• Journal of Positioning, Navigation, and Timing
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• v.4 no.2
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• pp.43-55
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• 2015

In the case of satellite navigation positioning, the shielding of satellite signals is determined by the environment of the region at which a user is located, and the navigation performance is determined accordingly. The accuracy of user position determination varies depending on the dilution of precision (DOP) which is a measuring index for the geometric characteristics of visible satellites; and if the minimum visible satellites are not secured, position determination is impossible. Currently, the GLObal NAvigation Satellite system (GLONASS) of Russia is used to supplement the navigation performance of the Global Positioning System (GPS) in regions where GPS cannot be used. In addition, the European Satellite Navigation System (Galileo) of the European Union, the Chinese Satellite Navigation System (BeiDou) of China, the Quasi-Zenith Satellite System (QZSS) of Japan, and the Indian Regional Navigation Satellite System (IRNSS) of India are aimed to achieve the full operational capability (FOC) operation of the navigation system. Thus, the number of satellites available for navigation would rapidly increase, particularly in the Asian region; and when integrated navigation is performed, the improvement of navigation performance is expected to be much larger than that in other regions. To secure a stable and prompt position solution, GPS-GLONASS integrated navigation is generally performed at present. However, as available satellite navigation systems have been diversified, finding the minimum satellite constellation combination to obtain the best navigation performance has recently become an issue. For this purpose, it is necessary to examine and predict the navigation performance that could be obtained by the addition of the third satellite navigation system in addition to GPS-GLONASS. In this study, the current status of the integrated navigation performance for various satellite constellation combinations was analyzed based on 2014, and the navigation performance in 2020 was predicted based on the FOC plan of the satellite navigation system for each country. For this prediction, the orbital elements and nominal almanac data of satellite navigation systems that can be observed in the Korean Peninsula were organized, and the minimum elevation angle expecting signal shielding was established based on Matlab and the performance was predicted in terms of DOP. In the case of integrated navigation, a time offset determination algorithm needs to be considered in order to estimate the clock error between navigation systems, and it was analyzed using two kinds of methods: a satellite navigation message based estimation method and a receiver based method where a user directly performs estimation. This simulation is expected to be used as an index for the establishment of the minimum satellite constellation for obtaining the best navigation performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.643-648
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• 2010

Portable fuel cells are commonly operated in the dead-end mode because of such as high fuel utilization. However, the performance of such systems deteriorates continuously with an increase in the amount of by-products such as water vapor and nitrogen. In this study, to verify the effect of water vapor on Proton Exchange Membrane Fuel Cells (PEMFCs), constant-load experiments were carried out for a current density of 600 mA/cm2 and a voltage of 0.4 V, respectively. The performance of the cell was more stable under constant voltage conditions than under constant current density conditions. Condensed water accumulated in the anode channel near the cell outlet. The experimental results show how the relative humidity (RH = 0.15, 0.4 and 0.75) of air at the cathode side affect the performance of PEMFCs with dead-end anode. At RH values higher than 0.15, the mean power density increased by up to 51% and the mean purge duration decreased by up to 25% compared to the corresponding initial values.

• Journal of the Korean Electrochemical Society
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• v.6 no.2
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• pp.93-97
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• 2003

The electrode for a supercapacitor was prepared using an amorphous ruthenium oxide, which was synthesized from ruthenium trichloride hydrate$(RuO_2{\cdot}nH_2O)$. A supercapacitor was assembled with an electrode of ruthenium oxide material on a current collector of tantalum, and an electrolyte of 4.8 M sulfuric acid. The result of the AC impedance analyses on $Ta/H_2SO_4(4.8 M)/Pt$ cell showed that tantalum was stable at the potential range of $0.0\~1.1V(vs. SCE)$. Therefore, Ta film could be used the supercapacitor as a current collector. The irreversible hydrolysis in the supercapacitor occurred over ca. 1.0V(vs.SCE) when the supercapacitor was protonated to 0.5V(vs. SCE). The supercapacitor protonated to 0.5V(vs.SCE) showed good electrochemical properties when it was tested at the potential range of 1.0V in the charge-discharge test. The potential range of the electrodes including the positive and the negative electrode was varied between -0.004 and 0.995V(vs. SCE). The potential ranges of the positive and the negative electrode were $-0.004\~0.515V(vs.\;SCE)\;and\; 0.515\~0.995V(vs.\;SCE)$, respectively.

• Journal of Environmental Science International
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• v.20 no.10
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• pp.1273-1284
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• 2011

The aim of this research was to evaluate the performance of insoluble electrode for the purpose of degradation of Rhodamine B (RhB) and oxidants generation [N,N-Dimethyl-4-nitrosoaniline (RNO, indicator of OH radical), $O_3$, $H_2O_2$, free Cl, $ClO_2$)]. Methods: Four kinds of electrodes were used for comparison: DSA (dimensional stable anode; Pt and JP202 electrode), Pb and boron doping diamond (BDD) electrode. The effect of applied current (0.5~2.5 A), electrolyte type (NaCl, KCl and $Na_2SO_4$) and electrolyte concentration (0.5~3.5 g/L) on the RNO degradation were evaluated. Experimental results showed that the order of RhB removal efficiency lie in: JP202 > Pb > BDD ${\fallingdotseq}$ > Pt. However, when concerned the electric power on maintaining current of 1 A during electrolysis reaction, the order of RhB removal efficiency was changed: JP202 > Pt ${\fallingdotseq}$ Pb > BDD. The total generated oxidants ($H_2O_2$, $O_3$, free Cl, $ClO_2$) concentration of 4 electrodes was Pt (6.04 mg/W) > JP202 (4.81 mg/W) > Pb (3.61 mg/W) > BDD (1.54 mg/W), respectively. JP202 electrode was the best electrode among 4 electrodes from the point of view of performance and energy consumption. Regardless of the type of electrode, RNO removal of NaCl and KCl (chlorine type electrolyte) were higher than that of the $Na_2SO_4$ (sulfuric type electrolyte) RNO removal. Except BDD electrode, RhB degradation and creation tendency of oxidants such as $H_2O_2$, $O_3$, free Cl and $ClO_2$, found that do not match. RNO degradation tendency were considered a simple way to decide the method which is simple it will be able to determinate the electrode where the organic matter decomposition performance is superior. As the added NaCl concentration was increases, the of hydrogen peroxide and ozone concentration increases, and this was thought to increase the quantity of OH radical.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.3
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• pp.140-147
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• 2005

We investigated the interactions between coastal waters of the Yeongil Bay, Korea, and oceanic waters of the Eastern Sea, as wet 1 as the development mechanism of vertical circulation currents in the bay. The oceanic waters of the bay have an average water temperature of $12.2{\sim}18.4^{\circ}C$ and salinity of $33.32{\sim}34.43$ PSU. Results of spectral analysis have shown that the period of revolution between oceanic and coastal waters is about 0.84-0.91 years in the surface waters and 1.84 years in the bottom layer. The wind direction in the bay shifts between SW and NE, with the main wind direction being SW during the winter period, and water mass movement is influenced by such seasonal variations in wind direction. Vertical circulation currents in the bay are structured by two phenomena: the surface riverine outflow layer from the Hyeong-san River into the open sea and the bottom oceanic inflow layer with high-temperature and salinity into the bay. These phenomena start the spring when the water mass is stable and become stronger in the summer when the surface cold water develops over a 10-day period. Consequently, tidal currents have little influence in the bay; rather, these vertical and horizontal circulation currents play an important role in the transport of the pollutant load from the inner bay to the open sea.

• Korean Journal of Clinical Pharmacy
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• v.26 no.3
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• pp.201-206
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• 2016

Objective: Direct current cardioversion for atrial fibrillation could be associated with the risk of thromboembolic events. Anticoagulation therapy with warfarin (INR 2.0-3.0) is recommended 3 weeks before and 4 weeks after cardioversion to reduce the risk of thromboembolism. This study evaluated warfarin therapy in pharmacist-managed anticoagulant services (ACS). Methods: This retrospective study was performed in 106 patients with atrial fibrillation from 2012 to 2013. The primary efficacy endpoint was the composite of stroke, transient ischemic attack, myocardial infarction, and cardiovascular death. The primary safety measure was major bleeding. To evaluate the peri-procedural effects of warfarin treatment, we studied whether target INR was maintained, as well as the maintenance period of the therapeutic range. Quality of treatment was measured by time in therapeutic range (TTR) by using the Rosendaal method. Results: There were no thromboembolic events, but TEE examination at time of cardioversion showed a left atrial thrombus in three patients (2.8%). Bleeding complications after cardioversion occurred in 2 patients (1.9%). The average INR value at the time of cardioversion was $2.59{\pm}0.8$, and was within the therapeutic range in 83 patients (78%). Analysis of the patients in whom the value was within the therapeutic range twice consecutively showed that the ratio of TTR was 80% and the therapeutic range was maintained in 67 patients (63%) for an average of 4.90 weeks prior to cardioversion. Similarly, 76 patients (72%) had a stable INR within the therapeutic range for an average of 5.70 weeks and a mean TTR of 83%. Conclusion: Pharmacists significantly contributed to appropriate warfarin treatment with close monitoring during cardioversion. Likewise, active pharmacist monitoring and systemic management should be considered to reduce thromboembolism and bleeding complications in the peri-cardioversion period.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.683-693
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• 2011

In this paper, a design of high current and broad-band microwave bias-tee was presented for a stable bias of a high power amplifier. An input impedance of bias-tee should be shown to 50 ohm with the wideband in order to be stably-biased the amplifier. For this design of the bias-tee, a capacitor of bias-tee for a DC block was designed with a high wide-band admittance by a parallel sum of capacitors, and a inductor for a RF choke and a DC feeding was designed with a high wide-band impedance by a series sum of inductors. As this inductor and capacitor for the sum has each SRF, band-limitation of lumped element was driven from SRF. This limitation was overcome by control of a resonance's quality factor with adding a resistor. 1608 SMD chips for design's element was mounted on the this pattern for the designed bias-tee. The fabricated bias-tee presented 10 dB of return loss and wide-band about 50 ohm input impedance at 10 MHz~10 GHz.

• Journal of Distribution Science
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• v.7 no.2
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• pp.29-44
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• 2009

The aim of this study was to theoretically examine the current status of TV home shopping business entities' expansion of business structure, and then look into TV home shopping business entities' preparation for the future business in their mature period. For this, the investigator examined literature home and abroad and then empirically carried out an experimental sale of household goods by selecting a model TV home shopping business entity. In order to understand current business structure of TV home shopping and increase sales, the investigator has changed price and then induced sales, focusing on the price of household goods. Study findings are as follows: As for the influence of TV home shopping household goods' price upon its sales, because TV home shopping business entities set in advance an efficiency unit-price per broadcast hour and carry out a sales strategy of reaching out the efficiency, they try to keep their sales with discounted price in the real sales setting of TV home shopping. But it is not an exclusive practice. General promotion became a common practice. The price of goods is the same with its life. Continuous discount events lower the reliability of goods and its supplier must bear the result. Overall sales after experiment increases by 13% and the sales efficiency also increases by 9%. Sales amount increases by 9% and a stable sales which is above average is achieved. The number of sales goods keeps 100%.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.10a
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• pp.15-15
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• 1999

In chip plating, several parameters must be taken into consideration. Current density, solution concentration, pH, solution temperature, components volume, chip and media ratio, barrel geometrical shape were most likely found to have an effect to the process yields. The 3 types of barrels utilized in chip plating industry are the conventional rotating barrel. vibrational barrel (vibarrel), and the centrifugal type. Conventional rotating barrel is a close type and is commonly used. The components inside the barrel are circulated by the barrel's rotation at a horizontal axis. Process yield has known to have higher thickness deviation. The vibrational barrel is an open type which offers a wide exposure to electrolyte resulting to a stable thickness deviation. It rotates in a vertical axis coupled with multi-vibration action to facilitate mixed up and easy transportation of components, The centrifugal barrel has its plated work centrifugally compacted against the cathode ring for superior electrical contact with simultaneous rotary motion. This experiment has determined the effect of barrel vibration intensity to the plating thickness distribution. The procedures carried out in the experiment involved the overall plating process., cleaning, rinse, Nickel plating, Tin-Lead plating. Plating time was adjusted to meet the required specification. All other parameters were maintained constant. Two trials were performed to confirm the consistency of the result. The thickness data of the experiment conducted showed that the average mean value obtained from higher vibrational intensity is nearer to the standard mean. The distribution curve shown has a narrower specification limits and it has a reduced variation around the target value, Generally, intensity control in vi-barrel facilitates mixed up and easy transportation of components, However, it is desirable to maintain an optimum vibration intensity to prevent solution intrusion into the chips' internal electrode. A cathodic reaction can occur in the interface of the external and internal electrode. $2HD{\;}+{\;}e{\;}{\rightarrow}20H{\;}+{\;}H_2$ Hydrogen can penetrate into the body and create pressure which can cause cracks. At high intensity, the chip's motion becomes stronger, its contact between each other is delayed and so plating action is being controlled. However, the strong impact created by its collision can damage the external electrode's structure thereby resulting to bad plating condition. 1 lot of chip was divided into two equal partion. Each portion was loaded to the same barrel one after the other. Nickel plating and tin-lead plating was performed in the same station. Portion A maintained the normal barrel vibration intensity and portion B vibration intensity was increased two steps higher. All other parameters, current, solution condition were maintained constant. Generally, plating method find procedures were carried out in a best way to maintained the best plating condition. After plating, samples were taken out from each portion. molded and polished. Plating thickness was investigated for both. To check consistency of results. 2nd trial was done now using different lot of another characteristics.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.2
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• pp.67-72
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• 2010

In this study, the impact on the circulating water system has been analyzed due to an installation of helical turbine to develop hydro-kinetic energy at the discharge channel of the power plant. Numerical simulations of velocity and pressure variations have been performed when one set of $3.6\;m\;{\times}\;1.5\;m$ sized helical turbine is installed at the outlet of discharge culvert. In case of mean sea level, change of downstream water surface elevation does not affect upstream elevation of the weir because its propagation is blocked by the seal well weir. However in case of highest high water level, change of downstream elevation affects upstream elevation because flow pattern in discharge culvert becomes the full pipe flow with submerged weir. Although an unstable pressure change occurs in upstream of the weir during the intial 10 minutes after beginning of the discharge, it becomes stable after that time. In addition, a rise of water surface elevation by 0.2 m is observed but it is concluded that it hardly affects the safety of circulating water pump (CWP) although its required power is increased more or less. Therefore, the increase of required power of CWP needs to be considered for evaluation of the helical turbine applicability.