Types Of Cores Research Articles

Investigation of effect of perforations in honeycomb sandwich structure for enhanced blast load mitigation

Sandwich structure is one of the blasts protecting and energy absorbing materials with different types of light weight cores. This article aimed at investigating blast response of hexagonal honeycomb sandwich structure having perforations along the cell height of core over conventional honeycomb cores. The study discussed the mechanics of deformation behavior of perforated sandwich structure to improve the energy absorption characteristics of the bare honeycomb core sandwich structure. Detailed numerical analysis is conducted to accurately produce the deformation process with finite element analysis using explicit software LS-DYNA®. Blast load resulting from 1 kg TNT on the sandwich structure is applied using Conventional Weapons Effects Program (ConWep) function available in LS-DYNA. Several different parameters consisting of varying sizes of perforation by changing d/l ratio, shape, number of perforations and different facesheet and backsheet thicknesses, and different scaled distances are investigated in detail. The results indicated that both size and shape and number of perforations have significant influence on reduction of blast impulse. The variation of facesheet and backsheet thicknesses without changing the overall thickness of the structure also has evident effect in blast resistance capability of perforated honeycomb sandwich structure. The blast mitigation and energy absorption capacity of honeycomb core sandwich structure can be improved with the provision of perforations and optimizing the arrangement of holes. The perforated honeycomb core is further investigated based on analytical formulation developed using single degree of freedom (SDOF) system analysis approach. Optimization study is done further to get the best configuration based on different design variable limits.

Algorithmic definitions of street network centrality sub-shapes: The case of superblocks

The shape and distribution of the most integrated streets, collectively called the integration core, is critical to the characterization of local and global street network types in the space syntax literature. The description of the shape, position, and distribution of integration cores relative to the underlying street networks, however, has remained largely intuitive. We propose analytic and algorithmic definitions of integration core types. We then study empirical and experimental superblock designs with rectangular boundaries, as a particular kind of urban spatial syntax. The analysis leads to a clear understanding of the different ways in which the local street network, internal to the superblock, is structured and interfaced with the perimeter. When used as part of an automated sorting and query process applied to a universe of experimentally generated designs, our definitions and algorithms provide new insights about the interplay between the local generators of street network differentiation and the emergent syntactic structures of the superblock as a whole.

Natural variation meets synthetic biology: Promiscuous trichome-expressed acyltransferases from Nicotiana.

Acylsugars are defensive, trichome-synthesized sugar esters produced in plants across the Solanaceae (nightshade) family. Although assembled from simple metabolites and synthesized by a relatively short core biosynthetic pathway, tremendous within- and across-species acylsugar structural variation is documented across the family. To advance our understanding of the diversity and the synthesis of acylsugars within the Nicotiana genus, trichome extracts were profiled across the genus coupled with transcriptomics-guided enzyme discovery and in vivo and in vitro analysis. Differences in the types of sugar cores, numbers of acylations, and acyl chain structures contributed to over 300 unique annotated acylsugars throughout Nicotiana. Placement of acyl chain length into a phylogenetic context revealed that an unsaturated acyl chain type was detected in a few closely related species. A comparative transcriptomics approach identified trichome-enriched Nicotiana acuminata acylsugar biosynthetic candidate enzymes. More than 25 acylsugar variants could be produced in a single enzyme assay with four N. acuminata acylsugar acyltransferases (NacASAT1-4) together with structurally diverse acyl-CoAs and sucrose. Liquid chromatography coupled with mass spectrometry screening of in vitro products revealed the ability of these enzymes to make acylsugars not present in Nicotiana plant extracts. In vitro acylsugar production also provided insights into acyltransferase acyl donor promiscuity and acyl acceptor specificity as well as regiospecificity of some ASATs. This study suggests that promiscuous Nicotiana acyltransferases can be used as synthetic biology tools to produce novel and potentially useful metabolites.

3D printed continuous carbon fiber reinforced thermoplastic composite sandwich structure with corrugated core for high stiffness/load capability

In this work, sandwich structure with trapezoidal corrugated cores was 3D printed by fused deposition modeling (FDM) method applying to short and continuous carbon fiber (CF) reinforced nylon filament. The split core of the sandwich structure was designed and fabricated. To investigate the bending characteristics for the sandwich structures, the three-point bending (3 PB) tests were conducted for the different core types. Consequently, it was found that the mechanical behavior and failure modes were significantly changed by core materials and the split number of cores. Also, the dramatic improvements in the mechanical performances (4.1 times higher specific flexural stiffness, 2.6 times larger specific load capability and 8.6 times larger energy absorption capability than those of PET foam core sandwich structure) could be obtained in corrugated sandwich structure which was 3D printed using continuous carbon fiber. This result comes from the precise fiber alignment of continuous carbon fiber along the core, which can be realized only by continuous CF 3D printing technology.

Quantification of Spatial Association between Commercial and Residential Spaces in Beijing Using Urban Big Data

Commercial and residential spaces are two core types of geographical objects in urban areas. However, these two types of spaces are not independent of each other. Spatial associations exist between them, and a thorough understanding of this spatial association is of great significance for improving the efficiency of urban spatial allocation and realizing scientific spatial planning and governance. Thus, in this paper, the spatial association between commercial and residential spaces in Beijing is quantified with GIS spatial analysis of the average nearest neighbor distance, kernel density, spatial correlation, and honeycomb grid analysis. Point-of-interest (POI) big data of the commercial and residential spaces is used in the quantification since this big data represents a comprehensive sampling of these two spaces. The results show that the spatial distributions of commercial and residential spaces are highly correlated, maintaining a relatively close consumption spatial association. However, the degrees of association between different commercial formats and residential spaces vary, presenting the spatial association characteristics of “integration of daily consumption and separation of nondaily consumption”. The commercial formats of catering services, recreation and leisure services, specialty stores, and agricultural markets are strongly associated with the residential spaces. However, the development of frequently used commercial formats of daily consumption such as living services, convenience stores, and supermarkets appears to lag behind the development of residential spaces. In addition, large-scale comprehensive and specialized commercial formats such as shopping malls, home appliances and electronics stores, and home building materials markets are lagging behind the residential spaces over a wide range. This paper is expected to provide development suggestions for the transformation of urban commercial and residential spaces and the construction of “people-oriented” smart cities.

Regulation of 2D DNA Nanostructures by the Coupling of Intrinsic Tile Curvature and Arm Twist.

The overwinding and underwinding of DNA duplexes between junctions have been used in designing left- and right-handed DNA origami nanostructures, respectively. For DNA tubes obtained from self-assembled tiles, only a theoretical approach of the intrinsic curvature of the tiles has been previously used to explain their formation. Details regarding the quantitative and structural descriptions of the tile's intrinsic curvature in DNA nanostructures have so far never been addressed. In this work, we designed three types of tile cores built around a circular scaffold using three- and four-branched junctions. Joining the tile cores with arms having two kinds of inter-tile distances, an odd and an even number of DNA half-turns, tended to form planar 2D lattices and tubes, respectively. Streptavidin bound to biotin was used as a labeling technique to characterize the inside and outside surfaces of the tubes and thereby the tile conformation of dihedrals with addressable faces. DNA tubes with either right- or left-handed chirality were obtained by the coupling of the intrinsic curvature of the tiles with the arm twist. We were able to assign the chiral indices (n,m) to a tube with its structure resolved by AFM at the single-tile level and therefore to estimate the global curvature of the tube (or its component tile) using a regular polygon model that approximated its transverse section. A deeper understanding of the integrated actions of different types of twisting forces on DNA tubes will be extremely helpful in engineering more elaborate DNA nanostructures in the future.

Obstetric gaslighting and the denial of mothers’ realities

Gaslighting is a type of abuse aimed at making victims question their sanity as well as the veracity and legitimacy of their own perspectives and feelings. In this article, we show how gaslighting can operate as a key, yet underexamined strategy of obstetric violence, or the institutional and interpersonal violation of women's rights during pregnancy, childbirth, and postpartum. We draw on forty-six in-depth, semi-structured interviews with mothers who experienced a traumatic childbirth to examine how obstetric providers gaslight mothers before, during and after childbirth when they deny – and thereby destabilize – mothers' realities. We identify and examine four core types of denials: denials of 1) mothers' humanity, 2) mothers' knowledge as valid, 3) mothers' judgements as rational and 4) mothers' feelings as legitimate. All four denials work to render mothers noncredible and their claims illegible within clinical encounters. In explicitly naming, theorizing, and examining obstetric gaslighting, our aims are threefold: 1) to uncover and theorize an underexamined mechanism of obstetric violence through a sociological lens, 2) to offer a typology of obstetric gaslighting's manifestations to aid scholars and practitioners in recognizing when obstetric gaslighting is occurring and 3) to advance a growing research program on gaslighting in medicine.

High-velocity impact resistance of doubly curved sandwich panels with re-entrant honeycomb and foam core

This work describes the high-velocity impact behavior of doubly curved sandwich panels. The sandwich panels are manufactured using carbon/fiber epoxy composite face sheets, polyurethane foam core and 3D-printed PLA plastic cellular auxetic (re-entrant) honeycombs. High-velocity impact tests are carried out by using a single-stage air gas gun test machine. A spherical steel projectile with the radius of 5 mm is impacted to the center of the specimens with the speed of 100 m/s. The experimental data are used to validate explicit finite element models of the doubly curved structures. An analytical model is also developed for the ballistic limit of the flat and doubly curved sandwich panels, and the analytical results are compared to those obtained from the numerical ones. Parametric numerical analyses of the high-speed impact of the curved sandwich panels are then carried out considering various radii of curvature of the panels. The results show that the energy absorption is increased as the curvature is decreased for the panels with both foam and re-entrant core. In addition, the core configuration provides a key role in the impact resistance of the sandwich panels. Re-entrant models show an increase in specific energy absorption (SEA) compared to the foam core types.

ERASE: Energy Efficient Task Mapping and Resource Management for Work Stealing Runtimes

Parallel applications often rely on work stealing schedulers in combination with fine-grained tasking to achieve high performance and scalability. However, reducing the total energy consumption in the context of work stealing runtimes is still challenging, particularly when using asymmetric architectures with different types of CPU cores. A common approach for energy savings involves dynamic voltage and frequency scaling (DVFS) wherein throttling is carried out based on factors like task parallelism, stealing relations, and task criticality. This article makes the following observations: (i) leveraging DVFS on a per-task basis is impractical when using fine-grained tasking and in environments with cluster/chip-level DVFS; (ii) task moldability, wherein a single task can execute on multiple threads/cores via work-sharing, can help to reduce energy consumption; and (iii) mismatch between tasks and assigned resources (i.e., core type and number of cores) can detrimentally impact energy consumption. In this article, we propose EneRgy Aware SchedulEr (ERASE), an intra-application task scheduler on top of work stealing runtimes that aims to reduce the total energy consumption of parallel applications. It achieves energy savings by guiding scheduling decisions based on per-task energy consumption predictions of different resource configurations. In addition, ERASE is capable of adapting to both given static frequency settings and externally controlled DVFS. Overall, ERASE achieves up to 31% energy savings and improves performance by 44% on average, compared to the state-of-the-art DVFS-based schedulers.

Physical Modification of Products Made of Soft Magnetic Materials under Texturing Effects

The results of improving physical properties of different types of magnetic cores made of soft magnetic crystalline and amorphous alloys based on siliceous iron are presented. Methods and modes of controlling orientational, dimensional and dynamic parameters of magnetic domains by means of a uniaxially textured complex of thermomagnetic, locally laser, and plane deformation effects have been developed. As a result, in electrical magnetic cores made of anisotropic iron-silicon steels of 3407, 3408 grades a decrease in eddy-current magnetic losses by 25–35% and an increase in magnetic permeability by 1.5–2 times have been achieved.

Comprehensive Analysis of Nanocrystalline Ribbon Cores in High-Power-Density Wireless Power Transfer Pads for Electric Vehicles

The nanocrystalline alloys are gradually used as shielding materials in wireless power transfer (WPT) systems with the development of high power density. In this article, the system properties of WPT using ferrite and four types of nanocrystalline cores are simulated by 3-D finite element analysis (FEA). Based on this, a novel shielding pad composed of nanocrystalline alloy and ferrite is designed to improve the WPT system properties. The WPT systems are preliminarily compared with 3-D FEA when the different nanocrystalline alloys are used in the novel shielding pad. The experimental WPT system for 85 kHz and 1.5 kW with a 24 cm air gap between the primary and secondary coils is built to validate the simulation. The results show that significantly greater shielding can be realized for the novel pad at the price of a slight decrease of transmission efficiency than conventional ferrite core.

Conditional Generative Adversarial Networks for 2D core grayscale image reconstruction from pore parameters

Digital cores are of great significance for reservoir structure simulation, oil and gas exploration and development. Most existing digital core reconstruction methods only generate binary cores with complicated implementation processes, among other problems. To address these problems, this study proposed a combination of core pore parameters and conditional generative adversarial network (CGAN) to realize the 2D reconstruction of core grayscale images from only pore parameters (namely, text-to-image synthesis). The current text-to-image synthesis approaches still have many difficulties in generating fine images, but the technologies of image-to-image generation have improved drastically in recent years. Therefore, the proposed method involves two stages to avoid the difficulty of directly generating core grayscale images from pore parameters. In stage I, we preprocessed core sample images to obtain binary-grayscale image pairs, and then used the CGAN to learn the mapping from core binary images to real sample images. At the same time, the pores in the binary images were segmented and extracted to construct the pore component library. In stage II, on the basis of the given pore parameters, the corresponding pores were randomly extracted from the pore component library to generate binary images, and then the generated binary images were used as input for the trained CGAN model to produce core grayscale images. The experimental results showed that the core grayscale images reconstructed by the proposed method meet the pore conditions and reflect the basic characteristics of real cores. • The reconstruction by our method is based on pore parameters rather than images. • The reconstruction is decomposed into two stages: “pore parameters to binary core” and “binary core to grayscale core”. • The method has a general validity and can reconstruct different types of cores according to the research requirements.

3D PRINTING OF BIO-INSPIRED CORES FOR OUT-OF-AUTOCLAVE SANDWICH STRUCTURES

The design and manufacture of sandwich structures allow for many variants related to core and skin types, but their fabrication is very limited with conventional technologies. Recent advances in 3D printing are creating new design possibilities, such as bio-inspired structures with more complex cellular units than the current ones, functional gradients, and curved panels. The present work has focused on two aspects; 1) the efficiency of the core inspired by the trabecular structure of beetle wings versus the conventional honeycomb, and 2) the feasibility of integrating these new cores with carbon fiber/epoxy prepreg skins for out-of-autoclave curing.  The results show that the ONYX® 3D printing cores obtained by filament extrusion technology and the skins manufactured by out-of-autoclave curing show good skin/core adhesion. On the other hand, the results of the flexural tests have shown that the stiffness of the sandwich panel with the trabecular structure is better than that of one of the honeycombs and the strength in both cases is similar. However, where substantial differences have been found between the two types of cores is in the quasi-static puncture resistance, that of the trabecular structure being 60% higher.

Vinyl- and chloromethyl-substituted mono-T8 and double-decker silsesquioxanes as specific cores to low generation dendritic systems.

We report the series of G1 and G1.5 dendritic systems with mono-T8 SQs and DDSQ as specific types of dendron and dendrimer cores, respectively. The trivinyl- and tri(chloromethyl)-derivatives were obtained via hydrolytic condensation followed by the hydrosilylation reaction, optimized to yield selectively β-products. Their structures were confirmed by spectroscopic and XRD analyses. It is the first example of double-decker SQs used as cores for the construction of a low generation of dendrimer featuring specific dumbbell frameworks expanding in two or four directions.

Automatic Classification of Cancer Pathology Reports: A Systematic Review

Pathology reports primarily consist of unstructured free text and thus the clinical information contained in the reports is not trivial to access or query. Multiple natural language processing (NLP) techniques have been proposed to automate the coding of pathology reports via text classification. In this systematic review, we follow the guidelines proposed by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA; Page et al., 2020: BMJ.) to identify the NLP systems for classifying pathology reports published between the years of 2010 and 2021. Based on our search criteria, a total of 3445 records were retrieved, and 25 articles met the final review criteria. We benchmarked the systems based on methodology, complexity of the prediction task and core types of NLP models: i) Rule-based and Intelligent systems, ii) statistical machine learning, and iii) deep learning. While certain tasks are well addressed by these models, many others have limitations and remain as open challenges, such as, extraction of many cancer characteristics (size, shape, type of cancer, others) from pathology reports. We investigated the final set of papers (25) and addressed their potential as well as their limitations. We hope that this systematic review helps researchers prioritize the development of innovated approaches to tackle the current limitations and help the advancement of cancer research.

A rock core wettability index using NMR T measurements

Wettability is a critical parameter that controls fluid flow and distribution as well as recovery efficiency in reservoir rocks. The sensitivity of Nuclear Magnetic Resonance (NMR) relaxation measurements to wettability is well-known. Here we develop a new approach to calculate a wettability index based on low field NMR transverse ( T 2 ) measurements which is simpler than existing models in the literature and still affords good agreement with Amott-Harvey and USBM wettability test results. The model relies on the emergence of a bulk like relaxation signal from the non-wetting phase in partially oil/water saturated cores. Unlike other models in the literature, which require T 2 measurements at up to four different saturation states, our model only requires measurements at two partial saturation states; irreducible brine ( S wi ) and residual oil ( S or ). The performance of the model was tested using experimental results from different core types aged with light and heavy oils containing varied amounts of asphaltene. Different wettability conditions with Amott-Harvey/USBM values ranging from −0.39 to 0.79 were thus tested. When compared with measured reference wettability indices from the Amott-Harvey or USBM method, the model prediction showed good agreement (the calculated mean absolute error was 0.10). Additionally, improved accuracy was achieved relative to existing comparable models in the literature for the range of samples considered. • This study presents a new model to calculate a wettability index based on NMR T 2 measurements. • The model requires less calibration points than most existing models. • The model relies on the emergence of a bulk like relaxation signal from the non-wetting phase in partially saturated cores. • The model is tested in different rock types including carbonates and sandstones. • The predicted wettability indices showed good agreement with measured reference values from the Amott-Harvey method.

The Gender of Math

The politics of math are of newfound concern today, due to the outsize influence of algorithms and code in contemporary life. While only a few years ago, tech authors were still hawking Silicon Valley as the great hope for humanity, today one is more likely to hear how Big Tech increases social inequality, how algorithms are racist, and how math is a weapon. Do algorithms discriminate along gendered lines? Do mathematical systems harbor an essential bias? This essay shows that mathematics has long been defined through an elemental gendering, that within such typing there exists a prohibition on mixing the types, and that the two core types themselves (geometry and arithmetic) are mutually intertwined using notions of hierarchy, foreignness, and priority. The author concludes that whatever incidental biases it may display, mathematics also contains an essential bias.

Mechanical response and strength characteristics of aluminum honeycomb sandwich panels for infrastructure engineering

The use of aluminium sandwich panels has been increased in a certain number of engineering applications from infrastructure systems and transportation to aircraft and naval engineering. Due to their structural efficiency these materials are ideal for applications where ratio of strength to weight is of crucial importance. In the current study the investigation of the strength characteristics of aluminium sandwich panels with aluminium honeycomb core and different types of skins is performed using both analytical models and experimental procedures. A series of strength tests such as tension, shear, three point bending and double cantilever beam were conducted on aluminium honeycomb-cored sandwich panel specimens with five different skins in order to examine the mode of failure and the mechanical behaviour of the structural elements. The experimental findings are compared to theoretical values while an attempt for the explanation of the mechanisms leading to failure such as buckling, delamination or debonding between core and skins is performed. The results occurring from the study are very useful for the enhancement of the mechanical behaviour of sandwich constructions, thus more intensive work must be carried out in order to understand the physical mechanisms leading to strength characteristics of sandwich panels.

Shear Bond Strength of Ceramic Veneers to Zirconia–Calcium Silicate Cores

Improving the bond strength of veneering ceramics to ZrO2-based cores remains a challenge. The purpose of this study was to evaluate the shear bond strength of different ZrO2 cores containing calcium silicate (CaSi) to veneering ceramics. Five types of ZrO2-based cores (n = 230) were divided into two groups: with or without oxygen plasma treatment. These were bound to two veneering ceramics (IPS e.max Ceram or VITA VM9). Shear bond strength of veneering ceramics to various cores was measured (n = 10), in addition to phase composition, surface morphology and contact angle of the cores. The results indicated that the plasma treatment had a significant effect on the water contact angle of the ZrO2-based cores, but had little effect on the bond strength. Regardless of plasma treatment, the highest strength value was recorded in the ZrO2 core specimen containing 20 wt % CaSi, when all cores were adhered to VITA VM 9 veneer. When using IPS e.max Ceram veneer, the shear bond strength of the plasma-treated 20 wt % CaSi-containing ZrO2 core was 16.6 ± 0.9 MPa higher than that of VITA In-Ceram YZ core control (13.4 ± 1.0 MPa) (p < 0.05). We conclude that the presence of 20 wt % CaSi in ZrO2 can improve the shear bond strength of zirconia-based cores to veneering ceramic.

Impact and post-impact response of lightweight CFRP/wood sandwich composites

Lightweight CFRP/wood sandwich composites receive considerable attention because they can be tailored to satisfy many specifications. Therefore, the damage modes during low velocity impact and compression after impact (CAI) of CFRP/wood sandwich laminate with different wood core types are investigated in this article. The effect of wood fiber orientation on the specific energy dissipation and CAI strength are studied. Results demonstrated that the laminate with balsa core wood, where the wood fibers are perpendicular to the CFRP face plies, shows higher impact load and dissipated energy due to the ability of wood cells to deform during impact and hence dissipate more energy. However, the laminate with birch core, where the wood fibers are parallel to the CFRP surface plies, reveals slightly larger CAI strength due to the role of wood fibers in sharing the load during compression. The damage initiated in the balsa core sandwich laminates at the impacted face and propagate to the unimpacted CFRP surface, while the opposite damage behavior occurs for the birch core sandwich laminate. The balsa core laminate showed larger specific impact load (load/density), dissipated energy (dissipated energy/density), and CAI strength (strength/density), reaching 2.21-, 2.24-, and 1.41-fold times compared to birch core laminates.