• Journal of Advanced Marine Engineering and Technology
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• v.29 no.7
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• pp.713-721
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• 2005

A marine diesel engine should realize optimal operation efficiency while reducing NOx, PM (Particulate Matters) and other emissions. Fuel injection systems that use electronic control can become an effective means of achieving that objective. However. it still needs some accurate and instant information in order to bring its ability into full potential while sailing on the sea. The important information of them are a shaft torque and continuous combustion pressures of all cylinders. The shaft torque and the propeller thrust described in this paper are measured at an intermediate shaft by using a unique principle that one of two electromagnet coils oscillates a vibrating strip which the length changes with force and the other coil picks up the change of the frequency of the vibrating strip. For further reference, the shaft power meter multiplied the torque by the shaft revolution has already had about 750 sets of sales performance. The research presented in this paper started about ten years ago and is concerned with the development of a combustion pressure sensor that uses the same principle. Recently, the pressure sensor which bears continuous operation has been developed after a hard struggle, that is, the system that consists of a shaft horsepower meter, a propeller thrust meter and a combustion pressure sensor has been completed and has been shown to be reliable. This paper describes the configuration of this system, the material of the combustion pressure sensor, the principle of that, and the improving point of the sensor, and, we finally consider the use of this system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.10
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• pp.823-832
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• 2014

Displaced non-Keplerian orbit, center of mass is displaced from orbit plane, enables special spacecraft missions. It requires continuous thrust to maintain the orbit, and solar sail is useful for this purpose. Equations for feasible region and stability analysis are derived for non-Keplerian orbit for general continuous thrust. Differences for solar sail spacecraft are discussed. Non-keplerian orbits are classified into four types. Location-specific required accelerations for orbit maintenance are calculated. Orbit stabilities of each orbit type are analyzed and verified by numerical simulations. In order to control non-Keplerian orbit in unstable region, a control algorithm using the real-time LQR control is developed and evaluated by numerical simulations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.122-128
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• 2004

In this paper, the vibration characteristics of a linear stepping motor(LSM) are analyzed using the ACSL. A magnetic equivalent circuit is based on the structure of the LSM, and then the electric equivalent circuit of the LSM is derived by solving equations for the magnetic equivalent circuit. A normal force is calculated using finite element method(FEM). And the vibration characteristics(continuous vibration) of the LSM are simulated by the ACSL(Advanced Continuous Simulation language) with the voltage equations, the thrust equation, the normal force equation and the kinetic equation.

• Economic and Environmental Geology
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• v.9 no.1
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• pp.13-26
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• 1976

The basic rocks distributed in the Okchon paleogeosynclinal zone have been previously considered as intrusive in majority, but as sedimentary parensis in few variety. The present study is to find out some clues to conclude otherwise, if any, by clarifying 1) the nature and characteristics of the rocks, 2) type of the associated sedimentary rocks if any, and 3) their occurrence in related to regional geologic structure. The finding are as follows: 1) The basic rocks are identified and classified to hornblende gabbro, amphibolite, basalt and andesite (in part metamorphosed to meta-volcanics), green schist and peridotite(which appears in separate locality from the others). 2) Associated sedimentary rocks which appear to overlie the basic rocks are known as Kunjasan and Baekwhasan formations. The two formations are probably same, but been used differently by different authers at different localities. The rocks is exclusively consisted of cherty looking siliceous quartzite and some localitis it shows very calcarious nature. The formation seems to indicate a sort of pelagic siliceous sediments although it contain some pebbles. 3) The basic rock suites are always underlain by the same continuous, great thrust, which separates the Okchon paleogeosyncline zone from the neogeosynclinal zone in the area studied. The comparison of Okchon basic rocks suite to the ophiolite suites in other parts of the world indicates some similarity with which the writers suggested the probalility of Okchon basic rocks being ophiolites that occur along ancient geosuture line now represented by the great thrust.

• Agricultural and Biosystems Engineering
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• v.4 no.1
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• pp.34-38
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• 2003

A mathematical model was developed for estimating the mechanical interrelation between characteristics of soil and main design factors of a tracked vehicle, and predicting the tractive performance of the tracked vehicle. Based on the mathematical model, a computer simulation program (TPPMTV) was developed in the study. The model considered the continuous change in tension for the whole track of a tracked vehicle, the analysis of shape and tension of the track segment between sprocket and first roadwheel, and the side thrust on both sides of grouser by the active earth pressure theory in predicting the tractive performance of a tracked vehicle. Also, the model contained not only sinkage depth of the track but the pressure distribution under the track in analyzing the side thrust. The effectiveness of the developed model was verified by performing the draw bar pull tests with a tracked vehicle reconstructed for test in loam soil with moisture content of 18.92％. The predicted drawbar pulls by the model were well matched to the measured ones. Such results implied that the model developed in the study could estimate the drawbar pulls well at various soil conditions, and would be very useful as a simulation tool for designing a tracked vehicle and predicting its tractive performance.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.306-313
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• 2004

The microwave discharge ion engine generates plasmas of both the main ion source and the neutralizer using 4㎓ microwave without discharge electrodes and hollow cathodes, so that long life and durability against oxygen and air are expected. The MUSES-C “HAYABUSA” asteroid explorer installing four microwave discharge ion engines “$\mu$10s” was launched into deep space by M-V rocket No.5 on May 9, 2003. After vacuum exposure and several runs of baking for reduction of residual gas the ion engine system established the continuous acceleration of the spacecraft toward the asteroid “ITOKAWA”. The Doppler shift measurement of the communication microwave revealed the performance of ion engines, which is 8mN thrust force for a single unit with 3,200sec specific impulse at 23mN/㎾ thrust power ratio. At the end of 2003 the accumulated operational time exceeded 8,000 hour and unit. HAYABUSA will execute the Earth swing-by on June 2004 and arrive at the asteroid in 2005 and return to Earth in 2007.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.1
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• pp.1-10
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• 2005

An aerodynamic shape optimization technique has been developed for helicopter rotor blades in hover based on a continuous adjoint method on unstructured meshes. The Euler flow solver and the continuous adjoint sensitivity analysis were formulated on the rotating frame of reference for hovering rotor blades. In order to handle the repeated evaluation of the design cycle efficiently, the flow and adjoint solvers were parallelized using a domain decomposition strategy. A solution-adaptive mesh refinement technique was adopted for the accurate capturing of the tip vortex. Applications were made for the aerodynamic shape optimization of Caradonna-Tung rotor blades and UH60 rotor blades in hover. The results showed that the present method is an effective tool to determine optimum aerodynamic shapes of rotor blades requiring less torque while maintaining the desired thrust level.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.9
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• pp.658-664
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• 2019

In the development of the liquid rocket engine using the pintle injector, spray characteristics such as spray angle, droplet size, and distribution of the droplets are dominant parameters. Three different kind of multi hole type pintle tip and a continuous type pintle tip were designed. In the case of multi hole pintle tip, SMD result did not have a significant difference depending on the number of holes. In analysis with visualization images, however, the droplets were uniformly distributed as the number of holes increased. Liquid droplets from continuous type pintle tip were finely atomized and dispersed uniformly than those from multi-hole type pintle tip. In addition, the thrust control by adjusting the liquid injection area of the pintle is suitable for the continuous type, which is easier to face-shutoff rather than the multi hole type. The spray angle of each pintle tip according to TMR was measured to derive a specific tendency and corresponding empirical formula.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.7-12
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• 2003

In this paper, S(stochastic)-eigenvalue concept and its S-eigenvector for linear continuous-time systems with probabilistic uncertainties are proposed. The proposed concept is concerned with the perturbation of eigenvalues due to the probabilistic variable parameters in the dynamic model of a plant. S-eigenstructure assignment scheme via the Sylvester equation approach based on the S-eigenvalue concept is also proposed. The proposed design scheme is applied to the longitudinal dynamics of open-loop-unstable aircraft with possible uncertainties in aerodynamic and thrust effects as well as separate dynamic pressure.

• Journal of Mechanical Science and Technology
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• v.18 no.6
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• pp.933-945
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• 2004

In this paper, S (stochastic)-eigenvalue concept and its S-eigenvector for linear continuous-time systems with probabilistic uncertainties is proposed. The proposed concept is concerned with the perturbation of eigenvalues due to the probabilistic variable parameters in the dynamic model of a plant. S-eigenstructure assignment scheme via the Sylvester equation approach based on the S-eigenvalue concept is also proposed. The proposed design schemes are illustrated by numerical examples, and applied to the longitudinal dynamics of open-loop-unstable aircraft with possible uncertainties in aerodynamic and thrust effects as well as separate dynamic pressure. These results explicitly characterize how S-eigenvalues in the complex plane may impose stability on S-eigenstructure assignment.