• Macromolecular Research
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• 제12권4호
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• pp.325-335
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• 2004

Molecular weight distributions of poly(vinyl neo-decanoate) produced by the bulk polymerization of the monomer to low conversions were investigated to obtain values of the rate constants for the chain transfer to monomer ( $C_{M}$). The value of $C_{M}$ of 7.5($\pm$0.6)${\times}$10$^{-4}$ was obtained from a logarithmic plot of the number distribution at 5,25, and 5$0^{\circ}C$, which suggests that the activation energy for chain transfer is on the order of 20-25 kJ ㏖$^{-1}$ . These plots were linear between the number and weight-average degrees of polymerization, but not over the whole molecular weight range for which a significant signal was observed in the gel permeation chromatography (GPC) trace. Modeling suggests that the deviations observed at high molecular weights can be explained by branching of the chains through chain transfer to the polymer, with a branching density as low as 10$^{-5}$ , without affecting the slope at low values of the number of monomer unit, N. This deviation from the expected distribution of linear chains was used to estimate the branching densities at low conversion.ion.

• 한국기계가공학회지
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• 제21권6호
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• pp.8-14
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• 2022

In this study reports experiments were conducted to determine the quality of weld beads of different materials, Al and Cu. Among the lasers used to make battery cells for electric vehicles, non-destructive testing was performed using deep learning to determine the quality of beads welded with the ARM laser. Deep learning was performed using AlexNet algorithm with a convolutional neural network structure. The results of quality identification were divided into good and bad, and the result value was derived that all the results were in agreement with 94% or more. Overall, the best welding quality was obtained in the experiment for the fixed ring beam output/variable center beam output, in the case of the fixed beam (ring beam) 500W and variable beam (center beam) 1,050W; weld bead failure was seldom observed. The tensile force test to confirm the reliability of welding reported an average tensile force of 2.5kgf/mm or more in all sections.

• 한국공간구조학회논문집
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• 제22권2호
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• pp.19-27
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• 2022

Visual inspection methods have limitations, such as reflecting the subjective opinions of workers. Moreover, additional equipment is required when inspecting the high-rise buildings because the height is limited during the inspection. Various methods have been studied to detect concrete cracks due to the disadvantage of existing visual inspection. In this study, a crack detection technology was proposed, and the technology was objectively and accurately through AI. In this study, an efficient method was proposed that automatically detects concrete cracks by using a Convolutional Neural Network(CNN) with the Orthomosaic image, modeled with the help of UAV. The concrete cracks were predicted by three different CNN models: AlexNet, ResNet50, and ResNeXt. The models were verified by accuracy, recall, and F1 Score. The ResNeXt model had the high performance among the three models. Also, this study confirmed the reliability of the model designed by applying it to the experiment.

• Journal of Platform Technology
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• 제11권1호
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• pp.72-84
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• 2023

With the rise of the Internet of Things, the security of such lightweight computing environments has become a hot topic. Lightweight block ciphers that can provide efficient performance and security by having a relatively simpler structure and smaller key and block sizes are drawing attention. Due to these characteristics, they can become a target for new attack techniques. One of the new cryptanalytic attacks that have been attracting interest is Neural cryptanalysis, which is a cryptanalytic technique based on neural networks. It showed interesting results with better results than the conventional cryptanalysis method without a great amount of time and cryptographic knowledge. The first work that showed good results was carried out by Aron Gohr in CRYPTO'19, the attack was conducted on the lightweight block cipher SPECK-/32/64 and showed better results than conventional differential cryptanalysis. In this paper, we first apply the Differential Neural Distinguisher proposed by Aron Gohr to the block ciphers HIGHT and GOST to test the applicability of the attack to ciphers with different structures. The performance of the Differential Neural Distinguisher is then analyzed by replacing the neural network attack model with five different models (Multi-Layer Perceptron, AlexNet, ResNext, SE-ResNet, SE-ResNext). We then propose a Related-key Neural Distinguisher and apply it to the SPECK-/32/64, HIGHT, and GOST block ciphers. The proposed Related-key Neural Distinguisher was constructed using the relationship between keys, and this made it possible to distinguish more rounds than the differential distinguisher.

• 천문학회보
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• 제46권1호
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• pp.47.4-48
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• 2021

Gravitationally lensed Type Ia supernovae may be the next frontier in cosmic probes, able to deliver independent constraints on dark energy, spatial curvature, and the Hubble constant. Measurements of time delays between the multiple images become more incisive due to the standardized candle nature of the source, monitoring for months rather than years, and partial immunity to microlensing. While currently extremely rare, hundreds of such systems should be detected by upcoming time-domain surveys. Others will have the images spatially unresolved, with the observed lightcurve a superposition of time delayed image fluxes. We investigate whether unresolved images can be recognized as lensed sources given only lightcurve information and whether time delays can be extracted robustly. We develop a method that we show can identify these systems for the case of lensed Type Ia supernovae with two images and time delays exceeding ten days. When tested on such an ensemble the method achieves a false positive rate of ≲5%, and measures the time delays with the completeness of ≳93% and with a bias of ≲0.5% for time delay ≳10 days. Since the method does not assume a template of any particular type of SN, the method has the potential to work on other types of lensed SNe systems and possibly on other transients.

• Ocean Systems Engineering
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• 제13권3호
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• pp.287-312
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• 2023

The global performance of a 15 MW floating offshore wind turbine, a newly designed semisubmersible floating foundation with multiple heave plates by CNOOC, is investigated with two independent turbine-floater-mooring coupled dynamic analysis programs CHARM3D-FAST and OrcaFlex. The semisubmersible platform hosts IEA 15 MW reference wind turbine modulated for VolturnUS-S and hybrid type (chain-wire-chain with clumps) 3×2 mooring lines targeting the water depth of 100 m. The numerical free-decay simulation results are compared with physical experiments with 1:64 scaled model in 3D wave basin, from which appropriate drag coefficients for heave plates were estimated. The tuned numerical simulation tools were then used for the feasibility and global performance analysis of the FOWT considering the 50-yr-storm condition and maximum operational condition. The effect of tower flexibility was investigated by comparing tower-base fore-aft bending moment and nacelle translational accelerations. It is found that the tower-base bending moment and nacelle accelerations can be appreciably increased due to the tower flexibility.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• 제25권6호
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• pp.473-480
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• 2022

Purpose: Low bone mineral density (BMD) is a complication in children with inflammatory bowel disease (IBD). There are limited data evaluating dual-energy x-ray absorptiometry (DXA) as a screening tool for low BMD in children with IBD. We performed a single site retrospective analysis of DXA use. Methods: Children aged 5-18 years with IBD diagnosed between 2013 to 2017 at the Royal Children's Hospital, Australia, were included. Patient demographics, measures of disease activity, DXA scores, and factors related to BMD were collected. Results: Over a median follow up of 5.1 (4-6.4) years, 72/239 (30.1%) children underwent DXA, and 28/239 (11.7%) children had a second DXA. Our DXA practice differed to consensus guidelines regarding initial screening based on height and/or body mass index (BMI) z-score (8/17 [47.1%]), and repeat surveillance (13/42 [31.0%]). Children had a median lumbar spine (LS) z-score -0.80 (-1.65-0.075). Children with LS z-score≤-2.0 (n=14) had lower weight (6.57 [1.78-23.7] vs. 51.1 [26.5-68.7], p=0.0002) and height centiles (3.62 [1.17-17.1] vs. 42 [16.9-67.1], p=0.0001), and higher faecal calprotectin (FCP) (3041 [1182-4192] vs. 585 [139-2419], p=0.009) compared to children with LS z-score>-2.0. No fractures were reported. Of 28 children who underwent a second DXA 1.6 (1.1-2.2) years following initial DXA, no significant change in z-scores occurred. Conclusion: Children with IBD had low BMD. In addition to height centile and weight centile, FCP was associated with lower BMD, and should be considered in DXA screening guidelines. Greater clinician awareness of DXA consensus guidelines is required. Future prospective studies are required.

• Preventive Nutrition and Food Science
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• 제22권3호
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• pp.172-183
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• 2017

Vitamin A and its metabolites modulate insulin resistance and regulate stearoyl-CoA desaturase 1 (SCD1), which are also known to affect insulin resistance. Here, we tested, whether vitamin A-mediated changes in insulin resistance markers are associated with SCD1 regulation or not. For this purpose, 30-week old male lean and glucose-intolerant obese rats of WNIN/GR-Ob strain were given either a stock or vitamin A-enriched diet, i.e. 2.6 mg or 129 mg vitamin A/kg diet, for 14 weeks. Compared to the stock diet, vitamin A-enriched diet feeding improved hyperglycemia and glucose-clearance rate in obese rats and no such changes were seen in lean rats receiving identical diets. These changes were corroborated with concomitant increase in circulatory insulin and glycogen levels of liver and muscle (whose insulin signaling pathway genes were up-regulated) in obese rats. Further, the observed increase in muscle glycogen content in these obese rats could be explained by increased levels of the active form of glycogen synthase, the key regulator of glycogen synthesis pathway, possibly inactivated through increased phosphorylation of its upstream inhibitor, glycogen synthase kinase. However, the unaltered hepatic SCD1 protein expression (despite decreased mRNA level) and increased muscle-SCD1 expression (both at gene and protein levels) suggest that vitamin A-mediated changes on glucose metabolism are not associated with SCD1 regulation. Chronic consumption of vitamin A-enriched diet improved hyperglycemia and glucose-intolerance, possibly, through the regulation of intracellular signaling and glycogen synthesis pathways of muscle and liver, but not associated with SCD1.

• Korean Journal of Mathematics
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• 제32권1호
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• pp.43-57
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• 2024

Given a domain X and a collection H of functions h : X → {0, 1}, the Vapnik-Chervonenkis (VC) dimension of H measures its complexity in an appropriate sense. In particular, the fundamental theorem of statistical learning says that a hypothesis class with finite VC-dimension is PAC learnable. Recent work by Fitzpatrick, Wyman, the fourth and seventh named authors studied the VC-dimension of a natural family of functions ℋ'²_t(E) : 𝔽²_q → {0, 1}, corresponding to indicator functions of circles centered at points in a subset E ⊆ 𝔽²_q. They showed that when |E| is large enough, the VC-dimension of ℋ'²_t(E) is the same as in the case that E = 𝔽²_q. We study a related hypothesis class, ℋ^d_t(E), corresponding to intersections of spheres in 𝔽^d_q, and ask how large E ⊆ 𝔽^d_q needs to be to ensure the maximum possible VC-dimension. We resolve this problem in all dimensions, proving that whenever |E| ≥ C_dq^d-1/(d-1) for d ≥ 3, the VC-dimension of ℋ^d_t(E) is as large as possible. We get a slightly stronger result if d = 3: this result holds as long as |E| ≥ C_3q^7/3. Furthermore, when d = 2 the result holds when |E| ≥ C_2q^7/4.

• Journal of Forest and Environmental Science
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• 제37권3호
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• pp.217-225
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• 2021

This study evaluated the species composition, diversity and phorophyte preference of epiphytes at the University of Port Harcourt located in southern part of Nigeria. Purposive sampling technique was used to select sites representing major avenues in the three campuses (Abuja, Choba and Delta) of the University. Data were collected on species name of phorophytes, number of individuals, diameter at breast height (dbh) and height, and species/number of epiphytes present on them. The points/sections of attachment of epiphytes on phorophytes were also recorded. A total of eight species of epiphyte belonging to six families were recorded in the study. Species diversity was higher in Abuja campus (Simpson 1-D=0.81; Shannon H=1.79), followed by Choba campus (Simpson 1-D=0.73; Shannon H=1.09) and Delta campus (Simpson 1-D=0.56; Shannon H=0.93). Species richness was highest in Abuja campus (n=8) followed by Delta campus (n=4) and Choba campus (n=3). Similarity in epiphyte species composition was highest between Choba and Delta campuses (85.71%), followed by Delta and Abuja campuses (66.67%) and lowest between Choba and Abuja campuses (54.55%). The family-Polypodiaceae, had the highest number of species (n=3). Microgramma owariensis had the highest relative abundance (27%) followed by Platycerium bifurcatum (26%) while Tillandsia utriculata and Peperomia pellucida had the least relative abundance (3%). Epiphyte abundance was weakly correlated with both the dbh and height of phorophytes. However, epiphytes were more abundant on phorophytes with rough/scaly/corky/flaky barks than on those with smooth barks. The planting of avenue tree species with rough barks is recommended to enhance the diversity of epiphytes in the study area.