人工Χ射线人造板剖面密度仪关键技术的研究
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摘要
近些年来,我国的人造板工业迅猛发展,在国民经济中也发挥着越来越重要的作用。人造板产品的质量性能与其剖面密度分布密切相关,对人造板的剖面密度分布进行精确检测,有助于改进热压工艺参数,提高人造板产品的质量,节能降耗,从而提高人造板生产企业的经济效益,促进我国木材工业的健康和可持续发展。
本研究主要解决人工X射线人造板剖面密度仪研制中的几个关键问题:确定剖面密度仪使用的X射线管、确定X射线管高压源的技术指标及评定仪器的特性,同时本研究还涉及系统其他方面的设计,包括X射线探测器和步进电机的选用、X射线的防护、编程和系统测试。通过理论探讨和实验分析,得到如下结论:
1、确定剖面密度仪使用的X射线管
用X射线检测平均密度在0.40-0.90g/cm3之间、尺寸为50mm×50mm的刨花板试件的剖面密度分布,选用20-50keV之间的X射线可使检测的灵敏度达到最佳,以前利用放射性同位素241Am发出的60keV的γ射线进行检测,检测的灵敏度并未达到最佳;选用20-50keV之间的X射线进行检测时,刨花板含水率和树种这两个因素的变化均会对其质量衰减系数有极显著的影响。用20-30keV的X射线进行检测时,施胶量因素对刨花板的质量衰减系数有极显著的影响,当X射线能量增加到40keV时,其影响处于显著水平,50keV时,其影响不显著;
2、确定X射线管高压源的技术指标
X射线管高压源的输出电压有三个不稳定因素——温度漂移、时间漂移和纹波电压,其中温度漂移和时间漂移这两个不稳定因素不会影响检测结果的不确定度,只有纹波电压能影响剖面密度检测结果的不确定度;
检测人造板剖面密度的X射线能量分别为20 keV、30 keV、40 keV和50 keV时,X射线管高压源的纹波系数必须分别低于1.5%、0.79%、0.60%和0.52%,才可以期望在(ρ? 0.01g /cm3 ,ρ+0.01g/cm3)的区间内包含了剖面密度ρ检测结果可能值的较大部分。
3、系统设计
本研究中剖面密度仪的X射线探测器选用塑料闪烁体与光电倍增管组成的闪烁探测器,步进电机选用混合式两相步进电机,外壳使用1mm厚的铅板制成;
用VB6.0语言编程实现从X射线强度计数到剖面密度值的转换,程序主要由以下几部分构成:自检、启动射线管、填写试件数据并设置步进速度、扫描计数、计算剖面密度、绘制密度曲线和退出程序;
X射线管的管电压和管电流处于40kV-1.0mA和50kV-1.0mA两种状态,是X射线管的两个标准工作状态;当X射线管工作在40kV-1.0mA状态时,X射线管出射射线的强度计数为1910,在确定试件边缘时,用强度计数1756作为边界值;X射线管工作在50kV-1.0mA状态时,出射X射线的计数为3415,确定试件边缘的计数边界值为3226;
当设置步进电机在1s时间间隔内的步长为1421时,可以认为其步进速度为0.10mm/s;当设置步进电机在1s时间间隔的步长为712时,步进速度为0.050mm/s。
4、仪器评定
根据JJF1094-2002《测量仪器特性评定》国家标准评定剖面密度仪的重复性和灵敏度特性。
利用基本方法、最大残差法和极差法三种方法评定剖面密度仪的重复性时,仪器检测发现试件边缘个别点的重复性相对较差,而内部大多数点的重复性较好;X射线管的管电压和管电流工作在50kV-1.0mA状态时,剖面密度仪的重复性优于其工作在40kV-1.0mA状态;当X射线管工作在50kV-1.0mA状态时,用三种方法计算得到的实验标准差的平均值分别在0.012-0.024、0.011-0.018和0.012-0.021之间。
评定人工X射线人造板剖面密度仪的灵敏度发现,检测不同试件时,仪器的灵敏度由剖面密度、X射线穿透的试件长度和人造板试件的质量衰减系数三个变量共同决定;检测同一试件时,灵敏度只随剖面密度变化,且二者成负指数关系,因此仪器在密度低的位置检测灵敏度较高,而在密度高的位置检测灵敏度较低。
Recent years, the wood-based panel industry of China has been developing rapidly, and playing a more and more important role in the country’s economy. The quality of wood-based panel products correlates closely to its vertical profile density. So to measure the vertical profile density of wood-based panel accurately, would be propitious to ameliorating the hot-pressing technical parameters, improving the quality of wood-based panel products, saving wood material and decreasing the energy consumption. And this would help the wood-based panel corporations to increase benefits and promot the healthy and sustainable development of China’s wood industry.
In this study, some key technologies were solved in developing the X-ray profile density analyzer for wood-based panel. The key technologies were to select the X-ray tube used in the instrument, to calculate the technical parameters of the high-voltage source connected to the X-ray tube, and to evaluate the characteristics of the instrument. And in this study, designing of other parts of the system were also refered, including selection of X-ray detector and stepping motor, X-ray radiological protection, programming and test of the system. After discussing in theory and analyzing the experiment data, the main results are summarized as following:
1. Selecting the X-ray tube used in the instrument
When X-ray among 20-50keV was used in measuring the vertical density profile of wood-based panel samples,whose density was among 0.4-0.9g/cm3 and dimension was 50mm×50mm,the best sensitivity would be got. The sensitivity of former measurement using 60keVγ-ray emitted from 241Am radioactive isotope wasn’t the best.
When measuring using 20-50keV X-ray, the effects of the two factors--moisture content and wood species of the panel--on the mass attenuation coefficient were both extremely significant. When measuring using 20-30keV X-ray, the effect of resin content on the mass attenuation coefficient was extremely significant. If the X-ray energy increased to 40keV, its effect was significant, and 50keV, its effect was not significant.
2. Calculating technical parameters of the high-voltage source connected to the X-ray tube
There are three factors related to the stability of the voltage output from the high-voltage source connected to the X-ray tube: temperature-drift, time-drift and ripple voltage, among whom the temperature-drift and time-drift don’t impact the uncertainty of the results. And only the ripple voltage can impact the uncertainty of the results.
If the X-ray energy used in measuring were 20keV, 30 keV, 40 keV, or 50 keV, the corresponding ripple voltage coefficient of the high-voltage source connected to X-ray tube must be lower than 1.5%,0.79%,0.60% and 0.52% so as to ensure most of the possible results can be included in (ρ? 0.01g /cm3 ,ρ+0.01g/cm3).
3. Designing system
In this study, scintillation detector made up of plastic scintilla and photomultiplier was selected as X-ray detector of the profile density analyzer. And hybrid two phases stepping motor was selected as its stepping motor. The shell of the instrument was made of 1mm-thick-lead.
VB6.0 language was used to programme to realize transition from X-ray intensity value to vertical density profile. The programme was made up of the following parts:self-check, startup of X-ray tube, filling-in data of sample,setting stepping speed,scanning sample and counting, computing vertical density profile, plotting the density curve and exiting the programme.
Tube voltage and current of X-ray tube being 40kV-1.0mA and 50kV-1.0mA are two normal working state of the tube. When X-ray tube working at 40kV-1.0mA state,the intensity value of X-ray from X-ray tube is 1910, and 1756 as intensity value is selected as boundary in determining sample’s edge. When X-ray tube working at 50kV-1.0mA state,the value of X-ray is 3415, and 3226 is selected as boundary in determining sample’s edge.
When setting step length of stepping motor in one second to 1421, the stepping speed can be considered as 0.10mm/s. When setting step length of stepping motor in one second to 721, the stepping speed is 0.050mm/s.
4. Evaluating the characteristics of the instrument
In this study, the characteristics of repeatability and sensitivity of the instrument measuring the vertical density profile, were evaluated according to JJF 1094-2002 National Standard“Evaluation of the Characteristics of Measuring Instruments”.
It was found after evaluating the repeatability of the X-ray profile density analyzer using basic method, largest residual error method and range method that, the repeatability of the instrument is bad when the few points near the edge of samples are measured, and the repeatability is good when instrument is measuring the points inside the samples. When the tube-voltage and tube-current of X-ray tube are working at 50kV-1.0mA state, the repeatability of the instrument is better than working at 40kV-1.0mA state. And when X-ray tube working at 50kV-1.0mA state, the average experiment standard deviations calculated in the three methods are 0.012-0.024、0.011-0.018 and 0.012-0.021.
It was found after evaluating the sensitivity of the X-ray profile density analyzer that, when measuring different samplesm, the sensitivity of the instrument is related to three factors: vertical density profile, length of X-ray traverses through in the samples and mass attenuation coefficients of samples. When measuring one sample, the sensitivity is only related to the vertical density profile, and their map is negative exponent. So sensitivity of the instrument is higher when it is measuring the lower density points, and the sensitivity is lower when it is measuring the higher density points.
本研究主要解决人工X射线人造板剖面密度仪研制中的几个关键问题:确定剖面密度仪使用的X射线管、确定X射线管高压源的技术指标及评定仪器的特性,同时本研究还涉及系统其他方面的设计,包括X射线探测器和步进电机的选用、X射线的防护、编程和系统测试。通过理论探讨和实验分析,得到如下结论:
1、确定剖面密度仪使用的X射线管
用X射线检测平均密度在0.40-0.90g/cm3之间、尺寸为50mm×50mm的刨花板试件的剖面密度分布,选用20-50keV之间的X射线可使检测的灵敏度达到最佳,以前利用放射性同位素241Am发出的60keV的γ射线进行检测,检测的灵敏度并未达到最佳;选用20-50keV之间的X射线进行检测时,刨花板含水率和树种这两个因素的变化均会对其质量衰减系数有极显著的影响。用20-30keV的X射线进行检测时,施胶量因素对刨花板的质量衰减系数有极显著的影响,当X射线能量增加到40keV时,其影响处于显著水平,50keV时,其影响不显著;
2、确定X射线管高压源的技术指标
X射线管高压源的输出电压有三个不稳定因素——温度漂移、时间漂移和纹波电压,其中温度漂移和时间漂移这两个不稳定因素不会影响检测结果的不确定度,只有纹波电压能影响剖面密度检测结果的不确定度;
检测人造板剖面密度的X射线能量分别为20 keV、30 keV、40 keV和50 keV时,X射线管高压源的纹波系数必须分别低于1.5%、0.79%、0.60%和0.52%,才可以期望在(ρ? 0.01g /cm3 ,ρ+0.01g/cm3)的区间内包含了剖面密度ρ检测结果可能值的较大部分。
3、系统设计
本研究中剖面密度仪的X射线探测器选用塑料闪烁体与光电倍增管组成的闪烁探测器,步进电机选用混合式两相步进电机,外壳使用1mm厚的铅板制成;
用VB6.0语言编程实现从X射线强度计数到剖面密度值的转换,程序主要由以下几部分构成:自检、启动射线管、填写试件数据并设置步进速度、扫描计数、计算剖面密度、绘制密度曲线和退出程序;
X射线管的管电压和管电流处于40kV-1.0mA和50kV-1.0mA两种状态,是X射线管的两个标准工作状态;当X射线管工作在40kV-1.0mA状态时,X射线管出射射线的强度计数为1910,在确定试件边缘时,用强度计数1756作为边界值;X射线管工作在50kV-1.0mA状态时,出射X射线的计数为3415,确定试件边缘的计数边界值为3226;
当设置步进电机在1s时间间隔内的步长为1421时,可以认为其步进速度为0.10mm/s;当设置步进电机在1s时间间隔的步长为712时,步进速度为0.050mm/s。
4、仪器评定
根据JJF1094-2002《测量仪器特性评定》国家标准评定剖面密度仪的重复性和灵敏度特性。
利用基本方法、最大残差法和极差法三种方法评定剖面密度仪的重复性时,仪器检测发现试件边缘个别点的重复性相对较差,而内部大多数点的重复性较好;X射线管的管电压和管电流工作在50kV-1.0mA状态时,剖面密度仪的重复性优于其工作在40kV-1.0mA状态;当X射线管工作在50kV-1.0mA状态时,用三种方法计算得到的实验标准差的平均值分别在0.012-0.024、0.011-0.018和0.012-0.021之间。
评定人工X射线人造板剖面密度仪的灵敏度发现,检测不同试件时,仪器的灵敏度由剖面密度、X射线穿透的试件长度和人造板试件的质量衰减系数三个变量共同决定;检测同一试件时,灵敏度只随剖面密度变化,且二者成负指数关系,因此仪器在密度低的位置检测灵敏度较高,而在密度高的位置检测灵敏度较低。
Recent years, the wood-based panel industry of China has been developing rapidly, and playing a more and more important role in the country’s economy. The quality of wood-based panel products correlates closely to its vertical profile density. So to measure the vertical profile density of wood-based panel accurately, would be propitious to ameliorating the hot-pressing technical parameters, improving the quality of wood-based panel products, saving wood material and decreasing the energy consumption. And this would help the wood-based panel corporations to increase benefits and promot the healthy and sustainable development of China’s wood industry.
In this study, some key technologies were solved in developing the X-ray profile density analyzer for wood-based panel. The key technologies were to select the X-ray tube used in the instrument, to calculate the technical parameters of the high-voltage source connected to the X-ray tube, and to evaluate the characteristics of the instrument. And in this study, designing of other parts of the system were also refered, including selection of X-ray detector and stepping motor, X-ray radiological protection, programming and test of the system. After discussing in theory and analyzing the experiment data, the main results are summarized as following:
1. Selecting the X-ray tube used in the instrument
When X-ray among 20-50keV was used in measuring the vertical density profile of wood-based panel samples,whose density was among 0.4-0.9g/cm3 and dimension was 50mm×50mm,the best sensitivity would be got. The sensitivity of former measurement using 60keVγ-ray emitted from 241Am radioactive isotope wasn’t the best.
When measuring using 20-50keV X-ray, the effects of the two factors--moisture content and wood species of the panel--on the mass attenuation coefficient were both extremely significant. When measuring using 20-30keV X-ray, the effect of resin content on the mass attenuation coefficient was extremely significant. If the X-ray energy increased to 40keV, its effect was significant, and 50keV, its effect was not significant.
2. Calculating technical parameters of the high-voltage source connected to the X-ray tube
There are three factors related to the stability of the voltage output from the high-voltage source connected to the X-ray tube: temperature-drift, time-drift and ripple voltage, among whom the temperature-drift and time-drift don’t impact the uncertainty of the results. And only the ripple voltage can impact the uncertainty of the results.
If the X-ray energy used in measuring were 20keV, 30 keV, 40 keV, or 50 keV, the corresponding ripple voltage coefficient of the high-voltage source connected to X-ray tube must be lower than 1.5%,0.79%,0.60% and 0.52% so as to ensure most of the possible results can be included in (ρ? 0.01g /cm3 ,ρ+0.01g/cm3).
3. Designing system
In this study, scintillation detector made up of plastic scintilla and photomultiplier was selected as X-ray detector of the profile density analyzer. And hybrid two phases stepping motor was selected as its stepping motor. The shell of the instrument was made of 1mm-thick-lead.
VB6.0 language was used to programme to realize transition from X-ray intensity value to vertical density profile. The programme was made up of the following parts:self-check, startup of X-ray tube, filling-in data of sample,setting stepping speed,scanning sample and counting, computing vertical density profile, plotting the density curve and exiting the programme.
Tube voltage and current of X-ray tube being 40kV-1.0mA and 50kV-1.0mA are two normal working state of the tube. When X-ray tube working at 40kV-1.0mA state,the intensity value of X-ray from X-ray tube is 1910, and 1756 as intensity value is selected as boundary in determining sample’s edge. When X-ray tube working at 50kV-1.0mA state,the value of X-ray is 3415, and 3226 is selected as boundary in determining sample’s edge.
When setting step length of stepping motor in one second to 1421, the stepping speed can be considered as 0.10mm/s. When setting step length of stepping motor in one second to 721, the stepping speed is 0.050mm/s.
4. Evaluating the characteristics of the instrument
In this study, the characteristics of repeatability and sensitivity of the instrument measuring the vertical density profile, were evaluated according to JJF 1094-2002 National Standard“Evaluation of the Characteristics of Measuring Instruments”.
It was found after evaluating the repeatability of the X-ray profile density analyzer using basic method, largest residual error method and range method that, the repeatability of the instrument is bad when the few points near the edge of samples are measured, and the repeatability is good when instrument is measuring the points inside the samples. When the tube-voltage and tube-current of X-ray tube are working at 50kV-1.0mA state, the repeatability of the instrument is better than working at 40kV-1.0mA state. And when X-ray tube working at 50kV-1.0mA state, the average experiment standard deviations calculated in the three methods are 0.012-0.024、0.011-0.018 and 0.012-0.021.
It was found after evaluating the sensitivity of the X-ray profile density analyzer that, when measuring different samplesm, the sensitivity of the instrument is related to three factors: vertical density profile, length of X-ray traverses through in the samples and mass attenuation coefficients of samples. When measuring one sample, the sensitivity is only related to the vertical density profile, and their map is negative exponent. So sensitivity of the instrument is higher when it is measuring the lower density points, and the sensitivity is lower when it is measuring the higher density points.
引文
[1]程放,高可城,施建平人造板剖面密度测定仪的研制,木材工业,2001,15(2):29-31,34.
[2]国家林业局.中国林业年鉴.北京:中国林业出版社,2007.
[3]国家林业局.《2008中国林业发展报告》摘要.http://www. forestry.gov.cn/distribution/2008/11/19/ lygk-2008-11-19-2067.html
[4] Estevao V.C.M. de Paula Design and fabrication of a mechanical device for“IN-SITU”measurement of density of a wood particle mat during pressing,A dissertation presented for the Doctor of philosophy degree,the University of Tennessee,Knoxville,1992,18-19
[5]吴章康,周定国,张宏健.木质人造板剖面密度分布的意义与研究进展.木材工业.2001,15(4):3-5.
[6] Robert D. Palardy,Bruce A. Haataja,Stephen M. Shaler,etc.Pressing of wood composite panels at mode- rate temperature and high moisture content.Forest products journal.1989,39(4):27-32.
[7] Winistorfer P.M.,Davis W.C. and Moschler W.W..A direct scanning densitometer to measure density profiles in wood composite products.Forest products journal.1986,36(11/12):82-86.
[8] Myron W Kelly.Critical Literature Review of Relationships between Processing Parameters and Physical Properties of Particleboard.(周定国等译).南林科技,1985.
[9] Winistorfer P M.Modeling and Comparing Vertical Density Profile.Wood and Fiber Science.1996,28(1): 133-14l.
[10] Suo S.Simulation Modeling of particleboard Density Profile.Wood and Fiber Science.1994.26(3):397-4l1.
[11] Thomas E G Harless.A Model to Predict the Density Profile of Particleboard. Wood and Fiber Science. 1987,19(1):8l-92.
[12]吉昂,陶光仪,卓尚军等.X射线荧光光谱分析.北京:科学出版社,2003年第一版.
[13] GB/T 4897.1-2003,刨花板第一部分:对所有板型的共同要求.
[14] JJF1094-2002,测量仪器特性评定.
[15]管宁,曲竞赛,王艳君.MWMY型木材微密度测定仪的研制.木材工业,1995,9(1):19-23,30.
[16] Theodore L Laufenberg.Using gamma radiation to measure density gradients in reconstituted wood products.Forest products journal,1986,36(2):59-62.
[17] Polge H.Fifteen Years of Wood Radiation Densitometry.Wood Science Technology, 1978,12:187-196.
[18] Heger L,Parker M L,Keunedy R W.X-ray densitometry:A technique and an example of application.Wood Science,1974,7(2):140-148.
[19] M L Hoag,T L Krahmer.Polychromatic X-Ray Attenuation Characteristics and Wood Densitometry Applications.Wood and Fiber Science,1991,23(1):23-31.
[20] D J Cown,B C Clement.A Wood Densitometer Using Direct Scanning With X-Rays. Wood Science and Technology,1983,17(2):91-99.
[21] Mike Hoag,M D McKimmy.Direct scanning X-ray densitometry of thin wood sections.Forest Produ- cts Journal,1988,38(1):23-26
[22]连广,王庭魁等.木材中X射线衰减规律的验证及吸收系数测定.林业科技,1990,(6):27-29.
[23]连广,王庭魁等. X射线强度直接计数法无损检测木材生长轮密度.东北林业大学学报,1990,18(5):39-42.
[24]阮锡根,潘惠新,李火根等.材性改良研究I.X射线木材密度测定.林业科学,1995,31(3):260-268.
[25]潘惠新,阮锡根,黄敏仁等.单色软X射线木材密度计的研制.南京林业大学学报,1996,20(3):6-10.
[26] C J Liu,James R Olson,Ye Tian,Qingbiao Shen. Theoretical Wood Densitometry:ⅠMass Attenuation Equations and Wood Density Models.Wood and Fiber Science, 1988, 20(1):22-34.
[27]冯星球,陈焕娣,张立芳.用X射线研究人造板材的密度梯度.南京林业大学学报,1995,19(4):62-66.
[28]周玉成,程放.木材工业自动化技术应用现状及展望.木材工业,2006,20(2):59-62.
[29]王婉华.X射线测定木材密度的基本理论和方法简介.南京林学院学报,1984,2:114-120.
[30] James R Olsen,C J Liu,Ye Tian,Qingbiao Shen.Theoretical Wood Densitometry:Ⅱ.Optimal X-ray Energy for Wood Density Measurement.Wood and Fiber science,1988.20(2):187-196.
[31] C J Liu,Ye Tian. Theoretical Wood Densitometry:Ⅲ.Mean Density and Density Variation on Stem Cross-sections. Wood and Fiber science, 1991, 23(2):273-289.
[32]梁景森,管宁.不同X射线源测定木材微密度的研究.木材工业,1990,4 (4):33-37.
[33]曾照祥.X射线实时成像系统分辨率及其影响因素.无损探伤,2003,27(6):10-13.
[34]魏风文.20世纪物理学史.南昌:江西教育出版社,1994.
[35]郭奕玲,沈慧君.物理学史(第2版).北京:清华大学出版社,2005.
[36]麦振洪.晶体X射线衍射的发现及其深远影响.现代物理志,2003,15(5):53-55.
[37]顾金虎,刘义保,杨波等.康普顿效应散射装置简介.物理与工程,2009,19(1):33-35,38.
[38] A.Haga, S.Senda, Y.Sakai, etc.A miniature X-ray tube.Applied Physics Letters.2004,84(12):2208.
[39] U.W.Arndt, J.V.P.Long,P.Duncumb.A microfocus X-ray tube used with focusing collimators. Journal of Applied Crystallography.1998,31:936-944.
[40] Michael Oren,Shree K. Nayar. Seeing beyond Lambert's law. Lecture Notes in Computer Science.1994, 801:269-280.
[41] James M.Vose,Neal H.Sullivan,Barton D.Clinton,etc.Vertical leaf area distribution,light transmittance, and application of the Beer-Lambert Law in four mature hardwood stands in the southern Appalachia- ns. Canadian Journal of Forest Research.1995,25:1036-1043.
[42]彭振生,王闻琦.光与物质作用的三种表现形式.宿州学院学报,2008,23(1):111-113.
[43]程守洙,江之永.普通物理学(第五版).高等教育出版社,1998年7月.
[44]姚启钧.光学教程(第3版).北京:高等教育出版社,2002:429.
[45]周世勋.量子力学教程.人民教育出版社,1981年5月.
[46]汪德新.量子力学.湖北科学技术出版社,2000年3月.
[47]曾谨言.量子力学.科学出版社,1982年1O月.
[48]屈少华.从光电效应看粒子的波动性.国际物理教育通讯,2005,36:81-83.
[49]刘彦安.光电效应与康普顿效应的异同.甘肃科技,2008,24(23):199-200.
[50]斯坎德尔·吾斯曼.光电效应和康普顿效应在概念上的比较.新疆教育学院学报.2006,22(2):152-154.
[51]李炳安,杨振宁,赵忠尧,电子对产生和湮灭.现代理物知识,2001,10(6):29—33.
[52]徐兵,彭欣,安玲.γ光子与物质作用产生次级光子的红限与紫限.长春师范学院学报(自然科学版),2008,27(4):19-24.
[53]王庆庆.γ射线在物质中的吸收.http://www.teach.ustc.edu.ca.
[54]王培元.如何提高刨花板质量.森工科技信息.1985(2)-l986(7)
[55]王贵涛,董双文,郭东升.剖面密度测定与人造板质量控制.木材工业,2005,19(1):37-39.
[56] A.A.Moslemi著,申宗圻,诸葛俊鸿,陆仁书译.碎料板.北京:中国林业出版社,1980.
[57] Otto Suchsland,D.E.Lyon,P.E.Short.Selected Properties of Commercial Medium-Density Fiberboards. Forest Products Journal.1987,28(9):45-49.
[58] Otto Suchsland, George E.Woodson.Effect of Press Cycle Variables on Density Gradient of Medium- Density Fiberboard.Proceedings of 8th International Particleboard Symposium. Washington State University. 1974:375-387.
[59]张宏健,赵立.PF-MDF剖面密度分布特征的研究.北京林业大学学报,1991,13(1):66-75.
[60] Phyllis,database for biomass and waste.Dutch:Energy research Center of the Netherlands (ECN),1998. http://www.ecn.nl/phyllis
[61] J H Hubbell,S M Seltzer.Tables of X-Ray Mass Attenuation Coefficients and Mass Energy- Absorption Coefficients. Gaithersburg, MD:National Institute of Standards and Technology, 1996.http://physics. nist.gov/PhysRefData/Xray Mass Coef/cover.html
[62]续九如,黄智慧.林业试验设计.1995年3月第一版.北京:中国林业出版社,1995.
[63] JJF1059-1999,测量不确定度评定与表示.
[64]黄正福.盖革计数器的数字显示.物理实验.2000,20(9):26-27.
[65]易荣清,崔明启,崔聪悟等.软X射线监测系统的建立与国际标准的比对.原子与分子物理学报,1998,15(1):58-62.
[66]卓韵裳,雷章云,曾宇等.NaI(TI)探测系统稳定性研究.清华大学学报(自然科学版).1996,36(l2):40-44.
[67]李正平,吴瑞生,张永明等.BGO晶体在密度计中应用的可行性研究.核电子学与探测技术.2001,21(6):477-479.
[68]李彦熹.二相混合式步进电机恒力矩细分驱动系统设计.仪器仪表用户.2009,16(1):39-41.
[69]黄楚芳,陈鸿.步进电机加减速控制器的设计.山西电子技术.2009,1:30-31.
[70]冯梦雅,化雪荟.两相混合步进电机恒转矩细分驱动设计及应用.机电工程技术.2009,38(3):103-105.
[71]国际原子能机构(IAEA)编著,王晓峰,周启甫等译.辐射、人与环境.原子能出版社.2006年第一版.
[72]国家环保总局核安全司编.辐射安全与防护的法律法规选编.原子能出版社.2006年第一版.
[73]谭浩强. Visual Basic程序设计(二级)教程.清华大学出版社.2002年第一版.
[74]王明枝王洁瑛李黎.木材表面粗糙度的分析.北京林业大学学报.2005,27(1):14-18.
[75]甘新基孟庆午.木材锯切表面粗糙度的测量.木材加工机械.2004,3:28-29.
[2]国家林业局.中国林业年鉴.北京:中国林业出版社,2007.
[3]国家林业局.《2008中国林业发展报告》摘要.http://www. forestry.gov.cn/distribution/2008/11/19/ lygk-2008-11-19-2067.html
[4] Estevao V.C.M. de Paula Design and fabrication of a mechanical device for“IN-SITU”measurement of density of a wood particle mat during pressing,A dissertation presented for the Doctor of philosophy degree,the University of Tennessee,Knoxville,1992,18-19
[5]吴章康,周定国,张宏健.木质人造板剖面密度分布的意义与研究进展.木材工业.2001,15(4):3-5.
[6] Robert D. Palardy,Bruce A. Haataja,Stephen M. Shaler,etc.Pressing of wood composite panels at mode- rate temperature and high moisture content.Forest products journal.1989,39(4):27-32.
[7] Winistorfer P.M.,Davis W.C. and Moschler W.W..A direct scanning densitometer to measure density profiles in wood composite products.Forest products journal.1986,36(11/12):82-86.
[8] Myron W Kelly.Critical Literature Review of Relationships between Processing Parameters and Physical Properties of Particleboard.(周定国等译).南林科技,1985.
[9] Winistorfer P M.Modeling and Comparing Vertical Density Profile.Wood and Fiber Science.1996,28(1): 133-14l.
[10] Suo S.Simulation Modeling of particleboard Density Profile.Wood and Fiber Science.1994.26(3):397-4l1.
[11] Thomas E G Harless.A Model to Predict the Density Profile of Particleboard. Wood and Fiber Science. 1987,19(1):8l-92.
[12]吉昂,陶光仪,卓尚军等.X射线荧光光谱分析.北京:科学出版社,2003年第一版.
[13] GB/T 4897.1-2003,刨花板第一部分:对所有板型的共同要求.
[14] JJF1094-2002,测量仪器特性评定.
[15]管宁,曲竞赛,王艳君.MWMY型木材微密度测定仪的研制.木材工业,1995,9(1):19-23,30.
[16] Theodore L Laufenberg.Using gamma radiation to measure density gradients in reconstituted wood products.Forest products journal,1986,36(2):59-62.
[17] Polge H.Fifteen Years of Wood Radiation Densitometry.Wood Science Technology, 1978,12:187-196.
[18] Heger L,Parker M L,Keunedy R W.X-ray densitometry:A technique and an example of application.Wood Science,1974,7(2):140-148.
[19] M L Hoag,T L Krahmer.Polychromatic X-Ray Attenuation Characteristics and Wood Densitometry Applications.Wood and Fiber Science,1991,23(1):23-31.
[20] D J Cown,B C Clement.A Wood Densitometer Using Direct Scanning With X-Rays. Wood Science and Technology,1983,17(2):91-99.
[21] Mike Hoag,M D McKimmy.Direct scanning X-ray densitometry of thin wood sections.Forest Produ- cts Journal,1988,38(1):23-26
[22]连广,王庭魁等.木材中X射线衰减规律的验证及吸收系数测定.林业科技,1990,(6):27-29.
[23]连广,王庭魁等. X射线强度直接计数法无损检测木材生长轮密度.东北林业大学学报,1990,18(5):39-42.
[24]阮锡根,潘惠新,李火根等.材性改良研究I.X射线木材密度测定.林业科学,1995,31(3):260-268.
[25]潘惠新,阮锡根,黄敏仁等.单色软X射线木材密度计的研制.南京林业大学学报,1996,20(3):6-10.
[26] C J Liu,James R Olson,Ye Tian,Qingbiao Shen. Theoretical Wood Densitometry:ⅠMass Attenuation Equations and Wood Density Models.Wood and Fiber Science, 1988, 20(1):22-34.
[27]冯星球,陈焕娣,张立芳.用X射线研究人造板材的密度梯度.南京林业大学学报,1995,19(4):62-66.
[28]周玉成,程放.木材工业自动化技术应用现状及展望.木材工业,2006,20(2):59-62.
[29]王婉华.X射线测定木材密度的基本理论和方法简介.南京林学院学报,1984,2:114-120.
[30] James R Olsen,C J Liu,Ye Tian,Qingbiao Shen.Theoretical Wood Densitometry:Ⅱ.Optimal X-ray Energy for Wood Density Measurement.Wood and Fiber science,1988.20(2):187-196.
[31] C J Liu,Ye Tian. Theoretical Wood Densitometry:Ⅲ.Mean Density and Density Variation on Stem Cross-sections. Wood and Fiber science, 1991, 23(2):273-289.
[32]梁景森,管宁.不同X射线源测定木材微密度的研究.木材工业,1990,4 (4):33-37.
[33]曾照祥.X射线实时成像系统分辨率及其影响因素.无损探伤,2003,27(6):10-13.
[34]魏风文.20世纪物理学史.南昌:江西教育出版社,1994.
[35]郭奕玲,沈慧君.物理学史(第2版).北京:清华大学出版社,2005.
[36]麦振洪.晶体X射线衍射的发现及其深远影响.现代物理志,2003,15(5):53-55.
[37]顾金虎,刘义保,杨波等.康普顿效应散射装置简介.物理与工程,2009,19(1):33-35,38.
[38] A.Haga, S.Senda, Y.Sakai, etc.A miniature X-ray tube.Applied Physics Letters.2004,84(12):2208.
[39] U.W.Arndt, J.V.P.Long,P.Duncumb.A microfocus X-ray tube used with focusing collimators. Journal of Applied Crystallography.1998,31:936-944.
[40] Michael Oren,Shree K. Nayar. Seeing beyond Lambert's law. Lecture Notes in Computer Science.1994, 801:269-280.
[41] James M.Vose,Neal H.Sullivan,Barton D.Clinton,etc.Vertical leaf area distribution,light transmittance, and application of the Beer-Lambert Law in four mature hardwood stands in the southern Appalachia- ns. Canadian Journal of Forest Research.1995,25:1036-1043.
[42]彭振生,王闻琦.光与物质作用的三种表现形式.宿州学院学报,2008,23(1):111-113.
[43]程守洙,江之永.普通物理学(第五版).高等教育出版社,1998年7月.
[44]姚启钧.光学教程(第3版).北京:高等教育出版社,2002:429.
[45]周世勋.量子力学教程.人民教育出版社,1981年5月.
[46]汪德新.量子力学.湖北科学技术出版社,2000年3月.
[47]曾谨言.量子力学.科学出版社,1982年1O月.
[48]屈少华.从光电效应看粒子的波动性.国际物理教育通讯,2005,36:81-83.
[49]刘彦安.光电效应与康普顿效应的异同.甘肃科技,2008,24(23):199-200.
[50]斯坎德尔·吾斯曼.光电效应和康普顿效应在概念上的比较.新疆教育学院学报.2006,22(2):152-154.
[51]李炳安,杨振宁,赵忠尧,电子对产生和湮灭.现代理物知识,2001,10(6):29—33.
[52]徐兵,彭欣,安玲.γ光子与物质作用产生次级光子的红限与紫限.长春师范学院学报(自然科学版),2008,27(4):19-24.
[53]王庆庆.γ射线在物质中的吸收.http://www.teach.ustc.edu.ca.
[54]王培元.如何提高刨花板质量.森工科技信息.1985(2)-l986(7)
[55]王贵涛,董双文,郭东升.剖面密度测定与人造板质量控制.木材工业,2005,19(1):37-39.
[56] A.A.Moslemi著,申宗圻,诸葛俊鸿,陆仁书译.碎料板.北京:中国林业出版社,1980.
[57] Otto Suchsland,D.E.Lyon,P.E.Short.Selected Properties of Commercial Medium-Density Fiberboards. Forest Products Journal.1987,28(9):45-49.
[58] Otto Suchsland, George E.Woodson.Effect of Press Cycle Variables on Density Gradient of Medium- Density Fiberboard.Proceedings of 8th International Particleboard Symposium. Washington State University. 1974:375-387.
[59]张宏健,赵立.PF-MDF剖面密度分布特征的研究.北京林业大学学报,1991,13(1):66-75.
[60] Phyllis,database for biomass and waste.Dutch:Energy research Center of the Netherlands (ECN),1998. http://www.ecn.nl/phyllis
[61] J H Hubbell,S M Seltzer.Tables of X-Ray Mass Attenuation Coefficients and Mass Energy- Absorption Coefficients. Gaithersburg, MD:National Institute of Standards and Technology, 1996.http://physics. nist.gov/PhysRefData/Xray Mass Coef/cover.html
[62]续九如,黄智慧.林业试验设计.1995年3月第一版.北京:中国林业出版社,1995.
[63] JJF1059-1999,测量不确定度评定与表示.
[64]黄正福.盖革计数器的数字显示.物理实验.2000,20(9):26-27.
[65]易荣清,崔明启,崔聪悟等.软X射线监测系统的建立与国际标准的比对.原子与分子物理学报,1998,15(1):58-62.
[66]卓韵裳,雷章云,曾宇等.NaI(TI)探测系统稳定性研究.清华大学学报(自然科学版).1996,36(l2):40-44.
[67]李正平,吴瑞生,张永明等.BGO晶体在密度计中应用的可行性研究.核电子学与探测技术.2001,21(6):477-479.
[68]李彦熹.二相混合式步进电机恒力矩细分驱动系统设计.仪器仪表用户.2009,16(1):39-41.
[69]黄楚芳,陈鸿.步进电机加减速控制器的设计.山西电子技术.2009,1:30-31.
[70]冯梦雅,化雪荟.两相混合步进电机恒转矩细分驱动设计及应用.机电工程技术.2009,38(3):103-105.
[71]国际原子能机构(IAEA)编著,王晓峰,周启甫等译.辐射、人与环境.原子能出版社.2006年第一版.
[72]国家环保总局核安全司编.辐射安全与防护的法律法规选编.原子能出版社.2006年第一版.
[73]谭浩强. Visual Basic程序设计(二级)教程.清华大学出版社.2002年第一版.
[74]王明枝王洁瑛李黎.木材表面粗糙度的分析.北京林业大学学报.2005,27(1):14-18.
[75]甘新基孟庆午.木材锯切表面粗糙度的测量.木材加工机械.2004,3:28-29.