High Integration Time Research Articles

An improved energy storage switched boost grid‐connected inverter for photovoltaic applications

When the traditional two-stage boost inverter is used in photovoltaic (PV) and energy storage systems, it is necessary to connect additional bidirectional conversion devices, which will increase the loss of the system and increase the complexity of system control. Therefore, an improved energy storage switched boost (ESSB) grid-connected inverter is proposed in this paper. The system has the advantages of high integration, high gain and dead time immunity. By controlling the duty cycle of the system, the energy management of the battery can be realized. The system consists of three parts: PV cells, ESSB network and grid-connected inverter. In order to maximize the energy utilization, this paper uses the disturbance observation method to track the maximum power point of PV cells, and formulates a set of energy management strategy to control the energy flow between the three energy units. Simulation and experiments verify the superiority of the topology and the feasibility of the energy storage strategy.

Highly precise AMCW time-of-flight scanning sensor based on parallel-phase demodulation

A novel amplitude-modulated continuous wave (AMCW) time-of-flight (ToF) scanning sensor based on parallel-phase demodulation is proposed and demonstrated. Contrast to the conventional AMCW ToF sensor which utilizes serial-phase demodulation, the proposed sensor processes each different phase shift demodulation independently in parallel manner, so that the proposed sensor can maintain high demodulation contrast and short total integration time. Based on these characteristics of parallel-phase demodulation, the proposed sensor platform can be implemented with 2D laser scanning system with a single photodetector, maintaining a moderate frame rate, high optical SNR, and very high pixel resolution. In the validating demonstration, the proposed AMCW ToF scanning sensor shows extremely low measured distance noise per reference distance of 0.056 % at 1.50 m with only 30 mW illumination power. Additionally, FHD scale (1920 × 1080) highly precise 3D depth map with 800 nsec integration time can be achieved using the proposed AMCW ToF scanning sensor.

Extended Kalman filter and extended sliding innovation filter in terahertz spectral acquisition

Terahertz spectral acquisition has a fundamental limitation in implementation due to long experimental acquisition time. The long experimental acquisition time in terahertz spectral acquisition is a result of the required high integration time associated with usable dynamic range signals acquired through delay stage interferometry. This work evaluates the effectiveness of a non-linear version of the Kalman Filter, known as the extended Kalman filter (EKF), and the recently developed extended sliding innovation filter (ESIF), for increasing dynamic range in terahertz spectral acquisition. The comparison establishes that the EKF and ESIF can reduce integration time (time constant) of terahertz spectral acquisition, with EKF reducing the integration time by a factor of 23.7 for high noise signals and 1.66 for low noise signals to achieve similar dynamic ranges. The EKF developed in this work is comparable to a nominal application of wavelet denoising, conventionally used in terahertz spectral acquisitions. The implementation of this filter addresses a fundamental limitation of terahertz spectral acquisition by reducing acquisition time for usable dynamic range spectra. Incorporating this real-time post-processing technique in existing terahertz implementations to improve dynamic range will permit the application of terahertz spectral acquisition on a wide array of time sensitive systems, such as terahertz reflection imaging, and terahertz microfluidics. This is the first implementation, to our knowledge, of Kalman filtering methods on terahertz spectral acquisition.

Upscaling UAS Paradigm to UltraLight Aircrafts: A Low-Cost Multi-Sensors System for Large Scale Aerial Photogrammetry

The use of unmanned aerial systems (UASs) has rapidly grown in many civil applications since the early 2010s. Nowadays, a large variety of reliable low-cost UAS sensors and controllers are available. However, contrary to ultralight aircrafts (ULAs), UASs have a too small operational range to efficiently cover large areas. Flight regulations prevailing in many countries further reduced this operational range; in particular, the “within visual line of sight” rule. This study presents a new system for image acquisition and high-quality photogrammetry of large scale areas (>10 km²). It was developed by upscaling the UAS paradigm, i.e., low-cost sensors and controllers, little (or no) on-board active stabilization, and adequate structure from motion photogrammetry, to an ULA platform. Because the system is low-cost (good quality-price ratio of UAS technologies), multi-sensors (large variety of available UAS sensors) and versatile (high ULA operational flexibility and more lenient regulation than for other platforms), the possible applications are numerous in miscellaneous research domains. The system was described in detail and illustrated from the flight and images acquisition to the photogrammetric routine. The system was successfully used to acquire high resolution and high quality RGB and multispectral images, and produced precisely georeferenced digital elevation model (DEM) and orthophotomosaics for a forested area of 1200 ha. The system can potentially carry any type of sensors. The system compatibility with any sensor can be tested, in terms of image quality and flight plan, with the proposed method. This study also highlighted a major technical limitation of the low-cost thermal infrared cameras: the too high integration time with respect to the flight speed of most UASs and ULAs. By providing the complete information required for reproducing the system, the authors seek to encourage its implementation in different geographical locations and scientific contexts, as well as, its combination with other sensors, in particular, laser imaging detection and ranging (LiDAR) and hyperspectral.

Rainfall rate and rain attenuation contour maps for preliminary “Simon Bolivar” satellite links planning in Venezuela

Predicting precipitation rate and rainfall attenuation are key aspects in planning and dimensioning of wireless communications systems operating at frequencies above 10 GHz, such as satellite communication systems at Ku and Ka bands. In this paper, contour maps of rainfall rate and rain attenuation are developed for the first time in Venezuela, based on 1-min rain rate statistics obtained from measurements carried out in Venezuela over at least 30 years period with a higher integration time and using Rice-Holmberg model, refined Moupfouma-Martin model and Recommendation ITU-R P.837-7, for rain rate estimation and Recommendation ITU-R P.618-13, Ramachandran-Kumar model, Yeo-Lee-Ong model and Rakshit-Adhikari-Maitra model, for rain attenuation prediction in “Simon Bolivar” satellite links in Venezuela. The overall results of both types of maps represent a useful tool for preliminary planning of those links in the country, specifically, in Ku and Ka bands

Mineralogical evolution of ceramic clays during heating. An ex/in situ X-ray diffraction method comparison study

Abstract The ceramic properties of clay materials heated at high temperature are largely dependent on the mineral reactions, which usually are followed by XRD analysis on pressed pieces that are heated at different temperatures. Nevertheless, the use of “in-situ” high temperature X-ray diffraction (HTXRD) to follow the evolution of the crystalline phases under controlled temperature provides more precision. In this paper, the mineralogical changes produced during firing (RT-1000 °C) of two clay materials of very different mineralogical composition, frequently used in the manufacture of bricks in the SE Spain, have been studied by XRD classical procedure and with HTXRD, and the results obtained were compared. Although the phases identified by both X-ray analyses were the same, temperatures for the mineralogical reactions seem to be different, probably due to the experimental conditions. The patterns obtained by ex-situ XRD were at a higher speed than those by in-situ HTXRD, and probably the equilibrium was not achieved for the most reactions. Because of the expansion of the mineral structure parameters occurred during heating the mineral reflections do not match with those found in the database JPCDS, neither the position nor intensities of some stable phases at high temperature. For the optimization of the interpretation of the HTXRD patterns, and to facilitate the kinetics of the new phases, it is necessary to work at a high integration time per step and a slow heating rate. The in-situ HTXRD investigations of ceramic materials can save time respect to the classical XRD study of test-pieces heated at different temperatures, and lead immediate information of the transformation occurring on heating, which can be useful to improve the most suitable firing temperature in the industry.

First Results of a GNSS-R Experiment From a Stratospheric Balloon Over Boreal Forests

The empirical results of a global navigation satellite systems reflectometry (GNSS-R) experiment onboard the Balloon EXperiments for University Students (BEXUS) 17 stratospheric balloon performed north of Sweden over boreal forests show that the power of the reflected signals is nearly independent of the platform height for a high coherent integration time T-c = 20 ms. This experimental evidence shows a strong coherent component in the forward scattered signal, as compared with the incoherent component, that allows to be tracked. The bistatic coherent reflectivity is also evaluated as a function of the elevation angle, showing a decrease of similar to 6 dB when the elevation angle increases from 35. to 70 degrees. The received power presents a clearly multimodal behavior, which also suggests that the coherent scattering component may be taking place in different forest elements, i.e., soil, canopy, and through multiple reflections canopy-soil and soil-trunk. This experiment has provided the first GNSS-R data set over boreal forests. The evaluation of these results can be useful for the feasibility study of this technique to perform biomass monitoring that is a key factor to analyze the carbon cycle.

Inkjet-assisted layer-by-layer printing of quantum dot/enzyme microarrays for highly sensitive detection of organophosphorous pesticides

We present a facile fabrication of layer-by-layer (LbL) microarrays of quantum dots (QDs) and acetylcholinesterase enzyme (AChE). The resulting arrays had several unique properties, such as low cost, high integration and excellent flexibility and time–saving. The presence of organophosphorous pesticides (OPs) can inhibit the AChE activity and thus changes the fluorescent intensity of QDs/AChE microscopic dot arrays. Therefore, the QDs/AChE microscopic dot arrays were used for the sensitive visual detection of OPs. Linear calibration for parathion and paraoxon was obtained in the range of 5–100 μg L−1 under the optimized conditions with the limit of detection (LOD) of 10 μg L−1. The arrays have been successfully used for detection of OPs in fruits and water real samples. The new array was validated by comparison with conventional high performance liquid chromatography-mass spectrometry (HPLC-MS).

이차원 마이크로볼로미터 FPA를 위한 이 단계 바이어스 전류 억제 방식을 갖는 픽셀 단위의 전류 미러 신호취득 회로

본 연구를 통해서 초점면 배열 이차원 마이크로볼로미터를 위한 픽셀 단위의 신호취득 회로를 연구하였다. 높은 응답도와 긴 적분시간을 갖는 픽셀 단위의 구조를 위해 이 단계 바이어스 전류 억제 방식을 갖는 전류 미러 입력회로를 제안하였다. 제안하는 회로는 0.35-㎛ 2-poly 4-metal CMOS 공정을 이용하여 설계했고, 마이크로볼로미터의 배열 크기는 320 × 240이며 픽셀 크기는 50 ㎛ × 50 ㎛이다. 제안하는 이 단계 바이어스 전류 억제 방식은 넓은 보정 범위에서 충분히 작은 보정 오차를 보이며, 설계 파라미터를 조정하여 보정 범위와 보정 오차를 간단히 최적화할 수 있다. 제안하는 회로는 높은 응답도와 1 ㎳ 이상의 긴 적분시간을 갖기 때문에 회로의 잡음등가온도차(NETD)를 26 mK까지 개선할 수 있고, 이는 기존회로의 잡음등가 온도차인 67 mK에 비해 매우 개선된 수치이다.

Experimental assessment of the kinetic parameters of the JSI TRIGA reactor

An experimental campaign has been carried out at the TRIGA reactor of the Jozef Stefan Institute, in order to assess its mean neutron generation time Λ and effective delayed neutron fraction βeff. For that, the cross spectral densities (CPSD) of two fission chambers have been taken. The reactor has been operated in five core configurations corresponding to different control rod and chamber positions. A method of comparison between the cross spectral densities using the Welch statistical test, without assuming any kinetic model, has been performed; it shows that it is possible to distinguish between those configurations provided an high enough integration time (above 3000s) is used. Assuming a point-kinetic model, the parameters Λ and βeff have been robustly derived by a Cohn-α technique. The generation time is found to be rather constant from a configuration to another, but configurations with different fuel loading and control rod position yield an effective delayed neutron fraction that differ at 1σ level. The experimental values for both parameters agree with the values provided by the TRIGA manufacturers.

Standoff Raman Spectroscopy of Explosive Nitrates Using 785 nm Laser

We have demonstrated that standoff Raman spectra of some nitrates could be obtained at distances ranging from 20 meters to 250 meters using an 11-inch reflecting telescope and a continuous wavelength 785 nm laser of 400 mW power coupled with a small portable spectrometer. The measurements were taken during both day and night, indoors and outdoors, for various integration times. Detection and identification of chemical and biological hazards within the forensic and homeland security contexts requires conducting the analysis in field while adapting a non-contact approach to the hazard. In this paper, we report the adequacy of a standoff Raman system with a 785nm laser for remote detection and identification of ammonium, sodium, and magnesium nitrates in bulk form. The results demonstrate that, as the standoff distances increases, there is a discernible attenuation in the intensity of the Raman signatures of the nitrates. To discriminate the background lights, improve the signal-to-noise ratio and trigger the weak characteristic bands, Raman spectra were also acquired using higher integration time. For the measurements taken at a 100 meter standoff distances, we were able to achieve a signal-to-noise ratio of about 10. For greater distances, due to the difficulty of locating the target using IR laser, a 50 mW green laser pointer at 485 nm wavelength is used before the IR laser is used for acquiring the Raman signals.

Design and characterization of a CMOS preamplifier for quantum well infrared photodetectors

A preamplifier based on the source-follower direct injection (SFDI) topology for use in read-out integrated circuits (ROIC) of quantum-well infrared photodetectors focal plane arrays (QWIP-FPA) is demonstrated. The fabricated circuit shows high linearity, high integration time (from hundreds of μs to few ms) and low current detection capabilities for a wide range of input current (order of few pA). This performance was achieved through the use of a Poly1-Poly2 capacitor that, although presenting some penalties in area consumption, provides a higher linearity, lower leakage current and higher temperature stability than all others capacitors found in literature. Secondary effects such as charge injection and clock feed-through are observed in the experimental results and classical techniques, like the use of DUMMY transistor, are shown to be effective in minimizing these effects and maximizing the linearity of the response. The overall results indicate that this circuit architecture has a great potential to be practically integrated in larger QWIP-FPA ROICs, showing an improved performance relating to previous works in literature.

Design and Implementation of FPGA Based Signal Processing Card

This paper describes the design of FPGA based signal processing card. An on board real time digital signal processing system is designed using FPGA. The platform can decode process of various kinds of digital and analog signals simultaneously. The design trend in this card is towards small size, high integration and fast real time processing. For the optimum performance a 16 bit 1 MSPS ADC is used which is interfaced with FPGA to make all the data processing onboard in real time. This card can be used in many signal processing based applications like audio signal processing, audio compression, digital image processing, video compression, speech processing, speech recognition, digital communications by interfacing several separate board using inbuilt I/O’s, each with a number of input channels that will communicate with each other in real time over a high speed communication link. The resulting images can be displayed directly on LCD or OLED panel displays using I/O’s peripherals. The project introduces many challenging issues, which are being addressed in turn with different prototype designs. These issues are the ADC performance, interfacing the ADCs to the FPGA, implementing the flexible processing algorithms and high speed interconnection between the boards.

Polarization‐dependent Raman spectroscopy of LiBH4 single crystals and Mg(BH4)2 powders

AbstractThe phonons and the crystal structure of the complex hydride LiBH4 are studied on single crystals using micro‐Raman spectroscopy. The symmetry of the modes is determined by polarization‐dependent measurements at liquid helium temperature, allowing a better comparison and a more reliable assignment to the computed phonon wavenumbers. This has led to the revision of some former assignments made from Raman measurements on polycrystalline samples. In addition, a higher integration time allowed the detection of very weak lines, so that 35 out of 36 predicted Raman lines have been identified. We have also performed explorative Raman measurements on Mg(BH4)2 powders. In contrast to LiBH4, the very poor crystallinity of this material inhibits the exploitation of the full potential of Raman spectroscopy. Only broad lines are observed, which we compare to phonon wavenumbers calculated for various possible structures using density functional theory. Copyright © 2011 John Wiley & Sons, Ltd.

Parathyroid hormone 1–34 enhances titanium implant anchorage in low-density trabecular bone: A correlative micro-computed tomographic and biomechanical analysis

The use of endosseous titanium implants is the standard of care in dentistry and orthopaedic surgery. Nevertheless, implantation in low-density bone has a poor prognosis and experimental studies show delayed implant anchorage following gonadectomy-induced bone loss. Intermittently administered human parathyroid hormone 1–34 [iahPTH(1–34)] is the leading bone anabolic therapy. Hence, this study assessed whether iahPTH(1–34) enhances titanium implant integration in low-density bone. Threaded titanium implants, 0.9 mm in diameter, were inserted horizontally into the proximal tibial metaphysis of 5-month-old rats, 7 weeks postorchiectomy (ORX). Subcutaneous administration of iahPTH(1–34), at 5, 25 and 75 μg/kg/day commenced immediately thereafter and lasted for 8 weeks. Quantitative micro-computed tomography (μCT) at the implantation site was carried out at 15 μm resolution using high energy and long integration time to minimize artifacts resulting from the high implant radiopacity. Osseointegration (OI) was calculated as percent implant surface in contact with bone (%OI) quantified as the ratio of “bone”-to-total voxels in contact with the implant. Additionally, the trabecular bone volume density (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and connectivity density (Conn.D) were measured in the peri-implant bone. All μCT parameters were stimulated by iahPTH(1–34) dose-dependently; the percent maximal enhancement was %OI = 143, BV/TV = 257, Tb.Th = 150, Tb.N = 140 and Conn.D = 193. The maximal values of %OI, BV/TV and Tb.Th in iahPTH(1–34)-treated ORX rats exceeded significantly those measured in the implantation site of untreated sham-ORX controls. The same specimens were then subjected to pullout biomechanical testing. The biomechanical parameters were also enhanced by iahPTH(1–34) dose-dependently, exceeding the values recorded in the sham-ORX controls. The percent iahPTH(1–34)-induced maximal enhancement was: ultimate force = 315, stiffness = 270 and toughness = 395. Except for the BV/TV and Tb.Th, there was no significant difference between the effect of the 25 and 75 μg/kg/day doses. There was a highly significant correlation between the morphometric and biomechanical parameters suggesting the use of quantitative CT as predictive of the implant mechanical properties. These findings demonstrate that iahPTH(1–34) effectively stimulates implant anchorage in low-density trabecular bone and thus the feasibility of administering iahPTH(1–34) to improve the clinical prognosis in low-density trabecular bone sites.

Light-activation of Teleost Rod Photoreceptor Elongation

Rod photoreceptors in the retinas of teleost fish undergo changes in cell length in response to changing ambient light intensities. In the dark rods shorten and in the light rods elongate. These movements are mediated by actin-dependent processes which occur in the ellipsoid and myoid of the inner segment. As an approach to examining the underlying intracellular signaling pathways that link light absorption to actin-dependent motility in the inner segment, we have investigated the quantitative aspects of the light stimulus required to activate elongation in isolated rod inner/outer segments (RIS-ROS) of the green sunfish (Lepomis cyanellus).The intensity thresholds and strength-duration characteristics of the light stimulus required to activate teleost rod elongation were found to differ from those reported to activate vertebrate rod membrane hyperpolarization. In response to brief pulses of light, RIS-ROS elongated in a graded manner, both as a function of increasing light pulse intensity and light pulse duration. Half maximal activation of light-induced RIS-ROS elongation was produced by a stimulus of roughly 6 × 1015 photons cm-2, which is calculated to bleach approximately 20% of the photopigment molecules in green sunfish rod outer segments. This degree of photopigment bleach is approximately 6-7 orders of magnitude greater than that required to elicit half maximal changes in membrane potential in other vertebrate rod preparations. Furthermore, the reciprocal relationship between light pulse intensity and duration in eliciting an equal elongation response held for relatively long light pulse durations. There was an approximately equal elongation response to light pulse durations of 15, 120, and 600 sec, that delivered roughly equal quanta. Over these light pulse durations, the temporal integration function is described by a single slope of -0·9 on log-log coordinates of stimulus intensity and duration. The integration time of the rod elongation response lasts for light pulse durations at least as long as 600 sec, which is approximately 3 orders of magnitude longer than that reported for rod membrane hyperpolarization. The high threshold and long integration time of the photoreceptive mechanisms mediating rod elongation indicate that the intracellular signals that regulate motility dramatically diverge from those regulating rod membrane hyperpolarization. A further implication of these results is that vertebrate rod photoreceptors possess different intensity thresholds and temporal processing mechanisms in the light-activation of distinct cell functions such as membrane hyperpolarization and cell elongation.

An approach for the search of extra-solar system planets taking advantage of the simultaneous wide spectral range and high resolution of a future planetary observatory in earth orbit

Over a large part of its spectrum, from the UV to the mid-IR, the emitted flux from a planet originates in the incident flux scattered by major atmospheric constituents and haze particles, or reflected on the surface, with a certain albedo coefficient. Therefore a strong correlation does exist between the planetary spectrum and the spectrum of the central star, with a wavelength shift which depends on the orbital velocity projection on the line of sight. Although absorption features from atmospheric constituents affect the planetary spectrum, they significantly decrease the correlation effect only when similar in narrowness to the stellar spectrum structures. Taking advantage of a wide spectral range, high resolution spectroscopy, high coronographic efficiency and long integration time, it is proposed to look for maxima in the cross-correlation functions between the spectra of selected nearby stars and their close surrounding space. Refering to the star spectrum auto-correlation function indicates the confidence level of possible detections. As compared to others, such an approach might extend the search to Earth-like planets. Algorithms are then presented and the potential performances are discussed and illustrated by using the solar spectrum as an exemple.