Two Classes of Optimal Fourth-Order Iterative Methods Free from Second Derivative for Solving Nonlinear Equations

This work proposes new fourth-order iterative methods to solve non-linear equations   . The iterative methods proposed here are presented by modifications of a third-order iterative method to be two classes of optimal fourth order. Convergence analysis was done for the iterative methods proposed in this paper. Multiple numerical examples were taken to explain the accuracy and efficiency of the proposed iterative methods

The implication Of BIM use on communication channels in design processes for Saudi architectural engineering (AE) firms

This research explores the implications of implementing building information modelling (BIM) on existing communication channels used in the design processes for professionals at architecture, engineering (AE) firms in the Kingdom of Saudi Arabia. Although considerable research on communication channels exists in terms of their effectiveness in collaborative environments, such as face to face meetings versus computer-mediated communication (CMC) technologies, to date relatively few studies have investigated the effect of implementing BIM on existing communication channel mechanisms at Saudi AE firms. In doing this research, three different concepts were mobilised in order to understand the dynamic processes of communication among diverse AE professionals in general, and within BIM collaborative environments in particular. Importantly, three different literatures: communication, team, and collaboration were considered as the main pillars of this study. In addition, this study reviewed theoretical communication process models (from linear to interaction processes), team theory, and cross-profession collaboration theory. Based on this review, 38 distinct factors were selected based on their impact on dynamic communication, team, and collaboration processes. These factors were grouped into three themes: 1) collaborative team characteristics; 2) leadership; and 3) methodology of information exchange. These themes were then used to develop an analytical framework to explore the implications and effects of BIM technology on the communication channels used by various professionals. Significantly, some overlap between these 38 factors was identified both within and across these themes, which subsequently assisted in developing the empirical research questions and in exploring further factors and their influence on communication channels during the qualitative data analysis process. To prepare for this research, a pilot study was first conducted on three Saudi AE organisations and one individual from the Saudi Ministry of Health. Based on the outcomes of this pilot study, a broader case study was then conducted on a leading Saudi AE firm that uses BIM. This study collected qualitative data through semi-structured interviews with 22 professionals in various departments at one prominent Saudi firm. The case study findings revealed that adopting BIM technology at this firm resulted in changes in the mechanisms used for communication channels among various professionals. Specifically, BIM adoption changed communication patterns (e.g. from formal to informal, and vice versa) and subsequently the type of communication channels used. As a result, one to one or group meetings paired with the use of hand sketches during such meetings emerged as the most preferred means of communication for these BIM users. In addition, when compared to the case study firm’s former CAD-based system, such changes were accompanied by reduced time spent on communication processes themselves and decreased dependence on previous communication channels (e.g. FTF meetings and email). However, no conclusive evidence emerged as to whether adopting BIM technology either reduced or increased the need for verbal communication at this firm. Importantly, this study concluded that adopting BIM changed the communication channels used at the firm, and that these changes were dynamic. Notably, the study results suggest that this phenomenon was a result of influences that were grouped into five themes: the communication protocols applied, the impact of rumours, the level of leadership, resistance to change, and the technical features of BIM technology. It is worth noting that of these five themes, four relate to the conditions and characteristics of the organisation, and the fifth concerns the characteristics of the BIM technology itself and the benefits it affords in improving information exchange processes. Given these findings, one could conclude that changes occurred in communication channels after the firm adopted BIM, and that these changes were due to the technical features of the technology and the organisational environment. However, the magnitude of the impact of the firm’s organisational environment had a major impact on these changes. With respect to contribution to knowledge, this study also found that the spread of rumours within or across the firm played a significant role in changing communication channels, either due to the process of verifying or responding to these rumours

Evaluation of Tribological aspects of Al-Si 12 alloy and their Metal Matrix hybrid Composites produced by Liquid-metal Forging Method

Particulate Aluminium Metal Matrix Composites (Al-MMC) have emerged as advanced engineering materials in view of their improved properties. Ceramic reinforced Al-MMC were more suitable because of being economical and exhibiting isotropic properties. Al-MMCs manufacturing methods are expensive, demand skilled and complex operations and vortex liquid metallurgy results into higher porosity. The liquid-metal forging/squeezed casting of stirred molten slurry can eliminate porosity as molten metal is pressurized during solidification forming near net shapes. During many instances, influence of process parameter (PP)s on mechanical part properties is being studied. In the present study, composites were produced using Al-Si12 alloy as base material, aluminium oxide and silicon carbide particles as reinforcements by varying the PPs. Tribological tests were conducted under dry sliding condition at room temperature showed hard reinforcements in Al alloy reduced the wear rate (WR) and increased the coefficient of friction (f) for all PPs. For PPs, increasing the squeeze pressure and decreasing the pouring and die preheating temperature resulted in a reduction of WR and f with an increase in normal load and sliding velocity. Initially f falls and then raised with an increase in normal load, but only raised with growing sliding velocity compared to Aluminium base material.

Evaluation of Tribological aspects of Al-Si 12 alloy and their Metal Matrix hybrid Composites produced by Liquid-metal Forging Method

Particulate Aluminium Metal Matrix Composites (Al-MMC) have emerged as advanced engineering materials in view of their improved properties. Ceramic reinforced Al-MMC were more suitable because of being economical and exhibiting isotropic properties. Al-MMCs manufacturing methods are expensive, demand skilled and complex operations and vortex liquid metallurgy results into higher porosity. The liquid-metal forging/squeezed casting of stirred molten slurry can eliminate porosity as molten metal is pressurized during solidification forming near net shapes. During many instances, influence of process parameter (PP)s on mechanical part properties is being studied. In the present study, composites were produced using Al-Si12 alloy as base material, aluminium oxide and silicon carbide particles as reinforcements by varying the PPs. Tribological tests were conducted under dry sliding condition at room temperature showed hard reinforcements in Al alloy reduced the wear rate (WR) and increased the coefficient of friction (f) for all PPs. For PPs, increasing the squeeze pressure and decreasing the pouring and die preheating temperature resulted in a reduction of WR and f with an increase in normal load and sliding velocity. Initially f falls and then raised with an increase in normal load, but only raised with growing sliding velocity compared to Aluminium base material.

Steering proton migration in hydrocarbons using intense few-cycle laser fields

Proton migration is a ubiquitous process in chemical reactions related to biology, combustion, and catalysis. Thus, the ability to control the movement of nuclei with tailored light, within a hydrocarbon molecule holds promise for far-reaching applications. Here, we demonstrate the steering of hydrogen migration in simple hydrocarbons, namely acetylene and allene, using waveform-controlled, few-cycle laser pulses. The rearrangement dynamics are monitored using coincident 3D momentum imaging spectroscopy, and described with a quantum-dynamical model. Our observations reveal that the underlying control mechanism is due to the manipulation of the phases in a vibrational wavepacket by the intense off-resonant laser field.Comment: 5 pages, 4 figure

Worrying about climate change

The paper discusses the impact of climate change on ten sectors: water, water desalination, energy, renewable energy supply, health, society, agriculture, economy, industry, and built environment. Each of the sectors has unique characteristics that require special consideration. Planning for climate change adaptation is among the most complex challenges cities are facing today. Climatic alterations put a strain on 1) energy needs for cooling/heating and release of anthropogenic heat, 2) mortality and morbidity due to air pollution and air turbidity, 3) productivity and wellbeing, and 4) accessibility to public spaces and social prosperity. There are many innovate ideas and proposals suggested in order to minimize the impact of climate change, but no simple solution exists because of the interdependence and fast-moving technological solutions, and the role of the policy makers in setting targets and providing finance for solutions

Carbon K-shell Photo Ionization of CO: Molecular frame angular Distributions of normal and conjugate shakeup Satellites

We have measured the molecular frame angular distributions of photoelectrons emitted from the Carbon K shell of fixed-in-space CO molecules for the case of simultaneous excitation of the remaining molecular ion. Normal and conjugate shake up states are observed. Photo electrons belonging to normal \Sigma -satellite lines show an angular distribution resembling that observed for the main photoline at the same electron energy. Surprisingly a similar shape is found for conjugate shake up states with \Pi -symmetry. In our data we identify shake rather than electron scattering (PEVE) as the mechanism producing the conjugate lines. The angular distributions clearly show the presence of a \Sigma -shape resonance for all of the satellite lines.Comment: 8 pages, 2 figure

A Closer Look at Precision Hard Turning of AISI4340: Multi-Objective Optimization for Simultaneous Low Surface Roughness and High Productivity

This article reports an extended investigation into the precision hard turning of AISI 4340 alloy steel when machined by two different types of inserts: wiper nose and conventional round nose. It provides a closer look at previously published work and aims at determining the optimal process parameters for simultaneously minimizing surface roughness and maximizing productivity. In the mathematical models developed by the authors, surface roughness at different cutting speeds, depths of cut and feed rates is treated as the objective function. Three robust multi-objective techniques, (1) multi-objective genetic algorithm (MOGA), (2) multi-objective Pareto search algorithm (MOPSA) and (3) multi-objective emperor penguin colony algorithm (MOEPCA), were used to determine the optimal turning parameters when either the wiper or the conventional insert is used, and the results were experimentally validated. To investigate the practicality of the optimization algorithms, two turning scenarios were used. These were the machining of the combustion chamber of a gun barrel, first with an average roughness (Ra) of 0.4 µm and then with 0.8 µm, under conditions of high productivity. In terms of the simultaneous achievement of both high surface quality and productivity in precision hard turning of AISI 4340 alloy steel, this work illustrates that MOPSA provides the best optimal solution for the wiper insert case, and MOEPCA results are the best for the conventional insert. Furthermore, the results extracted from Pareto front plots show that the wiper insert is capable of successfully meeting both the requirements of Ra values of 0.4 µm and 0.8 µm and high productivity. However, the conventional insert could not meet the 0.4 µm Ra requirement; the recorded global minimum was Ra = 0.454 µm, which reveals the superiority of the wiper compared to the conventional insert

Capture into Rydberg states and momentum distributions of ionized electrons

The yield of neutral excited atoms and low-energy photoelectrons generated by the electron dynamics in the combined Coulomb and laser field after tunneling is investigated. We present results of Monte-Carlo simulations built on the two-step semiclassical model, as well as analytic estimates and scaling relations for the population trapping into the Rydberg states. It is shown that mainly those electrons are captured into bound states of the neutral atom that due to their initial conditions (i) have moderate drift momentum imparted by the laser field and (ii) avoid strong interaction ("hard" collision) with the ion. In addition, it is demonstrated that the channel of capture, when accounted for in semiclassical calculations, has a pronounced effect on the momentum distribution of electrons with small positive energy. For the parameters that we investigated its presence leads to a dip at zero momentum in the longitudinal momentum distribution of the ionized electrons.Comment: 9 pages, 8 figures in one zip-archiv