Downlink channel spatial covariance estimation in realistic FDD massive MIMO systems

The knowledge of the downlink (DL) channel spatial covariance matrix at the BS is of fundamental importance for large-scale array systems operating in frequency division duplexing (FDD) mode. In particular, this knowledge plays a key role in the DL channel state information (CSI) acquisition. In the massive MIMO regime, traditional schemes based on DL pilots are severely limited by the covariance feedback and the DL training overhead. To overcome this problem, many authors have proposed to obtain an estimate of the DL spatial covariance based on uplink (UL) measurements. However, many of these approaches rely on simple channel models, and they are difficult to extend to more complex models that take into account important effects of propagation in 3D environments and of dual-polarized antenna arrays. In this study we propose a novel technique that takes into account the aforementioned effects, in compliance with the requirements of modern 4G and 5G system designs. Numerical simulations show the effectiveness of our approach.Comment: [v2] is the version accepted at GlobalSIP 2018. Only minor changes mainly in the introductio

Catalytic production of petrochemical products from bio-alcohols

Large-scale petrochemicals are typically produced using petroleum olefins as a feedstock. The desire to move toward a sustainable and environmentally friendly chemical industry has lead to interest in the use of bio-derived feedstocks such as alcohols which are currently being produced on an increasingly large scale by fermentation or from synthesis gas. The research investigated the direct catalytic production of ethylene, acetaldehyde, ethylene dichloride (EDC), and ethylene oxide (EO) from ethanol. Two approaches were considered: a) the use of a bi-functional catalyst that combines the dehydration capability with ethylene conversion and b) the use of a double catalytic bed system where ethanol was dehydrated over the 1st bed and the product ethylene was converted over the 2nd bed to yield the desired petrochemical product. The dehydration of ethanol was carried out over several zeolites at different operating temperatures, producing mainly ethylene and diethyl ether. The catalytic selective oxidation of ethanol was tested over silver and/or copper compounds supported on several zeolites. The effects of operating conditions, metal loading, and zeolite acidity were determined. High selectivity to acetaldehyde was achieved. Unfortunately, the direct production of EO from ethanol could not be achieved. The catalytic oxychlorination of ethanol was investigated using CuCl2 as the active compound and zeolites were used as either a support or as a pre-bed. EDC was produced via ethylene oxychlorination as well as the oxychlorination and disproportionation of ethyl chloride. The effects of operating conditions and CuCl2 loading were determined. Higher EDC yield was achieved over the dual-bed system compared to the bi-functional catalyst

Study on mixing characteristics in shaken microwell systems

Shaken microwell plates are widely used for early bioprocess development as they allow a large number of experiments to be performed in parallel by using small amount of materials. Despite their widespread use, microwell plates have not been characterised from an engineering viewpoint. In this study, mixing time measurements were carried out in two wells of square and cylindrical cross sections for small orbital diameter shaker, do = 3 mm, commonly used in commercial microwell platforms (i.e. ThermoMixer) and compared against measurements obtained in lab scale reactors for larger orbital diameters. The Dual Indicator System for Mixing Time (DISMT) method was employed for all the operating conditions investigated, and a range of rotational speeds was identified where mixing is less effective due to reduced free surface oscillation. An effective scaling parameter between microwell platforms and lab scale reactors was identified based on the natural frequency of the system, which depends only on fill volume, size and cross section of the reactor

Risk-Averse Optimization for Resilience Enhancement of Complex Engineering Systems under Uncertainties

With the growth of complexity and extent, large scale interconnected network systems, e.g. transportation networks or infrastructure networks, become more vulnerable towards external disruptions. Hence, managing potential disruptive events during the design, operating, and recovery phase of an engineered system therefore improving the system's resilience is an important yet challenging task. In order to ensure system resilience after the occurrence of failure events, this study proposes a mixed-integer linear programming (MILP) based restoration framework using heterogeneous dispatchable agents. Scenario-based stochastic optimization (SO) technique is adopted to deal with the inherent uncertainties imposed on the recovery process from nature. Moreover, different from conventional SO using deterministic equivalent formulations, additional risk measure is implemented for this study because of the temporal sparsity of the decision making in applications such as the recovery from extreme events. The resulting restoration framework involves a large-scale MILP problem and thus an adequate decomposition technique, i.e. modified Lagrangian dual decomposition, is also employed in order to achieve tractable computational complexity. Case study results based on the IEEE 37-bus test feeder demonstrate the benefits of using the proposed framework for resilience improvement as well as the advantages of adopting SO formulations

Design and real-time implementation of data-driven adaptive wide-area damping controller for back-to-back VSC-HVDC

This paper proposes a data-driven adaptive wide-area damping controller (D-WADC) for back-to-back VSC-HVDC to suppress the low frequency oscillation in a large-scale interconnected power system. The proposed D-WADC adopts a dual-loop control structure to make full use of the active and reactive power control of VSC-HVDC to improve the damping of the power system. A data-driven algorithm named the goal representation heuristic dynamic programming is employed to design the proposed D-WADC, which means the design procedure only requires the input and output data rather than the mathematic model of the concerned power system. Thus, the D-WADC can adapt to the change of operating condition through online weight modification. Besides, the adaptive delay compensator (ADC) is added to effectively compensate the stochastic delay involved in the wide-area feedback signal. Case studies are conducted based on the simplified model of a practical power system and the 16-machine system with a back-to-back VSC-HVDC. Both the simulation and hardware-in-loop experiment results verify that the proposed D-WADC can effectively suppress the low-frequency oscillation under a wide range of operating conditions, disturbances, and stochastic communication delays

Improving operating policies of large-scale surface-groundwater systems through stochastic programming

[EN] The management of large-scale water resource systems with surface and groundwater resources requires considering stream-aquifer interactions. Optimization models applied of large-scale systems have either employed deterministic optimization (with perfect foreknowledge of future inflows, which hinders their applicability to real-life operations) or stochastic programming (in which stream-aquifer interaction is often neglected due to the computational burden associated with these methods). In this paper, stream-aquifer interaction is integrated in a stochastic programming framework by combining the Stochastic Dual Dynamic Programming (SDDP) optimization algorithm with the Embedded Multireservoir Model (EMM). The resulting extension of the SDDP algorithm, named Combined Surface-Groundwater SDDP (CSG-SDDP), is able to properly represent the stream-aquifer interaction within stochastic optimization models of large-scale surface-groundwater resources systems. The algorithm is applied to build a hydroeconomic model for the Jucar River Basin (Spain), in which stream-aquifer interactions are essential to the characterization of water resources in the system. Besides the uncertainties regarding the economic characterization of the demand functions, the results show that the economic efficiency of the operating policies under the current system can be improved by better management of groundwater and surface resourcesThe data used in this study was obtained from the references included. This study was partially supported by the IMPADAPT project (CGL2013-48424-C2-1-R) with Spanish MINECO (Ministerio de Economia y Competitividad) and FEDER funds. It also received funding from the European Union's Horizon 2020 research and innovation programme under the IMPREX project (grant agreement: 641.811). The authors want to thank the editor, the associated editor and the reviewers for their comments and suggestions in order to increase the quality of the paper. Readers interested in requesting data about the results of the study may send an e-mail to [email protected], H.; Tilmant, A.; Pulido-Velazquez, M. (2017). Improving operating policies of large-scale surface-groundwater systems through stochastic programming. Water Resources Research. 53(2):1407-1423. https://doi.org/10.1002/2016WR019573S1407142353

Technical and economic feasibility of centralized facilities for solar hydrogen production via photocatalysis and photoelectrochemistry

Photoelectrochemical water splitting is a promising route for the renewable production of hydrogen fuel. This work presents the results of a technical and economic feasibility analysis conducted for four hypothetical, centralized, large-scale hydrogen production plants based on this technology. The four reactor types considered were a single bed particle suspension system, a dual bed particle suspension system, a fixed panel array, and a tracking concentrator array. The current performance of semiconductor absorbers and electrocatalysts were considered to compute reasonable solar-to-hydrogen conversion efficiencies for each of the four systems. The U.S. Department of Energy H2A model was employed to calculate the levelized cost of hydrogen output at the plant gate at 300 psi for a 10 tonne per day production scale. All capital expenditures and operating costs for the reactors and auxiliaries (compressors, control systems, etc.) were considered. The final cost varied from $1.60–$10.40 per kg H2 with the particle bed systems having lower costs than the panel-based systems. However, safety concerns due to the cogeneration of O_2 and H_2 in a single bed system and long molecular transport lengths in the dual bed system lead to greater uncertainty in their operation. A sensitivity analysis revealed that improvement in the solar-to-hydrogen efficiency of the panel-based systems could substantially drive down their costs. A key finding is that the production costs are consistent with the Department of Energy's targeted threshold cost of $2.00–$4.00 per kg H_2 for dispensed hydrogen, demonstrating that photoelectrochemical water splitting could be a viable route for hydrogen production in the future if material performance targets can be met

Cost/Benefit Evaluation Of Sulaibiya Wastewater Treatment Plant In Kuwait

In May 2001, the Government of Kuwait awarded a build, operate and transfer (BOT) contract to a local company to finance, design, build and operate an advanced wastewater treatment plant (WWTP) at Sulaibiya. The contract has a 30-year life, comprising 30 months of design and build and 27.5 years of operation and management. The total project cost was K.D. 116 million (US 442 million). The Sulaibiya plant currently treats up to 375 million imperial gallons.  It is designed for extension to 600 million imperial gallons and is the first of its kind to be built in the Middle East.  It is the largest in the world to use ultrafiltration (UF) and reverse osmosis (RO) for water purification. Ultrafiltration will remove all suspended solids and will provide a substantial reduction in micro biological activities. The main obstacle against the use of ultrafiltration membranes for WWTP has always been the higher operating cost of ultrafiltration. Up until now, this higher cost has prevented implementation of UF in all plants. A new membrane has been designed with the aim of tailoring it toward lowest total cost of ownership. Typical operating conditions have been used to quantify the following parameters for a potential large scale wastewater treatment system (UF + RO): amortization of investment in UF membranes and equipment; operating costs of the UF system; reduction in operating costs of the RO, when being compared against a conventional treatment system; and the increased output of the RO plant due to higher availability and shorter construction time. The total cost of ownership of a UF based RO plant has been determined (expressed in US/m3 of water produced). Taking all factors into account, the total cost of ownership of a dual membrane WWTP (UF + RO) will be 2–7% lower than the total cost of ownership of on conventional retreatment plant

Dynamic Testing of the NASA Hypersonic Project Combined Cycle Engine Testbed for Mode Transition Experiments

NASA is interested in developing technology that leads to more routine, safe, and affordable access to space. Access to space using airbreathing propulsion systems has potential to meet these objectives based on Airbreathing Access to Space (AAS) system studies. To this end, the NASA Fundamental Aeronautics Program (FAP) Hypersonic Project is conducting fundamental research on a Turbine Based Combined Cycle (TBCC) propulsion system. The TBCC being studied considers a dual flow-path inlet system. One flow-path includes variable geometry to regulate airflow to a turbine engine cycle. The turbine cycle provides propulsion from take-off to supersonic flight. The second flow-path supports a dual-mode scramjet (DMSJ) cycle which would be initiated at supersonic speed to further accelerate the vehicle to hypersonic speed. For a TBCC propulsion system to accelerate a vehicle from supersonic to hypersonic speed, a critical enabling technology is the ability to safely and effectively transition from the turbine to the DMSJ-referred to as mode transition. To experimentally test methods of mode transition, a Combined Cycle Engine (CCE) Large-scale Inlet testbed was designed with two flow paths-a low speed flow-path sized for a turbine cycle and a high speed flow-path designed for a DMSJ. This testbed system is identified as the CCE Large-Scale Inlet for Mode Transition studies (CCE-LIMX). The test plan for the CCE-LIMX in the NASA Glenn Research Center (GRC) 10- by 10-ft Supersonic Wind Tunnel (10x10 SWT) is segmented into multiple phases. The first phase is a matrix of inlet characterization (IC) tests to evaluate the inlet performance and establish the mode transition schedule. The second phase is a matrix of dynamic system identification (SysID) experiments designed to support closed-loop control development at mode transition schedule operating points for the CCE-LIMX. The third phase includes a direct demonstration of controlled mode transition using a closed loop control system developed with the data obtained from the first two phases. Plans for a fourth phase include mode transition experiments with a turbine engine. This paper, focusing on the first two phases of experiments, presents developed operational and analysis tools for streamlined testing and data reduction procedures