• Korean Journal of Materials Research
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• v.31 no.3
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• pp.132-138
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• 2021

Electrochromic devices (ECDs) have been drawing great attention due to their high color contrast, low power consumption, and memory effect, and can be used in smart windows, automatic dimming mirrors, and information display devices. As with other electronic devices such as LEDs (light emitting diodes), solar cells, and transistors, the mechanical flexibility of ECDs is one of the most important issue for their potential applications. In this paper, we report on flexible ECDs (f-ECDs) fabricated using an all-in-one EC gel, which is a mixture of electrolyte and EC material. The f-ECDs are compared with rigid ECDs (r-ECDs) on ITO glass substrate in terms of color contrast, coloration efficiency, and switching speed. It is confirmed that the f-ECDs embedding all-in-one gel show strong blue absorption and have competitive EC performance. Repetitive bending tests show a degradation of electrochromic performance, which must be improved using an optimized device fabrication process.

• Steel and Composite Structures
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• v.37 no.6
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• pp.711-731
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• 2020

This paper deals with free vibration of FG sandwich annular sector plates on Pasternak elastic foundation with different boundary conditions, based on the three-dimensional theory of elasticity. The plates with simply supported radial edges and arbitrary boundary conditions on their circular edges are considered. The influence of carbon nanotubes (CNTs) waviness, aspect ratio, internal pores and graphene platelets (GPLs) on the vibrational behavior of functionally graded nanocomposite sandwich plates is investigated in this research work. The distributions of CNTs are considered functionally graded (FG) or uniform along the thickness of upper and bottom layers of the sandwich sectorial plates and their mechanical properties are estimated by an extended rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The core of structure is porous and the internal pores and graphene platelets (GPLs) are distributed in the matrix of core either uniformly or non-uniformly according to three different patterns. The elastic properties of the nanocomposite are obtained by employing Halpin-Tsai micromechanics model. A semi-analytic approach composed of 2D-Generalized Differential Quadrature Method (2D-GDQM) and series solution is adopted to solve the equations of motion. The fast rate of convergence and accuracy of the method are investigated through the different solved examples. Some new results for the natural frequencies of the plate are prepared, which include the effects of elastic coefficients of foundation, boundary conditions, material and geometrical parameters. The new results can be used as benchmark solutions for future researches.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.6
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• pp.1139-1150
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• 2022

With the rapid development of SW Industry, softwares are everywhere in our daily life. The number of vulnerabilities are also increasing with a large amount of newly developed code. Vulnerabilities can be exploited by hackers, resulting the disclosure of privacy and threats to the safety of property and life. In particular, since the large numbers of increasing code, manually analyzed by expert is not enough anymore. Machine learning has shown high performance in object identification or classification task. Vulnerability detection is also suitable for machine learning, as a reuslt, many studies tried to use RNN-based model to detect vulnerability. However, the RNN model is also has limitation that as the code is longer, the earlier can not be learned well. In this paper, we proposed a novel method which applied BERT to detect vulnerability. The accuracy was 97.5%, which increased by 1.5%, and the efficiency also increased by 69% than Vuldeepecker.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.217-222
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• 2022

Information plays an important role in modern society. Most of the information is processed and moved in the digital space. In cyberspace, confidential communication based on resistance and security is fundamental. It is essential to protect the information sent and received over the network. However, information may be leaked and forged by unauthorized users. The effectiveness of the existing protection system decreases as an innovative technique is applied to identify the communication contents by a third party. Steganography is a technique for inserting secret information into a specific area of a medium. Stegganography and steganalysis techniques are at odds with each other. A new and sophisticatedly implemented system is needed to cope with the advanced steganalysis. To enhance step-by-step diffusion and irregularity, I propose a hybrid implementation technique of image steganography for Hangul messages based on layered encryption and variable ShiftRows. PSNR was calculated to measure the proposed steganography efficiency and performance. Compared to the basic LSB technique, it was shown that the diffusion and randomness can be increased even though the PSNR decreased by 1.45%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.115-119
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• 2023

The natural language processing models used in current artificial intelligence are huge, causing various difficulties in processing and analyzing data in real time. In order to solve these difficulties, we proposed a method to improve the efficiency of processing by using less memory and checked the performance of the proposed model. The technique applied in this paper to evaluate the performance of the proposed model is to divide the large corpus by adjusting the number of attention heads and embedding size of the BERT[1] model to be small, and the results are calculated by averaging the output values of each forward. In this process, a random offset was assigned to the sentences at every epoch to provide diversity in the input data. The model was then fine-tuned for classification. We found that the split processing model was about 12% less accurate than the unsplit model, but the number of parameters in the model was reduced by 56%.

• Steel and Composite Structures
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• v.48 no.3
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• pp.275-291
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• 2023

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with 3D-graphene foam reinforced polymer matrix composites (GrF-PMC) core and FG wavy CNT-reinforced face sheets. The porous graphene foam possessing 3D scaffold structures has been introduced into polymers for enhancing the overall stiffness of the composite structure. Also, 3D graphene foams can distribute uniformly or non-uniformly in the plate thickness direction. The effective Young's modulus, mass density and Poisson's ratio are predicted by the rule of mixture. In this study, the classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. It is explicated that 3D-GrF skeleton type and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. The plate's normalized natural frequency decreased and the straight carbon nanotube (w=0) reached the highest frequency by increasing the values of the waviness index (w).

• The Korean Journal of Franchise Management
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• v.7 no.2
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• pp.37-45
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• 2016

Purpose - This study aims to examine the impact of leadership on organizational trust and innovation performance, and to identify whether organizational trust plays a mediating role in the relationship between leadership and innovation performance. Also, this study attempts to find out how to improve organizational efficiency and effectiveness based on leadership-based or trust-based strategies. And, this research proposed that organizational trust plays a core mediating role in the relationship between transactional and transformational leadership and innovation performance. Research design, data, and methodology - In order to test the hypotheses of this study, the survey was conducted towards franchise coffee shop employees between November 7 and 18, 2016. We contacted top executives of coffee shop franchise headquarters and explained the purpose of this study. Among 150 questionnaires distributed, 123 were collected. Of these collected questionnaires, 102 questionnaires were coded and analyzed for further analysis. In order to test the unidimensionality and reliability of the factors, factor analysis and reliability test were performed using SPSS/PC+ 22.0. And, the hypotheses were tested using hierarchical mediated regression analysis. Result - The results are as follows. First, transactional leadership, and intellectual stimulation, motivation of transformational leadership had significant impacts on organizational trust. Second, organizational trust, transactional leadership, and influence of transformational leadership had significant impacts on innovation performance. Third, the mediating test of organizational trust showed that transactional leadership plays a partial mediator, and intellectual of transformational leadership plays a full mediator in the relationship between leadership and innovation performance. Conclusions - The implications of this study are as follows. First, the top management should provide their organizational members incentives or rewards based on their performance. Second, top management should identify and express a clear vision and desirable organizational goals for the future, present an idealized vision, and communicate to organizational members that the vision is achievable, also have organizational members to think creatively and find optimal solutions to difficult problems. In sum, this study revealed the important role of leadership in embedding organizational trust in and improving innovation performance of coffee shop employees and the mediating role of organizational trust in the influence of leadership on innovation performance.

• Steel and Composite Structures
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• v.51 no.1
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• pp.73-91
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• 2024

This paper has focused on presenting vibration analysis of trapezoidal sandwich plates with a damaged core and FG wavy CNT-reinforced face sheets. A damage model is introduced to provide an analytical description of an irreversible rheological process that causes the decay of the mechanical properties, in terms of engineering constants. An isotropic damage is considered for the core of the sandwich structure. The classical theory concerning the mechanical efficiency of a matrix embedding finite length fibers has been modified by introducing the tube-to-tube random contact, which explicitly accounts for the progressive reduction of the tubes' effective aspect ratio as the filler content increases. The First-order shear deformation theory of plate is utilized to establish governing partial differential equations and boundary conditions for the trapezoidal plate. The governing equations together with related boundary conditions are discretized using a mapping-generalized differential quadrature (GDQ) method in spatial domain. Then natural frequencies of the trapezoidal sandwich plates are obtained using GDQ method. Validity of the current study is evaluated by comparing its numerical results with those available in the literature. After demonstrating the convergence and accuracy of the method, different parametric studies for laminated trapezoidal structure including carbon nanotubes waviness (0≤w≤1), CNT aspect ratio (0≤AR≤4000), face sheet to core thickness ratio (0.1 ≤ ${\frac{h_f}{h_c}}$ ≤ 0.5), trapezoidal side angles (30° ≤ α, β ≤ 90°) and damaged parameter (0 ≤ D < 1) are carried out. It is explicated that the damaged core and weight fraction, carbon nanotubes (CNTs) waviness and CNT aspect ratio can significantly affect the vibrational behavior of the sandwich structure. Results show that by increasing the values of waviness index (w), normalized natural frequency of the structure decreases, and the straight CNT (w=0) gives the highest frequency. For an overall comprehension on vibration of laminated trapezoidal plates, some selected vibration mode shapes were graphically represented in this study.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.197-204
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• 1987

In order to know the growth of suspended cells by explant sources, the change of nitrogen contents of cultured cells following the growth periods, capability of micro-callus formation according to cell plating methods, growth of suspended cells on various media, and efficiency of micro-callus formation by using growth regulators and different N strengths were investigated. 1. When suspension culture was tried by using the callus induced from internode and petiole, cell fresh weight and packed cell volume increased with similar way and the growth reached at stationary phase after 12 culture days. 2. N-contents of cultured cells increased upto 3 days and decreased around 6days. But the values increased again upto 9 days, after that they showed gradual decreases. 3. Of cell plating methods, embedding method was the best for micro-callus formation. 4. Growth of suspened cells showed the rest performanoes, when they were cultured on LM medium with 1/2N strengths and BAP 0.01.2.4-D 0.1, and NAA $1.0mg/{\ell}$, after 15 cultured days(upto 76.9 folds). LM medium was better than MS or GD. The combination of auxin and cytokinin was better for cell growing than auxin-treatment only. 5. Micro-callus from single cell and small cell aggregates was formed only on MS and LM media with 2,4-D $1.0mg/{\ell}$.

• Korean Journal of Environmental Agriculture
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• v.18 no.4
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• pp.327-331
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• 1999

The purpose of this study was to find out the effects of slow-released nitrogen fertilizer (SRF) on the growth and yield of Chinese cabbage. The SRF used in this study was prepared by embedding urea into a waste paper slum. The underwater dissolution rate of SRF was very rapid during the first 12 hours and 60.4% of the embedded nitrogen was released after 72 hours. The SRF and urea was applied as nitrogen source and growth. yield, yield components, nitrogen uptake of Chinese cabbage were investigated a pot experiment. Maximum leaf length of Chinese cabbage was not different between SRF and urea treatments. Length and wish of head, number of leaf per head and fresh weight of Chinese cabbage were higher in SRF treatment than those in urea treatment, but the differences were not statistically significant. Comparing to the urea treatment, nitrogen content and nitrogen uptake efficiency of Chinese cabbage were significantly higher in SRF treatment. After the experiment, total soil nitrogen contents were not different between the SRF and urea treatments.