• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2001.11a
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• pp.146-150
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• 2001

Microwave model and high-frequency measurement of the ACF flip-chip interconnection was investigated using a microwave network analysis. S-parameters of on-chip and substrate were separately measured in the frequency range of 200 MHz to 20 GHz using a microwave network analyzer HP8510 and cascade probe. And the cascade transmission matrix conversion was performed. The same measurements and conversion techniques were conducted on the assembled test chip and substrate at the same frequency range. Then impedance values in ACF flip-chip interconnection were extracted from cascade transmission matrix. ACF flip chip interconnection has only below 0.1nH, and very stable up to 13 GHz. Over the 13 GHz, there was significant loss because of epoxy capacitance of ACF. However, the addition of SiO$_2$filler to the ACF lowered the dielectric constant of the ACF materials resulting in an increase of resonance frequency up to 15 GHz. High frequency behavior of metal Au stud bumps was investigated. The resonance frequency of the metal stud bump interconnects is higher than that of ACF flip-chip interconnects and is not observed at the microwave frequency band. The extracted model parameters of adhesive flip chip interconnects were analyzed with the considerations of the characteristics of material and the design guideline of ACA flip chip for high frequency applications was provided.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.9
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• pp.1549-1555
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• 2007

The complexity of modern power systems often makes it impractical to model it in its entirety for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of Frequency Dependent Network Equivalent (FDNE). The advantage of using z-domain fitting is that it can be directly implemented in a digital simulation program without any loss of accuracy. Fitting in the s-domain always requires "discretizing" a continuous system and the inherent approximations. This paper presents z-domain rational function formulation and demonstrates the use of it for the assessment of the transient response of the Lower South Island of New Zealand. Moreover by using a well publicized test system and providing complete information on the developed FDNE coefficients other researchers easily benchmark their work against this.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.9
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• pp.86-94
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• 1995

Bead shape in high frequency electric resistance (HER) pipe welding gives useful information on judging current welding conditon. In most welding process, heat input is controlled by skilled operators observing color and shape of bead. In this paper, a visual monitoring system is designed to observe bead shape in HERW pipe welding process by using structured light beam and a C.I.D(Charge injection device) camera. To avoid some difficul- ties arising in extracting stable features of stripe pattern and classifying the extracted features, Kohonen neural network is used to classify such bead shapes. The experimental results show accurate classification performance of the proposed method.

• Smart Structures and Systems
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• v.9 no.1
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• pp.21-33
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• 2012

In this study, a Lamb-wave based damage detection approach is proposed for damage localization in plate. A sensor network consisting of three PZT wafer type actuators/sensors is used to generate and detect Lamb waves. To minimize the complication resulted from the multimode and dispersive characteristics of Lamb waves, the fundamental symmetric Lamb mode, $S_0$ is selectively generated through designing the excitation frequency of the narrowband input signal. A damage localization algorithm based upon the configuration of the PZT sensor network is developed. Time-frequency analysis method is applied to purify the raw signal and extract damage features. Experimental result obtained from aluminum plate verified the proposed damage localization approach.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2006.04a
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• pp.467-472
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• 2006

The purpose of this paper is to check the structural safety of the network equipments by performing the static and dynamic finite element analysis. The stress and displacement of structures under static loading condition are evaluated to check whether satisfying the design requirement conditions. Since the computed natural frequencies are similar to the results of experiment. the model could be used for the response spectrum analysis where experimental acceleration value at each frequency are used as seismic input excitation. It is shown that the analysis results are a little bit larger than that of the experimental values. Also sensitivity analysis and optimization for the natural frequency are performed and it is found that the first natural frequency is very sensitive to the stiffness of the equipment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.552-559
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• 2012

In this paper, we introduce a frame structure of the satellite TDMA network and the synchronization method thereof. The primary station transmits a special burst called reference burst which provides reference time to network. By using this reference burst all nodes achieve initial acquisition and synchronization. We consider time drift due to the node and satellite mobility, time shift due to the node position, Doppler shift due to the node mobility and frequency offsets as important factors of the frame structure. Simulation results show that the proposed frame structure and synchronization method guarantee accurate synchronization performance when the node is even in low SNR as well as 25 kHz frequency offsets.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.569-575
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• 2013

In this paper, we present a photonic approach for generating highly stable coherent sub-terahertz (THz) signals for wireless communications. As proof-of-concept we transmit data at 100 GHz carrier frequency using on-off keying modulation and heterodyne detection. The sub-THz carrier signals are generated by photo-mixing two optical carrier signals at different frequencies, extracted from an optical frequency comb. We introduce a novel system to stabilize the phase of the optical carrier signals. Error-free transmission is successfully achieved up to a bit rate of 8.5 Gbit/s at 100 GHz.

• Journal of information and communication convergence engineering
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• v.2 no.3
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• pp.139-144
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• 2004

In order to transmit various types of multimedia data (i.e. voice, video, and data) over a wireless channel, the coding and modulation scheme needs to be flexible and capable of providing a variable quality of service, data rates, and latency. In this paper, we study a mobile multimedia COMA network combined with the concatenated Reed-Solomon/Rate Compatible Punctured Convolution code (RS/RCPC). Also, this paper propose the combination of concatenated RS/RCPC coder and COMA RAKE receiver for multimedia COMA traffic which can be sent over wireless channels. From the results, using a frequency selective Rayleigh fading channel model, it is shown that concatenated RS/RCPC coder at the wireless physical layer can be effective in providing reliable wireless multimedia CDMA network. And the proposed scheme that combine concatenated RS/RCPC coder and CDMA RAKE receiver provides a significant gain in the BER performance over multi-user interference and multipath frequency selective fading channels.

• Proceedings of the KIEE Conference
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• summer
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• pp.283-285
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• 2004

Modern power systems are very complex and to model them completely is impractical for electromagnetic transient studies. Therefore areas outside the immediate area of interest must be represented by some form of frequency dependent equivalent. This paper presents the formulation for developing 1 & 2 port Frequency Dependent Network Equivalent (FDNE) with the instantaneous term in S-domain and illustrates its use. This 1 & 2 Port FDNE have been applied to the CIGRE Benchmark Rectifier test AC system. The electromagnetic transient package PSCAD/EMTDC is used to assess the transient response of the 1 & 2 port (FDNE) developed with Norton Equivalent network.

• Steel and Composite Structures
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• v.46 no.3
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• pp.435-449
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• 2023

Time domain method and frequency domain method are commonly used in the current fatigue life calculation theory. The time domain method has complicated procedures and needs a large amount of calculation, while the frequency domain method has poor applicability to different materials and different spectrum, and improper selection of spectrum model will lead to large errors. Considering that artificial neural network has strong ability of nonlinear mapping and generalization, this paper applied this technique to random fatigue life prediction, and the effect of average stress was taken into account, thereby achieving more accurate prediction result of random fatigue life.