• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.5
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• pp.555-566
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• 2023

In this study, a composite phase change material (CPCM) produced using the SOL-GEL technique was developed as a thermal energy storage medium for low-temperature applications. Tetradecane and activated carbon (AC) were used as the core and supporting materials, respectively. The tetradecane phase change material (PCM) was impregnated into the porous structure of AC using the vacuum impregnation method, and a thin layer of silica gel was coated on the prepared composite using the SOL-GEL process, where tetraethyl orthosilicate (TEOS) was used as the silica source. The thermal performance of the CPCM was analysed using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC results showed that the pure tetradecane PCM had melting and freezing temperatures of 6.4℃ and 1.3℃ and corresponding enthalpies 226 J/g and 223.8 J/g, respectively. The CPCM exhibited enthalpy of 32.98 J/g and 27.7 J/g during the melting and freezing processes at 7.1℃ and 2.4℃, respectively. TGA test results revealed that the AC is thermally stable up to 500℃, which is much higher than the decomposition temperature of the pure tetradecane, which is around 120℃. Moreover, in the case of AC-PCM and CPCM thermal degradation started at 80℃ and 100℃, respectively. The chemical stability of the CPCM was studied using Fourier-transform infrared (FT-IR) spectroscopy, and the results confirmed that the developed composite is chemically stable. Finally, the surface morphology of the AC and CPCM was analysed using scanning electron microscopy (SEM), which confirmed the presence of a thin layer of silica gel on the AC surface after the SOL-GEL process.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06a
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• pp.75-87
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• 1996

This review is presented under the following headings: 1.Introduction 1.1 Brief review of the properties of AlN 1.2 Historical survey of work on ceramic and single crystal AlN 2.Thermochemical background 3.Crystal growth 4.Doping 5.Potential applications and future work The known properties of AlN which make it of interest for various are discussed briefly. The properties include chemical stability, crystal structure and lattice constants, refractive indices and other optical properties, dielectric constant, surface acoustic wave velocity and thermal conductivity. The history of work in single crystals, thin films and ceramics are outlined and the thermochemistry of AlN reviewed together with some of the relevant properties of aluminium and nitrogen; the problems encountered in growing crystals of AlN are shown to arise directly from these thermochemical relationships. Methods have been reported in the literature for growing AlN crystals from melts, solution and vapour and these methods are compared critically. It is proposed that the only practicable approach to the growth of AlN is by vapour phase methods. All vapour based procedures share the share the same problems: $.$the difficulty of preventing contamination by oxygen & carbon $.$the high bond energy of molecular nitrogen $.$the refractory nature of AlN (melting point~3073K at 100ats.) $.$the high reactivity of Al at high temperatures It is shown that the growth of epitactic layers and polycrystalline layers present additional problems: $.$chemical incompatibility of substrates $.$crystallographic mismatch of substrates $.$thermal mismatch of substrates The result of all these problems is that there is no good substrate material for the growth of AlN layers. Organometallic precursors which contain an Al-N bond have been used recently to deposit AlN layers but organometallic precursors gave the disadvantage of giving significant carbon contamination. Organometallic precursors which contain an Al-N bound have been used recently to deposit AlN layers but organometallic precursors have the disadvantage of giving significant carbon contamination. It is conclude that progress in the application of AlN to optical and electronic devices will be made only if considerable effort is devoted to the growth of larges, pure (and particularly, oxygen-free) crystals. Progress in applications of epi-layers and ceramic AlN would almost certainly be assisted also by the availability of more reliable data on the pure material. The essential features of any stategy for the growth of AlN from the vapour are outlined and discussed.

• Journal of the Korean Institute of Landscape Architecture
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• v.51 no.2
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• pp.81-93
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• 2023

The purpose of this study is to clarify the background of the plans and the spatial characteristics of the garden at the Anglo-Korean School, an educational institution established in Gaeseong in 1906 by Yun Chi-ho and the American Methodist Church. The time scope of the study is from 1906, when the school was opened, to the early 1920s, when the basic building structure of the school was completed. The spatial scope is the school complex, located in Gaeseong, and its affiliated facilities. The contents of the study include the planning background and purpose, spatial layout, and plants used in the school garden. This study reviewed Yun Ch'i-ho's papers and Warren A. Candler's papers at Emory University, documents, photos, and maps produced in the early 20th century. The results show that the school garden was first mentioned at the school's opening and that with a strong will, Yun Chi-ho insisted on establishing a school garden. The garden was located around the engineering department building and was divided into several sections and lots. Economic plants, such as fruit trees, comprised the garden and were sourced from the Methodist Church of the South, USA. This study reveals that the garden at the Anglo-Korean School functioned as a training ground for agriculture and horticulture education and was differentiated from Seowon, a traditional Korean academy that symbolically spaced Neo-Confucianism and that emphasized the views of the surrounding nature during the Joseon Dynasty.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.295-303
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• 2023

South Korea has recently witnessed an increasing number of seismic events, leading to a surge in studies focusing on seismic earth pressures, as well as the attributes of geological layers and ground where foundations are established. Consequently, earthquake-resistant design has become imperative to ensure the safety of subterranean structures. The slurry wall method, due to its superior wall rigidity, excellent water resistance, and minimal noise and vibration, is often employed in constructing high-rise buildings in urban areas. However, given the separation between panels that constitute the wall, slurry walls possess limited resistance to seismic loads in the longitudinal direction. As a solution, several studies have probed into the possibility of interconnecting slurry wall panels to augment their seismic performance. In this research, we developed and evaluated a method for linking slurry wall panels using mechanical joints, including concrete-confined steel pipes and headed bars, through mock-up tests. We also assessed the constructability of the suggested method and compared it with other analogous methods. Any challenges identified during the mock-up test were discussed to guide future research in resolving them. The results of this study aid in enhancing the seismic performance of slurry walls through the development of an interconnected panel method. Further research can build on these findings to address the identified issues and improve the efficacy and reliability of the proposed method.

• Journal of the Korean Geotechnical Society
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• v.22 no.9
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• pp.61-68
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• 2006

Recently the large scale civil engineering projects are being implemented by reclaiming the sea or utilizing seashore and river embankment areas. The reclaimed land and utilized seashore are mostly soft ground that doesn't have sufficient bearing capacity. This soft ground consists of fine-grained soil such as clayey and silty soils or large void soil like peat or loose sand. It has high ground water table and it may cause the failure and crock of building foundation by uplift pressure and ground water leakage. In this study, the permittivity and the transmissivity were evaluated with the applied normal pressure in the laboratory. The laboratory model tests were conducted by utilizing geocomposite drainage system for draining the water out to release the uplift pressure. The soil used in the laboratory drainage test was dredged soil from the reclaimed land where uplift pressure problems can arise in soil condition. Geocomposite drainage system was installed at the bottom of apparatus and dredged soil was layered with compaction. Subsequently the water pressure was supplied from the top of specimen and the quantities of drainage and the pore water pressure were measured at each step water pressure. The results of laboratory measurements were compared with theoretical values. For the evaluation of propriety of laboratory drainage test, 2-D finite elements analysis that can analyze the distribution and the transferring of pore water pressure was conducted and compared with laboratory test results.

• Phonetics and Speech Sciences
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• v.14 no.1
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• pp.21-28
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• 2022

Previous studies have provided important findings on children's speech production development. They have revealed that essentially all aspects of children's speech shift toward adult-like characteristics over time. Nevertheless, few studies have examined the perceptual aspects of children's speech tokens, as perceived by naive adult listeners. To fill the gap between children's production and adults' perception, we conducted cross-sectional perceptual studies of monosyllabic words produced by children aged two to six years. Monosyllabic words in the consonant-vowel-consonant form were extracted from children's speech samples and presented aurally to five listener groups (20 listeners in total). Generally, the agreement rate between children's production of target words and adult listeners' responses increases with age. The perceptual responses to tokens produced by two-year old children induced the largest discrepancies and the responses to words produced by six years olds agreed the most. Further analyses were conducted to identify the sources of disagreement, including the types of segments and syllable structure. This study makes an important contribution to our understanding of the development and perception of children's speech across age groups.

• Geophysics and Geophysical Exploration
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• v.25 no.4
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• pp.203-213
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• 2022

To understand an underlying geological structure via seismic imaging, the velocity information of the subsurface medium is crucial. Although the full-waveform inversion (FWI) method is considered useful for estimating subsurface velocity models, 3D FWI needs a lot-of computing power and time. Herein, we compare the calculation efficiency and accuracy of frequency-domain 2D and 3D acoustic FWIs. Thereafter, we demonstrate that the artifacts from 2D approximation can be partially suppressed via frequency-domain 2D FWI by employing diffraction angle filtering (DAF). By applying DAF, which employs only big reflection angle components, the impact of noise and out-of-plane reflections can be reduced. Additionally, it is anticipated that the DAF can create long-wavelength velocity structures for 3D FWI and migration.

• KIPS Transactions on Software and Data Engineering
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• v.11 no.12
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• pp.499-508
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• 2022

A lot of research has been carried out on the Hangeul generation model using deep learning, and recently, research is being carried out how to minimize the number of characters input to generate one set of Hangul (Few-Shot Learning). In this paper, we propose a CKFont2 model using only 14 letters by analyzing and improving the CKFont (hereafter CKFont1) model using 28 letters. The CKFont2 model improves the performance of the CKFont1 model as a model that generates all Hangul using only 14 characters including 24 components (14 consonants and 10 vowels), where the CKFont1 model generates all Hangul by extracting 51 Hangul components from 28 characters. It uses the minimum number of characters for currently known models. From the basic consonants/vowels of Hangul, 27 components such as 5 double consonants, 11/11 compound consonants/vowels respectively are learned by deep learning and generated, and the generated 27 components are combined with 24 basic consonants/vowels. All Hangul characters are automatically generated from the combined 51 components. The superiority of the performance was verified by comparative analysis with results of the zi2zi, CKFont1, and MX-Font model. It is an efficient and effective model that has a simple structure and saves time and resources, and can be extended to Chinese, Thai, and Japanese.

• Journal of Internet of Things and Convergence
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• v.9 no.3
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• pp.93-98
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• 2023

In this paper, an artificial neural network based on simulated annealing was constructed. The mapping relationship between the parameters of micro-scaled flow channels electrochemical machining and the channel shape was established by training the samples. The depth and width of micro-scaled flow channels electrochemical machining on stainless steel surface were predicted, and the flow channels experiment was carried out with pulse power supply in NaNO3 solution to verify the established network model. The results show that the depth and width of the channel predicted by the simulated annealing artificial neural network with "4-7-2" structure are very close to the experimental values, and the error is less than 5.3%. The predicted and experimental data show that the etching degree in the process of channels electrochemical machining is closely related to voltage and current density. When the voltage is less than 5V, a "small island" is formed in the channel; When the voltage is greater than 40V, the lateral etching of the channel is relatively large, and the "dam" between the channels disappears. When the voltage is 25V, the machining morphology of the channel is the best.

• Journal of Digital Convergence
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• v.20 no.3
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• pp.325-331
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• 2022

As IoT devices are used in various ways in an edge network environment, multiple studies are being conducted that utilizes the information collected from IoT devices in various applications. However, it is not easy to apply accurate IoT data immediately as IoT data collected according to network environment (interference, interference, etc.) are frequently missed or error occurs. In order to minimize mistakes in IoT data collected in an edge network environment, this paper proposes a management technique that ensures the reliability of IoT data by randomly generating signature values of IoT data and allocating only Security Information (SI) values to IoT data in bit form. The proposed technique binds IoT data into a blockchain by applying multiple hash chains to asymmetrically link and process data collected from IoT devices. In this case, the blockchainized IoT data uses a probability function to which a weight is applied according to a correlation index based on deep learning. In addition, the proposed technique can expand and operate grouped IoT data into an n-layer structure to lower the integrity and processing cost of IoT data.