• The Journal of Information Systems
• /
• v.25 no.4
• /
• pp.63-85
• /
• 2016

Purpose While the popularity of C2C auction platforms such as eBay is gradually decreased, this domain is still undermined to explain online bidding behaviors. Online bidders sometimes engage in impulsive bidding due to some of the online auction characteristics. Therefore, this study develops and tests a model of the impulsive bidding exhibited by online bidders in C2C auction platforms. Based on S-O-R framework, our model posits that both perceived time-pressure and competition intensity affect cognitive absorption which ultimately influences the impulsive bidding. Design/methodology/approach This study collected survey data from 214 C2C auction participants, who have prior experience on impulsive bidding and tested both measurement model and structural model by using CB-SEM (covariate-based structural equation modelling) technique. In this study, by using AMOS 20.0, we tested the measurement model for its overall fit, item reliability, and validity and further conducted the structural model to test our proposed hypotheses. Findings Based on our results, we found that perceived tim-pressure and competition intensity were positively related to cognitive absorption. We also found that the cognitive absorption was positively associated with impulsive bidding behavior. In this study, by developing our research model in S-O-R framework, we provide an alternative theoretical mechanism to describe online impulsive bidding behavior.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.11
• /
• pp.3775-3788
• /
• 2014

With the increasing number of the wireless and mobile networks, the way that people use the Internet has changed substantively. Wireless multimedia services, such as wireless video streaming, mobile video game, and mobile voice over IP, will become the main applications of the future wireless Internet. To accommodate the growing volume of wireless data traffic and multimedia services, cognitive radio (CR) and Information-Centric Network (ICN) have been proposed to maximize the utilization of wireless spectrum and improve the network performance. Although CR and ICN have high potential significance for the future wireless Internet, few studies have been conducted on collaborative operations of CR and ICN. Due to the lack of infrastructure support in multi-hop ad hoc CR networks, the problem is more challenging for video streaming services. In this paper, we propose a Cross-layer Video Streaming Mechanism (CLISM) for Cognitive Radio Ad Hoc Information Centric Networks (CRAH-ICNs). The CLISM included two distributed schemes which are designed for the forwarding nodes and receiving nodes in CRAH-ICNs. With the cross-layer approach, the CLISM is able to self-adapt the variation of the link conditions without the central network controller. Experimental results demonstrate that the proposed CLISM efficiently adjust video transmission policy under various network conditions.

• Journal of the Korea Safety Management & Science
• /
• v.14 no.3
• /
• pp.229-236
• /
• 2012

소프트웨어 기반의 시스템 설계과정에서 설계자가 고려해야 하는 요소들이 다양해지면서 시스템 설계가 점점 어려워지고 있다. 다양한 설계 요소들이 존재하지만 사용자의 특성 및 직무, 사용가능한 정보기술의 특성 등이 핵심적인 요소로 간주된다. 또한 정보기술이 발달하면서 인간과 시스템의 상호작용이 점점 인지적인 특징을 지니게 되었다. 따라서 사용성 높고, 효율적이면서 안전한 소프트웨어 기반의 시스템을 개발하기 위해서는 시스템 설계자가 사용자의 인지적인 요구사항 및 그들의 직무를 시스템 설계과정에서 체계적으로 다룰 수 있어야 한다. 그러나 소프트웨어 공학, 시스템 공학 및 인간-컴퓨터 상호작용 등에서의 전통적인 시스템 설계 방법은 이러한 설계자의 설계활동을 효과적으로 지원하는데 한계가 있었다. 그 대안으로 인지시스템공학(cognitive systems engineering; CSE)은 인간중심의 설계철학을 바탕으로 소프트웨어 기반의 복잡한 시스템 설계과정에서 설계자의 활동을 체계적으로 도와줄 수 있는 유용한 개념과 방법을 제공해주고 있다. CSE는 원래 사람이 실시간으로 감시 및 제어해야 하는 복잡한 사회기술적 시스템(예: 원자력발전소 및 공항관제소)의 분석, 설계 및 평가를 위해 태동한 학문이다. 그러나 CSE에서 제공하는 이론적 및 방법론적 프레임워크는 소프트웨어 기반의 시스템을 설계하는 데에도 유용하게 활용할 수 있는 충분한 가능성을 갖고 있다. 이 논문은 CSE의 근간을 이루는 핵심 개념 및 원칙을 고찰하고 소프트웨어 기반 시스템 설계에의 활용가능성 및 그 방안을 논의한다.

• Journal of Communications and Networks
• /
• v.17 no.2
• /
• pp.172-183
• /
• 2015

To provide an efficient link maintenance approach, we propose a cross layer medium access control (LM-MAC) protocol for multichannel cognitive radio ad hoc networks. Link establishment and reliable transmission are two key problems for a perfect link maintenance mechanism. Since the cognitive user (CU) pairs have to reestablish their links each frame, in the proposed MAC protocol, three different access modes are designed to guarantee transmission efficiency in continuous frames. To enhance the transmission reliability, each CU will create a father spectrum list (FSL) after joining in the network. FSL is divided into three groups of sub-channels with different functions to compensate the packet loss caused by the primary users' appearance and the deep fading. Meanwhile, since the transmitter and the receiver will share the same FSL, periodical cooperative sensing is adopted to further optimize the former problem. Finally, compared with the existing opportunistic multichannel (OMC)-MAC protocol, the proposed LM-MAC protocol achieves better system performance in terms of saturation throughput, continuity and access delay.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.9
• /
• pp.3075-3093
• /
• 2014

In this paper, we consider an advanced wireless user, called primary-secondary user (PSU) who is capable of harvesting renewable energy and connecting to both the primary network and cognitive radio networks simultaneously. Recently, energy harvesting has received a great deal of attention from the research community and is a promising approach for maintaining long lifetime of users. On the other hand, the cognitive radio function allows the wireless user to access other primary networks in an opportunistic manner as secondary users in order to receive more throughput in the current time slot. Subsequently, in the paper we propose the channel access policy for a PSU with consideration of the energy harvesting, based on a Partially Observable Markov decision process (POMDP) in which the optimal action from the action set will be selected to maximize expected long-term throughput. The simulation results show that the proposed POMDP-based channel access scheme improves the throughput of PSU, but it requires more computations to make an action decision regarding channel access.

• Journal of Microbiology and Biotechnology
• /
• v.32 no.2
• /
• pp.212-219
• /
• 2022

Recently, the efficacy of probiotics in treatment of neurodegenerative disorders has been reported in animal and clinical studies. Here, we assessed the effects of Bacillus coagulans JA845 in counteracting the symptoms of D-galactose (D-gal)/AlCl₃-induced Alzheimer's disease (AD) in a mice model through behavioral test, histological assessment and biochemical analysis. Ten weeks of pre-treatment with B. coagulans JA845 prevented cognitive decline, attenuated hippocampal lesion and protected neuronal integrity, which demonstrated the neuroprotective features of B. coagulans JA845 in vivo. We also found that supplementation of B. coagulans JA845 alleviated amyloid-beta deposits and hyperphosphorylated tau in hippocampus of D-gal/AlCl₃-induced AD model mice. Furthermore, B. coagulans JA845 administration attenuated oxidative stress and decreased serum concentration of inflammatory cytokines by regulating the Nrf2/HO-1 and MyD88/TRAF6/NF-κB pathway. Our results demonstrated for the first time that B. coagulans has the potential to help prevent cognitive decline and might be a novel therapeutic approach for the treatment of neurodegenerative diseases.

• Journal of Families and Better Life
• /
• v.16 no.3
• /
• pp.11-24
• /
• 1998

The purpose of this study was to develop the educational program model for adolescent substance abusers in relation to preventive and rehabilitative aspects. This educational program model was developed based not only on the social support theory ecological-developmental approach and cognitive-behavioral approach but also on previous studies. This model can be used both for adolescent substance abusers in early stage and in recovery stage. The main contribution of this study is that adolescent abusers will recover effectively through practicing this educational program model.

• The Mathematical Education
• /
• v.46 no.1 s.116
• /
• pp.1-18
• /
• 2007

The purpose of this study is to describe theoretical orientations guiding research in mathematics motivation and to discuss findings in terms of how they facilitate or inhibit achievement. First, definitions of motivation and distinctions among types of motivation in education are discussed. Second, theoretical approach and representative research from these approach are described. Third, a set of generalizable conclusions about the contextual factors, cognitive processes, and benefits of interventions that affect students' and teachers' motivational attitudes are noted. Last, criticisms regarding instrument, assessment, and use of theories in motivational research are raised.

• Journal of Advanced Navigation Technology
• /
• v.13 no.2
• /
• pp.201-207
• /
• 2009

Recently effective spectrum resource technologies have been studied using a game theorectical approach for cognitive radio networks. Radio resource management is required an effective scheme because the performance of a radio communication system much depends on it's effectiveness. In this paper, we suggest a game theoretical algorithm for adaptive power control which is required an effect scheme in cognitive radio networks. It will be a distributed network. In the network distributed cognitive radio secondary users require an adaptive power control. There are many results which are suggested some possibility of game theoretical approaches for communication resource sharing. However, we suggest a practical game algorithm to achieve Nash equilibrium of all secondary users using a Nash equilibrium theorem in this paper. Particularly, a game model was analyzed for adaptive power control of a cognitive radio network, which is involved in DSSS (Direct Sequence Spread Spectrum) techniques. In case of K=63 and N=12 in the DSSS network, the number of iteration was less than maximum 200 using the suggested algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.9
• /
• pp.3335-3356
• /
• 2015

In this paper, we analyze the connectivity of cognitive radio ad-hoc networks in a log-normal shadow fading environment. Considering secondary user and primary user's locations and primary user's active state are randomly distributed according to a homogeneous Poisson process and taking into account the spectrum sensing efficiency of secondary user, we derive mathematical models to investigate the connectivity of cognitive radio ad-hoc networks in three aspects and compare with the connectivity of ad-hoc networks. First, from the viewpoint of a secondary user, we study the communication probability of that secondary user. Second, we examine the possibility that two secondary users can establish a direct communication link between them. Finally, we extend to the case of finding the probability that two arbitrary secondary users can communicate via multi-hop path. We verify the correctness of our analytical approach by comparing with simulations. The numerical results show that in cognitive radio ad-hoc networks, high fading variance helps to remarkably improve connectivity behavior in the same condition of secondary user's density and primary user's average active rate. Furthermore, the impact of shadowing on wireless connection probability dominates that of primary user's average active rate. Finally, the spectrum sensing efficiency of secondary user significantly impacts the connectivity features. The analysis in this paper provides an efficient way for system designers to characterize and optimize the connectivity of cognitive radio ad-hoc networks in practical wireless environment.