Development of CNT reinforced Al2O3-TiO2 coatings for boiler tubes to improve hot corrosion resistance

This study examines the hot corrosion behaviour of plasma-coated T12 steel for 10 cycles of 100 h each in an industrial boiler. The coating contains CNT (carbon nanotubes) reinforced alumina-titania powders. The substrates were exposed to the boiler at 750 °C. A thermogravimetric examination was conducted to evaluate the kinetics of corrosion. Corroded samples were examined with scanning electron microscopy and x-ray diffraction analysis after the end of the corrosion cycle. This research study concludes that CNT-reinforced coatings provide better corrosion resistance than conventional alumina coatings in the boiler environment

Performance evaluation of dynamically flattened gain L-band RAMAN-EDFA-RAMAN hybrid optical amplifier for super dense wavelength division multiplexing system

In this paper, we have evaluated the performances of super dense Wavelength Division Multiplexing (SD-WDM) system with respect to flat gain. RAMAN-EDFA-RAMAN hybrid optical amplifier (HOA) is the backbone of the system. Further, this model has investigated the effects in terms of L-band flattened gain, output power, crosstalk, and bit error rate with 50 GHz channel spacing. Flat gain greater than 14 dB has obtained at 5 mW and reported the poor performances by 7 mW and 17 mW with the range of 188-192 THz. Gain variation < 2.1 dB has obtained. Highest output power has also obtained at 5 mW, 7Mw and 17 mW accordingly. Final conclusion has recommended that better gain flatness has attained without using any costly components such as gain equalizer and multi-pumping for SD-WDM system

Mechanical and microstructural properties of yttria-stabilized zirconia reinforced Cr3C2-25NiCr thermal spray coatings on steel alloy

In this research work, nano yttria-stabilized zirconia (YSZ) reinforced Cr3C2-25NiCr compo­site coatings were prepared and successfully deposited on ASME-SA213-T-22 (T22) boiler tube steel substrates using high-velocity oxy-fuel (HVOF) thermal spraying method. Different nanocomposite coatings were developed by reinforcing Cr3C2-25NiCr with 5 and 10 wt.% YSZ nanoparticles. The nanocomposite coatings were analysed by scanning elec­tron microscope (SEM)/Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) technique. The porosity of YSZ- Cr3C2-25NiCr nanocomposite coatings was found to be decreasing with the increase in YSZ content, and hardness has been found to be increasing with an increase in the percentage of YSZ in the composite coatings. The coating of 10 wt.% YSZ-Cr3C2-25NiCr showed the lowest porosity, lowest surface roughness, and highest microhardness among all types of coatings. This may be due to the flow of YSZ nanoparticles into the pores and gaps that exist in the base coatings, thus providing a better shield to the substrate material

Effect of nano yttria-stabilized zirconia on properties of Ni-20Cr composite coatings

In the present work, 5 and 10 wt.% yttria-stabilized zirconia (YSZ) nanoparticles were reinforced in Ni-20Cr powder and deposited on boiler tube steel using a high-velocity oxy-fuel spraying process. The effect of YSZ reinforcement on microhardness, surface roughness and porosity were investi­ga­ted. The hardness was the highest for nanocomposite coating reinforced with 10 wt.% YSZ and hard­ness was found to increase with a decrease in porosity. The coating microstructure and elements were characterized using field emission scanning electron microscopy (FE-SEM) with an energy dispersive spectroscope (EDS). The constituents of the coating were identified using X-ray diffracto­meter. It was found that the composite coating with 10 wt.% YSZ reinforced nanocomposite coating has the highest microhardness, in the range of 1008-1055 hv. During the coating process, nano YSZ particles were dispersed in the gaps between the micrometric Ni-20Cr particles, providing a better coating matrix than conventional Ni-20Cr. The Ni-20Cr with 10 wt.% of YSZ nanoparticles showed better results in terms of mechanical and microstructural properties during the investigation

Cost and Area Comparison Per Student of the Public Elementary Schools in Texas based on the Project Delivery Systems

It has been shown that there exists a correlation between the cost of construction of elementary schools and the project delivery systems. Previous research showed that Competitive Sealed proposal contract method of construction is $4000 cheaper than the Construction Manager at Risk method of construction per student for elementary school construction in Texas. This research investigates the elements causing construction cost variation in elementary schools of Texas by comparing and contrasting the two forms of contract documents, CSP and CMR. Two schools were selected for the study, although the schools are technically in different regions of Texas, the geological record suggests that there is not much difference in the techniques used for foundation construction and hence a reasonable comparison is possible. A comparison was completed of the contract documents for two elementary schools. School A was built using CSP and School B using CMR. The two schools were built for about$13000 per student in line with A. N. Reinisch’s findings for CSP contracts in Texas, but not CMR average costs. The two ISD’s who supplied the documents were clearly concerned at cost control and appear to have managed this process. The earlier findings of a cost difference between CSP and CMR are not overturned by this study. Future studies involving a greater number of schools and the development of a central database are recommended

A stress analysis method for fatigue life prediction of welded structures

In the case of structural weldments, the procedure for estimating fatigue life requires information concerning geometry of the object, loads and material. Detailed knowledge of stress fields in the critical regions of weldments is used to determine the fatigue life. The main theme of the research discussed in this thesis is to provide details of the methodology which has been developed to determine peak stress and associated non-linear through thickness stress distribution at the critical weld toe location by using only the geometry dependent stress concentration factors along with appropriate unique reference stress calculated in an efficient manner e.g. without modeling geometrical weld toe details. The peak stress at the weld toe can be subsequently used for estimating the fatigue crack initiation life. The non-linear through thickness stress distribution and the weight function method can be used for the determination of stress intensity factors and for the analysis of subsequent fatigue crack growth. Accurate peak stress estimation requires 3D fine mesh finite element (FE) models, accounting for the micro-geometrical features, such as the weld toe angle and weld toe radius. Such models are computationally expensive and therefore impractical. On the other hand, stresses at sharp weld corners obtained from 3D coarse FE meshes are inaccurate and cannot be used directly for fatigue life estimations. A robust, sufficiently accurate, efficient and practical approach is proposed for fatigue life estimation of welded structures based on 3D coarse mesh FE models. Another objective is to establish a methodology which is capable of accounting for the actual variability of stress concentration factors at welds, welding defects such as misalignment and incomplete penetration resulting from manufacturing processes. The proposed approach is capable of accounting for the effects from use of different material and effect of residual stresses from welding process. Residual stress information is obtained from a welding process simulation model, which has been validated against measured residual stress data. The proposed methodology has been validated using numerical and experimental data by analyzing different weldments of varying geometrical and load configurations. Further, the applicability of the stress field obtained from the proposed methodology is demonstrated by using it in a forward looking “Total Fatigue Life” concept based only on the fracture mechanics approach

Prevalence and risk factors of soil transmitted helminths from rural field practice area of a tertiary care center from northern India

Background: Soil-transmitted helminths (STH) are a major public health problem in our country, affecting the physical growth and cognitive development. STH infections are considered a leading cause of sickness, absenteeism and disability adjusted life years lost. Aim of the study was to assess the prevalence and risk factors of soil transmitted helminths (STH) in Farrukhabad district, India. Methods: A total of 1203 study subjects from 602 eligible households fulfilling the eligibilty criteria. Thus equal number of children and adults were recruited from rural and urban areas. In each household, one child participant of the age 1-15 years and one adult, older than 15 years, and willing to participate, were eligible to participate in this study. All enrolled subjects were provided with a screw- capped plastic container to collect their stool sample. The following day, a field worker visited the subject’s home to collect the container. Saline and iodine wet preparations were examined for the presence of nematode ova. All positive stool samples were re-examined by the McMaster egg counting technique to quantify the number of eggs per gram of stool.Results: Overall prevalence of STH was 14.3% (95% CI 4.4-19.2) among study subjects. Hookworm was the predominant STH identified with a prevalence of 11.3% (95% CI 1.1-17.4), followed by Ascaris lumbricoides with a prevalence of 4.5% (95% CI 0.5-7.6). Prevalence of STH was observed to be 13.2% (95% CI 8.7-17.2) and 7.6% (95% CI 4.4-10.7) in rural and urban areas respectively. Age category, residing in a field-hut, presence of cat at home, presence of untrimmed nails, open air defaecation, habitually eating food that has fallen on the ground, not washing hands with soap and water after defaecation, and consumption of deworming tablet turned out to be independent risk factors for acquiring STH infection in our study.Conclusions: Identification of at-risk groups along with Strategic planning and health education, awareness campaigns along with mass drug administration could reduce the burden of STH significantly.