• The Korean Journal of Applied Statistics
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• v.22 no.2
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• pp.249-260
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• 2009

Various methods have been suggested in developing the useful leading indicators to predict the actual realizations when time laps exist between policy plannings and future events. The recent economic crisis could have been relived if the information necessary to respond to the future evolutionary process is provided in advance. As the relations between the financial variables and the real economic activity become unstable because of the changes in the financial environment, this study attempts to estimate the capabilities of various internal and external term spreads in predicting the future business trend, followed by comparison and evaluation.

• Korean Journal of Ecology and Environment
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• v.38 no.4 s.114
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• pp.435-438
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• 2005

We observed the physical, chemical, and biological characteristics of an acidic lake, Lake Katanuma, from 1998 to 2002 at weekly or biweekly intervals, except during the winter. This volcanic lake has a dimictic thermal pattern. In summer, the volcanic heat supply at the lake bottom results in weak thermal stratification. In 1998, 1999, and 2002, short-term holomixis was observed during the stratification period, when the anoxic, hydrogen sulfide-rich water from the hypolimnion spread across the entire lake. In contrast, distinct short-term holomixis did not occur during the stratificatlon period in 2000 and 2001. However, the early onset of the autumn turnover in August 2000 and 2001 caused anoxic conditions to persist throughout the entire water column for more than 2 weeks. The anoxic and hydrogen sulfide-rich conditions affected population densities of chironomid larvae (Chironomus acerbiphilus) and planktonic algae (Chlamydomonas acidophila), both dominant species in Lake Katanuma. Thus, the interannual variations of limnological characteristics influenced the seasonal population changes of these species.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.33-39
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• 2022

This paper presents the long-term behavior of tunnel considering the degradation of concrete lining and surrounding soil. Tunnel is a composite structure which has supporting elements (shotcrete, lining, and rockbolt) and surrounding soils. These supporting elements and surrounding soils undergo the degradation as time goes. A proposed degradation function which has two parameters which control the residual strength and degradation shape was applied to the numerical analysis. The results showed the plastic zone was spread around tunnel due to the degradation leading to the increase in unstability of tunnel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.5
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• pp.443-450
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• 2013

We consider user pairing and resource allocation for the uplink of cellular systems employing virtual multiple input multiple output (MIMO). As a multiple access scheme, discrete Fourier transform spread orthogonal frequency division multiple access (DFTS-OFDMA) is adopted for more flexible resource allocation than single carrier (SC)-OFDMA adopted in the Long Term Evolution (LTE) system. We formulate the optimization problems of user pairing and resource allocation to maximize the throughput of the DFTS-OFDMA system under different constraints. The DFTS-OFDMA allowing non-contiguous subcarrier allocation and redundant user assignment provides a better throughput than the SC-FDMA at lower complexity in finding the optimal solution but at the cost of the increased control information indicating the allocated resources.

• Journal of Korean Society of Transportation
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• v.28 no.2
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• pp.135-150
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• 2010

This paper focuses on finding out which covenants are different among the concession agreements of Korean BTO projects and how these influenced IRR(Internal Rate of Return). That is, to figure out the political and economical determinants of IRR by analyzing the concession agreements which are the basic contract of implementing projects. As IRR is an index of profitability, so spread is an indicator of risk to collect debts. That's the reason why the analysis of spread is included. For the empirical analysis, the data of concession agreements for 75 projects and financial models are used. These 75 concession agreements are contracted from 1995 to 2008. The dependent variables are after tax nominal IRR and the spread of long term interest rates of 75 BTO projects. The independent variables are project's proceeding factors, the feasibility variables, the variables related to financial character and the variables related to covenants or the government's policy. The analysis shows that IRR has been influenced by the equity level of financial investors, the national government managed projects, the projects with minimum revenue guarantee (MRG), etc. And the equity level of financial investors, the national government managed projects and the implementation of supplementary project have an effect on spread also.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.22 no.6
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• pp.89-96
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• 2019

This study was carried out for management of the invasive alien plants in Mt. Inwang located in central Seoul. The invasive alien plants are 11 families, 34 genera, 30 taxa, and they are 10.8% of the total vascular plants(314 taxa). The ecosystem disturbed plants designated by the Korea environment ministry are 6 taxa : Rumex acetosella, Lactuca scariola, Ambrosia trifida var. trifida, Ambrosia artemisiifolia, Aster pilosus and Eupatorium rugosum. In the life-form, herbaceous perennials are 13 taxa(35.3%). In the continent of origin, the species from America are 20 taxa(58.8%). In the introduction time, the species of third period are 14 taxa(41.2%). In the diffusion grade, 5 grade species are 14 taxa(41.2%) and they are wide spread species. Mt. Inwang was designated as ecological scenery conservation area of Seoul in 2007. But Mt. Inwang is in high danger by the spread of invasive alien plants and ecosystem disturbed plants, due to artificial factors such as development pressure and the occurrence of byway trail. Therefore, Mt. Inwang needs systematic management of invasive alien plants and monitoring of long-term changes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.21-28
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• 2009

DFT-spread OFDM(Discrete Fourier Transform-Spread Orthogonal Frequency Division Multiplexing) is very effective for solving the PAPR(Peak-to-Average Power Ratio) problem. Therefore, the SC-FDMA(Single Carrier-Frequency Division Multiple Access) which is basically same to the DFT spread OFDM was adopted as the uplink standard of the 3GPP LTE ($3^{rd}$ Generation Partnership Project Long Term Evolution). Unlike the ordinary OFDM system, the SC-FDMA using DFT spreading method is vulnerable to the ICI(Inter-Carrier Interference) problem caused by the phase noise and IQ(In-phase/Quadrature) imbalance and effected FDE(Frequency Domain Equalizer). In this paper, the ICI effects from the phase noise and IQ imbalance which can be problems in uplink transmission are analyzed according the back-off level of HPA. Next, we propose the equalizer algorithm to remove the ICI effects. This proposed equalizer based on the FDE can be considered as up-graded and improved version of PNS(Phase Noise Suppression) algorithm. This proposed equalizer effectively compensates the ICI resulting from the phase noise and IQ imbalance. Finally, through the computer simulation, it can be shown that about SNR=14 dB is required for the $BER=10^{-4}$ after ICI compensation when the back-off is 4.5 dB, $\varepsilon=0.005$, $\phi=5^{\circ}$, and $pn=0.06\;rad^2$.

• Economic Analysis
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• v.25 no.2
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• pp.132-176
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• 2019

We use a time-varying parameter vector auto regression (TVP-VAR) model to understand the impact of U.S. monetary policy normalization on Korean financial markets and capital accounts. The U.S. monetary policy is represented by the federal funds rate, term premium and credit spread. During the U.S. monetary contraction period of 2004 to 2006, changes in the federal funds rate presented negative pressure on Korean financial markets. The changes in federal funds rate also led to a simultaneous contraction in inward and outward capital flows. However, the effects of a federal funds rate shock has been reduced since 2015. On the other hand, the effects of U.S. term premiums is getting stronger after the period of quantitative easing (QE). The influence of the U.S. credit spread also significantly increased after the global financial crisis. Simulation results show that a rise in the U.S. credit spread, which can be triggered by a contractionary monetary policy, can pose a larger adverse impact on the Korean economy than a rise in the federal funds rate itself. As for capital flows, a U.S. monetary policy contraction causes an outflow of foreign investment, but the repatriation of overseas investment by Korean residents can offset this outflow.

• The Journal of Industrial Distribution & Business
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• v.9 no.8
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• pp.41-50
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• 2018

Purpose - As an important participant in the financial markets, the commercial bank will be impacted by the interest rate marketization. Owing to the special condition of China, this paper tries to explore the impact of operating mechanisms between interest rate marketization and the profitability of the commercial Bank. Research design, data and methodology - This paper applies time series data from 2005 to 2016. Due to the short period of time series, autocorrelation often occurs. Therefore, the fully modified least squares(FMOLS) will be used to conduct an empirical analysis. The reason is that it can move off the autocorrelation between variables and disturbance term. And FMOLS also can make estimated cointegrating parameters closed to normal distribution. More importantly, in order to avoid spurious regressions, the Augmented Dickey-Fuller Test will be used to verify the stationarity of all variables. The total return of asset is treated as the profitability of commercial bank. The net interest spread is treated as a measurement of interest rate marketization. Both are regarded as dependent variables. The non-interest income or gross revenues and impaired loans or gross loans are treated as independent variables. The sixteen representative listed commercial banks are divided into three categories (state-owned, share-holding and city-owned) to conduct an estimation. Results - Via empirical analysis, the findings show that the net interest spread has a positive effect on the profitability of the commercial bank. More specifically, 1% increase in the net interest spread will lead 0.157% increase in the profitability of state-owned commercial bank, 0.269% increase in the profitability of share-holding commercial bank and 0.263% increase in the profitability of city-owned commercial bank. If regarding the sixteen listed commercial city as a whole, 1% increase in the net interest spread will lead 0.267% increase in the profitability of the commercial bank. Conclusions - As the interest rate marketization, the importance of interest rate on the profitability of commercial bank has become more and more significant. The empirical evidences also prove that the net interest spread can bring about the change of the commercial bank's profitability. Therefore, policy-makers of commercial banks should fully understand the operating mechanism between them.

• Steel and Composite Structures
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• v.10 no.1
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• pp.45-67
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• 2010

Composite steel-concrete structures are employed extensively in modern high rise buildings and bridges. This concept has achieved wide spread acceptance because it guarantees economic benefits attributable to reduced construction time and large improvements in stiffness. Even though the combination of steel and concrete enhances the strength and stiffness of composite beams, the time-dependent behaviour of concrete may weaken the strength of the shear connection. When the concrete loses its strength, it will transfer its stresses to the structural steel through the shear studs. This behaviour will reduce the strength of the composite member. This paper presents the development of an accurate finite element model using ABAQUS to study the behaviour of shear connectors in push tests incorporating the time-dependent behaviour of concrete. The structure is modelled using three-dimensional solid elements for the structural steel beam, shear connectors, concrete slab and profiled steel sheeting. Adequate care is taken in the modelling of the concrete behaviour when creep is taken into account owing to the change in the elastic modulus with respect to time. The finite element analyses indicated that the slip ductility, the strength and the stiffness of the composite member were all reduced with respect to time. The results of this paper will prove useful in the modelling of the overall composite beam behaviour. Further experiments to validate the models presented herein will be conducted and reported at a later stage.