Modeling Underdog Entrepreneurs Journey in Iran: A Mixed Method Approach

The term underdog entrepreneur (UE) is increasingly used among scholars to discuss successful disabled, immigrant, and necessity entrepreneurs who encounter significant challenges in their early lives. However, their characteristics and business obstacles in emerging economies remain unclear. This research offers insights by answering two questions: (1) how do physical, socio-cultural, and economic challenges motivate underdog individuals to become entrepreneurs? And (2) what are UEs’ unique challenges following establishing their ventures in Iran? First, this research develops a theoretical model by providing insights from 76 secondary data and 18 in-depth interviews using topic modeling. Subsequently, a survey method is conducted to collect data from underdog entrepreneurs in Iran. Structural Equation Modeling is performed to analyze the data and test the hypotheses. The findings reveal that negative situations create experiences, which lead to innovativeness, risk-tolerance, skilled communications, and persistence, which mediate the entrepreneurship journey. Moreover, UEs confront governmental, managerial, and environmental challenges to maintain their businesses in Iran's emerging economy. In the end, practical suggestions were presented to governors, entrepreneurs, and scholars regarding how they can manage these challenges, paving the way for UEs' success to positively impact economic growth.

A Monte Carlo Simulation-Based Approach to Solve Dynamic Sectorization Problem

In this study, two novel stochastic models are introduced to solve the dynamic sectorization problem, in which sectors are created by assigning points to service centres. The objective function of the first model is defined based on the equilibration of the distance in the sectors, while in the second one, it is based on the equilibration of the demands of the sectors. Both models impose constraints on assignments and compactness of sectors. In the problem, the coordinates of the points and their demand change over time, hence it is called a dynamic problem. A new solution method is used to solve the models, in which expected values of the coordinates of the points and their demand are assessed by using the Monte Carlo simulation. Thus, the problem is converted into a deterministic one. The linear and deterministic type of the model, which is originally non-linear is implemented in Python's Pulp library and in this way the generated benchmarks are solved. Information about how benchmarks are derived and the obtained solutions are presented.

A Numerical Study on Optimum Material and Design for Dental Trilayer Systems

This study investigated the impacts of geometry, thickness, and material on damage growth in a porcelain-metal restoration structure by utilizing a computational approach. Extended finite element method (XFEM) was used to find the critical loads causing the nucleation of radial cracks at the porcelain undersurface. Plastic deformation also was considered at the metal above the surface as another damage mechanism. The dental system consisted of a brittle outerlayer (porcelain)/metal (Pd/Co/Au alloys)-core/dentin-substrate trilayer system. A tungsten-carbide hemisphere as an indenter was used to apply a compressive loading on the structure. In addition, two different geometries were created to present the dental structure, cylinder, and tapered cylinder. The results showed that a harder and stiffer metal core can resist the initiation of radial cracks. It was also observed that the metal with thinner layers is more vulnerable to radial cracking. In all simulations, the tapered cylinder geometry showed to have higher critical loads in both damage modes. The optimum thickness for the porcelain layer was suggested to be 0.5 mm. The geometry of dental crown-like structures was found to be an important factor in damage initiation. The findings also proposed that the metal layer should not be designed very thin in order to prevent the formation of radial cracks. This numerical investigation also recommended that the stiffness of the metal layer is better to keep higher compared to other layers to hinder the initiation of radial cracks.

Comparing the Influence of Synthetic jets on Cooling the Angled Plates Versus Vertical and Horizontal Plates

Synthetic jets besides being used in heat transfer, have also been used to control turbulence and flow separation. In the previous decade, research on the applications of a synthetic jet has indicated that by using these types of jets, flow separation can be reduced or even stopped altogether. In addition, these jets have been utilized in unmanned aerial vehicles (UAVs) (to control separation on airfoils) and flight control. In this study, the jet is located perpendicular to the flat plane with fixed heat flux and the effect of some geometric parameters including the ratio of the distance between the jet and the impact plane to the nozzle width, the ratio of the impact plane length to the jet nozzle width, the ratio of synthetic jet width to width of the nozzle, the ratio of the hole height to the nozzle width, the angle of the impact plate as well as the diaphragm characteristics such as amplitude and frequency of the jet diaphragm in heat transfer were evaluated numerically by using OpenFOAM open-source software. The findings indicate that synthetic jets have very weak efficiency for cooling vertical panels. However, they are extremely effective on angled plates. Synthetic jets have more influence on angled planes than horizontal planes.

Investigating the Effect of Internal Pressure and Thickness of Thick-Walled Cylindrical Vessels on the Ratcheting Strains under Compressive Cycling Loading Using the Quasi-Creep Method

Thick-walled vessels have many applications in military, chemical, and aerospace industries and also in nuclear facilities. Increasing the internal pressure inside these vessels can take some of the layers of the vessel into the plastic zone. If this happens several times, we will see the accumulation of plastic strains called ratcheting. This paper assumes that the thick-walled vessel is subjected to a cyclic internal pressure between zero and a maximum value. In order to analyze this phenomenon, first, we present the quasi-creep method, and then we validate this method using the finite element Abaqus Software based on the combined hardening model. Then we employ this method to evaluate the effect of internal pressure and thickness of the vessel on the amount of ratcheting strains in different cycles. In the end, the results of this research and the accuracy and speed of the quasi-creep method are stated.

Numerical Study of the Effect of Different Variables on the Cooling of a Flat Plate Using a Synthetic Jet

A synthetic jet is caused by the periodic motion of a diaphragm within a cavity. There is one or more orifices or outlets in this cavity. The main advantage of this type of jet compared to a continuous jet is that the synthetic jet is composed of transverse flow, and therefore, it does not need a continuous source of fluid, unlike the continuous jet. In recent years, synthetic jets have received a great deal of attention so that they have been used in a wide range of applications such as controlling separation and turbulence, besides, the cooling of electronic equipment and propulsion. In the present study, the jet is placed perpendicular to the flat plane with constant heat flux, thereafter, the effect of some geometric parameters were evaluated numerically such as the ratio of the distance between the jet and the impinging plate to the nozzle width, the ratio of the impinging plate length to the jet nozzle width, the ratio of cavity width of the synthetic jet to the nozzle width, the ratio of the cavity height to the nozzle width, the angle of the impinging plate, besides, the diaphragm specifications including amplitude and frequency of the jet diaphragm in heat transfer using OpenFOAM open-source software. The results show that the frequency and the length of the impinging plate are the most effective parameters, respectively, in terms of the diaphragm and geometry.

Numerical Study of Blowing-Suction Ventilation Systems Performance

In most industrial processes, toxic pollutants and vapors are produced and released, which cause various diseases in people working in industry and irreparable damage to the environment. Industrial ventilation systems are considered as one of the most effective methods of reducing and controlling gaseous pollutants and dust particles. One of the effective systems in industrial ventilation is blowing -suction ventilation systems. In this study, the effect of flow ratio (ratio of blowing flow to suction flow) and direction of blowing jet air on the performance of blowing-suction ventilation system was investigated numerically. The mixing parameter has been used as an indicator to measure the performance of the ventilation system. The results showed that the performance of the ventilation system blowing-sucking by reducing the current ratio improved exponentially. It was also found that one of the ways to improve the performance of the blowing – suction ventilation system is to reduce the direction of the blowing angle.

Atomistic Study on the Mechanical Behavior of Silicon-Base Nanotubes

Recently, silicon nanotubes (SiNTs) have been successfully synthesized and have attracted many researchers to work on the different aspects of them. In the present study, the stress-strain curve along with the Young’s modulus as a significant mechanical property of single walled silicon nanotubes at different diameters are determined. The simulation is performed by the use of molecular dynamics based on the Tersoff-Brenner many-body potential energy function. The results of the total strain energy of nanotubes as an accurate and effective methodology are used to establish appropriate expressions for evaluating Young’s modulus of the nanotubes.

Risk Assessment and Analysis in Health, Safety and Environmental (HSE) Hazards of Bitumenous Waterproofing Industry Using HAZID Technique

Today, the use of risk assessment methods in various industries is expanding so that there are currently more than 70 types of different risk assessment methods in the world. These methods are usually used to identify, control and reduce the consequences of risks. The main methods of risk assessment are appropriate methods for risk assessment and their results can be used for management and decision-making to control and reduce its consequences. The purpose of this study is to identify and evaluate the risks to safety, health and the environment and to provide proposed and corrective solutions to reduce or eliminate HSE risks using the HAZID method. This descriptive cross-sectional study was performed for 4 months to identify the risks. For this purpose, a list of possible safety, health and environmental risks was prepared and the risk was evaluated by HAZID technique. In total, 5.15% of the identified risks are unacceptable, 20.62% are undesirable, 50.51% are acceptable, but 23.72% of the need for revision is minor. The results of this research include the implementation of measures such as safety training - professional training - inspection monitoring system - personnel safety management - preventive maintenance system management and forming a safety audit team - establishing regular House Keeping programs, etc. in identifying and Controls identified risks.

Fracture Analysis of Vacancy Defected Nitrogen Doped Graphene Sheets Via MD Simulations

The novel hexagonal monolayer sheet of carbon atoms, graphene, has attracted great attention due to their exceptional electrical and mechanical properties. Their phenomenally high strength and elastic strain, nevertheless, can be altered by structural defects due to stress concentration. In this paper, the fracture behaviour of graphene sheets and nitrogen doped graphene sheets with vacancies were investigated using molecular dynamics (MD) simulations at the different temperatures of 300K, 500K, and 900K. The results reveal a significant strength loss caused by both the defects and vacancies and doped nitrogen in graphene. The deformation process of graphene at various strain rate levels, with regard to the failure behaviour, is discussed. The validity of the proposed MD simulations is verified by comparing the simulation results with the available predictions from the quantized fracture mechanics.