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In this work, the linear responses of turbulent mean flow to both harmonic and stochastic forcing are investigated for supersonic channel flow. Well-established universal relations are utilized to obtain efficiently the mean profiles with a large parameter space, with the bulk Mach number up to 5 and the friction Reynolds number up to $10^4$ , so a systematic parameter study is feasible. The most amplified structure takes the form of streamwise velocity and temperature streaks forced optimally by the streamwise vortices. The outer peak of the pre-multiplied energy amplification corresponds to the large-scale motion, whose spanwise wavelength ( $\lambda _z^+$ ) is very insensitive to compressibility effects. In contrast, the classic inner peak representing small-scale near-wall motions disappears for the stochastic response with increasing Mach number. Meanwhile, the small-scale motions become much less coherent. A decomposition of the forcing identifies different effects of the incompressible counterpart and the thermodynamic components. Wall-cooling effects, arising with high Mach number, increase the spacing of the most amplified near-wall streaks; the spacing becomes nearly invariant with Mach number if expressed in semi-local units. Meanwhile, the coherence of stochastic response with $\lambda _z^+>90$ is enhanced, but on the other hand, with $\lambda _z^+ it is decreased. The geometrical self-similarity of the response in the mid- $\lambda _z$ range is still roughly satisfied, insensitive to Mach number. Finally, theoretical analyses of the perturbation equations are presented to help with understanding the scaling of energy amplification.

Space robotic manipulator (SRM) should be always performed in the given workspace for safety concern. This requires the system states such as rotation of each joint, attitude of base, and their velocities to be always constrained in the given boundaries. In this article, a new sliding mode control scheme based on a fixed time disturbance observer is proposed to realize the fixed time coordinate motion control of SRM with full-state constraints. Firstly, the tracking error and error velocity at the novel sliding manifold can converge to the equilibrium within a fixed time without violating their state constraints. Then, the control law working with the fixed time disturbance observer is designed to obtain the sliding manifold within a fixed time, which simultaneously guarantees the satisfaction of state constraints during the approaching stage. Unlike the most existing state constraint control schemes, the proposed controller does not include any Barrier Lyapunov Function (BLF) term of system states, and therefore the risk of controller outputting inappropriately high control commands is eliminated. Moreover, the proposed control scheme is compatible to the initial states violating the constraints, which thereby removes the assumption of feasible initial states. Furthermore, the proposed sliding manifold solves the singularity issue by a continuously varying power of tracking error, which thereby does not need an additional switch mechanism of manifold compared to the conventional fixed time controllers. The stability of the proposed control scheme is proven by using the Lyapunov theory, and the effectiveness is verified by numerical simulations.

The characteristic parameters of corrosion pits on the surface of steel wires in service bridges are discussed. The degradation of mechanical properties of corroded steel wires and its relationship with different corrosion evaluation parameters are studied through tensile test. Finally, the damage constitutive model of corroded steel wires is established by introducing the damage variable D. The results show that there are four types of corrosion pits on the surface of steel wires, including the deep ellipsoid, shallow ellipsoid, groove and saddle shape. The higher the corrosion degree of steel wires, the less the number of deep ellipsoidal pits, the more the number of groove and saddle pits. The average corrosion depth of steel wires is positively correlated with the maximum pit depth, width and length. The strength of corroded steel wires mainly depends on the maximum pit depth. In addition, compared with the new steel wire, the average yield strength and ultimate strength of old steel wires decrease due to the influence of corrosion and the discreteness increases. The similarity of probability density function of new and old steel wires is high, and the corrosion has little effect on the elastic modulus of steel wires. Finally, the model curve is in good agreement with the experimental curve, and the proposed damage model of corroded steel wires is basically accurate.

Polymer-dispersed liquid crystals (PDLCs) are very attractive due to their electrically switchable properties. However, current PDLC films still have problems such as high driving voltages, low contrast ratio (CR), and poor bending resistance and spacing stability. To solve these problems, a PDLC film with a system of coexisting polymer spacer columns and polymer network was proposed. First, based on the adhesive systems of IBMA and UV6301, the effects of IBMA concentration and LC content on the morphology of the polymer network and the electro-optical properties of PDLC were investigated, respectively. Then, the effects of the process conditions of mask polymerization such as temperature, time, and UV light intensity on the morphology and electro-optical properties of the polymer spacer columns were systematically investigated. It was found that PDLC films with the coexistence system exhibit both excellent electro-optical properties and outstanding bending resistance and spacing stability. Thus, it provides new practical possibilities for the preparation of high-performance PDLC films used in flexible devices.

Deep learning-based forest fire vision monitoring methods have developed rapidly and are becoming mainstream. The existing methods, however, are based on enormous amounts of data, and have issues with weak feature extraction, poor small target recognition and many missed and false detections in complex forest scenes. In order to solve these problems, we proposed a multi-task learning-based forest fire detection model (MTL-FFDet), which contains three tasks (the detection task, the segmentation task and the classification task) and shares the feature extraction module. In addition, to improve detection accuracy and decrease missed and false detections, we proposed the joint multi-task non-maximum suppression (NMS) processing algorithm that fully utilizes the advantages of each task. Furthermore, considering the objective fact that divided flame targets in an image are still flame targets, our proposed data augmentation strategy of a diagonal swap of random origin is a good remedy for the poor detection effect caused by small fire targets. Experiments showed that our model outperforms YOLOv5-s in terms of mAP (mean average precision) by 3.2%, APS (average precision for small objects) by 4.8%, ARS (average recall for small objects) by 4.0%, and other metrics by 1% to 2%. Finally, the visualization analysis showed that our multi-task model can focus on the target region better than the single-task model during feature extraction, with superior extraction ability.

The nonlinear analyses of the hypersonic and high-enthalpy boundary-layer transition had received little attention compared with the widely-studied linear instabilities. In this work, the oblique-mode breakdown, as one of the most available transition mechanisms, is studied using the nonlinear parabolized stability equations (NPSE) with consideration of the thermal-chemical non-equilibrium effects. The flow over a blunt cone is computed at a free-stream Mach-number of 15. The rope-like structures and the spontaneous radiation of sound waves are observed in the schlieren-like picture. It is also illustrated that the disturbances of the species mass and vibrational temperature near the wall are mainly generated by the product term of the wall-normal velocity disturbance and the mean-flow gradient. In comparison to the CPG flow, the TCNE effects destabilize the second mode and push upstream the N factor envelope. The higher growth rate of the oblique wave leads to stronger growth of the streamwise vortices and harmonic waves.

In this work, the stability of Mach 20 flows past a 6 deg wedge in thermal–chemical nonequilibrium (TCNE) is studied by means of linear parabolized stability equations (PSEs) in combination with ad...

Compared to the streamwise instability, the cross-flow instability in high-enthalpy flows has received relatively less attention, but the latter is of vital importance in the flow transition for practical configurations. This work aims to investigate the cross-flow primary and secondary instabilities in hypersonic and high-enthalpy boundary layers, considering thermochemical non-equilibrium (TCNE) effects. The numerical tools adopted include a high-order shock-fitting solver, nonlinear parabolized stability equations and secondary instability theory (SIT). The flow over a swept parabola is calculated at a free-stream Mach number of 16. It is found that TCNE has a destabilizing effect on the cross-flow mode with a non-catalytic wall. Two important non-dimensional parameters are summarized to explain this effect. One is the ratio between the wall and boundary-layer edge temperatures, and the other is the cross-flow Mach number. Due to nonlinear effects, the stationary cross-flow vortices evolve and exhibit the classic rollover structures as in lower-speed flows. Two different disturbance energy norms are used in the energy budget analysis to classify the secondary cross-flow instability modes. The results from SIT highlight the importance of type-IV modes in TCNE flows at the downwash region of the vortex. The type-IV modes arise with the combined contribution from the wall-normal (on top and trough of the vortex) and spanwise (in the downwash region) production terms. The type-I mode is dominant in the calorically perfect gas case with an adiabatic wall, whereas the type-IV mode has the largest growth rate in the TCNE cases irrespective of wall temperature variation.

The stability of hypersonic flows along a streamwise corner is studied here with bi-global stability theory for freestream Mach numbers 4.5 and 6.0. The steady laminar base flows are obtained by solving the corresponding self-similar solution for the corner plane and are in good agreement with direct numerical simulation. The base flow exhibits a pronounced low-speed region at the corner due to a secondary flow toward the corner causing an outflow along the corner bisector. The strength of the secondary flow increases with Mach number showing significant difference from the incompressible case. Two series of instability modes, corresponding to the slow and fast acoustic waves, are obtained in the Reynolds number-wavenumber stability diagram. In particular, the slow modes have higher frequencies and are of the second Mack modes stretched in the spanwise direction similar to the flat-plate boundary layer case. The leading slow mode has the most considerable growth rate, thus dominating the instability away from the corner. The fast instability mode F-I-even discovered in this work is an unique feature to the streamwise corner flow. This mode dominates the instability of the corner flow with increasing Mach-number effect.

A high sensitivity Class-3 ultra high-frequency (UHF) radio-frequency identification (RFID) system based on harmonic backscattering to achieve a long read-range is presented. Harmonic backscattering is a promising solution to solve the carrier leakage issue of UHF RFID reader to improve the sensitivity. In the proposed RFID system based on harmonic backscattering, the RFID reader transmits data with the fundamental frequency carrier and receives data with its second harmonic carrier, and the RFID tag employs a rectifier to generate both DC power and the second harmonic carrier for backscattering without impedance mismatch. The first harmonic Class-3 UHF RFID system based on National Instruments software defined radio platform is proposed and implemented. The proposed semi-passive harmonic RFID tag has − 20 dBm sensitivity. Test results show that the harmonic RFID system has a − 101 dBm sensitivity with the harmonic RFID tag whose signal-to-blocker ratio is − 7 dB at 20 m communication distance.

High-temperature effects need to be considered for a better design of hypersonic and reentry vehicles. They affect both the boundary layer flow and its flow transition, whose primary stages can be investigated through modal stability analysis. In this work, physical and numerical tools for high-temperature flows are presented and the efficiency of the new developed in-house boundary layer and stability solvers is tested. Specially, we focus on the stability of a flat plate flow in thermochemical non-equilibrium through an investigation of growth rates under the influence of various flow parameters.

The research on hypersonic boundary layer transition is a recent focal point in fluid dynamics. One of the effective numerical methods for transition study is the high-order shock-fitting method, which is especially suitable for dealing with shock-related interactions and removing post-shock oscillations as compared with shock-capturing methods. Currently, explicit time-stepping schemes are mainly used for shock-fitting methods. In comparison, implicit schemes have received less attention due to the extra complexity arising from dynamic shock and moving mesh, even though they can accelerate the convergence speeds for steady flows by up to an order of magnitude. In this paper, two implicit time-stepping methods, GMRES (generalized minimum residual) and LR (line-relaxation), are realized for the efficient calculation of steady flow fields using the 5th-order shock-fitting method. The gas models include both calorically perfect gas and 5-species thermal-chemical non-equilibrium gas required for high-speed and high-enthalpy flows. The results of test cases showed that the convergence rates of GMRES+LR and LR are 4 to 20 times faster than the explicit/semi-implicit Runge-Kutta schemes. Therefore, the usage of implicit GMRES and LR as time-stepping schemes raises the computational efficiency for obtaining steady boundary layer flows, which helps the important high-order shock-fitting methods play a greater role in the study of hypersonic boundary layer stability and transition.

Background There are limited population based data on the prevalence of asthma in China. The China Asthma and Risk factors Epidemiologic (CARE) survey was designed to understand the prevalence and risk factors for asthma in mainland China. Objectives The CARE survey aims to demonstrate the prevalence and risk factors of asthma in mainland China among adolescents (age >14 years) and adults. Methods The survey was performed between February 2010 and August 2012 in eight provinces/cities of seven areas in mainland China. The inhabitants (age, >14 years) recruited in this survey were through multi-stage cluster random sampling. Asthma diagnosis was based on medical history and lung function tests. Multivariable logistic regression was used to analyzed the risk factors for asthma. Results The study included 164 215 subjects (men, 79 692 [48.53%]; women, 84 523 [51.47%]). 2034 (1.24%) were asthmatic patients. Among all asthmatic patients, 521 (25.61%) were newly diagnosed. Univariable regression analysis showed that risk factors for asthma included smoking, first-degree relatives with asthma, allergic rhinitis, chronic bronchitis, COPD, pollinosis, allergic pneumonia, concomitant allergic diseases, BMI and raising pets. Multivariable logistic regression indicated that asthma risk factors included women, age stratification, smoking, first-degree relatives suffering from asthma or pollinosis, combined with allergic rhinitis, eczema or GERD. Conclusions We speculated that the prevalence of asthma is increasing in mainland China among individuals aged >14 years in the past 10 years. A number of risk factors were identified. The risk factors of asthma would be further elucidated in our future work. Clinical implications Our CARE study highlights that asthma epidemic in mainland China should be paid more attention.

The incidence and mortality of lung cancer remains so high that it is very urgent to develop an effective method for early detection of lung cancer. Serum can reflect physiological and pathological changes of human body, so FTIR spectroscopy was used to compare lung cancer patients' and healthy persons' serum in this study. The A1080/A1170 ratio might be potentially useful for distinguishing lung cancer patients' serum from healthy persons' serum. Moreover, the result of curve fitting indicated that the ratios of α-helix/antiparallel β-sheet were lower for lung cancer patients' serum than those for healthy persons' serum. These results indicated that IR spectra of serum might be potentially useful for detecting lung cancer.

A low-power, high-sensitive current converter for implantable electrochemical glucose sensor tags based on radio frequency identification is presented. The current converter can work in the incremental sigma delta (ΣΔ) converter mode or the dual-slope converter mode. The two modes can be switched automatically according to the input current value for the target measuring range from 10 fA to 1 nA. The dual-mode converter offers a 10 fA-input current sensitivity, 100 dB dynamic range and consumes 4.26 μW of power from a 1.5 V supply.

In this paper, FTIR spectroscopy was applied to compare the serum from leukemia patients with the serum from healthy persons. IR spectra of leukemia patients' serum were similar with IR spectra of healthy persons' serum, and they were all made up of proteins, lipids and nucleic acids, etc. In order to identify leukemia patients' serum and healthy persons' serum, the H1075/H1542, H1045/H1467, H2959/H2931 ratios were measured. The H2959/H2931 ratio had the highest significant difference among these ratios and might be a useful factor for identifying leukemia patients' serum and healthy persons' serum. Furthermore, from curve fitting, the RNA/DNA (A1115/A1028) ratios were observed to be lower in leukemia patients' serum than those in healthy persons' serum. The results indicated FTIR spectroscopic study of serum might be a useful tool in the field of leukemia research and diagnosis.

In this paper, FTIR microspectroscopy was used to identify broken cellular wall Ganoderma lucidum spores and G. lucidum spores. For IR spectra, broken cellular wall G. lucidum spores and G. lucidum spores were mainly different in the regions of 3000–2800, 1660–1600, 1400–1200 and 1100–1000 cm−1. For curve fitting, the results showed the differences in the protein secondary structures and the polysaccharide structures/content between broken cellular wall G. lucidum spores and G. lucidum spores. Moreover, the value of A1078/A1741 might be a potentially useful factor to distinguish broken cellular wall G. lucidum spores from G. lucidum spores. Additionally, FTIR microspectroscopy could identify broken cellular wall G. lucidum spores and G. lucidum spores accurately when it was combined with hierarchical cluster analysis. The result suggests FTIR microspectroscopy is very simple and efficient for distinction of broken cellular wall G. lucidum spores and G. lucidum spores. The result also indicates FTIR microspectroscopy may be useful for TCM identification.

In order to obtain unique information of Ganoderma lucidum spores, FTIR microspectroscopy was used to study G. lucidum spores from Anhui Province (A), Liaoning Province (B) and Shangdong Province (C) of China. IR micro-spectra were acquired with high-resolution and well-reproducibility. The IR spectra of G. lucidum spores from different areas were similar and mainly made up of the absorption bands of polysaccharide, sterols, proteins, fatty acids, etc. The results of curve fitting indicated the protein secondary structures were dissimilar among the above G. lucidum spores. To identify G. lucidum spores from different areas, the H1078/H1640 value might be a potentially useful factor, furthermore FTIR microspectroscopy could realize this identification efficiently with the help of hierarchical cluster analysis. The result indicates FTIR microspectroscopy is an efficient tool for identification of G. lucidum spores from different areas. The result also suggests FTIR microspectroscopy is a potentially useful tool for the study of TCM.

A green route for rapid synthesis of 2,2′-dithiobis(benzothiazole) (DM) by microwave irradiation is discussed. The reaction time was shortened to 5 min, and the yield of product was good.

This paper presents a 512-bit low power electrically programmable embedded non-volatile memory (eNVM) for the Internet of Things (IoT) applications. A novel memory bit cell which is fully compatible to the CMOS logic process is developed using dual tunneling gate structure. Costumer designed lateral double diffused MOS transistor (LDMOS) is proposed in a novel high voltage management circuit to improve the reliability and safety of the memory established by thin gate oxide transistors. In charge pump design, a frequency step-up scheme is proposed to control the current surge during writing operation, thus large voltage droops in the power supply is prevented, improving the stability of the system. The memory is implemented in a standard 0.13μm CMOS technology process. Measured results indicate that under the supply voltage of 1.2 V, it consumes 9.2 μW (22.9 μW) at the read (write) rate of 6.78 Mb/s (8 kb/s). Endurance characteristics under 100k program cycles stress test and data retention characteristics of up to 10 years are demonstrated.

Base on the China asthma and risk factors epidemiologic investigation (CARE study), we analyzed the current status of asthma control in China.With the multi-stage random cluster sampling method, epidemiological survey was performed among Chinese residents who aged over 14 years in 8 provinces (cities) from 2010 to 2011. Detailed clinic data of 2 034 asthma patients were collected via face-to-face home visit . Asthma was diagnosed based upon the history, clinical signs and lung function tests. The SPSS 12.0 was conducted for statistics analysis.This survey found that the prevalence rate of asthma in China was 1.24% (2 034/164 215), including 973 male and 1 061 female patients, with a mean age of (56 ± 18) years old. Consistent with the Global Initiative for Asthma (GINA) guidelines, 40.51% (824/2 034) and 42.58% (866/2 034) of our patients achieved control and partial control, respectively. According to the asthma control test (ACT) estimates, 15.63% (318/2 034) and 49.46% (1 006/2 034) of patients achieved full control (ACT 25) and well control(ACT 20-24), respectively. In the past year, 22.62% (460/2 034) of patients reported hospitalized and 26.99% (549/2 034) of patients reported emergency room visit at least one time due to asthma exacerbation. 61.80% (1 257/2 034) of patients were on daily us of medication. Inhaled corticosteroids (ICS) plus a long-acting β2 agonist (LABA) or solely ICS were used in 6.39% and 14.75% of patients, respectively. Theophylline treatment accounted for 29.11% (592/2 034). Oral glucocorticoid and oral leukotriene modifier (LTRA) treatment accounted for 9.49% (193/2 034) and 3.10% (63/2 034), respectively. According to the survey, 34.51% (702/2 034) of asthma patients reported a history of smoking . The percentage of asthma control in non smoking patients was higher than in smoking patients [43.24% (576/1 332) and 35.33% (248/702), respectively]. Meanwhile, the rates of both hospitalization and emergency due to asthma exacerbation in smoking asthma patients were significantly higher than nonsmoking asthma patients (27.35% and 31.77%, 20.12% and 24.47%, respectively).The situation of asthma control has been improved in China. However, compared with GINA guidelines, there is still a considerable gap. Smoking is one of the crucial factors that affect asthma control.

To survey the risk factors of asthma among the people aged over 14 years in China.Home visits for completing epidemiological questionnaires in accordance with stratified cluster random sampling survey were conducted in 8 provinces (cities) of China residents aged over 14 years from February 2010 to August 2011. Asthma was diagnosed based upon case history, clinical signs and lung function test. The SPSS 12.0 software was used for statistic analyses for the epidemiological status of asthma.Sampling population was composed of 180 099 subjects. Among 164 215 valid questionnaires, there were 79 692 males and 84 523 females, 2 034 had asthma. The overall prevalence rate was 1.2% (2 034/164 215). Correlation analyses showed that the risk factors were smoking (OR = 1.697, 95%CI: 1.547-1.861), breast feeding (OR = 0.801, 95%CI: 0.670-0.959), genetics (OR95%CI1, asthma (OR = 10.440, 95%CI: 8.991-12.112)), complications (OR95%CI1), body mass index (compared with normal weight, overweight (OR = 1.360, 95%CI: 1.212-1.531), obesity (OR = 10.631, 95%CI: 9.570-11.801)) and petting (OR95%CI1).Among Chinese asthmatics aged over 14, their risk factors include host (geneticsobesity) and environmental (smoking, breastfeeding, complicationspets) factors.