基于Multisim的差分放大电路基本形式仿真分析

模拟电路中常用的差分放大电路是构成直接耦合放大电路的基本电路单元,对于放大微弱信号有着极其重要的作用。本文分析了差分放大电路的基本性能和输入输出的四种不同接法,然后在理论分析的基础上,利用Multisim仿真软件提供的基本仿真分析方法,分别对差分放大电路的双端输出和单端输出进行了详细的仿真分析,测量了电路的静态工作点,电路的差模、共模特性,并对电路的输入、输出波形进行了分析。

Theoretical analysis on deflagration-to-detonation transition

The study on deflagration-to-detonation transition （DDT） is very important because this mechanism has relevance to safety issues in industries, where combustible premixed gases are in general use. However, the quantitative prediction of DDT is one of the major unsolved problems in combustion and detonation theory to date. In this paper, the DDT process is studied theoretically and the critical condition is given by a concise theoretical expression. The results show that a deflagration wave propagating with about 60% Chapman-Jouguet （C J） detonation velocity is a critical condition. This velocity is the maximum propagating velocity of a deflagration wave and almost equal to the sound speed of combustion products. When this critical condition is reached, a CJ detonation is triggered immediately. This is the quantitative criteria of the DDT process.

Correlation between receptor-interacting protein 140 expression and directed differentiation of human embryonic stem cells into neural stem cells

Overexpression of receptor-interacting protein 140（RIP140） promotes neuronal differentiation of N2 a cells via extracellular regulated kinase 1/2（ERK1/2） signaling.However,involvement of RIP140 in human neural differentiation remains unclear.We found both RIP140 and ERK1/2 expression increased during neural differentiation of H1 human embryonic stem cells.Moreover,RIP140 negatively correlated with stem cell markers Oct4 and Sox2 during early stages of neural differentiation,and positively correlated with the neural stem cell marker Nestin during later stages.Thus,ERK1/2 signaling may provide the molecular mechanism by which RIP140 takes part in neural differentiation to eventually affect the number of neurons produced.

Aggregation-caused quenching to crystallization-induced emission transformation:hydration-induced luminescence in crystal curcumin with tunable thermochromism for in vivo tracking

The development of solid-state materials with switchable luminescence in response to stimuli remains a challenge,especially for organic materials.While crystal water significantly impacts the absorption spectra of organic crystals,it is unclear whether the emission spectra of organic luminescent materials can be systematically manipulated by water.In this study,we successfully obtained curcumin monohydrate(Form X),a channel-type hydrate exhibiting crystallization-induced emission(CIE)at 608 nm(orange fluorescence),which contrasted with the conventional forms of aggregation-caused quenching(ACQ).Thermal treatment induced the release of hydration water,resulting in a new anhydrate(Form IV)that emitted yellow-green fluorescence with the emission peak at 575 nm.Additionally,this approach can be used to track the absorption of curcumin crystals following subcutaneous or intramuscular delivery.The hydratemediated single-crystal-to-single-crystal transition(SCSC)and its associated luminescence transition were reversible and responsive to temperature,offering a green approach for synthesizing and designing aggregation-induced-emission(AIE)-based intelligent luminescent devices for detecting air humidity or drug absorption.

Development of Wheel-Legged Biped Robots:A Review

The wheel-legged biped robot is a typical ground-based mobile robot that can combine the high velocity and high efficiency pertaining to wheeled motion and the strong,obstacle-crossing performance associated with legged motion.These robots have gradually exhibited satisfactory application potential in various harsh scenarios such as rubble rescue,military operations,and wilderness exploration.Wheel-legged biped robots are divided into four categories according to the open–close chain structure forms and operation task modes,and the latest technology research status is summarized in this paper.The hardware control system,control method,and application are analyzed,and the dynamic balance control for the two-wheel,biomimetic jumping control for the legs and whole-body control for integrating the wheels and legs are analyzed.In summary,it is observed that the current research exhibits problems,such as the insufficient application of novel materials and a rigid–flexible coupling design;the limited application of the advanced,intelligent control methods;the inadequate understanding of the bionic jumping mechanisms in robot legs;and the insufficient coordination ability of the multi-modal motion,which do not exhibit practical application for the wheel-legged biped robots.Finally,this study discusses the key research directions and development trends for the wheel-legged biped robots.

Wheel-legged In-pipe Robot with a Bioinspired Hook and Dry Adhesive Attachment Device

In-pipe robots have been widely used in pipes-with smooth inner walls.However,current in-pipe robots face challenges in terms of moving past obstacles and climbing in marine-vessel pipeline systems,which are affected by marine biofouling and electrochemical corrosion.This paper takes inspiration from the dual-hook structure of Trypoxylus dichotomus’s feet and gecko‑like dry adhesives,proposing an in-pipe robot that is capable of climbing on rough and smooth pipe inwalls.The combination of the bioinspired hook and dry adhesives allows the robot to stably attach to rough or smooth pipe inwalls,while the wheel-leg hybrid mechanism provides better conditions for obstacle traversal.The paper explores the attachment and obstacle-surmounting mechanisms of the robot.Moreover,motion strategies for the robot are devised based on different pipe structural features.The experiments showed that this robot can adapt to both smooth and rough pipe environments simultaneously,and its motion performance is superior to conventional driving mechanisms.The robot’s active turning actuators also enable it to navigate through horizontally or vertically oriented 90°bends.

Detachment Behavior of Gecko Toe in Functional Strategies for Bionic Toe

Geckos can efficiently navigate complex terrains due to their multi-level adhesive system that is present on their toes.The setae are responsible for the gecko’s extraordinary adhesion and have garnered wide attention from the scientific community.The majority of the reported works in the literature that have dealt with the peeling models mainly focus on the gecko hierarchical adhesive system,with limited attention given to investigating the influence of gecko toe structure on the detachment.Along these lines,to gain a deeper understanding of the rapid and effortless detachment abilities of gecko toes,the peeling behavior of gecko toes on vertical surfaces was primarily investigated in this work.More specifically,the detachment time of a single toe on a smooth acrylic plate was measured to be 0.41±0.21 s.Moreover,it was observed that the toe assumed a"U"-shaped structure upon complete detachment.Additionally,Finite Element Analysis(FEA)models for three different types of gecko toes were developed to simulate both the displacement-peel and the moment-peel modes.Increasing the segmentation of the adhesive layer led to a gradual decrease in the resultant force,as well as the normal and tangential components.Lastly,a gecko-inspired toe model was constructed and powered by Shape Memory Alloy(SMA).A systematic comparison between the vertical drag separation and the outward flip separation was also conducted.From our analysis,it was clearly demonstrated that outward peel separation significantly necessitated the reduction of the peeling force,thus confirming the advantageous nature of the outward motion in gecko toe detachment.Our data not only contribute to a deeper understanding of the gecko detachment behavior but also offer valuable insights for the advancement of the wall-climbing robot feet.

An Aerial–Wall Robotic Insect That Can Land, Climb, and Take Off from Vertical Surfaces

Insects that can perform flapping-wing flight,climb on a wall,and switch smoothly between the 2 locomotion regimes provide us with excellent biomimetic models.However,very few biomimetic robots can perform complex locomotion tasks that combine the 2 abilities of climbing and flying.Here,we describe an aerial–wall amphibious robot that is self-contained for flying and climbing,and that can seamlessly move between the air and wall.It adopts a flapping/rotor hybrid power layout,which realizes not only efficient and controllable flight in the air but also attachment to,and climbing on,the vertical wall through a synergistic combination of the aerodynamic negative pressure adsorption of the rotor power and a climbing mechanism with bionic adhesion performance.On the basis of the attachment mechanism of insect foot pads,the prepared biomimetic adhesive materials of the robot can be applied to various types of wall surfaces to achieve stable climbing.The longitudinal axis layout design of the rotor dynamics and control strategy realize a unique cross-domain movement during the flying–climbing transition,which has important implications in understanding the takeoff and landing of insects.Moreover,it enables the robot to cross the air–wall boundary in 0.4 s(landing),and cross the wall–air boundary in 0.7 s(taking off).The aerial–wall amphibious robot expands the working space of traditional flying and climbing robots,which can pave the way for future robots that can perform autonomous visual monitoring,human search and rescue,and tracking tasks in complex air–wall environments.

Effect of Dual Trigger In Vitro Fertilization and Intracytoplasmic Sperm Injection During the Gonadotropin-releasing Hormone-Antagonist Cycle on Final Oocyte Maturation and Cumulative Live Birth Rate in Women with Diminished Ovarian Reserve

Objective It is well known that a dual trigger treatment can improve clinical outcomes of in vitro fertilization(IVF)in high or normal ovarian responders.However,it is not clear whether dual triggering also benefits patients with diminished ovarian reserve(DOR).The aim of this study was to investigate whether a dual trigger treatment of gonadotropin-releasing hormone(GnRH)agonist combined with human chorionic gonadotropin(hCG)for final follicular maturation improves the cumulative live birth rate(CLBR)during the GnRH-antagonist cycle in patients with DOR.Methods This retrospective study included patients with DOR who received a GnRH-antagonist protocol during IVF and intracytoplasmic sperm injection(IVF-ICSI)cycles at Peking University People’s Hospital from January 1,2017 through December 31,2017.Oocyte maturation was triggered by GnRH combined with hCG(n=110)or hCG alone(n=71).Embryos were transferred on the third day after oocyte retrieval or during a subsequent freeze-thaw cycle.Patients were followed up for 3 years.Results The dual trigger treatment did not affect CLBR,which is an overall determinant of the success rate of assisted reproductive technology(ART).Women in the dual trigger group had significantly higher rates of fertilization than those in the hCG group(90.1%vs.83.9%,P=0.040).Conclusion Dual trigger with GnRH agonist and hCG did not improve CLBR in patients with DOR,but did slightly improve fertilization rate,oocyte count,and embryo quality.

Endometrial MicroRNA Signature during the Window of Implantation Changed in Patients with Repeated Implantation Failure

Background： At present, a diagnostic tool with high specificity for impaired endometrial receptivity, which may lead to implantation failure, remains to be developed. We aimed to assess the different endometrial microRNA （miRNA） signatures for impaired endometrial receptivity by microarray analysis. Methods： A total of 12 repeated implantation failure （RIF） patients and I0 infertile patients, who conceived and delivered after one embryo transfer attempt, were recruited as RIF and control groups, respectively. Endometrial specimens from the window of implantation （WOI） were collected from these two groups. MiRNA microarray was conducted on seven and five samples from the RIF and control groups, respectively. Comparative, functional, and network analyses were performed for the microarray results. Quantitative real-time polymerase chain reaction （PCR） was performed on other samples to validate the expression of specific miRNAs. Results： Compared with those in the control group, the expression levels of 105 miRNAs in the RIF group were found to be significantly up- or down-regulated （at least 2-fold） by microarray analysis. The most relevant miRNA functional sets of these dysregulated miRNAs were miR-30 family, human embryonic stern cell regulation, epithelial-mesenchymal transition, and miRNA tumor suppressors by tool for annotations ofmicroRNA analysis. Network regulatory analysis found 176 miRNA-mRNA interactions, and the top 3 core miRNAs were has-miR-4668-5p, has-miR-429, and has-miR-5088. Expression levels of the 18 selected miRNAs in new samples by real-time PCR were found to be regulated with the same trend, as the result ofmicroarray analysis. Conclusions： There is a significant different expression of certain miRNAs in the WOI endometrium for RIF patients. These miRNAs may contribute to impaired endometrial receptivity.

A multicenter prospective study of next-generation sequencing-based newborn screening for monogenic genetic diseases in China

Background Newborn screening(NBS)is an important and successful public health program that helps improve the long-term clinical outcomes of newborns by providing early diagnosis and treatment of certain inborn diseases.The develop-ment of next-generation sequencing(NGS)technology provides new opportunities to expand current newborn screening methodologies.Methods We designed a a newborn genetic screening(NBGS)panel targeting 135 genes associated with 75 inborn disorders by multiplex PCR combined with NGS.With this panel,a large-scale,multicenter,prospective multidisease analysis was conducted on dried blood spot(DBS)profiles from 21,442 neonates nationwide.Results We presented the positive detection rate and carrier frequency of diseases and related variants in different regions;and 168(0.78%)positive cases were detected.Glucose-6-Phosphate Dehydrogenase deficiency(G6PDD)and phenylketonuria(PKU)had higher prevalence rates,which were significantly different in different regions.The positive detection of G6PD variants was quite common in south China,whereas PAH variants were most commonly identified in north China.In addi-tion,NBGS identified 3 cases with DUOX2 variants and one with SLC25A13 variants,which were normal in conventional NBS,but were confirmed later as abnormal in repeated biochemical testing after recall.Eighty percent of high-frequency gene carriers and 60%of high-frequency variant carriers had obvious regional differences.On the premise that there was no significant difference in birth weight and gestational age,the biochemical indicators of SLC22A5 c.1400C>G and ACADSB c.1165A>G carriers were significantly different from those of non-carriers.Conclusions We demonstrated that NBGS is an effective strategy to identify neonates affected with treatable diseases as a supplement to current NBS methods.Our data also showed that the prevalence of diseases has significant regional charac-teristics,which provides a theoretical basis for screening diseases in different regions.

Electrodeposition Process for the Fabrication of Copper Dendrites Film with Stable Superhydrophobicity

Copper dendrites on the copper surface were successfully prepared by electrodeposition in acidic copper sulfate aqueous solution containing ethanol. The XRD （X-ray diffraction） patterns indicate that the Cu dendrites possess fcc （face-centered cubic） crystal structure. The contact angle of the as-prepared Cu dendrites surface without palmitic acid modification is almost 0~ and the surface is completely wetted by water. After modified with palmitic acid, the Cu dendrite surface shows superhydrophobicity with a contact angle of 160~. The polarization curves reveal that the superhydrophobic Cu dendrites surface exhibits a distinct passivation phenomenon, which could provide enhanced corrosion resistance for the substrate in the aqueous solution. The weight loss measurements show that the corrosion values of superhydrophobic surface is much lower than that of the bare copper, further meaning that the as-prepared surface has the anticorrosion performance.

Design and Theoretical Research on Aerial-Aquatic Vehicles:A Review

With the rapid development of unmanned aerial and underwater vehicles,various tasks,such as biodiversity monitoring,surveying,and mapping,as well as,search and rescue can now be completed in a single medium,either underwater or in the air.By systematically examining the water–air cross-medium locomotion of organisms,there has been growing interest in the development of aerial-aquatic vehicles.The goal of this review is to provide a detailed outline of the design and cross-medium theoretical research of the existing aerial-aquatic vehicles based on the research on the organisms capable of transiting between water and air.Although these designs and theoretical frameworks have been validated in many aerial-aquatic vehicles,there are still many problems that need to be addressed,such as inflexible underwater motion and unstable medium conversion.As a result,supplementation of the existing cross-medium biomimetic research,vehicle design,power selection,and cross-medium theory is urgently required to optimize the key technologies in detail.Therefore,by summarizing the existing designs and theoretical approaches on aerial-aquatic vehicles,including biomimetic research on water–air cross-medium locomotion in nature,different power selections,and cross-medium theoretical research,the relative problems and development trends on aerial-aquatic vehicles were thoroughly explored,providing significant help for the subsequent research process.

The effect of serum luteinizing hormone on trigger day with a GnRH antagonist protocol in IVF/ICSI treatment

Objective:To investigate the effect of serum luteinizing hormone(LH)on trigger day with a Gonadotrophinreleasing hormone(GnRH)antagonist protocol in patients receiving in vitro fertilization/intracytoplasmic sperm injection(IVF/ICSI)treatment for pregnancy outcomes.Methods:We retrospectively reviewed the medical documents of patients receiving IVF/ICSI with fresh embryo transfers from the Reproductive Medicine Center of Peking University People's Hospital between January 2016 and December 2018.730 patients were included and divided into three groups by their serum LH level determined on trigger day.All patients were categorized into Group A,Group B,and Group C based on LH concentrations<1.0 IU/L,1.0–5.0 IU/L,and from 5.0 to 10.0 IU/L on trigger day during the cycle,respectively.Comparisons were made between the three groups.Results:There was a significant difference in implantation rates between Group A and Group C(24.8%versus 40.1%,respectively,P<0.05).The clinical pregnancy rates(39.3%versus 54.3%,respectively,P=0.078)and live birth rate(LBR)(32.1%versus 46.5%,respectively,P=0.116),though the differences were not significant.Multivariate logistic regression analysis showed that the OR of Group C for clinical pregnancy(OR=1.849,P=0.040)and for LBR(OR=1.915,P=0.034)were significant using Group A as the base level.Conclusions:Our study has demonstrated that patients with higher serum LH levels(5.0–10.0 IU/L)on trigger day in the GnRH antagonist protocol may confer better clinical outcomes than those with lower LH levels(<1.0 IU/L).

Effects of Morphological Integrity of Secondary Feather on Their Drag Reduction in Pigeons

Flight feathers of birds interact with the air flow during flight.How the observed low drag and high lift values at wind speeds from 9.0 to 19.8 m/s can be achieved due to the feather aerodynamics remains unknown.In the present paper,we tested and compared morphological changes,drag reduction and flow visualization results of intact,damaged,and artificial feathers at different wind speeds in a wind tunnel.Through the analysis of the drag force and resultant force angle,we proved that the integrity of feathers,whose barbs are usually closely interconnected,played an important role in the drag,which potentially triggers excellent drag reduction performance.The wind tunnel tests indicated that intact secondary feathers had a surprisingly high maximum drag reduction property at v?=?9 m/s compared with the feathers,where the integrity of barbs was damaged.The hook cascades facilitated elasticity under pressure and suitable permeability in an intact feather,when the hooks were interlocked.It was indicated that the suitable permeability of intact feathers would prevent flow separation and reduce drag force at low wind speed;at high wind speed,elasticity under pressure and suitable permeability in an intact feather would facilitate strong squeezing effect,helping feathers withstand larger aerodynamic forces to which they might be subjected during flight.It was revealed that the intact secondary feather is a compromise between strong lift generation and drag reduction,which has a great significance for the bird’s flight.

The Unique Strategies of Flight Initiation Adopted by Butterflies on Vertical Surfaces

As the basis of flight behavior,the initiation process of insect flight is accompanied by a transition from crawling mode to flight mode,and is clearly important and complex.Insects take flight from a vertical surface,which is more difficult than takeoff from a horizontal plane,but greatly expands the space of activity and provides us with an excellent bionic model.In this study,the entire process of a butterfly alighting from a vertical surface was captured by a high-speed camera system,and the movements of its body and wings were accurately measured for the first time.After analyzing the movement of the center of mass,it was found that before initiation,the acceleration perpendicular to the wall was much greater than the acceleration parallel to the wall,reflecting the positive effects of the legs during the initiation process.However,the angular velocity of the body showed that this process was unstable,and was further destabilized as the flight speed increased.Comparing the angles between the body and the vertical direction before and after leaving the wall,a significant change in body posture was found,evidencing the action of aerodynamic forces on the body.The movement of the wings was further analyzed to obtain the laws of the three Euler angles,thus revealing the locomotory mechanism of the butterfly taking off from the vertical surface.

A Biomimetic Wheel-Track Wall-Climbing Robot Based on Rolling Adsorption Mechanism

Wall climbing robots have a wide range of applications in the field of transportation,petrochemicals,aerial construction,and other monitoring prospects;however,for complex defects on the wall,it is easy for the robot to fall off from attachment.This paper puts forward the bionic wheel-tracked rolling adsorption wall-climbing robots.The paper designs flexible material as sealing material for the negative pressure chamber of wall-climbing robots through the imitation of the biological mechanism of the insect adhesion pads.The material has the advantages of wear resistance,strong wall adaptability,large load,simple structure,etc.,and it has a highly reliable and stable adsorption ability on unstructured and complex walls.The mathematical model of adsorption of the wall-crawling robot is constructed in different wall environments,and the kinematic analysis is carried out.The influence of the leakage on the adsorption capacity due to the deformation of the flexible sealing material,defects of the wall surface and the air ducts formed under different roughnesses is analyzed.Through the fabrication and experiment of the prototype,the correctness of the theoretical analysis is verified.The measured load capacity of the robot is 2.47 times its own weight,and it has great obstacle-crossing ability.