A Nonlocal Operator Method for Partial Differential Equations with Application to Electromagnetic Waveguide Problem

A novel nonlocal operator theory based on the variational principle is proposed for the solution of partial differential equations. Common differential operators as well as the variational forms are defined within the context of nonlocal operators. The present nonlocal formulation allows the assembling of the tangent stiffness matrix with ease and simplicity, which is necessary for the eigenvalue analysis such as the waveguide problem. The present formulation is applied to solve the differential electromagnetic vector wave equations based on electric fields. The governing equations are converted into nonlocal integral form. An hourglass energy functional is introduced for the elimination of zero-energy modes. Finally, the proposed method is validated by testing three classical benchmark problems.     

A Bio-Inspired Global Finite Time Tracking Control of Four-Rotor Test Bench System

A bio-inspired global finite time control using global fast-terminal sliding mode controller and radial basis function network is presented in this article, to address the attitude tracking control problem of the three degree-of-freedom four-rotor hover system. The proposed controller provides convergence of system states in a pre-determined finite time and estimates the unmodeled dynamics of the four-rotor system. Dynamic model of the four-rotor system is derived with Newton’s force equations. The unknown dynamics of four-rotor systems are estimated using Radial basis function. The bio-inspired global fast terminal sliding mode controller is proposed to provide chattering free finite time error convergence and to provide optimal tracking of the attitude angles while being subjected to unknown dynamics. The global stability proof of the designed controller is provided on the basis of Lyapunov stability theorem. The proposed controller is validated by (i) conducting an experiment through implementing it on the laboratory-based hover system, and (ii) through simulations. Performance of the proposed control scheme is also compared with classical and intelligent controllers. The performance comparison exhibits that the designed controller has quick transient response and improved chattering free steady state performance. The proposed bio-inspired global fast terminal sliding mode controller offers improved estimation and better tracking performance than the traditional controllers. In addition, the proposed controller is computationally cost effective and can be implanted on multirotor unmanned air vehicles with limited computational processing capabilities.     

Hip Fracture Risk Assessment Based on Different Failure Criteria Using QCT-Based Finite Element Modeling

Precise evaluation of hip fracture risk leads to reduce hip fracture occurrence in individuals and assist to check the effect of a treatment. A subject-specific QCT-based finite element model is introduced to evaluate hip fracture risk using the strain energy, von-Mises stress, and von-Mises strain criteria during the single-leg stance and the sideways fall configurations. Choosing a proper failure criterion in hip fracture risk assessment is very important. The aim of this study is to define hip fracture risk index using the strain energy, von Mises stress, and von Mises strain criteria and compare the calculated fracture risk indices using these criteria at the critical regions of the femur. It is found that based on these criteria, the hip fracture risk at the femoral neck and the intertrochanteric region is higher than other parts of the femur, probably due to the larger amount of cancellous bone in these regions. The study results also show that the strain energy criterion gives more reasonable assessment of hip fracture risk based on the bone failure mechanism and the von-Mises strain criterion is more conservative than two other criteria and leads to higher estimate of hip fracture risk indices.     

Threshold shift method for reliability-based design optimization

Structural and Multidisciplinary Optimization - We present a novel approach, referred to as the “threshold shift method” (TSM), for reliability-based design optimization (RBDO). The...     

An innovative model for predicting the displacement and rotation of column-tree moment connection under fire

In this study, we carried out nonlinear finite element simulations to predict the performance of a column-tree moment connection (CTMC) under fire and static loads. We also conducted a detailed parameter study based on five input variables, including the applied temperature, number of flange bolts, number of web bolts, length of the beam, and applied static loads. The first variable is changed among seven levels, whereas the other variables are changed among three levels. Employing the Taguchi method for variables 2–5 and their levels, 9 samples were designed for the parameter study, where each sample was exposed to 7 different temperatures yielding 63 outputs. The related variables for each output are imported for the training and testing of different surrogate models. These surrogate models include a multiple linear regression (MLR), multiple Ln equation regression (MLnER), an adaptive network-based fuzzy inference system (ANFIS), and gene expression programming (GEP). 44 samples were used for training randomly while the remaining samples were employed for testing. We show that GEP outperforms MLR, MLnER, and ANFIS. The results indicate that the rotation and deflection of the CTMC depend on the temperature. In addition, the fire resistance increases with a decrease in the beam length; thus, a shorter beam can increase the fire resistance of the building. The numbers of flanges and web bolts slightly affect the rotation and displacement of the CTMCs at temperatures of above 400°C.     

An efficient optimization approach for designing machine learning models based on genetic algorithm

Neural Computing and Applications - Machine learning (ML) methods have shown powerful performance in different application. Nonetheless, designing ML models remains a challenge and requires further...     

Method for the pre-dimensioning of beveloid gears

Conical involute gears – also referred to as beveloid gears – are based on cylindrical involute gears, as both gear geometries are based on a basic rack. They differ from cylindrical gears in that the beveloid gears’ addendum modification along the face width is not constant, but linearly variable. This allows beveloid gears to transfer mechanical power with parallel, intersecting or even skewed axes up to shaft angles of approximately 20°, whereas bevel or hypoid gears are applied with larger shaft angles.Compared with both cylindrical and bevel gears, there is less knowledge available concerning the design of beveloid gears. Existing tools for contact analysis are based on predetermined main gearing data. Therefore a method to pre-dimension main beveloid gearing data based on application requirements was developed. Initially, equivalent cylindrical gears are dimensioned and then transformed into beveloid gears with the required mounting positions. The method involves pre-optimizing of beveloid gears with several targets. Firstly, to comply with selected boundaries of the addendum modification coefficient, as well as to minimize ease-off between the tooth flanks achieved by a centric contact pattern and ensure adequate tip clearance by reducing tip circles.The method was implemented in a software environment for tooth contact analysis and applied to a wide range of data sets. The evaluation demonstrated the efficient design of the main data of beveloid gears including pre-optimization to achieve the objectives mentioned previously. In further optimizations, the microgeometry of beveloid gears must be adapted regarding the gap that occurs between the flanks.     

Building an active material requirements planning system

A material requirements planning (MRP) system is usually implemented with several constraints, such as replenishment of inventories on a period-by-period bases, which obstruct its dynamic performance. This research proposes an active, bucketless, and real-time MRP system. The active MRP system utilizes hybrid architecture that includes an object-oriented database, fuzzy logic controllers, and neural networks. The object-oriented database, which maintains static data relationships, provides superior capabilities in reusability, complex structure operations, and potential integration. The complementary combination of fuzzy logic controllers and neural networks provides a model-free, human-like decision system. Adding triggers and assertions forms an active MRP model.     

Chemical biology approaches reveal conserved features of a C-terminal processing PDZ protease

Several proteases like the high temperature requirement A (HtrA) protein family containing internal or C-terminal PDZ domains play key roles in protein quality control in the cell envelope of Gram-negative bacteria. While several HtrA proteases have been extensively characterized, many features of C-terminal processing proteases such as tail-specific protease (Tsp) are still unknown. To fully understand these cellular control systems, individual domains need to be targeted by specific peptides acting as activators or inhibitors. Here, we describe the identification and design of potent inhibitors and activators of Tsp. Suitable synthetic substrates of Tsp were identified and served as a basis for the generation of boronic acid-based peptide inhibitors. In addition, a proteomic screen of E. coli cell envelope proteins using a synthetic peptide library was performed to identify peptides capable of amplifying Tsp's proteolytic activity. The implications of these findings for the regulation of PDZ proteases and for future mechanistic studies are discussed.     

An integration of production management rules and fabrication know-how for real-time cell production control

Between the steps of operation release and process control of the production activity control, no re-evaluation of the production organization is undertaken. However, the production organization can be technically optimized or modified. This level of production management is difficult to achieve, essentially because several fields come into play. It becomes apparent, however, that it is essential to integrate production management and production cell control in order to obtain advanced production systems which are more ‘reactive’ to technical and economic perturbations. In this paper, a contribution to the resolution of this problems is presented and the following ideas are introduced:

1. a control structure of production cells within “real-time production management functions”,

2. a control strategy of the cells by “scénario de production” (production scenario).

First of all, the functions of this control structure are described and then the principles of its generic utilization for the control of a complex production system are given. An executable production scenario is conceived according to the production management rules, the data and know-how of the fabricators also play a role. The last section of this paper describes, using an industrial example in the field of sub-contracted machining, the construction of such a scenario.