3,095 research outputs found
Case Histories of Poor Quality Contingency of Foundation Soil Improvement of 50,000 Kiloliters Oil Storage Tank
This paper introduces case histories of poor quality contingency of foundation soil improvement of 50,000 kiloliters oil storage tanks. Inhomogeneity of soft and hard soil layers in oil tank area, and in the process of construction, effective improvement measures had not been taken, and this produced bad effects to oil tank
Controlling the Intrinsic Josephson Junction Number in a Mesa
In fabricating intrinsic Josephson
junctions in 4-terminal mesa structures, we modify the conventional fabrication
process by markedly reducing the etching rates of argon ion milling. As a
result, the junction number in a stack can be controlled quite satisfactorily
as long as we carefully adjust those factors such as the etching time and the
thickness of the evaporated layers. The error in the junction number is within
. By additional ion etching if necessary, we can controllably decrease
the junction number to a rather small value, and even a single intrinsic
Josephson junction can be produced.Comment: to bu published in Jpn. J. Appl. Phys., 43(7A) 200
High quality electron beam acceleration by ionization injection in laser wakefields with mid-infrared dual-color lasers
For the laser wakefield acceleration, suppression of beam energy spread while keeping sufficient charge is one of the key challenges. In order to achieve this, we propose bichromatic laser ionization injection with combined laser wavelengths of 2.4 μ m and 0.8 μ m for wakefield excitation and triggering electron injection via field ionization, respectively. A laser pulse at 2.4 μ m wavelength enables one to drive an intense acceleration structure with a relatively low laser power. To further reduce the requirement of laser power, we also propose to use carbon dioxide as the working gas medium, where carbon acts as the injection element. Our three dimensional particle-in-cell simulations show that electron beams at the GeV energy level with both low energy spreads (around 1%) and high charges (several tens of picocoulomb) can be obtained by the use of this scheme with laser peak power totaling sub-100 TW
DLIP: Distilling Language-Image Pre-training
Vision-Language Pre-training (VLP) shows remarkable progress with the
assistance of extremely heavy parameters, which challenges deployment in real
applications. Knowledge distillation is well recognized as the essential
procedure in model compression. However, existing knowledge distillation
techniques lack an in-depth investigation and analysis of VLP, and practical
guidelines for VLP-oriented distillation are still not yet explored. In this
paper, we present DLIP, a simple yet efficient Distilling Language-Image
Pre-training framework, through which we investigate how to distill a light VLP
model. Specifically, we dissect the model distillation from multiple
dimensions, such as the architecture characteristics of different modules and
the information transfer of different modalities. We conduct comprehensive
experiments and provide insights on distilling a light but performant VLP
model. Experimental results reveal that DLIP can achieve a state-of-the-art
accuracy/efficiency trade-off across diverse cross-modal tasks, e.g.,
image-text retrieval, image captioning and visual question answering. For
example, DLIP compresses BLIP by 1.9x, from 213M to 108M parameters, while
achieving comparable or better performance. Furthermore, DLIP succeeds in
retaining more than 95% of the performance with 22.4% parameters and 24.8%
FLOPs compared to the teacher model and accelerates inference speed by 2.7x
Acceleration of on-axis and ring-shaped electron beams in wakefields driven by Laguerre-Gaussian pulses
The acceleration of electron beams with multiple transverse structures in wakefields driven by Laguerre-Gaussian pulses has been studied through three-dimensional (3D) particle-in-cell simulations. Under different laser-plasma conditions, the wakefield shows different transverse structures. In general cases, the wakefield shows a donut-like structure and it accelerates the ring-shaped hollow electron beam. When a lower plasma density or a smaller laser spot size is used, besides the donut-like wakefield, a central bell-like wakefield can also be excited. The wake sets in the center of the donut-like wake. In this case, both a central on-axis electron beam and a ring-shaped electron beam are simultaneously accelerated. Further, reducing the plasma density or laser spot size leads to an on-axis electron beam acceleration only. The research is beneficial for some potential applications requiring special pulse beam structures, such as positron acceleration and collimation
Tunable synchrotron-like radiation from centimeter scale plasma channels
Synchrotron radiation sources are immensely useful tools for scientific researches and many practical applications. Currently, the state-of-the-art synchrotrons rely on conventional accelerators, where electrons are accelerated in a straight line and radiate in bending magnets or other insertion devices. However, these facilities are usually large and costly. Here, we study a compact all-optical synchrotron like radiation source based on laser-plasma acceleration either in a straight or a curved plasma channel. With the laser pulse off-axially injected, its centroid oscillates transversely in the plasma channel. This results in a wiggler motion of the whole accelerating structure and the self-trapped electrons behind the laser pulse, leading to strong synchrotron-like radiations with tunable spectra. It is further shown that a palmtop ring-shaped synchrotron is possible with current high power laser technologies. With its potential of high flexibility and tunability, such light sources once realized would find applications in wide areas and make up the shortage of large synchrotron radiation facilities
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