Search results for: Hannah E. Power

Authors: Xiaobo Rui, Zhoumo Zeng, Yibo Li

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A novel tri-cantilever energy harvester with magnetic oscillator was presented, which could convert the ambient vibration into electrical energy to power the low-power devices such as wireless sensor networks. The most common way to harvest vibration energy is based on the use of linear resonant devices such as cantilever beam, since this structure creates the highest strain for a given force. The highest efficiency will be achieved when the resonance frequency of the harvester matches the vibration frequency. The limitation of the structure is the narrow effective bandwidth. To overcome this limitation, this article introduces a broadband tri-cantilever harvester with nonlinear stiffness. This energy harvester typically consists of three thin cantilever beams vertically arranged with Neodymium Magnets ( NdFeB)magnetics at its free end and a fixed base at the other end. The three cantilevers have different resonant frequencies by designed in different thicknesses. It is obviously that a similar advantage of multiple resonant frequencies as piezoelectric cantilevers array structure is built. To achieve broadband energy harvesting, magnetic interaction is used to introduce the nonlinear system stiffness to tune the resonant frequency to match the excitation. Since the three cantilever tips are all free and the magnetic force is distance dependent, the resonant frequencies will be complexly changed with the vertical vibration of the free end. Both model and experiment are built. The electromechanically coupled lumped-parameter model is presented. An electromechanical formulation and analytical expressions for the coupled nonlinear vibration response and voltage response are given. The entire structure is fabricated and mechanically attached to a electromagnetic shaker as a vibrating body via the fixed base, in order to couple the vibrations to the cantilever. The cantilevers are bonded with piezoelectric macro-fiber composite (MFC) materials (Model: M8514P2). The size of the cantilevers is 120*20mm2 and the thicknesses are separately 1mm, 0.8mm, 0.6mm. The prototype generator has a measured performance of 160.98 mW effective electrical power and 7.93 DC output voltage via the excitation level of 10m/s2. The 130% increase in the operating bandwidth is achieved. This device is promising to support low-power devices, peer-to-peer wireless nodes, and small-scale wireless sensor networks in ambient vibration environment.

Keywords: tri-cantilever, ambient vibration, energy harvesting, magnetic oscillator

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Authors: Shrikant V. Sangludkar, Dilip I. Sangotra, Sachin T. Bagde, Abhijeet A. Khandagale

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The paper discloses a controlled tracked humanoid robot moving platform. A driving and driven wheel are controlled by a control module to drive a robot body to move according to data signals of a monitoring module, in addition, remote transmission can be achieved, and a certain remote control function can be realized. A power management module circuit board looks after in used for providing electric drive for moving of the robot body and distribution of separate power source to be used in internal of robot system. An external port circuit board is arranged, the tracked robot moving platform can be used immediately for any data acquisition. The moving platform is simple and compact in structure, strong in adaptation performance, stable in operation and suitable for being operated in severe environments. Meanwhile, a layered modular installation structure is adopted, and therefore the moving platform is convenient to assemble and disassemble.

Keywords: moving platform, humanoid robot, embedded controlled drive, mobile robot, museum robots, self-localization, obstacle avoidance, communication

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Authors: T. Bensana, S. Mekhilef

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The methodology of vibration based condition monitoring technology has been developing at a rapid stage in the recent years suiting to the maintenance of sophisticated and complicated machines. The ability of wavelet analysis to efficiently detect non-stationary, non-periodic, transient features of the vibration signal makes it a demanding tool for condition monitoring. This paper presents a methodology for fault diagnosis of rolling element bearings based on wavelet envelope power spectrum technique is analysed in both the time and frequency domains. In the time domain the auto-correlation of the wavelet de-noised signal is applied to evaluate the period of the fault pulses. However, in the frequency domain the wavelet envelope power spectrum has been used to identify the fault frequencies with the single sided complex Laplace wavelet as the mother wavelet function. Results show the superiority of the proposed method and its effectiveness in extracting fault features from the raw vibration signal.

Keywords: preventive maintenance, fault diagnostics, rolling element bearings, wavelet de-noising

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Authors: Mohd Tariq

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The three phase system drives produce the problem of more torque pulsations and harmonics. This issue prevents the smooth operation of the drives and it also induces the amount of heat generated thus resulting in an increase in power loss. Higher phase system offers smooth operation of the machines with greater power capacity. Five phase variable-speed induction motor drives are commonly used in various industrial and commercial applications like tractions, electrical vehicles, ship propulsions and conveyor belt drive system. In this work, a comparative analysis of the different modulation schemes applied on the five-level five-phase Packed U Cell (PUC) inverter fed induction motor drives is presented. The performance of the inverter is greatly affected with the modulation schemes applied. The system is modeled, designed, and implemented in MATLAB^®/Simulink environment. Experimental validation is done for the prototype of single phase, whereas five phase experimental validation is proposed in the future works.

Keywords: Packed U-Cell (PUC) inverter, five-phase system, pulse width modulation (PWM), induction motor (IM)

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Authors: Felipe M. de Freitas, Ícaro V. Soares, Lucas L. L. Fortes, Sandro T. M. Gonçalves, Úrsula D. C. Resende

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There is a dispersed energy in Radio Frequencies (RF) that can be reused to power electronics circuits such as: sensors, actuators, identification devices, among other systems, without wire connections or a battery supply requirement. In this context, there are different types of energy harvesting systems, including rectennas, coil systems, graphene and new materials. A secondary step of an energy harvesting system is the rectification of the collected signal which may be carried out, for example, by the combination of one or more Schottky diodes connected in series or shunt. In the case of a rectenna-based system, for instance, the diode used must be able to receive low power signals at ultra-high frequencies. Therefore, it is required low values of series resistance, junction capacitance and potential barrier voltage. Due to this low-power condition, voltage multiplier configurations are used such as voltage doublers or modified bridge converters. Lowpass filter (LPF) at the input, DC output filter, and a resistive load are also commonly used in the rectifier design. The electronic circuits projects are commonly analyzed through simulation in SPICE (Simulation Program with Integrated Circuit Emphasis) environment. Despite the remarkable potential of SPICE-based simulators for complex circuit modeling and analysis of quasi-static electromagnetic fields interaction, i.e., at low frequency, these simulators are limited and they cannot model properly applications of microwave hybrid circuits in which there are both, lumped elements as well as distributed elements. This work proposes, therefore, the electromagnetic modelling of electronic components in order to create models that satisfy the needs for simulations of circuits in ultra-high frequencies, with application in rectifiers coupled to antennas, as in energy harvesting systems, that is, in rectennas. For this purpose, the numerical method FDTD (Finite-Difference Time-Domain) is applied and SPICE computational tools are used for comparison. In the present work, initially the Ampere-Maxwell equation is applied to the equations of current density and electric field within the FDTD method and its circuital relation with the voltage drop in the modeled component for the case of lumped parameter using the FDTD (Lumped-Element Finite-Difference Time-Domain) proposed in for the passive components and the one proposed in for the diode. Next, a rectifier is built with the essential requirements for operating rectenna energy harvesting systems and the FDTD results are compared with experimental measurements.

Keywords: energy harvesting system, LE-FDTD, rectenna, rectifier, wireless power systems

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Authors: Omar Awad, R. Mamat, F. Yusop, M. M. Noor, I. M. Yusri

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Fusel oil is a by-product obtained through the fermentation of some agricultural products. The fusel oil properties are closer to other alternative combustible types and the limited number of studies on the use of fusel oil as an alcohol derivative in SI engines constitutes to the base of this study. This paper experimentally examined the impacts of a by-product of alcohol, which is fusel oil by blending it with gasoline, on engine performance, combustion characteristics, and emissions in a 4-cylinder SI engine. The test was achieved at different engine speeds and a 60 % throttle valve (load). As results, brake power, BTE, and BSFC of F10 are higher at all engine speeds. Maximum engine BTE was 33.9%, at the lowest BSFC with F10. Moreover, it is worth seeing that the F10 under rich air-fuel ratio has less variation of COVIMEP compared to the F20 and gasoline. F10 represents shorter combustion duration, thereby, the engine power increased. NOx emission for F10 at 4500 rpm was lower than gasoline. The highest value of HC emission is obtained with F10 compared to gasoline and F20 with an average increase of 11% over the engine speed range. CO and CO2 emissions increased when using fusel oil blends.

Keywords: fusel oil, spark ignition engine, by-product alcohol, combustion characteristics, engine emissions, alternative fuel

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Authors: Y. T. Ku, S. W. Chen, J. R. Wang, C. Shih, Y. F. Chang

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In order to respond the policy decision of non-nuclear homes, Tai Power Company (TPC) will provide the decommissioning project of Kuosheng Nuclear power plant (KSNPP) to meet the regulatory requirement in near future. In this study, the computational fluid dynamics (CFD) methodology has been employed to develop a flow prediction model for boiling water reactor (BWR) with upper pool under decommissioning stage. The model can be utilized to investigate the flow behavior as the vessel combined with upper pool and continuity cooling system. At normal operating condition, different parameters are obtained for the full fluid area, including velocity, mass flow, and mixing phenomenon in the reactor pressure vessel (RPV) and upper pool. Through the efforts of the study, an integrated simulation model will be developed for flow field analysis of decommissioning KSNPP under normal operating condition. It can be expected that a basis result for future analysis application of TPC can be provide from this study.

Keywords: CFD, BWR, decommissioning, upper pool

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Authors: Ahmed Elkholy

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Most power transmission cases use gearing in general, and worm gearing, in particular for energy utilization. Therefore, designing gears for minimum weight and maximum power transmission is the main target of this study. In this regard, a new approach has been developed to estimate the load share and stress distribution of worm gear sets. The approach is based upon considering the instantaneous tooth meshing stiffness where the worm gear drive was modelled as a series of spur gear slices, and each slice was analyzed separately using a well-established criteria. By combining the results obtained for all slices, the entire worm gear set loading and stressing was determined. The geometric modelling method presented, allows tooth elastic deformation and tooth root stresses of worm gear drives under different load conditions to be investigated. On the basis of the method introduced in this study, the instantaneous meshing stiffness and load share were obtained. In comparison with existing methods, this approach has both good analytical accuracy and less computing time.

Keywords: gear, load/stress distribution, worm, wheel, tooth stiffness, contact line

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Authors: A. Maghoul, A. Rostampouryasouri, MR. Maghami

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The development of an urban design and power network planning has been gaining momentum in recent years. The integration of renewable energy with urban design has been widely regarded as an increasingly important solution leading to climate change and energy security. Through the use of passive strategies and solar integration with Urban Building Energy Modeling (UBEM) tools, architects and designers can create high-quality designs that meet the needs of clients and stakeholders. To determine the most effective ways of combining renewable energy with urban development, we analyze the relationship between urban form and renewable energy production. The procedure involved in this practice include passive solar gain (in building design and urban design), solar integration, location strategy, and 3D models with a case study conducted in Tehran, Iran. The study emphasizes the importance of spatial and temporal considerations in the development of sector coupling strategies for solar power establishment in arid and semi-arid regions. The substation considered in the research consists of two parallel transformers, 13 lines, and 38 connection points. Each urban load connection point is equipped with 500 kW of solar PV capacity and 1 kWh of battery Energy Storage (BES) to store excess power generated from solar, injecting it into the urban network during peak periods. The simulations and analyses have occurred in EnergyPlus software. Passive solar gain involves maximizing the amount of sunlight that enters a building to reduce the need for artificial lighting and heating. Solar integration involves integrating solar photovoltaic (PV) power into smart grids to reduce emissions and increase energy efficiency. Location strategy is crucial to maximize the utilization of solar PV in an urban distribution feeder. Additionally, 3D models are made in Revit, and they are keys component of decision-making in areas including climate change mitigation, urban planning, and infrastructure. we applied these strategies in this research, and the results show that it is possible to create sustainable and energy-efficient urban environments. Furthermore, demand response programs can be used in conjunction with solar integration to optimize energy usage and reduce the strain on the power grid. This study highlights the influence of ancient Persian architecture on Iran's urban planning system, as well as the potential for reducing pollutants in building construction. Additionally, the paper explores the advances in eco-city planning and development and the emerging practices and strategies for integrating sustainability goals.

Keywords: energy-efficient urban planning, sustainable architecture, solar energy, sustainable urban design

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Authors: Fatima Khurshid, Noor Ul Ain, Syed Abdul Rehman Kashif, Zainab Riaz, Abdullah Usman Khan, Muhammad Imran

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As the world is moving towards extra-high voltage (EHV) and ultra-high voltage (UHV) power systems, the performance requirements of power transformers are becoming crucial to the system reliability and security. With the transformers being an essential component of a power system, low health index of transformers poses greater risks for safe and reliable operation. Therefore, to meet the rising demands of the power system and transformer performance, researchers are being prompted to provide solutions for enhanced thermal and electrical properties of transformers. This paper proposes an approach to improve the health index of a transformer by using nano-technology in conjunction with bio-degradable oils. Vegetable oils can serve as potential dielectric fluid alternatives to the conventional mineral oils, owing to their numerous inherent benefits; namely, higher fire and flashpoints, and being environment-friendly in nature. Moreover, the addition of nanoparticles in the dielectric fluid further serves to improve the dielectric strength of the insulation medium. In this research, using the finite element method (FEM) in COMSOL Multiphysics environment, and a 2D space dimension, three different oil samples have been modelled, and the electric field distribution is computed for each sample at various electric potentials, i.e., 90 kV, 100 kV, 150 kV, and 200 kV. Furthermore, each sample has been modified with the addition of nanoparticles of different radii (50 nm and 100 nm) and at different interparticle distance (5 mm and 10 mm), considering an instant of time. The nanoparticles used are non-conductive and have been modelled as alumina (Al₂O₃). The geometry has been modelled according to IEC standard 60897, with a standard electrode gap distance of 25 mm. For an input supply voltage of 100 kV, the maximum electric field stresses obtained for the samples of synthetic vegetable oil, olive oil, and mineral oil are 5.08 ×10⁶ V/m, 5.11×10⁶ V/m and 5.62×10⁶ V/m, respectively. It is observed that for the unmodified samples, vegetable oils have a greater dielectric strength as compared to the conventionally used mineral oils because of their higher flash points and higher values of relative permittivity. Also, for the modified samples, the addition of nanoparticles inhibits the streamer propagation inside the dielectric medium and hence, serves to improve the dielectric properties of the medium.

Keywords: dielectric strength, finite element method, health index, nanotechnology, streamer propagation

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Authors: Tahany W. Sadak, Fouly, A. Anwer, M. Rizk

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The current investigation presents a study on the hydraulic performance of an electro-hydraulic servo solenoid valve controlled linear piston used in hydraulic systems. Advanced methods have been used to measure and record laboratory experiments, to ensure accurate analysis and evaluation. Experiments have been conducted under different values of temperature (28, 40 and 50 °C), supply pressure (10, 20, 30, 40 and 50 bar), system stiffness (32 N/mm), and load (0.0 & 5560 N). It is concluded that increasing temperature of hydraulic oil increases the quantity of flow rate, so it achieves an increase of the quantity of flow by 5.75 % up to 48.8 % depending on operating conditions. The values of pressure decay at low temperature are less than the values at high temperature. The frequency increases with the increase of the temperature. When we connect the springs to the system, it decreases system frequency. These results are very useful in the process of packing and manufacturing of fluid products, where the properties are not affected by 50 °C, so energy and time are saved.

Keywords: electro-hydraulic servo valve, fluid power control system, system stiffness, static and dynamic performance

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Authors: S. R. H. Baqri, T. Shahina, M. T. Hasan

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Pakistan is facing acute shortage of energy and looking for indigenous resources of the energy mix to meet the short fall. After the discovery of huge coal resources in Thar Desert of Sindh province, focus has shifted to coal power generation. The government of Pakistan has planned power generation of 20000 MW on coal by the year 2025. This target will be achieved by mining and power generation in Thar coal Field and on imported coal in different parts of Pakistan. Total indigenous coal production of around 3.0 million tons is being utilized in brick kilns, cement and sugar industry. Coal-based power generation is only limited to three units of 50 MW near Hyderabad from nearby Lakhra Coal field. The purpose of this presentation is to identify and redressal of issues of coal mining and utilization with reference to environmental hazards. Thar coal resource is estimated at 175 billion tons out of a total resource estimate of 184 billion tons in Pakistan. Coal of Pakistan is of Tertiary age (Palaeocene/Eocene) and classified from lignite to sub-bituminous category. Coal characterization has established three main pollutants such as Sulphur, Carbon dioxide and Methane besides some others associated with coal and rock types. The element Sulphur occurs in organic as well as inorganic forms associated with coals as free sulphur and as pyrite, gypsum, respectively. Carbon dioxide, methane and minerals are mostly associated with fractures, joints local faults, seatearth and roof rocks. The abandoned and working coal mines give kerosene odour due to escape of methane in the atmosphere. While the frozen methane/methane ices in organic matter rich sediments have also been reported from the Makran coastal and offshore areas. The Sulphur escapes into the atmosphere during mining and utilization of coal in industry. The natural erosional processes due to rivers, streams, lakes and coastal waves erode over lying sediments allowing pollutants to escape into air and water. Power plants emissions should be controlled through application of appropriate clean coal technology and need to be regularly monitored. Therefore, the systematic and scientific studies will be required to estimate the quantity of methane, carbon dioxide and sulphur at various sites such as abandoned and working coal mines, exploratory wells for coal, oil and gas. Pressure gauges on gas pipes connecting the coal-bearing horizons will be installed on surface to know the quantity of gas. The quality and quantity of gases will be examined according to the defined intervals of times. This will help to design and recommend the methods and procedures to stop the escape of gases into atmosphere. The element of Sulphur can be removed partially by gravity and chemical methods after grinding and before industrial utilization of coal.

Keywords: atmosphere, coal production, energy, pollutants

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Authors: Firdous Nizar, Carmela Cucuzzella

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This paper explores how the integrated design process (IDP) was adopted for an architectural project. The IDP is a relatively new approach to collaborative design in architectural design projects in Canada. It has gained much traction recently as the closest possible approach to the successful management of low energy building projects and has been advocated as a productive method for multi-disciplinary collaboration within complex projects. This study is based on the premise that there are explicit and implicit dimensions of power within the integrated design process (IDP) in the green building industry that may or may not lead to irreconcilable differences in a process that demands consensus. To gain insight on the potential gap between the theoretical promises and practical realities of the IDP, a review of existing IDP literature is compared with a case study analysis of a competition-based architectural project in Canada, a first to incorporate the IDP in its overall design format. This paper aims to address the undertheorized power relations of the IDP in a real project. It presents a critical assessment through the lens of the combined theories of deliberative democracy by Jürgen Habermas, with that of agonistic pluralism by political theorist Chantal Mouffe. These two theories are intended to more appropriately embrace the conflictual situations in collaborative environments, and shed light on the relationships of power, between engineers, city officials, architects, and designers in this conventional consensus-based model. In addition, propositions for a shift in approach that embraces conflictual differences among its participants are put forth based on concepts of critical spatial practice by Markus Meissen. As IDP is a relatively new design process, it requires much deliberation on its structure from the theoretical framework built in this paper in order to unlock its true potential.

Keywords: agonistic pluralism, critical spatial practice, deliberative democracy, integrated design process

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Authors: Shabnam Dadparvar, Laijin Shen

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This paper focuses on China’s policy in the Middle East and the rivalry with the U.S. The question is that what are the main factors on China’s Middle East policy and its competition with the U.S? The hypothesis regards to three effective factors: 'China’s energy dependency' on the Middle East, 'economy' and support for 'stability' in the Middle East. What is important in China’s competition with the U.S regarding to its Middle East policy is the substantial difference in ways of treating the countries of the region; China is committed to Westphalia model based on non-interference in internal affairs of the countries and respect the sovereignty of the governments. However, after 9/11, the U.S is seeking a balance between stability and change through intervention in the international affairs and in some cases is looking for a regime change. From the other hand, China, due to its dependency on the region’s energy welcomes America’s military presence in the region for providing stability. The authors by using a descriptive analytical method try to explain the situation of rivalry between China and the United States in Middle East. China is an 'emerging power' with high economic growth and in demand of more energy supply. The problem is that a rising power in the region is often a source of concern for hegemony.

Keywords: China's foreign policy, energy, hegemony, the Middle East

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Authors: Bharti Garg, Ashleigh Cousins, Pauline Pearson, Vincent Verheyen, Paul Feron

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The presence of SO₂ in power plant flue gases makes flue gas desulfurization (FGD) an essential requirement prior to post combustion CO₂ (PCC) removal facilities. Although most of the power plants worldwide deploy FGD in order to comply with environmental regulations, generally the achieved SO₂ levels are not sufficiently low for the flue gases to enter the PCC unit. The SO₂ level in the flue gases needs to be less than 10 ppm to effectively operate the PCC installation. The existing FGD units alone cannot bring down the SO₂ levels to or below 10 ppm as required for CO₂ capture. It might require an additional scrubber along with the existing FGD unit to bring the SO₂ to the desired levels. The absence of FGD units in Australian power plants brings an additional challenge. SO₂ concentrations in Australian power station flue gas emissions are in the range of 100-600 ppm. This imposes a serious barrier on the implementation of standard PCC technologies in Australia. CSIRO’s developed CS-Cap process is a unique solution to capture SO₂ and CO₂ in a single column with single absorbent which can potentially bring cost-effectiveness to the commercial deployment of carbon capture in Australia, by removing the need for FGD. Estimated savings of removing SO₂ through a similar process as CS-Cap is around 200 MMUSD for a 500 MW Australian power plant. Pilot plant trials conducted to generate the proof of concept resulted in 100% removal of SO₂ from flue gas without utilising standard limestone-based FGD. In this work, removal of absorbed sulfur from aqueous amine absorbents generated in the pilot plant trials has been investigated by reactive crystallisation and thermal reclamation. More than 95% of the aqueous amines can be reclaimed back from the sulfur loaded absorbent via reactive crystallisation. However, the recovery of amines through thermal reclamation is limited and depends on the sulfur loading on the spent absorbent. The initial experimental work revealed that reactive crystallisation is a better fit for CS-Cap’s sulfur-rich absorbent especially when it is also capable of generating K₂SO₄ crystals of highly saleable quality ~ 99%. Initial cost estimation carried on both the technologies resulted in almost similar capital expenditure; however, the operating cost is considerably higher in thermal reclaimer than that in crystalliser. The experimental data generated in the laboratory from both the regeneration techniques have been used to generate the simulation model in Aspen Plus. The simulation model illustrates the economic benefits which could be gained by removing flue gas desulfurization prior to standard PCC unit and replacing it with a CS-Cap absorber column co-capturing CO₂ and SO₂, and it's absorbent regeneration system which would be either reactive crystallisation or thermal reclamation.

Keywords: combined capture, cost analysis, crystallisation, CS-Cap, flue gas desulfurisation, regeneration, sulfur, thermal reclamation

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Authors: Hyeon Mi Noh, Ju Hyun Oh, Jung Hyun Jeong, Haeyoung Choi, Jung Hwan Kim

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The Er³⁺/Yb³⁺/Tm³⁺ tri-doped Y₂O₃ nanophosphors were synthesized by solvothermal method and its temperature dependence of the white upconversion emission has been studied by using 975 nm laser diode. The upconversion emission spectra in 1 mol% Er³⁺/5 mol% Yb³⁺/xTm³ tri-doped Y₂O₃ nanophosphors sintered at 1000 °C with x from 0 to 0.5 mol%. The blue emission intensity increase with Tm³⁺ concentration from 0 to 0.5 mol%, it is due to the 2F7/2→2F5/2 transition of Yb³⁺ around 10,000 cm-1 could easily reach the Tm³⁺ sates. The white light is composed with the blue (1G4→3H6 of Tm³⁺), green (2H11/2, 4S3/2→4I15/2 of Er³⁺), and red (4F9/2→4I15/2 of Er³⁺) upconversion radiations. The Y₂O₃: Er³⁺/Yb³⁺/Tm³⁺ nanophosphors show from white to green upconversion emission at power of 600 mW/cm² as sintering temperature increased. The calculated Commission Internationale de l’Eclairage (CIE) coordinates can be located in the white area with various sintering temperatures, in sintered at 1000 °C, and their color coordinates are very close to the standard white-light emission (0.33, 0.33). Their upconversion processes were explained by measuring the upconversion luminescence spectra and pump power dependence and energy level diagram.

Keywords: white upconversion emission, nanophosphors, energy transfer, solvothermal method

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Authors: Tania Sharmin Khaleque, Mohammad Ferdows

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The flow and heat transfer characteristics of a convection with temperature-dependent viscosity and thermal diffusivity along a vertical plate with internal heat generation effect have been studied. The plate temperature is assumed to follow a power law of the distance from the leading edge. The resulting governing two-dimensional equations are transformed using suitable transformations and then solved numerically by using fifth order Runge-Kutta-Fehlberg scheme with a modified version of the Newton-Raphson shooting method. The effects of the various parameters such as variable viscosity parameter β_1, the thermal diffusivity parameter β_2, heat generation parameter c and the Prandtl number Pr on the velocity and temperature profiles, as well as the local skin- friction coefficient and the local Nusselt number are presented in tabular form. Our results suggested that the presence of internal heat generation leads to increase flow than that of without exponentially decaying heat generation term.

Keywords: free convection, heat generation, thermal diffusivity, variable viscosity

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Authors: T. D. Gunneswara Rao, Mudimby Andal

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Research on the utilization of fly ash will no longer refer the fly ash as a waste material of thermal power plants. Use of fly ash in concrete making, makes the concrete economical as well as durable. The fly ash is being added to the concrete in three ways namely, as partial replacement to cement, partial replacement to fine aggregates and admixture. Addition of fly ash to the concrete in each one of the form mentioned above, makes the concrete more workable and durable than the conventional concrete. Studies on fly ash as partial replacement to cement gained momentum as such replacement makes the concrete economical. In the present study, an attempt has been made to understand the effects of fly ash on the workability characteristics and strength aspects of fly ash concretes. In India, major number of thermal power plants are producing low calcium fly ash. Hence, in the present investigation, low calcium fly ash has been used. Fly ash in concrete was considered for the partial replacement of cement. The percentage replacement of cement by fly ash varied from 0% to 40% at regular intervals of 10%. Moreover the fine aggregate to coarse aggregate ratio also has been varied as 1:1, 1:2, and 1:3. The workability tests revealed that up to 30% replacement of cement by fly ash in concrete mixes water demand for reduces and beyond 30% replacement of cement by fly ash demanded more water content for constant workability.

Keywords: cementing efficiency, compressive strength, low calcium fly ash, workability

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Authors: Nissim Avissar

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This paper aims to question the practice of bringing together people belonging to groups in conflict with the aim of bridging differences through universal empathy and interpersonal connections. It is argued that in cases where one group has the power, and the other is in a struggle to change the balance assuming universal equality between the groups and encouraging emphatic understanding is a non-emphatic practice. Accordingly, a new concept is posited–justice-sensitive empathy, conditioning empathy in such situations on the acknowledgement of an imbalance of power/injustice. With this reframing in mind, educational practices promoting social justice are discussed. In order to create conditions for justice-seeking or politically sensitive empathy, we need to go beyond the conventional definitions of empathy and offer other means and possibilities. Three possibilities are discussed. The first focuses on intra-group (as opposed to inter-group) processes within each group. It means temporary and tactical separation that may allow each group to focus on its own needs and values and perhaps to return to the dialogue more confidently. The second option emphasizes the notion of "constructive conflict," which means that each side still aspires to promote his own interests but without demolishing the other side (which is a rival but also an unwanted and forced partner). Here, alongside the "obligation to resist" and to act to promote justice as we view and understand it, we have to take into account the other side. The third and last option relates to the practice of Restorative Justice. This practice originated in the Truth and Reconciliation committees in South Africa, but it is now widely used in other contexts. Those committees had the authority to punish (or pardon) people; however, their main purpose was to seek truth and, from there, nourish reconciliation. This is the main idea of restorative justice; it seeks justice for the sake of restoring relationships. All the above options involve action and are aware of power relations (i.e., politics). They all seek justice. They may create conditions for the more conventional empathic practice to evolve, but no less than that, they are examples of justice-seeking and politically sensitive empathetic practice.

Keywords: education, empathy, justice, reconciliation

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Authors: Tara Panday, Despina Learmonth

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Sex work is often constructed as being an interaction between male clients and female sex workers. As a result, street-based male sex workers are continuously overlooked in the South African literature. This qualitative study explored male sex workers’ subjective experiences and constructions of their male clients’ identities and the client-sex worker relationship. This research was conducted from a social-constructionist perspective, which allowed for a deeper understanding of the reasons and context driving the choices and actions of male sex workers. Semi-structured face-to-face interviews were conducted with 10 South African men working as sex workers in Cape Town. Data was analysed through thematic analysis. The findings of the study construct the client-sex worker relationship in terms of a professional relationship, constrained choice, sexual identity and need, as well as companionship for pay, potentially highlighting underlying reasons for supply and demand. The data which emerged around the client-sex worker relationship and the clients’ identities also served to illuminate the power-dynamics in the client-sex worker relationship. This data increases insight into the exploitation and disempowerment experienced by male sex workers through verbal abuse, physical and sexual violence, and unfairly enforced laws and regulations. The findings of this study suggest that, in the context of South Africa, male sex workers' experiences of the client-sex worker relationship cannot be completely understood without considering the intersectionality of the triple stigmatisation of: the criminality of sex work, race, and the lack of economic power, which systematically maintains marginalization. Motivating for the Law Reform Commission to continue to review all emerging research may assist with guiding related policy and thereby, the provision of equal human rights and adequate health and social interventions for all sex workers in South Africa.

Keywords: human rights, prostitution, power relations, sex work

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Authors: Stacey Herzog, Mitchell McCleary, Istvan Kovacs

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Purpose: Maximal strength and maximal power are key athletic abilities in many sports disciplines. In recent years, velocity-based training (VBT) with a relatively high 75-85% 1RM resistance has been popularized in preparation for powerlifting and various other sports. The purpose of this study was to discover differences between beginner/intermediate and advanced lifters’ push/press performances after a heavy resistance-based BP training program. Methods: A six-week, three-workouts per week program was administered to 52 young, physically active adults (age: 22.4±5.1; 12 female). The majority of the participants (84.6%) had prior experience in bench pressing. Typical workouts began with BP using 75-95% 1RM in the 1-5 repetition range. The sets in the lower part of the range (75-80% 1RM) were performed with velocity-focus as well. The BP sets were followed by seated dumbbell presses and six additional upper-body assistance exercises. Pre- and post-tests were conducted on five test exercises: one-repetition maximum BP (1RM), calculated relative strength index: BP/BW (RSI), four-repetition maximal-effort dynamic BP for peak concentric velocity with 80% 1RM (4RV), 4-repetition ballistic pushups (BPU) for height (4PU), and seated medicine ball toss for distance (MBT). For analytic purposes, the participant group was divided into two subgroups: self-indicated beginner or intermediate initial resistance training status (BITS) [n=21, age: 21.9±3.6; 10 female] and advanced initial resistance training status (ATS) [n=31, age: 22.7±5.9; 2 female]. Pre- and post-test results were compared within subgroups. Results: Paired-sample t-tests indicated significant within-group improvements in all five test exercises in both groups (p < 0.05). BITS improved 18.1 lbs. (13.0%) in 1RM, 0.099 (12.8%) in RSI, 0.133 m/s (23.3%) in 4RV, 1.55 in. (27.1%) in BPU, and 1.00 ft. (5.8%) in MBT, while the ATS group improved 13.2 lbs. (5.7%) in 1RM, 0.071 (5.8%) in RSI, 0.051 m/s (9.1%) in 4RV, 1.20 in. (13.7%) in BPU, and 1.15 ft. (5.5%) in MBT. Conclusion: While the two training groups had different initial resistance training backgrounds, both showed significant improvements in all test exercises. As expected, the beginner/intermediate group displayed better relative improvements in four of the five test exercises. However, the medicine ball toss, which had the lightest resistance among the tests, showed similar relative improvements between the two groups. These findings relate to two important training principles: specificity and transfer. The ATS group had more specific experiences with heavy-resistance BP. Therefore, fewer improvements were detected in their test performances with heavy resistances. On the other hand, while the heavy resistance-based training transferred to increased power outcomes in light-resistance power exercises, the difference in the rate of improvement between the two groups disappeared. Practical applications: Based on initial training status, S&C coaches should expect different performance gains in maximal strength training-specific test exercises. However, the transfer from maximal strength to a non-training-specific performance category along the F-v curve continuum (i.e., light resistance and high velocity) might not depend on initial training status.

Keywords: exercise, power, resistance training, strength

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Authors: Nazim Mir-Nasiri, Hudyjaya Siswoyo Jo

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The paper describes conceptual design, control strategies, and partial simulation for a new fully autonomous lower limb wearable exoskeleton system for human motion enhancement that can support its weight and increase strength and endurance. Various problems still remain to be solved where the most important is the creation of a power and cost efficient system that will allow an exoskeleton to operate for extended period without batteries being frequently recharged. The designed exoskeleton is enabling to decouple the weight/mass carrying function of the system from the forward motion function which reduces the power and size of propulsion motors and thus the overall weight, cost of the system. The decoupling takes place by blocking the motion at knee joint by placing passive air cylinder across the joint. The cylinder is actuated when the knee angle has reached the minimum allowed value to bend. The value of the minimum bending angle depends on usual walk style of the subject. The mechanism of the exoskeleton features a seat to rest the subject’s body weight at the moment of blocking the knee joint motion. The mechanical structure of each leg has six degrees of freedom: four at the hip, one at the knee, and one at the ankle. Exoskeleton legs are attached to subject legs by using flexible cuffs. The operation of all actuators depends on the amount of pressure felt by the feet pressure sensors and knee angle sensor. The sensor readings depend on actual posture of the subject and can be classified in three distinct cases: subject stands on one leg, subject stands still on both legs and subject stands on both legs but transit its weight from one leg to other. This exoskeleton is power efficient because electrical motors are smaller in size and did not participate in supporting the weight like in all other existing exoskeleton designs.

Keywords: energy efficient system, exoskeleton, motion enhancement, robotics

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Authors: Sodiq Onawale, Xin Wang

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Integrating renewable energy sources (RES) alongside conventional energy sources (NRES) in the grid has introduced challenges that highlight the need for a detailed analysis of various performance factors. Factors such as active and reactive power losses, voltage deviation, transmission line loading, power factor, fast voltage stability index, and capacity factor require careful evaluation to understand their impact on grid performance. In this study, MATPOWER’s optimization tools are used to model both NRES and a combined NRES + RES setup. The analysis compares the performance of each configuration across these factors. Findings indicate that integrating RES with NRES generally enhances performance across most of the analyzed factors compared to using NRES alone. The insights from this study offer valuable guidance for grid operators and policymakers, aiding in the balanced integration of RES with NRES to optimize smart grid performance and resilience.

Keywords: smart grid, impact analysis, renewable energy integration, FVSI, transmission line loading

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Authors: Ira Joseph

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The LNG paradox addresses the issue of how the most expensive form of gas supply, which is LNG, will grow in an end user market where demand is most competitive, which is power generation. In this case, LNG demand growth is under siege from two entirely different directions. At one end is price; it will be extremely difficult for gas to replace coal in Asia due to the low price of coal and the age of the generation plants. Asia's coal fleet, on average, is less than two decades old and will need significant financial incentives to retire before its state lifespan. While gas would cut emissions in half relative to coal, it would also more than double the price of the fuel source for power generation, which puts it in a precarious position. In most countries in Asia other than China, this cost increase, particularly from imports, is simply not realistic when it is also necessary to focus on economic growth and social welfare. On the other end, renewables are growing at an exponential rate for three reasons. One is that prices are dropping. Two is that policy incentives are driving deployment, and three is that China is forcing renewables infrastructure into the market to take a political seat at the global energy table with Saudi Arabia, the US, and Russia. Plus, more renewables will lower import growth of oil and gas in China, if not end it altogether. Renewables are the predator at the gate of gas demand in power generation and in every year that passes, renewables cut into demand growth projections for gas; in particular, the type of gas that is most expensive, which is LNG. Gas does have a role in the future, particularly within a domestic market. Once it crosses borders in the form of LNG or even pipeline gas, it quickly becomes a premium fuel and must be marketed and used this way. Our research shows that gas will be able to compete with batteries as an intermittency and storage tool and does offer a method to harmonize with renewables as part of the energy transition. As a baseload fuel, however, the role of gas, particularly, will be limited by cost once it needs to cross a border. Gas converted into blue or green hydrogen or ammonia is also an option for storage depending on the location. While this role is much reduced from the primary baseload role that gas once aspired to land, it still offers a credible option for decades to come.

Keywords: natural gas, LNG, demand, price, intermittency, storage, renewables

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Authors: Abdessalem Abbassi, Ahlem Dakhlaoui, Lota D. Tamini

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In this paper, we analyze infinite discrete-time games between hydraulic and thermal power operators in the wholesale electricity market under Cournot competition. We consider a deregulated electrical industry where certain demand is satisfied by hydraulic and thermal technologies. The hydraulic operator decides the production in each season of each period that maximizes the sum of expected profits from power generation with respect to the stochastic dynamic constraint on the water stored in the dam, the environmental constraint and the non-negative output constraint. In contrast, the thermal plant is operated with quadratic cost function, with respect to the capacity production constraint and the non-negativity output constraint. We show that under imperfect competition, the hydraulic operator has a strategic storage of water in the peak season. Then, we quantify the strategic inter-annual and intra-annual water transfer and compare the numerical results. Finally, we show that the thermal operator can restrict the hydraulic output without compensation.

Keywords: asymmetric risk aversion, electricity wholesale market, hydropower dams, imperfect competition

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Authors: Huseyin Guler, Cigdem Kosar

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The aim of this study is to propose Bridge estimator for seasonal unit root tests. Seasonality is an important factor for many economic time series. Some variables may contain seasonal patterns and forecasts that ignore important seasonal patterns have a high variance. Therefore, it is very important to eliminate seasonality for seasonal macroeconomic data. There are some methods to eliminate the impacts of seasonality in time series. One of them is filtering the data. However, this method leads to undesired consequences in unit root tests, especially if the data is generated by a stochastic seasonal process. Another method to eliminate seasonality is using seasonal dummy variables. Some seasonal patterns may result from stationary seasonal processes, which are modelled using seasonal dummies but if there is a varying and changing seasonal pattern over time, so the seasonal process is non-stationary, deterministic seasonal dummies are inadequate to capture the seasonal process. It is not suitable to use seasonal dummies for modeling such seasonally nonstationary series. Instead of that, it is necessary to take seasonal difference if there are seasonal unit roots in the series. Different alternative methods are proposed in the literature to test seasonal unit roots, such as Dickey, Hazsa, Fuller (DHF) and Hylleberg, Engle, Granger, Yoo (HEGY) tests. HEGY test can be also used to test the seasonal unit root in different frequencies (monthly, quarterly, and semiannual). Another issue in unit root tests is the lag selection. Lagged dependent variables are added to the model in seasonal unit root tests as in the unit root tests to overcome the autocorrelation problem. In this case, it is necessary to choose the lag length and determine any deterministic components (i.e., a constant and trend) first, and then use the proper model to test for seasonal unit roots. However, this two-step procedure might lead size distortions and lack of power in seasonal unit root tests. Recent studies show that Bridge estimators are good in selecting optimal lag length while differentiating nonstationary versus stationary models for nonseasonal data. The advantage of this estimator is the elimination of the two-step nature of conventional unit root tests and this leads a gain in size and power. In this paper, the Bridge estimator is proposed to test seasonal unit roots in a HEGY model. A Monte-Carlo experiment is done to determine the efficiency of this approach and compare the size and power of this method with HEGY test. Since Bridge estimator performs well in model selection, our approach may lead to some gain in terms of size and power over HEGY test.

Keywords: bridge estimators, HEGY test, model selection, seasonal unit root

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Authors: Kashvi Jain, Adam Burston

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Right-wing social movements are a dominant force in American politics, as evidenced by the January 6th Insurrection, the prevalence of extremist conspiracy theories, and a nationwide surge in hate crime. Despite an abundance of scholarship on contemporary right-wing extremism, there is little scholarship that explains their rise. This paper examines how the white power movement developed through tactical innovation and strategic use of increasingly powerful digital technologies. Using qualitative content analysis of archived digital bulletin boards and websites, we examine right-wing extremists’ digital communication during three consequential time periods of tactical and technological innovation: pre-internet (1980s), web 1.0 (1990s), and web 2.0 (2000s). Our analysis suggests that right-wing activists innovatively exploited the features and affordances of digital technologies and their knowledge of free speech rights to spread supremacist collective identity and ideology. Beyond our empirical contribution, we offer policy advice that school administrators can employ to limit hate.

Keywords: leaderless resistance, technological affordances, anti-defamation league, white power movement, tactical

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Authors: Daljinder Singh, J.S.Dhillon, Balraj Singh

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According to no free lunch theorem, a single search technique cannot perform best in all conditions. Optimization method can be attractive choice to solve optimization problem that may have exclusive advantages like robust and reliable performance, global search capability, little information requirement, ease of implementation, parallelism, no requirement of differentiable and continuous objective function. In order to synergize between exploration and exploitation and to further enhance the performance of Bat algorithm, the paper proposed a modified bat algorithm that adds additional search procedure based on bat’s previous experience. The proposed algorithm is used for solving the economic load dispatch (ELD) problem. The practical constraint such valve-point loading along with power balance constraints and generator limit are undertaken. To take care of power demand constraint variable elimination method is exploited. The proposed algorithm is tested on various ELD problems. The results obtained show that the proposed algorithm is capable of performing better in majority of ELD problems considered and is at par with existing algorithms for some of problems.

Keywords: bat algorithm, economic load dispatch, penalty method, variable elimination method

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Authors: Ryunhye Kim

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Despite its relatively short history as an independent state, Qatar has emerged as a highly regarded Gulf state and global power. Since its independence in September 1971, the state has employed deliberate policy initiatives designed to put Qatar on the map and distinguish it from other Gulf states. Because Qatar and its neighbors are resource-poor apart from energy, whoever is first to introduce a unique aspect of branding not only takes the lead but assumes what is often an insurmountable advantage. This study examines three specific modes of branding undertaken by Qatar: (1) energy policies to utilize its natural gas to become a dominant supplier; (2) the deliberate construction of a distinct cultural brand utilizing sports, architecture, museums, and media; and (3) ‘niche diplomacy’ to serve as a mediator in regional and intra-national conflicts, especially as interlocutor between the United States and Arab regimes and Muslim groups. Gleaning data from a range of sources, this study analyzes the effectiveness and significance of Qatar’s place branding on the global stage, as well as potential disadvantages and limits in this branding, including problems encountered before and after the ‘Qatar crisis.’

Keywords: national branding, national-identity, Qatar, soft-power

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Authors: Je-Seok Shin, Wook-Won Kim, Jin-O Kim

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The offshore wind farm needs to be designed carefully considering economics and reliability aspects. There are many decision-making problems for designing entire offshore wind farm, this paper focuses on an inner grid layout which means the connection between wind turbines as well as between wind turbines and an offshore substation. A methodology proposed in this paper determines the connections and the cable type for each connection section using K-clustering, minimum spanning tree and cable selection algorithms. And then, a cost evaluation is performed in terms of investment, power loss and reliability. Through the cost evaluation, an optimal layout of inner grid is determined so as to have the lowest total cost. In order to demonstrate the validity of the methodology, the case study is conducted on 240MW offshore wind farm, and the results show that it is helpful to design optimally offshore wind farm.

Keywords: offshore wind farm, optimal layout, k-clustering algorithm, minimum spanning algorithm, cable type selection, power loss cost, reliability cost

Procedia PDF Downloads 385