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        검색결과 414

        62.
        2022.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Effect of sulfation processes on the physicochemical properties of ZrO2 and TiO2 nanoparticles were thoroughly investigated. SO4/ZrO2 and SO4/TiO2 catalysts were synthesized to identify the acidity character of each. The wet impregnation method of ZrO2 and TiO2 nanoparticles was employed using H2SO4 with various concentrations of 0.5, 0.75, and 1 M, followed by calcination at 400, 500, and 600 °C to obtain optimum conditions of the catalyst synthesis process. The highest total acidity was found when using 1 M SO4/ZrO2-500 and 1 M SO4/TiO2-500 catalysts, with total acidity values of 2.642 and 6.920 mmol/ g, respectively. Sulfation increases titania particles via agglomeration. In contrast, sulfation did not practically change the size of zirconia particles. The sulfation process causes color of both catalyst particles to brighten due to the presence of sulfate. There was a decrease in surface area and pore volume of catalysts after sulfation; the materials’ mesoporous structural properties were confirmed. The 1 M SO4/ZrO2 and 1 M SO4/TiO2 catalysts calcined at 500 °C are the best candidate heterogeneous acid catalysts synthesized in thus work.
        4,000원
        63.
        2021.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Anion assisted [4 + 2] cycloaddition reaction via indolo[2,3]-dienolate by reacting 1,2-dimethylindole-3-carboxaldehyde with aromatic nitriles using lithium diisopropylamide in terahydrofuran, a facile and convenient regiospecific route designed and developed for the synthesis of γ-carbolines.
        4,000원
        64.
        2021.12 KCI 등재후보 구독 인증기관 무료, 개인회원 유료
        Leiomyosarcoma is malignant mesenchymal tumor of smooth muscle and commonly encountered in the gastrointestinal tract of dogs. However, primary canine leiomyosarcoma in oral cavity is rare due to lack of smooth muscle in the oral tissue. A 13-year-old, neutered male Poodle presented a hard and immobile mass on the left maxilla. Imprinting cytology from the mass as well as fine-needle aspirated cytology from the left scapular lymph node revealed predominant spindle cells met malignancy criteria of the tumors, including coarse chromatin, high N/C ratio, nuclear molding, macro/multi-nucleoli with cigar-shaped nucleus. Radiography of the skull showed lysis of the nasopalatine bone, and mineral radiopacity in the mass. Computed tomography showed soft tissue attenuating mass from the left incisor teeth to the left retrobulbar space with loss of nasopalatine bone and medial wall of orbit. The histopathological examination showed irregularly arranged malignant spindle-shaped cells with oval or elongated nuclei. The nucleolus is distinct and moderate cellular polymorphism is observed. Mitotic figures are occasionally observed. The tumor cells are positive to vimentin, desmin, α-smooth muscle actin when immunohistochemistry was performed, and in Masson’s trichrome stain, tumor cells are stained as red. Overall, histopathologic exam and immunohistochemistry confirmed canine oral leiomyosarcoma. Because of the poor prognosis, the owner did not consent further treatment.
        4,000원
        67.
        2021.10 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Biomass of agricultural waste is getting increasing attention all over the world as it is a kind of renewable, abundantly available, low cost, and environmentally friendly resource. Preparation of activated carbon from agricultural waste via microwave-assisted chemical agent activation. The porosity, surface area, and functional and surface chemistry were featured by means of low-temperature nitrogen adsorption, Scanning Electron Microscopy, (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). The best conditions resulted in activated carbon with adsorption capacity of 517.5 mg/g and carbon yield of 80.99%. The activated carbons from carbonized tobacco stem with K2CO3 activation by microwave radiation is highest of surface area, and total pore volume corresponded to 2557 m2/g, and 1.647 cm3/g, respectively, with a high contribution of mesopores, microwave power of 700 W, and irradiation time of 30 min. The results of the review showed that chemical activation could develop both microporosity and mesoporosity. The findings support the potential to prepare high surface area and micropore-activated carbon from agricultural waste by microwave-induced chemical activation.
        4,800원
        73.
        2021.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The synthesis of graphene and graphene quantum dots (GQDs) employing various approaches with a range of precursors, chemicals, and parameters has been reported. Most of the top-down and bottom-up techniques employ strong and hazardous chemical environments, complicated and tedious procedures, are time-consuming, and often require special equipment. Another drawback of the techniques reported is the production of agglomerated, inhomogeneous, and non-dispersible graphene in aqueous solvents or organic solvents, thus limiting its application. This work specifically and comprehensively describes the electrochemical exfoliation of graphene and GQDs, which is often considered as a simple one-step, facile, non-hazardous, and highly efficient technique yet favourable for mass production. A brief discussion on the advantageous and challenges of the electrochemical technique and applications of the electrochemically exfoliated graphene and GQDs is also presented.
        5,200원
        74.
        2021.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Composite materials offer distinct and unique properties that are not naturally inherited in the individual materials that make them. One of the most attractive composites to manufacture is the aluminum alloy matrix composite, because it usually combines easiness of availability, light weight, strength, and other favorable properties. In the current work, Powder Metallurgy Method (PMM) is used to prepare Al2024 matrix composites reinforced with different mixing ratios of yttrium oxide (Y2O3) particles. The tests performed on the composites include physical, mechanical, and tribological, as well as microstructure analysis via optical microscope. The results show that the experimental density slightly decreases while the porosity increases when the reinforcement ratio increases within the selected range of 0 ~ 20 wt%. Besides this, the yield strength, tensile strength, and Vickers hardness increase up to a 10 wt% Y2O3 ratio, after which they decline. Moreover, the wear results show that the composite follows the same paradigm for strength and hardness. It is concluded that this composite is ideal for application when higher strength is required from aluminum composites, as well as lighter weight up to certain values of Y2O3 ratio.
        4,000원
        75.
        2021.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Molecules possessing harmine moiety are reported to exhibit marked fungicidal and bactericidal activities. In this study, various quinozilinium tetrafluoroborate salts were synthesized using acylic and cyclic oxoketene dithioacetals followed by cycloaromatization from Harmine. All of these synthesized compounds were characterized by 1H NMR, 13C NMR, Mass and CHN analysis. This methodology would find wide usage in the preparation of indolo quinozilinium -based library of small molecules useful for medicinal chemistry and in drug discovery.
        4,000원
        77.
        2021.04 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The important thing in the field of deep learning is to find out the appropriate hyper-parameter for image classification. In this study, the main objective is to investigate the performance of various hyper-parameters in a convolutional neural network model based on the image classification problem. The dataset was obtained from the Kaggle dataset. The experiment was conducted through different hyper-parameters. For this proposal, Stochastic Gradient Descent without momentum (SGD), Adaptive Moment Estimation (Adam), Adagrad, Adamax optimizer, and the number of batch sizes (16, 32, 64, 120), and the number of epochs (50, 100, 150) were considered as hyper-parameters to determine the losses and accuracy of a model. In addition, Binary Cross-entropy Loss Function (BCLF) was used for evaluating the performance of a model. In this study, the VGG16 convolutional neural network was used for image classification. Empirical results demonstrated that a model had minimum losses obtain by Adagrad optimizer in the case of 16 batch sizes and 50 epochs. In addition, the SGD with a 32 batch sizes and 150 epochs and the Adam with a 64 batch sizes and 50 epochs had the best performance based on the loss value during the training process. Interestingly, the accuracy was higher while performing the Adagrad and Adamax optimizer with a 120 batch sizes and 150 epochs. In this study, the Adagrad optimizer with a 120 batch sizes and 150 epochs performed slightly better among those optimizers. In addition, an increasing number of epochs can improve the performance of accuracy. It can help to create a broader scope for further experiments on several datasets to perceive the suitable hyper-parameters for the convolutional neural network. Dataset: https://www.kaggle.com/c/dogs-vs-cats/data
        4,000원
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