Ahmad Usman | Georgia Institute of Technology (original) (raw)
Papers by Ahmad Usman
Journal of Renewable and Sustainable Energy, 2017
Frontiers in Optics + Laser Science 2021, 2021
We demonstrate deep learning enabled forward modeling and inverse design of integrated silicon na... more We demonstrate deep learning enabled forward modeling and inverse design of integrated silicon nanophotonic grating. Predicted response by the forward modeling and predicted response and geometries by inverse design algorithm are shown with a prediction mean-square-error of the order of 10 − 4.
Frontiers in Optics 2017, 2017
We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI w... more We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI with high-Q TM-polarized resonant modes, which provide high-sensitivity and relatively large sensing area. The sensor performance is characterized using avidin-biotin surface chemistries.
IEEE Reviews in Biomedical Engineering, 2020
Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process ... more Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.
2016 IEEE Topical Conference on Biomedical Wireless Technologies, Networks, and Sensing Systems (BioWireleSS), 2016
In this paper, we present the design, fabrication and characterization of implantable coils, oper... more In this paper, we present the design, fabrication and characterization of implantable coils, operating at 13.56 MHz ISM band for biomedical applications. Rogers RO 4003C substrate was used for the prototype of the implantable coil while Rogers RO 3850 flexible substrate was used for the external transmitter coil. The Inkjet masking technique was used for the patterning the planar coil on the flexible substrate. Wireless power transfer efficiency measurements were conducted in free space and water environments, varying the operating distance between the prototype coils from 5mm to 20mm, featuring transfer efficiencies upto 55% and 35%, respectively.
2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021
Integrated silicon nanophotonics has enabled low-cost, compact, and densely integrated high perfo... more Integrated silicon nanophotonics has enabled low-cost, compact, and densely integrated high performance optical devices. On-chip grating couplers are realized for coupling light to these devices. These grating couplers are CMOS compatible, allow vertical coupling of light, dense integration, relaxed fiber-coupler alignment, polarization dependent operation, and ease of fabrication [1] , [2] . Conventional design of these nanophotonic gratings typically involves repeated electromagnetic simulations which are time consuming and resource inefficient. Recently, the data driven approaches based on machine learning algorithms, specifically inverse design approach has emerged as alternate to the design of integrated nanophotonic devices [3] , [4] .
Renewable and Sustainable Energy Reviews, 2013
2012 International Conference on Informatics, Electronics & Vision (ICIEV), 2012
ABSTRACT Orthogonal Frequency Division Multiplexing (OFDM) is a bandwidth efficient signaling sch... more ABSTRACT Orthogonal Frequency Division Multiplexing (OFDM) is a bandwidth efficient signaling scheme for digital communications that was first proposed by Chang. In OFDM, the spectrum of individual orthogonal subcarriers mutually overlaps, giving therefore an optimum spectrum efficiency. A data communications system based on OFDM is particularly sensitive to frequency offset in the channel. Frequency offset is a phenomena, which causes phase shift and hence, reduction in signal strength at the output of the filters matched to each of the carriers and introduces ICI from other carriers which are now no longer orthogonal to the filter. In OFDM the carriers are inherently closely spaced in frequency compared to the channel bandwidth, the tolerable frequency offset becomes a very small fraction of the channel bandwidth. This paper is based on the study and comparison of algorithms that estimate the carrier and sampling frequency offsets from the demodulated data signals in the receiver. An implementation of these techniques to correct the respective offsets along with the performance of these algorithms, via simulation, is also presented.
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2017
2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021
We demonstrated deep learning based inverse design of integrated silicon nanophotonic grating. Pr... more We demonstrated deep learning based inverse design of integrated silicon nanophotonic grating. Predicted geometries by the inverse design algorithm resulted in mean-square-error of the order of 10-4 while comparison of simulated and predicted transmission response.
IEEE Reviews in Biomedical Engineering, 2020
Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process ... more Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.
We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI w... more We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI with high-Q TM-polarized resonant modes, which provide high-sensitivity and relatively large sensing area. The sensor performance is characterized using avidin-biotin surface chemistries.
IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, 2017
This paper explores the current state of the art in silicon, organic, and glass interposer techno... more This paper explores the current state of the art in silicon, organic, and glass interposer technologies and their high-performance applications. Issues and challenges broadly encompassing electrical, mechanical, and thermal properties of these interposer technologies are discussed along with the proven and under research solutions pertaining to these challenges. An evaluation of high-performance applications for these three technologies provides a useful insight into the role of interposers for such applications. This paper is an effort to evaluate and compare the viability of silicon, organic, and glass interposer technologies for high-performance applications. This paper also discusses the future trends, promising advancements, and market requirements with special emphasis on glass interposer technologies as evaluated to be the most viable option for the future high-performance applications.
Ground mounted solar PV systems utilize a large amount of land that could otherwise be used for d... more Ground mounted solar PV systems utilize a large amount of land that could otherwise be used for different developmental activities, such as agricultural growth, fuel crops production, and industrial development. Utilizing the already built infrastructures such as building rooftops, parking sheds, and canal water systems for installation of solar PV projects has proven beneficial as it minimizes the procurement and opportunity cost of the land. Taking into consideration the best practices adopted globally, Pakistan must evolve its policy for a shift towards utilization of existing infrastructures rather than using prime lands for solar PV power projects. Building Integrated Photovoltaic (BIPV) systems have been effective for deployment and penetration of solar PV technology (SPVT) in different countries. In this paper, we present a case study, established on the basis of existing BIPV principles followed in developed countries. This case study proposes to utilize existing storm water drains, parking lots, and land across lake sites for solar PV system installation at an educational institution, National University of Sciences and Technology (NUST). A detailed analysis has been performed to evaluate the project's financial feasibility in terms of economic indexes such as Payback Period, Discounted Cash Flows, Net Present Value, and Internal Rate of Return. Results show that a 5 MW distributed solar PV system installed on an otherwise non-utilizable land at the university's premises shall provide a payback period of 7.09 years at an attractive internal rate of return of 13%. Published by AIP Publishing. [http://dx.doi.org/10.1063/1.4976143]
In this paper, we present the design, fabrication and characterization of implantable coils, ope... more In this paper, we present the design, fabrication and characterization of implantable coils, operating at 13.56 MHz ISM band for biomedical applications. Rogers RO 4003C substrate was used for the prototype of the implantable coil while Rogers RO 3850 flexible substrate was used for the external transmitter coil. The Inkjet masking technique was used for the patterning the planar coil on the flexible sub-strate. Wireless power transfer efficiency measurements were conducted in free space and water environments, varying the operating distance between the prototype coils from 5 mm to 20 mm, featuring transfer efficiencies upto 55% and 35% ,respectively.
The idea of Smart Grid has started to evolve more rapidly with the enhancement in Communication T... more The idea of Smart Grid has started to evolve more rapidly with the enhancement in Communication Technologies. Two way communication is a key aspect in realizing Smart Grids and is easily possible with the help of modern day advancements in both wired and wireless communication technologies. This paper discusses some of the major communication technologies which include IEEE specified ZigBee, WiMAX and Wireless LAN (Wi-Fi) technologies, GSM 3G/4G Cellular, DASH 7 and PLC (Power Line Communications), with special focus on their applications in Smart Grids. The Smart Grid environments and domains such as Home Area Automation, Substation Automation, Automated Metering Infrastructure, Vehicle-to-Grid Communications, etc. are considered as priority areas for developing smarter grids. The advancements, challenges and the opportunities present in these priority areas are discussed in this paper.
In this paper, an Impedance Source (Z-Source) Inverter based Indirect Field Oriented Control for ... more In this paper, an Impedance Source (Z-Source) Inverter based Indirect Field Oriented Control for a three phase induction motor drive is presented. The Z-Source Inverter consists of traditional switching network along with a unique LC passive symmetrical network between the dc front end and the switching network. The output AC Voltage can be controlled by either controlling the shoot through duty cycle (Dsh) or Modulation Index (M). A feedback control mechanism is proposed for controlling both shoot through duty cycle and the modulation index. Indirect Field Oriented Control strategy is implemented with an added capability of Synchronous Current Injection. It avoids the issues of controller saturation at high speeds as commonly seen in the traditional Hysteresis Band Controller based drives. Feedforward CEMF (Counter Electro-Magnetic Force) compensation is also introduced in the feedback loops of the controller to enhance the overall loop response. Simulation results are used to validate the proposed solution for high speeds.
Books by Ahmad Usman
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Journal of Renewable and Sustainable Energy, 2017
Frontiers in Optics + Laser Science 2021, 2021
We demonstrate deep learning enabled forward modeling and inverse design of integrated silicon na... more We demonstrate deep learning enabled forward modeling and inverse design of integrated silicon nanophotonic grating. Predicted response by the forward modeling and predicted response and geometries by inverse design algorithm are shown with a prediction mean-square-error of the order of 10 − 4.
Frontiers in Optics 2017, 2017
We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI w... more We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI with high-Q TM-polarized resonant modes, which provide high-sensitivity and relatively large sensing area. The sensor performance is characterized using avidin-biotin surface chemistries.
IEEE Reviews in Biomedical Engineering, 2020
Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process ... more Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.
2016 IEEE Topical Conference on Biomedical Wireless Technologies, Networks, and Sensing Systems (BioWireleSS), 2016
In this paper, we present the design, fabrication and characterization of implantable coils, oper... more In this paper, we present the design, fabrication and characterization of implantable coils, operating at 13.56 MHz ISM band for biomedical applications. Rogers RO 4003C substrate was used for the prototype of the implantable coil while Rogers RO 3850 flexible substrate was used for the external transmitter coil. The Inkjet masking technique was used for the patterning the planar coil on the flexible substrate. Wireless power transfer efficiency measurements were conducted in free space and water environments, varying the operating distance between the prototype coils from 5mm to 20mm, featuring transfer efficiencies upto 55% and 35%, respectively.
2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021
Integrated silicon nanophotonics has enabled low-cost, compact, and densely integrated high perfo... more Integrated silicon nanophotonics has enabled low-cost, compact, and densely integrated high performance optical devices. On-chip grating couplers are realized for coupling light to these devices. These grating couplers are CMOS compatible, allow vertical coupling of light, dense integration, relaxed fiber-coupler alignment, polarization dependent operation, and ease of fabrication [1] , [2] . Conventional design of these nanophotonic gratings typically involves repeated electromagnetic simulations which are time consuming and resource inefficient. Recently, the data driven approaches based on machine learning algorithms, specifically inverse design approach has emerged as alternate to the design of integrated nanophotonic devices [3] , [4] .
Renewable and Sustainable Energy Reviews, 2013
2012 International Conference on Informatics, Electronics & Vision (ICIEV), 2012
ABSTRACT Orthogonal Frequency Division Multiplexing (OFDM) is a bandwidth efficient signaling sch... more ABSTRACT Orthogonal Frequency Division Multiplexing (OFDM) is a bandwidth efficient signaling scheme for digital communications that was first proposed by Chang. In OFDM, the spectrum of individual orthogonal subcarriers mutually overlaps, giving therefore an optimum spectrum efficiency. A data communications system based on OFDM is particularly sensitive to frequency offset in the channel. Frequency offset is a phenomena, which causes phase shift and hence, reduction in signal strength at the output of the filters matched to each of the carriers and introduces ICI from other carriers which are now no longer orthogonal to the filter. In OFDM the carriers are inherently closely spaced in frequency compared to the channel bandwidth, the tolerable frequency offset becomes a very small fraction of the channel bandwidth. This paper is based on the study and comparison of algorithms that estimate the carrier and sampling frequency offsets from the demodulated data signals in the receiver. An implementation of these techniques to correct the respective offsets along with the performance of these algorithms, via simulation, is also presented.
IEEE Transactions on Components, Packaging and Manufacturing Technology, 2017
2021 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), 2021
We demonstrated deep learning based inverse design of integrated silicon nanophotonic grating. Pr... more We demonstrated deep learning based inverse design of integrated silicon nanophotonic grating. Predicted geometries by the inverse design algorithm resulted in mean-square-error of the order of 10-4 while comparison of simulated and predicted transmission response.
IEEE Reviews in Biomedical Engineering, 2020
Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process ... more Prostate Cancer (PCa) is one of the deadliest forms of Cancer among men. Early screening process for PCa is primarily conducted with the help of a FDA approved biomarker known as Prostate Specific Antigen (PSA). The PSA-based screening is challenged with the inability to differentiate between the cancerous PSA and Benign Prostatic Hyperplasia (BPH), resulting in high rates of false-positives. Optical techniques such as optical absorbance, scattering, surface plasmon resonance (SPR), and fluorescence have been extensively employed for Cancer diagnostic applications. One of the most important diagnostic applications involves utilization of nanoparticles (NPs) for highly specific, sensitive, rapid, multiplexed, and high performance Cancer detection and quantification. The incorporation of NPs with these optical biosensing techniques allow realization of low cost, point-of-care, highly sensitive, and specific early cancer detection technologies, especially for PCa. In this work, the current state-of-the-art, challenges, and efforts made by the researchers for realization of low cost, point-of-care (POC), highly sensitive, and specific NP enhanced optical biosensing technologies for PCa detection using PSA biomarker are discussed and analyzed.
We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI w... more We present highly-sensitive and compact label-free biosensors based on spiral resonators on SOI with high-Q TM-polarized resonant modes, which provide high-sensitivity and relatively large sensing area. The sensor performance is characterized using avidin-biotin surface chemistries.
IEEE TRANSACTIONS ON COMPONENTS, PACKAGING AND MANUFACTURING TECHNOLOGY, 2017
This paper explores the current state of the art in silicon, organic, and glass interposer techno... more This paper explores the current state of the art in silicon, organic, and glass interposer technologies and their high-performance applications. Issues and challenges broadly encompassing electrical, mechanical, and thermal properties of these interposer technologies are discussed along with the proven and under research solutions pertaining to these challenges. An evaluation of high-performance applications for these three technologies provides a useful insight into the role of interposers for such applications. This paper is an effort to evaluate and compare the viability of silicon, organic, and glass interposer technologies for high-performance applications. This paper also discusses the future trends, promising advancements, and market requirements with special emphasis on glass interposer technologies as evaluated to be the most viable option for the future high-performance applications.
Ground mounted solar PV systems utilize a large amount of land that could otherwise be used for d... more Ground mounted solar PV systems utilize a large amount of land that could otherwise be used for different developmental activities, such as agricultural growth, fuel crops production, and industrial development. Utilizing the already built infrastructures such as building rooftops, parking sheds, and canal water systems for installation of solar PV projects has proven beneficial as it minimizes the procurement and opportunity cost of the land. Taking into consideration the best practices adopted globally, Pakistan must evolve its policy for a shift towards utilization of existing infrastructures rather than using prime lands for solar PV power projects. Building Integrated Photovoltaic (BIPV) systems have been effective for deployment and penetration of solar PV technology (SPVT) in different countries. In this paper, we present a case study, established on the basis of existing BIPV principles followed in developed countries. This case study proposes to utilize existing storm water drains, parking lots, and land across lake sites for solar PV system installation at an educational institution, National University of Sciences and Technology (NUST). A detailed analysis has been performed to evaluate the project's financial feasibility in terms of economic indexes such as Payback Period, Discounted Cash Flows, Net Present Value, and Internal Rate of Return. Results show that a 5 MW distributed solar PV system installed on an otherwise non-utilizable land at the university's premises shall provide a payback period of 7.09 years at an attractive internal rate of return of 13%. Published by AIP Publishing. [http://dx.doi.org/10.1063/1.4976143]
In this paper, we present the design, fabrication and characterization of implantable coils, ope... more In this paper, we present the design, fabrication and characterization of implantable coils, operating at 13.56 MHz ISM band for biomedical applications. Rogers RO 4003C substrate was used for the prototype of the implantable coil while Rogers RO 3850 flexible substrate was used for the external transmitter coil. The Inkjet masking technique was used for the patterning the planar coil on the flexible sub-strate. Wireless power transfer efficiency measurements were conducted in free space and water environments, varying the operating distance between the prototype coils from 5 mm to 20 mm, featuring transfer efficiencies upto 55% and 35% ,respectively.
The idea of Smart Grid has started to evolve more rapidly with the enhancement in Communication T... more The idea of Smart Grid has started to evolve more rapidly with the enhancement in Communication Technologies. Two way communication is a key aspect in realizing Smart Grids and is easily possible with the help of modern day advancements in both wired and wireless communication technologies. This paper discusses some of the major communication technologies which include IEEE specified ZigBee, WiMAX and Wireless LAN (Wi-Fi) technologies, GSM 3G/4G Cellular, DASH 7 and PLC (Power Line Communications), with special focus on their applications in Smart Grids. The Smart Grid environments and domains such as Home Area Automation, Substation Automation, Automated Metering Infrastructure, Vehicle-to-Grid Communications, etc. are considered as priority areas for developing smarter grids. The advancements, challenges and the opportunities present in these priority areas are discussed in this paper.
In this paper, an Impedance Source (Z-Source) Inverter based Indirect Field Oriented Control for ... more In this paper, an Impedance Source (Z-Source) Inverter based Indirect Field Oriented Control for a three phase induction motor drive is presented. The Z-Source Inverter consists of traditional switching network along with a unique LC passive symmetrical network between the dc front end and the switching network. The output AC Voltage can be controlled by either controlling the shoot through duty cycle (Dsh) or Modulation Index (M). A feedback control mechanism is proposed for controlling both shoot through duty cycle and the modulation index. Indirect Field Oriented Control strategy is implemented with an added capability of Synchronous Current Injection. It avoids the issues of controller saturation at high speeds as commonly seen in the traditional Hysteresis Band Controller based drives. Feedforward CEMF (Counter Electro-Magnetic Force) compensation is also introduced in the feedback loops of the controller to enhance the overall loop response. Simulation results are used to validate the proposed solution for high speeds.