• Weed & Turfgrass Science
• /
• v.7 no.3
• /
• pp.283-283
• /
• 2018

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.1
• /
• pp.1-8
• /
• 2019

In December 2017, many collision accidents of small vessels, such as those between oil refineries and fishing boats, occurred near Yeonghung-do in Incheon. In order to prevent marine casualties from small vessels, the government is striving to improve the safety capabilities of ship operators by strengthening education and improving the working environment. They are providing education and refining training regulations for fishermen operating vessels under 5 tons. However, the situation includes certain vulnerabilities. In this study, we propose a collision prevention algorithm for small vessels using the Wireless Access in Vehicular Environments (WAVE) communication system, which is a new communication technique to prevent collisions with small ships. The collision avoidance algorithm used is based on DCPA/TCPA. Research analyses, simulation experiments and questionnaires have been conducted to define the criteria of DCPA/TCPA. As a result, the standard for DCPA was $8(L_a+L_b)$ and for TCPA was 2.5 min. Three different accident cases were selected, and this algorithm was applied to confirm alarm responses at certain times. This algorithm can provide information to the operators of small ships in advance to help them recognize potential collision situations.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.4A
• /
• pp.473-478
• /
• 2008

WAVE is a short-to-medium range communication standard that supports both public safety and private operations in roadside-to-vehicle and vehicle-to-vehicle communication environments. The core technology of physical layer in WAVE is orthogonal frequency division multiplexing (OFDM), which is sensitive to timing synchronization error. Besides, minimizing the latency in communication link is an essential characteristic of WAVE system. In this paper, a robust, low-complexity and small-latency timing synchronization algorithm suitable for WAVE system and its efficient hardware architecture are proposed. The comparison between proposed algorithm and other algorithms in terms of computational complexity and latency has shown the advantage of the proposed algorithm. The proposed architecture does not require RAM (Random Access Memory) which can affect the pipe lining ability and high speed operation of the hardware implementation. Synchronization error rate (SER) evaluation using both Matlab and FPGA implementation shows that the proposed algorithm exhibits a good performance over the existing algorithms.

• Journal of Environmental Science International
• /
• v.26 no.12
• /
• pp.1399-1405
• /
• 2017

We compared the spatial distribution of several heat stress indices (the Wet-Bulb Globe Temperature(WBGT) index, Environmental Stress Index (ESI), and Modified Discomfort Index(MDI)) for the heat wave of June 6~August 26, 2016, in Daegu. We calculated the heat stress indices using data from the high density urban climate observation network in Daegu. The observation system was established in February. 2013. We used data from a total of 38 air temperature observation points (23 thermometers and 18 automatic weather stations). The values of the heat stress indices indicated that the danger level was very high from 0900-2000h in downtown Daegu. The daily maximum value of the WBGT was greater than or equal to $35^{\circ}C$. The differences in the heat stress indices from downtown and rural areas were higher in the daytime than at nighttime. The maximum difference was about 4 before and after 1400h, and the time variations of the heat stress indices corresponded well. Thus, we were able to confirm that the ESI and MDI can be substituted with the WBGT index.

• Journal of the Korean Society for Marine Environment & Energy
• /
• v.8 no.1
• /
• pp.23-30
• /
• 2005

A numerical scheme is proposed which is applicable to the evaluation of wave field containing floating structures, and the method is utilized to estimate the effect of the floating breakwaters to be installed in Wonjeon port near Masan. The model is based on the mild-slope equation which is widely accepted for the calculation of wave modulation near shores and an additional term is introduced to consider the wave scattering associated with the thin floating structures such as floating breakwaters. The tranquility in Wonjeon port with the floating breakwater in the east side is calculated and compared with the one with a bottom-fixed breakwater. The present method is believed to provide an efficient way of quantitative measurement of the performance of floating breakwaters.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.25 no.3
• /
• pp.366-372
• /
• 2019

This study performed a numerical analysis of a 3D unsteady viscous flow in order to investigate ship motion responses running through regular waves of the platform supply vessel. The feasibility of numerical analysis was tested under the three regular wave conditions of the KRISO container ship (KCS) suggested at the 2010 Gothenburg CFD Workshop. The resulting resistance coefficient, heave motion, and pitch angle were compared with the model test of the harmonic analysis. Also, the ship motion response characteristics of the platform supply vessel were performed using the proven method of the KRISO container ship (KCS). The ship motions including the resistance coefficient, heave motion, and pitch angle according to the time series were investigated via harmonic analysis under regular waves condition of ${\lambda}/LPP=1.87$ and $H_S=0.078m$.

• Journal of the Korean Solar Energy Society
• /
• v.30 no.3
• /
• pp.71-80
• /
• 2010

This study carried out to understand the thermal characteristics of various surface material which compose the city through the observation in the summer. To examine passive cooling effect of planting of building, it is arranged four different materials that is natural grass, grass block, concrete slab and artificial grass. The results of this study are as follows; (1) Natural grass and grass block show the lower surface temperature because of the structures of leaf can do more thermal dissipation effectively. (2) There is little surface temperature between artificial grass and concrete. But there is little high surface temperature difference between natural grass and concrete because of latent heat effect. (3) The concrete can play a role of the tropical nights phenomenon as high heat capacity of concrete compare with other materials. (4) It is nearly same color in artificial grass and natural grass but there is large difference between natural grass and artificial grass at albedo. There is different albedo in near infrared ray range. (5) A short wave radiation gives more effect at the globe temperature than long wave radiation. (6) The artificial turf protected the slab surface temperature increase in spite of thin and low albedo materials.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.6
• /
• pp.142-149
• /
• 2019

In this study, the past erosion history and current status in the CHUNG-UI beach of Eulwang-dong, Jung-gu, Incheon-Si, South Korea were investigated and analyzed the wave with wave-induced current to investigate the causes of coastal erosion. As a result, the significant wave height ($H_{1/3}$) was in the range of 0.07~1.57 m and the mean value was 0.21 m. The maximum wave height ($H_{max}$) was in the range of 0.02-4.76m and the mean value was 0.27m. The vertical wave height and cycles were estimated through numerical model experiments of wave transformation. The 50-year frequency design wave height ranged from 0.82m to 3.75m. As a result of the experiment of wave-induced current, wave-induced current in the CHUNG-UI beach was decreased after the installation of the Detached breakwater and the Jetty. On the other hand, when the crest elevation was increased up to 5 m, there was no significant change, but when the crest elevation was increased to 8m, strong wave-induced current occurred around the submerged breakwaters due to lowered depth of water. In addition, the main erosion of the CHUNG-UI beach is due to the intensive invasion of the wave characteristics coming from the outer sea into the white sandy beach. The deformation of the wave centered on the front of the sandy beach caused additional longshore currents flowing parallel to the sandy beach and rip currents in the transverse direction, thus confirming that the longshore sediment was moved out of the front and out of the sea. The results of this study can be used as preliminary data for the recovery of the sand and the selection of efficient erosion prevention facilities.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.7
• /
• pp.1439-1444
• /
• 2005

AIS needs hish efficiency and safety in terms of operational management and, in the aspect of service range, it is time to minimize shadow regions through propagation evaluation of AIS transmitter. Thus this study analyzes shadow regions and the scope of propagation of waves from stations through the electric wave environment of AIS. First, this study examines the characteristics of AIS wave and draws up methods to analyze the scope of propagation of waves according to the characteristics. Second, this study finds out service regions and shadow regions of the 22 stations across the nation by analyzing the actual data based on climate and topography. Lastly, this study summarizes the results of wave conductivity evaluation and conductivity problems and proposes improvement measures.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.19 no.1
• /
• pp.78-84
• /
• 2013

The primary objective of the current work is to develop efficient numerical code to assess the resistance performance of the twin hull form. Resistance performance for the two different twin hull forms with asymmetric and symmetric mono hull using developed code are evaluated. Numerical calculations and model tests have been compared to validate a developed code used in the current work. Comparison were carried out through sinkages of the bow and stern, trim angle and wave-making resistance. Comparative analysis regarding hydrodynamic characteristic of different twin hull forms is worthy of application in the hull form development stage.