[en] The effect of humidity, particle hygroscopicity and size on the mass loading capacity of glass fiber HEPA filters has been studied. At humidifies above the deliquescent point, the pressure drop across the HEPA filter increased non-linearly with the areal loading density (mass collected/filtration area) of NaCl aerosol, thus significantly reducing the mass loading capacity of the filter compared to dry hygroscopic or non-hygroscopic particle mass loadings. The specific cake resistance, K₂, has been computed for different test conditions and used as a measure of the mass loading capacity. K. was found to decrease with increasing humidity for the non-hygroscopic aluminum oxide particles and the hygroscopic NaCl particles (at humidities below the deliquescent point). It is postulated that an increase in humidity leads to the formation of a more open particulate cake which lowers the pressure drop for a given mass loading. A formula for predicting K₂ for lognormally distributed aerosols (parameters obtained from impactor data) is derived. The resistance factor, R, calculated using this formula was compared to the theoretical R calculated using the Rudnick-Happel expression. For the non-hygroscopic aluminum oxide the agreement was good but for the hygroscopic sodium chloride, due to large variation in the cake porosity estimates, the agreement was poor

[en] The aqueous phase oxidation of SO₂ by H₂O₂ is believed to be the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective of this thesis is to quantify the importance of the noncloud liquid phase reactions of SO₂ by H₂O₂ in the atmosphere. In this thesis growth rates of submicron droplets exposed to SO₂ and H₂O₂ were measured using the tandem differential mobility analyzer (TDMA) technique. The technique uses differential mobility analyzers (DMAs) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charger capable of generating singly charged particles up to 1.0 μm was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH₄)₂SO₄ particles with SO₂ and H₂O₂ concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets ≥0.3 μm, the fractional diameter growth was independent of particle size and for droplets ≤0.2 μm, it decreased as particle size decreased. The observed decrease is due to NH₃ evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium and chemical kinetics. The experimental and theoretical results are in reasonable agreement

[en] Stability is the first and foremost factor responsible for the physical existence and functioning of a system. Simple rule of stability states a stable system like that of atomic nucleus should be composed of stable particles. Total six particles, four of mass, neutron, proton, electron and positron and two of energy, neutrino and antineutrino are real stable and only constitutent particles of the nucleus. They are emitted by the nucleus and their stability is equivalent to that of the nucleus. Neutron and proton constitute primary nuclear system, electron and positron are integral parts of secondary and neutrino and antineutrino belong to tertiary system of the nucleus. All three systems are integrated. The integration of systems provide efficiency, stability and high density of the nucleus. Short-lived particles whose life ranges from 10^-6 sec. to 10^-20 sec. are fragment particles and form by splitting of nucleons when nucleus is bombarded by particles in induced radioactivity

[en] We develop a class of tests for the structural stability of infinite order regression models, when the time of a structural change is unknown. Examples include the infinite order autoregressive model, the nonparametric sieve regression and many others whose dimensions grow to infinity. When the number of parameters diverges, the traditional tests such as the supremum of Wald, LM or LR statistic or their exponentially weighted averages diverge as well. However, we show that a suitable transformation of these tests converges to a proper weak limit as the sample size n and the dimension p grow to infinity simultaneously. In general, this limit distribution is different from the sequential limit, which can be obtained by increasing the order p of the standardized tied-down Bessel process in Andrews (1993). More interestingly, our joint asymptotic analysis discovers that the joint asymptotic distribution depends on a higher order serial correlation. We also establish a weighted power optimality property of our tests under certain regularity conditions. A new result on partial sums of random matrices is established. We examine finite-sample performance in a Monte Carlo study and illustrate the test with a number of empirical examples.

[en] Various mechanisms are under consideration as responsible for energy losses from the edge transport barrier (ETB) during type I Edge Localized modes (ELM) in H-mode plasmas. Recently [1] a model has been proposed based on the assumption that the increase of transport by ELM bursts is due to flows along magnetic field lines perturbed by ballooning-peeling MHD modes. In that consideration the energy losses due to convection of thermal particles and heat conduction of electrons has been taken into account. However, escape of superthermal charged particles along perturbed field lines may also contribute substantially. Similarly to electron heat conduction this loss channel should decrease with increasing plasma collisionality in agreement with experimental observations. In the present work the energy loss with superthermal particles is modelled by considering particles inside the separatrix starting to move along perturbed field lines from different positions and with diverse values of the initial perpendicular energy and parallel velocity. For these particles the equations for motion along field lines and energy conservation are solved numerically by taking into consideration the forces from the ambipolar parallel electric field and coulomb collisions with the background thermal particles which reduce the parallel velocity and total energy. The variation of the radial particle position due to parallel motion is calculated by using the inclination angle of perturbed field lines calculated according to the model in Ref. Only particles which reach the separatrix within the ELM crash time contribute to the energy loss in question and this constrains the space of their initial position, perpendicular energy and parallel velocity. The total loss is assessed by assuming a Maxwellian distribution over the initial energy and velocity and simple step-wise profiles of the plasma density and temperature at the edge with sharp gradients in the ETB. The simulation results are compared with the experimental data. (Author)

No abstract available

[en] Short communication

[en] A generalized methodology currently employed at JPL, was used to develop an analytical model for effects of high-energy electrons and interactions between electron and ultraviolet effects. Chemical kinetic concepts were applied in defining quantifiable parameters; the need for determining short-lived transient species and their concentration was demonstrated. The results demonstrates a systematic and cost-effective means of addressing the issues and show qualitative and quantitative, applicable relationships between space radiation and simulation parameters. An equally important result is identification of critical initial experiments necessary to further clarify the relationships. Topics discussed include facility and test design; rastered vs. diffuse continuous e-beam; valid acceleration level; simultaneous vs. sequential exposure to different types of radiation; and interruption of test continuity

[en] Special Truss Moment frame (STMF) is an open web truss moment frame, which dissipates the input seismic energy through a well-defined ductile special segment located near the mid-span of truss while other members of truss outside the special segment and columns are designed to remain elastic. In this paper, the performance and the fragility curve of STMFs consisting single and multiple vierendeel panels in the special segment are investigated. The seismic response of nine-story having the length to depth ratio of special segment 2.5 is considered to develop the fragility curve. The seismic response of each building was recorded by performing nonlinear incremental dynamic analyses. Each archetype modelled in nonlinear analysis program PERFORM-3D to carry out IDA under a suit of forty-four real Far Field ground motion records. Fragility curves were developed for these structures and the probability of exceedance at immediate occupancy (IO) level, Life safety (LS) level and Collapse performance (CP) level was assessed for two level of hazards, DBE level (10% probability of exceedance in 50 years) and MCE level (2% probability of exceedance in 50 years). For DBE level earthquake intensity, the probability of exceedance for the CP performance level of STMF building for both structure is marginal while at MCE level the probability of exceedance at CP performance level is 71% and 45% for single and multiple panels respectively. (Author)

[en] A method and apparatus for measuring thermal diffusivity and molecular relaxation processes in a sample material utilizing two light beams, one being a pulsed laser light beam for forming a thermal lens in the sample material, and the other being a relatively low power probe light beam for measuring changes in the refractive index of the sample material during formation and dissipation of the thermal lens. More specifically, a sample material is irradiated by relatively high power, short pulses from a dye laser. Energy from the pulses is absorbed by the sample material, thereby forming a thermal lens in the area of absorption. The pulse repetition rate is chosen so that the thermal lens is substantially dissipated by the time the next pulse reaches the sample material. A probe light beam, which in a specific embodiment is a relatively low power, continuous wave (Cw) laser beam, irradiates the thermal lens formed in the sample material. The intensity characteristics of the probe light beam subsequent to irradiation of the thermal lens is related to changes in the refractive index of the sample material as the thermal lens is formed and dissipated. A plot of the changes in refractive index as a function of time during formation of the thermal lens as reflected by changes in intensity of the probe beam, provides a curve related to molecular relaxation characteristics of the material, and a plot during dissipation of the thermal lens provides a curve related to the thermal diffusivity of the sample material