19,040 research outputs found
Synthesis of freestanding cupric oxide nanotubes with close ends from copper nanowires by the Kirkendall effect
No full textVertically grown cupric oxide semiconductors have a number of applications such as chemical sensors, nanogas sensors, and catalysts. Typically, a template based synthesis technique is used followed by an additional wet etching process for the synthesis of vertically oriented cupric oxide nanotubes. However, such a synthesis technique has some inherent disadvantages, notably, the obvious complexities involved in the process and the possibility of contamination and deformation of the structure. Here, the authors report the growth of freestanding copper nanostructures via metal organic chemical vapor deposition, followed by thermal oxidation. To the best of our knowledge, this is the first report of a successful synthesis of vertically aligned cupric oxide nanotubes with closed ends from copper nanowires. The synthesis was performed at 300 degrees C in air via the Kirkendall effect without the use of any template. Subsequently, the 5 mu m long copper nanowires having diameters of 70 nm were thermally oxidized to yield cupric oxide nanotubes with closed ends. The nanotubes were 5 mu m in length, and had wall thicknesses and diameters of 18 nm and 70-100nm, respectively. Transmission electron microscopy images clearly show that the nanotubes are comprised of crystalline cupric oxide. Furthermore, I-V characteristics of the nanotubes exhibit p-type semiconducting behavior. Our work suggests that the cupric oxide nanotubes may find applications in one-dimensional devices such as in the field of optics, as nanobiosensors and gas sensors. (C) 2016 American Vacuum Society.
The adoption and use of mobile application-based reward systems: Implications for offline purchase and mobile commerce
No full textCustomer reward systems have rapidly shifted from plastic cards schemes to mobile application-based initiatives, yet our understanding of the economic value of mobile reward systems has not kept pace with this development. Using an individual-level transaction and reward redemption dataset from a large multi-brand, offline food-and-beverage merchandiser, we examine the effects of reward app adoption on customers' offline purchase patterns and reward redemption behaviors by using a difference-indifference method with propensity score matching. An intriguing empirical issue is whether consumers redeem their reward points more aggressively and spend more out of pocket after adopting reward apps. Our results lend support to this argument. App engagement, which is measured by the frequency at which reward apps are activated, is positively associated with increasing cash expenditure and number of points redeemed. Furthermore, our findings imply that past reward point redemption increases the level of goodwill stock, which affects future cash expenditure
Positive Demand Spillover of Popular App Adoption: Implications for Platform Owners’ Management of Complements
No full textAs platform owners interact with end users and complementors, their demand side characteristics and performance affect the overall value creation of ecosystems. This research investigated how the emergence of popular complements on a mobile communication platform impacts the usage of other complementary products by the platform's end users and how platform owners can benefit from such demand spillovers. We identified two different forms of demand spillovers (i.e., backward and forward) and conceptualized how each subsequently affects platform expansion. On the basis of individual user-level app usage data, we empirically demonstrated how the presence of a popular app alters the demand structure of a platform through changes in the usage of other apps operating within it. The findings reveal that popular app adoption by users increases the number of apps used and the duration of app usage, excluding the usage of popular apps, only within the platform offering a popular app. These results support the existence of positive spillovers from popular complement adoption on a platform. Such positive within-platform spillovers are derived from both backward spillovers onto existing apps adopted before popular app adoption and forward spillovers onto new apps to be adopted after the uptake of favored apps. These patterns suggest that positive spillovers of popular app adoption occur through both the increased retrieval of existing apps and reduced uncertainty about newly released apps. Furthermore, forward spillover is considerably stronger than backward spillover, implying that platform owners can reap benefits by coordinating the launch of new complements and the promotion of less-known counterparts to end users with the emergence of a popular app. These results shed light on how platform owners can manage their complements and create value beyond direct contributions from popular complements.
Use of Deep Learning for Characterization of Microfluidic Soft Sensors
No full textSoft sensors made of highly deformable materials are one of the enabling technologies to various soft robotic systems, such as soft mobile robots, soft wearable robots, and soft grippers. However, major drawbacks of soft sensors compared with traditional sensors are their nonlinearity and hysteresis in response, which are common especially in microfluidic soft sensors. In this research, we propose to address the above issues of soft sensors by taking advantage of deep learning. We implemented a hierarchical recurrent sensing network, a type of recurrent neural network model, to the calibration of soft sensors for estimating the magnitude and the location of a contact pressure simultaneously. The proposed approach in this letter is not only able to model the nonlinear characteristic with hysteresis of the pressure response, but also find the location of the pressure.
In situ-prepared composite materials of PEDOT: PSS buffer layer-metal nanoparticles and their application to organic solar cells
No full textWe report an enhancement in the efficiency of organic solar cells via the incorporation of gold (Au) or silver (Ag) nanoparticles (NPs) in the hole-transporting buffer layer of poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), which was formed on an indium tin oxide (ITO) surface by the spin-coating of PEDOT:PSS-Au or Ag NPs composite solution. The composite solution was synthesized by a simple in situ preparation method which involved the reduction of chloroauric acid (HAuCl4) or silver nitrate (AgNO3) with sodium borohydride (NaBH4) solution in the presence of aqueous PEDOT:PSS media. The NPs were well dispersed in the PEDOT:PSS media and showed a characteristic absorption peak due to the surface plasmon resonance effect. Organic solar cells with the structure of ITO/PEDOT:PSS-Au, Ag NPs/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM)/LiF/Al exhibited an 8% improvement in their power conversion efficiency mainly due to the enlarged surface roughness of the PEDOT:PSS, which lead to an improvement in the charge collection and ultimately improvements in the short-circuit current density and fill factor. © 2012 Woo et al.1
Improving collection efficiency in two-photon endoscopy with reflective waveguiding
No full textTwo-photon endoscopy based on a gradient-index lens has been widely utilized for
studying cellular behaviors in deep-lying tissues with minimal invasiveness in vivo. Although
the efficient collection of emitted light is critical to attain high-contrast spatiotemporal
information, the intrinsic low numerical aperture of the endoscopic probe poses a physical
limitation. We report a simple solution to overcome this limit by incorporating a reflective
waveguide ensheathing the endoscopic probe, which improves the collection efficiency by
approximately two-fold. We describe its principle, fabrication procedure, optical
characterization, and utilities in biological tissues. © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement11sciescopu
Effect of size distribution in quantum dot infrared photodetectors
No full textThis work was supported in part by KOSEF through QSRC at Dongguk university, MOST through
National Research Laboratory (NRL), National R&D Project for Nano Science and Technology, Ministry of
Information and Communication through the Advanced Backbone IT technology Development Projec
A Novel Capacitorless DRAM Operated by Gate-Induced Drain-Leakage (GIDL) for Improved Sensing Window and Low Power Operation
No full textRecycling of waste tires by synthesizing N-doped carbon-based catalysts for oxygen reduction reaction
No full textCurrently, there are 1.5 billion waste tires (WTs) produced yearly, which has become a vital issue worldwide. In this study, we suggest to recycle rubbers and carbon black (CB) together by carbonizing rubbers in WTs. Sulfonation of WT rendered stable structure to carbonize rubbers, which are innately non-carbonizable. The following heat-treatment in Ar/NH3 atmosphere provided abundant nitrogen functional groups on resulting carbons including CB and carbonized rubbers, confirmed by X-ray photoelectric (XPS) spectroscopy and TEM micrographs. To validate them as oxygen reduction reaction (ORR) catalysts, a half-cell test in alkaline media was carried out. The N-doped catalyst with carbonized rubbers and CB exhibited a superior ORR activity to that with carbonized WTs without sulfonation and further those performance was comparable to a Pt/C catalyst. It is evident that carbonized rubbers induced higher nitrogen contents and larger electrochemical surface areas of the catalyst, which offered more active sites higher ORR activity. Therefore, we believed that the proposed approach introduced in this paper shows an effective solution to deal with WTs by envisioning alternative recycling pathway.
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