• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.1-10
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• 2018

This study proposes an immersive interaction optimized for the user's experience environment to provide an improved presence for both HMD and Non-HMD users in the asymmetric virtual reality (VR) environment. The core of the proposed immersive interaction is to distinguish the differences of the asymmetric environment between the HMD and Non-HMD users and present the optimized interaction to the user. And, in order to increase the presence by providing improved immersion in the asymmetric virtual reality environment given to each user, we design the walking interaction to improve the immersion of space for the HMD users, a hand-based interface that improves immersion by fully understanding and managing the situation through direct control. Finally, through the experiment using questionnaire, it is verified that the immersive interaction provides all users with an enhanced presence and specialized experience in each environment experience. Through these processes, we confirmed that the Non-HMD user can be immersed in an asymmetric virtual reality using by proposed interaction as participant rather than assistant with HMD user.

• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.49-59
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• 2018

Simulator sickness is one of the important side effect of virtual reality. Simulator sickness is influenced by various factors, and field of view (FOV) is one of them. The FOV is a viewing angle limited by the screen, and when the FOV is reduced, the simulator sickness is reduced, and the presence is lowered. Previous study developed a Dynamic FOV Restrictor (Center-fixed FOV Restrictor) to reduce simulator sickness while maintaining presence. It is a method that limits the FOV dynamically by reflecting the speed and angular velocity of the avatar. We also developed Eye-tracking Based Dynamic FOV Restrictor (Eye-tracking FOV Restrictor) by adding head rotations and eye movements. This study attempts to compare the simulator sickness and the presence of the No FOV Restrictor condition, the Center-fixed FOV Restrictor condition, and the Eye-tracking FOV Restrictor condition. The results showed that the simulator sickness of the Center-fixed FOV Restrictor condition is significantly lower than other two conditions. The results also showed that there were no significant differences in presence in three conditions. The interpretations and limitations of this study are discussed in this paper.

• Journal of the Korea Computer Graphics Society
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• v.24 no.3
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• pp.33-41
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• 2018

We present a secondary camera optimization method that helps the user exploring 3D virtual environment to precisely observe possible collisions between objects. The first role of our secondary camera is to automatically detect the area with the greatest possible collision. The second role is to show the detected area from a new angle of view that the current main camera cannot show. However, as the shapes of target objects are complex, the shape of the empty space between objects is also complex and narrow. It means that the space for the secondary camera position is highly constrained and its optimization can be very difficult. To avoid this difficulty and increase the efficiency of the optimization, we first compute a bisector surface between two target objects. Then, we limit the domain of the secondary camera's position on the bisector surface in the optimization process. To verify the utility of our method, we built a demonstration program in which the user can explore in a 3D virtual world and interact with objects by using a hand motion recognition device and conducted a user study.

• Journal of Broadcast Engineering
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• v.23 no.4
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• pp.559-573
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• 2018

Recently, one of the most actively applied image media in the most fields such as virtual reality (VR) is omni-directional or panorama image. This image is generated by stitching images obtained by various methods. In this process, it takes the most time to extract keypoints necessary for stitching. In this paper, we analyze the parameters involved in the extraction of SIFT keypoints with the aim of reducing the computation time for extracting the most widely used SIFT keypoints. The parameters considered in this paper are the initial standard deviation of the Gaussian kernel used for Gaussian filtering, the number of gaussian difference image sets for extracting local extrema, and the number of octaves. As the SIFT algorithm, the Lowe scheme, the originally proposed one, and the Hess scheme which is a convolution cascade scheme, are considered. First, the effect of each parameter value on the computation time is analyzed, and the effect of each parameter on the stitching performance is analyzed by performing actual stitching experiments. Finally, based on the results of the two analyses, we extract parameter value set that minimize computation time without degrading.

• KDI Journal of Economic Policy
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• v.27 no.1
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• pp.81-122
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• 2005

The paper aims to establish the characteristics of the Korean firms' R&D investment and to estimate the private rate of return to R&D investment. For the empirical analysis, a balanced panel data is constructed with 695 firms on 8 year observations. The panel data enables to characterize R&D investment of the Korean firms, which is mostly conformed to the 'stylized facts' of R&D investment that found in the previous studies on foreign firms. Klette model was used to estimate the private rate of return on R&D investment and depreciation rate of R&D capital. The paper estimates that the rate of return on R&D investment is 10.5% on average or 16.4% on median for the whole industry whereas manufacturing firms show 10.4% on average or 16.4% on median. The depreciation rate was estimated about 32.9% for whole industry, where it ranges from the minimum 11.6% for metal industry and 49.5% for services. The median estimate of the rate of return for R&D investment of Korean firms is roughly two times higher than real interest rates for the same period, which implies that R&D investment allows sizable rent in addition to the opportunity cost of capital investment.

• KDI Journal of Economic Policy
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• v.27 no.1
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• pp.1-38
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• 2005

Our paper aims to estimate a household consumption function in the presence of liquidity constraints as well as household characteristics. Empirical findings from a Korean cross-sectional data (National Survey of Household Income and Expenditure) reveal that several family characteristics, such as household size, number of working members, children in school, and educational level and age of the household head, turn out to be critical determinants of household consumption. Especially, the influence of household size on consumption decision is shown to be highly significant, not only indirectly through its impact on household income, but also directly by affecting the household's preference for consumption itself. While, the other family characteristics primarily influences household income. Our paper distinguishes itself from existing literature in that it greatly improves the explanatory power of the estimated household consumption function by measuring the degree of the liquidity constraint rather than simply identifying its presence. Based on the assumption that the present value of human capital is a function of household characteristics, the degree of the liquidity constraint is represented by the underestimated portion of the human capital. Such a method of implementing the liquidity constraint is useful in treating various types of assets according to their liquidity. Finally, our estimated household consumption function is applied to decompose cross-sectional variances of consumption inequality. The analysis confirms that the overall alleviation in liquidity constraints in Korea after the 1997 currency crisis reduced consumption inequality despite the worsening of income inequality and changes in the demographic composition of family characteristics during the same period.

• KDI Journal of Economic Policy
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• v.27 no.1
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• pp.185-209
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• 2005

This study examines ERPT with asymmetric response and both import and export market shares, using wool trade data. The study found that, asymmetric response may be as common as symmetric response. In addition, the responses (both in price and quantity demanded) to the changes in exchange rate are considerably different across goods, and even for the homogenous goods, across countries. In case of depreciation, the export price changes more than appreciation case in general, and as a result the destination price changes less. It is also found that the cases of excessive or perverse pass-through are found more frequently than reported by previous studies. This finding points out that strategic behavior of firms or unexpected response to exchange rate fluctuation takes place more frequently than we commonly expect or take, in particular at disaggregated levels. When the model considers asymmetric responses of the export price to appreciation and depreciation (of exporter's currency), the estimation provided that for 39 trade cases out of 83, export price responded to appreciation and depreciation in different fashions, although the normal response was the dominating phenomenon with 99 cases or about 60% out of 166 cases. Market shares affected the extent and direction of responses in select cases. These findings will have important implications for policy makers and traders.

• Journal of the Korea Organic Resources Recycling Association
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• v.26 no.2
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• pp.75-84
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• 2018

In this study, the analysis of torrefaction products was carried out for fueling of sewage sludge. The mixed samples were composed as follows : 50% of sewage sludge and 50% of rice husk and CR(Coffee Residue). In this experiment, the reaction time(30min, 60min) and temperature($200^{\circ}C$, $250^{\circ}C$, $300^{\circ}C$) were expressed as a single variable using SF(Severity Factor). As a result, it was confirmed that as the SF increased, the heating value and fuel ratio increased, but the CI(Combustibility Index) decreased. The heating value was similarly increased as CR(Coffee Residue) and SF increased. The fuel ratio range of mixed samples was equal to that of lignite(0.5~1.0) in case of SF lower than 6.19 and that of bituminous coal(1.0~1.8) in case of SF higher than 7.36 or above. The CI showed a stable range(3,000~5,500kcal/kg) in low SF as the content of mixed samples contained more rice husk than CR.

• Journal of Korean Foot and Ankle Society
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• v.22 no.2
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• pp.68-73
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• 2018

Purpose: This study compared the clinical outcomes of open repair, percutaneous repair, and minimal incision repair by Achillon in ruptured Achilles tendon. Materials and Methods: The outcomes of 12 patients with open repair (group 1), 8 patients with percutaneous repair (group 2), and 10 patients with minimal incision repair by Achillon (group 3) from February 2013 to March 2016 were analyzed retrospectively. The postoperative clinical evaluations were done by the American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot score, Arner-Linholm scale, mid-calf circumference difference, one-leg heel raise difference, visual analogue scale (VAS) for postoperative scarring, time to return to work, and complications. Results: No significant difference in the AOFAS ankle-hindfoot score, Arner-Linholm scale, and time to return to work was observed among three groups (p=0.968, 0.509, and 0.585). The mean differences in the mid-calf circumference in groups 1, 2, and 3 were 1.09, 0.73, and 0.58, respectively; groups 2 and 3 were significantly higher than group 1 (p=0.002). In addition, the mean VAS scores for postoperative scarring in groups 1, 2, and 3 were 7.0, 9.1, and 9.1, respectively; groups 2 and 3 were significantly higher than group 1 (p=0.001). The mean differences in one-leg heel raising in groups 1, 2, and 3 were 2.03, 1.91, and 1.33, respectively; group 3 was significantly higher than groups 1 and 2 (p=0.010). The complications encountered were one case of deep infection in group 1 and one case of sural nerve hypoesthesia in group 2. Conclusion: Minimal incision repair by Achillon is recommended as an effective surgical treatment for Achilles tendon rupture because it minimizes the risk of complications, leads to an improved tendon strength and healing, and achieves cosmetic satisfaction.

• KDI Journal of Economic Policy
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• v.28 no.2
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• pp.131-177
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• 2006

This paper examines a simultaneous determination of corporate control mechanisms, and its effects on firm performance. The corporate control mechanisms considered include the following; insider shareholding, institutional shareholding, the board of directors, dividend policy, and capital structure. This paper applies a simultaneous equation methodology and investigates the interdependence among the corporate control mechanisms. In the first part, the paper finds that firm-level variations of control mechanisms are large across time although average variations are relatively small. These variations are related to one another, which is confirmed by Granger causality test based on dynamic panel autoregression model. More specifically insider shareholding, institutional shareholding and outside director ratio cause each other. With regard to interdependence among the control mechanisms, 2SLS(two stage least squares) regression results show that insider shareholding and institutional shareholding are substitutes while institutional shareholding acts as complements to the ratio of outside members in the board of directors. Then in the second part, the paper examines the relationship between firm performance and corporate governance. Firm performance, measured by Tobin's Q, has a positive association with leverage ratio while that has a negative relation to outside director ratio. This suggests that there may be a room for reforming corporate governance in Korea. Specifically it is necessary to enhance the independence of the outside directors.