Fast Recovery Speed Research Articles

Fabrication of an efficient GLAD-assisted p-NiO nanorod/n-ZnO thin film heterojunction UV photodiode

The glancing angle deposition (GLAD) configuration in RF magnetron sputtering has been utilized to deposit p-type NiO nanorods, which are integrated with n-type ZnO thin film to realize a high performance p–n heterojunction diode for the efficient detection of UV photoradiation. The fabricated nano p-NiO/n-ZnO heterojunction shows excellent rectifying characteristics (rectification ratio ∼ 4 × 103) with a very low reverse saturation current (∼10−10 A). The heterojunction photodiode exhibits a high current gain (3.71 × 103), high photoresponsivity (3.24 × 105 A W−1), with a relatively fast response (∼200 ms) and recovery speed (∼25 ms) towards a very low UV intensity of 0.62 μW cm−2 (λ = 300 nm). Recombination tunneling and space-charge limited current are the probable conduction mechanisms at low and high applied voltages respectively for the fabricated heterojunction diode. The observed high response speed and excellent responsivity of the diode towards deep-UV (λ = 300 nm) radiation might lead to potential military applications such as missile tracking, in addition to optical communications.

Fast response/recovery performance of comb-like Co3O4 nanostructure

A new type of comb-like architecture with a hierarchical structure was prepared via a simple and effective hydrothermal strategy in the case of Co3O4. FESEM and TEM confirm the comb-like architecture of the hierarchical structure, and that the Co3O4 nanorods with secondary nanostructures are the building units. The studies of the sensing performance demonstrate that the as-synthesized comb-like Co3O4 nanostructures show excellent catalytic activity upon exposure to CO gases in comparison with rod-like Co3O4. Importantly, the comb-like Co3O4 nanostructure-based sensor shows a fast response and recovery speed for CO gas. It is believed that the strategy of combining the hierarchical nanostructure and catalytic activity of Co3O4 nanomaterials can further provide potential for applications as real-time monitoring gas sensors.

A three-dimensional hierarchical CdO nanostructure: Preparation and its improved gas-diffusing performance in gas sensor

In order to develop a gas sensor with improved gas-diffusing performance, a three-dimensional (3D) hierarchical CdO nanostructure with a novel bio-inspired morphology was reported. The CdO nanostructures which exhibit a profile of natural leaveleaf were synthesized via a solvothermal approach combining with an annealing process. The solvothermally synthesized CdS precursors were converted into CdO under an optimal annealing condition. In gas-sensing measurements, acetone and diethyl ether were employed as target gases. The results show that the as-fabricated gas sensor exhibits fast response and recovery speeds toward analytes. The mechanism for the improved performance was demonstrated from the gas diffusion through the 3D hierarchical nanostructure. The kinetic processes of gas adsorption and desorption show that the 3D leaveleaf-shaped structure is significant to achieve an enhanced diffusing property. Additionally, a principal component analysis method was used to investigate the recognizable ability of the presented sensor. It is found that acetone and diethyl ether can be distinguished clearly. These findings indicate that the bio-inspired CdO nanostructure can be a promising candidate for the development of fast-responding gas sensors. Moreover, such bio-inspired structure would be also valuable for the design of some other novel nanomaterials.

CO Sensing Properties of Electrochemical Gas Sensors Using an Anion-Conducting Polymer as an Electrolyte

An anion-conducting polymer (ACP) with large OH- .conductivity is very promising as an electrolyte of electrochemical gas sensors working at RT. Therefore, CO sensing properties of an electrochemical gas sensor using ACP as an electrolyte and carbon black (CB) powders loaded with n wt% noble metals (EC(nM/CB-ACP), n: 0.1-10, M: Pt, Pd or Au) as an electrode material were investigated in this study. Among the sensors tested, EC(10Pd/CB-ACP) and EC(10Pt/CB-ACP) showed comparatively large response and fast response and recovery speeds to CO in wet air (relative humidity: 57%) at 30oC. The magnitude of response of the sensors tends to decrease slightly with a decrease in RH.

Synthesis of Au decorated SnO2 mesoporous spheres with enhanced gas sensing performance

Au decorated mesoporous SnO2 spheres with a size range of 400–700 nm have been synthesized for gas sensing. Specifically, the mesoporous SnO2 spheres were fabricated through a solvothermal route followed by a thermal treatment process. The surface area of the mesoporous SnO2 spheres is 78.2 m2 g−1 and the pore size is ca. 10 nm. After being decorated by Au, the Au nanoparticles with sizes of ca. 5 nm were deposited on the surface and the inner wall of pores. Gas sensing tests showed that the Au decorated SnO2 mesoporous spheres exhibited superior gas sensing performances to CO and H2 in terms of high sensitivity and fast response and recovery speed, mainly attributed to the facts that the SnO2 mesoporous structure provides a high reaction surface area and abundant mesochannels for the probe gas and oxygen, and Au nanoparticles act as the catalyst to improve the reaction rate of the probe gas molecules with the oxygen ions.

수중음향통신에서 Peak Detector를 갖는 시간동기회복에 관한 연구

본 논문에서는 OQPSK(Offset Quadrature Phase Shift Keying) 변복조를 사용하는 수중음향통신에서 시간동기회복을 위해 기존의 Gardner TED(Timing Error Detector)에 Parabolic Peak Interpolation 을 사용하는 Peak Detector를 첨가하여 위상 수렴속도를 상승시켜 송신 데이터양의 감소를 도모하였다. Parabolic Peak Interpolation을 이용하여 지속적으로 국소 최대 또는 최소의 근사치로 이동한 후 Gardner TED를 적용하기 때문에 시간동기화 안정화를 속도를 빨리함으로써 Preamble 구간의 데이터양을 절반으로 줄일 수 있고 또한 Preamble 구간에서도 위상 수렴을 하지 못하는 임계치에서 제안한 방법을 시뮬레이션한 결과 임계점에서 BER(Bit Error Rate)이 약 23%정도 성능이 개선되는 것을 확인할 수 있었다. 또한 실제 동해에서 수집한 데이터를 사용하여 기존의 Gardner TED만 사용하는 방법과 성능 비교 결과 송수신기 사이의 거리가 3 km 이었을 때 제안한 방법을 적용한 경우 기존의 방법에 비해 Converge speed가 1.4배 이상 상승하는 것을 확인할 수 있었고, BER측면에서도 약 20%정도 상승하는 것을 확인할 수 있었다. This paper presents a timing recovery method using Gardner TED (Timing Error Detector) with a Peak Detector using Parabola Peak Interpolation in underwater acoustic communication. This method will have an eye to improve phase converge speed of timing recovery and reduced amount of Tx data. The OQPSK(Offset Quadrature Phase Shift Keying) modulation technique was considered. The proposed algorithm has faster recovery speed and more accurate than Gardner TED because the sampling values in the proposed algorithm are moved persistingly to maximum or minimum point using parabolic peak interpolation. when simulation performed using Preposed method, it improved BER (Bit Error Rate) performance about 23% And to evaluate the performances of the proposed algorithm the sea trial was performed in the Korean East Sea. And distance of a transmitter-receiver is 3 km each other. As a result, the proposed algorithm outperforms better BER performance about 20% of timing recovery than the Gardner method. Also Proposed method improved converge speed of timing recovery about 1.4 times better than Gardner method.

Synthesis of Nestlike ZnO Hierarchically Porous Structures and Analysis of Their Gas Sensing Properties

Nestlike 3D ZnO porous structures with size of 1.0-3.0 μm have been synthesized through annealing the zinc hydroxide carbonate precursor, which was obtained by a one-pot hydrothermal process with the assistance of glycine, Na(2)SO(4), and polyvinyl pyrrolidone (PVP). The nestlike 3D ZnO structures are built of 2D nanoflakes with the thickness of ca. 20 nm, which exhibit the nanoporous wormhole-like characteristic. The measured surface area is 36.4 m(2)g(-1) and the pore size is ca. 3-40 nm. The unique nestlike 3D ZnO porous structures provided large contacting surface area for electrons, oxygen and target gas molecules, and abundant channels for gas diffusion and mass transport. Gas sensing tests showed that the nestlike 3D ZnO porous structures exhibit excellent gas sensing performances such as high sensitivity and fast response and recovery speed, suggesting the potential applications as advanced gas sensing materials.

Graphene–nanowire hybrid structures for high-performance photoconductive devices

Graphene–CdS nanowire (NW) hybrid structures with high-speed photoconductivity were developed. The hybrid structure was comprised of CdS NWs which were selectively grown in specific regions on a single-layer graphene sheet. The photoconductive channels based on graphene–CdS NW hybrid structures exhibited much larger photocurrents than graphene-based channels and much faster recovery speed than CdS NW network-based ones. Our graphene–CdS NW structures can be useful because they were much faster than commercial CdS film-based photodetectors and had photocurrents large enough for practical applications.

ZnO nanowire Schottky barrier ultraviolet photodetector with high sensitivity and fast recovery speed

ZnO nanowire (NW) ultraviolet (UV) photodetectors have high sensitivity, while the long recovery time is an important limitation for its applications. In this paper, we demonstrate the promising applications of ZnO NW Schottky barrier as high performance UV photodetector with high sensitivity and fast recovery speed. The on/off ratio, sensitivity, and photocurrent gain are 4 × 105, 2.6 × 103 A/W, and 8.5 × 103, respectively. The recovery time is 0.28 s when photocurrent decreases by 3 orders of magnitude, and the corresponding time constant is as short as 46 ms. The physical mechanisms of the fast recovery properties have also been discussed.

The Role of NiO Doping in Reducing the Impact of Humidity on the Performance of SnO2‐Based Gas Sensors: Synthesis Strategies, and Phenomenological and Spectroscopic Studies

AbstractThe humidity dependence of the gas‐sensing characteristics in SnO2‐based sensors, one of the greatest obstacles in gas‐sensor applications, is reduced to a negligible level by NiO doping. In a dry atmosphere, undoped hierarchical SnO2 nanostructures prepared by the self‐assembly of crystalline nanosheets show a high CO response and a rapid response speed. However, the gas response, response/recovery speeds, and resistance in air are deteriorated or changed significantly in a humid atmosphere. When hierarchical SnO2 nanostructures are doped with 0.64–1.27 wt% NiO, all of the gas‐sensing characteristics remain similar, even after changing the atmosphere from a dry to wet one. According to diffuse‐reflectance Fourier transform IR measurements, it is found that the most of the water‐driven species are predominantly absorbed not by the SnO2 but by the NiO, and thus the electrochemical interaction between the humidity and the SnO2 sensor surface is totally blocked. NiO‐doped hierarchical SnO2 sensors exhibit an exceptionally fast response speed (1.6 s), a fast recovery speed (2.8 s) and a superior gas response (Ra/Rg = 2.8 at 50 ppm CO (Ra: resistance in air, Rg: resistance in gas)) even in a 25% r.h. atmosphere. The doping of hierarchical SnO2 nanostructures with NiO is a very‐promising approach to reduce the dependence of the gas‐sensing characteristics on humidity without sacrificing the high gas response, the ultrafast response and the ultrafast recovery.

High modulus ratio shape‐memory polymers achieved by combining hydrogen bonding with controlled crosslinking

AbstractA new type of poly(methyl acrylate)‐co‐(acrylic acid) (PMA‐AA) networks obtained by combining hydrogen bonding with controlled crosslinking exhibit full and rapid shape‐memory recovery. The structure, thermal properties, dynamical mechanical properties and shape‐memory effects of these networks were presented. High modulus ratios were achieved for the series of PMA‐AA networks based on intense self‐complementary hydrogen bonding in poly(acrylic acid) (PAA) segments. This lead to excellent shape‐memory effects with strain‐recovery ratio above 99%. Meanwhile, faster recovery speed was achieved by the synergistic effect of hydrogen bonding and controlled crosslinking compared to the linear PMA‐AA copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1241–1245, 2011

Effects of p and n pillar widths on electrical characteristicsof super junction SiGe power diodes

By combining merits of both SJ structure and SiGe material, a novel super junction (SJ) SiGe power diode is presented. The two important characteristics of SJ SiGe diode are its columnar structure of alternating p/n pillars substituting n- base region of conventional Si p+n-n+ diode and its far thinner strained SiGe p+ layer, which can overcome the drawbacks of conventional Si power switching diodes, such as when the reverse blocking voltage is higher, the forward voltage drop is larger and the reverse recovery time becomes longer. For the SJ SiGe diode with 20% Ge content, the following conclusions can be obtained compared with comparable conventional Si power diodes: the breakdown voltages increase by 1.6 times, the forward voltage drop is reduced by 60 mV (at a current density of 10 A/cm2) and the softness factor S increases by 2 times. Though the reverse recovery time is shortened slightly, the peak reverse current density decreases by 17% and the soft recovery characteristics is improved notedly. The key parameters of the p and n pillar widths have imporant effects on the forward conduction characteristic, reverse blocking characteristic and reverse recovery characteristic of SJ SiGe power diode. The smaller the pillar width becomes, the higher the breakdown voltage is and the lower the reverse leakage current is, whereas the forward voltage drop increases slightly. The pillar width has no obviously monotonic effect on the reverse recovery characteristic. If the width is too small, the soft reverse recovery characteristic is degenerated. To optimize the parameter of pillar width, we can obtain excellent SJ SiGe diode with fast recovery speed, high breakdown voltage and low forward drop at the same time.

Superior gas-sensing and lithium-storage performance SnO2 nanocrystals synthesized by hydrothermal method

SnO2 nanocrystals with diameters of 2.5–4.1 nm were successfully synthesized by a facile hydrothermal method. The as-synthesized SnO2 nanocrystals were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and high-resolution transmission electronic microscopy (HR-TEM) and nitrogen adsorption. Moreover, it was found that acetic acid played a crucial role in determining the dispersion and crystal size of the SnO2 samples. In addition, the as-synthesized SnO2 nanocrystals not only displayed excellent gas-sensing properties such as very fast response and recovery speed, excellent repeatability and good selectivity, but also high discharging capacity and good cycling performance in lithium ion batteries.

NO 2 sensing properties of macroporous In 2O 3-based powders fabricated by utilizing ultrasonic spray pyrolysis employing polymethylmethacrylate microspheres as a template

Macroporous (mp-) In 2O 3-based microspheres as a NO 2 sensing material were prepared by the pyrolysis of atomized In(NO 3) 3 aqueous solutions containing polymethylmethacrylate (PMMA) microspheres (150 nm in diameter) as a template. Well-developed spherical macropores (less than 100 nm in diameter) reflecting the morphology of the PMMA microsphere templates could be formed in the In 2O 3-based microspheres. The introduction of macropores into In 2O 3-based microspheres was very effective in improving the NO 2 response of their thick films fabricated on an alumina substrate equipped with interdigitated Pt electrodes (gap size: ca. 200 μm) by screen-printing. In addition, the addition of a little amount of SnO 2 to the mp-In 2O 3 microspheres not only lowered the resistance in air but also improved the NO 2 response. NO 2 sensing properties of non-stacked microspheres of the mp-In 2O 3 mixed with SnO 2 were also investigated by utilizing nano-gap Au electrodes (gap size: ca. 200 nm). The non-stacked microspheres showed fast response and recovery speeds to NO 2, because of better diffusion capability of NO 2.

Enhancing the Photon-Sensing Properties of ZnO Nanowires by Atomic Layer Deposition of Platinum

Platinum nanoparticles were uniformily deposited on ZnO nanowires for photon-sensing applications. The morphology, size, and concentration of Pt particles on the ZnO nanowires can be controlled by varying the number of atomic layer deposition reaction cycles. The Pt-decorated ZnO nanowires exhibit much faster photon response and recovery speeds than the pristine ZnO nanowires. This provides an efficient route for strongly enhancing the photon-sensing properties of nanostructured metal oxides and fabricating photodetectors with fast response and recovery speeds.

H 2 sensing properties of diode-type gas sensors fabricated with Ti- and/or Nb-based materials

A thermally oxidized TiO 2 or Nb 2O 5 film equipped with a top Pd film electrode and a bottom Ti or Nb plate electrode (Pd/MO( n)/M, MO: oxide film, M: metal plate, n: annealing temperature (°C)) has been investigated as a diode-type H 2 sensor under air or N 2 atmosphere. Pd/TiO 2( n)/Ti sensors showed relatively poor H 2 sensing properties in air, in comparison with Pd/anodic-TiO 2( n)/Ti sensors constructed with an anodized TiO 2 film equipped with a top Pd film electrode and a bottom Ti plate electrode, which were reported in our previous studies. On the other hand, Pd/Nb 2O 5( n)/Nb sensors showed relatively larger H 2 response with fast response and recovery speeds than Pd/TiO 2( n)/Ti sensors in air under high forward bias conditions. A Pd/Nb 2O 5(450)/Ti sensor, which was fabricated by radio-frequency magnetron sputtering of Nb metal on a Ti substrate followed by thermal oxidation at 450 °C, showed the largest H 2 response and relatively fast response and recovery speeds in air, among the sensors tested. In addition, H 2 response of the Pd/Nb 2O 5(450)/Ti sensor in air was much lower than that in N 2, but the logarithm of H 2 response was almost proportional to the logarithm of H 2 concentration in a wide range of H 2 concentration (10–8000 ppm) in air, and the H 2 sensitivity in air was much higher than that in N 2.

Novel moisture-sensitive shape memory polyurethanes containing pyridine moieties

In this communication, novel moisture-sensitive shape memory polyurethane (SMPU) was synthesized from 1,6-hexamethylene diisocyanate (HDI) and N,N-bis(2-hydroxylethyl) isonicotinamide (BINA) and 1,4-butanediol (BDO). Results show that the BINA based SMPUs have excellent moisture absorption properties which are not only influenced by the temperature, but also by the relative humidity (RH). As a result, high strain recovery with fast recovery speed is obtained after immersion in the moisture condition for a short time. FT-IR spectra provide a proof to the mechanism of moisture-sensitive SME which is based on the dissociation or disrupt of hydrogen bonding in the pyridine ring induced by moisture absorption. Thus, the strain recovery is achieved in the moisture-sensitive SMPUs by decreasing the glass transition temperature (Tg) below ambient temperature without external heating.

The Time Course of the Amplitude and Latency in the Auditory Late Response Evoked by Repeated Tone Bursts

This study provides a detailed description of the time course of amplitude and latency in the auditory late response (ALR) elicited by repeated tone bursts. Tone bursts (50 and 80 dB SPL) were presented via insert earphones in trains of ten with interstimulus intervals (ISIs) of 0.7 and 2 msec and an intertrain interval of 15 sec. Averages were derived independently for each tone burst within the train across the total number of train presentations. Participants were 14 normal-hearing young adults. Data were analyzed in terms of the amplitudes and latencies of the N1 and P2 waves of the ALR as well as the N1-P2 amplitude. The N1-P2 amplitude was a more stable measure than the amplitude of individual N1 and P2 peaks. The N1-P2 amplitude was maximal for the first tone burst and decreased in a nonmonotonic pattern for the remainder of the tone bursts within a stimulus train. The amplitude decrement was dependent on stimulus intensity and ISI. The latencies of N1 and P2 were maximal for the first tone burst and reduced approximately 20% for the rest of the stimuli in a train. The time course of N1 and P2 latencies was not dependent on stimulus intensity and ISI. The reduction of latency in the time course of the ALR might be related to the fact that neurons with shorter latencies had faster recovery speed from adaptation and/or refractoriness than those with longer latencies. This finding is meaningful in the context of future research to restore normal adaptation in abnormal hearing populations such as cochlear implant patients.

An effect analysis of hemihepatic vascular occlusion and pringle maneuver in Liver cancer operation

Objective To study the application and efficacy of hemihepatie vascular occlusion in HCC resection. Methods 90 ca-ses of HCC patients were roiled in and divided into two groups. Liver resection was performed with Pringle maneuver or hemihepatic vascular occhusion. Ischemia time, operative time, blood loss, postoperative liver function, the occurrence of complications and the recovery of gastro-intestinal function were recorded. The efficacy of the two occlusions was compared. Results There is no significant difference between hemibepatic vascular occlusion and Pringle maneuver in ischemia time, operative time, blood loss (P>0.05). However, there is signifi-cant difference in postoperative liver function, the occurrence of complications and intestinal function recovery time. The former is significant-ly superior to the latter (P<0.05). Conclusions The bemihepatic vascular occlusion and Pringle maneuver occlusion have no difference in ischemia time, operative time and blood loss. But bemihepatic vascular occlusion has less impact on liver function, lower rate of occur-rence of complications and faster recovery speed. Therefore, hemibepatie vascular occlusion is better than Pfingle maneuver occlusion in be-parle inflow occlusion in HCC surgery. Key words: Liver neoplasms/SU; Hepatectomy/MT

Near colorless all-solid-state switchable mirror based on magnesium-titanium thin film

Magnesium-titanium (Mg–Ti) thin film was applied to all-solid-state switchable mirror by magnetron sputtering. Mg–Ti thin film works as an anodic electrochromic material of optical switching layer of the device. For clear transparency and durability of the device, a composition of Mg–Ti thin film was optimized. Though a maximum transmittance at transparent state of the device decreased with increasing titanium content in the film, the device showed fast recovery speed to reflective state. The transmittance at a wavelength of 670nm of the device with Mg0.88Ti0.12 was reached from 0.1% (reflective state) to 36% (transparent state) within 15s by applying voltage. The reflectance was also reduced from 57% to 20% within 10s. The transparent state of the device with Mg0.88Ti0.12 thin film showed almost colorless state with a chromaticity coordinates of x=0.335 and y=0.336. In the viewpoint of transmittance and durability, the authors found that the device with Mg0.88Ti0.12 thin film was the most suitable for practical application.