Convex Minimization with Integer Minima in O~(n4)\widetilde O(n^4) Time

Given a convex function $f$ on $\mathbb{R}^n$ with an integer minimizer, we show how to find an exact minimizer of $f$ using $O(n^2 \log n)$ calls to a separation oracle and $O(n^4 \log n)$ time. The previous best polynomial time algorithm for this problem given in [Jiang, SODA 2021, JACM 2022] achieves $O(n^2\log\log n/\log n)$ oracle complexity. However, the overall runtime of Jiang's algorithm is at least $\widetilde{\Omega}(n^8)$, due to expensive sub-routines such as the Lenstra-Lenstra-Lov\'asz (LLL) algorithm [Lenstra, Lenstra, Lov\'asz, Math. Ann. 1982] and random walk based cutting plane method [Bertsimas, Vempala, JACM 2004]. Our significant speedup is obtained by a nontrivial combination of a faster version of the LLL algorithm due to [Neumaier, Stehl\'e, ISSAC 2016] that gives similar guarantees, the volumetric center cutting plane method (CPM) by [Vaidya, FOCS 1989] and its fast implementation given in [Jiang, Lee, Song, Wong, STOC 2020]. For the special case of submodular function minimization (SFM), our result implies a strongly polynomial time algorithm for this problem using $O(n^3 \log n)$ calls to an evaluation oracle and $O(n^4 \log n)$ additional arithmetic operations. Both the oracle complexity and the number of arithmetic operations of our more general algorithm are better than the previous best-known runtime algorithms for this specific problem given in [Lee, Sidford, Wong, FOCS 2015] and [Dadush, V\'egh, Zambelli, SODA 2018, MOR 2021].Comment: SODA 202

Charge-carrier balance for highly efficient inverted planar heterojunction perovskite solar cells

The charge-carrier balance strategy by interface engineering is employed to optimize the charge-carrier transport in inverted planar heterojunction perovskite solar cells. N,N-Dimethylformamide-treated poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and poly(methyl methacrylate)-modified PCBM are utilized as the hole and electron selective contacts, respectively, leading to a high power conversion efficiency of 18.72%

Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D

[EN] Single metal atoms and metal clusters have attracted much attention thanks to their advantageous capabilities as heterogeneous catalysts. However, the generation of stable single atoms and clusters on a solid support is still challenging. Herein, we report a new strategy for the generation of single Pt atoms and Pt clusters with exceptionally high thermal stability, formed within purely siliceous MCM-22 during the growth of a two-dimensional zeolite into three dimensions. These subnanometric Pt species are stabilized by MCM-22, even after treatment in air up to 540 degrees C. Furthermore, these stable Pt species confined within internal framework cavities show size-selective catalysis for the hydrogenation of alkenes. High-temperature oxidation-reduction treatments result in the growth of encapsulated Pt species to small nanoparticles in the approximate size range of 1 to 2 nm. The stability and catalytic activity of encapsulated Pt species is also reflected in the dehydrogenation of propane to propylene.This work was funded by the Spanish Government (Consolider Ingenio 2010-MULTICAT (CSD2009-00050) and MAT2014-52085-C2-1-P) and by the Generalitat Valenciana (Prometeo). The Severo Ochoa Program (SEV-2012-0267) is gratefully acknowledged. L.L. thanks ITQ for a contract. The authors also thank the Microscopy Service of UPV for the TEM and STEM measurements. The HAADF-HRSTEM works were conducted in the Laboratorio de Microscopias Avanzadas (LMA) at the Instituto de Nanociencia de Aragon (INA)-Universidad de Zaragoza (Spain), a Spanish ICTS National Facility. Some of the research leading to these results has received funding from the European Union Seventh Framework Program under Grant Agreement 312483-ESTEEM2 (Integrated Infrastructure Initiative-I3). R.A. also acknowledges funding from the Spanish Ministerio de Economia y Competitividad (FIS2013-46159-C3-3-P) and the European Union Horizon 2020 research and innovation programme under the Marie Sldodowska-Curie grant agreement No. 642742.Liu, L.; Díaz Morales, UM.; Arenal, R.; Agostini, G.; Concepción Heydorn, P.; Corma Canós, A. (2017). Generation of subnanometric platinum with high stability during transformation of a 2D zeolite into 3D. Nature Materials. 16(1):132-138. https://doi.org/10.1038/NMAT4757S132138161Boronat, M., Leyva-Perez, A. & Corma, A. Theoretical and experimental insights into the origin of the catalytic activity of subnanometric gold clusters: attempts to predict reactivity with clusters and nanoparticles of gold. Acc. Chem. Res. 47, 834–844 (2014).Flytzani-Stephanopoulos, M. & Gates, B. C. Atomically dispersed supported metal catalysts. Ann. Rev. Chem. Bio. Eng. 3, 545–574 (2012).Gates, B. C. Supported metal clusters: synthesis, structure, and catalysis. Chem. 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Microstructure and Thermoelectric Properties of (Bi0.48Sb1.52)Te3 Thick Films Prepared with Tape Casting Method

This paper reports the fabrication and characterization of (Bi0.48Sb1.52)Te3 thick films using a tape casting process on glass substrates. A slurry of thermoelectric (Bi0.48Sb1.52)Te3 was developed and cured thick films were annealed in a vacuum chamber at 500–600 °C. The microstructure of these films was analyzed, and the Seebeck coefficient and electric conductivity were tested. It was found that the subsequent annealing process must be carefully designed to achieve good thermoelectric properties of these samples. Conductive films were obtained after annealing and led to acceptable thermoelectric performance. While the properties of these initial materials are not at the level of bulk materials, this work demonstrates that the low-cost tape casting technology is promising for fabricating thermoelectric modules for energy conversion

ERMDS: A obfuscation dataset for evaluating robustness of learning-based malware detection system

Learning-based malware detection systems (LB-MDS) play a crucial role in defending computer systems from malicious attacks. Nevertheless, these systems can be vulnerable to various attacks, which can have significant consequences. Software obfuscation techniques can be used to modify the features of malware, thereby avoiding its classification as malicious by LB-MDS. However, existing portable executable (PE) malware datasets primarily use a single obfuscation technique, which LB-MDS has already learned, leading to a loss of their robustness evaluation ability. Therefore, creating a dataset with diverse features that were not observed during LB-MDS training has become the main challenge in evaluating the robustness of LB-MDS.We propose a obfuscation dataset ERMDS that solves the problem of evaluating the robustness of LB-MDS by generating malwares with diverse features. When designing this dataset, we created three types of obfuscation spaces, corresponding to binary obfuscation, source code obfuscation, and packing obfuscation. Each obfuscation space has multiple obfuscation techniques, each with different parameters. The obfuscation techniques in these three obfuscation spaces can be used in combination and can be reused. This enables us to theoretically obtain an infinite number of obfuscation combinations, thereby creating malwares with a diverse range of features that have not been captured by LB-MDS.To assess the effectiveness of the ERMDS obfuscation dataset, we create an instance of the obfuscation dataset called ERMDS-X. By utilizing this dataset, we conducted an evaluation of the robustness of two LB-MDS models, namely MalConv and EMBER, as well as six commercial antivirus software products, which are anonymized as AV1-AV6. The results of our experiments showed that ERMDS-X effectively reveals the limitations in the robustness of existing LB-MDS models, leading to an average accuracy reduction of 20% in LB-MDS and 32% in commercial antivirus software. We conducted a comprehensive analysis of the factors that contributed to the observed accuracy decline in both LB-MDS and commercial antivirus software. We have released the ERMDS-X dataset as an open-source resource, available on GitHub at https://github.com/lcjia94/ERMDS

Task Offloading Strategy Based on Mobile Edge Computing in UAV Network

When an unmanned aerial vehicle (UAV) performs tasks such as power patrol inspection, water quality detection, field scientific observation, etc., due to the limitations of the computing capacity and battery power, it cannot complete the tasks efficiently. Therefore, an effective method is to deploy edge servers near the UAV. The UAV can offload some of the computationally intensive and real-time tasks to edge servers. In this paper, a mobile edge computing offloading strategy based on reinforcement learning is proposed. Firstly, the Stackelberg game model is introduced to model the UAV and edge nodes in the network, and the utility function is used to calculate the maximization of offloading revenue. Secondly, as the problem is a mixed-integer non-linear programming (MINLP) problem, we introduce the multi-agent deep deterministic policy gradient (MADDPG) to solve it. Finally, the effects of the number of UAVs and the summation of computing resources on the total revenue of the UAVs were simulated through simulation experiments. The experimental results show that compared with other algorithms, the algorithm proposed in this paper can more effectively improve the total benefit of UAVs

Vitamin D Status for Chinese Children and Adolescents in CNNHS 2016–2017

Vitamin D is very important in maintaining children’s bone health because of its regulatory role in calcium and phosphate metabolism. To better understand vitamin D status and related risk factors of children and adolescents in China, this study analyzed the 25-hydroxyvitamin-D (25(OH)D) concentration of children and adolescents aged 6–17 years in China and assessed the risk factors of vitamin D deficiency and insufficiency. We analyzed the data of 25(OH)D concentration collected from the China National Nutrition and Health Survey of Children and Lactating Mothers in 2016–2017 (CNNHS 2016–2017). The age, sex, region type, ethnicities, season, weight and height were recorded, measured by unified questionnaire, equipment and standards. The concentration of 25(OH)D was detected by LC-MS/MS. A total of 64,391 participants from the cross-sectional study of CNNHS in 2016–2017 were included in this study. The median serum 25(OH)D concentration was 17.70 (13.20–22.68) ng/mL, 18.70 (14.10–23.80) ng/mL in boys and 16.60 (12.40–21.40) ng/mL in girls. The total prevalence rate of vitamin D deficiency and insufficiency was 65.98% when the cut-off was 20 ng/mL, 60.42% for boys and 71.99% for girls. According to the results of logistic regression analysis, girls aged above 12 y, living in midlands and northern regions, in spring and winter seasons and with abdominal obesity will have a significantly increased risk of vitamin D deficiency and insufficiency among Chinese children and adolescents. The results showed that vitamin D deficiency and insufficiency are very common among children and adolescents aged 6–17 y in China. They should be encouraged to have more effective sunlight exposure, increased intake of vitamin D from food or supplements in their diet, especially for those aged above 12 y, living in the northern or midlands areas, in spring and winter, and abdominally obese

Study on the Zinc Nutritional Status and Risk Factors of Chinese 6–18-Year-Old Children

Zinc is an essential micronutrient that is involved in several metabolic processes, especially children’s growth and development. Although many previous studies have evaluated the zinc nutritional status of children, there are very few reports on children aged 6–18 years old. Furthermore, there are few reports on children’s zinc nutrition status based on the Chinese population. According to WHO data, the prevalence of zinc deficiency in Asian countries is rather high and has resulted in high child mortality. In this study, we aimed to comprehensively assess zinc nutritional status and the prevalence of zinc deficiency among children aged 6–18 years in China based on nationally representative cross-sectional data. Subgroup comparisons were made under possible influencing factors. The potential risk factors of zinc deficiency were also discussed. A total of 64,850 children, equally male and female, were recruited from 150 monitoring sites in 31 provinces through stratified random sampling from China National Nutrition and Health Survey of Children and Lactating Mothers (CNNHS 2016–2017). Median and interquartile intervals were used to represent the overall zinc concentration levels and different subgroups. A Chi-square test was used to compare serum zinc levels and the prevalence of zinc deficiency in children under different group variables. In order to study the influencing factors of zinc deficiency, multiple logistic regression was utilized. It was found that the median concentration of serum Zn was 88.39 μg/dL and the prevalence of Zn deficiency was 9.62%. The possible influence factors for Zn deficiency were sex, anemia, nutritional status, city type and income. By conducting a subgroup analysis of the factors, it was found that males; those with anemia, stunting and low income; and children living in rural areas have a higher risk of Zn deficiency. This study offers a comprehensive analysis of Zn nutritional status among Chinese children, which provides reliable data for policy formulation to improve the zinc nutrition status of children