Indoor localization based on unsynchronized, low-complexity, passive radio frequency identificati... more Indoor localization based on unsynchronized, low-complexity, passive radio frequency identification (RFID) using the received signal strength indicator (RSSI) has a wide potential for a variety of internet of things (IoTs) applications due to their energy-harvesting capabilities and low complexity. However, conventional RSSI-based algorithms present inaccurate ranging, especially in indoor environments, mainly because of the multipath randomness effect. In this work, we propose RSSI-based localization with low-complexity, passive RFID infrastructure utilizing the potential benefits of large-scale MIMO technology operated in the millimeter-wave band, which offers channel hardening, in order to alleviate the effect of small-scale fading. Particularly, by investigating an indoor environment equipped with extremely simple dielectric resonator (DR) tags, we propose an efficient localization algorithm that enables a smart object equipped with large-scale MIMO exploiting the RSSI measureme...
Long-term behaviour of steel fibre reinforced concrete remains rather unknown and to a large exte... more Long-term behaviour of steel fibre reinforced concrete remains rather unknown and to a large extent unquantified by equations and standards. This paper studies experimentally the free drying shrinkage of steel fibre reinforced lightweight concrete during the first 28 days using 100 Â 100 Â 500 mm beams. The coarse lightweight material tested (LYTAG) is recycled and offers an alternative to gravel and quarry resources which are subjected to depletion in the future. Also, this material can lead to reduction in the mass of the structure which results in economical designs. However, LYTAG aggregate can absorb up to 15% of its own weight in water. This makes it susceptible to drying shrinkage both at young age and long-term due to environmental diffusion. Shrinkage can have a detrimental effect on the concrete by inducing cracks, creating therefore weak zones in the concrete. It is thought that fibres can have a favourable effect on the reduction of shrinkage due to their ability to bridge cracks. This could be vital particularly in large concrete flat slabs, joints, beams and even columns. This project uses modern hooked-end DRAMIX 3D and 5D fibres with different dosages V f and number of hooks and evaluates shrinkage for concrete with different characteristic strengths f ck. KEYWORDS: Lytag Á Hooked-end fibres Á Early-age shrinkage Á Drying shrinkage Á Shrinkage beams Á Environmental diffusion Á Cracks
A method is proposed to derive and validate material properties for lightweight fibrous concrete ... more A method is proposed to derive and validate material properties for lightweight fibrous concrete using experimental and numerical data. The coarse lightweight material tested (produced by LYTAG) is recycled and offers an alternative to gravel and quarry resources which are at risk of depletion in future. Also, this material can lead to reduction in the mass of the structure which results in economical designs. However, in comparison to normal weight aggregate concrete (NWAC), lightweight aggregate concrete (LWAC) tends to be more brittle as it typically shears through the aggregates leading to instantaneous drop in peak load in both compression and tension tests. Hence, to address this brittleness for LWAC, modern hooked-end DRAMIX fibres with different geometry (hooks), dosages (V f) and bond strengths (s b) are added to mixes with different strengths (f ck). This paper focuses on both tensile properties using a direct pullout and indirect notched beam tests, and compressive properties (f ck , E, l) using the conventional compression test for cylinders of plain and steel-fibre reinforced lightweight concrete (SFRLC). A tensile semiempirical multilinear r-x relation was derived besides compressive re and validated against available steel fibre reinforced concrete (SFRC) constitutive models for the tested fibrous notched beams using ABAQUS.
For a novel indoor-localization system, chipless tags with high retro-directive radar crosssectio... more For a novel indoor-localization system, chipless tags with high retro-directive radar crosssection (RCS) under wide-angle incidence are required as fixed landmarks. Tags based on dielectric resonators (DRs) were proposed to provide identification by resonance frequency coding. To achieve a satisfactory read range for the localization system, the low RCS levels of these tags require a major boost. A solution was found by adopting the metallic corner reflector which is known for high RCS levels over a wide bandwidth and over a wide angle of incidence. The study presents a novel corner reflector design where notches in the RCS spectral signature are created by the attachment of arrays of dielectric resonators to the metallic surfaces of corner reflectors. It is shown that notches appear due to the increased scattering of the resonators at resonance and by the power loss due to grating lobes formed in addition to the specular reflection from the arrays and from the metallic surfaces. Results from electromagnetic simulations are verified by measurements of an example dihedral corner reflector of 100 � 100 mm 2 plate size with two arrays of 3 � 3 DRs producing a notch signature at about 7 GHz. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
IEEE Antennas and Wireless Propagation Letters, 2020
This letter presents the integration of frequency selective surfaces (FSSs) with retroreflectors ... more This letter presents the integration of frequency selective surfaces (FSSs) with retroreflectors for the realization of chipless wireless indoor localization tag landmarks. As an example, the high radar cross section (RCS) of a trihedral corner reflector is signed with an FSS-based stopband filter, so that the backscattered power from several corner reflectors can be distinguished by a mobile reader according to the frequency response of the FSS. Measurement results with a 3 × 3 × 3 cm 3 trihedral corner reflector and a stopband FSS in a Rogers RT/Duroid 5880 high-frequency laminate at 90 GHz shows an RCS above −25 dBsqm for 90°c overage in the TM plane. Due to the high RCS, measurements at distances up to 4 m with a standard 25 dBi gain horn antenna and a vector network analyzer as a reader are shown. These preliminary results show the potential of the concept for applications such as indoor localization with sub-mm accuracy, where high bandwidths, but only a low number of bits, are needed for the identification of the tag landmarks.
Advances in Applied Mathematics and Mechanics, 2014
In this paper the problem − div(a(x,y)∇u) = f with Dirichlet boundary conditions on a square is s... more In this paper the problem − div(a(x,y)∇u) = f with Dirichlet boundary conditions on a square is solved iteratively with high accuracy for u and ∇u using a new scheme called “hermitian box-scheme”. The design of the scheme is based on a “hermitian box”, combining the approximation of the gradient by the fourth order hermitian derivative, with a conservative discrete formulation on boxes of length 2h. The iterative technique is based on the repeated solution by a fast direct method of a discrete Poisson equation on a uniform rectangular mesh. The problem is suitably scaled before iteration. The numerical results obtained show the efficiency of the numerical scheme. This work is the extension to strongly elliptic problems of the hermitian box-scheme presented by Abbas and Croisille (J. Sci. Comput., 49 (2011), pp. 239-267).
Dielectric resonators are placed in front of the metallic plane plate and corner reflectors. Exci... more Dielectric resonators are placed in front of the metallic plane plate and corner reflectors. Excitation of the resonant mode produces strong scattering of an incident plane wave which shows up as narrow notch in the mono-static radar cross section (RCS) spectral signature at the resonance frequency. Experimental proof at V-band is given with a corner reflector of centimetre size with spherical dielectric resonators of 0.8 mm diameter showing a notch at 64 GHz.
In a novel mm-wave localization system, dielectric resonators (DR) have been proposed as passive ... more In a novel mm-wave localization system, dielectric resonators (DR) have been proposed as passive chipless RFID tags to mark fixed reference nodes. To counter clutter and improve the limited read range due to the low RCS level of a DR at millimeter-wave frequencies we propose a combination of several DRs with a dielectric spherical lens which allows improvement of up to 30 dB. The paper presents the design principle and shows simulation results and experimental verification of a scaled tag operating in the 10–12 GHz range and covering a range of incidence angle of the reader signal of ± 50°. A frequency sweeping RF reader can identify the tag (information) by the peak of the RCS level at its DR resonant frequency. For a multiple-tag scenario we can realize up to 12 different tags which can be discriminated unambiguously by their resonant frequencies in a 1: 1.2 frequency bandwidth.
The RCS of flat cylindrical Dielectric Resonators (DR) is investigated and found to be too low fo... more The RCS of flat cylindrical Dielectric Resonators (DR) is investigated and found to be too low for an application of the resonators as tags in a novel indoor localization system at mm-wave frequencies. As a method to increase the RCS of a DR tag, we propose the combination with a constant-index spherical lens. The collimation and scattering properties of this lens type are found suitable for a combination with DRs. The optimum relative permittivity of the lens is found in the range of ϵr=1.6 to 2.8 and the optimum distance between lens surface and DR is found slightly larger than the radius of the DR. RCS enhancement is found to vary with the modes of the DR but increases approximately with the fourth power of the lens radius. However, RCS signatures become corrupted by scattering due to mismatch effects of large lenses such that the lens diameter has to be limited to 4 to 5 wavelengths with the RCS enhancement limited to about 30 to 35 dB. Simulation and experimental verification a...
The objective of the study was to establish relationship between the stock market measures and ec... more The objective of the study was to establish relationship between the stock market measures and economic growth in Tanzania. In order to achieve the objective, we need to examine the impact of stock market capitalization, total value of share traded and turnover on Tanzanian economy based on the time series data from 2000-2011. The unit root test and wnteestq (Portmanteau) tests were carried out. The findings suggest that Dares Salam Stock Exchange (DSE) has no effect on economic growth of Tanzania. We recommended that Tanzania government should establish financial policies, in order to encourage companies develop financial stock market culture, and enhance to push companies to initiate Initial Public Offering (IPO) instead of bank loans when money is needed to increase their investment.
International Journal of Business and Economics Research, 2016
Microfinance nowadays is about drawing the benefits of modern entrepreneurship downward to those ... more Microfinance nowadays is about drawing the benefits of modern entrepreneurship downward to those with low incomes relatively than endorse alternatives to free enterprise; "…it is a component of the post-Washington Consensus [30]" also not a substitute to the prevailing attitude. We adopted descriptive assessment techniques, the data were collected through interviewing or administering a questionnaire to a sample of 400 respondents, and analyzed by using SPSS software. There was strong negative correlation between multiple loans and positive corelation between business capacity and extent of higher interest rates charged. The study recommended that the business owner should focus on the level of the business capacity with loan proposed to be taken and make the comparisons of the daily business revenues operation and not the capital of the business initiatives.
... Nowee SM, Abbas A., Romagnoli JA, 2007, Optimization in seeded cooling crystallization: A par... more ... Nowee SM, Abbas A., Romagnoli JA, 2007, Optimization in seeded cooling crystallization: A parameter estimation and dynamic optimization study, Chemical Engineering and Processing, 46, 1096-1106. Sarker, D.; Rohani, S.; Jutan, A., 2006, Multi-Objective Optimization of ...
Pilomatrix carcinoma is the malignant counterpart of the pilomatrixoma which is a hamartoma of th... more Pilomatrix carcinoma is the malignant counterpart of the pilomatrixoma which is a hamartoma of the hair matrix. It is a rare locally aggressive skin tumor with a great tendency for recurrence but its metastatic potential is limited. We report a pilomatrix carcinoma with proven metastases to the lung in a 51-year old man who was admitted to the hospital for respiratory symptoms such as productive cough with green colored sputum and halitosis since one year ago.
While we believe that sample issues and measurement errors could contribute to the complexity of ... more While we believe that sample issues and measurement errors could contribute to the complexity of FDI-economic growth empirical analyses, the present work suggests that 99% of the mixed results are attributable to poor statistics, data treatment and model specifications. I.
Solar repowering of high pressure side feed water preheaters of post combustion carbon capture (P... more Solar repowering of high pressure side feed water preheaters of post combustion carbon capture (PCC) retrofitted power plants offers a promising capability to offset the power plant output penalty due to capture plant reboiler duty. In this work, a model based approach is used to investigate the technical, operational and control aspects of the solar thermal installation of the super structure (power plant + PCC + solar thermal plant). The base case is a 660 MWe PCC-retrofitted power plant operating at 100% capacity and 90% capture rate in Australia. This is repowered by a solar thermal plant consisting of (a) a parabolic trough solar collector field with 806,520 m 2 aperture area, (b) a thermal storage system with 8 full load hours of thermal storage and (c) an auxiliary gas heating unit, ensuring the solar thermal plant provides the high pressure side feed water preheating duty at all times without requirement to withdraw any steam from the power plant turbine circuit. A total of 230 MWth is provided from the solar thermal plant installation, being 100% supply for high pressure and intermediate feed water preheaters duty plus a surplus of 30% for maintaining the deaerator operation. A key feature here is trying to eliminate the frequent changes to the steam flow rate in the turbine circuit for solar feed water preheating and thus promoting ease of retrofit of repowering technology to PCC-retrofitted power plants. Details of the component sizing and modelling of solar thermal installation are provided and control and operating schemes are identified and analysed. A comprehensive dynamic model in TRNSYS dynamic modelling software is developed and used to analyse the solar thermal plant dynamic responses to external disturbances including climatic changes (Typical Meteorological data for Sydney is used). The analysis limitations and capabilities are highlighted. The model performance for month December is assessed showing its full capability to track the changes from power plant duty requirement and meteorological data within the time lapse of 0.01 s.
Different Fe 2 O 3 /ZnO nanocomposites were prepared by a simple solid-state reaction method, usi... more Different Fe 2 O 3 /ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe 2 O 3 and sodium hydroxide at room temperature. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe +3 to Zn +2 ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98-3.81eV and 2.75-2.98eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed.
Indoor localization based on unsynchronized, low-complexity, passive radio frequency identificati... more Indoor localization based on unsynchronized, low-complexity, passive radio frequency identification (RFID) using the received signal strength indicator (RSSI) has a wide potential for a variety of internet of things (IoTs) applications due to their energy-harvesting capabilities and low complexity. However, conventional RSSI-based algorithms present inaccurate ranging, especially in indoor environments, mainly because of the multipath randomness effect. In this work, we propose RSSI-based localization with low-complexity, passive RFID infrastructure utilizing the potential benefits of large-scale MIMO technology operated in the millimeter-wave band, which offers channel hardening, in order to alleviate the effect of small-scale fading. Particularly, by investigating an indoor environment equipped with extremely simple dielectric resonator (DR) tags, we propose an efficient localization algorithm that enables a smart object equipped with large-scale MIMO exploiting the RSSI measureme...
Long-term behaviour of steel fibre reinforced concrete remains rather unknown and to a large exte... more Long-term behaviour of steel fibre reinforced concrete remains rather unknown and to a large extent unquantified by equations and standards. This paper studies experimentally the free drying shrinkage of steel fibre reinforced lightweight concrete during the first 28 days using 100 Â 100 Â 500 mm beams. The coarse lightweight material tested (LYTAG) is recycled and offers an alternative to gravel and quarry resources which are subjected to depletion in the future. Also, this material can lead to reduction in the mass of the structure which results in economical designs. However, LYTAG aggregate can absorb up to 15% of its own weight in water. This makes it susceptible to drying shrinkage both at young age and long-term due to environmental diffusion. Shrinkage can have a detrimental effect on the concrete by inducing cracks, creating therefore weak zones in the concrete. It is thought that fibres can have a favourable effect on the reduction of shrinkage due to their ability to bridge cracks. This could be vital particularly in large concrete flat slabs, joints, beams and even columns. This project uses modern hooked-end DRAMIX 3D and 5D fibres with different dosages V f and number of hooks and evaluates shrinkage for concrete with different characteristic strengths f ck. KEYWORDS: Lytag Á Hooked-end fibres Á Early-age shrinkage Á Drying shrinkage Á Shrinkage beams Á Environmental diffusion Á Cracks
A method is proposed to derive and validate material properties for lightweight fibrous concrete ... more A method is proposed to derive and validate material properties for lightweight fibrous concrete using experimental and numerical data. The coarse lightweight material tested (produced by LYTAG) is recycled and offers an alternative to gravel and quarry resources which are at risk of depletion in future. Also, this material can lead to reduction in the mass of the structure which results in economical designs. However, in comparison to normal weight aggregate concrete (NWAC), lightweight aggregate concrete (LWAC) tends to be more brittle as it typically shears through the aggregates leading to instantaneous drop in peak load in both compression and tension tests. Hence, to address this brittleness for LWAC, modern hooked-end DRAMIX fibres with different geometry (hooks), dosages (V f) and bond strengths (s b) are added to mixes with different strengths (f ck). This paper focuses on both tensile properties using a direct pullout and indirect notched beam tests, and compressive properties (f ck , E, l) using the conventional compression test for cylinders of plain and steel-fibre reinforced lightweight concrete (SFRLC). A tensile semiempirical multilinear r-x relation was derived besides compressive re and validated against available steel fibre reinforced concrete (SFRC) constitutive models for the tested fibrous notched beams using ABAQUS.
For a novel indoor-localization system, chipless tags with high retro-directive radar crosssectio... more For a novel indoor-localization system, chipless tags with high retro-directive radar crosssection (RCS) under wide-angle incidence are required as fixed landmarks. Tags based on dielectric resonators (DRs) were proposed to provide identification by resonance frequency coding. To achieve a satisfactory read range for the localization system, the low RCS levels of these tags require a major boost. A solution was found by adopting the metallic corner reflector which is known for high RCS levels over a wide bandwidth and over a wide angle of incidence. The study presents a novel corner reflector design where notches in the RCS spectral signature are created by the attachment of arrays of dielectric resonators to the metallic surfaces of corner reflectors. It is shown that notches appear due to the increased scattering of the resonators at resonance and by the power loss due to grating lobes formed in addition to the specular reflection from the arrays and from the metallic surfaces. Results from electromagnetic simulations are verified by measurements of an example dihedral corner reflector of 100 � 100 mm 2 plate size with two arrays of 3 � 3 DRs producing a notch signature at about 7 GHz. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
IEEE Antennas and Wireless Propagation Letters, 2020
This letter presents the integration of frequency selective surfaces (FSSs) with retroreflectors ... more This letter presents the integration of frequency selective surfaces (FSSs) with retroreflectors for the realization of chipless wireless indoor localization tag landmarks. As an example, the high radar cross section (RCS) of a trihedral corner reflector is signed with an FSS-based stopband filter, so that the backscattered power from several corner reflectors can be distinguished by a mobile reader according to the frequency response of the FSS. Measurement results with a 3 × 3 × 3 cm 3 trihedral corner reflector and a stopband FSS in a Rogers RT/Duroid 5880 high-frequency laminate at 90 GHz shows an RCS above −25 dBsqm for 90°c overage in the TM plane. Due to the high RCS, measurements at distances up to 4 m with a standard 25 dBi gain horn antenna and a vector network analyzer as a reader are shown. These preliminary results show the potential of the concept for applications such as indoor localization with sub-mm accuracy, where high bandwidths, but only a low number of bits, are needed for the identification of the tag landmarks.
Advances in Applied Mathematics and Mechanics, 2014
In this paper the problem − div(a(x,y)∇u) = f with Dirichlet boundary conditions on a square is s... more In this paper the problem − div(a(x,y)∇u) = f with Dirichlet boundary conditions on a square is solved iteratively with high accuracy for u and ∇u using a new scheme called “hermitian box-scheme”. The design of the scheme is based on a “hermitian box”, combining the approximation of the gradient by the fourth order hermitian derivative, with a conservative discrete formulation on boxes of length 2h. The iterative technique is based on the repeated solution by a fast direct method of a discrete Poisson equation on a uniform rectangular mesh. The problem is suitably scaled before iteration. The numerical results obtained show the efficiency of the numerical scheme. This work is the extension to strongly elliptic problems of the hermitian box-scheme presented by Abbas and Croisille (J. Sci. Comput., 49 (2011), pp. 239-267).
Dielectric resonators are placed in front of the metallic plane plate and corner reflectors. Exci... more Dielectric resonators are placed in front of the metallic plane plate and corner reflectors. Excitation of the resonant mode produces strong scattering of an incident plane wave which shows up as narrow notch in the mono-static radar cross section (RCS) spectral signature at the resonance frequency. Experimental proof at V-band is given with a corner reflector of centimetre size with spherical dielectric resonators of 0.8 mm diameter showing a notch at 64 GHz.
In a novel mm-wave localization system, dielectric resonators (DR) have been proposed as passive ... more In a novel mm-wave localization system, dielectric resonators (DR) have been proposed as passive chipless RFID tags to mark fixed reference nodes. To counter clutter and improve the limited read range due to the low RCS level of a DR at millimeter-wave frequencies we propose a combination of several DRs with a dielectric spherical lens which allows improvement of up to 30 dB. The paper presents the design principle and shows simulation results and experimental verification of a scaled tag operating in the 10–12 GHz range and covering a range of incidence angle of the reader signal of ± 50°. A frequency sweeping RF reader can identify the tag (information) by the peak of the RCS level at its DR resonant frequency. For a multiple-tag scenario we can realize up to 12 different tags which can be discriminated unambiguously by their resonant frequencies in a 1: 1.2 frequency bandwidth.
The RCS of flat cylindrical Dielectric Resonators (DR) is investigated and found to be too low fo... more The RCS of flat cylindrical Dielectric Resonators (DR) is investigated and found to be too low for an application of the resonators as tags in a novel indoor localization system at mm-wave frequencies. As a method to increase the RCS of a DR tag, we propose the combination with a constant-index spherical lens. The collimation and scattering properties of this lens type are found suitable for a combination with DRs. The optimum relative permittivity of the lens is found in the range of ϵr=1.6 to 2.8 and the optimum distance between lens surface and DR is found slightly larger than the radius of the DR. RCS enhancement is found to vary with the modes of the DR but increases approximately with the fourth power of the lens radius. However, RCS signatures become corrupted by scattering due to mismatch effects of large lenses such that the lens diameter has to be limited to 4 to 5 wavelengths with the RCS enhancement limited to about 30 to 35 dB. Simulation and experimental verification a...
The objective of the study was to establish relationship between the stock market measures and ec... more The objective of the study was to establish relationship between the stock market measures and economic growth in Tanzania. In order to achieve the objective, we need to examine the impact of stock market capitalization, total value of share traded and turnover on Tanzanian economy based on the time series data from 2000-2011. The unit root test and wnteestq (Portmanteau) tests were carried out. The findings suggest that Dares Salam Stock Exchange (DSE) has no effect on economic growth of Tanzania. We recommended that Tanzania government should establish financial policies, in order to encourage companies develop financial stock market culture, and enhance to push companies to initiate Initial Public Offering (IPO) instead of bank loans when money is needed to increase their investment.
International Journal of Business and Economics Research, 2016
Microfinance nowadays is about drawing the benefits of modern entrepreneurship downward to those ... more Microfinance nowadays is about drawing the benefits of modern entrepreneurship downward to those with low incomes relatively than endorse alternatives to free enterprise; "…it is a component of the post-Washington Consensus [30]" also not a substitute to the prevailing attitude. We adopted descriptive assessment techniques, the data were collected through interviewing or administering a questionnaire to a sample of 400 respondents, and analyzed by using SPSS software. There was strong negative correlation between multiple loans and positive corelation between business capacity and extent of higher interest rates charged. The study recommended that the business owner should focus on the level of the business capacity with loan proposed to be taken and make the comparisons of the daily business revenues operation and not the capital of the business initiatives.
... Nowee SM, Abbas A., Romagnoli JA, 2007, Optimization in seeded cooling crystallization: A par... more ... Nowee SM, Abbas A., Romagnoli JA, 2007, Optimization in seeded cooling crystallization: A parameter estimation and dynamic optimization study, Chemical Engineering and Processing, 46, 1096-1106. Sarker, D.; Rohani, S.; Jutan, A., 2006, Multi-Objective Optimization of ...
Pilomatrix carcinoma is the malignant counterpart of the pilomatrixoma which is a hamartoma of th... more Pilomatrix carcinoma is the malignant counterpart of the pilomatrixoma which is a hamartoma of the hair matrix. It is a rare locally aggressive skin tumor with a great tendency for recurrence but its metastatic potential is limited. We report a pilomatrix carcinoma with proven metastases to the lung in a 51-year old man who was admitted to the hospital for respiratory symptoms such as productive cough with green colored sputum and halitosis since one year ago.
While we believe that sample issues and measurement errors could contribute to the complexity of ... more While we believe that sample issues and measurement errors could contribute to the complexity of FDI-economic growth empirical analyses, the present work suggests that 99% of the mixed results are attributable to poor statistics, data treatment and model specifications. I.
Solar repowering of high pressure side feed water preheaters of post combustion carbon capture (P... more Solar repowering of high pressure side feed water preheaters of post combustion carbon capture (PCC) retrofitted power plants offers a promising capability to offset the power plant output penalty due to capture plant reboiler duty. In this work, a model based approach is used to investigate the technical, operational and control aspects of the solar thermal installation of the super structure (power plant + PCC + solar thermal plant). The base case is a 660 MWe PCC-retrofitted power plant operating at 100% capacity and 90% capture rate in Australia. This is repowered by a solar thermal plant consisting of (a) a parabolic trough solar collector field with 806,520 m 2 aperture area, (b) a thermal storage system with 8 full load hours of thermal storage and (c) an auxiliary gas heating unit, ensuring the solar thermal plant provides the high pressure side feed water preheating duty at all times without requirement to withdraw any steam from the power plant turbine circuit. A total of 230 MWth is provided from the solar thermal plant installation, being 100% supply for high pressure and intermediate feed water preheaters duty plus a surplus of 30% for maintaining the deaerator operation. A key feature here is trying to eliminate the frequent changes to the steam flow rate in the turbine circuit for solar feed water preheating and thus promoting ease of retrofit of repowering technology to PCC-retrofitted power plants. Details of the component sizing and modelling of solar thermal installation are provided and control and operating schemes are identified and analysed. A comprehensive dynamic model in TRNSYS dynamic modelling software is developed and used to analyse the solar thermal plant dynamic responses to external disturbances including climatic changes (Typical Meteorological data for Sydney is used). The analysis limitations and capabilities are highlighted. The model performance for month December is assessed showing its full capability to track the changes from power plant duty requirement and meteorological data within the time lapse of 0.01 s.
Different Fe 2 O 3 /ZnO nanocomposites were prepared by a simple solid-state reaction method, usi... more Different Fe 2 O 3 /ZnO nanocomposites were prepared by a simple solid-state reaction method, using zinc acetate, α-Fe 2 O 3 and sodium hydroxide at room temperature. The characterization results showed that the morphology, crystallite size, BET surface area and optical absorption of the samples varied significantly with the Fe +3 to Zn +2 ratios. The nanocomposites show two absorption edges at ultraviolet and visible region. The optical band gap values of these nanocomposites were calculated to be about 3.98-3.81eV and 2.75-2.98eV, which show a red shift from that of pure ZnO. These red shifts are related to the formation of Fe s-levels below the conductive band edge of ZnO and effectively extend the absorption edge into the visible region. The growth mechanisms of the samples are proposed.
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Papers by Ali Abbas