Fast Approximate KK-Means via Cluster Closures

$K$-means, a simple and effective clustering algorithm, is one of the most widely used algorithms in multimedia and computer vision community. Traditional $k$-means is an iterative algorithm---in each iteration new cluster centers are computed and each data point is re-assigned to its nearest center. The cluster re-assignment step becomes prohibitively expensive when the number of data points and cluster centers are large. In this paper, we propose a novel approximate $k$-means algorithm to greatly reduce the computational complexity in the assignment step. Our approach is motivated by the observation that most active points changing their cluster assignments at each iteration are located on or near cluster boundaries. The idea is to efficiently identify those active points by pre-assembling the data into groups of neighboring points using multiple random spatial partition trees, and to use the neighborhood information to construct a closure for each cluster, in such a way only a small number of cluster candidates need to be considered when assigning a data point to its nearest cluster. Using complexity analysis, image data clustering, and applications to image retrieval, we show that our approach out-performs state-of-the-art approximate $k$-means algorithms in terms of clustering quality and efficiency

Framework to Guide Rail type Adhesive Lifting Scaffolding in the Design and Application of High-rise Residential Buildings

As to combine with specific engineering practice, this paper presents a framework to guide rail type adhesive lifting scaffolding in high-rise residential building design and constructions well as changed the traditional characteristics of steel pipe scaffold by using new standard truss and scaffold board design All the connecting parts are connected by bolt, using electric wrench to install, and implementing the overall tools, systematic design and installation. Engineering practice proved that the frame rail type adhesive lifting scaffold can not only speed up the construction progress, control costs and improve economic efficiency, but also be popularized in similar engineering

Practical Cross-system Shilling Attacks with Limited Access to Data

In shilling attacks, an adversarial party injects a few fake user profiles into a Recommender System (RS) so that the target item can be promoted or demoted. Although much effort has been devoted to developing shilling attack methods, we find that existing approaches are still far from practical. In this paper, we analyze the properties a practical shilling attack method should have and propose a new concept of Cross-system Attack. With the idea of Cross-system Attack, we design a Practical Cross-system Shilling Attack (PC-Attack) framework that requires little information about the victim RS model and the target RS data for conducting attacks. PC-Attack is trained to capture graph topology knowledge from public RS data in a self-supervised manner. Then, it is fine-tuned on a small portion of target data that is easy to access to construct fake profiles. Extensive experiments have demonstrated the superiority of PC-Attack over state-of-the-art baselines. Our implementation of PC-Attack is available at https://github.com/KDEGroup/PC-Attack.Comment: Accepted by AAAI 202

Effect of dark matter on shadows and rings of a brane-world black hole illuminated by various accretions

In this paper, by taking the accretions into account, the observational shadows and rings casted by the Brane-world black hole are numerically investigated when the observer located at the cosmological horizon. The results here show that the radius $r_p$ of photon sphere increased with cosmological parameter $\alpha$ and dark matter parameter $\beta$, while the impact parameter $b_p$ decreased with $\alpha$ and increased with $\beta$. For the thin-disk accretion, it turns out that the total observed intensity are mainly composed of the direct emission, while lensing ring and photon ring only contribute a small contribution and a negligible contribution, respectively. And, we find that shadow and rings exhibit some different and interesting features when the disk located at different positions. For the static and infalling spherical accretions, it is obvious that the size of shadow is always the same for both accretions, which means that shadow is only related to the geometry of space time in this case. The luminosity of shadow and photon sphere are closely related to the Doppler effect and the emissivity per unit volume $j({\nu_e})$. In addition, the influence of dark matter and cosmological constant on observed intensity of shadows and rings are carefully emphasized throughout of this paper. Finally, we obtained the burring images of shadows and rings by using the nominal resolution of the Event Horizon Telescope, and studied the upper limits on the X-clod dark matter parameter $\beta$ with the aid of the data of the shadow of M87.Comment: 66figures, 4tables, 26pages,accepted by SCIENCE CHINA Physics, Mechanics & Astronomy,202

High-mass Starless Clumps in the inner Galactic Plane: the Sample and Dust Properties

We report a sample of 463 high-mass starless clump (HMSC) candidates within $-60\deg<l<60\deg$ and $-1\deg<b<1\deg$. This sample has been singled out from 10861 ATLASGAL clumps. All of these sources are not associated with any known star-forming activities collected in SIMBAD and young stellar objects identified using color-based criteria. We also make sure that the HMSC candidates have neither point sources at 24 and 70 \micron~nor strong extended emission at 24 $\mu$m. Most of the identified HMSCs are infrared ($\le24$ $\mu$m) dark and some are even dark at 70 $\mu$m. Their distribution shows crowding in Galactic spiral arms and toward the Galactic center and some well-known star-forming complexes. Many HMSCs are associated with large-scale filaments. Some basic parameters were attained from column density and dust temperature maps constructed via fitting far-infrared and submillimeter continuum data to modified blackbodies. The HMSC candidates have sizes, masses, and densities similar to clumps associated with Class II methanol masers and HII regions, suggesting they will evolve into star-forming clumps. More than 90% of the HMSC candidates have densities above some proposed thresholds for forming high-mass stars. With dust temperatures and luminosity-to-mass ratios significantly lower than that for star-forming sources, the HMSC candidates are externally heated and genuinely at very early stages of high-mass star formation. Twenty sources with equivalent radius $r_\mathrm{eq}<0.15$ pc and mass surface density $\Sigma>0.08$ g cm$^{-2}$ could be possible high-mass starless cores. Further investigations toward these HMSCs would undoubtedly shed light on comprehensively understanding the birth of high-mass stars.Comment: 16 pages, 15 figures, and 5 tables. Accepted for publication in ApJS. FITS images for the far-IR to sub-mm data, H2 column density and dust temperature maps of all the HMSC candidates are available at https: //yuanjinghua.github.io/hmscs.html. Codes used for this work are publicly available from https://github.com/yuanjinghua/HMSCs_ca