Tars: Timeliness-aware Adaptive Replica Selection for Key-Value Stores

In current large-scale distributed key-value stores, a single end-user request may lead to key-value access across tens or hundreds of servers. The tail latency of these key-value accesses is crucial to the user experience and greatly impacts the revenue. To cut the tail latency, it is crucial for clients to choose the fastest replica server as much as possible for the service of each key-value access. Aware of the challenges on the time varying performance across servers and the herd behaviors, an adaptive replica selection scheme C3 is proposed recently. In C3, feedback from individual servers is brought into replica ranking to reflect the time-varying performance of servers, and the distributed rate control and backpressure mechanism is invented. Despite of C3's good performance, we reveal the timeliness issue of C3, which has large impacts on both the replica ranking and the rate control, and propose the Tars (timeliness-aware adaptive replica selection) scheme. Following the same framework as C3, Tars improves the replica ranking by taking the timeliness of the feedback information into consideration, as well as revises the rate control of C3. Simulation results confirm that Tars outperforms C3.Comment: 10pages,submitted to ICDCS 201

Dual-Core Photonic Crystal Fiber for Use in Fiber Filters

An asymmetrical dual-core photonic crystal fiber (DC-PCF), which possesses all circular air holes, is proposed. By setting appropriate geometrical parameters, the wavelength-selective coupling property is realized, and a compact optical filter with a short length of 1.83 mm based on the DC-PCF is designed. The spectral transmission characteristics of the filter are investigated by the beam propagation method. The results demonstrate that the optical filter possesses a bandwidth of ∼ 58 nm and small sidelobes. The proposed optical filter could be used in the integrated optical systems

Improving Strength and Microstructure of SiC Reticulated Porous Ceramic through In-Situ Generation of SiC Whiskers within Hollow Voids

SiC Reticulated Porous Ceramic with Excellent Strength and High-Density Ceramic Struts Was Successfully Prepared using the Polymer Replica Method, Followed by Pressureless Sintering under a Buried Charcoal Atmosphere. First, a Polyurethane (PU) Template Was Coated with a Si Slurry and Then a SiC-Containing Slurry, and Subsequently Heated under the Buried Charcoal Atmosphere. to Ensure Excellent Coating Ability of the Slurries, the Viscosity, Thixotropy, and Yield Stresses of the Si Slurry Were Optimized by Adjusting the Content of the Thickening Agent. during Heating, Si in the Coating Layer Reacted with the Residual C and CO Gas from the PU Template and Buried Charcoal, Forming SiC Whiskers that Filled Hollow Voids within the SiC Struts. Additionally, Catalyst Ferric Nitrate Was Added to the Si Slurry to Promote the Generation and Growth of SiC Whiskers. as a Result, When Compared to the Untreated SiC Reticulated Porous Ceramic, the SiC Reticulated Porous Ceramic Pre-Coated with Si Layers Exhibited Significant Improvements in Mechanical Strength and Thermal Shock Resistance, Despite Minor Differences in Porosity. Furthermore, an Industrial Test Conducted in the Copper Smelting Industry Showed that the Structure of SiC Reticulated Porous Ceramic, Prepared in This Study and Used as Filters, Remained Intact Even after 7 Days of Continuous Use. Meanwhile, a Significant Number of Inclusions Was Adhered to the Surfaces of the Filters. Therefore, the Processes Combined with In-Situ Generation of SiC Whiskers is an Ideal and Low-Cost Method for Fabricating SiC Filters with Excellent Properties

The research of the drilling pipe's small-scale mode used in acoustic telemetry while drilling

The acoustic telemetry technology while drilling has a greater advantage in the transmission rate and the application of media than the commercial mud pulse mode and electromagnetic wave mode. There are limits to the existence of the periodic drill pipe acoustic transmission transmission model, which can only calculate the acoustic transmission characteristics of two kinds of periodic structures and the acoustic transmission characteristics of the composite structures with arbitrary cross section, but the variable cross-section or various special-shaped drill strings. According to the characteristics of the small scale structure of drill string, a small scale model of the drill string in the data transmission is set up by using the theory of longitudinal vibration of structures, in which the small scale vibration transfer function of cylindrical rods with different variable cross sections is analyzed. According to certain boundary conditions, the vibration transfer characteristics of drill string are obtained, and the simulation research is completed.Показано, что технология акустической телеметрии в процессе бурения композитных структур имеет большое преимущество в скорости и способах передачи данных по сравнению с режимом электромагнитной волны и обычным методом измерения колебаний бура. Рассмотрены возможности метода акустической передачи данных бурильных труб, которые позволяют рассчитать акустические характеристики периодических структур и композитных структур при произвольном поперечном сечении и для различной специальной формы сверла. В соответствии с характеристиками мелкоструктурной бурильной скважины модель бурильных стержней рассматривается с помощью теории продольных колебаний конструкций, в которой анализируются малые передаточные вибрации цилиндрических стержней различных сечений

SelFLoc: Selective Feature Fusion for Large-scale Point Cloud-based Place Recognition

Point cloud-based place recognition is crucial for mobile robots and autonomous vehicles, especially when the global positioning sensor is not accessible. LiDAR points are scattered on the surface of objects and buildings, which have strong shape priors along different axes. To enhance message passing along particular axes, Stacked Asymmetric Convolution Block (SACB) is designed, which is one of the main contributions in this paper. Comprehensive experiments demonstrate that asymmetric convolution and its corresponding strategies employed by SACB can contribute to the more effective representation of point cloud feature. On this basis, Selective Feature Fusion Block (SFFB), which is formed by stacking point- and channel-wise gating layers in a predefined sequence, is proposed to selectively boost salient local features in certain key regions, as well as to align the features before fusion phase. SACBs and SFFBs are combined to construct a robust and accurate architecture for point cloud-based place recognition, which is termed SelFLoc. Comparative experimental results show that SelFLoc achieves the state-of-the-art (SOTA) performance on the Oxford and other three in-house benchmarks with an improvement of 1.6 absolute percentages on mean average recall@1