On Fila-King Conjecture in Dimension Four

We consider the following Cauchy problem for the four-dimensional energy critical heat equation \begin{equation*} \begin{cases} u_t=\Delta u+u^{3} ~&\mbox{ in }~ {\mathbb R}^4 \times (0,\infty),\\ u(x,0)=u_0(x) ~&\mbox{ in }~ {\mathbb R}^4. \end{cases} \end{equation*} We construct a positive infinite time blow-up solution $u(x,t)$ with the blow-up rate $\| u(\cdot,t)\|_{L^\infty({\mathbb R}^4)} \sim \ln t$ as $t\to \infty$ and show the stability of the infinite time blow-up. This gives a rigorous proof of a conjecture by Fila and King \cite[Conjecture 1.1]{filaking12}.Comment: 61 pages; any comment welcom

Trichotomy dynamics of the 1-equivariant harmonic map flow

For the 1-equivariant harmonic map flow from $R^2$ into $S^2$ \begin{equation*} \left\{ \begin{aligned} &v_t=v_{rr}+\frac{v_r}{r} - \frac{\sin(2v)}{2r^2} , ~\quad(r,t)\in R_+\times (t_0,+\infty),\\ &v(r,t_0)=v_0, \qquad\qquad\qquad\quad r\in R_+, \end{aligned} \right. \end{equation*} we construct global growing, bounded and decaying solutions with the initial data $v_0(r)$ satisfying v_0(0)=\pi ~\mbox{ and }~ v_0(r)\sim r^{1-\gamma} ~\mbox{ as }~ r\to+\infty, \quad \gamma>1. These global solutions exhibit the following trichotomy long-time asymptotic behavior \begin{equation*} \| v_r(\cdot,t) \|_{L^\infty ([0,\infty))} \sim \begin{cases} t^{\frac{\gamma-2}{2}}\ln t ~&\mbox{ if }~ 1<\gamma<2,\\ 1 ~&\mbox{ if }~ \gamma=2,\\ \ln t ~&\mbox{ if }~ \gamma>2,\\ \end{cases} ~\mbox{ as }~ t\to +\infty. \end{equation*}Comment: 30 pages; comments welcom

The trilateral game of privacy perception, financial regulation and central bank digital currency issuance

The goal of this study is to clarify how privacy protection affects the insurance of central bank digital currency (CBDC). By constructing a tripartite game model involving consumers, commercial banks, and regulators, this paper explores the impact of privacy protection on the issuance of CBDC. The findings show that privacy protection is critical to ensuring successful adoption of CBDCs. The central bank must strike a balance between protecting user privacy while also regulating usage and ensuring convenience for users. However, due to opportunistic behavior by both commercial banks and consumers during this process, negative reactions are possible. Based on the findings of this research, it is suggested that central banks should encourage commercial banks to participate in CBDC issuance by promoting appropriate data sharing and offering guidance. Additionally, they should focus on consumer education and expectation management to promote CBDC adoption. Commercial banks must also embrace digital transformation and adapt to the changing financial landscape to remain competitive while providing innovative financial services to customers

UniFuzz: Optimizing Distributed Fuzzing via Dynamic Centralized Task Scheduling

Fuzzing is one of the most efficient technology for vulnerability detection. Since the fuzzing process is computing-intensive and the performance improved by algorithm optimization is limited, recent research seeks to improve fuzzing performance by utilizing parallel computing. However, parallel fuzzing has to overcome challenges such as task conflicts, scalability in a distributed environment, synchronization overhead, and workload imbalance. In this paper, we design and implement UniFuzz, a distributed fuzzing optimization based on a dynamic centralized task scheduling. UniFuzz evaluates and distributes seeds in a centralized manner to avoid task conflicts. It uses a "request-response" scheme to dynamically distribute fuzzing tasks, which avoids workload imbalance. Besides, UniFuzz can adaptively switch the role of computing cores between evaluating, and fuzzing, which avoids the potential bottleneck of seed evaluation. To improve synchronization efficiency, UniFuzz shares different fuzzing information in a different way according to their characteristics, and the average overhead of synchronization is only about 0.4\%. We evaluated UniFuzz with real-world programs, and the results show that UniFuzz outperforms state-of-the-art tools, such as AFL, PAFL and EnFuzz. Most importantly, the experiment reveals a counter-intuitive result that parallel fuzzing can achieve a super-linear acceleration to the single-core fuzzing. We made a detailed explanation and proved it with additional experiments. UniFuzz also discovered 16 real-world vulnerabilities.Comment: 14 pages, 4 figure

The proportion of HIV disclosure to sexual partners among people diagnosed with HIV in China: A systematic review and meta-analysis

Background: Sexual behavior is one of the main routes of HIV/AIDS spread. HIV disclosure to sexual partners has been confirmed to be an important strategy for HIV/AIDS prevention and control. We conducted a systematic review and meta-analysis to pool proportions and characteristics of HIV disclosure to sexual partners among people diagnosed with HIV in China.Methods: We searched eight databases and extracted the data on HIV disclosure to partners. Heterogeneity of the data was tested with I2. Published bias subjectively and objectively analyzed through the funnel plot and Egger's regression test. Subgroup analyses were performed to explore the variation in the proportion by sexual partnership types (unclassified, regular, casual sexual partners), whether being men who have sex with men (MSM), and when to diagnose. The sources of heterogeneity were analyzed. Sensitivity analysis was carried out to evaluate the stability of the results.Results: Out of 3,698 studies, 44 were included in the review; 11 targeted on MSM. The pooled proportion of HIV disclosure to sexual partners was 65% (95% CI: 56%−75%; 34 studies). Sub-group analyses indicated the proportions of HIV disclosure to regular, casual and unclassified sexual partners were 63% (95% CI: 45%−81%; 31 studies), 20% (95% CI: 8%−33%; nine studies), and 66% (95% CI: 59%−73%; 14 studies), respectively. Fifty-seven percent (95% CI: 45%−69%; three studies) disclosed on the day of diagnosis, 62% (95% CI: 42%−82%; four studies) disclosed within 1 month, and 39% (95% CI: 2%−77%; four studies) disclosed 1 month later. Among MSM, the disclosure to regular male partners, regular female sexual partners, spouses, and casual partner were 47% (95% CI: 29%−65%; six studies), 49% (95% CI: 33%−65%; three studies), 48% (95% CI: 18%−78%; seven studies), and 34% (95% CI: 19%−49%; four studies), respectively.Conclusions: The disclosure prevalence of people diagnosed with HIV to sexual partners still need improving in China, and it varies among partner types, key populations, and time being diagnosed. HIV disclosure strategies and procedures need to be developed more detailed and tailored based on the pain points of disclosure status, so as to ultimately prevent HIV transmission through sexual contact.</p

Energy storage system modeling and control for power grid services

The fast growth of energy demand, the incorporation of renewable energy sources, and the necessity to ensure a reliable and stable power supply have brought significant challenges to the existing load frequency control (LFC) systems. In the context of modern power networks, LFC systems are required to maintain the balance between generated and consumed power to guarantee stable frequency and secure operation of the interconnected grids. Incorporating energy storage systems (ESS) into LFC schemes has emerged as a promising solution to address these challenges, thereby improving the overall system performance. In this paper, we first introduce the principles and concepts of primary and secondary frequency control, and analyze their impacts on power system frequency stability. Then, we formulate models for the load frequency control system components. Subsequently, based on the energy storage system’s characteristics including the internal structure, equivalent circuit structure, and frequency regulation ability in LFC system, three common energy storage system models for LFC are investigated: Li-ion Battery Energy Storage System, Superconducting Magnetic Energy Storage System, and Redox Flow Battery. In particular, we established the Linear incremental models for these three batteries and developed corresponding simulation models in Simulink. Finally, load frequency control models using these three energy storage sources are established for a single-area control system and simulated in MATLAB/Simulink. We compare and analyze the frequency fluctuation with and without the connection of the battery models, as well as the settling time. The state-of-charge of the batteries is also compared.Master of Science (Power Engineering

Performance analysis of organic Rankine cycles using different working fluids

Low-grade heat from renewable or waste energy sources can be effectively recovered to generate power by an organic Rankine cycle (ORC) in which the working fluid has an important impact on its performance. The thermodynamic processes of ORCs using different types of organic fluids were analyzed in this paper. The relationships between the ORC’s performance parameters (including evaporation pressure, condensing pressure, outlet temperature of hot fluid, net power, thermal efficiency, exergy efficiency, total cycle irreversible loss, and total heat-recovery efficiency) and the critical temperatures of organic fluids were established based on the property of the hot fluid through the evaporator in a specific working condition, and then were verified at varied evaporation temperatures and inlet temperatures of the hot fluid. Here we find that the performance parameters vary monotonically with the critical temperatures of organic fluids. The values of the performance parameters of the ORC using wet fluids are distributed more dispersedly with the critical temperatures, compared with those of using dry/isentropic fluids. The inlet temperature of the hot fluid affects the relative distribution of the exergy efficiency, whereas the evaporation temperature only has an impact on the performance parameters using wet fluid

FirmHunter: State-Aware and Introspection-Driven Grey-Box Fuzzing towards IoT Firmware

IoT devices are exponentially increasing in all aspects of our lives. Via the web interfaces of IoT devices, attackers can control IoT devices by exploiting their vulnerabilities. In order to guarantee IoT security, testing these IoT devices to detect vulnerabilities is very important. In this work, we present FirmHunter, an automated state-aware and introspection-driven grey-box fuzzer towards Linux-based firmware images on the basis of emulation. It employs a message-state queue to overcome the dependency problem in test cases. Furthermore, it implements a scheduler collecting execution information from system introspection to drive fuzzing towards more interesting test cases, which speeds up vulnerability discovery. We evaluate FirmHunter by emulating and fuzzing eight firmware images including seven routers and one IP camera with a state-of-the-art IoT fuzzer FirmFuzz and a web application scanner ZAP. Our evaluation results show that (1) the message-state queue enables FirmHunter to parse the dependencies in test cases and find real-world vulnerabilities that other fuzzers cannot detect; (2) our scheduler accelerates the discovery of vulnerabilities by an average of 42%; and (3) FirmHunter is able to find unknown vulnerabilities

Phylogeny and Integrative Taxonomy of the Genera Gymnaetoides and Pseudotachycines (Orthoptera: Rhaphidophoridae)

The genera Gymnaetoides and Pseudotachycines are endemic to China and are morphologically homogeneous. The few available diagnostic characters make species identification particularly challenging. Species cannot be classified according to the given generic diagnosis, and phylogenetic analyses have not been reported. Here, we reconstruct the phylogeny using Bayesian inference and maximum likelihood and employ four approaches to delimit species. The results suggest that both Gymnaetoides and Pseudotachycines are paraphyletic. Therefore, we revise their taxonomy based on the combination of morphological characters and molecular data. A new genus Homotachycines Zhu &amp; Shi gen. nov. is erected, and six new combinations are proposed. Species delimitation identifies 15 new species and one new subspecies: Gymnaetoides huangshanensis, G. petalus, G. yangmingensis, G. lushanensis, Pseudotachycines procerus, P. procerus guizhouensis, P. zhengi, P. nephrus, P. sagittus, P. fengyangshanensis, Homotachycines triangulus, H. quadratus, H. baokangensis, H. fusus, H. concavus, and H. qinlingensis sp. nov. Moreover, we find that the shapes of the dorsal lateral lobes and the dorsal median lobe of the male genitalia are also important characters for identifying these genera and that the shapes of the dorsal and lateral sclerites of the male genitalia are suitable for the classifications of species