A Comparative Study of the Oxidation and Wet Chemical Methods for Uncapping the Multi-Walled Carbon Nanotubes

Carbon nanotubes (CNTs) are generally capped at either end with a half of a fullerene. Hence, for storing different materials into the hollow space of CNTs, their caps need to be removed in the first step. In this study, we studied both the oxidation and wet chemical (acid-based) methods for opening the multi-walled carbon nanotubes (MWCNTs). In The oxidation method, 250 mg of CNTs were heated at 810 °C for 15 minutes in the air, and yielded about 56 % opened CNTs, while 78 % weight loss was recorded. The second sample with the same weight of the sample 1 was treated at 780 °C for 15 min. The weight loss and yielded uncapped CNTs were recorded 36 % and 47 %, respectively. The 780 °C was observed to be more appropriate than the higher temperature. In the acid-based method, the CNTs were refluxed in boiling nitric acid (65 % analar grade) at 110 °C for 12 h. In this case, about 80 % of the CNTs were thoroughly opened without any weight loss. The acid-based method was finally deduced to be more economical and efficient than the oxidation method. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3094

Uncapping Multi-Walled Carbon Nanotubes Using Wet Chemical and Oxidation Methods

Different materials can be introduced into hollow space of carbon nanotubes and result in very useful nanostructures for different applications such as energy storage, self-healing materials, nanocomposites, etc. In this study, the multi-walled carbon nanotubes were uncapped using two methods, oxidation with carbon dioxide or oxygen at elevated temperatures, and boiling carbon nanotubes in concentrated nitric acid chemical method was found to be more effective than the oxidation method, since the number of opened nanotubes was about 60 % more than that in oxidation method. Furthermore, unlike the oxidation method, no weight loss was observed in the chemical method. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3506

Investigating Wind Generation Investment Indices in Multi-Stage Planning

This paper presents a Multi-stage stochastic bilevel model for the expansion planning of Wind resources in power systems at a multi-stage horizon. In this paper, the power system consists of a combination of fossil fuel technologies and Wind resources for investment. Demand is characterized by a certain number of demand blocks. The uncertainty of demand for each this block (for each time period of the curve) is determined by the scenario. Afterwards, the suggested model is converted to a mathematical programming with some equilibrium constraints. Following that, after linearization, a mixed integer linear program is obtained. This framework is examined on the IEEE RTS 24-bus network. The obtained simulation results confirm that this model can be appropriately used as a means to analyze the behavior of investments in wind and thermal units

Generation expansion planning in electricity market considering uncertainty in load demand and presence of strategic GENCOs

This paper presents a new framework to study the generation capacity expansion in a multi-stage horizon in the presence of strategic generation companies (GENCOs). The proposed three-level model is a pool-based network-constrained electricity market that is presented under uncertainty in the predicted load demand modeled by the discrete Markov model. The first level includes decisions related to investment aimed to maximize the total profit of all GENCOs in the planning horizon, while the second level entails decisions related to investment aimed at maximizing the total profit of each GENCO. The third level consists of maximizing social welfare where the power market is cleared. The three-level optimization problem is converted to a one-level problem through an auxiliary mixed integer linear programming (MILP) using primal–dual transformation and Karush–Kuhn–Tucker (KKT) conditions. The efficiency of the proposed framework is examined on MAZANDARAN regional electric company (MREC) transmission network – a part of the Iranian interconnected power system. Simulation results confirm that the proposed framework could be a useful tool for analyzing the behaviour of investment in electricity markets in the presence of strategic GENCOs

Dynamic Carbon-Constrained EPEC Model for Strategic Generation Investment Incentives with the Aim of Reducing CO2 Emissions

According to the European Union Emissions Trading Scheme, energy system planners are encouraged to consider the effects of greenhouse gases such as CO 2 in their short-term and long-term planning. A decrease in the carbon emissions produced by the power plant will result in a tax decrease. In view of this, the Dynamic carbon-constrained Equilibrium programming equilibrium constraints (DCC-EPEC) Framework is suggested to explore the effects of distinct market models on generation development planning (GEP) on electricity markets over a multi-period horizon. The investment incentives included in our model are the firm contract and capacity payment. The investment issue, which is regarded as a set of dominant producers in the oligopolistic market, is developed as an EPEC optimization problem to reduce carbon emissions. In the suggested DCC-EPEC model, the sum of the carbon emission tax and true social welfare are assumed as the objective function. Investment decisions and the strategic behavior of producers are included at the first level so as to maximize the overall profit of the investor over the scheduling period. The second-level issue is market-clearing, which is resolved by an independent system operator (ISO) to maximize social welfare. A real power network, as a case study, is provided to assess the suggested carbon-constrained EPEC framework. Simulations indicate that firm contracts and capacity payments can initiate the capacity expansion of different technologies to improve the long-term stability of the electricity market

Coalition Formation of Microgrids with Distributed Energy Resources and Energy Storage in Energy Market

Power grids include entities such as home-microgrids (H-MGs), consumers, and retailers, each of which has a unique and sometimes contradictory objective compared with others while exchanging electricity and heat with other H-MGs. Therefore, there is the need for a smart structure to handle the new situation. This paper proposes a bilevel hierarchical structure for designing and planning distributed energy resources (DERs) and energy storage in H-MGs by considering the demand response (DR). In general, the upper-level structure is based on H-MG generation competition to maximize their individual and/or group income in the process of forming a coalition with other H-MGs. The upper-level problem is decomposed into a set of low-level market clearing problems. Both electricity and heat markets are simultaneously modeled in this paper. DERs, including wind turbines (WTs), combined heat and power (CHP) systems, electric boilers (EBs), electric heat pumps (EHPs), and electric energy storage systems, participate in the electricity markets. In addition, CHP systems, gas boilers (GBs), EBs, EHPs, solar thermal panels, and thermal energy storage systems participate in the heat market. Results show that the formation of a coalition among H-MGs present in one grid will not only have a significant effect on programming and regulating the value of the power generated by the generation resources, but also impact the demand consumption and behavior of consumers participating in the DR program with a cheaper market clearing price

Numerical investigation of conjugated heat transfer in a channel with a moving depositing front

This article presents numerical simulations of conjugated heat transfer in a fouled channel with a moving depositing front. The depositing front separating the fluid and the deposit layer is captured using the level-set method. Fluid flow is modeled by the incompressible Navier–Stokes equations. Numerical solution is performed on a fixed mesh using the finite volume method. The effects of Reynolds number and thermal conductivity ratio between the deposit layer and the fluid on local Nusselt number as well as length-averaged Nusselt number are investigated. It is found that heat transfer performance, represented by the local and length-averaged Nusselt number reduces significantly in a fouled channel compared with that in a clean channel. Heat transfer performance decreases with the growth of the deposit layer. Increases in Reynolds, Prandtl numbers both enhance heat transfer. Besides, heat transfer is enhanced when the thermal conductivity ratio between the deposit layer and the fluid is lower than 20 but it decreases when the thermal conductivity ratio is larger than 2

Investigating the Creativity and Its Influencing Factors among Medical Students

Background: Creativity is among the fundamental and constitutive features of humans, playing an important role in the development and growth of human beings and human civilization. The present study was conducted to investigate the creativity and factors influencing it among medical students.Methods: In this cross-sectional study, 320 medical students were randomly selected using stratified random sampling. Guilford's Creativity Questionnaire was used as data collection tool. Chi-Square test, and one-way analysis of Variance were used for data analysis, and the results were presented as frequency distribution tables.Results: Most of the participants (232 students (72.5%)) had moderate levels of creativity. The mean score was obtained as 49.59±5.59, 22.02± 3.29, 35.06± 4.62, 25.81±3.53, and 135.56±13.80, respectively for fluency, elaboration, originality, flexibility, and overall creativity. There was no significant relationship between overall score of creativity with gender, major, educational level, and place of residence, marital status, employment, and term of study (P≥0.05). However, there was a significant relationship between flexibility (P=0.001) and marital status (P=0.045).Conclusions: Given that about three-quarters of the participants had moderate scores while high creativity is indispensable for health care workers, educational planners need to foster this capability among the students