Fully bio-based Cellulose nanofiber/epoxy composites with both sustainable production and selective matrix deconstruction towards infinite fiber recycling systems

Design of nanocellulose-based composite materials suitable for selective disintegration, recovery and recycling of individual components is of great scientific and technical interest. Cellulose nanofiber/epoxy (CNF/EP) composites are candidate bio-based substitutes...

Effects of Hydrated Lime on High-Temperature Rheological Properties of High-Viscosity Modified Asphalt

High-viscosity modified asphalt (HVA) is widely used as the binder for permeable asphalt pavement, and hydrated lime (HL) attracts a strong technical interest as an effective moisture additive in asphalt for a long time. However, the application of HL in HVA has been rarely studied. The present study evaluates the influence of HL on the high-temperature rheological properties of HVA and selects the optimum HL content and fineness. The asphalt mortars of HVA and HL of different contents and fineness were prepared. Temperature scanning (DSR-TS), multiple stress creep recovery (MSCR) by using a dynamic shear rheometer, and scanning electron microscope (SEM) tests were carried out to evaluate the high-temperature rheological properties and microstructure morphology characteristics of the asphalt mortars. Based on the DSR-TS and MSCR tests, the results showed that high-temperature performance together with the ability to deformation resistance of HVA was improved apparently with the increase of the HL content. When the HL content is above 1.2, the stress sensitivity of HVA is lower. The SEM results clearly showed that the uniformity of asphalt mortars could be effectively guaranteed when the HL content was 1.2 and the fineness was 800 mesh. The HL fineness has little effect on the high-temperature performance of HVA. In summary, taking into account the high-temperature performance and microstructure of HVA with HL, the optimum HL content and fineness could be finally determined.

Slussen – the lock of Stockholm

<p>Slussen is situated in the inner city of Stockholm just south of the world heritage site Gamla Stan and the royal castle. This historical site and also second biggest traffic and transportation hub in Stockholm is at the moment undergoing a complete refurbishment due to new demands and requirements and due to the fact that the former traffic plant was in a very bad shape with severe settlements and outworn concrete structures. The old traffic structure from the 1930´s is replaced by a modern urban space and transportation node designed by Foster + Partner and Berg arkitekter, adopted to demands and requirements of the future i.e. increased capacity for pedestrians and cyclists, heavily increased discharge capacity for Lake Mälaren, attractive areas for the public close to the water and several restaurants and cafés.</p><p>This mega project (€ 1.4 Billion) cannot be described completely in a single paper so therefore two objects of special technical interest have been chosen and are described below: the water regulation system as well as the unique 3.400 Tons steel bridge, transported in one piece from China.</p>

EQUATIONS OF INTENSITY, DURATION AND FREQUENCY FOR THE PERUÍPE, ITANHÉM AND JUCURUÇU RIVER BASINS

The intense rainfall equations present a great technical interest for hydraulic works projects. In the State of Bahia, there are only 19 equations of intensity, duration and frequency modeling, requiring a greater number of equations for the State. The most recent ones are almost 15 years old, with only two in the Peruípe, Itanhém and Jucuruçu river basins. Thus, the objective of this work was to determine the parameters of the equations of intensity, duration and frequency (IDF) of the rainfall stations for different locations of the basins of the Peruípe, Itanhém and Jucuruçu rivers, located in the far southern Bahia State. Initially, 59 stations were selected, out of which only those with over 20 year-old data and records from 1980 onwards. Rainfall disaggregation was carried out using the method proposed by Cetesb (Environmental Company of the State of São Paulo, Brazil) and the parameters (K, a, b and c) were adjusted through nonlinear multiple regression using the nonlinear-generalized reduced gradient interaction method, where adjustment was evaluated by the coefficient of determination (R2). In the end, 29 equations were adjusted, with coefficient of determination greater than 0.99, therefore, improving the perspective of planning hydraulic works in the region. This correlation could also be observed by the regression equation of the observed data with the adjusted ones, where the slope coefficient of the line was close to 1.0 for all rainfall stations.

Enhanced Single-Degree-of-Freedom Analysis of Thin Elastic Plates Subjected to Blast Loading Using an Energy-Based Approach

Single-degree-of-freedom (SDOF) models are known to represent a valid tool in support of design. Key assumptions of these models, on the other hand, can strongly affect the expected predictions, hence resulting in possible overconservative or misleading estimates for the response of real structural systems under extreme actions. Among others, the description of the input loads can be responsible for major design issues, thus requiring the use of more refined approaches. In this paper, a SDOF model is developed for thin elastic plates under large displacements. Based on the energy approach, careful attention is given for the derivation of the governing linear and nonlinear parameters, under different boundary conditions of technical interest. In doing so, the efforts are dedicated to the description of the incoming blast waves. In place of simplified sinusoidal pressures, the input impulsive loads are described with the support of infinite trigonometric series that are more accurate. The so-developed SDOF model is therefore validated, based on selected literature results, by analyzing the large displacement response of thin elastic plates, under several boundary conditions and real blast pressures. Major advantage for the validation of the proposed SDOF model is obtained from experimental finite element (FE) and finite difference (FD) models of literature, giving evidence of a rather good correlation and confirming the validity of the presented formulation.

Curricula of Museum Education: International Instances

The application of curriculum theory and models of curriculum development to museum education helps inform the analysis of the representational, communicative, epistemological, and cognitive dimensions of the formal, informal, and nonformal learning that takes place in the museum setting. Museums and other in/nonformal learning environments implicitly and explicitly engage questions of worth inherent to curriculum inquiry. Within the Curriculum Studies field, such questions reflect both an historical and a contemporary concern with issues of diversity, accessibility, social justice, civic value, and human rights in school and non-school curriculum contexts. In addition to other curriculum analysis frameworks, international instances of museum education curricula can be understood through the lenses of three “human interests”: the technical, the practical, and the emancipatory. A preference for designing educational materials and experiences around predetermined objectives reflects a technical interest in museum curricula. Within this technical approach, which can also be conceptualized as curriculum as product, the success or failure of a curriculum depends on the degree to which the intended objectives are achieved. Curriculum as practice reflects a practical interest in the way understanding and knowledge are created (rather than simply transmitted) through the dynamic social interactions between teacher and learner. A curriculum as practice orientation aligns with constructivist views on museum learning. Representing an emancipatory interest in human liberation and the overcoming of oppressive social structures is the curriculum as praxis orientation. This approach to museum curricula often assumes a social justice goal of community empowerment that seeks to translate understanding or consciousness-raising into action.

A Novel All-Optical Sensor Design Based on a Tunable Resonant Nanocavity in Photonic Crystal Microstructure Applicable in MEMS Accelerometers

In view of the large scientific and technical interest in the MEMS accelerometer sensor and the limitations of capacitive, resistive piezo, and piezoelectric methods, we focus on the measurement of the seismic mass displacement using a novel design of the all-optical sensor (AOS). The proposed AOS consists of two waveguides and a ring resonator in a two-dimensional rod-based photonic crystal (PhC) microstructure, and a holder which connects the central rod of a nanocavity to a proof mass. The photonic band structure of the AOS is calculated with the plane-wave expansion approach for TE and TM polarization modes, and the light wave propagation inside the sensor is analyzed by solving Maxwell’s equations using the finite-difference time-domain method. The results of our simulations demonstrate that the fundamental PhC has a free spectral range of about 730 nm covering the optical communication wavelength-bands. Simulations also show that the AOS has the resonant peak of 0.8 at 1.644µm, quality factor of 3288, full width at half maximum of 0.5nm, and figure of merit of 0.97. Furthermore, for the maximum 200nm nanocavity displacements in the x- or y-direction, the resonant wavelengths shift to 1.618µm and 1.547µm, respectively. We also calculate all characteristics of the nanocavity displacement in positive and negative directions of the x-axis and y-axis. The small area of 104.35 µm2 and short propagation time of the AOS make it an interesting sensor for various applications, especially in the vehicle navigation systems and aviation safety tools.

Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

Design and Analysis of a Modular VTOL Drone With Bat-Inspired Wings

The future of technology lies in the diverse characteristics and capabilities of autonomous machines and devices and their application in many technical challenge. Rapid technology development, market globalization and availability of affordable electronics and controllers, have recently resulted in increased scientific and technical interest in drones as autonomous solutions for professional, as well as, amateur applications. On the other hand, researchers have been improving how manmade machines move through air by attempting to replicate animals motion by mimicking their aerial abilities. In this paper, we propose a development of a bio-inspired modular drone concept motivated by the bats agility, wingspan and wings folding into various shapes. The drone can be tailored for different applications, from sea port mapping, surveying, tank inspection and port traffic control to pollution monitoring and detection of illegal activities. The aerial performances of the drone allow it to be able to conduct windmills monitoring by connecting to their local monitoring units and send alerts to officials in real-time. This small bat-inspired drone is proposed to have an ability of performing flights with precisely defined trajectories. The accent will be put on the interchangeable wings, analysis of their dynamic attributes and transformation possibilities as a crucial segment of the overall drone performance. The design and fabrication process and the flight characteristics of the various wing configurations of the drone are discussed in details. Limitations of the drone, proposed solutions for further development and recommendations are also presented.