• KDI Journal of Economic Policy
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• v.12 no.4
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• pp.113-126
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• 1990

With the introduction of the national pension, efficient integration of Korea's four public pension schemes has been discussed. The main point of such discussions is whether to have a progressive scheme or an income-proportional one. Under the assumption of a perfect labor market, it has been proved in the income tax literature that the regressive tax scheme with the 0 % tax rate to the most able person (person earning highest income) is pareto efficient, if there is an incentive problem in the labor supply. In this paper, a life-cycle model with a linear benefit schedule, when there is uncertainty about future earning ability, is studied. It is proved that the second best pension scheme is that having a progressive benefit schedule. This result implies that integration into a progressive pension scheme, like the current national pension, is required not only for efficiency but also for equity.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.2
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• pp.200-208
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• 2003

This paper proposes a separation and feature extraction of image signals using the independent component analysis(ICA) based on neural networks of efficient learning rule. The proposed learning rule is a hybrid fixed-point(FP) algorithm based on secant method and momentum. Secant method is applied to improve the performance by simplifying the 1st-order derivative computation for optimizing the objective function, which is to minimize the mutual informations of the independent components. The momentum is applied for high-speed convergence by restraining the oscillation in the process of converging to the optimal solution. The proposed algorithm has been applied to the composite images generated by random mixing matrix from the 10 images of $512\times512$-pixel. The simulation results show that the proposed algorithm has better performances of the separation speed and rate than those using the FP algorithm based on Newton and secant method. The proposed algorithm has been also applied to extract the features using a 3 set of 10,000 image patches from the 10 fingerprints of $256\times256$-pixel and the front and the rear paper money of $480\times225$-pixel, respectively, The simulation results show that the proposed algorithm has also better extraction speed than those using the another methods. Especially, the 160 basis vectors(features) of $16\times16$-pixel show the local features which have the characteristics of spatial frequency and oriented edges in the images.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.12A
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• pp.2000-2011
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• 2001

In this Paper, we convert conventional low speed(1x, 6x) DVD systems designed by analog PLL(Phase Locked Loop) into digital PLL to operate at high speed systems flexibly, and present optimal DPLL model in high speed(20x) DVD systems. Especially, we focused on the design of DPLL that can overcome channel effects such as bulk delay, sampling clock frequency offset and asymmetry phenomenon in high speed DVD systems. First, the modified Early-Late timing error detector as digital timing recovery scheme is proposed. And the four-sampled compensation algorithm using zero crossing point as asymmetry compensator is designed to achieve high speed operation and strong reliability. We show that the proposed timing recovery algorithm provides enhanced performances in jitter valiance and SNR margin by 4 times and 3dB respectively. Also, the new four-sampled zero crossing asymmetry compensation algorithm provides 34% improvement of jitter performance, 50% reduction of compensation time and 2.0dB gain of SNR compared with other algorithms. Finally, the proposed systems combined with asymmetry compensator and DPLL are shown to provide improved performance of about 0.4dB, 2dB over the existing schemes by BER evaluation.

• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.14-21
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• 2011

A unit modular system is a construction method which installs on site by manufacturing 50%~90% of the whole process in the factory. This method can minimize the process in the site and maximize the operation, which will reduce the duration and improve the overall quality. The recent paradigm of construction is to be sustainable building. Modular system can be regarded as a sustainable building construction method because it can reduce the amount of construction waste by recycling partial or whole part of overdue building be torn down. A unit modular system is the answer to cope with the increasing market of small size housings. A unit modular system is the most appropriate option at this point. This research proposes the standard operation and construction process of modular system, which enable to optimal system. A case study of reconstructing small-size housing was introduced to support this proposal. Finished unit modular is the reasonable way. However, 80% of complication rate of the modular is the most rational when a defect occurrence during delivery is considered.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.5
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• pp.95-103
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• 2009

An efficient symbol time synchronization scheme for IEEE 802.11n MIMO-OFDM based WLAN systems using cyclic shift diversity (CSD) preamble is proposed. CSD is used to prevent unintentional beamforming when the same preamble signal is transmitted through transmit antennas. However, it is difficult to find a proper starting-point of the OFDM symbol with the conventional algorithms because of time offset by multi-peaks which are result from cross-correlation of received CSD preamble with a known short training symbol. In addition, the performance of symbol time sync. is affected by AGC and packet detection position. In this paper, an optimal symbol time synch. algorithm which is composed of the boundary detection scheme between LTS and OFDM symbols, the verification scheme for enhancement of boundary detection accuracy, and the SNR-varying threshold estimation scheme is proposed. Simulation result show that the proposed algorithm has performance gains of 4.3dB in SNR compared to the conventional algorithms at the rate of 1% sync. failure probability for $2{\times}2$ MIMO-OFDM system and 18dB at 0.1% when maximum frequency offset exists. It also can be applied to $4{\times}4$ MIMO-OFDM system without any modification. Hence, it is very suitable for MIMO-OFDM WLAN systems using CSD preamble.

• Journal of Environmental Health Sciences
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• v.31 no.5 s.86
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• pp.398-403
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• 2005

This study is undertaken to find the optimal method to make the decision on the degree of water pollution by comparison of K-WQI, KOE-WQI that is made for index with the water quality index and water quality environment standard of the Frame Act on Environment Policy as the result of survey for water quality reality on the major point of the Yeongsan river from 2002 to 2004. The water quality of major rivers has some differences depending on seasons. however, under the water quality standard by the $BOD_5$ density, most of rivers displayed the water quality level of $II{\sim}III$ grading, and on K-WQI that is classified by indexing for 10 categories of pH, DO, $BOD_5,\;COD,\;SS,\;T-N,\;NH_3-N,\;NO_{3^-}$ N, T-P, and E-Coli and classified into 5 groups from 100 points to 40 points, they displayed the score distribution of the first grade in water quality for $85{\sim}100$ points to the second grade in water quality for $70{\sim}84$ points. On KOE-WQI that is classified by indexing for 5 categories of pH, DO, $BOD_5$, COD and T-coli and classified into 5 groups from 90 points or above for outstanding and 29 points or below for very bad, and the water quality distribution is made ranged from the first grade in water quality for 90 points or more to the third grade in water quality for $69{\sim}50$ points. In addition, for the contribution of the water quality decline, the Environmental standard has significant dependency on the $BOD_5$ density, with K-WQI contributing in various water quality decline depending on the environment around the river area of $BOD_5,\;T-N,\;NH_3-N,\;NO_3-N,\;T-P$, and E-Coli, and KOE-WQI acting os the factor contributing to lower the water quality decline by $BOD_5$, COD, and T-coli. As such, the current water quality environment standard has high dependency on $BOD_5$ and KOE-WQI excludes some nitrogen and phosphorus that considers the river environment that the grade in water quality is set by some category, and K-WQI reflected well of the ecology environment of rivers with the diversity of the assessment factor as well as to have the low dependency of specific factor to be objective.

• Korean journal of food and cookery science
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• v.29 no.3
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• pp.291-300
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• 2013

This study was conducted to develop the optimum mixing rates of a functional instant pumpkin gruel including pumpkin powder and to have the high preference to all age groups. The produced of this study were to optimum the composite recipe by making instant pumpkin gruel, respectively, with the different 16 experimental point with 3 replicates of the weight of pumpkin powder ($X_1$), roasted soybean flour ($X_2$) and gelatinized rice flour ($X_3$), and by quantities of the using response surface methodology(RSM). The color, pH, viscosity, and sensory characteristics(appearance, color, flavor, taste, viscosity, overall acceptability) were dependent parameters. The color of instant pumpkin gruel L value decreased with increasing amounts of pumpkin powder and a value and b value increased. pH and viscosity increased with increasing amounts of pumpkin powder and roasted soybean powder. The optimal mixing percentage of pumpkin powder, roasted soybean flour and gelatinized rice flour were 5.25 g, 3.00 g and 4.50 g for overall quality of 5.72 g, 4.30 g and 3.00 g for maximum score of overall organoleptic quality, respectively.

• Journal of Korean Society of Transportation
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• v.22 no.7 s.78
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• pp.99-106
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• 2004

This paper presents some comparisons between Cournot-Nash and Stackelberg game in bi-level program, composed of both upper level program and lower level one. The upper level can be formulated to optimize a specific objective function, while the lower formulated to express travelers' behavior patterns corresponding to the design parameter of upper level problem. This kind of hi-level program is to determine a design parameter, which leads the road network to an optimal state. Bi-level program includes traffic signal control, traffic information provision, congestion charge and new transportation mode introduction as well as road expansion. From the view point of game theory, many existing algorithms for bi-level program such as IOA (Iterative Optimization Assignment) or IEA (Iterative Estimation Assignment) belong to Cournot-Nash game. But sensitivity-based algorithms belongs to Stackelberg one because they consider the reaction of the lower level program. These two game models would be compared by using an example network and show some results that there is no superiority between the models in deterministic case, but in stochastic case Stackelberg approach is better than that of Cournot-Nash one as we expect.

• KDI Journal of Economic Policy
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• v.26 no.2
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• pp.63-104
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• 2004

Economists have long been involved in various studies, theoretical and empirical, on the economic gains from innovative activities and as their outcome, intellectual properties. In Korea, however, research in this field has experienced rather slow progress, partly due to the lack of data availability and the awareness of its importance. This study attempts to measure the economic impact of patents on market value of firms from a microeconomic point of view. Analyses are performed to examine the ex-ante market valuation of patent acquisition activities by investigating the effect of patent acquisitions on daily stock prices as well as on annual market values. The study on the effect of a disclosure of granted patents on daily stock prices reveals that the economic value of a firm's patent acquisition is fairly high. The study on listed firms also reveals that a firm's patent registration stock has a positive and statistically significant effect on its year-end market value. Therefore, it can be concluded that the analysis performed in this study supports the validity of Korea's current patent system. The result, however, does not guarantee the optimality of current system. Studies on various aspects of intellectual property should follow to shape the system into a socially optimal one.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.13
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• pp.5289-5296
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• 2015

Background: Despite the decreased incidence, gastric cancer is still a frequent cause of cancer related death. The 1st line 2 or 3 drugs regimen is still a debatable issue. HER2 targeted therapy has emerged as the standard of care, but it is unavailable in the Brazilian Public Health System. The end-point of this trial was overall survival (OS) in patients with metastatic gastric cancer treated in a public university hospital in Brazil. The secondary end-points were efficacy and safety of regimens with 2 (F+P) or 3 (EOX) drugs to develop an institutional guideline to facilitate optimal treatments. Materials and Methods: In this retrospective study, 1st line regimens were evaluated for OS and PFS stratified by age and ECOG using Cox regression. Results: 47 patients were treated over the last 3 years. In 1st line, 29 were treated with F+P (mean 59.3 years, 34.5% ECOG 2 and a mean of 5.69 cycles) and 16 with EOX (mean 47 years, 18.8% ECOG 2 and a mean of 5.44 cycles). The median OS was 13.8 months (95%CI 10.7-16.9). Response was evaluated in 40 cases and was 64.3% for EOX and 37.5% for F+P (p=0.25). The median PFS was 9.5 months for EOX and 5.6 months for F+P (HR 0.85, 95%CI 0.41-1.74). However, among patients with ECOG 2 mPFS was 3.70 vs 5.40 months, respectively (p=0.86). Regimens showed similar manageable adverse events. A total of 34 patients suffered progression and 14 received $2^{nd}$ line therapy. Diffuse histology (HR 1.89, 95%CI 1.22-2.88), achieving 2nd line (HR: 0.25, 95%CI 0.11-0.58) and treatment response (HR 0.23, 95%CI 0.12-0.47) were OS prognostic factors. Conclusions: Patients treated in our hospital had outcomes compatible with the literature. The regimen choice should be related to patient features. Second line treatment should be considered.