Enhanced Broadband Manipulation of Acoustic Vortex Beams Using 3-bit Coding Metasurfaces through Topological Optimization.

The acoustic coding metasurfaces (ACMs) have the ability to manipulate complex acoustic behavior by reconstructing the coding sequence. In particular, the design of broadband coding enhances the versatility of ACMs. ACMs offer significant advantages over traditional metasurfaces, including a limited number of units and flexible wave control performance. The unit quantity is determined by 2n, with 1-bit utilizing 2 units, 2-bit using 4 units, and 3-bit employing 8 units. Utilizing multiple bits allows for precise control over the phase of sound waves and enables the realization of more intricate acoustic functions. To address the requirements of broadband multi-bit applications, this paper presents the development of novel 3-bit broadband reflected acoustic coding metasurfaces (BACMs) with eight coding units. These metasurfaces are systematically designed using the bottom-up topology optimization method. A constant phase difference of 45° can be achieved across all eight coding units within a broad frequency range. Additionally, the spiral distribution of phase differences enables the construction of an acoustic vortex metasurface. Moreover, by combining the convolution method, the strategies are outlined for constructing vortex-focusing metasurfaces and vortex beam manipulation metasurfaces. These 3-bit coding metasurfaces possess significant potential in the fields of acoustic particle suspension and acoustic communication.

Balancing Accuracy and Speed in Gaze-Touch Grid Menu Selection in AR via Mapping Sub-Menus to a Hand-Held Device.

Eye gaze can be a potentially fast and ergonomic method for target selection in augmented reality (AR). However, the eye-tracking accuracy of current consumer-level AR systems is limited. While state-of-the-art AR target selection techniques based on eye gaze and touch (gaze-touch), which follow the "eye gaze pre-selects, touch refines and confirms" mechanism, can significantly enhance selection accuracy, their selection speeds are usually compromised. To balance accuracy and speed in gaze-touch grid menu selection in AR, we propose the Hand-Held Sub-Menu (HHSM) technique.tou HHSM divides a grid menu into several sub-menus and maps the sub-menu pointed to by eye gaze onto the touchscreen of a hand-held device. To select a target item, the user first selects the sub-menu containing it via eye gaze and then confirms the selection on the touchscreen via a single touch action. We derived the HHSM technique's design space and investigated it through a series of empirical studies. Through an empirical study involving 24 participants recruited from a local university, we found that HHSM can effectively balance accuracy and speed in gaze-touch grid menu selection in AR. The error rate was approximately 2%, and the completion time per selection was around 0.93 s when participants used two thumbs to interact with the touchscreen, and approximately 1.1 s when they used only one finger.

Affective Colormap Design for Accurate Visual Comprehension in Industrial Tomography.

The design of colormaps can help tomography operators obtain accurate visual comprehension, thereby assisting safety-critical decisions. The research presented here is about deploying colormaps that promote the best affective responses for industrial microwave tomography (MWT). To answer the two research questions related to our study, we firstly conducted a quantitative analysis of 11 frequently-used colormaps on a segmentation task. Secondly, we presented the same colormaps within a crowdsourced study comprising two parts to verify the quantitative outcomes. The first part encoded affective responses from participants into a prevailing four-quadrant valence-arousal grid; the second part recorded participant ratings towards the accuracy of each colormap on MWT segmentation. We concluded that three colormaps are the best suited in the context of MWT tasks. We also found that the colormaps triggering emotions in the positive-exciting quadrant can facilitate more accurate visual comprehension than other affect-related quadrants. A synthetic colormap design guideline was consequently proposed.

Moment-to-Moment Continuous Attention Fluctuation Monitoring through Consumer-Grade EEG Device.

While numerous studies have explored using various sensing techniques to measure attention states, moment-to-moment attention fluctuation measurement is unavailable. To bridge this gap, we applied a novel paradigm in psychology, the gradual-onset continuous performance task (gradCPT), to collect the ground truth of attention states. GradCPT allows for the precise labeling of attention fluctuation on an 800 ms time scale. We then developed a new technique for measuring continuous attention fluctuation, based on a machine learning approach that uses the spectral properties of EEG signals as the main features. We demonstrated that, even using a consumer grade EEG device, the detection accuracy of moment-to-moment attention fluctuations was 73.49%. Next, we empirically validated our technique in a video learning scenario and found that our technique match with the classification obtained through thought probes, with an average F1 score of 0.77. Our results suggest the effectiveness of using gradCPT as a ground truth labeling method and the feasibility of using consumer-grade EEG devices for continuous attention fluctuation detection.

A Clinical Teaching Blended Learning Program to Enhance Registered Nurse Preceptors' Teaching Competencies: Pretest and Posttest Study.

BACKGROUND: Clinical nursing education provides opportunities for students to learn in multiple patient care settings, receive appropriate guidance, and foster the development of clinical competence and professionalism. Nurse preceptors guide students to integrate theory into practice, teach clinical skills, assess clinical competencies, and enhance problem-solving and critical thinking skills. Previous research has indicated that the teaching competencies of nurse preceptors can be transferred to students' clinical learning to enhance their clinical competencies. OBJECTIVE: This study aimed to develop a clinical teaching blended learning (CTBL) program with the aid of web-based clinical pedagogy (WCP) and case-based learning for nurse preceptors and to examine the effectiveness of the CTBL program on nurse preceptors' clinical teaching competencies, self-efficacies, attitudes toward web-based learning, and blended learning outcomes. METHODS: A quasi-experimental single-group pretest and posttest design was adopted. A total of 150 nurse preceptors participated in the CTBL program, which was conducted from September 2019 to December 2019. A set of questionnaires, including the clinical teaching competence inventory, preceptor self-efficacy questionnaire, attitudes toward web-based continuing learning survey, and e-learning experience questionnaire, was used to assess the outcomes before and after the CTBL program. RESULTS: Compared with the baseline, the participants had significantly higher total mean scores and subdomain scores for clinical teaching competence (mean 129.95, SD 16.38; P<.001), self-efficacy (mean 70.40, SD 9.35; P<.001), attitudes toward web-based continuing learning (mean 84.68, SD 14.76; P<.001), and blended learning outcomes (mean 122.13, SD 14.86; P<.001) after the CTBL program. CONCLUSIONS: The CTBL program provides a comprehensive coverage of clinical teaching pedagogy and assessment strategies. The combination of the WCP and case-based approach provides a variety of learning modes to fit into the diverse learning needs of the preceptors. The CTBL program allows the preceptors to receive direct feedback from the facilitators during face-to-face sessions. Preceptors also gave feedback that the web-based workload is manageable. This study provides evidence that the CTBL program increases the clinical teaching competencies and self-efficacies of the preceptors and promotes positive attitudes toward web-based learning and better blended learning outcomes. The health care organization can consider the integration of flexible learning and intellect platforms for preceptorship education.

A Dual-Readout Method for Biothiols Detection Based on the NSET of Nitrogen-Doped Carbon Quantum Dots-Au Nanoparticles System.

In this paper, a rapid, simple and highly sensitive method with dual-readout (colorimetric and fluorometric) based on the nanometal surface energy transfer (NSET) between nitrogen-doped carbon quantum dots (NCQDs) and gold nanoparticles (AuNPs) for detection of biothiols is described. Highly luminescent NCQDs were prepared via a simple one-step hydrothermal method by applying sucrose and glycine as carbon and nitrogen sources. The results showed the obtained NCQDs had an average particle diameter of 5 nm and highly luminescent. The maximum emission wavelength was 438 nm with an excitation wavelength of 360 nm. In this system, NCQDs and AuNPs were respectively treated as energy donors and energy acceptors, which enable the nanometal surface energy transfer (NSET) from the NCQDs to the AuNPs, quenching the fluorescence. However, biothiols was used as a competitor in the NSET by the strongly Au-S bonding to release NCQDs from the Au surface, which subsequently produces fluorescent signal recovery and the red-to-purple color change quickly. This probe showed rapid response, high selectivity and sensitivity for biothiols with dual colorimetric and fluorescent turn-on signal changes. The low detection limit was calculated as 20 nM by using L-cysteine acted as target melocules. The method was also successfully applied to the determination of biothiols in human serum samples, and the results were satisfying.

Kine-Appendage: Enhancing Freehand VR Interaction Through Transformations of Virtual Appendages.

Kinesthetic feedback, the feeling of restriction or resistance when hands contact objects, is essential for natural freehand interaction in VR. However, inducing kinesthetic feedback using mechanical hardware can be cumbersome and hard to control in commodity VR systems. We propose the kine-appendage concept to compensate for the loss of kinesthetic feedback in virtual environments, i.e., a virtual appendage is added to the user's avatar hand; when the appendage contacts a virtual object, it exhibits transformations (rotation and deformation); when it disengages from the contact, it recovers its original appearance. A proof-of-concept kine-appendage technique, BrittleStylus, was designed to enhance isomorphic typing. Our empirical evaluations demonstrated that (i) BrittleStylus significantly reduced the uncorrected error rate of naive isomorphic typing from 6.53% to 1.92% without compromising the typing speed; (ii) BrittleStylus could induce the sense of kinesthetic feedback, the degree of which was parity with that induced by pseudo-haptic (+ visual cue) methods; and (iii) participants preferred BrittleStylus over pseudo-haptic (+ visual cue) methods because of not only good performance but also fluent hand movements.

A web-based clinical pedagogy program to promote professional development for nurse preceptors: A quasi-experimental study.

OBJECTIVE: To examine the effectiveness of a web-based clinical pedagogy program on nurse preceptors' clinical teaching competency, self-efficacy, and attitudes toward web-based learning in comparison to face-to-face course. BACKGROUND: Preceptorship is a dynamic educational process that requires designing, and implementing various teaching strategies, evaluation, assessment and feedback. Web-based learning has been recognized as an effective learning approach for nursing professional development. DESIGN: A prospective quasi-experimental approach with two-group pre-test and post-test repeated measures was adopted. METHODS: The web-based clinical pedagogy program was provided to the preceptors in the experimental group, while control group received the face-to-face preceptorship course. Clinical Teaching Competence Inventory (CTCI), Preceptor Self-efficacy Assessment Instrument (PSEQ), and Attitudes toward Web-based Continuing Learning Survey (AWCLS) were used to evaluate preceptors' learning outcomes. Data were collected at three time points - before, immediately after the learning program, and after 6 months of the clinical teaching experience. RESULTS: A total of 150 nurses (75 participants/group) were recruited from a tertiary hospital in Singapore from July 2018 to June 2020. The results from the repeated measures analysis of covariance showed that there was a significant interaction effect (group x time) on the overall CTCI score after adjusting for covariate (F = 5.390, p = 0.005). However, there were no significant interaction effect (group x time) on PSEQ (F = 2.693, p = 0.070) and overall AWCLS score (F = 1.341, p = 0.264) between the two groups across the three time points. CONCLUSION: The web-based clinical pedagogy program produced outcomes comparable to the face-to-face program in terms of preceptors' clinical teaching competence and self-efficacy. The innovative and cost-effective web-based clinical pedagogy program provided professional development and the flexibility to accommodate preceptors' busy work schedules. Online learning has become increasingly popular during the COVID-19 pandemic and the web-based clinical pedagogy program was implemented when face-to-face workshop was not feasible.

Achromatic metasurfaces by dispersion customization for ultra-broadband acoustic beam engineering.

Metasurfaces, the ultra-thin media with extraordinary wavefront modulation ability, have shown great promise for many potential applications. However, most of the existing metasurfaces are limited by narrow-band and strong dispersive modulation, which complicates their real-world applications and, therefore require strict customized dispersion. To address this issue, we report a general methodology for generating ultra-broadband achromatic metasurfaces with prescribed ultra-broadband achromatic properties in a bottom-up inverse-design paradigm. We demonstrate three ultra-broadband functionalities, including acoustic beam deflection, focusing and levitation, with relative bandwidths of 93.3%, 120% and 118.9%, respectively. In addition, we reveal a relationship between broadband achromatic functionality and element dispersion. All metasurface elements have anisotropic and asymmetric geometries with multiple scatterers and local cavities that synthetically support internal resonances, bi-anisotropy and multiple scattering for ultra-broadband customized dispersion. Our study opens new horizons for ultra-broadband highly efficient achromatic functional devices, with promising extension to optical and elastic metamaterials.

Tunable Fluid-Type Metasurface for Wide-Angle and Multifrequency Water-Air Acoustic Transmission.

Efficient acoustic communication across the water-air interface remains a great challenge owing to the extreme acoustic impedance mismatch. Few present acoustic metamaterials can be constructed on the free air-water interface for enhancing the acoustic transmission because of the interface instability. Previous strategies overcoming this difficulty were limited in practical usage, as well as the wide-angle and multifrequency acoustic transmission. Here, we report a simple and practical way to obtain the wide-angle and multifrequency water-air acoustic transmission with a tunable fluid-type acoustic metasurface (FAM). The FAM has a transmission enhancement of acoustic energy over 200 times, with a thickness less than the wavelength in water by three orders of magnitude. The FAM can work at an almost arbitrary water-to-air incident angle, and the operating frequencies can be flexibly adjusted. Multifrequency transmissions can be obtained with multilayer FAMs. In experiments, the FAM is demonstrated to be stable enough for practical applications and has the transmission enhancement of over 20 dB for wide frequencies. The transmission enhancement of music signal across the water-air interface was performed to demonstrate the applications in acoustic communications. The FAM will benefit various applications in hydroacoustics and oceanography.

Lotus Metasurface for Wide-Angle Intermediate-Frequency Water-Air Acoustic Transmission.

Only 0.1% of the acoustic energy can transmit across the water-air interface because of the huge acoustic impedance mismatch. Enhancing acoustic transmission across the water-air interface is of great significance for sonar communications and sensing. However, due to the interface instability and subwavelength characteristics of acoustic metamaterials, wide-angle intermediate-frequency (10 kHz-100 kHz) water-air acoustic transmission remains a great challenge. Here, we demonstrate that the lotus leaf is a natural low-cost acoustic transmission metasurface, namely, the lotus acoustic metasurface (LAM). Experiments demonstrate the LAM can enhance the acoustic transmission across the water-air interface, with an energy transmission coefficient of about 40% at 28 kHz. Furthermore, by fabricating artificial LAMs, the operating frequencies can be flexibly adjusted. Also, the LAM allows a wide-angle water-to-air acoustic transmission. It will enable various promising applications, such as detecting and imaging underwater objects from the air, communicating between ocean and atmosphere, reducing ocean noises, etc.

Bioinspired Patterned Bubbles for Broad and Low-Frequency Acoustic Blocking.

Bubble crystals in water are expected to achieve the broad and low-frequency acoustic band gaps that are crucial for acoustic blocking. However, preparing patterned bubble crystals in water remains a challenge because of the instability of bubbly liquids. Here, inspired by biological superhydrophobic systems, we report a simple and rapid approach to prepare patterned bubble arrays in water and their applications in low-frequency acoustic blocking. Patterned bubbles with the desired size, shape, and position can be prepared. Single-layer bubble arrays can block the sounds at low frequencies because of local resonance. By varying the size and distance of the bubbles without changing the thickness, the operating frequency can change from 9 to 1756 kHz. Besides, by preparing multilayer bubbles, broad and low-frequency acoustic band gaps can be achieved, with the generalized width of γ (ratio of the bandgap width to its start frequency) reaching 1.26. This method provides a feasible strategy to control acoustic waves at low frequencies for applications such as acoustic blocking, focusing, imaging, and detecting.

A web-based clinical pedagogy program to enhance registered nurse preceptors' teaching competencies - An innovative process of development and pilot program evaluation.

BACKGROUND: Registered Nurse Preceptors guide students to integrate theory into practice, assess clinical competencies, and enhance problem-solving skills. Researches have indicated that the teaching competencies of nurse preceptors can be transferred to students' clinical learning. OBJECTIVES: The aims of the study are to develop a web-based clinical pedagogy (WCP) program for Registered Nurse Preceptors and conduct pilot program evaluation. DESIGN: A three-step process was applied to integrate the theoretical framework, evidence from the systematic review, and content validity by the experts and pilot test with the Registered Nurse Preceptors in the content and technical development of the program. The WCP program has unique features including use of dashboard, interactive videos, consultation with experts, discussion forum and backend data analysis. RESULTS: A committee of six content experts evaluated the comprehensiveness, appropriateness, and relevancy of the program. The item-Content Validity Index (CVI) score ranged from 0.83 to 1.00 and the scale-CVI score was 0.87, which indicated that the WCP program had a strong content validity. Ten nurse preceptors were invited to use the WCP program. Preceptors shared that the website was easy to use and navigate. They commented that the videos in each module are beneficial for nurses to understand the real situation in the clinical setting. This feature also makes the website more interactive. Feedback from preceptors was subsequently used to further refine the program. DISCUSSION AND CONCLUSION: The WCP program is an evidence-based program that provides a comprehensive coverage on clinical teaching pedagogy and assessment strategies. The unique web-based technology and interactive features provide a platform for nurse preceptors to discuss clinical encounters with peers and consult experts. The flexible and resource-rich nature of web-based learning encourages nurses to use it for continuing education.

Broadband single-phase hyperbolic elastic metamaterials for super-resolution imaging.

Hyperbolic metamaterials, the highly anisotropic subwavelength media, immensely widen the engineering feasibilities for wave manipulation. However, limited by the empirical structural topologies, the reported hyperbolic elastic metamaterials (HEMMs) suffer from the limitations of the relatively narrow frequency width, inflexible adjustable operating subwavelength scale and difficulty to further improve the imaging resolution. Here, we show an inverse-design strategy for HEMMs by topology optimization. We design broadband single-phase HEMMs supporting multipolar resonances at different prescribed deep-subwavelength scales, and demonstrate the super-resolution imaging for longitudinal waves. Benefiting from the extreme enhancement of the evanescent waves, an optimized HEMM at an ultra-low frequency can yield an imaging resolution of ~λ/64, representing the record in the field of elastic metamaterials. The present research provides a novel and general design methodology for exploring the HEMMs with unrevealed mechanisms and guides the ultrasonography and general biomedical applications.

High-transmission acoustic self-focusing and directional cloaking in a graded perforated metal slab.

A design strategy and its modeling for high-transmission acoustic self-focusing and directional cloaking in a two-dimensional (2D) and an axisymmetric three-dimensional (3D) gradient-index phononic crystal (GRIN-PC) are reported in this paper. A gradient perforated aluminum slab sandwiched by water is considered. A low-loss directional cloaking device is achieved by controlling the matching coefficient between the slab and the water. The anisotropy coefficient that affects the scattering properties is also introduced. Furthermore, the phase discontinuity for directional cloaking inside and outside the slab is overcome by introducing a non-gradient slab having a lower group velocity behind the GRIN slab as an acoustic delay device. In addition, an axisymmetric 3D directional cloaking structure is obtained by rotating the corresponding 2D structure around the slab axis.

Experimental evidence of large complete bandgaps in zig-zag lattice structures.

In this paper, experimental evidence of large complete bandgaps in a kind of light-weighted zig-zag lattice structure (ZLS) is presented. Ultrasonic experiments are conducted on the stainless steel slab designed with ZLS to detect the complete bandgaps. Also, the numerical simulations of the experiments by the finite element method are carried out. For comparison, we conduct the same experiments and numerical simulations on the stainless steel slab with straight lattice structure (SLS). Good agreement is obtained between the experimental and numerical results. The complete bandgaps of ZLS are successfully tested and no complete bandgap is found in SLS. The band structures and vibration modes of both ZLS and SLS are calculated via the finite element method to understand the experimental data. The effects of the geometry parameters of ZLS on the complete bandgaps are discussed in detail.