Search results

Multilevel inverters become very popular in medium voltage applications owing to their inherent capability of reconciling stepped voltage waveform with reduced harmonic distortion and electromagnetic interference. They have several disadvantages like more number of switching devices required and devices with high voltage blocking and need additional dc sources count to engender particular voltage. So this paper aims to propose a novel tri-source symmetric cascaded multilevel inverter topology with reduced number of switching components and dc sources.

A novel multilevel inverter has been suggested in this study, offering minimal switch count in the conduction channel for the desired voltage level under symmetric and asymmetric configurations. This novel topology is optimized to prompt enormous output voltage levels by employing constant power switches count and/or dc sources of voltage. The topology claims its advantages in generating higher voltage levels with lesser number of voltage sources, gate drivers and dc voltage sources.

The consummation of the proposed arrangement is verified in Matlab/Simulink R2015b, and an experimental prototype for 7-level, 13-level, 21-level, 29-level, 25-level and 49-level operation modes is constructed to validate the simulation results.

The proposed topology operated with six new algorithms for asymmetrical configuration to propel increased number of voltage levels with reduced power components.

The purpose of this study is to introduce a new type of sensor which uses microwave metamaterials and direct-coupled split-ring resonators (DC-SRRs) to measure the dielectric properties of solid materials in real time. The sensor uses a transmission line with a bridge-type structure to measure the differential frequency, which can be used to calculate the dielectric constant of the material being tested. The study aims to establish an empirical relationship between the dielectric properties of the material and the frequency measurements obtained from the sensor.

In the proposed design, the opposite arm of the bridge transmission line is loaded by DC-SRRs, and the distance between DC-SRRs is optimized to minimize the mutual coupling between them. The DC-SRRs are loaded with the material under test (MUT) to perform differential permittivity sensing. When identical MUT is placed on both resonators, a single transmission zero (notch) is obtained, but non-identical MUTs exhibit two split notches. For the design of differential sensors and comparators based on symmetry disruption, frequency splitting is highly useful.

The proposed structure is demonstrated using electromagnetic simulation, and a prototype of the proposed sensor is fabricated and experimentally validated to prove the differential sensing principle. Here, the sensor is analyzed for sensitivity by using different MUTs with relative permittivity ranges from 1.006 to 10 and with a fixed dimension of 9 mm × 10 mm ×1.2 mm. It shows a very good average frequency deviation per unit change in permittivity of the MUTs, which is around 743 MHz, and it also exhibits a very high average relative sensitivity and quality factor of around 11.5% and 323, respectively.

The proposed sensor can be used for differential characterization of permittivity and also as a comparator to test the purity of solid dielectric samples. This sensor most importantly strengthens robustness to environmental conditions that cause cross-sensitivity or miscalibration. The accuracy of the measurement is enhanced as compared to conventional single- and double-notch metamaterial-based sensors.

Restorative experiences relieve fatigue or stress, leading people to feel more energetic. Activation theory and the nature–dose framework hold travel duration as a crucial influence on restorative effects, yet these factors may not demonstrate a simple linear relationship. This paper, thus, aims to explore the relationship between travel duration and restoration based on a survey conducted during a seven-day holiday (the longitudinal data spanned two months); and explore the reasons for this relationship and the mechanisms for lasting restorative effects based on diary analysis.

Mixed methods were used in this study. Questionnaires regarding restorative effects were administered to 232 people at six time points before, during and after a holiday. Participants were also asked to keep a diary during their trips. Data were first tested for common method bias and were then processed via independent sample t-tests, analysis of variance and time-series analysis.

Restorative effects were consistently higher in the travel group than in the non-travel group. Additionally, an inverted U-shaped relationship emerged between travel duration and the restorative effects of a holiday; a moderate duration had stronger restorative effects than a duration that was too long or too short. More importantly, the study found that participants who traveled for a moderate duration (longer or shorter) engaged in non-judgmental challenging (relaxing) activities at least once. They also demonstrated greater eudaimonism (hedonism) and stronger, more sustained restoration versus the original set point. In addition, results revealed how travel activities, emotions, moderators and restorative effects were constructed.

Longitudinal data indicated an inverted U-shaped relationship between travel duration and restoration. Achieving lasting restorative effects requires effort and non-judgmental challenging activities for a moderate travel duration and frequency. The study uncovered mechanisms influencing the relationship between travel experiences and restorative effects. The results offer guidance for research on “travel prescriptions” and for the health and stress relief market.

Inverted U-shaped curve for different travel durations and restorative effects at T3.

The non-judgmental challenging group showed lasting and stronger restorative effects over the next two months.

恢复性体验是指从疲劳或压力状态恢复到感觉更好或更有活力的状态。基于激活理论和自然剂量框架, 旅行停留时长是恢复效果的一个关键变量, 但两者之间可能并不是简单的线性关系。本文旨在（1）基于两个月的纵向数据, 探讨固定假期旅行停留时长与恢复效果之间的关系; （2）根据假期日记内容进一步分析以上关系产生的可能原因及达到持久恢复效果的作用关系。

该研究采用了混合方法。在度假前、度假中和度假后的六个纵向时间点, 对232人进行了与恢复效果有关的问卷调查。且参与者在整个假期中每天记日记。对数据进行了常见方法偏倚、独立样本t检验、方差分析和时间序列分析。

（1）在整个调查期间, 旅行组的恢复效果始终高于非旅行组; （2）旅行停留时长与恢复效果之间的关系呈倒U型, 适度的旅行停留时长可以得到更好的恢复效果; （3）适度（太长或太短）旅行停留时长的参与者更多地参与非评判的挑战性（享乐性）的活动, 表现出更大的实现主义（享乐主义）倾向, 并获得了更强、更持久的恢复效果。进一步地, 研究结果揭示了旅游活动类型、情绪、调节变量和恢复性效果之间的作用关系。

纵向数据分析表明旅行停留时长和恢复效果之间呈现倒U型, 要实现持久的恢复效果需要努力参与非评判的挑战性活动。这项研究揭示了旅行体验和恢复效果之间的关系, 研究结果为促进旅游成为健康和压力缓解市场的处方提供了理论基础和实践指导。

Las experiencias reparadoras alivian la fatiga o el estrés, haciendo que las personas se sientan con más energía. La teoría de la activación y el marco naturaleza-dosis sostienen que la duración del viaje es una influencia crucial en los efectos reconstituyentes que provocan en las personas, aunque estos factores pueden no demostrar una relación lineal simple. Así pues, este artículo pretende 1) explorar la relación entre la duración del viaje y la recuperación de las personas, a partir de una encuesta realizada durante unas vacaciones de 7 días (los datos longitudinales abarcaron dos meses); y 2) explorar las razones de esta relación y los mecanismos de los efectos reparadores duraderos a partir del análisis de diarios.

En este estudio se utilizaron métodos mixtos. Se administraron cuestionarios sobre los efectos reconstituyentes a 232 personas en seis momentos antes, durante y después de unas vacaciones. También se pidió a los participantes que llevaran un diario durante sus viajes. En primer lugar, se comprobó que los datos no presentaran sesgos por métodos comunes y, a continuación, se procesaron mediante pruebas t de muestras independientes, análisis de la varianza y análisis de series temporales.

Los efectos reparadores fueron sistemáticamente mayores en el grupo que viajó que en el que no viajó. Además, surgió una relación en forma de U invertida entre la duración del viaje y los efectos reconstituyentes de las vacaciones; una duración moderada tuvo efectos reparadores más fuertes que una duración demasiado larga o corta. Por último, los participantes que viajaron durante una duración moderada (más larga o más corta) realizaron más actividades estimulantes no perjudiciales (relajantes). También demostraron un mayor eudaimonismo (hedonismo) y una recuperación más fuerte y sostenida en comparación con el punto de partida inicial. Los resultados revelaron cómo se relacionaban las actividades de viaje, las emociones, los moderadores y los efectos reparadores.

Los datos longitudinales indicaron una relación en forma de U invertida entre la duración del viaje y la recuperación de las personas. Lograr efectos reparadores duraderos requiere esfuerzo y actividades para una duración moderada del viaje. El estudio descubrió mecanismos que influyen en la relación entre las experiencias de viaje y los efectos reconstituyentes. Los resultados ofrecen orientaciones para la investigación sobre las “recetas de viaje” y para el mercado de la salud y el alivio del estrés.

In real life, excitations are highly non-stationary in frequency and amplitude, which easily induces resonant vibration to structural responses. Conventional control algorithms in this case cannot guarantee cost-effective control effort and efficient structural response alleviation. To this end, this paper proposes a novel adaptive linear quadratic regulator (LQR) by integrating wavelet transform and genetic algorithm (GA).

In each time interval, multiresolution analysis of real-time structural responses returns filtered time signals dominated by different frequency bands. Minimization of cost function in each frequency band obtains control law and gain matrix that depend on temporal-frequency band, so suppressing resonance-induced filtered response signal can be directly achieved by regulating gain matrix in the temporal-frequency band, leading to emphasizing cost-function weights on control and state. To efficiently subdivide gain matrices in resonant and normal frequency bands, the cost-function weights are optimized by a developed procedure associated to genetic algorithm. Single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) structures subjected to near- and far-fault ground motions are studied.

Resonant band requires a larger control force than non-resonant band to decay resonance-induced peak responses. The time-varying cost-function weights generate control force more cost-effective than time-invariant ones. The scheme outperforms existing control algorithms and attains the trade-off between response suppression and control force under non-stationary excitations.

Proposed control law allocates control force amounts depending upon resonant or non-resonant band in each time interval. Cost-function weights and wavelet decomposition level are formulated in an elegant manner. Genetic algorithm-based optimization cost-efficiently results in minimizing structural responses.

The purpose of this paper is to propose a competitiveness measurement system for start-ups considering multiple critical success factors.

The methodological approach uses concepts from key performance indicators (KPIs) and multi-criteria decision analysis (MCDA) based on the fuzzy AHP (FAHP) methodology to weight the criteria related to fundamental points of view (FPVs) and critical success factors (CSFs).

Data collection was performed with 21 specialists and 28 start-ups, which returned the weights and performance of CSFs and FPVs related to the start-ups’ competitiveness. The results show only one start-up had a highly competitive global performance. In addition, all start-ups showed low competitiveness related to industry 4.0 technologies.

The article collaborates with existing research as a starting point for discussions on the subject, considering that previous research did not address the measurement of the start-ups’ competitiveness level through multiple factors, as developed in this article. In addition, we provide decision-makers and other stakeholders in the start-up ecosystem with a robust measurement system to assess business competitiveness and diagnose the company’s situation.