• 천문학회보
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• 제44권2호
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• pp.59.3-59.3
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• 2019

The last two decades have seen an immense growth in our understanding of the physics of the birth and evolution of our Universe. However there are still many unanswered questions, such as: what is the nature of the dark energy, which drives the acceleration of the expansion of the Universe? Is the acceleration driven by a cosmological constant, some dynamical dark energy, or a modification of the gravitational force law on large scales? The next generation of radio observatories will conduct large area radio continuum and HI intensity mapping surveys, and so will make possible new and complimentary tests of these fundamental questions. In this talk I present the design of these next generation of surveys, current forecasts for the effectiveness of these cosmological probes, and results from precursor experiments.

• Elastomers and Composites
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• 제53권4호
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• pp.220-225
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• 2018

Resilient pads play a major role in reducing the impact of loads on a rail in a rail-fastening system, which is essentially used for a concrete track. Although a compression set test is commonly used to measure the durability of a resilient pad, the static spring constant is often observed to be different from the fatigue test. In this study, a modified compression set test method was proposed to monitor the variations in the compression set and static spring constant of a resilient pad with respect to temperature and time. In addition, the life of the resilient pad was predicted by performing an acceleration test based on the Arrhenius equation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1997년도 전력전자학술대회 논문집
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• pp.336-340
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• 1997

This paper is a study about motor technic of motion and feedforward control in order to shape cutting control on the machine tool. The shape error caused by delay of the servo system in the direction of radius at the time of circular cutting is reduced by feedforward control, shape error generated by the position command delay is minimized by using the acceleration/deceleration time constant after the interpolation. The study was verified to optimization of motion control on experiments of a vertical machining center of the machine tool.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.795-798
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• 1999

Deterioration induced by the freezing and thawing in concrete often leads to the reduction in concrete durability by the cracking or surface spalling. In this paper, the deterioration prediction model for concrete structures subjected to the irregular freeze-thaw was proposed from the results of accelerated laboratory test using the constant temperature condition and acceleration factor from the in-situ weather data.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.584-589
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• 1992

The 3-dimensional PPNG(Pure proportional navigation guidance) law was proposed about forty years ago, but the satisfactory analysis of its performance has not been presented since then. In this note, we prove under some reasonable assumptions that the missile guided according to this 3-dimensional PPNG law can always intercept a randomly maneuvering target if (1) the target acceleration varies with a certain bound, (2) the navigation constant is selected large and (3) the initial heading error is small. We introduce a Lyapunov-like method that proves to be a very powerful tool in obtaining our results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1994년도 추계학술대회 논문집
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• pp.969-974
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• 1994

The dynamic behavior of graphite/epoxy laminated composite shell structure due to low-velocity impact is investigated using the finite element method. In this analysis, the Newmark's constant-acceleration time integration algorithm is used. The impact response such as contact force, central deflection and dynamic strain history form shell structure analysis are compared with those form the plate non-linear analysis. The effects of curvature, impact velocity and mass of impactor on the composite shell are discussed.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2008년도 춘계학술대회
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• pp.273-282
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• 2008

To application Arrhenius model for OLED's lifetime, it's needed in high temperature test. Because OLED's character is changed in high temperature, it's important to find limit temperature. We found out $40^{\circ}C$ is proper temperature by result of tests. But that is not enough acceleration to apply in practical affairs. We find new stress to get a bigger accelerated constant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1991년도 하계학술대회 논문집
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• pp.641-644
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• 1991

Constant slip frequency operation of linear infliction motor is essential for the stable levitation. Control scheme for the constant slip frequency with general purpose frequency inverter is proposed, Speed sensing scheme with proximitity switch for the speed feedback is also proposed. Optimal slip frequency, at which normal force is equal to 0, is selected by the experiment. This slip frequency is a comand to the controller. It shows good characteristic during acceleration and deceleration.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 춘계학술대회 논문집
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• pp.9-9
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• 2010

The proton exchange membrane fuel cell (PEMFC) holds great promise of clean power. However, in practical applications which use the PEMFC as the power source, the output voltage from the fuel cell undergoes transient response especially during acceleration and deceleration. This paper presents the relationships between the internal voltage drop, voltage of time constant, time constant of FC1 and FC2 (in series and in parallel) charge curves and discharge curves respectively.

• Journal of Advanced Marine Engineering and Technology
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• 제30권6호
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• pp.760-769
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• 2006

This paper proposes an autopilot system using a fuzzy PID controller to satisfy performances required for the automatic navigation of ships under various marine circumstances. The existing autopilot system using a PD type controller has difficulties in eliminating a steady-state error and compensating nonlinear characteristics of ships. The autopilot system using the proposed fuzzy PID controller has a self-tuning ability, an ability to compensate nonlinear characteristics, and an ability to turn at constant angular velocity. Therefore. it can naturally make a steady-state error zero, compensate nonlinear dynamic effect of ships, have an adaptability to parameter variation owing to shallow water effect, and have an ability to turn ship's course rapidly without overshoot through procedures of acceleration, constant, and deceleration of angular velocity for large course-changing.