Transmittance Model Research Articles

Compositional dependence of optical and electrical properties of indium doped zinc oxide (IZO) thin films deposited by chemical spray pyrolysis

The structural and optoelectronic properties of undoped and indium doped zinc oxide (IZO) thin films grown on glass substrates through a simple reproducible custom-made pneumatic chemical spray pyrolysis technique are presented. X-ray diffraction (XRD) results showed a polycrystalline structure of hexagonal wurtzite phase growing preferentially along the (002) plane for the undoped sample. Increase in dopant content modified the orientation leading to more pronounced (100) and (101) reflections. Optical transmission spectra showed high transmittance of 80–90% in the visible range for all thin films. The optical band gap energy (Eg) was evaluated on the basis of the derivative of transmittance (dT/dλ) versus wavelength (λ) model and Tauc's extrapolation method in the region where the absorption coefficient, α ≥ 104 cm−1. The observed values of Eg were found to decrease generally with increasing In dopant concentration. From the figure of merit calculations a sample with 4 at.% In dopant concentration showed better optoelectronic properties.

Convex optimization–based multi-user detection in underwater acoustic sensor networks

Multi-carrier code-division multiple access is an important technical means for high-performance underwater acoustic sensor networks. Nevertheless, severe multiple access interference is a huge challenge. As the core technology, multi-user detection is used to eliminate multiple access interference. The traditional optimal detection algorithms (e.g. maximum likelihood) have very high computational complexity, and the performances of suboptimal detection methods (i.e. zero forcing, minimum mean square error, etc.) are poor. Therefore, taking into account the characteristics of underwater acoustic sensor networks, it is of great significance to design multi-user detection algorithms for achieving a tradeoff between the detection performance and the computational complexity in multi-carrier code-division multiple access systems. In this article, we design a transmitter model of underwater multi-carrier code-division multiple access system and then implement a multi-user detection algorithm based on convex optimization, which is named convex optimization–based algorithm. Next, we conduct the detection performance and computational complexity comparisons of maximum likelihood, zero forcing, minimum mean square error, and convex optimization–based algorithm. The results show that the performance of convex optimization–based algorithm is close to that of maximum likelihood, and the complexity is close to that of zero forcing. Therefore, a tradeoff between the computational complexity and the detection performance is realized in convex optimization–based algorithm. It means that convex optimization–based algorithm is suitable for the multi-user detection in multi-carrier code-division multiple access systems of underwater acoustic sensor networks.

Physical Layer Authentication Enhancement Using a Gaussian Mixture Model

Wireless networks strive to integrate information technology into every corner of the world. This openness of radio propagation is one reason why holistic wireless security mechanisms only rarely enter the picture. In this paper, we propose a physical (PHY)-layer security authentication scheme that takes advantage of channel randomness to detect spoofing attacks in wireless networks. Unlike most existing authentication techniques that rely on comparing message information between the legitimate user and potential spoofer, our proposed authentication scheme uses a Gaussian mixture model (GMM) to detect spoofing attackers. Probabilistic models of different transmitters are used to cluster messages. Furthermore, a 2-D feature measure space is exploited to preprocess the channel information. Training data for a spoofer operating through an unknown channel, a pseudo adversary model is developed to enhance the spoofing detection performance. Monte Carlo simulations are used to evaluate the detection performance of the GMM-based PHY-layer authentication scheme. The results show that the probability of detecting a spoofer is higher than that obtained using similar approaches.

Design of an OFDM System for VLC with a Viterbi Decoder

In this research, we designed digital signal processing (DSP) modeling using Matlab for visible light communications (VLC) systems using orthogonal frequency division multiplexing (OFDM). The DSP modeling comprises three main parts: transmitter, receiver, and channel models. The receiver is designed...

Suomi NPP VIIRS solar diffuser screen transmittance model and its applications.

The visible infrared imaging radiometer suite on the Suomi National Polar-orbiting Partnership satellite calibrates its reflective solar bands through observations of a sunlit solar diffuser (SD) panel. Sunlight passes through a perforated plate, referred to as the SD screen, before reaching the SD. It is critical to know whether the SD screen transmittance measured prelaunch is accurate. Several factors such as misalignments of the SD panel and the measurement apparatus could lead to errors in the measured transmittance and thus adversely impact on-orbit calibration quality through the SD. We develop a mathematical model to describe the transmittance as a function of the angles that incident light makes with the SD screen, and apply the model to fit the prelaunch measured transmittance. The results reveal that the model does not reproduce the measured transmittance unless the size of the apertures in the SD screen is quite different from the design value. We attribute the difference to the orientation alignment errors for the SD panel and the measurement apparatus. We model the alignment errors and apply our transmittance model to fit the prelaunch transmittance to retrieve the "true" transmittance. To use this model correctly, we also examine the finite source size effect on the transmittance. Furthermore, we compare the product of the retrieved "true" transmittance and the prelaunch SD bidirectional reflectance distribution function (BRDF) value to the value derived from on-orbit data to determine whether the prelaunch SD BRDF value is relatively accurate. The model is significant in that it can evaluate whether the SD screen transmittance measured prelaunch is accurate and help retrieve the true transmittance from the transmittance with measurement errors, consequently resulting in a more accurate sensor data product by the same amount.

The Preliminary Investigation on the Uncertainties Associated With Surface Solar Radiation Estimation in Mountainous Areas

In mountainous areas, surface solar radiation (SSR) exhibits high spatiotemporal variation at different slopes and aspects due to its great topographic relief. To get mountain SSR spatial distribution, remote sensing-based methods have been popularly used, which separate SSR into direct solar radiation, diffuse sky radiation, and adjacent terrain radiation. However, the methods are highly depended on the atmospheric and angular information derived from different data sources. To clearly address the uncertainties associated with the estimation, this letter conducted a preliminary comparison study by using different atmospheric transmittance models and digital elevation model (DEM) data to retrieve SSR in the Mt. Gongga region. The comparison results indicated that the uncertainty of the atmospheric constituent data greatly limited the performance of the physical atmospheric transmittance models. The resolution of DEM data also played an important role in SSR determination because of the determination of surface angular information. High-resolution (30-m) DEM data showed better performance than low one (90 m). In addition, the systematic underestimation of SSR estimation with the empirical model was significantly improved by using the averaging method with nearby pixel values. It indicated that the geometric errors of satellite image and DEM data should be considered in the estimation.

Signal coverage mapping of local radios

FM radio transmission is greatly affected by geography. Nepal faces particular problems in relation to variations in signal reach because of its varying topography. Radio signal coverage mapping indicates service areas of radio communication transmitting stations. The objectives of this study are to map the signal coverage of local radios (Kavre district) and to assess parameters affecting FM signal strength. The primary data were GPS coordinates of FM transmission stations and bearing of antenna. The secondary data regarding frequency of station, transmitter model, transmitter power, antenna model, and height of antenna from ground level were collected from respective FM stations. For elevation data freely available SRTMv3 was used. Combined Cartesian coverage maps for each FM stations were prepared using Radio Mobile software that showed varying signal strength of station in dBμV/m. The accuracy of the maps through field validation was observed to be 85%. Assessment of parameters affecting FM signal strength concluded that increase in antenna elevation, gain of antenna and power of transmitter increases the signal coverage.

Spectral dependence of electrical energy-based photosynthetic efficiency at single leaf and canopy levels in green- and red-leaf lettuces

The spectrum of light affects both the electrical energy consumption by plants and photosynthetic efficiency. In a plant factory, where light-emitting diodes (LEDs) serve as an alternative to solar light, the optimal spectrum of light should be carefully chosen to maximize the rate of photosynthesis and the electrical energy efficiency of the crop. The objectives of this study were to investigate the photosynthetic rate of different colored lettuces (reddish and green leaves), to quantify the spectral dependence of photosynthetic efficiency, and to optimize the LED spectrum for maximum canopy photosynthesis and electrical energy consumption in lettuce grown in a plant factory. Two lettuce cultivars (Lactuca sativa L.), ‘JeokChukMyeon’ and ‘CheongChukMyeon’, were assessed for light absorption and photosynthetic efficiency at the single leaf and canopy levels, and the relative consumption of electrical energy from the LED lights was measured at 18 narrow wavelength bands of 10 nm from 400 to 700 nm. Anthocyanin and chlorophyll content (SPAD value) were measured and correlated with leaf color. Light interception by the canopy was estimated with light transmittance models. The light absorption was similar among the green and reddish lettuce cultivars at most wavelengths, but slightly higher in the reddish leaves around 550 nm (green region). In the reddish leaves, photosynthetic rates per incident photon of a single leaf had two peaks at 650-660 and 400-410 nm, while the photosynthetic rate per absorbed photon had three peaks at 650-660, 400-410, and 540-560 nm. In the green region of the light spectrum, both photosynthetic rates per incident photon and those per absorbed photon were lower in the reddish cultivars than in the green cultivars. The spectral dependence of light absorption at the canopy level was much weaker than that at the single leaf level. The quantum yield and absorption of green light at the canopy level were nearly same as those of blue and red lights, indicating that the photosynthetic efficiency of green light at the canopy level was higher than that at the single leaf level. The relative electrical energy consumption was lower in the green region than in the red and blue regions. Therefore, the photosynthetic efficiency based on electrical energy consumption at the canopy level was much lower with green LEDs than with blue or red LEDs. These results describe the plant response to the light spectrum at the canopy level and can be useful for optimizing artificial lighting sources for maximum plant productivity and energy-savings in a plant factory.

Energy balance in Spectral Filter Array camera design

BackgroundMultispectral imaging permits to capture more spectral information on object surface properties than color imaging. This is useful for machine vision applications. Transmittance spectral filter arrays combined with a solid state sensor form an emerging technology used for snapshot acquisition. In spectral filter arrays technology, the sensitivities of the camera have critical consequences, not only on applications, but also in the viability of the system. We discuss how to balance the energy of each channel in single exposure multispectral imaging.MethodsWe propose a methodology to design filters that permits to reach an optimal balance of energy. We apply this method on practical illuminations combined with a Gaussian model of transmittance filters.Results and discussionOur results demonstrate that we can optimize energetically the global camera response with few efforts for several cases of illumination environments, for a given sensor and a number of spectral channels. This methodology can be embedded in an application-oriented optimization framework.ConclusionsThis methodology enables achieving a great range of optical design, and it can be embedded in an application-oriented optimization framework.

Degrees of Freedom of the Two-User MIMO Broadcast Channel with Private and Common Messages Under Hybrid CSIT Models

We establish the degree of freedom (DoF) regions of the two-user multiple-input multiple-output (MIMO) broadcast channel with a general message set (BC-GM), that includes private and common messages, under fast fading. Nine different channel state knowledge assumptions—collectively known as hybrid channel state information at the transmitter (CSIT) models—are considered wherein the transmitter has either perfect/instantaneous, delayed, or no CSI from each of the two receivers. General antenna configurations are addressed wherein the three terminals have arbitrary numbers of antennas. The DoF regions are established for the five hybrid CSIT models in which either both channels are unknown at the transmitter or each of the two channels is known perfectly or with delay. In the four remaining cases in which exactly one of the two channels is unknown at the transmitter, the DoF regions under the restriction of linear encoding strategies—also known as the linear DoF (LDoF) regions—are established. As the key to the converse proofs of the LDoF region of the MIMO BC-GM under such hybrid CSIT assumptions, we show that, when only considering linear encoding strategies, the CSI from the receiver with more antennas does not help if there is no CSI available from the receiver with fewer antennas. This result is conjectured to be true even without the restriction on the encoding strategies to be linear. If true, the LDoF regions obtained for the four hybrid CSIT cases herein will also be the DoF regions for those cases. Many of the results of this paper when specialized to even the two-message problems are new. These include the LDoF regions, when one of the two channels is not known, of the MIMO BC-GM when specialized to the MIMO BC with private messages. They also include the DoF/LDoF regions for all the hybrid CSIT models obtained by specializing the corresponding regions for the MIMO BC-GM to the case with degraded messages.

A Unified Geolocation Channel Model--Part I (Path Loss)

Indoor geolocation systems have emerged and have attracted a wide audience recently. There are three important components that constitute an indoor geolocation system: (1) transmitter, (2) receiver, and (3) indoor channel model. To some extent the primary transmitter design requirements are transmit power and a frequency or a set of frequencies of operation. The receiver is designed to operate at a certain distance from the transmitter and at the same frequency or set of frequencies of operation. Hence, any indoor channel model must take into account these two important design requirements. The indoor channel is perhaps very intriguing because multipath is ubiquitous due to high signal scattering, reflection, and refraction. It is been widely accepted in the literature that the two primary channel effects are (1) path loss and (2) multipath distribution. First, the path loss model is currently accepted to be a function of the transmitter and receiver geometry and frequency of operation. Second, the most widely used and accepted indoor channel multipath distribution models are Raleigh, Rician, and lognormal. As indicated in the second paper (or part II) the Rayleigh distribution is wider than Rician and Rician is wider than lognormal. This implies that the Rayleigh fading channel is the most severe and Rician fading is more severe than lognormal and lognormal is the least severe channel. Unfortunately, the dependency of the path factor on the frequency of operation in the context of a unified channel model is overlooked in the literature. Furthermore, there is no agreement on an indoor multipath distribution channel model. Although a unified channel model has not yet been found, in this paper we make a first attempt to present a unified channel model which consists of a unified path loss model and a unified multipath distribution model. The unified path loss model consists of an approach for linking together the path loss models of the three geolocation systems (macro-outdoor, micro-outdoor, and indoor) with the distance between the transmitter and receiver, R, and the frequency of operation, f. Although there are several parameters that affect the power loss factor, we consider R and f as the most important parameters for two reasons. Most of the geolocation systems presented in the literature are based on a direct measure of the time of travel; i.e., distance between the transmitter and receiver. The frequency of these systems varies; hence, the path loss factor varies as well. While unifying the path loss model was to some extent initiated in the literature, unifying the multipath distribution model is currently a silent quest in the literature. It appears that the tendency is to come up with newer and more sophisticated models that would explain the characteristics of the old models. The approach that we present in part II (on in a separate paper in the future) to unify the multipath distribution models is rather simple. The theoretical performance results are validated from the measurements currently reported in the literature.

面外熱駆動Auナノグレーティングを用いたマイクロ光学位相子の透過率変調

A reconfigurable transmittance modulation device for Au nanograting retarder that consisted of out-of-plane thermally-driven grating was designed, fabricated, and demonstrated. In this study, an Au nanograting that is known to exhibit giant birefringence was constituted by integrating MEMS thermal actuators. The thermally-driven grating was made of Au/SiO2 bimorph beams that period and slit width are 800 nm and 400 nm, respectively. The device is fabricated on a glass substrate with embedded Si as a sacrificial layer. The gap between the grating and the substrate is changed by applying driving current, and transmittance was changed affected by Fabry-Pérot interference. Transmittance peak wavelength for TE polarization was shifted up to 40 nm keeping the retardation of the Au nanograting. A calculation model of transmittance applying multilayer interference was proposed and demonstrated its effectiveness in TE polarization. By optimizing the design dimensions of the Au nanograting, it is expected to realize a microscale waveplate capable of transmittance modulation.

Quantifying the missing link between forest albedo and productivity in the boreal zone

Abstract. Albedo and fraction of absorbed photosynthetically active radiation (FAPAR) determine the shortwave radiation balance and productivity of forests. Currently, the physical link between forest albedo and productivity is poorly understood, yet it is crucial for designing optimal forest management strategies for mitigating climate change. We investigated the relationships between boreal forest structure, albedo and FAPAR using a radiative transfer model called Forest Reflectance and Transmittance model FRT and extensive forest inventory data sets ranging from southern boreal forests to the northern tree line in Finland and Alaska (N = 1086 plots). The forests in the study areas vary widely in structure, species composition, and human interference, from intensively managed in Finland to natural growth in Alaska. We show that FAPAR of tree canopies (FAPARCAN) and albedo are tightly linked in boreal coniferous forests, but the relationship is weaker if the forest has broadleaved admixture, or if canopies have low leaf area and the composition of forest floor varies. Furthermore, the functional shape of the relationship between albedo and FAPARCAN depends on the angular distribution of incoming solar irradiance. We also show that forest floor can contribute to over 50 % of albedo or total ecosystem FAPAR. Based on our simulations, forest albedos can vary notably across the biome. Because of larger proportions of broadleaved trees, the studied plots in Alaska had higher albedo (0.141–0.184) than those in Finland (0.136–0.171) even though the albedo of pure coniferous forests was lower in Alaska. Our results reveal that variation in solar angle will need to be accounted for when evaluating climate effects of forest management in different latitudes. Furthermore, increasing the proportion of broadleaved trees in coniferous forests is the most important means of maximizing albedo without compromising productivity: based on our findings the potential of controlling forest density (i.e., basal area) to increase albedo may be limited compared to the effect of favoring broadleaved species.

Perspectives on Filial Responsibility Among Uprooted Families From South Lebanon.

This study focuses on filial responsibilities among uprooted families. Views of 20 mothers and 20 adolescents and young adults from southern Lebanon residing in Israel were compared to identify the roles that adolescent children assume and the perceived effects of these roles. Eight domains of filial responsibilities were agreed upon: language broker, cultural broker, financial supporter and breadwinner, surrogate parent and sibling caretaker, emotional supporter of parents, mediator of family conflicts, heritage transmitter, and role model. The roles had simultaneous positive effects and negative effects. The discussion illustrates the importance of cultural context of country of origin and the host culture. Moreover, it suggests implications of the findings for research and practice.

High Speed Serial Interfaces in 2.5D Integrated Systems

Abstract High speed communication has been a topic of great interest in the last decade due to excessively high data rates required between chips especially pushed by the measurement equipment industry to support extremely high bandwidth data sampling. Serial communication is chosen to support these data rates which are pushing further and further into higher data rate regimes. It is important to understand how the 2.5D integration of chips on the interposer can support serial communication and what the designer can do to leverage the special features of interposer channel to achieve lower power and higher speed. This paper will present the interposer complete channel full 3D Electromagnetic simulation based model extraction. It also presents the simulation of channel with real serial communication transmitter and receiver circuit models to describe the proposed interposer performance for multi Gb/s data rates. Also a comparison is shown for different settings of transmitter and receiver circuits under the interposer channel.

On the potential of Wireless Sensor Networks for the in-situ assessment of crop leaf area index

A precise and continuous in-situ monitoring of bio-physical crop parameters is crucial for the efficiency and sustainability in modern agriculture. The leaf area index (LAI) is an important key parameter allowing to derive vital crop information. As it serves as a valuable indicator for yield-limiting processes, it contributes to situational awareness ranging from agricultural optimization to global economy. This paper presents a feasible, robust, and low-cost modification of commercial off-the-shelf photosynthetically active radiation (PAR) sensors, which significantly enhances the potential of Wireless Sensor Network (WSN) technology for non-destructive in-situ LAI assessment. In order to minimize environmental influences such as direct solar radiation and scattering effects, we upgrade such a sensor with a specific diffuser combined with an appropriate optical band-pass filter. We propose an implementation of a distributed WSN application based on a simplified model of light transmittance through the canopy and validate our approach in various field campaigns exemplarily conducted in maize cultivars. Since a ground truth LAI is very difficult to obtain, we use the LAI-2200, one of the most widely established standard instruments, as a reference. We evaluate the accuracy of LAI estimates derived from the analysis of PAR sensor data and the robustness of our sensor modification. As a result, an extensive comparative analysis emphasizes a strong linear correlation (r2=0.88, RMSE=0.28) between both approaches. Hence, the proposed WSN-based approach enables a promising alternative for a flexible and continuous LAI monitoring.

Modelling of an Actuator in the Vacuum Control System of an Autonomous Milking Machine

Abstract Design intents for an actuator of the suction pressure control system in an autonomous milking machine were presented. For determination of its dynamic properties step characteristic was taken. The considered object was described with transmittance and thermodynamic models. Models were identified and their parameters were adjusted. Computer simulation was carried out in MATLAB®-Simulink. Analysis of research results proved that the thermodynamic model allows more detailed reflection of dynamic characteristic of the real object. Its degree of imperfections is 0.99%. For the transmittance model a degree of imperfection with the value of 2.02% was obtained.

Perfect orthogonal waveform scheme used for high-resolution multiple-input multiple-output synthetic aperture radar system

We investigate multiple-input multiple-output (MIMO) synthetic aperture radar (SAR) scheme with an ultra-low side-lobe ratio performance for using complete complementary sequences (CCS) waveform. It is shown that the CCS can be applied in a MIMO SAR system to obtain high resolution in range direction. In addition, the azimuth channel scheme with the multiple subsequences of CCS is also considered. First, we introduce the concept of CCS and establish the transmitter model based on CCS in MIMO SAR system. Then, we propose the corresponding imaging algorithm for employing the CCS to accurately focus the raw data of the MIMO SAR system and derive the range cell migration correction. Considering the signal complexity, we make use of the CCS pairs to analyze the MIMO SAR imaging algorithm. Finally, simulation results demonstrate the validity and feasibility of the proposed MIMO SAR scheme and the potential advantage of CCS.

Experimental determination of parameters in models of indoor air temperature response to reduction in supplied energy

To diminish peaks of energy power demand in buildings, we need to determine parameters in transmittance models that describe indoor temperature response to changes in heating. This article discusses first- and second-order models as well as an integration model. Calculations deal with indoor temperature drop in the range to −2 K following the heating power reduction for a period of 4–6 h. The second-order model was found to be the most accurate in showing the decrease in temperature. The calculated values of parameters vary within wide ranges, with significant differences occurring even with values obtained in consecutive measurement series. It was shown that the use of averaged values produce large result errors in the predictions of indoor temperature changes. This renders an offline method useless and promotes an online method. The average value of the time constant in the first-order model correlates well with the value of the time constant calculated as a ratio of the heat storage mass to the room heat loss coefficient. This is true if we take into account exclusively this part of the building partition layer that contributes to the heat storage.

Design principles and field performance of a solar spectral irradiance meter

A solar spectral irradiance meter (SSIM), designed for measuring the direct normal irradiance (DNI) in six wavelength bands, has been combined with models to determine key atmospheric transmittances and the resulting spectral irradiance distribution of DNI under all sky conditions. The design principles of the SSIM, implementation of a parameterized transmittance model, and field performance comparisons of modeled solar spectra with reference radiometer measurements are presented. Two SSIMs were tested and calibrated at the National Renewable Energy Laboratory (NREL) against four spectroradiometers and an absolute cavity radiometer. The SSIMs’ DNI was on average within 1% of the DNI values reported by one of NREL’s primary absolute cavity radiometers. An additional SSIM was installed at the SUNLAB Outdoor Test Facility in September 2014, with ongoing collection of environmental and spectral data. The SSIM’s performance in Ottawa was compared against a commercial pyrheliometer and a spectroradiometer over an eight month study. The difference in integrated daily spectral irradiance between the SSIM and the ASD spectroradiometer was found to be less than 1%. The cumulative energy density collected by the SSIM over this duration agreed with that measured by an Eppley model NIP pyrheliometer to within 0.5%. No degradation was observed.