Extended state observer-based control with an adjustable parameter for a large ground-based telescope

The high-precision requirements will always be constrained due to the complicated operating conditions of the ground-based telescope. Owing to various internal and external disturbances, it is necessary to study a control method, which should have a good ability on disturbance rejection and a good adaptability on system parameter variation. The traditional proportional-integral(PI) controller has the advantage of simple and easy adjustment, but it cannot deal with the disturbances well in different situations. This paper proposes a simplified active disturbance rejection control law, whose debugging is as simple as the PI controller, and with better disturbance rejection ability and parameter adaptability. It adopts a simplified second-order extended state observer(ESO) with an adjustable parameter to accommodate the significant variation of the inertia during the different design stages of the telescope. The gain parameter of the ESO can be adjusted online with a recursive least square estimating method once the system parameter has changed significantly. Thus, the ESO can estimate the total disturbances timely and the controller will compensate them accordingly. With the adjustable parameter of the ESO, the controller can always achieve better performance in different applications of the telescope. The simulation and experimental verification of the control law was conducted on a 1.2-meter ground based telescope. The results verify the necessity of adjusting the parameter of the ESO, and demonstrate better disturbance rejection ability in a large range of speed variations during the design stages of the telescope.

Programmable Logic Based on Large Magnetoresistance of Germanium

We find extremely large low-magnetic-field magnetoresistance （~350% at 0.2 T and ~180% at 0.1 T） in germa- nium at room temperature and the magnetoresistanee is highly sensitive to the surface roughness. This unique magnetoelectric property is applied to fabricate logic architecture which could perform basic Boolean logic in- cluding AND, OR, NOR and NAND. Our logic device may pave the way for a high performance microprocessor and may make the germanium family more advanced.

Benchmark Dose Estimation for Cadmium-Induced Renal Effects Based on a Large Sample Population from Five Chinese Provinces

A survey involving 6103 participants from five Chinese provinces was conducted to evaluate the threshold value of urinary cadmium （UCd） for renal dysfunction as benchmark dose low （BMDL）. The urinary N-acetyl-13-D-glucosaminidase （UNAG） was chosen as an effect biomarker. The UCd BMDLs for UNAG ranged from 2.18μg/g creatinine （cr） to 4.26μg/g cr in the populations of different provinces. The selection of the sample population and area affect the evaluation of the BMDL. The reference level of UCd for renal effects was further evaluated based on the data of all 6103 subjects. With benchmark responses （BMR） of 10%/5%, the overall UCd BMDLs for males in the total population were 3.73/2.08 μg/g cr. The BMD was slightly lower in females, thereby indicating that females may be relatively more sensitive to Cd exposure than are males.

4.05 kW monolithic fiber laser oscillator based on home-made large mode area fiber Bragg gratings

With the increasing output power of the monolithic fiber laser oscillators, the stimulated Raman scattering （SRS） effect becomes one of the main limitations of power scaling. Employing fiber with a larger mode area is an effective technique to mitigate the SRS, but, for the monolithic fiber laser oscillators, the difficulty of the inscription of the high-reflection fiber Bragg gratings （FBGs） increases with the fiber mode area. In this work, we demonstrated a high-power monolithic fiber laser oscillator based on the home-made large mode area FBGs and ytterbium-doped fiber （YDF） with 25 μm core diameters. A maximum output power of 4.05 kW is achieved at the central wavelength of -1080 ？nm with a total 915 nm pump power of -6.7 kW. At the operation of 4.05 kW, the intensity of the Raman Stokes light is -25 dB below the signal laser, and the beam quality （M2-factor） is -2.2. To the best of our knowledge, this is the first detailed report of the monolithic fiber laser oscillator with an output power beyond 4 kW.