In the present study, novel Co3O4/NiO nanosponges designed for the photocatalytic degradation of organic contaminants were synthesized by a simple precipitation technique. The formation of sponge-like nanostructures w...In the present study, novel Co3O4/NiO nanosponges designed for the photocatalytic degradation of organic contaminants were synthesized by a simple precipitation technique. The formation of sponge-like nanostructures was clearly evident through the TEM analysis. The photocatalytic efficiency was tested against rhodamine B （RhB） and congo red （CR） dye solutions. Co3O4/NiO nanosponges showed excellent and enhanced photocatalytic efficacy compared to those of Co3O4, NiO nanoparticles, and standards like Ti02 and ZnO. The influence of paramount important operational parameters was explored and the conditions for the best photocatalytic efficiency were optimized. The trapping experiment revealed that the reactive oxygen species （ROS） identified was · OH radical. These findings certainly open up a new way for synthesizing a morphology dependent photocatalyst.展开更多
Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstruct...Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstructure of synthesized nanoparticles were analyzed by SEM and TEM. The vibration mode of nanoparticles was investigated using FTIR and Raman studies. The electrochemical behavior of the Ru- doped SnO2 electrode was evaluated in a 0.1 mol/L Na2SO4 solution using cyclic voltammetry. The 5% Ru-doped SnO2 electrode exhibited a high specific capacitance of 535.6 Fig at a scan rate 20 mV/s, possessing good conductivity as well as the electro- cycling stability. The Ru-doped SnO2 composite shows excellent electrochemical properties, suggesting that this composite is a promising material for supercapacitors.展开更多
The present work demonstrates the possibilities of hydrothermal trans- formation of Zn-AI layered double hydroxide （LDH） nanostructure by varying the synthetic conditions. The manipulation in washing step before hyd...The present work demonstrates the possibilities of hydrothermal trans- formation of Zn-AI layered double hydroxide （LDH） nanostructure by varying the synthetic conditions. The manipulation in washing step before hydrothermal treatment allows control over crystal morphologies, size and stability of their aqueous solutions. We examined the crystal growth process in the presence and the absence of extra ions during hydrothermal treatment and its dependence on the drug （diclofenac sodium （Dic- Na）） loading and release processes. Hexagonal plate-like crystals show sustained release with -90% of the drug from the matrix in a week, suggesting the applicability of LDH nanohybrids in sustained drug delivery systems. The fits to the release kinetics data indicated the drug release as a diffusion-controlled release process. LDH with rod-like morphology shows excellent colloidal stability in aqueous suspension, as studied by photon correlation spectroscopy.展开更多
The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththe...The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththese methods along with an online chatter detectionalgorithm is proposed for efficient determination of SLDs.To accomplish this, communication between the machinecontrol and chatter detection algorithm is established, andthe machine axes are controlled to change the spindle speedor depth of cut. The efficiency of the proposed method isanalyzed in this paper.展开更多
This paper presents an approach for determiningthe optimal cutting condition for milling thin-walled ele-ments with complex shapes. The approach is based on theinteraction between the thin-walled detail and its period...This paper presents an approach for determiningthe optimal cutting condition for milling thin-walled ele-ments with complex shapes. The approach is based on theinteraction between the thin-walled detail and its periodicexcitation by tooth passing, taking into account the highintermittency of such a process. The influence of theexcitation frequency on the amplitude of the detail oscil-lation during milling was determined by simulation andexperiments. It was found that the analytical results agreedwith experimental data. The position of the detail when thetooth starts to cut was evaluated through experiments. Theinfluence of this parameter on the processing state is pre-sented herein. The processing stability is investigated andcompared with the proposed approach. Thereafter, spectralanalyses are conducted to determine the contribution of thevibrating frequencies to the detail behavior during processing.展开更多
Simultaneous processes such as parallel turningor milling offer great opportunities for more efficientmanufacturing because of their higher material removalrates. To maximize their advantages, chatter suppressiontechn...Simultaneous processes such as parallel turningor milling offer great opportunities for more efficientmanufacturing because of their higher material removalrates. To maximize their advantages, chatter suppressiontechnologies for simultaneous processes must be devel-oped. In this study, we constructed an automatic chattersuppression system with optimal pitch control for shared-surface parallel turning with rigid tools and a flexibleworkpiece, integrating in-process chatter monitoring basedon the cutting force estimation. The pitch angle betweentwo tools is tuned adaptively in a position control system inaccordance with the chatter frequency at a certain spindlespeed, in a similar manner as the design methodology forvariable-pitch cutters. The cutting force is estimatedwithout using an additional external sensor by employing amulti-encoder-based disturbance observer. In addition, thechatter frequency is measured during the process by per-forming a low-computational-load spectrum analysis at acertain frequency range, which makes it possible to cal-culate the power spectrum density in the control system ofthe machine tool. Thus, the constructed system for automatic chatter suppression does not require any addi-tional equipment.展开更多
Geometric physically-based simulation systemscan be used for analyzing and optimizing complex millingprocesses, for example in the automotive or aerospaceindustry, where the surface quality and process efficiencyare l...Geometric physically-based simulation systemscan be used for analyzing and optimizing complex millingprocesses, for example in the automotive or aerospaceindustry, where the surface quality and process efficiencyare limited due to chatter vibrations. Process simulationsusing tool models based on the constructive solid geometry（CSG） technique allow the analysis of process forces, tooldeflections, and surface location errors resulting from five-axis machining operations. However, modeling complextool shapes and effects like runout is difficult using CSGmodels due to the increasing complexity of the shapedescriptions. Therefore, a point-based method for modelingthe rotating tool considering its deflections is presented inthis paper. With this method, tools with complex shapesand runout can be simulated in an efficient and flexibleway. The new modeling approach is applied to exemplarymilling processes and the simulation results are validatedbased on machining experiments.展开更多
Research on dynamics and stability of machin-ing operations has attracted considerable attention. Cur-rently, most studies focus on the forward solution ofdynamics and stability in which material properties and thefre...Research on dynamics and stability of machin-ing operations has attracted considerable attention. Cur-rently, most studies focus on the forward solution ofdynamics and stability in which material properties and thefrequency response function at the tool tip are known topredict stable cutting conditions. However, the forwardsolution may fail to perform accurately in cases whereinthe aforementioned information is partially known or var-ies based on the process conditions, or could involve sev-eral uncertainties in the dynamics. Under thesecircumstances, inverse stability solutions are immenselyuseful to identify the amount of variation in the effectivedamping or stiffness acting on the machining system. Inthis paper, the inverse stability solutions and their use forsuch purposes are discussed through relevant examples andcase studies. Specific areas include identification of processdamping at low cutting speeds and variations in spindledynamics at high rotational speeds.展开更多
The occurrence of chatter in milling processeswas investigated in this study. The prediction of the sta-bility lobes of metal cutting processes requires a model ofthe cutting force and a model of the dynamic machine t...The occurrence of chatter in milling processeswas investigated in this study. The prediction of the sta-bility lobes of metal cutting processes requires a model ofthe cutting force and a model of the dynamic machine toolbehavior. Parameter uncertainties in the models may leadto significant differences between the predicted and mea-sured stability behavior. One approach towards robuststability consists of running a large number of simulationswith a random sample of uncertain parameters and deter-mining the confidence levels for the chatter vibrations,which is a time-consuming task. In this paper, an efficientimplementation of the multi frequency solution and theconstruction of an approximate solution is presented. Theapproximate solution requires the explicit calculation of themulti frequency solution only at a few parameter points,and the approximation error can be kept small. This studyfound that the calculation of the robust stability lobe dia-gram, which is based on the approximate solution, is sig-nificantly more efficient than an explicit calculation at allrandom parameter points. The numerically determinedrobust stability diagrams were in good agreement with theexperimentally determined stability lobes.展开更多
Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibratio...Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibrations, and to investigate the effects of variousmachining parameters on this phenomenon. The dynamicproperties of the machine tool at the tool tip are obtainedbased on experimental modal analysis, and are used in themodel as the cutter dynamics. The model allows for thenatural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena thatoccur at the chip-tool interface ultimately leading tostable or unstable cutting. The model was used todemonstrate the effects of the machining parameters, suchas the axial depth of cut, radial immersion, and feed rate,on the occurrence of chatter. Additionally, the phenomenonof jumping out of the cut region could be observed in thismodel and its effect on the chatter process is demonstrated.The numerical model is verified based on comparisons withexperimental results.展开更多
The prediction of chatter vibration is influencedby many known complex phenomena and is uncertain. Wepresent a new effect that can significantly change the sta-bility properties of cutting processes. It is shown that ...The prediction of chatter vibration is influencedby many known complex phenomena and is uncertain. Wepresent a new effect that can significantly change the sta-bility properties of cutting processes. It is shown that themicroscopic environment of chip formation can have alarge effect on its macroscopic properties. In this work, acombined model of the surface regeneration effect and chipformation is used to predict the stability of turning pro-cesses. In a chip segmentation sub-model, the primaryshear zone is described with a corresponding materialmodel along layers together with the thermodynamicbehavior. The surface regeneration is modeled by the time-delayed differential equation. Numerical simulations showthat the time scale of a chip segmentation model is sig-nificantly smaller than the time scale of the turning process;therefore, averaging methods can be used. Chip segmen-tation can decrease the average shear force leading todecreased cutting coefficients because of the non-lineareffects. A proper linearization of the equation of motionleads to an improved description of the cutting coefficients.It is shown that chip segmentation may significantlyincrease the stable domains in the stability charts; fur-thermore, by selecting proper parameters, unbounded sta-bility domains can be reached.展开更多
文摘In the present study, novel Co3O4/NiO nanosponges designed for the photocatalytic degradation of organic contaminants were synthesized by a simple precipitation technique. The formation of sponge-like nanostructures was clearly evident through the TEM analysis. The photocatalytic efficiency was tested against rhodamine B （RhB） and congo red （CR） dye solutions. Co3O4/NiO nanosponges showed excellent and enhanced photocatalytic efficacy compared to those of Co3O4, NiO nanoparticles, and standards like Ti02 and ZnO. The influence of paramount important operational parameters was explored and the conditions for the best photocatalytic efficiency were optimized. The trapping experiment revealed that the reactive oxygen species （ROS） identified was · OH radical. These findings certainly open up a new way for synthesizing a morphology dependent photocatalyst.
文摘Synthesis of nanostructured Ru-doped SnO2 was successfully carried out using the reverse microemulsion method. The phase purity and the crystallite size were analyzed by XRD. The surface morphology and the microstructure of synthesized nanoparticles were analyzed by SEM and TEM. The vibration mode of nanoparticles was investigated using FTIR and Raman studies. The electrochemical behavior of the Ru- doped SnO2 electrode was evaluated in a 0.1 mol/L Na2SO4 solution using cyclic voltammetry. The 5% Ru-doped SnO2 electrode exhibited a high specific capacitance of 535.6 Fig at a scan rate 20 mV/s, possessing good conductivity as well as the electro- cycling stability. The Ru-doped SnO2 composite shows excellent electrochemical properties, suggesting that this composite is a promising material for supercapacitors.
文摘The present work demonstrates the possibilities of hydrothermal trans- formation of Zn-AI layered double hydroxide （LDH） nanostructure by varying the synthetic conditions. The manipulation in washing step before hydrothermal treatment allows control over crystal morphologies, size and stability of their aqueous solutions. We examined the crystal growth process in the presence and the absence of extra ions during hydrothermal treatment and its dependence on the drug （diclofenac sodium （Dic- Na）） loading and release processes. Hexagonal plate-like crystals show sustained release with -90% of the drug from the matrix in a week, suggesting the applicability of LDH nanohybrids in sustained drug delivery systems. The fits to the release kinetics data indicated the drug release as a diffusion-controlled release process. LDH with rod-like morphology shows excellent colloidal stability in aqueous suspension, as studied by photon correlation spectroscopy.
文摘The experimental determination of stability lobediagrams （SLDs） in milling can be realized by eithercontinuously varying the spindle speed or by varying thedepth of cut. In this paper, a method for combining boththese methods along with an online chatter detectionalgorithm is proposed for efficient determination of SLDs.To accomplish this, communication between the machinecontrol and chatter detection algorithm is established, andthe machine axes are controlled to change the spindle speedor depth of cut. The efficiency of the proposed method isanalyzed in this paper.
文摘This paper presents an approach for determiningthe optimal cutting condition for milling thin-walled ele-ments with complex shapes. The approach is based on theinteraction between the thin-walled detail and its periodicexcitation by tooth passing, taking into account the highintermittency of such a process. The influence of theexcitation frequency on the amplitude of the detail oscil-lation during milling was determined by simulation andexperiments. It was found that the analytical results agreedwith experimental data. The position of the detail when thetooth starts to cut was evaluated through experiments. Theinfluence of this parameter on the processing state is pre-sented herein. The processing stability is investigated andcompared with the proposed approach. Thereafter, spectralanalyses are conducted to determine the contribution of thevibrating frequencies to the detail behavior during processing.
文摘Simultaneous processes such as parallel turningor milling offer great opportunities for more efficientmanufacturing because of their higher material removalrates. To maximize their advantages, chatter suppressiontechnologies for simultaneous processes must be devel-oped. In this study, we constructed an automatic chattersuppression system with optimal pitch control for shared-surface parallel turning with rigid tools and a flexibleworkpiece, integrating in-process chatter monitoring basedon the cutting force estimation. The pitch angle betweentwo tools is tuned adaptively in a position control system inaccordance with the chatter frequency at a certain spindlespeed, in a similar manner as the design methodology forvariable-pitch cutters. The cutting force is estimatedwithout using an additional external sensor by employing amulti-encoder-based disturbance observer. In addition, thechatter frequency is measured during the process by per-forming a low-computational-load spectrum analysis at acertain frequency range, which makes it possible to cal-culate the power spectrum density in the control system ofthe machine tool. Thus, the constructed system for automatic chatter suppression does not require any addi-tional equipment.
文摘Geometric physically-based simulation systemscan be used for analyzing and optimizing complex millingprocesses, for example in the automotive or aerospaceindustry, where the surface quality and process efficiencyare limited due to chatter vibrations. Process simulationsusing tool models based on the constructive solid geometry（CSG） technique allow the analysis of process forces, tooldeflections, and surface location errors resulting from five-axis machining operations. However, modeling complextool shapes and effects like runout is difficult using CSGmodels due to the increasing complexity of the shapedescriptions. Therefore, a point-based method for modelingthe rotating tool considering its deflections is presented inthis paper. With this method, tools with complex shapesand runout can be simulated in an efficient and flexibleway. The new modeling approach is applied to exemplarymilling processes and the simulation results are validatedbased on machining experiments.
文摘Research on dynamics and stability of machin-ing operations has attracted considerable attention. Cur-rently, most studies focus on the forward solution ofdynamics and stability in which material properties and thefrequency response function at the tool tip are known topredict stable cutting conditions. However, the forwardsolution may fail to perform accurately in cases whereinthe aforementioned information is partially known or var-ies based on the process conditions, or could involve sev-eral uncertainties in the dynamics. Under thesecircumstances, inverse stability solutions are immenselyuseful to identify the amount of variation in the effectivedamping or stiffness acting on the machining system. Inthis paper, the inverse stability solutions and their use forsuch purposes are discussed through relevant examples andcase studies. Specific areas include identification of processdamping at low cutting speeds and variations in spindledynamics at high rotational speeds.
文摘The occurrence of chatter in milling processeswas investigated in this study. The prediction of the sta-bility lobes of metal cutting processes requires a model ofthe cutting force and a model of the dynamic machine toolbehavior. Parameter uncertainties in the models may leadto significant differences between the predicted and mea-sured stability behavior. One approach towards robuststability consists of running a large number of simulationswith a random sample of uncertain parameters and deter-mining the confidence levels for the chatter vibrations,which is a time-consuming task. In this paper, an efficientimplementation of the multi frequency solution and theconstruction of an approximate solution is presented. Theapproximate solution requires the explicit calculation of themulti frequency solution only at a few parameter points,and the approximation error can be kept small. This studyfound that the calculation of the robust stability lobe dia-gram, which is based on the approximate solution, is sig-nificantly more efficient than an explicit calculation at allrandom parameter points. The numerically determinedrobust stability diagrams were in good agreement with theexperimentally determined stability lobes.
文摘Chatter vibration is a major obstacle inachieveing increased machining performance. In thisresearch, a finite element model of chip formation in a 2Dmilling process is used to predict the occurrence of chattervibrations, and to investigate the effects of variousmachining parameters on this phenomenon. The dynamicproperties of the machine tool at the tool tip are obtainedbased on experimental modal analysis, and are used in themodel as the cutter dynamics. The model allows for thenatural development of vibration as the result of the chip-tool engagement, and accounts for various phenomena thatoccur at the chip-tool interface ultimately leading tostable or unstable cutting. The model was used todemonstrate the effects of the machining parameters, suchas the axial depth of cut, radial immersion, and feed rate,on the occurrence of chatter. Additionally, the phenomenonof jumping out of the cut region could be observed in thismodel and its effect on the chatter process is demonstrated.The numerical model is verified based on comparisons withexperimental results.
文摘The prediction of chatter vibration is influencedby many known complex phenomena and is uncertain. Wepresent a new effect that can significantly change the sta-bility properties of cutting processes. It is shown that themicroscopic environment of chip formation can have alarge effect on its macroscopic properties. In this work, acombined model of the surface regeneration effect and chipformation is used to predict the stability of turning pro-cesses. In a chip segmentation sub-model, the primaryshear zone is described with a corresponding materialmodel along layers together with the thermodynamicbehavior. The surface regeneration is modeled by the time-delayed differential equation. Numerical simulations showthat the time scale of a chip segmentation model is sig-nificantly smaller than the time scale of the turning process;therefore, averaging methods can be used. Chip segmen-tation can decrease the average shear force leading todecreased cutting coefficients because of the non-lineareffects. A proper linearization of the equation of motionleads to an improved description of the cutting coefficients.It is shown that chip segmentation may significantlyincrease the stable domains in the stability charts; fur-thermore, by selecting proper parameters, unbounded sta-bility domains can be reached.
