Search

Van der Waals (vdW) heterojunctions between single-walled carbon nanotubes (SWCNTs) and GaAs are potential candidates for optoelectronic devices owing to their direct bandgap, high carrier mobility...

Based on the support characteristics of new phased array radar, the evaluation index system of maintenance support capability of new phased array radar is constructed. And combining AHP with GRG, the index weight in the index system is calculated. Combined with the theory of center of gravity of cloud, the cloud model of the evaluation of maintenance supporting capability for the new phased array radar is constructed. The cloud model is used to evaluate the maintenance support capability of a typical new phased array radar, and the effectiveness of the method is verified by an example.

Lipid oxidation products (LOPs) are widely present in many lipid- containing foods. They usually enter the gastrointestinal tract from dietary sources and/or are produced in vivo. Part of LOPs were absorbed into the blood and transported into tissues. A growing bulk of evidence suggests that LOPs, mainly reactive aldehydes and oxysterols, are potentially involved in the pathogenesis of many chronic diseases, such as atherosclerosis, Alzheimer’s disease, and inflammatory bowel disease. This review summarizes the current knowledge of the adverse effects, cytotoxicity, and the main mechanisms of LOPs involvement in humans and animals.

Two kinds of four-layer nuclear batteries based on γ-ray, AlGaInP semiconductor PN junction, and ZnS:Cu fluorescent materials were prepared. One was a four-layer radio-voltaic nuclear battery (FRVB) with a volume of 1.00 cm3, and another is a four-layer dual-effect nuclear battery (FDEB) with a volume of 1.03 cm3. The output performance levels of the two batteries were tested with the irradiation of an X-ray tube. Results show that the output power of the nuclear battery in parallel is significantly greater than that in the series. However, the output power and power density of FDEB in parallel, which were 57.26 nW and 55.59 nW/cm3, respectively, both five times as high as those of FRVB in parallel. Each sub-cell of FDEB was connected in different ways according to actual requirements. Different output currents and voltages were obtained, whereas no difference was observed in output power. Moreover, the energy deposition of X-ray at each AlGaInP or ZnS:Cu layer in FDEB was simulated by using MCNP5. A small amount of energy deposition in the fluorescent layer significantly improved the electrical output performance of the nuclear battery. A multilayer dual-effect energy conversion mechanism improved the electrical output performance of the nuclear batteries.

Thrombosis, a critical event in blood vessels, not only is associated with myocardial infarction and stroke, but also accounts for considerable morbidity and mortality. Thrombolytic drugs are usually applied to the treatment of acute myocardial infarction, acute cerebral infarction and pulmonary embolism. However, thrombolytic drugs show limited efficacy in clinical practice because of the short half-life in plasma and systemic side effects. In this study, the cyclic RGD (cRGD) functionalized liposomes were prepared to encapsulate urokinase, a cheap and widely used thrombolytic drug in clinic and better thrombolysis efficacy was achieved. The flow cytometry analysis showed that the cRGD liposomes could bind to the activated platelets while not to the resting platelets. In vitro release study revealed that the release percentage reached plateau in about 5 h with 60% urokinase being released from liposomes. Results from the in vitro thrombolysis experiments demonstrated a good thrombolysis potential of the cRGD urokinase liposomes. The in vivo thrombolysis study demonstrated that the cRGD liposomes could significantly reduce the dose of urokinase by 75% while achieving the equivalent thrombolysis effect as the free urokinase in mouse mesenteric thrombosis model. In conclusion, the cRGD liposomes encapsulating urokinase hold great promise in clinic for better thrombolytic efficacy. Statement of Significance In this paper, the cRGD liposomes were prepared to encapsulate urokinase for targeted thrombolysis therapy. The cRGD liposomes could specifically bind to the activated platelets and could stably and continuously release its loaded urokinase. The mouse mesenteric thrombosis model was established to evaluate the thrombolysis effect of the cRGD urokinase liposomes. The results demonstrated that the cRGD liposomes could improve the thrombolytic efficacy by almost 4-fold over free urokinase. In conclusion, the cRGD liposomes encapsulating urokinase had great potential for the clinical treatment of thrombosis.

Low energy conversion efficiency and low output power are the major limiting factors of isotope batteries as miniature power supplies for the broad applications, such as micro-electromechanical systems and aerospace electronics. In this work, highly efficient x-ray radioluminescent batteries are demonstrated based on single-crystal scintillators and spectra-matched photovoltaic batteries. X-ray sources are chosen to reduce the backscattering loss, and cerium doped Gd3Al2Ga3O12 (GAGG:Ce) single-crystal scintillators are adopted to improve the radioluminescence efficiency and light coupling efficiency, for their high x-ray absorption ability and high light-yield. The bandgap of photovoltaic battery is also optimized to match the luminescence spectrum of GAGG:Ce to maximize the photovoltaic efficiency. An optimal radioluminescent battery is achieved with an output power of 13.4 μW/cm2 and a conversion efficiency of 1.28%, which is a 10.7-times improvement in the previous best reports (0.12%). This exciting progress indicates the promising potential of radioluminescent batteries in broad applications and will inspire the further exploration for the research community of radioisotope batteries.

In this paper, we study the band structure engineering of black phosphorus/graphene/MoS2 (BP/graphene/MoS2) van der Waals heterojunctions based on ab initio simulations. The density of state and charge density of BP/MoS2, bilayer-BP/MoS2, bilayer-BP/graphene/MoS2 and graphene/bilayer-BP/MoS2 heterojunctions are also investigated. It is found that the bandgaps of these four heterojunctions are smaller than the case of single layer BP or MoS2. When graphene is inserted into or stacked upon BP and MoS2 layers, the heterojunction can obtain a minimum bandgap and a higher density of state distribution. In the differential charge density diagram, electrons over the carbon, sulfur and phosphorus atoms are lost from those corresponding parts. These investigations based on the band structure engineering of 2D van der Waals heterojunctions can provide an effective guidance to manufacture the future nanoscale high performance photovoltaic and optoelectronic devices.

Background: In recent years, there has been a noticeable increase in research on krill oil (KO) for its health benefits. However, the action of KO in lowering blood pressure (BP) has not been studied yet. Therefore the aim of this study was to assess the ability of long-term KO supplementation to lower systolic BP (SBP) in spontaneously hypertensive rats (SHRs) and Sprague Dawley (SD) rats.; Results: Compared with the blank control (BC) SHRs administered edible soybean oil, the high-dose (500 mg kg-1 body weight (BW)) KO-supplemented SHRs in the 2nd, 3rd, 4th and 5th weeks following oral administration, the mid-dose (100 mg kg-1 BW) KO-supplemented SHRs in the 4th and 5th weeks following oral administration and the low-dose (20 mg kg-1 BW) KO-supplemented SHRs in the 5th week following oral administration showed significantly lower SBP (P < 0.05). However, supplementation of KO had no significant effect on the SBP of healthy SD rats. Meanwhile, 5 weeks of KO administration significantly increased the serum levels of nitric oxide (NO) and total NO synthase of SHRs (P < 0.05).; Conclusion: KO has an antihypertensive effect in SHRs that is associated with an NO-related mechanism. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

Graphene/GaAs heterojunction has been demonstrated by transferring monolayer graphene on the surface of n-GaAs substrate, and the carrier transfer at the interface has been investigated by monitoring Raman shift of graphene on different substrates. The photovoltaic behavior and rectifying characteristic of the graphene/GaAs heterojunctions enable us to fabricate high-performance self-powered photodetector at zero bias. The device has been demonstrated to be sensitive to visible/near-infrared light (405–850 nm) at room temperature, giving rise to maximum responsivity of 122 mA W−1 and detectivity of 4.3 × 1012 Jones with quick response and recover time (0.5 ms and 0.35 ms), respectively. Such high photoelectric response is attributed to the efficient photo-generated carrier separation and transfer at the interface, which is caused by the strong built-in electric field between grapheme and GaAs because of a large barrier (0.87 eV). Our results confirm that the graphene/GaAs heterojunction has a great potential for high performance self-powered broadband photodetectors.

Hepatocellular carcinoma (HCC) is an aggressive and rapidly fatal malignancy representing the common cancer worldwide. The specific cellular gene involved in carcinogenesis has not been fully identified. The ubiquitin-like modifier FAT10, a recently reported to be over-expressed in 90% of hepatocellular carcinoma (HCC) carcinomas, and might be regarded as an ideal target for HCC therapy. In the present study, we utilized DCs transduced with FAT10 recombinant adenovirus to elicit CTLs in vitro. In addition, the Trimera mice were immunized with the transduced DCs to elicit the immune response in vivo. The results demonstrated that transduced DCs could effectively induce specific CTL response against HCC without lysing autologous lymphocytes, but also significantly inhibit the tumor growth and prolong the life span of tumor bearing mice. These results suggest that FAT10 recombinant adenovirus transduced DCs might be a promising therapeutical strategy for treatment of HCC.

The photoelectric properties of In0.3Ga0.7As solar cells applied in laser wireless power transmission (LWPT) were studied when they were irradiated by 1070 nm continuous wave (CW) laser of various intensities. The influences of laser intensity on solar cell parameters extracted by the pollination algorithm were analyzed quantitatively. Results show that the conversion efficiency of the cell rose to the maximum and then decreased rapidly in the laser intensity range of 50–900 mW/cm2. With higher energy laser irradiation, the rise of ideality factor and reverse saturation current would lead to the degradation of voltage at the maximum power point, which was the main reason for the decrease of conversion efficiency. The results provide the basis for choosing the appropriate input energy in the case of different transmission systems.

Background Chronic venous insufficiency (CVI) is a common cause of leg pain and swelling and is commonly associated with varicose veins. It has significant socioeconomic consequences and is among the most common problems encountered in surgical practice. Although our current understanding of the pathogenesis of CVI is far from clear, there is a growing body of evidence suggesting a genetic contribution to the etiology of CVI. Methods By analyzing 254 CVI cases and 508 healthy controls in a Chinese population, we used a candidate gene approach to evaluate the association between a 7–base pair insertion/deletion (indel) polymorphism (rs3917) in the 3′ untranslated region (3′UTR) of the alpha-2 type I collagen gene (COL1A2) and CVI susceptibility. Logistic regression was used to analyze the association between rs3917 and CVI risk, adjusted for sex and age. Computational modeling was used to predict potential molecular mechanisms underlying the association. Results Logistic regression analysis revealed that subjects carrying indel or deletion/deletion genotypes had a significantly increased risk for CVI than individuals carrying insertion/insertion genotypes (adjusted odds ratio, 1.64; 95% confidence interval [CI], 1.10–2.45; P = 0.010). Carrying the 7–base pair deletion allele was associated with a 1.60-fold risk for CVI (95% CI, 1.11–2.31; P = 0.008). Computational modeling suggests that the rs3917 insertion allele lies within a predicted binding site (seed region) for microRNA-382 and that the deletion allele alters the affinity of microRNA–mRNA binding by disrupting the local structure of COL1A2 mRNA, presumably allowing for upregulated COL1A2 expression. Conclusions Taken together, our data suggest that common genetic variations in COL1A2 may influence CVI risk, possibly through microRNA-382–mediated regulation. Replication of our studies in other populations will strengthen our understanding of this association.

The aim of this study was to investigate the feasibility and safety of vena cava filter (VCF) placement via percutaneous puncture of the great saphenous vein (GSV) in the prevention of pulmonary embolisms. Using ultrasound positioning, VCF placement via percutaneous puncture of the GSV was performed on 12 patients with deep vein thrombosis (DVT) in the lower extremities. Transcatheter thrombolysis was conducted simultaneously. The postoperative filter position, puncture wound recovery and fluency of the GSV were observed. All filters were successfully released, with accurate positioning. No hematoma was observed at the puncture point during the perioperative period. In certain patients, local petechiae appeared around the puncture point during the thrombolysis period, which did not require special treatment. Re-examination using ultrasound revealed unobstructed blood flow in the GSV. VCF placement via percutaneous puncture of the GSV is a new filter placement method. The feasibility and safety of this method for the prevention of pulmonary embolisms has been demonstrated in a small number of sample cases.

A fiber-bundle approach for beam steering at the transmitter was recently proposed and investigated that allowed tracking of the receiver without the use of mechanical devices for mobile free-spaced optical (FSO) platforms experiencing misalignment due to movement and atmospheric turbulence. This paper investigates different transmitter configurations along with a general pointing, acquisition and tracking (PAT) algorithm on key parameters including power availability at the receiver, switching time, link recapturing time, and coverage area at the receiver plane. The alignment control algorithm with different ways to track receiver is also evaluated on these key parameters. The algorithm performance versus transmitted power, switching time and the threshold power for beam steering was examined. The investigation finds that a combination of switching combined with splitting of the light between fibers is a suitable solution to provide the best trade-off between link up time and the coverage area at the receiver, and thus is a good general purpose design choice, and the optical tracking system with target location information demands fewer efforts to recover and maintain the dynamic link than the one without the awareness of the receiver location information.

Purpose: To evaluate retrospectively the safety and retrievability of the Celect IVC filter. Materials and Methods: All patients undergoing Celect filter placement and retrieval during the period 2007‐2012 were assessed for complications and retrievability. Results: Of 620 patients who underwent Celect filter placement, 120 presented for removal. The indwelling time in these patients was 158.1 days 103.0 (range, 2‐518 d). There were 106 filters (88.3%) removed; 14 filters were left in situ for the following reasons: filter embedment (n ¼ 6), caval occlusion (n ¼ 3), retained thrombus (n ¼ 2), large floating thrombus in IVC (n ¼ 2), or tilt 4151 (n ¼ 1). With filters in place, five patients developed new pulmonary embolism (PE), and two others presented with severe abdominal pain. The available 115 pairs of placement and removal cavagrams suggested limb penetration in 99 cases (86.1%), intracaval migration 42 cm in 5, secondary tilt 4151 in 8, filter deformity in 10, retained thrombus within filters in 12, and IVC occlusion in 3. Among 38 available computed tomography (CT) scans, 9 scans (24%) showed asymptomatic limb penetration to the duodenum (n ¼ 6), aortic wall (n ¼ 2), or kidney (n ¼ 1). No filter fracture was found. Conclusions: This study showed a high penetration rate for Celect IVC filters, including penetrations that were symptomatic or involved adjacent structures. Penetration appears to correlate with indwelling time, suggesting that the filter should be removed as soon as PE protection is no longer indicated. Although most of the filters were removed, 5.8% of retrievals were unsuccessful because of technical failure.

The Amplatzer Vascular Plug (AVP) is an established embolic device that can be an excellent alternative to coils or detachable balloons to embolize medium to large vessels with high flow. The device is easy to use and can be precisely deployed in the target vessel with high resistance to migration and a low recanalization rate. The technical success of this device is high, indications for use are expanding, and no absolute contraindications have been reported. Since its introduction, the AVP has grown from a single device to a group of 4 models (AVP, AVP II, AVP III, and AVP 4). Each model has a unique design and features that fit different vascular anatomies, hemodynamic situations, and clinical scenarios. Therefore, the new models cannot simply be treated as replacements for older ones. Unpredictable occlusion time remains a major shortcoming for the new models of the AVP. Large vessel size, high flow status, and coagulopathy can prolong the occlusion time, which can offset the cost benefit, reduced procedure time, and reduced radiation dose typically seen with use of the AVP alone. Coils or multiple AVPs can be used to expedite the occlusion process, and large Gelfoam particles also can be used as an adjunct to achieve rapid and reliable occlusion with minimal cost.

Pointing, acquisition and tracking of a free-space optical node in a mobile network experiencing misalignment due to adverse factors including vibration, motion and atmospheric turbulence requires a different approach than traditional free-space optical transceivers. A recent fiber-bundle approach for beam steering at the transmitter was investigated to provide continuous beam coverage at the receiver without the application of mechanical devices. Utilizing multiple fibers-lenses sets at the receiver was also proposed to enhance the tolerance of optical link misalignment. This paper investigates the feasibility of applying multiple fibers with a single lens at the transmitter and multiple fiber-lenses sets at the receiver to improve the transmission performance on tolerating link misalignment. Two series of laboratorial experiments were implemented to compare the optical link robustness for different transceiver setups as the fiber-lens distance (zfl) was varied to modify the beam divergence: multi-fiber transmitter working with single-fiber-lens receiver and multi-fiber transmitter working with multi-fiber-lens receiver. The results showed that using multiple fibers in both the transmitter and the receiver reveals significant potential to maximize the up time of the link.

Self-assembled InAs/AlAs quantum dots embedded in a resonant tunneling diode device structure are grown by molecular beam epitaxy. Through the selective etching in a C 6 H 8 O 7 · H 2 O-K 3 C 6 H 5 O 7 · H 2 O-H 2 O 2 buffer solution, 310 nm GaAs capping layers are removed and the InAs/AlAs quantum dots are observed by field-emission scanning electron microscopy. It is shown that as-fabricated quantum dots have a diameter of several tens of nanometers and a density of 1010 cm-2 order. The images taken by this means are comparable or slightly better than those of transmission electron microscopy. The undercut of the InAs/AlAs layer near the edges of mesas is detected and that verifies the reliability of the quantum dot images. The inhomogeneous oxidation of the upper AlAs barrier in H 2 O 2 is also observed. By comparing the morphologies of the mesa edge adjacent regions and the rest areas of the sample, it is concluded that the physicochemical reaction introduced in this letter is diffusion limited.

Size, shape, position control, and self-organized lateral ordering of epitaxial semiconductor quantum dot (QD) arrays are demonstrated. This constitutes the prerequisite for the ultimate control of the electronic and optical properties of man-made semiconductor heterostructures at the single and multiple charge, spin, and photon level, including their quantum mechanical and electromagnetic interactions in view of applications such as quantum information processing and computing. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

(In,Ga)As sidewall quantum wires (QWires) are realized by chemical beam epitaxy along [01-1] mesa stripes on shallow-patterned InP (311)A substrates. The QWires exhibit strong lateral carrier confinement due to larger thickness and In composition compared to the adjacent quantum wells, as determined by cross-sectional scanning-tunneling microscopy and microphotoluminescence (micro-PL) spectroscopy. The PL of the (In,Ga)As QWires with InP and quaternary (Ga,In)(As,P) barriers reveals narrow linewidth, high efficiency, and large lateral carrier confinement energies of 60–70 meV. The QWires are stacked in growth direction with identical PL peak emission energy. The PL emission energy is not only controlled by the (In,Ga)As layer thickness but also by the patterned mesa height. Stacked (In,Ga)As QWires with quaternary barriers exhibit room temperature PL emission at 1.55 µm in the technologically important wavelength region for telecommunication applications. ©2005 American Institute of Physics

Purpose To evaluate the differences in efficiency and complications of metal stent insertion across versus above the main duodenal papilla (MDP) in patients with malignant obstruction of the common bile duct (CBD). Materials and Methods Records of 98 consecutive patients who underwent stent insertion for malignant CBD obstruction between 2004 and 2010 were retrospectively reviewed. Fifty-one patients (group 1) and 47 patients (group 2) were treated with stent insertion across and above the MDP, respectively. Primary stent patency, overall survival, complications, and changes in serum bilirubin level following stent insertion were assessed. Results Infection appeared in 12 and four patients, respectively, in groups 1 and 2. The respective mean primary stent patency times were 307.8 days ± 20.2 and 490.7 days ± 40.7, and mean survival times were 245.1 days ± 17.4 and 286.3 days ± 20.2. Bilirubin reduction rates were 55.7% ± 16.6 and 61.1% ± 13.7 at 1 week and 84.2% ± 5.7 and 86.2% ± 5.7 at 1 month in groups 1 and 2, respectively. In group 2, the rate of infection was significantly lower ( P = .044) and primary stent patency was longer ( P = .019). However, there was no significant difference between groups in survival time ( P = .074) or bilirubin reduction rate at 1 week ( P = .083) or 1 month ( P = .082). Conclusions Bile stent insertion above the MDP may achieve longer stent patency and a lower infection rate compared with placement across the MDP. For patients with malignant CBD obstruction, biliary stents should be placed above the papilla if papillary lesions are not invaded.

The purpose of this study is to retrospectively evaluate the prevalence and extent of Celect inferior vena cava (IVC) filter penetration.All patients with Celect filters who underwent CT between 2007 and 2012 were assessed for penetration and related complications.Of the 690 patients with Celect filters placed at our institution, 265 underwent CT for various reasons. The mean (SD) interval between filter placement and last CT was 167.8±264.8 days (median, 56 days; range, 0-1592 days). Penetration of primary leg was observed in 39% (95% CI, 29-51%) of patients within 30 days and 80% (95% CI, 70-87%) of patients within 90 days after placement. The mean number of penetrated legs per patient was 1.8 at 30 days and 2.1 at 90 days after placement. Penetration into adjacent organs occurred in 35 of 265 (13.2%) filters (in 45 IVC filter limbs); penetration into two structures occurred with 10 filters. The sites involved were the duodenum (n=22), aorta (n=9), psoas muscle (n=4), vertebral body (n=3), pancreas (n=2), adrenal gland (n=1), liver (n=1), right kidney (n=1), lymph node (n=1), and diaphragm (n=1). One patient presented with abdominal pain related to penetration.This study confirms a high penetration rate for Celect IVC filters and shows that CT can characterize the extent of leg penetration. Most cases of penetration were asymptomatic, but the likelihood of penetration increased over time.

Increased RF noise floor, crowded and scarce wireless spectrum, and security are issues challenging present-day aerial wireless communication. Optical wireless (or free-space optical (FSO)) is an alternative communication system applicable to air-to-air (A2A) or air-to-ground (A2G) applications. An FSO link is able to provide high bandwidth, low-power, and secure communication for various unmanned aerial systems (UASs) and ground nodes, including mobile and fixed stations. However, unlike RF, optical communication is highly sensitive to misalignment and platform instability that causes unavoidable communication interruptions. Developing aerial optical wireless communication systems requires modeling the effects of UAS instability on the FSO system performance, including FSO link throughput. This work aims to develop a rigid and simple modeling framework for A2A FSO communication links. The framework is abstract, general, and platform-independent. The model relates instability to averaged percentage alignment (APA), which can be used to predict throughput and other performance-related parameters. A planer arrays of optical transmitters and receivers is used and proposed as a promising technology for FSO communication with large field-of-view and diversity-ready performance. Also, a novel alignment model using geometric intersection is developed and analyzed against simulated and real multi-rotor platforms.

Purpose To determine the incidence of fracture and migration of the Celect inferior vena cava (IVC) filter at a single tertiary-care center. Materials and Methods Images obtained after placement of Celect IVC filters between August 2007 and January 2013 were retrospectively reviewed for evidence of device fracture and migration. The probability of filter fracture at 6 and 12 months after filter placement was estimated, and a 95% upper confidence bound was constructed. Results A total of 741 consecutive Celect filters were placed, and the following studies were subsequently evaluated: 301 abdominal radiographs, 282 abdominal computed tomography (CT) scans, 154 cavagrams, 19 lumbar spine radiographs, 462 chest radiographs, 108 chest CT scans, and 31 pelvic radiographs. The mean imaging follow-up interval was 5.78 months ± 8.80 (range, 0.01–56.03 mo). There was no filter fracture or en-bloc migration outside the IVC. Upper 95% confidence bounds for the probability of fracture were 1.8% at 6 months and 4.3% at 12 months. Intracaval filter migration of more than 2 cm (mean, 2.43 ± 0.12 cm; range, –2.54 to 2.99 cm) was seen in 3.9% of patients (21 of 534; 12 cranial and nine caudal). Conclusions No fracture of a Celect filter was observed in this large cohort over a relatively short follow-up interval. The results also suggest that the Celect filter has an adequate securing mechanism to prevent distant en-bloc or significant intracaval migration.

The response of collision velocity waveform to structure deformation in parts dynamic impact simulation was first analyzed in this paper, and a method of deriving structure deformation order by velocity waveform was then determined. By analyzing the relationship between longitudinal rail structure deformation modes and collision velocity waveform in vehicle impact simulation, the reliability of a method of reversely deriving structure deformation modes through speed waveform was verified afterwards. Finally this method was applied in vehicle collision test and the deformation modes of longitudinal rail structure were derived accurately which could provide reference for optimizations of car body structure subsequently.

A novel receiver and transmitter that utilize fiber bundles are under development to address the challenges associated with acquiring and maintaining a free-space optical link between mobile platforms in the presence of vibration and atmospheric turbulence. The fiber bundles allow for greater misalignment tolerance at the receiver and greater control over the spatial area covered by the transmitted beam upon reaching the receiver. This paper reports on a simulation-based investigation of design choices that optimize the performance of the system under several operating scenarios. The simulation incorporates prior experimental data into the theoretical calculations for optical propagation to better describe the performance of the physical designs. For a given link length and available power, the coverage area and collected power are controlled by the pattern of transmitters, beam divergence, and the receiver construction. The investigation finds that the coverage area of the receiver can be optimized for a given link length by proper choices of these parameters, and that similar parameters may provide near optimal performance at other wavelengths. Trade-offs between choices of the key parameters are explored as a function of link length. The results provide guidance on the further development of the overall system.

In order for mobile optical transceivers to communicate, the transceivers must be able to acquire and maintain a free-space optical link between them despite misalignments due to movement and the effects of atmospheric turbulence. Recently, novel transmitters and receivers, along with specifically designed control algorithms, were proposed that incorporated a fiber-bundle approach for improving the ease of acquiring and maintaining the link between two transceivers. Preliminary transmitter and receiver nodes have been constructed for testing the capabilities of this approach. This paper investigates the performance of a transmitter and receiver pair through experimental methods. The performance is evaluated on several key parameters, including initial acquisition time, up time of the link when perturbed by movement or simulated atmospheric impairment, and the link recapturing time once a connection is lost. The dependence of the key parameters is evaluated for different levels and types of perturbations, as well as design choices at the transmitter and receiver. The results show that the optical control system successfully recovered and maintained the link while the receiver was in motion, although the performance was impacted by the angular misalignment tolerance of the receiver. The strengths and limitations of the approach revealed by the experiments are also discussed, along with paths for further improvements.

This paper investigates the performance of a recently proposed control algorithm for mobile FSO node alignment through experimental methods. The performance is evaluated on coverage area at the receiver plane, the link recapturing time and the connection up-time during tracking. The dependence of performance on the transmitted power, switching time and the threshold power for beam steering was examined. The results show that the optical tracking system successfully recovered and maintained the link while the receiver was in motion and the signal coverage at the target area was enhanced significantly.

This paper reports on a simulation-based investigation of an optical wireless system using fiber-bundle based transmitters and receivers. The simulation incorporates both beam propagation theory and experimental data from evaluations of the individual components. The coverage area at the receiver is evaluated as a function of transmitter power, link length, misalignment, and the number of transmitter fibers employed. An optimum coverage area is achievable with proper selection of transmitter parameters for a given link length. Trade-offs between the number of fibers employed and the transmitter power are explored.

Since the need for high alignment accuracy of the transmitter and receiver to construct a viable connection is a primary challenge for mobile free-space optical (FSO) links, developing an efficient transmitter control system for acquisition and tracking is an urgent demand. This paper investigates a novel control algorithm within different transmitter designs in FSO mobile networks. The fiber bundles are utilized so that the beam deflection properties of a lens can be exploited to affect beam steering. After acquiring and processing the data from GPS, fisheye system as well as the receiver, the adaptive control system would help tracking the mobile receiver and providing optimum coverage over the target area. Initial analysis of the design indicates refinements in design and performance required to develop a practical control system.

In order to track, acquire and maintain a free-space optical link between mobile platforms experiencing misalignment due to movement and atmospheric turbulence requires a different approach than traditional free-space optical transceivers. Recently, a fiber-bundle approach for beam steering at the transmitter was proposed and investigated that allowed tracking of the receiver without the use of mechanical devices. This reduced the size and weight of the transmitter by reducing the dependence on stabilization systems. This paper investigates different approaches for controlling the distribution of light to the bundle to facilitate tracking of the receiver and hence maximizing up time of the link. These approaches include switching light between individual fibers in the bundle, splitting of light amongst multiple fibers and switching between groups of fibers, and splitting light between all of the fibers. Each approach is evaluated on key parameters including power availability at the receiver, switching time, projected up time between switches, and coverage area at the receiver plane. Both experimental and theoretical analyses of the system are presented to address the key parameters. The investigation finds that a combination of switching combined with splitting of the light between at most three fibers is a suitable solution for the target application of a hybrid disaster area wireless network.

International audience; Low-threshold current density InAs quantum dash lasers are demonstrated by reducing the energy inhomogeneous broadening through an optimised double-cap technique. A threshold current density for an infinite cavity length of 225 A/cm² (~45 A/cm² per stack) is obtained from a five-stack laser structure. The characteristic temperature above room temperature is 52 K, and this relatively low value results from the carrier leakage from the dash into the barrier (waveguide) region.

International audience; InAs quantum dash (QDH) and quantum dot (QD) lasers grown by molecular beam epitaxy on InP substrate are studied. The laser active zones with multiple stacked layers exhibit lasing wavelength at 1.55 μm. On these devices, the experimental threshold current density reaches its minimum value for a double stacked QDH/QD structure. Other basic laser properties such as gain and quantum efficiency are compared. QD lasers exhibit better threshold current densities but equivalent modal gain per layer than QDH. Finally, the analysis of the modal gain on QD lasers shows a promising potential for improvement.

Implementation of digital signal processing (DSP) algorithms in hardware, such as field programmable gate arrays (FPGAs), requires a large number of multiplications. In this paper, we introduce a novel multiplier structure that converts from 2's complement to canonical signed digit (CSD) representation in real time. The proposed algorithm increases the number of zero partial products (which can be simplified by shift operations) to approximately 66.7% compared with 50% for modified Booth's recoding. Also, the proposed hardware structure reduces the non-zero partial products to a minimum, and consequently the number of arithmetic operations in the carry-save structure is reduced. So, our proposed hardware decreases both the time required for multiplication and the power consumption of the multiplier. Furthermore, because the proposed structure uses real time CSD recoding, and does not require a fixed value for the multiplier input to be known a priori, the proposed multiplier can be used to implement digital filters with non-fixed filter coefficients, such as adaptive filters.

This paper introduces a novel signal exclusive adaptive average (SEAA) filter that offers good image denoising performance in applications characterized by impulsive or impulse-like noise. The proposed algorithm works well in suppressing impulse noise with noise ratios from 3% up to 60%. We begin by introducing a digital differentiation preprocessing step to quantify the increments in each local neighborhood of the noisy image. A homogeneity level map is then derived by adaptive thresholding and used to designate pixels as noise candidates. The initial selection is refined using a novel connected components labeling algorithm. Finally, the noise is attenuated by estimating the values of the noisy pixels with a linear filter applied exclusively to those neighborhood pixels not labeled as noise candidates. This approach bears similarity to several nonlinear techniques including alpha-trimmed means, selective averaging, and WMMR filters. Simulation results indicate that SEAA is better able to preserve 2-D edge structures from the original image and delivers better performance with less computational overhead as compared to competing nonlinear denoising algorithms

Implementation of digital signal processing (DSP) algorithms in hardware, such as field programmable gate arrays (FPGAs), requires a large number of multipliers. In this paper, we introduce a new multi-input Canonical Signed Digit (CSD) multiplier unit, which requires fewer shift/add/subtract operations and less CSD number conversion overhead; as a result, we can greatly reduce the power consumption and area requirements in the hardware implementation of DSP algorithms. Furthermore, because all the products are produced simultaneously, the multiplication speed and thus the throughput are improved. The developed multi-input multiplier unit is applied to implement digital filters with non-fixed filter coefficients, such as adaptive filters. The implementation cost of these digital filters can be further reduced by limiting the wordlength of the input signal with little or no sacrifice to the filter performance, which is confirmed by our simulation results. The proposed multiplier unit can also be applied to other DSP algorithms, such as digital filter banks or matrix and vector multiplications.

In this work, we develop novel control algorithms suitable for the smart shock absorber (SSA) component of the intelligent vehicle and bridge system (IVBS). The SSA control serves two IVBS purposes: 1) working as the vehicle suspension to increase driver comfort and controllability when the vehicle is on the pavement, and 2) reducing the vibration of highway bridges and thus prolonging bridge life. We propose and discuss in this paper algorithms targeted at the first purpose. Based on the application of active noise control techniques to an active suspension system, we introduce the clipped active noise control (clipped ANC) algorithm. The main advantage of this algorithm is that because it is adaptive, it can effectively balance the comfort and controllability. A simplified control algorithm based on the clipped ANC is also proposed to reduce the implementation cost. The simplified algorithm has no requirements for system modeling, so it substantially reduces the implementation cost. The effectiveness of our proposed algorithm is indicated by analyses, simulations and laboratory testing.

Vibration mitigation has become increasingly vital for the current highway bridge system. Since the main source of bridge vibrations comes from heavy trucks passing by, we propose a control system that can be installed on the trucks to help reduce bridges' vibration. The approach is based on the nonlinear black-box model of the truck-bridge interaction.

Xu, Y. et al. (see IEEE T-IP, vol.3, no.6, 1994) proposed an effective wavelet based spatially selective denoising algorithm. The performance of the algorithm depends on the noise power estimation. Pan, Q. et al. (see IEEE T-SP, vol.47, no.12, 1999) tried to improve the performance via a small modification. However, our simulation shows that both of these methods are sensitive to noise estimation. We analyze the sensitivity of these two methods and introduce a new spatially selective noise filter based on the UDWT (undecimated wavelet transform) that uses spatial correlation thresholding. Theoretic analysis and simulations show our algorithm improves the denoising effect. They also show that our proposed method is robust to errors in the noise power estimate. Because our approach is robust, we can relax the requirements for the estimation of the threshold without sacrificing performance, and so our method is more computationally efficient. We also put some perspective on the impact of employing nonorthogonal representations. Simulation results show the effectiveness of our proposed algorithm.

This paper considers a range of channel allocation schemes for High Speed Circuit Switched Data (HSCSD) over GSM and reports performance (blocking probability) and efficiency results. The channel allocation schemes studied differ in the way channels are packed (First Fit, Best Fit and Repacking), and in the connection admission policy. An overall performance comparison of the schemes is provided in order to gain insight into simplicity/efficiency tradeoffs.

This paper reports on a simulation-based investigation of a wavelength diverse free-space optical link with an emphasis on identifying design choices that optimize the performance of the system under different operating scenarios. The simulation incorporates experimental data into the theoretical calculations for optical propagation to better describe the performance of the physical designs. The performance is evaluated in terms of the coverage area at the receiver, which is a measure of misalignment tolerance and is dependent not only on wavelength but on other key parameters, such as link length, transmitted power, the pattern of transmitters, beam divergence, and the receiver construction. The investigation finds that the coverage area of the receiver can be optimized for a given wavelength by proper choices of these parameters, and that parameter choices exist that minimize the change in performance when switching between wavelengths or for variations in link parameters. The interrelationships among key parameters and their impact on the potential system performance are investigated. The results provide guidance on the further development of the overall system.

Purpose To retrospectively evaluate the safety and retrievability of the Celect IVC filter. Materials and Methods All patients undergoing Celect filter placement and retrieval between 2007 and 2012 were assessed for complications and retrievability. Results Of 690 patients who had Celect filter placement, 143 presented for removal. The indwelling time in these patients was 176.2 ± 150.3 days (range, 2-1413 d). A total of 125 filters (87.4%) were removed; 18 filters were left in situ for the following reasons: filter embedment (7), caval occlusion (3), retained thrombus (3), large floating thrombus in IVC (4), or tilt > 15° (1). With filters in place, 6 patients developed new pulmonary embolism and 2 others presented with severe abdominal pain. The available 135 pairs of placement and removal cavagrams suggested limb penetration in 112 cases (86.1%); intracaval migration > 2 cm in 5; secondary tilt > 15° in 8; filter deformity in 10; retained thrombus within filters in 13; and IVC occlusion in 3. Among 52 available CT scans, 11 cases (21%) demonstrated asymptomatic limb penetration to the duodenum (6), aortic wall (3), kidney (1) and liver (1). No filter fracture was found. Conclusion This study showed a high penetration rate for Celect IVC filters, including penetrations that were symptomatic or involved adjacent structures. Penetration appears to correlate with indwelling time, suggesting that the filter should be removed as soon as PE protection is no longer indicated. Although most of the filters were removed, 5.6% of retrievals were unsuccessful because of technical failure.

International audience; We report on the uniformity improvement of InAs quantum dashes (QDHs) grown by molecular beam epitaxy on InP (100) through optimizing double cap technique. Broad-area lasers were fabricated with an emission wavelength of 1.58 μm. A threshold current density of 360 A/cm2 was achieved for a five stack QDH structure and a cavity length of 1.2 mm. This results from a reduced inhomogeneous broadening (62 meV) and lower internal optical losses (7 cm-1). The achievement paves the way toward ultralow threshold semiconductor laser for telecommunications.

The authors report lateral positioning and number control of InAs quantum dots (QDs) on truncated InP (100) pyramids by selective-area metal organic vapor-phase epitaxy. With reducing QD number, sharp emission peaks are observed from individual and single QDs with wavelength tuned into the 1.55μm telecom region by insertion of ultrathin GaAs interlayers beneath the QDs. Regrowth of a passive waveguide structure around the pyramids establishes submicrometer-scale active-passive integration for efficient microcavity QD nanolasers and single photon sources.