SQL INNER JOIN 关键字 在表中存在至少一个匹配时，INNER JOIN 关键字返回行。 INNER JOIN 关键字语法SELECT column_name(s) FROM table_name1 INNER JOIN table_name2 ON table_name1.column_name=table_name2.column_name 注释： INNER JOIN 与 JOIN 是相同的。 原始的表 (用在例子中的)： Persons 表： Id_P LastName FirstName Address City 1 Adams John Oxford Street London 2 Bush George Fifth Avenue New York 3 Carter Thomas Changan Street Beijing Orders 表： Id_O OrderNo Id_P 1 77895 3 2 44678 3 3 22456 1 4 24562 1 5 34764 65 内连接（INNER JOIN）实例 现在，我们希望列出所有人的定购。 您可以使用下面的 SELECT 语句： SELECT Persons.LastName, Persons.FirstName, Orders.OrderNo FROM Persons INNER JOIN Orders ON Persons.Id_P=Orders.Id_P ORDER BY Persons.LastName 结果集： LastName FirstName OrderNo Adams John 22456 Adams John 24562 Carter Thomas 77895 Carter Thomas 44678 INNER JOIN 关键字在表中存在至少一个匹配时返回行。如果 Persons 中的行在 Orders 中没有匹配，就不会列出这些行。
Мито: A Blaine Bettinger, Ellen Johnson, Jose Ortiz A1a1* Michael Woo A1a1a Paul Uyesaka A2 Antoine Simon, Bianca Calvert, Fernando Andrade, Gary Felix, Heyward Robinson, Jeffrey Harrington, Kelly Sabrina Francia, Saysa Santos B Sylvia Bailey-Munoz B4c1b Becca Ling C Carson Lyon, Katherine Gibson, Marisela Meskus D martin downs D4a* Boonsri Dickinson D4i Jack Tihon, Joe Alv, Kristen Chase, Shawn Hoon, stuart kim D5* Shu Hwa Cheng E1a Andro Hsu F1a* Will Carey F1a1* Chia H G Hong ChangBum, Sanny Ryan G2 Michael Kenny H Aleksandr Avramenko, Andreas Stahl, Anna Betts, Anna Kasimova, Barbara Greck, Barbara Mills Diaz, Barbara Richardson, Belinda Dettmann, Bob Thomas, bruno benetti, Candace Sams, Carlton Mullis, Carol Wilkerson, charles steidel, Colin Simpson, connie fry, Connie VanValkenburg, Cristal Holland, Daniel MILICEVIC, Deborah Flanagan, Donald Cooley, Donna Stefani, Drew Hayes, Fred Garza, Fred Witherington, Frederick Coxen, Janet Turner, jb demotte, Jennifer Grannis, Jim Williams, Jonathan Hansen, Joris Calow, Joseph Engle II, Kaven Thibault, Kay McCord James, Lee Grana, Lino Colosso, Luis Saavedra, Mark Russell, Marti Jourden, Martin Warren, Matthew Lynde, Matthew Rae, Mauri Myllyla, Milton Spiegel III, NEUTRON D, Niall Foley, pamela rowe, Patricia Black, Patricia Liles, Phyllis Abbott, Richard Eichhorn, Richard Jennings, Richard Kenyon, Richard Tingblad, Robert Bagosy, Robert Beck, Robert Wright, Roger Hicks, Roman Tatusov, Rosalie Craine, Sean MacGorman Powell, Seth Gillespie, Sharon Lewis, Shawn A McMillan, Sherolyn Jones, Stephanie Rossiter, Stephen McGrath, Stephen Tomkins, Timothy Gall, Vincent Sanford, William Cooper, WILLIAM ROMINE H1 DOROTHY SMITH, rondle mathis H1* Aleksandar Totic, Alex Brennen, Alex Tregor, Andre Abrahami, Annette Musso, Beau Gunderson, Betsy Collins, Betsy Schiffman, Bonnie Montgomery, Cathy Guenther, Claire Weisz, Colleen Castello, Dario X. 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Karr-Bartley, Marion Aust, Mark McCroson, Michael Thomas, Nicola Benaglia, Robert Stubbs, Sunil Mujumdar, Syed Hassan U4b darrell chadderton, Larisa Lyotova, Lauren Page U5 Tracy Staudacher U5a* Andrey Zorin, Damien Marsic, Jennifer Scott, Paul Shenton, Proband 2, Proband 3 U5a1* Andrew Ostoyic, David Anderson, David Perkins, Debra Patek, Frederick Wahl, GEORGE CARTER, Iram Mirza, John Gregor, Matthew Thyer, Mauricio Lima, Reyna O'Neil, Scott Kandel, suzanne bradley, Taylor Robinson U5a1a Leeann M Williams U5b Margo Rhoades U5b1 Charles Thompson, Didier Vernade, Keith Croes, natasha saxonov, Serge Saxonov U5b1b* Janice Straight U5b1b1 Harri Set?l? 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摘自 《The War of Art-Break through the blocks and win your inner creative battle》 ， by Steven Pressfield. （P148-149,151） "Most of us define ourselves hierarchically and don’t even know it. It's hard not to. School, advertising, the entire materialist culture drills us from birth to define ourselves by others’ opinion. Drink this beer, get this job, look this way and everyone will love you. High school is the ultimate hierarchy. And it works; in a pond that small, the hierarchical orientation succeeds. There’s a problem with the hierarchical orientation, though. When the numbers get too big, the thing breaks down. In Massapequa High, you can find your place. Move to Manhattan and the trick no longer works. New York City is too big to function as a hierarchy. So is IBM. So is Michigan State. The individual in multitudes this vast feels overwhelmed, anonymous. He is submerged in the mass. He is lost. We have entered Mass Society. The hierarchy is too big. It doesn’t work any more. In the hierarchy, the artist looks up and looks down. The one place he can't look is that place he must: within. "
地球内核的熔融作用 Melting of the Earth’s inner core David Gubbins, Binod Sreenivasan, Jon Mound Sebastian Rost 地球的磁场是由液态铁核发电机产生的，它对应着上覆岩石地幔的冷却而对流着。地核由最里面向外冷却，生成固态的内核并释放驱动成分对流动轻元素 (1-3) 。地幔对流从地核中提取热量，其速率具有极大的侧向差异性 (4) 。 本文我们利用地球发电机 (geodynamo 模拟表明这些差异性转移到了内核边界处并足以引起向内核的热流。如果这发生在地球内部的话，将引起局部熔融作用。熔融作用所释放的较重的流体可以形成一个多成分层，该层已经由内核边界 150km 之上的地震波速异常观测所揭示出来 (5-7) 。 本研究为该层的存在提供了一个简明的解释，否则这将需要另外一些假说来解释，如内核对地幔的锁定 (locking) ，重力势能中心的转换 (7,8) ，或者是与固相线温度相同但成分从外核到内核之间变化的对流作用 (9) 。这些明显的与冷却相关的较细的下降流和与熔融相关的大量的上升流表明，熔融区域可能相当广泛，尽管保持地球发电机运行的冷却作用占据平均优势。 局部熔融与冷却作用同样也为内核自身的地震波异常提供了一种有效机制 ，这比目前所考虑到热流差异作用 (10) 更加强有力一些。 Nature原文链接： http://www.nature.com/nature/journal/v473/n7347/full/nature10068.html PDF下载： 2011-Nature-Melting of the Earth's inner core.pdf Nature同期有一篇介绍文章： http://www.nature.com/nature/journal/v473/n7347/full/473292a.html （以下是原文翻译，译者周春银） 地核只是被动地响应着地幔引起的不规则热流活动：它在这个耦合对流体系中扮演的是一个完全被动的角色。地幔对流所产生的核幔边界 (core-mantle boundary, CMB) 附近热流活动的差异性可能是巨大的。他们可以通过两种独立的方法来估计，一种是利用在假定的地幔底部的热边界层内的地震层析成像 (seismic tomography)(11) ，另一种是利用地幔对流研究 (4) 。两者均显示与平均热流相当的差异性。不均匀边界条件对核对流 (core convection)(12-14) 会产生巨大的影响，并且当背景对流 (background convection) 很小时，边界差异可以通过增强流体柱中的螺旋形运动来促进磁场的形成 (15) 。许多地球发电机模拟基于地震层析成像研究，利用热边界条件来解释地磁场的非轴对称时间平均值 (16-18) 、太平洋地区的低长期变化 (16,19) 、极性倒转的频率 (20) 、以及倒转过程中固有的极性转换途径 (21) 。 Figure 1: Effect of mantle inhomogeneity on heat flux distribution at the inner core surface. Heat fluxes are applied to the upper boundary ( a ) and calculated on the constant-temperature lower boundary ( b ) in a geodynamo simulation where the flow is strongly coupled to the boundary thermal anomalies ( q * = 0.45). The range of heat flux across the upper boundary ranges from 0.77 to 2.16 dimensionless units outwards and across the lower boundary ranges from −0.51 to 2.89 dimensionless units (negative values indicate heat flux into the inner core). This model uses an Ekman number 1.2 × 10 −4 , Rayleigh number 1.5 times the critical value for onset of convection, Prandtl number 1 and magnetic Prandtl number 10. (See the Methods section for definitions of these dimensionless numbers.) 我们根据由不均匀上边界热流和恒定下边界温度所驱动的数字地球发电机计算来研究内核边界 (inner-core boundary, ICB) 处的热流变化。有关我们发电机模型的详细介绍见 Methods 材料。利用层析成像边界条件 (11) 的样本足以说明下边界处向内的热流存在的可能性。重要参数 q* = (q max -q min )/(2q mean ) 计算了相对平均值而言 CMB 热流侧向变化的强度； q* = 0.15-0.45 这一范围得出的发电机模型，包括从相对未受边界条件影响的模型，到其中磁场几乎是静止的或者从统计学上说是“锁定”在边界的模型 (22) 。 Figure 2: Calculated heat flux on the lower boundary of a geodynamo model where q * = 0.15 for the upper boundary heat flux. Panels a and b are snapshots and c shows the time average over several magnetic diffusion times. Heat fluxes range from −0.287 to 2.126 ( a ), −0.124 to 1.976 ( b ) and −0.276 to 1.86 ( c ) for the time average. The parameters used in this model are the same as in Fig. 1 . Figure 1 显示了在 q*=0.45 时锁定的发电机模型中上下边界处的热流分布。 ICB 和 CMB 处的热流图像是成镜像的；热流负斑块指示熔融位置处向内核的热流，如果这是模型的一部分。 Figure 2 显示了在 q*=0.15 时的发电机模型的两幅快照以及时间平均值；仍然存在负热流斑块，尽管侧向变化很弱。在所有这些模型中，外核中的上升流分布很广，而下降流则垂直很细 (Fig 3) ，形成高 CMB 热流之下高 ICB 热流的集中斑块。熔融区域因此相对于熔融的总量来说是相对比较大的。但是我们也注意到，具有不同运行参数和浮力关系的发电机模型并不需要产生向下边界的热流活动：一个较弱的对流区域可能最有利于内核熔融作用，其中上边界处的侧向变化可以通过各种方式传播到下边界。 Figure 3: Temperature (colour contours) and fluid flow (arrows) on the equatorial section for the statistically locked tomographic model ( q * = 0.45). The lowest temperature is blue and the highest temperature is deep red. We note the narrow downwellings beneath cold regions (the two major ones coinciding with the ‘ring of fire’ around the Pacific) and broad upwellings (corresponding to the mid-Pacific and African superplume). This leads to relatively large areas of negative (melting) and low-positive heat flux on the ICB and relatively small areas of strong-positive heat flux (freezing). 当将热地球发电机模拟结果运用到地球时有三个负责因素必须考虑。第一个就是传播到绝热线下的热量。这在最近的一项地幔对流研究中被忽视掉，该研究考察了后钙钛矿 (postperovskite) 层和化学成分变化对贯穿 CMB 的热流活动的影响作用，以及它和地震剪切波速的相关性 (4) 。后钙钛矿对热流影响甚微但是对化学成分侧向变化影响较大，例如覆盖在 CMB 之上的深俯冲板块会极大地增大 q* 值。要将这些结果运用到地核对流中，我们必须首先去除传播到绝热温度梯度以下的热量。根据对 CMB 绝热梯度 (1 K/km) 和地核热导率 (k=50 W m -1 K -1 ) 的典型估计值，传播的热量为 50 m W m -2 ，与地幔对流计算 q mean 值相当。去除这一热量将大大提高 q* ，因为这会降低 q mean 到几乎零值而 q max -q min 不变化。实际上这里没有什么可以阻止 q* 变得无限大，正如在前人研究的最接近真实的地幔模型中 (TC-3.6 模型，具有可变的辉石含量 )(4) 的一样，这意味着地核顶部是热中立的 (neutral) 。大多数发电机模拟都受限于非常低的 q* 值，发电机模型不能解释广泛的侧向热流变化 (15,18) 。在我们具有内部加热作用的模型中发电机模型 q*≈1 也无法解释，但是具有基底加热和分层上层的发电机模型具有较大的 q* 仍然可以有效解释 (ref.23) 。地球液核的上部区域可能是稳定分层的，或者最多仅有非常微弱的对流 (24,25) ，因此对于地球来说可能应具有高 q* 值。有两个因素可能会随深度而增大 q* 。首先绝热梯度在 CMB 和 ICB 之间会随深度而减少 3 倍。在 ICB 绝热热量必须加回到模型结果中，减少任何进入内核的热流；但是减弱的绝热线使得这种效应相对非常微弱。其次，较细的下降流和球形结构倾向于会集中对流热量，增大侧向差异性。 第二个要考虑的复杂因素是化学成分对流。成分梯度是中立的或者说在 CMB 是稳定的 ( 假设没有轻元素进入到地幔中 ) ：地核顶部的对流纯粹是热力学上的。成分浮力在外核深部逐渐会主导热浮力作用，尤其是在 ICB 附近，如下面的计算所显示的一样。浮力表达为 ρ ( α c c+ α T T) g ，这里 ρ 是密度， g 是重力加速度， α T 是热膨胀系数， α c 是成分膨胀系数。成分变化因此具有等价热 α c / α T 。对比在各自的扩散方程中的热流和质量流发现，转换因子是 C p α c / α T ，这里 C p 是比热。在 ICB 凝固 1kg 的液体释放 L 焦耳的潜热和 ρ c kg 的质量以及等加热 C p α c c/ α T 焦耳。在浓度 (concentration) c=0.0252 的情况下，这对应着 ICB 处 0.6g /cm 3 的密度突变 ( 来自 PREM 模型 (26)) ，假设其中有 0.34g /cm 3 来自于纯铁的固 - 液相变 (27) ，那么有效浮力比 C p α c c/L α T =2.3 。在更大的 ICB 密度突变情况下成分浮力将会起主导作用甚至更大： 0.8 g /cm 3 时为 4.1 ， 1.0 g /cm 3 时为 5.8 。因此在 ICB 附近温度变化在浮力中的作用相对而言不是很重要，但是对于确定凝固速率以及通过释放轻元素来提供浮力作用来说很重要。上边界所产生的侧向温度变化将会通过成分对流以及辅助的热对流作用一直传播到 ICB ，所以我们预计在热力学或同密度 (codensity) 地球发电机模拟中所观测到 ICB 处的差异将会在一个热 - 化学体系中维持稳定。 第三个复杂因素就是多成分层可能的动力学影响。贯穿新熔的、重流体层的密度梯度比外核主体部分对流所产生的任何东西都大很多： 150-km 这一层的密度变化为 0.1 g /cm 3 ，而在相类似或更长范围内典型的对流密度波动为 10 -6 g/cm 3 或更低，这是根据 ICB 附近浮力 - 科里奥力平衡估计出来的 (28) 。这样大的密度梯度将会阻止下降流到达 ICB ，但是由凝固所产生的轻物质上升流 (plume) 将会穿越它，沿 ICB 向着凝固地区留下重流体并维持多成分层的混合作用。实验研究表明，如果熔融超过 20% 的凝固 (8) 上升流将会与该层混合，但是 ICB 上的上升流是由热效应所决定的而不是化学成分效应。还需要进一步的研究来认识这一层的作用。 CMB 处热流变化所形成的内核的区域性熔融作用，为外核底部所观测到的多成分层提供了简明解释。这同样也为固体内核本身的地震异常提供了一个有效的机制解释，因为熔融区域将会由最近产生的、预压过的物质所组成，而凝固区域将会含有最近形成的、松散物质层。热流差异性已经被用来解释内核的地震波异常 (29) ，但是实际的熔融作用将会产生更强的作用 (7) 。在两种情况下，地幔异常和保持位置的任何相关性都需要内核，在某种程度上整个地核，流动都锁定于地幔。如果这些观测能够与进一步的观测相容，尤其是如果多成分层最终并不需要内核锁定，他们将为地核演化、对流以及发电机提供重要的约束条件。 参考文献： 1. 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