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Experimental evidence is presented for isomer depletion through nuclear excitation by electron capture in molybdenum-93 nuclei.

Net radiation (Rn)is an important component of the modified Penman equation used to calculate reference evapotranspiration (ET0).Net radiometers, however, require continual maintenance to ensure that the data they generate are reliable. An equation is developed that estimates hourly Rnover wellwatered grass from meteorological data, such as solar radiation, vapor pressure, and air temperature, collected by weather stations in various regions in California. The equation is based on Monteith's daily net radiation equation. Empirical equations are also developed to quantify surface albedo and clear sky global transmissivity. The modified Monteith formula for net radiation is tested in coastal, desert, mountain, and interior valley regions within California. After examining the 1984–1989 data from weather stations in the various regions, the absolute mean error of calculated hourly Rnis within 10% of the measured hourly RnThe absolute mean error of daytime Rnduring θ>10degrees is within 8% of the measured RnThese errors represent an even smaller error in ET0estimates. The modified Monteith equation for Rndoes not require site specific correction factors.

The third-order reaction, H + O2 + M → HO2 + M, has been measured near the low-pressure limit at room temperature for M = He, Ne, Ar, Kr, O2, N2, and H2O and over an extended range of temperatures in a shock tube for M = Ar, O2, and N2. In all cases, H atoms were produced by the laser photolysis of NH3 and detected by atomic resonance absorption spectroscopy. The measurements are consistent with the available experimental record and, in particular, confirm the exceptionally high recombination rate constant when M = H2O. The standard theoretical analysis is applied to this entire experimental record to derive the value of the average energy change per collision, −ΔEall. The resulting −ΔEall values are sensible for all M but H2O. The problem with H2O motivates a change in the standard theoretical analysis that both rationalizes the behavior of H2O and also quantitatively changes the derived −ΔEall values for the other species of M. These changes involve three modifications of the standard treatment:  (1) explicit temperature dependence in the number of active rotational degrees of freedom contributing to the HO2* state density, (2) the replacement of Lennard-Jones potential for the HO2* + M interaction with an electrostatic + dispersion potential, and (3) the calculation of the collision rate between HO2* + M by a free rotor model for “complex formation” between the M and HO2*. The optimized values of −ΔEall that are produced from this new analysis have the following characteristics:  (1) the value of −ΔEall is the same for all rare gases, and (2) −ΔEall for di- and polyatomic molecules are enhanced relative to the rare gas atoms. This work supports the conclusions of previous trajectory studies that collision rates between activated complexes and bath gases are often underestimated while −ΔEall derived from recombination kinetics measurements are often overestimated.

X-ray-driven gamma emission describes processes that may release nuclear energy in a ‘clean’ way, as bursts of incoherent or coherent gamma rays without the production of radioactive by-products. Over the past decade, studies in this area, as a part of the larger field of quantum nucleonics, have gained tremendous momentum. Since 1987 it has been established that photons could trigger gamma emission from a long-lived metastable nuclear excited state of one nuclide and it appears likely that triggering in other isotopes will be demonstrated conclusively in the near future. With these experimental results have come new proposals for the creation of collective and avalanche-like incoherent gamma-ray bursts and even for the ultimate light source, a gamma-ray laser. Obviously, many applications would benefit from controlled bursts of gamma radiation, whether coherent or not. This paper reviews the experimental results and concepts for the production of gamma rays, driven by externally produced X-rays.

A dual feedforward controller for active noise control is presented. The first part of the controller is designed to cancel broadband noise, and the second part is an adaptive controller designed to cancel periodic noise. A simple technique to identify the parameters of the broadband controller is developed. An autoregressive moving-average model is used, and it is found that its stability is improved by prefiltering the test signal with a minimum-phase inverse of the secondary noise channel. The periodic controller uses an estimate of the fundamental frequency to cancel the first few harmonics of periodic noise. A computationally efficient adaptive technique based on least squares is developed to update the harmonic controller gains at each time step. Experimental results are included which demonstrate simultaneous cancellation of both random broadband noise and periodic noise

Net radiation (Rn) is an important component of the modified Penman equation used to calculate reference evapotranspiration (ET0). Net radiometers, however, require continual maintenance to ensure that the data they generate are reliable. An equation is developed that estimates hourly Rn over well‐watered grass from meteorological data, such as solar radiation, vapor pressure, and air temperature, collected by weather stations in various regions in California. The equation is based on Monteith's daily net radiation equation. Empirical equations are also developed to quantify surface albedo and clear sky global transmissivity. The modified Monteith formula for net radiation is tested in coastal, desert, mountain, and interior valley regions within California. After examining the 1984–1989 data from weather stations in the various regions, the absolute mean error of calculated hourly Rn is within 10&percent; of the measured hourly Rn The absolute mean error of daytime Rn during θ > 10 degrees is within 8&percent; of the measured Rn These errors represent an even smaller error in ET0 estimates. The modified Monteith equation for Rn does not require site specific correction factors.

Br-atom atomic resonance absorption spectrometry (ARAS) has been developed and applied to measure thermal decomposition rate constants for CF3Br (+ Kr)→CF3+Br (+ Kr) over the temperature range, 1222–1624 K. The Br-atom curve-of-growth (145<λ<163 nm) was determined using this reaction. For [Br]≤1×10¹² molecules cm⁻³, absorbance, (ABS)=1.410×10⁻¹³ [Br], yielding σ=1.419×10⁻¹⁴ cm². The curve-of-growth was then used to convert (ABS) to Br-atom profiles which were then analyzed to give measured rate constants. These can be expressed in second-order by k1=8.147×10⁻⁹ exp(−24488 K/T) cm³ molecule⁻¹ s⁻¹ (±33%, 1222≤T≤1624 K). A unimolecular theoretical approach was used to rationalize the data. Theory indicates that the dissociation rates are closer to second- than to first-order, i.e., the magnitudes are 30–53% of the low-pressure-limit rate constants over 1222–1624 K and 123–757 torr. With the known, E0=ΔH0⁰=70.1 kcal mole⁻¹, the optimized theoretical fit to the ARAS data requires 〈ΔE〉down=550 cm⁻¹. These conclusions are consistent with recently published data and theory from Kiefer and Sathyanarayana. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 859–867, 1998

This paper illustrates a simple, hand-crafted approach which can be used to design tracking controllers for rigid-link electrically-driven (RLED) robot manipulators. The control methodology is intuitively simple since it is based on concepts readily identified by most control engineers. To illustrate the approach, we develop a corrective tracking controller for the RLED robot dynamics which yields global exponential stability for the link tracking error under the assumption of exact model knowledge. To compensate for the uncertainties in the rigid-link electrically-driven robot model, we then design a corrective robust tracking controller which yields global uniform ultimate bounded stability of the link tracking error. The proposed controller is robust with regard to parametric uncertainties and additive bounded disturbances while correcting for the typically ignored electrical actuator dynamics.

A robust tracking controller for rigid-link electrically driven (RLED) robot manipulators operating in free-space or under motion constraints is introduced. Using models of the robot dynamics and environmental constraints, a dynamic model with decoupled position and force degrees of freedom is obtained for the mechanical subsystem with respect to a set of task-space coordinates. A robust tracking control is then formulated for the decoupled manipulator dynamics and the electrical actuator dynamics, which yields a global uniform ultimate bounded (GUUB) stability result for the position and velocity tracking error. The controller is robust with respect to parametric uncertainties and additive bounded disturbances in the RLED dynamic model. The controller requires measurement of the robot link positions, link velocities, and motor armature currents.

In this study experimental data are presented for the solubility of methane in 3.0 and 6.0 kmol/m³ (30.5 and 59.5 wt %) solutions of 2-(2-aminoethoxy)ethanol (which is also called diglycolamine). Temperatures in this study ranged from 25 to 125 °C and pressures to 13 MPa. The data were incorporated into a rigorous thermodynamic model that has been applied to other similar systems. The new data were then compared with the data available in the literature. In pure water and low amine concentrations it is demonstrated that the isobaric solubility exhibits a minimum. However, for high amine concentration there is a somewhat surprising result&sbd;the isobaric solubility is an increasing function of temperature over the range of temperature studied here.

An adaptive feedforward technique for active control of narrowband acoustic noise of unknown frequency is presented. A phase-locked loop is used to determine the fundamental frequency of the periodic component of the primary noise. Adaptive control of the residual noise is achieved with a least mean square method. Real time implementation is facilitated with an efficient recursive technique that is used to update the controller gains at each time step. Significant noise cancellation is demonstrated in physical experiments, which include additive broadband noise.

Data are presented for the solubility of methane and of ethane in a 3 kmol/m³ (34.7 mass %) solution of methyldiethanolamine. Temperatures in this study ranged from 25 to 130 °C and pressures to 13 MPa. The data were incorporated into a rigorous thermodynamic model that has been applied to other similar systems. The model is a combined Raoult's law−Henry's law approach. The solubilities in the alkanolamine solution are correlated in terms of the salting-in ratio, the ratio of the mole fraction solubility in the amine solution to that in pure water.

The model of Deshmukh and Mather (1981) is a popular method for correlating and predicting the vapor-liquid equilibria in systems containing acid gases (hydrogen sulfide and carbon dioxide) and aqueous solutions of alkanolamines. The model includes phase equilibrium between an aqueous liquid and a gas as well as chemical equilibrium in the aqueous phase. A recent review by Weiland et al. (1993) demonstrated the accuracy of the correlation. Presented here is a model based on that of Deshmukh and Mather (1981) for calculating the distribution of acid gases between two liquid phases - an aqueous phase and a non-aqueous liquid (typically a propane- or butane-rich liquid)In the new model the phase equilibrium is modeled using a modified Henry's law approach. Fugacities of the components in the non-aqueous phase are calculated using the Peng and Robinson (1976a) equation of state. All of the parameters in the model are taken from the literature. Thus the model represents a prediction of the behavior. It is demonstrated that the predictions are in good agreement with the available experimental data

Optical constants for tungsten measured ellipsometrically at room temperature in the visible spectrum are reported. Results are given for (011)-oriented tungsten characterized as clean by low-energy-electron diffraction, for the same surface saturated with oxygen, and for the surface after exposure to air at atmospheric pressure for several hours. Results are compared with earlier work and differences are attributed primarily to differences of surface contamination.

Optical constants, measured ellipsometrically at wavelengths between 400.0 and 632.8 nm, are reported for atomically clean (001) niobium. The results are compared with literature values.

A REVIEW of the literature gives some evidence which indicates that the polysaccharides of Hypnea species and Chondrus crispus (carrageenin) are identical. Clingman's study of H. specifera1showed these polysaccharides to contain D-galactose and 3,6-anhydro-D-galactose, the same basic components found on analysis of Chondrus extracts2. Hypnea extractives have a potassium-sensitive fraction (termed the ϰ-fraction3), as does Chondrus3, which are degraded by a cell-free bacterial preparation from Pseudomonas carrageenovora. This preparation is reported to be specific not just for carrageenin but for its ϰ-fraction4.

Presents a letter to the editor in response to colonel Gary W. Anderson's observations and recommendations in "Fallujah and the Future of Urban Operations," featured in the November 4, 2004 issue of "Marine Corps Gazette."