Breakdown characteristics of CF_3I/N_2/CO_2 mixture in power frequency and lightning impulse voltages

Trifluoroiodomethane(CF_3I) and its mixtures are believed to be prospective alternatives to sulfur hexafluoride(SF6), which has been included as a greenhouse gas. In this paper, the breakdown properties of a CF_3I/N_2/CO_2 mixture with the volume fraction of CF_3I fixed at 10% are investigated under power frequency and lightning impulse voltages. The experimental result shows that N_2 possesses higher power frequency and negative lightning impulse breakdown voltages than CO_2, but the power frequency and more negative lightning impulse breakdown voltages of the CF_3I/N_2/CO_2 mixture do not increase with the content of N_2. For the purpose of explaining this abnormal phenomenon, the ionization energies and excitation energies of CF_3I,N_2and CO_2 are calculated. The computation results indicate that the ionization energy of CF_3I is lower than the first excitation energy of N_2, but higher than the lowest excitation energy of CO_2,which means that CF_3I molecules are easily ionized by metastable N_2 molecules. The first excitation energy of N_2 is too high, which hinders its application as the buffer gas of CF_3I.     

Breakdown Electric Field of Hot 30% CF_3I/CO_2 Mixtures at Temperature of 300–3500 K During Arc Extinction Process

We calculated the uniform dielectric breakdown field strength of residual 30%CF_3I/CO_2 gas mixtures during the arc extinction process over the temperature range 300–3500 K at 0.1 MPa. The limiting reduced field strengths are decided by a balance of electron generation and loss based on chemical reactions estimated by the electron energy distribution function(EEDF), which employs the Boltzmann equation method with two-term expanding approximation in the steady-state Townsend(SST) condition. During the insulation recovery phase, the hot CF_3I/CO_2 gas mixtures have maximum dielectric strength at a temperature of about 1500 K. At room temperature 300 K, the electric strength after arc extinction(90.3 Td, 1 Td=10-21V·m2)is only 38% of the original value before arc(234.9 Td). The adverse insulation recovery ability of CF_3I/CO_2 gas mixtures in arc extinction hinders its application in electric circuit breakers and other switchgears as an arc quenching and insulating medium.     

Decomposition of Potent Greenhouse Gases SF6, CF4 and SF5CF3 by Dielectric Barrier Discharge

For their distinguished global warming potential(GWP100)and long atmosphere lifespan,CF_4,SF_6 and SF_5CF_3were significant in the field of greenhouse gas research.The details of discharging character and the optimal parameter were discussed by using a Dielectric Barrier Discharge(DBD)reactor to decompose these potent greenhouse gases in this work.The results showed that SF_6 could be decomposed by 92% under the conditions of 5 min resident time and3000 V applied voltage with the partial pressure of 2.0 k Pa,28.2 k Pa,and 1.8 k Pa for SF_6,air and water vapor,respectively.0.4 k Pa CF_4 could be decomposed by 98.2% for 4 min resident time with 30 k Pa Ar added.The decomposition of SF_5CF_3 was much more effective than that of SF_6 and CF_4and moreover,1.3 k Pa SF_5CF_3,discharged with 30 k PaO_2,Ar and air,could not be detected when the resident time was 80 s,40 s,and 120 s,respectively.All the results indicated that DBD was a feasible technique for the abatement of potent greenhouse gases.     

Identification of the normal and abnormal glow discharge modes in a neon-xenon gas mixture at low pressure

In this paper, we focused on the identification of the normal and abnormal glow discharge modes in a neon-xenon gas mixture at low pressure. We considered four gas mixtures: 90%Ne-10%Xe, 80%Ne-20%Xe, 70%Ne-30%Xe and 50%Ne-50%Xe at 1.5 Torr. The range of the gap voltage is 150–500 V. A one-dimensional fluid model with multiple species was used in this work, and the metastable state of the atoms as well as the radiation effects were integrated into the model too. The input data changed for each percentage in the gas mixture, and was calculated by BOLSIG+ software. The parameters of particle transport and their rate coefficients strictly depend on the mean electron energy. The results show that the neon ion density is negligible compared to the xenon ion density, mostly in the case of 50%Ne-50%Xe.     

单管法~(11)C-CH_3I的合成条件优化及胆碱生产与临床应用

通过对合成11C-CH3I所用试剂的用量、反应的载气流量、压力和反应温度、蒸发时间等条件进行优化,进而用柱色层法合成了11C-胆碱。在反应条件为:Li Al H4和57%HI的用量分别为0.3 mL和0.5 mL,反应的最佳载气流量和压力分别为27 mL/min、0.28 kPa,反应温度为180℃,蒸发时间为12 min下,11C-CH3I的校正后标记产率为62.2%±3.4%,放化纯度95%。临床脑胶质瘤和前列腺瘤疑似患者各1例在18F-FDG显像24 h后分别接受11C-胆碱检查,并与18F-FDG显像结果对照。显像结果表明,18F-FDG检查示低代谢区11C-胆碱均呈高代谢,联合用药可以更准确地区分病变的性质。     

11C-CH3I合成条件的优化

碳-11 碘代甲烷(11C-CH3I)是正电子药物甲基化不可缺少的重要标记试剂,它广泛用于合成11C-蛋氨酸、11C-胆碱、11C-Raclopride等碳标记正电子药物.我们利用11C-CH3I自动化合成模块对合成条件进行了优化,提高了合成设备产率和合成的稳定性.经过30批次的条件优化实验,获得了较高而且稳定的产率.产物总合成时间11min,放化产率(90.2±2.5)%,放化纯度＞98%,合成成功率100%.     

N-琥珀酰亚胺3 -[125I]碘苯甲酸酯(S125IB) 的放射化学合成

利用Iodogen法成功地对N-琥珀酰亚胺 3-(三正丁基锡)苯甲酸酯(ATE)进行了放射性碘-125标记,利用Sep-Pak硅胶柱实现了干扰蛋白标记的ATE及Iodogen与S125IB的分离,得到了放射性碘间标蛋白质有用的中间体S125IB,标记率93%以上。并研究了影响标记的因素,得出较佳标记条件为:ATE与 Na125I摩尔比6:1、氧化剂 Iodogen用量7mg、室温反应5min。     

3-正丁基锡-N-琥珀酰亚胺苯甲酸酯的合成及其125I标记

合成了3-正丁基锡-N-琥珀酰亚胺苯甲酸酯（ATE）和N-琥珀酰亚胺-3-碘苯甲酸酯（SIB），其产率分别为45．4％和71．4％，并用核磁、质谱、红外等对它们的结构进行了表征。对ATE进行了^125I标记，得到S^125IB，标记率可达93．0％，放化纯度〉98．0％。本方法为放射性药物碘的间接标记提供了重要参考。     

碳酸锂对Graves甲亢患者摄131I率的影响

为观察碳酸锂对Graves甲亢患者摄^131I率的影响，将15例24h摄^131I率＜55%，拟进行^131I治疗的Graves甲亢患者，给碳酸锂口服每日三次，每次250mg,6天后进行甲状腺摄^131I率测定。结果表明：患者口服碳酸锂后，甲状腺摄^131I率明显升高（P＜0.01).4h摄^131I率平均提高88%；6h摄^131I率平均提高73%；24h摄^131I率平均提高66%。根据服用碳酸锂后24h甲状腺摄^131I率，计算其治疗用^131I量为服用碳酸锂前的62%，平均减少了38%。因此碳酸锂可以大大提高Graves甲亢患者摄^131I率，降低甲亢患者治疗用^131I的剂量。     

An algorithm for fast calculation of ion range and damage distributions based on the boltzmann transport equation

Boltzmann transport equation (BTE) method using large energy intervals in ion scattering calculations can lead to significant errors in the calculation of ion and damage distributions. We pointed out that the inaccuracy is caused by the fact that the flux distribution in a transited energy state is not uniform. The flux is higher at its higher energy end because of a relatively higher cross section for a small energy transfer. Neglecting this difference and assuming an evenly distributed flux will lead to significant errors. The issue can be alleviated by using small energy intervals which inevitably increases computational times. We proposed to redistribute the flux among neighboring energy states around a transited energy state, with the redistribution weighted by their proximities to the mean value of transited energy. Therefore, ion range distributions can be calculated accurately with large energy intervals, thus significantly improving computational efficiency, i.e. by at least one order of magnitudes for 100 keV Si self ion irradiation.     

Determination of the 129I transmutation rate and 129I(n, 2n)128I correction using gas mass spectrometry

Two groups of ¹²⁹I and ¹²⁷I targets were analyzed using a gas quadrupole mass spectrometer (QMS) to determine the transmutation rates via the melting method. Sodium iodide was chosen to make the target. The iodine composition in the ¹²⁹I targets is 82.7% ¹²⁹I and 17.3% ¹²⁷I. The transmutation rate of the ¹²⁹I(n, γ)¹³⁰I reaction was determined by measuring the ¹³⁰Xe with QMS. An equivalent corrective method was brought out to correct the ¹²⁹I(n, 2n)¹²⁸I branch which is interfered with by the ¹²⁷I(n, γ)¹²⁸I reaction. And the correction formula was deduced in theory. For very little ¹²⁸Xe from the ¹²⁹I(n, 2n)¹²⁸I reaction, the equivalent corrective method could not be suitable here. However, it is suitable for the mass of ¹²⁸Xe from ¹²⁹I(n,2n)¹²⁸I reaction that reaches the accurately detective level of the mass spectrometry.     

低质量氦基混合气及其在小单元漂移室中应用的模拟研究

用Garfield、Magboltz和Heed程序包对4种氦基混合气：He／CH4(60／40)、He／C2H6(50／50)、He／C3H8(60／40)和He／iC4H10(80／20)的主要性能(包括电子漂移速度、电子扩散和洛伦兹角)以及小单元漂移室在上述4种混合气中的漂移性能进行了模拟研究。同时比较了两种不同尺寸小单元结构在He／C3H8(60／40)下的性能。     

~(211)At-3H_(11)McAb的免疫活性及体外杀伤效应研究

以间接标记法首先合成中间体对砹苯甲酸,再通过活化羧基反应联接到3H_(11)McAb上,制得~(211)At-3H_(11)McAb偶联物,放射性比度为18.5—61.1kBq/μg。ELISA法鉴定标记后的~(211)At-3H_(11)McAb的免疫活性与未标记3H_(11)McAb一致。实验表明:~(211)At-3H_(11)McAb对靶细胞杀伤效应高于~(211)At-IgG及Na~(211)At;当靶细胞先与一定量3H_(11)McAb或3G_9McAb(4μg)作用1h,可抑制~(211)At-3H_(11)McAb对靶细胞的杀伤效应,放射性比度不影响杀伤效应。     

碘［131I］原料液瓶中放射性废气收集装置的研制和应用

碘［¹³¹I］放射性药品生产过程中放射性原料液瓶开启时,瓶内积存的放射性废气集中释放,易造成放射性废气污染,以至排放超标。为实现放射性废气的半自动收集与暂存,本研究结合实际生产条件,克服热室尺寸受限、耐辐照、可操作性及通用性等难点,研制一套碘［¹³¹I］原料液瓶中放射性废气收集装置,并对收集的放射性废气进行测量和分析。结果表明,装置运行稳定可靠;通过收集并测量22批次的¹³¹I废气放射活度,表明收集量与环境温度存在一定相关性;使用三个收集瓶可充分收集储存。碘［¹³¹I］原料液瓶中放射性废气收集装置可有效收集碘［¹³¹I］原料液瓶开启过程中集中释放的放射性废气,降低对操作人员和环境的辐射影响。以上结果对其他碘［¹³¹I］放射性药品生产机构控制碘［¹³¹I］排放有一定借鉴意义。     

Magneto-optical effect of La0.7Ca0.3MnO3 at low temperature

1 Introduction Since the recent discovery of the colossal mag-neto resistance (CMR) phenomenon in hole-dopedmanganite, La1-xCaxMnO3 has been widely studied onaccount of their unique electronic and magnetic prop-erties, which vary with doping concentrations. Fordoping concentration x from 0.2 to 0.5, the materialsshow a transition from a paramagnetic insulator to aferromagnetic metal near the Curie temperature Tc [1, 2]Such insulator-metal (IM) transition phenomena con-necting with the CM…     

用Klein-Elsler法测量~3H、~(125)I双标记样品的条件选择

~3H和~(125)I是目前在生物学和医学中使用相当广泛的核素。用液体闪烁测量法测~(125)I近来也有很大发展。由于~(125)I标记化合物在一般实验室中都可制备,并且碘标记化合物可以达到较高的比放射性。故使用~3H、~(125)I双标记样品具有操作简便、费用低廉的优点。 我们采用Klein-Elsler法,利用计算Klein-Elsler值,以该值最大的一组测量道为分离效率最佳的双标记测量道。然后根据双标记样品在每一道的计数和每一种核素在两道的计数比值来求出两种核素各自的放射性大小。     

Investigation on the Dielectric Properties of CO2 and CO2-Based Gases Based on the Boltzmann Equation Analysis

In this paper,the dielectric properties of CO_2,CO_2/air,CO_2/O2,CO_2/N_2,CO_2/CF_4,CO_2/CH_4,CO_2/He,CO_2/H_2,CO_2/NH_3 and CO_2/CO were investigated based on the Boltzmann equation analysis,in which the reduced critical electric field strength(E/N)crof the gases was derived from the calculated electron energy distribution function(EEDF) by solving the Boltzmann transport equation.In this work,it should be noted that the fundamental data were carefully selected by the published experimental results and calculations to ensure the validity of the calculation.The results indicate that if He,H_2,N_2 and CH_4,in which there are high ionization coefficients or a lack of attachment reactions,are added into CO_2,the dielectric properties will decrease.On the other hand,air,O2,NH_3 and CF_4(ranked in terms of(E/N)_(cr) value in increasing order) have the potential to improve the dielectric property of CO_2 at room temperature.     

Characteristics of C_2 Radical in CHF_3 and CF_4 Electron Cyclotron Resonance Plasmas Studied by Optical Emission Spectroscopy

The characteristics of CHF3 and CF4 electron cyclotron resonance (ECR) plasma have been studied by optical emission spectroscopy (OES) and Langmuir probe. It is found that C2 radical is one of main compositions in both of the two plasmas. We investigated the relative concentration of C2 radical as a function of F (H) radical and ion density. The formation mechanism of C2 radical is analyzed.     

甲状腺癌病人~(131)I治疗对唾液腺功能的影响

甲状腺癌病人在接受碘 - 131治疗时 ,唾液腺也会浓聚131I而受到损伤。为了解大剂量131I治疗后 ,唾液腺损伤的程度以及与治疗剂量等方面的关系 ,用核素动态显像 ,定量计算唾液腺腺体的摄取率和排泄率。实验结果表明 ,全体病人组与正常人组相比较 ,摄取率没有显著性的差异(P >0 .0 5) ,而排泄率两组均存在显著性的差异 (P <0 .0 5)。随着治疗累积剂量的增加 ,摄取率和排泄率也渐次降低 ,37GBq以上组别的结果与正常人相比 ,摄取率和排泄率均存在显著性的差异(P <0 .0 5) ,37GBq以下各组仅排泄率上存在显著性差异 (P <0 .0 5)。颌下腺与腮腺相比较 ,颌下腺的受损程度较小。核素显像定量计算唾液腺摄取率和排泄率能反映腺体的功能及其受损程度 ,为临床诊疗提供一定的依据 ,接受131I剂量的大小与腮腺功能的影响程度呈正相关。     

Investigation of the performance of CF_3I/c-C_4F_8/N_2 and CF_3I/c-C_4F_8/CO_2 gas mixtures from electron transport parameters

CF_3I gas mixtures have attracted considerable attention as potential environmentally-friendly alternatives to SF_6 gas, owing to their excellent insulating performance. This paper attempts to study the CF_3I ternary gas mixtures with c-C_4F_8 and buffer gases N_2 and CO_2 by considering dielectric strength from electron transport parameters based on the Boltzmann method and synergistic effect analysis, compared with SF_6 gas mixtures. The results confirm that the critical electric field strength of CF_3I/c-C_4F_8/70 % CO_2 is greater than that of 30% SF_6/70% CO_2 when the CF_3I content is greater than 17%. Moreover, a higher content of c-C_4F_8 decreases the sensitivity of gas mixtures to an electric field, and this phenomenon is more obvious in CF_3I/c-C_4F_8/CO_2 gas mixtures. The synergistic effects for CF_3I/c-C_4F_8/70 % N_2 were most obvious when the c-C_4F_8 content was approximately 20%, and for CF_3I/c-C_4F_8/70 % CO_2 when the c-C_4F_8 content was approximately 10%. On the basis of this research,CF_3I/c-C_4F_8/70 % N_2 shows better insulation performance when the c-C_4F_8 content is in the15%–20% range. For CF_3I/c-C_4F_8/70 % CO_2, when the c-C_4F_8 content is in the 10%–15%range, the gas mixtures have excellent performance. Hence, these gas systems might be used as alternative gas mixtures to SF_6 in high-voltage equipment.