Pre-compensation of servo tracking errors through data-based reference trajectory modification

This paper presents a new dynamic error compensation approach with novel data-based closed-loop tuning scheme to enhance tracking accuracy of machine tool feed-drives. Both servo dynamics and friction disturbance induced positioning errors are pre-compensated by modifying the reference trajectory. Velocity and acceleration profiles of reference trajectory are modulated to achieve perfect tracking. Reference position profile is modified based on the pre-sliding friction regime to eliminate quadrant glitches. Optimal error compensation is achieved by a digital trajectory pre-filter whose parameters are tuned automatically by making on-the-fly iterative adjustments. Effectiveness of proposed compensation approach is validated experimentally in multi-axis feed-drive systems.     

A system-wide approach to minimize the operational cost of bench production in open-cast mining operations

International Journal of Coal Science & Technology - The production cycle of open-cast coal mines generally includes drilling, blasting, loading, hauling and coal preparation activities....     

Compatibility of a polycarboxylate-based superplasticiser with different set-controlling admixtures

The compatibility of specific combinations of chemical admixtures for cement pastes and mortars have been investigated. The consistency, setting time and compressive strength of cement pastes and mortars incorporating a polycarboxylate-based plasticizing admixture (PCA) with four different set-controlling admixtures (SCA); calcium formate (CF), tri-ethanolamine (TEA), mixture of calcium nitrite and nitrate salts (CNN blend) and sodium aluminate (SA) have been determined within the scope of this study. Fifty-two mortar and paste specimens with different amounts of PCA and SCA combinations have been prepared. Water/cement ratios of cement paste and mortar mixtures were 0.24 and 0.50, respectively. The paste mixtures have been prepared to determine the setting time data and the mortar mixtures have been used to determine the consistency and compressive strength values. Test results indicated that the PCA employed in this study, retards the setting time, improves consistency and reduces the early strength development of all paste and mortar mixtures at dosages greater than 0.4% by mass of cement. However, the use of different set-controlling admixtures in combination with PCA caused drastic changes in the performances of the mixtures depending on the type and amount of SCAs. It was concluded that, in order to reduce the setting time and increase the early strength of PCA incorporated mortars without causing consistency loss, the combination of PCA, and SCA should be optimized according to their types. A new 3D box-plot method has been used to determine the optimum admixture combinations for the desired properties. Maximum flow, shortest setting time and highest early strength criterion were the targets of the optimization. The most effective combination to obtain desired set acceleration and high early strength values was 1.8% PCA with 1.6% nitrite and nitrate salts based SCA by mass of cement. If consistency lost is in secondary importance, 1.8% PCA based plasticiser with 1% sodium aluminate based SCA may be an alternative combination. The proposed method can be used to optimize the targeted properties for a specific combination of cement, PCA and SCA.     

The IMA-6 pulsed magnetic analyzer

The principle of construction of the IMA-6 pulsed magnetic analyzer for testing the quality of thermal treatment, the mechanical properties, and the microstructure of articles of low-carbon, medium-carbon, and low-alloyed cold- and hot-rolled steels is described. The structural scheme, the performance characteristics, and examples of application of the instrument are presented.     

Design and evaluation of a mechanical nanomanufacturing system for nanomilling

This paper presents design and evaluation of a mechanical nanomanufacturing system for performing the nanomilling process. The nanomilling process uses a nanotool (an atomic force microscope probe tip) that is rotated at high speeds to fabricate three-dimensional (3D) nano-scale features on a sample surface. After explaining the kinematics of the two nanomilling process configurations, the nanomilling system, including the 3D piezoelectric actuator that rotates the nanotool, the nanopositioning stage that provides the feeding and depth motions, and the software program that controls the nanomilling motions are described. A measurement system is then constructed to measure the dynamic nanomilling motions. A compensation algorithm is developed to enable obtaining desired nanotool motions in the presence of frequency and amplitude-dependent nonlinearities of the 3D piezoelectric actuator. The nanomilling system is then evaluated directly by measuring the nanotool motions, and indirectly by assessing the accuracy of the fabricated nanoscale features. It was shown that the nanomilling system facilitates fabrication of complex nano-scale features with high accuracy through the high-stiffness nanotool assembly and high-frequency (compensated) nanotool motions.     

Towards occupant-centric simulation-aided building design: a case study

ABSTRACT

This paper aims at illustrating the importance of occupant modelling for decision-making during the building design process. It identifies the energy implications of conventional ways of modelling occupants for the design of office buildings. Furthermore, it presents a step towards bridging the gap between the research efforts and conventional practices within the field of building performance simulation (BPS) aided design. The paper first describes occupant-related assumptions that were made during the design process of a case study office building, obtained via stakeholder interviews. Then, the impact of these assumptions on the design decisions is examined through a simulation-based investigation. The stakeholder interviews revealed that professionals from each design discipline made significantly different assumptions about occupants. The simulation results showed that assumptions about occupants and their behaviour impacted predicted energy savings of some design decisions by a factor of five or more.     

An approximate method for static and dynamic analyses of symmetric wall‐frame buildings

In this study an approximate method based on the continuum approach and transfer matrix method for static and dynamic analyses of symmetric wall‐frame buildings is presented. The whole structure is idealized as a sandwich beam in this method. Initially the differential equation of this equivalent sandwich beam is written; shape functions for each storey can then be obtained by the solution of differential equations. By using boundary conditions and storey transfer matrices obtained from these shape functions, system modes and periods can be calculated. The reliability of the study is shown using several examples. A computer program has been developed in MATLAB and numerical samples have been solved for demonstration of the reliability of this method. The results of the samples show the agreement between the present method and other methods given in the literature. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and investigation of new cholesteryl carbamate-based liquid crystals

Journal of Materials Science: Materials in Electronics - Cholesteryl chloroformate which is known liquid crystal material was modified to give the new molecules a long-lasting LC phases with the...     

Porous 3D printed concrete beams show an environmental promise: a cradle-to-grave comparative life cycle assessment

3D Concrete Printing (3DCP) is a rapidly expanding area in the field of architecture, engineering, and construction, but very limited research has quantitatively investigated its environmental impact. The existing Life Cycle Assessment (LCA) studies on 3DCP lack clearly defined functional units of comparison, especially considering load-bearing structures. This paper investigates the potential environmental benefits of 3DCP over conventional concrete construction for structural beams based on a cradle-to-grave comparative LCA. Unlike existing studies, this paper employs a recarbonation model to account for the carbon offsetting from the use-stage of 3DP concrete, which shows significant results. The assessment includes three-beam designs, each analyzed for both prefabrication and on-site construction scenarios. While currently, 3DCP has a generally higher environmental impact due to the larger quantity of cement employed in the process, the reduction of material through infill optimization for printed beams is a promising design principle to positively offset the environmental impacts in the construction sector. The paper draws recommendations for future research on material- and recarbonation-efficient 3DCP design for load-bearing structures, as well as on material development, e.g. integration of larger aggregates and low-clinker cement.

Graphical abstract