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The working space of small motor stators is narrow, and most of them are manual winding. It is difficult to guarantee the uniform arrangement of enameled wires by multi-wire winding. To solve these problems, a three-phase parallel equivalent multi-wire winding robot is proposed to achieve large output torque of the motor. Firstly, according to the equivalent model, the structure of the large arm, small arm and manipulator is designed to determine the motion model of the winding robot. Euler's kinematics theory is used to analyze the change of the working position of the arm, and the rotation matrix of the arm and the constraint equation of the motion vector of each branch chain are established. The motion model of the arm and the manipulator are established using inverse kinematics and analytical analysis. The motion pose of each joint of the winding robot is studied to ensure that the robot realizes a three-phase parallel multi-wire winding motion. ADAMS software was used for kinematic simulation analysis of the winding robot. The displacement of the branch chain on the xyz axis was represented by the torque of the virtual motor to verify the correctness of the inverse kinematics solution and the closure condition of the manipulator block. Finally, the ROS simulation platform is built to simulate the joint motion planning of the winding robot to verify the multi-line parallel principle and the feasibility of the multi-line parallel winding hybrid robot. The research results of this paper provide a theoretical reference for multi-wire parallel winding equipment control.

As for ultra-precision grinding of difficult-to-process thin-walled complex components with ball-end grinding wheels, interference is easy to occur. According to screw theory and grinding kinematics, a mathematical model is established to investigate the interference and grinding characteristics of the ball-end wheel. The relationship between grinding wheel inclination angle, C axis rotation angle, grinding position angle and grinding wheel wear are analyzed. As the grinding wheel inclination angle increases, the C axis rotatable range decreases and the grinding position angle increases. The grinding position angle and wheel radius wear show a negative correlation with the C axis rotation angle. Therefore, a trajectory planning criteria for increasing grinding speed as much as possible under the premise of avoiding interference is proposed to design the grinding trajectory. Then grinding point distribution on the ball-end wheel is calculated, and the grinding characteristics, grinding speed and maximum undeformed chip thickness, are investigated. Finally, a complex structural component can be ground without interference, and surface roughness and profile accuracy are improved to 40.2 nm and 0.399 μm, compared with 556 nm and 3.427 μm before ultra-precision grinding. The mathematical model can provide theoretical guidance for the analysis of interference and grinding characteristics in complex components grinding to improve its grinding quality.

Dielectrics are electrical insulator materials, polarizable by opposite displacement of positive and negative ionized atoms via electric fields across the material’s thickness. Dielectrics are used in energy-storage capacitors, as key components in modern micro-/nanoelectronics, high-frequency and mobile communication devices, and life-saving microchips and other devices such as defibrillators and pacemakers implantable in humans. A key dielectric parameter is the dielectric constant (k), which largely controls the capacitance in capacitors with nanoscale area and dielectric layer thickness. Extremely high dielectric constants (k ≥1000) were observed in oxides (e.g., La1.8Sr0.12NiO4) with relaxor/ferroelectric materials and in combined semiconducting bulk properties with highly resistive grain boundaries. Giant dielectric constant films have also been demonstrated, based on integrating relatively low-dielectric-constant oxides into nanolaminate structures (e.g., TiOx/Al2O3; TiO2/HfO2) with tailored sublayer thicknesses, interfaces, and oxygen atom distributions. This overview article addresses the science and technology of high-dielectric-constant oxide materials with different compositions and structures.

The adherent behaviors of hydroxyl-terminated polybutadiene (HTPB), a typical high viscosity liquid widely used as a binder in rocket motor propellants, onto the copper (Cu) surfaces with/without the interference of Al nanoparticles were investigated by classical molecular dynamics (MD) simulations. The results indicate that HTPB molecules adsorbed directly onto Cu(001) surface exhibit the tendency to distribute parallel to the 〈110〉 crystal direction family as a result of tense atom arrangement along the close-packed crystal directions. The dynamic hydrogen-bonded network, formed by inter-/intra-molecular interactions among neighbouring hydroxyl groups, is also suggested to exert strong influence on the distribution of HTPB molecules. Moreover, Al nanoparticles have been proved to be readily enveloped by HTPB chains when placed close to the pure high viscosity liquid, which will in turn restrict the mobility of HTPB molecules, eventually resulting in the decrease of wettability of HTPB droplet on Cu surface. The flow slip behavior of HTPB liquid on Cu surface, regardless of the presence of Al nanoparticles, was tested and directly compared by confined shear simulations. The Al hemispheres, acting as convex obstacles on the flat surface, seem to be capable of suppressing the slippage of chain-like HTPB molecules, which will be easily entangled by local protrusions. Therefore, it can be inferred that the flow behavior and interfacial wettability of high viscosity liquid will be largely influenced by the discontinuous solid-phase particles dispersed in it.

Wetting test and classical molecular dynamics (MD) simulations were employed to investigate the adherent behaviors of hydroxyl-terminated polybutadiene (HTPB), a typical high viscosity liquid widely used as a binder in rocket motor propellants, onto the copper (Cu) surfaces with different topographies. Experimental data show that the microstructures protruding above the substrate surfaces can be ‘sensed’ by the HTPB droplet, which has been indicated by the smaller contact angles and higher interface tension for this specific liquid on the rough surfaces (featured with sinusoidal structures or square pillars) than that on the smooth surface. Simulation results reveal the atomic details of spreading process of HTPB chains, with diverse diffusion propensities presented on different surfaces. The HTPB droplet spreads widely on the smooth surface, exhibiting a roughly isotropic trend. On the contrary, the state of this high viscosity liquid on the sinusoidal-structured surface is featured by wide contact diffusion along the run of groove, but relatively restricted extension in the direction perpendicular to the groove, as a result of the barriers exerted by the nearest neighbouring peaks. The existence of nanoscale pillars increases the exterior surface area of Cu substrate, therefore the HTPB chains can penetrate deep to envelop the peripheries of the pillars, forming abundant direct contacts with Cu surface and producing a highest HTPB–Cu interaction energy, which well accords with the experimental results about the adherent strength of HTPB.

In this work, a special grinding machine tool using a small ball-end grinding wheel is designed to achieve ultra-precision grinding of complex components with small concave surfaces. A comprehensive error propagation model is established, considering kinematic errors, setup errors and structure parameters. Sensitivity analysis is performed by the Sobol' method to quantify the relationship between the errors, structure parameters and geometric accuracy of the machine tool. On this basis, error allocation is carried out, and the inclination angle of the grinding wheel spindle and the working range of the C-axis are optimized to reduce the influence of the setup errors on machining accuracy. Then, the predicted geometric accuracy of the machine is 0.3 μm, contributing only to half of the profile accuracy requirement for peak-to-valley PV

The self-developed mechanical processing quasi-field provides the campus engineering environment and the professional experimental teaching practice platform for young teachers in professional education. With the help of a series of professional curriculum supporting training, experiment, practical operation and design links, the practical teaching ability of young teachers can be improved from engineering task design, engineering practice operation to engineering problem solving through the synchronous interaction between classroom theory and engineering practice application. It provides teacher quality assurance for the transportation of high-quality engineering and scientific talents in high-end manufacturing field.

Localized CO2 laser repairing of surface damage on fused silica optics has been successfully applied in high-power laser system in the field of controllable nuclear fusion. In order to accurately predict the surface topography evolution and to reveal the intrinsic physical mechanism during the process of laser mitigation, experiments of localized CO2 laser mitigation were firstly carried out to analyze the features of mitigated craters under different laser powers. Then a multi-physics coupled mathematical model was developed based on the fluid control equation, heat and mass transfer equation and material phase transition kinetics to investigate the thermodynamic and kinetic behaviors of laser interaction with silica. The model considered the effects of Marangoni convection, gravity, capillary force and vaporization recoil pressure, as well as the nonlinear variation of physical parameters of silica material with respect to temperature. The results showed that with the increase of laser power, the material ablation and the appearance of raised rim occurred simultaneously. The depth of the mitigated crater increased sharply when the threshold for material ablation was attained, while the lateral dimension increased linearly. The vaporization recoil pressure was found to be the dominant factor for the formation of Gaussian crater with the raised rim feature. The capillary force caused the material at the edge of the molten pool to have a tendency to reflow after laser shutting down, but it was too small to change the surface topography. This work could significantly contribute to the understanding of laser mitigation process, which laid the foundation for the accurate prediction and evaluation of surface quality of CO2 laser repaired fused silica surface.

A new fault detection and tolerance (FDT) control strategy for current sensors of permanent magnet synchronous machine drive in filed-oriented control mode was introduced in this paper, based on the reasonable estimation of current amplitude. The propounded method can be applied to deal with a single or double signal-loss faults (two concurrent or independent faults), and shows the capability of online revision to gain variation and zero offset. Compared with the conventional observer-/model-based fault detection methods for current sensors, the proposed method only requires the information of three-phase currents and the position of motor rotor, instead of an accurate system model with explicit parameters. The improved simplicity and reliability makes this new method especially useful for FDT of current sensors in a real-time control system with limited computational capability. The feasibility and robustness of the proposed approach has been validated by extensive experiments under a wide variety of working conditions.

Complex structural components with small concave surfaces are widely needed in aerospace, optics, and electronic industry. On account of the interference between grinding wheel and workpiece and small concave surfaces, traditional grinding machine cannot realize the grinding process; hence, a specialized grinding machine tool with on-machine electric discharge truing function is needed. After analyzing the structural characteristics and processing requirements of the component, the kinematic chain and configuration were designed. The structure of the machine tool was divided into four function modules, and each module was designed, analyzed, and optimized, respectively. Then the finite element analysis (FEA) of the whole machine tool was conducted including static, modal, and harmonic response analysis to verify the performance of the machine and identify the weak links of the structure loop. The error model was established by screw theory to study the quantitative relationship between the static deformations and processing accuracy. Both finite element analysis and error model can provide guidance for further optimization. Finally, the performance of the machine tool was evaluated by the grinding and on-machine truing experiments, achieving the profile accuracy (PV) of 0.339 μm, surface roughness (Ra) of 50.2 nm, and the grinding wheel surface with diamonds distributing homogeneously. The results indicate that the developed machine tool can well satisfy the processing requirements of the component.

Nucleation and biomineralization of apatite on titanium-based material surfaces is crucial to improve surface biocompatibility, osseointegration, and rapid bone ingrowth in biomedical applications such as joint replacements. This work is designed to provide new insights on the molecular processes in the initial nucleation of calcium phosphate on TiO2 surface by means of classical molecular dynamics (MD) simulations. Aggregation of calcium and phosphate ions in pure aqueous solution was studied, and the free energies during ion adsorption was investigated by the calculation of PMFs. The MD results suggest surface hydroxylation rate and nanotopographies of TiO2 substrate contribute significantly to the initial nucleation of calcium phosphate. Our simulations suggest that surface hydroxyls on TiO2 provide active sites for the aggregation of calcium phosphate. Both calcium ions and phosphate ions could bind to the hydroxylated TiO2 surface directly or indirectly via the first water layer. Surface nanotopograp...

To meet the strict requirements for processing quality, the metal-bonded small ball-end diamond wheel (SBDW) has become a promising choice to process the hard and brittle materials with small concave surface. Unlike conventional diamond wheels, the profile accuracy of SBDW would so greatly affect the form accuracy of ground small concave surfaces that a truing system must be adopted to insure the accuracy of SBDW. Hence, the effects of kinematic parameters of the truing system on the on-machine electric discharge truing (EDT) of SBDW are investigated. The effects of the errors from kinematics, electrode geometry and relative position on truing are analyzed by establishing the mathematical model through screw theory. In the experiments, the effects of spindle speeds of SBDW and tool electrode on truing are investigated and the complex component with small concave surfaces is ground by the optimally trued SBDW. The results indicate that there are more factors affecting the dimension accuracy than profile accuracy of the trued SBDW. Each factor affects dimension accuracy equally, while the radial run-out error of grinding wheel spindle influences profile accuracy more significantly than others. The spindle speed of SBDW affects the profile accuracy more remarkably than that of tool electrode, and the relative speed between them affects the truing efficiency and surface quality of SBDW. The final profile error (PV) and surface roughness (Ra) of the practically ground component are 0.328 μm and 50.2 nm, respectively.

Micro-milling is a promising approach to repair the micro-defects on the surface of potassium dihydrogen phosphate (KDP) crystal. However, KDP crystal is difficult to machine due to its properties of soft-brittle and easy deliquescence. This study investigates the minimum undeformed chip thickness hm and the size effect in micro end-milling of KDP crystal by comprehensively analyzing cutting force, specific cutting force and machined surface quality. A model of the chip formation, which is capable of connecting the minimum undeformed chip thickness, the undeformed chip thickness and the periodicity of cutting force together, is developed to predict the value of minimum undeformed chip thickness. The normalized minimum undeformed chip thickness λe in terms of the ratio of the minimum undeformed chip thickness to the cutting edge radius re, is estimated to be 0.43 ≤ λe ≤ 0.48. The significantly non-proportional increase of specific cutting force indicates the existence of size effects when the ratio of feed per tooth to cutting edge radius ft/re is less than 0.7. The machined surface quality also reflects severe size effect by the phenomenon that the micro cracks and brittle pits appear on the groove base, and the value of surface roughness Ra is large when the ratio ft/re is less than 0.5. Furthermore, the surface quality deteriorates and the brittle cutting appears when the ratio ft/re is much larger than 1 which seems similar to macro-milling. The perfect machined surface with almost no ploughing effect and brittle cutting is achieved at a ratio ft/re of 0.7. Therefore, a feed per tooth, slightly larger than the minimum undeformed chip thickness but smaller than cutting edge radius, is recommended for micro-milling of KDP crystal or soft-brittle crystal.

Potassium dihydrogen phosphate (KH2PO4 or KDP) crystal is a typical soft-brittle optical crystal, and the size effect and brittle cutting mode are easy to appear in micro ball end-milling of KDP crystal. In this paper, micro-grooving experiments are conducted to study the size effect and brittle cutting in micro ball end-milling of KDP crystal with different feed rate and depth of cut. The cutting force, machined groove base quality and chip morphology are collected and analyzed carefully. The size effect is discovered by the phenomena of the existence of oscillations and relaxations in cutting force and hyper-proportional increase of specific cutting force, when the ratio of feed per tooth to cutting edge radius ft/re is less than 1. While the brittle cutting mode is detected through the existence of sharp fluctuations in cutting force and cracks on the groove base when the ratio ft/re is larger than 2. From the further comprehensive analysis of cutting force, specific cutting force, machined groove base quality and chip morphology, the cutting parameters with ratios of the maximum undeformed chip thickness in one cutting circle to cutting edge radius hmax/re around 0.14, 0.2 and 0.4 are regarded as size effect, optimal and brittle cutting points, respectively. The size effect, ductile cutting and brittle cutting zones are divided by the size effect and brittle cutting boundaries (points). Among the optimal points, the depth of cut of 2 μm with the ratio ft/re of 1 is the optimal cutting parameter for micro ball end-milling of KDP crystal.

This paper presents a new method of realizing vector control for the surface mounted permanent magnet synchronous machine (PMSM) using single phase current sensor. A simplified estimating method of phase current, which only requires the information from single phase current sensor and motor position sensor, has been proposed in this paper. Compared with the classical approaches, based on the reference current in synchronous rotor frame, the proposed method can get better accuracy, especially when there is a sudden change of the reference current. Furthermore, the method not relays on the model and parameters of PMSM and the control performance of current close-loop and also not sensitive to working conditions. The extensively experimental results under different work conditions, based on MATLAB/SIMULINK, have validated the feasibility and robustness of the proposed vector control method.

Small ball-end fine diamond grinding pins dressed by on-machine electrical discharge method are promising tools for ultra-precision grinding complex structural components of hard and brittle materials. Since the electrical discharge dressing can affect the grinding pin surface morphology, it is necessary to study the wear mechanism of the metal bonded fine diamond grinding pin dressed by electrical discharge. Electrical discharge dressing experiments and fused silica grinding experiments are conducted to investigate the relationship between grinding pin wear and the dressed grinding pin surface morphology, and analyze the influence of grinding pin wear on the grinding ratio G, surface roughness, and grinding force. The metal bond recast layer, the discharge crater around the diamond grit, and the diamond graphitization are the surface morphologies of the dressed grinding pin that affect the grinding pin wear. The wear modes of the grinding pin are micro-fracture, abrasion, metal bond wear, grit pull-out. Although metal bond wear accelerates the grinding pin wear, it is prone to improve the grinding pin self-sharpening. The grinding ratio, surface roughness, and grinding force variations with the fused silica sample removal volume further verify the analysis of the dressed grinding pin wear mechanism and the self-sharpening.

The hydrophobic stability to prevent Cassie-Wenzel (C-W) transition is an important property of superhydrophobic surfaces, which is mainly controlled by the micro/nano structure of surfaces. Based on the contact lines (CLs) around and inside the contact region, we analyzed the applied forces on a static sessile droplet deposited on the hydrophobic micropillar-structured surface. A simplified double-radius fitting method was derived to outline the contour of the droplet, and a force-balance model was gained to describe the critical conditions of the C-W transition. Compared with the classical force-balance models, the theoretical predictions from the proposed model agree much better with the experimental results. A reliable estimation of the critical conditions for the C-W transition during evaporation can be readily formed by integrating the depinning mechanism of the receding CL on the micro-patterned surfaces into our model, which obviously cannot be obtained by the classical force-balance models. The effects of gravity and surface tension in the proposed equilibrium model for the C-W transition reach a compromise. The introduction of surface tension acting on the apparent CL in our model will help to provide appropriate geometric parameters for microstructures on the superhydrophobic surfaces to achieve high hydrophobic stability.

To investigate the topographical dependency of protein adsorption, molecular dynamics simulations were employed to describe the adsorption behavior of the tenth type-III module of fibronectin (FN–III 10 ) on nanostructured rutile (110) surfaces. The results indicated that the residence time of adsorbed FN–III 10 largely relied on its binding mode (direct or indirect) with the substrate and the region for protein migration on the periphery (protrusion) or in the interior (cavity or groove) of nanostructures. In the direct binding mode, FN–III 10 molecules were found to be ‘trapped’ at the anchoring sites of rutile surface, or even penetrate deep into the interior of nanostructures, regardless of the presented geometrical features. In the indirect binding mode, FN–III 10 molecules were indirectly connected to the substrate via a hydrogen–bond network (linking FN–III 10 and interfacial hydrations). The facets created by nanostructures, which exerted restraints on protein migration, were suggested to play an important role in the stability of indirect FN–III 10 –rutile binding. However, a doubly unfavorable situation – indirect FN–III 10 –rutile connections bridged by a handful of mediating waters and few constraints on movement of protein provided by nanostructures – would result in an early desorption of protein.

The flow behavior of highly viscous casting explosives in micro-channels and special shaped moulds are critical factors affecting the formations of solid propellants and explosives. In the present work, the spreading property and flow behavior of hydroxyl-terminated polybutadiene (HTPB) binders, a major component of casting explosives, on Cu surfaces with nanostructures and perfluorosilylation were investigated by classical molecular dynamics simulations. Our results suggest that the atomic steps, exposed on the pit-/terrace-structured Cu surfaces, seem able to restrict the spreading of HTPB molecules from crossing over the step edges. After surface perfluorosilylation, the adhesive strength between HTPB and Cu substrate has decreased by nearly two orders of magnitude, resulting a vigorous travel of single HTPB molecules. Moreover, the cohesive strength between two adjacent HTPB droplets (-343.2 kcal/mol) is found to be higher than the adhesive strength of HTPB droplets on the perfluorosilylated smooth Cu surface (−85.7 kcal/mol). Thus, HTPB droplets could spread slowly on the perfluorosilylated Cu surface with a semi-spherical shape, irrespective of the presence of surface diatomic terraces. The reduced adsorption strength could also result in a slower infiltration speed of HTPB into the perfluorosilylated grooves and an increased slip performance on the perfluorosilylated surfaces.

Micro-/nano-topographies on the surface of titanium-based biomaterials are critical features responsible for protein adsorptions, and investigations into the underlying molecular mechanisms are essential to improving the biocompatibility of titanium-based biomaterials. In the present work, classical molecular dynamics simulations were conducted to study the synergetic influences of surface nanostructures, hydroxylation states and bioactive ions on the adsorption of collagen tripeptides onto the TiO2 surfaces. The nanostructures on the non-hydroxylated surface, i.e., grooves or ridges, favor the formation of highly ordered layers of water molecules at the surface, which create strong barriers for stable adsorptions of tripeptides. Surface hydroxylation, however, makes the water distribution less ordered and more dispersive on hydroxylated surfaces. Thus, tripeptides are able to adsorb stably on the hydroxylated grooves, by passing through the loosely packed water layers and forming hydrogen bonds with the surface hydroxyls. Moreover, the hydroxylation on the grooved surfaces also facilitates the aggregation of calcium/phosphate ions. Consequently, the intermediate calcium/phosphate ions reduce the energy barriers of compact water layers and provide active sites for tripeptide adsorption. The present computational study provides insights into the intrinsic mechanisms of peptide adsorptions on the nanostructured Ti-based biomaterial surface.

Potassium dihydrogen phosphate (KDP or KH2PO4) crystal is widely used as terminal frequency converters in inertial confinement fusion (ICF). However, KDP crystal is a typical difficult-to-cut optical crystal with the characteristic of soft-brittle. In this work, the relationship between cutting force and processed surface quality in micro ball end-milling of KDP crystal with various depth of cut and spindle speed is studied by carried out the micro-milling experiments. Fast Fourier Transform (FFT) algorithm is used to diagnose the recorded cutting force. The periodic change of cutting force and the cutting force after filtering noises can be got through FFT analysis. Through calculating the correlation coefficients between the static component of thrust force and roughness value Ra of machined grooves, as well as the peak-valley (P-V) value of thrust force and dimensional error of machined grooves, the roughness value Ra and dimensional error of machined grooves would be predicted by monitoring the static component and P-V value of the thrust force, respectively. The relatively large spindle speed helps to reduce the roughness value Ra. The spindle speed with moderate value is recommended to reduce the dimensional error of machined groove because the dimensional error of machined groove will increase when the spindle speed is small enough (causing brittle cutting) or large enough (reducing cutting stability).

Micro-milling is a promising approach to repair the micro-defects on the surface of KH2PO4 (KDP) crystal. The geometrical parameters of micro ball end mill will greatly influence the repairing process as a result of the soft brittle properties of KDP crystal. Two types of double-edged micro ball end mills were designed and a three-dimensional finite element (FE) model was established to simulate the micro milling process of KDP crystal, which was validated by the milling experiments. The rake angle of −45°, the relief angle of 45° and the cutting edge radius of 1.5–2 μm were suggested to be the optimal geometrical parameters, whereas the rake angle of −25° and the relief angle of 9° were optimal just for micro ball end mill of Type I, the configuration with the rake angles ranging from 0° to 35°, by fully considering the cutting force, and the stress–strain distribution over the entire tool and the cutting zone in the simulation. Moreover, the micro polycrystalline diamond (PCD) ball end mills adopting the obtained optimal parameters were fabricated by wire electro-discharge machining (WEDM) and grinding techniques, with the average surface roughness Ra of tool rake face and tool flank face ∼0.10 μm, and the cutting edge radius of the tool ∼1.6 μm. The influence of tool's geometrical parameters on the finished surface quality was verified by the cutting experiments, and the tool with symmetric structure was found to have a better cutting performance. The repairing outlines with Ra of 31.3 nm were processed by the self-fabricated tool, which could successfully hold the growth of unstable damage sites on KDP crystal.

The early adsorption stages of collagen onto nano-grooved rutile surface without hydroxylation were studied using molecular dynamics and steered MD simulations. On the basis of plane rutile (110), two kinds of models have been adopted: single groove and parallel grooves along [1-11] crystal orientation with various width dimensions. Initially, collagens were parallel or perpendicular to the groove orientation, respectively, in order to investigate the influence of groove width on collagen adsorption. The simulation result suggests that surface grooves could exert a strong effect on collagen adsorption: when collagen was parallel to the groove direction, adsorption was favored if the groove width matched well with the dimension of collagen. However, adsorption strength may decrease as the groove width expanded. As for the condition of collagen perpendicular to the groove orientation, collagen was difficult to bend and insert into grooves in the free adsorption procedure. But the steered MD simulation results reveal that more energy was consumed for collagen to insert into narrower grooves which may be interpreted as strong barrier for adsorption. We believe that adsorption will be favored if appropriate dimension match between dimension of collagen and the groove width was approached.

Structure design and fabricating methods of three-dimensional (3D) artificial spherical compound eyes have been researched by many scholars. Micro-nano optical manufacturing is mostly used to process 3D artificial compound eyes. However, spherical optical compound eyes are less at optical performance than the eyes of insects, and it is difficult to further improve the imaging quality of compound eyes by means of micro-nano optical manufacturing. In this research, nonhomogeneous aspheric compound eyes (ACEs) are designed and fabricated. The nonhomogeneous aspheric structure is applied to calibrate the spherical aberration. Micro milling with advantages in processing three-dimensional micro structures is adopted to manufacture ACEs. In order to obtain ACEs with high imaging quality, the tool paths are optimized by analyzing the influence factors consisting of interpolation allowable error, scallop height and tool path pattern. In the experiments, two kinds of ACEs are manufactured by micro-milling with different too path patterns and cutting parameter on the miniature precision five-axis milling machine tool. The experimental results indicate that the ACEs of high surface quality can be achieved by circularly milling small micro-lens individually with changeable cutting depth. A prototype of the aspheric compound eye (ACE) with surface roughness (R a) below 0.12 μm is obtained with good imaging performance. This research ameliorates the imaging quality of 3D artificial compound eyes, and the proposed method of micro-milling can improve surface processing quality of compound eyes.

The adsorption of collagen on the reduced rutile (110) surface with monatomic step defects in aqueous solution was modeled by classical molecular dynamics simulation. The step defects on the rutile surface were mainly parallel to the 1 1 ¯ 1 > crystal orientation. Possible binding modes including direct and indirect binding modes, that were the peptide interacted with substrate surface directly or via the first layer water molecules, and the structural properties of collagen were discussed in order to analyze the adsorption dynamics of collagen on the reduced rutile surface. The simulation results suggested that the initial poses of collagen on the rutile surface could influence the adsorption conformation of collagen. The reduced rutile surface, which could increase the density of water molecules in the first layer, would provide active sites for collagen adsorption. The direct binding mode was responsible for the stable adsorption of collagen. The indirect binding mode may play an important part at the initial adsorption stage, but itself alone could not ‘trap’ the collagen on the surface stably unless the direct binding mode had already been formed. In addition, the triple helical structure of collagen was sustained by the inner-chain hydrogen bonds among different chains.

Classical molecular dynamics (MD) simulations were employed to investigate the adsorption behaviors of arginine-glycine-aspartate (RGD) tripeptide onto the negatively charged hydroxylated/nonhydroxylated rutile (110) surfaces, mediated by biologically important cations (Na+ or Ca2+). The simulation results indicate that the inherent nature of the cation determines its binding strength, thereby regulating the adsorption geometry of the peptide. The sparse hydroxyl groups on the nonhydroxylated rutile diminish the probability of H-bond formation between RGD and the surface, resulting in an early desorption of the peptide even with a mediating Na+ ion. In contrast, the negatively charged aspartate (Asp) side chain is bridged to the negatively charged hydroxylated rutile by an inner-sphere Na+ ion, in coordination with the Asp-rutile hydrogen bonds at the anchoring sites. The inner- and outer-sphere Ca2+ ions are demonstrated to be capable of "trapping" RGD on both hydroxylated and nonhydroxylated rutile, in the absence of hydrogen bonds with the surface. The strongly bound inner-sphere mediating Ca2+ ion exerts a "gluing" effect on the Asp side chain, producing a tightly packed RGD-rutile complex, whereas a less localized distribution density of the outer-sphere mediating Ca2+ ion results in a higher mobility of the Asp side chain. The intramolecular interaction is suggested to facilitate the structural stability of RGD adsorbed on the negative rutile in a "horseshoe" configuration.

A simple and cost-effective software-based resolver to digital converter together with a permanent magnet synchronous motor control system were presented. The proposed method incorporates software generation of the resolver carrier and using anti-tangent calculation for synchronous demodulation of the resolver outputs signal in such a way that there is a substantial savings on hardware like the costly carrier oscillator and associated digital and analog circuits for amplitude demodulators. And the faults of amplitude imbalance and imperfect quadrature of resolver signal can also be detected and compensated by software online. Computer simulation results demonstrate the effectiveness and applicability of the proposed scheme.

The interaction of amino acids with inorganic materials at interfaces plays an important role in enhancing the biocompatibility of titanium-based alloys. The adsorption of a tripeptide, i.e. Pro-Hyp-Gly, on the hydroxylated rutile TiO2(110) surface was investigated by the MD simulations. The changes in free energy during the adsorption of both the tripeptide and calcium ions were calculated by using the PMF method in order to obtain the adsorption strength. The results suggested that the adsorption of the tripeptide on the TiO2 surface through the carboxyl groups in glycine residues can be more stable compared with other binding conformations. Special attention was focused on the cooperative adsorption of the tripeptide with the assistance of calcium ions. Calcium ions preferred to absorb at the tetradentate or monodentate sites on the negatively charged TiO2 surface. As a result of the strong attraction between the carboxyl group and calcium ions, the tripeptide can be pulled down to the surface by following the trajectory of the calcium ions, forming an indirect interaction with a sandwich structure of peptide–cation–TiO2. However, this indirect interaction could eventually transform to the direct adsorption of the tripeptide on the TiO2 surface with higher binding energy. The results may help to interpret the adsorption of peptides on inorganic materials in aqueous solution with ions.

The binding of a negatively charged residue, aspartic acid (Asp) in tripeptide arginine-glycine-aspartic acid, onto a negatively charged hydroxylated rutile (110) surface in aqueous solution, containing divalent (Mg(2+), Ca(2+), or Sr(2+)) or monovalent (Na(+), K(+), or Rb(+)) cations, was studied by molecular dynamics (MD) simulations. The results indicate that ionic radii and charges will significantly affect the hydration, adsorption geometry, and distance of cations from the rutile surface, thereby regulating the Asp/rutile binding mode. The adsorption strength of monovalent cations on the rutile surface in the order Na(+) > K(+) > Rb(+) shows a "reverse" lyotropic trend, while the divalent cations on the same surface exhibit a "regular" lyotropic behavior with decreasing crystallographic radii (the adsorption strength of divalent cations: Sr(2+) > Ca(2+) > Mg(2+)). The Asp side chain in NaCl, KCl, and RbCl solutions remains stably H-bonded to the surface hydroxyls and the inner-sphere adsorbed compensating monovalent cations act as a bridge between the COO(-) group and the rutile, helping to "trap" the negatively charged Asp side chain on the negatively charged surface. In contrast, the mediating divalent cations actively participate in linking the COO(-) group to the rutile surface; thus the Asp side chain can remain stably on the rutile (110) surface, even if it is not involved in any hydrogen bonds with the surface hydroxyls. Inner- and outer-sphere geometries are all possible mediation modes for divalent cations in bridging the peptide to the rutile surface.