选区激光烧结单组份金属粉末试验研究

选区激光烧结由于可以不受材料的限制,可以快速烧结出任意复杂的三维实体,被认为是最具发展前景的快速制造技术.用激光直接烧结金属粉末成形已成为目前研究的重点.本文用YAG激光对铝粉、铁粉、铅粉进行了对比烧结试验,同样条件下,不同的金属粉末激光烧结的结果不同,铝粉烧结球化现象严重,铅粉烧结伴有飞溅严重,铁粉烧结随着扫描速度的增加,烧结由连续金属线逐渐成为断续的以至球形金属颗粒.最后分析了激光烧结球化的机理.     

炮位侦察雷达面临的挑战及发展趋向

现代高、新技术推动了炮兵武器的发展，火炮射程增大、火力猛、精度高、反应快机动能力强、射弹弹道发生变化、伪装隐身技术先进。炮位侦察雷达面临技术、战术挑战，必须进一步提高性能。增大雷达作用距离，缩小体积、减轻重、提高机动性，采用自动定向系统，增加多目标处理能力，提高抗干扰和探测隐身目标能力。     

Chappuis-Wulf波段临边辐射臭氧廓线的反演

临边辐射探测技术是一种新型卫星探测技术,主要利用紫外-可见光-红外太阳散射光谱获得臭氧等痕量气体在垂直方向上的分辨率廓线信息.基于波长配对光谱分析法、乘代数重建技术以及SCIATRAN正向模型,用SCIAMACHY仪器临边辐射反演垂直高度为10～40 km、分辨率为1 km的臭氧数密度.首先,根据臭氧在Chappuis...     

乌鲁木齐市采暖期大气PM_(2.5)、PM_(10-2.5)中重金属污染水平评价

针对2007年12月至2008年1月在乌鲁木齐市采集的可吸入颗粒物(PM2.5-10和PM2.5),采用消解法和双道原子荧光光法(AFS)、电感耦合等离子体质谱仪法(ICP-AES)分析了样品中的5种重金属元素,并对MP10-2.5和PM2.5中重金属的污染水平和人类活动的贡献进行了评价.结果表明:PM10-2.5质量浓度平均值187μg/m3,超过国家二级标准(150μg/m3)的1.25倍、PM2.5质量浓度平均值为279μg/m3,超过美国EPA1997年颁布的PM2.5日平均值65的4.3倍.PM10-2.5和PM2.5中Pb的污染指数1Igeo10为重污染、Cd、Hg的Igeo10为严重污染.富集因子分析得出乌鲁木齐市Cd和Hg元素的EF值大于10,说明这些元素主要是人为源贡献,受土壤扬尘的影响较少;而Co、Pb元素的EF值在1～10之间,说明其主要来自自然来源.     

ATPF—a dedicated proton therapy facility

A proton therapy facility based on a linac injector and a slow-cycling synchrotron is proposed. To obtain good treatments for different cancer types, both the spot scanning method and the double-scattering method are adopted in the facility, whereas the nozzles include both gantry and fixed beam types. The proton accelerator chain includes a synchrotron of 250 MeV in maximum energy, an injector of 7 MeV consisting of an RFQ and a DTL linac, with a repetition rate of 0.5 Hz. The slow extraction using the third-order resonance and together with the RFKO method is considered to be a good method to obtain a stable and more-or-less homogenous beam spill. To benefit the spot scanning 200 between 60 MeV and 230 MeV. A new method method, the extraction energy can be as many as about - the emittance balancing technique of using a solenoid or a quadrupole rotator is proposed to solve the problem of unequal emittance in the two transverse planes with a beam slowly extracted from a synchrotron. The facility has been designed to keep the potential to be upgraded to include the carbon therapy in the future.     

基于树莓派的创意天气播报设计

天气预报是关键的气象工作之一,是宏观经济和国防建设服务的重要手段,对人们的生活起居起着非常大的作用。随着科学技术日新月异,人们获取天气数据的途径也有了极大的变化。气象部门始终紧跟发展的步伐,使天气信息传播渠道不断多样和融合。文章通过分析语音天气播报国内外的发展状况和发展趋势,概括API调用天气数据、室内温湿度数据的获取、语音识别等技术,对比总结了天气播报系统设计的方法,实现了基于树莓派的创意天气播报的设计。本成品能显示当天的天气、室内温度、自定位城市文字,同时实时播报当天天气、定位信息、穿搭建议等信息,并将播报出来的信息发送至指定邮箱,大大提高人们的生活质量。     

A 1550-nm linearly tunable continuous wave single-mode external cavity diode laser based on a single-cavity all-dielectric thin-film Fabry Pérot filter

A 1550-nm linearly tunable continuous wave (CW) single-mode external cavity diode laser (ECDL) based on a singlecavity all-dielectric thin-film Fabry-Pérot filter (s-AFPF) is proposed and realized in this paper. Its internal optical components as well as their operation mechanisms are introduced first, and then its longitudinal mode output characteristic is theoretically analyzed. Afterwards, we set up the experimental platform for the output characteristic measurement of this tunable ECDL; under different experimental conditions, we execute accurate and real-time measurements for the output central wavelength, output optical power, output longitudinal mode distribution, and the line-width of the tunable ECDL in its tuning process. By summing up the optimal experimental condition from the measured data, we obtain the optimal tunable ECDL relevant parameters: the tunable ECDL has a linear mode-hop-free wavelength tuning region of 1547.203 nm-1552.426 nm, a stable output optical power in the range of 40 μW-50 μW, and a stable output longitudinal mode distribution of a single longitudinal mode with a line-width in the range of 100 MHz-150 MHz. This tunable ECDL can be used in environmental gas monitoring, atomic and molecular laser spectroscopy research, precise measurements, and so on.     

粗细电缆低反射系数连接器阶梯电容的补偿设计

电缆与电缆连接器端面处不可避免地会出现机械段不连续,形成阶梯电容,干扰电磁波的正常传播,使得电缆与连接器的相应连接端面处反射系数增加。依据电磁波传输理论、射频电缆的参数理论和电缆连接器阶梯电容的错位补偿原理,推导出了电缆连接器高抗补偿绝缘垫片厚度的相对普适公式。针对电缆连接器与射频同轴细电缆SYV-50-7和射频同轴粗电缆SYV-50-17连接之间阶梯电容约0.1pF的情况,理论计算补偿绝缘垫片厚度应约为2mm,应用中可通过加工多个补偿厚度尺寸与理论计算值相邻的绝缘垫片,并在实际安装时进行调节,从而最终确定绝缘垫片的最佳补偿厚度。可以预见,合适的实验验证和优化,可使电缆与连接器端面连接处的阶梯电容减少,甚至消除,综合特性阻抗与电缆和连接器均匀一致,反射系数小于0.8%是可能的。     

Electromagnetic modeling of the CSNS Hion source extraction system

A Penning surface H^- ion source test stand has been developed for the China Spallation Neutron Source (CSNS) at the Institute of High Energy Physics (IHEP). H^- beams with a current up to 50 mA and a pulse length up to 520μs at a repetition rate of 25 Hz are obtained at present. In order to improve the extraction system based on both the results of the emittance measurements in experiment and the simulation results of the effect of the extraction system on the beam emittance, three dimensional electromagnetic finite element analysis and particle tracking are undertaken. First, the magnetic field of the deflecting magnet is studied in detail, and then the effect of the extraction geometry on the beam transport is also investigated.     

微波消解-溶出伏安法对食品中铜、铅、镉的同时测定

采用微波消解结合同位镀汞阳极溶出伏安法对茶叶、紫菜和西洋菜等食品中的铜、铅、镉进行了测定,并优化了微波消解、电解缓冲液、富集电位等实验条件。采用标准加入法定量,Cu、Pb、Cd的线性范围分别为0.040~1.768、0.080~1.768、0.040~1.768 mg/L,相关系数分别为0.998 4、0.998 2、0.997 0,检出限分别为0.008、0.016、0.008 mg/L,相对标准偏差(n=5)分别为4.1%、0.92%、2.0%。该方法测定茶叶、紫菜、西洋菜等实际样品的铜、铅、镉含量,加标回收率分别为98%~109%、94%~103%、100%~112%;将测定结果与原子吸收光谱法检测结果对比,表明此方法简便、快速,且具有较高的灵敏度、较好的选择性和可靠性。