Convergent Mode Research Articles

Method for controlling the area of the electrolyte outlets in the flow field simulation and experimental verification of electrochemical machining

Electrochemical machining (ECM) is regarded as a promising and cost-effective manufacturing method for difficult-to-cut materials with complex shapes and structures. Many methods have been successfully developed for the flow field state of machining gaps, which is a key factor affecting machining performance in ECM engineering practice. However, little attention has been given to the area of the electrolyte outlets. This study attempts to present a method for controlling the area of the electrolyte outlets in the flow field simulation and experimental verification of electrochemical machining. The simulation results indicate that the convergent outlet mode can effectively enhance the turbulent effect of the fluid in the inter-electrode gap, especially in the near-wall region, and improve the mass transfer effect of electrolyte. Meanwhile, the simulation results also showed that better material removal rate (MRR) and surface roughness can be obtained when the convergent degree is about 50–70% combined with the effects of bubble volume compression and flow velocity reduction. The experimental results confirmed that the convergent outlet mode can obtain better MRR and surface roughness. Energy-dispersive X-ray spectroscopy results of machined specimens showed that oxides with strong adhesion on the specimen’s surface were effectively eliminated due to stronger turbulence effect under convergent outlet conditions. This should be considered as the main reason for improving machining performance by changing the electrolyte outlet area. These conclusions can provide some useful assistance for ECM engineering practice.

Fast Convergent Stability Sliding Mode Control for Slotless Self Bearing Motor with Consideration of External Load Torque

Fast Convergent Stability Sliding Mode Control for Slotless Self Bearing Motor with Consideration of External Load Torque

The Inspiration of the International Student Management Service Mechanism of the University of Alberta to Universities in China - Taking China University of Geosciences (Beijing) as an example

As the window of China's education opens to the outside world and the boost of "double first-class" construction, how to strengthen the construction of management and service mechanism of education for students studying in China is an important issue facing the management workers of education for students studying in China. China University of Geosciences (Beijing) has made certain achievements by adopting the convergent management mode for education for students studying in China, but there are still some problems in the standardized process, departmental coordination, staff quality and information network level. The University of Alberta in Canada provides services for international students, and the time dimension covers four stages before arrival, when coming to the university, during study and after graduation, and the service team is specialized and student-oriented, and the successful experience achieved has great significance for the international study management services of Chinese universities, and Chinese universities can improve the service concept, improve the service quality, strengthen the team construction, form the service cooperation, enhance the Chinese universities, and can promote the connotative development of education for students studying in China by improving service concept, improving service quality, strengthening team building, forming service cooperation, improving service level, and doing a good job of alumni. Keywords: University of Alberta, International Students, International Student Services, China University of Geosciences (Beijing).

Study on the plasma plume structures in a cylindrical Hall thruster

The structures of two typical plume modes (divergent and convergent plume) and their respective formation mechanisms in a cylindrical Hall thruster are investigated. The non-monotonic distribution of the two-dimensional ion energy distribution function map is obtained to segment the plume into 5 levels with different energy interval. The test results of the ion current fraction indicate that the ion beams in Level III and IV were the main components of the two plume modes. For Level IV (enhanced significantly in the convergent mode), these ions with focusing structure could only originate from the upstream E × B field due to their similar high potential and identical variation tendency in the mode transition, where the electric field converges towards the axis. This is mainly responsible for the formation of convergent mode. On the other hand, for Level III (dominating the divergent mode), these ions with hollow structure and less acceleration voltage are speculated to originate from the downstream magnetic mirror field, where the electric field manifests a defocusing characteristic along the diverging magnetic field lines. This is mainly responsible for the formation of divergent mode. Through the thrust equivalent calculation method, it is revealed that the upstream acceleration associated with the E × B field is the dominant contributor to the enhancement of thrust in the convergent mode. This study on the complex plume structure would facilitate the understanding of the CHT acceleration mechanism and provide useful ideas for the optimization of electric field structure and enhancement of plume efficiency.

Assessment of the Severity of Left Anterior Descending Coronary Artery Stenoses by Enhanced Transthoracic Doppler Echocardiography: Validation of a Method Based on the Continuity Equation.

To verify whether the severity of coronary stenosis could be non-invasively assessed by enhanced transthoracic coronary echo Doppler in convergent color Doppler mode (E-Doppler TTE) over a wide range of values (from mild to severe). Color-guided pulsed wave Doppler sampling in the left anterior descending coronary artery (LAD) was performed in 103 diseased LAD segments (corresponding to 94 patients examined) as assessed by quantitative coronary angiography (QCA) or intracoronary ultrasound (IVUS). The E-Doppler TTE examinations consisted of measuring the velocity (vel) at the stenosis site and a reference adjacent segment. Then the continuity equation (C-Eq) was applied to calculate the percent cross-sectional area reduction (%CSA) at the stenosis site. The applied formula was: %CSA = 100 × (1 - [TVIref × 0.5]/TVIs). TVI = the time velocity integral at the stenosis [s] and the reference site [ref], respectively); 0.5 = the correcting factor for a parabolic profile was used only when the % accelerated stenotic flow was >122% (AsF = diastolic peak vel at first site - diastolic peak vel at second site/diastolic peak vel at second site × 100). E-Doppler TTE feasibility was 100%. Doppler and QCA/IVUS-derived %CSA stenosis showed very good agreement over a large range of values (from mild to severe), with no significant bias; the maximum difference between QCA/IVUS and transthoracic Doppler %CSA was mostly around 20% with a few patients exceeding this limit (limits of agreement = -27.53 to 23.5%). The scattering was slightly larger for the non-significant stenoses. The correlation was strong (r = 0.89, p < 0.001). E-Doppler TTE is a feasible and reliable method for assessing the severity of LAD stenosis by applying the C-Eq.

Heart Rate Lowering Significantly Increases Feasibility in Doppler Recording Blood Flow Velocity in Coronaries during Transthoracic Doppler Echocardiography.

Background: Coronary blood flow Doppler recording by Transthoracic Doppler in convergent mode (E-Doppler TTE) might be further improved by lowering heart rate (HRL) down to <60 bpm, since low HR < 60 b/m causes a disproportional lengthening of the diastole, so the coronaries are still for a longer time, very much improving the Doppler signal/noise ratio. Methods: A group of 26 patients underwent E-Doppler TTE before and after HR lowering in four branches of the coronary tree, namely, the left main (LMCA); left anterior descending (LAD), subdivided into three segments: proximal, mid and distal; proximal left circumflex (LCx); and obtuse marginal (OM). Color and PW coronary Doppler signal was judged by two expert observers as undetectable (SCORE 1), weak or with clutter artifacts (SCORE 2), or well delineated (SCORE 3). In addition, local accelerated stenotic flow (AsF) was measured in the LAD before and after HRL. Results: Beta-blockers significantly decreased the mean HR from 76 ± 5 to 57 ± 6 bpm (p < 0.001). Before HRL, the Doppler quality was very poor in the proximal and mid-LAD segments (median score value = 1 in both), while in the distal LAD, it was significantly better but still suboptimal (median score value = 1.5, p = 0.009 vs. proximal and mid-LAD score). After HRL, blood flow Doppler recording in the three LAD segments was strikingly improved (median score value = 3, 3 and 3, p = ns), so the effect of HRL was more efficacious in the two more proximal LAD segments. In 10 patients undergoing coronary angiography (CA), no AsF as expression of transtenotic velocity was detected at baseline. After HRL, thanks to the better quality and length of color flow, ASF was detected in five patients while in five others, it was not in perfect agreement with CA (Spearman correlation coefficient = 1, p < 0.01). The color flow in the proximal LCx and OM was extremely poor at baseline (color flow length 0 and 0, median (interquartile range) mm, respectively) and improved considerably after HRL (color flow length 23 [13.5] and 25 [12.0] mm, respectively, p < 0.001). Conclusions: HRL greatly improved the success rate of blood flow Doppler recording in coronaries, not only in the LAD, but also in the LCx. Therefore, AsF for stenosis detection and coronary flow reserve assessment can have wider clinical applications. However, further studies with larger samples are needed to confirm these results.

Adaptive Neural Network Extended State Observer-Based Finite-Time Convergent Sliding Mode Control for a Quad Tiltrotor UAV

The internal and external disturbance of the quad tiltrotor UAV stem from its rotor tilting motion and wind disturbance, which affect the control stability of the quad tiltrotor UAV in full flight. This paper proposes a control law design method based on the Adaptive Neural Network Extended State Observer-based Finite-Time Convergent Sliding Mode Control (ANNESO-FTCSMC). The adaptive neural network obtains the unknown total disturbance term that needs to be compensated in the finite-time convergent sliding mode control. An extended state observer is used to estimate the state variables of the controlled plant. The stability of the ANNESO-FTCSMC controller is proved with the Lyapunov stability theory. The unknown total disturbance as the expanded state variable of the state observer has the advantage of high adaptability, and the ANNESO-FTCSMC has a strong ability to compensate for the internal and external disturbances of the system. Compared with traditional sliding mode control, ANNESO-FTCSMC does not contain switching terms, so ANNESO-FTCSMC is chattering-free and converges faster. Based on this method, the flight control system of the quad tiltrotor UAV is designed and verified by hardware-in-loop simulation. The hardware-in-loop simulation results of attitude control in different flight modes and trajectory tracking control in full flight show that the ANNESO-FTCSMC controller is suitable for the flight control of quad tiltrotor UAV. Compared with the PID controller and ADRC controller, ANNESO-FTCSMC controller has more stable flight state of quad tiltrotor UAV under different flight modes and the same total disturbance. The transition process of ANNESO-FTCSMC controller from helicopter mode to airplane mode is also smoother and will not have large fluctuations. Therefore, ANNESO-FTCSMC controller has strong anti-disturbance and robustness.

A Stereodivergent–Convergent Chiral Induction Mode in Atroposelective Access to Biaryls via Rhodium-Catalyzed C–H Bond Activation

Understanding the reaction mechanisms, particularly the chiral induction mode, is critical for the development of new asymmetric catalytic reactions. Rhodium(III)-catalyzed C–H activation en route to atroposelective [4 + 2] annulative coupling with α-diazo β-ketoesters has been realized, affording axially chiral phenanthrenes in good to excellent enantioselectivity. A combination of experimental and computational studies revealed a nontraditional stereodivergent–convergent chiral induction mode. The reaction proceeded with a rhodafluorene intermediate, followed by competitive, constructive, and stereodivergent migratory insertions of the two Rh–C(aryl) bonds into the carbene species to give β-ketoester intermediates. Then, the other Rh–C(aryl) bond migratorily inserts into the ketone carbonyl group. Following this stereodetermining carbonyl insertion, an ester-chelated rhodium(III) alkoxide species bearing two poorly controlled chiral centers and a well-controlled C(sp2)–C(sp3) chiral axis is generated. The final product is delivered via stereoconvergent elimination of a rhodium(III) species with retention of the well-controlled axial chirality and with loss of the central chirality.

Flight testing verification of lateral-directional dynamic stability of gliding birds due to wing dihedral

PurposeUnlike conventional aircraft, birds can glide without a vertical tail. The purpose of this paper is to analyse the influence of dihedral angle spanwise distribution on lateral-directional dynamic stability by the simulation, calculation in the development of the bird-inspired aircraft and the flight testing.Design/methodology/approachThe gliding magnificent frigatebird (Fregata magnificens) was selected as the study object. The geometric and mass model of the study object were developed. Stability derivatives and moments of inertia were obtained. The lateral-directional stability was assessed under different spanwise distributions of dihedral angle. A bird-inspired aircraft was developed, and a flight test was carried out to verify the analysed results.FindingsThe results show that spanwise distribution changing of dihedral angle has influence on the lateral-directional mode stability. All of the analysed configurations have convergent Dutch roll mode and rolling mode. The key role of dihedral angle changing is to achieve a convergent spiral mode. Flight test results show that the bird-inspired aircraft has a well-convergent Dutch roll mode.Practical implicationsThe theory that birds can achieve its lateral-directional stability by changing its dihedral angle spanwise distribution may explain the stability mechanism of gliding birds.Originality/valueThis paper helps to improve the understanding of bird gliding stability mechanism and provides bio-inspired solutions in aircraft designing.

"We threw away the stones": a mixed method evaluation of a simple cookstove intervention in Malawi.

Background: Air pollution exposure is responsible for a substantial burden of respiratory disease globally. Household air pollution from cooking using biomass is a major contributor to overall exposure in rural low-income settings. Previous research in Malawi has revealed how precarity and food insecurity shape individuals' daily experiences, contributing to perceptions of health. Aiming to avoid a mismatch between research intervention and local context, we introduced a simple cookstove intervention in rural Malawi, analysing change in fine particulate matter (PM 2.5) exposures, and community perceptions. Methods: Following a period of baseline ethnographic research, we distributed 'chitetezo mbaula', locally-made cookstoves, to all households (n=300) in a rural Malawian village. Evaluation incorporated village-wide participant observation and concurrent exposure monitoring using portable PM 2.5 monitors at baseline and follow-up (three months post-intervention). Qualitative data were thematically analysed. Quantitative analysis of exposure data included pre-post intervention comparisons, with datapoints divided into periods of combustion activity (almost exclusively cooking) and non-combustion periods. Findings were integrated at the interpretation stage, using a convergent design mode of synthesis. Results: Individual exposure monitoring pre- and post-cookstove interventioninvolved a sample of 18 participants (15 female; mean age 43). Post-intervention PM 2.5 exposures (median 9.9μg/m 3 [interquartile range: 2.2-46.5]) were not significantly different to pre-intervention (11.8μg/m 3 [3.8-44.4]); p=0.71. On analysis by activity, background exposures were found to be reduced post-intervention (from 8.2μg/m 3 [2.5-22.0] to 4.6μg/m 3 [1.0-12.6]; p=0.01). Stoves were well-liked and widely used by residents as substitutes for previous cooking methods (mainly three-stone fires). Commonly cited benefits related to fuel saving and shorter cooking times. Conclusions: The cookstove intervention had no impact on cooking-related PM 2.5 exposures. A significant reduction in background exposures may relate to reduced smouldering emissions. Uptake and continued use of the stoves was high amongst community members, who preferred using the stoves to cooking over open fires.

Inversed Model-Based Disturbance Observer Base on Adaptive Fast Convergent Sliding Mode Control and Fixed-Time State Observer for Slotless Self-Bearing Motor

The slotless self-bearing motor (SSBM) is a motor with its self-bearing function. The mechanical structure of the motor is six symmetrical hexagonal shapes. The main control problem for this motor is disturbance and uncertainty rejection. Therefore, this paper proposes a new disturbance observer (DOB) based on an optimal fixed-time state observer (OFTSOB) and adaptive sliding mode control (SMC) for the motor. Firstly, the optimal state observer was used to construct to obtain the information of the states of the bearing-less motor system. Second, a new disturbance observer base on the fast speed reaching law is proposed for estimating the unknown dynamics and unpredicted uncertainty of the motor system. Third, the adaptive fast-reaching law-sliding mode control is designed to control the positions and rotational speed. Fourth, the proposed control system is proved via the Lyapunov theorem. Finally, the corrections of proposed method once again tested by using MATLAB simulation. The obtained results figured out that the proposed method is good at rejection disturbance and uncertainty and precision in control the movement and rotation. The novelties of the proposed method are that the gains of fixed-time observer were met by the support of optimal pole placement method, the disturbances were mostly rejected by a new reaching law of unknown input observer.

Characterization of a silent azaphilone biosynthesis gene cluster in Aspergillus terreus NIH 2624

Filamentous fungal secondary metabolites are an important source of bioactive components. Genome sequencing ofAspergillus terreusrevealed many silent secondary metabolite biosynthetic gene clusters presumed to be involved in producing secondary metabolites. Activation of silent gene clusters through overexpressing a pathway-specific regulator is an effective avenue for discovering novel fungal secondary metabolites. Replacement of the native promoter of the pathway-specific activator with the inducible Tet-on system to activate thetazpathway led to the discovery of a series of azaphilone secondary metabolites, among which azaterrilone A (1) was purified and identified for the first time. Genetic deletion of core PKS genes and transcriptional analysis further characterized thetazgene cluster to consist of 16 genes with the NR-PKS and the HR-PKS collaborating in a convergent mode. Based on the putative gene functions and the characterized compounds structural information, a biosynthetic pathway of azaterrilone A (1) was proposed.

"We threw away the stones": a mixed method evaluation of a simple cookstove intervention in Malawi.

Background: Air pollution exposure is responsible for a substantial burden of respiratory disease globally. Household air pollution from cooking using biomass is a major contributor to overall exposure in rural low-income settings. Previous research in Malawi has revealed how precarity and food insecurity shape individuals' daily experiences, contributing to perceptions of health. Aiming to avoid a mismatch between research intervention and local context, we introduced a simple cookstove intervention in rural Malawi, analysing change in fine particulate matter (PM 2.5) exposures, and community perceptions. Methods: Following a period of baseline ethnographic research, we distributed 'chitetezo mbaula', locally-made cookstoves, to all households (n=300) in a rural Malawian village. Evaluation incorporated village-wide participant observation and concurrent exposure monitoring using portable PM 2.5 monitors at baseline and follow-up (three months post-intervention). Qualitative data were thematically analysed. Quantitative analysis of exposure data included pre-post intervention comparisons, with datapoints divided into periods of combustion activity (almost exclusively cooking) and non-combustion periods. Findings were integrated at the interpretation stage, using a convergent design mode of synthesis. Results: Individual exposure monitoring pre- and post-cookstove interventioninvolved a sample of 18 participants (15 female; mean age 43). Post-intervention PM 2.5 exposures (median 9.9μg/m 3 [interquartile range: 2.2-46.5]) were not significantly different to pre-intervention (11.8μg/m 3 [3.8-44.4]); p=0.71. On analysis by activity, background exposures were found to be reduced post-intervention (from 8.2μg/m 3 [2.5-22.0] to 4.6μg/m 3 [1.0-12.6]; p=0.01). Stoves were well-liked and widely used by residents as substitutes for previous cooking methods (mainly three-stone fires). Commonly cited benefits related to fuel saving and shorter cooking times. Conclusions: The cookstove intervention had no impact on cooking-related PM 2.5 exposures. A significant reduction in background exposures may relate to reduced smouldering emissions. Uptake and continued use of the stoves was high amongst community members, who preferred using the stoves to cooking over open fires.

“We threw away the stones”: a mixed method evaluation of a simple cookstove intervention in Malawi

Background: Air pollution exposure is responsible for a substantial burden of respiratory disease globally. Household air pollution from cooking using biomass is a major contributor to overall exposure in rural low-income settings. Previous research in Malawi has revealed how precarity and food insecurity shape individuals’ daily experiences, contributing to perceptions of health. Aiming to avoid a mismatch between research intervention and local context, we introduced a simple cookstove intervention in rural Malawi, analysing change in fine particulate matter (PM 2.5) exposures, and community perceptions. Methods: Following a period of baseline ethnographic research, we distributed ‘chitetezo mbaula’, locally-made cookstoves, to all households (n=300) in a rural Malawian village. Evaluation incorporated village-wide participant observation and concurrent exposure monitoring using portable PM 2.5 monitors at baseline and follow-up (three months post-intervention). Qualitative data were thematically analysed. Quantitative analysis of exposure data included pre-post intervention comparisons, with datapoints divided into periods of combustion activity (almost exclusively cooking) and non-combustion periods. Findings were integrated at the interpretation stage, using a convergent design mode of synthesis. Results: Individual exposure monitoring pre- and post-cookstove intervention involved a sample of 18 participants (15 female; mean age 43). Post-intervention PM 2.5 exposures (median 9.9μg/m 3 [interquartile range: 2.2–46.5]) were not significantly different to pre-intervention (11.8μg/m 3 [3.8–44.4]); p=0.71. On analysis by activity, background exposures were found to be reduced post-intervention (from 8.2μg/m 3 [2.5–22.0] to 4.6μg/m 3 [1.0–12.6]; p=0.01). Stoves were well-liked and widely used by residents as substitutes for previous cooking methods (mainly three-stone fires). Commonly cited benefits related to fuel saving and shorter cooking times. Conclusions: The cookstove intervention had no impact on cooking-related PM 2.5 exposures. A significant reduction in background exposures may relate to reduced smouldering emissions. Uptake and continued use of the stoves was high amongst community members, who preferred using the stoves to cooking over open fires.

“We threw away the stones”: a mixed method evaluation of a simple cookstove intervention in Malawi

Background:Exposure to air pollution is responsible for a substantial burden of respiratory disease globally. Household air pollution from cooking using biomass is a major contributor to overall exposure in rural low-income settings. Previous research in Malawi has revealed how precarity and food insecurity shape individuals’ daily experiences, contributing to perceptions of health. Aiming to avoid a mismatch between research intervention and local context, we introduced a simple cookstove intervention in rural Malawi, analysing change in fine particulate matter (PM2.5) exposures, and community perceptions.Methods:Following a period of baseline ethnographic research, we distributed‘chitetezo mbaula’, locally made clay cookstoves, to all households (n=300) in a rural Malawian village. Evaluation incorporated village-wide participant observation and concurrent exposure monitoring using portable PM2.5monitors at baseline and follow-up (three months post-intervention). Qualitative data were thematically analysed. Quantitative analysis of exposure data included pre-post intervention comparisons, with datapoints divided into cooking and non-cooking (‘baseline’) periods. Findings were integrated at the interpretation stage, using a convergent design mode of synthesis.Results:Individual exposure monitoring pre- and post-cookstove intervention involved a sample of 18 participants (15 female; mean age 43). Post-intervention PM2.5exposures (median 9.9μg/m3[interquartile range: 2.2–46.5]) were not significantly different to pre-intervention (11.8μg/m3[3.8–44.4]); p=0.71. On analysis by activity, ‘baseline’ exposures were found to be reduced post-intervention (from 8.2μg/m3[2.5–22.0] to 4.6μg/m3[1.0–12.6]; p=0.01). Stoves were well-liked and widely used by residents as substitutes for previous cooking methods (mainly three-stone fires). Most cited benefits related to fuel saving and shorter cooking times.Conclusions:The cookstove intervention had no impact on cooking-related PM2.5exposures. A significant reduction in baseline exposures may relate to reduced smouldering emissions. Uptake and continued use of the stoves was high amongst community members, who preferred using the stoves to cooking over open fires.

Energy-efficient heat exchanger equipped with multiple short-length taper twisted tapes

This article presents an experimental study of the heat transfer characteristics and the pressure drop of the circular tube fitted with multiple short-length taper twisted tape in convergent and divergent mode with the pitch ratios of 3, 4 and 5 and full-length twisted tape of two different pitch length such as 10 and 14 cm. Tapered twisted tapes have a larger effect on the enhancement of heat transfer with the lower pressure drop compared with the short-length uniform width twisted tape. Based on constant pumping power and constant heat duty, short-length taper twisted tapes are performed better than full-length twisted tape. Based on the experimental data, correlations are developed by using the statistical analysis and the arrived results are within the acceptable limit.

Strong convergent LP11 beam for nanoparticles trapping

As the size of research objects reaches the nanometer level, there is an increasing desire to trap and detect nanoparticles. However, the means to trap and study individual nanoparticles is not mature. Here, we propose and demonstrate a method for trapping a single nanoparticle stably and moving it in a three-dimensional space using a single-mode optical fiber probe based on a strong convergent LP11 mode beam. The small mode field diameter of the LP11 beam and the particular probe structure are combined to obtain a nanoscale convergence area to trap a 100 nm nanoparticle stably. The proposed optical fiber tweezers have the advantages of high spatial resolution, simple structure, and easy operation. They are expected to be developed to control organelles in single cells, screen particles of different sizes, and extract virus cells.

Analysis of unsteady flow in compressor cascade based on modal DMD methods

The reduced-order model based on the modal decomposition method can capture the main characteristics of the compressor. In this part, dynamic mode decomposition (DMD) methods are used to analyze the flow in a high-speed compressor cascade. The methods can extract dynamic information of the flow field. Both the design and off-design conditions (-2°, 0°, 4°) are analyzed. The DMD methods can also obtain the global energy, time coefficient and spatial characteristics of the flow field. DMD mode energy of the characteristic frequency is the highest. The mode with the frequency doubling also has high energy at off-design points. The time coefficient obtained by DMD changes uniformly and eigenvalues are located on the unit circle, which indicates that there is no divergent or convergent mode.

Finite-Time Stability of Hybrid Systems With Unstable Modes

In this work, we study finite-time stability of hybrid systems with unstable modes. We present sufficient conditions in terms of multiple Lyapunov functions for the origin of a class of hybrid systems to be finite-time stable. More specifically, we show that even if the value of the Lyapunov function increases during continuous flow, i.e., if the unstable modes in the system are active for some time, finite-time stability can be guaranteed if the finite-time convergent mode is active for a sufficient amount of cumulative time. This is the first work on finite-time stability of hybrid systems using multiple Lyapunov functions. Prior work uses a common Lyapunov function approach, and requires the Lyapunov function to be decreasing during the continuous flows and non-increasing at the discrete jumps, thereby, restricting the hybrid system to only have stable modes, or to only evolve along the stable modes. In contrast, we allow Lyapunov functions to increasebothduring the continuous flows and the discrete jumps. As thus, the derived stability results are less conservative compared to the earlier results in the related literature, and in effect allow the hybrid system to have unstable modes.

Echolocation in soft-furred tree mice.

Echolocation is the use of reflected sound to sense features of the environment. Here, we show that soft-furred tree mice (Typhlomys) echolocate based on multiple independent lines of evidence. Behavioral experiments show that these mice can locate and avoid obstacles in darkness using hearing and ultrasonic pulses. The proximal portion of their stylohyal bone fuses with the tympanic bone, a form previously only seen in laryngeally echolocating bats. Further, we found convergence of hearing-related genes across the genome and of the echolocation-related gene prestin between soft-furred tree mice and echolocating mammals. Together, our findings suggest that soft-furred tree mice are capable of echolocation, and thus are a new lineage of echolocating mammals.