• The KSFM Journal of Fluid Machinery
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• v.13 no.5
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• pp.58-63
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• 2010

Optimal operation of turbo blowers connected in serial is analyzed by experimental measurements and numerical simulation with three-dimensional Navier-Stokes equations. The turbo blower system considered in the present study is widely used for the refuse collection system. Design optimization of the turbo blower using some design variables is also studied to enhance the performance of the blower. Throughout numerical simulation, it is found that the input energy reduction by optimal operation of the turbo blowers with the proper changes of the rotor's rotating frequency can be reduced a input energy for operating the blower system compared to the conventional on-off operation method theoretically. It is also found that the optimal design method is effective to enhance the performance of the turbo blower.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.6
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• pp.431-439
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• 2001

Recently, multi-room type heat pump system has aroused much attention, because it can achieve much reduction of installation cost and space as well as energy saving in companion with the single room type heat pump system. In the present study, performance characteristics of a 3 room type inverter driven heat pump system, which is widely spread in Japanese market, are measured.. In the single room operation, performances of a heat pump system such s the difference of compressor outlet and inlet pressures and the mass flowrate may increase with the increase of cooling capacity so that COP of the system decrease with the increase of cooling capacity. However, in the 2 room operation, mass flowrate and COP of the total system increase markedly as compared with the single room operation.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.964-967
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• 2006

Korea Railroad Research Institute (the following 'KRRI') built AGT test line in Gyeong San-city, Kyongsang-bukdo province, Korea on August, 2004. This test line is exclusively used for the test of the driverless rubber-tired AGT system, and applied with research result of AGT System Development Project like vehicles, power supply, control and signaling, track and infrastructure system. The test line is available for the test of rubber tired AGT system's performance, function, safety. In this paper, we described the operation system of test line for the test of performance, safety, reliability, and also system operation in emergency. Finally we present the operation result of test line.

• Journal of the Korean Society of Safety
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• v.8 no.4
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• pp.133-138
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• 1993

The stable and safe operation of a boiler system is essential for ensuring stability of the chemical processes. A dynamic simulation of a boiler drum was performed to identify the dynamics of the boiler drum. The obtained results represented that the variation of process variables disturb boiler system. So, disturbance rejection with tracking and constraints handing was necessary for stable operation of boiler drum. Among many controller, GPC has been known to show good performance in set point tracking than disturbance. In order to improve disturbance rejection performance measurable disturbance term was Introduced in basic GPC model. The controller which had tracking and disturbance rejection was designed for Improving the stable operation of a boiler system.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.4
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• pp.1521-1537
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• 2021

Through information hiding technique, secret message can be hidden in pictures. Stego-image quality and hiding capacity are two important metrics for information hiding. To enhance these metrics, many schemes were proposed by scholars in recent years. Some of them are effective and successful, but there is still a room for further improvement. A high capacity information hiding scheme (PAMO, Pixel-value Adjustment with Modulus Operation Algorithm) is introduced in this paper. PAMO scheme uses pixel value adjustment with modulus operation to hide confidential data in cover-image. PAMO scheme and some referenced schemes are implemented in Python and experiments are carried out to evaluate their performance. In the experiments, PAMO scheme shows better performance than other methods do. When secret message length is less than 72000 bits, the highest hiding capacity of PAMO can reach 7 bits per pixel, at the same time the PSNR of stego-images is greater than 30 dB.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.86-92
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• 2009

This paper presents development of 6kw ZVS(Zero Voltage Switching) boost converter by 4-parallel operation. To realize a high capacity converter with 6 kw, 4-parallel operation of 1.5kW unit module is proposed in this paper. To meet high ratio input to output voltage, isolated type booster converter is designed. To achieve ZVS operation of 4-switches of full bridge and protect a voltage overshoot caused by switch turn-off, simple active-clamp circuit is applied to the primary side. For parallel operation of 4-modules, master-slave control method is proposed to achieve input current sharing of 4-unit converter modules accurately. For performance tests, simulation is carried out. Also, load and experimental tests of the developed booster converter, 230Vdc/6kW, are carried out under various conditions. For field tests, the developed converter is applied for boosting a battery power to high DC_link voltage for a VSI inverter which starts a micro-turbine(MT) installed in vehicle and it's performance is verified through high speed motoring a MT up to tens of thousands of rpm.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.119-124
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• 2005

Decision of operation performance mode to minimize the energy consumption of urban rail vehicle. This paper analyses how much acceleration and deceleration of urban rail vehicle should be applied andhow to choose an operation mode to minimize energy consumption when train runs between station within the fixed operation time. The decided operation pattern satisfying the minimum energy consumption becomes a target trajectory and a basis for the controller design criteria. To make this goal it grasps the characteristics of urban rail vehicle, realize operation energy model of urban rail vehicle and verify the accuracy of embodied model the Matlab simulation with the same operation result of real route. It searches for operation pattern to minimize operation energy by changing the acceleration and deceleration on the imaginative route and proposes operation pattern minimizing energy consumption by applying real operation data between Dolgogee-Sukgye section of Seoul Metropolitan Subway Line 6.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.1
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• pp.79-91
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• 2023

In response to the recent surge in aviation demand, major airports and aviation authorities continue to make efforts to formulate arrival and approach procedures that take into account efficient aircraft separation, noise and environmental issues of carbon (CO2) emissions. In order to ensure efficient traffic control and environmental issues, as a result, a new concept Trombone, Point Merge, etc. have been introduced and widely used in the domestic airspace. However, these new concept procedures which do not properly reflect the characteristics of the aircraft operation performance and the FMS vertical descent guidance hinder flight efficiency as well as bring in turn negative factors such as level-off flight and the use of drag device at the busiest phase of the flight descent operation, like the Continuous Descent Operation (CDO). Accordingly, throughout modification the current Standard Terminal Arrival Route (STAR) and Instrument Approach Procedure(IAP) that reflect the aircraft descent performance and the FMS guidance, the flight operation safety and efficiency is expected to be improved eventually. We herewith analyze and propose the way of improving flight efficiency in the arrival operation procedure by supplementary modification which consequently contribute to the aviation industry international competitiveness.

• Journal of the Korean Society of Food Culture
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• v.22 no.2
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• pp.191-200
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• 2007

This study was designed to investigate the correlation between perceived TQM performance and organizational culture of dietitians. The objective of the study is to help the management of foodservice by providing a direction which will elevate perceived TQM performance of dietitians and presenting plans which will ensure effective dietitians. Questionnaires handed out to 308 dietitians worked in institutional foodservice operation including elementary, middle and high schools, hospitals, business and industries. In terms of TQM importance and performance, the more important dietitians perceived, the higher their performance level rose. Data form the IPA, external and internal customer satisfaction, executive ability, communication system and technology, information technology and application ability, food process, strategy, and leadership were required further improvement by dietitians. Of present organizational culture model, human relations model and open systems model were more likely to be adopted by dietitians in middle and high schools. According to the type of foodservice management, the open systems model was more preferred by dietitians from self-operated operations rather than respondents from contracted operations. Canonical correlation analysis between TQM performance and organizational culture showed canonical correlation to be higher (canonical correlations coefficient: .66). In conclusion, TQM performance-organizational culture showed higher canonical correlation. In the organizational culture, foodservice operation is capable of improving the aims for the rational goal model and the open systems model. The results showed that TQM performance and organizational culture had significant relationship, especially positive organizational culture emphasizing on internal process and rational goal model would have influence on TQM performance of dietitians. Foodservice operation, however, should recognize importance of open and development culture to improve dietitians' TQM performance. To apply open system foodservice organization should encourage dietitian and foodservice employees to challenge and compete for the works, Moreover, organizational effort such as information exchange program and support system should be established.

• Computers and Concrete
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• v.6 no.3
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• pp.203-223
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• 2009

Regression analysis (RA) can establish an explicit formula to predict the strength of High-Performance Concrete (HPC); however, the accuracy of the formula is poor. Back-Propagation Networks (BPNs) can establish a highly accurate model to predict the strength of HPC, but cannot generate an explicit formula. Genetic Operation Trees (GOTs) can establish an explicit formula to predict the strength of HPC that achieves a level of accuracy in between the two aforementioned approaches. Although GOT can produce an explicit formula but the formula is often too complicated so that unable to explain the substantial meaning of the formula. This study developed a Backward Pruning Technique (BPT) to simplify the complexity of GOT formula by replacing each variable of the tip node of operation tree with the median of the variable in the training dataset belonging to the node, and then pruning the node with the most accurate test dataset. Such pruning reduces formula complexity while maintaining the accuracy. 404 experimental datasets were used to compare accuracy and complexity of three model building techniques, RA, BPN and GOT. Results show that the pruned GOT can generate simple and accurate formula for predicting the strength of HPC.