Content uploaded by Charles Hin Joo Bong
Author content
All content in this area was uploaded by Charles Hin Joo Bong
Content may be subject to copyright.
A preview of the PDF is not available
Tools for Integrated River Flood Management (Hydraulics Modeling and Logical Framework Analysis)
Abstract
Hydraulics simulation can be used as a supporting tool for planning and developing a framework, such as Integrated Flood Management for river management. To demonstrate this, a hydraulics model for the Sarawak River Basin was run using InfoWorks RS software by Wallingford Software, UK. InfoWorks River Simulation (RS) was chosen because its applicability has been proven and widely used to model Malaysian rivers. The extraction of computed floodwater level and flood maps for different time intervals would produce the rate of floodplain submergence from river bank level. This information could be incorporated into a logical framework to support decisions on flood management measures. Thus, hydraulics models can be used as tools to provide the necessary decision parameters for developing logical frameworks which would act as to guide the planning when it involved various stakeholders’ participation.
The objective of the present paper is to propose a family of separate-type estimators of population mean in stratified random sampling in presence of non-response based on the family of estimators proposed by Khoshnevisan et al. (2007). Under simple random sampling without replacement (SRSWOR) the expressions of bias and mean square error (MSE) up to the first order of approximation are derived. The comparative study of the family with respect to usual estimator has been discussed. The expressions for optimum sample sizes of the strata in respect to cost of the survey have also been derived. An empirical study is carried out to shoe the properties of the estimators.
Results of an investigation are presented which was carried out to study the effect of silica filler structure on the effective crosslink density and on mechanical properties. Vulcanizates of silicone, SBR, and EPM were included in the work. A compression modulus method was used for crosslink density determination. The results showed that, in peroxide-cured silicone and EPM elastomers, the crosslink density increased with filler structure, but after cleavage of polymer-filler bonds by the NH//3-modified swelling environment, there was very little change of crosslink density with filler structure increase. The effect of increasing filler structure on crosslink density in the SBR elastomers was very slight, showing a small increase in progressing from discrete particles to low structure and thereafter no change. It is demonstrated that polymer-filler bonds are required, in combination with occluded volume, in order to achieve a substantial increase in both 200% modulus and crosslink density.
From studies of a series of accelerated sulfur vulcanizations of natural rubber, the structural basis of the reversion in macroscopic physical-mechanical properties has been determined. The amount of chemically induced trans-methine butadiene-like structure increases as the reversion process proceeds. When there is no observable reversion, there is no detectable trans-methine butadiene-like structure. The presence of the trans-methine butadiene-like structure is detrimental to the properties of the natural rubber vulcanizate. The vulcanization process involves two competing processes, namely, crosslinking and desulfuration. The latter process produces the trans-methine structure which is responsible for the reversion in properties.
This paper is concerned with the mechanisms of the vulcanization reversion of natural rubber which is dependent on the nature of the curing system, choice of accelerator, and the temperature and time of cure. Conventional cure systems which contain a high ratio of sulfur to accelerator have higher moduli at optimum cure, faster rates of cure, but are more vulnerable to reversion. The EV systems, which contain a low ratio of sulfur to accelerator, demonstrate good resistance to reversion but lower moduli at optimum cure and slower rates of cure. The sulfurless cure systems, which represent an extreme case, show greater reversion resistance than EV systems. Of the three accelerators tetramethyl thiuramdisulfide (TMTD), diphenylguanidine (DPG), and N-oxydiethylene benzothiazole-2-sulfenamide (MOR) studied, MOR gives the best performance, followed by DPG, then TMTD in terms of reversion resistance for the cure times studied.
SBR compounds were filled with 17 carbon blacks covering the whole range of rubber grades and tested for bound-rubber content. It was found that the bound-rubber content of a polymer at high loadings is higher for large surface-area carbon blacks. On the other hand, the bound-rubber content per unit of interfacial area in the compound (specific bound-rubber content) decreases with increasing specific surface area and filler loading. This observation was interpreted in terms of interaggregate multiple molecular adsorption, filler agglomeration, and change of molecular weight of rubber during mixing. When the comparison was carried out at critical loading of a coherent mass, the specific bound-rubber content was found to be higher for the high-surface-area products which are characterized by high surface energies. The critical loading of coherent mass of bound rubber also shows a strong surface-area dependence, indicating that large particle carbon blacks give high critical loadings. The measurements of bound rubber at high temperatures for carbon-black-filled compounds and in an ammonia atmosphere for silica-filled compounds suggest that bound rubber is caused essentially by physical adsorption.
As shown in previous papers of this series, the main feature of silicas with regard to surface energy, which distinguishes them from carbon blacks, is a low dispersive component, γsd, and a high specific component, γssp, of surface energy. The low γsd would result in a lack of interaction between filler and hydrocarbon rubbers, while the high γssp would suggest a high degree of agglomeration of the filler particles in the polymer matrix. In this study, the surface free energies and the energy distribution on the surfaces of precipitated silicas which had been modified with octadecyltrimethoxy silane, 3-thiocyanatopropyltriethoxy silane and bis(3-trimethoxysilylpropyl)-tetrasulfane, respectively, were investigated by chromatography at infinite dilution and at finite concentration. A comparison with the initial silica suggests a drastic decrease in surface energy, especially of the specific component, as a result of the modification and a strong dependence of surface energy on the chemical nature of the grafts and the ratio of these grafts. The energy distribution function shows that, while the surface of the ungrafted silica is heterogeneous, the heterogeneity of the fully modified surface is drastically reduced, particularly when the product was modified with octadecyltrimethoxy silane.
High fructose syrup (HFS) is a highly valued liquid sweetener for beverage, confectionery and processed food industry, owing to its special attributes like high solubility and non-crystalline nature. Even though 85% HFS production is from corn, increased food demand has necessitated the search for alternative substrates and starchy root crops like cassava and sweet potato are potential raw materials. However, the economic production needs direct use of the roots and simplification of the cost-intensive steps. This study aims at the direct enzymatic conversion of roots for HFS production. Glucose yield was compared from six treatment systems viz., liquezyme–dextrozyme (T1), Stargen (T2), Stargen in two split doses (T3), Spezyme–Stargen (T4), Stargen (60 °C;T5) and Spezyme–Stargen (60 °C; T6). Glucose was higher (22–25%) from cassava than sweet potato (14.0–15.7%), owing to the high starch content in cassava. Conversion to glucose was higher in T1–T4 (95–98%) compared to 88–92% for T5 and T6. Although the fructose yield was more from cassava (8.36–9.78%) than sweet potato (5.2–6.0%), percentage conversion was similar (37–38%) for both the roots. The cost of production of HFS could be reduced by the direct hydrolysis of root slurry using Stargen.
This paper is concerned with the production and properties of fuel pellets for use in energy from waste technologies. The analysis conducted was performed using feedstocks made up of residues from a range of Mechanical Biological Treatment plants. Such plants are likely to be utilised as future waste solutions in order for the UK to meet challenging EU solid waste treatment targets.Two major themes were examined, these were the physical and thermal characteristics of the extruded fuel pellets. This was further investigated in the context of the parameters required during production and the properties of the extruded product. Pelletised fuel was produced using a laboratory-scale ram-driven extruder. Analysis of the produced pellets was undertaken by testing the compressive strengths in a tensile testing machine. Devolatisation characteristics were measured in an inert atmosphere in an electric vertical tube furnace and mass balance.Results showed that the resultant pellet compressive strength was not influenced significantly by extrusion conditions. Analysis of the pellets in a high-temperature environment highlighted that there was evidence of several components devolatilising at ∼280 °C and ∼420 °C and that little of the sample was left post devolatisation. The study indicated that heating rate did not appear to affect amount of devolatisation i.e. waste derived briquettes devolatise quickly.
An unstructured model of hyaluronic acid (HA) fermentation by Streptococcus zooepidemicus considering the effect of glucose was proposed and validated. Experiments were performed in a glucose concentration range of 10–60gl−1 in a 2l bioreactor of batch mode. Three different models, namely, the Logistic equations for cell growth, the Logistic incorporated Leudeking–Piret-like equation for glucose consumption, and the Logistic incorporated Leudeking–Piret equation with time delay, Δt, for HA productions were proposed. The kinetic parameters were estimated by fitting the experimental data to the models. Simulation was made using the estimated kinetics parameter values and was compared with the experimental data. For glucose inhibition, S. zooepidemicus tolerated up to 40gl−1 glucose. Beyond this concentration, cell growth was inhibited. The Han and Levenspiel model and the Teissier-type model gave the best fit for all the systems studied with R2 of 0.997 and 0.985, respectively.