• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.617-630
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• 1996

In this paper, a shared-concurrent file system (S-CFS) is designed and implemented using conventional disks as disk arrays on a Workstation Cluster which can be used as a small-scale server. Since it is implemented on UNIX operating systems, S_CFS is not only portable and flexible but also efficient in resource usage because it does not require additional I/O nodes. The result of the research shows that on small-scale systems with enough disks, the performance of the concurrent file system on transaction processing applications is bounded by the bottleneck of CPUs computing powers while the performance of the concurrent file system on massive data I/Os is bounded by the time required to copy data between buffers. The concurrent file system,which has been implemented on a Workstation Cluster with 8 disks,shows a throughput of 388 tps in case of transaction processing applications and can provide the bandwidth of 15.8 Mbytes/sec in case of massive data processing applications. Moreover,the concurrent file system has been dsigned to enhance the throughput of applications requirring high performance I/O by controlling the paralleism of the concurrent file system on user's side.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.35-40
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• 2005

The demand for small and high-capacity optical data storage devices has rapidly increased. The areal density of optical disk is increased using higher numerical aperture objective lens and shorter wavelength source. A wafer-scale stacked micro objective lens with a numerical aperture of 0.85 and a focal length of 0.467mm for the 405nm blue- violet laser was designed and fabricated. A diffractive optical element (DOE) was used to compensate the spherical aberration of the objective lens. Among the various fabrication methods for micro DOE, the UV-replication process is more suitable for mass-production. In this study, an 8-stepped DOE pattern as a master was fabricated by photolithography and reactive ion etching process. A flexible mold was fabricated for improving the releasing properties and shape accuracy in UV-molding process. In the replication process, the effects of exposing time and applied pressure on the replication quality were analyzed. Finally, the shapes of master, mold and molded pattern were measured by optical scanning profiler. The deviation between the master and the molded DOE was less than 0.1um. The efficiency of the molded DOE was measured by DOE efficiency measurement system which consists of laser source, sample holder, aperture and optical power meter, and the measured value was $84.5\%$.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.22 no.2
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• pp.132-141
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• 2019

Foreign body (FB) ingestion of children is a common pediatric emergency requiring medical attention. Pediatric emergency physicians and gastroenterologists often encounter nervous and distressed situations, because of children presenting with this condition in the common clinical practice. When determining the appropriate timing and indications for intervention, physicians should consider multiple patient- and FB-related factors. The utilization of a flexible endoscopy is considered safe and effective to use in these cases, with a high success rate, for the effective extraction of FBs from the gastrointestinal tract of a child. Additionally, a Foley catheter and a magnet-attached Levin tube have been used for decades in the case of FB removal. Although their use has decreased significantly in recent times, these instruments continue to be used for several indications. Using a Foley catheter for this purpose does not require special training and does not necessarily require sedation of the patient or fluoroscopy, which serve as advantages of utilizing this method for foreign object retrieval. An ingested magnet or iron-containing FB can be retrieved using a magnet-attached tube, and can be effective to retrieve an object from any section of the upper gastrointestinal tract that can be reached. Simple and inexpensive devices such as Foley catheters and magnetattached tubes can be used in emergencies such as with the esophageal impaction of disk batteries if endoscopy cannot be performed immediately (e.g., in rural areas and/or in patients presenting at midnight in a facility, especially in those without access to endoscopes or emergency services, or in any situation that warrants urgent removal of a foreign object).

• KNOM Review
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• v.22 no.3
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• pp.1-12
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• 2019

Recently, researching using big data and AI has emerged as a major issue in the ICT field. But, the size of big data for research is growing exponentially. In addition, users of data transmission of existing network method suggest that the problem the time taken to send and receive big data is slower than the time to copy and send the hard disk. Accordingly, researchers require dynamic and flexible network technology that can transmit data at high speed and accommodate various network structures. SDN/NFV technologies can be programming a network to provide a network suitable for the needs of users. It can easily solve the network's flexibility and security problems. Also, the problem with performing AI is that centralized data processing cannot guarantee real-time, and network delay occur when traffic increases. In order to solve this problem, the edge-computing technology, should be used which has moved away from the centralized method. In this paper, we investigate the concept and research trend of SDN, NFV, and edge-computing technologies, and analyze the trends of data central network technologies used by combining these three technologies.