• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.460-468
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• 2021

This study investigated the enhanced combustion efficiency of an "air-cooled combustion system" with single F.D. fan, and performed a numerical analysis for the operation and design conditions to increase the combustion efficiency. The combustion efficiency in an actual combustor was compared before and after the structure modification. Numerical analysis for application of a single fan revealed the difficulty of forming a turbulence for circular combustion conditions. This is because the supply ratio of combustion air supplied into 2 flow paths becomes irregular in the combustion furnace due to a change in friction force and pressure in each flow path. Subsequently, two methods of supplying air into the combustion furnace were analyzed numerically to obtain the optimal combustion conditions of an air-cooled combustion system. The first method involved injecting the preheated combustion air after a 180~360 degree rotation from the outer wall, whereas in the second method, the combustion air was injected into the combustion furnace in a tangential direction after primary heat exchange outside the combustion furnace, by applying a rotatable vane structure in the combustion furnace. Results reveal that application of a single F.D. fan to the air injection into a rotatable combustion furnace is desirable for optimization of the combustion conditions for applying a duct structure having a dual cooling wall for the cooling of the outer wall of the combustion furnace, and for maintaining perfect mixing in the combustion furnace. We therefore confirmed enhanced combustion efficiency by comparing the actual combustion efficiency before and after structure modification.

• Journal of Power System Engineering
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• v.10 no.3
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• pp.11-16
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• 2006

The pressure fluctuation in the intake and exhaust pipe of 4 stroke-cycle diesel engine is caused by reciprocating motion of piston for suction of fresh air and exhaust of burned gas. this gas dynamic effect can be utilized for increase the volumetric efficiency. Many empirical studies have been carried out to investigate the effects of intake pulsating flow on the volumetric efficiency. However, when the gas dynamic effects are utilized for the variable speed engine to increase its performance, The speed range in which the maximum volumetric efficiency is limited and there occurs some difficulties in lay-out of intake system because it become too long. During induction process, as waves travel both directions, they are reflected and interacted each other and pressure waves are transmitted through it. Hence, the flow becomes more complex and unsteady flow. These pressure waves act upon intake pulsating flow and affects on the volumetric efficiency. In this paper the effects of pulsating flow of intake and exhaust pipes on volumetric efficiency were examined and evaluated. It was found that volumetric efficiency was affected by pulsating flow of intake and exhaust pipes.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.104-107
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• 2008

A case study is conducted by between using 3D integrated automatic design software(ABeamDeck, AAbutPier) and using autocad without program to validate the method. As a result, there are many profits introducing the 3D design in the construction, especially, to make up for defect of existing design method. 3D design will enhance the efficiency of construction tasks by supporting a system of sharing and exchanging information throughout all the stages of construction, from design, production and installation to maintenance.

• KSBB Journal
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• v.19 no.4
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• pp.284-287
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• 2004

The purpose of this study was to find an optimum extraction condition of acanthoside-D from acanthopanax cortex with supercritical carbon dioxide as a solvent. In this effort, effects of the extraction conditions including pressure, temperature and presence or absence of a cosolvent on the extraction efficiency were investigated. The ethanol, water or 50% methanol was used as a cosolvent whilst the operating pressure ranged from 200 bar to 300 bar. The acanthoside-D concentrations were determined by means of HPLC equipped with a UV detector. From the results, it was observed that increase of higher pressure led to the higher extraction efficiency. Further, water was found to be the best cosolvent among the entrainers tested.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.3
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• pp.1311-1324
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• 2019

In the traditional cellular network communication, the cellular user and the base station exchange information through the uplink channel and downlink channel. Meanwhile, device-to-device (D2D) users access the cellular network by reusing the channel resources of the cellular users. However, when cellular user channel conditions are poor, not only D2D user cannot reuse its channel resources to access the network, but also cellular user's communication needs cannot be met. To solve this problem, we introduced a novelty D2D communication mechanism in the downlink, which D2D transmitter users as half-duplex (HD) relays to assist the downlink transmission of cellular users with reusing corresponding spectrum. The optimization goal of the system is to make the cellular users in the bad channel state meet the minimum transmission rate requirement and at the same time maximize the throughput of the D2D users. In addition, i for the purpose of improving the efficiency of relay transmission, we use two-antenna architecture of D2D relay to enable receive and transmit signals at the same time. Then we optimized power of base station and D2D relay separately with consideration of backhaul interference caused by two-antenna architectures. The simulation results show that the proposed HD relay strategyis superior to existing HD and full-duplex (FD) models in the aspects of system throughput and power efficiency.

• Journal of Broadcast Engineering
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• v.21 no.2
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• pp.237-251
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• 2016

The conventional 3D-HEVC uses the depth data of the other view instead of that of the current view because the texture data has to be encoded before the corresponding depth data of the current view has been encoded, where the depth data of the other view is used as the predicted depth for the current view. Whereas the conventional 3D-HEVC has no other candidate for the predicted depth information except for that of the other view, the scalable 3D-HEVC utilizes the depth data of the lower spatial layer whose view ID is equal to that of the current picture. The depth data of the lower spatial layer is up-scaled to the resolution of the current picture, and then the enlarged depth data is used as the predicted depth information. Because the quality of the enlarged depth is much higher than that of the depth of the other view, the proposed scheme increases the coding efficiency of the scalable 3D-HEVC codec. Computer simulation results show that the scalable 3D-HEVC is useful and the proposed scheme to use the enlarged depth data for the current picture provides the significant coding gain.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.2
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• pp.29-37
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• 2009

National R&D programs play an important role in the development of a country in this age of the knowledge economy. Since many numbers of R&D programs compete for limited resources such as national R&D budget, the R&D program evaluation problem is a challenging decision-making problem faced by decision makers that deal with R&D management. In this sense, DEA(Data Envelopment Analysis) has been regarded as one of the most widely accepted methods to measure the relative efficiency of productivity of R&D programs. DEA is a methodology to measure and to evaluate the relative efficiency of a homogeneous set of decision-making units(DMUs) in a process which uses multiple inputs to produce multiple outputs. However, the sample of the R&D programs could consist of two or more naturally occurring subsets, thus exhibiting clear signs of heterogeneity such as different objectives. In such situations, the fairness of DEA is limited, for the nature of the relative efficiency of a DMU is likely to be influenced by its membership in a particular subset of the sample. In this study, we propose a methodology AI-DEA(attainment index DEA) allowing for reflecting decision maker's subjective judgement on difference among different subsets of R&D programs which have heterogeneous objectives. This methodology combines AHP and Delphi in order to decide the attainmnet index of each DMU for each outputs, and apply them to DEA model. We illustrate the proposed approach with a pilot evaluation of 13 programs involving 6 different subsets of Korean National R&D programs and compares the results of the original DEA model and AI-DEA model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.624-631
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• 2012

This paper presents a high-efficiency current mode class-D(CMCD) power amplifier for the 13.56 MHz band using a Guanella's 1:1 transmission-line transformer and filtering circuits at the output network. The second and third s are filtered out in the load network of the class-D amplifier. The implemented CMCD power amplifier exhibited a power gain of 13.4 dB and a high power-added efficiency(PAE) of 84.6 % at an output power of 44.4 dBm using the 13.56 MHz CW input signal. The second and third distortion levels were -50.3 dBc and -46.4 dBc at the same output power level, respectively.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.849-854
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• 2023

In this paper, a high-efficiency power amplifier was designed by applying the operating point Class J using LDMOS(laterally diffused metal oxide semiconductor) and optimizing the output matching circuit so that the second harmonic impedance becomes the reactance impedance. The designed power amplifier has a frequency of 108 ~ 110 MHz, Characteristics of PAE(power added efficiency) is 71.5% at P_SAT output (54.5 dBm), 55.5% at P_1dB output (51.5 dBm), and 24.38% at 45 dBm. The CSB(carrier with sideband) amplifier, which is the reference signal in the spatial modulation method, has an operating output of 45 dBm ~ 35 dBm, and linear SDM(sum in the depth of modulation) characteristics(40% ± 0.3%) were obtained. We measure the characteristics in amplitude modulation according to the bias operating point of the power amplifier for CSB and propose the optimal operating point to obtain linear modulation characteristics.

• Journal of Technology Innovation
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• v.24 no.4
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• pp.27-53
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• 2016

This case analyzed the efficiency of 79 R&D projects performed within one private research center in machine tools industry. DEA was used for efficiency analysis. Input variables were R&D investment expense and man-month. Output variables were achievement rate on target development period and expected net sales within 5-years. Samples are divided into product development, Prior technology development, and control technology development. The key result is that Prior technology showed the lowest efficiency because of high uncertainty. It was so difficult to determine its goals and to make its specific plans. With respect to scale, the proportions of CRS(constant returns to scale) were 34.6%, 14.3% and 38.9% for product development, prior technology, control technology respectively. As for IRS(increase returns to scale), they were 53.8%, 85.7% and 38.9% for product development, prior technology, control technology respectively. As for DRS(decrease returns to scale) they were 11.5%, 0% and 22.2% for product development, prior technology, control technology respectively. On the whole, in this case, insufficient input was more problematic than excessive input, which means the lack of investment in R&D. Prior technology can be the source of the future competitiveness of companies. To operate inefficient DMU efficiently, the optimal input should be managed and it is derived from comparison with the reference group.