• Journal of IKEEE
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• v.23 no.1
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• pp.80-90
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• 2019

Even though Non-Volatile Memory (NVM) is used for data storage, a page table should be built to access data in it. And this observation leads us to the Persistent Page Table (PPT) scheme that keeps the page table in NVM persistently. By the way, processors have different page table structures and really operational page table cannot be built without virtual and physical addresses of NVM. However, those addresses are determined dynamically when NVM storage is attached to the system. Thus, the PPT should have system-independent and also address-independent structure and really working system-dependent page table should be built from the PPT. Moreover, entries of PPT should be updated atomically and, in this paper, we describe the design of PPT that meets those requirements. And we investigate how file systems can decrease the journaling overhead with the swap operation, which is a new operation created by the PPT. We modified the Ext4 file system in Linux and experiments conducted with Filebench workloads show that the swap operation enhances file system performance up to 60%.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06a
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• pp.319-320
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• 2008

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.16-18
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• 2002

인터넷의 급속한 발달과 네트워크의 고속화로 인해 통신 기술이 발전하고 새로운 제품과 통신 장비들이 개발되고 있다. 또한 최근에 장비의 특성에 따라 최적화 되어있는 공개운영체제인 리눅스를 탑재한 임베디드 시스템의 개발이 가속화 되고 있다. 임베디드 시스템은 장비의 기능을 제어하고 활용할 수 있는 임베디드 운영체제를 포팅하고 있다. 이에 따라 본 논문에서는 네트워크 기능을 이용하고 제어하기 위해 임베디드 리눅스인 uCliunx를네트워크 장비에 포팅하고 포팅된 운영체제를 기반으로 라우터의 기능을 수행하도록 하기 위한 시스템 및 응용프로그램의 설계 및 구현에 관하여 논하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.11a
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• pp.6-7
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• 2012

낸드 플래시 메모리는 저장장치로서 널리 사용되는 소자이다. 플래시 메모리 기반의 저장장치 시스템에서 파일 시스템의 저널링 기능을 사용할 때, 플래시 메모리의 특징을 고려해주는 것이 필요하다. 본 연구에서는 플래시 메모리 기반의 저장장치 시스템에서 파일 시스템의 저널링 연산이 미치는 영향에 대해서 분석해 보고, 오버헤드가 될 만한 부분을 찾아본다. 이러한 오버헤드가 될 만한 부분을 찾아서 제거해줌으로써 플래시 메모리의 사용성을 증대시킬 수 있다.

• Korean Journal of Adult Nursing
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• v.27 no.1
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• pp.73-82
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• 2015

Purpose: This study examined the effects of peer assisted learning (PAL) using video recordings in standardized patients (SP) simulation. Methods: A mixed-method approach was adopted, in which quantitative data were supplemented with qualitative data. Research participants consisted of 49 nursing students, 24 of whom were assigned to the experimental group, and 25 to the control group. The 12 item instrument was used to measure perioperative care knowledge, while performance confidence was assessed with the 10 item questionnaire, and clinical critical thinking skills with the Clinical Critical Thinking Skill Test (CCTS). Qualitative data were collected using a reflective journaling and in-depth interviews. Results: Participants in the experimental group exhibited significantly higher levels of knowledge than those in the control group (t=5.43, p<.001), and were significantly more confident in their performances (F=52.33, p<.001). However, no significant differences were found between the experimental and the control groups with regard to CCTS (t=0.72, p=.477). A qualitative content analysis was conducted using the interview and reflective journaling data, in which six major themes were elicited from three codes. Conclusion: PAL employing video recordings is expected to be utilized as a teaching and learning strategy in simulation-based nursing practicum with greater frequency and longer period, given the positive effects observed in this study.

• Journal of KIISE
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• v.44 no.4
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• pp.363-373
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• 2017

Ext4 file system is widely used in various computing environments such as those of the PC, the server, and the Linux-based embedded system. Ext4, which uses a buffer for block I/O, provides fsync() system call to applications to guarantee the consistency of a specific file. A log of the analytical studies regarding the operation of Ext4 and the improvement of its performance has been compiled, but it has not been studied in detail in terms of kernel versions. We figure out that the behavior of fsync() system call is different depending on the kernel version. Between the kernel versions of 3.4.0 and 4.7.2, 3.4.0, 3.8.0, and 4.6.2 showed behavioral differences regarding the fsync() system call. The latency of fsync() in kernel 3.4.0 is longer than that of the more-advanced 3.7.10; meanwhile, the characteristics of 3.8.0 enabled the disruption of the Ext4 journaling order, but the ordered defect was solved with 4.6.2.

• The KIPS Transactions:PartA
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• v.14A no.1 s.105
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• pp.39-46
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• 2007

Recently flash memory is widely accepted as a storage devise of embedded systems for portability and performance reasons. Flash memory has many distinguishing features compared to legacy magnetic disks. Especially, a file system for flash memory usually assumes the form of log-structured file system and it employs garbage collector accordingly. Since the garbage collector can greatly affect the performance of file system, it should be designed carefully considering flash memory features. In this paper, we suggest a new garbage collector for existing JFFS2 (Journaling Flash File System II) file system. By extensive performance evaluation, we show that the proposed garbage collector achieves improved performance in terms of flash memory consumption rate, increased flash memory life time, and improved wear-leveling.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.367-374
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• 2001

Recently, LINUX cluster file systems based on the storage area network (SAN) have been developed. In those systems, without using a central file server, multiple clients sharing the whole disk storage through Fibre Channel can freely access disk storage and act as file servers. Accordingly, they can offer advantages such as availability, load balancing, and scalability. In this paper, we describe metadata management schemes designed for a new SAN-based LINUX cluster file system. First, we present a new inode structure which is better than previous ones in disk block access time. Second, a new directory structure which uses extendible hashing is described. Third, we describe a novel scheme to manage free disk blocks, which is suitable for very large file systems. Finally, we present how we handle metadata journaling. Through performance evaluation, we show that our proposed schemes have better performance than previous ones.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.22 no.2
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• pp.180-189
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• 2015

Purpose: The purpose of this study was to identify the types of errors that occurred and were recovered in a simulated transfusion scenario by nursing students. Methods: Twenty-eight teams of a total of 89 nursing students participated in a transfusion simulation using a high fidelity simulator. Data were collected by observing rule based errors and built in errors recovered according to the framework of Eindhoven model. Reflective journaling was used to identify perceived safety-threatening errors and commitment to improvement. Data were analyzed using descriptive statistics. Results: All teams committed the rule based errors in the scenario. The most common errors occurred in the coordination category related to communication with physician. Most of students perceived the transfusion reaction as a safety-threatening error. Conclusion: The findings indicate that students lack patient safety competence. The simulation training to decrease errors and improve safe practice provides nursing students with an effective strategy to develop patient safety competence.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.317-320
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• 2011

최근 PCM과 같은 비휘발성 메모리의 집적도의 급속한 향상과 함께 향후 고속의 바이트 단위의 접근이 가능한 스토리지 시스템이 등장할 것으로 예측되고 있다. 이 논문에서는 PCM 기반의 스토리지 시스템을 위한 저널링 파일시스템을 설계하였다. 하드디스크나 플래시 메모리와는 다른 PCM의 특성을 고려하여 현재의 저널링 파일시스템과 동일한 파일시스템 일관성을 제공하되 더 나은 성능을 보여주는 저널링 파일시스템을 설계하였다. 시뮬레이션을 통한 실험 결과는 제안된 저널링 파일시스템이 ext3 등의 기존 저널링 파일시스템보다 평균 59%의 쓰기량을 감소시켰음을 보여주었다.