Silicon field effect transistors as dual-use sensor-heater hybrids

We demonstrate the temperature mediated applications of a previously proposed novel localized dielectric heating method on the surface of dual purpose silicon field effect transistor (FET) sensor-heaters and perform modeling and characterization of the underlying mechanisms. The FETs are first shown to operate as electrical sensors via sensitivity to changes in pH in ionic fluids. The same devices are then demonstrated as highly localized heaters via investigation of experimental heating profiles and comparison to simulation results. These results offer further insight into the heating mechanism and help determine the spatial resolution of the technique. Two important biosensor platform applications spanning different temperature ranges are then demonstrated: a localized heat-mediated DNA exchange reaction and a method for dense selective functionalization of probe molecules via the heat catalyzed complete desorption and reattachment of chemical functionalization to the transistor surfaces. Our results show that the use of silicon transistors can be extended beyond electrical switching and field-effect sensing to performing localized temperature controlled chemical reactions on the transistor itself.     

Estimating the energy and exergy utilization efficiencies for the residential–commercial sector: an application

The main objectives in carrying out the present study are twofold, namely to estimate the energy and exergy utilization efficiencies for the residential–commercial sector and to compare those of various countries with each other. In this regard, Turkey is given as an illustrative example with its latest figures in 2002 since the data related to the following years are still being processed. Total energy and exergy inputs in this year are calculated to be 3257.20 and 3212.42 PJ, respectively. Annual fuel consumptions in space heating, water heating and cooking activities as well as electrical energy uses by appliances are also determined. The energy and exergy utilization efficiency values for the Turkish residential–commercial sector are obtained to be 55.58% and 9.33%, respectively. Besides this, Turkey's overall energy and exergy utilization efficiencies are found to be 46.02% and 24.99%, respectively. The present study clearly indicates the necessity of the planned studies toward increasing exergy utilization efficiencies in the sector studied.     

Electricity tariffs based on long-run marginal costs for central grid system of Oman

The electricity tariffs in Oman are subsidized and are based on a cost accounting approach and do not reflect the true cost incurred in generating, transmitting and distributing a kilowatt-hour of electricity at the consumer end. This paper presents the electricity tariff based on the estimation of long-run marginal cost at generation, 33 kV, and 415 voltage level for Ministry of Housing, Electricity & Water (MHEW) interconnected power system of Oman. The result shows that at the generation level a marginal kW costs US$ 75 per year and a marginal kWh costs 2.07 ¢/kWh. These costs increase as we move downstream from generation to consumer end. The average cost of electricity at the consumer end connected at 415 V is 6.52 ¢/kWh or 25.17 Bz/kWh.     

A novel multiple reflections technique to calibrate polygons and evaluation of its uncertainty of measurement

In the field of angle metrology, angle gauges and polygons are the material artefact standards. Conventionally, autocollimator along with indexing table, are used for the calibration of angle gauges and polygons. A novel multiple reflections method is devised at NPLI to improve the uncertainty of measurements during calibrations. A polygon under calibration is fixed at the centre of a Moore’s indexing table within eccentricity offset ± 20μm. A reference autocollimator is aligned to one of the face of the polygon. A flat reflector is fixed in the centre of a rotatable table. The rotatable table is arranged to collect the optical beam on to the flat reflector then deflected to same face of the polygon, wherefrom the light beam is received at the autocollimator. Thus the optical beam strikes the same face of the polygon twice. Therefore the resolution of the reference autocollimator is virtually doubled. In this experimental setup, two set of readings are obtained simultaneously. One set of the readings corresponds to conventional method and the second set of the readings belongs to the proposed novel method. The readings of the autocollimator are analysed and the results are discussed in the article. The results thus obtained by conventional method are compared with the results obtained using the proposed method. Using this novel calibration method, the uncertainty of measurement is improved from ± 0.39″ to ± 0.23″.     

Effect of reference state on the performance of energy and exergy evaluation of geothermal district heating systems: Balcova example

In this paper, we undertake a parametric study to investigate how varying reference temperature from 0 to 25 °C will affect the energy and exergy efficiencies of the Balcova geothermal district heating system (BGDHS) and develop two significant correlations (with a correlation coefficient of 0.99) that can be used for predicting the efficiencies. The exergy losses in the overall BGDHS are quantified and illustrated using exergy flow diagram particularly for a reference temperature of 11.4 °C for comparison purposes. This reference temperature is taken as an average value of the ambient temperatures measured during the past 5 years for the day of 2nd January to reflect the actual situation. The results show that the exergy losses within the system occur mainly due to the losses in pumps, heat exchangers, reinjection sections of the geothermal water back into reservoir and pipeline, and account for 1.75%, 8.84%, 14.20%, and 28.69%, respectively. In addition, we study energy and exergy efficiencies to determine the possibilities to improve the system, and energy and exergy efficiencies of the system are found to be 42.36% and 46.55%, respectively, for 2nd January 2004.     

Thermoeconomic analysis of energy utilization in the residential–commercial sector: An application

Thermoeconomic analysis is a very useful tool for investigators in engineering and other disciplines since its methodology includes the quantities such as mass, energy, exergy and cost. This study deals with this analysis of energy utilization in the residential–commercial sector (RCS). In this regard, the relations between capital costs and thermodynamic losses for subsectors in the RCS are investigated. In the analysis, Turkey is taken as an application country based on its actual and projected values for the years 1991, 1993, 1995, 1999, 2000 and 2001, and for the year 2020, respectively. It is observed from the results obtained that the maximum exergy destructions in the system particularly occur due to the utilization of the large-cost and high-quality energy sources like petroleum, natural gas carriers in the low-energy needs. In conjunction with this, the values for the total exergy losses are found to vary from 486.43 to 2797.28 PJ, while those for the improvement potential are obtained to range from 58.80 to 1870 PJ in the Turkish RCS for the analyzed years. The ratio of thermodynamic loss rate-to-capital cost values is also calculated to be in the range of 0.76–1.01. It is expected that the results presented here would be beneficial to the researchers, government administration and engineers working in the area of modeling the subsectors of countries using thermoeconomic analysis method.     

Removal of colour and COD from synthetic textile wastewaters using O3, PAC, H2O2 and HCO3-

This study aimed to investigate removal of colour and chemical oxygen demand (COD) from synthetic textile wastewaters using O3, powder activated carbon (PAC), H2O2 and HCO3- in a semi-batch reactor. 1:2 metal complex dyestuffs containing two molecules of dyestuffs versus a chromium atom was used. Experiments were conducted under the various pHs (3-12), temperatures (18-70 degrees C), ozone doses (164-493 mg min(-1)). The combined effect of substances used on the removal of colour and COD was investigated. The mechanisms of colour and COD removal on the PAC were explained on the basis of the results of Fourier transform infrared spectroscopy (FTIR). In addition, the zeta potential values of PAC, ozonated PAC and ozonated PAC contaminated with intermediates were determined. The zeta potential values and FTIR plots of PAC particulates showed that PAC acted as an adsorbent in the combined processes. It was thought that all of the substances used in the semi-batch reactor had the combined effect on the removal of colour and COD because of the short treatment time of 5 min and high efficiencies of the removal of colour and COD. The efficiencies of removal of colour and COD in combination were compared with adsorption and ozonation only. In this study, the efficiencies of colour and COD removal during a reaction time of 30 min were obtained as 99 and 95%, respectively. At the result of this study, it was concluded that O3, PAC and H2O2 were an important substances for the removal of colour and COD from synthetic textile wastewater when they were used in combination.     

Autophobicity-driven surface segregation and patterning of core-shell microgel nanoparticles

Core-shell microgel (CSMG) nanoparticles, also referred to as core-cross-linked star (CCS) polymers, can be envisaged as permanently cross-linked block copolymer micelles and, as such, afford novel opportunities for chemical functionalization, templating, and encapsulation. In this study, we explore the behavior of CSMG nanoparticles comprising a poly(methyl methacrylate) (PMMA) shell in molten PMMA thin films. Because of the autophobicity between the densely packed, short PMMA arms of the CSMG shell and the long PMMA chains in the matrix, the nanoparticles migrate to the film surface. They cannot, however, break through the surface because of the inherently high surface energy of PMMA. Similar thermal treatment of CSMG-containing PMMA thin films with a polystyrene (PS) capping layer replaces surface energy at the PMMA/air interface by interfacial energy at the PMMA/PS interface, which reduces the energy barrier by an order of magnitude, thereby permitting the nanoparticles to emerge out of the PMMA bulk. This nanoscale process is reversible and can be captured at intermediate degrees of completion. Moreover, it is fundamentally general and can be exploited as an alternative means by which to reversibly pattern or functionalize polymer surfaces for applications requiring responsive nanolithography.     

Hydrogen sensing properties of ZnO nanorods: Effects of annealing,temperature and electrode structure

In this study, the hydrogen (H₂) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H₂ sensor performance, the nanorods were heated at 500 °C in dry air. H₂ sensing measurements were done in the temperature range of 25–200 °C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the un-coated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure.