• Journal of Advanced Marine Engineering and Technology
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• v.28 no.2
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• pp.382-392
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• 2004

The usage of constant velocity (CV) joint is effective for motorboats on gliding regime of the motion. During transition on the gliding when angle of the CV differs from null on driving and driven composite shafts there are moments of the second order. Excitation of oscillations of the second order moments occurs when driving shafts transmits a variable torque. which generates through CV joint a lateral moment acting on the bearing. As a result of oscillations from a resonating harmonic of a shafting the harmonic with the greater or periodically varying amplitude for power condition trough transferring to nominal power 144kW. Beating conditions coincide with third mode having frequency 45.486 Hz. In that case there is high increasing of the equivalent stresses. The forming of the stiffness of the composite material is concerned to use most orientation of the layer angle in the range of $\pm$60 degrees relatively of shaft axis. Application of that angles for layer orientation gives possibility to avoid high disturbance of the shafting for motorboat transition regime.

• Journal of Power System Engineering
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• v.18 no.3
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• pp.73-78
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• 2014

Recently, Free cooling system usage has increased at many buildings in intermediate and winter season. Free cooling system is used to reduce the energy consumption of refrigeration in that season. Free cooling system is refrigeration system using cooled water. In general, this system is applied with the building having refrigeration load at all time such as a data center. In this study, energy consumption of a data center taking free cooling system in Ulsan was evaluated by the software HYSYS. the main result is as in the following : free cooling system is effective from January to April and from November to December. In case of Ulsna in 2013, using free coolng system is able to spend refrigeration energy of about 15% less than existing system. According to this result, it is appropriated that free cooling system is used in building having refrigeration load at all time such as data center.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.6
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• pp.33-38
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• 2011

In recent years, mobile devices and high-hearth because of the multi-functional, battery usage is increasing. But compared to the required computing power increases the battery's energy capacity of the research is going slowly. In this paper we use the battery discharge characteristics, can be used in battery research and to increase the effective capacity, wireless transmission of power from the system just by turning off the technology to extend battery life is explained. Experimental transmission of images through the standard battery drain intervals according to measuring battery life, and applications used in these experiments and heuristic to optimize battery run time was achieved.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.30 no.3
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• pp.130-142
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• 2018

We use heat pumps with thermal storage system to reduce peak usage of electric power during winters and summers. A heat pump stores thermal energy in a thermal storage tank during the night, to meet load requirements during the day. This system stabilizes the supply and demand of electric power; moreover by utilizing the inexpensive midnight electric power, thus making it cost effective. In this study, we propose a system wherein the thermal storage tank and heat pump are modeled using the TRNSYS, whereas the control simulations are performed by (i) conventional control methods (i.e., thermal storage priority method and heat pump priority method); (ii) region control method, which operates at the optimal part load ratio of the heat pump; (iii) load response control method, which minimizes operating cost responding to load; and (iv) dynamic programming method, which runs the system by following the minimum cost path. We observed that the electricity cost using the region control method, load response control approach, and dynamic programing method was lower compared to using conventional control techniques. According to the annual simulation results, the electricity cost utilizing the load response control method is 43% and 4.4% lower than those obtained by the conventional techniques. We can note that the result related to the power cost was similar to that obtained by the dynamic programming method based on the load prediction. We can, therefore, conclude that the load response control method turned out to be more advantageous when compared to the conventional techniques regarding power consumption and electricity costs.

• Journal of the Korea Computer Graphics Society
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• v.17 no.2
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• pp.37-43
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• 2011

OpenVG and SVG Tiny are the most widely used 2D vector graphics technologies for outputs in the various embedded environments including smart phones. Especially, to show high refresh rates on the high resolution screens, it is necessary to effectively accelerate them. Until now, OpenVG and SVG Tiny are available as hardware implementations such as the fully-dedicated graphics chips or full software implementations. Currently available vector graphics silicon chips are relatively expensive and require high power consumption. In contrast, previous full software implementations show lower performance even with almost 100% CPU usages, which would disrupt other multi-threaded applications, In this paper, we present a cost-effective way of accelerating both of OpenVG and SVG Tiny, based on the multimedia-processing hardware, which is wide-spread on the media devices and mobile phones. Through the effective use of these multimedia processors, we successfully accelerated OpenVG and SVG Tiny at least 3.5 times to at most 30 times, even with lower power consumption and lower CPU usage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.936-944
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• 2017

These days, research has been made for a variety of internet of things (IoT) technologies over industrial fields. The current research trend includes the effective adoption of the IoT technologies. But, most IoT researches assume a relatively complicated structure, which consists of sensor devices, gateway, network server, and application server. Of course, the structure has distinct merits in the aspects of flexibility and expandability. However, the complicated structure causes the system implementation overhead including high-cost implementation, and hinders the practical usage of IoT in the industry areas, which require a small-size network. In this paper, we propose a novel IoT system architecture, which guarantees the small-size network and the low-cost implementation. Also, we implement the infrastructure, which includes the RF433-based sensor network, the ARDUINO-YUN based gateway, and the application server using Apache/PHP/MySQL (APM) package. Finally, we present the effective power management scheme among these components.

• Journal of IKEEE
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• v.24 no.2
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• pp.632-637
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• 2020

The non-intrusive load monitoring (NILM) is an important way to cost-effective real-time monitoring the energy consumption and time of use for each appliance in a home or business using aggregated energy from a single recording meter. In this paper, we collect from the smart farm's power consumption data acquisition system to the server via an LTE modem, converted the total power consumption, and the power of individual electric devices into HDF5 format and performed NILM analysis. We perform NILM analysis using open source denoising autoencoder (DAE), long short-term memory (LSTM), gated recurrent unit (GRU), and sequence-to-point (seq2point) learning methods.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.391-395
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• 2016

In the last few decades, global electricity consumption has dramatically increased and has become drastically fluctuating and uncertain causing blackout. Due to the unexpected peak electricity demand, we need significant electricity supply. The solutions to these problems are smart grid system which is envisioned as future power system. Smart grid system can reduce electricity peak demand and induce effective electricity consumption through various price policies, demand response (DR) control methodologies, and state-of-the-art smart equipments in order to optimize electricity resource usage in an intelligent fashion. Demand response (DR) is one of the key technologies to enable smart grid. In this paper, we propose greedy technique for demand response smart grid system. The proposed scheme focuses on minimizing electricity bills, preventing system blackout and sacrificing user convenience.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.52-60
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• 2010

In this paper, we propose a dynamic power management framework for multi-core systems. We reduced the power consumption of multi-core processors such as Intel Centrino Duo and ARM11 MPCore, which have been used at the consumer electronics and personal computer market. Each processor uses a different technique to save its power usage, but there is no embedded multi-core processor which has a precise power control mechanism such as dynamic voltage scaling technique. The proposed dynamic power management framework is suitable for smart phones which have an operating system to provide multi-processing capability. Basically, our framework follows an intuitive idea that reducing the power consumption of idle cores is the most effective way to save the overall power consumption of a multi-core processor. We could minimize the energy consumption used by idle cores with application-targeted policies that reflect the characteristics of active workloads. We defined some properties of an application to analyze the performance requirement in real time and automated the management process to verify the result quickly. We tested the proposed framework with popular processors such as Intel Centrino Duo and ARM11 MPCore, and were able to find that our framework dynamically reduced the power consumption of multi-core processors and satisfied the performance requirement of each program.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.159-179
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• 2022

Often a network becomes complex, and multiple entities would get in charge of managing part of the whole network. An example is a utility grid. While the entire grid would go under a single utility company's responsibility, the network is often split into multiple subsections. Subsequently, each subsection would be given as the responsibility area to the corresponding sub-organization in the utility company. The issue of how to make subsystems of adequate size and minimum number of interconnections between subsystems becomes more critical, especially in real-time simulations. Because the computation capability limit of a single computation unit, regardless of whether it is a high-speed conventional CPU core or an FPGA computational engine, it comes with a maximum limit that can be completed within a given amount of execution time. The issue becomes worsened in real time simulation, in which the computation needs to be in precise synchronization with the real-world clock. When the subject of the computation allows for a longer execution time, i.e., a larger time step size, a larger portion of the network can be put on a computation unit. This translates into a larger margin of the difference between the worst and the best. In other words, even though the worst (or the largest) computational burden is orders of magnitude larger than the best (or the smallest) computational burden, all the necessary computation can still be completed within the given amount of time. However, the requirement of real-time makes the margin much smaller. In other words, the difference between the worst and the best should be as small as possible in order to ensure the even distribution of the computational load. Besides, data exchange/communication is essential in parallel computation, affecting the overall performance. However, the exchange of data takes time. Therefore, the corresponding consideration needs to be with the computational load distribution among multiple calculation units. If it turns out in a satisfactory way, such distribution will raise the possibility of completing the necessary computation in a given amount of time, which might come down in the level of microsecond order. This paper presents an effective way to split a given electrical network, according to multiple criteria, for the purpose of distributing the entire computational load into a set of even (or close to even) sized computational loads. Based on the proposed system splitting method, heavy computation burdens of large-scale electrical networks can be distributed to multiple calculation units, such as an RTDS real time simulator, achieving either more efficient usage of the calculation units, a reduction of the necessary size of the simulation time step, or both.