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Threshold voltage discrepancies in implanted Si atoms shifting between Ga sites and As sites by thermal stress in conductive-layer GaAs crystals on semi-insulating substrates were investigated. The results showed that carrier concentration at 0.25 micrometers decreased while peak carrier concentration increased. The thresholdvoltage discrepancies were caused by reoccupation of implanted Si atoms.

We have analyzed and calculated the temperature and strain sensitivities of a high-birefringence double-clad elliptical fiber. We propose a method to minimize these sensitivities without increasing fiber size or weight; this is achieved by selecting suitable fiber parameters--core ellipticity, ref index difference, and thickness of the inner cladding. In addition, we discuss the design of tempera strain-insensitive fibers which may be used in polarimetric strain or temperature sensors. This meth may also be used to minimize or enhance other external effects., A method is proposed to minimize the temperature and strain sensivities of a high-birefringence double-clad ellipical fiber without an increase in the fiber's size and weight by choosing the appropriate fiber parameters. A design for temperature- or strain-insensitive fiber can be applicable for polarimetric strain or temperature sensors and may be used to reduce or intensify other external influences.

Twenty-nanometer FePt films with 40% Fe content were deposited on MgO substrates at 300[degrees]C. A perfect (001) preferred orientation of FePt L[1.sub.0] phase was obtained. After 700[degrees]C annealing in vacuum, a room temperature perpendicular anisotropy of as high as 4.5 x [10.sup.7] erg/[cm.sup.3] can be obtained. The Curie temperature of the sample with 40% Fe content is far below the 50% Fe sample, which can effectively reduce the temperature of the thermal writing process. Furthermore, decay of magnetic anisotropy energy ([K.sub.u]) is much faster than saturated magnetization ([M.sub.s]) with rising temperature, which results in a domination of demagnetization (DM) energy at high temperature. Therefore, a further reduction of the switching field can be achieved. Finally, the films show almost the same magnetic properties during 10 times thermal writing processes from 25[degrees]C to 300[degrees]C, implying this media has high reliability for thermal writing process. Index Terms--Demagnetization, FePt with 40% Fe content, MgO substrate, perpendicular anisotropy, thermal writing.

Axially symmetric thermal stresses in the vicinity of a finite cylindrical crack in an elastic pipe are calculated. The surfaces of the crack are assumed to be insulated. The outer surface of the pipe is heated so as to maintain a constant temperature [T.sub.d], and the inner surface of the pipe is cooled so as to maintain a constant temperature [T.sub.b]. Expressions developed by Sharma are used to solve the problem. Stress intensity factors are defined and calculated numerically for several configurations of the pipe. [DOI: 10.1115/ 1.1598475]

Results demonstrate nonlinear characteristics of the temperature-frequency curves exhibited by the pretwisted composite laminated plates.

A study was conducted to characterize the temperature dependence of the photoluminescence spectra of silicon nanocrystallites determined by an inert-gas-ambient pulsed laser ablation method. Transmission electron microscopy was carried out to determine the mean diameter of the as-deposited samples. Results indicated that the temperature dependence of the peak energy and intensity of the photoluminescence was dependent on thermal processing.

The classical problem of the thermal explosion in a long cylindrical vessel is modified so that only a fraction [Alpha] of its wall is ideally thermally conducting while the remaining fraction 1-[Alpha] is thermally isolated. Partial isolation of the wall naturally reduces the critical radius of the vessel. Most interesting is the case when the structure of the boundary is a periodic one, so that the alternating conductive and isolated 1-[Alpha] parts of the boundary occupy together the segments 2[Pi]/N (N is the number of segments) of the boundary. A numerical investigation is performed. It is shown that at small [Alpha] and large N, the critical radius obeys a scaling law with the coefficients depending on N. For large N, the result is obtained that in the central core of the vessel the temperature distribution is axisymmetric. In the boundary layer near the wall having the thickness [approximately equal to] 2[Pi][r.sub.0]/N ([r.sub.0] is the radius of the vessel), the temperature distribution varies sharply in the peripheral direction. The temperature distribution in the axisymmetric core at the critical value of the vessel radius is subcritical.

The classical problem of thermal explosion is modified so that the chemically active gas is not at rest but is flowing in a long cylindrical pipe. Up to a certain section the heat-conducting walls of the pipe are held at low temperature so that the reaction rate is small and there is no heat release; at that section the ambient temperature is increased and an exothermic reaction begins. The question is whether a slow reaction regime will be established or a thermal explosion will occur. The mathematical formulation of the problem is presented. It is shown that when the pipe radius is larger than a critical value, the solution of the new problem exists only up to a certain distance along the axis. The critical radius is determined by conditions in a problem with a uniform axial temperature. The loss of existence is interpreted as a thermal explosion; the critical distance is the safe reactor's length. Both laminar and developed turbulent flow regimes are considered. In a computational experiment the loss of the existence appears as a divergence of a numerical procedure; numerical calculations reveal asymptotic scaling laws with simple powers for the critical distance.

Chen and Cheung's reformulated boundary integral equation was extended to solve notch problems in plane elasticity. The resultant heat flow Q and the resultant force -Y + iX were used to formulate the boundary conditions along the notch surface which created singular integral equations with a logarithmic kernel. Three different types of notches were considered to demonstrate the accuracy of the approach.

A study proposed a method with a plane strain model for solving composite problems. Some artificial out-of-plane thermal strains were introduced in a two-dimensional finite element analysis to develop this model. The artificial thermal strains were chosen to derive an identical stress field and still be able to determine the actual strains and displacements. The proposed technique provided savings in computational resources without forgoing accuracy.

The prediction of transient thermal behavior for composites carries important applications in fabrication processing and the materials' long-term performance. Accurate prediction of such behavior is costly when measured against standard memory storage and computation time in the finite element or difference methods. The flexibility/stiffness matrix method can be extended to cover such a transient thermoelasticity case for a multilayered anisotropic material.

The thermoelastic interaction problem of surface acoustic waves (SAW) in solids, namely the velocity dispersion and thermoelastic attenuation of SAW in continuous and layered type material, can be investigated by the thermal impedance approach. The weak thermoelastic coupling approximation in isotropic solids gives the value of thermal impedance. The thermoelastic SAW attenuation becomes zero in an ideal heat conductive layer.

A finite difference method for two-dimensional dynamic thermal stresses can be developed using integration along the bi-characteristics of a solid body. This method is mostly suitable for the analysis of two-dimensional stress wave propagation. The propagation, reflection and the interaction of the stress waves in a semi-infinite circular cylinder are studied by this method.

A response to a research paper on compensation law and its relation to the thermal aging of electric insulators is presented. It defends against the paper's criticism of the aging compensation effect (ACE) correlation culled from life test results as being empirical in origin and quality. It also points out the formal ACE correlation obtained from a later analysis of experimental data on a round robin life test. This is undermines the research paper's assertion, based on Eyring's rate theory, of the ACE correlation's physical significance.

The multilevel interconnection vias is examined using the finite-element method. Thermal stress and electron mobility is stunted due to increases in current density in integrated circuits, which can be estimated using coupled thermal and electrical conduction model in three dimensions. The ratio of via to track width determines the influence of geometry to temperature profile of the device while Joule heating and current density affects position of peak temperature.

The angular dependence of thermal switching in a single ferromagnetic particle was investigated using magnetic force microscopy. The results showed that the angular dependence was substantially different from that expected for coherent rotation. In the case of applied magnetic fields near the switching field, the time dependence of switching was unusual. This behavior indicated that multiple-energy barriers of similar height were involved in the switching process.

The Arrhenius model is extended to model the life data of a power-transformer insulation subjected to electrical and thermal stress. Thermal aging and combined thermal/electrical aging tests are conducted on Fish paper insulation to validate the theoretical model. A good fit is obtained between life predictions of the model and experimental results. The latter indicate a reduction in material life with increased thermal and combined thermal/electrical stress.

The thermal stability in vacuum of Cr/Sc multilayer thin films used as reflective optical components in soft x-ray instrumental has substantial dependence on incorporation of N. The studies have shown that the separation into the different multilayer periods is a consequence of redistribution of N within the Cr layers.

Thermal stability, sensitivity and noise of micron-scale magnetic tunnel junctions based on MgO tunnel barriers are analyzed for both the memory and sensing configurations. The junctions have shown solid high-temperature performance with substantial magnetoresistance and the thermal stability of these devices has depended on the exchange bias of the device.

The physical origin of the various residual stresses that are developed in the ceramic layer of the active region in a multilayer ceramic capacitor is determined. The compressive in-plane stress components are found to originate due to the difference in the in-plane thermal shrinkage between the ceramic and the metal electrodes.

The thermal and electrical characteristics of a heated microcantilever in air and helium over a wide range of pressures are reported. The measurement of thermal conductance around Kn = 1 (where Kn = Knudsen number) could help in the design and analysis of Pirani sensors and other microscale thermal sensors and actuators.

A swept-high frequency eddy current (SHFEC) methodology that can be used to determine the near-surface conductivity deviation profiles of shot-peened superalloy surfaces, from which residual stress state can be assessed nondestructively is presented. The findings have revealed that the piezoresistivity effect alone is not enough to convert the inverted conductivity profile into the residual stress profile, but the microstructural materials model can reconcile the nontrivial relationship between the conductivity and stress profiles.

Sensitive X-ray anomalous scattering techniques were used to investigate the mechanisms played by Ag as a surfactant in giant magetoresistance multilayers. The results of the investigations reveal that addition of Ag during deposition suppresses interfacial intermixing.

Planar and cross-sectional distributions of thermal stresses in an n-InP-based InGaAsP multiple quantum well wafer bonded with P-Si chemical surface activated bonding at 70 degrees Celsius and then annealed at 450 degrees C were analyzed. The tensile strains observed in the photoluminescence (PL) spectrum of the wafer caused a blue shift in the in the PL wavelength.

The temperature dependence of (super 17)O and (super 25)Mg NMR chemicals shifts in solid MgO was calculated by using a first-principles approach. The results of the study showed that the chemical shift behavior with temperature cannot be explained by thermal expansion alone.

The design and analysis of a horizontal thermal actuator common in Micro Electro Mechanical System (MEMS) applications is presented by using Finite Element Analysis, with the objective of exploring means to improve its sensitivity. The influence of variables like voltage and the dimensions of the cold arm of the actuator unit were examined by comprehensive, coupled thermal-stress analyses.

A ClpB variant, BAP, which associates with the ClpP peptidase and thereby is converted into a degrading disaggregase is engineered in a study. This activity switch of BAP to a degrading disaggregase does not support thermotolerance development, demonstrating that cell survival during severe thermal stress requires reactivation of aggregated proteins.

The processing induced changes of the Curie temperature (C(sub c)) in melt-spun ribbons of Nd2Fe14B with alpha-Fe in relation to their anomalous thermal expansion are reported. The d spacing of the (110) of alpha-Fe and (006) of 2-14-a indicates that changes in T(sub c) may be due to epitaxial stresses affecting the exchange coupling in the nanocomposite alloys.

The investigation of the thermal stress on a particularly precious artistic glass such as Arrigo Fiammingo located in the Cathedral of Perugia is illustrated. Stresses are due to the microclimate created in the space between the glass examined and the external protective glass, but overall it is because of the sunlight.

Reliability of epoxy molding compounds used in plastic packages of integrated circuit (IC) devices depends to a great extent on the level of thermal stresses. These are due primarily to the thermal expansion (contraction) mismatch of the epoxy and the silicon materials. In this analysis we assess the effect of silica fillers on the level of thermal stresses. We conclude that thermal stresses in the compound can indeed be reduced by the application of appropriate fillers. We found that the filler volume concentration does not have to be larger than 30 percent to keep the thermal stresses at a sufficiently low level. This number is close to the filler volume concentration of 30-40 percent in commercially available molding compounds. The obtained results and recommendations can be helpful in the analysis of stresses in, and physical design of, plastic packages. [DOI: 10.1115/1.1349422]

Steel pipelines buried in cold regions are subject to thermally induced axial loads, hoop stresses caused by the action of the fluids they convey, and differential settlements caused by factors such as thaw settlements, frost heave, and landslides. Due to these loads, pipelines may experience localized deformations well into the plasticity range of the pipe material. This paper presents an experimental program consisting of seven tests conducted to investigate and document the deformational behavior of full-scale pipes subjected to loads similar to those in the field. The specimens and loading conditions were carefully selected to match those in the field. A finite-element model was developed using the finite-element simulator ABAQUS to predict the local buckling behavior of pipes. The finite-element model was based on a large displacement, large rotation, finite-membrane-strain formulation and included material nonlinearity effects. The comparison between the numerical and the experimental results demonstrates the ability of the analytical model to predict the local buckling behavior of pipes when deformed well into the postyield range.

Superheater surfaces in oil shale steam boilers, constructed from pearlitic or austenitic alloys, are subject to intensive corrosion, primarily from the presence of chlorine in external deposits. The applicability of martensitic alloys X1OCrMoVNb91 and X2OCrMoV121 for superheaters has been examined and empirical equations to predict alloy corrosion resistance have been developed for the operational temperature range. Alloy 1OCrMoVNb91 is found highly suitable for superheaters in boilers firing fossil fuels that contain alkaline metals and chlorine. An abnormal dependence of corrosion resistance of martensitic alloys on temperature is revealed, namely that corrosion in presence of oil shale fly ash is more severe at 580 [degrees] C than at 620 [degrees] C. [DOI: 10.1115/1.1360693]

Oxidation kinetics of recently developed ferritic heat-resistant steels, HCM12A, NF616, and HCM2S, were investigated in a superheated steam to evaluate the effects of chemical composition of the steels, testing temperature (560-700 [degrees] C), steam pressure (1-10 MPa), and degrees of microstructural evolution by aging on oxidation. The contribution of alloyed Cr to oxidation resistance was pronounced above 600 [degrees] C, while no material dependency was found at 600 [degrees] C or lower. The apparent activation energy of the oxidation rate clearly changed at around 600 [degrees] C for NF616 and HCM12A. In contrast, HCM2S showed single activation energy over the range of temperatures. Although temperature and chemical composition were the major.factors, steam pressure also showed a clear negative effect on the oxidation rate in the lower temperature range, 570-600 [degrees] C. [DOI: 10.1115/1.1373656]

Earlier research work conducted at MIT and NIST indicated that CVN specimens with an initial temperature at or near 4K (-452 [degrees] F) actually fracture at temperatures significantly above 4K due to adiabatic heating. As a result of this work, ASTM E-23 test method on CVN testing was revised to incorporate a restriction that CVN tests are valid only at 77K (-320 [degrees] F) and warmer. ASME requested PVRC to assess the above CVN issue and provide an appropriate recommendation for the Code change or for a further Code change, if needed for vessels with MDMT colder than 77K. PVRC formed a Task Group under the Committee on Failure Modes. The TG undertook a program which included a review of the existing data and an experimental program to develop new [K.sub.Ic](J) data at 4K and 77K and CVN data at 77K. In the experimental program, a total of four 1-in-thick weldments were prepared from SA 240, Type 304 stainless steel plate using the SMAW process and E316L-15 electrodes. The electrodes purchased permitted the preparation of the weldments with four progressively higher levels of ferrite. The PVRC data and existing data were utilized in developing the recommendations to ASME. The recommendations are: use CVN tests (with 316L S.S. weld filler metal with FN [is less than or equal to] 5) at 77K with increased acceptance criterion of 21 mils lateral expansion; for welds not meeting the foregoing requirements, use ASTM E1820 [J.sub.Ic] tests at MDMT and the acceptance criterion for [K.sub.Ic](J) has been set at 120 ksi [square root of in]. This paper presents the test data, analysis and technical basis for the PVRC recommendations to ASME. [DOI: 10.1115/1.1376125]

At a T-junction in piping system, hot and cold water mixes in a whirl. The vibrating mixing boundary between the hot and cold water causes a temperature fluctuation on the inner surface of the pipe just after the connection point at the T-junction, and this temperature fluctuation yields a cyclic thermal stress near the pipe surface, resulting in crack initiation. In this study, the thermal stress distribution was analyzed for a semi-infinite plate model. The allowable water temperature range for the fatigue crack initiation was determined based on the mechanical fatigue test results. The thermal fatigue crack arrest behavior was analyzed based on the distributions of the stress intensity factor. The arrested crack depth is found to be in proportion to the reciprocal root of the frequency of the temperature fluctuation and is 3.8 mm for the frequency of 1 Hz. [DOI: 10.1115/1.1372327]

Micromagnetic simulations are performed to investigate the reversal process and the thermal stability of a grain of a typical perpendicular recording, media (Co-Cr). The integration of the LLG equation yields that the reversal process changes slowly and steadily from coherent rotation to nucleation with increasing column length. The region between homogeneous rotation and nucleation becomes smaller and is shifted to smaller column lengths if the damping constant is reduced from [Alpha] = 1 to [Alpha] = 0.02. In the weakly damped case very fast switching modes exist if the switching field is only slightly larger than the coercive field. In this small regime the switching time increases with higher switching fields. Using solutions of LLG simulations, energy barriers between the two stable states at zero field are estimated. For column lengths larger than 30 nm the energy barrier for inhomogeneous reversal processes are smaller than for coherent rotation. Index Terms--Energy barriers, fast switching, micromagnetics, perpendicular recording, thermal stability.

We investigated coupled granular/continuous (CGC) perpendicular media consisting of a continuous multilayer for high thermal stability and a granular host layer to reduce noise. The addition of Co/Pt multilayers increased the nucleation field of the Co[Cr.sub.18][Pt.sub12] medium from 0 to -2000 Oe. Moreover, the moment decay was reduced from 4.8% to 0.1% per decade. Compared to Co/Pd multilayer media, the CGC medium had a 10 dB higher signal-to-noise ratio (SNR). The granular host layer significantly improved the SNR in the high-density region over 10 kfc/mm. Compared to the Co[Cr.sub.20][Pt.sub.10] medium, the CGC medium had a 3 dB higher SNR in the low-density region. The medium noise for the CGC medium increased with the recording density, while the noise for the Co[Cr.sub.20][Pt.sub.10] medium remained constant from 10 to 20 kfc/mm. The approach using CGC medium improves both the SNR and the thermal stability. Index Terms--Continuous layer, granular layer, perpendicular media, signal-to-noise ratio, thermal stability.

The thermal stability in exchange coupled CoPtCrB trilayer structure medium (TL) is discussed and compared to that for the corresponding single layer (SL) medium. The time dependence of magnetization shows a nonlinear behavior. The magnetization decay rate is found to be reduced in TL when the applied field is close to the coercivity. The DC demagnetization (DCD) reversal mechanisms are investigated by magnetic force microscopy. It is observed that for the reversed field close to remanent coercivity of the TL and SL, very coarse magnetic structures appear. Index Terms--Antiferromagnetic coupling, magnetic recording, magnetic viscosity, MFM observation.

Schemes for SNR enhancement for advanced longitudinal recording media are discussed. SNR improvement is obtained by utilizing a bi-magnetic layer media, where the initial magnetic layer has lower magnetization, coercivity, and magnetic anisotropy, in comparison to the top magnetic layer. Further improvements in SNR and thermal stability are achieved using synthetic ferrimagnetic media. The selection of proper thickness and composition of the initial magnetic layer is important for the high performance of the synthetic ferrimagnetic media. Index Terms--High-density longitudinal recording, recording media, signal to noise ratio, thermal stability.

In this paper, we present a micromagnetic and analytical analysis of double layer media with antiferromagnetic exchange coupling. It has been found that in order to achieve good recording performance, strong interlayer exchange coupling and large thickness ratio are desired. When the thickness of the bottom layer is small, thermal activation assists the bottom layer to switch, which requires a smaller interlayer exchange coupling constant. Thermal stability of double layer AFC media has also been investigated with comparison to single layer media in the case of strong and weak interlayer exchange coupling. Index Terms--Antiferromagnetic exchange coupling, multilayer media, thermal activation, thermal stability.

We report magnetic measurements made on two CoCrPtTa thin film media, which were sputter deposited in identical conditions onto either CrMn or NiAl/CrMn underlayers grown on glass substrates. This produced films with [1120] and [1010] preferred orientations respectively. The films had stacking fault densities of 8 [+ or -] 1% and 13 [+ or -] 1% respectively. Increased magnetic viscosity and switching at low fields in the switching field distributions were observed which correlates well with the level of fcc-like regions. We find that the energy barriers to reversal in these films are dominated by the anisotropy field distribution rather than the distribution of grain-sizes. Furthermore, it is clear that even relatively low levels of stacking faults cause significant levels of thermally activated magnetization reversal which may cause reduced thermal stability of written information. Index Terms--Stacking faults, thermal activation.

This paper presents a study of the crack arrest tendency under cyclic thermal stress for an inner-surface circumferential crack in a finite-length cylinder with its edges rotation-restrained, when the inside of the cylinder is cooled from uniform temperature distribution. The effects of structural parameters and heat transfer condition on the maximum transient SIF for the problem were investigated with the formerly developed systematical evaluation methods. Then, a tentative value of threshold stress intensity range [Delta] [K.sub.th] being assumed as Well as Paris law, the evaluation of crack length for crack arrest under cyclic thermal stresses was carried out. Finally, a map to find the crack arrest point for a cylinder with mean radius to wall thickness ratio [R.sub.m]/W = 1 and a specific length H under various heat transfer conditions could be originated. From the map, it was predicted that when the heat transfer coefficient and/or initial wall-coolant temperature differences become large enough, the nondimensional crack arrest length saturates to a specific value and is no longer affected by those conditions. [DOI: 10.1115/1.1358840]

A pre-irradiation elevated-temperature stress is shown to have a significant impact on the radiation response of a linear bipolar circuit. Thermal cycling can lead to part-to-part variability in the radiation response of circuits packaged from the same wafer. In addition, it is demonstrated that a pre-irradiation elevated-temperature stress can significantly impact the enhanced low dose rate sensitivity (ELDRS) of the LM111 voltage comparator. Thermal stress moderates and, in some cases, eliminates ELDRS. The data are consistent with space charge models. These results suggest that there may be a connection between the mechanisms responsible for thermal-stress effects and ELDRS in linear circuits. Implications of these results for hardness assurance testing and mechanisms are discussed.