• KDI Journal of Economic Policy
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• v.13 no.1
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• pp.115-134
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• 1991

The role of pension plans in the macroeconomy has been a subject of much interest for some years. It has come to be recognized that pension plans may alter basic macroeconomic behavior patterns. The net effects on both savings and labor supply are thus matters for speculation. The aim of the present paper is to provide quantitative results which may be helpful in attaching orders of magnitude to some of the possible effects. We are not concerned with the providing empirical evidence relating to actual behavior, but rather with deriving the macroeconomic implications for a alternative possibilities. The pension plan interacts with the economy and the population in a number of ways. Demographic variables may thus affect both the economic burden of a national pension plan and the ability of the economy to sustain the burden. The tax transfer process associated with the pension plan may have implications for national patterns of saving and consumption. The existence of a pension plan may have implications also for the size of the labor force, inasmuch as labor force participation rates may be affected. Changes in technology and the associated changes in average productivity levels bear directly on the size of the national income, and hence on the pension contribution base. The vehicle for the analysis is a hypothetical but broadly realistic simulation model of an economic- demographic system into which is inserted a national pension plan. All income, expenditure, and related aggregates are in real terms. The economy is basically neoclassical; full employment is assumed, output is generated by a Cobb-Douglas production process, and factors receive their marginal products. The model was designed for use in computer simulation experiments. The simulation results suggest a number of general conclusions. These may be summarized as follows; - The introduction of a national pension plan (funded system) tends to increase the rate of economic growth until cost exceeds revenue. - A scheme with full wage indexing is more expensive than one in which pensions are merely price indexed. - The rate of technical progress is not a critical element in determining the economic burden of the pension scheme. - Raising the rate of benefits affects its economic burden, and raising the age of eligibility may decrease the burden substantially. - The level of fertility is an element in determining the long-run burden. A sustained low fertility rate increases the proportion of the aged in total population and increases the burden of the pension plan. High fertility has inverse effects.

• The Korean Journal of Financial Management
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• v.25 no.1
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• pp.1-22
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• 2008

This study is to evaluate, to the extent to, which advanced currency futures and emerging currency futures markets can predict accurately the future spot rate. To this end, Johansen's the maximum-likelihood cointegration method(1988, 1991) is adopted to test the unbiasedness and efficiency hypothesis. Also, this study is to estimate and compare a quantitative measure of relative efficiency as a ratio of the forecast error variance from the best-fitting quasi-error correction model to the forecast error variance of the futures price as predictor of the spot price in advanced currency futures with in emerging currency futures market. Advanced currency futures is British pound and Japan yen. Emerging currency futures includes Korea won, Mexico peso, and Brazil real. The empirical results are summarized as follows : First, the unbiasedness hypothesis is not rejected for Korea won and Japan yen futures exchange rates. This indicates that the emerging currency Korea won and the advanced currency Japan yen futures exchange rates are likely to predict accurately realized spot exchange rate at a maturity date without the trader having to pay a risk premium for the privilege of trading the contract. Second, in emerging currency futures markets, the unbiasedness hypothesis is not rejected for Korea won futures market apart from Mexico peso and Brazil real futures markets. This indicates that in emerging currency futures markets, Korea won futures market is more efficient than Mexico peso and Brazil real futures markets and is likely to predict accurately realized spot exchange rate at a maturity date without risk premium. Third, this findings show that the results of unbiasedness hypothesis tests can provide conflicting finding. according to currency futures class and forecasts horizon period, Fourth, from the best-fitting quasi-error correction model with forecast horizons of 14 days, the findings suggest the Japan yen futures market is 27.06% efficient, the British pound futures market is 26.87% efficient, the Korea won futures market is 20.77% efficient, the Mexico peso futures market is 11.55%, and the Brazil real futures market is 4.45% efficient in the usual order. This indicates that the Korea won-dollar futures market is more efficient than Mexico peso, and Brazil real futures market. It is therefore possible to concludes that the Korea won-dollar currency futures market has relatively high efficiency comparing with Mexico peso and Brazil real futures markets of emerging currency futures markets.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.61-73
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• 2014

This study reviewed an application of water quality estimation using an Airborne Hyperspectral Imagery (A-HSI) and tested a part of Han River water quality (especially suspended solid) estimation with available in-situ data. The estimation of water quality was processed two methods. One is using observation data as downwelling radiance to water surface and as scattering and reflectance into water body. Other is linear regression analysis with water quality in-situ measurement and upwelling data as at-sensor radiance (or reflectance). Both methods drive meaningful results of RS estimation. However it has more effects on the auxiliary dataset as water quality in-situ measurement and water body scattering measurement. The test processed a part of Han River located Paldang-dam downstream. We applied linear regression analysis with AISA eagle hyperspectral sensor data and water quality measurement in-situ data. The result of linear regression for a meaningful band combination shows $-24.847+0.013L_{560}$ as 560 nm in radiance (L) with 0.985 R-square. To comparison with Multispectral Imagery (MSI) case, we make simulated Landsat TM by spectral resampling. The regression using MSI shows -55.932 + 33.881 (TM1/TM3) as radiance with 0.968 R-square. Suspended Solid (SS) concentration was about 3.75 mg/l at in-situ data and estimated SS concentration by A-HIS was about 3.65 mg/l, and about 5.85mg/l with MSI with same location. It shows overestimation trends case of estimating using MSI. In order to upgrade value for practical use and to estimate more precisely, it needs that minimizing sun glint effect into whole image, constructing elaborate flight plan considering solar altitude angle, and making good pre-processing and calibration system. We found some limitations and restrictions such as precise atmospheric correction, sample count of water quality measurement, retrieve spectral bands into A-HSI, adequate linear regression model selection, and quantitative calibration/validation method through the literature review and test adopted general methods.

• The korean journal of orthodontics
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• v.25 no.5 s.52
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• pp.525-541
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• 1995

This study was designed to investigate force systems and tooth movements produced by retraction archwire during retraction of four maxillary incisors after the maxillary canine retraction into the maxillary first premolar extraction space using the computer-aided three-dimensional finite element method. A three-dimensional finite element model, consisting of 2248 elements and 3194 nodes, was constructed. The model consisted of maxillary teeth and surrounding periodontal membranes, .022'$\times$.028'-slot brackets, and 5 types of retraction archwires(.019'$\times$.025' stainless steel archwire) modeled using the beam elements. The contact between the wire and the bracket slot was modeled using the gap elements because of the non-linear elastic behaviors of the contact between them. The forces and moments, End displacements produced by retraction archwire were measured at various conditions to investigate the difference according to types of loops, magnitudes of activation force, gable angle, and anterior lingual root torque. The results were expressed quantitative and visual ways in the three-dimensional method. The following conclusions can be drawn from this study.1. When the tear-drop loop archwire was activated, the mesio-distal and lingual translational movements of the teeth helped to close the extraction space, but unwanted movements of the teeth including intrusions and extrusions, and rotational movements in each direction occurred. 2. Activation of T-loop archwire compared with those of other types of retraction archwires produced the least translational movements of the teeth helped to space closure and also the least unwanted movements of the teeth. 3. Increasing amount of activation in the tear-drop archwire led not only to increase of translational movements of the teeth helped to space closure, but also to increase of unwanted movements of the teeth. 4. Addition of gable bend in the tear-drop archwire helped anterior teeth to translational movements in the mesio-distal direction, but increased unwanted movements of the teeth 5. Addition of anterior lingual root torque in the tear-drop archwire helped central and lateral incisor to improve their facio-lingual inclination, but increased unwanted movements of the teeth.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.13 no.4
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• pp.197-209
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• 2018

Recently, many start-up failures occur as the number of attempts to start a business increases in a social atmosphere that encourages start-up. In particular, young entrepreneurs have a lower survival rate than general entrepreneurs because young entrepreneurs are challenging just with a simple idea to overcome the difficulties of employment while lacking prior knowledge and experience of business. Therefore, the reason for the failure of start-up is lack of preparation for start-up and lack of entrepreneurship. The purpose of this study is to develop a measurement tool to build a basic framework for entrepreneurship development and start - up preparation activities for young people. To develop an entrepreneurship measurement tool, researchers developed a preliminary question through qualitative research methods such as literature research, focus group interview, and expert verification. After that, researchers surveyed 102 entrepreneurs using quantitative research method and to verify the construct validity of the measurement tool, the final entrepreneurship measurement tool was completed through exploratory factor analysis and confirmatory factor analysis. The entrepreneurship measurement tool developed through this research process consists of 7 components and 15 measurement items. First, in the step of 'confirming entrepreneurial intention', two items of 'self-analytic competence', three items of 'ability of establishing start-up philosophy'are contained. Second, in the step of 'drawing up a start-up model', two items are contained in each category such as, 'ability of eliciting entrepreneurial idea,' 'ability of analyzing idea validity,' 'competence of planning a venture start-up model'. Third, in the step of 'planning the venture start-up,' two items are contained in each category such as, 'business-plan presentation competency,' 'ability of implementing organizational system.'. The measurement tool of entrepreneurship is meaningful as it could help young entrepreneur find out their lacking competence in preparing their start-ups and strengthen necessary competences by measuring their own entrepreneurship. Rather in the entrepreneurship education, basic data that can diagnose the entrepreneurship of young entrepreneurs is provided.

• The Korean Journal of Nuclear Medicine
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• v.30 no.4
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• pp.484-492
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• 1996

To detect ischemic tissue in experimental model of cerebral ischemia made by middle cerebral artery(MCA)-occlusion, we acquired triple image of $^{99m}Tc$-glucarate, [$^{18}F$]fluoro-deoxyglucose (FDG), and 2,3,5- triphenyltetrazolium (TTC) staining. We made cerebral infarction either with reperfusion (after occlusion of 2 hours) or without reperfusion in 10 Sprague-Dawley rats by inserting thread to MCA through internal carotid artery. After 22 hours, we injected 740 MBq of $^{99m}Tc$-glucarate and 55.5 MBq of [$^{18}F$]FDG through tail vein. Each 1 mm slice of rat brains was frozen and exposed to imaging plate for 20 minutes in freezer to get an [$^{18}F$]FDG image. After 20 hours enough to fade radioactivity of [$^{18}F$]FDG, the slices were again imaged by BAS1500 for $^{99m}Tc$-glucarate uptake. Finally, these brain tissues were stained with TTC. Semi-quantitative visual analysis was done by grading 0 to 3 points according to the degree of uptakes($^{99m}Tc$-glucarate) and decreased uptakes([$^{18}F$]FDG and TTC). Ten rats survived with neurologic symptoms. TTC staining confirmed the development of infarction. The size of the infarction was relatively larger in the group without reperfusion. [$^{18}F$]FDG images were similar to TTC-stained images. However, we found regions with intermediate uptake which were not stained with TTC. We found regions with intermediate [$^{18}F$]FDG uptake where TTC staining was normal. $^{99m}Tc$-glucarate uptake was round only in TTC non-stained region. In the TTC stained regions, there were no uptake of $^{99m}Tc$-glucarate. We could not find clear relation between $^{99m}Tc$-glucarate uptake with [$^{18}F$]FDG uptake. This was partly because percent uptake of $^{99m}Tc$-glucarate was so small (less than 1 percent of injected dose) and because there were quite heterogeneity of patterns of [$^{18}F$]FDG uptake and TTC. With these findings, we could conclude that $^{99m}Tc$-glucarate were taken up only in part of ischemic tissues which were proven to be nonviable. The establishment of MCA-occluded rat model with or without reperfusion and triple imaging for $^{99m}Tc,\;^{18}F$ and TTC helped the characterization of $^{99m}Tc$-glucarate uptakes. Further work is needed to clarify the meaning or diversities or [$^{18}F$]FDG and TTC and their relation with $^{99m}Tc$-glucarate.

• Korean Journal of Ecology and Environment
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• v.39 no.2 s.116
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• pp.198-208
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• 2006

This research was to apply a multi-metric approach, so called the Index of Biological Integrity (IBI) as a tool for biological evaluations of water environments, to a wadable stream. For the study, we surveyed 5 sampling locations in Kap Stream during August 2004 ${\sim}$ September 2005. We also compared the biological data with long-term water quality data, obtained from the Ministry of Environment, Korea and physical habitat conditions based on the Quantitative Habitat Evaluation Index (QHEI). We used ten metric systems for the IBI model to evaluate biological stream health. Overall IBI values in Kap Stream averaged 24 (range: 20${\sim}$30, n=5), indicating a "fair ${\sim}$ poor" conditions according to the modified criteria of Karr (1981) and US EPA(1993). Exclusive of 4th survey, average IBI values at the upstream reach (S1 ${\sim}$ S3)and downstream reach (S4 ${\sim}$ S5) were 20 and 24, respectively. However, in 4th survey the averages were 21 and 20 in the upstream and downstream reaches, respectively. This difference was larger in the upstream than in the downstream because of physical condition disturbed during summer monsoon. Values of the QHEI varied from 75(fair condition) to 148 (good condition) and values of QHEI in the S3 were significantly (P=0.001, n=5) lower than other sites. Biochemical oxygen demand (BOD), chemical oxygen demand (COD), total nitrogen (TN) and total phosphorus (TP) were greater by 3 ${\sim}$ 8 fold in the downstream than in the upstream reach. We believe that present IBI approach applied in this study may be used as a key tool to set up specific goals for restoration of Kap Stream.

• Geophysics and Geophysical Exploration
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• v.1 no.2
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• pp.127-135
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• 1998

The Born approximation is widely used for solving the complex scattering problems in electromagnetics. Approximating total internal electric field by the background field is reasonable for small material contrasts as long as scatterer is not too large and the frequency is not too high. However in many geophysical applications, moderate and high conductivity contrasts cause both real and imaginary part of internal electric field to differ greatly from background. In the extended Born approximation, which can improve the accuracy of Born approximation dramatically, the total electric field in the integral over the scattering volume is approximated by the background electric field projected to a depolarization tensor. The finite difference and elements methods are usually used in EM scattering problems with a 2D model and a 3D source, due to their capability for simulating complex subsurface conductivity distributions. The price paid for a 3D source is that many wavenumber domain solutions and their inverse Fourier transform must be computed. In these differential equation methods, all the area including homogeneous region should be discretized, which increases the number of nodes and matrix size. Therefore, the differential equation methods need a lot of computing time and large memory. In this study, EM modeling program for a 2D model and a 3D source is developed, which is based on the extended Born approximation. The solution is very fast and stable. Using the program, crosshole EM responses with a vertical magnetic dipole source are obtained and the results are compared with those of 3D integral equation solutions. The agreement between the integral equation solution and extended Born approximation is remarkable within the entire frequency range, but degrades with the increase of conductivity contrast between anomalous body and background medium. The extended Born approximation is accurate in the case conductivity contrast is lower than 1:10. Therefore, the location and conductivity of the anomalous body can be estimated effectively by the extended Born approximation although the quantitative estimate of conductivity is difficult for the case conductivity contrast is too high.

• Progress in Medical Physics
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• v.15 no.4
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• pp.202-209
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• 2004

Flat panel based digital radiography (DR) systems have recently become useful and important in the field of diagnostic radiology. For DRs with amorphous silicon photosensors, CsI(TI) is normally used as the scintillator, which produces visible light corresponding to the absorbed radiation energy. The visible light photons are converted into electric signal in the amorphous silicon photodiodes which constitute a two dimensional array. In order to produce good quality images, detailed behaviors of DR detectors to radiation must be studied. The relationship between air exposure and the DR outputs has been investigated in many studies. But this relationship was investigated under the condition of the fixed tube voltage. In this study, we investigated the relationship between the DR outputs and X-ray in terms of the absorbed energy in the detector rather than the air exposure using SPEC-l8, an X-ray energy spectrum model. Measured exposure was compared with calculated exposure for obtaining the inherent filtration that is a important input variable of SPEC-l8. The absorbed energy in the detector was calculated using algorithm of calculating the absorbed energy in the material and pixel values of real images under various conditions was obtained. The characteristic curve was obtained using the relationship of two parameter and the results were verified using phantoms made of water and aluminum. The pixel values of the phantom image were estimated and compared with the characteristic curve under various conditions. It was found that the relationship between the DR outputs and the absorbed energy in the detector was almost linear. In a experiment using the phantoms, the estimated pixel values agreed with the characteristic curve, although the effect of scattered photons introduced some errors. However, effect of a scattered X-ray must be studied because it was not included in the calculation algorithm. The result of this study can provide useful information about a pre-processing of digital radiography.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.208-220
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• 2016

Automatic Mountain Meteorology Observation System (AMOS) is an important ingredient for several climatological and forest disaster prediction studies. In this study, we select the optimal sites for AMOS in the mountain areas of Honam and Jeju in order to prevent forest disasters such as forest fires and landslides. So, this study used spatial dataset such as national forest map, forest roads, hiking trails and 30m DEM(Digital Elevation Model) as well as forest risk map(forest fire and landslide), national AWS information to extract optimal site selection of AMOS. Technical methods for optimal site selection of the AMOS was the firstly used multifractal model, IDW interpolation, spatial redundancy for 2.5km AWS buffering analysis, and 200m buffering analysis by using ArcGIS. Secondly, optimal sites selected by spatial analysis were estimated site accessibility, observatory environment of solar power and wireless communication through field survey. The threshold score for the final selection of the sites have to be higher than 70 points in the field assessment. In the result, a total of 159 polygons in national forest map were extracted by the spatial analysis and a total of 64 secondary candidate sites were selected for the ridge and the top of the area using Google Earth. Finally, a total of 26 optimal sites were selected by quantitative assessment based on field survey. Our selection criteria will serve for the establishment of the AMOS network for the best observations of weather conditions in the national forests. The effective observation network may enhance the mountain weather observations, which leads to accurate prediction of forest disasters.