Degradation of Furfural by UV/O3 Technology

Furfural in aqueous solution was treated by UV/O3 method.The results show that the removal rate of furfural is severely enhanced and the synergism phenomenon appears when ultraviolet and ozone are present together.The influences of experimental parameters such as pH,the intensity of light and the negative-positive ions on furfural degradation were investigated.The results indicate that furfural(300 mg/L) is almost completely degraded after 3 h under the optimum conditions.The intermediate in the furfural de...     

毛细管区带电泳技术快速分离检测爆炸残留物中的无机离子

利用间接紫外毛细管区带电泳方法完成了对爆炸残留物中7种无机离子(K+,NH+4,NO-2,NO-3,SO2-4,ClO-3,ClO-4)的分离检测。阳离子测定采用的缓冲体系为10 mmol/L吡啶（pH 4.5）-3 mmol/L冠醚,K+和NH+4在2.6 min内达到基线分离,检出限分别为0.25 mg/L和0.10 mg/L(S/N=3)。阴离子测定采用的缓冲体系为40 mmol/L硼酸-1.8 mmol/L重铬酸钾-2 mmol/L硼酸钠（pH 8.6）,氢氧化四甲铵为电渗流改性剂,5种阴离子在4.6 min内达到基线分离,检出限为0.10～1.85 mg/L。该方法已成功地应用于实际爆炸物样品种类的判定分析,取得了很好的结果。     

一个1+1对转涡轮的初步设计

本文初步尝试１＋１对转涡轮设计,试图发现区别于常规涡轮设计存在的问题,探索对转涡轮设计体系的组成和应用策略,对１＋１对转涡轮给出初步评价。     

便携式红外甲烷浓度测试仪的研制

利用红外吸收原理,研制一种测量1．33um波段甲烷浓度的测试仪,该仪器的特点是测量时不受其他气体成份影响,体积小,精度高,采用数字显示,操作简单,适合野外条件下使用。     

Design of a β=0.45, f=350 MHz Spoke Cavity

Recently intensive studies have been done on superconducting cavities (e.g. spoke cavity, reentrant cavity, and ch cavity), which are used as accelerating structures in the low and medium energy part of high power high intensity proton or ion accelerators. many experiments have shown that spoke cavity is a good candidate for low energy part. it is also promising to be used for the medium β area. so a β=0.45 spoke cavity is being studied at Peking university. in this paper, the structural and electromagnetic design of a β=0.45, f=350mhz spoke cavity is reported in detail. the calculated rf parameters (e.g. Q, r/Q, peak surface fields and dissipated power) indict a potential of good acceleration.     

A New Measurement of Electron Beam Emittance with Cerenkov Radiation “Double Imaging” Method

A new way in electron beam emittance measurement with Cerenkov radiation "double imaging" method is proposed in this paper. In the standard emittance measurements with optical diagnostics such as Cerenkov radiation, OTR (Optical Transition Radiation), fluorescence screen or BMP (beam profile monitor) etc., the emittance is indirectly calculated through quadrupole-scanning technique, with the prior ssumption that the beam phase space density distribution is ellipse, which will certainly induce systematic error when the beam profile is quite irregular or the space-charge effects can not be omitted. In proposed method, the Cerenkov radiation pass through a 1-meter focal-length thin convex lens, and a CCD camera is used to capture two images of Cerenkov radiation at the focal plane and at the image plane of the lens respectively. Then, with image processing technique, we acquire the angular divergence information of the electron beam from the image of the focal plane and the radial distribution information from the image of the image plane, which we call Cerenkov radiation "double imaging" method. Therefore, the emittance can be directly attained according to the definition of the RMS emittance. By this method, we can measure the actual phase space distributions without making any prior assumptions about the density distributions. Compared with other general measurements, this "double imaging" method has advantages of simpler equipment, higher precision and wider application. This paper also presents the computer simulation results of emittance measurement on the DC-SC (DC-Superconducting) photocathode injector of PKU-SCAF (Peking University Superconducting Accelerator Facility) being built at Peking University.     

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针对国家标准GB/T18215.1-2000中规范的"差压式流量计示值修正公式",从以下方面进行了讨论: (1)干气体流量检测示值修正公式; (2)湿气体干部分流量检测示值修正公式; (3)气体组分改变时流量检测示值修正公式.国标中规范的修正公式是建立在: "当气体的温度、压力变化时,其密度也随着发生改变,相同的差压值(设计状态与工作状态)所对应的流量值是不同的".本文认为:当气体工作温度、压力等参数偏离设计条件时,同一质量流量在节流装置前后产生的设计状态与工作状态差压是不同的.这一基础要领的分岐,影响着所有修正公式.     

Low Temperature Preparation and Absorption Spectra of Nanocrystalline Pb1-xLaxTiO3 Thin Film on ITO Conducting Glass Substrate

Nanocrystalline precursors of Pb_1-xLa_xTiO₃ (PLT, x=0.06, 0.10, 0.14 and 0.20) thin film were prepared on ordinary ITO conducting glass substrate using sol-gel and pulling method. After the precursors were calcined at low temperature of 185-400℃ in air atmosphere for 1-6 h, the resulted nanocrystalline thin film was characterized by XRD, SEM and AFM. The spectra show that the solid state chemical reaction and the grain size of the nanocrystalline thin film relate not only to the precursor preparing method, but also to the distribution of different components in the precursor. The UV-VI spectrum measurement of the transparent PLT film indicates that its optical absorption bands have extended into the visible region and a change in its absorption pattern with the increase of mean grain size was also observed. As the transparent nanocrystalline PLT thin film with small grain size possesses wider optical absorption band in range of 320-800 nm, the material of Pb_1-xLa_xTiO₃ with suitable component and mean grain size can be used in the fabrication of dye-sensitized photoelectronchemistry solar cell instead of TiO₂. And the higher photoelectric efficiency can be expected.     

维生素A的自述:还记得小时候被胡萝卜支配的恐惧吗?

文章以第一人称介绍了维生素A的基本信息、生理功能、影响因素及相关生活常识。     

Coating Qualities Evaluation for Alkali-Metal Atomic Vapor Cells Based on Frustrated Total Internal Reflection

To realize accurate measurement of coating thickness and surface reliefs for alkali-metal vapor cells, a measurement method based on frustrated total internal reflection （FTIR） is proposed. Firstly, the phenomenon of frustrated total internal reflection and the theory of coating thickness measurement based on FTIR are introduced. Then a coating thickness measuring system based on FTIR is established and the coating thickness measuring experiment is carried out. Next, surface reliefs are obtained by analyzing distributions of the data of coating thickness. The experimental results indicate that the FTIR method can measure coating thickness exactly with an accuracy better than 2 nm, which can satisfy the evaluation of coating qualities for alkali-metal vapor cells.