2016年电视广播大学电大《钢筋混凝土结构设计与砌体结构》期末必备考试小抄【终极排版，直接打印】 .doc

电大钢筋混凝土结构设计与砌体结构考试小抄1预应力砼构件的主要优点有哪些？答：提高了构建的抗裂能力；增大了构件的刚度；充分利用高强度材料；扩大了构件的应用范围。2张拉控制应力如何确定？为什么先张法的控制应力略高于后张法?答：指张拉预应力钢筋时，张拉设备的测力仪表所指示的总张拉力除以预应力钢筋截面面积得出的拉应力值；由于先张法中钢筋分批张拉以及预应力钢筋与张拉台座之间的温差等因素产生的预应力损失，是张拉控制应力值提高。3 预应力损失由哪些？减少各项损失的措施是什么？不同张拉方式损失是如何组合的？先张法、后张法的第一批、第二批预应力损失分别是什么？答：张拉端锚具变形和钢筋内缩引起的预应力损失l1;减少垫片，采用变形小的锚具，后张法采用两端张拉预应力钢筋与孔管壁之间的摩擦力引起的预应力损失l2;超张拉，两端张拉混凝土加热养护时，受张拉的钢筋与承受拉力的设备之间的温差引起的预应力损失l3;采用两阶段升温养护方法；预应力钢筋的应力松弛引起的预应力损失l4;超张拉混凝土收缩和徐变引起的预应力损失l5；采用高标号水泥，减少水泥用量，采用级配好的骨料，加强振捣，提高混凝土的密实性，加强养护，减少混凝土收缩，采用高效减水剂减少水灰比，控制混凝土应力，防止发生非线性徐变用螺旋式预应力钢筋作配筋的环形构件，由于混凝土的局部挤压引起的预应力损失l6;直径d越大损失越小，d较大时，l6忽略不计。 先张法构件第一批预应力损失：l1+l2+l3+l4;后张法构件第一批预应力损失：l1+l2;先张法构件第二批预应力损失：l5；后张法构件第二批预应力损失：l4+l5+l64张拉控制应力为什么不能过大也不能过小？答：（1）太小就起不了提高有效应力的作用；（2）con过大会：个别钢筋可能被拉断施工阶段可能会引起构件某些部位受拉甚至开裂，还可能使后张法构件端部混凝土产生局部受压破坏 使开裂荷载和破坏荷载相近，一旦出现裂缝，将很快破坏，即产生无预兆性的脆性破坏 增大预应力钢筋的松弛损失。5单层厂房结构作用荷载有哪些？各种荷载的传递路径是怎样的？答：恒载包括各种构件、维护结构及固定设备的自重;活载包括屋面活载、雪荷载、积灰荷载、风荷载、吊车荷载等。横、竖向荷载主要通过横向平面排架传至地基。纵向荷载通过纵向平面排架传至地基。6柱间支撑作用：承受由抗风柱和屋盖横向水平支撑传来的山墙风载，由屋盖结构传来的纵向水平地震作用及由吊车梁传来的吊车纵向水平制动力，并将它们传给基础。柱间支撑作用是承受由抗风柱和屋盖横向水平支撑传来的山墙风载，由屋盖结构传来的的纵向水平地震作用及由吊车梁传来的吊车纵向水平制动力，并将它们传给基础，还能提高厂房的纵向刚度。7在确定计算简图时作了哪些假设？如何提取排架的计算简图？答：做如下假定1柱下端嵌固于基础中，固定端位于基础顶面。2柱顶与屋架或屋面梁为铰接，只能传递竖向轴力和水平剪力，不能传递弯矩。3横梁为轴向刚度很大的刚性连杆。在假定基础上得到横向排架的计算模型，在该计算模型基础上加以荷载就成为排架结构的计算简图。8牛腿的破坏形态有哪些？答：弯压破坏；斜压破坏；剪切破坏；此外还有因加载板过小而导致加载板下混凝土局部压碎破坏，因纵向受拉钢筋锚固不良而拔出等破坏。 9柱下独立基础的设计内容有哪些？这些内容满足后能防止哪些破坏？基础高度应满足哪两个要求？答：内容有:确定基础底面尺寸和基础高度；计算基础底板配筋并采用必要的构造措施等。能够防止柱周边或变阶处的截面产生冲切破坏。防止在基础底板基净反力作用下，因两个方向均产生向上的弯曲而破坏。10什么是刚性基础？什么是柔性基础？答：刚性基础是指用砖、石、灰土、混凝土等抗压强度大而抗弯、抗剪强度小的材料做的基础（受刚性角的限制）；柔性基础是指用抗拉、抗弯、抗压、抗剪均较好的钢筋混凝土材料做的基础。11框架结构的布置方法有几种？各种结构布置方法有什么优缺点？答：框架结构有横向承重布置（优点：可以在一定程度上改善房屋横向与纵向刚度相差较大的缺点，其联系梁的截面高度一般比主梁小，窗户尺寸可以设计得大些，室内采光好，通风好）、纵向承重布置（优点;便于管线沿纵向穿行，当地基沿房屋纵向不够均匀时，纵向框架可在一定程度上调整这种不均匀性；缺点：房屋的横向抗侧移刚度小）双向承重布置（整体性受力好性能好，特别适合对房屋结构的整体性要求较高和楼面荷载较大的情况下采用）12如何选取承重框架的计算单元?答：跨度：跨左右两边柱截面形心轴之间的距离；层高：底层柱高从基础顶面算至柱顶标高处；中间标高：从下一层楼面标高算至层面标高；顶层标高：从顶层楼面标高算至层面标高13框架在竖直荷载作用下内力近似求解有哪些方法？该方法的假设条件是什么？ 答：分层法基本假定：在竖向荷载作用下，框架侧移小， 因而忽略不计；每层梁上的荷载对其他各层梁的影响很小，可以忽略不计，因此每层梁上的荷载只在该层梁及与该层相连的柱上 分配和传递。叠代法：基本假定：不考虑框架侧移；考虑框架侧移时；系数法：基本假定：两个相邻跨的跨长相差不超过短跨跨长的20%；活载与恒载之比不大于3； 荷载的均匀布置；框架梁截面为矩形时14挑梁、过梁应进行哪几个方面计算？答：跳梁：抗颠覆计算；极限承载力计算；构造要求过梁：极限承载力计算；构造要求15砌体局压破坏有哪些破坏特征？答：因竖向裂缝的发展而破坏；劈裂破坏；局部受压面积附近的砌体压坏。16影响砌体抗压强度的主要因素有哪些？答：一、砌体材料的物理、力学性能：块体和砂浆的强度; 块体规整程度尺寸；砂浆的变形与和易性；二、砌体工程施工质量：灰缝砂浆饱满度；块体砌筑时的含水率；灰缝厚度；砌体组砌方法。17砌体受弯破坏形态及特征是怎样的？答：分为三种破坏形态:a) 当截面内的拉应力使砌体沿齿缝截面破坏，称为砌体沿齿缝截面弯曲受拉； b) 砌体沿块体缝面破坏，称为砌体沿块体截面弯曲受拉；c) 砌体沿通缝截面破坏，称为砌体沿通缝截面弯曲受拉。18在哪些情况下需要考虑砌体抗压强度设计值的调整系数？答：有吊车房屋砌体，跨度不小于9m的梁下烧结普通砖砌体，跨度不小于7.2m的梁下烧结多孔砖、蒸压灰砂砖、蒸压粉煤灰砖、混凝土和轻骨料混凝土砌块砌体，a为0.9.对于无筋砌体构件，其截面面积小于0.3m2时，a为其截面面积加0.7对于配筋砌体构件，当其截面面积小于0.2m2时，a为其截面面积加0.8当砌体用水泥砂浆砌筑时，队表2-4表2-9的数值，a为0.9.队表2-10的数值，a为0.8；对于配筋砌体构件，当其中的砌体采用水泥砂浆砌筑时，仅对砌体的强度设计值乘以调整系数a。当施工质量控制等级为c级时，a为0.89.当验算施工中房屋的构件时，a为1.119墙体布置方案有哪些？各自优缺点及应用情况？答：横墙承重（优点：横墙间距小且数量较多，横向刚度较大、整体性好、抵抗风荷载、地震作用以及调整地基不均匀沉降的能力较强，结构简单以及施工方便，因纵墙不承重致建筑立面易处理以及门窗的布置和大小较灵活， 缺点：因纵墙较密，建筑平面布置不灵活。应用：房间大小固定、横墙间距较密的住宅、宿舍、旅馆以及办公楼等）；纵墙承重（优点：建筑平面灵活，与横墙承重结构相比，墙体材料用量较少、屋楼盖构件用料较多， 缺点：横向刚度较差、纵墙上门窗洞口的布置大小受一定的限制。 应用：用于开间较大的教学楼、医院、食堂、仓库）；纵横墙承重（优点：房屋沿纵、横向刚度均较大且砌体应力较均匀，具有较强的抗风能力，占地面积相同的条件下，外墙面积较少， 应用：多层塔式住宅等）；框架承重（优点：内部形成大空间，平面布置灵活，易满足使用要求；与全框架结构相比，可节约钢材、水泥。降低房屋造价， 缺点：因横墙较少，房屋的空间刚度较差。抵抗地震能力和地基不均匀沉降能力弱，应用于商餐厅以及多层工业厂房等）四种型式。20在砌体结构中设置圈梁的目的是什么？答：增强房屋的整体刚度；防止地基不均匀沉降或较大振动荷载等对房屋引起的不利影响；提高墙体抗剪、抗弯、承重的能力。1验算柱的受压承载力： 柱顶截面验算查表得到f=，沿截面长边方向按偏心受压验算：，沿截面短边方向按轴心受压验算：同上。2局部受压承载力验算查表得到砌体抗压强度设计值为f=， ，局部受压承载力满足要求。3排架上风荷载标准值：1预应力砼构件的主要优点有哪些？答：提高了构建的抗裂能力；增大了构件的刚度；充分利用高强度材料；扩大了构件的应用范围。2张拉控制应力如何确定？为什么先张法的控制应力略高于后张法?答：指张拉预应力钢筋时，张拉设备的测力仪表所指示的总张拉力除以预应力钢筋截面面积得出的拉应力值；由于先张法中钢筋分批张拉以及预应力钢筋与张拉台座之间的温差等因素产生的预应力损失，是张拉控制应力值提高。3 预应力损失由哪些？减少各项损失的措施是什么？不同张拉方式损失是如何组合的？先张法、后张法的第一批、第二批预应力损失分别是什么？答：张拉端锚具变形和钢筋内缩引起的预应力损失l1;减少垫片，采用变形小的锚具，后张法采用两端张拉预应力钢筋与孔管壁之间的摩擦力引起的预应力损失l2;超张拉，两端张拉混凝土加热养护时，受张拉的钢筋与承受拉力的设备之间的温差引起的预应力损失l3;采用两阶段升温养护方法；预应力钢筋的应力松弛引起的预应力损失l4;超张拉混凝土收缩和徐变引起的预应力损失l5；采用高标号水泥，减少水泥用量，采用级配好的骨料，加强振捣，提高混凝土的密实性，加强养护，减少混凝土收缩，采用高效减水剂减少水灰比，控制混凝土应力，防止发生非线性徐变用螺旋式预应力钢筋作配筋的环形构件，由于混凝土的局部挤压引起的预应力损失l6;直径d越大损失越小，d较大时，l6忽略不计。 先张法构件第一批预应力损失：l1+l2+l3+l4;后张法构件第一批预应力损失：l1+l2;先张法构件第二批预应力损失：l5；后张法构件第二批预应力损失：l4+l5+l64张拉控制应力为什么不能过大也不能过小？答：（1）太小就起不了提高有效应力的作用；（2）con过大会：个别钢筋可能被拉断施工阶段可能会引起构件某些部位受拉甚至开裂，还可能使后张法构件端部混凝土产生局部受压破坏 使开裂荷载和破坏荷载相近，一旦出现裂缝，将很快破坏，即产生无预兆性的脆性破坏 增大预应力钢筋的松弛损失。5单层厂房结构作用荷载有哪些？各种荷载的传递路径是怎样的？答：恒载包括各种构件、维护结构及固定设备的自重;活载包括屋面活载、雪荷载、积灰荷载、风荷载、吊车荷载等。横、竖向荷载主要通过横向平面排架传至地基。纵向荷载通过纵向平面排架传至地基。6柱间支撑作用：承受由抗风柱和屋盖横向水平支撑传来的山墙风载，由屋盖结构传来的纵向水平地震作用及由吊车梁传来的吊车纵向水平制动力，并将它们传给基础。柱间支撑作用是承受由抗风柱和屋盖横向水平支撑传来的山墙风载，由屋盖结构传来的的纵向水平地震作用及由吊车梁传来的吊车纵向水平制动力，并将它们传给基础，还能提高厂房的纵向刚度。7在确定计算简图时作了哪些假设？如何提取排架的计算简图？答：做如下假定1柱下端嵌固于基础中，固定端位于基础顶面。2柱顶与屋架或屋面梁为铰接，只能传递竖向轴力和水平剪力，不能传递弯矩。3横梁为轴向刚度很大的刚性连杆。在假定基础上得到横向排架的计算模型，在该计算模型基础上加以荷载就成为排架结构的计算简图。8牛腿的破坏形态有哪些？答：弯压破坏；斜压破坏；剪切破坏；此外还有因加载板过小而导致加载板下混凝土局部压碎破坏，因纵向受拉钢筋锚固不良而拔出等破坏。 9柱下独立基础的设计内容有哪些？这些内容满足后能防止哪些破坏？基础高度应满足哪两个要求？答：内容有:确定基础底面尺寸和基础高度；计算基础底板配筋并采用必要的构造措施等。能够防止柱周边或变阶处的截面产生冲切破坏。防止在基础底板基净反力作用下，因两个方向均产生向上的弯曲而破坏。10什么是刚性基础？什么是柔性基础？答：刚性基础是指用砖、石、灰土、混凝土等抗压强度大而抗弯、抗剪强度小的材料做的基础（受刚性角的限制）；柔性基础是指用抗拉、抗弯、抗压、抗剪均较好的钢筋混凝土材料做的基础。11框架结构的布置方法有几种？各种结构布置方法有什么优缺点？答：框架结构有横向承重布置（优点：可以在一定程度上改善房屋横向与纵向刚度相差较大的缺点，其联系梁的截面高度一般比主梁小，窗户尺寸可以设计得大些，室内采光好，通风好）、纵向承重布置（优点;便于管线沿纵向穿行，当地基沿房屋纵向不够均匀时，纵向框架可在一定程度上调整这种不均匀性；缺点：房屋的横向抗侧移刚度小）双向承重布置（整体性受力好性能好，特别适合对房屋结构的整体性要求较高和楼面荷载较大的情况下采用）12如何选取承重框架的计算单元?答：跨度：跨左右两边柱截面形心轴之间的距离；层高：底层柱高从基础顶面算至柱顶标高处；中间标高：从下一层楼面标高算至层面标高；顶层标高：从顶层楼面标高算至层面标高13框架在竖直荷载作用下内力近似求解有哪些方法？该方法的假设条件是什么？ 答：分层法基本假定：在竖向荷载作用下，框架侧移小， 因而忽略不计；每层梁上的荷载对其他各层梁的影响很小，可以忽略不计，因此每层梁上的荷载只在该层梁及与该层相连的柱上 分配和传递。叠代法：基本假定：不考虑框架侧移；考虑框架侧移时；系数法：基本假定：两个相邻跨的跨长相差不超过短跨跨长的20%；活载与恒载之比不大于3； 荷载的均匀布置；框架梁截面为矩形时14挑梁、过梁应进行哪几个方面计算？答：跳梁：抗颠覆计算；极限承载力计算；构造要求过梁：极限承载力计算；构造要求15砌体局压破坏有哪些破坏特征？答：因竖向裂缝的发展而破坏；劈裂破坏；局部受压面积附近的砌体压坏。16影响砌体抗压强度的主要因素有哪些？答：一、砌体材料的物理、力学性能：块体和砂浆的强度; 块体规整程度尺寸；砂浆的变形与和易性；二、砌体工程施工质量：灰缝砂浆饱满度；块体砌筑时的含水率；灰缝厚度；砌体组砌方法。17砌体受弯破坏形态及特征是怎样的？答：分为三种破坏形态:a) 当截面内的拉应力使砌体沿齿缝截面破坏，称为砌体沿齿缝截面弯曲受拉； b) 砌体沿块体缝面破坏，称为砌体沿块体截面弯曲受拉；c) 砌体沿通缝截面破坏，称为砌体沿通缝截面弯曲受拉。18在哪些情况下需要考虑砌体抗压强度设计值的调整系数？答：有吊车房屋砌体，跨度不小于9m的梁下烧结普通砖砌体，跨度不小于7.2m的梁下烧结多孔砖、蒸压灰砂砖、蒸压粉煤灰砖、混凝土和轻骨料混凝土砌块砌体，a为0.9.对于无筋砌体构件，其截面面积小于0.3m2时，a为其截面面积加0.7对于配筋砌体构件，当其截面面积小于0.2m2时，a为其截面面积加0.8当砌体用水泥砂浆砌筑时，队表2-4表2-9的数值，a为0.9.队表2-10的数值，a为0.8；对于配筋砌体构件，当其中的砌体采用水泥砂浆砌筑时，仅对砌体的强度设计值乘以调整系数a。当施工质量控制等级为c级时，a为0.89.当验算施工中房屋的构件时，a为1.119墙体布置方案有哪些？各自优缺点及应用情况？答：横墙承重（优点：横墙间距小且数量较多，横向刚度较大、整体性好、抵抗风荷载、地震作用以及调整地基不均匀沉降的能力较强，结构简单以及施工方便，因纵墙不承重致建筑立面易处理以及门窗的布置和大小较灵活， 缺点：因纵墙较密，建筑平面布置不灵活。应用：房间大小固定、横墙间距较密的住宅、宿舍、旅馆以及办公楼等）；纵墙承重（优点：建筑平面灵活，与横墙承重结构相比，墙体材料用量较少、屋楼盖构件用料较多， 缺点：横向刚度较差、纵墙上门窗洞口的布置大小受一定的限制。 应用：用于开间较大的教学楼、医院、食堂、仓库）；纵横墙承重（优点：房屋沿纵、横向刚度均较大且砌体应力较均匀，具有较强的抗风能力，占地面积相同的条件下，外墙面积较少， 应用：多层塔式住宅等）；框架承重（优点：内部形成大空间，平面布置灵活，易满足使用要求；与全框架结构相比，可节约钢材、水泥。降低房屋造价， 缺点：因横墙较少，房屋的空间刚度较差。抵抗地震能力和地基不均匀沉降能力弱，应用于商餐厅以及多层工业厂房等）四种型式。20在砌体结构中设置圈梁的目的是什么？答：增强房屋的整体刚度；防止地基不均匀沉降或较大振动荷载等对房屋引起的不利影响；提高墙体抗剪、抗弯、承重的能力。，4剪力分配法求内力：5截面尺寸估算(mm)：6反弯点法：顶层：柱抗侧刚度：d=12ei/ 1验算柱的受压承载力： 柱顶截面验算查表得到f=，沿截面长边方向按偏心受压验算： ， ，沿截面短边方向按轴心受压验算：同上。2局部受压承载力验算查表得到砌体抗压强度设计值为f=， ，局部受压承载力满足要求。3排架上风荷载标准值：，4剪力分配法求内力：5截面尺寸估算(mm)：6反弯点法：顶层：柱抗侧刚度：d=12ei/ 请您删除一下内容，o(_)o谢谢！2016年中央电大期末复习考试小抄大全，电大期末考试必备小抄，电大考试必过小抄acetylcholine is a neurotransmitter released from nerve endings (terminals) in both the peripheral and the central nervous systems. it is synthesized within the nerve terminal from choline, taken up from the tissue fluid into the nerve ending by a specialized transport mechanism. the enzyme necessary for this synthesis is formed in the nerve cell body and passes down the axon to its end, carried in the axoplasmic flow, the slow movement of intracellular substance (cytoplasm). acetylcholine is stored in the nerve terminal, sequestered in small vesicles awaiting release. when a nerve action potential reaches and invades the nerve terminal, a shower of acetylcholine vesicles is released into the junction (synapse) between the nerve terminal and the effector cell which the nerve activates. this may be another nerve cell or a muscle or gland cell. thus electrical signals are converted to chemical signals, allowing messages to be passed between nerve cells or between nerve cells and non-nerve cells. this process is termed chemical neurotransmission and was first demonstrated, for nerves to the heart, by the german pharmacologist loewi in 1921. chemical transmission involving acetylcholine is known as cholinergic. acetylcholine acts as a transmitter between motor nerves and the fibres of skeletal muscle at all neuromuscular junctions. at this type of synapse, the nerve terminal is closely apposed to the cell membrane of a muscle fibre at the so-called motor end plate. on release, acetylcholine acts almost instantly, to cause a sequence of chemical and physical events (starting with depolarization of the motor endplate) which cause contraction of the muscle fibre. this is exactly what is required for voluntary muscles in which a rapid response to a command is required. the action of acetylcholine is terminated rapidly, in around 10 milliseconds; an enzyme (cholinesterase) breaks the transmitter down into choline and an acetate ion. the choline is then available for re-uptake into the nerve terminal. these same principles apply to cholinergic transmission at sites other than neuromuscular junctions, although the structure of the synapses differs. in the autonomic nervous system these include nerve-to-nerve synapses at the relay stations (ganglia) in both the sympathetic and the parasympathetic divisions, and the endings of parasympathetic nerve fibres on non-voluntary (smooth) muscle, the heart, and glandular cells; in response to activation of this nerve supply, smooth muscle contracts (notably in the gut), the frequency of heart beat is slowed, and glands secrete. acetylcholine is also an important transmitter at many sites in the brain at nerve-to-nerve synapses. to understand how acetylcholine brings about a variety of effects in different cells it is necessary to understand membrane receptors. in post-synaptic membranes (those of the cells on which the nerve fibres terminate) there are many different sorts of receptors and some are receptors for acetylcholine. these are protein molecules that react specifically with acetylcholine in a reversible fashion. it is the complex of receptor combined with acetylcholine which brings about a biophysical reaction, resulting in the response from the receptive cell. two major types of acetylcholine receptors exist in the membranes of cells. the type in skeletal muscle is known as nicotinic; in glands, smooth muscle, and the heart they are muscarinic; and there are some of each type in the brain. these terms are used because nicotine mimics the action of acetylcholine at nicotinic receptors, whereas muscarine, an alkaloid from the mushroom amanita muscaria, mimics the action of acetylcholine at the muscarinic receptors. acetylcholine is the neurotransmitter produced by neurons referred to as cholinergic neurons. in the peripheral nervous system acetylcholine plays a role in skeletal muscle movement, as well as in the regulation of smooth muscle and cardiac muscle. in the central nervous system acetylcholine is believed to be involved in learning, memory, and mood. acetylcholine is synthesized from choline and acetyl coenzyme a through the action of the enzyme choline acetyltransferase and becomes packaged into membrane-boundvesicles. after the arrival of a nerve signal at the termination of an axon, the vesicles fuse with the cell membrane, causing the release of acetylcholine into thesynaptic cleft. for the nerve signal to continue, acetylcholine must diffuse to another nearby neuron or muscle cell, where it will bind and activate areceptorprotein. there are two main types of cholinergic receptors, nicotinic and muscarinic. nicotinic receptors are located at synapses between two neurons and at synapses between neurons and skeletal muscle cells. upon activation a nicotinic receptor acts as a channel for the movement of ions into and out of the neuron, directly resulting indepolarizationof the neuron. muscarinic receptors, located at the synapses of nerves with smooth or cardiac muscle, trigger a chain of chemical events referred to as signal transduction. for a cholinergic neuron to receive another impulse, acetylcholine must be released from the receptor to which it has bound. this will only happen if the concentration of acetylcholine in the synaptic cleft is very low. low synaptic concentrations of acetylcholine can be maintained via a hydrolysis reaction catalyzed by the enzyme acetylcholinesterase. this enzyme hydrolyzes acetylcholine into acetic acid and choline. if acetylcholinesterase activity is inhibited, the synaptic concentration of acetylcholine will remain higher than normal. if this inhibition is irreversible, as in the case of exposure to many nerve gases and some pesticides, sweating, bronchial constriction, convulsions, paralysis, and possibly death can occur. although irreversible inhibition is dangerous, beneficial effects may be derived from transient (reversible) inhibition. drugs that inhibit acetylcholinesterase in a reversible manner have been shown to improve memory in some people with alzheimers disease. abstract expressionism, movement of abstract painting that emerged in new york city during the mid-1940s and attained singular prominence in american art in the following decade; also called action painting and the new york school. it was the first important school in american painting to declare its independence from european styles and to influence the development of art abroad. arshile gorky first gave impetus to the movement. his paintings, derived at first from the art of picasso, mir, and surrealism, became more personally expressive. jackson pollocks turbulent yet elegant abstract paintings, which were created by spattering paint on huge canvases placed on the floor, brought abstract expressionism before a hostile public. willem de koonings first one-man show in 1948 established him as a highly influential artist. his intensely complicated abstract paintings of the 1940s were followed by images of woman, grotesque versions of buxom womanhood, which were virtually unparalleled in the sustained savagery of their execution. painters such as philip guston and franz kline turned to the abstract late in the 1940s and soon developed strikingly original stylesthe former, lyrical and evocative, the latter, forceful and boldly dramatic. other important artists involved with the movement included hans hofmann, robert motherwell, and mark rothko; among other major abstract expressionists were such painters as clyfford still, theodoros stamos, adolph gottlieb, helen frankenthaler, lee krasner, and esteban vicente. abstract expressionism presented a broad range of stylistic diversity within its largely, though not exclusively, nonrepresentational framework. for example, the expressive violence and activity in paintings by de kooning or pollock marked the opposite end of the pole from the simple, quiescent images of mark rothko. basic to most abstract expressionist painting were the attention paid to surface qualities, i.e., qualities of brushstroke and texture; the use of huge canvases; the adoption of an approach to space in which all parts of the canvas played an equally vital role in the total work; the harnessing of accidents that occurred during the process of painting; the glorification of the act of painting itself as a means of visual communication; and the attempt to transfer pure emotion directly onto the canvas. the movement had an inestimable influence on the many varieties of work that followed it, especially in the way its proponents used color and materials. its essential energy transmitted an enduring excitement to the american art scene. science and technology is quite a broad category, and it covers everything from studying the stars and the planets to studying molecules and viruses. beginning with the greeks and hipparchus, continuing through ptolemy, copernicus and galileo, and today with our work on the international space station, man continues to learn more and more about the heavens. from here, we look inward to biochemistry and biology. to truly understand biochemistry, scientists study and see the unseen bystudying the chemistry of biological processes. this science, along with biophysics, aims to bring a better understanding of how bodies work from how we turn food into energy to how nerve impulses transmit.analytic geometry, branch ofgeometryin which points are represented with respect to a coordinate system, such ascartesian coordinates, and in which the approach to geometric problems is primarily algebraic. its most common application is in the representation of equations involving two or three variables as curves in two or three dimensions or surfaces in three dimensions. for example, the linear equationax+by+c=0 represents a straight line in thexy-plane, and the linear equationax+by+cz+d=0 represents a plane in space, wherea, b, c,anddare constant numbers (coefficients). in this way a geometric problem can be translated into an algebraic problem and the methods of algebra brought to bear on its solution. conversely, the solution of a problem in algebra, such as finding the roots of an equation or system of equations, can be estimated or sometimes given exactly by geometric means, e.g., plotting curves and surfaces and determining points of intersection. in plane analytic geometry a line is frequently described in terms of its slope, which expresses its inclination to the coordinate axes; technically, the slopemof a straight line is the (trigonometric) tangent of the angle it makes with thex-axis. if the line is parallel to thex-axis, its slope is zero. two or more lines with equal slopes are parallel to one a