• Aerospace Engineering and Technology
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• v.10 no.1
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• pp.63-69
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• 2011

In this study, we developed a dispersion analysis program of the gas-generator cycle liquid propellant rocket engine by expanding the mode analysis software(GEMAT). The performance dispersions of an engine that are arisen from the internal dispersion factors of engine's sub-components were formulated and solved to find the effects of each dispersion factor. We were also able to present the calculation method to find the required pressure margin for the compensation of those dispersion to satisfy the required performances of engine. Using this method, we could propose a novel procedure of compensating during the ground firing test which would induce the performance improvement by lessening the pumps discharge pressures or augmenting the combustion chamber pressure.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.1
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• pp.133-146
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• 1999

The charge operation of an ice storage system has been analyzed in this paper. The thermal characteristics of major components of the ice storage system. i.e., the refrigerator and the ice storage tank are evaluated from performance tests on an existing ice storage system. Based on the measured data for thermal characteristics, a simulation is carried out for the charge operation and the effect of the refrigerator size on the system performance is investigated. The results indicate that the larger the refrigerator size for a given storage capacity, the lower the inlet temperature of the ice storage tank so that the lower the efficiency of charge operation. It is also found that there exists an optimal size of the refrigerator with which the ice storage at the end of the charge operation is maximized, but the complete charge is not possible even with the optimally sized refrigerator. This leads to the result that the design capacity of the storage tank should be larger than the required amount of cold energy for the daytime cooling considering the practically chargeable amount of cold energy during the nighttime. Where the cooling load sharing of the storage is 40%, the nominal capacity of an ice storage tank needs to be larger than the required storage amount by 30%.

• Korean Journal of Optics and Photonics
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• v.12 no.4
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• pp.281-288
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• 2001

In this study we carried out athermalization analysis and tests to meet the required optical performance for thennal imaging systems even if the systems were operating over a wide temperature range. By using optical design programs such as Code- V and SIGMA2100, the simulation for athermalization was done with FPA thermal imaging system. In the athermalization test putting the thermal imaging system and collimator into a temperature chamber, the images depending on the temperature were recorded on video tape. In particular, the zoom thermal imaging system with two dimensional array detector was tested to check the result of the athermalization simulation. As a result, it was proved to meet the required optical performance for the thermal imaging system within $-32-+50^{\circ}C$ temperature range. range.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.4
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• pp.370-378
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• 2008

It is reported to develop the driving pump for the Low Noise Large Cavitation Tunnel(LOCAT) which is under construction at Maritime & Ocean Engineering Research Institute(MOERI). For low background noise condition of the LOCAT, it is crucial not only the best pump efficiency but also no cavity occurrence at any operating conditions. Design condition of the pump is determined by considering the required pump headrise, flow quantity, shaft rotation velocity and pump diameter. Performance analysis of the pump is conducted using commercial CFD codes ($BladeGen^+$, CFX-10), and the predicted results are verified by a series of model tests. Cavity was not observed at any operating condition in the model test, which were conducted at the midium cavitation tunnel of MOERI. The optimum pump for LOCAT, named as LP-11, was successfully developed through a series of pump design processes composed of blade design, performance analysis and model test.

• Proceedings of the ESK Conference
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• 1993.04a
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• pp.10-17
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• 1993

An object-oriented database was developed as a framesork for integrating into ergonomic interface models data for workplace modelling and ergonomic evaluation functions as well as basic anthropometric data required to construct a man model. In order to develop an ergonomic man model representing operators that interact with his working evnironments, not only anthro- pometric data but also efficient handling of such data and accurate representation of the work- space are needed as a prerequistite to proper ergonomic evaluation. Most existing man models are not, however, capable of fully utilizing these data due to the lack of a generallized formalism of data handling, which results in system performance degradation or a potential difficulty when the system is upgraded. In this research, these three sets of data with distinct characteristics were incorporated into a comon integrated database required to manipulate an ergonomic interface model fully coupled with the man model itself. An object- oriented scheme was sued for the database design Specifically, UniSQL/X, an object-oriented database management system and the X-window system on SPARC workstation were used for implementation. The ergonomic man model generated from the object-oriented database is found to possess great flexibility and performance compared to existing ergonomic interface models or ergonomic CAD systems.

• Journal of Communications and Networks
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• v.18 no.1
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• pp.123-131
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• 2016

The high-availability seamless redundancy (HSR) protocol is one of the most important redundancy IEC standards that has garnered a great deal of attention because it offers a redundancy with zero recovery time, which is a feature that is required by most of the modern substation, smart grid, and industrial field applications. However, the HSR protocol consumes a lot of network bandwidth compared to the Ethernet standard. This is due to the duplication process for every sent frame in the HSR networks. In this paper, a novel algorithm known as the reducing multicast traffic (RMT) is presented to reduce the unnecessary redundant multicast traffic in HSR networks by limiting the spreading of the multicast traffic to only the rings that have members associated with that traffic instead of spreading the traffic into all the network parts, as occurs in the standard HSR protocol. The mathematical and the simulation analyses show that the RMT algorithm offers a traffic reduction percentage with a range of about 60-87% compared to the standard HSR protocol. Consequently, the RMT algorithm will increase the network performance by freeing more bandwidth so as to reduce HSR network congestion and also to minimize any intervention from the network administrator that would be required when using traditional traffic filtering techniques.

• Journal of Communications and Networks
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• v.18 no.4
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• pp.619-628
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• 2016

This paper describes a theoretical framework for rate allocation to maximize the power efficiency of overall heterogeneous wireless networks whose users are assumed to have multihoming capabilities. Therefore, the paper first presents a power consumption model considering the circuit power and radio transmission power of each wireless network. Using this model, two novel power efficient rate allocation schemes (PERAS) for multihoming services are proposed. In this paper, the convex optimization problem for maximizing the power efficiency over wireless networks is formulated and solved while guaranteeing the required quality of service (QoS). Here, both constant bit rate and variable bit rate services are considered. Furthermore, we extend our theoretical framework by considering the sleep-operation management of wireless networks. The performance results obtained from numerical analysis reveal that the two proposed schemes offer superior performance over the existing rate allocation schemes for multihoming services and guarantee the required QoS.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.6
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• pp.608-614
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• 2015

Nitrogen oxide(NOx) emission reductions are required to meet the strict emission regulations for environmental protection. Most of the Exhaust Gas Recirculation(EGR) system applied to a diesel engine can relatively decrease the NOx at a low cost, but it has a disadvantage in that the PM generation is promoted due to the hot intake air temperature. Thus, high heat exchange efficiency of the EGR cooler is required for an effective removal of NOx. In this study, heat exchange efficiency for various types of heat exchangers used in EGR cooler was measured under same conditions, and determined best heat exchange performance shape depending on type of heat exchanger.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 1997.11a
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• pp.617-624
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• 1997

Over 100 experiments have been conducted at the University of Maryland to evaluate the performance of a water mist fire suppression system for protection of an interstitial space below a raised subfloor. Experiments are conducted as part of an ongoing research effort to compare the fire suppression capabilities of various water mist system designs in a raised subfloor space. Water mist system design parameters considered in the investigation include means of actuation, concentration of water mist required for extinguishment of fires, and delivery mechanisms of water mist within close proximity to the fire. Delivery of the required concentration of water mist within close proximity to the fire is a principal factor governing the adequacy of water mist systems. Two sets of experiments have been conducted to document the performance of water mist system designs. One set is involved in documenting the concentration of water mist as a function of position within the space. The second set of experiments is concerned with the ability of water mist system designs to control fires in the space. One result of the research is the assessment of the ability of a water mist system to control fires at particular locations as a function of water mist density at that location.

• The Journal of Korea Robotics Society
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• v.16 no.3
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• pp.223-231
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• 2021

In this paper describes the research and development of a pipe robot for pipe rehabilitation construction of old water pipes. After the water supply pipe construction, the pipe is leaking, damaged, and aging due to corrosion. Eventually, resistance to the flow of water in lower supply efficiency and contaminated water such as rusty water, finally in various consumer complaints. In order to solve this problem, rehabilitation construction robot technology is required to secure the construction quality of pipe rehabilitation construction and restore the function of the initial construction period. The developed pipe rehabilitation construction robot required a hydraulic actuator for high traction and was equipped with a small hydraulic supply device. In addition, we have developed a hydraulic cylinder and a link system that supports the pipe inner diameter to develop a single pipe robot corresponding to 500 to 800mm pipe diameter. The analysis and experimental verification of the driving performance and unit function of the developed pipe reconstruction robot are explained, and the result of the integrated performance test of the pipe reconstruction robot at the water supply pipe network site is explained.