MACS PACK


There is unquestionably a substantial engineering component in manufacturing ceramics. There is also a very critical scientific component tliat involves understanding and controlling tire physical chemistry of surfaces. Not only are a number of different unit process steps required to manufacture a ceramic, but each unit process has its own set of requirements for optimization. Often, tire requirements to optimize one step are diametrically opposed to Arose for anotlier unit process. This necessitates compromise in order to optimize tire complete manufacturing process. For example, while a fine-particle-size powder provides a high surface area and driving force for sintering, electrostatic attraction and van der Waals forces promote agglomeration of fine particles and make tliem difficult to mix, pack, and compact. As a compromise, a practical lower limit of 0.1 pm diameter particles, is typical in advanced ceramic powder processing.  [c.2764]

Motor Carrier Cases, Supetintendent of Documents, U.S. Government Printing Office, Washiagton, D.C., cited (Volume) MCC (Page).  [c.264]

Fig. 5.8. (a) Packing of the unequally sized ions of sodium chloride to give a f.c.c. structure KCl and MgO pack in the same v/ay. (b) Packing of ions in uranium dioxide this is more complicated than in NaCi because the U and O ions are not in 1 1 ratio.  [c.52]

Using the command mar gin (mag, phase, w) gives  [c.394]

The properties of the solids most commonly encountered are tabulated. An important problem arises for petroleum fractions because data for the freezing point and enthalpy of fusion are very scarce. The MEK (methyl ethyl ketone) process utilizes the solvent s property that increases the partial fugacity of the paraffins in the liquid phase and thus favors their crystallization. The calculations for crystallization are sensitive and it is usually necessary to revert to experimental measurement.  [c.172]

High frequency Eddy current probing-. This apphcation covers an excitation frequency range from some 100 Hz to about 1 MHz, where the induced signal exceeds the noise of a ohmic antenna. As shown in fig. 1 a conventional normal conducting Eddy current probe is used for field generation and sampling. The signal current of the pick up coil is coupled inductively into the SQUID inductance. This results in an input magnetic flux, that is converted into a voltage by the SQUID.  [c.298]

PVDF film is readily commercially available in thicknesses up to 110 pm. If film of this thickness is bonded to a rigid substrate, the peak response is at a frequency of about 3.7 MHz which corresponds to the thickness of the layer being a quarter wavelength. This frequency is rather high for most Lamb wave testing since Fig 1 shows that even on a I mm thick  [c.716]

Practically speaking, however, solids may possess sufficient plasticity to flow, at least slowly, such that the methods of capillarity may be applied. An early experiment on thin copper wires provided a measure of the surface tension of copper near its melting point of 1370 dyn/cm [1]. The sintering process, driven by a reduction of surface energy through minimization of surface area, occurs because of bulk and surface mobility in metals and other solids. Surface scratches on silver heal [2], and copper or silver spheres fuse with flat surfaces of the same metal [3] below the melting point. The distance from the melting point is variable small ice spheres develop a connecting neck if touching at -10°C, and a detailed study of the kinetics of the process is needed to determine the relative importance of surface and bulk diffusion [4, 5]. Some systems are sensitive to other conditions sintering rates for MgO increase with ambient humidity [6]. Sintering is, of course, very important in the field of catalysis, where consolidation of small supported metal particles reduces surface area and the number of active sites. The rate law may be of the form  [c.257]

Figure Bl.11.4. Hydrogen-decoupled 100.6 MHz C NMR spectrum of paracetamol. Both graphical and numerical peak integrals are shown. Figure Bl.11.4. Hydrogen-decoupled 100.6 MHz C NMR spectrum of paracetamol. Both graphical and numerical peak integrals are shown.
In Lakestani (10) modelling work performed within the PISC III project is validated against experiments. Figure 1 shows the pulse echo response from the lower edge of a 10 mm vertical strip-like crack at centre depth 55 mm. The probe has the size 20 mm by 22 ram, is of SV type with angle 45 and has centre frequency 2.2 MHz and an assumed bandwidth of 2 MHz. The calibration is perfomed by a side-drilled hole of diameter 9.5 mm and centre depth 60 mm (the  [c.158]

In Fig. 2 an additional comparison with Lakestani (1992) is performed. This is a more difficult case because the centre depth of the crack is only 8 mm. It is still the pulse echo response from the lower edge of a 10 mm vertical strip-like crack that is shown. The probe has the size 20 mm by 22 mm, is of SV type with angle 60 and has centre frequency 2.04 MHz and an assumed bandwidth of 2 MHz. The calibration is by a side-drilled hole of diameter 9.5 mm and eentre depth 13 ram (the depth of the diffracting edge). The effects of the far field approximation for the probe is illustrated in the figure by giving curves for one, four and ten element probes. A single element probe is clearly insufficient although the peak location is correct and the peak value is only 6 dB too high. The difference between four and ten elements is for practical purposes negligible (the near field length of each element is less then 5 mm for the four element probe so this is not surprising). The agreement between UTDefect and the experiment is satisfactory, having in mind that the depth to the edge is about half the probe side so that the exact pressure distribution beneath the probe could be important.  [c.159]

SQUID electronics The output voltage of the bare SQUID is not linear in the input flux, but it is periodic with a flux period of = 2- 10 D Vs. In order to linearize the output signal of the SQUID it is driven in a negative feed back loop (flux locked loop) The output voltage of the loop generates a flux at the SQUID inductance in order to compensate the input flux. The sensor works as a null detector. To keep the SQUID in a proper setpoint we use a carrier frequency method at 6 MHz. This SQUID electronics is shown in the upper right part of fig. 5. The lower right part of fig. 5 shows the Eddy current part of the electronics. An oscillator, variable in frequency, provides the power for Eddy current excitation. Sirtrultaneously it gives a frequency reference to a two channel lock in demodulator in the signal path. The phase setting of the demodidator is variable, but the phase relation of both chatmels is frxed orthogonal. So a phase plane monitoring is possible.  [c.301]

Surface defects, high frequency We investigated defects on the surface of Ni-based alloys. This material is used for high performance gas turbine blades. The prefered excitation frequency for surface detection is about 1 MHz for this material. Although the electronics for demodulation and filtering difler for the SQUID read out and the conventional read out, we took care to have equal filter characteristics for the demodulated signal. The example we show in fig.6 is the signal of a 2 mm deep hairline crack. The probe for both measurements is a ferritic core coil. The signal to noise ratio in both cases is nearly identical at a level of about 75 dB. In the scheme of fig.2 we are well above the cut off frequency R/L, where no benefit from the SQUID is to be expected. When applying a low inductance planar cod, we can preserve the resolution of the SQUID system We will refer to the advantage of planar pick up coils later.  [c.301]

Signal can be recorded in 64 kB program buffer, stored in disk file and retrieved on demand. All the cards parameters (injection voltage amplitude and frequency in a range firom 1 kHz up to 600 kHz for SFT6000A card or up to 5 MHz for SFT6000N card, gain, high-pass and low-pass filters, phase shill, output channel attenuators and automatic or manual balance) can be set independently in each of 16 working channels for one card. They are stored in a disk file and each working channel with predefined settings can be selected at any time.  [c.390]

Tests have been carried out on a variety of plates of different materials and thicknes.ses. It has been shown that the interdigital transducers can be operated over the frequeney range 0.5 to 4 MHz, modes being strongly excited when the wavelength at which the transducer is designed to operate and the excitation frequency applied correspond to a point on the dispersion curves. As expected, excitation of the anti-symmetric modes is much stronger than that of the symmetric modes at their respective non-dispersive points. The excitation signal is typically a toneburst enclosed in a Hanning window generated by an arbitrary function generator and fed to the transmitting transformer via a power amplifier giving a signal of approximately lOOV peak-peak. It has been found that a 20 cyele toneburst generally provides the best compromise between pure mode generation and signal length (and hence spatial resolution). Details of these initial tests can be found in [15,16].  [c.717]

In order to get an extremely high resolution and a small dead zone" (after the transmitter pulse) single amplifier states must have a bandwidth up to 90 MHz ( ), and a total bandwidth of 35 MHz (-3 dB) can be reached (HILL-SCAN 3010HF). High- and low-pass filters can be combined to band-passes and provide optimal A-scans. All parameters are controlled by software.  [c.858]

The HILL-SCAN 30XX boards enable ultrasonic inspections from 50 kHz (concrete inspections) to 35 MHz (inspection of thin layers) with a signal to noise ratio up to 60 dB. The gain setting range of the receiver is 106 dB. High- and low pass filters in the receiver can be combined to band-passes, so that optimal A-scans are displayed.  [c.859]

During the attenuation measurements. Transducer 1 was excited with a narrowband tone burst with center frequency 18 MHz, see Figure 1 for a schematic setup. The amplitude of the sound pressure was measured at Tranducer 2 by means of an amplitude peak detector. A reference amplitude, Are/, was measured outside the object as shown at the right hand side of Figure 1. The object was scanned in the j y-plane and for every position, (x, y), the attenuation, a x, y), was calculated as the quotient (in db) between the amplitude at Transducer 2, A[x, y), and Are/, i.e., a(x,y) = lOlogm Pulse echo measurements and preprocessing  [c.889]

An important group of electrical phenomena concerns the nature of the ion distribution in a solution sunounding a charged surface. To begin with, consider a plane surface bearing a uniform positive charge density in contact with a solution phase containing positive and negative ions. The electrical potential begins at the surface as said decreases as one proceeds into the solution in a manner to be determined. At any point the potential if/ determines the potential energy ze of an ion in the local field where z is the valence of the ion and e is the charge on the electron. The probability of finding an ion at a particular point will depend on the local potential tluough a Boltzmann distribution, g-ze4iikT jjj analogy (q the distribution of a gas in a gravitational field where the potential is mgh, and the variation of concentration with altitude is given by  [c.169]

There has been much interest in the mobility of species adsorbed on or in layer and cage minerals such as clays and zeolites (see Fig. XVII-26 for an illustrative structure of the latter). As one example, in the case of benzene adsorbed on a zeolite, C NMR showed a line broadening (and hence correlation time) which increased with , the number of molecules per cage, up to n = 4. Beyond this point there was a rapid line narrowing, indicating that a new, highly mobile phase was present [99]. In a study of chemisorbed methanol on MgO, C NMR indicated molecules to be rigidly bound below a half monolayer coverage but that higher coverages produced isotropically rotating molecules [100]. As another illustration, zeolite rho is a relatively flexible zeolite with useful catalytic properties. Xenon-129 NMR spectroscopy indicates this flexibility and also that there can be rapid exchange between two kinds of adsorption sites [101-103]. Finally, it has been possible to determine the long-range diffusion coefficient of N2 in commercial zeolite crystals, using pulsed field gradient NMR. Values of ranging from 10 to 10 cm /sec were found [103a].  [c.588]

As a final example, similar spectroscopy was carried out for CO2 physisorbed on MgO(lOO) [99]. Temperatures were around 80 K and equilibrium pressures, as low as 10 atm (at higher temperatures, CO2 chemsorbs to give surface carbonate). Here, the variation of the absorbance of the infrared bands with the polarization of the probe beam indicated that the surface CO2 phase was highly oriented.  [c.636]

Submonolayer Phases and Phase Transitions. There is now a considerable literature on two-dimensional (2D) phases and phase transformations for a variety of species physically adsorbed on clean, smooth surfaces such as those of alkali halide crystals, exfoliated graphite, and cleaved MgO. As an example, the phase diagram for O2 on graphite is shown in Fig. XVII-17. Graphite is a popular surface because of the freedom of the basal plane surface from defects. Note that most of the diagram involves temperatures below the three-dimensional (3D) or bulk melting point of 55 K. There is a low-density solid phase, 6, and several higher-density solid phases (e, f 1, 2) having different unit cell orientations but the same density. The O2 molecules lie flat on the surface in the 5 phase, but in the higher-density phases they are perpendicular to it and their lattice is not commensurate (i.e., is not in register with the graphite lattice). There is a 2D liquid phase and a critical temperature of 64 K. Thorny and Duval, in a useful review [100], note that the 2D critical temperature is usually about 0.4 of the 3D Tc-  [c.636]

Figure Bl.l 1.10 offers an example. It shows the 400 MHz H NMR spectrum of a-I-methylglucopyranose, below two fiirther spectra where H-decoupling has been applied at H-1 and H-4 respectively. The main results of the decouplings are arrowed. Irradiation at the chemical shift position of H-1 removes the smaller of the two couplmgs to H-2. This proves the saccharide to be in its a fonn, i.e. with ( ) xi 60° rather than 180°, according to the Karplus relationship given previously. Note tliat both the H-1 resonance and the overlapping solvent peak are almost totally suppressed by the saturation, caused by the decoupling irradiation. The H-4 resonance is a near-triplet, created by the two large and nearly equal couplings to H-3 and H-5. In both tliese cases, ( ) 180°. The spectrum in this shift region is complicated by the methyl singlet and by some minor peaks from impurities. However, these do not affect the decoupling process, beyond being severely distorted by it. Genuine effects of decoupling are seen at the H-3 and the H-5 resonances only. Figure Bl.l 1.10 offers an example. It shows the 400 MHz H NMR spectrum of a-I-methylglucopyranose, below two fiirther spectra where H-decoupling has been applied at H-1 and H-4 respectively. The main results of the decouplings are arrowed. Irradiation at the chemical shift position of H-1 removes the smaller of the two couplmgs to H-2. This proves the saccharide to be in its a fonn, i.e. with ( ) xi 60° rather than 180°, according to the Karplus relationship given previously. Note tliat both the H-1 resonance and the overlapping solvent peak are almost totally suppressed by the saturation, caused by the decoupling irradiation. The H-4 resonance is a near-triplet, created by the two large and nearly equal couplings to H-3 and H-5. In both tliese cases, ( ) 180°. The spectrum in this shift region is complicated by the methyl singlet and by some minor peaks from impurities. However, these do not affect the decoupling process, beyond being severely distorted by it. Genuine effects of decoupling are seen at the H-3 and the H-5 resonances only.
Several other features of the figure merit attention. The two hydroxymethyl resonances, H-6a at 3.79 ppm and H-6b at 3.68 ppm, are separated in shift because of the chiral centres present, especially the nearby one at C-5. (One should note that a chiral centre will always break the synunetry of a molecule, just as an otherwise synmietrical coffee mug loses its symmetry whilst grasped by a right hand.) H-5 is thus distinctive in showing tlu-ee coupling coimections, and could be assigned by this alone, in the absence of other information. Also, the (H-6a to H-6b) cross-peak gives the general impression of a tilt parallel to the diagonal, whereas some of the other cross-peaks show the opposite tilt. This appearance of a tilt in the more complex cross-peaks is the deliberate consequence of completing the COSY pulse sequence with a 45° rather than a 90° pulse. It actually arises from selective changes of intensity in the component peaks of the off-diagonal multiplet. The parallel  [c.1459]

A different set of approaches uses simple physical properties to control the system [184], To demonstrate this type of problem, consider an even simpler branching problem where, upon excitation, two possible degenerate products are simultaneously produced. An example would be to photo-dissociate a diatom AB and produce different states of the system one state labelled A + B, in which B is electronically excited and A is receding away slowly and another state, labelled A + B, in which B is in the ground state and A is receding rapidly (so that the total energy is in both cases equal). The sunplest method of controlling the A + B versus A + B production rate would be to mix two different pathways for obtaining A + B and A + B for example, mixing a field of frequency or with a phase-lagged third hamionic of a field which is tliree times lower in frequency (see figure B3.4.18)  [c.2322]

The spectral selection approach [1, 16 and F7] is based on the fact that purely lifetime-limited line widths for electronic transitions of molecules rarely exceed 10-20 MHz, whereas the apparent width of the electronic origin in condensed-phase molecular spectra is typically orders of magnitude greater even in single crystals and certainly in polymers and glasses. At temperatures below 4 K, where little thennal population of phonons is possible, this additional width is ascribed to slightly different local environments for different chromophores, each giving rise to a slightly different spectral shift. Wlren a spectrally narrow laser (bandwidth on the order of the intrinsic lifetime-limited width) is tuned through the ensemble-broadened electronic origin, only those cliromophores on resonance with that particular laser frequency can absorb, and as the laser is tuned into the wings of the spectral line, the number of molecules on resonance approaches either zero or one (figure Cl.5.1) and figure Cl.5.2. In practice this works best when tuning to the red side of the electronic origin on the blue side, the zero-phonon lines (pure  [c.2485]

Combinatorial chemistry has significantly increased the nurnjjers of molecules that can be synthesised in a modern chemical laboratory. The classic approach to combinatorial synthesis involves the use of a solid support (e.g. polystyrene beads) together with a scheme called split-mix. Solid-phase chemistry is particularly appealing because it permits excess reagent to be used, so ensuring that the reaction proceeds to completion. The excess  [c.727]

In view of the great avidity of phosphorus pentoxide for water, the apparatus used in this experiment should be assembled before the pentoxide is weighed out. Fit a 500 ml. bolt-head flask to a water-condenser (see Fig. 59, p. 100). Disconnect the flask, then twist some glazed paper into the form of a cone, and push the narrow end of the latter (slightly opened) into the neck of the flask. Using a rough balance, weigh out on pieces of glazed paper first 20 g. of dry acetamide, and then (as quickly as possible) 35 g. of phosphorus pentoxide. With the aid of a spatula, tip the pentoxide without delay down the paper cylinder into the flask, then add the acetamide similarly, remove the paper, and at once cork the flask and mix the contents by gentle shaking. (Before throwing away the paper used for weighing the pentoxide, wet it thoroughly, otherwise residual pentoxide may cause it to smoulder and possibly inflame.) Now heat the flask by direct application of a Bunsen burner, using however a luminous smoky flame, and applying it uniformly over the bottom of the flask. The acetamide melts and then the  [c.121]

The peak at mje = 98 is taken as the arbitrary standard. The height of the other peaks is measmed relative to it. Once this matrix has been established, ordered sets of mass spectral peak heights at mfe = 69, 83, 84, and 98 constitute the experimental b vector for an unknown mixture that contains or may contain the four  [c.55]

Some liquids are practically immiscible e.g., water and mercury), whilst others e.g., water and ethyl alcohol or acetone) mix with one another in all proportions. Many examples are known, however, in which the liquids are partially miscible with one another. If, for example, water be added to ether or if ether be added to water and the mixture shaken, solution will take place up to a certain point beyond this point further addition of water on the one hand, or of ether on the other, will result in the formation of two liquid layers, one consisting of a saturated solution of water in ether and the other a saturated solution of ether in water. Two such mutually saturated solutions in equilibrium at a particular temperature are called conjugate solutions. It must be mentioned that there is no essential theoretical difference between liquids of partial and complete miscibility for, as wdll be shown below, the one may pass into the other with change of experimental conditions, such as temperature and, less frequently, of pressure.  [c.17]


See pages that mention the term MACS PACK : [c.45]    [c.249]    [c.393]    [c.394]    [c.394]    [c.395]    [c.395]    [c.396]    [c.415]    [c.573]    [c.573]    [c.573]    [c.723]    [c.857]    [c.640]    [c.941]    [c.1357]    [c.1574]    [c.49]    [c.192]    [c.248]   
Turboexpanders and Process Applications (0) -- [ c.196 , c.197 , c.199 ]