• Journal of Positioning, Navigation, and Timing
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• v.5 no.2
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• pp.67-74
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• 2016

In this paper, time comparison is performed with standardization institution in Japan using a Two-Way Satellite Time and Frequency Transfer (TWSTFT) technique as one of the methods for high precision time comparison. To analyze the performance of time comparison in the TWSTFT method, time comparison results via the Global Positioning System (GPS) code and carrier wave are analyzed. Through the time comparison performance, frequency stability is analyzed using modified Allan deviation and by this result, characteristics of time comparison of the TWSTFT that is utilized in international time comparison are presented.

• Journal of the Chungcheong Mathematical Society
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• v.24 no.4
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• pp.687-693
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• 2011

This paper gives the stochastic comparison results for the first passage time distributions in the M/G/1 retial queue.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.3
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• pp.245-255
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• 2023

Time comparison techniques are necessary for generating and keeping Coordinated Universal Time (UTC) and distributing standard time clocks. Global Navigation Satellite System (GNSS) Common View, GNSS All-in-View, Two-Way Satellite Time and Frequency Transfer (TWSTFT), Very Long Baseline Interferometry (VLBI), optical fiber, and Network Time Protocol (NTP) based methods have been used for time comparison. In these methods, GNSS based time comparison techniques are widely used for time synchronization in critical national infrastructures and in common areas of application such as finance, military, and wireless communication. However, GNSS-based time comparison techniques are vulnerable to jamming or interference environments and it is difficult to respond to GNSS signal disconnection according to the international situation. In response, in this paper, Code-Division Multiple Access (CDMA) based All-to-All TWSTFT operation method is proposed. A software-based simulation platform also was designed for performance analysis in multi-TWSTFT signal environments. Furthermore, code and carrier measurement jitters were calculated in multi-signal environments using the designed simulation platform. By using the technique proposed in this paper, it is anticipated that the TWSTFT-based time comparison method will be used in various fields and satisfy high-performance requirements such as those of a GNSS master station and power plant network reference station.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.11
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• pp.1238-1246
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• 1992

We developed a time comparison system using the ranging signal of the geostationary meteorological satellite(GMS). By using the system time comparison between the KRISS(Korea Research Institute of Standards and Science) cesium atomic clock and the GMS ranging signal has been carried out and the results have shown that the precision of time comparison at KRISS is about 10 ns. For the more accurate measurements we calibrated the receiver delay time between KRISS receiver and CRL(Communications Research Laboratory) receiver by using the portable GMS receiver.

• Journal of applied mathematics & informatics
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• v.7 no.2
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• pp.539-552
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• 2000

In this paper, we established the general comparison principles for IVP of impulsive differential equations with time variables, which strictly extend and improve the precious comparison results obtained by V. Lakes. et.al . and S.K.Kaul([3]-[7]). Whit the general comparison results, we constructed the monotone iterative sequences of solution for IVP of such equations which converges the maximal and minimal and minimal solutions , respectively.

• Journal of Korean Physical Therapy Science
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• v.27 no.3
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• pp.56-66
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• 2020

Background: The purpose of this study was to investigate the effects of pulsed-ultrasound intervention and continued-ultrasound on the PPT (pressure pain threshold), CK (creatine kinase) and LDH (lactate dehydrogenase) recovery of before EIMD (exercise-induced muscle damage). Design: Randomized Controlled Trial. Methods: Thirty subjects who are student in their 20s at a university participated in this study, these subjects were assigned into three groups, a control group (n=10), experiment group I (n=10), and experiment group II (n=10). The subjects in experimental group were intervened by pulsed-ultrasound and continued-ultrasound, while ones on control group weren't by any intervention after induced EIMD. Results: First, In the comparison of the PPT, there were significant variations with the lapse the time in three groups (p<.001) and there was a significant interaction of time and group (p<.001). In the among group comparison, the PPT of experimental group II was significantly larger than those of other groups (p<.01). Second, In the comparison of the CK, there were significant variations with the lapse the time in three groups (p<.001) and there was a significant interaction of time and group (p<.001). In the among group comparison, the CK of experimental group II was significantly smaller than those of other groups (p<.001). Third, In the comparison of the LDH, there were significant variations with the lapse the time in three groups (p<.001) and there was a significant interaction of time and group (p<.001). In the among group comparison, the LDH of experimental group II was significantly smaller than those of other groups (p<.001). Conclusion: The above results revealed that the continued-ultrasound intervention before an exercise had a positive effect of muscle function after EIMD. Therefore we can consider the continued ultrasound as a considerable intervention method to prevent or reduce an exercise injury.

• Journal of Korean Physical Therapy Science
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• v.28 no.3
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• pp.30-41
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• 2021

Background: The purpose of this study was to investigate the effects of WBC on the pressure pain threshold, CK and LDH after exercise-induced muscle injury. Design: A Randomized Controlled Trial. Methods: In this study, these subjects were assigned into three groups, a control group (n=10), experiment group I (n=10) and experiment group II (n=10). The subjects in experimental group I were intervened by WBC (-130℃, 3 minutes) before induced EIMD, experimental group II were intervened by WBC (-130℃, 3 minutes) after induced EIMD and control group weren't by any intervened after induced EIMD. Results: First, In the comparison of the PPT, there were significant variations with the lapse the time in three groups (p<.001) and there was a significant interaction of time and group (p<.001). In the among group comparison, the PPT of experimental group II was significantly larger than those of other groups (p<.01). Second, In the comparison of the CK, there were significant variations with the lapse the time in three groups (p<.001) and there was a significant interaction of time and group (p<.001). In the among group comparison, the CK of experimental group II was significantly smaller than those of other groups (p<.001). Third, In the comparison of the LDH, there were significant variations with the lapse the time in three groups (p<.01) and there was a significant interaction of time and group (p<.001). In the among group comparison, the LDH of experimental group II was significantly smaller than those of other groups (p<.001). Conclusion: The above results revealed that the WBC intervention after an exercise had a positive effect of muscle function after EIMD.

• Journal of Positioning, Navigation, and Timing
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• v.12 no.2
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• pp.201-209
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• 2023

Time comparison techniques are required for generating and keeping Coordinated Universal Time (UTC) and to distribute standard clocks. These techniques play an important role in various fields, including science, finance, military, and communication. Among these techniques, Two-Way Satellite Time and Frequency Transfer (TWSTFT) ensures a relatively high accuracy, with a time comparison accuracy at a nanosecond level. However, TWSTFT systems have some limitations, such as the dependency on extra network links. In this paper, we propose an improved method for TWSTFT system operation and design a message structure for the suggestion. Additionally, we estimate the data rate and redundancy for the new TWSTFT signal with the designed message structure.

• Information Systems Review
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• v.5 no.1
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• pp.97-111
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• 2003

With the spread of electronic commerce on the Internet, comparison shopping sites with agent technique are getting popular for the best shopping. However, most consumers are still spending much time to search for the best price through the sites because each of them may show a different price even for the same goods or a site does not show any information about specific goods. Additionally, the search for the best price of the goods like books and CDs may cause the system to be overloaded and the response time to be long due to an on-line real-time search. In this paper, we have designed and implemented a meta-search system for comparison shopping sites with a local database and memory cache to resolve the above problems. The proposed system collects and maintains the price information of popular goods among the comparison shopping sites using several software agents. The experimental results show that our system is an efficient meta-comparison shopping engine and reduces the latency of the response time with little overhead.