• Journal of the Korean Society for Precision Engineering
• /
• v.19 no.10
• /
• pp.92-98
• /
• 2002

End mill is an essential tool to generate complex surface in workpiece and it has been developed with various materials and tool shapes. The most important factor to evaluate the performance of end mill is still the wear characteristics of flank face. In addition to the flank wear, the tool edge roughness generated by the chipping is another important factor in aspects of material property and machinability evaluation and affects the quality of machined surface. Up to now, there is no direct method for measurement of tool edge roughness. In this study, the tool edge roughness of flat end mill is indirectly measured along the axial direction of workpiece. The theoretical equation is derived in consideration of tool geometry. Finally, the optimal conditions to measure the tool edge roughness by the proposed method are presented through the theoretical review and experimental identification.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.04a
• /
• pp.1083-1087
• /
• 1997

End milling is available for machining the variable shape of products and has brrn widely applied in many Manufacturing industries. The surface finish of machined parts determines quality and functionality of products. Surface roughness causes friction,noise,fracture, glossiness and seizure, so many research had been performed to precisely. In particular an experimental analysis was carried out to investigate the influence ofsurface roughness on the fractal dimension. This parameter was assumed to contain not only information of roughness but also extra meaning. Experiments which were performed under various cutting conditions to compare fractal dimension with surface roughness R /sab a/ show fractal dimension to be useful parameter for determining of roughness.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.826-830
• /
• 2000

Sculptured surface machining plays a vital role in the process of bring new Products to the market place. A great variety of products rely on this technology for the production of the dies and moulds used in manufacturing. And, the use or CNC machines and CAD/CAM system has become a vital parts or product development process. But, cusp is inevitable by-product in sculptured surface machining, and it is very difficult to calculate the cusp height correctly. In this study, an analytical cusp height model is proposed considering the radius of the ball end mill, radius of machined workpiece and the inclined angle of convex or concave circular surface. Experiments were performed to check the validity of this proposed model and experimental results showed that the proposed cusp model were very effective.

• Korean Journal of Pharmacognosy
• /
• v.37 no.4 s.147
• /
• pp.307-313
• /
• 2006

Reactive oxygen species (ROS) and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic nephropathy by hyperglycemia. To find natural agents improving diabetic nephropathy, 63 natural resources which used to the treatment of diabetes mellitus in a folk remedy were investigated with an in vitro system employing radical scavenging activity and inhibitory activity of AGEs formation. In results, the extracts of Aspalathus linearis, Rubus coreanus, Rosa rugosa, and Epimedium koreanum significantly inhibited the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical with $IC_{50}$ values less than $10{\mu}g/ml$. The extracts of Zea mays, Cucurbita moschata, Cudrania tricuspidata, and Aspalathus linearis effectively reduced the formation of AGEs compared with the positive control $N-acetyl-_L-cystenine$ (NAC) and aminoguanidine (AG). In addition, the extracts of Aspalathus linearis, Commelina communis, Cornus officinalis, and Lespodeza cuneata showed the all inhibitory activity against DPPH radical and AGEs formation. Also, these resources definitely showed the radical scavenging activity against peroxynitrite $(ONOO^-)$ and hydroxyl radical $({\cdot}OH)$ relating to high glucose-induced ROS production. Thus, these results suggest that some natural resources may regulate the initiation and progression of diabetic nephropathy through inhibition of ROS production and AGEs formation.

• Korean Journal of Pharmacognosy
• /
• v.46 no.3
• /
• pp.260-267
• /
• 2015

Advanced glycation end products (AGEs) have been postulated to play a central role in the development of diabetic complications. A variety of different agents that inhibit AGEs have been under investigation. In this study, 111 herbal medicines from China have been investigated with an in vitro evaluation system using AGEs formation inhibitory activity. Of these, 9 herbal medicines (IC₅₀: <5 μg/ml) were found to have significant AGEs formation inhibitory activity. Particularly, herbal medicines Barleria cristata (leaves), Calotropis gigantea (stems), Ardisia virens (leaves), Dalbergia yunnanensis (leaves) Pittosporum runcatum (leaves), Ardisia japonica (leaves), Rhododendron racemosum (twigs), Oxyria sinensiss (aerial parts), Pyrrosia calvata (whole plants), showed more potent inhibitory activity (approximately 15-40 fold) than the positive control aminoguanidine (IC₅₀: 76.47 μg/ml).

• Korean Journal of Pharmacognosy
• /
• v.46 no.3
• /
• pp.250-259
• /
• 2015

Advanced glycation end products (AGEs) have been implicated in diabetic complications. In this study, the inhibitory effect on AGEs formation of 156 Korean herbal medicines has been evaluated. Among them, 15 Korean herbal medicines were showed to have significant effect (IC₅₀: <10 μg/ml) compared to positive reference, aminoguandine (IC₅₀: 76.47±4.81 μg/ml). Especially, four herbal medicines, Alnus firma (leaves, IC₅₀: 3.25±0.10 μg/ml), Juncus decipiens (whole plants, IC₅₀: 4.30±0.44 μg/ml), Smilax china (stems, IC₅₀: 3.55±0.21 μg/ml), and Vicia amoena (Aerial parts, IC₅₀: 4.25±0.06 μg/ml) showed more potent inhibitory activity approximately 8-24 fold) than the positive control aminoguanidine.

• Korean Journal of Pharmacognosy
• /
• v.46 no.3
• /
• pp.268-278
• /
• 2015

In this study, 80 herbal medicines from Vietnam have been investigated with an in vitro evaluation system using advanced glycation end products (AGEs) formation inhibitory activity. Of these, 10 herbal medicines (IC₅₀: <5 μg/ml) were found to have significant AGEs formation inhibitory activity. Particularly, herbal medicines Strobilanthes pateriformis (aerial parts), Rhodamnia dumetorum (twigs), Glochidion rubrum (twigs), Dipterocarpus obtusifolius (twigs), Bombax ceiba (twigs), Amesiodendron chinense (twigs), Bauhinia coccinea (twigs), Lithocarpus laouanensis (twigs), Bauhinia bracteata (twigs) and Connarus paniculatus (twigs), showed more potent inhibitory activity (approximately 16-31 fold) than the positive control aminoguanidine (IC₅₀: 76.47 μg/ml).

• Korean Journal of Pharmacognosy
• /
• v.40 no.4
• /
• pp.388-393
• /
• 2009

Advanced glycation end products (AGEs) have been implicated in the development of diabetic complications. The AGEs inhibitors or cross-link breakers attenuate various functional and structural manifestations of diabetic complications. In this study, 64 herbal medicines from China and Vietnam have been investigated with an in vitro evaluation system using AGEs inhibitory activity. Of these, eight herbal medicines ($IC_{50}$<50 ${\mu}g$/ml) were found to have strong AGEs inhibitory activity compared with aminoguanidine (14 days, $IC_{50}$=75.98 ${\mu}g$/ml; 28 days, $IC_{50}$=88.27 ${\mu}g$/ml). Particularly, four herbal medicines, Buddleja officinalis (whole plant), Syzygium cuminii (leaf), Eugenia caryophyllate (seed), and Paeonia suffruticosa (root) showed more potent inhibitory activity (approximately 5-6 fold) than the positive control aminoguanidine.

• The Korean Journal of Physiology and Pharmacology
• /
• v.18 no.1
• /
• pp.1-14
• /
• 2014

During long standing hyperglycaemic state in diabetes mellitus, glucose forms covalent adducts with the plasma proteins through a non-enzymatic process known as glycation. Protein glycation and formation of advanced glycation end products (AGEs) play an important role in the pathogenesis of diabetic complications like retinopathy, nephropathy, neuropathy, cardiomyopathy along with some other diseases such as rheumatoid arthritis, osteoporosis and aging. Glycation of proteins interferes with their normal functions by disrupting molecular conformation, altering enzymatic activity, and interfering with receptor functioning. AGEs form intra- and extracellular cross linking not only with proteins, but with some other endogenous key molecules including lipids and nucleic acids to contribute in the development of diabetic complications. Recent studies suggest that AGEs interact with plasma membrane localized receptors for AGEs (RAGE) to alter intracellular signaling, gene expression, release of pro-inflammatory molecules and free radicals. The present review discusses the glycation of plasma proteins such as albumin, fibrinogen, globulins and collagen to form different types of AGEs. Furthermore, the role of AGEs in the pathogenesis of diabetic complications including retinopathy, cataract, neuropathy, nephropathy and cardiomyopathy is also discussed.

• The Korean Journal of Physiology and Pharmacology
• /
• v.22 no.2
• /
• pp.193-201
• /
• 2018

Connective tissue growth factor (CTGF) is a novel fibrotic mediator, which is considered to mediate fibrosis through extracellular matrix (ECM) synthesis in diabetic cardiovascular complications. Statins have significant immunomodulatory effects and reduce vascular injury. We therefore examined whether fluvastatin has anti-fibrotic effects in vascular smooth muscle cells (VSMCs) and elucidated its putative transduction signals. We show that advanced glycation end products (AGEs) stimulated CTGF mRNA and protein expression in a time-dependent manner. AGE-induced CTGF expression was mediated via ERK1/2, JNK, and Egr-1 pathways, but not p38; consequently, cell proliferation and migration and ECM accumulation were regulated by CTGF signaling pathway. AGE-stimulated VSMC proliferation, migration, and ECM accumulation were blocked by fluvastatin. However, the inhibitory effect of fluvastatin was restored by administration of CTGF recombinant protein. AGE-induced VSMC proliferation was dependent on cell cycle arrest, thereby increasing G1/G0 phase. Fluvastatin repressed cell cycle regulatory genes cyclin D1 and Cdk4 and augmented cyclin-dependent kinase inhibitors p27 and p21 in AGE-induced VSMCs. Taken together, fluvastatin suppressed AGE-induced VSMC proliferation, migration, and ECM accumulation by targeting CTGF signaling mechanism. These findings might be evidence for CTGF as a potential therapeutic target in diabetic vasculature complication.