• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.1-9
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• 1987

In this paper, the acquisition performance of a receiver that utilizes a non-coherent digital correlator is analyzed. In order to analyze the acquisition performance, the probability density function of a receiver output random variable has been derived approximately. Using this function, the acquisition performance of the coarse acquisition code receiver in a global positioning system is analyzed.

• Speech Sciences
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• v.10 no.2
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• pp.145-157
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• 2003

Vowels are classified by the shapes of vocal tract. These shapes form constriction points along the tract, which have an influence on such vocal tract resonance as F1, F2, F3, and so on. The formant frequency is influenced by aperture and placement of tongue and the intensity is influenced by air pressure of subglottis. The object of this study compares to characterize the spectral outputs of oral and nasal spectra for the formant frequencies and intensity of Korean oral vowels. Subjects consisted of 20 normal persons (10 male and 10 female) without laryngeal pathology. The speech sample included /a/, /e/, /i/, /o/, /u/ of Korean oral vowels. The spectrum of each vowel was analysed by Nasal View and Real Analysis Program using Dr. Speech. The result showed that nasal intensity is decreased manifestly from F1 to F2. But oral intensity and Intensity is decreased little bit from F1 to F2. The most of values of nasal formant frequency is similarity oral formant frequency and Formant frequency or little bit smaller.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.442-450
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• 1994

In this paper, the tracking of SFH/MFSK signals by using a paeallel correlator and a bank of BPF which is implemented by DFT recursively is studied. During symbol period, M-ary signal`s spectrum is analyzed by the step of n multiple of sampling period. The bank of BPF output which is stored for hop duration input to the parallel correlator. The time difference of the receiver and the transmitter is corrected by using sampling position and correlation time at which the largest output of correlator is generated. Syncronization signal detection rate and distribution of the largest output of correlator are evaluated by computer simulation in HF channel evironments for the performance analysis of proposed tracking method.

• Journal of IKEEE
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• v.12 no.1
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• pp.43-50
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• 2008

In this paper, the output and temperature characteristics for an optical signal of the fiber bragg grating have been considered. Also, output characteristics which depend on the temperature changes have been investigated for an all-optic add/drop multiplexer based on the fiber bragg grating and Mach-Zehnder interferometer. From the obtained results, they show that the center wavelength of output spectrum shifts approximately 0.01230 nm/$^{\circ}C$ within a temperature range $-30^{\circ}C{\sim}90^{\circ}C$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.656-661
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• 2002

Multipass Ti:sapphire amplifier for the light source of lidar was developed in an angular-multiplexing, and the characteristics of output energy and spectrum was investigated. In the two-stage multipass amplifier, we obtained the maximum output energy of 42 mJ, the amplification gain of 21 dB and the output efficiency of 26% on the wavelength of 790 nm. In the tuning range of 715~930nm the spectral linewidth is 0.05 $cm^{-1}$ /. The conversion efficiencies of 35% for SHG at 780 m and 13% for THG at 390 nm are obtained respectively. The continuous tunabilities of 240~306 m UV region and 360~460 nm in deep-blue region could be achieved.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1954-1956
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• 2000

In this paper, when void of XLPE was existed, electrical tree was growth in branch-type, and it was growth in bush-type when void of XLPE was not existed. Moreover, charge magnitude of partial discharge by deterioration time of XLPE sample was about proportion to output voltage of AE signals. When void was existed, charge magnitude of partial discharge, the output voltage Vp-p value of AE signals were increased with increasing deterioration time. However, when void were not existed, charge magnitude of partial discharge, the output voltage Vp-p value of AE signals were increased in fast deterioration time, but it were decreasing at after in middle deterioration time. Frequency spectrum response of AE signal was about 100-250[kHz].

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.97-101
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• 2000

We proposed and demonstrated a new scheme for subtracting the source excess noise from the output of the fiber-optic gyroscope. Unlike the previous methods, this scheme has an advantage of not requiring a delaying fiber for source noise detection and can be simply applied to fiber gyroscope operating at the proper frequency. By usmg this scheme. the proper frequency component of the source excess noise was subtracted from the gyroscope output. As a result, we obtained the reduction of noise by 12 dB (electrical) which was measured from the noise floor spectrum in the fiber gyroscope modulated at the proper frequency. We also obtarned !be random walk coefficient of thc gyro output reduced by a factor of 3.5. f 3.5.

• Current Optics and Photonics
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• v.6 no.4
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• pp.407-412
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• 2022

We report on a diode-laser-pumped mode-locked Yb:KGW laser system, which delivers ultrashort pulses down to 89 fs at a repetition rate of 63 MHz, with an average power of up to 5.6 W. A fiber-coupled diode laser at 981 nm, operated with a compact driver, is used to optically pump the gain crystal via an off-axis parabolic mirror. A semiconductor saturable-absorber mirror is used to initiate the pulsed operation. Laser characteristics such as the pulse duration, spectrum bandwidth, and output power are investigated by varying the intracavity dispersions via changing the number of bounces between negative-dispersive mirrors within the cavity. Short pulses with a duration of 89 fs, a center wavelength of 1,027 nm, and 3.6 W of output power are produced at a group-velocity dispersion (GVD) of -3,300 fs². As the negative GVD increases, the pulse duration lengthens but the output power at the single-pulse condition can be enhanced, reaching 5.6 W at a GVD of -6,600 fs². Because of pulse broadening at high negative GVDs, the highest peak intensity is achievable at a moderate GVD with our system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.4
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• pp.1976-1981
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• 2013

In this paper, we propose a frequency-domain interference cancellation algorithm for direct-sequence spread spectrum systems. In the previously proposed frequency-domain interference cancellation algorithms that protocol defines the rules concerning the collection of means of Transmission Control Protocol (TCP: Transmission Control Protocol) is the most widely used in the transport layer. Two-way traffic through the network path to the same end-to-end transfer of data in the opposite direction between pairs of nodes are infused with two or more TCP connection using the network traffic patterns from the exchanger and routers share results of approval. Per-flow input/output structure of matter using the LTS online reaction when evaluated as this is the most important factor. TCP-MT when the connection duration is one of the largest performance gains.

• The Journal of the Acoustical Society of Korea
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• v.42 no.2
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• pp.94-101
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• 2023

A deep neural network composed of encoders and decoders, such as U-Net, used for speech enhancement, concatenates the encoder to the decoder through skip-connection. Skip-connection helps reconstruct the enhanced spectrum and complement the lost information. The features of the encoder and the decoder connected by the skip-connection are incompatible with each other. In this paper, for complex-valued spectrum based speech enhancement, Self-Attention (SA) method is applied to skip-connection to transform the feature of encoder to be compatible with the features of decoder. SA is a technique in which when generating an output sequence in a sequence-to-sequence tasks the weighted average of input is used to put attention on subsets of input, showing that noise can be effectively eliminated by being applied in speech enhancement. The three models using encoder and decoder features to apply SA to skip-connection are studied. As experimental results using TIMIT database, the proposed methods show improvements in all evaluation metrics compared to the Deep Complex U-Net (DCUNET) with skip-connection only.