EVALUATION OF TWO OBJECTIVE METHODS TO OPTIMIZE KVP AND PERSONNEL EXPOSURE USING A DIGITAL INDIRECT FLAT PANEL DETECTOR AND SIMULATED VETERINARY PATIENTS

It is important to optimize digital radiographic technique settings for small animal imaging in order to maximize image quality while minimizing radiation exposure to personnel. The purpose of this study was to evaluate two objective methods for determining optimal kVp values for an indirect flat panel digital detector. One method considered both image quality and personnel exposure as endpoints and one considered only image quality. Phantoms simulated veterinary patients of varying thicknesses with lesions of varying sizes. Phantoms were exposed to a range of kVp values (60, 81, 100, and 121), using different mAs settings for each phantom. Additionally, all phantoms were exposed to a standard test exposure of 100 kVp/2.5 mAs. Scattered radiation was recorded and used as a measure of personnel exposure. When personnel exposure was considered, a figure of merit was calculated as an endpoint of optimization. The optimal kVp value for each phantom was determined based on the highest signal difference‐to‐noise ratio with or without inclusion of the figure of merit. When personnel exposure was not considered, increasing kVp resulted in higher signal difference‐to‐noise ratios and personnel exposure increased when both patient thickness and kVp increased. Findings indicated that a single standard technique of 100 kVp/2.5 mAs was only optimal for most medium‐sized patients. Images of thinner patients should be made with a lower kVp. Very large patients require a higher kVp than 100 regardless of the optimization method used. Personnel exposure from optimized techniques was low and not expected to exceed annual occupational dose limits.     

茶叶及其茶水中铁、铜、锰的含量测定

为了解不同产地茶叶微量元素的含量变化,采用火焰原子吸收光谱法(FAAS)对信阳毛尖(不发酵茶)、福建铁观音(半发酵茶)、云南普洱(发酵茶)3种茶叶及茶水样品中的微量元素铁、铜、锰分别进行了测定。结果表明,3种茶叶及其相应茶水中微量元素的含量均为Mn>Fe>Cu,同种元素在不同茶叶中的含量有一定差别;从微量元素溶出率的大小看,元素的溶出与元素总量无关。Cu、Fe和Mn的回收率分别为97.0%~105.5%、81.9%~97%和83%~93%。     

Properties of Esterified Wood Prepared with Maleic Anhydride ／ Tetrabr Omophthalic Anhydride ／ Glycerol Mixture

For overcoming disadvantages of wood, an esterification process was employed and tetrabromophthalic anhydride (TBPA) was used as a reactive chemical agent to prepare an esterified wood with the high dimensional stability, flame resistance, and resistance to biodegradation from water-leaching. The experimental results indicated that esterification of wood plus maleic anhydride / tetrabromophthalic anhydride / glycerol could endow wood with dimensional stability, the antiswelling efficiency during water absorption (ASEw), reduction in water absorptivity (RWA), antiswelling efficiency during moisture absorption (ASEm),moisture excluding efficiency (MEE), and oxygen index (OI) of treated wood increased with an increase in the weight percent gain(WPG). And the treated wood showed great decay resistance and resistance to water leaching, too.     

北京山区主要针叶林可燃物空间连续性研究——可燃物垂直连续性与树冠火发生

以北京山区主要针叶林（侧柏林和油松林）为研究对象,通过对林分中乔木、灌木、草本和枯枝落叶层的可燃物负荷量进行调查与分析,定量研究了森林可燃物的垂直分布规律。根据各可燃物种类负荷量垂直分布和树冠火发生的关系,建立了可燃物垂直连续性指数和评估等级,对2个针叶林的树冠火发生的危险性进行了评估与分析。结果表明:侧柏林发生树冠火的可能性较高,油松林相对较低;从垂直连续性指数看,侧柏林为1.002,高度连续,油松林为0.893,中度连续;侧柏林发生树冠火的危险性大于油松林,说明该指标能较好地描述和解释针叶林的可燃物垂直连续性及树冠火发生的危险性。      

虹鳟复口吸虫病的研究——Ⅰ一种新的复口吸虫及其早期发育史观察

一种新的复口吸虫在中国虹鳟养殖场饲养的虹鳟(Salmo gairdneri)眼内发现,定名为山西复口吸虫新种(Diplostomulum shanxinensisn.sp)。虹鳟被严重感染后能引起角膜破裂或玻璃体脱落,即所谓“寄生虫性白内障病”,小鱼可导致消瘦或死亡,成鱼则可能影响性腺发育。胞蚴和尾蚴在萝卜螺(Lymnaea auricularia)内发现。尾蚴钻入鱼宿主的皮肤后到达鱼眼球水晶体内。尾蚴在虹鳟眼内发育成囊蚴阶段需时80天,而在白鲢(Aristichthys nobilis)眼内发育则只需要33天。     

硼酸铵-磷酸氢二铵协效阻燃杨木单板的制备与表征研究

利用极限氧指数、水平垂直燃烧测试、热重分析(TGA)和扫描电镜(SEM)比较研究了硼酸铵与磷酸氢二铵复配阻燃杨木单板的阻燃性能及热解特性。结果表明：磷酸氢二铵的阻燃性能优于硼酸铵,两者复配使用时具有明显的协效性;质量浓度为20%的复合阻燃剂溶液处理杨木单板的氧指数和残炭量最高,分别为61%和53.5%,在水平垂直燃烧试验中也显现出优异的阻燃性能;复合阻燃剂降低了热解阶段的初始分解温度、峰值分解温度和各阶段的表观活化能;燃烧后的SEM分析表明,阻燃剂的加入使得杨木单板在燃烧过程中形成了保护层,有效阻止了热和氧气的交换,从而提高了杨木单板的阻燃性能。     

肉牛血液中矿物质元素的含量与变化研究

用原子吸收光谱法对肉牛血液中的Cu,Zn,Fe和用火焰法对Mg,K进行测定.其结果是Cu,Zn,Fe,Mg,K分别为0.402±0.18μg/mL,2.530±0.75μg/mL,412.562±67.52μg/mL,26.580±3.04μg/mL,371.422±172.704μg/mL.Cu,Zn的含量偏低;Fe,Mg,K的含量符合要求.并研究了不同的海拔高度、性别、饲养水平及妊娠与否等条件下肉牛血液中矿物质元素的变化,其结果为不同海拔高度、年龄、性别、饲养水平和妊娠与否的肉牛血液全血中的Cu,Zn,Fe,Mg,K 5种元素的含量差异不显著,不同年龄组中Zn的含量差异显著,其他元素差异不显著.     

W火焰锅炉燃用劣质煤的燃烧调整——以大唐华银株洲发电有限公司为例

针对煤源严重不足,对1025t/h W型火焰锅炉进行最大限度使用本地攸县劣质煤的掺烧调整试验.通过对一次风速、风温,送风量及二次风挡板,消旋叶片、乏气风挡板,以及入炉煤的混合掺烧方式等方面的调整和试验.使锅炉具备了掺烧75％攸县劣质煤的能力,适应煤种的能力大大增强.     

马来海松基环氧纳米复合材料的制备及性能研究

以松香为原料,通过Diels-Alder加成制备了马来海松酸酐(MPA),再经过酯化、闭环反应得到了马来海松基环氧树脂(MPA-ER),并用FT-IR和1 H NMR对MPA和MPA-ER的结构进行了表征.进一步将多壁碳纳米管(MWCNTs)与MPA-ER共混制备了一系列的MPA-ER/MWCNTs复合材料,对其力学性...     

BL-环保阻燃剂与常见无机阻燃剂对比研究初探

介绍了由北京林业大学人造板研发中心研制的BL-环保阻燃剂,通过压制刨花板并检测其阻燃性能、物理力学性能,对BL-环保阻燃剂与常用无机阻燃剂的性能进行了比较。