Synthesizing trees from samples

TPO67Passage 1．．Crop EngineeringParagraph 1: Our current ability to precisely engineer crop genomes was preceded by a long history of genetic manipulation in agriculture. Human impact and its accompanying effects began early in our history at many tropical and subtropical sites around the globe. Our ancestors were omnivores, consuming whatever plant or animal material they fortuitously encountered. Even then, humans had considerable effects on the environment, reducing and even driving to extinction populations of the animal species they hunted and expanding the distribution of plants by accidentally distributing seeds as they migrated.Paragraph 2: Humans probably first realized that seeds could yield a stable food supply through agriculture when they observed plants arising from refuse or wasteland, perhaps fruit trees growing along forest and jungle paths from discarded or defecated seeds or else vegetables sprouting in garbage dumps at temporary settlements. A more organized approach to agriculture began about eight to ten thousand years ago coincidentally at a number of locations around the globe. The most diverse farming developed in the Near East, with legumes, cereals flax, sesame, and fruit trees. At about the same time, New World residents were growing beans, maize, squashes, and potatoes, and Asian farmers were beginning to cultivate rice. Paragraph 3: These early domesticated crops foreshadowed the overwhelming changes contemporary agriculture has wrought in plants. Humans soon learned to separate varieties that could be grown as crops from wild types in order to prevent characteristics undesirable for cultivation from mingling with those selected for farming. Continued selection of crops with desirable characteristics increased the separation between feral (wild) and managed plants and accelerated the diminishing diversity and more limited variation found in today's crops. Paragraph 4: The simplest way to select crops is to save seeds preferentially from plants with beneficial traits, and the first farmers selected for large seeds and fruit, increased seed production, lack of dormancy, faster germination, higher annual yield, and reduced seed scattering. The success of this early selection resulted in an accelerating impact of agriculture on crop diversity and feral plants. Crops quickly became commodities, moved and traded over a rapidly widening area, so that many plants were distributed well beyond their previous ranges, and some throughout the globe.Paragraph 5: Three phenomena have characterized the more recent impact of agriculture on Earth. ■The first was the increase in human population, which has doubled at shorter and shorter intervals over the last thousand years. ■The result was increased acreage under cultivation and a fundamental remodeling of the globe toward managed rather than wild ecosystems. ■ By 1998 there were 3,410,523,800 acres of land under cultivation worldwide, an area larger than the United States. ■ Entire ecosystems have disappeared, others remain but arethreatened, and the sheer volume of people and area of farmland have been major forces of biological change.Paragraph 6: The second event through which agriculture modifi e d our planet was European colonization. Previously, migration and trade had moved crops between countries and continents, but the Europeans inaugurated an unprecedented dispersal of biological material worldwide. Maize, tomatoes, and potatoes were transported from the New World to the Old; wheat, rye, and barley were carried from the Old World to the New; and rice, soybeans, and alfalfa were moved from their Asian sources to every arable continent. Each of these and innumerable other introductions conveyed not only unique material but also assemblages of introduced plant pests and diseases that today cause the majority of pest-management problems around the world.Paragraph 7: The third factor shaping the nature of agriculture and the envirorunent alike is the increasing precision with which we have selected and bred crops. This acuity stemmed from many advances, but at its heart lies the work of two men-one, the English naturalist Charles Darwin, and the other, an Austrian monk, Gregor Mendel. The concepts of evolution and genetics were not their work alone, but both of them were decades ahead of their colleagues in synthesizing the companion concepts of natural selection and inheritance that are at the core of all contemporary biological science and that form the substrate upon which biotechnology grew.Paragraph 1Our current ab山ty to precisely engineer crop genomes was preceded by a long history of genetic manipulation in agriculture. Human impact and its accompanying effects began early in our history at many tropical and subtropical sites around the globe. Our ancestors were omnivores, consuming whatever plant or animal material they fortuitously encountered. Even then, humans had considerable effects on the environment, reducing and even driving to extinction populations of the animal species they hunted and expanding the distribution of plants by accidentally distributing seeds as they migrated.1. According to paragraph 1, all of the following are true of early humans EXCEPT:A.They fed on any plants and animals that they foundB.They significantly reduced the number of animal species through huntingC.They spread plants from one place to another as they migrated.D.They introduced new animal species to different parts of the world.Paragraph 2:Humans probably first realized that seeds could yield a stable food supply through agriculture when they observed plants arising from refuse or wasteland, perhaps fruit trees growing alongforest and jungle paths from discarded or defecated seeds or else vegetables sprouting in garbage dumps at temporary settlements. A more organized approach to agriculture began about eight to ten thousand years ago coincidentally at a number of locations around the globe. The most diverse farming developed in the Near East, with legumes, cereals flax, sesame, and fruit trees. At about the same time, New World residents were growing beans, maize, squashes, and potatoes, and Asian farmers were beginning to cultivate rice.2. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential informationA. Humans first saw fruit trees growing along pathways and vegetables growing on garbage dumps in temporary settlements and started cultivating them for a steady food supply.B. Humans living in temporary settlements noticed that fruit trees and vegetables that they could cultivate for a constant supply of food were growing in waste areasC. Humans saw plants growing in waste areas at temporary settlements and got the idea that they could plant seeds to ensure a constant supply of foodD. Humans maintained a constant food supply by planting fruit trees along pathways and vegetables in garbage dumps and other waste areas in temporary settlements3. Why does the author include the information that "New World residents were growing beans, maize, squashes, and potatoes"?A. To support the claim that organized agriculture developed in different parts of the world at the same timeB.To indicate that different crops were grown in different parts of the worldC.To argue against the idea that the most diverse farming occurred in the Near EastD.To indicate that New World farmers cultivated a larger number of crops than Asian farmers did.Paragraph 3: These early domesticated crops foreshadowed the overwhelming changes contemporary agriculture has wrought in plants. Humans soon learned to separate varieties that could be grown as crops from wild types in order to prevent characteristics undesirable for cultivation from mingling with those selected for farming. Continued selection of crops with desirable characteristics increased the separation between feral (wild) and managed plants and accelerated the diminishing diversity and more limited variation found in today's crops.4.Which of the following can be inferred from paragraph 3 about plants with undesirable characteristics?A.Farmers cultivated them only when plants with desirable characteristics were not available.B. Farmers did not let them grow near plants that were selected for cultivation as cropsC.They enabled farmers to more properly manage the plants that were selected for cultivation as cropsD.They provided farmers with a limited variety of plants to select for cultivation as cropsParagraph 4: The simplest way to select crops is to save seeds preferentially from plants with beneficial traits, and the first farmers selected for large seeds and fn儿t,increased seed production, lack of dormancy, faster germination, higher annual yield, and reduced seed scattering. The success of this early selection resulted in an accelerating impact of agriculture on crop diversity and feral plants. Crops quickly became commodities, moved and traded over a rapidly widening area, so that many plants were distributed well beyond their previous ranges, and some throughout the globe.5.Which of the following is mentioned in paragraph 4 as an effect of crops becoming commodities?A.Fam记rs were able to cultivate a greater variety of crops than they used to.B.Trade routes quickly developed as people moved crops from one place to another.C.Plants became widely distributed outside their places of origin.D. F eral plants were quickly wiped out as more crops were cultivated for trading. Paragraph 6: The second event through which agriculture modified our planet was European colonization. Previously, migration and trade had moved crops between countries and continents, but the Europeans inaugurated an unprecedented dispersal of biological material worldwide. Maize, tomatoes, and potatoes were transported from the New World to the Old; wheat, rye, and barley were ca订ied from the Old World to the New; and rice, soybeans, and alfalfa were moved from their Asian sources to every arable continent. Each of these and innumerable other introductions conveyed not only unique material but also assemblages of introduced plant pests and diseases that today cause the majority of pest-management problems around the world.6. The word "inaugurated" in the passage is closest in meaning toA. EncouragedB.observedC.achievedD.introduced.7.Which of the following is mentioned in paragraph 6 as one of the effects of moving crops from one part of the world to another part of the world?A.Europeans were able to successfully colonize other continentsB.Plant pests and diseases became more widespread.C.Some crops failed to grow very well at their new locationsD.New ways to manage pests and diseases that affected crops were introducedParagraph 7: The third factor shaping the nature of a griculture and the environment alike is the increasing precision with which we have selected and bred crops. This acuity stemmed from many advances, but at its heart lies the work of t wo men-one, the English naturalist Charles Darwin, and the other, an Austrian monk, Gregor Mendel. The concepts of evolution and genetics were not their work alone, but both of t hem were decades ahead of t heir colleagues in synthesizing the companion concepts of n atural selection and inheritance that are at the core of all contemporary biological science and that form the substrate upon which biotechnology grew.8.Which of the following is mentioned in paragraph 7 as being true of Charles Darwin and Gregor Mendel?A.They were the first to integrate the concepts of n atural selection and inheritanceB.They were the first to encourage the use of biotechnology in agricultureC.They were the first to work on evolution and genetics at the same timeD.They were the first to provide farmers with information on selecting and breeding crops.Paragraph 5: Three phenomena have characterized the more recent impact of a griculture on Earth. ■The first was the increase in human population, which has doubled at shorter and shorter intervals over the last thousand years. ■The result was increased acreage under cultivation and a fundamental remodeling of the globe toward managed rather than wild ecosystems.■ By 1998 there were 3,410,523,800 acres ofland under cultivation worldwide, an area larger than the United States. ■ Entire ecosystems have disappeared, others remain but are threatened, and the sheer volume of people and area of farmland have been major forces of biological change.9.Look at the four squares [ ■] that indicate where the following sentence could be added to the passage Where would the sentence best fit?This large-scale agriculture has actually resulted in a decrease in biological diversity.Click on a square[■] to add the sentence to the passage. To select a different location, click on a different square.10. Directions: An introductory sentence for a brief summary of the passage is provided below Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage Some sentences do not belong in the sun皿ary because they express ideas that are not presented in the passage or are minor ideas in the passage This question is worth 2 points. Drag your answer choices to the spaces where they belong. To remove an answer choice, click on it. To review the passage VIEW TEXTAgriculture has had a tremendous effect on the environment.Answer choices:A. Humans have affected plants through the process of selective breeding for more than 10,000 years.B. Domesticated plants fever affected ecosystems worldwide as they have spread through human migration, trade, and colonizationC.A greater variety of crops was cultivated in the Near East than in the New World and AsiaD.The wide distribution of plants throughout the world has led to the development of effective pest management techniques aimed at protecting plants against pests and diseases.E.Biotechnology, based on the concepts of natural selection and inheritance, has enhanced farmers'ability to select and grow crops with valuable characteristics.F.Farmers have developed methods of crop selection and breeding that do not adversely affect the environment following the work of Darwin and Mendel.。

第 43 卷第 1 期2024年 1 月Vol.43 No.1Jan. 2024中南民族大学学报（自然科学版）Journal of South-Central Minzu University（Natural Science Edition）利用自相似性实现医学图像合成的生成对抗网络李帅先，谭桂梅，刘汝璇，唐奇伶*（中南民族大学生物医学工程学院，武汉430074）摘要基于深度卷积的跨模态医学图像合成网络具有从大规模数据资源中学习非线性映射关系以进行局部生成的优势，但现有方法忽略了医学图像具有特征自相似性的特点，仅通过卷积来提取像素级别的特征信息，导致深层特征提取能力不足和语义信息表达不充分.为此，提出了基于图注意力块（Graph Attention Block，GAB）和全局块注意力块（Global Patch Attention Block，GPAB）的生成对抗网络（Graph Attention Block and Global Patch Attention Block GenerativeAdversarial Networks，GGPA-GAN）.其中，用图注意力块和全局块注意力块捕捉医学图像切片间以及切片内的自相似性，进行深层特征的提取.此外，在生成器中加入二维位置编码，利用图像的空间位置信息来增强语义信息的表达能力. 在HCP_S1200数据集和ADNI数据集上的实验结果表明，提出的网络在3T-7T、T1-T2的脑部MRI图像合成任务中相较于其他网络取得了最优的结果.在3T-7T脑部MRI图像合成任务中，相比Pix2pix合成方法，该方法在峰值信噪比（Peak Signal-to-Noise Ratio）、结构相似性指数（Structural Similarity Index）和平均绝对误差（Mean Absolute Error）方面分别提升了0.55、0.007和6.55.在T1-T2脑部MRI图像合成任务中，相比Pix2pix合成方法，在PSNR、SSIM和MAE分别提升了0.68、0.006和8.77.这些结果充分证明了此方法的有效性，为临床诊断提供了有力的帮助.关键词脑磁共振图像；深度学习；医学图像合成；图注意力；位置编码中图分类号TP391.4 文献标志码 A 文章编号1672-4321（2024）01-0078-12doi：10.20056/ki.ZNMDZK.20240111A generative adversarial networks for medical image synthesisbased on self-similarityLI Shuaixian，TAN Guimei，LIU Ruxuan，TANG Qiling*（College of Biomedical Engineering， South-Central Minzu University， Wuhan 430074， China）Abstract The cross-modal medical image synthesis network based on deep convolution has the advantage of learning nonlinear mapping relationships from large-scale data resources to perform local generation. However，the existing methods overlook the inherent feature self-similarity of medical images and only extract pixel-level feature information through convolution， which results in insufficient deep feature extraction capability and inadequate semantic information representation. Therefore， a Generative Adversarial Network（Graph Attention Block and Global Patch Attention Block Generative Adversarial Networks， GGPA-GAN） is proposed based on Graph Attention Block（GAB）and Global Patch Attention Block（GPAB）. GAB and GPAB are utilized to capture the self-similarity between and within slices of medical images，which enable deep feature extraction. Additionally，2D positional encoding in the generator is incorporated by using spatial position information of the images to enhance the expression capability of semantic information. The experimental results on the HCP_S1200 dataset and ADNI dataset demonstrate that the proposed network achieves superior performance compared to other networks in synthesizing brain MRI images across 3T-7T and T1-T2 modalities. In the 3T-7T brain MRI image synthesis task， the method outperforms the Pix2pix synthesis method with improvements of 0.55 in Peak Signal-to-Noise Ratio （PSNR）， 0.007 in Structural Similarity Index （SSIM）， and 6.55 in Mean Absolute Error （MAE）. For the T1-T2 brain MRI image synthesis task， the method surpasses the Pix2pix method with improvements of 0.68 in PSNR，0.006 in SSIM，and 8.77 in MAE. These results fully prove the effectiveness of the proposed method and provide powerful help for clinical diagnosis.Keywords brain magnetic resonance imaging； deep learning； medical image synthesis； graph attention； positional encoding收稿日期2023-05-21* 通信作者唐奇伶（1973-），男，副教授，博士，研究方向：医学图像处理，E-mail：*****************基金项目湖北省自然科学基金资助项目（2008CDB392）；中央高校基本科研业务费专项资金资助项目（CZY22014）第 1 期李帅先，等：利用自相似性实现医学图像合成的生成对抗网络医学图像在临床诊断中起着至关重要的作用，它为医生提供了非侵入性的方法，帮助医生观察和分析病人体内的内部结构，更准确地诊断疾病［1-3］.然而，由于技术、设备、成本和患者安全等因素的限制，有时并不能获得所需的医学图像［4］.医学图像合成技术可以根据已有的图像数据，通过计算机算法和人工智能技术生成逼真的医学图像，有效地解决数据不足、成本高昂等问题.在从核磁共振成像（Magnetic Resonance Imaging，MRI）的T1加权图像合成T2加权图像中，T1加权脑图像可以清晰地显示灰质和白质组织，而T2加权脑图像可以描绘皮层组织中的流体，两种图像组合可以帮助医生更准确地识别异常病变组织，更准确地诊断疾病.在从MRI的3T图像合成7T图像中，由于3T图像的空间分辨率受到限制，很难观察到较小的大脑结构，如海马体等.但是，7T图像可以提供更高质量的图像.由于7T图像的成本相对较高且不普及［5］，但医学图像合成技术可以用来生成近似于7T 的高质量图像，为医生提供更准确、全面的诊断依据.近年来，深度学习在医学图像合成领域取得了实质性的突破［6-8］.基于深度学习的图像合成方法共享一个通用框架，该框架使用数据驱动的方法进行图像强度映射.工作流程通常包括一个网络训练阶段，用于学习输入与其目标之间的映射，以及一个预测阶段，用于从输入中合成目标图像.相比于传统的基于地图集、字典学习等方法，基于深度学习的方法更具有普适性，可以更好地解决医学图像合成问题［9］.GAO等［10］基于深度卷积神经网络（Deep Convolutional Neural Networks，DCNN），即编码器-解码器神经网络架构，以学习源图像和目标图像之间的非线性映射，实现图像合成. LI等［11］使用卷积神经网络（Convolutional Neural Network，CNN）从相应的MRI数据中估计缺失的正电子发射断层扫描（PET）数据.QU等［12］通过在UNet网络中加入来自空间域和小波域的互补信息，实现了从3T MRI合成7T MRI图像的任务. CHARTSIAS等［13］提出了一种用于MRI图像生成的网络结构，能够自动用现有的模态图像还原缺失的模态图像.ZHANG等［14］提出了一种双域CNN框架，该框架分别在空间域和频域中使用两个并行的CNN，通过傅里叶变换相互交互，从3TMRI合成7T MRI图像.基于生成对抗网络（Generative Adversarial Networks，GAN）的医学图像合成是近年来备受关注的研究热点之一［15-18］.NIE等［5］将GAN结合自动上下文模型和全卷积神经网络，从MRI图像合成CT图像、3T MRI合成7T MRI图像. WOLTERINK等［19］使用GAN将低剂量CT图像转换为常规剂量CT图像. KAWAHARA等［20］基于具有两个卷积神经网络的GAN预测框架，实现T1加权的MRI图像和T2加权的MRI图像的相互生成.YANG等［21］基于循环一致性生成对抗网络（Cycle Consistent GAN， CycleGAN）模型用于非成对的MR图像到CT图像的合成. YANG等［22］通过利用条件生成式对抗网络（Conditional GAN，CGAN）的深度学习模型，实现T1加权和T2加权的MRI图像的互转.当前利用卷积神经网络处理医学图像合成任务中，通常依靠堆叠大量卷积层来增加网络的深度或宽度，以更好地拟合非线性关系.此外，一些网络结构如残差结构、U-Net结构也被广泛应用于医学图像合成，以提高性能和改善效果.然而，很少有工作专注于医学图像本身的特点，缺乏对其特有特征的考虑，导致网络在深层特征提取的能力和表征方面存在不足.医学图像中存在大量特征相似性较高的图像块.图1呈现了不同患者的7T MRI脑图像（Sample1、Sample2、Sample3），其中相似的图像块可能在同一张切片内不同位置之间（绿色框），或者在连续的切片中同一位置之间（红色框）.医学图像具有自相似性特点，即重要的结构和特征在不同空间位置上以相似的方式出现.为此，本文提出了两种注意力块.首先，图结构方法可以模拟不同CT切片之间的结构连续性和相互作用［16］.本文在图像的连续切片下构建了以图像块（patch）为单位的拓扑结构，通过图注意力捕捉医学图像连续切片的关联性，使网络在不同切片之间共享和传递信息，提高特征的学习能力.该方法通过图注意力块（Graph Attention Block，GAB）实现.其图1 7T MRI图像在不同样本下的内部切片示例Fig.1　Internal slice examples of 7T MRI images in different samples79第 43 卷中南民族大学学报（自然科学版）次，本文同样构建以图像块为单位的全局块注意力块（Global Patch Attention Block，GPAB）来捕捉同切片下的非局部相似性，建立全局的相互关系，使网络更好地理解同一切片中不同区域之间的关联性，并通过设计一个并行的特征提取单元，该单元通过将GAB和GPAB结合，来进行深度特征提取.与自然语言序列中的位置信息类似，图像中不同像素之间的位置关系也可以提供重要的上下文信息（黄色框、黄线），对这些位置关系进行位置编码可为网络提供更多的语义信息.此外，在不同样本下的相同位置的切片中（黄色框、紫线），也存在相似的空间结构和位置关系，通过加入位置编码使网络进一步提高对数据特征关系的理解和学习能力.本文在GAN框架下，提出了基于图注意力块和全局块注意力块的生成对抗网络（Graph AttentionBlock and Global Patch Attention Block Generative Adversarial Networks，GGPA-GAN），在生成器加入GAB和GPAB以及二维位置编码，丰富语义信息和提升特征表达能力，提高图像合成的精确度.1　方法为了更好地实现源图像到目标图像的合成，本文使用生成对抗网络作为框架进行学习.如图2所示，GGPA-GAN由两部分组成：生成器（G）和判别器（D）.生成器由编码器、深层特征提取单元和解码器组成，目的在于生成与真实目标图像相似的合成目标图像.判别器由卷积神经网络和全连接层组成. 判别器的任务是评估生成器生成的合成目标图像是否与真实目标图像足够相似.在训练过程中，生成器会不断优化自己的参数，最小化其生成的图像与真实图像之间的差异.同时，由于判别器的存在，生成器也会受到来自判别器的反馈，不断改进自己的生成策略，以尽可能地欺骗判别器.通过这种对抗训练方式，生成器和判别器可以互相协作，不断提高网络的性能，最终生成高质量的图像.1.1　生成器网络结构生成器可以分为3个阶段，第一个阶段是编码阶段，编码器通过逐层的卷积操作实现下采样来捕捉图像不同层次的特征.第二个阶段是深层特征提取阶段，通过由GAB和GPAB构建的深层特征提取单元加强网络对图像特征的感知和提取.第三个阶段是解码阶段，对各层特征图进行整合后使用解码器实现上采样，最后经过1×1的卷积进行通道降维，完成输出.这个阶段是对前面阶段提取的特征进行重建和还原.生成器的结构采用了逐层提取、加强感知能力、逐层重建的策略，通过多层次的处理来捕捉图像的不同特征，以合成高质量的图像输出.如图3所示为生成器网络内部结构.1.1.1　编码器与解码器图4为生成器网络中的编码器内部结构，编码器包括卷积层、激活层、池化层和位置编码.在每个卷积层中，输入图像会与一组内核进行卷积运算，每个内核可以捕捉图像的局部特征，使网络能够有效地学习图像的特征表示.激活层使用整流线性单元（ReLU激活函数）为神经网络增加非线性运算，其将负输入替换为零，并保持正输入不变.池化层使用最大化池化（MaxPool）用来提取特征图中的最显著的特征，并降低特征映射的维度.位置编码可为网络提供位置信息，该方法将在下文进行介绍.此外，引入残差连接可以使网络更容易学习恒等映射，提高网络性能和训练效率.该网络使用三个卷积层（Conv1、Conv2和Conv3）以增加网络深度.其图2 GGPA-GAN的内部结构Fig.2　Internal structure of GGPA-GAN 80第 1 期李帅先，等：利用自相似性实现医学图像合成的生成对抗网络中，Conv1和Conv2是一个3 × 3内核大小、填充为1、步长为1的卷积层.Conv2的卷积核数量是Conv1的两倍，以使特征通道数增加.通过卷积核大小为2 ×2，步长为2的MaxPool 使特征图大小缩小一半.本文中，编码器和解码器具有相同的网络结构和层数，唯一区别在于解码器将编码器中的池化层替换为反卷积层，用于将低维特征图恢复为高维特征图.解码器中的反卷积层使用的卷积核大小为2 × 2、步长为2.本文中的生成器网络包含4个编码器和4个解码器.1.1.2　深层特征提取单元本文的深层特征提取单元位于图3蓝色框区域.该单元将GAB 和GPAB 相结合，其中GAB 用于捕捉切片之间的相似性，而GPAB 用于捕捉切片内不同图像块的相似性.同时，通过引入残差连接来保留图像的细节信息.原始特征图经过这两种块并行处理后，再将它们的输出进行通道连接.最后，使用卷积核大小为1 × 1的卷积操作，将通道数恢复为原始的通道数.1.2　判别器网络结构判别器包括3个卷积核大小依次为8 × 8，4 × 4，4 × 4的卷积层、批量归一化层（BN ）、ReLU 激活函数层，紧接着还有3个全连接层将数据扁平化，卷积层的卷积核数量依次为8、64、256，全连接层中输出节点数为256、64和1.在最后一层，利用tanh 激活函数作为评估器，得出输入图像是真实图像的概率.图5为判别器网络内部结构.1.3　位置编码对于医学图像合成，医学图像通常具有较高的空间分辨率和较复杂的结构.因此在医学图像合成中准确地捕捉到这些空间位置信息对于合成图像的质量至关重要.位置编码是一种将空间位置信息嵌入到特征表示中的方法，通过位置编码学习到图像中不同位置的特征和相对位置之间的关系，从而提高模型的空间感知能力.如图6所示为本文的位置编码内部结构，H 、W 、D 分别为特征图的高度、宽度和通道数.本文将Transformer 模型［23］中提出的1D 位置编码技术调整为2D ，公式如（1）~（4）所示：PE (x ，y ，2i )=sin(x 100004i D)，（1）PE (x ，y ，2i +1)=cos (x100004i D)，（2）PE (x ，y ，2j +D2)=sin (y100004i D)，（3）图3 生成器网络内部结构Fig.3　Internal structure of the generator network图5 判别器网络内部结构Fig.5　Internal structure of the discriminator network图4 生成器网络中的编码器内部结构Fig.4　Internal structure of the encoder in a generator network81第 43 卷中南民族大学学报（自然科学版）PE (x ，y ，2j +1+D2)=cos(y 100004jD)，（4）式中：x 和y 指定为水平和垂直位置坐标值，即(x ，y )为二维空间的一个坐标点；i ，j 是[0，D /4)中的整数.位置编码得到的位置信息图具有与特征图相同的大小和维度.位置编码的每个维度都由特定频率和相位的正弦信号组成，表示水平方向或垂直方向.本文使用的时间范围从1到10000.不同的时间尺度等于D /4，对应于不同的频率.对于每个频率，在水平/垂直方向上生成正弦/余弦信号.所有这些信号被串联成D 个维度，前一半维度为水平位置的编码，后一半维度为垂直位置的编码.最后将位置信息和特征图相加，作为输出.该位置编码具有不向神经网络添加新的可训练参数的优点.1.4　图注意力块（GAB ）在图注意力块中，将图像数据转换成一张图结构，将不同的图像块作为图中的节点，节点之间的关系构成了图中的边.通过连接不同切片中相同坐标位置的图像块起来，构建出一张具有结构连续性的图.选取其中一切片内的图像块作为中心节点，将其相邻两个切片同坐标位置的图像块作为邻居节点与其关联.这些图像块间存在着不同细节的信息，导致它们之间存在差异.故在中心节点附近选取了若干个节点作为补充.这一点在于图像的任何一个图像块并不是单独存在，图像块会与周围数个像素信息相关联，使中心节点与邻居节点进行相互交互的同时，中心节点可以从周围像素组中弥补缺失.图注意力网络（Graph Attention Networks ，GAT ）既能充分结合局部特征又能保留整体的结构信息［24-25］.本文构建以图像块作为节点的图结构.其中图像块的大小为h × w ，相邻切片的同位置共有n 1个图像块相连接，输入维度为［h × w ，n 1］.其中的中间切片的图像块与周围相邻的k 个像素相连接，将k个元素重塑为一个矩阵，使输入维度为［h × w ，n 2］.最终，特征向量的总输入维度为［h × w ，n ］，其中，n =n 1 + n 2.以图7为例，不同颜色的方块代表着一个像素，图中以2 × 2个像素大小为一图像块，首先将相邻三切片提取的三个图像块（3 × 2 × 2个像素）重塑为4 × 3的矩阵，然后将与中间切片的图像块相关联的12个像素重塑为4 × 3的矩阵，将所有矩阵拼接后可得到4 × 6大小的特征矩阵.特征矩阵的每一列可以被视为该图的一个节点，每对列之间相似性可以视为图的一条边.根据特征矩阵与构建的拓扑结构，得到邻接矩阵，来描述图中节点之间的连接关系.在邻接矩阵中，如果节点i 和节点j 之间有连接，则邻接矩阵的第i 行第j 列和第j 行第i 列的元素值为1，否则为0.最后，通过同时输入邻接矩阵和特征矩阵到GAT 层进行计算，完成对图数据的处理.对于特征图X ∈R H ×W ×C （H 、W 、C 分别为特征图的高度、宽度和通道数），图像块的大小为H /n ×W /n ，其中n 为尺度因子，使图像块能够与特征图的尺寸相匹配.如图8（a ）所示，该图以第i 个节点的节点特征h i →，以及相关联的5个节点为例描述GAT 层的计算过程.图注意力层的输入是一组节点特征，h ={h 1→，h 2→，…，h n →}，h i →∈R d ，通过利用相邻节点的相似性，得到一组新的节点特征，h '={h →'1，h →'2，…，h →'n }，h →'i ∈R d '.为了更新特征，一个可学习的共享线性变换权重矩阵W 将应用于每个节点，以生成更深层的特征.然后在节点上执行一个共享的自注意机制e ，e ：R d ×R d →R ，e ij 为每条边(i ，j )的注意力分数，表示为相邻节点j 对节点i 的重要性.eij =e ()W h →i ，W h →i=LeakyReLU ()a T⋅() W h →i W h →i ，（5）式中：a ∈R 2d '，W ∈R d '×d 被学习，||表示向量串联. LeakyReLU 为一个非线性激活函数.这些注意力分数在所有邻居j ∈N i 中经过Softmax 标准化，注意力图6 二维位置编码内部结构Fig.6　Internal structure of the two -dimensional position encoding图7 图注意力块（GAB ）的内部结构Fig.7　Internal structure of the Graph Attention Module （GAM ）82第 1 期李帅先，等：利用自相似性实现医学图像合成的生成对抗网络函数定义为：a ij =Softmax j ()e ()h →i ，h →j ，=exp ()e ()h →i ，h →j∑j '∈N iexp ()e ()h →i ，h →j '.（6）通过标准化注意系数计算相邻节点变换特征的加权平均值（σ是非线性函数），作为节点h i →的新表达形式：h ′i →=σ(∑j ∈N iαij⋅W h →j ).（7）多头注意力机制是提取深层特征的有效扩展方式.在图8（b ）中，红色圆圈和蓝色圆圈分别代表第i 个节点及其最近的5个相邻节点.不同颜色箭头表示独立的注意力计算，图中展示了3个注意力头.假设对于每张图结构均使用M 个独立的注意力机制，每个注意力机制都能够使用公式（7）来获取第i 个节点的更新特征.将M 个独立的注意力机制更新后的特征向量连接在一起，进行平均处理，得到最终的节点特征.这个过程可以从不同的注意力机制中获取更加丰富和准确的特征信息，提高模型的性能.此过程如下所示：h →'i =σ(1M∑m =1M∑j ∈N ia m ij W mh →j )，（8）式中，a m ij 和W m是计算的标准化注意力系数和第m个注意力机制的线性变换权重矩阵.1.5　全局块注意力块（GPAB ）为探索医学图像同切片内的特征相似性，本文提出在图像切片内基于图像块的全局块注意力块（GPAB ），该块可以通过从全局范围内获取图像中的信息，因此能够更好地捕捉长距离依赖关系，增强局部特征.如图9所示为GPAB 的内部结构.该块以图像块为单位进行相似度匹配，将每个图像块的特征作为全局特征的一部分，并通过在全局特征中计算相似度矩阵来衡量每个图像块与全局特征关系，此相似度矩阵是多维度的.对多维相似度矩阵进行Softmax 函数运算，得到一组注意力权重.最后，每个图像块与全局特征按照对应注意力权重通过哈达玛运算进行加权求和，得到该图像块的最终表示.给定图像特征图X ，该注意力定义为：Z i ，j =∑g ，hexp ()ϕ()X i ，j ，X g ，h∑u ，vexp ()ϕ()X i ，j，X u ，vψ(X g ，h)，（9）式中：（i ，j ）、（g ，h ）和（u ，v ）是特征图X 的坐标元组，ϕ(∙，∙)为相似性函数，被定义为：ϕ(X i ，j ，X u ，v )=θ(X i ，j )Tδ(X u ，v )，（10）式中：θ(X )、δ(X )、ψ(X )是特征表达函数，通过1×1的卷积实现.θ(X )=W θX ，φ(X )=W φX ， ψ(X )=W ψX ，其中，W θ，W φ，W ψ为可学习的参数；X i ，j ，X g ，h ，X u ，v 为大小、维度相等的图像块.GAB 与GPAB 相同，图像块的大小设置为H /n ×W /n ，其中n 为尺度因子.1.6　基于对抗性学习下的损失函数本文将对抗性损失应用于生成器网络及其判别器网络.对抗性损失函数可以定义为：图8 图注意力层流程图与多头图注意力机制Fig.8　Process diagram of the Graph Attention Layer and theMulti -head Graph Attention Mechanism图9 GPAB 的内部结构Fig.9　Internal structure of GPAB83第 43 卷中南民族大学学报（自然科学版）L GAN(G，D)=E I X，I Y∼P data ()I X，I Y[log10D(I X，I Y)]+EI X∼P data ()I Xéëlog10(1-D(I X，G(I X)))ùû，（11）式中：G表示生成器，D表示判别器，I X表示输入图像，I Y表示相应的真实图像.训练中，生成器G试图生成与真实图像I Y相比足够逼真的合成图像G(I X).判别器D的任务是区分真实的医学图像I Y和合成的医学图像G(I X).生成器G试图最小化该损失函数，而判别器D则试图最大化该损失函数，即：G*= argmin G max D L GAN(G，D).除了对抗性损失函数外，生成器的损失函数还包括L1损失来引导生成器生成高质量的图像.生成器G的L1损失项：L L1(G)=E I X，I Y∼P data ()I X，I YIY-G()I X1.（12）GGPA-GAN网络的整体损失函数为：G*=arg min max G D L GAN(G，D)+λL L1(G)，（13）式中，λ用于控制L1损失函数和对抗性损失函数之间的权重分配.2　实验2.1　数据集本文的3T-7T MRI合成任务使用的图像数据来自HCP数据集［26］（Human Connectome Project，人类连接组项目）.本文的T1-T2 MRI合成任务使用的图像数据来自ADNI数据集［27］（Alzheimer's Disease Neuroimaging Initiative，阿尔茨海默症神经影像学倡议）.针对3T-7T MRI任务，本文使用80例成对的3T MRI和7T MRI图像，并对所有3T MRI和7T MRI图像进行尺寸固定，空间分辨率为180×256×256，体素分辨率为1.0 mm×0.8 mm×0.7 mm.针对T1-T2 MRI任务，本文同样使用80例成对的T1 MRI 和T2 MRI图像，并将所有T1、T2 MRI的空间分辨率固定为180×256×256，体素分辨率为0.9 mm×0.9 mm×3 mm.所有采集图像均为具有清晰脑部纹理、丰富细节特征的高质量数据，且均经过类间、类内的刚性配准，以保证严格对齐.对于每例数据，将原始强度值线性缩放到[-1，1].将所有数据分为训练集与测试集，每个任务随机选取62例用于网络训练的训练集图像，18例用于测试网络泛化性能的测试集图像.测试集与训练集不重叠，以确保模型的泛化性能和可靠性.2.2　实验环境硬件设备：CPU：Intel Xeon Gold ********* GHz×72；GPU：NVIDIA TITAN RTX 24 G×2；内存：64 G；软件配置：操作系统为64位Ubuntu18.04.6 LTS； Python 3.7； Pytorch 1.6.0.2.3　实验参数设置在训练过程中，Batch-size设置为32，每个批次大小为16×256×256.使用ADAM优化器实现网络参数优化，网络总轮数设置为300轮.初始学习率0.0002，动量参数为0.9，权重衰减为0.005.2.4　评价指标本文采用峰值信噪比（Peak Signal-to-noise Ratio，PSNR）和结构相似性指数（Structural Similarity Index，SSIM）以及平均绝对误差（Mean Absolute Error，MAE）三种指标来评估合成图像的质量.其中，PSNR 是一种广泛应用于评估图像清晰度的指标，它基于像素点之间的误差来衡量合成图像与真实图像之间的差异.在计算PSNR时，均方误差（Mean Squared Error，MSE）越小则PSNR越大，代表着合成图像的效果越好.峰值信噪比PSNR的计算公式如下：MSE=1N∑i=1N (I(i)-Syn(I(i)))2，（14）PSNR=10⋅log10(MAX2MSE)，（15）式中：I（i）表示真实图像中某个像素点的像素值，Syn（I（i））表示在体素空间中合成图像相应像素点的像素值.SSIM从3个方面评价合成图像与真实图像的差距：亮度、对比度和结构，值的范围在(0，1)，值越大表示两张图像越相似.结构相似性指数SSIM的计算如下所示：SSIM=()2μRμS+c1()2σS+c2()μR2+μS2+c1()σR2+σS2+c1，（16）式中：μR和μS分别表示真实图像和合成图像的均值，σR、σS为真实图像和合成图像的协方差.c1= (k1L)2，c2= (k2L)2为常数，L是像素值的动态范围，在本文中L=7，k1=0.01，k2=0.03.MAE是计算每个像素值之间的绝对差异，再取平均值，因此是一种评估两个图像之间平均差异的方法.MAE越小，两张图像越相似.平均绝对误差MAE的计算如下：MAE=1H×W∑i=1H∑j=1W||X()i，j-Y()i，j，（17）式中：H和W分别表示图像的高度和宽度，X和Y分84第 1 期李帅先，等：利用自相似性实现医学图像合成的生成对抗网络别表示合成图像和原始真实图像.2.5　对比实验及分析为了验证本文提出的模型性能，本文将其与4种现有模型进行比较，它们分别是UNet++［28］、TransUNet ［29］、Pix2pix ［16］和CycleGAN ［21］.其中，分别将AttentionUNet 和TransUNet 作为生成器网络嵌入到本文的GAN 架构中作为对比，以证明本文生成器网络在深层特征提取方面卓越的成效.UNet++网络在UNet 基础上进行升级，该网络加入了深度监督机制，将跳跃连接改进为密集的短连接，可以抓取不同层次的特征，并将它们通过叠加的方式进行整合.TransUNet 同时具有Transformers 和U -Net 的优点，相比于传统的卷积神经网络，TransUNet 使用了Transformer 结构，使得模型可以自适应地学习到图像中的全局和局部特征.Pix2pix 与CycleGAN 为如今主流的医学图像合成方法.Pix2pix 是一种基于条件生成对抗网络（CGAN ）的方法，通过专注于保持逐像素的强度相似性来合成整个图像.CycleGAN 是使用对抗性损失函数合成图像，同时通过一个循环一致性损失函数保持图像的原始语义信息.2.5.1　定性评估对3T -7T MRI 和T1-T2 MRI 两个任务进行了定性比较实验，图10为本文方法与4种对比方法在相同测试图像下的矢状面和轴位面上进行3T -7T MRI 任务测试的定性比较结果.可见大多数对比方法不能很好地恢复图像细节.如CycleGAN 的局部放大结果整体非常模糊，而本文方法合成的图像比对比方法拥有更清晰的细节.图11所示为本文方法与4种对比方法在矢状面和轴位面上进行T1-T2任务中的定性比较结果图.可见与3T -7T 任务相比，T1与T2图像具有边界模糊、噪声、对比度差的特点，本文在任务中能较为清晰地还原图像的轮廓与细节特征，边缘也较为平滑.综上，本文方法的合成效果优于其他4种对比的合成方法.2.5.2　定量评估实验利用PSNR 、SSIM 、MAE 客观评价指标在3T -7T MRI 、T1-T2 MRI 两个任务中测试了18例MRI 图像，本文方法的表现均优于对比的4种合成方法，本文方法及4种对比合成方法在PSNR 、SSIM 、MAE 的测试结果折线图分别如图12-13所示，其中绿色折线表示本文方法的客观评价结果，评价结果平均值如表1所示.图10 本文方法与 4种对比方法在 3T 合成7T MRI 任务中的定性比较结果Fig.10　Qualitative comparison results of the proposed algorithm and four comparison algorithms in the 3T to 7T MRI synthesis task85。

2016 NO.03SCIENCE & TECHNOLOGY INFORMATION科技报告导读173 科技资讯 SCIENCE & TECHNOLOGY INFORMATION simulated working conditions. For the technical problem of that it is difficult to make efficient use of the waste heat at medium temperature, this report constructs two 1.x effect absorption refrigeration cycles. The simulation results show that the COP of the 1.x effect absorption refrigeration cycles is 20% higher than that of conventional single effect cycle at some simulated working conditions. To validate the performance of the proposed new cycles and theory model used in this report, an experimental system of a 1.x effect absorption refrigeration cycle is designed and built, which is one type of 1.x effect absorption refrigeration cycle. The experimental research shows that, when evaporation temperature is 5℃, absorption temperature and condensation temperature are 40℃, if the generation temperature reaches to 135.3℃, the COP of the new cycle is about 0.9 and 20% higher than that of conventional single effect cycle, when generation temperature is 127℃,absorption temperature and condensation temperature are 40℃, if the evaporation temperature reaches to 10℃, the COP of the ejector-absorption combined refrigeration system is about 1 and 30% higher than that of conventional single effect cycle.Then the performance of the constructed new cycles being better than that of conventional cycle is proved by experiment.Key Words :Absorption Refrigeration；Cycle Configuration；Cooling Availability；Theoretical Analysis；Experimental Study 阅读全文链接（需实名注册）：/xiangxiBG.aspx?id=48493&flag=1&flag=1基于条纹反射测量技术的太阳能热发电聚光镜面形检测方法研究卢振武 魏秀东(中国科学院长春光学精密机械与物理研究所)摘 要：提出了基于条纹反射测量技术的太阳聚光器面形检测方法，使用投影仪在光屏上投射黑白相间的正弦条纹，经被测镜反射后成像于相机，采用四步相移算法计算像面上和光屏上点的对应关系，然后运用迭代算法拟合被测镜方程及镜面上各个点法线方向。

为了：With a view to doing sth. (With a view to avoiding the inhomogeneous dispersion of rare-earth complexes within the silica matrix)with the aim of …(we have also investigated the preparation of cyclam-containing hybrid materials in the presence of a surfactant template with the aim of locating the cyclam moieties inside the framework.)In the goal to …（In the goal to extend the range of properties of these materials)In an effort to …(In an effort to produce new propene polymerisation catalyst systems which yield high molecular mass polypropylene with even greater specific isotacticities we have investigated the catalytic activity of mesoporous silicates with included chiral ansa-metallocenes.)首次：a original route to＋n. (a original route to Eu3+ containing hybrid materials.)相应的：the corresponding materials副产物：byproduct场发射扫描电镜：field-emission scanning electron microscopy平均半径：mean diameter (with 100μm mean diameter)就…而言：with respect to… (The preparation of mesoporous silicas which exhibit good hydrothermal stability (in hot water and under steaming conditions) is one ofthe most important requirements with respect to their use.)除了…之外：in addition to… (another V(V) species in distorted octahedral coordination starts to appear in addition to V10O286- for high vanadium content of V/(V+ Si) ) 48%.)Aside from… (Aside from a thicker pore wall, the framework crosslinkingwas higher than for conventional MCM-41, as indicated by 29Si MASNMR.)除了…：Except for… (Except for a slight decrease in the d spacing, compaction at 185 MPa does not have any significant effect on the XRD pattern of AlMCM4.)except that… (The experimental procedures were exactly as described aboveexcept that during the secondary synthesis the heating at 150 °C was performedfor 96, 140 or 168 h.)save for… (Incorporation of organic functional groups (MPTMS) inside thestructures appeared to have little influence on the structure and morphology ofthe mesostructures, save for slight lattice and pore diameter contractions uponincreasing organosilane group loading.)定向生长：The phased growth产生…：gi ve rise to… (The latter method gives rise to MCM-41 materials of excellent quality, but seems to be less convenient, since the structure directing agentsrequired are not readily available and need to be synthesized.)生物活性分子：bioactive molecules范例：paradigm剧烈地：vigorously代替…：in place of… (by using n-butanol as co-surfactant in place of ethanol)本身的，固有的：intrinsic摩尔比：a liquid/solid ratio of 50; an olefin/TBHP molar ratio of 4好的结果：a positive effect on…有…的结构：with…architecture (Organically-modified mesoporous silica spheres with MCM-41 architecture)with… type of structure (A series of new mesoporous silica materials withMCM-41 type of structure containing a homogeneous layer of organicfunctional groups inside the pores was prepared using a co-condensationmethod under low surfactant concentration condition.)残留的：residual红外：Fourier transform infrared spectroscopy (FTIR),因素：factor数量级的：order-of–magnitude (order-of–magnitude enhancements)与…一致：In accord with…(In accord with the tetrahedral siting of aluminum, the Br¢nsted acidity of these steamstable mesostructures was verified throughcumene cracking experiments.)Consistent with… (Consistent with elemental analysis, an increase in the Alconcentration on the framework walls was observed by XPS analysis.)be identical to… (A 150 °C onset decomposition temperature is consistentlyobserved for externally adsorbed on MCM-41 and is identical to thatobserved for pure 1.)be consistent with… (This is consistent with the incorporation of increasingamounts tetrahedral Al into the framework and is in part due to the longerAl–O bond length compared to the Si–O bond.)be in line with…(This is in line with the notion that the acid-mademesoporous materials are, in general, less stable than those synthesized viathe alkaline route.)50% 的Si被官能化：50% organo-functionalization of the framework silicon sites部分地：in part (We attribute the unique hydrothermal stability of Al-MSU-S at least in part to the retention of a zeolite-like connectivity of AlO4 and SiO4 tetrahedraupon assembling the zeolite seeds into a mesostructure.)在…的支持下：in support of…(in support of the importance of a zeolite-like connectivity)在…的基础上：On the basis of… (On the basis of the relationship between 27Al chemical shift and the mean bond angle in framework aluminosilicates, the meanAl-O-Si angle is substantially smaller (by~8°) in Al-MSU-S than inpreviously reported forms of Al-MCM-41.)比…好：be superior over…(the catalytic activities of the new materials are superior over conventional materials such as Al-MCM-41 and Al-SBA-15.)outperform (In the alkylation and isomerization reactions, the hybrid catalystsignificantly outperformed some of the alternative solid resin catalystscurrently used, e.g., Nafion resin NR 50 and Amberlyst-15.)归因于…：be assigned that…(This phenomenon is also assigned that the preformed L nanoclusters are fixed in the wall of mesoporous aluminosilicates by theassembly of preformed zeolite L precursors with surfactant micelle.)be attributable to…(It is clear that the improved hydrothermal stability ofMSUG, like SBA-15, is attributable in large part to the thicker frameworkwalls (2.5 nm) in comparison to MCM-41, KIT-1, and SBA-3.)be attributed to… (The instability of these structures has been attributed inpart to the thinness and incomplete crosslinking of the pore walls)be due to…(It was concluded that the increased acidity of hydrothermallytreated CAH5 and CAP10 was due to an increase in the Al/Si ratio in theframework.)在…之中：Of the three forms of polypropene, the highly ordered, high molecular mass isotactic form is the most important.研究热点：active area of research (The application of acid zeolites for the production of fine chemicals is currently an active area of research)所有的样品：all of the samples控温装置：temperature controller压力表：pressure gauge更具体的说：More specifically ( The TDS process consists of a direct displacement of quaternary alkylammonium surfactant cation by desired silyl group, whichin fact is the replacement of electrostatic interactions at theorganic-inorganic interface by covalent bonds. More specifically, theinteracting pairs ≡Si-O-∙∙∙S+ (≡Si-O- is a unit of silicate oligomer and S+ isthe surfactant cation) are replaced by covalent bonds ≡Si-O-SiR`2R.)差异：discrepancy (However, a large discrepancy observed for the model with hydrolyzed side groups led us to the conclusion that alkoxy groups did not hydrolyze during the TDS process.)与…相关：correlate with…(The aforementioned changes correlate with the silane’s size.)be associated with…(In the published progress, several reasons areassociated with the enhanced hydrothermal stability of mesoporous silica.)be linked to…(We show that the amount of gold incorporated within thematerials is linked to the amount of mercapto functions and varies from 1.05to 16.1 wt %.)经验方法：empirical fashions. (However, because zeolite nucleation and growth is not well understood at a molecular level, most of the zeolite syntheses haveevolved according to empirical fashions.)倾向…：be inclined toward…(On the other hand, the product after 2 days of aging was inclined toward various distribution of Al in the framework, resulting in highSi/Al ratio.)不是…而是…：be not…but rather be… (Energy minimizations show that Na cations in site I are not at the centers of hexagonal prisms, but rather are in one oftwo symmetric SI sites displaced by about 0.6 Å along the [111]direction.)be not…but …(However, in contrast to zeolitic materials, thetemplates are not single organic molecules but liquidcrystallineself-assembled surfactant molecules. )受制于…：be subjected to…(nomeric bonded phases are subject to serious effects arising primarily from an unsatisfactory hydrolytic stability of the Si-O-Si-Clinkage, particularly under moderately acidic or slightly alkaline elutionconditions, and to a lesser extent from a relatively limited organic coverage.) 原则上：In principle (In principle, this method should provide not only a closer attachment and a denser coverage of organic functionalities but also a morehydrolytically stable bonded phase than that obtained by the correspondingSi-O-Si-C linkage)由…组成：be comprised of… (The purpose of our work is to explore the possibility of synthesizing zeolites that are comprised of intergrowths of cubic andhexagonal stackings of faujasite sheets and vary in the ratio ofcubic/hexagonal content.)突破：breakthrough (A recent breakthrough in improving both the hydrothermal stability and acidity of mesoporous aluminosilicates has been made through the use of nanoclustered zeolite seeds as frameworkprecursors)相当地：comparatively (It was concluded that the enhanced reactivity was a result of a comparatively short pore length and the more facile access of the reagents tothe acidic sites on the framework walls.)不大可能：It is unlikely that… (It is unlikely that the framework wall of MCM-41 can be transformed to a crystalline zeolite phase while still maintaining thehexagonal MCM-41 mesostructure.)如上所述：As stated above (As stated above, this band arises from the five-membered ring of vibrations of pentasil zeolite building subunits.)不同的时间：different periods of time (Structural changes caused by heating in water at 373 K for different periods of time(from 3 hours to 32 days) and bycalcination at 973-1273 K were investigated in order to assess thehydrothermal and thermal stability of FDU-1.)更重要的是…：What is more important is… (What is more important is that within themesoscale pore walls, micropore arrays with more or less periodicityare found (especially in those areas marked with circles or rectangles inFigures 7 and 8).More importantly (More importantly, there are significant structuraldifferences between MCM-41 and HMS silicas.)是合理的：it is logical to do… (Based on these observations it is logical to conclude that the small particles are (nonframework) amorphous silica which is removedduring refluxing (by dissolution), leaving the Al-grafted MCM-41framework (i.e., the large particle aggregates) intact.)最令人感兴趣的是：Of particular interest are (were) …(Of particular interest areAl-containing materials which may be used as solid acid catalysts.) 以…为代价：be at the expense of… (The increase in wall thickness is at the expense of pore diameter which reduces from 31.6 Å for PSMCM to 25.8 Å forAlMCM5.)对…敏感：be sensitive to … (It was also observed that the course of the hydrothermal restructuring was very sensitive to the experimental conditions, such astemperature.)为了比较：For comparison purposes (For comparison purposes we prepared Al-grafted amorphous silica using an ACH solution of Al concentration 0.24 mol/l andalso subjected PSMCM to alumination by 0.24 mol/l solutions of aluminiumchloride or sodium aluminate. )由于：Owing to… (Owing to the weak hydrogen bonding interactions, more than 90% of the neutral template can be recovered by a simple extraction procedure using ethanol as extracting solvent.)注意到…：be aware of… (We are aware of only two reports that provide some insight into the thermal stability of OMSs with cage-like pores at temperatures up to1123 K, and two reports on the hydrothermal stability of these materials,including the aforementioned work on FDU-1.)keep in mind that (However, we must keep in mind that the reaction itselfwill be very efficient if each absorbed photon can lead to the the formation ofa product molecule.)与…成正比：be proportional to… (Based on the pore size distribution shown in Figure 3, the amount of these structural defects formed is proportional to the amountof Al substituted in the sample.)与…成反比：be inversely proportional to… (The quantum yield for an ideal system, Φ, is proportional to the rate of the charge transfer processes and inverselyproportional to the sum of the charge transfer rate and the electron holerecombination rate)在…中占主导：be prevailing in… (Such a structure is prevailing in HCM, as can be found from the TEM images at lower magnification.)在图的右下角：in the bottom right corner of the image对…有害：be detrimental to…(Too high an ssembly temperature, however, is detrimental to mesostructure ormation through S0I0 assembly pathways.)对…有益：be conducive to… (The extremely high specific surface areas are conducive to high catalytic activity.)参看下文：vide infra参看上文：vide supra与…不同：be different from (The formation mechanism, composition, and properties are different from those of MCM-41 materials synthesized under alkalineconditions.)受到关注：be of concern (However, the stability of these materials in aqueous solutions is of concern.)一开始：at [in] the outset (It should be noted at the outset that a clean, uncoated silica surface is perfectly wetting, such that the contact angle of water on a fullyhydroxylated silica surface is zero.)有益于…：be conducive to… (Moreover, the large diameter and wormhole nature of the pore channels in these oxides are conducive to the formation of functionalmaterials in which the reactive species are highly dispersed within theframework and quantitatively accessible for reaction with adsorbatemolecules.)受…启发：be inspired by… (Our procedure was inspired by that described by Prouzet et al. leading to MSU silica by using tergitol as structure-directing agent.)不管…：regardless of whether… (Both titaniasupported catalysts exhibited higher activity for CO oxidation than the silica, supported ones, regardless of whetherthey were pre-treated in H2 or not.)irrespective of… (Platinum-free, white AMM-Ti exhibited only a very weakactivity, irrespective of excitation in the UV or visible spectral region.)这样就…：in such a way as…(However, the ligand-assisted templating technique provided a shielding effect by the inorganic components on the amphiphilehead groups in such a way as to favor selfassembly versus solubilization ofthe templating agents.)在其他条件相同时：Under otherwise the same conditions (Under otherwise the same conditions, a HMS-SO3H prepared via co-condensation gave 52%yield within 10 h, presumably because of its more open structure.) 被…影响，顺序是…：The light-conversion efficiency of the valence isomerization ofquadricyclene to its ring-opened isomer norbornadiene isinfluenced by the identity of the photocatalyst (TiO2, CdS, orZnO) and the solvent (CH2Cl2, CH3CN, or THF) used, with thechemical yield of ring-closed product decreasing in thefollowing order CdS > TiO2>ZnO and CH2Cl2> CH3CN >THF.大多：in most cases (The selective photofluorination of olefins, phosphines, andphosphites on illuminated TiO2in the presence of AgF inacetonitrile produces, in most cases, a single fluorinatedproduct.)服从于…：be amenable to (Toxic phosphorus-containing substrates are amenable tophotocatalyzed decomposition, ultimately to completelymineralized products, over illuminated semiconductorsuspensions.)因为：in the sense that (The excitation of a weak transition will not effectively induce aphotochemical reaction in the sense that few of the deliveredphotons will actually be absorbed.)与…竞争：In competition with…(In competition with charge transfer to adsorbedspecies is electron and hole recombination.)与…对照：in total contrast to… (Complete mineralization has been achieved in the caseof lanthanide oxide doped TiO2 photocatalysts in totalcontrast to the formation of intermediates in case ofnonmodified TiO2.)是…倍：be…times (The equilibrium dark adsorption of salicylic acid and t-cinnamic acidis ca.three times and two times higher, respectively, on thelanthanide oxide modified catalysts as compared to the nonmodifiedTiO2 catalyst.)不是这样：that was not the case (When an electrode coated with 1 was irradiated at different wavelengths in a standard photoelectrochemical cell, a photocurrentwas observed also in the visible region; that was not the case whenunmodified titania was employed.)不足：drawback（A serious drawback in such systems, however, is that the surfactants）研究目的：main objectives失重（热重分析）：weight-loss。