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This paper explores two-phase immersion cooling using sealed enclosures of dielectric fluid as a technique to achieve compact, power dense converters on a single printed circuit board (PCB). The proposed approach employs passive circulation of the fluid and does not introduce system complexity beyond a heat exchanger required to condense the vapour. A test apparatus representing six 650 V, 150 A semiconductor switches in an inverter rejecting heat to a 65$\,^{\circ }$C water cooling loop is developed. Pool boiling experiments on a flat surface in Novec 7000 dielectric fluid demonstrate critical heat flux of 43 W cm$^{-2}$ at a saturation temperature of 94$\,^{\circ }$C and a corresponding pressure of 593 kPa. By augmenting the surface with pin fins (representative of a heat spreader attached to a switch) and grit blasting to improve the surface micro-geometry, the maximum heat transfer coefficient increased from 1.5 W cm$^{-2}$ K$^{-1}$ to 3.4 W cm$^{-2}$ K$^{-1}$ with a corresponding reduction in switch temperature from 125$\,^{\circ }$C to 107$\,^{\circ }$C at the total power dissipation of 186 W. A practical implementation with comparable thermal performance to the experimental apparatus but minimised volume of 0.12 L is presented. This yields a Cooling System Performance Index of 37 WL$^{-1}$ K$^{-1}$, including the heat exchanger and printed circuit board with switches, decoupling capacitors and gate drivers.

Visual guided motor imagery (MI) is commonly used in stroke rehabilitation, eliciting event-related desynchronization (ERD) in EEG. Previous studies found that immersion level and visuo-tactile stimulation could modulate ERD during visual guided MI, and both of two factors could also improve sense of ownership (SOO) over target limb (or body). Additionally, the relationship was also reported between the performance of MI and SOO. This study aims to investigate whether immersion and visuo-tactile stimulation affect visual guided MI through the SOO over virtual body in stroke patients. Nineteen stroke patients were recruited. The experiment included two phases (i.e., SOO induction and visual guided MI with SOO) that was manipulated across four conditions in a within-subject design: 2×2 , i.e., immersion (VR, 2D monitor display) × multisensory stimulation (visuo-tactile stimulation, observation without tactile stimulation). Results found peaks ERD amplitude during MI were significantly higher in stronger SOO conditions than weaker SOO conditions. Interestingly, the ERD during visual guided MI under the condition of vision only in VR and visuo-tactile stimulation in 2D monitor are similar, which indicates that SOO may be an important factor behind this phenomenon (due to the similar SOO between these two conditions). A moderate correlation was also found between SOO scores and peaks ERD amplitude during MI. This study discussed the possible factor underlying the effects of immersion and multisensory stimulation on visual guided MI in post-stroke patients, identifying the effect of SOO in this process, and could be referred in future studies for coming up with better MI paradigms for stroke rehabilitation.

The virtual derivatives computation and successive derivations of virtual inputs in an adaptive backstepping controller cause the explosion of complexity. Moreover, the feedback linearization has poor robustness features and necessitates exact estimation of the feedback control law’s coefficients. Due to measurement noise, the model-based estimation techniques for identifying uncertainties result in inaccurate gradient and Hessian calculations. Such limitations lead to model and measurement uncertainties that prevent effective stabilization and control of nonlinear systems. Machine learning-based data-driven approaches offer effective tools for identifying dynamical systems and uncertainties with minimal prior knowledge of the model structure. Therefore, the contribution of this research is two-fold: First, the general controller design theory is proposed which utilizes the idea of an invariant target manifold giving rise to a non-degenerate two form, through which the definition of certain passive outputs and storage functions leads to a generation of control law for stabilizing the system. Since the above concepts are linked with the Immersion and Invariance (I&I) design policy and the passivity theory of controller design, the proposed methodology is labeled as the “Passivity and Immersion (P&I) based approach”. Second, the proposed P&I approach is integrated with a Bayesian nonparametric approach, particularly the Gaussian Process for stabilization and control of the partially unknown nonlinear systems. The effectiveness of the proposed methodologies has been evaluated on an inverted pendulum using MATLAB in the presence of input-output uncertainties.

Background: The use of renewable energies is extended due to their valuable features such as abundant and clarity. The microgrids that include the renewable energies are widely used in various applications such as power supplying of remote areas, increasing the network reliability, reducing the greenhouse gas emission, reducing the consumption demand, eliminating the consumption peaks, and so on. But, energy management in the these systems in an challenging problem. Because, there are some natural perturbations such as variation output load, grid-side faults and changes of irradiation and temperature. Aim and Objective: The problem is to design a controller to regulate the output voltage/energy under aforementioned disturbances. Methods: The paper presents a new approach for energy management in Photovoltaic (PV)/Battery/Fuel Cells (FC) systems. The uncertainties are compensated by the new optimization rules based on Immersion and Invariance (I&I) theorem and proposed deep learning type-2 fuzzy logic compensator (T2FLC). The objective function of T2FLC is to minimize the tracking error in presence of perturbations. The adaptation rules are derived such that the I&I stabilization criterions are satisfied. Both rules and fuzzy sets (FSs) of T2FLCs are optimized by guaranteed stability rules to tackle the effect of perturbations and estimation errors. Results and Discussion: It is shown that a well voltage/energy regulation performance is achieved under variation of temperature, suddenly changes of load and variation of irradiation. A comparison with similar controllers demonstrates the superiority of the suggested approach. Conclusion: The suggested regulator do not depend on the mathematical models, and results in good accuracy under difficult conditions, then it can be used in various applications.

As a new form of social commerce, live-streaming shopping (LSS) provides customers with vivid real-time communication/interaction. However, there is limited research investigating the impacts of gamification in LSS. Thus, this study explores the relationships between gamification, customers’ engagement and purchase intention in LSS. A research model is formulated, and a questionnaire-based online survey is administrated to LSS viewers for empirically validating the model. Through the analysis of 272 collected questionnaires by using SPSS and AMOS, this study shows that gamification elements (including reward and competition) can enhance customers’ engagement (comprising sense of presence and immersion) and purchase intention. Moreover, sense of presence significantly mediates the indirect effects of reward and competition on purchase intention, but immersion does not mediate such effects. Stores and brands can design LSS programs with reward and competition to enhance customers’ sense of presence, immersion and purchase intention. Strategically, they should focus more on presence than immersion to better achieve their goals of LSS.

Extended Reality (XR) applications, which may encompass Augmented Reality (AR) and Virtual Reality (VR), commonly involve immersive virtual environments that are based on real physical environments. Transmitting the extensive color and depth image data for representing a physical environment over a communication network to create a corresponding immersive environment at a remote location is very challenging due to the enormous data volumes and the time constraints of real-time immersion. We explore semantic compression, which conveys the semantic meaning of the data through color-codes (CCs) to reduce the transmitted data volume. The creation of an immersive environment conventionally involves five steps (with corresponding output): calibration (single-frame point cloud), registration (registered point cloud), volume reconstruction (voxel frame), marching cubes (meshes), and rendering (3D environment). We develop the novel cXR+ semantic compression that splits the volume reconstruction into a client-side virtual network function (VNF) that represents the registered point cloud as CCs for network transmission to a server-side VNF that decodes the CCs to obtain the voxel frames so as to complete the volume reconstruction. We consider an analogous splitting of the calibration into two VNFs with Graph Coloring (GC) compression of the color and depth image data as a comparison benchmark. Additionally, we consider the transmission of the raw and JPG compressed point cloud data as well as the volume reconstruction at the client-side and subsequent transmission of the voxel frames as benchmarks. We conduct measurements of the compression (computing) time, transmission time, compression ratio, and reconstruction accuracy for real-world data sets so as to elucidate the trade-offs in employing voxel-based semantic compression for transmitting immersive environments over communication networks.

Point cloud streaming has recently attracted research attention as it has the potential to provide six degrees of freedom movement, which is essential for truly immersive media. The transmission of point clouds requires high-bandwidth connections, and adaptive streaming is a promising solution to cope with fluctuating bandwidth conditions. Thus, understanding the impact of different factors in adaptive streaming on the Quality of Experience (QoE) becomes fundamental. Point clouds have been evaluated in Virtual Reality (VR), where viewers are completely immersed in a virtual environment. Augmented Reality (AR) is a novel technology and has recently become popular, yet quality evaluations of point clouds in AR environments are still limited to static images. In this paper, we perform a subjective study of four impact factors on the QoE of point cloud video sequences in AR conditions, including encoding parameters (quantization parameters, QPs), quality switches, viewing distance, and content characteristics. The experimental results show that these factors significantly impact the QoE. The QoE decreases if the sequence is encoded at high QPs and/or switches to lower quality and/or is viewed at a shorter distance, and vice versa. Additionally, the results indicate that the end user is not able to distinguish the quality differences between two quality levels at a specific (high) viewing distance. An intermediate-quality point cloud encoded at geometry QP (G-QP) 24 and texture QP (T-QP) 32 and viewed at 2.5m can have a QoE (i.e., score 6.5 out of 10) comparable to a high-quality point cloud encoded at 16 and 22 for G-QP and T-QP, respectively, and viewed at a distance of 5m. Regarding content characteristics, objects with lower contrast can yield better quality scores. Participants’ responses reveal that the visual quality of point clouds has not yet reached an immersion level as desired. The average QoE of the highest visual quality is less than 8 out of 10. There is also a good correlation between objective metrics (e.g., color Peak Signal-to-Noise Ratio (PSNR) and geometry PSNR) and the QoE score. Especially the Pearson correlation coefficients of color PSNR is 0.84. Finally, we found that machine learning models are able to accurately predict the QoE of point clouds in AR environments. The subjective test results and questionnaire responses are available on GitHub: https://github.com/minhkstn/QoE-and-Immersion-of-Dynamic-Point-Cloud.

In order to keep constant DC-link voltage of a flywheel energy storage system (FESS) discharge in a wide rotational speed range, the control structure of the FESS is comprised of an inner current loop and an outer DC-link voltage loop. Since the dynamic equation of the DC-link voltage in the FESS discharge is nonlinear, it is difficult for some controllers to make the DC-link voltage in discharge be constant as the rotational speed is varying in a large range. Considering the nonlinearity of the DC-link voltage in discharge and the fast discharge requirements of the FESS, an immersion and invariance manifold (I&IM) adaptive nonlinear controller for a constant DC-link voltage is proposed via methodology of immersed in the invariant manifold. The stability of the control algorithm and the influence of the parameter error on the stability are verified by the Lyapunov stability theory, and the influence of the parameters error on the steady state and transient characteristics of the closed-loop system is analyzed numerically. It is proved that the closed-loop system satisfies the global uniform asymptotic stability conditions at the equilibrium point, and the error of the model parameters does not affect the equilibrium point of the system. Finally, the effectiveness of the I&IM adaptive nonlinear controller were studied by simulation and experiment. The results show that the DC-link voltage in discharge remains stable when switching the system load in cases of different rotational speeds and loads.

Development of effective thermal management techniques is essential in enabling further technical advances and wide public acceptance of lithium-ion based battery electrical storage. Both stationary battery arrays and electric vehicle (EV) batteries are pressed to enable charging and discharging at faster C rates, increased amp-hour capacity, longer service life and increased safety. All of these are dependent on more efficient and safer thermal management solutions. Traditional air cooling and indirect liquid cooling (cold plate) methods have limitations in effectiveness and weight. Engineered Fluids has recently completed a series of experiments demonstrating the high efficiency of Single-phase Liquid Immersion Cooling (SLIC) technology for the thermal management of Li-ion batteries. This article reviews the results of these experiments and discusses some of the issues and solutions for battery thermal management, and outlines the proper design of battery thermal management systems. We will discuss such topics as active cooling versus passive cooling, liquid cooling versus air cooling, cooling and heating versus cooling only systems, and relative needs of thermal management for VRLA, NiMH, and Li-Ion batteries.

We describe a new measurement technique to determine the refractive index (RI) of solid particles by monitoring the simultaneous scattering of light from suspension with a camera and the value of the RI with a refractometer. Our immersion solid matching method is based on the solidification process of the liquid continuously changing the RI as a function of time. The principle of the determination is based on finding the RI matching point of the particle and the liquid during the solidification. The traditional liquid immersion method is based on a set of immersion liquids with different refractive indices, while the proposed method requires only a small amount of a single immersion liquid. The method was tested using calcium fluoride (CaF2) particles with a varnish immersion liquid. The RI value of CaF2 was obtained to be consistent with the literature values, thus indicating the proper functioning of the proposed procedure. [ABSTRACT FROM AUTHOR]

In view of the effect of water on the physical and mechanical parameters of natural gypsum rock, in this study, gypsum rock in the goaf of a gypsum mine was selected as the research object, and gypsum rock samples were prepared with different immersion times. In addition, uniaxially tests were performed separately on the gypsum rock samples. Compression and scanning electron microscopy experiments were carried out to analyze the effects of immersion time on the uniaxial compressive strength, elastic modulus, Poisson’s ratio, and microstructure of gypsum. The results show that the uniaxial compressive strength and elastic modulus of gypsum are inversely proportional to the water content. However, the Poisson’s ratio is direly proportional to the water content, and the failure mode is destroyed by the brittle fracture of a single crack and is transformed into the shear ductile failure of the Y-shaped crack. Microscopically, with increasing immersion time, the bonds in the crystal of the microporous cracks and microcrack tips are weakened by hydrolysis, and the macroscopic structure is complicated by the internal structure of gypsum, and the end of the crack is expanded by the compressive action of water. Based on the damage mechanics, the evolution equation of gypsum soaking softening damage based on time factor was derived. The relationship between the brittleness coefficient and softening damage variable is revealed, providing a theoretical basis for the determination of the softening degree of gypsum in the goaf.

An adaptive control law is proposed in this paper for body-fixed hovering over an asteroid with an unknown gravity field and an unknown rotation rate. The unknown parameters and irregular shape of an asteroid make the hovering problem challenging. To facilitate the controller design, first, it is assumed that the required parameters are attainable, and then a body-fixed hovering controller is designed using the backstepping approach. Based on the immersion and invariance theory, an adaptive law is devised to estimate the unknown parameters in conjunction with the backstepping controller. To overcome the integrability obstacle arising in the adaptive law design, the regressor matrix is decomposed to two matrices: a Jacobian matrix and a non-Jacobian matrix, and an auxiliary matrix is introduced into the latter to form a Jacobian matrix. Then, a bounded function is employed to dynamically scale the estimate errors and its dynamics is elaborately constructed to stabilize the system. A Lyaponuv function is constructed for the entire closed-loop system to achieve the stabilization conditions by LaSalle's theorem, and the bounded scaling function much simplifies the analysis. Finally, numerical simulations demonstrate the effectiveness of the proposed control scheme.

With the speedy progress in electrical engineering field globally, power electronics course has aroused attention from academic community. English immersion teaching methods applied to power electronics course aim to introduce advanced counterpart academic knowledge from abroad to China and equip students and teaching staffs with international views as well as English-oriented logical and critical thinking in power electronics, and thus to promote power electronics development in China in the long term. By utilizing English immersion teaching methods for power electronics course, which involves problem-based learning, English-project-based assessment method and English-based laboratory operation, the challenges that the innovative teaching methods confront could be solved during each process of power electronics course. For further illustration, English immersion teaching methods for energy storage will be analysed as a study case. Consequently, the new English immersion teaching methods for power electronics course in China can be spread and applied in other non-native English-speaking countries to upgrade and reform power electronics course and related discipline.

The current experimental study examined whether different degrees of immersive and interactive experience made a difference in users’ perceptions and intention to adopt a novel VR-based MR training system. In this paper, virtual reality was used as an educational technology that allowed users to virtually rotate 3-D objects and helped to enhance their spatial ability, which would be particularly useful in future careers in STEM. A 2 (display) $\times \,\, 2$ (controller) $\times \,\, 2$ (gender) experimental design was conducted. Researchers used a 2-D monoscopic display and a stereoscopic display to manipulate two different conditions of immersion, while a computer mouse and a hand-held controller were applied to measure the effects from two different levels of interactivity. Gender was examined due to prior research suggesting that males were better at MR tasks than females. The dependent variables were various perceptions and behavioral intentions developed from relevant theories in technology acceptance. The results showed that users’ positive perceptions and intention to use the novel MR system were amplified whenever better immersive and interactive experiences were provided simultaneously, or when the inferior immersive and interactive experiences were offered at the same time. Females under a better immersive environment perceived better feelings of enjoyment, confirmation, satisfaction, and behavioral intention, compared with their male counterparts. Theoretical contributions in perceptions and use intention of educational technology, with a specific focus on VR, were discussed. Practical implications for developers of educational technology and K-12/college educators were provided.

Immersion plays a crucial role in video watching, leading viewers to a positive experience, such as increased engagement and decreased fatigue. However, few studies measure immersion while watching videos, and questionnaires are typically used in the measurement of immersion for other applications. These methods may rely on the viewer's memory and cause biased results. Therefore, we propose an objective immersion detection model by leveraging people's gaze behavior while watching videos. In a lab study with 30 participants, an in-depth analysis is carried out on a number of gaze features and machine learning (ML) models to identify the immersion state. Several gaze features are highly indicative of immersion and ML models with these features are able to detect an immersion state of video watchers. Post-hoc interviews demonstrate that our approach is applicable to measure immersion in the middle of watching a video, where some practical issues are discussed as well. [ABSTRACT FROM AUTHOR]

The head-mounted display (HMD) form factor is an essential element that influences the various emotions users experience during their virtual reality (VR) sessions. In particular, it has been announced that the VR experience highly depends on the user’s field of vision because it blocks the user’s view of the real world and transmits information exclusively in the virtual world. Users with eye diseases wore vision aids to experience VR environments or used them without sufficient vision. Furthermore, this problem led to factors that reduced the user’s sense of immersion and ease of use. In this paper, we analyzed how providing users with adjusted human vision via diopter dial affects the improvement of VR user experiences. The experimental procedure consisted of 2D video and 360-degree video as audiovisual content, as well as sitting mode games and room-scale mode games as playable content. We measured the immersion and sickness of the experimental environment using each verified questionnaire on the 5-point Likert scale and the discomfort score for each experimental content to measure the degree of discomfort. The experimental environment is Phase 1, where users experienced VR while wearing vision aids, and Phase 2, where users experience VR with human vision adjustment using a diopter dial without vision aids. The difference between the evaluation results of both experimental environments was 1.56 for immersion, 2.35 for sickness, and 3.85 for discomfort. Additionally, user feedback was gathered through in-depth interviews to enhance the reliability of the statistical analysis. Through these results, we confirmed that human vision adjustment using the diopter dial provides users with an improved form factor, reduces discomfort and sickness, and enhances the immersive feeling of the VR environment through improved display visibility.