Assessing and predicting changes in vegetation cover associated with military land use activities using field monitoring data at Fort Hood, Texas

We assessed short-term impacts of changes in military training load on vegetative cover at Fort Hood, TX. From 1989 to 1995, permanent field transects were monitored for vegetative cover and land use disturbance using standard army monitoring methods [Land Condition Trend Analysis (LCTA)]. Land use intensity (training load) was quantified and used to develop a model to predict future vegetation cover values. We found that standard Army monitoring methods detected changes in installation resources associated with changes in training load. Increased training loads were associated with increased measures of disturbance, decreased ground cover, and decreased aerial vegetative cover. We found that the spatial pattern of disturbance and vegetation cover remained relatively constant over the study period despite large variations in overall training load. Our model used the consistency in spatial cover patterns over time and the strong relationship between training load and vegetation cover to predict the impact of future training loads on vegetation.     

Nonlinear forced vibrations of an initially-deformed electrically-conducting layer in a magnetic field

Institute of Applied Problems of Mechanics and Mathematics, Academy of Sciences of the Ukrainian SSR, Lvov. Translated from Prikladnaya Mekhanika, Vol. 25, No. 4, pp. 82–88, April, 1989.     

Mechanical instability of amorphous polymeric networks: Asymmetric deformation under symmetric biaxial tension

Asymmetric deformation of a symmetrically loaded rubber sheet was observed, many years ago, by Treloar in his experiments on natural rubber. The problem has recently been studied by Kearsley, and the possibility of asymmetric deformations in an equi-biaxial state of force is predicted by the use of phenomenological constitutive relations. In the present study, the problem is analyzed in relation to the molecular constitution of rubber networks. It is shown that mechanical instability in symmetrically loaded networks may be possible only for limited choices of molecular parameters such as junction functionality, degree of crosslinking, and the degree of swelling during crosslinking and during deformation. Stability of multiple valued deformations is discussed by thermodynamic considerations of the elastic potential.     

Vibration-vibration energy transfer in gaseous HBr

The vibration-vibration energy transfer of HBr gas initially excited to the first vibrational state has been observed. Collisional pumping to the V = 2 level is measured by monitoring the fluorescence of the 2−1 transition. The rate constant for the process: HBr(V=0) + HBr(V=2) → 2HBr(V=1) is found to be 1.4×10⁵ sec⁻¹ torr⁻¹.     

Mathematical modeling of local gradient processes in inertial thermomechanical systems

Conclusions Using methods of thermodynamics of nonequilibrium processes and of mechanics of a continuous medium, a model is constructed of a third body, making it possible to describe mutually related physicomechanical fields with account of their gradients. It has been shown that inclusion of the gradient of the chemical potential field takes into account the features of the fields considered in the near-surface region of the body. Based on the determination of the chemical potential, thermodynamic stability criteria have been formulated.We provided the thermodynamic justification of generalized thermomechanics. It is based on determining the energy of motion in the phase space of the momenta of motion, and makes it possible to describe the increments in the internal energy and in the energy of motion within the same approximations.Institute of Applied Mechanical and Mathematical Problems, Ukrainian Academy of Sciences, L'vov. Translated from Prikladnaya Mekhanika, Vol. 28, No. 12, pp. 3–23, December, 1992.     

Two point problems and analyticity of solutions of abstract parabolic equations

Fort ∈ [a, b], letA(t) be the unbounded operator inH ^0,p (G) associated with an elliptic-boundary value problem that satisfies Agmon’s conditions on the rays λ=±iτ, τ ≥0. Existence and uniqueness results are obtained for weak and strict solutions of two-point problems of the type (du/dt)−A(t) u(t) =f(t),E ₁(α)u (α)=u _α,E ₂ (β)u (β)=u _β. Here [α, β) χ- [a, b],E ₁ (α) andE ₂ (β) are spectral projections associated withA(α) andA(β) respectively, andA(α)E ₁ (α) and =A (β)E ₂ (β) are infinitesimal generators of analytic semigroups. WhenA(t) andf(t) are analytic in a convex, complex neighborhoodO of [a, b] we show that for someθ _i ,i=1,2, any solution ofdu/dt =A(t)u (t)=f(t) in [a, b] is analytic and satisfies the above equation in the setO∩{t; t ≠ a, t ≠ b, | arg (t −a) | <θ ₁, | arg (b −t) |θ ₂}. Research partially supported by N. N. F. grant at Brandeis University.     

Infrared multiphoton excitation of small molecules

The collisionless infrared excitation by short CO₂ laser pulses of the molecules SO₂, OCS, NO₂, NH₃ and DN₃ is compared with that of larger molecules. The average number of photons absorbed per molecule and the fraction of molecules dissociated depends predominantly on the laser intensity, while for larger molecules with higher densities of vibrational states the excitation is primarily determined by the laser fluence.