17 results on '"Junyong Park"'
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2. Steganography from perfect codes on Cayley graphs over Gaussian integers, Eisenstein–Jacobi integers and Lipschitz integers
- Author
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Jon-Lark Kim and JunYong Park
- Subjects
Applied Mathematics ,Computer Science Applications - Published
- 2022
- Full Text
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3. A computationally efficient approach to estimating species richness and rarefaction curve
- Author
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Seungchul Baek and Junyong Park
- Subjects
Statistics and Probability ,Computational Mathematics ,Statistics, Probability and Uncertainty - Published
- 2022
- Full Text
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4. Fundamental principles and development of proximity-field nanopatterning toward advanced 3D nanofabrication
- Author
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Junyong Park, Youngjin Ham, Kisun Kim, Seokwoo Jeon, Haomin Chen, Gwangmin Bae, Donghwi Cho, Gayea Hyun, Sang-Hyeon Nam, and Seonggon Han
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Materials science ,Nanostructure ,business.industry ,Holography ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Interference lithography ,law.invention ,Nanolithography ,Interference (communication) ,law ,General Materials Science ,Electrical and Electronic Engineering ,Photonics ,0210 nano-technology ,business ,Nanoscopic scale ,Lithography - Abstract
Three-dimensional (3D) nanoarchitectures have offered unprecedented material performances in diverse applications like energy storages, catalysts, electronic, mechanical, and photonic devices. These outstanding performances are attributed to unusual material properties at the nanoscale, enormous surface areas, a geometrical uniqueness, and comparable feature sizes with optical wavelengths. For the practical use of the unusual nanoscale properties, there have been developments for macroscale fabrications of the 3D nanoarchitectures with process areas over centimeter scales. Among the many fabrication methods for 3D structures at the nanoscale, proximity-field nanopatterning (PnP) is one of the promising techniques that generates 3D optical holographic images and transforms them into material structures through a lithographic process. Using conformal and transparent phase masks as a key factor, the PnP process has advantages in terms of stability, uniformity, and reproducibility for 3D nanostructures with periods from 300 nm to several micrometers. Other merits of realizing precise 3D features with sub-100 nm and rapid processes are attributed to the interference of coherent light diffracted by phase masks. In this review, to report the overall progress of PnP from 2003, we present a comprehensive understanding of PnP, including its brief history, the fundamental principles, symmetry control of 3D nanoarchitectures, material issues for the phase masks, and the process area expansion to the wafer-scale for the target applications. Finally, technical challenges and prospects are discussed for further development and practical applications of the PnP technique.
- Published
- 2021
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5. Artificial intelligence for springback compensation with electric vehicle motor component
- Author
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Hyunsung Choi, Piemaan Fazily, Junyong Park, Yongnam Kim, Joon Ho Cho, Jaekun Kim, and Jeong Whan Yoon
- Subjects
General Materials Science - Published
- 2022
- Full Text
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6. Steganographic schemes from perfect codes on Cayley graphs
- Author
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Junyong Park, Jon-Lark Kim, and Soohak Choi
- Subjects
Discrete mathematics ,Code (set theory) ,Cayley graph ,Hamming bound ,Applied Mathematics ,020206 networking & telecommunications ,0102 computer and information sciences ,02 engineering and technology ,Type (model theory) ,01 natural sciences ,Computer Science Applications ,Finite field ,010201 computation theory & mathematics ,Scheme (mathematics) ,Computer Science::Multimedia ,0202 electrical engineering, electronic engineering, information engineering ,Abelian group ,Hamming code ,Mathematics - Abstract
The main purpose of this paper is to give a new and general way to obtain steganographic schemes from perfect codes on Cayley graphs, motivated by the F5 algorithm based on binary Hamming codes. We obtain the steganography based on perfect Hamming codes as a special case and also give various equivalent conditions for the existence of a perfect code on a k-regular Abelian Cayley graph. Then we show that a perfect code on an Abelian Cayley graph produces a proper steganographic scheme. We further compute the various parameters for the steganographic scheme of type [n, k] over a finite field $$\mathbb {F}_q$$ arising from a linear [n, n − k, d] code over $$\mathbb {F}_q$$ and find also parameters for some steganographic schemes from perfect codes in k-regular Abelian Cayley graphs.
- Published
- 2019
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7. A Spectral Measure for the Information Loss of Temporal Aggregation
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Bu Hyoung Lee and Junyong Park
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Statistics and Probability ,Series (mathematics) ,05 social sciences ,Aggregate (data warehouse) ,Process (computing) ,White noise ,01 natural sciences ,Measure (mathematics) ,Automatic summarization ,Reduction (complexity) ,010104 statistics & probability ,0502 economics and business ,Statistics ,050211 marketing ,0101 mathematics ,Mathematics ,Data reduction - Abstract
We develop a spectral measure to trace the relative distance and direction of information loss resulting from temporal aggregation of a stationary time series process. Temporal aggregation is utilized as not only the reduction in the data size but also the summarization of process information. However, it is inevitable that the aggregation leads to substantial structural changes, the so-called information loss on the original process structure. Using the proposed measure, we quantify the aggregation effect in terms of the relative distance of the standardized spectral densities between “the original process to white noise” and “the aggregate process to white noise.” In addition, we suggest a guideline to identify the marginal order of temporal aggregation where the aggregation produces less information loss while providing more effective data reduction. As an illustration, we analyze the monthly CRSP log returns between January 1926 and December 2008.
- Published
- 2020
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8. Two-sample test for sparse high-dimensional multinomial distributions
- Author
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Amanda Plunkett and Junyong Park
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Statistics and Probability ,Zero (complex analysis) ,Asymptotic distribution ,High dimensional ,Function (mathematics) ,01 natural sciences ,Test (assessment) ,010104 statistics & probability ,03 medical and health sciences ,0302 clinical medicine ,Dimension (vector space) ,Applied mathematics ,030211 gastroenterology & hepatology ,Multinomial distribution ,Two sample ,0101 mathematics ,Statistics, Probability and Uncertainty ,Mathematics - Abstract
In this paper we consider testing the equality of probability vectors of two independent multinomial distributions in high dimension. The classical Chi-square test may have some drawbacks in this case since many of cell counts may be zero or may not be large enough. We propose a new test and show its asymptotic normality and the asymptotic power function. Based on the asymptotic power function, we present an application of our result to a neighborhood-type test which has been previously studied, especially for the case of fairly small p values. To compare the proposed test with existing tests, we provide numerical studies including simulations and real data examples.
- Published
- 2018
- Full Text
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9. A Methodology for Fatigue Reliability Assessment Considering Stress Range Distribution Truncation
- Author
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Ho-Kyung Kim, JunYong Park, and Yeun Chul Park
- Subjects
business.industry ,020101 civil engineering ,02 engineering and technology ,Structural engineering ,Expected value ,Paris' law ,First-order reliability method ,0201 civil engineering ,Stress (mechanics) ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Solid mechanics ,Calibration ,Truncation (statistics) ,business ,Reliability (statistics) ,Civil and Structural Engineering ,Mathematics - Abstract
Not all loads contribute to fatigue crack propagation in the welded detail of steel bridges when they are subjected to variable amplitude loading. For fatigue assessment, therefore, non-contributing stress cycles should be truncated. However, stress range truncation is not considered during typical fatigue reliability assessment. When applying the first order reliability method, stress range truncation occurs mismatch between the expected number of cycles to failure and the number of cycles obtained at the time of evaluation, because the expected number of cycles only counts the stress cycles that contribute to fatigue crack growth. Herein, we introduce a calibration factor to coordinate the expected number of cycles to failure to the equivalent value which includes both contributing and non-contributing stress cycles. The effectiveness of stress range truncation and the proposed calibration factor was validated via case studies.
- Published
- 2018
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10. Testing homogeneity of proportions from sparse binomial data with a large number of groups
- Author
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Junyong Park
- Subjects
Statistics and Probability ,Homogeneity (statistics) ,05 social sciences ,Mathematics - Statistics Theory ,Statistics Theory (math.ST) ,Data application ,01 natural sciences ,Binomial distribution ,010104 statistics & probability ,0502 economics and business ,Statistics ,FOS: Mathematics ,0101 mathematics ,050205 econometrics ,Mathematics - Abstract
In this paper, we consider testing the homogeneity for proportions in independent binomial distributions, especially when data are sparse for large number of groups. We provide broad aspects of our proposed tests such as theoretical studies, simulations and real data application. We present the asymptotic null distributions and asymptotic powers for our proposed tests and compare their performance with existing tests. Our simulation studies show that none of tests dominate the others; however, our proposed test and a few tests are expected to control given sizes and obtain significant powers. We also present a real example regarding safety concerns associated with Avandia (rosiglitazone) in Nissen and Wolski (New Engl J Med 356:2457–2471, 2007).
- Published
- 2018
- Full Text
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11. Fatigue life assessment for a composite box girder bridge
- Author
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Ho-Kyung Kim and JunYong Park
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Stress (mechanics) ,Engineering ,business.industry ,Fillet weld ,Solid mechanics ,Box girder ,Structural engineering ,business ,Finite element method ,Bridge (nautical) ,Reliability (statistics) ,Civil and Structural Engineering ,Vibration fatigue - Abstract
Two conventional methods, the nominal stress method and the hot spot stress method, are examined for the fatigue assessment of a steel box girder bridge while considering the effect of the modeling options on the estimated fatigue life. Two analytical models, a simplified global analytical model and a refined local finite element analytical model, are developed for the evaluation of the stress ranges induced by a fatigue truck. The field tests are conducted for validating the analytical models as well as for direct fatigue assessment via an ambient vibration test. The local modeling options that are examined are the inclusion of the fillet weld itself in the refined analytical model and the mitigation of the concentrated stress at the web plate, considering stress dispersion over the width of the attachment. The fatigue life is estimated for three different nonexceedance probabilities, considering different partial factors according to the accuracy of the analysis method as well as the reliability of the estimated fatigue loading for a specific bridge site. Through a comparative analysis, the potential differences in estimated fatigue lives according to the assessment methods and the modeling options are quantitatively discussed.
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- 2014
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12. Reliability-based evaluation of load carrying capacity for a composite box girder bridge
- Author
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JunYong Park, Ho-Kyung Kim, and Hyun-Joong Kim
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Stress (mechanics) ,Shear (sheet metal) ,Engineering ,business.industry ,Dynamic loading ,Box girder ,Structural engineering ,Design load ,business ,Finite element method ,Bridge (nautical) ,Reliability (statistics) ,Civil and Structural Engineering - Abstract
The load carrying capacity of a composite open-top steel box girder bridge was evaluated, based on a reliability-based method, and potential differences from conventional approaches were evaluated. A practical analysis model was utilized in evaluating the Rating Factor (RF) after verification with a rigorous full finite element analysis model with solid and plate elements. The accuracy of the analysis models was validated in terms of displacements and distribution factors through static loading tests. Dynamic effects were also estimated from the dynamic loading tests. The load factors, proposed for the purpose of evaluation based on recently accumulated statistical data, were utilized in evaluating RF. The RFs were evaluated for maximum positive flexure, negative flexure, and shear regions along the bridge. The calculated RF with the load factors for evaluation purposes was higher by 35% than that with design load factors. The proposed method also produces a 29% increase in RF compared to the conventional allowable stress design approach. Consequently, the proposed reliability-based procedure would be expected to permit a more economical assessment of bridge performance to be made.
- Published
- 2013
- Full Text
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13. Reversible creation of nanostructures between identical or different species of materials
- Author
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Jae Hong Park, Dong-Eon Lee, Sungho Ko, Kwang Soo Yoo, Hyun-Ik Jang, Junyong Park, Chi Won Ahn, and Seokwoo Jeon
- Subjects
Work (thermodynamics) ,Materials science ,Nanostructure ,Silicon ,chemistry ,Metallic materials ,chemistry.chemical_element ,General Materials Science ,Nanotechnology ,General Chemistry ,Soft materials ,Surface energy - Abstract
In this study, accurate nanostructures with various aspect ratios are created on several types of material. This work is highly applicable to the energy, optical, and nano-bio fields, for example. A silicon (Si) nano-mold is preserved using the method described, and target nanostructures are replicated reversibly and unlimitedly to or from various hard and soft materials. It is also verified that various materials can be applied to the substrates. The results confirm that the target nanostructures are successfully created in precise straight line structures and circle structures with various aspect ratios, including extremely high aspect ratios of 1:18. It is suggested that the optimal replicating and demolding process of nanostructures with high aspect ratios, which are the most problematic, could be controlled by means of the surface energy between the functional materials. Relevant numerical and analytical studies are also performed. It is possible to expand the applicability of the nanostructured mold by adopting various backing materials, including rounded substrates. The scope of the applications is extended further by transferring the nanostructures between different species of materials including metallic materials as well as identical species.
- Published
- 2012
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14. Guided random walk through some high dimensional problems
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Junyong Park and Jayanta K. Ghosh
- Subjects
Statistics and Probability ,Estimation ,Mathematical optimization ,Multivariate statistics ,business.industry ,Inference ,High dimensional ,Machine learning ,computer.software_genre ,Random walk ,Bayes' theorem ,Multiple comparisons problem ,Statistics::Methodology ,Artificial intelligence ,Statistics, Probability and Uncertainty ,business ,computer ,Random matrix ,Mathematics - Abstract
We survey some recent work in high dimensional multiple testing estimation and other multivariate inference problems depending on random matrices and graphical problems. Different approaches to these problems are explored featuring classical procedures like the Benjamini-Hochberg multiple tests, empirical Bayes and Bayes tests and estimates and use of shrinkage as a major method in estimation. The choice of topics reflects to some extent our taste and interests.
- Published
- 2010
- Full Text
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15. Estimating the Mean of High Valued Observations in High Dimensions
- Author
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Eitan Greenshtein, Junyong Park, and Ya'acov Ritov
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Statistics and Probability ,Combinatorics ,Bayes' theorem ,Nonparametric statistics ,Value (computer science) ,Estimator ,Random variable ,Sparse vector ,Mathematics - Abstract
Let Y i ∼ N(μ i, 1), i = 1, …,n, be independent random variables. We study the problem of estimating the quantity S = Σ{i|C
- Published
- 2008
- Full Text
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16. Analysis of intensity and sensitivity of single- and multiple-channel RF head coilsin 3.0-T MRI system
- Author
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Janggeun Cho, Chulhyun Lee, and Junyong Park
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Physics ,medicine.diagnostic_test ,Field (physics) ,business.industry ,General Physics and Astronomy ,Magnetic resonance imaging ,Field strength ,Pulse sequence ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology ,Intensity (physics) ,Optics ,Nuclear magnetic resonance ,Electromagnetic coil ,medicine ,General Materials Science ,Radio frequency ,business ,Sensitivity (electronics) ,General Environmental Science - Abstract
High-resolution anatomical and functional images can be acquired using high- andultrahigh-field magnetic resonance imaging (MRI) systems. An increase in the mainmagnetic field strength results in high resolution but suffers from thedisadvantage of field nonuniformity in the radio frequency (RF). To overcome thisRF field inhomogeneity, parallel RF transmission system and sensitivity encodingare widely used. Our experimental results showed that the best signal intensity was in transmit andreceive mode head coil, except for the T2-weighted fast field echo (FFE). The bestsignal-to-noise ratio (SNR) was in the 32-channel head coil. In general, multiple-channel coils have been known as more efficient materials interms of SNR. However, they may not be as important in experiments where intensityis an important factor. Therefore, a suitable coil should be selected using apulse sequence.
- Published
- 2014
- Full Text
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17. Erratum to: Fatigue life assessment for a composite box girder bridge
- Author
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Ho-Kyung Kim and JunYong Park
- Subjects
Engineering ,business.industry ,Composite number ,Solid mechanics ,Forensic engineering ,Box girder ,Fatigue life assessment ,Structural engineering ,business ,Bridge (interpersonal) ,Civil and Structural Engineering - Published
- 2015
- Full Text
- View/download PDF
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