Photothermal Deflection Spectroscopy of Amorphous, Nanostructured and Nanocomposite Thin Films

The energy needs of the modern world are growing day by day, while sources of non-renewable fossil fuels are limited, so there is a need to efficiently use the existing resources and explore renewable energy sources. In order to harvest, store and efficiently utilize renewable energy, we need to explore new materials and improve the performance of existing ones. Among others, hydrogenated amorphous silicon (a-Si:H) with high optical absorption in the visible range of electromagnetic spectrum, is a low cost material for solar cells. But the efficiency of such solar cells is comparatively low because of intrinsic defects associated with its material structure and its degradation under illumination. Also the optical transparency and electrical conductivity of the window electrode are important factors that affect solar cell performance. Transparent and conducting carbon-based films (TCCF) have great potential to be used as electrodes in optoelectronics due to their transparency and high electrical conductivity. TCCF are not yet as competitive with indium-tin oxide (ITO) as transparent electrical conductors. In order to improve the efficiency of such materials, one needs to understand and curtail the defects for better cell performance. This study is an experimental investigation of the optical and thermal properties of solar-grade materials and nanocomposites using photothermal deflection spectroscopy (PDS). PDS is a non-contact experimental technique based on the mirage effect. An automated PDS setup was assembled that is capable of measuring weak optical absorptions and thermal properties of thin film samples. A complementary setup, the 3-omega method, for thermal conductivity measurement was also built and used to compare the results obtained by the two methods. However, our primary focus was on the PDS setup as a non-contact, non-destructive and sensitive technique. Also the role of convection heat transfer in PDS in the presence of highly thermally conducting nanoparticles in photothermal fluid is investigated. The defects formation in a-Si:H thin films under light soaking was investigated and a model is proposed for self-repair of defects in thin films. Also optical, electrical and thermal properties of a set of graphene/graphene-like platelet thin films were investigated. A relationship between the electrical and thermal conductivities of these samples was established that could be applied to a large class of graphene-based thin films. The trade-off between electrical and thermal properties, along with transparency, will help the design of applications where electrical conductance, thermal management and transparency are required

THE DURABILITY ASPECTS AND BOND STRENGTH OF RUBBERCRETE CONTAINING NANO SILICA

Crumb rubber is product from the processed waste scrap tire which is non-biodegradable and threat to environment. One of common usage of crumb rubber is production of concrete containing crumb rubber or rubbercrete. Rubbercrete contribute a lot of benefits such low density, good thermal resistivity, and high ductility. Adverse effect of rubbercrete strength of the concrete is decreased as percentage of crumb rubber added increased. This is due to physical properties of crumb rubber that repels water make the adhesion between cement and aggregate decreased. Nano silica is widely used nowadays and found can increase the compressive strength of concrete. Nanosilica works as filler in the empty spaces in the concrete particles. It acts as nucleation of the hydrated products resulting in the improvement of concrete hydration rate of the concrete proving in the high early strength of concrete containing nano silica. Thus nano silica is proven can improve the transition zone between aggregates and cement paste. Hence, in this research, we believe by adding nano silica in the rubbercrete, the nano silica will overcome the problem of decreasing in strength of rubbercrete as a matter of fact, creating a concrete that have both high ductile properties and high strength. In these studies, 0, 5, 10, 15, and 20 weights % of rubber crumbs with respect to fine aggregate is added to the concrete. The type of w/c used for the concrete containing crumb rubber is 0.41, 0.57 and 0.68 accordingly. For increasing the concrete compressive strength, 1, 3 and 5% of nano silica were introduced to the rubber containing concrete with respect to cementitios material. For the concrete containing nano silica and crumb rubber the w/c ratio used only 0.57. The mixture schemes for measuring the 28 day compressive strengths and bond strength were performed according to ACI standard. After that the durability aspect and bond strength of the concrete were tested according to BS EN 12393 and ASTM C234 1999. Result show that by adding nano silica in the concrete mixture containing crumb rubber, it counterpart the weakness of cubbercrete which low in strength. The porosity and permeability of the concrete also decrease by adding nano silica in the rubbercrete

Wheat growth and phytoavailability of copper and zinc as affected by soil texture in saline-sodic conditions

Nutrient disorders in saline-sodic soils can adversely affect crop growth. In order to evaluate the growth response of wheat (Triticum aestivum L.) to Cu and Zn and the phytoavailability of these essential elements, a pot experiment was conducted in three different textured saline-sodic soils [sandy loam (SL), sandy clay loam (SCL) and clay (C)] having an ECe 8.63, 8.80, 8.98 dS m–1 and SAR 21.66, 23.48, 24.84 (mmol L–1)1/2 respectively. Seven treatments including levels of Cu (4, 6 and 8 mg kg–1) and levels of Zn (4, 6 and 8 mg kg–1) were separately applied together with a single control treatment. Dry matter yield (straw + grain) of wheat increased up to 35.2% with Cu and up to 31.2 % with Zn application relative to the control. As soil clay content increased, dry matter yield decreased up to 39.2% in SCL and up to 62.7% in C soil when compared to SL soil. Application of Cu increased the concentration in both wheat straw and grains up to 2.46 and 2.20 mg kg–1 DW respectively relative to the control. Zinc concentration in wheat straw and grains was also increased up to 29.97 and 29.40 mg kg–1 DW respectively relative to the controls. Copper application significantly increased Zn concentrations in wheat plants

Post operative sore throat: Comparison between Macintosh versus video laryngoscope in patients intubated by trainee anaesthetists - A randomised control trial

Objectives: Postoperative sore throat (POST) is a common complication related to endotracheal intubation. The aim of this study was to compare the incidence of POST in patients intubated by trainee anaesthetist using Video Laryngoscope™ (VDL) or Conventional Macintosh Laryngoscope (CL).Methods: Total 110 patient scheduled for elective laparoscopic cholecystectomy were included from main operating room of Aga Khan University Hospital between June 2017-2018. The standardized perioperative protocol was used for general anaesthesia. Selected patients were randomly allocated into conventional laryngoscopy (CL) group or video laryngoscopy (VDL) group. The evaluation of sore throat was done at 1st, 12th and 24th hour postoperatively using a ten-point visual analogue scale.Results: The demographic characteristics, including intubation time, related complications or any other maneuver required were similar between the groups. The incidence of POST at 1st hour was 47% patients in CL group and 38% in VDL group (p=0.335). At 12th hour, 34.5% patients in CL and 38% in VDL reported POST (p=0.692). Similarly at 24th hour, 25% patients in CL and 16% in VDL group reported POST (p=0.669).Conclusions: There was no significant difference in incidence of POST for patients intubated by trainee anaesthetists using either CL or VDL. Objective evidence of training and laryngoscope technique can impact of POST

Impact of Work Environment on Teachers’ Job Satisfaction A Case Study of Private Business Universities of Pakistan

The main purpose of the study was to check the relationship between work environment and teachers’ job satisfaction in private business universities of Karachi, Pakistan. The factors that include in work environment are freedom of teachers, involvement of teachers, management policies, co-workers’ relationships and employer – employee relationships used as independent variables and teachers’ job satisfaction used as a dependent variable. The structured 5 points likert scale questionnaire was used to collect the data from 105 private business universities’ teachers from Pakistan. The data was analyzed through SPSS 17 by using statistical tools such as descriptive statistical, Pearson correlation and simple linear regression. The results indicate that there is a positive relationship between all factors of work environment and job satisfaction in teachers. Research also found that the employer – employee relationships is most important factor of work environment in private business universities of Pakistan. It is suggested that the universities’ management should focus on favorable work environment particularly the factor of relationship between employer and employee to increase the job satisfaction amongst teachers, which may lead to higher performance. As research only was conducted with teachers of private business universities of Pakistan, it cannot be generalized to all sectors of country. Variables and sample size should be increased in the future research to get the better results. Keywords: Work Environment, Job satisfaction, Teacher, Education Sector, Private Universities Area of Research: Human Resource Management, Educatio

Self-Commissioning of AC Motor Drives

In modern motion control and power conversion applications, the use of inverter-fed electrical machines is fast growing with continuous development in the field of power electronics and drives. The Variable Voltage Variable Frequency (VVVF) supply for electrical machines gives superior performance in terms of speed control, efficiency and dynamics compared to the machines operated directly from the mains. In one of the most basic configurations, a drive system consists of a closed loop speed control that has a current controller inside the loop. For effective and stable current control, the controller gains need to be set according to the parameters of the machine at hand. Besides, accurate parameter information is helpful in ensuring better machine exploitation as well as maintaining higher efficiency in various operating modes and conditions. The traditional methods of determining machine parameters consist of extensive machine testing under prescribed supply and ambient conditions. These methods become impracticable when the machine cannot be isolated from its load or the test equipment cannot be made available. Under such conditions, the alternatives are needed that use only the available hardware included in a standard drive to completely define the machine parameters. Self-commissioning thus comes into play in such situations. The automatic determination of machine electrical parameters before the drive is put in continuous operation is called self-commissioning of the drive system. In this thesis, self-commissioning of AC electric motors is studied, analyzed and results are presented for the implementation of different self-commissioning methods either proposed in the literature or developed in the course of this research. By far the commonest control strategy of AC machines is the vector control that allows dc machine like decoupled control of machine flux and torque. The separation of flux and torque producing current components depends heavily on the parameters of the machine at hand. In case the parameters fed to the controller do not match the actual machine parameters, the control performance deteriorates both in terms of accuracy and efficiency. For synchronous machines using permanent magnets, the magnetic model of the machine is important both for flux estimation accuracy at low speeds and for deriving maximum torque out of machine per ampere of input stator current. The identification of the magnetic model of permanent magnet synchronous machines requires special tests in a laboratory environment by loading the machine. A number of machine parameter identification methods have been studied in the past and proposed in the literature. As the power amplifier implied is almost always an inverter, the estimation of machine parameters at start-up by generating special test signals through the inverter have been researched in depth and are investigated in this thesis. These techniques are termed as offline parameter identification strategies. Other methods that focus on parameter updating during routine machine operation are called online parameter estimation methods. In this thesis, only the offline identification schemes are studied and explored further. With continuous improvements in power semiconductor devices' switching speeds and more powerful microprocessors being used for the control of electric drives, generating a host of test signals has been made possible. Analysing the machine response to the injected test signals using enhanced computational power onboard is relatively easier. These conditions favour the use of even more complex test strategies and algorithms for self-commissioning and to reduce the time required for conducting these tests. Moreover, the universal design of electric drives renders the self commissioning algorithms easily adaptable for different machine types used in industry. Among a number of AC machines available on the market, the most widely used in industrial drives are considered for study here. These include AC induction and permanent magnet synchronous machines. Induction machines still play a major part in industrial processes due, largely, to their ruggedness and maintenance-freeness; however, the permanent magnet machines are fast replacing them as competitive alternatives because of their low volume-to-power, weight-to-power ratios and higher efficiency. Their relatively light weight makes these machines a preferred choice in traction and propeller applications over their asynchronous counterpart

Characterization of carbon nanotubes grown by chemical vapour deposition

Carbon nanotubes (CNTs), discovered by Ijima in 1991, are one of the allotropes of carbon, and can be described as cylinders of graphene sheet capped by hemifullerenes. CNTs have excellent electrical, mechanical, thermal and optical properties and very small size. Due to their unique properties and small size, CNTs have a great potential for use in electronics, medical applications, field emission devices (displays,scanning and electronprobes/microscopes) and reinforced composites. CNTs can be grown by different methods from a number of carbon sources such as graphite, CO,C2H4, CH4 and camphor. Under certain conditions, a metallic catalyst is used to initiate the growth. The three main methods used to grow CNTs are: Arc-discharge, laser ablation (LA) and chemical vapour deposition (CVD). In the present work CNTs were grown from a mixture of camphor (C10H16O) and ferrocene (C10H10Fe) using Chemical Vapour Deposition (CVD) and argon was used as a carrier gas. The iron particles from ferrocene acted as catalysts for growth. The substrates used for the growth of CNTs were crystalline Si and SiO2 (Quartz) placed in a quartz tube in a horizontal furnace. Several parameters have been found to affect the CNT growth process. The effects of three parameters: growth temperature, carrier gas (Ar) flow rate and catalyst concentration were investigated in the present work in order to optimize the growth conditions with a simple and economical CVD setup. The samples were characterized using electron microscopy (EM), thermogravimetirc analysis (TGA), Raman and FTIR spectroscopy techniques. It was found that the quality and yield of the CNTs were best at 800??C growth temperature, 80sccm flow rate and 4% catalyst concentration

Global Financial Crisis And Its Impact On Textile Industry In Pakistan

This research investigates the impact of Global Financial Crisis on textile industry clusters in Pakistan.  A cross sectional data were collected from 25 textile industries by using simple random technique and data were analysis by using E-Views software. Structural questionnaire was the basic tool for measures the performance of textile industry in financial recession in Pakistan.  It was revealed that the industry is in urgent need of financial and technological investments.  It was revealed that Global financial crisis has negative impact on the export of textile industry in Pakistan.  The export of textile related products has decreased by 20 percent due to decrease in textile demand.  It was further revealed that textile industry facing problems such as electricity and high taxes