Divine causality and human free will: Ṭūsī’s solution and its historical background

This article aims to delve into the approach of Ḫwāǧa Naṣīr ad-Dīn Ṭūsī to a fundamental philosophical question concerning human agency: How can human free will coexist with a necessitating causal framework, where every effect is bound by its complete cause? Ṭūsī’s solution, which left a lasting impact on subsequent philosophical discussions on the issue, particularly within Shiite scholarly circles, revolves around the introduction of a differentiation between types of causes. I will examine Ṭūsī’s elucidation delineated in two of his works: Ǧabr wa Qadar in Persian and a concise Arabic text on Afʿāl al-ʿibād. Additionally, I will endeavor to uncover the historical origins and intellectual influences that may have shaped Ṭūsī’s approach to the question of human free will

Long-range sediment transport in the world’s oceans by stably stratified turbidity currents

Peer reviewedPublisher PD

Multi-objective Optimization of a Ridesharing System Performance

Ridesharing is a shared vehicle service with the potential to meet the growing travel demand due to population increase, economic growth, and shortage in transportation infrastructure capacity. Compared to the current system of predominantly using personal vehicles, ridesharing services reduce the number of vehicles while providing mobility services to the same number of people with no additional investment in the transportation infrastructure. One of the big challenges in implementing ridesharing services is matching drivers and riders. Conflicts between matching-objectives to comply with the interests of diverse stakeholders influence the efficiency of ridesharing in a transportation system. This study investigates the conflicts between two ridesharing matching-objectives minimization of systemwide Trip Time (TT) and minimization of systemwide Vehicle Miles Traveled (VMT) by adopting a multi-objective optimization technique. The optimization results indicate that it is possible to have an acceptable reduction in TT and VMT by optimizing the conflicts between conflicting objectives in a ridesharing system. Tradeoff analysis indicates the benefits of a multi-objective optimization model in a ridesharing system by optimizing ridesharing system performance considering multiple conflicting matching-objectives

The measurement of bovine pericardium density and its implications on leaflet stress distribution in bioprosthetic heart valves

Purpose: Bioprosthetic Heart Valves (BHVs) are currently in widespread use with promising outcomes. Computational modeling provides a framework for quantitatively describing BHVs in the preclinical phase. To obtain reliable solutions in computational modeling, it is essential to consider accurate leaflet properties such as mechanical properties and density. Bovine pericardium (BP) is widely used as BHV leaflets. Previous computational studies assume BP density to be close to the density of water or blood. However, BP leaflets undergo multiple treatments such as fixation and anti-calcification. The present study aims to measure the density of the BP used in BHVs and determine its effect on leaflet stress distribution. Methods: We determined the density of eight square BP samples laser cut from Edwards BP patches. The weight of specimens was measured using an A&D Analytical Balance, and volume was measured by high-resolution imaging. Finite element models of a BHV similar to PERIMOUNT Magna were developed in ABAQUS. Results: The average density value of the BP samples was 1410 kg/m3. In the acceleration phase of a cardiac cycle, the maximum stress value reached 1.89 MPa for a density value of 1410 kg/m3 , and 2.47 MPa for a density of 1000 kg/m3(30.7% difference). In the deceleration, the maximum stress value reached 713 and 669 kPa, respectively. Conclusion: Stress distribution and deformation of BHV leaflets are dependent upon the magnitude of density. Ascertaining an accurate value for the density of BHV leaflets is essential for computational models.Comment: 13 pages, 7 figure

Design Improvement of Transcatheter Aortic Valves for Aortic Stenosis Patients

Aortic valve disease is a common condition in patients above 60 years of age and is associated with significant morbidity and mortality. Aortic valve stenosis is characterized by the narrowing of the aortic valve, which can be quite debilitating. This disease is treated with transcatheter aortic valve replacement (TAVR), which is a rapidly expanding alternative to open-heart surgical aortic valve replacement (SAVR). Although TAVR is a less invasive than SAVR, long-term durability of the transcatheter aortic valves could be the Achilles heel of the procedure. Thus, the main objective of this research was to improve the design of transcatheter aortic valves using experimental testing and design analysis. After the design, building, and testing phases of four differing valves, it was seen that there are benefits to two specific designs. One design was a TAV based on a native aortic valve while the other was a TAV geometry that was optimized by finite element modeling. The native valve performed well during diastole based on its average regurgitation volume, while the optimized valve performed well during systole based on its average positive pressure difference and effective orifice area

Applications of Particle Swarm Optimization Algorithm to Solving the Economic Load Dispatch of Units in Power Systems with Valve-Point Effects

Reduction of operating costs in power system in order to return the investment costs and more profitability has vital importance in power industry. Economic Load Dispatch (ELD) is one of the most important issues in reducing operating costs. ELD is formulated as a nonlinear optimization problem with continuous variables within the power plants. The main purpose of this problem is optimal planning of power generation in power plants with minimum cost by total units, regarded to equality and inequality constraints including load demand and the range of units' power productivity. In this article, Economic Load Dispatch problem has been modeled by considering the valve-point loading effects with power plants' constraints such as: the balance of production and consumption in system, the forbidden zones, range of production, increasing and decreasing rates, reliability constraints and network security. To solve the problem, Particle Swarm Optimization (PSO) Algorithms has been employed. To evaluate the effectiveness of the proposed method, the problem has been implemented on a power system with 15 generating units and the results have been evaluated.DOI:http://dx.doi.org/10.11591/ijece.v4i6.672

Modeling, Stability Analysis, and Control of Distributed Generation in the Context of Microgrids

One of the consequences of competitive electricity markets and international commitments to green energy is the fast development and increase in the amount of distributed generation (DG) in distribution grids. These DGs are resulting in a change in the nature of distribution systems from being "passive", containing only loads, to "active", including loads and DGs. This will affect the dynamic behavior of both transmission and distribution systems. There are many technical aspects and challenges of DGs that have to be properly understood and addressed. One of them is the need for adequate static and dynamic models for DG units, particularly under unbalanced conditions, to perform proper studies of distribution systems with DGs (e.g., microgrids). The primary objective of this thesis is the development and implementation of dynamic and static models of various DG technologies for stability analysis. These models allow studying systems with DGs both in the long- and short-term; thus, differential and algebraic equations of various DGs are formulated and discussed in order to integrate these models into existing power system analysis software tools. The presented and discussed models are generally based on dynamic models of different DGs for stability studies considering the dynamics of the primary governor, generators, and their interfaces and controls. A new comprehensive investigation is also presented of the effects of system unbalance on the stability of distribution grids with DG units based on synchronous generator (SG) and doubly-fed induction generator (DFIG) at different loading levels. Detailed steady-state and dynamic analyses of the system are performed. Based on voltage and angle stability studies, it is demonstrated that load unbalance can significantly affect the distribution system dynamic performance. Novel, simple, and effective control strategies based on an Unbalanced Voltage Stabilizer (UVS) are also proposed to improve the system control and the stability of unbalanced distribution systems with SG- and DFIG-based DGs