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Silver nanowires (AgNWs) have become an efficient electrode candidate for stretchable electronics. We report the effects of directional stretching in microprism-mediated AgNW stretchable electrodes on polyurethane (PU) substrates. The wavy substrate is fabricated using a customized microprism on polyethylene terephthalate. AgNWs on stretchable PU substrates show stable normalized resistance up to 35% strain under parallel uniaxial stretching. This performance is much better than AgNWs on bare PU substrate or on wavy PU under perpendicular stretching, which can only sustain 10%-15% strain before significant increase in normalized resistance. Finite element simulations were conducted to reveal the strain distribution and variation in the AgNW electrodes on both bare and wavy PU substrates when stretched along parallel and perpendicular directions. Comparing to AgNW electrodes on bare PU and on wavy PU under perpendicular stretching, the wavy PU surface relief features can effectively alleviate the strain in the AgNW network when stretched along parallel direction, leading to better performance. [ABSTRACT FROM AUTHOR]

This paper describes an offset-free model predictive control (MPC) algorithm using a disturbance observer (DOB) to control the active/reactive powers of a three-phase ac/dc converter. The strategy of this paper is twofold. One is the use of DOB to remove the offset error, and the other is the proper choice of the weighting matrices of a cost index to provide fast error decay with small overshoot. The DOB is designed to estimate the unknown disturbances of the ac/dc converter following the standard Luenberger observer design procedure. The proposed MPC minimizes a one-step-ahead cost index penalizing the predicted tracking error by performing a simple membership test without any use of numerical methods. A systematic way for choosing the weights of the cost index, which guarantees the global stability of the closed-loop system, is proposed. Use of the DOB eliminates the offset tracking errors in the real implementation. Using a 25-kW ac/dc converter, it is experimentally shown that the proposed MPC enhances the power tracking performance while considerably reducing the mutual interference of the active/reactive powers as well as the output voltage. [ABSTRACT FROM PUBLISHER]

This paper presents a control scheme for the dynamic performance improvement of an AC/DC converter using the model predictive direct power control (MPDPC) with a duty cycle. In the MPDPC, the active and reactive power is simultaneously controlled with a single cost function. If either of the two control targets has a large power variation, the control weight is concentrated on one side, which causes mutual interference. Because of such mutual interference, the control dynamics of the AC/DC converter deteriorates. Due to the control weight being concentrated on one side using the single cost function, even if the control dynamics of the other side decreases, the dynamic performance of the system is improved by reconfiguring the cost function that has the weighting factor to minimize the decline of the system dynamics that is caused by the mutual interference. The effectiveness of the proposed control scheme is verified by comparing its results with those of the conventional MPDPC. The results are obtained through the simulations and experiments. [ABSTRACT FROM PUBLISHER]

In this paper, we fabricated and evaluated a flowmeter with a sub-micron sized piezoresistive layer for the measurement in the small area. For the small area detection, the sensing material should be reduced as well as sensor body. We use the FIB system to reduce the size of the sensing material and obtain the sub-micron sized line width. The device is fabricated with the standard MEMS process, and the platinum layer is selected as the piezoresistive material considering the electrical conductivity. The 0∼4m/s air flows are applied to the flowmeter and the experimental results shows the negative sensitivity output with -3.22E−5/ms−1. This negative value is due to the additional materials like carbon and gallium. The various experiments including stability and repeatability are performed, and the repeated operation shows stable output signals with less than 9.6% variation. Through those experiment results, the FIB assisted platinum layer is suitable for the piezoresistive detection and a flowmeter can be applied to measurement of flow rate in the small area. [ABSTRACT FROM AUTHOR]

We fabricated and evaluated a flowmeter with a corrugation structure for various applications. The device measures the air flow rate using the air drag force, and the corrugation structure is adopted for the more deformation which brings the higher sensitivity. The flowmeter is fabricated with standard CMOS process, and the strain is measured with the piezoresistive material, platinum. The fabricated flowmeter measures the small air flow rate to 0.2 m/s and has a wide measurement range up to 7 m/s. The stability and repeatability characteristics are investigated, and around 5% uniform results are obtained. The flowmeter is used for the 2-dimensional measurement, and the air flow rate and direction are determined with the compensated vector calculation. [ABSTRACT FROM PUBLISHER]

The original version of the Supplementary Information associated with this Article contained an error in page 6 Supplementary Fig. The original version of this Article contained an error in page 6 line 13 which incorrectly read 'However, the heat conductance (along the direction normal to the substrate) is dependent on the relative substrate thickness, which for thin NOA63 and the thick glass substrate are 543.38 and 37.5 [W K SP -1 sp ]'. [Extracted from the article]