Integrated On-line Instrumentation System of Magnetic Properties Measurement

A portable microcomputer-controlled inspection system has been developed for detection of magnetic properties of soft magnetic materials. It incorporates custom designed software for control of the magnetic field during operation such as demagnetization, field sweeping, and for data logging and analysis. Results are recorded using a 12-bit analog to digital converter and are then stored on disk. The magnetic hysteresis loop and Barkhausen noise data can be converted into important magnetic parameters: coecivity, remanence, and hysteresis loss, Barkhausen amplitude, and Barkhausen noise energy. This system incorporated with the magnetostriction, and magnetoacoustic emission, is then related with the nondestructive detection of material degradation.

Frost Resistance of Pervious Concrete Mixed with Waste Glass Powder

The contents of waste glass powder(WGP)(0%,10%,15%,20%,25%)and water-binder ratio(W/C)(0.24,0.26,0.28)were used as influencing factors,and the quality loss rate(Δm)and compressive strength loss rate(Δfc)were used as characterization parameters.The Ca/Si ratio and main element contents of C-S-H gels with different WGP content were investigated by energy dispersive spectrometry(EDS).The pore structure evolution characteristics of WGP composite cementing materials were investigated by low field nuclear magnetic resonance(NMR).UsingΔfc as the index of frost resistance degradation and Weibull function,the frost resistance degradation of glass doped pervious concrete(WGP-PC)was modeled.The results show that,with WGP,for the same number of cycles,Δm andΔfc decrease and increase with the increase of WGP.Under the same WGP content,Δm andΔfc decrease first and then increase with the increase of W/C.After 100 freeze-thaw cycles,the samples with WGP content of 20%and W/C of 0.26 have the best freeze-resistance.Microscopic tests show that with the increase of WGP content,the Ca/Si ratio of C-S-H gel decreases at first and then increases with the increase of WGP content.The extreme value of Ca/Si is 2.36 when WGP is added by 20%.The pore volume of hardened paste with 20%WGP content decreased by 18.6%compared with that of cement system without WGP.The overall compactness of the specimen was improved.On the basis of the test data,a life prediction model was established according to Weibull function.The experiment showed thatΔfc could be used as a durability degradation index,and the slope of the reliability curve became gentle after WGP was added,which reduced the damage degradation rate of PC.W/C was 0.26.It's about 5000 hours.

Study of Individual Characteristic Abdominal Wall Thickness Based on Magnetic Anchored Surgical Instruments

Background：Magnetic anchored surgical instruments （MASI）,relying on magnetic force,can break through the limitations of the single port approach in dexterity.Individual characteristic abdominal wall thickness （ICAWT） deeply influences magnetic force that determines the safety of MASI.The purpose of this study was to research the abdominal wall characteristics in MASI applied environment to find ICAWT,and then construct an artful method to predict ICAWT,resulting in better safety and feasibility for MASI.Methods：For MASI,ICAWT is referred to the thickness of thickest point in the applied environment.We determined ICAWT through finding the thickest point in computed tomography scans.We also investigated the traits of abdominal wall thickness to discover the factor that can be used to predict ICAWT.Results：Abdominal wall at C point in the middle third lumbar vertebra plane （L3） is the thickest during chosen points.Fat layer thickness plays a more important role in abdominal wall thickness than muscle layer thickness.＂BMI-ICAWT＂ curve was obtained based on abdominal wall thickness of C point in L3 plane,and the expression was as follow：f（x） =P1 × x^2 ＋ P2 x x ＋ P3,where P1 =0.03916 （0.01776,0.06056）,P2 =1.098 （0.03197,2.164）,P3 =-18.52 （-31.64,-5.412）,R-square：0.99.Conclusions：Abdominal wall thickness of C point at L3 could be regarded as ICAWT.BMI could be a reliable predictor of ICAWT.In the light of ＂BMI-ICAWT＂ curve,we may conveniently predict ICAWT by BMI,resulting a better safety and feasibility for MASI.

Modeling the rail surface unevenness of a high-precision radio telescope

This study proposed a coarse-fine mixed model for describing the rail surface unevenness of an ultra-large fully steerable radio telescope （Qi Tai Telescope） with a diameter of 110 meters. The rail surface unevenness includes information on error arising from two different scales, i.e., the long-period- short-change and the short-period-long-change. Consequently, in this study an idea of a mixed model was proposed, in which trigonometric and fractal functions were, respectively, used to describe infor- mation on error from two scales. Key parameters were determined by using the least squares method and the wavelet transform method, and finally, a specific mathematical expression of the model was obtained by optimization. To validate the effectiveness of the new modeling method, the mixed model was then used to describe the rails of the Green Bank Telescope, the Large Millimeter Telescope, and a radio telescope in Miyun, Beijing. A comparative study revealed that the maximum error was less than 15 %, thus the result was superior to those of existing modeling methods.