PDM++: Planning Framework from a Construction Requirements Perspective

Construction requirements represent the key preconditions for construction. These include topological precedence, key resources, space requirements, etc. Consequently, identifying them is necessary for feasible construction planning to be achieved. Despite this, little attention has been given to the impact of construction requirements on a project schedule, possibly because of the lack of a good tool for representing these requirements. This paper distinguishes construction requirements into static and dynamic types, according to changes in the need of the requirement during its life cycle. A modeling framework, PDM++, is then proposed. The framework deals with schedule constraints arising from both static and dynamic construction requirements, provides greater semantic expression to capture schedule constraints unambiguously, and facilitates the representation of interdependent conditional relationships. The concept of meta-intervals is also devised to represent complex requirements involving several activities and schedule constraints, and it facilitates modeling at higher levels of plan abstractions. Finally, an illustrative case study is presented to show the applicability of PDM++ in representing schedule constraints and alternative scheduling from a construction requirements perspective.     

A novel polyurethane prepolymer as toughening agent: Preparation,characterization, and its influence on mechanical and flame retardant properties of phenolic foam

A novel phosphorus‐ and silicon‐containing polyurethane prepolymer (PSPUP) was synthesized by the chemical reaction of phenyl dichlorophosphate with hydroxy‐terminated polydimethylsiloxane (HTPDMS) and subsequently with toluene‐2,4‐diisocyanate. The structure of PSPUP was confirmed by Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance. Afterward, a series of phenolic foams (PF) with different loadings of PSPUP toughening agent were prepared. The apparent density and scanning electron microscopy results showed that the addition of PSPUP can increase the apparent density of phenolic foam. The compressive, impact and friability test results showed that the incorporation of PSPUP into PF dramatically improved the compressive strength, impact strength, and reduced the pulverization ratio, indicating the excellent toughening effect of PSPUP. The limiting oxygen index of PSPUP modified phenolic foams remained a high value and the UL‐94 results showed all samples can pass V0 rating, indicating the modified foams still had good flame retardance. The thermal properties of the foams were investigated by thermogravimetric analysis under air atmosphere. Moreover, the thermal degradation behaviors of the PF and PSPUP/PF were investigated by real‐time Fourier transform infrared spectra. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of Acetic Acid as Catalyst on the Properties of Epoxy Foam

In this study, the effect of acetic acid used as catalyst in promoting the decomposition rate of blowing agent (sodium bicarbonate) in epoxy foam was done. Hard epoxy foam was produced using mechanical mixing technique. Epoxy foam has been tested with adding acetic acid at 5 phr and different content of sodium bicarbonate which are 0, 5, 10, 15, and 20 phr, respectively. The effect of acetic acid on the viscosity, density, mechanical properties, and dielectric constant has been studied. The results were compared between with and without acetic acid in the system. Viscosity reading was increased with increasing the content of sodium bicarbonate due to the rapid production of bubbles that created porosity in the structure of epoxy foam. The addition of acetic acid is able to reduce the dielectric constant. In overall, the density, flexural strength and modulus dropped for the epoxy foam with acetic acid as compared to that of without acetic acid.     

A fully-coupled simulation of vortical structures in a large-scale buoyant pool fire

A numerical study simulating the temporal vortical structures of a large-scale buoyant pool fire has been carried out using a fully-coupled Large Eddy Simulation (LES) model which incorporates all essential subgrid scale (SGS) turbulence, combustion, radiation and soot chemistry considerations. Based on the strained laminar flamelet approach, a scalar dissipation conditioned SGS combustion model is introduced to distinguish the highly non-equilibrating burn and extinguishment of flamelets commonly found in pool fires. Numerical results from the present model are validated and compared against a one-meter diameter methane pool fire experimental data and predictions from other LES field models. The predicted time-averaged velocity and temperature profiles have been found to be in good agreement with the experimental data and those numerical results. Qualitative comparisons of instantaneous velocity field against experimental data have revealed that the dynamic phenomena of large-scale vortical structures and its associated puffing behaviour of pool fire are well captured. Quantitative comparisons of velocity time history and pulsation frequency also show close agreement against experimentally evaluated quantities.     

Characterization of different forms of vulcanized natural rubbers as elastomer spacer and toughening agent in two-matrix filled epoxy/natural rubber/graphene nano-platelets system

This paper compares the effects of different forms of vulcanized natural rubbers on the physical, mechanical, thermal, and electrical performances of filled epoxy systems. In this study, natural rubber (NR), liquid natural rubber (LNR), and recycled natural rubber (rNR) were introduced into filled epoxy systems. The results show that flexural strength, modulus, and toughness properties of filled epoxy system were enhanced with NR phases, as compared to those with LNR and rNR. Scanning electron micrograph revealed that the particle sizes of NR phases dispersed within epoxy matrix were smaller and more uniform, as compared to those with LNR and rNR phases. Incorporation of NR phases has improved the thermal stability of filled system, followed by LNR and rNR. This is attributed to more heat energy needed to overcome good interfacial bonding between epoxy matrix and small NR phases. X-ray diffraction analysis result showed that filled epoxy/NR/GNP system has higher 2θ values, indicated that d-spacing in between GNP nano-fillers has the closer distance. Electrical bulk conductivity values of filled epoxy/NR/GNP system were the highest. Small NR phases acted as elastomer spacers, which provided better “GNP packing efficiency” and realigned the GNP nano-fillers to form more effective conductive pathways for electrons hopping. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47188.     

Ototoxicity of sodium nitroprusside

Nitric oxide (NO) not only has normal physiological roles like vasodilation and neurotransmission in the living organism, it could also have possible neurodestructive effects under certain pathological conditions. The present study aimed to determine whether direct exposure of guinea pig cochlea to a NO donor like sodium nitroprusside (SNP), or a nitric oxide synthase (NOS) inhibitor like N(G)-nitro-L-arginine methyl ester (L-NAME), would cause damage to the auditory hair cells. A piece of gelfoam was placed on the round window of the right ear of adult albino guinea pigs. It was then soaked with 0.1 ml of SNP (3.4 microM), 0.1 ml of L-NAME (9.3 microM or 18.5 microM) or 0.1 ml of injection water, the vehicle used to dissolve the above chemicals. Twelve animals receiving SNP were perfused 1 day, 2, 3 and 7 days later, with three animals being used for each survival period. Six animals receiving L-NAME were allowed to survive up to 7 days before perfusion. Eight animals receiving injection water or 0.45% saline were used as controls. With the scanning electron microscope, the inner and outer hair cells were counted over a 1 mm length of the basilar membrane in each turn of every cochlea. The results showed that, in animals treated with L-NAME at both concentrations stated, no significant loss of either inner or outer hair cells was noted in any part of the cochlea studied. However, as early as 1 day after SNP treatment, a striking loss of inner and outer hair cells was observed in the three lower turns of the cochlea. Damage to the outer hair cells was extended to the apical turn with increasing survival period, but no significant loss of inner hair cells was evident in the apical turn at any of the survival periods studied. To rule out the possibility that the effects were due to the presence of cyanide, a metabolite of SNP, hydroxycobalamin was introduced into the scala tympani of three animals through a cannula-osmotic pump device during SNP treatment. There was no significant difference in the results between the groups with and without hydroxycobalamin infusion 7 days after SNP treatment. The present study suggests that an excessive production of NO in the inner ear could lead to extensive loss of hair cells.     

Linamarin sensors: interference-based sensing of linamarin using linamarase and peroxidase

An interference-based linamarin sensor is developed. Horseradish peroxidase (HRP) is adsorbed on a pyrolytic graphite (PG) electrode, and then linamarase from cassava is cross-linked with glutaraldehyde on the electrode surface. The prepared bienzyme electrode is poised at -300 mV vs Ag/AgCl for 40 s to reduce dissolved O(2) to H(2)O(2) at the PG surface. The potential is then stepped to 0 mV, at which point the accumulated H(2)O(2) is reduced, though the O(2) reduction does not proceed. Since the H(2)O(2) reduction is catalyzed by HRP, the transient cathodic current is inhibited by cyanide, which is liberated from linamarin by linamarase. Therefore, the transient current is a function of the linamarin concentration. This sensor responds to 1 × 10(-5)-5 × 10(-3) M linamarin and can estimate a linamarin concentration of a cassava extract.     

The conservation-redevelopment dilemma in Singapore: The case of the Kampong Glam historic district

Conservation-redevelopment conflicts are increasingly gaining prominence on the urban agendas of cities in the developing world. This paper examines the role urban conservation plays within the broader framework of national ideology and policies in Singapore, a city which faces intensive redevelopment pressures. It explains how, from the perspective of the state, redevelopment and conservation can both be accommodated within the ambit of modernist planning and goals. After outlining various preservation and conservation schemes initiated by state agencies, the paper goes on to argue that, contrary to state rhetoric and despite the fact that conservation is given some priority in the planning of the city, the conservation-redevelopment dilemma has not been solved but has taken on new dimensions in the 1990s. Specifically, the paper shows by means of a case study of the Kampong Glam Historic District that conflict arises because gazetted monuments and conservation areas often slice up the organic form and texture of cultural hearths in an arbitrary fashion, legislating boundaries between a defended zone perceived to be of historical value and an excluded landscape, which is threatened with excision.     

A Study of Particle Rebounding Characteristics of a Gas–Particle Flow over a Curved Wall Surface

The particle rebounding characteristics of a gas–particle flow over a cylindrical body is investigated. With the aid of both computational and experimental approaches, the mean particle flow patterns, comprising both incident and rebound particles resulting from the impact of particles on a curved wall surface, are examined. In the experimental investigation, a two-dimensional Laser Doppler Anemometry (LDA) technique is used in the immediate vicinity of the body surface to measure the instantaneous incident and rebound particle velocities. The Reynolds-Averaging Navier-Stokes equations are solved for the continuum gas phase, and the results are used in conjunction with a Lagrangian trajectory model to predict the particle-rebound behavior in the immediate vicinity of the cylindrical wall. The computational observations, also confirmed through experiments, reveal a particle rebound zone where the mean particle flow pattern is significantly modified due to the contribution of the rebound particles during the process of particle–wall impact interaction. This particle rebound zone is found to be a function of mainly the Stokes number (particle inertia), and to a lesser extent on the fluid Reynolds number (gas flow condition), except for high gas flow velocities and restitution coefficients (particle-wall impact characteristics). Analysis of the effect of the above-mentioned parameters on the rebounding particle flow characteristics and their interrelationship has provided a better understanding of the behavior of particle flow impinging on a solid wall body. The beneficial contributions of the experimental and computational approaches in their ability to better quantify the particle–wall impact interaction phenomena present additional foundational investigations that could be further undertaken to better comprehend the particle behavior in curved wall surfaces. Such invaluable information has direct applications to industrial devices such as commercial heat exchangers and inertial impactors.     

A COMPARISON OF DIFFERENT TECHNIQUES FOR WATER-BASED EXTRACTION OF PECTIN FROM ORANGE PEELS

The extraction of pectin from orange peels has been studied using microwave and conventional extraction, with operating conditions including different extraction periods, different solvent pHs, and different types of solvent systems. The extracted pectin from orange peels was initially precipitated with concentrated ethanol and was quantified by the carbazole assay. For microwave extraction, the greatest total amount of pectin yield was found to be 5.27% on a dry basis for 15 minutes of extraction, although the greatest amount of material per unit time (%/min) was obtained after 5 minutes. This amount was the same as that extracted using Soxhlet extraction for three hours. The 15-minute microwave extraction period was further investigated at pH values of 1.5, 2.0, 5.5, and 10.0. The greatest amount of pectin was extracted from orange peels at the most strongly acidic condition of pH 1.5. The effect of a solvent system containing ethanol and EDTA (ethylenediamine tetraacetic acid) with a 15-minute extraction period and a pH of 1.5 was studied, giving approximately double the amount of pectin extracted using distilled water.