Unsupervised Log Message Anomaly Detection

Amir Farzad,T. Aaron Gulliver 한국통신학회 2020 ICT Express Vol.6 No.3

Log messages are now broadly used in cloud and software systems. They are important for classification and anomaly detection as millions of logs are generated each day. In this paper, an unsupervised model for log message anomaly detection is proposed which employs Isolation Forest and two deep Autoencoder networks. The Autoencoder networks are used for training and feature extraction, and then for anomaly detection, while Isolation Forest is used for positive sample prediction. The proposed model is evaluated using the BGL, Openstack and Thunderbird log message data sets. The results obtained show that the number of negative samples predicted to be positive is low, especially with Isolation Forest and one Autoencoder. Further, the results are better than with other well-known models.

Radiologic and Clinical Outcomes of Surgery in High Grade Spondylolisthesis Treated with Temporary Distraction Rod

Farzad Omidi-Kashani,Alireza Hootkani,Lida Jarahi,Manizheh Rezvan,Amir Moayedpour 대한정형외과학회 2015 Clinics in Orthopedic Surgery Vol.7 No.1

Background: Surgical techniques used in the treatment of patients with high grade lumbar spondylolisthesis (> 50% slippage) areusually associated with a great deal of controversies. We aim to evaluate the surgical outcomes of high grade spondylolisthesistreated with an intraoperative temporary distraction rod. Methods: We retrospectively studied 21 patients (14 females and 7 males), aged 50.4 ± 9.2 years, who had high grade lumbarspondylolisthesis that was treated with intraoperative temporary distraction rods, neural decompression, pedicular screw fixation,and posterolateral fusion involving one more intact upper vertebra. The mean follow-up period was 39.2 months. Radiologic andclinical outcomes were measured by slip angle, slip percentage, correction rate, Oswestry Disability Index (ODI), visual analoguescale (VAS), patient’s satisfaction rate in the pre- and postoperative period. Data were analyzed by SPSS ver. 11.5. Results: Analysis of the preoperative visits and final follow-up visits indicated that surgery could improve ODI, lumbar VAS, andleg VAS from 60.5% to 8.2%, from 6.7 to 2.2, and from 6.9 to 1.3, respectively. Slip angle and slip percentage were also changedfrom –8° to –15° and from 59.2% to 21.4%, respectively. Mean correction rate at the final follow-up visit was 64.1%. Loss of correctionwas insignificant and a neurologic complication occurred in one patient due to misplacement of one screw. Excellent andgood levels of satisfaction were observed in 90.5% of the patients. Conclusions: In the surgical treatment of refractory high grade spondylolisthesis, the use of a temporary distraction rod to reducethe slipped vertebra in combination with neural decompression, posterolateral fusion, and longer instrumentation is associatedwith satisfactory clinical and radiologic outcomes.

Development of a Nonlinear Conical Spring Bracing System for Framed Structures Subjected to Dynamic Load

Amir Fateh,Farzad Hejazi,Mohd Saleh Jaafar,Izian Abd. Karim 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.1

In this study, a nonlinear conical spring bracing (NCSB) system that can be applied as a lateral resistance component in framed structures was developed to mitigate the vibration effects of earthquake and wind. The NCSB device consists of two solid telescopic conical springs attached to steel wire ropes. The application of NCSB in framed structures, particularly moment-resisting steel frame (MRSF), improves the seismic behavior of the frame because of the variable action of the NCSB device. NCSB stiffness is not considerable in the low to medium vibration range compared with structural stiffness. Therefore, the inherent ductility of MRSF is unaffected because of the addition of the NCSB device to the frame. However, with its large displacement value, NCSB stiffness increases and prevents excessive displacement in structures. A mathematical model of the NCSB device that considers the effect of cable stiffness is developed and implemented in program code. Furthermore, the seismic behavior of eight types of NCSB applications in frames subjected to different earthquake accelerations is evaluated in terms of displacement, velocity, and acceleration, as well as compared with bare and brace frames. Results reveal the reduction influences of the NCSB device on framed structures. The best geometric configuration for the NCSB system is also determined by using the proposed numerical analysis.

Experimentally Validated Finite Element Analysis for Evaluating Subsurface Damage Depth in Glass Grinding Using Johnson-Holmquist Model

Farzad Pashmforoush,Amir Esmaeilzare 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.12

Subsurface damages (SSD) induced during grinding of brittle materials influence mechanical and physical properties of the machined specimen. Experimental evaluation of SSD is very expensive and time consuming due to need for performing various grinding testes in one hand and post-grinding processes such as angle polishing in another hand. Meanwhile, theoretical investigation lacks accuracy due to the various simplifications involved with theoretical models. Hence, a numerical study was performed to analyze SSD in optical glass grinding using finite element method. The constitutive material behavior of glass was defined based on the Johnson-Holmquist model. Performing FEM simulations, the SSD depth was obtained for various combinations of process parameters. Based on the statistical analysis of variance, feed velocity was found to be the most significant parameter followed by depth of cut and cutting velocity. The numerical results were then compared with experimental observations using angle polishing technique and Scanning Electron Microscopy. This comparison reveals good performance of FEM in prediction of SSD depth. Finally, an empirical/ mathematical model was developed to express SSD depth as a function of process parameters. The regression model revealed that by increasing feed velocity and cutting depth, SSD depth increases, while by increasing cutting velocity, SSD depth decreases.

Lumbar Spinal Stenosis: Who Should Be Fused? An Updated Review

Farzad Omidi Kashani,Ebrahim Ghayem Hasankhani,Amir Ashjazadeh 대한척추외과학회 2014 Asian Spine Journal Vol.8 No.4

Lumbar spinal stenosis (LSS) is mostly caused by osteoarthritis (spondylosis). Clinically, the symptoms of patients with LSS can be categorized into two groups; regional (low back pain, stiffness, and so on) or radicular (spinal stenosis mainly presenting as neurogenic claudication). Both of these symptoms usually improve with appropriate conservative treatment, but in refractory cases, surgical intervention is occasionally indicated. In the patients who primarily complain of radiculopathy with an underlying biomechanically stable spine, a decompression surgery alone using a less invasive technique may be sufficient. Preoperatively, with the presence of indicators such as failed back surgery syndrome (revision surgery), degenerative instability, considerable essential deformity, symptomatic spondylolysis, refractory degenerative disc disease, and adjacent segment disease, lumbar fusion is probably recommended. Intraoperatively, in cases with extensive decompression associated with a wide disc space or insufficient bone stock, fusion is preferred. Instrumentation improves the fusion rate, but it is not necessarily associated with improved recovery rate and better functional outcome.

Application of the differential transformation method for nonlocal vibration analysis of functionally graded nanobeams

Farzad Ebrahimi,Majid Ghadiri,Erfan Salari,Seied Amir Hosein Hoseini,Gholam Reza Shaghaghi 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.3

In this study, the applicability of differential transformation method (DTM) in investigations on vibrational characteristics of functionallygraded (FG) size-dependent nanobeams is examined. The material properties of FG nanobeam vary over the thickness based on thepower law. The nonlocal Eringen theory, which takes into account the effect of small size, enables the present model to be effective in theanalysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton’s principle. The obtained resultsexactly match the results of the presented Navier-based analytical solution as well as those available in literature. The DTM is alsodemonstrated to have high precision and computational efficiency in the vibration analysis of FG nanobeams. The detailed mathematicalderivations are presented and numerical investigations performed with emphasis placed on investigating the effects of several parameters,such as small scale effects, volume fraction index, mode number, and thickness ratio on the normalized natural frequencies of the FGnanobeams. The study also shows explicitly that vibrations of FG nanobeams are significantly influenced by these effects. Numericalresults are presented to serve as benchmarks for future analyses of FG nanobeams.

Controlled Synchronization of Nonlinear Teleoperation in Task-space with Time-varying Delays

Amir Zakerimanesh,Farzad Hashemzadeh,Ali Torabi,Mahdi Tavakoli 제어·로봇·시스템학회 2019 International Journal of Control, Automation, and Vol.17 No.8

This paper introduces a novel control framework for bilateral teleoperation system with the redundant remote robot to ensure the end-effectors’ position tracking while satisfying a sub-task control such as obstacle avoidance in the presence of the nonlinear dynamics for the manipulators and bounded time-varying delays in the communication channels. The asymptotic stability of the closed-loop dynamics is studied using a Lyapunov-Krasovskii functional under conditions on the controller parameters and the maximum values of time-varying delays. Simulation and experimental results are provided to validate the theoretical findings.

Association between Circulating Irisin and C-Reactive Protein Levels: A Systematic Review and Meta-Analysis

Elham Eslampour,Farzad Ebrahimzadeh,Amir Abbasnezhad,Mohammad Zeinali Khosroshahi,Razieh Choghakhori,Omid Asbaghi 대한내분비학회 2019 Endocrinology and metabolism Vol.34 No.2

Background: Although previous studies have demonstrated that irisin plays an anti-inflammatory role in the body, conflicting results have been reported regarding the correlation between serum levels of irisin and C-reactive protein (CRP). The present metaanalysis was conducted to further investigate the correlation between irisin and CRP levels. Methods: We systematically searched PubMed, the Cochrane Library, Web of Science, Embase, SCOPUS, and Ovid to retrieve studies assessing the correlation between irisin and CRP levels. Meta-analyses were performed using a random-effects model, and the I2 index was used to evaluate heterogeneity. Results: Of the 428 studies that were initially found, 14 studies with 2,530 participants met the inclusion criteria for the meta-analysis. The pooled effect size was calculated as 0.052 (95% confidence interval, −0.047 to 0.152; P=0.302). Subgroup analyses identified s ignificant, positive, but weak correlations between CRP and irisin levels in cohort studies, studies conducted among healthy participants, studies in which the male-to-female ratio was less than 1, in overweight or obese subjects, and in studies with a samplesize of at least 100 participants. Conclusion: The present meta-analysis found no overall significant correlation between irisin and CRP levels, although a significant positive correlation was found in overweight or obese subjects. Well-designed studies are needed to verify the results of the present meta-analysis.

Evaluating Kyphosis and Lordosis in Students by Using a Flexible Ruler and Their Relationship with Severity and Frequency of Thoracic and Lumbar Pain

Sedigheh-Sadat Mirbagheri,Amir Rahmani-Rasa,Farzad Farmani,Payam Amini,Mohammad-Reza Nikoo 대한척추외과학회 2015 Asian Spine Journal Vol.9 No.3

Study Design: A cross-sectional, descriptive study. Purpose: This study aimed to investigate the relationship between kyphosis and lordosis measured by using a flexible ruler and musculoskeletal pain in students of Hamadan University of Medical Sciences. Overview of Literature: The spine supports the body during different activities by maintaining appropriate body alignment and posture. Normal alignment of the spine depends on its structural, muscular, bony, and articular performance. Methods: Two hundred forty-one students participated in this study. A single examiner evaluated the angles of lumbar lordosis and thoracic kyphosis by using a flexible ruler. To determine the severity and frequency of pain in low-back and inter-scapular regions, a tailor-made questionnaire with visual analog scale was used. Finally, using the Kendall correlation coefficient, the data were statistically analyzed. Results: The mean value of lumbar lordosis was 34.46°±12.61° in female students and 22.46°±9.9° in male students. The mean value of lumbar lordosis significantly differed between female and male students (p <0.001). However, there was no difference in the level of the thoracic curve (p =0.288). Relationship between kyphosis measured by using a flexible ruler and inter-scapular pain in male and female students was not significant (p =0.946). However, the relationship between lumbar lordosis and low back pain was statistically significant (p =0.006). Also, no significant relationship was observed between abnormal kyphosis and frequency of inter-scapular pain, and between lumbar lordosis and low back pain. Conclusions: Lumbar lordosis contributes to low back pain. The causes of musculoskeletal pain could be muscle imbalance and muscle and ligament strain.