Remarks on Solving Methods of Nonlinear Equations

Abstract: In the field of mechanical engineering, many practical problems can be converted into nonlinear problems, such as the meshing problem of mechanical transmission. So the solution of nonlinear equations has important theoretical research and practical application significance. Whether the traditional Newton iteration method or the intelligent optimization algorithm after the popularization of computers, both them have been greatly enriched and developed through the continuous in-depth research of scholars at home and abroad, and a series of improved algorithms have emerged. This paper mainly reviews the research status of solving nonlinear equations from two aspects of traditional iterative method and intelligent optimization algorithm, systematically reviews the research achievements of domestic and foreign scholars, and puts forward prospects for future research directions

CEO Inside Debt and Overinvestment

Theoretical studies suggest that overinvestment is driven by equity holders’ desire to shift wealth from debt holders, while underinvestment is driven by equity holders’ desire to prevent the enhancement of debt-holder wealth. Therefore, debt holders have a stronger incentive to eliminate overinvestment than to eliminate underinvestment. We find that firms with higher inside-debt ratios are less likely to overinvest. Firms with above-median CEO inside-debt ratios drive this negative effect. These results support our expectation that CEO inside debt serves as a curb on overinvestment in order to prevent a wealth shift from debt holders to equity holders

Updated insights into 3D architecture electrodes for micropower sources

Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined

An Investigation of the Effect of Chitosan on Isothermal Crystallization, Thermal Decomposition, and Melt Index of Biodegradable Poly(L-lactic acid)

Biodegradable chitosan (CS) was introduced into another biodegradable poly(L-lactic acid) (PLLA) to prepare the PLLA/CS composites, and the effect of CS on thermal behavior and melt index of PLLA was investigated using modern testing technologies including optical depolarizer, thermogravimetric analysis instrument, and melt index instrument. The relevant testing results showed that both crystallization temperature and CS concentration affected the isothermal crystallization behavior of PLLA. Compared to neat PLLA, the t1/2 of PLLA/5% CS decreased from 2991.54 s to the minimum value 208.76 s at 105°C. However, the t1/2 of PLLA/CS composites in high crystallization temperature zone was different from that in low crystallization temperature zone. The increase of CS concentration and heating rate made the thermal decomposition temperature of PLLA/CS composites shift to higher temperature. The melt index results indicated that 3% CS made the fluidity of PLLA become better

cis-Bis(1,10-phenanthroline-κ2 N,N′)bis­(thio­cyanato-κN)magnesium(II)

The title compound, [Mg(NCS)2(C12H8N2)2], has been synthesized from the hydro­thermal reaction of MgCl2, KSCN, 1,10-phenanthroline and H2O. Its structure is isotypic with the MnII, FeII, CoII, NiII, CuII and ZnII analogues. The MgII cation has a slightly distorted octa­hedral geometry containing four N atoms from two 1,10-phenanthroline mol­ecules and two N atoms from two thio­cyanate anions. The asymmetric unit contains one-half mol­ecule, and the complete complex has 2 symmetry

Multifunctional Carbon Fibre Reinforced Hierarchical Composites based on Vertical Graphene

Carbon fibre reinforced polymer (CFRP) is becoming increasingly popular in various areas owing to its high strength to weight ratio and high resistance to corrosion compared with metal rivals. However, there are also some drawbacks, such as poor resistance to crack propagation, low electrical and thermal conductivity in thickness direction, which are dominated by the inherent nature of interface and matrix in composites. These drawbacks limited the wider application of CFRP, while developing multifunctional composite is a good solution to these issues. The additive nature of the manufacturing processes of CFRP makes it possible to introduce other functionalities, such as improved strength, improved electrical conductivity, and energy storage capability. This thesis aims to develop carbon fibre (CF) reinforced multifunctional composites by combining CFs with vertical graphene (VG). Such a combination can improve the mechanical and electrical properties of CFRP and create a platform for the introduction of other nanomaterials, such as silver nanowires (AgNWs) and manganese dioxides (MnO2) nanoflowers, to develop multifunctional composites. Firstly, VGs were deposited onto CFs through a plasma enhanced chemical vapor deposition. Multiple characterizations were then conducted on the resulted VG modified CFs. These results showed that VGs grafted on the CF dramatically increased the surface roughness and surface wettability. The interfacial shear strength between CF and epoxy matrix was enhanced without significant tensile strength degradation on CF. Next, conductive AgNWs were added into epoxy matrix and combined with VG modified CFs to improve the electrical conductivity of composites, which has potential application in the lightning strike protection of composite structures. Then, MnO2 nanoflowers were introduced onto the VG modified CFs through an electrochemical deposition process and enabled the CFs with energy storage capability. A structural supercapacitor was developed as an example of multifunctional composites with VG&MnO2 modified CF electrodes and polymer electrolyte. Lastly, aiming at the poor cycling stability of MnO2 modified CF electrode, a multilayer electrode structure was developed to achieve the long-term cycling stability. In achieving these, important scientific contributions are made to the developing methods of multifunctional CF reinforced composites, which broad the application of CFRP and enable the further lightweight design of CFRP in the future

The juxtamembrane and carboxy-terminal domains of Arabidopsis PRK2 are critical for ROP-induced growth in pollen tubes.

Polarized growth of pollen tubes is a critical step for successful reproduction in angiosperms and is controlled by ROP GTPases. Spatiotemporal activation of ROP (Rho GTPases of plants) necessitates a complex and sophisticated regulatory system, in which guanine nucleotide exchange factors (RopGEFs) are key components. It was previously shown that a leucine-rich repeat receptor-like kinase, Arabidopsis pollen receptor kinase 2 (AtPRK2), interacted with RopGEF12 for its membrane recruitment. However, the mechanisms underlying AtPRK2-mediated ROP activation in vivo are yet to be defined. It is reported here that over-expression of AtPRK2 induced tube bulging that was accompanied by the ectopic localization of ROP-GTP and the ectopic distribution of actin microfilaments. Tube depolarization was also induced by a potentially kinase-dead mutant, AtPRK2K366R, suggesting that the over-expression effect of AtPRK2 did not require its kinase activity. By contrast, deletions of non-catalytic domains in AtPRK2, i.e. the juxtamembrane (JM) and carboxy-terminal (CT) domains, abolished its ability to affect tube polarization. Notably, AtPRK2K366R retained the ability to interact with RopGEF12, whereas AtPRK2 truncations of these non-catalytic domains did not. Lastly, it has been shown that the JM and CT domains of AtPRK2 were not only critical for its interaction with RopGEF12 but also critical for its distribution at the plasma membrane. These results thus provide further insight into pollen receptor kinase-mediated ROP activation during pollen tube growth

A Hybrid Secure Scheme for Wireless Sensor Networks against Timing Attacks Using Continuous-Time Markov Chain and Queueing Model

Wireless sensor networks (WSNs) have recently gained popularity for a wide spectrum of applications. Monitoring tasks can be performed in various environments. This may be beneficial in many scenarios, but it certainly exhibits new challenges in terms of security due to increased data transmission over the wireless channel with potentially unknown threats. Among possible security issues are timing attacks, which are not prevented by traditional cryptographic security. Moreover, the limited energy and memory resources prohibit the use of complex security mechanisms in such systems. Therefore, balancing between security and the associated energy consumption becomes a crucial challenge. This paper proposes a secure scheme for WSNs while maintaining the requirement of the security-performance tradeoff. In order to proceed to a quantitative treatment of this problem, a hybrid continuous-time Markov chain (CTMC) and queueing model are put forward, and the tradeoff analysis of the security and performance attributes is carried out. By extending and transforming this model, the mean time to security attributes failure is evaluated. Through tradeoff analysis, we show that our scheme can enhance the security of WSNs, and the optimal rekeying rate of the performance and security tradeoff can be obtained. View Full-Tex