3,914 research outputs found
Fabrication of nano-precision PDMS replica using two-photon photopolymerization and vacuum pressure difference technique
No full textDetermination of an optimal configuration of operating policies for Direct-Input-Output manufacturing systems using the Taguchi method
No full textSome modem manufacturing systems have workstations directly integrated with a centralized storage and handling system for work-in-process. We consider a Direct-Input-Output manufacturing system(DIOMS) which has a number of machine centers placed along a built-in automated storage/retrieval system(AS/RS). The storage/retrieval(S/R) machine handles parts placed on pallets for the machine centers located at either one or both sides of the AS/RS. This paper investigates the operational aspect of DIOMS by the Taguchi method. Four operating policies including input sequencing control. dispatching rule for the S/R machine, machine center-based part type selection rule, and storage assignment policy are treated as design factors. For the performance characteristics, mean flow time and throughput are adopted. The number of machine centers, the number of part types, demand rate, processing time and the rate of each part type. vertical and horizontal speed of the S/R machine, and the size of a local buffer in the machine centers am considered as noise factors in generating various DIOMS environments. A robust design experiment with inner and outer orthogonal arrays are conducted by computer simulation, and an optimal configuration of operating policies is presented which consists of a combination of the level of each design factor. The validity of the optimal configuration is investigated by comparing its SN ratios with those obtained by an experiment with full factorial designs
Leading chiral logarithms of KS→γγ and KS→γl+l− at two loops
No full textAbstractWe obtain the leading divergences at two-loop order for the decays KS→γγ and KS→γl+l− using only one-loop diagrams. We then find the double chiral logarithmic corrections to the decay branching ratio of KS→γγ and to the decay rate for KS→γl+l−. It turns out that these effects are numerically small and therefore make a very small enhancement on the branching ratio and decay rate. We also derive an expression for the corrections of type logμ×LEC. Numerical analysis done for the process KS→γγ shows that these single logarithmic effects can be sizable but come with opposite signs with respect to the double chiral logarithms
Performance of small stack for intermediate temperature-operating solid oxide fuel cells using stainless steel interconnects
No full textDetermination of an Optimal configuration of Operating Policies for Direct-input-output Manufacturing Systems Using the Taguchi Method
No full textDNMT1-mediated SPINT2 expression drives early senescence by suppressing c-Met signaling in human fibroblasts
No full textCellular senescence is a critical process involved in aging and related disorders, yet the molecular triggers of early senescence remain elusive. Here, we identify DNA methyltransferase 1 (DNMT1) downregulation as a key trigger of early senescence and establish serine protease inhibitor Kunitz type 2 (SPINT2) as its critical downstream effector. Using replicative and oxidative stress-induced senescence models of primary human diploid fibroblast, we observed persistent upregulation of SPINT2 and inverse downregulation of DNMT1, preceding senescence-associated beta-galactosidase activity, a conventional senescence marker. Pharmacological inhibition and siRNA-mediated knockdown of DNMT1 significantly increased SPINT2 expression and induced senescence, showing mitigated effects by SPINT2 knockdown. Furthermore, SPINT2 overexpression alone induced senescence. Methylation-specific sequencing identified four CpG sites in SPINT2 promoter, that became hypomethylated at early transition of senescence and upon DNMT1 suppression. Functional analyses revealed that DNMT1-mediated SPINT2 expression induced c-Met inhibition, triggering senescence. Transcriptomic profiling identified 17 commonly deregulated c-Met signaling genes in both senescence models, with COL27A1, STAM2, and CBL validated as key downstream targets of SPINT2/c-Met signaling. These findings establish DNMT1-mediated SPINT2 upregulation as a novel epigenetic mechanism driving senescence initiation via c-Met inhibition, providing insights into the early stage of senescence and potential therapeutic targets for aging-related diseases
Ratcheting and fatigue behavior of a copper alloy under uniaxial cyclic loading with mean stress
No full textStress-control fatigue tests have been conducted on a copper alloy at room temperature with and without mean stress. Ratcheting strain was measured to failure under four sets of stress amplitude and mean stress. The ratcheting strain versus cycle curve is similar to the conventional creep curve under static load consisting of primary, steady-state and tertiary stages. The steady-state rate and ratcheting strain at failure increase with mean stress for a given stress amplitude and with stress amplitude for a given mean stress. Ratcheting strain increases as the stress rate decreases. The S-N curve approach and mean stress models of Smith-Watson-Topper and Walker yielded good correlation of fatigue lives in the life range of 10(2)-10(5) cycles. (C) 2008 Elsevier Ltd. All rights reserved.X117169sciescopu
Particle collision statistics in turbulent flows with kinematic simulation
No full textColliding droplets or particles in turbulent flows are important in applications ranging from rain formation in clouds to aerosol production in process engineering. To reduce the computational costs when simulating such flows, kinematic simulation (KS) is frequently applied as a cheap surrogate for direct numerical simulation (DNS) of the turbulent flow field. In this work, we provide for the first time a systematic validation of the particle collision statistics that result from KS. We show that while the particle collision frequencies for particles with different Stokes numbers are in good agreement with DNS reference data, a more detailed inspection of the flow field and particle concentration characteristics reveals significant differences between KS and DNS
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