• Journal of Wetlands Research
• /
• v.17 no.4
• /
• pp.436-446
• /
• 2015

It is suggested investigating method about the existing state of demand in this study. The total demand of 357 water amenity zones in 2014 is estimated based on the growth curve models. The effects of population density and distances between water amenity zones and metropolises populated over 1 million are investigated on each river system. The suitability like RMSE and MAPE of logistic and gompertz models are considered to select more suitable model for each water amenity zone. Demand for water amenity zones in 2014 is seemed to be rather high at Han Gang river system and Chungcheongbukdo after analyzing. The influence of population density is rarely effective except Geum Gang river system. The influence of metropolis on the demand for water amenity zones is higher at Geum Gang river system than others.

• The Korean Journal of Emergency Medical Services
• /
• v.12 no.3
• /
• pp.129-135
• /
• 2008

Purpose : This study was to analyze the demand for emergency ambulance service and to characterize the factors associated with the demand. Method : The basis for the model was from the actual demand for public emergency ambulance and socioeconomic and geographic characteristics. Multiple regression analyses were done for the related characteristics of public ambulance service. Result : The model explained total demand with a high degree of accuracy : the coefficient of determination($R^2=0.96$). For the regression, the set of variables indicative of low socioeconomic status were all significant. It showed the inappropriate use of public ambulance system. Public ambulance demand increased in higher housing density, low income, male unemployment and female labor force. Conclusion : The demand for public ambulances appeared to be highly predictable, using a simple linear model employing socioeconomic variables, quality of service variables, and land use variables. Low-income families tended, to use the public ambulance system more often than higher income. Area having elderly people or children also made many calls. Estimated demand calls were stable and had a tendency to be similar incident types.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.21 no.7
• /
• pp.1306-1312
• /
• 2017

The route request (RREQ) packet is selectively re-broadcasted in the routing protocols that improve the broadcast storm problem of the ad-hoc on-demand routing protocol (AODV). However, in a low node density scenario, the connectivity of these selective rebroadcast schemes becomes less than that of the AODV. In order to clarify the requirements of these selective re-broadcast routing protocols, it is necessary to investigate the relationship between the node density and the connectivity. In this paper, we drive a probability to preserve the connectivity of the GAODV at an intermediate rebroadcast node. In addition, we present an intuitive method to approximate the end-to-end connectivity of the GAODV. We draw the required node density to guarantee the connectivity of 0.9 and 0.99 through computer simulations, and verify the validity of the derived theoritical connectivity by comparing with the simulation results.

• Journal of Korean Society of Transportation
• /
• v.14 no.1
• /
• pp.69-80
• /
• 1996

In most cities, travel demand is distributed along long corridors and its destinations tend to concentrate in a central business district. For this kind of many-to-one or one-to-many travel demand pattern, a zonal operation of buses can be an efficient bus operation technique in which a long bus-demand corridor is divided into service zones and each service zone is provided with its own bus route connecting the service zone and single destination separately. This paper develops models of the total transportation costs for a single-zone operation and 2-zonal operation of buses for a long demand corridor with single destination in terms of various cost parameters, demand density, bus operation speeds, and location of the boundary between two service zones. In this study the total transportation cost is assumed to consist of the bus operation cost, passenger waiting cost and passenger travel time cost. It was proved that a zonal operation of buses can be more efficient than a single-zone operation for certain circumstances of the system and an boundary condition between two operation techniques was obtained. Also, several case studies were performed for various values of the cost parameters.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.4D
• /
• pp.489-496
• /
• 2011

Bike system is one of the green transportation systems and spotlighted recently. In the TOD (Transit-Oriented Development) based transportation and urban planning, bike system will be the major part as linkage modes. In this paper, bike demand estimation model was firstly established in Korea, with considering of personal and household characteristics of traveller, social and economic characteristics of city, weather conditions, and so on. The model reflects population density, the number of students except elementary school students, the number of vehicles, the length of bike roads, and monthly income. The adjusted $R^2$ was 0.738: the model is highly fitted. The results of this paper yield bike demand estimation in the urban planning area: further estimated results will be using to determine economic feasibility and size of bike facility. In other words, this paper is expected to provide the theoretical basis that supporting justification and investment efficiency of bike plans, which are actively progressed recently.

• The KIPS Transactions:PartC
• /
• v.12C no.4 s.100
• /
• pp.535-542
• /
• 2005

This paper proposes an on-demand ad hoc routing protocol, Node Density Based Routing (NDBR), which enhances the routing performance applying a new method to establish alternate patlis. It is important to reserve alternate paths for the route from source to destination in mobile ad hoc networks that are susceptible to failure due to the movement or the power exhaustion of mobile nodes. NDBR aims to establish a route that contains more alternate paths toward the destination by involving intermediate nodes with relatively more adjacent nodes in a possible route, and introduces a new routing criterion called 'node density.' This approach can localize the effects of route failures, and reduce control traffic overhead and route reconfiguration time by enhancing the reachability to the destination node without source-initiated route re-discoveries at route failures. This paper describes the route setup procedure using node density and the route re-configuration procedures employing alternate path information at the intermediate nodes. We show the performance of our routing schemes through a series of simulations using the Network Simulator 2 (ns-2).

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.2
• /
• pp.107-113
• /
• 2018

Maintaining adequate residual chlorine concentration is an important criteria to provide secure drinking water. The chlorine decay can be influenced by unstable flow due to the transient event caused by operation of hydraulic devices in the pipeline system. In order to understand the relationship between the transient event and the chlorine decay, the probability density function based on the water demand curve of a hypothetical water distribution system was used. The irregular transient events and the same number of events with regular interval were assumed and the fate of chlorine decay was compared. The chlorine decay was modeled using a generic chlorine decay model with optimized parameters to minimize the root mean square error between the experimental chlorine concentration and the simulated chlorine concentration using genetic algorithm. As a result, the chlorine decay can be determined through the number of transients regardless of the occurrence intervals.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.6
• /
• pp.1276-1282
• /
• 2013

This paper proposes a stochastic modeling of plug-in electric vehicles (PEVs) distribution in power systems, and analyzes the corresponding clustering characteristic. It is essential for power utilities to estimate the PEV charging demand as the penetration level of PEV is expected to increase rapidly in the near future. Although the distribution of PEVs in power systems is the primary factor for estimating the PEV charging demand, the data currently available are statistics related to fuel-driven vehicles and to existing electric demands in power systems. In this paper, we calculate the number of households using electricity at individual ending buses of a power system based on the electric demands. Then, we estimate the number of PEVs per household using the probability density function of PEVs derived from the given statistics about fuel-driven vehicles. Finally, we present the clustering characteristic of the PEV distribution via case studies employing the test systems.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.6 no.6
• /
• pp.42-48
• /
• 1992

This paper shows a reasonable design standard of substation facility density and demand factor in office buildings, that was made by the systematic and statistical way considering actual conditions, such as investigated electric equipment capacity, electric power consumption, etc for 121 buildings. The saving of electric equipment investment, the decrease of power loss, the improvement of facilities utilization and the decrease of electric power rates an be contributed by the application of the design standard must be applied by the revision of current regulations and laws.

• Journal of the Korean Wood Science and Technology
• /
• v.43 no.5
• /
• pp.548-557
• /
• 2015

This study investigated environmental assessments of leachate containing formaldehyde from medium density fiberboard (MDF) disposed in laboratory-scale simulated landfills. Environmental impact assessment of leachate was conducted by measuring formaldehyde, toxicity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), bacterial enumeration, and pH. Amount of formaldehyde in leachate from MDF in soil decreased to the level of soil only treatment by 28 days, and toxicity decreased as the amount of formaldehyde decreased. BOD and COD levels in leachate from the treatments containing MDF exceeded permissible discharge levels of BOD or COD throughout the experimental period. The pH levels of all treatment were within permissible discharge range except on day 0. Fewer bacteria were observed in leachate from MDF in soil treatment than other treatments (MDF only, cured UF resin in soil, and soil only). Consequently, the leachate from disposal of MDF in soil detrimentally affect on environment. However, soil buffered formaldehyde leaching and pH on leachate in this study. Waste MDF may be required the pre-water soaking treatment for leaching formaldehyde to reclaim on land.