• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.11C
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• pp.694-701
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• 2011

This paper addresses a synchronization technique based on an adaptive combining of the sub-correlation functions obtained from multiband sine phased binary offset carrier (BOC) signals, allowing a BOC signal receiver to deal with multiband sine phased BOC signals. Specifically, we first obtain the sub-correlation functions composing the BOC autocorrelation function, and then, re-combine the sub-correlation functions generating a correlation function with no side-peak. Finally, by replacing the BOC autocorrelation with the correlation function with no side-peak in the delay lock loop, the proposed scheme performs unambiguous signal tracking. The proposed synchronization scheme is applicable to generic sine phased BOC signals. Numerical results demonstrate that the proposed scheme provides a performance improvement over the conventional unambiguous schemes in terms of the tracking error standard deviation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.7
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• pp.552-558
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• 2014

In this paper, we propose a side-peak cancellation technique of composite binary offset carrier (CBOC) signals for e-navigation. First, we divide a CBOC sub-carrier into several sub-carrier pulses, and then, observe that CBOC autocorrelation is the sum of multiple sub-correlation functions. Finally, we propose a novel correlation function with no side-peak and a sharp main-peak by combining the sub-correlation functions to improve the positioning accuracy. From numerical results, we confirm that the proposed correlation function with a sharp main-peak provides a better positioning performance than the conventional correlation functions in terms of the tracking error standard deviation.

• Journal of the Korean Society of Physical Medicine
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• v.18 no.2
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• pp.41-48
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• 2023

PURPOSE: Falls are caused by a decline in physical and cognitive function. A quantitative evaluation tool that can comprehensively evaluate motor and cognitive functions for elderly people with an impaired physical function. This study assessed the clinical application potential by confirming the correlation between the physical function tests, cognitive and the stepping trail-making test (S-TMT). METHODS: Fourteen community-dwelling older patients (65-75 years) were recruited. The study conducted cognitive function tests with the trail-making test (TMT-A, B), and physical function tests (6-minute walking test (6MWT), short physical performance battery (SPPB), and timed up and go (TUG)). The results of were analyzed using SPSS version 21.0. Descriptive statistics were used for the general characteristics of the study subjects, and the correlations between S-TMT, other functional tests were examined through Pearson's correlation analysis. The statistical significance was set to .05. RESULTS: S-TMT had a significant positive correlation with the TUG (r = .588^*) and trail-making test-B (TMT-B) (r = .689^*, p < .05). Furthermore, S-TMT showed a negative correlation between SPPB (r = -.397) and 6MWT (r = -.422), but it was not statistically significant. CONCLUSION: S-TMT is a cognitive-gait dual-task performance evaluation tool that can be performed safely. A significant correlation was confirmed between the TUG test and the TMT-B. S-TMT is a dual-task screening tool that can evaluate both physical and cognitive functions simultaneously.

• Journal of Soil and Groundwater Environment
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• v.16 no.2
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• pp.30-40
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• 2011

In this study, we compared the analysis results before and after the detrending for the data. According to the comparison results, correlation functions were not much changed while autocorrelation and spectral density functions were largely varied. Especially, time series data with a long-term variation trend showed a distinctive difference. This study demonstrated a usefulness of the detrending for a further analysis.

• Journal of applied mathematics & informatics
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• v.30 no.5_6
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• pp.903-911
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• 2012

Let $\{u(t)\}$ and $\{u(dt)\}$ be two maximal length sequences of period $2^n-1$. The cross-correlation is defined by $C_d({\tau})=\sum{_{t=0}^{2^n-2}}(-1)^{u(t+{\tau})+v(t)$ for ${\tau}=0,1,{\cdots},2^n-2$. In this paper, we propose a new proof for finding the values and the number of occurrences of each value of $C_d({\tau})$ when $d=2^{k-2}(2^k+3)$, where $n=2k$, $k$ is a positive integer.

• Journal of Communications and Networks
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• v.14 no.5
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• pp.540-545
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• 2012

In this paper, the lagged cross-correlation of two probability density functions constructed by kernel density estimation is proposed, and by maximizing the proposed function, adaptive filtering algorithms for supervised and unsupervised training are also introduced. From the results of simulation for blind equalization applications in multipath channels with impulsive and slowly varying direct current (DC) bias noise, it is observed that Gaussian kernel of the proposed algorithm cuts out the large errors due to impulsive noise, and the output affected by the DC bias noise can be effectively controlled by the lag ${\tau}$ intrinsically embedded in the proposed function.

• Dementia and Neurocognitive Disorders
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• v.22 no.4
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• pp.139-147
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• 2023

Background and Purpose: Dual walking task such as crossing over an obstacle may serve as an excellent tool for predicting early cognitive decline. Thus, this study aimed to investigate correlation between walking while crossing over an obstacle and executive functions under different gait phases to validate the use of walking with an obstacle for predicting early cognitive decline. Methods: A cross-sectional study was conducted on 48 elderly individuals from 2 day-care centers and 3 welfare-centers in Seoul and Gyeonggi, Korea. Executive function tests (Trail Making Test, Stroop test) and dual walking tests (gait speed, cadence, stance time, gait cycle time) were performed and compared using partial correlation analysis. Results: There were significant correlations between executive function and most of the gait variables (stance time, cadence, and gait cycle time) (p<0.05) when crossing over an obstacle while walking. Especially, stance time exhibited significant correlations with most executive functions (p<0.05). Conclusions: When evaluating executive function during walking with an obstacle, post-obstacle-crossing phase and stance time need to be observed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6C
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• pp.763-769
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• 2004

It is known that a bent function corresponds to a perfect nonlinear function, which makes it difficult to do the differential cryptanalysis in DES and in many other block ciphers. In this paper, for an odd prime p, quadratic p-ary bent functions defined on finite fields are given from the families of p-ary sequences with optimal correlation properly. And quadratic p-ary bent functions, that is, perfect nonlinear functions from the finite field F $_{p^{m}}$ to its prime field $F_{p}$ are constructed by using the trace functions. trace functions.

• Journal of the Korean Statistical Society
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• v.22 no.2
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• pp.339-345
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• 1993

It is well known that distribution of functions of eigen values and vectors of a certain matrix plays an important role in multivariate analysis. This paper deals with the transformation of a correlation-type random matrix to its eigen values and vectors. Properties of the transformation are also considered. The results obtained are applied to express the joint distribution of eigen values and vectors of the correlation matrix when sample is taken from a m-variate spherical distribution.

• The Journal of Korean Physical Therapy
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• v.30 no.1
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• pp.35-40
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• 2018

Purpose: This study examined whether the quality of life of parents of children with cerebral palsy is affected by the functions, activities, participation, and environmental factors using an ICF-CY check list. Methods: This study recruited in 26 parents of children with cerebral palsy. The functions, activities, participation, and environmental factors of the children were evaluated using ICF-CY checklist. To measure the quality of life of parents, this study used world health organization quality of life (WHOQOL-BREF), which was composed of a total of 26 questions. The GMFCS (gross motor function classification system) was used to assess the degree of disability in the children. Multiple regression analysis was performed to examine the effects of the ICF-CY checklist on the quality of life. Correlation analysis was performed to examine the correlation between GMFCS and WHOQOL. Results: The functions, activities, participation, and environmental factors were significantly different from WHOQOL-BREF. On the other hand, the contextual factor showed a significant difference in the neuromusculoskeletal and movement-related functions (b7), and service, systems, and policies (e5)(p<0.05). Conclusion: This study suggests that the functions and environmental factors affect the quality of life of parents of children with cerebral palsy. Therefore, these findings suggest that contextual factors, such as neuromusculoskeletal and movement-related functions (b7), and service, systems and policies (e5), which can be facilitators, should be considered for improving the quality of life of parents of children with cerebral palsy.