Proper Ac Research Articles

Electrically induced cancellation and inversion of piezoelectricity in ferroelectric Hf0.5Zr0.5O2

HfO2-based thin films hold huge promise for integrated devices as they show full compatibility with semiconductor technologies and robust ferroelectric properties at nanometer scale. While their polarization switching behavior has been widely investigated, their electromechanical response received much less attention so far. Here, we demonstrate that piezoelectricity in Hf0.5Zr0.5O2 ferroelectric capacitors is not an invariable property but, in fact, can be intrinsically changed by electrical field cycling. Hf0.5Zr0.5O2 capacitors subjected to ac cycling undergo a continuous transition from a positive effective piezoelectric coefficient d33 in the pristine state to a fully inverted negative d33 state, while, in parallel, the polarization monotonically increases. Not only can the sign of d33 be uniformly inverted in the whole capacitor volume, but also, with proper ac training, the net effective piezoresponse can be nullified while the polarization is kept fully switchable. Moreover, the local piezoresponse force microscopy signal also gradually goes through the zero value upon ac cycling. Density functional theory calculations suggest that the observed behavior is a result of a structural transformation from a weakly-developed polar orthorhombic phase towards a well-developed polar orthorhombic phase. The calculations also suggest the possible occurrence of a non-piezoelectric ferroelectric Hf0.5Zr0.5O2. Our experimental findings create an unprecedented potential for tuning the electromechanical functionality of ferroelectric HfO2-based devices.

Promjene u stanju uhranjenosti, navikama tjelesne aktivnosti i prehrani djece u osnovnoj školi tijekom epidemije COVID-19

Aim: The COVID -19 pandemic has changed the way people live, and children are particularly at risk because of their vulnerable age. The aim of this work was to evaluate the changes in nutritional status, physical activity, and eating habits of elementary school- aged children during the Covid 19 pandemic. Methods: The study was conducted from February to April 2021 and included 197 primary school children, 100 boys, and 97 girls. A questionnaire was used to collect data on lifestyle, eating habits, and physical activity outside school. The Mediterranean Diet Qual- ity Index for children and adolescents was used to determine membership in the Mediterranean diet. The kinanthropological and anthropological data of the students were obtained from the diary of the physical education and health teacher. Results: The average rating of the quality of the children’s diet, as determined by the Mediterranean Diet Quality Index for Children and Adolescents, showed a moderate affiliation with the Mediterranean diet. Before online instruction, 65.9% of students ate break- fast daily, whereas during online instruction, 75.7% ate breakfast (p< 0.001). Results showed that students exercised statistically sig- nificantly more before online instruction than during online instruction (p< 0.05). Students had weaker kinanthropological scores than before beginning online instruction. Conclusions: According to the results, students’ diet is of average quality, and some habits, such as breakfast, have improved, while physical activities have decreased significantly during the pandemic. Therefore, the promotion of proper nutrition and physical ac- tivity through public health programs should be emphasized to educate both children and parents about the importance of proper nutrition, physical activity, and responsible use of various media.

Proposal of time domain impedance spectroscopy to determine precise dimensionless figure of merit for thermoelectric modules within minutes

Several techniques exist that use a thermoelectric element (TE) or module (TM) to measure precise dimensionless figure of merit (zT), both qualitatively and quantitatively. The techniques can be applied using both alternating (AC) and direct current (DC). Herein, the transient Harman (TH) and impedance spectroscopy (IS) methods were investigated as direct zT measurement techniques using identical TM, which showed that zT at 300 K was 0.767 and 0.811 within several minutes and several hours, respectively. The zT values differed despite the use of the same TM, which revealed that measuring ohmic resistance using DC and pulse DC is potentially misleading owing to the influence of Peltier heat on current flow. In this study, time domain impedance spectroscopy (TDIS) was proposed as a new technique to measure zT using proper DC and AC. zT obtained using TDIS was 0.811 within several minutes using the time and frequency domains, and was perfectly consistent with the result of the IS method. In conclusion, the TDIS is highly appropriate in estimating zT directly using only proper electrometric measurements, and without any heat measurements.

Optimized Design for AC Filter and Switching Frequency of Parallel-Connected Inverters With Global Synchronous Pulsewidth Modulation

This article proposes a new optimized design method for AC filter and switching frequency of parallel-connected inverters with global synchronous pulse width modulation (GSPWM) to improve the efficiency or reduce the cost. Being different from the traditional design methods that only focus on the individual inverter itself, the quantity of parallel-connected inverters and the operational principles of GSPWM are involved as the key considerations for designing the proper ac filter values and switching frequencies. In specific, the general principles and the realization details are comprehensively elaborated. Experimental results are presented to verify the proposed theoretical findings.

(Invited) Dielectrophoretic Capture and Detection of Microbial Pathogens Using Nanoelectrode Arrays

Rapid and highly sensitive detection of pathogenic microbes is critical for food safety and environmental protection. To achieve this, it requires combining novel sample preparation techniques and extremely sensitive detection methods. In this presentation, I summarize a series of studies in my lab on developing a nanoscale dielectrophoresis (DEP) device for effective capturing and concentrating pathogenic particles such as viral and bacterial particles in a fluidic chip. This technique was then integrated with various detection methods such as fluorescence imaging, surface enhanced Raman spectroscopy (SERS) and real-time impedance measurements for quantitative assessment of the pathogen concentration. Due to the small size (~1 micron for bacterial cells and ~100 nm for viral particles), it is challenging to capture and concentrating these pathogenic particles from dilute solutions. Here we demonstrate that the highly focused electric field at the tip of an embedded nanoelectrode array can be utilized to generate a large DEP force to effectively manipulate pathogenic particles. The nanoelectrode array was made of vertically aligned carbon nanofibers (VACNFs), about 5 micron in length and 100 nm in diameter, and embedded in a SiO2 film. It was placed at the bottom of a microfluidic channel against a macroscopic indium tin oxide (ITO) top electrode, forming a DEP device in “points-and-lid” configuration. We have shown that E. coli DHα5 cells flowing through the channel can be effectively captured and concentrated at the desired microscale areas inside the channel using a small AC voltage (~6-10 Vpp). This device is particularly effective in capturing viral particles (such as bacteriophage T4r) due to the comparable size between the viral particles and the exposed VACNF tip. To achieve specific detection, the DEP chip has been integrated with a Raman probe for SERS measurements of nanotag-labelled E. coli DHα5 cells. The SERS nanotags are based on iron oxide-gold (IO-Au) core-shell nanoovals (NOVs) of ~50 nm in size, which are coated with QSY21 Raman reporters and attached to E. coli cells through specific antibodies. The combination of the greatly enhanced Raman signal by the SERS nanotags and the effective DEP concentration significantly improves the detection limit and speed. The SERS signal has been fully validated with fluorescence microscopy measurements under all DEP conditions. A concentration detection limit as low as 210 cfu/mL using a portable Raman system has been obtained with a DEP capture time of only ~50 s. The detection has been validated in purified solutions as well as complex samples including chicken broth, soil solution and apple juice. Real-time impedance measurements has also been demonstrated as a feedback during DEP capture of vaccinia viral particles. By controlling the proper AC voltage, the nucleic acid contents in the viral particles can be released by opening the envelope with electroporation under the high electric field at the VACNF tips. These results demonstrate the potential to develop a compact portable system for rapid and highly sensitive detection of specific pathogens. Furthermore, this technique is based on physical method and the pathogenic particles are fully released after the AC voltage is turned off, making it a robust device that can be repeatedly used.

Bias dependent conduction and relaxation mechanism study of Cu5FeS4 film and its significance in signal transport network

Here we have reported the electric and dielectric properties of a Bornite (Cu5FeS4) film using non-destructive complex impedance spectroscopy (CIS) in the frequency range 40 Hz–20 MHz and bias voltage range 0–0.8 V. A typical hydrothermal reaction was carried out to obtain the Cu5FeS4 material. Thereafter, we fabricated the film of the synthesized material and analysed its various properties as a function of frequency and dc bias voltages. The CIS analysis at room temperature (303 K) for different forward dc bias voltages shows that the bulk resistance plays a predominant role in conduction mechanism. The complex impedance (Nyquist) plots are well modelled with grain and grain boundary resistance by introducing proper ac equivalent circuit. The impedance loss spectra showed that the relaxation peak shifts towards the higher frequency with increasing bias voltages, which implies the possibility of a charge hopping between the localized charge states. Furthermore, we find that dielectric constant ( $${\varepsilon ^\prime }$$ ), dielectric loss ( $${\varepsilon ^{\prime \prime }}$$ ), electrical modulus ( $${{\text{M}}^*}$$ ) and ac/dc conductivity of the Cu5FeS4 film are strongly frequency dependent. The values of $${\varepsilon ^\prime }$$ and $${\varepsilon ^{\prime \prime }}$$ decreases whereas ac conductivity increases with increasing frequency. High frequency and low frequency dielectric constant of the material are found to be 3.48 and in the order of 104 respectively. Electrical modulus study is introduced for better explanation of conductivity relaxation phenomenon. Finally, we investigated the variation of ac/dc conductivity with forward dc bias voltages. This confirmed the presence of a hopping mechanism for electrical transport in our system, which can be best explained on the basis of jump relaxation model. Overall, this extensive study based on complex impedance spectroscopy demonstrates the dielectric relaxation behaviour of Cu5FeS4 film and also shed light on hopping induced conduction mechanism.

EP22.15: Feasibility of automated recognition of fetal abdominal circumference on antenatal ultrasound by using convolutional neural network

By using convolutional neural network (CNN), a program was designed to recognise fetal AC plane on ultrasound which takes account of physicians' decision process, anatomical structures, and the characteristics of ultrasound image. We planned to evaluate the feasibility of automated recognition of appropriate AC plane by machine learning using CNN. This study included seventy singleton pregnancies between 20+0∼34+6 weeks of gestation without intra-abdominal anomalies and we analysed 458 AC images. Transverse AC images acquired by three different qualified physicians. Following thirty-five cases of training on recognition of proper AC plane by previously described machine learning program, 458 AC images were reviewed by two certificated obstetricians and were evaluated in adequacy. And inter-observer agreement was analysed by using Cohen's kappa coefficient. There was statistically difference between human and CNN in recognition of appropriate AC plane. Inter-observer agreement between two obstetricians was 94.88% (Kappa value 0.85), however, inter-observer agreements between CNN and each obstetricians were 60.48% (Kappa value 0.11) and 62.45 % (Kappa value 0.15), respectively, There were considerable differences between human and CNN program in recognition of appropriate AC plane. Improvement is needed that fine recognition of fetal abdominal structures which define proper AC plane by feedback into CNN program.

Adaptive Sensorless Control of PMSGs-Based Offshore Wind Farm and VSC-HVdc Stations

This paper proposes sensorless control strategies for an offshore wind farm (OWF) and voltage source converter high voltage direct current (VSC-HVdc) stations. The extended Kalman filter provides an estimation of the speeds and rotor positions of permanent magnet synchronous generators (PMSGs) of OWF, the dc voltage at dc-bus and the dc voltages of the both VSC-HVdc stations. The OWF, composed of 150 variable speed wind turbines based on PMSGs, is considered in this paper, where each generator is connected in series by its own ac-dc converter to dc-bus. Only one dc-ac inverter converts the dc-bus voltage to a proper ac voltage of wind farm ac-bus. The HVdc transmission system based on a three-level neutral point clamped VSC is used for the interconnection between the OWF and the onshore grid via two dc cables. Detailed modeling and control strategies are developed for each individual component of the system. Simulation results show the effectiveness of the proposed method to manage the desired HVdc system operation.

Inductance Measurement for PMSM Using Instantaneous Flux Linkage Method

The dq-axis inductances are important for the voltage decoupling control, torque estimation and steady-state performance analysis of a PMSM machine. In this paper, a measurement method is proposed based on the dq-axis instantaneous flux linkages calculation. The rotor is locked by a positive d-axis current, and then a proper AC current is assigned respectively to the d and q-axis reference current in order to cover the various current ranges. The instantaneous flux linkages are calculated by the integration of dq-axis current and voltage offline. Finally, dq-axis inductances are computed by the integrated flux linkages divided by the dq-axis current.

Market Impact of Macroeconomic Announcements: Do Surprises Matter?

Current research of market impact caused by macroeconomic announcements is based on regressing asset returns on macroeconomic surprises, S(t) ~ A(t) – E(t), where A(t) and E(t) are actual and expected (consensus) values of macroeconomic indicators at time t, correspondingly. We found that regressing returns of SPDR ETF SPY on actual change, AC(t) ~ A(t) – A(t-1), and expected change, EC(t) ~ E(t) – A(t-1), yield statistically significant indicators similar to those for S(t). These indicators somewhat vary for the periods 2004-2008 and 2009-2013. The advantage of AC(t) is that it is not based on the subjective nature of consensus. As for EC(t), it does not have a look-ahead bias since E(t) are published a few days prior to A(t). Hence CE(t) can be used for short-term forecasting. We show that with proper fitting, AC-, EC-, and S-based indexes can be used for qualitative modeling the SPY price dynamics. However, the effects of macroeconomic announcements alone do not describe the strength of the bull market in 2009-2014.

High-Frequency AC-Link PV Inverter

In this paper, a high-frequency ac-link photovoltaic (PV) inverter is proposed. The proposed inverter overcomes most of the problems associated with currently available PV inverters. In this inverter, a single-stage power-conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the input voltage, maximum power point tracking, generating low-harmonic ac at the output, and input/output isolation. This inverter is, in fact, a partial resonant ac-link converter in which the link is formed by a parallel inductor/capacitor ( LC) pair having alternating current and voltage. Among the significant merits of the proposed inverter are the zero-voltage turn-on and soft turn-off of the switches which result in negligible switching losses and minimum voltage stress on the switches. Hence, the frequency of the link can be as high as permitted by the switches and the processor. The high frequency of operation makes the proposed inverter very compact. The other significant advantage of the proposed inverter is that no bulky electrolytic capacitor exists at the link. Electrolytic capacitors are cited as the most unreliable component in PV inverters, and they are responsible for most of the inverters' failures, particularly at high temperature. Therefore, substituting dc electrolytic capacitors with ac LC pairs will significantly increase the reliability of PV inverters. A 30-kW prototype was fabricated and tested. The principle of operation and detailed design procedure of the proposed inverter along with the simulation and experimental results are included in this paper. To evaluate the long-term performance of the proposed inverter, three of these inverters were installed at three different commercial facilities in Texas, USA, to support the PV systems. These inverters have been working for several months now.

AC Power Losses Model for Planar Windings With Rectangular Cross-Sectional Conductors

In this letter, a method to calculate the ac losses, including skin effect and proximity losses, in planar windings with rectangular cross-sectional conductors is proposed. The aim is proposing proper ac losses expressions similar to the formulas available for round cross-sectional wires, to be used for the calculation of the ac losses and the optimization of planar magnetic windings implemented in the printed circuit board. The proposed model is based on the decomposition into conduction and proximity losses. Conduction losses only depend on the properties of the conductor, whereas proximity losses are calculated by using the orthogonal decomposition of the magnetic fields in which the conductors are immersed. Functions including the frequency and geometrical dependences of the both types of losses are extracted by means of finite element method simulation. Finally, several prototypes are used to verify the proposed expressions and some design considerations are also outlined.

A Multiport AC Link PV Inverter With Reduced Size and Weight for Stand-Alone Application

In this paper, a multiport high-frequency ac link inverter is proposed as the power electronic interface between the photovoltaic (PV) modules, battery energy storage system, and three-phase ac load. In this inverter, a single-stage power conversion unit fulfills all the system requirements, i.e., inverting dc voltage to proper ac, stepping up or down the voltage, generating low harmonic ac current at the output, and input/output isolation. The ac link is formed by a parallel ac inductor/capacitor <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(LC)$</tex></formula> pair having low reactive ratings. A single-input/single-output partial resonant inverter has already been proposed by the present authors. This paper verifies the possibility of extending this topology to multiport partial resonant converters. The proposed converter is believed to overcome most of the shortcomings associated with the currently available multiport PV inverters. It is a single-stage ac link power conversion system with zero voltage turn on and soft turn off of the switches, which has very small switching losses, compact size, and light weight. The proposed converter does not contain any electrolytic capacitors at the link, which increases the reliability of this converter to a great extent. In the proposed inverter, PV side and ac side are isolated; however, if galvanic isolation is required, a single-phase high-frequency transformer can be added to the link. This converter can both step up or down the voltage, regardless of the presence of a transformer. Although this configuration is extendable to the grid-connected applications, in this paper, only the stand-alone application is considered. The performance of the proposed multiport inverter is verified through simulations and experiments.

On the heterophase liquid thermodynamics and cooperative dynamics

The thermodynamics and cooperative dynamics of heterophase liquid states is considered taking into account frustration and volumetric interaction of the solid-like uctuons . It is found that the glass transition temperature range is scaled by difference of the frustration parameter and mean energy of the volumetric interaction. A model of the cooperative relaxation with nite cooperatively rearranging domains is considered. The ctitious Kauzmann and Vogel-Fulcher temperatures are determined. It is found that they are close to a proper ac- curacy. Correlation of the temperatures of glass transition, Vogel-Fulcher and iideali glass transition (as it is determined in the mode coupling model) is considered too. The heterophase uctuations model (HPFM) is based on the idea of heterophase structure of glass forming liquids (1{5). Consecutive consideration shows that in a heterophase state (HPS), molecular clusters (uctuons) of specied short-range order (SRO) are statistically signican t en- tities rather than single molecules. As a result, the supramolecular interactions determine the thermodynamics and dynamics of the glass forming liquids. Equation for the free energy of HPS is deduced within the framework of HPFM taking into account frustration and volumetric interaction of the uctuons (5, 6). The model of the cooperative relaxation dynamics of HPS developed in (2, 3) describes the -relaxation rate in terms of the free energy. The developed theory is a proper base for the analysis of experimental data on thermodynamics, structure and cooperative relaxation of the glass-forming liquids (2{4). The Vogel-Fulcher and Kauzmann temperatures (TVF and TK) (7{9) and the temperature of the \ideal" glass transition determined within the framework of the mode-coupling model (TMCT) (10, 11) are in use at the analysis and rationalization of experimental data. At TK the extrapolated entropy of liquid becomes equal to that of crystal or, in other words, the congurational entropy of liquid is going to zero. In (9, 12) it is assumed that a critical point is located at Kauzmann temperature, TK < Tg while TVF is the assumed singular point of the cooperative relaxation (7, 8). The relaxation time at this point is exp (TK=(T TK)). The empiric Vogel-Fulcher formula was obtained by Adam and Gibbs in a theoretical model (13). They connected the size of the cooperatively rearranging domain with the congurational entropy of liquid. The size increases with the congurational entropy decrease while at TK it goes to innit y. As a result, TK is a singular point of the cooperative relaxation and TK = TVF. Though TK and TVF are not accessible for a direct observation, the formulas obtained in Gibbs-DiMarzio and Adam-Gibbs (AG) models (along with the empiric denition by Kauzmann) make it possible to rationalize and t the experimental data on the liquid congurational entropy and relaxation cooperative rates. Determination of TMCT is given in terms of the basic relations of thermodynamic and dynamic properties of glass-forming liquids under special assumptions (10, 11). The predicted \ideal" glass transition has not been observed yet but this model and its consequences have been under consid-

Degradation of methyl orange by composite photocatalysts nano-TiO 2 immobilized on activated carbons of different porosities

Composite photocatalysts TiO 2 immobilized on granular activated carbons with different porosities (TiO 2/AC) were prepared by a novel approach, dip-hydrothermal method using peroxotitanate as precursor. The TiO 2/AC composites were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and the nitrogen absorption. Their photocatalytic activity was evaluated by degradation of methyl orange (MO). The results showed that nano-TiO 2 particles of anatase type were well deposited on the activated carbon surface. The porosity of activated carbon had significant influence on the adsorption, the amount of TiO 2 deposited on the external surface of AC and the activity of composite photocatalysts. The composite TiO 2/AC made from proper mesoporosity AC exhibited higher catalytic activity than the mixture of powdered TiO 2 with AC. Furthermore, the mechanism of synergistic effect of AC adsorption and TiO 2 photocatalysis was discussed.

The Study of the Electrochemical Graining Process in NaBO&lt;sub&gt;2&lt;/sub&gt;- H&lt;sub&gt;3&lt;/sub&gt;BO&lt;sub&gt;3&lt;/sub&gt; Solution and Grain Appearance on the Surface of Aluminum Alloy

The mainly process of electrochemical graining on 6063 aluminum alloy included graining at alternating current, anodizing and chemical coloring. The graining used NaBO2- H3BO3 system as film-forming solution, proper AC current density, treating time, temperature , adding agents and solution concentration were ascertained through operating orthogonal experiment, the grain of appropriate density and width could be obtained, the grained surface of aluminum alloy presented intergranular corrosion in the graining zone, the appearance was improved after anodizing, enough thick anodizing film could make intergranular corrosion eliminated. Cyclic voltammetry experiment was used to preliminarily explaine the grain process, the main cause of graining zone formation was hydrogen evolution.

Quantum tunneling of magnetization inFe-substitutedMn12studied by ac magnetic susceptibility

Quantum tunneling of magnetization (QTM) in an $\mathrm{Fe}$-substituted single molecular magnet ${\mathrm{Mn}}_{11}\mathrm{Fe}$ has been studied by ac susceptibility measurements in ${\mathrm{Mn}}_{11}\mathrm{Fe}∕{\mathrm{Mn}}_{12}$ mixed crystal. Although the blocking temperature of the ${\mathrm{Mn}}_{11}\mathrm{Fe}$ is lower than $2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, a tunneling peak at a static magnetic field of $6\phantom{\rule{0.3em}{0ex}}\mathrm{kOe}$ was observed in the ac susceptibility with a suitable ac frequency $(9873\phantom{\rule{0.3em}{0ex}}\mathrm{Hz})$ at $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. This work also elucidates a way to choose the proper ac frequency to observe the QTM at a relatively higher temperature $(T&gt;{T}_{B})$.

Measurement of doping concentration in boron-doped diamond film from capacitance spectroscopy

Schottky barrier structure and metal-insulator-semiconductor structure have been fabricated on boron-doped diamond film samples, which were grown using the microwave enhanced chemical vapor deposition method. By measuring the capacitance-voltage (CV) spectroscopies of both structures, boron acceptor concentration of ∼1017 cm−3 in the diamond samples has been measured. In the CV measurement, the influences from interface states, non-boron deep centers, emission/capture time constant distribution of boron acceptors and diamond resistance have been considered. It shows that proper ac modulation frequency should be selected in the measurement. It also shows that, in the measurement of dopant concentration in wide gap semiconductors, the CV measurement of the semiconductor Schottky barrier structure is a better choice, because Ohmic contact problem can be avoided.

A Mechanism for Enhancing the Reproduced Voltage on the Ring-Type-Head/Electroless-Deposited Perpendicular Double-Layered Media System

A mechanism was investigated for enhancing the reproduced voltage of a recording system combining a ring head with a electroless-deposited perpendicular double-layered medium. The mechanism of enhancement is thought to consist of the following two effects: the "phase synchronization" (PS) effect, due to a semi-hard magnetic underlayer, and the "double-layering" (DL) effect, due to the soft magnetic underlayer. By proper ac erasing of the reproduced signal through the action of the underlayer (at an underlayer coercivity of H <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c(u)</inf> =50 Oe) in a CoNiReP/CoB double-layered medium, the PS effect was confirmed to appear at recording densities up to about 90 kFRPI. The enhancement of the reproduced voltage at densities higher than 90 kFRPI was still observed after such ac erasure, and originates solely in the DL effect.

リングヘッド／無電解めっき垂直二層膜媒体系における再生出力増大機構

A mechanism was investigated for enhancing the reproduced voltage of the ring-type-head/electroless-deposited perpendicular double-layered medium system. The enhancement mechanism was considered to combine the fo1lowing two effects: the “phase synchronization (PS) effect”, due to a semihard magnetic underlayer, and the “double-layered (DL) effect”, due to a softmagnetic underlayer. By proper AC erasing of the reproduced signal due to the underlayer (underlayer coercivity (Hc(u)=50Oe) on a CoNiReP/CoB double-layered medium, the PS effect was confirmed to appear until the recording density of the region was less than 90 kFRPI. The enhancement of the reproduced voltage in a region where the density was higher than 90 kFRPI was still observed after such a proper AC erasing process, and it originated solely from the DL effect.