Robust Parameter Estimation of an Empirical Manoeuvring Model Using Free-Running Model Tests

The work presents the identification and validation of the hydrodynamic coefficients for the surge, sway, and yaw motion. This is performed in two ways: using simulated data and free-running test data. The identification and validation with the simulation data are carried out using a 25° turning test and a 20°−20° zigzag manoeuvring test. For the free-running test data, two zigzag manoeuvres are used: 30°−30° zigzag for identification and 20°−20° zigzag for validation. A nonlinear manoeuvring model is proposed based on the standard Euler equations, and the hydrodynamic coefficients are computed using empirical equations. To obtain robust results, the truncated singular value decomposition is employed to diminish the multicollinearity and the parameter uncertainties due to noise. The validation is carried out by comparing the result of the measured values with the predictions obtained using the manoeuvring models. Finally, a sensitivity analysis for the simulation data is performed to understand the influence of the parameters in the manoeuvres.

EKF-DRNN autopilot for VLCC heading hybrid control

An online Extended Kalman Filter (EKF)-Dynamic Recurrent Neural Network (DRNN) autopilot implementation strategy for Very Large Crude Carrier (VLCC) heading hybrid control with uncertain dynamics is designed in this paper. The autopilot scheme is based on a DRNN control model, which learns VLCC dynamic characteristics, while the VLCC heading control is estimated by the EKF to minimize squared course error. The online EKF-DRNN autopilot provides optimal control on the basis of fuel-saving evaluation criteria using the heading deviation and rudder angle. Therefore, the autopilot output is guaranteed to converge to the desired VLCC trajectory asymptotically. The proposed strategy is evaluated by applying it to VLCC Yuan Kun Yang from COSCO Shipping, and works excellently under different loads, speed and weather conditions. The VLCC heading hybrid controller is also assessed by ‘Z’ manoeuvring and turning test, and the superiority of the online EKF-DRNN autopilot is demonstrated. The remote online monitoring of Yuan Kun Yang’s main navigation data shows that it improved fuel-saving properties despite worsening weather conditions causing increased yawing.

Minocycline Promotes Functional Recovery in Ischemic Stroke by Modulating Microglia Polarization Through STAT1/STAT6 Pathways

BackgroundIncreasing evidence suggests that microglia experience two distinct phenotypes after acute ischemic stroke (AIS): a deleterious M1 phenotype and a neuroprotective M2 phenotype. Promoting the phenotype shift of M1 microglia to M2 microglia is thought to improve functional recovery after AIS. Minocycline, a tetracycline antibiotic, can improve functional recovery after cerebral ischemia in pre-clinical and clinical research. However, the role and mechanisms of minocycline in microglia polarization is unclear.MethodsUsing the transient middle cerebral artery occlusion - reperfusion (MCAO/R) model, we treated mice with saline or different minocycline concentration (10, 25, or 50 mg/kg, i.p., daily for 2 wk) at 24 h after reperfusion. Neurobehavioral evaluation, rotarod test, and corner turning test were carried out on day 14 after reperfusion. Then, neuronal injury, reactive gliosis, and microglia polarization were performed on day 7 following MCAO/R. Finally, we treated primary microglial cultures with LPS (Lipopolysaccharide; 100 ng/mL) plus IFN-γ (20 ng/mL) 24 h to induce M1 phenotype and observed the effects of minocycline on the M1/M2-related mRNAs and the STAT1/STAT6 pathway.ResultsWe found that a 14-day treatment with minocycline increased the survival rate and promoted functional outcomes evaluated with neurobehavioral evaluation, rotarod test, and corner turning test. Meanwhile, minocycline reduced the brain infarct volume, alleviated neuronal injury, and suppressed reactive gliosis on day 7 following MCAO/R. Moreover, we observed an additive effect of minocycline on microglia polarization to the M1 and M2 phenotypes in vivo and in vitro. In the primary microglia, we further found that minocycline prevented neurons from OGD/R-induced cell death in neuron-microglia co-cultures via regulating M1/M2 microglia polarization through the STAT1/STAT6 pathway. ConclusionMinocycline promoted microglial M2 polarization and inhibited M1 polarization, leading to neuronal survival and neurological functional recovery. The findings deepen our understanding of the mechanisms underlying minocycline-mediated neuroprotection in AIS.

Path Following of a Water-Jetted USV Based on Maneuverability Tests

Due to the high propulsive efficiency and better maneuverability under high speed, the water-jetted unmanned surface vehicle (USV) is widely studied and used. This paper presents complete maneuvering tests and control algorithm designed for a twin water-jetted USV model. Firstly, a wireless network control platform is established, and maneuvering tests, for instance, an inertia test, zig-zag test and turning test, are carried out to verify the maneuverability of the USV. In light of the complexity and uncertainty of ship sailing and ship handling, the Human Simulated Intelligent Control (HSIC) method is utilized to optimize the response time, accuracy and robustness of the controller. Finally, for the path following and track rectification part, a Line of Sight (LOS) algorithm is improved and proved practicable with triangle/square path tests. The proposed intelligent navigation algorithm specially designed for matching with the control methods, showing satisfactory improvements on the motion control and path following of the specific USV.

Removal mechanism of machinable ceramics and theoretical model of cutting force in turning operation

The removal mechanism of machinable ceramics in turning was studied, and a theoretical model of cutting force based on energy theory was proposed. Based on the turning test of machinable ceramics and kinematics analysis of the tool-workpiece system, a model of tool-workpiece contact zone considering the tool tip arc radius was established. The crack propagation path and three stages of the crack development were analyzed from the stress perspective. Then the energy of the crack system was studied, and the brittle fracture energy which is more suitable for brittle materials was put forward. Based on the principle of energy conservation, a correction theoretical model of cutting force was established, which was verified by turning experiments of machinable ceramics. The results indicated that the predicted values of the model were in good agreement with the experimental values. Both theoretical model and experimental results demonstrated that the cutting force decreased as cutting speed increased, and increased as cutting depth and feed rate increased. This model enabled an in-depth understanding of the interaction action between the cutting tool and work materials involved in the turning of machinable ceramics.

Experimental Study on the Nonlinear Behavior of a Sailing Container Ship under Landslide-Induced Surges

Surges induced by rock landslides that enter water at a high speed are extremely destructive. The initial surge height and spread characteristic are important references used in disaster precaution and risk assessment. In this study, twenty groups of orthogonal experiments of landslide-induced impulse wave were conducted, the details of the self-propulsion of ships were designed, the values of the propeller, rudder, and shafting were calculated, and the model of the propeller and rudder was processed. The validity of the model system was verified from a turning test, zig-zag maneuver test, and free attenuation test. The interactions between landslides and water and between landslide-induced wave and ships are analyzed by performing an orthogonal model test and determining the difference among the initial wave heights of landslide surges caused by different landslide volumes. The model test can compare and analyze the influences of different landslide volumes and navigation positions on the nonlinear behavior of ships, thereby proposing control methods and measures for safe sailing in waters with landslide-induced surges and providing a theoretical basis for disaster prevention and reduction in the channel of a reservoir area or a hydraulic structure.

Mit Einzelzähnen schneller zum Verschleiß*/Faster to wear with single teeth

Standzeittests an Kreissägewerkzeugen sind in der Regel zeit- und materialintensiv. Am Institut für Werkzeugmaschinen (IfW) der Universität Stuttgart wird der Aufwand mithilfe von Einzahnversuchen deutlich verringert. Die Versuche basieren auf einem Leistendrehtest, der sich an die ehemalige VDI-Richtlinie VDI 3324 anlehnt und auf Drehmaschinen durchgeführt werden kann. Durch einfach gestaltete, wechselbare Leisten entsteht eine für das Sägen typische Schnittunterbrechung und es können beliebige Werkstoffe berücksichtigt werden.   Live time tests on circular saw tools are usually time-consuming and material-intensive. At the Institute for Machine Tools (IfW) of the University of Stuttgart, the required effort can be significantly reduced by conducting single tooth tests. The tests are based on a block turning test which adopts the former VDI guideline VDI 3324 and can be used on lathes. Simply designed and exchangeable blocks allow the typical cut interruption for sawing and consider any materials.

Influence of Particle Size on Machinability Behavior in Turning of AA6061-AlN Composites

Machinability of the composites and achieving the dimensional accuracy in addition to surface finish at an economic machining rate is still the topic for numerous researchers. The current article describes the variation in machinability characteristics of AA6061-AlN composites under various sizes of reinforcements. Cutting speed, cutting depth and feed rate are preferred to perform the turning test. Cutting force, surface roughness and flank wear are identified to appraise the machinability characteristics. For an identical machining condition, the nano particle reinforced composite has less surface roughness and minimal flank wear and a greater cutting force than the other composites. An increment in cutting speed raises the flank wear and declines the surface roughness and cutting force for all composites. The findings from the experimental investigation help to utilize the turning process for machining the composites with various sizes of reinforcement at the economic rate of machining without compromising the surface quality.

Usability of CAPTCHA in Online Communities and Its Link to User Satisfaction

Completely automated public turning test to tell computers and humans apart (CAPTCHA) is a security mechanism that is used by online communities to block spam and hacking. Today, there are a large number of sophisticated CAPTCHAs that are robust; however, most of them are unusable. This chapter describes a study to examine types and characteristics of Text CAPTCHAs used by top 50 online communities. Furthermore, the chapter is the first of its type to develop a scale to measure usability of text CAPTCHA and to examine the relationships between dimensions of CAPTCHA and perception of usability and satisfaction with registration process in online communities. Factor analysis and equation modeling study suggests that text-based CAPTCHA can be measured on four reflective dimensions of (1) content, (2) visual layout, (3) distortion, and (4) service in which correlate significantly to users' sanctification with online community.

Probability-Statistical Estimation Method of Feed Influence on As-Turned Finish of Steels and Non-Ferrous Metals

Based on the experimental data on the roughness parameter Ra, which stands for the mean arithmetic deviation of the profile, as obtained in the process of turning test specimens from different materials with constant elements of the cutting mode (depth a and velocity v) and structural-geometric parameters of the cutting tool, but with different feed rates f, the probability-statistical method for estimating the influence of feed rate f on the resulting surface roughness by the parameter Ra is proposed using the theory of a small sample.