• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.51-62
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• 2017

A design optimization method is applied for the flow path design of RBCC engine, an important factor for the determining the propulsion performance operating at air-breathing mode. A design optimization was carried out to maximize the specific impulse of the RBCC engine by using a genetic algorithm based on the Kriging model. Results are analyzed using ANOVA and SOM. Design conditions of ramjet and scramjet mode are selected as Mach number 4 at 20 km altitude and Mach number 7 at 30 km, respectively. The optimized design presents that the specific impulse is increased by 7% and 10% on each condition than the baseline design.

• Convergence Security Journal
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• v.22 no.2
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• pp.105-114
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• 2022

This paper is presents an intelligent control system that visualizes the direction of arrival for hearing impaired using personal mobility, and aims to recognize and prevent dangerous situations caused by sound such as alarm sounds and crack sounds on roads. The position estimation method of sound source uses a machine learning classification model characterized by generalized correlated phase transformation based on time difference of arrival. In the experimental environment reproducing the road situations, four classification models learned after extracting learning data according to wind speeds 0km/h, 5.8km/h, 14.2km/h, and 26.4km/h were compared with grid search cross validation, and the Muti-Layer Perceptron(MLP) model with the best performance was applied as the optimal algorithm. When wind occurred, the proposed algorithm showed an average performance improvement of 7.6-11.5% compared to the previous studies.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.19 no.5
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• pp.40-51
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• 2020

Much time has passed since Korea's expressway congestion-threshold speed was revised in 2011. In the meantime, various expressway environments have changed owing to improved performance of vehicles, expanded operations of transport competition (i.e., the KTX), and increased speed limits along some expressway sections. In addition, the speed that expressway users expect to travel at is also increasing. Therefore, through a survey, this study investigates expressway users' perceptions of congestion, and reviews the adjustment of the expressway speed congestion threshold by analyzing expressway traffic flow. One result of the survey confirms that the threshold speed expressway users consider to be congestion has slightly increased. Analyzing traffic and speed data through a K-means algorithm found that the threshold speed for congestion is 60 km/h. In addition, assuming the congestion threshold speed increase from 40 km/h to 50 km/h and 60 km/h, frequently congested expressway sections are identified, determining that 50 km/h is appropriate as a congestion threshold for proper expressway mobility management.

• Atmosphere
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• v.22 no.1
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• pp.1-12
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• 2012

The Atmospheric motion vectors (AMVs) derived using infrared (IR) channel imagery of geostationary satellites have been utilized widely for real-time weather analysis and data assimilation into global numerical prediction model. As the horizontal resolution of sensors on-board satellites gets higher, it becomes possible to identify atmospheric motions induced by convective clouds ($meso-{\beta}$ and $meso-{\gamma}$ scales). The National Institute of Meteorological Research (NIMR) developed the high resolution visible (HRV) AMV algorithm to detect mesoscale atmospheric motions including ageostrophic flows. To retrieve atmospheric motions smaller than $meso-{\beta}$ scale effectively, the target size is reduced and the visible channel imagery of geostationary satellite with 1 km resolution is used. For the accurate AMVs, optimal conditions are decided by investigating sensitivity of algorithm to target selection and correction method of height assignment. The results show that the optimal conditions are target size of 32 km ${\times}$ 32 km, the grid interval as same as target size, and the optimal target selection method. The HRV AMVs derived with these conditions depict more effectively tropical cyclone OMAIS than IR AMVs and the mean speed of HRV AMVs in OMAIS is slightly faster than that of IR AMVs. Optimized mesoscale AMVs are derived for 6 months (Feb. 2010-Jun. 2010) and validated with radiosonde observations, which indicates NIMR's HRV AMV algorithm can retrieve successfully mesoscale atmospheric motions.

• Convergence Security Journal
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• v.23 no.5
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• pp.29-34
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• 2023

KMS (Knowledge Management System) is used by various organizations to share information. This KMS includes important information as well as basic information used by each organization. To protect infortant information stored in KMS, many KMS use user identification and authentication features. In such a KMS security environment, if the account information of a user who can access the KMS is leaked, a malicious attacker using the account information can access the KMS and access all authorized important information. In this study, we propose KMS with user access control function that can protect important information even if user account information is leaked. The KMS with the user access control function proposed in this study protects the stored files in the KMS by applying an encryption algorithm. Users can access important documents by using tokens after logging in. A malicious attacker without a Token cannot access important files. As a result of checking the unit function for the target user access control function for effectiveness verification, it was confirmed that the access control function to be provided by KMS is normally provided.

• Journal of the Korean Institute of Intelligent Systems
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• v.11 no.1
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• pp.76-81
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• 2001

전자교통신호등은 차량이 교차로에 많을 때에는 교통신호주기를 연장할 수 있고, 교차로에 차량이 적을 경우에는 교통신호주기를 단축할 수 있다. 그러나, 요즈음과 같이 교통체증이 많아서 평균주행속도가 10Km-20Km일 때에는 전자신호등의 기능을 수행할 수 없다. 본 논문에서는 퍼지 규칙을 이용하여 최단경로검색 및 최적 녹색시간 알고리즘을 제안한다. 컴퓨터 모의실험결과 앞 막힘 현상이 발생하는 경우에는 평균 승용차 대기시간 및 평균주행속도를 10%-32% 가량 개선시킬 수 있음을 입증하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.10a
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• pp.600-602
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• 2022

This paper proposes an algorithm that cancels the jamming and interference in the 433 MHz band promoted by the Ministry of Science and ICT at the physical layer level so that the drone operation distance can be extended up to 20 km.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.1
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• pp.35-42
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• 2001

The primitive polynomial on GF(q) is used in the area of the scrambler, the error correcting code and decode, the random generator and the cipher, etc. The algorithm that generates efficiently the primitive polynomial on GF(q) was proposed by A.D. Porto. The algorithm is a method that generates the sequence of the primitive polynomial by repeating to find another primitive polynomial with a known primitive polynomial. In this paper, we propose the algorithm that is improved in the A.D. Porto algorithm. The running rime of the A.D. Porto a1gorithm is O($\textrm{km}^2$), the running time of the improved algorithm is 0(m(m+k)). Here, k is gcd(k, $q^m$-1). When we find the primitive polynomial with m odor, it is efficient that we use the improved algorithm in the condition k, m>>1.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.3
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• pp.281-287
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• 2023

Establishing a ship's passage plan is an essential step before it starts to sail. The research related to the automatic generation of ship passage plans is attracting attention because of the development of maritime autonomous surface ships. In coastal water navigation, the land, islands, and navigation rules need to be considered. From the path planning algorithm's perspective, a ship's passage planning is a global path-planning problem. Because conventional global path-planning methods such as Dijkstra and A^* are time-consuming owing to the processes such as environmental modeling, it is difficult to modify a ship's passage plan during a voyage. Therefore, the D^* algorithm was used to address these problems. The starting point was near Busan New Port, and the destination was Ulsan Port. The navigable area was designated based on a combination of the ship trajectory data and grid in the target area. The initial path plan generated using the D^* algorithm was analyzed with 33 waypoints and a total distance of 113.946 km. The final path plan was simplified using the Douglas-Peucker algorithm. It was analyzed with a total distance of 110.156 km and 10 waypoints. This is approximately 3.05% less than the total distance of the initial passage plan of the ship. This study demonstrated the feasibility of automatically generating a path plan in coastal navigation for maritime autonomous surface ships using the D^* algorithm. Using the shortest distance-based path planning algorithm, the ship's fuel consumption and sailing time can be minimized.

• Economic and Environmental Geology
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• v.30 no.6
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• pp.625-635
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• 1997

A back projection algorithm is applied to 216 Pn travel time measurements to image lateral variations of compressional velocity in the uppermost mantle in the Korean Peninsula. We obtained an average P-velocity value for the uppermost mantle of $7.90{\pm}0.18km/sec$, and an average mantle P-velocity gradient of $5.3{\times}10^{-3}s^{-1}$ for the Korean Peninsula. The final 3-D velocity image in the uppermost mantle is characterized by a low-velocity (about $7.77{\pm}0.12km/sec$) region in the southeast area of the Korean peninsula, which is called 'Kyongsang Basin' and by high-velocity(${\geq}8.08km/sec$) region in the northern area of the Korean Peninsula(Hamkyong and Pyongan provinces). The crustal thicknesses are calculated for the 10 subregions. The crustal thickness of the northern part(${\geq}39^{\circ}N$) of the Korean Peninsula is 33.0-36.0 km, on the contrary, that of the southern part(< $39^{\circ}N$) is 30.7~33.7 km. The velocity image obtained in this study is somewhat consistent with previous S-P travel time studies and gravity studies.