Aaberg booths

The first methanol bus in the world was placed in revenue service in Auckland, New Zealand in June 1981. It was a Mercedes O 305 city bus using the M 407 hGO methanol engine. This vehicle operated in revenue service for several years with mixed results. Fuel economy on an equivalent energy basis ranged from 6 to 17% mote than diesel fuel economy. Power and torque matched the diesel engine and drivers could not detect a difference. ReHabiUty and durabihty of components was a problem. Additional demonstrations took place in Berlin, Germany and in Pretoria, South Africa, both in 1982.  [c.428]

If the network comprises mixed exchanger specification, then an additional degree of uncertainty is introduced into the capital cost target. Applying the -factor approach to a single exchanger, where both streams require the same specification, there is no error. In practice, there can be different specifications on two streams being matched, and (pc for specifications involving shell-and-tube heat exchangers with different materials of construction and pressure rating. This does not present a problem, since the exchanger can be designed for different materials of construction or pressure rating on the shell side and the tube side of a heat exchanger. If, for example, there is a mix of streams, some requiring carbon steel and some stainless steel, then some of the matches involve a corrosive stream on one side of the exchanger and a noncorrosive stream on the other. The capital cost of such exchangers will lie somewhere between the  [c.232]

The first major hazard in process plants is fire, which is usually regarded as having a disaster potential lower than both explosion or toxic release. However, fire is still a major hazard and can, under the worst conditions, approach explosion in its disaster potential. It may, for example, give rise to toxic fumes. Let us start by examining the important factors in assessing fire as a hazard.  [c.255]

In Sec. 6.3 it was mentioned that some problems, known as threshold problems, do not have a pinch. They need either hot utility or cold utility but not both. How should the approach be modified to deal with the design of threshold problems  [c.371]

A first approach to testing, ASTM D 1094, is to create, using a potassium phosphate reagent, a separation between two layers, hydrocarbon and aqueous. The degree of separation of the two phases is estimated by attributing a grade from 1 to 3 and the appearance of the interface by five levels of observation 1, lb, 2, 3, and 4. The specifications establish both the quality of separation (2 is the maximum) and the appearance of the interface (lb maximum).  [c.250]

To give some structure to the process design it is common to present information and ideas in the form of process flow schemes (PFS). These can take a number of forms and be prepared in various levels of detail. Atypical approach is to divide the process into a hierarchy differentiating the main process from both utility and safety processes.  [c.239]

A novel optimization approach based on the Newton-Kantorovich iterative scheme applied to the Riccati equation describing the reflection from the inhomogeneous half-space was proposed recently [7]. The method works well with complicated highly contrasted dielectric profiles and retains stability with respect to the noise in the input data. However, this algorithm like others needs the measurement data to be given in a broad frequency band. In this work, the method is improved to be valid for the input data obtained in an essentially restricted frequency band, i.e. when both low and high frequency data are not available. This  [c.127]

We used the concept of sound velocity dispersion for explanation of the shift of pulse energy spectrum maximum, transmitted through the medium, and correlation of the shift value with function of medium heterogeneity. This approach gives the possibility of mathematical simulation of the influence of both medium parameters and ultrasonic field parameters on the nature of acoustic waves propagation in a given medium.  [c.734]

As we have mentioned, the particular characterization task considered in this work is to determine attenuation in composite materials. At our hand we have a data acquisition system that can provide us with data from both PE and TT testing. The approach is to treat the attenuation problem as a multivariable regression problem where our target values, y , are the measured attenuation values (at different locations n) and where our input data are the (preprocessed) PE data vectors, u . The problem is to find a function iy = /(ii ), such that i), za jy, based on measured data, the so called training data.  [c.887]

In addition these directives had to be decided unanimously by the European Council which made their adoption cumbersome and slow. These directives are now referred to as old approach directives. A radical change was needed so that the Community legislation could respond to the needs of both, the completion of the internal market for the products concerned, and the need to offer to industry a flexible legislative environment which would encourage technical progress.  [c.937]

That Global Approach requires that the proeedures to prove compliance of a product with the essential requirements in New Approach directives should be chosen from amongst nine procedures referred to as modules. These modules range from a procedure which does not involve the intervention of a third party, the manufacturer s own production control, to procedures with full intervention of that party at both levels, at the design and at the manufacturing stage.  [c.939]

The first approach - quality through NDT laboratory accreditation - is widely used both in Western and Eastern Europe and is realized on rules and procedures specified in the EN 45000 series and EAL -G15 Accreditation for Non-Destructive Testing Laboratories .  [c.956]

A comprehensive approach to the quality assurance in NDT would combine both approaches. It creates and maintains conditions for the people protection, safe operation of objects and products and preservation of the environment.  [c.956]

Unprotected steel corrodes at a rate which is generally assumed to be 0.1 to 0.2mm per annum. Factors that influence the actual rate of corrosion include the maintenance program applied by the owner - particularly preservation of protective coatings, efficiency of cathodic protection systems in ballast tanks, corrosive properties of the cargo carried and environmental factors such as temperature and humidity. Under extreme conditions it has been known for the annual rate of corrosion on unprotected steel exposed on both surfaces to approach 1mm.  [c.1048]

The statistical mechanical approach, density functional theory, allows description of the solid-liquid interface based on knowledge of the liquid properties [60, 61], This approach has been applied to the solid-liquid interface for hard spheres where experimental data on colloidal suspensions and theory [62] both indicate 0.6 this  [c.62]

The film pressure is defined as the difference between the surface tension of the pure fluid and that of the film-covered surface. While any method of surface tension measurement can be used, most of the methods of capillarity are, for one reason or another, ill-suited for work with film-covered surfaces with the principal exceptions of the Wilhelmy slide method (Section II-6) and the pendant drop experiment (Section II-7). Both approaches work very well with fluid films and are capable of measuring low values of pressure with similar precision of 0.01 dyn/cm. In addition, the film balance, considerably updated since Langmuir s design (see Section III-7) is a popular approach to measurement of V.  [c.114]

Calculate 7wh for the cyclohexane-water interface using the Good-Fowkes approach. Repeat the calculation using Eq. IV-13. Compare both results with the experimental value and comment.  [c.156]

The atomic unit (AU) of dipole moment is that of a proton and electron separated by a distance equal to the first Bohr orbit, oq. Similarly, the au of polarizability is Oq [125]. Express and o for NH3 using both the cgs/esu and SI approach.  [c.250]

In the quantum mechanics of atoms and molecules, both perturbation theory and the variational principle are widely used. For some problems, one of the two classes of approach is clearly best suited to the task, and is thus an established choice. Flowever, in many others, the situation is less clear cut, and calculations can be done with either of the methods or a combination of both.  [c.51]

Research over the past decade has demonstrated that a multidimensional TST approach can also be used to calculate an even more accurate transmission coefficient than for systems that can be described by the fiill GLE with a non-quadratic PMF. This approach has allowed for variational TST improvements [21] of the Grote-Hynes theory in cases where the nonlinearity of the PMF is important and/or for systems which have general nonlinear couplmgs between the reaction coordinate and the bath force fluctuations. The Kramers turnover problem has also been successfiilly treated within the context of the GLE and the multidimensional TST picture [22]. A multidimensional TST approach has even been applied [H] to a realistic model of an Sj 2 reaction and may prove to be a promising way to elaborate the explicit microscopic origins of solvent friction. Wliile there has been great progress toward an understanding and quantification of the dynamical corrections to the TST rate constant in the condensed phase, there are several quite significant issues that remain largely open at the present time. For example, even if the GLE were a valid model for calculating the dynamical corrections, it remains unclear how an accurate and predictive microscopic theory can be developed for the friction kernel q(t) so that one does not have to resort to a molecular dynamics simulation [17] to calculate this quantity. Indeed, if one could compute the solvent friction along the reaction coordinate in such a maimer, one could instead just calculate the exact rate  [c.890]

Recently, it has been shown that both the detection and generation of ultrafast THz pulses can be carried out usmg the electro-optic effect in thin films of materials such as ZnTe, GaAs and InP that are pumped in the near-IR [49]. The generation efficiency is similar to that of the photoconducting anteima approach, but the electro-optic scheme offers two extremely significant advantages. First, the detection bandwidth can be extremely large, up to 30-40 THz under optimum conditions [49]. Second, it is possible to directly image the THz field with such spectrometers. Such approaches therefore make possible the THz imaging of optically opaque materials with a compact, all solid-state, room-temperature system [50]  [c.1249]

Inelastic electron collisions can be roughly divided mto two regimes those in which the kinetic energy of the projectile electron greatly exceeds the energy of the target atom or molecule s electrons excited by the collision, and those in which the projectile and target electron energies are comparable. In the higher-energy region the target electrons are little disturbed by the approach and departure of the projectile the excitation occurs suddenly when the projectile is very close to tlie target. In the lower-energy region, the interaction proceeds on a time scale comparable to the orbital period of the target electrons both projectile and target electrons make significant adjustments to one another s presence. In some such cases, it may even make sense to consider the electron-target complex as a transient negative ion.  [c.1314]

Another example of the difficulty is offered in figure B3.1.5. Flere we display on the ordinate, for helium s (Is ) state, the probability of finding an electron whose distance from the Fie nucleus is 0.13 A (tlie peak of the Is orbital s density) and whose angular coordinate relative to that of the other electron is plotted on the abscissa. The Fie nucleus is at the origin and the second electron also has a radial coordinate of 0.13 A. As the relative angular coordinate varies away from 0°, the electrons move apart near 0°, the electrons approach one another. Since both electrons have opposite spin in this state, their mutual Coulomb repulsion alone acts to keep them apart.  [c.2160]

Some people prefer to use the multiple time step approach to handle fast degrees of freedom, while others prefer to use constraints, and there are situations in which both techniques are applicable. Constraints also find an application in the study of rare events, where a system may be studied at the top of a free energy barrier (see later), or for convenience when it is desired to fix a thennodynamic order parameter or ordering direction  [c.2253]

This chapter discussed the importance of human reliability in process accidents. It reviewed the databases that are presently available. It presented Internet addresses from which the most current data may be obtained. It discussed how human errors have caused or affected plant accidents. The SHARP method was presented for integrating HRA into a PSA. Next, it introduced ten methods for assessing and modeling human error mostly using expert judgment. Statistical human error data sources were presented with a preponderance coming from the nuclear power industry. The chapter concluded with the presentation of two of the more popular methods. First an example of an assessment of human error for operator actuation of the ADS, and. second as an ciltemative a discussion of the HRA event tree approach. Both of these methods are widely used in current PSAs. A integrated approach applying each of the methods as needed is presented from Luckas, et al. (1986). Here the analysis concentrated on an anticipated transient without scram (ATWS) sequence with the closure of the main steam isolation valves. With this background, we c.in now attack the problem of reliability modeling of complex systems in the next chapter.  [c.184]

Since heteroarynes are thus seen to be subject to strong orientation effects, the detection of the occurrence of the aryne mechanism and the evaluation of the extent of its participation require a special approach. Both the aryne and Sj Arl mechanisms can occur together, and variation of the leaving group on a substrate (e.g., 2-halonaphthalenes) can cause a complete shift from the aryne (2-chloro, -bromo, and -iodo) to the Sj Arl mechanism (2-fluoro) see also Section II, D, 1.  [c.154]

Whether this approach works in practice is easily tested. We can take a problem and design all possible nonintegrated sequences and then heat integrate those sequences and compare. Freshwater and Ziogou and Stephanopoulos, Linnhoff, and Sophos have carried out extensive numerical studies on sequences of simple distillation columns both with and without heat integration. One interesting result from the study of Freshwater and Ziogou was that the configuration that achieved the greatest energy saving by integration often already had the lowest energy requirement prior to integration. When this was not so, the difference in energy consumption between the integrated configuration with the lowest energy import and the one based on the nonintegrated configuration that required the least energy was usually minimal.  [c.142]

O. Venard. Eddy current tomography a bayesian approach with a compound weak membrane-beta prior model. In Advances in Signal Processing for Non Destructive Evaluation of Materials, 1997.  [c.333]

Two simulation methods—Monte Carlo and molecular dynamics—allow calculation of the density profile and pressure difference of Eq. III-44 across the vapor-liquid interface [64, 65]. In the former method, the initial system consists of N molecules in assumed positions. An intermolecule potential function is chosen, such as the Lennard-Jones potential, and the positions are randomly varied until the energy of the system is at a minimum. The resulting configuration is taken to be the equilibrium one. In the molecular dynamics approach, the N molecules are given initial positions and velocities and the equations of motion are solved to follow the ensuing collisions until the set shows constant time-average thermodynamic properties. Both methods are computer intensive yet widely used.  [c.63]

As a very direct method for measuring x, the surface is extended by means of two barriers that move apart at a velocity such that d In /d/ is constant. The dilation or depletion of the film results in a higher surface tension, measured by means of a Wil-helmy slide positioned at the center between the two barriers, where no liquid motion occurs. The procedure was applied to surfactant solutions [118]. An alternative approach is that of generating longitudinal waves by means of an oscillating barrier and observing the amplitude and phase lag of the motion of a small test particle [119,120] or of the film pressure [121]. On analysis, the data yield both E and the sum of and x. One may also measure the rate of change of surface dipole orientation, as obtained from the change in contact potential, following a change in surface area [122].  [c.120]

The various treatments were discussed by Stigter and Dill [115]. They tested the data of Mingins et al. for sodium octadecyl sulfate at the n-heptane-water interface [116] using both a virial equation and the Davies approach, modifying the latter to allow for the discrete size of the polar head group. The corrected Davies equation gave a much improved fit to the data. Alternatively, Gaines [117] applied the surface phase approach to ionized films, obtaining fairly good agreement with data.  [c.556]

Although the transition to difhision control is satisfactorily described in such an approach, even for these apparently simple elementary reactions the situation in reality appears to be more complex due to the participation of weakly bonding or repulsive electronic states which may become increasingly coupled as the bath gas density increases. These processes manifest tliemselves in iodine atom and bromine atom recombination in some bath gases at high densities where marked deviations from TronnaF behaviour are observed [3, 4]. In particular, it is found that the transition from Lto is significantly broader than  [c.846]

A second recent development has been the application 46 of the initial value representation 47 to semiclassically calculate A3.8.13 (and/or the equivalent time integral of the flux-flux correlation fiinction). While this approach has to date only been applied to problems with simplified hannonic baths, it shows considerable promise for applications to realistic systems, particularly those in which the real solvent bath may be adequately treated by a fiirther classical or quasiclassical approximation.  [c.893]

This is connnonly known as the transition state theory approximation to the rate constant. Note that all one needs to do to evaluate (A3.11.187) is to detennine the partition function of the reagents and transition state, which is a problem in statistical mechanics rather than dynamics. This makes transition state theory a very usefiil approach for many applications. However, what is left out are two potentially important effects, tiiimelling and barrier recrossing, bodi of which lead to CRTs that differ from the sum of step frmctions assumed in (A3.11.1831.  [c.993]

The distinctive chemical and physical properties of surfaces and interfaces typically are dominated by the nature of one or two atomic or molecular layers [2, 3], Consequently, usefiil surface probes require a very high degree of sensitivity. How can this sensitivity be achieved For many of the valuable traditional probes of surfaces, the answer lies in the use of particles that have a short penetration depth through matter. These particles include electrons, atoms and ions, of appropriate energies. Some of the most familiar probes of solid surfaces, such as Auger electron spectroscopy (AES), low-energy electron diffraction (FEED), electron energy loss spectroscopy (EELS) and secondary ion mass spectroscopy (SIMS), exploit massive particles both approaching and leaving the surface. Other teclmiques, such as photoemission spectroscopy and inverse photoemission spectroscopy, rely on electrons for only half of the probing process, with photons serving for the other half These approaches are complemented by those that directly involve the adsorbate of interest, such as molecular beam techniques and temperature progranuned desorption (TPD). While these methods are extremely powerfiil, they are generally restricted to—or perfonn best for—probing materials under high vacuum conditions. This is a significant limitation, since many important systems are intrinsically incompatible with high vacuum (such as the surfaces of most liquids) or involve interfaces between two dense media. Scaiming tuimellmg microscopy (STM) is perhaps the electron-based probe best suited for investigations of a broader class of interfaces. In this approach, the physical proximity of the tip and the probe penuits the method to be applied at certain interfaces between dense media.  [c.1264]

In view of the diversity of material systems to which the SHG/SFG method has been applied and the range of the infonnation that tlie method has yielded, we cannot give a comprehensive account of the teclmique in this chapter. For such accounts, we must refer the reader to the literature, particularly as summarized in various review articles [12, 13, 14, 15, 16,11, 18, 19, 20, 21, 22, 23, 24, 25, 26 and 27] and monographs [10, 28, 29]. Our aim here is only to present an overview of the subject in which we attempt to describe the basic principles. The chapter is organized in the following fashion. We first outline basic theoretical considerations relevant to the teclmique, both in a brief general discussion of nonlinear optics and in a specific description of the nonlinear response of interfaces. After a few words about experimental teclmiques for surface SHG/SFG measurement, we devote the remainder of the chapter to describing the type of mfomiation that may be extracted from the nonlinear measurements. We have attempted at least to mention the different classes of infonnation that have been obtained, such as adsorbate coverage or vibrational spectroscopy. In most cases, the corresponding approach has been widely and fruitfully applied in many experimental studies. Although we offer some representative examples, space does not pennit us to discuss these diverse applications in any systematic way.  [c.1265]

The treatment of this section has been based on an assumed nonlinear surface response and has dealt entirely with electromagnetic considerations of excitation and radiation from the interface. A complete theoretical picture, however, includes developing a microscopic description of the surface nonlinear susceptibility. In the discussion in section Bl.5.4. we will introduce some simplified models. In this context, an important first approxunation for many systems of chemical interest may be obtained by treating the surface nonlinearity as arising from the composite of individual molecular contributions. The molecular response is typically assumed to be that of the isolated molecule, but in the sunnnation for the surface nonlinear response, we take into account the orientational distribution appropriate for the surface or interface, as we discuss later. Local-field corrections may also be included [4T, 42]. Such analyses may then draw on the large and well-developed literature concerning the second-order nonlinearity of molecules [43, 44]. If we are concerned with the response of the surface of a clean solid, we must typically adopt a different approach one based on delocalized electrons. This is a challenging undertaking, as a proper treatment of the linear optical properties of surfaces of solids is already diflScult [45]. Nonetheless, in recent years significant progress has been made in developing a fiindamental theory of the nonlinear response of surfaces of both metals [46, 47,  [c.1278]

Several other improvements of the inversion-recovery scheme employ advanced tools of modem NMR spectroscopy polarization transfer and two-dimensional spectroscopy (see fiirther reading). The basic design of selected pulse sequences is compared with the simple inversion-recovery scheme in figure Bl.13.5 taken from Kowalewski and Maler [24], where references to original papers can be found. The figure Bl.13.5(a), where thick rectangular boxes denote the 180° /-spin pulses and thin boxes the corresponding 90° pulses, is a representation of the inversion-recovery sequence with the continuous saturation of the protons. In figure B1.13.5(b), the inverting /-spin pulse is replaced by a series of pulses, separated by constant delays and applied at both the proton and the /-spm resonance frequencies, which creates a more strongly polarized initial /-spin state (the polarization transfer teclmique). In figure B1.13.5(c), a two-dimensional (2D) NMR teclmique is employed. This type of approach is particularly usefiil when the sample contains many heteromiclear IS spin pairs, with different /s and different. S s characterized by slightly different resonance frequencies (chemical shifts), resulting in crowded spectra. In a generic 2D experiment, the NMR signal is sampled as a fiinction of two time variables t is the miming tune during which the FID is acquired (different  [c.1508]

Since the AFM is connnonly used under ambient conditions, it must be home in mind that the sample is likely to be covered with multilayers of condensed water. Consequently, as the tip approaches the surface, a meniscus fonus between tip and surface, introducing an additional attractive capillary force. Depending on the tip radius, the magnitude of this force can be equal to or greater than that of the van der Waals forces and is observed clearly in the approach curve [98]. In fact, this effect has been exploited for the characterization of thin liquid lubricant films on surfaces [95]. The capillary forces may be eliminated by operation in ultrahigh vacuum, provided both tip and sample are baked, or, most simply, by carrying out the experiment under a contamination-free liquid enviromuent, using a liquid cell [99].  [c.1696]

Scherer et al [205. 206] showed how to prepare, using interferometric methods, pairs of laser pulses with known relative phasing. These pulses were employed in experiments on vapour phase I2, in which wavepacket motion was detected in tenns of fluorescence emission. A more general approach, which can be used in principle to generate pulse sequences of any type, is to transfomi a single input pulse into a shaped output profile, with the intensity and phase of the output under control tln-oughout. The idea being exploited by a number of investigators, notably Warren and Nelson, is to use a programmable dispersive delay line constructed from a pair of diffraction gratings spaced by an active device that is used either to absorb or phase shift selectively the frequency-dispersed wavefront. The approach favoured by Warren and co-workers exploits a Bragg cell driven by a radio-frequency signal obtained from a frequency synthesizer and a computer-controlled arbitrary wavefomi generator [207]. Nelson and co-workers use a computer-controlled liquid-crystal pixel array as a mask [208]. In the fiiture, it is likely that one or both of these approaches will allow execution of currently impossible nonlinear spectroscopies with highly selective infomiation content. One can take inspiration from the complex pulse sequences used in modem multiple-dimension NMR spectroscopy to suppress unwanted interfering resonances and to enliance selectively the resonances from targeted nuclei.  [c.1990]

The projector augmented-wave (PAW) DFT method was invented by Blochl to generalize both the pseudopotential and the LAPW DFT teclmiques [M]- PAW, however, provides all-electron one-particle wavefiinctions not accessible with the pseudopotential approach. The central idea of the PAW is to express the all-electron quantities in tenns of a pseudo-wavefiinction (easily expanded in plane waves) tenn that describes mterstitial contributions well, and one-centre corrections expanded in tenns of atom-centred fiinctions, that allow for the recovery of the all-electron quantities. The LAPW method is a special case of the PAW method and the pseudopotential fonnalism is obtained by an approximation. Comparisons of the PAW method to other all-electron methods show an accuracy similar to the FLAPW results and an efficiency comparable to plane wave pseudopotential calculations [, ]. PAW is also fonnulated to carry out DFT dynamics, where the forces on nuclei and wavefiinctions are calculated from the PAW wavefiinctions. (Another all-electron DFT molecular dynamics teclmique using a mixed-basis approach is applied in [84].)  [c.2214]

The method consists of solving the above equation in a standard step-by-step maimer, for example using a predictor-corrector algoritlnn. The right-hand side is calculated by simulating both phases at constant T and P in separate, uncoupled boxes. At intervals, a small change in T (the independent variable) is made m both boxes, and this is accompanied by a change in P (the dependent variable) as dictated by the differential equation solver. The approach relies on a starting point at which the two phases are at thennodynamic equilibrium, Ap = 0 thereafter the Clapeyron equation, if solved accurately, should guarantee that equilibrium is maintained. The method has been applied to the liquid-vapour coexistence curve [177. 178] and to the melting and sublimation curves [179] for the Leimard-Jones system it was also extended by Agrawal and Kofke [180] to study the melting transition of a large family of soft-sphere systems, showing the emergence of the bee phase as being stable relative to fee for high enough softness parameters. Various teclmical details of this approach have been discussed [178. 179] and possible sources of inaccuracy considered.  [c.2270]

See pages that mention the term Aaberg booths : [c.1058]    [c.166]    [c.327]    [c.330]    [c.679]    [c.1012]    [c.887]    [c.1248]    [c.1297]   
Industrial ventilation design guidebook (2001) -- [ c.881 , c.882 , c.883 ]