Sustainable ammonia production through process synthesis and global optimization

Current ammonia production technologies have a significant carbon footprint. In this study, we present a process synthesis and global optimization framework to discover the efficient utilization of renewable resources in ammonia production. Competing technologies are incorporated in a process superstructure where biomass, wind, and solar routes are compared with the natural gas-based reference case. A deterministic global optimization-based branch-and-bound algorithm is used to solve the resulting large-scale nonconvex mixed-integer nonlinear programming problem (MINLP). Case studies for Texas, California, and Iowa are conducted to examine the effects of different feedstock prices and availabilities. Results indicate that profitability of ammonia production is highly sensitive to feedstock and electricity prices, as well as greenhouse gas (GHG) restrictions. Under strict 75% GHG reductions, biomass to ammonia route is found to be competitive with natural gas route, whereas wind and solar to ammonia routes require further improvement to compete with those two routes. © 2018 American Institute of Chemical Engineers AIChE J, 65: e16498 2019     

ABCG5/G8 Deficiency in Mice Reduces Dietary Triacylglycerol and Cholesterol Transport into the Lymph

The adenosine triphosphate‐binding cassette (ABC) transporter G5/G8 is critical in protecting the body from accumulating dietary plant sterols. Expressed in the liver and small intestine, it transports plant sterols into the biliary and intestinal lumens, thus promoting their excretion. The extent to which G5/G8 regulates cholesterol absorption remains unclear. G5/G8 is also implicated in reducing the absorption of dietary triacylglycerols (TAG) by unknown mechanisms. We hypothesized that G5/G8 suppresses the production of chylomicrons, and its deficiency would enhance the absorption of both dietary TAG and cholesterol. The aim of this study was to investigate the effects of G5/G8 deficiency on lipid uptake and secretion into the lymph under steady‐state conditions. Surprisingly, compared with wild‐type mice (WT) (n = 9), G5/G8 KO (n = 13) lymph fistula mice given a continuous intraduodenal infusion of [3H]‐TAG and [14C]‐cholesterol showed a significant (P < 0.05) reduction in lymphatic transport of both [³H]‐TAG and [¹⁴C]‐cholesterol, concomitant with a significant (P < 0.05) increase of [³H]‐TAG and [¹⁴C]‐cholesterol accumulated in the intestinal lumen. There was no difference in the total amount of radiolabeled lipids retained in the intestinal mucosa between the two groups. G5/G8 KO mice given a bolus of TAG showed reduced intestinal TAG secretion compared with WT, suggesting an independent role for G5/G8 in facilitating intestinal TAG transport. Our data demonstrate that G5/G8 deficiency reduces the uptake and secretion of both dietary TAG and cholesterol by the intestine, suggesting a novel role for the sterol transporter in the formation and secretion of chylomicrons.     

A note on the existence conditions for fault detection and isolation observers

This paper proves that the necessary and sufficient conditions for the existence of FDI observers given by Hou and Muller (Theorem 3) are incorrect. A necessary correction to their theorem is presented and proved. A simple and useful condition is also proposed for the existence of the FDI observers with a rigorous proof. Examples illustrate the effectiveness of the proposed existence condition.     

Building a Platform to Bridge Low End Mobile Phones and Cloud Computing Services

Two waves of technology are dramatically changing daily life: cloud computing and mobile phones. New cloud computing services such as webmail and content rich data search have emerged. However, in order to use these services, a mobile phone must be able to run new applications and handle high network bandwidth. Worldwide, about 3.45 billion mobile phones are low end phones;they have low bandwidth and cannot run new applications. Because of this technology gap, most mobile users are unable to experience cloud computing services with their thumbs. In this paper, a novel platform, Thumb-in-Cloud, is proposed to bridge this gap.Thumb-in-Cloud consists of two subsystems: Thumb-Machine and Thumb-Gateways. Thumb-Machine is a virtual machine built into a low end phone to enable it to run new applications. Thumb-Gateways can tailor cloud computing services by reformatting and compressing the service to fit the phone' s profile.     

Modeling a solar-powered double bed novel composite adsorbent (silica activated carbon/CaCl2)-water adsorption chiller

During the past few decades, the growing demand for air conditioning has caused a significant increase in demand for primary energy resources. Adsorption cooling system is one of the technologies which could be powered by renewable energy. This study aims to improve the performance of a solar-powered adsorption chiller by applying a novel composite adsorbent, a mixture of activated carbon, silica gel and calcium chloride. Modeling is established to investigate the cooling performance of a composite adsorbent based adsorption chiller driven by flat-type solar collectors with three different configurations of glaze: (1) single glazed cover; (2) double glazed cover and (3) transparent insulation material (TIM) cover. The simulation results show that the coefficient of performance (COP) and the specific cooling power (SCP) of the adsorption chiller depend hugely on the solar collector temperature. It is found that a double glazed cover shows the best cooling performance and 30 m² is the most optimized solar collector area. Two to three hours of pre-heating time is required to initiate the desorption process of the adsorber in a day of operation. This newly developed silica activated carbon/CaCl₂ composite material as adsorbent used in the adsorption chiller could achieve a high mean COP_sc of 0.48. Its satisfactory performance suggests that this novel composite material has a potential to be used in the adsorption chiller system even if it is powered by unstable solar energy.     

Field synergy principle analysis on fully developed forced convection in porous medium with uniform heat generation

In the presence of uniform heat source, the energy equation for forced convective heat transfer in porous medium between two parallel plates is solved for fully developed flow. Field synergy analysis is performed with emphasis on the intersection angle between the velocity vector and temperature gradient vector with the inclusion of heat generation. Maximum local intersection angle corresponds to location with the highest resistance to heat convection. Relationship between Nusselt number and field synergy for forced convection in the presence of heat generation is studied. It is necessary to define a modified intersection angle in order to compare the wall heat transfer coefficient for convective heat transfer processes with uniform heat source.     

Evaluation the potential economic impacts of Taiwanese biomass energy production

The Taiwanese rice paddy land set-aside program diverts a substantial land area. Given today’s high energy prices and interests in energy security, that set-aside area could be converted to produce bioenergy feedstocks. This study evaluates the economic and environmental impacts of such a policy change using a Taiwanese agricultural sector model. The results show that such a strategy provides increased farm revenue, increased rural employment, increased energy sufficiency and reduced greenhouse gas emissions but also increased government expenditures. These outcomes indicate that the agricultural sector could play a positive role by producing renewable energy.     

A case study of the structural responses of a tall building in Singapore subjected to close‐in detonations

The response of tall buildings has been a major concern in metropolitan cities, especially with the recent surge in extreme activities targeted at structures with viable commercial values. This paper discusses a study carried out on the structural behaviour of a 2D frame, modelled to represent a tall building with ABAQUS. The model frame was subjected to a charge of the equivalent weight of 1 ton of TNT but placed at two varying cases of 5 and 10‐m standoff distances. Plane‐strain elements that incorporate the feature of material nonlinearity were utilized to model the structural components of the building and the simulated blast overpressures were obtained from the CONWEP software. The effects of large deformations of beams and columns corresponding to the short time loading duration depicted by the explosions were analysed from a local perspective. The extent of the damage is based on a local index defined as the ratio of curvatures. These local indices are consequently used to determine the possibility of disproportionate collapse of the frame from a global perspective. Finally, the provision of more ductile structural detailing is recommended to enhance the structural integrity of the building, increasing its resilience against blast attacks. Copyright © 2009 John Wiley & Sons, Ltd.     

Digital control strategies for sinewave-output cycloconverters

Digital control strategies for obtaining sinewave output for a current-source cycloconverter with fast dynamic response are presented. The proposed dual-multiprocessor control system ensures high-quality output. By means of a parameter estimator, it is possible to deduce the instantaneous voltage reference for the cycloconverter without resorting to a high-gain loop. With an appropriate forgetting factor chosen, the estimator is capable of fast tracking, and a reliable, stable voltage reference is thereby produced. Improvement using digital feedback control is achieved by adjusting the loop gain according to the instantaneous input reference level. The resulting current source shows excellent steady-state and transient performance in response to system disturbances, and it generally achieves good waveforms. It also works for induction motor loads under normal running conditions and should find wide application as an adjustable-frequency high-performance power convertor