Shape Modification Research Articles

Multiple treatments with strategic substitutes

We develop an empirical framework to identify and estimate the effects of treatments on outcomes of interest when the treatments are the result of strategic interaction (e.g., bargaining, oligopolistic entry, peer effects). We consider a model where agents play a discrete game of complete information and strategic substitutability, whose equilibrium actions (i.e., binary treatments) determine a post-game outcome in a nonseparable model with endogeneity. Due to the simultaneity in the first stage, the model as a whole is incomplete and the selection process fails to exhibit the conventional monotonicity. Without imposing parametric restrictions or large support assumptions, this poses challenges in recovering treatment parameters. To address these challenges, we establish a monotonic pattern of the equilibria in the first-stage game in terms of the number of treatments selected. Based on this finding, we derive bounds on the average treatment effects (ATE’s) under nonparametric shape restrictions and the existence of excluded exogenous variables. We show that the instrument variation that compensates strategic substitution helps solve the multiple equilibria problem. We apply our method to data on airlines and air pollution in cities in the U.S. We find that (i) the causal effect of each airline on pollution is positive, and (ii) the effect is increasing in the number of firms but at a decreasing rate.

Modification of conventional peak shapes to accurately represent spectral asymmetry: High-Resolution X-ray photoelectron spectra of [C4C1Pyrr][NTf2] and [C8C1Im][NTf2] ionic liquids

X-ray photoelectron spectroscopy (XPS) is one of the most widely used techniques for surface characterization. Analysis of XPS data is challenging and requires the analyst to fit the data with synthetic line shapes to reach physically meaningful interpretations. Experimental spectral envelopes, however, are complex and display asymmetric features that are often ignored or attributed to additional chemical components. The high-resolution XPS spectra of [C4C1Pyrr][NTf2] and [C8C1Im][NTf2] all exhibit a degree of asymmetry which is systematically observed at the higher binding energy side of photoemission envelopes. We present the development of a refined fitting procedure for XPS spectra of these ionic liquid-based systems which include (a) Shirley background offset necessary to account for the insulator-like region and (b) spectral asymmetry in C 1s and N 1s regions. Further, Shirley and trapezoid components are applied to compensate for inelastic scattering taking place during electron transitions as high as 7.8 eV above the start of the fitting region in C 1s high-resolution spectrum. To demonstrate the fitness of this model, we present an analysis of a 2:1 mixture of [C4C1Pyrr][NTf2]: [C8C1Im][NTf2].

Fast 3D Liver Segmentation Using a Trained Deep Chan-Vese Model

This paper introduces an approach for 3D organ segmentation that generalizes in multiple ways the Chan-Vese level set method. Chan-Vese is a segmentation method that simultaneously evolves a level set while fitting locally constant intensity models for the interior and exterior regions. First, its simple length-based regularization is replaced with a learned shape model based on a Fully Convolutional Network (FCN). We show how to train the FCN and introduce data augmentation methods to avoid overfitting. Second, two 3D variants of the method are introduced, one based on a 3D U-Net that makes global shape modifications and one based on a 3D FCN that makes local refinements. These two variants are integrated in a full 3D organ segmentation approach that is capable and efficient in dealing with the large size of the 3D volumes with minimal overfitting. Experiments on liver segmentation on a standard benchmark dataset show that the method obtains 3D segmentation results competitive with the state of the art while being very fast and having a small number of trainable parameters.

An Evolutional Topology Optimization of Electric Machines for Local Shape Modification and Visualization of Sensitivity Distribution Based on CMA‐ES

This paper presents an evolutional topology optimization of electric machines, which works like gradient‐based local search methods, based on the covariance matrix adaptation evolution strategy (CMA‐ES). The present method enables to improve the performance of initial machine shapes without computing the deviation of the objectives. Moreover, for the resultant shapes obtained by the present topology optimization method, this paper also presents a sensitivity analysis method based on the normal distribution which is used to seek for solutions in CMA‐ES. Using the present sensitivity analysis method, important parts which contribute to improve a machine characteristic can be visualized. The two present methods are applied to the optimization problem of a synchronous reluctance motor. It is shown that initial rotor shapes defined by designers can effectively be modified using the present optimization method. Moreover, it is also shown that the sensitivity distributions with respect to some machine characteristics are visualized by the present method. In addition, each machine characteristic is respectively improved by modifying the machine shape according to the respective sensitivities. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Improving the efficiency of FRP-Confined square concrete column by rounding the sharp edges and circularizing the flat sides

This study is carried out to assess a new shape modification technique for the square columns to enhance the effectiveness of the fibre reinforced polymer (FRP) confinement with less enlargement in the cross-sectional size. The technique was implemented by rounding the sharp edges and attaching four precast concrete pieces with a segmental circular shape. A total of 21 concrete specimens were prepared to be tested under uniaxial compressive loading. In addition to the proposed technique, circularization that was suggested by the previous studies and confinement of the square section with rounded corners were implemented for comparison purposes. Furthermore, different confinement scenarios such as full and partial wrapping were conducted. All the specimens were confined with a single layer of the glass FRP (GFRP). The suggested shape modification technique succeeded to enhance the ultimate axial strength and strain of the concrete specimen with less increase in the cross-sectional size. Moreover, the actual rupture strain of the GFRP jacket significantly increased compared with the previous shape modification technique. A theoretical investigation is conducted to validate the experimental results, and good agreement was observed between the test results and the predicted results.

Silver Nanoparticle Labels for Electrochemical Detection of Bioassays

Electrochemistry plays a major role in immunosensor development because of its higher sensitivity, simplicity, portability, and rapidity compared to more common enzymatic, fluorescent and radioactive labelling methods. Silver nanoparticles (AgNPs) have been identified as potential electrochemical labels for such immunoassays. Characterizing the composition, size, shape, and surface modifications of the AgNP is important to achieve expected analytical performance of the bio assay. Here we are interested in studying the effect of nanoparticle shape towards the electrochemical detection of a metallo-immunoassay using Au-Ag galvanic exchange (GE) reaction followed by anodic stripping voltammetry. We observe that during GE between electrogenerated Au3+ and the Ag labels, a thin shell of Au forms on the surface of the NP and prevent further exchange. This shell is more porous when GE proceeds on silver nanocubes (AgNCs) compared to spherical silver nanoparticles (sAgNPs), and therefore, more exchange occurs when using AgNCs. More interestingly, optimizing the ratio of the two types of AgNP labels, we could able to decrease the LOD of a biological assay designed to detect a heart failure biomarker (NT-proBNP) without compromising the dynamic range compared to using either of the two labels independently. This made it possible to achieve the clinically relevant range for NT-proBNP analysis used by physicians for heart failure risk stratification.

In vivo targeting capacities of different nanoparticles to prostate tissues based on a mouse model of chronic bacterial prostatitis.

Chronic bacterial prostatitis usually occurs in men and seriously affects the quality of life of patients. The efficacy of chronic bacterial prostatitis treatment is limited by the difficulty for free drugs (e.g., antibiotics) to penetrate the prostate epithelium and target inflammatory tissues. The advent of nanotechnology offers the possibility to address this issue, such as the development of targeted nanoparticle delivery strategies that may overcome these important limitations. The physicochemical properties of nanoparticles, such as particle size, shape and surface modification ligands, determine their targeting effectiveness. In this study, nanoparticles with different physicochemical properties were prepared to explore and confirm their targeting capacities to inflammatory prostate tissues of chronic bacterial prostatitis, focusing on the effects of size and different modification ligands on the targeting performance. In vivo and ex vivo imaging results verified that folic acid-modified nanoparticles with a particle size of 180–190 nm via tail intravenous injection had the optimal targeting efficiency to prostate tissues. Our results provide an experimental basis and reference value for targeted therapy of prostate-related diseases with nanotechnology in the future.

Comparison of aerodynamic coefficients of tall tapered triangular building modified with golden spiral in plan

Better designs are mostly better geometries. Geometric shape modifications in buildings can greatly improve the aerodynamic performance as well as add to the aesthetics of the buildings. The present study involves a comparison of aerodynamic coefficients of a triangular building with slight changes in the plan. Force and pressure coefficients are compared among the buildings with tapering regular triangle in plan, tapering triangular plan modified with rounded corners, and tapering triangular plan modified with Golden spiral geometry in all possible wind attack directions. Numerical method was used with the help of ANSYS CFX and the k-epsilon turbulence model was used in this simulation. Pressure coefficients are compared locally and the problem of huge suction due to rounded corner modification can be reduced to a considerable extent by the Golden spiral geometry. The Drag coefficients are compared and the golden spiral has the least values in all possible directions of wind attack.

Hadronic resonances in heavy-ion collisions at NICA energies and their reconstruction in the MPD setup

The short-lived hadronic resonances are used to study the properties of the hot and dense medium produced in the relativistic heavy-ion collisions. The resonance masses and widths, yields and mean transverse momenta measured in the hadronic decay channels probe different stages of the nuclear collisions and are most sensitive to strangeness production, collective flow and hadronization mechanisms as well as to lifetime and density of the hadronic phase. In this contribution, we discuss line shape modifications for short-lived resonances and their consequences for the yields and shapes of the production spectra measured in heavy-ion collisions at intermediate collision energies, [Formula: see text][Formula: see text]GeV. Capabilities of the MPD facility at NICA to reconstruct resonances in Bi+Bi collisions at [Formula: see text][Formula: see text]GeV are presented and discussed.

Differences in erythrocytes size and shape in prediabetes and diabetes assessed by two microscopy techniques and its association with dietary patterns. Pilot study.

Hemorheology and microcirculation alterations are caused by erythrocyte size and shape (ESS) modifications. People´s diets can alter erythrocyte functions and membrane fluidity by changing cell membrane components. The aim was to identify differences in ESS obtained by scanning electron (SEM) and atomic force microscopy (AFM) in people with prediabetes and type 2 diabetes (T2DM) and assess their relationship with dietary patterns. The study population included 31 participants (14 healthy, 11 with prediabetes, and 6 with T2DM). Dietary intake was assessed by a food frequency questionnaire, and dietary patterns were obtained using principal component analysis. ESS (diameter, height, axial ratio, thickness, and concave depth) were obtained by SEM and AFM. Differences in ESS between groups were observed with SEM (height) and AFM (height, axial ratio, and concave depth). T2DM presented smaller erythrocytes, more elongated and more altered forms. Two dietary patterns were identified: (1) Unhealthy: more refined cereals, high-fat dairy, fast food, sugary beverages, and fewer fruits, fish, seafood, low-fat dairy, and water. (2) Prudent: higher consumption of refined cereals, vegetables, poultry, low-fat dairy and nuts, and lower tortillas, eggs, high-fat dairy, and legumes. Tertile 3 of the Unhealthy dietary pattern had 80% of healthy participants. A difference in diameter and height (0.44 and 0.32 μm, respectively) obtained by SEM was observed when comparing tertile 2 (smaller erythrocytes) versus tertile 3 in the Unhealthy dietary pattern. SEM and AFM are excellent tools to assess ESS. Unhealthy dietary patterns might be associated with altered ESS. HIGHLIGHTS: SEM and AFM are excellent tools to assess erythrocyte size and shape modifications. Two dietary patterns were identified: healthy and prudent. Smaller erythrocytes were observed in the second tertile of the unhealthy pattern.

Hull Form Optimization of Fishing Vessels by Adoption of Stern Wedge and Bilge Keel

The most recent ships incorporate a number of significant design enhancements to improve the vessel’s seaworthiness. Bulbous bow, bilge keel, stern wedge, stern tunnel, spray rails, and others are examples. A stern wedge is a small modification of the buttock lines aft of station 19 1/2. The use of this hull design feature on small high-speed planning craft for the purpose of improved powering performance is an accepted naval architectural practice. However, its use on fishing vessels is uncommon. A bilge keel is a marine gear that reduces the tendency for a ship to roll. Hull shape modifications such as bilge keel can potentially increase safety by reducing roll motions. These enhancements have not been adopted or evaluated on fishing vessels, despite the fact that they have been employed on seagoing ships. The installation of bilge keels on fishing vessels was found to have a significant influence on the roll motion of the vessels, boosting their safety and efficiency. When compared to normal trawlers, the installation of bilge keels increased roll period by at least 40% and reduced roll amplitude by 16%.

Risk-averse design of tall buildings for uncertain wind conditions

Reducing the intensity of wind excitation via aerodynamic shape modification is a major strategy to mitigate the reaction forces on supertall buildings, reduce construction and maintenance costs, and improve the comfort of future occupants. To this end, computational fluid dynamics (CFD) combined with state-of-the-art stochastic optimization algorithms is more promising than the trial and error approach adopted by the industry. The present study proposes and investigates a novel approach to risk-averse shape optimization of tall building structures that incorporates site-specific uncertainties in the wind velocity, terrain conditions, and wind flow direction. A body-fitted finite element approximation is used for the CFD with different wind directions incorporated by re-meshing the fluid domain. The bending moment at the base of the building is minimized, resulting in a building with reduced cost, material, and hence, a reduced carbon footprint. Both risk-neutral (mean value) and risk-averse optimization of the twist and tapering of a representative building are presented under uncertain inflow wind conditions that have been calibrated to fit freely-available site-specific data from Basel, Switzerland. The risk-averse strategy uses the conditional value-at-risk to optimize for the low-probability high-consequence events appearing in the worst 10% of loading conditions. Adaptive sampling is used to accelerate the gradient-based stochastic optimization pipeline. The adaptive method is easy to implement and particularly helpful for compute-intensive simulations because the number of gradient samples grows only as the optimal design algorithm converges. The performance of the final risk-averse building geometry is exceptionally favorable when compared to the risk-neutral optimized geometry, thus, demonstrating the effectiveness of the risk-averse design approach in computational wind engineering.

Inference in a Class of Optimization Problems: Confidence Regions and Finite Sample Bounds on Errors in Coverage Probabilities

This article describes three methods for carrying out nonasymptotic inference on partially identified parameters that are solutions to a class of optimization problems. Applications in which the optimization problems arise include estimation under shape restrictions, estimation of models of discrete games, and estimation based on grouped data. The partially identified parameters are characterized by restrictions that involve the unknown population means of observed random variables in addition to structural parameters. Inference consists of finding confidence intervals for functions of the structural parameters. Our theory provides finite-sample lower bounds on the coverage probabilities of the confidence intervals under three sets of assumptions of increasing strength. With the moderate sample sizes found in most economics applications, the bounds become tighter as the assumptions strengthen. We discuss estimation of population parameters that the bounds depend on and contrast our methods with alternative methods for obtaining confidence intervals for partially identified parameters. The results of Monte Carlo experiments and empirical examples illustrate the usefulness of our method.

Optically tunable metal-dielectric diffractive structures

Hybrid metal-polymer micropillar arrays are elaborated by solvent-assisted embossing techniques and subsequent gold deposition. The polymer is poly(methyl methacrylate) (PMMA) grafted with Disperse Red 1 (DR1) azobenzene derivatives. This photochromic material exhibits spectacular photomechanical properties. Under off-normal $p$-polarized illumination in the absorption band of the DR1, the metal-polymer hybrid micropillars bend in a direction determined by the light polarization. The deformation remains stable when the light excitation is turned off. The optically driven modification of the pillar shape allows us to tune the optical properties of the pillar arrays. Very large intensity changes are measured in the diffraction spectra at zero order (specular reflection), first order, and second order, with almost on and off switching of the diffraction efficiency. The photoinduced bending of the micropillars can be fully reversed by switching the linear light polarization to the orthogonal $s$-polarization state. This allows us to restore the initial optical properties of the pillar array. The polarization-controlled reversibility of the pillar deformation suggests a complex photoinduced deformation mechanism involving stress and stress release assisted by the change in the viscoelastic properties of the polymer under illumination in the absorption band of the DR1 chromophore.

Shape-constrained estimation in functional regression with Bernstein polynomials

Shape restrictions on functional regression coefficients such as non-negativity, monotonicity, convexity or concavity are often available in the form of a prior knowledge or required to maintain a structural consistency in functional regression models. A new estimation method is developed in shape-constrained functional regression models using Bernstein polynomials. Specifically, estimation approaches from nonparametric regression are extended to functional data, properly accounting for shape-constraints in a large class of functional regression models such as scalar-on-function regression (SOFR), function-on-scalar regression (FOSR), and function-on-function regression (FOFR). Theoretical results establish the asymptotic consistency of the constrained estimators under standard regularity conditions. A projection based approach provides point-wise asymptotic confidence intervals for the constrained estimators. A bootstrap test is developed facilitating testing of the shape constraints. Numerical analysis using simulations illustrates improvement in efficiency of the estimators from the use of the proposed method under shape constraints. Two applications include i) modeling a drug effect in a mental health study via shape-restricted FOSR and ii) modeling subject-specific quantile functions of accelerometry-estimated physical activity in the Baltimore Longitudinal Study of Aging (BLSA) as outcomes via shape-restricted quantile-function on scalar regression (QFOSR). R software implementation and illustration of the proposed estimation method and the test is provided.

Interval optimization design of a submersible surface ship form considering the uncertainty of surrogate model

The integrated design of the ship form is a key issue in the design of submersible surface ship (SSS). In the simulation-based design (SBD) framework, lack of sample data leads to uncertainty in the surrogate model. In this paper, first, a hull cross-section shape modification technology, the self-fusion method, was used to change the ship form, and a fourth-order response surface model was introduced to establish surrogate model of hydrodynamic performance. Second, total resistance in the surface condition and one at a diving depth of 0.48 m were selected as the optimization targets. Third, an automated computing platform was developed to integrate the modules to improve computing efficiency and accuracy. Finally, to explore the adaptability of the ship form scheme, the interval optimization analysis method was introduced into uncertainty optimization. Among them, the interval variable was the surrogate model accuracy, and the targets were the minimum median and the minimum radius of the weighted resistance of cross-domain cases. A two-layer nested optimization system was chosen. Results show that resistance of the optimal SSS was reduced. The interval optimization results were compared with the deterministic optimization results, and the feasibility of hull shape interval optimization was verified.

Wind Pressure Distribution on the Façade of Stand-Alone Atypically Shaped High-Rise Building Determined by CFD Simulation and Wind Tunnel Tests

The investigation of wind pressure distribution on a façade of an atypically shaped 162 m tall building is discussed in this paper. The horizontal cross-section was changed with the height of the structure (the square in the bottom part and the polygon in the top). The surface of the structure was smooth. A structural system was created using a combination of the tube structural system and exoskeleton structure. The building was stand-alone, located in urban terrain. In this case, the information in standards were not sufficient for its design. Therefore, other available tools had to be used for the determination of required input parameters (mean external pressure coefficients). At first, wind tunnel tests (WT) were performed on a reduced-scale model (1:300). Then, the obtained results were compared with data from a computational fluid dynamics (CFD) simulation. The accuracy of the simulation was evaluated by the method of three metrics. Short descriptions of the reduced-scale model, boundary layer wind tunnel, used measuring devices, and the methodology of tests are mentioned. The aim of this research was to identify the influence of the shape modification on the values of mean external pressure coefficients (in the comparison with the original shape, which was the cuboid). In the case of the cuboid, good agreement between the values determined by the CFD and the values from Eurocode was achieved. Larger discrepancies occurred on the roof. The modification of the total shape of the structure from the cuboid to atypical structure had the positive effect on the mean values of external pressure coefficients cpe. These values were smaller (at some levels significantly). Mainly, this effect was noticeable on the leeward side. For the wind directions 0° and 180°, the changes of the values were relatively large. For the other two wind directions (45° and 67.5°), the values on the windward sides were similar. The large advantage of this atypical structure is that the negative pressures on side walls and leeward side are smaller in the comparison with the cuboid. This is very useful for the fixing of façade components, where the values of negative pressures are larger than the positive pressures on the cladding in the larger heights.

Shape-supervised Dimension Reduction: Extracting Geometry and Physics Associated Features with Geometric Moments

In shape optimisation problems, subspaces generated with conventional dimension reduction approaches often fail to extract the intrinsic geometric features of the shape that would allow the exploration of diverse but valid candidate solutions. More importantly, they also lack incorporation of any notion of physics against which shape is optimised. This work proposes a shape-supervised dimension reduction approach. To simultaneously tackle these deficiencies, it uses higher-level information about the shape in terms of its geometric integral properties, such as geometric moments and their invariants. Their usage is based on the fact that moments of a shape are intrinsic features of its geometry, and they provide a unifying medium between geometry and physics. To enrich the subspace with latent features associated with shape’s geometrical features and physics, we also evaluate a set of composite geometric moments, using the divergence theorem, for appropriate shape decomposition. These moments are combined with the shape modification function to form a Shape Signature Vector (SSV) uniquely representing a shape. Afterwards, the generalised Karhunen–Loève expansion is applied to SSV, embedded in a generalised (disjoint) Hilbert space, which results in a basis of the shape-supervised subspace retaining the highest geometric and physical variance. Validation experiments are performed for a three-dimensional wing and a ship hull model. Our results demonstrate a significant reduction of the original design space’s dimensionality for both test cases while maintaining a high representation capacity and a large percentage of valid geometries that facilitate fast convergence to the optimal solution. The code developed to implement this approach is available at https://github.com/shahrozkhan66/SSDR.git . • Shape signature vector (SSV) comprises a shape modification vector and geometric moments (GM). • Karhunen–Loève expansion of SSV results in a shape-supervised space (SSS). • GM can induce the notion of physics resulting in a physics-informed SSS. • SSS retains higher geometric variance with fewer latent variables. • SSS is robust and compact, providing accelerated optimisation convergence.

Impact of runner crown shape modifications on the onset of the precessing vortex core

In this experimental study, a passive flow control concept is provided to extend the stable part load operation regime by shifting the rise of the precessing vortex core (PVC), also known as vortex rope, toward lower mass flows respectively deeper part loads. A parametrized runner crown design working as a passive flow control device is derived. This control device aims for shifting the bifurcation point of the PVC to lower flow rates. To determine the most influential design parameters and derive an optimized runner crown design, a design of experiments (DoE) approach is used. This DoE approach is based on data obtained from differential pressure sensors inside the draft tube wall of a generic hydro turbine test rig using air as working fluid. By means of stochastic modeling, the growth rate of the PVC mode is derived from the statistics of the measured pressure signals. The growth rate is used to estimate the bifurcation point of the PVC characterized by a certain normalized flow rate. It is shown that the stable part load operation regime is extended by up to 25% due to the passive impact of the modified runner crown. Moreover, the operational range featuring considerable PVC-induced pressure oscillations is diminished and the pressure recovery of the draft tube is improved compared to the baseline case.

Improved PWM Methods to Reduce the Common Mode Voltage of the Five-Phase Open-Winding Drive Topology

With the phase angle and shape modifications for carriers, two improved carrier-based pulse width modulation (CPWM) methods with common-mode voltage (CMV) suppression effects for the five-phase open-winding drive topologies are introduced. Theoretical analysis reveals that, by employing reversed triangular carriers for two inverters under the carrier-reversed PWM (CRPWM), CMV contributions of two bridge legs belonging to the same phase can be cancelled, realizing the zero CMV effect. By dynamically employing positive and negative sawtooth carriers for all bridge legs under the carrier-switching PWM (CSPWM), the CMV contribution of each inverter can be reduced, decreasing both the amplitude and step frequency of the CMV. Current qualities and dead-time effects on CMV under the above PWM methods are analyzed. Moreover, performances of two PWM methods are verified by experiments implemented on a five-phase open-winding topology with the induction motor load.