Infiltration under Ponded Conditions

Ponded infiltration processes occur in agricultural lands irrigated by flooding of their soil surface or under insufficient drainage conditions. The existing equations describing the phenomenon of vertical infiltration under ponded conditions have not considered the actual contribution of the pressure head gradient to the flow. In this study, simple equations are proposed to describe the horizontal and vertical infiltration under various ponding heads incorporating the actual contribution of the pressure head gradient to the flow. Six soils with known hydraulic properties, covering a wide range of soil textures, were used. Horizontal and vertical infiltration data are obtained by numerical simulation for all soils studied using the Hydrus-1D code. To validate the accuracy of the proposed equations, the solutions of horizontal and vertical infiltrations provided by the proposed equations were compared with numerically simulated ones provided by the Hydrus 1-D. The analysis of the results showed a very good agreement in all soils studied. The proposed vertical infiltration equation was also compared to a simple and accurate equation which does not incorporate the actual contribution of the pressure head gradient to the flow and differences between them were observed in all soils studied.

Simple Equations Method and Non-Linear Differential Equations with Non-Polynomial Non-Linearity

We discuss the application of the Simple Equations Method (SEsM) for obtaining exact solutions of non-linear differential equations to several cases of equations containing non-polynomial non-linearity. The main idea of the study is to use an appropriate transformation at Step (1.) of SEsM. This transformation has to convert the non-polynomial non- linearity to polynomial non-linearity. Then, an appropriate solution is constructed. This solution is a composite function of solutions of more simple equations. The application of the solution reduces the differential equation to a system of non-linear algebraic equations. We list 10 possible appropriate transformations. Two examples for the application of the methodology are presented. In the first example, we obtain kink and anti- kink solutions of the solved equation. The second example illustrates another point of the study. The point is as follows. In some cases, the simple equations used in SEsM do not have solutions expressed by elementary functions or by the frequently used special functions. In such cases, we can use a special function, which is the solution of an appropriate ordinary differential equation, containing polynomial non-linearity. Specific cases of the use of this function are presented in the second example.

Diffusion of chloride from seawater into the concrete analysis: a literature review on implemented approaches

Infrastructures near the sea, such as ports, offshore platforms, bridges, and coastal buildings, are affected by seawater due to the coastal region. Chloride, contained in seawater, causes a decrease in the strength and durability of the concrete. Some researchers have published a paper on analyzing the penetration of chloride ions into concrete under different coastal environments and predicted chloride diffusion in concrete with computational modeling. This paper aims to review the existing literature related to various laboratory work tests and analytical methods in evaluating the diffusion of chloride from seawater into concrete. A set of forty papers were collected and reviewed that were published from 2011 until 2020 for studying. The review showed that chloride diffusion was a complex process and affected by many factors such as material properties, curing time, immersion/exposure time, and environmental conditions. Various experimental methods in the Laboratory were conducted using concrete specimens made from various materials in the exposed and submerged conditions. Researches in the field were carried out on existing structures with a certain building age using non-destructive testing. Meanwhile, the analytical methods applied simple equations and numerical simulation computational software.

An Enhanced Parallelisation Model for Performance Prediction of Apache Spark on a Multinode Hadoop Cluster

Big data frameworks play a vital role in storing, processing, and analysing large datasets. Apache Spark has been established as one of the most popular big data engines for its efficiency and reliability. However, one of the significant problems of the Spark system is performance prediction. Spark has more than 150 configurable parameters, and configuration of so many parameters is challenging task when determining the suitable parameters for the system. In this paper, we proposed two distinct parallelisation models for performance prediction. Our insight is that each node in a Hadoop cluster can communicate with identical nodes, and a certain function of the non-parallelisable runtime can be estimated accordingly. Both models use simple equations that allows us to predict the runtime when the size of the job and the number of executables are known. The proposed models were evaluated based on five HiBench workloads, Kmeans, PageRank, Graph (NWeight), SVM, and WordCount. The workload’s empirical data were fitted with one of the two models meeting the accuracy requirements. Finally, the experimental findings show that the model can be a handy and helpful tool for scheduling and planning system deployment.

Determining the fuel consumption of a public city bus in urban traffic

The fuel consumption of a public transport bus depends on many factors. Various speeds, acceleration and deceleration modes, stopping times at bus stops and congestion, as well as the load depending on the number of transported passengers have a significant impact on the fuel consumption of the city bus. It is difficult to investigate the influence of these factors on fuel consumption using simple equations to determine the energy efficiency of vehicles. A very useful method in this case is the VSP (Vehicle Specific Power) method. The fuel consumption model based on this method uses a number of parameters. Taking into account the measurement data obtained from the actual mileage of city buses, the relevant parameters of the model were determined. The verified model was used in the process of computer simulation aimed at determining the fuel consumption of the bus in urban traffic. Particular attention was paid to the study of the impact of traffic during rush hours and congestion on fuel consumption. The impact and significance of the selected parameters on the fuel consumption of the city bus were also assessed using computer simulations.

On the Use of Composite Functions in the Simple Equations Method to Obtain Exact Solutions of Nonlinear Differential Equations

We discuss the Simple Equations Method (SEsM) for obtaining exact solutions of a class of nonlinear differential equations containing polynomial nonlinearities. We present an amended version of the methodology, which is based on the use of composite functions. The number of steps of the SEsM was reduced from seven to four in the amended version of the methodology. For the case of nonlinear differential equations with polynomial nonlinearities, SEsM can reduce the solved equations to a system of nonlinear algebraic equations. Each nontrivial solution of this algebraic system leads to an exact solution of the solved nonlinear differential equations. We prove the theorems and present examples for the use of composite functions in the methodology of the SEsM for the following three kinds of composite functions: (i) a composite function of one function of one independent variable; (ii) a composite function of two functions of two independent variables; (iii) a composite function of three functions of two independent variables.

Design recommendations to prevent global out-of-plane instability of rectangular reinforced concrete ductile walls

Observations of out-of-plane (OOP) instability in the 2010 Chile earthquake and in the 2011 Christchurch earthquake resulted in concerns about the current design provisions of structural walls. This mode of failure was previously observed in the experimental response of some wall specimens subjected to in-plane loading. Therefore, the postulations proposed for prediction of the limit states corresponding to OOP instability of rectangular walls are generally based on stability analysis under in-plane loading only. These approaches address stability of a cracked wall section when subjected to compression, thereby considering the level of residual strain developed in the reinforcement as the parameter that prevents timely crack closure of the wall section and induces stability failure. The New Zealand code requirements addressing the OOP instability of structural walls are based on the assumptions used in the literature and the analytical methods proposed for mathematical determination of the critical strain values. In this study, a parametric study is conducted using a numerical model capable of simulating OOP instability of rectangular walls to evaluate sensitivity of the OOP response of rectangular walls to variation of different parameters identified to be governing this failure mechanism. The effects of wall slenderness (unsupported height-to-thickness) ratio, longitudinal reinforcement ratio of the boundary regions and length on the OOP response of walls are evaluated. A clear trend was observed regarding the influence of these parameters on the initiation of OOP displacement, based on which simple equations are proposed for prediction of OOP instability in rectangular walls.

Review on Ship Manoeuvrability Criteria and Standards

Possible reduction of the installed power on newly designed merchant ships triggered by requirements of the Energy Efficiency Design Indices (EEDI) raised concern in possible safety degradation and revived interest in manoeuvrability standards to make them capable to compensate for negative effects of underpowering. A substantial part of the present article presents a detailed analytical review of general principles laid in the foundation of consistent safety standards in the naval architecture and analysis of the existing IMO manoeuvrability criteria and standards. Possible ways of extension of the existing standards to embrace situations associated with adverse sea and wind conditions are discussed and modification of the present standards related to the directional stability is considered as one of the possible solutions. At the same time, it was found that introduction of additional standards for the ship controllability in wind is justified, and the second part of the contribution is dedicated to developing a theoretical basis useful for devising such standards. This includes obtaining a set of analytical solutions related to the steady motion in wind and analysis of wind-tunnel data which resulted in simple equations for conservative generalized envelopes for the aerodynamic forces which are especially convenient for standardizing purposes. Possible design decisions aimed at augmentation of the ship’s capacity to resist adverse environmental factors are outlined.

Significance of Stable Crack Extension to Fatigue Crack Growth

A long-overlooked aspect of fatigue crack growth is the potential contribution to it, of stable crack extension (SCE). Reduction in specimen size and increase in magnitude of cyclic loading will induce increased contribution of SCE. SCE as a load interaction effect is manifest in disproportionately high crack extension due to periodic overloads. SCE can exceed by more than an order of magnitude estimates of crack growth from the da/dN versus DK relationship. Simple equations are proposed to account for SCE in fatigue crack growth. A numerical analysis is performed to characterize the significance of SCE to constant amplitude and variable amplitude fatigue crack growth.

Global Tree Taper Modelling: A Review of Applications, Methods, Functions, and Their Parameters

Taper functions are important tools for forest description, modelling, assessment, and management. A large number of studies have been conducted to develop and improve taper functions; however, few review studies have been dedicated to addressing their development and parameters. This review summarises the development of taper functions by considering their parameterisation, geographic and species-specific limitations, and applications. This study showed that there has been an increase in the number of studies of taper function and contemporary methods have been developed for the establishment of these functions. The reviewed studies also show that taper functions have been developed from simple equations in the early 1900s to complex functions in modern times. Early taper functions included polynomial, sigmoid, principal component analysis (PCA), and linear mixed functions, while contemporary machine learning (ML) approaches include artificial neural network (ANN) and random forest (RF). Further analysis of the published literature also shows that most of the studies of taper functions have been carried out in Europe and the Americas, meaning most taper equations are not specifically applicable to tropical tree species. Developing well-conditioned taper functions requires reducing the variation due to species, measurement techniques, and climatic conditions, among other factors. The information presented in this study is important for understanding and developing taper functions. Future studies can focus on developing better taper functions by incorporating emerging remote sensing and geospatial datasets, and using contemporary statistical approaches such as ANN and RF.