• Journal of the Korean Wood Science and Technology
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• v.13 no.2
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• pp.3-13
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• 1985

This study was carried out to investigate the effects of presteaming on the drying rate and drying defects of 3 cm - thick Quercus acutissima. Specimens for presteaming were steamed green at $100^{\circ}C$ for 4 hours and then kiln-dried to 10 percent moisture, content with controls, using the kiln-drying schedule ($T_4-C_2$) recommended by Rasmussen. The results obtained were as follows: 1. Presteaming reduced drying time approximately 18 percent from 70 to 10 percent moisture content. 2. The effect of presteaming on surface checking was not significant. 3. Presteamed specimens showed the reduction in end checking compared with controls. 4. Percents of boards with collapse, cupping, and honeycomb of presteamed specimens were slightly lower than those of controls. 5. Dry lumber grade of presteamed specimens was better than that of controls. Percent of first grade boards of presteamed specimens was 20 percent higher than that of controls and percents of second and third grade boards of presteamed specimens were 15 and 5 percent lower than those of controls, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1359-1366
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• 2010

Recently, many electronic control techniques for vehicles have been developed and applied. One of the technologies can be X-by-wire such as throttle-by-wire, brake-by-wire, steer-by-wire, and etc, in which most of mechanical parts are replaced into electrical wire and actuators. In this study, the effect of throttle-by-wire and brake-by-wire control systems on vehicle velocity control, especially in a school zone, are taken into consideration. The number of accidents reported in school zones is higher than that in other places. The reason for this is that many vehicle drivers do not obey speed limit regulations. Moreover, some of the students are careless while crossing the streets. Therefore, in this study, we attempt to develop a method using throttle-by-wire and brake-by-wire control systems for automatically reducing the vehicle speed such that it will be within the speed limit. First, an engine model and a transmission system model are developed for a specific vehicle model. Second, speed reduction is carried out such that the reduction follows a pre-designed cubic spline trajectory; the trajectory is determined such that rapid deceleration, which causes discomfort to the driver and passengers, can be prevented, for which a fuzzy-PID control algorithm is applied for the trajectory following control. Finally, simulation results are presented to verify the performance of the proposed speed reduction control system.

• Journal of Hydrogen and New Energy
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• v.21 no.6
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• pp.487-492
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• 2010

For developing a two-stroke free-piston hydrogen engine with high efficiency and low emission, determination of the scavenging type is one of the most important factor. In this research, backfire characteristics for loop scavenging were analyzed with the number of piston crevice volume and piston expansion speed. Rapid Compression Expansion Machine, RCEM was used for combustion research of the free piston $H_2$ engine in the experiment. As the results, it was shown that although backfire occurring in a loop scavenging type can be partially controled by a complete exhaust of burned gas, possibility of backfire basically exist due to the structure which piston crevice volumes contact with fresh mixture in a scavenging port. However, a loop scavenging may be considered as combustion chamber of a free piston $H_2$ engine from the point of view that backfire does not occur nearby lean equivalence ratio obtained high thermal efficiency. It was also analyzed that an advances of backfire occurrence timing with increase of the fuel-air equivalence ratio were due to promotion of flame propagation into piston crevice volumes by decrease of the quenching distance.

• Journal of the Korean Wood Science and Technology
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• v.44 no.3
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• pp.295-301
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• 2016

In this study, relationship between seed origin and growth rate of Alnus glutinosa from different seed collection (Yugoslovia, ltaly, United Kingdom, Bulgaria) was investigated with focused on anatomical properties as wood fiber length, vessel element length and diameter. Alnus glutinosa showed diffuse-porous wood with scalariform perforation in alternate pitting. Ray height was 9~11 in tangential section and ray number were 16~26 in cross section. There were no differences on latewood focused on wood fiber length, length and diameter of vessel element, but difference on earlywood. Other than Yugoslavian seed, there was better growth rate with shorter wood fiber and vessel element length on latewood. However, seed from Yugoslovain showed better growth rate with longer wood fiber and vessel element length than other 3 seed orgins.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.26-36
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• 2008

Currently, the pedestrian signal timing model has no consideration on the characteristics of different land use patterns and pedestrian behaviors during pedestrian signal timing calculation. This study intended to propose pedestrian signal timing models that could reflect the inherent characteristics of pedestrian and land use patterns. For this study, three major variables affecting the length of signal timing were identified: walking speed, perception-reaction time, and density-delay time. Then, the representative values of each variable were estimated through the field studies. By combining this information, several pedestrian signal timing models were developed. The data in this paper can be used for future references, and the walking environments for pedestrians could be improved by applying the models suggested in this paper.

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.113-118
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• 2016

The walking speed of handicapped people generally is slower than that of normal people. So it is difficult for them to cross at crosswalks within the allotted time provided by the traffic light. This problem can be solved by expanding the time of the traffic light. However, if the latency of the traffic light is increased without distinguishing the handicapped among all other pedestrians, the efficiency of traffic signal lights will decrease. In this paper, we propose a smart traffic signal connecting mechanism between the previous pedestrian traffic signal and a pedestrian's device (smartphone). This Smart pedestrian traffic light, through this mechanism, minimizes traffic congestion by providing additional walking time only to the handicapped among pedestrians. This crosswalk traffic light recognizes the handicapped using a technique called Internet of things (IOT). In this paper, we extract the data necessary to build an effective smart crosswalk traffic light mechanism through simulation techniques. We have extracted different kinds of traffic signal times with our virtual simulation environment to verify the efficiency of the smart crosswalk pedestrian traffic light system. This approach can validate the effective delay time of the traffic signal time through a comparison based on number of pedestrians.

• Journal of the Korean Geographical Society
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• v.46 no.4
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• pp.425-441
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• 2011

Ridge traversing trail in Mount Jiri National Park is classified as flat, gully-like, unilateral, and asymmetric bilateral, paths based on a location and gradient of paths. These types are interchangeable due to a drainage condition of trail surfaces. Using a rapid survey, the trail is 135.9 cm wide, 23.6 cm deep and $5.1^{\circ}$ in a gradient, respectively. All treads have been compacted due to human trampling. The path width is affected by a slope aspect and a distribution of Sasa borealis. An asymmetric path is wider than a symmetric path. A soil erosion rate is equivalent to $68.9cm^2/year$ for the period from 1960 to 2009, suggesting that the trail has been widened 2.7 cm/year and the tread lowered 0.4 cm/year. Trampling and needle ice action combined with rainwash induced by a pipeflow are dominant erosion processes contributing to the trail expansion.

• International Journal of Highway Engineering
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• v.10 no.3
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• pp.47-56
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• 2008

Generally, accident exposure at intersections is relatively higher than that at roadway segments due to more possibility of merging, diverging, turning, crossing, and weaving maneuver. Furthermore, the traffic accident rate at intersections has been rapidly increasing since 1990's. Since there is more opportunity of conflict at unsignalized intersection, frequency and severity of traffic accident are more severe than signalized intersections. The purpose of the study is to analyze factors causing vehicle crashes and provide intersection design guidelines to improve intersection safety. For this study, vehicle to vehicle crash data of 116 rural 3 legs unsignalized were collected and field surveys were conducted for traffic and geometric conditions. Ordered probit models were developed to analyze the severity of crashes. It was found that weather, obstacles in minor roadsides, presence of major exclusive right lane, presence of major road crosswalk, difference between posted speed of major road and minor road, land-use around intersections, shoulder width of major road, ADT of major road are significant factors for intersection safety.

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.53-63
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• 2008

Even though accident frequencies in roadway segments have been decreasing since 2000, there has been increasing the number of vehicle crashes at intersections. Due to this increase, safety problems at intersection recently started to be regarded as significant issues. The purpose of this study is to analyze the effects of road conditions, traffic operational conditions, and other influencing condition on intersection safety. Then a traffic accident frequency prediction model to evaluate the safety at intersections was developed based on the correlations between influencing factors and vehicle crashes. In this research, critically significant factors affecting vehicle crashes at rural four-legs signalized intersections were investigated. It was found that Poisson regression was the best fit method to developing a accident frequency modeling using the collected data in this study. Through this study, it was concluded that exclusive left turn lane, crosswalk, posted speed, lighting, angle, and ADT are significant influencing factors on the intersection safety.

• Journal of Korean Society for Geospatial Information Science
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• v.21 no.3
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• pp.3-9
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• 2013

As interest in green growth picks up, the importance of bicycles which are an environment friendly means of communication has been magnified. However, bicycle routes which are the base of bicycles are designed without considering topographic elements and thus many users are experiencing inconvenience in using bicycles. The present study presents a routing technique to select optimal routes when selecting routes in commuting to school utilizing bicycles. To this end, a formula for optimum route calculation considering slope and intersections was drawn and a method to select optimum routes by applying modified Dijkstra Algorithms was studied. According to the results, the bicycle routes for commuting to school should be selected by the shortest time rather than the shortest distances to the destination, because it required reach the destination faster. Therefore when selecting the routes, it must be based on the shortest time considering waiting time due to crosswalks or crossroads and speed variations due to slopes.