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Niels Leergaard Pedersen - One of the best experts on this subject based on the ideXlab platform.

  • minimizing tooth Bending Stress in spur gears with simplified shapes of fillet and tool shape determination
    Engineering Optimization, 2015
    Co-Authors: Niels Leergaard Pedersen
    Abstract:

    The strength of a gear is typically defined relative to durability (pitting) and load capacity (tooth-breakage). Tooth-breakage is controlled by the root shape and this gear part can be designed because there is no contact between gear pairs here. The shape of gears is generally defined by different standards, with the ISO standard probably being the most common one. Gears are manufactured using two principally different tools: rack tools and gear tools. In this work, the Bending Stress of involute teeth is minimized by shape optimization made directly on the final gear. This optimized shape is then used to find the cutting tool (the gear envelope) that can create this optimized gear shape. A simple but sufficiently flexible root parameterization is applied and emphasis is put on the importance of separating the shape parameterization from the finite element analysis of Stresses. Large improvements in the Stress level are found.

  • Improving Bending Stress in spur gears using asymmetric gears and shape optimization
    Mechanism and Machine Theory, 2010
    Co-Authors: Niels Leergaard Pedersen
    Abstract:

    Bending Stress plays a significant role in gear design wherein its magnitude is controlled by the nominal Bending Stress and the Stress concentration due to the geometrical shape. The Bending Stress is indirectly related to shape changes made to the cutting tool. This work shows that the Bending Stress can be reduced significantly by using asymmetric gear teeth and by shape optimizing the gear through changes made to the tool geometry. However, to obtain the largest possible Stress reduction a custom tool must be designed depending on the number of teeth, but the Stress reductions found are not very sensitive to small design changes. This observation suggests the use of two new standard cutting tools.

  • reducing Bending Stress in external spur gears by redesign of the standard cutting tool
    Structural and Multidisciplinary Optimization, 2009
    Co-Authors: Niels Leergaard Pedersen
    Abstract:

    For the design of gears the Stress due to Bending plays a significant role. The Stress from Bending is largest in the root of the gear teeth, and the magnitude of the maximum Stress is controlled by the nominal Bending Stress and Stress concentration due to the geometric shape of the tooth. In this work the Bending Stress of involute teeth is minimized by shape optimizing the tip of the standard cutting tool. By redesign of the tip of the standard cutting tool we achieve that the functional part of the teeth stays the same while at the same time the root shape is changed so that a reduction of the Stresses results. The tool tip shape is described by different parameterizations that use the super ellipse as the central shape. For shape optimization it is important that the shape is given analytically. The shape of the cut tooth that is the envelope of the cutting tool is found analytically. The parameterization includes the standard ISO tooth. Practical simple changes in the design of the tool tip is shown to result in large reduction of the Bending Stress, keeping at the same time the engage part of the tooth unchanged. This leads to gears that have unchanged functionality based on the involute design, and these can be engaged with existing designs. The presented new cutting tools are custom tools specific for a given gear.

Jiyoun Jeong - One of the best experts on this subject based on the ideXlab platform.

  • base pair mismatch can destabilize small dna loops through cooperative kinking
    Physical Review Letters, 2019
    Co-Authors: Jiyoun Jeong
    Abstract:

    : Base-pair mismatch can relieve mechanical Stress in highly strained DNA molecules, but how it affects their kinetic stability is not known. Using single-molecule fluorescence resonance energy transfer, we measured the lifetimes of tightly bent DNA loops with and without base-pair mismatch. Surprisingly, for loops captured by stackable sticky ends which leave single-stranded DNA breaks (or nicks) upon annealing, the mismatch decreased the loop lifetime despite reducing the overall Bending Stress, and the decrease was largest when the mismatch was placed at the DNA midpoint. These findings suggest that base-pair mismatch increases Bending Stress at the opposite side of the loop through an allosteric mechanism known as cooperative kinking. Based on this mechanism, we present a three-state model that explains the apparent dichotomy between thermodynamic and kinetic stability.

  • base pair mismatch can destabilize small dna loops through cooperative kinking
    bioRxiv, 2019
    Co-Authors: Jiyoun Jeong
    Abstract:

    Base pair mismatch can relieve mechanical Stress in highly strained DNA molecules, but how it affects their kinetic stability is not known. Using single-molecule Fluorescence Resonance Energy Transfer (FRET), we measured the lifetimes of tightly bent DNA loops with and without base pair mismatch. Surprisingly, for loops captured by stackable sticky ends, the mismatch decreased the loop lifetime despite reducing the overall Bending Stress, and the decrease was largest when the mismatch was placed at the DNA midpoint. These findings show that base pair mismatch transfers Bending Stress to the opposite side of the loop through an allosteric mechanism known as cooperative kinking. Based on this mechanism, we present a three-state model that explains the apparent dichotomy between thermodynamic and kinetic stability of DNA loops.

E Zalnezhad - One of the best experts on this subject based on the ideXlab platform.

  • investigating the fretting fatigue life of thin film titanium nitride coated aerospace al7075 t6 alloy
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2013
    Co-Authors: E Zalnezhad, Ahmed A D Sarhan, M Hamdi
    Abstract:

    Application of surface modification methods is expected to be a supreme solution to diminishing fretting damage. In this study, our aim was to improve the fretting fatigue life of Al7075-T6 alloy by covering it with a TiN thin film hard coating using the magnetron sputtering technique. Coated specimens with the best surface hardness, adhesion strength and roughness were tested with a rotating Bending fatigue test machine. The fatigue results indicate that fretting was significantly detrimental and reduced the fatigue life of uncoated specimens, while a slighter decrease was observed for coated samples with high surface hardness and adhesion. The fretting fatigue lives of coated specimens with high surface hardness and adhesion strength improved 61% and 16% at high Bending Stress and 39% and 77% at low Bending Stress, respectively, in comparison to the uncoated specimens. In addition, the lowest surface roughness resulting from thin film TiN coating improved the fretting fatigue life of specimens by 18% at low cyclic fatigue, while at high cyclic fatigue the result was reversed.

Tetsu Tanaka - One of the best experts on this subject based on the ideXlab platform.

  • novel local Stress evaluation method in 3d ic using dram cell array with planar mos capacitors
    IEEE International D Systems Integration Conference, 2015
    Co-Authors: Seiya Tanikawa, Hisashi Kino, Takafumi Fukushima, Mitsumasa Koyanagi, Tetsu Tanaka
    Abstract:

    Three-dimensional integrated circuit (3D IC) is one of the promising ways to enhance IC performance. Each IC chip is mechanically connected by organic adhesive and metal microbumps. Coefficient of thermal expansion (CTE) mismatch between materials causes local Bending Stress in IC chips, leading to negative effects in IC performance. In this study, we have fabricated a test structure with DRAM cell array having planar MOS capacitors. Using the test structure, we measured both DRAM chip Bending profiles and retention time modulations of DRAM cell array. Consequently, we have successfully demonstrated that the local Bending Stress in IC chips can be two-dimensionally evaluated using the DRAM cell array with planar MOS capacitances. This evaluation methods leads to realization of 3D IC with high reliability.

  • consideration of microbump layout for reduction of local Bending Stress due to cte mismatch in 3d ic
    IEEE International D Systems Integration Conference, 2015
    Co-Authors: Hisashi Kino, Seiya Tanikawa, Takafumi Fukushima, Mitsumasa Koyanagi, H Hashiguchi, Yohei Sugawara, Shunsuke Ikegaya, Tetsu Tanaka
    Abstract:

    Three-dimensional IC (3D IC) has attracted much attention as a promising method to enhance IC performance. Recently, great interests in mechanical reliability are increasing among 3D IC researchers for production of 3D IC. Conventional 3D ICs consist of vertically stacked several thin IC chips those are electrically connected with lots of through-Si vias (TSVs) and metal microbumps. Metal microbumps are surrounded by organic adhesive called underfill material. In general, coefficient of thermal expansion (CTE) of the underfill material is larger than that of metal microbumps. This CTE difference induces local Bending Stress in thinned IC chips. This local Bending Stress would affect transistor reliability in thinned IC chips. Therefore, we should suppress the local Bending Stress to realize 3D IC with high reliability. In this work, we present design guideline of microbump layout which can suppress the local Bending Stress in 3D-stacked several thin IC chips.

  • minimization of keep out zone koz in 3d ic by local Bending Stress suppression with low temperature curing adhesive
    Electronic Components and Technology Conference, 2014
    Co-Authors: Hisashi Kino, Seiya Tanikawa, Takafumi Fukushima, Mitsumasa Koyanagi, H Hashiguchi, Yohei Sugawara, Kangwook Lee, Tetsu Tanaka
    Abstract:

    Three dimensional IC (3D IC) has lots of through-Si vias (TSVs) and metal microbumps for electrical connection between stacked IC chips, and also has organic adhesives to enhance the mechanical strength of 3D IC. However, the coefficient of thermal expansion (CTE) mismatch between microbumps and organic adhesives generate the local Bending Stress in thinned IC chips. Therefore, Keep-Out-Zone (KOZ) for transistors must be considered in 3D IC design to eliminate characteristic fluctuations and degradations due to the local Bending Stress. In this study, for the first time, we evaluated the effects of low temperature curing adhesive on both the local Bending Stress and the resultant transistor characteristics for decrease in KOZ of 3D IC.

Harold D. Kim - One of the best experts on this subject based on the ideXlab platform.

  • Probing the elastic limit of DNA Bending
    Nucleic acids research, 2014
    Co-Authors: Harold D. Kim
    Abstract:

    Sharp Bending of double-stranded DNA (dsDNA) plays an essential role in genome structure and function. However, the elastic limit of dsDNA Bending remains controversial. Here, we measured the opening rates of small dsDNA loops with contour lengths ranging between 40 and 200 bp using single-molecule Fluorescence Resonance Energy Transfer. The relationship of loop lifetime to loop size revealed a critical transition in Bending Stress. Above the critical loop size, the loop lifetime changed with loop size in a manner consistent with elastic Bending Stress, but below it, became less sensitive to loop size, indicative of softened dsDNA. The critical loop size increased from ∼60 bp to ∼100 bp with the addition of 5 mM magnesium. We show that our result is in quantitative agreement with the kinkable worm-like chain model, and furthermore, can reproduce previously reported looping probabilities of dsDNA over the range between 50 and 200 bp. Our findings shed new light on the energetics of sharply bent dsDNA.