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Optically pumped gas molecular terahertz (THz) lasers are promising for generating high-power and high-beam-quality coherent THz radiation. However, for pulsed gas THz lasers, the temporal behavior of the output THz pulse has rarely been investigated. In this study, the temporal behavior of a pulsed gas THz pumped by a fundamental-mode TEA CO

It is challenging for the multi-spectral photodetector to have a compact structure, high spectral resolution, and high detection efficiency. This paper reports on a new approach for compact multi-spectral visible light detecting based on the hexagonal lattice silver nanodisk arrays atop optical cavity substrates. Through numerical calculations and optimizations of experiments, we verified that the narrow band responsivity of the photodetector was caused by coupling the surface plasmonic resonances and cavity mode. The multi-spectral photodetector exhibited that the minimum FWHM and the maximum responsivity of was achieved to be 80 nm and 91.5 mA·W-1, respectively. Besides, we also analyzed the influence of the proposed structure on the energy wastage by numerical comparison. The proposed way for multi-spectral photodetector is promising to be an excellent design for the narrow band spectral detection. The design can also be easily integrated with CMOS devices and applied to other spectral regimes for different applications.

An efficient and widely tunable Si-prism-array coupled terahertz-wave parametric oscillator (TPO) with a very narrow linewidth is demonstrated by using a shallow surface cross-pump configuration. The shallow surface cross-pumping form was realized by totally reflect the pump beam at the THz-wave exit surface. Widely THz-wave tuning range of 0.6–3.9 THz is realized with a 1-mm diameter pump, and the high-frequency end even reached 5.5 THz with a 2-mm diameter pump to increase the nonlinear gain length. The measured Stokes linewidth was 0.07 nm, which is compressed by 70% for that of the conventional TPOs. The highest THz-wave output energy of 2.4 μJ was achieved at 2 THz under 15 mJ pumping, corresponding to an energy conversion efficiency of 1.6 × 10−4. The mechanism of the frequency-selection effect in cross-pumped stimulated polariton scatterings was discussed by calculating the single-pass parametric gain for different phase mismatches.

Lint percentage of seed cotton is one of the important bases for pricing in the trading segment. Unfortunately, the conventional methods of lint percentage are manually operated, which relies on the abundant experience of experts, and restrained by personal, physical and environmental factors. Up to date, the calculation of the lint percentage of seed cotton has not fully automated. In this paper, we proposed a non-destructive detection method for automatically obtaining lint percentage of seed cotton based on optical penetration imaging and machine vision, for the first time to our knowledge. The cotton seed image was obtained by the penetration imaging setup with a LED white backlight source. To accurately identify the number of cotton seeds, the image features of the cotton seed was studied and three key features was been found, which are the circumference, area, and greyscale value, respectively. A calculation system based on the three key features was presented to process the images and then automatically calculate the lint percentage of seed cotton. The first step of the system is to segment the original image using adaptive thresholding followed by morphological operations. Afterwards, the number of cotton seed was obtained by the three key features of the cotton seed. Then, the lint percentage was achieved by a professional industry formula. The suggested lint percentage detection methods were verified by the experiments with two seed cotton varieties samples of H219 and ZHM19. The experimental results indicated that the detection average accuracy of the developed system for seed cotton varieties H219 and ZHM19 were 96.33% and 95.40%

The paper proposed and verified a method of object edge detection based on the innovative defect spot working mode of the position-sensitive detector (PSD). With the output characteristics of the PSD in the defect spot mode and the size transformation properties of a focused beam, edge-detection sensitivity could be improved. Calibration experiments with the piezoelectric transducer (PZT) and object edge-detection experiments indicate that the object edge-detection sensitivity and accuracy of our method could reach 1 and 20 nm, respectively. Therefore, this method can be widely used in high-precision alignment, geometric parameters measurement, and other fields.

High-bandwidth and high-speed plasmonic interconnection is a long-term goal in constructing next-generation optoelectronic integrated circuits (OEICs). Here, we report a strategy to achieve plasmon...

Recent discoveries in the field of graphene-based heterostructures have led to the demonstration of high-performance photodetectors. However, the studies to date have been largely limited to the heterojunction with a Schottky barrier, restricted by an inevitable compromise between photoresponsivity and photodetectivity. Here, a new class of graphene-based tunneling photodetectors is introduced by inserting the Al2O3 tunneling layer between silicon and graphene. The photocarriers can tunnel through the designed insulator layer which simultaneously blocks the dark current, thus maintaining high photodetectivity with desirable photoresponsivity. We further modulate the thickness of the Al2O3 layer to explore the tunneling mechanism for the photocarriers, in which a photoresponsivity of 0.75 A/W, a high current ratio of 4.8 × 103 and a photodetectivity of 3.1 × 1012 Jones are obtained at a 13.3-nm-thick Al2O3 layer. In addition, the fabrication process is compatible with conventional semiconductor processing, providing further flexibility to large-scale integrated photodetectors with high performance.

Plasmonic metallic nanostructure/silicon composites are gaining increasing attention due to their NIR photodetection capability and potential compatibility with CMOS technology. However, those kind...

Due to the surface plasmon induced hot electrons effect, noble metallic nanostructures as photosensitizer have been widely applied for extending the photoresponse spectra of wideband semiconductors to visible range. However, most of those researches only focused on how to extend the photoresponse spectra and to improve the hot electrons injection efficiency, few investigations about the effect of hot electrons injection process on the photocurrent transient variation. In this paper, we firstly extended the photoresponse spectra of IGZO phototransistors to visible range by decorating the channels with the Au nanoparticles (AuNPs), and then specifically investigated the influence of plasmon induced hot electrons injection process on the photocurrent by observing the photocurrent transient curve of AuNPs decorated IGZO phototransistors under different illumination conditions (405 nm, 532 nm, 658 nm). It was found that AuNPs decorated IGZO phototransistors show an overshoot peak at the rising edge (falling edge) of the photocurrent curve under 658 nm illumination (dark), while the bare IGZO phototransistors don't show this phenomenon. We proposed a dynamic transportation model of hot electrons to explain the possible reason and also found that the generation and injection efficiency of hot electrons are strongly dependent on the magnitude and location of the electric field enhancement. These findings will have a great significance for understanding the mechanism of plasmon induced hot electrons transfer process at the metallic/semiconductor interface and designing novel hot electrons based optoelectronic devices .

Here, an efficient narrow-band optical photodetector is realized by using hexagonal nanodisk array based on a P-N junction. The photodetector can effectively separate incident spectrum. The wavelength of the maximum responsivity in different array is red-shift with the increase of the period. The maximum detection efficiency can reach 95%.

Metasurface filters are a compact, lightweight, and inexpensive solution for the miniaturized hyperspectral imaging system. However, the emerging applicability of these filters is limited by the trade-off between spatial and spectral resolutions. In this study, we establish and experimentally demonstrate a compact hyperspectral photodetection method using random all-dielectric metasurface filters that are directly integrated on the detectors. Based on compressive sensing algorithms, the compact photodetectors can accurately reconstruct the incident spectrum in the visible range. The minimum full width at half maximum (FWHM) of the spectrum reconstructed is 4.8 nm, which fully satisfies the requirements of hyperspectral imaging. The proposed method may be applied in the design, development, and measurement of compact hyperspectral imaging systems.

A high power gas terahertz laser based on L-shaped cavity was demonstrated. We, for the first time, investigated the output performances of D2O gas 385 μm THz laser by optimizing the output coupler transmittance of the L-shaped cavity both in theory and experiment. Under the pump energy of 1.6 J, the optimum output coupler transmittance was about 0.78 and the optimum gas pressure was about 500 Pa. Up to 8.4 mJ pulse energy at 385 μm was achieved at output coupler transmittance of 0.8, corresponding to a photon conversion efficiency of 43.7%. Pulse width of 120 ns, and beam quality factor M2 of 1.58 were obtained at the highest output energy. In addition, the experimental results are in agreement with the theoretical simulation results.

A modified three-level laser kinetics model for a pulsed high-power optically pumped gas terahertz laser is introduced and used to model the lasing kinetics process of a gas terahertz laser system. We, for the first time to our knowledge, investigated the time evolution dynamics process of the pump intensity, population distribution among the energy levels, pump and THz signal gain coefficient, and the THz laser intensity within the pulsed D2O gas THz laser. High-power THz pulse with peak power of about 7.4 kW and pulse width of 145 ns at wavelength of 385 μm were obtained in the simulation, using an incident pump pulse with peak power of 2.2 MW and pulse width of 110 ns. THz pulse delay of 40 ns and pulse broadening of 35 ns were quantitatively analyzed. In addition, the experimental results for the pulse profile, pulse width, pulse broadening, pulse energy, and peak power are in agreement with the theoretical simulation results.

Plasmonic interconnection is one kind of the possible methods to construct next-generation optoelectronic integrated circuits. In this paper, the plasmonic interconnection device based on Ge in infrared band is constructed, through efficient electron-hole pair generation, the device can achieve high photocurrent response (0.25A/W). Because of the low plasmon coupling efficiency of the conventional basic periodic gratings, this paper optimized the design of the coupling structure and improved the coupling efficiency by 4 times through constructing a binary Bragg/periodic grating coupler which can realize unidirectional plasmon coupling with a simulated extinction ratio of 12.5 dB. The devices can be easily fabricated by single-step electron beam lithography and lift-off process. The experimental results verified a 3.5 times improvement in the SPPs current of the designed plasmonic interconnection device, which provides a technical path to realize efficient plasmon transmission and detection for on-chip optoelectronic interconnection.

Objective The objective was to compare estimates of childhood influenza vaccination across 7 consecutive influenza seasons based on 2 survey systems. Methods We analyzed data from the National Health Interview Survey (NHIS) and the National Immunization Survey–Flu (NIS-Flu) using Kaplan-Meier survival analysis to estimate receipt, based on parental report, of at least 1 dose of influenza vaccine among children aged 6 months to 17 years. Results We found no significant increasing trend in influenza vaccination coverage among children overall from 2012 to 2018 based on the NHIS or from 2012 to 2019 based on the NIS-Flu. We found 4 seasons with a significant increase in influenza vaccination coverage compared with the previous season (2012-2013 [NHIS, NIS-Flu], 2013-2014 [NIS-Flu], 2017-2018 [NHIS], and 2018-2019 [NIS-Flu]). As of the 2018-2019 season, based on NIS-Flu, influenza vaccination coverage was only 62.6%. Children with health conditions that put them at increased risk for complications from influenza had higher influenza vaccination coverage than children without these health conditions for all the seasons studied except 2014-2015. For all seasons studied, influenza vaccination coverage estimates for children were higher based on NIS-Flu data compared with NHIS data. Trends across seasons and differences in vaccination coverage between age groups were similar between the 2 surveys. Conclusions Influenza vaccination coverage among children appears to have plateaued. Only about half of the children in the United States were vaccinated against influenza. Improvements in measurement of influenza vaccination and development and review of strategies to increase childhood influenza vaccination coverage are needed.

Influenza vaccination is the primary way to prevent influenza, yet influenza vaccination coverage remains low in the United States. Previous studies have shown that children residing in rural areas have less access to healthcare and lower vaccination coverage for some vaccines. Influenza vaccination coverage among children 6 months–17 years by rural/urban residence during the 2011–12 through 2018–19 influenza seasons was examined using National Immunization Survey-Flu data. The Council of American Survey Research Organizations response rates for National Immunization Survey-Flu ranged from 48% to 65% (2011–12 through the 2017–18 seasons) for the landline sample and 20%–39% (2011–12 through the 2018–19 seasons) for the cellular telephone sample. Children residing in rural areas had influenza vaccination coverage that ranged from 7.9 (2012–13 season) to 12.6 (2016–17 season) percentage points lower than children residing in urban areas, and ranged from 4.5 (2012–13 season) to 7.4 (2016–17 season) percentage points lower than children residing in suburban areas. The differences in influenza vaccination coverage among rural, suburban, and urban children were consistent over the eight seasons studied. Lower influenza vaccination coverage was observed among rural children regardless of child’s age, mother’s education, household income, or number of children under 18 years of age in the household. Rural versus urban and suburban differences in influenza vaccination coverage remained statistically significant while adjusting for selected sociodemographic characteristics. A better understanding of the reasons for lower childhood influenza vaccination coverage for children in rural and suburban areas is needed.

Background Provider recommendation is associated with influenza vaccination receipt. The objectives of this study were to estimate the percentage of children 6 months–17 years for whom a provider recommendation for influenza vaccination was received, identify factors associated with receipt of provider recommendation, and evaluate the association between provider recommendation and influenza vaccination status among children. Methods National Immunization Survey-Flu (NIS-Flu) parentally reported data for the 2013–14, 2014–15, and 2015–16 seasons were analyzed. Tests of association between provider recommendation and demographic characteristics were conducted using Wald chi-square tests and pairwise comparison t-tests. Multivariable logistic regression was used to determine variables independently associated with receiving provider recommendation and the association between provider recommendation and influenza vaccination status. Results Approximately 70% of children had a parent report receiving a provider recommendation for influenza vaccination for their child. The strongest association between receipt of provider recommendation and demographic characteristics was with child’s age, with younger children (6–23 months, 2–4 years, and 5–12 years) being more likely to have a provider recommendation than older children (13–17 years). In addition, children living in a household above poverty with household income >$75,000 were more likely to have a parent report receipt of a provider recommendation than children living below poverty. Children with a provider recommendation were twice as likely to be vaccinated than those without. Conclusions This study affirms the importance of provider recommendation for influenza vaccination among children. Ensuring that parents of all children receive a provider recommendation may improve vaccination coverage.

Through the establishment of a pair of spur gear contact models, based on Hertz contact theory, the tooth surface contact stress is calculated; then the Ansys finite element analysis software is used to simulate and analyse the stress distribution. Through the analysis and comparison of the two results, it is proved that the contact stress calculated by Hertz theory is relatively small, which is close to the results of the finite element simulation analysis. Theoretical calculation can verify the accuracy of the finite element simulation analysis model, and the finite element simulation analysis provides an effective way to accurately calculate the contact stress of the tooth surface.

Involute spur gears generate heat due to tooth surface meshing friction. Excessive temperature rising affects transmission accuracy and reduces work reliability.. By establishing the normalized coordinates of the meshing curve and based on the frictional heat generation theory, the mathematical analysis model of the meshing surface heating is studied, the factors affecting the average heat flux density of meshing are explored, and the distribution law of these factors along the normalized coordinate of the meshing is analysed. The analysis shows that the tangential velocity of the meshing point and the half-bandwidth of the time domain contact have the greatest influence on the average heat flow density; the average heat flow density distribution of the driving wheel and the driven wheel are similar. The heat flow density of the driving wheel is greater than that of the driven wheel. Tooth shape modification minimizes tooth surface meshing contact stress, reduces meshing heat generation, controls temperature rise and improves transmission reliability.

The Beiligaimiao magmatic Ni-Cu sulfide deposit is located in the northern rim of the North China Block, which was an active continental margin related to the southward subduction of the Paleo-Asian oceanic plate to the north in the Paleozoic. This deposit has never been studied before but is an excellent example of sulfide mineralization in arc settings that have been commonly overlooked by exploration geologists worldwide. Sulfide mineralization in the deposit is hosted in a mafic-ultramafic complex that consists of a small ultramafic body surrounded by an older and much larger gabbroic intrusion. Disseminated sulfide zones are present in both intrusive bodies but only those close to the surface within the ultramafic body have been mined in the past. The sulfide-mineralized ultramafic body is composed of olivine websterite and orthopyroxenite with a gradational contact between them. SIMS U-Pb dating of zircon crystals from a large olivine websterite sample yields a crystallization age of 269.4 ± 2.1 Ma, which is ∼25 Ma younger than the Erbutu subduction-related magmatic Ni-Cu sulfide deposit that occurs ∼50 km to the north. Orthopyroxene crystals in the Beiligaimiao ultramafic rocks have Mg # [100 Mg/(Mg + Fe), molar] of 77–78, significantly lower than those in the ultramafic rocks of the Erbutu deposit. Olivine crystals in the Beiligaimiao ultramafic rocks have forsterite (Fo) contents from 72 to 75 mol%, which are also significantly lower than those in the ultramafic rocks of the Erbutu deposit (Fo, 86–88 mol%). The mineral chemical data indicate a more fractionated parental magma for the former. Ca-depletion in olivine (i.e., 34 S values of sulfide separates from the Beiligaimiao deposit are 1.7 to 2.5‰, significantly lower than those for the Erbutu deposit but still slightly higher than the MORB value (−1.5 to 0.5‰). Olivine websterites in the Beiligaimiao deposit have e Nd from −8.9 to −9.5 and ( 87 Sr/ 86 Sr) i close to 0.7075, which are similar to those of an enriched lithospheric mantle. An orthopyroxenite sample from the deposit has much lower e Nd (−12.6) coupled with much higher ( 87 Sr/ 86 Sr) i ratio (0.7132), indicating ∼25% crustal contamination. The Sr-Nd-S isotope data support the premise that both crustal contamination and addition of crustal sulfur played a role in triggering sulfur saturation in the parental magma of the Beiligaimiao deposit. Since the immediate country rocks are exclusively gabbros, these processes likely took place at depth. The close temporal and spatial association of the Beiligaimiao and Erbutu deposits points to the possibility that more Permian arc-type magmatic sulfide deposits are yet to be discovered in the region.

To realize multiple-band perfect absorption, a novel nanostructure consisting of subwavelength periodic metallic grating and a thick metallic substrate, separated by a thin dielectric spacer(MGDM), is proposed in this paper. Compared with the structures without the dielectric spacer, the designed MGDM nanostructure not only possesses the absorption peaks caused by the Fabry-Perot resonance in the grating slits, but also possesses additional absorption peaks. Numerical simulation results show that the additional absorption peaks are caused by the gap plasmon resonance in the dielectric spacer. Besides, the influence of structural parameters on the absorption properties of MGDM are also thoroughly investigated. The combination of Fabry-Perot resonance and the gap plasmon resonance in the proposed MGDM provide another route for designing multiple-band perfect absorber nanostructures, which have an extensive applications in photo-detecting, photo-conversion or photo-harvesting.

We report on the mid-infrared (MIR) and terahertz (THz) wave spectra of D2O gas pumped using a fundamental transverse mode transversely excited atmospheric CO2 laser with an emission wavelength of 9.26 μm. We obtain MIR emission lines at center wavelengths of 9.262, 9.491, and 9.752 μm, which correspond to the vibrational-energy-level-transition lines of D2O. We observe an intense THz stimulated Raman emission line of 385 μm and a weak cascade-transition line of 359 μm for transitions from rotational levels 422 to 413 and 413 to 404 in the first-excited vibration state of the D2O molecule gas. We establish a four-energy-level system for modeling the laser kinetics of the dual-wavelength (385 and 359 μm) superradiation THz laser. For the optically pumped D2O gas 385 μm THz laser, in considering the cavity effect and insertion loss of a THz cavity oscillator, an approximation treatment of the THz laser kinetics can be made based on a three-energy-level system.

A high-quality and stable electron device of aligned gold nanogap arrays is demonstrated by using a well-controlled method with electron beam lithography and focused ion beam. Sub-30-nm nanogap arrays could be precisely fabricated with reproducibility. Field emission (FE) properties of the nanogaps are directly measured in the vacuum chamber of scanning electron microscopy with a nanomanipulator. Experimental investigation and calculations are carried out to reveal the transition process from the leakage current to the FE. Importantly, the controllable method could allow us to readily construct varying nanospacings. Besides, we also illustrate the independence of emission current on the vacuum degree over a large range, widening the applied range of the devices. These studies clearly demonstrate that electronic devices with sub-30-nm vacuum channel can be readily achieved by coupling varying nanogaps into nanostructures. It may pave the way for exploring the physics in tunneling transport devices, and therefore enable a new generation of high-performance, high-speed and low-cost electronic devices.

Hybrid nanostructures of quantum dots(QDs) and metallic nanostructure are attractive for future use in a variety of optoelectronic devices. For photodetection applications, it is important that the photoluminescence (PL) of QDs is quenched by the metallic nanostructures. Here, the quenching efficiency of CdSe/ZnS core-shell quantum dots (QDs) with different sized gold nanoparticles (NPs) films through energy transfer is investigated by measuring the PL intensity of the hybrid nanostructures. In our research, the gold NPs films are formed by the post-annealing of the deposited Au films on the quartz substrate. We find that the energy transfer from the QDs to the Au NPs strongly depends on the sizes of the Au NPs. For CdSe/ZnS QDs direct contact with the Au NPs films, the largest energy transfer efficiency are detected when the resonance absorption peak of the Au NPs is nearest to the emission peak of the CdSe/ZnS QDs. However, when there is a PMMA spacer between the QDs layer and the Au NPs films, firstly, we find that the energy transfer efficiency is weakened, and the largest energy transfer efficiency is obtained when the resonant absorption peak of the Au NPs is farthest to the emission peak wavelength of CdSe/ZnS QDs. These results will be useful for the potential design of the high efficiency QDs optoelectronic devices.

Introduction Depending upon influenza vaccination history, children aged 6 months–8 years need one or two doses of influenza vaccine to be considered fully vaccinated. The objectives of this study were to quantify the percentage of children aged 6 months–8 years who were fully vaccinated against influenza based on parental report, overall, by state, and by sociodemographic characteristics, and to examine sociodemographic characteristics associated with being fully vaccinated. Methods Data from the National Immunization Survey-Flu for the 2012–2013 and 2013–2014 influenza seasons were analyzed in 2015 using the Kaplan–Meier method to produce vaccination coverage estimates. Wald chi-square tests were used to test for bivariate associations, and Cox proportional hazards models were used to test for demographic characteristics independently associated with the child being fully vaccinated. Results The percentages of children aged 6 months–8 years who were fully vaccinated during the 2012–2013 and 2013–2014 influenza seasons were 41.0% and 45.2%, respectively. Full vaccination varied widely by state and was more likely for children requiring only one dose. Based on the statistical models, children likely to be fully vaccinated were older, non-black, had a mother with an education >12 years, or lived in a high-income household. Conclusions Most children in the U.S. are not fully vaccinated against influenza. Reminder systems and interventions that reduce or remove barriers to children receiving their second doses of influenza vaccine may improve full influenza vaccination coverage among all children.

Objective:This was a 12-week randomized, placebo-controlled trial to assess the efficacy of quetiapine monotherapy in the treatment of posttraumatic stress disorder (PTSD).Method:Eighty patients were randomly assigned to treatment with either quetiapine or placebo. The primary outcome measure was the Clinician-Administered PTSD Scale (CAPS). Secondary efficacy measures included the CAPS subscales, the Davidson Trauma Scale, the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impressions (CGI) scales for severity of Illness and improvement, the Hamilton Depression Rating Scale (HAM-D), and the Hamilton Anxiety Rating Scale (HAM-A). Safety measurements included adverse events, vital signs, the Abnormal Involuntary Movement Scale, the Barnes Akathisia Scale, the Simpson-Angus Scale, and the Arizona Sexual Experiences Scale.Results:After a 1-week placebo run-in, quetiapine was started at a daily dosage of 25 mg and increased to a maximum of 800 mg; the average was 258 mg (range, 50–800 mg). ...

Performance of plamson induced hot electrons-based photodetectors largely relies on the photon absorption capability. To improve the optical absorption, many perfect absorbers based on the periodic metallic nanostructures have been designed and fabricated through low-throughput, costly and time-consuming lithographic processes, which seriously limit the future potential applications of plasmonic hot electrons optoelectronics devices. Here, a large-scale, broadband absorber consisting of ITO film, ZnO layer, Au film and Al nanospike array substrate was designed and fabricated for hot electrons-based photodetection. The new designed absorber's absorptivity can be up to 70% in the broad wavelength range from 400 nm to 800 nm (even up to 90% in the wavelength range from 400-550 nm) and most of the absorption comes from the Au film, which is effective for the generation of hot electrons. The enhanced broadband absorption is ascribed to the surface plasmon polariton mode and localized surface plasmon resonance mode supported by the nanospike arrays. The influence of geometry and material parameters on the optical absorption properties is also specifically investigated through numerical simulation. The efficient and broadband absorption of a nanospikes device results in a much larger photocurrent compared with that of a planar reference device. Our approach, which is compatible with large-scale manufacturing, paves the way for the practical implementation of hot electrons-based optoelectronic devices.

Hot electron can break through the native limitation of silicon energy gap and expand its photo-response range. Plasmon modes improve detectors responsivity by the high hot electrons production. In this letter, we designed a C-shaped groove array carved on gold/silicon substrate, and numerically studied its optical properties and hot electron responsivity. An especial electromagnetic resonance (the dipole toroidal mode) can be excited in this nanostructure, which brings a nearly perfect absorption (∼98%) at 1395 nm and a higher responsivity. Our simple design demonstrated an effective hot electron photodetector without extra collect electrodes.

Temporal behavior of the pump pulses, residual pump pulses, and THz pulses for optically pumped D2O gas molecules was investigated by using a tunable TEA CO2 laser as the pumping source. The pulse profiles of pump laser pulses, residual pump pulses, and the THz output pulses were measured, simultaneously, at several different gas pressures. For THz pulse, the pulse delay between the THz pulse and the pump pulse was observed and the delay time was observed to increase from 40 to 70 ns with an increase in gas pressure from 500 to 1700 Pa. Both THz pulse broadening and compression were observed, and the pulse broadening effect transformed to the compression effect with increasing the gas pressure. For the residual pump pulse, the full width at half maximum (FWHM) of the main pulse decreased with increasing gas pressure, and the main pulse disappeared at high gas pressures. The secondary pulses were observed at high gas pressure, and the time intervals of about 518 and 435 ns were observed between the THz output pulse and the secondary residual pump pulse at the pressure of 1400 Pa and 1700 Pa, from which the vibrational relaxation time constants of about 5.45 and 5.55 μs Torr were obtained.

The field of vision of the driver will become narrower and the recognition capability will significantly decrease to the object in the dark. The hidden danger will increase when the headlight high beam light of opposite car is on because drivers feel dazzling. A kind of active near infrared camera system with auto-control lamps for night safety driving is presented in this paper. The captured infrared images of objects are preprocessing. The objects characters are shown after image segmentation and image morphologic processing. The results can be shown in displays, which improve driver's judging accuracy. When the light intensity detected by silicon photodiode is above the threshold, voltage threshold comparison circuit will generate a signal to close the high beam and open the dipped beam. This design can escape the driver's dazzle and save energy. Simulating and experimental results show that the system can decrease the judging loss rate of drivers to objects in night.

We demonstrate the possibility for integrating field emitters with two-dimensional (2D) graphene for directly transferred vacuum nanoelectronics. Improved field emission (FE) properties were revealed with few-layer graphene (FLG) decorated with gold nanoparticles (Au NPs). An in situ field emission measurement on the local graphene film was applied, achieving a maximum current density of 37.8 mA cm−2. The graphene–Au NP nanocomposite retains a turn-on electric field of 3.84 V μm−1, which is much lower than the pristine graphene, and the emission has been proved to be very stable. With graphene directly transferred onto a pre-prepared structure, we demonstrate the possibility of improving the efficiency of manufacturing large scale nano-devices with high-precision integration. The direct transferred vacuum devices are supposed to combine the advantages of vacuum nano-electronics with individual access, high integration density or nano-precision, offering promising features for future vacuum integrated applications.

There have been many investigations performed for color filtering based on surface plasmon resonances in recent years. However, research results on color filters integrated on the silicon-based photodetectors are infrequently reported. At present, problems including low light transmission, wide full width at half maximum (FWHM), and poor color tunability exist in the light filters integrated on the silicon-based photodetectors. We propose and numerically demonstrate a light filter with the periodic nanostructure and dielectric multi-layers integrated on the silicon substrate. Continuously tunable transmission visible spectra (400 ∼ 760 nm) are applied for the proposed filters. Hybrid resonant modes including plasmonic resonances and waveguide modes result in the extraordinary light transmission in the proposed filters. The simulations indicate that the integrated filter has more than 75% transmission and less than 25 nm full width at half maximum (FWHM) of the transmission curve for the destined wavelength. The proposed filter provides a solution for the combination of color filters with the silicon-based photosensors like CMOS photodiodes.

Due to its atomically ultrathin morphology and superior optoelectronic properties, graphene has been broadly studied and utilized in phototransistors, photoconductors, or heterojunction nanostructures. However, in practical devices, the disadvantages of graphene should be concerned for its high dark current, very low on/off ratio, and high-priced fabrication cost. We report the photodetecting of the graphene/insulator/silicon heterojunction. The insulator layer is optimized to achieve balanced optoelectronic properties in terms of an Iph/Idark ratio of 4.17 × 103, a responsivity of 35 mA W−1, and a detectivity of 6.39 × 1010 Jones at a wavelength of 658 nm, with low operating voltage and static power dissipation (0.84 nW). Besides, response speed and degradation in the environment are tested. The mechanisms are revealed and analyzed by I-V measurements.

We propose the utilization of a light-modulated scanning tunneling microscope (LM-STM) to study the plasmonenhanced photoemission and tunneling effect between metal tip and Au nanostructures on conductive substrate. The periodic Au nanorods are fabricated by electron beam lithography (EBL) and the topography is imaged using atom force microscopy (AFM) and STM. With irradiation of continuous lasers at 532 and 805 nm, the performance of electron tunneling emission is measured under STM’s ramp mode. We show that, by exciting localized surface plasmon resonances (LSPRs), a tiny laser intensity of around 1 W/cm2 along with a bias voltage less than 50 mV can activate a significantly enhanced tunneling current. This method has the potential for analyzing electron energy states and transport characteristics of surface plasmon.

Employing the edge effect and localized surface plasmon resonance effect, an enhanced photoemission is obtained from a carbon nanotube (CNT) arrays modified with gold nanoparticles. Compared with the unpatterned CNTs, the quantum efficiency of patterned CNTs is improved from 3.69×10−6 to 1.85×10−5. After modification with gold nanoparticles, the quantum efficiency of patterned CNTs is further raised to 4.98×10−5. This work makes CNTs as a promising material for the high stability and high efficiency photocathode.

Introduction Staying home when sick can reduce the spread of influenza. The objectives of this study were to quantify the percentage of workers who had paid sick leave (PSL) benefits, examine sociodemographic characteristics that may be associated with having these benefits, and examine the association between having PSL benefits and use of sick days and influenza vaccination status. Methods The public-use dataset from the 2009 National H1N1 Flu Survey (NHFS) were analyzed in 2017. Wald chi-square tests and t-tests were used to test for associations between having PSL benefits and sociodemographic characteristics and industry and occupation groups, the associations between having PSL benefits and seeking treatment when sick with influenza-like illness (ILI), and taking days off work when sick with ILI. Logistic regression was used to determine variables associated with having PSL benefits and the association between having PSL benefits and influenza vaccination status. Results Sixty-one percent of employed adults reported having PSL benefits during the 2009–10 influenza season. Being younger, female, Hispanic, less educated, or a farm/blue collar worker were associated with reduced likelihood of having PSL benefits. Not having PSL benefits was associated with a lower likelihood of receiving an influenza vaccination and visiting a health professional when sick with ILI. Conclusions The percentage of workers who have PSL benefits differs by sociodemographic characteristics and industry/occupation groups. Offering PSL benefits along with promoting influenza vaccination and encouraging employees with ILI to stay home can increase influenza vaccination coverage and help control the spread of influenza.

Ginned cotton’s quality is one significant factor to evaluate the cotton grade and influence the yarn qualities. Ginned cotton is always mixed with contaminants during picking, storing, drying, transporting, purchasing, and processing. Manual evaluation is time consuming, labor intensive, and unreliable. This paper proposed a fast feature extraction algorithm is presented for the measurement of cotton defects in ginned cotton within a complex background. The edge of cotton defects are extracted from fusion of three channel image of color image. A criterion based on areas is proposed to achieve fast morphological analysis. The different defects can be inspected automatically based on different thresholds. The comparison experiments between measuring system and technician were done and analyzed. The costing time of measuring system was less than 30 seconds, and accuracy was 89.5%. The measuring results show the method can meet with the requirement of grade determination of ginned cottons.

The Vaccines for Children (VFC) program provides vaccines at no cost to children who are Medicaid-eligible, uninsured, American Indian or Alaska Native (AI/AN), or underinsured and vaccinated at Federally Qualified Health Centers or Rural Health Clinics. The objective of this study was to compare influenza vaccination coverage of VFC-entitled to privately insured children in the United States, nationally, by state, and by selected socio-demographic variables.Data from the National Immunization Survey-Flu (NIS-Flu) surveys were analyzed for the 2011-2012 and 2012-2013 influenza seasons for households with children 6 months-17 years. VFC-entitlement and private insurance status were defined based upon questions asked of the parent during the telephone interview. Influenza vaccination coverage estimates of children VFC-entitled versus privately insured were compared by t-tests, both nationally and within state, and within selected socio-demographic variables.For both seasons studied, influenza coverage for VFC-entitled children did not significantly differ from coverage for privately insured children (2011-2012: 52.0%±1.9% versus 50.7%±1.2%; 2012-2013: 56.0%±1.6% versus 57.2%±1.2%). Among VFC-entitled children, uninsured children had lower coverage (2011-2012: 38.9%±4.7%; 2012-2013: 44.8%±3.5%) than Medicaid-eligible (2011-2012: 55.2%±2.1%; 2012-2013: 58.6%±1.9%) and AI/AN children (2011-2012: 54.4%±11.3%; 2012-2013: 54.6%±7.0%). Significant differences in vaccination coverage among VFC-entitled and privately insured children were observed within some subgroups of race/ethnicity, income, age, region, and living in a metropolitan statistical area principle city.Although finding few differences in influenza vaccination coverage among VFC-entitled versus privately insured children was encouraging, nearly half of all children were not vaccinated for influenza and coverage was particularly low among uninsured children. Additional public health interventions are needed to ensure that more children are vaccinated such as a strong recommendation from health care providers, utilization of immunization information systems, provider reminders, standing orders, and community-based interventions such as educational activities and expanded access to vaccination services.

A modified transmission line model with the equivalent capacitors is proposed to describe extraordinary optical transmission (EOT) of the sub-wavelength slit with different inner walls. The equivalent capacitors can effectively explain the discontinuity of the interface at which the surface wave propagates. The transmittance calculated with this model is in accordance with finite difference time domain (FDTD) calculations. This modified analytical model provides a methodology to analyze the transmission properties of sub-wavelength slits with different inner walls. The results show that if well-designed and manufactured, sub-wavelength curved slits have the ability to enhance the optical transmission in the visible region or the infrared region.

Sub-wavelength metallic tapered gratings with different-shaped slit walls are proposed in this research report. The transmission properties of the gratings have been investigated by finite difference time domain (FDTD) method. The simulation indicates that the transmission spectra strongly depend on the shapes of the slit walls. For TM-polarized light with normal incidence, the transmission coefficient and the bandwidth in the tapered gratings with the concave-parabolic slit walls are larger compared with the gratings with the convex-parabolic walls. For TE polarized light with normal incidence, the simulated results are reverse. In the visible range, the valley positions or peak positions of the transmission spectra are almost unchanged for all the gratings with different-shaped slit walls. The interaction of the electromagnetic (EM) waves on the slit walls with impendence match model has also been proposed in this paper.

The semiconductor laser is the important part in the semiconductor laser frequency standard. The quality of light frequency standard depends on line width and stability of laser. Semiconductor laser is very sensitive to environmental changes, such as the temperature, humidity and so on. The driving voltage and circuit and the temperature compensation are significant to laser output stability. The paper put forward a novel method to drive the semiconductor laser based on constant voltage source. The experimental results show that the circuit is simple, reliable, and high-precision. After improvement, the driving source of laser can promise parameters: constant-current range is from 0 to 250 mA, and the drift of current is less than 10 −6 , and stability is 10 −5 . The drift of frequency of laser drive with the circuit is within 10 −5 nm.

A high-quality device of aligned gold nanogap arrays is demonstrated by using a well-controlled method with electron beam lithography (EBL). Sub-30 nm nanogap arrays could be precisely fabricated with reproducibility. Importantly, the controllable method could allow us to readily construct varying nano-spacings and exhibit distinct FE properties. These studies clearly demonstrate that sub-30 nm vacuum channel can be readily achieved by coupling varying nanogaps into nanostructures or extended to additional functionalities, e.g. shape modification or multiple dimensional materials. It may pave the way for exploring the physics in tunneling transport devices, and therefore enable a new generation of high performance, high speed and low cost electronic devices.

A new laser kinetics model (LKM) of gas Terahertz (THz) laser has been improved and the output characteristics of a pulse gas 385 μm THz laser have been simulated and compared with the associated experimental data. Pump absorption coefficient (PAC) and pulse profile were determined using the experimental method, which provided reliable reference basis for approximated treatment of the model. The equations were solved numerically by the Runge–Kutta numerical method and some THz output characteristics, such as output power, pulse shape and pulse energy were theoretically investigated. The simulation and experimental results are in good agreement.

This paper presents a set of formulae for estimating the light spot position projected on a quadrant detector (QD). A novel method of annular segmentation calculus (ASC) is designed to analyze the detecting light spot of QD. The influences of the spot movement mode, spot energy distribution, and dead area to the dynamic range and the detection sensitivity are analyzed. It is shown in simulations that our new formulae have achieved a much better results to increase measurement accuracy. It is also shown that on the condition of the same spot size, the detection sensitivity of Gaussian distribution is prior to uniform distribution. The detection sensitivity of diagonal mode is better than cross mode. The detection sensitivity increases with increase in the size ratio of dead area to spot. The simulating and experimental results show that the measuring range of QD is 400 μm, and the resolution is 50 μm. The study presented here will be beneficial in developing the nanomechanical displacement detection techniques.