• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.5D
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• pp.671-677
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• 2011

A diversity of railway network function enhancement projects such as the double tracking, electrification, and direct operation have been actively executed to improve the railway service. When the new rapid transit is provided, how many people will use it instead of other transports? How will the railway choice behavior be changed? Accordingly, in this paper, the applicability of diverted travel demand forecast methods, by Revealed Preference(RP) and Stated Preference(SP) data was reviewed for Daegu metropolitan rail rapid transit service. As the result of combining RP and SP data, including the sequential and simultaneous approach, the total travel time and travel cost parameters are of the right sign and are highly significant. The simultaneous approach is more efficient in terms of the estimation of coefficients. In particular, methods to improve validity of the Mixed RP/SP models, when RP data is used proportionally, the diverted travel demand can be easily identified by railway fare and travel time service level. Therefore, it is considered that this will practically apply even in other regions as well as Daegu metropolitan railway.

• Journal of Korea Trade
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• v.23 no.2
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• pp.1-13
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• 2019

Purpose - This paper empirically investigates the competition effect of exports between Korea and China in their common-export markets considering market sophistication. Modern market sophistication includes an importing country's aggregate demand for products of high quality, design, novelty, eco-friendliness, and even IPR protection. Using an empirical analysis to identify the demand for product quality across countries, this paper estimates the effects of market sophistication on the competition between Korean exports and Chinese products. Design/Methodology - Our empirical model considers the relationship between an importing country's consumer sophistication and the export competition between Korea and China. This study employs the existing theoretical framework to identify the aggregate demand for product quality across countries. Using a quite direct measurement (the consumer sophistication index, our analysis investigates the differential effects of Korea's export market sophistication, particularly in markets where Korean exports are in competition with similar Chinese products. Findings - Our main findings can be summarized as follows: the negative effects of the export competition between Korea and China on Korea's exports are stronger in third markets where consumers are less sophisticated while the effects are not as pronounced in markets where consumers are more sophisticated. This result, however, best applies to differentiated goods which significantly vary in product quality. Originality/value - Existing studies focus on the supply side of production and make the assumption that the market preference for export quality is identical across countries. This paper attempts to evaluate the export competition between Korea and China from the demand-side perspective. This area of trade studies is underexplored both empirically and in theory, although the issue has long been important to Korean and world trade.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.2
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• pp.494-513
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• 2019

A multi-channel access problem based on hypergraph model in ultra-dense small cell networks is studied in this paper. Due to the hyper-dense deployment of samll cells and the low-powered equipment, cumulative interference becomes an important problem besides the direct interference. The traditional binary interference model cannot capture the complicated interference relationship. In order to overcome this shortcoming, we use the hypergraph model to describe the cumulative interference relation among small cells. We formulate the multi-channel access problem based on hypergraph as two local altruistic games. The first game aims at minimizing the protocol MAC layer interference, which requires less information exchange and can converge faster. The second game aims at minimizing the physical layer interference. It needs more information interaction and converges slower, obtaining better performance. The two modeled games are both proved to be exact potential games, which admit at least one pure Nash Equilibrium (NE). To provide information exchange and reduce convergecne time, a cloud-based centralized-distributed algorithm is designed. Simulation results show that the proposed hypergraph models are both superior to the existing binary models and show the pros and cons of the two methods in different aspects.

• KDI Journal of Economic Policy
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• v.44 no.2
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• pp.1-28
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• 2022

This paper studies how COVID-19 has affected the labor market in Korea through a general equilibrium model with multiple industries and occupations. In the model, workers are allocated to one of many occupations in an industry, and industrial or occupational shocks alter the employment structure. I calibrate the model with Korean data and identify industrial and occupational shocks, referred to here as COVID-19 shocks, behind the employment dynamics in 2020 and 2021. I find that COVID-19 shocks are more severe for those with jobs with a higher risk of infection and in those that are more difficult to do from home. Interestingly, the relationship between COVID-19 shocks and infection risk weakened as the pandemic progressed, whereas the relationship between COVID-19 shocks and easiness of work-from-home strengthened. I interpret the results as meaning that the pandemic may direct future technological changes to replace tasks that require contact-intensive steps, and I simulate the impact of such technological changes through the lens of the model. The results show that such technological changes will lower the demand for manual workers compared to the demands for other occupations. This contrasts with the earlier trend of job polarization, where manual workers continued to increase their employment share, with the share of routine workers secularly declining at the same time.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 1999.12a
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• pp.21-25
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• 1999

Planning support systems(PSS) add more advanced spatial analysis functions than Geographic information systems(GIS) and intertemporal functions to the functions of spatial decision support systems(SDSS). This paper reports the continuing development of a PSS providing a framework that facilitates urban planners and civil engineers in conducting coherent deliberations about planning, design and operation & maintenance(O&M) of water-distribution networks for urban growth management. The PSS using dynamic optimization model, modeling-to-generate-alternatives, value engineering(VE) and life-cycle cost(LCC) can generate network alternatives in consideration of initial cost and O&H cost. Users can define alternatives by the direct manipulation of networks or by the manipulation of parameters in the models. The water-distribution network analysis model evaluates the performance of the user-defined alternatives. The PSS can be extended to include the functions of generating sewer network alternatives, combining water-distribution and sewer networks, eventually the function of planning, design and O&H of housing sites. Capacity expansion by the dynamic water-distribution network optimization model using MINLP includes three advantages over capacity expansion using optimal control theory(Kim and Hopkins 1996): 1) finds expansion alternatives including future capacity expansion times, sizes, locations, and pipe types of a water-distribution network provided, 2) has the capabilities to do the capacity expansion of each link spatially and intertemporally, and 3) requires less interaction between models. The modeling using MINLP is limited in addressing the relationship between cost, price, and demand, which the optimal control approach can consider. Strictly speaking, the construction and O&M costs of water-distribution networks influence the price charged for the served water, which in turn influence the. This limitation can be justified in rather small area because price per unit water in the area must be same as that of neighboring area, i.e., the price is determined administratively. Planners and engineers can put emphasis on capacity expansion without consideration of the relationship between cost, price, and demand.

• Spatial Information Research
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• v.5 no.2
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• pp.185-194
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• 1997

Spatial decision support systems(SDffi), a new class of decision support system(DSS), result from the melding together of GIS and DSS, Planning support systems(PS5) add more advanced spatial analysis functions than GIS and intertemporal functions to the functions of SDSS. This paper reports the development of a planning support system providing a framework that facilitates urban planners and civil engineers in conducting coherent deliberations about the generation of satisficing sewers. 1he planning support system for the generation of satisficing sewers(PS5/GSS) was designed from the understanding that land use and development drive the demand for storm and sanitary sewers. Through four stages of supply, demand, alternative generation, and evaluation, PSS/GSS integrates basic planning, preliminary design, and engineering design of sewer. GIS and graphic user interface are excellent toolboxes for designing sewer networks, estimating the quantity of wastewater, and showing generated alternative sewers. A sewer model using simulation tedmique can generate an initial sewer. Users can define alternative sewers by the direct manipulation of sewer networks or by the manipulation of parameters in the sewer model. The sewer model evaluates the performance of the user defined alternatives.

• Environmental and Resource Economics Review
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• v.30 no.2
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• pp.237-268
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• 2021

As variable renewable sources rapidly increase due to the Energy Transition plan, integration cost of renewable sources to the power system is rising sharply. The increase in variable renewable energy reduces the capacity factor of existing traditional power capacity, and this undermines the efficiency of the overall power supply, and demand resources are drawing attention as a solution. In this study, we analyzed how much electric vehicle demand resouces, which has great potential among other demand resources, can reduce power supply costs if it is used as a flexible resource for renewable generation. As a methodology, a stochastic form of power system optimization model that can effectively reflect the volatile characteristics of renewable generation is used to analyze the cost induced by renewable energy and the benefits offered by electric vehicle demand resources. The result shows that virtual power plant-based direct control method has higher benefits than the time-of-use tariff, and the higher the proportion of renewable energy is in the power system, the higher the benefits of electric vehicle demand resources are. The net benefit after considering commission fee for aggregators and battery wear-and-tear costs was estimated as 67% to 85% of monthly average fuel cost under virtual power plant with V2G capability, and this shows that a sufficient incentive for market participation can be offered when a rate system is applied in which these net benefits of demand resources are effectively distributed to consumers.

• Environmental and Resource Economics Review
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• v.33 no.2
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• pp.159-178
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• 2024

This study aims to assess the direct and indirect impacts of local fiscal expenditures on water quality. Panel data spanning from 2010 to 2018 for 173 cities and districts in Korea are assembled, and a two-stage dynamic panel model is utilized for our estimation. The empirical findings reveal several key insights. Firstly, local fiscal expenditures on water quality are effective in ameliorating both Biological Oxygen Demand (BOD) and Total Phosphorus (T-P). Notably, the direct impact on T-P surpasses that on BOD in the short and long run. Secondly, expenditures dedicated to water quality improvement demonstrate a positive effect on local economic growth, and an inverted U-shaped relationship is observed between BOD and local economic growth. Due to the positive linkage, the indirect effect on BOD suggests, on average, a deterioration in water quality during local economic growth. Thirdly, concerning BOD, the direct effect of government expenditure on water quality improvement outweighs the indirect effect, but in the case of T-P, the indirect effect is not significant, and the total effect is solely determined by the direct impact. Despite local fiscal expenditures potentially exacerbating water quality through regional economic growth, the study finds that the direct enhancement of water quality remains a more substantial factor in the short and long run.

• Structural Engineering and Mechanics
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• v.83 no.2
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• pp.229-244
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• 2022

This paper investigates the seismic performance of buildings designed using DDBD (Direct Displacement based Design) and FBD (Force based Design) approaches from the probabilistic viewpoint. It aims to estimate the collapse capacity of structures and assess the adequacy of seismic design codes. In this regard, (i) IDA (Incremental Dynamic Analysis) curves, (ii) interstory drift demand distribution curves, (iii) fragility curves, and (iv) the methodology provided by FEMA P-695 are applied to examine two groups of RC moment resistant frame buildings: 8-story structures with different plans, to study the effect of different span arrangements; and 3-, 7- and 12-story structures with a fixed plan, to study the dynamic behavior of the buildings. Structural modeling is performed in OpenSees software and validated using the results of an experimental model. It is concluded that increasing the building height would not significantly affect the response estimation of IDA and fragility curves of DDBD-designed structures, while the change in span arrangements is effective in estimating responses. In the investigation of the code adequacy, unlike the FBD approach, the DDBD can satisfy the performance criteria presented in FEMA P-695 and hence provide excellent performance.

• Management & Information Systems Review
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• v.36 no.2
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• pp.81-92
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• 2017

This study was to investigate the elasticity in tourism demand of Chinese tourists visiting Malaysia through ARDL models by using Chinese tourists arrivals, GDP, CPI, transportation costs and others. When China was implementing an open-door policy with foreign countries in the early 15th century, the movement of Chinese was very limited, and then communication between China and other countries was very weak. However, the Chinese government persistently and entirely implemented an open-door policy by participating in the World Trade Organization(WTO) in 2001. The Chinese government has opened the economy through foreign direct investment by providing various incentives for foreign investment. As a result, inbound and outbound Chinese movements increased in the early 21st century. China was one of the top five most visited tourist destinations in the world by 2016, and also Chinese tourists traveling abroad increased, so they made Malaysia a popular tourists destination because of increase sharply to around 1.41 million. This study examined the significance of major economic factors affecting the increase in Chinese tourists arriving in Malaysia. Other factors that induced their arrival included income, tourism prices, transportation costs and promotional activities. Short-run shocks from the Asian economic crisis and the outbreak of SARS were included to understand how tourism demand in Malaysia was affected. Finally this study found that the combination of the ARDL and the Error Correction Model were useful to statistically estimate the elasticities of tourism demand.