• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.3 s.357
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• pp.18-25
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• 2007

In sensor networks, sensor nodes have limited computational capacity, power and memory. Thus energy efficiency is one of the most important requirements. How to extend the lifetime of wireless sensor networks has been widely discussed in recent years. However, one of the most effective approaches to cope with power conservation, network scalability, and load balancing is clustering technique. The function of a cluster head is to collect and route messages of all the nodes within its cluster. Cluster heads must be changed periodically for low energy consumption and load distribution. In this paper, we propose an energy-aware cluster head selection algorithm and Distance Estimation-based distributed Clustering Algorithm (DECA) in wireless sensor networks, which exchanges cluster heads for less energy consumption by distance estimation. Our simulation result shows that DECA can improve the system lifetime of sensor networks up to three times compared to the conventional scheme.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.8
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• pp.40-47
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• 2010

In this paper, we propose a probability method to determine minimum capacity of energy storage system(ESS) for Micro Grid(MG). Because of high capital cost of ESS, it's very important to determine optimal capacity of ESS and for stable operation of MG and we should determine minimum capacity of ESS. The proposed method has abilities to consider forced outage rate of generators and intermittent of non-dispatchable generators and minimum capacity make MG keep energy balancing by oneself.

• Journal of Biomedical Engineering Research
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• v.22 no.6
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• pp.543-550
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• 2001

In this study, ground reaction force(GRF) and energy consumption of fixed. single-axis and multi-axis Prosthetic ankle assemblies were investigated to show the biomechanical evaluation for trans-tibial amputees. In the experiments. two male and two female trans-tibial amputees were tested with fixed, sin91e-axis and multi-axis Prosthetic ankle assembly. A three-dimensional gait analysis was carried out to derive the ratio of GRF to weight as the percentage of total stance Phase for nine Points Energy consumption of each Prosthetic ankle assembly was measured while subjects walked at 2km/h. 3km/h and the most comfortable walking speed on the treadmill The results showed that multi-axis ankle was superior to the other two ankle assemblies for the characteristic of forwarding and breaking forces. Fixed ankle was relatively superior to the other two ankle assemblies for gait balancing and movement of the center fur mass Compared to the other ankle assembly. sing1e-axis type showed lower energy consumption over 2.3km/h walking speed .

• Journal of Industrial Technology
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• v.40 no.1
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• pp.7-12
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• 2020

Lithium-ion cells have become the go-to energy source across all applications; however, dendritic growth remains an issue to tackle. While there have been various research conducted and possible solutions offered, there is yet to be one that efficiently rules out the problem without, however, introducing another. This paper seeks to present a fast charging method and system to which lithium-ion batteries are charged while maintaining their lifetime. In the proposed method, various lithium cells are charged under multiple profiles. The parameters of charge profiles that inflict damage to the cell's electrodes are obtained and used as thresholds. Thus, during charging, voltage, current, and temperature are actively controlled under these thresholds. In this way, dendrite formation suppressed charging is achieved, and battery life is maintained. The fast-charging system designed, comprises of a 1.5kW charger, an inbuilt 600W battery pack, and an intelligent BMS with cell balancing technology. The system was also designed to respond to the aging of the battery to provide adequate threshold values. Among other tests conducted by KCTL, the cycle test result showed a capacity drop of only 0.68% after 500 cycles, thereby proving the life maintaining capability of the proposed method and system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.1B
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• pp.10-15
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• 2009

Recently, there are tendency that wireless sensor network is one of the important techniques for the future IT industry and thereby application areas in it are getting growing. Researches based on the hierarchical network topology are evaluated in good at energy efficiency in related protocols for wireless sensor network. LEACH is the best well known routing protocol for the hierarchical topology. However, there are problems in the range of message broadcasting, which should be expand into the overall network coverage, in LEACH related protocols. Thereby, this paper proposes a new clustering scheme to solve the co-shared problems in them. The basic idea of our scheme is using the inherent memory restrictions in sensor nodes. The results show that the proposed scheme could support the load balancing by distributing the clusters with a reasonable number of member nodes and thereby the network life time would be extended in about 1.8 times longer than LEACH.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.111-118
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• 2010

Recently, LCD TV using LED backlight has a great attention due to its low power consumption, slim construction, mercury free, wide color gamut and fast response. For the uniform brightness of the LCD panel, multi channel LEDs and DC/DC converter for each LED are required in conventional system. Therefore energy conversion efficiency is poor, the system size bulky and the cost of production high. To overcome these above mentioned drawbacks, a new current-balancing multi-channel LED driver is proposed in this paper. It can not only drive multi-channel LEDs with one DC/DC converter but also provide all LEDs with constant balanced current. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for 46" LCD TV.

• Korea Journal of Cosmetic Science
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• v.1 no.1
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• pp.1-9
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• 2019

The identification of compounds with anti-senescence activity in cell culture system is a first step in aging research. Given that pyruvate can be used energy source by conversion to acetyl-CoA in mitochondria, and protects cultured cell from various stress-induced cell damage and cell death, synthetic media (e.g., DMEM) often includes 1 mM pyruvate, which is very higher than the pyruvate concentration in human blood (approximately 30 ��M). However, the use of medium containing high concentration of pyruvate is not suitable for screening anti-senescence compounds, because pyruvate also protects against the cellular senescence of primary human dermal fibroblasts (NHDFs) through NAD+ generated during conversion to lactate. In this study, four extracts, i.e., Sprouted seed and fruit complex, Poncirus trifoliata fruit extract, Jaum balancing complex, and Prunus mume extract were used for evaluation of different anti-senescence effect in the absence or presence of 0.1 mM pyruvate, similar to the physiological pyruvate concentration. The senescence in NHDFs cultured with DMEM in the presence of 0.1 mM pyruvate (approximately the physiological concentration in human blood) is accelerated, as observed in pyruvate deprivation conditions. The cytotoxicity of the Poncirus trifoliata fruit extract was protected by pyruvate, and Jaum balancing complex and Prunus mume extract had anti-senescence activity in the presence of 0.1 mM pyruvate, but not in the absence of pyruvate. Given that pyruvate is a powerful protector against both cytotoxicity and cellular senescence, the screening of candidate agents for anti-senescence in high pyruvate conditions using an in vitro cell culture system is not valid. Therefore, we recommend the use of a low concentration of pyruvate to evaluate the anti-senescence effects of candidates, which is more similar to in vivo aging conditions than excessive stress-induced senescence models, to exclude the effect of excessive pyruvate in vitro.

• KIPS Transactions on Computer and Communication Systems
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• v.4 no.9
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• pp.315-320
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• 2015

In cloud computing, server virtualization supports one or more virtual machines loaded on multiple operating systems on a single physical host server. Migration of a VM is moving the VM running on a source host to another physical machine called target host. A VM live migration is essential to support task performance optimization, energy efficiency and energy saving, fault tolerance and load balancing. In this paper, we propose open source based adaptive VM live migration technique. For this, we design VM monitoring module to decide VM live migration and open source based full-virtualization hypervisor.

• KIISE Transactions on Computing Practices
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• v.20 no.9
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• pp.483-491
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• 2014

Contemporary computer systems exploits DVFS (Dynamic Voltage/Frequency Scaling) technology for balancing performance and power consumption. The efficiency of DVFS depends on how much performance we get for larger power consumption due to elevated CPU frequency. Especially for memory-bounded applications, higher CPU frequency often does not result in higher performance. In this paper, we present an upper bound of CPU frequency scaling based on memory accesses. It is observed that the performance gain due to higher CPU frequency is limited by memory accesses (last level cache misses) per instructions by experiments. Using the results, we present the CPU frequency upper bound with little performance gain. Experimental results show that for a memory-bounded application, applying the frequency upper bound enhances the energy efficiency of the application by above 30%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.135-138
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• 2006

We developed an engine system design program by balancing the pressure-mass-power relation which can be acquired from each component's specification. In gas generator type open-cycle rocket engine system it is possible to distinguish the variables into two categories, which are input variables and requirement variables. We define 11 design variables corresponding to the 11 balance equations as functions of pressure, mass and power of target engine system. We solved these equations by Newton method. As an example we designed gas generator cycle engine system and finally we could conclude that this developed program is well suited to the engine system design.