Search

The application of fluoropolymers in energetic materials has attracted increasing attention. The effect of poly(vinylidene difluoride) (PVDF) content on thermal reaction and combustion performance of MnO2-Al nanothermite was reported. Nanothermite samples were prepared by electrospray with the content of PVDF from 0 wt.% to 30 wt.%. Thermal reaction processes influenced by PVDF content were tested by simultaneous thermal analysis (TG-DSC). Finally, ignition threshold tests were designed, and combustion processes were recorded. The results showed that the components of nanothermite materials were evenly distributed and stable. The content of PVDF had a significant influence on thermal reaction process, which is divided into four stages. Ignition threshold was represented by value of instantaneous ignition current. With the increase of PVDF content, ignition threshold decreased first and then tended to a stable value. Besides, PVDF content had important effects on the combustion speed of the samples. This work has practical significance for designing thermite-based ignition propellant. [ABSTRACT FROM AUTHOR]

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO3/KClO4 (Kp) nanothermite was prepared and the Al/MoO3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO3/Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g− 1, increasing by approximately 33% of 1486 J·g− 1 of the Al/MoO3 nanothermite, and activation energy of 269.66 kJ·mol− 1, which demonstrated higher stability than the Al/MoO3 nanothermite (205.64 kJ·mol− 1). During the combustion test, the peak pressure of the Al/MoO3/Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s− 1, much higher than 0.188 MPa and 6.27 MPa·s− 1 of the Al/MoO3 nanothermite. The combustion products of Al/MoO3 nanothermite were Al2O3, MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO3/Kp nanothermite were Al2O3, MoO, and KCl, indicating complete reaction. Their "coral-like" morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO3/Kp nanothermite is attributed to the melt and decomposition of Kp into O2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites. [ABSTRACT FROM AUTHOR]

Metal matrix ceramic composites have high hardness, good wear and corrosion resistance, but the high percentage of WC ceramic composites are prone to cracking, which leads to limited applications. It was proposed to prepare 316L and 60 wt.% WC/NiCu shell stacked structure composites with single layer thicknesses of 0.4 mm, 0.6 mm, 0.8 mm and 1 mm, respectively, using directed energy deposition technique. The results show that the shell stacked structure consumes a large amount of fracture energy through toughening mechanisms such as ligament bridging, crack deflection, and microcracking to make the material better able to withstand the load, the hardness of the metal substrate is enhanced by the diffusion of WC particles and soft and hard phase elements. The shell stacked structure, with a single layer thickness of 0.6 mm, demonstrated excellent resistance to crack damage when subjected to a compressive load of 18000N. [ABSTRACT FROM AUTHOR]

This paper focuses on the position control of the quadruped robot hydraulic drive unit (HDU). The proposed control strategy has the advantages of excellent output tracking performance, strong robustness, no chattering and low computational complexity. HDU has the characteristics of nonlinearity and parameter uncertainty, coupled with unpredictable external interference, which makes it difficult to achieve precise position control. In this paper, we first establish the mathematical model of the HDU based on the actual parameters and obtain the state space of the system. Through the pole placement, the simplified system can easily achieve the expected control goal. Then, the state equation of the error system is constructed, and the nonlinearity, parameter uncertainty and external interference of the HDU are summarized as the matched and unmatched uncertainties of the system. The integral sliding mode control (ISMC) is used to derive the control law, and the response characteristics of the system when pole placement and state feedback H∞ control are used for the nominal control are compared. It can be concluded that the system with state feedback H∞ control for nominal control has stronger robustness and can resist the unmatched uncertainties. Finally, the control law of the simplified system is used as feedforward and combined with the ISMC of the error system, the output tracking control framework of the HDU is proposed. Simulations and experiments show that the proposed control method has excellent tracking performance and strong robustness. [ABSTRACT FROM AUTHOR]

Cystic fibrosis (CF) is a rare autosomal recessive disease with only one pathogenic gene cystic fibrosis transmembrane conductance regulator (CFTR). To identify the potential pathogenic mutations in a Chinese patient with CF, we conducted Sanger sequencing on the genomic DNA of the patient and his parents and detected all 27 coding exons of CFTR and their flanking intronic regions. The patient is a compound heterozygote of c.2909G > A, p.Gly970Asp in exon 18 and c.1210-3C > G in cis with a poly-T of 5T (T5) sequence, 3 bp upstream in intron 9. The splicing effect of c.1210-3C > G was verified via minigene assay in vitro, indicating that wild-type plasmid containing c.1210-3C together with T7 sequence produced a normal transcript and partial exon 10-skipping-transcript, whereas mutant plasmid containing c.1210-3G in cis with T5 sequence caused almost all mRNA to skip exon 10. Overall, c.1210-3C > G, the newly identified pathogenic mutation in our patient, in combination with T5 sequence in cis, affects the CFTR gene splicing and produces nearly no normal transcript in vitro. Moreover, this patient carries a p.Gly970Asp mutation, thus confirming the high-frequency of this mutation in Chinese patients with CF. [ABSTRACT FROM AUTHOR]

This paper focuses on active compliance control of hydraulic quadruped robot, especially the analysis of the inner-loop of the coupled system. Current researches on active compliance control regard the bandwidth of the inner loop of the system as infinite, while ignoring that the extra-load will cause the inner-loop response characteristics to deteriorate when the leg is in the stance phase. In this work, we first briefly introduced the structure of the robot, and its kinematics and dynamics are analyzed. Next, the robot's active compliance control framework is established, and the inner-loop two-cylinder coupling system is analyzed in depth. It can be concluded that the existence of low frequency poles in the system is the main reason for the poor response characteristics. Then through the analysis of the state equation and transfer function matrix of the multi-input multi-output system, we show that the equivalent hydraulic spring stiffness (EHSS) is the main factor affecting the zero-pole distribution. Furthermore, we optimize the structure to increase the EHSS to improve the response characteristics of the system. Finally, the co-simulation platform and single-leg experiment bench are introduced. The simulation and experimental results show that the response speed of the inner-loop control is significantly improved after optimization, and the robot with active compliance control strategies can significantly reduce the impact of the foot. [ABSTRACT FROM AUTHOR]

Tumor metastasis remains an obstacle in cancer treatment and is responsible for most cancer-related deaths. Nm23-H1 is one of the first metastasis suppressor proteins discovered with the ability to inhibit metastasis of many cancers including breast, colon, and liver cancer. Although loss of Nm23-H1 is observed in aggressive cancers and correlated with metastatic potential, little is known regarding the mechanisms that regulate its cellular level. Here, we examined the mechanisms that control Nm23-H1 expression in breast cancer cells. Initial studies in aggressive MDA-MB-231 cells (expressing low Nm23-H1) and less invasive MCF-7 cells (expressing high Nm23-H1) revealed that mRNA levels correlated with protein expression, suggesting that transcriptional mechanisms may control Nm23-H1 expression. Truncational analysis of the Nm23-H1 promoter revealed a proximal and minimal promoter that harbor putative binding sites for transcription factors including CTCF and EGR1. CTCF and EGR1 induced Nm23-H1 expression and reduced cell migration of MDA-MB-231 cells. Moreover, CTCF and EGR1 were recruited to the Nm23-H1 promoter in MCF-7 cells and their expression correlated with Nm23-H1 levels. This study indicates that loss of Nm23-H1 in aggressive breast cancer is apparently caused by downregulation of CTCF and EGR1, which potentially drive Nm23-H1 expression to promote a less invasive phenotype. [ABSTRACT FROM AUTHOR]

In order to improve the energy density of polytetrafluoroethylene/aluminum (PTFE/Al), titanium hydride (TiH2) was added as a high-energy additive, and thermogravimetry–differential scanning calorimetry (TG-DSC), quasi-static compression and Split-Hopkinson pressure bar (SHPB) tests were conducted to investigate the chemical reaction mechanism and mechanical response of PTFE/Al/TiH2. The results of TG-DSC indicate that TiH2 first decomposes to form titanium and hydrogen, and titanium reacts with PTFE to produce TiF3, and then with the temperature rising, titanium reacts with carbon and excessive aluminum to generate TiC and Al3Ti. Under quasi-static compression, the strength of PTFE/Al/TiH2 specimens can reach 108.8 Mpa, 14.2% higher than that of PTFE/Al, the special burning flames during the reaction and XRD patterns of the reaction residues consistently indicate that TiH2 has participated in the reaction and react completely, achieving its purpose as a high-energy additive. Under dynamic compression tests, PTFE/Al/TiH2 composites show obvious strain hardening and strain rate hardening effects, and the yield strength and compressive strength are sensitive to strain rates; the established Johnson-Cook (JC) constitutive model can describe the mechanical response of PTFE/Al/TiH2 material well. In addition, the ignition threshold of PTFE/Al/TiH2 drops to 22.78 m/s, less than that of PTFE/Al (23.74 m/s), and the ignition delay time is advanced from 650-700 to 100-150 μs as the impact velocity increase. [ABSTRACT FROM AUTHOR]

During photodynamic therapy (PDT) it is important to monitor the treatment progress to achieve the intended therapeutic outcome. Chemiluminescence (CL) provides a sensitive and selective means for 1O2detection. In our study, by comparing CL with the corresponding in situPDT treatment protocols and the treatment effect, the results indicate that the treatment outcome for tumors was governed by a set of dosimetry factors with a rather complicated relationship, but there was a remarkable connection between tumor treatment effect and CL. In conclusion, CL can be used in in vivoPDT to determine the dose of tumor treatment and monitor the treatment threshold. By monitoring CL it is feasible to determine PDT dose to predict tumor treatment effect. [ABSTRACT FROM AUTHOR]

BitTorrent achives great success in its high performance for file distribution. It is commonly believed that this owes to Tit-for-Tat strategy adopted in choking algorithm for incentive in BitTorrent protocol. But there are still many issues in incentive mechanism in BitTorrent. In this paper, we study Tit-for-Tat strategy by constructing a game model in P2P environments and deducing the constraint under which the strict Tit-for-Tat is an equilibrium strategy. We then enhance and adapt the Tit-for-Tat strategy to the dynamic property in P2P networks, and deduce the constraint under which it is still an equilibrium strategy. We also study through simulations the performance improvement of the enhanced Tit-for-Tat, and give suggestion on how to choose proper system parameters under different network conditions. Finally, based on the enhanced Tit-for-Tat strategy, we propose a method to improve incentive in BitTorrent networks to cope with free-riding and fairness issues. [ABSTRACT FROM AUTHOR]

A peer-to-peer hierarchical replica location mechanism (PRLM) was designed for data grids to provide better load balancing capability and scalability. Global replica indexes of the PRLM are organized based on even distributed Chord (ED-Chord) structure. The locality can optimize queries on local replica indexes of virtual organizations. ED-Chord protocol collects the node identifiers information using a distributed method and assigns optimal identifiers for new nodes to make them more uniformly distributed in the entire identifier space. Theoretical analysis and simulations show that PRLM provides good performance, scalability and load balancing capability for replica location in data grids. [ABSTRACT FROM AUTHOR]

To improve the thermal and combustion properties of nanothermites, a design theory of changing the state of matter and structural state of the reactants during reaction was proposed. The Al/MoO 3 /KClO 4 (Kp) nanothermite was prepared and the Al/MoO 3 nanothermite was used as a control. SEM and XRD were used to characterize the nanothermites; DSC was used to test thermal properties; and constant volume and open combustion tests were performed to examine their combustion performance. Phase and morphology characterization of the combustion products were performed to reveal the mechanism of the aluminothermic reaction. The results show that the Al/MoO 3 /Kp nanothermite exhibited excellent thermal properties, with a total heat release of 1976 J·g - 1 , increasing by approximately 33% of 1486 J·g - 1 of the Al/MoO 3 nanothermite, and activation energy of 269.66 kJ·mol - 1 , which demonstrated higher stability than the Al/MoO 3 nanothermite (205.64 kJ·mol - 1 ). During the combustion test, the peak pressure of the Al/MoO 3 /Kp nanothermite was 0.751 MPa, and the average pressure rise rate was 25.03 MPa·s - 1 , much higher than 0.188 MPa and 6.27 MPa·s - 1 of the Al/MoO 3 nanothermite. The combustion products of Al/MoO 3 nanothermite were Al 2 O 3 , MoO, and Mo, indicating insufficient combustion and incomplete reaction, whereas, the combustion products of Al/MoO 3 /Kp nanothermite were Al 2 O 3 , MoO, and KCl, indicating complete reaction. Their "coral-like" morphology was the effect of reactants solidifying after melting during the combustion process. The characterization of reactants and pressure test during combustion reveals the three stages of aluminothermic reaction in thermites. The excellent thermal and combustion performance of Al/MoO 3 /Kp nanothermite is attributed to the melt and decomposition of Kp into O 2 in the third stage. This study provides new ideas and guidance for the design of high-performance nanothermites., (© 2024. The Author(s).)