Dynamical Modeling and Dynamic Characteristics Analysisof a Coaxial Dual-Rotor System

The dual-rotor structure serves as the primary source of vibration in aero-engines. Understanding itsdynamical model and analyzing dynamic characteristics, such as critical speed and unbalanced response, arecrucial for rotor system dynamics. Previous work introduced a coaxial dual-rotor-support scheme for aeroengines,and a physical model featuring a high-speed flexible inner rotor with a substantial length-to-diameter ratiowas designed. Then a finite element (FE) dynamic model based on the Timoshenko beam elements and rigid bodykinematics of the dual-rotor system is modeled, with the Newmark method and Newton–Raphson method used forthe numerical calculation to study the dynamic characteristics of the system. Three different simulation models,including beam-based FE (1D) model, solid-based FE (3D) model, and transfer matrix model, were designed tostudy the characteristics of mode and the critical speed characteristic of the dual-rotor system. The unbalancedresponse of the dual-rotor system was analyzed to study the influence of mass unbalance on the rotor system. Theeffect of different disk unbalance phases and different speed ratios on the dynamic characteristics of the dual-rotorsystem was investigated in detail. The experimental result shows that the beam-based FE model is effective andsuitable for studying the dual-rotor system.

Analysis and Research on Aerodynamic Characteristics of Quad Tilt Rotor Aircraft

For the quad tilt rotor aircraft, a computational fluid dynamics method based on multiple reference frames (MRF) was used to analyze the influence of aerodynamic layout parameters on the aerodynamic characteristics of the quad tilt rotor aircraft. Firstly, a numerical simulation method for the interference flow field of the quad tilt rotor aircraft is established. Based on this method, the aerodynamic characteristics of isolated rotors, rotor combinations at different lateral positions on the wing, and rotor rotation directions under different inflow velocities were calculated and analyzed, in order to grasp their aerodynamic interference laws and provide reference for the design and control theory research of such aircraft.

Detection and characteristics analysis of the western subarctic front using the high-resolution SST product

Oceanic front plays a significant role in the ocean vertical mixing and the regulation of air-sea interaction,among others.The western branch of the subarctic front(WSAF)located in the Northwest Pacific has attained lots of attention given its strong intensity and widespread influence on this region.In this study,we take advantage of the merged sea surface temperature(SST)at a high spatial resolution of 0.05°to investigate the characteristics of WSAF.The front detection algorithm that combines the Sobel operator and histogram analysis is adopted.It is advantageous in both preserving the front intensity represented by the SST gradient as well as reducing the detection noise level.We systematically applied this algorithm to the daily SST products for front detection,based on which the WSAF characteristics including its intensity,occurrence of frequency,latitudinal position and coverage area are then extracted.WSAF is mostly located within a small latitude range between 40°N and 41°N with a clear seasonal trend in its intensity that peaks in the winter and troughs in the summer.The seasonal variation of WSAF intensity is almost consistent throughout the temporal period of interest from 2010 to 2018.Similar seasonality is observed for its occurrence of frequency with the winter-summer contrast reaching up to5%.The findings presented here shall help better interpret the WSAF characteristics in the long-term run as well as their impact on the regional weather and climate patterns at high spatial resolution.

Analysis on Climatic Characteristics of High Temperature Weather in Longdong Region

Using meteorological data from 8 national basic meteorological observation stations in Qingyang City of Longdong region from 1972 to 2021,the causes and change characteristics of high-temperature weather were analyzed,and targeted countermeasures and suggestions were proposed for residents' production,life,and energy security supply affected by high-temperature weather.The results showed that①affected by global warming,the annual average temperature,annual average maximum temperature,annual extreme maximum temperature,days of daily maximum temperature≥30℃,and days of daily maximum temperature≥35℃in Longdong region were all showing an upward trend;②due to the different terrain and soil properties of the underlying surface,the increase in high temperature weather varied in different regions.Due to the influence of desert and hilly terrain,the frequency and days of high temperature occurrence were relatively high in the central and northern parts of Qingyang City.Due to the climate regulation of the Ziwuling Mountains,the days of high temperature in the central and southern parts was significantly less than that in the central and northern parts;③if the warm high pressure ridge on the Qinghai-Tibet Plateau developed strongly in summer,the temperature of the closed warm center reached 0-4℃on the 500 hPa of high-altitude weather map.If the warm air mass developed eastward,it often led to sustained high temperature weather in Longdong region;④when the El Nino phenomenon occurred,the subtropical high in the western Pacific developed strongly in summer,with a center located northward,which was stable,with little movement.It was dry,sunny,hot,and rainless in Longdong region,and the high temperature weather was more significant than that in normal years.

Short-time maritime target detection based on polarization scattering characteristics

In this paper,a detection method combining Cameron decomposition based on polarization scattering characteristics in sea clutter background is proposed.Firstly,the Cameron decomposition is exploited to fuse the radar echoes of full polarization channels at the data level.Due to the artificial material structure on the surface of the target,it can be shown that the non-reciprocity of the target cell is stronger than that of the clutter cell.Then,based on the analysis of the decomposition results,a new feature with scattering geometry characteristics in polarization domain,denoted as Cameron polarization decomposition scattering weight(CPD-SW),is extracted as the test statistic,which can achieve more detailed descriptions of the clutter scattering characteristics utilizing the difference between their scattering types.Finally,the superiority of the proposed CPD-SW detector over traditional detectors in improving detection performance is verified by the IPIX measured dataset,which has strong stability under short-time observation in threshold detection and can also improve the separability of feature space zin anomaly detection.

Dynamic impact experiment and response characteristics analysis for 1:2 reduced-scale model of hydraulic support

It is significant to research the impact resistance properties of hydraulic support due to its key support role in the fully mechanized mining face.However,it is difficult for the entire hydraulic support to implement the impact experiment underground and analyze the response characteristic.Therefore,a dynamic impact experiment for the entire hydraulic support was proposed in this paper,where a 1:2 reducedscale model of hydraulic support was designed and its response characteristics under dynamic impact load were analyzed.Firstly,a comprehensive monitoring scheme was proposed to achieve an effective monitoring for dynamic response of hydraulic support.Secondly,a multi-scale impact experiment was carried out for the entire hydraulic support and dynamic behaviors of hydraulic support under the multi-scale impact load were revealed by experimental data.Then a dynamic impact experiment of the entire hydraulic support was simulated in ADAMS with the same experiment conditions,and the experimental and simulation data were verified mutually.Finally,the characteristics of energy conversion and dissipation of the entire experiment system after impact were analyzed.The experiment results showed that the impact resistance properties of hydraulic support largely depended on the initial support conditions and different vertical rigidities affected energy distribution proportion of the entire support system.

Analysis of Frequency Characteristics and Sensitivity of Compliant Mechanisms

Based on a modified pseudo-rigid-body model,the frequency characteristics and sensitivity of the large-deformation compliant mechanism are studied.Firstly,the pseudo-rigid-body model under the static and kinetic conditions is modified to enable the modified pseudo-rigid-body model to be more suitable for the dynamic analysis of the compliant mechanism.Subsequently,based on the modified pseudo-rigid-body model,the dynamic equations of the ordinary compliant four-bar mechanism are established using the analytical mechanics.Finally,in combination with the finite element analysis software ANSYS,the frequency characteristics and sensitivity of the compliant mechanism are analyzed by taking the compliant parallel-guiding mechanism and the compliant bistable mechanism as examples.From the simulation results,the dynamic characteristics of compliant mechanism are relatively sensitive to the structure size,section parameter,and characteristic parameter of material on mechanisms.The results could provide great theoretical significance and application values for the structural optimization of compliant mechanisms,the improvement of their dynamic properties and the expansion of their application range.

Characteristics analysis for cold water patches off the Jiangsu coast in the last 35a

The daily and monthly-mean characteristics of cold water patches （CWPs） off the Jiangsu coast in 35 a of 1982-2016 are examined based on advanced very high resolution radiometer （AVHRR） data. Most of the CWPs are found to occur in the warm and hot months （May-September）, with some CWPs in the cool and cold months （October-April）. The average radius and intensity of the monthly-mean CWPs are about 81 km and 0.6℃, respectively. The average difference in the sea surface temperature （SST） between the centers of the CWPs and the nearshore is about 2.0℃. The correlation analysis between the CWPs, winds and tides indicates that most of the CWPs occurred during the southerly winds, with some CWPs occurring during the northerly winds. The average intensity of the CWPs during spring tides is slightly stronger than that during neap tides in the warm and hot months, and the difference is very small in the cool and cold months.

Floating Clamping Mechanism of PT Fuel Injector and Its Dynamic Characteristics Analysis

PT fuel injector is one of the most important parts of modern diesel engine.To satisfy the requirements of the rapid and accurate test of PT fuel injector,the self-adaptive floating clamping mechanism was developed and used in the relevant bench.Its dynamic characteristics directly influence the test efficiency and accuracy.However,due to its special structure and complex oil pressure signal,related documents for evaluating dynamic characteristics of this mechanism are lack and some dynamic characteristics of this mechanism can＇t be extracted and recognized effectively by traditional methods.Aiming at the problem above-mentioned,a new method based on Hilbert-Huang transform（HHT） is presented.Firstly,combining with the actual working process,the dynamic liquid pressure signal of the mechanism is acquired.By analyzing the pressure fluctuation during the whole working process in time domain,oil leakage and hydraulic shock in the clamping chamber are discovered.Secondly,owing to the nonlinearity and nonstationarity of pressure signal,empirical mode decomposition is used,and the signal is decomposed and reconstructed into forced vibration,free vibration and noise.By analyzing forced vibration in the time domain,machining error and installation error of cam are revealed.Finally,free vibration component is analyzed in time-frequency domain with HHT,the traits of free vibration in the time-frequency domain are revealed.Compared with traditional methods,Hilbert spectrum has higher time-frequency resolutions and higher credibility.The improved mechanism based on the above analyses can guarantee the test accuracy of injector injection.This new method based on the analyses of the pressure signal and combined with HHT can provide scientific basis for evaluation,design improvement of the mechanism,and give references for dynamic characteristics analysis of the hydraulic system in the interrelated fields.

Analysis of Characteristics of Atmospheric Pollution from Main Pollutants in Binzhou City

Based on the data of six main pollutants（ PM（2. 5）,PM（10）,SO2,NO2,O3,and CO） and temperature（ the maximum temperature and the minimum temperature） in Binzhou City during 2014-2016,the annual and monthly variations in the concentrations of these main pollutants in Binzhou City were analyzed,and the correlations between PM（2. 5） and other pollutants were discussed using SPSS software. The results showed that the concentrations of PM（2. 5）,PM（10）,SO2,NO2,and CO in Binzhou City reduced gradually,while O3 concentration fluctuated from 2014 to 2016. The concentrations of PM（2. 5）,PM（10）,SO2,NO2,and CO in winter were higher than that in summer,while O3 concentration showed an opposite trend.There was a strongly positive correlation between PM（2. 5） and PM（10） concentration,and PM（2. 5） concentration correlated positively with SO2,NO2 and CO concentration,while it correlated negatively with O3 concentration,the maximum temperature,and the minimum temperature respectively.

Clinical characteristics of myotonia congenita in China Literature analysis of the past 30 years

AIM： To understand the distinct, clinical features of myotonia congenita in China. METHODS： Case reports of myotonia congenita were retrieved from the Chinese Journal Full-text database, dating between 1980 and 2007, and analyzed for clinical characteristics of myotonia congenita. RESULTS： There were 35 published reports and 258 cases about myotonia congenita. Six reports （62 cases） were excluded due to lack of clinical data, imprecise diagnosis, or duplication. Finally, 29 published reports and 196 cases （140 males and 56 females） were included in this analysis. About 78.6% of patients were diagnosed with myotonia congenita before the age of 20, and among these, 86.1% were classified as dominant inheritance. Lower and upper extremities were frequently affected with severe symptoms. Eyelids, mouth and lingual muscles, and trunk muscles and cervical muscles were less frequently involved. However, muscles for swallowing, sphincter muscles, and smooth muscles were not involved. There were no reports of cataracts, cardiac conduction block, or dyscrinism. myotonia congenita symptoms were induced or aggravated by cold temperatures in 71.9% of the patients and warming-up effect occurred in 95.6% of the patients. Muscle hypertrophy was observed in 69.6% and percussion of muscles in 76.5% of the patients. Myotonia potential or myotonia-like potential was detected in all patients using electromyography. Muscle fiber swelling or hypertrophy was frequently detected through muscular biopsy. CONCLUSION： Myotonia congenita frequently occurs in males before the age of 20, in particular as the autosomal dominant form of myotonia congenita. Skeletal muscles throughout the body, especially the lower and upper extremities, are involved. However, muscles for swallowing, sphincter muscles, and smooth muscles are not involved. Warming-up effect is the main characteristic of myotonia congenita.

Variation Characteristics and Mutation Analysis of the Temperature in Fangchenggang of Guangxi in Recent 55 Years

[Objective] The research aimed to analyze change characteristics and mutation situation of the temperature in Fangchenggang of Guangxi from 1955 to 2009. [Method] Based on actual temperature observation data in Fangchenggang of Guangxi from 1955 to 2009, by using linear trend estimation, Mann-Kendall and cumulative anomaly, change characteristics and mutation situation of the temperature in the city in recent 55 years were analyzed. [Result] Annual average temperature had an obvious rising trend in Fangchenggang in recent 55 years, which was basically consistent with that in whole country. Summer, autumn and winter average temperatures all had obvious warming trends except that the trend in spring. Summer, winter and annual average temperature jumps occurred in the 1980s. Autumn average temperature jump occurred in the end of 1970s while spring average temperature had no jump. The situation in winter was that a transition from low stage to high stage happened in the middle period of 1980s, while transitions of the annual, spring, summer and autumn average temperatures from low stage to high stage happened in the middle and later periods of 1990s. [Conclusion] The research provided decision-making basis for going after advantages and avoiding disadvantages, guiding agricultural production and using climate resource in the zone sufficiently and reasonably.

Analysis on the Change Characteristics of Climate in Suizhong in Recent 55 Years

[Objective] The research aimed to study the variation characteristics of climate in Suizhong in recent 55 years.[Method] Based on the meteorological observation data (temperature,sunshine,precipitation,etc.) in Suizhong County during 1956-2010,the variation trend,the time and stability which stably passed one threshold of meteorological factors were analyzed by using the linear regression,five-day sliding average and deviation coefficient.The change characteristics of climate in Suizhong County in recent 55 years were grasped.[Result] In recent 55 years,the temperature in Suizhong presented the rise trend.In recent 25 years (1986-2010),the temperature rise was obvious.The rise ranges of winter average temperature and average minimum temperature were big.Moreover,the variation range was big,and the stability was bad.The variation trends of frost-free period and ≥10 ℃ accumulated temperature were basically consistent with that of temperature.The sunshine hours overall presented the decline trend,which wasn’t obvious.It presented the rise trend in winter half year and the decline trend in summer half year.The decline trend in summer was obvious.The rainfall overall presented the decline trend.Spring precipitation presented the rise trend.The precipitation in summer and autumn presented the decline trend.The variation range of precipitation in winter was big,and the stability was bad.The variation range of precipitation in summer was small,and the stability was good.[Conclusion] The research provided the basis for management department understanding and grasping the variation characteristics of local climate,disaster prevention and reduction.

Dynamics Response and Non⁃linear Characteristics Analysis of Complex Planar 2⁃DOF Mechanism with Revolute Clearances

There are clearances in mechanism because of manufacture and assembly error,which reduces operation life and working accuracy of mechanism and has a great impact on dynamical responses.At the moment,research in this area mainly focuses on single degree⁃of⁃freedom mechanism considering one clearance,while research of multi⁃DOF mechanism considering multi⁃clearance is less.With the purpose of studying the dynamical characteristics of complex multi⁃DOF mechanism with multi⁃clearances,a dynamic model was developed.The dynamic responses of 2⁃DOF mechanism with two clearances under different positions,values,and numbers of clearance were analyzed.The displacement,velocity,acceleration,collision force,and the axis trajectory at clearance were then given.In addition,there is a limited amount of literature on chaotic phenomena,which mainly focuses on the chaotic phenomena of end⁃effector of mechanism.But in this paper,the non⁃linear characteristics were analyzed by chaotic phenomenon of clearance joint,then chaotic phenomenon was identified by Poincarémappings and phase diagrams.Bifurcation diagrams were given.The results will offer a reliable technical support for the study of dynamical responses of planar mechanisms and the analysis of chaotic phenomena.

Analysis of the VWP Product Characteristics in One Strong Rainstorm Process

[Objective] The aim was to study the characteristics in VWP period characteristics in one strong rainstorm process.[Method] Based on the previous studies,the VWP product characteristics in early period of strong rainstorm,during the development and the end period in Hunan Province on April 8,2008 were studied.[Result] Before the occurrence of rainstorm,the destruction of low layer 'ND' layer indicated the increase of water vapor content layer.The intrusion of cold and dry air in the middle layer led to unstable layer;during the maintaining period of rainstorm,the strong vertical shear in the low layer led to the occurrence of strong rainstorm.The cold air in the boundary layer penetrated and led the rainstorm to the most prevailing stage.There was hailstorm on the ground.Before the disappearance of rainstorm(after 17:59),the entire wind field changed into consecutive 'ND' layer and it suggested that the strong convective cloud was far away from the location of radar,and indicated the end of rainstorm.[Conclusion] The study provided reference and basis for the pre-warning of rainstorm for temporary reporter.

Analysis on the Characteristics of Rainstorm in Hanbin District of Ankang City during 1961-2003

[Objective] The research aimed to analyze the rainstorm characteristics in Hanbin District of Ankang City in 43 years. [Method] By using the daily and hourly precipitation data in Hanbin District of Ankang City during 1961-2003, the occurrence rule and variation characteristics of rainstorm weather in 43 years in the zone were analyzed. [Result] The distribution of rainstorm days in Hanbin District of Ankang City had the obvious season characteristic. The earliest rainstorm days occurred in May and started to increase in June. It frequently happened in July, August and gradually decreased in September. The latest rainstorm finished in the middle ten-day of October. The storm rainfall and days in Hanbin District of Ankang City during 1961-2003 both presented the obvious linear increase trend. From the 1970s to the end of 1980s, it was the period when the storm rainfall was more. The rainstorm days during the 1960s-early 1970s and early 1990s were fewer. The rainstorm days were more from the metaphase of 1970s to late 1980s and after the metaphase of 1990s. The time distribution characteristic of hourly precipitation in the rainstorm days was obvious and based mainly on the single peak type. The time mainly concentrated in the daytime, and the short-time strong precipitation was more. [Conclusion] The research provided the reference basis for accurately forecasting the rainstorm occurrence, disaster prevention and reduction work.

Analysis of Capacitance-Voltage-Temperature Characteristics of GaN High-Electron-Mobility Transistors

The capacitance-voltage characteristics of AIGaN/GaN high-electron-mobility transistors （HEMTS） are measured in the temperature range of 223-398K. The dependence of capacitance on frequency at various temperatures is analyzed. At lower temperatures, the capacitance decreases only very slightly with frequency. At higher frequencies the curves for all temperatures tend to one capacitance value. Such behavior can be attributed to the interface states or the dislocations.

Analysis of characteristics of a pneumatic miniature robotic system

This paper described the structure of a flexible miniature robotic system which can move in human cavities, and then analyzed the characteristics of the robotic system in detail. The mobile mechanism of the miniature robotic system is soft; it makes inchworm-like movement driven by a 3-DOF pneumatic rubber actuator and holds its positions by air chambers. The driving characteristic models in axial and bending directions of the actuator were set up and the kinemics equations of the robotic system were set up. Experiments had been done through an electro-pressure control system, by which the pneumatic robotic system can be controlled with high accuracy. It is suitable for moving in human cavities for medical inspection.

Analysis of the Self-Protection Characteristics of a 1.5T Bitter-Like HTS Magnet Operated at 65K

We present a conceptual configuration of a high-temperature superconducting（HTS）magnet made from REBCO（Re=Rare Earth,B=Barium,C=Copper,O=Oxide）annular plates,called a Bitter-like HTS magnet,which can operate in persistent current mode without joint resistance and can be excited by a flux pump and without current leads and a persistent power supply.An REBCO annular magnet which can generate 1.5 T corresponding to the operating current density 80%of critical current density of the magnet at an operating temperature of65 K is conceptually designed.Then the thermal stability of the magnet is numerically simulated by Comsol software.Whein a piece of RBCO annular plate quenches,the maximum released energy is its stored energy because each REBCO annular plate in the Bitter-like magnet is in parallel.To calculate the stored energy in the REBCO annular plate,the inductance of every annular plate,including self-inductance and mutual inductance,is calculated.Compared with the minimum quench energy（MQE）and stored energy in one REBCO annular plate,the stored energy in one REBCO annular plate is always smaller than the MQE,and the REBCO annular plate will not be damaged even though the stored energy in the REBCO annular plate is fully released,which indicates that this 1.5 T Bitter-like magnet has the property of self-protection.

Analysis on the psychological characteristics of patients with acute iridocyclitis

【正】Dear Sir,I am Dr.Wei Sun,from the Department of Ophthalmology,the Fourth Affiliated Hospital of China Medical University,Eye Hospital of China Medical University,shenyang,Liaoning Province,China.I write to present our study on the psychological characteristics of patients with acute iridocyclitis.Studies showed stimulation from patient’s external environment could influence their psychological state,persisting neural endocrine disorders that might lead to a series of physiological and psychological changes in the human body[1-6].It was confirmed many ocular diseases were