• Journal of Korean Society of Steel Construction
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• v.22 no.1
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• pp.55-65
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• 2010

To effectively secure and execute the national budget, it is very important to estimate the reasonable construction cost of each process in the construction of public facilities and works. The construction cost is generally estimated at the time when the design of the targeted structures has been completed. Without detailed sectional drawings and with only simple information on bridge structures in the planning stage or in the early design stage. it would be very difficult to predict the approximate construction cost. In this study, a more efficient and appropriate approximate construction cost estimation model in the planning stage and in the early design stage is presented and verified as reliable by analyzing the construction cost data of 61 existing steel box girder bridges from previous studies. The results of this study show that when the construction cost that was predicted using the construction cost estimation model in the design stage was compared with the cost from the conventional standards, the suggested model in this study produced results with a very high confidence level.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.331-342
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• 2017

To ensure the successful launch of the Korea pathfinder lunar orbiter (KPLO) mission, the Korea Aerospace Research Institute (KARI) is now performing extensive trajectory design and analysis studies. From the trajectory design perspective, it is crucial to prepare contingency trajectory options for the failure of the first lunar brake or the failure of the first lunar orbit insertion (LOI) maneuver. As part of the early phase trajectory design and analysis activities, the required time of flight (TOF) and associated delta-V magnitudes for each recovery maneuver (RM) to recover the KPLO mission trajectory are analyzed. There are two typical trajectory recovery options, direct recovery and low energy recovery. The current work is focused on the direct recovery option. Results indicate that a quicker execution of the first RM after the failure of the first LOI plays a significant role in saving the magnitudes of the RMs. Under the conditions of the extremely tight delta-V budget that is currently allocated for the KPLO mission, it is found that the recovery of the KPLO without altering the originally planned mission orbit (a 100 km circular orbit) cannot be achieved via direct recovery options. However, feasible recovery options are suggested within the boundaries of the currently planned delta-V budget. By changing the shape and orientation of the recovered final mission orbit, it is expected that the KPLO mission may partially pursue its scientific mission after successful recovery, though it will be limited.

• Journal of Astronomy and Space Sciences
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• v.41 no.1
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• pp.43-60
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• 2024

Korea Pathfinder Lunar Orbiter (KPLO) is South Korea's first space exploration mission, developed by the Korea Aerospace Research Institute. It aims to develop technologies for lunar exploration, explore lunar science, and test new technologies. KPLO was launched on August 5, 2022, by a Falcon-9 launch vehicle from cape canaveral space force station (CCSFS) in the United States and placed on a ballistic lunar transfer (BLT) trajectory. A total of four trajectory correction maneuvers were performed during the approximately 4.5-month trans-lunar cruise phase to reach the Moon. Starting with the first lunar orbit insertion (LOI) maneuver on December 16, the spacecraft performed a total of three maneuvers before arriving at the lunar mission orbit, at an altitude of 100 kilometers, on December 27, 2022. After entering lunar orbit, the commissioning phase validated the operation of the mission mode, in which the payload is oriented toward the center of the Moon. After completing about one month of commissioning, normal mission operations began, and each payload successfully performed its planned mission. All of the spacecraft operations that KPLO performs from launch to normal operations were designed through the system operations design process. This includes operations that are automatically initiated post-separation from the launch vehicle, as well as those in lunar transfer orbit and lunar mission orbit. Key operational procedures such as the spacecraft's initial checkout, trajectory correction maneuvers, LOI, and commissioning were developed during the early operation preparation phase. These procedures were executed effectively during both the early and normal operation phases. The successful execution of these operations confirms the robust verification of the system operation.

• International Journal of Air-Conditioning and Refrigeration
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• v.13 no.1
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• pp.51-60
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• 2005

This paper reviews the studies on the pressure drop and the heat transfer in microchannels. Although a lot of studies about the single-phase flow have been done until now, conflicting results are occasionally reported about flow transition from laminar flow to turbulent flow, friction factor, and Nusselt number. Some studies reported the early flow transition due to relatively greater wall effect like surface roughness, but the other studies showed that the flow transition occurred at the Reynolds number of about 2300 and the early flow transition might be due to less accurate measurement of the channel geometry. Also, there have been arguments whether the conventional relation based upon continuum theory can be applied to the fluid flow and the heat transfer in microchannels without modification or not. The studies about the two-phase flow in microchannels have been mostly about investigating the flow pattern and the pressure drop in rectangular channels using two-component, two-phase flow like air/water mixture. Some studies proposed correlations to predict two-phase flow pressure drop in microchannels. They were mostly based on Lockhart-Martinelli model with modification on C-coefficient, which was dependent on channel geometry, Reynolds number, surface tension, and so on. Others investigated the characteristics of flow boiling heat transfer in microchannels with respect to test parameters such as mass flux, heat flux, system pressure, and so on. The existing studies have not been fully satisfactory in providing consistent results about the pressure drop and the heat transfer in microchannels. Therefore, more in-depth studies should be done for understanding the fundamentals of the transport phenomena in the microchannels and giving the basic guidelines to design the micro devices.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.351-352
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• 2006

There are many methodologies fur doing analysis of system's reliability in early design stage. Among the methods, PRISM is, as compared to MIL-HDBK-217, a newly developed technology but not easy to use. Because PRISM provides models that predict a part failure rate and field database, called EPRD and NPRD that can be combined with prediction models. This paper presents some capabilities of the prediction models in PRISM and usability of EPRD and NPRD database in system level reliability prediction.

• Journal of Animal Science and Technology
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• v.52 no.1
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• pp.29-36
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• 2010

This experiment was conducted to evaluate the influence of phase feeding methods on growth performance, carcass characteristics, pork quality, and economical efficiency in growing-finishing pigs. A total of 120 crossbred pigs ([Yorkshire ${\times}$ Landrace] ${\times}$ Duroc), average initial body weight 25.23 ${\pm}$ 2.66 kg, were allotted to 5 treatments by body weight and sex in a randomized complete block (RCB) design. Each treatment had 6 replicates with 4 pigs per pen. The treatments were 1) A (fed late weaner feed during whole phase), 2) B (fed late weaner feed in growing phase and grower feed in finishing phase), 3) C (fed grower feed during whole phase), 4) D (fed grower feed in growing phase and early finisher feed in early and late finishing phase), 5) E (fed grower feed in growing phase, early finisher feed in early finishing phase and late finisher feed in late finishing phase). Commercial diets bought from private feed company were used for this experiment. During the early growing phase (6 wks), treatments A and B showed higher growth performance than that of other treatments (P<0.05). However, growth performance tended to be similar among treatments at 10 wks after feeding and there was no difference in time of market weight (13 wks). Moreover, blood urea nitrogen (BUN) concentration was lowered in treatment E than other treatments during whole experimental period (P<0.01). Carcass characteristics and pork quality were measured when body weight of pigs reached at 110.33 ${\pm}$ 2.1 kg. Days to market weight (110 kg), quality grade, pork color, and pork pH did not show any significant difference among treatments. These results suggested that phase feeding based upon growth stages of pigs showed no detrimental effects on growth performance and the pork quality. Moreover, feed cost was saved approximately 37% by phase feeding method without delaying of days to market weight compared to general conventional feeding method (B) of swine farm in Korea.

• Journal of the Korean Society for Railway
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• v.6 no.1
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• pp.1-9
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• 2003

This article proposes an integrated systems engineering and safety analysis model for safety-critical systems development. A methodology in system design for safety is considered during the early phase of the development life cycle of systems engineering process. The evolution of the design automation technology has enabled engineers to perform the model-based systems engineering. A Computer-Aided Systems Engineering(CASE) tool, CORE, is utilized to integrate the systems engineering model with a system safety analysis model. The results of the functional analysis phase can drive the analysis of the system safety. An example of Communications-Based Train Control(CBTC) system for an Automated Guided Transit(AGT) system demonstrated an application of the integrated model.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.34 no.3
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• pp.8-15
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• 2011

The computer-based simulation tools are currently used overwhelmingly to simulate the performance of automotive designs. Then, the search for an optimal solution that satisfies a number of performance requirements usually involves numerous iterations among several simulation tools. Therefore, meta-modeling techniques are becoming widely used to build approximations of computationally expensive computer analysis tools. The set-based approach proposed in the first report of a four-part paper has been a test bed for the innovation of vehicle structure design process in the Structural Design and Fabrication Committee of JSAE(Society of Automotive Engineers of Japan). In the second report, the proposed design approach is illustrated with a side-door impact beam design example using meta-modeling techniques.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.323-333
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• 2016

In this study, the uncertainty requirements for orbit, attitude, and burn performance were estimated and analyzed for the execution of the $1^{st}$ lunar orbit insertion (LOI) maneuver of the Korea Pathfinder Lunar Orbiter (KPLO) mission. During the early design phase of the system, associate analysis is an essential design factor as the $1^{st}$ LOI maneuver is the largest burn that utilizes the onboard propulsion system; the success of the lunar capture is directly affected by the performance achieved. For the analysis, the spacecraft is assumed to have already approached the periselene with a hyperbolic arrival trajectory around the moon. In addition, diverse arrival conditions and mission constraints were considered, such as varying periselene approach velocity, altitude, and orbital period of the capture orbit after execution of the $1^{st}$ LOI maneuver. The current analysis assumed an impulsive LOI maneuver, and two-body equations of motion were adapted to simplify the problem for a preliminary analysis. Monte Carlo simulations were performed for the statistical analysis to analyze diverse uncertainties that might arise at the moment when the maneuver is executed. As a result, three major requirements were analyzed and estimated for the early design phase. First, the minimum requirements were estimated for the burn performance to be captured around the moon. Second, the requirements for orbit, attitude, and maneuver burn performances were simultaneously estimated and analyzed to maintain the $1^{st}$ elliptical orbit achieved around the moon within the specified orbital period. Finally, the dispersion requirements on the B-plane aiming at target points to meet the target insertion goal were analyzed and can be utilized as reference target guidelines for a mid-course correction (MCC) maneuver during the transfer. More detailed system requirements for the KPLO mission, particularly for the spacecraft bus itself and for the flight dynamics subsystem at the ground control center, are expected to be prepared and established based on the current results, including a contingency trajectory design plan.

• Journal of Korean Institute of Architectural Sustainable Environment and Building Systems
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• v.12 no.6
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• pp.606-617
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• 2018

Increased density of racks has resulted in increased use of data center cooling energy and the needs for energy efficient cooling systems has increased. In response to these needs, ASHRAE presented a performance indicator, which is Mechanical Load Component (MLC), for the purpose of evaluating systems at the design stage. However, the MLC metrics presented in the current standard can only be determined for system compliance and compared alternative systems with the system configuration completed. Therefore, there are limitations to considering MLC from the early stages of design. In this study, to extend the scope of application of MLC in the design phase, the design factors of the main equipment comprising the cooling system are classified by the MLC load component and interrelations between design factors were identified.