Sharif Digital Repository

The study design is a prospective, case-control. The aim of this study was to develop a reliable measurement technique for the assessment of lumbar spine kinematics using digital video fluoroscopy in a group of patients with low back pain (LBP) and a control group. Lumbar segmental instability (LSI) is one subgroup of nonspecific LBP the diagnosis of which has not been clarified. The diagnosis of LSI has traditionally relied on the use of lateral functional (flexion-extension) radiographs but use of this method has proven unsatisfactory. Fifteen patients with chronic low back pain suspected to have LSI and 15 matched healthy subjects were recruited. Pulsed digital videofluoroscopy was used... 

In the present research, proton exchange membranes based on partially sulfonated poly (ether sulfone) (S-PES) with various degrees of sulfonation were synthesized. It was found that the increasing of sulfonation degree up to 40% results in the enhancement of water uptake, ion exchange capacity and proton conductivity properties of the prepared membranes to 28.1%, 1.59 meq g -1, and 0.145 S cm -1, respectively. Afterwards, nanocomposite membranes based on S-PES (at the predetermined optimum sulfonation degree) containing various loading weights of organically treated montmorillonite (OMMT) were prepared via the solution intercalation technique. X-ray diffraction patterns revealed the... 

In this paper, the effects of different parameters on the hairiness of siro-jet spun yarns, such as the nozzle pressure, the distance between the front roller nip and inlet of the nozzle, and jet structure were investigated. Using the Taguchi method, it was concluded that the factor air pressure has the strongest effect and the factor distance between the front roller nip and inlet of the nozzle does not have a significant effect on the performance of the siro-jet spinning system in reducing yarn hairiness. A computational fluid dynamics model was developed to simulate the airflow pattern inside the jets. The effect of air pressure and the jet structure was simulated using Fluent 6.3... 

Different analysis methods have been used for voltage stability assessment. In comparison with static analysis methods, little work has been done on dynamic analysis of large interconnected power systems. Voltage instability can be studied effectively with a combination of static approaches and time simulations. This paper discusses voltage stability assessment using mixed static and dynamic techniques. Using static methods, a voltage stability based ranking is carried out to specify faint buses, generators and links in power system. The system is analyzed for most severe conditions. Then, time domain simulation is performed for the conditions determined by voltage instability ranking. The... 

Background and Objective: Changes in the cervical spine curvature leads to increased shear force and compression stress on cervical spine and axial loading in different cervical segments. The objective of this study was to compare the general and segmental curvature in the upper and lower cervical spine of women with postural neck pain and Forward Head Posture (FHP), women without neck pain but with FHP and healthy women. Material and Methods: 45 women were divided into three groups: 15 women with postural neck pain and FHP, 15 women without neck pain but with FHP and 15 healthy women. Photography was used to assess neck posture while cervical spine curvature was measured using fluoroscopy... 

This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market. Investment decisions are fundamentally based on total revenues gained by investors. In most electricity markets, the complementary mechanisms are designed to ensure a desired level of reliability while covering investment costs of the suppliers. In such an environment, investment decisions are highly sensitive to expectation of price signals in both of energy market and capacity mechanisms. In this work, the system dynamics concepts are used to model the structural characteristics of electricity market such as, long-term firms' behavior and relationships... 

The advent of agile methodologies, though contributing much to software development processes, had a more profound impact on project management processes. Through supporting adaptability in their process frameworks, agile methodologies deviated from conventional project management approaches. This novel attitude has resulted in the emergence of an agile framework for project management. The Agile Project Management Framework (APMF) consists of fine-grained project management practices applied in agile methodologies, and is fast emerging as an alternative to the conventional project management framework. However, there are deficiencies in both frameworks that prevent developers from enhancing... 

Catalysts as the dynamo of chemical reactions along with solvents play paramount roles in organic transformations in long-lasting modes. Thus, developing effective and biobased catalysts in nontoxic solvents is highly in demand. In this report, carbon quantum dots (CQDs) functionalized with-lysine (Lys-CQDs) were generated from entirely nature-derived materials; they were demonstrated to be a promising catalyst for C-N bond formation in choline chloride urea (ChCl/U), a natural deep eutectic solvent (NADES). Among a number of synthesized CQDs, Lys-CQD turned out to be a powerful catalyst in the model reaction with aniline to afford phenyl urea. This type of transformation is important... 

This paper develops a system dynamics model to analyze the impacts of different kinds of capacity payment as investment incentive mechanisms in Iranian electricity market. Since it is aimed that the incurred capital and operating costs of generation technologies be recovered in Iranian electricity pool, the noncompetitive capacity payment mechanism has been introduced for this purpose in order to encourage new investments in electric power generation system. In the current mechanism, the capacity payments are designated to the generating units in the whole country electricity market. An annual base value of capacity payment is proposed based on recovering the capital cost of a benchmark... 

This paper proposes a time simulation model for long-term wind capacity investment decisions in the presence of electricity market and tradable green certificate (TGC) market. Investment decisions and wind capacity development are fundamentally based on incentives gained from both these markets. In TGC market, the tradable certificates are issued to renewable generation companies for each megawatt-hour of electricity generation. Distribution companies are obligated to support fraction of their electricity consumptions from renewable sources. The dynamics of prices in both markets are simulated in a system dynamics model to trace the dynamics of wind capacity investment. Such a decision model... 

This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market with significant wind power generation. In such an environment, investment and construction decisions are based on price signal feedbacks and imperfect foresight of future conditions in electricity market. System dynamics concepts are used to model structural characteristics of power market such as, long-term firms' behavior and relationships between variables, feedbacks and time delays. For conventional generation units, short-term price feedback for generation dispatching of forward market is implemented as well as long-term price expectation for... 

This paper proposes a dynamic time simulation model for long-term generation capacity investment decisions in the presence of either perfect or imperfect electricity market. The model is based on system dynamics concept in which the dynamics of capacity construction is traced using the forecast of electricity price cleared in the short-term electricity market. Both the perfect and oligopolistic competitions are considered and a market power index is defined to evaluate the competition level of the electricity market. The short-term and long-term dynamic analysis are used to represent the generation firms' behavior in bidding strategy and capacity investment, respectively. Both possibilities... 

In this study, a time simulation model for long-term wind capacity investment decisions in the presence of an electricity market and a tradable green certificate (TGC) market is proposed. Decisions related to the investments in the wind capacity are fundamentally based on incentives gained from both of these markets. Fundamental concepts and models of these markets are described. The TGC price trend-following and value-trading strategies for both generation and distribution companies and the regulatory policies for the limitation of TGC holding time and TGC borrowing fraction are included. In this study, a new dynamic model of coupled TGC and electricity markets is considered in order to...