Search

Background: After the discovery of membrane-reversible electroporation decades ago, the procedure has been used extensively in biology, biotechnology and medicine. The research on the basic mechanism has increasingly attracted attention. Although most research has focused on models that consider all atomic and molecular interactions and much atomic-level information can be obtained, the huge computational demand limits the models to simulations of only a few nanometers on the spatial scale and a few nanoseconds on the time scale. In order to more comprehensively study the reversible electroporation mechanism of phospholipid membrane on the nanoscale and at longer time intervals of up to 100 ns, we developed a dipalmitoylphosphatidylcholine (DPPC) phospholipid membrane model with the coarse-grained Martini force field. The model was tested by separately examining the morphology of the phospholipid membrane, the hydrophilic channel size, the distribution of the voltage potential on both sides of the membrane, and the movement of water molecules and ions during electroporation.Results: The results showed that the process went through several stages: (1) the formation of the pore with defects originating on the surface. (2) The maintenance of the pore. The defects expanded to large pores and the size remains unchanged for several nanoseconds. (3) Pore healing stage due to self-assembly. Phospholipid membrane shrunk and the pore size decreased until completely closed. The pores were not circular in cross-section for most of the time and the potential difference across the membrane decreased dramatically after the pores formed, with almost no restoration of membrane integrity even when the pores started to close.Conclusions: The mechanism of the reversible electroporation process on the nanoscale level, including defects, expansion, stability, and pore closing stages on a longer time scale of up to 100 ns was demonstrated more comprehensively with the coarse-grained Martini force field, which took both the necessary molecular information and the calculation efficiency into account. [ABSTRACT FROM AUTHOR]

Marx generator using all-solid-state devices has been studied for many years. Higher parameters are always the demand for new applications. Traditional all-solid-state Marx generator can output high voltage due to its series topology, but the current is always limited by the switch. In this paper, a stage-stage paralleled topology of Marx generator for high current has been proposed. Topology structure and driving mode comparison for current balance have been analyzed. The paralleled driving mode for the current balance and the shaping waveform has been proposed. For experiment, a four-stage-four-paralleled Marx generator with metal–oxide–semiconductor field-effect transistors (MOSFETs) has been constructed with output pulses 2.2 kV, 730 A (depending on the load), rise time of 31 ns, fall time of 56 ns, and adjustable pulsewidth from 400 to 800 ns. [ABSTRACT FROM AUTHOR]

Background: Pulmonary nodules are an early imaging indication of lung cancer, and early detection of pulmonary nodules can improve the prognosis of lung cancer. As one of the applications of machine learning, the convolutional neural network (CNN) applied to computed tomography (CT) imaging data improves the accuracy of diagnosis, but the results could be more consistent. Purpose: To evaluate the diagnostic performance of CNN in assisting in detecting pulmonary nodules in CT images. Material and Methods: PubMed, Cochrane Library, Web of Science, Elsevier, CNKI and Wanfang databases were systematically retrieved before 30 April 2023. Two reviewers searched and checked the full text of articles that might meet the criteria. The reference criteria are joint diagnoses by experienced physicians. The pooled sensitivity, specificity and the area under the summary receiver operating characteristic curve (AUC) were calculated by a random-effects model. Meta-regression analysis was performed to explore potential sources of heterogeneity. Results: Twenty-six studies were included in this meta-analysis, involving 2,391,702 regions of interest, comprising segmented images with a few wide pixels. The combined sensitivity and specificity values of the CNN model in detecting pulmonary nodules were 0.93 and 0.95, respectively. The pooled diagnostic odds ratio was 291. The AUC was 0.98. There was heterogeneity in sensitivity and specificity among the studies. The results suggested that data sources, pretreatment methods, reconstruction slice thickness, population source and locality might contribute to the heterogeneity of these eligible studies. Conclusion: The CNN model can be a valuable diagnostic tool with high accuracy in detecting pulmonary nodules. [ABSTRACT FROM AUTHOR]

This study intends to achieve simultaneous vibration suppression and energy harvesting using a variant form of nonlinear energy sink (NES). The proposed apparatus is not a true NES as its spring is not essentially nonlinear. In a previous study [22] (Journal of Sound and Vibration, 333 (20) (2014)), it has been shown that the apparatus demonstrates the transient behaviors similar to those of the NES. As a sequel, the present paper focuses on harmonically forced responses of the system. First, the approximate solutions of steady state responses are derived. Using the approximate solutions, the steady state behaviors are investigated by using the numerical continuation method. This is followed by an experimental study. The study has shown that under harmonic excitation, the proposed apparatus functions similarly to the NES with the typical behaviors such as strongly modulated responses, amplitude jumping, excitation level dependence, etc. Overall, the apparatus meets the design objectives: the vibration suppression and energy harvesting in a broadband manner. [ABSTRACT FROM AUTHOR]

This paper focuses on suppression of free vibration of single degree-of-freedom systems that possess time delay. The switchable stiffness (SS) control strategy is reviewed. The implication of time delay is examined. It shows that the system delay can cause malfunction of the direct SS control. To overcome this problem, the two time-delay control strategies are proposed. The first strategy named as half period delay SS control introduces an intentional delay such that the switch action takes place in a half of oscillation period later. The second strategy named as quarter period delay SS control is to add an intentional delay such that the switch action occurs in a quarter of oscillation period later. In this case, the SS control law is inverted. An apparatus consisting of an electromagnetic (EM) spring is developed to validate the proposed strategies. The stiffness models of the system are established. In computer simulation, three cases have been examined. In case A, the system is simplified as linear and the dynamics of the EMs is neglected. In case B, the stiffness models are used and the dynamics of the EMs is neglected. In case C, the stiffness models are used and the dynamics of the EMs is considered. An experimental study is conducted in real time. The results have validated the observations obtained from the computer simulations. [ABSTRACT FROM AUTHOR]

The parallel operation of array microhollow cathode (MHC) discharges is studied to generate high density of electrons owing to its multichannel MHC discharges. To ignite all the holes synchronously in one pulse, a pretrigger device is introduced, which is composed of three layers (two electrode layers and a dielectric layer). With the pretrigger process, some initial electrons can be injected into the holes, which makes array MHCs easier to ignite and improves the behavior of parallel operation. In this paper, the array MHC discharges with pretrigger in one pulse mode are presented and the influence on the parallel operation of the pretrigger process is studied. At last, the simulation result is given to have a better understanding of the pretrigger mechanism. [ABSTRACT FROM AUTHOR]

• A non-traditional nonlinear energy sink (NES) is proposed for the purpose of vibration suppression and energy harvesting. • A multi-objective optimization is conducted to examine the trade-off between vibration suppression and energy harvesting. • The optimal performance of the proposed non-traditional NES is compared with that of an optimally tuned non-traditional TMD. • An experimental study is conducted to validate the simulation results. In this article, an apparatus is proposed for simultaneous vibration suppression and energy harvesting in a broad frequency band. Traditionally, both the spring and the damper of a vibration absorber are directly connected to a primary system. Alternatively, a non-traditional way is to place the damper of the vibration absorber between the absorber mass and the base. A nonlinear energy sink (NES) is a type of nonlinear vibration absorber with an essential nonlinearity. When a strong nonlinear oscillator with a small linear stiffness is weakly coupled to a primary system, it behaves similarly to the NES, which is termed "variant NES". In the proposed apparatus, a variant NES is arranged in the non-traditional way in which a cantilever beam is placed between a pair of continuous-contact blocks which force the beam to deflect nonlinearly. An electromagnetic energy harvester, which also acts as a damper in the non-traditional variant NES, is formed by attaching a pair of permanent magnets to the free end of the beam and fixing a pair of coils to the base. The transient performances of the developed apparatus are investigated in terms of vibration suppression and energy harvesting using numerical simulation and compared with those of an optimum non-traditional vibration absorber. The simulation results are validated by an experimental study. It is found that the proposed non-traditional variant NES exhibits typical NES characteristics such as 1:1 resonance, targeted energy transfer (TET), and an initial energy threshold. With the prerequisite of TET being established under high-level initial energy, the best trade-off between vibration suppression and energy harvesting is achieved when the NES's oscillation decays slowly under low electrical damping or quickly under high electrical damping. [ABSTRACT FROM AUTHOR]

The risk of tauopathies depends in part on the levels and modified composition of six Tau isoforms in the human brain. Abnormal phosphorylation of the Tau protein and the shift of the ratio of 3R Tau to 4R Tau are presumed to result in neurofibrillary pathology and neurodegeneration. Glycation has recently been linked to dementia and metabolic syndrome. To determine the contribution of Tau protein glycation and phosphorylation on Tau aggregation propensity, the assembled kinetics were examined in vitro using Thioflavin T fluorescence assays. We found that glycation and phosphorylation have different effects on aggregation propensity in different Tau isoforms. Different Tau proteins play important parts in each tauopathies, but 3R0N, fetal Tau protein, has no effect on tauopathies. Conversely, 4R2N has more modified sites and a higher tendency to aggregate, playing the most important role in 4R tauopathies. Finally, Glycation, which could modulate Tau phosphorylation, may occur before any other modification. It also regulates the 3R to 4R ratio and promotes 4R2N Tau protein aggregation. Decreasing the sites of glycation, as well as shifting other Tau proteins to 3R0N Tau proteins has potential therapeutic implications for tauopathies. [ABSTRACT FROM AUTHOR]

Various kinds of switches exhibit significant function in the field of pulse power. Among them Photoconductive Semiconductor Switch (PCSS) stands out because of its numerous advantages, such as low time jitter, fast response, high repetition rate, compact size, easy integration and so on. Laser Diode (LD) is small in size, low-cost and can be easily integrated compared with traditional laser devices. Waveguide tube is a kind of laser transmission device. By using LDs which emits laser pulse with a dominant wavelength of 905 nm and a waveguide tube, three different shapes of laser spot are obtained to trigger a semi-insulating GaAs PCSS which has vertical structure. Laser energy and laser power are fixed to 1 μJ and 33.3 W separately. As the illuminating area on the PCSS differs with different shapes of laser spot, the influences of average trigger energy per unit area to the output characteristics of the PCSS are studied. The experiment results demonstrate that not only the total trigger energy but also the energy density influences the characteristics of PCSS. This paper presents related experiment results, and some further discussions are given. [ABSTRACT FROM PUBLISHER]

This study focuses on the control of a novel active vibration isolator using an adaptive backstepping approach. The developed active isolator is introduced and its dynamic model is presented. It is shown that the unknown nonlinear restoring force and damping parameter pose control challenges. The nonlinear restoring force is approximated as a polynomial with unknown coefficients. Adaptive control is chosen as a suitable approach to tackle the control challenges. An existing lower-order adaptive backstepping controller is modified in order to include the actuator dynamics and avoid the zero convergence of the estimated parameter vector. An extensive experimental study is conducted to test the effectiveness of the modified controller. The performance of the controller is compared with that of the lower-order controller. The results from several testing scenarios are presented and interpreted, and the issues related to parameter estimation and control performance are addressed. [ABSTRACT FROM PUBLISHER]

Abstract: This paper investigates energy harvesting using nonlinear energy sink. First a novel apparatus is described in detail outlining how the essential nonlinearity and energy harvesting are achieved. Then the system modeling is addressed, including the equations of motion for the mechanical system and the electromechanical system, and a formula for the transduction factor. The experimental identification is conducted to determine several key parameters and relationships. Using the established models, a computer simulation is carried out to investigate the apparatus׳s performance under transient responses in terms of vibration absorption and energy harvesting. Finally experiments are conducted to validate the simulation results. It is shown that the system performs well, being capable of energy localization as well as broad band vibration absorption. The system is also shown to be capable of harvesting energy. [Copyright &y& Elsevier]

This paper presents the design for a novel all solid-state sub-microsecond pulse generator for dielectric barrier discharges (DBDs). This generator consists of a MARX generator, Blumlein transmission lines (BTLs) and one magnetic switch (MS). As a power supply, the all solid-state MARX generator is capable of outputting nanosecond-pulses with a voltage peak of up to 20 KV. The key elements are BTLs which are charged by the MARX generator. Due to the unmatched impedance of DBD load, energy stored in BTLs begins to oscillate through DBD load after the MS turns on. The violent oscillation lasts until all the energy is consumed. During the violent oscillation, over ten discharges are excited in 5 µs under a single-shot condition. Thus, extremely intense plasma can be produced due to the accumulation effect. The alternating-current decaying voltage over the MS has a demagnetization effect, and DC reset circuit can therefore be spared. Experiments with matched resistor load were also carried out, and rectangular pulses with voltage up to 20 kV and duration of 220 ns were obtained. The ratio of the energy consumed by the resistor from the energy stored in the BTLs is 84.9%. The DBD images under a single shot and 100 Hz are presented. [ABSTRACT FROM PUBLISHER]

A microhollow cathode discharge (MHCD) array was operated at atmospheric pressure with a pulse voltage of 2.5 kV supplied by a trigger circuit. Triggered by this MHCD array, a gas switch with an annular plate structure operated under a voltage of 27 kV with a fall time of 30 ns and a current of 400 A with a rise time of 15 ns was investigated. It is used for discharging the charge stored in a capacitor of 4 nF through a resistor of 50 \Omega. The advantages of the switch are obvious: a compact trigger with lower trigger voltage. An electrical model including MHCD capacitance is built, and the simulation results agree well with the experimental results. [ABSTRACT FROM PUBLISHER]

SUMMARY This work examines the characteristics of a unique active vibration isolator controlled by a time-delayed position feedback technique. The system under study possesses an appreciable time delay caused by the actuator dynamics. Firstly, direct absolute position and relative position feedbacks are considered. The study reveals several main differences between a negative position feedback and a positive position feedback. Secondly, stability analysis of the delayed position feedback is carried out. Two different feedbacks are studied, namely the delayed negative and delayed positive position feedbacks. The stability chart is determined, and various root loci of the closed-loop systems are presented. Thirdly, an optimum controller design methodology is presented. A numerical optimization is conducted to find an optimum controller for each of the considered control cases. Lastly, an experimental study is conducted to validate the analytical and numerical results and demonstrate the effectiveness of the optimum controllers. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This paper is concerned with numerical simulation of both dynamic stability and responses of beams on elastic foundations under a pulsating axial parametric load in a single matrix method. First, the equation of motion of a beam on an elastic foundation with damping is derived and decoupled into a Mathieu–Hill equation. Three different elastic foundations are considered and compared: Winkler, Pasternak, and Hetenyi models. Then a novel numerical simulation algorithm is proposed to investigate both the dynamic stability and the responses of the beam simultaneously. Accurate instability diagrams are obtained by the numerical simulation and are substantiated by vibration response curves obtained from the same method. These numerically accurate diagrams are used to calibrate the approximate instability boundaries of various orders of Hill infinite determinants from the classical Bolotin method for the first time. A detailed discussion is presented on effects of various aspects including elastic foundation models, damping, and static and dynamic loads. The results provide insights into the efficient and safe application of beams on elastic foundations in engineering. The proposed numerical method can be extended to analyze dynamic stability and vibrations of systems under arbitrary parametric excitations where Mathieu–Hill equations are involved. [ABSTRACT FROM AUTHOR]

Abstract: This work examines the characteristics of a unique active vibration isolator and develops a control strategy for it. The proposed active vibration isolator is introduced and its dynamic model is presented. A characterization study is conducted to identify system parameters. It is shown that with a simple proportional feedback the closed-loop system has a very narrow stability margin due to the inherent dynamics of the actuator. To improve the stability of the closed-loop system and enhance the performance of vibration isolation, a phase compensator is incorporated in the control scheme. An optimization problem is formulated to determine the optimum controller parameters by minimizing the 2nd norm of the displacement transmissibility. Both absolute position feedback and relative position feedback are considered. In real time implementation, an automatic on/off switching strategy is devised to take full advantage of both the active isolator and passive isolator. The experimental results show that with the proposed control scheme, the isolator is capable of suppressing base excitations effectively. [ABSTRACT FROM AUTHOR]

Abstract: The paper presents a newly designed electromagnetic vibration absorber (EMVA), whose stiffness is on-line tunable. The EMVA is capable of suppressing vibration of the primary system excited by a harmonic force with a variable frequency. The EMVA consists of a clamped–clamped aluminum beam and a permanent magnet that is embedded in the center of the beam and placed between two poles of a C-shaped electromagnet. By varying the current of the electromagnet, stiffness of the EMVA can be adjusted instantaneously such that the absorber frequency can be tuned. A detailed characterization of the EMVA is presented. The effective stiffness of the absorber is determined numerically and validated experimentally. To test its effectiveness in vibration suppression, the EMVA is used to track two types of the exciting frequency variations: multi-step and linear. The response of the absorber mass is used to tune the EMVA to ensure that the absorber frequency equals the exciting frequency. [Copyright &y& Elsevier]

Abstract: This study focuses on extraction of frequency information of a linear time-varying system using free response data. Frequency information is obtained from the pseudo-modal parameters that were defined in a previous study. A subspace-based identification algorithm is introduced. An improved version is proposed to make the algorithm less sensitive to measurement noise. An axially moving cantilever beam is used as the experimental system. A dynamic model is presented to show that lateral vibration of the axially moving cantilever beam is governed by a linear time-varying model. A computer simulation is conducted to compare the true pseudo-modal parameters and approximate ones that can be identified using the improved algorithm. The experimental study focuses on the capabilities of the algorithm and the factors that affect the identification results. A method of grouping identified structural pseudo-natural frequencies is proposed. Limitations of the algorithm are discussed. [Copyright &y& Elsevier]

In this paper a piecewise linear nonlinear energy sink (PLNES) is developed for the purpose of simultaneous vibration suppression and energy harvesting. The apparatus consists of a cantilever beam attached by a mass at its free end. The beam is situated between a pair of double-stop blocks to constrain its lateral deflection. The stiffness characterization is conducted experimentally. The two combined systems, referred to as weak coupling and strong coupling, are constructed by attaching the PLNES to a stiff primary system and a flexible primary system, respectively. A computer simulation is conducted to investigate the transient performances of the two systems in terms of the targeted energy transfer and energy harvesting. The simulation results are examined by time responses, wavelet transform spectra, and the frequency energy plots. A multi-objective optimization is carried out to investigate the trade-off between vibration suppression and energy harvesting of the two systems. An experimental study is conducted to validate the simulation results. [ABSTRACT FROM AUTHOR]

• Equation of motion for viscoelastic columns with semi-rigid connections is derived. • Approximate boundaries of dynamic stability of viscoelastic systems are obtained. • A novel numerical simulation method is proposed for dynamic stability and responses. • Effects of various factors on viscoelastic column stability are investigated. Dynamic stability of structures is an essential topic in civil engineering analysis and design because collapse of critical structures due to dynamic excitations would cause loss of properties or even fatalities. This paper conducts theoretical analysis and numerical simulation investigations on both stability and responses of viscoelastic columns with semi-rigid connections/supports subjected to axial parametric loads. The equation of motion for the viscoelastic column is derived and decoupled into an ordinary differential equation with periodic coefficients by describing the viscoelasticity as the linear Kelvin–Voigt model. Theoretical analysis is performed by the method of harmonic balance and the approximate boundaries of dynamic stability are obtained. A novel numerical simulation method is proposed to investigate both dynamic stability and vibration responses of viscoelastic columns with semi-rigid connections. The approximate boundaries are calibrated by the numerical results. The effects of the material's viscoelasticity, the supports' rigidity, damping, and the static and dynamic component loads on the column stability are investigated through the numerical analysis. Two key findings of the study are that the greater the rigidity of the supports, the larger both the natural frequency and the critical dynamic load; and the viscosity of materials has a great positive impact on the dynamic stability of viscoelastic columns. The proposed method can be extended to systems under arbitrary periodic parametric excitations. [ABSTRACT FROM AUTHOR]

Background: The use of high-frequency electric welding technology for intestinal end-to-end anastomosis holds significant promise. Past studies have focused on in vitro, and the safety and efficacy of this technology is uncertain, severely limiting the clinical application of this technology. This study investigates the impact of compression pressure, energy dosage, and duration on anastomotic quality using a homemade anastomosis device in both in vitro and in vivo settings. Methods: Two hundred eighty intestines and 5 experimental pigs were used for in vitro and in vivo experiments, respectively. The in vitro experiments were conducted to study the effects of initial pressure (50–400 kpa), voltage (40–60 V), and time (10–20 s) on burst pressure, breaking strength, thermal damage, and histopathological microstructure of the anastomosis. Optimal parameters were then inlaid into a homemade anastomosis and used for in vivo experiments to study the postoperative porcine survival rate and the pathological structure of the tissues at the anastomosis and the characteristics of the collagen fibers. Results: The anastomotic strength was highest when the compression pressure was 250 kPa, the voltage was 60 V, and the time was 15 s. The degree of thermal damage to the surrounding tissues was the lowest. The experimental pigs had no adverse reactions after the operation, and the survival rate was 100%. 30 days after the operation, the surgical site healed well, and the tissues at the anastomosis changed from immediate adhesions to permanent connections. Conclusion: High-frequency electric welding technology has a certain degree of safety and effectiveness. It has the potential to replace the stapler anastomosis in future and become the next generation of new anastomosis device. [ABSTRACT FROM AUTHOR]

An approach that combines the transfer matrix method (TMM) and single variable model updating is proposed to determine the natural frequencies and mode shapes of a cantilever beam formed by an adhesively bonded single lap joint (SLJ). When the TMM is applied to the SLJ beam, the key is to determine the effective density and effective elastic modulus for the overlap region element. In this study, the effective density is determined using a volume fraction approach and the effective elastic modulus is determined using a single variable model updating approach. This approach is compared with a commonly used additive approach to determine the overlap region effective elastic modulus. The performance of the proposed single variable model updating approach is evaluated using a finite element model and experimental testing as benchmarks. The proposed single variable TMM model updating approach consistently outperforms the additive approach for the single lap joint specimens considered. Further, the robustness and general applicability of the overlap region effective elastic modulus are demonstrated, including its ability to deal with uncertainty. Insights about the impact of selected structural modifications on the natural frequencies of the single lap joint specimens are discussed. [ABSTRACT FROM AUTHOR]

Electroporation has been widely used in biology, medicine, and the food industry as a means to transport various molecules through the cell membrane. The phenomenon of electroporation is the result of cell membrane damage caused by the application of an electric field. In order to understand more precisely how cells function, we established a dielectric model of a spherical cell and analyzed its characteristics by the finite element method. The effects of altering different electrical parameters were determined. The results showed that the electric field strength was positively related to the transmembrane voltage (TMV) and pore density. There was a minimum electric field strength necessary to induce a critical TMV for the formation of pores. Pulse width also had to be long enough to charge the cell membrane, compared with the normal membrane charging time constant of about 1 μs. When the pulse width was shorter than the charging time constant, it was necessary to increase pulse frequency to create a high enough TMV. The rise-time of the electric pulse also affected electroporation: a fast rise-time pulse not only allowed penetration of the plasma membrane but also the organelle membrane. With slow rise-time pulse, the organelle was shielded from electroporation. This study defines the response characteristics of electrical parameters on the electric load cell and establishes the specificity of parameters for different purposes. [ABSTRACT FROM AUTHOR]

Objectives: To identify prognostic CT features that predict recurrence in patients with resectable pancreatic body/tail adenocarcinoma (PBTA) and construct a CT-based nomogram for preoperative risk stratification. Methods: A total of 258 patients with resectable PBTA who underwent upfront surgery were retrospectively enrolled (development cohort, n = 172; validation cohort, n = 86), and their clinical and CT features were analyzed. Stepwise Cox proportional hazard analysis was performed to identify prognostic features and construct a predictive nomogram for recurrence-free survival (RFS). The prognostic performance of the CT-based nomogram was validated and compared to the 8th American Joint Committee on Cancer (AJCC) pathological staging system. Results: In the development cohort, the following five CT features for predicting recurrence were identified to construct the nomogram: tumor density in the venous phase, tumor necrosis, adjacent organ invasion, splenic vein invasion, and superior mesenteric vein/portal vein abutment. In the validation cohort, the CT-based nomogram showed a concordance index of 0.65 (95% confidence interval: 0.58–0.73), which was higher than the 8th AJCC staging system. The area under the curves of the nomogram for predicting recurrence at 0.5, 1, and 2 years were 0.66, 0.71, and 0.72, respectively. Patients were categorized into high- and low-risk groups with 1-year recurrence probabilities of 0.73 and 0.43, respectively. Conclusions: The proposed nomogram provided accurate recurrence risk stratification for patients with resectable PBTA in a preoperative setting and may be used to facilitate clinical decision-making. Clinical relevance statement: The proposed CT-based nomogram, based on easily available CT features, may serve as an effective and convenient tool for stratifying further the recurrence risk of patients with pancreatic body/tail adenocarcinoma. Key Points: • The CT-based nomogram, incorporating five commonly used CT features, successfully preoperatively stratified patients with resectable PBTA into distinct prognosis groups. • Tumor density in the venous phase, tumor necrosis, splenic vein invasion, adjacent organ invasion, and superior mesenteric vein/portal vein abutment were associated with RFS in patients with resectable PBTA. • The CT-based nomogram exhibited better predictive performance for recurrence than the 8th AJCC staging system. [ABSTRACT FROM AUTHOR]

Tetracycline is one of the widely used antibiotic drugs, but it also causes severe water pollution. This research applied a pulsed dielectric barrier discharge (DBD) plasma reactor of coaxial configuration with a screw-type high-voltage electrode to treat tetracycline in an aqueous solution, which was recycled to flow over the surface of the inner electrode. The effects of discharge voltage, initial concentration, and pH value of tetracycline on the degradation efficiency, total organic carbon (TOC) removal rate, kinetic rate constant (${k}$), and energy efficiency were investigated. The results show that 92.3% degradation efficiency and 65.01% TOC removal rate of tetracycline were achieved at the initial concentration of 50 mg/L, corresponding to the energy efficiency of 20.24 g/(kW $\cdot \text{h}$). The tetracycline degradation efficiencies were dependent on the initial concentration from 5 to 75 mg/L, which led to the decrease of the degradation kinetic rate constant from 0.518 to 0.077 min $^{-1}$. The TOC removal rate of tetracycline was strongly enhanced at higher pH values from 1.5 to 10.5, with the optimum value at 7.5. The intermediate products of tetracycline produced by the plasma treatment were analyzed by liquid chromatography mass spectrometry (LC-MS), which show that the aromatic ring, amino group, and the double bonds were mainly attacked by the hydroxyl radical and other reactive oxygen species. A possible degradation pathway has also been proposed. [ABSTRACT FROM AUTHOR]

Underwater sparks have long been used in many fields, but up until now there are no widely accepted model for them. In this article we present a more practical model for them, taking into account the nature of the plasma of pulsed discharge in water, where the following corrections are included: (1) correction of the ionization potentials; (2) pressure caused by the effect of charge interaction on the bound state electrons; (3) line spectra; and (4) mass flow caused by evaporation, condensation, and bubble wall ablation. Using this model, the time-varying pressure, temperature, and density can be obtained for given circuit parameters. The simulation results are in good agreement with the experimental measurements. We also give a simulation with capacitance of 1.25 nF, initial voltage of 4×10[sup 4] V, circuit inherent inductance of 20 nH, and circuit resistance of 15 mΩ; the maxima of the pressure, temperature, and electron density are about 5×10[sup 4] K, 5×10[sup 3] atm, and 4×10[sup 26] m[sup -3], respectively. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

(1) Background: To investigate the correlation between the integrity of the left dual-stream frontotemporal network mediated by the arcuate fasciculus (AF) and uncinate fasciculus (UF), and acute/subacute post-stroke aphasia (PSA). (2) Methods: Thirty-six patients were recruited and received both a language assessment and a diffusion tensor imaging (DTI) scan. Correlations between diffusion indices in the bilateral LSAF/UF and language performance assessment were analyzed with correlation analyses. Multiple linear regression analysis was also implemented to investigate the effects of the integrity of the left LSAF/UF on language performance. (3) Results: Correlation analyses showed that the diffusion indices, including mean fractional anisotropy (FA) values and the fiber number of the left LSAF rather than the left UF was significantly positively associated with language domain scores (p < 0.05). Multiple linear regression analysis revealed an independent and positive association between the mean FA value of the left LSAF and the percentage score of language subsets. In addition, no interaction effect of the integrity of the left LSAF and UF on language performance was found (p > 0.05). (4) Conclusions: The integrity of the left LSAF, but not the UF, might play important roles in supporting residual language ability in individuals with acute/subacute PSA; simultaneous disruption of the dual-stream frontotemporal network mediated by the left LSAF and UF would not result in more severe aphasia than damage to either pathway alone. [ABSTRACT FROM AUTHOR]

This paper puts forward a repetitive high-voltage pulse modulator, consisting of a step-up pulse transformer to decrease the number of needed semiconductor switches, and a bipolar Marx generator to reduce the turns ratio of PT, leakage inductance, and distributed capacitance, and also to improve the pulse shape. An equivalent circuit of the proposed modulator considering parasitic elements is established. Based on the equivalent circuit, circuit operation is analyzed in detail. In order to verify the theory analysis and circuit operation, simulations are conducted. In addition, a laboratory prototype is implemented. The simulations and experimental results of resistive load and dielectric-barrier discharges load turn out matched quite well with the theory analysis, demonstrating that the prototype can operate with a voltage amplitude in the range of 0–25 kV, a repetition rate of 0.1–5-kHz stably. [ABSTRACT FROM AUTHOR]

Excellent performances such as ultrafast rise-time, low jitter, good synchronization and high electric-field strength make photoconductive semiconductor switches (PCSSs) have a wider prospect of application. Among other parameters, it is very important to evaluate the on-state resistance of the PCSS. In this paper, the influence of bias voltage, on-state current and trigger position on the on-state resistance of GaAs PCSS is described. We extracted the relationship between the elements mentioned above and the on-state resistance from our experimental data. The on-state resistance decreases with increasing bias voltage as well as increasing on-state current. The best trigger position was evaluated to be on the cathode. The on-state resistance increases as the trigger position shifts from cathode to anode gradually. The experimental results are further discussed in this paper. [ABSTRACT FROM AUTHOR]

When driving capacitive loads, pulses with steep falling edges are difficult to obtain using conventional pulsed power modulators, which also makes them unsuitable for operating at higher frequencies. In this paper, a repetitive high voltage pulse adder is described, which can generate nearly rectangular pulses even with capacitive loads. This pulse adder is based on solid-state switches, and each power stage contains two Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs): one set which outputs high voltage pulses and the other set which is used to dissipate charges stored in the load and distributed capacitors. Testing the proposed pulse adder with dielectric barrier discharge (DBD) loads, nearly rectangular pulses are obtained. In our present work, a 40-stage modulator has been built and successfully operates at an output voltage of 30 kV and a repetitive frequency of 20 kHz. The rise and fall times are less than 200 ns, and a minimum pulse width of 6 μs was obtained. This prototype has been applied in DBD experiment research. [ABSTRACT FROM AUTHOR]

This paper explores the feasibility of a new triggering technology that is based on reversed-LTD (linear transformer driver) principle. The triggering technology which is named as LTD-trigger has a similar structure to LTD device, but it operates reversely relative to LTD. The LTD-trigger is small size and can obtain multiple trigger pulsed voltages flexible with one single primary high-voltage pulsed power supply. It reduces the delay and jitter time due to the intrinsic advantages from coaxial configuration over the conventional triggering method. The paper analyzed the working principle of LTD-trigger by establishing an equivalent circuit model and an experimental prototype, which is able to generate 20 trigger pulses with voltage amplitude of about 22 kV and rise time of about 75 ns. Simulation and experimental results show a good performance of synchronization among the output trigger pulses of different cavities. Taking some fault factors into consideration, the experimental results show the reliability of LTD-trigger. [ABSTRACT FROM AUTHOR]

In many pulsed power applications, high voltage and high frequency square pulses are needed. Traditional Marx type modulators based on solid-state switches often couldn't meet the requirements, especially on frequency and waveform. To solve the problems, a novel solid-state pulsed power modulator based on charging and driving by magnetic ring transformers is introduced in this paper. In order to obtain pulses with steep voltage edges on various kinds of loads, half bridges formed by MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) switches are used in the modulator. The usage of magnetic rings makes the stray capacitance become one of the most important aspects to distort the output voltage waveforms. The effect of stray parameters on output waveforms is analyzed in detail in this paper. According to the analysis, this paper deals with a design of the pulsed power modulator with isolated recharge for dielectric barrier discharge (DBD) research, In order to design much more suitable pulse modulators, some methods are described to reduce the influence of the stray parameters. [ABSTRACT FROM AUTHOR]

An all solid-state Marx modulator utilizing Insulated Gate Bipolar Translators (IGBTs) is capable of outputting pulses with variable pulse width, repetitive pulse frequency and varying voltage amplitude. But the relatively slow turn-on speed of IGBT with high current loads result in slow rise time of output pulses. If a magnetic switch (MS) is combined with an all solid-state Marx, it will be quite simple to obtain nanosecond pulses with rise times under 100 ns. In this paper, several topologies for pulsed generators are proposed based on an all solidstate Marx and MS. When MS is connected in series with Marx, the rise time of the 200-Ampere load pulse is reduced from 560 ns to 85 ns. Besides, the switch-on loss of all IGBTs is considerably reduced. When a peaking capacitor is added, a 30 kV exponential decaying pulse with a rise time of 36 ns is obtained on a 100 ? resistor load. When the peaking capacitor is replaced by 20 m long pulse forming line (PFL), a 12.4 kV rectangular pulse with 223 ns pulse width (full width at half maximum), 44 ns rise time and 56 ns fall time is obtained on a 50 Ω resistor load. When the PFL is replaced by a Blumlein Transmission Line (BTL), the amplitude of the load voltage can be doubled on the price of a larger pre-pulse. Besides, generator with BTLs is quite proper for dielectric barrier discharge (DBD) loads. Experiments show that over 10 DBDs are excited in 4 μs under a single shot, which means extremely intense plasma is produced due to the accumulation effect. This phenomenon suggests great potential value for industrial applications. [ABSTRACT FROM AUTHOR]

This paper considers the problem of the adaptive fuzzy tracking control for a class of nonaffine stochastic nonlinear systems without lower triangular form. By using fuzzy logic systems' universal approximation property, an adaptive fuzzy controller is proposed, which guarantees that all the signals in the closed-loop system are bounded in the sense of mean quartic value and the output tracking error eventually converges to a small neighborhood around the origin. Simulation results are provided to illustrate the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the di/dt capability and the turn-on action of conventional thyristors (including common thyristor and GTO) under short pulse conditions. Although the common thyristor is proven to be not adequate for pulse application, the GTO behaves excellently and it exhibits the potential of being operated in the case of much higher di/dt and pulse current than its rated values. Multi-cell PSpice simulation model of GTO was developed to evaluate influence factors of current distribution in thousands units of the GTO. It was found that forward transport time (TF) of excess carriers flowing through base region in each unit mainly determines the current distribution. If some unit has smaller TF, it will bear larger current compared with others in the turn-on process and thus has the risk of overheating. The use of magnetic switch in series with GTO can greatly reduce the power dissipation in the process and guarantee the GTO?s safe operation. Our tests have originally resulted in a maximum di/dt of 6 kA/μs for a 10-μs half-sine wave current pulse of 17.3 kA amplitude by using a GTO, whose rated RMS on-state current is 1500 A and di/dt capability is 800 A/μs. The measurements show that turn-on losses and conduction losses are less than 0.5 J. [ABSTRACT FROM AUTHOR]

To investigated morphological variability of vertebral artery (VA) origin and its entrance level into cervical transverse foramina by computed tomography angiography (CTA). To retrospectively investigated CTA of 223 subjects (446 VA courses). Investigated were origin of the VA and its level of entrance into vertebral transverse foramen with notification of the sex and side of variation. The VA entered the C6 transverse process in 91.70% of specimens (409 out of 446 VA courses). Abnormal entrance of VA was observed in 8.30% of specimens (37 VA courses), with the level of entrance into the C3, C4, C5, or C7 transverse foramen at 0.22%, 2.47%, 4.71% and 0.90% respectively. Comparably, the overall variability of abnormal origin of VA was 1.57% (7 out of 466 VA courses), in which the left vertebral arteries all arose from aortic arch. The variation rate of vertebral entrance rose up to 50% in abnormal origin subgroup. When comparing subgroups of subjects with normal and abnormal origin, there was significance difference in the frequency of entrance variation in the level of transverse foramen (p < 0.001). Abnormal entrance and origin of VA were observed in 8.30% and 1.57% of VA courses, which can be accurately appeared by CTA. Regarding to the subgroups of abnormal origin, the frequency of entrance variation was significantly increased in the level of transverse foramen compared to that of normal origin. [ABSTRACT FROM AUTHOR]

In this paper, a self-triggering linear transformer driver (LTD) technology based on the principle of electromagnetic induction is presented. A detailed circuit model of the self-triggering LTD module is established in PSPICE to explore the feasibility of the self-triggering method. Through simulation and analysis, an original design of a prototype self-triggering LTD is established. Some factors, which influence the performance of the self-triggering LTD are demonstrated and analyzed thoroughly in this paper, such as peaks of induced trigger voltages and pre-magnetizing. Simulation results indicate that all induction cavities in the self-triggering LTD module can be triggered with an easier external trigger method and the cavity triggering sequence is acceptable. The peak current at the output of self-trigger LTD module is in the range of 0.96 MA to 1.01 MA and the 10-90% rise time is about 31ns in the simulation. [ABSTRACT FROM PUBLISHER]

The application of non-thermal plasma excited by strong electric fields is becoming a key technology for water treatment because of the efficient generation of oxidants, such as hydroxyl radicals, and no secondary pollution. In this paper, a water treatment system mainly consisting of a pulsed power generator and a dielectric barrier discharge reactor was constructed. The reactor consists of five rows of staggered positive and negative electrodes and separating plates. Wastewater dropped into the discharge area from the tiny holes in the separating plates. Degradation of indigo carmine solution was attempted by this system. The effects of discharge time, discharge voltage, frequency, initial pH value, and H2O2 were studied. The degradation rate came to 100% in 8 minutes at the voltage of 30 kV and frequency of 200 Hz under the initial concentration of 450 mg/L. The energy cost of the degradation of indigo carmine reached 80 g/kWh. [ABSTRACT FROM PUBLISHER]

The success rate of the electrosurgical high-frequency electric field welding technique lies in reasonable control of the welding time. However, the final impedance value used to control the welding time varies due to differences in tissue size and the welding method during the welding process. This study aims to introduce a new reference indicator not limited by impedance size from dynamic impedance to achieve an adequate weld strength with minimal thermal damage, providing feedback on the tissue welding effect in medical power supplies. End-to-end anastomosis experiments were conducted with porcine small intestine tissue under seven levels of compression pressure. The dynamic impedance changes were analyzed, combined with compression pressure, temperature, moisture, and collagen during welding. The welding process was divided into three stages according to the dynamic impedance, with impedance decreasing in Period Ⅰ and impedance increasing in Period Ⅲ. Period Ⅲ was the key to high-strength connections due to water evaporation and collagen reorganization. The dynamic impedance ratio is defined as the final impedance divided by the minimum impedance, and successful welding would be predicted when detecting the dynamic impedance ratio over 4 (n = 70, p < 0.001). Dynamic impedance monitoring can be used as a macroscopic real-time prediction of the anastomosis effect. [ABSTRACT FROM AUTHOR]

In this study, an adaptive neural backstepping control scheme is proposed for a class of strict‐feedback non‐linear systems with unmodelled dynamics, dynamic disturbances and input saturation. To solve the difficulties from the unmodelled dynamics and input saturation, a dynamic signal and smooth function in non‐affine structure subject to the control input signal are introduced, respectively. Radial basis function (RBF) neural networks are used to approximate the packaged unknown non‐linearities, and an adaptive neural control approach is developed via backstepping, which guarantees that all the signals in the closed‐loop system are semi‐globally uniformly ultimately bounded in mean square. The main contributions of this note lie in that a control strategy is provided for a class of strict‐feedback non‐linear systems with unmodelled dynamics uncertainties and input saturation, and the proposed control scheme does not require any information of the bound of input saturation non‐linearity. Simulation results are used to show the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, the problem of the adaptive neural control is considered for a class of pure-feedback stochastic nonlinear systems. Based on the radial basis function (RBF) neural networks' universal approximation property, an adaptive neural controller is developed via backstepping technique. It is shown that the proposed controller can guarantee that all the signals in the closed-loop system are bounded in the sense of mean quartic value. Compared with the existing results on adaptive control of stochastic pure-feedback nonlinear systems, the main novelty of this note is that a systematic design procedure is presented for a class of pure-feedback stochastic nonlinear systems with a more general form of the diffusion term. Simulation results are presented to demonstrate the effectiveness of the proposed scheme. [Copyright &y& Elsevier]

The photoconductive semiconductor switches (PCSSs) have two operating modes, i.e., linear mode and nonlinear mode (also “lock-on” mode). The low bias voltage and high trigger energy are needed when the switch is operated in a linear mode, but the high bias voltage and low trigger energy are needed when the switch is operated in a nonlinear mode. When the GaAs PCSS is triggered under the condition of the low bias voltage and low trigger energy, the on-state characteristic of the switch is similar to that in the linear mode but different from the nonlinear mode. We refer to this mode as “linear-alike mode.” In this paper, a research on the GaAs PCSS triggered by a laser diode in different low bias voltages is reported. The performance of linear-alike mode is analyzed and an equation used to calculate the on-state current is put forward, on the basis of which a method to measure the ionization rate is presented. [ABSTRACT FROM AUTHOR]

Suppression of secondary electron emission (SEE) by surface coating technology on metal materials has important applications in many fields, for which the investigation on new coating materials with low secondary electron yield (SEY) is desired significantly. In this study, the maximum SEY of nickel (Ni) substrate was reduced from 2.30 to 0.75 (67 % reduction) after a carbon nano-onion (CNO) coating prepared by plasma enhanced chemical vapor deposition (PECVD), and the SEY less than 1 means that some problems caused by secondary electron (SE) multiplication on metal materials could be solved completely. Various measurements, material characterization and CASINO Monte Carlo model simulation indicated that the low SEY characteristic of CNO coating could be attributed to two main mechanisms: Firstly, true SEs emitted from the surface of CNO could be reabsorbed by the adjacent CNO attributed to the micrometer scale undulating structure formed by the accumulation of CNO on the coating surface; Secondly, the defects degree of CNO directly affects the emission of true SE, which plays the role of low-energy electron capturing trap. This discovery can provide a reference for future coating production. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: This paper focuses on the problem of adaptive fuzzy tracking control for a class of nonlinear multi-input and multi-output (MIMO) time-delay systems in strict-feedback form. The time delays in the systems may be time-varying. Based on Razumikhin functional method, the state feedback adaptive fuzzy tracking controllers are constructed via backstepping technique. The proposed adaptive fuzzy controllers guarantee that all the signals in the closed-loop system are bounded and the system''s outputs converge to a small neighborhood of the reference signals. Three examples are used to illustrate the effectiveness of the proposed approach. [Copyright &y& Elsevier]

Three-dimensional thermoelastic analysis of simply supported rectangular plates with variable thickness and subjected to thermomechanical loads is investigated. An approximate analytical solution method is proposed. The temperature field and the displacements are represented by a double harmonic series, respectively. First, the heat conduction equation is solved analytically to obtain the nonlinear temperature series with unknown coefficients. Then the three-dimensional equilibrium differential equations are analytically solved to obtain the displacement component series with unknown coefficients. Thus the stress component series can be determined. The unknown coefficients in the temperature series and stress component series are approximately determined by using the upper surface and lower surface conditions of the plate. With the proposed procedure, the solutions satisfy the governing differential equations, the loading conditions, and the simply supported boundary conditions. The proposed solution method shows a good convergence and the results agree well with those obtained from a commercial finite element software, ANSYS. Two examples are used to demonstrate the effectiveness of the proposed solution method. The simultaneous effects of temperature change and applied mechanical load on the behavior of the plate are examined. [ABSTRACT FROM AUTHOR]

By utilizing power semiconductor switches, especially high-voltage insulated gate bipolar transistors (IGBTs), as main switches, Marx modulators have demonstrated many advantages such as variable pulse length and pulse-repetition frequency, snubberless operation, and inherent redundancy. However, the relatively slow turn-on speed of the IGBT influences the pulse rise time of the Marx modulator. In this paper, a newly developed all-solid-state pulsed-power generator is proposed. This generator consists of a Marx modulator based on discrete IGBTs and a magnetic pulse-sharpening circuit, which is employed to compress the rising edge of the Marx output pulse. The experimental results are presented with a maximum voltage of 20 kV, a rise time of 200 ns, a pulse duration of 500 ns (full-width at half-maximum), and a repetition rate of 5 kHz on a 285- \Omega resistive load. The output power of the generator is 2.5 kW, and the average power in one pulse is 1 MW. The design methods of the IGBT drive circuits and the parameter calculation of the magnetic pulse-sharpening circuit are introduced in detail in this paper. The factors influencing the performance of the generator are also discussed. [ABSTRACT FROM PUBLISHER]