Principal Component Analysis of Galaxy Clustering in Hyperspace of Galaxy Properties

Ongoing and upcoming galaxy surveys are providing precision measurements of galaxy clustering. However a major obstacle in its cosmological application is the stochasticity in the galaxy bias. We explore whether the principal component analysis (PCA) of galaxy correlation matrix in hyperspace of galaxy properties (e.g. magnitude and color) can reveal further information on mitigating this issue. Based on the hydrodynamic simulation TNG300-1, we analyze the cross power spectrum matrix of galaxies in the magnitude and color space of multiple photometric bands. (1) We find that the first principal component $E_i^{(1)}$ is an excellent proxy of the galaxy deterministic bias $b_{D}$, in that $E_i^{(1)}=\sqrt{P_{mm}/\lambda(1)}b_{D,i}$. Here $i$ denotes the $i$-th galaxy sub-sample. $\lambda^{(1)}$ is the largest eigenvalue and $P_{mm}$ is the matter power spectrum. We verify that this relation holds for all the galaxy samples investigated, down to $k\sim 2h/$Mpc. Since $E_i^{(1)}$ is a direct observable, we can utilize it to design a linear weighting scheme to suppress the stochasticity in the galaxy-matter relation. For an LSST-like magnitude limit galaxy sample, the stochasticity $\mathcal{S}\equiv 1-r^2$ can be suppressed by a factor of \ga 2 at $k=1h/$Mpc. This reduces the stochasticity-induced systematic error in the matter power spectrum reconstruction combining galaxy clustering and galaxy-galaxy lensing from $\sim 12\%$ to $\sim 5\%$ at $k=1h/$Mpc. (2) We also find that $\mathcal{S}$ increases monotonically with $f_\lambda$ and $f_{\lambda^2}$. $f_{\lambda,\lambda^2}$ quantify the fractional contribution of other eigenmodes to the galaxy clustering and are direct observables. Therefore the two provide extra information on mitigating galaxy stochasticity

LOW-TEMPERATURE SINTERED (ZnMg)2SiO4 MICROWAVE CERAMICS WITH TiO2 ADDITION AND CALCIUM BOROSILICATE GLASS

The low-temperature sintered (ZnMg)2SiO–TiO2 microwave ceramic using CaO–B2O3–SiO2 (CBS) as a sintering aid has been developed. Microwave properties of (Zn1-xMgx)2SiO4 base materials via sol-gel method were highly dependent on the Mg-substituted content. Further, effects of CBS and TiO2 additives on the crystal phases, microstructures and microwave characteristics of (ZnMg)2SiO4 (ZMS) ceramics were investigated. The results indicated that CBS glass could lower the firing temperature of ZMS dielectrics effectively from 1170 to 950°C due to the liquid-phase effect, and significantly improve the sintering behavior and microwave properties of ZMS ceramics. Moreover, ZMS–TiO2 ceramics showed the biphasic structure and the abnormal grain growth was suppressed by the pinning effect of second phase TiO2. Proper amount of TiO2 could tune the large negative temperature coefficient of resonant frequency (tf) of ZMS system to a near zero value. (Zn0.8Mg0.2)2SiO4 codoped with 10 wt.% TiO2 and 3 wt.% CBS sintered at 950°C exhibits the dense microstructure and excellent microwave properties: εr = 9.5, Q·f = 16 600 GHz and tf = −9.6 ppm/°C

Microwave Dielectric Properties of (1-x)Ba_(3.75)Nd_(9.5)Cr_(0.25)Nb_(0.25)Ti_(17.5)O_(54)-x NdAlO_3 Ceramics

This study presents the microwave dielectric properties calculation of (1-x)Ba_(3.75)Nd_(9.5)Cr_(0.25)Nb_(0.25)Ti_(17.5)O_(54)–xNdAlO_3 ceramics where x denotes the volume molar fraction. From X-ray diffraction results, the solid solution limit is calculated to be about 0.76, where it forms a single BaNd_2Ti_4O_(12) phase in Region I (0≤x<0.76), and both BaNd_2Ti_4O_(12) and NdAlO_3 coexist in Region II (0.76≤x<1). The solid solution limit is confirmed by independently calculating it from the dielectric constant data. There is less than 4% deviation between the measured dielectric constant (εr) and the one calculated from the Maxwell-Wagner formula. The total quality factor (Q) remains almost constant in Region I and increases rapidly with the volume molar fraction of NdAlO_3 in Region II. The measured Q×f, where f is the resonant frequency, is also consistent with the calculated value in both regions. The temperature coefficient at the resonant frequency is −1.4 ppm/°C, which agrees well with the calculated value of 0 ppm/°C. In addition, we observed a close correlation between the bulk density and the phase evolution

Analysis of Vibration Attenuation and Energy Consumption of Blasting Demolition Chimney: A Case Study

Demolishing a tall chimney by directional blasting can save time and cost. However, the blasting vibration and the touchdown vibration of the parts of the chimney falling to the ground will cause noise disturbance to the local residents. To reduce the vibration effect of blasting demolition of the chimney, taking the 180 m high chimney in Jiaozuo, China, as the engineering background, the loose accumulation body with a right-angled trapezoid section 3-6 m thick was piled with three kinds of graded gravel particles as the buffer layer. According to the site restrictions, the chimney was demolished by directional blasting in two stages. The vibration propagation and attenuation rules of the blasting demolition of the chimney were analyzed and touchdown vibrations of two parts of the chimney were monitored also. Results show that the low frequency vibrations generated by the blasting and chimney touchdown have a greater impact on the surrounding environment. The vibration velocity and energy attenuation represent a form of power function. With the increase of the number of chimney touchdowns, the energy absorption rate of the loose accumulation body becomes lower. The obtained conclusions in this study can provide a reference for the similar blasting demolition practice

Security and Privacy on Generative Data in AIGC: A Survey

The advent of artificial intelligence-generated content (AIGC) represents a pivotal moment in the evolution of information technology. With AIGC, it can be effortless to generate high-quality data that is challenging for the public to distinguish. Nevertheless, the proliferation of generative data across cyberspace brings security and privacy issues, including privacy leakages of individuals and media forgery for fraudulent purposes. Consequently, both academia and industry begin to emphasize the trustworthiness of generative data, successively providing a series of countermeasures for security and privacy. In this survey, we systematically review the security and privacy on generative data in AIGC, particularly for the first time analyzing them from the perspective of information security properties. Specifically, we reveal the successful experiences of state-of-the-art countermeasures in terms of the foundational properties of privacy, controllability, authenticity, and compliance, respectively. Finally, we summarize the open challenges and potential exploration directions from each of theses properties

Towards an Accurate and Secure Detector against Adversarial Perturbations

The vulnerability of deep neural networks to adversarial perturbations has been widely perceived in the computer vision community. From a security perspective, it poses a critical risk for modern vision systems, e.g., the popular Deep Learning as a Service (DLaaS) frameworks. For protecting off-the-shelf deep models while not modifying them, current algorithms typically detect adversarial patterns through discriminative decomposition of natural-artificial data. However, these decompositions are biased towards frequency or spatial discriminability, thus failing to capture adversarial patterns comprehensively. More seriously, successful defense-aware (secondary) adversarial attack (i.e., evading the detector as well as fooling the model) is practical under the assumption that the adversary is fully aware of the detector (i.e., the Kerckhoffs's principle). Motivated by such facts, we propose an accurate and secure adversarial example detector, relying on a spatial-frequency discriminative decomposition with secret keys. It expands the above works on two aspects: 1) the introduced Krawtchouk basis provides better spatial-frequency discriminability and thereby is more suitable for capturing adversarial patterns than the common trigonometric or wavelet basis; 2) the extensive parameters for decomposition are generated by a pseudo-random function with secret keys, hence blocking the defense-aware adversarial attack. Theoretical and numerical analysis demonstrates the increased accuracy and security of our detector with respect to a number of state-of-the-art algorithms

Pressure-Arching Characteristics of Fractured Strata Structure during Shallow Horizontal Coal Mining

It is an important problem for the alternated strong and weak roof weighting to threat the safety of working face during shallow coal mining and the total thickness breaking of the thin bedrock to cause the serious ground subsidence. To reveal the mechanism of the abnormal mining damage, the pressure-arching rule in overlying strata was studied. Based on the monitoring data of the typical shallow coal working face, the mechanical models of the symmetrical stress arch, the squeezed arch and the hinged structure of the fractured strata were established, and the difference of the load bearing capacity between the structures and the influencing factors was analysed by the deduced formula calculation. Then the evolution characteristics of the pressure-arch in the fractured strata were revealed by the numerical simulation analysis. The results show that the global pressure-arch of multilayer strata always exits in the surrounding rock and moves forward with continuous mining. The single pressure-arch and hinged structure are formed in each stratum under the global pressure-arch. The pressure-arch enables the fractured strata to carry load efficiently, and the instability of the pressure-arch can cause strong roof weighting and ground subsidence. These conclusions provide a theoretical reference for the stability control of the overlying strata structure under shallow coal mining

Potential Risk Analysis of Tailings Dam Under Preloading Condition and Its Countermeasures

It is very important for mine production safety to ensure the stability of the tailings dam. Taking a flatland tailings pond as the background, a threedimensional computational model was built based on a tailings dam under mullock heap preloading condition. Considering the current operating water level conditions, a liquid-solid coupling analysis of the model was conducted.The deformation characteristics of the tailings dam were revealed during successive preloading at the front of the dam. The safety factor and the potential slide face of the tailings dam were calculated under different conditions using the strength reduction method. The results show that the tailings dam in its current condition is basically stable, but if the mullock heap continues to be heightened, the tailings dam will become unstable. Therefore, in order to limit the height of the mullock heap, establishing a monitor and early warning mechanism are put forward to ensure mine production safety