• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.187-190
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• 2012

An experimental study was performed to provide the effect of PM reduction and the improvement of diesel alternative ratio utilizing diesel-natural gas dual-fuel combustion mode in a retrofit 3.4-liter diesel engine. In order to achieve the same power as the original diesel engine, engine control unit (ECU) of the dual-fuel engine was calibrated. As a result, diesel alternative ratio was found that the maximum value of diesel alternative ratio was about 96%. Finally PM emission experiment was performed in C1-8 mode cycle and it was shown PM emission was extremely reduced down to $7.42{\ast}10^{-7}g/kWh$ comparing with mechanical diesel engine.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.2
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• pp.137-142
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• 2003

Two existing continuous-time models for the current-mode control have presented noticeable differences in their small-signal predictions. As an attempt to clarify the origin of these disparities, this paper presents an alternative way of deriving a continuous-time model for the current-model control. The results of this paper would provide insights to comprehend the dissimilarity in the modeling method and final results of the earlier models of current-mode control models.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.218-222
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• 2002

Two existing continuous-time models for the current-mode control have presented noticeable differences in their small-signal predictions. As an attempt to clarify the origin of these disparities, this paper presents an alternative way of deriving a continuous-time model for the current-model control. The results of this paper would provide insights to comprehend the dissimilarity in the modeling method and final results of the earlier models of current-mode control.

• Smart Structures and Systems
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• v.17 no.3
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• pp.363-389
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• 2016

Deficient modes that cannot be always identified from different sets of measurement data may exist in the application of operational modal analysis such as the stochastic subspace identification techniques in large-scale civil structures. Based on a recent work using the long-term ambient vibration measurements from an instrumented cable-stayed bridge under different wind excitation conditions, a benchmark problem is launched by taking the same bridge as a test bed to further intensify the exploration of mode identifiability. For systematically assessing this benchmark problem, a recently developed SSI algorithm based on an alternative stabilization diagram and a hierarchical sifting process is extended and applied in this research to investigate several sets of known and blind monitoring data. The evaluation of delicately selected cases clearly distinguishes the effect of traffic excitation on the identifiability of the targeted deficient mode from the effect of wind excitation. An additional upper limit for the vertical acceleration amplitude at deck, mainly induced by the passing traffic, is subsequently suggested to supplement the previously determined lower limit for the wind speed. Careful inspection on the shape vector of the deficient mode under different excitation conditions leads to the postulation that this mode is actually induced by the motion of the central tower. The analysis incorporating the tower measurements solidly verifies this postulation by yielding the prevailing components at the tower locations in the extended mode shape vector. Moreover, it is also confirmed that this mode can be stably identified under all the circumstances with the addition of tower measurements. An important lesson learned from this discovery is that the problem of mode identifiability usually comes from the lack of proper measurements at the right locations.

• Journal of the Korean Institute of Gas
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• v.19 no.6
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• pp.34-39
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• 2015

Recently, most of the energy consumed in vehicle is derived from fossil fuels. For this reason, the demand for clean, renewable and affordable alternative energy is forcing the automotive industry to look beyond the conventional fossil fuels. Natural gas represents today a promising alternative to conventional fuels for vehicles propulsion, because it is characterized by a relatively low cost, better geopolitical distribution than oil, lower environmental impact, higher octane number and a higher self ignition temperature. Above all, CNG is an environmentally clean alternative to the existing spark ignition engines with the advantages of minimum change. In this study was installed bi-fuel system that a conventional 2 liters gasoline engine was modified to run on natural gas by a gas injection system. Experiments were mainly carried on the optimization of an ECU control strategy affecting the emission characteristics of CNG/Gasoline bi-fule vehicle. The test results shown that CO2 emission in bi-fuel mode was reduced 16% compared to gasoline fuel in the NEDC mode. Also the amount of CO and HC emissions in bi-fuel and gasoline modes were found to equality. But Compared to gasoline, the bi-fuel mode resulted in higher NOx emissions.

• ETRI Journal
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• v.29 no.5
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• pp.694-696
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• 2007

This letter presents an adaptive coefficient scanning method for intra mode coding in H.264. The proposed adaptive scanning uses six alternative scanning orders based on the intra prediction mode. Experimental results show that the proposed method improves the coding efficiency up to 3% compared to conventional scanning methods without additional computations.

• Journal of the Korean Institute of Landscape Architecture
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• v.28 no.1
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• pp.19-28
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• 2000

The purposes of this study are two folds: a) to introduce conjoint choice model to research the choice behavior of theme park users, and b) to suggest the strategies to strengthen the competitiveness of theme parks. The major four theme parks in Seoul metropolitan areas were selected as study areas. A leading polling agency was employed to select 432 respondents by probability sampling and to conduct face-to-face interview. Both alternative generating and choice set generating fractional factorial design were conducted simultaneously to meet the necessary and sufficient conditions for calibration of the conjoint choice model. Dummy coding was used to represent the attribute levels, and the alternative-specific model was calibrated. The goodness-of-fit of the model was quite satisfactory($\rho$$^2$=0.47950), and most parameters values had to expected sign and magnitude. Car was preferred transport mode to shuttle bus for visiting theme parks ; however the most ideal attribute levels only were estimated significantly. Most attribute levels of shuttle bus were estimated significantly except the Dream Land, which is the least attractive park among study areas. Simulation results showed that the shuttle bus was a mode worth providing to switch the current car dominant visiting pattern of theme parks, which will be one the effective strategies to attract more patrons, especially for potential users adjacent to parks. Several ideals were suggested for future researches, in terms of utilization of more general utility function and new base alternative, and inclusion of more salient attributes such as constraints in the model.

• Journal of Korean Society of Transportation
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• v.12 no.3
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• pp.29-47
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• 1994

Although subway system continues to be the backbone of transportation systems in a city like Seoul, there will still be areas across the city where subway services are not avaliable. Interest has steadily grown to fill this missing routes in overall urban transportation system. Light Rail Transit (L.R.T) system has been recently thought to be an appropriate mode of transportation by businessmen, professionals and transportation industry. In this regards, the purpose of this study is to explore whether L.R.T can be a feasible form of urban rail mode in the context of Seoul. First, the study develops the mathematical models to derive optimum route networks and stations. Integer Programming is employed to determine whether alternative routes are financially viable from the viewpoint of revenue maximization principles. Second, mathematical models developed are applied to Yoido area in order to examine the validity of model structures. The models constructed turns out be capable of handling alternative routes and stations. Application of models are successfully carried out to derive financially feasible set of routes and stations.

• Proceedings of the KSR Conference
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• 2009.05b
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• pp.387-392
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• 2009

Measurement of dynamic characteristics are widely used to detect defects in mechanical or civil structures. The most common approach is to measure changes in frequency spectrum or mode shapes using accelerometers. An alternative to using mode shapes is using stain modes. Strain is more sensitive to local defects than displacement, and hence stain modes measurement is an efficient in structural health monitoring. This paper deals with dynamic monitoring of a beam structure using strain sensors. Resistive strain gages and FBG strain gages are used and their characteristics are compared. It has been known that resistive strain gages are week to EMI environment and suffers from noise at high frequency range. It has been shown that the FBG sensor is a good alternative that overcomes such difficulties.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1769-1775
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• 2004

In presence of collision between two rigid bodies, they exhibit impulsive behavior to generate physically feasible state. When the frictional impulse is involved, collision resolution can not be easily made based on a simple Newton's law or Poisson's law, mainly due to possible change of collision mode during collision, For example, sliding may change to sticking, and then sliding resumes. We first examine two conventional methods: the method of mode evolution by differential equation, and the other by linear complementarity programming. Then, we propose a new method for mode evolution by solving only algebraic equations defining mode changes. Further, our method attains the original nonlinear impulse cone constraint. The numerical simulation will elucidate the advantage of the proposed method as an alternative to conventional ones.