On the Unipolar Generator: An Experimental and Theoretical Study

When studying the phenomenon of the induced electromotive force, which originates from Faraday’s unipolar inductor, the contrast between Faraday’s view of the magnetic field dynamic lines and the theory of relativity is revealed. In order to remove this contradiction, this phenomenon was studied in depth, theoretically and experimentally, using an experimental setup similar to Faraday’s. Calculations of the induced electromotive force, based on relativity on the one hand and on Faraday’s view on the other were made with the help of measurements of the magnetic field components. Accurate magnetic field measurements are confirmed by analytical calculations. Precise-induced electromotive force measurements confirmed Faraday’s view and contradicted the theory of relativity.

Coexistence of unipolar and bipolar modes in Ag/ZnO/Pt resistive switching memory with oxygen-vacancy and metal-Ag filaments

In this study, the unipolar resistive switching （URS） and bipolar resistive switching （BRS） are demonstrated to be coexistent in the Ag/ZnO/Pt memory device, and both modes are observed to strongly depend on the polarity of forming voltage. The mechanisms of the URS and BRS behaviors could be attributed to the electric-field-induced migration of oxygen vacancies （Vo） and metal-Ag conducting filaments （CFs） respectively, which are confirmed by investigating the temperature dependences of low resistance states in both modes. Furthermore, we compare the resistive switching （RS） characteristics （e.g., forming and switching voltages, reset current and resistance states） between these two modes based on Vo- and Ag-CFs. The BRS mode shows better switching uniformity and lower power than the URS mode. Both of these modes exhibit good RS performances, including good retention, reliable cycling and high-speed switching. The result indicates that the coexistence of URS and BRS behaviors in a single device has great potential applications in future nonvolatile multi-level memory.

Coexistence of Bipolar and Unipolar Resistive Switching Behavior in Ag/ZnMn_2O_4/p^+-Si Device

ZnMn_2O_4 thin films were deposited by a sol-gel technique onto a p+-Si substrate, and a RRAM device with the Ag/ZnMn_2O_4/p^+-Si structure was fabricated. The microstructure of ZnMn_2O_4 films and the resistive switching behavior of Ag/ZnMn_2O_4/p^+-Si device were investigated. ZnMn_2O_4 thin films had a spinel structure after annealing at 650 °C for 1 h. The Ag/ZnMn_2O_4/p^+-Si device showed unipolar and/or bipolar resistive switching behavior, exhibiting different ION/IOFF ratio and switching endurance properties. In bipolar resistive switching, high-resistance-state(HRS) conduction was dominated by the space-charge-limited conduction mechanism, whereas the filament conduction mechanism dictated the low resistance state(LRS). For unipolar resistive switching, HRS and LRS were controlled by the filament conduction mechanism. For bipolar resistive switching, the conduction process can be explained by the space-charge region of the p-n junction.

SPICE modeling of flux-controlled unipolar memristive devices

Unipolar memristive devices are an important kind of resistive switching devices. However, few circuit models of them have been proposed. In this paper, we propose the SPICE modeling of flux-controlled unipolar memristive devices based on the memristance versus state map. Using our model, the flux thresholds, ON and OFF resistance, and compliance current can easily be set as model parameters. We simulate the model in HSPICE using model parameters abstracted from real devices, and the simulation results show that the proposed model caters to the real device data very well, thus demonstrating that the model is correct. Using the same modeling methodology, the SPICE model of charge-controlled unipolar memristive devices could also be developed. The proposed model could be used to model resistive memory cells, logical gates as well as synapses in artificial neural networks.

Comparison of performance between bipolar and unipolar double-frequency sinusoidal pulse width modulation in a digitally controlled H-bridge inverter system

By deriving the discrete-time models of a digitally controlled H-bridge inverter system modulated by bipolar sinu- soidal pulse width modulation （BSPWM） and unipolar double-frequency sinusoidal pulse width modulation （UDFSPWM） respectively, the performances of the two modulation strategies are analyzed in detail. The circuit parameters, used in this paper, are fixed. When the systems, modulated by BSPWM and UDFSPWM, have the same switching frequency, the stabil- ity boundaries of the two systems are the same. However, when the equivalent switching frequencies of the two systems are the same, the BSPWM modulated system is more stable than the UDFSPWM modulated system. In addition, a convenient method of establishing the discrete-time model of piecewise smooth system is presented. Finally, the analytical results are confirmed by circuit simulations and experimental measurements.

Bias polarity-dependent unipolar switching behavior in NiO/SrTiO_3 stacked layer

The identification of the switching location has been a key technology to tune the physical properties of unipolar resistive switching（RS） cells.Here we report the RS properties of Au/Ni O/Sr Ti O3（STO）/Pt memory cells.The switching repeatability is closely related to the applied bias polarity,which is different from the scenario of the Au/STO/Pt cells reported in our previous researches.The high resistance in positive bias is greater than that in negative bias.The R（T）–R0I^2 R（T） plot of the on-state I–V curve shows a regular shape only with a slight bend and an abnormal shape with an abrupt increase and decrease under negative and positive bias,respectively.These comparative experimental results reveal that the conductance filament consisting of oxygen vacancies grows from the cathode to the anode.The spatial RS location is identified with the weaker part along the conductance filament length direction,which should be near the Ni O/STO interface and STO/Pt interface under positive and negative bias,respectively.

Differences in Non-suicidal Self-injury Behaviors between Unipolar Depression and Bipolar Depression in Adolescent Outpatients

Objective Non-suicidal self-injury(NSSI)has a higher prevalence in adolescents with depressive disorders than in community adolescents.This study examined the differences in NSSI behaviors between adolescents with unipolar depression(UD)and those with bipolar depression(BD).Methods Adolescents with UD or BD were recruited from 20 general or psychiatric hospitals across China.The methods,frequency,and function of NSSI were assessed by Functional Assessment of Self-Mutilation.The Beck Suicide Ideation Scale was used to evaluate adolescents’suicidal ideation,and the 10-item Kessler Psychological Distress Scale to estimate the anxiety and depression symptoms.Results The UD group had higher levels of depression(19.16 vs.17.37,F=15.23,P<0.001)and anxiety symptoms(17.73 vs.16.70,F=5.00,P=0.026)than the BD group.Adolescents with BD had a longer course of NSSI than those with UD(2.00 vs.1.00 year,Z=−3.39,P=0.001).There were no statistical differences in the frequency and the number of methods of NSSI between the UD and BD groups.Depression(r=0.408,P<0.01)and anxiety(r=0.391,P<0.01)were significantly and positively related to NSSI frequency.Conclusion Adolescents with BD had a longer course of NSSI than those with UD.More importantly,NSSI frequency were positively and strongly correlated with depression and anxiety symptoms,indicating the importance of adequate treatment of depression and anxiety in preventing and intervening adolescents’NSSI behaviors.

PHOTOACOUSTIC GENERATION OF FOCUSED QUASI-UNIPOLAR PRESSURE PULSES

The photoacoustic effect was employed to generate short-duration quasi-unipolar acoustic pressure pulses in both planar and spherically focused geometries.In the focal region,the temporal profile of a pressure pulse can be approximated by the first derivative of the temporal profile near the front transducer surface,with a time-averaged value equal to zero.This approximation agreed with experimental results acquired from photoacoustic transducers with both rigid and free boundaries.For a free boundary,the acoustic pressure in the focal region is equal to the sum of a positive pressure that follows the spatial profile of the optical energy deposition in the medium and a negative pressure that follows the temporal profile of the laser pulse.

Reversible alternation between bipolar and unipolar resistive switching in La-SrTiO_3 thin films

The alternation from bipolar to unipolar resistive switching is observed in perovskite La0.01Sr0.99TiO3 thin films. These two switching modes can be activated separately depending on the compliance current （Icomp） during the electroforming process： with a higher Icomp （5 mA） the unipolar resistance switching behavior is measured, while the bipolar resistance switching behavior is observed with a lower Icomp （1 mA）. On the basis of I–V characteristics, the switching mechanisms for the URS and BRS modes are considered as being a change in the Schottky-like barrier height and/or width at the Pt/La-SrTiO3 interface and the formation and disruption of conduction filaments, respectively.

A "Superpower" instead of "Unipolarity"

The power position and influence of a country depend on its comprehensive national power based on economics. While addressing to the press in Kansas on July 6, 1971, President Nixon noted: "Comparing to our overwhelming position at the end of World War II, the United States is now facing immense challenges that we have never expected before. " He added, "In terms of economics, the United States is no longer a dominant power or an overwhelming global power. At present, there exist not only two superpowers. In consideration of eco-

Healthy individuals vs patients with bipolar or unipolar depression in gray matter volume

BACKGROUND Previous studies using voxel-based morphometry(VBM)revealed changes in gray matter volume(GMV)of patients with depression,but the differences between patients with bipolar disorder(BD)and unipolar depression(UD)are less known.AIM To analyze the whole-brain GMV data of patients with untreated UD and BD compared with healthy controls.METHODS Fourteen patients with BD and 20 with UD were recruited from the Mental Health Center of Shantou University between August 2014 and July 2015,and 20 nondepressive controls were recruited.After routine three-plane positioning,axial T2WI scanning was performed.The connecting line between the anterior and posterior commissures was used as the scanning baseline.The scanning range extended from the cranial apex to the foramen magnum.Categorical data are presented as frequencies and were analyzed using the Fisher exact test.RESULTS There were no significant intergroup differences in gender,age,or years of education.Disease course,age at the first episode,and Hamilton depression rating scale scores were similar between patients with UD and those with BD.Compared with the non-depressive controls,patients with BD showed smaller GMVs in the right inferior temporal gyrus,left middle temporal gyrus,right middle occipital gyrus,and right superior parietal gyrus and larger GMVs in the midbrain,left superior frontal gyrus,and right cerebellum.In contrast,UD patients showed smaller GMVs than the controls in the right fusiform gyrus,left inferior occipital gyrus,left paracentral lobule,right superior and inferior temporal gyri,and the right posterior lobe of the cerebellum,and larger GMVs than the controls in the left posterior central gyrus and left middle frontal gyrus.There was no difference in GMV between patients with BD and UD.CONCLUSION Using VBM,the present study revealed that patients with UD and BD have different patterns of changes in GMV when compared with healthy controls.

Schmitt, Kant, and the Theory of International Relations： Reflecting the Problems of Just War, Unipolarism, and Political Realism

Concerning international relations theory, the work of Immanuel Kant was hitherto reflected in terms of the liberal paradigm, particularly of the democratic peace, whereas Carl Schmitt was predominantly associated with the assumptions of political realism or--at least for a short period Nazi imperialism. However, these differences seem to have taken a back seat since both thinkers have been adopted to legitimate the convictions of imperial liberalism. In contrast, this article will show that Schmitt and Kant have essentially more in common than generally assumed but do precisely argue against just war theory, humanitarian interventions, and a unipolar world. On the other hand, Kant＇s liberal and Schmitt＇s illiberal theory do not apply to the classical paradigms of intemational relations. Instead, Schmitt＇s Political Theology and Kant＇s Political Philosophy will be compared along with the antagonistic logic （and ethics） of political existentialism and a peaceful interdependence between states and nations. Considering the contemporary crisis of world order, it should be even plausible that the two dominating paradigms of future international relations might be formed by Kantian and Schmittian premises. Thus, the aim of this paper is not to match Kant and Schmitt once again with the usual approaches in international relations theory but to stretch its theoretical and conceptual spectrum by extracting the inventive contribution both thinkers made to important topics of IR.

Reduction of Unipolar Leakage Flux and Torque Ripple in Consequent-pole PM Vernier Machine

This paper proposes a new consequent-pole permanent magnet vernier machine(CPMVM),which can be regarded as a combination of two conventional CPMVM with opposite polarities.Based on the simplified axial magnetic circuit model,it is verified that the proposed CPMVM can reduce the unipolar leakage flux.In order to reduce the torque ripple of machine and improve the output torque of machine,the flux barrier is placed on the rotor of the proposed machine.Then,the parameters of the proposed CPMVM are optimized and determined.Moreover,the electromagnetic performance,including no-load air-gap flux density,average torque and torque ripple,flux linkage,back-electromotive force,cogging torque,average torque,torque ripple,power factor and loss,is compared with conventional surface-mounted permanent magnet vernier machine(SPMVM)and CPMVM.Finally,it is demonstrated that proposed CPMVM with flux barrier can effectively reduce the unipolar leakage flux and greatly reduce the torque ripple of machine.Also,compared with the SPMVM,the proposed CPMVM with flux barrier saves more than 45%of the permanent magnet material without reducing output torque.

Grey matter volume abnormalities in patients with bipolar I depressive disorder and unipolar depressive disorder:a voxelbased morphometry study

Bipolar disorder and unipolar depressive disorder（UD） may be different in brain structure. In the present study,we performed voxel-based morphometry（VBM） to quantify the grey matter volumes in 23 patients with bipolar I depressive disorder（BP1） and 23 patients with UD,and 23 age-,gender-,and educationmatched healthy controls（HCs） using magnetic resonance imaging. We found that compared with the HC and UD groups,the BP1 group showed reduced grey matter volumes in the right inferior frontal gyrus and middle cingulate gyrus,while the UD group showed reduced volume in the right inferior frontal gyrus compared to HCs. In addition,correlation analyses revealed that the grey matter volumes of these regions were negatively correlated with the Hamilton depression rating scores. Taken together,the results of our study suggest that decreased grey matter volume of the right inferior frontal gyrus is a common abnormality in BP1 and UD,and decreasedgrey matter volume in the right middle cingulate gyrus may be specifi c to BP1.

Unipolar electrogram in identification of successful targets for radiofrequency catheter ablation of focal atrial tachycardia

Objective To analyze the unipolar electrogram from successful and unsuccessful ablation sites of focal atrial tachycardia (AT), and to evaluate its value in the identification of successful targets.Methods Fifteen consecutive patients with focal AT were referred for radiofrequency catheter ablation (RFCA). Both unipolar (from the tip electrode of ablating catheter) and bipolar (from the distal pair of electrode of ablating catheter) electrograms were used to identify the ablation targets of focal AT.Results Successful ablation was echieved in 14 patients. Radiofrequency energy was delivered at a total of 27 sites. The bipolar electrograms associated with successful ablation sites showed earlier atrial deflection relative to P wave onset (36 ms±15 ms vs 30 ms±11 ms, P <0.05) than the electrograms associated with failed ablation sites. At the 14 successful ablation sites, the unipolar electrograms displayed a completely negative atrial wave (“QS” morphology ) beginning with intrinsic deflection. However, at the 13 unsuccessful ablation sites,a “rS” morphology of atrial wave was shown on the unipolar electrogram.Conclusion The “QS” morphology of the atrial wave on unipolar electrograms appears to represent a reliable marker for identifying the successful ablation targets of focal AT, with a high sensitivity and specificity .

High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices

Free-space optical communication is a very promising alternative to fiber communication systems,in terms of ease of deployment and costs.Midinfrared light has several features of utter relevance for free-space applications:low absorption when propagating in the atmosphere even under adverse conditions,robustness of the wavefront during long-distance propagation,and absence of regulations and restrictions for this range of wavelengths.A proof-of-concept of high-speed transmission taking advantage of intersubband devices has recently been demonstrated,but this effort was limited by the short-distance optical path(up to 1 m).In this work,we study the possibility of building a long-range link using unipolar quantum optoelectronics.Two different detectors are used:an uncooled quantum cascade detector and a nitrogen-cooled quantum well-infrared photodetector.We evaluate the maximum data rate of our link in a back-to-back configuration before adding a Herriott cell to increase the length of the light path up to 31 m.By using pulse shaping,pre-and post-processing,we reach a record bitrate of 30 Gbit s−1 for both two-level(OOK)and four-level(PAM-4)modulation schemes for a 31-m propagation link and a bit error rate compatible with error-correction codes.

Near-UV electroluminescence in unipolar-doped, bipolar-tunneling GaN/AlN heterostructures

Cross-gap light emission is reported in n-type unipolar GaN/AlN double-barrier heterostructure diodes at room temperature.Three different designs were grown on semi-insulating bulk GaN substrates using molecular beam epitaxy(MBE).All samples displayed a single electroluminescent spectral peak at 360 nm with full-width at half-maximum(FWHM)values no greater than 16 nm and an external quantum efficiency(EQE)of≈0.0074%at 18.8 mA.In contrast to traditional GaN light emitters,p-type doping and p-contacts are completely avoided,and instead,holes are created in the GaN on the emitter side of the tunneling structure by direct interband(that is,Zener)tunneling from the valence band to the conduction band on the collector side.The Zener tunneling is enhanced by the high electric fields(~5×106 V cm^(−1))created by the notably large polarization-induced sheet charge at the interfaces between the AlN and GaN.

Enhanced unipolar electrical fatigue resistance and related mechanism in grain-oriented Pb(Mg_(1/3)Nb_(2/3))O_(3)-Pb(Zr,Ti)O_(3)piezoceramics

Piezoceramics with high and fatigue-resisted piezoelectric properties are strongly desired for actuator ap-plications.In this work,textured Pb(Mg_(1/3)Nb_(2/3))O_(3)-Pb(Zr,Ti)O_(3)ceramics with Lotgering factor F_(001)∼98%were fabricated by templated grain growth technique.Strong[001]c-grain orientation(f∼90%and r∼0.22)of the textured ceramics effectively produced about 230%enhanced piezoelectric coefficient d_(33)^(∗)(i.e.,S_(max)/E_(max))and substantially improved unipolar electrical fatigue resistance.Unipolar polarization P max and d_(33)^(∗)of the textured ceramics were nearly maintained up to 106 unipolar cycles,while 19%and 14%degradations were respectively observed from randomly oriented counterparts.Especially,normal-ized d_(33)^(∗)of the textured ceramics shows better unipolar fatigue resistance than those of piezoceramics reported previously.Much lower bipolar strain asymmetryγs(∼4%)was observed from the textured samples fatigued after 106 unipolar cycles as compared toγs∼23%for randomly oriented counterparts.While charged defect accumulation model described the serious fatigue deteriorations in randomly ori-ented ceramics,the current work revealed that substantially enhanced unipolar fatigue resistance of the textured ceramics is mainly associated with the inherent fatigue anisotropy,weakened local bias fields owing to both enhanced domain mobility and lower defect density near grain boundaries/interfaces,and increased intrinsic contribution due to more tetragonal content.These superior characteristics suggest the great potential of textured ceramics for high-performance and robust actuator applications.

Cortical functional connectivity features between bipolar and unipolar depression patients

Objective To explore the differences of cortico-cortical functional connectivity features among patients with bipolar and unipolar depression in resting state.Methods Whole-head magnetoencephalography scan was performed in an resting state condition in 12 bipolar depression patients,27 unipolar depression patients and

Lattice strain induced by trace Pt single atoms in nickel for accelerating industrial hydrogen evolution

Strategically designing the electrocatalytic system and cleverly inducing strain is an effective approach to balance the cost and activity of Pt-based electrocatalysts for industrial-scale hydrogen production.Herein,we present a unipolar pulsed electrodeposition(UPED) strategy to induce strain in the Ni lattice by introducing trace amounts of Pt single atoms(SAs)(0.22 wt%).The overpotential decreased by 183 mV at 10 mA cm^(-2) in 1.0 M KOH after introducing trace amounts of Pt_(SAs).The industrial electrolyzer,assembled with Pt_(SAs)Ni cathode and a commercial NiFeO_(x) anode,requires a cell voltage of 1.90 V to attain 1 A cm^(-2) of current density and remains stable for 280 h,demonstrating significant potential for practical applications.Spherical aberration corrected scanning transmission electron microscopy(AC-STEM),X-ray absorption(XAS),and geometric phase analysis(GPA) indicate that the introduction of trace amounts of Pt SAs induces tensile strain in the Ni lattice,thereby altering the local electronic structure and coordination environment around cubic Ni for enhancing the water decomposition kinetics and fundamentally changing the reaction pathway.The doping-strain strategy showcases conformational relationships that could offer new ideas to construct efficient hydrogen evolution reaction(HER) electrocatalysts for industrial hydrogen production in the future.