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        검색결과 4,227

        3.
        2024.04 구독 인증기관·개인회원 무료
        Green pesticides, derived from natural sources, have gained wider attention as an alternative approach to synthetic pesticides in managing polyphagous pests like Spodoptera litura. In this study, the methanolic flower extract of Nyctanthes arbor-tristis (Mx-Na-t) was subjected to chemical screening, and major peak area derivatives 3-Hydroxy-1,2-dimethyl-4(1H)-pyridone (3H-dp) and Tyrosol (Ty-ol) were identified. The toxicity against S. litura larvae of Mx-Na-t (at 500 ppm) was highest in third instars (96.4%), and for 3H-dp and Ty-ol (at 5 ppm) in II instars (76.5% and 81.4%, respectively). The growth and development of S. litura larvae and pupae were significantly reduced by all three extract and phytochemical treatments. Fecundity rates also declined with the treatments, from 1,020 eggs (control) to 540 eggs (Mx-Na-t), 741 eggs (3H-dp), and 721 eggs (Ty-ol). The extract and its active constituents decreased adult emergence and slowed total larval development in a dosedependent manner. The major gut enzymes of S. litura decreased in young larvae (II instar) exposed to Mx-Na-t, 3H-dp, and Ty-ol. Fourth instar midgut tissues were severely damaged by Mx-Na-t (250 ppm), 3H-dp, and Ty-ol (2.5 ppm) treatments, which induced structural damage to the epithelial cells and gut lumen. The earthworm Eisenia foetida was used to test for non-target toxicity. Crude Mx-Na-t at 500 ppm (13% and 3%) and 3H-dp (9.3% and 2.1%) and Ty-ol (10.2% and 1.5%) at 5 ppm produced lower mortality than the synthetic chemical cypermethrin at 1.0 ppm (27% and 18%) in filter paper and artificial soil assays, respectively. In addition, there was no significant change in earthworm weights under all three phytochemical treatments compared to controls. Additionally, the in-silico predictions of BeeTox and ProTox II indicated little or no toxicity toward honey bees and other nontargets associated with 3H-dp and Ty-ol. Overall these phyto-chemicals offer an effective pest management strategy.
        4.
        2024.03 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Oral bacterial infections substantially affect the development of various periodontal diseases and oral cancers. However, the molecular mechanisms underlying the association between Fusobacterium nucleatum (F. nucleatum ), a major periodontitis (PT)-associated pathogen, and these diseases require extensive research. Previously, our RNAsequencing analysis identified a few hundred differentially expressed genes in patients with PT and peri-implantitis (PI) than in healthy controls. Thus, in the present study using oral squamous cell carcinoma (OSCC) cells, we aimed to evaluate the effect of F. nucleatum infection on genes that are differentially regulated in patients with PT and PI. Human oral squamous cell carcinoma cell lines OSC-2O, HSC-4, and HN22 were used. These cells were infected with F. nucleatum at a multiplicity of infection of 100 for 3 hours at 37℃ in 5% CO2. Gene expression was then measured using reverse-transcription polymerase chain reaction. Among 18 genes tested, the expression of CSF3, an inflammation-related cytokine, was increased by F. nucleatum infection. Additionally, F. nucleatum infection increased the phosphorylation of AKT, p38 MAPK, and JNK in OSC-20 cells. Treatment with p38 MAPK (SB202190) and JNK (SP600125) inhibitors reduced the enhanced CSF3 expression induced by F. nucleatum infection. Overall, this study demonstrated that F. nucleatum promotes CSF3 expression in OSCC cells through p38 MAPK and JNK signaling pathways, suggesting that p38 MAPK and JNK inhibitors may help treat F. nucleatum-related periodontal diseases by suppressing CSF3 expression.
        4,000원
        5.
        2024.03 구독 인증기관·개인회원 무료
        6.
        2024.03 구독 인증기관·개인회원 무료
        In South Korea, the level of Highway Pavement Management System (HPMS) was developed since early 2000. During this time numbers of professional pavement condition monitoring equipment were developed and applied in the actual field. One of the remarkable results is 3D Pavement condition Monitoring profiler vehicle (3DPM) designed and developed in Korea Expressway Corporation Research Division (KECRD). Thanks to this equipment, The surface condition of current pavement can successfully be monitored and proper following management strategy cab be established. However, the inner condition of pavement layer cannot be monitored dur to limitation of 3DPM equipment. In this paper, Bending Beam Rheometer (BBR) mixture creep test was performed to verify the effectiveness of current 3DPM equipment. It was found that the current 3DPM equipment has reasonable feasibility on surveying pavement condition.
        7.
        2024.03 구독 인증기관·개인회원 무료
        Evaluation of low temperature performance of asphalt mixture is significant not only for mitigating transverse thermal cracking but also for preventing potential traffic accidents. In addition, the engineers in pavement agency need to inform the proper pavement section where urgent management is needed. Since early 2000, Korea Expressway Corporation Research Division (KECRD) developed an 3D Pavement condition Monitoring profiler vehicle (3DPM) to survey expressway pavement surface condition precisely. The management of whole expressway network became more precise, effective and efficient than before due to application of 3DPM and HPMS. One thing recommended is: performing extensive mechanical test and corresponding data analysis work procedure to further strengthen the feasibility of current 3DPM approach and HPMS. In this paper two activities were considered: first, the pavement section where the urgent care is recommended is selected by means of 3DPM approach. Then asphalt mixture cores were acquired on that specified section then low temperature fracture test: Semi Circular Bending (SCB) test, was performed. The mechanical parameters, energy release rate and fracture toughness were computed then compared. It is concluded that the current 3DPM approach in KEC can successfully evaluate and analyze selected pavement condition. However, more extensive experimental works are needed to further strengthen the current pavement analyzing approaches.
        8.
        2024.03 구독 인증기관·개인회원 무료
        본 연구는 특수한 조건에서의 줄눈 콘크리트포장의 설계 및 성능에 관한 분석을 목적으로 한다. 줄눈 콘크리트포장은 시멘트 콘크리트 포장의 한 형태로, 오랜 기간 도로 포장형식으로 사용되어 왔다. 이 포장 방식은 철근을 사용하지 않는 대신, 콘크리트 슬래브의 균열을 줄눈을 통해 유도하고, 다월바와 타이바를 통해 슬래브에 생기는 응력을 줄이는 방식이 다. 대한민국의 다양한 지역 환경과 계절적 특성은 도로 포장설계에 주요한 인자로 적용된다. 특히, 슬래브의 부등건조수 축이 평탄성 문제의 주요 원인으로 지적되며, 이는 온습도의 변화에 의해 발생한다. 본 연구에서는 3차원 유한요소해석 을 활용하여 줄눈 콘크리트포장 슬래브의 거동을 분석하고, 콘크리트 슬래브의 두께, 줄눈 간격, 타이바 및 다웰바의 배 치 등 주요 설계 변수의 영향을 평가한다. 이러한 설계 인자들이 슬래브의 응력과 변위에 미치는 영향을 확인하며, 다양 한 환경 조건 하에서의 설계 방법의 유효성을 검증한다. 본 연구는 줄눈 콘크리트포장의 실제 배치 방식을 모델링하여, 기존 설계 방식의 보안 사항을 파악하고, 설계 기준 내에서의 주요 인자 변화를 통해 부등건조수축을 완화할 수 있는 방 안을 제시한다. 이를 통해, 특수 환경 조건에서의 온습도 영향을 고려한 효율적인 포장 설계 방안을 도출함으로써, 도로 포장의 평탄성과 내구성 향상에 기여하고자 한다.
        9.
        2024.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this study, we investigated the microstructure and piezoelectric properties of 0.96(K0.456Na0.536)Nb0.95Sb0.05-0.04 Bi0.5(Na0.82K0.18)0.5ZrO3 (KNNS-BNKZ) ceramics based on one-step and two-step sintering processes. One-step sintering led to significant abnormal grain (AG) growth at temperatures above 1,085 °C. With increasing sintering temperature, piezoelectric and dielectric properties were enhanced, resulting in a high d33 = 506 pC/N for one-step specimen sintered at 1,100 °C (one-step 1,100 °C specimen). However, for one-step 1,115 °C specimen, a slight decrease in d33 was observed, emphasizing the importance of a high tetragonal (T) phase fraction for superior piezoelectric properties. Achieving a relative density above 84 % for samples sintered by the one-step sintering process was challenging. Conversely, two-step sintering significantly improved the relative density of KNNS-BNKZ ceramics up to 96 %, attributed to the control of AG nucleation in the first step and grain growth rate control in the second step. The quantity of AG nucleation was affected by the duration of the first step, determining the final microstructure. Despite having a lower T phase fraction than that of the one-step 1,100 °C specimen, the two-step specimen exhibited higher piezoelectric coefficients (d33 = 574 pC/N and kp = 0.5) than those of the one-step 1,100 °C specimen due to its higher relative density. Performance evaluation of magnetoelectric composite devices composed of one-step and twostep specimens showed that despite having a higher g33, the magnetoelectric composite with the one-step 1,100 °C specimen exhibited the lowest magnetoelectric voltage coefficient, due to its lowest kp. This study highlights the essential role of phase fraction and relative density in enhancing the performance of piezoelectric materials and devices, showcasing the effectiveness of the two-step sintering process for controlling the microstructure of ceramic materials containing volatile elements.
        4,000원
        10.
        2024.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In compliance with environmental regulations at sea and the introduction of unmanned autonomous ships, electric propulsion ships are garnering significant attention. Induction machines used as propulsion electric motor (PEM) have maintenance advantages, but speed control is very complicated and difficult. One of the most commonly used techniques for speed control is DTC (direct torque control). DTC is simple in the reference frame transformation and the stator flux calculation. Meanwhile, two-level and three-level voltage source inverters (VSI) are predominantly used. The three-level VSI has more flexibility in voltage space vector selection compared to the two-level VSI. In this paper, speed is controlled using the DTC method based on the specifications of the PEM. The speed controller employs a PI controller with anti-windup functionality. In addition, the characteristics of the two-level VSI and three-level VSI are compared under identical conditions. It was confirmed through simulation that proper control of speed and torque has been achieved. In particular, the torque ripple was small and control was possible with a low DC voltage at low speed in the three-level VSI. The study confirmed that the application of DTC, using a three-level VSI, contributes to enhancing the system's response performance.
        4,000원
        11.
        2024.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 실험에서는 α-Al2O3 지지체에 무전해도금을 이용하여 Pd-Ag-Cu 분리막을 제조하였다. Pd, Ag, Cu는 각각 무 전해도금을 통해 지지체 표면에 코팅하였고, 합금의 형성을 위해 무전해도금 중간에 H2, 500°C의 조건에서 18 h 동안 열처리 를 진행하였다. 이를 통해 제조된 Pd-Ag-Cu 분리막은 SEM을 통해 표면을 관찰하였으며, Pd 분리막의 두께는 7.82 μm, Pd-Ag-Cu 분리막의 두께는 3.54 μm로 측정되었다. EDS와 XRD 분석을 통해 Pd-Ag-Cu 합금이 Pd-78%, Ag-8.81%, Cu-13.19%의 조성으로 형성된 것을 확인하였다. 기체투과 실험은 H2 단일가스와 H2/N2 혼합가스에서 실험을 진행하였다. H2 단일가스에서 측정한 수소 분리막의 최대 H2 flux는 Pd 분리막의 경우 450°C, 4 bar에서 74.16 ml/cm2·min이고, Pd-Ag-Cu 분리막의 경우 450°C, 4 bar에서 113.64 ml/cm2·min인 것을 확인하였고, H2/N2 혼합가스에서 측정한 separation factor의 경우 450°C, 4 bar에서 각각 2437, 11032의 separation factor가 측정되었다.
        4,000원
        12.
        2024.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Composite-based piezoelectric devices are extensively studied to develop sustainable power supply and selfpowered devices owing to their excellent mechanical durability and output performance. In this study, we design a leadfree piezoelectric nanocomposite utilizing (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) nanomaterials for realizing highly flexible energy harvesters. To improve the output performance of the devices, we incorporate porous BCTZ nanowires (NWs) into the nanoparticle (NP)-based piezoelectric nanocomposite. BCTZ NPs and NWs are synthesized through the solidstate reaction and sol-gel-based electrospinning, respectively; subsequently, they are dispersed inside a polyimide matrix. The output performance of the energy harvesters is measured using an optimized measurement system during repetitive mechanical deformation by varying the composition of the NPs and NWs. A nanocomposite-based energy harvester with 4:1 weight ratio generates the maximum open-circuit voltage and short-circuit current of 0.83 V and 0.28 A, respectively. In this study, self-powered devices are constructed with enhanced output performance by using piezoelectric energy harvesting for application in flexible and wearable devices.
        4,000원
        13.
        2024.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The limitation of markers for chronic oral diseases such as oral lichen planus (OLP) and burning mouth syndrome (BMS) is a diagnostic challenge for clinicians. The pathogenesis of OLP and BMS is not yet fully understood. Therefore, diagnoses are mainly based on the observation of clinical features and history, rather than established markers. C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are used to determine the state of inflammation; however, these markers have some limitations. Recently, a new inflammatory marker, pentraxin-3 (PTX3), has been identified in other systemic inflammatory diseases. PTX3 is a member of the pentraxin family and is classified as a long pentraxin. PTX3 is found in various human tissues, whereas the classical short pentraxin, CRP, is secreted only in the liver. PTX3 is a marker of autoimmune diseases and periodontitis. However, there are no studies on PTX3 in OLP and BMS; therefore, we sought to determine if PTX3 can be a diagnostic marker for OLP and BMS. PTX3 was found to be correlated with other inflammatory markers, suggesting its diagnostic value for inflammatory oral diseases. We also found that the PTX3 levels were lower in patients with OLP and BMS. ESR levels were elevated in the OLP and BMS groups, but CRP levels were not. Despite these associations, no correlation was found between PTX3 expression and other known clinical features of OLP and BMS. We suggest that PTX3 plays a role in the immunological and neurological pathways involved in the complex pathogenesis of OLP and BMS.
        4,000원
        14.
        2024.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        New piezoelectric and triboelectric materials for energy harvesting are being widely researched to reduce their processing cost and complexity and to improve their energy conversion efficiency. In this study, BaTiO3 films of various thickness were deposited on Ni foams by R.F. magnetron sputtering to study the piezoelectric and triboelectric properties of the porous spongy structure materials. Then piezoelectric nanogenerators (PENGs) were prepared with spongy structured BaTiO3 and PDMS composite. The output performance exhibited a positive dependence on the thickness of the BaTiO3 film, pushing load, and poling. The PENG output voltage and current were 4.4 V and 0.453 μA at an applied stress of 120 N when poled with a 300 kV/cm electric field. The electrical properties of the fabricated PENG were stable even after 5,000 cycles of durability testing. The triboelectric nanogenerators (TENGs) were fabricated using spongy structured BaTiO3 and various polymer films as dielectrics and operated in a vertical contact separation mode. The maximum peak to peak voltage and current of the composite film-based triboelectric nanogenerator were 63.2 V and 6 μA, respectively. This study offers new insights into the design and fabrication of high output nanogenerators using spongy structured materials.
        4,000원
        15.
        2024.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Al2O3 has excellent sintering properties and is important in semiconductor manufacturing processes that require high-temperature resistance and chemical inertness in a plasma environment. In this study, a comprehensive analysis of the chemical characteristics, physical properties, crystal structure, and dispersion stability of three commercially available Al2O3 powders was conducted. The aim was to provide a technological foundation for selecting and utilizing appropriate Al2O3 powders in practical applications. All powders exhibited α-Al2O3 as the main phase, with the presence of beta-phase Na2O-11Al2O3 as the secondary phase. The highest Na+ ion leaching was observed in the aqueous slurry state due to the presence of the secondary phase. Although the average particle size difference among the three powders was not significant, distinct differences in particle size distribution were observed. ALG-1SH showed a broad particle size distribution, P162 exhibited a bimodal distribution, and AES-11 displayed a uniform unimodal distribution. Highconcentration Al2O3 slurries showed differences in viscosity due to ion release when no dispersant was added, affecting the electrical double-layer thickness. Polycarboxylate was found to effectively enhance the dispersion stability of all three powders. In the dispersion stability analysis, ALG-1SH exhibited the slowest sedimentation tendency, as evidenced by the low TSI value, while P162 showed faster precipitation, influenced by the particle size distribution.
        4,000원
        16.
        2024.01 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        In this investigation, samples of the chemical (Hg1-xPbxBa2Ca1.8Mg0.2Cu3O8+δ) were prepared utilizing a solid-state reaction technique with a range of lead concentrations (x = 0.0, 0.05, 0.10, and 0.20). Specimens were pressed at 8 tons per square centimeter and then prepared at 1,138 K in the furnace. The crystalline structure and surface topography of all samples were examined using X-ray diffraction (XRD) and atomic force microscopy (AFM). X-ray diffraction results showed that all of the prepared samples had a tetragonal crystal structure. Also, the results showed that when lead was partially replaced with mercury, an increase in the lead value impacted the phase ratio, and lattice parameter values. The AFM results likewise showed excellent crystalline consistency and remarkable homogeneity during processing. The electrical resistivity was calculated as a function of temperature, and the results showed that all samples had a contagious behavior, as the resistivity decreased with decreasing temperature. The critical temperature was calculated and found to change, from 102, 96, 107, and 119 K, when increasing the lead values in the samples from 0.0 to 0.05, 0.10, and 0.20, respectively.
        4,000원
        17.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Hierarchically porous carbon foam composites with highly dispersed Fe2O3 nanoparticles confined in the foam pores, facilely fabricated by hydrolysis-driven emulsion polymerization strategy. The as-generated acidic conditions of Fe3+ hydrolysis could catalyze the polymerization of phenolic resin, and the carbon-based composite materials containing iron oxides were obtained in situ. The structural characterization results show that HCF@Fe2O3 NPs-2 electrode has the largest specific surface area (549 m2/ g) and pore volume (0.46 cm3/ g). Electrochemical results indicates that typical HCF@Fe2O3 NPs-2 electrode displays good capacitive properties. including high specific capacitance (225 F/g at 0.2 A/g current density). Excellent magnification performance (capacity retention rate 80% as current density increases from 0.2 to 10 A/g). At the same time, HCF@SnO2 NPs was successfully synthesized by replacing hydrolyzed tin tetrachloride with ferric chloride. This study provides a new idea for the preparation of metal oxide–carbon matrix composites, and also highlights the potential of such carbon foams in application of energy storage.
        4,000원
        18.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Pharmaceutical products occurring in freshwater bodies create numerous problems for the water bodies owing to their bio-toxic nature. In order to remove such pharmaceutical pollutants, a novel Er-doped Bi4O5Br2/ g-C3N5 nanocomposite was prepared by one-pot synthesis and applied for the photocatalytic removal process. The Er ions doped on the surface of Bi4O5Br2/ g-C3N5 nanocomposite exhibited 97% degradation of tetracycline in 60 min under visible light irradiation, which is higher than pure g-C3N5 and Bi4O5Br2 photocatalysts. The improved photocatalytic properties are attributed to the outstanding visible light harvesting capacity and quick charge carrier separation efficiency which greatly reduced the recombination rate in the heterojunctions. Based on radical trapping experiments, the •O2 −, h+ and •OH radicals played a prominent role in the photodegradation reactions under visible light. Finally, the ternary Er-doped Bi4O5Br2/ g-C3N5 nanocomposite is effectively recyclable with quite a stable photocatalytic removal rate. This work enables a new perspective on the rational design of rare-earth-based nanocomposites for various pharmaceutical pollutants treatment processes.
        4,000원
        19.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Exploring cheap and efficient oxygen evolution reaction (OER) catalysts is extremely vital for the commercial application of advanced energy storage and conversion systems. Herein, a self-supporting Co3S4/ S-doped reduced graphene oxide ( Co3S4/S-rGO) film catalyst is successfully prepared by a blade coating coupled with high-temperature annealing strategy, and its morphology, structure and composition are measured and analyzed. It is substantiated that the as-synthesized Co3S4/ S-rGO film possesses unique self-supporting structure, and is composed of uniformly dispersed Co3S4 nanoparticles and highly conductive S-rGO, which benefit the exposure of catalytic sites and electron transfer. By reason of the synergistic effect of the two individual components, the self-supporting Co3S4/ S-rGO film catalyst displays outstanding catalytic performance towards OER. As a consequence, the Co3S4/ S-rGO film catalyst delivers an overpotential of 341 mV at 10 mA cm-2, and the current attenuation rate is only 2.6% after continuous operation for 4 h, verifying excellent catalytic activity and durability. Clearly, our results offers a good example for the construction of high-performance self-supporting carbon-based composite film catalysts for critical electrocatalytic reactions.
        4,000원
        20.
        2023.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 연구는 중국의 3세 유아의 놀이성과 자기 조절력이 사회적 유능성 에 미치는 영향을 파악하고자 하였다. 이를 위해 중국 산시성에 위치한 공·사립 유치원 5곳에 재원 중인 3세 유아 600명을 대상으로 담임교사를 통해 설문지 조사를 수행하였다. 해당 유치원의 원장 및 담임교사에게 설문지를 위한 방문 및 온라인으로 협조문을 보내 참여 의사 확인 후 ‘문권성(问卷星)’ 온라인 플랫폼을 통해 설문자료를 수집하였다. 수집된 설문지는 SPSS 23.0 프로그램을 이용하여 빈도분석, 탐색적 요인분석과 신뢰도 분석, 다중회귀분석을 수행하였다. 이를 통해 유아교육 현장에서 유아의 놀이성과 자기조절력을 향상시킬 수 있는 교수·학습 방법을 모색 하는데 도움을 주고자 한다. 또한 유아의 사회적 유능성을 증진시키는데 필요한 교사교육 및 프로그램 개발에도 기초자료를 제공하고자 한다.
        6,300원
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