Ahmad Hassan - Academia.edu (original) (raw)

Papers by Ahmad Hassan

To assess the effects of co-opetition—simultaneous competition and collaboration—on competitive a... more To assess the effects of co-opetition—simultaneous competition and collaboration—on competitive aggressiveness, this article relates one aspect of embeddedness—tie strength—to the volume and complexity of a firm’s competitive actions. Findings from our study of firms in the U.S. software industry suggest that strong ties increase the volume and complexity of competitive actions. Results also suggest that action volume is negatively related to the interaction between tie strength and both multimarket contact and resource similarity. However, results show that neither resource similarity nor multimarket contact did have direct or moderating effects on the relationship between tie strength and action complexity. Keywords competition, collaboration, competitive aggressiveness In recent years, strategy researchers have paid increasing attention to understanding the competitive actions taken by firms (Chen, 1996; Ferrier, 2001; Grimm & Smith, 1997). However, significant gaps in our unders...

Electronics

We consider the problem of simultaneous diagonalization of Hermitian matrices for the desired and... more We consider the problem of simultaneous diagonalization of Hermitian matrices for the desired and co-channel interference terms of millimeter-wave (mmWave) multi-user multiple-input multiple-output systems. The joint unitary eigenvectors and the corresponding eigenvalues are known to assist in the mathematical tractability of key performance metrics, such as outage probability, ergodic capacity, and spectral efficiency. We formulate the signal-to-interference-plus-noise ratio in a canonical quadratic form and subsume the digital baseband beamforming vectors in the weight matrices of channels at the transmitter side. Next, a real scalar objective function is defined, which quantifies the correlation loss due to joint-diagonalization. The objective function is then maximized using baseband beamforming under the hardware constraints of the mmWave system. Through simulations, the proposed beamforming algorithm is evaluated by employing several non-linear optimization sub-routines, and i...

This study aims to study the significant Israeli Hebrew influence on the Arabic spoken and writte... more This study aims to study the significant Israeli Hebrew influence on the Arabic spoken and written natively by Israeli Arabs (Arab 48). It aims to shed light on the sociolinguistic situation of Arabic in Israel, by reviewing the complex situation of linguistic diglossia and Linguistic Interference in these two Semitic languages. Israeli Arabs, and Israeli Jews, who are speakers of Hebrew, have daily contact in many fields of life. These two languages are in close contact, and thereby many mutual influences are enabled between them. As a result, a great deal of mutual linguistic influence is observed in each language. This study shows that Hebrew elements are very widespread in all linguistic fields of the Arabic spoken by Israeli Arabs. Israeli Hebrew lexical items have permeated all areas of professional, educational, administrative, Economical, and social activities in everyday life discourse in all styles and registers of the spoken language and, to a lesser extent, written langu...

This paper deals with the quantitative assessment of the unreliability of migration between habit... more This paper deals with the quantitative assessment of the unreliability of migration between habitat patches in terms of ecological corridor unreliabilities that are known only with uncertainty. The corridor unreliabilities are treated herein as log-normally distributed random variables, and hence the assessment becomes a doublystochastic one. The paper utilizes the multi-affine nature of the reliability function in deriving exact formulas for the mean and variance of the system unreliability, as well as accurate formulas for its third and fourth central moments. These formulas involve the nominal values of certain partial derivatives. The multi-affine nature is also beneficial in the development of an alternative method that involves powers rather than derivatives. These two analytical methods of moments agree reasonably with one another and with the results of Monte Carlo simulations. Several test cases are considered for typical ecology problems with corridor unreliabilities that ...

Iranian Journal of Pharmaceutical Research, 2008

The potential to cause tissue damage by metal ions is the matter of widespread investigation. Tit... more The potential to cause tissue damage by metal ions is the matter of widespread investigation. Titanium salts are widely used in industry for ceramic painting, in pharmacy for tablet coating and making chemical sunscreens and in medicine as photo catalysts with bactericidal activity. This may address the idea that the exposure to these salts could play a role in metabolic disorders. In this study the effect of Ti on liver contents of lipid fractions was investigated. Male Wistar rats (200-250 g) were used for the experiments. Groups of animals were injected for 10 days with 2.5 mg/kg of titanium chloride, as acute dose and for 30 and 60 days with 0.75 mg/kg as chronic doses. At the end of the experimental period animals were anaesthetized, the abdomens were opened and the livers were perfused with appropriate buffer. Livers were then removed immediately and used fresh or kept frozen until the analysis. Livers were then homogenized and their contents of triglycerides and phospholipids...

Sensors

This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-... more This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-orthogonal multiple-access (MISO-NOMA) system under the Rayleigh fading channel in the presence of an eavesdropper. We suppose a worst-case scenario that an eavesdropper has ideal user detection ability. In particular, we suggest an optimization-based beamforming scheme with MISO-NOMA to improve the security and outage probability of a cell-edge user while maintaining the quality of service of the near-user and degrading the performance of the eavesdropper. To this end, power allocation coefficients are adjusted with the help of target data rates of both the users by utilizing a simultaneous wireless information and power transfer with time switching/power splitting protocol, where the near-user is used to forward the information to cell-edge user. The analytical results demonstrate that our beamformer analysis can achieve reduced outage probability of cell-edge user in the presence of t...

Ordinary Jerusalem, 1840-1940

This is an open access chapter distributed under the terms of the prevailing CC-BY-NC-ND License ... more This is an open access chapter distributed under the terms of the prevailing CC-BY-NC-ND License at the time of publication.

Proceedings of the 53rd Hawaii International Conference on System Sciences

Sensors

Closed-form evaluation of key performance indicators (KPIs) of telecommunication networks help pe... more Closed-form evaluation of key performance indicators (KPIs) of telecommunication networks help perform mathematical analysis under several network configurations. This paper deals with a recent mathematical approach of indefinite quadratic forms to propose simple albeit exact closed-form expressions of the expectation of two significant logarithmic functions. These functions formulate KPIs which include the ergodic capacity and leakage rate of multi-user multiple-input multiple-output (MU-MIMO) systems in Rayleigh fading channels. Our closed-form expressions are generic in nature and they characterize several network configurations under statistical channel state information availability. As a demonstrative example of the proposed characterization, the derived expressions are used in the statistical transmit beamformer design in a broadcast MU-MIMO system to portray promising diversity gains using standalone or joint maximization techniques of the ergodic capacity and leakage rate. ...

Pharmaceuticals

Extended overuse and misuse of antibiotics and other antibacterial agents has resulted in an anti... more Extended overuse and misuse of antibiotics and other antibacterial agents has resulted in an antimicrobial resistance crisis. Bacteriophages, viruses that infect bacteria, have emerged as a legitimate alternative antibacterial agent with a wide scope of applications which continue to be discovered and refined. However, the potential of some bacteriophages to aid in the acquisition, maintenance, and dissemination of negatively associated bacterial genes, including resistance and virulence genes, through transduction is of concern and requires deeper understanding in order to be properly addressed. In particular, their ability to interact with mobile genetic elements such as plasmids, genomic islands, and integrative conjugative elements (ICEs) enables bacteriophages to contribute greatly to bacterial evolution. Nonetheless, bacteriophages have the potential to be used as therapeutic and biocontrol agents within medical, agricultural, and food processing settings, against bacteria in ...

Business Information Systems

Supply chain risks negatively affect the success of an OEM in automotive industry. Finding releva... more Supply chain risks negatively affect the success of an OEM in automotive industry. Finding relevant information for supply chain risk management (SCRM) is a critical task. This investigation utilizes machine learning to find risk within textual documents. It contributes to the supply chain management (SCM) by designing (i) a conceptual model for supply risk identification in textual data. This addresses the requirement to see the direct connection between data analytics and SCM. (ii) An experiment in which a prototype is evaluated contributes the requirement to have more empirical insight in the interdisciplinary field of data analytics in SCRM.

COVID-19 pandemic has caused significant morbidity and mortality around the world. The disease se... more COVID-19 pandemic has caused significant morbidity and mortality around the world. The disease severity ranges from mild upper respiratory infection to severe lower respiratory and cardiac illness. Acute respiratory distress syndrome (ARDS) is the most serious complication and results in diffuse inflammatory alveolar damage, respiratory failure, and death. Components of the Renin-Angiotensin-Aldosterone-System (RAAS) are involved in an inflammatory reaction in the lungs. Various studies have shown that blocking RAAS peptides in the lungs especially angiotensin-converting enzyme (ACE) and type-1 angiotensin receptor (ATR1) reduces lung injury, improves respiratory function, and is associated with better clinical outcomes in the COVID-19 patients. We suggest that angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARBs) – drugs that block RAAS peptides – be considered for a repurposed use in COVID-19 induced lung injury.

Journal of Management Research

Project portfolio management (PPM) is an important area of interest in many organizations. There ... more Project portfolio management (PPM) is an important area of interest in many organizations. There is a wide literature on each of many different aspects of PPM. The central purpose of the current paper is to focus on a specific sub-area of PPM, namely the project portfolio selection (PPS) problem. Specifically, we develop a new methodology that will aid management in choosing from a set of candidate project proposals, a subset of those project proposals that align with strategic objectives of the organization. Research methodology is based on the data envelopment analysis (DEA) construct to compare a set of decision making units (such as proposed projects) to arrive at an efficiency score for each member of this competing set, derive the best performers, generate an efficiency frontier and quantify inefficiency in the non-best performers. While DEA has been applied in numerous settings, the unique feature of the project portfolio application is the presence of two sets of data, namel...

Journal of the Chinese Institute of Engineers

Abstract This work presents modeling and performance analysis of beamforming in non-cooperative m... more Abstract This work presents modeling and performance analysis of beamforming in non-cooperative multi-user multiple-input multiple-output (MU-MIMO) cellular systems using stochastic geometry based abstraction models. Particularly, a downlink MU-MIMO system is investigated in which an array of antenna elements at the base stations (BS) serves several user devices. We derive the closed-form expression of the complimentary cumulative distribution function (CCDF) of signal-to-interference-plus-noise ratio (SINR) representing the coverage probability for orthogonal pilot sequences and thereby characterize a number of related special cases. Moreover, closed-form expressions are also obtained for the CCDF of signal-to-interference ratio (SIR) for non-orthogonal pilot sequences and we also derive useful special cases of it and identify the support region of our analysis. Lastly, we define the numerical expression of ergodic capacity and utilize a partial fraction expansion to solve a simple form. Our contribution in this work is twofold, we not only provide a pedagogical tutorial-like exposition of stochastic geometry technique to model terrestrial networks, but also augment the existing literature in the field with aspects of frequency reuse factor, an indicator function for pilot usage, and the effect of pilot contamination. Simulation results are presented to support the theoretical part.

IEEE Transactions on Computers

This paper studies the problem of efficiently utilizing hybrid memory systems, consisting of both... more This paper studies the problem of efficiently utilizing hybrid memory systems, consisting of both Dynamic Random Access Memory (DRAM) and novel Non-Volatile Memory (NVM) in database management systems (DBMS) for online analytical processing (OLAP) workloads. We present a methodology to determine the database operators that are responsible for most main memory accesses. Our analysis uses both cost models and empirical measurements. We develop heuristic decision procedures to allocate data in hybrid memory at the time that the data buffers are allocated, depending on the expected memory access frequency. We implement these heuristics in the MonetDB column-oriented database and demonstrate performance improvement and energy-efficiency as compared to state-of-the-art application-agnostic hybrid memory management techniques.

Wireless Personal Communications

This communication attempts to characterize the performance metrics of downlink Massive MU-MIMO s... more This communication attempts to characterize the performance metrics of downlink Massive MU-MIMO systems impaired by cochannel interference and additive noise over a Rayleigh fading environment. We obtain close-form solutions for the probability density function of signal-to-interference-plus-noise ratio (SINR) and the sum ergodic capacity. The proposed work structures SINR in a quadratic form and thereby imposes a condition on its signal and interference power for a large transmit antenna diversity order; the conditional form is then analyzed using a distance correlation metric. Eventually, the sum ergodic capacity is expressed in a close-form by means of a residue theory approach and validated using the Monte Carlo simulation means.

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES

In this paper, we characterize the performance metrics of a multiuser multipolarized antenna syst... more In this paper, we characterize the performance metrics of a multiuser multipolarized antenna system in a Rayleigh fading channel. We start by formulating a downlink system model that features a multiuser scenario in the presence of additive noise and a multipolarized antenna system; this is followed by evaluation of the outage probability in closed form. This is done by deriving the cumulative distribution function (CDF) of the signal-to-interference-plusnoise ratio using the approach of the ratio of indefinite quadratic forms. We thereby characterize the gradient of this CDF with respect to the combining vectors. Eventually, we obtain the optimum combining vectors by minimizing the outage probability via interior-point optimization technique. Simulation and theoretical results of our analysis are closely matched, which validates our analysis. Our findings suggest that the performance of the triple polarized antenna is better than that of the dual polarized antenna system for low signal-to-noise ratio (SNR) values in terms of outage probability; this situation, however, reverses for high SNR value.

Chemical biology & drug design, Jan 29, 2018

Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the curre... more Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the current study, roxithromycin (ROX) was successfully labeled with technetium-99m for early diagnosis of bacterial infection and discrimination between septic and aseptic inflammation. The highest radiochemical purity of ≥95% was achieved by investigating different labeling parameters such as pH, ligand/reducing agent concentration, temperature, and amount of stabilizing agent. For this purpose, 0.3-0.5 mg ligand, 2-6 μg SnCl ·2H O as a reducing agent at basic pH (8-10 pH) and 2 mg mannitol used as a stabilizing agent, in the end, 370 MBq Tc added into the reaction vials and incubated for a wide range of temperature (-4 to 65°C). The percent radiochemical purity of Tc-roxithromycin was assessed with the help of the radio-thin-layer chromatography technique. The characterization studies were carried out using electrophoresis and Radio-HPLC techniques as well as saline stability and serum stabili...

Journal of medical imaging (Bellingham, Wash.), 2018

The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose... more The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose is highly dependent on the proprietary x-ray source information. To address this, this study develops a method to precisely estimate the x-ray spectrum and bowtie (BT) filter thickness of the x-ray source based on physical measurements and calculations. The static x-ray source of the CT localizer radiograph was assessed to measure the total filtration at the isocenter for the x-ray spectrum characterization and the BT profile (air-kerma values as a function of fan angle). With these values, the utilized BT filter in the localizer radiograph was assessed by integrating the measured air kerma in a full 360-deg cycle. The consistency observed between the integrated BT filter profiles and the directly measured profiles pointed to the similarity in the utilized BT filter in terms of thickness and material between the static and rotating x-ray geometries. Subsequently, the measured air kerma ...

To assess the effects of co-opetition—simultaneous competition and collaboration—on competitive a... more To assess the effects of co-opetition—simultaneous competition and collaboration—on competitive aggressiveness, this article relates one aspect of embeddedness—tie strength—to the volume and complexity of a firm’s competitive actions. Findings from our study of firms in the U.S. software industry suggest that strong ties increase the volume and complexity of competitive actions. Results also suggest that action volume is negatively related to the interaction between tie strength and both multimarket contact and resource similarity. However, results show that neither resource similarity nor multimarket contact did have direct or moderating effects on the relationship between tie strength and action complexity. Keywords competition, collaboration, competitive aggressiveness In recent years, strategy researchers have paid increasing attention to understanding the competitive actions taken by firms (Chen, 1996; Ferrier, 2001; Grimm & Smith, 1997). However, significant gaps in our unders...

Electronics

We consider the problem of simultaneous diagonalization of Hermitian matrices for the desired and... more We consider the problem of simultaneous diagonalization of Hermitian matrices for the desired and co-channel interference terms of millimeter-wave (mmWave) multi-user multiple-input multiple-output systems. The joint unitary eigenvectors and the corresponding eigenvalues are known to assist in the mathematical tractability of key performance metrics, such as outage probability, ergodic capacity, and spectral efficiency. We formulate the signal-to-interference-plus-noise ratio in a canonical quadratic form and subsume the digital baseband beamforming vectors in the weight matrices of channels at the transmitter side. Next, a real scalar objective function is defined, which quantifies the correlation loss due to joint-diagonalization. The objective function is then maximized using baseband beamforming under the hardware constraints of the mmWave system. Through simulations, the proposed beamforming algorithm is evaluated by employing several non-linear optimization sub-routines, and i...

This study aims to study the significant Israeli Hebrew influence on the Arabic spoken and writte... more This study aims to study the significant Israeli Hebrew influence on the Arabic spoken and written natively by Israeli Arabs (Arab 48). It aims to shed light on the sociolinguistic situation of Arabic in Israel, by reviewing the complex situation of linguistic diglossia and Linguistic Interference in these two Semitic languages. Israeli Arabs, and Israeli Jews, who are speakers of Hebrew, have daily contact in many fields of life. These two languages are in close contact, and thereby many mutual influences are enabled between them. As a result, a great deal of mutual linguistic influence is observed in each language. This study shows that Hebrew elements are very widespread in all linguistic fields of the Arabic spoken by Israeli Arabs. Israeli Hebrew lexical items have permeated all areas of professional, educational, administrative, Economical, and social activities in everyday life discourse in all styles and registers of the spoken language and, to a lesser extent, written langu...

This paper deals with the quantitative assessment of the unreliability of migration between habit... more This paper deals with the quantitative assessment of the unreliability of migration between habitat patches in terms of ecological corridor unreliabilities that are known only with uncertainty. The corridor unreliabilities are treated herein as log-normally distributed random variables, and hence the assessment becomes a doublystochastic one. The paper utilizes the multi-affine nature of the reliability function in deriving exact formulas for the mean and variance of the system unreliability, as well as accurate formulas for its third and fourth central moments. These formulas involve the nominal values of certain partial derivatives. The multi-affine nature is also beneficial in the development of an alternative method that involves powers rather than derivatives. These two analytical methods of moments agree reasonably with one another and with the results of Monte Carlo simulations. Several test cases are considered for typical ecology problems with corridor unreliabilities that ...

Iranian Journal of Pharmaceutical Research, 2008

The potential to cause tissue damage by metal ions is the matter of widespread investigation. Tit... more The potential to cause tissue damage by metal ions is the matter of widespread investigation. Titanium salts are widely used in industry for ceramic painting, in pharmacy for tablet coating and making chemical sunscreens and in medicine as photo catalysts with bactericidal activity. This may address the idea that the exposure to these salts could play a role in metabolic disorders. In this study the effect of Ti on liver contents of lipid fractions was investigated. Male Wistar rats (200-250 g) were used for the experiments. Groups of animals were injected for 10 days with 2.5 mg/kg of titanium chloride, as acute dose and for 30 and 60 days with 0.75 mg/kg as chronic doses. At the end of the experimental period animals were anaesthetized, the abdomens were opened and the livers were perfused with appropriate buffer. Livers were then removed immediately and used fresh or kept frozen until the analysis. Livers were then homogenized and their contents of triglycerides and phospholipids...

Sensors

This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-... more This paper studies the cell-edge user’s performance of a secure multiple-input single-output non-orthogonal multiple-access (MISO-NOMA) system under the Rayleigh fading channel in the presence of an eavesdropper. We suppose a worst-case scenario that an eavesdropper has ideal user detection ability. In particular, we suggest an optimization-based beamforming scheme with MISO-NOMA to improve the security and outage probability of a cell-edge user while maintaining the quality of service of the near-user and degrading the performance of the eavesdropper. To this end, power allocation coefficients are adjusted with the help of target data rates of both the users by utilizing a simultaneous wireless information and power transfer with time switching/power splitting protocol, where the near-user is used to forward the information to cell-edge user. The analytical results demonstrate that our beamformer analysis can achieve reduced outage probability of cell-edge user in the presence of t...

Ordinary Jerusalem, 1840-1940

This is an open access chapter distributed under the terms of the prevailing CC-BY-NC-ND License ... more This is an open access chapter distributed under the terms of the prevailing CC-BY-NC-ND License at the time of publication.

Proceedings of the 53rd Hawaii International Conference on System Sciences

Sensors

Closed-form evaluation of key performance indicators (KPIs) of telecommunication networks help pe... more Closed-form evaluation of key performance indicators (KPIs) of telecommunication networks help perform mathematical analysis under several network configurations. This paper deals with a recent mathematical approach of indefinite quadratic forms to propose simple albeit exact closed-form expressions of the expectation of two significant logarithmic functions. These functions formulate KPIs which include the ergodic capacity and leakage rate of multi-user multiple-input multiple-output (MU-MIMO) systems in Rayleigh fading channels. Our closed-form expressions are generic in nature and they characterize several network configurations under statistical channel state information availability. As a demonstrative example of the proposed characterization, the derived expressions are used in the statistical transmit beamformer design in a broadcast MU-MIMO system to portray promising diversity gains using standalone or joint maximization techniques of the ergodic capacity and leakage rate. ...

Pharmaceuticals

Extended overuse and misuse of antibiotics and other antibacterial agents has resulted in an anti... more Extended overuse and misuse of antibiotics and other antibacterial agents has resulted in an antimicrobial resistance crisis. Bacteriophages, viruses that infect bacteria, have emerged as a legitimate alternative antibacterial agent with a wide scope of applications which continue to be discovered and refined. However, the potential of some bacteriophages to aid in the acquisition, maintenance, and dissemination of negatively associated bacterial genes, including resistance and virulence genes, through transduction is of concern and requires deeper understanding in order to be properly addressed. In particular, their ability to interact with mobile genetic elements such as plasmids, genomic islands, and integrative conjugative elements (ICEs) enables bacteriophages to contribute greatly to bacterial evolution. Nonetheless, bacteriophages have the potential to be used as therapeutic and biocontrol agents within medical, agricultural, and food processing settings, against bacteria in ...

Business Information Systems

Supply chain risks negatively affect the success of an OEM in automotive industry. Finding releva... more Supply chain risks negatively affect the success of an OEM in automotive industry. Finding relevant information for supply chain risk management (SCRM) is a critical task. This investigation utilizes machine learning to find risk within textual documents. It contributes to the supply chain management (SCM) by designing (i) a conceptual model for supply risk identification in textual data. This addresses the requirement to see the direct connection between data analytics and SCM. (ii) An experiment in which a prototype is evaluated contributes the requirement to have more empirical insight in the interdisciplinary field of data analytics in SCRM.

COVID-19 pandemic has caused significant morbidity and mortality around the world. The disease se... more COVID-19 pandemic has caused significant morbidity and mortality around the world. The disease severity ranges from mild upper respiratory infection to severe lower respiratory and cardiac illness. Acute respiratory distress syndrome (ARDS) is the most serious complication and results in diffuse inflammatory alveolar damage, respiratory failure, and death. Components of the Renin-Angiotensin-Aldosterone-System (RAAS) are involved in an inflammatory reaction in the lungs. Various studies have shown that blocking RAAS peptides in the lungs especially angiotensin-converting enzyme (ACE) and type-1 angiotensin receptor (ATR1) reduces lung injury, improves respiratory function, and is associated with better clinical outcomes in the COVID-19 patients. We suggest that angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARBs) – drugs that block RAAS peptides – be considered for a repurposed use in COVID-19 induced lung injury.

Journal of Management Research

Project portfolio management (PPM) is an important area of interest in many organizations. There ... more Project portfolio management (PPM) is an important area of interest in many organizations. There is a wide literature on each of many different aspects of PPM. The central purpose of the current paper is to focus on a specific sub-area of PPM, namely the project portfolio selection (PPS) problem. Specifically, we develop a new methodology that will aid management in choosing from a set of candidate project proposals, a subset of those project proposals that align with strategic objectives of the organization. Research methodology is based on the data envelopment analysis (DEA) construct to compare a set of decision making units (such as proposed projects) to arrive at an efficiency score for each member of this competing set, derive the best performers, generate an efficiency frontier and quantify inefficiency in the non-best performers. While DEA has been applied in numerous settings, the unique feature of the project portfolio application is the presence of two sets of data, namel...

Journal of the Chinese Institute of Engineers

Abstract This work presents modeling and performance analysis of beamforming in non-cooperative m... more Abstract This work presents modeling and performance analysis of beamforming in non-cooperative multi-user multiple-input multiple-output (MU-MIMO) cellular systems using stochastic geometry based abstraction models. Particularly, a downlink MU-MIMO system is investigated in which an array of antenna elements at the base stations (BS) serves several user devices. We derive the closed-form expression of the complimentary cumulative distribution function (CCDF) of signal-to-interference-plus-noise ratio (SINR) representing the coverage probability for orthogonal pilot sequences and thereby characterize a number of related special cases. Moreover, closed-form expressions are also obtained for the CCDF of signal-to-interference ratio (SIR) for non-orthogonal pilot sequences and we also derive useful special cases of it and identify the support region of our analysis. Lastly, we define the numerical expression of ergodic capacity and utilize a partial fraction expansion to solve a simple form. Our contribution in this work is twofold, we not only provide a pedagogical tutorial-like exposition of stochastic geometry technique to model terrestrial networks, but also augment the existing literature in the field with aspects of frequency reuse factor, an indicator function for pilot usage, and the effect of pilot contamination. Simulation results are presented to support the theoretical part.

IEEE Transactions on Computers

This paper studies the problem of efficiently utilizing hybrid memory systems, consisting of both... more This paper studies the problem of efficiently utilizing hybrid memory systems, consisting of both Dynamic Random Access Memory (DRAM) and novel Non-Volatile Memory (NVM) in database management systems (DBMS) for online analytical processing (OLAP) workloads. We present a methodology to determine the database operators that are responsible for most main memory accesses. Our analysis uses both cost models and empirical measurements. We develop heuristic decision procedures to allocate data in hybrid memory at the time that the data buffers are allocated, depending on the expected memory access frequency. We implement these heuristics in the MonetDB column-oriented database and demonstrate performance improvement and energy-efficiency as compared to state-of-the-art application-agnostic hybrid memory management techniques.

Wireless Personal Communications

This communication attempts to characterize the performance metrics of downlink Massive MU-MIMO s... more This communication attempts to characterize the performance metrics of downlink Massive MU-MIMO systems impaired by cochannel interference and additive noise over a Rayleigh fading environment. We obtain close-form solutions for the probability density function of signal-to-interference-plus-noise ratio (SINR) and the sum ergodic capacity. The proposed work structures SINR in a quadratic form and thereby imposes a condition on its signal and interference power for a large transmit antenna diversity order; the conditional form is then analyzed using a distance correlation metric. Eventually, the sum ergodic capacity is expressed in a close-form by means of a residue theory approach and validated using the Monte Carlo simulation means.

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES

In this paper, we characterize the performance metrics of a multiuser multipolarized antenna syst... more In this paper, we characterize the performance metrics of a multiuser multipolarized antenna system in a Rayleigh fading channel. We start by formulating a downlink system model that features a multiuser scenario in the presence of additive noise and a multipolarized antenna system; this is followed by evaluation of the outage probability in closed form. This is done by deriving the cumulative distribution function (CDF) of the signal-to-interference-plusnoise ratio using the approach of the ratio of indefinite quadratic forms. We thereby characterize the gradient of this CDF with respect to the combining vectors. Eventually, we obtain the optimum combining vectors by minimizing the outage probability via interior-point optimization technique. Simulation and theoretical results of our analysis are closely matched, which validates our analysis. Our findings suggest that the performance of the triple polarized antenna is better than that of the dual polarized antenna system for low signal-to-noise ratio (SNR) values in terms of outage probability; this situation, however, reverses for high SNR value.

Chemical biology & drug design, Jan 29, 2018

Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the curre... more Roxithromycin is a second-generation macrolide antibiotic derived from erythromycin. In the current study, roxithromycin (ROX) was successfully labeled with technetium-99m for early diagnosis of bacterial infection and discrimination between septic and aseptic inflammation. The highest radiochemical purity of ≥95% was achieved by investigating different labeling parameters such as pH, ligand/reducing agent concentration, temperature, and amount of stabilizing agent. For this purpose, 0.3-0.5 mg ligand, 2-6 μg SnCl ·2H O as a reducing agent at basic pH (8-10 pH) and 2 mg mannitol used as a stabilizing agent, in the end, 370 MBq Tc added into the reaction vials and incubated for a wide range of temperature (-4 to 65°C). The percent radiochemical purity of Tc-roxithromycin was assessed with the help of the radio-thin-layer chromatography technique. The characterization studies were carried out using electrophoresis and Radio-HPLC techniques as well as saline stability and serum stabili...

Journal of medical imaging (Bellingham, Wash.), 2018

The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose... more The accuracy of Monte Carlo (MC) simulations in estimating the computed tomography radiation dose is highly dependent on the proprietary x-ray source information. To address this, this study develops a method to precisely estimate the x-ray spectrum and bowtie (BT) filter thickness of the x-ray source based on physical measurements and calculations. The static x-ray source of the CT localizer radiograph was assessed to measure the total filtration at the isocenter for the x-ray spectrum characterization and the BT profile (air-kerma values as a function of fan angle). With these values, the utilized BT filter in the localizer radiograph was assessed by integrating the measured air kerma in a full 360-deg cycle. The consistency observed between the integrated BT filter profiles and the directly measured profiles pointed to the similarity in the utilized BT filter in terms of thickness and material between the static and rotating x-ray geometries. Subsequently, the measured air kerma ...