Stepwise Switching Research Articles

Electrothermally Triggered Broadband Optical Switch Films with Extremely Low Power Consumption

Smart films with transmittance switching capabilities based on thermal stimuli are widely used in many optoelectronic applications. Despite the development of stably switchable materials, transition temperature control and broadband stepwise transmittance switching remain challenging topics. Additionally, reduction of the energy consumption during switching is also required. Here, we introduce an electrothermally driven film with switchable transmittance produced by stacking paraffin-immobilized polydimethylsiloxane gel on a transparent heater based on an aligned Cu/Ni network. The film shows stepwise transmittance switching capability with extremely low power consumption because of the controlled melting point of paraffin and the high-efficiency transparent heater.

Mechanically triggered reversible stepwise tricolor switching and thermochromism of anthracene-o-carborane dyad.

A novel single organic molecule-carborane conjugate, CAN, was synthesized in a high yield via a modified nickel-catalyzed cross-coupling reaction incorporating an anthracene unit and an o-carborane moiety. CAN exhibits multiple functions of tricolored mechanochromism and mechanically triggered thermochromism. The fluorescence could be switched from blue to bright yellow then to pink by grinding. The robust and reversible thermochromic process was triggered by the mechanical force. The locally excited (LE) state emission, intermolecular excimer formation and twisted intermolecular charge transfer (TICT) are the primary origins of this tricolor switching property. High temperature sensitivity of the heavily ground CAN powders contribute to the mechanical force induced TICT emission enhancement and color switching.

The effect of the conductivity of drift chamber walls on the dynamics of a relativistic electron beam with a virtual cathode

The effect of conductivity of walls of a drift chamber of the axial vircator on the behavior of a relativistic electron beam with a supercritical current was investigated. The dynamics of a relativistic electron beam is shown to be characterized by the formation of a virtual cathode of complex structure with two or three potential minima in the azimuthal direction, which rotate around the drift space axis. It is established that variation in the conductivity of drift chamber walls leads to stepwise switching of the generation frequency and a sharp change in the output power. Dependences of the output radiation power of the investigated vircator system on the conductivity of drift chamber walls for two characteristic regimes of the dynamics of a relativistic electron beam were obtained.

Biomimicking lubrication superior to fish skin using responsive hydrogels

The slippery mucus produced by fish skin is important to protect fish against predator attack, allowing fish to swim faster and remain elusive because of the ultra-low coefficient of friction (COF) of fish skin. To mimic this slick skin, responsive hydrogels that respond to external stimuli, including pH and temperature, were prepared. These hydrogels were found to perform better than fish skin: not only was an ultra-low COF achieved but multiple tunable COFs from ultra-low to ultra-high were discovered using sequential regulation of pH and temperature. The tunable COF was achieved through conformational changes in the molecular chains in the responsive hydrogel that were induced by the external stimuli. Swelling of both pH- and thermal-responsive polymer chains of the hydrogel resulted in an ultra-low COF; the pH-responsive component, shrink as a result of dehydration caused by a pH change, led to a moderate COF, whereas the two components simultaneous shrink brought out a very high COF. The three levels of COF under different states can be reversibly switched multiple times by sequential regulation of pH and temperature. This reversible tunability in friction performance is likely to have a significant impact on the design of hydrogel-based actuation devices. Fish excrete hydrophilic biopolymers with ultralow ‘coefficients of friction’ onto their skin to improve their mobility in water. Artificial hydrogels, which trap copious quantities of water molecules inside three-dimensional polymer networks, also have low frictional coefficients and have been targeted for use as biomimetic artificial joint materials and actuators. Their natural counterparts — hydrophilic biopolymers — are usually unable to react to external stimuli and therefore unable to alter their friction. Feng Zhou and colleagues from the Chinese Academy of Sciences in China have demonstrated that a hydrogel can adjust its frictional behavior on demand. The authors improved on their previous discovery — a thermally-responsive acrylamide hydrogel containing graphene oxide flakes — by adding pH-sensitive methacrylate components into the polymer network. Modifying environmental conditions enabled the hydrogel to undergo stepwise switching from ultralow to high friction states — a reversible transformation ideal for producing micromechanical surfaces with ‘autobraking’ capabilities. Stimulus-sensitive composite hydrogels with both pH and temperature responsiveness were prepared to simulate the mucus on fish skin and were found to have superior performance to that of the mimicked substance. The coefficients of friction (COFs) of the gels were found to be easily tunable, from a low to moderate, and then a high level. Importantly, the COF can be reversibly switched for many times by the sequential regulation of external pH and temperature.

Removal and recovery of Ni2 + from electroplating rinse water using electrodeionization reversal

The removal and recovery of Ni2+ from simulated electroplating rinse water by electrodeionization reversal (EDIR), i.e., electrodeionization using periodic changes in polarity, was studied. Based on the EDIR characteristic curves, the appropriate applied stack voltage was determined to be 30V. The influence of the polarity reversal period on EDIR performance was examined. In addition, a stepwise stream switching mode was proposed to reduce Ni2+ loss. The experimental results showed that the duration of polarity reversal should not be greater than 4h to prevent the formation of metal hydroxide precipitates. Additionally, the EDIR process with a polarity reversal period of 4h and stepwise stream switching mode exhibited good separation performance, removing 97.0% of Ni2+ from the feed solution and simultaneously recovering these ions into a concentrate stream with a high concentration of 3961mg·L−1. The current efficiency was 32.6%, and the corresponding energy consumption to treat 1m3 of water was 1.02 KW·h. Thus, EDIR has considerable potential for the recovery and reuse of heavy metal ions from electroplating rinse water.

メサドンへの段階的なオピオイド変更が有用であった1例

【緒言】わが国でのメサドンの使用は, 先行する強オピオイドからの変更に限られており, 先行オピオイドを中止してメサドンを開始するstop－and－go (SAG)法が推奨されている. 【症例】悪性腸腰筋症侯群による難治性疼痛に対し, モルヒネとケタミンの併用からメサドンにSAG法で変更した. 一時的に疼痛が増強したが, モルヒネの再開と約2週間の併用によって疼痛緩和を得た. 【考察】本症例のように疼痛コントロールが不良でメサドンに変更する場合には, 段階的に置き換える方法がSAG法よりも有用であると考える. メサドンは, 過量投与の問題を考慮して少なめに開始するのが安全であり, 疼痛の増強を回避するためには, より柔軟な初回投与量の設定や用量調節の検討が必要と考える. 併用している鎮痛補助薬をメサドンへの変更時に継続する妥当性, 特にNMDA受容体拮抗作用がメサドンと重複するケタミンを継続することの妥当性については, 今後も議論を深める必要がある.

Closed-Loop Control of Renal Perfusion Pressure in Physiological Experiments

This paper presents the design, experimental modeling, and control of a pump-driven renal perfusion pressure (RPP)-regulatory system to implement precise and relatively fast RPP regulation in rats. The mechatronic system is a simple, low-cost, and reliable device to automate the RPP regulation process based on flow-mediated occlusion. Hence, the regulated signal is the RPP measured in the left femoral artery of the rat, and the manipulated variable is the voltage applied to a dc motor that controls the occlusion of the aorta. The control system is implemented in a PC through the LabView software, and a data acquisition board NI USB-6210. A simple first-order linear system is proposed to approximate the dynamics in the experiment. The parameters of the model are chosen to minimize the error between the predicted and experimental output averaged from eight input/output datasets at different RPP operating conditions. A closed-loop servocontrol system based on a pole-placement PD controller plus dead-zone compensation was proposed for this purpose. First, the feedback structure was validated in simulation by considering parameter uncertainty, and constant and time-varying references. Several experimental tests were also conducted to validate in real time the closed-loop performance for stepwise and fast switching references, and the results show the effectiveness of the proposed automatic system to regulate the RPP in the rat, in a precise, accurate (mean error less than 2 mmHg) and relatively fast mode (10-15s of response time).

Step-wise safe switching control of a constant turning force system

In this paper, we present the application of multivariable step-wise safe switching (MSWSS) in order to control a constant turning force system under varying cutting conditions. The non-linear part of the plant's model is considered to be unknown and it is approximated by a set of linearised models which are derived through identification around corresponding operating points. State feedback proportional-integral controllers are designed to achieve sufficiently fast settling time and keep the cutting force at the appropriate level as the cutting depth varies with time. The controllers are designed using a metaheuristic search algorithm so as to achieve the required performance simultaneously for two adjacent operating points. A state observer is used to estimate the acceleration of the servomechanism that determines the feed rate of the cutting machine. Closed-loop performance is illustrated through simulation results.

Electrically tunable Lyot filter for fast wavelength switching of diode-pumped solid-state disk lasers

A new setup for fast wavelength switching of an Yb:YAG disk laser uses a lithium niobate Lyot filter. It is modeled by the Jones matrix formalism and it is tested experimentally. Applying a high voltage to the Lyot filter leads to stepwise wavelength switching of the laser with a minimum step size of 91 pm determined by the intra-cavity etalon ensuring longitudinal single-mode operation. The maximum step size achieved with the current driving electronics amounts to 0.6 nm at 500 Hz switching frequency. This setup shows high spatial and temporal laser beam stabilities.

Reduction-Induced Switching of Single-Molecule Conductance of Fullerene Derivatives

The effect of electrochemical reduction on the single-molecule conductance of fullerene C60 derivatives was studied by scanning tunneling microscopy. Three types of C60 derivatives were synthesized, a monoadduct having an amino-terminated linker and two bisadducts having two linkers at different positions (trans2 and trans3). Each C60 derivative was immobilized on a gold surface by an amino-gold linkage, confirmed by infrared reflection-absorption spectroscopy. The immobilized C60 derivatives showed reversible and multiple reduction peaks in the cyclic voltammogram in dimethylformamide (DMF) at almost the same potentials as those in solution, showing the redox properties of the molecules are intact on gold. Single-molecule conductances of the bisadducts, which can span between a scanning tunneling microscopy (STM) tip made of gold and substrate with the two linkers, were determined by the STM break-junction measurements in water and DMF. The conductances were 6.1+/-4.5 nS in water and 4.9+/-1.7 nS in DMF for the trans2 bisadduct and 8.4+/-3.4 nS in water and 7.9 nS+/-2.8 in DMF for the trans3 bisadduct. By using a potential-controlled STM setup, the tunneling current through a single molecule was recorded with sweeping the potentials of the tip and substrate. The trans2 bisadduct showed significant changes in the current when the reductions of the C60 moiety occur. Some current curves showed multiple peaks, and the other curves showed stepwise increase and decrease at the C60 reduction and subsequent reoxidation. Statistical analysis afforded stepwise switching of the conductance as the average behavior and suggested that the electron tunneling through the C60 derivative is enhanced as it accepts electrons.

Conductance Hysteresis and Switching in a Single-Molecule Junction

Voltage-controlled conductance hysteresis and stepwise switching in a reversible manner were observed in a single-molecule double-barrier junction defined by a scanning tunneling microscope (STM) at ∼10 K. In situ visualization and characterization of the junction using the STM revealed that the charge bistability of a single molecule on a polar alumina film is responsible for the conductance hysteresis and switching. It was also found that the relative stability between different charge states depends on the multiple adsorption configurations of molecules on the surface.

Logic-based switching controllers – A stepwise safe switching approach

The present work proposes a new logic-based safe switching technique, called here Stepwise Safe Switching. This technique is based on the description of the process with linear approximants which are valid in operating areas around a finite number of nominal operating points of the process. Switching takes place between common controllers for adjacent nominal operating points. Moreover, the switching between the controllers is allowed to take place only when the process has reached an operating point. The proposed technique guarantees stability and good performance for all transitions between operating points that lie in the neighborhoods of the nominal operating points of the process. This way a simple to design and easy to implement solution that provides good performance despite the drawback of lack of knowledge of the process dynamics can be derived. The proposed technique is successfully applied to control an isothermal CSTR process, described by three linear approximants around corresponding nominal operating points.

In-line liquid-crystal microcell wave plates and their application for high-speed, reset-free polarization mode dispersion compensation in 40-Gbit/s systems.

We describe the design, fabrication, and performance of a high-speed, continuously tunable, and reset-free polarization controller based on nematic liquid-crystal (NLC) microcell wave plates fabricated directly between the tips of optical fibers. This controller utilizes a pulsed driving scheme and optimized NLC materials to achieve a stepwise switching speed of 1 deg/micros, for arbitrary rotation angles with moderately low voltages. This compact microcell design requires no bulk optical components and has the potential to have low insertion loss. We describe the performance of these devices when implemented in polarization mode dispersion compensators for 40 Gbit/s systems. The good optical properties and the nonmechanical, high-speed, and low-power operation suggest that this type of device might be considered for some applications in dynamic compensation of polarization mode dispersion, polarization analysis, polarization division demultiplexing, and polarization scrambling in high-speed optical communication systems.

Magnetization of small arrays of interacting single-domain particles

We have prepared tailored small arrays of single-domain Ni nanomagnets exhibiting an easy-axis perpendicular to the substrate surface. Using ballistic Hall micromagnetometry we probe the magnetization under different tilt angles. For an array of 13 nanomagnets with 700 nm spacing, we observe distinct plateau values in the hysteresis loop indicating the stepwise switching of these particles. The observed hierarchy of reversal comes close to a model on the basis of the magnetostatic interparticle interaction.

Metastable shunt paths in a-Si solar cells

We have studied the time/voltage dependence of current transients in several different a-Si solar cell structures and have found they reveal more about the basic shunt mechanism. In single-junction cells, we see stepwise current changes that increase in size and number with reverse bias and can be removed with forward bias. This stepwise, on and off switching suggests a discrete shunt path conduction mechanism. The kinetics of these metastable shunt paths show that both the “on-state” and “off-state” possess memory. Cells without the Al doped ZnO layer (Al)ZnO between the cell and the back contact metal show no metastable switching. We associate the stepwise features with the textured substrate and the switching metastability with contact to (Al)ZnO. Switching in triple-junction cells occurs with hundreds of oscillations at each step.

Unsteady heat transfer in He II with cylindrical geometry

Heat transfer in He II with cylindrical geometry, involving stepwise switching on of a heater which forms an internal cylinder, is investigated in this paper using numerical methods. The problem is solved within the framework of the hydrodynamics of superfluid turbulence (HST), in which the density of the vortex tangle L reaches its equilibrium value with respect to the value of the velocity of the normal component (the so-called adiabatic approximation). In this paper we consider two different cases: the adiabatic one, which corresponds to an isolated system; and the isothermal one, which corresponds to a system immersed in a bath filled with He II at a given temperature. The results obtained and those evolved from Dresner's approach are compared using a newly introduced parameter, the Dr number.

Study of the demagnetization and optimization of the magnetic field of perpendicular ferromagnetic thin films usingesub-μ m lithography

The succesful fabrication using holographic lithography of a submicron grating reducing the demagnetizing field of a perpendicular ferromagnetic thin film is reported. An increase in the extraordinary Hall effect by a factor 3 is measured. The presence of holes in the film lowers the coercive field and causes a stepwise switching.

Heat transfer in He II with stepwise switching on of heater

The problem of the dynamics of temperature and normal velocity fields in He II with stepwise switching on of a plane heater is investigated in this paper using numerical methods. The problem is solved in the framework of the hydrodynamics of superfluid turbulence in which the density of vortex tangle, L, reaches its equilibrium value with respect to the value of the relative velocity, v ns = ( v n - v s). Such an approximation, the so-called adiabatic approximation, is valid at times much larger than the time for development of turbulence, τ v. The results obtained are compared with other known solutions of similar problems and with experimental data.

A Motion Detection Method on Video Image by Using Hierarchical Pixels

AbstractIt is not easy to extract significant information from image data concerning the motion and the structure of an object, but this technique is indispensable to the future development of video coding and recognition of a moving object. The block matching method [1] is employed widely as a motion detection method in the motion‐compensated interframe coding. However, it has a problem in that the motion is estimated by the prediction error power minimization condition, which may lead to an instability in accurate motion detection. This paper proposes a new block matching method that has the following features: the motion is estimated and detected by stepwise switching from larger block size to smaller block size; by this scheme, the motion detection accuracy and the spatial resolution can be improved, and the processing complexity can also be reduced without degrading the detection accuracy.