Solar cycle variation of real CME latitudes

With the assumption of radial motion and uniform longitudinal distribution of coronal mass ejections (CMEs), we propose a method to eliminate projection effects from the apparent observed CME latitude distribution. This method has been applied to SOHO LASCO data from 1996 January to 2006 December. As a result, we find that the real CME latitude distribution had the following characteristics: (1) High-latitude CMEs ($\theta>60^{\circ}$ where $\theta$ is the latitude) constituted 3% of all CMEs and mainly occurred during the time when the polar magnetic fields reversed sign. The latitudinal drift of the high-latitude CMEs was correlated with that of the heliospheric current sheet. (2) 4% of all CMEs occurred in the range $45^{\circ}\leq\theta\leq60^{\circ}$. These mid-latitude CMEs occurred primarily in 2000, near the middle of 2002 and in 2005, respectively, forming a prominent three-peak structure; (3) The highest occurrence probability of low-latitude ($\theta< 45^{\circ}$) CMEs was at the minimum and during the declining phase of the solar cycle. However, the highest occurrence rate of low-latitude CMEs was at the maximum and during the declining phase of the solar cycle. The latitudinal evolution of low-latitude CMEs did not follow the Sp\"{o}rer sunspot law, which suggests that many CMEs originated outside of active regions.Comment: 4 pages, 4 figures, accepted by ApJ Lette

Study on failure mechanism on rechargeable alkaline zinc–Air battery during charge/discharge cycles at different depths of discharge

Background: Zinc-air battery (ZAB) is a promising candidate for energy storage, but the short cycle life severely restricts the wider practical applications. Up to date, no consensus on the dominant factors affecting ZABs cycle life was reached to help understanding how to prolong the ZAB’s cycle life. Here, a series of replacement experiments based on the ZAB were conducted to confirm the pivotal factors that influence the cycle life at different depths of discharge (DOD).Method: The morphology and composition of the components of the battery were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical titration analyses.Result: SEM images and XRD results revealed that the failure of the zinc anode gradually deepens with the increase of DOD, while the performance degradation of the tricobalt tetroxide/Carbon Black (Co3O4/CB) air cathode depends on the operating time. The concentration of CO32− depends on the charge/discharge cycle time. The replacement experiments results show that the dominant factors affecting the ZAB’s cycle life is the reduction of active sites on the surface of Co3O4/CB air cathode at a shallow DOD, while that is the carbonation of the electrolyte at a deep DOD. The reduction of active sites on the surface of Co3O4/CB air cathode is caused by the coverage of K2CO3 precipitated by carbonation of the electrolyte, suggesting that the carbonation of the alkaline electrolyte limits ZAB’s cycle life.Conclusion: Therefore, this work not only further discloses the failure mechanism of ZAB, but also provides some feasible guidance to design a ZAB with along cycle life

Solvability of a Coupled System of Fractional Differential Equations with Periodic Boundary Conditions at Resonance

By using the coincidence degree theory, we study the existence of solutions for a coupled system of fractional differential equations with periodic boundary conditions. A new result on the existence of solutions of the indicated fractional boundary-value problem is obtained.Із використанням теорії збігу степенів досліджено існування розв'язків зв'язаних систем диференціальних рівнянь дробового порядку з періодичними граничними умовами. Встановлено новий результат щодо існування розв'язків граничної задачі дробового порядку

Backdoor Attack against Object Detection with Clean Annotation

Deep neural networks (DNNs) have shown unprecedented success in object detection tasks. However, it was also discovered that DNNs are vulnerable to multiple kinds of attacks, including Backdoor Attacks. Through the attack, the attacker manages to embed a hidden backdoor into the DNN such that the model behaves normally on benign data samples, but makes attacker-specified judgments given the occurrence of a predefined trigger. Although numerous backdoor attacks have been experimented on image classification, backdoor attacks on object detection tasks have not been properly investigated and explored. As object detection has been adopted as an important module in multiple security-sensitive applications such as autonomous driving, backdoor attacks on object detection could pose even more severe threats. Inspired by the inherent property of deep learning-based object detectors, we propose a simple yet effective backdoor attack method against object detection without modifying the ground truth annotations, specifically focusing on the object disappearance attack and object generation attack. Extensive experiments and ablation studies prove the effectiveness of our attack on two benchmark object detection datasets, PASCAL VOC07+12 and MSCOCO, on which we achieve an attack success rate of more than 92% with a poison rate of only 5%

A comparative analysis of delay propagation on departure and arrival flights for a chinese case study

In recent years, flight delay costs the air transportation industry millions of dollars and has become a systematic problem. Understanding the behavior of flight delay is thus critical. This paper focuses on how flight delay is affected by operation-, time-, and weather-related factors. Different econometric models are developed to analyze departure and arrival delay. The results show that compared to departure delay, arrival delay is more likely to be affected by previous delays and the buffer effect. Block buffer presents a reduction effect seven times greater than turnaround buffer in terms of flight delays. Departure flights suffer more delays from convective weather than arrival flights. Convective weather at the destination airport for flight delay has a greater impact than at the original airport. In addition, sensitivity analysis of flight delays from an aircraft utilization perspective is conducted. We find that the effect of delay propagation on flight delay differs by aircraft utilization. This impact on departure delay is greater than the impact on arrival delay. In general, specific to the order of flights, the previous delay increases the impact on flight on-time performance as a flight flies a later leg. Buffer time has opposite effects on departure and arrival delay, with the order increasing. A decrease in buffer time with the order increasing, however, still has a greater reduction effect on departure delay than arrival delay. Specific to the number of flights operated by an aircraft, the more flights an aircraft flies in a day, the more the on-time performance of those flights will suffer from the previous delay and buffer time generally

Towards sequence-selective DNA recognition withdesigned major groove binders

This thesis is mainly focused on the design, synthesis and DNA binding studies of aminobenzyl and guanidinium calix[4]arene dimers. The work consists of two parts. The first part of my Ph.D. work was focused on the synthesis and DNA binding studies of Dimer A and Dimer B. In order to broaden the scope of the investigation, the corresponding monomeric calixarenes (Monomer A and Monomer B) were also synthesized. Compared with anilino-calix[4]arenas (R. Zadmard, T. Schrader, Angew. Chem. Int. Ed. 2006, 45, 2703 –2706), these dimers and monomers are water-soluble, and bind to DNA with much higher affinity (binding constants: 1000000–100000000 M-1 in 2 mM Hepes buffer with 150 mM NaCl). When investigating the properties of new DNA binding molecules, one initial goal is to establish their mode of binding to DNA. Because direct structure information from a crystal or NMR structure was not yet available in my work, several other biophysical experiments have been designed and performed between calixarenes and different nucleic acids with varying base composition and conformation. The following results from established binding assays strongly support a major groove binding mode: (1). The DAPI displacement assay indicates that the calixarene dimers and DAPI can simultaneously bind to poly (dAdT) – poly (dAdT). Because DAPI occupies the minor groove, the dimeric calixarenes should reside in the major groove. (2). Ethidium bromide displacement assays, fluorescence titrations, and circular dichroism measurements indicate that calixarene dimers strongly prefer nucleic acids with a wide, shallow or even major groove; while low affinities are observed for nucleic acids with a narrow, deep or rugged major groove, which must be widened before complexation occurs. This characteristic also implies that the accessible area for our ligands is on the major groove side, contrary to the well-known slim oligoamide binders, which target the minor groove. In line with these observations, it was noticed that changes in shape and width of the minor groove had no influence on the ligands’ affinities. Dimer A Dimer B Monomer A Monomer B Unfortunately, Dimer A and Dimer B showed similar affinities for different DNA duplexes. Therefore, we planed to replace the simple alkyl bridge between both calixarenes by a fragment which should be able to bind specific sequences of DNA in the promoter region of each gene. Heterocyclic oligoamides were found out. They consist of N-methylpyrrole, 3-hydroxypyrrole and N-methyl imidazole amino acid building blocks (P. B. Dervan, Bioorganic & Medicinal Chemistry 2001, 9, 2215–2235.). In the second part of my Ph.D. work, a calixarene dimer with a triimidazole bridge (Dimer C) was synthesized. Dimer C Because in minor grooves, N-methylimidazoles of polyamides could recognize the positive electrostatic potential of amino groups of guanine bases via hydrogen bonds, it was assumed that Dimer C, which contained a triimidazole bridge, could prefer a major groove with large positive potentials. Moreover, because the triimidazole bridge is slim, it was also assumed that Dimer C should prefer a narrow major groove, which could offer the appropriate shape for the bridge’s recognition. In view of the above-mentioned assumptions, we found that the major groove of poly dG – poly dC fulfilled both requirements. Therefore, it was predicted that Dimer C should show the high affinity for poly dG – poly dC. Ethidium bromide displacement assays, fluorescence titrations, and circular dichroism measurements imply that Dimer C is a major groove binder. Furthermore, as we expected, these experiments indicate that Dimer C showed stronger preference for this specific DNA duplex: poly dG – poly dC. It was also observed that Dimer C frequently showed reduced affinity to other DNA duplexes. Probably, the decrease in affinity is related to their wider major grooves, in which the slim triimidazole bridge will not produce extensive close van der Waals contacts, and the whole ligand itself shows orientational disorder. Another explanation is the unfavorable electrostatic potentials, because these DNA duplexes have more neutral areas in major grooves than does poly dG – poly dC. Herein, we present a proposed mechanism of DNA binding by Dimer C: the cationic moieties on the upper rim of the calixarenes form hydrogen bonds with nucleobases as well as phosphate groups of the nucleic acid, the butoxy tail is toward the free solution, and the triimidazole bridge binds along the major groove and recognizes the amino groups of nucleobases