A waste-derived lithium metasilicate basic catalyst

A mixed product of lithium metasilicate (74%) and minor proportions of calcium carbonate, lithium carbonate and calcium hydroxide was prepared by hydrothermal synthesis from waste green container glass in 4 M lithium hydroxide solution at 125 °C. The reaction product was characterised by powder X-ray diffraction and Fourier transform infrared spectroscopy. The lithium metasilicate product was found to be a successful heterogeneous catalyst for the Knoevenagel synthesis of ethyl trans-α-cyanocinnamate from benzaldehyde and ethyl cyanoacetate

Optimization in VHTS Satellite System Design with Irregular Beam Coverage for Non-Uniform Traffic Distribution

Very High Throughput Satellites (VHTS) have a pivotal role in complementing terrestrial networks to increase traffic demand. VHTS systems currently assume a uniform distribution of traffic in the service area, but in a real system, traffic demands are not uniform and are dynamic. A possible solution is to use flexible payloads, but the cost of the design increases considerably. On the other hand, a fixed payload that uses irregular beam coverage depending on traffic demand allows maintaining the cost of a fixed payload while minimizing the error between offered and required capacity. This paper presents a proposal for optimizing irregular beams coverage and beam pattern, minimizing the costs per Gbps in orbit, the Normalized Coverage Error, and Offered Capacity Error per beam. We present the analysis and performance for the case study and compare it with a previous algorithm for a uniform coverage area

Forward Link Optimization for the Design of VHTS Satellite Networks

The concept of geostationary VHTS (Very High Throughput Satellites) is based on multibeam coverage with intensive frequency and polarization reuse, in addition to the use of larger bandwidths in the feeder links, in order to provide high capacity satellite links at a reduced cost per Gbps in orbit. The dimensioning and design of satellite networks based on VHTS imposes the analysis of multiple trade-offs to achieve an optimal solution in terms of cost, capacity, and the figure of merit of the user terminal. In this paper, we propose a new method for sizing VHTS satellite networks based on an analytical expression of the forward link CINR (Carrier-to-Interference-plus-Noise Ratio) that is used to evaluate the trade-off of different combinations of system parameters. The proposed method considers both technical and commercial requirements as inputs, including the constraints to achieve the optimum solution in terms of the user G/T, the number of beams, and the system cost. The cost model includes both satellite and ground segments. Exemplary results are presented with feeder links using Q/V bands, DVB-S2X and transmission methods based on CCM and VCM (Constant and Variable Coding and Modulation, respectively) in two scenarios with different service areas

Historical Reconstruction of Subordination in a Local Context: Agroecosystems with Sugarcane in Veracruz, Mexico

Objective: Rebuild the historical transformation of agroecosystems based on sugarcane in the sub-humid tropic, as a consequence of the change in public policies of the Mexican State in the last three decades. Design/methodology/approach: The transformation of sugar cane agroecosystems was studied in the continuum of reality, as changes in their resource management and management practices. Thus, methodologies used included life stories, field diary, and documentary review. The information collected was transcribed and classified in a database, using keywords for their previous identification by categories. The statements were identified and ordered based on their content, interpretation, and underlying concepts. Results: During the last century, public policies directed towards the sugar sector encouraged the existence of sugarcane agroecosystems as a monoculture. This implied changes in the management of time, work organization, orientation of the production, dependence on credits driven by the mills, and a process encouraged by the individualization of production, eroding the collective and solidarity work that lay behind other crops. Study limitations/implications: It is important to compare these findings with other investigations done in sugar cane producing municipalities. Findings / conclusion: Neoliberal public policies aiming the sugar sector deepened the producers' financial dependence on mills; as a consequence, they lost their autonomy in the management and use of their agroecosystems.Objective: Rebuild the historical transformation of agroecosystems based on sugarcane in the sub-humid tropic, as a consequence of the change in public policies of the Mexican State in the last three decades. Design/methodology/approach: The transformation of sugar cane agroecosystems was studied in the continuum of reality, as changes in their resource management and management practices. Thus, methodologies used included life stories, field diary, and documentary review. The information collected was transcribed and classified in a database, using keywords for their previous identification by categories. The statements were identified and ordered based on their content, interpretation, and underlying concepts. Results: During the last century, public policies directed towards the sugar sector encouraged the existence of sugarcane agroecosystems as a monoculture. This implied changes in the management of time, work organization, orientation of the production, dependence on credits driven by the mills, and a process encouraged by the individualization of production, eroding the collective and solidarity work that lay behind other crops. Study limitations/implications: It is important to compare these findings with other investigations done in sugar cane producing municipalities. Findings / conclusion: Neoliberal public policies aiming the sugar sector deepened the producers' financial dependence on mills; as a consequence, they lost their autonomy in the management and use of their agroecosystems

Cooperative Multi-Agent Deep Reinforcement Learning for Resource Management in Full Flexible VHTS Systems

Very high throughput satellite (VHTS) systems are expected to have a huge increase in traffic demand in the near future. Nevertheless, this increase will not be uniform over the entire service area due to the non-uniform distribution of users and changes in traffic demand during the day. This problem is addressed by using flexible payload architectures, which allow the allocation of payload resources flexibly to meet the traffic demand of each beam, leading to dynamic resource management (DRM) approaches. However, DRM adds significant complexity to VHTS systems, so in this paper we discuss the use of one reinforcement learning (RL) algorithm and two deep reinforcement learning (DRL) algorithms to manage the resources available in flexible payload architectures for DRM. These algorithms are Q-Learning (QL), Deep Q-Learning (DQL) and Double Deep Q-Learning (DDQL) which are compared based on their performance, complexity and added latency. On the other hand, this work demonstrates the superiority a cooperative multiagent (CMA) decentralized distribution has over a single agent (SA)

Convolutional Neural Networks for Flexible Payload Management in VHTS Systems

Very high throughput satellite (VHTS) systems are expected to have a large increase in traffic demand in the near future. However, this increase will not be uniform throughout the service area due to the nonuniform user distribution, and the changing traffic demand during the day. This problem is addressed using flexible payload architectures, enabling the allocation of the payload resources in a flexible manner to meet traffic demand of each beam, leading to dynamic resource management (DRM) approaches. However, DRM adds significant complexity to the VHTS systems, which is why in this article, we are analyzing the use of convolutional neural networks (CNNs) to manage the resources available in flexible payload architectures for DRM. The VHTS system model is first outlined, for introducing the DRM problem statement and the CNN-based solution. A comparison between different payload architectures is performed in terms of DRM response, and the CNN algorithm performance is compared by three other algorithms, previously suggested in the literature to demonstrate the effectiveness of the suggested approach and to examine all the challenges involved

Factores que afectan la producción agrícola bajo riego: cómo medirlos y estudiar su efecto

Hay varios grupos de factores que afectan el rendimiento de los cultivos agrícolas bajo riego; entre ellos destacan los meteorológicos, los de manejo y los relativos a la variabilidad espacial de los terrenos. Los primeros pueden afectar de forma seria los rendimientos y es poco lo que puede hacerse para aminorar su efecto. Los de manejo dependen en gran parte de las decisiones que tomen los productores y de los medios que disponen para realizar sus actividades. El tercer grupo, que depende de la variabilidad espacial de los terrenos, tiene un notable efecto para los productores que rentan tierras que han sido cultivadas por otros productores o que presentan variabilidad debido a condiciones físicas del suelo y la forma en que se han manejado. En el Distrito de Riego 038 de Río Mayo, en Sonora, México, se le ha dado el seguimiento a los cultivos durante varios años mediante sensores remotos satelitales y se han podido medir los efectos de estos factores, así como generar recomendaciones para aminorar los impactos negativos en los rendimientos. El objetivo de este trabajo es mostrar los resultados obtenidos y la manera de hacerlos del conocimiento de los productores, mediante un visor en Internet

Morphologically and compositionally tuned lithium silicate nanorods as high-performance carbon dioxide sorbents

The effective capturing of carbon dioxide using regenerable high capacity sorbents is a prerequisite for industrial applications aiming at CO2 capture and sequestration. The removal of CO2 directly from chemical reaction environments at high temperature is a less energy intensive method of its separation with the added benefit of improved efficiency in equilibrium limited reactions. However, the separation of CO2 at the typical reaction temperatures of 573-1073 K is a challenging task due to the non-availability of absorbents with kinetics comparable to reaction rates. Moreover their poor durability due to sintering and particle growth on prolonged use at high temperature is also an impediment to their practical application. Herein, we demonstrate the development of an efficient CO2 absorbent material, made of Li4SiO4 nanorods, with ultrafast sorption kinetics as well as remarkable durability. These nanorods enabled easier surface reaction with CO2 due to shorter diffusion pathways for lithium from the bulk to the surface of the rods permitting extremely fast absorption of CO2. Furthermore, the compositional tuning of the materials helped to realize absorbents with extraordinary CO2 absorption rates of 0.72 wt% s-1 at 100% CO2/923 K. The exceptional performance of these absorbents at lower temperatures (573-823 K) as well as lower CO2 pressures (0.15 atm) demonstrates their potential in practical CO2 separation applications. © 2016 Royal Society of Chemistry