Conditions For Various Types Research Articles

Initial?boundary-value problem for the relativistic string with massive ends

It is shown that the initial-boundary-value problem for a relativistic string with masses at the ends can be solved for the most general form of specification of the initial position and initial velocities of the points of the string. An investigation is made of the connection between the freedom in the parametrization of the initial curve and the reparametrization invariance preserving linearity of the equations of motion of the string. The posed problem is solved by extending the solution determined by the initial conditions from the restricted initial region to the entire world surface of the string by means of boundary conditions of various types: the mass at a given end is equal to zero, is infinitely large, or is finite. In the last case it is shown that the problem of the extension reduces to the solution of a normal system of ordinary differential equations. Specific examples are considered.

Nested Case-Control Studies

The nested case-control study design (or the case-control in a cohort study) is described here and compared with other designs, including the classic case-control and cohort studies and the case-cohort study. In the nested case-control study, cases of a disease that occur in a defined cohort are identified and, for each, a specified number of matched controls is selected from among those in the cohort who have not developed the disease by the time of disease occurrence in the case. For many research questions, the nested case-control design potentially offers impressive reductions in costs and efforts of data collection and analysis compared with the full cohort approach, with relatively minor loss in statistical efficiency. The nested case-control design is particularly advantageous for studies of biologic precursors of disease. To advance its prevention research agenda, NIH might be encouraged to maintain a registry of new and existing cohorts, with an inventory of data collected for each; to foster the development of specimen banks; and to serve as a clearinghouse for information about optimal storage conditions for various types of specimens.

Near-resonance highly nonlinear gas oscillations in tubes

Near-resonance highly nonlinear ideal perfect gas oscillations in tubes are studied numerically for boundary conditions of various types. The oscillations are initiated by weak periodic perturbations at one end of the tube. As distinct from earlier studies [1–10], the oscillation amplitudes were not assumed to be small and the entropy increase at the shock waves formed was taken into account. Periodic flow regimes result as a limit of the solution of a Cauchy problem for one-dimensional time-dependent gasdynamic equations. The frequency responses of the oscillations under consideration are determined for boundary conditions of various types. It is shown that in specific cases the attainment of a periodic regime is accompanied by the appearance of long-wave modulations. The “repeated resonance” effect is revealed. This is due to the change in the tube's natural acoustic frequency, which takes place during the heating of the gas in the tube by the shock waves traveling in it.

Stability condition for the explicit algorithms of the time domain analysis of Maxwell's equations

This letter presents the derivation of the stability condition for various types of time domain algorithms used in the solution of linear hyperbolic differential equations that arise in the investigation of transient electromagnetic fields. The stability condition of the algorithm is derived by investigating the properties of operators in suitably defined Hilbert spaces. Compared to the classical von Neumann stability analysis, the functional analysis approach gives more general results that can be easily applied to some recent and possible future time domain schemes. >

On stability in local controllability problems for discrete nonlinear systems*

Sufficient conditions for various types of local controllability for a general class of discrete nonlinear inclusions have been given in Ref.15. In this paper we prove that these conditions also imply local controllability of perturbed inclusion as well. The stability of controllability for discrete convex Inclusions is also considered

Lipschitz stability of impulsive systems of differential equations

In the present paper notions of Lipschitz stability of the zero solution of impulsive systems of differential equations with fixed moments of impulse effect arc introduced. Sufficient conditions for various types of uniform Lipschitz stability are obtained and the relations between these options are investigated The results obtained are used for the investigation of the uniform Lipschitz stability of the zero solution of linear impulsive systems of differential equations.

Practical Guidance for Flux Chamber Measurements of Fugitive Volatile Organic Emission Rates

Abstract Hazardous waste sites and industrial facilities contain area sources of fugitive emissions. Emission rate measurements or estimates are necessary for air pathway assessments for these sources. Emission rate data can be useful for the design of emission control and remediation strategies as well as for predictive modeling for population exposure assessments. This paper describes the use of a direct emission measurement approach – the enclosure approach using an emission isolation flux chamber – to measure emission rates of various volatile organic compounds (VOCs) from contaminated soil and water. A variety of flux chamber equipment designs and operating procedures have been employed by various researchers. This paper contains a review of the design and operational variables that affect the accuracy and precision of the method. Guidance is given as to the optimum flux chamber design and operating conditions for various types of emission sources. Also presented is a generic quality control program that gives the minimum number of duplicate, blank, background, and repeat samples that should be performed.

The perturbation method in problems of the dynamics of inhomogeneous elastic rods

The regular perturbation method (the small-parameter method) is developed in order to investigate the dynamics of weakly inhomogeneous rods with arbitrary distributed loads and boundary conditions of various types leading to self-conjugate boundary-value problems. The approach rests on the introduction of a perturbed argument, namely, the Euler variable, and a suitable representation of the eigenfunctions. It enables one to carry out uniform constructions of the basis and the eigenvalues, as well as the frequencies with any required accuracy in terms of the small parameter using quadratures of known functions. To illustrate the effectiveness, an example involving inhomogeneous rods with hinged left-hand ends and free right-hand ends and with box-shaped and circular cross-sections whose dimensions depend linearly on the coordinate are investigated and computed.

Lipschitz stability of impulsive systems of differential equations

Notions ofLipschitz stability of the zero solution of impulsive systems of differential equations with fixed moments of impulse effect are introduced. Sufficient conditions for various types of uniform Lipschitz stability are obtained and the relations between these notions are investigated. The results obtained are used for the investigation of the uniform Lipschitz stability of the zero solution of linear impulsive systems of differential equations.

Global stability of sets for impulsive differential systems by Lyapunov's direct method

In the present paper the question of global stability of sets of sufficiently general type with respect to systems of impulsive differential equations is considered.It is proved that with the existence of piecewise continuous functions of the type of Lyapunov's functions, with certain properties, is a sufficient condition for various types of global asymptotic stability.

On the global stability of sets for impulsive differential systems by Lyapunov's direct method

In the present paper the question of global stability of sets of sufficiently general type with respect to systems of impulsive differential equations is considered It is proved that the existence of piecewise continuous functions of the type of Lyapunov's functions with certain properties is a sufficient condition for various types of global asymptotic stability

Estimation of sensible heat flux from measurements of surface radiative temperature and air temperature at two meters: Application to determine actual evaporation rate

From measurements of sensible heat flux ( H), using the simplified aerodynamic approach, and measurements of surface thermal infrared temperature ( T s), both in arid and semi-arid areas of Tunisia, it is shown that a simple linear relationship can be used to estimate H from the difference ( T s- T a), T a being the air temperature at 2 m. It is also pointed out that this relationship can be used in unstable conditions for various types of surface roughness. Application to determine actual evaporation rate is made using the similarity of the H/ Rn instantaneous values at noon with the average daily values of H/ Rn.

Global stability of sets for systems with impulses

The question of global stability of sets of sufficiently general type with respect to systems of differential equations with impulses is considered. It is proved that the existence of piecewise continuous functions of the type of Lyapunov's functions with certain properties is a sufficient condition for various types of global asymptotic stability.

Stability of sets for impulsive systems

Problems related to the stability and asymptotic stability of sets of sufficiently general type with respect to impulsive systems are considered. The research is done by means of piecewise continuous anxiliary functions which are an analogue of the classical Lyapunov functions. It is proved that the existence of such functions with certain properties is a sufficient condition for various types of stability and asymptotic stability of sets with respect to impulsive systems.

Temporal variation of rainfall intensity from convective Cloud – A theoretical approach

The rainfall intensity from convective clouds vary during the period of rainfall. In the present paper a mathematical expression has been deduced for the temporal variation of rainfall intensity in terms of terminal velocity v, drop diameter D and drop size distribution ND and an effort has made to lay down the condition for various types of temporal variation of rainfall intensity mathematically and the physical significance of various expressions were tried to explain. It is shown that the presence or absence of updraft during precipitation reaching ground is an important controlling factor. It has also been shown that the drop size distribution also plays a significant role.

Controllability of nonlinear discrete systems without differentiability assumption

The paper gives another approach to studying controllability of nonlinear discrete systems, which is based on proving the support principle for some boundary problems involving locally Lipschitzian set-valued maps. The approach enables us to develop sufficient conditions for various types of local controllability of nonlinear non-stationary discrete systems without differentiability assumption. For linear discrete systems with constrained states and controls, necessary and sufficient conditions for local controllability are given.

Charge orderings and lattice distortions in complex TCNQ salts

A model for the description of charge orderings and distortions in complex TCNQ salts involving intra- and interchain electron interactions and electron-lattice couplings is investigated. Its thermodynamical properties are analysed in the limit of infinitely strong intramolecular Coulomb repulsion, treating intermolecular interactions within the two-sublattice H-F approximation. Stability conditions for various types of orderings are determined. Site charge ordering and dimerization accompanied by bond charge ordering are found to coexist only in a limited range of parameters diminished by the hopping and the electron-phonon coupling via Coulomb forces. Depending on the value of the latter, interaction phase transitions in the system can be continuous or not. Intermolecular Coulomb interaction stabilizes site charge ordering but it can also essentially enhance transition temperatures and energy gap in dimerized phases. For experimentally reliable values of parameters the energy gaps predicted by the model are in good agreement with those observed in D +(TCNQ) − 2.

Influence of the spatial structure of the gain on the dynamic properties of a laser

The influence of the longitudinal periodic structure of the gain and of coherent and noncoherent interaction of radiation with matter on the amplitude and frequency-phase self-modulation of laser radiation is investigated, for the case where the active medium partly fills the resonator. An analysis and a computer experiment are used to derive conditions for various types of mode locking.

Popillia japonica 1 : Effect of Soil Moisture and Texture on Survival and Development of Eggs and First Instar Grubs 2

Egg and 1st-instar survival as a function of soil texture and moisture was estimated under laboratory conditions. These stages were found to be resistant to extreme moisture conditions in various types of soils. Delays in egg development were observed particularly in saturated soils. These results are used in developing a mathematical model of survival of the early instars under variable moisture conditions, and simulations are compared with field data. Field survival was highly variable and correlated only partially to model outputs. Probable causes of the discrepancies are discussed.

Controllability of stochastic linear systems

In the paper necessary and sufficient conditions for various types of stochastic controllability of the linear stochastic system of the form d x = Ax d t + Bu d t + C d w r , x(0) = x 0 are given. Some possible extensions are indicated as well.