Preparation and Characterization of Sulfated Cellulose Nanocrystalline and its Composite Membrane for Removal of Tetracycline Hydrochloride in Water

The removal of antibiotic pollutants remaining in the environmental media has been a big challenge nowadays.Herein,we report a facile and green approach to fabricate an eco-friendly composite membrane without addition of any toxic polymers or chemical cross-linking agents to effectively remove the tetracycline hydrochloride in Water.Firstly,the sulfated cellulose nanocrystalline(CNC) was obtained via hydrolysis of sulfuric acid by using microcrystalline cellulose(MCC) as raw material under ultrasonic condition.The as-prepared CNC has a nanowhisker dimension with 200.2 ± 110.2 nm in length,15.7 ± 9.3 nm in width,and 7.2 ± 3.1 nm in height.The obtained CNC is cellulose type I as determined by X-ray diffraction(XRD),while its crystallinity index(Crl) can reach 82.3%.Then,the composite membrane derived from the obtained CNC and commercial mixed cellulose ester(MCE)membrane was facilely prepared through vacuum dewatering process,which is applied to remove tetracycline hydrochloride(Th) in solution.The results showed that the removal efficiency of Th through the neat MCE was only28 ± 4%,while it could be improved to 58 ± 5% and 89 11%,respectively,by filtering through composite membranes with different contents of CNC deposition.Such effect is derived from the combine factors based on both steric hindrance(sieving) and electrostatic interaction(Donnan) effect of the composite membranes.The development of related CNC materials and composite fabrication processes is in favor of cost-effective and "green"polymer composites for the remediation of increasing antibiotic pollution and the purification of contaminated water nowadays.

Reliability analysis of arresting hook engaging arresting cable for carrier-based aircraft influenced by multifactors

The carrier-based aircraft landing and arrest process is complex and nonlinear,and includes the coupling effect between the aircraft and arresting system.It has many uncertain factors,which lead to difficulty in the reliability analysis.To make the reliability analysis more accurate and effective,this paper presents some studies.Taking a certain type of carrier-based aircraft as the research object,a dynamic model of the landing and arrest cable was established,and the accuracy of the model was verified using laboratory test results.Based on the model,this paper shows how the key parameters,including the sinking velocity,pitch angle and horizontal velocity,affect the collision rebound performance of the arresting hook.After that,a limit state equation of the arresting hook system’s reliability was established.For the implicit limit state equation,a surrogate model of the reliability of the arresting hook was established using the Support Vector Machine(SVM)method,and then reliability analysis was carried out using the Monte Carlo method.Finally,it was explained in detail how the key parameters affect the reliability of the hook engaging the arresting cable,and some meaningful conclusions were obtained.This analysis method and its results can provide a reference for the top-level parameter design of carrier-based aircraft and reliability research on the arresting systems.

An architecture decomposition method of pneumatic catapult system based on OPM and DSM

The architecture strategy of the Unmanned Aerial Vehicle(UAV)pneumatic launch system should continue to evolve to adapt to complex and variable operating environments.Architecture representation,decomposition perspective,and cluster analysis play a vital role in the early phase of system architecture development.In order for the system to emerge anticipated and desirable intrinsic functional properties,an architecture decomposition method based on the ObjectProcess Methodology(OPM)and Design Structure Matrix(DSM)is put forward in this paper.The OPM is proposed to model the UAV launch process formally,and the matrix representation of the architecture of the pneumatic launch system is established.After the extension of the definition and operations of DSM,with the Idicula-Gutierrez-Thebeau Algorithm plus(IGTA+)clustering algorithm,the transformation of the pneumatic launch system architecture from process decomposition to function decomposition is demonstrated in this paper.The analysis shows that the architecture decomposition of the pneumatic launch system meets the functional requirements of stakeholders.

Disparities of Heatwave-Related Preterm Birth in Climate Types—China,2012-2019

What is already known about this topic?An association between prenatal heatwave exposure and the risk of preterm birth was found.However,the disparities in heatwave-related preterm birth across different climate types have not been examined.What is added by this report?This nationwide case-crossover study investigated the association between heatwave exposure and preterm birth across different Köppen-Geiger climate types.Among pregnant women residing in the arid-desertcold climate type,exposure to compound heatwaves was found to be associated with a significantly higher risk of preterm birth{adjusted odds ratios(AORs)ranged from 1.55[95%confidence interval(CI):1.21-1.97]to 2.11(95%CI:1.35-3.31)}.In contrast,among pregnant women residing in the tropical monsoonal climate type,exposure to daytime-only heatwaves was associated with an increased risk of preterm birth[AORs ranged from 1.25(95%CI:1.03-1.51)to 1.37(95%CI:1.05-1.77)].

Parameter effects on high-speed UAV ground directional stability using bifurcation analysis

A loss of ground directional stability can trigger a high-speed Unmanned Aerial Vehicle(UAV)to veer off the runway.In order to investigate the combined effects of the key structural and operational parameters on the UAV ground directional stability from a global perspective,a fully parameterized mathematical high-speed UAV ground nonlinear dynamic model is developed considering several nonlinear factors.The bifurcation analysis procedure of a UAV ground steering system is introduced,following which the simulation efficiency is greatly improved comparing with the time-domain simulation method.Then the numerical continuation method is employed to investigate the influence of the nose wheel steering angle and the global stability region is obtained.The bifurcation parameter plane is divided into several parts with different stability properties by the saddle nodes and the Hopf bifurcation points.We find that the UAV motion states will never cross the bifurcation curve in the nonlinear system.Also,the dual-parameter bifurcation analyses are presented to give a complete description of the possible steering performance.It is also found that BT bifurcation appears when the UAV initial rectilinear velocity and the tire frictional coefficient vary.In addition,results indicate that the influence of tire frictional coefficient has an opposite trend to the influence of initial rectilinear velocity.Overall,using bifurcation analysis method to identify the parameter regions of a UAV nonlinear ground dynamic system helps to improve the development efficiency and quality during UAV designing phase.

Bifurcation analysis of dual-sidestay landing gear locking performance considering joint clearance

Sidestay lock mechanism is an important part of landing gear system,and the locking performance can be analyzed based on changes in its stability.However,during numerical continuation analysis of fully-rigid dual-sidestay landing gear without clearance,it has been found that the appearance of bifurcation points does not necessarily imply that both sidestay links can be locked synchronously.This problem reveals the limitations of fully-rigid model with ideally-articulated in solving dual-sidestay mechanisms with extremely high motion sensitivity.Therefore,this study proposes a bifurcation analysis method for synchronous locking of dual-sidestay landing gears,which takes into consideration the joint clearance.For in-depth analysis of this problem,we initially build kinematic and mechanical models of a landing gear mechanism that consider joint clearance.Then,the models are solved based on continuation.The fundamental causes of synchronous locking are discussed in detail,and the number of bifurcation points is found to be closely related to whether the landing gear is completely locked.Finally,the effects of structural parameters on the synchronous locking are analyzed,and the feasible region of parameters satisfying synchronous locking condition is given,which agrees well with the test results.

Study on modal characteristics and vibration reduction of an aircraft rotor–stator brake-induced squeal system

Based on the modal coupling theory,the rotor and stator contact stiffness and axial relative velocity are considered to build an electric aircraft brake dynamic system model in this study.Both the complex modal analysis and transient dynamic analysis methods are used to study the aircraft brake squeal performance and vibratory mechanism.The unstable vibration modes indicate that the out-of-plane vibration plays an important role and the feed-in energy is larger than the output energy in the brake rotor–stator module so that brake squeal takes place.Then the influences of the contact stiffness,friction damping and frictional coefficient on the brake squeal system are carried out,laying the foundation for the three proposed vibration suppression methods.Results show that the coefficient negative-slope condition will intensify the vibration.Also,a linear relationship between the squeal factor and the frictional coefficient is obtained to provide a guidance to predict squeal stability under more conditions.Vibration reduction design shows that adding a damping layer to the brake mechanism and chamfering the edge of braking stators both can reduce brake squeal effectively,while slotting braking stators is invalid in aircraft braking system.