• Journal of agriculture & life science
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• v.45 no.6
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• pp.279-289
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• 2011

The purpose of this study is to estimate efficiency of item-based agricultural cooperative by using Data Envelopment Analysis. A proposed method employs a bootstrapping approach to generating efficiency estimates through Monte Carlo simulation resampling process. The technical efficiency, pure technical efficiency, and scale efficiency measure of item-based agricultural cooperative is 0.80, 0.87, 0.93 respectively. However the bias-corrected estimates are less than those of DEA. We know that the DEA estimator is an upward biased estimator. In technical efficiency, average lower and upper confidence bounds of 0.726 and 0.8747. According to these results, the DEA bootstrapping model used here provides bias-corrected and confidence intervals for the point estimates, it is more preferable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.451-457
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• 2006

A peer-to-peer(P2P) network is inherently vulnerable to malicious attacks from participating peers because of its open, flat, and autonomous nature. This paper addresses the problem of effectively defending from active attacks of malicious peers at bootstrapping phase and at online phase, respectively. We propose a secure membership handling protocol to protect the assignment of ID related things to a newly joining peer with the aid of a trusted entity in the network. The trusted entities are only consulted when new peers are joining and are otherwise uninvolved in the actions of the P2P networks. For the attacks in online phase, we present a novel message structure applied to each message transmitted on the P2P overlay. It facilitates the detection of message alteration, replay attack and a message with wrong information. Taken together, the proposed techniques deter malicious peers from cheating and encourage good peers to obey the protocol of the network. The techniques assume a basic P2P overlay network model, which is generic enough to encompass a large class of well-known P2P networks, either unstructured or not.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.17 no.2
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• pp.3-17
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• 2007

Receiver access control scheme is proposed to protect multicast distribution tree from DoS(Denial-of Service) attack induced by unauthorized use of IGMP(Internet group management protocol), by extending the security-related functionality of IGMP. Based on a specific network and business model adopted for commercial deployment of IP multicast applications, key management scheme is also presented for bootstrapping the proposed access control as well as accounting and billing for CP(Content Provider), NSP(Network Service Provider), and group members.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.1
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• pp.53-60
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• 2004

This work describes a l0b 150 MSample/s CMOS pipelined A/D converter (ADC) based on advanced bootsuapping techniques for higher input bandwidth than a sampling rate. The proposed ADC adopts a typical multi-step pipelined architecture, employs the merged-capacitor switching technique which improves sampling rate and resolution reducing by $50\%$ the number of unit capacitors used in the multiplying digital-to-analog converter. On-chip current and voltage references for high-speed driving capability of R & C loads and on-chip decimator circuits for high-speed testability are implemented with on-chip decoupling capacitors. The proposed AU is fabricated in a 0.18 um 1P6M CMOS technology. The measured differential and integral nonlinearities are within $-0.56{\~}+0.69$ LSB and $-1.50{\~}+0.68$ LSB, respectively. The prototype ADC shows the signal-to-noise-and-distortion ratio (SNDR) of 52 dB at 150 MSample/s. The active chip area is 2.2 mm2 (= 1.4 mm ${\times}$ 1.6 mm) and the chip consumes 123 mW at 150 MSample/s.

• Environmental and Resource Economics Review
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• v.18 no.1
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• pp.105-138
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• 2009

This study investigates the spatial distribution of the degree of water pollutants in Han River using data obtained by the water pollution observation stations. This study estimates a non -parametric kernel density function for each water pollutants, and tests a significant difference between two estimated distribution functions. Next, Generalized Entropy inequality indices are evaluated and this research tests difference of inequality indices between two years using bootstrapping method. Lastly in a dynamic of view, it is analyzed that there are significant changes in the ranking of water pollution level. Estimation results show that the degree of inequality in spatial distribution of water pollution tends to be stable or decreasing for last 15 years in a great part of water pollutants, and ranking of water pollution level hardly changes in Han River.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.1444-1445
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• 2008

최근 Wireless Local Area Network(WLAN), Wide-band Code Division Multiple Access(WCDMA), CDMA2000, Bluetooth 등 다양한 모바일 통신 시스템에 대한 수요가 증가하고 있다. 이와 같은 모바일 통신 시스템에는 70dB이상의 SFDR(Spurious Free Dynamic Range)을 가진 ADC(Analog-to-Digital Converter)가 사용된다. 본 논문에서는 모바일 통신 시스템을 위한 SFDR 70dBc의 성능을 제공하는 10비트, 100Msps 파이프라인 ADC를 제안한다. 제안한 ADC는 요구되는 해상도 및 속도 사양을 만족시키기 위해 3단 파이프라인 구조를 채택하였으며, 입력단 SHA(Sample and Hold)회로에는 Nyquist 입력에서도 10비트 이상의 정확도로 신호를 샘플링하기 위해 부트스트래핑 기법 기반의 샘플링 스위치를 적용하였다. residue amplifier 회로에는 전력을 줄이기 위해 8배 residue amplifier 대신 3개의 2배 ressidue amplifier를 사용하였다. ADC의 높은 사양을 만족시키기 위해서는 높은 이득을 가지는 op-amp가 필수적이다. 제안한 ADC 는 0.18um CMOS 공정으로 설계되었으며, 100Msps의 동작 속도에서 70dBc 수준의 SFDR과 60dB 수준의 SNDR(Signal to Noise and Distortion Ratio)을 보여준다.

• 한국벤처창업학회:학술대회논문집
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• 2023.11a
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• pp.139-143
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• 2023

최근 교사들의 잇단 극단적 선택으로 학교의 변화와 상황에 대한 문제의식이 사회적으로 날로 높아지고 있다. 교직에 대한 선호도가 급격히 떨어지고 교직 이직 비율도 빠르게 높아지고 있어 교육의 질을 걱정하기에 이르렀다. 드러난 문제가 원인의 하나일 수 있으나 많은 연구에서 교사들의 직무스트레스가 심각한 수준임을 밝히고 있고, 학교교육 현장에는 교사들이 조직에 몰입하기 어려운 다양한 문제들이 있음을 밝히고 있다. 그럼에도 교육현장에서는 학생, 교사들이 함께 성장할 수 있고 모두가 만족하는 교육 활동을 실현시키고 변화와 혁신을 통해 교육역량을 높이고자 지속적으로 노력하고 있다. 본 연구는 초등학교 교사의 직무스트레스와 감정 노동이 조직몰입에 미치는 영향을 조사 분석하고 두 변인 즉 직무스트레스와 감정 노동이 직무몰입에 미치는 영향에서 긍정심리자본의 매개 효과를 알아보는데 그 목적이 있다. 교사 직무스트레스 실태를 종합적으로 파악하고자 관계 요인, 업무요인, 정책 요인으로 나누어 분석(김종민 외, 2018. 경기도교육연구원)하고 특히 스트레스 요인 중 가장 비중 있는 감정 노동 부분은 분리하여 더 상세히 분석하고자 한다. 이를 위해 경기도, 경기도, 서울, 전라남도 소재 초등학교교사 500명을 대상으로 자료를 수집하여 SPSS 20.0 프로그램을 활용하여 변인들의 기술통계치를 산출하고자 한다. 초등교사의 인구통계학적 변인간에 유의한 차이가 있는지 확인하기 위해 t-검정과 일원배치 분산분석(ANOVA)을 실시한다. 그리고 연구에 포함된 변인들간의 상관계수를 산출하고 Baron과 Kenny(1986)의 절차에 따른 3단계 회귀분석과 부트스트래핑(bootstrapping) 기법을 적용하여 매개효과의 유의성을 검증하고자한다.

• Journal of Korea Port Economic Association
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• v.37 no.3
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• pp.75-91
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• 2021

Due to increased competition in supply side to reduce operational costs, port professionals have experienced extreme pressure, which demanded academicians to develop the model for efficient port operations from the industry perspective. Among many ports in the world, U.S. ports are our primary interest to analyze in our study for its high volume of cargoes transacted in the U.S. ports. We primarily employed DEA (Data Envelopment Analysis) technique to research the productivity of U.S. ports and applied the algorithm of double bootstrapped DEA proposed by Simar & Wilson (2007) to further investigate the driving forces of the performance of U.S. port operations. The external variables employed in our study comprise onDock Rail, Channel Depth, Location, Area, Acres, ForeignCargoRatio, and TEUChange, out of which onDock Rail, Acres, ForeignCargoRatio, and TEUChange were significant. In order to evaluate the effects of methodology selection, we conducted the same analysis applying the Censored model (Tobit) and contrasted the outcomes drawn from the two different techniques. Based on the findings from this work we proposed managerial implications and concluded.

• KIISE Transactions on Computing Practices
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• v.21 no.2
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• pp.109-114
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• 2015

This paper presents a computational model on the transfer of airborne fine particles to analyze the similarities and influences among the 25 districts in Seoul by quantifying a time series data collected from each district. The properties of each district are driven with the model of a time series of the fine particle concentrations, and the calculation of edge-based weights are carried out with the transfer entropies between all pairs of the districts. We applied a modularity-based graph clustering technique to detect the communities among the 25 districts. The result indicates the discovered clusters correspond to a high transfer-entropy group among the communities with geographical adjacency or high in-between traffic volumes. We believe that this approach can be further extended to the discovery of significant flows of other indicators causing environmental pollution.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.12 s.354
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• pp.55-64
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• 2006

This work proposes a calibration-free 14b 70MS/s 0.13um CMOS ADC for high-performance integrated systems such as WLAN and high-definition video systems simultaneously requiring high resolution, low power, and small size at high speed. The proposed ADC employs signal insensitive 3-D fully symmetric layout techniques in two MDACs for high matching accuracy without any calibration. A three-stage pipeline architecture minimizes power consumption and chip area at the target resolution and sampling rate. The input SHA with a controlled trans-conductance ratio of two amplifier stages simultaneously achieves high gain and high phase margin with gate-bootstrapped sampling switches for 14b input accuracy at the Nyquist frequency. A back-end sub-ranging flash ADC with open-loop offset cancellation and interpolation achieves 6b accuracy at 70MS/s. Low-noise current and voltage references are employed on chip with optional off-chip reference voltages. The prototype ADC implemented in a 0.13um CMOS is based on a 0.35um minimum channel length for 2.5V applications. The measured DNL and INL are within 0.65LSB and l.80LSB, respectively. The prototype ADC shows maximum SNDR and SFDR of 66dB and 81dB and a power consumption of 235mW at 70MS/s. The active die area is $3.3mm^2$.