The effect of ceramic fiber on the rheological and mechanical properties of porous Al2O3 ceramics

Kamrun Nahar Fatema,Hyung Mi Lim,Joung Sook Hong,Kee Sung Lee,Ik Jin Kim 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.1

Porous ceramics having oriented pores find widespread use in filtration, insulation, biomaterials, and catalysis. Because of theshape of the interconnected pores, porous alumina (Al2O3) ceramics synthesized via direct foaming have poor mechanicalstrength. The physical and mechanical characteristics of porous Al2O3 ceramics were systematically explored in this work bymodulating the microstructure and rheological properties by the inclusion of ceramic fibers. Because of the incorporation ofceramic fibers, the fiber-containing wall structure is generated in porous ceramics. The physical properties and mechanicalstrength of porous ceramics increase as the fiber content increases. To stabilize the wet foam and enhance the mechanicalproperties of the porous ceramics, ceramic fibers are added to the Al2O3 colloidal suspension. With 2.0 wt.% ceramic fibers,wet foam stability of 84% was obtained. Adequate addition of 2.0 wt.% ceramic fibers in the slurry may improve compressivestrength, however excess fibers reduce compressive strength. The load-bearing capacity and elastic modulus of sinteredsamples were determined using the Hertzian indentation method. The load-bearing capacity and elastic modulus increasedfrom 65.35 to 235.45 N and 28.52 to 270.75 MPa, respectively, as the ceramic fiber content increased from 0.5 to 3.0 wt.%.

Implementation of IoT Using Flask Web Server

Kamrun Nahar(나하르 캄룬),Tae-Kook Kim(김태국) 대한전자공학회 2022 대한전자공학회 학술대회 Vol.2022 No.6

Biological Activities of Five Weed Extracts against Callosobruchus chinensis L. (Coleoptera: Bruchidae)

Md Abdul Ahad,Mst Kamrun Nahar,Md Ruhul Amin,Sang Jae Suh,Yong Jung Kwon 한국응용곤충학회 2015 한국응용곤충학회지 Vol.54 No.2

Mimosa pudica (미모사), Argemone mexicana (멕시코 가시양귀비) Leucus aspara (꿀풀과 일종), Polygonum hydropiper (여뀌), Blumea lacera (국화과 일종) 등 5종의 식물 헥산추출물들의 팥바구미 성충에 대한 살충, 성충우화억제력 및 녹두 종실피해 방제력이 검증되었다. 그 결과, 밭바구미 성충 살충력은 35-69%이었으며, 녹두에 추출물을 처리한 후 성충우화 방제율은 33-63%, 종실 피해 방제율은 13-49%이었다. 추출물의 농도가 증가할수록 살충력, 성충우화 및 종실피해 방제율 등이 증가하는 것으로 나타났다. 이와 같이 5종의 식물 헥산추출물들은 밭바구미 친환경 방제제로 이용가능성이 있을 것으로 판단된다. This study was conducted with n-hexane extracts of sensitive plant Mimosa pudica, mexican poppy Argemone mexicana, panimarich Leucus aspara, water pepper Polygonum hydropiper and shialmutra Blumea lacera weeds against pulse beetle Callosobruchus chinensis (Coleoptera: Bruchidae) for protection of mung bean Vigna radiata grains. The LC50 values of the weed extracts ranged from 4.5 to 6.4, 4.1 to 5.6 and 3.6 to 5.5 g/100 mL at 24, 48 and 72 hours of post treatment, respectively. The extracts showed 35 to 69% fecundity and 33 to 63% adult emergence inhibitory effect on the pest, and revealed 13 to 49% grain protection of mung beans. Insect mortality, fecundity and adult emergence inhibitory effects, and grain protection activity increased with increased concentration of the extracts. The shialmutra followed by water pepper extracts revealed better performances in fecundity and adult beetle emergence inhibitory effect compared to the other weeds. The findings proved that the n-hexane extracts of the five weeds are sources of botanical insecticides which may be used in the integrated management of C. chinensis.

Surface modifi cation and electrochemical performance of KMnO 4 -ultra-surface area activated carbon (USAC) composites as cathode material

Zambaga Otgonbayar,Kamrun Nahar Fatema,Md Nazmodduha Rafat,Jihyeon Ryu,양선혜,Ick-Jun Kim,Won Chun Oh 한국세라믹학회 2020 한국세라믹학회지 Vol.57 No.5

The goal of this study was to analyse the impact of a combination of a sub-active material (KMnO 4 ) with surface modifi cation to the activated carbon surface for enhanced cathode performance. Activated carbon with ultra-specifi c surface area (USAC, TCK-PBM, 2560.4 m 2 /g) was used for the preparation of our composite with potassium permanganate (KMnO 4 ). The physical characteristics of this As-treated USAC sample were analysed through XRD, SEM and EDX analysis. The XRD analysis was used to examine structural properties; surface analysis undertaken by SEM; EDX analysis was used to measure the metal content of the sample as well as the content after treatment with KMnO 4 . It was shown USAC treated with KMnO 4 had more than a 10.5 μg acidic group by the Boehm titration method. The electrochemical properties of KMnO 4 -USAC were investigated for varying electrolyte concentration (0.1, 0.5, 1.2 and 6 M) at ambient temperature (25 °C) and the electrode showed great electrochemical performance after ten cycles.

Nitric oxide-induced salt stress tolerance in plants: ROS metabolism, signaling, and molecular interactions

Mirza Hasanuzzaman,Hirosuke Oku,Kamrun Nahar,M. H. M. Borhannuddin Bhuyan,Jubayer Al Mahmud,Frantisek Baluska,Masayuki Fujita 한국식물생명공학회 2018 Plant biotechnology reports Vol.12 No.2

Nitric oxide (NO), a non-charged, small, gaseous free-radical, is a signaling molecule in all plant cells. Several studies have proposed multifarious physiological roles for NO, from seed germination to plant maturation and senescence. Nitric oxide is thought to act as an antioxidant, quenching ROS during oxidative stress and reducing lipid peroxidation. NO also mediates photosynthesis and stomatal conductance and regulates programmed cell death, thus providing tolerance to abiotic stress. In mitochondria, NO participates in the electron transport pathway. Nitric oxide synthase and nitrate reductase are the key enzymes involved in NO-biosynthesis in aerobic plants, but non-enzymatic pathways have been reported as well. Nitric oxide can interact with a broad range of molecules, leading to the modification of protein activity, GSH biosynthesis, S-nitrosylation, peroxynitrite formation, proline accumulation, etc., to sustain stress tolerance. In addition to these interactions, NO interacts with fatty acids to form nitro-fatty acids as signals for antioxidant defense. Polyamines and NO interact positively to increase polyamine content and activity. A large number of genes are reprogrammed by NO; among these genes, proline metabolism genes are upregulated. Exogenous NO application is also shown to be involved in salinity tolerance and/ or resistance via growth promotion, reversing oxidative damage and maintaining ion homeostasis. This review highlights NO-mediated salinity-stress tolerance in plants, including NO biosynthesis, regulation, and signaling. Nitric oxide-mediated ROS metabolism, antioxidant defense, and gene expression and the interactions of NO with other bioactive molecules are also discussed. We conclude the review with a discussion of unsolved issues and suggestions for future research.

Exogenous jasmonic acid modulates the physiology, antioxidant defense and glyoxalase systems in imparting drought stress tolerance in different Brassica species

Md. Mahabub Alam,Masayuki Fujita,Kamrun Nahar,Mirza Hasanuzzaman 한국식물생명공학회 2014 Plant biotechnology reports Vol.8 No.3

This study examined the ability of jasmonicacid (JA) to enhance drought tolerance in different Brassicaspecies in terms of physiological parameters, antioxidantsdefense, and glyoxalase system. Ten-day-oldseedlings were exposed to drought (15 % polyethyleneglycol, PEG-6000) either alone or in combination with0.5 mM JA. Drought significantly increased lipoxygenaseactivity and oxidative stress, levels of malondialdehyde andH2O2. Drought reduced seedling biomass, chlorophyll (chl)content, and leaf relative water content (RWC). Droughtincreased proline, oxidized ascorbate (DHA) and glutathionedisulfide (GSSG) levels. Drought affected differentspecies differently: in B. napus, catalase (CAT) and glyoxalaseII (Gly II) activities were decreased, while glutathione-S-transferase (GST) and glutathione peroxidase(GPX) activities were increased in drought-stressed comparedto unstressed plants; in B. campestris, activities ofglutathione reductase (GR), glyoxalase I (Gly I), GST, andGPX were increased, monodehydroascorbate reductase(MDHAR), dehydroascorbate reductase (DHAR), CAT andother enzymes were decreased; in B. juncea, activities ofascorbate peroxidase, GR, GPX, Gly I were increased; GlyII activity was decreased and other enzymes did notchange. Spraying drought-stressed seedlings with JAincreased GR and Gly I activities in B. napus; increasedMDHAR activity in B. campestris; and increased DHAR,GR, GPX, Gly I and Gly II activities in B. juncea. JAimproved fresh weight, chl, RWC in all species, dry weightincreased only in B. juncea. Brassica juncea had the lowestoxidative stress under drought, indicating its naturaldrought tolerance capacity. The JA improved drought toleranceof B. juncea to the highest level among studiedspecies.