Showing 399 results for Sign
Volume 18, Issue 1 (3-2018)
Abstract
Nowadays, diagnosis of diseases with high precision, high speed, low-cost and non-invasive approaches has become a necessity. In this regard, taking pulse signal is very easy and inexpensive, which due to the availability and feasibility of the process, can be very useful in the rapid diagnosis heart disease. If we can use the appropriate signal processing and intelligent methods in such a way that its accuracy and total cost equal those of other corresponding methods, we can say that we have reached a valuable achievement; in the current study we pursue the same purpose. In the first step, pressure pulse signals of 45 Coronary Arterial Disease (CAD) patients and 45 healthy persons are acquired from the left fingers using Task Force Monitor (TFM). Then the signals are filtered by wavelet transform (db6) and the wrong items are discarded. Then, the features corresponding to the CAD and healthy states are extracted which based on Time Domain Analysis. Finally, by choosing the best features, the data of healthy people and patients (CAD) are classified with Support Vector Machine (SVM) classifier by the accuracy rate of more than 85%.
Volume 18, Issue 1 (5-2018)
Abstract
In signalized intersections and at the onset of the yellow phase, drivers often come across a dilemma situation where they are unable to stop comfortably before the stop line or clear the intersection (without excessive acceleration) prior to the onset of the red signal phase. yellow time is designed to inform drivers about passing time and preventing extreme changes in cars' speed in timing of intersections with traffic lights. However, studies have confirmed that drivers face high level of uncertainty during yellow time. drivers visually sample their surroundings while driving so they are able to change their behavior based on other vehicles’ movements, the roadway environment and traffic signal data. This implies that drivers’ behaviors are affected by surrounding factors such as other vehicles’ headway or intersection conditions. In the dilemma zone, drivers’ decisions are influenced not only by their own condition (e.g., distance to the stop line, speed, red time)but also by the surrounding environment at an intersection. The primary goal of the research described here was to develop a comprehensive knowledge of the stopping characteristics of dilemma zone drivers at signalized intersections. Physical, traffic, timing and phasing of intersections and weather conditions are assessed factors. The research performed here involved macroscopic evaluation of driver behavior; thus, characteristics of individual drivers were not investigated as it was not feasible to determine information such as age, experience, route familiarity, and sex of each driver. This study investigates actual data of traffic cameras and central smart program in four intersections in Qazvin in which traffic lights are set up. Peak, normal sunny and rainy conditions and drivers' behavior in yellow and red times are studied using binary logit model. A field study was performed using a video-based data collection system to record several attributes related to the behavior of the last vehicle to go through and the first vehicle to stop in each lane during each yellow interval. The researchers concluded that a driver’s decision to stop or go through when presented with a yellow indication is complex but can be predicted reasonably well based on several factors. Pedestrians in streets(Coef.=-0,61241; p-value=0,0177), time passed in red phase(Coef.=-0.53836; p-value=0,0177), and headway(Coef.=-1,89062; p-value=0,0854) are the most effective factors on drivers' pauses in yellow or red phase. High speed of cars(Coef.=+0,172; p-value=0,0087) and also waiting time (red phase) (Coef.=+0,864; p-value=0,0095) are the most influential factors on drivers motion in yellow or red phases. I addition, in the situations in which drivers distance to intersection is less than one meter at the beginning of yellow phase and speed is higher than 20 m/s, passing probabilities are 74 and 90%, respectively. One of the innovations of this study is evaluating the effect of rain on the behavior of drivers. The results of model show the possibility that the drivers pass the traffic light in yellow or red phase will be increased by rising the amount of rainfall. Our results are able to inform officials about drivers' behavior at intersections with traffic lights and facilitate their control and surveillance.
Volume 18, Issue 2 (7-2014)
Abstract
One of the applicable techniques which are used for modeling and solving optimization problems is response surface methodology (RSM). Response surface methodology is a collection of tools for fitting a surface to a set of data and determines optimal levels, this method used of a regression model for optimization problems Some real world problems include determining optimum values of input variables in order to obtain the desired levels of output variable (response surface variable). In this paper considering the Importance of four factors: Cooling Time, Pressure of injection, injection Speed and Heater temperature as the independent input variables for the variables of effective input factors and the response surface quantity and qualitative variable (Twin and Concurrently) in relation between input variables and response surface variables with the nonlinear regression model. Response variables would be crisp and fuzzy, for this Reason has been used of bi-level programming and fuzzy dual response surface methodology. Then the optimal value of each parameter is obtained by Meta-Heuristics algorithm (NSGA-II).
Volume 18, Issue 2 (9-2014)
Abstract
In a documentary credit relationship, the person for the favor of whom the credit is openned, is not necessarily the last supplier. In fact, he hopes to buy goods from the last supplier and deliver it to the buyer. Transfer of credit is the third alternative rather than the beneficiary of the credit. It gives the first beneficiary right to benefit from differce of transferred credit and original credit prices. It also allows him/her to assign his/her obligations about that credit document delivery. There is disagreement about the legal nature of transfer of credit. The group argued that the benefits of credit can be transferred to a third party conditionally, so the legal nature of transfer is similar to the assignment of benefits. Others believe that as transfer of credit take places, the original legal relation will nullify, and a new relation between the second beneficiary and the transferring bank will be created. So, they believe that the legal nature of transfer of credit is more likely to novation. Various studies’ assessment shows that, despite of some differences between novation and transfer of credit, legal nature of the former is very similar to novation rather than other legal establishments.
* Corresponding author’s E-mail: s.mr.hosseiny@gmail.com
Volume 18, Issue 2 (6-2015)
Abstract
Objective: Eukaryotic proteins generally have signal peptides which are not only crucial for their secretion efficiencies but are important for their expression levels. Coagulation factor IX (FIX) is a glycoprotein that plays a fundamental role in the blood coagulation pathway. Reduced levels or dysfunctional FIX are associated with hemophilia B. This study investigates the function of the human prothrombin signal peptide in an attempt to improve the human FIX (hFIX) secretion efficiency in a heterologous expression system. With this aim, we have used the SignalP and PrediSi programs for in silico evaluation of the signal peptide efficiency prior to conducting this experiment.
Methods: We used molecular techniques to amplify and join the coding region of the human prothrombin signal peptide to the cDNA of mature hFIX. The chimeric fragment was examined for transient expression in a mammalian cell line (HEK293T) in comparison with the native hFIX, under a CMVp regulation. Using the neural network-based prediction programs, we evaluated the scores for cleavage position and secretion efficiency of the human prothrombin and hFIX signal peptides. The expression efficiencies of hFIX expressed by the recombinant cells were analyzed by RT-PCR and ELISA.
Results: In silico analysis more efficiently predicted the human prothrombin signal peptide with a high score compared to the native hFIX signal peptide. This data was confirmed by the RT-PCR and ELISA results obtained from expression analyses at the RNA and protein levels, respectively.
Conclusion: The present study showed that the signal peptide derived from the human prothrombin has the potential for efficient secretion of hFIX as evidenced by the results taken from a transient expression system. The results were consistent with in silico analysis. This replacement could be evaluated in a stable state condition.
Volume 18, Issue 2 (4-2018)
Abstract
The main objective is to improve Hilbert-Huang transform using the advantages of non-linear entropy-based features in the time and frequency domain to reduce noise effects. In addition, applying appropriate entropy-based features lead to restrict information redundancy and overcome the need for dimension reduction, in the fault detection of a rotating system. To modify the Hilbert-Huang method, the effect of added noise on various types of nonlinear entropy-based features is investigated for each intrinsic mode functions (IMFs) which extracted by ensemble empirical mode decomposition algorithm. Considering the approximate entropy (ApEn) sensitivity to noise, an evaluation index is presented for selecting the proper amplitude of the added noise based on the approximate entropy and mutual information coefficient of the different IMFs. Subsequently, taking into account the high capability of permutation entropy (PeEn) and marginal Hilbert spectrum entropy (MHE) in the signal characteristic, a threshold is determined for fault detection based on their values associated to the main IMF which has the highest value of mutual information coefficient. As a result, the permutation entropy values and marginal Hilbert spectrum entropy of the main IMF can be used for detection of any deviation from normal operation of the rotor bearings system, regardless of the fault type. Consequently, to determine the type of defect, the higher-order spectra have been used.The bi-spectrum of envelope is calculated. This bi-spectrum is employed to identify the coupling between the rotating frequency and fault-characteristic frequencies, for misalignment and unbalanced fault diagnosis of a rotating machinery vibration simulation system
Volume 18, Issue 2 (4-2018)
Abstract
The purpose of this article is to system design methodology of Propellant Management Device (PMD) for hydrazine fuel tank which used in low (zero) gravity conditions. To this end, the suggestion system design flowchart has three main steps that concluded: step one, Tank design and modeling; step two, PMD design and modeling and step three, stored fuel treatment simulation and analysis. In the design flowchart has performed the result of each step based on mission inputs. Therefore, rejected results in each step led to vary the related parameters. Thus Solid Works software is used to primary PMD and tank modeling. Then, numerical simulation is performed to consider PMD's performance and to illustrate the capillary phenomenon for continues fuel transferring in zero-gravity conditions.Also, numerical methods are used to analysis of the tank and the fuel behavior inside the tank with PMD to optimize system design parameters. Hence, Ansys software used to finalize modelling, analysis, meshing and consideration of fuel behavior in PMD by utilizing the Volume Of Fluid (VOF) method. The optimal system parameters related to specifications of PMD with maximum performance of mass and volume flow rates in zero gravity. In conclusion, by comparing the results (PMD performance) with experimental and existing results will be verified.
Volume 18, Issue 2 (7-2018)
Abstract
Electrification is one of the appropriate solutions to increase the railway network capacity. However, use of this solution without provision of the sufficient capacity and required infrastructure through the whole of the network, may not acceptably increase the attracted railway demand. In such cases, the electrification project may be uneconomical. This research aims to propose an algorithm to identify which bottlenecks of the network must be removed, in order to justify the electrification of a specific railway corridor. We investigated the electrification of the railway corridor at north of Iran. This corridor has a substantial capability for absorption of the freight transportation demand. The railway freight demand related to all of the origin-destination pairs of Iranian railway network, along with the capacities of all block sections of the network are considered as inputs of the problem. for freight assignment in the railway network, FARS (Freight Assignment in Railway System) software was used. This Iranian software is developed by transportation research center of Isfahan University of Technology (IUT), in 2013. The assignment method used in this software is based on Incremental assignment. Different scenarios are considered and two main criteria are employed to compare the scenarios: tonnage of increase in railway freight demand, and economic index of benefit to cost called Net Present Value. According to the results, the electrification of the railway corridor at north of Iran, with no resolution of the bottlenecks in other locations of the network, cannot absorb a remarkable demand. The individual electrification of the mentioned corridor can only increase the absorbed freight demand from 1.65 million tons to 1.95 million tons, which is not considered an impressive progress. In this scenario, the Net Present Value (NPV) index and Net Uniform Annual (NUA) index are negative, which implies that the execution of this scenario is uneconomical. The low increase of the demand absorption is due to the existence of the capacity bottlenecks in other parts of the railway network. The existence of these bottlenecks prevents the complete usage of the added capacity potential emerged from the electrification. Consequently, the possibility of handling the transportation demand at north of Iran would be limited. By using the algorithm proposed in the present study, the main bottlenecks which prevent the load flow through the network, were identified. Then, by execution of the capacity increase scenarios for the identified bottlenecks, the absorption of the railway freight demand was increased to 3.97 million tons, with positive values for both NPV and NUA indices, which imply the economic justification of the railway electrification at north of Iran, simultaneously with improvements for capacity bottlenecks at other parts of the railway network. In other words, to achieve the absorption of the freight demand of the railway corridor in north part of Iran, it is not adequate to merely increase the capacity of this corridor itself. The railway electrification project in a specified part of the network is preferred to be performed simultaneously by the capacity improvement projects in other parts of the network. The proposed algorithm can be used in decision making for justifying the railway electrification projects.
Volume 18, Issue 3 (5-2018)
Abstract
Laser surface hardening is one of the modern technology used to improve the surface of materials in order to modification of tribological properties. This paper investigate the ability of laser surface hardening of AISI 410 martensitic stainless steel using a continuous high power diode laser with a maximum power of 1600w. Laser power, scanning speed and focal plane position are variable parameters in this research. The effect of the process parameters on the hardness, depth and width of the hardened layer has been investigated. The results show that with increasing laser power and reducing the scanning speed, higher hardness and hardening depth are obtained. Results also reveal that width of hardened layer increases by increasing in focal plane position and reduction the laser power. Modeling of controllable variables (laser power, scanning speed and focal plane position) by Response Surface Methodology method to study the effect of process input parameters on how to change responses, and analysis of ANOVA tables, providing regression equation for output parameters, analysis The Surface Plots, Interaction Plots of the input parameters, were investigated. The results show that in RSM modeling method, the effect of laser power parameter on the results of maximum hardness, depth and width of hardness is more than the parameters of the focal plane position and scanning speed. Due to percentage of coverage of the parameters by the regression equations the RSM method is a suitable model for investigating the effects of the surface hardening process by diode laser.
Volume 18, Issue 3 (5-2018)
Abstract
The design process of an Autonomous Underwater Vehicle (AUV) requires mathematical model of subsystems or disciplines such as guidance and control, payload, hydrodynamic, propulsion, structure, trajectory and performance and their interactions. In early phases of design, an AUV are often encountered with a high degree of uncertainty in the design variables and parameters of system. These uncertainties present challenges to the design process and have a direct effect on the AUV performance. Multidisciplinary Design Optimization (MDO) is an approach to find both optimum and feasible design and robust design is an approach to make the system performance insensitive to variations of design variables and parameters. It is significant to integrate robust design and MDO for designing complex engineering systems in optimal, feasible and robust senses. In this paper, an improved robust MDO methodology is developed for conceptual design of an AUV under uncertainty with considering tactic and system design simultaneously. In this methodology, Uncertain MultiDisciplinary Feasible (UMDF) framework is introduced as uncertain MDO framework. Two evolutionary algorithms are also used as Pareto-based Multi-Objective optimizers and results of two algorithms are compared. The results of this research illustrate that the new proposed robust multidisciplinary design optimization framework can carefully set a robust design for an AUV with coupled uncertain disciplines.
Volume 18, Issue 3 (5-2018)
Abstract
Reliability-based design optimization (RBDO) has been used for optimizing engineering systems in presence of uncertainties in design variables, system parameters or both of them. RBDO involves reliability analysis, which requires a large amount of computational effort, especially in real-world application. To moderate this issue, a novel and efficient Surrogate-Assisted RBDO approach is proposed in this article. The computational intelligence and decomposition based RBDO procedures are combined to develop a fast RBDO method. This novel method is based on the artificial neural networks as a surrogate model and Sequential Optimization and Reliability Assessment (SORA) method as RBDO method. In SORA, the problem is decoupled into sequential deterministic optimization and reliability assessment. In order to improve the computational efficiency and extend the application of the original SORA method, an Augmented SORA (ASORA) method is proposed in this article. In developed method, A criterion is used for identification of inactive probabilistic constraints and refrain the satisfied constraints from reliability assessment to decrease computational costs associated with probabilistic constraints. Further, the variations of shifted vectors obtained for satisfied constraints are controlled to be exactly equal to zero for the next RBDO iteration. Several mathematical examples with different levels of complexity and a practical engineering example are solved and results are discussed to demonstrate efficiency and accuracy of the proposed methods.
Volume 18, Issue 3 (9-2018)
Abstract
It is well known that structures designed by current codes experience large inelastic deformations during major earthquakes. However, current seismic design practice in almost all seismic design provisions such Iranian Seismic Code is based on elastic structural behavior and accounts for inelastic behavior only in an indirect manner through certain modification factors such as strength reduction factor. Under moderate to severe earthquakes, inelastic activity, including severe yielding and buckling of structural members can be unevenly distributed in the structure, which may result in global collapse or costly repair work. Recently, a new design method has been developed and referred to as Performance-Based Plastic Design (PBPD). This method directly accounts for inelastic behavior by using pre-selected target drift and yield mechanism as key performance limit states. In this paper, for the first time, the effect of soil-structure interaction (SSI) on drift demands distribution along the height of the steel moment frame (SMF) structures designed with performance-based-plastic design (PBPB) approach under strong ground motions are parametrically investigated. The soil beneath the structure is considered as a homogeneous elastic half space and is modelled using the concept of Cone Models. For the the steel moment frame structures, the design base shears are calculated by using the modified energy balance equation and new lateral force distribution based on inelastic analyses. The new distribution of the lateral forces for performance-based plastic design was used from shear proportioning factors that were derived from the relative distribution of maximum story shears obtained from nonlinear dynamic analyses. Then, plastic design method is employed to design the beams and columns with the calculated design base shear and to satisfy the requirements for strong column-weak beam mechanism, which results in the pre-selected yield mechanism. The plastic design procedure proposed herein can be one of the simplified approaches without requiring sophisticated computer nonlinear analyses, by using the preselected yield mechanisms and target drifts. The energy dissipation capacity of the structure designed by these procedures can be less than that required to prevent collapse under severe ground motions. The purpose of this design procedure is to avoid collapse mechanisms characterized by poor energy dissipation capacity, such as soft-story mechanisms. To this end, the plastic hinges should be developed only in beams and at the column bases of the structure during severe earthquakes. The system is then subjected to 20 different earthquake ground motions and the analyses are performed directly in time domain using direct step-by-step integration method. Effect of various parameters including fundamental period, inelastic behavior, SSI key parameters on strength reduction factor and structural damage distribution are examined. The adequacy of different lateral loading patterns is also parametrically investigated. Results indicate that only mid-rise SMFs designed based on current PBPB approach could have the best performance in SSI systems. It is also demonstrated that under slight and moderate SSI effects, SMFs designed according to various load patterns tend to more uniform distribution as compared to the fixed-base counterparts. However, all of them lose their efficiency when the SSI effects and inelastic response are pronounced. Moreover, the influence of SSI key parameters, fundamental period and ductility ratio on dispersion of the drift results are evaluated and discussed.
Volume 18, Issue 4 (1-2015)
Abstract
Claims and, as a result, disputes have become one of the inherent attributes of construction industry. Most projects’ stakeholders know claims as the most destructive events in this industry. There are some possibilities of claims occurrence by both contract sides, especially contractors in most of the projects with different project delivery systems. Although it is not possible to eliminate the possibility of claims, the occurrence of claims in the projects can be prevented by identifying their main origins and causes. Data collection in this study was done, through organized study and semi-structured interview with experts and also the consideration of related documents that led us to reach 400 relevant cases for claims in Design-Build projects. After analysis of these cases by the researchers, the model of claim package was developed, which represents the fourth part of the claims. Then, the factors associated with each of the four parts were identified. First section contains the 48 most important claim origins. The second section includes 43 causes of claims. The third section includes 4 types of claims, and the fourth one includes 6 types of claim request. Then the forth part of the claim package model was distributed among the experts by closed questionnaire, and the most important cases of each part were identified. The identification of these claims can be useful in predicting future claims, and minimizing their effects in the similar ones.
Volume 18, Issue 4 (1-2016)
Abstract
Objective: This study attempted to generate monospecific antibodies through immunization with recombinant proteins and subsequent purification by synthetic peptides (the PrIPeP model).
Methods: The SRY gene was cloned on a pet-28a vector and the recombinant protein was expressed in the Escherichia coli (E.coli) BL21 strain. The purified antigen was emulsified in Freund’s adjuvant and injected into rabbits according to a standard time table. Then, a specific peptide was designed, synthesized, and conjugated to sepharose 4B to generate an affinity purification column. As a control, the peptide was conjugated to KLH and used for immunization, as above. Antisera against the conjugated peptide (Pep-antisera) and SRY recombinant protein (Pro-antisera) were evaluated by ELISA and subsequently subjected to the affinity purification column. Sensitivity and specificity of the purified antibodies against SRY recombinant protein as well as negative controls (recombinant HSFY, RBMY, and RPSFY) were assessed by Western blot analysis.
Results: Titration by ELISA confirmed proper immunization and specificity of both antigens. Western blot analysis validated the specificity and sensitivity of the IgG class purified antibodies.
Conclusion: By applying the PrIPeP model, it is possible to develop antibodies against the native structure of a protein whilst avoiding challenges of peptide-carrier protein conjugation.
Volume 18, Issue 4 (11-2018)
Abstract
Time history analysis, which is the most important analysis tool in performance-based seismic design, has become more and more popular worldwide. In the seismic design, seismic demand is mainly governed by three factors including the peak value of ground motion, the characteristic of earthquake spectrum and duration. An earthquake intensity index of ground motions is normally used as a scaling parameter that is critical for seismic analysis and design. A number of researchers have, from their own perspective, proposed various intensity indices. However, due to the complexity and randomness of earthquake motion, it has been a difficult task to accurately evaluate the applicability of various existing intensity indices. In addition, an objective and quantitative method is lacking in the evaluation of the applicability of such indices. This has been a challenging issue in seismic engineering research and has become a fundamental problem in performance-based seismic design. Nonlinear structural response is often highly sensitive to the scaling of input ground motions. Thus, many different ground motion scaling methods have been proposed. The “severity” of an earthquake ground motion is often quantified by an intensity measure, IM, such as peak ground acceleration, PGA, or spectral acceleration at a given period. The PGA of a record was a commonly used IM in the past. More recently, spectral response values such as spectral acceleration at the fundamental period of vibration have been used as IM. Scaling of ground motions to a given spectral level at the fundamental period of vibration significantly decreases the variability in the maximum demand observed in the structural system. However, it is widely known that for records with the same spectral acceleration at the fundamental period of vibration value, spectral shape will affect the response of multi-degree of- freedom and nonlinear structures, because spectral values at other periods affect the response of higher modes of the structure as well as nonlinear response when the structure’s effective period has lengthened. Similar attention to the influence of nonlinear behavior of a structure on the period of vibration led to an IM that accounts for period softening to reduce variability at high levels of maximum inter-story drift ratio, drift demands larger than 5%, for composite structures. Previous studies have focused on evaluation of different ground motion scaling methods in single-degree-of freedom and buildings of multi-degree-of-freedom with shear-type behavior or common steel-moment frame structures. However, over the last decade, the performance-based seismic design philosophy has emerged as a promising and efficient seismic design approach. The novel Performance-based plastic design (PBPD) approach explicitly accounts for the inelastic behavior of a structural system in the design process itself. PBSD approaches based on plastic analysis and design concepts were recently developed for different lateral load resisting systems such as steel moment resisting frames, steel braced frames, etc. In these design methods a pre-selected yield/failure mechanism and a uniform target drift (based on inelastic behavior) were considered as performance objectives. The analytical validation of these methods showed that structures designed using these methods were very effective in achieving the pre-selected performance objectives. Considering a gradual shift towards PBSD for seismic design methods in general, this study is aimed at examining the effects of six different IMs on the estimation and distribution of the maximum inter-story drift for three short, moderate, and long-period steel-moment resisting frames designed with PBPD method buildings using the concepts of efficiency and sufficiency. An ensemble of 42 far-filed earthquake ground motion without pulse characteristics were used and scaled based on two target spectrum MCE and Design Response Spectrum to conduct nonlinear dynamics analyses by using OPENSEES. Results indicate that, the cod-compliant scaling method was not reliable for nonlinear dynamic analyses of structures designed by PBPD method, and cloud be very sensitive to the ground motion characteristics. Among them, depending on the number of stories, the three scaling methods including scaling ground motions to a given PGA and those that take into account for periods of higher modes generally decrease the variability in the maximum demand observed in the structural systems.
Volume 18, Issue 4 (11-2018)
Abstract
Nowadays with development of urbanity, request for dwelling has increased extremely. In all the cases the steel structures as for the high speed of construction have a special status. Among the defect of steel buildings than concrete type is higher cost of construction. Hence, occasionally the fabricators with a view to imparting of advantage of both the construction speed and some deal decreasing providing cost of steel lateral bracing, use the steel buildings with reinforced concrete shear wall as lateral bearing system. Hence, study in the field of analysis and design of this structure system seems necessary. At present, one of the most important goals of earthquake engineers is predicting of the structures behavior versus future earthquakes. Today, it has become evident that structures designed on the basis of the existing regulations sustain extensive damages in under intense earthquakes. Thus, performance-oriented design as a method based on acceptance of expected displacement and ductility has been considered. In earthquake engineering, it is imperative to determine the capacity and the seismic demand of the structure in terms of performance. The performance assessment of nonlinear systems is a complex task requiring appropriate analytical methods suitable for modeling the behavior of the structure against the earthquake. The incremental dynamic analysis is an analytical tool which can be used to assess performance in earthquake engineering. This method is able to estimate the seismic demand and limit states of the capacity of a structure under seismic loading using suitable records scales to several levels. Utilizing this method, one can attain better understanding of the behavior of a structure from elastic to destruction conditions. In the present research, dynamic analysis of the time history and the robust software OpenSees have been employed considering the geometric nonlinear effects of materials for seven buildings having 3, 6, 9, and 12 stories and two plans. The structures under consideration are analyzed using incremental dynamic analysis and the robust Opensees software subsequent to the design phase and considering the designed sections, gravity loading characteristics and specifications and seismic parameters. Then, graphing the cluster curves and IDA quantiles the buildings under consideration are assessed. Although the results of this study indicate better performance of the moderate structures in comparison to the short and rise structures, it seems that the proper height of a structure with respect to the characteristics of the soil of its construction site and the parameters of the resonance and damping between the structure and the soil (the effect of soil and structure interaction) and the frequency content of the acceleration records of the first mode in the region. The seismic intensity estimation parameter (which is considered in this study, the first-mode spectral acceleration) is a determinant factor in reflecting the behavior of the earthquake acceleration record applied to the structure. In order to conduct a detailed study with the IDA analysis, it is necessary to select the severity criterion in a way that best describes the content of the selected accelerogram.
Volume 18, Issue 4 (12-2018)
Abstract
In the real world, dispersion of suppliers and demanders prevents market formation. Kidney market is a true example of such markets that is not formed due to thin features. To tackle the problem, one needs to design a mechanism that can both revive the market and ensure the most efficient supply-demand matching. A matching is efficient when no other matching can allocate agents to a better place, or cannot strongly allocate an agent to a better place. To this end, the mechanism should be designed to allocate agents to their highest preferences, so that agents cannot make another better choice. In this study, information on 20 patient-donor pairs was recorded at a clearing house in Hamedan province in 2016. After processing data, the patients’ preferences were ordered in terms of matching blood group, illness period, donor’s age, kinship relationship with donor, and gender of donor. Then, a mechanism was designed to match 17 patients with the most efficient kidneys. When patient ith matches donor ith and registers at the clearing house, the mechanism can offer her/his the most efficient kidney. If a given patient finds a donor better than his/her peer donor, then he/she will leave his/her peer donor. Otherwise, he/she matches her paired donor.
Volume 18, Issue 5 (11-2018)
Abstract
One of the effective ways to mitigate earthquake damage in structures is passive control of structures. Yielding metallic dampers economic passive control devices. Not only yielding metallic dampers are easy to erect, but they can also be used as a passive control systems easily. In this paper, the aim is to develop a design procedure for steel structures equipped with a combination of yielding metallic dampers so that, dampers will experience specific nonlinear behavior when subjected to various seismic hazard levels. For this purpose, the first step is providing seismic hazard spectra with different return periods for the intended site of construction. In this research, this step has been taken by using the Tehran probabilistic analysis hazard project data and then plotting uniform hazard spectra with 75-year, 475-year, 975-year and 2475-year return periods. After determination of uniform hazard spectra with mentioned return periods, behaviors of structures equipped with yielding metallic dampers have been investigated in the form of one-storey one-span, one-storey two-span and multi storey multi span frames. Required equations for behavior of these structures under monotonic loading is developed. In the beginning of design process, the performance criteria for the structure and the damper is set and by using the derived equations, design of single degree of freedom frames based on performance criteria has been carried out. These single degree of freedom structures have different periods and strength reduction factors. After designing the single degree freedom structures, nonlinear static analysis results have been compared with result of nonlinear time history analysis. For this purpose, 7 earthquake records have been chosen and scaled based on Iranian code of practice for seismic resistant design of buildings and used for dynamic analysis. Results showed that all performance criteria of 75-year and 475-year hazard levels have been satisfied but for 975-year and 2475-year hazard levels, six cases have not satisfied the desired critera with 6 percent error. In order to verify the presented numerical analysis of multi degree of freedom structures, an experimental study has been chosen and the results of these two works have been compared. This verification showed that the presented analysis can model the structures and dampers with acceptable accuracy. Performance criteria of multi degree freedom structures have also been proposed. Three, 3-storey, 6-storey and 9-storey buildings equipped with dampers have been designed and based on proposed method and the desired performance of dampers have been achieved. Time history analysis have been carried out for each return period. For these analyises, 7 earthquake records were chosen and scaled based on Iranian code of practice for seismic resistant design of buildings. Comparison of performance point displacement levels and the displacements obtained from 28 nonlinear analyses, showed up to 13 percent error. Meanwhile, the displacement levels of each set of dampers for 75-year, 475-year, 975-year and 2475-year return periods, confirmed efficiency of proposed design method and all dampers met the mentioned performance criteria. The results also showed that when hazard level increased, the difference between the results of nonlinear time history analyses and static nanlinear analyses have also increased.
Volume 18, Issue 5 (11-2018)
Abstract
The seismic design of the structures is subjected to uncertainties originating from various sources. To ensure that a safe design is achieved, the uncertainties must be considered in the seismic design process. The reliability-based seismic design is the proper approach that directly takes into account the uncertainties. In this approach the performance objectives are reliability-based seismic criteria expressed either in terms of an annual probability of exceeding a given performance level or in terms of a probability of exceeding a given performance level conditioned on the seismic intensity corresponding to a specific hazard level. It is obvious that the ultimate aim of the reliability-based seismic design of a building is not only to satisfy the reliability-based seismic criteria, but also to minimize initial or life-cycle cost. The reliability-based seismic design optimization (RBDO) is the method that achieves the most economic design satisfying the reliability-based seismic criteria (probabilistic constraints). However, the RBDO is less preferred. This is because to ensure that reliability-based seismic criteria are achieved, the statistics parameters of the seismic demand and capacity must be determined through the results of the nonlinear dynamic analyses. On the other hand, the use of the nonlinear dynamic analyses in the RBDO method can lead to the increase of the computational cost so that the personal computers require several years to run it. In this study, a method to produce the reliability-based economic seismic design is proposed. Reliability-based seismic criteria are expressed in terms of a mean annual probability of exceeding a given performance level. The main goals are to ensure satisfying the reliability-based seismic criteria through the use of the results of the incremental dynamic analyses and to produce the economic seismic design within reasonable computing time. The proposed method achieves the two goals through determining the optimum design of the force-based design method that satisfies the reliability-based seismic criteria. The optimum design of the force-based design method depends on the value of the response modification factor. The value of the response modification factor of a building, which leads to satisfying the reliability-based seismic criteria, is in the range of one to a maximum value. From an economic point of view, the desirable value of the response modification factor is the maximum one, which results in a minimum design base shear and accordingly in an economic design. In order to respond to the two main goals, the method aims to determine the maximum value of the response modification factor of a building so that leads to satisfying the reliability-based seismic criteria. The proposed method is used to produce the seismic design of a 4-story building for two reliability-based seismic criteria. The steel special moment resisting frame is considered as the lateral load resisting system in the studied building. The results reveal that the proposed method can efficiently produce the economic seismic designs satisfying the reliability-based seismic criteria within reasonable computing time.While the designed frame by Zacharenaki et al using existing RBDO method can not satisfy specifications of reliability and this is shown the ability and efficiency of the proposed method.
Volume 18, Issue 6 (10-2018)
Abstract
Laser percussion drilling is one of the advanced drilling processes that its numerous advantages have extended the applications of this process. This study focuses on experimental investigation of laser percussion drilling using Nd:YAG laser on titanium alloy Ti6Al4V sheets with various thickness which is widely used in industry. In this paper the effects of the input parameters peak power, pulse width, frequency, assist gas type, gas pressure and sheet thickness on the most important process outputs include hole entrance diameter, hole exit diameter, hole taper angle, hole entrance circularity and hole exit circularity were studied. Statistical analysis was employed to analyze the experimental data and significant parameters in each response are presented. For conducting the experiments “Design of Experiments” method and for modelling “Response Surface Methodology” were used. The results obtained show that sheet thickness affects all outputs. After that frequency and pulse width, peak power and assist gas type respectively are the most significant parameters influence process outputs. Gas pressure only affects the hole entrance circularity. For this alloy to achieve a hole with high quality, it is recommended to work at lower peak power and frequency, shorter pulse width and higher assist gas pressure with Nitrogen as assist gas.