Multivariable control strategy based on bifurcation analysis of an industrial gas-phase polymerization reactor

In an industrial gas-phase polyethylene reactor, the safe operating range of temperature is rather narrow. Even within this temperature range, temperature excursions must be avoided because they can result in low catalyst productivity and significant changes in product properties. If the manipulated variable for temperature control saturates (i.e., the cooling water valve position is completely open), then the reactor operates without a feedback temperature controller, leading to oscillatory behavior and limit cycles. In this work, it has been demonstrated that the saturation in the manipulated variable and the complex non-linear dynamic behavior are removed when auxiliary manipulated variables, obtained by bifurcation analysis, are used in a multivariable control strategy for the reactor temperature control. Two control structures are proposed and compared considering their impact in the reactor production and polymer melt index. In the first control structure, the designed PID controller for the reactor temperature is considered and a switching strategy with a PI controller for the auxiliary manipulated variables is included. In the second control structure, the designed PID controller for the reactor temperature is also used, however, a MPC controller for the auxiliary manipulated variables is considered. The results suggest that the use of gain-scheduling strategy in the PID temperature controller with a MPC controller for the auxiliary manipulated variables avoids the saturation of the manipulated variable and, hence, the undesired non-linear dynamic behavior, reducing the production loss and improving the product quality.     

The contextualization of divergent outlooks in a Greenfield master-planned community: a pathway towards reflexivity

Comprehensive design schemes and specifications have progressively shaped Master-Planned Communities (MPCs). The market largely predetermines these outcomes, with background input from communities. Therefore, this paper endeavours to define the fundamental structures that generate differences between market actors and residents within the North Lakes MPC. This study employs ‘habitus theory’, which is a sociological phenomenon describing the divergence of personal outlooks and expertise. The application of this theory is thus illustrative of the evolution of distinct observations within MPCs. Contemporary studies have under-researched these inherent gaps between communities, authorities, and critics, and these frictions could be exacerbated within restrictive developmental contexts. Epistemic and objectified content analyses collated over many years and sources will uncover the underlying differences between the relevant groups. These analyses will enable the progression of a framework for understanding power relation biases and how reflexivity can enhance current consultative methods.     

Electrochemical conversion of switchgrass and poplar in molten carbonate direct carbon fuel cell

One way of sustaining fuel cell technology is using renewable and sustainable energy means provided by biomass. This article explores switchgrass and poplar in a molten carbonate electrolyte direct carbon fuel cell. It investigates their electrochemical conversions and provides results of power density, current density, open circuit voltage (OCV) and other parameters. The biomasses were pyrolysed at 800°C to produce carbon fuels. Biomass carbon fuels were mixed with molten carbonate and subjected to different operating conditions (600–800°C) in the fuel cell. The electrochemical performances of the poplar fuel were better than those experienced with switchgrass fuel. At 800°C the OCV of poplar fuel (1.08?V) has higher output than switchgrass (0.87?V). The peak power density recorded for poplar fuel was 23.91?mW/cm² while switchgrass fuel was lower at 21.60?mW/cm². Poplar fuel (81.53?mA/cm²) gave a maximum current density with switchgrass fuel lower at 74.00?mA/cm².     

Effect of cellulase/glucanase/xylanase (Roxazyme G2) enzymes combination on nutrients utilisation of vegetable meal (Amaranthus cruentus) fed as sole dietary protein source in rat assay

Amaranthus cruentus vegetable meal (ACVM) had 23% crude protein. Ca, Na, K, Mg and Fe were abundant at 2.0 g kg^?1, 7.1 g kg^?1, 4.8 g kg^?1, 2.5 g kg^?1, 1109 mg kg^?1, respectively. P‐phosporous, oxalates and tannins were noticeable. Lysine, methionine and cystine were limiting. Weight gain for rats on the reference (casein) diet 2 at 6.30 g ±2.87 was highest (P < 0.05) followed by diet 6 (12% ACVM with enzyme supplementation) at 5.01 g ±2.42. Feed intakes were similar (P > 0.05) for rats on the reference diet and for rats on 10% and 12% with/without enzyme supplementation ranging from 42.90 g ± 4.52 in reference diet to 45.12 g ± 3.64. Nitrogen retention was highest for rats on reference diet but similar (P > 0.05) to rats on 12% enzyme supplemented diet at 0.53 ± 1.12 and 0.53 ± 2.10, respectively. Other investigated protein evaluation parameters revealed similar results among rats kept on reference diet and the rats on ACVM based diets with enzyme supplementations. Enzyme supplementation had a complimentary role in ACVM nutrition in rat trial.     

Using PLS-SEM technique to model construction organizations' willingness to participate in e-bidding

The push for the use of e-bidding is on the increase. In many countries, e-bidding has become part of the public procurement reform. However, previous studies have reported the low uptake of e-bidding in the construction industry. This study develops a theoretical structural model representing the impact six latent variables on the willingness of construction organizations to participate in e-bidding. Data from a questionnaire survey of 64 respondents from clients, contractors, consultants, and suppliers organizations was used to analyze the model. The result of the data analysis suggests that perceived barriers, cost, the perceived benefits of e-bidding and security concerns are the factors influencing willingness participate in e-bidding with perceived barriers being the most significant influencing factor. The perception about the adequacy of the existing traditional paper-based tendering and the perception about the non-readiness of business partners are the underlying barriers that need to be addressed when introducing e-biding. This study also discovers that when the respondents concern about the cost of e-bidding is high, their reported willingness to participate in e-bidding is higher when the perceived benefits is high that when the perceived benefits is low. To enhance the participation of the industry in e-bidding, public sector and large private clients would need to take leadership by making bidder's capability for e-bidding and e-project management at all project phases a criteria in bid evaluation. E-bidding developers and promoters need to use test project cases to monitor, measure, and document the benefits of e-bidding. To disseminate the perceived benefits, promoters would need to work closely with industry professional associations to develop promotional programmes linked to continuous professional development (CPD) points. The analytical approach used in this study should assist other researchers who might wish to address a similar research problem under a similar data and model constraints.     

Legal Framework for Alternative Dispute Resolution: Examination of the Singapore National Legal System for Arbitration

Effectiveness of any alternative dispute resolution (ADR) method depends on the national legal system to which it is subjected. In Singapore, the increasing growth in the use of ADR methods may be adduced to developments in the Singapore legal environment. This paper reviews the characteristics of the Singapore national legal system for arbitration. It examines how the legal system facilitates effective use of ADR. By its features, the Singapore national legal system ensures parties’ autonomy but deters parties from taking opportunistic advantage of the voluntary nature of ADR. It enables procedural flexibility, and confidentiality of arbitration proceedings. It insulates the arbitration process from intervention from the Singapore courts and from corruption; and it provides maximum judicial support in the arbitral process. Hence, it ensures that disputes can be brought to a conclusion within a reasonable amount of time, at a reasonable cost, as well as preserving business relationships. The Singapore legal system insures the integrity of arbitration and the independence of arbitrators and arbitral institutions by immunity provisions. In addition, the legal system enhances the use of mediation and conciliation in a sequential tier with arbitration by providing a time limit for mediation or conciliation to terminate should they fail to produce a mutually acceptable settlement. In Singapore, the court system is generally known to be efficient; hence, ADR faces the practical challenge of becoming lengthier than court proceedings. The continuing search for and use of expedited arbitration procedures by arbitral institutions such as the Singapore International Arbitration Centre should reduce this challenge. This paper provides useful information on how a national legal system may be designed to support the use of ADR methods and facilitate their effectiveness.     

Induction of preterm labor in the rabbit by antiprogesterone

On the 25th day of pregnancy, 14 New Zealand white rabbits were treated orally with 500 mg of the progesterone (P)-synthesis inhibitor: Isoxazol. This treatment was repeated 12 hours (n = 6) or 24 hours (n = 8) later. An additional group of 6 rabbits received at the same time the solvent, without Isoxazol, to serve as vehicle controls. From day 26 onward all these 20 animals were induced every day with a single i.v. injection of 100 mU oxytocin until they delivered. The 14 Isoxazol rabbits responded to oxytocin on day 27.7 plus or minus 0.2 (Mean plus or minus S.E.), while the vehicle controls failed to respond until day 30.3 plus or minus 0.4 of pregnancy (p smaller than 0.001). Progesterone assays in the uterine vein plasma showed that, in comparison with 14 untreated controls of similar gestational age, plasma P of the 14 Isoxazol rabbits was significantly reduced (p smaller than 0.01). The vehicle controls became inducable when their P was endogenously lowered to the level at which oxytocin readily provokes parturition near term. Neither Isoxazol, nor oxytocin altered the normally low prostaglandin F levels of the uterine vein plasma, indicating that Isoxazol provokes premature inducability in the rabbit through P-withdrawal, rather than through an elevation of PG-levels.     

Zn(II) Complex Catalyzed Coupling Aquathermolysis of Water-Heavy Oil-Methanol at Low Temperature

A Zn(II) coordination complex was synthesized, characterized, and used for catalytic aquathermolysis of heavy oil at low temperatures for the first time. The effects of water content and catalyst concentration on aquathermolysis were investigated. And then a tri-component coupling aquathermolysis of waterheavy oil-methanol was designed and the reaction conditions were investigated. With the catalyst and methanol, the reaction occurred at temperatures as low as 180°C. The viscosity of the product was also substantially reduced from around 24 400 to 6420 mPa s by the decomposition of the large hydrocarbon molecules.