Optimized sixth-order monotonicity-preserving scheme by nonlinear spectral analysis

In this paper, sixth-order monotonicity-preserving optimized scheme (OMP6) for the numerical solution of conservation laws is developed on the basis of the dispersion and dissipation optimization and monotonicity-preserving technique. The nonlinear spectral analysis method is developed and is used for the purpose of minimizing the dispersion errors and controlling the dissipation errors. The new scheme (OMP6) is simple in expression and is easy for use in CFD codes. The suitability and accuracy of this new scheme have been tested through a set of one-dimensional, two-dimensional, and three-dimensional tests, including the one-dimensional Shu-Osher problem, the two-dimensional double Mach reflection, and the Rayleigh-Taylor instability problem, and the three-dimensional direct numerical simulation of decaying compressible isotropic turbulence. All numerical tests show that the new scheme has robust shock capturing capability and high resolution for the small-scale waves due to fewer numerical dispersion and dissipation errors. Moreover, the new scheme has higher computational efficiency than the well-used WENO schemes

c-axis preferential orientation of hydroxyapatite accounts for the high wear resistance of the teeth of black carp (Mylopharyngodon piceus)

Biological armors such as mollusk shells have long been recognized and studied for their values in inspiring novel designs of engineering materials with higher toughness and strength. However, no material is invincible and biological armors also have their rivals. In this paper, our attention is focused on the teeth of black carp (Mylopharyngodon piceus) which is a predator of shelled mollusks like snails and mussels. Nanoscratching test on the enameloid, the outermost layer of the teeth, indicates that the natural occlusal surface (OS) has much higher wear resistance compared to the other sections. Subsequent X-ray diffraction analysis reveals that the hydroxyapatite (HAp) crystallites in the vicinity of OS possess c-axis preferential orientation. The superior wear resistance of black carp teeth is attributed to the c-axis preferential orientation of HAp near the OS since the (001) surface of HAp crystal, which is perpendicular to the c-axis, exhibits much better wear resistance compared to the other surfaces as demonstrated by the molecular dynamics simulation. Our results not only shed light on the origin of the good wear resistance exhibited by the black carp teeth but are of great value to the design of engineering materials with better abrasion resistance

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

Culture complex, Westerpark, Amsterdam

A design method of combining bottom-up and top-down ideas, realizing a culture complex building.Architectural EngineeringArchitectureArchitecture and The Built Environmen

Capacitive Sensor Interface Using an Inverter-Based Period Modulator

This thesis discusses the basic principles, circuit implementation and measurements of an inverter-based capacitive-sensor interface based on period modulation. The interface employs an inverter-based OTA and comparator to increase the current efficiency. Moreover, it applies new circuit techniques to reduce the die size and to reduce noise. A prototype interface has been implemented in a 0.16 ?m CMOS process to prove these concepts. The measurement results show that it can achieve more than 10 bit resolution consuming 14 ?A from a 1 V supply. The die size and energy efficiency have improved by more than an order-of-magnitude compared to previous interfaces based on period modulation.MicroElectronicsMicro-electronics and Computer EngineeringElectrical Engineering, Mathematics and Computer Scienc

Formation of Methane and Carbon Dioxide Hydrates in Bulk and in Porous Media

Gashydraatvorming is een kristallisatieproces. Dit proces bestaat uit twee fases, respectievelijk nucleatie (de vorming van nucleatie kernen) en hydraatgroei (degroei van kleine nucleatiekernen tot grote hydraatkristallen). Deze twee fases van het kristallisatieproces worden in het binaire systeem gekenmerkt door de nucleatietijd en de halfwaardetijd. De resultaten laten een afname zien in nucleatietijd naar mate oververzadiging en roersnelheid toenemen. Bovendien vermindert de nucleatietijd als gevolg van het geheugeneffect wanneer de experimenten worden uitgevoerd met `gebruikt' water. Dit geheugeneffect is beschreven door andere auteurs [98, 149] en kan worden verklaard door het bestaan van (water) hydraatstructuren na dissociatie van gashydraten. De structurering van de water-moleculen is waarschijnlijk gewaarborgd door de overvloed aan waterstofbruggen in de waterfase bij lage temperaturen door de aanwezigheid van opgeloste gastmoleculen. De tweede fase, de daadwerkelijke groei van gashydraten, bleek ongevoelig te zijn voor veranderingen in de mate van oververzadiging. De groei neemt toe met een verhoging van de roersnelheid; echter, het geheugeneffect van water heeft een licht negatief effect op de groei van het gashydraat. Daarom is niet nucleatie, maar kristalgroei de snelheidslimiterende stap tijdens gashydraatvorming. Uit experimenten in het binaire systeem bleek ook, dat, bij gelijke mate van oververzadiging, de kristalgroei van CO2 hydraten sneller is dan van CH4 hydraten. Dit wijst er op dat, kinetisch gezien, de vorming van CO2 hydraten gunsitiger is dan de vorming van CH4 hydraten. Bevindingen resulterend van experimenten in het ternaire systeem ondersteunen deze theorie. In het ternaire systeem blijken bij iedere geteste initiele druk CO2 moleculen makkelijker te vangen in kooien van watermoleculen dan CH4 moleculen (Hoofdstuk 4). Ondanks dat de CH4 concentratie in de gevormde gashydraten toeneemt met de initiele druk, bevatten de ontstane gashydraten nog steeds meer CO2 dan CH4. De formatie van methaanhydraat bij lage druk (lager dan de evenwichtsdruk van de H - Lw - V curve voor het CH4 + H2O systeem) wordt bevestigd. Dit betekent dat de aanwezigheid van een `makkelijkere' gashydraatvormer, zoals CO2, er voor kan zorgen dat de CH4 hydraat wordt gestabiliseerd. Experimenten, waarbij van een gasmix van 50/50 CH4/CO2 gashydraten worden gevormd, lieten zien dat de hoogste CH4 en CO2 scheidings effcientie wordt behaald bij een druk lager dan 3.5 MPa. Hierbij wordt in de gasfase een verandering van 18% van de initiele CH4 molfractie gevonden. Bulkexperimenten hebben tastbaar bewijs geleverd dat CH4 in de al gevormde methaanhydraten kan worden uitgewisseld met CO2 zonder dat er dissociatie van de gashydraten optreedt (Hoofdstuk 4). Echter, de vervanging vindt plaats op een zeer geringe diepte, vlakbij het scheidingsvlak tussen de gasfase en de gashydraten. Hierdoor functioneren CO2-rijke hydraatlagen als een schild en belemmeren verdere penetratie van CO2 in dieper gelegen methaanhydraatlagen en werken de migratiestroom van CH4 naar de gasfase tegen. Ten gevolge hiervan is het noodzakelijk dat eerst dissociatie van de CO2 hydraatlagen plaats vindt, alvorens er CH4 vrij kan komen uit de lager gelegen gashydraatlagen. Als gevolg is een lagere druk dan de evenwichtsdruk nodig voor de dissociatie van de CH4 hydraten. De CO2 hydratvorming werd ook bestudeerd in een kern bestaand uit gelijmde glazen kralen (Hoofdstuk 5). De vorming van gashydraat in dit poreuze medium werd voornamelijk waargenomen in het bovenste gedeelte van de horizontal gepositioneerde kern waar gas en connaat water zich bevinden. In het onderste gedeelte van de kern, voornamelijk gevuld met de CO2 verzadigde waterige vloeibare fase, werd een lokale distributie van gashydraatvorming geconstateerd, die moeilijk te detecteren valt op CT beelden. Drie verschillende regimes konden onderscheiden worden in het proces van gashydraat vorming: een reactie gelimiteerd regime, een di®usie gelimiteerd regime en een pre-evenwichtsregime. Uit de data komt naar voren dat de temperatuur en de snelheid waarmee het gas geinjecteerd wordt weinig invloed hebben op de vorming van gashydraten. Modelleren en numerieke simulaties van gelijktijdige methaanwinning en CO2 injectie in een klasse II gashydraat accumulatie hebben aangetoond dat door injectie van CO2 de productie van CH4 stijgt in vergelijking tot de methaanproductie door alleen drukvermindering (Hoofdstuk 6). In het beste geval nam de totale CH4 productie toe met 60% door de injectie van CO2. Ook kan uit de experimenten worden geconcludeerd dat CO2 op een effciente wijze kan worden opgeslagen in de vorm van hydraten. Slechts 2 mol% van het geinjecteerde CO2 werd hergeproduceerd. Uit de simulaties blijkt dat CO2 hydraten zich direct onder de lagen met CH4 hydraten vormen; de warmte die vrij komt bij deze CO2 hydraten formatie versterkt de verdere dissociatie van CH4 gashydraten.Geoscience & EngineeringCivil Engineering and Geoscience

Human Target Tracking in Multistatic Ultra-Wideband Radar

Multistatic ultra-wideband radar is acknowledged to be useful for human tracking in indoor surveillance. In this thesis, a global signal processing chain for detection and localization of moving human targets using a multistatic ultra-wideband radar system is proposed. The design options for the system are presented, and the required signal processing steps are summarized. They include critical steps of tracking, target feature extraction,and target association. A decentralized tracking approach is designed for indoor surveillance. The 1D bistatic tracking rejects clutter and multipath significantly. The 2D tracker employs the global nearest neighbor based Kalman filter to track targets in Cartesian coordinates. The algorithm performance is compared with that of the conventional centralized approach on both simulated and experimental data, and shown to improve clutter and multipath rejection. For feature extraction, the advantages of using range-Doppler imaging are analyzed. The hypothesis-testing based and the Keystone transform based range migration compensation approaches are extended to eliminate the Doppler widening effect in range-Doppler processing of ultra-wideband radar. The proposed compensation approaches are applied to both simulated and experimental data. Special attention is then devoted to the critical issue of target association. Two slow-time features, video time density function and self-similarity matrix, are proposed to characterize target responses in different receiving channels. They indicate the slow-time evolution characteristic of the moving human targets, while staying invariant to radar observation angles. Auction algorithm based global nearest neighbor approach is proposed to tackle the measurement-to-measurement association issue. The decentralized tracking approach is experimentally verified on measured data for indoor detection and location of multiple human targets. Finally, as a by-product of human target feature analysis, range-Doppler surface is proposed to demonstrate the overall target information in range-Doppler video sequence. The conclusion emphasizes the main achievements and highlights the novelties. The recommendation for future work is presented finally to point out potential research topics related to this thesis.Micro-electronicsElectrical Engineering, Mathematics and Computer Scienc

Structure-Aware Sparse Bayesian Learning-Based Channel Estimation for Intelligent Reflecting Surface-Aided MIMO

This paper presents novel cascaded channel estimation techniques for an intelligent reflecting surface-aided multiple-input multiple-output system. Motivated by the channel angular sparsity at higher frequency bands, the channel estimation problem is formulated as a sparse vector recovery problem with an inherent Kronecker structure. We solve the problem using the sparse Bayesian learning framework which leads to a non-convex optimization problem. We offer two solution techniques to the problem based on alternating minimization and singular value decomposition. Our simulation results illustrate the superior performance of our methods in terms of accuracy and run time compared with the existing works.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.Signal Processing System

Green operations of belt conveyors by means of speed control

Belt conveyors can be partially loaded due to the variation of bulk material flow loaded onto the conveyor. Speed control attempts to reduce the belt conveyor energy consumption and to enable the green operations of belt conveyors. Current research of speed control rarely takes the conveyor dynamics into account so that speed control lacks applicability. Based on our previous research, this paper will provide an improved three-step method to determine the minimum speed adjustment time. This method can be summarized as Estimation-Calculation-Optimization and ECO in short. The ECO method takes both the potential risks and the conveyor dynamics into account. It is expected to keep belt conveyors in good dynamic behaviors in transient operations. After discussing the ECO method, this research takes a long inclined belt conveyor of an import dry bulk terminal as case study. Based on the suggested acceleration time, a speed controller is built and computational simulations are carried out to evaluate the energy savings and the conveyor dynamics. Experimental results prove that the application of the ECO method ensures the healthy dynamic performance of belt conveyors under speed control in transient operations. Annually, the average electricity consumption of the single conveyor can be reduced by over 10% with around 90 tons reduction of emission. The direct economic benefit can reach up to more than €10,000 in terms of the electricity utilization per year.Accepted Author ManuscriptTransport Engineering and Logistic

Use pressure data below seat cushions to evaluate comfort

During a flight, passengers spend most of their time sitting in their seats. Studying the comfort and discomfort while passengers are sitting is helpful to improve the overall comfort during a flight. Pressure mats are commonly used in studies to collect pressure distribution in order to research sitting comfort. Different from most past studies, in which pressure mats are placed on the top of the cushions, the focus of this paper is to show the potential of placing pressure mat below the seat cushion. Three identical cushions differing in stiffness were prepared. The pressure distribution of 12 sitting postures was collected from 33 subjects both at the top as well as at the bottom of the foam in a randomized order. After sitting on each cushion, the participant was asked to leave the seat and complete a sitting comfort and discomfort questionnaire. The results show that the softest cushion got the highest rank in short-term comfort and lowest rank in short-term discomfort. The recorded pressure distributions both on the top and at the bottom of the foam can influence comfort and discomfort. This indicates the potential to use pressure distributions under the foam to evaluate the perceived comfort and discomfort in sitting, which might reduce the intrusive feeling of theparticipants in comfort studies.Mechatronic DesignMaterials and Manufacturin