• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.161-182
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• 2018

We carried out a series of linear cutting machine tests to assess the cutting performance of a pick cutter in sedimentary rock. The specimens were Linyi sandstone from China and Concrete (rock-like material, conglomerate). Using the small scaled LCM system, we estimated the cutter force and specific energy under different cutting conditions. The cutter forces (cutting and normal) increased with penetration depth and cutter spacing in two rock types, and it was affected by the strength of specimens. On the other hand, the ratio of the peak cutter force to the mean cutter force was influenced by cutting characteristic and composition of rock rather than rock strength. The cutting coefficient was affected by the friction characteristic between rock and pick cutter rather than the cutting conditions. Therefore, the optimal cutting angle can be determined by considering of cutting coefficient and resultant force of pick cutter. The optimum cutting condition was determined from the relationship between the specific energy and cutting condition. For two specimens, the optimum s/p ratio was found to be two to four, and the specific energy decreased with the penetration depth. The result from this study can be used as background database to understand the cutting mechanism of a pick cutter, also it can be used to design for the mechanical excavator.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.274-280
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• 2020

In this paper, the effect of atmospheric turbulence is numerically modeled and analyzed via a phase-screen model, in regard to long-range optical energy transfer using coherent beam combination. The coherent-beam-combination system consists of three channel beams pointing at a target at a distance of 1-2 km. The phase and propagation direction of each channel beam are assumed to be corrected in an appropriate manner, and the atmospheric turbulence that occurs while the beam propagates through free space is quantified with a phase-screen model. The phase screen is statistically generated and constructed within the range of fluctuations of the structure constant Cn2 from 10-15 to 10-13 [m-2/3]. Particularly, in this discussion the shape, distortion, and combining efficiency of the 3-channel combined beam are calculated at the target plane by varying the structure constant used in the phase-screen model, and the effect of atmospheric turbulence on beam-combination efficiency is analyzed. Analysis with this numerical model verifies that when coherent beam combination is used for long-range optical energy transfer, the received power at the target can be at least three times the power obtainable by incoherent beam combination, even for maximal atmospheric fluctuation within the given range. This numerical model is expected to be effective for analyzing the effects of various types of atmospheric-turbulence conditions and beam-combination methods when simulating long-range optical energy transfer.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.1
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• pp.39-55
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• 2022

This study carried out the laboratory tests for AE signal attenuation to determine the attenuation coefficient (α) of silo concrete in Gyeongju low and intermediate-level disposal environments. The concrete samples were prepared by satisfying the concrete mixing ratio used in the Gyeongju disposal silo, and these samples were additionally exposed depending on the temperature conditions and saturation and, dry condition. As a result of attenuation tests according to the transmission distance on three concrete specimens for each disposal condition, the AE amplitude and absolute energy measured on the saturated concrete were higher than that of the dry concrete in the initial range of the signal transmission distance, but the α of the saturated concrete was higher than that of the dry concrete. Regardless of the saturation and dry conditions, the α tended to decrease as the temperature increases. The α had a more major influence on the saturation and dry condition than the temperature condition, which means that the saturation and dry condition is the main consideration in measuring the signal attenuation of a concrete disposal structure. The α of concrete in the disposal environment expect to be used to predict the integrity of silos concrete in Gyeongju low and intermediate-level disposal environments by estimating the actual AE parameter values at the location of cracks and to determine the optimum location of sensors.

• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.111-116
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• 2012

Far-infrared observations provide crucial data for the investigation and characterisation of the properties of dusty material in the Interstellar Medium (ISM), since most of its energy is emitted between ~ 100 and $200{\mu}m$. We present the first all-sky image from a sensitive all-sky survey using the Japanese AKARI satellite, in the wavelength range $50-180{\mu}m$. Covering > 99% of the sky in four photometric bands with four filters centred at $65{\mu}m$, $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ wavelengths, this achieved spatial resolutions from 1 to 2 arcmin and a detection limit of < 10 MJy $sr^{-1}$, with absolute and relative photometric accuracies of < 20%. All-sky images of the Galactic dust continuum emission enable astronomers to map the large-scale distribution of the diffuse ISM cirrus, to study its thermal dust temperature, emissivity and column density, and to measure the interaction of the Galactic radiation field and embedded objects with the surrounding ISM. In addition to the point source population of stars, protostars, star-forming regions, and galaxies, the high Galactic latitude sky is shown to be covered with a diffuse filamentary-web of dusty emission that traces the potential sites of high latitude star formation. We show that the temperature of dust particles in thermal equilibrium with the ambient interstellar radiation field can be estimated by using $90{\mu}m$, $140{\mu}m$, and $160{\mu}m$ data. The FIR AKARI full-sky maps provide a rich new data set within which astronomers can investigate the distribution of interstellar matter throughout our Galaxy, and beyond.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.1
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• pp.40.3-41
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• 2017

Korea Astronomy and Space Science Institute The observation of particles and waves using a single satellite inherently suffers from space-time ambiguity. Recently, such ambiguity has often been resolved by multi-satellite observations; however, the inter-satellite distances were generally larger than 100 km. Hence, the ambiguity could be resolved only for large-scale (> 100 km) structures while numerous microscale phenomena have been observed at low altitude satellite orbits. In order to resolve those spatial and temporal variations of the microscale plasma structures on the topside ionosphere, SNIPE mission consisted of four (TBD) nanosatellites (~10 kg) will be launched into a polar orbit at an altitude of 700 km (TBD). Two pairs of satellites will be deployed on orbit and the distances between each satellite will be from 10 to 100 km controlled by a formation flying algorithm. The SNIPE mission is equipped with scientific payloads which can measure the following geophysical parameters: density/temperature of cold ionospheric electrons, energetic (~100 keV) electron flux, and magnetic field vectors. All the payloads will have high temporal resolution (~ 16 Hz (TBD)). This mission is planned to launch in 2020. The SNIPE mission aims to elucidate microscale (100 m-10 km) structures in the topside ionosphere (below altitude of 1,000 km), especially the fine-scale morphology of high-energy electron precipitation, cold plasma density/temperature, field-aligned currents, and electromagnetic waves. Hence, the mission will observe microscale structures of the following phenomena in geospace: high-latitude irregularities, such as polar-cap patches; field-aligned currents in the auroral oval; electro-magnetic ion cyclotron (EMIC) waves; hundreds keV electrons' precipitations, such as electron microbursts; subauroral plasma density troughs; and low-latitude plasma irregularities, such as ionospheric blobs and bubbles. We have developed a 6U nanosatellite bus system as the basic platform for the SNIPE mission. Three basic plasma instruments shall be installed on all of each spacecraft, Particle Detector (PD), Langmuir Probe (LP), and Scientific MAGnetometer (SMAG). In addition we now discuss with NASA and JAXA to collaborate with the other payload opportunities into SNIPE mission.

• Journal of Astronomy and Space Sciences
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• v.35 no.3
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• pp.201-210
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• 2018

The characterization of detectors installed in space- and ground-based instruments is important to evaluate the system performance. We report the development of a detector performance test system for astronomical applications using the Andor iKon M CCD camera. The performance test system consists of a light source, monochromator, integrating sphere, and power meters. We adopted the Czerny-Tuner monochromator with three ruled gratings and one mirror, which covers a spectral range of 200-9,000 nm with a spectral resolution of ~1 nm in the visible region. Various detector characteristics, such as the quantum efficiency, sensitivity, and noise, can be measured in wide wavelength ranges from the visible to mid-infrared regions. We evaluated the Korea Astronomy and Space Science Institute (KASI) detector performance test system by using the performance verification of the Andor iKon-M CCD camera. The test procedure includes measurements of the conversion gain ($2.86e^-/ADU$), full well capacity ($130K\;e^-$), nonlinearity, and pixel defects. We also estimated the read noise, dark current, and quantum efficiency as a function of the temperature. The lowest measured read noise is $12e^-$. The dark current at 223 K was determined to be $7e^-/s/pix$ and its doubling temperature is $5.3^{\circ}C{\pm}0.2^{\circ}C$ at an activation energy of 0.6 eV. The maximum quantum efficiency at 223 K was estimated to be $93%{\pm}2%$. We proved that the quantum efficiency is sensitive to the operating temperature. It varies up to 5 % in the visible region, while the variation increases to 30 % in the near-infrared region. Based on the comparison of our results with the test report by the vendor, we conclude that our performance test results are consistent with those from the vendor considering the test environment. We also confirmed that the KASI detector performance test system is reliable and our measurement method and analysis are accurate.

• Journal of Advanced Navigation Technology
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• v.19 no.6
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• pp.552-557
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• 2015

Recent performed by recognizing a user's location, various services have been tailored focus on short-range wireless communication technology. A beacon in which is attracting attention as next-generation technology. Beacon is a terminal by utilizing the frequency of the non-audible area can not be bluetooth and human sending and receiving terminals and information, Apple recently iBeacon like a low-power Bluetooth (BLE; bluetooth low energy) based beacon showing a tendency to rise into the mainstream there. Services using a beacon is basically installs the terminal in a certain place indoor. It is characterized by providing the user the services to catch the user's position, even automatically take a separate action. Various types of location-based service provided by the target interior space began to attract attention. A variety of location-based services are provided in the interior space in order to be successfully deployed and provide guidance to the interior space, the movement route and the like are essentially required to build various types of information. In this paper, for efficient indoor positioning by varying the signal strength of the beacon in such areas were measured and analyzed.

• Korean Journal of Remote Sensing
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• v.12 no.1
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• pp.1-16
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• 1996

Korea Aerospace Research Institute(KARI) is developing a Korea Multi-Purpose Satellite I(KOMPSAT-I) which accommodates Electro-Optical Camera(EOC), Ocean Color Imager(OCI), Space Physics Sensor(SPS) for cartography, ocean color monitoring, and space environment monitoring respectively. The satellite has the weight of about 500 kg and is operated on the sun synchronized orbit with the altitude of 685km, the orbit period of 98 minutes, and the orbit revisit time of 28days. The satellite will be launched in the third quarter of 1999 and its lifetime is more than 3 years. EOC has cartography mission to provide images for the production of scale maps, including digital elevation models, of Korea from a remote earth view in the KOMPSAT orbit. EOC collects panchromatic imagery with the ground sample distance(GSD) of 6.6m and the swath width of 15km at nadir through the visible spectral band of 510-730 nm. EOC scans the ground track of 800km per orbit by push-broom and body pointed method. OCI mission is worldwide ocean color monitoring for the study of biological oceanography. OCI is a multispectral imager generating 6 color ocean images with and <1km GSD by whisk-broom scanning method. OCI is designed to provide on-orbit spectral band selectability in the spectral range from 400nm to 900nm. The color images are collected through 6 primary spectral bands centered at 443, 490, 510, 555, 670, 865nm or 6 spectral bands selected in the spectral range via ground commands after launch. SPS consists of High Energy Particle Detector(HEPD) and Ionosphere Measurement Sensor(IMS). HEPD has mission to characterize the low altitude high energy particle environment and to study the effects of radiation environment on microelectronics. IMS measures densities and temperature of electrons in the ionosphere and monitors the ionospheric irregularities in KOMPSAT orbit.

• Korean Institute of Interior Design Journal
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• v.23 no.3
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• pp.153-163
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• 2014

The eco-friendly elements are important for new construction and renovation and redevelopment of the buildings. The green buildings are related with minimizing environmental pollution and how to live with nature throughout the entire process of demolishing and building. The purpose of this paper is to study on eco-friendly business buildings in the trend of mandatory green building certification system. The analysis of this paper is comparative studies on practices at eleven domestic eco-friendly business buildings through site survey on design framework of green buildings. The design framework of eleven this buildings is six kinds of skills on technical, renewable, ecological, cultural, healthy, social. The eleven this buildings in the new & renewable energy and IT technology of technical sector are satisfied with the framework. But, domestic most advanced eco-friendly business buildings are placed difference between almost the two times on the lower buildings at comparative evaluation. The three of this buildings are gratified rainwater harvesting and waste recycling systems for renewable and recycle. The buildings have an excellent aspects of technology and ecology. The benefits of this buildings are related with future compulsory zero energy house to take technical advantage of renewable energy. However, the buildings reflecting the regional culture types is insufficient. The buildings should be supplemented as follows. This buildings are need to have the social enhancement programs and design for convenient space of community residents, through health and comfort of on workplace. Moreover, this buildings have features of coexisting with human beings and nature friendly with the aim of realizing the sustainable development. The social enhancement programs through regional cultural aspects with ecology are related with individual and community livings in harmony, non-hierarchical communal lifes. The development of the cultural aspects provide for consensus about the local community and creating sustainable communities. Thus, The buildings are to have energy saving, pleasant and healthy living environment and interactive individual and community livings in harmony.

• Advances in Energy Research
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• v.4 no.4
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• pp.299-323
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• 2016

Cylindrical parabolic solar concentrators of small concentration ratio are attractive options for working temperatures around $120^{\circ}C$. The heat gained can be utilized in many applications such as air conditioning, space heating, heating water and many others. These collectors can be easily manufactured and do not need to track the sun continuously. Using a heat pipe as a solar absorber makes the system more compact and easy to install. This study is devoted to modeling a system of cylindrical parabolic solar concentrators of small concentration ratio (around 5) fitted with a heat pipe absorber with a porous wick. The heat pipe is surrounded by evacuated glass tube to reduce thermal losses from the heat pipe. The liquid and vapor flow equations, energy equation, the internal and external boundary conditions were taken into consideration. The system of equations was solved and the numerical results were validated against available experimental and numerical results. The validated heat pipe model was inserted in an evacuated transparent glass tube as the absorber of the cylindrical parabolic collector. A calculation procedure was developed for the system, a computer program was developed and tested and numerical simulations were realized for the whole system. An experimental solar collector of small concentration, fitted with evacuated tube heat pipe absorber was constructed and instrumented. Experiments were realized with the concentrator axis along the E-W direction. Results of the instantaneous efficiency and heat gain were compared with numerical simulations realized under the same conditions and reasonably good agreement was found.