A Multi-objective Dynamic Optimization Approach to Project Schedule Management: A Case Study of a Gas Field Construction

Ramin Ansari,Mohammad Khalilzadeh,M. Reza Hosseini 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.3

In today's changing conditions, the random disturbances have caused complexity into the construction project management. In this study, a multi-objective approach is proposed to determine the size of the time buffers in engineering and construction projects. The problem is formulated as a two-stage stochastic programming model. In order to examine the efficiency of the model, the proposed method was compared to the classic and extended critical chain management approaches. The validation is performed using simulation experiments carried out in the benchmark data test and a real case of an engineering project. The numerical examples and case studies were presented to validate the proposed methodology. The results demonstrate the efficiency of the proposed multi-objective time buffering method in the actual situation. The outcomes indicate that the proposed robust buffer sizing method results in a more stable plan, as against the traditional methods.

Dynamic Optimization for Analyzing Effects of Multiple Resource Failures on Project Schedule Robustness

Ramin Ansari 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.5

This study develops hybrid modeling and algorithmic frameworks for analyzing the mutual effects of multiple sources of uncertainty on the quality and the robustness of construction schedules. To cope with multiple sources of disruptions, i.e., random resource failures and severe weather conditions, this paper develops a simulation-optimization model that aims to generate delay resistant project schedules. The Variable Neighborhood Search (VNS) is hybridized with an event-driven simulation framework to generate efficient and robust solutions for computationally expensive resource-constrained project scheduling problems (RCPSP). The simulation experiments have been carried out by a flexible modeling framework that can be adopted by project experts to design construction schedules subject to the uncertainty associated with the multiple resource failure. The problem is mathematically formulated as a bi-objective optimization model aiming to minimize the project makespan and maximize a novel surrogate robustness function simultaneously. The computational results of the proposed VNS method have been compared with those obtained from the commercial optimization solvers. The simulation-optimization model's application is demonstrated through a case study of the hydropower plant construction project with multiple renewable and non-renewable resources. Based on an extensive statistical analysis of real-life scenarios, this study contributes to a trade-off analysis of project makespan and robustness in construction projects. The t-test statistical analysis results indicate the significance of the project's average delay reduction by implementing the robust project schedule. The outcomes confirm that the designed framework can generate a more efficient project schedule with a higher rate of protection compared with the existing robust approaches.

Hyperhomocysteinemia and Neurologic Disorders: a Review

Ramin Ansari,Ali Mahta,Eric Mallack,Jin Jun Luo 대한신경과학회 2014 Journal of Clinical Neurology Vol.10 No.4

Homocysteine (Hcy) is a sulfur-containing amino acid that is generated during methionine metabolism. It has a physiologic role in DNA metabolism via methylation, a process governed bythe presentation of folate, and vitamins B6 and B12. Physiologic Hcy levels are determined primarily by dietary intake and vitamin status. Elevated plasma levels of Hcy (eHcy) can be causedby deficiency of either vitamin B12 or folate, or a combination thereof. Certain genetic factorsalso cause eHcy, such as C667T substitution of the gene encoding methylenetetrahydrofolate reductase. eHcy has been observed in several medical conditions, such as cardiovascular disorders, atherosclerosis, myocardial infarction, stroke, minimal cognitive impairment, dementia,Parkinson’s disease, multiple sclerosis, epilepsy, and eclampsia. There is evidence from laboratory and clinical studies that Hcy, and especially eHcy, exerts direct toxic effects on both thevascular and nervous systems. This article provides a review of the current literature on the possible roles of eHcy relevant to various neurologic disorders.

A Risk-Oriented Buffer Allocation Model Based on Critical Chain Project Management

Parviz Ghoddousi,Ramin Ansari,Ahmad Makui 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

In this study, a multi-attribute buffer sizing method is proposed aimed at maximizing the robustness of the buffered schedule generated. The project attributes concerning the network complexity, flexibility criteria, criticality index and robustness measures are considered through the buffer sizing process. The methodology presented is based on the critical chain buffer management methodology, yet innovative metrics are presented to deal with the uncertainties associated with the critical and non-critical chains. The buffer sizing method proposed eliminates the previous limitations and attempts to economically determine the size of the feeding and project buffers. Additionally, a risk analysis is performed to examine the effects of external factors on buffer sizes. The weaknesses of the existing buffer sizing approaches were overcome in the critical chain project management, and a novel buffer sizing method was established based on internal and external risk aspects. A simulation experiment is conducted in order to prove the effectiveness of the method proposed. The computational results of implementing the method on a real case study specify that the method proposed generates more stable project plans at a lower cost, compared with those generated using traditional buffer sizing methods.

Conceptualization and development of a questionnaire to determine physical activity barriers

Maryam Selk-Ghaffari,Bahar Hassanmirzaei,Amin Nakhostin-Ansari,Behnaz Mahdaviani,Mohammad Saeid Khonji,Reyhaneh Aghajani,Maedeh Gholami-Mehrabadi,Afifeh Khosravi,Ramin Kordi 한국운동영양학회 2022 Physical Activity and Nutrition (Phys Act Nutr) Vol.26 No.2

[Purpose] Considering the role of physical activity on public health and the high prevalence of physical inactivity worldwide, determining physical activity barriers is critical and will be a road map for future planning. This study aimed to develop a comprehensive questionnaire to determine physical activity barriers. [Methods] By reviewing previous studies, the main domains of the questionnaire were established. A physical activity expert interviewed 20 individuals aged 18 to 65 years. The results were evaluated by an expert panel for a content validity index. Face validity, test-retest reliability, and internal consistency were established on 204 individuals. [Results] The content validity index in all items was within the acceptable range (>0.85). Face validity was appropriate, and the misunderstanding index was < 20% in all items. Test-retest reliability in the final questionnaire in all items based on Cohen’s kappa was > 0.20, indicating fair agreement. Internal consistency with Cronbach’s alpha of 0.63 was within the acceptable range. [Conclusion] The study revealed that the newly designed survey is valid, accurate, and reliable. The use of this comprehensive tool by policymakers would help them properly identify the perceived barriers, and thus perform better physical activity interventions as promotional health programs.

Acute effects of one session dry needling on a chronic golfer’s elbow disability

Ardalan Shariat,Pardis Noormohammadpour,Amir Hossein Memari,Noureddin Nakhostin Ansari,Joshua A. Cleland,Ramin Kordi 한국운동재활학회 2018 JER Vol.14 No.1

A 40-year-old retired male elite athlete with more than 20 years’ experience in wrestling and bodybuilding with mild elbow pain and disability of 2 years presented to our clinic reporting an acute pain in medial aspect of the elbow. Physical examination revealed symptoms of left Golfer’s elbow during target-directed movements. The results of sonography in left elbow showed low level of hypo echo irregularity and increased blood flow in color Doppler mode in the common flexor origin. The pain amplitude was moderate at rest and extremely high during kinetic and intentional movements. During last 2 years, the patient tried different types of therapy including manual therapy, Transcutaneous electrical nerve stimulation and also received a variety of injections none of which were effective for reducing pain and disability. This is the first study showed that one sessions of dry needling improved both pain and disability and helped to return to a normal life and exercise training.