105 research outputs found
Comparison of computations with Boussinesq-like models and laboratory measurements
No full textIt is already known for a long time that one of the major discrepancies between computations with Boussinesq-like models and measurements, is due to the inaccurate representation of the linear frequency dispersion in the Boussinesq-like long wave models. A comparison of various models as given in Dingemans (1973) showed already large differences between the frequency dispersion of various models. A comparison with measurements in a flume (Dingemans, 1976) showed that the computed wave profiles were also found in the measurements, but at a different location. This was ascribed to the inaccurate frequency dispersion
Boussinesq modelling with higher-order dispersion; derivation and numerical modelling
No full textIn this thesis the modelling of water wave propagation over uneven bottoms using Boussinesq-like models with higher-order frequency dispersion is studied. Boussinesq-like equations describe the propagation of weakly non-linear shallow water waves. As for long waves the depth-dependence of the velocity field is almost absent, the vertical coordinate z has been removed in deriving Boussinesq-like models. A problem with Boussinesq-like models which were in use some time ago, is that they do not have particularly good frequency dispersion characteristics, especially not at depths where practical problems had to be solved. Therefore, many efforts have been spent to improve the dispersion characteristics. Dingemans (1994b) has started with a higher-order dispersion relation written in the form of a rational polynomial as obtained by Schaffer and Madsen (1994). Using operator correspondence four different Boussinesq-like models with only third and lower derivatives can be derived for horizontal bottom. Uneven bottom terms can be obtained with some mathematical operations. In this manner a total number of 48 different models is obtained each with four degrees of freedom. By comparing the linear shoaling coefficient with the exact linear shoaling coefficient the degrees of freedom are optimized. It turned out that 24 models have exactly the same linear shoaling coefficient, which is very accurate up to kh=5. However, the models (may) differ in higher-order shoaling behaviour. The higher-order shoaling is invesitigated by solving the models numerically using the Keller's Box compact difference scheme. This scheme is implicit and therefore unconditionally stable and it has a second-order accuracy. The procedure is to rewrite the set of two third-order partial differential equations to a set of six first-order partial differential equations by introducing four more variables. The system of linear finite difference equations has block-diagonal structure, which fits in a 17 diagonal matrix and is solved by a Thomas algorithm. Subsequently, a weakly reflecting boundary condition is formulated by the Sommerfeld radiation condition for the classical shallow water equations together with a sponge layer resulting in a reflection coefficient of 0(10-3). The numerical models are validated against the measurements used in the intercomparison study of Dingemans (1994a). It turned out that the best correspondence with measurements is obtained by four models with essentially the same accuracy. It is concluded that the new Boussinesq-like equations with higher-order dispersion has increased the applicability of Boussinesq modelling for wave propagation over uneven bottoms and that Keller's Box method is a very suitable method for integrating Boussinesqlike equations.Hydraulic EngineeringCivil Engineering and Geoscience
Innovations in optimizing treatment of non-small cell lung cancer with EGFR targeted tyrosine kinase inhibitors: Exploring clinical practice and plasma
No full textIn this thesis we searched for innovations in optimizing treatment of NSCLC with EGFR-TKI, which is started by the introduction in Chapter 1. In Chapter 2 we describe the results of the randomized phase III NVALT18 trial in patients with EGFR-WT non-squamous NSCLC. The detrimental effect of the combination of docetaxel and intercalated erlotinib was evident with shorter PFS (1.9 vs 4.0 months, p=0.01) as well as OS (4.7 vs 10.6 months, pThe exploration of the toxic limit of the 3rd generation EGFR-TKI osimertinib in patients with EGFR-mutated NSCLC is found in Chapter 3. The correlation between osimertinib exposure (defined as clearance) and severe toxicity, as well as the exposure-efficacy relationship were investigated. Osimertinib clearance (exposure) was significantly correlated with severe toxicity in multivariate competing risk analysis (HR 0.91, 95% CI 0.83-0.99), with an optimal toxic limit of 259 ng/mL determined by ROC curve. The results of chemotherapy regimens after progression on EGFR-TKI in patients with EGFR-mutated NSCLC are presented in Chapter 4. In this retrospective study patients do benefit substantially from chemotherapy after progression on EGFR-TKI, albeit shorter than the duration of response of first line targeted therapy. In Chapter 5 plasma ddPCR (Biorad) and NGS (Oncomine cfDNA lung assay v1) are compared to tissue NGS results in patients with EGFR-mutated NSCLC. The plasma results showed high agreement on the level of a specific mutation like p.T790M and p.L858R, but NGS provides a broader coverage and is therefore able to detect more different driver mutations. Concordance of plasma with tissue is high. In Chapter 6 we searched for targetable mutations in a population with suspected metastasized lung cancer when molecular analysis of tissue was not feasible. A possible target for treatment was detected in 7 out of 55 patients. Although the coverage of the Oncomine V1 panel was a limiting factor in the ability to detect all possible targets for treatment which are expanding rapidly, we still were able to identify patients with a possibility of targeted treatment who were otherwise not detected. Chapter 7 outlines the course of mutations in cfDNA upon start of targeted therapy, and identifies predictive features in plasma during treatment with EGFR-TKI in patients with EGFR-mutated NSCLC. Plasma clearance of the primary EGFR mutation, and of p.T790M when applicable, after 6 and 12 weeks of therapy was evaluated. The absence of this so called plasma conversion correlated with a shorter PFS (5.5 vs 17.0 months, p=0.002) and OS (14.0 vs 25.5 months, p=0.003). In Chapter 8 the summary, general discussion and future perspectives are presented
Azomethine-based Donor Materials for Organic Solar Cells
No full textSolution processable organic photovoltaics (OPVs) are attracting much attention because of their anticipated advantages such as low cost, flexibility, lightweight, and the potential to be produced on a large scale. The photoactive layer of OPVs consists of a blend of an electron donating and an electron accepting material. Over the last 20 years, a plethora of (record breaking) electron?donating materials have been reported, which are mostly synthesized via transition metal mediated aryl?aryl coupling reactions. These chemistries, however, make use of expensive metal catalysts, inert reaction conditions and require time?consuming product purification steps. In order to offer a more economic route towards OPVs we have explored novel conjugated azomethine?based (–N=CH–) donor materials and the initial results are presented in this thesis. The azomethine bond is isoelectronic to the vinyl bond (–CH=CH–) and displays similar optoelectronic and thermal properties. In addition, azomethines offer significant advantages over vinylenes as they can be prepared using Schiff base condensation chemistry under near ambient reaction conditions. Expensive catalysts are not required and water is the only by?product. The main objective of this research is to explore the use of azomethine?based donor materials in bulk heterojunction solar cells. The design and synthesis of azomethine?based polymers, (hyper?branched) oligomers, small?molecules (both linear and star?shaped) and their performance in photovoltaic devices will be presented in this thesis.Aerospace Structures and MaterialsAerospace Engineerin
Design and Properties of SWCNT-Polyetherimide Nanocomposites
No full textThe main objective of the research presented in the thesis is to explore non-functionalized single-walled carbon nanotubes (SWCNTs) as reinforcing nanofiller in all-aromatic thermoplastic poly(etherimide)s. The role of polymer geometry and how this affects the morphological and thermo-mechanical properties of the SWCNT-PEI nanocomposites were investigated. The inclusion of SWCNTs in aBPDA-P3, an amorphous non-linear polyetherimide matrix had no effect on the morphology and thermo-mechanical properties of the matrix. In ODPA-P3, a more linear amorphous polyetherimide matrix, the SWCNTs act as a nucleating agent with the polymer crystallinity increasing linearly with SWCNT content to 45% (at 2.4 vol.% SWCNT). TEM measurements showed that the SWCNTs become embedded within the crystal lattice of the polymer matrix. The result is a significant increase in thermo-mechanical properties; the storage modulus (E’) above Tg increased by a factor 105 GPa and the elastic modulus from stress-strain measurements increased with a reinforcement efficiency (dY/dVf) of 170 GPa. Our findings show that the polyetherimide backbone geometry determines whether the polymer is good host for SWCNTs. To investigate the role of polymer morphology on the final nanocomposite properties, we compared SWCNT nanocomposites based on amorphous ODPA-P3 with that of a semi-crystalline BPDA-P3. In semi-crystalline BPDA-P3, the SWCNTs were found to exist within the amorphous domains of the BPDA-P3 matrix. Using the Halpin-Tsai equation, the effective SWCNT modulus was found to be ~100 GPa which is significantly lower than the 640 GPa obtained for ODPA-P3 SWCNT. By application of an isothermal step above the Tm of the nanocomposites during imidization, the conversion of the crystalline ordering around the CNT to an amorphous morphology in ODPA-P3 results in a significant reduction in the reinforcement efficiency, i.e. from 170 GPa to 30 GPa. The reinforcement efficiency for semi-crystalline and amorphous BPDA-P3 nanocomposites remains constant at 30 GPa. By comparing reinforcement efficiencies of ODPA-P3 with SWCNTs residing in contrasting morphologies, we have shown that having a crystalline-SWCNT interface is critical in obtaining nanocomposites with improved thermo-mechanical performance over the neat polymer. We have also compared ODPA-P3 nanocomposites based on 0-D fullerenes (C60) with 1-D SWCNTs. The inclusion of C60 in ODPA-P3 induces crystallization (40% at 0.6 vol.%) of the polymer matrix. At 40% crystallinity, the E’ above Tg in ODPA-P3 C60 is a mere 0.01 GPa, which is substantially lower than the 1.2 GPa observed in the ODPA-P3 SWCNT nanocomposite. By comparing mechanical property improvements as a function of crystal content in the matrix, the elastic modulus of nanocomposites with 100% crystal content could be calculated and was found to be 5.8 GPa for ODPA-P3 C60 and 10.4 GPa for ODPA-P3 SWCNT. The presence of the cylindrical crystalline coating around the CNT was found to aid in stress-transfer from the matrix to the SWCNTs.Novel Aerospace MaterialsAerospace Engineerin
Disciple among the Disciples. :A Biblical Model for Preaching
No full textABSTRACT: Disciple among the Disciples. A Biblical Model for Preaching In this article the author discusses the differences between Roman Catholic and Protestant homiletics in the Netherlands. First he assesses a quite old book written by Ernst Henau which is one of the few books about preaching from a Catholic perspective. Henau suggests that preaching from the Bible is not really possible, because the Scriptures are too difficult to understand and Catholic ministers are too often not capable of interpreting Scripture. Next the author of the article reflects about Dingemans’ book, the most important Dutch handbook of protestant preaching. Dingemans argues that protestant preaching was too often focused on a one-way communication. Dingemans delineates several models of preaching and criticizes all of them, because the minister is too often only the teacher and his audience is too often only the listeners. Dingemans wants to correct this one way model and argues that the preacher has to become also one of the listeners among other listeners. Because there is very few Catholic homiletic literature, this Protestant handbook is often used at Catholic seminaries and theology departments. Dingemans’ viewpoint, however, is not very relevant for Catholic preachers. They are usually already quite attuned to their audiences and probably should rather devote more attention to the content of their sermons especially by studying the Bible more. The author of the article presents Luke 24:13-35 as an alternative model for Catholic and Protestant preachers. The minister is invited to follow the footsteps of Jesus by becoming a disciple among the disciples. That may eventually make the preacher a real teache
Liquid Crystal Sulfonated Aramids as Proton Exchange Membranes for Fuel Cell Applications
No full textTwo sulfonated aramids, poly(2,2’-disulfonylbenzidine terephthalamide) (PBDT) and poly(2,2’-disulfonylbenzidine isophthalamide) (PBDI) were synthesized with the aim to explore their unique morphology for proton exchange membrane applications. Due to the different polymer structures, PBDT forms a nematic liquid crystal, whereas PBDI is isotropic. Both polymers show excellent thermal stabilities (Td5% > 400 oC), high storage moduli (E’ = 3 – 15 GPa) and crosslinked films are flexible and easy to handle. Pulsed-field-gradient NMR diffusometry reveals that the in-plane water diffusion in the nematic PBDT membrane is as high as 3.3x10-10 m2/s, whereas the diffusion in amorphous PBDI is only 2.5x10-10 m2/s. Whereas neat and crosslinked PBDI shows isotropic diffusion, neat PBDT shows a high diffusion anisotropy (D?/D? = 3.0), which increases as a function of crosslink density (D?/D? = 4.6 at 80% crosslinking). This diffusion anisotropy is substantially higher than that typically observed for low molecular weight liquid crystals and for oriented polymeric conductors such as Nafion® (D?/D? ~ 2.0). The nematic order in the PBDT membrane also promotes directed ionic conductivity, i.e. Na+ conductivity in PBDT is 2.24 x 10-2 S/cm and 1.67 x 10-2 S/cm for PBDI, respectively. We propose that the rigid-rod PBDT chains form nano-scale hydrophilic channels, which act as pathways for transporting water molecules and ions.Aerospace Structures and MaterialsAerospace Engineerin
Hamiltonian Formulation of Water Waves: 1D-formulation, numerical evaluations and examples
No full textThis report describes the formulation, numerical implementation and application of a weakly nonlinear wave model for finite depth based on a Hamiltonian formulation (see Radder, 1992). Due to the type of non-linearity explicitly accounted for in the expansion of the kernel of the Hamiltonian density (sum of kinetic and potential energy per unit surface area), the model is valid for waves of small, but finite amplitude and fairly long wave length (compared to the water depth) in roughly the same sense many 'Boussinesq-type' models are. There are, however, a few significant differences. Firstly, the Hamiltonian density in the present formulation is always positive definite: a condition necessary to ensure good dynamical behavior of the model equations for numerical computation. Secondly, the dispersion equation obtained from the linearized version of the equations is exact. This property results in a better modelling of the phase relations (hence the wave asymmetry at a given location) of the superharmonic field which evolves from the primary wave system due to surface non-linearity. More importantly, it is possible to remove the restriction of waves being long through a proper inclusion of the 'short-wave' non-linearity in the expansion of the kernel. This results in a uniformly valid model unlike most of the weakly nonlinear models which are valid over either deep or shallow water. Further, it is discussed in the text that even for long waves the 'short-wave' non-linearity becomes locally important near the crest of a wave as the surface curvature increases. Implementation of 'short-wave' non-linearity is therefore considered as one of the first priorities i n the future developments of the model. Two numerical models have been developed: a time-domain model and a pseudo-spectral model based on the sinc-series for the global approximations. The numerical code based on the sinc-series requires less computing time and gives the option of choosing higher-order interpolation for computing derivatives and integrals over local intervals. An incident train of sinusoidal waves has been represented in the computation by a packet of sinusoidal waves of finite length with the leading edge a few wave-lengths behind the bar. Details of the geometry and significance of this test can be found in chapter 7. In spite of a practical disadvantage due to the way the input conditions must be specified in the code (we have an initial-value problem) these models can now be used to study nonlinear evolutions of non-breaking waves over varying depth. Attempts to introduce effects of wave breaking have not met with much success yet. In the first phase, an integral criterion has been implemented to determine if the instantaneous surface shape should lead to breaking. Application of the criterion to computed surface elevation for conditions observed to have given rise to mild breaking in laboratory tests shows that breaking stage is not reached. It is believed that this difference between the computed results and the laboratory observations is caused by the omission of the 'short-wave' non-linearity (under prediction of the surface steepness), rather than the failure of the integral criterion. This is another aspect which underscores the importance of implementation of 'short-wave' non-linearity. Finally to conclude, comparison of the computed results with the experimental measurements and in a wider context with several 'Boussinesq-type' models (see Dingemans, 1994a) provides strong motivation for further developments of the model. This is further supported by the inherent theoretical appeal of the formulations used. As summarized in chapter 9, the major recommendations for future work are: \u95 The formulation of a boundary-value problem instead of an initial-value problem. This greatly enhances the practical usefulness of the program. \u95 Inclusion of short-wave non-linearity. For applicability over the full range of deep to shallow water of a nonlinear wave model, inclusion of short-wave non-linearity is needed. Furthermore, it has been shown that for wave breaking also the inclusion of short-wave nonlinearity is needed to obtain more realistic breaker indices. \u95 Further study of wave breaking characteristics after inclusion of short-wave non-linearity. \u95 Effect of steeper bottom slopes on the wave behavior
Reactiesnelheid van zuurstof met oplossingen van hydrochinon en van metol
No full textApplied Science
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