Simplified Simulation Approach Research Articles

Research on Course-Changing Performance of a Large Ship with Spoiler Fins

The poor maneuverability inherent to large ships is a non-negligible problem that restricts the development of the shipping industry, as large ships can only cruise at an excessively conservative speed when they encounter complicated traffic conditions; nevertheless, ship collision accidents still occasionally occur. In the present study, the novel concept of spoiler fins for modern large ships is proposed. In order to assess their effectiveness in enhancing ship maneuverability, a KRISO container ship (KCS) was selected to carry a pair of spoiler fins, after which a simplified simulation approach for saving the calculation resource was designed for ship collision avoidance conditions, and a full-scale numerical model, including the ship hull, fin, and fluid field domain, was established. Transient-state hydrodynamic forces were calculated during collision avoidance maneuvers using the CFD method; the pressure and velocity contours around the ship were demonstrated; and the ship motion trajectories under different initial ship speeds were simulated and predicted through the adoption of overset mesh and 6-DOF dynamic mesh techniques. Eventually, the improved course-changing performance, dependent on the spoiler fins, was validated.

Trim Analysis and Structured H-Infinity Control of Wing-Docked Multibody Aircraft

A wing-docked multibody aircraft is a novel configuration being explored as a balanced solution between efficiency and structural resilience for very long-endurance aviation. The presence of wingtip hinges complicates the dynamics and control of this class of aircraft but has thus far only been analyzed in specific cases. In this work, we make a comprehensive exploration of parameter space of the multibody trim problem and stability and demonstrate the treatment of the control problem using the robust H∞ synthesis technique. We propose a simplified simulation approach to the static trim analysis and demonstrate key observations relating to the configurations and open-loop dynamic stability of multibody aircraft in general. An interpolated parameter-scheduling model using the hinge angle as a scheduling parameter is established, based on which the structured multimodel H∞ synthesis method is employed to synthesize the robust flight controllers. Simulation results show that the designed controllers are capable of configuration control within the range of possible trim solutions and have also achieved good control effectiveness in path following and disturbance rejection. The proposed trim analysis and control techniques serve to provide a systematic benchmark study on wing-docked multibody aircraft dynamics, which is valuable to the development of this research area.

Effect of attached outlets on the dynamic response of arch dams

Attached outlets are integral components of arch dams to discharge flood. However, they are usually neglected in the current seismic analysis of arch dams for simplicity. This paper aims to analyze the effect of attached outlets on the nonlinear seismic response of arch dams. For this purpose, a 235 m high arch dam is analyzed as a case study. The results indicate that the effect of attached outlets on the seismic response of arch dams depends on the ground motion intensity. For the ground motions with a low peak ground acceleration (PGA), the effect of attached outlets on the concrete damage is slight and local, which is consistent with the existing perception. However, as the ground motion intensity increases, their effect extends to the entire dam body. In contrast, the influence of attached outlets on the joint opening is typically observed at the middle contraction joints. Furthermore, the model analysis demonstrates that the inertia effect of attached structures is the primary contribution to these phenomena. Finally, a simplified simulation approach is used for incorporating the influence of attached outlets by coalescing the mass to the dam surface.

AlGaN/GaN superlattice-based multichannel RF transistors for high linearity and reliability: a simplified simulation approach

Multichannel RF power amplifiers offer high frequency operation, high current and RF power, combined with excellent linearity. 3D and 2D simulation is used to investigate how changes in device architecture impact both the linearity and off-state reliability, allowing an improved linear design which does not compromise reliability. Linearity is assessed by extraction of , and third order intercept (TOI) as a function of gate bias, using a straightforward 2D approximation which is computation time and resource efficient compared to the full 3D simulation normally used for these devices. Off-state reliability is assumed to be linked to dielectric failure, and hence peak electric field as a measure of reliability is evaluated at gate corners and edges using a full 3D simulation. It is found that introducing a channel number-dependent doping in the AlGaN/GaN-based superlattice structure can be used to enable an improved transconductance–linearity. It is also found that there is a strong increase in TOI as gate dielectric thickness or fin width is increased. On the other hand, in order to maintain reliability, increased fin height is found to be essential in order to reduce electric field as dielectric thickness is increased. Finally, a device architecture for improving linearity, power and reduced OFF-state field is suggested.

Improvement of Plasma Reactor Design for Methane Pyrolysis by Simulation

AbstractHydrogen generation by plasma reactors from methane is a promising technology. Although, much research is done on accurately describing the plasma, fewer was focused on the reactor design optimization. By altering the design, the velocity profiles and heat transport can be managed in such a way that the conversion of methane can be increased. Through a simplified simulation approach, it was possible to increase the gliding arc reactor conversion from 30 to 50 %, which was tested by experiments. Similar finding resulted from the microwave plasma simulation, where simulations showed a potential rise from 66 % to 84 %.

Cinco-Based Approach for Agent Petri Net Models

In this paper, a simplified simulation approach of the Agent Petri Nets (APN) model is proposed to facilitate and accelerate the development and evaluation of system models. The main idea is to apply the new trends of model-driven approach to the design of specific tools and provide facilities to evaluate quickly the developed system. The CINCO tooling suite is used to full generation of a specific graphical modelling tool for the APN model. The simulation code is simply added to the generated code. This tool allows users to build models based on Agent Petri Nets formalism and at the same time to execute these models. Combined APN with the CINCO tool greatly simplifies the development of modelling applications and allows users to get an early experience with a prototype system. To highlight the ability of the proposed tool, a real-life example of a traffic light adaptive system is considered and discussed here.

Phase-Specific Strain Hardening and Load Partitioning of Cold Rolled Duplex Stainless Steel X2CrNiN23-4

Multi-phase materials often times consist of constituents with high contrasts in phase-specific mechanical properties. Here, even after homogeneous plastic deformation phase-specific residual stresses develop that may affect the components behaviour in service. For numerical simulation of phase-specific residual stresses, knowledge of the particular phase-specific strain hardening behaviour is essential. In this study, the strain hardening of ferrite and austenite in cold rolled duplex stainless steel of type X2CrNiN23-4 is investigated. By means of X-ray diffraction, the phase-specific load partitioning and residual stress evolution are analysed for uniaxial load application in three directions within the sheets plane, taking into account the sheet metals phase specific anisotropy. In order to assess the necessity for experimental determination of anisotropic phase specific behaviour, the strain hardening parameters, derived from only one loading direction, are implemented in a mean-field approach for prediction of phase-specific stresses. A simplified simulation approach is applied that only considers macroscopic plastic anisotropy and results are compared to experimental findings. For all investigated loading directions, it was observed that austenite is the high-strength phase. This load partitioning behaviour was confirmed by the evolution of phase-specific residual stresses as a result of uniaxial elasto-plastic loading. With the simplified and fast numerical approach, satisfying results for prediction of anisotropic phase-specific (residual) stresses are obtained.

Handling Uncertainty in Financial Decision Making: A Clustering Estimation of Distribution Algorithm With Simplified Simulation

In financial decision making models, parameters are usually obtained based on historical data, which involve strong uncertainties. In some cases, the fluctuation caused by environmental uncertainty may even be more significant than that caused by utilizing different strategies. Such phenomenon makes the optimization and uncertainty handling in finical optimization a great challenge. In this article, a group insurance portfolio problem is considered as an instance of financial optimization with strong uncertainty. To handle uncertainty, we first analyze the feature of the problem and discover that in such kind of optimization problem with strong uncertainty, the solutions are strongly relative to the scenario. In view of the scenario-relevant feature, a simplified simulation approach is designed. Only one scenario is simulated for each generation in the evolution process to deal with the uncertainties. Combining this approach with a clustering estimation of distribution algorithm, a new algorithm (CEDA-SS) is proposed. Estimation of current profit is made by Monte Carlo (MC) simulation based on historical data. Solutions in each generation are evaluated in the same scenario. Two kinds of clustering mechanisms are applied to further improve the performance of the algorithm. Moreover, a comparison mechanism based on the Wilcoxon rank sum test is proposed to evaluate the performance of the algorithms. Experimental results show that the proposed CEDA-SS is suitable for the group insurance portfolio problem and it outperforms other uncertain evolutionary algorithms.

The role of stress state and stress triaxiality in lifetime prediction of solder joints in different packages utilized in automotive electronics

This work presents an overview on the role of the stress state and stress Triaxiality Factor (TF, see Eq. (1)) in lifetime prediction of solder connections. According to various literature sources, the TF is one of the most important factors influencing initiation of ductile fracture (Bao and Wierzbicki, 2004; Davis and Connelly, 1959). It is widely reported that lifetime of the ductile materials decreases under hydrostatic tension when combined with high TF-values. Recent investigations report that the compressive hydrostatic stress state combined with a high shearing load and low (or even zero) TF-values also contributes to failure (Bao and Wierzbicki, 2005; Kweon, 2002; Nielsen and Tvergaard, 2011).Two package types, the Loss Free Packaging (LFPAK) and the Plastic Ball Grid Array (PBGA), were investigated by means of FE-simulation on Board- and System-Level, and presented damage prediction was compared with an experimental data. In the LFPAK and BGA solder joints the regimes of hydrostatic tension and compression during temperature cycles are evaluated and compared with distribution of equivalent von Mises stress, stress intensity (maximum shear stress) and triaxiality factor. The multiaxial effects were included in both, lifetime prediction and fracture location: the damage related variables, inelastic strain and energy density, were modified in an APDL post-processing routine based on the state of hydrostatic stress and corresponding TF for each time increment. Further, using a simplified simulation approach, the path of the crack propagation was calculated according to the distribution of the TF-modified and non-modified inelastic strain. It is shown that when including multiaxial effects by modification of damage related variables a better correlation between calculated and experimentally observed crack path is achieved.

Hydrotropic Solubilization of Lipophilic Drugs for Oral Delivery: The Effects of Urea and Nicotinamide on Carbamazepine Solubility-Permeability Interplay.

Hydrotropy refers to increasing the water solubility of otherwise poorly soluble compound by the presence of small organic molecules. While it can certainly increase the apparent solubility of a lipophilic drug, the effect of hydrotropy on the drugs’ permeation through the intestinal membrane has not been studied. The purpose of this work was to investigate the solubility–permeability interplay when using hydrotropic drug solubilization. The concentration-dependent effects of the commonly used hydrotropes urea and nicotinamide, on the solubility and the permeability of the lipophilic antiepileptic drug carbamazepine were studied. Then, the solubility–permeability interplay was mathematically modeled, and was compared to the experimental data. Both hydrotropes allowed significant concentration-dependent carbamazepine solubility increase (up to ∼30-fold). A concomitant permeability decrease was evident both in vitro and in vivo (∼17-fold for nicotinamide and ∼9-fold for urea), revealing a solubility–permeability tradeoff when using hydrotropic drug solubilization. A relatively simplified simulation approach based on proportional opposite correlation between the solubility increase and the permeability decrease at a given hydrotrope concentration allowed excellent prediction of the overall solubility–permeability tradeoff. In conclusion, when using hydrotropic drug solubilization it is prudent to not focus solely on solubility, but to account for the permeability as well; achieving optimal solubility–permeability balance may promote the overall goal of the formulation to maximize oral drug exposure.

Assessing Cloud Transient Impacts of Solar and Battery Energy Systems on Grid Inertial Responses

To assess the dynamic impact of intermittency of rapidly increasing solar photovoltaic generation on the grid, this article presents the modeling and integration of the components that need to be considered, including the solar photovoltaic plant, battery energy storage system, grid-tied interface, and associated control systems. The complexity and accuracy of these models are suitable for evaluating the transient impact on bulk power systems. Of particular interest is the grid inertial response in such situations as different penetration levels of solar generation and fast cloud transient induced solar generation decrease coupled with outages that recurrently occur in the grid, e.g., a generator trip. The impact of such events on the grid frequency responses is investigated using a simplified simulation approach to account for the locational or spatial irradiance variation patterns and cloud movements. Responsive battery energy storage systems are recognized as an effective means to improve the inertial response.

Evaluation of a simplified simulation approach for thin film type gated field emitters

A simplified simulation approach aiming at reducing computational complexity has been proposed for gated field emitters. In this approach, a thin-film cold cathode consisting of quasi-one-dimensional nanoemitters is modeled as a flat metallic thin-film. The surface of the thin-film is divided into equal-size grids. Fowler–Nordheim parameters fitted with experimental current-voltage data are used to calculate emission current from these individual grids. The statistics of the total emission current and its distribution between the gates and the anode are analyzed by summing the currents from all of the grids. The validity of the proposed approach is evaluated by comparing the simulation results with experimental data from gated carbon nanotube (CNT) thin-film field emitters. CNTs at the edge of the CNT film stand out as superior emitters, and proper consideration of such emitters plays a critical role in determining the validity of the proposed approach.

Simulation of fluid flow in and around a porous windscreen

Fluid dynamic simulation of wind noise (turbulent pressure fluctuations) around porous microphone windscreens in an atmospheric flow is made difficult by the broad range of spatial scales, from large atmospheric eddies down to the pore size of the windscreen, that is involved. Here, we describe a simplified simulation approach that is based on two new insights: (1) the ability of linear fluid flow approximations to describe wind noise [Z.C. Zheng and B. K. Tan, J. Acoust. Soc. Am. 113, 161–166 (2003)] and (2) a new set of macroscopic, time-domain relaxational equations for the linear interaction of a fluid flow with a porous material [D. K. Wilson, V. E. Ostashev, and S. L. Collier, J. Acoust. Soc. Am. 116, 1889–1892 (2004)]. An upstream flow condition consisting of quasiwavelets (analogous to turbulent eddies) is also used to create well-developed, realistic turbulence. This simulation approach is shown to provide detailed simulations of the production of pressure fluctuations in and around a porous windscreen.

Prediction of Shape Distortions for a Curved Composite C-spar

This paper presents predictions and validations of shape distortions of a curved C-spar, using a simulation tool developed in the general purpose FE-program ABAQUS. The simulation tool is based on a simplified mechanical constitutive model that accounts for the mechanisms identified in a previous experimental study concerning the influence from the cure schedule on shape distortions. The main objective of the present paper is to validate the simplified constitutive model and a simplified simulation approach. The feasibility for simulation of shape distortions of a component with relatively complex shape has also been investigated.