Organic electrochemical transistors based on a dielectrophoretically aligned nanowire array

In this study, we synthesized an organic electrochemical transistor (OECT) using dielectrophoresis of a carbon nanotube-Nafion (CNT-Nafion) suspension. Dielectrophoretically aligned nanowires formed a one-dimensional submicron bundle between triangular electrodes. The CNT-Nafion composite nanowire bundles showed p-type semiconductor characteristics. The drain-source current decreased with increasing gate voltage. The nanowire bundles showed potential as pH sensor because the drain-source current ratio varied linearly according to the gate voltage in pH buffers

The Non-Linear Relationship Between CEO Compensation Incentives And Corporate Tax Avoidance

This study examines the effect of CEO compensation incentives on corporate tax avoidance. Unlike prior literature that assumes a monotonic relation between executive compensation incentives and tax avoidance, we find a non-linear relation between the two. Specifically, we find that CEO compensation incentives exhibit a positive relation with corporate tax avoidance at low levels of compensation incentives, whereas they show a negative relation at high levels of compensation incentives. We further find that the non-linear relationship between CEO compensation incentives and corporate tax avoidance does not exist for the subsample of S&P500 firms. Collectively, we provide evidence of the two counter effective forces, namely, - the incentive alignment effect and the risk-reducing effect, - that help explain the effect of CEO compensation incentives on tax avoidance

Design of energy-efficient high-speed wireline transceiver

Energy efficiency has become the most important performance metric of integrated circuits used in many applications ranging from mobile devices to high-performance processors. The power problem permeates both computing and communication systems alike. Especially in the era of Big Data, continuously growing demand for higher communication bandwidth is driving the need for energy-efficient high-speed I/O serial links. However, the rate at which the energy efficiency of serial links is improving is much slower than the rate at which the required data transfer bandwidth is increasing. This dissertation explores two design approaches for energy-efficient communication systems. The first design approach maximizes the energy efficiency of a transceiver without any performance loss, and as a prototype, a source-synchronous multi-Gb/s transceiver that achieves excellent energy efficiency lower than 0.3pJ/bit is presented. To this end, the proposed transceiver employs aggressive supply voltage scaling, and multiplexed transmitter and receiver synchronized by low-rate multi-phase clocks are adopted to achieve high data rate even at a supply voltage close to the device threshold voltage. Phase spacing errors resulting from device mismatches are corrected using a self-calibration scheme. The proposed phase calibration method uses a single digital delay-locked loop (DLL) for calibrating all the phases, which makes the calibration process insensitive to the supply voltage level. Thanks to this technique, the proposed multi-Gb/s transceiver operates robustly and energy-efficiently at a very low supply voltage. Fabricated in a 65nm CMOS process, the energy efficiency and data rate of the prototype transceiver vary from 0.29pJ/bit to 0.58pJ/bit and 1Gb/s to 6Gb/s, respectively, as the supply voltage is varied from 0.45V to 0.7V. In the second approach, observing that the data traffic in a real system is bursty, a full-rate burst-mode transceiver that achieves rapid on/off operation needed for energy-proportional systems is presented. By injecting input data edges into the oscillator embedded in a classical type-II digital clock and data recovery (CDR) circuit, the proposed receiver achieves instantaneous phase-locking and input jitter filtering simultaneously. In other words, the proposed CDR combines the advantages of conventional feed-forward and feedback architectures to achieve energy-proportional operation. By controlling the number of data edges injected into the oscillator, both the jitter transfer bandwidth and the jitter tolerance corner are accurately controlled. The feedback loop also corrects for any frequency error and helps improve the CDR's immunity to oscillator frequency drift during the power-on and -off states. This also improves the CDR's tolerance to consecutive identical digits present in the input data. Fabricated in a 90nm CMOS process, the prototype receiver instantaneously locks onto the very first data edge and consumes 6.1mW at 2.2Gb/s. Owing to its short power-on time, the overall transceiver's energy efficiency varies only from 5.4pJ/bit to 10.7pJ/bit when the effective data rate is varied from 2.2Gb/s to 0.22Gb/s

Visual content analysis of visitors’ engagement with an instagrammable exhibition

This study aims to show how a museum exhibition designed to encourage visitors to take pictures can affect visitors’ behavior. We analyzed visitors’ engagement with the Yumi's Cell Special Exhibition (hereafter Yumi) held in South Korea, employing computer vision for the analysis of visitors’ Instagram pictures. Our research questions are: What types of pictures do visitors post on Instagram during or after their visit? And can Yumi’s instagrammable features make visitors interact more with the exhibition? We also formulated two corresponding hypotheses: Visitors are primarily interested in taking selfies in the instagrammable environment; and visitors struck more active poses when taking pictures in an instagrammable exhibition than in a traditional art exhibition. Through the image analysis of Instagram posts of the exhibition, we found many pictures of people, but the proportion of selfies was relatively limited. This suggests that visitors were more interested in interacting with the exhibition rather than taking selfies. This has also been confirmed by the pose analysis, which showed that the participatory feature of the exhibition encouraged visitors to take photos in active poses, interacting, mimicking, and performing. The framework presented and the findings offer insights about how to design exhibitions to increase visitors’ participation

Reliable diameter control of carbon nanotube nanowires using withdrawal velocity

Carbon nanotube (CNT) nanobundles are widely used in nanoscale imaging, fabrication, and electrochemical and biological sensing. The diameter of CNT nanobundles should be controlled precisely, because it is an important factor in determining electrode performance. Here, we fabricated CNT nanobundles on tungsten tips using dielectrophoresis (DEP) force and controlled their diameters by varying the withdrawal velocity of the tungsten tips. Withdrawal velocity pulling away from the liquid-air interface could be an important, reliable parameter to control the diameter of CNT nanobundles. The withdrawal velocity was controlled automatically and precisely with a one-dimensional motorized stage. The effect of the withdrawal velocity on the diameter of CNT nanobundles was analyzed theoretically and compared with the experimental results. Based on the attachment efficiency, the withdrawal velocity is inversely proportional to the diameter of the CNT nanobundles; this has been demonstrated experimentally. Control of the withdrawal velocity will play an important role in fabricating CNT nanobundles using DEP phenomena.110Ysciescopu

Fabrication of functional micro- and nanoneedle electrodes using a carbon nanotube template and electrodeposition

Carbon nanotube (CNT) is an attractive material for needle-like conducting electrodes because it has high electrical conductivity and mechanical strength. However, CNTs cannot provide the desired properties in certain applications. To obtain micro- and nanoneedles having the desired properties, it is necessary to fabricate functional needles using various other materials. In this study, functional micro- and nanoneedle electrodes were fabricated using a tungsten tip and an atomic force microscope probe with a CNT needle template and electrodeposition. To prepare the conductive needle templates, a single-wall nanotube nanoneedle was attached onto the conductive tip using dielectrophoresis and surface tension. Through electrodeposition, Au, Ni, and polypyrrole were each coated successfully onto CNT nanoneedle electrodes to obtain the desired properties

One-directional flow of ionic solutions along fine electrodes under an alternating current electric field

Electric fields are widely used for controlling liquids in various research fields. To control a liquid, an alternating current (AC) electric field can offer unique advantages over a direct current (DC) electric field, such as fast and programmable flows and reduced side effects, namely the generation of gas bubbles. Here, we demonstrate one-directional flow along carbon nanotube nanowires under an AC electric field, with no additional equipment or frequency matching. This phenomenon has the following characteristics: First, the flow rates of the transported liquid were changed by altering the frequency showing Gaussian behaviour. Second, a particular frequency generated maximum liquid flow. Third, flow rates with an AC electric field (approximately nanolitre per minute) were much faster than those of a DC electric field (approximately picolitre per minute). Fourth, the flow rates could be controlled by changing the applied voltage, frequency, ion concentration of the solution and offset voltage. Our finding of microfluidic control using an AC electric field could provide a new method for controlling liquids in various research fields

CSAI analysis of non-crimp fabric cross-ply laminate manufactured through wet compression molding process

The main purpose of the present work is to demonstrate mechanical performance of a wet-compression-molding (WCM) composite product through conventional compressive-strength-after-impact (CSAI) analysis. Biaxial non-crimp fabric (NCF) is utilized to manufacture laminated composite panels. Specimens are cut from the panels and tested to characterize fundamental mechanical properties of the NCF composite. The volume fractions of fibers and voids are also measured to evaluate the quality of the WCM product. Impact tests are carried out to examine impact resistance of the composite structure. Numerous impact characteristics at various energy levels are quantitatively measured. Internal failure patterns and damage extent are revealed via X-ray CT. Compression tests on the impacted plates are followed to evaluate structural integrity and damage tolerance (SIDT). 3D DIC technique is employed and distinct buckling responses dependent on impact energy levels are successfully visualized. Experimental results are showing a promising potential of the WCM process as one of the alternatives to the conventional autoclave-based fabrication method