• International Journal of Precision Engineering and Manufacturing
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• 제6권1호
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• pp.23-30
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• 2005

The air-jet loom represents a major step in the development of shutterless weaving due to its ability to weave a wide range of yarns at high speeds. The air-jet weaving involves inserting a pre-measured length of yarn through the wraps, which is shed by means of compressed air. The analysis of air flow characteristic of the main nozzle and acceleration tube is required for improving the loom performance. In this paper, we examined the effects of the main nozzle with different acceleration tubes as well as diameters. Also, we compared the performance of a straight-type tube with a Laval-type tube and the effect of installing a suction hole on the acceleration tube.

• 한국분무공학회지
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• 제8권2호
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• pp.16-23
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• 2003

The Air-jet loom represents a major step in the development of shutterless weaving due to its ability to weave a wide range of yarns at high speeds. The Air-jet weaving involvers, inserting a pre-measured length of yam through the wrap, is sheds by meads of compressed air. The analysis of air flow characteristic of the main nozzle and acceleration tube is required for the loom performance. h this paper We examined the effect of the main nozzle with different acceleration tubes as well as diameters. And also, we compared the performance of straight type tube with laval type tube and of according to be suction hole on the acceleration tube, respectively.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.536-542
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• 2008

The rocket technology has the best reliability and the high acceleration performance currently. In addition, next generation propulsion system is acquired to low cost and high payload percentage at that same time. This work is to improve the performance of Diskshaped MHD accelerator which is expected as the one of the solution. In this study we have been focusing on the swirl vane. It is so important to know that how the swirl vane contribute the plasma and its performance. As results, the gas velocities of r-component with inlet swirl were increased about over 3000m/s at the channel exit. And then static gas pressure were also reduced, we found that the case with inlet swirl gives the good influence to the acceleration performance. And the difference of the acceleration by positive and negative inlet swirl is that gas velocity of $\theta$-component may operate to the electric field.

• 한국기계가공학회지
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• 제19권11호
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• pp.58-63
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• 2020

The fuel injection amount and timing along with the ignition timing for the gasoline engine of a racing car were adjusted using an electronic control unit (ECU), and the engine performance was evaluated through an acceleration test. The fuel map for the fuel injection amount and ignition map for the ignition timing were derived. Using the transient throttle control, the air-fuel ratio could be maintained at a constant value even in the case of a sudden throttle operation. In the flat shift, ignition blocking was more effective than fuel blocking. In a 75 m acceleration test, the required duration without and with ECU control was 4.47 s and 3.99 s, respectively. Notably, the acceleration could be improved by approximately 10.7% when the ECU control was implemented.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년도 제30회 춘계학술대회논문집
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• pp.103-106
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• 2008

본 연구에서는 발사체 비행 중 가속도의 변화로 발생하는 엔진 입구압력의 변화를 고려하여 엔진의 구성품에 미치는 영향을 고찰하였고 그에 따른 엔진 성능 변화를 예측하였다. 엔진의 입구압은 탱크 내의 추진제 수두와 가압 압력 및 압력 손실 등으로 정의되며 이에 따라 발사체가 비행하면서 추진제 소모와 가속도 변화에 의해 입구압력이 변하게 된다. 입구압이 변할 때 펌프 토출압이 변하고 그에 따른 유량 변화로 가스발생기의 압렵변화가 발생하며, 이는 터빈의 출력변화로 이어져 다시 펌프의 토출압 변화로 나타남을 알 수 있었고, 이는 궁극적으로 주연소실의 연소압 변화를 이끌면서 엔진의 성능이 변화함을 알 수 있었다.

• 한국항해학회지
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• 제24권3호
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• pp.103-111
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• 2000

From a ship's safe operation point of view, it is very important to estimate the navigational safety in a seaway. The seakeeping performance can be defined as the ability of a ship to go to sea, and to accomplish its missions successfully and safely even in adverse environmental conditions. There are several factors presently adopted for evaluating seakeeping performance. But a hardware of the system considering all these factors has not been developed since some of them can not be measured by sensors. In this paper, a synthetic method of evaluating navigational safety is developed by measuring the vertical and lateral acceleration. An experiment by using real measuring carried out on board the T/S 'HANNARA' The equipment was measured every 4 hours for more than 30 minutes the acceleration by accelerometer, analyzed its acceleration values and calculated navigational dangerousness. As the results of this on board experiment, the system is carried conviction to be useful as evaluating seakeeping performance.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.134-135
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• 2016

To evaluate anti-corrosion performance of rebar in concrete according to the amount of chloride and inhibitor, electrochemical impedance spectroscopy(EIS) method was conducted in this study. For the anti-corrosion performance evaluation according to time, Impedance of rebar in concrete was measured before and after 5 cycle of corrosion acceleration. As a results, The impedance of rebar in concrete added chloride decreased than before corrosion acceleration. However impedance of other specimens was maintained or increased than before corrosion acceleration.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.1
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• pp.327-332
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• 2006

In airborne gravimetry, there are two data streams. One is the specific force measured by an air/sea gravimeter or accelerometers, the other is kinematic acceleration measured by DGPS. And the difference of them provides the gravity disturbance information. To satisfy the requirement of most applications, an accuracy of 1mGal $(1mCal=10^{-5}m/s^{2})$ with a spatial resolution of 1km is the aim of current airborne gravimetry. There are two different methods to derive the kinematic acceleration. The generally used method is to differentiate the position twice, and the position can be calculated by commercial DGPS software. The main defect of this method is that integer ambiguities need to be fixed to get the precise position solution, but it's not a trivial thing for long base line. And to fix integer ambiguities, the noisier iono-free measurement is used. When differentiation is applied, noise is amplified and will influence the accuracy of acceleration. The other method is to get carrier phase acceleration by differentiate the carrier phase first, and then using the acceleration of GPS satellite to derive the vehicle acceleration. The main advantages include that fixing integer ambiguities is not needed anymore, position can be relaxed to about 10 meters, and smoother acceleration can be got since iono-free measurement is not needed. In some literatures, it's considered that the dynamic performance of the second method is inferior to that of the first. Through analysis, it is found that the performance degradation in dynamic environment results from the simplification of the GPS carrier phase observable model. And an iterative algorithm is presented to compensate the model error. Using a dynamic GPS data from an aeromagnetic survey, the importance of this compensation is showed at last.

• 한국항해학회지
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• 제18권2호
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• pp.19-40
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• 1994

Several factors can be chosen for evaluating seakeeping performance, such as deck wetness, propeller racing, slamming, rolling, vertical acceleration and vertical bending moment, in consi-deration of the safety of human being, cargo and ship. In fact, there are few developments for an evalua-tion method of seakeepting performance correponding with each ship's characteristics. The purpose of this paper is to develop an quantitative evaluation method of seakeeping performance according to ship types. The scope and the method of this study are as follow. (1) Obtain each response amplitude of ship's motion in waves by Ordinary Strip Method and apply it to short-crested, irregular wave for random process of the factors on seakeeping performance. (2) Define the evaluation index, the dangerousness, the maximum dangerousness and the evaluation diagram. (3) Figure out the different characteristics according to ship types by computer simulation of evaluating seakeeping performance. (4) Adopt vertical acceleration and one of rolling or lateral acceleration as the factors on seakeeping performance by clarifying the correlation of stochastic process. This study developed an evaluation method coincident with each ship's characteristics, and suggested a device for application to actual ship. This method might be useful in developing the practical system of seakeeping performance in accordance with ship types. The ship models for computer simulation are 175m container ship types, 93m tranning ship HANARA as passenger ship type, 259m bulk-carrier type and 164m pure car-carrier type.

• 동력기계공학회지
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• 제7권4호
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• pp.67-73
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• 2003

The entry guidance design involves trajectory optimization and generation of a drag acceleration profile as the satisfaction of trajectory conditions during the entry flight. The reference trajectory is parameterized and optimized as piecewise linear functions of the velocity. A regularization technique is employed to achieve desired properties of the optimal drag profile. The regularized problem has smoothness properties and the minimization of performance index then prevents the drag acceleration from varying too fast, thus eliminating discontinuities. This paper shows the trajectory control using the simple control law as well as the information of reference drag acceleration.