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Although current EU regulations, such as EU Directive 2015/1189 on the eco-design of solid fuel boilers and Directive 2015/1188, in accordance with the Machinery Directive 2006/42/EC, require manufacturers to meet specific emission requirements for CE marking, the routine and regular onsite testing of household heating appliances is still not mandatory in many EU countries. This research endeavour addressed this gap by evaluating the effectiveness of the Bacharach method as a rapid and cost-effective tool for assessing flue gas quality, particularly in terms of particulate matter mass concentration. This study also compared the results of the Bacharach method with those obtained from two commercially available portable analysers. The research outcomes demonstrate that the Bacharach method, in combination with an innovative evaluation approach, offers a viable solution, enabling the swift and economical assessment of flue gas quality with the primary objective of determining the boiler class according to the limits specified by standard EN 303-5 under operating conditions. The modified Bacharach method for measuring TSP in solid fuel-fired boilers provides qualitatively similar results to the commercially used SM500 and STM225 instruments. The modified Bacharach methodology was primarily developed for comparison to the boiler class 3 limit (i.e., 125 and 150 mg/m3). The study revealed that the modified Bacharach method, when applied to biomass-based boilers, exhibited higher accuracies in the case of classification into classes 3 and 4, whereas fossil fuel-based boilers demonstrated higher accuracy in the case of class 5 limits.

Servo presses achieve high formability by using different punch motion curves, thereby increasing their applicability in conventional processing fields. In this study, the punch motion curves of servo presses were optimized, and the effects of punch motion curves on the springback of U-shaped sheet metal were explored. Subsequently, the optimal punch motion curve was determined, and the springback effect after processing was investigated. Different punch motion curves were proposed and simulated for comparison with the results of conventional methods, and the equivalent stress values obtained using different motion curves and mold angles were analyzed. DEFORM software was used to conduct simulations to determine the differences between processing methods. In addition, the spring-go, springback, load–stroke characteristics, and stress and strain distributions of U-shaped sheet metal were investigated. The conventional motion curve resulted in springback, stress, strain, and required processing force higher than those achieved by the curves proposed in this study. The smaller the movement difference in the motion curve of the servo press was, the lower the springback, stress, and strain were. These results indicate that the punch motion curves obtained for different types of processing can serve as a reference for selecting appropriate parameter values for servo presses.

Purpose: We sought to analyze the biomechanical effects which both different numbers and locations of screws have on three different clavicle hook plates, as well as any possible causes of sub-acromial bone erosion and peri-implant clavicular fractures.Methods: This study built thirteen groups of finite element models using three different clavicle hook plates (short plates, long plates, and posterior hook offset plates) in varying numbers and locations of the screws. The von Mises stress distribution of the clavicle and hook plate, as well as the reaction force of the acromion was evaluated.Results: The results show that inserting screws in all available screw holes on the hook plate produces a relatively large reaction force on the acromion, particularly in the axial direction of the bone plate. The fewer the screws implanted into the clavicle hook plate, the larger the area of high-stress distribution there is in the middle of the clavicle, and also, the higher the stress distribution on the clavicle hook plate.Conclusion: This study provides orthopedic physicians with the biomechanical analysis of different numbers and locations of screws in clavicle hook plates to help minimize surgical complications.

Age-related macular degeneration (AMD) may be associated with ABCA4 variants and is characterized by the accumulation of visual cycle-byproduct lipofuscin. Reducing retinol-binding protein 4 (RBP4), a retinol transporter protein, may reduce lipofuscin production. This study aims to assess the associations between plasma RBP4, the ABCA4 variation, and AMD severity. Sixty-seven participants were grouped into healthy/mild AMD (n = 32) and severe AMD (n = 35) groups. The latter group was older than the former group and had higher levels of RBP4 (36.8 ± 8.3 vs. 30.4 ± 7.0 μg/mL, p = 0.0012). The ten participants with six ABCA4 linked-variants had higher RBP4 than those without (37.8 ± 7.7 vs. 32.4 ± 7.9 μg/mL; p = 0.026), and eight of them had severe AMD. Univariate analyses showed that severe AMD was related to older age (OR, 1.26; 95% CI, 1.13–1.40; p < 0.0001) and to higher RBP4 levels (OR, 1.12; 95% CI, 1.04–1.20; p = 0.003), whereas the linked ABCA4 variants had no associations. After adjustment, however, only age remained significantly associated with severe AMD. This pilot study shows a trend of higher plasma RBP4 levels in severe AMD or the ABCA4-linked variants, and further age-matched studies are warranted.

The traditional tool center point (TCP) calibration method requires the operator to use their experience to set the actual position of the tool center point. To address this lengthy workflow and low accuracy, while improving accuracy and efficiency for time-saving and non-contact calibration, this paper proposes an enhanced automatic TCP calibration method based on a laser displacement sensor and implemented on a cooperative robot with six degrees of freedom. During the calibration process, the robot arm will move a certain distance along the X and Y axes and collect the information when the tool passes through the laser during the process to calculate the runout of the tool, and then continue to move a certain distance along the X and Y axes for the second height calibration. After the runout angle is calculated and calibrated by triangulation, the runout calibration is completed and the third X and Y axis displacement is performed to find out the exact position of the tool on the X and Y axes. Finally, the tool is moved to a position higher than the laser, and the laser is triggered by moving downward to obtain information to complete the whole experimental process and receive the calibrated tool center position. The whole calibration method is, firstly, verified in the virtual simulation environment and then implemented on the actual cooperative robot. The results of the proposed TCP calibration method for the case of using a pin tool can achieve a positioning deviation of 0.074 and 0.125 mm for the robot moving speeds of 20 and 40 mm/s, respectively. The orientation deviation in the x-axis are 0.089 and −0.184 degrees for the robot moving speeds of 20 and 40 mm/s, respectively. The positioning repeatability of ±0.083 mm for the moving speed of 20 mm/s is lower than ±0.101 mm for the speed of 40 mm/s. It shows that lower moving speed can obtain higher accuracy and better repeatability. This result meets the requirements of TCP calibration but also achieves the purpose of being simple, economical, and time-saving, and it takes only 60 s to complete the whole calibration process.

Spherical porous air bearing (SPAB) systems have been extensively used in various mechanical engineering applications. SPABs are promising materials in high-rotational speed, high-precision, and high-stiffness instruments. In SPAB systems, a rotor is supported by gas bearings, which provides higher rotational speed and lower heat generation environment than oil bearings do. Furthermore, SPAB does not cause deformation. Although, the supporting force of gas bearings is less, their stability is better than that of oil films. However, because the pressure distribution in the gas films is nonlinear, they are prone to failure at specific critical speeds, rotor imbalances, or inappropriate operations, which results in nonperiodic or chaotic motion and causes structural fatigue to the system. To understand and control the operating conditions of the SPAB systems during the nonperiodic motion, first, the governing equations of the SPAB system were solved to obtain the dynamic behavior of the rotor center. Then, the performance of the SPAB system were examined under different operating conditions by generating the maximum Lyapunov exponents (MLEs). However, the calculation process of MLE is extremely time consuming and complex. To solve this problem efficiently, a high-precision machine learning (ML)-based MLE prediction model was proposed in this study. The results show that the training process can be finished within few minutes, and the prediction process is able to be completed within few seconds. Meanwhile, the results demonstrate the merit of using the machine learning method for solving the MLE prediction problem and shorten the calculation time significantly. The proposed prediction model achieves excellent prediction outcome and it is more efficient and precise than traditional iteration scheme for the calculation of MLE. The feasibility of the proposed model is validated and the results also are the major contribution of this study.

The present study proposes a machine learning approach for optimizing turning parameters in such a way as to maximize the turning precision. The Taguchi method is first employed to optimize the turning parameters, and the experimental results are then used to train three machine learning models to predict the turning precision for any given values of the input parameters. The model which shows the best prediction performance (XGBoost) is further improved through the use of a synthetic minority over-sampling technique for regression with Gaussian noise (SMOGN) and four different optimization algorithms, including center particle swarm optimization (CPSO). Finally, the performances of the various models are evaluated and compared using the leave-one-out cross-validation technique. The experimental results show that the XGBoost model, combined with SMOGN and CPSO, provides the best performance, and is a useful tool for predicting the machining error of turning. The method can also reduce the cost of obtaining the optimized turning parameters corresponding with the predicted machining error.

Servo press technology is gaining attention because its punch motion curve offers greater formability than that of a conventional stamping press. This study investigated the effect of punch motion curves on the circular cup extrusion–drawing process. Various punch motion curves were analyzed, and the optimal curve for application was determined. Both the extrusion–drawing process and spring back of U-shaped sheet metal were investigated. In the circular cup extrusion–drawing process, the punch motion curve of a conventional stamping press (Case A) and three punch motion curves of a servo press (Cases B–D, the strokes of which differed from that of Case A by 0.5, 1.5, and 2.5 mm, respectively) were compared, particularly regarding the effect of the coefficient of friction on the circular cup extrusion–drawing process. The simulation analysis was performed using the software program DEFORM. A set of simulated parameters were compared with experimental results. The formability, cup shape, cup height, cup thickness, extrusion force–displacement curve, stress distribution, and strain distribution were analyzed for the design of the die required. Additionally, experimental and simulation results were compared to determine the reliability and precision of the DEFORM simulations. The results indicated that the conventional punch motion curve resulted in a shorter cup, greater stress, greater strain, and the need for a greater extrusion force. By contrast, the servo punch motion curves resulted in taller cups, less stress, and less strain. The findings can serve as a reference for the development of servo presses.

Machining refers to a variety of processes, in which a cutting tool is used to remove the unwanted material from a workpiece. Tool wear, advertently or inadvertently, occurs after long-time use. It is crucial to monitor the tool wear so that the cutting tool can deliver the best performance and meet the technological challenges nowadays. In this paper, through different fractional-order chaotic systems, i.e., Chen-Lee, Lorenz, and Sprott, extension theory is proposed to predict the tool life. The results of the three chaotic systems are compared. The centroid of the 2-D plane of dynamic errors is used as the characteristics. Four wear states are defined in accordance with different levels of surface roughness, i.e., normal, slight, moderate, and severe. The boundaries of the four states are identified according to the locations of the centroid generated with the systems of different fraction orders. The boundaries are then fed into the extension model, and the relational function calculation is performed. In this way, the identification of tool state can be easily achieved. The experiment results indicate that Chen-Lee system and the Lorenz systems exhibit the same diagnosis rate (97.375%), higher than that of the Sprott system (35.75%). It is demonstrated that the two chaotic systems are fit for use with the method proposed in this paper. It is also proven that Chen-Lee and Lorenz fractional-order master-slave chaotic systems are very effective for tool life monitoring. The robustness of diagnosis is also greatly improved.

Chatter, the vibration between the workpiece and cutting tool, is a common phenomenon during the milling process. Traditionally, the Fourier transform analysis is mainly used to extract the features and determine whether chatter occurs. In this paper, an innovative and practical chatter identification method combining fractional order chaotic system and extension theory is proposed. A lathe spindle with embedded sensors is used in this study. The boundary of chattering state of the lathe spindle is decided by the center of gravity of phase plane of dynamic errors. The boundaries are then fed into extension model and relational function calculation is performed. In this way, chatter identification can be easily achieved based on the position of the chaotic center of gravity. The three chaotic systems, i.e. Lorenz, Chen-Lee, and Sprott, of different fractional orders are used and their results are compared. Compared with the traditional methods, the Fourier transform is time-consuming in terms of mathematical operations and adverse to the establishment of a real-time system. This paper uses the characteristics of the chaotic systems sensitive to input signals in order to more capably detect the boundary state from normal cutting to chattering cutting and more efficiently identify the chatter. The experiment results indicate that the Chen-Lee system (93.5%) exhibits have better chatter diagnosis rate than Lorenz (92.75%) and Sprott (69%) systems. The Chen-Lee system even reaches a diagnosis rate of 100% for orders 0.5 ~ 0.7. Therefore, the method presented in this paper has a very high diagnosis rate and is thus very effective for chatter identification of machine tools.

Ball bearings are important parts of all modern rotating machines. Their function is to reduce friction, support rotating shafts and spindles, and bear loads. Bearing damage can result in abnormal vibrations, cause machine malfunction, and even be dangerous. In this study, analysis of four different ball-bearing conditions was carried out: normal bearings and bearings with inner ring, rolling body, and outer ring malfunction. This was based on electromechanical vibration signals produced on a fault diagnosis simulation platform. The objective was to use a series of signal processing analytical methods to build a set of identification models used to forecast malfunction. Wavelet packet transform technology was first used to process the vibration signal. The signals were pre-processed and analyzed before eigenvalue calculation was done to analyze the signal changes which allowed determination of the nature of the bearing malfunction to be made. The extracted eigenvalues and ball-bearing status categories were input to the support vector machine for model training and testing. Finally, the constructed model parameters were integrated with particle swarm optimization, and the artificial fish-swarm algorithm was used to obtain the optimal parameters for the classifier, and this improved the accuracy of malfunction classification.

In recent years, the opposed high-speed gas bearing system has been gradually valued and used in the field of precision machinery, especially for precision instruments and mechanisms requiring high speed, high precision, and high rigidity. Although the bearing capacity is not as good as the oil film bearings, it can provide a working environment where the rotor can generate high speed and low heat without deformation of the shaft, and the gas pressure distribution of clearance in bearing also has better stability. Due to the strong nonlinearity of the gas film pressure function of gas bearings and the fact that the actual shaft system possesses dynamic problems including critical speed, spindle imbalance or improper bearing design, it will cause the rotation process of the shaft to produce a nonperiodic motion and instability, and even chaotic motion under certain parameters. And these irregular movements can even cause machine damage or process delays when serious, so in order to understand the process of working under the conditions where the system will have a nonperiodic phenomenon and to avoid the occurrence of irregular vibration especially chaos. In this paper, the opposed high-speed gas bearing system feature will be discussed in detail with three different numerical analysis methods, i.e. the finite difference method, perturbation method, and mixing method. The relevant theories include dynamic trajectories, spectrum analysis, bifurcation diagram, Poincare map, and the maximum Lyapunov exponents. From the results of nonlinear dynamic behavior of the rotor center, periodic and nonperiodic motions occur at different rotor masses and bearing parameters, respectively. Especially, for the chaos of shaft exists at specific intervals and can be distinguished efficiently. Meanwhile, it is found to ensure that the bearing system can suppress the phenomena of chaos actively by adjusting the bearing parameters, and reduce the system loss caused by irregular vibration. It is expected to be an important basis for designing a precision shaft or mechanism and to enhance the stability and performance of bearing system.

Active hybrid aerodynamic and aerostatic bearing system has gradually become more valued in recent years for its application in the precision machine field, especially for precision instruments and mechanisms that require high rotational speed, high precision, and high rigidity support. In this system, air lubricated bearing is mainly used for support. Although the carrying capacity is not as high as oil film bearings, air lubricated bearings can provide a work environment where the rotor (spindle) will not experience axial deformation at high rotational speed and low heat generation. In practice, spindle system dynamic problems include critical speed, spindle imbalance, and improper bearing design, which can cause the spindle system to produce aperiodic motion, instability, and even chaotic motion under certain parameters and conditions during its operation. If severe, these irregular motions may cause machine damage or delay production. In order to understand what type of work situation can produce aperiodic phenomenon, and to prevent irregular vibration and reduce instantaneous air hammer effect, the finite difference method and mixed method are used to explore the related characteristics for spindle system. Meanwhile, relevant theories including bifurcation diagram, Poincare map, spectrum response phenomenon, and maximum Lyapunov exponents are applied to analyze rotor non-linear dynamic behavior. In addition, we verified the non-linear motion parameter conditions to prevent spindle system from falling into the instable status during design. The objective is to lower the probability of chaotic phenomenon in the system and reduce damage caused by irregular vibrations in the system. The result of this study can serve as a reference when designing precision spindle systems or mechanisms.

In this paper an analysis of the nonlinear dynamic behavior and control of an atomic force microscope system is described. Phase plane trajectories, spectrum analysis, bifurcation analysis, the Poincare cross-section, the maximal Lyapunov exponent, and other numerical analysis methods were used to observe and verify the dynamic characteristics and the differential equations for the system. The results showed that at specific excitation frequencies, the system will exhibit nonlinear behavior that may be cyclic, multi-cyclic or acyclic. A Psim circuit simulation using the same parameters showed the same nonlinear behavior, as did laboratory circuit implementations. The results also showed than an understanding and control of the dynamic characteristics would not be an easy task. However, they could be used as a basis for the suppression and control of nonlinear behavior and vibration in atomic force microscope systems. A proportional-derivative system was also used, with particle swarm optimization, to find the control parameters K p and K D and a fuzzy controller was used to compare the results. The controller simulation and hardware implementation both effectively inhibited the nonlinear behavior and were most helpful for the control and enhancement of measurement accuracy.

To manufacture metal products of accurate size and shape by deep drawing requires the precise control of a number of variables. The problem of spring-back after the load has to be avoided, and the prevention of cracks in the product requires careful control of the punch load. In this study, where drawing experiments and simulations were carried out on thin sheets of SUS304 stainless steel, the influence of the scale effect on the thin sheets also needed consideration. This was accomplished by the use of an updated Lagrangian formulation and finite element analysis. Material behavior was simulated using a micro-elastoplastic material model, the performance of which was compared with that of models involving conventional materials. The Dynaform LS-DYNA solver was used for simulation analysis, and pre and postprocessing were carried out to obtain material deformation history as well as to determine thickness change, distribution and material stress, and prepare strain distribution maps. Scaling was necessary to account for the effect of the thickness of the sheet and the relationship between punch load and stroke, the distribution of thickness, stress and strain, and the maximum size (d) of the flanged hole and the maximum height of the flange. The simulation results were compared with experimental results to confirm the accuracy of the three-dimensional finite element analysis of the elastoplastic deformation. The results showed that the size of the fillet radius of the hole (Br) had an effect on the punch load, which increased with an increase in Br. However, the minimum thickness of the formed flange decreased with an increase in Br. The maximum principal stress/strain and height of the flange also increased with an increase in Br. The punch fillet radius (Rp) also had an impact on the process. The punch load decreased with the increase in Rp, while the minimum thickness increased slightly. The average values of the minimum thickness for three models were 0.148, 0.0775, and 0.0374 mm. The forming ratio also had an influence on the process. When the forming limit of the square hole flange was FLR = 0.84, cracking occurred in the corners of the flange, and wrinkles formed over the undrawn area of the sheet. These findings can serve as a valuable reference for the design of deep drawing processes.

This study aims to analyze the stainless steel micro round tube external threading process for the influence of different outer threading pitches (0.25 mm, 0.4 mm) and outer diameters (Ø1.9, Ø1.94, Ø2). This study also analyzes the effects of different friction factors (0.1, 0.3, 0.5, 0.7, and 0.9) and different tube thicknesses (0.4, 0.45, 0.5, 0.55, and 0.6 mm) on the threading process. This study considers size effect to use corrected material parameters for the microtube to conduct the finite element analysis by DEFORM-3D software. The goal is to understand stainless steel (SUS304) micro round tube threading and the difference by using macro material parameter analysis. The historic forming data from the simulation and experiment of threading processing are presented, and the corresponding stress/strain distribution and thread shape are also calculated. The experiment results are compared to the simulation results to verify the reliability of this analysis method. The result shows that the torque/stress/strain obtained by the modified model is always lower than by Swift’s model. It means that the size effect can be considered to apply on the forming process and provided proper torque to form the external thread of the micro round tube, e.g., the maximum torque of the round die for M2 × 0.25 occurs over the fourth stroke. For the influence of the outer diameter of the micro round tube, the larger diameter induces the larger maximum torque on the round die for M2 × 0.4, but for the smaller pitch of M2 × 0.25, the larger maximum torque is not influenced by the diameter of the tube. When the pitch of the round die is increased, the torque, stress and strain are also increased relatively. As the friction factor and torque between the round die and tube increase, the stress and strain become lower. Changing the tube thickness will not significantly change the torque, the stress, and the strain. These results guide the simulation and experiment of optimized micro round tube threading development and design to reduce cost and increase product quality.

In this study, the subject of investigation was the dynamic double pendulum crank mechanism used in a robotic arm. The arm is driven by a DC motor though the crank system and connected to a fixed side with a mount that includes a single spring and damping. Robotic arms are now widely used in industry, and the requirements for accuracy are stringent. There are many factors that can cause the induction of nonlinear or asymmetric behavior and even excite chaotic motion. In this study, bifurcation diagrams were used to analyze the dynamic response, including stable symmetric orbits and periodic and chaotic motions of the system under different damping and stiffness parameters. Behavior under different parameters was analyzed and verified by phase portraits, the maximum Lyapunov exponent, and Poincaré mapping. Firstly, to distinguish instability in the system, phase portraits and Poincaré maps were used for the identification of individual images, and the maximum Lyapunov exponents were used for prediction. GoogLeNet and ResNet-50 were used for image identification, and the results were compared using a convolutional neural network (CNN). This widens the convolutional layer and expands pooling to reduce network training time and thickening of the image; this deepens the network and strengthens performance. Secondly, the maximum Lyapunov exponent was used as the key index for the indication of chaos. Gaussian process regression (GPR) and the back propagation neural network (BPNN) were used with different amounts of data to quickly predict the maximum Lyapunov exponent under different parameters. The main finding of this study was that chaotic behavior occurs in the robotic arm system and can be more efficiently identified by ResNet-50 than by GoogLeNet; this was especially true for Poincaré map diagnosis. The results of GPR and BPNN model training on the three types of data show that GPR had a smaller error value, and the GPR-21 × 21 model was similar to the BPNN-51 × 51 model in terms of error and determination coefficient, showing that GPR prediction was better than that of BPNN. The results of this study allow the formation of a highly accurate prediction and identification model system for nonlinear and chaotic motion in robotic arms.

Dual-directional coupled aerodynamic bearing (DCAB) systems have received considerable attention over the past few years. These systems are primarily used to solve air lubrication problems in high-precision mechanisms and equipment that run at a high rotational speed and require high rigidity and precision. DCABs have the advantages of axial and radial thrust and provide high rigidity, dual-directional support, and high load-carrying capacity. In DCAB systems, the nonlinearity of the air film pressure and dynamic problems, such as critical speed, unbalanced air supply, or poor design, can cause the instability of the rotor-bearing system and phenomena such as nonperiodic or chaotic motion under certain parameters or conditions. Therefore, to investigate what conditions lead to nonperiodic phenomena and to avoid irregular vibration, the properties and performance of the DCAB system were explored in detail by using three numerical methods for verifying the accuracy of the numerical results. The rotor behavior was also studied by analyzing the spectral response, the bifurcation phenomenon, Poincaré maps, and the maximum Lyapunov exponent. The numerical results indicate that chaos occurs in the DCAB system for specific ranges of the rotor mass and bearing number. For example, when the rotor mass (mr) is 5.7 kg, chaotic regions where the maximum Lyapunov exponents are greater than 0 occur at bearing number ranges of 3.96–3.98 and 4.63–5.02. The coupling effect of the rotor mass and bearing number was also determined. This effect can provide an important guideline for avoiding an unstable state.

For some years, bi-directional porous aero-thrust bearing systems have been receiving much attention. They are now applied extensively where there is a need for rigidity in high-precision instruments and mechanisms that run at high speed. Although the carrying capacity of gas bearings is not as good as that of oil film bearings, the heat generated at high speed is lower and does not cause spindle deformation. Under certain conditions, the shaft will display unstable non-periodic movement, and this can even become chaotic. This irregular behavior, when serious, can even damage the mechanical parts, cause a breakdown, and stop production. The aim of this study was to gain an understanding of this phenomenon and the conditions under which it might arise and to find a means for avoiding irregular vibrations and eliminating the air hammer effect that accompanies them. A detailed examination of the related characteristics of a gas bearing shaft system was carried out using numerical value analysis such as the finite difference and differential transformation methods. An analysis of the nonlinear dynamic behavior of the main axis was then carried out using bifurcation diagrams, Poincaré sections, and spectral response.

In recent years, spiral-grooved air bearing systems have attracted much attention and are especially useful in precision instruments and machines with spindles that rotate at high speed. Load support can be multidirectional and this type of bearing can also be very rigid. Studies show that some of the design problems encountered are dynamic and include critical speed, nonlinearity, gas film pressure, unbalanced rotors, and even poor design, all of which can result in the generation of chaotic aperiodic motion and instability under certain conditions. Such irregular motion on a large scale can cause severe damage to a machine or instrument. Therefore, understanding the conditions under which aperiodic behaviour and vibration arise is crucial for prevention. In this study, numerical analysis, including the Finite Difference and Differential Transformation Methods, is used to study these effects in detail in a front opposed-hemispherical spiral-grooved air bearing system. It was found that different rotor masses and bearing number could cause undesirable behaviour including periodic, subperiodic, quasi-periodic, and chaotic motion. The results obtained in this study can be used as a basis for future bearing system design and the prevention of instability.

An investigation of nonlinear probe behavior in an atomic force microscope, caused by different excitation frequencies, was carried out as well as an analysis and subsequent regulation using particle swarm optimization in combination with proportional–derivative control. The dynamic behavior was resolved by numerical analysis using the atomic force microscope probe governing equations and the properties were examined using phase portrait, bifurcation diagrams, Poincaré maps, and the maximum Lyapunov exponent. The results show that excitation frequency ratio can actuate periodic, sub-harmonic, and chaotic behavior in the system under certain conditions. A proportional–derivative controller was employed to control the chaos, and particle swarm optimization was used to find the proportional–derivative parameters. Integral absolute error was used to evaluate the quality of the parameters for the performance indicator. The generation of nonlinear behavior and a chaotic state may be effectively suppressed to improve the stability and performance of an atomic force microscope system.

A composite ultrasonic process is used to extract five constituent components of green tea, namely caffeine, catechin, epigallocatechin gallate, epicatechin, and chlorogenic acid. The optimal parameters of the extraction process are determined using the robust Taguchi design method. The extracted products are analyzed using gas chromatography and high-performance liquid chromatography. The experimental results confirm the effectiveness of the proposed ultrasonic technique in extracting the components of interest. Moreover, it is shown that the optimal extraction parameters depend on the particular component. In general, the present findings provide a useful reference for further research on the processing of green tea.

Meshfree algorithms offer a convenient way of solving nonlinear steady-state problems in arbitrary plane areas surrounded by complicated boundary shapes. The simplest of these is the polynomial expansion approach. However, it is rarely utilized as a primary tool for this purpose because of its rather ill-conditioned behavior. A well behaved polynomial expansion algorithm is presented in this paper which can be more effectively used to solve the steady-state Allen-Cahn (AC) equation for heat transfer in thin films. In this method, modified polynomial expansion was used to cope with each iteration of the steady-state Allen-Cahn equation to produce nonlinear algebraic equations where multiple scales are automatically determined by the collocation points. These scales can largely decrease the condition number of the coefficient matrix in each nonlinear system, so that the iteration process converges very quickly. The numerical solutions were found to be accurate and stable against moderate noise to better than 7.5%. Computational results verified the method and showed the steady-state Allen-Cahn equation for heat transfer in thin films could easily be resolved for several arbitrary plane domains.

Fermentation techniques are applied for the biotechnology and are widely used for food manufacturing, materials processing, chemical reaction, and so forth. Different fluids and types of blades in the tank for fermentation cause distinct flow and stress field distributions on the surface between fluid and blade and various flow reactions in the tank appear. This paper is mainly focused on the analysis of flow field with different fluid viscosities and also studied the stress field acting on the blades with different scales and shapes of them under specific rotational speed. The results show that the viscosity of fluid influences the flow field and stress distributions on the blades. The maximum stress that acts on the blade is increased with the increasing of viscosity. On the other hand, the ratio of blade length to width influences stress distributions on the blade. At the same time, the inclined angle of blade is also the key parameter for the consideration of design and appropriate inclined angle of blade will decrease the maximum stress. The results provide effective means of gaining insights into the flow and stress distribution of fermentation process.

This work theoretically studies the temperature rise behavior in laser-irradiated layered tissue, which was stratified into skin, fat, and muscle. Taking the effect of microstructural interaction into account, a modified non-Fourier equation of bioheat transfer was developed based on the nonlinear form of the dual-phase-lag model. The broad beam irradiation method was adopted to calculate the laser energy deposition in tissues. The nonlinear high order partial differential equation and the complicated boundary conditions at the interface between two adjacent layers cause some mathematical difficulties. It is not easy to deal with such a problem. Therefore, a hybrid numerical scheme has been proposed to solve the present problem. The comparison between the linear and nonlinear effects of phase lag times on bioheat transfer has been made.

The present study uses the differential transformation method to solve the governing equations of the coronary artery system and then analyzes the dynamic behavior of the system by means of phase portraits, power spectra, bifurcation diagrams, and Poincaré maps. Also, a master-slave control system is proposed to suppress the nonlinear chaotic behavior of the coronary artery system. The results show that the dynamic behavior of the coronary artery system is significantly dependent on the magnitude of the vibrational amplitude. Specifically, the motion changes from T-periodic to 2T-periodic, then from 4T-periodic to 8T-periodic, and finally to chaotic motion with windows of periodic motion as the vibrational amplitude is increased from 0.3 to 0.6 and from 4.5 to 5.9. In addition, it is shown that the proposed control scheme enables the coronary artery system to be synchronized to any state asymptotically such that the risk of cardiopathy is reduced.

This paper is focused on developing a compensation module for reducing the thermal errors of a computer numerical control (CNC) milling machine. The thermal induced displacement variations of machine tools are a vital problem that causes positioning errors to be over than 65%. To achieve a high accuracy of machine tools, it is important to find the effective methods for reducing the thermal errors. To this end, this study first used 14 temperature sensors to examine the real temperature fields around the machine, from which four points with high sensitivity to temperature rise were selected as the major locations for creating the representative thermal model. With the model, the compensation system for controlling the displacement variation was developed. The proposed model has been applied to the milling machine. Current results show that the displacement variations on the x- and y-axes and the position error at the tool center were controlled within 20 µm when the compensation system was activated. The feasibility of the compensation system was successfully demonstrated in application on the milling operation.