• Biomedical Science Letters
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• v.15 no.2
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• pp.119-126
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• 2009

This study investigated the effect of Corni Fructus(Cornus officinalis Sieb. et Zucc.) extract on hyperglycemia and renal function in streptozotocin-induced diabetic rats. Male Sprague-Dawley rats were divided into three groups including normal control(NC), diabetic control(DC), and diabetic treatment with Corni Fructus(DCF). Over a 4-week experimental period, Corni Fructus aqueous extract was administered orally at 500 mg/kg BW/day. The final fasting serum glucose, serum urea nitrogen, triglyceride, urinary total protein level, and relative weight of the left kidney in the DCF group were significantly lower than the DC group. Serum insulin level in the DCF group was higher than the DC group by 23%. The renal xanthine oxidase and superoxide dismutase activities in the DCF group were significantly lower than the DC group. The renal catalase activity in the DCF group was significantly higher than the DC group. In conclusion, these results indicated that Corni Fructus can reduce glucose level and prevent or retard the development of diabetic complication via its antioxidative effect and protecting against diabetic renal damage in streptozotocin-induced diabetic rats.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.8
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• pp.1561-1570
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• 2009

Being different from traditional mobile communication networks or wireless LAN with access points, ad hoc network can provide direct communications between homogeneous stations. Thus, it can be considered as a much advanced network. Somehow, many researches have been done to enhance system performance of ad hoc networks up to now, one of which is cooperative communications. In this paper, a cooperative MAC protocol, called CO-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides more enhanced system throughput especially when frame transmission error probability is high than DCF scheme, which is the key protocol in IEEE 802.11 standard, and rDCF scheme.

• Toxicological Research
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• v.25 no.2
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• pp.93-99
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• 2009

This study investigated the effect of Corni Fructus (Cornus officinalis Sieb. et Zucc.) extract on blood glucose and insulin resistance in db/db mice. Seven weeks old male mice were divided into normal control group (NC), diabetic control group (DC) and Corni Fructus treated diabetic group (DCF). Over an 8-week experimental period, Corni Fructus extract was administered orally at 500 mg/kg BW/day. Corni Fructus inhibited increase in blood glucose level during the OGTT (oral glucose tolerance test). At 8 weeks after beginning of the experiment, blood glucose level in the DCF group was significantly lower (p<0.01) than the DC group. Final fasting serum glucose and triglyceride in the DCF group were significantly lower (p<0.05) than the DC group by 32% and 41% respectively. Serum insulin did not differ among the NC, DC and DCF groups. The mRNA expression of adiponectin, GLUT 4 and PPAR-$\gamma$ in adipose tissue in the DC group were significantly lower than the NC group and they were higher in the DCF group than the DC group by 76%, 130% (p<0.05) and 43%, respectively. In conclusion, these results indicated that Corni Fructus would have antidiabetic effects via improving insulin resistance in favor of higher glucose utilization and reducing blood glucose level in db/db mice.

• Journal of Advanced Navigation Technology
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• v.21 no.2
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• pp.187-192
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• 2017

The compensation characteristics of the distorted WDM channels compensated for by dispersion management (DM) and optical phase conjugation in the long-haul (50 fiber spans ${\times}80km$) transmission link with the randomly distributed single mode fiber (SMF) length and residual dispersion per spans (RDPS) are investigated as a function of the arrangement of SMF and dispersion compensating fiber (DCF) and the control position of net residual dispersion (NRD). It is confirmed that the compensation effect of the distorted WDM channels strongly depends on the arragement of SMF and DCF, rather than the control position of NRD.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.9A
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• pp.1075-1082
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• 2004

Wireless LAN is a rather mature communication technology connecting mobile terminals. IEEE 802.11 is a representative protocol among Wireless LAN technologies. The basic medium access control (MAC) mechanism of IEEE 802.11 is called distnbuted coordination function (DCF). DCF shows poor throughput and high drop rate as the number of stations and offered traffic load increase. In this paper we propose an effective mechanism using dynamic mimmum contention window(CWmin) in wireless LAN~ and show that performance improves via simulations. Proposed dynamic CWmin scheme exhibits superior performance as the number of stations and offered load grow. As, our proposed scheme is expected to be more effective in highly densed wireless LAN environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.4
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• pp.758-765
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• 2008

Wide-spread deployment of infrastructure WLANs has made Wi-Fi an integral part of today's Internet access technology. WLANs suffer from degraded system throughput and each node's throughput fluctuates significantly in the saturation regime. In this paper, we propose a link layer traffic control mechanism which controls the offered load of DCF system. It is shown that the link layer traffic controller can improve DCF system throughput and reduce nodes' throughput fluctuation with properly controlled offered load. We propose a dynamic traffic control algorithm which can find an optimal offered load and show its performance improvement with ns-2 simulation.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.285-286
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• 2006

• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.35-36
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• 2007

We report a probe using a single double clad fiber (DCF) for fluorescence spectroscopy. Bidirectional separate transmission for excitation and fluorescence light in a single fiber was implemented. A DCF coupler made by side-polished method could extract none but the collected fluorescence signals propagating in inner cladding mode, thereby diminishing the interference of silica background generated by the excitation in core mode. The experimental results show that the fluorescence spectra of biological tissues obtained using the DCF probes have much less silica background than using a standard multiple-mode fiber.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.281-283
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• 2007

DCF 프로토콜 상에서 성공적인 패킷 전송을 위해서는 CW 값이 최솟값이 되어야 한다. 성공적인 전송을 위해서는 CW 값이 알맞아야 한다. 이것은 충돌을 유발할 수 있으므로 CW값은 경쟁레벨과 같은 길이가 되어야 한다. Slow CW Decrease(SD)는 경쟁레벨을 유지할 수 있는 방법을 제공한다. 본 논문에서는 Idle and Collision time Ratio(ICR)을 이용한 향상된 SD 방법을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.394-396
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• 2005

IEEE 802.11를 비롯한 여러 무선 네트워크에서는 multi-rate을 활용한 시스템 성능향상에 관한 연구가 진행되고 있다. 그 중에 한가지 연구결과로 제안된 방법이 rDCF.이다. 만약 Mesh 네트워크에서 rDCF를 동작시킨다면, 시스템 throughput의 증가, Packet delay의 감소와 항께 채널상태에 따라 포워딩 전략을 다르게 함으로써 채널 error의 영향이 줄어들 것으로 기대해 볼 수 있다. 하지만 기존의 rDCF를 아무런 revision 없이 Mesh 네트워크에 적용하기에는 spatial reuse 측면에서 비효율적이다. Mesh 네트워크에서는 외부 네트워크와 access point 지점이 되는 portal쪽으로 traffic이 집중되는 것이 일반적이므로 portal에 가까울수록 traffic간의 contention도 가중되므로 시스템 전체 성능에 영향을 미치게 된다. 이러한 문제를 줄이기 위하여 무선 네트워크 환경에서 spatial reuse 측면을 향상시킴으로써 동시에 진행되는 communication 수를 늘리는 방법이 있다. 그러므로 본 논문에서 rDCF의 spatial reuse를 늘임으로써 좀더 Mesh Network위에서도 효율적으로 작동할 수 있는 기법을 제시하고자 한다.