Fundamental Physical Considerations Research Articles

Modeling Signal-to-Noise Ratio of CMOS Image Sensors with a Stochastic Approach under Non-Stationary Conditions.

A stochastic model for characterizing the conversion gain of Active Pixel Complementary metal-oxide-semiconductor (CMOS) image sensors (APS), assuming stationary conditions was recently presented in this journal. In this study, we extend the stochastic approach to non-stationary conditions. Non-stationary conditions occur in gated imaging applications. This new stochastic model, which is based on fundamental physical considerations, enlightens us with new insights into gated CMOS imaging, regardless of the sensor. The Signal-to-Noise Ratio (SNR) is simulated, allowing optimized performance. The conversion gain should be determined under stationary conditions.

The quest for the next information processing technology

Fundamental physical considerations indicate that the scaling of devices that use electron charge as the information carrier will limit within the next one to two decades. The Nanoelectronics Research Initiative (NRI), a joint industry-government program, has been developed to fund university research seeking devices that utilize alternative physical information carriers or non-equilibrium switching mechanisms to continue the historical cost and performance trends of information technology. Three research centers have been established to pursue five research vectors that have been identified as critical to the effort to replace the electronic switch. A brief history and rationale for NRI is given and the projects currently underway are described in the context of the five research vectors.

Research directions and challenges in nanoelectronics

The search for alternate information processing technologies to sustain Moore's Law improvements beyond those attainable by scaling of charge-based devices encompasses several key technologies. Some of these technologies were explored at the Third Workshop on Silicon Nanoelectronics and Beyond (SNB III) held at the National Science Foundation in Washington DC in December 2005. They included: (1) non-charge-based devices; (2) devices operated out of thermal equilibrium; (3) alternative interconnect systems; (4) thermal extraction limits and technologies; and (5) fabrication via directed self-assembly. Although this paper was inspired by this highly successful workshop, it is not intended as a summary, but rather an assessment by the authors of some of the fundamental physical considerations evident at the present time.

Preface

The eleventh volume of the Annual Review of Heat Transfer marks the beginning of this successful serial publication in the new millennium and continues with the fine tradition of reviewing and communicating new, important developments in the general field of heat transfer. The chapters presented in the past decade of the Annual Review deal with a significant, emerging topic by starting from fundamental physical considerations and then proceeding in a logical fashion to the forefront of recent developments and future challenges. The contributing authors are both young and well-established in these emerging fields. Volume 10 illustrated well this special characteristic of the Annual Review, providing informative chapters on bioheat and mass transfer modeling, plasma chemical thermophysics, radiation scattering from rough surfaces, molecular dynamics in microscale thermophysics, turbulent heat transfer modeling, and the initiation and growth of solidification shrinkage voids. To further illustrate the special characteristic of the Annual Review, the present volume provides new, emerging topics such as laser-liquid interactions, surface impacting of molten droplets, rapid solidification, nucleation and boiling in micro-structures, optical measurement of surface temperature, confined jet impingement, oscillatory convection and advanced heat exchangers with external fields. As we begin this volume in the new millennium, the editor is deeply grateful to the participating authors for their excellent contributions, to Begell House for providing invaluable editorial assistance, and to the heat transfer community for its continuing support and input. Thank you all of you for your dedication during the past decade.

Investigating time-temperature superpositioning in crosslinked polymers using the tube-junction model

This article examines the application of time–temperature superpositioning (TTS) in certain thermorheologically complex polymers using a recently developed phenomenological model that describes crosslinked polymer viscoelasticity based on fundamental physical considerations. The model's capability to calculate both isochronal temperature sweeps and isothermal frequency sweeps of storage and loss moduli allows us to simulate conditions typical of certain thermorheologically complex polymers. We use the model to generate modulus frequency sweeps over the limited range of frequencies that are typically accessible to experiments. We apply TTS to shift these sweeps along the frequency axis to construct master curves. The model master curves are then compared with the model's “true” moduli curves over the full frequency domain at the reference temperature. This comparison suggests that nonsuperposability may go unnoticed if we only rely on the smoothness of the storage modulus master curve. Superpositioning to achieve a smooth loss modulus master curve tends to be more reliable. This has serious implications for assessing the reliability of relaxation moduli and creep compliance master curves that have no associated loss component that can be used to assess the quality of superpositioning. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 127–142, 1999

Fundamental Discreteness Limitations of CosmologicalN‐Body Clustering Simulations

Fundamental physical considerations and past tests suggest that there may be a problem with discreteness error in N-body methods widely used in cosmological clustering studies. This could cause problems with accuracy when coupled to hydrodynamics codes. We therefore investigate some of the effects that discreteness and two-body scattering may have on N-body simulations with realistic cosmological initial conditions. We use an identical subset of particles from the initial conditions for a 1283 particle-mesh (PM) calculation as the initial conditions for a variety of particle-particle-particle mesh (P3M) and tree code runs. The force softening length and particle number in the P3M and tree code runs are varied, and results are compared with those of the PM run. In particular, we investigate the effect of mass resolution (or equivalently the mean interparticle separation) since most high-resolution codes only have high resolution in gravitational force, not in mass. We show the evolution of a wide variety of statistical measures. The phase-insensitive two-point statistics, P(k) and ξ(R), are affected by the number of particles when the force resolution is held constant and differ in different N-body codes with similar parameters and the same initial conditions. Phase-sensitive statistics show greater differences. Results converge at the mean interparticle separation scale of the lowest mass-resolution code. As more particles are added but the absolute scale of the force resolution is held constant, the P3M and the tree runs agree more and more strongly with each other and with the PM run that had the same initial conditions, suggesting that the time integration is converging. However, they do not particularly converge to a PM run that continued the power-law fluctuations to small scales. This suggests high particle density is necessary for correct time evolution, since many different results cannot all be correct. Our results showing the effect of the presence or absence of small-scale initial power suggest that leaving it out is a considerable source of error on comoving scales of the missing wavelengths, which can be resolved by putting in a high particle density. Since the codes never agree well on scales below the mean comoving interparticle separation, we find little justification to use results on these scales to make quantitative predictions in cosmology. The range of values found for some quantities spans 50%, but others, such as the amount of mass in high-density regions, can be off by a factor of 3 or more. Our results have strong implications for applications such as the density of galaxy halos, early generation objects such as QSO absorber clouds, etc.

Preface

This ninth volume of the serial publication, Annual Review of Heat Transfer, continues the fine tradition of providing improved communication on new, important developments in the general field of heat transfer. As in previous volumes, each chapter in the Annual Review deals with a significant, emerging topic by starting from fundamental physical considerations and then proceeding in a logical fashion to the forefront of recent developments and future challenges. The contributing authors are either young but upcoming, or well-established leaders in these emerging fields. A list of the topics covered in the past two volumes illustrates well this special characteristic of the Annual Review. Volume 7 contained excellent chapters on significant, but wide-ranging heat transfer research and developments in micro- and nano-scale optical and optoelectronic devices, growth of dendritic crystals, polymeric composite processing, active enhancement using electric field, direct-contact transfer with droplets, clean-up of underground toxic wastes, and fluidized beds, while Volume 8 considered such important topics as heat transfer in microelectronics, Rayleigh-Bénard convection, aerodynamics of flame surfaces, radiative transfer in non-isothermal inhomogeneous media, heat pipe analysis and simulation, and high heat flux spray cooling. Continuing with this tradition, the present volume provides informative chapters on bioheat transfer, large scale surface radiative transport, radiative transfer in fibrous media, combustion in porous media, turbine blade coolant passage heat transfer, external flow film boiling, heat transfer in oscillatory flows, and two-dimensional annular flow. The editor is deeply grateful to the participating authors for their excellent contributions, to Begell House for providing invaluable editorial assistance, and to the heat transfer community for its continuing support and input.

Preface

The serial publication, Annual Review of Heat Transfer, focuses on new, important developments in the general field of heat transfer. As in the previous volumes, each chapter in the Annual Review deals with a significant, emerging topic by starting from fundamental physical considerations and then proceeding in a logical fashion to the forefront of recent developments and future challenges. The contributing authors are either young and upcoming, or well-established leaders in these emerging fields. A list of the topics covered in the last two volumes illustrates this special characteristic of the Annual Review. Volume 6 considered heat transfer topics in bio-optical imaging, ultrafine structures (aerogels), multi-phase modeling of alloy solidification, liquid jet impingement, interface measurements, CVD diamond layers, and molecular and microscale transport phenomena; Volume 7 contained excellent chapters on significant, but wide-ranging heat transfer research and developments in micro- and nano-scale optical and optoelectronic devices, growth of dendritic crystals, polymeric composite processing, active enhancement using electric fields, direct-contact transfer with droplets, clean-up of underground toxic wastes, and fluidized beds. Following this distinctive character, the present volume provides important contributions on heat transfer in microelectronics, Rayleigh-Benard convection, aerodynamics of flame surfaces, radiative transfer in non-isothermal inhomogeneous media, heat pipe analysis and simulation, and high heat flux spray cooling. The editor wishes to express his deep gratitude to the participating authors for their outstanding contributions, to Begell House for providing consistently excellent editorial assistance, and to the heat transfer community for its continuing support and input.

A single-pass design method for high-frequency inductors

As the operating frequency and the power rating of power electronic converters increase, the design of high-efficiency inductors and transformers becomes more difficult. Many design procedures described in the literature make use of numerous nomograms, and several iterations of the procedure are normally required. It has been particularly difficult to teach magnetic component design to undergraduate students. From several points of view, it is highly desirable to simplify and demystify the design procedure if possible. In this article we present such a simplified, easy-to-understand design procedure for small, naturally cooled, high-frequency (in excess of 10 kHz) inductors and transformers. The procedure is based on fundamental physical considerations that are easily understood, and the design process is a noniterative single-pass procedure.

A New Series of Equations for the Adsorption Isotherm Curves on Microporous Adsorbents

The traditional version of the volume-filling micropore theory (VFMT) uses the assumption of Gaussian (or quasi-Gaussian) distribution of micropores in energy (or size). This assumption is not concluded from fundamental physical considerations. It has been shown that for most active carbons the Gibbs' energy distribution of micropores takes place. The general form of isotherm curve for the adsorption of simple gases has been derived. The calculations with comparison with the known experimental data have been made. The results of the calculations differ much from those of the traditional version of VFMT. A new theoretical isotherm for the adsorption of vapors on active carbons has been proposed, based on the consideration of the Gibbs' energy distribution of micropores. The theoretical isotherm has been applied to some known experimental data. The square relative dispersion is low or moderate

Preface

The serial publication, Annual Review of Heat Transfer, continues to fulfill its original objective of providing improved communication on new, important developments in the general field of heat transfer. The previous volumes have clearly established the fine tradition that each chapter in the Annual Review deals with a significant, emerging topic by starting from fundamental physical considerations and then proceeding in a logical fashion to the forefront of recent developments and future challenges The contributing authors are either young but upcoming, or well-established leaders in these emerging fields. A list of the topics covered in the past two volumes illustrates well this special characteristic of the Annual Review. Volume 4 presented discussions on chaos, fractal analysis, thermal shock in solids, thermal processing of materials, species-controlled condensation, heterogeneous propellant combustion, mixing of vaporizing droplet sprays, and fouling heat transfer, while Volume 5 considered such topics as supercomputing, thin film laser processing, Monte Carlo Methods, unsteady heat convection across obstruction, thermally induced flow effects, partially saturated permeable surfaces, boiling in porous media, impacting sprays, and mist cooling for air heat exchangers. Following this distinctive character, the present volume contains excellent chapters on significant, but wide-ranging heat transfer topics related to bio-optical imaging, ultrafine structures (aerogels), multiphase modeling of alloy solidification, liquid jet impingement, interface measurements, CVD diamond layers, and molecular and microscale transport phenomena. The editor wishes to express his deep gratitude to the participating authors for their outstanding contributions, to Begell House for providing excellent editorial assistance, and to the heat transfer community for its continuing support and input.

Calculation of depth distribution functions in films using an electron scattering model

AbstractAn electron scattering model which has proved reliable in predicting both characteristic and continuous radiation depth distributions in bulk samples is further developed to cope with the quantification of depth distribution curves in thin films. The validity of the extended model is checked by comprehensive comparisons of calculated emitted x‐ray intensities with experimental data. The deviations obtained are generally small, the root‐mean‐square error being ∼5%. The results of calculations quantifying the effect of the substrate material on the shape of the depth distribution function in the film are also presented. The curves obtained are discussed in light of known theories and of fundamental physical considerations. The new model generates curves which correspond at least qualitatively with what is to be expected from basic principles and with the results of recent Monte Carlo simulations.

A new development of an equivalent circuit model for magnetostatic forward volume wave transducers

A three-port equivalent circuit model of microstrip transducers used for the generation and detection of magnetostatic forward volume waves (MSFVW) is derived from fundamental physical considerations. In this circuit model, each microstrip MSFVW transducer is modeled as a three-port circuit incorporating a frequency-dependent series reactance, a frequency-dependent lossless transformer, and a lossy transmission line. Circuit parameters are determined in closed form by the use of solutions of pertinent boundary-value problems. The effects of parasitics, for example, capacities of bonding pads, are easily taken into account. Some typical transducer configurations are analyzed numerically. The three-port model developed is in excellent agreement with experiments. The model can be applied directly to nonuniform arrays of microstrips weighted by varying the separation between strip centers and the widths of successive strips or reversing the current direction of some groups of strips.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Thermodynamics and its value as an energy policy tool

Of all the fundamental physical considerations that enter into the determination of personal and collective energy policy, only one can be quantitatively addressed through thermodynamics: this is the minimal use of energy resources to achieve conservation of scarce energy supplies. Thermal efficiency (redefined in this work as effectiveness coefficient) has been widely used in evaluating energy exchanges, but this procedure gives no consideration to quality of energy being used. Thermodynamics indicates that different energy quantities also can have different energy quality and efficient use of energy requires a matching of the energy quality supplied to that required for the given task. Thermodynamic efficiency as a “figure of merit” in evaluating energy exchanges has the advantage of considering energy quality. It does not, however, give information to assist in the trade-offs between energy resources and the other considerations that must be made in the formulation of an energy policy.