• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.3
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• pp.128-137
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• 2013

Due to the global warming and air pollution, interest in renewable energies has increased in recent years. In particular, the crisis of the depletion of fossil energy resources in the near future has accelerated the renewable energy technologies. Among the renewable energy resources, oceans covering almost three-fourths of earth's surface have an enormous amount of energy. For this reason, various approaches have been made to harness the tremendous energy potential. In order to achieve two purposes: to improve harbor water quality and to use wave energy, this study proposed a sea water exchange structure applying an Oscillating Water Column (OWC) wave generation system that utilizes the air flow velocity induced by the vertical motion of water column in the air chamber as a driving force of turbine. In particular, the airflow velocity in the air chamber was estimated from the time variations of water surface profile computed by using 3D-NIT model based on the 3-dimensional irregular numerical wave tank. The relationship of the frequency spectrums between the computed airflow velocities and the incident waves was analyzed. This study also discussed the characteristics of frequency spectrums in the air chamber according to the presence of the structure, wave deformations by the structure, and the power of the water and air flows were also investigated. It is found that the phase difference exists in the time series data of water level fluctuations and air flow in the air chamber and the air flow power is superior to the fluid flow power.

• Journal of Food Hygiene and Safety
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• v.30 no.4
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• pp.343-349
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• 2015

A study survey about the rice cake producers completing the food hygiene education in Korea was investigated by characteristics of the rice cake business. The difference between their online and offline awareness of food hygiene education were compared. The average age of rice cake producers is 50 (40.1%), with a high school education (52.6%), 10-20 years of service (34.3%) showed the highest percentage. In relation to sales and work area, workshop personnel are engaged in two (79.5%), An area of less than $99.17m^2$ (92.0%), rent (60.2%) with most paying a monthly rental amount of less than 1 million won (54.8%). There were 228 accident cases in three years (an annual average of 2.4%), manufacturing, Processing the item number was less than 20 types of analysis (86.7%). Case of food hygiene education graduates are women, the lower the age, the higher the education level, was preferred online. Online education was chosen because of 'time, economic, convenience'(73.7%). Online graduates have recognized that health education is more conducive to business. There was no significant difference between the sales online and offline graduates. For hygienic management response was that online graduates are well above the 7.4% offline graduates. Online and offline graduates 60.7% appeared to be more satisfied than the previous training institutions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.795-804
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• 1999

The increasing number of users of mobile communication systems and the corresponding need for increased system capacity require the use of a modulation scheme which is both power and spectrally efficient. In this paper, we numerically calculate the BER performance of DS/CDMA-BPSK system in different fading channel (Rayleigh, Rician, Shadow Rician). Also, we calculate BER performance and the channel capacity of DS/CDMA-BPSK system which is constant or nearly constant envelopes in 3-state fading channel model. The Shadow Rician fading model described in this paper apply the parameters of the Canadian Mobile Satellite (MSAT). And we assume that the 3-state fading channel model is consist of Rayleigh fading state, Rician fading state, and shadow Rician fading state. This model can be used as a basis for the simulation of the land mobile satellite channel. The dynamic 3-state fading channel model is considered corresponding to different environments and the transitions between these environments. From the numerically calculate results, the DS/CDMA-BPSK system with MUI-20, PG-511 can not achieve the BER performance ($P_b\leq10^{-5}$). And the channel capacity did not meet the system requirement. Also, we know that the BER performance is depend m the occupancy probability of radio channel and the degree of shadow. From the results, we how that during shadowed time intervals it is necessary to use some form of error control coding and receiver diversity in order to support reliable data communication.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.1
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• pp.23-34
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• 2010

As the number of user increases according to the improvement of the network, the multi-thread schemes are used to process the service requests of several users who are connected simultaneously. The static thread pool scheme has the problem of occupying a static amount of system resources. On the other hand, the dynamic thread pool scheme can control the number of threads according to the users' requests. However, it has disadvantage that this scheme cannot react to the requests which are larger than the maximum value assigned. In this paper, a web server using a learning-based dynamic thread pool scheme is suggested, which will be running on a server programming of a multi-thread environment. The suggested scheme adds the creation of the threads through the prediction of the next number of periodic requests using Auto Regressive scheme with the web server apache worker MPM (Multi-processing Module). Unlike previous schemes, in order to set the exact number of the necessary threads during the unchanged number of work requests in a certain period, K-Nearest Neighbor algorithm is used to learn the number of threads in advance according to the number of requests. The required number of threads is set by comparing with the previously learned objects. Then, the similar objects are selected to decide the number of the threads according to the request, and they create the threads. In this paper, the response time has decreased by modifying the number of threads dynamically, and the system resources can be used more efficiently by managing the number of threads according to the requests.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.51-56
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• 2014

High-availability seamless redundancy (HSR) is a protocol for fault-tolerant Ethernet (FTE) networks. It provides two frame copies and each copy is forwarded on a separate physical path, which provides zero fail-over time. Therefore, the HSR is becoming a potential candidate for various real-time FTE applications. However, the generation and circulation of unnecessary frames due to the duplication of every sending frame is inherent drawback of HSR. Such drawback degrades the performance of the network and may deplete its resources. In this paper, we present a new algorithm called port locking (PL) based on the media access control (MAC) address to solve the abovementioned problem in popular connected-rings network. Our approach makes the network gradually learn the locations of the source and the destination nodes without relying on network control frames. It then prunes all the rings that do not contain the destination node by locking corresponding rings' entrance ports. With the PL algorithm, the traffic can be significantly reduced and therefore the network performance will be greatly enhanced specially in a large scale connected-rings network. Analytical results are provided to validate the PL algorithm.

• Journal of the Korean Geographical Society
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• v.39 no.3
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• pp.321-343
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• 2004

In principal, the original form of Eupchi landscape in Naepo reflects a traditional idea regarding direction as a connection with one's fortune and naturalization strategy of power. In reality, the weight for the landscape inside the castle town was distinct by locality according to the conditions of natural geographies and main function of the castle town. In other words, the traditional Eupchi landscape was shaped under the fixed principles but it was simultaneously reflecting the local temporality and spatiality. As Chosun Dynasty went under the Japanese colonization, Eupchi in the traditional period started to evolve into a modem city. That is to say, the traditional Eupchi as a political place became to change into the center of capital accumulation, stronghold of economy and education, and center of town beyond the function as a place for government and administration. Therefore, the process of change from the landscape of Eupchi to a modem city was a kind of revolution in the form and function, and it was also a very rapid rearrangement of social space. The disparate element of landscape and double social space worked as a vital inertial element in the urban structure of Naepo area until the post independence and evolution of landscape.

• Journal of Bio-Environment Control
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• v.9 no.1
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• pp.20-26
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• 2000

This study aims at analyzing physical and chemical properties of perlite substrate. Particles of substrate were divided into five categories In size: gravel, very-coarse, coarse, medium and fine grade. Particles of very-coarse and greater grades in perlite substrate occupied 98.5％ of total particles. The air phase of total particles was distributed between 76.8％ and 87.7％ with especially showing that of very-coarse grade was lower than that of coarse or smaller one. However, the liquid and solid phases were vice versa. The cation exchange capacity (CEC) measured was highest in the fine grade. In drainage experiments, the water being drained from the substrate increased with the ratio of drain area, and the 65~70％ of total water reduced within five minutes after irrigation. The drained volume was proportional to the depth of the substrate, which contained about 2mL.cm$^2$：by depth (cm). Due to quick reduction of the water in the substrate, the pF value increased in four minutes after irrigation and showed the highest negative correlation ($R^2$＝0.997) with the moisture content of the substrate. The physical and chemical properties including drainage characteristics analyzed in this study can be, therefore, utilized to control the moisture content of perlite substrate, efficiently.

• Journal of Korean Society of Forest Science
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• v.101 no.3
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• pp.480-487
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• 2012

This study was conducted to search the effects of debris barrier on the benthic macroinvertebrate. Gimcheon was selected as the survey site as it has relatively stable ecosystem with constantly running water. The survey was conducted 6 times before and after the construction of debris barrier from February in 2009 to October in 2010. In the first survey before construction, the identified species were 36 species belonged to 22 families, 9 order, 4 class, and 4 phylum. The figure slightly decreased to 30 species belonged to 18 families, 7 order, 2 class, and 2 phylum in the sixth survey after construction. Before construction, occupation ratio of EPT taxa was showed in the following order: Ephemeroptera (50.0%, 85.0%), Trichoptera (35.3%, 10.0%), and Plecopteran (14.8%, 5.0%). After construction, it was showed in the following order: Trichoptera (50.3%, 68.0%), Ephemeroptera (42.1%, 29.4%), and Plecopteran (7.5%, 2.7%). Ephemeroptera was the highest before construction. Trichoptera increased rapidly after construction. The Diversity, Richness, Evenness, and Dominance indices were all turned low in the second survey right after the construction. However, each index tended to increase with the course of time. In Functional Feeding Groups, GC type was the highest of 60.7% before construction. After construction, SC(53.1%) and FC(35.4%) increased rapidly and they became stabilized since the third survey. The result of this study reveals that debris barrier greatly affects the Aquatic Ecosystem right after its construction, but the system becomes stable and returns to normal with the course of time (about 18 months). Therefore, the study considering various influence factors such as time is required to recover completely through further long-term monitoring.

• Journal of Korean Society of Transportation
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• v.34 no.2
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• pp.191-206
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• 2016

Pedestrian performance measurement has generally used the average values of pedestrian volumes and speeds from a sample, although each individual's pedestrian behavior of the sample is mainly affected by his/her socio-economic and physical characteristics. In particular, if such individual characteristics of the sample have wide variations, the average values are hard to be representative. In this respect, this study found that a platoon of pedestrians had a major effect on their pedestrian flows on sidewalks. The more platoons was mixed on pedestrian roads, the lower pedestrian flow rate was. The indexes such as a pedestrian flow rate and an occupancy space are typically calculated by pedestrian volumes in a given period of time regardless of the existence of a platoon. However, it is plausible that a pedestrian speed and a level of pedestrian congestion can be different under the equal amount of pedestrian volumes. Therefore, this study suggested criteria for determining level of service for pedestrian considering platoon effects and confirmed that two places had different pedestrian LOSs because of the platoon effects, even if they showed the same pedestrian flow rate.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.8
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• pp.619-630
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• 2003

We present a method of runtime configuration scheduling in reconfigurable SoC design. As a model of computation, we use a popular formal model of computation, hierarchical FSM (HFSM) with synchronous dataflow (SDF) model, in short, HFSM-SDF model. In reconfigurable SoC design with HFSM-SDF model, the problem of configuration scheduling becomes challenging due to the dynamic behavior of the system such as concurrent execution of state transitions (by AND relation), complex control flow (HFSM), and complex schedules of SDF actor firing. This makes it hard to hide configuration latency efficiently with compile-time static configuration scheduling. To resolve the problem, it is necessary to know the exact order of required configurations during runtime and to perform runtime configuration scheduling. To obtain the exact order of configurations, we exploit the inherent property of HFSM-SDF that the execution order of SDF actors can be determined before executing the state transition of top FSM. After obtaining the order information and storing it in the ready configuration queue (ready CQ), we execute the state transition. During the execution, whenever there is FPGA resource available, a new configuration is selected from the ready CQ and fetched by the runtime configuration scheduler. We applied the method to an MPEG4 decoder and IS95 design and obtained up to 21.8% improvement in system runtime with a negligible overhead of memory usage.