• International Journal of Aeronautical and Space Sciences
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• v.13 no.2
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• pp.170-187
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• 2012

Recent years have seen an outpour of revived interest in the use of airships for a number of applications.Present day developments in materials, propulsion, solar panels, and energy storage systems and the need for a more eco-oriented approach to flight are increasing the curiosity in airships, as the series of new projects deployed in recent years show; moreover, the exploitation of the always mounting simulation capabilities in CAD/CAE, CFD and FEA provided by modern computers allow an accurate design useful to optimize and reduce the development time of these vehicles.The purpose of this contribution is to examine the different aspects of airship development with a review of current modeling techniques for airship dynamics and aerodynamics along withconceptual design and optimization techniques, structural design and manufacturingtechnologies and, energy system technologies. A brief history of airships is presented followed by an analysis of conventional and unconventional airships including current projects and conceptual designs.

• International Journal of Aeronautical and Space Sciences
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• v.10 no.1
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• pp.67-74
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• 2009

In general, the lunar landing stage can be divided into two distinct phases: de-orbit and descent, and the descent phase usually comprises two sub-phases: braking and approach. And many optimization problems of minimal energy are usually focused on descent phases. In these approaches, the energy of de-orbit burning is not considered. Therefore, a possible low perilune altitude can be chosen to save fuel for the descent phase. Perilune altitude is typically specified between 10 and 15km because of the mountainous lunar terrain and possible guidance errors. However, it requires more de-orbit burning energy for the lower perilune altitude. Therefore, in this paper, the perilune altitude of the intermediate orbit is also considered with optimal thrust programming for minimal energy. Furthermore, the perilune altitude and optimal thrust programming can be expressed by a function of the radius of a parking orbit by using continuation method and co-state estimator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.8
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• pp.648-653
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• 2014

Fly-wheel, gimbal antenna, mechanical gyro and cryocooler with moving parts generate a micro-vibration during their on-orbit operation. For the acquisition of high quality image of observation satellite, additional technical efforts are required to reduce the micro-vibration level from the vibration sources. In this study, we proposed a passive isolation system combined with a tuned mass damper-type energy harvester to generate electrical energy from the micro-vibration which has always been subjected to useless isolation objectives. The feasibility of the system has been investigated through the numerical simulation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.5
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• pp.385-393
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• 2011

As the economic growth achieved and the straight road was increased. so, the tunnel built more than before. In these days, lighting of tunnel entrance is important for safety and comfortable driving. Most of the tunnel lighting depend on artificial lighting and they use a lot of energy. In this paper, as a research for illumination improvement and saving energy at tunnel, reflecting mirror system is suggested. The performance of the system was evaluated with respect to various aspects. By applying a reflective mirror system, tunnel lighting and environment can be improved. This study is a preliminary study for developing a system to save energy of tunnel artificial lighting.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.5
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• pp.15-21
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• 2003

This paper presents field measurements on daylighting and electric lighting with dimming controlled systems for a small office in Seoul, Korea. And the main purpose of this study is to provide the evaluation data of lighting energy performance when a dimming system is installed. For the performance evaluation, the mock-up room(3.6x7.2x2.6[m]) was used for the actual test. The results of this study were as follows; 1) The correlation between daylight illuminance at a workplane(Ed) and the photosensor signal(Sd) was an important factor affecting the performance of daylight responsive dimming system, 2) The mock-up office space gained a sufficient workplace illuminance of 579[lux] with the dimming control system 3) About 53[%J of monthly lighting energy could be saved using the dimming control system.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.7
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• pp.590-600
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• 2012

In this research, generalized sizing methods were studied that can be applied to an aircraft which uses solar cell or fuel cell as energy sources. To consider multiple propulsion systems and energy resources, multiple power paths were modeled and the weight of consumable and non-consumable energy was reflected in the weight change calculation for each mission segments. In the constraint analysis, power to weight ratio was selected instead of thrust to weight ratio and used in the sizing process of balancing power and energy.

• Journal of Hydrogen and New Energy
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• v.22 no.1
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• pp.100-108
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• 2011

The use of biogas as an energy source reduces the chance of possible emission of two greenhouse gases, $CH_4$ and $CO_2$, into the atmosphere at the same time. Its nature of being a reproducible energy source makes its use even more attractive. This research if for the hydrogen production through the steam reforming of the biogas. The biogas utilized 3D-IR matrix burner in which the surface combustion is applied. The nickel catalyst was used inside a reformer. Parametric screening studies were achieved as Steam/Carbon ratio, biogas component ratio, Space velocity and Reformer temperature. When the condition of Steam/Carbon ratio, $CH_4/CO_2$ ratio, Space velocity and Refomer temperature were 3.25, 60%:40%, 19.32L/$g{\cdot}hr$ and $700^{\circ}C$ respectively, the hydrogen concentration and methane conversion rate were showed maximum values. Under the condition mentioned above, $H_2$ concentration was 73.9% and methane conversion rate was 98.9%.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.82-82
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• 2016

To find the relationship between solar flares and halo CMEs using stereoscopic observations, we investigate 182 flare-associated halo CMEs among 306 front-side halo CMEs from 2009 to 2013. We have determined the 3D parameters (radial speed and angular width) of these CMEs by applying StereoCAT to multi-spacecraft data (SOHO and STEREO). For this work, we use flare parameters (peak flux and fluence) taken from GOES X-ray flare list and 2D CME parameters (projected speed, apparent angular width, and kinetic energy) taken from CDAW SOHO LASCO CME catalog. Major results from this study are as follows. First, the relationship between flare peak flux (or fluence) and CME speed is almost same for both 2D and 3D cases. Second, there is a possible correlation between flare fluence and CME width, which is more evident in 3D case than 2D one. Third, the flare fluence is well correlated with CME kinetic energy (CC=0.63). Fourth, there is an upper limit of CME kinetic energy for a given flare fluence (or peak flux). For example, a possible CME kinetic energy ranges from 1030.6 to 1033 erg for a given X1.0 class flare. Our results will be discussed in view of the physical mechanism of solar eruptions.

• KIEAE Journal
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• v.17 no.5
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• pp.87-94
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• 2017

Purpose: Prefabricated modular space such as a container construction has recently been interested unlike the conventional construction method, and their scale have expanded from small buildings such as cafes, houses and pensions to shopping centers, complex cultural spaces where shows and exhibitions are possible doing. In this way, the container is in the spotlight as an advantage such as mobility, flexibility, correspondence, economic efficiency, recyclability and so on. However, there are no specific guidelines and standard design methods in aspects of structural calculation, functional insulation and environmental configuration. Therefore, as the first step to resolve these problems, this study has focused on the field of environmental performance of container construction, presented appropriate guidelines and searched ways to improve performances. Method: For this study, seven types of the modular building were chosen and compared, and their energy performances have been analyzed using a proven simulation tool. Essential methodology and terminology were examined to estimate and judge their efficiency. Result: In conclusion, energy performances depend on specific configuration of combined unit spaces, and design guidelines cold be set up for promoting their use in the practical field.

• Journal of Astronomy and Space Sciences
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• v.38 no.1
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• pp.55-63
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• 2021

The universe is well known to be consists of dark energy, dark matter and the standard model (SM) particles. The dark matter dominates the density of matter in the universe. The dark matter is thought to be linked with dark photon which are hypothetical hidden sector particles similar to photons in electromagnetism but potentially proposed as force carriers. Due to the extremely small cross-section of dark matter, a large amount of data is needed to be processed. Therefore, we need to optimize the central processing unit (CPU) time. In this work, using MadGraph5 as a simulation tool kit, we examined the CPU time, and cross-section of dark matter at the electron-positron collider considering three parameters including the center of mass energy, dark photon mass, and coupling constant. The signal process pertained to a dark photon, which couples only to heavy leptons. We only dealt with the case of dark photon decaying into two muons. We used the simplified model which covers dark matter particles and dark photon particles as well as the SM particles. To compare the CPU time of simulation, one or more cores of the KISTI-5 supercomputer of Nurion Knights Landing and Skylake and a local Linux machine were used. Our results can help optimize high-energy physics software through high-performance computing and enable the users to incorporate parallel processing.