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Facing a great deal of Lifelog data and complex information, how to extract valuable information and making it easily understood for users is the most urgent and important issue. This paper introduces a method to find personal trajectories from a Lifelog dataset named informative lifelogging which the author collected over the past 8 years. After introducing the Lifelog system and the data structure, this paper propose a method to find personal trajectory in the dataset. Experiment result in the last chapter shows the correctness of this method. The method proposed in this paper provides some way of managing and retrieving the Lifelog data efficiently.

The authors began collecting personal informative lifelogging data in 2011. The data collected in this article is a discontinuous data set, each of which includes one or more images, a GPS message, a description of a location, and a description of the text, we call this informative lifelogging. However, for the purposes automatically building a story from a huge collection of unstructured egocentric data presents major challenges. This paper first introduces the structure and characteristics of the collected data and uses the DB-scan algorithm to classify the data. Then a model for generating a story is proposed, and a model of story generation based on a story template is proposed in the model. The author implemented a complete software system through code, described a story generation model, and gave the key algorithm to generate stories. Through this system, 418 stories were generated automatically, of which 62% of the stories were particularly accurate. The experimental results verify that it is feasible to automatically generate stories based on personal Informative lifelogging data.

The high temperature of the grinding area at the engineering ceramic materials processing is one of the main factors affecting the quality of processing and the performance of parts. In order to reveal the law of temperature distribution of silicon, nitride ceramic grinding and its mechanism of action on surface quality. The process of machining silicon nitride ceramic material is simulated based on the established molecular dynamics model of the nanometric grinding of silicon nitride. The influence of grinding parameters on the nanometric grinding process is studied from the variation law of grinding temperature and the evolution of system energy, as well as the formation of grinding surface and metamorphic layer during machining. And the results of the experiment were compared with the theoretical research. With the increasing of grinding depth and speed of diamond grains, the energy released during the deformation and amorphous phase change of the atomic lattice get increased, and the grinding temperature get increased. The high grinding temperature will cause amorphous phase change in silicon nitride ceramics, and the amorphous atoms are recombined with the atomic bonds of the processed surface to form a metamorphic layer of the processed surface. The effect of grinding parameters on temperature changes from large to small is grinding wheel line speed, workpiece feeding speed, and grinding depth. There is an important effect on improving the surface machining quality and the service life of parts of engineering ceramics such as silicon nitride from the results of this paper, and it also plays an important role in reducing the effect of grinding temperature on the surface quality.

Si3N4-GCr15 (silicon nitride-bearing steel) friction pair is often used in high-speed bearings. The molecular dynamics model of graphene additive lubricating oil (mixed oil) is developed to study the effect of graphene as a nano lubricant additive on the thermal conductivity of the lubricating oil. With the research temperature range of 298~532 K, the results of internal molecular dynamics simulation show that the thermal conductivity of mixed oil increases with the increase in the graphene mass fraction at 298 K. When the temperature is higher than 298 K, the thermal conductivity of the mixed oil increases first and then decreases with the increase of the graphene mass fraction. When the mass fraction of graphene is constant, the thermal conductivity of the mixed oil increases first and then decreases with the increase of temperature. An experiment was designed to investigate the heat transfer coefficient for mixed lubricating oil at test specimen surface. Experiments show that an appropriate amount of graphene is added to improve the convective heat transfer between the lubricating oil and the test piece. However, as the amount of graphene added increases, the viscosity of the mixed oil increases, thereby inhibiting the fluid flow behaviour, resulting in a decrease in the convective heat transfer coefficient. This shows that only an appropriate amount of graphene additive has a cooling effect on Si3N4-GCr15 friction pair.

Friction between silicon nitride (Si3N4) and bearing steel (GCr15) affects the hybrid bearing performance. The effects of graphene as an additive in n-hexadecane (C16H34) lubricating oil on the lubricating properties of a Si3N4-GCr15 friction pair were studied. The effects of pressure and shear velocity on the coefficient of friction and friction force were probed experimentally, while the changes in the van der Waals energy, shear stress, and thickness of the solid film in the lubrication area were simulated by molecular dynamics methods. Graphene additives increased the van der Waals energy and thickness of the solid film in the lubrication region, while reducing the shear stress of the Si3N4-GCr15 friction pair, coefficient of friction, and friction force. Furthermore, the lower the overall shearing velocity, the lower was the van der Waals energy and shear stress, and the thicker was the solid film. Finally, as the pressure and shear velocity increased, graphene exerted a greater influence on the lubricating properties of the Si3N4-GCr15 friction pair.

Full ceramic bearing can work under a wide range of temperatures, but the thermal deformation difference between the ceramic outer ring and steel pedestal has a great increase with the rise of temperature and leads to obvious impact and friction. In this paper, the thermal deformation difference is considered and the fit clearance is taken as the boundary condition of the dynamic model. Investigations on the dynamic response of the outer ring are conducted, and the effect of thermal-related fit clearance is analyzed at different working temperatures and rotation speeds through parametric study and experiments. Results show that the vibration of the outer ring grows with the temperature and shows different changes with rotation speed as the temperature changes. The variation of working temperature brings difference in the interactions between the outer ring and the pedestal, and the trends of vibration with rotation speed also change at different temperatures. Impact and friction make great contributions to the interactions between the outer ring and the pedestal and show different changes with temperature. This study puts forward a method for the calculation of bearing vibration at variable temperatures and provides theoretical basis for the application of the full ceramic bearings.

This paper takes the ball diameter difference into consideration in the nonlinear dynamic model of the full ceramic bearing. The interactions between the elements of the bearing are derived based on the dynamic theory of the rolling bearing. The sound radiation is obtained using the sub-source decomposition method, and a verification experiment is carried out on the motorized spindle test rig to assess the precision of the model. The rotation speed, axial preload and radial loads are selected as influence factors, and parametric investigations are conducted to study the impact of the factors on the interactions between the elements. The circumferential distributions of the sound radiation are investigated, and parameters including sound pressure level and peak directivity angle are taken as evaluation indexes. Results show that the ball diameter difference has significant impact on the sound radiation of full ceramic bearings, and the impact grows with rotation speed. The sound directivity is closely related to the forces acting on the inner ring, and is affected by the axial and radial loads in different ways. This study provides information for the bearing acoustic characteristics, and is relevant for the design and operation of ceramic bearings.

As an extremely important component, flow field plays an important role in a proton exchange membrane (PEM) fuel cell. In this study, a two-dimensional model of interdigitated flow field was developed to simulate the effect of outlet channel width on PEM fuel cell performance using COMSOL Multiphysics, and the simulated results coincided accurately with the experimental results. From the results, the PEM fuel cell performance with narrower outlet channel width was better than that with conventional outlet channel width, since the molarity distribution of oxygen in the porous medium and the electrolyte current density distribution at the membrane cross section were more uniform, and the drainage capacity was stronger. The simulated results have certain reference significance for the design and optimization of interdigitated flow field.

In this paper, the event-triggered adaptive distributed observer is applied to solve the problem of cooperative output regulation for discrte-time linear multi-agent systems. Firstly, we propose two distributed event-triggered strategies, one is relative threshold event-triggered strategy, the other is switching threshold event-triggered strategy. Then we apply these two event-triggered strategies to an adaptive distributed observer, which does not need each follower to know the leader’s matrix information, so it can be fully distributed. Finally, the effectiveness of the method is illustrated by digital simulation.

This paper focuses on the distribution characteristics of the radiation noise for a full-ceramic angular contact ball bearing (FCACBB). A model for calculating the radiation noise of a FCACBB was established based on the bearing dynamic characteristics and sound radiation theory, and the effectiveness and accuracy of the method were verified by corresponding experiments. The variation of the radiation noise for a FCACBB with the rotational speed was analyzed. The directivity of the sound field in the circumferential direction was found. The variation trends of the radiation noise in the friction load zone and the impact load zone were discussed. The attenuation of the radiation noise in the radial direction and in the axial direction was investigated. The directivity angle and the degree of directivity of the sound field were explored at different radial and axial distances. The results show that the inhomogeneous contacts between the bearing components in the circumferential direction result in different degrees of friction and impact vibration at different locations, which makes the radiation noise of the FCACBB have a larger component in the radial direction than in the axial direction. The conclusions can provide a reference for predicting the radiation noise of FCACBBs and further optimizing the sound field.

Ceramic angular contact ball bearing is widely used in a high-speed motorised spindle because of their excellent properties such as wear resistance, high temperature resistance, and corrosion resistance. In this study, the characteristics and influencing factors of the radiation noise for a full ceramic angular contact ball bearing applied in the motorised spindle are investigated. Based on a single factor test method, the variations of bearing noise with preload, oil supply, and rotation speed were investigated, and then, the optimal preload and oil supply under the specific speed were obtained. The sound field directivity in the circumferential distribution of the bearing noise was discussed, and the reasons for the uneven distribution of the sound field were elucidated. According to the experimental results, a prediction model on the radiation noise of a full ceramic angular contact ball bearing under certain conditions was proposed. The conclusions will provide a reference for reducing the radiation noise of full ceramic angular contact ball bearings in high-speed operation and improving the bearing performance.

A thermal deformation prediction model of a high-speed motorized spindle is important for improving machining accuracy and reducing the thermal error in the spindle. The convective heat transfer coefficient reflects the internal heat exchange capacity of a motorized spindle. In the finite element thermal analysis of a motorized spindle, the heat transfer coefficient is used as the boundary condition to calculate the temperature field and thermal deformation. The accuracy of the convective heat transfer coefficient has the most evident effect on the thermal deformation prediction of the motorized spindle. In this paper, a method for optimizing the heat transfer coefficient based on the biogeography optimization algorithm is proposed for the 100MD60Y4 motorized spindle. The proposed method is used to develop a thermal deformation prediction model of an intelligent accurate motorized spindle. Accurate prediction of the thermal deformation of the motorized spindle is realized using the experimental data of the surface temperature of the motorized spindle. Experimental results show that the average prediction error after the optimization of the spindle bearing temperature is 0.22 °C. The average prediction error in the thermal deformation of the spindle is 0.72 μm. The developed model is more accurate compared with the conventional thermal deformation prediction model of the motorized spindle.

Material properties are of great significance for structural safety. In this paper, the mechanical property tests are described and fatigue crack propagation (FCP) behavior for material that had experienced a certain number (10e7) of pre-cyclic stress (PCS) cycles are analyzed. The results illustrate that the material properties increase with the increase of PCS level for relatively lower PCS, and decrease with further increase of PCS. The FCP experiment shows that the FCP rates of the specimens subjected to PCS become lower than that of the specimen without PCS. ‘Turning’ points are clearly shown in the FCP rate curves, indicating that the FCP rate in the range of small ΔK is more sensitive to PCS. This paper presents a bi-linear approximation to describe the FCP behavior and predict the FCP life. It is found that the PCS has ‘coaxing’ effect on material FCP behavior. The fracture morphologies of the material with and without PCS are analyzed to discuss the ‘coaxing’ effect on microstructures. The PCS decreases the void number and void size in fatigue crack initiation zone, decreases the striation width in FCP zone, and increases the dimple size in final rupture zone.

The thermal deformation of motorized spindle has a great influence on the precision of numerical control (NC) machine tools. Thus, it is crucial to predict the thermal deformation in the design and operation control phase by numerical simulation and improve the precision of NC machine tools. In order to achieve this, an accurate thermal deformation prediction model for motorized spindle is required. In this paper, a model for predicting the thermal error of motorized spindle based on finite element method and parameter optimization is proposed. Levenberg-Marquardt (LM) method is applied to optimize the heat transfer coefficient of motorized spindle by using surface temperature data measured. The optimized heat transfer coefficient is then taken as one of the boundary condition of the finite element model. The boundary conditions about heat of the finite element model are obtained by energy loss experiment. The proposed model is validated by experimental results, and the results have shown well correlation.

This paper mainly focuses on the calculation and analysis on the radiation noise of the angular contact ball bearing applied to the ceramic motorized spindle. The dynamic model containing the main working conditions and structural parameters is established based on dynamic theory of rolling bearing. The sub-source decomposition method is introduced in for the calculation of the radiation noise of the bearing, and a comparative experiment is adopted to check the precision of the method. Then the comparison between the contribution of different components is carried out in frequency domain based on the sub-source decomposition method. The spectrum of radiation noise of different components under various rotation speeds are used as the basis of assessing the contribution of different eigenfrequencies on the radiation noise of the components, and the proportion of friction noise and impact noise is evaluated as well. The results of the research provide the theoretical basis for the calculation of bearing noise, and offers reference to the impact of different components on the radiation noise of the bearing under different rotation speed.

This paper solves the leader-following consensus problem for a class of second-order multi-agent systems with input quantized by a newly proposed adaptive dynamic quantizer. The novel dynamic quantizer is an adaptive quantizer that combines the logarithmic quantizer and the uniform quantizer by introducing dynamic gain parameters to achieve quantizer adaptive adjustment. It has advantages of logarithmic, uniform, and adaptive dynamic quantizers in ensuring reducible communication expenses and acceptable quantizer errors for better system performance. On this basis, we transform the guide way climbing frame (GWCF) under ideal conditions into a second-order multi-agent system and solve the motion synchronization problem of GWCF. Finally, we illustrate our approach by numerical examples.

Using response surface methodology, two-target parameter mathematical models for a 100MD60Y4 motorized spindle are established using biogeography-based optimization. Air supply pressure, fuel supply rate, and oil supply interval are the independent variables, while the spindle temperature increase and oil mist PM2.5cumulative volume distribution percentage are the response variables. Biogeography-based optimization is used to find a set of optimal lubrication system parameters with the constraint of a small temperature increase in the motorized spindle at 30,000 r/min while considering the influence of oil mist particle size on environmental quality. After lubrication system parameter optimization, comparing the particle size distribution density and temperature increase between the biogeography-based optimization model’s calculated values and the experimental test results, the errors were 1.8% and 1.17%, respectively.

Radiation noise (RN) is an important parameter for representing the characteristics of a bearing. By simplifying a ball bearing as a mass–spring–damping system, the differential equations for the vibration of an angular contact ceramic ball bearing (ACCBB) are established from the view of energy conservation considering nonlinear contact stiffness and damping. Then, the RN model of the bearing is constructed by Helmholtz's acoustic theory. The bearing noise is calculated using the proposed model, and the corresponding experiments are performed to confirm the model precision. The bearing noise consists of the noise at the characteristic frequency of each component; the rotational frequency is the primary contributor to the bearing noise. The radiation noise first increases with increasing rotational speed and the sound pressure level (SPL) has a high peak value at a critical speed of 28,000 r·min−1. Then, the noise decreases with increasing rotational speed. The directivity of sound field is discussed at different rotational speed. With increasing the rotational speed, the directivity level (DL) increases and the directivity angle (DA) skews towards the rotation direction. The research provides a theoretical basis to analyze the RN generated by ACCBBs at different rotational speeds.

Recently, the engineering structural ceramics as friction and wear components in manufacturing technology and devices have attracted much attention due to their high strength and corrosion resistance. In this study, the tribological properties of Si3N4/Si3N4 sliding pairs were investigated by adding few-layer graphene to base lubricating oil on the lubrication and cooling under different experimental conditions. Test results showed that lubrication and cooling performance was obviously improved with the addition of graphene at high rotational speeds and low loads. For oil containing 0.1 wt% graphene at a rotational speed of 3000 r&middot, min&minus, 1 and 40 N loads, the average friction coefficient was reduced by 76.33%. The cooling effect on Si3N4/Si3N4 sliding pairs, however, was optimal at low rotational speeds and high loads. For oil containing 0.05 wt% graphene at a lower rotational speed of 500 r&middot, 1 and a higher load of 140 N, the temperature rise was reduced by 19.76%. In addition, the wear mark depth would decrease when adding appropriate graphene. The mechanism behind the reduction in friction and anti-wear properties was related to the formation of a lubricating protective film.

Since a nonlinear relationship exists between the position coordinates of the rotation axes and components of the tool orientation, the tool will deviate from the required plane, resulting in nonlinear errors and deterioration of machining accuracy. Few attempts have been made to obtain a general formula and common rules for nonlinear error because of the existence of various kinematic structures of machine tools with orthogonal configuration. This paper analyzes the relationship between the deviation of cutter location points and motion of tool orientations. Five-axis CNC machine tools are divided into two groups according to the configuration of the two rotational joints and the home position. Motions of the tool are regarded as a combination of translation and rotation. A model for error calculation is then built. The maximum deviation of the tool with respect to the reference plane generated by the initial and the final orientation is used to quantify the magnitude of the errors. General formulas are derived and common change rules are analyzed. Finally, machining experiment is conducted to validate the theoretical analysis. The research has important implications on the selection of a particular kinematic configuration that may achieve higher accuracy for a specific machining task.

The thermal characteristics of a motorized spindle are the main determinants of its performance, and influence the machining accuracy of computer numerical control machine tools. It is important to accurately predict the thermal field of a motorized spindle during its operation to improve its thermal characteristics. This paper proposes a model to predict the temperature field of a high-speed and high-precision motorized spindle under different working conditions using a finite element model and test data. The finite element model considers the influence of the parameters of the cooling system and the lubrication system, and that of environmental conditions on the coefficient of heat transfer based on test data for the surface temperature of the motorized spindle. A genetic algorithm is used to optimize the coefficient of heat transfer of the spindle, and its temperature field is predicted using a three-dimensional model that employs this optimal coefficient. A prediction model of the 170MD30 temperature field of the motorized spindle is created and simulation data for the temperature field are compared with the test data. The results show that when the speed of the spindle is 10,000 rpm, the relative mean prediction error is 1.5%, and when its speed is 15,000 rpm, the prediction error is 3.6%. Therefore, the proposed prediction model can predict the temperature field of the motorized spindle with high accuracy.

Grinding parameters are of great concern in the success of processing good quality ceramic bearing outer rings. Practical grinding of ceramics demands appropriate parameters in respect of acceptable ceramic surfaces. In this work, a CNC grinder, MK2710, equipped with diamond grinding wheels, was used to grind ZrO 2 and Si 3 N 4 bearing outer rings with changing processing parameters. In order to promote the grinding quality, a series of tests were conducted to optimize the processing parameters in each process. The results showed that the outer ring surface quality has been improved and roughness (Ra) of the outer ring raceway decreased to 0.03 μm and the roundness tolerance diminished. Experiments indicated that proper grinding parameters are necessities for efficiency-processing of ceramic bearing outer rings and also help to promote grinding qualities of ceramic materials.

It is pretty significant for fault diagnosis timely and accurately to improve the dependability of industrial processes. In this study, fault diagnosis of nonlinear and large-scale processes by variable-weighted kernel Fisher discriminant analysis KFDA based on improved biogeography-based optimisation IBBO is proposed, referred to as IBBO-KFDA, where IBBO is used to determine the parameters of variable-weighted KFDA, and variable-weighted KFDA is used to solve the multi-classification overlapping problem. The main contributions of this work are four-fold to further improve the performance of KFDA for fault diagnosis. First, a nonlinear fault diagnosis approach with variable-weighted KFDA is developed for maximising separation between the overlapping fault samples. Second, kernel parameters and features selection of variable-weighted KFDA are simultaneously optimised using IBBO. Finally, a single fitness function that combines erroneous diagnosis rate with feature cost is created, a novel mixed kernel function is introduced to improve the classification capability in the feature space and diagnosis accuracy of the IBBO-KFDA, and serves as the target function in the optimisation problem. Moreover, an IBBO approach is developed to obtain the better quality of solution and faster convergence speed. On the one hand, the proposed IBBO-KFDA method is first used on Tennessee Eastman process benchmark data sets to validate the feasibility and efficiency. On the other hand, IBBO-KFDA is applied to diagnose faults of automation gauge control system. Simulation results demonstrate that IBBO-KFDA can obtain better kernel parameters and feature vectors with a lower computing cost, higher diagnosis accuracy and a better real-time capacity.

The cathode flow field design of a proton exchange membrane (PEM) fuel cell is essential to fuel cell performance, which directly affects the uniformity of reactant distribution and the ability to remove water. In this paper, the single serpentine flow field design on the cathode side is optimized to reach a high performance by controlling the rib groove rate (the ratio of the number of grooved ribs to the number of total ribs). The rib groove starts from the inlet side and then evenly distributes over the ribs. Four rib groove rates are selected in this study, namely, 0, 1/3, 2/3, and 1. A three-dimensional PEM fuel cell model is used to analyze the output performance of the fuel cell. The results indicate that the rib groove design has a significant effect on the distribution of oxygen at the cathode side, the density of the membrane current, the concentration of water vapor under the rib, and the fuel cell output performance. The output performance of the fuel cell improves with the increased rib groove rate. However, when the rib groove rate is greater than 2/3, its impact on the overall performance of the fuel cell begins to slow down. The PEM fuel cells exhibit the best output performance when the rib groove rate is 1.

The effect of ball diameter difference is quite obvious in full ceramic bearings due to the great stiffness, and leads to the problem of uneven loading in starved lubricated conditions. This paper takes the uneven loading condition into consideration in the dynamic model, and a verification experiment is carried out for the assessment of calculation accuracy. The factors of ball diameter tolerance, the arrangements of balls and the number of balls have impact on the interactions between the inner ring and the loaded balls, and the trends of sound radiation are studied in depth. The amplitude of sound radiation is used to show the interaction between the elements, and uneven loading conditions can be evaluated by the sound directivity. Results show that the tolerance is a key factor that has impact on the sound radiation, and the sound radiation and directivity have obvious change with the ball diameter tolerance. The arrangements of balls have impact on the sound radiation by changing the diameter difference between adjacent balls, and the loaded area of each loaded ball varies with the number of balls. The cases with different numbers of loaded balls are discussed, and the relations between the uneven loading conditions and sound radiation are investigated. This study proposes a method for the study of uneven loading conditions, and provides theoretical basis for the optimal design of full ceramic bearings.

For full ceramic ball bearings, cracks occur frequently in the spalling on the rings, which leads to impacts on the bearing dynamic characteristics. In this paper, the spalling is set on the outer ring, and the dynamic model considering the effect of crack is proposed. The crack is considered to be related to the strain energy, and the effect on the stiffness of the outer ring is also analyzed. Results show that the appearance of cracks leads to the reduction of the full ceramic bearing stiffness, and the vibration amplitude of bearing increases. The effect of a crack depends on its size, and the vibration of the bearing with cracks of different widths and depths vary greatly. This study provides theoretical basis for the calculation of full ceramic bearing and is of great significance for the state monitoring and fault diagnosis.

Tooth wear is one of the main reasons that lead to gear failure. The amount of wear is nonlinearly related to temperature, lubrication, load, and various random factors of materials, with obvious randomness and slow time-varying characteristics. Wear is a nonstationary random process, which has no accurate mathematical model or accurate reliability estimation method. This article proposes a reliability model of spur gears which works under a nonstationary random process that exceeds the limit, and the time-varying wear reliability is studied based on the level crossing analysis method. The wear at tooth root is revised in the calculation under the nonstationary random process, and the reliability curves are obtained afterwards. An experiment is carried out on the spur gear meshing test rig, and the reliability model and wear performance are verified and analyzed. Results obtained with the proposed tooth surface wear reliability model match well with the experimental results. Therefore, this model is applicable for situations under a nonstationary random process. The new method makes contribution to the assessment of gear running status and is of great significance in the prediction of wear life under a nonstationary random process.

The removal mechanism of silicon nitride ceramic under high-speed grinding is studied in this article, and grinding parameters are optimized. The efficiency of grinding is improved. The diamond gra...