Although the pedagogy of blended learning in higher education has been well-accepted since 2000, its dimension has been changing, mainly due to the incessant technological innovations. The impact ...recorded on students' experience has been reliant on various factors. Some of these factors are cultural diversity, technical abilities, level of organisational support, language difficulties, educational background, learning environment, and instructional design, among others. In this study, the acceptance and use of technology by international MBA students have been reassessed in the blended learning environment. The motivation for the selection of the cohort of international MBA students as a sample was to enable the inclusion of diversity as one of the focal points of the study. A two-cycle model of action research was adopted to reassess the use of technology and compare the attainment of learning outcomes between the blended and traditional learning approaches. Moreover, multiple regressions were employed using the unified theory of acceptance and use of technology (UTAUT) to test the significance of each variable collected from the survey on the students' learning experience and engagement. Our results have suggested that students' engagement is determined by positive learning experience without any bias toward traditional or blended learning approach. Students' age group was found to be relevant in the determination of behavioural intention, social influence, effort expectancy, performance expectancy and facilitating conditions towards the effective use of technology and blended learning. Students' gender was an irrelevant factor in the success of a blended learning approach.
In this paper, a long-range dual-band rectenna for harvesting ambient radio frequency (RF) energy from GSM/900 and GSM/1800 is presented. Theoretical analysis of the proposed dual-band impedance ...matching network (IMN) is conducted using a modified <inline-formula> <tex-math notation="LaTeX">\Pi </tex-math></inline-formula>-section matching network (MN). The RF-rectifier is integrated with a dual-band inverted-F monopole antenna. The rectenna circuit complexity is minimized by introducing a dual-band IMN, which plays a significant role in improving the harvester RF-to-dc power conversion efficiency (PCE). Measurement results of the proposed design achieved a peak RF-to-dc PCE of 12.93% and 8.0% for an input power of −30 dBm at 0.9 GHz, and 1.8 GHz, respectively. The RF harvester ambiance measurement attained an output dc voltage of 0.374 V. The circuit generates 0.747 V using a low-powered bq25504-674 evaluation module (EVM). Thus, adequate energy management of the proposed rectenna can be used to power many low-powered devices from the harvested ambient RF energy.
This paper proposes the design of an efficient ambient solar energy harvesting (SEH) system with enhanced protection for low‐power devices. The proposed SEH system is designed and fabricated on a 1.6 ...mm Flame Retardant 4 (FR4) substrate using EasyEDA software. The harvester consists of a 3 W monocrystalline solar panel, a solar charger module with maximum power point tracking, a lithium‐ion rechargeable battery and a battery protection integrated circuit, and a DC–DC converter. Each of the SEH system component modules is optimized for better performance. The proposed energy harvester achieves a peak power conversion efficiency of 81.22% with a total output power of 2.35 W by using a CN3791 battery charger module. This approach is cost‐effective, highly sustainable, and virtually maintenance‐free. It can be deployed in various low‐powered devices such as wireless sensor network nodes and Internet of Things microcontrollers to extend their battery lifetimes, thereby achieving environmental‐friendly and sustainable energy harvesting.
This paper presents the deployment of a hybrid energy harvesting system that combines a wireless energy harvesting (EH) system and a 6 V, 170 mA monocrystalline solar energy derived from the Sun’s ...rays. The hybrid energy harvesting (HEH) system comprises the rectifier, the solar cell panel, the charging circuit, and the EM4325 embedded RFID tag. This study aims to design an efficient EH system capable of increasing the read range of an active RFID tag. The proposed approach integrates a meandered line radio frequency identification (RFID) tag with an EM4325 IC chip as the receiver antenna. A halfwave doubler RF rectifier circuit is connected to the antenna using a 50 Ω SMA connector to convert the captured RF waves into usable electrical power. A solar energy charging module equipped with a Maximum Power Point Tracking (MPPT) system, a rechargeable lithium-ion battery, and a DC-DC converter is configured to manage and store the harvested energy efficiently. The UHF tag antenna operates at 919 MHz, achieving a peak gain of 3.54 dB. The proposed rectenna achieves a maximum measured harvested power conversion efficiency (PCE) of 55.14% for an input power (Pin) of 15 dBm at a distance of 5.10 cm, while the solar cell panel realizes 3.92 W of power. Experimental results demonstrate the hybrid harvester system’s effectiveness, achieving a PCE of 86.49% at an output voltage (VDC) of 5.35 V. The main advantage of this approach is the creation of a compact hybrid RF and solar EH system by combining the solar cell panel with the antenna, thus enabling multi-functionality.
Abstract
This paper described a four-band implantable RF rectifier with simplified circuit complexity. Each RF-rectifier cell is sequentially matched to the four operational frequencies to accomplish ...the proposed design. The proposed RF rectifier can harvest RF signals at 1.830, 2.100, and white space Wi-Fi bands between 2.38 to 2.68 GHz, respectively. At 2.100 GHz, the proposed RF harvester achieved a maximum (radio frequency direct current) RF-to-DC power conversion efficiency (PCE) of 73.00% and an output DC voltage
$$V_{DC}$$
V
DC
of 1.61 V for an RF power of 2 dBm. The outdoor performance of the rectenna shows a
$$V_{DC}$$
V
DC
of 0.440 V and drives a low-power bq25504-674 evaluation module (EVM) at 1.362 V. The dimension of the RF-rectifier on the FR-4 PCB board is 0.27
$$\lambda _{g}$$
λ
g
$$\times$$
×
0.29
$$\lambda _{g}$$
λ
g
. The RF-rectifier demonstrates the capacity to effectively utilize the frequency domain by employing multi-band operation and exhibiting a good impedance bandwidth through a sequential matching technique. Thus, by effectively controlling the rectenna’s ambient performance, the proposed design holds the potential for powering a range of low-power biomedical implantable devices. (BIDs).
In this paper, a compact rectifier, capable of harvesting ambient radio frequency (RF) power is proposed. The total size of the rectifier is 45.4 mm × 7.8 mm × 1.6 mm, designed on FR-4 substrate ...using a single-stage voltage multiplier at 900 MHz. GSM/900 is among the favorable RF Energy Harvesting (RFEH) energy sources that span over a wide range with minimal path loss and high input power. The proposed RFEH rectifier achieves measured and simulated RF-to-dc (RF to direct current) power conversion efficiency (PCE) of 43.6% and 44.3% for 0 dBm input power, respectively. Additionally, the rectifier attained 3.1 V DC output voltage across 2 kΩ load terminal for 14 dBm and is capable of sensing low input power at −20 dBm. The work presents a compact rectifier to harvest RF energy at 900 MHz, making it a good candidate for low powered wireless communication systems as compares to the other state of the art rectifier.
The paper re-examines whether investors can predict oil and gas stock prices for abnormal returns using autocorrelation-based trading and filter rules and moving average strategies. In this paper, ...short and long lengths moving averages are employed and their performances are measured against the returns from simple buy and hold investment strategy. As a result, the paper finds that employed trading rules do not indicate that investors can make abnormal returns in oil and gas stocks. Moreover, the performances of short and long moving averages in predicting abnormal returns also do not suggest a conclusive evidence that any of the moving averages can result in more returns compared to others.
The Black's leverage effect hypothesis postulates that a negative stock return innovation increases the financial leverage of a firm since the value of equity decreases at a given level of debt, ...which, in turn, creates a higher equity return volatility in the future. The paper is aimed at investigating the authenticity of the Black's leverage effect hypothesis and the relationship between negative stock returns and the financial leverage of the UK oil and gas stocks from 2004 to 2015. For each stock, exponential generalised autoregressive conditional heteroscedasticity model was estimated using Fama-French-Carhart 4-factor asset pricing model to extract the difference between the effects of negative and positive stock return innovations, regarded as leverage effect. The leverage effect parameter was further regressed on the financial leverage ratios of the book value of long-term debt to total assets, interest expenses to total assets and long-term debt to market value of equity to examine whether variation in the leverage parameter was as a result of variation in the firm's financial leverage. The findings of the study show that Fama-French-Carhart four risk factors of market, size effect, value and momentum were significant in the stock returns of most of the oil and gas companies. The mixed results in the significance level of the factors were attributed to the differences in individual firm characteristics. An evidence of leverage effect was also found in all the oil and gas stock returns but no evidence to suggest it was derived from the changes in the financial leverage of the companies. The implication of these findings for financial managers in the oil and gas industry was that while asset pricing frameworks such as CAPM and its extensions are relevant in determining oil stock returns, the level of gearing is irrelevant, albeit it has been recognised as one of the determinants of the firm's level of risk.
The design of a wideband circular-slot antenna for RF signal harvesting is reported in this work. The proposed design frequency range accommodates the leading contributors to the available RF signals ...accessible by the RFEH node. These widely utilized frequency bands comprise GSM1800, UMTS2100, Wi-Fi2.450, and LTE2600. The antenna geometry comprises circular-ring radiating component filled with two orbital circular and rectangular slots. At the bottom plane, a pair of rectangular and semirectangular-circle slits are integrated. The antenna presented is designed on a double layer of 1.6 mm high FR-4 substrate. The source antenna achieved a simulated and measured impedance bandwidth (BW) of 1.510 and 1.590 GHz, amounting to 68% and 73% fractional BW (FBW), covering -10 dB reflection coefficient (|S11|) between 1.640 to 3.150 GHz and 1.550 to 3.140 GHz, in that order. The wideband circular-slot source antenna realized a maximum measured gain of 1.88, 2.13, 2.81, 3.22, and 4.32 dBi for 1.800, 2.100, 2.450, 2.650, and 3.20 GHz, respectively. The proposed design dimension on the printed board is 0.61 λg × 0.70 λg. The improved antenna gain is obtained from a circular parasitic patch coupled to the defected ground structure (DGS) for better RF energy harvesting in an ambient environment.
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