• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2011년도 춘계학술대회 논문집
• /
• pp.618-626
• /
• 2011

Recent development of related technologies and efficient utilization of the entire country for the purpose of railway construction, and plans are being accelerated. the railway noise has been improved by increasing the high speed railway station, and accelerating the existing trains. Nord2000 which is an overseas noise prediction equation could not be applied directly to the domestic railway vehicles. So the specific vehicles in the Nordic countries which is a similar specification to domestic trains should be selected. Nord2000's accuracy was compared to Schall03, CRN's. Prediction of Ground impedance and Roughness class were carried out at different. In this paper, the result of selected vehicles for Nord2000 was as follows. S-1aX2 was for express trains, N-$^*2c$-3b was for Mugunghwa, S-Pass/wood was for Saemaul, N-4a was for freight trains, N-3a was for subway, the calculation time for Nord2000 took longer than others, in addition, Ground absorption was indispensable to calculate a noise map for Nord2000. As a result, CRN's prediction noise levels at Wonju-si was closest to the measurements. However, the predicted noise levels of Nord2000 was the most accurate.

• 간호행정학회지
• /
• 제16권3호
• /
• pp.348-359
• /
• 2010

Purpose: This study aimed to evaluate the performance of Clinical Research Nurses (CRNs) and the importance of their roles at the Regional Clinical Trial Centers (RCTCs). Method: A questionnaire focused on the role of CRNs was crafted by a researcher and the content validity was verified by a panel of experts on clinical research. The subjects of this study were 91 CRNs and Clinical Research Coordinators (CRCs), who were Korean registered nurses working at nine RCTCs. 77 subjects yielded valid data were analyzed using descriptive analysis, the Mann-Whitney U test, Spearman's rank order correlation coefficient, and Kruskal-Wallis test. Results: The performance of CRNs and the recognition in the importance of their roles were statistically significant different in age, education, CRN careers, positions, employment status and the phase of clinical trial. The role of direct caregiver was performed most often by CRNs. The role of coordinator of care and research (pre-study) was considered the most important role but performed the least frequent. Conclusions: The role of CRNs can easily be differentiated from CRCs who are not registered nurses. The domains of CRNs should be clearly identified and established. Moreover, research should be carried out on CRN training programs to cultivate competence in CRNs.

• 한국결정성장학회지
• /
• 제27권5호
• /
• pp.223-228
• /
• 2017

Aluminum nitride (AlN) powder was successfully synthesized at low temperature via carbothermal reduction and nitridation (CRN) assisted by microwave heating. The synthesis processes of AlN powder were investigated with X-ray diffraction, FE-SEM, FT-IR and TGA/DSC. Aluminum nitrate was used as an oxidizer and aluminum source, urea as fuel, and glucose as carbon source. These starting materials were mixed with D.I water and reacted in a flask at $100^{\circ}C$ for 20 minutes. After the reaction was finished, black foamy intermediate product was formed, which was considered to be an amorphous $Al_2O_3$ particles through intermediate product obtained by solution combustion synthesis (SCS) at the results of X-ray diffraction patterns and FT-IR. This intermediate product was nitridated at temperatures of $1300^{\circ}C$ and $1400^{\circ}C$ in $N_2$ atmosphere by a microwave heating furnace and then decarbonated at $600^{\circ}C$ for 2 hours in air. It should be noticed from FE-SEM images that as nitridated particles, identified as AlN from X-ray diffraction patterns, are covered with carbon residues. After decarbonating the nitridated powders, the spherical pure AlN powders were obtained without alumina and their particle sizes were dependent on the nitridating temperature with high temperature of $1400^{\circ}C$ giving large particles of around 70~100 nm.

• Journal of Communications and Networks
• /
• 제17권4호
• /
• pp.406-418
• /
• 2015

Cognitive radio networks (CRNs) have emerged as a promising solution to the problem of spectrum under utilization and artificial radio spectrum scarcity. The paradigm of dynamic spectrum access allows a secondary network comprising of secondary users (SUs) to coexist with a primary network comprising of licensed primary users (PUs) subject to the condition that SUs do not cause any interference to the primary network. Since it is necessary for SUs to avoid any interference to the primary network, PU activity precludes attempts of SUs to access the licensed spectrum and forces frequent channel switching for SUs. This dynamic nature of CRNs, coupled with the possibility that an SU may not share a common channel with all its neighbors, makes the task of multicast routing especially challenging. In this work, we have proposed a novel multipath on-demand multicast routing protocol for CRNs. The approach of multipath routing, although commonly used in unicast routing, has not been explored for multicasting earlier. Motivated by the fact that CRNs have highly dynamic conditions, whose parameters are often unknown, the multicast routing problem is modeled in the reinforcement learning based framework of learning automata. Simulation results demonstrate that the approach of multipath multicasting is feasible, with our proposed protocol showing a superior performance to a baseline state-of-the-art CRN multicasting protocol.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권12호
• /
• pp.3037-3054
• /
• 2013

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users' cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU's spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.

• Journal of Communications and Networks
• /
• 제18권1호
• /
• pp.112-122
• /
• 2016

Cognitive radio (CR) is considered an attractive technology to deal with the spectrum scarcity problem. Multi-radio access technology (multi-RAT) can improve network capacity because data are transmitted by multiple RANs (radio access networks) concurrently. Thus, multi-RAT embedded in a cognitive radio network (CRN) is a promising paradigm for developing spectrum efficiency and network capacity in future wireless networks. In this study, we consider a new CRN model in which the primary user networks consist of heterogeneous primary users (PUs). Specifically, we focus on the energy-efficient resource allocation (EERA) problem for CR users with a special location coverage overlapping region in which heterogeneous PUs operate simultaneously via multi-RAT. We propose a two-tier crossover genetic algorithm-based search scheme to obtain an optimal solution in terms of the power and bandwidth. In addition, we introduce a radio environment map to manage the resource allocation and network synchronization. The simulation results show the proposed algorithm is stable and has faster convergence. Our proposal can significantly increase the energy efficiency.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 G
• /
• pp.3313-3315
• /
• 1999

Si direct bonding(SDB) technology is very attractive for both Si-on-insulator(SOI) electric devices and MEMS applications because of its stress free structure and stability. This paper presents on pre-bonding according to HF pre-treatment conditions in Si wafer direct bonding. The characteristics of bonded sample were measured under different bonding conditions of HF concentration, and applied pressure. The bonding strength was evaluated by tensile strength method. The bonded interface and the void were analyzed by using SEM and IR camera respectively. A bond characteristic on the interface was analyzed by using IT- IR. Si-F bonds on Si surface after HF pre-treatment are replaced by Si-OH during a DI water rinse. Consequently, hydrophobic wafer was bonded by hydrogen bonding of Si $OH{\cdots}(HOH{\cdots}HOH{\cdots}HOH){\cdots}OH-Si$. The bond strength depends on the HF pre-treatment condition before pre- bonding (Min:$2.4kgf/crn^2{\sim}Max:14.9kgf/crn^2$)

• ETRI Journal
• /
• 제44권3호
• /
• pp.400-412
• /
• 2022

In cognitive radio networks (CRNs), the computational complexity of resource allocation algorithms is a significant problem that must be addressed. However, the high computational complexity of the optimal solution for tackling resource allocation in CRNs makes it inappropriate for use in practical applications. Therefore, this study proposes a power-based pricing algorithm (PPA) primarily to reduce the computational complexity in downlink CRN scenarios while restricting the interference to primary users to permissible levels. A two-stage approach reduces the computational complexity of the proposed mathematical model. Stage 1 assigns subcarriers to the CRN's users, while the utility function in Stage 2 incorporates a pricing method to provide a power algorithm with enhanced reliability. The PPA's performance is simulated and tested for orthogonal frequency-division multiplexing-based CRNs. The results confirm that the proposed algorithm's performance is close to that of the optimal algorithm, albeit with lower computational complexity of O(M log(M)).

• 한국콘텐츠학회논문지
• /
• 제16권4호
• /
• pp.347-358
• /
• 2016

ICT분야는 지난 20여 년간 산업촉진 및 효율성 제고 측면에서 강력한 정부주도로 정보화를 추진하여 많은 성과를 거두었고, 현재에도 국내 산업을 견인하고 있다. ICT분야가 주목을 받는 만큼 특허 분쟁도 심화되었고 ICT분야의 특허 확보도 매우 중요해졌다. 특허는 기업의 기술혁신의 수준을 평가하는 대표적인 척도로 인식되어 기업의 성과를 측정하는데 많이 활용되고 있다. 그러나 기존의 연구는 특허의 양(量)적인 성장이 기업 경영성과에 영향을 미치는가에 대한 연구가 대부분으로 질(質)적 수준에 대한 연구는 미진하였다. 본 연구에서는 국가산업을 기인하는 ICT 기업이 보유한 특허의 질적 수준이 경영성과에 영향을 미치는지 분석하였다. 즉, 특허의 질적 수준을 측정하는 척도인 기술혁신 활동 집중도가 기업의 성장성과 수익성에 영향을 미치는지 분석하였다. 연구결과, 기술혁신 활동 집중도의 현시기술우위 지수(RTA)와 집중률 지수(CRn)는 기업의 성장성과 수익성에 유의한 영향을 미치는 것으로 나타났다. 본 연구를 통하여 ICT분야에서 특허의 질적 수준이 높을수록 기업의 성장성 및 수익성에 정(+)의 영향을 미칠 수 있다는 것을 검증한 바, 특허의 질적 수준 연구가 미미한 상황에서 차후 연구에 대한 새로운 출발점을 제시할 수 있을 것으로 기대된다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2004년도 제26회 학술발표회 초록집
• /
• pp.64-64
• /
• 2004