• 응용통계연구
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• 제22권4호
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• pp.723-733
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• 2009

K-평균 군집분석이 가지는 두 가지 근본적인 어려움은 사전에 미리 군집 수를 정해야 하는 문제와 초기 군집중심에 따라 결과가 달라질 수 있는 문제이다. 본 연구에서는 이러한 문제를 해결하기 위한 자동화 K-평균 군집분석 절차를 제안하고, R을 이용하여 구현한 결과를 제공한다. 자동화 K-평균 군집분석에서 제안된 절차는 처음 단계로서 계층적 군집분석을 행한 후 이를 이용하여 군집 수와 초기 군집수를 자동으로 정하고, 다음 단계로 이 결과를 이용하여 K-평균 군집분석을 수행하는 방법을 택하였다. 처음 단계에서 이용된 계층적 군집분석 방법으로는 Ward의 군집분석을 한 후에 Mojena의 규칙을 이용하여 군집 수를 정하는 방법을 택하거나, 모형근거 군집분석방법을 수행한 후에 BIC 값을 이용하여 군집 수를 정하는 방법을 이용하였다. 제안된 자동화 K-평균 군집절차에는 대량자료의 분석에도 용이하게 이용될 수 있도록 반복된 표본추출 방법을 이용하여 군집 수 및 군집 중심을 구하는 절차를 포함하였다. 구현된 R 프로그램은 www.knou.ac.kr/ sskim/autokmeans.r에서 제공하고 있다.

• Journal of Biosystems Engineering
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• 제27권5호
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• pp.433-450
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• 2002

The daily food intake for dairy cows has to be effectively controlled to breed a sound group of cows as well as to enhance the productivity of the cows. But, feed stuffs are fed in the common bulk for a group of cows in most cases despite that the individual food intake has to be varied. To obtain the feed for each cow, both the nutrient requirements and the nutrient composition of fred have to be provided in advance, which are based on the status of cows such as weigh marginal weight amount of milk, fat concentration in milk, growth and milking stages, and rough feed ratio, etc. Then, the mixed ration fur diet would be computed by the nutrient requirements constraints. However, when TMR (Total Mixed Ration) is conventionally supplied for a group of cows, it is almost impossible to get an optimal feed mixed ration meeting the nutrient requirements of each individual cow since the constraints are usually conflicting and over-constrained although they are linear. Hence, addressed in this paper is a simulated annealing (SA) technique to find the food intake for dairy cows, considering the characteristics of individual or grouped cows. Appropriate parameters fur the successful working of SA are determined through preliminary experiments. The parameters include initial temperature, epoch length. cooling scheduling, and stopping criteria. In addition, a neighborhood solution generation method for the effective improvement of solutions is presented. Experimental results show that the final solution for the mixture of feed fits the rough feed ratio and some other nutrient requirements such as rough fiber, acid detergent fiber, and neutral detergent fiber, with 100 percent, while fulfilling net energy for lactating, metabolic energy, total digestible nutrients, crude protein, and undegraded intake protein within average five percent.

• 한국전자파학회논문지
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• 제14권8호
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• pp.816-822
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• 2003

본 논문에서는 전력이 제한된 환경에서 사용이 고려되고 있는 터보 TCM(Turbo Trellis Coded Modulation)에 대하여 낮은 복잡도를 갖는 효율적인 반복복호 제어기법을 제안한다. 터보 부호의 복호 과정에서 반복 복호수를 증가하면 성능이 향상되지만 어느 정도의 반복 복호수 이상에서는 성능 향상이 거의 나타나지 않는다. 따라서 복호 계산량과 복호지연을 감소시킬 수 있도록 반복 복호과정을 효율적으로 정지시킬 수 있는 반복복호 제어가 필요하다. 본 논문은 복호지연 및 반복복호 첫수를 줄일 수 있는 효율적인 알고리즘을 제시한다. 제안 기법은 터보 TCM 복호화 과정에서 궤환되는 외부부가정보의 특성에 따른 임계치를 이용하여 반복 복호수를 가변적으로 제어하는 기법이다. 성능 분석 결과 제안구조는 복호과정의 계산량과 지연을 성능 저하 없이 효율적으로 감소시킬 수 있음을 보여준다.

• 의학교육논단
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• 제10권2호
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• pp.25-44
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• 2008

Objectives: Through using of the strong research method like a Randomized Controlled Trial: RCT, we have to heighten quality of Medical Education study. I'd like to introduce "CONSORT", which stands for Consolidated Standards of Reporting Trials. Contents: Preventive Service Task Force(200l) in USA proposed Levels of evidence for enlarging evidence-based Practice: EBP. And the CONSORT was introduced, which encompasses various initiatives developed by the CONSORT Group to alleviate the problems arising from inadequate reporting of randomized controlled trials (RCTs). the CONSORT has 13 guides like these: 1. How participants were allocated to interventions 2. Scientific background and explanation of rationale 3. Eligibility criteria for participants. The settings and locations where the data were collected. 4. Precise details of the interventions intended for each group and how and when they were actually administered 5. Specific objectives and hypotheses 6. Clearly defined primary and secondary outcome measures, When applicable. any methods to enhance the quality of measurements (e.g., multiple observations, training of assessors) 7. How sample size was determined. When applicable, explanation of any interim analyses and stopping rules 8. Method used to generate the random allocation sequence, Details of any restriction [of randomization] 9. Method used to implement the random allocation sequence 10. Who generated the allocation sequence, who enrolled participants. and who assigned participants to their groups 11. Whether or not participants, those administering the interventions, and those assessing the outcomes were blinded to group assignment. If done, how the success of blinding was evaluated 12. Statistical methods used to compare groups for primary outcome(s), Methods for additional analyses, such as subgroup analyses and adjusted analyses 13. Flow of participants through each stage (a diagram is strongly recommended) Specifically, for each group report the numbers of participants randomly assigned. receiving intended treatment, completing the study protocol. and analyzed for the primary outcome. Results and Conclusion: Randomized Controlled Trial: RCT guided of CONSORT will contribute to do stronger evidence-based medical studies.

• Journal of Audiology & Otology
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• 제25권4호
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• pp.199-208
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• 2021

Background and Objectives: No known studies have investigated the influence of stimulus polarity on the Auditory Brainstem Response (ABR) elicited from level-specific (LS) chirp. This study is important as it provides a better understanding of the stimulus polarity selection for ABR elicited from LS chirp stimulus. We explored the influence of stimulus polarity on the ABR from LS chirp compared to the ABR from click at 80 dBnHL in normal-hearing adults. Subjects and Methods: Nineteen adults with normal hearing participated. The ABRs were acquired using click and LS chirp stimuli using three stimulus polarities (rarefaction, condensation, and alternating) at 80 dBnHL. The ABRs were tested only on the right ear at a stimulus rate of 33.33 Hz. The ABR test was stopped when the recording reached the residual noise level of 0.04 μV. The ABRs amplitudes, absolute latencies, inter-peak latencies (IPLs), and the recorded number of averages were statistically compared among ABRs at different stimulus polarities and stimuli combinations. Results: Rarefaction polarity had the largest ABR amplitudes and SNRs compared with other stimulus polarities in both stimuli. There were marginal differences in the absolute latencies and IPLs among stimulus polarities. No significant difference in the number of averages required to reach the stopping criteria was found. Conclusions: Stimulus polarities have a significant influence on the ABR to LS chirp. Rarefaction polarity is recommended for clinical use because of its larger ABR peak I, III, and V amplitudes than those of the other stimulus polarities.

• 대한청각학회지
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• 제25권4호
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• pp.199-208
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• 2021

Background and Objectives: No known studies have investigated the influence of stimulus polarity on the Auditory Brainstem Response (ABR) elicited from level-specific (LS) chirp. This study is important as it provides a better understanding of the stimulus polarity selection for ABR elicited from LS chirp stimulus. We explored the influence of stimulus polarity on the ABR from LS chirp compared to the ABR from click at 80 dBnHL in normal-hearing adults. Subjects and Methods: Nineteen adults with normal hearing participated. The ABRs were acquired using click and LS chirp stimuli using three stimulus polarities (rarefaction, condensation, and alternating) at 80 dBnHL. The ABRs were tested only on the right ear at a stimulus rate of 33.33 Hz. The ABR test was stopped when the recording reached the residual noise level of 0.04 μV. The ABRs amplitudes, absolute latencies, inter-peak latencies (IPLs), and the recorded number of averages were statistically compared among ABRs at different stimulus polarities and stimuli combinations. Results: Rarefaction polarity had the largest ABR amplitudes and SNRs compared with other stimulus polarities in both stimuli. There were marginal differences in the absolute latencies and IPLs among stimulus polarities. No significant difference in the number of averages required to reach the stopping criteria was found. Conclusions: Stimulus polarities have a significant influence on the ABR to LS chirp. Rarefaction polarity is recommended for clinical use because of its larger ABR peak I, III, and V amplitudes than those of the other stimulus polarities.

• 대한교통학회:학술대회논문집
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• 대한교통학회 1995년도 제27회 학술발표회
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• pp.3-32
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• 1995

The Highway Capacity Manual specifies procedures for evaluating intersection performance in terms of delay per vehicle. What is lacking in the current methodology is a comparable quantitative procedure for ass~ssing the safety-based level of service provided to motorists. The objective of the research described herein was to develop a computational procedure for evaluating the safety-based level of service of signalized intersections based on the relative hazard of alternative intersection designs and signal timing plans. Conflict opportunity models were developed for those crossing, diverging, and stopping maneuvers which are associated with left-turn and rear-end accidents. Safety¬based level-of-service criteria were then developed based on the distribution of conflict opportunities computed from the developed models. A case study evaluation of the level of service analysis methodology revealed that the developed safety-based criteria were not as sensitive to changes in prevailing traffic, roadway, and signal timing conditions as the traditional delay-based measure. However, the methodology did permit a quantitative assessment of the trade-off between delay reduction and safety improvement. The Highway Capacity Manual (HCM) specifies procedures for evaluating intersection performance in terms of a wide variety of prevailing conditions such as traffic composition, intersection geometry, traffic volumes, and signal timing (1). At the present time, however, performance is only measured in terms of delay per vehicle. This is a parameter which is widely accepted as a meaningful and useful indicator of the efficiency with which an intersection is serving traffic needs. What is lacking in the current methodology is a comparable quantitative procedure for assessing the safety-based level of service provided to motorists. For example, it is well¬known that the change from permissive to protected left-turn phasing can reduce left-turn accident frequency. However, the HCM only permits a quantitative assessment of the impact of this alternative phasing arrangement on vehicle delay. It is left to the engineer or planner to subjectively judge the level of safety benefits, and to evaluate the trade-off between the efficiency and safety consequences of the alternative phasing plans. Numerous examples of other geometric design and signal timing improvements could also be given. At present, the principal methods available to the practitioner for evaluating the relative safety at signalized intersections are: a) the application of engineering judgement, b) accident analyses, and c) traffic conflicts analysis. Reliance on engineering judgement has obvious limitations, especially when placed in the context of the elaborate HCM procedures for calculating delay. Accident analyses generally require some type of before-after comparison, either for the case study intersection or for a large set of similar intersections. In e.ither situation, there are problems associated with compensating for regression-to-the-mean phenomena (2), as well as obtaining an adequate sample size. Research has also pointed to potential bias caused by the way in which exposure to accidents is measured (3, 4). Because of the problems associated with traditional accident analyses, some have promoted the use of tqe traffic conflicts technique (5). However, this procedure also has shortcomings in that it.requires extensive field data collection and trained observers to identify the different types of conflicts occurring in the field. The objective of the research described herein was to develop a computational procedure for evaluating the safety-based level of service of signalized intersections that would be compatible and consistent with that presently found in the HCM for evaluating efficiency-based level of service as measured by delay per vehicle (6). The intent was not to develop a new set of accident prediction models, but to design a methodology to quantitatively predict the relative hazard of alternative intersection designs and signal timing plans.

• 대한교통학회지
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• 제23권4호
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• pp.7-16
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• 2005

항공기 운항에서 이륙과 착륙단계는 가장 어려우며 많은 사고가 발생되는 위험한 과정이다. 이륙단계에서 발생될 수 있는 비상상황 가운데 가장 심각한 것은 이륙단념이다. 이륙단념 관련 사고의 대부분은 활주로 이탈사고로 연결되었는데 이와 관련하여 미국 NTSB는 사고발생의 주원인을 이륙이나 정지를 결심하는 시간지연으로 분석하였다. 본 연구는 이와 같은 이륙단념속도(시간)에 대한 조종사들의 인지도와 적합성을 검토하였는데, 먼저 현장에서 항공기를 운용하는 조종사를 대상으로 한 이륙단념 설문을 통하여 이와 관련된 인지여부를 비롯한 기초자료를 측정하였고, 그 후 무작위로 선정된 조종사를 대상으로 모의비행장치(Simulator)를 이용하여 이륙단념 상황을 부여하고 이에 따른 반응시간을 측정하여 현재 적용하는 기준과 비교하였다. 설문 결과, 일부 조종사들은 비행규정에 적용된 이륙단념의 기준과 현행 절차를 불만족스럽게 생각하고 있었다. 모의비행장치의 측정결과, 현장조종사의 이륙단념시간이 항공기 비행규정보다 1.5 초 더 소요되는 것으로 나타났으며 결국 현행 규정에 의한 Y1 속도에서 이륙단념을 하는 경우, 활주로 이탈로 이어질 가능성이 높은 것으로 분석되었다. 따라서 이륙단념 사고를 줄이기 위해서는 관련 규정에 대한 지속적인 교육이 필요하며, 실제로 안전한 이륙단념을 위하여 $V_1$ 속도를 6노트 줄여서 사용하여야 이륙단념에 대한 안전성이 확보될 것이다.

• 대한교통학회지
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• 제21권5호
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• pp.97-110
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• 2003

교차로 시거는 안전하게 교차로를 운영하기 위하여 필요한 기본적인 요소 중의 하나임에도 불구하고 외국선진국에 비하여 우리나라에서는 아직까지 이에 대한 체계적인 연구경험이 부족한 실정이다. 즉 미국을 위시한 세계 여러 나라에서는 이미 많은 노력을 들여 자신들의 고유한 운전자 특성 및 행태, 차량의 운행특성, 기타 환경조건의 영향 등을 고려한 교차로 시거 기준을 마련하여 사용하고 있으나 이와는 대조적으로 우리나라의 경우는 미국의 설계기준을 거의 여과 없이 준용하여 사용하고 있다. 본 연구에서는 이러한 국내외 연구여건을 감안하여 최근 미국과 유럽 선진국에서 유용성이 널리 알려져 있는 AASHTO(2001) 시거모형을 활용하여 우리나라 도시지역의 비신호 교차로에 적합한 교차로 시거를 산정하여 보고자 한다. 이 시거모형은 안전제동거리(Safe Stopping Distance)를 바탕으로 발전된 기존의 시거모형과는 달리 운전행태에 따른 임계간격(Critical Gap)을 이용하여 개발된 모형으로서 교차로 주변에서 발생하는 상황을 손쉽게 모형에 포함시킬 수 있을 뿐만 아니라 운전자의 안전에 관한 행태적 측면까지 고려할 수 있도록 개선된 것이다. 연구의 결과에 의하면 국내와 미국의 도로설계에 적용되고 있는 운전행태별 시거기준과 비교하여 본 연구에서 산정한 시거가 전반적으로 작은 값으로 추정되고 있어 현재 우리 나라 교차로의 설계에 적용되는 기준치들이 매우 보수(안전)적인 경향이 있음을 발견하였다.

• 대한인간공학회지
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• 제34권1호
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• pp.45-62
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• 2015

Objective: The purpose of this study is to investigate the effect of personality type on human performance tool compliance in nuclear power plants (NPPs) and to propose general recommendations for an enhancement of its practical utilization. Background: Various guidelines, regulating criteria, and recommendations have been developed to prevent human errors in NPPs. Despite these efforts, the accidents sometimes caused by human errors have steadily occurred, and therefore, various human performance tools have been adopted as countermeasures against human errors. The major and inevitable contributing factors among the many hazards to human errors might be the trait and personality, which are considered to be the inner world of humans. Thus, we try to investigate the utilization of human performance tools by considering the different types of operating crew personalities, and we suggested more practical recommendations to prevent human errors according to the personality. Method: We developed the Questionnaire using the Big 6 (HEXACO) models, which are human performance tools for workers in NPPs, and individual (condition) variables to investigate the effect of personality types on human performance tools. We slightly modified them to help the survey respondents understand them better. A survey was conducted for ordinary people over the age of 20. SPSS 22.0 was used to perform a correlation analysis and a hierarchical regression analysis to find the relationship between personality types and human performance tools. Results: The utilization of human performance tools shows significant differences statistically by personality. The correlation result reveals that the types of Honesty (H), Extraversion (X), Conscientiousness (C), and Openness to experience (O) show a higher utilization of human performance tools. In hierarchical regression results, human performance tools of task preview, questioning attitude, stopping when unsure, self-checking, effective communication, and place-keeping show a higher utilization with personality types. However, the Agreeableness (A) type did not show significant differences statistically with human performance tools. Conclusion: We tried to investigate the utilization of human performance tools by considering the different types of human personality and provide more practical recommendations to prevent human errors according to the personality. These results will be able to prevent human errors owing to the characteristics (advantages and disadvantages) of personality types. Application: This information can be utilized as guidelines for proactive recommendations according to the workers' personalities for more practical human performance tools to prevent human errors in an NPP.