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Effective Diffusivity as a Diagnostic of Synoptic Scale Events
No full text本研究利用有效擴散率診斷槽線形狀窄化與變寬的過程、南極極渦波動破碎，以及大西洋的熱帶氣旋生成過程。有效擴散率的概念與邊界層動力的K理論是一致的，假想次網格次度的大氣運動和分子擴散行為類似，所以可以診斷次網格尺度的混合程度。利用非輻散的風場平流被動追蹤物質，根據被動追蹤物質的結構計算有效擴散率，有效擴散率愈大，表示大氣流場處於愈劇烈混合的狀態，愈小則表示混合愈微弱。由槽線的個案研究，顯示最大的有效擴散率出現在羅士比波破碎的區域，而核心渦旋的有效擴散率最小。由南極極渦的個案研究，顯示有效擴散率可以詮釋飛機觀測的臭氧濃度在很短的距離內有很大幅度的變化。
中層的相對溼度是熱帶氣旋生成的重要因素之一，近來研究指出有發展的熱帶擾動在隨著東風波移動的座標上，有氣旋式封閉流線結構，此結構又稱為育兒袋，育兒袋不僅有利於累積渦度，還可以保護濕對流，使其不易受到乾空氣逸入而消散。本研究用有效擴散率診斷中高層乾空氣逸入作用對大西洋的熱帶氣旋生成影響，診斷個案為2010年大西洋颱風季源自於非洲東風波的熱帶擾動。研究結果顯示在700hPa以上，有發展的熱帶擾動位於混合程度比較微弱的大氣流場，沒有發展的擾動則是位於劇烈混合的大氣流場，混合程度和有發展的相比可以達到5倍以上。有效擴散率配合衛星水氣影像，顯示沒發展的熱帶擾動在中高層有乾空氣逸入，而有發展的擾動幾乎沒有乾空氣逸入。由熱帶氣旋生成的個案研究，顯示有效擴散率分析和類似育兒袋熱帶氣旋生成理論是相輔相成的。本研究顯示有效擴散率配合衛星水氣影像，對於分析大西洋的熱帶氣旋生成是很有用的診斷工具。The effective diffusivity diagnosis is used to obtain a basic insight into the two-dimensional transport and mixing properties of synoptic scale events such as trough thinning processes, wave breaking of Antarctic polar vortex and both a developing and non-developing disturbance during the 2010 Atlantic hurricane season. Effective diffusivity is used as a mixing diagnostic on a passive tracer subject to diffusion and advection by the non-divergent part of observed winds. Large/small effective diffusivity corresponds to strong/weak mixing. For the trough event, the filaments are regions of large effective diffusivity, which suggests strong mixing. For the Antarctic polar vortex, the effective diffusivity shows that strong mixing occurs at the edge of stratospheric polar vortex. This is in good qualitative agreements between effective diffusivity and measurements of chemical tracers taken by the NASA ER-2 aircraft.
The tropical cyclone formation has long been recognized to form in regions of approximately circular flow. Recent studies showed that a region of recirculation, also called pouch, along a propagating Easterly wave occurred in all genesis cases. We use effective diffusivity as a diagnosis that can identify the transport and mixing properties around the tropical disturbances. The effective diffusivity diagnosis is used to evaluate the intrusion of dry air into Gaston, which did not re-develop into a tropical cyclone, and the intrusion of dry air into Karl, which did become a tropical cyclone and later a major hurricane. The northwestern region of Gaston shows a strong mixing region at 700hPa and 500hPa, allowing mixing dry air into Gaston to be quite effective. On the other hand, the Karl is in a weak mixing environment where the Karl is slightly affected by the dry air. The results show that the effective diffusivity diagnosis of mixing can be useful in understanding the tropical cyclogenesis
Characteristics of Clay Minerals from the Taiwan Chelungpu Fault Drilling Project
No full text地震一直是人們最注意的天然災害之一，因為其對我們的生命安全以及財富有極大的影響。其中，地震斷層，就是地震最主要的來源之一，對地震斷層的活動特性及其機制有進一步的瞭解，就能增加對人們的保障，以及減少可能的損失。
車籠埔斷層於西元1999年發生錯動，造成數千人死亡，以及數萬人無家可歸。所以，對車籠埔斷層作詳盡的研究是有其必要性的，若能瞭解斷層帶與圍岩之間的物理化學作用，將對其斷層機制可以有更深入之瞭解。臺灣車籠埔深鑽計畫，便油然而生。
要探討車籠埔斷層之斷層帶可能產生之物理化學作用，就必須先確定主要滑動帶之位置。唯有研究主要滑動帶的特性，才能瞭解其錯動可能之機制。所以，本文第一個工作就是利用黏土礦物的特徵判斷可能於1999年產生錯動之主要滑動帶。由於地震斷層滑動會釋放大量的摩擦熱，並且可能在滑動帶產生高溫造成岩石熔融，使礦物相改變。觀察斷層帶礦物相的特徵之後，發現黏土含量在位於深度1,111公尺處大量減少，而且礦物相與圍岩迥然不同，說明在此深度的斷層帶可能是921集集地震的滑動面。
再者，黏土礦物有不同溫度的崩解反應，所以本文的第二個研究，便是利用其不同的熱崩解特性對車籠埔斷層之三個斷層帶（深度分別為1,111、1,153、1,222公尺）曾經遭受的溫度作初步的估計，而所得到之溫度估計可以作為計算摩擦熱最重要的參數，溫度，提供一個良好限制。研究結果顯示主要滑動帶曾經達到的溫度最高，其次是深度1,153公尺的斷層帶，最低則是深度1,222公尺的斷層帶。
當然，風化作用也是產生黏土礦物另一個重要的過程，所以本文的第三個工作，便是將車籠埔斷層的黏土礦物特徵由南到北，由淺到深作系統性地分析，並提供風化作用對黏土礦物可能產生之影響作定性及定量的描述。其結果顯示，深鑽計畫中的材料可以忠實的呈現或保持滑動帶曾發生的物理或化學作用，而地表的材料則否，同時也說明深鑽計畫的重要性。The earthquake is one of the natural disasters that is harmful for safety and wealth of mankind. Seismic faults are the major source to produce earthquakes. Therefore, investigations of the characteristics and mechanisms of a seismic fault could protect people from dangers and damages.
The Chelungpu Fault, Taiwan produced a northward propagating rupture on September 21, 1999 resulting in an Mw 7.6 earthquake. It made thousands of people dead and produced serious destructions in central Taiwan areas. It is necessary to obtain more information on the Chelungpu fault zone properties, and to investigate fault mechanisms via understanding the physical and chemical processes in principal slip zone (PSZ) and/or slip surfaces. The Taiwan Chelungpu-fault Drilling Project (TCDP), therefore, is performed to extract deep materials for the investigation of faulting mechanism.
To realize the possible physical and chemical processes through fault zones and to investigate the faulting mechanism of the Chelungpu fault, the principal slip zone (PSZ) should be identified. In this study we recognize the PSZ of the Chelungpu fault related to 1999 Chi-Chi within its characteristics of clay minerals in the fault zone. The Taiwan Chelungpu-fault Drilling Project (TCDP) Hole-A recovered continuous core samples across the rupture zone of the 1999 Chi-Chi earthquake (Mw7.6). Studying in-situ chemical properties sequentially from fresh-fault-zone materials of the Chelungpu fault provides insight into possible faulting mechanisms. Distinct anomalies of mineral assemblages at the 1111-m fault zone of TCDP Hole-A are found to be: (1) A decrease in clay content within the primary slip zone (PSZ); and (2) A significant decline of illite, disappearance of chlorite and kaolinite, and spike in smectite within the PSZ. Meanwhile, features relating to melting or amorphous material in the PSZ have been observed by SEM and TEM. The results suggest that the PSZ might have experienced generation of glassy materials such as pseudotachylyte by the expense of clay minerals due to strong shear heating, then prompt alteration of pseudotachylyte into smectite. Characteristics of clay minerals and images obtained from electronic microscopes in the PSZ thus imply that pseudotachylyte possibly developed during the 1999 Chi-Chi earthquake, but quickly altered into smectite. This particular phenomenon may explain why pseudotachylyte is rarely found in exhumed hydrated fault zones.
To investigate the coseismic frictional temperature in seismogenic fault zones, we examine the characteristics of clays in the Chelungpu-fault zones with isothermal heating experiments, Scanning Electron Microscope coupled to an Energy Dispersive spectrometer (SEM/EDX), and Thermogravimetry analysis (TGA). In the TCDP case (Taiwan Chelungpu fault Drilling Project), three fault zones of the Chelungpu-fault system were identified at the depth of 1111m, 1153m, and 1,222m (described as FZ1111, FZ1153, and FZ1222 hereafter), respectively. The clay mineral assemblages of FZ1111 show evidence of melting, and the temperature in a ~2 cm band within the black gouge zone is estimated to be from 900°C to 1,100°C by comparing the SEM images of in situ natural samples with those of heated materials, and the finding of no recrystallization of kaolinite-amorphous aluminosilicates-spinel in the fault samples. The clay mineral assemblages of FZ1153 suggested that kaolinite has been broken down by the thermal decomposition/dehydroxylation but chlorite has not. The clay characteristics and results of SEM/EDX and TGA constrain the faulting temperature from 500°C to 900°C, with a spatial distribution up to ~1.3 m. The clay characteristics of FZ1222 indicated that clays were changed by experiencing high temperature acid fluids, instead of thermal decomposition/dehydroxylation processes, and that the temperature is localized in ~2 cm and ranges from 350°C to 500°C, the lowest temperature among three fault zones. The estimates of temperature ranges, and thermal anomaly intervals among three fault zones provide important information and constraints on the physical and chemical processes, coseismic dynamic weakening mechanism, and earthquake energy budget in the future.
Chemical weathering is also an important process to produce clay minerals. We systematically analyze the characteristics of clay minerals from north to south and along the depth of the Chelungpu fault. The Chelungpu fault, with northward propagating ruptures, was created as a result of the Mw 7.6 earthquake which struck Central Taiwan on 21 September 1999. To investigate its true faulting mechanism, we examined the clay mineralogy and major element geochemistry of the host rocks of the Chelungpu fault from four outcrops, Fengyuan (455.3 m in depth), Nantou (211.9 m in depth), and Taiwan Chelungpu fault Drilling Project (2003 m in depth). The outcrops are spanned roughly 70 km along the fault. Mineralogical and chemical results of the host rocks revealed different degrees of chemical weathering, and its intensity could be further understood through the relative clay percentage of smectite, illite chemistry index, and illite crystallinity. These mineralogical proxies combined with the chemical index of alteration (CIA) and the intensity of chemical weathering indicate that the degree of chemical weathering is a function of depth, i.e., the most severe on the surface and the mildest in the TCDP samples. The mineralogical and geochemical data obtained in this study also suggest that chemical weathering, rather than leaching, seems to be the main driving force for the phase change of clay. The amount of smectite produced by chemical weathering varies with depth, and it argues against a previously suggested idea that weak-fault behaviours were caused by the presence of smectite on the surface. The observations of clay mineralogy and major element geochemistry in this study indicate that the presence of smectite in the outcrops may not play a significant role during faulting, and suggest that fault-weakening as a result of the presence of smectite cannot be applied to the Chelungpu fault
Experimental and Numerical Study on the Mechanism of Nucleation by Re-condensation
No full text此研究根據Chen (1999)提出的「再凝結核化機制」假說，進一步探討引擎燃燒過程產生將空氣中既有氣膠粒子轉換為更多較小新粒子的過程。此過程中，氣懸粒子的數量濃度增加，但在質量濃度上並沒有增加。本研究嘗試同時以實驗與數值模式相互檢驗，測出引擎燃燒過程對氣懸粒子數量濃度和粒徑譜的影響，求得定量的關係。 實驗的部分延續並改進黃 (2005)利用機車引擎燃燒實測，分析進氣氣體之粒子濃度(Ni)與燃燒所產生之粒子濃度(No)間的關係。實驗結果顯示，隨著Ni增加，No亦增加，但部分實驗顯示當Ni達約2*10^4 #/cm^3時，No增加的趨勢減緩甚至下降，顯示其過程並非是簡單的蒸發、凝結核化而已，推測可能牽涉到粒子是否完全蒸發以及核化所需相對濕度與相對酸度之供給量問題，這部分進一步以數值模擬來探討相關機制。 數值模擬結果顯示，雖然Ni愈高，蒸發產生愈大量的酸氣及可凝結氣體，進而有愈高的核化速率，但當Ni太高時，反而會提早在比較高溫且相對濕度較低的情況下就開始核化，反而會降低了核化速率。此外，當Ni太多時，雖然會提供較多的酸氣，但殘留下未蒸發的氣懸粒子也會增多，而酸氣及水氣會吸附在殘留的粒子上，降低核化。殘留的粒子太多時，也會加快粒子間碰撞的速率而降低數量濃度，所以No隨著Ni的增加會有一個高峰值。目前由實驗及數值模擬的結果顯示，兩者間有著相似的趨勢。This study intend to verify the mechanism of “nucleation by re-condensation” proposed by Chen (1999), which hypothesize that engine combustion tend to convert existing ambient aerosol particles into more numerous and smaller particles without affecting the total aerosol mass. Both experimental and numerical studies are conducted in this research to prove this hypothesis. The laboratory experiment follows the procedure of Huang(2005) but with improvements that allow more quantitative analysis of the processes. Huang(2005) proved the aerosol number concentration is increased after a motor engine combustion. The results show that the output number concentration (No) in the exhaust air generally increases with increasing input number concentration (Ni) in the intake air, except in a few occasions, when Ni is roughly greater than 2*104 #/cm3, No becomes less. This implies that the nucleation by re-condensation process involves not simply evaporation and nucleation but also the amount of residual particles and timing of nucleation, which depends on the supply of relative acidity and relative humidity Numerical simulation of aerosol evolution is designed to analyze the details of these mechanisms. Simulation results show that, when Ni increases, there is more condensable acid vapor available, this generally leading to higher nucleation rates. However, as more acid vapor is available, the nucleation would start early at which time the air temperature is higher thus the relative humidity is lower. At some point the lower relative humidity produces a lower nucleation rate. Therefore, when the Ni is too high, the nucleation rate actually decreases. In addition, as Ni increases, the number of residual particles may also increase The residual particles would absorb the acid vapor thus decrease the nucleation rate, as well as collect the newly formed particles, both cause the total number concentration to decrease. So, the relation between Ni and the maximum No is not linear, and there exist an optimal Ni that produces the highest No. Some of the observation results also reveal such features.誌謝……………………………………………………………………i文摘要………………………………………………………………ii文摘要………………………………………………………………iii錄……………………………………………………………………v目錄…………………………………………………………………vii目錄…………………………………………………………………xi一章 前言………………………………………………………1二章 機車廢氣實驗……………………………………………62.1實驗儀器簡介…………………………………………………6 2.1.1 氣懸粒子產生器…………………………………………6 2.1.2 氣懸粒子徑譜儀…………………………………………6 2.2實驗I……………………………………………………………7 2.2.1 實驗設計…………………………………………………7 2.2.2 實驗結果與討論…………………………………………9 2.3實驗II…………………………………………………………11 2.3.1 實驗設計…………………………………………………11 2.3.2 實驗結果與討論…………………………………………11 2.4 實驗I & 實驗II結果討論……………………………………12三章 機車廢氣數值模擬………………………………………14 3.1 模式架構………………………………………………………14 3.1.1 雙組份核化模組…………………………………………14 3.1.2 數值架構…………………………………………………14 3.1.3撞併過程…………………………………………………15 3.2 模擬I…………………………………………………………15 3.2.1 實驗設計…………………………………………………15 3.2.2 模擬結果與討論…………………………………………16 3.3 模擬 II………………………………………………………18 3.3.1 實驗設計…………………………………………………18 3.3.2 模擬結果與討論…………………………………………18 3.4 模擬I & 模擬II結果討論……………………………………20四章 結果與討論………………………………………………22 4.1 實驗部分……………………………………………………22 4.2 數值模擬部分………………………………………………23 4.3 討論與應用…………………………………………………24五章 結論………………………………………………………25考文獻……………………………………………………………27圖…………………………………………………………………30表…………………………………………………………………6
Tunnel Magnetoresistance Under Proximity Effect in NiFe/CoFe/Al2O3/CoFe/Nb
No full text摘要
磁性穿隧接面由鐵磁/絕緣/鐵磁所構成，穿隧磁電阻效應的高低主要取決於「鐵磁/絕緣」介面上的磁性和電子組態。藉由引入超導層，在鐵磁/超導鄰近效應中，我們來觀察鐵磁層中電子傳輸是否受到超導層影響。經由對照組我們發現在低溫進入超導態時，反平行態電阻受到超導層鈮的影響隨著溫度降低而降低，而平行態電阻則不受超導影響，其現象就是磁電阻率的降低。
在不同厚度的鈮，我們發現鈮厚度在低於100 nm時，磁電阻率在超導態時明顯不受影響。比較鈮厚度500 nm，鈮厚度在150 nm ~250 nm時，磁電阻率在溫度降低至超導轉變溫度時會有延遲降低的現象。Abstract
The magnetic tunnel junctions (MTJs) are consisted of ferromagnet/insulator/ferromagnet (FM/I/FM). Tunnel magnetoresistance (TMR) is strongly influenced by the electronic and magnetic properties at the FM/I interface. Considering the proximity effect in ferromagnet/superconductor (FM/SC), we sputtered Nb on the top FM layer of pseudo spin-valve (PSV) magnetic tunnel junctions to observe how the superconducting Nb influences the FM layer. With the help of the contrast experiment, we find that the resistance of the antiparallel state maybe influenced by Nb and it becomes lower below the superconducting transition temperature (Tc). However, the resistance in paralleled state is not significantly influenced by Nb, resulting in the decrease of TMR values.
In the thickness dependence of Nb, we find that TMR is not apparently influenced in SC state as the thickness of Nb is below 100 nm. Comparing with that in the case of 500 nm Nb thickness, the TMR value shows retarding decrease as cooling through Tc for those of Nb thickness between 150 nm and 250 nm.目 錄
第一章 簡介 1
第二章 基本原理 3
2.1 磁電阻 3
2.1.1普通磁電阻 4
2.1.2異向性磁電阻 4
2.1.3龐磁阻 5
2.1.4巨磁阻 5
2.1.5穿隧磁電阻 7
2.2 超導體 11
2.2.1零電阻和邁斯納效應 11
2.2.2倫敦方程和超導穿透深度 13
2.2.3鄰近效應 16
2.3.2磁性與超導的相互影響 17
第三章 實驗技術 18
3.1 超高真空系統 18
3.1.1抽氣系統 18
3.1.2真空壓力計 21
3.2 濺鍍系統 23
3.2.1直流和交流濺鍍 23
3.2.2磁控濺鍍 25
3.3元件製程 26
3.4四點量測法 28
第四章 實驗結果與分析 29
4.1 NiFe/CoFe/Al2O3/CoFe/Nb(500nm) 31
4.2 Superconducting thickness dependence 44
4.3超導穿透深度和磁電阻率的關係 61
第五章 結論 63
第六章 參考資料 6
Temperature estimates of coseismic heating in clay-rich fault gouges, the Chelungpu fault zones, Taiwan
No full textMaturation-dependent microstructure length scale in the corpus callosum of fixed rat brains by magnetic resonance diffusion–diffraction
No full text
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
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