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KVM 기반 가상화 환경에서 CPU 스케줄링 관점으로 본 Network I/O 성능간섭 현상 분석
강동화(Donghwa Kang),이경운(Kyungwoon Lee),박현찬(Hyunchan Park),유혁(Chuck Yoo) 한국정보과학회 2016 정보과학회 컴퓨팅의 실제 논문지 Vol.22 No.9
가상화 기술은 한정된 물리자원을 추상화하여 다수의 가상 자원 형태로 사용자에게 제공하는 기술로써 자원 활용률을 높이고 유동적으로 서비스를 제공할 수 있다는 장점이 있다. 하지만 한정된 물리자원을 다수의 가상머신이 공유하는 가상화 기술의 특성상, 자원 공유로 인한 성능 간섭 현상이 발생하는 문제가 있다. 이는 호스트 운영체제의 CPU 스케줄러가 가상머신에서 실행중인 프로세스의 특성을 고려하지 않고 스케줄링 하기 때문이다. 이러한 문제를 해결하기 위해 다양한 연구들이 진행되었지만 실제 근본적인 성능 간섭의 원인 분석에 대해서는 다루고 있지 않다. 본 논문에서는 KVM 기반 가상화 환경에서 가상머신의 성능 간섭의 원인을 분석하기 위해 다양한 시나리오에서의 프로파일링을 수행하고, 그 결과를 분석하여 CPU 스케줄링 관점에서 성능 간섭 현상의 원인과 그 해결 방안을 제시한다. Server virtualization provides abstraction of physical resources to users and thus accomplishes high resource utilization and flexibility. However, the characteristics of server virtualization, such as the limited number of physical resources shared by virtual machines, can cause problems, mainly performance interference. The performance interference is caused by the fact that the CPU scheduler running on the host operating system schedules virtual machines without considering the characteristics of the virtual machine’s internal process. To address performance interference, a number of research activities to improve performance interference have been conducted, but do not deal with the fundamental analysis of performance interference. In this paper, in order to analyze the cause of performance interference, we carry out profiling in a variety of scenarios in a virtualized environment based on KVM. As a result, we analyze the phenomenon of the performance interference in terms of CPU scheduling and propose an efficient scheduling solution.
Development of the Korean Developmental Screening Test for Infants and Children (K-DST)
Chung, Hee Jung,Yang, Donghwa,Kim, Gun-Ha,Kim, Sung Koo,Kim, Seoung Woo,Kim, Young Key,Kim, Young Ah,Kim, Joon Sik,Kim, Jin Kyung,Kim, Cheongtag,Sung, In-Kyung,Shin, Son Moon,Oh, Kyung Ja,Yoo, Hee-Jeo The Korean Pediatric Society 2020 Clinical and Experimental Pediatrics (CEP) Vol.63 No.11
Background: Most developmental screening tools in Korea are adopted from foreign tests. To ensure efficient screening of infants and children in Korea, a nationwide screening tool with high reliability and validity is needed. Purpose: This study aimed to independently develop, standardize, and validate the Korean Developmental Screening Test for Infants and Children (K-DST) for screening infants and children for neurodevelopmental disorders in Korea. Methods: The standardization and validation conducted in 2012-2014 of 3,284 subjects (4-71 months of age) resulted in the first edition of the K-DST. The restandardization and revalidation performed in 2015-2016 of 3.06 million attendees of the National Health Screening Program for Infants and Children resulted in the revised K-DST. We analyzed inter-item consistency and test-retest reliability for the reliability analysis. Regarding the validation of K-DST, we examined the construct validity, sensitivity and specificity, receiver operating characteristic curve analysis, and a criterion-related validity analysis. Results: We ultimately selected 8 questions in 6 developmental domains. For most age groups and each domain, internal consistency was 0.73-0.93 and test-retest reliability was 0.77-0.88. The revised K-DST had high discriminatory ability with a sensitivity of 0.833 and specificity of 0.979. The test supported construct validity by distinguishing between normal and neurodevelopmentally delayed groups. The language and cognition domain of the revised K-DST was highly correlated with the K-Bayley Scales of Infant Development-II's Mental Age Quotient (r=0.766, 0.739), while the gross and fine motor domains were highly correlated with Motor Age Quotient (r=0.695, 0.668), respectively. The Verbal Intelligence Quotient of Korean Wechsler Preschool and Primary Scales of Intelligence was highly correlated with the K-DST cognition and language domains (r=0.701, 0.770), as was the performance intelligence quotient with the fine motor domain (r=0.700). Conclusion: The K-DST is reliable and valid, suggesting its good potential as an effective screening tool for infants and children with neurodevelopmental disorders in Korea.
Kihoon Jeon,Sanghwa Chung,Donghwa Yoo 한국정보과학회 2020 Journal of Computing Science and Engineering Vol.14 No.2
Owing to the development of the Internet of Things (IoT) paradigm, the energy consumption of devices and the reliability of communication have become important issues. Enhanced TSCH technology introduces a technique to select high-quality channels by using energy detection in the TSCH protocol to improve the reliability of communication in a dynamic environment where interference changes. However, it is difficult to apply ETSCH technology to a multi-hop network because the node that performs energy detection consumes more energy than the node that does not. In this article, we propose an adaptive channel-quality estimation (ACE), which flexibly adjusts the duty cycle of energy detection according to whether interference dynamically changes or not. ACEs are generally applicable regardless of the degree of change of interference, which improves energy efficiency. Also, we present ACE-blacklisting based TSCH (ACEBTSCH) that uses ACE and local channel blacklisting to blacklist the wireless channel based on energy detection in a multi-hop network. Experimental results show that ACEB-TSCH has a performance improvement of 15.94% over TSCH and 8.59% over PDR-blacklisting based TSCH.
전기화학적 금속 3D 프린터의 적층 조건 연구를 통한 마이크로 코일 제작
김영국(Young-Kuk Kim),강동화(Donghwa Kang),김성빈(Sung-Bin Kim),유봉영(Bongyoung Yoo) 한국표면공학회 2020 한국표면공학회지 Vol.53 No.4
In this study, we produced a coil of micro-pattern that can be used for electromagnetic wave absorber, heating material, wireless charging, sensor, antenna, etc. by using electrochemical additive manufacturing method. Currently, it contains research contents for manufacturing a micro pattern coil having practicality through control of process control variables such as applied voltage, distance between electrode, and nozzle injection. Circulation of the electrolyte through the nozzle injection control can significantly contribute to improving the surface characteristics of the coil because of minimizing voltage fluctuations that may occur during the additive manufacturing process. In addition, by applying the pulse method in the application of voltage, the lamination characteristics of the plated body were improved, which showed that the formation of a fine line width plays an important role in the production of a micro pattern coil. By applying the pulse signal to the voltage application, the additive manufacturing characteristics of the produced product were improved, and it was shown that the formation of a fine line width plays an important role in the production of a micro pattern coil.