• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.1 no.1
• /
• pp.73-81
• /
• 1989

The purpose of this study is augmentation of heat transfer without additional power in a rectangular impinging air jet. As a method of passive heat transfer augmentation in a two-dimensional air jet, heat transfer surface of flat plate with rods is used. This study, particularly in the wall jet rigeon, investigates the effect of the clearance between the flat plate and rod. Mechanism of heat transfer enhancement is investigated by measuring the local heat transfer coefficient. It is concluded that the superposition of the effects of flow accelerlation through the clearance between the flat plate and the rod, and reattachment of the flow was the cause of the excellent performance. The overall heat transfer rate of flat plate with rods is about 1.5 times larger than that of flat plate without rods.

• International Journal of Control, Automation, and Systems
• /
• v.6 no.1
• /
• pp.135-141
• /
• 2008

A new approach to $H_{\infty}$ multi-step prediction is developed by applying the innovation analysis theory. Although the predictor is derived by resorting to state augmentation, nevertheless, it is completely different from the previous works with state augmentation. The augmented state here is considered just as a theoretical mathematic tool for deriving the estimator. A distributed algorithm for the Riccati equation of the augmented system is presented. By using the reorganized innovation analysis, calculation of the estimator does not require any augmentation. A numerical example demonstrates the effect in reducing computing burden.

• Journal of applied mathematics & informatics
• /
• v.32 no.1_2
• /
• pp.267-284
• /
• 2014

The multiresolution analysis for Legendre multiwavelets are given, anti-derivatives of Legendre multiwavelets are used for the numerical solution of differential equations, a special form of multilevel augmentation method algorithm is proposed to solve the disrete linear system efficiently, convergence rate of the Galerkin methods is given and numerical examples are presented.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.33 no.8
• /
• pp.299-309
• /
• 1984

This paper proposes the adapter for interrupting capacity augmentation of circuit breaker which can be applied in case of shortage in a existing circuit breaker's interrupting capacity due to utility system extension. The adapter utilizes two winding type of reactor instead of single winding type of reactor and the control of 2ry circuit is excuted by a triac interlocked with the system protective relays actuation so as to cut out the reactor by short circuit of the 2ry winding in normal situation and to cut in the reactor by open circuit of the 2ry winding in abnomal situation such as short circuit accident. As a result of the theoritical analysis and experiment, it is proved that the adaptor can reduce the voltage crop and iron loss due to the reactor signigicantly in normal system condition and do a role of reactor upon the power system accident.

• Journal of Aerospace System Engineering
• /
• v.4 no.1
• /
• pp.19-22
• /
• 2010

The accuracy and integrity of global navigation satellite systems (GNSS) can be improved by using GNSS augmentation systems. Large ionospheric spatial gradient, during ionosphere storm, is a major threat for using GNSS augmentation systems by increasing the spatial decorrelation between a reference system and users. Ionosphere decorrelation behavior can be analyzed by using dual frequency GPS data. GNSS receivers have their own biases, called inter-frequency bias (IFB) between dual(P1 and P2) frequencies and they must be accurately estimated before computing ionosphere delays. GPS network data in Korea is used to compute each receiver's IFB, and their estimation accuracy and variability are analyzed. IFB estimation methodology to apply for ionosphere gradient analysis is discussed.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.4
• /
• pp.369-377
• /
• 2023

This paper presents the analysis results of navigation performance of Korea Augmentation Satellite System (KASS) test signals. Performance analysis was performed with Global Positioning System (GPS) and Satellite Based Augmentation System (SBAS) signals received from 7 KASS reference stations. And the performances were analyzed in terms of the signal strength, statistics for each SBAS message, coverage of ionospheric correction, accuracy, integrity, continuity, and availability. In addition, the navigation solutions provided by commercial receiver was analyzed and the performance experienced by general users was presented. Lastly, directions for further improvement of the KASS system were addressed. These performance analysis results can be used to confirm the feasibility of utilizing KASS in user applications.

• Journal of the Korean Arthroscopy Society
• /
• v.12 no.1
• /
• pp.12-17
• /
• 2008

Purpose: This study presents clinical results of anterior cruciate ligament(ACL) augmentation using autogenous two-strand semitendinosus tendon in the treatment of partial ACL tears with preservation of residual portion. Materials and Methods: From January 2004 to June 2006, twenty two patients who had an ACL injury underwent ACL augmentation using autogenous two-strand semitendinosus tendon were enrolled in this study. We evaluated the clinical results with regard to clinical findings(range of motion, Lachman test, pivot shift test), standard knee scales(Lysholm, Modified Feagin Scoring System), and KT-1000 arthrometer testing. Results: At minimum one year postoperatively, there was no limitation of range of motion. Lachman and pivot shift tests were negative in all knees. On instrumented anterior laxity test by KT-1000 arthrometer, mean side to side difference was improved from 4.6mm preoperatively to 1.7mm postoperatively. Average Lysholm score was improved from 70 to 92. Ninety one percent of cases were rated as good or excellent in Modified Feagin Scoring System. Conclusion: Augmentation using autogenous two-strand semitendinosus tendon with preservation of residual portion of the ACL seems to be an acceptable method for restoring knee stability and proprioceptive function.

• Journal of Positioning, Navigation, and Timing
• /
• v.12 no.1
• /
• pp.23-35
• /
• 2023

Korea Augmentation Satellite System (KASS) is a satellite-based augmentation system (SBAS) that provides approach procedure with vertical guidance-I (APV-I) level corrections and integrity information to Korea territory. KASS is used to monitor navigation performance in real-time, and this paper introduces the design, implementation, and verification process of mission monitoring (MIMO) in KASS. MIMO was developed in compliance with the Minimum Operational Performance Standards of the Radio Technical Commission for Aeronautics for Global Positioning System (GPS)/SBAS airborne equipment. In this study, the MIMO system was verified by comparing and analyzing the outputs of reference tools. Additionally, the definition and derivation method of accuracy, integrity, continuity, and availability subject to MIMO were examined. The internal and external interfaces and functions were then designed and implemented. The GPS data pre-processing was minimized during the implementation to evaluate the navigation performance experienced by general users. Subsequently, tests and verification methods were used to compare the obtained results based on reference tools. The test was performed using the KASS dataset, which included GPS and SBAS observations. The decoding performance of the developed MIMO was identical to that of the reference tools. Additionally, the navigation performance was verified by confirming the similarity in trends. As MIMO is a component of KASS used for real-time monitoring of the navigation performance of SBAS, the KASS operator can identify whether an abnormality exists in the navigation performance in real-time. Moreover, the preliminary identification of the abnormal point during the post-processing of data can improve operational efficiency.

• Journal of Positioning, Navigation, and Timing
• /
• v.5 no.4
• /
• pp.193-202
• /
• 2016

The Korea Augmentation Satellite System (KASS), which is under development in Korea as a Satellite Based Augmentation System (SBAS) is expected to broadcast SBAS messages to air space in Korea according to the international standards defined by the International Civil Aviation Organization (ICAO) and the Radio Technical Commission for Aeronautics (RTCA). Around 13 SBAS messages are broadcast in every second to transmit augmentation information which can be applicable to a wide area in common. Each of the messages requires a different update interval and time-out according to the characteristics, purpose, and importance of transmitted information, and users should receive and combine multiple SBAS messages to calculate SBAS augmented information. Thus, a time to take acquiring first SBAS position by users differs depending on broadcasting various SBAS messages with which order and intervals. The present paper analyzes the considerations on message scheduling for broadcasting of KASS augmentation information and proposes a design of KASS message scheduler using the considerations. Compared to existing SBAS systems, which have a wide range of service area, a service area of the KASS is limited to Korea only. Thus, the numbers of ionosphere grid points and satellites to be augmented are expected to be smaller than those of existing SBAS. By reflecting this characteristic to the proposed design, shortening of broadcast interval of KASS message is verified compared to existing SBAS and a measure to increase a speed of acquisition of user navigation solution is proposed utilizing remaining message slots. The simulation result according to the proposed measure showed that the maximum broadcast interval can be reduced by up to 20% compared to that of existing SBAS, and users can acquire KASS position solution faster than existing SBAS.

• Journal of Advanced Navigation Technology
• /
• v.20 no.1
• /
• pp.8-14
• /
• 2016

High-level conceptual design analysis results of satellite communication system for Korea augmentation satellite system (KASS) satellite communication system, which is a part of KASS and consisted of KASS uplink Stations and two leased GEO is presented in this paper. We present major functions such as receiving correction and integrity message from central processing system, taking forward error correction for the message, modulating and up converting signal and conceptual design analysis for concepts for design process, GEO precise orbit determination for GEO ranging that is additional function, and clock steering for synchronization of clocks between GEO and GPS satellites. In addition to these, KASS requires 2.2 MHz for SBAS Augmentation service and 18.5 MHz for Geo-ranging service as minimum bandwidths as a results of service performance analysis of GEO ranging with respect to navigation payload(transponder) RF bandwidth is presented. These analysis results will be fed into KASS communication system design by carrying out final analysis after determining two GEOs and sites of KASS uplink stations.