Photothermal and Electrical Characterization of Zno-Based Varistor Systems

Photopyroelectric spectroscopy is a powerful tool for examining the optical properties related to non-radiative de-excitation processes in materials. This technique consists of using a thin photopyroelectric (PPE) film in intimate contact with a solid sample on which modulated monochromatic light beam is incident. The non-radiative de-excitation process within the solid causes the sample temperature to fluctuate and PPE signal is produced in PPE transducer as a result of this temperature fluctuation. Varistor is a voltage dependant resistor and is used as a protective device to regulate transient voltage surges of unwanted magnitudes caused by lightning and switching of circuits containing inductors, capacitors, and can inflict serious damages on machinery and other equipments. In this study, the electrical properties of ZnO based varistor doped with different additives are investigated in conjunction with the photothermal properties. The wavelength of incident light is kept in the range from 300 to 800 nm and the PPE spectrum with reference to the doping level, sintering conditions is discussed. The energy band-gap or shortly as band-gap is determined from the plot (ρhυ)2 vs hυ. The band-gap is reduced from 3.2 eV (pure ZnO) to about 1.9 eV for single additive MnO2 or when it is used with the combination of other additives. The steepness factors σA (in A-region), and σB (in B-region), which characterize the slope of exponential optical absorption are discussed in conjunction with the band-gap which give the information about the disordering of the structure. It was also found that the value of band-gap slightly increases or decreases in 13 material systems in the range of 0.03 to 0.05 eV. It was found that the secondary phases such as Bi4Ti3O12, Zn2TiO4, Zn7Sb2O12 are grain suppressors. The maximum and minimum relative densities for all systems in this study are about 96 %, 78 %, respectively. The maximum grain size was found to be 82 μm when ZnO was doped with MnO2, Co3O4, Bi2O3, TiO2 for 3 hour sintering time. It was found that the TiO2 is a strong grain enhancer; Sb2O3 is a strong grain suppressor upto certain doping level. SEM and EDX results show that the additives Bi2O3, Y2O3, Er2O3, Dy2O3 and Pr6O11 are segregated at the grain boundaries and at the triple point junctions. EDX analysis show that the Co, Mn, Ti ions are distributed on the grain surfaces as well as grain boundaries. Current-voltage characteristics of the varistor show that the varistor voltage increases with the decrease of grain size. The value of barrier height increases with the increase of the nonlinear coefficient and vice versa but it deviates in some cases. The value of band-gap decreases due to the increase in the structural disordering and increases due to the decrease in the structural disordering. It is found that the increase or decrease in the band-gap ranges from 0.03 to 0.05 eV in all cases but this ranges from 0.1 to 0.3 eV only for xBi2O3 and xPr6O11 doped ZnO system. The change in the value of the band- gap in conjunction with the nonlinearity of the doped ZnO can be categorized in four cases as both band-gap and nonlinearity increases in system 5, band-gap decreases and nonlinearity increases in system 2, system 10 and system 11, band-gap increases and nonlinearity decreases in system 6, system 8 and system 13, both band-gap and nonlinearity decreases in system 7, system 9, and system 12. System 12 which is Bi2O3, TiO2, Co3O4, doped ZnO with and without Sb2O3 at different sintering temperatures is the best system found in which both band-gap and nonlinearity decreases having the maximum value of nonlinearity that is 7.9 at the sintering temperature of 1210 oC for one hour sintering time with 0.02 mol% Sb2O3. The second best system found in the project is System 13 which is Bi2O3, TiO2, MnO2, doped ZnO with and without Sb2O3 at different sintering temperatures in which band-gap increases and nonlinearity decreases with the maximum value of nonlinearity that is 18.6 at the sintering temperature of 1180 oC for one hour sintering time with Sb2O3

The variation of optical absorption edge with sintering time for the ceramic ZnO + xMnO2-Bi2O3-TiO2

Photopyroelectric spectroscopy is used to study the variation of optical absorption of the ceramic xMn02 - 0.4 Bi2O3 - 0.4 TiO2 - ZnO, x = 0, 0.4 mol% sintered for 1-4 hours at the isothermal temperature, 1220°C. The wavelength of incident light, modulated at 12 Hz, is kept in the range 310 to 810 nm. The band-gap energy is reduced from 3.2 eV (for pure ZnO) to 2.83 eV for 0 mol% MnO2 for 1 hour sintering time and decreases further with the further increase of sintering time. Eg is decreased to 2.39 eV for 1 hour sintering time after the addition of 0.4 mol% of MnO2 in the ceramic combination. It is reduced to a value 1.9 eV with the further increase of sintering time. The variation of steepness factor σA and σB which characterizes the slop of exponential optical absorption, is correlated with the variation of Eg, sintering time and doping of MnO2. Microstructure and compositional analysis of the selected areas are analyzed using SEM and EDAX

Effect of heat treatment on the optical properties of ceramic ZnO-MnO-Dy2O3.

Photopyroelectric spectroscopy is used to investigate the optical absorption behaviour of the ceramic composite (ZnO + 1 MnO + y Dy2O3), where y = 0 - 2 mol%. Ceramics were sintered at 1200 and 1300°C for 1 and 5 h. PPE spectrum with reference to the doping level and sintering time is discussed. Optical energy band-gap (Eg) is determined from the plot (ρhυ)2 vs hυ. It is found that the the value of Eg is reduced from 3.2 (pure ZnO) to 2.15 eV at the 0 mol% of Dy2O3 and is further reduced to 2.04 eV at the 2 mol% of Dy2O3 for 5 h sintering time at the 1300°C sintering temperature. Steepness factor σA and σB which characterizes the slope of exponential optical absorption is discussed with reference to the variation in the value of Eg. The phase constitution is determined by XRD analysis. Microstructure and compositional analysis are analyzed using SEM and EDAX. The maximum grain size and density of the ceramic were found to be 14 μm, 89%, respectively

Exploring Play of Children with Sensory Impairments in Special Schools at Karachi, Pakistan

Prevalence of disabilities in Pakistan is 2.4 % (3.2 million), with 7 % population suffering from hearing impairments. This study focuses on many aspects of development including physical development, which have never been studied exclusively in developing countries. This pilot study was aimed to explore play pattern of children with hearing & speech impairments in school settings, Karachi, Pakistan. In this article play behaviors of 53 children with sensory impairments aged 8-12 years were explored. Observations were recorded through semi-structured checklist, using norm-based time sampling procedure, recording various types of behavior in a group play context. Three major play categories were observed and recorded under: a) Social Play; proximity and attentiveness b) Cognitive Play; level of child’s involvement and purpose for engaging in the activity c) Non- Play; marked by absence of focus. Frequently observed play behavior was; group play under cognitive play; games with rules and functional play behavior; engagement of child in physical activities for the enjoyment of physical sensation and in non-play behavior active conversation, rough and tumble play, recorded. Study findings reveal the importance of play as an essential component for healthy child development. Dire need of capacity building of school staff and of caregivers regarding child development and importance of play was felt at larger scale

Photopyroelectric Spectroscopic Studies of ZnO-MnO2-Co3O4-V2O5 Ceramics

Photopyroelectric (PPE) spectroscopy is a nondestructive tool that is used to study the optical properties of the ceramics (ZnO + 0.4MnO2 + 0.4Co3O4 + xV2O5), x = 0–1 mol%. Wavelength of incident light, modulated at 10 Hz, was in the range of 300–800 nm. PPE spectrum with reference to the doping level and sintering temperature is discussed. Optical energy band-gap (Eg) was 2.11 eV for 0.3 mol% V2O5 at a sintering temperature of 1025 °C as determined from the plot (ρhυ)2 versus hυ. With a further increase in V2O5, the value of Eg was found to be 2.59 eV. Steepness factor ‘σA’ and ‘σB’, which characterize the slope of exponential optical absorption, is discussed with reference to the variation of Eg. XRD, SEM and EDAX are also used for characterization of the ceramic. For this ceramic, the maximum relative density and grain size was observed to be 91.8% and 9.5 μm, respectively

Extending Transit Facility to India: Implications for Pakistan’s Bilateral Trade with Afghanistan

The paper examines patterns of bilateral trade between Pakistan, India, Afghanistan and CARs. It also investigates whether providing India transit route to Afghanistan has opportunity costs for Pakistan’s trade potential with Afghanistan and CARs. In 2009, Pakistan’s exports to Afghanistan amount to US$ 1.3 billion which make up for 7.8 % of Pakistan’s total exports. For the same year, India’s exports to Afghanistan stand at 471 million dollars which make 0.3 % of India’s total exports. Looking at the product wise composition of Pakistan’s exports to Afghanistan, mineral fuels, oils, distillation products are on the top with share of around 29%. Salt, sulpher, earth, plaster, lime and cement and cereals have a share of around 11 %. While animal, vegetable fats and oils, cleavage products and articles of iron and steel have the share of around 7%. On the other hand, the top five exports of India to Afghanistan are man-made filaments with 42 % share, pharmaceutical products with 11 % share, electric and electronic equipment with 7% share and rubber and articles with 6% share. Clearly there is no overlap between exports of Pakistan and India to Afghanistan. Nonetheless Pakistan has already lost its market share to India in pharmaceuticals. The tariff applied to Pakistan by Afghanistan on pharmaceuticals is 2.50 % while India which enjoys Preferential Trade Agreement with Afghanistan only faces an average tariff of 0.60% on pharmaceuticals. Pharmaceuticals are Pakistan’s top performing exports to CARs with 42.5 % share of total exports to CARs. India also exports pharmaceuticals to CARs but its share in total exports to CARs is only 25.5 %. In Afghanistan, Pakistan has clearly lost its market share to India due to presence of preferential tariffs for India in Afghanistan. If Pakistan provides transit route to India for its exports to Afghanistan, cheaper pharmaceuticals of Indian origin can then be re-exported to CARs capturing Pakistan’s market share in CARs. Much like pharmaceuticals there are other Pakistani products which are likely to lose out to India in Afghanistan and CARs if India is provided transit route to Afghanistan. The Wagah-Peshawar-Torkham route which roughly extends up to 800 km is probably the shortest possible one between India and Afghanistan; which would greatly reduce the logistics cost of shipping goods from India to Afghanistan and beyond. In addition to that, the preferential treatment currently enjoyed by Indian products in Afghanistan under the PTA would further cost Pakistani goods by eroding their competitiveness in the Afghan market. In the absence of a robust mechanism to contain the informal trade, allowing Indian goods a passage through Pakistan’s territory would, in all likelihood, worsen the smuggling situation, something Pakistan can ill afford to accept. Therefore, under the circumstances, there are clear economic disadvantages to Pakistan in extending the transit facility to India without adequate safeguards and preferably a quid pro quo, be it political or economic.International Trade, Transit Trade Agreements, Pakistan, India, Afghanistan, Sectoral Analysis

Hybrid-Microgrid Planning, Sizing and Optimization for an Industrial Demand in Pakistan

Industrial sector is of great significance for the economic growth of every country. The energy crisis in Pakistan has become the prime stumbling block in the economic development of the country. There are many industrial processes that need uninterrupted supply; even a trivial outage can cost millions of dollars. The main cause of "load shedding" in Pakistan is that it produces a major portion of its energy from fossil fuels, whose price and demand is constantly increasing. Most of the customers at industrial and commercial level use Diesel Generator (DiG) as a reliable alternative source of electrical power when grid supply is unavailable. The use of DiG during loading shedding hours would increase the Cost of Energy (COE) per kWh and also enhance environmental emissions. Pakistan has a wide range of renewable power sources like bioenergy, wind, solar, hydel, geothermal etc. The distinct emphasis on the implementation of an industrial microgrid in Faisalabad, Pakistan has been specified in this paper. The prospective benefits of the microgrid fall into three major kinds: cost reduction, fuel saving, and improved environmental emissions. The optimized objective of this work is to maximize these benefits. Moreover while designing the hybrid microgrid system it encounters many design challenges like sizing of the components, system feasibility, COE, system reliability etc. This study contributes to the ongoing studies about hybrid microgrid system and draws attention to the optimal design and sizing considering several techno-economic factors including Net Present Cost (NPC), COE, supply reliability, capacity shortage constraint, battery state of charge (SOC), dispatch strategy, PV power generation and PV array tracking systems. Different cases are studied; microgrid sizing, techno-economic exploration, sensitivity analysis and environmental effects are addressed using (Hybrid Optimization Model for Electric Renewables) HOMER. The results show that COE and environmental emissions have been significantly reduced for the proposed system

Functional and radiological outcomes of atypical femur fractures among elderly in Karachi, Pakistan

Objective: To assess the functional and radiological outcomes in a unique class of fractures i.e. atypical femur fractures and to assess the effects of osteoblastic agents in healing.Methods: It is a retrospective observational study conducted at Aga Khan University Hospital, Karachi, Pakistan. All patients with atypical femur fractures who were surgically managed with intramedullary nailing from January, 2013 to June, 2017 and with a follow-up till December 2019, were included in the study. Radiological outcomes were expressed as mean healing time and functional outcomes were recorded as mean Short Musculoskeletal Functional Assessment (SMFA) score.Results: A total of twenty-four patients were included in this study. Mean age of patients was 65.8 ± 8 years. Mean healing time was 10 ±3.2 months post operatively. Two patients underwent redo procedures. No other complications like paresthesia or weakness was observed in any patients. All the patients reported a good score on SMFA ranging from 19% to 31%.Conclusion: Intra-medullary nailing shows a promising result in treatment of atypical femur fractures. Use of post-operative osteoblastic supplements showed statistically significant results with early healing time (p=0.008 [95% CI])

Early experience of dynamic hip screw with spiral blade and locking side plate for the stabilization of trochanteric fractures.

Abstract OBJECTIVE: To evaluate early experience with helical hip system in osteoporotic elderly patients with per-trochanteric fractures. METHODS: The retrospective study was conducted at Aga Khan University Hospital, Karachi, and comprised records of patients having low-velocity pertrochanteric fractures who were fixed with spiral blade Dynamic Helical Hip Systemfrom July to December 2014 and were followed up for a minimum of 3 months. Demographic variables and clinical outcomes were noted from the medical records whereas operative details were recorded from the operative note. Radiological variables and outcomes were assessed by viewing appropriate pre-operative, post-operative and follow-up radiographs. RESULTS: Of the 32 patients in the study, 14(44%) were men and 18(56%) were women, with an overall mean age of 77.81±7.04 years and mean body mass index of 25.99±4.13 kg/m2. Of the total, 1(3.13%) patient had implant cut-out, 1(3.13%) had myocardial infarctionand 2(6.2) expired. CONCLUSIONS: The introduction of spiral blade dynamic hip screw manifested favourable results and good clinical and radiological outcomes with low cut-out rates

Modified SERVQUAL model and effects of customer attitude and technology on customer satisfaction in banking industry: mediation, moderation and conditional process analysis

Banks are very important financial services sector, and in banking sector there is an intense competition amongst the local and foreign banks throughout the world. The objective of this research is to analyse the effects of perceived value and customer trust, and role of technology in banking service qualities and customers’ satisfaction in Pakistani context. For this purpose we employed modified SERVQUAL model with four dimensions such as empathy, competence, reliability, and online service. An adapted questionnaire was used to carry out this survey research, and collected 830 responses from the customers of Pakistani banking industry. We used factor analysis, confirmatory factor analysis, and bootstrapping methods to carry out this research. The results of the study demonstrated that our four-dimensional model of modified SERVQUAL has a significant impact on overall customer satisfaction. It is further concluded from the bootstrapping method that modified SERVQUAL dimensions and customer satisfaction are positively mediated by the perceived value and trust. Finally, it is also concluded that the implementation of technology serves as moderating variable in the banking sector. The outcomes of this research are beneficial to the senior management of banking sector in order to implement the effective and customised online banking structure to gain competitive advantages, and provide vibrant online banking services that enhance the standard and ease of services to the customers and earn their confidence. The originality and novelty of this research provide a significant contribution in the application of SERVQUAL model specifically for the banking service quality dimensions and customer satisfaction in marketing research