• Journal of Korean Society on Water Environment
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• v.24 no.6
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• pp.793-800
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• 2008

Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

• Journal of Ocean Engineering and Technology
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• v.32 no.3
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• pp.184-191
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• 2018

Recently, as sea ice in the Arctic has been decreasing due to global warming, it has become easier to develop oil and gas resources buried in the Arctic region. As a result, Russia, the United States, and other Arctic coastal states are increasingly interested in the development of oil and gas resources, and the demand for offshore structures to support Arctic sea resources development is expected to significantly increase. Since offshore structures operating in Arctic regions need to secure safety against various drifting ice conditions, the concept of an ice-strengthened design is introduced here, with a priority on calculation of ice load. Although research on the estimation of ice load has been carried out all over the world, most ice-load studies have been limited to estimating the ice load of the icebreaker in a non-oblique state. Meanwhile, in the case of Arctic offshore structures, although it is also necessary to estimate the ice load according to oblique angles, the overall research on this topic is insufficient. In this paper, we suggest algorithms for calculating the ice load of managed ice (pack ice, 100% concentration) in an oblique state, and discuss validity. The effect of oblique angle according to estimated ice load with various oblique angles was also analyzed, along with the impact of ship speed and ice thickness on ice load.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.5
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• pp.587-596
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• 2008

For Wireless internet service in Metropolitan area, optimum location selection for base station and cell planning are critical process in determining service coverage by accurate prediction of Wave Propagation Characteristics. Due to different kinds of characteristics in service area such as lay of land, natural feature and material, height and width of artificially made building, it has a great impact on the transmission and distance recovery of wireless network service. Therefore, these facts may cause substantial barriers in predicting & analyzing the expected level of service quality and providing it to subscribers. In this thesis, we have simulated the process to improve quality and coverage of the service by adjusting the location of Base station and the antenna angle that influence the service after the basic location of base station is selected according to the wave prediction model. Based on this simulations test, we have demonstrated the results in which subscribers would get higher quality of wireless internet service along with bigger coverage and the improved quality in the same service coverage area through optimization process of base station.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.3
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• pp.1105-1109
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• 2015

Chemoresistance is the most common cause of chemotherapy failure during breast cancer (BCA) treatment. It is generally known that the mechanisms of chemoresistance in tumors involve multiple genes and multiple signaling pathways,; if appropriate drugs are used to regulate the mechanisms at the gene level, it should be possible to effectively reverse chemoresistance in BCA cells. It has been confirmed that chemoresistance in BCA cells could be reversed by ginsenoside Rh2 (G-Rh2). Preliminary studies of our group identified some drugresistance specific miRNA. Accordingly, we proposed that G-Rh2 could mediate drug-resistance specific miRNA and corresponding target genes through the gene regulatory network; this could cut off the drug-resistance process in tumors and enhance treatment effects. G-Rh2 and breast cancer cells were used in our study. Through pharmaceutical interventions, we could explore how G-Rh2 could inhibit chemotherapy resistance in BCA, and analyze its impact on related miRNA and target genes. Finally, we will reveal the anti-resistance molecular mechanisms of G-Rh2 from a different angle in miRNA-mediated chemoresistance signals among cells.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.43 no.6
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• pp.407-414
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• 2017

Objectives: The study was designed to evaluate the efficacy of performing a second, repeat anterior maxillary distraction (AMD) to treat residual cleft maxillary hypoplasia. Materials and Methods: Five patients between the ages of 12 to 15 years with a history of AMD and with residual cleft maxillary hypoplasia were included in the study. Inclusion was irrespective of gender, type of cleft lip and palate, and the amount of advancement needed. Repeat AMD was executed in these patients 4 to 5 years after the primary AMD procedure to correct the cleft maxillary hypoplasia that had developed since the initial procedure. Orthopantomogram (OPG) and lateral cephalograms were taken for evaluation preoperatively, immediately after distraction, after consolidation, and one year postoperatively. The data obtained was tabulated and a Mann Whitney U-test was used for statistical comparisons. Results: At the time of presentation, a residual maxillary hypoplasia was observed with a well maintained distraction gap on the OPG which ruled out the occurrence of a relapse. Favorable movement of the segments without any resistance was seen in all patients. Mean maxillary advancement of 10.56 mm was achieved at repeat AMD. Statistically significant increases in midfacial length, SNA angle, and nasion perpendicular to point A distance was achieved (P=0.012, P=0.011, and P=0.012, respectively). Good profile was achieved for all patients. Minimal transient complications, for example anterior open bite and bleeding episodes, were managed. Conclusion: Addressing the problem of cleft maxillary hypoplasia at an early age (12-15 years) is beneficial for the child. Residual hypoplasia may develop in some patients, which may require additional corrective procedures. The results of our study show that AMD can be repeated when residual deformity develops with the previous procedure having no negative impact on the results of the repeat procedure.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.5
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• pp.373-382
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• 2013

In this paper, in order to analyze the performance of a decoy system for ship defense against an anti-ship missile(ASM) with an infrared image(IIR) seeker, the modeling and engagement simulation program is introduced. The IIR seeker on the ASM detects the infrared signal of ship from a distance and approaches the ship based on proportional navigation guidance(PNG) or impact angle control guidance(IACG). Hence the guidance performance of the ASM is basically depend on the target tracking algorithm of the seeker as well as the infrared signal of the ship. Using the developed program, we can investigate the effect of the ship decoy system such as flares and surface cooling system of the ship with respect to various kinds of tracking algorithms of the IIR seeker of the ASM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.3
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• pp.217-223
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• 2013

A digital retrodirective antenna system is easy to modify and upgrade because it can control the phase information of the output signal toward opposite direction to input signal without a priori knowledge of the arrival direction. Due to this advantage, it is possible to perform fast beam tracking. In this paper, a design digital retrosirective array antenna system according to the number of antenna array by using only one digital PLL which finds angle of delayed phase and we test BER performance of this system. When we transmit data at actual communication system, the data modulated onto carrier frequency in order to shift spectrum from base band to another band. So we simulate system considering carrier frequency according to the number of antenna array. As a result, carrier frequency has no impact on the performance.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.382-385
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• 2007

Constantly enhancing positioning accuracy by the Global Positioning System (GPS) technique is of great importance, but challenging, especially after the GPS positioning technique has been improved considerably during the past two decades. The associated main error sources have been reduced substantially, if not eliminated. Troposhpeic influence with its highly temporal and spatial variability appears to be one of the major error sources. It is hence an increased interest among GPS researchers to reduce the tropospheric influence or delay. Two techniques have been commonly implemented to correct the tropospheric impact. The first technique, known as parameter estimation, characterizes the path delay with empirical models and the parameters of interest are determined from the GPS measurements. The second strategy, termed as external correction, involves independent path delay measurements. The present study is an integration of both techniques in which the parameter estimation as well as external correction are used to correct the path delay for $110{\sim}210$ km range baselines. Twenty-four parameters have been obtained in 24 hours solution by setting the cutoff angle at 3 and 15 degrees for parameter estimation strategy. Measurements from meteorological instruments and water vapor radiometer (WVR) are applied in the GPS data processing, separately, as an external strategy of present research work. Interesting results have been found, indicating more stable repeatability in baseline when the external correction strategy is applied especially with the inclusion of WVR observations. The offset of an order of 1 cm is found in the baselines determined by the two strategies. On the other hand, parameter estimation exhibits more stable in terms of GPS height repeatability. The offset in the GPS height determined by the two strategies is on the order of few centimeters.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.3
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• pp.297-304
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• 2016

A numerical simulation has been performed for the penetration of a long-rod penetrator into a metal block (ceramic-tile-inserted 4340-steel plate). The impact velocity is 1.5km/s at a normal incidence angle. The first two validations are conducted for a semi-infinite block measuring the depth of penetration (DOP). The material model of ceramic is the JH-2 (Johnson-Holmquist) model. The predicted DOP values are in close agreement with the experimental data. Then, the primary simulation is performed by varying the position of the confined ceramic tile for three types of thickness of ceramic tile. The residual velocity, residual mass and residual kinetic energy of the long-rod are obtained from the simulation. Based on these predicted values, the trend of the ballistic performance of the protective structure is estimated. In addition, the mass efficiency is calculated in order to determine the performance of the ceramic-tile-inserted metal block. Finally, the optimum protective structure is identified.

• Journal of Biosystems Engineering
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• v.29 no.3
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• pp.217-224
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• 2004

This research was conducted to test the feasibility of utilizing high-pressure water jets of over 1.0㎫ as a means of breaking and peeling garlic bulbs. High-pressure plunger pumps and flat-spray nozzles of varying orifice diameters and spray angles were utilized to supply water jets into a prototype peeling chamber made of transparent acrylic plates. Water jets were discharged from a total of six nozzles installed in such a way that three parallel nozzles face the other three. The cross-sectional area of the peeling chamber and the installation angle of the nozzles had critical effects on peeling performance. Small cross-sectional area was required so that total impact force of water jets on garlic could be increased. The optimum installation angles were around 4, 8, and 16$^{\circ}$ for the nozzles having 15, 40, and 65$^{\circ}$ spray angles, respectively. Best performance with 61.4% of completely-peeled garlics was obtained at a pressure of 1.94㎫ and a flow rate of 9.07 $\ell$/min for each nozzle. The peeling efficiency of the system was generally unsatisfactory due to the limited flow rate of the plunger pumps utilized. For better performance, it is recommended to increase flow rate while reducing operating pressure by utilizing other type of pumps.