• 한국자동차공학회논문집
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• 제5권2호
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• pp.94-110
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• 1997

In the present study, a mean torque predictive model has been proposed and experimentally validated. It includes induction air mass model, fuel delivery model and mean production mode. Air induction and fuel delivery model considering dynamic behaviors of air induction and fuel delivery were proposed to predict the air-fuel ratio excursions under transient condition. Torque function model reflects thermal efficiency, volumetric efficiency, friction and effect of spark timing. In the spark timing model, knock limit and acceleration retard are included. Experiments were carried out to validate the simulation model for the step changes of throttle at constant engine speed. The results show reasonable agreements between simulation and experiment at fully warmed condition. Using this model, fueling strategies are varied with fast throttle open and it can predict air-fuel ratio excursion and IMEP.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2006년도 춘계공동학술대회 논문집
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• pp.348-353
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• 2006

Autonomous and intelligent resource model (AIR-model) defines a building-block of complex systems to pursue value creation by means of diverse resources, referred to as an AIR-unit, and presents a collaboration model with the AIR-units. An AIR-unit represents a piece of resources, such as machines, labor, raw materials, and other assets, considered individually by a complex system as means to accomplish given tasks. It is defined with its own service capability and a goal, and pursues achieving the goal by means of the capability. Moreover, an Air-unit is equipped with autonomy and intelligence, whereby it makes a decision on its course of action on its own initiative. Air-units collaborate on system operations with each other through goal-oriented negotiations. In this research, distinctive features of the AIR-model are addressed and described in detail. Principal components of the AIR-model are also designed via object-oriented modeling techniques. A prototype system based on the AIR-model is finally presented as an embodiment tool of a fractal manufacturing system (FrMS).

• 설비공학논문집
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• 제12권7호
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• pp.632-641
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• 2000

The present study concerns the simulation of supply-air control in a variable air volume (VAV) system. A stratified lumped thermal model (multi-zone model) is suggested to predict local thermal response of an air-conditioned space. The effects of various thermal parameters such as the cooling system capacity, the thermal mass of air-conditioned space, the time delay of thermal effect, and the building envelope heat transmission are investigated in detail. Further, the influence of control parameters, PI control factor and the sensor location on a VAV system is quantitatively delineated. The results obtained show that the previous homogeneous lumped thermal model (1-zone model) may predict a significantly different thermal response in the air-conditioned space according to the sensor location.

• 한국환경과학회지
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• 제17권9호
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• pp.993-1003
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• 2008

Interior space in most buildings is divided into several zones. The most important factors relating to the indoor air environment are temperature, airflow, humidity, and contaminant concentration. An integrated multizone model to predict these environmental factors simultaneously was developed. Also, a computer program for this model was written by the language of VISUAL BASIC. The proposed model was applied to a apartment with five rooms that had been tested by Chung. Comparison of predicted results by this study with measured results by Chung showed that their variations were within 14% for airflow rates, 1% for temperatures, 12% for humidities, and 5% for concentrations. It was seen that the opening operation schedule of building has a significant effect on the air moisture md contaminant removal. Thus, this model may be available for predicting the indoor air environment and may be contributed to design the ventilation plan for controling of indoor air quality.

• International Journal of Air-Conditioning and Refrigeration
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• 제9권3호
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• pp.46-56
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• 2001

The present study concerns the numerical simulation of a supply airflow control in a variable air volume (VAY) system. A stratified thermal model (multi-zone model) is suggested to predict a local thermal response of an air-conditioned space. The effects of various thermal parameters such as the cooling system capacity, the thermal mass of an air-conditioned space, the time delay of thermal effect, and the building envelope heat transmission are investigated. Further, the influence of control parameters such as the supply air temperature, the PI control factor and the thermostat location on a VAV system is quantitatively delineated. The results obtained show that the previous homogeneous lumped thermal model (single zone model) may overestimate the time taken to the set point temperature. It is also found that there exist the appropriate ranges of the control parameters for the optimal airflow control of the VAV system.

• 한국대기환경학회지
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• 제11권3호
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• pp.299-302
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• 1995

Many air quality models have been used for Environmental impact assessments. Miller-Holzworth model suggested by Holzworth is a simple air quality model is frequently used for air quality assessments in korea. Miller-Holzworth model suggested by Holzworth is a simple air quality model for the ground-level area source, The model estimates the pollutants concentration averaged over the wind centerline. An error involved in the Miller-Holzworth model was first indentified by Calder in 1977. But the model has been used without correction for unsuitable cases in Korea. This paper corrected that error and modified model formulation for application to urban and rural areas.

• 한국대기환경학회지
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• 제14권6호
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• pp.563-576
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• 1998

To study the influences of the emission sources during lune 13∼15 1997 in Seoul, MESOPVFF II model has been used. The MESOPVFF II model includes terrain effects, chemical transformation and removal processes. Data of 20 surface meteorological stations and the upper air station on mid-west area in Korea were used as a DWM (Diagnostic Wind Model) input data. This model is likely to be applicable because the predicted SO2 concentration was well matched with measured 502 concentration in Seoul and Kyonggido. In generally air pollutants in Seoul have major influence on the other cities but the result of modeling appeared also air pollutants of the other cities influence on Seoul. Finally, in the case of calculating the air quality by diffusion model, the influences of air pollutants emitted in metropolitan area as well as the emission rate in modeling area should be considered.

• 한국환경과학회지
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• 제7권6호
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• pp.745-751
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• 1998

The well-mixed room model has been traditionally used to predict the concentrations of contaminants in indoor environments. However, this is inappropriate because the flow fields in many indoor environments distribute contaminants non-uniformly, due to imperfect air mixing. Thus, some means used to describe an imperfectly mixed room are needed. The simplest model that accounts for imperfect air mixing is a two-zone model. Therefore, this study on development of computer program far the two-zone model is carried out to propose techniques of estimating the concentration of contaminants in the room. To do this, an important consideration is to divide a room into two-zone, i.e. the lower and upper zone assuming that the air and contaminants are well mixed within each zone. And between the zones the air recirculation is characterized through the air exchange parameter. By this basic assumption, the equations for the conservation of mass are derived for each zone. These equations are solved by using the computational technique. The language used to develope the program is a VISUAL BASIC. The value of air exchange coefficient($f_12$) is the most difficult to forecast when the concentrations of contaminants in an imperfectly mixed room are estimated by the two-zone model. But, as the value of $f_12$ increases, the air exchange between each zone increases. When the value of $f_12$ is approximately 15, the concentrations in both zone approach each other, and the entire room may be approximately treated as a single well-mixed room. Therefore, this study is available for designing of the ventilation to improve the air quality of indoor environments. Also, the two-zone model produces the theoretical base which may be extended to the theory for the multi-zone model, that will be contributed to estimate the air pollution in large enclosures, such as shopping malls, atria buildings, atria terminals, and covered sports stadia.

• 한국환경보건학회지
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• 제23권4호
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• pp.57-66
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• 1997

Successful energy conservation and good indcfor air quality (IAQ) are highly dependent on ventilation system. Air filtration is a primary solution of indoor air control strategies in terms of reducing energy consumption and improving ihdoor air quality. A conventional system with bypass filter, as it is called variable-air-volume/bypass filtration system (VAV/BPFS), is a variation of the conventional variable air volume (VAV) systems, which is designed to eliminate indoor air pollutant and to save energy. Bypass filtration system equipped with a high-efficiency particulate filter and carbon absorbent provides additional cleaned air into indoor environments and maintain good IAQ for human health. The objectives of this research were to compare the relative total decay rate of indoor air pollutant concentrations, and to develop a mathematical model simulating the performance of VAV/BPFS. All experiments were performed in chamber under the controlled conditions. The specific conclusions of this research are: 1. The VAV/BPFS system is more efficient than the VAV system in removing indoor air pollutant concentration. The total decay rates of aerosol, and total volatile organic compound (TVOC) for the VAV/BPFS system were higher than those of the conventional VAV system. 2. IAQ model predictions of each pollutant agree closely with the measured values. 3. According to IAQ model evaluation, reduction of outdoor supply air results in decreased dilution removal rate and on increased bypass filtration removal rate with the VAV/BPFS. As a results, we recommends the VAV/BPFS as an alternative to conventional VAV systems.

• International Journal of Naval Architecture and Ocean Engineering
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• 제10권4호
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• pp.427-438
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• 2018

The reduction of $CO_2$ emissions has been a key target in the marine industry since the IMO's MEPC published its findings in 2009. Air lubrication method is one of the mature technologies for commercialization to reduce the frictional resistance and enhance fuel efficiency of ships. Air layer is formed by the coalescence of the injected air bubbles beyond a certain air flow rate. In this study, a model ship (${\lambda}=33.33$) of a 50,000 ton medium range tanker is equipped with an air lubrication system. The experiments were conducted in the 100 m long towing tank facility at the Pusan National University. By selecting optimal air injector configuration and distribution ratio between two injectors, the total resistance of model $R_{TM}$ was able to be reduced down to 18.1% in the model scale. Key issue was found to suppress the sideway leakage of injected air by appropriate injection parameters.