• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.2
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• pp.19-27
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• 2016

Maritime transport is now regarded as one of the main contributors to global climate change by virtue of its $CO_2$ emissions. Meanwhile, slow steaming, i.e., slower ship speed, has become a common practice in the maritime industry so as to lower $CO_2$ emissions and reduce bunker fuel consumption. The practice raised various operational decision issues in terms of shipping companies: how much ship speed is, how much to bunker the fuel, and at which port to bunker. In this context, this study addresses an operation problem in a shipping companies, which is the problem of determining the ship speed, bunkering ports, and bunkering amount at the ports over a given ship route to minimize the bunker fuel and ship time costs as well as the carbon tax which is a regulatory measure aiming at reducing $CO_2$ emissions. The ship time cost is included in the problem because slow steaming increases transit times, which implies increased in-transit inventory costs in terms of shippers. We formulate the problem as a nonlinear lot-sizing model and suggest a Lagrangian heuristic to solve the problem. The performance of the heuristic algorithm is evaluated using the data obtained from reliable sources. Although the problem is an operational problem, the heuristic algorithm is used to address various strategic issues facing shipping companies, including the effects of bunker prices, carbon taxes, and ship time costs on the ship speed, bunkering amount and number of bunkering ports. For this, we conduct sensitivity analyses of these factors and finally discuss study findings.

• Journal of The Korean Association For Science Education
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• v.24 no.6
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• pp.1049-1062
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• 2004

In this study, various scientific viewpoints of 'motion of objects' were analyzed from the Aristoteles age to the Newton age. From the analysis, a questionnaire was developed which was including causes of motion, forms of motion, and preservation quantity of movement. The conceptions of pre-service science teachers were researched by the questionnaire developed in this study based on the science historical viewpoints. The subjects were twenty sophomore students of physic education major and thirty four of other science education major who majored common science education also in a college. Most of the pre-service teachers of physical education major had inertia and Newton's force conception related to the question situations of 'causes of motion' and 'forms of motion'. But a lot of the pre-service teachers of physic education major and other science education major had viewpoints of Descartes or Huygens related to the question situation of 'preservation quantity of movement'. Only few pre-service teachers regardless of major had Newton's viewpoint which represented in current Korean science curriculum for secondary school.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.6
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• pp.816-824
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• 2010

The forces applying to an object in the transferring pipe of waste are analyzed and the equation of motion is established in this paper. It is shown that the equation of motion becomes the 1st order non-linear differential equation. Using its general solution, the velocity of the object in the transferring pipe of waste can be expressed in the explicit form. Noting that the velocity of object is impact velocity to the elbow or curved part of the transferring pipe of waste, the kinetic energy of the object can be calculated and the necessary impact strength of inner wall is obtained. The velocity of object is also calculated and presented in the graphic forms with the condition of air velocity 30m/sec. The impact test of cast basalt tube is carried out by the free fall of a weight and the test results show that the impact strength of the cast basalt tube is sufficient to apply to protecting inner wall of the transferring pipe of waste.

• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.21-29
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• 2017

For the efficient and stable operation of autonomous vehicles or advanced driver assistance systems being actively studied nowadays, it is important to determine the positions of the vehicle accurately and economically. A satellite based navigation system is mainly used for positioning, but it has a limitation in signal blockage areas. To overcome this limitation, sensor fusion methods including additional sensors such as an inertial navigation system have been mainly proposed but the high sensor cost has been a problem. In this work, we develop a vehicle position estimation algorithm using in-vehicle sensors and a low-cost imaging sensor without any expensive additional sensor. We determine the vehicle positions using the velocity and yaw-rate of a car from the in-vehicle sensors and the position and attitude of the camera based on the single photo resection process. For the evaluation, we built a prototype system, acquired test data using the system, and estimated the trajectory. The proposed algorithm shows the accuracy of about 40% higher than an in-vehicle sensor only method.

• Journal of Navigation and Port Research
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• v.33 no.8
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• pp.505-511
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• 2009

Vessels on anchoring are frequently dragged due to the increased area of wind pressure by enlargement of ship's size and sudden gust of winds in recent years. In the view point of the ship's navigators, the proper measurements corresponding to the dragging of anchor should be taken into account concerned about the time for the occurring of dragging by the external forces such as wind and wave, the pattern and speed of dragging and the possibility of collisions with any other vessels or obstacles. In this paper, it was examined the actual dragging anchor in T.S. HANBADA due to the wind and waves. From this case, it was found the critical external forces by which she was begun to dragged comparing the force by the wind, frictional resistance, drifting force and ship motion moment with the holding power. Also, through the analysis of the dragging pattern, it was known the alteration range of heading angle, swinging width and dragging speed etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.356-361
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• 2020

This paper presents a lightweight milli-scale crawling robot that can crawl on both sides, which was inspired by the movement of insects. This robot has an excellent ability to overcome obstacles, such as the narrow gaps and the rough terrain. In addition, the robot can crawl steadily and rapidly through triangular alternation, such as ants or cockroaches. The process of smart composite microstructures (SCM) was employed to make a lightweight robot structure. The SCM process replaced the conventional mechanical parts with flexure joints and composite links, which allows the weight of the robot to be reduced. In addition, the robot structure was robust against external impacts owing to the compliance of the constituent materials. Using the SCM process, the robot weighed only 32g with twelve legs in total on both sides. The robot showed a crawling speed of 0.52m/s on the front side and 0.42m/s on the backside.

• Journal of Life Science
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• v.19 no.12
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• pp.1698-1704
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• 2009

Gemcitabine is an anticancer drug used to treat a variety of solid tumors. The drug is rapidly inactivated by cytidine deaminase in plasma and its hydrophilicity restricts the extent of quantification that is possible using reversed-phase liquid chromatography. In this paper, we report a rapid and precise method to analyze velocity and peak efficiency using ultra-performance liquid chromatography (UPLC) with a reversed-phase column. The retention periods of gemcitabine and 2'-deoxycytidine at 283 nm were 3.2 and 2.1 min, respectively. The assay provided highly linear results in the range of $0.1{\sim}20{\mu}g/ml$ ($r^2$ > 0.999). The coefficients of variation of the intra-day and inter-day assays were less than 10.0%. We observed that the estimated average concentrations of the intra-day and inter-day assays ranged from 97.3 to 113.5% to verify the accuracy. These results suggest that this new reversed-phase UPLC method is a rapid and reliable way of determining gemcitabine levels.

• The Mathematical Education
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• v.57 no.3
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• pp.311-328
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• 2018

In school mathematics, the concept of an average is not a concept that is limited to a unit of statistics. In particular, high school students will learn about arithmetic mean and geometric mean in the process of learning absolute inequality. In calculus learning, the concept of average is involved when learning the concept of average speed. The arithmetic mean is the same as the procedure used when students mean the test scores. However, the procedure for obtaining the geometric mean differs from the procedure for the arithmetic mean. In addition, if the arithmetic mean and the geometric mean are the discrete quantity, then the mean rate of change or the average speed is different in that it considers continuous quantities. The average concept that students learn in school mathematics differs in the quantitative nature of procedures and objects. Nevertheless, it is not uncommon to find out how students construct various mathematical concepts into mathematical knowledge. This study focuses on this point and conducted the interviews of the students(three) in the second grade of high school. And the expression of students in the process of average concept formation in arithmetic mean, geometric mean, average speed. This study can be meaningful because it suggests practical examples to students about the assertion that various scholars should experience various properties possessed by the average. It is also meaningful that students are able to think about how to construct the mean conceptual properties inherent in terms such as geometric mean and mean speed in arithmetic mean concept through interview data.

• International Journal of Highway Engineering
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• v.12 no.2
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• pp.63-69
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• 2010

Since speed limit enforcement in school zones is the most important to reduce the occurrence of severe child related accidents, school zones typically have a speed limit of 30km/h. However, it is found that the majority of vehicles passing school zones are traveling over 30km/h. This indicates that school zones are not being effectively operated to achieve the main objective which is the reduction of child related accidents. This study aims to identify the factors affecting the violation of speed limits in school zones through the results of field survey from 8 elementary schools. The results showed that time period, the number of lanes, the width of sidewalks, and the status of colored pavement were found to be highly associated with the violation of speed limits in school zones at the 95% significance level. The results of this study may provide some insights for making safe environments around schools.

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.663-669
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• 2009

The purpose of this study was to investigate the functional role of foot effectiveness when humans execute running turn maneuvers. Foot rotation angle at the starting turn and body angle at the vertical axis were analyzed through three-dimensional image analysis and ground reaction force analysis. Then, we created a simple equation: foot effectiveness = total foot rotation angle/total body rotation angle at the vertical axis. This equation made it possible to explain the dynamics of angular running turns. We analyzed data from running turns(0, 30, and 60) at average initial running velocities of 4.5, as well as rotations around the vertical axis during the running turns. As a result, the stance time, foot placement, and left and right force increased.