Compact Sections Research Articles

Infinite in Between by Carolyn Mackler (review)

Reviewed by: Infinite in Between by Carolyn Mackler Deborah Stevenson, Editor Mackler, Carolyn Infinite in Between. HarperTeen/HarperCollins, 2015 [480p] Trade ed. ISBN 978-0-06-173107-5 $17.99 E-book ed. ISBN 978-0-06-232305-7 $10.99 Reviewed from galleys Ad Gr. 8-12 At the start of freshman year, Gregor, Whitney, Zoe, Jake, and Mia are all in the same freshman orientation group in their Vermont school, and together they write letters to their future selves to read upon their graduation. The book follows each of the five on their journey through those four years as they remain distantly aware of one another or become more closely involved. There’s a lot of drama in those four years: Gregor’s father dies; Whitney cycles through her friend group and deals with being biracial in a white community; Zoe adjusts to the distance from her alcoholic movie-star mother; Jake comes out; Mia explores her identity from indie nerd to hottie and back again. The book is structured episodically, broken up into compact sections identified by month, within which are a few two- to three-page chapters that follow the character named at the beginning. The effect is like a detailed look through the yearbooks from somebody else’s school, as events happen in quick snapshots but the narrative marches steadily on. Unfortunately, characterization is thin; the short dips into the kids’ lives focus mostly on stuff that happens to them rather than who they are, so they’re more compelling for their situations than for themselves, and the dizzying array of secondary and tertiary characters makes it even harder to keep track of the protagonists. There’s still fascination in following a group of people over time, especially when so many of the threads conclude in romantic triumph, so readers may enjoy seeing the multiple plots play out and the cast successfully achieve graduation. Copyright © 2015 The Board of Trustees of the University of Illinois

Unitary evolution and uniqueness of the Fock representation of Dirac fields in cosmological spacetimes

We present a privileged Fock quantization of a massive Dirac field in a closed Friedmann-Robertson-Walker cosmology, partially selected by the criteria of invariance of the vacuum under the symmetries of the field equations, and unitary implementation of the dynamics. When quantizing free scalar fields in homogeneous and isotropic spacetimes with compact spatial sections, these criteria have been shown to pick out a unique Fock representation (up to unitary equivalence). Here, we employ the same criteria for fermion fields and explore whether that uniqueness result can be extended to the case of the Fock quantization of fermions. For the massive Dirac field, we start by introducing a specific choice of the complex structure that determines the Fock representation. Such structure is invariant under the symmetries of the equations of motion. We then prove that the corresponding representation of the canonical anticommutation relations admits a unitary implementation of the dynamics. Moreover, we construct a rather general class of representations that satisfy the above criteria, and we demonstrate that they are all unitarily equivalent to our previous choice. The complex structures in this class are restricted only by certain conditions on their asymptotic behavior for modes in the ultraviolet sector of the Dirac operator. We finally show that, if one assumes that these asymptotic conditions are in fact trivial once our criteria are fulfilled, then the time-dependent scaling in the definition of the fermionic annihilation and creation-like variables is essentially unique.

The current distribution in the electrodes of electrosurgical instruments during welding of biological tissues

The analysis of the current density distribution in the electrodes of electrosurgical instruments during welding of soft biological tissues was performed. For that, the solution algorithm was developed, and the elliptic problem that simulates the skin effect in the compact section conductors was solved. Verification of the mathematical model of the current density distribution in a monopolar electrode by comparing with the experimental data during surgical operation of welding the retina to the choroid was carried out. The mathematical model shows that high-frequency current hardly flows in a round electrode and this explains the formation of coagulation rings in practical studies of contact retina welding. This model is a one-dimensional elliptic problem for modeling the skin effect in conductors. By changing the current frequency in the electrodes it is possible to influence the width of the coagulation ring and solve the problem of its optimization since too great width of the ring leads to a more traumatic course of the operation, and too small - does not provide the quality and strength of the weld.

Dynamical symmetry enhancement near IIA horizons

We show that smooth type IIA Killing horizons with compact spatial sections preserve an even number of supersymmetries, and that the symmetry algebra of horizons with non-trivial fluxes includes an sl(2,R) subalgebra. This confirms the conjecture of [1] for type IIA horizons. As an intermediate step in the proof, we also demonstrate new Lichnerowicz type theorems for spin bundle connections whose holonomy is contained in a general linear group.

Gauge-invariant perturbations in hybrid quantum cosmology

We consider cosmological perturbations around homogeneous and isotropic spacetimes minimally coupled to a scalar field and present a formulation which is designed to preserve covariance. We truncate the action at quadratic perturbative order and particularize our analysis to flat compact spatial sections and a field potential given by a mass term, although the formalism can be extended to other topologies and potentials. The perturbations are described in terms of Mukhanov-Sasaki gauge invariants, linear perturbative constraints, and variables canonically conjugate to them. This set is completed into a canonical one for the entire system, including the homogeneous degrees of freedom. We find the global Hamiltonian constraint of the model, in which the contribution of the homogeneous sector is corrected with a term quadratic in the perturbations, that can be identified as the Mukhanov-Sasaki Hamiltonian in our formulation. We then adopt a hybrid approach to quantize the model, combining a quantum representation of the homogeneous sector with a more standard field quantization of the perturbations. Covariance is guaranteed in this approach inasmuch as no gauge fixing is adopted. Next, we adopt a Born-Oppenheimer ansatz for physical states and show how to obtain a Schrödinger-like equation for the quantum evolution of the perturbations. This evolution is governed by the Mukhanov-Sasaki Hamiltonian, with the dependence on the homogeneous geometry evaluated at quantum expectation values, and with a time parameter defined also in terms of suitable expectation values on that geometry. Finally, we derive effective equations for the dynamics of the Mukhanov-Sasaki gauge invariants, that include quantum contributions, but have the same ultraviolet limit as the classical equations. They provide the master equation to extract predictions about the power spectrum of primordial scalar perturbations.

Optimization of a horizontal slot waveguide biosensor to detect DNA hybridization.

A full-vectorial H-field formulation-based finite element approach is used to optimize a biosensor structure incorporating a horizontal slot waveguide. It is designed to detect DNA hybridization through the change of the effective index of the waveguide structure. The key parameters, such as normalized power confinement, power density, change in effective index, and sensitivity are presented by optimizing the device parameters of the slot waveguide. It is shown here that a 90.0μm long compact Mach-Zehnder section can be designed with horizontal slot waveguide to detect DNA hybridization and for a ring resonator arrangement a sensitivity of 893.5nm/RIU is obtained.

Effect of local instability on capacity of steel beams exposed to fire

This paper presents results from numerical studies on the behavior of fire exposed steel beams by taking into consideration temperature-induced sectional instabilities. A three-dimensional nonlinear finite element model is developed to evaluate the response of fire exposed steel beams under both flexural and shear effects. This model is applied to investigate the effect of sectional slenderness on the onset of local instability and capacity degradation in steel beams exposed to fire. Results from finite element analyses are utilized to evaluate failure of beams under different limit states including flexure, shear, sectional instability and deflection criteria. These results show that under certain loading scenarios and sectional configurations, shear capacity in steel beams can degrade at a higher pace than that of moment capacity. In addition, results from numerical studies infer that room temperature classification of steel beams based on local stability, can change with fire exposure time; a compact section at ambient conditions can transform to a non-compact/slender section under high temperature effects. This can induce temperature-induced local buckling in steel sections and lead to failure prior to attainment of failure under flexural yield and/or shear limit state.

Pure quasifree states of the Dirac field from the fermionic projector

We consider the quantized free massive Dirac field on oriented and globally hyperbolic ultrastatic slab spacetimes with compact spatial section and demonstrate how a gauge invariant, pure and quasifree state on the C*-completion of the self-dual CAR-algebra can be extracted from the fermionic projector construction of Finster and Reintjes. This state is analogous to the ‘SJ-state’ of the free scalar field recently discussed in the literature. We prove that this state generically fails to be Hadamard. However, we also show how a modified version of the construction, inspired by the work of Brum and Fredenhagen, yields states that are Hadamard. We also relate the Hadamard condition to the finiteness of fluctuations of Wick polynomials.

Fire performance of restrained welded steel box columns

The objectives of this study is to investigate the effect of weld details (CJP or PJP), the load ratios, and the width-to-thickness ratios on the fire performance of unprotected welded steel box columns at 500°C. Upon the experimental works, five column specimens were loaded to their ultimate state at room temperature and ten unprotected column specimens were loaded by steady-state method up to 500°C.In this study it is found that local buckling is the failure mode observed for the column specimen tested either at room temperature or in the fire condition. At 500°C, unprotected CJP steel box columns show superior fire behavior compared to the columns fabricated by PJP which are more susceptible to premature cracking at the corner welds. CJP box columns with non-compact sections and no discernible cracks are able to sustain design loads of 0.8ϕPn for 2h under temperature conditions of 500°C. At 500°C, the fire resistance of PJP box columns can be enhanced by decreasing the applied loads and/or the width-to-thickness ratios. But, the fire resistance of steel box columns would be reduced significantly whenever the premature cracks were existed in the corner welds. Based on the result of this study, it is found that CJP box columns would be a better choice than PJP box columns for unprotected steel box columns under 500°C. If CJP is not feasible in practical application and PJP is used instead, it is strongly suggested to design a compact section for those PJP box columns.

Right/Left-Handed Transmission Lines Based on Coupled Transmission Line Sections and Their Application Towards Bandpass Filters

Novel metamaterial structures featuring left-handed (LH) and composite right/left-handed (CRLH) character are presented. The proposed unit cells utilize sections of coupled transmission lines. It is shown that by taking advantage of the coupling between transmission lines an additional degree of freedom is achieved, and therefore, the design process of artificial transmission lines is more flexible. The general behavior of each of the proposed circuits is presented and analyzed. Moreover, the design equations are formulated and the design process of each unit cell is described. The usefulness and validity of the proposed unit cells are illustrated and verified by the design and measurements of compact artificial transmission line sections utilizing the presented structures. Moreover, possible applications are discussed.

Substrate Moisture Content Effects on Growth and Shelf Life of Angelonia angustifolia

Wilting during shelf life is a major cause of postharvest shrink for bedding plants shipped long distances from production greenhouses to retail outlets. The objective of this research was to determine if irrigation at lower, constant substrate moisture content (SMC) during greenhouse production would be a feasible way to acclimate plants for reduced shrinkage during shelf life while potentially conserving irrigation water. In two separate experiments conducted in the fall and spring seasons, rooted plugs of Angelonia angustifolia ‘Angelface Blue’ (angelonia) were grown in greenhouse production until a marketable stage in substrates irrigated at SMC levels of 10%, 20%, 30%, and 40% using a controlled irrigation system. At the end of the greenhouse production stage, plants were irrigated to container capacity and subjected to a simulated shipping environment in shipping boxes in the dark for 2 days. After shipping, plants were placed back in the greenhouse and watered minimally to simulate a retail environment. Data were taken at the end of each stage, i.e., greenhouse production, simulated shipping, and simulated retail. Results indicated that as SMC decreased from 40% to 10%, plants were shorter in height but had proportional and more compact flowering sections. The volume of water received by the 40% SMC plants was three times greater (fall) and 12 times greater (spring) than the 20% SMC plants during greenhouse production and two times greater (fall) and nine time greater (spring) during simulated retail. During production, midday water potentials decreased as the SMC levels decreased, but at the end of the simulated retail, the midday water potentials were the same, suggesting that plants that were drought-stressed during production were acclimated to lower water levels experienced in retail settings. Overall, the 20% SMC treatment produced the best postharvest quality plant resulting from reduced plant height without detrimental effects on flowering. The results demonstrate that while conserving water, controlled irrigation at a lower SMC can produce high-quality plants that have equal shelf life to those that are irrigated at high levels.

Simulation and optimization of extrusion process of cylindrical work-pieces prepared from plasticized charge mixtures of powder and composite materials in strew presses

The article describes a mathematical model of calculating the extrusion process of long powder compacts and composite materials with the help of screw presses through the facilities having local sectional area reduction of the forming channel. The stress field calculation in the various materi- al deformation centers along the overall length of the channel is carried out with the use of the discrete theory of plasticity. It is shown how, varying the form of channel surface, material extrusion rate in the zone of local channel section reduction and the compact section area, to select their com- bination being optimum for extrusion process.

Removing the Faddeev-Popov zero modes from Yang-Mills theory in spacetimes with compact spatial sections

It is well known that in de Sitter space the (free) minimally coupled massless scalar field theory does not admit any de Sitter--invariant Hadamard state. Related to this is the fact that the propagator for the massive scalar field corresponding to the de Sitter--invariant vacuum state diverges in the massless limit, with the infrared-divergent term being a constant. Since the Faddeev-Popov ghosts for the covariantly quantized Yang-Mills theory are minimally coupled massless scalar fields, it might appear that de Sitter symmetry would be broken in the ghost sector of Yang-Mills theory in de Sitter space. It is shown in this paper that the modes responsible for de Sitter symmetry breaking can be removed in a way consistent with BRST invariance and that a de Sitter--invariant theory can be constructed. More generally, it is shown that the spatially constant modes (the zero modes) of the Faddeev-Popov ghosts can be disposed of in a wide class of spacetimes with compact spatial sections. Then, the effective theory obtained by removing the zero modes, which contains a nonlocal interaction term, is shown to be equivalent to the theory corresponding to using a Faddeev-Popov-ghost propagator with the constant infrared-divergent term removed, provided that one can freely integrate by parts in the spacetime integral at the vertex for the ghost interaction term.

The evolution of a spatially homogeneous and isotropic universe filled with a collisionless gas

We review the evolution of a spatially homogeneous and isotropic universe described by a Friedmann-Robertson-Walker spacetime filled with a collisionless, neutral, simple, massive gas. The gas is described by a one-particle distribution function which satisfies the Liouville equation and is assumed to be homogeneous and isotropic. Making use of the isometries of the spacetime, we define precisely the homogeneity and isotropicity property of the distribution function, and based on this definition we give a concise derivation of the most general family of such distribution functions. For this family, we construct the particle current density and the stress-energy tensor and consider the coupled Einstein-Liouville system of equations. We find that as long as the distribution function is collisionless, homogenous and isotropic, the evolution of a Friedmann-Robertson-Walker universe exhibits a singular origin. Its future development depends upon the curvature of the spatial sections: spatially flat or hyperboloid universes expand forever and this expansion dilutes the energy density and pressure of the gas, while a universe with compact spherical sections reaches a maximal expansion, after which it reverses its motion and recollapses to a final crunch singularity where the energy density and isotropic pressure diverge. Finally, we analyze the evolution of the universe filled with the collisionless gas once a cosmological constant is included.

Retrofit of a soft-story woodframe building using SMA devices with full-scale hybrid test verification

Soft-story woodframe buildings are prevalent in much of California and for decades have been recognized as a disaster preparedness problem for both the owners/tenants and community as a whole. Retrofit programs for these at-risk buildings have been proposed with the first such program in a major city mandated in San Francisco in 2013. In this paper, a seismic retrofit methodology for soft-story woodframe buildings is presented. The methodology utilizes seismic response modification devices that consist of a compact steel section for energy dissipation and shape memory alloy (SMA) wire for re-centering capability, should that be needed. The device can be installed within a scissor-jack brace which is known for its compact footprint and high displacement magnification factor. These characteristics make it suitable mainly because of the need for placement in or near short wall segments characteristic of the bottom floor of soft-story woodframe buildings. The retrofit methodology using the SMA-steel device in a scissor-jack brace was developed and exemplified on a three-story soft-story woodframe building. Nonlinear time history analysis was conducted to quantify the performance of the retrofitted building for a suite of earthquakes. Experimental validation consisted of a full-scale hybrid test of the three-story building with the seismic retrofit represented numerically in the first-story serving as the numerical substructure, and the upper two stories represented physically in the laboratory. The results of the full-scale hybrid test are presented thereby validating the proposed seismic retrofit using SMA-steel devices in scissor-jack braces.

Investigation of Lateral-Torsional Buckling Strength Trends in Monosymmetric Stepped I-Beams Subjected to Several Loading Conditions

일축대칭 I형 단면보의 횡-비틀림 좌굴강도를 고려하는 데 있어서 강도기준 하중조건이 순수휨 작용시가 아님을 보여주는 연구가 제시된 바 있다. 이러한 연구결과는 오랫동안 적용해온 순수휨 작용시 가장 작은 횡-비틀림 좌굴강도를 보인다는 접근과는 다른 방법이다. 이에 본 연구에서는 제안된 새로운 경향을 확인하고 일축대칭 스텝보를 적용한 경우에도 같은 경향을 보이는 지 확인하고자 한다. 본 논문에는 다양한 하중조건을 고려하고 있으며 단면은 조밀단면을 적용하였다. 연구에 사용된 유한요소해석 프로그램은 ABAQUS이며, 스텝보에 적용한 일축대칭도는 0.5~0.9이다. 또한 본 연구에 고려한 해석모델의 <TEX>$L_b/h$</TEX>(지간/보 높이)비율은 20이다. 본 해석연구를 통하여 얻어진 새로운 경향과 결론을 자세하게 본 논문에 기술하였다. It has been proven in recent studies that for monosymmetric I-section beams, in considering bending moment diagrams caused by any combination of applied end moments and transverse loads acting at the shear centre, the lowest critical lateral torsional buckling moment does not necessarily correspond to uniform bending. This finding is different from the intuitive expectation that researchers have that for lateral torsional buckling of thin walled beams, the lowest critical lateral torsional buckling moment always corresponds to a uniform bending moment diagram. To determine the applicability of the findings stated, considering stepped beams, this study will be focusing on the comparison of the lateral torsional buckling strength trends in monosymmetric I-beams having doubly stepped and compact cross section. Several loading conditions will be applied to see the effect of different moment diagrams having different inflection points on the lateral torsional buckling strength of stepped beams. The study will be made using the finite element program, ABAQUS. The study will investigate stepped beams having monosymmetric ratios ranging from 0.5 to 0.9. These ratios correspond to varying bottom flange width while keeping the top flange width unchanged. Unbraced length to height ratio of the beam to be analyzed is 20. Finally, the findings for this study will be shown using illustrative figures and conclusions will be made.

Global attractors for the discrete Klein–Gordon–Schrödinger type equations

The purpose of this work is to investigate the asymptotic behaviours of solutions for the discrete Klein–Gordon–Schrödinger type equations in one-dimensional lattice. We first establish the global existence and uniqueness of solutions for the corresponding Cauchy problem. According to the solution's estimate, it is shown that the semi-group generated by the solution is continuous and possesses an absorbing set. Using truncation technique, we show that there exists a global attractor for the semi-group. Finally, we extend the criteria of Zhou et al. [S. Zhou, C. Zhao, and Y. Wang, Finite dimensionality and upper semicontinuity of compact kernel sections of non-autonomous lattice systems, Discrete Contin. Dyn. Syst. A 21 (2008), pp. 1259–1277.] for finite fractal dimension of a family of compact subsets in a Hilbert space to obtain an upper bound of fractal dimension for the global attractor.

Investigation of ductility in hybrid and high strength steel beams

Compactness and lateral support configuration provisions for design of steel beams are formulated so as to ensure that the resulting beam exhibits adequate ductility. It appears from the current research that slenderness limitations are not valid for beams made of the high strength steel grades. In this paper an attempt is made to study on influence of flange and web slenderness as well as lateral support spacing of homogenous and hybrid welded I-sections made of high strength steel on member ductility. For this purpose an experimentally verified nonlinear numerical analysis of the local and overall stability was performed. These beams are subjected to constant moment loading a new theoretical method is proposed to calculate the rotation capacity for this loading type. A comparative study was carried out between this method and numerical study results to ensure the accuracy of proposed method. In this research realistic material behavior and residual stresses were adopted in finite element models. Results have shown that using the high strength steel in cross sections subjected to bending has a significant effect on flexural behavior of these members. Meanwhile, in present study, interaction between the flange and web slenderness ratios was evaluated in accordance to AISC criteria for compact sections.

Design and test of a NbTi prototype coil for a low beta section

The design of superconducting quadrupoles for a proton and antiproton low beta section and the test of a prototype coil are presented. Previous studies [1,2] show that high gradient and short quadrupole magnets are required for a compact low beta section in order to allow the insertion of such a magnetic system with minor changes of the lattice [3]; each quadrupole is 400 mm long and has to provide a magnetic induction gradient of 60 T/m. A beam pipe of at least 120 mm diameter is required to avoid beam loss during injection and before the beam cooling. The magnetic design of the superconducting magnets for the low beta section is presented, together with a detailed discussion of the quench protection design. Two prototype coils were produced and one of them was tested. A detailed description of the test setup and a full discussion of the results will be presented.

Design studies for the next generation electron ion colliders

The next generation Electron Ion Collider (EIC) at Thomas Jefferson National Accelerator Facility (JLAB) utilizes a figure-8 shaped ion and electron rings. EIC has the ability to preserve the ion polarization during acceleration, where the electron ring matches in footprint with a figure-8 ion ring. The electron ring is designed to deliver a highly polarized high luminous electron beam at interaction point (IP). The main challenges of the electron ring design are the chromaticity compensation and maintaining high beam polarization of 70% at all energies 3–11 GeV without introducing transverse orbital coupling before the IP. The very demanding detector design limits the minimum distance between the final focus quadrupole and the interaction point to 3.5 m which results in a large β function inside the final focus quadrupoles leading to increased beam chromaticity. In this paper, we present a novel chromaticity compensation scheme that mitigates IP chromaticity by a compact chromaticity compensation section with multipole magnet components. In addition, a set of spin rotators are utilized to manipulate the polarization vector of the electron beam in order to preserve the beam polarization. The spin rotator solenoids introduce undesired coupling between the horizontal and vertical betatron motion of the beam. We introduce a compact and modular orbit decoupling insert that can fit in the limited space of the straight section in the figure-8 ring. We show a numerical study of the figure-8 ring design with the compact straight section, which includes the interaction region, chromaticity compensation section, and the spin rotators, the figure-8 design performance is evaluated with particle tracking.