• Geomechanics and Engineering
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• 제7권2호
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• pp.183-200
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• 2014

The expansivity of clayey soils is a complicated phenomenon which may affect the stability of geotechnical structures and geo-environmental projects. In all common factors for the monitoring of soil expansion, less attention is given to anion type of pore space solutions. Therefore, this paper is concerned with the impact of various concentrations of different inorganic salts including NaCl, $Na_2SO_4$, and $Na_2CO_3$ on the macro and microstructure behavior of the expandable smectite clay. Comparison of the responses of the smectite/NaCl and smectite/$Na_2SO_4$ mixtures indicates that the effect of anion valance on the soil engineering properties is not very pronounced, regardless of the electrolyte concentration. However, at presence of carbonate as potential determining ions (PDIs) the swelling power increases up to 1.5 times compared to sulfate or chloride ions. The samples with $Na_2CO_3$ are also more deformable and show lower osmotic compressibility than the other mixtures. This demonstrates that the barrier performance of smectite greatly decreases in case of anions with the non-specific adsorption (e.g., $Cl^-$ and $SO{_4}^{2-}$) as the salinity of solution increases. Based on the results of the X-ray diffraction and sedimentation tests, the high soil volumetric changes upon exposure to carbonate is attributed to an increase in the repulsive forces between smectite basic unit layers due to the PDI effect of $CO{_3}^{2-}$ and increasing the pH level which enhance the buffering capacity of smectite. The study concluded that the nature of anion through its influence on the re-arrangement of soil microstructure and osmotic phenomena governs the hydro-mechanical parameters of expansive clays. It seems not coinciding with the double layer theory of the Gouy-Chapman double layer model.

• Journal of Forest and Environmental Science
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• 제27권3호
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• pp.151-156
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• 2011

Seeds of Xanthoceras sorbifolia Bunge were collected from two plantations and two superior trees in Inner Mongolia: and one plantation and one superior tree in Liaoning, China in late August, 2011. Yellowhorn or goldenhorn is an important tree species, from the aspects of source of edible oil and biodiesel and pioneering capacity of degraded and desert land. Characteristics investigated were seed length, width, and weight: weight and volume of 1,000 seeds: and weight and volume of one-liter seeds. The seeds of Qingsonglingxiang No. 1, growing alone in an open space, showed the highest values in seed length (16.08 mm), width (14.48 mm) and weight (1.40 g), while those of Tree No. 160 in Ar Khorqin Banner were the lowest ones: that is, 11.48mm for length, 11.81 mm for width, and 0.73 g for weight, respectively. Traits of seeds varied quite much between trees and among areas; for example, Tree No. 38 and No. 160 produced quite different seeds in several traits, although they are adjacent to each other in the same farm. Weight of 1,000 seeds varied from 718.0 g to 1,010.1 g and volume from 0.76 L to 1.52 L. Weight of one-liter seeds were 522.3 g to 688.2 g, while the number of seeds were 603 to 935. Seeds which were soaked in the water at $4^{\circ}C$ for 2 days showed the highest germination rate (89%) in a 30-day test, which was about 10% to 40% higher than those of non-treatment and dipping treatment at $36^{\circ}C$ followed by keeping under room temperature for 2 days. 81% of seeds in the wet sand at room temperature germinated, while 23% of seeds deprived of seed coat germinated. It is necessary to understand seed traits to select superior clones or provenances for the increased, unfluctuating production of seed.

• 한국지리정보학회지
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• 제24권3호
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• pp.10-31
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• 2021

본 연구를 통해 정의된 용도복합 개념은 세 가지 이상의 주요 도시기능의 복합을 의미하며 도시공간의 경제적, 사회적, 환경적 가치를 동시에 실현하기 위한 수단을 의미한다. 이러한 정의 하에서 서울의 용도복합 현상을 탐구하였다. 상대적 엔트로피 개념을 사용하여 단위 지역인 법정동을 기준으로 복합도(R.E.)를 측정하였으며 도시기능의 유형은 용도복합의 정의에서 도출한 개념을 통해 건축물 층별 용도를 유형화하여 계량화하였다. 서울의 용도복합 현상은 복합도(R.E.) 0.631 이하를 '복합아님', 복합도(R.E.) 0.631 초과 0.884 미만을 '불균형 복합', 복합도(R.E.) 0.884 이상 0.991 미만을 '균형복합', 복합도(R.E.) 0.991 이상을 '완전균형복합'의 단계로 구분하여 용도복합 현상을 해석하는 기준으로 지표화하였다.

• Imaging Science in Dentistry
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• 제51권3호
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• pp.223-235
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• 2021

Purpose: This study aimed to summarize the impact of neck and head radiation treatment on maxillofacial structures detected on panoramic radiographs. Materials and Methods: In this systematic review, the authors searched PubMed Central, Embase, Scopus, Cochrane Central Register of Controlled Trials, Web of Science, and Google Scholar for original research studies up to February 2020 that included the following Medical Subject Headings keywords: words related to "radiotherapy" and synonyms combined with keywords related to "panoramic radiography" and "oral diagnosis" and synonyms. Only original studies in English that investigated the maxillofacial effects of radiotherapy via panoramic radiographs were included. The quality of the selected manuscripts was evaluated by assessing the risk of bias using Cochrane's ROBINS-I tool for non-randomized studies. Results: Thirty-three studies were eligible and included in this review. The main objectives pertained to the assessment of the effects of radiation on maxillofacial structures, including bone architecture alterations, periodontal space widening, teeth development abnormalities, osteoradionecrosis, and implant bone loss. The number of participants evaluated ranged from 8 to 176. Conclusion: The interaction between ionizing radiation and maxillofacial structures results in hazard to the tissues involved, particularly the bone tissue, periosteum, connective tissue of the mucosa, and endothelium. Hard tissue changes due to radiation therapy can be detected on panoramic radiographs.

• 한국융합학회논문지
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• 제12권9호
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• pp.31-37
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• 2021

최근들어 가전시장에서 융합기술을 이용한 제품 차별화는 소비자로부터 많은 호응을 얻고 있다. 그러나 에어컨 제품은 기계적 운영에서 센서와 플랫폼이 결합된 인공지능을 위한 융합기술이 적용하는 초기단계에 있어서 많은 연구개발이 필요한 분야이다. 본 논문에서는 IR-UWB 기술을 이용한 비접촉 방식의 생체신호(호흡수, 이동) 수집기술을 개발하였다. 생체신호를 이용하여 사용자의 위치에 따라 에어컨 방향을 제어한다. 또한 최적의 수면 환경을 제공하기 위해 수면상태를 모니터링 한다. 감성조명과 ASMR은 안락하고 감성적인 삶의 공간을 제공하기 위해 개발되었다. 그리고 개발된 융합기술을 기반으로 편리하고 안락한 휴식공간을 제공하는 지능형 스마트 에어컨 서비스 플랫폼을 제안하였다.

• 접착 및 계면
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• 제22권3호
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• pp.106-110
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• 2021

최근 친환경 소재, 특히 부산물을 활용한 연구가 주목을 받고 있다. 본 연구에서는 비료 제조 시 발생하는 공정 부산물인 석고(CaSO₄)를 고밀도 폴리에틸렌(High density polyethylene, HDPE)에 충전한 복합재료의 물성을 조사하였다. Co-rotating twin screw extruder를 이용하여 석고의 함량을 0~20 wt% 충전하여 복합재료를 제조하고 이의 기계적, 유변학적, 열적 특성을 평가하였다. 그 결과 인장강도는 미충전 HDPE 대비 4.1% 이하로 물성 저하가 크지 않다. 석고의 함량이 증가할수록 열적 안정성이 향상되었고 석고의 함량이 복합재료의 점도 특성에 거의 영향을 끼치지 않는 것을 확인하였다.

• 천문학회지
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• 제54권4호
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• pp.129-137
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• 2021

It has been established that the acoustic mode parameters of the Sun and Sun-like stars vary over activity cycles. Since the observed variations are not consistent with an activity-related origin, even Sun-like stars showing out-of-phase changes of mode frequencies and amplitudes need to be carefully studied using other observational quantities. In order to test whether the presumed relations between the global seismic parameters are a signature of the stellar activity cycle, we analyze the photometric light curve of HD 49933 for which the first direct detection of an asteroseismic signature for activity-induced variations in a Sun-like star was made, using observations by the CoRoT space telescope. We find that the amplitude of the envelope significantly anti-correlates with both the maximum frequency of the envelope and the width of the envelope unless superflare-like events completely contaminate the light curve. However, even though the photometric proxy for stellar magnetic activity appears to show relations with the global asteroseismic parameters, they are statistically insignificant. Therefore, we conclude that the global asteroseismic parameters can be utilized in cross-checking asteroseismic detections of activity-related variations in Sun-like stars, and that it is probably less secure and effective to construct a photometric magnetic activity proxy to indirectly correlate the global asteroseismic parameters. Finally, we seismically estimate the mass of HD 49933 based on our determination of the large separation of HD 49933 with evolutionary tracks computed by the MESA code and find a value of about 1.2M_☉ and a sub-solar metallicity of Z = 0.008, which agrees with the current consensus and with asteroseismic and non-asteroseismic data.

• 한국응용과학기술학회지
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• 제35권4호
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• pp.1031-1037
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• 2018

수용성 비이온고분자인 Polyvinylalcohol (PVA), Polyvinylpyrrolidone (PVP), Hydroxypropyl cellusoe (HPC)와 iodine과의 착물 형성에 대한 계면활성제의 영향을 알아보기 위해 Sodiumdodecylsulfate을 포함하는 수용액에서 이들 사이의 반응을 수행하였다. PVP와 HPC에서 tri-iodide band의 적색 이동에 의하여 착물이 만들어졌다는 것을 알게되었고, PVA-iodine 착물에서는 500 nm 부근에서 고유의 특색있는 띠를 나타내었다. SDS 계면활성제의 존재는 PVA-iodine 착물의 파괴를 가져왔고, 고유의 푸른색도 사라지게 만들었다. 그러나 SDS 단량체는 PVP, HPC와 iodine의 착물 형성을 도와주는 경향을 나타내었다. 고분자 용액에서 겔이 만들어지는 것을 방해하는 n-propanol은 고분자-iodine 착물이 형성되는 것을 도와주었다. SDS가 있을 때와 없을 경우의 영향을 알아보기 위해 순수한 HPC와 HPC-iodine 착물을 만들고 이들의 성질을 조사하였다.

• 한국분말재료학회지
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• 제26권1호
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• pp.49-57
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• 2019

Layered $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode materials single- and dual-doped by the rare-earth elements Ce and Nd are successfully fabricated by using a coprecipitation-assisted solid-phase method. For comparison purposes, non-doping pristine $LiNi_{0.83}Co_{0.11}Mn_{0.06}O_2$ cathode material is also prepared using the same method. The crystal structure, morphology, and electrochemical performances are characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) mapping, and electrochemical techniques. The XRD data demonstrates that all prepared samples maintain a typical ${\alpha}-NaFeO_2$-layered structure with the R-3m space group, and that the doped samples with Ce and/or Nd have lower cation mixing than that of pristine samples without doping. The results of SEM and EDS show that doped elements are uniformly distributed in all samples. The electrochemical performances of all doped samples are better than those of pristine samples without doping. In addition, the Ce/Nd dual-doped cathode material shows the best cycling performance and the least capacity loss. At a 10 C-rate, the electrodes of Ce/Nd dual-doped cathode material exhibit good capacity retention of 72.7, 58.5, and 45.2% after 100, 200, and 300 cycles, respectively, compared to those of pristine samples without doping (24.4, 11.1, and 8.0%).

• 디지털융복합연구
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• 제17권3호
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• pp.227-234
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• 2019

본 연구는 교육인프라가 취약한 아프리카 국가들의 교육 콘텐츠, 교실환경, 그리고 ICT기술에 대한 종합적인 보급을 위한 블록형 스마트교실 모델 제시를 목표로 한다. 수업관리시스템, 전력관리시스템 및 교실환경 관리시스템을 통합하는 상황별 솔루션을 제시하고, 아프리카 지역의 국가별 경제적, 비경제적 여건에 최적화가 가능한 융합 모델이 될 것이다. 이는 기존의 서비스, 콘텐츠, 솔루션에 대한 독립적 연구개발이나 단일 컨테이너로 보급된 기존교실과는 차별화되는 효율적인 모델이 될 수 있을 것이다. 이러한 통합 연구 과정을 통해 기존 컨테이너교실에서 나타나는 공간과 기능적 한계를 극복하고 이러닝 기술 고도화에 대비한 융통성 있는 공간을 구축한다. 향후 보다 다양한 지역의 교육 및 인프라 여건에 부합하는 성능과 모델에 대한 탐구로 후속 연구의 깊이와 범위의 확장이 가능할 것이다.