Fast, vision-based line-following schemes for micro-aerial vehicles in nuclear environments

Many nuclear power plants are reaching the end of their economic lifetime and the decommissioning of legacy nuclear facilities is an important challenge in the next few decades. Since the radiation level in these facilities is significant, autonomous robots are likely to be a large part of the solution. For this purpose, the mapping and inspection of nuclear facilities can be performed using autonomous Micro Aerial Vehicles (MAVs). Recently, there are many studies on achieving a stable and reliable MAV flight to perform accurate missions with high performance. Since human access is highly restricted in nuclear environments, conventional navigation systems are not able to complete many of the required tasks. Track follower MAVs have been implemented in many applications, such as water channels and railway inspections. To illustrate some of the issues involved, this research considers a line-following method and compares two attitude controllers. The approach can be divided into three tasks: 1) the image processing algorithm, 2) the path planning strategy and 3) attitude stabilisation. The environment under study contains a ground floor with predetermined red tracks over which the MAV moves. We explain each task briefly in the following. Image Processing: First, a colour detection algorithm is applied to form a thresholded image. To make the image smoother and to reduce noise effects, Dilation and Erosion algorithms are applied. Then, in each iteration, a vector is created by the boundary layer of the provided image. Morphological operations are performed to remove small discontinuities for each cluster. Here the goal is to find the midpoint of each cluster, known as keypoints. Finally, the obtained vector should be re-mapped to its original image matrix. Path Planning: The methodology for selecting the appropriate target point is to compare the distance between the keypoints and the target. For the take-off phase, the keypoint with smaller y in the image frame is chosen and, for the remaining iterations, the keypoint with lower distance to the target is selected. Then, the desired velocity in the body frame is calculated. Attitude Controller Design: Two controllers are considered to stabilise the attitude of the MAV. First, a linear Proportional-Integral-Derivative (PID) controller is selected. A linear PID control for yaw torque is derived. Subsequently, a conventional sliding surface for the yaw channel is defined and, by applying Lyapunov’s direct method, the stability of the system is guaranteed. The yaw control torque is derived as a function of the designed positive sliding gain. Finally, to avoid chattering phenomenon, one can approximate the discontinuous signum function with the hyperbolic one

Do spinal cord-injured individuals with stronger sense of coherence use different psychological defense styles?

Objectives: Although the importance of sense of coherence (SOC) and psychological defense mechanisms (PDMs) in the process of coping has been demonstrated, it has not yet been clarified whether individuals with stronger SOC use specific PDMs.Study design: Cross-sectional. Setting: Iran. Methods: Demographic and injury-related variables including injury level, time since injury, American Spinal Cord Association (ASIA) Scale and Spinal cord independence measure-III were collected among individuals with spinal cord injury (SCI). SOC was assessed by the Short-form Sense of Coherence Scale. PDMs were identified using 40-version of the Defense Style Questionnaire. Results: Neurotic defense style was the most commonly used style especially. The overall most commonly used PDM was 'rationalization', which was used by 95. Individuals with stronger SOC used more mature style (P=0.001, r=0.52), particularly 'humor' and 'suppression' mechanisms (P<0.0001 and 0.024, respectively). There was a negative correlation between stronger SOC and the use of immature defenses including passive aggression (P=0.001, r=-0.51), acting out (P=0.001, r=-0.48), isolation (P=0.009, r=-0.50), autistic fantasy (P=0.010, r=-0.30) and somatization (P<0.0001, r=-0.62). Married individuals had significantly stronger SOC (P=0.01). Age, gender, age at the time of injury incidence, time since injury, ASIA score and cause of injury were not determinants of SOC. Conclusion: In this study, PDMs, which are more probable to be used by individuals with stronger SOC, have been identified. Mature defenses including 'humor' and 'suppression' are used by stronger SOC more often, whereas immature mechanisms are less likely to be used. © 2016 International Spinal Cord Society

Optimal feeding strategy of diafiltration buffer in batch membrane processes

This work addresses the optimal control strategy of diafiltration buffer utilisation in discontinuous membrane processes that are designed to fulfil the twin aims of concentration and fractionation. The problem of optimal process operation is formulated using a general membrane response model that encounters concentration-dependent flux and rejections. We consider two problems, operation time minimisation and diluant consumption minimisation, and we apply theory of optimal control and derive necessary conditions of optimality. Through selected case studies from the literature, we demonstrate how to apply the proposed methodology to determine optimal time-dependent wash-water feeding policy. The analytical results are confirmed by numerical computations, using numerical methods of dynamic optimisation. The presented methodology allows decision makers to analyse suboptimality of conventional diafiltration strategies in terms of processing time and diluant consumption. Results show that depending on the complexity of the membrane response model, it may be attractive to implement optimal trajectory

Estimation and prediction of optical properties of PA6/TiO2 nanocomposites

Nanocomposites are used in many scientific and industrial applications in recent times. In polymer nanocomposites, nanoparticles are used as the main component in creation which has always been considerable. Nano TiO2 as a nanoparticle has a very strong light scattering effect which can replace the ordinary TiO2 in less amounts of usage. In this research, optical properties of the PA6/nano TiO2 nanocomposite are studied using Mie scattering theory. Mie theory uses the relative refractive index of a small particle to calculate the light scattering efficiency of a material. At first, experimental and estimated properties of a nanocomposite film containing nano TiO2 particles with 40 nm radius are compared. Optical properties of nanocomposites are then predicted with various particle sizes as a result of this research. Results show that by taking the refractive index as an intrinsic property of a particle, it is possible to estimate the optical properties with a defined size and in addition it can help to predict these properties for different particle sizes

Ocena za pomocą optoelektronicznego urządzenia nowej konstrukcji wpływu długości oczka na fluktuację amplitudy przędzy wprowadzanej do dziewiarki obwodowej do dzianin rządkowych

The present paper investigates the effects of knitted loop length on yarn fluctuation amplitude during feeding into a circular knitting machine. Variation of yarn tension causes a change in the loop length and yarn fluctuation amplitude. In order to study the behaviour of the yarn fluctuation amplitude during the feeding process, a new optical IR electronic monitoring system was designed and developed. Experiments were carried out on an industrial single jersey knitting machine with a plain knitted pattern and polyester 150 denier continuous filament yarn for three different knitted loop lengths. Evaluating the fluctuation amplitudes recorded by analysis of variance revealed that an increase in the loop length will cause a highly significant decrease in the yarn fluctuation amplitude.Zmiany naprężenia przędzy powodują zmianę w długości oczka i fluktuację amplitudy przędzy. W celu zbadania zachowania się przędzy podczas zmian amplitudy w czasie procesu wprowadzania przędzy do maszyny opracowano i wykonano nowy elektroniczno-optyczny (IR) system monitoringu. Badania przeprowadzono na przemysłowej dziewiarce dla dzianin o splocie lewo prawym stosując przędzę z ciągłych włókien poliestrowych o masie liniowej 150 dtex. Stosowano trzy różnej długości oczka. Ocena zarejestrowanych fluktuacji amplitudy oraz analiza wariancyjna wykazały że wzrost długości powoduje bardzo wyraźny spadek fluktuacji amplitudy przędzy