The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recover...The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.展开更多
Liver tumors segmentation from computed tomography (CT) images is an essential task for diagnosis and treatments of liver cancer. However, it is difficult owing to the variability of appearances, fuzzy boundaries, het...Liver tumors segmentation from computed tomography (CT) images is an essential task for diagnosis and treatments of liver cancer. However, it is difficult owing to the variability of appearances, fuzzy boundaries, heterogeneous densities, shapes and sizes of lesions. In this paper, an automatic method based on convolutional neural networks (CNNs) is presented to segment lesions from CT images. The CNNs is one of deep learning models with some convolutional filters which can learn hierarchical features from data. We compared the CNNs model to popular machine learning algorithms: AdaBoost, Random Forests (RF), and support vector machine (SVM). These classifiers were trained by handcrafted features containing mean, variance, and contextual features. Experimental evaluation was performed on 30 portal phase enhanced CT images using leave-one-out cross validation. The average Dice Similarity Coefficient (DSC), precision, and recall achieved of 80.06% ± 1.63%, 82.67% ± 1.43%, and 84.34% ± 1.61%, respectively. The results show that the CNNs method has better performance than other methods and is promising in liver tumor segmentation.展开更多
Photoacoustic technology in combination with molecular imaging is a highly effective method for accurately diagnosing brain glioma. For glioma detection at a deeper site, contrast agents with higher photoacoustic imag...Photoacoustic technology in combination with molecular imaging is a highly effective method for accurately diagnosing brain glioma. For glioma detection at a deeper site, contrast agents with higher photoacoustic imaging sensitivity are needed. Herein, we report a MoS_2–ICG hybrid with indocyanine green(ICG) conjugated to the surface of MoS_2 nanosheets. The hybrid significantly enhanced photoacoustic imaging sensitivity compared to MoS_2 nanosheets. This conjugation results in remarkably high optical absorbance across a broad near-infrared spectrum, redshifting of the ICG absorption peak and photothermal/photoacoustic conversion efficiency enhancement of ICG. A tumor mass of 3.5 mm beneath the mouse scalp was clearly visualized by using MoS_2–ICG as a contrast agent for the in vivo photoacoustic imaging of orthotopic glioma, which is nearly twofold deeper than the tumors imaged in our previous report using MoS_2 nanosheet. Thus, combined with its good stability and high biocompatibility, the MoS_2–ICG hybrid developed in this study has a great potential for high-efficiency tumor molecular imaging in translational medicine.展开更多
The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect.The couple stress fluid flow model introduces the le...The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect.The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity.Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids.The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes.Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions.The time to reach the temporal maximum increases as the reaction constant K increases.The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.展开更多
The electroplated(111)-oriented nanotwinned-Cu(nt-Cu) film was utilized as substrate for Ag and Cu sinter joining to improve the weak interface connection between the metal paste and the substrate.It was found that bo...The electroplated(111)-oriented nanotwinned-Cu(nt-Cu) film was utilized as substrate for Ag and Cu sinter joining to improve the weak interface connection between the metal paste and the substrate.It was found that both Cu and Ag sinter joints using(111)-oriented nt-Cu film exhibited a higher bonding strength than that using traditional random-oriented Cu film.Especially,the joints sintered with Cu paste on(111)-oriented nt-Cu film possessed a higher bonding strength of 53.7 MPa at the sintering condition of 300 °C,0.4 MPa in N2 atmosphere,compared to that on random-oriented Cu film with a value of 31.3 MPa.The results show that as metal substrate layer,the(111)-oriented nt-Cu film can improve the connection performance of Ag and Cu sinter joints,which could further promote their application in dieattachment technology for the next-generation power semiconductors.展开更多
An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coup...An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coupled governing equations is carried out with the aid of an unconditionally stable Crank–Nicolson type of numerical scheme. Numerical results for the steady-state velocity, temperature as well as the time histories of the skin-friction coefcient and Nusselt number are presented graphically and discussed. It is seen that for all flow variables as the couple stress control parameter, Co, is amplified, the time required for reaching the temporal maximum increases but the steady-state decreases.展开更多
Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy(THz-TDS) system.A voice coil motor stage based optical delay line(VCM-ODL) is...Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy(THz-TDS) system.A voice coil motor stage based optical delay line(VCM-ODL) is developed to provide a rather simple and robust structure with both the high scanning speed and the large delay length.The developed system is used for THz spectroscopic measurements and imaging of the corneal tissue with different amounts of water content,and the measurement results show the consistence with the reported results,in which the measurement time using VCM-ODL is a factor of 360 shorter than the traditional motorized optical delay line(MDL).With reducing the water content a monotonic decrease of the complex permittivity of the cornea is observed.The two-term Debye relaxation model is employed to explain our experimental results,revealing that the fast relaxation time of a dehydrated cornea is much larger than that of a hydrated cornea and its dielectric behavior can be affected by the presence of the biological macromolecules.These results demonstrate that our THz spectrometer may be a promising candidate for tissue hydration sensing and practical application of THz technology.展开更多
In this paper,we give four general results on linear extension of isometries between the unit spheres inβ-normed spaces.These results improve the corresponding theorems in β-normed spaces.
Accurate and automatic segmentation of hyper-acute ischemic infarct from magnetic resonance imaging is of great importance in clinical trials. Manual delineation is labor intensive, exhibits great variability due to u...Accurate and automatic segmentation of hyper-acute ischemic infarct from magnetic resonance imaging is of great importance in clinical trials. Manual delineation is labor intensive, exhibits great variability due to unclear infarct boundaries, and most importantly, is not practical due to urgent time requirement for prompt therapy. In this paper, segmentation of hyper-acute ischemic infarcts from diffusion weighted imaging based on Support Vector Machine (SVM) is explored. Experiments showed that SVM could provide good agreement with manual delineations by experienced experts to achieve an average Dice coefficient of 0.7630.121. The proposed method could achieve significantly higher segmentation accuracy and could be a potential tool to assist clinicians for quantifying hyper-acute infarction and decision making especially for thrombolytic therapy.展开更多
In this paper,the spray and combustion characteristics of diesel/butanol-blended fuels were studied within a high-temperature and high-pressure constant volume chamber equipped with a single-hole injector.Two blends w...In this paper,the spray and combustion characteristics of diesel/butanol-blended fuels were studied within a high-temperature and high-pressure constant volume chamber equipped with a single-hole injector.Two blends with 80%diesel/20%butanol and 60%diesel/40%butanol mixed by volume were tested in this study.The pure diesel B0 was also tested here as a reference.The spray penetration,flame lift-off length,and soot optical thickness were obtained through high-speed schlieren imaging,OH*chemiluminescence,and diffused back-illumination extinction imaging technique,respectively.The thermogravimetric curves of different fuels were obtained through a thermogravimetric analyzer.The results showed that butanol/diesel blends presented a longer ignition delay(ID)and flame lift-off length compared with pure diesel,and such finding was mainly caused by the lower cetane number and higher latent heat of vaporization of n-butanol.With the increase in the n-butanol ratio,soot production in the combustion process decreased significantly.Given the shorter ID period,the soot distribution of pure diesel reached a steady state earlier than the blends.展开更多
Effective heat dissipation is a crucial issue in electrochemical energy storage devices. Thus, it is highly desirable to develop high-performance electrode materials with high thermal conductivity. Here, we report a f...Effective heat dissipation is a crucial issue in electrochemical energy storage devices. Thus, it is highly desirable to develop high-performance electrode materials with high thermal conductivity. Here, we report a facile one-step electrodeposition method to synthesize ternary cobalt nickel sulfide(CoNi_2S_4)flower-like nanosheets which are grown on graphite foil(GF) as binder-free electrode materials for supercapacitors. The as-fabricated GF/CoNi_2S_4 integrated electrode manifested an excellent thermal conductivity of 620.1 W·m^(-1)·K^(-1) and a high specific capacitance of 881 F·g^(-2) at 5 mA cm^(-2), as well as good rate capability and cycling stability. Ultimately, the all-solid-state symmetric supercapacitor based on these advanced electrodes demonstrated superior heat dissipation performance during the galvanostatic charge-discharge processes. This novel strategy provides a new example of effective thermal management for potential applications in energy storage devices.展开更多
Terrain classification and force assistance strategies in complex environments have always piqued the interest of many researchers.For wearable soft exosuits,inaccurate terrain recognition can easily introduce undesir...Terrain classification and force assistance strategies in complex environments have always piqued the interest of many researchers.For wearable soft exosuits,inaccurate terrain recognition can easily introduce undesired assist forces that can easily injure the wearer.Because of these problems,we introduced a depth camera into the exosuit system,perform classification of terrain based on a Vision Transformer(ViT),and optimized the control algorithm,which is known as a ViT-Based Terrain Recognition System(TTRS).First,we used the Transformer algorithm to achieve a considerable classification effect in terrain recognition.We also introduced terrain recognition as prior knowledge into the force assistance strategy of the exosuit,providing different force assistance to the exosuit in different terrains.Subsequently,we performed human experiments with seven able-bodied people(six males and one female).The promising results demonstrate that our classification accuracy can reach 99.2%under six different terrains and that it can smoothly switch the force–assist curve in different terrains to better adapt to the complex terrain and improve the walking effect.The aforementioned terrain recognition algorithms and force–assist strategies may positively influence the study of soft exosuit,powered prostheses,and orthotics.展开更多
Today, exoskeletons are widely applied to provide walking assistance for patients with lower limb motor incapacity. Most existing exoskeletons are under-actuated, resulting in a series of problems, e.g., interference ...Today, exoskeletons are widely applied to provide walking assistance for patients with lower limb motor incapacity. Most existing exoskeletons are under-actuated, resulting in a series of problems, e.g., interference and unnatural gait during walking. In this study, we propose a novel intelligent autonomous lower extremity exoskeleton(Auto-LEE), aiming at improving the user experience of wearable walking aids and extending their application range.Unlike traditional exoskeletons, Auto-LEE has 10 degrees of freedom, and all the joints are actuated independently by direct current motors, which allows the robot to maintain balance in aiding walking without extra support.The new exoskeleton is designed and developed with a modular structure concept and multi-modal human-robot interfaces are considered in the control system. To validate the ability of self-balancing bipedal walking, three general algorithms for generating walking patterns are researched, and a preliminary experiment is implemented.展开更多
Modulating basal ganglia circuitry is of great signifcance in the improvement of motor function in Parkinson’s disease(PD).Here,for the frst time,we demonstrate that noninvasive ultrasound deep brain stimulation(UDBS...Modulating basal ganglia circuitry is of great signifcance in the improvement of motor function in Parkinson’s disease(PD).Here,for the frst time,we demonstrate that noninvasive ultrasound deep brain stimulation(UDBS)of the subthalamic nucleus(STN)or the globus pallidus(GP)improves motor behavior in a subacute mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP).Immunohistochemical c-Fos protein expression confrms that there is a relatively high level of c-Fos expression in the STN-UDBS and GP-UDBS group compared with sham group(both p<0.05).Furthermore,STN-UDBS or GPUDBS signifcantly increases the latency to fall in the rotarod test on day 9(p<0.05)and decreases the time spent climbing down a vertical rod in the pole test on day 12(p<0.05).Moreover,our results reveal that STN-UDBS or GP-UDBS protects the dopamine(DA)neurons from MPTP neurotoxicity by downregulating Bax(p<0.001),upregulating Bcl-2(p<0.01),blocking cytochrome c(Cyt C)release from mitochondria(p<0.05),and reducing cleaved-caspase 3 activity(p<0.01)in the ipsilateral substantia nigra(SN).Additionally,the safety of ultrasound stimulation is characterized by hematoxylin and eosin(HE)and Nissl staining;no hemorrhage or tissue damage is detected.Tese data demonstrate that UDBS enables modulation of STN or GP neural activity and leads to neuroprotection in PD mice,potentially serving as a noninvasive strategy for the clinical treatment of PD.展开更多
With the continuous development of wearable electronics,health care and smart terminals,highly performance flexible pressure sensors present a huge application prospect.In this study,by introducing the micro-array str...With the continuous development of wearable electronics,health care and smart terminals,highly performance flexible pressure sensors present a huge application prospect.In this study,by introducing the micro-array structured electrodes and dielectric layers with high dielectric constant,capacitive pressure sensor fabricated with a brand new preparation strategy and highly sensitive is proposed.The prepared micro-array structure is the basis for sensors with high sensitivity.Besides,the contact area between the two electrodes changes from linear to planar with the increased loading,which result in a wider linear responding range.In addition,by introducing ceramic dielectric material-barium titanate(BT)fillers into the dielectric layer to increase it’s the dielectric constant,the sensitivity of the sensor shows two-fold increase.Moreover,the sensitivity gradients can be tuned by changing the loading contents of BT particles.Hence,compared with parallel board capacitive sensors with ordinary dielectric layer,these sensors exhibit excellent performance as follow,high sensitivity(up to 4.9 kPa^(-1))under low pressure range(0-2500 Pa),low detection limit(<1.7 Pa),short response time(<50 ms),a stable response over 5000 loading-unloading cycles,bending stability and an adjustable sensitivity.Further,the flexible pressure sensor can detect the pressure of the water droplets and monitor human movement behavior.With the facile design and excellent comprehensive properties,the flexible pressure sensor provides a new approach to improve the sensitivity and shows a broad application prospects in the wearable electronics,health care and smart terminals.展开更多
With the development in next-generation semiconductor power devices,the power devices based on silicon carbide(SiC)and gallium nitride(GaN)are expected to replace the traditional Si-based power devices[1–6].However,t...With the development in next-generation semiconductor power devices,the power devices based on silicon carbide(SiC)and gallium nitride(GaN)are expected to replace the traditional Si-based power devices[1–6].However,the foreseeable harsh operating environment such as heavy thermal-load or extremely temperature cycle required more reliable interconnection technology[4,7-9].展开更多
An analytical solution is presented to describe the emission/sorption of volatile organic compounds (VOCs) from/on multiple single-layer materials coexisting in buildings. The diffusion of VOCs within each material is...An analytical solution is presented to describe the emission/sorption of volatile organic compounds (VOCs) from/on multiple single-layer materials coexisting in buildings. The diffusion of VOCs within each material is described by a transient diffusion equation. All diffusion equations are coupled with each other through the equation of mass conservation in the air. The analytical solution is validated by the experimental data in literature. Compared to the one-material case, the coexistence of multiple materials may decrease the emission rate of VOCs from each material. The smaller the diffusion coef-ficient is, the more the emission rate decreases. Whether a material is a source or a sink in the case of multiple materials coexisting is not affected by the diffusion coefficient. For the case of multiple mate-rials with different partition coefficients, a material with a high partition coefficient may become a sink. This may promote the emission of VOCs from other materials.展开更多
In recent years,the electroencephalography(EEG)brain-computer interface(BCI)has been researched in the area of upper-limb prosthesis control due to the promise of being able to record neurological signals which follow...In recent years,the electroencephalography(EEG)brain-computer interface(BCI)has been researched in the area of upper-limb prosthesis control due to the promise of being able to record neurological signals which follow activation patterns in the cortex directly from the brain with non-invasive electrodes.This is seen as a way of bypassing the limitation posed by acquiring neuromuscular signals predominantly with electromyography(EMG)directly from the stump,which possesses residual limb anatomy post-amputation.In this study,the sequential forward selection algorithm to form a 10-optimal-channel representation,alongside an extended signal feature vector was applied,to investigate the motion intent decoding performance of EMG-only,EEG-only,and a fused EMG-EEG sensing configuration for four transhumeral amputees with varying stump lengths.The results showed a considerable improvement for the EMG-only configuration with the advanced feature vector,but only a small increase for the EEG-only,and thus a marginal improvement when information from both signals was fused together.This is likely due to the EEG requiring a greater number of channels spread across the skull to provide a reliable intent decoding.Further work will now involve optimisation studies to find a greater representation of electrode representation and parsimony,to minimise the number of channels while boosting motion intent decoding accuracy.展开更多
As modern electronics are developed towards miniaturisation,high-degree integration and intelligentisation,a large amount of heat will be generated during the operation of devices.How to efficiently remove needless he...As modern electronics are developed towards miniaturisation,high-degree integration and intelligentisation,a large amount of heat will be generated during the operation of devices.How to efficiently remove needless heat is becoming more and more crucial for the lifetime and performance of electronic devices.Many efforts have been made to improve the thermal conductivity of polymer composites,which is an important component of electronics.Herein,the authors report on preparation of boron nitride micosphere/epoxy composites.The cross-plane thermal conductivity of the resultant composites is up to 1.03 Wm‒1K‒1.This is attributed to the thermally conductive network formed by the peeled hexagonal boron nitride flakes.Thanks to the superior thermal stability of boron nitride micosphere,the boron nitride micosphere/epoxy composite shows a decreased coefficient of thermal expansion(53.47 ppm/K)and an increased glass transition temperature(147.2℃)compared with the pure epoxy resin.In addition,the boron nitride micosphere/epoxy composite exhibits a lower dielectric constant compared with that of the hexagonal boron nitride/epoxy composite.This strategy can potentially pave the way for the design and fabrication of materials with high cross-plane thermal conductivity and lower dielectric properties.展开更多
基金supported by the National Natural Science Foundation of China(Grant 51305437)Guangdong Innovative Research Team Program of China(Grant201001D0104648280)
文摘The wheel-rail adhesion control for regenerative braking systems of high speed electric multiple unit trains is crucial to maintaining the stability,improving the adhesion utilization,and achieving deep energy recovery.There remain technical challenges mainly because of the nonlinear,uncertain,and varying features of wheel-rail contact conditions.This research analyzes the torque transmitting behavior during regenerative braking,and proposes a novel methodology to detect the wheel-rail adhesion stability.Then,applications to the wheel slip prevention during braking are investigated,and the optimal slip ratio control scheme is proposed,which is based on a novel optimal reference generation of the slip ratio and a robust sliding mode control.The proposed methodology achieves the optimal braking performancewithoutthewheel-railcontactinformation.Numerical simulation results for uncertain slippery rails verify the effectiveness of the proposed methodology.
文摘Liver tumors segmentation from computed tomography (CT) images is an essential task for diagnosis and treatments of liver cancer. However, it is difficult owing to the variability of appearances, fuzzy boundaries, heterogeneous densities, shapes and sizes of lesions. In this paper, an automatic method based on convolutional neural networks (CNNs) is presented to segment lesions from CT images. The CNNs is one of deep learning models with some convolutional filters which can learn hierarchical features from data. We compared the CNNs model to popular machine learning algorithms: AdaBoost, Random Forests (RF), and support vector machine (SVM). These classifiers were trained by handcrafted features containing mean, variance, and contextual features. Experimental evaluation was performed on 30 portal phase enhanced CT images using leave-one-out cross validation. The average Dice Similarity Coefficient (DSC), precision, and recall achieved of 80.06% ± 1.63%, 82.67% ± 1.43%, and 84.34% ± 1.61%, respectively. The results show that the CNNs method has better performance than other methods and is promising in liver tumor segmentation.
基金National Natural Science Foundation of China (NSFC) Grants 91739117, 81522024, 81427804, 61405234, 81430038 and 61475182National Key Basic Research (973) Program of China Grant 2014CB744503 and 2015CB755500+3 种基金Guangdong Natural Science Foundation Grant 2014B050505013 and 2014A030312006Shenzhen Science and Technology Innovation Grant JCYJ20170413153129570, JCYJ20160531175040976, JCYJ 20150521144321005, JCYJ20160608214524052, JCYJ201604221 53149834 JCYJ20150731154850923SIAT Innovation Program for Excellent Young Researchers 201510
文摘Photoacoustic technology in combination with molecular imaging is a highly effective method for accurately diagnosing brain glioma. For glioma detection at a deeper site, contrast agents with higher photoacoustic imaging sensitivity are needed. Herein, we report a MoS_2–ICG hybrid with indocyanine green(ICG) conjugated to the surface of MoS_2 nanosheets. The hybrid significantly enhanced photoacoustic imaging sensitivity compared to MoS_2 nanosheets. This conjugation results in remarkably high optical absorbance across a broad near-infrared spectrum, redshifting of the ICG absorption peak and photothermal/photoacoustic conversion efficiency enhancement of ICG. A tumor mass of 3.5 mm beneath the mouse scalp was clearly visualized by using MoS_2–ICG as a contrast agent for the in vivo photoacoustic imaging of orthotopic glioma, which is nearly twofold deeper than the tumors imaged in our previous report using MoS_2 nanosheet. Thus, combined with its good stability and high biocompatibility, the MoS_2–ICG hybrid developed in this study has a great potential for high-efficiency tumor molecular imaging in translational medicine.
文摘The unsteady natural convective couple stress fluid flow over a semi-infinite vertical cylinder is analyzed for the homogeneous first-order chemical reaction effect.The couple stress fluid flow model introduces the length dependent effect based on the material constant and dynamic viscosity.Also, it introduces the biharmonic operator in the Navier-Stokes equations, which is absent in the case of Newtonian fluids.The solution to the time-dependent non-linear and coupled governing equations is carried out with an unconditionally stable Crank-Nicolson type of numerical schemes.Numerical results for the transient flow variables, the average wall shear stress, the Nusselt number, and the Sherwood number are shown graphically for both generative and destructive reactions.The time to reach the temporal maximum increases as the reaction constant K increases.The average values of the wall shear stress and the heat transfer rate decrease as K increases, while increase with the increase in the Sherwood number.
文摘The electroplated(111)-oriented nanotwinned-Cu(nt-Cu) film was utilized as substrate for Ag and Cu sinter joining to improve the weak interface connection between the metal paste and the substrate.It was found that both Cu and Ag sinter joints using(111)-oriented nt-Cu film exhibited a higher bonding strength than that using traditional random-oriented Cu film.Especially,the joints sintered with Cu paste on(111)-oriented nt-Cu film possessed a higher bonding strength of 53.7 MPa at the sintering condition of 300 °C,0.4 MPa in N2 atmosphere,compared to that on random-oriented Cu film with a value of 31.3 MPa.The results show that as metal substrate layer,the(111)-oriented nt-Cu film can improve the connection performance of Ag and Cu sinter joints,which could further promote their application in dieattachment technology for the next-generation power semiconductors.
文摘An analysis is performed to study transient free convective boundary layer flow of a couple stress fluid over a vertical cylinder, in the absence of body couples. The solution of the time-dependent non-linear and coupled governing equations is carried out with the aid of an unconditionally stable Crank–Nicolson type of numerical scheme. Numerical results for the steady-state velocity, temperature as well as the time histories of the skin-friction coefcient and Nusselt number are presented graphically and discussed. It is seen that for all flow variables as the couple stress control parameter, Co, is amplified, the time required for reaching the temporal maximum increases but the steady-state decreases.
基金Project supported by the National Natural Science Foundation of China(Grant No.61205101)the Shenzhen Municipal Research Foundation,China(Grant Nos.GJHZ201404171134305 and JCYJ20140417113130693)the Marie Curie Actions-International Research Staff Exchange Scheme(IRSES)(Grant No.FP7 PIRSES-2013-612267)
文摘Spectroscopic measurements and terahertz imaging of the cornea are carried out by using a rapid scanning terahertz time domain spectroscopy(THz-TDS) system.A voice coil motor stage based optical delay line(VCM-ODL) is developed to provide a rather simple and robust structure with both the high scanning speed and the large delay length.The developed system is used for THz spectroscopic measurements and imaging of the corneal tissue with different amounts of water content,and the measurement results show the consistence with the reported results,in which the measurement time using VCM-ODL is a factor of 360 shorter than the traditional motorized optical delay line(MDL).With reducing the water content a monotonic decrease of the complex permittivity of the cornea is observed.The two-term Debye relaxation model is employed to explain our experimental results,revealing that the fast relaxation time of a dehydrated cornea is much larger than that of a hydrated cornea and its dielectric behavior can be affected by the presence of the biological macromolecules.These results demonstrate that our THz spectrometer may be a promising candidate for tissue hydration sensing and practical application of THz technology.
文摘In this paper,we give four general results on linear extension of isometries between the unit spheres inβ-normed spaces.These results improve the corresponding theorems in β-normed spaces.
文摘Accurate and automatic segmentation of hyper-acute ischemic infarct from magnetic resonance imaging is of great importance in clinical trials. Manual delineation is labor intensive, exhibits great variability due to unclear infarct boundaries, and most importantly, is not practical due to urgent time requirement for prompt therapy. In this paper, segmentation of hyper-acute ischemic infarcts from diffusion weighted imaging based on Support Vector Machine (SVM) is explored. Experiments showed that SVM could provide good agreement with manual delineations by experienced experts to achieve an average Dice coefficient of 0.7630.121. The proposed method could achieve significantly higher segmentation accuracy and could be a potential tool to assist clinicians for quantifying hyper-acute infarction and decision making especially for thrombolytic therapy.
基金Supported by the National Natural Science Foundation of China(Grant No.52276116)Shenzhen Basic Key Research Project(Grant No.JCYJ20200109115414354).
文摘In this paper,the spray and combustion characteristics of diesel/butanol-blended fuels were studied within a high-temperature and high-pressure constant volume chamber equipped with a single-hole injector.Two blends with 80%diesel/20%butanol and 60%diesel/40%butanol mixed by volume were tested in this study.The pure diesel B0 was also tested here as a reference.The spray penetration,flame lift-off length,and soot optical thickness were obtained through high-speed schlieren imaging,OH*chemiluminescence,and diffused back-illumination extinction imaging technique,respectively.The thermogravimetric curves of different fuels were obtained through a thermogravimetric analyzer.The results showed that butanol/diesel blends presented a longer ignition delay(ID)and flame lift-off length compared with pure diesel,and such finding was mainly caused by the lower cetane number and higher latent heat of vaporization of n-butanol.With the increase in the n-butanol ratio,soot production in the combustion process decreased significantly.Given the shorter ID period,the soot distribution of pure diesel reached a steady state earlier than the blends.
基金financially supported by the National Natural Science Foundation of China (21203236)Shenzhen Peacock Plan (KQCX2015033117354154)+1 种基金Shenzhen basic research plan (JCYJ2015052114432090)the Science & Technology Project of Educational Commission of Jiangxi Province, China (GJJ161198)
文摘Effective heat dissipation is a crucial issue in electrochemical energy storage devices. Thus, it is highly desirable to develop high-performance electrode materials with high thermal conductivity. Here, we report a facile one-step electrodeposition method to synthesize ternary cobalt nickel sulfide(CoNi_2S_4)flower-like nanosheets which are grown on graphite foil(GF) as binder-free electrode materials for supercapacitors. The as-fabricated GF/CoNi_2S_4 integrated electrode manifested an excellent thermal conductivity of 620.1 W·m^(-1)·K^(-1) and a high specific capacitance of 881 F·g^(-2) at 5 mA cm^(-2), as well as good rate capability and cycling stability. Ultimately, the all-solid-state symmetric supercapacitor based on these advanced electrodes demonstrated superior heat dissipation performance during the galvanostatic charge-discharge processes. This novel strategy provides a new example of effective thermal management for potential applications in energy storage devices.
基金supported by the NSFC-Shenzhen Robotics Research Center Project(U2013207)the National Natural Science Foundation of China(62273325 and U1913207)+2 种基金the Research Project of"Quancheng Scholars"of weight-bearing walking assisting exosuit rigid-flexible bionic mechanism and motion mode adaptive controlthe SIAT-CUHK Joint Laboratory of Robotics and Intelligent Systems International Science&Technology Cooperation Program of China(2018YFE0125600)the National Natural Science Foundation of China(62003327).
文摘Terrain classification and force assistance strategies in complex environments have always piqued the interest of many researchers.For wearable soft exosuits,inaccurate terrain recognition can easily introduce undesired assist forces that can easily injure the wearer.Because of these problems,we introduced a depth camera into the exosuit system,perform classification of terrain based on a Vision Transformer(ViT),and optimized the control algorithm,which is known as a ViT-Based Terrain Recognition System(TTRS).First,we used the Transformer algorithm to achieve a considerable classification effect in terrain recognition.We also introduced terrain recognition as prior knowledge into the force assistance strategy of the exosuit,providing different force assistance to the exosuit in different terrains.Subsequently,we performed human experiments with seven able-bodied people(six males and one female).The promising results demonstrate that our classification accuracy can reach 99.2%under six different terrains and that it can smoothly switch the force–assist curve in different terrains to better adapt to the complex terrain and improve the walking effect.The aforementioned terrain recognition algorithms and force–assist strategies may positively influence the study of soft exosuit,powered prostheses,and orthotics.
基金Project supported by the Shenzhen Robotics Research Center Projectthe National Natural Science Foundation of China(No.U1613219)+1 种基金the Shenzhen Technology Project,China(No.JSGG20160301160759264)the Shenzhen Overseas Innovation and Entrepreneurship Research Program,China(No.KQJSCX20170731164301774)
文摘Today, exoskeletons are widely applied to provide walking assistance for patients with lower limb motor incapacity. Most existing exoskeletons are under-actuated, resulting in a series of problems, e.g., interference and unnatural gait during walking. In this study, we propose a novel intelligent autonomous lower extremity exoskeleton(Auto-LEE), aiming at improving the user experience of wearable walking aids and extending their application range.Unlike traditional exoskeletons, Auto-LEE has 10 degrees of freedom, and all the joints are actuated independently by direct current motors, which allows the robot to maintain balance in aiding walking without extra support.The new exoskeleton is designed and developed with a modular structure concept and multi-modal human-robot interfaces are considered in the control system. To validate the ability of self-balancing bipedal walking, three general algorithms for generating walking patterns are researched, and a preliminary experiment is implemented.
基金We wish to thank Dr.Jun Jia(Capital Medical University)for assisting us with experimental design and Dr.Yunhui Liu(Shenzhen Institutes of Advanced Technology)for technical guidance.This work was supported by the National Natural Science Foundation of China(Grants nos.81527901,11534013,11774371,11574341,11674347,and 11874381)Natural Science Foundation of Guangdong Province(2017B030306011)Youth Innovation Promotion Association CAS(2018393).
文摘Modulating basal ganglia circuitry is of great signifcance in the improvement of motor function in Parkinson’s disease(PD).Here,for the frst time,we demonstrate that noninvasive ultrasound deep brain stimulation(UDBS)of the subthalamic nucleus(STN)or the globus pallidus(GP)improves motor behavior in a subacute mouse model of PD induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP).Immunohistochemical c-Fos protein expression confrms that there is a relatively high level of c-Fos expression in the STN-UDBS and GP-UDBS group compared with sham group(both p<0.05).Furthermore,STN-UDBS or GPUDBS signifcantly increases the latency to fall in the rotarod test on day 9(p<0.05)and decreases the time spent climbing down a vertical rod in the pole test on day 12(p<0.05).Moreover,our results reveal that STN-UDBS or GP-UDBS protects the dopamine(DA)neurons from MPTP neurotoxicity by downregulating Bax(p<0.001),upregulating Bcl-2(p<0.01),blocking cytochrome c(Cyt C)release from mitochondria(p<0.05),and reducing cleaved-caspase 3 activity(p<0.01)in the ipsilateral substantia nigra(SN).Additionally,the safety of ultrasound stimulation is characterized by hematoxylin and eosin(HE)and Nissl staining;no hemorrhage or tissue damage is detected.Tese data demonstrate that UDBS enables modulation of STN or GP neural activity and leads to neuroprotection in PD mice,potentially serving as a noninvasive strategy for the clinical treatment of PD.
基金financially supported by National Natural Science Foundation of China(21571186)National key R&D project from minister of science and technology of China(2016YFA0202702)+1 种基金Shenzhen Basic Research Plan(JCYJ20170818162548196)Youth Innovation Promotion Association of the Chinese Academy of Sciences(2017411).
文摘With the continuous development of wearable electronics,health care and smart terminals,highly performance flexible pressure sensors present a huge application prospect.In this study,by introducing the micro-array structured electrodes and dielectric layers with high dielectric constant,capacitive pressure sensor fabricated with a brand new preparation strategy and highly sensitive is proposed.The prepared micro-array structure is the basis for sensors with high sensitivity.Besides,the contact area between the two electrodes changes from linear to planar with the increased loading,which result in a wider linear responding range.In addition,by introducing ceramic dielectric material-barium titanate(BT)fillers into the dielectric layer to increase it’s the dielectric constant,the sensitivity of the sensor shows two-fold increase.Moreover,the sensitivity gradients can be tuned by changing the loading contents of BT particles.Hence,compared with parallel board capacitive sensors with ordinary dielectric layer,these sensors exhibit excellent performance as follow,high sensitivity(up to 4.9 kPa^(-1))under low pressure range(0-2500 Pa),low detection limit(<1.7 Pa),short response time(<50 ms),a stable response over 5000 loading-unloading cycles,bending stability and an adjustable sensitivity.Further,the flexible pressure sensor can detect the pressure of the water droplets and monitor human movement behavior.With the facile design and excellent comprehensive properties,the flexible pressure sensor provides a new approach to improve the sensitivity and shows a broad application prospects in the wearable electronics,health care and smart terminals.
文摘With the development in next-generation semiconductor power devices,the power devices based on silicon carbide(SiC)and gallium nitride(GaN)are expected to replace the traditional Si-based power devices[1–6].However,the foreseeable harsh operating environment such as heavy thermal-load or extremely temperature cycle required more reliable interconnection technology[4,7-9].
基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education, China
文摘An analytical solution is presented to describe the emission/sorption of volatile organic compounds (VOCs) from/on multiple single-layer materials coexisting in buildings. The diffusion of VOCs within each material is described by a transient diffusion equation. All diffusion equations are coupled with each other through the equation of mass conservation in the air. The analytical solution is validated by the experimental data in literature. Compared to the one-material case, the coexistence of multiple materials may decrease the emission rate of VOCs from each material. The smaller the diffusion coef-ficient is, the more the emission rate decreases. Whether a material is a source or a sink in the case of multiple materials coexisting is not affected by the diffusion coefficient. For the case of multiple mate-rials with different partition coefficients, a material with a high partition coefficient may become a sink. This may promote the emission of VOCs from other materials.
基金National Natural Science Foundation of China under Grants:#U1613222,#81850410557The Shenzhen Science and Technology Programme:#SGLH20180625142402055Chinese Academy of Sciences(CAS)President's International Fellowship Initiative Grant:#2019PB0036。
文摘In recent years,the electroencephalography(EEG)brain-computer interface(BCI)has been researched in the area of upper-limb prosthesis control due to the promise of being able to record neurological signals which follow activation patterns in the cortex directly from the brain with non-invasive electrodes.This is seen as a way of bypassing the limitation posed by acquiring neuromuscular signals predominantly with electromyography(EMG)directly from the stump,which possesses residual limb anatomy post-amputation.In this study,the sequential forward selection algorithm to form a 10-optimal-channel representation,alongside an extended signal feature vector was applied,to investigate the motion intent decoding performance of EMG-only,EEG-only,and a fused EMG-EEG sensing configuration for four transhumeral amputees with varying stump lengths.The results showed a considerable improvement for the EMG-only configuration with the advanced feature vector,but only a small increase for the EEG-only,and thus a marginal improvement when information from both signals was fused together.This is likely due to the EEG requiring a greater number of channels spread across the skull to provide a reliable intent decoding.Further work will now involve optimisation studies to find a greater representation of electrode representation and parsimony,to minimise the number of channels while boosting motion intent decoding accuracy.
基金The authors acknowledge the financial support from National Natural Science Foundation of China(no.51603226)the National Key R&D Project from Minister of Science and Technology of China(2016YFA0202702)Shenzhen Fundamental Research Program(JCYJ20150831154213681).
文摘As modern electronics are developed towards miniaturisation,high-degree integration and intelligentisation,a large amount of heat will be generated during the operation of devices.How to efficiently remove needless heat is becoming more and more crucial for the lifetime and performance of electronic devices.Many efforts have been made to improve the thermal conductivity of polymer composites,which is an important component of electronics.Herein,the authors report on preparation of boron nitride micosphere/epoxy composites.The cross-plane thermal conductivity of the resultant composites is up to 1.03 Wm‒1K‒1.This is attributed to the thermally conductive network formed by the peeled hexagonal boron nitride flakes.Thanks to the superior thermal stability of boron nitride micosphere,the boron nitride micosphere/epoxy composite shows a decreased coefficient of thermal expansion(53.47 ppm/K)and an increased glass transition temperature(147.2℃)compared with the pure epoxy resin.In addition,the boron nitride micosphere/epoxy composite exhibits a lower dielectric constant compared with that of the hexagonal boron nitride/epoxy composite.This strategy can potentially pave the way for the design and fabrication of materials with high cross-plane thermal conductivity and lower dielectric properties.
