Ring-type Electrodes Research Articles

Electrohydrodynamic Printing of Biodegradable PLGA Micro‐Patterns on 3D Polymer Structures

AbstractBiodegradable polymers such as polylactic‐co‐glycolic acids (PLGA) are used for various implantable devices such as tissue scaffolds, drug delivery devices, and biosensors in different forms. However, high‐resolution patterning of biodegradable polymers on implantable devices has not been explored much yet. While electrohydrodynamic printing (EHD) can achieve high‐resolution printing compared to other printing methods, EHD printing of PLGA solutions is rarely attempted due to unstable printing. Such printing instability originates from the volatile nature of PLGA inks, and it causes nozzle clogging or change of ink conditions during printing. Here, PLGA ink formulation and a voltage input profile are studied for stable and high‐resolution EHD printing. Addition of glycerol at an optimal ratio as well as the control of voltage pulse shape strongly influenced both the stability and resolution of EHD printing of PLGA patterns. With the optimized inks and voltage inputs, stable printing of PLGA micropatterns down to 5 µm is achieved on both conductive and insulating surfaces for controlled drug release. Furthermore, use of a ring type electrode allows for EHD printing of PLGA micropatterns on 3D surfaces of PLLA tubes and stent struts.

Development of capacitance sensor for void fraction measurement in a packed bed of spheres

A capacitance void fraction sensor (CVS) is applied to measure the volumetric averaged void fraction in a packed bed of spheres. The void fraction in the packed bed is one of the most important parameters to evaluate cooling characteristics in a porous debris bed during a severe accident of nuclear reactors, and the quantitative void fraction measuring technique for such porous flow channels should be developed. The CVS is a very simple method, and the void fraction is estimated from the electrical capacitance measured between the electrodes installed on the pipe. Generally, the linear relationship or Maxwell equation could be applied to estimate the void fraction from the capacitance measured by the CVS. However, the electrical field in the packed bed becomes complex due to the existence of spheres. Therefore, they may not be applied to the void fraction estimation in the packed bed. In this study, the CVS with a ring-type electrode configuration is used for the sphere-packed beds, and the applicability of the CVS is investigated. At first, the particle size and the pipe diameter are varied in the packed test section, and X-ray transmission imaging is used to clarify the relation between the void fraction and the capacitance in the packed bed. Then, it is found that the void fraction can be obtained by the coefficient in Maxwell's equation, depending on the packed bed properties. Finally, the measurement accuracy of the CVS for the sphere-packed bed is estimated by comparing it with a volumetric method, and the availability of the proposed method is shown.

Analytical Potentials for the Efficient Simulation of Planar and Axisymmetric Ion Mirrors

In this paper, we obtained analytical equations for electrostatic fields of two-dimensional planar and axially symmetric mirrors with piecewise-constant and piecewise-linear potentials on electrode surfaces located symmetrically in parallel planes or on a cylindrical surface, in particular, in the presence of an additional end electrode. The results can be used for the efficient optimization of aberration properties of time-of-flight mass analyzers and electrostatiс ion traps with gridless ion mirrors based on both standard planar or ring-type electrodes with finite gaps between them and PCB plates.

Corrosion Monitoring of Reinforcing Bar in Concrete Under Different Corrosive Environments

Reinforced concrete structures have been widely used for social infrastructures because of their high strength. However, it currently has been passed over 50 years since many infrastructures constructed, and the deterioration in durability is a problem. The corrosion of reinforcing bars due to neutralization of concrete and adhesion of airborne sea salt, and the concrete cracking by corrosion products is considered as the main cause of deterioration. Therefore, in order to properly maintain and manage the infrastructure structure, it is necessary to understand the corrosion deterioration behavior of the reinforcing bars in the concrete. In this study, wet and dry cyclic corrosion test was conducted using concentric ring type electrodes of carbon steel covered with mortar. The difference in corrosion behavior of reinforcing bars due to covering thickness and corrosion test conditions was investigated by continuously measuring the impedance between two electrodes. Furthermore, the diffusion behavior of water and chloride ions in mortar part was observed, and the correlation with corrosion behavior was investigated The concentric ring type electrodes of carbon steel were used as the monitoring electrodes, and they were covered with the different thickness of mortar (hereinafter, the mortar electrode). The composition of the mortar was coarse aggregate: cement: water = 3: 1: 0.6. 10 kg/m3 NaCl was added to the mortar to accelerate corrosion. The covering thickness was set to 3, 10 mm. The corrosion test was carried out by wet and dry cycle, and the electrochemical impedance at two frequencies of 10 mHz and 10 kHz was continuously measured during the corrosion test. A core having a height of 50 mm and a diameter of 40 mm was prepared with the same composition of mortar. The prepared cores were immersed in 0.1 mol/L NaCl solution for several hours. The permeation state of water and chloride ion was investigated by water leakage test agent and fluorescent X - ray analysis. Changes in the corrosion rate of the mortar electrode prepared by underwater curing in the wet and dry cyclic corrosion process were continuously measured. Although there was some variation, corrosion rate decreased in the immersion process, regardless of the thickness of the mortar. The corrosion rate of the electrode with 3 mm mortar showed higher value than that with 10 mm mortar. The changes in corrosion rate and solution resistance in each cycle of corrosion test were examined. The solution resistance gradually decreases in the wet process, and the value showed a minimum in the drying process. This means that diffusion rate of the solution is slow in the mortar. Since the decrease in solution resistance corresponds to the increase in corrosion rate, it is considered that the increase in corrosion rate is due to wetting by the permeated solution. There was a large fluctuation in the electrode with 3 mm mortar, whereas the electrode with 10 mm mortar always showed a low solution resistance value regardless of process of the corrosion test. This difference in wetting environment can affect the change in corrosion rate and corrosion behavior.

Dielectric Electroactive Polymer Membrane Actuator with Ring-type Electrode as Driving Component of a Tactile Actuator

We present a driving concept of a tactile actuator based on a dielectric electroactive polymer using a ring-type electrode. This electrode is located around a deflectable membrane. The fabrication process and tests of the tactile actuator including integration into a hydraulic amplifier design are presented proving the concept of the novel actuation. The tactile actuator exhibits a maximum measured deflection of 124±7μm for an applied voltage of 4200V. The membrane thickness and the total thickness of the actuator including hydraulic amplifier were 30 and about 570μm, respectively.

Intense Ar Plasma Array Jet With Ring-Type Focusing Electrode

A new plasma array jet with an additional ring-type focusing electrode is proposed to obtain an extended and intense Ar plasma jet focused on a central glass tube at atmospheric pressure. To investigate the role of the ring-type electrode, the sinusoidal voltages of 9 kV and frequency of 30 kHz were applied to three different electrode configurations, such as only ringtype electrode, only probe-type electrodes, and both the ringand probe-type electrodes. As a result, the ring-type electrode is confirmed to play a significant role in spatially focusing the charge particles ignited by the exposed probe-type electrodes, thereby producing a stable and intense Ar plasma jet under atmospheric pressure.

Control of surface charge on insulating hollow cylinder by using shield-ring in vacuum

In vacuum, insulators acquire charge due to well-known Secondary Electron Emission Avalanche (SEEA), and the charge is considered harmful for the insulation of high voltage vacuum devices. This paper deals with the charge depression effect of a shieldring, a ring type electrode, which is often applied to high voltage devices in order to relax the electric field near the triple junction on a cathode. In the present study a shield-ring is located in an insulating hollow cylinder made of Al2O3. The charge distribution on the inner surface is measured by employing an electrostatic probe located outside of the cylinder. The probe has scanned the whole surface of the cylinder and produced a probe output pattern that varies in shape depending on the ring height. On the other hand, we have calculated the charge distribution on the inner surface of the cylinder by employing a rotationally symmetric i.e. two dimensional simulation method relying on the SEEA mechanism. Giving the calculated distribution, we have further calculated the probe output by using a three dimensional simulation method. The calculated and measured probe output patterns show a reasonable agreement for several ring heights tested in this study. Based on these experimental and analytical results, we have revealed the effectiveness of using a shield-ring to depress the SEEA charging.

Generating diffuse discharge via repetitive nanosecond pulses and line-line electrodes in atmospheric air

Diffuse discharge in atmospheric air can generate extremely high power density and large-scale non-thermal plasma. An achievable method of generating diffuse discharge is reported in this paper. Based on the resonance theory, a compact high-voltage repetitive nanosecond pulse generator (HRNPG) has been developed as discharge excitation source. The HRNPG mainly consists of repetitive charging circuit, Tesla transformer and sharpening switch. With the voltage lower than 1.0 kV, the primary repetitive charging circuit comprises two fast thyristors as low-voltage switches. A spiral Tesla transformer is designed to provide a peak transformation ratio of more than 100. The HRNPG prototype is capable of generating a pulse with over 100 kV peak voltage and ~30 ns rise-time at the repetition frequency of 500 Hz. Using the copper line electrodes with a diameter of 0.4 mm, the gaps with highly non-uniform electric field are structured. With the suitable gap spacing and applied pulse, the glow-like diffuse discharge has been generated in line-type and ring-type electrode pairs. Some typical images are presented.

정전용량변화를 이용한 링거액소진감지장치의 구현

Electrostatic capacitance measurement method in a fine hose was proposed, in which two ring-type electrodes were disposed on the hose in the direction of fluid flow instead of the conventional face-to-face electrodes. With the proposed electrode structure, we realized a Ringer's solution exhaustion detector for an IV(invasive vein) injection set. On a 4 mm-diameter hose of IV set, we disposed two ring-type electrodes of 10 mm width at a distance of 5 mm each other and obtained 0.72 pF and 2.51 pF for air and 10 % dextrose Ringer's solution in the hose, respectively. The capacitance between the two electrodes varied with the hose-wraparound coverage of electrode as well as the width of electrode and the distance between the electrodes. For hose-wraparound electrode coverage of 75 %, the capacitance varied from 0.62 pF to 1.98 pF with the Ringer's solution level between the two electrodes. A charge amplifier converted the capacitance. variation into electric signal and a comparator was used to detect whether Ringer's solution was exhausted or not. The result was delivered to a host using a RF transmitter with 320 MHz carrier frequency.

ミニチャンネルのボイド率計測技術開発(混相流動,<特集>第13回動力・エネルギー技術シンポジウム)

Capacitance type electro-void fraction meters with various geometries of electrodes were developed for two-phase flow measurement in tubes of 1mm in the smallest diameter. Ring-type electrodes were applied to measure void fraction. The principle of the meter is that the electrical capacitance depends on integrated dielectricity of gas-liquid two-phase flow with void fraction. A high-frequency power supply enables to measure the low electrical capacitance of the water including purified water. It was confirmed with the air-water two-phase flow experiments that void fraction can be obtained in real time way every 50 milliseconds. Void fraction in the experiments ranged from 0% to higher than 90%. The void fraction was correlated with the electric capacitance by a linear function for the ring-electrode under the atmospheric condition.

Visualization of math expressions through modality-nonspecific signals

Acquiring reasonable math skills is essential for the visually disabled pupils and students. Research in electro-tactile pattern perception has shown that involving the resources of visual cortex into acquisition of tactile percepts augments comprehension of the encoded information for users with a sensory limitation. This paper describes matching software designed to facilitate the learning process of 13 electro-tactile patterns (eTPs) denoting eight math numbers and five arithmetic operators. Electro-tactile unit and software were used to shape stabilized monophasic current pulses provided through the pen coated with embedded double-strip ring type electrode. The performance of ten subjects was investigated in terms of the number of repetitions required to memorize and match the eTPs, and in terms of the recognition error committed in the matching phase of the test. The analysis of the data collected indicated that the novice-to-expert transition was significantly above chance when the results obtained in the first and the last test sessions were statistically compared. A permutation puzzle game which was also designed to induce the same ten blindfolded players to mobilize the perceptive skills and deploy individual playing tactics to manipulate the eTPs encoding math numbers and expressions for rebuilding simple arithmetic equations. The results of the use of the proposed gameplay technique are discussed. Upon learning and training, the eTPs could be employed to assign math numbers and arithmetic operators to communicate mathematics content.

On the design of electrical conductance probes for foam drainage applications: Assessment of ring electrodes performance and bubble size effects on measurements

This work examines critical design aspects of electrical conductance probes for measuring the liquid fraction in foams. These include the electrodes’ size, shape, separation distance and intrusiveness as well as issues such as the excitation current frequency, multiplexing, data reduction to liquid fraction, etc. Measurements are performed with ring type electrodes, flush mounted on a test vessel wall at different heights to provide a measure of the longitudinal variation of liquid fraction in the foam. Runs are also performed with traditional disk and rod type electrodes immersed in the foam. The electrically determined local liquid fraction is compared with the photographically determined local bubble size distribution at the wall as well as with the volumetrically determined global liquid fraction in the entire vessel. For the examined protein-polysaccharide stabilized wet foam, drainage is negligible for a substantial initial period of time and only later a liquid fraction gradient emerges. In this no-drainage period, comparison of the local electrical signal with the local bubble size distributions reveals that the bubble size affects the liquid fraction. Moreover, a strong correlation is found between bubble size and onset of drainage.

ＥＣＦジェット駆動マイクロフィンガの提案とラージモデルの特性評価

Electro-Conjugate Fluid (ECF) is a dielectric and functional fluid, which produces jet-flow (ECF-jet) by applying high voltage between electrodes. It is ascertained that a strong ECF-jet is generated under a nonuniform electric field, for example around a needle-ring electrode pair consisting of a needle-type electrode and a ring-type electrode. This study proposes and realizes a novel microactuator with 2 degree of freedom motion using ECF-jet generated by the needle-ring electrode pair. In this paper, first, we propose a novel microactuator using ECF-jet (ECF micro finger). The ECF micro finger consists of a finger-tube with three chambers, made of three flexible tubes, and a jet generator with three needle-ring electrode pairs. When the ECF-jet is applied to the chambers, the pressurized chambers are expanded, the other chambers are shrunk and the finger is bent. Next, a large model of the proposed ECF micro finger is fabricated. Finally, he static characteristics of the large model are experimentally investigated

ＥＣＦジェットによる発生圧力を応用したチューブ形ＥＣＦマイクロアクチュエータ

Electro-Conjugate Fluid (ECF) is a kind of dielectric and functional fluid, which produces jet-flow (ECF-jet) by applying high voltage between electrodes. The purpose of this study is the realization of a novel microactuator using an ECF-jet. It is ascertained that a strong ECF-jet is generated under a non-uniform electric field. Therefore, in this paper, a pair of needle-type and ring-type electrodes (a needle-ring electrode pair) are used to obtain a stronger ECF-jet. First, influences of parameters of the needle-ring electrode pair on the pressure due to an ECF-jet are experimentally investigated. Second, a novel microactuator using an ECF-jet with the needle-ring electrode pair is proposed and fabricated, which is driven based on the principle of Bourdon tubes. Finally, the characteristics of the fabricated tube-type ECF microactuator are experimentally investigated.

Geophysical Resistivity Imaging for Upper Layer of Shield TBM Tunnel Ceiling

ABSTRACT Recently shield TBM tunnelings are being applied to subway construction in Korean cities. Generally these kinds of tunnelings have the problems in the stability of ground such as subsidence because urban subway is constructed in the shallow depth. A sinkhole occurred on the road just above the tunnel during tunneling in Kwangju, so a survey for upper layer of the tunnel was needed. But conventional Ground Probing Radar can't be applicable due to the presence of steel-mesh screen in the shield segment, so no existent geophysical method is applicable in this site. Because the outer surface of each shield segment is electrically insulated, dipole-dipole resistivity method which is popular in engineering site investigation, was tried to this survey for the first time. Specially manufactured flexible ring-type electrodes were installed into the grouting holes at an interval of 2.4 m on the ceiling. The K-Ohm II system which has been developed by KIGAM and tested successfully in many sites, was used in this site. The system consists of 1000Volt-1Ampere constant-current transmitter, optically isolated 24 bit sigma-delta A/D conversion receiver—maximum 12 channel simultaneous measurements, and graphical automatic acquisition software for easy data quality check in real time. Borehole camera logging with circular white LED lighting was also done to investigate the state of the layer. Measured resistivity data lack of some stations due to failing opening lids of holes, shows general high-low trend well. The dipole-dipole resistivity inversion results discriminate (1) one approximately 4 meter diameter cavity (grouted but incompletely hardened, so low resistivity—less than 30ωm), (2) weak zone (100–200ωm), and (3) hard zone (high resistivity—more than 1000ωm) very well for the distance of 320 meters. The 2-D inversion neglects slight absolute 3-D effect, but we can get satisfactory and useful information. Acquired resistivity section and video tapes by borehole camera logging will be reserved and reused if some problem occurs in this site in the future.

산화아연 피뢰기 소자와 전극사이에 발생하는 방전광 현상

본 논문에서는 산화아연(이하 ZnO) 피뢰기 열화진행의 한 요인으로 예측되는 전극과 ZnO소자 사이에서 발생하는 방전광 현상에 관한 연구를 수행하였다. 이를 위해 8/20[㎲], 최대 10[kA]의 뇌임펄스전류를 발생시키는 뇌임펄스전류 발생장치를 설계?제작하였다. 실험결과, 상·하부의 전극 부근에서 발생하는 방전광의 형상은 인가되는 뇌임펄스의 극성에 따라 다르게 나타났으며 상대적으로 (-)극의 전극부근에서 방전광이 더 강하고 활발하게 발생하는 것으로 관찰되었다. 또한 전극의 면적에 따른 방전광의 세기는 전극의 면적이 증가할수록 감소하는 것으로 관측 되었다. 동시에 전극과 소자의 접촉상태도 방전광의 발생과 매우 밀접한 관계가 있는 것으로 확인되었다. 따라서 배전급 ZnO피뢰기의 기존 전극구조는 보완이 필요하며 ZnO 피뢰기 제품의 성능향상 및 지속적인 성능유지를 위해서는 환형구조 대신 내부면적이 있는 원판구조로 교체하는 것이 바람직하다고 판단된다.

ECFジェットを用いたマイクロマニピュレータの試作と特性評価(J22-3 センサ・アクチュエータシステムとその知能化(3),J22 センサ・アクチュエータシステムとその知能化-実環境で活躍するメカトロニクスを目指して)

Electro-Conjugate Fluid (ECF) is a kind of dielectric fluids and a kind of functional fluids, which produces jet-flow(ECF-jet) by applying high voltage between electrodes. In addition, a strong ECF-jet is generated under ununiform electric field. Therefore, in this study, a pair of needle-type and ring-type electrodes (needle-ring pair) is used for generating ECF-jet. It is ascertained that the pressure due to ECF jet from needle-ring pair is increased by miniaturizing dimensions of the electrodes. The characteristics are suitable for micro manipulator. Therefore, the purpose of this study is the realization of novel micro manipulators using ECF-jet. In this paper, first, characteristics of ECF-jet from needle-ring pair are experimentally investigated. Second, a novel micro manipulator which is actuated by the same principle as well-known Bourdon tubes is fabricated. Third, static characteristics of the micro manipulator is experimentally investigated. Finally, another type micro manipularor, finger-type ECF micro manipulator is fabricated. Future works are fabrication and investigation of a microhand constructed with more than three finger-type ECF micro manipulators.

帯電エアロゾル流による沈着・再飛散同時現象 沈着層に及ぼす粒子の電荷と外部電界の影響

Formation of particle deposition layer was investigated as a simultaneous phenomenon of particle deposition and reentrainment in a turbulent aerosol flow. Aerosol particles passed through a corona charger were pneumatically transported into a glass tube equipped with a ring-type electrode, and the deposition layers formed on the tube wall in various conditions were quantitatively analyzed with particular attention to the effects of particle charge and external electric field on the deposition layer. The charged particles formed a deposition layer of a filmy pattern around the electrode being independent of the polarity of particle charge and applied voltage. The mass of deposition layer increased with elapsed time and became constant after an equilibrium state of particle deposition and reentrainment. The time dependency was represented by an exponential equation; the time constant decreased with increasing particle charge and/or applied voltage, and the equilibrium mass of deposition layer increased with the particle charge. Furthermore, it was found that appropriate arrangement of electrodes to control external electric field eliminates the filmy pattern deposition layer.

High-brightness, AlGaInP-based, visible light-emitting diode for efficient coupling with POF

A high-brightness light-emitting diode (LED) is fabricated using the AlGaInP based quaternary double heterostructure. The ring type electrode is used in the top contact in order to spread the current efficiently and also to enhance the coupling efficiency with the fiber. The fabricated LED has a light output as high as 1.7 mW at the bias current of 100 mA. The far-field radiation divergences are found to be approximately 100 and 70/spl deg/ for the LED's, with and without molding. These LED's offer coupling efficiency as high as 70% and 35%, with the step index (SI) plastic optical fiber (POF) after using the molded and hybrid ball lens, respectively. The increases of the coupling efficiency are due to the use of the ring-shaped top electrode, concentrating the emission mostly at the center. >

Parametric effects on the void fraction measurement by capacitance transducers

The main purpose of this work is to study the effects of (1) geometry, size and materials of electrodes, (2) flow pattern, and (3) electrode position with respect to a dielectric boundary on the void fraction measurement by capacitance transducers. A set of theoretical relative capacitance formulas for a test section, which is equipped with a pair of strip-type electrodes and in which an annular or stratified flow is present, is derived based on the concept of capacitance in series and parallel. From the experimental results, relationships between the measured relative capacitance and void fraction are obtained for both annular and stratified flow systems under static condition. This result is compared with theoretical predictions. From this study it is found that (1) the strip-type electrodes are more sensitive than ring-type electrodes for both annular and stratified flows, (2) electrode size does not affect the relative capacitance versus ( 1 − α) curve, and (3) electrode position is important for stratified flows but it has no effect on annular flows.