Special Angle Research Articles

Total 3s Emission Yield as Bulk-Sensitive Probe for a True Soft X-ray Absorption Spectrum?

The detection of the true soft X-ray absorption typically needs specially prepared submicrometer thin samples for transmission measurements. Bulk experiments instead have to rely on yield methods, for example, electron yield with limitations for insulating samples, sensitivity to applied fields, and with limited bulk sensitivity. Fluorescence yield methods instead do not have those limitations but have been found to deviate, in general, from the absorption spectrum. We demonstrate that restricting the detection to the 3s fluorescence channel (with the detector at a special angle where all polarizations contribute equally) restores the true X-ray absorption spectrum for all 3d-metal L2,3 edges. These theoretically derived results are rationalized by the lack of 3s-3d interaction in the core-excited state. Comparing X-ray absorption versus 3s-PFY for arbitrary detection geometries for both linear and circular polarized light, deviations appear that can become as large as 15%.

Flow behavior and microstructure evolution of a TiBw/TA15 composite with network-distributed reinforcements during interrupted hot compression

Interrupted hot compression tests were performed on a TiBw/TA15 composite with network architecture to study its flow behavior and microstructure evolution during a two-step deformation process. The microstructure was observed by electron backscatter diffraction (EBSD) and the high-temperature β grain boundaries were reconstructed through several special misorientation angles. The fraction of the primary α (αp) phase declined during the heat preservation process. The flow stress exhibited a lower value due to softening upon reloading compared to that observed prior to the interruption. In addition, the hold time and deformation temperature were important factors influencing the composition of the matrix phase, and the αp phase disappeared with increasing hold time and temperature. The high-temperature β grains became longer with a larger average aspect ratio when the deformation temperature reached 1283 K. Both TiB reinforcement and the αp phase restrained the growth of β grains, preventing hot deformation at higher temperatures and resulting in longer inter-pass holding times due to the absence of the αp phase. The low strain rates resulted in a significant β phase grain growth because of sufficient time and the lack of constraints. The optimized process parameters, which can provide guidance to actual production, were obtained in this study.

Laser-plasma interactions in magnetized environment

Propagation and scattering of lasers present new phenomena and applications when the plasma medium becomes strongly magnetized. With mega-Gauss magnetic fields, scattering of optical lasers already becomes manifestly anisotropic. Special angles exist where coherent laser scattering is either enhanced or suppressed, as we demonstrate using a cold-fluid model. Consequently, by aiming laser beams at special angles, one may be able to optimize laser-plasma coupling in magnetized implosion experiments. In addition, magnetized scattering can be exploited to improve the performance of plasma-based laser pulse amplifiers. Using the magnetic field as an extra control variable, it is possible to produce optical pulses of higher intensity, as well as compress UV and soft x-ray pulses beyond the reach of other methods. In even stronger giga-Gauss magnetic fields, laser-plasma interaction enters a relativistic-quantum regime. Using quantum electrodynamics, we compute a modified wave dispersion relation, which enables correct interpretation of Faraday rotation measurements of strong magnetic fields.

Magic angles for fibrous incompressible elastic materials

In the analysis of the mechanical behaviour of fibre-reinforced incompressible elastic bodies, there is a special angle of orientation of the fibres which leads to a particular mechanical response. This angle has been called a ‘magic angle’ due to its appearance as if by magic in many different aspects of the mechanics of fibrous solids including several examples in biology. It occurs most commonly not only in structural elements composed of circular cylindrical tubes or cylinders reinforced by helically wound fibres but also in flat thin sheets reinforced by fibres in the plane. The occurrence of such a special angle was classically demonstrated using a simple purely geometric analysis in the context of a lattice composed of a single family of helically woundinextensiblefibres. Recently, the magic angle concept has been discussed in the framework of nonlinear hyperelasticity for anisotropic materials with detailed constitutive modelling. Our purpose here is to describe some other contexts in which the magic angle occurs starting from earlier work in a special theory of linear elasticity for inextensible fibres and proceeding to relatively accessible models of hyperelasticity. We discuss the role of the magic angle in the quasi-isotropic mechanical response of fibre-reinforced composites as well as the implications for material instability.

PROFIL KESALAHAN MAHASISWA PADA MATA KULIAH ANALISIS KOMPLEKS

This research is used to analyze the error profile encountered by STKIP PGRI Pacitan students in the course of Complex Analysis on the subject of PolarShape. The type of research used is qualitative descriptive. Subjects used as many as 2 students. Data collection methods used are test methods andinterview methods. The results of this study are on Misunderstanding, Transformation Errors and Process Errors. Misunderstanding is to assume thesymbol R = r when R ≠ r. Then assume that in calculating the root of the value of negative/positive just the same, even though the end result also remains the same. And it is often reversed between the values of x and y. Transformation error is inverted in determining x and y for cos arc formula. While the Process Error is unable to determine the magnitude of a special angle adjusted to the location of the point of z. weak in calculating the powers in the form of fractions. And wrong in drawing the z-point coordinates.

ТЕРРОРИСТИЧЕСКИЙ РЕКРУТИНГ НА ПОСТСОВЕТСКОМ ПРОСТРАНСТВЕ: СОВРЕМЕННЫЕ ТЕНДЕНЦИИ И РИСКИ ДЛЯ РОССИИ

The object of the author’s research is terrorism, as a threat to the national security of the Russian Federation. The subject area is the problem of terrorist recruitment on the scale of the post-Soviet space. The main purpose of the article is to assess the risks of terrorist recruitment for the Russian Federation in a special territorial angle - the post-Soviet space. The authors completed the following research stages: selection of potential collaborating countries of the recruitment system, the comparative analysis and ranking of these states with subsequent identification of the most likely participants in the system, identification of forms and potential scenarios of terrorist recruiting. The researchers come to the conclusion that the conditions for terrorist recruitment have developed to the greatest degree in Tajikistan, Kyrgyzstan and Azerbaijan. Probable form of recruiting can be, for example, prison jamaat, and the environment for it- a migration corridor or a pseudo-religious community.

Effect of twist on single-mode fiber-optic 3 × 3 couplers

Abstract In the fabricating process of a 3 × 3 fused tapered coupler, the three fibers are usually twisted to be close-contact. The effect of twist on 3 × 3 fused tapered couplers is investigated in this paper. It is found that though a linear 3 × 3 coupler may realize equal power splitting ratio theoretically by twisting a special angle, it is hard to be fabricated actually because the twist angle and the coupler’s length must be determined in advance. While an equilateral 3 × 3 coupler can not only realize approximate equal power splitting ratio theoretically but can also be fabricated just by controlling the elongation length. The effect of twist on the equilateral 3 × 3 coupler lies in the relationship between the equal ratio error and the twist angle. The more the twist angle is, the larger the equal ratio error may be. The twist angle usually should be no larger than 90° on one coupling period length in order to keep the equal ratio error small enough. The simulation results agree well with the experimental data.

Simulation of redistributive and erosive effects in a-Si under Ar+ irradiation

Abstract Ion beams are frequently used in industry for composition control of semiconducting materials as well as for surface processing and thin films deposition. Under certain conditions, low- and medium energy ions at high fluences can produce nanoripples and quantum dots on the irradiated surfaces. In the present work, we focus our attention on the study of irradiation of amorphous silicon (a-Si) target with 250 eV and 1 keV Ar+ ions under different angles, taking into special consideration angles close to the grazing incidence. We use the molecular dynamics (MD) method to investigate how much the cumulative displacement of atoms due to the simulated ion bombardment contribute to the patterning effect. The MD results are subsequently analysed using a numerical module Pycraters that allows the prediction of the rippling effect. Ripple wavelengths estimated with Pycraters are then compared with the experimental observations, as well as with the results obtained by using the binary collisions approximation (BCA) method. The wavelength estimation based on the MD results demonstrates a better agreement with the experimental values. In the framework of the utilized analytical model, it can be mainly attributed to the fact that the BCA ignores low energy atomic interactions, which, however, provide an important contribution to the displacement of atoms following an ion impact.

Optimization design and performance analysis of a novel asymmetric compound parabolic concentrator with rotation angle for building application

A novel asymmetric lens-walled compound parabolic concentrator (ALCPC) for integration with the building south wall was proposed and manufactured. Besides of the asymmetric lens-walled structure, the special rotation angle at the bottom is also introduced to optimize the performance. The electrical and optical performance of the ALCPC-PV was detailed analyzed through the experiment and ray tracing simulation. The indoor experiment was conducted by a solar simulator (Oriel Sol3A Model 90943A) from Newport Corporation at the dark environment with the temperature of 25 °C. Form the experiment results, the ALCPC increases the maximum power by a ratio of 1.74x compared to the bare cell. The decrease of the geometric concentration ratio is mainly due to manufacturing errors, mismatch losses, series resistance losses, etc. The optical performance of the ALCPC was also investigated by the software Lighttools, and the optical efficiency and the distribution percentage of the energy collected through the total internal reflection and the specular reflection at different incidence angles are identified at various incidence angles. A good agreement is observed between the experiment results and the ray tracing results. The optical efficiency at the incidence angles of 0–60° is all within 90% of its peak value which means that the proposed ALCPC can achieve 60° acceptance angle with high optical efficiency that it shows a good potential as a static concentrator for the building south wall integration.

TEACHING MEDIA DEVELOPMENT OF MATHEMATIC IN THE MATERIALS TRIGONOMETRY SUM AND TWO ANGLES DIFFERENCE BY USING GUI MATLAB

Abstract. The aim of this research is to develop teaching media for mathematics specifically for materials on trigonometry using GUI Matlab. This media can be used as teaching and learning aid for students at senior high school, grade XI in the first semester. This learning media consists of instructions on how to use the media, learning materials, exercises and profile. The trigonometry materials which are discussed in this learning media consist of the sum and difference of two angles. The limitation on the angles that can be used are special angles in the interval -360o £ a,b £ 360o. The special angles are 0o, ±30o, ±45o, ±60o, ±90o, ±120o, ±135o, ±150o, ±180o, ±210o, ±225o, ±240o, ±270o, ±300o, ±315o, ±330o, and ±360o. The trigonometry functions such as sinus, cosine and as well as the operation addition (+) and subtraction (-) can be selected by hitting the appropriate button. Within each step, there is a check button and a next button to check the input true or false. If the value that entered incorrectly then the next step will not displayed and warning box will appear to report the location of error. Users have to fix the error in order to continue to the next step. Keywords: teaching learning media, trigonometry, GUI Matlab

TEACHING MEDIA DEVELOPMENT OF MATHEMATIC IN THE MATERIALS TRIGONOMETRY SUM AND TWO ANGLES DIFFERENCE BY USING GUI MATLAB

Abstract. The aim of this research is to develop teaching media for mathematics specifically for materials on trigonometry using GUI Matlab. This media can be used as teaching and learning aid for students at senior high school, grade XI in the first semester. This learning media consists of instructions on how to use the media, learning materials, exercises and profile. The trigonometry materials which are discussed in this learning media consist of the sum and difference of two angles. The limitation on the angles that can be used are special angles in the interval -360o £ a,b £ 360o. The special angles are 0o, ±30o, ±45o, ±60o, ±90o, ±120o, ±135o, ±150o, ±180o, ±210o, ±225o, ±240o, ±270o, ±300o, ±315o, ±330o, and ±360o. The trigonometry functions such as sinus, cosine and as well as the operation addition (+) and subtraction (-) can be selected by hitting the appropriate button. Within each step, there is a check button and a next button to check the input true or false. If the value that entered incorrectly then the next step will not displayed and warning box will appear to report the location of error. Users have to fix the error in order to continue to the next step. Keywords: teaching learning media, trigonometry, GUI Matlab

Reliability study on the common three methods of substitution parameter estimation

A good estimation with high reliability of substitution parameter is the premise of all kinds of economical analyses with CES function. With great limitation of data availability, more or less compromises were adopted in most domestic literatures for substitution parameter estimation. But no one knows if those compromises are acceptable or not? In this paper, three popular methods to estimate parameters of CES function were compared in theoretical and empirical way, with a special angle of parameter unit. It was found that the unit of parameter directly and remarkably affects the results of estimation, and only the method of estimating with the first order condition (FOC for short) of CES production could produce reasonable and stable estimation of substitution parameter, while the estimation results of the other two methods were deeply involved in the influence of variable unit. Therefore, the FOC model was strongly recommended in most case of substitution parameter evaluation, unless full evidence of its value, zero near enough.

Elastic analytical solutions and angular distributions near spot weld nugget in lap-shear specimens

Spot welding has been a remarkably important joint method for automotive body engineering. Based on a simplified two-dimensional analytical model in a lap-shear specimen, the elastic analytical solutions near spot weld nugget are theoretically derived to analyze stress distributions. A Cartesian coordinate system is centered at the center of the nugget, and the shear or resultant force acting on the nugget is marked as the positive x-direction. The results show that the normalized radial and hoop stresses are negative at the angle intervals between [66.25°, 113.75°] and [246.25°, 293.74°], while the normalized shear stress is negative at the angle intervals between [0°, 90°] and [180°, 270°]. It can be observed that the locations with the initial yielding failure change gradually from the normalized radial distance of 1.34 to the circumference of the spot weld nugget, and finally to the infinity as the angle increases. The normalized effective stress could approach to 1.84 as the normalized radial distance goes to infinity. In addition, the obtained analytical solutions are validated in the comparison with numerical results. The locations with peak Von Mises stresses along the circumference of the spot weld nugget have a good agreement with the analytical solutions. It indicates that the initial yielding locations would likely occur at the four special angles of the spot weld nugget. Therefore, the derived stress distributions in this study are beneficial for analyzing yielding failure behavior or evaluating damage evolution on engineering structures jointed with spot welds.

L'héritage de Craya, pour une approche statistique à points multiples de la turbulence homogène anisotrope

Some elements are given on the very multiform career of Antoine Craya. In addition to a strong involvement in applied hydraulics in Grenoble, he was very influential on the research of his colleagues: to give only a few examples of well-known scientists in the Lyon–Grenoble area, he inspired the doctoral work on wall-jets by Jean Mathieu, the doctoral work on channel flow by Geneviève Comte-Bellot, and the dominant research area of René Moreau on magnetohydrodynamic (MHD) turbulence. The main part of this article is devoted to the legacy of Antoine Craya, from his own doctoral dissertation (1957). Inspired by G.I. Taylor probably more than by G. Batchelor, he contributed to establish the concept of HAT (Homogeneous Anisotropic Turbulence), as a useful intermediate step between HIT (Homogeneous Isotropic Turbulence) and fully statistically inhomogeneous turbulent flows. For this purpose, a mean flow with space-uniform velocity gradient can inject energy and anisotropy to a fluctuating flow, and statistical homogeneity is restricted to fluctuations. Complete equations for two-point second-order and three-point third-order velocity correlations were written, both in physical space and in Fourier space, in order to exactly solve mixed pressure–velocity correlations thanks to the incompressibility constraint. Antoine Craya is well known for the use of the eponymous frame of reference, thanks to Jacks Herring (1974). Later recognized as a spectral counterpart of a general decomposition in terms of toroidal/poloidal/dilatational modes, this frame leads to expressing the spectral tensors of correlation with a minimal number of scalar (or pseudo-scalar) descriptors, without loss of information and for arbitrary anisotropy. Craya provided us with a special angle of attack of the so-called RDT (Rapid Distortion Theory) and triadic closures, even if he did not work directly on them. Accordingly, this paper is also an opportunity to come back on the long history of RDT, including the Spectral Linear Theory as a better nomenclature, especially for recent studies. As far as possible, historical milestones are recalled throughout this article, and one recovers the Lagrangian formalism of Cauchy, emphasized by Uriel Frisch as well, with the use of a ‘Cauchy matrix’ in connection with linear theory. Finally, it is shown how the legacy of Craya is present in new (not addressed by him) domains, such as stratified turbulence and MHD turbulence. We discuss how further (past 1957) approaches, by Keith Moffatt (spectral linear theory, 1967), and Steven Orszag (triadic closure for HIT, as EDQNM, Eddy Damped Quasi-Normal Approximation, 1970) can be integrated in a general approach to anisotropic turbulence, which still benefits from Craya's legacy. A synoptic scheme for the description of multipoint statistics is re-discussed on this occasion. More incidentally, connections with Kraichnan theories and with the formalism of Kármán–Howarth–Monin equation(s) are touched upon.

Comparison of Solution Options for Line-Source Generated Short-Waves in a Wedge with Neumann and Robin Conditions on Respective Faces: Application to Waves on a Plane Beach

High-frequency waves generated by a moving oscillatory line source over a plane beach are examined in the context of a linear non-hydrostatic theory. The work complements a recent study by the author of low-frequency wave generation in a similar environment (Q. Jl. Mech. Appl. Math.68 (2015) 421–460) and provides a special case of a wider class of problems to which belong also a number of problems on electromagnetic diffraction by impedance wedges currently of considerable interest. The latter are generally treatable only by numerical techniques and the opportunity is seized here to examine a comparison between such numerically generated solutions and analytic solutions which can be and are derived and evaluated for the water wave problem. In common with the electromagnetic problems, the water-wave solution is formulated in terms of an inverse Kontorovich–Lebedev transform the inversion of which is considered both by direct quadrature and by residue composition while the spectral function of the transform is also determined in two different ways namely as (i) (for special wedge angles) a semi-closed form entire function and (ii) a numerical solution of a singular integral equation (as commonly encountered in the electromagnetic problems) valid for more general wedge angles. It is concluded that the residue composition technique can be fraught with difficulties and, where spectral function structure allows, should be replaced by the strategy of direct numerical inversion. For the water-wave problem, the anticipated resonances at edge wave frequencies are shown to exist and their strengths prove to be consistent with the well-known findings of Ursell though the process of successfully detecting these purely from the numerical model is shown to be somewhat error prone.

Um olhar para as cidades: Richard Morse e a história urbana no Brasil

Richard Morse, a North-American historian best known for his work Prospero’s Mirror, a comparative study of Anglo-America and Iberian-America published in the 1980s, is also the author of a seminal book on the history of São Paulo: From Community to Metropolis: A Biography of São Paulo, Brazil, first published in 1954 and republished in 1970. This book from his early years was a kind of study platform that allowed Morse to tread a path through the history of cities to understand society from a singular viewpoint. As he became a professor of Latin American History in the United States, Morse privileged in his courses the study of cities, an approach that provided him with access to society from a special angle, providing clues to understanding the Western culture. The main goal of this paper is to shed light on the way Morse devised his courses, to discuss the outcomes of his ideas in the urban historical studies today in Brazil

Particular features of the optical properties of an anisotropic metamaterial with a near-zero dielectric permittivity

The propagation of an electromagnetic wave through a layer of a uniaxial anisotropic metamaterial with the components of its permittivity tensor close to zero and the reflection of the wave from the layer have been considered. The occurrence of transmission maxima of the electromagnetic wave at specific angles of incidence has been confirmed. It has been shown that, when studying this effect, one cannot neglect the absorption, because this neglecting leads to unrealistic predictions, such as a total transmission of the wave by the layer of the anisotropic metamaterial at special angles of incidence of the wave.

Ion beam planarization of diamond turned surfaces with various roughness profiles.

The effectiveness of ion beam planarization (IBP) to reduce surface roughness of diamond turned NiP surfaces was investigated. The surfaces with various spatial wavelengths and depths of turning marks were spray-coated and planarized with broad ion beam. The ion beam planarization was performed at a special angle where the etching rate of photoresist is closely similar to NiP. It is found that the combined process of spray-coating and ion-beam-planarization can effectively reduce the surface roughness of diamond turned NiP. The spatial wavelength and depth of turning marks have limited influence on surface roughness reduction rate. The final surface roughness after ion beam planarization is 30%~40% of the original roughness, irrespective of spatial wavelength and depth of turning marks. Extending planarization time does not alter surface quality after photoresist is etched away. These results show that the IBP is applicable to roughness minimization of diamond turned surfaces.

Continuously tunable polarization-independent zeroth-order fiber comb filter based on polarization-diversity loop structure

By selecting some optimal wave retarder combination (WRC) groups, we propose and experimentally implement a continuously tunable polarization-independent zeroth-order fiber comb filter based on a polarization-diversity loop structure. The selected WRC groups contain a set of two quarter-wave retarders (QWRs), a set of a QWR and a half-wave retarder (HWR), and a set of an HWR and a QWR. The filter was formed using a polarization beam splitter (PBS), one of the three selected WRC groups, and high birefringence fiber (HBF). One end of HBF was butt-coupled to the PBS so that its slow axis should be oriented at 45° for the horizontal axis of the PBS, and the other end was connected to the WRC group. Three kinds of comb filters were fabricated with the three selected WRC groups. Through theoretical analysis on light polarization conditions for continuous spectral tuning and filter transmittances, eight special azimuth angle sets of two wave retarders, which gave the transmittance function eight different phase shifts of 0 to –7π/4 with a –π/4 step, were found for each WRC group. Theoretical prediction was verified by experimental demonstration. It was also confirmed that the filter could be continuously tuned by the appropriate control of wave retarders.

Energy and moiré patterns in 2D bilayers in translation and rotation: A study using an efficient discrete–continuum interlayer potential

Layered 2D materials consist of a stack of 2D materials interacting weakly via van der Walls (vdW) forces. The vdW interactions are modeled using long-range interlayer potentials, such as Lennard-Jones (LJ) and Kolmogorov–Crespi (KC), that are expensive to compute in atomistic and multiscale simulations. We propose a discrete–continuum (DC) effective potential for LJ and KC that includes full atomistic resolution in the short range and a continuum integral approximation outside. This reduces the computational cost by two orders of magnitude while retaining excellent accuracy. With this method, we examine the relation between stacking states and interlayer energy of a graphene bilayer under relative in-plane translations and rotations. We compare the performance of LJ and KC and characterize the moiré patterns under rotation. We find that the energy of an infinite graphene bilayer is constant with rotation (with discontinuities at special angles) and explain this in terms of the moiré pattern supercell. We also find that the saddle point (SP) stacking configuration becomes the stable ground state (as opposed to AB stacking) when the bilayer is compressed.