Active Disturbance Rejection Control for Uncertain Nonlinear Systems With Sporadic Measurements

This paper deals with the problem of active disturbance rejection control (ADRC) design for a class of uncertain nonlinear systems with sporadic measurements. A novel extended state observer (ESO) is designed in a cascade form consisting of a continuous time estimator, a continuous observation error predictor, and a reset compensator. The proposed ESO estimates not only the system state but also the total uncertainty, which may include the effects of the external perturbation, the parametric uncertainty, and the unknown nonlinear dynamics. Such a reset compensator, whose state is reset to zero whenever a new measurement arrives, is used to calibrate the predictor. Due to the cascade structure, the resulting error dynamics system is presented in a non-hybrid form, and accordingly, analyzed in a general sampled-data system framework. Based on the output of the ESO, a continuous ADRC law is then developed. The convergence of the resulting closed-loop system is proved under given conditions. Two numerical simulations demonstrate the effectiveness of the proposed control method.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Bart De Schutte

樹舌靈芝之成份研究

[[abstract]]摘 要: 從樹芝之甲醇萃取液中分離得到以下九種化合物: ergosta -7 , 22 -dien -3β-yl- palmitate (1) , alnusenone (2) , fridelin (3) , ergosta -7 , 22 -dien -3 - one (4) , ergosta -7 , 22 -dien -3β-ol (5) , ergosterol (6) , ergosterol peroxide 和9 (11)-dehydro -ergosterol peroxide 之混晶 (7) , ergosta- 5 , 8 , 22 - trien -3β, 15 -diol (8) , β-D-glucosamine 之長鏈衍生物 (9) 。其中 化合物 (1)、(7)、(8)為首次由樹舌中分離得到，(9) 為新化合物。 前 言： 樹舌，學名Ganoderma applanatum (Pers. ) Pat., 屬於擔子菌門，帽菌目，多孔菌 科，中名：樹舌，梅寄生，別名：赤色酵母菌，平蓋靈芝，扁芝外。藥物名稱：赤色 酵母菌，菌體多年生，無柄，側生，厚半圓形，隆起扁平，有同心環紋或波形瘤狀隆 起。殼皮淡黃色，灰色，肉桂色或紅黑色，性屬溫和，味略苦，主治食道癌 ，有 關樹舌之成份研究報告以日本為主，成份屬於類固醇有五種，三 類有十種 。為 了更深入探究其成份，故著手從事本文的研究。 實驗部份： 本實驗所用的樹舌，購至和平西路3 段27號, 萬山靈芝館, 已乾燥切碎片，重3.9 公 斤。以40L 甲醇熱萃取三次 (50∼60℃) 。甲醇濾液依次以正己烷，氯仿等溶劑萃取 ，得到正己烷可溶層20 , 氯仿可溶層56 , 以及甲醇 /水層深褐色的黏稠油狀液體 , 由正己烷可溶層經矽膠管柱色層法 (沖提液: 正己烷 /乙酸乙酯 = 40/1-2/1 ) , 得到化合物 (1)–(6) , 氯仿可溶層經矽膠管柱色層法 (沖提液: 氯仿 /甲醇 = 60/ 1-1/1 ) 得化合物 (7)–(9) 。

[[alternative]]Security mechanism for distributed systems

[[abstract]]第一章緒論 １．１研究背景與動機 １．２研究目的 １．３研究方法與步驟 １．４重要名詞解釋 １．５論文結構 第二章相關文獻探討 ２．１非對稱性金匙演算法 ２．２安全機制 ２．２．１亂數產生器 ２．２．２金匙產生機制 ２．２．３使用者認証機制 ２．３分散式系統安全環境 ２．３．１OSI 安全環境架構 ２．３．２ECMA安全環境架構 ２．３．３Kerberos安全環境架構 第三章分散式系統安全機制之規劃 ３．１安全需求分析 ３．２安全機制之規劃 ３．２．１ADKG機制之規劃 ３．２．２DUA 機制之規劃 第四章ADKG機制之設計 ４．１SSPRB 產生器之設計 ４．１．１SSPRB 產生器之架構 ４．１．２SSPRB 產生器之分析與比較 ４．２ADKG機制之架構 ４．２．１金匙產生階段 ４．２．２金匙檢查階段 ４．２．３金匙載入階段 ４．３ADKG機制之分析與比較 第五章DUA 機制之設計 ５．１DUA 機制之架構 ５．１．１使用者登記階段 ５．１．２使用者認証階段 ５．２DUA 機制之分析與比較 ５．２．１DUA 機制之實例 ５．２．２安全性分析與比較 第六章結論與建議 ６．１研究結論 ６．２研究建議 參考書目 #9303503 #9303503

Review of the action of organic matter on mineral sediment flocculation

Sediment is found throughout the world’s alluvial plain rivers, estuarine coasts and adjacent seas and is thereby a key factor in major ecosystems. Suspended mineral sediment can affect the biological activity of microorganisms and plants, by reducing light penetration in the water column or by binding to organic matter. Biological processes can, in turn, affect the physical and chemical properties of the sediment particles and influence the adhesion between particles. They can facilitate the sediment aggregation (flocculation) through bridging, patching and sweep, while biological decay will mainly help to disintegrate organic matter rich flocs. Biological activity also affects the properties of flocs (structure, density, sedimentation rate and composition). This activity is itself influenced by environmental conditions (like temperature, light and nutrient fluxes). Sediment flocculation thus involves complex relationships between several physical, chemical and biological factors. The role of biology in particular needs to be better integrated in sediment transport models, through the interaction between mineral clay particles, microorganisms and their excreted polymers (Extra Polymeric Substances, i.e., EPS). In this article, a summary of the state-of-the-art research regarding sediment flocculation is given. In particular, the action of organic matter on fine-grained sediment flocculation is discussed. The aim of the article is to provide a more comprehensive understanding of bio-sediment dynamics and give an outlook on remaining research questions.Environmental Fluid Mechanic

Seasonal variation of floc population influenced by the presence of algae in the Changjiang (Yangtze River) Estuary

The variation of the floc population in the Changjiang Estuary has been studied for both winter and summer season as a function of the presence of living (micro)algae. The influence of algae has been characterized through the use of the chlorophyll-a concentration to suspended sediment concentration (CC/SSC) ratio. Two whole tidal cycle sampling campaigns were carried out and a full set of parameters (particle size distribution, particle concentration, salinity, velocities, chlorophyll-a concentration) was recorded as function of time for 6 vertical depths. It is found that the floc population can be described by three particle classes. The two most dynamic classes (microflocs and macroflocs) co-exist in the water column. It was nonetheless found, due to the correlation between CC/SSC and particle sizes that the system is at steady state, both in summer and in winter. This can be explained by the limited flocculation ability between the classes due to their segregation in the water column. In winter, macroflocs are found at the top of the water column but their amount and size are very reduced with a mean CC/SSC value of 13 ± 11 μg g−1. In summer, algae-rich macroflocs are abundant at the top of the water column with a mean CC/SSC value of 21 ± 18 μg g−1, especially at flood tide. Microflocs, on the other hand, have a higher density and are generally found deeper in the water column. At high water slack, both macroflocs and microflocs will settle but will never catch-up. The fact that the flocs are at steady-state in terms of flocculation is of importance for sediment transport modelling.Accepted Author ManuscriptCoastal EngineeringEnvironmental Fluid Mechanic

A study of in-situ sediment flocculation in the turbidity maxima of the Yangtze Estuary

In order to improve our understandings of temporal and vertical variations of sediment flocculation dynamics within the turbidity maxima (TM) of the highly turbid Yangtze Estuary (YE), we deployed LISST-100C, a laser instrument for in-situ monitor of the sizes and concentrations of flocculated particles in a wet season. Field data in terms of vertical profiles of flow velocity, suspended sediment concentration (SSC), salinity, flocculated particle size distribution and volume concentration were obtained, based on field works conducted at consecutive spring, moderate, and neap tides. Data analyses show that the mean floc diameters (DM) were in the range of 14–95 μm, and flocculation exhibited strong temporal and vertical variations within a tidal cycle and between spring-neap cycles. Larger DM were observed during high and low slack waters, and the averaged floc size at neap tide was found 57% larger than at spring tide. Effective density of flocs decreased with the increase of floc size, and fractal dimension of flocs in the YE was mainly between 1.5 and 2.1. We also estimated the settling velocity of flocs by 0.04–0.6 mm s−1 and the largest settling velocity occurred also at slack waters. Moreover, it is found that turbulence plays a dominant role in the flocculation process. Floc size decreases significantly when the shear rate parameter G is > 2-3 s−1, suggesting the turbulence breaking force. Combined effects of fine sediment flocculation, enhanced settling process, and high sediment concentration resulted in a large settling flux around high water, which can in part explain the severe siltation in the TM of the YE, thus shedding lights on the navigation channel management.Environmental Fluid Mechanic

How have the river discharges and sediment loads changed in the Changjiang River basin downstream of the Three Gorges Dam?

Streamflow and sediment loads undergo remarkable changes in worldwide rivers in response to climatic changes and human interferences. Understanding their variability and the causes is of vital importance regarding river management. With respect to the Changjiang River (CJR), one of the largest river systems on earth, we provide a comprehensive overview of its hydrological regime changes by analyzing long time series of river discharges and sediment loads data at multiple gauge stations in the basin downstream of Three Gorges Dam (TGD). We find profound river discharge reduction during flood peaks and in the wet-to-dry transition period, and slightly increased discharges in the dry season. Sediment loads have reduced progressively since 1980s owing to sediment yield reduction and dams in the upper basin, with notably accelerated reduction since the start of TGD operation in 2003. Channel degradation occurs in downstream river, leading to considerable river stage drop. Lowered river stages have caused a ‘draining effect’ on lakes by fostering lake outflows following TGD impoundments. The altered river–lake interplay hastens low water occurrence inside the lakes which can worsen the drought given shrinking lake sizes in long-term. Moreover, lake sedimentation has decreased since 2002 with less sediment trapped in and more sediment flushed out of the lakes. These hydrological changes have broad impacts on river flood and drought occurrences, water security, fluvial ecosystem, and delta safety.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Coastal Engineerin

Quantification of Tidal Asymmetry and Its Nonstationary Variations

Tidal wave deformation and tidal asymmetry widely occur in tidal estuaries and lagoons. Tidal asymmetry has been intensively studied because of its controlling role on residual sediment transport and large‐scale morphological evolution. There are several methods available to characterize tidal asymmetry prompting the need for an overview of their applicability and shortcomings. In this work we provide a brief review and evaluation of two methods, namely, the harmonic method and the statistical method. The latter comprises several statistical measures that estimate the probability density function and various forms of skewness. We find that both the harmonic and statistical methods are effective and have complementary advantages. The harmonic method is applicable to predominantly semidiurnal or diurnal regimes, while the statistical methods can be used in mixed tidal regimes. Assisted by harmonic data, a modified skewness measure can isolate the contribution of different tidal interactions on net tidal asymmetry and also reveal its subtidal variations. The application of the skewness measure to nonstationary river tides reveals stronger tidal asymmetry during spring tides than neap tides, and the nonlinear effects of river discharges on tidal asymmetry in the upper and lower regions of long estuaries.Coastal Engineerin

The role of algae in fine sediment flocculation: In-situ and laboratory measurements

The precise interactions between organic and inorganic particles in the context of flocculation is an on-going topic of research. The suspended particulate matter (SPM) found in estuaries is composed of both organic and inorganic particles with specific particle size distributions (PSD's). These PSD's are a function of the hydrodynamic conditions, suspended sediment concentration (SSC), organic matter composition, salinity and seasonal variations. A field campaign was carried out in August 2015 in the turbidity maximum zone of the Yangtze Estuary, where the SPM dynamics were recorded. The concentration of algae in the water column was indirectly measured through the chlorophyll-a concentration (CC). We show that there is a strong correlation between SSC and CC in the whole water column, for the whole tidal cycle. Additional flocculation experiments in the laboratory confirm that the largest observed flocs are predominantly organic-based, and that salinity alone could not induce the flocculation of the Yangtze mineral particles. A key parameter for the maximal floc size is the algae concentration to sediment concentration ratio. When this ratio is high, the D50 is high and vice-versa.Accepted Author ManuscriptEnvironmental Fluid Mechanic

Dynamic anti-collision A-star algorithm for multi-ship encounter situations

For the complex multi-ship encounter scenarios, this article proposes a dynamic collision avoidance path planning algorithm based on the A-star algorithm and ship navigation rules, namely Dynamic Anti-collision A-star (DAA-star) algorithm. A dynamic search mechanism of the DAA-star algorithm considering time factors is designed to enable the collision avoidance for situations with known moving obstacles. A quaternion ship domain is generated based on Automatic Identification System (AIS) data, and the navigation risk cost is calculated with the combination of the quaternion ship domain and potential field. The searching constraints conforming with the Regulations for Preventing Collision at Sea (COLREGS) rules are set for the DAA-star algorithm to guarantee the safety of collision avoidance. Meanwhile, the individual ship maneuverability constraints and maneuverability differences from ship to ship are both considered in the proposed DAA-star algorithm, which can solve the path planning problem with dynamic obstacles in multi-ship encounter scenarios. The simulation results show that, compared with the traditional A-star algorithm and dynamic A-star algorithm, the DAA-star algorithm can generate more reasonable dynamic and static obstacle avoidance paths in complex navigation scenarios in the trade-off between the navigation risk and economical efficiency.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic