In recent decades, reinforced soil retaining walls have gained popularity due to their ease of construction and low costs. Utilizing polymeric straps for soil reinforcement provides a straightforward and economical way to enhance the strength and deformation characteristics of retaining earth walls. However, these polymeric straps lack adequate pullout resistance, owing to the absence of transverse members. To address this issue, a U-shaped end-bend can be added to the strap, which creates a surface that enhances passive resistance. Although construction codes generally emphasize the use of high-quality granular materials as backfills for reinforced soil retaining walls, many construction projects are characterized by local soils that consist of marginal cohesive materials, making them unsuitable for backfills. A promising solution to reduce project costs in reinforced wall construction is the sandwich method, which involves encasing the reinforcement in a thin layer of granular soil within the backfill. This technique not only improves the pullout resistance of the reinforcement but also allows the enclosed layer to serve as a drainage system. This research investigates the pullout behavior of straps with both direct and U-shaped ends in sand and clay backfills through a series of large-scale pullout tests. Additionally, the impact of the sandwich method on enhancing the pullout resistance of U-shaped polymeric straps is examined.

In the present research, inelastic behavior of cold-formed steel frames with strap bracing was studied under cycling loading using finite element (FE) method. All of frame members including tracks, studs, and braces were modeled using two dimensional shell elements. The screw connections of braces to studs were simulated using connector elements. The shear and axial strength of screws were determined considering the screw pull-out and hard contact of braces to studs. The failure mechanism and resultant base shear were compared with the experimental measurements. The results showed a good agreement between developed FE model and experimental data. The shear and tensile forces of screws at different stages of loading, as well as the behavior in elastic and inelastic regions, were evaluated using the developed model. It was concluded that the buckling and yielding of braces are the most effective factors on the cyclic behavior of cold-formed steel frames; and that cyclic behavior of cold-formed steel frames with strap bracing can be accurately determined using the proposed FE model.

Three-axis-magnetometers (TAMs) are widely utilized as a key component of attitude determination subsystems and as such are considered the corner stone of navigation for low Earth orbiting (LEO) space systems. Precise geomagnetic-based navigation demands accurate calibration of the magnetometers. In this regard, a complete online calibration process of TAM is developed in the current research that considers the combined effects of environmental and instrumental errors including biases, non-orthogonally parameters, and the scale factors, without the need for clean room facilities. The sensor characteristics are estimated utilizing Kalman filter for a micro electro-mechanical sensor(MEMS)-based TAM standing on the experimental measured outputs in a noisy laboratory environment. Moreover, the stochastic TAM behavior is identified using the method of Allan variance analysis (AVA) through a six-hour static test. Subsequently, the nonlinear/non-Gaussian problem of attitude estimation, using a set of calibrated strap-down magnetometers is addressed utilizing the unscented particle filter (UPF), developed for the removal of colored-noise. Comparison of the estimated attitude, represented by quaternion parameters, with the true orientations demonstrates an acceptable level of accuracy of the developed calibration technique for small LEO space systems. Analysis of the root mean square error of the estimated attitude illustrates an accuracy of less than one degree for all axes. This is an ideal result, given the fact that MEMS-based magnetometers have been utilized.

Diagonal Strap bracing is one of the most applicable lateral bracing systems in light steel framing (LSF). In practice, one or more panels of Gypsum Wall Boards (GWBs) is used for the cladding of strap braced frames. Usually, the effect of these GWBs in modelling and design is neglected by designers, but this effect can affect the seismic performance of the system. In this paper, firstly, a simple numerical method is developed to model the monotonic and cyclic behavior of cold-formed strap braced shear walls together with GWBs. Then, the effects of GWB on the lateral characteristics and seismic performance levels of shear walls are evaluated. It is found that neglecting GWB in the lateral design or modeling of LSF is not rational and GWB can increase the dissipation of earthquake energy, lateral strength and stiffness of the walls. Also, the shear wall composed of strap bracing and SWBs reaches a certain performance level in a less drift ratio in comparison to to only strap braced system.

A numerical dynamic-aerodynamic interface for simulating the separation dynamics of constrained strap-on boosters jettisoned in the atmosphere is presented. Two commercial solvers: a 6DOF multi-body dynamic solver and a numerical time-dependent flow solver are integrated together with an interface code to constitute a package that presents real-time dynamic/aerodynamic coupled analysis. Dynamic unstructured mesh approach is employed using local remeshing methods in respect of bodies motion with a second-order upwind accurate 3D Euler solver. This interface can simulate multi body separation dynamics interaction with aerodynamic effects to complete separation mechanisms like springs, thrusters, joints and so on. The flow solver is validated by the Titan IV launch vehicle experimental data. The separation integration is used for a typical launch vehicle with two strap-on boosters using spring ejector mechanism and spherical constraint joints acting in the dense atmosphere. Hence, the aim of the presented interface is to facilitate the integration of complicated separation mechanisms with a full numerical CFD aerodynamic solver.

In a strap down magnetic compass, heading angle is estimated using the Earth's magnetic field measured by Three-Axis Magnetometers (TAM). However, due to several inevitable errors in the magnetic system, such as sensitivity errors, non-orthogonal and misalignment errors, hard iron and soft iron errors, measurement noises and local magnetic fields, there are large error between the magnetometers' outputs and actual geomagnetic field vector. This is the necessity of magnetic calibration of TAM, especially in navigation application to achieve the true heading angle. In this paper, two methodologies, including clustering swinging method and clustering velocity vector method are presented for magnetic compass calibration. Several factors for clustering process have been introduced and analyzed. The algorithms can be applied in both low-cost MEMS magnetometer and high-accuracy magnetic sensors. The proposed calibration algorithms have been evaluated using in-ground and in-flight tests. It can be concluded from the experimental results that, applying the clustering calibration algorithms bring about a considerable enhancement in the accuracy of magnetic heading angle.

In this paper, a new method based on optimal combination of inertial sensors; in process of initial alignment for strap down navigation system; is proposed. The equations of initial alignment are usually based on accelerometer outputs and/or gyroscope outputs, depending on sensor’s accuracy. Our initial alignment algorithm leads to linear combination of output vectors. Although the error of this method is independent of sensor’s biases, unfortunately the coefficient of this combination is unknown. Knowledge of designer or sensor’s accuracy is a normal solution, but that obviously will not lead to the best estimation. The proposed idea is utilizing genetic algorithm to achieve optimal combination of sensors. In this regard, the optimal transformation matrix must be estimated, and the performance index is a function of alignment error. Final result of optimization problem is the best coefficient to combine outputs. The simulation results show excellent performance of proposed algorithm.

The line of sight (LOS) rate is a parameter that is needed to calculate the acceleration applied to missiles by the proportional guidance laws in order to hit the target. This rate is usually measured using gimbaled seekers. However, if the type of missile seeker be strap down, the LOS rate must be calculated from deriving the missile's seeker output angles or estimation methodes. The derivation method is not desirable due to the noisy output of the seekers and low pass filters are needed to achieve an acceptable output, which will cause a lag in the guidance loop. In this paper, a discrete time extended state observers will be designed to estimate the LOS rate. The advantage of the time discontinuity of the observer is that issues related to the implementation of the observer on the processors, such as the choice of sampling time, considered from the design level and examined in computer simulation.

Considering the common diseases that occur in the heart valves, it is possible that these valves can be replaced with artificial valves. This article examines different types of polymeric valves for the possibility of replacement in the human body. Different models are compared and the optimal valve is presented. For complete information, refer to the text of the article.