Estimating 40 years of nitrogen deposition in global biomes using the SCIAMACHY NO2 column

Owing to human activity, global nitrogen (N) cycles have been altered. In the past 100 years, global N deposition has increased. Currently, the monitoring and estimating of N deposition and the evaluation of its effects on global carbon budgets are the focus of many researchers. NO₂ columns retrieved by space-borne sensors provide us with a new way of exploring global N cycles and these have the ability to estimate N deposition. However, the time range limitation of NO₂ columns makes the estimation of long timescale N deposition difficult. In this study we used ground-based NO_x emission data to expand the density of NO₂ columns, and 40 years of N deposition (1970–2009) was inverted using the multivariate linear model with expanded NO₂ columns. The dynamic of N deposition was examined in both global and biome scales. The results show that the average N deposition was 0.34 g N m^–2 year^–1 in the 2000s, which was an increase of 38.4% compared with the 1970s’. The total N deposition in different biomes is unbalanced. N deposition is only 38.0% of the global total in forest biomes; this is made up of 25.9%, 11.3, and 0.7% in tropical, temperate, and boreal forests, respectively. As N-limited biomes, there was little increase of N deposition in boreal forests. However, N deposition has increased by a total of 59.6% in tropical forests and croplands, which are N-rich biomes. Such characteristics may influence the effects on global carbon budgets.     

Estimating NO2 dry deposition using satellite data in eastern China

The spatial and temporal characters of ground-level NO₂ concentration over eastern China were retrieved from the monthly averaged tropospheric NO₂ column densities from Global Ozone Monitoring Experiment (GOME, data used in this study are from April 1996 to December 2002) and Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY, data used in this study are from January 2003 to December 2011) measurements. Together with the NO₂ concentration and the dry deposition velocity maps of eastern China, the fluxes of NO₂ dry deposition were estimated for three specific regions. The results indicated that the surface NO₂ concentration in eastern China increased dramatically from 1996 to 2011, and it showed distinct regional and seasonal variational characteristics. The highest concentration occurred in winter while the lowest occurred in summer. There was also variation in the spatial distribution with the peak value of NO₂ concentration appearing in the plains of north China (R1), the Yangtze River delta (R2), and the Pearl River delta (R3). A sharp increase of NO₂ concentration appeared in R1 and R2, while it was invariant or showed an obvious decrease in R3 during the period of 1996–2011. Furthermore, we compared the NO₂ dry deposition fluxes estimated from the ground-level NO₂ concentration and the dry deposition velocity of NO₂ with the mass concentration of NO₂ dry deposition that, measured from the control experiments and by consulting the published literature, showed a significant correlation (P < 0.001) and had a high R value (R = 0.73). The results also indicated that the NO₂ dry deposition fluxes increased over eastern China, with a maximum value of 8.25 kg N ha^?1 yr^?1 from 1996 to 2011 in R3, while the value was characterized by fluxes of less than 2.27 kg N ha^?1 yr^?1 in R2. When comparing the NO₂ dry deposition over different land covers, the values distinctly peaked over artificial surfaces and evergreen forests, with maximum values of 10.07 and 9.49 kg N ha^?1 yr^?1 in R1, 5.05 and 4.94 kg N ha^?1 yr^?1 in R2, and 20.95 and 23.15 kg N ha^?1 yr^?1 in R3. However, the lowest value of NO₂ dry deposition flux appeared over needleleaf forests, with 0.53, 0.24, and 1.29 kg N ha^?1 yr^?1 for R1, R2, and R3, respectively.     

Validation of Ozone Monitoring Instrument NO2 measurements using ground based NO2 measurements at Zvenigorod,Russia

We present the results of comparison between Ozone Monitoring Instrument (OMI) data of NO₂ measurements (Collection 3) onboard the NASA EOS-Aura satellite and correlative ground-based twilight measurements at Zvenigorod station in Russia in 2004–2008. Compared quantities are unpolluted column and tropospheric column amounts of NO₂ which are standard products of OMI measurements. The NO₂ columns observed by our ground-based instrument have been interpolated to the time of OMI measurements using a one-dimensional photochemical model. According to our comparison, the OMI unpolluted NO₂ columns underestimate ground-based measurements by (0.084 ± 0.025)?×?10¹⁵ molecules/cm², or (3.2 ± 0.9)%. The correlation coefficient between the OMI and ground-based unpolluted NO₂ columns is 0.92. The tropospheric NO₂ columns derived from OMI measurements are on average by (1.8 ± 0.5)?×?10¹⁵ cm^?2, or approximately 40%, less than those derived from ground-based measurements. The correlation coefficient between these data is about 0.3. Reasons for this discrepancy are discussed.     

Factor analysis using column cross-validation

Factor analysis using column cross-validation is discussed. The principles underlying abstract (AFA) and target factor analysis (TFA) are briefly recalled. Column cross-validation (CCV) is proposed as an objective approach to establish the number of principal factors. A system of programs (COM-FACTA) achieving the analysis is used to perform AFA, TFA and CCV. Spectrophotometric data from the aqueous reaction between nickel ions and ethylenediaminetetraacetic acid are used to illustrate the method.     

Modeling the atmospheric deposition and stormwater washoff of nitrogen compounds

We investigated the suitability of integrating deterministic models to estimate the relative contributions of atmospheric dry and wet deposition onto an urban surface and the subsequent amounts removed by stormwater runoff. The CIT airshed model and the United States Environmental Protection Agency Storm Water Management Model (SWMM) were linked in order to simulate the fate and transport of nitrogen species through the atmosphere and storm drainage system in Los Angeles, California, USA. Coupling CIT and SWMM involved defining and resolving five critical issues: (1) reconciling the different modeling domain sizes, (2) accounting for dry deposition due to plant uptake, (3) estimating the fraction of deposited contaminant available for washoff, (4) defining wet deposition inputs to SWMM, and (5) parameterizing the SWMM washoff algorithm. The CIT–SWMM interface was demonstrated by simulating dry deposition, wet deposition, and stormwater runoff events to represent the time period from November 18, 1987 to December 4, 1987 for a heavily urbanized Los Angeles watershed discharging to Santa Monica Bay. From November 18th to December 3rd the simulated average dry deposition flux of nitrogen was 0.195 kg N/ha-day to the watershed and 0.016 kg N/ha-day to Santa Monica Bay. The simulated rainfall concentrations during the December 4th rainfall event ranged from 3.76 to 8.23 mg/l for nitrate and from 0.067 to 0.220 mg/l for ammonium. The simulated stormwater runoff event mean concentrations from the watershed were 4.86 mg/l and 0.12 mg/l for nitrate and ammonium, respectively. Considering the meteorology during the simulation period, the CIT and SWMM predictions compare well with observations in the Los Angeles area and in other urban areas in the United States.     

Forecasting of traffic origin NO and NO2 concentrations by Support Vector Machines and neural networks using Principal Component Analysis

The main aim of this paper is to predict NO and NO₂ concentrations four days in advance comparing two artificial intelligence learning methods, namely, Multi-Layer Perceptron and Support Vector Machines on two kinds of spatial embedding of the temporal time series. Hourly values of NO and NO₂ concentrations, as well as meteorological variables were recorded in a cross-road monitoring station with heavy traffic in Szeged in order to build a model for predicting NO and NO₂ concentrations several hours in advance. The prediction of NO and NO₂ concentrations was performed partly on the basis of their past values, and partly on the basis of temperature, humidity and wind speed data. Since NO can be predicted more accurately, its values were considered primarily when forecasting NO₂. Time series prediction can be interpreted in a way that is suitable for artificial intelligence learning. Two effective learning methods, namely, Multi-Layer Perceptron and Support Vector Regression are used to provide efficient non-linear models for NO and NO₂ times series predictions. Multi-Layer Perceptron is widely used to predict these time series, but Support Vector Regression has not yet been applied for predicting NO and NO₂ concentrations. Grid search is applied to select the best parameters for the learners. To get rid of the curse of dimensionality of the spatial embedding of the time series Principal Component Analysis is taken to reduce the dimension of the embedded data. Three commonly used linear algorithms were considered as references: one-day persistence, average of several-day persistence and linear regression. Based on the good results of the average of several-day persistence, a prediction scheme was introduced, which forms weighted averages instead of simple ones. The optimization of these weights was performed with linear regression in linear case and with the learning methods mentioned in non-linear case. Concerning the NO predictions, the non-linear learning methods give significantly better predictions than the reference linear methods. In the case of NO₂ the improvement of the prediction is considerable; however, it is less notable than for NO.     

Thick film NO2 Sensor

 Thick film technology was used to manufacture a solid-state electrochemical nitrogen dioxide sensor. The prepared sensor has a linear dependence of electromotive force that is based in the NO₂ concentration level. This paper presents discussion on a thick-film sensor that has a much smaller dimension and shorter response time as compared to typical ceramic solid-state electrochemical devices. Received: 26 February 1996/Accepted: 27 June 1996     

On global optimization using interval arithmetic

A method for finding all global minimizers of a real-valued objective function of several variables is presented. For this purpose a problem-oriented type of number is used: the set of real compact intervals. The range of the objective function over a rectangular set is estimated by natural interval extension of a suitable modelling function. An algorithm for interpolation and approximation in multidimensional spaces is developed. This optimization method can be applied successfully to conventionally, e.g. with real arithmetic, programmed functions.     

用column generation算法规划网络编码业务

网络编码能够有效降低网络中关键边的资源消耗,改善网络的负载均衡。但是普通的启发式路由算法通常只能为单个业务寻找最优路由,无法优化网络的整体性能。运用column generation算法对网络编码业务进行规划,为松弛系数赋予具体的物理含义,并据此进行路径更新,有针对性地为每个业务寻找路由。与启发式算法相比,column generation从整体上提高了网络的吞吐量,改善了网络的负载均衡。同时,与普通ILP算法相比,column generation算法无需计算大量备选路径,且函数始终处于收敛状态,不会产生振荡,求解总时间缩短了23.5％,总代价优化2.5％。     

Spatiotemporal variations of tropospheric column nitrogen dioxide over Jing-Jin-Ji during the past decade

Of all anthropogenic pollutants, nitrogen dioxide (NO₂) has the most negative effect on atmospheric chemistry. In this study, measurements of tropospheric column NO₂ obtained from the ozone monitoring instrument (OMI) are used to investigate temporal and spatial dynamics of NO₂. Temporal and spatial distributions of tropospheric NO₂ concentrations obtained from OMI over the Beijing-Tianjin-Hebei (Jing-Jin-Ji) region from 2007 to 2016 are presented, and annual changes and trends in the seasonal cycle are shown. Annual amounts of NO₂ are found to firstly increase then decrease, where after reaching a maximum in 2012 they begin a progressive yearly decline. NO₂ shows significant cyclical seasonal characteristics over Jing-Jin-Ji, with maximum values in winter and minimum in summer. In addition, the spatial distribution is unbalanced, and Beijing-Tianjin-Tangshan and Shijiazhuang-Xingtai-Handan are found to be highly polluted areas. The many complex factors affecting variations in NO₂ are analysed in this article, and the impact of meteorological factors and human activities are emphasized. It is considered that temperature and precipitation are natural factors influencing NO₂ concentration but there is a stronger negative relationship between tropospheric column NO₂ and temperature. Optimization of the energy structure is thus considered to be important and a reduction in energy consumption is required to control the concentration of pollutants. Coal combustion is a major anthropogenic factor in increasing NO₂ concentrations, and there is a strong correlation between higher amounts of NO₂ and coal consumption in the Jing-Jin-Ji region.     

Valve stiction estimation using global optimisation

Valve stiction is the most frequent cause of loop oscillations. Thus, detecting and quantifying this valve problem is essential to ensuring plant profitability. In this work, a novel one-stage procedure to estimate stiction parameters is proposed using a two-parameter stiction model. The optimisation problem is computed using a global optimisation algorithm. These two propositions make the stiction computation more efficient and computationally faster than the currently available method. The applicability of the proposed approach is illustrated using a large number of simulated and industrial valves. Moreover, to isolate the impact of each proposition, the novel method is compared with the currently available technique, which is based on a two-stage scheme. The results show that the global optimisation algorithm is more efficient than the direct search and genetic algorithms, as previously proposed by Jelali (2008). The two-stage procedure provides a better estimate of the apparent stiction, whereas the one-stage procedure provides a better slipjump value.     

NO_2气体传感器敏感材料

描述了近十年来用作NO2 气体传感器的酞菁类和氧化物半导体敏感材料。总结了这两类材料的成膜条件、薄膜表面形态和结构以及它们的敏感特性。为优化薄膜的气敏特性提供了参考     

Enhancing nanoparticle deposition using actuated synthetic cilia

We use computational modeling to probe the utility of actuated synthetic cilia lining walls of a microfluidic channel for enhancing the deposition of nanoparticles dispersed in a viscous fluid filling the channel. We demonstrate that elastic cilia actuated by a sinusoidal force applied to their free ends generate circulatory secondary flows facilitating nanoparticle transport. We identify optimal operational conditions in which the effect of cilia beating on particle deposition is maximized. Our simulations also reveal that cilia transition to a three-dimensional beating pattern when the actuation force exceeds a critical value. This transition is associated with buckling instability experienced by elastic cilia. Our findings guide the optimal design of ciliated microfluidic systems for uses such as deposition of particulates onto sensory surfaces and microfluidic mixing.     

Cloud and cloud shadow masking for Sentinel-2 using multitemporal images in global area

ABSTRACT

Sentinel-2 data provided the opportunity for complementary data to existing missions including Landsat and SPOT. In this study, multitemporal cloud masking (MCM) used to detect cloud and cloud shadow masking for Landsat 8 was improved to detect cloud and cloud shadow for Sentinel-2 data. This improvement takes advantages of the spectral similarity between Landsat 8 and Sentinel-2. To assess the reliability of the new MCM algorithm, several data selected from different environments such as sub-tropical South, tropical, and sub-tropical North were evaluated. Moreover, these data have heterogeneous land cover and variety of cloud types. In visual assessment, the algorithm can detect cloud and cloud shadow accurately. In the statistical assessment, the user’s and producer’s accuracies of sample in sub-tropical environments of cloud masking was 99% and 96%, respectively, and cloud shadow masking was 99% and 98%, respectively. In addition, the user’s and producer’s accuracies of sample in tropical environments of cloud masking was 100% and 95%, respectively, and cloud shadow masking was 100% and 92%, respectively. Compared to Fmask, MCM has higher accuracies in most of the results of cloud and cloud shadow masking in both sub-tropical and tropical environments. The results showed that the improved-MCM algorithm can detect cloud and cloud shadow for Sentinel-2 data accurately in all scenarios and the accuracies are significantly high.     

Ferroelectric liquid crystal aligned on SiO2 thin films using ion‐beam deposition

Abstract— Results for a ferroelectric‐liquid‐crystal (FLC) display cell, aligned on inorganic SiO₂ thin‐film surfaces by using oblique ion‐beam sputtering deposition on the substrates, is presented. A large deposition angle from 60° to 80° can be employed for the thin alignment layer, with thicknesses varying from 5 to 40 nm. Two types of uniform alignment, chevron (before electrical treatment) and quazi‐bookshelf (after electrical treatment), were studied. High‐quality alignment on large‐sized substrates was also easily be achieved because of the linear design of the ion‐beam sputtering source, which was previously a significant challenge for FLC on SiO_x layers.     

Approximate branch-and-bound global optimization using B-spline hypervolumes

This paper presents a B-spline-based branch-and-bound algorithm for unconstrained global optimization. The key components of the branch-and-bound, a well-known algorithm paradigm for global optimization, are a subdivision scheme and a bound calculation scheme. For these schemes, we first introduce a B-spline hypervolume to approximate an objective function defined in a design space, where the approximation is based on Latin-hypercube sampling points. We then describe a proposed algorithm for finding global solutions approximately within a prescribed tolerance. The algorithm includes two procedures that are performed iteratively until all stopping conditions are satisfied. One involves subdivision into mutually disjoint subspaces and computation of their bound information, both of which are accomplished by using B-spline hypervolumes. The other updates a search tree that represents a hierarchical structure of subdivided subspaces during the solution process. Finally, we examine the computational performance of the proposed algorithm on various test problems that cover most of the difficulties encountered in global optimization. The results show that the proposed algorithm is complete without using heuristics and has good potential for application in large-scale NP-hard optimization.     

Accelerating column generation for aircraft scheduling using constraint propagation

We discuss how constraint programming can improve the performance of a column generation solution process for the NP-hard Tail Assignment problem in aircraft scheduling. Combining a constraint model of a relaxed Tail Assignment problem with column generation, we achieve substantially improved performance. A generalized preprocessing technique based on constraint propagation is presented that can dramatically reduce the size of the flight network. We also present a heuristic preprocessing method based on the costs of connections, and show how constraint propagation can be used to improve fixing heuristics. Proof of concept is provided using real world Tail Assignment instances.     

Total ozone column measurements using an ultraviolet multi-filter radiometer

We have developed and used a method to retrieve total ozone column (TOC), from Ultraviolet Multi-filter Rotating Shadowband Radiometer (UVMFR) measurements in combination with radiative transfer model calculations. Look-up tables of ratios of the direct solar irradiance at (DI) 305 and 325nm in terms of TOC, solar zenith angle, and aerosol optical depth (AOD) have been constructed and compared with TOC retrievals estimated directly from UVMFR irradiance measurements. Sensitivity analysis of the influence of AOD on the calculated TOC has been investigated and found to be 1 Dobson unit per 0.1 change in AOD. We also examined the impact of ozone effective temperature on the TOC retrieval and found that it leads to a 0.9% change in TOC per K. UVMFR direct irradiance measurements in Athens, Greece, during the period July 2009–May 2014 were used to create a time series of high-temporal-frequency measurements (1 min for cloudless conditions) of TOC, which facilitated an analysis of the diurnal variation of TOC. Comparison of the TOC retrievals from the UVMFR with co-located and synchronous daily TOC retrievals from a Brewer MKIV spectrophotometer showed very good agreement (correlation coefficient 0.98). Daily TOC retrievals from the UVMFR were within ±3% compared with the ones measured by the Ozone Monitoring Instrument overpasses on board the Aura satellite.     

Signature verification using global and grid features

In this work, algorithms for extracting global geometric and local grid features of signature images were developed. These features were combined to build a multi-scale verification function. This multi-scale verification function was evaluated using statistical procedures. Results indicated that the multi-scale verification function yielded a lower verification error rate and higher reliability than the single-scale verification function using either global geometric or local grid feature representation. The correct verification rate of the multi-scale system was more than 90% in rejecting skilled forgeries and was perfect in rejecting simple forgeries based on a limited database.     

Data-stream-based global event monitoring using pairwise interactions

The problem of global state observation is fundamental to distributed systems and to the analysis of data streams. Many interactions in distributed systems can be analyzed in terms of the building block formed by the pairwise interactions of intervals at two processes. Considering causality-based pairwise interactions by which two processes may interact with each other, there are 40 orthogonal interaction types. For each pair of processes (_Pi,_Pj)$(P_i,P_j)$, let interaction type _ri,j$r_{i,j}$ be of interest. This paper examines the problem: “If a global state of interest to an application is specified in terms of such pairwise interaction types, one per pair of processes, how can such a global state be detected?” A solution identifies a global state in which the interaction type specified for each process pair is satisfied. This paper formulates the specific conditions on the communication structures to determine which of the intervals being examined at any time may never satisfy the stipulated interaction type for that pair of processes, and therefore that interval(s) need no longer be considered as forming a part of any solution. Based on this theory, the paper proposes two on-line distributed algorithms to solve the problem.