• Journal of Satellite, Information and Communications
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• v.6 no.2
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• pp.102-106
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• 2011

Space Environment including Solar activities such as Solar explosion, Corona Mass Ejection(CMS) is always not friendly for human. Especially it may be fatal to artificial satellites. The lifetime of geostationary communication satellites are reducing due to plasma such as electrons, protons etc. emitting from Sun. This is because the active components constituting communication satellite are easily affected by plasma. Even though the radiation shielding on the components can be a way to prevent, the cost will be high. So the appropriate shielding is necessary and the study on space environment is also. In this study spacecraft anomalies will be investigated from low earth orbit to deep space spacecraft and the correlation between spacecraft anomalies and space environment events including space explosion, geomagnetic storms etc is analyzed.

• Proceedings of the KSRS Conference
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• v.1
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• pp.398-401
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• 2006

Dual channel Radiometer for Earth and Atmospheric Monitoring (DREAM) is the main payload on Science and Technology SATellite-2 (STSAT-2) of Korea. DREAM is two-channel microwave radiometer with linear polarization, and operating at center frequencies of 23.8 GHz and 37 GHz. An equation for DREAM calibration is derived which accounts for losses and re-radiation in the microwave components of the radiometer due to physical temperature. This paper describes the radiometric calibration equation to get antenna temperature ($T_A$) from the measured output data. At lower altitude, the measured deep space temperature is contaminated by middle atmosphere and earth radiation. In this paper, we presented the detail mathematical formulation to find the altitude up to which cold source brightness temperature is not affected by earth and middle atmosphere radiation. The DREAMPFM data is used to calculate the performance parameters (linearity, sensitivity, dynamic range, and etc.) of the system.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.90-98
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• 2022

The output of an infrared (IR) sensor mounted on an EO/IR payload is known to change during a mission period in an orbital environment. As it is required to calibrate the output of the IR sensor periodically to obtain high-quality images, an on-board black body system is mounted on the payload. All systems operating in the space environment require performance tests on ground to verify the target performance in the orbital environment. Therefore, it is also required to test the black body system to verify the performance of the surface temperature uniformity and the estimated representative temperature error within the target temperature range in the operating environment. In this study, calibration of the estimated representative temperature error and verification of the thermal performance of the black body system were conducted by performed a performance test in the thermal vacuum chamber applying deep space radiation cooling effect of an orbital environment.

• Radiation Oncology Journal
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• v.2 no.1
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• pp.139-148
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• 1984

The CT findings of 46 cases of nasopharyngeal cancer were analyzed and compared with clinical tumor staging. They are composed of 28 cases $(61\%)$ of squamous cell carcinoma, 13cases $(28\%)$ of undifferentiated carcinoma, 4 cases $(9\%)$of lymphoma and 1 case $(2\%)$ of adenoid cystic carcinoma. The results were as follows : 1. The most common CT findings of nasopharyngeal cancers are air·way asymmetry including obliteration of Rosenmuller fossa, orifice of Eustachian tube and asymmetric obliteration of parapharyngeal fat. 2. Other involved anatomic sites are carotid sheath area, oropharynx, paranasal sinuses especially sphenoid sinus, cervical lymph nodes, nasal cavity and skull base or middle cranial fossa. 3. CT does significantly influence on the tumor staging of the nasopharynx cancers, but has a definite value in evaluating deep tissue invasion of the cancers especially to parapharyngeal space or carotid sheath area. 4. CT seems to be essential for staging work-up, estimating the prognosis, and assessing the effect of radiotherapy of the nasopharyngeal cancer because it clearly shows the whole extent of the tumors including deep tissue invasion.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.770-778
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• 2013

Solar sail propulsion uses solar radiation pressure to propel spacecraft without propellant, and it is useful for deep-space missions and continuos orbit maneuver missions. After a brief introduction of solar sail dynamics, locally optimal trajectories in Sun-centered and Earth-centered orbits are analyzed. Numerical simulations for the optimal trajectories are performed. Trajectory for the rendezvous with Halley comet is generated, and different planet escape methods are compared.

• Journal of The Korean Astronomical Society
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• v.40 no.1
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• pp.1-7
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• 2007

About 10 percent of quasars are known to exhibit deep broad absorption troughs blueward of prominent permitted emission lines, which are usually attributed to the existence of outflows slightly above he accretion disk around the supermassive black hole. Typical widths up to 0.2c of these absorption roughs indicate the velocity scales in which special relativistic effects may not be negligible. Under he assumption of the ubiquity of the broad absorption line region in quasars, the broad emission line flux will exhibit Thomson scattered components from these fast outflows. In this paper, we provide our Monte Carlo calculation of linear polarization of singly Thomson scattered line radiation with the careful considerations of special relativistic effects. The scattering region is approximated by a collection of rings that are moving outward with speeds ${\upsilon}=c{\beta}<0.2c$ near the equatorial plane, and the scattered line photons are collected according to its direction and wavelength in the observer's rest frame. We find that the significantly extended red tail appears in the scattered radiation. We also find that the linear degree of polarization of singly Thomson scattered line radiation is wavelength-dependent and hat there are significant differences in the linear degree of polarization from that computed from classical physics in the far red tail. We propose that the semi-forbidden broad emission line C III]1909 may be significantly contributed from Thomson scattering because this line has small resonance scattering optical depth in the broad absorption line region, which leads to distinct and significant polarized flux in this broad emission line.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.2315-2324
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• 2023

Space nuclear reactors are becoming popular in deep space exploration owing to their advantages of high-power density and stability. Following the fourth-generation nuclear reactor technology, a conceptual design of the dual drum-controlled space molten salt reactor (D²-SMSR) is proposed. The reactor concept uses molten salt as fuel and heat pipes for cooling. A new reactivity control strategy that combines control drums and safety drums was adopted. Critical physical characteristics such as neutron energy spectrum, neutron flux distribution, power distribution and burnup depth were calculated. Flow and heat transfer characteristics such as natural convection, velocity and temperature distribution of the D²-SMSR under low gravity conditions were analyzed. The reactivity control effect of the dual-drums strategy was evaluated. Results showed that the D²-SMSR with a fast spectrum could operate for 10 years at the full power of 40 kWth. The D²-SMSR has a high heat transfer coefficient between molten salt and heat pipe, which means that the core has a good heat-exchange performance. The new reactivity control strategy can achieve shutdown with one safety drum or three control drums, ensuring high-security standards. The present study can provide a theoretical reference for the design of space nuclear reactors.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.8-15
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• 2018

worker-centered safety management for hazardous areas in the plant is required. The causes of gas accidents in the past five years are closely related to the behavior of the operator, such as careless handling of the user, careless handling of the suppliers, and intentional, as well as equipment failure and accident of thought. In order to prevent such accidents, real-time monitoring of hazardous areas in the plant is required. However, when installing a camera in a work space for real-time monitoring, problems such as human rights abuse occur. In order to prevent this, an infrared camera with low resolution with low exposure of the operator is used. In real-time monitoring, image analysis is performed using CNN algorithm, not human, to prevent human rights violation.

• Elastomers and Composites
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• v.59 no.1
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• pp.22-33
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• 2024

Passive radiative cooling is a promising technology for cooling objects without energy input. Passive radiative cooling works by radiating heat from the surface, which then passes through the atmosphere and into space. Achieving efficient passive radiative cooling is mainly accomplished by using materials with high emissivity in the atmospheric window (8-13 ㎛). Research has shown that polymers tend to exhibit high emissivity in this spectral range. In addition to elastomers, other materials with potential for passive radiative cooling include metal oxides, carbon-based materials, and polymers. The structure of a passive radiative cooling device can affect its cooling performance. For example, a device with a large surface area will have a greater amount of surface area exposed to the sky, which increases the amount of thermal radiation emitted. Passive radiative cooling has a wide range of potential applications, including building cooling, electronics cooling, healthcare, and transportation. Current research has focused on improving the efficiency of passive radiative cooling materials and devices. With further development, passive radiative cooling can significantly affect a wide range of sectors.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.15
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• pp.6041-6046
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• 2014

Objective: Liposarcoma (LPS) is the most common soft tissue sarcoma and accounts for approximately 20% of all mesenchymal malignancies, often occurring in deep soft tissue of retroperitoneal space. Accurate preoperative diagnosis is therefore necessary. We explored whether computed tomography (CT) could be used to differentiate between the various types of retroperitoneal liposarcoma (RPLS). Method: Forty-seven cases of RPLS, diagnosed surgically and histologically, were analyzed retrospectively. CT features were correlated with postoperative pathological appearance. Results: The study radiologist identified 29, 11, 2, 2 and 3 RPLS as atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL), dedifferentiated liposarcoma (DDL), myxoid/round cell liposarcoma (ML/RCL), pleomorphic liposarcoma (PL) and mixed-type liposarcoma. Analysis of CT scans revealed the following typical findings of the different subtypes of RPLS: ALT/WDL was mainly visible as a well-delineated fatty hypodense tumor with uniform density and integrity margin; DDL was marked by the combination of focal nodular density and hypervascularity. ML/RCL, PL and mixed liposarcoma showed malignant biological behaviour and CT findings need further studies. Conclusions: CT scanning can reveal important details including internal components, margins and surrounding tissues. Based on CT findings, tumor type can be roughly evaluated and biopsy location and therapeutic scheme guided.