• Carbon letters
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• v.12 no.3
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• pp.180-183
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• 2011

Li metal is accepted as a good counter electrode for electrochemical impedance spectroscopy (EIS) as the active material in Li-ion and Li-ion polymer batteries. We examined the existence of signal noise from a Li-metal counter quantitatively as a preliminary study. We suggest an electrochemical cell with one switchable electrode to obtain the exact impedance signal of active materials. To verify the effectiveness of the switchable electrode, EIS measurements of the solid electrolyte interphase (SEI) before severe $Li^+$ intercalation to SFG6 graphite (at > ca. 0.25 V vs. Li/$Li^+$) were taken. As a result, the EIS spectra without the signal of Li metal were obtained and analyzed successfully for the following parameters i) $Li^+$ conduction in the electrolyte, ii) the geometric resistance and constant phase element of the electrode (insensitive to the voltage), iii) the interfacial behavior of the SEI related to the $Li^+$ transfer and residence throughout the near-surface (sensitive to voltage), and iv) the term reflecting the differential limiting capacitance of $Li^+$ in the graphite lattice.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1944-1947
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• 2005

In this paper, the control of a prosthetic arm using the flex sensor signal is described. The flex sensors are attached to the biceps and triceps brchii muscle. The signals are passed a differential amplifier and noise filter. And then the signals are converted to digital data by PCI 6036E ADC. From the data, position and velocity of arm joint are obtained. Also motion of the forearm - flexion and extension, the pronation and supination are abstracted from the data by proposed algorithm. A two D.O.F arm with RC servo-motor is designed for experiment. The arm length is 200 mm, weight is 4.5 N. The rotation angle of elbow joint is $120^{\circ}$. Also the rotation angle of the wrist is $180^{\circ}$. Through the experiment, we verified the possibility of the prosthetic arm control using the flex sensor signal. We will try to improve the control accuracy of the prosthetic arm continuously.

• Journal of Magnetics
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• v.17 no.4
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• pp.298-301
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• 2012

In order to know the effect of surface irregularity in the detection of local wall thinning of pipeline using pulsed eddy current (PEC), the lift-off effects on PEC signal have been investigated. Three kinds of parameters in the PEC signal, which is "peak amplitude", "time to peak amplitude" and "time to zero crossing" are analyzed to separate the lift-off effects in the PEC signal. The distance from sensor to the bottom of sample which is the total thickness of combined insulator and sample is kept constant. The magnitude of the differential peak amplitude is increased with increasing sample thickness, the time to peak amplitude is increased with increasing the sample thickness. To determine the effect of lift-off, a number of balanced transient responses combining wall thinning locations and lift-off distances were plotted.

• Proceedings of the KIEE Conference
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• summer
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• pp.342-344
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• 2004

In conventional small signal stability analysis, system is assumed to be invariant and the state space equations are used to calculate the eigenvalues of state matrix. However, when a system contains switching elements such as FACTS devices, it becomes non-continuous system. In this case, a mathematically rigorous approach to system small signal stability analysis is by means of eigenvalue analysis of the system periodic transition matrix based on discrete system analysis method. In this research, RCF(Resistive Companion Form) method is used to analyse small signal stability of a non-continuous system including switching elements'. Applying the RCF method to the differential and integral equations of power system, generator, controllers and FACTS devices including switching elements should be modeled in the form of state transition matrix. From this state transition matrix eigenvalues which are mapped to unit circle can be calculated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.2
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• pp.107-112
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• 2006

The previous acquisition method of GPS receiver for reference station adopts not only the coherent integration method but also the non-coherent integration method in order to enhance sensitivity under noisy environment. However, under noisy environment, the previous GPS signal acquisition method causes the non-coherent integration loss which is a major factor among losses that can be caused during GPS signal acquisition. The non-coherent integration loss also increases with the strength of the received noise. This paper has intention of analyzing the performance of the GPS signal acquisition method proposed to effectively enhance sensitivity of DGPS reference receiver under noisy environment. This paper presents that the proposed GPS signal acquisition method suppresses the non-coherent integration loss through post-processing simulation. Furthermore, with regard to the mean acquisition time, it is shown that the number of search cells of the proposed GPS signal acquisition method is much fewer than that of the previous GPS signal acquisition method.

• Journal of Navigation and Port Research
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• v.35 no.8
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• pp.619-624
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• 2011

A significant factor limiting the ranging accuracy of Loran (Long Range Navigation) signal is the additional secondary factor (ASF) in the time of arrival (TOA) measurements. Precise ASF values are essential if Loran deliver the high absolute accuracies demanded for aircraft approach, maritime harbour entrance. We measured the absolute propagation delay between Pohang Loran signal and Loran receiver output signal by comparing with Cesium atomic clock. In this study we measured ASFs between Pohang 9930M station and the 12 measurement points in the Yeongil Bay by using the measurement technique of absolute time delay. The measurement points were spaced at interval of 3 km by 3 km. An E-field antenna and an H-field antenna were used to improve the accuracy of ASF measurements and a DGPS (Differential GPS) receiver was used for accurate positions. We have gotten the result that the measured ASFs were compared with the predicted ASFs through this measurement technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6A
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• pp.685-692
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• 2008

In this paper, we propose a timing recovery loop for Inmarsat mini-m system downlink receiver. Inmarsat mini-m system requires a timing recovery loop which is robust in frequency offset and has fast acquisition because Inmarsat mini-m system specification requires frequency tolerance is required of ${\pm}924$ Hz (signal bandwidth: 2.4 kHz) and acquisition time of UW (Unique Word) signal duration (15ms).Therefore, we propose a timing recovery loop which is suitable for Inmarsat mini-m system. The proposed timing recovery loop adopted noncoherent UW detector and differential ELD which applied differential UW signal for stability and fast acquisition in frequency offset environment. Simulation results show that the proposed timing recovery loop has stable operation and fast acquisition in frequency offset environment for the system.

• Journal of Convergence Society for SMB
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• v.6 no.3
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• pp.49-55
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• 2016

This paper proposes an adaptive video signal transmission scheme in order to ensure the QoS (Quality of Service) of user requirements. SVC (Scalable Video Coding) is an effective transmission scheme, because that can transmit video signal according to the video layer's weight. However, in previous works, those adaptive transmission systems which are considered about the various channel environments and user requirements have not been insufficiently studied. So, we propose the SVC signal transmission using inter-layer differential OVSF code allocation scheme in MC-CDMA. The proposed scheme is able to obtain each layer signal's protection order and control the sub-block of MC-CDMA by feedback information from receiver. Therefore, our proposed scheme is possible to provide the video quality for each users according to variable channel environments. The simulation results demonstrate the enhancement of proposed system in terms of BER performance.

• Investigative Magnetic Resonance Imaging
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• v.4 no.2
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• pp.107-112
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• 2000

Purpose : To evaluate the usefulness of comparison of the signal intensity of uterine septum in the differential diagnosis of bicornuate and septate uterus on magnetic resonance (MR) imaging. Materials and methods : Preoperative MR imaging findings of surgically proven 5 bicornuate and 6 septate uteri were retrospectively analyzed. Because preoperative differential diagnosis of both was possible in all cases in terms of the intercornual distance, external contour of uterine fungus, and divergent angle of two uterine cavities, these criteria were excluded in this study. The signal intensity of uterine septum in patients with bicornuate and septate uterus was analyzed on T1-weighted and fast spin echo T2-weighted images obtained in the axial and coronal planes, using a 1.5-T MR scanner. The signal intensity of uterine septum especially on T2-weighted images was compared with that of myometrium or junctional zone. Results : The signal intensity of uterine septum in patients with bicornuate uterus (n=5) and septate uterus (n=6) was similar to that of myometrium in all cases on T1-weighted images. The septum of bicornuate uterus (n=5) on fast spin echo T2-weighted images was isointense with myometrium in three and hypointense in two cases. The uterine septum of septate uterus (n=6) on T2-weighted images was isointense with myometrium in two, hypointense in two, and isointense with or more hypointense than junctional zone in two cases. No patient showed different signal intensity between upper and lower uterine septum. Conclusion : Because the MR signal intensity of the uterine septum in bicornuate or septate uterus is variable, it should not be used alone in the differential diagnosis of them. In these clinically important differentiation, therefore, comprehensive analysis of MR findings in terms of the external contour of uterine fundus, intercornual distance, divergent angle of two uterine cavities, in addition to the signal intensity of the uterine septum, should be considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.10A
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• pp.807-815
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• 2003

MultiCode-CDMA (MC-CDMA) system of chip level MPSK incorporating with clipper (MP-CDMA)[l] shows constant envelope signal which can mitigate the performance degradation due to nonlinear transmit amplifier. In this paper, modulation is modified to carry out differential encoded MPSK rather than MPSK. The modified system is called DMP-CDMA. DMP-CDMA using differential detection has advantages on receiver complexity and pilot overhead. However, it is inferior to coherent detection by about 4.0dB due to inherent power inefficiency of noncoherent detection and the error propagation. Multiple symbol differential detection is employed in order to improve DMP-CDMA using differential detection. As the result, the performance of DMP-CDMA system is improved about 3.6dB compared to differential detection.