9 research outputs found
A Study on the Estimate Wind Blown Sand in Taichung Harbor
Abstract
The purpose of this study proposed herein is to research which understand about grain size, grain density, grain water content, wind velocity and wind blown sand in Taichung Harbor, at one time we observing the wind blown sand and wind velocity by sand sampler and multi-layer anemometer, further, estimates wind blown sand by
Kawamura dimension analyze.
The results of data by regression analysis that can be derived by power expression between wind velocity and wind blown sand, the grain size, grain density have negative relationship with wind blown sand, however, grain water content have no relationship with wind blown sand at 0.3% water content, moreover, the BSNE is closed than H-2 to estimates fluctuation of sand dune in Taichung Harbor. Two adjust estimates equation of wind blown sand by
BSNE sand sampler
(Q / d50 * U0.2 * σ) = 6.56 * 10-4 * ( U0.2^2 / g * d50 * σ/ρ )^0.8458(1)
H-2 sand sampler
(Q / d50 * U0.2 * σ) = 2.5 * 10-4 * ( U0.2^2 / g * d50 *σ/ρ )^0.7214(2)
Key Words : wind blown sand, BSNE, wind velocity, wind tunnel.摘要
本研究之目的在以現地觀測方法從事台中港海岸飛砂量之調查,以探討砂粒粒徑、密度、含水率及風速與飛砂量之關係,研究中以BSNE及H-2二種不同型式之集砂器,配合多層風速計進行飛砂量與風速之觀測,進而對中島飛砂量之因次分析式加以驗證、比較、探討與分析。
經由線性迴歸分析,綜合研究所得結果得知,風速與飛砂量呈指數極顯著關係,而砂粒密度及中值粒徑則與飛砂量呈負相關;又飛砂量與0.3 %極低含水率之砂粒,彼此間並無顯著關係;再者,BSNE集砂器較H-2集砂器之觀測結果更接近中島因次分析推估之飛砂量;將二種不同型式集砂器分析所得之飛砂量推估式,經由率定修正後為:
BSNE型集砂器:
(Q/ d50 * U0.2 * σ) = 6.56 * 10-4 * ( U0.2^2 / g * d50 * σ/ρ )^0.8458(1)
H-2型集砂器:
(Q/ d50 * U0.2 * σ) = 2.5 * 10-4 * ( U0.2^2 / g * d50 * σ/ρ )^0.7214 (2)
所得之結果,可提供相關工程規劃之重要參考依據。
關鍵字:飛砂量、BSNE、風速、風洞試驗目錄
摘要 I
Abstract II
目錄 III
圖目錄 V
表目錄 VII
第一章 緒論 I
一、前言 1
二、研究動機與目的 2
(一)研究動機 2
(二)研究目的 3
第二章 前人研究 5
一、飛砂機制之研究 5
(一)風速垂直分佈 5
(二)飛砂量與高度之關係 6
(三)砂粒之物理性質 7
二、飛砂量推估式 11
(一)飛砂量推估式 11
三、集砂器之研究 14
(一)水平式集砂器 14
(二)垂直式集砂器 14
第三章 理論依據 16
一、風速垂直分佈 16
二、飛砂量公式 16
第四章 研究試區及方法 18
一、試區概況 18
(一)地理位置 18
(二)氣象 18
(三)地質 21
二、研究方法 24
(一)風速與風向之觀測 24
(二)飛砂量之觀測 25
(三)砂粒粒徑分析 28
(四)砂粒密度分析 28
(五)空氣密度 28
(六)砂粒含水率分析 28
第五章 結果與討論 29
一、風速之特性 29
(一)風速之垂直分佈之分析 29
(二)風速 與摩擦風速 之影響 29
(三)風速 與粗糙長度 之關係 30
二、飛砂量之定性分析 33
(一)飛砂量與風速之關係 34
(二)飛砂量與砂粒大小之關係 37
(三)飛砂量與砂粒密度之關係 40
(四)飛砂量與砂粒含水率之關係 43
(五)飛砂量與高度之關係 45
三、飛砂量之推估 46
(一)中島因次推估式 46
(二)飛砂量實測與推估值之關係 50
(三)飛砂量推估之驗證 52
第六章 結論與建議 56
一、結論 56
二、建議 57
參考文獻 58
圖目錄
圖1-1 研究流程圖 4
圖2-1 砂面上風速垂直分佈(Bagnold, 1954) 6
圖2-2 不同粒徑下之門檻值風速(Pye, 1990) 8
圖2-3 摩擦風速下之粒徑平均跳躍高度方程式(Pye, 1990) 9
圖2-4 不同摩擦風速下砂粒之運動型態(Pye, 1990) 10
圖2-5 H-2型集砂器(單位:cm) 14
圖4-1 台中港試區位置 18
圖4-2 台中港風花圖 22
圖4-3 台中地質圖 23
圖4-4 多層風杯風速計 24
圖4-5 BSNE集砂器 25
圖4-6 集砂器構造圖(1) 26
圖4-8 H-2型水平集砂器 27
圖5-1 與 關係圖 30
圖5-2 與 關係圖 30
圖5-3 與 之關係(BSNE) 35
圖5-4 與 之關係(H-2) 36
圖5-5 與 之關係圖(BSNE) 38
圖5-6 不同高度下飛砂量與中值粒徑分布圖(BSNE) 38
圖5-7 與 之關係圖(H-2) 39
圖5-8 與 關係圖(BSNE) 41
圖5-9 與 關係圖(H-2) 42
圖5-10 與 關係圖(BSNE) 43
圖5-11 與 關係圖(H-2) 44
圖5-12 飛砂量與高度之關係(BSNE) 45
圖5-13 與 48
圖5-14 與 50
圖5-15 實測值與推估值之關係(BSNE) 51
圖5-16 實測值與推估值之關係(H-2) 51
圖5-17 2005年11月份堆砂量等高線分布 54
圖5-18 2006年1月份堆砂量等高線分布 55
表目錄
表3-1 各物理量之因次 17
表4-1 梧棲氣象資料統計表 19
表4-2 梧棲氣象站基本資料 20
表5-1(1) 風速觀測分析 31
表5-1(2) 風速觀測分析 32
表5-2 BSNE型垂直集砂器實驗資料 33
表5-3 H-2型垂直集砂器實驗資料 34
表5-4 中島因次分析資料(BSNE) 47
表5-5 中島因次分析資料(H-2) 49
表5-6 台中港堆砂量(2005年11月~2006年1月) 52
表5-7 飛砂推估量(2005年11月~2006年1月) 5
The Study of Reversible Data Hiding Mechanisms
資訊隱藏即是將機密資料藏入偽裝隱蔽物內,使未被授權的對象無法有效地於媒體中偵測得知機密資料。然資訊藏量與偽裝隱蔽物品質是很難取捨的問題,如何在資訊藏量與影像品質中取得平衡,一直是學者們努力的目標。
常見的可逆式資訊隱藏主要分為四類:差值擴張法、直方圖位移法、預測運算法與雙偽裝影像法。其中雙偽裝影像法除了有效減低負載影像的失真程度外,更有效避免了像素溢位問題,為學界熱烈研究的一個方向。後續發展的中間對折策略運用雙偽裝影像法,其配合調整藏入資料的範圍,更減輕了資料藏入後對載體的失真影響。然而,前述方法在頻繁出現大數值狀況下,均有著影像品質急遽衰退的問題。
本論文提出三種編碼方式,有效降低在編碼階段造成修改量過大的問題。其一為「頻率編碼策略」,經由統計原本預嵌入值的出現頻率,有效減少最大值頻率進而減緩嵌入後圖形的變異程度。此法所獲得的PSNR值較前人提出的方法為高,在較為平滑的機密圖像上,更有著明顯的效益。
其二為為「似性編碼法」,藉由整合鄰近像素的相似性以及出現頻率等考量,應用編碼簿適當的處理相鄰像素為較小的編碼值,進而有效的維持較高偽裝影像品質。實驗結果證明,在大多數的圖像中,似性編碼法的PSNR值相較類同的研究有著大幅的精進。
第三個方法為一種動態編碼策略,此法不僅可有效的降低編碼過程最大值出現的頻率,更可以即時的進行編碼與解譯的動作。藉由此種特性,動態編碼策略更有著多樣化的應用層面。
未來,吾人將進一步的分析複雜圖像的相關編碼相關參數與演算法,進而提升偽裝影像的品質。亦考量將相關演算法整合水印相關應用,以期提升演算法的強健性。Data hiding is a scheme that embeds secret data in cover media. With the scheme, hackers cannot efficiently detect the secret data from the stego-media. Over the past decade, many techniques have been proposed for data hiding. However, most of them suffer from the problem of trade-off between payload and image distortion.
There are four types of reversible data embedding methods, such as difference expansion, histogram shifting, prediction error expansion, and dual-image hiding scheme. The dual-image hiding scheme is the one that could generate slightly image distortion and avoids the underflow and overflow problems.
Based on dual-image hiding scheme, Center Folding Strategy (CFS) takes the median to reduce each decimal digit for decreasing the modification level. Thus, embedding the transferred digits into the cover image does not lead to the acute distortion of the image. However, both of dual-image hiding scheme and CFS cannot reduce the frequent occurrence of the maximum absolute value, and this disadvantage diminishes the visual quality of the resulting stego-image.
In the dissertation, three encoding methods are proposed to effectively decrease the modification level in the data embedding stage. One of them is the frequency-based encoding method that decreases the occurrence of the larger absolute digit and the level of modifications. The PSNR value of the frequency-based encoding method increases significantly in comparison with the previous methods. For smooth secret images, the image quality of the scheme is higher than those obtained from other methods.
The second scheme is the similarity-based encoding method that integrates with the neighboring pixel similarity and the frequency-based encoding method, and then by utilizing the similarity of adjacent pixels of the codebook as the smaller coding value, the method further enhances the quality of stego-images. Experimental results show that the PSNR value of the similarity-based method in most images is higher than that of other similar studies.
The third method is a dynamic encoding strategy. The strategy not only reduces the frequency of occurrence of the largest value but processes all the procedures of data encoding and transmits them immediately. With the advantage of the dynamic encoding technique, the proposed strategy has wide applications.
In the future, the correlation coefficient among the embedding algorithm in the complex images will be analyzed to further enhance the quality of the embedded images. In addition, the proposed method integrated with the watermarking scheme will be studied to achieve a higher degree of robustness.摘要 i
Abstract ii
Table of Content iv
List of Figures vi
List of Table viii
1. Introduction 1
1.1 Research Motivation 1
1.2 Contribution 7
1.3 Organization 7
2. Related Methods 9
2.1 Data Hiding 9
2.2 Reversible Data Hiding 11
2.3 Difference Expansion (DE) method 12
2.4 Histogram Shifting Method 14
2.5 Prediction Error Expansion 16
2.6 Dual-Images Hiding Method 17
2.6.1 Dual Imaging Technique Based on EMD 17
2.6.2 The Direction-Based Dual-Image Methods 18
2.6.3 (k, n)-Image Reversible Hiding Method 21
2.6.4 Magic Matrix Hiding Method 22
2.7 Center Folding Strategy (CFS) 23
3. Novel Reversible Data Hiding Schemes in Dual Stego-Image 27
3.1 Frequency-Based Encoding Strategy 27
3.1.1 Embedding Procedure 28
3.1.2 Extraction and Recovery Procedure 32
3.1.3 Summery 34
3.2 Similarity-Based Encoding Strategy 35
3.2.1 Embedding Procedure 36
3.2.2 Extraction and Recovery Procedure 39
3.2.3 Summery 41
3.3 The Dynamic Encoding Strategy 42
3.3.1 Embedding Procedure 42
3.3.2 Extraction and Recovery Procedure 46
3.3.3 Summery 50
4. Experiment and Analysis 51
4.1 The Experimental Parameters 51
4.2 The Experimental Result 52
5. Conclusions 65
References 6
A Study on the Aeolian Sand Flux by Bucking Π Theorem
The purpose of this study that measure Aeolian sand flux in Taichung and Miaoli coast. Aeolian sand flux and wind velocity which is measured with H-2 sand trap and multi-layer anemometer. The relationship among sand size, sand moisture, wind velocity and Aeolian sand flux which can be obtained though a method call Buckinghamπtheorem. Our results show that linear regression model is goodness of fit. In addition to, the result presents that is not significance level in Pearson correction between wind velocity and fraction wind velocity. Wind fraction velocity is not good significance level in Pearson correction as well as wind velocity for Aeolian sand flux.本研究目的以現地觀測方法從事台中縣及苗栗縣海岸飛砂量之觀測,研究中以H-2型集砂器,配合多層風速計進行飛砂量與風速之觀測,另一方面將砂粒中值粒徑、砂粒密度、砂粒含水量、重力加速度、風速及飛砂量等相關因子,利用白金漢π定理推導飛砂量推估公式,並將公式進行迴歸分析,結果呈線性迴歸模式最佳。另研究發現本試區之風速與摩擦風速並無相關性,對於現地飛砂量與摩擦風速之關係,不如以接近地表面之風速做代表還更具影響性
Application of Geometric Correction Method to Remotely Piloted Vehicle (RPV) Airscape Image for Surveying and Analysis of Disaster Areas
A+Study+on+Estimate+of+Wind+Aeolian+Sand+Flux+at+Yuanli+Coastally+in+Miaoli+County
The purpose of this study which is discussed about grain size, grain density, grain water content, wind velocity and Aeolian sand at Yuanli coastally. In this paper, the Aeolian sand flux is catch by sand sampler, and wind velocity data which is measure by multi-layer anemometer. Meanwhile, this paper of examination that use regression analysis to discuss the Aeolian sand factor in influence.
The results of regression analysis that can be derived by line expression between wind velocity and Aeolian sand, the grain size, grain density have negative relationship with Aeolian sand. However, the grain water content have no relationship with Aeolian sand at 0.3% water content. in addition to estimates of Aeolian sand flux by π Theorem which is:**: significance 1% *: significance 5%本研究之目的在以現地觀測方法從事苑裡海岸飛砂量之調查,探討砂粒比重、密度、含水率及風速與飛砂量之關係。研究中以BSNE集砂器,配合多層風速計進行飛砂量與風速之觀測,進而對影響飛砂量之因子進行線性迴歸分析。綜合研究所得結果得知,風速與飛砂量呈線性顯著關係,而砂粒密度及中值粒徑則與飛砂量呈負相關;又飛砂量與0.3%極低含水率之砂粒,彼此間並無顯著關係。另依柏金漢π定理進行因次分析所得之飛砂量推估式為:**:顯著水準1% *:顯著水準5
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