On the Adversarial Robustness of Subspace Learning

In this paper, we study the adversarial robustness of subspace learning problems. Different from the assumptions made in existing work on robust subspace learning where data samples are contaminated by gross sparse outliers or small dense noises, we consider a more powerful adversary who can first observe the data matrix and then intentionally modify the whole data matrix. We first characterize the optimal rank-one attack strategy that maximizes the subspace distance between the subspace learned from the original data matrix and that learned from the modified data matrix. We then generalize the study to the scenario without the rank constraint and characterize the corresponding optimal attack strategy. Our analysis shows that the optimal strategies depend on the singular values of the original data matrix and the adversary's energy budget. Finally, we provide numerical experiments and practical applications to demonstrate the efficiency of the attack strategies

Analysis of the Double Object Construction from Corpus Study

The study of the double object construction (DOC for short) (S+V+N1+N2) has been one of the most heated topics in modern linguistics, and a lot of studies have been made on this language phenomenon. The previous studies are mainly centered on its structural or semantic classifications from the perspective of syntax. However, there are not enough studies on the semantic diversity of nouns cases. With the help of sentences from BNC, the paper studies features of nouns in DOC, from which we make a contrastive study of DOC in Chinese and English.Key words: DOC; A contrastive study; Corpu

Displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil based on microscopic visualization experiments

 In order to study the microscopic oil displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil, the indoor microscopic visualization displacement experiments were carried out. The flooding experiment of heavy oil was conducted by using water, osmotic modified oil displacing agent (a kind of polymeric surfactant) and water-in-oil emulsion (obtained by mixing polymeric surfactant and heavy oil) as displacing phases to study the mechanism of polymeric surfactant to enhance oil recovery in heavy oil reservoir. The experimental results show that the polymeric surfactant can increase the viscosity of the water phase, reduce the water-oil mobility ratio, expand the swept area, and there is no obvious fingering phenomenon which occurs during water flooding. The polymeric surfactant has the surfactant characteristics which can reduce the interfacial tension between oil and water to promote the formation of oil droplets with smaller droplet diameter. And the interfacial film composed of polymeric surfactant molecules will be formed on the surface of oil droplets to prevent the coalescence of oil droplets and improve the flow ability of oil phase. The water-in-oil emulsion can be miscible with the oil in heavy oil displacement process, and thus sweeps the areas such as the dead pores which cannot be swept by water and polymeric surfactant flooding, which increases the sweep efficiency to a certain extent.Cited as: Xu, F., Chen, Q., Ma, M., Wang, Y., Yu, F., Li, J. Displacement mechanism of polymeric surfactant in chemical cold flooding for heavy oil based on microscopic visualization experiments. Advances in Geo-Energy Research, 2020, 4(1): 77-85, doi: 10.26804/ager.2020.01.0

Broadband RCS Reduction of Antenna with AMC Using Gradually Concentric Ring Arrangement

This paper proposes a new method to the broadband RCS reduction with the artificial magnetic conductor (AMC) surfaces. The AMC surfaces can introduce a zero-degree reflection phase shift to incident waves. The phase difference between the antenna and AMC structures is 180°. Therefore, the AMC structures can be used to achieve RCS reduction. However, the bandwidth of zero-degree reflection phase of AMC structures is very narrow. In light of this, a novel gradually concentric ring arrangement AMC (GCRA-AMC) which can be applied to achieve the broadband RCS reduction is presented. The simulated and measured results show that the radiation performance of antennas is preserved when the GCRA-AMC is used. The RCS of the antenna with GCRA-AMC has been considerably reduced in a broad frequency band. The largest RCS reduction is more than 17 dB

Transcriptomic analysis reveals the molecular mechanisms underlying osteoclast differentiation in the estrogen-deficient pullets

Several previous reports have suggested that estrogen (E2) is a vital signal responsible for the reg-ulation of skeletal homeostasis and bone remodeling in mammals. E2 could efficiently accelerate the growth of medullary bone in pullets during sexual maturity. Fur-thermore, the low E2 level can strengthen the mechanical bone functions in female hens. However, mechanistic studies to describe the effects of E2 on bone in pullets during the initiation of the puberty period are remaining elusive. Therefore, the aim of this study was to explore the effect of inhibiting E2 biosynthesis on the biomechani-cal properties and its molecular mechanism during sexual maturity of pullets. In this study, a total of 90 Hy-line Sonia pullets with comparable body weight at 13 wk of age were selected and categorized into 2 separate groups. Daily, 0.5 mg/4 mL of letrozole (LZ) was orally adminis-tered to the treatment (TRT) group and 4 mL of saline to the control (CON) group of pullets for 6 wk. Com-pared with the CON group, a lower plasma E2 level was observed in the TRT group. Furthermore, plasma P, Gla protein (BGP), and 1,25-dihydroxy vitamin D3 (1,25-(OH)2D3) levels were markedly suppressed, whereas the plasma alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) levels were signifi-cantly elevated. Moreover, the cortical bone thickness and breaking strength of the tibia and femur, the bone mineral density of the humerus, and the bone mineral content of the humerus as well as the femur were increased significantly. The expression levels of 340 dif-ferentially expressed genes (DEGs) differed signifi-cantly between the CON and TRT group in the tibia at 19 wk of age. Among them, 32 genes were up-regulated, whereas 308 were down-regulated in the TRT group. The variations in candidate genes associated with oste-oclast differentiation and cell adhesion may indicate that LZ inhibits E2 biosynthesis, consequently, reduces osteoclast differentiation by suppressing inter-cellular communication and cells attaching to extracellular matrix components. Taken together, the present study demonstrated that inhibiting E2 synthesis during sex-ual maturity of pullets decreased osteoclast differentia-tion and considerably enhanced bone quality

The influence of negative life events on college students’ suicidal ideation: the mediating role of entity theory and the moderating role of meaning in life

Suicidal ideation is a desire, thought, or conception that is closely associated with suicide, which is an important risk factor for suicidal behavior. Negative life events may impact college students’ suicidal ideation. According to the suicide susceptibility-stress model, the interaction between susceptibility factors and stressors may influence college students’ suicidal ideation. The present study investigated the role of entity theory and meaning in life in the influence of negative life events on suicidal ideation among college students. A nationwide questionnaire survey was conducted among 938 college students. The Beck Scale for Suicide Ideation, the Implicit Personality Theory Questionnaire, the Adolescent Life Events Scale, and the Meaning in Life Questionnaire were used. The results showed that negative life events were positively correlated with suicidal ideation, entity theory played a mediating role, and meaning in life moderated the mediation of entity theory. Finally, meaning in life and entity theory may bring some benefits to college students; that is, when faced with negative life events, meaning in life and entity theory may attenuate students’ suicidal ideation

Predicting the critical drainage induced by soil seepage failure during pumping in foundation pit construction

In the construction of foundation pits with shallow groundwater levels, improper control of pumping strength often leads to soil penetration failure, resulting in engineering accidents, casualties, and property losses. Currently, existing research mainly focuses on soil conditions, settlement deformation prediction, construction pumping measures, etc., and rarely involves the critical pumping quantity. However, the critical pumping quantity is a key parameter for pumping safety in foundation pit construction and there is no effective method to calculate or test this parameter. Based on Darcy’s law and the equivalent infinitesimal formula, and the formula for calculating the permeability coefficient of pumping tests recommended by the specification for borehole pumping test of hydropower projects （NB/T 35103—2017）, this study deduced the expressions of critical pumping quantity of the seepage failure under four conditions, including submersible incomplete hole, submersible integral hole, confined water incomplete hole and confined water integral hole. To ensure that the calculated result is more effective, the calculated expression was modified by introducing correction coefficient. The results indicate that the relationship between the critical drawdown volume for inducing soil permeability failure in the four cases and the critical permeability velocity is linear, suggesting that measuring the critical permeability velocity of the soil at the site can determine the critical drawdown volume. In a case study of basement excavation in Hohhot, it is found that the cobble layer has the highest potential for water permeability failure. Laboratory measurements revealed a critical permeability velocity for its failure of 7.1×10−4 m/s. To prevent damage to this layer during pumping, an artesian well SJ1 with a designed critical drawdown volume of 174.45 m3/d was used, and actual pumping volumes were controlled within 150 m3/d without observing any permeability failures, demonstrating applicability of the proposed method. Therefore, compared to existing qualitative experience-based methods for predicting critical drawdown volumes in basement excavation, the quantitative calculation method holds greater practical application value