• 경영과학
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• 제23권3호
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• pp.133-156
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• 2006

The ubiquitous technology, leading the stream of change in telecommunication market, makes VoIP a foundation technology to enter NGN era. With this trend in mind, VoIP providers try to satisfy customer needs and invest on R&D in order to survive in this emerging market. The critical issues to VoIP providers are two fold the first one is to find out the quality attributes of Internet telephony service; and the second one is to assess the impact they have on customer satisfaction, customer loyalty and customer performance. In this study, we attempt to empirically answer the above two issues employing SEM (structural equation modeling) and AHP (analytic hierarchy process), and suggest strategic guidelines for successful deployment of Internet telephony service.

• Molecules and Cells
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• 제42권3호
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• pp.252-261
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• 2019

The omega-3 fatty acid docosahexaenoic acid (DHA) is known to induce apoptosis and cell cycle arrest via the induction of reactive oxygen species (ROS) production and endoplasmic reticulum (ER) stress in many types of cancers. However, the roles of DHA in drug-resistant cancer cells have not been elucidated. In this study, we investigated the effects of DHA in cisplatin-resistant gastric cancer SNU-601/cis2 cells. DHA was found to induce ROS-dependent apoptosis in these cells. The inositol 1,4,5-triphosphate receptor ($IP_3R$) blocker 2-aminoethyl diphenylboninate (2-APB) reduced DHA-induced ROS production, consequently reducing apoptosis. We also found that G-protein-coupled receptor 120 (GPR120), a receptor of long-chain fatty acids, is expressed in SNU-601/cis2 cells, and the knockdown of GPR120 using specific shRNAs alleviated DHA-mediated ROS production and apoptosis. GPR120 knockdown reduced the expression of ER stress response genes, similar to the case for the pre-treatment of the cells with N-acetyl-L-cysteine (NAC), an ROS scavenger, or 2-APB. Indeed, the knockdown of C/EBP homologous protein (CHOP), a transcription factor that functions under ER stress conditions, markedly reduced DHA-mediated apoptosis, indicating that CHOP plays an essential role in the anti-cancer activity of DHA. These results suggest that GPR120 mediates DHA-induced apoptosis by regulating $IP_3R$, ROS, and ER stress levels in cisplatin-resistant cancer cells, and that GPR120 is an effective chemotherapeutic target for cisplatin resistance.

• The Korean Journal of Physiology and Pharmacology
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• 제14권4호
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• pp.235-240
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• 2010

Toll-like receptors (TLRs) functionally expressed in salivary epithelial cells, but their roles remain elusive. Among TLRs family, TLR3 is activated by dsRNA, a byproduct of viral infection. The aim of this study was to investigate the role of TLR3 in the inflammatory immune responses using HSG cells. Reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR and ELISA were performed to identify expression of TLRs and TLR3-mediated chemokine inductions. The chemotaxis assay of activated T lymphocytes was also performed. Treatment of HSG cells with polyinosinic: polycytidylic acid (poly(I:C)) significantly increased interferon-$\gamma$-inducible protein 10 (IP-10), interferoninducible T-cell $\alpha$ chemoattractant (I-TAC), and regulated on activation, normal T-cells expressed and secreted (RANTES) gene expressions in a concentration-dependent manner. Anti-TLR3 antibody blocked the increases of IP-10 and I-TAC genes. Poly(I:C)-induced increases of IP-10 and I-TAC were also confirmed at protein levels from cell lysates, but their release into extracellular medium was detected only in IP-10. We found that the culture media from HSG cells stimulated with poly(I:C) significantly increases T lymphocyte migration. Our results suggest that TLR3 plays an important role in chemokine induction, particularly IP-10, in salivary epithelial cells.

• 대한안전경영과학회지
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• 제11권3호
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• pp.199-207
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• 2009

IP Telephony service was restricted to an outgoing call and low quality since the trust domestic IP Telephony service launch of Saerome co. Ltd, in Jan. 2000. However, Interest of IP Telephony service, which is substituted for PSTN, has been highly elated because of the developed equipment softswitch and new technology. This kind of importance and marketing of VoIP are recognized to telecommunication providers. With this trend, they try to administrate customer satisfaction and invest R&D to survive in this hard competition and unexpected change. To achieve this objective, they should try to realize the searching process of the quality decision attribution (QDA). However, there is little research on the aspect of service quality of Internet telephony so far. For this, the investigator established the tangibles, the reliability, the responsibility, the assurance, the empathy, the charge with information sources as core elements. In order to examine the influence of IP Telephony service upon the attitudes toward a brand and the purchase intention.

• 품질경영학회지
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• 제42권3호
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• pp.477-496
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• 2014

Purpose: This paper has examined the impact of open innovation business model in technology commercialization with the data from 30 companies of manufacturing firms in South Korea. Methods: The findings provide support for distinguishing five hypotheses relating to development time, IP management, sales, firm size and R&D intensity. To test the hypotheses, data were collected using via e-mail and fax. Small and medium-sized (less than 300 employees) and large industrial firms were chosen for this study. Results: The result shows that openness in its business model is positively associated with successful technology commercialization. Conclusion: The major findings and the implications are: First, as the business model gets more open, development period of technology will be more favorable which gets benefit from rising costs of innovation. Second, as the business model gets more open, large portion of sales are created from new products. Thus, the problem of shorter product life in the market which affects large portion of market revenue can be solved through an open business model. Third, in general, R&D intensity, firm size and the level of IP management affect determination of business model types. The findings also suggest that companies need to increasingly address their external technology exploitation process instead of focusing on their internal innovation processes.

• Journal of Applied Biological Chemistry
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• 제65권4호
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• pp.239-245
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• 2022

지혈이 일어나는 과정에서 혈소판의 정상적인 활성화가 중요하지만, 혈소판의 과도하거나 비정상적인 활성화는 뇌졸중, 죽상동맥 경화증 및 혈전증과 같은 심혈관 질환을 유발할 수 있다. 따라서, 혈소판 활성화를 조절하거나 억제할 수 있는 새로운 물질의 발견은 심혈관 질환의 예방 및 치료에 도움이 될 수 있다. Artemether는 Artemisia annua의 유효성분으로 알려진 artemisinin의 유도체로서 말라리아 치료에 효과적이라고 보고된 바 있고, 항산화 및 대사 효소 억제를 통해 기능하는 것으로 알려져 있다. 그런데, 혈소판 활성화 및 응집에 있어서의 artemether의 역할과 collagen으로 유도한 사람 혈소판에서 artemether의 작용기전은 현재까지 알려진 바가 없다. 본 연구는 artemether가 collagen에 의해 유도된 혈소판 활성화와 혈전 형성에 어떤 영향을 미치는 지 연구하였다. 그 결과, cAMP level이 artemether에 의해 유의하게 증가되었고, cAMP-의존성 kinase의 기질인 VASP 및 IP₃R이 인산화되었다. Artemether에 의한 IP₃R 인산화는 세포질 내로의 Ca²⁺ 동원을 억제하였고, 인산화된 VASP는 혈소판 막에 위치한 αIIb/β₃ 불활성화를 일으켜 fibrinogen 결합을 억제하였다. 결과적으로, artemether는 thrombin으로 유도한 fibrin clot의 형성을 억제하였다. 따라서, 우리는 artemether가 과도한 혈소판 활성화 및 혈전 형성으로 인한 심혈관 질환의 효과적인 예방 및 치료제로 작용할 수 있음을 제안한다.

• Journal of Applied Biological Chemistry
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• 제66권
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• pp.402-407
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• 2023

혈소판 응집의 조절은 정상적인 지혈을 유지하는 데 중요하지만 비정상적이거나 과도한 혈소판 응집은 뇌졸중, 죽상동맥 경화증 및 혈전증과 같은 심혈관 질환에 기여할 수 있다. 따라서 혈소판 응집을 제어하거나 억제할 수 있는 물질을 식별하는 것은 이러한 상태의 예방 및 치료를 위한 유망한 접근 방식이다. Artemisia 또는 Scopolia 속 식물에서 추출한 artemisinin은 항암 및 알츠하이머병 연구와 같은 다양한 분야에서 가능성을 보여주었다. 그러나 artemisinin이 혈소판 활성화 및 혈전 형성에 영향을 미치는 구체적인 역할과 메커니즘은 아직 완전히 밝혀지지 않았다. 이 연구는 혈소판 활성화 및 혈전 형성에 대한 artemisinin의 효과를 조사하였다. 그 결과, cAMP 생성과 cAMP 의존성 kinase에 대한 기질인 VASP 및 IP₃R의 인산화가 artemisinin에 의해 유의미하게 증가되었다. IP₃R의 인산화는 조밀한 관형 시스템에서 정상적으로 동원되는 Ca²⁺를 억제하였고, VASP의 인산화는 αIIb/β₃ 혈소판 막 불활성화를 통한 fibrinogen 결합을 억제하였다. 마지막으로, artemisinin은 thrombin이 유발하는 혈전 형성을 농도의존적으로 억제하였다. 따라서 우리는 artemisinin이 혈소판 활성화의 효과적인 예방 및 치료제로 작용하여 비정상적인 혈소판 응집 및 혈전 형성으로 인해 유발되는 심혈관 질환의 개선에 기여할 수 있음을 제안한다.

• Journal of Communications and Networks
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• 제2권1호
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• pp.46-57
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• 2000

Ongoing standardization effort on 3G cellular system in 3GPP (UNTS) is based on GPRS core network and promises a global standard for systems capable of offering ubiquitous access to internet for mobile users. Considered radio access systems(FDD CDMA, TDD CDMA, and EDGE) are optimized for robust mobile use. However, there are alternative relatively high-rate radio interfaces being standardized for WLAN (IEEE802.11 and HIPER-LAN/2) which are capable of delivering significantly higher data rates to static or semi-static terminals with much less overhead. Also WPANs(BLUETOOTH, IEEE802.15), which will be present in virtually every mobile handset in the near future, are offering low cast and considerable access data rate and thus are very attractive for interworking scenarios. The prospect of using these interfaces as alternative RANs inthe modular UMTS architecture is very promising. Additionally, the recent inclusion of M-IP in the UMTS R99 standard opens the way for IP-level interfacing to the core network. This article offers an overview into WLAN-Cellular interworking. A brief overview of GPRS, UMTS cellular architectures and relevant WLAN standards is given. Possible interworking architectures are presented.

• Journal of Advanced Marine Engineering and Technology
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• 제39권7호
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• pp.744-753
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• 2015

본 논문에서는 해사위성기반의 VoIP 서비스를 위한 해상용 통합 커뮤니케이션 기술 개발에 관한 연구를 수행하였다. 최근 스마트폰과 모바일기기가 대중화되면서 해상에서도 인터넷기반 유무선 통합기술의 수요가 증가하고 있으며, 특히 가격 경쟁력이 높고 다양한 서비스를 제공할 수 있는 VoIP 제품과 서비스 모델에 대한 관심이 높아지고 있다. 따라서 본 논문에서는 첫째, 아날로그 게이트웨이 모듈을 장착하여 기존 선박용 장비와 연동이 가능하며 육상용 시스템 대비 80%이상 소형화 된 해상 VoIP 모듈을 개발하고 둘째, 해상용 VoIP 서비스 핵심요소기술인 통신 데이터 사용량 최소화 기술이 적용된 해상위성통신용 텍스트/음성/영상 엔진을 개발한다. 마지막으로 다자간 메시지 및 클라우드 방식의 메시지 대화지원, 전화번호 기반의 통화기능 지원과 개인 공간에서 육상과 음성 및 영상통화 지원이 가능한 해상용 통합 커뮤니케이션을 설계하고 단위 모듈을 개발하여 성능을 검증하였다.

• 약학회지
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• 제48권6호
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• pp.352-357
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• 2004

Atrial myocytes have two functionally separate groups of ryanodine receptors (RyRs): those at the periphery colocalized with L-type $Ca^{2+}$channels (DHPRS) and those a t the cell interior not associated with DHPRs. $Ca^{2+}$ current ($I_{ca}$) directly gates peripheral RyRs on action potential and the subsequent peripheral $Ca^{2+}$ release propagates into the center of atrial myocytes. The mechanisms that regulate the $Ca^{2+}$+ propagation wave remain Poorly understood. Using 2-D confocal$Ca^{2+}$ imaging, we examined the role of inositol 1,4,5-trisphosphate receptor (IP $_3R$) and mitochondria on ($I_{ca}$)- gated local $Ca^{2+}$ signaling in rat atrial myocytes. Blockade of IP $_3R$ by xestospongin C (XeC) partially suppressed the magnitudes of I ca-gated central and peripheral $Ca^{2+}$ releases with no effect on $I_{ca}$. Mitochondrial staining revealed that mitochondria were aligned with ${\thickapprox}2-{\mu}m$ separations in the entire cytoplasm of ventricular and atrial myocytes. Membrane depolarization induced rapid mitochondrial $Ca^{2+}$ rise and decay in the cell periphery with slower rise in the center, suggesting that mitochondria may immediately uptake cytosolic $Ca^{2+}$, released from the peripheral SR on depolarization, and re-release the $Ca^{2+}$ into the cytosol to activate neighboring central RyRs. Our data suggest that the activation of IP $_3R$ and mitochondrial $Ca^{2+}$ handing on action potential may serve as a cofactor for the $Ca^{2+}$ propagation from the DHPR-coupled RyRs to the DHPR-uncoupled RyRs with large gaps between them.