The effect of cutting force model coefficient variability on process planning in milling

This thesis describes the effect of force model uncertainty on process planning. Specifically, the statistical variations in model predicted machining forces while cutting aluminum, carbon steel, stainless steel and titanium are determined. An accurate estimate of the variability is essential for use in process planning to determine appropriate factors of safety when setting cutting conditions that are both safe and efficient. Force model coefficient calibration is described and the variability in the coefficients is determined through a least squares regression of a large number of experimental cuts. It is shown that the variability increases with changes in the calibration cutting conditions, e.g. radial depth of cut and spindle speed. Monte Carlo simulations of the cutting force are then used to determine the mean and standard deviation of the resultant peak force. A factor of safety is established for process planning using the mean plus three standard deviations. Statistically, 99.86% of the actual peak cutting forces should fall below the predicted value. The maximum expected peak force can be determined for each tool move in a NC program and used to select safe cutting conditions

Pose Detection and Control of Unmanned Underwater Vehicles (UUVs) Utilizing an Optical Detector Array

As part of the research for development of a leader-follower formation between unmanned underwater vehicles (UUVs), this study presents an optical feedback system for UUV navigation via an optical detector array. Capabilities of pose detection and control in a static-dynamic system (e.g. UUV navigation into a docking station) and a dynamic-dynamic system (e.g. UUV to UUV leader-follower system) are investigated. In both systems, a single light source is utilized as a guiding beacon for a tracker/follower UUV. The UUV uses an optical array consisting of photodiodes to receive the light field emitted from the light source. For UUV navigation applications, accurate pose estimation is essential. In order to evaluate the feasibility of underwater distance detection, the effective communication range between two platforms, i.e. light source and optical detector, and the optimum spectral range that allowed maximum light transmission are calculated. Based on the light attenuation in underwater, the geometry and dimensions of an optical detector array are determined, and the boundary conditions for the developed pose detection algorithms along with the error sources in the experiments are identified. As a test bed to determine optical array dimensions and size, a simulator, i.e. numerical software, is developed, where planar and curved array geometries of varying number of elements are analytically compared and evaluated. Results show that the curved optical detector array is able to distinguish 5 degree- of-freedom (DOF) motion (translation in x, y, z-axes and pitch and yaw rotations) with respect to a single light source. Analytical pose detection and control algorithms are developed for both static-dynamic and dynamic-dynamic systems. Results show that a 5 x 5 curved detector array with the implementation of SMC is reasonably sufficient for practical UUV positioning applications. The capabilities of an optical detector array to determine the pose of a UUV in 3-DOF (x, y and z-axes) are experimentally tested. An experimental platform consisting of a 5 x 5 photodiode array mounted on a hemispherical surface is used to sample the light field emitted from a single light source. Pose detection algorithms are developed to detect pose for steady-state and dynamic cases. Monte Carlo analysis is conducted to assess the pose estimation uncertainty under varying environmental and hardware conditions such as water turbidity, temperature variations in water and electrically-based noise. Monte Carlo analysis results show that the pose uncertainties (within 95% confidence interval) associated with x, y and z-axes are 0.78 m, 0.67 m and 0.56 m, respectively. Experimental results demonstrate that x, y and z-axes pose estimates are accurate to within 0.5 m, 0.2 m and 0.2 m, respectively

Characterization of optical communication in a leader-follower unmanned underwater vehicle formation

As part of the research to development an optical communication design of a leader-follower formation between unmanned underwater vehicles (UUVs), this paper presents light field characterization and design configuration of the hardware required to allow the use of distance detection between UUVs. The study specifically is targeting communication between remotely operated vehicles (ROVs). As an initial step in this study, the light field produced from a light source mounted on the leader UUV was empirically characterized and modeled. Based on the light field measurements, a photo-detector array for the follower UUV was designed. Evaluation of the communication algorithms to monitor the UUV’s motion was conducted through underwater experiments in the Ocean Engineering Laboratory at the University of New Hampshire. The optimal spectral range was determined based on the calculation of the diffuse attenuation coefficients by using two different light sources and a spectrometer. The range between the leader and the follower vehicles for a specific water type was determined. In addition, the array design and the communication algorithms were modified according to the results from the light field

Pose Detection and control of multiple unmanned underwater vehicles using optical feedback

This paper proposes pose detection and control algorithms in order to control the relative pose between two Unmanned Underwater Vehicles (UUVs) using optical feedback. The leader UUV is configured to have a light source at its crest which acts as a guiding beacon for the follower UUV which has a detector array at its bow. Pose detection algorithms are developed based on a classifier, such as the Spectral Angle Mapper (SAM), and chosen image parameters. An archive look-up table is constructed for varying combinations of 5-degree-of-freedom (DOF) motion (i.e., translation along all three coordinate axes as well as pitch and yaw rotations). Leader and follower vehicles are simulated for a case in which the leader is directed to specific waypoints in horizontal plane and the follower is required to maintain a fixed distance from the leader UUV. Proportional-Derivative (PD) control (without loss of generality) is applied to maintain stability of the UUVs to show proof of concept. Preliminary results indicate that the follower UUV is able to maintain its fixed distance relative to the leader UUV to within a reasonable accuracy

Flux Correlators and Semiclassics

We consider correlators for the flux of energy and charge in the background of operators with large global $U(1)$ charge in conformal field theory (CFT). It has recently been shown that the corresponding Euclidean correlators generically admit a semiclassical description in terms of the effective field theory (EFT) for a conformal superfluid. We adapt the semiclassical description to Lorentzian observables and compute the leading large charge behavior of the flux correlators in general $U(1)$ symmetric CFTs. We discuss the regime of validity of the large charge EFT for these Lorentzian observables and the subtleties in extending the EFT approach to subleading corrections. We also consider the Wilson-Fisher fixed point in $d=4-\epsilon$ dimensions, which offers a specific weakly coupled realization of the general setup, where the subleading corrections can be systematically computed without relying on an EFT.Comment: 33 pages, 8 figure

The response of total testing process in clinical laboratory medicine to COVID-19 pandemic

Following a pandemic, laboratory medicine is vulnerable to laboratory errors due to the stressful and high workloads. We aimed to examine how laboratory errors may arise from factors, e.g., flexible working order, staff displacement, changes in the number of tests, and samples will reflect on the total test process (TTP) during the pandemic period. In 12 months, 6 months before and during the pandemic, laboratory errors were assessed via quality indicators (QIs) related to TTP phases. QIs were grouped as pre-, intra- and postanalytical. The results of QIs were expressed in defect percentages and sigma, evaluated with 3 levels of performance quality: 25th, 50th and 75th percentile values. When the pre- and during pandemic periods were compared, the sigma value of the samples not received was significantly lower in pre-pandemic group than during pandemic group (4.7σ vs. 5.4σ, P = 0.003). The sigma values of samples transported inappropriately and haemolysed samples were significantly higher in pre-pandemic period than during pandemic (5.0σ vs. 4.9σ, 4.3σ vs. 4.1σ; P = 0.046 and P = 0.044, respectively). Sigma value of tests with inappropriate IQC performances was lower during pandemic compared to the pre-pandemic period (3.3σ vs. 3.2σ, P = 0.081). Sigma value of the reports delivered outside the specified time was higher during pandemic than pre-pandemic period (3.0σ vs. 3.1σ, P = 0.030). In all TTP phases, some quality indicators improved while others regressed during the pandemic period. It was observed that preanalytical phase was affected more by the pandemic

Evaluation of Detector Array Designs for Optical Communication Between Unmanned Underwater Vehicle

The communication interface is essential for unmanned underwater vehicles (UUVs) to interact with each other or with a stationary target, such as docking station. In this paper, we investigate different optical array designs using a simulator. In addition to the hardware characteristics (e.g., sensitivity of the detectors and noise sources), the environmental conditions affecting the light field underwater were also taken into account. The simulator product is an image of the light field sensed by the detector array. The simulator product provides a signature that allows the UUV to track its position and orientation with respect to a light source. A variety of motion types (i.e., translation in the x, y, z directions including rotation about these axes) were analytically tested and evaluated for different array designs. The results from the simulator are to be validated against empirical measurements conducted in the water tank facilities in the Ocean Engineering Laboratory at the University of New Hampshire. Preliminary results suggest that unique image signatures can be obtained for the relative translational and rotational motion between two platforms

Investigation of frp effects on damaged arches in historical masonry structures [Tarihi yigma yapilardaki hasarli kemerler üzerinde frp etkisinin incelenmesi]

The present paper deals with experimental behavior of deformed brick masonry arches strengthened with the fiber reinforced polymer (FRP). Seven arches were fabricated using commercial clay brick and low strength lime-based mortar, trying to mimic historical structures. After reaching sufficient strength (28 day strength), one arch called reference specimen is tested under the ultimate load and other arches are given damage to a certain extent. Then six different strengthening arrangements, including different dimensions of FRP strips, spike anchors and joint grouting are implemented on six arches damaged. The numerical modeling of damaged masonry arches strengthened with FRP is performed using a commercially available structural analysis program and the numerical results are compared with the experimental ones. The experimental results show that the capacity of damaged masonry arch strengthened increases at least 58% in comparison with unstrengthened masonry arches and strengthening of joints with epoxy resin is an effective alternative to increase the damaged masonry arch capacity

The Effect of Surface Waves on Airborne Lidar Bathymetry (ALB) Measurement Uncertainties

Airborne Lidar Bathymetry (ALB) provides a rapid means of data collection that provides seamless digital elevation maps across land and water. However, environmental factors such as water surface induce significant uncertainty in the ALB measurements. In this study, the effect of water surface on the ALB measurements is characterized both theoretically and empirically. Theoretical analysis includes Monte Carlo ray-tracing simulations that evaluate different environmental and hardware conditions such as wind speed, laser beam footprint diameter and off-nadir angle that are typically observed in ALB survey conditions. The empirical study includes development of an optical detector array to measure and analyze the refraction angle of the laser beam under a variety of environmental and hardware conditions. The results suggest that the refraction angle deviations ( 2 σ ) in the along-wind direction vary between 3–5° when variations in wind speed, laser beam footprint size and the laser beam incidence angle are taken into account