• Korean Journal of Environmental Biology
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• v.40 no.4
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• pp.387-397
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• 2022

The germination characteristics of the resting cysts of Pheopolykrikos hartmannii collected from the southern coastal sediments of Korea were studied at different temperature conditions, and the morphology and phylogeny of the germlings were examined. The resting cysts of Ph. hartmannii were round and characterized by a red accumulation body and many arrow-like spines and could germinate at temperature of 10 to 30℃. High germination rates (>90%) were observed at 15 and 20℃, indicating that the resting cysts could act as seed populations for the bloom initiation of Ph. hartmannii in Korean coastal waters in early summer or early fall. The morphology of the germlings was generally consistent with the previous description, and an apical groove characterized by a fully enclosed loop was observed. Phylogenetic analysis based on large SubUnit (LSU) rRNA gene sequences revealed that the germlings shared an identical sequence with the Korean and American isolates of Ph. hartmannii and was a sister clade of Polykrikos species.

• Composites Research
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• v.19 no.5
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• pp.28-33
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• 2006

In this paper, we have studied the complex permittivities and their influence on the design of microwave absorbers of E-glass fabric/epoxy composite laminates containing three different types of carbon-based nano conductive fillers such as carbon black (CB), carbon nano fiber (CNF) and multi-wall nano tube (MWNT). The measurements were performed fur permittivities at the frequency band of 0.5 GHz$\sim$18.0 GHz using a vector network analyzer with a 7 mm coaxial air line. The experimental results show that the complex permittivities of the composites depend strongly on the natures and concentrations of the conductive fillers. The real and imaginary parts of the complex permittivities of the composites were proportional to the filler concentrations. But, depending on the types of fillers and frequency band, the increasing rates of the real and imaginary parts with respect to the filler concentrations were all different. These different rates can have an effect on the thickness in designing the single layer microwave absorbers. The effect of the different rates at 10 GHz was examined by using Cole-Cole plot; the plot is composed of a single layer absorber solution line and measured permittivities from these three types of composites. Single layer absorbers of 3 different thicknesses using carbon nano materials were fabricated and the -10 dB band of absorbing performances were all about 3 GHz.

• Journal of Industrial Convergence
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• v.21 no.3
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• pp.189-194
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• 2023

Recently, various studies on flexible electronic devices have been performed. In this study, the potential of Ag nanowires was evaluated as a material to replace the ITO transparent conductive film. Ag nanomaterials were formed on the glass by a novel brush coating method and an argon plasma evaporation method based on atmospheric pressure plasma. First, the Ag solution is coated on the glass with a brush, and the remaining solvent is removed with atmospheric plasma. During this process of solvent evaporation, a sound is generated by the reaction between the atmospheric plasma and the solvent. Therefore, the remaining amount of the solvent can be confirmed. In order to observe optical properties and electrical results such as reflectance, transmittance, and absorbance according to the number of coatings of the film, the results were analyzed by coating up to 5 times. For the purpose of investigating the interaction of light with Ag nanowires, reflectance and transmittance were measured while changing the wavelength of light from 200 nm to 800 nm. In the case of absorbance, the trend of increasing light absorption of the Ag nanowires according to the coating was clearly confirmed. The electrical properties showed a great change from the time of coating more than 4 times, and in particular, the resistance value was lower than kΩ/cm2 when the coating was applied 5 times. Based on these optical and electrical results, we plan to verify the possibility of a transparent conductive film by applying it to electronic devices in the future.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.59 no.1
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• pp.35-43
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• 2023

Sensory evaluation of shucking pressure, pressure holding time, seeding method, difference in full shucking rate in the aquaculture area and shucking oyster was performed using an ultra-high pressure oyster shucking machine. The reaching time for each target pressure is 2.2-2.4 MPa/sec in the range of 180 MPa to 240 MPa. had a rate of pressure rise. There was a difference of 0.5-1.7℃ in the range of 24-27℃ in the seawater temperature before and after the pressure treatment inside the pressure vessel, but there was no specific increase or decrease in seawater temperature. When only the shucking pressure is increased without the pressure holding time, the critical shucking pressure at which the oyster shell is opened and the flesh is peeled in the range of 200 to 220 MPa. When the critical shucking pressure is reached, the oyster sample in the closed vessel is expected to be shucked by about 40%. If there is no pressure holding time when judged only by full shucking, an increase in pressure of about 1.5 MPa is required to further shuck 3% of the oyster population. The oyster samples cultivated in the south coast of Korea were subject to full shucking under the conditions of 220 MPa shucking pressure and two minutes (120 seconds) of pressure holding time, and the difference in the pressure of the oysters according to the oyster seeding method and the farming area was minute. Finally, the condition of 220 MPa of shucking pressure and three minutes of pressure holding time was the best at 1.52 when the result of the sensory evaluation performed manually was set to 1.0. Next was 1.4 under the conditions of 220 MPa of shucking pressure and one minute of pressure holding time (60 seconds), and 1.3 under the condition of 220 MPa and two minutes of pressure holding time (120 seconds). Therefore, it is considered that the most desirable shucking conditions, considering the efficiency and sensory evaluation results, are the conditions of 220 MPa shucking pressure and two to three minutes of pressure holding time.

• Journal of the Korean Geotechnical Society
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• v.38 no.3
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• pp.35-42
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• 2022

The N-value from the Standard Penetration Test (SPT), which is one of the representative in-situ test, is an important index that provides basic geological information and the depth of the bearing layer for the design of geotechnical structures. In the aspect of time and cost-effectiveness, there is a need to carry out a representative sampling test. However, the various variability and uncertainty are existing in the soil layer, so it is difficult to grasp the characteristics of the entire field from the limited test results. Thus the spatial interpolation techniques such as Kriging and IDW (inverse distance weighted) have been used for predicting unknown point from existing data. Recently, in order to increase the accuracy of interpolation results, studies that combine the geotechnics and deep learning method have been conducted. In this study, based on the SPT results of about 22,000 holes of ground survey, a comparative study was conducted to predict the depth of the bearing layer using deep learning methods and IDW. The average error among the prediction results of the bearing layer of each analysis model was 3.01 m for IDW, 3.22 m and 2.46 m for fully connected network and PointNet, respectively. The standard deviation was 3.99 for IDW, 3.95 and 3.54 for fully connected network and PointNet. As a result, the point net deep learing algorithm showed improved results compared to IDW and other deep learning method.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.134-141
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• 2022

To improve the performance of aluminum-air batteries, it is very important to understand the effect of electrolytes on the electrochemical properties of electrodes. In this study, the effects of electrolyte cations on the electrochemical redox reactions proceeding at the negative and positive electrodes were investigated using electrolytes having the same anion but different cations such as NaCl, LiCl, CaCl₂, and ZnCl₂. It was confirmed by discharge test, scanning electron microscopy and X-ray diffraction analysis that electrolyte cations affect the discharge potential and specific capacity of the electrode. Precipitates were formed on the surface of the positive electrode by Ca²⁺ and Zn²⁺ ions, resulting in degradation of the performance of the positive electrode. In addition, Ca²⁺ ions passivated the negative electrode and accelerated the performance degradation. This suggests that the positive ions of the electrolyte have different effects on the electrochemical performance of the positive and negative electrodes.

• Journal of Aerospace System Engineering
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• v.16 no.1
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• pp.86-96
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• 2022

The development trend of jet fighter's avionics system architecture is the digitization of subsystem component functions, increased RF sensor sharing, fiber optic channel networks, and modularized integrated structures. The avionics system architecture of the fifth generation jet fighters (F-22, F-35) has evolved into an integrated modular avionics system based on computing function integration and RF integrated sensor systems. The integrated modular avionics system of jet fighters should provide improved combat power, fault tolerance, and ease of jet fighter control. To this aim, this paper presents the direction and requirements of the next-generation jet fighter's avionics system architecture through analysis of the fifth generation jet fighter's avionics system architecture. The core challenge of the integrated modularized avionic system architecture requirements for next-generation fighters is to build a platform that integrates major components and sensors into aircraft. In other words, the architecture of the next-generation fighters is standardization of systems, sensor integration of each subsystem through open interfaces, integration of functional elements, network integration, and integration of pilots and fighters to improve their ability to respond and control.

• Journal of Broadcast Engineering
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• v.27 no.1
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• pp.104-123
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• 2022

Style transfer based on neural network provides very high quality results by reflecting the high level structural characteristics of images, and thereby has recently attracted great attention. This paper deals with the problem of resolution limitation due to GPU memory in performing such neural style transfer. We can expect that the gradient operation for style transfer based on partial image, with the aid of the fixed size of receptive field, can produce the same result as the gradient operation using the entire image. Based on this idea, each component of the style transfer loss function is analyzed in this paper to obtain the necessary conditions for partitioning and padding, and to identify, among the information required for gradient calculation, the one that depends on the entire input. By structuring such information for using it as auxiliary constant input for partition-based gradient calculation, this paper develops a recursive algorithm for super high-resolution image style transfer. Since the proposed method performs style transfer by partitioning input image into the size that a GPU can handle, it can perform style transfer without the limit of the input image resolution accompanied by the GPU memory size. With the aid of such super high-resolution support, the proposed method can provide a unique style characteristics of detailed area which can only be appreciated in super high-resolution style transfer.

• Design Convergence Study
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• v.16 no.4
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• pp.1-16
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• 2017

As the local manufacturing industry has entered a phase of stagnation, service and product design based on user experience has been highlighted as an alternative for the innovation. However, SMEs(Small and Medium-sized Enterprises) are still struggling to overcome the current crisis. One of the reasons is that SMEs do not have enough contact points with the validated UX firms and experts. Thus, SMEs has a high barrier to invest in new opportunity area, user experience. In this study, we aim to figure out UX experts' competence to perform the UX method to solve the UX problems based on the KSA framework(Knowledge, Skill, Attitude). Based on the literature review and expert workshop, we grouped the UX method according to the similarity of the competence required to conduct the method. With cluster analysis, 5 different groups of UX method were defined based on the competence, Panoramic Analysis, Meticulous Observation and Analysis, Intuitive Interpretation, Agile Visualization, and Logical Inspection. The results would be applied to compose a portfolio of UX experts and to implement a mechanism that could recommend the professional experts to the company.

• Resources Recycling
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• v.32 no.2
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• pp.19-32
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• 2023

A novel method for the synthesis of titanium hydride powder from titanium tetrachloride via the magnesiothermic reduction in an hydrogen gas atmosphere was investigated. To examine the influence of temperature on the formation of titanium hydride, the reduction was conducted at 1023~1123 K under 1 atm of hydrogen gas atmosphere for approximately 30 min. Subsequently, the titanium hydride powder was sintered by maintaining the temperature for 0~120 min, and the decrease in the oxygen concentration of the powder was investigated. The experimental results showed that TiH_1.924 was produced at 1023 K, whereas mixtures of TiH_1.924 and TiH_1.5 were produced at 1073 K and 1123 K. In addition, the hydrogen concentration in the powder decreased with increasing temperature. The concentration of oxygen in the powder decreased with increasing temperature and sintering time owing to the decrease in the specific surface area of the powder. The minimum concentration of oxygen was 0.246 mass% when the mixture of TiH_1.924 and TiH_1.5 was obtained at 1073 K and a sintering time of 120 min.