• Macromolecular Research
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• v.15 no.4
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• pp.370-378
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• 2007

Mechanical stimulation is known to activate several cellular signal transduction pathways, leading to the induction of signaling molecules and extracellular matrix (ECM) proteins, thereby modulating cellular activities, such as proliferation and survival. In this study, primary human dermal fibroblasts (HDFs) were seeded onto chitosan-based scaffolds, and then cultured for 3 weeks in a bioreactor under a cyclic strain of 1 Hz frequency. Compared to control samples cultured under static conditions, the application of a cyclic strain stimulated the proliferation of HDFs in I week, and by week 3 the thickness of the cell/scaffold composites increased 1.56 fold. Moreover, immunohistochemical staining of the culture media obtained from the cell/scaffold samples subjected to the cyclic strain, revealed increases in the expression and secretion of ECM proteins, such as fibronectin and collagen. These results suggest that the preconditioning of cell/scaffold composites with a cyclic strain may enhance the proliferation of HDFs, and even facilitate integration of the engineered artificial dermal tissue into the host graft site.

• Journal of Mechanical Science and Technology
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• v.14 no.10
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• pp.1051-1060
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• 2000

Linear cyclic systems (LCS's) are a class of systems whose dynamic behavior changes cyclically. Such cyclic behavior is ubiquitous in systems with fundamentally repetitive motions (e. g. all rotating machinery). Yet, the knowledge of the noise and vibration transmission paths in LCS's is quite limited due to the time-varying nature of their dynamics. The first part of this two-part paper derives a generic expression that describes how the noise and/or vibration are transmitted between two (or multiple) locations in the LCS's. An analysis via the Fourier series and Fourier transform (FT) plays a major role in deriving this expression that turns out to be transfer function dependent upon the cycle position of the system. The cyclic nature of the LCS' transfer functions is shown to generate a series of amplitude modulated input signals whose carrier frequencies are harmonic multiples of the LCS' fundamental frequency. Applicability of signal processing techniques used in the linear time-invariant systems (LTIS's to the general LCSs is also discussed. Then, a criterion is proposed to determine how well a LCS can be approximated as a LTIS. In Part II, experimental validation of the analyses carried out in Part I is provided.

• Korean Chemical Engineering Research
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• v.55 no.4
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• pp.556-560
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• 2017

A hemoglobin/silver nanoparticle heterolayer was fabricated for bioelectronic device with electrochemical signal-enhancement effect. As a device element, a hemoglobin, the metalloprotein, contained the heme group that showed the redox property was introduced for charge storage element. For electron transfer facilitation, a silver nanoparticle was introduced for electrochemical signal facilitation, the hemoglobin was immobilized onto Au substrate using chemical linker 6-mercaptohexanoic acid (6-MHA). Then, the silver nanoparticle was immobilized onto fabricated hemoglobin/6-MHA heterolayers by layer-by-layer (LbL) method. The surface morphology and surface roughness of fabricated heterolayer were investigated by atomic force microscopy (AFM). The redox property of hemoglobin/silver nanoparticle heterolayer was investigated by a cyclic voltammetry (CV) experiment for obtaining an oxidation potential and reduction potential. Moreover, for the assessing charge storage function, a chronoamperometry (CA) experiment was conducted to hemoglobin/silver nanoparticle-modified heterolayer electrode using oxidation and reduction potentials, respectively. Based on the results, the fabricated hemoglobin/silver nanoparticle heterolayer showed that an increased charge storage effect compared to hemoglobin monolayer-modified electrode.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2409-2416
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• 2014

In this paper, an automatic recognition algorithm for linearly modulated signals like PSK, QAM under noncoherent asynchronous condition is proposed. Frequency, phase, and amplitude characteristics of digitally modulated signals are changed periodically. By using this characteristics, cyclic moments and higher order cumulants based features are utilized for the modulation recognition. Hierarchial decision tree method is used for high speed signal processing and totally 4 feature extraction parameters are used for modulation recognition. In the condition where the symbol number is 4,096, the recognition accuracy of the proposed algorithm is more than 95% at SNR 15dB. Also the proposed algorithm is effective to classify the signal which has carrier frequency and phase offset.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.4
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• pp.206-211
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• 2005

We describe the design for a correlator and an access code generator in bluetooth system. These are used for a connection setting, a packet decision and a clock synchronization between Bluetooth units. The correlator consists of two blocks; carry save adder based on Wallace tree and threshold-value decision block. It determines on an useful packet and clock-synchronization for input signal of 1.0Mbps through the sliding-window correlating. The access-code generator also consists of two blocks; BCH(Bose-Chadhuri-Hocquenghem) cyclic encoder and control block. It generates the access-codes according to four steps' generation process based on Bluetooth standard. In order to solve synchronization problem, we make use of any memory as a pseudo random sequence. The proposed correlator and access-code generator were coded with VHDL. An FPGA Implementation of these modules and the simulation results are proved by Xilinx chip. The critical delay and correlative margin based on synthesis show the 4.689ns and the allowable correlation-error up to 7-bit.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.4
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• pp.313-319
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• 2017

Fiber optics sensors that have been mainly applied to aerospace areas are now finding applicability in other areas, such as transportation, including railways. Among the sensors, the fiber Bragg grating (FBG) sensors have led to a steep increase due to their properties of absolute measurement and multiplexing capability. Generally, the FBG sensors adhere to structures and sensing modules using adhesives such as an epoxy. However, the measurement errors that occurred when the FBG sensors were used in a long-term application, where they were exposed to environmental thermal load, required calibration. For this reason, the thermal curing of adhesives needs to be investigated to enhance the reliability of the FBG sensor system. This can be done at room temperature through cyclic thermal load tests using four types of specimens. From the test results, it is confirmed that residual compressive strain occurs to the FBG sensors due to an initial cyclic thermal load. In conclusion, signals of the FBG sensors need to be stabilized for applying them to a long-term SHM.

• ETRI Journal
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• v.45 no.2
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• pp.277-290
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• 2023

This paper proposes a method that can reduce the complexity of a system matrix by analyzing the characteristics of a pseudoinverse matrix to receive a binomial frequency division multiplexing (BFDM) signal and decode it using the least squares (LS) method. The system matrix of BFDM can be expressed as a band matrix, and as this matrix contains many zeros, its amount of calculation when generating a transmission signal is quite small. The LS solution can be obtained by multiplying the received signal by the pseudoinverse matrix of the system matrix. The singular value decomposition of the system matrix indicates that the pseudoinverse matrix is a band matrix. The signal-to-interference ratio is obtained from their eigenvalues. Meanwhile, entries that do not contribute to signal generation are erased to enhance calculation efficiency. We decode the received signal using the pseudoinverse matrix and the removed pseudoinverse matrix to obtain the bit error rate performance and to analyze the difference.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.2009-2019
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• 2013

In this paper, we propose an automatic modulation recognition algorithm based on cyclic moment and new modified cumulant for analog and digital modulation signals. It is noteworthy that each modulated signal has different cycle frequency characteristics according to its order of cyclic moment. By means of this characteristics as classification features, various modulated signals can be efficiently classified. Also, to identify modulated signals having the same cycle frequency characteristics, we take advantage of the additional classification factors such as variations of envelope and phase as well as modified cumulant. The proposed algorithm was evaluated by considering the number of symbols, SNR, and frequency offset. In the simulation condition where the number of gathered symbols was about 819, and SNR and frequency offset were above 10dB and below 25%, respectively, the average accuracy of the proposed algorithm was more than 95%.

• ETRI Journal
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• v.24 no.3
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• pp.247-250
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• 2002

In this paper, we propose three symbol syn-chronization schemes for Orthogonal Frequency Division Multiplex (OFDM) systems. The cyclic extension preceding OFDM symbols is of decisive importance for these schemes. The first scheme uses the phase-differential coding of the received OFDM signal. The second and the third schemes use the length of the received OFDM signal. All three schemes make symbol synchronization possible, even though there is a frequency off-set in the system. Simulation results show that these schemes can be used to synchronize an OFDM system over AWGN and multi-path fading channels.

• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.6-16
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• 2010

Since OFDM system suffers from high peak-to average power ratio(PAPR) drawbacks, more energy has been converted to seek for a new substitutable system which can maintain OFDM system's inherent virtues while avoid its defects. Consequently, a new multicarrier system called as CI/OFDM system has been proposed which applied carrier interferometry(CI) code to OFDM system. Due to its low PAPR advantage and orthogonal property, it has received more and more attention. Simultaneously, an old technique called single carrier(SC) system has retaken its attractions for the same purposes. This paper analyzes two cyclic prefixed transmission schemes variants of OFDM system: 1.carrier interferometry-Orthogonal Frequency-Division Multiplexing (CI/OFDM); 2. Cyclic prefixed single carrie(CP-SC) with frequency domain equalization. We compare the achievable bit rate transmission of the two systems in terms of signal to noise ratio(SNR) by mathematical derivation. We demonstrated that CI/OFDM achieves a bit higher transmission bit rate to that of the CP-SC with frequency domain equalizer.