• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.968-970
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• 2009

Peer-Assisted CDN은 CDN과 P2P 기술을 상호보완적으로 이용해서 많은 사용자들에게 효율적으로 콘텐츠를 전송한다. 본 논문에서는 Peer-Assisted CDN과 전통적인 CDN, P2P 시스템의 성능 비교를 위한 간단한 성능 분석 모델을 제시한다. 그리고 실재 트레이스를 기초로 트래픽, 전송량, 다운로드 속도 측면에서 Peer-Assisted CDN과 CDN의 성능을 비교 한다. 본 논문의 결과에 따르면, Peer-Assisted CDN이 총 업로드 용량, 다운로드 속도, 확장성 측면에서 일반 CDN 보다 우수하다.

• Clinical and Experimental Reproductive Medicine
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• v.28 no.2
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• pp.147-153
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• 2001

Objective: The present study was performed to investigate the efficiency of partial laser assisted hatching (p-LAH; lased 1/2 ZP width from ZP edge) on hatching of mouse blastocysts. Methods: We used non-contact $1.48{\mu}m$ diode laser (MTM, Switzland) to create a precise hole on zona pellucida. 2-cell embryos were collected from the mouse (ICR) oviduct at 48 hours after hCG administration. Collected 2-cell embryos were cultured in the P-1 medium supplemented with 0.4% BSA. For experiments, embryos at 8-cell stage were used after $20{\sim}22$ hours in culture. After conventional (c-LAH) or partial laser assisted hatching, the embryos were further cultured in P-1 medium supplemented with 0.4% BSA for 3 days. To compare efficiency of complete and partial laser assisted hatching, hatching rate, hatching time and blastocyst diameter and zona pellucida thickness at hatching time were investigated. Embryos were examined every 12 hours. Blastocyst diameter and zona pellucida thickness at hatching time were measured with an ocular micrometer. Results: Hatching rates of p-LAH group (84.2%) was significantly higher than that of control group (39.3%), but there was no difference between the p-LAH (84.2%) and c-LAH (91.2%). p-LAH group was hatched 12 hours earlier than control group, but hatched 12 hours later than c-LAH group. The diameter of blastocyst at hatching time of p-LAH group ($113.1{\pm}6.4{\mu}m$) was smaller than that of control group ($122.2{\pm}5.0{\mu}m$), but larger than that of c-LAH group ($102.2{\pm}2.7{\mu}m$). Zona pellucida thickness at hatching time of p-LAH group ($6.4{\pm}0.9{\mu}m$) was thicker than that of control group ($4.5{\pm}1.5{\mu}m$), but thinner than that of c-LAH group ($10.0{\pm}0.8{\mu}m$). Conclusion: These results suggest that p-LAH may maintains the cell arrangement of early embryos to ensure successful development and prevent precocious hatching of blastocyst when compare to c-LAH and conventional (acidic tyrode) AH. Thus, p-LAH may provide a valuable and effective AH technique for human ART program.

• Clinical and Experimental Reproductive Medicine
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• v.41 no.2
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• pp.68-74
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• 2014

Objective: In search of an ideal method of assisted hatching (AH), we compared the effects of conventional micropipette-AH and laser-AH on the blastocyst formation rate (BFR) and blastocyst cell numbers. Methods: Four-to five-week-old ICR female mice were paired with male mice after superovulation using Pregnant mare's serum gonadotropin (PMSG) and hCG. The two-cell embryos were flushed from the oviducts of female mice. The retrieved two-cell embryos underwent one of five AH procedures: single mechanical assisted hatching (sMAH); cross mechanical assisted hatching (cMAH); single laser assisted hatching (sLAH); quarter laser assisted hatching (qLAH); and quarter laser zona thinning assisted hatching (qLZT-AH). After 72 hours incubation, double immunofluorescence staining was performed. Results: Following a 72 hours incubation, a higher hatching BFR was observed in the control, sMAH, cMAH, and sLAH groups, compared to those in the qLAH and qLZT-AH groups (p<0.05). The hatched BFR was significantly higher in the qLAH and qLZT-AH groups than in the others (p<0.05 for each group). The inner cell mass (ICM) was higher in the control and sMAH group (p<0.05). The trophectoderm cell number was higher in the cMAH and qLAH groups (p<0.05). Conclusion: Our results showed that the hatched BFR was higher in groups exposed the the qLAH and qLZT-AH methods compared to groups exposed to other AH methods. In the qLAH group, although the total cell number was significantly higher than in controls, the ICM ratio was significantly lower in than controls.

• Journal of Broadcast Engineering
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• v.24 no.2
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• pp.251-263
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• 2019

Recently the huge demand for Internet media streaming has dramatically increased the cost of the CDN (Content Delivery Network) and the need for a means to reduce it is increasing day by day. In this situation, a P2P-assisted DASH technology has recently emerged, which uses P2P (Peer-to-Peer) communications based on WebRTC (Web Real-Time Communication) standards to reduce the CDN cost. This paper proposes an algorithm that can significantly improve CDN cost savings in this technology by selecting peers based on the transport history. Also we implemented this algorithm in an experimental system and, after setting experimental conditions that emulate the actual mobile network environment, we measured the performance of the experimental system. As a result, we demonstrated that the proposed algorithm can achieve higher CDN cost savings compared to the conventional algorithm where peers are selected at random.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.1
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• pp.188-210
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• 2022

As a promising technique to support tremendous numbers of Internet of Things devices and a variety of applications efficiently, mobile edge computing (MEC) has attracted extensive studies recently. In this paper, we consider a MEC-assisted peer-to-peer (P2P) mobile communication system where MEC servers are deployed at access points to accelerate the communication process between mobile terminals. To capture the tradeoff between the time delay and the energy consumption of the system, a cost function is introduced to facilitate the optimization of the computation and communication resources. The formulated optimization problem is non-convex and is tackled by an iterative block coordinate descent algorithm that decouples the original optimization problem into two subproblems and alternately optimizes the computation and communication resources. Moreover, the MEC-assisted P2P communication system is compared with the conventional P2P communication system, then a condition is provided in closed-form expression when the MEC-assisted P2P communication system performs better. Simulation results show that the advantage of this system is enhanced when the computing capability of the receiver increases whereas it is reduced when the computing capability of the transmitter increases. In addition, the performance of this system is significantly improved when the signal-to-noise ratio of hop-1 exceeds that of hop-2.

• The Journal of Korean Physical Therapy
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• v.28 no.2
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• pp.71-76
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• 2016

Purpose: This study was conducted to assess the effects of robot-assisted gait training with visual feedback on gait, balance, and balance confidence in patients with chronic stroke. Methods: Thirty subjects with chronic stroke were randomly assigned to two groups: the experimental group (n=15) and the control group (n=15). The experimental group performed robot-assisted gait training for 30 minutes and the control group performed gait training with assisted devices training for 30 minutes after both groups performed conventional physical therapy for 30 minutes. Both groups performed the therapeutic interventions for 5 days per week, for a period of 4 weeks. For assessment of the 10 m walking test (10 MWT), Figure of 8 on the walk test (F8WT), Timed-Up and Go test (TUG), and Berg Balance Scale (BBS) were used to test the gait and balance, and the Korean version of the Activities-specific Balance Confidence Scale was used to test the balance confidence. Results: The experimental group showed significant improvement in the 10 MWT and the K-ABC (p<0.05), and the control group showed significant improvement in the BBS and the TUG (p<0.05). In four measurements, there were significant differences between the two groups (p<0.05), and the control group showed significant improvement in the F8WT at pre and post intervention (p<0.05). Conclusion: This study demonstrated that Robot-assisted gait training with visual feedback is an effective intervention for improving straight gait abilities and balance confidence, while the control group showed some improvement in curve gait and balance. Thus, we suggest both Robot-assisted gait training with visual feedback and gait training with assisted devices training exercise as a therapeutic intervention in chronic stroke rehabilitation.

• Korean Journal of Radiology
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• v.23 no.2
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• pp.246-255
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• 2022

Objective: To determine the usefulness of Silent MR angiography (MRA) for evaluating intracranial aneurysms treated with stent-assisted coil embolization. Materials and Methods: Ninety-nine patients (101 aneurysms) treated with stent-assisted coil embolization (Neuroform atlas, 71 cases; Enterprise, 17; LVIS Jr, 9; and Solitaire AB, 4 cases) underwent time-of-flight (TOF) MRA and Silent MRA in the same session using a 3T MRI system within 24 hours of embolization. Two radiologists independently interpreted both MRA images retrospectively and rated the image quality using a 5-point Likert scale. The image quality and diagnostic accuracy of the two modalities in the detection of aneurysm occlusion were further compared based on the stent design and the site of aneurysm. Results: The average image quality scores of the Silent MRA and TOF MRA were 4.38 ± 0.83 and 2.78 ± 1.04, respectively (p < 0.001), with an almost perfect interobserver agreement. Silent MRA had a significantly higher image quality score than TOF MRA at the distal internal carotid artery (n = 57, 4.25 ± 0.91 vs. 3.05 ± 1.16, p < 0.001), middle cerebral artery (n = 21, 4.57 ± 0.75 vs. 2.19 ± 0.68, p < 0.001), anterior cerebral artery (n = 13, 4.54 ± 0.66 vs. 2.46 ± 0.66, p < 0.001), and posterior circulation artery (n = 10, 4.50 ± 0.71 vs. 2.90 ± 0.74, p = 0.013). Silent MRA had superior image quality score to TOF MRA in the stented arteries when using Neuroform atlas (4.66 ± 0.53 vs. 3.21 ± 0.84, p < 0.001), Enterprise (3.29 ± 1.59 vs. 1.59 ± 0.51, p = 0.003), LVIS Jr (4.33 ± 1.89 vs. 1.89 ± 0.78, p = 0.033), and Solitaire AB stents (4.00 ± 2.25 vs. 2.25 ± 0.96, p = 0.356). The interpretation of the status of aneurysm occlusion exhibited significantly higher sensitivity with Silent MRA than with TOF MRA when using the Neuroform Atlas stent (96.4% vs. 14.3%, respectively, p < 0.001) and LVIS Jr stent (100% vs. 20%, respectively, p = 0.046). Conclusion: Silent MRA can be useful to evaluate aneurysms treated with stent-assisted coil embolization, regardless of the aneurysm location and type of stent used.

• Journal of Communications and Networks
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• v.10 no.4
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• pp.422-429
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• 2008

Mobile peer-to-peer (P2P) systems have recently got in the limelight of the research community that is striving to build efficient and effective mobile content addressable networks. Along this line of research, we propose a new peer-to-peer file sharing protocol suited to mobile ad hoc networks (MANET). The main ingredients of our protocol are network coding and mobility assisted data propagation, i.e., single-hop communication. We argue that network coding in combination with single-hop communication allows P2P file sharing systems in MANET to operate in a more efficient manner and helps the systems to deal with typical MANET issues such as dynamic topology and intermittent connectivity as well as various other issues that have been disregarded in previous MANET P2P researches such as addressing, node/user density, non-cooperativeness, and unreliable channel. Via simulation, we show that our P2P protocol based on network coding and single-hop communication allows shorter file downloading delays compared to an existing MANET P2P protocol.

• Journal of Broadcast Engineering
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• v.25 no.1
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• pp.94-104
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• 2020

Currently media consumption over fixed/mobile Internet is mostly conducted by adaptive media streaming technology such as DASH (Dynamic Adaptive Streaming over HTTP), which is an ISO/IEC MPEG (Moving Picture Experts Group) standard, or some other technologies similar to DASH. All these heavily depend on the HTTP caches that ISPs (Internet Service Providers) are obliged to provide sufficiently to make sure fast enough Web services. As a result, as the number of media streaming users increases, ISPs' burden for HTTP cache has been greatly increased rather than CDN (Content Delivery Network) providers' server burden. Hence ISPs charge traffic cost to CDN providers to compensate for the increased cost of HTTP caches. Recently in order to reduce the traffic cost of CDN providers, P2P (Peer-to-Peer)-assisted DASH system was proposed and a peer selection algorithm that maximally reduces CDN provides' traffic cost was investigated for this system. This algorithm, however, tends to concentrate the burden upon the selected peer. This paper proposes a new peer selection algorithm that distributes the burden among multiple peers while maintaining the proper reduction level of the CDN providers' cost. Through implementation of the new algorithm in a Web-based media streaming system using WebRTC (Web Real-Time Communication) standard APIs, it demonstrates its effectiveness with experimental results.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.327-335
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• 2021

In this study, we sought to investigate how animal-assisted therapy using therapy dogs affects the relationship between children's self-esteem and age. The subjects of the study were 20 children in the lower grades of elementary school in I City who were recommended by a school social worker and their homeroom teacher, and 10 control groups of 10 experimental groups were selected. From October 1st to December 17th, 2019, the program conducted an animal-mediated treatment program once a week for 50 minutes for 12 sessions. Using SPSS 20.0 for verification, the experimental and control groups were analyzed by performing pre- and post-relationship calm scale measurements of self-esteem and age. As a result, first, the overall self-esteem of the experimental group (Z = -2.75, p<.05), the self-esteem at home (Z = -2.02, p<.05), and the academic self-esteem (Z = -2.06, p<. 05) shows a statistically significant difference. Second, significant differences were shown in overall peer relationships(Z=-3.83, p<.05), scrupulosity(Z=-2.68, p<.05), and empathy(Z=-2.81, p<.05) in the experimental population. Therefore, in this study, it was confirmed that animal-assisted therapy using therapy dogs had a positive effect on the relationship between children's self-esteem and age.