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The dynamic support stiffness (DSS) of assembled bearings in high-speed motorized spindles (HSMSs) is the main factor affecting the rotor's operating stiffness which, in turn, directly affects the machining accuracy of HSMSs. This paper establishes a thermo-mechanical coupled quasi-static model of the DSS of assembled bearings, providing a theoretical model for analysing the combined effects of preloading method, assembly form, thermal expansion and external load. An experimental method is designed to quantitatively measure the DSS of assembled bearings in HSMSs. By combining the modelling with experimental measurements, the effects of radial force and speed on the radial and axial DSS of the assembled bearings in an HSMS are investigated. The results show that the radial DSS of the front and rear bearings increases with radial force and decreases with speed; while the axial DSS of the front bearings decreases with radial force and speed, and the axial stiffness of the rear bearings is less affected by the radial force and speed under the condition of constant-pressure preload. The proposed experimental device can accurately measure the DSS of assembled bearings at speeds of up to 30000 r/min. This study provides a new theoretical model and experimental method for the estimation and quantitative measurement of DSS in assembled bearings in HSMSs. [ABSTRACT FROM AUTHOR]

The rotor operating stiffness of high-speed motorized spindles (HSMSs) is key to machining accuracy. Because HSMSs are difficult to load due to their high speeds, a contact loading device was developed to test rotor operating stiffness. The dynamic support stiffness of the front/rear bearings (DSSB) is the main factor affecting the rotor operating stiffness. Two novel experimental schemes for measuring the DSSB are proposed: (1) indirect measurement—by analysing deformation displacements at two points on the external loading rod of the HSMS and (2) direct measurement—by eddy current sensors installed near the front/rear bearings. Based on the experimental device and two experimental schemes, the influences of working condition parameters on the DSSB were tested. The results show that the proposed experimental device and two experimental schemes can effectively and accurately measure rotor operating stiffness and DSSB at speeds of up to 30,000 rpm. However, because the tapered connection gap between the loading rod and rotor increases the measured deformation displacement, the DSSB measured by the indirect measurement scheme was relatively small. The DSSB decreases with speed and increases with radial force and working temperature. This study provides a new experimental basis for the quality inspection of finished HSMSs and the verification of theoretical bearing stiffness models. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate accurate and effective experimental methods for measuring the frictional loss of bearings (FLB) in mechanical systems and to measure the effect of various operating parameters on the frictional loss of high-speed mechanical systems. Design/methodology/approach: Two novel methods were studied in this paper to measure the FLB: the free-deceleration method and the energy-balance method. A special high-speed motorised spindle and a friction loss test rig were designed and built to measure the effects of rotational speed, lubrication, preload and operating temperature on the FLB. Findings: The experimental results showed that the frictional torque of bearings increases initially but then decreases with an increase in rotational speed. Similarly, the FLB decreases initially and then increases with an increase in temperature because of the influence of the viscosity–temperature relationship of the lubricant and the thermomechanical coupling factor. The optimal lubricant flow was determined, and the effectiveness of a novel preload online adjusting device was verified through experiments. Originality/value: The research results of this paper provide the basis and methods for the measurement, reduction and prediction of the FLB in mechanical systems. [ABSTRACT FROM AUTHOR]

Abstract: An experimental study on the phase change behavior of organic phase change materials (PCMs) in porous building materials is reported. Three kinds of porous materials and two kinds of PCMs were used. The phase change behavior of organic PCMs and phase change composites was measured by means of differential scanning calorimetry (DSC). The pore structure of the porous materials was characterized by means of mercury intrusion porosimetry (MIP). X-ray fluorescence spectrometry (XRF) and Fourier transformation infrared spectroscopy (FTIR) were used to characterize the chemical properties of porous materials and phase change materials. Quite different phase change behaviors were found for these two kinds of PCMs in porous materials. For capric acid with a functional group of –COOH, a remarkable elevation of melting temperature was found when confined in porous materials. But for paraffin with only inactive functional groups of –CH2 and –CH3, no elevation or depression of the melting temperature was found when confined in the porous materials. The interaction between functional groups of PCM molecules and alkaline spots on the inner pore surface of the porous materials and the Clapeyron equation were used to explain the different shift of the phase change temperature of capric acid and paraffin in porous materials. [Copyright &y& Elsevier]

The teleoperation system has attracted a lot of attention because of its advantages in dangerous or unknown environments. It is very difficult to develop an operating system that can complete complex tasks in a completely autonomous. This paper proposes a robot arm control strategy based on gestures and visual perception. The strategy combines the advantages of humans and robots to obtain a convenient and flexible interaction model. The hand's data were obtained by Leap-Motion. Then a neural network algorithm was used to classify the nine gestures, which were used for robots control through a finite state machine. The control mode switched between indicative control and mapping control. The robot acquired an autonomous grasp ability by incorporating YOLO 6D, depth data and a probabilistic roadmap planner algorithm. The robot completed most of the trajectory independently, while a few flexible trajectories required users to do mapping actions. This interactive mode reduces the burden of the users to a certain extent that makes up for the shortcomings of traditional teleoperation. [ABSTRACT FROM AUTHOR]

This paper deals with the dynamical modeling and posture control of the electromechanical actuator (EMA)-based thrust vector control (TVC) system for aircraft engines. Addressing the issues of the large inertia and low stiffness existing in the TVC system driven by EMA, this paper established a 2-DOF mathematical model to describe the EMA dynamic characteristics. In order to overcome the influence of the motion coupling of the TVC-EMA existing in the pitching and yawing channels, we presented a kind of dual-channel coordinated-control method which realizes the TVC for the swung aircraft engine based on the inverse kinematics. This control strategy uses the command Euler's angle transformation to solve the desired actuator linear lengths and tracks the desired lengths via the compound control law composed of robust PID, with the lead compensation and bang–bang control in the two actuators. The hybrid experimental simulation system based on dSPACE was set up, the control parameters of the compound control methods were confirmed by offline simulation based on MATLAB, and the load experiments of circular motion and step response were implemented on the test system. The simulation and test results show that the designed thrust vector controller can achieve the satisfactory control performances. [ABSTRACT FROM AUTHOR]

By introducing an easy knapsack-type problem, a probabilistic knapsack-type public key cryptosystem (PKCHD) is proposed. It uses a Chinese remainder theorem to disguise the easy knapsack sequence. Thence, to recover the trapdoor information, the implicit attacker has to solve at least two hard number-theoretic problems, namely integer factorization and simultaneous Diophantine approximation problems. In PKCHD, the encryption function is nonlinear about the message vector. Under the re-linearization attack model, PKCHD obtains a high density and is secure against the low-density subset sum attacks, and the success probability for an attacker to recover the message vector with a single call to a lattice oracle is negligible. The infeasibilities of other attacks on the proposed PKCHD are also investigated. Meanwhile, it can use the hardest knapsack vector as the public key if its density evaluates the hardness of a knapsack instance. Furthermore, PKCHD only performs quadratic bit operations which confirms the efficiency of encrypting a message and deciphering a given cipher-text. [ABSTRACT FROM AUTHOR]

The interaction between curcumin and pepsin was investigated by fluorescence, synchronous fluorescence, UV–vis absorption, circular dichroism (CD), and molecular docking. Under physiological pH value in stomach, the fluorescence of pepsin can be quenched effectively by curcumin via a combined quenching process. Binding constant ( K a ) and binding site number ( n ) of curcumin to pepsin were obtained. According to the theory of Förster's non-radiation energy transfer, the distance r between pepsin and curcumin was found to be 2.45 nm within the curcumin–pepsin complex, which implies that the energy transfer occurs between curcumin and pepsin, leading to the quenching of pepsin fluorescence. Fluorescence experiments also suggest that curcumin is located more closely to tryptophan residues than tyrosine residues. CD spectra together with UV–vis absorbance studies show that binding of curcumin to pepsin results in the extension of peptide strands of pepsin with loss of some β-sheet structures. Thermodynamic parameters calculated from the binding constants at different temperatures reveal that hydrophobic force plays a major role in stabilizing the curcumin–pepsin complex. In addition, docking results support the above experimental findings and suggest the possible hydrogen bonds of curcumin with Thr-77, Thr-218, and Glu-287 of pepsin, which help further stabilize the curcumin–pepsin complex. [ABSTRACT FROM AUTHOR]

Highlights: [•] Silencing of cre1 resulted in derepression of cellulase gene expression. [•] Silencing of cre1 led to significantly enhanced enzyme production capability. [•] CREI acted as a repressor of xyr1 transcription under inducing conditions. [•] RNAi is a feasible method for improving cellulase productivity in Trichoderma koningii. [Copyright &y& Elsevier]

14-3-3 proteins are conserved regulatory proteins present in all eukaryotic cells that control numerous cellular activities via targeted protein interactions. To elucidate the interaction between P14-3-3 from Physarum polycephalum and actin in living cells, PCR and DNA recombination were used to generate various P14-3-3 and actin constructs. Yeast two-hybrid assay and FRET were employed to characterize the interaction between P14-3-3 and actin. The two-hybrid assay indicated that P14-3-3 N-terminal 76-108 amino acids and the C-terminal 207-216 amino acids played an important role in mediating interactions with actin, and the actin N-terminal 1-54 amino acids and the C-terminal 326-376 amino acids are also crucial in the interactions with the mPa, a P14-3-3 with mutations at Ser62 (Ser62 → Gly62). Mutations to potential phosphorylation sites did not affect interactions between P14-3-3 and actin. FRET results demonstrated that P14-3-3 co-localized with actin with a FRET efficiency of 22.2% and a distance of 7.4 nm and that P14-3-3 N-terminal 76-108 and C-terminal 207-216 amino acids were important in mediating this interaction, the truncated actin peptides without either the N-terminal 1-54 or C-terminal 326-376 amino acids interacted with P14-3-3, consistent with the results obtained from the yeast two-hybrid assay. Based on data obtained, we identified critical actin and P14-3-3 contact regions. [ABSTRACT FROM AUTHOR]

Abstract: Polyetheretherketone–hydroxyapatite nanocomposite materials are investigated for the purpose of improving the bonding between polyetheretherketone (PEEK) matrix and hydroxyapatite (HA) fillers since their debonding deteriorates the otherwise superior antifatigue properties of PEEK materials. The nanocomposites are successfully produced by incorporating lab-prepared HA nanoparticles, up to 15.0vol%, to PEEK matrix via a compounding and injection molding process. The microstructures of the composite samples are observed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallization and phase structure of the composites are examined by differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements. The mechanical properties of the composites are evaluated, and their tensile strength reaches 98MPa at 5.0vol% HA. Most importantly the study suggests that there is no debonding occurring between the well-dispersed HA nanoparticles and PEEK matrix, which provides a promising way to overcome the debonding issue of the PEEK–HA composites. [Copyright &y& Elsevier]