1,247 research outputs found
Experimental study on energy consumption of computer numerical control machine tools
Machining processes are responsible for substantial environmental impacts due to their great energy consumption. Accurately characterizing the energy consumption of machining processes is a starting point to increase manufacturing energy efficiency and reduce their associated environmental impacts. The energy calculation of machining processes depends on the availability of energy supply data of machine tools. However, the energy supply can vary greatly among different types of machine tools so that it is difficult to obtain the energy data theoretically. The aim of this research was to investigate the energy characteristics and obtain the power models of computer numerical control (CNC) machine tools through an experimental study. Four CNC lathes, two CNC milling machines and one machining center were selected for experiments. Power consumption of non-cutting motions and material removal was measured and compared for the selected machine tools. Here, non-cutting motions include standby, cutting fluid spraying, spindle rotation and feeding operations of machine tools. Material removal includes turning and milling. Results show that the power consumption of non-cutting motions and milling is dependent on machine tools while the power consumption of turning is almost independent from the machine tools. The results imply that the energy saving potential of machining processes is tremendous
Interaction effect in two-dimensional Dirac fermions
Based on the Dirac equations in the two-dimensional flux model, we
study the interaction effects both in nontrivial gapped and gapless Dirac
equations with numerical exact diagonalization method. In the presence of the
nearest and next nearest neighbor interactions: for nontrivial gapped Dirac
equation, the topological phase is robust and persists in a finite region of
the phase diagram; while for gapless Dirac equation, charge-density-wave and
stripe phases are identified and the phase diagram in plane is
obtained. When the next-next-nearest neighbor interaction is further included
to gapless Dirac equation, the topological phase expected in the mean-field
theory is absent. Our results are related to the possibility of dynamically
generating topological phase from the electronic correlations.Comment: 7 pages, 8 figures. More discussins are added; accepted for
publication in Physical Review
Optimizing measurement-based cooling by reinforcement learning
Conditional cooling-by-measurement holds a significant advantage over its
unconditional (nonselective) counterpart in the average-population-reduction
rate. However, it has a clear weakness with respect to the limited success
probability of finding the detector in the measured state. In this work, we
propose an optimized architecture to cool down a target resonator, which is
initialized as a thermal state, using an interpolation of conditional and
unconditional measurement strategies. An optimal measurement-interval
for unconditional measurement is analytically derived for
the first time, which is inversely proportional to the collective dominant Rabi
frequency as a function of the resonator's population in the end of
the last round. A cooling algorithm under global optimization by the
reinforcement learning results in the maximum value for the cooperative cooling
performance, an indicator to measure the comprehensive cooling efficiency for
arbitrary cooling-by-measurement architecture. In particular, the average
population of the target resonator under only rounds of measurements can
be reduced by four orders in magnitude with a success probability about
Therblig-embedded value stream mapping method for lean energy machining
To improve energy efficiency, extensive studies have focused on the cutting parameters optimization in the machining process. Actually, non-cutting activities (NCA) occur frequently during machining and this is a promising way to save energy through optimizing NCA without changing the cutting parameters. However, it is difficult for the existing methods to accurately determine and reduce the energy wastes (EW) in NCA. To fill this gap, a novel Therblig-embedded Value Stream Mapping (TVSM) method is proposed to improve the energy transparency and clearly show and reduce the EW in NCA. The Future-State-Map (FSM) of TVSM can be built by minimizing non-cutting activities and Therbligs. By implementing the FSM, time and energy efficiencies can be improved without decreasing the machining quality, which is consistent with the goal of lean energy machining. The method is validated by a machining case study, the results show that the total energy is reduced by 7.65%, and the time efficiency of the value-added activities is improved by 8.12% , and the energy efficiency of value-added activities and Therbligs are raised by 4.95% and 1.58%, respectively. This approach can be applied to reduce the EW of NCA, to support designers to design high energy efficiency machining processes during process planning
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