mohammad rahimi | Islamic Azad University Lamerd Branch (original) (raw)

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Papers by mohammad rahimi

The current study was an attempt to explore the underlying factor structures of the new TPCF ques... more The current study was an attempt to explore the underlying factor structures of the new TPCF questionnaire designed to determine EFL teachers’ perceptions of the effectiveness of corrective feedbacks (CFs). To this end, both male and female EFL teachers from private language institutes were conveniently selected to participate in the study. To come up with a suitable sample for construct validation (factor analysis), care was taken to select at least 125 participants (5 participants per item included in the final version of TPCF). Two research instruments were utilized in the current study including an interview and a newly designed questionnaire by the researcher. The findings revealed that underlying factor structures of the new TPCF included type of error & type of CF, time of feedback & teachers’ strategy, proficiency level & preplanning, perceived by learners, negative impression & gender difference, dominance, correction & CF enhancement. In addition, a new TPCF questionnaire ...

Embedded networked sensing systems have been successfully applied to environmental monitoring in ... more Embedded networked sensing systems have been successfully applied to environmental monitoring in a wide range of applications. These first results have demonstrated a potential for advancing fundamental environmental science methods and environmental management capability as well as for providing future methods for safeguarding public health. While substantial progress in sensor network performance has appeared, new challenges have also emerged. Specifically, the inevitable and unpredictable time evolution of environmental phenomena introduces sensing uncertainty and degrades the performance of event detection, environment characterization, and sensor fusion.

A key challenge in sensor networks is ensuring the sustainability of the system at the required p... more A key challenge in sensor networks is ensuring the sustainability of the system at the required performance level, in an autonomous manner. Sustainability is a major concern because of severe resource constraints in terms of energy, bandwidth and sensing capabilities in the system. In this paper, we envision the use of a new design dimension to enhance sustainability in sensor networks -the use of controlled mobility. We argue that this capability can alleviate resource limitations and improve system performance by adapting to deployment demands. While opportunistic use of external mobility has been considered before, the use of controlled mobility is largely unexplored. We also outline the research issues associated with effectively utilizing this new design dimension. Two system prototypes are described to present first steps towards realizing the proposed vision.

IEEE Journal of Selected Topics in Signal Processing, 2008

Abstract—We present an energy-efficient high resolution image acquisition approach based on a two... more Abstract—We present an energy-efficient high resolution image acquisition approach based on a two-tiered system comprising low-cost, low-power, non-actuated, extremely resource-con-strained stereo image sensor platforms and more capable but more power-...

Large-scale networks of battery-operated wireless image sensors have become technologically feasi... more Large-scale networks of battery-operated wireless image sensors have become technologically feasible. However, it is still unclear how we can benefit from large-scale deployments of imagers. In this paper, we argue that using a large number of low-power image sensors is useful and necessary in many cases. For instance, occluded environments cannot be efficiently observed with a small number of cameras. In this case, distributed imagers can provide better coverage due to minimum infrastructure requirements and availability in large numbers. Additional benefits, such as pose diversity, statistical advantages, and multiple perspectives are discussed in detail using application examples and qualitative arguments.

A key challenge in sensor networks is ensuring the sustainability of the system at the required p... more A key challenge in sensor networks is ensuring the sustainability of the system at the required performance level, in an autonomous manner. Sustainability is a major concern becuase of severe resource constraints in terms of energy, bandwidth and sensing capabilities in the system. In this paper, we envision the use of a new design dimension to enhance sustainability of in sensor networks -the use of controlled mobility. We argue that this capability can alleviate resource limitations and improve system performance by adapting to deployment demands. While opportunistic use of external mobility has been considered before, the use of controlled mobility is largely unexplored. We also outline the research issues associated with effectively utilizing this new design dimension. Two system prototypes are described to present first steps towards realizing the proposed vision.

Monitoring environmental phenomena by distributed sensor sampling confronts the challenge of unpr... more Monitoring environmental phenomena by distributed sensor sampling confronts the challenge of unpredictable variability in the spatial distribution of phenomena often coupled with demands for a high spatial sampling rate. The introduction of actuation-enabled robotics sensors permits a system to optimize the sampling distribution through runtime adaptation. However, such systems must efficiently dispense sampling points or otherwise suffer from poor temporal response. In this paper we propose and characterize an active modeling system. In our approach, as the robotic sensor acquires measurement samples of the environment, it builds a model of the phenomenon. Our algorithm is based on an incremental optimization process where the robot supports a continuous, iterative process of 1) collecting samples with maximal coverage in the design space, 2) building the environmental model 3) predicting sampling point locations that contribute the greatest certainty regarding the phenomenon 4) and sampling the environment based on a combined measure of information gain and navigation and sampling cost. This can provide significant reductions in the magnitude of field estimation error with a modest navigational trajectory time. We evaluate our algorithm through a simulation, using a combination of static and mobile sensors sampling light illumination field.

International Journal of Distributed Sensor Networks, 2006

much as an order of magnitude or even change the relative performance order of two alternative al... more much as an order of magnitude or even change the relative performance order of two alternative algorithms. This pointed out the need to evaluate sensor network systems with data representing a wide range of realworld scenarios. For each algorithm in our case study, we identified a small set of data characteristics essential to the algorithm's performance. This defined a unique feature of our synthetic data generation framework and made both synthetic data generation and evaluation scalable. To support systematic algorithm evaluation and robust algorithm design and deployment, our synthetic data generation toolbox can generate 1. irregular topology data based on empirical models which will maintain important features of the experimental data; and 2. data corresponding to a wide range of parameter values.

The current study was an attempt to explore the underlying factor structures of the new TPCF ques... more The current study was an attempt to explore the underlying factor structures of the new TPCF questionnaire designed to determine EFL teachers’ perceptions of the effectiveness of corrective feedbacks (CFs). To this end, both male and female EFL teachers from private language institutes were conveniently selected to participate in the study. To come up with a suitable sample for construct validation (factor analysis), care was taken to select at least 125 participants (5 participants per item included in the final version of TPCF). Two research instruments were utilized in the current study including an interview and a newly designed questionnaire by the researcher. The findings revealed that underlying factor structures of the new TPCF included type of error & type of CF, time of feedback & teachers’ strategy, proficiency level & preplanning, perceived by learners, negative impression & gender difference, dominance, correction & CF enhancement. In addition, a new TPCF questionnaire ...

Embedded networked sensing systems have been successfully applied to environmental monitoring in ... more Embedded networked sensing systems have been successfully applied to environmental monitoring in a wide range of applications. These first results have demonstrated a potential for advancing fundamental environmental science methods and environmental management capability as well as for providing future methods for safeguarding public health. While substantial progress in sensor network performance has appeared, new challenges have also emerged. Specifically, the inevitable and unpredictable time evolution of environmental phenomena introduces sensing uncertainty and degrades the performance of event detection, environment characterization, and sensor fusion.

A key challenge in sensor networks is ensuring the sustainability of the system at the required p... more A key challenge in sensor networks is ensuring the sustainability of the system at the required performance level, in an autonomous manner. Sustainability is a major concern because of severe resource constraints in terms of energy, bandwidth and sensing capabilities in the system. In this paper, we envision the use of a new design dimension to enhance sustainability in sensor networks -the use of controlled mobility. We argue that this capability can alleviate resource limitations and improve system performance by adapting to deployment demands. While opportunistic use of external mobility has been considered before, the use of controlled mobility is largely unexplored. We also outline the research issues associated with effectively utilizing this new design dimension. Two system prototypes are described to present first steps towards realizing the proposed vision.

IEEE Journal of Selected Topics in Signal Processing, 2008

Abstract—We present an energy-efficient high resolution image acquisition approach based on a two... more Abstract—We present an energy-efficient high resolution image acquisition approach based on a two-tiered system comprising low-cost, low-power, non-actuated, extremely resource-con-strained stereo image sensor platforms and more capable but more power-...

Large-scale networks of battery-operated wireless image sensors have become technologically feasi... more Large-scale networks of battery-operated wireless image sensors have become technologically feasible. However, it is still unclear how we can benefit from large-scale deployments of imagers. In this paper, we argue that using a large number of low-power image sensors is useful and necessary in many cases. For instance, occluded environments cannot be efficiently observed with a small number of cameras. In this case, distributed imagers can provide better coverage due to minimum infrastructure requirements and availability in large numbers. Additional benefits, such as pose diversity, statistical advantages, and multiple perspectives are discussed in detail using application examples and qualitative arguments.

A key challenge in sensor networks is ensuring the sustainability of the system at the required p... more A key challenge in sensor networks is ensuring the sustainability of the system at the required performance level, in an autonomous manner. Sustainability is a major concern becuase of severe resource constraints in terms of energy, bandwidth and sensing capabilities in the system. In this paper, we envision the use of a new design dimension to enhance sustainability of in sensor networks -the use of controlled mobility. We argue that this capability can alleviate resource limitations and improve system performance by adapting to deployment demands. While opportunistic use of external mobility has been considered before, the use of controlled mobility is largely unexplored. We also outline the research issues associated with effectively utilizing this new design dimension. Two system prototypes are described to present first steps towards realizing the proposed vision.

Monitoring environmental phenomena by distributed sensor sampling confronts the challenge of unpr... more Monitoring environmental phenomena by distributed sensor sampling confronts the challenge of unpredictable variability in the spatial distribution of phenomena often coupled with demands for a high spatial sampling rate. The introduction of actuation-enabled robotics sensors permits a system to optimize the sampling distribution through runtime adaptation. However, such systems must efficiently dispense sampling points or otherwise suffer from poor temporal response. In this paper we propose and characterize an active modeling system. In our approach, as the robotic sensor acquires measurement samples of the environment, it builds a model of the phenomenon. Our algorithm is based on an incremental optimization process where the robot supports a continuous, iterative process of 1) collecting samples with maximal coverage in the design space, 2) building the environmental model 3) predicting sampling point locations that contribute the greatest certainty regarding the phenomenon 4) and sampling the environment based on a combined measure of information gain and navigation and sampling cost. This can provide significant reductions in the magnitude of field estimation error with a modest navigational trajectory time. We evaluate our algorithm through a simulation, using a combination of static and mobile sensors sampling light illumination field.

International Journal of Distributed Sensor Networks, 2006

much as an order of magnitude or even change the relative performance order of two alternative al... more much as an order of magnitude or even change the relative performance order of two alternative algorithms. This pointed out the need to evaluate sensor network systems with data representing a wide range of realworld scenarios. For each algorithm in our case study, we identified a small set of data characteristics essential to the algorithm's performance. This defined a unique feature of our synthetic data generation framework and made both synthetic data generation and evaluation scalable. To support systematic algorithm evaluation and robust algorithm design and deployment, our synthetic data generation toolbox can generate 1. irregular topology data based on empirical models which will maintain important features of the experimental data; and 2. data corresponding to a wide range of parameter values.