Study Of Principle Research Articles

Digital Doherty Amplifier With Enhanced Efficiency and Extended Range

In this paper, a digital Doherty power amplifier (PA) with improved efficiency performance over a wide power range is proposed. The efficiency enhancement is achieved by using a digitally controlled dynamic input power distribution scheme implemented to improve the active load modulation mechanism and to minimize the drive power waste into the peaking branch at backed-off power levels. Furthermore, the proposed distribution scheme causes the premature saturation of the carrier amplifier of the proposed Doherty PA and results in an extended range of high back-off efficiency. A comprehensive study of the operational principle of the proposed efficiency-extended digital Doherty PA is provided to demonstrate its merits and to enlighten its operation. In particular, the current and power profiles of the proposed digital Doherty PA are exposed and its efficiency characteristics analyzed. For experimental validation, the proposed Doherty PA is implemented within the dual-input digitally driven architecture based on a 10-W gallium-nitride transistor. Using a one-carrier Worldwide Interoperability for Microwave Access signal with a 9-dB peak-to-average power ratio and 10-MHz bandwidth, the digitally linearized efficiency-extended Doherty PA exhibited an excellent drain efficiency of 50% along with - 38 dB of relative constellation error. The efficiency enhancement is 7% in comparison to a conventional fully analog Doherty PA.

Algebraicity of formal varieties and positivity of vector bundles

We propose a positivity condition for vector bundles on a projective variety and prove an algebraicity criterion for formal schemes. Then we apply the algebraicity criterion to the study of formal principle in algebraic geometry.

Influence of a localized defect on acoustic field correlation in a reverberant medium

The work presented in this paper is concerned with the fundamental study of a damage detection principle in a reverberant medium, based on ambient acoustic noise correlation. The aim here is to theoretically investigate the sensitivity of the correlation of received signals to a local defect. The acoustic reverberation in the medium is modeled by a random process and an empirical description of the defect behavior is deduced from its experimental characterization. A global parameter r, corresponding to the energy ratio between the change in the correlation function caused by the defect and the defect-free correlation, is defined and theoretically derived. It is shown to essentially depend on the reverberation properties of the medium and the relative positions of the noise source, the sensor(s) and the defect. The theoretical expression of r is experimentally validated in a particular 2D-case (metallic plate) and then used to define the detection range and the optimal placements of the sensors.

Lorentz Trial Function for the Hydrogen Atom: A Simple, Elegant Exercise

The quantum semester of a typical two-semester physical chemistry course is divided into two parts. The initial focus is on quantum mechanics and simple model systems for which the Schrödinger equation can be solved in closed form, but it then shifts in the second half to atoms and molecules, for which no closed solutions exist. The underlying principle that bridges this chasm is the variational method, which is easily the most important guiding principle for the construction of approximate wavefunctions including molecular orbitals. Students frequently encounter difficulties crossing this bridge, even when they did well in the first half. One contributing factor is the dilemma of the variational method that variational problems tend to be either too trivial or mathematically too involved to clearly show the concepts at work. Here, a Lorentz trial function for the hydrogen atom is discussed, a very elegant, yet straightforward example that somewhat alleviates this dilemma. Together with the standard example of a Gauss trial function and the exact solution, the Lorentz function provides an opportunity for an in-depth study of the variational principle before applying it to heavier atoms and molecules.

Diffusion Channel of Generic Technology in Equipment Manufacturing Industry

Based on the study of characteristics, classification, and propagation principle of equipment manufacturing generic technology, a technological diffusion model of equipment manufacturing generic technology is developed in this paper. Utilizing the established model, the diffusion approach of digital design technology which is one kind of the equipment manufacturing generic technology is analyzed, which is an empirical study of technological diffusion method of equipment manufacturing common technology. The study is meaningful to accelerate the technological diffusion speed of equipment manufacturing and promote the development of equipment manufacturing industry.

Application of Secondary Electron Composition Contrast Imaging Method in Microstructure Studies on Cathode Materials of TWT

The study of the secondary electron composition contrast imaging method have been developed with a conventional scanning electron microscope (SEM) equipped with ultra-thin window energy dispersive X-ray spectrometer (EDS). On the basis of the study of the principle of secondary electron emission, secondary electron composition contrast imaging method has been investigated, and the ranges of its application were also discussed. This method was applied in the microstructure studies on cathode materials of TWT (traveling wave tube). The results showed that, compared with backscattered electron image, the secondary electron image could also reveal composition contrast well in certain conditions. Furthermore, the resolution of secondary electron composition contrast image is higher. In some cases, the secondary electron image could distinguish impurities which might bring wrong results. In the microstructure studies on cathode materials of TWT, compared with backscattered electron image, secondary electron composition contrast imaging method is reasonable and practicable.

A basic study of a triangular magnet chain for locomotion control

This paper introduces a theoretical (magnetic and robotic) and experimental study of a robotic locomotion principle utilizing a triangular artificial magnetic chain with a rotating magnetic field for biomedical applications. A three-axis Helmholtz coil system with external controller (joystick) controls the moving direction of the proposed magnet chain according to changes of the plane of the rotating magnetic field. The proposed magnet chain consists of three NdFeB magnets, and its magnetic property depends on dipoles interaction. Also, motion dynamics bring about a magnetic torque analyzed by robotics. A total magnetic moment on the triangular magnet chain provides magnetic torque in the rotating magnetic field, and a geometric property produces a stable movement for robotic locomotion.

The Study of the First Principle for Layer of Si/Ge

Using the plane-wave ultrasoft pseudopotential method and generalized gradient approximation which based on the first-principles density functional theory, the bond length, energy band structure and density of states of the layer of Si/Ge were calculated. The results show that, compared with the single-crystal Si layers, Si-Ge bond length get longer and the population decrease in the layer of Si/Ge . It can be seen from the energy band structure that the band structure width of the layer of Si/Ge decreases. The optical properties calculations show that, compared with the single-crystal Si layers, the absorption band of the layer of Si/Ge get narrower, and the absorption band-edge obviously get red-shift.

E. T. A. Hoffmann and the Serapiontic Principle: Critique and Creativity (review)

Brown, Hilda Meldrum, E. T. A. Hoffmann and the Principle: Critique and Creativity. Studies in German Literature, Linguistics, and Culture. Rochester, NY: Camden House, 2006. 206 pp. + index. Despite the copious attention E. T A. Hoffmann has attracted as one of the great storytellers of the nineteenth century, he has far less often received acclaim as a romantic theoretician until the past two decades - rather, critics usually regarded him as flighty, superficial, and inconsistent in comparison to his earlier colleagues. Hilda Meldrum Brown's study of the Serapiontic principle, treating what she considers Hoffmann's attempt to unify some of his aesthetic principles under a single perspective, reflects a new critical direction that appreciates Hoffmann as a serious and profound thinker. Her work reveals how the principle serves as theoretical underpinning for, and as observable performance of, the creative process she traces in Hoffmann's writing. Brown clearly does not intend an interpretation of the works as the main thrust of her analysis, but rather investigates the operation of the principle in them. Perhaps the most significant aspect of this study is its scope: instead of restricting herself to the four-volume collection of tales Hoffmann published under the title Die Serapionsbruder (1819-21), as earlier studies have done, Brown seizes the opportunity to follow the red thread of this concept through much of Hoffmann's overall production of novellas, stories, and Marchen, from the earlier collections of Fantasie- and Nachtstucke through the later Prinzessin Brambilla and the posthumously published Des Vetters Eckfenster. She demonstrates a vast and deep knowledge of Hoffmann's works, as well as of the critical traditions informing the most recent analyses of the tales. Even more significant is her nuanced grasp of Hoffmann's creative genius, which repudiates the unfortunate myths that have plagued Hoffmann's reputation and appreciation as a first-rate theoretician, ever since early critics dismissed him as merely an overly imaginative inebriate. Brown divides her book into two main sections: in the first, she discusses Hoffmann's formulation of the principle and its significant evolution over the fourteen years of the artist's literary career. As Brown's investigation makes clear, long before the four volumes oi Die Serapionsbruder appeared, Hoffmann had already accomplished significant work and had laid a strong theoretical foundation, especially in his famous preface to the Fantasiestucke (1814-16) in praise of Jacques Callot's fanciful, early seventeenth-century woodcuts of commedia dell'arte characters. In the Overture to the first part of this study, she maintains that the Callot essay is the earliest developed formulation, emphasizing the activity of inneres Schauen while focusing the center of the creative process in the artist's utilization of the fantastic and the grotesque. Important elements include irony, the combination of both the serious and the comic throughout life as well as in art, and finally the importance of the reception process, especially the interactive aspect of narrative technique (29). Reception is crucial in virtually all of Hoffmann's works: the author or editor draws the reader time and again into the creative process as an active participant, and the act of reading becomes a parallel to authorship itself. …

Experimental and Theoretical Study of the New Image Force Microscopy Principle (Invited Paper)

ABSTRACTA new technique in microscopy is demonstrated in which the domain of Atomic Force Microscopy (AFM) is extended to optical spectroscopy at the nanometer scale. Molecular resonance of feature sizes down to the single molecular level were detected and imaged purely by mechanical detection of the force gradient between the interaction of the optically driven object molecular dipole and its mirror image in a Platinum coated scanning probe tip. We provide full experimental details including a basic theory for this new technique. The microscopy and spectroscopy technique is extendable to frequencies ranging from radio to infrared and the ultra violet.

Computer-assisted analysis of public discourse: a case study of the precautionary principle in the US and UK press

Content analysis of newspaper publications has become a major scientific method of the analysis of public discourse. Within the framework of content analysis, we suggest a computer-assisted method to extract the most important topics of this discourse in an objective, quantifiable manner. The method combines frequency and proximity analysis of the text population, selection of the key words, text modification based on a key word dictionary, factor analysis of the modified text population, and factor interpretation. We illustrate the concept by applying the method to study the major topics discussed in the US and UK prestige press that relate to the precautionary principle. Precautionary principle is a concept of preventing environmental damage under scientific uncertainty. The analysis demonstrates the difference between the major topics of the precautionary principle discussion in the US and UK press. In the US, it revolves around an emphasis on the action on global warming, international trade on genetically modified food, environment pollution, the risks of new technologies, and cost-benefit analysis (CBA). In the UK, the major discussion topics include threats to agriculture and farmers, climate change economics, national and EU regulations, and commercial fishing. Other discussion topics, such as health and pollution, water safety regulations, meat safety and trade, and GMO regulations are shared between the countries. The US sample demonstrates more negative views towards the precautionary principle, which is presented as a threat to the US economic interests.

Dental implant treatment for two adjacent missing teeth in the maxillary aesthetic zone: a comparative pilot study and test of principle

The aim of this prospective comparative pilot study was to evaluate hard and soft peri-implant tissues in patients with a missing adjacent central and lateral upper incisor treated with either one implant and an implant crown with a cantilever or two implants with solitary implant crowns up to 1 year after functional loading. In the "Implant-cantilever group", five patients were treated with one dental implant in the region of the central incisor (NobelReplace Groovy Regular Platform). In the "Implant-implant group", five patients were treated with two adjacent dental implants: at the position of the central incisor (NobelReplace Groovy Regular Platform) and at the position of the lateral incisor (NobelReplace Groovy Narrow Platform). Implant survival, pocket probing depth, papilla index, marginal bone level and patient satisfaction were assessed during a 1-year follow-up period. No implants were lost during the 1-year follow-up. Mean pocket probing values of the implants were comparable between the two groups. Papilla index scores in both groups were relatively low, pointing towards a compromised papilla. Marginal bone loss was minimal and comparable between the groups. Patient satisfaction was very high in both groups. In this 1-year prospective comparative study, no large differences in hard- and soft-tissue levels could be shown between patients with a missing central and lateral upper incisor treated with either one implant and an implant crown with a cantilever or two implants with solitary implant crowns.

Management intensity – not biodiversity – the driver of ecosystem services in a long-term row crop experiment

A positive role for biodiversity is assumed for managed ecosystems. We conducted a 12-year study of this sustainability principle, through separate manipulation of management intensity and crop diversity. The site was located in southwest Michigan, representative of rain-fed production, with high climate variability and well-drained soils. Provisioning services of grain and protein yield were monitored, simultaneous with supporting services of soil fertility, C and N, and regulating services associated with water quality (N-use efficiency and nitrate-N leached in gravimetric lysimeters). Surprisingly, a strong role for management was shown, and almost nil for crop diversity. Organic management (ORG) sustained soil fertility, augmented soil C (36% increase), enhanced N retention (50% decrease in nitrate-N leaching) and improved N-use efficiency, compared to conventional, integrated (INT) management. Provisioning of grain – quantity, quality and temporal yield stability – was highest in INT continuous maize (monoculture and biculture) with an annual yield of 6.4 Mg ha −1, compared to ORG of 5.1 Mg ha −1. Biodiverse rotational systems (three and six species) produced 25% lower yield, but the grain was of high quality. A focus on ORG management rather than crop diversity is suggested as a means to sequester C, and produced grain in a semi-closed system.

A Theoretical Study of the Separation Principle in Size Exclusion Chromatography

The principle of polymer separation in size exclusion chromatography (SEC) is studied based on a classical equilibrium partitioning theory. The task is to examine the correlation between the mean span dimension of polymer chains and their equilibrium partition coefficients with confining pores. Using an extended formulation of the recently developed confinement analysis from bulk structures (CABS) method, we calculate the partition coefficients for both linear and branched polymer chains with cylindrical pores—a model pore geometry that is considered to be more realistic for voids in SEC columns than the commonly considered slit model. The partition coefficients plotted as a function of the mean span dimension relative to the pore diameter are truly universal for wide pores and nearly so for flexible polymer chains with different architectures (linear, star, two-branch-point, and comb) in the range of the partition coefficient relevant to SEC separation. We also examine the correlation between the mean sp...

MILD PRO-p-GROUPS AS GALOIS GROUPS OVER GLOBAL FIELDS

This paper is devoted to finding new examples of mild pro-p-groups as Galois groups over global fields, following the work of Labute ([6]). We focus on the Galois group [Formula: see text] of the maximal T-split S-ramified pro-p-extension of a global field k. We first retrieve some facts on presentations of such a group, including a study of the local-global principle for the cohomology group [Formula: see text], then we show separately in the case of function fields and in the case of number fields how it can be used to find some mild pro-p-groups.

A biomimetic piezoelectric pump: Computational and experimental characterization

Flow pumps have been developed for classical applications in Engineering, and are important instruments in areas such as Biology and Medicine. Among applications for this kind of device we notice blood pump and chemical reagents dosage in Bioengineering. Furthermore, they have recently emerged as a viable thermal management solution for cooling applications in small-scale electronic devices. This work presents the performance study of a novel principle of a piezoelectric flow pump which is based on the use of a bimorph piezoelectric actuator inserted in fluid (water). Piezoelectric actuators have some advantages over classical devices, such as lower noise generation and ease of miniaturization. The main objective is the characterization of this piezoelectric pump principle through computational simulations (using finite element software), and experimental tests through a manufactured prototype. Computational data, such as flow rate and pressure curves, have also been compared with experimental results for validation purposes.

On the Precarious Path of Reverse Neuro-Engineering

In this perspective we provide an example for the limits of reverse engineering in neuroscience. We demonstrate that application of reverse engineering to the study of the design principle of a functional neuro-system with a known mechanism, may result in a perfectly valid but wrong induction of the system's design principle. If in the very simple setup we bring here (static environment, primitive task and practically unlimited access to every piece of relevant information), it is difficult to induce a design principle, what are our chances of exposing biological design principles when more realistic conditions are examined? Implications to the way we do Biology are discussed.

A Fourth Moment Inequality for Functionals of Stationary Processes

In this paper, a fourth moment bound for partial sums of functionals of strongly ergodic Markov chains is established. This type of inequality plays an important role in the study of the empirical process invariance principle. This inequality is specially adapted to the technique of Dehling, Durieu, and Volný (2008). The same moment bound can be proved for dynamical systems whose transfer operator has some spectral properties. Examples of applications are given.

A Fourth Moment Inequality for Functionals of Stationary Processes

In this paper, a fourth moment bound for partial sums of functionals of strongly ergodic Markov chains is established. This type of inequality plays an important role in the study of the empirical process invariance principle. This inequality is specially adapted to the technique of Dehling, Durieu, and Volný (2008). The same moment bound can be proved for dynamical systems whose transfer operator has some spectral properties. Examples of applications are given.

On the duality principle in option pricing: semimartingale setting

The purpose of this paper is to describe the appropriate mathematical framework for the study of the duality principle in option pricing. We consider models where prices evolve as general exponential semimartingales and provide a complete characterization of the dual process under the dual measure. Particular cases of these models are the ones driven by Brownian motions and by Levy processes, which have been considered in several papers. Generally speaking, the duality principle states that the calculation of the price of a call option for a model with price process S=e H (with respect to the measure P) is equivalent to the calculation of the price of a put option for a suitable dual model S′=e H′ (with respect to the dual measure P′). More sophisticated duality results are derived for a broad spectrum of exotic options.