Search

The operation speed of dynamic random access memory devices has been increasing with respect to the evolution of electronic devices. This in turn has induced a decrease in the allowed time for the operation. Therefore, the effective capacitance degradation in which the capacitance gradually decreases with increasing frequency of applied ac voltage is a severe concern for decreasing capacitance during fast operation, in addition to inducing reliability degradation. Hence, in this article, the origin of capacitance degradation depending on operation frequency, also called “frequency dependence” of the capacitance, was revealed. By performing dc and ac nonlinearity analyses, the effect of defects, especially oxygen vacancies, on the electrical properties of metal-insulator-metal (MIM) capacitors was investigated. Eventually, the mechanism of frequency dependence related to oxygen vacancy in the insulator of the MIM capacitor was identified. [ABSTRACT FROM AUTHOR]

Cyber-physical system (CPS) communications for safely and effectively operating a mission-critical infrastructure must be securely protected to prevent the infrastructure from becoming vulnerable. The protection scheme used must be resilient and light-weighted for CPS field devices having constrained computing and communicating resources, and also scalable for control servers associating with a large number of the field devices. In addition, CPS applications such as smart metering require end-to-end privacy protection. However, as shown in this paper, none of conventional security schemes comprehensively meets the above requirements; group security schemes scale well for a massive number of devices but are weak in terms of privacy protection and resilience; point-to-point security schemes such as IPsec inherently have resilience but are limited to address scalability and thinness requirements. Motivated by the limitations of conventional security schemes, we design new group security scheme, resilient end-to-end message protection (REMP), exploiting the following notions: long-term keys per-node that are given by REMP authentication server, encryption keys per message sent that are probabilistically derived from a long-term key, and end-to-end authenticators per message sent that consist of a message sender’s identity and a message authentication code. Compared with conventional group security schemes, we improve end-to-end security strength in terms of confidentiality, integrity, message source authentication, and key exposure resilience, while preserving scalability and extensibility. [ABSTRACT FROM AUTHOR]

In order to impart resistance switching capability to polymer-based composite, one-dimensional conductive nanomaterials such as carbon nanotube (CNT) and carbon nanofiber (CNF) were wrapped with TiO2 conformal layer for passivation, and embedded in polymer matrix to form a networklike distribution within it. The CNT-TiO2 and CNF-TiO2-embedded composites, respectively, exhibited the reproducible resistance switching behavior of the high on/off ratio, along with the good switching stability under repetitive switching measurements. Furthermore, it is notable that the presence of defect site or incomplete formation of the TiO2 passivation layer on the conductive component would significantly alter the switching performance. The advantages of our approach include the simple and mass-production capable fabrication procedure along with the sustainable switching performance suitable to promising nonvolatile memory device applications. [ABSTRACT FROM AUTHOR]

We propose an approach for retrieving a sequence of natural sentences for an image stream. Since general users often take a series of pictures on their experiences, much online visual information exists in the form of image streams, for which it would better take into consideration of the whole image stream to produce natural language descriptions. While almost all previous studies have dealt with the relation between a single image and a single natural sentence, our work extends both input and output dimension to a sequence of images and a sequence of sentences. For retrieving a coherent flow of multiple sentences for a photo stream, we propose a multimodal neural architecture called coherence recurrent convolutional network (CRCN), which consists of convolutional neural networks, bidirectional long short-term memory (LSTM) networks, and an entity-based local coherence model. Our approach directly learns from vast user-generated resource of blog posts as text-image parallel training data. We collect more than 22 K unique blog posts with 170 K associated images for the travel topics of NYC, Disneyland , Australia, and Hawaii. We demonstrate that our approach outperforms other state-of-the-art image captioning methods for text sequence generation, using both quantitative measures and user studies via Amazon Mechanical Turk. [ABSTRACT FROM PUBLISHER]

Piezoelectric actuators have been spotlighted as a promising candidate for vibration motors, but their application is limited due to their inherent low output displacement and high operating frequency in small volume. In this paper, a resonant piezoelectric vibrator with a high output displacement of 427 μm at a low haptic frequency of 188.8 Hz was developed within a diameter of 10 mm and a thickness of 3.4 mm for haptic smart device applications. In the proposed resonant piezoelectric vibrator, a circular piezoelectric unimorph excites a mass–spring system on the circular piezoelectric unimorph at a natural frequency to maximize the vibration of the mass–spring system. The thickness ratio of the elastic layer to the piezoelectric layer and the thickness of the piezoelectric layer were theoretically optimized to maximize the displacement of the circular piezoelectric unimorph considering the attachment of the spring. A spiral spring with a low spring constant was utilized to assign the first natural frequency of the mass–spring system within the haptic frequency that humans can sense sensitively. Furthermore, the natural frequencies and output displacement of the proposed resonant piezoelectric vibrator were calculated and verified by using finite-element analyses. Finally, we prototyped the proposed resonant piezoelectric vibrator and confirmed that measured results match well with simulated ones. [ABSTRACT FROM PUBLISHER]