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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
431

Development and Optimization of Novel Emulsion Liquid Membranes Stabilized by Non-Newtonian Conversion in Taylor-Couette Flow for Extraction of Selected Organic and Metallic Contaminants

Park, Yonggyun 19 May 2006 (has links)
Extraction processes employing emulsion liquid membranes (ELMs), water-in-oil emulsions dispersed in aqueous phase, have been shown to be highly efficient in removing a variety of organic and inorganic contaminants from industrial wastewaters. As a result, they have been considered as alternative technologies to other more common separation processes such as pressure-driven membrane processes. Unfortunately, a widespread use of the ELM process has been limited due to the instability of emulsion globules against fluid shear. Breakup of emulsions and subsequent release of the internal receptor phase to the external donor phase would nullify the extraction process. Numerous studies have been, therefore, made in the past to enhance the stability of ELMs. Examples include adding more surfactants into the membrane phase and increasing the membrane viscosity. However, increased stability has been unfortunately accompanied by loss in extraction efficiency and rate in most reported attempts. The primary objective of this research is to apply the ELMs in a unique contacting device, a Taylor-Couette column, which provides a relatively low and uniform fluid shear that helps maintaining the stability of emulsion without compromising the extraction efficiency of a target compound. The ELM used in this study is made of membrane phase converted into non-Newtonian fluid by polymer addition, which provides additional uncommon remedy for the problem. This innovative ELM process was optimized to treat various types of simulated industrial wastewaters containing selected phenolic compounds and heavy metals. Experiments performed in this study suggested that the newly developed ELM process achieved exceptionally high overall removal efficiencies for the removal of these target compounds in relatively short contact time. Mechanistic predictive models were further developed and verified with the experimental data. Combined with the experimental data and novel mathematical predictive models, this study is expected to have a high impact on immediate practices of emulsion liquid membrane technologies in relevant industries.
432

Policy interia hypothesis or unobserved variable hypothesis in Taiwan¡¦s Interest-rate rule?

Shiu, Kai-hung 29 June 2011 (has links)
This paper adopts an modle with endogenous variable to investigates policy inertia hypothesis or unobserved variable hypothesis in Taiwan¡¦s interest-rate rule 1981- 2010. Empirical result suggests that both policy inertia and omitted variable hypothesis are important in monetary policy in Taiwan,which is consistent with that of Gerlach- Kristen (2004).
433

The Taylor Rule ¢w Research of Monetary Policy: A Case for Asia Pacific Countries

Sheng, Yao-Ping 21 July 2011 (has links)
This paper investigates whether the ¡§Taylor rule¡¨ can appropriately describe the Central Bank¡¥s monetary policy in Asia-Pacific countries. The countries under consideration were export-oriented countries that adopted floating exchange rate system, and affected by the Asian financial crisis. They include Taiwan, Korea, Philippines, Thailand, Indonesia, Japan, Singapore. In addition we divide the sample period into two sub period based on the mid-1997 outbreak of the Asian financial crisis, to check the robustness of our results from the whole period. Furthermore, we investigate that the central bank cares for the quarterly inflation, or annual inflation. The results over the whole period showed that the Taylor rule describe Central Bank¡¥s monetary policy except for Thailand, Japan and Singapore. The Taylor rule can not describe Japan's monetary policy when the period before Asian financial crisis is adopted. Besides, in addition to Thailand, the central banks concerned quarterly inflation rates than annual inflation rates.
434

Simultaneous and instantaneous measurement of velocity and density in rayleigh-taylor mixing layers

Kraft, Wayne Neal 15 May 2009 (has links)
There are two coupled primary objectives for this study of buoyancy-driven turbulence. The first objective is to create a new diagnostic for collection of measurements to capture the physics of Rayleigh-Taylor (RT) mixing. The second objective is to use the new diagnostic to specifically elucidate the physics of large Atwood number, ( )( )2 1 2 1 / ρ ρ ρ ρ + − = t A , RT mixing. Both of these objectives have been satisfied through the development of a new hot-wire diagnostic to study buoyancy-driven turbulence in a statistically steady gas channel of helium and air ( 6 . 0 03 . 0 ≤ ≤ t A ). The capability of the diagnostic to simultaneously and instantaneously measure turbulent velocity and density fluctuations allows for a unique investigation into the dynamics of Rayleigh-Taylor mixing layers at large At, through measurements of turbulence and mixing statistics. The new hot-wire diagnostic uses temperature as a fluid marker for helium and air, which is possible due to the Lewis number ~ 1 (Le = ratio of thermal diffusivity to mass diffusivity) for helium and air, and the new diagnostic has been validated in an At = 0.03 mixing layer. The energy density spectrum of v′ ′ ρ , measured experimentally for the first time in RT mixing, is found to closely follow the energy distribution of v′ , up to the Reynolds numbers investigated ( ( ) mix t h gA h υ 6 2 Re 2 / 3 = ~ 1450). Large At experiments, with At = 0.6, have also been achieved for the first time in a miscible RT mixing layer. An asymmetric penetration of the bubbles (rising fluid) and spikes (falling fluid) has been observed, resulting in measured self similar growth parameters αb = 0.060 and αs = 0.088 for the bubbles and spikes, respectively. The first experimental measurements of turbulent velocity and density fluctuations for the large At case, show a strong similarity to lower At behaviors when normalized. However conditional statistics, which separate the bubble (light fluid) and spike (heavy fluid) dynamics, has highlighted differences in v′ ′ ρ and rms v′ in the bubbles and spikes. Larger values of v′ ′ ρ and rms v′ were found in the downward falling spikes, which is consistent with the larger growth rates and momentum of the spikes compared to the bubbles. These conditional statistics are a first in RT driven turbulence.
435

Experimental and Numerical Study of Molecular Mixing Dynamics in Rayleigh- Taylor Unstable Flows

Mueschke, Nicholas J. 16 January 2010 (has links)
Experiments and simulations were performed to examine the complex processes that occur in Rayleigh�Taylor driven mixing. A water channel facility was used to examine a buoyancy-driven Rayleigh�Taylor mixing layer. Measurements of �uctuating den- sity statistics and the molecular mixing parameter were made for Pr = 7 (hot/cold water) and Sc 103 (salt/fresh water) cases. For the hot/cold water case, a high- resolution thermocouple was used to measure instantaneous temperature values that were related to the density �eld via an equation of state. For the Sc 103 case, the degree of molecular mixing was measured by monitoring a di�usion-limited chemical reaction between the two �uid streams. The degree of molecular mixing was quanti- �ed by developing a new mathematical relationship between the amount of chemical product formed and the density variance 02. Comparisons between the Sc = 7 and Sc 103 cases are used to elucidate the dependence of on the Schmidt number. To further examine the turbulent mixing processes, a direct numerical simu- lation (DNS) model of the Sc = 7 water channel experiment was constructed to provide statistics that could not be experimentally measured. To determine the key physical mechanisms that in�uence the growth of turbulent Rayleigh�Taylor mixing layers, the budgets of the exact mean mass fraction em1, turbulent kinetic energy fE00, turbulent kinetic energy dissipation rate e 00, mass fraction variance gm002 1 , and mass fraction variance dissipation rate f 00 equations were examined. The budgets of the unclosed turbulent transport equations were used to quantitatively assess the relative magnitudes of di�erent production, dissipation, transport, and mixing processes. Finally, three-equation (fE00-e 00-gm002 1 ) and four-equation (fE00-e 00-gm002 1 -f 00) turbulent mixing models were developed and calibrated to predict the degree of molecular mix- ing within a Rayleigh�Taylor mixing layer. The DNS data sets were used to assess the validity of and calibrate the turbulent viscosity, gradient-di�usion, and scale- similarity closures a priori. The modeled transport equations were implemented in a one-dimensional numerical simulation code and were shown to accurately reproduce the experimental and DNS results a posteriori. The calibrated model parameters from the Sc = 7 case were used as the starting point for determining the appropri- ate model constants for the mass fraction variance gm002 1 transport equation for the Sc 103 case.
436

A recursive formula for computing Taylor polynomial of quantile

Kuo, Chiu-huang 28 June 2004 (has links)
This paper presents a simple recursive formula to compute the Taylor polynomial of quantile for a continuous random variable. It is very easy to implement the formula in standard symbolic programming system, for example Mathematica (Wolfram, 2003). Applications of the formula to standard normal distribution and to the generation of random variables for continuous distribution with bounded support are illustrated.
437

D-optimal designs for combined polynomial and trigonometric regression on a partial circle

Li, Chin-Han 30 June 2005 (has links)
Consider the D-optimal designs for a combined polynomial of degree d and trigonometric of order m regression on a partial circle [see Graybill (1976), p. 324]. It is shown that the structure of the optimal design depends only on the length of the design interval and that the support points are analytic functions of this parameter. Moreover, the Taylor expansion of the optimal support points can be determined efficiently by a recursive procedure.
438

Two essays on monetary policy under the Taylor rule

Suh, Jeong Eui 01 November 2005 (has links)
In this dissertation, two questions concerning monetary policy under the Taylor rule have been addressed. The first question is on, under the Taylor rule, whether a central bank should be responsible for both bank supervision and monetary policy or whether the two tasks should be exercised by separate institutions. This is the main focus of Chapter I. The second question is on whether the Taylor rule plays an important role in explaining modern business cycles in the United States. The second question has been covered by Chapter II. The implications of the first chapter can be summarized as follows: (i) it is inevitable for the central bank to have a systematic error in conducting monetary policy when the central bank does not have a bank supervisory role; (ii) without a bank supervisory role, the effectiveness of monetary policy cannot be guaranteed; (iii) because of the existence of conflict of interests, giving a bank supervisory role to the central bank does not guarantee the effectiveness of monetary policy, either; (iv) the way of setting up another government agency, bank regulator, and making the central bank and the regulator cooperate each other does not guarantee the effectiveness of monetary policy because, in this way, the systematic error in conducting monetary policy cannot be eliminated; (v) in the view of social welfare, not in the view of the effectiveness of monetary policy, it is better for the central bank to keep the whole responsibility or at least a partial responsibility on bank supervision. In the second chapter, we examined the effect of a technology shock and a money shock in the context of an RBC model incorporating the Taylor rule as the Fed??s monetary policy. One thing significantly different from other researches on this topic is the way the Taylor rule is introduced in the model. In this chapter, the Taylor rule is introduced by considering the relationship among the Fisher equation, Euler equation and the Taylor rule explicitly in the dynamic system of the relevant RBC model. With this approach, it has been shown that, even in a flexible-price environment, the two major failures in RBC models with money can be resolved. Under the Taylor rule, the correlation between output and inflation appears to be positive and the response of our model economy to a shock is persistent. Furthermore, the possibility of an existing liquidity effect is found. These results imply that the Taylor rule does play a key role in explaining business cycles in the United States.
439

The One and the Many: A Reconstruction and Critique of Charles Taylor¡¦s Political Philosophy

Hsu, Chia-hao 11 September 2008 (has links)
The purpose of this thesis is to investigate the often-ignored inherent philosophical connection between Charles Taylor¡¦s ontological argument (philosophical anthropology) and his political scheme. Taylor articulates a moral realist understanding of the plurality of values and an ontological statement of human agency, and tries to demostrate a possibility of reconciliation between essentially conflicting values and cultures. In Taylor¡¦s view, ¡§the many¡¨ does not necessarily entail tragical choices among values, as Isaiah Berlin famously asserted, but can be possibly mediated through the common human agency with the hope that we can eventually reach one true consensus. Based on this uniquely Taylorian understanding of human condition, Taylor¡¦s political scheme can be seen as an effort to ameliorate the deep-rooted malaise within Western modernity, and find a common ontological ground among community members and citizens by which deliberations can be facilitated. The thesis will go on to examine Taylor¡¦s two most inspiring political assertions, namely, the polilics of recognition and civic humanism, in detail. I will argue that although Taylor optimistically believes that a common moral and cultural understanding can help forming and be transformed into a common political common good within a given community, the connection between these two levels of commonality is fairly weak. Moreover, what liberals object is precisely Taylor¡¦s attempt to equate cultural common understanding with a form of political common good.
440

Gas gun studies of armature-rail interface wear effects

Jackson, Tyler Andrew 18 November 2010 (has links)
The objective of this work has been to investigate the applicability of the gas gun to study the armature-rail interface wear characteristics relevant to rail gun operations. The approach involved developing constitutive models for armature materials (aluminum 6061) as well as oxygen-free high-thermal conductivity copper as the rail material. Taylor rod-on-anvil impact experiments were performed to validate the accuracy of constitutive strength models by correlating predictions of dynamic simulations in ANSYS AUTODYN with experimental observations. An optical comparator was used to discretize the cross sectional deformation profile of each rod-shaped sample. Parameters of the Johnson-Cook strength model were adjusted for each material to match deformation profiles obtained from simulations with profiles obtained from impact experiments. The fitted Johnson-Cook model parameters for each material were able to give overall deformed length and diameter values within 2% of the experimentally observed data. Additional simulations were then used with the validated strength model parameters to design the geometry involving cylindrical rods of armature material accelerated through a concentric cylindrical extrusion die made of copper, to emulate the interface wear effects produced in a rail gun operation. Experiments were conducted using this geometry and employing both the 7.62mm and 80mm diameter gas guns. Microstructural analysis was conducted on interfaces of the recovered samples from both designs. Hardness measurements were also performed along the interface layer to evaluate the structure formation due to solid-state wear or melt formation. The stress and strain conditions resulting in the observed microstructural effects were correlated with predictions from numerical simulations performed using the validated material models. The overall results illustrate that the stress-strain conditions produced during acceleration of Al through hollow concentric copper extrusion die, result in interface deformation and wear characteristics that are influenced by velocity. At velocities (less than 800m/s), interface wear leads to formation of layer dominated by solid-state alloying of Cu and Al, while higher velocities produce a melted and re-solidified aluminum layer. Hence, use of different armature (Al-based) and rail (Cu-based) materials can be evaluated with the gas-gun set-up employed in the current work to study the effects of interface wear ranging from formation melt layer to solid-state alloying as a function of material properties and velocity.

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