分析大口径凹形结构散射的一种混合射线方法

在大口径凹形结构散射的特点及有关分析方法的基础上 ,提出了一类基于复射线方法和几何绕射方法的分析处理大口径凹形结构散射的混合射线方法 ,即用复射线法计算反射场 ,以几何绕射法来计算边缘绕射场。基于所设计的便于工程上实现的计算流程 ,有关分析及相关结果说明了这一方法的可行性和可靠性。

基于混合射线追踪的矿井电磁波分析方法

矿井无线通信设备的传输距离和天线安装位置有关,为不影响行人和行车,无线通信设备天线一般安装在顶板或巷帮附近,因此需要研究适用于收发天线位于顶板或巷帮附近时矿井电磁波的分析方法及电磁波传播特性。首先用射线追踪法计算出收发点在巷帮或顶板附近时的接收信号强度明显高于其位于巷道截面中心附近的接收信号强度,证明了射线追踪法不适用于研究收发点同时位于巷帮附近时的电磁波传播特性。在传统射线追踪法的基础上,提出了修正射线追踪模型,设计了发射点或接收点位于顶板和巷帮交界线上以及在同一顶板或巷帮时有效射线的判定方法,细化了每个反射点入射能量的路径损耗和反射损耗,减小了射线追踪法计算信号强度的波动范围,并扩大了该方法在巷道内的适用范围。为进一步提高射线追踪法在整个巷道截面内的适用性,在修正射线追踪模型和位置衰减系数的基础上,提出了混合射线模型,给出位置衰减系数的定义和表达式,在煤矿辅助运输巷道内开展了收发天线在巷道内不同水平位置处接收信号强度变化的测量实验,根据现场测量数据和修正射线追踪模型的仿真数据,计算出天线沿巷道水平位置变化的水平位置衰减系数。实验表明:相同误差条件下,修正射线追踪模型在巷道截面中心区域外的适用范围比传统射线追踪法提高了25%。混合射线追踪法在整个巷道水平范围内仿真值和测量值之间的纵向平均误差均小于5 dB。这表明,提出的混合射线追踪法扩大了传统射线追踪法的适用范围,可以更准确地计算出天线靠近巷帮时,矿井电磁波传播特性,为矿井无线通信设备天线的安装、优化布置提供指导。

快中子及混合射线照射后细胞周期再分布研究

探讨应用流式细胞技术 (FCM )检测经6 0 Coγ射线、快中子照射和两者混合射线照射后的艾氏腹水癌细胞周期再分布的变化。方法 将艾氏腹水癌细胞接种在小鼠皮下 7d后 ,分别采用单一快中子射线DT2 0 0cGy ,单一6 0 Coγ射线DT6 5 0cGy ,混合射线快中子 10 0cGy + 6 0 Coγ射线32 5cGy照射肿瘤部位。在照射后不同时间 ,将各组小鼠处死取瘤体 ,进行FCM分析。 结果 单一6 0Coγ射线照射后主要表现为G2 期阻滞。在 2 4h的直方图中观察到S期丢失现象。快中子表现为对细胞的直接杀伤和G1 期阻滞 ;混合射线对细胞周期的影响表现了快中子和6 0 Coγ射线照射的双重特点。结论 应用混合射线得到了与单一快中子照射相同效应。提示应用混合射线治癌将是提高肿瘤局部控制率 ,减少晚期损伤的有效治疗方式。

中子、^(137)Csγ射线及混合辐射对淋巴细胞微核的影响

目的:比较中子、^(137)Csγ射线及中子/γ射线混合照射对人淋巴细胞微核、核质桥和核芽的影响。方法:将两名志愿者的外周血淋巴细胞随机分为对照组、中子、^(137)Csγ射线和中子/γ射线混合照射组,用胞质分裂阻滞法分析不同处理组人淋巴细胞微核率、核质桥率以及核芽率的差异;结果:外周血淋巴细胞经中子、^(137)Csγ射线和混合照射后的CB微核率高于对照组,经中子和混合照射后的CB微核率高于^(137)Csγ射线照射组,中子/γ射线混合照射后的人淋巴细胞微核率高于中子照射组,差异具有统计学意义(P<0.01);中子/γ射线混合照射诱导的核质桥率和核芽率高于对照组,差异具有统计学意义(P<0.05)。结论:以微核率为生物终点,中子/γ射线混合照射对人淋巴细胞引起的损伤严重,说明混合照射可能存在一定的协同作用。

快中子及混合线照射人成骨肉瘤OS-732细胞系的实验观察

目的 :观察快中子及光子对人成骨肉瘤细胞系OS 732的杀伤作用。方法 :用快中子、光子及混合射线照射OS 732细胞系 ,检测各组细胞受照射后的集落形成率。结果 :单次照射后第 10天 ,混合线组对该细胞系集落形成的抑制作用明显弱于单中子及单光子组。结论 :单次照射后第 10天 ,单纯快中子及单纯光子对该细胞系集落形成的抑制作用明显强于混合线组 。

左乳癌根治术后胸壁3DCRT与3DCRT加电子线混合照射的剂量学研究

目的:探讨左乳癌改良根治术后胸壁三维适形照射和三维适形加电子线照射的剂量学特点。方法:选取左乳癌改良根治术后10例患者,采用pinnacle3 9.10计划系统分别设计胸壁三维适形照射和三维适形加电子线照射计划,比较两种计划的剂量学参数。结果:Dmax、Dmix、Dmean、V90、3DCRT较3DCRT+E升高,差异均有统计学意义(P<0.05);V95、V100、3DCRT略低于3DCRT+E,差异无统计学意义(P>0.05);V105、V110、3DCRT较3DCRT+E高,其中V105差异有统计学意义(P<0.05);CI和D53DCRT+E较3DCRT高,3DCRT+E优于3DCRT,差异有统计学意义(P<0.05);HI和D95差异无统计学意义(P>0.05)。危及器官左肺V5、V10、V15、V20、V30、V40和Dmean3DCRT+E较3DCRT总体升高,除V40差异无统计学意义外(P>0.05),其余参数差异均有统计学意义(P<0.05),右肺Dmean3DCRT+E稍高,差异无统计学意义(P>0.05);心脏受照剂量3DCRT+E总体呈升高趋势,其中V5、V10、V15和V40差异均有统计学意义(P<0.05)。结论:总体上靶区剂量分布3DCRT优于3DCRT+E,但3DCRT+E适形度、靶区高剂量D5和高剂量体积V105和V110优于3DCRT;3DCRT+E对危及器官剂量左肺和心脏的保护并不优于3DCRT。可能是0.5 cm厚的等效填充物不能有效的降低9Me V电子线等对左肺和心脏表面剂量所致。因此、建议每一个患者在治疗前应该选择最佳厚度等效填充物和电子线能量、混合射线的剂量比例等,并通过放射治疗计划系统下制定个体化的治疗方案。

纵波和转换波AVO联合反演技术

纵波和转换波AVO联合反演,增加了反演问题的约束条件,因而使反演方程的稳定性得到了提高,而密度参数作为未知数与波阻抗一起参与反演,则增加了一个重要的岩性参数。应用射线追踪法来确定共角度道集旅行时,所采用的混合射线追踪法是在矩形网格三点扰动法基础上的一种改进,取矩形网格的3个点,在Fermat最小旅行时原则下求取中间点的位置,而不是任意扰动,因此计算速度比扰动法快。数值模拟结果证明了P波和PS波AVO联合反演的可行性。

接触内外照射的放射职业人员健康状况对比研究

目的 对长期接触低剂量电离辐射的工作人员进行辐射流行病学调查 ,对单纯接触X射线与接触多种射线的工作人员健康状况进行对比研究 ,为保障放射职业工作人员的健康和辐射安全管理提供科学依据。方法 按照《放射工作人员健康管理规定》中的要求 ,对广东省 999名放射职业人员的进行健康检查并对资料进行统计分析。结果 接触多种放射线 (既接触X射线同时又接触α射线、β射线、γ射线等 )与单纯接触X射线的职业人员在眼晶状体混浊率、血小板计数、外周血淋巴细胞微核率、甲状腺激素水平等方面比较 ,差异有显著性。结论 接触混合射线比单纯接触X射线对健康的影响大 ,因此 。

^(252)Cf中子后装治疗机剂量测量方法初步研究

目的:研究252Cf中子后装治疗机中子-γ射线混合场的中子和γ射线剂量测量方法。方法:利用一个对中子和γ射线灵敏度响应基本相同的组织等效电离室和一个仅对γ射线响应而对中子基本无响应的石墨电离室测量中子-γ射线混合场剂量,并应用计算值验证测量结果。结果:通过计算关键参数,测量出距离放射源分别为2.5 cm、5 cm、7.5 cm和10 cm处的中子剂量率和γ射线剂量率,其测量值与计算值相比最大偏差为-5.22%。结论:应用双电离室方法可精确测量中子-γ射线混合场。

左乳癌改良根治术后放疗中不同照射技术的剂量学研究

目的分析左乳癌改良根治术后胸壁、内乳及锁骨上淋巴结放疗中不同放射治疗技术的剂量学特点。方法通过在Elekta Monaco治疗计划系统中对10例左乳癌改良根治术患者分别制定混合射线照射方式(3DCRT+elec)、调强放射治疗(Intensity Modulated Radiation Therapy,IMRT)、分段弧段旋转容积调强(VMATpart)和连续弧段旋转容积调强(VMATcont)四种放射治疗计划,比较分析CTV、肺、心脏、左冠状动脉前支区域、右乳和甲状腺的各项剂量参数。结果左乳癌改良根治术后的患者采用3DCRT+elec照射,靶区剂量较差但对正常器官的保护较好,IMRT、VMATpart和VMATcont计划靶区均具有好的均匀性和适形度,其中VMATcont计划中左肺、左冠状动脉前支区域和心脏的高剂量区域体积要低于其他三种照射方式。结论在临床实践中医学物理师可制定多种计划方式根据临床需要进行个性化选择,VMATcont具有潜在的优势。

基于蒙特卡罗方法的复合材料辐射屏蔽设计

在乏燃料后处理厂的工作环境中可能存在着低能中子-γ射线混合辐射,严重威胁工作人员的人身安全。本文针对上述混合辐射环境,利用蒙特卡罗程序Geant4模拟计算了一种钨/硼纤维增强含硼/铋聚合物复合材料中不同材料参数对低能中子和γ射线综合防护效果的影响。结果显示,此种钨/硼纤维复合材料对低能中子和γ射线均具有良好的屏蔽效果。文章证实了纤维垂直排布方式具有比平行排布方式更优的屏蔽效果,且垂直排布方式下透过粒子束的强度分布更加均匀。此外,在聚合物基体中掺杂一定质量分数的硼/铋可以进一步增强复合材料的辐射屏蔽效果。依据这些结果我们认为此种复合材料可以为后处理厂等辐射环境中的防护服及相关防护用具提供参考。

Thermoluminescence Response and Its Deconvolution on Crystalline Higher Order Mixtures of Alkali Halides Exposed to Gamma-Rays for Dosimetric Use

Alkali halides crystals have been the subject of intense research. High order crystalline one phase mixtures （high order： more that binary） studied by TL （thermoluminiscence technique） proved having persistent peaks along the time after the radiation to which they are exposed. In general in alkali halide crystals the traps associated with highest recorded temperature peaks in the TL due to radiation damage have greater permanence in time too. These features are useful for dosimetric applications. In this work, temperature thermoluminescence glow peaks of ternary and quaternary mixed alkali halide crystals have been studied. The study has been focused on their high temperature glow peaks after being subjected to thermal treatments at 373, 573, and 673 K. The glow peaks of high temperature were isolated and studied 24 h and 48 h after irradiation. The parameters of the recombination processes associated to these peaks were obtained using a glow peak shape method. Orders of kinetics were higher than 1.0 and the activation energy greater than 1.2 eV. The results suggest that such materials have a high potential as dosimeter and energy storage materials.

Reduction of Panzhihua titanium-bearing oxidized pellets by CO-N_2-H_2 gas

The effect of H_2 gas content on the reduction of Panzhihua titanomagnetite concentrate pellets by carbon monoxide was investigated by isothermal reduction experiment using CO-N_2-H_2 gas mixtures in a vertical electric resistance furnace.The morphology and phase transformation of reduced samples obtained were detected by scanning electron microscopy,energy disperse spectroscopy analysis and X-ray diffractometry respectively.The results show that increasing H_2 content will enhance the initial stage of reduction rate apparently.There are two reasons responsible for this effect,one is that H_2 accelerates the chemical reaction,and the other is that the addition of H_2 gas can improve the porosity of pellet intensively.It is noteworthy that this effect is more obvious when the reduction temperature reaches 1473 K with sticking phenomenon happening.There are no crystalline phases which can be found such as ulvospinle,ilmenite,ferrous-pseudobrookite and any titanium oxide except titanomagnetite(TTM).The reduction progress is suggested as follows:1) Fe_2O_3→Fe_3O_4→FeO→Fe;2) Fe_2TiO_5→Fe_2TiO_4+Fe_3O_4→TTM.Element Al migrates and gets enriched in high titanium content iron ores,and eventually Al to Ti molar ratio is 1:3.Al is likely to dissolve in titanium iron oxides to form a kind of composite iron compound,which results in the restrain of reduction.

Analysis of Residues Formed during the Liquefaction Process of Wheat Straw

Wheat straw(WS) was liquefied to analyze the reaction process of WS under the acid-catalyzed conditions. WS was liquefied almost completely in the presence of ethylene carbonate/ethylene glycol(EC/EG) blend solvents within 40min at 150 ℃. The residues with different liquefaction time were investigated by SEM, FTIR, and XRD. The residues exhibited loose structure and rough surface due to the presence of stacked irregular platelets. The FTIR results demonstrated that lignin was more easily liquefied in the presence of EC/EG blend solvents than cellulose because the bands of cellulose were stronger and the bands of lignin were much weaker during the liquefaction process of WS. Moreover, the XRD result of all residues declared that WS was gradually liquefied, dissolved and decomposed to small fragments of lower molecular weight, and condensed in part in the later stage of liquefaction.

A Ternary Ruthenium（II） 2,2′ ：6′,2″-Terpyridine Complex Having Intramolecular Tr-Tr Stacking Interaction with Ancillary Benzyl Groups of the Mixed Ligand

A new ruthenium（II） complex with two different types oftridentate ligands was synthesized, 2,2′：6′,2″-terpyridine （tpy） and 2,6-Bis（（N-benzyl）aminomethyl）pyridine （bbap）： [Ru（tpy）（bbap）]2＋ （1）. This compound was designed to form intramolecular π-π stacking interaction between tpy and substituted benzyl groups of bbap. The single-crystal X-ray diffraction analysis revealed that 1 crystallized with orthorhombic space group Aea2 and the ruthenium center has a distorted octahedral coordination geometry with fully chelated tpy and bbap ligands. Simultaneously, in the crystal structure of 1, the central part of ligating tpy was stacked and sandwiched with a pair of capped benzyl substituent groups of bbap, the nearest atomic distance being N...C = 3.28 A.

Determination Multipole Mixing Ratios and Transition Strengths of Gamma Rays from Level Studies of 93Mo （p, nγ） Reaction

The multipole mixing ratios have been calculated by a2-ratio method, from levels of 93Mo（p, nγ） reaction. The branching ratios of such γ-transitions are used to calculate the total gamma widths. Besides, the transition strengths and probabilities have been calculated for γ-transitions from excited states whose life times have been reported previously. The results are found to be in general in good agreement with the previous results populated from the previous work.

CHANGES OF IMMUNE FUNCTIONS AFTER RADIATION，BURNS AND COMBINED RADIATION－BURN INJURY IN RATS

The changes of several immune functions were observed in rats after they were inflicted with 6 Gy gamma rays irradiation, 15% TBSA full thickness brun and the combination of the 2 injuries. It was found that the functions of thymocytes and splenocytes suffered the most severe suppression in the 24th to 72nd hour after radiation injury and began to recover on the 7th day. In the rats with burn injury, the suppression on thymocytes and splenocytes were significantly less severe than that after radiation and recovered more rapidly. The effects of combined radiation-burn injury showed several characteristics. The suppression on the thymocytes was more severe with slower recovery as compared with that after single radiation injury only. The suppression on the splenocytes as a whole was similar to that after single radiation injury , but in the early stage after combined injury, the suppression was far more severe than that after radiation Escharectomy and skin grafting on the burn wounds on the lst day after combined injury could accelerate the recovery on both the thymocytes and splenocytes. Our findings indicated that the severity of the suppression on the immune functions due to combined radiation-burn injury might depend on the size of the burn wounds.

Crystallographic Parameters and Band Gap of CdSxSe1-x Mixed Crystals

Crystals of CdSxSe1-x alloys have been grown from the vapour phase. Some of the physical properties, such as lattice parameters, crystal structure and x-rays data of CdSxSe1-x alloys were determined using x-ray diffractometry. X-ray diffractometry has shown that CdS-CdSe mixed crystals had the wurtzite structure for all compositions between CdS and CdSe. The lattice parameters （both a and c） were found to show a linear dependence with composition. The dependence of the lattice parameters of a and c on composition can be expressed as： a（x） = 4.165 ＋ 0.16x; c（x） = 6.713 ＋ 0.27x. The variation of band gap with composition was determined for these samples from optical absorption measurements, which showed that the band gap varied smoothly and monotonically, but not linearly over the composition range typical results were found between 2.42-1.74 eV at room temperature.