27 research outputs found
Polymer Dispersed Liquid Crystal Films Based on E7
No full textPolymeric materials containing dispersed microdroplets of liquid crystal (Polymer Dispersed Liquid Crystals, PDLC's) can be used as displays. PDLC's are translucent due to scattering of light by the liquid crystal (LC) droplets. Using an electric field the LC-molecules align parallel to the applied field, which will cause transparency if the refractive indices of the liquid crystal and the transparent polymer matrix match each other...Applied SciencesMaterials Science and Chemical EngineeringFunctional Properties and Application
Dielectric Characterisation of Anisotropic Gels
No full textLiquid Crystal (LC) systems working on the principle of light scattering, for example Polymer Dispersed Liquid Crystals, are of great interest. A recently developed gel system containing a low molecular weight liquid crystal and a liquid crystalline polymer (LCP) network can also be used for electrically induced scattering. The gel system can be formed by interconnecting phases of free LC-molecules and crosslinked network molecules. In order to induce isotropic light scattering a homeotropic oriented gel system was developed. The structure and the concentration of the network was found to have an effect on the resultant light scattering and optical measurements showed the existence of little domains in the gels. To study these domains dielectric measurements were used to characterise the gel system and to find more information about the domains. The presence of the domains give rise to the socalled Maxwell-Wagner effects: accumulation of charges at the interface of the domains will give an increase in the dielectric constant and this can be measured using dielectric relaxation measurements. To support the characterisation of the gel system DSC-measurements were performed, which showed the characteristic transitions of the LC and the LCP network. Using a standard cell with circular electrodes of ITO and Au dielectric measurements were performed. Electrode polarisation was observed in all samples (pure lc and gels containing 7 w/w% LCP-network), which is caused by ion conductivity in the sample. Activation energies of the observed relaxations are close to values found for ion conductivity. The model found for the observed relaxations with Boukamp Equivalent Circuits fits the model known for electrode polarisation. Maxwell-Wagner effects due to the presence of the domains were not observed. They were probably overruled by the electrode polarisation. A higher conductivity was observed after curing with a UV-source for both the pure LC and the gels. The increase in conductivity can not fully be explained by the increase of conductivity of the pure LC. ITO-electrodes caused disturbtion in the measurements and deflected results were obtained. Electrode polarisation in ionic conducting materials might be avoided using a bias during the dielectric measurements. The ions will be trapped in the sample by the electric field and the epsilon perpendicular will be measured. The observed relaxations will be due to the sample and not due to the mobility of the ions. Measurements with the gels system could give useful information about the domains as the electrode polarisation is not occurring. Further experiments should be focussed on the use of a bias during these measurements.Applied SciencesMaterials Science and Chemical EngineeringPolymers and Organic Chemistry, Technologie van Macromoleculaire Stoffe
A data analysis to bed dynamics in the Western Scheldt estuary
No full textMorphological parameter estimation and deformation analysis near the shoal of Walsoorden (Western Scheldt).GeomaticsDelft Institute of Earth Observation and Space Systems (DEOS)Aerospace Engineerin
The Design and Implementation of a Key Performance Indicator Dashboard for KE-chain
No full textKE-works is a six years old company which aims to optimise the product development process in industrial applications. To accomplish this, KE-works deploys a web-application called KE-chain. KEchain is an engineering workflow management system with the objective to increase the efficiency of the product development process through better control, more efficient distribution, access and use of product-related information. Users have the possibility to set-up a project, manage the tasks belonging to this project, and control the workflow and information distribution. With KE-chain users are able to create structure in the heap of information that composes their product and, when used right, improve the process of their project development. One of the key elements in optimising the product development process is the monitoring of the available data to give users insight in the status of the project. Currently it is difficult to get a good overview of a project within KE-chain and it is not possible to see what tasks are cirtical at a certain moment. A common way of showing the status or performance of systems is the use of Key Performance Indicators (KPI’s). These indicators, for example in the form of a graph or a table, can quickly give information about the performance of a system. KE-works has decided that it wants to give its users an overview in the formof a project-specific dashboard with KPI widgets. Therefore the assignment is to design and develop an integrated KPI dashboard into KE-chain. To design the KPI dashboard, which we named KE-board, we shortly researched the field of Performance Measurement to get an overview of the different approaches for the design of KPI’s. As a basis for the design we have adopted the Lean methodology [1] which has been used by KE-works in the past. In our research we have actually connected the Lean wastes to measures in KE-chain. To do this, we have chosen a bottom-up approach, which means we started by identifying the available data, after which we extracted several groups of measures. We have interviewed several clients of KEworks, the users of KE-chain. From these interviews we deducted which groups of measures were important for which user roles. To verify which measures are of importance for these dashboards, we have questioned and interviewd the consultants of KE-works. By combining the results of the interviews and the questionnaires we designed 7 KPI widgets. Finally, we created KE-board and integrated it into KE-chain in five weeks of implementation. After that we have evaluated the complete dashboard by interviewing the consultants of KE-works. On top of that, we have sent them a questionnaire in which they rated the functionality of the widgets to see if they contribute to their purpose and achieve the goals that we set for them. KE-board has been received well by the management and employees of KE-works and according to the extensive evaluation we can state that it definitely contributes to the optimization of the product development process in KE-chain.Computer ScienceComputer ScienceElectrical Engineering, Mathematics and Computer Scienc
From Dutch Short-Lived to Antarctic Long-Lived Stable Boundary Layers
No full textStable boundary layers (SBLs) are a common aspect of the earth’s atmosphere and are characterized by a stable density stratification in which the temperature increases with height. This typically occurs during the night, resulting in a short-lived stable boundary layer, or persistently throughout the polar winter, resulting in a longlived stable boundary layer. Due to their associated cold surface temperatures, stable boundary layers can stimulate the formation of radiation fog or frost near the surface, which may negatively impact human activities and result in large economic losses. However, despite their omnipresence, a comprehensive understanding of their dynamical behavior is still lacking.Atmospheric Remote Sensin
Reviewing the EU Emissions Trading Scheme (Part II): Priorities for Short-Term Implementation. CEPS Task Force Reports No. 57, 1 March 2006
No full text[From the Introduction]. This report constitutes Part II of the twin reports of the CEPS Task Force on Reviewing the EU Emissions Trading Scheme. The Part I report, which was presented to the UK Presidency on 7 July 2005,1 focused on a number of short-term implementation issues including transparency requirements for the National Allocation Plans (NAPs), the definition of installations, treatment of small installations, new entrants, closure and transfer rules, allocation methodologies, the possibility of opt-ins as well as monitoring, reporting and verification. This follow-up Part II report examines deep-seated topics such as whether the EU Emission Trading System (ETS) contributes to meeting Kyoto Protocol targets, economic impacts, effects on investment and the potential inclusion of aviation. These issues lie at the interface of NAP phase II and the longterm formal 2006 review. Neither of the two reports (Part I or Part II) examines issues related to the formal review of the EU ETS, which the Directive calls for no later than June 2006. Since this formal review, which will lead to an amendment of the Directive by co-decision, is likely to trigger a fundamental and longer-term debate, it is being treated in a separate CEPS Task Force launched in early 2006. After a status report of the ETS and a reminder of some fundamentals in sections 1 and 2, the following sections cover investment incentives (3), competitiveness (4 and 5) and aviation (6). The main findings of the report are contained in the Executive Summary, including Key Messages & Recommendations and an extended Full Summary. Appendix 1 presents a list of members of the Task Force and invited guests and speakers
Modeling heat transfer in the vegetation-soil continuum
No full textThis thesis contributes to the scientific underpinning of the battle against fruit frost. Fruit frost is the freezing damage to blossoms when in the growing season the night temperature drops below 0±C. This results in damaged or undeveloped fruits, and a yield loss for the fruit farmer. Several techniques against fruit frost have been developed, including sprinkling and wind machines, often in combination with meteorological models, for example, to predict air temperature. However, the contribution of heat exchange with the soil to moderate orchard temperatures is often not included. In this thesis, this heat transfer is investigated, as an increase of heat transfer from the soil to the orchard during the night is a potential remedy against fruit frost. The research is based on measurements for soil temperature, soil heat flux, and soil moisture from two locations (1. Haarweg (Gelderland), The Netherlands 2. Bushland (Texas), The U.S.A.). First, a numerical model is developed to calculate the temperature and soil heat flux profiles for a soil layer. The results are compared to the results of an already developed analytical model. Second, the thermal parameters, that are of influence on the heat transfer, are analyzed by assessing a) their robustness in relation to the model and b) their relation to soil moisture. Because a numerical model is more flexible for shorter periods of data compared to an analytical model (because of underlying assumptions), it can be used to relate the parameters to (daily) varying soil moisture. Third, the numerical model for heat transfer is extended to the vegetation layer, and, again, the results are compared to analytical results. The model is created by assuming homogeneity in both separate layers and by discretizing the governing heat equation over the domain. The results show that the model reproduces temperature and soil heat flux in the soil layer with similar accuracy as the analytical, harmonic model. One thermal parameter, the diffusivity, is robust and does not show a clear dependency on soil moisture. The model is however sensitive to deviations in the other parameter, the heat conductivity. The model shows a clear relation between conductivity and soil moisture, and from this, a site-specific quantitative relation is determined. This relation however is only valid in the investigated region of moisture variation and we recommend future research to cover data in a broader range of soil moisture. Overall, we conclude that the model successfully reproduced the temperature and soil heat flux throughout the full vegetation-soil continuum
Resting-State Functional Connectivity Characteristics of Resilience to Traumatic Stress in Dutch Police Officers
No full textBackgroundInsights into the neurobiological basis of resilience can have important implications for the prevention and treatment of stress-related disorders, especially in populations that are subjected to high-stress environments. Evaluating large-scale resting-state networks (RSNs) can provide information regarding resilient specific brain function which may be useful in understanding resilience. This study aimed to explore functional connectivity patterns specific for (high) resilience in Dutch policemen after exposure to multiple work-related traumatic events. We investigated resting-state functional connectivity (RSFC) of the salience network (SN), limbic network, and the default-mode network (DMN). MethodsResting-state functional MRI scans were obtained from trauma-exposed executive personnel of the Dutch police force and non-trauma-exposed recruits from the police academy. Participants were divided into three groups: a resilient group (n = 31; trauma exposure; no psychopathology), a vulnerable group (n = 32; trauma exposure, psychopathology), and a control group (n = 19; no trauma exposure, no psychopathology). RSFC of the three networks of interest was compared between these groups, using an independent component analysis and a dual regression approach. ResultsWe found decreased resilience-specific positive RSFC of the salience network with several prefrontal regions. The DMN and limbic network RFSC did not show resilience-specific patterns. ConclusionThis study shows a differential RSFC specific for resilient police officers. This differential RSFC may be related to a greater capacity for internal-focused thought and interoceptive awareness, allowing more effective higher-order responses to stress in highly resilient individuals.Stress-related psychiatric disorders across the life spa
Resting-state functional connectivity characteristics of resilience to traumatic stress in Dutch police officers
No full textBackground: Insights into the neurobiological basis of resilience can have important implications for the prevention and treatment of stress-related disorders, especially in populations that are subjected to high-stress environments. Evaluating large-scale resting-state networks (RSNs) can provide information regarding resilient specific brain function which may be useful in understanding resilience. This study aimed to explore functional connectivity patterns specific for (high) resilience in Dutch policemen after exposure to multiple work-related traumatic events. We investigated resting-state functional connectivity (RSFC) of the salience network (SN), limbic network, and the default-mode network (DMN).Methods: Resting-state functional MRI scans were obtained from trauma-exposed executive personnel of the Dutch police force and non-trauma-exposed recruits from the police academy. Participants were divided into three groups: a resilient group (n = 31; trauma exposure; no psychopathology), a vulnerable group (n = 32; trauma exposure, psychopathology), and a control group (n = 19; no trauma exposure, no psychopathology). RSFC of the three networks of interest was compared between these groups, using an independent component analysis and a dual regression approach.Results: We found decreased resilience-specific positive RSFC of the salience network with several prefrontal regions. The DMN and limbic network RFSC did not show resilience-specific patterns.Conclusion: This study shows a differential RSFC specific for resilient police officers. This differential RSFC may be related to a greater capacity for internal-focused thought and interoceptive awareness, allowing more effective higher-order responses to stress in highly resilient individuals.Stress-related psychiatric disorders across the life spa
