This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the r...This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the rail foot.As a contactless method,EMATs could overcome some known limitations of conventional ultrasonic techniques,but require further validation.Differ-ent campaigns of experimental tests were performed,evaluating,by means of a probability of detection approach,the response of the technique to several artificial semi-elliptical flaws of increasing size and by considering two sensors characterized by different working frequencies.In contact,static tests allowed to assess the basic feasibility of the inspection technique and showed a linear response to defect size,saturating when defect width exceeded the rail web thickness.Dynamic tests allowed to introduce the effects of lift-off on signal responses.During all tests,the higher-frequency sensor outperformed the lower-frequency one.Finally,full-scale bogie tests on an indoor permanent track installation,comprehensive of defec-tive rails,confirmed the higher flaw detection rates of the higher-frequency sensor,with minimal detection failures despite occasional false alarms.EMATs showed encouraging results for in-motion rail inspection:with further technical development and optimization,this technique could enhance ultrasonic rail inspection by diagnostic trains.展开更多
Alpha-voltaic cell is a type of micro nuclear battery that provides several decades of reliable power in the nano watt to microwatt range,supplying for special applications where traditional chemical batteries or sola...Alpha-voltaic cell is a type of micro nuclear battery that provides several decades of reliable power in the nano watt to microwatt range,supplying for special applications where traditional chemical batteries or solar cells are difficult to operate.However,the power conversion efficiency of the alpha-voltaic cells reported are still far behind the theoretical limit,making the development of alpha-voltaic cell challenging.Developing advanced semiconductor transducers with higher efficiency in converting the energy of alpha particles into electric energy is proving to be necessary for realizing high-power conversion efficiency.Herein,we propose an alpha-voltaic cell based on SiC PIN transducer that includes a sensitive region with an area of 1 cm^(2),a width of 51.2μm,and a charge collection efficiency of 95.6%at 0 V bias.We find that optimizing the unintentional doping concentration and crystal quality of the SiC epitaxial layer can significantly increase the absorption and utilization of the energy of alpha particles,resulting in a 2.4-fold enhancement in power conversion efficiency compared with that of the previous study.Electrical properties of the SiC alpha-voltaic cell are measured using an He-ion accelerator as the equivalentα-radioisotopes,with the best power conversion efficiency of 2.10%and maximum output power density of 406.66 nW cm-2 is obtained.Our research makes a big leap in SiC alpha-voltaic cell,bridging the gap between micro nuclear batteries and practical applications in micro-electromechanical systems,micro aerial vehicles,and tiny satellites.展开更多
In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of...In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of the antisymmetric Lamb wave is always dominated by out-of-plane components,using bias magnetic field perpendicular to plate surface is kind of inefficient.In this paper,the performance of both the normal bias magnetic field EMAT(NB-EMAT)and the parallel bias magnetic field EMAT(PB-EMAT)for transmitting and receiving A0 mode Lamb waves are thoroughly studied.The mechanisms of these two structures are elaborated.First,the finite element models of both structures are established.The magnetic fields of these two EMATs are numerically calculated and the results are compared with experiments.Then,the Lorentz force distributions excited by the two EMATs are compared to prove the feasibility of improving the excitation efficiency of MLC-EMAT by selecting the direction of bias magnetic field.Furthermore,the excitation efficiencies of NB-EMAT and PB-EMAT are quantitatively analyzed and compared in simulation software.Results show that the excitation efficiency of PB-EMAT is 108%higher than NB-EMAT.Finally,several groups of comparative experiments are conducted to verify the conclusion obtained through numerical calculation.Experimental results show that by simply replacing the tradition NB-EMAT with PB-EMAT,the excitation efficiency can be greatly increased by more than 50%.If PB-EMATs are used as both the receiver and transmitter,the excitation efficiency can be further increased by 113%.展开更多
This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating tra...This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.展开更多
Signal transducer and activator of transcription（STAT）is a unique protein family that binds to DNA,coupled with tyrosine phosphorylation signaling pathways,acting as a transcriptional regulator to mediate a variety ...Signal transducer and activator of transcription（STAT）is a unique protein family that binds to DNA,coupled with tyrosine phosphorylation signaling pathways,acting as a transcriptional regulator to mediate a variety of biological effects.Cerebral ischemia and reperfusion can activate STATs signaling pathway,but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging（DWI）in rats after cerebral ischemia/reperfusion.Here,we established a rat model of focal cerebral ischemia injury using the modified Longa method.DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient.STAT3 protein expression showed no significant change after reperfusion,but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours.Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area.These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.展开更多
A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil ...A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.展开更多
This paper describes an innovative, genetic algorithm based inverse model of nonlinear transducer. In the inverse modeling, using a genetic algorithm, the unknown coefficients of the model are estimated accurately. T...This paper describes an innovative, genetic algorithm based inverse model of nonlinear transducer. In the inverse modeling, using a genetic algorithm, the unknown coefficients of the model are estimated accurately. The simulation results indicate that this technique provides greater flexibility and suitability than the existing methods. It is very easy to modify the nonlinear transducer on line. Thus the method improves the transducer's accuracy. With the help of genetic algorithm (GA), the model coefficients' training are less likely to be trapped in local minima than traditional gradient based search algorithms.展开更多
Signal transducer and activator of transcription 3(STAT3), a member of the STAT family, is a key regulator of many physiological and pathological processes. Significant progress has been made in understanding the tran...Signal transducer and activator of transcription 3(STAT3), a member of the STAT family, is a key regulator of many physiological and pathological processes. Significant progress has been made in understanding the transcriptional control, posttranslational modification, cellular localization and functional regulation of STAT3. STAT3 can translocate into the nucleus and bind to specific promoter sequences, thereby exerting transcriptional regulation. Recent studies have shown that STAT3 can also translocate into mitochondria, participating in aerobic respiration and apoptosis. In addition, STAT3 plays an important role in inflammation and tumorigenesis by regulating cell proliferation, differentiation and metabolism. Conditional knockout mouse models make it possible to study the physiological function of STAT3 in specific tissues and organs. This review summarizes the latest advances in the understanding of the expression, regulation and function of STAT3 in physiological and tumorigenic processes.展开更多
Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a...Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.展开更多
BACKGROUND Study shows that signal transducer and activator of transcription 3(STAT3) can increase the Warburg effect by stimulating hexokinase 2 in breast cancer and upregulate lactate dehydrogenase A and pyruvate de...BACKGROUND Study shows that signal transducer and activator of transcription 3(STAT3) can increase the Warburg effect by stimulating hexokinase 2 in breast cancer and upregulate lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 in myeloma. STAT3 and pyruvate kinase M2(PKM2) can also be activated and enhance the Warburg effect in hepatocellular carcinoma. Precancerous lesions are critical to human and rodent hepatocarcinogenesis. However, the underlying molecular mechanism for the development of liver precancerous lesions remains unknown. We hypothesized that STAT3 promotes the Warburg effect possibly by upregulating p-PKM2 in liver precancerous lesions in rats.AIM To investigate the mechanism of the Warburg effect in liver precancerous lesions in rats.METHODS A model of liver precancerous lesions was established by a modified Solt-Farber method. The liver pathological changes were observed by HE staining and immunohistochemistry. The transformation of WB-F344 cells induced with Nmethyl-N'-nitro-N-nitrosoguanidine and hydrogen peroxide was evaluated by the soft agar assay and aneuploidy. The levels of glucose and lactate in the tissue and culture medium were detected with a spectrophotometer. The protein levels of glutathione S-transferase-π, proliferating cell nuclear antigen(PCNA), STAT3,and PKM2 were examined by Western blot and immunofluorescence.RESULTS We found that the Warburg effect was increased in liver precancerous lesions in rats. PKM2 and p-STAT3 were upregulated in activated oval cells in liverprecancerous lesions in rats. The Warburg effect, p-PKM2, and p-STAT3 expression were also increased in transformed WB-F344 cells. STAT3 activation promoted the clonal formation rate, aneuploidy, alpha-fetoprotein expression,PCNA expression, G1/S phase transition, the Warburg effect, PKM2 phosphorylation, and nuclear translocation in transformed WB-F344 cells.Moreover, the Warburg effect was inhibited by stattic, a specific inhibitor of STAT3, and further reduced in transformed WB-F344 cells after the intervention for PKM2.CONCLUSION The Warburg effect is initiated in liver precancerous lesions in rats. STAT3 activation promotes the Warburg effect by enhancing the phosphorylation of PKM2 in transformed WB-F344 cells.展开更多
The design method of a 6-axis force robot's transducer based on the Stewartplatform is detailed. For this purpose, the sensitivity isotropy evaluation criteria of thetransducer are defined, and by the aid of compu...The design method of a 6-axis force robot's transducer based on the Stewartplatform is detailed. For this purpose, the sensitivity isotropy evaluation criteria of thetransducer are defined, and by the aid of computer, the relationships between the criteria and theparameters of all the transducers based on the Stewart platform are investigated within thegeometric model of the solution space, which can provide the theoretical background for the optimalconstruction design of the 6-axis force transducer related to the sensitivity isotropy.展开更多
Hepatocellular carcinoma is one of the most common cancers worldwide,and a leading cause of cancer-related death.Owing to unsatisfactory clinical outcomes under the current standard of care,there is a need to search f...Hepatocellular carcinoma is one of the most common cancers worldwide,and a leading cause of cancer-related death.Owing to unsatisfactory clinical outcomes under the current standard of care,there is a need to search for and identify novel and potent therapeutic targets to improve patient outcomes.Sorafenib is the first and only approved targeted therapy for the treatment of hepatocellular carcinoma.Besides functioning as a multiple tyrosine kinase,sorafenib also acts via a kinase-independent mechanism to target signal transducer and activator of transcription 3(STAT3) signaling in hepatocellular carcinoma cells.STAT3 is a key regulator of inflammation,cell survival,and tumorigenesis of liver cells,and the high percentage of hepatocellular carcinoma cells with constitutively active STAT3 justifies targeting it for the development of novel therapeutics.Sorafenib inactivates STAT3 and STAT3-related signaling by inducing a conformational change in and releasing the autoinhibition of Src homology region 2 domaincontaining phosphatase-1.This phosphatase negatively regulates STAT3 activity,which leads to the subsequent apoptosis of cancer cells.The novel anti-cancer property of sorafenib will be discussed in this review,not only adding information regarding its mechanism of action but also providing an innovative approach for the development of cancer therapeutics in the future.展开更多
The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic t...The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.展开更多
Cracks, especially small cracks are di cult to be detected in oil and gas transportation pipelines buried underground or covered with layers of material by using the traditional ultrasonic inspection techniques. There...Cracks, especially small cracks are di cult to be detected in oil and gas transportation pipelines buried underground or covered with layers of material by using the traditional ultrasonic inspection techniques. Therefore, a new com?posite ultrasonic transducer array with three acoustic beam incidence modes is developed. The space model of the array is also established to obtain the defect reflection point location. And the crack ultrasound image is thus formed through a series of small cubical elements expanded around the point locations by using the projection of binariza?tion values extracted from the received ultrasonic echo signals. Laboratory experiments are performed on a pipeline sample with di erent types of cracks to verify the e ectiveness and performance of the proposed technique. From the image, the presence of small cracks can be clearly observed, in addition to the sizes and orientations of the cracks. The proposed technique can not only inspect common flaws, but also detect cracks with various orientations, which is helpful for defect evaluation in pipeline testing.展开更多
This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric ...This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.展开更多
High intensity focused ultrasound(HIFU)therapy is an effective method in clinical treatment of tumors,in order to explore the bio-heat conduction mechanism of in multi-layer media by concave spherical transducer,tempe...High intensity focused ultrasound(HIFU)therapy is an effective method in clinical treatment of tumors,in order to explore the bio-heat conduction mechanism of in multi-layer media by concave spherical transducer,temperature field induced by this kind of transducer in multi-layer media will be simulated through solving Pennes equation with finite difference method,and the influence of initial sound pressure,absorption coefficient,and thickness of different layers of biological tissue as well as thermal conductivity parameter on sound focus and temperature distribution will be analyzed,respectively.The results show that the temperature in focus area increases faster while the initial sound pressure and thermal conductivity increase.The absorption coefficient is smaller,the ultrasound intensity in the focus area is bigger,and the size of the focus area is increasing.When the thicknesses of different layers of tissue change,the focus position changes slightly,but the sound intensity of the focus area will change obviously.The temperature in focus area will rise quickly before reaching a threshold,and then the temperature will keep in the threshold range.展开更多
An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great ...An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great potential for air-coupled applications,mainly because of their low acoustic impedance.In this study,an air-coupled CMUT array is designed as an air parametric array.A hexagonal array is proposed to improve the directivity of the sound generated.A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell.The CMUT array is then fabricated by a wafer bonding process with high consistency.The performances of the CMUT are tested to verify the accuracy of the finite element analysis.By optimizing the component parameters of the bias-T circuit used for driving the CMUT,DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission.Finally,the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.展开更多
AIM： To study the effect of Hepatitis C virus nonstructural 5A （HCV NSSA） on IFNα induced signal transducer and activator of transcription-1 （STAT1） phosphorylation and nuclear translocation.METHODS： Expression...AIM： To study the effect of Hepatitis C virus nonstructural 5A （HCV NSSA） on IFNα induced signal transducer and activator of transcription-1 （STAT1） phosphorylation and nuclear translocation.METHODS： Expression of STAT1 Tyr701 phosphorylation at different time points was confirmed by Western blot, and the time point when p-STAT1 expressed most, was taken as the IFN induction time for further studies. Immunocytochemistry was used to confirm the successful transient transfection of NS5A expression plasmid. Immunofluorescene was performed to observe if there was any difference in IFNα-induced STAT1 phosphorylation and nuclear translocation between HCV NSSA-expressed and non-HCV NSSA-expressed cells. Western blot was used to compare the phosphorylated STAT1 protein of the cells.RESULTS： Expression of HCV NS5A was found in the cytoplasm of pCNS5A-transfected Huh7 cells, but not in the PRC/ CMV transfected or non-transfected cells, STAT1 Tyr701 phosphorylation was found strongest in 30 min of IFN induction, STAT1 phosphorylation and nuclear import were much less in the presence of HCV NS5A protein in contrast to pRC/CMV-transfected and non-transfected cells under fluorescent microscopy, which was further confirmed by Western blot.CONCLUSION： HCV NSSA expression plasmid is successfully transfected into Huh7 cells and HCV NS5A protein is expressed in the cytoplasm of the cells. IFN-α is able to induce STAT1 phosphrylation and nuclear translocation, and this effect is inhibited by HCV NS5A protein, which might be another possible resistance mechanism to interferon alpha therapy.展开更多
A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and...A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and crosstalk just with a single conventional calibration approach. In this paper, a hybrid model comprising calibration matrix and SVM model for calibrating linearity and nonlinearity respectively is built up. The calibration matrix is determined by linear artificial neural network （ANN）, and the SVM is used to compensate for the nonlinear cross coupling among each dimension. A simulation of the calibration of a multi-dimensional sensor is conducted by the SVM hybrid calibration method, which is then utilized to calibrate a six-component force/torque transducer of wind tunnel balance. From the calibrating results, it can be indicated that the SVM hybrid calibration method has improved the calibration accuracy significantly without increasing data samples, compared with calibration matrix. Moreover, with the calibration matrix, the hybrid model can provide a basis for the design of transducers.展开更多
A novel traveling wave ultrasonic motor was proposed. The structure of the motor is rather simple and different from the conventional traveling wave ultrasonic motors. Its production processes are very convenient. It ...A novel traveling wave ultrasonic motor was proposed. The structure of the motor is rather simple and different from the conventional traveling wave ultrasonic motors. Its production processes are very convenient. It is composed of a stator constituted with a ring and a bar shaped transducer and two cone shaped rotors. The rotors were pressed on inner surface of the ring by means of a pre-pressure system. The bar shaped transducer has a sand- wich-like configuration,where two sets of piezoelectric element are bolted. One set excites a longitudinal vibration of the bar, and the other set excites a flexural vibration of the bar. The ring＇s traveling wave excited with the longitudinal vibration and the bending vibration of the bar transducer was simulated with FEM （finite element method）. The prototype of the motor was made and investigated experimentally for its performance. Its maximum torque and rotating speed are 0.25 N · m and 50 r/min, respectively.展开更多
基金funded in the frame of the Joint Research Centre (JRC) Trasporti, established at Fondazione Politecnico di Milano, through contract C40/2019 “JRC Trasporti-Metodologie per l’ispezione delle rotaie nei riguardi della formazione di cricche”
文摘This study explores the feasibility of electromagnetic acoustic transducers(EMATs)for ultrasonic rail inspection,focusing on bulk wave generation from the rail head and on defect detection at the central part of the rail foot.As a contactless method,EMATs could overcome some known limitations of conventional ultrasonic techniques,but require further validation.Differ-ent campaigns of experimental tests were performed,evaluating,by means of a probability of detection approach,the response of the technique to several artificial semi-elliptical flaws of increasing size and by considering two sensors characterized by different working frequencies.In contact,static tests allowed to assess the basic feasibility of the inspection technique and showed a linear response to defect size,saturating when defect width exceeded the rail web thickness.Dynamic tests allowed to introduce the effects of lift-off on signal responses.During all tests,the higher-frequency sensor outperformed the lower-frequency one.Finally,full-scale bogie tests on an indoor permanent track installation,comprehensive of defec-tive rails,confirmed the higher flaw detection rates of the higher-frequency sensor,with minimal detection failures despite occasional false alarms.EMATs showed encouraging results for in-motion rail inspection:with further technical development and optimization,this technique could enhance ultrasonic rail inspection by diagnostic trains.
基金financially supported by the National Natural Science Foundation of China(Nos.12050005,11922507,and 12205016)supported by Major State Basic Research Development Program of China(No.2021YFB3201000)。
文摘Alpha-voltaic cell is a type of micro nuclear battery that provides several decades of reliable power in the nano watt to microwatt range,supplying for special applications where traditional chemical batteries or solar cells are difficult to operate.However,the power conversion efficiency of the alpha-voltaic cells reported are still far behind the theoretical limit,making the development of alpha-voltaic cell challenging.Developing advanced semiconductor transducers with higher efficiency in converting the energy of alpha particles into electric energy is proving to be necessary for realizing high-power conversion efficiency.Herein,we propose an alpha-voltaic cell based on SiC PIN transducer that includes a sensitive region with an area of 1 cm^(2),a width of 51.2μm,and a charge collection efficiency of 95.6%at 0 V bias.We find that optimizing the unintentional doping concentration and crystal quality of the SiC epitaxial layer can significantly increase the absorption and utilization of the energy of alpha particles,resulting in a 2.4-fold enhancement in power conversion efficiency compared with that of the previous study.Electrical properties of the SiC alpha-voltaic cell are measured using an He-ion accelerator as the equivalentα-radioisotopes,with the best power conversion efficiency of 2.10%and maximum output power density of 406.66 nW cm-2 is obtained.Our research makes a big leap in SiC alpha-voltaic cell,bridging the gap between micro nuclear batteries and practical applications in micro-electromechanical systems,micro aerial vehicles,and tiny satellites.
基金supported by the Foundation of Guangxi Key Laboratory of Manufacturing System and Advanced Manufacturing Technology(No.17-259-05-005Z)Innovation Project of GUET Graduate Education(No.2025YCXS016)。
文摘In traditional meander line coil electromagnetic acoustic transducer(MLC-EMAT)structures,the bias magnetic field is usually set to be along the normal direction of plate surface.However,since the particle vibration of the antisymmetric Lamb wave is always dominated by out-of-plane components,using bias magnetic field perpendicular to plate surface is kind of inefficient.In this paper,the performance of both the normal bias magnetic field EMAT(NB-EMAT)and the parallel bias magnetic field EMAT(PB-EMAT)for transmitting and receiving A0 mode Lamb waves are thoroughly studied.The mechanisms of these two structures are elaborated.First,the finite element models of both structures are established.The magnetic fields of these two EMATs are numerically calculated and the results are compared with experiments.Then,the Lorentz force distributions excited by the two EMATs are compared to prove the feasibility of improving the excitation efficiency of MLC-EMAT by selecting the direction of bias magnetic field.Furthermore,the excitation efficiencies of NB-EMAT and PB-EMAT are quantitatively analyzed and compared in simulation software.Results show that the excitation efficiency of PB-EMAT is 108%higher than NB-EMAT.Finally,several groups of comparative experiments are conducted to verify the conclusion obtained through numerical calculation.Experimental results show that by simply replacing the tradition NB-EMAT with PB-EMAT,the excitation efficiency can be greatly increased by more than 50%.If PB-EMATs are used as both the receiver and transmitter,the excitation efficiency can be further increased by 113%.
基金Project supported by the National Natural Science Foundation of China(Grant No.12474440).
文摘This paper proposes a method to generate Bessel-like collimated beams with suppressed side lobes using the flexural vibration modes of a fixed boundary circular plate,which is excited by a longitudinally vibrating transducer in a ring excitation manner.The factors affecting the generation of Bessel-like collimated beams are investigated by theoretical analysis,numerical simulation and experimental methods.The results indicate that Bessel-like wave can be generated by a thin circular plate with fixed boundaries.The third-order mode of the circular plate can be modified to generate a collimated beam with suppressing side lobes when it is excited in a ring excitation manner and the excitation position lies between the first two nodal circles of the plate.As the excitation radius increases,the main lobe width of the resulting Bessel-like collimated beam decreases,the extent of the focusing region increases,and the amplitude of the side lobes initially increases and then decreases.Based on the simulation results,a prototype Bessel-like collimated beam generation system is made and measured experimentally.The experimental results are in good agreement with the numerical results.The Bessel-like collimated beam can be generated by the proposed system,which has potential application in the fields of long-range detection,imaging of highly attenuated materials,and airflow acceleration.
文摘Signal transducer and activator of transcription（STAT）is a unique protein family that binds to DNA,coupled with tyrosine phosphorylation signaling pathways,acting as a transcriptional regulator to mediate a variety of biological effects.Cerebral ischemia and reperfusion can activate STATs signaling pathway,but no studies have confirmed whether STAT activation can be verified by diffusion-weighted magnetic resonance imaging（DWI）in rats after cerebral ischemia/reperfusion.Here,we established a rat model of focal cerebral ischemia injury using the modified Longa method.DWI revealed hyperintensity in parts of the left hemisphere before reperfusion and a low apparent diffusion coefficient.STAT3 protein expression showed no significant change after reperfusion,but phosphorylated STAT3 expression began to increase after 30 minutes of reperfusion and peaked at 24 hours.Pearson correlation analysis showed that STAT3 activation was correlated positively with the relative apparent diffusion coefficient and negatively with the DWI abnormal signal area.These results indicate that DWI is a reliable representation of the infarct area and reflects STAT phosphorylation in rat brain following focal cerebral ischemia/reperfusion.
文摘A high performance current and voltage measurement system has been developed in power system. The system is composed of two parts: one current measurement element and one voltage measurement element. A Rogowski coil and a capacitive voltage divider are used respectively for the line current and voltage measurements. Active electronic components are used to modulate signal, and power supply for these components is drawn from power line via an auxiliary current transformer. Measurement signal is transmitted by optical fibers, which is resistant to electromagnetic induction and noise. With careful design and the use of digital signal processing technology, the whole system can meet 0.5% accuracy for metering and provides large dynamic range coupled with good accuracy for protective relaying use.
文摘This paper describes an innovative, genetic algorithm based inverse model of nonlinear transducer. In the inverse modeling, using a genetic algorithm, the unknown coefficients of the model are estimated accurately. The simulation results indicate that this technique provides greater flexibility and suitability than the existing methods. It is very easy to modify the nonlinear transducer on line. Thus the method improves the transducer's accuracy. With the help of genetic algorithm (GA), the model coefficients' training are less likely to be trapped in local minima than traditional gradient based search algorithms.
基金Supported by National Natural Science Foundation of China,No.30930013
文摘Signal transducer and activator of transcription 3(STAT3), a member of the STAT family, is a key regulator of many physiological and pathological processes. Significant progress has been made in understanding the transcriptional control, posttranslational modification, cellular localization and functional regulation of STAT3. STAT3 can translocate into the nucleus and bind to specific promoter sequences, thereby exerting transcriptional regulation. Recent studies have shown that STAT3 can also translocate into mitochondria, participating in aerobic respiration and apoptosis. In addition, STAT3 plays an important role in inflammation and tumorigenesis by regulating cell proliferation, differentiation and metabolism. Conditional knockout mouse models make it possible to study the physiological function of STAT3 in specific tissues and organs. This review summarizes the latest advances in the understanding of the expression, regulation and function of STAT3 in physiological and tumorigenic processes.
基金Project(10974115) supported by the National Natural Science Foundation of China
文摘Facing the problems lack of considering the non-uniform distribution of the static bias magnetic field and computing the panicle displacements in the simulation model of electromagnetic acoustic transducer （EMAT）, a multi-field coupled model was established and the finite element method （FEM） was presented to calculate the entire transduction process. The multi-field coupled model included the static magnetic field, pulsed eddy current field and mechanical field. The FEM equations of the three fields were derived by Garlerkin FEM method. Thus, the entire transduction process of the EMAT was calculated through sequentially coupling the three fields. The transduction process of a Lamb wave EMAT was calculated according to the present model and method. The results show that, by the present method, it is valid to calculate the particle displacement under the given excitation signal and non-uniformly distributed static magnetic field. Calculation error will be brought about if the non-uniform distribution of the static bias magnetic field is neglected.
基金Supported by the National Natural Science Foundation of China,No.81070319the Beijing Natural Science Foundation of China,No.7102013the Beijing Municipal Education Commission Research Program,China,No.KM201610025004
文摘BACKGROUND Study shows that signal transducer and activator of transcription 3(STAT3) can increase the Warburg effect by stimulating hexokinase 2 in breast cancer and upregulate lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 in myeloma. STAT3 and pyruvate kinase M2(PKM2) can also be activated and enhance the Warburg effect in hepatocellular carcinoma. Precancerous lesions are critical to human and rodent hepatocarcinogenesis. However, the underlying molecular mechanism for the development of liver precancerous lesions remains unknown. We hypothesized that STAT3 promotes the Warburg effect possibly by upregulating p-PKM2 in liver precancerous lesions in rats.AIM To investigate the mechanism of the Warburg effect in liver precancerous lesions in rats.METHODS A model of liver precancerous lesions was established by a modified Solt-Farber method. The liver pathological changes were observed by HE staining and immunohistochemistry. The transformation of WB-F344 cells induced with Nmethyl-N'-nitro-N-nitrosoguanidine and hydrogen peroxide was evaluated by the soft agar assay and aneuploidy. The levels of glucose and lactate in the tissue and culture medium were detected with a spectrophotometer. The protein levels of glutathione S-transferase-π, proliferating cell nuclear antigen(PCNA), STAT3,and PKM2 were examined by Western blot and immunofluorescence.RESULTS We found that the Warburg effect was increased in liver precancerous lesions in rats. PKM2 and p-STAT3 were upregulated in activated oval cells in liverprecancerous lesions in rats. The Warburg effect, p-PKM2, and p-STAT3 expression were also increased in transformed WB-F344 cells. STAT3 activation promoted the clonal formation rate, aneuploidy, alpha-fetoprotein expression,PCNA expression, G1/S phase transition, the Warburg effect, PKM2 phosphorylation, and nuclear translocation in transformed WB-F344 cells.Moreover, the Warburg effect was inhibited by stattic, a specific inhibitor of STAT3, and further reduced in transformed WB-F344 cells after the intervention for PKM2.CONCLUSION The Warburg effect is initiated in liver precancerous lesions in rats. STAT3 activation promotes the Warburg effect by enhancing the phosphorylation of PKM2 in transformed WB-F344 cells.
基金This project is supported by National 863 plan(No.512-9804-02)Robotics Laboratory,Chinese Academy of Sciences Foundation, China
文摘The design method of a 6-axis force robot's transducer based on the Stewartplatform is detailed. For this purpose, the sensitivity isotropy evaluation criteria of thetransducer are defined, and by the aid of computer, the relationships between the criteria and theparameters of all the transducers based on the Stewart platform are investigated within thegeometric model of the solution space, which can provide the theoretical background for the optimalconstruction design of the 6-axis force transducer related to the sensitivity isotropy.
文摘Hepatocellular carcinoma is one of the most common cancers worldwide,and a leading cause of cancer-related death.Owing to unsatisfactory clinical outcomes under the current standard of care,there is a need to search for and identify novel and potent therapeutic targets to improve patient outcomes.Sorafenib is the first and only approved targeted therapy for the treatment of hepatocellular carcinoma.Besides functioning as a multiple tyrosine kinase,sorafenib also acts via a kinase-independent mechanism to target signal transducer and activator of transcription 3(STAT3) signaling in hepatocellular carcinoma cells.STAT3 is a key regulator of inflammation,cell survival,and tumorigenesis of liver cells,and the high percentage of hepatocellular carcinoma cells with constitutively active STAT3 justifies targeting it for the development of novel therapeutics.Sorafenib inactivates STAT3 and STAT3-related signaling by inducing a conformational change in and releasing the autoinhibition of Src homology region 2 domaincontaining phosphatase-1.This phosphatase negatively regulates STAT3 activity,which leads to the subsequent apoptosis of cancer cells.The novel anti-cancer property of sorafenib will be discussed in this review,not only adding information regarding its mechanism of action but also providing an innovative approach for the development of cancer therapeutics in the future.
基金supported by National Natural Science Foundation of China(Grant Nos.51075012,10772008)Beijing Municipal Natural Science Foundation of China(Grant No.1122005)
文摘The fundamental shear horizontal（SH0） wave has several unique features that are attractive for long-range nondestructive testing（NDT）. By a careful design of the geometric configuration, electromagnetic acoustic transducers（EMATs） have the capability to generate a wide range of guided wave modes, such as Lamb waves and shear-horizontal（SH） waves in plates. However, the performance of EMATs is influenced by their parameters. To evaluate the performance of periodic permanent magnet（PPM） EMATs, a distributed-line-source model is developed to calculate the angular acoustic field cross-section in the far-field. Numerical analysis is conducted to investigate the performance of such EMATs with different geometric parameters, such as period and number of magnet arrays, and inner and outer coil widths. Such parameters have a great influence on the directivity of the generated SH0 waves that arises mainly in the amplitude and width of both main and side lobes. According to the numerical analysis, these parameters are optimized to obtain better directivity. Optimized PPM EMATs are designed and used for NDT of strip plates. Experimental results show that the lateral boundary of the strip plate has no perceivable influence on SHO-wave propagation, thus validating their used in NDT. The proposed model predicts the radiation pattern ofPPM EMATs, and can be used for their parameter optimization.
基金Supported by National Natural Science Foundation of China(Grant No.51375217)
文摘Cracks, especially small cracks are di cult to be detected in oil and gas transportation pipelines buried underground or covered with layers of material by using the traditional ultrasonic inspection techniques. Therefore, a new com?posite ultrasonic transducer array with three acoustic beam incidence modes is developed. The space model of the array is also established to obtain the defect reflection point location. And the crack ultrasound image is thus formed through a series of small cubical elements expanded around the point locations by using the projection of binariza?tion values extracted from the received ultrasonic echo signals. Laboratory experiments are performed on a pipeline sample with di erent types of cracks to verify the e ectiveness and performance of the proposed technique. From the image, the presence of small cracks can be clearly observed, in addition to the sizes and orientations of the cracks. The proposed technique can not only inspect common flaws, but also detect cracks with various orientations, which is helpful for defect evaluation in pipeline testing.
基金Project supported by the National Natural Science Foundation of China (No. 50875057)the Natural Scientific Research Innova-tion Foundation in Harbin Institute of Technology,China (No. HIT. NSRIF.2008.50)
文摘This paper presents a piezoelectric-metal structure called a drum transducer. An equation for calculating the resonance frequency of the drum transducer is obtained based on thin plate elastic theory of piezoelectric and metal material combined with the Rayleigh-Ritz method. The finite element method (FEM) was used to predict the excitation frequency of the drum transducer. To verify the theoretical analysis, the input impedance characteristic of the drum transducer was measured using an experimental method. The results obtained from theoretical analysis were in very good agreement with those from the FEM and experimental results. The effect of geometrical changes to the thick-walled steel ring of the drum transducer at the first resonance frequency is also described. The calculated results were found to be in good agreement with the FEM results. The results indicate that the first resonance frequency of the drum decreases with the increasing inner diameter of the thick-walled steel ring.
基金Project(11174077)supported by the National Natural Science Foundation of ChinaProject(11JJ3079)supported by the Hunan Provincial Natural Science Foundation of ChinaProjects(12C0237,11C0844)supported by the Science Research Program of Education Department of Hunan Province,China
文摘High intensity focused ultrasound(HIFU)therapy is an effective method in clinical treatment of tumors,in order to explore the bio-heat conduction mechanism of in multi-layer media by concave spherical transducer,temperature field induced by this kind of transducer in multi-layer media will be simulated through solving Pennes equation with finite difference method,and the influence of initial sound pressure,absorption coefficient,and thickness of different layers of biological tissue as well as thermal conductivity parameter on sound focus and temperature distribution will be analyzed,respectively.The results show that the temperature in focus area increases faster while the initial sound pressure and thermal conductivity increase.The absorption coefficient is smaller,the ultrasound intensity in the focus area is bigger,and the size of the focus area is increasing.When the thicknesses of different layers of tissue change,the focus position changes slightly,but the sound intensity of the focus area will change obviously.The temperature in focus area will rise quickly before reaching a threshold,and then the temperature will keep in the threshold range.
基金the National Key R&D Program of China(Nos.2017YFA0205103 and 2018YFE020505)the National Natural Science Foundation of China(Nos.81571766 and 61771337)+1 种基金the Natural Science Foundation of Tianjin,China(No.17JCYBJC24400)the“111”Project of China(No.B07014).
文摘An air parametric array can generate a highly directional beam of audible sound in air,which has a wide range of applications in targeted audio delivery.Capacitive micromachined ultrasonic transducer(CMUTs)have great potential for air-coupled applications,mainly because of their low acoustic impedance.In this study,an air-coupled CMUT array is designed as an air parametric array.A hexagonal array is proposed to improve the directivity of the sound generated.A finite element model of the CMUT is established in COMSOL software to facilitate the choice of appropriate structural parameters of the CMUT cell.The CMUT array is then fabricated by a wafer bonding process with high consistency.The performances of the CMUT are tested to verify the accuracy of the finite element analysis.By optimizing the component parameters of the bias-T circuit used for driving the CMUT,DC and AC voltages can be effectively applied to the top and bottom electrodes of the CMUT to provide efficient ultrasound transmission.Finally,the prepared hexagonal array is successfully used to conduct preliminary experiments on its application as an air parametric array.
基金Supported by National Natural Science Foundation of ChinaNo. 39670671, No. 30471531
文摘AIM： To study the effect of Hepatitis C virus nonstructural 5A （HCV NSSA） on IFNα induced signal transducer and activator of transcription-1 （STAT1） phosphorylation and nuclear translocation.METHODS： Expression of STAT1 Tyr701 phosphorylation at different time points was confirmed by Western blot, and the time point when p-STAT1 expressed most, was taken as the IFN induction time for further studies. Immunocytochemistry was used to confirm the successful transient transfection of NS5A expression plasmid. Immunofluorescene was performed to observe if there was any difference in IFNα-induced STAT1 phosphorylation and nuclear translocation between HCV NSSA-expressed and non-HCV NSSA-expressed cells. Western blot was used to compare the phosphorylated STAT1 protein of the cells.RESULTS： Expression of HCV NS5A was found in the cytoplasm of pCNS5A-transfected Huh7 cells, but not in the PRC/ CMV transfected or non-transfected cells, STAT1 Tyr701 phosphorylation was found strongest in 30 min of IFN induction, STAT1 phosphorylation and nuclear import were much less in the presence of HCV NS5A protein in contrast to pRC/CMV-transfected and non-transfected cells under fluorescent microscopy, which was further confirmed by Western blot.CONCLUSION： HCV NSSA expression plasmid is successfully transfected into Huh7 cells and HCV NS5A protein is expressed in the cytoplasm of the cells. IFN-α is able to induce STAT1 phosphrylation and nuclear translocation, and this effect is inhibited by HCV NS5A protein, which might be another possible resistance mechanism to interferon alpha therapy.
基金National Science Foundation of China(Grant No.10772142)National Natural Science Key Foundation of China(Grant No.10832002)the Fundamental Research Funds for the Central Universities
文摘A hybrid calibration approach based on support vector machines （SVM） is proposed to characterize nonlinear cross coupling of multi-dimensional transducer. It is difficult to identify these unknown nonlinearities and crosstalk just with a single conventional calibration approach. In this paper, a hybrid model comprising calibration matrix and SVM model for calibrating linearity and nonlinearity respectively is built up. The calibration matrix is determined by linear artificial neural network （ANN）, and the SVM is used to compensate for the nonlinear cross coupling among each dimension. A simulation of the calibration of a multi-dimensional sensor is conducted by the SVM hybrid calibration method, which is then utilized to calibrate a six-component force/torque transducer of wind tunnel balance. From the calibrating results, it can be indicated that the SVM hybrid calibration method has improved the calibration accuracy significantly without increasing data samples, compared with calibration matrix. Moreover, with the calibration matrix, the hybrid model can provide a basis for the design of transducers.
基金Funded by the National Natural Sciences Foundation of China (No.10874090)Jiangsu Provincial High-Tech Project of China (No.BG2006005)
文摘A novel traveling wave ultrasonic motor was proposed. The structure of the motor is rather simple and different from the conventional traveling wave ultrasonic motors. Its production processes are very convenient. It is composed of a stator constituted with a ring and a bar shaped transducer and two cone shaped rotors. The rotors were pressed on inner surface of the ring by means of a pre-pressure system. The bar shaped transducer has a sand- wich-like configuration,where two sets of piezoelectric element are bolted. One set excites a longitudinal vibration of the bar, and the other set excites a flexural vibration of the bar. The ring＇s traveling wave excited with the longitudinal vibration and the bending vibration of the bar transducer was simulated with FEM （finite element method）. The prototype of the motor was made and investigated experimentally for its performance. Its maximum torque and rotating speed are 0.25 N · m and 50 r/min, respectively.
