922 resultados para shifting bottleneck procedure
Resumo:
A newly synthesized and crystalographically characterized napthelene-pyrazol conjugate, 1-(5-phenyl-1H-pyrazole-3-ylimino)-methyl]-naphthalen-2-ol (HL) behaves as an Al(III) ion-selective chemosensor through internal charge transfer (ICT)-chelation-enhanced fluorescence (CHEF) processes in 100 mM HEPES buffer (water-DMSO 5 : 1, v/v) at biological pH with almost no interference of other competitive ions. This mechanism is readily studied from electronic, fluorimetric and H-1 NMR titration. The probe (HL) behaved as a highly selective fluorescent sensor for Al(III) ions as low as 31.78 nM within a very short response time (15-20 s). The sensor (HL), which has no cytotoxicity, is also efficient in detecting the distribution of Al(III) ions in HeLa cells via image development under fluorescence microscope.
Resumo:
Following the recent work of the authors in development and numerical verification of a new kinematic approach of the limit analysis for surface footings on non-associative materials, a practical procedure is proposed to utilize the theory. It is known that both the peak friction angle and dilation angle depend on the sand density as well as the stress level, which was not the concern of the former work. In the current work, a practical procedure is established to provide a better estimate of the bearing capacity of surface footings on sand which is often non-associative. This practical procedure is based on the results obtained theoretically and requires the density index and the critical state friction angle of the sand. The proposed practical procedure is a simple iterative computational procedure which relates the density index of the sand, stress level, dilation angle, peak friction angle and eventually the bearing capacity. The procedure is described and verified among available footing load test data.
Resumo:
The present work deals with the structural and efficient down-shifting (DS) and up-conversion (UC) luminescence properties of erbium ion (Er3+) doped nanocrystalline barium sodium niobate (Ba2Na1-3xErxNb5O15, where x = 0, 0.02, 0.04 and 0.06) powders synthesized via novel citrate-based sol-gel route. The monophasic nature of the title compound was confirmed via x-ray powder diffraction followed by FT-IR studies. High-resolution transmission electron microscopy (HRTEM) facilitated the establishment of the nanocrystalline phase and the morphology of the crystallites. The Kubelka-Munk function, based on diffused reflectance studies and carried out on nano-sized crystallites, was employed to obtain the optical band-gap. The synthesized nanophosphor showed efficient DS/PL-photoluminescence and UC luminescence properties, which have not yet been reported so far in this material. The material emits intense DS green emission on excitation with 378 nm radiation. Interestingly, the material gives intense UC emission in the visible region dominated by green emission and relatively weak red emission on 976 nm excitation (NIR laser excitation). Such a dual-mode emitting nanophosphor could be very useful in display devices and for many other applications.
Resumo:
We present an improved procedure on the approach to determine the stability of polystyrene spheres at microscopic particle levels by means of artificially induced particle collisions with the aid of optical tweezers [J.Chem.Phys. 119, 2399(2003)]. The basic consideration on this new development is that the major contribution to the sticking probability for a particle pair caught into the optical trap for a short period is from its single collision; therefore, if the trapping duration for the pair is taken to be short, the accumulated sticking probability will be a good approximation for the single collision. The experimental procedure associated with this approximation does not resort to exactly controlling the short trapping duration or request the trapping duration correction as previously reported and therefore it is more practical and applicable for broader range of the stability ratio. The experimental results under different electrolyte concentrations by the new procedure are consistent with those from the turbidity measurements.
Resumo:
This paper provides a numerical approach on achieving the limit equilibrium method for 3D slope stability analysis proposed in the theoretical part of the previous paper. Some programming techniques are presented to ensure the maneuverability of the method. Three examples are introduced to illustrate the use of this method. The results are given in detail such as the local factor of safety and local potential sliding direction for a slope. As the method is an extension of 2D Janbu's generalized procedure of slices (GPS), the results obtained by GPS for the longitudinal sections of a slope are also given for comparison with the 3D results. A practical landslide in Yunyang, the Three Gorges, of China, is also analyzed by the present method. Moreover, the proposed method has the advantages and disadvantages of GPS. The problem frequently encountered in calculation process is still about the convergency, especially in analyzing the stability of a cutting corner. Some advice on discretization is given to ensure convergence when the present method is used. However, the problem about convergency still needs to be further explored based on the rigorous theoretical background.
Resumo:
The divergence of properties from one location to another within a soil mass is termed spatial variability, which traditionally includes three parameters the mean, the standard deviation, and the scale of fluctuation, in order to stochastically describe a soil property. Among them, determining the scale of fluctuation in the evaluation of spatial variability of soil profiles is not easy due to soil condition complexity. A simplified procedure is presented in the paper to determine the scale of fluctuation combined recurrence averaging and weighted linear regression. The alternative approach utilizes widely usable spreadsheet to solve the problem more directly and efficiently.
Resumo:
This thesis considers in detail the dynamics of two oscillators with weak nonlinear coupling. There are three classes of such problems: non-resonant, where the Poincaré procedure is valid to the order considered; weakly resonant, where the Poincaré procedure breaks down because small divisors appear (but do not affect the O(1) term) and strongly resonant, where small divisors appear and lead to O(1) corrections. A perturbation method based on Cole's two-timing procedure is introduced. It avoids the small divisor problem in a straightforward manner, gives accurate answers which are valid for long times, and appears capable of handling all three types of problems with no change in the basic approach.
One example of each type is studied with the aid of this procedure: for the nonresonant case the answer is equivalent to the Poincaré result; for the weakly resonant case the analytic form of the answer is found to depend (smoothly) on the difference between the initial energies of the two oscillators; for the strongly resonant case we find that the amplitudes of the two oscillators vary slowly with time as elliptic functions of ϵ t, where ϵ is the (small) coupling parameter.
Our results suggest that, as one might expect, the dynamical behavior of such systems varies smoothly with changes in the ratio of the fundamental frequencies of the two oscillators. Thus the pathological behavior of Whittaker's adelphic integrals as the frequency ratio is varied appears to be due to the fact that Whittaker ignored the small divisor problem. The energy sharing properties of these systems appear to depend strongly on the initial conditions, so that the systems not ergodic.
The perturbation procedure appears to be applicable to a wide variety of other problems in addition to those considered here.
Resumo:
Deference to committees in Congress has been a much studied phenomena for close to 100 years. This deference can be characterized as the unwillingness of a potentially winning coalition on the House floor to impose its will on a small minority, a standing committee. The congressional scholar is then faced with two problems: observing such deference to committees, and explaining it. Shepsle and Weingast have proposed the existence of an ex-post veto for standing committees as an explanation of committee deference. They claim that as conference reports in the House and Senate are considered under a rule that does not allow amendments, the conferees enjoy agenda-setting power. In this paper I describe a test of such a hypothesis (along with competing hypotheses regarding the effects of the conference procedure). A random-utility model is utilized to estimate legislators' ideal points on appropriations bills from 1973 through 1980. I prove two things: 1) that committee deference can not be said to be a result of the conference procedure; and moreover 2) that committee deference does not appear to exist at all.