Suchergebnisse

According to the characteristics of the reactor internal structure of nuclear power plants, the vibration of the secondary core support pillar in water can be modeled as the vibration of the cantilever beam structure under the action of transverse flow, and its first beam mode is highly likely to be activated. It is thus necessary to dedicate a separate study on the first-order beam mode. In this work, we study the secondary core support pillar in nuclear reactor AP1000 under the action of transverse flow and focus on the derivation of its static cantilever deflection mode shape function in order to lay a foundation for the calculation of hydrodynamic added mass and frequency for the nuclear reactor internal components and their structural integrity evaluation. First, we proposed a set of nonlinear differential equations for the analysis of the single cantilever beam. Second, to solve the nonlinear differential equations, we used a boundary shooting framework in combination with the Runge–Kutta method. The results of the numerical simulation agree with the analytical solution to a very high degree, which demonstrates the effectiveness of the simulation method. Finally, we solved the static deflection mode shape function of the secondary core support pillar under the normal operating conditions. The nonlinear differential model and simulation method proposed in this paper can be used to solve the static cantilever deflection mode shape function of the equipment support tube.

In vitro diagnosis (IVD) has become a hot topic in laboratory research and achievement transformation. However, due to the high cost, and time-consuming and complex operation of traditional technologies, some new technologies are being introduced into IVD, to solve the existing problems. As a result, IVD has begun to develop toward point-of-care testing (POCT), a subdivision field of IVD. The pandemic has made governments and health institutions realize the urgency of accelerating the development of POCT. Microfluidic paper-based analytical devices (μPADs), a low-cost, high-efficiency, and easy-to-operate detection platform, have played a significant role in advancing the development of IVD. μPADs are composed of paper as the core material, certain unique substances as reagents for processing the paper, and sensing devices, as auxiliary equipment. The published reviews on the same topic lack a comprehensive and systematic introduction to μPAD classification and research progress in IVD segmentation. In this paper, we first briefly introduce the origin of μPADs and their role in promoting IVD, in the introduction section. Then, processing and detection methods for μPADs are summarized, and the innovative achievements of μPADs in IVD are reviewed. Finally, we discuss and prospect the upgrade and improvement directions of μPADs, in terms of portability, sensitivity, and automation, to help researchers clarify the progress and overcome the difficulties in subsequent μPAD research.

Abstract. Detachments of large parts of low-angle mountain glaciers in
recent years have raised great attention due to their threats to lives and
properties downstream. While current studies have mainly focused on
post-event analysis, a few opportunities have presented themselves to assess
the potential hazards of a glacier prone to detachment. Here we present a
comprehensive analysis of the dynamics and runout hazard of a low-angle
(∼20∘) valley glacier, close to the Qinghai–Tibet
railway and highway, in the East Kunlun Mountains on the Qinghai–Tibet
Plateau. The changes in morphology, terminus position, and surface elevation
of the glacier between 1975 and 2021 were characterized with a stereo-image
pair from the historical KH-9 spy satellite, six digital elevation models
(DEMs), and 11 high-resolution images from Planet Labs. The surface flow
velocities of the glacier tongue between 2009 and 2020 were also tracked
based on cross-correlation of Planet images. Our observations show that the
glacier snout has been progressively advancing in the past 4 decades,
with a stepwise increase in advance velocity from 4.55±0.46ma-1 between 1975 and 2009 to 30.88±2.36ma-1 between 2015 and 2020. DEM differencing confirms the
glacial advance, with surface thinning in the source region and thickening
in the tongue. The net volume loss over the glacier tongue was about
11.21±2.66×105 m3 during 1975–2018. Image
cross-correlation reveals that the surface flow velocity of the glacier
tongue has been increasing in recent years, with the mean velocity below
4800 m more than tripling from 6.3±1.8ma-1 during
2009–2010 to 22.3±3.2ma-1 during 2019–2020. With
a combined analysis of the geomorphic, climatic, and hydrologic conditions
of the glacier, we suggest that the flow of the glacier tongue is mainly
controlled by the glacier geometry, while the presence of an ice-dammed lake
and a supraglacial pond implies a hydrological influence as well. Taking the
whole glacier and glacier tongue as two endmember avalanche sources, we
assessed the potential runout distances of these two scenarios using the
angle of reach and the Voellmy–Salm avalanche model. The assessments show
that the avalanche of the whole glacier would easily travel a distance that would threaten the safety of the railway. In contrast, the detachment of the
glacier tongue would threaten the railway only with a small angle of reach
or when employing a low-friction parameter in the Voellmy–Salm modeling.