Experimental Study on Tilt Adjustment Technique of Tripod Bucket Jacket Foundation for Offshore Wind Turbine in Sand

For the tripod bucket jacket foundations used in offshore wind turbines, the probable critical tilt angles should be avoidedduring tilt adjustment operation. Thus, these critical values must be identified by engineers, and remedial techniques mustbe established prior to the occurrence of the problem. Model tests were carried out for typical tilting conditions of tripodbucket foundations, which were allowed to tilt freely at various penetration depths without interruption by manualoperation. After the foundation ceased its tilting, some measures, such as water pumping, water injection, air injection, or acombination of the above methods, were enabled for adjustment. The research results showed two critical values in thetilting state of the tripod bucket jacket foundation, namely the terminal and allowable angles. In the installation condition,the terminal angle was negatively correlated with the initial penetration depth, but the opposite was observed with theremoval condition. The allowable angle was less than or equal to the terminal angle. The allowable angle in the installationwas related to the terminal angle. The critical angles all varied linearly with the initial penetration depth. When tiltingduring installation, adjustment measures can be used in the order of high drum pumping, low drum water injection, highdrum pumping and low drum water injection, air injection, and exhaust. When tilting during removal, the sequential use oflow drum water injection, air, and exhaust was applied. For buckets that were sensitive to angle changes, adjustmentmeasures of the “point injection” mode can be selected.

Tilt adjustment for a portable absolute atomic gravimeter

For an atomic gravimeter,the measured value of the Earth’s gravity acceleration g is the projection of the local gravity on the direction of Raman laser beams.To accurately measure the g,the Raman laser beams should be parallel to the g direction.We analyze the tilt effect of the Raman beams on g measurement and present a general method for the tilt adjustment.The systematic error caused by the tilt angle is evaluated as 0(+0,0.8)µGal(1µGal=10 nm/s^2)and the drift is also compensated in real time.Our method is especially suitable for the portable atomic gravimeter which focuses on the mobility and field applications.

A new compensation method for temperature-dependent gain tilt in L-band EDFA by adjusting only inserted VOA

A novel compensation method for temperature-dependent gain tilt of L-band erbium-doped fiber amplifier (L-EDFA) is proposed, in which the attenuation between stages is the only parameter to be adjusted. A simple linear relationship between the attenuation and the erbium fiber coil temperature was derived theoretically. When the erbium fiber coil temperature cycles from 26 to 70C, the gain tilt variation less than 0.3 dB is achieved experimentally by adjusting only the pre-inserted variable optical attenuator (VOA).

Exponential tilted likelihood for stationary time series models

Depending on the asymptotical independence of periodograms,exponential tilted(ET)likelihood,as an effective nonparametric statistical method,is developed to deal with time series in this paper.Similar to empirical likelihood(EL),it still suffers from two drawbacks:the nondefinition problem of the likelihood function and the under-coverage probability of confidence region.To overcome these two problems,we further proposed the adjusted ET(AET)likelihood.With a specific adjustment level,our simulation studies indicate that the AET method achieves a higher-order coverage precision than the unadjusted ET method.In addition,due to the good performance of ET under moment model misspecification[Schennach,S.M.(2007).Point estimation with exponentially tilted empirical likelihood.The Annals of Statistics,35(2),634–672.https://doi.org/10.1214/009053606000001208],we show that the one-order property of point estimate is preserved for the misspecified spectral estimating equations of the autoregressive coefficient of AR(1).The simulation results illustrate that the point estimates of the ET outperform those of the EL and their hybrid in terms of standard deviation.A real data set is analyzed for illustration purpose.