• Journal of Internet Computing and Services
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• v.12 no.4
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• pp.35-43
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• 2011

Cognitive Radio (CR) ad hoc network is highly considered as one of promising future ad hoc networks, which enables opportunistic access to under-utilized licensed spectrum. Similarly to other CR networks, the spectrum sensing is a prerequisite in CR ad hoc network. Collaborative spectrum sensing can help increasing sensing performance. For such an infrastructureless network, however the coordination for the sensing collaboration is really complicated due to the lack of a central controller. In this paper, we propose a novel collaborative spectrum sensing scheme in which the final decision is made by the node with the highest data reliability based on a sequential Dempster Shafer theory. The collaboration of sensing data is also executed by the proposed contention-aware reporting mechanism which utilizes the sensing data reliability order for broadcasting spectrum sensing result. The proposed method reduces the collecting time and the overhead of the control channel due to the efficiency of the ordered sequential combination while keeping the same sensing performance in comparison with the conventional cooperative centralized spectrum sensing scheme.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 1998.04a
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• pp.304-308
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• 1998

Technical advances in computer networks and the Internet bring a new communication era and provide effective solutions for cooperative works and research. These technological advances introduced the concept of cyberspace that many people involve reseach and a project at different locations at the same time. In this paper, we present a fast and effective interaction protocol that is aeapted to the COLAB(COIIaborative LABoratory) Systems which use a high-speed ATM Network. The CCOLAB systems is developed for researchers those who are doing a large project on the collaborative research environment. The interaction protocol that we developed supports multi-session and multi-channel on the TCP/IP Network and provides more flexible solution to control multimedia data on the network.

• Journal of Communications and Networks
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• v.11 no.4
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• pp.350-358
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• 2009

In a wireless sensor network (WSN) setting, this paper presents a distributed decision-making framework and illustrates its application in an online structural health monitoring (SHM) system. The objective is to recover a damage severity vector, which identifies, localizes, and quantifies damages in a structure, via distributive and collaborative decision-making among wireless sensors. Observing the fact that damages are generally scarce in a structure, this paper develops a nonlinear 0-norm minimization formulation to recover the sparse damage severity vector, then relaxes it to a linear and distributively tractable one. An optimal algorithm based on the alternating direction method of multipliers (ADMM) and a heuristic distributed linear programming (DLP) algorithm are proposed to estimate the damage severity vector distributively. By limiting sensors to exchange information among neighboring sensors, the distributed decision-making algorithms reduce communication costs, thus alleviate the channel interference and prolong the network lifetime. Simulation results in monitoring a steel frame structure prove the effectiveness of the proposed algorithms.

• International journal of advanced smart convergence
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• v.10 no.1
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• pp.62-74
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• 2021

We compare Over-the-Tops (OTTs), Netflix and Amazon Prime Video (APV) with five success factors of innovation. Firstly, Netflix offers better personalized service than APV, because APV has collaborative filtering algorithms to recommend safe bets, not the customers really want. Secondly, APV' user interface is undercooked to lock the members in, even if it has more content and better price offer than Netflix retaining its loyal customers despite the price increase. Thirdly, Netflix has simple subscription model with three tiering, but APV has complicated pricing model having annual and monthly, APV and Prime Video (AV) app, Amazon subscription and extra payment of Amazon Prime Channels (APCs). Fourthly, Amazon has fewer partnership than Netflix especially when it comes to local TV series. Instead, Amazon has live TV channel collaboration including sports content. Lastly, both have strategic and operational agility in their organization well.

• Asia pacific journal of information systems
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• v.23 no.1
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• pp.45-63
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• 2013

The purpose of this research is on the identification of the effects of perceived interactivity formed by the electronic collaborative referral system on the organizational loyalty. Two channels through which the effects proceeded were investigated. One is the "system channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ intention of using the system ${\rightarrow}$ organization loyalty" (hypothesis 1, 2), that is the channel which anticipates that a better understanding on the interactivity of the inter-organizational system makes the intention of the using the system strong, and this strong intention results the higher organization loyalty. The other is "organization channel" which consists of "interactivity of the inter-organizational system ${\rightarrow}$ perceived interactivity on the counterpart ${\rightarrow}$ perceived relation benefits with the counterpart ${\rightarrow}$ organization loyalty" (hypothesis 3, 4, 5). The channel means that as the perceived interactivity of users on the inter-organizational system becomes greater, the perceived interactivity with the counterpart is increasing. And this makes the users feel that more benefits can be obtained by the relationship with system providing organization, and finally makes the organization loyalty that is the intention to maintain the relationship greater. The corroborative evidence data confirm the two channels are obtained by questing on the electronic referral system of Samsung Medical Center to the doctors of the first and second collaborated hospitals or clinics, and by analyzing statistically. The verification result for the "system channel" showed that as the perception on the interactivity of inter-organizational system was increasing, the intention for consistent using increased(support hypothesis 1), and then the organization loyalty that is the relationship maintaining indication by using the referral system also increased(support hypothesis 2). And the confirmation result for the "organization channel" indicated that the perceptive interactivity on the counterpart increased as the understanding on the interactivity of inter-organizational system increased(support hypothesis 3), consecutively, with the intuitive relation benefits increase with the counterpart(support hypothesis 4) the organization loyalty means the intention to maintain the relationship was confirmed to increase(support hypothesis 5). These results demonstrate that when the perceived interactivity in using many systems at the collaboration between organizations is increasing, the positive image on the systems creates the consistent system using intention, and the positive image increases the wants for preserving the relationship with counter organization. In addition, the perceived interactivity of inter-organizational system users affects directly on the perceived interactivity of the counter organization, so the important role of inter-organizational system in promoting the interactivity between cooperative counterparts was recognized. And the perceived interactivity on the counter organization become greater, the influence on the perceived benefits from cooperation is positive. Therefore, the perceived interactivity by using inter-organizational system was confirmed as a prerequisite for the continuous relationship.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.4
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• pp.1-7
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• 2009

In this paper, the author presents the MIMO(Multi-Input Multi-Output) receiver algorithm with the capability of inter-cell or inter-sector interference cancellation over multi-antenna OFDM(Orthogonal Frequency Division Multiplexing) systems. As contrast with the previous research dealing with the filtering scheme at the time domain, the proposed algorithm is presented as the pre-filtering scheme which can be applicable to the frequency domain. Note that the proposed one can be implemented only by pilot symbols which are used in the channel estimation. In addition, it is analytically confirmed that the proposed scheme can be applied for either MIMO( C-SM(Collaborative-Spatial Multiplexing)) interference or SIMO(Single-Input Multi-Out) interference. The proposed receiver algorithm is verified by simulations over UL-PUSC SR off in IEEE 802.16e standard. From simulation results, it is confirmed that the proposed one can be applicable regardless of the kind of interference. Furthermore, it is verified that the performance is guaranteed even under Ole severe effect of interference and the improvement of system throughput is guaranteed.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.5
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• pp.431-436
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• 2015

As a number of TV programs broadcast today, researches about TV program recommender system have been studied and many researchers have been studying recommender system to produce recommendation with high accuracy. Recommender system recommends TV program to user by using metadata like genre, plot or calculating users' preferences about TV programs. In this paper, we propose a new TV program Collaborative Filtering Recommender System that exploits viewing time pattern like viewing ratio, relation with finish time and recently viewing history to calculate preference for high-quality of recommendation. To verify usefulness of our research, we also compare our method which utilizes viewing time patterns and baseline which simply recommends TV program of user's most frequently watched channel. Through this experiments, we show that our method very effectively works and recommendation performance increases.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.514-524
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• 2007

Recent advances in the speed of multi-rate wireless local area networks (WLANs) and the proliferation of WLAN devices have made rate adaptive, opportunistic scheduling critical for throughput optimization. As WLAN traffic evolves to be more symmetric due to the emerging new applications such as VoWLAN, collaborative download, and peer-to-peer file sharing, opportunistic scheduling at the downlink becomes insufficient for optimized utilization of the single shared wireless channel. However, opportunistic scheduling on the uplink of a WLAN is challenging because wireless channel condition is dynamic and asymmetric. Each transmitting client has to probe the access point to maintain the updated channel conditions at the access point. Moreover, the scheduling decisions must be coordinated at all clients for consistency. This paper presents JUDS, a joint uplink/downlink opportunistic scheduling for WLANs. Through synergistic integration of both the uplink and the downlink scheduling, JUDS maximizes channel diversity at significantly reduced scheduling overhead. It also enforces fair channel sharing between the downlink and uplink traffic. Through extensive QualNet simulations, we show that JUDS improves the overall throughput by up to 127% and achieves close-to-perfect fairness between uplink and downlink traffic.

• YAKHAK HOEJI
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• v.58 no.2
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• pp.141-149
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• 2014

Background: Oriental lifestyle for treating diseases has been developed and well-accepted for a long time among Koreans. Sasang Constitution theory, originated from Korean traditional medicine, suggests that medication treatment should be differentiated by each patient's body classification (So-yang [SY], So-eum [SE], Tae-yang [TY], and Tae-eum [TE]), in contrary to western medicine's theory that medication should be applied equally by disease indication without such classification. However, the pharmacotherapeutic outcomes of these theories have not been compared to date. In this study, we aimed to compare the two theories by evaluating blood pressure (BP), which is lowered as a therapeutic outcome, among hypertensive patients taking angiotensin II receptor blockers (ARBs) or calcium channel blockers (CCBs), two most commonly used antihypertensive classes in Korea. Methods: From April 2006 to June 2012, we retrospectively collected data on hypertensive patients with Sasang Constitution classification at Kyunghee University Hospital at Gangdong, one of the East-West collaborative medical centers in Korea. We collected information on age, gender, underlying diseases, antihypertensive drugs (ARB, CCB, ARB+CCB), and BP by reviewing the electronic medical records. We excluded patients with missing blood pressure at baseline or follow-up, or those who had a change in their antihypertensive drug class during follow-up. Results: We selected a total of 573 patients (SY: 165, SE: 158, TY: 0, TE: 250). Baseline BPs were on average 139.0/82.0 mmHg for SY, 137.8/78.5 mmHg for SE, and 138.7/79.2 mmHg for TE. In all three groups, CCBs were the most prescribed, followed by combination therapy with ARB+CCB, then ARBs. BP reduction after 1 month of initial medication was significantly different among the drug classes, but not in Sasang constitutional classification (ARB [SY: -12.4/-4.7, SE: -12.3/-2.5, TE: -8.6/-1.8], CCB [SY: -12.3/-5.4, SE: -13.0/-2.3, TE: -10.8/-6.0], ARB+CCB [SY: -15.6/-6.7, SE: -18.4/-8.1, TE: -20.2/-6.7], drug [$P{\leq}0.05$/P>0.05], constitutional type [P>0.05/P>0.05]). Conclusion: We observed significant differences in reduction of blood pressure by classes of drugs (ARB+CCB>CCB>ARB) but not by Sasang constitutional classification. Therefore, current approach of antihypertensive pharmacotherapy assisted by Western medicine is appropriate for treatment of hypertension. However, further larger scale or prospective studies are required in order to confirm these results.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.655-660
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• 2001

The performance test of a centrifugal compressor for APU(Auxiliary Power Unit) which is developed by the collaborative research of KARI and Samsung TechWin has been conducted. The investigated compressor consists of a curved inlet, a centrifugal impeller, a channel diffuser and a plenum chamber. The experiments were carried out in an open-loop centrifugal compressor test rig driven by a turbine. For three different diffusers, overall performance data were obtained at 80%, 90% and 97% of design speed. For the initially designed wedge-type diffuser, test results showed that the compressor was operated at a higher mass flow rate than the design requirement. By reducing the diffuser throat area, the compressor operating range was shifted to lower mass flow rate range. The test result of redesigned wedge-type diffuser showed high pressure loss. To reduce the diffuser loss, diffuser inlet radius was increased and airfoil-type of diffuser was adopted. This airfoil-type diffuser showed reasonal results in terms of design requirement.