The pile groups support large foundation structures which often experience cyclic torsional loads. Several theoretical and experimental investigations were carried out on pile groups under axial and ...lateral cyclic loads; however, the study of the response of cyclic torsional loads on pile foundation groups remains elusive. This paper proposes a numerical scheme to capture the behavior of the symmetrical pile group in the flow-controlled geomaterial under cyclic torsional loading. Based on the numerical scheme, three-dimensional finite element analysis was performed to capture the nonlinear response of the pile group using a computational program. The results from the numerical analysis have been compared with the experimental observations. The peak twist and peak shear stress logarithmically decrease and then become asymptotic after a number of cycles of loading for a pile group (2,2) in a flow-controlled geomaterial. A set of cyclic degradation parameters of flow-controlled geomaterial is identified for the pile group and presented as a function of dilation.
The problem of deriving decision-making policies, subject to some formal specification of behavior, has been well-studied in the control synthesis, reinforcement learning, and planning communities. ...Such problems are typically framed in the context of a non-deterministic decision process, the non-determinism of which is optimally resolved by the computed policy. In this paper, we explore the derivation of such policies in Markov decision processes (MDPs) subject to two types of formal specifications. First, we consider steady-state specifications that reason about the infinite-frequency behavior of the resulting agent. This behavior corresponds to the frequency with which an agent visits each state as it follows its decision-making policy indefinitely. Second, we examine the infinite-trace behavior of the agent by imposing Linear Temporal Logic (LTL) constraints on the behavior induced by the resulting policy. We present an algorithm to find a deterministic policy satisfying LTL and steady-state constraints by characterizing the solutions as an integer linear program (ILP) and experimentally evaluate our approach. In our experimental results section, we evaluate the proposed ILP using MDPs with stochastic and deterministic transitions.
This paper presents the effect of confined granular fill on the efficiency of embedded PZT (Lead Zirconate Titanate) patches. The experiments are carried out to capture the dynamic response of ...confined granular fill and voltage output. The dynamic response of the system is analysed using the fast Fourier transformation (FFT) of vibration and digital static cone penetrometer (DSCP) test at various excitation frequencies. The peak pick method is used to determine the damping loss factor and natural frequency. The efficiency of voltage generation of embedded PZT patches is influenced by the depth of embedment, excitation frequency, location, and engineering properties of the confined granular fill. The results show that the influence of vibration frequency and placement of PZT on the output voltage should be considered. The thickness and engineering properties of granular soil affect the efficiency of voltage output. This study emphasizes the utility of PZT patches in the subgrade and structural health monitoring of various geotechnical structures.
The energy harvesting from ambient vibrations in the confined granular fill along the expressways and highways is a prospective power source for varied engineering applications. This paper presents ...the study of charge density, voltage output, and power from the PZT (lead zirconate titanate) patches embedded in dynamically loaded confined granular fill. The effect of the alignment of PZT patches, thickness ratio, material properties of the confined granular fill, and retaining structure on the voltage output is investigated. It provides the scope for the evaluation of voltage output directly from the stress-strain response, position of the PZT patch, and the engineering properties of the confined granular fill. The alignment of PZT patches in the horizontal and vertical directions has been examined analytically to optimize voltage outputs. The results indicate that the modulus ratio of the material, alignment of PZT patches, and gradation of infill material significantly affect the voltage generation. A relationship for voltage and power output has been proposed for a set of engineering applications. The observed voltage output is found appropriate for wide-ranging implements classified as low- (LRA), medium- (MRA), and high- (HRA) resistance applications. It is proposed to be up-scaled using multiple patches embedded throughout the confined granular fill and pavements subjected to continuous dynamic loads.
In this study, a new model was presented for computing strength of rock masses based upon in-situ observations of RQD popularly known as rock quality designation. This model links up the rock mass ...parameters from in-situ investigations with the strength parameters of jointed rocks obtained from laboratory scale experimental observations. Using the constitutive relation, the author derived a pressure and damage sensitive plastic parameter to determine strength of rock masses for varied extents of discontinuity and pressure induced damage. The test results show that plasticity characterized by hardening and softening inclusive of damage invariably depends upon mean pressure and extent of deformations already experienced by rock masses. The present work explores the test data that reveal the dependence of in-situ strength on incremental joint parameters obtained from the joint number, joint orientation, joint roughness, gouge parameters and water pressure. Substituting the relationship between the RQD and modified joint factor with that between modulus ratio and strength ratio, the model shows successfully that using damage inclusive plastic parameter and RQD provides a relationship for estimating the strength of rock masses. One of the main objectives of this work is to illustrate that the present model is sensitive to plasticity and damage together in estimating in-situ strength of rock masses in foundations, underground excavation and tunnels.
A fuzzy logic (FL)–based modeling approach is employed for geogrid-reinforced subgrade soil of unpaved roads. A review of the literature reveals that fuzzy logic has not been used for predicting the ...behavior of geogrid-reinforced subgrade. This paper presents FL-based two models with fuzzy Triangular and Gaussian membership functions for input and output variables. It consists of eight input parameters/factors, namely, reinforced/unreinforced section, depth of reinforcement, liquid limit, plastic limit, plasticity index, optimum moisture content, maximum dry unit weight, and soaked/unsoaked condition, and California bearing ratio (
CBR
) as an output parameter. The fuzzy rules are deduced from the experimental data. The laboratory
CBR
tests were performed on the subgrade soil reinforced with geogrid. The precision of models was examined by comparing the predicted
CBR
values with the experimental
CBR
values for Triangular and Gaussian membership functions. The sensitivity analysis reflects a set of dominant parameters. The results indicated a significant improvement in the
CBR
value of geogrid-reinforced subgrade soil due to the inclusion of geogrid. The range for optimal depth of geogrid reinforcement is found to be 36 to 60% of the thickness of the soil layer. The potentialities of FL were found to be satisfactory.
The engineering structures consist of machine foundations, pavement, subgrade, bridge abutment, railway track, retaining wall, and contact geo-material. These structures are subjected to ambient ...mechanical vibration due to dynamic loads. The mechanical vibration of the structures can be utilized for power generation using the electromechanical conversion characteristics of the piezoelectric material. This paper captures recent advances in modelling PEH (piezoelectric energy harvester) and numerical techniques for power generation from structures. The electromechanical coupling of the structures with PEH is the key factor for the voltage and power output. The coupling techniques of structures and energy harvesters are significantly affected by the variables, namely fundamental frequency, the contact pressure of loading, the geometry of the structure, moving load frequency, placement of harvester, and dynamic response of the contact material. The mode of operation of PEH (31 vs. 33 modes) significantly influences the dynamic input and power output from the structure-power generation system. The present study demonstrates the potential of power generation from mechanical vibration of geo-structures has been classified as low, moderate, and high power output. It recommends the coupling parameters for the structural design to improve the efficacy of power generation from the ambient vibration of geo-structures.
Information leaks via side channels remain a challenging problem to guarantee confidentiality. Static analysis is a prevalent approach for detecting side channels. However, the side-channel analysis ...poses challenges to the static techniques since they arise from non-functional aspects of systems and require an analysis of multiple traces. In addition, the outcome of static analysis is usually restricted to binary answers. In practice, real-world applications may need to disclose some aspects of the confidential information to ensure desired functionality. Therefore,
quantification
techniques are necessary to evaluate the resulting threats. In this paper, we propose a dynamic analysis technique to detect and quantify side channels. Our novel approach is to split the problem into two tasks. First, we learn a timing model of the program as a neural network. While the program implements the functionality, the neural network models the non-functional property that does not exist in the syntax or semantics of programs. Second, we analyze the neural network to quantify information leaks. As demonstrated in our experiments, both of these tasks are feasible in practice—making the approach a significant improvement over state-of-the-art side channel detectors and quantifiers. Thus, our key technical contributions are (a) a
binarized neural network
architecture that enables side-channel discovery and (b) a novel
MILP-based counting algorithm
to estimate the side-channel strength. On a set of benchmarks, we show that neural network models the timing of programs with thousands of methods precisely. We also show that neural networks with thousands of neurons can be efficiently analyzed to quantify information leaks via timing side channels.
Inductive approaches to deductive verification has gained widespread adoption in the control and verification of safety-critical dynamical systems. The practical success of barrier certificates ...attests to their effectiveness and ongoing theoretical and practical refinement. However, when verification conditions are non-inductive, various strategies are employed to address this issue. One strategy is to strengthen the property until they arrive at an inductive proof. However, it is not always obvious how one must strengthen a property. Notions of strenghtening are particularly non-obvious when the properties of interest are more expressive than safety or reachability. An alternative technique is to instead consider structural changes. These structural changes may either be to consider novel notions of induction such as <inline-formula><tex-math notation="LaTeX">k</tex-math></inline-formula>-induction, or to encode additional information similar to dimension lifting. We posit that reformulating or restructuring of the system is fundamental to inductive approaches. This position article provides an overview of barrier certificate based verification approaches and their connection to system restructuring. We discuss the opportunities, challenges, and open problems in this emerging field, paving the way for future research in the verification of safety-critical dynamical systems. The framework of restructuring of a system holds promise for advancing deductive verification, enhancing system safety, and promoting design insights.
The need to reduce the use of fossil fuels and greenhouse gas (GHG) emissions produced by the transport sector has generated a clear increasing trend in transportation electrification and the future ...of energy and mobility. This paper reviews the current research trends and future work for power electronics-based solutions that support the integration of photovoltaic (PV) energy sources and smart grid with charging systems for electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEV). A compressive overview of isolated and non-isolated DC–DC converters and AC–DC converter topologies used to interface the PV-grid charging facilities is presented. Furthermore, this paper reviews the modes of operation of the system currently used. Finally, this paper explores the future roadmap of research for power electronics solutions related to photovoltaic (PV) systems, smart grid, and transportation electrification.
PDF
