• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.9
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• pp.6274-6281
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• 2015

Radio-based train control system has driving headway shortening effect by real-time train interval control using two-way radio communication between onboard and wayside systems, and reduces facility investment because it does not require any track-circuit. Automatic train protection(ATP), the most significant part of the radio-based train control system, makes sure a safe distance between preceding and following trains, based on real-time train location tracing. In this paper, we propose the overall ATP train interval control algorithm to control the safe interval between trains, and preprocessing-based speed profile calculation algorithm to improve the processing speed of the ATP. The proposed speed profile calculation algorithm calculates the permanent speed limit for track and train in advance and uses as the most restrictive speed profile. If the temporary speed limit is generated for a particular track section, it reflects the temporary speed limit to pre-calculated speed profile and improves calculation performance by updating the speed profile for the corresponding track section. To evaluate the performance of the proposed speed profile calculation algorithm, we analyze the proposed algorithm with O-notation and we can find that it is possible to improve the time complexity than the existing one. To verify the proposed ATP train interval control algorithm, we build the train interval control simulator. The experimental results show the safe train interval control is carried out in a variety of operating conditions.

• The KIPS Transactions:PartA
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• v.13A no.4 s.101
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• pp.343-350
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• 2006

In this paper, wireless internet proxy server clusters are used for the wireless internet because their caching, distillation, and clustering functions are helpful to overcome the limitations and needs of the wireless internet. A wireless Internet proxy server cluster needs a systematic scalability, simple communication structure, cooperative caching, and serving Hot Spot requests. In our former research, we proposed the CD-A structure which can be scalable in a systematic way and has a simple communication structure but it has no cooperative caching. A hash based load balancing can be used to solve the problem, but it can not deal with Hot Spot request problem. In this paper, we proposed a shared storage based wireless internet proxy server cluster which has a systematic scalability, simple communication structure, cooperative caching, and serving Hot Spot requests. The proposed method shares one cache directory and it has advantages: advantages of the existing CD-A structure, cooperative caching, and serving Hot Spot requests. We performed experiments using 16 PCs and experimental results show high performance improvement of the proposed system compared to the existing systems in Hot Spot requests.

• The KIPS Transactions:PartC
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• v.10C no.4
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• pp.433-440
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• 2003

According as the real economic activities are carried out in the cyber world and the identity problem of a trade counterpart emerges, digital signature has been diffused. Due to the weakness for real-time validation using the validation method of digital signature, Certificate Revocation List, On-line Certificate Status Protocol was introduced. In this case, every transaction workload requested to verify digital signature is concentrated of a validation server node. Currently this method has been utilized on domestic financial transactions, but sooner or later the limitation will be revealed. In this paper, the validation method will be introduced which not only it can guarantee real-time validation but also the requesting node of certificate validation can maintain real-time certificate status information. This method makes the revocation management node update the certificate status information in real-time to the validation node while revoking certificate. The characteristic of this method is that the revocation management node should memorize the validation nodes which a certificate holder uses. If a certificate holder connects a validation node for the first time, the validation node should request its certificate status information to the above revocation management node and the revocation management node memorizes the validation node at the time. After that, the revocation management node inform the revocation information in real-time to all the validation node registered when a request of revocation happens. The benefits of this method are the fact that we can reduce the validation time because the certificate validation can be completed at the validation node and that we can avoid the concentration of requesting certificate status information to a revocation node.

• The Transactions of the Korea Information Processing Society
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• v.6 no.12
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• pp.3447-3455
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• 1999

Database correctness is guaranteed by standard transaction scheduling schemes like two-phase locking for the context of concurrent execution environment in which short-lived ones are normally mixed with long-lived ones. Traditional syntax-oriented serializability notions are considered to be not enough to handle in particular various types of transaction in terms of duration of execution. To deal with this situation, altruistic locking has attempted to reduce delay effect associated with lock release moment by use of the idea of donation. An improved form of altruism has also been deployed in extended altruistic locking in a way that scope of data to be early released is enlarged to include even data initially not intended to be donated. In this paper, we first of all investigated limitations inherent in both altruistic schemes from the perspective of alleviating starvation occasions for transactions in particular of short-lived nature. The idea of two-way donation locking(2DL) has then been experimented to see the effect of more than single donation in distributed database systems. Simulation experiments shows that 2DL outperforms the conventional two-phase locking in terms of the degree of concurrency and average transaction waiting time under the circumstances that the size of long-transaction is in between 5 and 9.

• Journal of the Korean Institute of Gas
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• v.19 no.2
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• pp.29-36
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• 2015

This study is an 1-D numerical study prior to modification of diesel engine for power plants to natural gas/diesel dual fuel engine using GT-Power with 1.5MW diesel engine for power generation. Natural gas injector was installed to intake manifold for dual fuel engine model. Effects on engine performance and characteristics were investigated when dual fuel is used in unmodified diesel engine. The analysis was done under 5 conditions from 0% to 40% of mixing rate on 720RPM engine speed. As a result of research, the engine performance was decreased as increasing ratio of natural gas. Engine brake power was decreased by 18.4% under 40% mixing rate condition. To clarify the reason, effects of injection timing and period were evaluated with DOE method. Considering this result, optimization was done for these parameters. Also, comparison between performances of dual fueled engine and diesel engine was made after optimizing the timing of injection by DOE method. As a result, engine brake power was decreased by 8.55% under mixing rate 40% condition showing 12.5% improvement.

• Tunnel and Underground Space
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• v.30 no.2
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• pp.164-179
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• 2020

Applying the limit state design method to geotechnical structures, accuracy and reliability of its design are mainly affected by parameters for geotechnical site characteristics, such as unit weight, Poisson's ratio, deformation modulus, cohesion and frictional angle. When the structures are located in weathered ground, especially, cohesion and frictional angle of ground are closely related with decision of parameters for structures' load and ground's resistance. Therefore, the accurate determination of these parameters, which are commonly obtained from field measurement, such as borehole shear test, are essential for optimum design of geotechnical structures. The 38 case studies, in this study, have been analyzed for understanding the importance of these parameters in designing the ground structures. From these results, importance of field measurement was also ascertained. With these evaluations, an apparatus for determining the strength characteristics, which are fundamental in limit state design (LSD) method, have been newly developed. This apparatus has an improved function as following the ASTM suggestion. Through the field application of this apparatus, the strong point of minimizing the possibility of error occurrence during the measurement has been verified and authors summarized that the essential parameters for LSD can be qualitatively obtained by this apparatus for determination of strength characteristics of weathered ground.

• Korean Journal of Optics and Photonics
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• v.16 no.4
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• pp.384-391
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• 2005

A polymer optical microring resonator, which is laterally coupled to a straight bus waveguide, has been proposed and demonstrated using a nanoimprint technique. The propagation loss of the ring waveguide and the optical power coupling between the ring and bus waveguides was calculated by using a beam propagation method, then the dependence of the device performance on them was investigated using a transfer matrix method. We have especially introduced an imprint stamp incorporating a smoothing buffer layer made of a silicon nitride thin film. This layer played an efficient role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing the scattering loss. As a result the overall Q factor of the resonator was greatly increased. Also it reduced the gap between the ring and bus waveguides effectively to enhance the coupling between them, without relying on the direct writing method based on an e-beam writer. As for the achieved device performance at the wavelength of 1550 nm, the quality factor, the extinction ratio, and the free spectral range were ~103800, ~11 dB, and 1.16 m, respectively.

• Korean Journal of Poultry Science
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• v.20 no.3
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• pp.141-149
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• 1993

In order to develop a poultry manure dryer, a pilot dryer was designed and drying experiments were conducted to investigate the drying characteristics of poultry manure. According to the results, the pilot dryer could be operated without any air pollution problems. When poultry manure was dried from 79.2%(w.b. basis) moisture content, the final moisture content ranged from 38.7% to 57.9% depending upon the drying conditions. The drying results showed that drying rate was 189.8~198.0 kg/h and moisture evaporation rate was 124.0~125.4kg-$H_2$O/L. For this drying, electricity requirement was 9.5~19.3 Wh/kg and fuel consumption rate was 6.9~9.3 kg-$H_2$O/L with 50.2~65.1% thermal efficiency.

• Membrane Journal
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• v.16 no.4
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• pp.303-312
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• 2006

The asymmetric hybrid membranes of polyethersulfone (PES) and $ZrO_2$ nanoparticles were prepared via new one-step procedure combining simultaneously the phase-inversion method and the sol-gel technique. The optimum contents of $Zr(PrO)_4\;and\;HNO_3$ catalyst were determined by the adsorption experiments of phosphate anion onto the resulting hybrid membranes. The maximum adsorption of phosphate anion is obtained at the conditions of 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES and 30 mL $HNO_3$ addition per 1 mL $Zr(PrO)_4$. Variation of morphology, performance and incorporated $ZrO_2$ amount of the resulting hybrid membranes were discussed and determined using SEM, pure water flux, TGA, ICP, XRD and contact angle measurements. Increasing $Zr(PrO)_4$ addition into casting solution, pure water flux is increased and $ZrO_2$ amount in the hybrid membrane is maximized at the conditions 0.15 mL $Zr(PrO)_4$ addition per 1 mL PES. The prephosphatation of PES-$ZrO_2$ hybrid membrane was studied to modify the surface characteristics of membrane. Ultrafiltration of bovine serum albumin (BSA) solution was performed in a dead-end cell using both a bare (non-phosphated) and a phosphated hybrid membrane. It is revealed that both the permeate flux and BSA rejection were increased as about 40% by prephosphatation of hybrid membrane. These results may be explained on the basis of the increase of membrane hydrophilicity, which was determined from contact angle measurements.

• Journal of Korean Society of Transportation
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• v.19 no.6
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• pp.105-118
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• 2001

Incident detection rate and false alarm rate are the key measures tot estimating the performance of automatic incident detection algorithms. It is, however inherently very difficult to improve the two measures simultaneously. The main purpose of this study is to present some methods for solving the problem. For this, an incident detection algorithm has been designed in this study. The algorithm is consisted of two functions, one for detecting incident and another for detecting congestion. A logic for distinguishing non-recurrent congestion from recurrent congestion was employed in the algorithm. The new algorithm basically requires speed, flow, and occupancy data for defining incident situation, but the algorithm is able to perform this task without one of the three parameters. The performance of the algorithm has been evaluated by using the field data collected from Interstate Highway 880 in Bay Area, California. The empirical analysis results are very promising and thus, the algorithm proposed may be very useful for the analysts. This paper presents some empirical test results for the performance of California incident detection algorithm, only for the reference purpose.