• Structural Engineering and Mechanics
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• 제43권5호
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• pp.657-678
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• 2012

The mismatch of ply orientations in composite laminates can cause high interlaminar stress concentrations near the free edges. Evaluation of these interlaminar stresses and their role in the progressive damage analysis of laminates is desirable. Recently, the authors developed a new method to relate the physically based micromechanics approach with the meso-scale CDM considering matrix cracking and induced delamination. In this paper, the developed method is applied for the analysis of edge effects in various angle-ply laminates such as $[10/-10]_{2s}$, $[30/-30]_{2s}$ and $[45/-45]_{2s}$ and comparing the results with available traditional CDM and experimental results. It is shown that the obtained stress-strain behaviors of laminates are in good agreement with the available experimental results and even in better agreement than the traditional CDM results. Variations of the stresses and stiffness components through the laminate thickness and near the free edges are also computed and compared with the available CDM results.

• 대한의생명과학회지
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• 제16권2호
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• pp.91-95
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• 2010

Meso-dihydroguaiaretic acid (MDGA) is a medicinal herbal product isolated from the bark of Machilus thunbergii Sieb. et Zucc. (Lauraceae). It exhibits a neuroprotective effect and also exerts cytotoxicity to certain cancer cells. In the present study, we investigated whether or not MDGA inhibits inflammatory reaction through the inhibition of nitric oxide (NO) generation. The results showed that MDGA (5~$25 {\mu}M$) inhibited 100 ng/ml lipopolysaccharide (LPS)- induced NO generation in macrophage Raw 264.7 cells in a concentration-dependent manner. We also measured the cytotoxic effects of MDGA on Raw 264.7 cells and found no evidence of cytotoxicity. The inhibition of NO generation by MDGA was consistent with the inhibitory effect on the expression of inducible nitric oxide synthase (iNOS). In addition, MDGA inhibited the LPS-induced gene expression of $interleukin-1{\beta}$ $(IL-1{\beta})$ as well as tumor necrosis $factor-{\alpha}$ $(TNF-{\alpha})$. The present results may provide that MDGA has anti-inflammatory properties through inhibition of the toll-like receptors (TLRs) pathway, and suggest that MDGA can be used as an anti-inflammatory agent.

• Computers and Concrete
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• 제24권3호
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• pp.207-222
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• 2019

This paper has presented an effective and accurate meso-scale finite element model for simulating the fracture process of concrete under compression-shear loading. In the proposed model, concrete is parted into four important phases: aggregates, cement matrix, interfacial transition zone (ITZ), and the initial defects. Aggregate particles were modelled as randomly distributed polygons with a varying size according to the sieve curve developed by Fuller and Thompson. With regard to initial defects, only voids are considered. Cohesive elements with zero thickness are inserted into the initial mesh of cement matrix and along the interface between aggregate and cement matrix to simulate the cracking process of concrete. The constitutive model provided by ABAQUS is modified based on Wang's experiment and used to describe the failure behaviour of cohesive elements. User defined programs for aggregate delivery, cohesive element insertion and modified facture constitutive model are developed based on Python language, and embedded into the commercial FEM package ABAQUS. The effectiveness and accuracy of the proposed model are firstly identified by comparing the numerical results with the experimental ones, and then it is used to investigate the effect of meso-structure on the macro behavior of concrete. The shear strength of concrete under different pressures is also involved in this study, which could provide a reference for the macroscopic simulation of concrete component under shear force.

• Computers and Concrete
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• 제33권6호
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• pp.671-688
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• 2024

The modeling efficiency of concrete meso-models close to real concrete is one of the important issues that limit the accuracy of mechanical simulation. In order to improve the modeling efficiency and the closeness of the numerical aggregate shape to the real aggregate, this paper proposes a method for generating a two-dimensional concrete meso-model based on pixel matrix and skeleton theory. First, initial concrete model (a container for placing aggregate) is generated using pixel matrix. Then, the skeleton curve of the residual space that is the model after excluding the existing aggregate is obtained using a thinning algorithm. Finally, the final model is obtained by placing the aggregate according to the curve branching points. Compared with the traditional Monte Carlo placement method, the proposed method greatly reduces the number of overlaps between aggregates by up to 95%, and the placement efficiency does not significantly decrease with increasing aggregate content. The model developed is close to the actual concrete experiments in terms of aggregate gradation, aspect ratio, asymmetry, concavity and convexity, and old-new mortar ratio, cracking form, and stress-strain curve. In addition, the cracking loss process of concrete under uniaxial compression was explained at the mesoscale.

• 한국공작기계학회논문집
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• 제16권2호
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• pp.23-29
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• 2007

Fracture behavior of brittle solids such as rocks, ceramics and concrete is closely related to microcracking. A meso-scale analysis method using the natural element method is proposed for the analysis of material damage of brittle microcracking solids. The microcracking is assumed to occur along Voronoi edges in the Voronoi diagram generated using the nodal points as the generators. The mechanical effect of microcracks is considered by controlling the material constants in the neighborhood of the microcracks. The proposed meso analysis method is applied to the simulation of the microcracking behaviors of brittle solids subjected to uniaxial and biaxial macrostress. The obtained results are in good agreement with the results by computational damage mechanics model. The validity of the proposed method has been demonstrated by these numerical examples.

• Journal of Microbiology and Biotechnology
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• 제5권5호
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• pp.250-256
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• 1995

The ddh gene encoding meso-diaminopimelate (meso-DAP)-dehydrogenase (DDH) in Brevibacterium lactofermentum was isolated by complementation of the Escherichia coli dapD mutation. It was supposed from subcloning experiments and complementation tests that the evidence for DDH activity appeared in about 2.5 kb Xhol fragmented genome. The 2.5 kb Xhol fragment containing the ddh gene was sequenced, and an open reading frame of 960 bp encoding a polypeptide comprising 320 amino acids was found. Computer analysis indicated that the deduced amino acid of the B. lactofermentum ddh gene showed a high homology with that of the Corynebacterium glutamicum ddh gene.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.377-382
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• 2005

This paper describes the design of micro machine tools system for mechanical machining of micro/meso scale mechanical parts. The micro machining systems such as $\mu-Late$, $\mu-milling/drilling$ machine and $\mu-grinding$ machine are the basic elements constructing $\mu-factory$ which gains more attention recently because of increasing needs of mico and nano-parts in various industrial and medical area. A miniaturized 3-axis milling machine with VCM stage and air spindle and palm-top size micro-late are designed, and air bearing stage and stepwise linear motion system with PZT are studied for motion system. The micro cutting characteristics are investigated experimentally, and reconfigurable machine structures are also considered.

• Bulletin of the Korean Chemical Society
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• 제13권1호
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• pp.59-64
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• 1992

The contrasting behaviour of meso-and d,l-$D_3$-trishomocubylidene-$D_3$-trishomocubane (1 and 2) in the electrophilic addition reaction, the former giving rearranged spiro compound (1a and 1b) and the latter giving 1,2-adduct (2a and 2b), has been explained as arising from the secondary steric effects based on computational evidence. As the degree of out-of-plane deformation of the olefinic carbon atoms increases with reaction progress, the resulting internal congestion in the region behind the double bond becomes unbearably large in meso-1. The absence of symmetry plane across the double bond of d,l-2 helps for the closing fragments to adjust themselves.

• 한국산업융합학회 논문집
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• 제9권1호
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• pp.87-91
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• 2006

This research exposes the process of carbonization of solid waste from the city and the method of activated, as well as the process of meso-porous under several test conditions. In addition, it is expected that the active carbon obtained through this process can be used as filter for air and sewage treatment, and can absorb dioxin(as almost 60-80% of meso-porous and porous properties area) unlike the existing active carbon.

• 대한핵의학회지
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• 제29권1호
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• pp.110-117
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• 1995

Tc-99m Labeled hexamethylenepropyleneamineoxime ([$^{99m}Tc$]-HMPAO) is a famous amino-oxime compound and is widely used to construct SPECT images of cerebral blood flow. To investigate the relationship between chemical structure and radiolabeling in these kind of diamine-oxime compounds, we synthesized seven compounds by Schiff's base formation and successive reduction with sodium borohydride. They were (RR/SS )-4,8-diaza-3,6,6,9-tetramethylundecane-2,10-dione bisoxime (2), (RR/SS/meso)-4,8-diaza-3,9-dimethy-lundecane-2,10-dione bisoxime (4), (RR/SS/meso)-4,8-diaza-3,10-dimethyldodecane-2,11-dione bisoxime (5), (RR/SS/meso)-4,7-diaza-3,6,6,8-tetramethyldecane-2,9-dione bisoxime (8), (RR/SS/meso)-4,7-diaza-5,6-cyclohexyl-3,8-dimethyldecane-2,9-dione bisoxime (10), (RR/SS/meso)-3,4-bis(1-aza-2-methyl-3-oxime-1-butyl)-benzoic acid (12), and (RR/SS/ meso)-2,3-bis(1-aza-2-methyl-3-oxime-1-butyl) benzophenone (14). Chemical structures of all the synthesized compounds were identified by taking $^1H$ spectrum. Among them, 2 and 4 are propyleneamine oxime (PnAO), 6 is butyleneamine oxime (BnAO) and 8, 10, 12 and 14 are ethyleneamine oxime (EnAO). Each compound (0.5 mg) was incubated with stannous chloride (0.5 g - 8 g), carbonate-bicarbonate buffer (final concentration = 0.1 M, pH 7 - pH 10) and Tc-99m-pertechenate (1 ml). Tc-99m labeling of these compounds were checked by ITLC (acetone), ITLC (normal saline), reverse phase TLC (50 % acetonitrile) and ITLC (ethyl acetate). According to the results, EnAO's were not labeled by Tc-99m in any of above condition. About 11 % of maximum labeling efficiency was obtained with BnAO. However, 4 (PnAO) was labeled with Tc-99m to 85 % which is similar to the labeling efficiency of 2 (HMPAO). Hydrophilic impurity (9 % ) was the most significant problem with the labeling of 4, however, pertechnetate (3 % ) and colloid (3 %) were minor problem. In conclusion, we synthesized seven diamine blsoxlme compounds. Among them, four EnAO compounds were not labeled by Tc-99m. A BnAO was labeled poorly and two PnAO's were labeled well. These labeling can be explained by tertiary structure of their Tc-99m chelate.