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Online education has significantly gained popularity due to new technology and more importantly, the growing impact of the digitalization of the economy. Despite its prominent advantages such as accessibility, affordability and flexibility, the effectiveness of online education is still a constant debate and needs extensive investigations in different research contexts. This study aimed to evaluate the effectiveness of online learning in comparison to traditional learning in the context of English language teaching. This descriptive study was undertaken with learners of English as a foreign language (EFL) in English proficiency preparation classes, employing an online questionnaire together with final scores of proficiency tests. The results revealed that the participants had relatively positive perceptions towards online learning in all four aspects: course content, teachers, learning environment and course supports. The significant finding was that when comparing the final results of the VSTEP exams, the online learners generally were able to perform better than the learners in traditional classrooms, though the difference was not largely remarkable. Online education in the new normal will continue to excel and the effectiveness of this learning mode certainly needs further investigation from different perspectives.

In Vietnam, the demand for enhancing speaking skills is continuously increasing. Selecting appropriate and effective teaching strategies, therefore, is essential. Scaffolding strategies are considered one of the most effective in enhancing speaking performance. This research is conducted to investigate EFL teachers’ perceptions of the impact of scaffolding strategies on learners’ speaking performance and teachers’ practices on scaffolding strategies in speaking classes. Both quantitative and qualitative data are collected from 186 EFL teachers working at language centers in southern Vietnam. The results reveal that scaffolding strategies are highly appreciated. The benefits are detailedly analyzed beside suggested solutions for existing challenges in utilizing these strategies to scaffold learners in speaking classes.

LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode materials can operate at extremely high voltages and have exceptional energy density. However, their use is limited by inherent structure instability during charge/discharge and exceptionally oxidizing Ni4+ at the surface. Herein, we have developed a citrate-assisted deposition concept to achieve a uniform lithium-conductive LiNbO3 coating layer on the NCM523 surface that avoids self-nucleation of Nb-contained compounds in solution reaction. The electrode–electrolyte interface is therefore stabilized by physically blocking the detrimental parasitic reactions and Ni4+ dissolution whilst still maintaining high Li+ conductivity. Consequently, the modified NCM523 exhibits an encouraging Li-storage specific capacity of 207.4 mAh g−1 at 0.2C and 128.9 mAh g−1 at 10C over the range 3.0–4.5 V. Additionally, a 92% capacity retention was obtained after 100 cycles at 1C, much higher than that of the pristine NCM523 (73%). This surface engineering strategy can be extended to modify other Ni-rich cathode materials with durable electrochemical performances.

A series of novel single and double branched carbazole-based red-absorbing cationic dyes without (CSI and CDI) and with (CST and CDT) a thiophene spacer have been synthesized for p-type dye-sensitized solar cells ( p -DSSCs). The introduction of the red-absorbing cationic acceptor/thiophene spacer led to the broadening and bathochromic shift of the absorption maxima from an onset of 600 nm for CSI to 800 nm for CDT as well as improved molar absorptivity. The introduction of the double branching/thiophene spacer lowered the lowest unoccupied molecular orbital (LUMO) levels of CDI, CST, and CDT, making their potentials more positive than that of CSI. Among these, the double branched CDI exhibited the highest conversion efficiency of 0.112%. Furthermore, all of the dyes examined outperformed the standard C343 dye (0.062%), measured under similar fabrication conditions. Despite the decreased photovoltaic performance as a result of the introduction of the thiophene spacer, overall, the double branched dyes exhibited better interfacial charge transfer that led to higher J SC and V OC values compared to those of singly branched dyes. Electrochemical impedance spectroscopy analysis showed that double branched dyes have much lower charge transfer resistance and increased hole lifetime than single branched dyes. Density functional theory (DFT) and time-dependent DFT calculations were performed to theoretically characterize the optical and electrochemical properties of the synthesized dyes.

The efficiency of tandem pn-dye-sensitized solar cells (pn-DSCs) has been limited by the poor performance of the available p-DSCs. A facile approach of introducing a compact NiO blocking layer into an active NiO photocathode network of p-DSCs and pn-DSCs is presented to enrich the power conversion efficiency (PCE) using a Co2+/3+ redox mediator. Two photoelectrodes sensitized with different dyes (SQ for n-DSC and P1 for p-DSC) have a complementary nature in absorbing solar irradiation at different wavelengths. The constructed pn-DSC demonstrates an enhanced photovoltage compared to n-DSC, resulting in an overall PCE of 1.486%. This PCE is further improved to 1.913% by the addition of an optimized NiO blocking layer to the p-DSC; this was prepared via spin-coating with a nickel acetate precursor solution. All photovoltaic parameters were significantly increased with the introduction of a blocking layer compared to a bare cell.

Two double branched organic dyes (T1I and T2I) were synthesized, characterized, and employed as photosensitizers in p-type dye-sensitized solar cells (p-DSSC); we have compared with corresponding s...

In this paper, we have studied the effect of LiI and I2 concentrations on the photovoltaic properties of dye-sensitized solar cells (DSSCs) based on NiO. For all concentrations of iodine, the photo...

Metal-organic frameworks (MOFs) have lately obtained great attention of scientists as potential materials applied for supercapacitor electrodes. Due to their crystalline structure, MOFs show proper electrochemical double-layer capacitance at the enlarged specific surface area of the material and the mechanical supports for the composite materials. In this study, Zn-MOF was synthesized and composited with reduced graphene oxide (rGO) to be applied as a supercapacitor electrode material. To improve the electrodes working performance, polyaniline (PANI) was synthesized by different methods and added to the composite. The electrochemical properties of these materials were studied to identify the effect of PANI and Zn-MOF on the electrode materials. Among the composites obtained, the best specific capacitance of about 372 F/g was obtained at 0.1 A/g charge-discharge analysis of rGO/Zn-MOF@PANI sample due to its large surface with high pores sizes. The capacitance retentions of electrodes were also tested to decipher the effect caused by varied composites fabrication.

The introduction of different thicknesses of a compact NiO blocking layer coating with different spin speeds on FTO and followed by a coating of photoactive NiO electrode for p-type dye-sensitized solar cells (p-DSCs). This study examined the fabrication of a compact NiO blocking layer by decomposing an ethanolic precursor solution of nickel acetate tetrahydrate. The DCBZ dye used as the photosensitizer for the NiO electrode in the p-DSCs device and their performances have been analyzed. The enhancement of photovoltaic performance and resulted from an increase in the power conversion efficiency (η). The electrochemical impedance spectroscopy (EIS) measurement demonstrated that charge recombination was suppressed when a compact NiO blocking layer was applied. The results showed that the best p-DSC was achieved by employing 3000 rpm spin-coated process for different times of blocking layer.

A photoactive NiO electrode for p-type dye-sensitized solar cells (p-DSCs) has been equipped by the introduction of different coatings of a compact NiO blocking layer. This study examined the facile process for the fabrication of a compact NiO blocking layer by decomposing an ethanolic precursor solution of nickel acetate tetrahydrate. The P 1 -dye used as the photosensitizer for the NiO electrode in the p-DSCs device and their performances have been analyzed. The enhancement of both short-circuit photocurrent (Jsc) and fill factor (FF) resulted in a twofold increase in the power conversion efficiency (η). The electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) measurements demonstrated that charge recombination was suppressed when a compact NiO blocking layer was applied. The best p-DSC was achieved by employing spin-coated process for twice. The carrier lifetime of all the devices with a compact NiO blocking layer was improved compared to the bare cell.

Polymer nanocomposites that based on combination of nanomaterials (such as nanoparticles, nanotubes, nanorods, nanofibers, and nanosheets) and polymeric matrices are receiving great attention in research and application. However, separate and homogenous dispersion rather than aggregates of nanoparticles into matrices meet big difficulty due to large interaction between nanoparticles. The poor dispersion leads to low properties of nanocomposites. In this study, we find out the appropriate method to separately disperse cerium oxides (CeO2) nanoparticles into natural rubber, aiming to increase mechanical properties of natural rubber. The SEM images were used to evaluate the dispersion of nano CeO2 in natural rubber matrix. The mechanical properties of nanocomposites were measured after vulcanization to investigate effects of nano CeO2 amount on prepared composite. The findings exhibited that the addition of CeO2 by dispersion of nano CeO2 in water via ultrasonication before mixing with rubber latex, signific...

Two new ullazine-based organic dyes have been synthesized for applications in nanocrystalline TiO2-based dye-sensitized solar cells (DSSCs). Overall conversion efficiencies up to 3.63% were obtained for DSSCs based on these dyes. The dye with a tert-butyl antenna exhibited a higher and redshifted absorption pattern resulting in increased light-harvesting property. Compared to the unsubstituted dye, the photocurrent density, open-circuit photovoltage and overall power conversion efficiency (PCE) of solar cells based on the tert-butyl substituted dye are improved. The decreased PCE of the solar cell based on unsubstituted dye results mainly from the increased recombination rate and decreased electron lifetime, as evidenced from impedance and photovoltage decay measurements. Density functional theory (DFT) and time-dependent DFT calculations were performed to predict the geometries, electronic structure, and the optical and electrochemical properties of the dyes.

Two simple organic dyes (J1 and J2) containing julolidine as the electron donor were synthesized. The simple structure of julolidine attached to the cyanoacetic acid group formed two compounds (anion and neutral forms of E-CCVJ), which showed two different efficiencies when applied to dye-sensitized solar cells (DSSCs). Overall conversion efficiencies of 0.91% and 1.21% were obtained for DSSCs based on the cyanoacetic acid (J1) and cyanoacetate (J2) derived dyes, respectively. Compared to the cyanoacetic acid terminated dye, the current density, open circuit voltage and conversion efficiency of the solar cells based on cyanoacetate dye were increased by approximately 24%, 8% and 32%, respectively. The electrochemical impedance analysis showed that the better charge transfer of TiO2 (e-) and electron lifetime (τ(e)) for J2 dye as compared with J1. The power conversion efficiency was found to be quite sensitive to small structural changes to the anchoring moiety.

 Abstract—Chroma-key is an application which is used many in video industries, TV programs. In this paper, we present an efficient algorithm for Chroma-key and its FPGA implementation. In the proposed method, we firstly employ K-means to segment input frames in to a trimap including background, foreground, and unknown regions. In the next stage, we utilize comparison of confident neighborhood pixels to refine unknown region to separate background and foreground regions. In order to apply the proposed algorithm for real-time chroma-key effect, we implement its VLSI architecture on Bitec Cyclone III development board. Our design is able to perform Chroma-key process with pleasing quality HD video in real-time.

This paper presents a new image denoising method using block classification in Contourlet domain. The noise image is divided into 8×8 blocks. These blocks can be decomposed by the Contourlet into directional subbands while the block classification method provides the directional feature of input blocks. Based on this directional information, we propose the different thresholding processes with each input block. Thus, the new denoising algorithm proposed achieves better tradeoff between details retain and noises removal. Several experimental results show that the proposed new function is very effective and gives better performance both in terms of PSNR and in visual quality.

This paper presents a design and implementation of a real-time video denoising on FPGA. The video noise is decomposed into directional subbands by using contourlet transform. Thus, Gaussian noise in video frames can be removed significantly by an adaptive thresholding technique. Besides, to process video in real-time, a hardware design of proposed video denoising is implemented on FPGA. In order to achieve highest throughput, we design full pipeline architecture for hardware design. Experimental results show that our design can process with throughput of up to 150 Megapixels per second, which is totally suitable for high definition (HD) video processing.