Front-induced transitions control THz waves

Relativistically moving dielectric perturbations can be used to manipulate light in new and exciting ways beyond the capabilities of traditional nonlinear optics. Adiabatic interaction with the moving front modulates the wave simultaneously in both space and time, and manifests a front-induced transition in both wave vector and frequency yielding exotic effects including non-reciprocity and time-reversal. Here we introduce a technique called SLIPSTREAM, Spacetime Light-Induced Photonic STRucturEs for Advanced Manipulation, based on the creation of relativistic fronts in a semiconductor-filled planar waveguide by photoexcitation of mobile charge carriers. In this work, we demonstrate the capabilities of SLIPSTREAM for the manipulation of terahertz (THz) light pulses through relativistic front-induced transitions. In the sub-luminal front velocity regime, we generate temporally stretched THz waveforms, with a quasi-static field lasting for several picoseconds tunable with the front interaction distance. In the super-luminal regime, the carrier front outpaces the THz pulse and a time-reversal operation is performed via a front-induced intra-band transition. We anticipate our platform will be a versatile tool for future applications in the THz spectral band requiring direct and advanced control of light at the sub-cycle level.

Nano-channel-based physical and chemical synergic regulation for dendrite-free lithium plating

Uncontrollable dendrite growth resulting from the non-uniform lithium ion (Li+) flux and volume expansion in lithium metal (Li) negative electrode leads to rapid performance degradation and serious safety problems of lithium metal batteries. Although N-containing functional groups in carbon materials are reported to be effective to homogenize the Li+ flux, the effective interaction distance between lithium ions and N-containing groups should be relatively small (down to nanometer scale) according to the Debye length law. Thus, it is necessary to carefully design the microstructure of N-containing carbon materials to make the most of their roles in regulating the Li+ flux. In this work, porous carbon nitride microspheres (PCNMs) with abundant nanopores have been synthesized and utilized to fabricate a uniform lithiophilic coating layer having hybrid pores of both the nano- and micrometer scales on the Cu/Li foil. Physically, the three-dimensional (3D) porous framework is favorable for absorbing volume changes and guiding Li growth. Chemically, this coating layer can render a suitable interaction distance to effectively homogenize the Li+ flux and contribute to establishing a robust and stable solid electrolyte interphase (SEI) layer with Li-F, Li-N, and Li-O-rich contents based on the Debye length law. Such a physical-chemical synergic regulation strategy using PCNMs can lead to dendrite-free Li plating, resulting in a low nucleation overpotential and stable Li plating/stripping cycling performance in both the Li‖Cu and the Li‖Li symmetric cells. Meanwhile, a full cell using the PCNM coated Li foil negative electrode and a LiFePO4 positive electrode has delivered a high capacity retention of ∼ 80% after more than 200 cycles at 1 C and achieved a remarkable rate capability. The pouch cell fabricated by pairing the PCNM coated Li foil negative electrode with a NCM 811 positive electrode has retained ∼ 73% of the initial capacity after 150 cycles at 0.2 C.

PHYSICAL DISTANCING ALARM SYSTEM BASED ON PROXIMITY SENSOR AND MICROCONTROLLER

Keeping an interaction distance between 1 to 2 m is one of the health protocols during the COVID-19 pandemic. This attempt was made to reduce the spread of the Coronavirus. On the other hand, this health protocol activity is often overlooked, whether intentionally or not. According to the mechanism of the Coronavirus spreading in the form of droplets that comes out during communication, sneezing, or coughing, maintaining distance can be the best effort to minimize the transmission of this virus. Therefore, the availability of a simple, accurate and user-friendly physical distancing alarm system could be a solution in the implementation of this health protocol. In this study, a prototype of a physical distancing alarm based on a distance sensor and a microcontroller in the form of an identity card was developed. Several steps are conducted in developing of this system, namely designing the instrumentation system and testing the performance of the system. System performance is tested through variations in the distance and angle of the objects. The measurement results show that the system can detect objects in front of the sensor up to a distance of 2.8m and an angle of for a distance of 1m. The measurement using different angles of objects was performed for objects on the left and right sides of the sensor. In addition, a warning alarm will be on when the distance of the object exceeds the allowed distance.

Evolutionary Distance of Gene-Gene Interactions: Estimation under Statistical Uncertainty

Consider the functional interaction of gene A to an interaction subject X; for instance, it is the gene-gene interaction if X represents for a gene, or gene-tissue interaction (expression status) if X for a tissue. In the simplest case, the status of this A-X interaction is r=1 if they are interacted, or r=0 otherwise. A fundamental problem in molecular evolution is, given two homologous (orthologous or paralogous) genes A and B, to what extent their functional overlapping could be by the means of interaction networks. Given a set of interaction subjects (X1, … XN), it is straightforward to calculate the interaction distance (IAB) between genes A and B, by a Markov-chain model. However, since the high throughput interaction data always involve a high level of noises, reliable inference of r=1 or r=0 for each gene remains a big challenge. Consequently, the estimated interaction distance (IAB) is highly sensitive to the cutoff of interaction inference which is subject to some arbitrary. In this paper we will address this issue by developing a statistical method for estimating IAB based on the p-values (significant levels). Computer simulations are carried out to evaluate the performance of different p-value transformations against the uncertainty of interaction networks.

The Semantic Meaning of Hand Shapes and Z-Dimension Movements of Freehand Distal Pointing on Large Displays

It is difficult to select small targets in freehand distal pointing on large displays due to physical fatigue and jitter. Previous research proposed many solutions but not through the semantic meaning of hand behaviors. The purpose of this study is to investigate the hand behaviors, including hand shapes and motions in the Z-dimension between small and large target selections, by means of two controlled experiments. The generated results indicated that the following: (1) when interacting with a large display from a remote distance, users preferred to complete a low-precision task by the whole hand while using the finger in high-precision tasks. As a result, users moved small targets by the index finger gesture while moving large targets by open hand gesture; (2) selection of small targets led to hand stretching which might reduce the interaction distance; (3) the orientation had significant effects on hand motions in the Z-dimension. The relationship between orientation and hand motions in the Z-dimension is similar to a sinusoidal function; (4) mouse-like pointing had much impact on freehand interaction. Based on these results, some design guidelines for freehand interaction and design suggestions for freehand pointing were discussed.

Distance Learning and Interactivity

This chapter explores the meaning of interaction in distance learning. It focuses on the main models of interaction that may appear during the learning procedure and centers to student-student interaction, student-teacher interaction, and finally student-content interaction. Through literature review, definitions are explored and clarified. The whole chapter is a small effort to give the reader a clarification and a perspective on interaction, distance learning, and how they are both connected to each other.