• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.71-77
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• 2014

For a long-term space mission, filling process of cryogenic liquid propellant is operated on a space vehicle in space. A vent process during transfer and filling of cryogenic propellant is needed to maintain the fuel tank pressure at a safe level due to its volatile characteristic. It is possible that both liquid and vapor phases of the cryogenic propellant are released simultaneously to outer space when the vent process occurs under low gravity environment. As a result, the existing filling process with venting not only accompanies wasting liquid propellant, but also consumes extra fuel to compensate for the unexpected momentum originated from the vent process. No-Vent Fill (NVF) method, a filling procedure without a venting process of cryogenic liquid propellant, is an attractive technology to perform a long-term space mission. In this paper, the preliminary experimental results of the NVF process are described. The experimental set-up consists of a 9-liter cryogenic liquid receiver tank and a supply tank. Liquid nitrogen ($LN_2$) is used to simulate the behavior of cryogenic propellant. The whole situation in the receiver tank during NVF is monitored. The major experimental parameter in the experiment is the mass flow rate of the liquid nitrogen. The experimental results demonstrate that as the mass flow rate is increased, NVF process is conducted successfully. The quality and the inlet temperature of the injected $LN_2$ are affected by the mass flow rate. These parameters determine success of NVF.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.600-607
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• 2008

Reliable wireless transmission of data generated by the flight critical subsystems or mission equipments of the unmanned aerial system is critical for mission success. As the UAS system becomes more sophisticated, its dependency on a reliable high rate radio communication system also increases. This requirement is applied not only during the operation phase but also in the early development test phase. This paper introduces a practical cost-effective communication system for a UAS. The downlink module combines analog NTSC video signal with onboard data, and send them using 2.4 GHz carrier wave. The uplink system has less a severe requirement on the bandwidth, and thus uses 430 MHz signal. This paper also presents a sample packet structure which can be adopted for many UAS of similar class.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.212-225
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• 2015

UAV (Unmanned Aerial Vehicle), the pilotless plane or drone, draws researchers' attention at these days for its extended use to various area. The research was initiated for military use of the UAV, but the area of applicable field is extended to surveillance, communication, and even delivery for commercial use. As increasing the interest in UAV, the needs of research for operating the flying object which is not directly visible when it conducts a certain mission to remote place is obviously grown as much as developing high performance pilotless plane is required. One of the project supported by government is related to the use of UAV for logistics fields and controlling UAV to deliver the certain items to isolated or not-easy-to-access place is one of the important issues. At the initial stage of the project, the previous researches for controlling UAV need to be organized to understand current state of art in local researches. Thus, this study is one of the steps to develop the unmanned system for using in military or commercial. Specifically, we focused on reviewing the approaches of controlling UAV from origination to destination in previous in-country researches because the delivery involves the routing planning and the efficient and effective routing plan is critical to success to delivery mission using UAV. This routing plan includes the method to avoid the obstacles and reach the final destination without a crash. This research also present the classification and categorization of the papers and it could guide the researchers, who conduct researches and explore in comparable fields, to catch the current address of the research.

• Journal of Digital Convergence
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• v.15 no.10
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• pp.83-92
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• 2017

The purpose of this study is to establish the Balanced Score Card for 'I Company' which is a small and medium sized manufacturing company in Busan City. It is suitable for SMEs and suitable for the management environment. The study was intended to contain the detailed needs of managers and employees when developing the performance measurement system. It also allowed other SMEs to benchmark through this study. We also proposed a solution to the problems after BSC construction. In addition, BSC has been developed for the purpose of shifting business strategy from RDS to SSS in accordance with changes in the demand market environment. Strategy Maps were divided into the whole company level and each team level. You can look at strategic goals, core success factors, and key performance indicators at each glance. Finally, we developed a smart performance evaluation system that can easily calculate the score, strategic goal, key success factor, weight of key performance indicators, target score, performance, and achievement rate by creating a smart chart. Have significance.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.9
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• pp.916-922
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• 2009

Because thermal design of satellite carrying out mission in space is performed by thermal analysis result using thermal mathematical model, accuracy of thermal mathematical model is important and it can be improved by model correlation. Correlation steps of satellite thermal math model are composed of modeling of satellite configuration placed in thermal vacuum chamber, verification of correspondence between thermal math model and real satellite configuration, and adjustment of modeling parameters from major part to minor part etc. In this study, correlation success criteria was established and correlation for satellite thermal math model was performed using result of thermal vacuum test of satellite structure-thermal model to meet the success criteria. The overall results satisfied the criteria and this correlated thermal model was applied for detailed thermal design of satellite.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.38 no.4
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• pp.11-21
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• 2015

In order to achieve success in ground operations, searching for moving targets is one of critical factors. Usually, the system of searching for adversary ground moving targets has complex properties which includes target's moving characteristics, camouflage level, terrain, weather, available search time window, distance between target and searcher, moving speed, target's tactics, etc. The purpose of this paper is to present a practical quantitative method for effectively searching for infiltrated moving targets considering aforementioned complex properties. Based upon search theories, this paper consists of two parts. One is infiltration route analysis, through terrain and mobility analysis. The other is building dynamic probability maps through Monte Carlo simulation to determine the prioritized searching area for moving targets. This study primarily considers ground moving targets' moving pattern. These move by foot and because terrain has a great effect on the target's movement, they generally travel along a constrained path. With the ideas based on the terrain's effect, this study deliberately performed terrain and mobility analysis and built a constrained path. In addition, dynamic probability maps taking terrain condition and a target's moving speed into consideration is proposed. This analysis is considerably distinct from other existing studies using supposed transition probability for searching moving targets. A case study is performed to validate the effectiveness and usefulness of our methodology. Also, this study suggests that the proposed approach can be used for searching for infiltrated ground moving target within critical time window. The proposed method could be used not only to assist a searcher's mission planning, but also to support the tactical commander's timely decision making ability and ensure the operations' success.

• Korea Trade Review
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• v.48 no.1
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• pp.263-285
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• 2023

The purpose of this study is to examine the business model, growth process, and success factors of the successful super app Gojek in the Southeast Asian and Indonesian markets. Gojek's business model analysis focused on the business canvas (9 blocks) that many companies have used to establish business models. Gojek's growth process was analyzed based on timeline. Gojek 1.0 is from the start of the ride hailing service. Gojek 2.0 is a leap forward into a life-friendly platform. Gojek 3.0 is a process of expanding and diversifying domestic and foreign businesses. Gojek 4.0 is a stage of changing to GoTo through mergers with Tokopedia, and setting a higher leap forward. Based on this, the success factors of Gojek are ① Hyperlocalization ② First mobile ③ A company that is loved through mission execution ④ Provide financial inclusion ⑤ Business expansion and diversification through mergers and acquisitions and partnerships ⑥ Entry into overseas markets ⑦ Attracting various partners and investment ⑧ Lock-in effect and hyperpersonalization. The implications obtained through this study and the limitations and direction of the study were discussed.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.459-475
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• 2018

In the field of aerospace engineering, accurate control of a spacecraft's orientation is often very important to mission success. Therefore, attitude control is a technically plentiful and extensively studied subject in controls literature during recent decades. This investigation of spacecraft attitude control is assumed to address two important aspects of the problem solutions. One sliding mode anti-disturbance control for utilization of faulty actuator components and another one disturbance observer based control to improve the pointing accuracy in the absence of anti-vibration equipment for the elastic appendages like a solar panel. Simultaneous occurrence of vibration due to flexible appendages and reaction degradation due to failure in attitude actuators complicates this case. The advantage of this method is acquisition proper control by the combination of disturbance observer and sliding mode compensation that form a fault tolerant control for the concerned satellite attitude control system. Furthermore, the proposed composite method indicates that occurrence the failure in actuators and even elastic solar panel vibration effect may be handled directly without reconfiguring the control components or providing piezoelectric devices. It's noteworthy, attitude quaternion and angular velocity commands are robustly tracked via controllers to become inclined to zero.

• The Journal of Korea Robotics Society
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• v.13 no.3
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• pp.151-156
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• 2018

Military robots are expected to play an important role in the future battlefield, and will be actively engaged in dangerous, repetitive and difficult tasks. During the robots perform the tasks a human operator controls the robots in a supervisory way. The operator recognizes battlefield situations from remote robots through an interface of the operator control center, and controls them. In the meantime, operator workload, controller interface, robot automation level, and task complexity affect robot operability. In order to assess the robot operability, we have developed ROSim (Robot Operational Simulator) incorporating these operational factors. In this paper, we introduce the results of applying ROSim experimentally to the assessment of reconnaissance robot operability in a battle field. This experimental assessment shows three resulting measurements: operational control workload, operational control capability, mission success rate, and discuss its applicability to the defense robot research and development. It is expected that ROSim can contribute to the design of an operator control center and the design analysis of a human-robot team in the defense robot research and development.

• Aerospace Engineering and Technology
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• v.6 no.1
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• pp.165-172
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• 2007

A space launch vehicle is a very complex system composed of many kinds of components. It is necessary for even a small piece of components in it to be free of defects, malfunctions and to operate normally for the sake of the mission success. For these reasous, a variety of tests are carried out. Burn-in test is to detect latent material and workmanship defects which occurs early in the components use. Developed countries for the space technology have considered the burn-in test for flight vehicles in the standard test documents and performed it. Referred to the documents, application methods of burn-in test will be considered for the components of domestic space launch vehicles such as KSLV-I in this document.