A large and growing body of literature has investigated diverse impacts of solar power technologies, in particular, solar home systems (SHS) in the developing economies. These studies evaluated ...either the social or economic impacts of solar photovoltaic (PV) technology adoption, often both, as a socio-economic analysis. A few other studies investigated the environmental impacts only. On the other hand, some studies considered the drivers and barriers of this technology adoption. However, studies considering all these factors – impacts, drivers, barriers – together to derive an overall picture of solar electricity deployment as a part of energy decentralization rarely occur in the literature. This study has taken into account this gap in the literature and tried to analyze all the factors together through the lens of the energy cultures framework (ECF) and provide insights into the interplay that exists between these factors. The ECF revealed that the drivers of SHS adoption are dominated by the ‘cognitive norms’ of the adopters. In contrast, the significant barriers belong to the ‘material culture’ of the people. This study further indicates the policy implications of energy decentralization. These findings might be a useful source of information for energy policymakers towards formulating a sustainable national electricity generation plan for developing economies to meet the United Nations sustainable development goals.
•Impacts of solar home system (SHS) adoption are explored for the developing world.•Social, economic, and environmental impacts of SHS adoption are identified.•Drivers and barriers of SHS adoption are investigated through the energy cultures framework.•Related policy implications for developing countries are indicated.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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The macrokinetic features of combustion in the Ta-Zr-B system were studied. Combustion is characterized by spin mode, suggesting the limiting role of gas-phase mass transfer of ...reagents. The mechanism of chemical reactions and phase formation in combustion wave was discussed. Primary layers of tantalum and zirconium borides were detected in the preheating zone at temperatures below the melting point of the reagents. After zirconium and boron melt, the temperature in the combustion zone reaches its maximum and zirconium diboride precipitates out of the oversaturated solution. Powders with a grain size of 1–3 μm were fabricated and hot-pressed into dense ultra-high-temperature ceramics (UHTCs). Boride ceramics with the record-setting hardness of 70 GPa, Young's modulus of 594 GPa, and elastic recovery of 96% were obtained. The measured heat conductivity of the solid solution (Zr,Ta)B2 was equal to 35–42 W/m K. Plasma torch tests demonstrated high oxidation resistance of the obtained ceramics at 2900–3000 °C.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Porous silicon nitride ceramics with high flexural strength and high porosity were directly fabricated by self-propagating high temperature synthesis (SHS). The effects of N2 pressure and Si particle ...size on the phase composition, microstructure, and mechanical property were investigated. N2 influences not only the thermodynamics but also the kinetics of the SHS as initial reactant. Flexural strength ranged between 67 MPa and 134 MPa with increasing N2 pressure. On the other hand, flexural strength ranged from 213 MPa to 102 MPa with different Si particle sizes. This plays an important role on the final diameter and length of β-Si3N4 grains and the formation mechanism of porous Si3N4 ceramics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Vanadium carbide is important for industrial applications because of its high hardness, high temperature resistance, high chemical, and thermal stability. It is generally obtained from the reaction ...between V and C powders at a high temperature ranging from 1100 to 1500°C. Investigations on these high strength, high abrasion resistant, hard materials have been intensified in recent years and consequently, significant improvements have been achieved. In this study, VC alloys are produced with low cost processes, by reducing the oxides of their components by SHS methods and ball mill-assisted carbothermal reduction. In the experimental stage, V2O5 was used as oxidized Vanadium source, Cblack as carbon source, magnesium and Cblack as reductant. In the study, VC powders were synthesized by two different methods and optimum production conditions were determined. Furthermore, the effect of different stoichiometric charge components and the effect of experiment durations were realized by X-ray diffraction, HSC Chemistry, and SEM analyses for different reductants.
Titanium diboride (TiB2) is a low-density refractory material belonging to the family of ultra-high temperature ceramics (UHTCs). This paper reports on the production and microstructural and optical ...characterization of nearly fully dense TiB2, with particular interest to its potential utilization as novel thermal solar absorber. Monolithic bulk samples are produced starting from elemental reactants by a two-step method consisting of the Self-propagating High-temperature Synthesis (SHS) followed by the Spark Plasma Sintering (SPS) of the resulting powders. The surface of obtained samples has-been characterized from the microstructural and topological points of view. The hemispherical reflectance spectrum has been measured from 0.3 to 15µm wavelength, to evaluate the potential of this material as solar absorber for future concentrating solar plants.
•A fully dense monolithic titanium diboride (TiB2) ceramic is produced from elemental reactants by a two-step SHS+STS method.•For the first time, optical properties of bulk TiB2 are experimentally investigated for solar absorber applications.•TiB2 has comparable performance with respect to other diborides and spectral selectivity superior to SiC.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Progressive collapse performance of steel connections are studied.•Focus is given to practical beam-to-SHS column connections.•Three full scale tests are performed on double-span ...systems.•Comprehensive finite element (FE) models are established and discussed.
This paper comprehensively discussed the performance of practical beam-to-SHS column connections against progressive collapse. Three full scale tests were performed on double-span systems subjected to the typical column loss scenario, where three connection types were covered in the test programme, namely, welded flange-weld web connection with internal diaphragms (specimen I-W), welded flange-bolted web connection with internal diaphragms (specimen I-WB), and welded flange-bolted web connection with short through diaphragms (specimen ST-WB). The test results, including failure modes/sequence, load–deformation responses and stress conditions, were presented in detail, and the load transfer mechanism over the entire loading process was thoroughly discussed. Comprehensive finite element (FE) models were then established to enable further discussion of the test results. Both experimental and FE results showed satisfactory ductility supply and load resistance of the three specimens, although specimen ST-WB exhibited the lowest ductility against initial fracture due to evident non-symmetrical stress distribution over the width of the beam flange. For the post-peak response, specimens I-WB and ST-WB showed reasonable regaining of the resisting load at later catenary stage due to a sufficient redistribution of the stress at the bolted shear tab connections, but limited post-peak load resistance was shown for specimen I-W which underwent quick propagation of the crack over the entire beam section. A simplified energy balance analysis showed that when a sudden column loss scenario is considered, progressive collapse may be triggered upon the initial fracture of the bottom beam flange of all the specimens.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•Dense heterophase HfB2–SiC ceramics produced by hot pressing of SHS powders.•The best heat resistance was observed for the ceramics with 8 % SiC under gas-dynamic conditions.•A dense protective ...layer consisting of HfO2/HfSiO4 grains is formed on the surface during oxidation.•Ceramics exhibits: heat capacity - 0.38 J/(g × K), thermal diffusivity - 40.9 mm2/s, and thermal conductivity - 89.7 W/(m × K).
The kinetics and the mechanism of oxidation of ceramics based on HfB2 and SiC, manufactured by elemental self-propagating high-temperature synthesis followed by hot pressing were investigated. The synthesis product contained HfC(x) and HfO2 as impurity phases. Depending on the ratio between the main components, the samples were characterized by high structural and chemical homogeneity, porosity of 3–6 vol%, hardness up to 29 GPa, bending strength of 500–600 MPa, fracture toughness of 5.6–8.9 MPa × m1/2, and thermal conductivity of 86.0–89.7 W/(m × K). The oxidation was performed under static conditions at 1650 °C and upon exposure to a high-enthalpy gas flow. A dense layer consisting of HfO2/HfSiO4 grains formed on the surface of the ceramics during both oxidation conditions; the space between the grains was filled with amorphous SiO2–B2O3. The best heat resistance was observed for the ceramics with 16 wt% SiC for static conditions and 8 wt% SiC for gas-dynamic conditions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
This article presents a multi-subharmonic switching (SHS) digital power amplifier (PA) architecture for enhancing power back-off (PBO) efficiency while achieving watt-level output power. The proposed ...phase-interleaved architecture provides the inherent cancellation of the subharmonic components in the PBO region, alleviating the burden of the matching network. The proposed multi-SHS scheme can be further combined with a class-G operation to create a greater number of efficiency peaks in the PBO region. A transformer-based, three-way power combiner and a triple-stacking class-D driver are utilized to obtain watt-level output power. The proof-of-concept PA prototype is implemented with a switched-capacitor PA (SCPA) architecture in 65-nm CMOS and achieved 30-dBm peak power at 1.9 GHz, with 45.9%/41.3%/35.3%/32.2%/24.2% drain efficiency located at 0-, -3.5-, -7.0-, -9.5-, and -12-dB PBO, respectively. The average efficiency was 31.4% in real-time operation with a 7.2-dB peak-to-average power ratio (PAPR) modulated signal.
Academic writing has always been one of the hardest skills to develop as it requires mastery of the language. With the unforeseen pandemic, developing the said skills of the learners in ...this generation has become harder as new modes of instruction that are unfamiliar to both teachers and students emerge. With that, the main focus of this study is to identify the types and frequency of errors the students commit in writing academic papers in an attempt to provide the best possible interventions to remediate them. To achieve these objectives, 15 position papers were collected and analyzed. Error analysis designed by Gass and Selinker in 2008 was applied. In the end, results have been tabulated in descending sequence in which grammar appeared as the most frequent error. Strategies, such as the use of AI in checking grammar, and interventions, such as giving feedback and drafting, are recommended.
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