Geochemical and Process Engineering Challenges for Geothermal Power Generation

Handling of the geothermal fluid, which is typically a complex mixture of salt solution and dissolved gases, is one of the main challenges for designing and operating reliable and efficient geothermal power plants. In the geothermal fluid loop, undesired mineral precipitation and fluid‐material interactions must be prevented and the design and dimensioning of all components must be adapted according to the characteristics of the geothermal fluid. This paper outlines geochemical and process engineering aspects as well as research activities in these fields and introduces the Groß Schönebeck site, which is a central site for geothermal research.     

Automated robotic grinding by low-powered manipulator

A new robotic grinding process has been developed for a low-powered robot system using a spring balancer as a suspension system. To manipulate a robot-arm in the vertical plane, a large actuator torque is required due to the tool weight and enormous gravity effect. But the actuators of the robot system always exhibit a limited torque capacity. This paper presents a cheap and available system for precise grinding tasks by a low-powered robot system using a suspension system. For grinding operations, to achieve position and force-tracking simultaneously, this paper presents an algorithm of the hybrid position/force-tracking scheme with respect to the dynamic behavior of a spring balancer. Material Removal Rate (MRR) is developed for materials SS400 and SUS304. Simulations and experiments have been carried out to demonstrate the feasibility of the proposed system.     

Management of sustainable manufacturing systems-a review on mathematical problems

The ever-growing awareness of environmental protection has significantly influenced the method of manufacturing products. Due to the introduction of new processes, the management of sustainable manufacturing shows different characteristics to those of traditional systems. Sustainable manufacturing systems have attracted a great deal of attention in the past 20 years as an emerging manufacturing approach. Particularly in the last 10 years, the number of papers focusing on the topic of sustainable manufacturing systems’ management has increased rapidly. More and more practical factors have been considered and integrated into this area which makes it more complex, but closer to reality. This paper aims to classify the mathematical problems dealing with the management of sustainable manufacturing systems. More than 100 related papers mainly from 1994 to 2015 have been selected and reviewed and divided into three categories according to the main elements in a manufacturing system: production planning and control, inventory management and control and manufacturing network design. The development of each category is summarised and the corresponding mathematical problems are discussed to provide a general overview of the relevant research fields and identify future research directions.     

Effect of vanadium and tin additives on structural and magnetic properties of Bi-YIG nano-particles

In this research work, substituted tin and vanadium garnets Y_2.5Bi_0.5Fe_2?2xSn_xFe_3?xV_x O₁₂ (0?≤?x?≤?0.2) were prepared by mechanochemical processing following with 10 h milling and post-annealing at different temperatures. Physical properties of samples were studied by X-ray diffraction analysis (XRD), Far-infrared spectroscopy (Far-IR), and field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometer (VSM). XRD patterns of prepared garnets show that the samples are all single phase with garnet structure at 900 °C. Further, the average crystallite size was calculated by Debye–Scherrer, and Williamson–Hall methods. We also studied the magnetic properties of prepared samples by using a vibrating sample magnetometer (VSM). Experiments showed that the maximum value of vanadium that can be entered in the garnet structure is 0.2.

     

In situ vibration enhanced pressure slip casting of submicrometer alumina powders

This paper presents a novel method for improvement of particle packing in consolidation of submicrometer alumina powders by pressure slip casting. In this method, filtration cell is subjected to a mechanical vibration field with constant frequency of 50 Hz and vibration amplitudes ranging from 0 (no vibration) to 2 mm. Filtration rate, thickness and green density of the fabricated samples were measured to investigate the influence of vibration on filtration characteristics. It was revealed that employment of vibration can significantly increase filtration rate. Furthermore, there is an optimum vibration amplitude which results in the structure with the highest packing density. This value is shifted to higher vibration amplitudes as more concentrated alumina slurries is used. As the available formulation based on Darcy's law could not predict the results of the present investigation, a “Correction Factor” was utilized in order to increase the accuracy of the prediction in the presence of a vibration field.     

Analysis of shear rate effects on drag reduction in turbulent channel flow with superhydrophobic wall

We examined the shear rate effect on drag reduction of superhydrophobic surfaces with different slip lengths. For this purpose, turbulent channel flow was considered at the friction Reynolds numbers of Reτ = 180, 395, 500. By using Navier＇s slip condition it is shown that increasing shear rate leads to the greater reduction in drag force and also more reduction occurs in larger slip length. Based on the results, more than 25% drag reduction happens at a friction Reynolds number of Reτ= 500 for slip length of 1 ×10 5 m. The simulation results suggest that reduction in drag force occurs because slip condition reduces the Reynolds stresses, also weakens vorticity filed and the near-wall coherent structures, and therefore turbulence production is decreased.     

Tolerance analysis of mechanical assemblies based on modal interval and small degrees of freedom (MI-SDOF) concepts

Tolerance analysis is a key analytical tool for estimation of accumulating effects of the individual part tolerances on the design specifications of a mechanical assembly. This paper presents a new feature-based approach to tolerance analysis for mechanical assemblies with geometrical and dimensional tolerances. In this approach, geometrical and dimensional tolerances are expressed by small degrees of freedom (SDOF) of geometric entities (faces, feature axes, edges, and features of size) that are described by tolerance zones. The uncertainty of dimensions and geometrical form of features due to tolerances is mathematically described using modal interval arithmetic. The two concepts of modal interval analysis and SDOF are combined to describe the tolerance specifications. The algorithm is presented which explains the steps and the procedure of tolerance analysis. The proposed method is compatible with the current GD&T standards and can incorporate GD&T concepts such as various material modifiers (maximum material condition, least material condition, and regardless of feature size), envelope requirement, and bonus tolerances. This method can take into account multidimensional effects due to geometrical tolerances in tolerance analysis. The application of the proposed method is illustrated through presenting an example problem and comparing results with tolerance charting method.