• Korean Journal of Remote Sensing
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• v.30 no.2
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• pp.331-339
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• 2014

Determination of an ionospheric delay scale factor, which converts ground-based ionospheric delay into low Earth orbit ionospheric delay, using the international reference ionosphere model is proposed. Ionospheric delay from international GNSS service model combined with IRI-derived scale factor is evaluated with NASA GRACE satellite data. At approximately 480km altitude, mean and standard deviation of the scale factor are 0.25 and 0.01 in 2004. The scale factor reaches high in night time and Spring and Fall seasons. Ionospheric delay error by the proposed method has a mean of 3.50 TECU in 2004.

• Korean Journal of Construction Engineering and Management
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• v.8 no.6
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• pp.159-166
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• 2007

Work delay is one of the facts that make the reliability of construction projects decrease. Therefore, it is important to classify and prioritize the delay factors. This research analyzed key delay factors in apartment house construction through survey. The results of analysis are as follows. (1) Insufficient work force is the key delay factor in structural and finish work. (2) Improper craft of worker is the key delay factor in electrical work. (3) Incompletion of proceeding work is the key delay factor in mechanical work.

• Journal of the Korea Institute of Building Construction
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• v.9 no.2
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• pp.55-61
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• 2009

In order to conduct construction projects effectively, the work delay factors would be managed by planned construction schedules. As construction works are delayed ceaselessly, the solution is to select and manage the key factors which delay the work ceaselessly. The subjects of this study were an apartment houses of reinforced concrete structure. Hidden work delay factor were extracted, the surveys were conducted and occurrence, severity and detection of each factor were analyzed. With this result, final orders of priority were fixed and key management factors were deducted and presented.

• Journal of Cadastre & Land InformatiX
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• v.51 no.1
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• pp.97-110
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• 2021

This study estimated the delay factor, which is the ratio of travel time at the speed limit and travel time at the actual speed using real-time traffic information in Seoul. The actual travel speed on the road was lower than the maximum speed of the road and the travel speed was the slowest during the rush hour. As a result of accessibility analysis based on travel speed during the rush hour, the travel time at the actual speed was 37.49 minutes on average. However, the travel time at the speed limit was 15.70 minutes on average. This result indicated that the travel time at the actual speed is 2.4 times longer than that at the speed limit. In addition, this study proposedly defined the delay factor as the ratio of accessibility by the speed limit and accessibility to actual travel speed. As a result of delay factor analysis, the delay factor of Seoul was 2.44. The results by the administrative district showed that the delay factor in the north part areas of the Han River is higher than her south part areas. Analysis results after applying the relationship between road density and traffic volume showed that as the traffic volume with road density increased, the delay factor decreased. These results indicated that it could not be said that heavy traffic caused longer travel time. Therefore, follow-up research is needed based on more detailed information such as road system shape, road width, and signal system for finding the exact cause of increased travel time.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.1
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• pp.91-102
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• 1996

The multicast routing algorithm is necessary to transmit multimedia traffic efficiently in ATM (asynchronous transfer mode) networks. In this paper, we propose the multicast routing algorithm which is based on VP/VC characteristic. The proposed algorithm is based on VP tree concept and using cost function which is based on VP/VC switching. The cost funication is composed of link cost, delay and weighting factor on delay and the weighting factor is calculated by delay sensitivity of the traffic. The proposed algorithm can choose delay bounded path which satisfies delay constraint, moreover it can choose optimal path among VPs which has the same link cost and satisfying delay constraint. With controlling weighting factor, proposed algorithm can set-up efficient path. When the weighting factor sets to be between 0.8 and 1, experimental results show that the perforance of proposed scheme is approximated to that of cost optimal algorithm and strongly delay optimized algorithm.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.2
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• pp.71-81
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• 2022

In order for electro-optical tracking system (EOTS) to have accurate target coordinate, accurate navigation results are required. If an integrated navigation system is configured using an inertial measurement unit (IMU) of EOTS and the vehicle's navigation results, navigation results with high rate can be obtained. Due to the time-delay of the navigation results of the vehicle in the EOTS and scale factor errors of the EOTS IMU in high-speed and high dynamic operation of the vehicle, it is much more difficult to have accurate navigation results. In this paper, an integrated navigation system of EOTS which compensates time-delay and scale factor error is proposed. The proposed integrated navigation system consists of vehicle's navigation system which provides time-delayed navigation results, an EOTS IMU, an inertial navigation system (INS), an augmented Kalman filter and integration Kalman filter. The augmented Kalman filter outputs navigation results, in which the time-delay of the vehicle's navigation results is compensated. The integration Kalman filter estimates position, velocity, attitude error of the EOTS INS and accelerometer bias, accelerometer scale factor error, gyro bias and gyro scale factor error from the difference between the output of the augmented Kalman filter and the navigation result of the EOTS INS. In order to check performance of the proposed integrated navigation system, simulations for output data of a measurement generator and land vehicle experiments were performed. The performance evaluation results show that the proposed integrated navigation system provides more accurate navigation results.

• Journal of Drive and Control
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• v.17 no.1
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• pp.44-50
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• 2020

For the requirement of accurate tracking control and the safety of physical human-robot interaction, torque control is basically desirable for humanoid robots. Because of the complexity of humanoid robot dynamics, the TDC (time-delay control) is practical because it does not require a dynamic model. However, there occurs a considerable error due to discontinuous non-linearities. To solve this problem, the TDC-FLC (fuzzy logic compensator) is applied to humanoid robots. The applied controller contains three factors: a TDE (time-delay estimation) factor, a desired error dynamic factor, and FLC to suppress the TDE error. The TDC-FLC is easy to execute because it does not require complicated humanoid dynamic calculations and the heuristic fuzzy control rules are intuitive. TDC-FLC is implemented on the whole body of a humanoid, not on biped legs even though it is performed by a virtual humanoid robot. The simulation results show the validity of the TDC-FLC for humanoid robots.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.05a
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• pp.191-192
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• 2011

The construction projects contain a lot of variables and risk affecting productivity. The duration of the project must be recognized important as for quality, unit cost and safety. There is need for improving work efficiency by investigating relationship of works to prevent delay. This study focuses on analysing the delay factors of steel staircase system to suggest regression model that enables construction productivity estimation. The position of the observers and construction delay factors were expressed by the independent variable of the regression model and productivity was expressed by a dependent variable. This paper suggests quantitative productivity and it is expected that will be helpful estimating application in construction new technologies.

• Korean Journal of Construction Engineering and Management
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• v.9 no.5
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• pp.214-226
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• 2008

Construction delay caused considerable losses to project parties. Avoiding construction delays is important to save costs for project stakeholders. The main objective of this paper is to identify major causes of construction delays of apartment construction projects in Vietnam. Sixteen causes of delay were identified through a questionnaire survey of 166 professionals. Factor analysis was employed to categorize these causes. The results of the survey revealed the main causes of delay of apartment projects in Vietnam are: (1) owner's and contractor'S financial difficulties; (2) lack of experienced contractors; (3) late delivery of materials; (4) late construction site handover; (5) owner's late payments for completed works; (6) low bid prices; (7) inappropriate construction method; and (8) defective works and unnecessary reworks. Factor analysis uncovered that causes of delay can be grouped under five categories labeled the five INs: incompetence, ineffectiveness, inadequateness, inapplicableness and inconceivableness. Comparative analysis between the Vietnam construction industry (VCI) and the Korea construction industry (KCI) has been performed to infer valuable lessons for researchers and practitioners in the VCI and the KCI. Comparative analysis indicated that main causes of delay in the VCI somewhat differ from main causes of delay in the KCI. However, "contractor'S financial difficulties", "late construction site handover", "unnecessary rework", "incapable designers", "site clearance difficulties" are common causes of delay in the VCI as well as the KCI. The findings of this research can be used as a guideline to overcome problems in the VCI as well as in other construction industries. Since Korea has emerged as the first largest foreign investor in Vietnam, the results of this study may be useful not only to practitioners and researchers in Vietnam but also to participants in Korea.

• Journal of the Korea Society for Simulation
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• v.16 no.1
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• pp.1-9
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• 2007

The development of efficient Qualify of Service (QoS) routing algorithms in high speed networks is extremely difficult to achieve, because in order to operate, divergent services require various quality conditions. If the parameter of concern is to measure the delay on a specific link, the routing algorithm obtains the Least Delay (LD) path. Meanwhile, if the parameter is to measure the link cost, the Least Cost (LC) path is calculated. The Delay Constrained Least Cost (DCLC) path problem of the mixed issues on the LD and LC has been shown to be NP-hard. The path cost of LD path is relatively more expensive than that of the LC path, and the path delay of the LC path is relatively higher than that of the LD path in the DCLC problem. In this paper, we introduce the new factor for balancing cost and delay. The simulation result shows that our introduced factor is satisfied to solve the DCLC problem.