• Clean Technology
• /
• v.26 no.1
• /
• pp.65-71
• /
• 2020

Various solar hybrid energy conversion processes, which have both the advantages of renewable energy sources and fossil energy sources, have been developed in the world because stable and predictable energy supplies, such as electricity and natural gas, are necessary for modern societies. In particular, a solar hybrid energy conversion process based on a dual fluidized bed process concept has been expected as the promising solution for sustainable energy supply via thermochemical conversions, such as pyrolysis, combustion, gasification, and so on, because solar thermal energy could be captured and stored in fluidized bed materials. Therefore, the attrition and heat transfer characteristics of silicon carbide and alumina particles used for fluidized bed materials for the solar hybrid energy conversion process were studied in an ASTM D5757 reactor and a bubbling fluidized bed reactor with 0.14m diameter and 2m height. These characteristics of novel fluidized bed materials were compared with those of sand particles which have widely been used as a fluidized bed material in various commercial fluidized bed reactors. The attrition resistances of silicon carbide and alumina particles were higher than those of sand particles while the average values of heat transfer coefficient in the bubbling fluidized bed reactor were in the range of 125 ~ 152 W m^-2K^-1.

• Journal of Pharmaceutical Investigation
• /
• v.38 no.3
• /
• pp.177-182
• /
• 2008

The purposes of this study were to prepare dual-layered coated compact pellets containing three nutrients Glucose, Chromium picolinate, Vitamin C) for rumen bypass. The core compact pellets were prepared by an extrusionspheronization method and then double layered coated with pH independent EC (ethyl cellulose) and pH-dependent polymers ($Eudragit^{(R)}$ E100) using a fluid-bed spray coater. Depending on the coating levels of EC and $Eudragit^{(R)}$ E100, release profiles were variable in simulated rumen (pH 6.8) and abomasums (pH 2.0) fluid using USP apparatus I (basket method). When compact pellets were coated with EC (about 10% level in inner layer) and then $Eudragit^{(R)}$ E100 (20% level in outer layer) in a dual-layered manner, rumen-bypass delivery resisting rumen fluid followed by release in abomasums fluid could possible. The friability was also satisfactory based on chewing behavior of ruminants. The dual-layered coated compact pellets showed smooth surface and distinct inner/outer layers using scanning electron microscopy (SEM). The current rumen bypass delivery system can be also applicable to deliver other nutrients in ruminants.

• Clean Technology
• /
• v.10 no.3
• /
• pp.159-168
• /
• 2004

Benzene adsorption experiment was carried out for activated carbon and zeolite 13X adsorbents. Single column and dual column packed with two adsorbents were used to investigate the dynamic adsorptive characteristics. Effect of feed flow rate on the breakthrough curve was not significant. Specific adsorption amount of benzene for activated carbon was larger than that for zeolite 13X. On the contrary, adsorption amount per column volume was larger for zeolite 13X column because the density of zeolite 13X was larger. In the dynamic experiment using dual adsorbents column, length of mass transfer zone was changed by the feed direction. Breakthrough time was longer and breakthrough curve was sharper when activated carbon was packed in feed inlet and zeolite 13X was packed in column outlet. Also breakthrough time and breakthrough curve slope were affected by the packing ratio of the two adsorbents.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.10
• /
• pp.1377-1384
• /
• 2003

An analysis has been performed for active thermal control of the KOMPSAT monopropellant rocket engine assembly, i.e., dual thruster module(DTM). The main efforts of this work have been directed at determining proper heater sizes for propellant valves and catalyst beds necessary to maintain their temperatures within specified temperature ranges under KOMPSAT environment and operational conditions. The TAS incorporated with TRASYS thermal radiation analyzer was used to establish a complete heat transfer model which allows to predict the DTM temperature as a function of time. The thermal analysis has been performed in transient mode to verify the appropriate power for catalyst bed heaters necessary to increase catalyst bed temperature to the required value within a specified period of time. Similar analysis has been executed to validate the heater power for the thermostatically controlled primary and redundant heater circuits used to prevent hydrazine freezing, i.e., single fault. Moreover the effect of the radiative property of thermal control coating of heat shield was examined. Thruster firing condition was also simulated for the heat soakback condition. As a consequence, all thermal analysis results for DTM satisfactorily met the thermal requirements for the KOMPSAT DTM under the worst case average voltage, i.e. 25 volt.

• Journal of the Korean Society for Precision Engineering
• /
• v.23 no.4 s.181
• /
• pp.183-190
• /
• 2006

Digital 3D Real Object Duplication System (RODS) consists of 3D Scanner and Solid Freeform Fabrication System (SFFS). It is a device to make three-dimensional objects directly from the drawing or the scanning data. In this research, we developed an office type SFFS based on Three Dimensional Printing Process and an industrial SFFS using Dual Laser. An office type SFFS applied sliding mode control with sliding perturbation observer (SMCSPO) algorithm for control of this system. And we measured process variables about droplet diameter measurement and powder bed formation etc. through experiments. In case of industrial type SFFS, in order to develop more elaborate and speedy system for large objects than existing SLS process, this study applies a new Selective Dual-Laser Sintering (SDLS) process and 3-axis Dynamic Focusing Scanner for scanning large area instead of the existing f lens. In this process, the temperature has a great influence on sintering of the polymer. Also the laser parameters are considered like that laser beam power, scan speed, and scan spacing. Now, this study is in progress to evaluate the effect of experimental parameters on the sintering process.

• Journal of the Korea Society for Simulation
• /
• v.15 no.4
• /
• pp.87-96
• /
• 2006

Wireless Sensor Network (WSN) is researched in various filed. Underwater Sensor Network (UWSN) is used various purpose such as underwater environment monitoring. But, WSN is researched in the terrestrial that uses mainly radio frequency, The existing terrestrial research is incongruent to apply to underwater. Therefore, we propose UWSN architecture that considers underwater environment. In this paper, UWSN applied cluster technique and functional node constructs. Each cluster collects and sends cluster data. Dual super cluster head receives cluster data and transmits each in the base-station. We implement WSN routing algorithm, and construct test-bed and analyze cluster data receive rate.

• Journal of the Institute of Convergence Signal Processing
• /
• v.3 no.1
• /
• pp.27-32
• /
• 2002

In this study, we fabricated the advanced telemetry system that transmitting media use radio frequency(RF) for the middle range measurement of the physiological signals and receiving media use optical for electromagnetic interference problem. The telemetry system within a size of 65$\times$125$\times$45mm consists of three parts: RF transmitter, optical receiver and physiological signal processing CMOS one chip. Advantages of proposed telemetry system is wireless middle range(50m) FM transmission, reduce electromagnetic interference to a minimum which enables a comfortable bed-side telemetry system. The monitoring system was designed in the structure of dual-processor for the real time processing. The use of the one channel in our study made it possible the real time wavelet transformation of electrocardiogram data of 360Hz, 16 bits for every 1.42 seconds.

• The Korean Journal of Nuclear Medicine Technology
• /
• v.15 no.1
• /
• pp.34-38
• /
• 2011

Purpose: The SUV is a widely used semi-quantitative index in PET for the estimation of radio-tracer accumulation in VOI. In this study, SUVs from three different PET/CT scanners were assessed, and differences between SUVs were evaluated. Materials and Methods: The PET/CT scanners which were assessed in this study were GEMINI, GEMINI TF 64 (Philips) and Biograph True Point True V 40 (Siemens). The NEMA PET phantom (Data Spectrum Corp., USA) was used to evaluate SUVs. The NEMA PET phantom has6.8 kg weight and three hot inserts. Two different activity distributions for the background and inserts were tested. The activity ratio were 3.7:3.7:7.4:11.1 MBq (1:1:2:3) and 1.85:7.4:9.25:11.1MBq (1:4:5:6) for each of background, insert 1, insert 2 and insert 3. Acquisition time was 2 minutes per bed position and NEMA PET phantom could be covered by two bed positions for all PET/CT scanners. The SUVs from each PET/CT scanner were compared with calculated true value. Results: For both activity ratios, all scanners showed similar results. The differences between each scanner were insignificant. Each scanner showed 91.2%, 85.9% and 87.2% of true SUV for GEMINI, GEMINI TF 64, Biograph True Point TrueV, respectively. Conclusion: For all scanners, SUVs were slightly lower than true value. However, the difference between scanners was insignificant. The SUVs from these scanners would be clinically meaningful if their consistent underestimation is kept in mind.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.5
• /
• pp.919-926
• /
• 2000

The experiment in this study was conducted as a part of an effort to evaluate filter performance with pilot-filters consisting of one mono-media and two dual-media columns. Particle distribution analysis using a particle counter is more sensitive and better than turbidity analysis in observing particle detachments and a breakthrough. In sand media filters having 1.5 m of available head, caution is needed in the head loss of the late stages of filtration, and for dual-media filters, appropriate media configuration and effluent Quality monitoring should be used for preventing the final breakthrough. Also the time of particle breakthrough in the dual media filter can be deferred by increasing bed depth, and it is necessary to use a filtration aid prior to filtration to prevent breakthrough of these intermediate sized particles in high filtration rate.

• Korea Journal of Hospital Management
• /
• v.12 no.1
• /
• pp.51-74
• /
• 2007

This study applied Data Envelopment Analysis to a set of Korean Public Corporation Medical Centers and Japanese Municipal Hospitals to compare their relative human resource efficiencies. Based on the data provided on the inputs and outputs, the analysis showed Japanese municipal hospitals were relatively efficient than Korean hospitals. The result of analysing BCC model shows 5 hospitals in Japan and 7 in Korea with an efficiency rating of less than 1 as considered relatively inefficient. For the inefficient hospitals the manner in which inefficient hospitals may be made efficient were indicated by the managerial strategies based on dual variables. A subsequent analysis of Wilcoxon rank-sum test revealed that the medical revenue per medical expense, labor cost per value added revenue were statistically significant between efficient and inefficient Korean hospitals and medical revenue per medical expense, labor cost per value added revenue, bed occupancy rate, average length of stay, rate of personnel expenses per medical revenue were statistically significant between efficient and inefficient Japanese hospitals.