• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.19 no.4
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• pp.443-457
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• 2015

We consider the M/M/c/c queues in which the customers blocked to enter the service facility retry after a random amount of time and some of idle servers can leave the vacation. The vacation time and retrial time are assumed to be of phase type distribution. Approximation formulae for the distribution of the number of customers in service facility and the mean number of customers in orbit are presented. We provide an approximation for M/M/c/c queue with general retrial time and general vacation time by approximating the general distribution with phase type distribution. Some numerical results are presented.

• Journal of Medicine and Life Science
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• v.16 no.3
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• pp.60-63
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• 2019

The rate of suicide is the 5th leading cause of death in Korea. Moreover, suicide is the 1st cause of death in from 2nd to 4th decade. In order to treat suicide attempters who have visited the emergency room and to prevent retries, it is necessary to understand the nature of the suicide and to take the right approach. Suicide is more than doubled in women, and retry rates are high among patients with a history of suicide. Suicidal means are throat, fall, gas poisoning, poisoning and drowning. All suicide attempters should suspect and treat cervical spine injury and airway management, and rapid hyperbaric oxygen therapy is recommended for carbon monoxide addicts. Interviewing a suicide attempter requires a sympathetic attitude and examines the underlying depression or adaptation disorders. Interdisciplinary care with mental health departments is necessary, and interventions in emergency roombased suicide attempt management work can be helpful to connect with the community.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.01a
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• pp.243-246
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• 2015

최근 사물 인터넷(Internet of things) 의 발달에 따라, 스마트 디바이스 간의 네트워크 및 이를 구축할 수 있는 기술에 대한 수요가 급증하고 있다. 이러한 스마트 디바이스 간의 저 전력 저 손실 네트워크(Low power and Lossy network) 환경에서 쓰이는 대표적인 프로토콜로 CoAP(Constrained Application Protocol)가 있으며, 해당 프로토콜은 다양한 네트워크 환경에 유연하게 적용할 수 있도록 패킷 재전송 주기 설정 옵션을 가진다. 하지만 하나의 디바이스에서 네트워크 환경이 패킷 손실 및 지연여부를 구분 할 수 없기 때문에, 네트워크 상태 파악을 위해서는 수신과 응답 양측 디바이스의 패킷 흐름을 확인해야 하는 문제점이 있다. 본 논문에서는 프로토콜의 정보를 기반으로 네트워크 상태를 파악 할 수 있는 새로운 필드 값을 적용하여 CoAP 패킷 재전송 주기를 네트워크 환경의 상태에 따라 동적으로 설정해주는 알고리즘을 제안한다. 제안된 기법은 동적으로 재전송 주기를 설정함으로써, 패킷 손실에 의한 서비스 장애 극복 및 패킷 지연 상황에서의 불필요한 패킷 재전송을 방지하여 에너지 효율성을 향상시키고 서비스 안정성을 보장한다.

• The Journal of the Korea Contents Association
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• v.11 no.11
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• pp.34-41
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• 2011

The MAC of IEEE 802.11 WLAN to control data transmission uses two control methods called DCF and PCF. The DCF uses BEB backoff algorithm based on CSMA/CA. The BEB backoff algorithm shows excellent performance relatively in situation that competition between stations is less, but its performance is decreases as the competition increases. This paper proposes and analyses mathematically an enhanced backoff algorithm. To reduce the collision probability, the proposed algorithm increases the contention window to maximum after collision and decreases the contention window smoothly after successful transmission. To prove efficiency of proposed algorithm, simulations are conducted and analyzed.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.3
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• pp.81-89
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• 2012

This paper presents a set of controlled simulated statical and engineering mechanical experiments accessible via the virtual world environment (VWE) and virtual physics lab S/W. Online courses of the university offering courses and/or programs online are growing and the number of students want education in ways which fit their personal places, e-learning is becoming more important and ubiquitous each year. In this study, first of all, question is rather 'How do we execute the learning effectiveness of e-learning courses?' than 'Why does they need e-learnig or VW-learning?'. In particular, is it possible to effectively teach mechanical engineering courses online? The answer was 'No'. So, there is little research on many of these questions. And another important question is 'Is e-learning cost effective?'. For the answer, This research provided that an instructional design model is used to 'How to think and apply the Newtonian forces' in the virtual physics lab S/W. Collected data from student are administered in the spring semester when students studied 'Introduction to Bio-resources and Systems Engineering'. Results show that a cadre of students can take highly interactively physical properties of mechanical engineering in the virtual laboratory environment. Those show that VWE is greater than that of a similar real world presentation or experimental lab, since most of students are delighted to modify and retry modeling works in the VWE.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1815-1820
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• 2017

In this paper, a study was conducted to estimate the maximum muscle strength which is a standard for selecting exercise intensity in weight training. We designed a device that estimates the muscle fatigue from the EMG signal, expecting to show a correlation between peak muscle strength and fatigue. Curl - Dumbbell was performed using a 4 kg dumbbell and the frequency change of the EMG was observed. At this time, the designed device acquires the signal using the MCU and finally Matlab was used to confirm the change in the center frequency value. The results of 10 subjects were analyzed using SPSS regression analysis. The statistical results showed a correlation of $R^2$ 0.583 and Significant probability of 0.010, and the relation of Y = 8.144-2.097 (slope (MDF)) was obtained. In conclusion, if the wearable device is manufactured in the form of a wearable device and the user can recommend the exercise intensity, the system will be able to retry the more efficient exercise.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.351-360
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• 2022

Autonomous vehicles require precise knowledge of their position, velocity and orientation in all weather and traffic conditions in any time. And, these information is effectively used for path planning, perception, and control that are key factors for safety of vehicle driving. For this purpose, a high precision GNSS technology is widely adopted in autonomous vehicles as a core localization and navigation method. However, due to the lack of infrastructure as well as cost issue regarding GNSS correction data communication, only a few high precision GNSS technology will be available for future commercial autonomous vehicles. Recently, a high precision GNSS sensor that is based on a Broadcast-RTK system to dramatically reduce network maintenance cost by utilizing the existing broadcasting network is released. In this paper, we present the performance test result of the broadcast-RTK-based commercial high precision GNSS receiver to test the feasibility of the system for autonomous driving in Korea. Massive measurement campaigns covering of Korea region were performed, and the obtained measurements were analyzed in terms of ambiguity fixing rate, integer ambiguity loss recovery, time to retry ambiguity fixing, average correction information update rate as well as accuracy in comparison to other high precision systems.

• International Journal of Advanced Culture Technology
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• v.12 no.2
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• pp.299-308
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• 2024

This study aims to explore improvement measures for the linkage system between the police and social welfare agencies in responding to domestic violence and child abuse issues in South Korea by comparing and analyzing the current systems in South Korea, the United States, and the United Kingdom. Despite the legal and institutional foundations for victim protection and perpetrator correction in each country, the effectiveness of actual cooperation faces several limitations. In South Korea, the level of cooperation is insufficient due to the lack of information sharing, role conflicts, and ambiguity of cooperation procedures. The United States and the United Kingdom operate more systematic cooperation programs, showing notable achievements in mental health crisis intervention and domestic violence response. To improve the linkage system in South Korea, this study proposes the following measures: (1) developing a clear cooperation protocol, (2) conducting regular education and training programs, (3) establishing an integrated information system, and (4) strengthening the victim-centered approach. Implementing these measures will contribute to more effective responses to domestic violence and child abuse issues, ultimately leading to a healthier and safer society by reducing social costs through victim protection and perpetrator correction.

• Journal of Chest Surgery
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• v.50 no.6
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• pp.443-447
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• 2017

Background: The inferior vena cava filter (IVCF) is very effective for preventing pulmonary embolism in patients who cannot undergo anticoagulation therapy. However, if a filter is placed in the body permanently, it may lead to other complications. Methods: A retrospective study was performed of 159 patients who underwent retrievable Cook Celect IVCF implantation between January 2007 and April 2015 at a single center. Baseline characteristics, indications, and complications caused by the filter were investigated. Results: The most common underlying disease of patients receiving the filter was cancer (24.3%). Venous thrombolysis or thrombectomy was the most common indication for IVCF insertion in this study (47.2%). The most common complication was inferior vena cava penetration, the risk of which increased the longer the filter remained in the body (p=0.032, Exp(B)=1.004). Conclusion: If the patient is able to retry anticoagulation therapy and the filter is no longer needed, the filter should be removed, even if a long time has elapsed since implantation. If the filter cannot be removed, it is recommended that follow-up computed tomography be performed regularly to monitor the progress of venous thromboembolisms as well as any filter-related complications.

• The Journal of the Korea Contents Association
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• v.20 no.7
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• pp.149-160
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• 2020

The purpose of this study is to analyze factors affecting a grade maintenance of the non-graded group by LTCI(Long-Term Care Insurance, NHIS). The predictors were examined grade maintenance of the non-graded group(non-grade of A, B, C). The results were as follows: this study found that predisposing factors of the grade maintenance of non-graded of LTCI were significantly related to age, sex, death. Enabling factors of the grade maintenance of non-graded of LTCI were significantly related to household state, income level. Need factors of the grade maintenance of non-graded of LTCI were significantly related to dementia, grade of first grading, retry of applying for long-term care assessment. Based on the finding of study, implications and future research directions were discussed for policy considerations.