• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.5B
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• pp.338-347
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• 2012

In this paper, we propose the cooperative transmission scheme (CTS) for system throughput maximization in OFDMA based enterprise femtocell networks. In our scheme, the user equipment (UE) can receive the desired signal from serving femtocell BS (fBS) as well as an adjacent fBS. Thus, UE achieves an improved signal to interference plus and noise ratio (SINR) by the synchronized two signals. The performances of this strategy consider not only the call-level quality of service (QoS) but also the packet-level QoS. We first measure the call blocking probability and utilization for the downlink resources for various offered load in femtocell. Based on that, the outage probability and effective throughput of the system are simulated. Simulation results show that the proposed scheme can reduce the outage probability for enterprise femtocell compared with conventional systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.9C
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• pp.922-927
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• 2009

Utilization problem of the limited spectrum is the one of the most important issues in wireless communication systems. Cognitive radio technique which is finding and utilizing frequency holes is also one of those techniques. Specially, the spectrum sensing technique to detect the primary user signal is a core technology in cognitive radio area. In this paper, we propose the spectrum sensing algorithm using Bussgang theorem. The proposed algorithm calculates the statistical difference between the Gaussian noise and the primary user signal by applying Bussgang theorem to the received signal. The algorithm is not affected by noise uncertainty and can detect the primary user signal in the very low SNR environment. We evaluate the algorithm through computer simulations with 12 ATSC A/74 DTV signal captures based on IEEE 802.22 WRAN and formulate the sensing threshold for the proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.4B
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• pp.227-233
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• 2007

According to the recent development of network technology, the demands of users are diversified and the needs of multimedia traffic are increasing. In general, UDP(User Datagram Protocol) traffic is used to transport multimedia data, which satisfied the real-time and isochronous characteristics. UDP traffic competes with TCP traffic and incur the network congestion. However, TCP traffic performs network congestion control but does not consider the receiver's status. Thus, it is not appropriate in case of streaming services. In this paper, we solve a fairness problems and proposed a network algorithm based on RTP/RTCP(Real-time Transport Protocol/Realtime Transport Control Protocol) in view of receiver status. The POBA(Priority Ordered Buffer Algorithm), which applies priorities in the receiver's buffer and networks, shows that it provides the appropriate environment for streaming services in view of packet loss ratio and buffer utilization of receiver's buffer compared with the previous method.

• Resources Recycling
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• v.22 no.5
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• pp.35-42
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• 2013

Solvent extraction experiments have been performed to investigate an optimum condition to separate Nd and Pr from chloride solutions using PC88A and D2EHPA. In our experimental ranges, the distribution coefficients of Nd were higher than those of Pr. In both of PC88A and D2EHPA extractant system, our results indicated that the increase in concentration ratio of extractant to metal had a great effect on the extraction and separation of the two metals. In extraction with saponified D2EHPA, the initial pH of the aqueous solution and saponification degree had some effect on the extraction of the two metals but little effect on the separation factor.

• Journal of the East Asian Society of Dietary Life
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• v.26 no.1
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• pp.55-62
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• 2016

As interest in health has recently increased, many researchers have investigated the utilization of functional foods by confectioneries and bakeries. However, research on loaf bread containing beets has not been conducted. To investigate the optimal ratio of beet in loaf bread containing beet powder, characteristics of loaf bread according to 2%(B2), 4%(B4), and 6%(B6) beet powder per wheat flour were examined. The experimental results were as follows. Fermentation rate was reduced as content of beet powder increased compared with the control, whereas pH levels of dough and loaf bread significantly increased as content of beet powder increased. As content of beet powder increased, volume of loaf bread decreased, whereas specific volume increased. There was no significant difference in volume of loaf bread between the samples. As far as color changes are concerned, as content of beet powder increased, L value decreased, whereas a and b values increased with significant differences between the samples. Characteristics were examined by sensory evaluation of loaf bread containing beet powder. Color of inner texture and peel color of loaf bread significantly increased as content of beet powder increased. Size of air pores was largest in B4, and there was no significant difference in the uniformity of loaf bread between the control and experiment groups. As content of beet powder increased, rigidity of bread was reduced. Control showed the highest elasticity, whereas moisture level was highest in B2 with no significant differences between the samples. The flavor of beet was stronger as content of beet powder increased. In the preference test, B4 showed the highest preference scores for texture, flavor, taste, and overall likeness but not appearance. The experimental results showed that B4 among all control and experimental groups had the most suitable baking characteristics and an optimum content of beet powder. Therefore, B4 can be considered as the most appropriate for making loaf bread containing 4% beet powder in terms of physical and sensory characteristics. This is a new product that satisfies overall sensory preferences and has improved functionality.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.989-996
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• 2011

An understanding of the concentrated solar flux is critical for the analysis and design of solar-energy-utilization systems. The current work focuses on the development of an algorithm that uses the Monte Carlo ray-tracing method with excellent flexibility and expandability; this method considers both solar limb darkening and the surface slope error of reflectors, thereby analyzing the solar flux. A comparison of the modeling results with measurements at the solar furnace in Korea Institute of Energy Research (KIER) show good agreement within a measurement uncertainty of 10%. The model evaluates the concentration performance of the KIER solar furnace with a tracking accuracy of 2 mrad and a maximum attainable concentration ratio of 4400 sun. Flux variations according to measurement position and flux distributions depending on acceptance angles provide detailed information for the design of chemical reactors or secondary concentrators.

• Clean Technology
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• v.18 no.4
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• pp.410-418
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• 2012

The performance of the ammonia injection gun (AIG) used for maximizing the utilization of reducing agent in the selective catalytic reduction (SCR) system is decided by several parameters such as the pattern of flow distribution, geometry of the air distribution manifold (ADM) and the array and geometry of nozzles. In the study, the uniformity of jet flows from the nozzles in AIG was analyzed statistically by using the computational fluid dynamics (CFD) method to evaluate the role of design parameters on the performance of the SCR system. The uniformity of jet flows from the nozzles is being deteriorated with increasing the supplying flow rate to the AIG. Distribution rates to each branch pipe become lower with decreasing distance to the header, and flow rates from nozzle are also reduced with decreasing distance to the header. The uniformity of jet flows from nozzles becomes stable significantly when the ratio of summative area of nozzles to each sectional area of the branch pipe is below 0.5.

• Korea Journal of Hospital Management
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• v.22 no.4
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• pp.113-122
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• 2017

The purpose of the study was to investigate the patient, disease and hospital characteristics which affect treatment result and early complication for inpatients with psychiatric comorbidity. We analyzed data on 19,806 patients of the Korea Centers for Disease Control and Prevention from 2012 to 2014, Korea National Hospital discharge in-depth data. Frequency, chi-square and logistic regression analysis was performed, using STATA 12.0. According to logistic regression analysis, gender(Odds ratio(OR)=0.776, 95% confidence interval(CI)=0.686-0.878), insurance type(OR=0.853, CI=0.731-0.995), operation(OR=0.424, CI=0.350-0.513), disposition(OR= 39.307, CI=34.394-44.923), beds(300-499, OR=0.470, CI=0.377-0.585; 500-999, OR=0.462, CI=0.395-0.541; 1000 over, OR=0.598, CI=0.480-0.745) were significant predictors of treatment result. And insurance type(OR=1.527, CI=1.241-1.879), CCI(3 over, OR=1.865, CI=1.534-2.266), operation(OR=5.399, CI=4.562-6.389), disposition(OR=1.279, CI=1.013-1.614), district(Metropolitan city, OR=0.519, CI=0.407-0.661; Non-metropolitan OR=0.469, CI=0.383-0.574), beds(500-999, OR=2.799, CI=1.986-3.944; 1000 over, OR=2.109, CI=1.429-3.113) were significant predictors of early complication. This research would be used as a basic data of high quality of medical care and efficient resource utilization in order to detect and minimize the negative medical treatment results of inpatients with psychiatric comorbidity.

• The Transactions of the Korea Information Processing Society
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• v.6 no.3
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• pp.699-709
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• 1999

This paper is aimed at defining items of analysis using SNMP MIB-II for the purpose of managing the Internet based network running on TCP/IP protocol, and then utilize these items, in conjunction with various Web technology and JAVA to design and implement a Web based interface of a management system to analyze the performance and status of the Internet. Among the required items in order to accomplish this task are utilization, interface packet transmission rate, I/O traffic ratio, and so on. Based on these items, the actual analysis is carried out by the Web interface according to the type of analysis. For instance, the interface executes the function of real-time analysis, collection processing, elementary analysis and detailed analysis. The demand of the user is fed into the Web interface which carried out a real-time analysis with the client system which in turn will eventually produce the results of the analysis. In order words, the interface acts as a mediator server for the analysis system. Furthermore, a protocol for exchange of data and messages between the server and the analysis system, the MATP protocol, was also designed. Finally, the results obtained through the system presented in this paper were displayed on screen according to the type of analysis. The system realized in this paper uses We technology and is independent of platform and allows the user to determine the performance of Internet at his/her own host according to the selected items of analysis.

• Korean Journal of Environmental Agriculture
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• v.30 no.3
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• pp.234-242
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• 2011

BACKGROUND: Cultivation of winter cover crops is strongly recommended to increase land utilization efficiency, animal feeding material self-production, and to improve soil and environmental quality. METHODS AND RESULTS: Four major winter crops (barley, Chinese milk vetch, hairy vetch, and rye) having different C/N ratio were seeded in silt loam paddy soil in the November 2007 and the aboveground biomass was harvested on the late May 2008 to evaluate its effectiveness as green manure, and root biomass distribution was characterized at the different depth (0-60 cm) to study its effect on physical properties and carbon sequestration in soil. During this experiment, the naturally growing weed in the rice paddy soil in Korea, short awn foxtail (Alopecurus aequalis Sobol), was considered as control treatment. Above-ground biomass of all cover crops selected was significantly higher than that of the control treatment (2.8 Mg/ha). Comparatively higher above-ground biomass productivity of rye and barley (15.8 and 13.5 Mg/ha, respectively) suggested that these cover crops possibly had the highest potential as a green manure and animal feeding material. Root biomass production of different cover crops followed the same trend as that for their above ground biomass. Rye (Secale cereal) might have the highest potential for soil C accumulation (7893 C kg/ha) by root biomass development, and then followed by barley (6985 C kg/ha), hairy vetch (6467 C kg/ha), Chinese milk vetch (6671 C kg/ha), and control (5791 C kg/ha). CONCLUSION(s): Cover crops like rye and barley having high biomass productivity might be the most effective winter cover crops to increase organic carbon distribution in different soil aggregates which might be beneficial to improve soil structure, aeration etc. and C sequestration.