Determination of dynamic flexure model parameters for ship angular deformation measurement

In ship angular deformation measurement, Kalman filter used to estimate the deformation angle requires accurate dynamic flexure parameters. Traditionally, these dynamic flexure parameters are empirically set according to previous experience or determined from previously collected experimental data. Inevitably, the Kalman filter will perform poorly when the current application environment is differ with those used in the filter design. To overcome this problem, we propose an alternative on-line approach to estimate the dynamic flexure parameters based on the attitude difference measured by two laser gyro units. Specifically, the Tufts-Kumaresan (T-K) method is introduced to solve the unknown parameters of the dynamic flexure model from the computed attitude difference. Simulation results show that the proposed method can estimate the dynamic flexure parameters in real-time with a high degree of accuracy even in serious noise polluted conditions. A further advantage of the proposed approach is that it does not require a priori knowledge of the dynamic flexure characteristics

Coupling influence of ship dynamic flexure on high accuracy transfer alignment

This work investigates a new error source for angular velocity or attitude-based transfer alignment, which is caused by the coupling influence of dynamic flexure with ship angular motion. Most traditional studies do not consider this coupling error, as they often assume that dynamic flexure and ship angular motion are uncorrelated. However, the correlation between the dynamic flexure and the ship angular motion generally exists, which will cause a static error in measurements. We adopt the Bernoulli-Euler beam as a simplified ship vibration model to obtain the phase and amplitude relationships for the ship dynamic flexure angle and the ship angular motion. Simulation experiments are then conducted to test the phase delay on alignment accuracy based on the angular velocity matching approach. It is found that the estimation error has a strong correlation with this phase delay, and the error behaves like a sin wave function with the phase delay angle variation. The coupling error of ship dynamic flexure with ship angular velocity is deduced based on the spatial geometric modelling method, and the analysis demonstrates that this coupling error exists in angular velocity or attitude matching systems, which depends on the phase delay and amplitude ratio of ship dynamic flexure and angular velocity

Online Estimation of Ship Dynamic Flexure Model Parameters for Transfer Alignment

Abstract — This paper presents an online approach for estimating the dynamic flexure model parameters in shipboard transfer alignment (TA). Traditionally, the application of Kalman filters (KFs) to the TA process is often restricted because of the lack of real-time information on dynamic flexure characteristics, and a KF designed on the basis of inaccurate parameters of the dynamic flexure model will result in a large alignment error. To overcome this difficulty, a parameter estimation algorithm is proposed in this paper, which utilizes the angular increment difference measured by the master inertial navigation system (MINS) and the slave inertial navigation system. Specifically, the Tufts–Kumaresan method is introduced to compute the unknown parameters of the dynamic flexure model from the angular increment correlation function. Our simulation results show that the proposed method can estimate the dynamic flexure parameters with a high degree of accuracy, even in low signalto-noise ratio conditions. This parameter estimation method does not require aprioriknowledge of dynamic flexure characteristics and, therefore, provides the shipboard sensors with an accurate and rapid-response capability for alignment with the MINS. Index Terms — Dynamic flexure, Gauss–Markov process, parameter estimation, transfer alignment, Tufts–Kumaresan method

Fatigue Life Estimation for Suspenders of a Three-Pylon Suspension Bridge Based on Vehicle–Bridge-Interaction Analysis

Fatigue damage of suspenders is a main concern during the life-cycle maintenance of arch bridges and suspension bridges. This paper presents a practical framework for estimating the fatigue life of suspenders under repeated traffic loads by taking a three-pylon suspension bridge as an example. First, the basic theory of vehicle–bridge interaction (VBI) is introduced and a finite element model of the bridge structure is established. Second, the fatigue load spectrum is defined in detail based on the analysis of WIM (weigh-in-motion) data. And then, parametric analysis is carried out to clarify the influence of road roughness, vehicle speed, and driving lanes. Among which, the time-dependent stress laws are simulated according to the defined fatigue load spectrum and the stress range is counted through the Rain flow counting method. At last, the fatigue life of uncorroded suspenders and naturally corroded suspenders is estimated by an S–N curve and Miner cumulative damage criterion. Results reveal that the fatigue life of suspenders is more than 100 years if no corrosion happens, while less than 20 years for short suspenders considering the influence of natural corrosion

Buformin suppresses osteosarcoma via targeting AMPK signaling pathway

Buformin has been reported to be a powerful anticancer drug by activating the AMPK signal. Herein, we aimed to investigate the effects of buformin on osteosarcoma

Subclinical hypothyroidism in pregnant rats impaired learning and memory of their offspring by promoting the p75NTR signal pathway

Objective: Maternal hypothyroidism during pregnancy can affect the neurodevelopment of their offspring. This study aimed to investigate the effects of maternal subclinical hypothyroidism (SCH) on spatial learning and memory, and its relationship with the apoptotic factors in cerebral cortex of the offspring. Methods: Female adult Wistar rats were randomly divided into three groups (n = 15 per group): control (CON) group, SCH group and overt hypothyroidism (OH) group. Spatial learning and memory in the offspring were evaluated by long-term potentiation (LTP) and Morris water-maze (MWM) test. The protein expression of the p75 neurotrophin receptor (p75NTR), phospho-c-Jun N-terminal kinase (p-JNK), the pro-apoptotic protein p53 and Bax were detected by Western blotting. Results: The Pups in the SCH and OH groups showed longer escape latencies in the MWM and decreased field-excitatory post synaptic potentials in LTP tests compared with those in the CON group. p75NTR, p-JNK, p53 and Bax expression levels in the cerebral cortex increased in pups in the SCH and OH groups compared with those in the CON group. Conclusions: Maternal SCH during pregnancy may impair spatial learning and memory in the offspring and may be associated with the increased apoptosis in the cerebral cortex