• Journal of Climate Change Research
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• v.8 no.1
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• pp.21-30
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• 2017

Recently, There has been much discussed about unused space. This space can be used in a variety of ways. Utilizing it as a facility, craft shop, and utilizing renewable energy generation facilities. Especially, in terms of climate change should be supplied renewable energy. Renewable energy needs to be developed in terms of responding to climate change, and the recent Paris agreement is also emphasizing the importance of renewable energy. In particular, renewable energy needs to be widely disseminated. And renewable energy is limited space. In this regard, idle land can provide opportunities for securing new renewable energy generation facilities. The introduction of new and renewable energy facilities in idle space can enhance the self-sufficiency rate of the local community, which is significant in terms of responding to climate. In this study, to investigate the possibility of utilizing a unused space for a photovoltaic power generation facility, we investigated the amount of electricity which could be generated through photovoltaic power generation, and the economic effects, using a RETScreen model. The results showed that 9,738 MWh of power can be generated and that $4,540tCO_2eqcan$ be saved. Regarding the economic effect, the net present value of the facility was shown to be 2,247,389,020 KRW. As the net present value was shown to be positive, we believe that the installation of a photovoltaic power generation facility in an unused space would have a positive economic effect. We found the net present value following the fluctuation of the SMP price to be positive, though there was some variation. However, as the economic efficiency was shown to be low because the net present value in relation to the maintenance costs was negative, we believe that maintenance costs must be taken fully into account when evaluating economic efficiency. In particular, as subsidies can be used to cover maintenance costs which must be factored into photovoltaic power generation, we believe that photovoltaic power generation can have an economic effect. Because spaces not currently in use can have a positive economic effect as renewable energy power generation facilities, and can also contribute to the reduction of greenhouse gas emissions, unused spaces are thought to greatly help local governments to cope with climate change as well as reinforcing their related capabilities. We believe our study will help local governments with decisions relating to unused real estate utilization in the future.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.3117-3129
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• 2022

Deeply understanding the phase change of thin liquid sodium film inside wick pore is very important for further studying high-temperature sodium heat pipe's heat transfer. For the first time, the evaporation and condensation of thin liquid sodium film are investigated by the Lennard-Jones potential of molecular dynamics. Based on the startup and normal operation of the sodium heat pipe, three different cases are simulated. First, the equilibrium is achieved and the Mass Accommodation Coefficients of the three cases are 0.3886, 0.2119, 0.2615 respectively. Secondly, the non-equilibrium is built. The change of liquid film thickness, the number of gas atoms, the net evaporation flux (J_net), the heat transfer coefficient (h) at the liquid-gas interface are acquired. Results indicate that the magnitude of the J_net and the h increase with the basic equilibrium temperature. In 520-600 K (the startup of the heat pipe), the h has approached 5-6 W m^-2 K^-1 while liquid film thickness is in 11-13 nm. The fact shows that during the initial startup of the sodium heat pipe, the thermal resistance at the liquid-gas interface can't be negligible. This work is the complement and extension for macroscopic investigation of heat transfer inside sodium heat pipe. It can provide a reference for further numerical simulation and optimal design of the sodium heat pipe in the future.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.37 no.3
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• pp.232-239
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• 2001

For the purpose of providing the basic data on the improved fishing gear and the man power saving, which contribute to enhance fishing efficiency of set net in the coast of Jeju Island, this study analyzed the catch of two fishing place for the past 3 years in order to compare the fishing efficiency between rectngular set net and pound net, which have been used for fishing with being attached to the set net fishing place in coast of Jeiu Island, Thereby the result is as follows ; 1. When using pound net, the total amount of catch during 1997 to 1999 was 2 times more than that of when using rectangular set net. 2. When using Pound net, the catch of squid, mackerel, rabbit fish and Yellow tail during 1997 to 1999 was 1.8 times more than that of when using rectangular set net.. 3. In case of rectangular set net, CPUE marked 10.1㎏ with horse amckerel, 20.5㎏ with squid, 18.0㎏ with rabbit fish and 2.2㎏ with Yellow tail, and in case of pound net, CPUE marked 57.5 ㎏ with horse mackerel, 30.0㎏ with squid, 25.0 with rabbit fish and 4.7㎏ with yellow tail, and on the whole CPUE of poind net marked higher. 4. In case of rectangular set net, the catch ratio for fishing operation marked 64% with horse mackerel, 79% with squid, 39% with rabbit fish and 14% with yellow tail, and in case of pound net, the catch ratio fishing operation marked 18% with horse mackerel, 85% with souid 40% with rabbit fish and 14% with yellow tail, and accordingly it showed the result that the catch ratio for fishing operation was higher with the case of rectangular set net, but higher with the case of pound net.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.32 no.1
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• pp.7-15
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• 1996

Full scale experiment was carried out in the southern sea of Korea to compare some important factors tested in the model experiment. The results obtained can be summarized as follows ; 1. The changing aspect of mouth performance of the full scale net was almost coincided with the results obtained by the model experiment. The vertical opening(H) and the opening area(S) can be expressed as a function of the towing velocity(V) as H=48.78. $e^0.38V$(unit: m, k't) S= 1,443 .$e^-0.25V$(unit: $m^2V$, k't) 2. The changing aspect of working depth of the full scale net was almost coincided with the results obtained by the model experiment. The depth(D) can be expressed as a function of the towing velocity(V) and the warp length(L) as D=92.49.$V^1.37$(unit: m, k't, L= 150m) D= 12.07+0.32. L (unit: m, V=2k't) [)= - 7.90+0.22 . L (unit: m, V=3k't) 3. Some problems were found to operate A - type full scale net by common bottom pair trawlers. The problems can be summarized as follows; (1) Entangling of wing and square head ropes while net casting.(2) Man power needed and time spent for net hauling by common bottom trawlers increased considerably.( 3) Tearing of nettings caused by over -load of tension and entangling of net pendant while net hauling. To solve these problems, the trawlers are favorable to be equipped with variable pitch propeller and llet drum. While the net is favorable to be constructed with trifurcated net pendant in stead of quadrifurcated net pendant used at present.

• IEMEK Journal of Embedded Systems and Applications
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• v.15 no.5
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• pp.227-234
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• 2020

In this paper, we propose wav-U-Net to improve speech enhancement in heavy noisy environments, and it has implemented three principal techniques. First, as input data, we use 128 modified Mel-scale filter banks which can reduce computational burden instead of 512 frequency bins. Mel-scale aims to mimic the non-linear human ear perception of sound by being more discriminative at lower frequencies and less discriminative at higher frequencies. Therefore, Mel-scale is the suitable feature considering both performance and computing power because our proposed network focuses on speech signals. Second, we add a simple ResNet as pre-processing that helps our proposed network make estimated speech signals clear and suppress high-frequency noises. Finally, the proposed U-Net model shows significant performance regardless of the kinds of noise. Especially, despite using a single channel, we confirmed that it can well deal with non-stationary noises whose frequency properties are dynamically changed, and it is possible to estimate speech signals from noisy speech signals even in extremely noisy environments where noises are much lauder than speech (less than SNR 0dB). The performance on our proposed wav-U-Net was improved by about 200% on SDR and 460% on NSDR compared to the conventional Jansson's wav-U-Net. Also, it was confirmed that the processing time of out wav-U-Net with 128 modified Mel-scale filter banks was about 2.7 times faster than the common wav-U-Net with 512 frequency bins as input values.

• Journal of Internet Computing and Services
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• v.18 no.5
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• pp.61-67
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• 2017

In this paper we introduce two experimental results from classification of Instagram images and some valuable lessons from them. We have tried some experiments for evaluating the competitive power of Convolutional Neural Network(CNN) in classification of real social network images such as Instagram images. We used AlexNet and ResNet, which showed the most outstanding capabilities in ImageNet Large Scale Visual Recognition Challenge(ILSVRC) 2012 and 2015, respectively. And we used 240 Instagram images and 12 pre-defined categories for classifying social network images. Also, we performed fine-tuning using Inception V3 model, and compared those results. In the results of four cases of AlexNet, ResNet, Inception V3 and fine-tuned Inception V3, the Top-1 error rates were 49.58%, 40.42%, 30.42%, and 5.00%. And the Top-5 error rates were 35.42%, 25.00%, 20.83%, and 0.00% respectively.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.11
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• pp.2419-2422
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• 2010

The current marine internal communication systems are usually composed of NMEA0183, NMEA2000, and MiTS protocols which are located on the physical layer based on RS-422, RS-485, CAN, and EtherNet. However, general vessel communication method have a weak point that must establish the extra private line. But, the power line communication has advantage over general vessel communication method as it uses AC220V/DC24V without changing line. Therefore, we will propose a new bridge based on the DC-PLC(power Line communication) technique which support the NMEA0183 protocol inside vessel network systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.197-200
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• 2011

Many routing protocols have been proposed for low-power and ad-hoc networks where energy awareness and reliability are essential design issues. This paper proposes a dynamic routing protocol for low-power and ad-hoc networks. A dynamic path cost function is defined considering the constraints and characteristics of low-power and ad-hoc networks. The cost function can be applied flexibly depending on the characteristics of the networks. The performance of the proposed method is evaluated using a QualNet network simulator.

• Nuclear Engineering and Technology
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• v.54 no.5
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• pp.1813-1824
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• 2022

This paper shows the verification work of SARAX code system in the reactor core transient calculation based on the simplified EBR-II Benchmark. The SARAX code system is an analysis package developed by Xi'an Jiaotong University and aims at the advanced reactor R&D. In this work, a neutron-photon coupled power calculation model and a spatial-dependent reactivity feedback model were introduced. To verify the models used in SARAX, the EBR-II SHRT-45R test was simplified to an ULOF transient with an input flowrate change curve by fitting from reference. With the neutron-photon coupled power calculation model, SARAX gave close results in both power fraction and peak power prediction to the reference results. The location of the hottest assembly from SARAX and reference are the same and the relative power deviation of the hottest assembly is 2.6%. As for transient analysis, compared with experimental results and other calculated results, SARAX presents coincident results both in trend and absolute value. The minimum value of core net reactivity during the transient agreed well with the reported results, which ranged from -0.3$ to -0.35$. The results verify the models in SARAX, which are correct and able to simulate the in-core transient with reliable accuracy.

• IE interfaces
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• v.17 no.2
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• pp.200-207
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• 2004

Because the designed workflow may contain potential errors which may result in deadlocks, livelocks and so on, it is important to analyze the correctness of a workflow definition before it is put into the run time environment. Proposed in this paper is a transformation procedure of an UML activity diagram into a Petri net for the analysis of a workflow. By combining the strengths of easy-to-use functionality of an activity diagram and the analysis power of a Petri net, workflow analysts in the enterprise can model and analyze various kinds of workflow definition more easily and accurately.