Dimensional Defects Research Articles

Chern insulator transitions with Wilson fermions on a hyperrectangular lattice

A $U(1)$ gauge theory coupled to a Wilson fermion on a $2+1$ dimensional cubic lattice is known to exhibit Chern insulator like topological transitions as a function of the the ratio $M/R$ where $M$ is the fermion mass and $R$ is the Wilson parameter. I show that, with $M$ and $R$ held fixed, a rectangular lattice with anisotropic lattice spacing can exhibit distinct topological phases as a function of the lattice anisotropy. As a consequence, a $2+1$ dimensional lattice theory without any domain wall in the fermion mass can still exhibit chiral edge modes on a $1+1$ dimensional defect across which lattice spacing changes abruptly. Likewise, a domain wall in the fermion mass on a uniform rectangular lattice can exhibit discrete changes in the number and chirality of zero modes as a function of lattice anisotropy. The construction presented in this paper can be generalized to higher dimensional space-time lattices.

Super-resolution Optical Spectroscopy of Nanoscale Emitters within a Photonic Atom Probe.

Atom Probe Tomography (APT) is a microscopy technique allowing for the 3D reconstruction of the chemical composition of a nanoscale needle-shaped sample with a precision close to the atomic scale. The photonic atom probe (PAP) is an evolution of APT featuring in situ and operando detection of the photoluminescence signal. The optical signatures of the light-emitting centers can be correlated with the structural and chemical information obtained by the analysis of the evaporated ions. It becomes thus possible to discriminate and interpret the spectral signatures of different light emitters as close as 20 nm, well beyond the resolution limit set by the exciting laser wavelength. This technique opens up new perspectives for the study of the physics of low dimensional systems, defects and optoelectronic devices.

Calibrating a profile measurement system for dimensional inspection in rail rolling mills

Modern, high-speed, railway transportation requires rails to conform strictly to requirements specified in various standards. One key requirement is the conformance of the dimensions of the rail cross section to those of the corresponding rail model, within tight tolerances. This paper deals with a system for dimensional quality inspection during the manufacture of railway rails. Optical triangulation is used to build a profile from laser lines projected on the rails from four different locations. Then, the profile is compared to that of the corresponding rail model. The differences between certain numerical values (the dimensions) for the profile and the model are compared to standard tolerances for each dimension in order to detect dimensional defects. As a prerequisite for this, the cameras used to capture the laser lines must be calibrated. Standard calibration plates are unsuitable for sheet-of-light calibration in a production environment, as determining the location of the laser emitters relative to the plates would be an issue. For this reason, a cylinder-based calibration target is used instead. Different calibration algorithms are discussed and compared to said standard calibration. The results of accuracy and repeatability tests in the production environment are also shown. The accuracy of the system is found to be appropriate for the purpose of quality inspection under the requirements of applicable rail standards.

Quantum extremal islands made easy. Part I. Entanglement on the brane

Recent progress in our understanding of the black hole information paradox has lead to a new prescription for calculating entanglement entropies, which involves special subsystems in regions where gravity is dynamical, called quantum extremal islands. We present a simple holographic framework where the emergence of quantum extremal islands can be understood in terms of the standard Ryu-Takayanagi prescription, used for calculating entanglement entropies in the boundary theory. Our setup describes a d-dimensional boundary CFT coupled to a (d−1)-dimensional defect, which are dual to global AdSd+1 containing a codimension-one brane. Through the Randall-Sundrum mechanism, graviton modes become localized at the brane, and in a certain parameter regime, an effective description of the brane is given by Einstein gravity on an AdSd background coupled to two copies of the boundary CFT. Within this effective description, the standard RT formula implies the existence of quantum extremal islands in the gravitating region, whenever the RT surface crosses the brane. This indicates that islands are a universal feature of effective theories of gravity and need not be tied to the presence of black holes.

The Need for a New Approach to Soldering in High Pressure Die Casting

Soldering remains one of the most common defects in high pressure die casting (HPDC). It is most simply defined as aluminum stuck to the die surface. At ejection, the stuck aluminum gouges the casting resulting in dimensional and leaking defects. For nearly 50 years, a thermodynamics and kinetics understanding of soldering has been accepted while explicitly assuming that other mechanisms are not important. It will be shown that this thermodynamics and kinetics modeling approach cannot adequately explain three common observations in die casting foundries. First, soldering occurs much faster than the measured intermetallic growth rate based on diffusion couple experiments. Second, the alloys that are industrially observed to solder less form intermetallic phases quicker and dissolve the steel faster than alloys that solder more rapidly. Finally, the intermetallic layer is not strong enough to enable the buildup commonly observed on soldered dies. For these reasons, it is proposed that a new soldering modeling approach is required to gain a better understanding of the soldering mechanism and prevent the soldering defect in die casting.

A FRAMEWORK TO EXTRACT STRUCTURAL ELEMENTS OF CONSTRUCTION SITE FROM LASER SCANNING

Abstract. This paper proposes a framework to automatic extract structural elements of reinforced concrete buildings from laser scanning data, which can be used in dimensional quality control and surface defect identification. The framework deploys both spatial information of a point cloud and contextual knowledge of building structures to extract the structural elements in a sequential order: floors and ceilings, walls, columns and beams. The method starts to extract a subset data containing candidate points of the structural elements and segmentation methods and filtered based contextual knowledge subsequently apply to obtain the final points of the elements. In this framework, a combination between kernel density estimation and a cell-patch-based region growing are to extract the floors, ceilings and walls, while the points of the columns and beams are achieved through a voxel-based region growing. 23.5 million data points of one story of the building is used to test a performance of the proposed framework. Results showed all structural components are successfully extracted. Moreover, completeness, correctness, and quality indicated through point-based performance report larger than 96.0%, 96.9% and 93.0%, respectively while overlap rates of the floors, ceilings and walls are no less than 95.3%. Interestingly, an executing time of the proposed method is about 7.7seconds per a million point.

Measurement uncertainty estimation of gap and profile in the automotive sector

In this paper, a methodology is described aiming at assessing the variability causes, affecting the measurement instruments typically used in the automotive sector for the analysis of dimensional defects of coupled components, to check the conformity of the width of the gap between two adjacent parts and the profile, i.e. the alignment of the two surfaces. The inspection may be performed by means of different gap/flush tools, such as feeler gages, calipers and Laser scanner devices; depending on the choice, a different measurand has to be considered. The obtained measurements need to be consistent, because these devices are used indistinctly, depending on the severity of the control and on the typology of the control itself. The paper proposes a methodology to verify the metrological conformity of measurements provided by both traditional and laser-based instruments, so that it is possible to interpret them in an interchanging manner. A 3D geometric model is realized, used as a basis for the analysis of the most influencing uncertainty causes and measurement biases. The methodology will demonstrate to be able to identify and evaluate in a parametric way, the typical variability causes of the instruments considered. It will also highlight possible improvements in the integration of the obtained results.

Ventricular tachyarrhythmias prediction in patients with ischemic cardiomyopathy

Aim. To identify predictors of ventricular tachyarrhythmias (VTA) in patients with ischemic cardiomyopathy.Materials and methods. The study included 40 patients (males - 36, mean age - 63,4 ± 7,8 years) with coronary artery disease (CAD), II-III functional class of chronic heart failure, left ventricle ejection fraction 35% or less, without sustained VTA and cardioverter-defibrillator (CD) implantation indications (primary prevention of the sudden cardiac death). Patients before CD implantation underwent 6-minute walk test, echocardiography, heart rate variability (HRV) analysis and cardiac single-photon emission computed tomography with 123I-meta-iodobenzylguanidine (123I-MIBG). All patients after CD implantation were followed-up during two years and divided into two groups. The 1-st group consisted of patients with VTA events, the 2-nd group - without VTA events.Results. The 1-st group consisted of 36 (90,0%) patients, the 2-nd group - 4 (10,0%) patients. The univariate ROC-analysis showed that the low values of the HRV, reflecting a decrease of the parasympathetic effect on the heart, as well as an increase in indexed left ventricle volumetric and dimensional indicators (end-diastolic and end-systolic indices) and 123I-MIBG accumulation defect on early and delayed scintigrams, reflecting an increase of the sympathetic effect on the heart leaded to frequent occurrences of the VTA (p=0,0001). The multivariate ROC-analysis demonstrated that only LF (p=0,0136), which associated with sympathoparasympathetic imbalance, leaded to frequent occurrences of the VTA. Also, increase of the VTA predictive ratio, calculated according to this predictive model, more than 0,8936 leaded to frequent occurrences of the VTA (p=0,0001).Conclusion. In patients with ischemic cardiomyopathy, the predominance of sympathetic and a decrease of parasympathetic effects on the heart, assessed by the analysis of heart rate variability, is a predictor of the life-threatening ventricular arrhythmias.

Defect detection method for rail surface based on line-structured light

• A novel rail defect detection scheme before welding is designed. • A registration algorithm based on feature points is presented to align data. • A dynamic defect detection algorithm is proposed for real-time detection. • Results show that the proposed method has higher accuracy and practicability. Based on intensive study on rail surface defect, a rail surface defect inspection scheme is proposed in this paper. With high-precession structured laser sensors, the original data are collected by industrial control computer and transformed into dimensional point cloud pattern. According to analysis of the specific feature of rail surface, a registration method is proposed to re-construct the digital rail surface. To achieve a high-precision detection result, a novel curve fitting model is established and accordingly a dynamic defect detection algorithm is improved to adapt to the successive production process based on the former study. Within the detailed study process, for each single frame data, a judge method is developed for noise elimination and specific feature defect detection. Finally, by studying successive frames of data points (actually cloud points), multiple frames data are dynamically computed to judge if there is a defect area on rail surface. In this paper, to avoid the random influence of minor factors, a probability threshold is introduced to judge defect points in the algorithm, which increases the anti-interference and decreases instability in the defect detection process. To verify the effect of proposed method, an experimental bench is developed in research process. Experimental results show that the detection method has reliable stability and anti-interference possibly influenced by minor factors like oxygen layer detection and characters area detection on rail surface. Compared with traditional two dimensional defect detection methods, the algorithm proposed in this paper is less computationally intensive and more suitable for online detection on rail surface.

How a-Type Anomalies Can Depend on Marginal Couplings.

Even dimensional defects and boundaries in conformal field theory support type a anomalies on their world volume. We show that the one-point functions of marginal operators, in the presence of defects and boundaries, are anomalous, and that the Wess-Zumino consistency condition relates them to the derivative of the a anomaly with respect to the marginal coupling. We also argue that the constant term F for odd dimensional surfaces can depend on marginal parameters.

A Comparative Study of Dimensional Tolerancing Capabilities and Microstructure Formation between Binder Jet Additively Manufactured Sand Molds and Olivine Green Sand Molds for Metalcasting of A356.0

The development of additive manufacturing in the 1980s led to a revolution in various metalcasting processes as early as the 1990s, including the use of polymer 3D printing for the manufacture of sand casting patterns. While additive manufacturing has entered many metalcasting processes, including both expendable and permanent mold processes, this paper specifically examines the sand casting process. ExOne’s development of binder jetting technology over the last 20 years has allowed designers in the sand casting field to directly 3D print sand molds for metalcasting. Use of binder jet additively manufactured sand molds allows for quicker turnaround time for testing prototypes, new gating designs, and for producing one-off parts. Additive manufacturing of sand molds for metalcasting may implement any of the same foundry sands as green sand processes, but uses a furan binder instead of the traditional mixture of bentonite clay and water. The use of a chemical binder had led to questions about the resulting dimensional capabilities and mechanical properties of the castings produced by the mold. This study investigated the dimensional tolerancing capabilities, surface finish, mechanical properties, microstructure, and defects present in identical castings made from both a traditional olivine green sand molding process and a binder jet additively manufactured silica sand molding process. It was concluded that binder jet additively manufactured sand molds are capable of either equal or better dimensional accuracy and tolerance capabilities than traditional olivine green sand molds. The olivine green sand parts had an average of approximately 1 μm better surface finish than the binder jet sand molds; however, it is likely that both the addition of sea coal to the green sand and the difference in final part color significantly affected this result. The mean hardness of the binder jet parts was 58.9 HBW with a standard deviation of 5.6 HBW, compared to the mean of the green sand parts of 47.7 HBW with a standard deviation of 7.2 HBW. The hardness findings were confirmed by the presence of a finer microstructure in the binder jet parts than the green sand parts. While both types of molds produced parts with defects, a greater variety of defects was evident in the olivine green sand molds. Porosity tended to move toward the surface of the olivine green sand parts, but was relatively evenly spread through the additively manufactured sand mold parts.

Spectroscopy and photoionization of C+ ions by the relativistic eigenchannel R-matrix method

SynopsisThe scattering matrices of C+ are calculated by using our relativistic eigenchannel R-matrix method. With the merits of the analytical continuation properties of the scattering matrices, lots of atomic dynamical data with accuracy are obtained. Much physical quantities are acquired by applying the multichannel quantum defect theory (MQDT) procedure. The present calculated results are in good agreement with the available experimental data, which has been shown by the newly proposed projected high dimensional quantum defect graph (symmetrized), namely JHANGZ plot.

Efficient and Effective Dimension Control in Automotive Applications

In automotive industry, the production line for assembling mechanical parts of vehicles must place and weld hundreds of components on the right positions of the platform. The accuracy of deploying the components has great impact on the quality and performance of the produced vehicle. To ensure the assembly accuracy, a critical task in the production process is the so-called dimension quality control. The current state of practice in automotive industries is mainly based on a manual process where experienced engineers use production data to identify accuracy problems and suggest solutions for corrections on fixture adjustment in the assembly line. It is an extremely inefficient process, which typically takes the engineers around ten days for one batch of vehicles and a year to achieve the required assembly accuracy for final production. In this article, we present an automatic technique for dimension control. We formulate the dimension control problem as a constraint programming problem and present a refinement method to prune the exploration space. Our technique can not only identify the wrongly deployed parts leading to dimensional defects, but also provide high-quality fixture adjustment decisions. Experiments conducted on industrial production data from BMW Brilliance Automotive demonstrate the significantly improved efficiency and effectiveness of dimension control in automotive industries with our approach.

Defects Engineering with Multiple Dimensions in Thermoelectric Materials.

Going through decades of development, great progress in both theory and experiment has been achieved in thermoelectric materials. With the growing enhancement in thermoelectric performance, it is also companied with the complexation of defects induced in the materials. 0D point defects, 1D linear defects, 2D planar defects, and 3D bulk defects have all been induced in thermoelectric materials for the optimization of thermoelectric performance. Considering the distinct characteristics of each type of defects, in-depth understanding of their roles in the thermoelectric transport process is of vital importance. In this paper, we classify and summarize the defect-related physical effects on both band structure and transport behavior of carriers and phonons when inducing different types of defects. Recent achievements in experimental characterization and theoretical simulation of defects are also summarized for accurately determining the type of defects serving for the design of thermoelectric materials. Finally, based on the current theoretical and experimental achievements, strategies engaged with multiple dimensional defects are reviewed for thermoelectric performance optimization.

Marginal deformations and defect anomalies

We deform a defect conformal field theory by an exactly marginal bulk operator and we consider the dependence on the marginal coupling of flat and spherical defect expectation values. For even dimensional spherical defects we find a logarithmic divergence which can be related to a $a$-type defect anomaly coefficient. This coefficient, for defect theories, is not invariant on the conformal manifold and its dependence on the coupling is controlled to all orders by the one-point function of the associated exactly marginal operator. For odd-dimensional defects, the flat and spherical case exhibit different qualitative behaviors, generalizing to arbitrary dimensions the line-circle anomaly of superconformal Wilson loops. Our results also imply a non-trivial coupling dependence for the recently proposed defect $C$-function. We finally apply our general result to a few specific examples, including superconformal Wilson loops and R\'enyi entropy.

Holographic fundamental matter in multilayered media

We describe a strongly coupled layered system in 3+1 dimensions by means of a top-down D-brane construction. Adjoint matter is encoded in a large-Nc stack of D3-branes, while fundamental matter is confined to (2 + 1)-dimensional defects introduced by a large-Nf stack of smeared D5-branes. To the anisotropic Lifshitz-like background geometry, we add a single flavor D7-brane treated in the probe limit. Such bulk setup corresponds to a partially quenched approximation for the dual field theory. The holographic model sheds light on the anisotropic physics induced by the layered structure, allowing one to disentangle flavor physics along and orthogonal to the layers as well as identifying distinct scaling laws for various dynamical quantities. We study the thermodynamics and the fluctuation spectrum with varying valence quark mass or baryon chemical potential. We also focus on the density wave propagation in both the hydrodynamic and collisionless regimes where analytic methods complement the numerics, while the latter provides the only resource to address the intermediate transition regime.

Improved Spring-Back Compensation Strategy through Location Optimized Part Position in the Dies

Further increasing requirements to the quality of car body components represent a huge challenge for the process planner. As the elastic energy is changing in each stamping operation, it is quite challenging to decide how to compensate which stamping operation. The belonging process definition is known as the compensation strategy. A key prerequisite of an appropriate compensation strategy is a proper location of the part in all stamping operations along the process chain. Proper means that the distance of the part to the die must be minimal to prevent any undefined shift of the part in the die and thus unwanted deformations when closing the dies. Both shifting and deformations would cause dimensional deviations and surface defects. Today different strategies are applied to meet these requirements at least approximately. Strategies, which are published in different papers yet, can only provide suboptimal results. Here a new compensation strategy is being presented, which fulfils the requirement to a proper part location not only in the trimming dies, which corresponds to the so-called Drawshell Strategy, but also in the restriking dies. An important advantage of the respective strategy is that it generally can be applied on all multistage car body stamping operations.

Using Axisymmetric Smoothed Finite Element Method (S-FEM) to Analyze Pressure Piping with Defect in ABAQUS

Pressure piping is the most productive way for large-volume compressed natural gas (CNG) transportation. In pipeline constructions, the thickness at the point where two pipes join together is often not consistent due to the mismatch in dimensions, and thus stress concentrations can often occur at the pipe joints, causing safety concerns. Therefore, it is important to accurately analyze the key influencing factors of dimensional mismatch defects, providing a theoretical basis for the preliminary design and post-repair of pipelines. This work uses the smoothed finite element method (S-FEM) that has been proven accurate in stress analysis compared with the traditional FEM. Since geometry and load of the pressure piping are axisymmetric, a novel axisymmetric S-FEM element is first developed, coded and integrated in ABAQUS using the User-defined Element Library (UEL). Intensive studies are then carried out to examine the effects of different levels of mismatch in the thicknesses of two joined pipes and the effects of the radius of the transitional fillet used to bridge the mismatches. It is found that the maximum hoop stress reduces as the radius of the transitional fillet increases. For the thinner section of the pipe, the maximum hoop stress is only affected by the thickness mismatch.

Design of one dimensional defect based photonic crystal by composited superconducting material for bio sensing applications

A novel biosensor based on 1-D defect photonic crystal is suggested to be consisting of alternate layers of SiO2 and Air. At the middle, there exists a cavity layer encapsulated with a composite layer of superconducting and dielectric materials. The blood samples are infiltrated in the cavity. The sensitivity is calculated at different parameters including filling factor of superconducting materials, the temperature, and the width of the cavity. Results indicate that the sensitivity decrease slightly as temperature increases and sensitivity increases as filling factor increases and thickness of cavity increases.

Electrical Insulation Tape Winding and Inspection System

An electrical insulation web winding and optical inspection system has been developed to provide semiautomatic material handling and machine vision inspection of composite electromagnet coil insulation materials. Composite electrical insulation for electromagnet conductor insulation typically comprises a nonconductive woven filler (typically S-Glass), nonconductive film (typically Kapton®), and fixating resin. Prior to the subject system, the stock woven filler and film used to assemble the composite structure were inspected manually for dimensional and foreign matter presence, which did not provide 100% inspection. The subject system features a web handling reel-to-reel transfer mechanism that includes an open-loop web positional alignment device to maintain the web centerline position. A machine vision system is used to optically inspect passing web materials for dimensional defects and foreign materials. This system is capable of inspection of single web woven filler material and/or colaminated woven filler material and nonconductive film. A detected defect automatically terminates web movement, generates an alarm, and records images of the defects on a media storage device. Prototype material inspections performed by the subject machine on approximately 21 567 m (70 759 ft) of material detected 174 pieces of debris.