Fine classification of crops based on an inductive transfer learning method with compact polarimetric SAR images

Compact polarimetric synthetic aperture radar (CP SAR) reduces fully polarimetric SAR system complexity and expands the imaging swath. Generally, fine classification of crop types relies on many labeled training samples. However, due to the temporal interval of crop phenology and ground environment variations over time, training samples from one dataset usually perform poorly for another. Therefore, in this study, transfer learning is introduced to crop classification to ensure classification accuracy by improving reusability of training samples. A stable and robust inductive transfer learning method, i.e. the Transfer Bagging-based Ensemble Learning (TBEL) algorithm, is proposed. The main idea is to select an adequate number of representative samples from unlabeled datasets to characterize each class in the target domain based on limited labeled samples and construct a classifier set to classify the target domain. This study investigates CP SAR data performance in transfer learning for crop classification. The proposed algorithm in the experimental study is compared with six typical methods (Subspace Alignment (SA), CORrelation ALignment (CORAL), Joint Distribution Adaptation (JDA), Balanced Distribution Adaptation (BDA), Transfer Bagging (TrBagg), and Bagging-based Ensemble Transfer Learning (BETL)). The experimental results show that the crop classification accuracy based on the TBEL algorithm is more stable, with an improved overall classification accuracy of 2–6%. Classifying the same rice harvest stage in the cross-year domain has the highest overall accuracy of 92.2%. Wheat fields in different scenes are also classified. Based on the TBEL algorithm, the overall classification accuracy improves by 1–10% compared with typical methods, with an accuracy of at least 87.6%. Furthermore, by testing the CP mode classification performance over various crops in transfer learning, we find that the circular CP mode performs better than the linear mode in most cases. This conclusion agrees with single-scene applications and was first verified in transfer learning.</p

Scatter plots of temporal signatures of individual key locations.

<p>A-B: Distribution of individual clusters in a 2D space defined by the temporal activity (percentage of tweets relative to the total number of tweets in the cluster) during different hours of the day. A: morning vs. evening. B: morning vs. afternoon. Clusters with similar land use attributes have a similar distribution of tweets within the twenty-four cycle. Hexagonal binning was used to display the common (mode) land use attribute in each bin.</p

Similarity of common land use types among Twitter users and the Travel Tracker survey individuals.

<p>A-C: Violin plots of similarity of common land use types between Twitter users and the Travel survey individuals compared to the control group (a random sample from the land use map of Chicago for rank one (A), rank two (B) and rank three (C). Each sample is made of 10,000 individuals in case of Twitter and the travel survey and 10,000 random land use parcel in the case of the random map sample.</p

Twitter temporal signatures.

<p>A-D: Twitter users’ temporal signatures aggregated by land use type for all users during weekdays (A-B) and weekends (C-D). Weekdays were defined as Mondays to Fridays while Weekends include Saturdays and Sundays. Signatures were normalized by the total number of tweets counts in a land use class to allow comparisons.</p

Fabrication of CaO-Based Sorbents for CO₂ Capture by a Mixing Method

Three types of sorbent were fabricated using various calcium and support precursors via a simple mixing method, in order to develop highly effective, durable, and cheap CaO-based sorbents suitable for CO₂ capture. The sorption performance and morphology of the sorbents were measured in a thermogravimetric analyzer and a scanning electron microscopy, respectively. The experimental results indicate that cement is a promising low-cost support precursor for contributing to the enhancement of cyclic CO₂ sorption capacity, especially when organometallic calcium precursors were used. A sorbent (with 75% CaO content) made from calcium l-lactate hydrate and cement showed the highest CO₂ sorption capacity of 0.36 g of CO₂/g of sorbent and its capacity decreased only slightly after 70 cycles of carbonation and calcination

Spatial uncertainty.

<p>A: Box plots of the distribution of spatial uncertainty index grouped by rank; an index value of one indicates that all the tweets in a cluster are in the close proximity of a single land use parcel. Notice the strong left-skewed distribution, which indicates that the majority of the parcels are uniquely associated with a particular parcel. B: Log-log distribution of number of parcels per unique users grouped by activity types.</p

Behavior of CaO/CuO Based Composite in a Combined Calcium and Copper Chemical Looping Process

Integration of chemical looping combustion into calcium looping is an attractive approach to solving the problem of energy requirement for the regeneration of CaO-based sorbent. In this work, the behavior of MgO supported CaO/CuO composite in the new combined process (CaCuCL) was investigated. The composite was prepared via a simple wet mixing method and measured via a thermogravimetric analyzer for its chemical performance. It appears that the component of Cu/CuO has a significant influence on the cyclic performance of CaO, which is probably caused by the “wrapping” of Cu/CuO outside, due to its low melting point. However, this negative effect can be greatly reduced by using appropriate operating conditions in the successive reactions. When tested for 68 cycles, all synthetic sorbents showed good reactivity and stability of the Cu/CuO component, although loss-in-capacity of CaO was stilled observed

Confusion matrix of Twitter land use classification.

<p>Confusion matrix of Twitter land use classification.</p

Semantics of top tweeted-from locations.

<p>A-B: Count of unique users grouped by land use types and ranks of their top ten key locations; absolute count (A) and normalized count (B). C-D: Count of surveyed individuals who reported their stay times at different locations during the day grouped by land use types and ranks (based on the duration of stay); absolute count (C) and normalized count (D). Data were extracted from the travel survey of Chicago and present an estimate of the preferential return of Chicago residents at the time of the survey.</p

High-Temperature Pressure Swing Adsorption Process for CO₂ Separation

This paper presents a novel pressure swing adsorption process and the development of specifically designed sorbents for the process. It is operated at high temperature (650–800 °C) using the reversible reaction of calcium oxide with CO₂, i.e., CaO + CO₂ ⇄ CaCO₃. The new process directly stores the reaction heat released from the forward reaction in the sorbent and then releases it for sorbent regeneration under reduced CO₂ partial pressure, so that the need of pure oxygen for oxy-fuel combustion is avoided. Two potential problems of the new process, namely, loss in capacity and slow and unmatched reaction rates of chemical-controlled carbonation and calcination, were discussed in detail. Three specifically designed calcium-based sorbents showed stable performance during 92 isothermal carbonation–calcination cycles at either 680 or 750 °C. The calcination rate was significantly enhanced by increasing the reaction temperature and the introduction of steam to match the reaction rate of chemical-controlled carbonation. This pressure swing adsorption process could be used for low-cost CO₂ separation using specifically designed sorbents under carefully selected operating conditions