An Experimental study of Graphene Quantum Dots as a Potential Fluorescent, Anti-Bacterial Additive for Water Based Paint

An experimental study of Graphene quantum dots was conducted as a potential fluorescent, anti-bacterial additive for water-based paints using GQDs synthesized from L Glutamine. The L-Glutamine was polymerized to form light blue GQDs of low fluorescence intensity, which lost all fluorescence once added to the paint. The GQDs were tested for antibacterial properties against the growth of E.coli but failed to inhibit any growth. Raman and UV/vis spectroscopy were also conducted to determine functional groups as well as to determine peak light absorbance trends. While it was concluded that this method of GQD synthesis did not result in a promising additive for water-based paints, future research could continue the antibacterial testing by adding low concentrations of hydrogen peroxide as well as testing other facile methods of synthesis

Нагрев и пределы частотного регулирования асинхронного двигателя, работающего с наименьшими годовыми приведенными затратами

Исследуется тепловой режим асинхронного двигателя, оптимизированного по минимуму годовых приведенных затрат при переменной частоте питающего напряжения. Определены пределы регулирования скорости. Показана целесообразность оптимизации двигателя по экономическому критерию

The Reconfiguration of Public Authority in Developing Countries

In recent years, several scholars of world politics have observed a relocation of authority in different issue areas of global policy-making. This development appears to be particularly evident in the field of global climate politics where a number of authors have highlighted the gradual loss of authority by national governments and the emergence of new spheres of authority dominated by actors other than the nation-state. In fact, due to the existence of a regulatory gap in this policy domain, various new governance arrangements have emerged which work simultaneously at different levels (some top-down and others bottom-up) to cope with the problem of climate change. However, despite several broader descriptions and mapping exercises, we have little systematic knowledge about their workings, let alone their impact on political-administrative systems. Given these shortcomings, in this paper we explore how (and how far) different types of globally operating governance arrangements have caused changes in the distribution of authority within national governments and their public administration. We will focus on two stylized governance arrangements: one that operates bottom-up (i.e. Transnational City Networks, TCNs) and another that operates top-down (i.e. Reducing Emissions from Deforestation and Forest Degradation, REDD+). Departing from our hypotheses that the former is likely to lead to more decentralization and the latter to more centralization of environmental policy making, we will present some preliminary findings from our case studies in Brazil, India, Indonesia, and South Africa

Implementation of Vibration Signals Receiving Unit on Raspberry Single-Board Computers

The paper dedicated to vibration measurement system development on the Raspberry Pi basis. Main features of the solution are low-cost, easy access to components and functionality and flexibility provided by Raspberry Pi usage. Circuit solution and configuring procedures are presented and described. In particular, block diagram of the vibration measurement system with piezo-electric sensors. Two variants of the vibration measurement system, on the Raspberry Pi B+ and Raspberry Pi 3B correspondingly, were implemented and tested as well. In addition, two variants of impedance-matching device were implemented. Conducted and described experiments confirm performance both separate components and the whole solution. Presented results are applicable for correlation leak detectors new algorithmic solutions and in educational process

Werkzeugmaschinen mit Beinen - die Hexapod-Maschinen

Kaum eine andere Entwicklung im Werkzeugmaschinenbau hat das Aussehen und die konstruktive Struktur der Maschinen so sehr verändert wie die Einführung einer neuen Kinematik, die nicht mehr auf den gewohnten, seit jeher unverändert kartesisch zueinander angeordneten Maschinenachsen beruht, sondern auf einem Bewegungsgebilde aus miteinander verbundenen Antriebsstreben und Gelenkstäben, den „Vielbeinern“ oder – wie sie in der Fachwelt genannt werden – den Tripoden beziehungsweise den Hexapoden. Die Bezeichnung Hexapod hat sich inzwischen im internationalen Sprachgebrauch zum Oberbegriff der gesamten Maschinengattung entwickelt. Die neuen Maschinen bieten völlig neue Perspektiven in der Bewegungsflexibilität und Dynamik und eröffnen bezüglich der Bemühungen um die Verbesserung und Weiterentwicklung der Werkzeugmaschinen weitreichende Perspektiven

Determination of the shear angle in the orthogonal cutting process

Determination of the shear angle by experimental and analytical methods, as well as by numerical simulation, is presented. Experimental determination of the shear angle was performed by analyzing the chip roots obtained by the method of cutting process quick stop through purposeful fracture of the workpiece in the area surrounding the primary cutting zone. The analytical determination of the shear angle was carried out using the chip compression ratio and was based on the principle of a potential energy minimum. Measurement of the shear angle in the numerical simulation of orthogonal cutting was performed using the strain rate pattern of the machined material at the selected simulation moment. It was analyzed how the parameters of the Johnson-Cook constitutive equation and the friction model affect the shear angle value. The parameters with a predominant effect on the shear angle were determined. Then the generalized values of these parameters were established with a software algorithm based on identifying the intersection of the constitutive equation parameter sets. The use of generalized parameters provided the largest deviation between experimental and simulated shear angle values from 9% to 18% and between simulated and analytically calculated shear angle values from 7% to 12%.the German Research Foundation (DFG

Numerical modeling of cutting characteristics during short hole drilling : part 2 - modeling of thermal characteristics

The modeling of machining process characteristics and, in particular, of various cutting processes occupies a significant part of modern research. Determining the thermal characteristics in short hole drilling processes by numerical simulation is the object of the present study. For different contact conditions of the workpiece with the drill cutting inserts, the thermal properties of the machined material were determined. The above-mentioned properties and parameters of the model components were established using a three-dimensional finite element model of orthogonal cutting. Determination of the generalized values of the machined material thermal properties was performed by finding the set intersection of individual properties values using a previously developed software algorithm. A comparison of experimental and simulated values of cutting temperature in the workpiece points located at different distances from the drilled hole surface and on the lateral clearance face of the drill outer cutting insert shows the validity of the developed numerical model for drilling short holes. The difference between simulated and measured temperature values did not exceed 22.4% in the whole range of the studied cutting modes.German Research Foundation (DFG

Numerical modeling of cutting characteristics during short hole drilling : modeling of kinetic characteristics

Analyzing the cutting process characteristics opens up significant opportunities to improve various material machining processes. Numerical modeling is a well-established, powerful technique for determining various characteristics of cutting processes. The developed spatial finite element model of short hole drilling is used to determine the kinetic characteristics of the machining process, in particular, the components of cutting force and cutting power. To determine the component model parameters for the numerical model of drilling, the constitutive equation parameters, and the parameters of the contact interaction between the drill and the machined material on the example of AISI 1045 steel machining, the orthogonal cutting process was used. These parameters are determined using the inverse method. The DOE (Design of Experiment) sensitivity analysis was applied as a procedure for determining the component models parameters, which is realized by multiple simulations using the developed spatial FEM model of orthogonal cutting and the subsequent determination of generalized values of the required parameters by finding the intersection of the individual value sets of these parameters. The target values for the DOE analysis were experimentally determined kinetic characteristics of the orthogonal cutting process. The constitutive equation and contact interaction parameters were used to simulate the short hole drilling process. The comparison of experimentally determined and simulated values of the kinetic characteristics of the drilling process for a significant range of cutting speed and drill feed changes has established their satisfactory coincidence. The simulated value deviation from the corresponding measured characteristics in the whole range of cutting speed and drill feed variation did not exceed 23%.German Research Foundation (DFG