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81.
Poly(methyl methacrylate) containing a small amount of pendant 2,2,6,6-tetramethylpiperidinyl group was found to be miscible with poly(styrene-co-acrylonitrile) and with poly(α-methyl styrene-co-acrylonitrile). The poly(α-methyl styrene-co-acrylonitrile) blends exhibited lower critical solution temperatures. Phase separation of the poly(styrene-co-acrylonitrile) blends could not be induced by heating up to 270°C. 相似文献
82.
M. N. Charalambides S. M. Goh L. Wanigasooriya J. G. Williams W. Xiao 《Journal of Materials Science》2005,40(13):3375-3381
The mechanical and frictional properties of foods have received considerable attention in recent years as accurate material data are needed for the simulation of large scale processing operations as well as providing a basis for product quality and development. In this study, uniaxial compression tests were performed on bread flour/water dough. Cylindrical samples of various heights and diameters were tested under both lubricated and non lubricated conditions. The stress-strain data showed a dependency on sample dimensions when no lubricant was used due to surface friction effects. This dependency was eliminated when silicon oil of 500 centistokes viscosity was used as a lubricant and the true stress-strain data were obtained experimentally. A theoretical expression derived from an equilibrium analysis of a compressed disc under frictional conditions was used to determine the coefficient of friction and the true stress-strain curve from unlubricated data. The true stress-strain data were also determined by an empirical extrapolation procedure. Finally, an iterative numerical procedure based on Finite Element Analysis confirmed the calculated values for both the coefficient friction and the true stress-strain curve. 相似文献
83.
BACKGROUND: Skin cancer is the seventh most common cancer in Singapore. This study was performed to determine the pattern of skin cancers seen in a tertiary referral skin hospital. METHODS: Histologically confirmed skin cancers, seen between 1980 and 1991, were analyzed according to age, sex, race, site, and presence/absence of preexisting skin conditions. RESULTS: Of a total of 520 patients, the commonest skin cancer was basal cell carcinoma (BCC) (36.5%), followed by squamous cell carcinoma (SCC) (24.4%), Bowen's disease (16.7%), and mycosis fungoides (9.0%). Malignant melanomas (2.7%) were rare. The sharp increase (26.2%) in BCC in the recent 3 years was largely contributed by a fivefold increase of non-resident Caucasian patients with BCC. All types of skin cancers were more common in Chinese (78.1%) and less frequent in the more pigmented races (9.4%). The men to women ratio was 1.72:1. The peak age distribution was in the 51-70-year group, with the exception of mycosis fungoides (31-50 years). The commonest site involved in BCC was the head and neck (67.0%) and in Bowen's disease the trunk (33.3%). Squamous cell carcinoma was found on the head and neck and the lower extremities with equal frequency (29.3%) and 46.2% of all SCC on the lower extremities occurred in leprosy patients with chronic trophic ulcers. Of patients with Bowen's disease involving the nonsunexposed parts (trunk and upper extremities), 42.6% had probable arsenic exposure evident either from the history or clinical examination. Malignant melanomas were commonly located on the foot (71.4%). CONCLUSIONS: The commonest skin cancers seen were BCC, SCC, Bowen's disease, and mycosis fungoides. There were differences in the site distribution of SCC, Bowen's disease, and malignant melanomas in our study when compared to studies in Caucasians. 相似文献
84.
Recently, Goh and Wang (1989) presented a unified approach for solving cross-section structural optimization problems under general constraints. In a continual development of the above unified approach, two important extensions have been made to enhance its versatility. They allow the optimization of variable piecewise segmental lengths and/or variable interior point constraint positions. This sequel paper shows how these extensions are incorporated in the unified approach and presents the derivation of gradient expressions (required in the optimization routine) of the objective functional and constraints with respect to these new variables. Some illustrative examples are solved to demonstrate the new features in the approach. Furthermore, a recent refinement in handling continuous state constraints is presented.On sabbatical leave from the Department of Civil Engineering, National University of Singapore, Kent Ridge, Singapore 0511 相似文献
85.
Rework has become one of the most common concerns in construction projects. This study aims to investigate the client-related rework (CRR) in Singapore-based building projects. To achieve the objectives, a literature review and questionnaire survey was conducted and data were collected from 381 projects performed by 51 companies. The results confirmed that the client contributed most to rework. 41 of the 51 companies (80.4%) experienced CRR, and 226 of the 381 projects (59.3%) experienced CRR, which increased project cost by 7.1% and caused 3.3 weeks' delay on the average. Additionally, “replacement of materials by the client” was the cause with the highest frequency of occurrence, while “change of plans or scope by the client” contributed most to CRR and exerted most impact on project cost, schedule and quality performance. This study expands the literature and provides an in-depth understanding of the CRR in Singapore for both practitioners and researchers. 相似文献
86.
Silicon/silicon carbide (Si/SiC) core–shell nanowires grown on quartz substrates by hot-wire chemical vapor deposition were studied. Nickel was used as a catalyst to induce the growth of these core–shell nanowires followed by the vapor–solid–solid growth mechanism. The nanowires were grown by varying substrate-to-filament distance; ds-f from 1.9 to 3.1 cm with an interval of 0.4 cm. Lower ds-f produced a high density of straight core–shell nanowires. A highly crystalline single crystal Si core of the nanowires was produced at lower ds-f as well. Presence of Si and SiC nano-crystallites embedded within an amorphous matrix in the shell of the nanowires exhibited a high intensity of photoluminescence emission spectra from 600 to 1000 nm. The effects of the ds-f on the structural and optical properties of the nanowires are discussed. 相似文献
87.
T. N. Goh 《Quality and Reliability Engineering International》2014,30(8):1191-1195
Routine applications of design of experiments (DOE) by non‐mathematicians assume that each response value is static in nature, i.e. with an expected value that is constant for a given set of input factor settings. When this assumption is not valid, it is important to capture the dynamic characteristics of the response for effective process or system characterization, monitoring, and control. With the purpose of recognizing the self‐changing nature of the response owing to factors other than those built into the DOE, thereby gaining a better ability to shape the behavior of the response, this paper describes the reasoning and procedure needed for such ‘parametric responses’, via common techniques of mathematical modeling and optimization. The procedure is intuitive but essential and useful in DOE studies as these become increasingly popular by practitioners in the context of improvement projects such as those related to Six Sigma or stand‐alone performance optimization initiatives. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
88.
89.
All‐Carbon Nanoarchitectures as High‐Performance Separation Membranes with Superior Stability 下载免费PDF全文
Kunli Goh Wenchao Jiang Huseyin Enis Karahan Shengli Zhai Li Wei Dingshan Yu Anthony G. Fane Rong Wang Yuan Chen 《Advanced functional materials》2015,25(47):7348-7359
The application of graphene‐based membranes is hindered by their poor stability under practical hydrodynamic conditions. Here, nanocarbon architectures are designed by intercalating surface‐functionalized, small‐diameter, multi‐walled carbon nanotubes (MWCNTs) into reduced graphene oxide (rGO) sheets to create highly stable membranes with improved water permeability and enhanced membrane selectivity. With the intercalation of 10 nm diameter MWCNTs, the water permeability reaches 52.7 L m?2 h?1 bar?1, which is 4.8 times that of pristine rGO membrane and five to ten times higher than most commercial nanofiltration membranes. The membrane also attains almost 100% rejection for three organic dyes of different charges. More importantly, the membrane can endure a turbulent hydrodynamic flow with cross‐flow rates up to 2000 mL min?1 and a Reynolds number of 4667. Physicochemical characterization reveals that the inner graphitic walls of the MWCNTs can serve as spacers, while nanoscale rGO foliates on the outer walls interconnect with the assimilated rGO sheets to instill superior membrane stability. In contrast, intercalating with single‐walled nanotubes fails to reproduce such stability. Overall, this nanoarchitectured design is highly versatile in creating both graphene‐rich and CNT‐rich all‐carbon membranes with engineered nanochannels, and is regarded as a general approach in obtaining stable membranes for realizing practical applications of graphene‐based membranes. 相似文献
90.
Keewah Chan Zarina AspanutBoontong Goh Muhamad Rasat MuhamadSaadah A. Rahman 《Thin solid films》2011,519(15):4952-4957
Nanostructured materials fabricated by dispersing metal particles on the dielectric surface have potential application in the field of nanotechnology. Interfacial metal particles/dielectric matrix interaction is important in manipulating the structural and optical properties of metal/dielectric films. In this work, a thin layer of gold (Au) was sputtered onto the surface of silicon oxide, SiOx (0.38 < x < 0.68) films which was deposited at different N2O/SiH4 flow rate ratios of 5 to 40 using plasma enhanced chemical vapor deposition (PECVD) technique prior to the annealing process at 800 °C. FTIR spectra demonstrate the intensity and full-width at half-maximum (FWHM) of Si-O-Si stretching peaks are significantly dependent on the N2O/SiH4 flow-rate ratio, η. The films deposited at low and high N2O/SiH4 flow rate ratios are dominated by the oxygen and silicon contents respectively. The size and concentration of Au particles distributed on the surface of SiOx films are dependent on the N2O/SiH4 flow-rate ratio. High concentrations of Au nanoparticles are distributed evenly on the surface of the film deposited at N2O/SiH4 flow-rate ratio of 30. Crystallinity and crystallite sizes of Au are enhanced after the thermal annealing process. Appearance of surface plasma resonance (SPR) absorption peaks at 524 nm for all samples are observed as a result of the formation of Au particles. The annealing process has improved SPR peaks for all the as-deposited films. The energy gap of the as-deposited Au/SiOx films are in the range of 3.58 to 4.38 eV. This energy gap increases after the thermal annealing process except for the film deposited at η = 5. 相似文献