Organization-oriented technology opportunities analysis based on predicting patent networks: a case of Alzheimer’s disease

Scientometrics - This study aims to investigate how to test and assess the dichotomy of roles from an organization-oriented perspective for technology opportunity analysis, in context of the...     

Bistable resistive switching of a sputter-deposited Cr-doped SrZrO/sub 3/ memory film

Sputter-deposited Cr-doped SrZrO/sub 3/-based metal-insulator-metal structures exhibited bistable resistive reversible switching as observed under bias voltage and voltage pulse. The ratio of resistance of the two leakage states (high-H, low-L) was about five orders of magnitude. The conduction of the L-state satisfied Frenkel-Poole emission and that of the H-state followed ohmic mechanism, causing the resistance ratio to decrease with increasing bias voltage. The transition time of H- to L-state was five orders of magnitude higher than that of L- to H-state. The transition from H- to L-state was the restricted part for reversible switching operation. The difference in transition time of the two states should be related to the respective conduction mechanisms.     

Torque and current control of induction motor drives for inverter switching frequency reduction

In this paper, an indirect field-oriented control (FOC) induction motor (IM) drive with instantaneous current and torque control is presented. This proposed control scheme employs hysteresis current and torque controllers to regulate the stator currents. The torque controller is proposed to serve the current controller so that full advantage of the zero voltage vector can be taken to reduce the switching frequency of the inverter. As a result, the actual stator currents can follow the current references as closely as possible, and the current ripple and torque ripple can be greatly decreased compared with the conventional adaptive pulsewidth modulation control method. To verify the feasibility of the proposed scheme, computer simulations and experiment results demonstrate that the proposed method can obtain a high-performance IM drive system.     

Assessing the environmental impact of five Pd-based catalytic technologies in removing of nitrates

Emerging technologies involving chemical catalytic processes to remove nitrate from water have proven efficient and cost-effective. However, the environmental impact of noble metals and metals at the nanoscale used in these processes has become a topic of serious concern. The aim of this research was to develop a system for evaluating the environmental impact of technologies associated with Pd-based catalytic denitrification. This research performed life cycle assessment (LCA) based on a detailed analysis of the technologies to examine the environmental burden associated with all stages of the removal process. We then applied analytical hierarchy process (AHP) to determine the weights of various burdens. We implemented the proposed system to determine the relative environmental friendliness of 5 processes used for the removal of nitrate. These five methods use Cu-Pd/TNTs, H₂ + Pd-Cu/TiO₂, Pd-Cu/TiO₂, Pd/ZnO, and Pd-Cu/FeO as catalysts for the removal of nitrate. The results indicate that the use of palladium and the consumption of electricity have a major environmental impact; while the use of Pd-Cu/TiO₂ as catalyst was the most environmentally friendly of the five processes evaluated.     

Identical-length nanowire arrays in anodic alumina templates

Arrays of nanowires with identical length are fabricated by using ultrasound to remove the length fluctuation among nanowires, which are deliberately grown in burette-shaped nanochannels on an anodic anumina film. The process allows the fabrication of 10 micron Ag-nanowire arrays with length fluctuation as small as 0.09%. By integrating the process with a focused-ion-beam-based lithographic method to grow nanowires into selective nanochannels in an array, we fabricate arrays of uniform-length nanowires that are arranged in a custom-designed lateral geometry. The ability to fabricate such artificial nanomaterials paves the way for the exploitation of their unusual optical, electrical, and thermal properties.     

Biphasic bone graft prepared using a gel-foaming technique

Synthetic bone graft has gained considerable attention because of an increase in the aged population. In the present study, a biphasic bone graft composed of hydroxyapatite (HAp) and calcium sulfate (CS) is prepared using a gel-foaming technique. The gel is prepared at a temperature as low as 35 °C; many pores are introduced into the gel through an agitation process. The foamed gel can be cut into any shape and size. After sintering, the porosity of the biphasic bone graft is approximately 70%. Depending on the HAp/CS ratio, the amount of macropores and micropores can be tailored. The macropores of approximately 130 μm diameter are interconnected with each other through openings of 40 μm size. The biphasic bone graft exhibits no cytotoxicity; preosteoblast cells can adhere and proliferate on the surface of the fabricated bone graft. However, migration of these cells into the bone graft is considerably limited in the in vitro study. When the biphasic bone graft is implanted into the distal femur of rats, with the combined effect of osteoblast and osteoclast cells, more than 90% of the bone graft is degraded after 3 months. New trabeculae bone and bone marrow are observed within the bone defect. The HAp/CS composite can thus be used as degradable bone grafts.     

Effective product quantization-based indexing for nearest neighbor search

Multimedia Tools and Applications - Product quantization is a widely used lossy compression technique that can generate high quantization levels by a compact codebook set. It has been conducted in...     

Current status of resistive nonvolatile memories

Several emerging nonvolatile memories (NVMs) such as ferroelectric memory, magnetoresistive rams and ovonic universal memory are being developed for possible applications. Resistive random access memory (RRAM) is another interesting competitor in the class of NVMs. The RRAM is based on a large change in electrical resistance when the memory film is exposed to voltage or current pulses, and can keep high or low resistance states without any power. The ideal RRAM should have the superior properties of reversible switching, long retention time, multilevel switching, simple structure, small size, and low operating voltage. Perovskite oxides, transition metal oxides, and molecular materials were found to have resistive memory properties. This presentation reviews the ongoing research and development activities on future resistance NVMs technologies incorporating these new memory materials. The possible basic mechanisms for their bistable resistance switching are described. The effect of processing, composition, and structure on the properties of resistive memory materials and consequently the devices are discussed.     

An improved two-frequency method of capacitance measurement forSrTiO3 as high-k gate dielectric

An improved two-frequency method of capacitance measurement for the high-k gate dielectrics is proposed. The equivalent circuit model of the MOS capacitor including the four parameters of intrinsic capacitance, loss tangent, parasitic series inductance, and series resistance is developed. These parameters can be extracted by independently measuring the capacitor at two different frequencies. This technique is demonstrated for high-k SrTiO₃ gate dielectrics and the results show that the calibrated capacitances are invariant over a wide range of frequency. In addition, the extracted loss tangent, inductance and resistance are independent on gate voltage and frequency. The effect of series resistance on the frequency dispersion of the capacitance can be also explained by this model. These results indicate that this modified technique can be incorporated in the routine capacitance-voltage (C-V) measurement procedure providing the physically meaningful data for the high-k gate dielectrics     

Morphological evolution of porous nanostructures grown from a single isolated anodic alumina nanochannel

Porous anodic aluminum oxide (AAO) membranes have been widely used as templates for growing nanomaterials because of their ordered nanochannel arrays with high aspect ratio and uniform pore diameter. However, the intrinsic growth behavior of an individual AAO nanochannel has never been carefully studied for the lack of a means to fabricate a single isolated anodic alumina nanochannel (SIAAN). In this study, we develop a lithographic method for fabricating a SIAAN, which grows into a porous hemispherical structure with its pores exhibiting fascinating morphological evolution during anodization. We also discover that the mechanical stress affects the growth rate and pore morphology of AAO porous structures. This study helps reveal the growth mechanism of arrayed AAO nanochannels grown on a flat aluminum surface and provides insights to help pave the way to altering the geometry of nanochannels on AAO templates for the fabrication of advanced nanocomposite materials.