Hidden Markov Models based intelligent health assessment and fault diagnosis of rolling element bearings.

Hidden Markov Models (HMMs) have become an immensely popular tool for health assessment and fault diagnosis of rolling element bearings. The advantages of an HMM include its simplicity, robustness, and interpretability, while the generalization capability of the model still needs to be enhanced. The Dempster-Shafer theory of evidence can be used to conduct a comprehensive evaluation, and Stacking provides a novel training strategy. Therefore, the HMM-based fusion method and ensemble learning method are proposed to increase the credibility of quantitative analysis and optimize classifiers respectively. Firstly, vibration signals captured from bearings are decomposed into intrinsic mode functions (IMFs) using ensemble empirical mode decomposition (EEMD), and then the Hilbert envelope spectra of main components are obtained; Secondly, multi-domain features are extracted as model input from preprocessed signals; Finally, HMM-based intelligent health assessment framework and fault diagnosis framework are established. In this work, the life cycle health assessment modeling is performed using a few training samples, the bearing degradation state is quantitatively evaluated, normal and abnormal samples are effectively distinguished, and the accuracy of fault diagnosis is significantly improved.

Fresh evidence on connectedness between prominent markets during COVID-19 pandemic.

Various empirical studies have examined the nexus between financial markets, but this study focused on the comovement among prominent markets. Our study examines the interrelationship among main financial markets, i.e., stock, oil, and commodity during the recent pandemic. The interconnections among the selected markets are investigated using a battery of wavelet coherence tools and the Granger causality test. From the wavelet coherence analysis, our findings indicate strong co-movements among the VIX, oil volatility, and commodity prices during pandemic and localized in all scales and over the sample period. The dependency strength among the considered economies is noted to increase in pandemic, which implies increased short- and long-term benefits for the investors. Moreover, Our result exhibits a feedback causality between OVIX and crude oil, VIX and S&P 500, and gasoline and VIX. Interestingly, a unidirectional causality exists between VIX and crude oil, S&P 500 and crude oil, Brent and crude oil, gasoline, crude oil, and VIX and OVIX. We advocate that the findings will be helpful for portfolio managers, investors, and officials around the world.

Smarter and Greener Cities After COVID-19: An Integrated Decision-Making Framework to Prioritize Investment Alternatives.

Locking down cities to curb the transmission of coronavirus brought the global economy to a grinding halt. Cities are like engines of growth; when they stop, so does the growth. Therefore, it becomes paramount to build cities that continue to function and do not collapse amidst any crisis. Since economic recovery is underway, this paper examines priority areas for investment to expedite recovery and build back stronger cities. These areas are evaluated based on their contribution to revitalizing public health, economic, social, energy, and environmental sectors. For the analysis, analytical network process (ANP) and fuzzy-VIKOR are applied. ANP obtains the relative importance of sectors and their respective critical factors after solving a complex relationship among them. The economic sector has the highest weight of 25.8% among the five sectors, while job creation has the highest weight of 10.3% among the fifteen factors. Fuzzy-VIKOR is used to evaluate different areas and it is found that renewable energy has a greater contribution to the sustainable recovery of major sectors and the long-term aim of building inclusive green and resilient cities. These insights shall contribute to the conversations already ongoing among city governments, urban planners, civil society organizations, and city dwellers seeking practical solutions to unprecedented challenges posed by the pandemic.

A comparative analysis of renewable and non-renewable energy generation to relegate CO2 emissions and general costs in household systems.

Ensuring adequate implementation of solar energy for providing environment-friendly energy to the household sector, which can considerably abate pollutants in the environment and make power industry structure sustainable, is necessary for developing countries. Comparison in terms of environmental and cost impacts of renewable energy (hybrid solar system) with non-renewable energy sources, water and planning development authority (WAPDA), and diesel generators (DGs) has been examined in the household sector of Pakistan. Primary data of hybrid solar systems have been obtained from 10 different households segregated them into two categories according to their income as medium-income households (MIHs) and lower income households (LIHs) containing 5 kW and 3 kW of hybrid solar energy systems, respectively. While operating with a hybrid solar energy system instead of a non-renewable energy system, in terms of average generated power and average running load, carbon dioxide (CO2) emissions can be reduced up to 8,446.6 kg CO2 and 6,131.725 kg CO2, respectively, in the next 25 years. Comparison of costs indicated that renewable energy has a comparatively low cost per electric unit. It can pay back its total installation cost in just 8 years and can save a sum of $4,936.4375, along with many more ecological, economic, and societal benefits. Pakistan can efficiently utilize solar energy to relegate CO2 emissions and general costs as it has distinct geographical features to access sunlight in most days of the year.

Impact of stock market, renewable energy consumption and urbanization on environmental degradation: new evidence from BRICS countries.

This study examines links between Morgan and Stanley capital Investment (MSCI), foreign direct investment (FDI), renewable energy, urbanization, and trade openness on environmental degradation in (Brazil, Russia, India, China, South Africa) BRICS countries. In this study, generalized method of moment (GMM) estimation is applied on a data set ranging from 1993 to 2018. Results illustrate that stock market index price (MSCI) has negative relationship on CO2 emissions in India, China, Russia, and South Africa and has positive relationship in Brazil. One possible reason for this is strong environmental regulations and their enforcement by Brazilian government. The study also finds that trade openness, FDI, and urbanization have a significant positive relationship on environmental degradation. The impact of stock market development on environmental degradation varies among BRICS countries. Our outcomes have significant policy implications. For example, the policy makers have to initiate effective strategies to promote the renewable energy sources to meet the increasing demand for energy by replacing the use of conventional energy such as coal, gas, and oil. This will help to reduce the CO2 emissions from fossil fuel and ensure sustainable stock market development in the BRICS nations. BRICS countries who have taken the initiative and formulated policies for businesses to conserve the environment play a positive role compared to those who do not.

Energy trilemma based prioritization of waste-to-energy technologies: Implications for post-COVID-19 green economic recovery in Pakistan.

As lockdown eases, economic activities resume in Pakistan. If the country continues to follow business-as-usual (BAU) then it is anticipated that carbon output could surge past pre-COVID-19 levels - that means more disasters in future. Thus, it is an unprecedented opportunity to shift from BAU and achieve carbon-neutral and nature-positive economic recovery - green economic recovery (GER). To fuel the GER, access to modern, equitable, affordable and sustainable energy is paramount. This study explores waste-to-energy (WtE) as an alternative green fuel for GER. Seven WtE technologies are prioritized based on the concept of energy trilemma - energy security, energy equity, and environmental sustainability. For the evaluation, an energy trilemma based decision support framework is developed using most prominent multi-criteria decision-making (MCDM) methods. The fuzzy set theory is integrated with MCDM methods to minimize uncertainty in results. Sixteen experts are engaged to score each WtE technology with respect to every energy trilemma dimension and sub-dimension. Gasification technology is found to be the most feasible option for WtE generation in Pakistan whereas Torrefaction technology is least favorable. It is concluded that the need to shift towards sustainable energy is more than ever to limit the carbon emission and prevent future crisis.

Regional disparities in Preventive measures of COVID-19 pandemic in China. A study from international students' prior knowledge, perception and vulnerabilities.

The COVID-19 pandemic needs immediate solution before inflicting more devastation. So far, China has successfully controlled transmission of COVID-19 through implementing stringent preventive measures. In this study, we analyze the effectiveness of preventive measures taken in thirteen regions of China based on the feedback provided by 1135 international students studying in China. The study uses factor analysis combined with varimax rotation of variables. It was found that awareness raising and dispersing actionable knowledge regarding trust and adapting measures remained significantly important. Therefore, recognition of information gaps, improvements in the level of alertness, and development of preventive measures in each sector are imperative. The findings of this study revealed that trust, students' health, waste disposal, and the efforts of the Chinese government/international institute of education to prevent this pandemic were significantly and positively associated with preventive measures. The results showed that prior knowledge, global pandemics, and food and grocery purchases were firmly related to the preventive measures of COVID-19. Moreover, anxiety, transportation, and economic status were negatively related to the preventive measures. During this epidemic situation, international students suffered various types of mental stresses and anxiety, especially living in most affected regions of China. The study adopted a mixed (qualitative and quantitative) approach where the findings can act as a set of guidelines for governmental authorities in formulating, assisting in the preparation, instructing, and guiding policies to prevent and control the epidemic COVID-19 at national, local, and divisional levels.

Stock market comovements among Asian emerging economies: A wavelet-based approach.

Stock market, is one of the most important financial market which has a close relationship with a country's economy, due to which it is often called the barometer of the economy. Over the past 25 years, the stock markets have been affected by different global economic shocks. Various researchers have analyzed different aspects of these effects one by one, however, this study is an assessment of stock market interrelationship of emeriging Asian economies which include most of the East Asian, and Southeast Asian emerging economies with special focus on China for past decades during which different crisis occurred. We used Morgan Stanley capital international (MSCI) daily indices data for each stock market and compared Chinese stock market with the stock markets of India, Pakistan, Malaysia, Singapore, and Indonesia. We analyzed the data through the individual wavelet power spectrum, cross-wavelet transform and wavelet coherence, to determine the correlation and volatility among the selected stock markets. These model have the power to analyze co-movements among these countries with respect to both frequency and time spaces. Our findings show that there are co-movement patterns of higher frequencies during the crises periods of 1997, 2008 and 2015. The dependency strength among the considered economies is noted to increase in the crisis periods, which implies increased short- and long-term benefits for the investors. From a financial point of view, it has been determined that the co-movement strength among the emerging economies of Asia may have an effect on the VaR (Value at Risk) levels of a multi-country portfolio. Furthermore, the stock market of China shows a high correlation with the other six Asian stock emerging markets in both high and low-frequency spectrums. The association of the south and east Asian stock market with Chinese stock markets show the interconnection of these economies with the economy of China since past two decades. These findings are useful for investors, portfolio managers and the policymaker around the globe.

New environmental performance index for measuring sector-wise environmental performance: a case study of major economic sectors in Pakistan.

The study develops slack-based environmental performance index (SBEPI) to conduct the environmental performance of Pakistan's major sectors of the economy, which include agriculture, manufacturing, transport, power, construction, and mining and quarrying (M&Q) sectors. The index computes environmental efficiency scores based on three critical indicators, total primary energy consumption (input indicator), gross domestic product (desirable output), and CO2 emission (undesirable output). The study undertakes analysis for a period of 10 years from 2008 to 2017. SBEPI score of 1 is set to indicate efficient performance, while score of 0 translates inefficient performance. The results of the studied period reveal that all the sectors underperform for considered indicators. For instance, the top-performing agriculture sector could only achieve an SBEPI score of 0.00008275. The analysis also does not reflect any signs of performance improvement for the studied sectors. To validate the results of this study and highlight the advantages of SBEPI, the study compared SBEPI results with conventional environmental index (EI). The comparison results reveal that SEBPI results are more realistic and the index holds higher discriminatory power than conventional EI. Based on this study's results, some policy recommendations for the government and other sectoral leaders to improve sectoral environmental performance are provided.

The clinical analysis of 157 cases with colorectal polyps treated by endoscopic therapy / 中国基层医药

Objective To analyze the clinical feature,the endoscopic treatment,therapy of complication of colorectal polyps.Methods According to polyps'size,location and shape in 157 patients with colorectal polyps,corresponding endoscopic treatment method was selected and observed the complication of the endoscopic treatment and therapeutic efficacy.Results 219 colorectal polyps were found in 157 patients.Colorectal polyps occurred frequently in rectum and sigmoid colon.Moreover,inflammatory polyps and hyperplastic polyp were the majority,and a small portion of polyps may turn cancerous.By using endoscopic therapy,hemorrhage was found in 12 samples,and the bleeding ratio was only 5.5％.Conclusion A diversity of methods used in endoscopic therapy of colorectal polyps is safe,efficient,resulting in less complications.