An experimentally based analytical model for the shear capacity of FRP-strengthened reinforced concrete beams

This paper deals with the shear strengthening of Reinforced Concrete (RC) flexural members with externally bonded Fiber-Reinforced Polymers (FRPs). The interaction between an external FRP and an internal transverse steel reinforcement is not considered in actual code recommendations, but it strongly influences the efficiency of the shear strengthening rehabilitation technique and, as a consequence, the computation of interacting contributions to the nominal shear strength of beams. This circumstance is also discussed on the basis of the results of an experimental investigation of rectangular RC beams strengthened in shear with “U-jacketed” carbon FRP sheets. Based on experimental results of the present and other investigations, a new analytical model for describing the shear capacity of RC beams strengthened according to the most common schemes (side-bonded and “U-jacketed”), taking into account the interaction between steel and FRP shear strength contributions, is proposed. Russian translation published in Mekhanika Kompozitnykh Materialov, Vol. 44, No. 3, pp. 339–356, May–June, 2008.     

Analysis of the data recorded by the Mont Blanc neutrino detector and by the Maryland and Rome gravitational-wave detectors during SN1987A

Summary The data recorded by the gravitational wave and the neutrino detectors mentioned in the title have been analysed over a period of several days that includes the Mont Blanc 5ν burst occurrence time. A correlation is found during a period of about two hours roughly centred on the 5ν burst, independently between Maryland and Mont Blanc and Rome and Mont Blanc. The probability that these two correlations be due to chance is of the order of between 10⁻⁶ and 10⁻⁵. It is found that this effect is mainly due to a dozen of large Maryland and Rome events distributed during the above two-hour period.

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Riassunto I dati registrati con le antenne gravitazionali ed i rivelatori di neutrini indicati nel titolo sono stati analizzati in un periodo di vari giorni, includendo il tempo di occorrenza dell'evento di 5 neutrini rivelato al Monte Bianco. è stata trovata una correlazione durante circa due ore centrata al tempo dei 5ν, indipendentemente Maryland/Monte Bianco e Roma/Monte Bianco. La probabilità che queste due correlazioni siano dovute al caso è dell'ordine di 10⁻⁶÷10⁻⁵. è stato trovato che questo effetto è dovuto essenzialmente ad una dozzina di segnali registrati a Roma e in Maryland durante il sopramenzionato periodo di due ore.

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Резюме Проводится анализ данных, зарегистрированных нейтринным детектором на Мон Блане и детекторами гравитационных волн в Мэриленде и Риме, за период, охватывающий несколько дней, которые включают время появления 5ν вспышки на Мон Блане. Обнаружена корреляция в течение приблизительно двух часов, центр которой приблизительно совпадает со временем 5ν вспышки, независимо в данных Мэриленд и Мон Блан и в данных Рим и Мон Блан. Вероятность того, что эти две корреляции являются случайными, имеет порядок величины 10⁻⁶÷10⁻⁵. Обнаружено, чтот эффект обусловлен в основном дюжиной сигналов, зарегистрированных в Риме и Мэриленде в течение периода около двух часов.

     

Chiral 1,3-oxathianes via stereoselective addition-cyclization of hydroxythiols to electron-poor acetylenes

A novel preparation of chiral 1,3-oxathianes via nucleophilic addition of hydroxy-thiols to electron-poor acetylenes, followed by iodine catalyzed photoinduced cyclization is reported. The stereochemical outcome of the reaction is determined with a conformational study based on n.O.e. ¹H-NMR differential spectroscopy experiments.     

Conversion of bis(trichloromethyl) carbonate to phosgene and reactivity of triphosgene, diphosgene, and phosgene with methanol(1)

Triphosgene was decomposed quantitatively to phosgene by chloride ion. The reaction course was monitored by IR spectroscopy (React-IR), showing that diphosgene was an intermediate. The methanolysis of triphosgene in deuterated chloroform, monitored by proton NMR spectroscopy, gave methyl chloroformate and methyl 1,1, 1-trichloromethyl carbonate in about a 1:1 ratio, as primary products. The reaction carried out in the presence of large excess of methanol (0.3 M, 30 equiv) was a pseudo-first-order process with a k(obs) of 1.0 x 10(-)(4) s(-)(1). Under the same conditions, values of k(obs) of 0.9 x 10(-)(3) s(-)(1) and 1.7 x 10(-)(2) s(-)(1) for the methanolysis of diphosgene and phosgene, respectively, were determined. The experimental data suggest that, under these conditions, the maximum concentration of phosgene during the methanolysis of triphosgene and diphosgene was lower than 1 x 10(-)(5) M. Methyl 1,1,1-trichloromethyl carbonate was synthesized and characterized also by the APCI-MS technique.     

Effect of cosmic rays on the resonant gravitational wave detector at temperature T=1.5 K

The interaction between cosmic rays and the gravitational wave bar detector is experimentally studied with the aluminum bar at temperature of T=1.5 K. The results are compared with those obtained in the previous runs when the bar was at T=0.14 K. The results of the run at T=1.5 K are in agreement with the thermo-acoustic model; no large signals at unexpected rate are noticed, unlike the data taken in the run at T=0.14 K. The observations suggest a larger efficiency in the mechanism of conversion of the particle energy into vibrational mode energy when the aluminum bar is in the superconductive status.     

Increasing the bandwidth of resonant gravitational antennas: the case of explorer

Resonant gravitational wave detectors with an observation bandwidth of tens of hertz are a reality: the antenna Explorer, operated at CERN by the ROG Collaboration, has been upgraded with a new readout. In this new configuration, it exhibits an unprecedented useful bandwidth: in over 55 Hz about its center operating frequency of 919 Hz the spectral sensitivity is better than 10(-20) Hz(-1/2). We describe the detector and its sensitivity and discuss the foreseeable upgrades to even larger bandwidths.     

Development of XUV lasers at the RAL Central Laser Facility

Recent progress in the development of XUV lasers by research teams using high-power and ultrashort-pulse Nd: glass and KrF laser facilities at the Rutherford Appleton Laboratory is reviewed. Injector-amplifier operation and prepulse enhanced output of the Ge XXIII collisional laser driven by a kilojoule glass laser, enhanced gain in CVI recombination with picosecond CPA drive pulses from a glass laser, and optical field ionization and XUV harmonic generation with a KrF CPA laser are described.     

Quadratic Interaction Functional for General Systems of Conservation Laws

For the Glimm scheme approximation \({u_\varepsilon}\) to the solution of the system of conservation laws in one space dimension

$$u_t + f(u)_x = 0, \qquad u(0, x) = u_0(x) \in \mathbb{R}^n,$$

with initial data u ₀ with small total variation, we prove a quadratic (w.r.t. Tot. Var. (u ₀)) interaction estimate, which has been used in the literature for stability and convergence results. No assumptions on the structure of the flux f are made (apart from smoothness), and this estimate is the natural extension of the Glimm type interaction estimate for genuinely nonlinear systems.

More precisely, we obtain the following results:

• a new analysis of the interaction estimates of simple waves;
• a Lagrangian representation of the derivative of the solution, i.e., a map \({\mathtt{x}(t, w)}\) which follows the trajectory of each wave w from its creation to its cancellation;
• the introduction of the characteristic interval and partition for couples of waves, representing the common history of the two waves;
• a new functional \({\mathfrak{Q}}\) controlling the variation in speed of the waves w.r.t. time.

This last functional is the natural extension of the Glimm functional for genuinely nonlinear systems.

The main result is that the distribution \({D_{t} \hat \sigma_k(t,w)}\) is a measure with total mass \({\leq \mathcal{O}(1) {\rm Tot. Var.} (u_0)^2}\) , where \({\hat{\sigma}_k(t, w)}\) is the speed given to the wave w by the Riemann problem at the grid point \({(i\varepsilon, \mathtt{x}(i\varepsilon, w)), t \in [i\varepsilon, (i + 1)\varepsilon)}\).     

Formation of plasma channels in the interaction of a nanosecond laser pulse at moderate intensities with helium gas jets

We report on a detailed study of channel formation in the interaction of a nanosecond laser pulse with a He gas jet. A complete set of diagnostics is used in order to characterize the plasma precisely. The evolution of the plasma radius and of the electron density and temperature are measured by Thomson scattering, Schlieren imaging, and Mach-Zehnder interferometry. In gas jets, one observes the formation of a channel with a deep density depletion on axis. Because of ionization-induced defocusing which increases the size of the focal spot and decreases the maximum laser intensity, no channel is observed in the case of a gas-filled chamber. The results obtained in various gas-jet and laser conditions show that the channel radius, as well as the density along the propagation axis, can be adjusted by changing the laser energy and gas-jet pressure. This is a crucial issue when one wants to adapt the channel parameters in order to guide a subsequent high-intensity laser pulse. The experimental results and their comparison with one-dimensional (1D) and two-dimensional hydrodynamic simulations show that the main mechanism for channel formation is the hydrodynamic evolution behind a supersonic electron heat wave propagating radially in the plasma. It is also shown from 2D simulations that a fraction of the long pulse can be self-guided in the channel it creates. The preliminary results and analyses on this subject have been published before [V. Malka et al., Phys. Rev. Lett. 79, 2979 (1997)].     

Evaluation and preliminary measurement of the interaction of a dynamical gravitational near field with a cryogenic gravitational wave antenna

We present a detailed analysis of the effect of the gravitational field generated by a small rotating quadrupole on a graviational wave antenna and we report on the preliminary measurement of this effect on the Explorer 2270 kg cryogenic gravitational wave antenna of the Rome group. The induced signal had an amplitude twenty times larger than the detector noise when the antenna was equipped with an FET amplifier and was easily detected without requiring integration in time. We remark that with this method we were able to make an absolute calibration of a gravitational wave antenna.