STUDY ON WOOD COMPOSITES DENSITY UNIFORMITY BY X-RAY

X-ray is irradiated in some wood composites(multi-layer particleboard.sin-gle-layer particleboard,reconsolidated wood,).According to the gray degree principle(0-255 grade degree)and the corresponding relation between density and gray,X-raynegatives are scanned.The numbers and pictures of every degree density are obtained andaccurate composite densities are counted.

THE PROGRESS ON SPACE ASTRONOMY IN CHINA DURING 2000-2002

In this paper main achievements in the area of space astronomy are summarized.During the flight of cosmic Gamma-Ray Burst Spectrometer(GRBS) onboard spacecraft Shenzhou-2(launched on 2001-01-10), much observational results of cosmic γ-ray burst and solar X, γ-ray burst are obtained. The preliminary analysis on space data has lead to some interesting results. Besides it, some other long-term space astronomy programs are briefly described here.

Preliminary experimental study and simulation of an energy-tunable quasi-monochromatic laser-Compton X/γ-ray source

We propose a slanting collision scheme for Compton scattering of a laser light against a relativistic electron beam. This scheme is suitable to generate an energy-tunable X/γ-ray source. In this paper, we present theoretical study and simulation of the spectral, spatial and temporal characteristics of such a source. We also describe two terms laser-Compton scattering （LCS） experiments at the 100 MeV Linac of Shanghai Institute of Applied Physics, where quasi-monochromatic LCS X-ray energy spectra with peak energies of ～ 30 keV are observed successfully. These preliminary investigations are carried out to understand the feasibility of developing an energy-tunable quasi-monochromatic X/γ-ray source, the future Shanghai Laser Electron Gamma Source.

Measurement of ^(59)Co(ai,x)reaction cross sections with the fast neutrons based on the ^(9)Be(p,n)reaction

The cross sections of the ^(59)Co(n,x)reaction in the average energy range of 15.2-37.2 MeV were meas-ured using activation and an off-line γ-ray spectrometric technique.The neutrons were generated from the ^(9)Be(p,n)reaction with proton beam energies of 25-45 MeV at the MC-50 Cyclotron facility of the Korean Institute of Radi-ological and Medical Sciences(KIRAMS).Theoretical cal lculations of neutron-induced reactions on ^(59)Co were per-formed using the nuclear model code TALYS-1.9.The results for the ^(59)Co(n,x)reactions were compared with the theoretical values obtained using TALYS-1.9 and the literature data provided in EXFOR and the TENDL 2019 nuc-lear data library.The theoretical values obtained using TALYS-1.9 with adjusted parameters are comparable to the experimental data.The measured reaction cross sections of a few radionuclides are new,and the others are compar-able to the literature data,and thus,they can strengthen the database.The present study on cross sections leads to useful insight into the mechanisms of ^(59)Co(n,x)reactions.

Spiral CT arthrography of multiplanar reconstruction and virtual arthroscopy technique in diagnosis of knee with internal derangements

Objective:To evaluate the values of spiral CT arthrography with multiplanar reconstruction and virtual arthroscopy technique i n diagnosis of internal derangements of the knee. Methods:Ten bovine knees were used for experiment. The menisci , anterior and posterior cruciate ligaments and cartilage of these 10 bovine kne es were injured with a hook. Each of the joints was injected with 100 ml air, th en soon scanned with a PQ6000 spiral computed tomography scanner. The data obtai ned was input into the work station, and multiplanar reconstruction technique wa s used to illustrate lesions in the knees. The results of CT diagnosis were comp ared to those found by gross inspection of the specimens. Clinically, 10 knees o f 9 patients diagnosed as internal derangement were evaluated with the same meth od after 50-70 ml air was injected into each of the joints. Nine months later, the data of 2 patients were used for CT endoscopy reconstruction. The results we re compared with intraoperative findings. Results:Experimentally, the sensitivity and specificity were 88.9 % and 93.9 % by detection of meniscal abnormalities, 85.7 % and 10 0% by detection of cruciate ligament lesions, and 72.7 % and 100% by detectio n of cartilage damage, respectively. Clinically, the sensitivity and specificity were 90.0 % and 95.0 % by detection of meniscal lesion. As to ligament, t he figures were 85.7 % and 100% respectively. Images of virtual arthroscopy s imulated the images of real arthroscopy. Conclusions:Spiral CT arthrography of multiplanar reconstructi on technique offers fine images of internal structures of the knee, with clear b order and internal structure. It is an accurate method for detecting meniscal, cruciate and collateral ligament and cartilaginous lesions that cause internal d erangement of the knee. Virtual arthroscopy technique is a hopeful method for de tecting reasons of derangement of the knee.