• Journal of Information Processing Systems
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• v.16 no.3
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• pp.699-717
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• 2020

Propagation time on permissionless blockchain plays a significant role in terms of stability and performance in the decentralized systems. A large number of activities are disseminated to the whole nodes in the decentralized peer-to-peer network, thus causing propagation delay. The stability of the system is our concern in the first place. The propagation delay opens up opportunities for attackers to apply their protocol. Either by accelerating or decelerating the propagation time directly without proper calculation, it brings numerous negative impacts to the entire blockchain system. In this paper, we thoroughly review and elaborate on several parameters related to the propagation time in such a system. We describe our findings in terms of data communication, transaction propagation, and the possibility of an interference attack that caused an extra propagation time. Furthermore, we present the influence of block size, consensus, and blockchain scalability, including the relation of parameters. In the last session, we remark several points associated with the propagation time and use cases to avoid dilemmas in the light of the experiments and literary works.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.6
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• pp.576-584
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• 2003

This paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. Constructing a imaginary second-phase giving time delay to load currents, making single-phase system into the system that has two phases, complex calculation is possible. In the previous method, it made a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle), but in proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used to the second phase. Instantaneous calculation of harmonic current is possible, because two phase have different phase. In this paper, it was done with instantaneous calculation using the rotating reference frames(RRF) that synchronizes with source-frequency, a reference of compensation currents, not applying to instantaneous reactive power theory which uses the existed fixed reference frames. The simulation and experiment about R-L loads using the current source were carried out, and the effect of the proposed method was preyed through the result of this experiment.

• Korean Journal of Radiology
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• v.1 no.3
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• pp.142-151
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• 2000

Objective: To determine the optimal scan timing for contrast-enhanced magnetic resonance angiography and to evaluate a new timing method based on the arteriovenous circulation time. Materials and Methods: Eighty-nine contrast-enhanced magnetic resonance angiographic examinations were performed mainly in the extremities. A 1.5T scanner with a 3-D turbo-FLASH sequence was used, and during each study, two consecutive arterial phases and one venous phase were acquired. Scan delay time was calculated from the time-intensity curve by the traditional (n = 48) and/or the new (n = 41) method. This latter was based on arteriovenous circulation time rather than peak arterial enhancement time, as used in the traditional method. The numbers of first-phase images showing a properly enhanced arterial phase were compared between the two methods. Results: Mean scan delay time was 5.4 sec longer with the new method than with the traditional. Properly enhanced first-phase images were found in 65% of cases (31/48) using the traditional timing method, and 95% (39/41) using the new method. When cases in which there was mismatch between the target vessel and the time-intensity curve acquisition site are excluded, erroneous acquisition occurred in seven cases with the traditional method, but in none with the new method. Conclusion: The calculation of scan delay time on the basis of arteriovenous circulation time provides better timing for arterial phase acquisition than the traditional method.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1480-1482
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• 2005

The major causes of power quality deterioration are harmonic current through semiconductor switching device, due to use of nonlinear loads such as diodes rectifier or thyristor rectifiers. In response to this concerns, this paper presents a new control method of single-phase active power filter(APF) for the compensation of harmonic current components in nonlinear loads. In order to make the complex calculation to be possible, the single-phase system that has two phases was made by constructing a imaginary second-phase giving time delay to load currents. In the conventional method, a imaginary-phase lagged to the load current T/4(here T is the fundamental cycle) was made. But in this proposed method, the new signal, which has the delayed phase through the filter, using the phase-delay property of low-pass filter, was used as the second phase. As this control method is applied to the system of single phase, an instantaneous calculation was done rather by using the rotating reference frames that synchronizes with source-frequency than by applying instantaneous reactive power theory that uses the conventional fixed reference frames.

• 제어로봇시스템학회:학술대회논문집
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• 2004.08a
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• pp.1915-1919
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• 2004

In this paper, we propose a new discrete-time predictive current controller for a PMSM(Permanent Magnet Synchronous Motor). The main objectives of the current controllers are to ensure that the measured stator currents tract the command values accurately and to shorten the transient interval as much as possible, in order to obtain high-performance of ac drive system. The conventional predictive current controller is hard to implement in full digital current controller since a finite calculation time causes a delay between the current sensing time and the time that it takes to apply the voltage to motor. A new control strategy in this paper is seen the scheme that gets the fast adaptation of transient current change, the fast transient response tracking and is proposed simplified calculation. Moreover, the validity of the proposed method is demonstrated by numerical simulations and the simulation results will be verified the improvements of predictive controller and accuracy of the current controller.

• Journal of Internet Computing and Services
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• v.6 no.6
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• pp.117-125
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• 2005

The dominator tree presents the dominance frontier from directed graph to the tree. we present the effective algorithm for constructing the dominator tree from arbitrary directed graph. The reducible flow graph was reduced to dominator tree after dominator calculation. And the irreducible flow graph was constructed to dominator-join graph using join-edge information of information table. For reducing the dominator tree from dominator-join graph, we implement the effective sequency reducible algorithm and delay reducible algorithm. As a result of implementation, we can see that the delay reducible algorithm takes less execution time than the sequency reducible algorithm. Therefore, we can reduce the flow graph to dominator tree effectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.79-84
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• 2017

This paper is a multi-input multi-path (Multiple-input multiple-output: MIMO) using a space-alternating generalized expectation maximization(SAGE) algorithm in the parameter channel and determine the channel estimation performance. Estimated by the algorithm, SAGE time-varying channel environment, the channel parameters estimated from the parameters of the channel measured in the island region 781 of the band in order to compare the performance and compares the original data. This allows you to check the performance of the algorithm SAGE and is highly stable to delay spread (Delay Spread), the diffusion angle of arrival (Arrive of Angular Spread) performance in terms of accuracy down through the SAGE algorithm for estimating a more general calculation parameters.

• Journal of the Korean Society of Industry Convergence
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• v.22 no.3
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• pp.251-257
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• 2019

This paper proposes a new measurement method using virtual power concept to measure the effective value of 3-phase voltage with variable frequency. The conventional effective value measurement method uses a method of integrating data sampled during one or half cycle of the power voltage and averaging it. In this method, since the effective voltage is calculated every cycle, a time delay occurs in the measured effective voltage and it is s a problem to measure the effective value of a device whose frequency varies from time to time, such as a generator. The proposed 3-phase voltage rms measurement method has an advantage that it can measure accurate voltage RMS value regardless of measurement frequency variation. In particular, there is an advantage in that it is possible to measure a 3-phase effective voltage rather than an average value of the effective voltage of each phase in a 3-phase unbalance voltage. In addition, the validity of the proposed method is verified by using the Psim simulation tool and the experimental results are analyzed by applying the proposed measurement algorithm to the actual three phase synchronous generator voltage measurement experiment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.1
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• pp.146-154
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• 2007

In this paper, we have presented a real-time transfer mechanism for the delay-sensitive data in WSNs (Wireless Sensor Networks). The existing methods for real-time data transfer select a path whose latency is shortest or the number of hops is least. Although the approaches of these methods are acceptable, they do not always work as efficiently as they can because they had no consideration for the link error rates. In the case of transmission failures on links, they can not guarantee the end-to-end real-time transfer due to retransmissions. Therefore, we have proposed an algorithm to select a real-time transfer path in consideration of the link error rates. Our mechanism estimates the 1-hop delay based on the link error rate between two neighboring nodes, which in turn enables the calculation of the expected end-to-end delay. A source node comes to choose a path with the shortest end-to-end delay as a real-time route, and sends data along the path chosen. We performed various experiments changing the link error rates and discovered that this proposed mechanism improves the speed of event-to-sink data transfer and reduces delay jitter. We also found that this mechanism prevents additional energy consumption and prolongs network lifetime, resulting from the elative reduction of transmission failures and retransmissions.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.642-648
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• 2009

Determining the total duration for a construction project is an integral part of project management in the construction industry. This is to ensure the project and all its associated activities can be carried out and completed within the time frame stipulated. There are several commonly used scheduling methods and techniques in project management, some of which involves manual calculation while others involve computer software. This paper looks into the various time determination methods, extracting out their differences and similarities. It also seeks to draw out the problems when determining time for projects, especially those encountered of case studies. Based on the results from the case studies, there were delays on certain projects even though time determination had been carried out rigorously prior to the commencement of the projects. This paper seeks to develop a time determination model, which incorporates risk management techniques into the calculations in order to improve the method for time estimation to minimize the chances of project delay.