• Aerospace Engineering and Technology
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• v.1 no.2
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• pp.132-140
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• 2002

By utilizing OSMI (Ocean Scanning Multi-spectral Imager) onboard KOMPSAT-1, the moon can be imaged. Because the moon has no atmosphere and reflects sun lights at a constant rate, it can be the radiance source for calibration of OSMI. But there are a lot of risks which made KOMPSAT-1 enter into safe-hold mode. So planning the imaging of the moon with OSMI should be determined seriously with consideration to information on KOMPSAT-1 operation, the moon, the sun, etc. But it takes a long time for determining the imaging time of the moon using MCE(Mission Control Element) simulator and there are operational problems to be solved. In this paper, fast simulator for determining imaging time for the moon with OSMI has been developed. The proper timeline for imaging the moon and the position of the moon image in OSMI image coordinates and the phase of the moon are determined. STK was used for acquiring information on KOMPSAT-1, the moon, the sun and the characteristitcs of OSMI are considered. As a result, we can determine imaging time of the moon with OSMI much faster and efficiently.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.1
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• pp.15-20
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• 2016

The existing multiple modulus-based self-recovering equalization type has not been applied to initial equalization. Instead, it was used for steady-state performance improvement. In this paper, for the self-recovering equalization type that considers the multiple modulus as a desired response, the initial convergence performance was improved by extending the dynamics of the errors using error boosting and their characteristics were analyzed. Error boosting in the proposed method was carried out in proportion to a symbol decision for the equalizer output. Furthermore, having the initial convergence capability by extending the dynamics of errors, it showed excellent performance in the initial convergence rate and steady-state error level. In particular, the proposed method can be applied to the entire process of equalization through a single algorithm; the existing methods of switching over or the selection of other operation modes, such as concurrent operating with other algorithms, are not necessary. The usefulness of the proposed method was verified by simulations performed under the channel conditions with multipath propagation and additional noise, and for performance analysis of self-recovering equalization for high-order signal constellations.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.2
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• pp.88-97
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• 2021

The controller of the gas turbine engine is a component that needs to be developed for the development of the gas turbine engine because it is impossible to get the technology transferred from the engine manufacturer due to the import and export regulation. As a part of the engine control logic research, the Korea Aerospace Research Institute conducted a failure diagnostic research using a small gas turbine engine. Before simulating the engine fault, the ground test was performed to analyze normal behavior and performance of engine. Afterwards, the control logic analysis test equipment was established to simulate various engine fault. It is intended to provide background knowledge to engine control logic research for various engine failure conditions.

• Journal of Aerospace System Engineering
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• v.16 no.5
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• pp.78-85
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• 2022

Multicopter-type unmanned aerial vehicles (UAV) are increasingly for cargo transportation to mountainous and island regions, image information acquisition in disaster areas, and emergency rescue transport. In order to successfully perform these tasks, the aircraft structure must be able to safely support the loads induced by flight conditions while ensuring the vibration and aeroelastic stability of the prop-rotor. This study introduced a structural analysis model of a 40kg payload multicopter with an engine-generator hybrid power system. The deformation and stress distribution are investigated depending on the load conditions. In addition, the vibration characteristics and aeroelastic stability of the prop-rotor were also presented to flight speed and aircraft pitch angle. The maximum thrust generated by the prop-rotor and the landing load applied to the multicopter under normal and emergency landing conditions were reviewed., It confirmed that the structure could support without failure. In addition, it confirmed that the damping characteristics of each primary locate in the constant region according to the aircraft's flight speed and the prop-rotors rotating speed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1163-1170
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• 2016

A hardware implementation of ultra-lightweight block cipher algorithm PRESENT which was specified as a standard for lightweight cryptography ISO/IEC 29192-2 is described. The PRESENT crypto-processor supports two key lengths of 80 and 128 bits, as well as four modes of operation including ECB, CBC, OFB, and CTR. The PRESENT crypto-processor has on-the-fly key scheduler with master key register, and it can process consecutive blocks of plaintext/ciphertext without reloading master key. In order to achieve a lightweight implementation, the key scheduler was optimized to share circuits for key lengths of 80 bits and 128 bits. The round block was designed with a data-path of 64 bits, so that one round transformation for encryption/decryption is processed in a clock cycle. The PRESENT crypto-processor was verified using Virtex5 FPGA device. The crypto-processor that was synthesized using a $0.18{\mu}m$ CMOS cell library has 8,100 gate equivalents(GE), and the estimated throughput is about 908 Mbps with a maximum operating clock frequency of 454 MHz.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.12
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• pp.1129-1135
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• 2013

In this, three types of natural gas were employed to investigate the effect of low-calorific natural gas on the performance of and emissions from a heavy-duty CNG engine. The performance and emission characteristics were analyzed by conducting a full-load test, WHSC mode test, and WHTC mode test. The results showed that the torque of low-calorific natural gas with $9,800kcal/Nm^3$ of higher heating value decreased by 4.4 compared to that of the current natural gas with $10,400kcal/Nm^3$ of heating value. With low-calorific fuels, CO, $CO_2$, and $NO_x$ emissions decreased. However, THC emissions increased. According to the WHSC and WHTC mode test results, the thermal efficiency increased and the emission characteristics showed a similar trend to the full-load test results. Low-calorific natural gases cause a decrease in torque at full-load operation conditions and an increase in hydrocarbon emissions.

• Journal of Aquaculture
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• v.11 no.2
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• pp.125-132
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• 1998

The results of experimental culture for Koran mitten crab, Eriocheir japonicus at different outdoor culture methods such as rice field, pond, and vinyl house from July 21, 1994 to October 23, 1995 were summaried as fellows. 1. The water temperature was 2${\circ}C$~32${\circ}C$ during the culture periods from July 21, 1994 to October 23, 1995, and it ranged from 15${\circ}C$ to 30${\circ}C$ during the terms showing the intake habit of feed with these temperature maintained for 281 days of 460days of the total cultur periods. 2. The gain weight of Korean mitten crabs was 1,711.3g at the rice field, and 1,565.4g at the pond, and 1.220.0g at the vinyl house. The survial rate was 22.7% at the pond, and 18.7% at the rice field, and 18.3% at the vinyl house with the average survial rate of 19.9%. The daily growth rate of cauapace width was 0.64% at the rice field, and 0.61% at the pond, and 0.59% at the vinyl house. And the gain weight and the daily growth rate were the best at the rice field. 3. When the culture was finished, the frequency of carapace width of 4.0~4.9cm was 57.1% at the rice field, and 33.3% at the vinyl house. Therefore, culture at the rice field for the cultur of mitten card was considered to be the best outdoor culture method from the point of view in the fast growth and polyculture feasibility with paddy rice.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.103-110
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• 2010

In this paper, a new mode changeable asymmetric full bridge dc/dc converter is proposed to solve the freewheeling current problem of the conventional zero voltage switching(ZVS) phase shift full bridge(PSFB) dc/dc converter of low output voltage and high output current applications. The proposed converter is operated as an asymmetric full bridge converter when the duty cycle is less than 50% and active clamp full bridge converter when the duty cycle is greater than 50%. As a result, since its freewheeling current is eliminated, the conduction loss is lower than that of the conventional ZVS PSFB dc/dc converter. Moreover, ZVS of all power switches can be ensured along a wide load ranges and output current ripple is very small. Therefore, high efficiency of the proposed converter can be achieved. Especially since its operation mode is changed to the active clamp full bridge converter during hold up time and can be operated with 50~100% duty ratio, it can produce the stable output voltage along wide input voltage range. The operational principles, theoretical analysis and design considerations are presented. To confirm the operation, validity and features of the proposed converter, experimental results from a 1.2kW($400V_{dc}/12V_{dc}$) prototype are presented.

• Journal of Korean Society of Steel Construction
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• v.15 no.6 s.67
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• pp.673-681
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• 2003

This paper describes the experiment that determines the ultimate strength of new uniplanar T-joints made of cold-formed square hollow sections. The new T-joint focused on the configuration of a branch member that is oriented 45 degrees to the plane of the truss and welded to the chord member whose web is stiffened with plate. The strength and failure mode are examined using the existing strength formula for the branch-rotated T-joint $(16.7{\leq}2{\gamma}(B/T){\leq}33.3$ and $0.63{\leq}{\beta}(b1/B){\leq}0.7)$. The test result shows that the capacity of the stiffened joint increases with thicker stiffening plate. The failure mode of the specimen $(2{\gamma}=33.3)$ is stiffened with plate changes from M2 (flange failure) to M3 (combined failure). On the other hand, the failure mode of the specimen $(2{\gamma}=16.7)$ is stiffened with plate changes from M1 ( web failure) to M2 (flange failure)

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.464-469
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• 2019

A remote monitoring panel and control system was developed to control various valves and access control chambers, including gas shutoff valves used in CBR(Chemical, Biological and Radiological) facilities. The remote monitoring panel consisted of a main panel installed in the NBC (Nuclear, Biological and Chemical) control room and auxiliary panel installed in the clean room, and the size was divided into pure control and control including CCTV. This system can be monitored and controlled remotely according to the situation where an explosion door and gas barrier door can occur during war and during normal times. This system is divided into normal mode and war mode. In particular, it periodically senses the operation status of various valves, sensors, and filters in the CBR facilities to determine if each apparatus and equipment is in normal operation, and remotely alerts situation workers when repair or replacement is necessary. Damage due to the abnormal operation of each device in the situation can be prevented. This enables control of the blower, supply and exhaust damper, emergency generator, and coolant pump according to the state of shutoff valve and positive pressure valve in the occurrence of NBC, and prevents damage caused by abrupt inflow of conventional weapons and nuclear explosions.