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Drought is a complex natural phenomenon that occurs throughout the world. Analyzing and grasping the occurrence and development of drought events is of great practical significance for preventing drought disasters. In this study, the Standardized Precipitation Evapotranspiration Index (SPEI) was adopted as a drought index to quantitatively analyze the temporal evolution, spatial distribution, and gridded trend characteristics of drought in the Yellow River basin (YRB) during 1961–2015. The duration and severity of drought events were extracted based on run theory, and the best-fitted Copula models were used to combine the drought duration and severity to analyze the drought return period. The results indicated that: (1) the drought showed a non-significant upward trend in the YRB from 1961 to 2015, and drought events became more serious after the 1990s; (2) the month and season with the most serious drought was June and summer, with an average SPEI value of −0.94 and −0.70; (3) the seasons with an increasing drought trend were spring, summer, and autumn; (4) the most serious drought lasted for 16 months in the YRB, with drought severity of 12.44 and drought return period of 115.18 years; and (5) Frank-copula was found to be the best-fitted one in the YRB. The research results can reveal the evolution characteristics of drought, and provide reference and basis for drought resistance and reduction in the YRB.

Concepts of resolving set and metric basis has enjoyed a lot of success because of multi-purpose applications both in computer and mathematical sciences. For a connected graph G(V,E) a subset W of V(G) is a resolving set for G if every two vertices of G have distinct representations with respect to W. A resolving set of minimum cardinality is called a metric basis for graph G and this minimum cardinality is known as metric dimension of G. Boron nanotubes with different lattice structures, radii and chirality's have attracted attention due to their transport properties, electronic structure and structural stability. In the present article, we compute the metric dimension and metric basis of 2D lattices of alpha-boron nanotubes.

Pakistan is a developing economy with a mainstay shifting gradually from agriculture to industry. Improving lifestyles, population growth, and rapid urbanization have led to a continuous increase in the demand of energy. The demand-supply gap amounts to 5000 MW on average which reaches 7000 MW in the month of July when the energy demand is at peak. This shortfall causes 4%–7% loss to the gross domestic product. Energy demand is at a constant peak of 8%–10% per annum. Fossil fuels make 61% of energy mix, while the share of renewables is less than 1%. This situation calls for careful analysis and review of Pakistan's energy dynamics and to explore the potential of renewable energy resources. Biomass, a promising resource of renewable energy, is abundantly available in Pakistan. Biomass is found in various forms from firewood to crop residues to municipal solid waste. About 50% of domestic energy requirements are fulfilled by fuelwood and 34% by animal and crop residues. However, the availability of fuelwood reduces as the rate of growth of forests has shrunk to 8.8%. Other biomass resources like charcoal are used at the minor level. Bagasse produced by 70 sugar industries in the country has been found to be sufficient for the generation of 5700 GWh of electricity. Major crop residues include cotton stalks, wheat straw, rice straw, sugarcane trash, and corn stalk having production of 49.4, 34.581, 16.75, 7.83, and 5.325 million tons, respectively. Collective processing residues per annum of these crops amount to 25.271 million tons having a power generation potential of 689.25 TWh annually. Animal dung also offers encouraging potential of power generation. The total number of animals in the country is 51 million. The potential of electricity generation from animal dung at the national level has been estimated to be 4761 to 5554 MW. The municipal solid waste potential for production of energy by biochemical and thermochemical conversion is 216 kWh/t and 552 kWh/t, respectively. It was found that the country possesses potential of successfully running 15 million biogas plants. This review, which policymakers and researchers may find to be useful, revealed that biomass energy could help to achieve the target of increasing share of renewables in energy mix of the country from less than 1% to 5% by 2030 as envisaged by the Government of Pakistan.

This work investigated the effects of shyness and lack of confidence as psychological barriers on EFL learner' speaking skill, particularly at the public sector colleges, universities and the sub-campuses of these universities located in the South Punjab, Pakistan. This project was scheduled to use a mixed-method type. Majority of the students indicated that there is an insignificant and negative relationship between the variables of shyness, lack of confidence and speaking English achievements. Since, as the shyness and lack of confidence increases, the speaking achievement decreases and as the shyness and lack of confidence decreases the speaking achievement increases. Findings from the explored work indicate that EFL teachers firstly, cultivate proper teaching circumstances by providing pupils adequate interval to prepare themselves for a conversational activity, develop a mind map to generate ideas, and offer learners plentiful time span to accomplish the given task well in the class.

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Resolving set and metric basis has become an integral part in combinatorial chemistry and molecular topology. It has a lot of applications in computer, chemistry, pharmacy and mathematical disciplines. A subset S of the vertex set V of a connected graph G resolves G if all vertices of G have different representations with respect to S. A metric basis for G is a resolving set having minimum cardinal number and this cardinal number is called the metric dimension of G. In present work, we find a metric basis and also metric dimension of 1-pentagonal carbon nanocones. We conclude that only three vertices are minimal requirement for the unique identification of all vertices in this network.

This research paper studies the impact of social media, specifically, Facebook and YouTube, on vocabulary acquisition of ESL learners. Using data collected from 30 students studying at the Department of English, IIUI, Islamabad and online responses from teachers with PhD in English, we strove to find out how learners are assisted by social media in vocabulary acquisition. It was discovered through the responses that the majority of teachers and students believe that vocabulary acquisition is improved through social media as it enhances the level of interest of students in second language learning. Overall, this study allows us to analyze the differences in the learning habits of ESL (English as Second Language) learners in a typical classroom environment using the new electronic media which is social media.