14,295 research outputs found
Revealing aeroelastic effects on low-rise roof structures in turbulent winds via isogeometric fluid–structure interaction
No full textAeroelastic effects, which affect the dynamic responses of low-rise roof structures to extreme wind conditions, are often neglected or oversimplified in current wind engineering design standards and applications. However, it is crucial to understand the details of those aeroelastic effects for performance-based wind engineering. This paper presents an isogeometric fluid–structure interaction (FSI) tool to investigate the aeroelastic effects of wind pressure distributions on roof structures under different turbulent wind conditions. A representative low-rise roof structure is simulated with an FSI model using an Arbitrary Lagrange-Eulerian-based variational multi-scale formulation coupled with isogeometric Kirchhoff-Love shells. The simulation results are compared to the quasi-steady approach and wind load provisions from ASCE 7-22. It shows that the quasi-steady approach and the design standard underestimate the pressure fluctuations, indicating the necessity of using FSI simulations to capture the aeroelastic effect for the roof of low-rise structures. This paper also studies the impacts of different roof configurations, e.g., the number of roof panels and inflow turbulent intensity, on the distribution of pressure coefficients and roof deflections. For the given mean wind speed, the mean pressure coefficient remains almost the same regardless of the turbulent intensity and roof configuration. However, the pressure fluctuation (standard deviation) varies significantly with the turbulence intensity and roof configuration. The aeroelastic effect also leads to complicated roof deflections at the crucial location having the maximum pressure coefficient. The paper first describes the mathematical details of the FSI model and simulation setup. Then, the pressure coefficients by the FSI simulation and design code are compared. Finally, the roof deflection with different inlet turbulence intensities and roof configurations are presented and discussed
Combining Q(T) and small-x resummations
No full textWe analyze transverse momentum (Q(T)) resummation of a colorless final state, e.g. Higgs production in gluon fusion or the production of a lepton pair via the Drell-Yan mechanism, in the limit where the invariant mass of the final state is much less than the center-of-mass energy, i.e. Q(2) << s. We show how the traditional resummation of logarithms of Q(T)/Q can be supplemented with the resummation of the leading logarithmic contributions at small x = Q(2)/s and we compute the necessary ingredients to perform such joint resummation
17β-Estradiol nongenomically induces vascular endothelial H2S release by promoting phosphorylation of cystathionine γ-lyase
No full textEstrogen exerts its cardiovascular protective role at least in part by regulating endothelial hydrogen sulfide (H2S) release, but the underlying mechanisms remain to be fully elucidated. Estrogen exerts genomic effects, i.e. those involving direct binding of the estrogen receptor (ER) to gene promoters in the nucleus, and nongenomic effects, mediated by interactions of the ER with other proteins. Here, using human umbilical vein endothelial cells (HUVECs), immunological detection, MSbased analyses, and cGMP and H2S assays, we show that 17β-estradiol (E2) rapidly enhances endothelialH2S release in a nongenomic manner. We found that E2 induces phosphorylation of cystathionine γ-lyase (CSE), the key enzyme in vascular endothelial H2S generation. Mechanistically, E2 enhanced the interaction of membrane ERα with the Gα subunit Gαi-2/3, which then transactivated particulate guanylate cyclase-A (pGC-A) to produce cGMP, thereby activating protein kinaseGtype I (PKGI). We also found that PKG-Iβ, but not PKG-Iβ, interacts with CSE, leading to its phosphorylation, and rapidly induces endothelial H2S release. Furthermore, we report that silencing of either CSE or pGC-A in mice attenuates E2-induced aorta vasodilation. These results provide detailed mechanistic insights into estrogen's nongenomic effects on vascular endothelial H2S release and advance our current understanding of the protective activities of estrogen in the cardiovascular system
LD side-pumped high beam quality passive Q-switched and mode-locked Nd:YAG laser based on SESAM
No full textWe report a LD side-pumped fundamental-mode (Mx(2) = 1.35 and My(2) = 1.27) passive Q-switched and mode-locked Nd:YAG laser based on a semiconductor saturable absorber mirror (SESAM). At a pump current of 12.5 A, the average output power of 5.68 W with 80 kHz repetition rate and 2 mu s pulse width of the Q-switched envelope was generated. The repetition rate of the mode-locked pulse within the Q-switched envelope of 88 MHz was achieved
Bulbophyllum hamatum Q. Yan, X. W. Li & J. Q. Wu 2021, sp. nov.
No full textBulbophyllum hamatum Q. Yan, X.W. Li & J.Q. Wu, sp. nov. (Ḃǘ卷瓣兰; Fig. 1) Diagnosis. Bulbophyllum hamatum resembles B. omerandrum in free lateral sepals, petals bearing fimbriate-ciliate margin, and fleshy recurved ligulate lip, but differs in hooked or falcate stelidia, caudate dorsal sepal and petals, and ovoid column wings. Type. CHINA. Hubei, Wufeng County, Wufeng Town, Shuitantou Village, epiphytic on tree or moss rocks in the subtropical evergreen broad-leaved forest, elev. 959 m, 30°6´16˝E, 110°39´6˝N, 21 April 2021, Q. Yan 4001 (holotype: HIB!) Description. Epiphytic or lithophytic herb. Rhizome creeping, 2 mm in diam., rooting from base of pseudobulbs. Pseudobulbs 1–7 cm apart on rhizome, narrowly pyriform to subcylindric, 1–2.5 cm, 0.3–1.2 cm in diam., with a terminal leaf. Petiole 1–2 cm; leaf oblong, 3–8.5 × 0.7–1.6 cm, thick, leathery, base cuneate, apex obtuse and retuse, mid-vine concave adaxialy, convex abaxialy. Scape arising from base of pseudobulb, erect, usually 5–9 cm; condensed raceme 2–4-flowered; peduncle slender, ca. 1 mm in diam., 2 or 3 tubular sheaths, placed sparsely; floral bracts ovate, cymbiform, 8–12 mm. Pedicel and ovary 1.2–2 cm, densely purple spotted. Flowers yellowish white. Dorsal sepal broadly ovate, 6–10 × 5 mm, apex long acuminate to caudate, margin entire, 4–5-veined; lateral sepals usually free, narrowly falcate-lanceolate, 16–22 × 5 mm, base adnate to column foot, margin entire, twisted near base and divergent, apex acuminate. Petals ovate or ovate-triangular, 5 × 4 mm, tip caudate with a thread 2–3 mm, margins finely erose to deeply lacerate distally, 3-veined; lip recurved, ligulate, ca. 6 mm, fleshy, base attached to end of column foot by a mobile joint, apex obtuse and apiculate, sparsely finely papillate on both sides. Column ca. 5 mm, with ovoid wings at upper part; foot curved, ca. 4mm, with free part ca. 3 mm; stelidia hooked or falcate, ca. 2 mm; anther cap comblike on apical margin; pollinia 4, in 2 pairs. Etymology. The specific epithet “ hamatum ” refers to the hooked or falcate stelidia in this new species. Phenology. Flowering in April to May, fruiting in May. Distribution and habitat. B. hamatum grows in Wufeng County, Hubei, China, on damp moss rocks and trees in the subtropical evergreen broad-leaved forest at the elevation 950–1200 m. Three subpopulations were found around the type locality. Taxonomic note: B. hamatum mainly differs from B. omerandrum in hooked or falcate stelidia. The morphological differences between them were summarized in Table 1 and Fig. 2.Published as part of Yan, Qi, Li, Xin-Wei & Wu, Jin-Qing, 2021, Bulbophyllum hamatum (Orchidaceae), a new species from Hubei, central China, pp. 269-272 in Phytotaxa 523 (3) on pages 269-271, DOI: 10.11646/phytotaxa.523.3.9, http://zenodo.org/record/559148
Numerical modeling and experimental analysis on coupled torsional-longitudinal vibrations of a ship's propeller shaft
No full textA simplified lumped-mass model was established using ordinary differential equations, focusing on the coupled torsional-longitudinal vibrations of a ship's propeller shaft. The numerical simulation based on the presented algorithm was then developed and the dynamic behavior was investigated. A theoretical solution setup with simple model was solved to demonstrate the accuracy of the proposed lumped-mass model. Based on this model, the coupled natural frequencies and the maximum acceleration of each direction were determined. Experimental tests were conducted to validate the applicability of the numerical model, over a range of rotational speeds and loading conditions. It is found that the natural frequencies are unaffected while the maximum acceleration are increased with the rotational speed as well as the loading. Natural frequencies representing other directions are induced by the coupling effect, and enhance the dynamical response. The ultimate response in the direction without excitation is enlarged because of the coupling effect. An appropriate coupling stiffness coefficient value has been proposed based on the discussion on modeling and experimental results
A 20.1 W Solid-State Laser Pumped by 887 nm with High Efficiency and TEM00 Mode
No full textHigh efficiency, TEM00 mode, high repetition rate laser pumped by 887 nm is reported. 20.1 W output laser emitting at 1064 nm is achieved in a 0.3 at % Nd-doped Nd:YVO4, which absorbs pumping light of 30.7 W at 887 nm. The opto-optic efficiency and the slope efficiency are 65.5 and 88.5%, respectively. The stable Q-switching operation worked well at 100 kHz and the beam quality is near diffraction-limit with M-2 factor measured as M-2 approximate to 1.2. And the pulse waveform is analyzed in this paper
Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System
No full textLi Q, Xu H, Zhang Q, Wang X, Li ZG. Dynamics Simulation of Remotely Operated Vehicle-Fiber Optic Micro Cable System. Presented at the WCICA2008, Chongqing, China
Measurement of the differential and double-differential Drell-Yan cross sections in proton-proton collisions at root s=7 TeV
No full textMeasurements of the differential and double-differential Drell-Yan cross sections are presented using an integrated luminosity of 4.5 (4.8) fb−1 in the dimuon (dielectron) channel of proton-proton collision data recorded with the CMS detector at the LHC at s√ = 7 TeV. The measured inclusive cross section in the Z-peak region (60–120 GeV) is σ(ℓℓ) = 986.4 ± 0.6 (stat.) ± 5.9 (exp. syst.) ± 21.7 (th. syst.) ± 21.7 (lum.) pb for the combination of the dimuon and dielectron channels. Differential cross sections dσ/dm for the dimuon, dielectron, and combined channels are measured in the mass range 15 to 1500 GeV and corrected to the full phase space. Results are also presented for the measurement of the double-differential cross section d2σ/dm d|y| in the dimuon channel over the mass range 20 to 1500 GeV and absolute dimuon rapidity from 0 to 2.4. These measurements are compared to the predictions of perturbative QCD calculations at next-to-leading and next-to-next-to-leading orders using various sets of parton distribution functions
Measurement of the low-mass Drell-Yan differential cross section at √s = 7 TeV using the ATLAS detector
No full textThe differential cross section for the process Z/γ ∗ → ℓℓ (ℓ = e, μ) as a function of dilepton invariant mass is measured in pp collisions at s√ = 7 TeV at the LHC using the ATLAS detector. The measurement is performed in the e and μ channels for invariant masses between 26 GeV and 66 GeV using an integrated luminosity of 1.6 fb−1 collected in 2011 and these measurements are combined. The analysis is extended to invariant masses as low as 12 GeV in the muon channel using 35 pb−1 of data collected in 2010. The cross sections are determined within fiducial acceptance regions and corrections to extrapolate the measurements to the full kinematic range are provided. Next-to-next-to-leading-order QCD predictions provide a significantly better description of the results than next-to-leading-order QCD calculations, unless the latter are matched to a parton shower calculation
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