1,721,445 research outputs found
Supramolecular nanostructures of luminescent organoboron polymers
No full textOver the past several decades, organoboron compounds have been widely studied with respect to applications as reagents in organic synthesis, Lewis acid catalysts, luminescent materials, chemical sensors, ceramic precursors and nuclear detectors. Besides the basic physical and chemical properties, materials for most practical applications require favorable processing characteristics. Polymeric materials are advantageous in this respect and especially, self-assembled functional polymeric nanostructures are promising for the development of new optical, electronic, biological and energy-related materials. Therefore, research on the synthesis and properties of well-defined boron-containing polymers is an emerging area that has drawn great interest of chemists and material scientists. This dissertation describes a “molecule-polymer-material” bottom-up methodology for the fabrication of nanostructured materials based on luminescent organoboron polymers. A series of novel organoboron monomers with tunable photophysical properties and excellent stability were developed via efficient organic and organometallic reactions. Using reversible addition-fragmentation chain transfer (RAFT) polymerization, well-defined luminescent organoboron homopolymers and block copolymers with controlled molecular weight and narrow molecular weight distribution were successfully synthesized. Core-crosslinked star polymers with a luminescent boron quinolate core were also achieved by “arm-first” RAFT polymerization of a difunctional boron quinolate crosslinker. These block copolymers and star polymers serve as versatile building blocks for nanostructure fabrication. In selective solvents, the block copolymers and star polymers form self-assembled nanostructures, such as micelles, vesicles, large spherical and spindle-shaped aggregates. By introducing pyridine-functionality onto the block copolymer structure, luminescent polymeric Lewis bases were synthesized and utilized for the preparation of polymer/inorganic co-assembled nanostructures. The borinic acid functionalized block copolymers act as effective H-bonding donors that form supramolecular co-assemblies with poly(4-vinylpyridine) (H-bonding acceptor). Triarylborane compounds and polymers have been utilized as chemical sensors for toxic anions, such as fluoride and cyanide. Through rational polymer architecture design, we synthesized a series of dimesitylphenylborane-functionalized polymers, including homopolymer, block copolymer and block-random copolymers, for F- binding studies. For the first time, (1) we elucidate the chain-architecture effect on F- binding and observed amplified fluorescence quenching for the homopolymer structure; (2) a dual responsive chemical sensor for F- was developed based on the block copolymer micelles in DMF, that F- binding leads to the fluorescence quenching and the dissociation of block micelles; (3) the positively charged block-random copolymer was found to be an effective F- sensor in polar solvents, such as DMF and DMF/water mixture, due to the electrostatic interaction.Ph. D.Includes bibliographical referencesIncludes vitaby Fei Chen
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
sj-pdf-1-eji-10.1177_20587392211051945 – Supplemental Material for Optimal timing for laparoscopic cholecystectomy in the treatment of gallbladder calculi incarceration
No full textSupplemental Material, sj-pdf-1-eji-10.1177_20587392211051945 for Optimal timing for laparoscopic cholecystectomy in the treatment of gallbladder calculi incarceration by Jian-Heng Bao, Yu-Jie Wang, Hai-Tao Shang, Cheng-Fei Hao, Jun-Jian Liu, De-Lin Zhang, Shu-Wang Han and Zhong-Lian Li in European Journal of Inflammation</p
A Study of Parents' Working-Time and Their Flexible Demands for After-School Child Care
No full text在本文的第一章，研究者就實際所觀察到的社會現象：有些家長必須在週末或是夜間工作時，這些家長如何解決照顧學童的問題做為本文的研究動機，並探討國內外工作時間彈性化與學童課後托育需求彈性化之相關性。第二節的文獻回顧則探討工作時間彈性化、婦女就業、學童課後托育之相關文獻。在第三節研究者提出研究分析架構：即以學童家長的家庭支持系統及家長職業與工作時間彈性化這兩個角度出發，來了解家長對於托育時間彈性化和托育服務多元化的需求。第四節為研究方法，研究者除了使用文獻分析法，同時也使用深度訪談法來訪問二十位家長。本文第五節則是簡單的章節安排說明。
在第二章的內容部份，第一節主要討論勞動市場與工作時間彈性化的全球性發展，第二節主要探討婦女就業趨勢，將對學童課後托育需求有何影響。由於企業追求彈性積累，因此在人力使用上追求以最小成本達到最大效益，企業最常見的彈性化用人策略為內部數量彈性化，例如：延長員工下班時間，以責任制名義來要求員工把當日的工作完成，因此影響到家長無法準時下班去安親班接孩子下課。隨著女性受高等教育人數的增加，也帶動婦女勞動參與的提升，進而影響到對安親班的需求增加，就婦女從事的行業來看，以從事服務業的比例最高，而服務業的工作時間又更具多樣化，因此，有些婦女在週末或是夜間必須要工作時，就無法親自照顧學童，在這種情況之下，婦女必須有賴於配偶或是其他家庭支持。但是，當這樣的支持系統不穩定時，家長對安親班開放時間彈性化、服務多元化的需求則會增加。
在第三章第一節裡，研究者主要討論國外學童課後托育機構種類及方案，研究者蒐集了美國、日本及英國這三個國家的課後托育方案資料。在美國方面，「二十一世紀社區學習中心」方案鼓勵社區人士參與學童課後照顧工作，結合社區與學校資源，讓更多學童得到更完善的照顧，除此之外，根據美國教育部對此方案所做的評估報告也指出，此方案實施後，對於提高學童母親就業以及學童的心理安全感有相當正向的幫助。在日本方面，日本強調兒童保育應以遊戲為活動內容主軸，強調透過遊戲來增加學童的學習興趣，以及學習與人互動。在英國方面，其托育服務的特色在於在市場機制的驅策下，由民間業者提供多樣化的托育時段及托育內容，例如：臨時性托育、假日娛樂方案、早餐俱樂部及課後俱樂部。在本文第二節，研究者先探討我國課後托育之興起原因，並針對目前台灣所遇到的課後托育問題做一檢討，研究者歸納出三點問題，包括：收托時間與家長工作時間無法充分配合、家長需求與法規限制的衝突、強調市場機制而忽略弱勢學童的托育需求，研究者並針對這三項問題，提供可能的解決方式。
在本文的第四章，研究者整理了週間工作組與週末及夜間工作組家長，對於課後托育有何彈性化需求。第一節與第二節分別整理訪談週間工作組和週末工作組家長的簡要逐字稿資料，包括：家長基本資料、影響工作時間延長的因素、家長對安親班的期待、家長讓孩子週末去安親班的意願及期待服務內容、以及家長週末時間可能的時間安排、家中照顧學童的支持系統、家長需要的臨托時段及期待服務內容。最後在第三節依家長工作時間及家長月收入做需求比較分析，研究者發現：無論是週間工作組或是週末或夜間工作組的分家長，對於安親班最大的期待，就是希望安親班可以協助家長輔導孩子把學校的功課完成；在週末托育需求方面，這兩組樣本的家長，約有八成的家長表示對於週六時段有托育需求，其中家長最希望在週六提供多元化的才藝課程；在期待安親班延長時段需求方面，大約有四成的家長表示，希望安親班可以開放至晚上九點。
本文的第五章是論文摘要與研究結果，最後研究者再針對研究結果，給予課後托育業者及政府相關建議。第一章 緒論 6
第一節 研究動機及目的 6
第二節 文獻探討 10
一、勞動市場及婦女就業變化趨勢 10
二、學童課後托育相關文獻 16
第三節 研究架構 22
第四節 研究方法 24
第五節 本文章節安排 25
第二章 家長工作時間彈性化與學童課後托育需求 26
第一節 勞動市場與工作時間彈性化的全球性發展 26
一、企業使用勞動彈性化策略類型 26
二、彈性工作的多元形式 29
三、工作時間彈性化的發展 32
第二節 國內外婦女就業狀況及趨勢 35
一、影響婦女勞動參與之因素 35
二、我國女性人力資源概況 37
三、從家庭生命周期理論來看有偶婦女勞動參與率 38
四、國外婦女就業狀況 40
第三章 國內外學童課後托育需求彈性化狀況 45
第一節 國外學童課後托育機構種類及方案 45
一、美國二十一世紀社區學習中心方案 45
二、日本以學童為本位的課後托育 51
三、英國多樣化的課後托育服務 53
第二節 台灣學童課後托育服務之興起與問題 56
一、課後托育服務興起原因 56
二、台灣學童課後托育服務問題之探討 57
第四章 訪談家長工作時間與學童課後托育需求彈性化之關係
第一節 週間工作組家長對課後托育的需求 64
第二節 週末或夜間工作組家長對課後托育需求 73
第三節 比較分析 81
一、依家長工作時間做需求比較分析 81
二、依家長月收入做需求比較分析 89
第五章 結論與建議 92
第一節 論文摘要及研究發現 92
第二節 建議與未來展望 99
參考文獻 102
附錄一 109
附錄二 11
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Tissue Characterization by Information-theoretic Entropy of Ultrasound Signal
No full text傳統的超音波灰階影像，俗稱B-mode(Brightness-mode)，已廣泛的運用在臨床醫學，主要功用在於定性呈現生物組織結構形態與輪廓。然而，超音波灰階影像的亮度會受到許多因素影響，如系統增益、動態範圍、與操作者經驗等。此外，為避免斑點效應(speckle effect)影響影像品質，通常在現有醫用超音波系統中，較微弱的超音波逆散射訊號會被濾除，但需注意的是，超音波逆散射訊號與組織內部散射子的特性，例如大小、形狀、密度、濃度等有關，因此散射訊號的濾除會使得灰階影像無法提供散射子定量訊息，這對於疾病早期偵測，或者組織良惡性判定有某程度上的困難。 基於超音波逆散射訊號的本質為隨機訊號，因此在過去許多研究者皆使用統計模型來描述超音波逆散射訊號的機率密度函數，以輔助灰階影像於臨床診斷之不足。這些統計模型主要包括Rayleigh、K、homodyned K、generalized K、以及Nakagami模型。其中又以Nakagami統計模型最能描述不同種類的超音波散射分佈。但在某些情況下，如訊號存在非線性效應、或者訊號經過非線性處理後，逆散射訊號便不再遵守Nakagami統計分佈，這限制了統計模型使用上的廣泛性與通用性。 為解決此問題，本研究提出以超音波逆散射訊號的訊息理論熵來定量組織特性。訊息理論熵的優勢在於它本身不受限於訊號僅能遵循某種特定的統計模式的條件下，也能反映出組織內部的散射子特性。為探索這個想法，我們以仿體實驗方式來進行驗證。首先進行超音波影像掃描系統之架設，此系統掛載不同頻率之超音波換能器進行影像掃描。之後我們製作不同散射子濃度之仿體，並使用系統對仿體進行資料擷取與灰階成像。同時對影像包絡訊號進行訊息理論熵的計算，採用三種訊息理論熵(i.e. Shannon, Renyi, Tsallis entropy)，以探討訊息理論熵隨散射子濃度變化之趨勢與結果，並與Nakagami統計模型做比較，評比利用不同方法判讀散射子濃度的優勢與缺點，以及這些方法與超音波頻率之間影響為何，整理出無本質斑點效應與具本質斑點效應的仿體之特性化結果。驗結果顯示，利用Nakagami統計模型定量仿體組織的結果顯示，在低頻聚焦式探頭下能顯示的動態範圍最佳，但是隨著頻率提高時，相同濃度範圍下所能顯示的動態範圍會縮小，主要原因在於訊號的機率分佈會隨著頻率增加往pre-Rayleigh分佈靠近。而以訊息理論熵來定量組織特性的結果，以Tsallis entropy在不同組織特性 鑑別濃度的效果最佳，除了具有高動態範圍優勢，隨著頻率提高能增加對應散射子濃度的線性程度，且在具本質斑點效應的影響下，仍然可以應用在濃度較高的組織上。The conventional ultrasound gray scale image the so-called B-mode image (Brightness-mode), has been widely applied in the clinical medicine. Its primary purpose is to qualitatively present the structure, shape and contour of the biological tissue. However, the brightness of the B-mode image is would be affected by many factors, such as system gain, dynamic range, operator’s experience and etc. Besides, in order to avoid the speckle effect on the image quality, the weaker backscattering signal is typically removed in the existing medical ultrasound systems. Note that ultrasound backscattering signal is related to the properties of scatterers in tissues, such as, size, shape, density and concentration. Therefore, the filtering of scattering signal makes the B-mode image difficult to provide the quantitative information of scatterers, which in turn influences the early detection and classification on benign and malignant tissues.ased upon the fact that the essence of ultrasound backscattering signal belongs to random signals, many researchers explored using statistical models to describe the probability density function of backscattering echoes to complement the deficiency of B-scan. The statistical models mainly include Rayleigh, K, homodyned K, generalized K, and Nakagami, in which Nakagami statistical model can encompass all scattering conditions in ultrasound. But, under certain circumstances, the backscattered statistics do not obey the Nakagami distribution anymore once there are some nonlinear effects or processing on the backscattering signals. This limits the practical applications of statistical models.n order to solve the problem, this study proposed using information-theoretic entropy of ultrasonic backscattering signal to quantify the properties of tissue. The superiority of information-theoretic entropy lies in that it can reflect the scatterer properties without any limitation due to statistical models on the backscattering echoes. To explore the idea, we carried out experiments on phantoms. First of all, we set up ultrasound image scanning system, which holds the ultrasonic transducer with different frequencies for image scanning. Subsequently, we made phantoms with different scattering concentrations and deal with data acquisition and gray image formation. Meanwhile, we use the envelope signals to calculate three information-theoretic entropies (i.e. Shannon, Renyi, Tsallis.) to explore the entropies as a function of scatterer concentrations. The results between using Nakagami models and entropies will be compared and discuss the effects of ultrasonic frequencies and background speckles on the performance of entropy to characterize tissues. he show the Nakagami parameter has a better dynamic range to detect the variation of scatterer concentration when low frequency focused transducer was used. With the increase in frequency, the dynamic range decreased in the same range of scatterer concentration as frequency increases. The main reason is that the probability distribution of signal will be close to pre-Rayleigh distribution with increasing the ultrasound frequency. Tsallis entropy has an outstanding performance to quantify the scatterer concentration. Besides a high dynamic range, its relationship with scatterer concentration would become more linear by increasing ultrasonic frequency. Meanwhile, under the influence of background speckle effect, it also can be applied to tissues with higher scatterer concentration.中文摘要 ibstract iii錄 v索引 vii索引 ix謝 x一章 緒論 1.1 前言 1.2 研究背景 3.3 文獻回顧 4.3.1 超音波逆散射訊號統計模型 4.3.2 超音波訊息理論熵 6.4 研究目的 8二章 理論基礎 10.1 超音波簡介 10.1.1 聲波傳遞的基本原理 10.1.2 聲速與衰減 12.1.3 反射與折射 13.1.4 超音波探頭構造與聲場 14.1.5 超音波影像之軸向解析度 16.1.6 超音波影像之側向解析度 18.2 超音波散射分析 20.2.1 超音波散射現象 20.2.2 分析單一散射子之散射現象 20.2.3 分析多散射子之散射現象 22.3 逆散射統計模型 25.3.1 Rayleigh統計分佈 25.3.2 Rician統計分佈 26.2.3 K統計分佈 27.3.4 Nakagami統計分佈 28.4 訊息理論熵原理 29.4.1 訊息理論熵之基本原理 29.4.2 訊息理論熵之計算 30三章 實驗材料與方法 31.1 超音波影像系統架構 31.1.1 馬達掃描方式 33.1.2 程式設計流程與操作介面 34.2 實驗仿體製作 36.2.1 無本質斑點效應之仿體 37.2.2 存在本質斑點效應之仿體 37.3 數據處理步驟 40.3.1 超音波逆散射訊號處理 40.3.2 Nakagami參數計算 40.3.3 訊息理論熵計算 41四章 實驗結果與討論 42.1 無本質斑點效應之仿體 42.1.1 B-mode影像與訊號機率密度函數 42.1.2 定量參數分析 53.1.3 討論 59.2 存在本質斑點效應之仿體 62.2.1 B-mode影像與訊號機率密度函數 62.2.2 定量參數分析 66.2.3 討論 70五章 結論與未來展望 71.1 結論 71.2 未來展望 72考文獻 7
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