• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.107-110
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• 2017

According to researches, while the speed of processor and network in embedded devices is fast enough to meet user requirement, the IO speed is recognized as the main performance bottleneck. Meanwhile it is known that more than 70 percent of IOs are issued from SQLite database. Many researches related SQLite performance optimization is based on WAL mode because WAL mode optimized for write IO performance. In this paper, I propose to optimize SQLite with Atomic Write in the Rollback Journal Mode, which is mainly used in Android and Tizen. I have observed that Atomic Write have a significant write performance improvement(300%) by reducing write, file sync operation and memory usage improvement(80%). Additionally it can block JOJ(Journaling of Journal) and extend the life of the flash memory.

• Journal of KIISE
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• v.42 no.2
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• pp.169-176
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• 2015

The atomic write technique is a good solution to solve the problem of the double write buffer. The atomic write technique needs modified I/O subsystems (i.e., file system and I/O schedulers) and a special SSD that guarantees the atomicity of the write request. In this paper, we propose the writing unit aligned block allocation technique (for EXT4 file system) and the merge prevention of requests technique for the CFQ scheduler. We also propose an atomic write-supporting SSD which stores the atomicity information in the spare area of the flash memory page. We evaluate the performance of the proposed atomic write scheme in MariaDB using the tpcc-mysql and SysBench benchmarks. The experimental results show that the proposed atomic write technique shows a performance improvement of 1.4~1.5 times compared to the double write buffer technique.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.1134-1136
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• 2012

SQLite는 임베디드 환경에 최적화된 경량형 로컬 데이터베이스 시스템으로서, 대부분의 스마트폰을 비롯한 임베디드 시스템과 사용자 애플리케이션에 라이브러리로 사용되고 있다. SQLite는 데이터베이스 시스템의 중요한 특성인 Atomic Write를 보장하기 위하여 롤백 저널(Rollback Journal)과 WAL(Write-Ahead Log)의 두 가지 저널링 알고리즘 가운데 하나를 선택하여 사용한다. 본 연구에서는 이 두 알고리즘의 동작 원리를 분석하고 동작 성능을 측정하여 그 원인을 분석하고 개선 가능성을 보인다.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.543-552
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• 2001

To process transactions in fully replicated database, an atomic broadcast is mainly used. In this case of using atomic broadcast, transactions can be delayed because of the coordinating step among servers before processing the transaction. In this paper, we propose an algorithm to resolve the problem of transaction delay. In the proposed algorithm, the transactions are processed by using the optimistic method. The operations of a transaction are performed in the site that it is submitted and its write operations its updates atomically in all replicated sites. Since the serializability of transaction is ensured by checking the sequence number of transactions in the completion-inspection step.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.11
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• pp.1079-1089
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• 2015

In this paper, we propose a method to evaluate the material properties of high-yield strength materials exceeding 10GPa from spherical indentation. Using a regression equation considering four indentation variables, we map the load displacement relation into a stress-strain relation. To calculate the properties of high-strength materials, we then write a program that produces material properties using the loading / unloading data from the indentation test. The errors in material properties computed by the program are within 0.3, 0.8, and 6.4 for the elastic modulus, yield strength, and hardening coefficient, respectively.

• Journal of The Korean Association For Science Education
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• v.24 no.5
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• pp.902-915
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• 2004

Science drama can be an useful tool for understanding the nature of science, Science-Technology-Society relationship by providing indirect experiences to young students. Specific science concept and knowledge can also be learned with high interests. In this study, to explore the usefulness of science drama in elementary science lessons, two scripts of science drama and lesson plans were developed and implemented. Six step model for science drama lessons was also suggested. One was 'Manhattan Project' which dealt with social, ethical responsibility in using science & technology (science argument drama), and the other was 'Mom, My blood type is O' which explained the heredity of blood type (science concept drama). Two teachers were asked to write their journals during preparation and implementation of science drama lessons, and the lessons were observed by the researcher and video taped for analysis. Some students were interviewed just after the lessons by the teacher and all students were asked to write their impressions, change of their thought, what is leant etc. Overall responses of students and teachers on the two science drama lessons were very positive, 'Mom, My blood type is O' got more positive responses, and girls were more positive than boys. Some students anticipated another science drama even suggest topics for it. 'Mom, My blood type is O' was successful in making students (grade 3) understand the knowledge related with heredity of blood type (71% of the students got perfect answer). In 'Manhattan Project' students (grade 5) perceived more diverse location of responsibility after the lesson, but the danger and harmfulness of atomic power was embossed. This implied the need of more careful planning for the relevant learning activities before and after the play of science drama.Two teachers perceived the science drama as a new, useful tool for some subject which is hard to deal with by other teaching method. They were also satisfied with students' high interest and engagement during the science drama lessons but the extra time and effort for the lessons were pointed out as a main difficulties.