Blowup solutions of Grushin's operator

In this note, we consider the blowup phenomenon of Grushin's operator. By using the knowledge of probability, we first get expression of heat kernel of Grushin's operator. Then by using the properties of heat kernel and suitable auxiliary function, we get that the solutions will blow up in finite time.Comment:

Effects of High Intensity Interval Training on Children’s Health and Physical Fitness

The effect of high intensity interval training on children’s health is the focus of experts and scholars worldwide. After the outline of “Building a Strong Country in Sports” was issued in 2019, China’s attention to sports has reached a peak. However, the proportion of obese or myopic children in schools at all levels is still high, and the problem of low physical fitness of Chinese students is still serious. The purpose of this study was to review previous studies to explore the effects of high intensity interval training on children’s health and physical fitness. We reviewed relevant literature both in Chinese and English, sorted out and summarized the research results. We found that high intensity interval training has a positive impact on children’s health and physical fitness, can significantly improve children’s muscle strength and cardiopulmonary endurance, and can effectively reduce fat mass in overweight and obese children. Meanwhile, the high intensity interval training has higher training pleasure. Therefore, high intensity interval training can be used as an effective exercise method for children. It is suggested to handle the relationship scientifically and reasonably among individual differences, training time, and training intensity. We should pay attention to the group training workload for overweight and obese children, adopt the principle of gradual improvement, and gradually improve the ability and health level of overweight and obese children

THE BIOLOGY OF PHENACOCCUS AZALEAE KUWANA, A PEST OF BUNGE PRICKLY ASH (ZANTHOXYLUM BUNGEANUM MAXIM) FOREST IN NORTHERN CHINA

THE BIOLOGY OF PHENACOCCUS AZALEAE KUWANA, A PEST OF BUNGE PRICKLY ASH (ZANTHOXYLUM BUNGEANUM MAXIM) FOREST IN NORTHERN CHINA. Phenacoccus azaleae Kuwana (Hemiptera: Coccoidea: Pseudococcidae) is a major new pest of bunge prickly ash forest in northern China, where it causes high tree mortality when present for two consecutive years. This paper reports on the biology of this pest in northern China, where it has been studied since 1995. The life cycle can be divided into eight phases, two of which cause severe injury to the host plant, through the feeding of: (a) the 3rd-instar nymphs and adult females between late March and mid-May, and (b) the young nymphs which are present on the leaves between late June and October. The adult sex ratio was 6-7TM:1¢. The various development stages are described. Of the natural enemies, ladybirds (Coccinellidae) and lacewings (Neuroptera) were the major predators, but they were not abundant in the newly- infested areas. In addition, a few parasitic Hymenoptera were recorded but appeared to be ineffective. Key words: Aphis gossypii, Papilio xuthus, Podagri comeiashirahatai, Calloides magnificus, Agrilus zanthoxylumi, plum, elm, Azalea, Japan, Korea, voltinism, development, population dynamics, damage, Lasius fuliginosus, L. niger, sex ratio, growth rate, Harmonia axyridis, Coccinella septempunctata, Chrysopa

Influence of the Arctic Oscillation on the Vertical Distribution of Wintertime Ozone in the Stratosphere and Upper Troposphere over Northern Hemisphere

The influence of the Arctic Oscillation (AO) on the vertical distribution of stratospheric ozone in the Northern Hemisphere in winter is analyzed using observations and an offline chemical transport model. Positive ozone anomalies are found at low latitudes (0–30°N) and there are three negative anomaly centers in the northern mid- and high latitudes during positive AO phases. The negative anomalies are located in the Arctic middle stratosphere (~30 hPa, 70–90°N), Arctic upper troposphere/lower stratosphere (UTLS, 150–300 hPa, 70–90°N), and mid-latitude UTLS (70–300 hPa, 30–60°N). Further analysis shows that anomalous dynamical transport related to AO variability primarily controls these ozone changes. During positive AO events, positive ozone anomalies between 0–30°N at 50–150 hPa are related to the weakened meridional transport of the Brewer–Dobson circulation (BDC) and enhanced eddy transport. The negative ozone anomalies in the Arctic middle stratosphere are also caused by the weakened BDC, while the negative ozone anomalies in the Arctic UTLS are caused by the increased tropopause height, weakened BDC vertical transport, weaker exchange between the mid-latitudes and the Arctic, and enhanced ozone depletion via heterogeneous chemistry. The negative ozone anomalies in the mid-latitude UTLS are due mainly to enhanced eddy transport from the mid-latitudes to the equatorward of 30°N, while the transport of ozone-poor air from the Arctic to the mid-latitudes makes a minor contribution. Interpreting AO-related variability of stratospheric ozone, especially in the UTLS, would be helpful for the prediction of tropospheric ozone variability caused by AO

High-performance and Scalable Software-based NVMe Virtualization Mechanism with I/O Queues Passthrough

NVMe(Non-Volatile Memory Express) is an industry standard for solid-state drives (SSDs) that has been widely adopted in data centers. NVMe virtualization is crucial in cloud computing as it allows for virtualized NVMe devices to be used by virtual machines (VMs), thereby improving the utilization of storage resources. However, traditional software-based solutions have flexibility benefits but often come at the cost of performance degradation or high CPU overhead. On the other hand, hardware-assisted solutions offer high performance and low CPU usage, but their adoption is often limited by the need for special hardware support or the requirement for new hardware development. In this paper, we propose LightIOV, a novel software-based NVMe virtualization mechanism that achieves high performance and scalability without consuming valuable CPU resources and without requiring special hardware support. LightIOV can support thousands of VMs on each server. The key idea behind LightIOV is NVMe hardware I/O queues passthrough, which enables VMs to directly access I/O queues of NVMe devices, thus eliminating virtualization overhead and providing near-native performance. Results from our experiments show that LightIOV can provide comparable performance to VFIO, with an IOPS of 97.6%-100.2% of VFIO. Furthermore, in high-density VMs environments, LightIOV achieves 31.4% lower latency than SPDK-Vhost when running 200 VMs, and an improvement of 27.1% in OPS performance in real-world applications

A Regulatory Module Controlling Homeostasis of a Plant Immune Kinase

Plant pattern recognition receptors (PRRs) perceive microbial and endogenous molecular patterns to activate immune signaling. The cytoplasmic kinase BIK1 acts downstream of multiple PRRs as a rate-limiting component, whose phosphorylation and accumulation are central to immune signal propagation. Previous work identified the calcium-dependent protein kinase CPK28 and heterotrimeric G proteins as negative and positive regulators of BIK1 accumulation, respectively. However, mechanisms underlying this regulation remain unknown. Here we show that the plant U-box proteins PUB25 and PUB26 are homologous E3 ligases that mark BIK1 for degradation to negatively regulate immunity. We demonstrate that the heterotrimeric G proteins inhibit PUB25/26 activity to stabilize BIK1, whereas CPK28 specifically phosphorylates conserved residues in PUB25/26 to enhance their activity and promote BIK1 degradation. Interestingly, PUB25/26 specifically target non-activated BIK1, suggesting that activated BIK1 is maintained for immune signaling. Our findings reveal a multi-protein regulatory module that enables robust yet tightly regulated immune responses

High-throughput, combinatorial synthesis of multimetallic nanoclusters

Multimetallic nanoclusters (MMNCs) offer unique and tailorable surface chemistries that hold great potential for numerous catalytic applications. The efficient exploration of this vast chemical space necessitates an accelerated discovery pipeline that supersedes traditional “trial-and-error” experimentation while guaranteeing uniform microstructures despite compositional complexity. Herein, we report the high-throughput synthesis of an extensive series of ultrafine and homogeneous alloy MMNCs, achieved by 1) a flexible compositional design by formulation in the precursor solution phase and 2) the ultrafast synthesis of alloy MMNCs using thermal shock heating (i.e., ∼1,650 K, ∼500 ms). This approach is remarkably facile and easily accessible compared to conventional vapor-phase deposition, and the particle size and structural uniformity enable comparative studies across compositionally different MMNCs. Rapid electrochemical screening is demonstrated by using a scanning droplet cell, enabling us to discover two promising electrocatalysts, which we subsequently validated using a rotating disk setup. This demonstrated high-throughput material discovery pipeline presents a paradigm for facile and accelerated exploration of MMNCs for a broad range of applications

Experimental and theoretical studies of spray cooling for high power electronics

Spray cooling as a promising thermal management scheme has received much attention from modern industrial and technological applications, such as power electronics, nuclear power generation, high-power lasers and high-power conversion systems. The present work focused on the fundamental investigations of the spray characteristics of spray nozzles in free spray atomisation and in spray cooling. Theoretical models were developed to study the heat transfer in the non-boiling and boiling regimes of spray cooling. A closed loop system was developed to study the applications of using a multi-nozzle array on large area high heat load electronics cooling. Furthermore, the effects of structured surfaces on the spray cooling performance were scrutinised. Two optical techniques, Phase Doppler Anemometry (PDA) and Particle Image Velocimetry (PIV) were used to characterise the spray structures of pressure swirl nozzles. In free spray atomisation, the spray characteristics were found to be highly dependent on the axial distance. The spray cone produced by the pressure swirl nozzles evolved from a hollow spray cone to a full spray cone with the increase of axial distance. In spray atomisation under spray impingement, the spray cone formation of pressure swirl nozzle is largely dependent on the temperature of the impinged surface. The spray cone of a pressure swirl nozzle expands after impinging on a surface with a relatively high temperature. As a result, the impinging droplet flux near the centre of the spray cone decreases and the spray cone changes from a full spray cone to a hollow spray cone. The heat transfer experiments show that the effects of nozzle-to-surface distance on the heat transfer performance are complex and dependent on surface temperature. The expansion of the spray cone has significant effects on the surface temperature non-uniformity and heat transfer coefficient in spray cooling. A thin film flow model was developed to estimate the thickness of the liquid film formed under spray impingement. On the basis of the thin film flow model, a heat transfer model was developed to study the heat transfer in the non-boiling regime of spray cooling. The modelling results showed that the local film thickness was sensitive to the local droplet flux density and the droplet impingement cooling was the primary heat transfer mechanism in the non-boiling regime of spray cooling. To better understand the heat transfer in the boi ling regime of spray cooling, a numerical model based on the experimental spray characteristics was proposed to investigate the dynamics of droplet impingement, bubble boiling as well as their interplay in the spray cooling process. The effects of heat flux, droplet diameter, and droplet impingement frequency on the dynamics of bubble boiling were investigated. The numerical model showed that the fluxes of the collapsed bubbles due to the limited bubble size, as well as the punctured bubbles due to the droplet impingement increased as heat flux increased. A smaller impinging droplet is favourable for bubble boiling due to the more secondary nuclei induced as well as the larger fractions of the bubbles punctured at bigger diameters. A prototype of a high power closed loop spray cooling system using Rl34a as the working fluid was constructed to study the feasibility of using a multi-nozzle array on a 6U electronic card cooling. Fifty four pressure swirl nozzles were assembled in an array of 9 x 6 to cover a 6U card surface. Simple drainage concepts were introduced in the spray chamber design. The experimental results show a promising prospect of using multi-nozzle arrays on large area power electronics cooling. Heat removal of 16 kW is achieved on the 6U card surface by maintaining the surface temperature below 26.5°C. High heat transfer coefficient (up to 2.8 W /cm2 · K) and high liquid evaporation fraction (up to 0.88) are obtained. Without affecting the surface temperature non-uniformity, the control of chamber pressure is able to maintain the same operating temperature of a device at different heat loads. Experiments were conducted to study the thermal effects of differently scaled structure surfaces in an Rl34a spray cooling system. Results show that the arrangement of macro- fins plays a more important role in the cooling performance of macro-structured surfaces rather than a simple increase in the wetted area. Microstructures improve the heat transfer performance by enhancing the capillary effects and providing more potential nucleation sites on the heated surface. Taking the smooth flat surface as a reference, the micro-structured flat surface achieves a relative heat transfer enhancement of 32% compared to the 36% of the macrostructured surfaces, while the multiscale-structured surfaces which combine the features of micro- and macro- structures gain a heat transfer enhancement of up to 65%. Besides, the macro-structured surfaces prolong the transition period before CHF occurs and shorten the duration that the heated surface remains in film boiling after the occurrence of CHF while powering off the heat source.DOCTOR OF PHILOSOPHY (MAE