Uniform Segment Research Articles

A Stochastic Model of Cortical Microtubule Anchoring and Mechanics Provides Regulatory Control of Microtubule Shape.

The organization of cortical microtubule arrays play an important role in the development of plant cells. Until recently, the direct mechanical influence of cell geometry on the constrained microtubule (MT) trajectories have been largely ignored in computational models. Modelling MTs as thin elastic rods constrained on a surface, a previous study examined the deflection of MTs using a fixed number of segments and uniform segment lengths between MT anchors. It is known that the resulting MT curves converge to geodesics as the anchor spacing approaches zero. In the case of long MTs on a cylinder, buckling has been found for transverse trajectories. There is a clear interplay between two factors in the problem of deflection: curvature of the membrane and the lengths of MT segments. Here, we examine the latter in detail, in the backdrop of a circular cylinder. In reality, the number of segments are not predetermined and their lengths are not uniform. We present a minimal, realistic model treating the anchor spacing as a stochastic process and examine the net effect on deflection. We find that, by tuning the ratio of growth speed to anchoring rate, it is possible to mitigate MT deflection and even prevent buckling for lengths significantly larger than the previously-derived critical buckling length. We suggest that this mediation of deflection by anchoring might provide cells with a means of preventing arrays from deflecting away from the transverse orientation.

RESEARCH ON THE DISTRIBUTION OF AIRBNB ACCOMMODATION IN MAJOR EUROPEAN DESTINATIONS

The Airbnb platform, one of the most popular platforms of its kind, is present worldwide, with a variety of accommodations, depending on the type of accommodation it offers (single room, whole apartment, etc.). In this article, we set out to analyse the spatial allocation of accommodation and the density of Airbnb listings in comparison with hotel establishments in Europe. For the spatial analysis of Airbnb accommodations we used data from the Inside Airbnb website and QGIS, an application used for geographic information systems (GIS) that supports visualization, editing, and analysis of geospatial data. In this way, we created a geospatial database that helped us better understand the dynamics of each location. After analysing the data we concluded that a consequence of the concentration of Airbnb accommodation is that life in these areas has become more expensive and more crowded for locals. Airbnb accommodation has caused inconvenience not only to hotel owners but also to locals. In addition, Airbnb is having a strong impact on the rental market by increasing rental prices. Another trend that can be seen from the distribution of Airbnb accommodation is that in cities with a seafront location, accommodation is located close to beaches and most accommodation is of the entire home/apartment type. Differences in the frequency of use and prices of listings highlight the geographical inequality in the benefits and impact of Airbnb’s activity. The Airbnb offer is not a uniform segment of tourist accommodation and its effects on destinations are important and should therefore be analysed in relation to the territorial context.

Crosstalk in Elliptical Sensor Arrays for Current Measurement

Contactless current sensors that use arrays of magnetic field sensors are a good alternative to core-based current sensors because the omission of the magnetic core offers many advantages. Particularly, circular sensor arrays have proven to feature good robustness against various error sources. As rectangular bus bars are frequently used for local high-current power distribution systems, elliptic arrays would require less space than circular arrays. Up until now, no publication on magnetic interference errors of elliptic sensor arrays has been presented. This article examines the crosstalk error for different sensor distribution methods, aspect ratios, numbers of sensors, and offset angles with calculations and measurements. Therefore, an interference conductor is positioned at different angles and distances relative to the elliptic arrays. We show that the crosstalk error can be reduced with our elliptic designs in comparison to a circular design with an equal number of sensors and an equal length of the semimajor axis. The projection distribution typically offers a five times smaller crosstalk error compared to the uniform curve segment length distribution. To support the design of elliptical arrays, instructions for the optimization against interference errors for elliptic sensor arrays are given in this article. Thus, an optimal offset angle for the reduction of the crosstalk error is presented.

Mechanical Characteristics of Variable Cross‐Section Immersed Tunnels under Spatial Differential Settlement

This work establishes a fine model reflecting the characteristics of immersed tube structures to study the spatial mechanical characteristics of variable cross section immersed tunnels. Then, the mechanical behavior of the pipe segments under differential deformation is explored, based on which we propose a formula for estimating the shear key force and analyze the corresponding failure mechanism and failure mode. Thus, the critical points of the pipe segment design are specified. The results show that, first, the variable cross section segment bears more sectional internal force (over 47%) than the uniform cross section segment in actual cases, which should be fully considered in practical reinforcement design. Bearing deformation alternatively occurs at different shear keys, implying an apparent spatial stiffness matching problem. Second, the pipe segments show overall settlement under longitudinal bending, failing to satisfy the assumption of deformed plane sections. The force on the shear keys varies with the quadratic function of the longitudinal bending degree, and the dislocation magnitude has a positive near‐linear relationship with the bending degree. Third, when subjected to torsion, the shear keys of the weak sidewalls are sheared to resist torsion. Then, this force is laterally transferred to the top and bottom plates and jointly shared by the adjacent shear keys, explaining why shear is adjusted with structural deformation. Fourth, under the action of spatial differential deformation, the shear force is mainly undertaken by the vertical shear keys. When the structure is subjected to bending, compression and shear failure occur at the end angle of the middle wall shear key, and its root junction experiences tension and shear failure. When subjected to longitudinal torsion, the local tension and shear failure at the root of the shear key on the soft subgrade side cause a joint failure. Finally, based on the bearing characteristics, failure mechanism, and failure mode of variable cross section immersed tunnels, the idea of strengthening immersed tube structures is put forward, which can guide similar engineers.

Exploring the chain of effects between local identity and expatriate consumers’ preference for local food brands

PurposeTheorizing about consumer’s cultural identity has led to a greater understanding of why consumers choose and consume certain brands and products. The influence of cultural identity has traditionally been studied primarily in a consumer’s country of origin, neglecting its potential relevance for understanding the consumption choices of sojourners and expatriates. This paper aims to investigate how the length of stay (LOS) in a foreign country, as a manifestation of local identity, shapes expatriate consumers’ food brand preferences.Design/methodology/approachThis study draws on social identity theory and cultural branding literature to examine the mechanisms through which local identity drives preference for local food brands among expatriate consumers. Data from a cross-sectional survey of 180 USA and UK expatriates living in the Greater Middle East were analysed using structural equation modelling.FindingsLocal identity (measured through LOS in the host country) appears to exert an indirect effect on the consumption of local food brands through social ties with a local community. Next, social ties with a local community enhance local food brand preferences (LFBP) and this relationship is fully mediated by the global food brand preference (GFBP) where GFBP weakens the preference for local food brands and vice versa. In addition, the heterogeneity of interplay effects between local and global food brands can be attributed to the local food brand value signalling. The study finds that the higher perceived value of local food brands lowers the negative impact the GFBP has on LFBP and vice versa. The hypothesized effects in the model remain robust when controlling for moderating effect of age and the expatriate’s country of origin.Research limitations/implicationsThe current study investigates the consumer behaviour of the expatriate consumer segment. As this study focuses only on expatriates currently living in countries of the Greater Middle East, its findings should be tested in other regions and with diverse subject samples.Practical implicationsExpatriates should not be treated as a uniform consumer segment but, instead, should be evaluated as unique individuals whose inclination towards local food brands depends on their: ability to establish and verify their local identity through developing social ties with the local community and reliance on global food brands. Moreover, findings demonstrate that brand managers should focus on increasing their perceived value by showcasing quality, reliability, innovation and performance, factors that reassure expatriate consumers when choosing local, over global food brands.Originality/valueThis study goes beyond the traditional focus on local identity in the domestic setting and sets out to investigate the chain of effects on LFBPs in the expatriate setting. Empirical evidence shows that an expatriate’s higher integration in a local community via social ties confirms their local identity, and thus exerts a stronger impact on a preference for local food brands. The study’s results demonstrate that the preference for local food is dependent on an expatriate consumer’s reliance on global food brands and the impact of global food preferences on local food preferences is moderated by the perceptions of the local food brand value. Additionally, findings suggest that the negative effects of global food brands are stronger for older expatriates and expatriates coming from the USA.

Cosmopolitanism and expatriate’s preference for host country food: The conditional effects of experiential capital and retail development

AbstractIn this paper we explore the insufficiently addressed domain of expatriates’ preference for local (host country) food. Extant literature on this segment of consumers shows that tensions created by moving abroad are also reflected in their varying preference for host country foods. By drawing on social identity theory, we investigate how a cosmopolitan identity drives a preference for host country food under the contingent effects of an expatriate's experiential capital and host country's retail development. Based on a unique dataset of 293 expatriates living in six countries of the Greater Middle East, the findings from binary logistic regression model show that cosmopolitanism significantly explains expatriate's preference for host country food. We also show that the dimensions of experiential capital have countervailing moderating effects on this relationship whereas in countries with lower levels of retail development, the relationship between cosmopolitanism and expatriates’ preference for host country food becomes stronger. The findings of this study imply that cosmopolitan expatriates should not be considered a uniform segment as previous studies have advocated. Eventually, this study offers valuable contributions to literature that investigates the influence of socio‐cultural identities in food consumption as well as to literature dealing with expatriate consumer behaviour.

Array Diagnosis and DOA Estimation for Coprime Array under Sensor Failures.

A coprime array of sensors can achieve degrees of freedom (DOFs) by possessing a uniform linear array segment of size in the difference coarray. However, the structure of difference coarray is sensitive to sensor failures. Once the sensor fails, the impact of failure sensors on the coarray structure may decrease the DOFs and cause direction finding failure. Therefore, the direction of arrival (DOA) estimation of coprime arrays with sensor failures is a significant but challenging topic for investigation. Driven by the need for remedial measures, an efficient detection strategy is developed to diagnose the coprime array. Furthermore, based on the difference coarray, we divide the sensor failures into two scenarios. For redundant sensor failure scenarios, the structure of difference coarray remains unchanged, and the coarray MUSIC (CO-MUSIC) algorithm is applied for DOA estimation. For non-redundant sensor failure scenarios, the consecutive lags of the difference coarray will contain holes, which hinder the application of CO-MUSIC. We employ Singular Value Thresholding (SVT) algorithm to fill the holes with covariance matrix reconstruction. Specifically, the covariance matrix is reconstructed into a matrix with zero elements, and the SVT algorithm is employed to perform matrix completion, thereby filling the holes. Finally, we employ root-MUSIC for DOA estimation. Simulation results verify the effectiveness of the proposed methods.

Computational Comparison between the Altura Aortic Endograft Configuration and the Classic Bifurcated Idealized Designs

The Altura (Alt) endograft is a new design, lacking the classic main body with the flow divider. Instead, 2 proximal D-shaped endografts form a round circumference in the aortic neck for secure sealing and land in the iliac arteries in a cross-limb fashion. The aim of this computational study was to compare hemodynamically this model with the classic bifurcated (Bif) and cross-limb (Cx) endograft designs of equal total length. All 3D endograft models were created using the finite volume analysis application ANSYS CFX (Ansys Inc., Canonsburg, PA, USA). The Alt inlet was constructed as 2 opposing D-shaped sections. The flow was quantified by time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), relative residence time (RRT), and helicity. The displacement forces were also compared for all models with computational fluid dynamics analysis. The Alt design was associated with lower forces (range 4.0-5.9Ν) than Bif (4.17-6.15N) and Cx (4.43-6.53N). The 2-piece inlet site of the separated limbs of Alt has higher TAWSS than the uniform inlet segment of the Cx and the Bif model. Most importantly, the mid-segment and distal segment of the limbs in the Alt design present higher TAWSS in a greater area than the other 2 models. The inlet of the Alt design showed higher OSI than the other accommodations and similar or comparable OSI values along their mid-limb and distal limb segments. The range, location, and values or RRT were comparable between the 3 models. Helicity in the iliac limbs is more prominent in the crossed accommodations (Alt and Cx). Only small differences in the hemodynamic indices and displacement forces were detected between the Alt and classic accommodations. From this point of view, the Alt design could be theoretically considered not inferior to other widely used endograft configurations.

Current state and development of Airbnb accommodation offer in 167 countries

ABSTRACT The paper examines the size, structure, distribution, dynamics, and use of Airbnb accommodation offer in 167 countries. Web-scrapping Airbnb website in fall 2018 and 2019 resulted in a datasets on 5.7 million listings, including 3.6 million active listings which have been rented out (reviewed) during the last year. Listings are divided into four groups based on types of properties and numbers of offers hosted by one platform user. The results show that the platform is most commonly used to rent out entire apartments by multi-hosts. The numbers of Airbnb listings in countries depend on the level of economic development and size of inbound tourism. One third of Airbnb supply is located in big cities, another one third near seacoasts. Airbnb offer grows most quickly in its relatively new markets, while in primary urban destinations of some European countries it is stable or decreases. The offer of professional hosts is growing more quickly than of peer-to-peer hosts. Differences in the frequency of use and prices of listings exaggerate the geographical unevenness in benefits and impacts of Airbnb activity. Airbnb supply is not a uniform segment of tourist accommodation and its effects on destinations should be considered in relation to territorial context.

Soft hand perception based on embedded optical fiber bending sensor

The perception capability of soft humanoid hand is very important to the implementation of friendly interactive and dexterous operation. The flexible optical bending sensor which is easy to be embedded into the soft finger is comprised of light emitting diode (LED), optical fiber and photo-sensitive sensor. The roughened optical fibers can generate light overflow. And the bend degree of soft fingers can be obtained by detecting the loss of light energy. The abilities of continuous movement detection, action gestures and object size recognition are implemented according to the following operations: ① calibrating the initial (unbent) and maximum bending statuses of soft fingers with normalization method; ② segmenting the normalized data by uniform, nonuniform and hysteresis segment method; ③ merging together the information of five fingers. The experiment results show that the proposed optical fiber bending sensor is able to detect the continuous sinusoidal movement status, correctly recognize various gestures and grasping postures and the object size. Combining hysteresis subsection method, the shortcoming of single point subsection oscillating near subsection point is overcome, and the recognition rate is improved. This optical flexible bending sensor has the advantages of electromagnetic immunity and easy to be embedded. It has important application value in soft robotic hand or soft actuator.

A Numerical Mode Matching Method for Wave Scattering in a Layered Medium with a Stratified Inhomogeneity

Numerical mode matching (NMM) methods are widely used for analyzing wave propagation and scattering in structures that are piecewise uniform along one spatial direction. For open structures that are unbounded in transverse directions (perpendicular to the uniform direction), the NMM methods use the perfectly matched layer (PML) technique to truncate the transverse variables. When incident waves are specified in homogeneous media surrounding the main structure, the total field is not always outgoing, and the NMM methods rely on reference solutions for each uniform segment. Existing NMM methods have difficulty handing grazing incident waves and special incident waves related to the onset of total internal reflection, and are not very efficient at computing reference solutions for nonplane incident waves. In this paper, a new NMM method is developed to overcome these limitations. A hybrid Dirichlet-Robin boundary condition is proposed to ensure that nonpropagating and nondecaying wave field components are not reflected by truncated PMLs. Exponential convergence of the PML solutions based on the hybrid Dirichlet--Robin boundary condition is established theoretically. A fast method is developed for computing reference solutions for cylindrical incident waves. The new NMM is implemented for two-dimensional structures and polarized electromagnetic waves. Numerical experiments are carried out to validate the new NMM method and to demonstrate its performance.

Estimating traffic performance on Spanish two-lane highways. Case study validation

Spanish standards rely on the procedures of the U.S. Highway Capacity Manual (HCM) in order to analyze traffic efficiency. Given the differences in road environment, driving behavior and vehicles’ performance, the HCM procedure would not be completely suitable for application to Spanish conditions. Moreover, the effect of passing restrictions is considered through the percentage of no-passing zones and significant variations on the horizontal alignment are not included on the uniform segment identification; which can lead to unrealistic results.The objective of this paper is to twofold: (1) modify the HCM two-lane highway analysis procedure for Spanish conditions considering the effect of passing restrictions and highway alignment variations on two-lane highway operation; (2) compare on one case study the results from the proposed approach and the HCM analysis procedure.The results indicate that solely geometry was not enough to characterize traffic operation on the straighter alignments (almost tangent), where speed dispersion was up to 20 km/h, and passing restrictions should be also included. Moreover, PTSF varied significantly depending on average passing zone lengths. The case study indicated that the proposed methodology provides more accurate estimates than the HCM on actual (in operation) two-lane highways.The proposed approach combines the effect on highway performance of passing restrictions, as considered on the US HCM, and highway alignment, as considered directly on the German HCM. The impact of trucks is modeled through the percentage of trucks rather than PCEs values, as it is common practice in Spain and Germany. This approach is simpler and more flexible to model the impact of trucks, passing restrictions and highway alignment on the different performance measures.

Packaging and Characteristics of a Tapered Fiber Sensor for Refractive-Index Measurements

In this study, we demonstrate the design and fabrication of a tapered fiber sensor with a sensing application based on a new (high-sensitivity) package. We study the effect of various geometric parameters such as the uniform segment diameter, the uniform segment length, and the incident angle of the optical wave on the tapered fiber sensor sensitivity for evanescent sensing. Our study shows that high sensitivity of the tapered fiber can be realized by optimizing its parameters. In addition, we design a novel packaging of a tapered-fiber sensor, which can efficiently ensure a uniform stress and reduce the cross sensitivity caused by stress in liquid detection using a tapered fiber sensor. We report the experimental results obtained using this tapered fiber sensor for refractive-index measurements. As the refractive index of liquids varies from 1.417 to 1.423, the measurement results show that the refractive-index sensitivity of the tapered fiber sensor is as high as 4860 nm/RIU.

Directional release of the stored ultrashort light pulses from a tunable Bragg-grating microcavity.

We demonstrate numerically the ability for directionally releasing the stored ultrashort light pulse from a microcavity by means of two-pulse nonlinear interaction in a cascading Bragg grating structure. The setting is built by a chirped grating segment which is linked through a uniform segment, including a tunable microcavity located at the junction between the two components. Our simulations show that stable trapping of an ultrashort light pulse can be achieved in the setting. The stored light pulse in a microcavity can be possibly released, by nonlinearly interacting with the lateral incident control pulse. Importantly, by breaking the symmetry of potential cavity, the stably trapped light pulse can be successfully released from the microcavity to the expected direction. Owing to the induced optical nonlinearity, the released ultrashort light pulses could preserve their shapes, propagating in a form of Bragg grating solitons through the uniform component, which is in contrast to the extensively studied light pulse trappings in photonic crystal cavities which operate at the linear regime.

Analiza slobodnih poprečnih oscilacija jednostepenastih Timošenkovih i Ojler-Bernulijevih štapova koršćenjem modifikovanog Hencky-evog modela kinematičkog lanca segmenata

In this paper, free transverse vibration of single-stepped Timoshenko and Euler-Bernoulli beams consisting of two uniform homogeneous segment with attached springs and lumped masses at the beam ends is analysed by using the modified Hencky bar-chain model. The effects of the springs and masses at the beam ends on the natural frequencies and mode shapes of the stepped beam is examined. Theoretical considerations are accompanied by numerical examples to illustrate the accuracy of the modified Hencky bar-chain model. The paper extends the application range of the modified Hencky bar-chain model in the field of vibration analysis of mechanical systems.

Micro pressure sensor with three degrees of freedom resonator

In this paper a micro pressure sensor having three degrees of freedom (DOF) resonating beam is proposed. The sensor comprises of a silicon square diaphragm, silicon frame with islands supporting a 3 DOF resonating beam made of silicon nitride. The analytical model of the non uniform diaphragm with islands as non uniform segment is designed and developed. The dimensions of the diaphragm and islands are optimized for linearity, high sensitivity and high stress distribution at free edges of the island for the applied input pressure range of 0–20 bar. The 3 DOF resonator and the resonator integrated with diaphragm are modelled numerically in COMSOL and CoventorWare respectively. Sensitivity analysis is carried out using analytical and numerical model and the proposed pressure sensor with 3 DOF resonator is found to have 5 % higher sensitivity as compared to the pressure sensor designed with single DOF resonating beam.

Biomedical segmented polyurethanes based on polyethylene glycol, poly(ε-caprolactone-co-D,L-lactide), and diurethane diisocyanates with uniform hard segment: Synthesis and properties

ABSTRACTIn the study, a new approach for synthesizing biomedical segmented polyurethanes (SPUs) based on polyethylene glycol (PEG, Mn = 800), poly(ε-caprolactone-co-D,L-lactide) (PCLA) and aliphatic diurethane diisocyanates with a long uniform hard segment was developed. By the chain extension of a mixture of PEG diol and PCLA diol with diurethane diisocyanates based on inexpensive 1,6-hexanediisocyanate, three SPUs (SPU-I, SPU-II, and SPU-III) with different contents of hydrophilic segments (PEG) and hard segments were obtained. The chemical structures of diurethane diisocyanates, PCLA and SPUs were confirmed by 1H NMR, 13C NMR, FT-IR, HR-TOF-MS, and GPC. The SPU films exhibited similar thermostability, indicating that the hard segment content marginally affects on the thermostability. From the results of differential scanning calorimetry, two glass transition temperatures were observed, suggesting the microphase separation of soft and hard segments. The SPU films exhibited satisfactory mechanical properties with ultimate stress of 17.4–22.3 MPa and strain at break of 890–1060%, and the initial modulus increased with the increasing content of hard segments. In vitro degradation studies indicated that the time of SPU films to become fragments was 22–33 days, and the degradation rate increased with the increasing content of hydrophilic segments in SPU. Hence, the degradation time of SPU films could be controlled by adjusting the PEG content in SPU, which made them good candidates for further biomedical applications. Studies of in vitro drug release were conducted using vitamin B1 as model drugs. Drug-loaded films exhibited a high initial release rate and matrix-controlled release for more than two weeks, thereby demonstrating a promising material for a long-acting controlled release system. Cytotoxicity test of film extracts and cell attachment on the film surface were conducted using L929 mouse fibroblasts, and the results indicated that the SPU films possess excellent cytocompatibility and cell adhesive ability.

Free Vibration Analysis for Shells of Revolution Using an Exact Dynamic Stiffness Method

An exact generalised formulation for the free vibration of shells of revolution with general shaped meridians and arbitrary boundary conditions is introduced. Starting from the basic shell theories, the vibration governing equations are obtained in the Hamilton form, from which dynamic stiffness is computed using the ordinary differential equations solver COLSYS. Natural frequencies and modes are determined by employing the Wittrick-Williams (W-W) algorithm in conjunction with the recursive Newton’s method, thus expanding the applications of the abovementioned techniques from one-dimensional skeletal structures to two-dimensional shells of revolution. A solution for solving the number of clamped-end frequenciesJ0in the W-W algorithm is presented for both uniform and nonuniform shell segment members. Based on these theories, a FORTRAN program is written. Numerical examples on circular cylindrical shells, hyperboloidal cooling tower shells, and spherical shells are given, and error analysis is performed. The convergence of the proposed method onJ0is verified, and comparisons with frequencies from existing literature show that the dynamic stiffness method is robust, reliable, and accurate.

Diagnosis of Buildings’ Thermal Performance - A Quantitative Method Using Thermography Under Non-steady State Heat Flow

This study describes a quantitative method using thermography to measure the thermal performance of complete building envelope elements that are subjected to non-steady state heat flow. The method presumes that thermal properties of external walls, like conductivity, could still be obtained by a linear regression over values of independent measurements. And therefore could be used during fluctuating indoor and outdoor thermal conditions. The method is divided into two parts. First, the convection heat transfer coefficient is measured by heat flux meters (HFM) and thermography. And then, the overall heat transfer coefficient of a complete building element is measured by thermography to include all non-uniformities.In this study the thermal performance of a 140mm thick laminated timber wall was measured. The wall was subjected to the outdoor weather conditions in Östersund, Sweden during January and February. The measurement values were found to have a large disparity as expected due to the rapid change in weather conditions. But still a linear regression with low confidence interval was obtained. The thermography results from a small uniform wall segment were validated with HFM measurements and 4% difference was found, which suggest that the two methods could be equally effective. Yet, thermography has the advantage of measuring surface temperature over large area of building element. The overall heat transfer coefficient of a large wall area was found to be 11% higher in comparison to the HFM measurements. This indicates that thermography could provide a more representative result as it captures areas of imperfections, point and linear thermal bridges.

A B-spline curve extension algorithm

B-spline curve extension is an important operation in computer aided design systems. In this paper, we present a new extension algorithm for B-spline curves. The algorithm uses curve unclamping to generate a uniform B-spline curve segment from the original curve and gradually extends the segment to pass through every target point. Algorithms of uniform B-spline curves are used such that our algorithm has a low time cost and can easily handle arbitrary-order derivative constraints at the target points. Generalization for non-uniform rational B-spline curve extension is also discussed, and examples show the efficiency of our method.