fuel cell truck. In this study, a hydrogen storage system is built and analyzed. The expansion length of the storage vessel at maximum operating pressure (87.5 MPa) was calculated with ABAQUS, and then the optimized system was designed and built. The leak and bubble tests were performed on the built storage system. The leakage of the system was measured to be under 5 cc/hr. Hence, it can be used as a research test for the safety evaluation of leading systems of hydrogen fuel-powered commercial vehicles.

• Steel and Composite Structures
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• v.52 no.3
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• pp.377-390
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• 2024

Analyzing thermoelastic, elastoplastic, and residual stresses is pivotal for deepening our insights into material characteristics, particularly in the engineering of advanced materials like functionally graded materials (FGM). This research delves into these stress types within a thick-walled sphere composed of Al-SiC FGM, employing a detailed successive approximation method (SAM) to pinpoint stress distributions under varied loading scenarios. Our investigation centers on how the sphere's structure responds to different magnitudes of internal pressure. We discover that under various states-thermoelastic, elastoplastic, and residual-the radial stresses are adversely impacted, manifesting negative values due to the compressive nature induced by internal pressures. Notably, the occurrence of reverse yielding, observed at pressures above 410 MPa, merits attention due to its significant implications on the sphere's structural integrity and operational efficacy. Employing the SAM allows us to methodically explore the nuanced shifts in material properties across the sphere's thickness. This study not only highlights the critical behaviors of Al-SiC FGM spheres under stress but also emphasizes the need to consider reverse yielding phenomena to maintain safety and reliability in their application. We advocate for ongoing refinement of analytical techniques to further our understanding of stress behaviors in various FGM configurations, which could drive the optimized design and practical application of these innovative materials in diverse engineering fields.

• Korean Chemical Engineering Research
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• v.49 no.5
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• pp.644-651
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• 2011

Storing hydrogen in solid state hydride is one of the best promising methods for the future hydrogen economy. The total performance of such systems depends on the rate at which the amount of mass and heat migration is supplied to solid hydride. Therefore, an accurate modeling of the heat and mass transfer is of prime importance in optimizing the design of such systems. In this work, Hydrogen storage in Pt-CNTs hydrogen reactor has been intensively investigated by solving 2 dimensional mathematical models. Using a CFD computer software, systematic studies have been performed to elucidate the effect of heat and mass transfer during hydrogen charging periods. It was revealed that the optimized design of hydrogen storage vessel can prevent the increase of system temperature and the charging time due to the convective cooling effects inside the vessels at even high charging pressure. Because none has reported the critical issues of heat and mass transfer for CNT based hydrogen storage system, this work can support the first insight of the optimal design for solid state hydrogen storage system based on CNT in the near future.

• Journal of the Korea Organic Resources Recycling Association
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• v.8 no.2
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• pp.77-84
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• 2000

Aim to get operation factors, an In-vessel Composting of Wastewater Sludge was operated. The composting equipment is consisted of three chamber, 1st, 2nd and 3rd consequently. In the results, the temperature of fermentation had shown that 1st fermentation chamber(F/C) temperature was higher than that of 2nd and 3rd fermentation chamber. The temperature was steady in all steps during the sludge being composted, the ranges of each step were $50^{\circ}{\sim}59^{\circ}C$ of 1st F/C, $41^{\circ}{\sim}50^{\circ}C$ of 2nd F/C, and $32^{\circ}{\sim}37^{\circ}C$ of 3rd F/C. Organic material content of the end product was 28% and that of pH was 7.5. Properties of the compost which have been composted on optimized condition, were shown that is acceptable to use as a fertilizer. Even in the winter time, the composting system was working well without any trouble. According to result of investigation, the end-product of the system was satisfied with the standard for a fertilizer usage. HRT(hydraulic retention time) of entire process was appropriated to be 14 days(0.9 days at drying and 3.5, 4.4, 5.2 days at each step of fermentations, respectively).

• Journal of Korea Port Economic Association
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• v.31 no.1
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• pp.37-49
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• 2015

According to outstanding maritime economists from domestic and overseas, shipping lines or ships' enlargement reduce fixed costs, and assist realization of scale of economy of shipping. On the contrary, recent Korean liquidity crisis on the shipping lines (SL) has been focused on the leading companies such as Hanjin Shipping (HJS), Korealines, and STX Pan Ocean. In this respect, this study aims to review Korean SLs' strategies and suggest the optimal solution between the specialization and enlargement. For these purposes, this research adopts slack based measure data envelopment analysis (SBM-DEA) model as a research methodology. As for decision making units (DMUs), SLs which have increased the vessel numbers and belonged to top tier group in year 2013, are selected. The results are comprised with two aspects. Firstly, HJS, KMTC, Korea LNG Trading (KLT), EUKOR, and Sinokor Tanker show the most efficient in regard to constant return to scale (CRS) model. Secondly, HJS, KMTC, KLT, Daerim, Chungang, Sinnokor Tanker, and EUKOR are the most efficient companies in terms of variable return to scale (VRS) model. Lastly, these results could be affected to the management philosophy and can answer the following question. Which is the most optimized SL?s management decision making, enlargement or specialization?

• Journal of Korean Neurosurgical Society
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• v.64 no.5
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• pp.732-739
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• 2021

Objective : Early successful reperfusion is associated with favorable outcomes in acute ischemic stroke (AIS). The purpose of this study was to achieve successful recanalization by a combined mechanical thrombectomy technique, the Aspiration-Retriever Technique for Stroke (ARTS), which is composed of a flexible large lumen distal access catheter and a retrievable stent as the first-line strategy of mechanical thrombectomy. Methods : We retrospectively reviewed 62 patients with AIS who underwent mechanical thrombectomy from 2018 to 2019 at our institute by a senior neurointerventionalist. Among them, patients who were treated using the ARTS technique with the soft torqueable catheter optimized for intracranial access (SOFIA^®; MicroVention-Terumo, Tustin, CA, USA) as the first-line treatment were included. Patients who had tandem occlusions or underlying intracranial artery stenosis were excluded. The angiographic and clinical outcomes were evaluated. The angiographic outcome was analyzed by the rate of successful recanalization, defined as a Thrombolysis in Cerebral Infarction score of 2b or 3 at the end of all procedures and the rate of successfully achieving the first pass effect (FPE), defined as complete recanalization with a single pass of the device. The clinical outcomes included the National Institutes of Health Stroke Scale (NIHSS) score, modified Rankin Scale (mRS), and mortality. Results : A total of 27 patients (mean age, 59.3 years) fulfilled the inclusion criteria. The successful recanalization rate was 96% (n=26) while the FPE rate was 41% (n=11). The mean post-procedural NIHSS change was -3.0. Thirteen patients (48%) showed good clinical outcomes after thrombectomy with the ARTS technique (mRS at 90 days ≤2). Postoperative complications occurred in seven of 25 patients : hemorrhagic transformation in six patients (22%) and distal embolization in one patient (4%). Mortality was 15% (n=4). Conclusion : Although the clinical outcomes using the ARTS technique with a flexible large lumen distal access catheter performed as the frontline thrombectomy in patients with AIS were not significantly superior than those of other studies, this study showed a high rate of successful endovascular recanalization which was comparable to that of other studies. Therefore, ARTS using the SOFIA^® catheter can be considered as the first choice of treatment for AIS due to large vessel occlusion.