544 research outputs found
A Continued Fraction Resummation Form of Bath Relaxation Effect in the Spin-Boson Model
In the spin-boson model, a continued fraction form is proposed to
systematically resum high-order quantum kinetic expansion (QKE) rate kernels,
accounting for the bath relaxation effect beyond the second-order perturbation.
In particular, the analytical expression of the sixth-order QKE rate kernel is
derived for resummation. With higher-order correction terms systematically
extracted from higher-order rate kernels, the resummed quantum kinetic
expansion (RQKE) approach in the continued fraction form extends the Pade
approximation and can fully recover the exact quantum dynamics as the expansion
order increases.Comment: accepted by J. Chem. Phy
Effects of Altitude on Fire Smoke Diffusion in Semi-Lateral Smoke Exhaust Highway Tunnels
This paper aims to study the effects of altitude and the size of smoke outlet on fire smoke diffusion and discharge in semi-lateral smoke exhaust highway tunnels. At first, simulations of semi-lateral smoke exhaust highway tunnels were carried out in FDS (Fire Dynamics Simulator), then the distribution laws of temperature, CO concentration, smoke mass flow, and visibility in the tunnel under the conditions of different altitudes and smoke outlet areas were analyzed to figure out the effects of altitude and size of smoke outlet on fire smoke diffusion and discharge in the said tunnels. The results suggest that, in case of the same fire source power, the velocity of smoke diffusion increases with the altitude; for curves of different altitudes, the tunnel roof temperature features are basically the same, that is, the higher the altitude, the higher the temperature at the tunnel roof. When the fire source power is 20 MW, the smoke mass flow at the smoke outlet decreases with the increase of altitude, but the CO concentration grows with it, indicating that the smoke exhaust efficiency is higher in high-altitude areas. When the altitude reaches 4200 m and the fire source power is 20 MW, with the increase of smoke outlet area, the smoke discharge effect of the tunnel shows an upward trend, taking both the smoke discharge effect and economy into consideration; the smoke outlet should take a size of 4 x 3 m
Try with Simpler -- An Evaluation of Improved Principal Component Analysis in Log-based Anomaly Detection
The rapid growth of deep learning (DL) has spurred interest in enhancing
log-based anomaly detection. This approach aims to extract meaning from log
events (log message templates) and develop advanced DL models for anomaly
detection. However, these DL methods face challenges like heavy reliance on
training data, labels, and computational resources due to model complexity. In
contrast, traditional machine learning and data mining techniques are less
data-dependent and more efficient but less effective than DL. To make log-based
anomaly detection more practical, the goal is to enhance traditional techniques
to match DL's effectiveness. Previous research in a different domain (linking
questions on Stack Overflow) suggests that optimized traditional techniques can
rival state-of-the-art DL methods. Drawing inspiration from this concept, we
conducted an empirical study. We optimized the unsupervised PCA (Principal
Component Analysis), a traditional technique, by incorporating lightweight
semantic-based log representation. This addresses the issue of unseen log
events in training data, enhancing log representation. Our study compared seven
log-based anomaly detection methods, including four DL-based, two traditional,
and the optimized PCA technique, using public and industrial datasets. Results
indicate that the optimized unsupervised PCA technique achieves similar
effectiveness to advanced supervised/semi-supervised DL methods while being
more stable with limited training data and resource-efficient. This
demonstrates the adaptability and strength of traditional techniques through
small yet impactful adaptations
Orecchio: Extending Body-Language through Actuated Static and Dynamic Auricular Postures
In this paper, we propose using the auricle â the visible part of the ear â as a means of expressive output to extend body language to convey emotional states. With an initial exploratory study, we provide an initial set of dynamic and static auricular postures. Using these results, we examined the relationship between emotions and auricular postures, noting that dynamic postures involving stretching the top helix in fast (e.g., 2Hz) and slow speeds (1Hz) conveyed intense and mild pleasantness while static postures involving bending the side or top helix towards the center of the ear were associated with intense and mild unpleasantness. Based on the results, we developed a prototype (called Orrechio) with miniature motors, custommade robotic arms and other electronic components. A preliminary user evaluation showed that participants feel more comfortable using expressive auricular postures with people they are familiar with, and that it is a welcome addition to the vocabulary of human body language
Host-Guest Complexation of Amphiphilic Molecules at the Air-Water Interface Prevents Oxidation by Hydroxyl Radicals and Singlet Oxygen
The oxidation of antioxidants by oxidizers imposes great challenges to both living organisms and the food industry. Here we show that the hostâguest complexation of the carefully designed, positively charged, amphiphilic guanidinocalix[5]arene pentadodecyl ether (GC5Aâ12C) and negatively charged oleic acid (OA), a wellâknown cell membrane antioxidant, prevents the oxidation of the complex monolayers at the airâwater interface from two potent oxidizers hydroxyl radicals (OH) and singlet delta oxygen (SDO). OH is generated from the gas phase and attacks from the top of the monolayer, while SDO is generated inside the monolayer and attacks amphiphiles from a lateral direction. Fieldâinduced droplet ionization mass spectrometry results have demonstrated that the hostâguest complexation achieves steric shielding and prevents both types of oxidation as a result of the tight and âsleeved inâ physical arrangement, rather than the chemical reactivity, of the complexes
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