The seewo interactive whiteboard (IWB) for ESL teaching: How useful it is?

The perceived usefulness (PU) of a technology is critical for its final adoption; however, what makes an interactive whiteboard (IWB) perceived useful remains unclear. This study aims to investigate how pre-service teachers perceive the usefulness of Seewo interactive whiteboards for ESL (English-as-a-second-language) instruction. We recruited 80 pre-service ESL teachers, divided them into 16 groups, provided five weeks of training, and conducted focus group interviews to gather qualitative feedback. The data were analyzed using grounded theory techniques with the aid of the software Nvivo. Three research questions were addressed: how pre-service ESL teachers perceive the usefulness of Seewo IWB in terms of its functions that enhance the learning process (PU-process), how they perceive the usefulness of Seewo IWB in terms of its functions that improve learning outcomes (PU-outcome), and how they perceive the non-usefulness of Seewo IWB. The findings shed light on the determinants of the perceived usefulness (PU) concept, which is crucial for fostering a higher intention to accept technology.

Effects of Dentin Ablation by a Q-Switching Er:YSGG Laser with a High Pulse Repetition Rate.

Objective: The aim of the study was to evaluate the characteristics of dentin ablation with a high pulse repetition rate Q-switching 2.79 µm laser. Materials and methods: Dentin was ablated using a homemade Q-switching Er:YSGG laser with a high pulse repetition rate. Er:YSGG radiation was applied with a pulse energy of 1 or 10 mJ for 100 or 3 Hz pulse repetition rate, respectively. A scanning electron microscope (SEM) was used to observe the microstructures of dentin samples after ablation. Teeth were irradiated in vitro with a 100 Hz pulse repetition rate under two different modes: free running and Q-switching. A thermocouple was applied to measure the temperature in the pulp cavity during ablation. Results: A 100 or 3 Hz Q-switching laser was used to irradiate dentin for 30 and 100 sec, respectively. There was no significant difference in ablation mass loss between the two conditions. The SEM photographs showed more dentinal tubules and no damage in the ablation area when using the 100 Hz Q-switching laser. The temperature of the pulp cavity was maintained below 41°C when using a Q-switching laser. Conclusions: The Q-switching Er:YSGG laser with a high pulse repetition rate exhibited greater ablation efficiency and better morphology than the low pulse repetition rate Q-switching laser. The experimental results also demonstrate the significant advantage of the Q-switching laser over free-running lasers for protecting dental pulp tissue. The Q-switching Er:YSGG laser with a high pulse repetition rate is expected to become an efficient new dental tool.

Enhanced energy density of PVDF-based nanocomposites via a core-shell strategy.

In recent years, high energy density polymer capacitors have attracted a lot of scientific interest due to their potential applications in advanced power systems and electronic devices. Here, core-shell structured TiO2@SrTiO3@polydamine nanowires (TiO2@SrTiO3@PDA NWs) were synthesized via a combination of surface conversion reaction and in-situ polymerization method, and then incorporated into the poly(vinylidene fluoride) (PVDF) matrix. Our results showed that a small amount of TiO2@SrTiO3@PDA NWs can simultaneously enhance the breakdown strength and electric displacement of nanocomposite (NC) films, resulting in improved energy storage capability. The 5 wt% TiO2@SrTiO3@PDA NWs/PVDF NC demonstrates 1.72 times higher maximum discharge energy density compared to pristine PVDF (10.34 J/cm3 at 198 MV/m vs. 6.01 J/cm3 at 170 MV/m). In addition, the NC with 5 wt% TiO2@SrTiO3@PDA NWs also demonstrates an excellent charge-discharge efficiency (69% at 198 MV/m). Enhanced energy storage performance is due to hierarchical interfacial polarization among their multiple interfaces, the large aspect ratio as well as surface modification of the TiO2@SrTiO3 NWs. The results of this study provide guidelines and a foundation for the preparation of the polymer NCs with an outstanding discharge energy density.

High-conversion-efficiency tunable mid-infrared BaGa4Se7 optical parametric oscillator pumped by a 2.79-µm laser.

A mid-infrared BaGa4Se7 optical parametric oscillator with high conversion efficiency and beam quality is demonstrated, which is pumped by a 2.79-µm electro-optically Q-switched Cr, Er:YSGG laser. A pulse energy of 3.5 mJ with a pulse width of 21 ns at 10 Hz is obtained in the range of 3.94-9.55 µm, and the beam quality factors are measured to be Mx2=5.0 and My2=4.6. The optical-to-optical conversion efficiency is 18.9%, and the slope efficiency is 31.6%, which is a 59% improvement on the best of the previously reported slope efficiencies for BaGa4Se7-based OPOs.

Widely tunable and narrow-bandwidth pulsed mid-IR PPMgLN-OPO by self-seeding dual etalon-coupled cavities.

Integrating narrow-bandwidth and wavelength tunability together is crucially important in upgrading the applications of optical parametric oscillators (OPO). Here, we have demonstrated a widely tunable, narrow-bandwidth and efficient mid-IR OPO pumped by a single-longitudinal-mode pulsed Yb-fiber laser. By restricting the bandwidth of the oscillated signal via self-seeding dual etalon-coupled cavities, the bandwidth of the idler can be suppressed to about 0.35 nm, with a wide tunable range of 2.85-3.05 µm, which can be achieved by synergistically adjusting the temperatures of PPMgLN crystal and one of the etalons. The maximum idler power at 3.031 µm is 2.67 W with an optical-to-optical conversion efficiency of 17.4%.

Mid-infrared ZGP-OPO with a high optical-to-optical conversion efficiency of 75.7.

We experimentally demonstrate a ZnGeP2 based optical parametric oscillator (ZGP-OPO) with a record of the optical-to-optical conversion efficiency. To improve the conversion efficiency, we design and construct a double-pass pumped high-gain OPO and a matched large-sized high-peak-power pump beam to suppress the spatial walk-off and conversion. Pulse energy of 19 mJ with pulse width of 27.8 ns at 5 Hz in the mid-infrared 3-5 µm waveband is obtained in the doubly resonated ZGP-OPO, the beam quality M2 is about 9.6, and the corresponding optical-to-optical conversion efficiency reaches up to 75.7%.

A Q-switched Ho:YAG laser assisted nanosecond time-resolved T-jump transient mid-IR absorbance spectroscopy with high sensitivity.

Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 µm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

High peak power Q-switched Er:YAG laser with two polarizers and its ablation performance for hard dental tissues.

An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

2.79 µm high peak power LGS electro-optically Q-switched Cr,Er:YSGG laser.

A flash lamp pumped Cr,Er:YSGG laser utilizing a langasite (LGS) crystal as an electro-optic Q-switch is proposed and demonstrated. It is proved that a LGS crystal with relatively high damage threshold can be used as the electro-optic Q-switch at 2.79 µm, and 216 mJ pulse energy with 14.36 ns pulse width is achieved. Its corresponding peak power of pulse can reach 15 MW, to our knowledge the best result at a 2.79 µm wavelength.

520 mJ langasite electro-optically Q-switched Cr, Tm, Ho:YAG laser.

A flash lamp pumped 2.09 µm Cr, Tm, Ho:YAG laser utilizing a self-grown La(3)Ga(5)SiO(14) crystal as the electro-optic Q-switch generator is proposed and demonstrated for the first time. Operating at 3 Hz repetition rate, 520 mJ pulse energy with 35 ns pulse width is achieved by optimizing the Q-switch delay time and compensating for the thermal depolarization with a quarter-wave plate. The corresponding peak power is 14.86 MW, and the Q-switched-to-normal-mode energy extraction efficiency is 66.3%. To our knowledge, this Q-switched giant pulse is the best result reported to date in 2.09 µm laser resonator.

[Optimally designing the probe of the near infrared oximeter to detect human tissue oxygen saturation non-invasively].

Human tissue oxygen saturation (rSO2) can be monitored non-invasively and in real time by near infrared spectroscopy (NIRS) based on spatially-resolved spectroscopy. To expand the clinical applications of the NIRS oximeter developed by our group based on the above principle, the accuracy of rSO2 must be ensured and enhanced as far as possible. In the present paper, the influences of the probe configuration, especially the distance between the detectors and the wavelength discreteness of the light source, on the accuracy of rSO2 were discussed. The results indicate that (1) to obtain rSOz accurately, two detectors need to be used, where the distance between them should be in the range of 5-20 mm and they should be both at least 20 mm apart from the light source; (2) there can be significant error in rSO2 (> 10%) induced by the discreteness of the two emission wavelengths especially the shorter one of the light source, so the real emission wavelengths must be accurately measured and the corresponding extinction coefficients of deoxygenated and oxygenated hemoglobin (Hb and HbO2) must be used in order to avoid this error. The above conclusions can be the guidance to optimally design the probe, which has been achieved in our NIRS oximeter.