• Journal of the Korean Society for Aviation and Aeronautics
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• v.31 no.2
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• pp.55-65
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• 2023

Due to extreme urbanization, ground transportation in the city center is saturated, and problems such as the lack of expansion infrastructure and traffic congestion increase social costs. To solve this problem, a 3D mobility platform, Urban Air Mobility (UAM), has emerged as a new alternative. A vertiport is a physical space that conducts a similar role to an airport terminal. Vertiport consists of take-off and landing facilities (TLOF, Touchdown and Lift-Off area), space for boarding and disembarking from UAM aircraft (gates), taxiways, and passenger terminals. The type of vertiport (structure, number of facilities) and concept of operations are key variables that determine the number of UAM aircraft that can be accommodated per hour. In this study, a capacity calculation method was presented using an optimization technique (Deterministic Integer Linear Programming). The absolute capacity of the vertiport was calculated using an optimization technique, and a sensitivity analysis was also performed.

• Korean Chemical Engineering Research
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• v.56 no.1
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• pp.139-142
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• 2018

Silicon (Si) is a promising anode material for next-generation lithium ion batteries (LIBs) because of its high capacity of 4,200 mAh/g ($Li_{4.4}Si$ phase). However, the large volume expansion of Si during lithiation leads to electrical failure of electrode and rapid capacity decrease. Generally, a binder is homogeneously mixed with active materials to maintain electrical contact, so that Si needs a particular binding system due to its large volume expansion. Polyvinyl alcohol (PVA) is known to form a hydrogen bond with partially hydrolyzed silicon oxide layer on Si nanoparticles. However, the decrease of its cohesiveness followed by the repeated volume change of Si still remains unsolved. To overcome this problem, we have introduced the electrospinning method to weave active materials in a stable nanofibrous PVA structure, where stresses from the large volume change of Si can be contained. We have confirmed that the capacity retention of Si-based LIBs using electrospun PVA matrix is higher compared to the conservative method (only dissolving in the slurry); the $25^{th}$ cycle capacity retention ratio based on the $2^{nd}$ cycle was 37% for the electrode with electrospun PVA matrix, compared to 27% and 8% for the electrodes with PVdF and PVA binders.

• Journal of Technology Innovation
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• v.26 no.4
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• pp.173-198
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• 2018

In this paper, we analyze the determinants of the adoption of industrial robots using the data from 42 countries, and thereby examine the factors underlying the rapid expansion of industrial robots in Korea. To this end, the industrial robot data for the years 2001-2016 were drawn from the World Robotics dataset of the International Federation of Robotics (IFR). The explanatory variables included labor market environment variables and innovation capacity variables extracted from the dataset of the relevant international organizations. For data analysis, the Arellano-Bond dynamic panel analysis was performed to control for the endogeneity problem of some explanatory variables. The empirical results confirmed the exceptionally rapid expansion of industrial robots in Korea as compared to other countries, even when considering the national income level, employment cost, and innovation capacity. This phenomenon could be attributed to both the demand-side and supply-side factors. For one thing, changes in the labor market environment, such as an increase in employment costs, have led to an increase of the corporate demand for industrial robots. For another, the supply-side factors, such as an increase in the capital intensity and innovation capacity of companies, have also contributed to the widespread adoption of industrial robots.

• Journal of the Korean Operations Research and Management Science Society
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• v.5 no.1
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• pp.39-51
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• 1980

This paper deals with the problem of determining the capacity expansion timing and sizes of conduits and feeder cables for a given cable network configuration of a single exchange ares, which minimizes the present worth of total costs. The planning horizon is infinite and the demand of line pairs at each cabinet is assumed to be determininstically growing. As a solution method, the heuristic branch-and-bound algorithm of Freidenfelds and Mclaughlin is elaborated by adding details and some minor modifications, which generates a good near-optimal solution with far less computation than would otherwise be possible. We also develop a computer program, which is shown to be effective and efficient through the test run of an illustrative example.

• Journal of Korean Port Research
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• v.11 no.1
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• pp.13-28
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• 1997

Today the congestion problem is a problem for the most of the cities to solve. Especially, traffic congestion in the big cities is occurring regardless of the rush-hours. Because the transportation facilities secured in the big cities are very low, and the financial resources and sites for the expansion of new transportation facilities are also limited. Therefore the appropriate Transportation system Management(TSM) techniques which could improve the transportation system are absolutely required to solve the transportation problems instead of the expansion of the transportation facilities in the big cities. The purpose in this study was to review the travel characteristics on the Pretimed Signalized - Intersections under the study in Pusan area, construct the travel systems during the different time-periods based upon the travel characteristics reviewed, and finally suggest the optimal travel systems which could reduce the traffic delay and fuel consumption of the Pretimed Signalized - Intersections based upon the travel system constructed. Based upon the results, it could be concluded that the pretimed signal system based upon the on-peak periods should not be applied to all the different time-periods on the Pretimed Signalized - Intersections(PSI) to reduce traffic delay and fuel consumption, and increase the travel capacity on the intersections in Pusan area.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.886-892
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• 2007

This paper presents examples of trolley wire resistance influential on the movement of tensioning devices. Therefore, this study is on the examples of trolley wire resistance which keep tensioning devices from working properly to the expansion and contraction in accordance with temperature change of overhead trolley wire system such as messenger wire and contact wire. Trolley wire resistance interrupts the working of tensioning device and drops the capacity of trolley wire. Reduced trolley wire capacity lowers the performance of current collection and has a bad effect on electrical train operation. So it is desirable to reduce the factors increasing trolley wire resistance to the minimum from the designing and construction stage of overhead trolley wire system. This study will introduce this problem and suggest the solution.

• Journal of Korean Port Research
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• v.8 no.2
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• pp.79-105
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• 1994

Today travel demand in the City of Pusan is increasing with the wide scope of activity and the better living circumstances as a big city with a population of about 4 million. Also, the transportation problem of Pusan city becomes one of the severest urban problems with travel demand increasing in spite of the continuous expansion of the transportation facilities. The purpose in this study is to find the travel characteristics on the arterial under the study, construct the optimal Transportation System Management(TSM) which could increase the travel capacity of the arterial based upon the optimal travel systems constructed. Thus, it was concluded that more emphasis should be of the automobiles into the Downtown areas, increase the travel capacity of the arterial through Mass Transportation System(MTS) including the HOV lanes or the Bus Exclusive Lanes instead.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.645-648
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• 2008

The expansion joint is an important part of the bridge, but the failure is occurred on the non-shrinkage concrete which is connected to the slab of the bridge and the expansion joint, and the other problem is the release of anchors in expansion joint due to the impact and vibration during the driven car on the bridge, especially an overloaded car. In this study, to overcome the failure of non-shrinkage of concrete, high impact resisting mortar is developed. The high impact resisting mortar shall be a polyurethane material compounded with an aggregate system to develop excellent flexibility characteristics, high load bearing capacity.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.11a
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• pp.134-137
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• 2006

Satisfying the customer orders with a short lead-time is one of the essential and competitive factors for business units under a mass customization environment. To shorten the lead-time for fulfilling various orders entails the production capacity expansion and efficient operational policy. Most business firms utilize the multiple production lines or facilities to cope with this business and manufacturing environment by making the manufacturing and distribution more flexible. In this study, we introduce the operational problem determining the joint production and delivery policy in an environment where multiple products are manufactured with more than one production lines. Also, we propose the heuristic solution approach for determining the product-line selection and joint lot size for this problem.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.4
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• pp.856-873
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• 2011

Reversible watermarking is an open problem in information hiding field, with embedding the encoded bit '1' or '0' into some sensitive images, such as the law enforcement, medical records and military images. The technique can retrieve the original image without distortion, after the embedded message has been extracted. Histogram-based scheme is a remarkable breakthrough in reversible watermarking schemes, in terms of high embedding capacity and low distortion. This scheme is lack of capacity control due to the requirement for embedding large-scale data, because the largest hidden capacity is decided by the amount of pixels with the peak point. In this paper, we propose a reversible watermarking scheme to enlarge the number of pixels with the peak point as large as possible. This algorithm is based on an adaptive edge-guided interpolation, furthermore, hides messages by interpolation-error, i.e. the difference between the original and interpolated image value. Simulation results compared with other state-of-the-art reversible watermarking schemes in this paper demonstrate the validity of the proposed algorithm.