• Journal of the Korean Solar Energy Society
• /
• v.31 no.2
• /
• pp.120-127
• /
• 2011

Solar array has the following nonlinear characteristic, such as whose output current increases, output voltage is reduced. For this reason, boost converter with solar array system is always controlled to remain on the maximum power point of the solar array. In this case, we are not focused on the output of the solar array and not consider efficiency of the boost converter, which is assumed reliable. But efficiency of the converter also should be considered, which affects the total efficiency of the overall solar energy system. In this paper, efficiency calculation of the boost converter using power balance method is proposed, which will be used for a powerful reference before hardware realization.

• Journal of Energy Engineering
• /
• v.23 no.4
• /
• pp.9-18
• /
• 2014

These test methods, the current domestic vehicles fuel economy calculation method is tested on a dynamometer for vehicles after you have installed the vehicle, given the test mode(FTP-75 & HWFET mode, etc.) are measured by vehicle emissions and fuel economy by seeking to have the results approach, the carbon balance method. At this point, using the carbon balance method is a test method was developed seeking fuel for a standard fuel properties, where the value of the constant and saved test was measured in THC, CO, $CO_2$ has a value calculation. Therefore, use fuel which is changed every time you test the fuel properties characteristics are not considered exactly. In this study, using the carbon balance method and fluid flow rate of the fuel used in the actual test is measured by comparing the results with the flow measurement methods, properties of the fuel used for the test attribute to study ways that can be considered, taking into account the physical attributes of a more diverse fuel line and fuel economy improved measurement methods that can be reviewed.

• Journal of the Korea Society of Computer and Information
• /
• v.23 no.10
• /
• pp.57-63
• /
• 2018

The operating system for an isolated microgrid, which is completely disconnected from the central power system, aims at preventing blackouts and minimizing power generation costs of diesel generators through efficient operation of the energy storage system (ESS) that stores energy produced by renewable energy generators and diesel generators. In this paper, we predict the amount of renewable energy generation using the weather forecast and build an optimal diesel power generation plan using a genetic algorithm. In order to avoid inefficiency due to inaccurate prediction of renewable energy generation, our search algorithm imposes penalty on candidate diesel power generation plans that fail to maintain the SOC (state of charge) of ESS at an appropriate level. Simulation experiments show that our optimization method for maintaining an appropriate SOC balance can prevent the blackout better when compared with the previous method.

• Steel and Composite Structures
• /
• v.15 no.4
• /
• pp.439-449
• /
• 2013

In this study simply supported nonlinear Euler-Bernoulli beams resting on linear elastic foundation and subjected to the axial loads is investigated. A new kind of analytical technique for a non-linear problem called He's Energy Balance Method (EBM) is used to obtain the analytical solution for non-linear vibration behavior of the problem. Analytical expressions for geometrically non-linear vibration of Euler-Bernoulli beams resting on linear elastic foundation and subjected to the axial loads are provided. The effect of vibration amplitude on the non-linear frequency and buckling load is discussed. The variation of different parameter to the nonlinear frequency is considered completely in this study. The nonlinear vibration equation is analyzed numerically using Runge-Kutta $4^{th}$ technique. Comparison of Energy Balance Method (EBM) with Runge-Kutta $4^{th}$ leads to highly accurate solutions.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.5 s.38
• /
• pp.7-13
• /
• 2006

In the present study, we develop an analysis module to be applicable to design of sliding thrust bearings. The pressure equation is solved by using the finite element method. Average lubricant temperature is obtained from using the energy balance method. The module developed has been applied to three types of thrust bearing, such as tapered-land thrust bearings of angular and diamond types, and tilting-pad thrust bearings. Effects of the dam of the tapered-lad thrust bearings have also been investigated. It has been seen that the tapered-land thrust bearings of angular type result in the highest load capacity, while the tilting pad thrust bearings result in the lowest lubricant temperature. It has also been seen that the dam in the tapered-land thrust bearings increases both the load capacity and lubricant temperature.

• Korean Journal of Community Nutrition
• /
• v.7 no.3
• /
• pp.336-344
• /
• 2002

In this study, nutrient intake status and energy expenditure were examined to investigate the nutritional status of the elderly in a rural community. The results obtained by questionaries, the 24 hour recall method, and time-diary were as follows: The elderly men surveyed were 73.8 years old, on the average. The elderly women surveyed were 73.5 years old, on the average. The proportion of the elderly with diseases was 51.9%. Most of the subjects (86.1%) had a regular meal pattern of consuming three meals a day. The average daily energy intake of the rural elderly was much lower than the Korean RDA. The dietary assessment data showed that each energy intake of the males and the females was 79.5% and 84.3% of the RDA, respectively. The dietary intake of Ca, Fe, niacin, thiamin, and riboflavin was lower than the Korean RDA, and that of P and Vitamin C was adequate. The Fe intake was significantly different with respect to age and sex (p < 0.05). Although, in both elderly men and elderly women it decreased with age, the elderly men's intake was lower than the elderly women's. The heights of the elderly men and the elderly women was 159.7 cm and 147.5 cm, respectively, and the weights were 60.0 kg and 52.2 kg, respectively, and the BMI was in the moderate range. Heights significantly decreased with age (p < 0.05). According to daily living schedules, leisure time (11.0 hour) was the longest, physiological time (9.6 hours) was next, and work time (3.4 hours) was the shortest. Energy expenditure significantly decreased with age (p < 0.01). Energy intake also decreased with aging. Energy balance (energy expenditure/energy intake) was 93.4% in elderly men and 104.0% in elderly women. Especially, in elderly men in the 65 to 74 age range, the energy balance was the lowest, and the nutrient intake was also much lower than that of elderly women.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.10a
• /
• pp.19-24
• /
• 1997

In this study, we extend the application of the interface-matrix(IM) method for reflector modeling to Analytic Flux Expansion Nodal (AFEN) method. This include the modifications of the surface-averaged net current continuity and the net leakage balance conditions for IM method in accordance with AFEN fomular. AFEN-interface matrix (AFEN-IM) method has been tested against ZION-1 benchmark problem. The numerical result AFEN-IM method shows 1.24% of maximum error and 0.42% of root-mean square error in assembly power distribution, and 0.006%Δk of neutron multiplication factor. This result proves that the interface-matrix method for reflector modeling can be useful in AFEN method.

• Nuclear Engineering and Technology
• /
• v.48 no.3
• /
• pp.673-683
• /
• 2016

This paper analyzes the accuracy of the methods used in calibrating the thermal power of Nigeria Research Reactor-1 (NIRR-1), a low-power miniature neutron source reactor located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria. The calibration was performed at three different power levels: low power (3.6 kW), half power (15 kW), and full power (30 kW). Two methods were used in the calibration, namely, slope and heat balance methods. The thermal power obtained by the heat balance method at low power, half power, and full power was $3.7{\pm}0.2kW$, $15.2{\pm}1.2kW$, and $30.7{\pm}2.5kW$, respectively. The thermal power obtained by the slope method at half power and full power was $15.8{\pm}0.7kW$ and $30.2{\pm}1.5kW$, respectively. It was observed that the slope method is more accurate with deviations of 4% and 5% for calibrations at half and full power, respectively, although the linear fit (slope method) on average temperature-rising rates during the thermal power calibration procedure at low power (3.6 kW) is not fitting. As such, the slope method of power calibration is not suitable at lower power for NIRR-1.

• Journal of Power Electronics
• /
• v.19 no.6
• /
• pp.1486-1495
• /
• 2019

Dealing with the DC link fault poses a technical problem for an HVDC based on a modular multilevel converter. The fault suppressing mechanisms of several sub-module topologies with DC fault current blocking capacity are examined in this paper. An improved half-bridge sub-module topology with double direction control switch is also designed to address the additional power consumption problem, and a sub-module topology called hybrid double direction blocking sub module (HDDBSM) is proposed. The DC fault suppression characteristics and sub-module capacitor voltage balance problem is also analyzed, and a self-startup method is designed according to the number of capacitors. The simulation model in PSCAD/EMTDC is built to verify the self-startup process and the DC link fault suppression features.

• ETRI Journal
• /
• v.41 no.3
• /
• pp.326-336
• /
• 2019

A wireless power transfer technique can solve the power capacity problem in wireless rechargeable sensor networks (WRSNs). The charging strategy is a wide-spread research problem. In this paper, we propose a demand-based charging strategy (DBCS) for WRSNs. We improved the charging programming in four ways: clustering method, selecting to-be-charged nodes, charging path, and charging schedule. First, we proposed a multipoint improved K-means (MIKmeans) clustering algorithm to balance the energy consumption, which can group nodes based on location, residual energy, and historical contribution. Second, the dynamic selection algorithm for charging nodes (DSACN) was proposed to select on-demand charging nodes. Third, we designed simulated annealing based on performance and efficiency (SABPE) to optimize the charging path for a mobile charging vehicle (MCV) and reduce the charging time. Last, we proposed the DBCS to enhance the efficiency of the MCV. Simulations reveal that the strategy can achieve better performance in terms of reducing the charging path, thus increasing communication effectiveness and residual energy utility.