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This study establishes a method for predicting ground vibrations caused by railway tunnels in unsaturated soils with spatial variability.

First, an improved 2.5D finite-element-method-perfect-matching-layer (FEM-PML) model is proposed. The Galerkin method is used to derive the finite element expression in the ub-pl-pg format for unsaturated soil. Unlike the ub-v-w format, which has nine degrees of freedom per node, the ub-pl-pg format has only five degrees of freedom per node; this significantly enhances the calculation efficiency. The stretching function of the PML is adopted to handle the unlimited boundary domain. Additionally, the 2.5D FEM-PML model couples the tunnel, vehicle and track structures. Next, the spatial variability of the soil parameters is simulated by random fields using the Monte Carlo method. By incorporating random fields of soil parameters into the 2.5D FEM-PML model, the effect of soil spatial variability on ground vibrations is demonstrated using a case study.

The spatial variability of the soil parameters primarily affected the vibration acceleration amplitude but had a minor effect on its spatial distribution and attenuation over time. In addition, ground vibration acceleration was more affected by the spatial variability of the soil bulk modulus of compressibility than by that of saturation.

Using the 2.5D FEM-PML model in the ub-pl-pg format of unsaturated soil enhances the computational efficiency. On this basis, with the random fields established by Monte Carlo simulation, the model can calculate the reliability of soil dynamics, which was rarely considered by previous models.

The past few decades have witnessed a phenomenal progress in our understanding of employee mobility as a critical driver and consequence of various outcomes for individuals, organizations, industries, and economies. In the process, researchers have tackled several important issues in conducting empirical research on employee mobility. This chapter provides a critical discussion of the extant literature focusing on five broad areas: identification of mobility, timing of mobility, outcomes of mobility and their operationalization, model identification, and other related issues. In doing so, this article identifies some of the empirical choices and methodologies adopted in prior mobility studies, evaluates those practices, and suggests areas of improvements for the practice. It is hoped that future studies will benefit from this chapter's insight by building on the best practices from the literature while continuously and successfully tackling the issues that have been challenging the researchers on this increasingly important topic of scholarly inquiry.

The decoupling and asynchrony properties of the content‐based publish‐subscribe paradigm makes it very appealing for dynamic wireless networks, like those that often occur in pervasive computing scenarios. Unfortunately, most of the currently available content‐based publish‐subscribe middleware do not fit the requirements of such extreme scenarios, in which the network is subject to very frequent topological reconfigurations due to mobility of nodes. In this paper we propose a protocol for content‐based message dissemination tailored to Mobile Ad Hoc Networks (MANETs) showing frequent topological changes. Message routing occurs without the support of any network‐wide dispatching infrastructure thus eliminating the need of maintaining such infrastructure on top of a physical network continuously changing its topology. The paper reports an extensive simulation study that confirms the suitability of the proposed approach along with a stochastic analysis of the central mechanism adopted by the protocol.

The paper aims to predict longitudinal deformation of a tunnel caused by grouting under the tunnel bottom in advance according to the grouting parameters, which can ensure the safety of the tunnel structure during the grouting process and also help to design the grouting parameters.

The paper adopted the analytical approach for calculating the longitudinal deformation of a shield tunnel caused by grouting under a tunnel, including usage of the Mindlin’s solution, the minimum potential energy principle and case validation.

The paper provides a variational method for calculating the longitudinal deformation of a shield tunnel in soft soil caused by grouting under the tunnel, which has high computational efficiency and accuracy.

This paper fulfils an identified need to study how the longitudinal deformation of a shield tunnel in soft soil caused by grouting under the tunnel can be calculated.

The application of servo steel struts enables the active control of the excavation-induced deformation in foundation pits. However, there is currently only one design axial force for each servo steel strut, which requires in-situ axial force adjustments based on the experience of site engineers. The purpose of this study is to develop a method for determining the design axial forces of servo steel struts at different excavation steps.

In this study, a hybrid method for determining the design axial forces of servo steel struts in different excavation steps was established based on the combination of the elastic foundation beam model and nonlinear optimisation.

The hybrid method is capable of providing a better set of design axial forces than the original design method. The lateral wall displacement and bending moment could be better controlled. Ordinary steel struts should be prevented from being set between servo steel struts to avoid axial force losses.

The axial forces of the servo steel struts at different excavation steps should be designed to achieve better deformation control effects. Moreover, a well-designed set of axial forces can also reduce the internal forces of the retaining structure.

The hybrid method enables the determination of the design axial forces of servo steel struts at different excavation steps, which can guide axial force adjustments in practical projects.

Existing studies show that firms may have an incentive to use share repurchases opportunistically, thereby taking advantage of market participants’ confirmation bias that share repurchase is a signal of undervaluation. This study aims to investigate whether signaling costs and accounting transparency can serve as tools to identify opportunistic share repurchases.

The authors measure signaling costs by using two share repurchase methods (direct and indirect share repurchase) with different share repurchase costs, and measure accounting transparency using the history of earnings timeliness. The authors further measure long-term performance following share repurchases using operating performance and stock returns. Lastly, the authors compare the long-term performances between the groups defined by share repurchase method and earnings timeliness level.

The authors find that indirect share repurchase firms with a history of poor earnings timeliness experience unfavorable long-term performance, while other share repurchase firms do not. This finding reinforces the view that some share repurchases may be driven by managerial opportunism. In particular, when firms with a history of poor earnings-reporting behavior choose a low-cost repurchase method, their share repurchases may be motivated by managerial opportunism.

The findings suggest that past earnings timeliness and the signaling costs of a repurchase together are useful predictors of false signaling. Moreover, they suggest that investors can – at least in part – predict opportunistic share repurchases by using signaling costs and accounting transparency.

IN recent years the bogie type of multi‐wheel undercarriage has been introduced on the medium and heavy range of aircraft. The trend began because of the necessity of keeping runway loadings to a minimum and the difficulty of stowing a large diameter single wheel in the wing or fuselage during flight. By spreading the main undercarriage ground reaction through two, four or more wheels, existing runways are able to accommodate heavier aircraft, while faster operational flight speeds have resulted in relatively thinner wing sections aggravating the stowage problem of the undercarriage. The interpretation of the bogie into practical undercarriages with their manifold performance duties has led to several types of mechanisms each with distinctive dynamical features. One such mechanism is the semi‐articulated bogie type and its general features have been previously described, The claims made for this undercarriage have been substantiated through several years of successful operational experience. Since this particular arrangement has obvious future applications both as a twin‐ or multi‐wheel version and, as it possesses characteristic dynamical features, it is considered appropriate to place on record the analysis of its landing performance.

Logistics real estate has been experiencing a recent rebirth led by the growth of retailing and e-commerce. Although these sectors are looking for facilities matching their logistics needs, the identification of the most suitable building becomes a challenging task. To date, from both the practitioner’s and academic perspectives there is a lack of models for assessing the quality of logistics facilities together with functionality (i.e. whether a warehouse is suitable for hosting a given logistics activity). The purpose of this paper is to fill this gap by developing a rating model for assessing the quality and functionality of logistics facilities.

A three-pronged methodology was adopted. First, a Systematic Literature Network Analysis (SLNA) was carried out to identify the relevant features that must be taken into consideration when assessing logistics real estate. Second, a Delphi method involving experts in the field was used to fine-tune the list of features that emerged from the SLNA process and to evaluate the importance of each feature from a company perspective. The rating model was developed and validated through pilot tests on 27 logistics facilities.

The rating model is divided into four sections: location, technical specifications, external spaces and internal areas. As an output, the model determines the building quality and main functionality, together with a gap analysis to detect the weakest emerging elements.

This research fills an identified research gap in the logistics real estate literature. Specifically, it offers a quantitative and shared evaluation method, which can be used to estimate building quality and functionality, thus extending the scope of the previous assessment methods available.

The purpose of this study is to experimentally and numerically scrutinize the heat transfer enhancement in pool boiling and condensation by changing the hydrophilicity or hydrophobicity properties of the working fluid, i.e. by use of nanofluid solution.

For specifying the effects of nanoparticle concentration on heat transfer properties, two different nanofluid solutions (h-BN/DCM and SiO₂/DCM) at three different volumetric concentrations were prepared and tested under different heat flux conditions. Boiling curves, alterations in pressure with heat flux and heat transfer coefficients for both boiling and condensation processes were obtained and viscosity measurements were performed for dichloromethane (DCM) and each working fluid was prepared. In addition, a series of numerical simulations, via computational fluid dynamics approach, was performed for specifying the evaporation–condensation phenomena and temperature and velocity distributions.

Nanoparticle addition inside the base fluid increased the thermal characteristics of the base fluid significantly. For the experimental results of h-BN/DCM nanofluid, the increment rate in heat transfer coefficient for saturation boiling, after-saturation boiling and condensation processes was found as 27.59%, 14.44% and 15%, respectively.

The novelty of this comparison study is that there is no such experimental and numerical comparison study in literature for DCM fluid, which concentrates on thermal performance enhancement and compares the effect of different kinds of nanoparticles on heat transfer characteristics for boiling–condensation processes.