• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.10
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• pp.479-485
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• 2001

In this paper, we introduce a charge pump phase-locked loop (PLL) architecture which employs a precharge phase frequency detector (PFD) and a sequential PFD to achieve a high frequency operation and a fast acquisition. Operation frequency is increased by using the precharge PFD when the phase difference is within $-{\pi}{\sim}{\pi}$ and acquisition time is shortened by using the sequential PFD and the increased charge pump current when the phase difference is larger than ${\pm}{\pi}$. So error detection range of the proposed PLL structure is not limited to $-{\pi}{\sim}{\pi}$ and a high frequency operation and a higher speed lock-up time can be achieved. The proposed PLL was designed using 1.5 ${\mu}m$ CMOS technology with 5V supply voltage to verify the lock in process. The proposed PLL shows successful acquisition for 200 MHz input frequency. On the other hand, the conventional PLL with the sequential PFD cannot operate at up to 160MHz. Moreover, the lock-up time is drastically reduced from 7.0 ${\mu}s\;to\;2.0\;{\mu}s$ only if the loop bandwidth to input frequency ratio is regulated by the divide-by-4 counter during the acquisition process. By virtue of this dual PFDs, the proposed PLL structure can improve the trade-off between acquisition behavior and locked behavior.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.4
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• pp.891-896
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• 2011

This paper describes the differential voltage-to-frequency converter which is realized current conveyor circuits. The output frequency of the differential voltage-to-frequency converter is proportional to the difference of two input voltages. The designed circuit is simulated by HSPICE. The range of input voltage difference is from several volts to several milli-volts. From the simulation results the error is less than from -1.9% to +1.8% compared to the calculated values.

• Ocean Systems Engineering
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• v.7 no.1
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• pp.53-74
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• 2017

Ship shaped FPSO (Floating Production, Storage and Offloading) units are the most commonly used floating production units to extract hydrocarbons from reservoirs under the seabed. These structures are usually much larger than general cargo ships and have their natural frequency outside the wave frequency range. This results in the response to first order wave forces acting on the hull to be negligible. However, second order difference frequency forces start to significantly impact the motions of the structure. When the difference frequency between wave components matches the roll natural frequency, the structure experiences a significant roll motion which is also termed as second order roll. This paper describes the theory and numerical implementation behind the calculation of second order forces and motions of any general floating structure subjected to waves. The numerical implementation is validated in zero speed case against the commercial code OrcaFlex. The paper also describes in detail the popular approximations used to simplify the computation of second order forces and provides a discussion on the limitations of each approximation.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.1-6
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• 2007

Two impedance imaging systems of multi-frequency electrical impedance tomography (MFEIT) and magnetic resonance electrical impedance tomography (MREIT) are described. MFEIT utilizes boundary measurements of current-voltage data at multiple frequencies to reconstruct cross-sectional images of a complex conductivity distribution (${\sigma}+i{\omega}{\varepsilon}$) inside the human body. The inverse problem in MFEIT is ill-posed due to the nonlinearity and low sensitivity between the boundary measurement and the complex conductivity. In MFEIT, we therefore focus on time- and frequency-difference imaging with a low spatial resolution and high temporal resolution. Multi-frequency time- and frequency-difference images in the frequency range of 10 Hz to 500 kHz are presented. In MREIT, we use an MRI scanner to measure an internal distribution of induced magnetic flux density subject to an injection current. This internal information enables us to reconstruct cross-sectional images of an internal conductivity distribution with a high spatial resolution. Conductivity image of a postmortem canine brain is presented and it shows a clear contrast between gray and white matters. Clinical applications for imaging the brain, breast, thorax, abdomen, and others are briefly discussed.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.4
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• pp.85-95
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• 1998

In this paper, a new watermarking method for a copy protectionof images is proposed. The proposed method adaptively embeds a watermark in the frequency domain of images using human visual system model. For this purpose, the Just Noticeable Differences(JNDs) of each frequency coeffeicient value of a luminance plane is first found using Watson and Solomon's visual system model. An invisible maximum watermark value with is different in every position according to the characteristics of images is determined usig JND and Minkowski metric. A low frequency domain is divided into two sets based on a PN-sequence to protect thewatermark from the attack. The watermarks are added to one set of coefficients and detecting a watermark, the difference between the mean values of absolute coefficient values of both sets is calculated. The embedded watermark is tested using statistical hypothesis based on test static dertermined by the ean difference. To demonstrate the perfromance of the proposed method, the new watermarking method is applied to a high frequency image and low frequency images. Experimenatal results show the watermark is invisible and robust to JPEGlossy compression and noise.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.3088-3090
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• 2000

In this paper, we introduce a charge pump PLL architecture which employs precharge phase frequency detector(PFD) and sequential PFD to achieve high frequency operation and fast acquisition. Operation frequency is increased by using precharge PFD when the phase difference is within -${\pi}\;{\sim}\;{\pi}$ and acquisition time is shortened by using sequential PFD and increased charge pump current when the phase difference is larger than |${\pi}$|. SO error detection range of proposed PLL structure is not limited to -${\pi}\;{\sim}\;{\pi}$. By virtue of this multi-phase frequency detector structure, the maximum operating frequency of 423MHz at 2.5V and faster acquisition were achieved by simulation.

• Journal of Families and Better Life
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• v.17 no.3
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• pp.159-170
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• 1999

This study analyzes the relationships between social networks and loneliness. Subjects of this study are male and female undergraduate students residing in Soul and Jeonju city Questionaires were and the obtained results were analyzed through SPSS PC+ The results are as follows 1) The size of general social networks doesnt's show difference between male and female students but at the of intimate social networks female students' one is bigger than male students' And female students' contact frequency via telephone is higher than male students' but the direct contact frequency did not show the difference: 2) The bigger the size of social networks is and the higher the contack frequency is the more the mount of social supports female students get. And the bigger the size of social networks is the more the amount of social support male students get. But among male students there are no relationships between the contact frequency and the amount of social supports 3) The size and co tact frequency of social networks is negatively related to loneliness among female and male students 4) The amount of social supports explaines the degree of loneliness at 23% among female students and 18% among male students.

• The Journal of the Acoustical Society of Korea
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• v.29 no.6
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• pp.381-387
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• 2010

Both timbral features and spatial features are important in the assessment of multichannel audio coding systems. The prediction model, extending the ITU-R Rec. BS. 1387-1 to multichannel audio coding systems, with the use of spatial features such as ITDDist (Interaural Time Difference Distortion), ILDDist (Interaural Level Difference Distortion), and IACCDist (InterAural Cross-correlation Coefficient Distortion) was proposed by Choi et al. In that model, ITDDistswere only computed for low frequency bands (below 1500Hz), and ILDDists were computed only for high frequency bands (over 2500Hz) according to classical duplex theory. However, in the high frequency range, information in temporal envelope is also important in spatial perception, especially in sound localization. A new model to compute the ITD distortions of temporal envelopes in high frequency components is introduced in this paper to investigate the role of such ITD on spatial perception quantitatively. The computed ITD distortions of temporal envelopes in high frequency components were highly correlated with perceived sound quality of multichannel audio sounds.

• Phonetics and Speech Sciences
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• v.6 no.3
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• pp.49-56
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• 2014

This research compared the features of respiration and phonation between practical musicology students and general male students, according to their smoking status. Participants of this research are 15 practical musicology male students attending ${\bigcirc}{\bigcirc}$ university and 16 general ${\bigcirc}{\bigcirc}{\bigcirc}$ university students. The participants, both non-smokers and smokers with 5-years of smoking history have no history of voice disease in any case and have normal cognitive functions. The results indicated that, first, there is not a notable difference in the respiratory activity status(FVC, FEV1, FEV1/FVC), regardless of major and smoking status. In MPT, even though there is no significant difference in accordance with their majors, considering smoking status, the smoker group was shorter than non-smoker group significant difference statistically (p<.01). Second, the divisions of participants' major did not show significant difference in Fo, jitter, shimmer, and NHR in the vowel prolongation task. However, the smoker group showed a significantly higher degree of jitter and shimmer than the non-smoker group (p<.05) as Fo and NHR shows no difference. In the case of VRP, maximum frequency and frequency range of the practical group are significantly higher than normal group statistically (p<.001). Moreover, although the difference of the minimum frequency shown at the statistic is not significant, practical group showed a higher tendency of frequency than normal group (p=.051). In conclusion, even though there is no difference in respiratory activity between the smoker group and non-smoker group, the MPT of the smoker group is shorter than that of non-smoker group. In addition, the smoker group showed a higher degree of jitter and shimmer than the non-smoker group. MPT is related to the valve action of vocal fold that passes through the glottis. Thus, it is interpreted that the smoker group has a lower quality of voice and valve action of the vocal fold. Also, the practical group has a higher degree of maximum frequency and frequency range than the normal group. This research can function as basic data for vocal characteristics for the majors in relation to the voice-specializing.

• Speech Sciences
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• v.14 no.1
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• pp.105-119
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• 2007

The purpose of this study is to examine Korean students' production and perception of word-final stop voicing in light of their overseas experience. Subjects were English native speakers, Korean university students with residence experience in America, Korean university students without residence experience in America, and Korean elementary school students. They participated in both production and perception tests. Results showed that the students' production and perception with residence experience in America appeared quite similar to those of the English native speakers. In the production tests, we noticed somewhat different results in temporal and frequency features. The one-year residence in America had some influence on their frequency features, but not the temporal features in the word final stop production. That difference could be seen in the perception tests, too. We could not find any difference in the identification test of the final release environment between the Korean university students who had studied abroad and those who didn't. Rather the difference could be found in the cue influence test in both the final release and non-release environments.