• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1283-1285
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• 1996

This paper proposed frequency estimation the method of distorted sinusoidal signals by harmoics. An approximate estimation based on FFT and the accurate basic frequency was estimated by proposed method with Fourer Series, and the harmonics were estimated by the basic frequency. The sinusoidal signals is extracted by filter banks based on the estimated hamonics. The rate of basic and hamonics power is estimated by the extracted sinusoidal signals and we developed their algorithm and programs.

• Earthquakes and Structures
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• v.24 no.2
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• pp.91-96
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• 2023

In this article, the vibration response of elastic nanocomposite beams with enhanced damping by nanoparticles is presented based on the mathematical model. Damp construction is considered by spring and damper elements based on the Kelvin model. Exponential shear deformation beam theory (ESDBT) has been used to model the structure. The mixed model model is used to obtain the effective properties of the structure including compaction effects. Using the energy method and Hamilton's principle, the equations of motion are calculated. The beam frequency is obtained by analytical method. The purpose of this work is to investigate the effect of volume percentage of nanoparticles and density, length and thickness of the beam on the frequency of the structure. The results show that the frequency increases with the increase in volume percentage of nanoparticles.

• 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.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.634-636
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• 2008

This paper proposes a frequency detection method based on an advanced zero-crossing technique. Zero-crossing method for detecting frequency is one of the most widely used methods today. Although it is simple to apply, it requires extra hardware in implementation due to its limitations in accuracy. The proposed method models the error generated during zero crossing linearization and compensated for it in real time which makes it simple and accurate. The validity of the method and its applicability in anti-islanding detection of distributed generators was confirmed through simulation.

• Structural Engineering and Mechanics
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• v.39 no.5
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• pp.703-716
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• 2011

The accurate dynamic analysis of structures is usually performed by a fine finite element discretization with very large number of degrees of freedom. Apart from modal analysis, one can reduce the number of final equations by assuming the deformed shape of the structure as a linear combination of independent Ritz vectors. The efficiency of this method relies heavily on the vectors selected. In this paper, a new set of Ritz vectors is proposed. It is primarily proved that these vectors are linearly independent. Subsequently, various two and three-dimensional examples are analyzed based on the proposed method. In each case, the results are compared with the ones obtained based on usual Ritz and modal analysis methods. It is finally concluded that the proposed method is very effective and efficient method for dynamic analysis of structures in frequency domain.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.240-240
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• 2000

This paper presents two algorithms based on the concept of the frequency domain adaptive filter(FDAF). First the frequency domain recursive least squares(FRLS) algorithm with the overlap-save filtering technique is introduced. This minimizes the sum of exponentially weighted square errors in the frequency domain. To eliminate discrepancies between the linear convolution and the circular convolution, the overlap-save method is utilized. Second, the sliding method of data blocks is studied Co overcome processing delays and complexity roads of the FRLS algorithm. The size of the extended data block is twice as long as the filter tap length. It is possible to slide the data block variously by the adjustable hopping index. By selecting the hopping index appropriately, we can take a trade-off between the convergence rate and the computational complexity. When the input signal is highly correlated and the length of the target FIR filter is huge, the FRLS algorithm based on the block processing technique has good performances in the convergence rate and the computational complexity.

• Journal of IKEEE
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• v.22 no.4
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• pp.999-1005
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• 2018

This paper proposed a search-based high resolution frequency estimation method in power systme. The proposed frequency estimation method adopts a slope-based adaptive search as a base of adaptive estimation structure. The architectural and operational parameters in this adaptive algorithm are changed using the information from context layer analysis of the signals including a localized full-search of spectral peak. The convergence rate of the proposed algorithm becomes much faster than those of other conventional slope-based adaptive algorithms by effectively reducing search range with the application of the localized full-search of spectrum peak. The improvements in accuracy and convergence rate of the proposed algorithm are confirmed through the performance comparison with other representative frequency estimation methods, such as, DFT(discrete Fourier transform) method, ECKF(extended complex Kalman filter), and MV(minimum variable) method.

• Journal of the Korean Society of Industry Convergence
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• v.27 no.5
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• pp.1069-1080
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• 2024

Recently, vision-based displacement(VBD) has been attracting attention as a convenient and economical method. VBD has the advantage of being easy to install and operate, but it also has the disadvantage of being difficult to obtain results that reflect high-frequency characteristics well. On the other hand, indirect displacement measurement through double integration of acceleration may in some cases result in distortion in the low-frequency region, making integration itself impossible. Therefore, neither can be a suitable method alone for measuring the dynamic displacement of bridges under moving loads. In this context, this paper studies how to obtain more accurate dynamic displacement responses of bridges over the entire frequency range by combining two methods, VBD and acceleration integration. The practical applicability was examined through simulation and model experiments. The simulation results show that both basic methods have fundamental limitations in each frequency range, while the combined method can be an good alternative to overcome these limitations. The applicability of the combination method through model experiments also showed relatively good results, but the results were inferior to those in the theoretical case. The reason is that errors in each basic measurement methods are transferred to the combined method. In other words, it is important that the basic measurement method also secures sufficient accuracy at least in each advantageous frequency band. In conclusion, combining the strengths of different methods to create a better alternative is always a good approach, and the method in this paper is meaningful in that it demonstrates one such alternative.

• Journal of Communications and Networks
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• v.9 no.2
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• pp.118-127
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• 2007

We propose a link adaptation and selection method for the links constituting an orthogonal frequency division multiplexing (OFDM) based wireless relay network. The proposed link adaptation and selection method selects the forwarding, modulation, and channel coding schemes providing the highest end-to-end throughput and decides whether to use the relay or not. The link adaptation and selection is done for each sub-channel based on instantaneous signal to interference plus noise ratio (SINR) conditions in the source-to-destination, source-to-relay and relay-to-destination links. The considered forwarding schemes are amplify and forward (AF) and simple adaptive decode and forward (DF). Efficient adaptive modulation and coding decision rules are provided for various relaying schemes. The proposed end-to-end link adaptation and selection method ensures that the end-to-end throughput is always larger than or equal to that of transmissions without relay and non-adaptive relayed transmissions. Our evaluations show that over the region where relaying improves the end-to-end throughput, the DF scheme provides significant throughput gain over the AF scheme provided that the error propagation is avoided via error detection techniques. We provide a frame structure to enable the proposed link adaptation and selection method for orthogonal frequency division multiple access (OFDMA)-time division duplex relay networks based on the IEEE 802.16e standard.