A nonlinear creep model for surrounding rocks of tunnels based on kinetic energy theorem

The initiating condition for the accelerated creep of rocks has caused difficulty in analyzing the whole creep process.Moreover,the existing Nishihara model has evident shortcomings in describing the accelerated creep characteristics of the viscoplastic stage from the perspective of internal energy to analyze the mechanism of rock creep failure and determine the threshold of accelerated creep initiation.Based on the kinetic energy theorem,Perzyna viscoplastic theory,and the Nishihara model,a unified creep constitutive model that can describe the whole process of decaying creep,stable creep,and accelerated creep is established.Results reveal that the energy consumption and creep damage in the process of creep loading mainly come from the internal energy changes of geotechnical materials.The established creep model can not only describe the viscoelasticeplastic creep characteristics of rock,but also reflect the relationship between rock energy and creep deformation change.In addition,the research results provide a new method for determining the critical point of creep deformation and a new idea for studying the creep model and creep mechanical properties.

幼儿园教师师德养成的内涵、困境与出路

要提升幼儿园教师队伍质量与整体形象,关键在于幼师的"成人"之教,重点在于幼师德性的养成.幼儿园教师不仅需要遵循习俗道德,而且要有更高的德性追求,努力成为德性与智识都充分发展、和谐发展的人.然而,当前幼师专业化程度低、培养层次低、待遇差等都阻碍了其师德的养成.为此,我们应把好生源质量关,提高培养质量,完善以"师德养成"为中心的评价机制,建立合理的用人机制,为幼师师德养成提供条件保障.

Assessment of piloting behavior impact on landing risk of transport aircraft

The human factors and their interaction with other factors play an important role in the flight safety of transport aircraft.In this paper,a paradigm of risk assessment for transport aircraft interacting with piloting behaviors is proposed,with focus on landing which is the most accident-prone flight stage in aviation safety statistics.Model-based flight simulation serves as our data source for landing risk analysis under uncertainties.A digital pilot in the loop that reflects the human piloting behaviors is employed to facilitate simulation efficiency.Eight types of unsafe events in landing are identified from statistics.On this basis,the landing safety boundary is extracted via stochastic simulation to divide safety and hazardous flight status domains,which con-tributes to flight status management and risk warning.The simulation results indicate that appro-priate piloting behavior,which is active response and fast target acquisition with minimum overshoot and fluctuation,shows benefit to landing safety.The subset simulation technique is employed to further refine the boundary with less computational workload.Furthermore,the effect of airspeed,windspeed,and other factors on landing risk is also discussed.The proposed risk assess-ment method would help optimize operation procedure and develop targeted pilot training program.

Friction between a single platelet and fibrinogen

Friction has been considered to mediate physiological activities of cells,however,the biological friction between a single cell and its ligand-bound surface has not been thoroughly explored.Herein,we established a friction model for single cells based on an atomic force microscopy(AFM)combined with an inverted fluorescence microscopy(IFM)to study the friction between a highly sensitive platelet and fibrinogen-coated surface.The study revealed that the friction between the platelet and fibrinogen-coated tip is mainly influenced by specific ligand–receptor interaction.Further,we modeled the biological friction,which consists of specific interaction,non-specific interaction,and mechanical effect.Besides,the results suggested that the velocity can also affect specific ligand–receptor interactions,resulting in the friction change and platelet adhesion to fibrinogen surfaces.The study built a friction model between a single cell and its ligand-bound surface and provided a potential method to study the biological friction by the combination of AFM and IFM.

Auto-updating model-based control for thrust variation mitigation and acceleration performance enhancement of gas turbine aero-engines

Model-based control shows promising potential for engine performance improve-ment and future aero-propulsion requirements.In this paper,an auto-updating thrust variation mitigation(AuTVM)control approach using on-board model strategies is proposed for gas tur-bine aero-engines under in-service degradation effects,which aims at active thrust regulation and acceleration protection in a simultaneous way.The AuTVM control is integrated with an on-line block,based on a reliable on-board engine model,and an off-line part for the periodical update of control parameters via post-flight engine monitoring data.The core feature of the AuTVM control is a set of auto-updating loops within the on-line part,including thrust regu-lation loop,surge margin loop,turbine entry temperature loop,and the steady loop,whose con-trol parameters are periodically adjusted with increasingflight cycles.Meanwhile,an industrial sensor-based baseline controller and two tailored model-based controllers,i.e.,a thrust variation mitigation(TVM)controller withfixed gains and a self-enhancing active transient protection(SeATP)controller with pro-active transient protection and passive thrust control,are also developed as comparison bases.Numerical simulations for idle to full-power acceleration tests are carried on a validated aero-thermal turbofan engine model using publicly available degra-dation data.Simulation results demonstrate that both new engines and severely degraded en-gines regulated by the AuTVM controller show significant thrust response enhancement,compared to the baseline controller.Moreover,thrust variation at the maximum steady state of degraded engines,which exists within the SeATP controller and the baseline controller,is suppressed by the proposed AuTVM controller.Robustness analysis against degradation uncer-tainties and sensor accuracy confirms that the AuTVM controller owns a closer maximum steady-state thrust distribution to the desired value than those of the SeATP and the baseline controller while utilizing transient margins of controlled engines more effectively.Hence,the control performance of the AuTVM controller for in-service engines is guaranteed.

Pyrylium-based porous organic polymers via Knoevenagel condensation for efficient visible-light-driven heterogeneous photodegradation

Pyrylium salts are a type of representative and convincing example of versatility and variety not only as a nodal point in organic transformations but also as an attractive building block in functional organic materials. Herein, we report an effective synthetic protocol to fabricate a new pyrylium-containing porous organic polymers(POPs), named TMP-P, via Knoevenagel condensation with 2,4,6-trimethylpyrylium salt(TMP) as the key building block and 1,4-phthalaldehyde as the linker. The resulting ionic polymer TMPP exhibited efficient visible-light-driven heterogeneous photodegradation of Rhodamine B, owing to the presence of wide visible light absorption and a narrow optical band gap triggered pyrylium core in the framework.

Multiple hierarchy risk assessment with hybrid model for safety enhancing of unmanned subscale BWB demonstrator flight test

To explore the low-speed characteristics of the Blended-Wing-Body(BWB)configuration for future civil aircraft,a series of unmanned subscale demonstrators have been developed and tested by our research team.During this process,specific safety risks deriving from uncertain design features,system unreliability,and insufficient personnel experience caused continuous flight test mishaps and the risk mechanism was not clear.Local and trial-and-error learning driven safety improvements took few effects on mishap prevention,so our focus was turned to look for systematic safety strategies.This paper establishes a systems theory based hybrid model to integrate the physical system reliability analysis techniques with the system dynamics method for illustrating the multiple risk interactions of the demonstrator flight test involving organizational,human resource and technical system factors.Using the prior BB-5 demonstrator as a case,the hybrid model simulation represents its historical risk evolution process,which verifies the model rationality.Derived risk control strategies reduced the mishap rate of a new demonstrator called BB-6 Sprit.The paper also shows the extended hybrid model can be applied on safety management of unmanned aerial vehicles from the initial period of vehicle development.

In situ monitoring of the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET

Microemulsions are promising drug delivery systems for the oral administration of poorly watersoluble drugs. However, the evolution of microemulsions in the gastrointestinal tract is still poorly characterized,especially the structural change of microemulsions under the effect of lipase and mucus. To better understand the fate of microemulsions in the gastrointestinal tract, we applied small-angle X-ray scattering(SAXS) and fluorescence resonance energy transfer(FRET) to monitor the structural change of microemulsions under the effect of lipolysis and mucus. First, the effect of lipolysis on microemulsions was studied by SAXS, which found the generation of liquid crystalline phases. Meanwhile, FRET spectra indicated micelles with smaller particle sizes were generated during lipolysis, which could be affected by CaCl_2, bile salts and lecithin. Then, the effect of mucus on the structural change of lipolysed microemulsions was studied. The results of SAXS and FRET indicated that the liquid crystalline phases disappeared, and more micelles were generated. In summary, we studied the structural change of microemulsions in simulated gastrointestinal conditions by SAXS and FRET, and successfully monitored the appearance and disappearance of the liquid crystalline phases and micelles.

Framework Zr Stabilized PtSn/Zr-MCM-41 as a Promising Catalyst for Non-oxidative Ethane Dehydrogenation

Non-oxidative ethane dehydrogenation is a promising route to produce ethene.Herein,PtSn supported catalysts were investigated to achieve better ethane dehydrogenation performance by introduction of different Zr promoters,i.e.,framework Zr and ZrO_(2),to mesoporous MCM-41.In-situ XRD,TEM and CO chemisorption show that aggregation of metal particles and phase segregation of Pt_(3)Sn to Pt and PtSn_(3) at high temperature occur for PtSn/M,leading to bad ethane dehydrogenation activity.Strong interaction be-tween ZrO_(2) and PtSn species,as proved by XPS,results in restrained metal particles,which promotes the initial reactivity.However,Pt phase generated on surface is disadvantageous for the desorption of produced ethene as indicated by CO-IR and C_(3)H_(6)-TPD,and pyridine-IR and NH_(3)-TPD indicate strong acidity generated.Both deactivate the catalyst rapidly by deep dehydrogenation and coking.Moderate interaction between PtSn species and Si-O-Zr with much weaker acidity is formed when framework Zr is incorporated into MCM-41,which benefits the dispersion of metal particles,formation of Pt_(3)Sn/Pt species and stabilization of metal species from phase segregation.Outstanding initial ethane conversion and ethene selectivity of ca.99%were achieved for the optimal PtSn/ZrM,which is more coking-tolerant and stable by generating graphitic carbon mainly on support instead of active metals.

Battery package design optimization for small electric aircraft

The increasing gross weight of electric Unmanned Aerial Vehicle(UAV) poses a challenge in practical applications. The range and endurance of the electric UAV are limited by the fixed mass of the battery package. In this work, a design optimization method for the battery package topology of small electric UAV is proposed to enhance the performance. To improve the accuracy of the method, the dynamic battery model and simplified electric component models are presented.These models are utilized by the trajectory optimization method, which takes the dynamic characteristic into consideration to calculate the aircraft performance. The direct optimal control method is used for solving the trajectory optimization problem, and this method is tested on a small blended-wing-body electric aircraft. The test result shows that the range and energy-consumption are mainly influenced by the parallel topology of the battery package, while the flight time in climb phase is more sensitive to the series topology. It is deduced that the range-and energy-optimal design points can be considered concurrently in design optimization. The work proves the feasibility of integrating the trajectory optimization and battery package design.

Adjunctive sepsis therapy with aminophylline(STAP):a randomized controlled trial

Background:Sepsis is a serious disease caused by infection.Aminophylline has anti-asthma and anti-inflammatory effects.We aimed to explore the safety and effect of aminophylline in sepsis.Methods:We conducted a clinical randomized controlled trial involving 100 patients diagnosed with sepsis within 48 h after intensive care unit(ICU)admission in two sites.All patients were randomized in a 1:1 ratio to receive standard therapy with or without aminophylline.The primary clinical outcome was all-cause mortality at 28 days.Results:From September 27,2018 to February 12,2020,we screened 277 septic patients and eventually enrolled 100 patients,with 50 assigned to the aminophylline group and 50 to the usual-care group.At 28 days,7 of 50 patients(14.0%)in the aminophylline group had died,compared with 16 of 50(32.0%)in the usual-care group(P=0.032).Cox regression showed that the aminophylline group had a lower hazard of death(hazard ratio=0.312,95%confidence interval:0.129–0.753).Compared with the usual-care group,patients in the aminophylline group had a longer survival time(P=0.039 by the log-rank test).The effects of aminophylline on vasopressor dose,oxygenation index,and sequential organ failure assessment score were timedependent with treatment.There were no significant differences in total hospitalization days,ICU hospitalization days,and rates of serious adverse events(all P>0.05).No adverse events were observed in the trial.Conclusions:Aminophylline as an adjunct therapy could significantly reduce the risk of death and prolong the survival time of patients with sepsis.Trial registration:ChiCTR.org.cn,ChiCTR1800019173.

Imaging of Structure Evolution in Solidifying Al–Bi Immiscible Alloys by Synchrotron Radiography

Using synchrotron X-ray imaging technique,the segregation evolution in solidifying Al-10 wt% Bi immiscible alloys was investigated at different cooling rates.Irrespective of the cooling rate,most of the Bi solute appeared at the upper part of the sample after solidification.The reason for this Bi enrichment phenomenon is different for different cooling rates.Besides Marangoni motion,positive segregation,which has rarely been noticed before,can also make Bi solute transfer to the hot top zone.It is also found that,bubbles（or pores） appear in solidifying Al-10 wt% Bi alloys,and the number of bubbles（or pores） increases with the increase of the cooling rate,while the size of the bubbles（or pores） decreases.

Branding Macao＇s External Image Through Strategic Communication： A Descriptive Study

Many national governments have employed strategic communication in promoting their external images. Though somewhat a sub-nation since its handover to China in 1999, the Macao Special Administrative Region Government （MSARG） finds it imperative to apply strategic communication to its place branding in its regional and international communities. Taking on the former Portuguese colony for an in-depth analysis, this study describes the perception of, knowledge about, and practice on strategic communication by the MSARG communication officials. The findings, though limited, seem reconcilable with the analytical assumptions of strategic communication studies in the west.