• Journal of Power Electronics
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• v.15 no.4
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• pp.964-973
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• 2015

This paper presents a simple approach for the selective harmonic elimination (SHE) of multilevel inverter based on the transistor-clamped H-bridge (TCHB) family. The SHE modulation is derived from the sinusoidal voltage-angle equal criteria corresponding to the optimized switching angles. The switching angles are computed offline by solving transcendental non-linear equations characterizing the harmonic contents using the Newton-Raphson method to produce an optimum stepped output. Simulation and experimental tests are conducted for verification of the analytical solutions. An Altera DE2 field-programmable gate array (FPGA) board is used as the digital controller device in order to verify the proposed SHE modulation in real-time applications. An analysis of the voltage total harmonic distortion (THD) has been obtained for multiple output voltage cases. In terms of the THD, the results showed that the higher the number of output levels, the lower the THD due to an increase number of harmonic orders being eliminated.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.37-38
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• 2014

본 논문은 다중 모듈 통합형 태양광 발전 시스템의 발전 단가를 낮추기 위한 MPPT(Maximum Power Point Tracking) 방법에 관한 것이다. 기존의 다중 모듈 통합형 태양광 발전 시스템에서는 각 모듈마다 MPPT 동작을 필요로 하기 때문에 전류센서와 전압센서를 모두 사용하며, 이는 발전 단가를 상승시키는 원인 중 하나가 된다. 본 논문에서는 시스템의 제작비용을 낮추기 위하여 다중 모듈 통합형 태양광 발전 시스템에서 상대적으로 가격이 비싼 전류센서의 사용을 줄여, 여러 개의 모듈에서도 하나의 전류센서만을 사용하는 MPPT 방법을 제안하고 PSIM 시뮬레이션과 실험을 통해 입증하고자 한다.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.09a
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• pp.442-449
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• 2003

This paper presents a robust hybrid control system for seismic response control of a cable-stayed bridge. Because multiple control devices are operating, a hybrid control system could alleviate some of restirctions and limitations that exist when each system is acting alone. A LQG algorithm with on-off control scheme, H$_2$ and H$_{\infty}$ control algorithms with various frequency weighting filters are used to improve the controller robustness of the active control part in the hybrid control system. The numerital simulation results show that control performances of robust hybrid control systems are similar to those of the hybrid control system with LQG algorithm. Furthermore, it is verified that robust hybrid control systems are more robust than the hybrid control system with LQG algorithm and there are no signs of instabilities in the $\pm$5％ stiffness matrix perturbed system. Therefore, the proposed hybrid control system have a good robustness for stiffness matrix perturbation without loss of control effectiveness.

• International Journal of Computer Science & Network Security
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• v.22 no.1
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• pp.276-282
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• 2022

One of the most essential foundations upon which big institutions rely in delivering cloud computing and hosting services, as well as other kinds of multiple digital services, is the security of infrastructures for digital and information services throughout the world. Distributed denial-of-service (DDoS) assaults are one of the most common types of threats to networks and data centers. Denial of service attacks of all types operates on the premise of flooding the target with a massive volume of requests and data until it reaches a size bigger than the target's energy, at which point it collapses or goes out of service. where it takes advantage of a flaw in the Transport Control Protocol's transmitting and receiving (3-way Handshake) (TCP). The current study's major focus is on an architecture that stops DDoS attacks assaults by producing code for DDoS attacks using a cloud controller and calculating Round-Tripe Time (RTT).

• Smart Structures and Systems
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• v.30 no.1
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• pp.1-15
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• 2022

This article focuses on stability analysis and fuzzy controller synthesis for large neural network (NN) systems consisting of several interconnected subsystems represented by the NN model. Advanced and fuzzy NN differential inclusion (NNDI) for stability based on the developed algorithm with H infinity can be designed based on the evolved biological design. This representation is constructed using sector linearity for NN models. Sector linearity transforms a non-linear model into a linear model based on proposed operations. New sufficient conditions are realized in the form of LMI (linear matrix inequalities) to ensure the asymptotic stability of the trans-Lyapunov function. This transforms the nonlinear model into a linear model based on multiple rules. At last, a numerical case study with simulations is derived as illustration to prove its feasibility in real nonlinear structures.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.3
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• pp.43-51
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• 2023

Slotted ALOHA (S-ALOHA) is a classical medium access control protocol widely used in multiple access communication networks, supporting distributed random access without the need for a central controller. Although stability and delay have been extensively studied in existing works, most of these studies have assumed ideal channel conditions or independent fading, and the impact of time-correlated wireless channels has been less addressed. In this paper, we investigate the queueing delay performance in S-ALOHA networks under time-correlated channel conditions by utilizing a Gilbert-Elliott model. Through simulation studies, we demonstrate how temporal correlation in the wireless channel affects the queueing delay performance. We find that stronger temporal correlation leads to increased variability in queue length, a larger probability of having queue overflows, and higher congestion levels in the S-ALOHA network. Consequently, there is an increase in the average queueing delay, even under a light traffic load. With these findings, we provide valuable insights into the queueing delay performance of S-ALOHA networks, supplementing the existing understanding of delay in S-ALOHA networks.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.123-125
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• 2011

A SATA hard disk has been widely used in recent years and NCQ is one of its crucial features. Despite the development from IDE to SATA disk, there is still much room for improvement for a SATA disk. In addition, until now a hard disk is a black box to us and it is very hard to make research at the level of a disk controller. To enhance the performance of NCQ, we try to do I/O clustering over the requests, which combines multiple sequential requests into a single large one. To evaluate the effect of an I/O clustering mechanism, we created a simple but practical SATA hard disk simulator. Experimental results show that the proposed approach is effective in enhancing the I/O performance of a SATA disk.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.4B
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• pp.604-612
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• 2000

In order to satisfy the desired QoS level associated with each existing connection, ATM networks require traffic policing during a connection. Users who respect the contract should receive the function of transparent traffic policing without any interruption. However, contract violations should be detected and mediated immediately. So we propose a CAM type policing controller to allow user cell streams to minimize additional delay. The proposed policing scheme controls policing actions including traffic shaping by suitably spacing cells on each virtual circuit. This policing action is based on parallel processing of multiple cell stream which arrive in ATM multiplexed virtual circuits. We have developed an analytical model of the proposed policing scheme to examine the amount of cell loss and delay, which depends on traffic load, the size of policing buffers and minimum spacing cell time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.3
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• pp.684-690
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• 2010

Most of the existing SoCs have shared bus architecture which always has a bottleneck state. The more IPs are in an SOC, the less performance it is of the SOC, Therefore, its performance is effected by the entire communication rather than CPU speed. In this paper, we propose cross-bar switch bus architecture for the reduction of the bottleneck state and the improvement of the performance. The cross-bar switch bus supports up to 8 masters and 16 slaves and parallel communication with architecture of multiple channel bus. Each slave has an arbiter which stores priority information about masters. So, it prevents only one master occupying one slave and supports efficient communication. We compared WISHBONE on-chip shared bus architecture with crossbar switch bus architecture of the SOC platform, which consists of an OpenRISC processor, a VGA/LCD controller, an AC97 controller, a debug interface, a memory interface, and the performance improved by 26.58% than the previous shared bus.

• Journal of Biosystems Engineering
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• v.37 no.4
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• pp.225-232
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• 2012

Purpose: Accurate monitoring of information from various agricultural vehicles is one of the most important factors for appropriate management strategy of field operations. While there has been a number of study and design on applications of sensors and actuators for data acquisition and control system in tractor, incompatibility between various customized hardware and software has become a major obstacle to the universal deployment in real field operation. International standard for implementation of electronic control unit (ECU) in agricultural vehicles has becoming a mandatory requirement for inter-operation compatibility in the international trade of agricultural vehicle industries. The ISO 11783 standard is basically based upon well known communication technology designated using the controller area network (CAN) bus. While CAN bus could provide 1.0 Mbps of communication speed, the standard only recommended 250 kbps. Methods: This study presents the implementation and evaluation of ISO 11783 for tractor electronic control units (TECU)with a higher transmission rate from multiple ECU than 250 kbps. Throughput and loss rate of the developed prototype were calculated across manipulated bus load for laboratory experimental tests, and the maximum requirement of transmission rate by ISO 11873 was satisfied with lower than 60% of bus load. Results: Field tests with a TECU implemented to process messages from global positioning system (GPS) receiver resulted that the root mean square error of position information was lower than 4 m with 0.5 m/s as a travelling speed. Conclusions: Results of this study represent the utilization of the international standard ISO 11783 to providepractical developments in terms with the inter-operability of TECU.