• Journal of the Korean Society of Marine Environment & Safety
• /
• v.23 no.2
• /
• pp.131-138
• /
• 2017

Lately, Internet-based vessels have begun to appear at sea with the development of ICT. Thereby crews have gained easy Internet access through increased smartphone portability. However, the side effects of smartphone use while on watch, have not been studied seriously despite being a reality. In this study, simulation experiments were carried out using a Ship Handling Simulator in order to distinguish the risks of using a smartphone while on watch. Proximity Evaluation, Control Evaluation, Subjective Evaluation and Situation Awareness to the dangerous situation were used to quantify risk during simulation, and analysis results were compared with cases when using and not using a smartphone. It was found that the degree of risk increased between 1.3 to 3 times given smartphone use. Consequently, this paper represents foundation for the restriction of smartphone use and proposes smartphone usage guideline for ship navigation.

• Journal of Navigation and Port Research
• /
• v.31 no.1 s.117
• /
• pp.1-6
• /
• 2007

The evaluation of safety of simulated maneuvers is frequently analysed by so called goal-line or point of interest in Korea. For the purpose of warning the risk in the proximity measure composed of only the goal-line analysis, this paper utilized Korea Institute of Maritime and Fisheries Technology(KIMFT) which houses a real-time, full-mission shiphandling simulator to examine the goal-line and in-length analyses in the outbound channel of Kwangyang port as an example. It used a 15,000 TEU container ship as a model under environmental conditions of the northwestly 26-knot wind and 2.2-knot ebb current. The result of two analyses showed the probability invading the channel boundary obtained by the goal-line analysis is a little greater than that of the in-length analysis. Therefore it was acknowledged that the proximity measure by the goal-line analysis alone may be followed by some risk. In addition, this paper was to suggest the closest distance to channel boundary from the ship's edge as one of proximity measures, instead of using the ship's deviation from the centerline of channel.

• Journal of Navigation and Port Research
• /
• v.32 no.8
• /
• pp.577-582
• /
• 2008

In order to ascertain the effect of ship's speeds, in maneuver under the condition of strong cross current in the breakwater channel of Busan port, this paper is to deal with the analyses of vessel proximity measures, vessel controllability measures, and ship handlers' subjective evaluation measures of simulated maneuvers, which were carried out by 76 ship handlers who conned Panamax bulk carrier of 60,000 DWT, The set and drift of current are southwesterly and 2 knots. The speeds of the model ship are 5 knots & 10 knots respectively. The followings are concluded. ${(1)}$ In the approaches of the breakwater of Busan port, ship handlers psychologically tend not to give the drift angle of more than $10^{\circ}$ bemuse ship's head points out of the entrance. ${(2)}$ Ship handlers' subjective evaluation, vessel proximity and controllability measures are relatively larger under the speed of 5 knots than under that of 10 knots. due to direct pressure of strong current. ${(3)}$ A single index of controllability measures was suggested, by removing their units.

• Journal of the Korean Geographical Society
• /
• v.36 no.4
• /
• pp.434-443
• /
• 2001

Differing from the existing method to optimize the statistical proximity, the new optimization method was developed to maximize the spatial proximity among the unit areas of choropleth map. 25 choropleth maps were made using 5 classification methods(maximum BEI, maximum TEI, equal interval, natural break, n-tile) for 5 classes(3∼7) and were analyzed to elucidate the effectiveness of classification methods on the basis of 3 evaluation indeces (TEI, BEI, $C_{F}$). The results from the maximum TEI and maximum BEI were evaluated as relatively stable and effective compared to those from other classification methods. But they showed the opposite trends owing to the trade-off relationships. Meanwhile, the resets from the natural break method got higher marks, which was also identified through the analysis using a new $alpha$-index.x.

• Proceedings of the Korean Information Science Society Conference
• /
• 2003.04c
• /
• pp.374-376
• /
• 2003

본 논문에서는 Fussy C-Means (FCM) 알고리즘에 의해 계산된 퍼지 클러스터들에 대한 평가 인덱스를 제안한다. 제안된 인덱스는 퍼지 클러스터들간의 인접성(inter-cluster proximity)을 이용한다. 클러스터 인접성을 도입함으로써 클러스터간의 중첩 정도를 계산할 수 있다. 따라서, 인접성 값이 낮을수록 클러스터들은 공간에 잘 분포하게 됨을 알 수 있다. 다양한 데이터 집합에 대한 실험을 통해서 제안된 인덱스의 효율성과 신뢰성을 검증하였다.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.4
• /
• pp.119-125
• /
• 1989

This paper presents a method of analog signal processing for a coordinate transformation. Through the proposed method, two-dimensional position information obtanided from any type of null-detector can be transformed into the information with repect to world coordinate system. In order to implement the method, a null- detection device which consists of four optical proximity sensor is developed. Through the experiments for performance evaluation, the effectiveness of the proposed method has been demonstrated.

• International Journal of Highway Engineering
• /
• v.14 no.5
• /
• pp.201-206
• /
• 2012

PURPOSES: This study evaluated a measuring technique for tire-pavement interaction noise that uses a noble close proximity (NCPX) method as well as for noise level measured inside of a car (e.g., Inside Noise Level) in term of rumble strips constructed at a tall gate. METHODS: According to the measurements of NCPX and inside noise level (INL), 1/3 octave band frequency analysis and overall noise level calculation were conducted in order to evaluate noise levels of NCPX and INL, depending on types of rumble strips. RESULTS: The tested sections of general concrete pavement surface and two different types of rumble strips were evaluated, using 1/3 octave band frequency analysis and overall noise level. From the analyzed results, it can be concluded that rumble strips generate a relatively huge noise levels when compared to the concrete pavement surface. CONCLUSIONS: Noting that above 3 dBA different noise levels can let drivers know that they are getting close to toll gate; therefore, they should apply their brakes. Thus, the noise levels of rumble strips are required to be reduced, based on considering the neighbors living near toll gates.

• Journal of the Korea Concrete Institute
• /
• v.15 no.3
• /
• pp.504-511
• /
• 2003

Environmental noise at high intensities directly affects human health by causing hearing loss. Although scientific evidence currently is not conclusive, noise is suspected of causing or aggravating other diseases. Environmental noise indirectly affects human welfare by interfering with sleep, thought, and conversation. Noise emission from motorized vehicle includes power unit noise, tire/pavement noise and aerodynamic noise. Among them, tire/pavement noise is noise emission from interaction of the tire and road surface when the vehicle cruises over the surface of pavement. In general, portland cement concrete(PCC) pavement is known to create more noise than asphaltic surfaces though it has the advantage of durability and superior surface friction. However, the results of preliminary laboratory test showed exposed aggregate concrete(EAC) has and effect on reducing tire/pavement noise. Based on the laboratory test. pilot construction of exposed aggregate concrete pavement was completed and series of in-situ measurements were conducted for noise analysis including the pass-by noise measurement and the close-proximity method. Conclusively, it is expected that tire/pavement noise represent significant portion of noise levels at higher frequencies and it would be reduced on special textures of pavement such as exposed aggregate concrete.

• Journal of Astronomy and Space Sciences
• /
• v.38 no.3
• /
• pp.165-173
• /
• 2021

Apophis is a near-Earth object with a diameter of approximately 340 m, which will come closer to the Earth than a geostationary orbit in 2029, offering a unique opportunity for characterizing the object during the upcoming encounter. Therefore, Korea Astronomy and Space Science Institute has a plan to propose a space mission to explore the Apophis asteroid using scientific instruments such as a laser altimeter. In this study, we evaluate the performance metrics of a laser altimeter using a pseudorandom noise modulation technique for the Apophis mission, in terms of detection probability and ranging accuracy. The closed-form expression of detection probability is provided using the cross correlation between the received pulse trains and pseudo-random binary sequence. And the new ranging accuracy model using Gaussian error propagation is also derived by considering the sampling rate. The operation range is significantly limited by thermal noise rather than background noise, owing to not only the low power laser but also the avalanche photodiode in the analog mode operation. However, it is demonstrated from the numerical simulation that the laser altimeter can achieve the ranging performance required for a proximity operation mode, which employs commercially available components onboard CubeSat-scale satellites for optical communications.

• Environmental Engineering Research
• /
• v.23 no.4
• /
• pp.420-429
• /
• 2018

Soil stabilization is a soil remediation technique that reduces the mobility of heavy metals in soils. Although it is a well-established technique, it is nonetheless essential to perform a follow-up chemical assessment via a leaching test to evaluate the immobilization of heavy metals in the soil matrix. Unfortunately, a standard chemical assessment is not sufficient for evaluation of the biological functional state of stabilized soils slated for agricultural use. Therefore, it is useful to employ a pyrosequencing-based microbial community analysis for the purpose. In this study, a recently stabilized site in the proximity of an exhausted mine was analyzed for bacterial diversity, richness, and relative abundance as well as the effect of environmental factors. Based on the Shannon and Chao1 indices and rarefaction curves, the results showed that the stabilized layer exhibited lower bacterial diversity than control soils. The prevalence of dominant bacterial populations was examined in a hierarchical manner. Relatively high abundances of Proteobacteria and Methylobacter tundripaludum were observed in the stabilized soil. In particular, there was substantial abundance of the Methylobacter genus, which is known for its association with heavy metal contamination. The study demonstrated the efficacy of (micro)biological assessment for aiding in the understanding and post-management of stabilized soils.