• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.440-449
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• 2008

In this paper, we propose a 16-QAM carrier recovery loop which is suitable for the implementation of Inmarsat M4 system receiver. Because the frequency offset of ${\pm}924\;Hz$ on signal bandwidth 33.6 kHz is recommended in Inmarsat M4 system specification, carrier recovery loop having stable operation in the channel environment with large relative frequency offset is required. the carrier recovery loop which adopts only PLL can't be stable in relatively large frequency offset environment. Therefore, we propose a carrier recovery loop which has stable operation in large relative frequency offset environment for Inmarsat M4 system. The proposed carrier recovery loop employed differential filter-based noncoherent UW detector which is robust to frequency offset, CP-AFC for initial frequency offset acquisition using UW signal, and 16-QAM DD-PLL for phase tracking using data signal to overcome large relative frequency offset and achieve stable carrier recovery performance. Simulation results show that the proposed carrier recovery loop has stable operation and satisfactory performance in large relative frequency offset environment for Inmarsat M4 system.

• 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.

• ETRI Journal
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• v.28 no.3
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• pp.275-281
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• 2006

A very simple and efficient scheme for jitter reduction is proposed for a carrier frequency recovery loop using phase differential frequency estimation, which estimates the current frequency offset based on the difference of the average phases of two successive intervals. Analytical and numerical results presented in this paper show that by simply overlapping the observation intervals by half for frequency offset estimations, both the steady-state and transient performances can be improved. The proposed scheme does not require any additional hardware circuitry, but results in improved performance even with reduced complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.4C
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• pp.371-376
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• 2010

In this paper, we propose a new fast carrier recovery algorithm for high-order QAM systems. The proposed algorithm detects carrier frequency offset from the phase differences among the received symbols directly and combines it with the conventional carrier recovery, so that it is possible to achieve the carrier recovery with wide tracking range and fast acquisition time. Simulation results show that the proposed carrier recovery method reduces acquisition time at large frequency offset and low signal-to-noise ratio (SNR).

• Journal of the Ergonomics Society of Korea
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• v.25 no.2
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• pp.197-204
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• 2006

The purpose of this study was to investigate the relationship between the cumulative fatigue of trunk muscles and the period of recovery time during repetitive lifting and lowering task with two different frequencies(4 times/min and 6 times/ min). Eight healthy males with no prior history of LBD(low back disorders) volunteered for this study. Subjects had 2, 3, 4, and 5 minutes recovery time respectively while they were preforming the lifting and lowering task at 15% level of MVC. EMG signals from six trunk muscles were collected and the fatigue level was analyzed quantitatively. In results, the fatigue levels of LES(left elector spinae), RLD(right lattissimus dorsi), LLD(left lattissimus dorsi), RRA(right rectus abdominis) and LRA(left rectus abdominis) were recovered when 3 minutes recovery time was given at 4 times/min frequency. However, the fatgue level of RES(right elector spinae) was recovered when 4 minutes recovery was given. On the other hand, when 6 times/min frequency was used, the RLD, LLD, RRA and LRA were recovered at 5 minutes of recovery time. But for RES and LES, it took longer than 5 minutes to be recovered. This results can be applied to design the adequate length of recovery time to control the cumulative fatigue of trunk muscles in industry with repetitive lifting and lowering task.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.6 no.1
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• pp.17-30
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• 2008

This study was investigated the effects of pain and functional recovery when low frequency electrical stimulation and aquatic exercise applied to sciatic nerve injured rats. The rats were assigned into four groups; Group I(n=20, control group), Group II(n=20, low frequency electrical stimulation group), Group III(n=20, aquatic exercise group), Group (n=20, applied low frequency electrical stimulation and aquaatic exercise group). Each IV group measured hot plate examination, sciatic nerve functional index(SFI), c-fos.. In hot plate examination, group II, IV showed effect than group Iat 14 days after injured(p<0.01) and group III, Ⅳ showed effect than group I at 21, 28 days after in-jured(p<0.01, p<0.001). In SFI, group II, III, IV showed effect II, III, IV than group I and group IV showed effect than group II at 14, 21 days after injured(p<0.001). group II, III, IV showed effect than group I at 28 days after injured(II = p<0.01, III and IV = p<0.001). Effects of pain and function recovery when low frequency electrical stimulation and aqua-exercise applied to sciatic nerve injured rats, group Ⅳ were most effected to sciatic nerve injured rats. As well as group II and III were effected to sciatic nerve injured rats.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.11
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• pp.540-547
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• 2005

One of the roles of AGC is to regulate the frequency of power systems. AGC is also used to control the frequency of Korean Power System. AGC control strategies depend on system characteristics and the requirements of the systems to which those are applied. Korean Power System consists of one control area and does not have tie-lines. In this research, an AGC control strategy is suggested to avoid conflict with governor dynamics and to enhance frequency recovery It shows good performance for regulation and frequency recovery. This control strategy is expected to be applied to New EMS in KPX to get reasonable AGC regulation and frequency recovery performance.

• Korean Journal of Acupuncture
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• v.32 no.1
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• pp.20-29
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• 2015

Objectives : The objectives of this study is to compare the effects of electroacupuncture(EA), warm needling(WN) and Radio Frequency warm needling(RFWN) stimulations on the acupoints at the artificially damaged ankles of Sprague-Dawley rats, which could be classified as the Grade 3. Methods : The foot weight bearing force ratio(FWBFR) of ankle sprain was measured first at 24 hours after without any other stimulations. Pain Recovery Index(PRI) represents the analgesic level, and modified Pain Recovery Index(mPRI) shows the accumulated recovery level. PRI was measured at 2 hours after each stimulus on GB34, GB39 and GB42, and mPRI was during 7 days. Results : EA stimulation of GB34 and GB39 acupoint in grade 3 ankle sprain showed a marked analgesic and recovery effect. RFWN of GB42 exhibited significant analgesic and pain recovery effect. RFWN of GB34 resulted in pain recovery effect but not analgesic effects, and RFWN of GB39 resulted in analgesic effect 2 hours after but not pain recovery. However, WN did not affect the pain recovery among three acupoints at all. Conclusions : In the Grade 3 ankle sprain model, the difference of analgesic effects were explained by the acupoints and the stimulation methods according to the accumulated recovery effects during 7 days. It is insufficient to determine that a certain acupoint has a specific analgesic effect depending on the stimulation method by the results of this study. Therefore, the effects of each stimulation on the acupoints in any other meridians at the sprained ankle should be compared and analyzed.

• ETRI Journal
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• v.30 no.2
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• pp.275-281
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• 2008

A 40 Gb/s clock and data recovery (CDR) module for a fiber-optic receiver with improved phase-locked loop (PLL) circuits has been successfully implemented. The PLL of the CDR module employs an improved D-type flip-flop frequency acquisition circuit, which helps to stabilize the CDR performance, to obtain faster frequency acquisition, and to reduce the time of recovering the lock state in the event of losing the lock state. The measured RMS jitter of the clock signal recovered from 40 Gb/s pseudo-random binary sequence ($2^{31}-1$) data by the improved PLL clock recovery module is 210 fs. The CDR module also integrates a 40 Gb/s D-FF decision circuit, demonstrating that it can produce clean retimed data using the recovered clock.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.51 no.2
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• pp.78-85
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• 2002

We introduce a rotational decision-directed joint algorithm of blind equalization coupled with carrier recovery for 32-QAM demodulation with high symbol rate. The proposed carrier recovery, which we call a rotational decision-directed carrier recovery(RDDCR), removes the residual phase difference by rotating the decision boundary for the kth received symbol by the frequency detector output of the (k-1)th received symbol. Since the RDDCR includes the function of PLL loop filter by rotating the decision boundary, it gives a simpler demodulator structure. The rotational decision-directed blind equalization(RDDBE) with the rotated decision boundary based on the Stop-and-Go Algorithm(SGA) operated during tracking the frequency offset by the RDDCR and removes intersymbol interference due to multipaths and channel noise. Test results show that symbol error rate of $10^{-3}$ is obtained before the forward error correction when SNR equals 15dB with 150KHz of carrier frequency offset and two multipaths, which is the channel condition for 32-QAM receiver.