• Membrane Journal
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• v.16 no.1
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• pp.31-38
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• 2006

The ceramic microfiltration system with periodic $N_2$-back-flushing was operated for treating paper wastewater discharged from a company making toilet papers by recycling milk or juice cartons. Two kinds of alumina membranes with 7 channels used here for recycling paper wastewater. The optimal filtration time interval for HC04 membrane with $0.4{\mu}m$ pore size was lower value of 4 min than 16 min for HC10 with $1.0{\mu}m$ pore size at fixed back-flushing time 40 sec, trans-membrane pressure $1.0kg_f/cm^2$ and back-flushing pressure $5.0kg_f/cm^2$. From the results of TMP effect at fixed filtration time interval and back-flushing time, the lower TMP was better on membrane fouling because high TMP could make easily membrane cake and fouling inside membrane structure. However, we could acquire the highest volume of total permeate at the highest TMP for the reason that TMP was driving force in our filtration system to treat paper wastewater. Then the permeate water of low turbidity was acquired in our microfiltration system using multi channels ceramic membranes, and the treated water could be reused in paper process.

• Journal of the Korean Geotechnical Society
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• v.19 no.2
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• pp.65-74
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• 2003

Most of land reclamation projects are being implemented along the south and west coastal lines of the Korean Peninsula. The earth structures and in-ground LNG tank, and buildings can be constructed using artificial freezing method on the reclaimed land to control the uplift pressure caused by capillary forces. In this study, upon freezing a saturated soil in a closed-system from the top, a considerable frost heaving pressure was developed. Decomposed granite soils, silty soil, and sandy soil were used in the laboratory freeze test which is sometimes subjected to thermal gradients under closed-systems. A major concern has been the ability to predict the frost heaving pressure over the results of relatively short-term laboratory tests. The frost heaving pressure arising within the soil samples and the temperature of the samples inside were monitored with time elapse. The degree of saturation versus heaving pressure curve is presented for each soil sample and the maximum pressure is closely related to this curve. TDR apparatus was used to measure the volumetric water content by the measurement of unfrozen water contents of frozen soils. Unfrozen water increased in soils containing a high percentage of fine-grained particles. In fine-grained soils with strong attractive farces between soil grains and water molecules, additional water is attracted into the pores leading to further volume changes and ice segregation.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.2
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• pp.163-170
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• 1992

Color of kimchi juice was measured instrumentally to evaluate the quality of Korean cabbage kimchi during fermentation at 4$^{\circ}C$ and 16$^{\circ}C$ . These results were compared with those of chemical analyses of kimchi juice and sensory evaluation for kimchi. Chemiral analyses and sensory evaluation showed that the kimchi has reached pH 4.3, the pH value under an optimum ripening period, after 3-days fermentation at 16$^{\circ}C$ with almost the highest contents of vitamin C and carotenoids as well as desirable sour taste and texture. At 4$^{\circ}C$ the kimchi was unripened after 6-days fermentation. At 16$^{\circ}C$, $L^{*}$ value of kimchi juice did not show any significant change during fermentation periods. However, $a^{*}$ value increased until day 4$^{\circ}C$ and thereafter decreased sharply. $b^{*}$ value increased until day 3 and then showed no change. High correlations were seen between volume of kimchi juice, pH, total acidity and $L^{*}$or $b^{*}$ value, and between carotenoid content and $a^{*}$ value, respectively. It was desirable to use color $a^{*}$ or $b^{*}$ value of kimchi juice to evaluate the quality of kimchi. The kimchi was under an over-ripening period when $a^{*}$ value was equal to or lower than the initial value, or when $b^{*}$ value was almost constant. Predicting an optimum ripening period was possible by using a proportional value of $a^{*/}$ $b^{*}$ , i.e., unripening period, 1 $\geq$ and near 1 ; optimum ripening period, near 0.8 ; over-ripening period, < 0.8.eriod, < 0.8.d, < 0.8.

• Korean Chemical Engineering Research
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• v.54 no.2
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• pp.248-254
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• 2016

Efficacious wastewater treatment is essential for increasing sewage sludge volume and implementing strict environmental regulations. The operation cost of sludge treatment amounts up to 50% of the total costs for wastewater treatment plants, therefore, an economical sludge destruction method is crucially needed. Amid several destruction methods, wet air oxidation (WAO) can efficiently treat wastewater containing organic pollutants. It can be used not only for sludge destruction but also for useful by-product production. Volatile fatty acids (VFAs), one of many byproducts, is considered to be an important precursor of biofuel and chemical materials. Its high reaction condition has instituted the study of gravity pressure reactor (GPR) for an economical process of WAO to reduce operation cost. Simulation of subcritical condition was conducted using Aspen Plus with predictive Soave-Redlich-Kwong (PSRK) equation of state. Conjointly, simulation analysis for GPR depth, oxidizer type, sludge flow rate and oxidizer injection position was carried out. At GPR depth of 1000m and flow rate of 2 ton/h, the conversion and yield of VFAs were 92.02% and 0.17g/g, respectively.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.11 s.114
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• pp.1021-1029
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• 2006

In this paper, we designed and implemented a dual wideband dipole type antenna for the reception of S-DMB (Satellite Digital Multimedia Broadcasting) and 2.4/5 GHz WLAN(Wireless Local Area Network) signals. The proposed antenna based on conventional monopole type dual band antenna was implemented as planar wideband dipole type antenna with the volume of $8{\times}33.8{\times}1.68mm^3$. The proposed antenna is printed type on FR4 substrate of 1.6 mm thick and composed of a dipole type antenna for low frequency band and two symmetric structured resonance elements for high frequency band. We confirmed antenna area with dense surface current for each frequency band with simulation. By varying the length of the antenna area with dense surface current, we could vary resonance frequency of each frequency band separately. Impedance bandwidths$(VSWR{\leq}2)$ are 362 MHz(14.23 %) for 2 GHz band and 1188 MHz(22.13, %) for 5 GHz band which show wideband characteristic. Measured maximum gains were 4.33 dBi for 2 GHz band and 5.48 dBi for 5 GHz band which showed improved performance. And the implemented antenna has a good omni-directional radiation pattern characteristic.

• Journal of the Korean Society of Food Science and Nutrition
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• v.39 no.10
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• pp.1509-1515
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• 2010

In this study, sponge cakes were prepared with substitution of 5, 10, 15, and 20% banana powder. The specific gravity and viscosity tended to increase as the ratio of banana powder increased. The foaming stability was highest at the 10% substitution level. The control group had significantly higher moisture content and volume index than the banana powder samples. The crust color values (a, b) decreased significantly with increased content of banana powder, but the a value increased. Crumb colors values (L, b) decreased as banana powder content increased while the a value increased. In terms of textural characteristics, the samples containing 5, 15, and 20% banana powder had significantly higher hardness than the 0 and 10% samples. Fracturability and resilience were maximal with 15% and 5%, respectively. Adhesiveness and chewiness were not significantly different among the samples. In the sensory evaluation, scores for banana flavor, coarseness, color, flavor, softness, and overall acceptability increased as the level of banana powder content increased. Sweetness was not significantly different among the samples. The control group had significantly higher egg-flavor as compared to the samples containing banana powder. The results indicated that substituting 10% banana powder to sponge cake is optimal for quality and provides a product with reasonably high overall acceptability.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.2
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• pp.104-115
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• 2014

Abundance and composition of marine debris on 13 beaches of Tongyeong City, South Korea were surveyed in 2013 Autumn. The average quantity of macro debris (>25 mm) was about 30 particle/$m^2$ and that of micro debris (1 mm-25 mm) was about 26,971 particle/$m^2$. This is a very high level compared with other areas of South Korea and the other countries. Among the 7 material types of debris (styrofoam, hard plastic, fiber, metal, glass, wood and others), styrofoam composed a large portion: 75% of macro debris and 98% of micro debris. And among the 'whole' styrofoam debris items whose original volume is remained more than 50%, styrofoam buoy debris composed 93%. This result suggests that the beaches surveyed are seriously contaminated by marine debris, and most of its sources are aquaculture styrofoam buoys. Management of styrofoam buoy debris used for oyster aquaculture in Tongyeong City is important not only for Tongyeong city, but also for other areas, because Tongyeong city hosts the biggest number of oyster aquaculture areas in South Korea.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.1
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• pp.235-240
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• 2006

The paper will give an overview of the mission of GalTeC and then concentrate on two main aspects. The first more detailed aspect, is the analysis of the key performance parameters for the Galileo system services and presenting a technical overview of methods and algorithms used. The second more detailed aspect, is the service volume prediction including service dimensioning using the Prediction tool. In order to monitor and validate the Galileo SIS performance for Open Service (OS) and Safety Of Life services (SOL) regarding the key performance parameters, different analyses in the SIS domain and User domain are considered. In the SIS domain, the validation of Signal-in-Space Accuracy SISA and Signal-in-Space Monitoring Accuracy SISMA is performed. For this purpose first of all an independent OD&TS and Integrity determination and processing software is developed to generate the key reference performance parameters named as SISRE (Signal In Space Reference Errors) and related over-bounding statistical information SISRA (Signal In Space Reference Accuracy) based on raw measurements from independent sites (e.g. IGS), Galileo Ground Sensor Stations (GSS) or an own regional monitoring network. Secondly, the differences of orbits and satellite clock corrections between Galileo broadcast ephemeris and the precise reference ephemeris generated by GalTeC will also be compared to check the SIS accuracy. Thirdly, in the user domain, SIS based navigation solution PVT on reference sites using Galileo broadcast ephemeris and the precise ephemeris generated by GalTeC are also used to check key performance parameters. In order to demonstrate the GalTeC performance and the methods mentioned above, the paper presents an initial test result using GPS raw data and GPS broadcast ephemeris. In the tests, some Galileo typical performance parameters are used for GPS system. For example, the maximum URA for one day for one GPS satellite from GPS broadcast ephemeris is used as substitution of SISA to check GPS ephemeris accuracy. Using GalTeC OD&TS and GPS raw data from IGS reference sites, a 10 cm-level of precise orbit determination can be reached. Based on these precise GPS orbits from GalTeC, monitoring and validation of GPS performance can be achieved with a high confidence level. It can be concluded that one of the GalTeC missions is to provide the capability to assess Galileo and general GNSS performance and prediction methods based on a regional and global monitoring networks. Some capability, of which first results are shown in the paper, will be demonstrated further during the planned Galileo IOV phase, the Full Galileo constellation phase and for the different services particularly the Open Services and the Safety Of Life services based on the Galileo Integrity concept.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.6
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• pp.1775-1781
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• 2008

The effects of the type of curing agent on the swelling of the natural rubber(NR) sponge applicable to the self-sealing layer of a helicopter fuel tank were investigated. The curing systems employed were peroxide and mixed ones of sulfur and peroxide. The NR compounds were prepared in a kneader and a roll-mill. The compounds were partially cured in a press at high pressure and subsequently cured fully with expansion in another press at atmospheric pressure. The apparent density of the NR sponge was measured and the cell structure was observed with scanning electron microscopy. The swelling experiments were performed at room temperature using toluene, iso-octane, and an aircraft fuel as a solvent. More rapid volume swelling of the NR sponge cured by peroxide was achieved than cured by sulfur and peroxide with similar amount of curing agent added in rubber compounds. The apparent density and cell structure of the sponge were extremely sensitive to the amount of peroxide, which influences again the swelling behavior of the NR sponge. It is important to control properly two reactions of decomposition of foaming agent and crosslinking of NR in the mold to obtain rapid swelling of the NR sponge on contact of the fuel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.54-59
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• 2017

GGBFS (Ground Granulated Blast Furnace Slag) is a byproduct with engineering advantages and HVSC (High Volume Slag Concrete) is widely attempted due to active utilization and reduction of eco-load. In the present work, characteristics of drying shrinkage and early-aged behavior are evaluated for the concrete with 65% replacement ratio of GGBFS and 50MPa of design strength. For the work, 3 different mix conditions are considered and several tests including slump flow, compressive strength, drying and autogeneous shrinkage are performed. From the test, OPC 100 mixture without replacement shows higher strength development before 7 days, however the strength reduction in concrete replaced with GGBFS is not significant due to sufficient free water for cement hydration. OPC 100 mixture also shows significant drying shrinkage due to a great autogeneous shrinkage before 3 days. In the concrete with GGBFS replacement, the drying shrinkage behavior is improved due to relatively small deformation by autogeneous shrinkage. The mixture (OPT BS 65) with lower w/b ratio (0.27) and unit content of water ($160kg/m^3$) shows more improved shrinkage behavior than BS 65 mixture which has simple replacement of GGBFS with 0.30 of w/b and $165kg/m^3$ of water unit content.