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1
Södermann, Olle, et Daniel Topgaard. « Varying the gradient pulse length gives valuable information in NMR diffusometry ». Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-197077.
Texte intégral
2
Södermann, Olle, et Daniel Topgaard. « Varying the gradient pulse length gives valuable information in NMR diffusometry ». Diffusion fundamentals 2 (2005) 133, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14476.
Texte intégral
3
St, Pierre Taunya Allyson. « Modelling the muscles of the lower extremity : The effect of varying joint angles on muscle length ». Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6241.
Texte intégralRésumé :
Polynomial regression was used to describe the relationship between lengths of the five muscles of interest and lower extremity joint angle(s). A difference between the genders was observed, so the male and female data were separated and five regression equations (one per muscle) were fitted to each data set. In an attempt to build general regression equations normalization and transformation of the data was performed, but these manipulations of the data did not lead to predictive equations. Addition of leg segment length, for the monoarticular muscles, and height, for the biarticular muscles, as independent variables did significantly increase model fit. The general regression model was quantitatively compared to the leg segment lengths and the actual observed values. It was also qualitatively compared to two other models. Results showed that while the general regression model is good at predicting muscle function, it is not a very accurate predictor of muscle length.
4
Gittens, Shaun. « Neural network generation of temporal sequences from single static vector inputs using varying length distal target sequences ». College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6710.
Texte intégralRésumé :
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Computer Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
5
Tempel, Philipp [Verfasser], et Andreas [Akademischer Betreuer] Pott. « Dynamics of cable-driven parallel robots with elastic and flexible, time-varying length cables / Philipp Tempel ; Betreuer : Andreas Pott ». Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2019. http://d-nb.info/1207836842/34.
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6
Bauer, Michael. « Dynamical characterization of Markov processes with varying order ». Master's thesis, [S.l. : s.n.], 2009. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200900153.
Texte intégral
7
Gavit, Sarah A. « Varying tether lengths for modifying orbital eccentricities ». Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15236.
Texte intégralRésumé :
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985.MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO.
Includes bibliographical references.
by Sarah K. Gavit.
M.S.
8
Tenny, Joseph S. « Numerical Simulations in Electro-osmotic Flow ». BYU ScholarsArchive, 2004. https://scholarsarchive.byu.edu/etd/186.
Texte intégralRésumé :
The developing flow field in a parallel plate microchannel, induced by wall motion, has been modeled numerically. This type of flow simulates the physical driving mechanism that exists in electro-osmotically generated flow with large channel diameter-to-Debye length ratios (Z). The physics of the flow field were compared between the moving wall model (MWM) and electro-osmotic flow (EOF) at Reynolds numbers of 1 and 1800, and Z > 2500. Also, Z-values between 50 and 500 were studied to investigate the accuracy of the MWM. Results show that for Z-values greater than 100 the MWM shows good agreement with EOF. The dynamics of the developing flow field for the MWM were explored for channel length-to-hydraulic diameter ratios (aspect ratio) of 5, 10, 20 and 40 at ten Reynolds numbers, Re (based on the wall velocity), below Re < 2000. The results show that far from the inlet the maximum fluid velocity occurs at the walls, as is expected, and the minimum velocity occurs at the channel center. Near the channel inlet, however, the centerline velocity is not a minimum but reaches a local maximum due to a resulting pressure imbalance generated by the wall motion. As the aspect ratio increases, the centerline velocity tends to approach the wall velocity far downstream from the inlet. Increases in the Reynolds number have the opposite effect on the centerline velocity. The hydrodynamic developing region, defined by that section of the channel where the wall shear stress is changing, also depends on the channel aspect ratio and Re, and is greater than the developing region for classical pressure-driven flow of a parallel plate channel. Also, the flow field physics was analyzed for a process called electro-mobility focusing (EMF). EMF is a process that separates and detects species of like charge with the use of electro-phoresis and EOF utilizing a varying voltage gradient. The velocity distribution and the effective diffusion were solved for analytically, for both a linear and non-linear voltage gradient, using the MWM and the creeping flow approximations. The resulting equations aid in optimizing the detection system by forcing the lowest effective diffusion (uniform velocity profile) to the detection location.
9
Boonprasit, Wimonrat. « A study of producing smoother gradients in the flexographic process on oriented polypropylene with UV ink by varying screening techniques, gradient lengths and the surrounding / ». Link to online version, 2006. https://ritdml.rit.edu/dspace/handle/1850/2289.
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Kaczmarczyk, Stefan. « Non-stationary responses on hoisting cables with slowly varying length ». Thesis, 1999. http://hdl.handle.net/10413/6875.
Texte intégralRésumé :
Cables in hoisting installations, due to their flexibility, are susceptible to vibrations. A common arrangement in industrial hoisting systems comprises a driving winder drum, a steel wire cable, a sheave mounted in headgear, a vertical shaft and a conveyance. This system can be treated as an assemblage of two connected interactive, continuous substructures, namely of the catenary and of the vertical rope, with the sheave acting as a coupling member, and with the winder drum regarded as an ideal energy source. The length of the vertical rope is varying during the wind so that the mean catenary tension is continuously varying. Therefore, the natural frequencies
of both subsystems are time-dependent and the entire structure represents
a non-stationary dynamic system. The main dynamic response, namely lateral vibrations of the catenary and longitudinal vibrations of the vertical rope, are caused by various sources of excitation present in the system. The most significant sources are loads due to the winding cycle acceleration/deceleration profile and a mechanism applied on the winder drum
surface in order to achieve a uniform coiling pattern. The classical moving frame approach is used to derive a mathematical model describing the non-stationary response of the system. First the longitudinal response and passage through primary resonance is examined. The response is analyzed using a combined perturbation and numerical technique. The method of multiple scales is used to formulate a uniformly valid perturbation expansion for the response near the resonance, and a system of first order ordinary differential equations for the slowly varying amplitude and phase of the response results. This system is integrated numerically on a slow time scale. A model example is discussed, and the behaviour of the essential dynamic properties of the system during the transition through resonance is examined. Interactions between various types of vibration within the system exist. The sheave inertial coupling between the catenary and the vertical rope subsystems
facilitates extensive interactions between the catenary and the vertical rope motions. The nature of these interactions is strongly non-linear. The lateral vibration of the catenary induces the longitudinal oscillations in the vertical system and vice-versa. In order to analyze dynamic phenomena arising due these interactions the nonlinear partial-differential equations of motion are discretised by writing the deflections in terms of the linear, free-vibration modes of the system, which result in a non-linear set of coupled, second order ordinary differential equations with slowly varying coefficients. Using this formulation, the dynamic response of an existing hoisting installation, where problematic dynamic behaviour was observed, is simulated numerically. The simulation predicts strong modal interactions during passage
through external, parametric and internal resonances, confirming the autoparametric and non-stationary nature of the system recorded during its operation. The results of this research demonstrate the non-stationary and non-linear behaviour of hoisting cables with slowly varying length. It is shown that during passage through resonance a large response may lead to high oscillations in the cables' tensions, which in turn contribute directly to fatigue damage effects. The results obtained show also that the non-linear coupling in the system promotes significant modal interactions during the passage through the instability regions. The analysis techniques presented in the study form a useful tool that can be employed in determining the design parameters of hoisting systems, as well as in developing a careful winding strategy, to ensure that the regions of excessive dynamic response are avoided during the normal operating regimes.Thesis (Ph.D.)-University of Natal, Durban, 1999.
11
SAHARAN, YOGESH KUMAR. « EFFECT OF TAPERING ON SKIN FRICTION OF PILE OF VARYING LENGTH ». Thesis, 2017. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15965.
Texte intégralRésumé :
Development of building presents several problems related to the design and assessment of pile foundations. Specially tall buildingsbplay a key rolenin current urban strategies and regeneration. Among these combinations of vertical, lateral and torsional forces to the piles due to the eccentricity of wind action on vertical projections of multistoried tall buildings is of particular interest.
The Design and analysis of pile foundation present a complex problem to the engineers because of several factors that affect the foundation behaviour. Such factors include mode of loading, soil properties, pile geometry, placement and method of construction .The mode and magnitude of loads transferred from the super structures will influence the selection of pile foundation to resist the imposed loads. Torsional forces are also acting on the pile and IS 2911 for pile foundation has not considered torsional forces for pile designing but it should be considered.
Therefore, objectives of the present work are:
(1) Mechanism of applying torque to piles.
(2) Comparison of angle of twist and torsional strain energy between tapered pile and cylindrical pile
of same diameter
(3) Experimentally to examine basic pile soil interactions in the modal pile subjected to torque in the context of study torque/angle of twist.
A mechanism of applying torque to a single pile was fabricated. Experiments on two piles were performed. Torque on piles was applied using the above said mechanism. Experiments were performed by increasing the depth of piles. When we increased the depth of pile at regular intervals with the different torques for increasing angle of twist till the failure angle of twist is achieved.
12
Pu, Jaan H., Songdong Shao et Y. Huang. « Shallow sediment transport flow computation using time-varying sediment adaptation length ». 2014. http://hdl.handle.net/10454/8342.
Texte intégralRésumé :
YesBased on the common approach, the adaptation length in sediment transport is normally estimated in the temporal independence. However, this approach might not be theoretically justified as the process of reaching of the sediment transport equilibrium stage is affected by the flow conditions in time, especially for those fast sediment moving flows, such as scour-hole developing flow. In this study, the 2D shallow water formulation together with a sediment continuity-concentration (SCC) model were applied to flow with mobile sediment boundary. A time-varying approach was proposed to determine the sediment transport adaptation length to treat the flow sediment erosion-deposition rate. The proposed computational model was based on the Finite Volume (FV) method. The Monotone Upwind Scheme of Conservative Laws (MUSCL)-Hancock scheme was used with the Harten Lax van Leer-contact (HLLC) approximate Riemann solver to discretize the FV model. In the flow applications of this paper, a highly discontinuous dam-break fast sediment transport flow was used to calibrate the proposed time-varying sediment adaptation length model. Then the calibrated model was further applied to two separate experimental sediment transport flow applications documented in literature, i.e. a highly concentrated sediment transport flow in a wide alluvial channel and a sediment aggradation flow. Good agreements with the experimental data were presented by the proposed model simulations. The tests prove that the proposed model, which was calibrated by the discontinuous dam-break bed scouring flow, also performed well to represent the rapid bed change and the steady sediment mobility conditions.
The National Natural Science Foundation of China NSFC (Grant Number 20101311246), Major State Basic Research Development Program (973 program) of China (Grant Number 2013CB036402) and Open Fund of the State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University of China (Grant Number SKLH-OF-1103).
13
Shu-hung, Wang, et 王樹宏. « Synthesis of Time-Varying IIR Filters with Finite Word-Length Using Integer Programming ». Thesis, 1998. http://ndltd.ncl.edu.tw/handle/21584331699894871031.
Texte intégralRésumé :
碩士國立臺灣科技大學
電子工程技術研究所
86
This thesis addresses the problem of designing finite word-length infinite impulse response (IIR) digital filters, which can be formulated as a discrete optimization problem. The design technique utilizes the local search algorithm of the integer programming which defines a larger search space by allowing the filter coefficients to be time-varying.In the computer simulation, the recursive digital filters are implemented in the direct form, whose filter coefficients expressed in block floating-point format are periodically time-varying (PTV). The cost function is defined by some measure of the difference between the impulse response of the synthesized filter and the desired impulse response (the Green function). The proposed scheme can be applied to the design of time-invariant and time-varying IIR filters. In synthesizing time-invariant filters, it has been demonstrated that the proposed scheme is superior to the traditional time-invariant search method under certain conditions.
14
Huang, Weicheng, et 黃偉誠. « Kalman Filter Implementations for Power System Time-Varying Harmonic Estimation under Finite-Word-Length Effects ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/14266926240826161037.
Texte intégralRésumé :
碩士亞洲大學
光電與通訊學系碩士班
100
The effective harmonic estimation for power signals is always an important task in the field of power quality assessment. Due to the development of advanced metering infrastructure (AMI), monitoring of power quality has attracted much attention in recent years. Even though the technology of instrumentation has grown up, the advanced analysis algorithms are still not widely adopted. This is because these approaches usually suffer from the computational consumptions. To reduce the cost and to promote the implementations of power quality monitoring devices in AMI, the finite-word-length (FWL) effects of Kalman filter are taken into account. With the considered effects and related analysis of robustness, the optimal implementations of Kalman filter can be determined and redesigned for the required hardware.
15
Yi, Po-Wei, et 易柏維. « Using varying length of fiber bundle to reduce the laser speckle of endoscope illumination source ». Thesis, 2019. http://ndltd.ncl.edu.tw/handle/s9u85x.
Texte intégralRésumé :
碩士國立陽明大學
生醫光電研究所
107
In order to not only reduce the section of endoscope but also maintain sufficient brightness. We utilize a high coherent semiconductor laser as the light source. But it also accompanies speckle generation. When the high coherent light source transmitts to the screen or the object, the surface of the object is not smooth, resulting in the scattered light to interfere, which affects the image quality. Therefore, reducing the speckle to enhance image clarity is the goal of the experiment. We use customized fiber, buzzer, and laser speckle reducer to lower speckle contrast. The customized fiber is made by fiber bundle. Each fiber with different lengths. The difference of length is a multiple of the coherence length of the laser light. These three methods the change the mode of the light transmission, thereby reducing the coherent of the laser source. Due to reduce the coherent of the light source, reducing the generation of the speckle. And analysis the image obtained by each method by signal-to-noise ratio and flatness. The result show that the customized fiber obtains the best speckle removal and the most uniform image. Compared to the high speckle contrast image from using single fiber. This method can observe the object clearly. But when we introduce the two fibers into the otoscope, it’s almost without speckle pattern in the image. Base on this reason, we speculate that the special fiber bundle can reduce the spot contrast should be the difference in spatial distribution instead of temporal delay. As the otoscope is the fiber bundle with same length of each fiber. Fibers split one source into multiple light source. Each light source may generate speckle pattern. According to the superposition of all speckle, the spot contrast is lower. Customized fiber, without noise, and more convenient than laser speckle reducer. It can be applied to ultra-slim endoscope developed by us. The application not only provides sufficient brightness but also reduces the problem of speckle. It has the potential to develop into a commodity by improving the stability.
16
Panth, Nisha. « Differential effects of saturated fatty acids of varying chain length on lipid profiles in healthy individuals ». Thesis, 2019. http://hdl.handle.net/1959.13/1406167.
Texte intégralRésumé :
Masters Research - Master of Philosophy (MPhil)Saturated fatty acid (SFA) intake has been linked with increased blood lipid concentrations and increased cardiovascular disease (CVD) risk. Current dietary guidelines consider all SFA as a single group and encourage to reduce saturated fat consumption to 10% of daily energy intake. However, not only the number, position and configuration of double bonds, but also the chain length of SFA have been shown to be a major determinant of their metabolic fate. Short-chain (SCFA, 2-4 carbons long, found in butter and products of fibre and resistant starch fermentation) and medium-chain (MCFAS, 6-12 carbons long, found in coconut and palm kernel oil) are absorbed directly through the villi of the intestinal mucosa and transported to the liver via the portal circulation. In contrast, long-chain (LCSFAS, >12 carbons, found in animal fats and dairy products) follow complex metabolic pathways including chylomicron synthesis in the intestinal villi, secretion into the thoracic lymph, hydrolysis of some triglycerides by lipoprotein lipase into free fatty acids which are transferred to the peripheral tissues (including muscle) followed by chylomicron remnants being taken up into the liver for further metabolism. This, together with the fact that humans spend most of their time in the postprandial state, suggests that saturated fat type may play an important role in overall lipid metabolism and modulation of CVD risk. Therefore, it was hypothesised that consumption of SCFA and MCFAS reduce blood lipid levels compared with LCSFAS. Our first aim, addressed in chapter 3, was to to establish the basis for our hypothesis, conducting systematic review and meta analysis of the literature assessing the differential effects of chain lengths of SFA on blood lipids. The findings from this chapter demonstrate that the consumption of MCFAS enriched diets increased high-density lipoprotein cholesterol (HDL-C) and apolipoprotein A-I (apo A-I) levels compared to LCSFAS diet without any significant effect on triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels. In chapter 4, we aimed to determine if SFA of different chain lengths would differentially influence postprandial lipid levels. In a randomised cross-over design, we investigated the effect of a meal (sweet biscuits) rich in either SCFA or MCFAS or LCSFAS on postprandial lipids (TG, TC, LDL-C, and HDL-C). The results presented in this chapter demonstrate that the postprandial triglyceride response following MCFAS was lower compared to LCSFAS and that predominant fatty acid in the meal is a determinant of the lipemic response. In conclusion, while this study has highlighted the differential effects of chain lengths of SFA on blood lipids. These results draw attention to the evidence that guidelines on SFA must consider the fatty acid chain length and importantly, the diverse SFA containing foods (processed and unprocessed meats, dairy products, eggs, coconut and palm oils, chocolate) that may possess harmful, neutral or even beneficial effects in relation to cardiovascular health.
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« A novel link buffer size and queue length estimation algorithm and its application on bandwidth-varying mobile data networks ». 2012. http://library.cuhk.edu.hk/record=b5549031.
Texte intégralRésumé :
隋著移動數據網絡的迅速發展，世界各地部署著不同制式的3G，HSPA和LTE網絡，這給移動互聯網應用帶來新的機遇和挑戰。不像他們的對手, 有線網絡，移動數據網絡有較長的延遲，較高的包率，以及急劇波動的頻寬。為了應付這些挑戰，移動無線基站往往配備較大的緩衝區（KBs以至數百多MBs），以吸收短期的頻寬波動，並促進鏈路層重傳。然而，由於大部分互聯網協議，並特別是TCP，全都假設路由器只擁有較小緩衝區，所以在移動網絡的大型緩衝區下，往往導致TCP展現出次優的性能。本論文解決兩個根本性的問題來克服這一項挑戰。首先，我們開發了一種新算法 (SoD）專門來估計網絡的鏈路緩衝區的大小和隊列長度。在今天的3G移動數據網絡，本文以大量網絡數據驅動的模擬結果證明 SoD 表現優於現有的算法，如 Max-min 和 Loss-pair。另外，我們採用 SoD算法來創造新的TCP擁塞控制模塊以解決移動網絡的大型緩衝區以及的頻寬波動問題。這個新的TCP變種，稱為 TCP- QA，在模擬情況以及移動數據網絡下均表現出大大優於現有的TCP變種，包括TCP CUBIC ，TCP Vegas，TCP Westwood，和FAST TCP。The rapidly emerging mobile data networks fueled by the world-wide deployment of 3G, HSPA, and LTE networks created new opportunities and challenges for developing mobile Internet applications. Unlike their wired counterpart, mobile data networks are known to exhibit longer delay, higher packet loss rate, and rapidly fluctuating bandwidth. To tackle these challenges mobile radio base stations are often equipped with large buffers (from hundreds of KBs to multi-MBs) to absorb short-term bandwidth fluctuations and to facilitate link-layer retransmissions. However as most Internet protocols in general, and TCP in particular, were designed with the assumption of small router buffer size, the large buffer in mobile networks can and do interact, often negatively, with the Internet protocols, leading to sub-optimal performance. This work tackles two fundamental problems in overcoming this challenge. First, we developed a novel Sum-of-Delays (SoD) algorithm specifically designed to estimate the link buffer size and queue length of bandwidth-varying networks. Extensive trace-driven simulation results showed that SoD outperforms existing algorithms such as max-min and loss-pair by orders of magnitude in today’s 3G mobile data networks. Second, we apply the SoD algorithm to TCP’s congestion control module to incorporate and compensate for the mobile network’s large buffer size. This new TCP variant, called TCP-Queue-length-Adaptive (TCP-QA), substantially outperforms existing TCP variants including TCP CUBIC, TCP Vegas, TCP Westwood, and FAST TCP.
Detailed summary in vernacular field only.
Chan, Chi Fung.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2012.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
Abstract --- p.ii
摘要 --- p.iii
Acknowledgements --- p.iv
Contents --- p.v
Chapter Chapter 1 --- Introduction --- p.1
Chapter Chapter 2 --- Background and Related Work --- p.5
Chapter 2.1 --- Link Buffer Size Estimation --- p.6
Chapter 2.2 --- Queue Length Estimation --- p.8
Chapter 2.3 --- Performance over Fixed Networks --- p.10
Chapter 2.4 --- Performance over Bandwidth-Varying Networks --- p.15
Chapter Chapter 3 --- Sum-Of-Delay Method --- p.19
Chapter Chapter 4 --- Performance Evaluation --- p.22
Chapter 4.1 --- Link Buffer Size Estimation in Fixed Bandwidth Networks --- p.23
Chapter 4.2 --- Link Buffer Size Estimation in Variable Bandwidth Networks --- p.25
Chapter 4.3 --- Queue Length Estimation in Fixed Bandwidth Networks --- p.28
Chapter 4.4 --- Queue Length Estimation in Variable Bandwidth Networks --- p.31
Chapter 4.5 --- Convergence --- p.34
Chapter 4.6 --- Limitations in Passive Estimation --- p.40
Chapter Chapter 5 --- Impact of Competing Traffic --- p.42
Chapter 5.1 --- Simulation Setup --- p.42
Chapter 5.2 --- Link Buffer Size Estimation --- p.44
Chapter 5.3 --- Queue Length Estimation --- p.50
Chapter 5.4 --- Discussions --- p.54
Chapter Chapter 6 --- TCP-Queue-Length-Adaptive (TCP-QA) --- p.56
Chapter 6.1 --- Challenges in Mobile Networks --- p.57
Chapter 6.2 --- Queue-Length-Adaptive Congestion Control --- p.59
Chapter 6.3 --- Performance Comparisons --- p.65
Chapter Chapter 7 --- Summary and Future Work --- p.76
Bibliography --- p.78
18
Bauer, Michael. « Dynamical characterization of Markov processes with varying order ». Master's thesis, 2008. https://monarch.qucosa.de/id/qucosa%3A18013.
Texte intégralRésumé :
Time-delayed actions appear as an essential component of numerous systems especially in evolution processes, natural phenomena, and particular technical applications and are associated with the existence of a memory. Under common conditions, external forces or state dependent parameters modify the length of the delay with time. Consequently, an altered dynamical behavior emerges, whose characterization is compulsory for a deeper understanding of these processes. In this thesis, the well-investigated class of time-homogeneous finite-state Markov processes is utilized to establish a variation of memory length by combining a first-order Markov chain with a memoryless Markov chain of order zero. The fluctuations induce a non-stationary process, which is accomplished for two special cases: a periodic and a random selection of the available Markov chains. For both cases, the Kolmogorov-Sinai entropy as a characteristic property is deduced analytically and compared to numerical approximations to the entropy rate of related symbolic dynamics. The convergences of per-symbol and conditional entropies are examined in order to recognize their behavior when identifying unknown processes. Additionally, the connection from Markov processes with varying memory length to hidden Markov models is illustrated enabling further analysis. Hence, the Kolmogorov-Sinai entropy of hidden Markov chains is calculated by means of Blackwell’s entropy rate involving Blackwell’s measure. These results are used to verify the previous computations.
19
Rastani, Robin Renee. « Effects of varying dry period length on lactation performance, efficiency of production and reproduction, and energy status of dairy cattle ». 2005. http://catalog.hathitrust.org/api/volumes/oclc/65518300.html.
Texte intégral
20
Chou, Te-Hsin, et 周德昕. « Broadband Half-Width Microstrip Leaky-Wave Antenna Array with Shortened Length and Half-Width Microstrip Leaky-Wave Antenna Arrays with Varying-Periodicity Vias to Control the Propagation Characteristics ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/fbcw94.
Texte intégralRésumé :
碩士國立交通大學
電信工程研究所
103
In this thesis, we use the broadband tapered half-width microstrip leaky-wave antenna to be the unit element and design an eight element antenna array. We use the half-width structure to simplify the conventional feeding structure, which is 180°out of phase. In the half-width structure, the PEC wall is constructed by via holes conducting the two metallic layers on substrate. The advantages of this structure are: (I) simple feeding structure fed by microstrip line ; (II) pure mode excitation and no need to suppress mode ; (III) reduced size as compared to the full-width structure ; (IV) less interaction in an array design. Based on the characteristics of the first higher order leaky-mode for the microstrip antenna, this thesis proposes a scheme for the empirical design of half-width microstrip leaky-wave antenna arrays . The measured bandwidth of the antenna has a return loss less than -10 dB from 6.5 GHz to 30 GHz, yielding a relative band width of 4.29 : 1. In this thesis, we also propose a novel coupled-mode scheme for the empirical design of half-width microstrip leaky-wave antenna arrays with varying periodic vias to control the propagation characteristics optimization of bandwidth. Based on the measurement results, we realize a bandwidth of 2 GHz in previously antenna array.
21
McNamee, Jeff. « Accuracy of momentary time sampling a comparison of varying interval lengths using SOFIT / ». 2004. http://www.oregonpdf.org.
Texte intégralRésumé :
Thesis (Ph. D.)--Oregon State University, 2004.Includes bibliographical references (leaves 41-49). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.
22
McNamee, Jeff B. « Accuracy of momentary time sampling : a comparison of varying interval lengths using SOFIT ». Thesis, 2003. http://hdl.handle.net/1957/30142.
Texte intégralRésumé :
The U.S. Department of Health and Human Services has made the promotion
of regular physical activity a national health objective, and experts believe that
physical education can play a significant role in the promotion of physical activity.
Feasible measurement tools to assess physical activity behavior, by physical
educators, are lacking. One validated instrument is the System for Observing Fitness
Instruction Time (SOFIT; McKenzie, Sallis & Nader, 1991). SOFIT's physical
activity data are collected using momentary time sampling (MTS) with a 20-second
interval length and provide estimates of Moderate to Vigorous Physical Activity
(MVPA). Whether variations in interval lengths would adversely affect the accuracy
of the MVPA data has not been investigated. From a clinical perspective, if physical
education teachers are to utilize MTS procedures for on-going assessment they will
require longer time intervals to collect accurate MVPA data. Therefore, this project
sought to determine the accuracy of MVPA levels collected through varying
observation tactics (i.e., 20s, 60s, 90s, 120s, 180s, and random) relative to those
collected through duration recording (DR). Video records of 30 randomly selected
elementary school physical education classes were utilized for this study. Utilizing
modified physical activity codes from SOFIT, the researchers collected MTS data
regarding students' MVPA at varying interval lengths (i.e., 20s, 60, 90s, 120s, 180s,
and random). Three statistical techniques, Pearson-product moment (PPM) correlation
coefficients, Repeated Measures Analysis of Variance (RM ANOVA), and Average
Error (AE), were utilized to demonstrate concurrent validity of the varying interval
lengths. Results demonstrated moderate-low to high correlations between the 20s,
60s, 90s, and random interval lengths and the DR tactic during the total class. The
RM ANOVA indicated similarity between all the varying interval lengths and the DR
tactic for total class observation. The MTS procedure that created the least amount of
AE across classes was the 20s variable followed by the 60s, random, and 90s
variables. These findings build empirical evidence for the use of a 60s, random, and
90s MTS procedure for the purpose of MVPA assessment by physical educators.Graduation date: 2004
23
You, Guan-Lin, et 尤冠霖. « Compaction and Decompaction of DNA by Cationic and Anionic Gemini Surfactants of Varying Spacer Lengths ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/5q5f48.
Texte intégralRésumé :
碩士國立中央大學
化學工程與材料工程學系
104
For an efficient delivey into the nuclei of human cells, the therapeutic DNAs of a gene therapy need to be compacted to protect them from the enzymatic hydrolysis or external chemical/biochemical stresses; the reduced DNA sizes by compaction also facilitate their delivery to the nuclei. On the other hand, decompaction of the compacted DNAs, which restores the DNAs to their native conformations and re-activates the gene expression, is a prerequisite for an effective gene therapy. Conventional cationic and anionic surfactants are often studied for their respective capabilities to compact and de-compact DNAs, with their potential of being a safe non-virus gene delivery system evaluated. Following this research interst, the present study develops a novel DNA compaction/decompaction system based on gemini surfactants. Gemini surfactants are dimers of two conventional surfactant molecules connected with a spacer. Due to this unique molecular structure, gemini surfactants commonly display superior surface activities than their conventional counterparts, with their molecular structure and material properties tunable via modulating the spacer. Here, we synthesize cationic and anionic gemini surfactants of varying spacer lengths to investigate how and why the change in the molecular structures of the gemini surfactants affects their DNA compaction/decompaction efficacy by using UV-vis spectrophotometer, dynamic light scattering, atomic force microscopy, circular dichroism and small-angle x-ray scattering. The gemini surfactants are proven competent in the DNA compact/decompaction, and the gemini surfactants with the 6-carbon long spacer are observed to display higher DNA compaction/decompaction efficiency than the one with the 3-carbon long spacer. The discrepancy in the DNA compaction efficacy might arise from the differences in the ionization degrees of the cationic gemini surfactants and in the self-assembled structures of the DNA-surfactant complexes. For the DNA decompaction, the difference in hydrophobicity and ionization of the anionic gemini surfactants may potentially lead to the difference in efficacy. The present study therefore explains the mechanisms underlying the DNA compaction/decompaction by gemini surfactants in terms of molecular property and supramolecular structure.
24
Chen, Wei-Cheng, et 陳威誠. « Effect of Varying the Alkyl Chain Lengths and Core Structures of Liquid Crystal Molecules on the Formation of Blue Phases ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/t9rx4r.
Texte intégralRésumé :
碩士大同大學
化學工程學系(所)
99
The primary research work of this study is an attempt to correlate the structure-property relationship of the formation of blue phases in chiral liquid crystals in terms of variation of the achiral alkyl chain length (m), chiral alkyl chain length (n), structure of the rigid core, and achiral alkyl chain length (m) without ether linkage in the chiral liquid crystal materials. Thus, the optically active alcohols, 1-ethyloxy-2-propanol, 1-propyloxy-2-propanol, 1-butyloxy-2-propanol, 1-pentyloxy-2-propanol, 1-hexyloxy-2-propanol, were designed and synthesized by reacting (S)-propylene oxide with alkyl alcohols under basic condition. In consequence, three novel homologous series of chiral materials, (R)-6-(1-alkyloxy-2-propyl)naphth-2-yl 4-alkyloxybenzoate, I(m=6-9, n=1-2), (R)-4-(1-alkyloxy-2-propyl)biphenyl 4-alkyloxybenzoate, II(m=6-9, n=1, 4, 5), (R)-4-(1-alkyloxy-2-propyl)biphenyl 4-heptylbenzoate, III(n=1-4), derived from these alcohols were synthesized for the investigation of the effect of the achiral alkyl chain length (m), ether linking group, chiral tail alkyl chain length (n) and rigid core structures on the mesomorphic. The mesomorphic phases and their corresponding transition temperatures were primarily characterized by the microscopic textures and DSC thermograms. The results of compounds I(m, n) composed of the rigid core structure of PhCOONa and chiral group of optical activity 1-ethyloxy-2-propanol and 1-propyloxy-2-propanol, showed that compound I(m=6-9, n=1) and I(m=6, 8, 9, n=2) exhibits the mesophases sequence of N*-Cr., and the compound I(m=7, n=2) exhibits the mesophases sequence of BPII-N*-Cr.. With the exception of I(m=7, n=2) that exists the widest temperature range of enantiotropic BPII phase. The results of compounds II(m=6-9, n=1, 4, 5) composed of the same chiral group but differed in the rigid core structure (PhCOOPhPh) as compounds I(m, n). The compound II(m=8, n=2) exhibits the mesophases sequence of SmA*-Cr., the compound II(m=7, n=5) exhibits the mesophases sequence of BPI-N*-SmA*-Cr., the compound II(m=6-9, n=4) and I(m=8, n=5) exhibits the mesophases sequence of BPII-BPI-N*-SmA*-Cr., The widest temperature range of BP phases for these compounds appeared at II(m=9, n=4). The results of compound III(n=1-4), the composed of the same rigid core structure as compound II(m, n) but differed in the achiral group where a reducible ether linkage is introduced, the compounds III(n=1) exhibit the mesophases sequence of SmA*-Cr., the compounds III(n=2) exhibit the mesophases sequence of BPI-N*-Cr., the compounds III(n=3-4) exhibit the mesophases sequence of BPII-BPI-N*-Cr.. In general, the results of mesomorphic phases show that compounds with the short alkyl lengths (n=1-2) at chiral groups generally suppress the formation of BP phase, however, compounds with longer length (n=3-5) enhance the thermal stability of BP phase. The results also show that, when the rigid core structures of the molecules change from PhCOONa to PhCOOPhPh, the clear point is increased and the stability of blue phase is also increased. Moreover, when extending the alkyl length (m) of achiral tail, the clear point is increased but the thermal stability of blue phase display no significant difference. Compounds having achiral group without ether linkage between the core display lower clear point, and lower the thermal stability of blue phase as compared to the compounds having ether linkage between the core and achiral alkyl chain. Among these three series of chiral compounds, compound II(m=9, n=4) has the widest BP phase temperature range (cal. 3.9℃), where BPI and BPII formed.