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An Experiment to Explain Depth of Cut Notch Wear of Ceramic Tools in Ni- based Super-alloy Machining

厦门大学学报（自然科学版） 2002年第S1期41卷 86-87页

作者： WANG Zhi-gang 1, HE Ning 2 (1. Dept. of Mechanical Engineering, national university of singapore, singapore 2. Dept. of Mechanical Engineering, Nanjing university of Aero.& Astro , Nanj ing 210016, China)

Inconel 718, a high temperature alloy, is extensive ly used in aircraft, gas engines and nuclear-power plants. It is generally known that the life of ceramic cutting tools in machining Inconel 718 is often restric ted by depth-of-cut (DOC) notch wear. In view of the number of various factors involved and the variety of tool materi als and cutting conditions available, the analysis of the DOC notch wear is very difficult. According to previous work concerning the DOC notch wear of ceramics tools, some Al 2O 3 - and Si 3N 4 -based ceramics tools have show n that the degree of tool notching depends on the thermal shock resistance of a tool material and thermal gradients (interrupted cutting, use of flood coolants) . Other observations suggest that there are chemical interactions between the to ol material and the work-piece. At the same time, an analytical technique based on thermodynamic properties for estimating cutting tool wear was proposed. Howe ver, so far, there is no concrete and convincing explanation for the DOC notch w ear. In all previous studies on the DOC notch wear, it is often assumed that notch we ar happened in the contacting region of the cutting tool and the work-piece, wh ile the exact position of notch wear is always neglected. In his article, He Ning measured the distance l n between tool nose and the center of DOC notch wear, and calculated the theoretical working length l d ― the ideal distance between the DOC notch center and the intersection of th e theoretical depth of cut line and the cutting edge. He found that l n is always greater than l d. It means that the position of the DOC notch is not at the depth of cut line, but out of the theoretical cutting area. He supposed that the saw-tooth shaped burrs and fin-shaped chip edges cause the DOC no tch wear, because only the saw-tooth shaped burrs and fin-shaped chip edges ha ve effect on the tools at the region of notch wear. Although He described the reason of notch wear and did some theoreti

关键词： notch wear ceramic tool high speed machining

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Stability of randomly amplified polymorphic DNA fingerprinting in genotyping clinical isolates of Helicobacter pylori

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World Journal of Gastroenterology 2003年第9期9卷 2021-2024页

作者： Feng-Chan Han Han-Chong Ng Bow Ho department of Microbiology,Faculty of Medicine,national university of singapore,5 Science Drive 2,singapore 117595,Republic of singapore department of Microbiology Faculty of Medicine National University of Singapore Republic of Singapore. biohanfc@***

AIM: Hpylorigenomes are highly diversified. This project was designed to genotype Hpyloriisolates by the polymerase chain reaction (PCR)-based randomly amplified polymorphic DNA (RAPD) fingerprinting technique and to verify its stability by Southern blotting and DNA ***: Clinical isolates of Hpyloriwere cultured from gastric antra and cardia of 73 individuals, and genomic DNA was prepared for each isolate. RAPD was carried out under optimized conditions. 23S rDNA was regarded as an internal control, and a 361 bp rDNA fragment (RDF) was used as a probe to screen the RAPD products by Southern *** RDFs from different clinical isolates and the flanking regions (both upstream and downstream) of four RDFs were amplified and ***: Hpyloriisolates from different individuals had different RAPD profiles, but the profiles for isolates cultured from different gastric sites of a given individual were identical in all but one case. Isolates from 27 individuals were RDF positive by Southern blotting. Sequences of the RDFs and their flanking regions were almost the same between the RDF positive and negative isolates as determined by Southern blotting. There was no binding site for random PCR primer inside the ***: RAPD is very useful in genotyping H pylori grossly on a large scale. However, it seems unstable in amplification of low yield fragments, especially those that do not appear as visible bands on the agarose gel stained with EB, since the palmer is partially matched to the template.

关键词：幽门螺杆菌基因型聚合酶链反应基因多态性

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Rate-oriented perceptual image coding using contrast-based quantization

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Chinese Optics Letters 2010年第4期8卷 381-383页

作者：余卫宇田菁 School of Electronic and Information Engineering South China University of Technology School of Electrical and Electronic Engineering Nanyang Technological University

A new image coding approach is proposed by controlling the quantization step via minimizing the perceptual distortions（in terms of image＇s contrast measurement）.The proposed method is a rate-oriented contrast-based approach,which is in contrast to the conventional quality-oriented contrast-based image *** algorithm achieves a higher perceptual quality performance against several methods developed previously.

关键词： Visual communication

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Effect of rock mass structure and block size on the slope stability——Physical modeling and discrete element simulation

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Science China(Technological Sciences) 2005年第Z1期48卷 1-17页

作者： LI Shihai1, LIAN Zhenzhong1,2 & J. G. Wang3 1. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2. Graduate School, Chinese Academy of Sciences, Beijing 100060, China 3. Tropical Marine Science Institute, national university of singapore, singapore 119260 Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100060 China Tropical Marine Science Institute National University of Singapore Singapore 119260 Singapore

This paper studies the stability of jointed rock slopes by using our improved three-dimensional discrete element methods (DEM) and physical modeling. Results show that the DEM can simulate all failure modes of rock slopes with different joint configurations. The stress in each rock block is not homogeneous and blocks rotate in failure development. Failure modes depend on the configuration of joints. Toppling failure is observed for the slope with straight joints and sliding failure is observed for the slope with staged joints. The DEM results are also compared with those of limit equilibrium method (LEM). Without considering the joints in rock masses, the LEM predicts much higher factor of safety than physical modeling and DEM. The failure mode and factor of safety predicted by the DEM are in good agreement with laboratory tests for any jointed rock slope.

关键词： rock masses, slope stability, DEM simulation, block size effect, joints configuration effect, limit equilibrium method.

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Identification of *** specific DNA sequences between two clinical isolates from NUD and gastric ulcer by SSH

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World Journal of Gastroenterology 2003年第8期9卷 1747-1751页

作者： Feng-Chan Han Min Gong Han-Chong Ng Bow Ho, department of Microbiology, Faculty of Medicine, national university of singapore, 5 Science Drive 2, singapore 117595, Republic of singapore department of Microbiology Faculty of Medicine National University of Singapore. biohanfc@***

AIM: The genomes of Helicobacter pylori(H. pylori) from different individuals are different. This project was to identify the strain specific DNA sequences between two clinical H. pylori isolates by suppression subtractive hybridization (SSH).METHODS: Two clinical H. pylori isolates, one from gastric ulcer (GU, tester) and the other from non-ulcer dyspepsia (NUD, driver), were cultured and the genomic DNA was prepared and submitted to AluⅠdigestion. Then two different adaptors were ligated respectively to the 5′-end of two aliquots of the tester DNA fragments and SSH was made between the tester and driver DNA. The un-hybridized tester DNA sequences were amplified by two sequential PCR and cloned into pGEM-T-Easy Vector. The tester strain specific inserts were screened and disease related DNA sequences were identified by dot ***: Among the 240 colonies randomly chosen, 50contained the tester strain specific DNA sequences. Twenty three inserts were sequenced and the sizes ranged from 261 bp to 1 036 bp. Fifteen inserts belonged to the *** plasmid pHPO100 that is about 3.5 kb and codes a replication protein A. Other inserts had patches of homologous to the genes of H. pylori in GenBank. Various patterns of dot blots were given and no GU strain unique DNA sequences were found when 4 inserts were used as probes to screen the genomic DNA from 27 clinical isolates, 8 from GU, 12 from duodenum ulcer (DU), 4 from GU-DU, 2 from NUD and 1from gastric cancer (GC). But a 670 bp DNA fragment (GU198)that was a bit homologous to the 3′-end of the gene of thymidylate kinase was positive in 7 GU strains (7/8), 3 GUDU strains (3/4) and 3 DU strains (3/12). A 384 bp fragment (GU79) of the replication gene A (repA) was positive only in 4 H, pylori isolates, 2 from GU and 2 from ***: Differences exist in the genes of different *** isolates. SSH is very effective to screen H. pylori strain specific DNA sequences between two clinical isolates,and some of

关键词：胃溃疡消化不良幽门螺杆菌抑制性减数杂交

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Intracellular Glutathione Detection using MnO2-Nanosheet-Modified Upconversion Nanoparticles

Intracellular Glutathione Detection using MnO2-Nanosheet-Mod...

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中国化学会第28届学术年会

作者： Renren Deng 1,Xiaogang Liu 1,2 1 department of Chemistry,national university of singapore,singapore 117543 2 Institute of Materials Research and Engineering,3 Research Link,singapore 117602

＜正＞We report a novel design,based on a combination of lanthanide-doped upconversion nanoparticles and manganese dioxide nanosheets,for rapid,selective detection of glutathione in aqueous solutions and living *** th...

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Establishment and characterisation of lfabp-EGFP-LC3 transgenic zebrafish:an in vivo model system to study autophagy in liver

Establishment and characterisation of lfabp-EGFP-LC3 transge...

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“细胞活动生命活力”——中国细胞生物学学会全体会员代表大会暨第十二次学术大会

作者： Jianzhou Cui~1,Tina Huey-Fen Sim~2,Zhiyuan Gong~2,Han-Ming Shen~1 1.Dcpartment of Epidemiology and Public Health,national university of singapore,singapore 117597,singapore 2.department of Biological Sciences,national university of singapore,singapore 117543,singapore

In recent years,autophagy has emerged as an important theme in biology and medicine,mainly due to its increasingly understood functions in various biological processes,such as cell survival/cell death, metabolism,and *** importantly,autophagy is closely implicated in many human diseases, such as cancer and neurodegenerative *** zebrafish,Danio rerio,represents a vertebrate species which has been widely used for studying developmental biology and ***,zebrafish has also been used to study molecular mechanisms of a variety of diseases including *** is one of the most important organs for autophagy ***,we generated a transgenic zebrafish line with liver specific GFP-LC3 *** model was validated by using atg3 knockdown,as well as chemical autophagy inducers and *** believe that this transgenic line will be a useful in vivo model system to study autophagy in zebrafish,and to examine the involvement of autophagy in biology and disease.

关键词： zebrafish autophagy liver Atg3 knockdown morpholino everolimus

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Experimental and discrete element numerical analysis of side slope instability induced by fissure water underlying impervious bed

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Science China(Technological Sciences) 2005年第Z1期48卷 65-80页

作者： LIU Bingshan1, LI Shihai1, ZHANG Lei1,2 & WANG Jianguo31. Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2. Graduate School, Chinese Academy of Sciences, Beijing 100060, China 3. Tropical Marine Science Institute, national university of singapore, 10 Kent Ridge Crescent, singapore 119260 Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Graduate School Chinese Academy of Sciences Beijing 100060 China Tropical Marine Science Institute National University of Singapore 10 Kent Ridge Crescent Singapore 119260 Singapore

When the sliding mass contains impervious bed, rainfall can infiltrate into mountain via crevices and form higher artesian aquifer at impervious bed inferior. This will decrease slip resistance and increase sliding forces of the sliding mass, thus lowering the safety factor, and inducing landslide disasters. In this paper, a landslide experimental apparatus is designed for experimental studies on the mechanism of this type of landslides. Meanwhile, the non-dimensional parameters in the model experiment are taken into account using dimensional analysis. The experimental results show that (1) the ratio of the cleft water pressure to the overlying pressure is a crucial parameter affecting the stability of the slope; (2) when the shut-in pressure reaches 80% of the normal component of the pressure on the slip surface made up of rock and soil, landslide will occur; (3) the whole slope will start to slide when the shut-in pressure is equal to the normal component of the pressure formed by the overlying rock and soil on the upper 30% area. In this article, a discrete element method simulation is used to investigate the influence of cleft water pressure and shearing strength on the landslide stability. It can be concluded that the critical value of Ccr, ?cr, which determines the slide mass stability, increases with the increase of the water pressure; if the water pressure reaches a high level, the stability of the slide mass depends mainly on C, while the influence of ? becomes smaller than C.

关键词： impervious bed, rainfall infiltration, pore water pressure, landslide experiment, displacement monitor, discrete element method.

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Rational Design of Functional Two-Dimensional Molecular Nanostructure Arrays on Surfaces

Rational Design of Functional Two-Dimensional Molecular Nano...

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2011中国材料研讨会

作者： Wei CHEN,1,2 1 department of Chemistry,national university of singapore 2 department of Physics,national university of singapore

Creation of well-ordered functional molecular arrays at the nanometer scale is one of the key issues in the development for future molecular-or nano-electronic devices,solid-state quantum

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AN　APPROACH　TO　EMPIRICAL　DATA　PREPROCESSING　FOR　BOTH　CURVES　AND　SURFACES　AND　ITS　APPLICATIONS

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Computer Aided Drafting,Design and Manufacturing 1996年第2期6卷 1-16页

作者： Qu Ruibin.(department of mathematics national Univerity of singapore 10 Kent Ridge Crescent singapore,119260)

Some local algorithms for the,preprocessing,of empirical data for both curves and surfaces are proposed so that the modified data,a polygon for curve data and a triangulation for surface data,can be used not only to approximate the given data with required accuracy,but also to preserve the shape and geometric and mathematical properties of the data such as convexity and monotonicity *** algorithms would produce small errors (O(h￣4)) if the initial data are accurate and reasonably distributed.

关键词： ss:Triangulation approximation surface algorithm shape preservation data faring

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