Intersection Region Research Articles

Simulation Analysis of The Thickness Effect Towards Mechanical Aspects in The Design of Centrifugal Pump Casing

The strength of the centrifugal pump is crucial to ensure the safe pump operating when endure to unintended pumping condition. The presence of the solid particles and sudden increase of pressure may lead to the damage on the casing of a centrifugal pump and it becomes critical when the thickness of the casing is thin. This study aims to investigate the effects of the thickness on the mechanical aspects such as stress, strain and displacement in the casing design by using finite element (FE) analysis. The structure of the pump casing with various thicknesses is analyzed via FE-based software. The correlation of the wall thickness with the mechanical aspects is studied. The critical region with high stress was spotted in the simulation. The simulation results revealed the wall thickness demonstrated a polynomial correlation to the displacement and strain. The stress of the casing showed the linear correlation with the thickness. The critical region was noticed at the intersection region of the pump casing. The mechanical aspects of the pump casing were improved with the increment of the wall thickness in the pump casing design.

New insight into the photoinduced wavelength dependent decay mechanisms of the ferulic acid system on the excited states.

The ferulic acid (FA) is a kind of phenolic acid widely exists in nature plants. Apart from its medicinal values, the FA is also widely applied in cosmetic industry. Recently, it was found to have potential applications in commercial sunscreens for its strong photostability and photoprotection property from harmful UV rays. Such excellent property lies in the ultrafast decay process of the FA system when exposure to the UV light, but the underlying detailed relaxation pathway is still less clear-cut. In the current work, high-level ab initio electronic structure calculations and on-the-fly surface hopping dynamics simulations were employed to explore the photoinduced decay mechanism of the FA system both on the S1 and S3 states in the gas phase. The results provide a reasonable explanation for the wavelength dependent decay patterns of FA system. The S1 state decay pathway is driven by a re-emission process to dissipate excess energy. While for the S3 state deactivation process, the pathway is dominated by a non-adiabatic process driven by the internal conversion process through the conical intersection regions. A S3-S1-S0 two step decay pattern is proposed, and the pathways are mainly driven by a puckering distortion motion of the aromatic ring and a twisting motion around the bridging double bond. The calculation results contribute to a better understanding of detailed dynamics behavior of the FA deactivation process, and provide theoretical guidance for further design of efficient and environmentally friendly sunscreens.

Crossed chiral band approximation for wide-band self-collimation of light

We propose a perspective to the evaluation of the wide bandwidth phenomenon for low-symmetric photonic structures, by introducing the band tailoring and chiral band approximation on the self-collimation effect. In the case of the crossing of the bands, we claim the excitation of the lower mode can provide the utilization of the entire bandwidth by suppressing the intersection regions where the frequencies tend to mix. Thereby, we design broadband self-collimation capable, defect-free photonic structures and examine their performances. A fractional bandwidth of 0.35 () and 0.37 () are achieved for radii of and , respectively. We explore the full-range collimation by using transmission and E-field intensity analyses in addition to band diagrams and group velocity dispersions. Moreover, we indicate all-angle collimation validity even for highly tilted sources up to an angle of .

Spectral Diagnostics of the Dynamics of the Formation of a Homoconjugated Complex [HCN.H.NCH

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH]+ linear complex along the profile of the proton transition reaction path is given, and the laws governing the diagnostic parameters, that is, potential descriptors of the dynamics of this process, are determined. We calculated the surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the reaction path of the proton transition in the system under study. When the fragments [HCNH]+ and NCH approach each other, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν(NH) varies along the reaction path from ~3600 to ~500 cm–1. An abrupt frequency change is observed in the region of intersection of the terms ν(NH) and ν(CN).

Strain Sensor with Both a Wide Sensing Range and High Sensitivity Based on Braided Graphene Belts.

Recent years have witnessed significant development of flexible strain sensors in a variety of fields. Nevertheless, the challenge of integrating a broad sensing range (>50%) with high sensitivity [gauge factor (GF) value > 100 over the entire sensing strain] in one single flexible strain sensor still exists. Herein, we prepared a flexible strain sensor based on braided graphene belts (BGBs) and dragon skin. Such a BGB strain sensor exhibits an integration of a wide sensing range (up to 55.55%) and high sensitivity (GF value > 175.16 through the entire working range). Besides, this BGB strain sensor also demonstrates a minute monitoring limit (0.01%), low hysteresis and overshoot behaviors, and reliable cycling repeatability (>6000 cycles). The SEM microscopy observations reveal that the skew angle and intersection regions of graphene belts are mainly responsible for the desirable sensing performance. Finally, the successful detection of full-range human motions, from subtle actions to vigorously joint-related movements, reflects great potential of the BGB strain sensor in the application of wearable instruments.

Stable water isotopes and accumulation rates in the Union Glacier region, Ellsworth Mountains, West Antarctica, over the last 35 years

Abstract. Antarctica is well known to be highly susceptible to atmospheric and oceanic warming. However, due to the lack of long-term and in situ meteorological observations, little is known about the magnitude of the warming and the meteorological conditions in the intersection region between the Antarctic Peninsula (AP), the West Antarctic Ice Sheet (WAIS) and the East Antarctic Ice Sheet (EAIS). Here we present new stable water isotope data (δ18O, δD, d excess) and accumulation rates from firn cores in the Union Glacier (UG) region, located in the Ellsworth Mountains at the northern edge of the WAIS. The firn core stable oxygen isotopes and the d excess exhibit no statistically significant trend for the period 1980–2014, suggesting that regional changes in near-surface air temperature and moisture source variability have been small during the last 35 years. Backward trajectory modelling revealed the Weddell Sea sector, Coats Land and Dronning Maud Land (DML) to be the main moisture source regions for the study site throughout the year. We found that mean annual δ18O (δD) values in the UG region are negatively correlated with sea ice concentrations (SICs) in the northern Weddell Sea but not influenced by large-scale modes of climate variability such as the Southern Annular Mode (SAM) and the El Niño–Southern Oscillation (ENSO). Only mean annual d-excess values show a weak positive correlation with the SAM. On average annual snow accumulation in the UG region amounts to 0.245 m w.e. a−1 in 1980–2014 and has slightly decreased during this period. It is only weakly related to sea ice conditions in the Weddell Sea sector and not correlated with SAM and ENSO. We conclude that neither the rapid warming nor the large increases in snow accumulation observed on the AP and in West Antarctica during the last decades have extended inland to the Ellsworth Mountains. Hence, the UG region, although located at the northern edge of the WAIS and relatively close to the AP, exhibits rather stable climate characteristics similar to those observed in East Antarctica.

BedSect: An Integrated Web Server Application to Perform Intersection, Visualization, and Functional Annotation of Genomic Regions From Multiple Datasets.

A large number of genomic regions, such as transcription factor binding sites (TFBSs) captured from next generation sequencing (NGS) data analyses or those available from the public resource database ENCODE, are generally overlapped to answer a variety of biological questions. Though several command-line tools are available to perform such an analysis, there is a notable lack of an integrated webserver application with which to identify genomic region intersections, generate publication-ready plots depicting subsets of the overlapped regions, and perform functional annotation. Thus, there is an ardent need for a comprehensive and user-friendly webserver application that allows the users to either upload multiple datasets or select from the integrated Gene Transcription Regulation Database (GTRD). We thus introduce BedSect (http://imgsb.org/bedsect/.), which not only fulfils the above criteria but also performs intersection analysis along with visualization of the intersection regions as an UpSet and correlation plot using the integrated Shiny application. Moreover, analyses, including functional annotation, gene ontology, and biological pathways enrichment for the identified unique and intersected genomic regions, can also be performed using the integrated GREAT tool. To view the genomic regions in the genome browser, the inbuilt hyperlink for UCSC can redirect the user to visualize the results as custom tracks.

Спектральная диагностика динамики образования гомосопряженного комплекса [HCN.H.NCH]-=SUP=-+-=/SUP=-

A quantum-mechanical analysis of the manifestations of the NHN hydrogen bond in the vibrational spectra of the [HCN.H.NCH] + linear complex along the proton transfer reaction profile is given, and the laws governing the diagnostic parameters — potential descriptors of the dynamics of this process — are established. The surface of the potential energy and harmonic frequencies of normal vibrations along the profile of the proton transfer reaction path in the system studied are calculated. It has been shown that when the [HCNH] + and NCH fragments come closer together, a noticeable distortion of the forms of their skeletal vibrations occurs, up to complete mixing into the symmetric and antisymmetric forms. The frequency of the longitudinal vibration of the central proton ν (NH) varies along the reaction path from ~ 3600 to ~ 500 cm-1. In the region of intersection of the terms ν (NH) and ν (CN) an abrupt nature of frequency change is detected.

A SART algorithm for area integral model in desktop micro-CT system

Due to the finite size of detector unit, the area integral model (AIM) is closer to reality than the line integral model (LIM) when X-ray beams passing through a sample cast to CCD. A simultaneous algebraic reconstruction technique (SART) algorithm for AIM is proposed for improved image quality. First, a cone-beam to parallel-beam rearranged step was performed to simplify the model computation. Then, a judgement formula was used to quickly find the cells to be traversed by a strip-shaped X-ray beam and an effective method was presented to calculate intersection region. Via the comparison, both simulation and experiment show that this area-based SART has better reconstruction quality than traditional line-based SART. The algorithm is demonstrated the ability to micro-CT reconstruction. This AIM approach could be adapted for other iterative algorithms in fan-beam or small cone- angle beam CT geometry.

Self-optimizing attainable regions of the anaerobic treatment process: Modeling performance targets under kinetic uncertainty

Despite the advantage of model-based design, anaerobic digesters are seldom designed using biokinetic models due to lack of reliable kinetic coefficients and/or systematic approaches for incorporating kinetic models into digester design. This study presents a systematic framework, which couples practical identifiability, uncertainty quantification and attainable region (AR) concepts for defining process performance targets, especially when reliable kinetic coefficients are unavailable. Within the framework, we introduce the concept of self-optimizing ARs, which define performance targets that results in near optimal operation in spite of variations in kinetic coefficients. Using the case of modified Hill model, only 3 out of the 6 model parameters (unidentifiable set) are responsible for the model prediction uncertainty. The uncertainty bands (mean, 10th percentile and 90th percentile) on the model states has been computed using the Monte Carlo Simulation procedure and attainable regions for the different levels of uncertainty has been constructed and the boundaries interpreted into digester structures. The self-optimizing attainable regions have been defined as the intersection region of the attainable regions corresponding to the mean, 10th percentile and 90th percentile. Incorporating uncertainty significantly reduces performance targets of the process but increases self-optimality in defining performance targets. Unlike the attainable region, which represents the limits of achievability for defined kinetics, the self-optimizing attainable region represents the set of all possible states attainable by the system even in cases of kinetic uncertainty. In summary, the concept of self-optimizing ARs provides a systematic way of defining process performance targets and making economic decisions under conditions of uncertainty.

COMPRESSIVE PROPERTIES OF AUXETIC STRUCTURES WITH CONTROLLED STIFFNESS OF STRUT JOINTS

Presented paper deals with experimental study on compressive properties of auxetics with controlled stiffness of strut joints. The variable strut joints properties were simulated by adding extra amount of material in the struts’ intersection regions. Four groups of inverted honeycomb structures were prepared by multi-jet 3D printing and tested in quasi-static compression. The structure collapsed gradually, however after the first collapse, failure in entire cross-section occurred due to the brittle nature of the base material. The behavior up to the first collapse was consistent among the specimens within each group, while differed slightly subsequently. With higher reinforcement in the joints, results showed increasing stress at the first collapse (ultimate compressive stress) while the strain at the first collapse remained unchanged. The auxetic behaviour became less significant with increasing joints’ reinforcement.

Searching for further evidence for cloud–cloud collisions in L1188

In order to search for further observational evidence of cloud–cloud collisions in one of the promising candidates, L1188, we carried out observations of multiple molecular lines toward the intersection region of the two nearly orthogonal filamentary molecular clouds in L1188. Based on these observations, we find two parallel filamentary structures, both of which have at least two velocity components being connected with broad bridging features. We also found a spatially complementary distribution between the two molecular clouds, as well as enhanced 13CO emission and 12CO self-absorption toward their abutting regions. At the most blueshifted velocities, we unveil a 1 pc-long arc ubiquitously showing 12CO line wings. We discover two 22 GHz water masers, which are the first maser detections in L1188. An analysis of line ratios at a linear resolution of 0.2 pc suggests that L1188 is characterised by kinetic temperatures of 13–23 K and H2 number densities of 103–103.6 cm−3. On the basis of previous theoretical predictions and simulations, we suggest that these observational features can be naturally explained by the scenario of a cloud–cloud collision in L1188, although an additional contribution of stellar feedback from low-mass young stellar objects cannot be ruled out.

Assessing the infinitely expanding intersection region for the development of large-scale multipoint laser Doppler velocimetry

Multipoint laser Doppler velocimetry (MLDV) has been effective for non-invasively measuring the flow velocity distribution with a high-spatial and high-time resolution. The flow velocity can be estimated using a scattered light signal by seeding particles passing through a fringe pattern formed in the intersection region of two laser beams. The shape of this intersection region can be easily changed by changing the optical components and positions of the lasers. An infinitely expanding intersection region is proposed in the present paper. A wide intersection region was indicated by the measurement results of flow velocity. The intersection region is evaluated using a flow channel (1.4 mm × 1.4 mm). The area of the operating measurement region exceeds 150 mm in the horizontal direction and is less than ±10 mm in the vertical direction. This new MLDV is referred to as a large-scale MLDV.

Experimental and numerical analysis of a novel tubular joint for transmission tower

A novel type of tubular X-joint is evaluated in this study which combines both flange connection and welded connection for practical steel tube transmission tower. Full-scale experiments are carried out to investigate the monotonic behavior of the joints under both axial tensile and compressive load. The failure modes, load-displacement curves, load-strain curves, deformation development and ultimate strength are studied and discussed. Non-linear finite element analysis of the proposed tubular X-joint not only captures the discernible behavior observed during the tests to verify the experimental results, but also help study stress distribution that cannot be directly measured during the tests. Both experimental and numerical results show that the novel type of joints have adequate bearing capacity with good safety margin and the weak parts are mainly concentrated on the vicinity of intersection regions. Finally, several different design codes are used to calculate the ultimate strength of the proposed joints under investigation. The difference between experimental results and current design methods can be attributed to the fact that the connection adopted in the joints is different from the conventional welded tubular X-joint in codes.

HARDI Segmentation via Fourth-Order Tensors and Anisotropy Preserving Similarity Measures

In this work, we discuss the higher-order tensors appearing in high angular resolution diffusion tensor imaging, and we have tested two segmentation methods, the Riemannian spectral clustering and the deformable models, using several projections of the fourth-order tensors to the second-order ones, and diverse similarity measures on them. High angular resolution diffusion imaging has proved its effectiveness in modeling white matter brain structures along with the fiber intersection regions, which is of high importance in brain research. Along with other known projections, we observe that the diagonal components of the flattened fourth-order tensors also live in the well-known Riemannian symmetric space of symmetric positive-definite matrices. We discuss and compare several natural approximations of the distance on the latter space to be used in clustering and segmentation algorithms. The results show that some of the projections unfold the geometry of the higher-order tensors very well, and we also propose the exploitation of the spherical linear interpolation spectral quaternion metric, which proves to be very effective. The latter claims are supported by experimental comparison of the effectiveness of our algorithms with the more usual logarithmic Euclidean and spectral quaternionic metrics, in particular in the presence of noise. Our methods allow to distinguish individual objects in complex structures with high curvatures and crossings.

Nonadiabatic Photochemistry Induced by Inaccessible Conical Intersections.

Conical intersections are ubiquitous in photochemical processes, where nonadiabatic transfer induces ultrafast nonradiative decay from an excited state. Although they eluded experimental detection until the 1990s, today three diagnostic attributes are generally associated with photochemical reactions through conical intersections: ultrafast electronic dynamics, negligible fluorescence, and coherent wavepacket transfer. Here, we use generalized quantum dynamics simulations to show that coherent nonadiabatic transfer of excited vibrational wavepackets can occur even without reaching the conical intersection region. Instead, the wavepacket remains distant from the conical intersection throughout. In some topographies, an energetically inaccessible conical intersection can be completely avoided, yet still induce substantial nonadiabatic transfer with ultrafast transfer efficiencies that are nearly identical to those of direct transfer through a conical intersection. These results reveal that the diagnostic properties of conical intersections are not actually specific to decay pathways traveling directly through the intersection funnel, as is the common interpretation, but can also arise from alternative pathways that do not reach the intersection. This suggests that the diagnostic features and experimental signals associated with conical intersections should be reassessed, and the concept of pathways through a conical intersection as the "paradigm of photochemistry" may need to be adjusted.

Terahertz Generation Enhanced by Nonlinear Filaments Interaction in Liquids

Enhanced terahertz (THz) radiation was observed in liquids via interaction of two noncollinear filaments of ultrashort pulses. As compared with THz generation driven by one filament, the observed enhancement was attributed to asymmetric plasma current due to filament-induced multiple frequency components in liquids. By tuning the relative polarization angles and pulse energies of the interacting filaments, we demonstrated that the interaction of the two filaments gave rise to plasma density modulation and high-intensity laser field in the intersection region, which resulted in blue-shifted supercontinuum generation. The newly generated blue frequency components enhanced asymmetric plasma current when it combined with the fundamental-wave filament at 800 nm, which led to stronger THz generation.

The Numerical Analysis of the Flow on the Smooth and Nonsmooth Boundaries by IBEM/DBIEM

The value of the tangential velocity on the Boundary Value Problem (BVP) is inaccurate when comparing the results with analytical solutions by Indirect Boundary Element Method (IBEM), especially at the intersection region where the normal vector is changing rapidly (named nonsmooth boundary). In this study, the singularity of the BVP, which is directly arranged in the center of the surface of the fluid computing domain, is moved outside the computational domain by using the Desingularized Boundary Integral Equation Method (DBIEM). In order to analyze the accuracy of the IBEM/DBIEM and validate the above-mentioned problem, three-dimensional uniform flow over a sphere has been presented. The convergent study of the presented model has been investigated, including desingularized distance in the DBIEM. Then, the numerical results were compared with the analytical solution. It was found that the accuracy of velocity distribution in the flow field has been greatly improved at the intersection region, which has suddenly changed the boundary surface shape of the fluid domain. The conclusions can guide the study on the flow over nonsmooth boundaries by using boundary value method.

From Light Absorption to Cyclization: Structure and Solvent Effects in Donor‐Acceptor Stenhouse Adducts

AbstractDonor‐acceptor Stenhouse adducts (DASAs) have emerged in the last years as novel reversible photoswitches characterized by the light‐induced interconversion between a linear open‐chain isomer and a compact closed‐ring isomer. Despite the considerable interest for potential applications (due to their changes in size, color and polarity), several steps of the photoswitching mechanism are still not completely understood, hence limiting the rational design of these compounds. Herein we propose a complete computational study of the switching mechanism by means of TD‐DFT and CASPT2//CASSCF calculations. Special attention is paid to the excited state pathway, leading to a previously unknown general scenario with common features for different DASAs: After light absorption, a rotational energy barrier needs to be overcome in order to reach a conical intersection region with the ground state, whose topology and relative energy is investigated based on different solvents and acceptor moieties. Then, the evolution of the compounds in the ground state is considered by calculating different minima until the formation of the final closed form. Finally, the eventual reverse thermal path was also considered. We offer herein a complete mechanistic description which allows for an overall comparison with available experimental results.

Investigation of wind tunnel wall effect and wing-fuselage interference regarding the prediction of wing aerodynamics and its influence on the horizontal tail

The calculation of aerodynamic characteristics of a wing is the basic problem for aerodynamic design of aircraft. Wing aerodynamics can be determined experimentally and numerically. The method of fixing the wing in the test chamber of wind tunnel is related to disturbance of flow through the wing. When the wing is entirely fixed in the test chamber, the disturbance is usually caused by the sting connecting the wing to the test chamber. The experiments in this paper fixed the wing by clamping to the wind tunnel wall at the wing symmetry surface (root section). With this wing fixation, it was possible to take advantage of the wingspan twice, but to obtain the 3D wing experiment results, it was necessary to evaluate the impact of the wind tunnel wall effect. As for aircrafts, the aerodynamic force of the aircraft’s wing will have certain difference than that of the wing alone. The intersection region between the wind tunnel wall and wing root (for the experiment), as well as between the fuselage and wing root have complex interactions of boundary layers, in particular separation phenomena in the boundary layers. By solving the differential equation for viscous flows, it was possible to visualize the picture of streamlines and flow separations in this interference region and the aerodynamic characteristics of the wing. The singularity method was also used to compare results within its application range. The aerodynamic coefficients in the two cases with and without interference were analyzed. Complex interactions in the interference region could alter the predicted aerodynamic force calculated for the wing alone, which should be estimated. Very strong separations in the wing-fuselage interference region at large angles of attack turned into vortices at the rear impacting on the horizontal tail aerodynamics that is related to the balance problem of the aircraft.