Virtual Wall Research Articles

Study on the wetting characteristics of liquid-Al/ SiO2 interface with Si content in liquid-Al

Aiming to address the issue of aluminum slag adhering to the interior walls of vacuum lifting ladles in the aluminum electrolysis industry, Molecular dynamics simulations are employed to investigate the wetting behavior and adhesion characteristics of aluminum droplets on silica surfaces. Our findings indicate that with an increase in silicon content within the droplets, wetting diminishes and complete wetting of the silica substrate by aluminum droplets is not achieved. The presence of silicon reduces both the melting point temperature and surface tension of aluminum droplets, leading to a significant increase in contact angle and a corresponding decrease in wettability. Moreover, an elevated silicon content within molten aluminum droplets substantially decreases their interaction energy with the substrate surface. The virtual wall method is applied to examine average separation force and work of separation for detaching aluminum droplets from the substrate, revealing that adhesion characteristics are predominantly governed by mutual adhesive forces. This paper presents an atomic-level analysis elucidating how silicon as an alloying element influences adhesion between liquid aluminum and solid surfaces.

Latency-free real-time auralisation in hemi-anechoic chambers

Real-time auralisation allows users to interact with a simulated acoustical room, providing a more responsive way of evaluating acoustical performance than pre- recorded auralisation. Nevertheless, real-time auralisation is computationally intensive and, therefore, susceptible to latency. This paper presents a novel latency-free real-time auralisation method that enables users to auralise a simulated acoustical event with self-excitation more accurately than current methods. The method uses a loudspeaker system inside a hemi-anechoic chamber. By exploiting the inherent floor reflection of the hemi-anechoic chamber, the impulse response can be trimmed to compensate for the total latency of the loudspeaker system. The method's validity is demonstrated with measurements presenting virtual wall reflections arriving at the correct time at the listening position. The influence of the speaker placement regarding latency is discussed. This method enables users to evaluate a given response more accurately than conventionally possible.

Wall, Wall in the Mirror: Which Is the Sturdiest of Them All?

This research examines the comparative effectiveness of physical versus virtual border walls in managing illegal border crossings along the U.S.-Mexico border, focusing on Yuma, Arizona, and Laredo, Texas. It addresses the question of which type of infrastructure is more efficient in reducing migration and how these approaches influence crossing patterns. Previous studies have largely concentrated on other factors of migration such as economic conditions, overlooking the role of evolving border security systems. This gap in the literature calls for a deeper analysis of these evolving strategies. Utilizing U.S. Customs and Border Protection data from 2020 to 2024, the study analyzes border encounters in these regions, employing time series analysis to investigate shifts in crossing rates and demographic trends. Our findings reveal that physical barriers are effective when properly maintained but lose deterrence power when consistent maintenance and construction is absent. Conversely, virtual walls provide consistent monitoring but are less effective in significantly deterring crossings. Both methods present significant ethical concerns, as physical walls drive migrants to more dangerous routes, while virtual walls amplify surveillance and privacy issues. We conclude that a hybrid approach, integrating physical and technological solutions, could better balance migration management with ethical border enforcement.

The Current Role of Analytical Psychology in Maintaining Fictitious Boundaries that are Promoted through the Race Lie: A call to dismantle the virtual wall that exists through attitudes of white supremacy.

In 1928, the American Anthropological Association declared that "Anthropology provided no scientific basis for discrimination against any people on the ground of racial inferiority, religious affiliation, or linguistic heritage" (Guthrie, 1976/1998/2004, p. 30). In 1945, Jung denounced race theory as a pseudo-science. In 1950, UNESCO released its statement denouncing race. Long discredited as scientifically invalid, the race concept still holds uncanny value and significance for Americans and Europeans. In effect, the concept seems to be mysteriously linked to the limited accessibility and the limited economic support that is allotted to people of colour, internationally. This paper will explore the global implications of Jung's expressed attitude towards people of colour prior to 1945, which I identify as an attitude of white supremacy, an attitude that stands in direct contrast to the analytical ethos, as expressed by the International Association for Analytical Psychology (IAAP). This attitude may promote the continuance of racialized beliefs and behaviours within the planning and provision of care to individuals in need of medical and mental health services. It is requested that a written acknowledgment of harm be added to the works of C. G. Jung.

Exact discrete-time stability analysis of multi-DOF haptic rendering: Impact of multi-rate, time-delay, and mechanical parameters

Previous studies on the stability analysis of haptic devices have predominantly focused on single-DOF devices, thereby limiting attention to multi-DOF devices, particularly those employing multi-rate sampling schemes. In this paper, we introduce a formulation for the coupled dynamics between the haptic device and the virtual environment for a multi-DOF haptic device controlled using a dual-rate sampling scheme. Subsequently, we analyze its stability through the application of a dynamic decoupling strategy within an exact discrete-time state-space framework while the device is engaged in rendering a virtual wall along one of its operational space coordinates. Furthermore, we explore how the combined influence of the dual-rate sampling approach, time delay, and the mechanical design affects the stability boundaries of the multi-DOF haptic device at a fixed workspace location as well as within the entire usable workspace. Additionally, we utilize a model-order reduction (MOR) framework to simplify the determination of the device’s stability limits, irrespective of the specific combinations of time delay and sampling rates employed.

Fast-response liquid crystal display device with trapezoidal pixel electrodes

ABSTRACT A fast response liquid crystal display (LCD) with trapezoidal pixel electrodes is proposed. The trapezoidal shape of the pixel electrode generates a slanted electric field, eliminating the need for a non-zero pre-tilt angle to prevent random domain formation in the LC. Additionally, the absence of a pre-tilt angle enhances viewing angles. During operation, LC molecules can form virtual walls, increasing anchoring energy and improving response time. At 38% transmittance, the response time is 5.1 ms, while at 60% transmittance, it increases to 8.3 ms. With a circular polariser, the device achieves a contrast ratio of 200:1 and a viewing cone of approximately 18°. Consequently, the trapezoidal pixel electrode FFS cell is suitable for fast LCDs used in automotive displays and digital signage. Its narrow viewing angles with a circular polariser also make it ideal for personal privacy displays and certain mobile displays.

Effects of Wall and Freespace Damping Levels on Virtual Wall Stiffness Classification.

Virtual damping is often employed to improve stability in virtual environments, but it has previously been found to bias perception of stiffness, with its effects differing when it is introduced locally within a wall/object or globally in both the wall and in freespace. Since many potential applications of haptic rendering involve not only comparisons between two environments, but also the ability to recognize rendered environments as belonging to different categories, it is important to understand the perceptual impacts of freespace and wall damping on stiffness classification ability. This study explores the effects of varying levels of freespace and wall damping on users' ability to classify virtual walls by their stiffness. Results indicate that freespace damping improves wall classification if the walls are damped, but will impair classification of undamped walls. These findings suggest that, in situations where users are expected to recognize and classify various stiffnesses, freespace damping can be a factor in narrowing or widening gaps in extended rate-hardness between softer and stiffer walls.

Automatic Route Design by Stepwise Subdivision of Virtual Walls —Reduces Route Length and Speeds Up Execution Time—

With the development of autonomous driving technology utilizing machine learning, AI, and sensors, research on autonomous driving control has become more active, and a large number of innovative studies are underway. In the near future, all autonomous vehicle fleets will be able to communicate with each other for sharing information and overall optimal traffic control will be achieved. One of the vehicle control systems that are based on the premise of such a fully automated society is the “signal-less intersection.” There is an intersection traffic control method that achieves safe and rational route selection by using virtual walls (VWs), which are virtual obstacles, but there are issues in terms of total route length and reduction of computation time. To address the issues, we propose a method that (1) prunes unneeded paths and (2) arranges VWs in a stepwise manner. The effectiveness of the proposed method was evaluated by simulation, and the results showed that the total route length and execution time were reduced.

Virtual wall: Numerical model on interaction between trees and building façade to quantify heat exchange and microclimate in urban context

When simulating a building's energy demand, the tree surroundings should be accounted in their shade and reshaping microclimate, just representing an envelope layer as a virtual wall. This study delves into the effects of such tree-induced virtual walls on building energy dynamics, with a dataset derived from 24 distinct samples of building façades and adjacent trees within a campus environment. An experiment was designed to validate microclimate simulation that captures variations in sheltered radiation and temperature reductions. The study introduces and calculates the dynamic and static equivalent heat transfer coefficients and thermal resistances for the virtual wall. The findings reveal significant correlations between the calculated coefficients and resistances, and various factors such as seasonality, weather conditions, and façade orientation. The equivalent thermal resistance value for south façade is highest on sunny days, reaching up to 3.7 m2·K/W, and on cloudy days, east façade has the highest equivalent heat transfer coefficient and thermal resistance values, at around 8.5 W/m2·K and 10.3 m2·K/W, respectively. Moreover, the study reveals that the tree's impact is primarily determined by its height and canopy area, with the equivalent heat transfer coefficient negatively correlated with tree height and canopy area, and positively correlated with building height.

P‐264: Fast‐Response FFS LC Device with Multi‐rubbing Angle for VR Applications

In this paper, we propose new fast response FFS LC devices with virtual walls by using alternating (or multi) rubbing directions, which can be generated by using photo‐alignment. These new devices can offer much‐enhanced response‐speed compared to the conventional FFS LC device. By choosing different types of “local” LC molecular arrangements or designs (easily achievable by using photo‐alignment), we may be able to alter the virtual wall pitch length, and hence also alter the response speed and transmission of these fast response LC devices. These new designs can provide a new and alternative approach to generating virtual walls by “locally” varying the rubbing angle using photo‐alignment. These devices are attractive for VR applications where high speed operation of liquid crystal devices is required.

Elevating haptic interfaces: Dual‐rate sampling and field programmable gate array implementation for multi‐degree‐of‐freedom performance enhancement

AbstractIn this work, our primary focus centered on exploring the adaptability of the dual‐rate sampling scheme proposed earlier to enhance the performance of multi‐degree‐of‐freedom (multi‐DOF) impedance‐based haptic interfaces. The scheme employed independent sampling rates in a haptics controller, effectively mitigating the issue of reduced Z‐width at higher sampling rates. A key aspect of our investigation was the intricate implementation of the dual‐rate sampling scheme on a field programmable gate array (FPGA). This implementation on a logic hardware FPGA was challenging and led to the effective comparison of the uniform‐rate and dual‐rate sampling schemes of the multi‐DOF haptic controller. We used an in‐house developed two‐DOF pantograph as the haptic interface and an FPGA for implementing the controller strategy. FPGA‐based implementation presented challenges that were vital in testing controller performances at higher sampling rates. Virtual wall experiments were conducted to determine the stable and unstable interactions with the virtual wall. To complement the experimental results, we simulated the haptics force law for multi‐DOF system on Simulink/MATLAB. Notably, the dual‐rate sampling approach maintained the Z‐width of the two‐DOF haptic interface, even at higher controller sampling rates, distinguishing it from the conventional two‐DOF uniform‐rate control scheme. For example, employing a dual‐rate sampling combination of 20–2 kHz consistently ensured the stable rendering of a maximum virtual stiffness of approximately 700 N/mm and maintained a reliable virtual damping range spanning from 0 to 5 Ns/mm. In contrast, the 20 kHz uniform‐rate sampling approach failed to ensure interface stability in the presence of virtual damping, ultimately resulting in the unsuccessful implementation of any virtual stiffness at higher sampling rates. This work, therefore, establishes the potential of dual‐rate sampling in the realm of haptic technology, with practical applications in multi‐DOF systems.

Shaking a container full of perfect liquid; a tractable case, a torus shell, exhibits a virtual wall

Manipulation (‘shaking’) of a rigid container filled with incompressible liquid starting from stationary generally results in some displacement, or mixing, of the liquid within it. If the liquid also has zero viscosity, a ‘perfect’ or ‘Euler’ liquid, Kelvin’s theorems dramatically simplify the flow analysis. Response is instantaneous; stop the container and all liquid motion stops. In fact an arbitrary manipulation can be considered as alternating infinitesimal translations and rotations of the container. Relative to the container, the liquid is stationary during every translation. Infinitesimal rotations (an infinitesimal vector along the rotation axis) resolve into three orthogonal components in the container frame. Each generates its own infinitesimal liquid displacement vector field. Their combined consequences are usually obscure. Rather than a volume flow, a surface flow in 3D is considerably easier, the liquid slipping freely in a shell, sandwiched between two nested closed surfaces with constant infinitesimal gap. The closedness avoids extra boundaries. The two dimensionality admits a scalar streamfunction determined by the container angular velocity vector. Manipulation of the container angular velocity at will, usually leads to an infinitely rich variety of area preserving re-configurations of the liquid. In particular, any chosen point of the liquid can be moved, in the shell container frame, to any other chosen point. However, for a torus (shell) with a small enough hole (diameter < 0.195 torus diameter), there exists a virtual wall, a hypothetical axial cylinder intersecting the torus. No matter how the torus is manipulated, liquid inside the cylinder stays inside; outside stays outside. The analysis, solving for the streamfunction, is based on the relative vorticity, and the conformal mapping of a torus to a (periodic) rectangle, which lead to a fairly simple convolution integral formula for the flow.

A volume-conservation particle shifting scheme for moving particle method simulating free-surface flow

AbstractIn this study, a novel particle shifting scheme for the moving particle method simulating free surface flow is developed. The overall method is based on the framework of least square moving particle semi-implicit (LSMPS) method, enabling accurate and stable treatment of wall boundary without configuration of dummy or virtual wall particles. To avoid volume expansion, a volume-conservation particle shifting (VCPS) model is developed. An additional term considering the variation of particle numerical density is incorporated into the VCPS model to avoid volume expansion. Several numerical simulations are calculated to validate the effectiveness of the VCPS. It is demonstrated that LSMPS incorporating with VCPS shows satisfactory accuracy and superior capability to conserve volume.

Interchange flow control with dynamic obstacles optimized using genetic algorithms—a concept of virtual walls

Interchange flow control with dynamic obstacles optimized using genetic algorithms—a concept of virtual walls

Effect of chevron-shaped wetting patterns on oil film thickness in cylinder-on-disc contact under starved lubrication or limited lubricant supply

This study addresses the oil starvation problem in roller bearing line contacts and proposes a novel Chevron-shaped wetting/oleophilic pattern on the bearing track to enhance oil replenishment. Validation through optical cylinder-on-disc lubrication film tests reveals the impact of the pattern on inlet oil supply and film thickness. Notably, a Chevron pattern oriented opposite to disc movement significantly increases film thickness. Wetting is more pronounced in oleophilic areas (Chevron pattern), forming an inverted V-shaped "virtual wall" that directs lubricant backflow toward the center and reduces side leakage. A pattern length equal to the bearing track width was found to be more effective compared to smaller sizes, as the oil side ridges are located on the oleophobic and oleophilic boundaries, which capitalizes the wettability step effect more effectively. This research provides a basis for designing oleophobic surfaces with improved anti-wear and anti-friction properties.

Development of a low-cost upper-body rehabilitation robot for home use.

The inability to use one's hands or arms greatly restricts the ability to perform daily activities. After a developmental or acquired injury, the intensity and frequency of rehabilitation exercises are essential. To alleviate the burden on the healthcare system, robotic systems have been developed to support clinicians' interventions. However, these systems are often bulky and expensive, limiting their use to specific clinical settings and making them impractical for home use. This paper presents the development of an affordable and easy to install 2-DOF five-bar linkage robot designed to be used at home. This work aims to reduce the cost of the robot through actuation optimization, mechanical optimization and 3D printing. The architecture and links length are chosen to optimize the robot's performance in the required workspace. Using sensor feedback, impedance control algorithms and multiple types of exercise such as virtual walls guidance are implemented. Finally, a user interface was programmed to facilitate the robot's use.

Electrical Muscle Stimulation for Kinesthetic Feedback in AR/VR: A Systematic Literature Review

This paper presents a thorough review of electrical muscle stimulation (EMS) in the context of augmented reality (AR) and virtual reality (VR), specifically focusing on its application in providing kinesthetic feedback. Our systematic review of 17 studies reveals the growing interest and potential of EMS in this domain, as evidenced by the growing body of literature and citations. The key elements presented in our review encompass a catalog of the applications developed to date, the specifics of the stimulation parameters used, the participant demographics of the studies, and the types of measures used in these research efforts. We discovered that EMS offers a versatile range of applications in AR/VR, from simulating physical interactions like touching virtual walls or objects to replicating the sensation of weight and impact. Notably, EMS has shown effectiveness in areas such as object handling and musical rhythm learning, indicating its broader potential beyond conventional haptic feedback mechanisms. However, our review also highlights major challenges in the research, such as inconsistent reporting of EMS parameters and a lack of diversity in study participants. These issues underscore the need for improved reporting standards and more inclusive research approaches to ensure wider applicability and reproducibility of results.

Direct Comparisons of Upper-Limb Motor Learning Performance Among Three Types of Haptic Guidance With Non-Assisted Condition in Spiral Drawing Task.

In robot-assisted rehabilitation, it is unclear which type of haptic guidance is effective for regaining motor function because of the lack of direct comparisons among multiple types of haptic guidance. The objective of this study was to investigate the effects of different types of haptic guidance on upper limb motor learning in a spiral drawing task. Healthy young participants performed two experiments in which they practiced the drawing movement using a robotic manipulandum with a virtual wall (Path guidance), running direction pushing and virtual wall (Path & Push guidance), restriction to the target movement (Target guidance), or without haptic guidance (Free guidance). Experiment 1 compared the learning effects of the four types of guidance. Experiment 2 investigated the effects of pre-learning with Path, Path & Push, or Target guidance on post-learning with Free guidance. In Experiment 1, Free guidance demonstrated the greatest learning effect, followed by Path guidance, which showed a significantly greater improvement in task performance than the other two types of guidance. In Experiment 2, the type of pre-learning did not influence post-learning with Free guidance. The results suggested that learning with Path guidance showed a slightly slower but comparable effect to Free guidance and was the most effective among the three types of haptic guidance. The superiority of Path guidance over other haptic guidance was interpreted within the framework of error-based learning, in which the intensity of sensory feedback and voluntary motor control play important roles.

Performance analysis of a novel metamaterial-inspired substrate-integrated cavity for 5G applications

The functionality of a fully planar metamaterial-inspired substrate-integrated cavity is thoroughly investigated in the present work. The electromagnetic field confinement of the proposed device is realized with the utilization of broadside-coupled complementary split ring resonators that operate as a virtual electric wall. The numerical results from the eigenvalue analysis verify the presence of the fundamental resonances with a noteworthy quality factor. Subsequently, full-wave simulations are conducted to validate the resonance functionality of the proposed device, with excitation achieved using the metallic core of a coaxial cable. Numerical results highlighted, also, the radiation capabilities exploiting the inherent openings in the device due to the complementary resonators.

Leveraging Artificial Intelligence to Reduce Human-Animal Conflict in India

The case focuses on the use of artificial intelligence (AI) and computer vision (CV) technologies to solve a socially complex issue of human-animal conflict in the geographical regions surrounding the Tadoba Andhari Tiger Reserve (TATR) in Maharashtra state in central India. Due to an increasing tiger population, the villages surrounding the TATR often encountered tigers that strayed outside the reserve, sometimes leading to injuries or fatalities either to the humans or the wild animals involved. Valiance, a technology company, collaborated with the Forest department and other local stakeholders to create a computer vision based AI virtual wall system as a pilot project. The technology solution monitored the location 24hrs a day 7 days a week and had the capability of identifying tigers, leopards, and other predators, and sending out automated, real time alerts to help prevent human-animal conflict situations. Based on the outcome of the pilot, the solution could be refined and then a wider rollout could be planned.