18 results on '"Vahdati, N."'
Search Results
2. Reaction Prediction using Density Functional Theory Calculations: A Study into the Synthesis of Safranal via Diels-Alder Reactions
- Author
-
Wagner, G., primary, Vahdati, N., additional, Howkins, A., additional, and Cubitt, L., additional
- Published
- 2011
- Full Text
- View/download PDF
3. A new hydraulic engine mount design without the peak frequency
- Author
-
Tikani, R., primary, Vahdati, N., additional, Ziaei-Rad, S., additional, and Esfahanian, M., additional
- Published
- 2010
- Full Text
- View/download PDF
4. A new hydraulic engine mount design without the peak frequency.
- Author
-
Tikani, R., Vahdati, N., Ziaei-Rad, S., and Esfahanian, M.
- Subjects
- *
ACTIVE noise & vibration control , *AUTOMOBILE engine mounts , *HYDRAULIC machinery , *DYNAMIC stiffness , *WORKING fluids , *FREQUENCIES of oscillating systems , *ENGINE design & construction - Abstract
Hydraulic engine mounts are generally applied to the aerospace and automotive applications for the purpose of cabin noise and vibration reduction. By careful selection of mount design parameters, at a certain frequency called the notch frequency, the dynamic stiffness will be smaller than the static stiffness. Following the notch frequency there will be a frequency, called the peak frequency, where the dynamic stiffness is much higher than the static stiffness. Increase in the dynamic stiffness above the static stiffness is not desirable because of the increase in transmitted force to the airframe or the chassis. Here in this paper, a new hydraulic engine mount design is proposed that uses two working fluids. This new design has two notch frequencies and two peak frequencies. Under special conditions, the peak frequency can be eliminated. As a result, one can obtain a hydraulic engine mount design with only one notch frequency but no peak frequency, by using a controllable fluid or a high viscosity fluid as one of the working fluids. The new hydraulic engine mount design, its mathematical model, and some discussions on the simulation results are presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2011
- Full Text
- View/download PDF
5. Measurement of a large impulse torque including measurand reconstruction
- Author
-
Saunders, Lauderbaugh, L.K., and Vahdati, N.
- Published
- 1999
- Full Text
- View/download PDF
6. A review on therapeutic drug monitoring of immunosuppressant drugs
- Author
-
Mohammadpour, N., sepideh elyasi, Vahdati, N., Mohammadpour, A. H., and Shamsara, J.
- Subjects
Sirolimus ,surgical procedures, operative ,Cyclosporine ,Review Article ,Mycophenolic acid ,Therapeutic drug monitoring ,Tacrolimus - Abstract
Immunosuppressants require therapeutic drug monitoring because of their narrow therapeutic index and significant inter-individual variability in blood concentrations. This variability can be because of factors like drug-nutrient interactions, drug-disease interactions, renal-insufficiency, inflammation and infection, gender, age, polymorphism and liver mass. Drug monitoring is widely practiced especially for cyclosporine, tacrolimus, sirolimus and mycophenolic acid. CYCLOSPORINE: Therapeutic monitoring of immunosuppressive therapy with cyclosporine is a critical requirement because of intra- and inter-patient variability of drug absorption, narrow therapeutic window and drug induced nephrotoxicity. MYCOPHENOLIC ACID MPA: Some reasons for therapeutic drug monitoring of MPA during post-transplant period include: relationship between MPA pharmacokinetic parameters and clinical outcomes, Inter-patient pharmacokinetic variability for MPA despite fixed MMF doses, alternations of MPA pharmacokinetics during the first months after transplantation, drug- drug interaction and influence of kidney function on MPA pharmacokinetic. SIROLIMUS: A recent review of the pharmacokinetics of sirolimus suggested a therapeutic range of 5 to 10 μg l(-1) in whole blood. However, the only consensus guidelines published on the therapeutic monitoring of sirolimus concluded that there was not enough information available about the clinical use of the drug to make recommendations. TACROLIMUS: Sudies have shown, in kidney and liver transplant patients, significant associations of low tacrolimus concentrations with rejection and of high concentrations with nephrotoxicity. Although the feasibility of a limited sampling scheme to predict AUC has been demonstrated, as yet, trough, or pre-dose, whole blood concentration monitoring is still the method of choice.
7. Design and evaluation of collaborative decision-making application for patient care in the emergency department.
- Author
-
Shams-Vahdati N, Shams Vahdati S, and Samad-Soltani T
- Abstract
Background and Aims: Collaboration has become a crucial element of effective healthcare delivery in the emergency department (ED). In high-pressure environments, healthcare providers can prioritize patients by consulting with other specialists to gain diverse perspectives and arrive at a shared understanding of the best course of action. It was conducted for the purpose of designing and evaluating the collaborative decision-making application for patient care in the ED., Methods: The present applied research study was conducted between April 1, 2021 and May 31, 2023 at Imam Reza Hospital of Tabriz University of Medical Sciences. The study was conducted in three phases: exploration, development, and evaluation, utilizing modern technologies such as Flutter and Node.js to design and program the application. The effectiveness of the system was evaluated using established measures, including the think-aloud protocol, user experience questionnaire, and Likert-scale questionnaires developed by Ghadri et al., Results: The average scale for attractiveness was 2.03, perspicuity was 2.90, efficiency was 2.40, dependability was 1.93, stimulation was 2.48, and novelty was 2.78. Additionally, 71% of physicians gave a very good rating to the accessibility of necessary information at any time, motivation to use the system for accessing information, usefulness of the system compared to the time spent using it throughout the day. Furthermore, 57% of physicians gave a very positive rating to sharing information and knowledge, ease of using the search function and accessing the system, user control and monitoring, free access to the system, and support from colleagues and system users., Conclusion: The study suggests that introducing Information and Communication Technology such as medical apps can improve healthcare delivery by streamlining patient care, promoting effective teamwork, and reducing medical errors and treatment delays., Competing Interests: The authors declare no conflict of interest., (© 2024 The Authors. Health Science Reports published by Wiley Periodicals LLC.)
- Published
- 2024
- Full Text
- View/download PDF
8. Cost-Effective Corrosion Detection Sensor for Above-Ground Oil and Gas Flowlines.
- Author
-
Vahdati N, Shiryayev O, Parapurath SM, Yap FF, and Butt H
- Abstract
A sensor for monitoring of the external corrosion of small-diameter aboveground oil and gas pipelines (called flowlines), based on fiber-optic strain sensing, is proposed. The working principle of our proposed sensor relies on the use of a pre-stressed sacrificial structure made of the same material as the pipeline and monitoring changes in the measured strain that occur due to deterioration caused by corrosion to the structure. We present the development of analytical equations that allow designing the sensor structure to achieve the desired strain values. The analysis was verified using commercial finite element analysis (FEA) software. The proposed sensor is simple and cost-effective and can be easily manufactured. It can be deployed on existing overground pipelines without any modification to the pipeline structure. While it is not capable of measuring the corrosion rate continuously, it can provide a measurement of the average corrosion rate over the life span of its sacrificial metal structure.
- Published
- 2022
- Full Text
- View/download PDF
9. Compliant Mechanism-Based Sensor for Large Strain Measurements Employing Fiber Optics.
- Author
-
Shiryayev O, Vahdati N, Yap FF, and Butt H
- Subjects
- Finite Element Analysis, Optical Fibers, Fiber Optic Technology, Robotics
- Abstract
We propose a sensor design for measurement of large strains where direct application of a fiber optic strain gauge is impossible due to the stiffness mismatch between the optical fiber and the structure under test. The sensor design is based on a rhombus type compliant mechanism, which functions to attenuate input strain and transfer it to the ends of the sensing beam with the mounted optical strain gauge. We developed an analytical model of the sensor, which allows us to relate actuation forces, input displacement/strain, and output strain. The analytical model was verified with the finite element analysis and validated against an experimental prototype. The prototype sensor was able to handle input strains exceeding ±2.5 × 10
5 µε. Potential application areas of the proposed sensor include compliant elastomeric structures, wearables, and soft robotics.- Published
- 2022
- Full Text
- View/download PDF
10. Magnetic Internal Corrosion Detection Sensor for Exposed Oil Storage Tanks.
- Author
-
Aljarah A, Vahdati N, and Butt H
- Abstract
Corrosion in the oil and gas industry represents one of the major problems that affect oil production and transportation processes. Several corrosion-inspection technologies are in the market to detect internal and external corrosion of oil storage tanks, but inspection of storage tanks occurs every 3 to 7 years. In between inspection interval, aggressive corrosion can potentially occur, which makes the oil and gas industry vulnerable to accidents. This study proposes a new internal corrosion detection sensor based on the magnetic interaction between a rare-earth permanent magnet and the ferromagnetic nature of steel, used to manufacture oil storage tanks. Finite element analysis (FEA) software was used to analyze the effect of various sensor parameters on the attractive force between the magnet and the steel. The corrosion detection sensor is designed based on the FEA results. The experimental testing of the sensor shows that it is capable of detecting internal metal loss due to corrosion in oil storage tanks within approximately 8 mm of the internal surface thickness. The sensor showed more than two-fold improvement in the detection range compared to previous sensor proposed by the authors. Furthermore, the sensor of this paper provides a monitoring rather than occasional inspection solution.
- Published
- 2021
- Full Text
- View/download PDF
11. External Corrosion Detection of Oil Pipelines Using Fiber Optics.
- Author
-
Vahdati N, Wang X, Shiryayev O, Rostron P, and Yap FF
- Abstract
Oil flowlines, the first "pipeline" system connected to the wellhead, are pipelines that are 5 to 30.5 cm (two to twelve inches) in diameter, most susceptible to corrosion, and very difficult to inspect. Herein, an external corrosion detection sensor for oil and gas pipelines, consisting of a semicircular plastic strip, a flat dog-bone-shaped sacrificial metal plate made out of the same pipeline material, and an optical fiber with Fiber Bragg Grating (FBG) sensors, is described. In the actual application, multiple FBG optical fibers are attached to an oil and gas pipeline using straps or strips or very large hose clamps, and, every few meters, our proposed corrosion detection sensor will be glued to the FBG sensors. When the plastic parts are attached to the sacrificial metals, the plastic parts will be deformed and stressed; thus, placing the FBG sensors in tension. When corrosion is severe at any given pipeline location, the sacrificial metal at that location will corrode till failure and the tension strain is relieved at that FBG Sensor location, and therefore, a signal is detected at the interrogator. Herein, the external corrosion detection sensor and its design equations are described, and experimental results, verifying our theory, are presented., Competing Interests: The authors declare no conflicts of interest. The funding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; and in the decision to publish the results.
- Published
- 2020
- Full Text
- View/download PDF
12. Detection of Internal Metal Loss in Steel Pipes and Storage Tanks via Magnetic-Based Fiber Optic Sensor.
- Author
-
Almahmoud S, Shiryayev O, Vahdati N, and Rostron P
- Abstract
A monitoring solution was developed for detection of material loss in metals such as carbon steel using the force generated by permanent magnets in addition to the optical strain sensing technology. The working principle of the sensing system is related to the change in thickness of a steel plate, which typically occurs due to corrosion. As thickness decreases, the magnetostatic force between the magnet and the steel structure also decreases. This, in turn, affects the strain measured using the optical fiber. The sensor prototype was designed and built after verifying its sensitivity using a numerical model. The prototype was tested on steel plates of different thicknesses to establish the relationship between the metal thickness and measured strain. The results of experiments and numerical models demonstrate a strong relationship between the metal thickness and the measured strain values., Competing Interests: The authors declare no conflict of interest. The funding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.
- Published
- 2018
- Full Text
- View/download PDF
13. Analytical Modeling Tool for Design of Hydrocarbon Sensitive Optical Fibers.
- Author
-
Al Handawi K, Vahdati N, Shiryayev O, and Lawand L
- Abstract
Pipelines are the main transportation means for oil and gas products across large distances. Due to the severe conditions they operate in, they are regularly inspected using conventional Pipeline Inspection Gages (PIGs) for corrosion damage. The motivation for researching a real-time distributed monitoring solution arose to mitigate costs and provide a proactive indication of potential failures. Fiber optic sensors with polymer claddings provide a means of detecting contact with hydrocarbons. By coating the fibers with a layer of metal similar in composition to that of the parent pipeline, corrosion of this coating may be detected when the polymer cladding underneath is exposed to the surrounding hydrocarbons contained within the pipeline. A Refractive Index (RI) change occurs in the polymer cladding causing a loss in intensity of a traveling light pulse due to a reduction in the fiber's modal capacity. Intensity losses may be detected using Optical Time Domain Reflectometry (OTDR) while pinpointing the spatial location of the contact via time delay calculations of the back-scattered pulses. This work presents a theoretical model for the above sensing solution to provide a design tool for the fiber optic cable in the context of hydrocarbon sensing following corrosion of an external metal coating. Results are verified against the experimental data published in the literature., Competing Interests: The authors declare no conflict of interest.
- Published
- 2017
- Full Text
- View/download PDF
14. Corrosivity Sensor for Exposed Pipelines Based on Wireless Energy Transfer.
- Author
-
Lawand L, Shiryayev O, Al Handawi K, Vahdati N, and Rostron P
- Abstract
External corrosion was identified as one of the main causes of pipeline failures worldwide. A solution that addresses the issue of detecting and quantifying corrosivity of environment for application to existing exposed pipelines has been developed. It consists of a sensing array made of an assembly of thin strips of pipeline steel and a circuit that provides a visual sensor reading to the operator. The proposed sensor is passive and does not require a constant power supply. Circuit design was validated through simulations and lab experiments. Accelerated corrosion experiment was conducted to confirm the feasibility of the proposed corrosivity sensor design., Competing Interests: The authors declare no conflict of interest.
- Published
- 2017
- Full Text
- View/download PDF
15. Assessing chilling and drought tolerance of different plant genera on extensive green roofs in an arid climate region in Iran.
- Author
-
Vahdati N, Tehranifar A, and Kazemi F
- Subjects
- Desert Climate, Iran, Plants, Conservation of Natural Resources, Droughts
- Abstract
The harsh and stressful growing environment of extensive green roofs especially in arid environments allows a limited range of plant species to survive. Therefore, achieving plantings to survive in such conditions is a significant challenge. This paper describes an experiment investigating plant selections for extensive green roofs based on chilling (cold season) and drought (warm season) conditions of Iran. Nine species were selected from the three major taxonomic and functional plant groups that are commonly used on extensive green roofs including grasses, groundcovers and sedums. The species namely Agropyron cristatum, Festuca aurundinacea, Festuca ovina, Potentila sp., Frankinia thymifolia, Vinca minor, Sedum acre, Sedum spurinum, Carpobrotus edulis were imposed to natural chilling in autumn and winter using a randomized complete block design. For spring and summer, irrigation regimes at levels (48, 72 and 96 h intervals) in a factorial experiment based on a randomized complete block design with four replications were applied. The results showed that Agropyron cristatum, Frankinia thymifolia and Carpobrotus edulis were the best plants from each class. Carpobrotus edulis was the best choice for cold and warm seasons and this was followed by Frankinia thymifolia and Potentila sp. Vinca minor performed well in the cold seasons and Sedum spurinum appeared to be excellent in the warm seasons. The plants of the experiment showed significantly different appearances in different watering regimes. Little differences in drought tolerances were observed among the forbs and grasses, which must be watered during warm seasons. However, the succulents responded very well to the drought and low watering regimes. Overall, succulents and groundcovers were considered more appropriate for application in warm and cold seasons, respectively. According to the findings, drought and cold weather conditions cannot be a major obstacle for developing extensive green roofs in Iran if considerations are made on selecting its plant species., (Copyright © 2017 Elsevier Ltd. All rights reserved.)
- Published
- 2017
- Full Text
- View/download PDF
16. Relationship between Patient Demographic Characteristics, Valproic Acid Dosage and Clearance in Adult Iranian Patients.
- Author
-
Aghebati T, Foroughipour M, Azarpazhooh MR, Mokhber N, Hasanzadeh Khayat M, Vahdati N, and Mohammadpour AH
- Abstract
Objectives: As there are conflicting findings regarding the clearance-dose and patient characteristics relationships for valproic acid (VPA), this study was conducted to investigate the relationship between patient demographic characteristics, VPA dosage and the drug clearance in adult Iranian patients., Materials and Methods: Patients (N= 47) were either on monotherapy with VPA or were under co-treatment with drugs that have no effect on VPA pharmacokinetic (PK) profile. All of the patients received VPA at therapeutic dose. Steady state trough plasma concentrations of VPA were determined by Fluorescence Polarization Immunoassay (FPIA) and VPA apparent clearance (CL/F) were calculated in each patient., Results: Mean VPA dose and VPA CL/F were 8.93±2.2 mg/kg/day and 0.65±0.55 l/hr respectively. No significant correlations were found between VPA CL/F and patients' age, TBW and VPA dose. VPA CL/F values of male and female patients were compared and no significant difference between these two groups was noted (P> 0.05). Significant correlation between VPA dose and total trough plasma concentration was found (P= 0.001). Mean total VPA plasma concentration was 54.51±23.74 mg/l., Conclusion: Our study showed PK of VPA was not affected by age, sex, TBW and VPA dose. However, for detailed results and construction of VPA PK model in Iranian patients, it is necessary to evaluate VPA PK in a larger sample size with different VPA doses, age and TBW ranges.
- Published
- 2012
17. A review on therapeutic drug monitoring of immunosuppressant drugs.
- Author
-
Mohammadpour N, Elyasi S, Vahdati N, Mohammadpour AH, and Shamsara J
- Abstract
: Immunosuppressants require therapeutic drug monitoring because of their narrow therapeutic index and significant inter-individual variability in blood concentrations. This variability can be because of factors like drug-nutrient interactions, drug-disease interactions, renal-insufficiency, inflammation and infection, gender, age, polymorphism and liver mass. Drug monitoring is widely practiced especially for cyclosporine, tacrolimus, sirolimus and mycophenolic acid. CYCLOSPORINE: Therapeutic monitoring of immunosuppressive therapy with cyclosporine is a critical requirement because of intra- and inter-patient variability of drug absorption, narrow therapeutic window and drug induced nephrotoxicity. MYCOPHENOLIC ACID MPA: Some reasons for therapeutic drug monitoring of MPA during post-transplant period include: relationship between MPA pharmacokinetic parameters and clinical outcomes, Inter-patient pharmacokinetic variability for MPA despite fixed MMF doses, alternations of MPA pharmacokinetics during the first months after transplantation, drug- drug interaction and influence of kidney function on MPA pharmacokinetic. SIROLIMUS: A recent review of the pharmacokinetics of sirolimus suggested a therapeutic range of 5 to 10 μg l(-1) in whole blood. However, the only consensus guidelines published on the therapeutic monitoring of sirolimus concluded that there was not enough information available about the clinical use of the drug to make recommendations. TACROLIMUS: Sudies have shown, in kidney and liver transplant patients, significant associations of low tacrolimus concentrations with rejection and of high concentrations with nephrotoxicity. Although the feasibility of a limited sampling scheme to predict AUC has been demonstrated, as yet, trough, or pre-dose, whole blood concentration monitoring is still the method of choice.
- Published
- 2011
18. High frequency testing of rubber mounts.
- Author
-
Vahdati N and Saunders LK
- Subjects
- Aircraft, Elasticity, Equipment Design, Fourier Analysis, Models, Theoretical, Stress, Mechanical, Viscosity, Computer Simulation, Materials Testing instrumentation, Materials Testing methods, Rubber, Vibration
- Abstract
Rubber and fluid-filled rubber engine mounts are commonly used in automotive and aerospace applications to provide reduced cabin noise and vibration, and/or motion accommodations. In certain applications, the rubber mount may operate at frequencies as high as 5000 Hz. Therefore, dynamic stiffness of the mount needs to be known in this frequency range. Commercial high frequency test machines are practically nonexistent, and the best high frequency test machine on the market is only capable of frequencies as high as 1000 Hz. In this paper, a high frequency test machine is described that allows test engineers to study the high frequency performance of rubber mounts at frequencies up to 5000 Hz.
- Published
- 2002
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.