Chattering-free sliding mode control with a fuzzy model for structural applications

Keyvan Aghabalaei Baghaei,Hosein Ghaffarzadeh,S. Ali Hadigheh,Daniel Dias-da-Costa 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.69 No.3

This paper proposes a chattering-free sliding mode control (CFSMC) method for seismically excited structures. The method is based on a fuzzy logic (FL) model applied to smooth the control force and eliminate chattering, where the switching part of the control law is replaced by an FL output. The CFSMC is robust and keeps the advantages of the conventional sliding mode control (SMC), whilst removing the chattering and avoiding the time-consuming process of generating fuzzy rule basis. The proposed method is tested on an 8-story shear frame equipped with an active tendon system. Results indicate that the new method not only can effectively enhance the seismic performance of the structural system compared to the SMC, but also ensure system stability and high accuracy with less computational cost. The CFSMC also requires less amount of energy from the active tendon system to produce the desired structural dynamic response.

Finite Element Modeling and Nonlinear Analysis for Seismic Assessment of Off-Diagonal Steel Braced RC Frame

Keyvan Ramin,Mitra Fereidoonfar 한국콘크리트학회 2015 International Journal of Concrete Structures and M Vol.9 No.1

The geometric nonlinearity of off-diagonal bracing system (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three dimensional finite element modeling. Nonlinear static analysis is considered to obtain performance level and seismic behaviour, and then the response modification factors calculated from each model’s pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behaviour and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

Total Disc Arthroplasty for Treating Lumbar Degenerative Disc Disease

Keyvan Mostofi 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.1

Study Design: Lumber disc arthroplasty is a technological advancement that has occurred in the last decade to treat lumbar degenerative disk diseases. Purpose: The aim of this retrospective study was to establish the impact and outcomes of managing patients with lumbar degenerative disk disease who have been treated with lumbar total disc arthroplasty (TDA). Overview of Literature: Several studies have shown promising results following this surgery. Methods: We reviewed the files of 104 patients at the Department of Neurosurgery in Colmar (France) who had been operated on by lumbar spine arthroplasty (Prodisc) between April 2002 and October 2008. Results: Among the 104 patients, 67 were female and 37 were male with an average age of 33.1 years. We followed the cases for a mean of 20 months. The most frequent level of discopathy was L4–L5 with 62 patients (59.6%) followed by L5-S1 level with 52 patients (50%). Eighty-three patients suffered from low back pain, 21 of which were associated with radiculopathy. The status of 82 patients improved after surgery according to the Oswestry Disability Index score, and 92 patients returned to work. Conclusions: The results indicate that TDA is a good alternative treatment for lumbar spine disk disease, particularly for patients with disabling and chronic low back pain. This technique contributes to improve living conditions with correct patient selection for surgery.

Foramen Magnum Meningioma: Some Anatomical and Surgical Remarks through Five Cases

Keyvan Mostofi 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.1

Study Design: Foramen magnum meningioma foramen magnum meningioma (FMM) represents 2% all of meningiomas. The clinical symptomatology is usually insidious and consists of headache, neck pain and hypoesthesia in C2 dermatome. Because of their location, the management is challenging. Purpose: The purpose of this paper is to present our experience in the surgery of FMM. Overview of Literature: Since 1938, numerous series have been published but they are very heterogeneous with high variability of location and surgical approaches. Methods: During two years, we operated 5 patients with FMM. All the patients had magnetic resonance imaging (MRI) with angio- MRI to study the relationship between tumour and vertebral artery (VA). In all the cases, we used prone position. Results: In one case, considering the tumour localization (posterior and pure intradural) the tumour was removed via a midline suboccipital approach with craniotomy and C1–C2 laminectomy. In all other cases, meningiomas were posterolateral (classification of George) with extradural extension in one case. In all cases, VA was surrounded by tumor. So, we opted for a modified postero-lateral approach with inverted L incision, craniotomy and C1–C2 laminectomy without resect occipital condyle. Epidural part of VA was identified and mobilized laterally. Once VA was identified we opened dura mater and began to remove the tumour. Conclusions: In this paper, we present five cases of operated FMM, describe our approaches, the reason of each approach and propose some surgical remarks.

Reliability of the Path of the Sciatic Nerve, Congruence between Patients’ History and Medical Imaging Evidence of Disc Herniation and Its Role in Surgical Decision Making

Keyvan Mostofi,Reza Karimi Khouzani 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.2

Study Design: The prevalence of disc herniation is estimated to be about 100 000 new cases per year in France and disc herniation accounts for 25% to 30% of surgical activity in Departments of Neurosurgery. Classically, sciatica is expected to follow its specific dermatome—L5 or S1—. In clinical practice, we regularly encounter patients showing discrepancy between clinical sciatica and imaging findings. Purpose: The aim of this paper is to review the medical concept and management of sciatica pain in patients showing this discrepancy. Overview of Literature: To the best of our knowledge, this subject has not yet been discussed in the medical literature. Methods: The medical records of 241 patients who were operated on for L5 or S1 sciatica caused by disc herniation were reviewed. Results: We found an apparent clinicoradiological discrepancy between sciatica described by patients on one side and magnetic resonance imaging (MRI) finding on the other side in 27 (11.20%) patients. We did not find any other abnormalities in the preoperative and postoperative period. All of these patients underwent lumbar discectomy via posterior interlaminar approach. Three months after surgery, 25 patients (92.59%) had been totally relieved of sciatica pain. Two patients (7.41%) continued to experience sciatica in spite of the surgery. Conclusions: The discrepancy between clinical sciatica and disc herniation level on MRI is not rare. Management of this discrepancy requires further investigation in order to avoid missing the diagnosis and treatment failure.

Lack of Altered BECN1 Gene Expression in Iranian Patients with Acute Myeloid Leukemia

Keyvan, Ladan,Bidoki, Seyed Kazem,Abdollahi, Davood Zare,Mansouri, Neda,Hashemi, Mehrdad,Tabatabaei, SA Mortazavi,Fardmanesh, Hediyeh,Meimandi, Mansour,Ayatollahi, Seyed Majid,Movafagh, Abolfazl Asian Pacific Journal of Cancer Prevention 2016 Asian Pacific journal of cancer prevention Vol.17 No.12

Acute myeloid leukemia (AML), one of the most prevalent leukemia types in adults, demonstrates great heterogeneity in molecular and clinical terms. Hence, there is a necessity to the mechanisms involved in AML generation in order to determine optimal treatment. This cross sectional study aimed to assess changes in BECN1 gene expression in with blood samples from 30 AML patients, compared with samples from 15 healthy persons. RNA was extracted and cDNA was synthesized and Real Time PCR applied to determine BECN1 gene expression. The results showed no significant differences in BECN1 gene expression between patients with AML and normal controls (P > 0.05). It appears that expression of BECN1 does not play a significant role in genesis of AML leukemia.

Experimental and numerical investigation of lead-rubber dampers in chevron concentrically braced frames

Zeynali, Keyvan,Saeed Monir, Habib,Mirzai, Nadia M.,Hu, Jong Wan Elsevier 2018 Archives of Civil and Mechanical Engineering Vol.18 No.1

<P><B>Abstract</B></P> <P>This paper presents a theoretical and experimental evaluation of the application of lead rubber dampers (LRD) in the chevron bracing of structures. This device consists of a circular lead core with several layers of steel and rubber plates that are sandwiched together. This damper was manufactured at the earthquake engineering laboratory of Urmia University and installed inside a SDOF steel frame. The frame was placed on a shaking table, and its responses under several earthquake excitations were recorded. A 3D finite element model was created for the device, and hyper-elastic properties were determined for the rubber layers. To check the effectiveness of the device in mitigating the responses of multi-story frames, several nonlinear time history analyses were conducted on the structures using three earthquake excitations. The results indicate that significant reductions in the stories’ drift can be achieved by installing lead-rubber dampers in the chevron bracing.</P>

Human red blood cell recognition enhancement with three-dimensional morphological features obtained by digital holographic imaging

Jaferzadeh, Keyvan,Moon, Inkyu SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS 2016 JOURNAL OF BIOMEDICAL OPTICS Vol.21 No.12

Lossless and lossy compression of quantitative phase images of red blood cells obtained by digital holographic imaging

Jaferzadeh, Keyvan,Gholami, Samaneh,Moon, Inkyu The Optical Society 2016 Applied Optics Vol.55 No.36

<P>In this paper, we evaluate lossless and lossy compression techniques to compress quantitative phase images of red blood cells (RBCs) obtained by an off-axis digital holographic microscopy (DHM). The RBC phase images are numerically reconstructed from their digital holograms and are stored in 16-bit unsigned integer format. In the case of lossless compression, predictive coding of JPEG lossless (JPEG-LS), JPEG2000, and JP3D are evaluated, and compression ratio (CR) and complexity (compression time) are compared against each other. It turns out that JP2k can outperform other methods by having the best CR. In the lossy case, JP2k and JP3D with different CRs are examined. Because some data is lost in a lossy way, the degradation level is measured by comparing different morphological and biochemical parameters of RBC before and after compression. Morphological parameters are volume, surface area, RBC diameter, sphericity index, and the biochemical cell parameter is mean corpuscular hemoglobin (MCH). Experimental results show that JP2k outperforms JP3D not only in terms of mean square error (MSE) when CR increases, but also in compression time in the lossy compression way. In addition, our compression results with both algorithms demonstrate that with high CR values the three-dimensional profile of RBC can be preserved and morphological and biochemical parameters can still be within the range of reported values. (C) 2016 Optical Society of America</P>

A Cooperative Use of Stochastic Dynamic Programming and Non-Linear Programming for Optimization of Reservoir Operation

Mohsen Saadat,Keyvan Asghari 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5

Stochastic Dynamic Programming (SDP) is a conventional procedure to extract optimal reservoir operating policies. SDP appliesexhaustive search based on the total combinations of discrete values of state variables. The accuracy of SDP can be improved byincreasing the number of intervals of inflow or reservoir volume domain; however, increasing the inflow intervals is limited andincreasing the reservoir volume intervals does not guarantee the regular improvement of results. This study attempts to determine thenear optimum discrete reservoir volume values by cooperating SDP and non-linear programming (CSDP) optimization modules, sothe acceptable performance is achieved by limited intervals of the state variables. Towards this end, the objective function is utilizedwith a hedging policy to control the amount of the monthly reservoir release. The non-linear programming optimization moduleembodied in SDP, determines the proper values of reservoir volume taking into account the hedging policy and available constrains. Considering various numbers of inflow and reservoir volume intervals, the conventional SDP results are implemented and comparedto CSDP approach. Our comparisons indicate an improved reliability performance obtained in the CSDP technique. A DistanceBased Interpolation Formula (DBIF) is also illustrated and applied to employ optimal operating polices for reservoir operationmanagement. Findings show better performance of DBIF as compared to conventional methods like Multiple Linear Regression(MLR) during long-time simulation of reservoir operation.