• 한국생물공학회:학술대회논문집
• /
• 2002.04a
• /
• pp.121-125
• /
• 2002

Rhodococcus rhodochrous IGTSS (ATCC 5396S) can break organo sulfur compounds such as dibenzothiophene. Since the environment for biodesulfurization process is invariably hydrophobic, parameters in hydrophobic systems should be examined. For the model oil, hexadecane-containing 5.43mM dibenzothiophene, the volumetric desulfurization rate was decreased with the oil-to-aqueous phase ratio up to 50%. The rate declined sharply after 48h because the cell activity, which is refreshed by medium exchange, was lost. To supply the exhausted nutrients, medium exchange was performed. At 30% oil phase, most of DBT was removed by medium exchange on 48h, and the rate was 2.03mg $DBT_{removed}/L_{dispersion}-hr.$ At 50% oil phase, medium exchange on 60h was performed and the rate was 1.79mg $DBT_{removed}/L_{dispersion}-hr.$ The 300mL flask system was scaled up to a 5-L bioreactor system. On 60 h, a medium exchange was performed and the rate was 5.28mg $DBT_{removed}/L_{dispersion}-hr.$ and all of DBT was removed. It means that we can use the biodesulfurization process even 10 the high oil-to-water phase by some appropriate methods such as controlled feeding of key nutrients and the dilution or removal of some toxic metabolites by continuous reactor.

• Fisheries and Aquatic Sciences
• /
• v.14 no.4
• /
• pp.421-428
• /
• 2011

We conducted modeling experiments to evaluate the residence times and exchange rates of seawater in Gamak Bay, located on the southern coast of the Korean Peninsula. The results revealed that pollutants are more quickly dispersed in a fixed grid rather than in a variable grid system. Pollutant concentrations decayed exponentially with time after release near the mouth of the bay, whereas no exponential variations were seen at the northwest end of the bay. The mean exchange rate of the seawater was 1.58% per day in the variable grid system, and the residence time of pollutants was greater than 288 days in Gamak Bay. Conversely, the exchange rate of seawater in Gamak Bay, as revealed by the particle tracking method, was 65% over a 50-day simulation. The results suggest that the seawater exchange in Gamak Bay is so low that pollutants are likely to remain in the bay indefinitely.

• International Commerce and Information Review
• /
• v.13 no.4
• /
• pp.229-249
• /
• 2011

The exchange rate change has been increased since the time when the floating exchange rate system was introduced in Korea. As a result, the increase of the exchange rate changes raised the risk in international trades in Korea. Also after Bretton Woods System broke down, the increasing exchange rate fluctuation raised the risk in international trade. The purpose of this dissertation is to study whether this incomplete pass-through exists in Korean export industry and furthermore to measure the markup rate of the export price using real data since Global Financial Crisis. The estimation results of the export price determination model by Error Correction Model shows that the export price of Korea has been greatly influenced by the export prices and exchange rates against U.S. Dollar of rival countries, domestic producer price as well as the Korean Won-U.S. Dollar exchange rate and also business coincidence index of U.S. in demand. Particularly, the pass-through rate of Korean Won-U.S. Dollar exchange rate to export price is estimated to be incomplete, which contrasts with the propositions of traditional exchange rate determination approach, e. g. elasticity approach, monetary approach, etc.

• Journal of Intelligence and Information Systems
• /
• v.3 no.1
• /
• pp.47-68
• /
• 1997

This paper discusses a method of modified Elman network(1990) for nonlinear predictions and its a, pp.ication to forecasting daily exchange rate returns. The method consists of two stages that take advantages of both time domain filter and modified feedback networks. The first stage straightforwardly employs the filtering technique to remove extreme noise. In the second stage neural networks are designed to take the feedback from both hidden-layer units and the deviation of outputs from target values during learning. This combined feedback can be exploited to transfer unconsidered information on errors into the network system and, consequently, would improve predictions. The method a, pp.ars to dominate linear ARMA models and standard dynamic neural networks in one-step-ahead forecasting exchange rate returns.

• The Korean Journal of Applied Statistics
• /
• v.23 no.1
• /
• pp.81-93
• /
• 2010

Korea experienced a financial crisis in 1997. Since then Korea economy has undergone severe change such as exchange rate regime from the market average exchange rate system to the free floating exchange rate system in 1997, and the currency rate fluctuation has been widening. We empirically analyze the determination of the Won/Dollar exchange rate based on the monetary approach. We employ Lucas (1982), Bilson (1978) and Frankel (1979) models and consider some mixed models. We make use of monthly data of money supply, income, interest rate, capital balance, terms of trade, and the yen/dollar exchange rate over the period 1990-2009. We compare the empirical results of cointegration tests and the vector error correction model(VECM) from the two regimes, the pre and post korean financial crisis. The won/dollar exchange rate has long-run relationship with the variables in the monetarist models in the two regimes. For the post crisis regime, the Bilson model is the best and the long run variables also affect the short run dynamics of the won/dollar exchange rate.

• KIEAE Journal
• /
• v.14 no.2
• /
• pp.29-36
• /
• 2014

The ground source heat pump (GSHP) system has attracted much of attention, because of its stability of heat production and the high efficiency of the system. Performance of the heat exchanger is dependent on the soil temperature, the ground thermal conductivity, the operation schedule, the pipe placement and the design temperature. However, in spite of the many variables of these systems, there have been few research on the effect of the systems on system performance. In this study, analysis of the heat exchange rate according to soil temperature and grout material was conducted by numerical simulation. Furthermore, the heat distribution around the ground heat exchanger was presented on the different conditions of grout and underground temperature by the simulation.

• Journal of the Korean Solar Energy Society
• /
• v.34 no.2
• /
• pp.66-72
• /
• 2014

Ground source heat pump system can achieve high efficiency of performance by utilizing annually constant underground temperature to provide heat source for space heating and cooling. Generally, the depth of constant-temperature zone under the ground depends on surface heat flux and soil properties. The deeper the ground heat exchanger is installed, the higher the heat exchange rate can be acquired. However, in order to optimally design the system, it is necessary to consider both the installation cost and the system performance. In this study, performance analysis of ground source heat pump system according to the depth has been conducted through the case study.

• Journal of Bio-Environment Control
• /
• v.10 no.1
• /
• pp.10-14
• /
• 2001

The cooling effect of a fog cooling system has a close relationship to air flow and relative humidity in the greenhouse. From the VETH chart for cooling design, a cooling efficiency can be improved by means of increasing the air exchange rate and the amount of sprayed water. In the no shading experimental greenhouse by time control, when average air exchange rate was 0.77 times.min$^{-1}$ and spray water amount was 2,009g, inside temperature of the greenhouse was 31$^{\circ}C$ that was almost close to outside temperature and cooling efficiency was 82%. When average air exchange rate was close to temperature of the greenhouse that was no cooling and 70% shading greenhouse environment. When average air exchange rate was 2.59times.min$^{-1}$ , spray water amount was 2,009g and shading rate was 70%, inside relative humidity of the greenhouse was increased was 2,009 g and shading rate was 70%, inside relative humidity of the greenhouse was increased, but temperature was not decreased. When average air exchange rate was 2.33 times.min$^{-1}$ and spray water amount was 2,009g, inside temperature was 31.4 and at that time maximum wind speed at the air inlet of greenhouse was 1.9m.s$^{-1}$ . Since time controller sprayed amount of constant water at a given interval, some of sprayed water remained not to be evaporated, which increased relative humidity and decreased cooling efficiency. Because the shading screen prevented air flow in the greenhouse, it also caused the evaporation efficiency to be decreased. In order to increase cooling efficiency, it was necessary to study on controling by relative humidity and air circulation in the greenhouse.

• Journal of Korea Trade
• /
• v.23 no.5
• /
• pp.87-101
• /
• 2019

Purpose - This paper examines the effectiveness of the foreign exchange risk insurance system in the promotion of SME exports in Korea. The purpose of this study is to analyze the short-term and long-term responses of SME exports to foreign exchange risk insurance support policies. Based on these empirical studies, we would like to present some operational improvements to the operation of the foreign exchange risk insurance system. Design/methodology - In order to analyze the effect of exchange risk insurance on the exports of SMEs, a VAR model consisting of foreign exchange risk insurance underwriting values, export relative price, and domestic demand pressure, including export volume, was established. The study began with tests of the stationarity of time series data. The unit root tests showed that all concerned variables were non-stationary. Accordingly, the results of the cointegration test showed that the tested variables are not cointegrated. Finally, an impulse response function and variance decomposition analysis were conducted to analyze the impulse of foreign exchange risk insurance on exports of SMEs. Findings - As a result of estimating the VAR (1) model, foreign exchange risk insurance was found to be significant at a 1% significance level for SME' export promotion. In the impulse response analysis, SMEs' export response to the impulse of foreign exchange risk insurance showed that exports gradually increased until the third quarter, and then slowed down. However, the impulse did not disappear, and appeared continuously. Originality/value - This study analyzed the effect of foreign exchange insurance on exports of SMEs by applying the VAR model. In particular, this study is the first to analyze the short-term and long-term effects of foreign exchange risk insurance on exports of SMEs. The empirical evidence in the current study have a policy implication for the policy authority to support and promote the foreign exchange risk insurance in the effect of exchange rate volatility on Korea' export SMEs.

• The Korean Journal of Financial Studies
• /
• v.6 no.1
• /
• pp.335-356
• /
• 2000

This paper examines the time series dynamics of spot and forward exchange rates and Eurocurrency deposit rates for four bilateral relationships vis a vis the U.S. dollar using daily data. The equilibrium implied by covered interest parity provides a theoretical foundation from which to estimate and analyze the dynamic properties of each system of exchange rates and interest rates. The structural statistical model is identified by relying on the implied cointegration vectors and long-run neutrality restrictions.