• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.4
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• pp.255-265
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• 1999

CTD castings and current observations are taken in June, July and October, 1997 and May and July, 1998 to investigate the effect of the Keum River dyke on the structure of physical properties and the type of the Keum River estuary. Tide and tidal current relation shows that the ebbing is longer than the flooding by 1.5 hours with the early current reversing before high tide. In the rainy season (May to July), frequent large fresh water discharge during the ebbing from the dyke changes vertical salinity difference and time variation of salinity greatly near the head of the estuary, where salinity becomes lower than 2‰ in summer fresh water flooding. Halocline developed by the fresh water discharge makes two-layer structure, of which strength and depth increase in the low tide. The relationship between tide phase and surface salinity variation shows the phase lag of 2.5 hours near the head of the estuary but the standing wave relation down the estuary. This phase lag implies that a low salinity water diluted by the fresh water discharge for 2-3 hours in the ebb period moves with tidal excursion. In the dry season, vertical salinity difference reduces significantly. We calculate stratification and circulation parameters using the observed salinity structure, surface current and fresh water discharge. The Keum River estuary shows a partially mixed type, changing the stratification parameter from the rainy to the dry season. Mean flows of observed tidal current at lower and upper layer are landward and seaward, which are consistent with the circulation of a partially mixed estuary. Based upon the estuary type and circulation we suggest that the suspended materials will move toward the upstream due to low-layer mean flow and then the Keum River estuary will be a deposit environment.

• Clean Technology
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• v.13 no.1 s.36
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• pp.28-33
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• 2007

We measured cloud points of Poly(methylmethacrylate) (PMMA) in various solvents using the high-pressure variable volume view cell apparatus. The solvents used for dissolving PMMA were chlorodifluoromethane (HCFC-22), dimethylether (DME), 1,1,1-trifluoroethane (HFC-143a), 1,1-difluoroethane (HFC-152a) and 1,1,1,2-tetrafluoroethane (HFC-134a), and the effect of $CO_2$ concentration on the phase behavior of $PMMA+HCFC-22+CO_2$ system and $PMMA+DME+CO_2$ system was observed. PMMA was dissolved well in HCFC-22 from about 340 K, 5MPa and in DME from about 300 K, 28MPa. However, PMMA was not dissolved at all up to 423.15 K, 160MPa in the other fluorine compound such as HFC-l43a, HFC-152a and HFC-134a. PMMA+HCFC-22, $PMMA+HCFC-22+CO_2$ and PMMA+DME systems exhibit the lower critical solution temperature (LCST) behavior, however, $PMMA+DME+CO_2$ system exhibits the upper critical solution temperature (UCST) behavior. In the $CO_2$ mixture, the cloud point pressure of PMMA was increased dramatically proportional to the amount of $CO_2$ added, and from this result, it was known that $CO_2$ could be used as an antisolvent for fabricating PMMA nano-particles. And the cloud point of PMMA could be controlled by changing the concentration of $CO_2$.

• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.100-107
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• 2013

Unlike general microwave, QRD (Quadratic Residue Diffusor) Microwave used in this study is known as a new technology that enhances the sterilization effect with low power because it is possible to induce the average sterilization by changing wavelength phase difference. Therefore, basic research was conducted on the function that could sterilize culture media for plant factory by using environmentally friendly and low energy consuming QRD Microwave. The results are as follows: It was confirmed that there was no external deformation in the polyurethane foam and rock wool medium when changing the microwave level between 2 and 8 kW in different water content of culture media. However, PDA solid media at 2 kW were not dissolved in 60 and 180 seconds. All of the media were dissolved in other processing. There was little difference in the microwave irradiation level and surface temperature of the strain according to the processing time between Bacillus sp. and Burkholderia sp. In the sterility test according to the microwave irradiation level and processing time, it was confirmed that both Bacillus sp. and Burkholderia sp. grew in the microwave level 2 kW regardless of time. In the microwave level 6 kW, all experimental groups except the processing of Burkholderia sp. for 60 seconds were sterilized, and all of Bacillus sp. was killed in the all experimental groups. In the microwave level 8 kW, it was confirmed that both Bacillus sp. and Burkholderia sp. were sterilized regardless of time. The temperature in microwave-processed media after contaminating strains to each medium was maintained at more than 100 in polyurethane foam and rock wool medium after 60 seconds. In general, it was shown that it was possible to sterilize after 60 seconds. Therefore, it is considered that Bacillus sp. and Burkholderia sp. which are the biggest problems in the plant factory can be adequately sterilized by QRD Microwave used in this study.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.1-2
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• 2011

Hybrid rockets have lately attracted attention as a strong candidate of small, low cost, safe and reliable launch vehicles. A significant topic is that the first commercially sponsored space ship, SpaceShipOne vehicle chose a hybrid rocket. The main factors for the choice were safety of operation, system cost, quick turnaround, and thrust termination. In Japan, five universities including Hokkaido University and three private companies organized "Hybrid Rocket Research Group" from 1998 to 2002. Their main purpose was to downsize the cost and scale of rocket experiments. In 2002, UNISEC (University Space Engineering Consortium) and HASTIC (Hokkaido Aerospace Science and Technology Incubation Center) took over the educational and R&D rocket activities respectively and the research group dissolved. In 2008, JAXA/ISAS and eleven universities formed "Hybrid Rocket Research Working Group" as a subcommittee of the Steering Committee for Space Engineering in ISAS. Their goal is to demonstrate technical feasibility of lowcost and high frequency launches of nano/micro satellites into sun-synchronous orbits. Hybrid rockets use a combination of solid and liquid propellants. Usually the fuel is in a solid phase. A serious problem of hybrid rockets is the low regression rate of the solid fuel. In single port hybrids the low regression rate below 1 mm/s causes large L/D exceeding a hundred and small fuel loading ratio falling below 0.3. Multi-port hybrids are a typical solution to solve this problem. However, this solution is not the mainstream in Japan. Another approach is to use high regression rate fuels. For example, a fuel regression rate of 4 mm/s decreases L/D to around 10 and increases the loading ratio to around 0.75. Liquefying fuels such as paraffins are strong candidates for high regression fuels and subject of active research in Japan too. Nakagawa et al. in Tokai University employed EVA (Ethylene Vinyl Acetate) to modify viscosity of paraffin based fuels and investigated the effect of viscosity on regression rates. Wada et al. in Akita University employed LTP (Low melting ThermoPlastic) as another candidate of liquefying fuels and demonstrated high regression rates comparable to paraffin fuels. Hori et al. in JAXA/ISAS employed glycidylazide-poly(ethylene glycol) (GAP-PEG) copolymers as high regression rate fuels and modified the combustion characteristics by changing the PEG mixing ratio. Regression rate improvement by changing internal ballistics is another stream of research. The author proposed a new fuel configuration named "CAMUI" in 1998. CAMUI comes from an abbreviation of "cascaded multistage impinging-jet" meaning the distinctive flow field. A CAMUI type fuel grain consists of several cylindrical fuel blocks with two ports in axial direction. The port alignment shifts 90 degrees with each other to make jets out of ports impinge on the upstream end face of the downstream fuel block, resulting in intense heat transfer to the fuel. Yuasa et al. in Tokyo Metropolitan University employed swirling injection method and improved regression rates more than three times higher. However, regression rate distribution along the axis is not uniform due to the decay of the swirl strength. Aso et al. in Kyushu University employed multi-swirl injection to solve this problem. Combinations of swirling injection and paraffin based fuel have been tried and some results show very high regression rates exceeding ten times of conventional one. High fuel regression rates by new fuel, new internal ballistics, or combination of them require faster fuel-oxidizer mixing to maintain combustion efficiency. Nakagawa et al. succeeded to improve combustion efficiency of a paraffin-based fuel from 77% to 96% by a baffle plate. Another effective approach some researchers are trying is to use an aft-chamber to increase residence time. Better understanding of the new flow fields is necessary to reveal basic mechanisms of regression enhancement. Yuasa et al. visualized the combustion field in a swirling injection type motor. Nakagawa et al. observed boundary layer combustion of wax-based fuels. To understand detailed flow structures in swirling flow type hybrids, Sawada et al. (Tohoku Univ.), Teramoto et al. (Univ. of Tokyo), Shimada et al. (ISAS), and Tsuboi et al. (Kyushu Inst. Tech.) are trying to simulate the flow field numerically. Main challenges are turbulent reaction, stiffness due to low Mach number flow, fuel regression model, and other non-steady phenomena. Oshima et al. in Hokkaido University simulated CAMUI type flow fields and discussed correspondence relation between regression distribution of a burning surface and the vortex structure over the surface.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.10
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• pp.1475-1481
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• 2003

The aim of this paper was to use the Cornell Net Carbohydrate and Protein System (CNCPS), that reports diet energy and protein value and animal requirements, as net energy for lactation ($NE_1$) and metabolizable protein (MP) respectively, to evaluate some rations for lactating Italian Mediterranean buffaloes. The investigation was carried out on six farms in the province of Caserta (southern Italy), where the milk production was controlled four times monthly on 10 animals (changing every time) chosen at different lactation days (5 categories): <2 months (A), 2-4 months (B), 4-6 months (C), 6-8 months (D), >8 months (E). Milk fat and protein were determined. Diet $NE_1$ and MP were estimated with the CPM-Dairy program (1998) using diet component chemical characteristics; then energy and protein intakes were estimated. $NE_1$ and MP requirements were estimated with two methods: 1) using CPM-Dairy that considers produced milk, fat and protein content, lactation phase and body condition score as main factors; 2) by applying the theory that to produce 1 kg of energy corrected milk, the buffalo needs 3.56 MJ of $NE_1$ and the efficiency to convert the absorbed aminoacids into milk protein is lower than cow (CNCPS). As regards energy, with method 1 the requirements were satisfactory starting from category A (4 out of 6 farms) and category B (5/6 farms); however, a surplus resulted for category E (5/6 farms). With method 2 a deficit in category A (5/6 farms) and B (3/6 farms) was observed, while the energy requirements were satisfied for all categories except E, where on only one buffalo farm had a surplus of energy intake. As regards protein, with method 1 the requirements were substantially satisfied for all the categories except E (3/6 farms); with method 2 the MP trend was much less favourable than with method 1. Indeed, a protein deficit was observed for all animals in categories A and B (5/6 farms). Moreover, on one farm the protein intake never satisfied animal requirements. In our experimental conditions, the use of the CNCPS to characterise diets for lactating buffalo and to calculate their requirements led to satisfactory results. By contrast, we cannot say the same for method 2, which applies a lower use efficiency of NE and MP for lactation in buffalo compared to cow.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.11
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• pp.133-143
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• 1998

The viewers primarily watch a television under the surround light source of an incandescent or a fluorescent light. When human visual system has been adapted chromtically under the different surround light, the same chromaticities elicit quite different color appearnaces. Therefore, the corresponding color reproduction is the most suitable objective of a color television system. In this paper, an efficient corresponding color reproduction method based on the chromatic adaptation of human visual system is proposed in which colors in the display have the same appearance as the colors in the original would have had if they had been illuminated by standard illuminant ($D_{65}$). The chromaticities that appeared neutral in human visual system were determined by the Hunt's experimental results of the color adaptation in picture viewing situations and the corresponding chromaticity coordinates of stimuli in chromatic adaptation were obtained by the Bartleson's theory. Also, the corresponding color reproduction is realized by changing the phase and the gain of the demodulation axes in television receiver. Experimental results show that the proposed corresponding color displayed on the television is better than that of the conventional colorimetric color reproduction under the surround light sources.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.1
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• pp.81-89
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• 2017

In this paper, we propose a gait pattern recognition method for intelligent prosthesis that enables walking in various environments of femoral amputees. The proposed gait mode changing method is a single sensor based algorithm which can discriminate gait surface and gait phase using only strain gauges sensor, and it is designed to simplify the algorithm based on multiple sensors of existing intelligent prosthesis and to reduce cost of prosthesis system. For the recognition algorithm, we analyzed characteristics of the ground reaction force generated during gait of normal person and defined gait step segmentation and gait detection condition, A gait analyzer was constructed for the gait experiment in the environment similar to the femoral amputee. The validity of the paper was verified through the defined detection conditions and fabricated instruments. The accuracy of the algorithm based on the single sensor was 95%. Based on the proposed single sensor-based algorithm, it is considered that the intelligent prosthesis system can be made inexpensive, and the user can directly grasp the state of the walking surface and shift the walking mode. It is confirmed that it is possible to change the automatic walking mode to switch the walking mode that is suitable for the walking mode.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.9
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• pp.825-830
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• 2009

Pharmaceutical compounds enter the water environment through the diverse pathways. Because their concentration in the water environment was frequently detected in the level of ppt to ppb, the monitoring system should be optimized as much as possible for finding appropriate management policies and technical solutions. One Factor At a Time (OFAT) approach approximating the response with a single variable has been preferred for the optimization of LC-MS/MS operational conditions. However, it is common that variables in analytical instruments are interdependent. Therefore, the best condition could be found by using the statistical optimization method changing multiple variables at a time. In this research, response surface analysis (RSA) was applied to the LC-MS/MS analysis of emerging antibiotic compound, sulfamethoxazole, for the best sensitivity. In the screening test, fragmentation energy and collision voltage were selected as independent variables. They were changed simultaneously for the statistical optimization and a polynomial equation was fit to the data set. The correlation coefficient, $R^2$ valuerepresented 0.9947 and the error between the predicted and observed value showed only 3.41% at the random condition, fragmentation energy of 60 and collision voltage of 17 eV. Therefore, it was concluded that the model derived by RSA successfully predict the response. The optimal conditions identified by the model were fragmentation energy of 116.6 and collision voltage of 10.9 eV. This RSA can be extensively utilized for optimizing conditions of solid-phase extraction and liquid chromatography.

• Journal of the Korean Vacuum Society
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• v.15 no.2
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• pp.194-200
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• 2006

Self-assembled InAs/InAl(Ga)As quantum dots (QDs) were grown on InP substrates by a molecular-beam epiaxy, and their structural and optical properties were investigated by atomic force microscopy (AFM), transmission electron microscopy (TEM), and room-temperature photoluminescence (PL). AFM images indicated that the InAs quantum structures showed various shapes such as quantum dashes, asymmetric and symmetric QDs mainly caused by the initial surface conditions of InAl(Ga)As with the intrinsic phase separation. For the buried InAs QDs in an InAlGaAs matrix, the average lateral size and height of QDs were 23 and 2 nm, respectively. By changing the growth conditions for the QD samples, the emission wavelength of $1.55{\mu}m$ was obtained, which is one of the wavelength windows for fiber optic communications.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.8
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• pp.695-700
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• 2014

In the present study, the melting temperature depression of Sn nanoparticles manufactured using the modified evaporation method was investigated. For this purpose, a modified evaporation method with mass productivity was developed. Using the manufacturing process, Sn nanoparticles of 10 nm size was manufactured in benzyl alcohol solution to prevent oxidation. To examine the morphology and size distribution of the nanonoparticles, a transmission electron microscope was used. The melting temperature of the Sn nanoparticles was measured using a Differential scanning calorimetry (DSC) which can calculate the endothermic energy during the phase changing process and an X-ray photoelectron spectroscopy (XPS) used for observing the manufactured Sn nanoparticle compound. The melting temperature of the Sn nanoparticles was observed to be $129^{\circ}C$, which is $44^{\circ}C$ lower than that of the bulk material. Finally, the melting temperature was compared with the Gibbs Thomson and Lai's equations, which can predict the melting temperature according to the particle size. Based on the experimental results, the melting temperature of the Sn nanoparticles was found to match well with those recommended by the Lai's equation.