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Degradation prognostic plays a crucial role in increasing the efficiency of health management for rolling element bearings (REBs). In this paper, a novel four-step data-driven degradation prognostics approach is proposed for REBs. In the first step, a series of degradation features are extracted by analyzing the vibration signals of REBs in time domain, frequency domain and time-frequency domain. In the second step, three indicators are utilized to select the sensitive features. In the third step, different health state labels are automatically assigned for health state estimation, where the influence of uncertain initial condition is eliminated. In the last step, a multivariate health state estimation model and a multivariate multistep degradation trend prediction model are combined to estimate the residence time in different health status and remaining useful life (RUL) of REBs. Verification results using the XJTU-SY datasets validate the effectiveness of the proposed method and show a more accurate prognostics results compared with the existing major approaches.

The recent advances in the synthesis and applications of raspberry ketone are reviewed in this paper. Different methods, including chemical synthesis, biotechnological methods, and extraction, are compared, and the applications of raspberry ketone in flavour and fragrance, medicinal chemistry and tobacco manufacture are also discussed. Finally, the research perspective of raspberry ketone are also prospected.

In order to investigate the effects of turbulent airflow from coal cutting (TACC) on the pollution characteristics of coal dust, the pollution behaviors of coal dust under the action of system ventilation airflow (SVA) only (Condition 1) and the addition of TACC disturbance (Condition 2) were respectively simulated and verified through a comparison with the field measurement data. The results show that the effects of TACC on the pollution characteristics of coal dust cannot be ignored on the operation site. TACC could not only enhance the turbulent intensity in the flow field, but also induce the positive deviation of airflow. The airflow with a velocity of about 1.0∼1.75 m/s in the footway space moved from the region X=0.3∼36.8 m, Y=4.1∼4.5 m under Condition 1 to the region X=-5.1∼26.5 m, Y=3.8∼4.5 m under Condition 2. After the addition of TACC disturbance, the absolute value of positively-deviated airflow velocity component in the operational range of rear drum driver rose from 0∼0.8 m/s to 0.2∼1.8 m/s. Meanwhile, the flow field under Condition 2 could effectively cause lateral dispersion of coal dust to the footway space, which led to an increase in the lateral dispersion scale of coal dust. Under Condition 2, the region polluted by cutting-induced coal dust moved forward by 11.3 m along the negative direction of X-axis, and the peak coal dust concentration along the footway space was approximately doubled.

This article is concerned with the existence of traveling wave solutions for a discrete diffusive ratio-dependent predator-prey model. By applying Schauder’s fixed point theorem with the help of suitable upper and lower solutions, we prove that there exists a positive constant c* such that when c > c*, the discrete diffusive predator-prey system admits an invasion traveling wave. The existence of an invasion traveling wave with c = c* is also established by a limiting argument and a delicate analysis of the boundary conditions. Finally, by the asymptotic spreading theory and the comparison principle, the non-existence of invasion traveling waves with speed c < c* is also proved.

To explore the effects of downwind and upwind coal cutting on dust pollution in a fully mechanized mining face, the airflow-dust migration was simulated by using ANSYS-FLUENT software, and the follow-up spraying dust control method was optimized according to the differences in dust concentration distribution during downwind and upwind coal cutting. The results show that during downwind and upwind coal cutting, the average airflow velocity of the fully mechanized mining face is about 1.053 m/s. During downwind coal cutting, the dust generated by the shearer mainly pollutes the mining area and the area within 0–50 m on its downwind side, while the dust generated by the advancing support mainly pollutes the mining area and the sidewalk area within 0–20 m on the downwind side of shearer. During upwind coal cutting, the dust generated by the shearer mainly pollutes the vicinity of the drum and the area within 0–45 m on its downwind side, while the dust generated by the advancing support mainly pollutes the sidewalk area within 0–30 m on the downwind side of shearer. In view of the differences in dust concentration during downwind and upwind coal cutting, the dust concentration in the working face was divided into four areas and the follow-up spraying dust control method was optimized. The field measurement results indicate that compared with the original spraying facility, the optimized opening mode raises the average dust removal rates of total dust and respirable dust in the working face by 52.1% and 43.8% during downwind coal cutting and by 53.6% and 42.3% during upward coal cutting.

We present for the neutron-star low-mass X-ray binary 4U 1636–53, and for the first time for any source of kilohertz quasi-periodic oscillations (kHz QPOs), the two-dimensional behaviour of the fractional rms amplitude of the kHz QPOs in the parameter space defined by QPO frequency and photon energy. We find that the rms amplitude of the lower kHz QPO increases with energy up to $\sim \!\!12$ keV and then decreases at higher energies, while the rms amplitude of the upper kHz QPO either continues increasing or levels off at high energies. The rms amplitude of the lower kHz QPO increases and then decreases with frequency, peaking at $\sim \!\!760$ Hz, while the amplitude of the upper kHz QPO decreases with frequency, with a local maximum at around $\sim \!\!770$ Hz, and is consistent with becoming zero at the same QPO frequency, $\sim \!\!1400$ Hz, in all energy bands, thus constraining the neutron-star mass at $M_{NS} \le 1.6 \, \mathrm{M}_{\odot }$, under the assumption that this QPO reflects the Keplerian frequency at the inner edge of the accretion disc. We show that the slope of the rms energy spectrum is connected to the changing properties of the kHz QPOs in different energy bands as its frequencies change. Finally, we discuss a possible mechanism responsible for the radiative properties of the kHz QPOs and, based on a model in which the QPO arises from oscillations in a Comptonizing cloud of hot electrons, we show that the properties of the kHz QPOs can constrain the thermodynamic properties of the inner accretion flow.

This paper is concerned with the stability of non-monotone traveling waves for a discrete diffusion equation with monostable convolution type nonlinearity. By using the anti-weighted energy method and nonlin-ear Halanay’s inequality, we prove that all noncritical traveling waves (waves with speeds c > c*, c* is minimal speed) are time-exponentially stable, when the initial perturbations around the waves are small. As a corollary of our stability result, we immediately obtain the uniqueness of the traveling waves.

Objective: To investigate the mid-and long-term clinical effects of tricuspid valvuloplasty with the implantation of an artificial plastic ring. Methods: Data of 677 patients who had functional tricuspid regurgitation and left cardiac valve disease and underwent tricuspid valvuloplasty and left cardiac valve surgery were retrospectively. Among these patients, 353 underwent simple suture annuloplasty (group A) while the rest 324 patients underwent artificial plastic ring annuloplasty (group B). The two-year and more-than-two-year clinical and ultrasonocardiograph (UCG) follow-up data of the two groups were obtained and compared. Results: A total of 600 patients (88.6%) completed the long-term follow-up (more than two years). The two-year follow-up showed no significant difference in the incidence of mild tricuspid regurgitation between the two groups (82.2% vs. 92.7%, P=0.37). However, there were significantly more cases that developed into moderate to severe tricuspid regurgitation in group A than in group B (17.8% vs. 7.3%, P=0.031). The long-term follow-up revealed that the recurrence rate of tricuspid regurgitation in group B was significantly lower than that in group A (11.0% vs. 25.0%, P=0.029), and the ratio of cases developing into moderate to severe tricuspid regurgitation in group A was significantly higher than that in group B (28.9% vs. 9.9%, P=0.007). The comparison between the two intra-group time segments showed that the development of tricuspid regurgitation in group A was significantly increased (28.9% vs. 17.8%, P=0.022), but in group B it was relatively stable (9.9% vs. 7.3%, P=0.52). Conclusions: Artificial ring annuloplasty is associated with significantly less tricuspid regurgitation than simple suture annuloplasty.

This paper studies the asymptotic stability for a class of neutral systems with mixed time-varying delays. Through utilizing some Wirtinger-based integral inequalities and extending the convex combination technique, the upper bound on derivative of Lyapunov-Krasovskii (L-K) functional can be estimated more tightly and three mixed-delay-dependent criteria are proposed in terms of linear matrix inequalities (LMIs), in which the nonlinearity and parameter uncertainties are also involved, respectively. Different from those existent works, based on the interconnected relationship between neutral delay and state one, some novel triple integral functional terms are constructed and the conservatism can be effectively reduced. Finally, two numerical examples are given to show the benefits of the proposed criteria.

To solve the problem that the switched reluctance motor (SRM) may have harmful impact on the shaft during the starting process, a half-S soft starting control method is proposed. The switch signal is given based on the discrete position signal of SRM without the requirement of accurate rotor position information. In the process of the motor from static to rotation, the current step chopping soft starting is adopted to prevent the phase current from flowing; In starting acceleration stage, the edge signal of discrete position is used as the control period. By using sliding mode control, the increment of the rotation speed is identical at each position signal interval. The speed increased exponentially within the rated output power of motor. Through using Matlab/Simulink environment and switched reluctance motor drive platform, this method was validated, and the results reveals that the proposed method is able to achieve smooth starting and reduce the harmful impact on the mechanical system which shows high application value in the development field of SRM type electric vehicle.

We investigate the relation between the parameters of the energy spectrum and the frequency and amplitude of the kilohertz quasi-periodic oscillations (kHz QPOs) in the low-mass X-ray binary 4U 1636$-$53. We fit the $3-180$-keV spectrum of this source with a model that includes a thermal Comptonisation component. We show that the frequencies of both kHz QPOs follow the same relation as a function of the parameters of this spectral component, except for a systematic frequency shift, whereas the rms fractional amplitude of each QPO follows a different relation with respect to those same parameters. This implies that, while the dynamical mechanism that sets the frequencies of the QPO can be the same for both kHz QPOs, the radiative mechanisms that set the amplitudes of the lower and the upper kHz QPO are likely different. We discuss the implications of these results to the modelling of the kHz QPOs and the possibility that the lower kHz QPO reflects a resonance between the Comptonising medium and the photons from the accretion disc and/or the neutron star surface., Comment: 7 pages, 4 figures, 2 tables. Accepted for publication in MNRAS

The asymptotical stability for a class of neutral systems with time-varying delay and restricted nonlinearity is investigated. Firstly, during choosing the Lyapunov–Krasovskii functional (LKF), two adjusting scalars \(\alpha ,\beta \in (0,1]\) will be introduced and they can effectively reduce the conservatism once the upper bound of delay derivative is very large. Then by utilizing some integral inequalities, the much tighter bound on LKF derivative is presented and some previously ignored information can be fully utilized by employing an extended convex combination technique. Furthermore, two stability criteria are presented in terms of LMIs and they can be easily checked. Finally, some numerical examples with comparing results can illustrate the superiorities of the derived results.

This paper mainly addresses the position and attitude tracking control for a small quadrotor UAV via discrete-time sliding mode control (DSMC). Firstly, the linear extrapolation method is used to transform the continuous-time system into discrete-time system. Based on the discrete-time system, the discrete-time flight controllers are designed to perform position and attitude tracking control of the quadrotor UAV. In addition, new conditions are given ensuring the discrete-time system is asymptotically stable. Lastly, based on the kinematic and dynamic model of the quadrotor UAV, extensive simulations are performed to illustrate that the proposed control method has a good performance in terms of stabilization and tracking control.

While there are many dynamical mechanisms and models that try to explain the origin and phenomenology of the quasi-periodic oscillations (QPOs) seen in the X-ray light curves of low-mass X-ray binaries, few of them address how the radiative processes occurring in these extreme environments give rise to the rich set of variability features actually observed in these light curves. A step towards this end comes from the study of the energy and frequency dependence of the phase lags of these QPOs. Here we used a methodology that allowed us to study, for the first time, the dependence of the phase lags of all QPOs in the range of 1 Hz to 1300 Hz detected in the low-mass X-ray binary 4U 1636-53 upon energy and frequency as the source changes its states as it moves through the colour-colour diagram. Our results suggest that within the context of models of up-scattering Comptonization, the phase lags dependencies upon frequency and energy can be used to extract size scales and physical conditions of the medium that produces the lags.

A green and efficient protocol for the synthesis of N-(2-hydroxyethyl)anilines by the selective alkylation reaction in ionic liquid [BMIM]BF4 (1-butyl-3-methylimidazolium tetrafluoroborate) has been developed, eliminating the need for toxic and expensive catalysts and volatile organic solvents. The effects of the amount of ionic liquid, temperature, time, and substrate structure on the reaction were investigated. The conversion and selectivity of N-(2-hydroxyethyl)anilines obtained in ionic liquid [BMIM]BF4 are significantly increased in comparison to those traditional methods. Furthermore, the ionic liquid could be easily separated and reused at least five times. It provided a simple and efficient alternative way for the industrial synthesis of N-(2-hydroxyethyl)anilines.

In this article, based on Lyapunov–Krasovskii functional approach and improved delay-partitioning idea, a new sufficient condition is derived to guarantee a class of delayed neural networks to be asymptotically stable in the mean-square sense, in which the probabilistic time-varying delay is addressed. Together with general convex combination method, the criterion is presented via LMIs and its solvability heavily depends on the sizes of both time delay range and its derivative, which has wider application fields than those present ones. It can be shown by the numerical examples that our method reduces the conservatism much more effectively than earlier reported ones. Especially, the conservatism can be further decreased by thinning the delay intervals.

This article is concerned with the robust control issues of direct-driven permanent magnetic synchronous generator without mechanical sensors. In this study, a novel nonlinear model reference adaptive backstepping control method is proposed. Extended electromotive force estimation-based rotor position and rotational velocity estimation methods are adopted, in which the stator parameters are identified online. Since the identified parameters are merely used in extended electromotive force estimator, the mathematically controlled plant cannot reflect the actual model, which decreases the robustness of the control. To provide a high-performance robust controller against uncertainties in stator parameters and mechanical torque fluctuation, a torque observer is adopted, and an adaptation law is derived with the identified parameters and estimated mechanical torque, in the sense of the Lyapunov theory. Meanwhile, the feasibility of the substitution of the actual stator parameters and state vector with estimated values is mathematically demonstrated based on the Lyapunov theory. Simulation experiments have been carried out both in surface permanent magnetic synchronous generator and interior permanent magnetic synchronous generator, and the results show that compared to the conventional process-interaction decoupling controller, the proposed controller has better disturbance rejection performance against wind speed perpetuation and parameter uncertainties.

Recently, the neutron star X-ray binary EXO 0748-676 underwent a transition to quiescence. We analyzed an XMM-Newton observation of this source in quiescence, where we fitted the spectrum with two different neutron-star atmosphere models. From the fits we constrained the allowed parameter space in the mass-radius diagram for this source for an assumed range of distances to the system. Comparing the results with different neutron-star equations of state, we constrained the distance to EXO 0748-676. We found that the EOS model 'SQM1' is rejected by the atmosphere model fits for the known distance, and the 'AP3' and 'MS1' is fully consistent with the known distance.

Time-resolved spectra during the cooling phase of thermonuclear X-ray bursts in low-mass X-ray binaries (LMXBs) can be used to measure the radii and masses of neutron stars. We analyzed ~ 300 bursts of the LMXB 4U 1636-53 using data from the Rossi X-ray Timing Explorer. We divided the bursts in three groups, photospheric radius expansion (PRE), hard non-PRE and soft non-PRE bursts, based on the properties of the bursts and the state of the source at the time of the burst. For the three types of bursts, we found that the average relation between the bolometric flux and the temperature during the cooling phase of the bursts is significantly different from the canonical $F \propto T^4$ relation that is expected if the apparent emitting area on the surface of the neutron star remains constant as the flux decreases during the decay of the bursts. We also found that a single power law cannot fit the average flux-temperature relation for any of the three types of bursts, and that the flux-temperature relation for the three types of bursts is significantly different. Finally, for the three types of bursts, the temperature distribution at different flux levels during the decay of the bursts is significantly different. From the above we conclude that hard non-PRE bursts ignite in a hydrogen-rich atmosphere, whereas for soft non-PRE and PRE bursts the fuel is helium-rich. We further conclude that the metal abundance in the neutron star atmosphere decreases as the bursts decay, probably because the heavy elements sink faster in the atmosphere than H and He.

A series of 4-amino-6-benzimidazole-pyrimidines was designed to target lymphocyte-specific tyrosine kinase (Lck), a member of the Src-family kinases (SFKs). These type II inhibitors were optimized using a cellular Lck-dependent proliferation assay and are capable of inhibiting Lck at single-digit nanomolar concentrations. This scaffold is likely to serve a valuable template for developing potent inhibitors of a number of SFKs.

A series of 4-amino-6-benzimidazole-pyrimidines was designed to target lymphocyte-specific tyrosine kinase (Lck), a member of the Src kinase family. Highly efficient parallel syntheses were devised to prepare analogues for SAR studies. A number of these 4-amino-6-benzimidazole-pyrimidines exhibited single-digit nanomolar IC50s against Lck in biochemical and cellular assays. These 4-amino-6-benzimidazole-pyrimidines represent a new class of tyrosine kinase inhibitors.

After a silence of some 32 years, the high-mass X-ray binary (HMXB) 4U1901+03 produced an outburst in Feb. 2003. With the observed data of RXTE (Rossi X-ray Timing Explorer) over a 5 month duration, we have made a systematic study of the pulse profile of this source, and obtained its time evolution and its correlation with the photon energy. It is found that the variations of the pulse profile and the pulse fraction with the accretion rate of the binary system exhibit a stepwise evolution, and that the pulse fraction reaches its peak at energies under ten KeV. The complex variation of the pulse profile indicates that the pulse profile can not be explained by a single geometrical or physical model, rather, it must be related with both the viewing angle and the radiation mechanism. The observed features are here discussed in terms of the standard radiation model of pulsars.

As an extension study, FTIR and molecular simulation methods were combined in the present paper to analyze the H-bond interactions resulting from multiple donors and acceptors that have led to self-assembly based on segmented polyurethane with carboxyl (PUc) and poly(4-vinylpyridine) (P4VP) in our previous work. Of them, FTIR was used to analyze the H-bonding types and interactions as well as their changes before and after self-assembly; molecular mechanics (MM/COMPASS) was used to study the effect of possible conformations on the H-bonds involved and analyze the most probable H-bond patterns; quantum mechanics (QM/B3LYP) was used to help confirm the experimental FTIR band assignments and calculate the H-bond energy. It was found that two types of H-bonds exist, namely, COOH...P4VP (type I) and (OCO)NH...P4VP (type II), based on OH and NH as the strong donors in the interaction between PUc and P4VP. Strong evidence has been obtained for a type II H-bond, which is the specialty in PUc/P4VP assembly. The type I and type II H-bonding energies are -11.293 and -7.150 kcal/mol, respectively. The forming probability of the type I H-bond accounts for 95.87%, while that of the type II H-bond is 4.13%, showing the primary driving force for the assembly based on PUc and P4VP is still the H-bond between COOH and P4VP, yet the H-bonds based on NH and pyridyl in P4VP cannot be ignored.

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized at the molecular level by the expression of Bcr-abl, a 210-kDa fusion protein with deregulated tyrosine kinase activity. Encouraged by the clinical validation of Bcr-abl as the target for the treatment of CML by imatinib, we sought to identify pharmacological agents that could target this kinase by a distinct mechanism. We report the discovery of a new class of Bcr-abl inhibitors using an unbiased differential cytotoxicity screen of a combinatorial kinase-directed heterocycle library. Compounds in this class (exemplified by GNF-2) show exclusive antiproliferative activity toward Bcr-abl-transformed cells, with potencies similar to imatinib, while showing no inhibition of the kinase activity of full-length or catalytic domain of c-abl. We propose that this new class of compounds inhibits Bcr-abl kinase activity through an allosteric non-ATP competitive mechanism.

A study of the changes in crystal perfection of polyamide 66 (PA66) and polyamide 66/clay nanocomposites (PA66CN) due to different thermal processing was carried out. We designed three series of thermal processing including melt-quench (MQ), post-annealing MQ sample (MQA), and melt–slow cooling–annealing (MSA). The annealing temperature was set as 180 or 210 °C, which is within Brill temperature range of PA66. Fourier transform infrared (FT-IR) spectroscopy and wide angle X-ray diffraction (WAXD) were employed to characterize the perfection in short-range order and long-range order structures, respectively. The results showed that the crystal perfection of PA66 and PA66CN with different thermal processing is quite different, and the changing fashions with thermal processing for different ordered structures are not similar. In this work, MSA is optimal thermal processing for high crystallinity and crystal perfection. Exfoliated nanoclay layers exert considerable impact on the perfection of long-range ordered structures, but little on that of short-range ordered ones.

The miscibility, crystallization behavior, and component interactions of two binary blends, poly(L-lactide) (L-PLA)/poly(vinylpyrrolidone) (PVP) and poly(D,L-lactide) (DL-PLA)/PVP, were studied with differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopy. The composition-dependent changes of the glass-transition temperature (Tg) and degree of crystallinity (Xc) of the L-PLA phase indicated that L-PLA and PVP were immiscible over the composition range investigated. However, the sharp decrease of Xc with increasing PVP content in the second heating run demonstrated that the cold crystallization process of L-PLA was remarkably restricted by PVP. In DL-PLA/PVP blends, the existence of two series of isolated Tg's indicated that DL-PLA and PVP were phase-separated, but evidence showed that there was some degree of interaction at the interface of the two phase, especially for the blends with low DL-PLA contents. FTIR measurements showed that there was no appreciable change in the spectra of L-PLA/PVP with respect to the coaddition of each component spectrum, implying the immiscibility of the two polymers. In contrast to L-PLA, the intermolecular interaction between DL-PLA and PVP was detected by FTIR; this was evidenced by the observation of a high-frequency shift of the CO stretching vibration band of PVP with increasing DL-PLA content, which suggested some degree of miscibility. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 973–979, 2003

Continuous epitope sequences were selected from immunogenic Bb proteins by epitope mapping. The identified epitope sequences were synthesized by solid phase peptide synthesis and purified by high performance liquid chromatography. Each epitope was conjugated individually to a multifunctional poly(ethylene glycol) (PEG) carrier. The result PEG-peptide conjugates were used as antigens in ELISA for diagnosis of Lyme disease. The results showed that the defined epitope peptides were Lyme disease specific and could be used in a format of PEG-peptide conjugate as the antigen to achieve improved sensitivity and specificity.

Multifunctional carboxylic acids have been used as crosslinking agents for cotton and wood pulp cellulose. In our previous research, we found that a polycarboxylic acid esterifies cellulose through the formation of a 5-membered cyclic anhydride intermediate by the dehydration of two carboxyl groups. In this research, we studied the formation of cyclic anhydride intermediates by different isomers of cyclohexanedicarboxylic acid (CHA) so that we can elucidate the effects of molecular structure on the formation of the anhydride intermediates. We found that both cis-and trans-1,2-CHA form 5-membered anhydride intermediates when temperature reaches their melting points and that cis-1,2-CHA forms the cyclic anhydride at temperatures lower than does trans-1,2-CHA. 1,3-CHA forms 6-membered cyclic anhydride at temperatures much higher than its melting point. The formation of a 5-membered cyclic anhydride intermediates takes place at temperatures lower than that of a 6-membered anhydride. This is probably the main reason why those polycarboxylic acids with their carboxylic acid groups bonded to the adjacent carbons of the molecular backbones are more effective crosslinking agents for cellulose than those with their carboxylic groups bonded to the alternative carbons. No formation of cyclic anhydride was found for 1,4-CHA. The formation of a five-membered cyclic anhydride was accelerated by monosodium phosphate, which is used as a catalyst for the esterification of cotton cellulose by polycarboxylic acids.

The thermal pyrolysis of carboxymethyl hydroxypropyl sesbania gum and hydroxypropyl sesbania gum in air and nitrogen atmospheres were studied in order to establish the thermal stability of carboxymethyl hydroxypropyl sesbania gum. The results indicate that the stability of carboxymethyl hydroxypropyl sesbania gum against pyrolysis is higher than that of hydroxypropyl sesbania gum. The main state of carboxymethyl hydroxypropyl sesbania gum and hydroxypropyl sesbania gum can be assigned as random noncrystalline.