Measurement of the high energyγ-rays from heavy ion reactions usingČerenkov detector

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the γ-rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident γray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The γresponse and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of 0.022(4) + 0.51(2)∕E^(1/2)_(γ) for water and 0.0026(3) + 0.446(3)∕E^(1/2)_(γ) for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm × 30 cm × 30 cm and 60 cm × 60 cm ×120 cm, respectively, to detect high-energy γ-rays at 160 MeV. The Hough transform method was applied to reconstruct the direction of the incident γ-rays, providing the ability to experimentally distinguish the high-energy γ-rays produced in the reactions on the target from random background cosmic-ray muons.

Artificial neural network-based method for discriminating Compton scattering events in high-purity germaniumγ-ray spectrometer

To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.

分布式水文-土壤-植被模式的改进及气候水文Off-line模拟试验

文中对引进的高分辨率 (94 2 .5m× 94 2 .5m)分布式水文 土壤 植被模式 (DHSVM) ,针对海、滦河流域的特点进行了改进 ,主要包括 :(1)改变蒸散发模拟方法 ,用改进的Penman Monteith模式模拟海滦河流域的蒸发 ,较好地模拟出 1a内的两个峰值 ,最大值出现在 4～ 6月 ,次大值出现在 7～ 8月 ;(2 )改变水文模式结构 ,用多站点气候观测资料内插到模式网格点 ,充分实现了分布式水文模拟 ;(3)发展新的水文、植被、土壤参数化方案 ,对 33个参数分区计算和确定 ,并重点对土壤孔隙度 φ、土壤蓄水能力θfc、叶面指数LAI、随机阻抗γs 等 11个参数进行调试和修订 ,提高了水文模拟精度。用改进的DHSVM模式分别对滦河、桑干河流域蒸散发、地下水位、土壤湿度、土壤水下渗、产流、汇流与径流等水文过程进行Off line模拟试验 ,模拟结果与实测值一致性较好 ,滦河流域 1979～ 1991年、桑干河流域 1979～ 1987年水文模拟效率系数分别为 0 .89和 0 .82 。

A Land Surface Model(IAP94) for Climate Studies PartI:Formulation and Validation in Off-line Experiments

The IAP (Institute of Atmospheric Physics) land-surface model (IAP94) is described. This model is a comprehensive one with detailed description for the processes of vegetation, snow and soil. Particular attention has been paid to the cases with three water phases in the surface media. On the basis of the mixture theory and the theory of fluid dynamics of porous media, the system of universal conservational equations for water and heat of soil, snow and vegetation canopy has been constructed. On this background, all important factors that may affect the water and heat balance in media can be considered naturally, and each factor and term possess distinct physical meaning. In the computation of water content and temperature, the water phase change and the heat transportation by water flow are taken into account. Moreover, particular attention has been given to the water vapor diffusion in soil for arid or semi-arid cases, and snow compaction. In the treatment of surface turbulent fluxes, the difference between aerodynamic and thermal roughness is taken into account. The aerodynamic roughness of vegetation is calculated as a function of canopy density, height and zero-plane displacement. An extrapolation of log linear and exponential relationship is used when calculating the wind profile within canopy. The model has been validated against field measurements in off-line simulations. The desirable model′s performance leads to the conclusion that the IAP94 is able to reproduce the main physical mechanisms governing the energy and water balances in the global land surface. Part II of the present study will concern the validation in a 3-D experiment coupled with the IAP Two-Level AGCM.

Designing and Optimization of an Off-line Programming System for Robotic Belt Grinding Process

Off-line programming （OLP） system becomes one of the most important programming modules for the robotic belt grinding process, however there lacks research on increasing the grinding dexterous space depending on the OLP system. A new type of grinding robot and a novel robotic belt grinding workcell are forwarded, and their features are briefly introduced. An open and object-oriented off-line programming system is developed for this robotic belt grinding system. The parameters of the trimmed surface are read from the initial graphics exchange specification （IGES） file of the CAD model of the workpiece. The deBoor-Cox basis function is used to sample the grinding target with local contact frame on the workpiece. The numerical formula of inverse kinematics is set up based on Newton＇s iterative procedure, to calculate the grinding robot configurations corresponding to the grinding targets. After the grinding path is obtained, the OLP system turns to be more effective than the teach-by-showing system. In order to improve the grinding workspace, an optimization algorithm for dynamic tool frame is proposed and performed on the special robotic belt grinding system. The initial tool frame and the interval of neighboring tool frames are defined as the preparation of the algorithm. An optimized tool local frame can be selected to grind the complex surface for a maximum dexterity index of the robot. Under the optimization algorithm, a simulation of grinding a vane is included and comparison of grinding workspace is done before and after the tool frame optimization. By the algorithm, the grinding workspace can be enlarged. Moreover the dynamic tool frame can be considered to add one degree-of-freedom to the grinding kinematical chain, which provides the theoretical support for the improvement of robotic dexterity for the complex surface grinding.

An off-line simulation of land surface processes over the northern Tibetan Plateau

In order to further understand the land surface processes over the northern Tibetan Plateau, this study produced an off-line simulated examination at the Bujiao site on the northern Tibetan Plateau from June 2002 to April 2004, using the Noah Land Surface Model （Noah LSM） and observed data from the CAMP/Tibet experiment. The observed data were neces- sarily corrected and the number of soil layers in the Noah LSM was changed from 4 to 10 to enable this off-line simulation and analysis. The main conclusions are as follows： the Noah LSM performed well on the northern Tibetan Plateau. The simulated net radiation, upward longwave radiation, and upward shortwave radiation demonstrated the same remarkable annual and seasonal variation as the observed data, especially the upward longwave radiation. The simulated soil temperatures were acceptably close to the observed temperatures, especially in the shallow soil layers. The simulated freezing and melting processes were shown to start from the surface soil layer and spread down to the deep soil layers, but they took longer than the observed processes. However, Noah LSM did not adequately simulate the soil moisture. Therefore, additional high-quality, long-term observations of land surface-atmosphere processes over the Tibetan Plateau will be a key factor in proper adiustments of the model parameters in the future.

A word level segmentation for off-line Arabic characters

Segmentation of cursive text has been one of the major problems in Arabic writing. The problem is the shape of the letter which is context sensitive, depending on it’s location within a word. Many text recognition systems recognize text imagery at the character level and assemble words from the recognized characters. Unfortunately this approach does not work with Arabic text. In this paper we describe a new approach to segment Arabic text imagery at a word level, without analyzing individual characters. This approach avoids the problem of individual characters segmentation, and can overcome local errors in character recognition.

Off-line simulation of robot welding of radar pedestal

A study of the interference simulation based on robot welding of the radar pedestal was carried out by using the KUKA Sim Pro simulation software and off-line program technology. Compared with the actual robot welding process, it was found that the trajectory of the simulated robot welding process in line with that recorded in the actual welding process, and the actual limit and interference appeared at the same place as the simulation process. There was no interference phenomenon on the outside weld-seam; on the internal weld-seam, especially on the weld-joint of support plate connected to the cylinder, a phenomenon of interference appeared. It was helpful to use the simulation method to guide the actual robot welding so as to protect robot from impacting and reduce the weld defects.

Study on path planning and compensation of off-line programming for thick walled curve welding

Thick walled curve welding are usually joined by multi-layer and multi-pass welding, which quality and efficiency could be improved by off-line programming of robot welding. However, the precision of off-line programming welding path was decreased due to the deviation between the off-line planned welding path and the actual welding path. A path planning algorithm and a path compensation algorithm of multi-layer and multi-pass curve welding seam for off-line programming of robot welding are developed in this paper. Experimental results show that the robot off-line programming improves the welding efftcieney and precision for thick walled curve welding seam.

Generalization ability of a CNNγ-ray localization model for radiation imaging

Inγ-ray imaging,localization of theγ-ray interaction in the scintillator is critical.Convolutional neural network(CNN)techniques are highly promising for improvingγ-ray localization.Our study evaluated the generalization capabilities of a CNN localization model with respect to theγ-ray energy and thickness of the crystal.The model maintained a high positional linearity(PL)and spatial resolution for ray energies between 59 and 1460 keV.The PL at the incident surface of the detector was 0.99,and the resolution of the central incident point source ranged between 0.52 and 1.19 mm.In modified uniform redundant array(MURA)imaging systems using a thick crystal,the CNNγ-ray localization model significantly improved the useful field-of-view(UFOV)from 60.32 to 93.44%compared to the classical centroid localization methods.Additionally,the signal-to-noise ratio of the reconstructed images increased from 0.95 to 5.63.

Study on Color Information Degradation Induced byγ-ray Radiation in CMOS Cameras

Theγ-rays are widely and abundantly present in strong nuclear radiation environments,and when they act on the camera equipment used to obtain environmental visual information on nuclear robots,radiation effects will occur,which will degrade the performance of the camera system,reduce the imaging quality,and even cause catastrophic consequences.Color reducibility is an important index for evaluating the imaging quality of color camera,but its degradation mechanism in a nuclear radiation environment is still unclear.In this paper,theγ-ray irradiation experiments of CMOS cameras were carried out to analyse the degradation law of the camera’s color reducibility with cumulative irradiation and reveal the degradation mechanism of the color information of the CMOS camera underγ-ray irradiation.The results show that the spectral response of CMOS image sensor(CIS)and the spectral transmittance of lens after irradiation affect the values of a^(*)and b^(*)in the LAB color model.While the full well capacity(FWC)of CIS and transmittance of lens affect the value of L^(*)in the LAB color model,thus increase color difference and reduce brightness,the combined effect of color difference and brightness degradation will reduce the color reducibility of CMOS cameras.Therefore,the degradation of the color information of the CMOS camera afterγ-ray irradiation mainly comes from the changes in the FWC and spectral response of CIS,and the spectral transmittance of lens.

SPECTRAL TECHNIQUES FOR OFF-LINE TESTING AND DIAGNOSIS OF COMPUTER SYSTEMS

In this paper we present some of our recent results on applications of spectral techniques over finite fields to the problems of testing and diagnosis of computer systems.

费米耀变体的多波段γ-ray辐射

从Fermi/LAT第3期源表(3FGL)中选取了920个Blazar样本,包含414个平谱射电源(Flat Spectrum Radio Quasar,FSRQ)和506个蝎虎天体(BL Lac object,BL Lac),其中有226个HBL,140个IBL和140个LBL.研究了所有Blazar样本及其子类FSRQ,BL Lac,HBL和LBL样本的射电1.4 GHz光度分别与γ-ray在0.1,0.3,1,3及10 GeV处光度之间的相关性。结果表明:对总样本及所有子类样本,1.4 GHz光度与γ-ray各频率处的光度均存在强的正相关性,但对于不同的子类样本,这种相关性随γ-ray频率的变化趋势不同;BL Lac的相关性好于FSRQ,而HBL的相关性与LBL相似。总的来说,随着γ-ray辐射频率的增加,相关性有减弱的趋势。但是,对于不同的样本,相关性随γ-ray频率增加有不同的变化趋势。因此,同一频率下不同子类Blazar的γ-ray辐射机制存在差异,同一样本在不同频率下的γ-ray辐射机制也有差异.在γ-ray辐射中,BL Lac的辐射来自同步自康普顿(SSC)过程的成分比FSRQ的多,而HBL的与LBL的相似.FSRQ的γ-ray辐射机制比BL Lac更为复杂。

Hypoglycemic activities of flowers of Xanthoceras sorbifolia and identification of anti-oxidant components by off-line UPLC-QTOF-MS/MS-free radical scavenging detection

Objective: To identify phytochemical constituents present in the extract of flowers of Xanthoceras sorbifolia and evaluate their anti-oxidant and anti-hyperglycemic capacities.Methods: The AlCl3colorimetric method and Prussian Blue assay were used to determine the contents of total flavonoids and total phenolic acids in extraction layers, and the bioactive layers was screened through anti-oxidative activity in vitro. The Waters ACQUITY UPLC system and a Waters ACQUITY UPLC BEH C18column(2.0 mm × 150 mm, 5 μm) were used to identify the ingredients. And anti-oxidative ingredients were screened by off-line UPLC-QTOF-MS/MS-free radical scavenging. The ameliorative role of it was further evaluated in a high-fat, streptozotocin-induced type 2 diabetic rat model and the study was carried out on NADPH oxidase(PDB ID: 2CDU) by molecular docking.Results: Combined with the results of activity screening in vitro, the anti-oxidative part was identified as the ethyl acetate layer. A total of 24 chemical constituents were identified by liquid chromatographymass spectrometry in the ethyl acetate layer and 13 main anti-oxidative active constituents were preliminarily screened out through off-line UPLC-QTOF-MS/MS-free radical scavenging. In vivo experiments showed that flowers of X. sorbifolia could significantly reduce the blood glucose level of diabetic mice and alleviate liver cell damage. Based on the results of docking analysis related to the identified phytocompounds and oxidase which involved in type 2 diabetes, quercetin 3-O-rutinoside, kaempferol-3-O-rhamnoside, isorhamnetin-3-O-glucoside, and isoquercitrin showed a better inhibitory profile.Conclusion: The ethyl acetate layer was rich in flavonoids and phenolic acids and had significant anti-oxidant activity, which could prevent hyperglycemia. This observed activity profile suggested X. sorbifolia flowers as a promising new source of tea to develop alternative natural anti-diabetic products with a high safety margin.

A novel control strategy for reproducing the floor motions of high-rise buildings by earthquake-simulating shake tables

To enable the experimental assessment of the seismic performance of full-scale nonstructural elements with multiple engineering parameters(EDPs),a three-layer testbed named Nonstructural Element Simulator on Shake Table(NEST)has been developed.The testbed consists of three consecutive floors of steel structure.The bottom two floors provide a space to accommodate a full-scale room.To fully explore the flexibility of NEST,we propose a novel control strategy to generate the required shake table input time histories for the testbed to track the target floor motions of the buildings of interest with high accuracy.The control strategy contains two parts:an inverse dynamic compensation via simulation of feedback control systems(IDCS)algorithm and an offline iteration procedure based on a refined nonlinear numerical model of the testbed.The key aspects of the control strategy were introduced in this paper.Experimental tests were conducted to simulate the seismic responses of a full-scale office room on the 21^(st)floor of a 42-story high-rise building.The test results show that the proposed control strategy can reproduce the target floor motions of the building of interest with less than 20%errors within the specified frequency range.

电子束和γ-ray对UHMWPE纤维的辐照效应对比研究

γ-ray和电子束是高能辐照源,高能射线不仅可以处理被加工物表面,同时可深入其内部,且工艺控制简单,可进行常温或者低温加工,具有节能、无环境污染等特点.分别采用γ-ray和电子束辐照超高相对分子质量聚乙烯(UHMWPE)纤维,采用电子自旋共振(ESR)、红外光谱(IR)、差示扫描量热法(DSC)、X射线衍射(XRD)、扫描电镜(SEM)、凝胶含量和拉伸实验等表征手段对不同的辐照效应进行研究,旨在改善纤维表面惰性,探索合理使用两种辐射源辐照改性材料的适用范畴,为更好地利用辐照技术对UHMWPE纤维表面改性提供理论依据.

Methods for obtaining characteristic γ-ray net peak count from interlaced overlap peak in HPGe γ-ray spectrometer system

For a characteristic c-ray with interlaced overlap peak, and the case where its reliable and credible net count cannot be obtained using the current high-purity germanium(HPGe) multichannel γ-ray spectrum software, two new methods are proposed herein to obtain the γ-ray net peak count from the interlaced overlap peak in the HPGe cray spectrometer system, of which one is the symmetric conversion method based on Gaussian distribution and the other is where the energy average value of two close γ-rays is regarded as the γ-ray energy. The experimental results indicate that the two methods mentioned above are reliable and credible. This study is significant for the development of better γ-ray spectrum processing software for measuring complex γ-ray spectra concerning the nuclear reaction cross section, neutron activation analysis, and analysis of transuranium elements, using an HPGe detector.

Similar therapeutic effects of ^(125I) seed radiotherapy andγ-ray radiotherapy on lacrimal gland adenoid cystic carcinoma

AIM:To evaluate the survival outcomes of patients with lacrimal gland adenoid cystic carcinoma who underwent eye-sparing surgery combined with ^(125I)seed implantation radiotherapy or local externalγ-ray radiotherapy.METHODS:In this retrospective comparative case series,the clinical records of 27 primary and 8 recurrent patients were reviewed.Univariate and multivariate analyses were used to identify risk factors associated with distant metastasis(DM),and the overall survival(OS)after the initial surgery was analyzed.RESULTS:The median follow-up after radiotherapy was 36 mo(range 6-120 mo).At the last follow-up after radiotherapy,26(74.3%)patients had no evidence of disease,7(20%)patients had DM,2(5.9%)patients died of DM,and 1 patient with DM was lost to follow-up.Univariate analyses showed that duration of symptoms,bone destruction,T stage classification,and wide excision surgery were risk factors influencing DM(P<0.05).The 5-year and 10-year OS rates after the initial surgery were 95.8%and 79.9%,respectively.The 5-year DM-free survival and disease-free survival rates after radiotherapy were 66.4%and 52.7%,respectively.CONCLUSION:^(125I)seed radiotherapy and local externalγ-ray radiotherapy may have similar therapeutic effects in preventing DM.Patients with T1/T2 stage disease have a better prognosis than those with T3/T4 stage disease.

Comparative Study on Effects of Low Energy N^+ Implantation and γ-ray Radiation on Heredity and Development of Arabidopsis Thaliana

In order to compare the contemporary and genetic variation effect on Arabidop-sis thaliana treated with N+ implantation and 7-ray radiation, the authors did some statistical comparison on the germinating rate and the development period, and analyzed the content of soluble proteins, the activity of some enzymes, isoenzymes profile, and along with the variation in genome DNA of two generations by RAPD. With N+ implantation there was an analogical 'saddle model' relationship between doses and the plant development, soluble proteins, the activity of some enzymes and isoenzymes profile. A certain connection might exist between the similar dose-effect relations among enzymes activity, isoenzymes profile and content of soluble proteins. Maybe, there also exists a certain connection between the mutants of development period and that of DNA variations, between the hereditability of the effect of N+ implantation on the isoenzymes, the activities of enzymes and the hereditability of DNA variations. So it is presumed that the implanted ions, maybe, have participated in metabolism process of organism including that of genome DNA, to consequently affect vital process, such as the changes of gene structure, gene expression manner and gene repair mechanism, and finally result in mutation on phenotype and molecular level. Furthermore, the results definitely showed that mutagenic mechanism induced by N+ implantation is very complicated and is much different from that induced by traditional 7-ray radiation.

Laser-induced damage threshold in HfO_2/SiO_2 multilayer films irradiated by β-ray

Post-processing can effectively improve the resistance to laser damage in multilayer films used in a high power laser system. In this work, HfO_2/SiO_2 multilayer films are prepared by e-beam evaporation and then β-ray irradiation is employed as the post-processing method. The particle irradiation affects the laser induced damage threshold(LIDT),which includes defects, surface roughness, packing density and residual stress. The residual stress that is relaxed during irradiation changes from compressive stress into tensile stress. Our results indicate that appropriate tensile stress can improve LIDT remarkably. In view of the fact that LIDT rises from 8 J/cm^2 to 12 J/cm^2, i.e., 50% increase, after the film has been irradiated by 2.2×10^(13)/cm^2 β-ray, the particle irradiation can be used as a controllable and desirable postprocessing method to improve the resistance to laser induced damage.