Characterization of a Spiking Neuron Model via a Linear Approach

In the past decade, characterizing spiking neuron models has been extensively researched as an essential issue in computational neuroscience. In this thesis, we examine the estimation problem of two different neuron models. In Chapter 2, We propose a modified Izhikevich model with an adaptive threshold. In our two-stage estimation approach, a linear least squares method and a linear model of the threshold are derived to predict the location of neuronal spikes. However, desired results are not obtained and the predicted model is unsuccessful in duplicating the spike locations. Chapter 3 is focused on the parameter estimation problem of a multi-timescale adaptive threshold (MAT) neuronal model. Using the dynamics of a non-resetting leaky integrator equipped with an adaptive threshold, a constrained iterative linear least squares method is implemented to fit the model to the reference data. Through manipulation of the system dynamics, the threshold voltage can be obtained as a realizable model that is linear in the unknown parameters. This linearly parametrized realizable model is then utilized inside a prediction error based framework to identify the threshold parameters with the purpose of predicting single neuron precise firing times. This estimation scheme is evaluated using both synthetic data obtained from an exact model as well as the experimental data obtained from in vitro rat somatosensory cortical neurons. Results show the ability of this approach to fit the MAT model to different types of reference data

Optimal Online Charging Coordination of Plug in Electric Vehicles in Unbalanced Grids for Ancillary Voltage Support

This PhD thesis will propose an optimal online charge control through genetic algorithm for G2V coordination of PEVs (OL-C-TP) in unbalanced systems. Moreover the algorithm will be extended to also include V2G coordination and offer ancillary voltage support (OL-CD-TPQ) by considering two different methods based on the utility time-of-day prices for exporting reactive power and droop controller for decentralized exporting of reactive power. Then the performance of OL-CD-TPQ by switching PEVs in three phase unbalanced networks is improved

Calibration of flame ionization detector for chlorinated hydrocarbons

Relative Responses and Calibration Factors were developed for several volatile organic (mostly chlorinated) priority pollutant species in order to use one single stable compound (e.g.Benzene) for daily instrument calibration. This would replace the procedure of using a standard mixture of target compounds (25-35). This is of particular advantage because the standard mixture may not have all species stable or may show loss of some components relative to others due to wall adsorption in the standard (compressed gas) stainless steel cylinder. The use of a single standard species was made possible by developing accurate relative response and calibration factors of all target compounds relative to Benzene in this case. The response and calibration factors were obtained by injecting the targeted compounds for both vapor and liquid standards into the GC and then analysing and comparing the results for accuracy and precision. Results from this analysis showed that this is a viable and even preferential way to standardize the GC for routine quantitative analysis of a number of organic species. Liquid injection is the most acceptable method for determining relative response factors and calibration factors of compounds with boiling temperature above 60 C. Results from gaseous mixture of species shows low accuracy for compounds with boiling temperature above 110 C. These results for high boiling point vapors were all low and probably due to a combination of wall absorption, reaction with stainless steel tubing and cylinder and incomplete transfer of compounds into the vapor standard cylinder. When developing calibration factors we obtained a linearity for the RRF\u27s of these compounds with positive slope showing response enhancement for chlorine substituted compounds on FI detector at standard conditions. This is in contrast with previous investigators studies which employed older detector designs. Recent engineering improvement (1970 to present) in FI detector design and geometry with optimized combustion, flow velocities, improved electrodes (for ion collection) may account for the differences

A hybrid model for multi-objective capacitated facility location network design problem

One of the primary concerns on many traditional capacitated facility location/network problems is to consider transportation and setup facilities in one single objective function. This simple assumption may lead to misleading solutions since the cost of transportation is normally considered for a short period time and, obviously, the higher cost of setting up the facilities may reduce the importance of the transportation cost/network. In this paper, we introduce capacitated facility location/network design problem (CFLNDP) with two separate objective functions in forms of multi-objective with limited capacity. The proposed model is solved using a new hybrid algorithm where there are two stages. In the first stage, locations of facilities and design of fundamental network are determined and in the second stage demands are allocated to the facilities. The resulted multi-objective problem is solved using Lexicography method for a well-known example from the literature with 21 node instances. We study the behaviour of the resulted problem under different scenarios in order to gain insight into the behaviour of the model in response to changes in key problem parameters

Modeling the spatial distribution of crop cultivated areas at a large regional scale combining system dynamics and a modified Dyna-CLUE: A case from Iran

Agricultural land use pattern is affected by many factors at different scales and effects that are separated by time and space. This will lead to simulation models that optimize or project the cropping pattern changes and incorporate complexities in terms of details and dynamics. Combining System Dynamics (SD) and a modified Conversion of Land Use and its Effects (CLUE) modelling framework, this paper suggests a new dynamic approach for assessing the demand of different crops at country-level and for predicting the spatial distribution of cultivated areas at provincial scale. As example, a case study is presented for Iran, where we have simulated a scenario of future cropping pattern changes during 2015–2040.The results indicated a change in the spatial distribution of cultivated areas during the next years. An increase in the proportion of rice is expected in northern Iran, whereas the proportion of wheat is increasing in the mountainous western areas. Wheat and barley crops are expected to become dominant within the cropping system throughout the country regions

Assessing the effects of dexmedetomidine and labetalol on changes in heart rate and blood pressure after laryngoscopy compared to a control group

Background: One of the objectives of a smooth laryngoscopy is to minimize hemodynamic changes. The goal of this study was to assess the effects of dexmedetomidine and labetalol on heart rate and blood pressure changes after laryngoscopy compared to a control group. Materials and Methods: This was a double-blind clinical trial conducted on 120 patients aged between 18 and 60 years, who were candidates for surgery, under general anesthesia, at Alzahra hospital in Isfahan during 2017-2018. Patients were randomly allocated to three groups of being administered dexmedetomidine or labetalol and a control group. The patient's age, weight, height, gender and clinical data including mean blood pressure (BP), heart rate, systolic BP, diastolic BP and oxygen saturation during 1, 3, 5 and 10 minutes after intubation were collected and analyzed using repeated measure analysis. Results: The average age of patients who were candidates for surgery was 42.62 +/- 1.40. 52 percent (63 patients) were male subjects. The results showed no significant difference in mean BP, diastolic BP, systolic BP or oxygen saturation (p>0.05) in the three groups. But the difference in heart rate between the three groups was statistically significant. The heart rate in the dexmedetomidine group was significantly lower than the labetalol and control groups (p=0.00). Conclusion: Results of the current study showed that using labetalol provided desirable hemodynamic stability compared to dexmedetomidine and caused less hemodynamic disturbances

Parameters of lower extremities alignment view in Iranian adult population

Normal axial alignment restoration in lower extremities is crucial for surgeons performing reconstructive surgeries. Since reference normal values of axial alignment are affected by age, sex, and ethical issues, we tried to scrutinize these parameters in Iranian adults and compare them with normal values in literatures. Through a cross-sectional design, standing axial alignment views of lower extremities were surveyed from 100 volunteers (50 males and 50 females) aged between 15-32 years. The lower extremities alignment variables were evaluated during two separate measurements. Total average values were used for comparison among genders. Tibiofemoral mechanical angle depicted mean varus of 1.5 degrees in an Iranian population that was significantly higher in male participants. The Mean angle between anatomical and mechanical axes of the femur was 5.7 ± 1.2º. The Knee joint was shown to be medially inclined 3.6 ± 1.7º in men comparing 2 ± 2º of women with a significant difference. Joint line congruence angle was medially inclined in all of the study participants with a mean of 1 ± 1.6º. To compare with anthropometric studies of western populations, Iranian participants had more varus lower limb alignment. It seemed mainly because of larger medially inclined knee joint (knee-joint obliquity). This finding along with more compensatory ankle valgus is similar to results of other Asian studies. Such racial variation should be considered in designing appropriate systems in reconstructive surgery. © 2015 Tehran University of Medical Sciences. All rights reserved

A Cross Entropy-Based Heuristic for the Capacitated Multi-Source Weber Problem with Facility Fixed Cost: Cross entropy for continuous location problems

This paper investigates a capacitated planar location-allocation problem with facility fixed cost. A zone-based fixed cost which consists of production and installation costs is considered. A nonlinear and mixed integer formulation is first presented. A powerful three stage Cross Entropy meta-heuristic with novel density functions is proposed. In the first stage a covering location problem providing a multivariate normal density function for the associated stochastic problem is solved. The allocation values considering a multinomial density function are obtained in the second stage. In the third stage, single facility continuous location problems are solved. Several instances of various sizes are used to assess the performance of the proposed meta-heuristic. Our approach performs well when compared with the optimizer GAMS which is used to provide the optimal solution for small size instances and lower/upper bounds for some of the larger ones