• Title/Summary/Keyword: Ground Operations

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The signal system operation plan research for a Tilting train introduction (국내 틸팅열차 도입을 위한 신호시스템 운영방안 연구)

  • Lee, Hoon-Koo;Lee, Nam-Hyeong;Lee, Soo-Hwan;Lee, Young-Ho;Baek, Jong-Hyen
    • Proceedings of the KSR Conference
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    • 2009.05a
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    • pp.1999-2004
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    • 2009
  • Since 2003, the domestic ground signalling system of the Kyeongbu and Honam lines has been steadily improving with the introduction of the ATP system and application of the system to the train is actively being pursued for 2009 target. Therefore, new ground signalling systems are being installed to the trains and track conditions to control the train speed to a maximum of either 80km/h, 120km/h, 150km/h, or 160km/h. As well, considering safe breaking distance, block signalling has been installed and also the change over times of the track switching device has been adjusted according to the train speed. Since the new Tilting trains will be running faster than present trains, at speeds over 180 km/h, we anticipate that there will be problems with present signalling facilities. Therefore this paper attempts to examine the various problems with the interface between the ATP signalling system and the new Tilting trains and also it will propose the most effective operating plan based upon case studies of successful foreign operations.

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GPS Jamming Resilient Location-based Routing for Unmanned Ground Vehicle Networks (무인 지상 차량 네트워크에서 GPS 재밍에 강인한 위치기반 라우팅)

  • Lee, Jinwoo;Jung, Woo-Sung;Kim, Yong-joo;Ko, Young-Bae;Ham, Jae-Hyun;Choi, Jeung-Won
    • Journal of the Korea Institute of Military Science and Technology
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    • v.18 no.4
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    • pp.432-440
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    • 2015
  • UGVs(Unmanned Ground Vehicles) are robots that can substitute humans in reconnaissance operations of potentially dangerous and contaminated sites. Currently, there have been active research on utilizing UGVs in military environments. Much resrach has been focused on exploiting the weakness of topology-based routing and instead utilize location-based routing for the networking of UGVs. It is generally assumed that location-based routing methods can fully utilize the location information gained from GPS. However, this may not be possible in tactical environments due to enemy GPS jamming and LOS(Line of Sight) limitations. To solve this problem, we propose a location-based routing scheme utilizing low control message that can calibrate the location information using GPS information as well as location of neighboring UGV, movement direct and speed information. Also utilizing topology-based routing scheme to solve incorrect location information in GPS jamming region.

Prototype Development of a Three-wheel Riding Cultivator and Its Basic Performance

  • Lee, Beom Seob;Yoo, Soonam;Lee, Changhoon;Choi, Il Su;Choi, Yong;Yun, Young Tae
    • Journal of Biosystems Engineering
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    • v.43 no.4
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    • pp.285-295
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    • 2018
  • Purpose: The aim of this study is to develop a three-wheel riding cultivator for improving the performance of the current four-wheel riding cultivators in the market. Methods: A prototype three-wheel riding cultivator with the rated power of 15.5-kW, a primary hydrostatic and a two-speed selective gear transmission shifts, front/rear three-wheel drive, a hydraulic wheel tread adjustment, and the mid-section attachment of the major implements was designed and constructed. Its specifications and basic performance are investigated. Results: The maximum speeds of the prototype at the low and high stages were measured to be approximately 7.31, and 11.29 km/h in forward travel, respectively, and approximately 3.60, and 6.37 km/h in rearward travel, respectively. The minimum ground clearance is shown to be 670 mm. The rotating speeds of the power takeoff (PTO) shaft at the low and high stages are shown to be approximately 795 and 1,140 rpm, respectively. The tread of the rear wheels, the minimum radius of turning, and the maximum lifting height of the parallel link device are measured to be within 1,320-1,720 mm, 2.80 m, and 390 mm, respectively. Approximately 25.3% and 74.7% of the total weight of the prototype are distributed in the front and rear wheels on flat ground, respectively. When the tread of rear wheels increased from 1,320 to 1,720 mm, the left and right static lateral overturning angles increased from $33.4^{\circ}$ to $39.1^{\circ}$ and from $29.0^{\circ}$ to $36.1^{\circ}$, respectively. Conclusions: The prototype three-wheel riding cultivator showed a wide range of travel and PTO speeds, high minimum ground clearance, small minimum radius of turning, and easy control of the rear wheel tread. Further, the easy observation of cultivating operations by mid-mounting the implements can improve quality of work. Therefore, the prototype is expected to contribute to the riding mechanization of cultivating operations for various upland crops in Korea.

A Study on the Cost Estimation Model Development of the Defense M&S System Software (국방 M&S체계 소프트웨어 비용 추청모델 개발에 관한 연구)

  • Kim, Jang-Hyun;Jung, Choong-Young
    • Journal of the military operations research society of Korea
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    • v.36 no.3
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    • pp.69-81
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    • 2010
  • Since the mid-nineties, Republic of Korean Army has officially adapted information technology. Starting with the Chang-Jo 21('99) training M&S Model, around seventy types of the M&S system software, including Ground Operations & Resources Requirement Analysis Model ('10), developed by Republic of Korea Army or foreign counterparts have been utilized. However, as the existing cost estimations of the Defense M&S system software fail to reflect the acquisition and development environment, the estimated costs have been frequently overestimated or underestimated. This paper provides a suitable cost estimation model for the Defense M&S system software by presenting the software cost drivers which reflect the unique software development environment of the Defense.

A Geometric Compression Method Using Dominant Points for Transmission to LEO Satellites

  • Ko, Kwang Hee;Ahn, Hyo-Sung;Wang, Semyung;Choi, Sujin;Jung, Okchul;Chung, Daewon;Park, Hyungjun
    • International Journal of Aeronautical and Space Sciences
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    • v.17 no.4
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    • pp.622-630
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    • 2016
  • In the operation of a low earth orbit satellite, a series of antenna commands are transmitted from a ground station to the satellite within a visibility window (i.e., the time period for which an antenna of the satellite is visible from the station) and executed to control the antenna. The window is a limited resource where all data transmission is carried out. Therefore, minimizing the transmission time for the antenna commands by reducing the data size is necessary in order to provide more time for the transmission of other data. In this paper, we propose a geometric compression method based on B-spline curve fitting using dominant points in order to compactly represent the antenna commands. We transform the problem of command size reduction into a geometric problem that is relatively easier to deal with. The command data are interpreted as points in a 2D space. The geometric properties of the data distribution are considered to determine the optimal parameters for a curve approximating the data with sufficient accuracy. Experimental results demonstrate that the proposed method is superior to conventional methods currently used in practice.

Development of a hydraulic power transmission system for the 3-point hitch of 50-kW narrow tractors

  • Chung, Sun-Ok;Kim, Yong-Joo;Choi, Moon-Chan;Lee, Kyu-Ho;Ha, Jong-Kyou;Kang, Tae-Kyoung;Kim, Young-Keun
    • Korean Journal of Agricultural Science
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    • v.43 no.3
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    • pp.450-458
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    • 2016
  • High performance small and mid-sized tractors are required for dryland and orchard operations. A power transmission system is the most important issue for the design of high performance tractors. Many operations, such as loading and lifting, use hydraulic power. In the present study, a hydraulic power transmission system for the 3-point hitch of a 50 kW narrow tractor was developed and its performance was evaluated. First, major components were designed based on target design parameters. Target operations were spraying, weeding, and transportation. Main design parameters were determined through mathematical calculation and computer simulation. The capacity of the hydraulic cylinder was calculated taking the lifting force required for the weight of the implements into consideration. Then, a prototype was fabricated. Major components were the lifting valve, hydraulic cylinder, and 3-point hitch. Finally, performance was evaluated through laboratory tests. Tests were conducted using load weights, lift arm sensor, and lift arm height from the ground. Test results showed that the lifting force was in the range of 23.5 - 29.4 kN. This force was greater than lifting forces of competing foreign tractors by 3.9 - 4.9 kN. These results satisfied the design target value of 20.6 kN, determined by survey of advanced foreign products. The prototype will be commercialized after revision based on various field tests. Improvement of reliability should be also achieved.

A Study on the Development of Advanced LOSA Method (진보된 LOSA 방법론 개발에 관한 연구 )

  • Jihun Choi
    • Journal of Advanced Navigation Technology
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    • v.27 no.4
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    • pp.351-355
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    • 2023
  • The need for Advanced LOSA arises from the limitations and drawbacks of traditional LOSA. Amended LOSA aims to address some of the shortcomings of the original methodology and make it more effective and relevant to current aviation safety needs. Some of the key reasons for developing Advanced LOSA include Enhancing the scope, Improving data collection and analysis, Providing more targeted safety recommendations. First, Traditional LOSA mainly focuses on flight deck operations, but Advanced LOSA expands the scope to include other operational areas such as cabin operations, ground handling, and maintenance. Second, Advanced LOSA can build a Forecasting System that can predict the future through data collection and data analysis. Third, Advanced LOSA aims to provide more specific and targeted safety recommendations based on the Aviation data collection and Aviation data analysis. Overall, Advanced LOSA seeks to improve aviation safety by addressing the limitations of traditional LOSA and providing a more comprehensive and effective methodology for identifying and mitigating safety risks in aviation operations.

Consideration on the Relation between Vibration Level and Peak Particle Velocity in Regulation of Ground Vibration (지반진동 규제기준에서 진동레벨과 진동속도의 상호관계에 대한 고찰)

  • Choi, Byung-Hee;Ryu, Chang-Ha
    • Explosives and Blasting
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    • v.30 no.2
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    • pp.1-8
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    • 2012
  • The only law related to airblast and ground vibration control in Korea is the Noise and Vibration Control Act enforced by the Ministry of Environment. But this law mainly deals with the annoyance aspects of noises and vibrations in ordinary human life. Hence, the law defines the safety criteria of ground vibration as the vibration level (VL) of dB(V) unit. The ground vibrations produced from blasting, however, have the unique characteristics that can be shown in shock vibrations, and the duration is also very short compared to the vibrations from machinery, tools or facilities. Hence, vibration regulations for blasting operations usually define the safety criterion as the peak particle velocity (PPV) considering the effect of ground vibrations to structural damage. Notwithstanding, there are several attempts that predict VL from PPV or estimate VL based on the scaled distances (SD; in unit of $m/kg^{1/2}$ or $m/kg^{1/3}$) without considering their frequency spectra. It appears that these attempts are conducted mainly for the purpose of satisfying the law in blasting contracts. But, in principle there could no correlation between peaks of velocity and acceleration over entire frequency spectrum. Therefore, such correlations or estimations should be conducted only for the waves with the same or very similar frequency spectra.

A Comparative Study on Heat Loss in Rock Cavern Type and Above-Ground Type Thermal Energy Storages (암반공동 열에너지저장과 지상식 열에너지저장의 열손실 비교 분석)

  • Park, Jung-Wook;Ryu, Dongwoo;Park, Dohyun;Choi, Byung-Hee;Synn, Joong-Ho;Sunwoo, Choon
    • Tunnel and Underground Space
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    • v.23 no.5
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    • pp.442-453
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    • 2013
  • A large-scale high-temperature thermal energy storage(TES) was numerically modeled and the heat loss through storage tank walls was analyzed using a commercial code, FLAC3D. The operations of rock cavern type and above-ground type thermal energy storages with identical operating condition were simulated for a period of five consecutive years, in which it was assumed that the dominant heat transfer mechanism would be conduction in massive rock for the former and convection in the atmosphere for the latter. The variation of storage temperature resulting from periodic charging and discharging of thermal energy was considered in each simulation, and the effect of insulation thickness on the characteristics of heat loss was also examined. A comparison of the simulation results of different storage models presented that the heat loss rate of above-ground type TES was maintained constant over the operation period, while that of rock cavern type TES decreased rapidly in the early operation stage and tended to converge towards a certain value. The decrease in heat loss rate of rock cavern type TES can be attributed to the reduction in heat flux through storage tank walls followed by increase in surrounding rock mass temperature. The amount of cumulative heat loss from rock cavern type TES over a period of five-year operation was 72.7% of that from above-ground type TES. The heat loss rate of rock cavern type obtained in long-period operation showed less sensitive variations to insulation thickness than that of above-ground type TES.

Numerical simulations on electrical resistivity survey to predict mixed ground ahead of a TBM tunnel (TBM 터널 전방 복합지반 예측을 위한 전기 비저항 탐사의 수치해석적 연구)

  • Seunghun Yang;Hangseok Choi;Kibeom Kwon;Chaemin Hwang;Minkyu Kang
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.25 no.6
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    • pp.403-421
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    • 2023
  • As the number of underground structures has increased in recent decades, it has become crucial to predict geological hazards ahead of a tunnel face during tunnel construction. Consequently, this study developed a finite element (FE) numerical model to simulate electrical resistivity surveys in tunnel boring machine (TBM) operations for predicting mixed ground conditions in front of tunnel faces. The accuracy of the developed model was verified by comparing the numerical results not only with an analytical solution but also with experimental results. Using the developed model, a series of parametric studies were carried out to estimate the effect of geological conditions and sensor geometric configurations on electrical resistivity measurements. The results of these studies showed that both the interface slope and the difference in electrical resistivity between two different ground formations affect the patterns and variations in electrical resistivity observed during TBM excavation. Furthermore, it was revealed that selecting appropriate sensor spacing and optimizing the location of the electrode array were essential for enhancing the efficiency and accuracy of predictions related to mixed ground conditions. In conclusion, the developed model can serve as a powerful and reliable tool for predicting mixed ground conditions during TBM tunneling.