Application of experimental non-linear control based on generic algorithm to a polymerization reactor

The dynamics of free radical polymerization of styrene and on-line control of temperature in a cooling jacketed batch polymerization reactor is investigated. The benzoyl peroxide initiator is introduced into the reactor once at the beginning of the reaction to obtain the desired monomer conversion and the desired average chain length in a minimum reaction time. The optimal constant set temperature, which is generally realized in industrial applications, and the set profile are used as two different optimal operating conditions. The temperature control of the polymerization reactor is achieved experimentally and theoretically. The control of nonlinear systems has progressed considerably, and various nonlinear process model based control techniques have appeared in the literature. The problem is how to tune the controller in order to obtain comparable closed loop responses. Generic model control (GMC) is applied and the performance of the control results are compared with the previously published control results.     

The development of an audit technique to assess the quality of safety barrier management

This paper describes the development of a management model to control barriers devised to prevent major hazard scenarios. Additionally, an audit technique is explained that assesses the quality of such a management system. The final purpose of the audit technique is to quantify those aspects of the management system that have a direct impact on the reliability and effectiveness of the barriers and, hence, the probability of the scenarios involved.

First, an outline of the management model is given and its elements are explained. Then, the development of the audit technique is described. Because the audit technique uses actual major hazard scenarios and barriers within these as its focus, the technique achieves a concreteness and clarity that many other techniques often lack. However, this strength is also its limitation, since the full safety management system is not covered with the technique. Finally, some preliminary experiences obtained from several test sites are compiled and discussed.     

Variation in rubber chemistry and dynamic mechanical properties of the milking liner barrel with age

The milking liner is the interface between the milking machine and the cow. Liner properties important to milking performance were investigated for liners of different ages using discriminating tests rather than the normal, rubber-industry quality control-based tests. Large variations in the liner mechanical properties occurred depending on where the sample was taken; stiffness increased 4-fold 40 to 50 mm below the top of the liner. This was related to changes in the chemistry of the rubber created by absorption of milk-derived products (MDP) into the rubber and losses of formulation components, particularly 50% of the plasticizer and all of the antidegradent 40 to 50 mm below the top of the liner, with age and use. The presence of MDP leads to calcium and phosphate deposits on the inner surface of the liner barrel where the MDP was absorbed. The detailed liner properties can be used to explain the forces on the cow's teat and its reactions and effects on milk flow behavior, and to guide future liner development.     

Investigation of the Sharkskin melt instability using optical Fourier analysis

An optical method allowing the characterization of melt flow instabilities typically occurring during an extrusion process of polymers and polymer compounds is presented. It is based on a camera-acquired image of the extruded compound with a reference length scale. Application of image processing and transformation of the calibrated image to the frequency domain yields the magnitude spectrum of the instability. The effectiveness of the before mentioned approach is shown on Styrene-butadiene rubber (SBR) compounds, covering a wide range of silica filler content, extruded through a Göttfert capillary rheometer. The results of the image-based analysis are compared with the results from the sharkskin option, a series of highly sensitive pressure transducers installed inside the rheometer. A simplified version of the code used to produce the optical analysis results is included as supplementary material. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48806.     

A review of varietal change in roots,tubers and bananas: consumer preferences and other drivers of adoption and implications for breeding

This review of the literature on varietal change in sub-Saharan Africa looks in detail at adoption of new varieties of bananas in Uganda, cassava in Nigeria, potato in Kenya, sweetpotato in Uganda and yams in Côte d’Ivoire. The review explored three hypotheses about drivers of varietal change. There was a strong confirmation for the hypothesis that insufficient priority given to consumer-preferred traits by breeding programmes contributes to the limited uptake of modern varieties (MVs) and low varietal turnover. Lack of evidence meant the second hypothesis of insufficient attention to understanding and responding to gender differences in consumer preferences for quality and post-harvest traits was unresolved. The evidence on the third hypothesis about the informal seed system contributing to slow uptake of MVs was mixed. In some cases, the informal system has contributed to rapid uptake of MVs, but often it appears to be a barrier with inconsistent varietal naming a major challenge.     

Evidence of debromination of decabromodiphenyl ether (BDE-209) in biota from a wastewater receiving stream

Decabromodiphenyl ether (BDE-209) is a high production volume flame retardant. To date, regulation and control of its environmental release have been minimal. Once in the environment, BDE-209 may encounter conditions favoring debromination, potentially forming congeners with greater toxicity, bioaccumulation potential, and persistence. However, (photolytic and in vivo) debromination has only been demonstrated under laboratory scenarios. To examine whether debromination was likely in the field, PBDE congener profiles were tracked from a wastewater treatment plant (sludge) to receiving stream sediments and associated aquatic biota. BDE-209 and 23 additional PBDEs were detected. Sludge congener profiles resembled the commercial penta- and deca- formulations, suggesting minimal -209 debromination during wastewater treatment. Similar profiles were observed in surficial sediments at the outfall and downstream. However, sunfish (Lepomis gibbosus), creek chub (Semotilus atromaculatus), and crayfish (Cambarus puncticambarus sp. c) collected near the outfall contained tri- through deca-PBDEs, including congeners not detected in the commercial deca-mixture, sludges or sediments (BDE-179, -184, -188, -201, and -202). A previous in vivo laboratory study identified these as -209 debromination products. This supports the hypothesis that metabolic debromination of -209 does occur in the aquatic environment under realistic conditions. Hence assessments that assume no BDE-209 debromination may underestimate associated bioaccumulation and toxicity attributable to the less brominated congeners produced.     

Using Design Projects for Program Assessment

Engineering education is undergoing an assessment of its own. Organizations responsible for engineering education are looking at themselves in an attempt to improve their total quality as well as the quality of the programs they assess. The reasons for these changes include issues relating to cost, efficiency and quality of engineering education programs, and the increased demand for accountability by constituencies (state legislatures, students, employers). The ability to work in a group and to acquire and assimilate new knowledge effectively is another key requirement of graduate engineers and is difficult to assess. This article describes the national and local forces for more definitive outcome assessment and how we have responded to those forces. The article in particular describes how we have used senior design projects as an important part of undergraduate program assessment.     

Similarities and differences between working memory and long-term memory: Evidence from the levels-of-processing span task.

Two experiments compared the effects of depth of processing on working memory (WM) and long-term memory (LTM) using a levels-of-processing (LOP) span task, a newly developed WM span procedure that involves processing to-be-remembered words based on their visual, phonological, or semantic characteristics. Depth of processing had minimal effect on WM tests, yet subsequent memory for the same items on delayed tests showed the typical benefits of semantic processing. Although the difference in LOP effects demonstrates a dissociation between WM and LTM, we also found that the retrieval practice provided by recalling words on the WM task benefited long-term retention, especially for words initially recalled from supraspan lists. The latter result is consistent with the hypothesis that WM span tasks involve retrieval from secondary memory, but the LOP dissociation suggests the processes engaged by WM and LTM tests may differ. Therefore, similarities and differences between WM and LTM depend on the extent to which retrieval from secondary memory is involved and whether there is a match (or mismatch) between initial processing and subsequent retrieval, consistent with transfer-appropriate-processing theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electro-Optics and Band Gap Energies of Nanosilver-Coated TiO_2 Nanotubes on Titanium Metal

TiO_2 nanotubes on Ti metal surface were prepared by the electrochemical anodization method. Then, nanosilver was deposited onto the nanotubes by the electroless dip coating and the anodization. The obtained TiO2 nanotubes were examined by using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, cyclic voltammetry, and UV–Vis. The electrochemical band gap(E_g~(CV)) of the nanosilver-coated TiO_2 nanotubes prepared by the anodization was found as 1.54 eV. Using the UV–Vis measurements, the optical band gap energy(E_g~(op).) was calculated as 1.51 eV for the Ag/TiO_2 nanotubes obtained by electroless dip coating. The electrical conductivity of the TiO_2 nanotubes also increased from 3.0 9 10-4 to 34.7 S/cm after nano Ag deposition by the anodization method.These Ag/TiO_2 nanotubes with low band gap and high electrical conductivity are desirable for the applications in electronics, Li-ion batteries, and solar cells.     

Operational and maintenance data collection

This article presents an effort to collect operational and maintenance data on 240 power generation, power distribution and heating, ventilation, and air conditioning (HVAC) items, including gas turbine generators, diesel engine generators, electrical switchgear, cables, circuit breakers, boilers, piping, valves, pumps, motors, and chillers.