Search

Calculations of temperature coefficients of the elastic surface wave velocity and delay time were performed for the propagation along the X axis of a rotated Y cut plane of LiNbO3 and LiTaO3. Measurements of the temperature dependence of the delay time of the elastic surface wave were also performed for the propagation along the X axis of a 131° rotated Y cut plane of LiNbO3 in the temperature range from liquid He to room temperatures. The experimental value, 70×10-6/°C, of the temperature coefficient of the delay time from 173 K to room temperature agrees with the calculated value, 72.7×10-6/°C. However, the coefficient becomes 16×10-6/°C near liquid He temperatures.

We establish a set of conditions which must be satisfied in order to make the equivalent photon spectrum (and also the virtual photon's polarization) Lorentz-invariant. We insist in particular on the condition that the virtual photon's emission angle must be small.

A new Fano-type estimate is proved for multiway channels. It yields upper bounds on the numbers of codewords and the products of these numbers in a code for a channel with s senders and r receivers in the case all senders send messages simultaneously to all receivers. The result is based on a new approach, which makes an approximation argument previously used by Ahlswede (1971b) and Ulrey (1974) unnecessary. It also leads to better Fano-estimates than the ones obtained by these authors. Our approach is canonical for weak converses of coding theorems for multiway channels and applies also in other communication situations.

A generalization of Wilson's renormalization group equation is discussed. A large class of equivalent fixed points exists for each fixed point. The eigen perturbations fall into two classes: (i) scaling operators whose scaling exponents are independent of the fixed point within the class of equivalent fixed points, and (ii) redundant operators whose exponents depend on the choice of the renormalization group equation. The exponents of the redundant operators are spurious since the free energy depends only on the scaling fields of the scaling operators but not on the scaling fields of the redundant operators.

The results of an experimental study of the thermal conductivity of a gas mixture of acetonirile (CH3CN) and argon in an electric field (E) are presented. The concentration dependences obtained for the thermal conductivity are compared with the theory in which it is assumed that the probabilities of direct and reverse transitions are not equal to one another for molecule-molecule collisions and are equal for molecule-atom collisions.

The National Weather Service River Forecast System describes a method and details computer programs of efficient operational use of a conceptual hydrologic model for river forecasting. A new format has been established for the retrieval of hourly precipitation data and daily observations (from the National Climatic Center, NOAA). A computer program is provided to perform all steps to convert the basic precipitation data to areal means. A procedure and computer programs needed for calibrating the basic conceptual model to a large number of basins in a reasonable time are described. The basic conceptual model has wide applicability. The inclusion of a snow-pack model and additions to the channel-routing procedure planned for the near future will make the model applicable over nearly all of the United States.

The validity of a condensing curve is accepted. As an alternative to the incremental calculation of the heat transfer area and pressure drop a rapid calculation method is presented, in which the local overall heat transfer coefficient and differential pressure drop is calculated at only three points (Simpson's rule). In the case of desuperheating, total condensing and subcooling there is one such point in each of the three sections.

A gadolinium molybdate single crystal β'–Gd2(MoO4)3 grown by the Czochralski technique was observed by using chemical etching and X-ray transmission topography. It was found that there were flat helical dislocations and rows of flat closed loop dislocations having axes parallel to the directions in this crystal. The Burgers vectors were found to be parallel to the axes of these dislocations. Moreover, one to one correspondence between the etch-pits and the images of dislocations in X-ray topographs was observed.

The most favourable pH value of the electrolyte of the International Weston cell has proved to be pH = 1.4 ± 0.2 which guarantees an emf having a drift of only about ±0.2μV/year when all precautions are taken in the manufacture of the cells. NO3- ions influence the pH value of the electrolyte and should therefore be avoided in the cells.

A finite strip method is presented for determining the initial buckling stresses of any structure consisting of a series of thin flat isotropic plates rigidly connected together at their longitudinal edges. Each plate may be subjected to a combination of longitudinal and transverse compression, longitudinal in-plane bending, and shear, and it is assumed that the buckling mode, of whatever type, is sinusoidal in the longitudinal direction. Due to the presence of shear, the perturbation forces and displacements which occur at the edges of component plates during buckling are out of phase, and this is accounted for by defining their magnitudes in terms of complex quantities. Stiffness matrices relating the amplitudes of these forces and displacements are derived using an approximate method based upon assumed displacement functions across the width of the plate. It is shown how the method can be used to calculate natural frequencies of prismatic structures, and finally an indication of the accuracy of the method is given together with some illustrative results.

The paper deals with the bidirectional speed control of a split-field dc series motor by commutating the two fields alternately to the supply using SCR switches. The whole system is simulated on an analog computer to investigate the effect of system parameters on its static and dynamic performances. Optimum values for the components of the control circuit are also suggested.

(1974). Overcoming Organizational Constraints on Creativity and Innovation. Research Management: Vol. 17, No. 3, pp. 29-33.

Physical parallels of transmission lines with communication circuits and railroad signal circuits cause induced voltages which may interfere with normal operation. Due to the demand for more efficient uses of existing rights-of-way, and to the trend toward higher line currents and voltages, such parallel problems will become more frequent and more difficult. This paper recommends a system approach to the problem in which candid discussion, mutual understanding and a willingness to adopt new techniques can benefit both utilities. New limits are discussed, new computational techniques mentioned, and the general subject of inductive coordination is covered. Shielding, protection systems and substation problems are examined.

The effect of solvent on the “BrBr” stretching mode of the PyBr 2 complex, and on the torsion modes of benzaldehyde, acrolein, disulphur dichloride, chloral, n -propyl chloride and acetaldehyde has been examined. The shifts are large in all cases, and can be ascribed to the polarisation of the solute molecule in its equilibrium configuration. The solvent shift suggests that the minimum energy configuration of chloral is OCl staggered.

Detailed studies on the environmental aspects of aquatic plant control in irrigation canals with herbicides indicate that herbicides properly applied do not preclude use of treated water for crop irrigation or potable water. Current registration of some herbicides is examined for this purpose. /ASCE/

We describe an experimental device (cell, electric supply, optic and electronic systems) meant to obtain the electric field induced infrared spectra of gases. The rotational-vibrational spectrum of nitrogen is presented as an example.

The positron angular correlation curves were measured along the [100], [110] and [111] directions of NiO single crystals. A simple calculation based on the localized ion model shows that the measured anisotropy is ascribed to the uncompleted 3d orbitals of Ni with a slight covalent mixing of oxygen 2p orbitals.

The uniform, uniaxial elongation of polyethylenes of various crystallinity and the effect of strain rate on this process are analyzed. Quantitative relations between the stress, the degree of elongation, and the strain rate are established, and the factors controlling the uniform, uniaxial elongation of polyethylenes are defined.

The ductility of a single-phase Ni–20% Cr alloy and two precipitation-hardened Ni–20% Cr-base alloys, hardened by Ni3(Al, Ti) and Ni3(Al,Nb), respectively, has been studied over a range of temperature at various strain rates. The results show that the alloy hardened by Ni3(Al,Nb), while less ductile than the single-phase alloy, is superior to that hardened by Ni3(Al,Ti) with respect to both tensile strength and elongation at fracture. In the single-phase alloy, there are two ductility troughs for a given strain rate when the strain rate is slow but in the two-phase alloys and at high strain rate in the single-phase alloy a single trough is obtained.Metallographic examination has indicated that the ductility behaviour of the single-phase alloy can be correlated with structural changes, void formation leading to a low elongation at fracture but recovery and recrystallization increasing ductility, presumably by relieving internal stresses at the grain boundaries. It is suggested that an important con...

Measurements of thermoelectric power and resistivity have been made on three dilute alloys of chromium in copper in magnetic fields up to 3 T. The measurements covered the temperature range 0.3 to 10K and the samples contained 5, 27 and 110 ppm chromium. The results were used to extract from various relevant theories estimates of the Kondo temperature TK, the antiferromagnetic exchange energy J and other parameters appropriate to describe the behaviour of chromium dissolved in copper.

The present paper is concerned with Almansi's problem in the linear theory of micropolar elasticity. The problem is solved using the results from [8], [10–13].

In iron-doped rutile (TiO2) charge compensation is necessary since most of the iron substitutes as Fe3+ for Ti4+. The well known EPR spectrum of iron-doped rutile is due to Fe3+ substitutional ions in a perfect lattice. However, EPR measurements at 9.2 GHz revealed several additional EPR spectra which are explained as due to substitutional Fe3+ ions disturbed by nearest-neighbour oxygen vacancies, protons and Ti4+ interstitials. The number of nearest-neighbour oxygen vacancies and protons was determined from the EPR measurements. In pure rutile the number of oxygen vacancies was determined from measurements of the absorption line at 6.6*103 cm-1 which is associated with polarons. Since the number of EPR centres associated with oxygen vacancies is nearly the same as the number of oxygen vacancies it is concluded that the former are mainly located near to iron ions.

The author discusses the significance and measurement of the frequency and shape of acoustic emissions. He considers theoretical descriptions of acoustic emission and compares them with experimental evidence. He considers the implications of this understanding of the nature of acoustic emission and illustrates these implications by a description of a programme of investigation at AERE Harwell. This programme added to our knowledge of acoustic emission and the author considers the results in the light of other experiments. He concludes that spectral analysis could complement the use of amplitude distribution and ring-down counting but not enough is yet known of the general meaning of the spectrum of an acoustic emission.

Chemical and physical observations within a strong pycnocline in the Sea of Marmara suggest the concurrent development of a thermohaline step structure and of spikes in the vertical distributions of chemical variables. Calculations based on a multivariate form of a two-component mixing model indicate a vertical mixing scale near 22 m.

At present, the fatigue provision in most design specifications in this country is based upon test data presented in the form of modified Goodman diagrams. The recent AISC specification is based upon a constant-range criterion. In any event, neither the randomness of fatigue lives nor that of applied loads is being considered. In this paper, a simple and reliability-based procedure is presented for the fatigue design of structures. The probability distribution for repeated loads can be obtained from dynamic analysis or field measurements. In addition, the stress-life-probability relations are available from single-stress-level laboratory tests. With an initial configuration of the structure, the distribution of repeated stresses can be computed. Then, the life of the structure can be predicted using a cumulative-damage criterion and an acceptable probability of failure. The computed life is compared with the design life, and the design can be modified in an iterative manner.

Using a 1m radius bent crystal spectrograph, the X-ray K absorption edge of zirconium in zirconium metal, zirconium oxide, zirconium tetrachloride and in zirconium oxychloride has been studied. In all the compounds investigated, it has been observed that the absorption discontinuity shifts towards the high energy side with respect to the pure metal. The shift which is due to the change in the distribution of the valence electrons is a maximum in the case of zirconium nitrate. The relative magnitude of the shifts in the compounds studied are tentatively explained on the basis of considerations involving electronegativity and interatomic distances.

A three-dimensional constitutive relationship for the fiber-reinforced composite with a nonlinearly elastic matrix material is derived. The composite is modeled by a medium consisting of thin nonlinear matrix layers alternating with effective linearly elastic fibrous layers. Shear wave propagations are investigated. The formation of shock wave, its stability and growth behaviors are discussed.

A method is presented for determining the primary thermal radiation coefficients for a layer of dissipating and absorbing material. The capacities computed for layers of different thickness by using these coefficients are in good agreement with experimental measurements.

Quantitative texture measurements using crystallite orientation distribution functions have been made on both phases of the Al-33 wt% Cu eutectic alloy as a function of strain and strain-rate during superplastic deformation at 713 K. The details of the texture changes can be interpreted in terms of grain boundary sliding, dislocation motion and diffusion creep. Grain boundary sliding is shown to be a maximum at maximum m , but while multiple slip in the aluminium-rich phase is important at high strain-rates slip also makes a contribution to deformation at maximum m . In the CuAl 2 phase anisotropic diffusion creep is an important deformation mechanism.

The normal spectral emittance (λ = 0.645Jμ) was determined for vanadium between 1100 and 1750 K and for tantalum between 1200 and 2600 K, at pressures below 10-6 mm Hg for elec-trochemically and mechanically polished surfaces. The emittance was found to decrease with increase in temperature. It was also lower for the electrochemically polished surface. An empirical equation was fitted to the experimental data, and it was used to predict the emittances up to the melting points.

This paper describes a unique circuit called a dual timer. The circuit was designed to be versatile and universal in consumer electronics applications. The circuit can operate in monostable as well as astable mode. This circuit can be used not only in linear circuitry but in digital circuitry as well since it operates from 5 volts to 15 volts and its output is TTL compatible. Each timer is basically comprised of two comparators (one for trigger and one for threshold, refer to Figure 1) a flip flop and a totem-pole output stage.

We consider the costly surveillance of a stochastic system with a finite state space and a finite number of actions in each state. There is a positive cost of observing the system and the system earns at a rate depending on the state of the system and the action taken. A policy for controlling such a system specifies the action to be taken and the time to the next observation, both possibly random and depending on the past history of the system. A form of the long range average income is the criterion for comparing different policies. If RΔ denotes the class of policies for which the times between successive observations of the system are random variables with cumulative distribution functions on [0, Δ], Δ < ∞, we show that there exists a nonrandomized stationary policy that is optimal in RΔ. Furthermore, for sufficiently large Δ, this optimal policy is independent of Δ.

The jumbogroup frequency supply (jfs) provides accurate and reliable synchronization signals to L5 jumbogroup multiplex carrier supplies. The jfs output-signal frequency is held to within several parts in 1010 of an input reference frequency. This extraordinary accuracy is achieved by digital frequency control of a precision quartz oscillator. The excellent reliability required when the jfs serves over 100,000 two-way voice circuits is achieved by redundant power and signal feeds, one-for-one protection of key circuits, and automatic protection switching. In addition to its L5 application, the jfs will also serve as a regional frequency supply in a new synchronizing frequency distribution network that will upgrade the entire Bell System transmission plant.