Search results

The purpose of this work was to characterize NiMn₂O₄ spinel-based thermistor powder, to use it in screen printing technology to fabricate temperature sensors, to study their performance for different sintering temperatures of thermistor layer, with and without insulative cover, as well as to investigate stability of the fabricated thermistors and their applicability in water quality monitoring.

After the characterization of starting NiMn₂O₄ spinel-based thermistor powder, it was converted to thick film paste which was screen printed on alumina substrate. Thermistor layers were sintered at four different sintering temperatures: 980°C, 1050°C, 1150°C and 1290°C. An interdigitated pattern of Ag-Pd conductive layer was used to reduce the resistance. Temperature-resistance characteristics were investigated in air and water, with and without insulative cover atop the thermistor layer. Stability of the fabricated thermistors after aging at 120°C for 300 h was also examined.

Thick film NiMn₂O₄ spinel thermistors, prepared by screen printing and sintering in the temperature range 980°C–1290°C, exhibited good negative temperature coefficient (NTC) characteristics in the temperature range −30°C to 145°C, including high temperature coefficient of resistance, good stability and applicability in water.

This study explores the range of sintering temperature that can be applied for NiMn₂O₄ thermistor thick films without compromising on the temperature sensing performance in air and water, as well as stability of the thermistors after aging at elevated temperatures.

Unconventional machining processes, particularly ultrasonic vibration cutting (UVC), can overcome such technical bottlenecks. However, the precise mechanism through which UVC affects the in-service functional performance of advanced aerospace materials remains obscure. This limits their industrial application and requires a deeper understanding.

The surface integrity and in-service functional performance of advanced aerospace materials are important guarantees for safety and stability in the aerospace industry. For advanced aerospace materials, which are difficult-to-machine, conventional machining processes cannot meet the requirements of high in-service functional performance owing to rapid tool wear, low processing efficiency and high cutting forces and temperatures in the cutting area during machining.

To address this literature gap, this study is focused on the quantitative evaluation of the in-service functional performance (fatigue performance, wear resistance and corrosion resistance) of advanced aerospace materials. First, the characteristics and usage background of advanced aerospace materials are elaborated in detail. Second, the improved effect of UVC on in-service functional performance is summarized. We have also explored the unique advantages of UVC during the processing of advanced aerospace materials. Finally, in response to some of the limitations of UVC, future development directions are proposed, including improvements in ultrasound systems, upgrades in ultrasound processing objects and theoretical breakthroughs in in-service functional performance.

This study provides insights into the optimization of machining processes to improve the in-service functional performance of advanced aviation materials, particularly the use of UVC and its unique process advantages.

This study aims to propose an adaptive fractional-order sliding mode controller to solve the problem of train speed tracking control and position interval control under disturbance environment in moving block system, so as to improve the tracking efficiency and collision avoidance performance.

The mathematical model of information interaction between trains is established based on algebraic graph theory, so that the train can obtain the state information of adjacent trains, and then realize the distributed cooperative control of each train. In the controller design, the sliding mode control and fractional calculus are combined to avoid the discontinuous switching phenomenon, so as to suppress the chattering of sliding mode control, and a parameter adaptive law is constructed to approximate the time-varying operating resistance coefficient.

The simulation results show that compared with proportional integral derivative (PID) control and ordinary sliding mode control, the control accuracy of the proposed algorithm in terms of speed is, respectively, improved by 25% and 75%. The error frequency and fluctuation range of the proposed algorithm are reduced in the position error control, the error value tends to 0, and the operation trend tends to be consistent. Therefore, the control method can improve the control accuracy of the system and prove that it has strong immunity.

The algorithm can reduce the influence of external interference in the actual operating environment, realize efficient and stable tracking of trains, and ensure the safety of train control.

The electrical properties of piezoelectric vibrators have a crucial influence on the operating state of ultrasonic motors. In order to solve the problem that the current piezoelectric vibrator generates a large amount of heat during vibration to degrade its performance, which in turn affects the normal operation of ultrasonic motors, this paper prepares a novel piezoelectric vibrator and tests its maximum vibration velocity under the working condition, which is more than twice as much as that of the current commercial PZT-8.

The crystal structures of the samples were analyzed by using an X-ray diffractometer. For microstructure observation, samples were observed by scanning electron microscope (SEM). The quasi-static piezoelectric coefficient meter (ZJ-3AN) was used for piezoelectric measurement. Dielectric properties were measured by utilizing an impedance analyzer (Agilent 4294A) with a laboratory heating unit. Ferroelectric hysteresis loops were obtained using a ferroelectric analyzer (Radiant, Multiferroic 100). A Doppler laser vibrometer (Polytec PSV-300F, Germany) and a power amplifier were used for piezoelectric vibration measurements, during which the temperature rise was determined by an infrared radiation thermometer (Victor 303, China).

The ceramics exhibit enhanced piezoelectric performance at 0.1–0.4 mol% of Yb doping contents. The ceramic of 0.4 mol% Yb reaches the maximal internal bias field and presents a larger mechanical quality factor of 1,692 compared with that of 0.2 mol% Yb-doped ceramic, in spite of a slightly decreased dielectric constant of 439 pC/N, the unit of the piezoelectric constant, which is the ratio of the local charge (pC) to the frontal force (N) and electromechanical coupling coefficient of 0.63. The vibrator with this large mechanical quality factor ceramic displays a vibration velocity of up to 0.81 m/s under the constraint of 20 °C temperature rising, which is much higher than commercial high-power piezoelectric ceramics PZT-8.

The enhanced high-power properties of the piezoelectric vibrator by Yb doping may provide a potential application for the high-performance USM and offer the possibility of long-term stable operation under high power for special equipment like USM. In the subsequent phase of research, the novel PZT-based high-power piezoelectric vibrator can be utilized in the USM, and the motor's performance will be evaluated under aerospace conditions to objectively assess the reliability of the piezoelectric vibrator.

Eradicating extreme poverty remains one of the most significant and challenging sustainable development goals (SDGs) in the Middle East and North African (MENA) region. The latest World Bank statistics from 2018 show that extreme poverty in MENA increased from 2.6% to 5% between 2013 and 2015. MENA ranks third among developing regions for extreme poverty and fell short of halving extreme poverty by 2015 – the target established by the United Nations’ (UN) millennium development goals, the precursor to the SDGs. The purpose of this study is to analyze the impact of financial inclusion on extreme poverty for a sample of 34 countries over the period 1990–2017.

Using system general method of moments dynamic panel estimation methodology on annual data for 11 MENA countries and 23 emerging markets (EMs) over the period 1990 – 2017, this study begins by estimating the impact of financial inclusion – using measures of access and usage – on the eradication of extreme poverty by 2030, the first goal of the SDGs.

The results of the study indicate that, on one hand, financial access measures have a positive, statistically significant impact on reducing extreme poverty for the full sample and the MENA region. The second part of the study uses a gap analysis against four poverty targets – 0%, 1.5%, 3% and 5% – and shows that no MENA country and few EM countries will be able to close the extreme poverty gap and reach the target of 0% by 2030 by depending solely on improvements in financial access. These targets are based on the two benchmarks set by the World Bank and the UN, with intermediaries to capture error and give a fuller picture of what is possible. However, if improvements in financial inclusion alone can bring every EM and MENA country except Djibouti and Romania to bring the most accessible target of reducing global extreme poverty to no more than 5% by 2030.

While research on poverty reduction in the region tends to focus on financial development and governance, less attention has been paid to the role of financial inclusion. SDG 1 – eliminating poverty in all its forms – explicitly highlights the importance of access to financial services. Indeed, evidence from Argentina, India, Kenya, Malawi, Niger and other countries demonstrates the ways in which financial inclusion can impact poverty (Klapper, El-Zoghbi and Hess, 2016). When people are included in the financial system, they are better able to improve their health, invest in education and business and make choices that benefit their entire families. Financial inclusion advances governments, too: introducing vast segments of the population into the financial system by digitizing social transfers, for example, can cut government costs and reduce leakage, with benefits that ripple across society. Yet, the links between financial inclusion and poverty reduction in MENA are less established. This study aims to analyze the importance of financial inclusion in addressing extreme poverty by 2030, the year UN member states set as a target for achieving the SDGs.

Legislation plays a vital role in solving carbon emissions reduction and climate change issues. China began to implement a low-carbon economic policy in 2010, but the effect of the policy needs to be evaluated. Accordingly, this paper aims to discuss China’s low-carbon policy through exploring the following two questions, namely, whether the policy effect reaches the expected goal and whether the policy effects will balance economic development and emission reduction. Then, the paper puts forward suggestions for the improvement of China’s low-carbon policy.

This paper is organized around three distinct aspects of policy effect evaluation. This paper uses the synthetic control method to construct a policy effect evaluation model and conducts a quasi-natural experiment. The paper selects annual panel data from 2003 to 2015, which is selected from 33 provinces. A comparative analysis of carbon dioxide emissions, energy consumption and economic development between Hubei Province and Liaoning Province.

The results reveal that the implementation of the low-carbon pilot province policy in 2010 has a significant impact on the emission reduction effect of Liaoning Province, but the impact on the emission reduction effect of Hubei Province is not significant. The carbon emission trading system implemented in 2012 has reduced the emission reductions in Hubei Province and Liaoning Province has achieved better emission reduction effects after the implementation of this policy. After the implementation of the policy, the economic development of Hubei Province has been improved, but it has not brought help to the economic development of Liaoning Province. These findings provide new insights into the use of an emissions trading system for improving economic development and ultimately facilitate the attainment of the broader goal of sustainability.

This paper proposes an innovative policy effect evaluation method by considering the status of unit gross domestic product, fixed asset investment in the energy industry, energy consumption, emission reduction technology innovation and other evaluation indicators. This paper contributes to broadening current methods of policy effect evaluation in China.

The purpose of this study is to examine the impact of economic growth, trade openness and manufacturing on CO2 emissions in India.

The study employed autoregressive distributive lag (ARDL) bounds test approach and uses CO2 emissions, trade, manufacturing and GDP per capita to examine the relationship using an annual time series data from World Development Indicators during 1971 to 2016.

Results depict that there exists a long-run relationship between CO2 emissions and other variables. Trade openness significantly reduces CO2 emissions, whereas manufacturing and GDP have a significant and positive impact on CO2 in the long run.

The findings of the study contribute to the body of knowledge by providing new evidence on the relationship between developmental metrics and the environment. These findings are critical for policymakers and regulatory bodies to focus on economic development without jeopardizing environmental degradation.

In order to keep its commitment to sustainability, India needs to develop policies that encourage cleaner production methods and establishment of non-polluting industries. Simultaneously, it must disincentivize industries that emit CO2 by policy frameworks such as carbon taxes, pollution taxes or green taxes.

None of studies examine at how these environmental factors interact in India. Kilavuz and Dogan (2020) used the same variables, but their scope was limited to Turkey. As a result, the study is the first to examine this relationship for India, contributing to the body of knowledge on economic growth, manufacturing, trade openness and environmental concerns.

This study aims to investigate the service performances of a new full-section asphalt concrete waterproof sealing structure (FSACWSS) for the high-speed railway subgrade through on-site tracking, monitoring and post-construction investigation.

Based on the working state of the waterproof sealing structure, the main functional characteristics were analyzed, and a kind of roller-compacted high elastic modulus asphalt concrete (HEMAC) was designed and evaluated by several groups of laboratory tests. It is applied to an engineering test section, and the long-term performance monitoring and subgrade dynamic performance testing system were installed to track and monitor working performances of the test section and the adjacent contrast section with fiber-reinforced concrete.

Results show that both the dynamic performance of the track structure and the subgrade in the test section meet the requirements of the specification limits. The water content in the subgrade of the test section is maintained at 8–18%, which is less affected by the weather. However, the water content in the subgrade bed of the contrast section is 10–35%, which fluctuates significantly with the weather. The heat absorption effect of asphalt concrete in the test section makes the temperature of the subgrade at the shoulder larger than that in the contrastive section. The monitoring value of the subgrade vertical deformation in the test section is slightly larger than that in the contrastive section, but all of them meet the limit requirements. The asphalt concrete in the test section is in good contact with the base, and there are no diseases such as looseness or spalling. Only a number of cracks are found at the joints of the base plates. However, there are more longitudinal and lateral cracks in the contrastive section, which seriously affects the waterproof and sealing effects. Besides, the asphalt concrete is easier to repair, featuring good maintainability.

This research can provide a basis for popularization and application of the asphalt concrete waterproof sealing structure in high-speed railways.

The relationship between risk and return has been widely analysed in the scope of listed companies. However the present literature leaves uncovered an important study area with regards to privately held firms. In order to cover this gap, this study analyses the risk-return trade-off in the context of private enterprises. Furthermore, the authors incorporate the contingent effect of being a family firm on the abovementioned relationship.

Using information from the SABI (Sistema de Análisis de Balances Ibéricos) database, a sample of 2,297 private manufacturing firms were analysed for the period of 2009–2016. So as to ascertain the proposed hypotheses, dynamic panel data methodology was applied. Specifically, the authors estimated the two-step general method of moments (GMM).

The obtained findings reveal that, according to prospect theory arguments, privately held firms adopt a conservative attitude toward risk when results are higher than a target level, while becoming risk seeking when results are lower than a target level. Moreover, the fact of being a family firm softens the risk-return relationship both when performance is above the target level and also when firms find themselves in the lowest performing case.

This article is, to the best of the authors' knowledge, one of the first studies dealing with the risk-return relationship in a privately held firm context. Moreover, the inclusion of being a family firm as a contingent factor in the abovementioned link is a complete novelty.

La relación riesgo-rentabilidad ha sido ampliamente analizada en el ámbito de las empresas cotizadas. Sin embargo, la literatura existente deja al descubierto una importante área de estudio en relación con las empresas no cotizadas. Para cubrir esta brecha, el presente estudio analiza el binomio riesgo-rentabilidad en el contexto de empresas privadas. Adicionalmente, incorporamos el efecto contingente de ser una empresa familiar sobre esta relación.

Utilizando información de la base de datos SABI (Sistema de Análisis de Balances Ibéricos) se analizó una muestra de 2.297 empresas manufactureras privadas para el período 2009–2016. Para comprobar las hipótesis propuestas se aplicó la metodología de datos de panel, específicamente, utilizamos el Método de los Momentos Generalizado (GMM).

Los resultados muestran que, de acuerdo con la Teoría Prospectiva, las empresas no cotizadas presentan una mayor aversión al riesgo cuando su nivel de rentabilidad es superior al valor de referencia establecido, mientras que presentan una mayor propensión al riesgo cuando su rentabilidad es inferior al valor de referencia. Además, el hecho de ser una empresa familiar suaviza la relación riesgo-rentabilidad en ambos escenarios.

Este es uno de los primeros estudios en abordar la relación riesgo-rentabilidad en el contexto de empresas no cotizadas. Además, la inclusión de ser una empresa familiar como factor contingente es completamente novedosa.

This paper aims to estimate the impact of the 2000s commodity boom in the major Latin American economies.

The author used a structural vector autorregresive analysis where the selection of variables is conditional on a New Keynesian Model for a small open economy.

The evidence indicates that the Argentinean nominal exchange rate appreciated less while its output and inflation grew more than those of the other nations when subjected to commodity shocks. These results are interpreted as a more aggressive leaning-against-the-wind intervention by Argentina, probably to avoid the Dutch disease. Although the effects with regard to output were indeed stronger in Argentina, this was only at the expense of higher inflation and volatility suffered during the boom.

At the time of the writing of this paper, no work had evaluated Argentinean underperformace to the manner in which its exchange rate policy was handled in comparison with the rest of the region during the boom. This paper intends to fill this gap.