• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.546-551
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• 2014

This paper proposes an opportunistic subchannel allocation (OSA) scheme for relay-based marine communication networks to improve a sum-rate capacity. In most previous works for relay-based networks, each RS delivers the data received from the BS immediately to the corresponding ships in each frame. The achievable data-rate of the two-hop transmission (BS-RS and RS-ship links) is thus limited by the channel quality between BS-RS and RS-ship links. Hence, the radio resources can be wasted according to the difference in the channel quality between the BS-RS link and the RS-ship link. The proposed OSA scheme reduces the waste of radio resources by efficiently and independently allocating the radio resources at the BS-RS link and at the RS-ship link according to the channel quality of each link. The proposed OSA scheme, however, increases the computational complexity, because the BS finds the optimal OFDMA resource by checking the channel quality of all BS-RS links and RS-ship links. The simulation results show that the sum-rate capacity of the proposed OSA scheme improves maximum 14.0% compared with the conventional scheme.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.1
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• pp.229-237
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• 2014

Background: Dentists are typically the first professionals who are approached to treat ailments within the oral cavity. Therefore they should be well-equipped in detecting suspicious lesions during routine clinical practice. This study determined the levels of knowledge on early signs and risk factors associated with oral cancer and identified which factors influenced dentist participation in prevention and early detection of oral cancer. Materials and Methods: A survey on dentists' knowledge and their practices in prevention and early detection of oral cancer was conducted using a 26-item self-administered questionnaire. Results and Conclusions: A response rate of 41.7% was achieved. The level of knowledge on early signs and risk habits associated with oral cancer was high and the majority reported to have conducted opportunistic screening and advised patients on risk habit cessation. Factors that influenced the dentist in practising prevention and early detection of oral cancer were continuous education on oral cancer, age, nature of practice and recent graduation. Notably, dentists were receptive to further training in the area of oral cancer detection and cessation of risk habits. Taken together, the study demonstrated that the dental clinic is a good avenue to conduct programs on opportunistic screening, and continuous education in these areas is necessary to adequately equip dentists in running these programs. Further, this study also highlighted knowledge deficits and practice shortcomings which will help in planning and developing programs that further encourage better participation of dentists in prevention and early detection of oral cancer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1077-1083
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• 2015

In this paper, we introduce an energy-efficient opportunistic interference alignment (OIA) scheme that greatly improves the sum-rates in multi-cell uplink networks. Each user employs optimal transmit vector design and power control in the sense of minimizing the amount of generated interference to other-cell base stations while satisfying a required signal quality. As our main result, it is shown that owing to the reduced interference level, the proposed OIA schemes attains larger sum-rates than those of OIA with no power control for almost all signal-to-noise ratio regions. In addition, when both zero-forcing and minimum mean square error (MMSE) detectors are employed at the receiver along with the OIA scheme, it is shown that the OIA scheme with MMSE detection shows superior performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8A
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• pp.798-803
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• 2006

An opportunistic scheduling is adopted to improve the capacity of the system by exploiting the multiuser diversity of multiuser MIMO(MU-MIMO) systems. However it requires the large amount of feedback carrying the channel quality information(CQI) of each user to the transmitter, The considered per user unitary and rate control(PU2RC) needs to feedback the preferred preceding index and its CQIs, and it has a defect in scheduling the streams for the grouped user. In order to overcome these drawbacks, a novel feedback reduction scheme is proposed in this paper. It employs transmitter controlled preceding and opportunistic feedback(TCP-OFB). The simulation results demonstrate that TCP-OFB shows comparable performance to PU2RC while it only requires far reduced feedback load.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.10
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• pp.4662-4677
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• 2018

The dynamic opportunistic device-to-device (DO-D2D) network will frequently emerge in the fifth generation (5G) wireless communication due to high-density and fast-moving mobile devices. In order to improve the Quality of Experience (QoE) of users with different computing capacity devices in the DO-D2D network, in this paper, we focus on the study of how to reduce the packets retransmission delay and satisfy heterogeneous devices. To select as many devices as possible to transmit simultaneously without interference, the concurrent transmitters-selecting algorithm is firstly put forward. It jointly considers the number of packets successfully received by each device and the device's connectivity. Then, to satisfy different devices' demands while primarily ensuring the base-layer packets successfully received by all the devices, the layer-cooperation instantly decodable network coding is presented, which is used to select transmission packets combination for each transmitter. Simulation results illustrate that there is an appreciable retransmission delay gain especially in the poor channel quality network compared to the traditional base-station (BS) retransmission algorithm. In addition, our proposed algorithms perform well to satisfy the different demands of users with heterogeneous devices.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.61-67
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• 2016

Opportunistic incremental relaying (OIR) system effectively overcomes the degradations caused by the fading of the wireless channel, and efficiently utilizes the wireless resources. Most of the OIR studies, however, assume spatially fixed relays. The user terminals which are usually served as relays move continuously, the assumption that the relays are fixed is not realistic. In this paper, the location of the spatially random user terminals are modeled by the Poisson point process, and the performance of an OIR system is derived. We noticed that the performance of the OIR system improves with the spatially random relays as well as with the fixed relays. Also the intensity of the relays and the transmitting directions toward the destination affect the performances. The performances of the maximal ratio combining (MRC) and the selection combining (SC) at the destination are compared.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.9
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• pp.5101-5105
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• 2013

The incidence and mortality of cervical cancer remains high in India even after sixty years of introduction of the Pap smear (cervical cytology) which is an effective means of identifying preinvasive lesions of carcinoma cervix. The morbidity and mortality due to cervical cancer has come down drastically in countries with well established screening programmes at national level. This study aims at screening women for cervical cancer opportunistically during their visit to hospital and to study various types of neoplastic and non-neoplastic lesions of the cervix by cervical smear study (Pap smear study). In the present study, a total of 350 cervical smears were studied. The age of patients ranged from 19 years to 80 years with mean age being 37.5 years. Out of 350 cases, the diagnosis of neoplasia was given in 43 cases and 258 cases were diagnosed as inflammatory smears. Forty-cases were normal and 9 cases were inadequate to evaluate. Forty-three patients who were found to have neoplastic lesions on cytology were referred for further investigations like colposcopy and biopsy to confirm the diagnosis and avail proper treatment. Limitation of the present study was small sample size as all female patients aged between 20 and 60 years visiting hospital were not included in the screening, other screening tests like VIA (visual inspection with acetic acid test) and HPV DNA (human papilloma virus) tests were not done. Until the time centrally organised screening programmes for cervical cancer are established in India, arrangements should be made for hospital based opportunistic screening for all women attending hospital. The cost effectiveness of different screening tests for cervical cancer should be evaluated.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.2
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• pp.244-255
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• 2009

The purpose of this study was 1) to inquire into characteristics of apparel manufacturers and distributors in China, 2) to classify private Guanxi and organizational relationship type, 3) to find differences in private Guanxi to enterprise type and the class of participations' position, and 4) to also find effects of private Guanxi on organizational relationship. Apparel manufacturers and distributors in China participated in the study. Random sampling method was used to collect the data. Data from 173 questionnaires were used for the statistical analysis. Descriptive analysis, factor analysis, Cronbach's alpha coefficient, t-test, and regression analysis were conducted. Two factors of private Guanxi were classified(i.e., affective Guanxi, instrumental Guanxi). Three factors of organizational relationship type were identified(i.e., opportunistic relationship, cooperative relationship, vertical relationship). The results indicated that distributors regarded affective Guanxi as important more than manufactures and employees regarded affective Guanxi and instrumental Guanxi as important more than presidents. Distributors regarded cooperative relationship as important more than manufactures. Employees regarded organizational relationship as important more than presidents. Affective Guanxi positively affected on cooperative relationship and vertical relationship but negatively affected on opportunistic relationship. Instrumental Guanxi positively affected on opportunistic relationship and vertical relationship. The result of this study may give valuable information to retail merchandisers and strategists who participated in fashion business in China.

• Tuberculosis and Respiratory Diseases
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• v.45 no.2
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• pp.465-469
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• 1998

Acute respiratory failure with diffuse pulmonary infiltration was occurred in a patient with malignant lymphoma 1month after the $8^{th}$ CHOP chemotherapy. The ground glass and consolidation appearances on chest C-T in this immunodeficient patient could be presented in many clinical situations such as pneumonia by opportunistic infections (fungal, parasites, viral, and usual bacterial pathogens), anti-tumor drug's pulmonary toxicity and tumor invasion. And the other diseases of acute interstitial pneumonitis, alveolar proteinosis, BOOP, puhnonary edema and alveolar hemorrhage, which could present the same radiological findings, should included in differential diagnosis. This patient was diagnosed as the opportunistic pneumonia by Pneumocystis carinii and probably Cytomegalovirus through bronchoalveolar lavage and transbronchial lung biopsy

• Journal of Communications and Networks
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• v.15 no.1
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• pp.77-86
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• 2013

Cognitive radio (CR) has emerged as one of effective methods to enhance the utilization of existing radio spectrum. Main principle of CR is that secondary users (SUs) are allowed to use the spectrum unused by primary users (PUs) without interfering PU's transmissions. In this paper, PUs operate on a slot-by-slot basis and SUs try to exploit the slots unused by PUs. We propose OSA protocols in the single channel and we propose an opportunistic spectrum access (OSA) protocols in the multi-channel cognitive radio networks with one control channel and several licensed channels where a slot is divided into contention phase and transmission phase. A slot is divided into reporting phase, contention phase and transmission phase. The reporting phase plays a role of finding idle channels unused by PUs and the contention phase plays a role of selecting a SU who will send packets in the data transmission phase. One SU is selected by carrier sense multiple access / collision avoidance (CSMA/CA) with request to send / clear to send (RTS/CTS) mechanism on control channel and the SU is allowed to occupy all remaining part of all idle channels during the current slot. For mathematical analysis, first we deal with the single-channel case and we model the proposed OSA media access control (MAC) protocol by three-dimensional discrete time Markov chain (DTMC) whose one-step transition probability matrix has a special structure so as to apply the censored Markov chain method to obtain the steady state distribution.We obtain the throughput and the distribution of access delay. Next we deal with the multi-channel case and obtain the throughput and the distribution of access delay by using results of single-channel case. In numerical results, our mathematical analysis is verified by simulations and we give numerical results on throughput and access delay of the proposed MAC protocol. Finally, we find the maximum allowable number of SUs satisfying the requirements on throughput and access delay.