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Hossein Ahmadvand

Publications and source records attributed to Hossein Ahmadvand.

10 recordsLinked to original sources

Latency and Privacy-Aware Resource Allocation in Vehicular Edge Computing

The rapid increase in the number of connected vehicles has led to the generation of vast amounts of data. As a significant portion of this data pertains to vehicle-to-vehicle and vehicle-to-infrastructure communications, it is predominantly generated at the edge. Considering the enormous volume of data, real-time applications, and privacy concerns, it is crucial to process the data at the edge. Neglecting the management of processing resources in vehicular edge computing (VEC) could lead to numerous challenges as a substantial number of vehicles with diverse safety, economic, and entertainment applications, along with their data processing, emerge in the near future [1]. Previous research in VEC resource allocation has primarily focused on issues such as response time and privacy preservation techniques. However, an approach that takes into account privacy-aware resource allocation based on vehicular network architecture and application requirements has not yet been proposed. In this paper, we present a privacy and latency-aware approach for allocating processing resources at the edge of the vehicular network, considering the specific requirements of different applications. Our approach involves categorizing vehicular network applications based on their processing accuracy, real-time processing needs, and privacy preservation requirements. We further divide the vehicular network edge into two parts: the user layer (OBUs) is considered for processing applications with privacy requirements, while the allocation of resources in the RSUs and cloud layer is based on the specific needs of different applications. In this study, we evaluate the quality of service based on parameters such as privacy preservation, processing cost, meeting deadlines, and result quality. Comparative analyses demonstrate that our approach enhances service quality by 55% compared to existing state-of-the-art methods.

cs.PF

Method-Level Bug Severity Prediction using Source Code Metrics and LLMs

In the past couple of decades, significant research efforts are devoted to the prediction of software bugs. However, most existing work in this domain treats all bugs the same, which is not the case in practice. It is important for a defect prediction method to estimate the severity of the identified bugs so that the higher-severity ones get immediate attention. In this study, we investigate source code metrics, source code representation using large language models (LLMs), and their combination in predicting bug severity labels of two prominent datasets. We leverage several source metrics at method-level granularity to train eight different machine-learning models. Our results suggest that Decision Tree and Random Forest models outperform other models regarding our several evaluation metrics. We then use the pre-trained CodeBERT LLM to study the source code representations' effectiveness in predicting bug severity. CodeBERT finetuning improves the bug severity prediction results significantly in the range of 29%-140% for several evaluation metrics, compared to the best classic prediction model on source code metric. Finally, we integrate source code metrics into CodeBERT as an additional input, using our two proposed architectures, which both enhance the CodeBERT model effectiveness.

cs.SE

Complex magnetoelectric effect in PFN-PT/CoFe$_{2-x}$Zn$_x$O$_4$ bulk particulate composites

The structural, dielectric, magnetic, and magnetoelectric (ME) properties of particulate composites containing lead-iron niobate and lead titanate piezoelectric 0.94[PbFe$_{0.5}$Nb$_{0.5}$O$_3$]-0.06[PbTi$_{0.5}$O$_3$] (PFN-PT) and Zn-substituted cobalt ferrite magnetostrictive CoFe$_{2-x}$Zn$_{x}$O$_4$ (CF$_{2-x}$Z$_{x}$O); 0.6(PFN-PT)/0.4(CF$_{2-x}$Z$_{x}$O), x=0, 0.025, 0.1, 0.2, 0.3 (with ratio of 60 Wt\% ferroelectric and 40 Wt\% ferrite); have been investigated. We investigated the ME voltage coefficient as a complex quantity for all composite samples using the dynamic piezomagnetic coefficient, $q^{ac}$=$\partial λ^{ac}/{\partial H}$. The results reveal that tuning the magnetostrictive phase has a strong effect on the real part of the ME voltage coefficient. Doping zinc into cobalt ferrite modified the magnetic properties of the magnetic phase, such as magnetic anisotropy and coercive field, and hence the ME properties. The highest ME coefficient value of 12.33 $\frac{mV}{cm. Oe}$ was obtained for x=0.1 at the magnetic field of 755 Oe. In addition, the magnetic field at which the maximum value of the ME coefficient was observed ($H_{peak}$) strongly depends on the value of Zn substitution. The results were interpreted using the magnetic field dependence of the CF$_{2-x}$Z$_{x}$O magnetostriction.

cond-mat.mtrl-sci

Revisiting the magnetic and crystal structure of multiferroic KNiPO$_4$

The magnetic, dielectric and structural properties of type-I multiferroic KNiPO$_4$ have been investigated by neutron powder diffraction, magnetization, dielectric and high temperature synchrotron-XRD measurements. Below the Néel transition of $T_\mathrm{N}$ = 25 K, KNiPO$_4$ displays a weakly non-collinear antiferromagnetic (AFM) structure with the orientation of the Ni$^{2+}$ magnetic moments mainly along $a$ axis. The compound crystallizes in the polar orthorhombic $Pna2_1$ space group at room temperature. A second-order structural phase transition corresponding to the onset ferroelectricity is observed at around $T_\mathrm{C}\sim$ 594(3)$^\circ$C, above which the crystal structure of KNiPO$_4$ adopts the centrosymmetric $Pnma$ space group. The compound also displays another structural phase transition at $T_\mathrm{0}\sim$ 469 -- 488$^\circ$C, with a first-order character, which is attributed to the rearrangement of oxygen ligands, resulting in a change in the nickel ion co-ordination from four to five.

cond-mat.str-el

DV-DVFS: Merging Data Variety and DVFS Technique to Manage the Energy Consumption of Big Data Processing

Data variety is one of the most important features of Big Data. Data variety is the result of aggregating data from multiple sources and uneven distribution of data. This feature of Big Data causes high variation in the consumption of processing resources such as CPU consumption. This issue has been overlooked in previous works. To overcome the mentioned problem, in the present work, we used Dynamic Voltage and Frequency Scaling (DVFS) to reduce the energy consumption of computation. To this goal, we consider two types of deadlines as our constraint. Before applying the DVFS technique to computer nodes, we estimate the processing time and the frequency needed to meet the deadline. In the evaluation phase, we have used a set of data sets and applications. The experimental results show that our proposed approach surpasses the other scenarios in processing real datasets. Based on the experimental results in this paper, DV-DVFS can achieve up to 15% improvement in energy consumption.

cs.PF

Magnetic and structural properties of Ni-substituted magnetoelectric Co$_4$Nb$_2$O$_9$

The magnetic and structural properties of polycrystalline Co$_{4-x}$ Ni$_x$ Nb$_2$ O$_9$ (x=1,2) have been investigated by neutron powder diffraction, magnetization and heat capacity measurements, and density functional theory (DFT) calculations. For x=1, the compound crystallizes in the trigonal P$\bar{3}$c1 space group. Below T$_N$ = 31 K it develops a weakly non-collinear antiferromagnetig structure with magnetic moments in the ab-plane. The compound with x=2 has crystal structure of the orthorhombic Pbcn space group and shows a hard ferrimagnetic behavior below T$_C$ =47 K. For this compound a weakly non-collinear ferrimagnetic structure with two possible configurations in ab plane was derived from ND study. By calculating magnetic anisotropy energy via DFT, the ground-state magnetic configuration was determined for this compound. The heat capacity study in magnetic fields up to 140 kOe provide further information on the magnetic structure of the compounds.

cond-mat.mtrl-sci

DV-ARPA: Data Variety Aware Resource Provisioning for Big Data Processing in Accumulative Applications

In Cloud Computing, the resource provisioning approach used has a great impact on the processing cost, especially when it is used for Big Data processing. Due to data variety, the performance of virtual machines (VM) may differ based on the contents of the data blocks. Data variety-oblivious allocation causes a reduction in the performance of VMs and increases the processing cost. Thus, it is possible to reduce the total cost of the job by matching the VMs with the given data blocks. We use a data-variety-aware resource allocation approach to reduce the processing cost of the considered job. For this issue, we divide the input data into some data blocks. We define the significance of each data block and based on it we choose the appropriate VMs to reduce the cost. For detecting the significance of each data portion, we use a specific sampling method. This approach is applicable to accumulative applications. We use some well-known benchmarks and configured servers for our evaluations. Based on the results, our provisioning approach improves the processing cost, up to 35% compared to other approaches.

cs.DC

Analysis and Evaluation of Real-time and Safety Characteristics of IEEE 802.11p protocol in VANET

The need for safety in transportation systems has increased the popularity and applicability of Vehicular Ad-Hoc Networks (VANETs) in recent years. On-time reception and processing of alarms caused by possible accidents as well as the preventive actions have important roles in reducing human and financial losses in road accidents. In such cases, the performance of safety applications should be evaluated and guaranteed to show whether or not they can ensure the safety of humans and cars. In this paper, we analyze the behavior of Vehicular Ad-Hoc Networks by checking the real-time properties of the IEEE 802.11p protocol using a Colored Petri Net model. To analyze the performance of related standards, simulations are conducted using CPNTools. Standards from European Telecommunications Standards Institute (ETSI), and Vehicle Safety Communications (VSC) are evaluated in this research. We will show that such standards may not completely fulfill the safety requirements in particular situations.

cs.NI

The effect of grain boundaries on the domain wall dynamics in Pr$_{1-x}$Ag$_x$MnO$_3$ manganites

We performed detailed ac susceptibility measurements on Pr$_{1-x}$Ag$_x$MnO$_3$ ($x$=0.15, 0.20) manganites and observed unusual and interesting features, which are associated with the domain walls and the effects of grain-boundaries on their movements. It is shown that the ac field, frequency, temperature, thermal cycling and grain coupling significantly influence the real and especially imaginary parts of the ac susceptibility. We argue that the cooperative depinning of the domain walls from the grain-boundaries accompanying with a large distance movements of the walls leads to the appearance of an anomaly at low temperatures. The anomaly is observed above a threshold ac field and depends on the intergrain coupling. The results show that in the powdered form of bulk samples, the anomaly disappears and the ac field dependence of the $χ'$ and $χ"$ suppresses. Below the anomaly temperature, significant and unusual thermal hysteresis occurs in the real and especially imaginary parts of the ac susceptibility. Thermal hysteresis depends on the thermal cycling and indicates thermally irreversible wall pinning and depinning. The susceptibility is practically frequency-independent in the temperature range of thermal hysteresis i.e. below the anomaly. The frequency dependence of ac susceptibility between the anomaly temperature and the transition temperature is discussed by considering the temperature dependence of the relaxation process of the domain walls.

cond-mat.str-el

Investigation of the role of Ag in Pr$_{1-x}$Ag$_x$MnO$_3$ manganites

X-Ray diffraction, ac susceptibility and electrical resistivity measurements were performed in order to investigate the effect of Ag substitution for Pr in the polycrystalline Pr$_{1-x}$Ag$_x$MnO$_3$ (0.0$\leq$x$\leq$0.25) manganites. The XRD results show that the samples crystallize in the O'-orthorhombic structure with a cooperative Jahn-Teller deformation. We give evidence that the Ag$^{+}$ is not substituted at the Pr$^{3+}$ site in the PrMnO$_{3}$ structure. The increase of $T_{C}$ up to 130 K is suggested to be due to further oxidation of manganite grains by the oxygen released from the metallic silver at high temperatures. No metal-insulator transition was observed in the samples.

cond-mat.str-el