Search

Benefiting from the structural characteristics of the ball-end milling cutter and the tool motion characteristics during the cutting process, the high speed ball-end milling process can be directly used to manufacture discrete surface micro-pits texture with different sizes and distributions. The influencing mechanism of the interval and distribution of the micro-pit texture on the antifriction performance was investigated by combining Fluent fluid simulation and reciprocating sliding friction test under oil immersion lubrication condition. Results show that the textured surface with micro-pit features shows obvious antifriction ability. The friction coefficient of textured surface was reduced by 61.5 % compared with that of polished specimens. The interval can influence the oil film bearing capacity and then the antifriction ability. The most significant friction reduction effect was achieved when the micro-pit interval was 900 μm. Additionally, the friction coefficient can be further reduced by optimizing the distribution of the micro-pits. The friction coefficient decreased to 0.121 for the orientation angle 70° condition.

Satellite-terrestrial networks are emerging as the next-generation networking paradigm for Beyond-5 G (B5G) and 6 G networks. Meanwhile, Mobile Edge Computing (MEC) is envisioned as the key technology to provide network services within the proximity of users, by deploying computing resource in ground locations that are close to users. With the fast deployment of Low-Earth-Oribt (LEO) satellites, a new paradigm of MEC is emerging by enabling LEO satellites serving as edge servers in lower orbits that are close to ground users. In this way, the ground users can be further served by LEO satellites in lower orbits instead of conventional high-orbit satellites. Also, since LEO satellites provide shorter paths from users to services, the performance is enhanced compared with ground MEC networks. In this paper, we aim to enable low-latency network services in a Satellite Edge Computing (SEC) network that integrates the MEC and satellite-terrestrial networks. In particular, we consider that each network service is composed of a sequence of Virtualized Network Functions (VNFs), where the traffic of user requests has to be processed by the VNFs in a service chain in the specified order before reaching its destination. To this end, we first formulate a delay-aware service chaining problem in an SEC network to minimize the average delay of implementing a user request, by jointly placing VNFs to LEO satellites in the SEC network and routing the traffic of each user request from its source to destination. We then devise an approximation algorithm with an approximation ratio for the problem in an SEC network with a single user request, by devising a novel concept of chaining orbit and auxiliary graph construction technique. We also design an online algorithm for the online delay-aware service chaining problem in an SEC network, if user requests arrive into the system without the knowledge of their arrivals and the network delays are uncertain. We finally evaluate the performance of the proposed algorithms using real satellite network topologies, and results show that the proposed algorithms achieve 28.5% lower delay than their counterparts.

Smart power grid is a two-way interconnected network in which information plays a fundamental role in the process of energy transmission and distribution. The smart grid is based on combining ICT with the processing capabilities of computers and electrical systems to increase communication between users. However, smart grids are exposed to a variety of malicious cyber-attacks that can lead to the destruction of basic infrastructure and disrupt communication between the grid and users. Meanwhile, by authenticating the authenticated users, cyber-security can be created in the smart grid. One of the main components of a smart power grid is smart meters. However, to maintain security in a communication, smart meter authentication alone is not enough and it must be ensured that the electricity company’s server is not forgery. Therefore, there is a need for two-way authentication between the smart meter on the home side and the electricity company server. The present work provides a key management layout (based on the elliptic curve cryptography) with two-way authentication for communication outside the home area network The proposed solution is two-way authentication among the smart meter and the security associate in the power company. In other words, the proposed methodology creates a solution to establish a connection between valid users and the smart grid. The proposed protocol evaluates the behavior of cyber-attacks on the smart grid. Attacks such as man-in the middle attacks and retransmission attacks are considered. It was found that, the proposed methodology improves the reliance between smart grid and authenticated users with the increase of secure communications. Moreover, the proposed protocol can prevent an extensive experiment attack. The results also showed that, as the false factor increases, the detection time by the proposed algorithm increases. As the false factor increases from 0.1 to 0.3, the detection time increases by 1.4 s.

To select the optimum tool material for the cutting of marine high-strength steels using a hole-opening equipment in the marine environment, this article conducted a comparative study on the corrosion property, tribological behavior and cutting performance of cermet, cemented carbide and coated tools. The results reveal that the coated tool materials have good corrosion resistance with coating protection, and poor wear resistance with adhesive and corrosive wear in artificial seawater, and present moderate cutting performance. In addition, the cemented carbide tool materials show poor corrosion resistance and good wear resistance due to the lubrication effect of corrosion products in artificial seawater, but have bad cutting performance with a high flank wear value. Moreover, the cermet tool materials present acceptable corrosion and wear resistance with adhesive and corrosive wear in artificial seawater and have the excellent cutting performance. Taking into account the corrosion resistance, wear resistance and cutting performance of tool materials and regarding cutting performance as an important indicator, the cermet tool materials with superior comprehensive performances are suitable for the cutting of marine high-strength steels in the marine environment.

Nickel-titanium shape memory alloys have been widely used in medical fields due to their unique shape memory effect, superelasticity, corrosion resistance and biocompatibility. However, there are still many processing difficulties to achieve required machined surface quality due to their high toughness and low elasticity. This paper proposes a sequential processing operations including milling, burnishing and electrochemical polishing. The effects of electrochemical parameters on surface quality, such as surface roughness, work hardening and surface grain size, are investigated in detail using orthogonal experiment. It is found that the electrochemical polishing parameters have the most significant effect on improving the surface roughness. With adjusting electrochemical polishing parameters, the surface roughness can be reduced to one tenth of the original value obtained by milling operations. Moreover, the current density in electrochemical polishing has more important influence on the surface quality than the distance and polishing time does, respectively. The conditions of 1.5A/cm2current density, 7cm electrode distance and 20s polishing time can obtain the lower surface roughness, hardening degree and the larger grain size. The effects of electrochemical parameters on surface roughness, work hardening and grain size are related to each other. The degree of work hardening can be qualitatively estimated by surface roughness and grain size to avoid damage to the machined surface.

Aim:The systematic review assessed the effect of mindfulness-based interventions on the quality of life among women with breast cancer. Methods:PubMed, Cochrane library, EMBASE, Web of Science and CINAHL databases were searched for studies published. Our review assessed the effect of mindfulness-based interventions (Mindfulness-Based Stress Reduction [MBSR] intervention and Mindfulness-Based Cognitive Therapy [MBCT]) on quality of life for women with breast cancer. Two authors independently assessed the quality of all included studies using the Downs and Black Quality Index. Results:The search finally identified 15 studies. The MBSR intervention showed a significant effect between groups. The MBCT intervention also showed good effect on quality of life. Adverse events were inadequately reported. Conclusion:The MBSR intervention on quality of life among women with breast cancer was effective and safe. The effect of MBCT intervention on quality of life still needs more research.

Liver injury is a serious clinical syndrome that characterized by inflammatory response. Engeletin is known to have anti-inflammatory activity. However, the effects of engeletin on liver injury remain unclear. We aimed to assess the protective effect of engeletin on Lipopolysaccharide (LPS)/d-galactosamine (D-gal)-induced liver injury in mice. Engeletin was administered intraperitoneally 1 h before and 12 h after LPS/D-gal treatment. The results showed that engeletin treatment on LPS/D-gal-induced liver injury in mice have a significant protective effect, as confirmed by the attenuation of liver histopathologic changes, MPO activity, and serum AST and ALT levels. At the meanwhile, it also showed that engeletin inhibited the levels of IL-β and TNF-α in serum and liver tissues. Besides, engeletin blocked the activation of NF-κB induced by LPS/D-gal and induced the expression of PPAR-γ in a dose-dependently manner. These findings suggested that engeletin may have a protective effect against liver injury.

To provide guidance for the tool materials selection in the machining of high-strength steels, this article outlines the application of fuzzy comprehensive evaluation method for the cutting performance evaluation of cemented carbide tools, ceramic tools, and cermet tools. The results indicate that cermets with the best comprehensive cutting performance are chosen as the optimum tool materials for the machining of high-strength steels. Moreover, the severe adhesion wear characteristics of cemented carbide tools are detrimental to the surface quality of workpieces. The obvious crater wear and furrow-like scratches caused mainly by abrasive wear, as well as adhesive wear can shorten the life of ceramic tools. The sharp cutting edge and good wear resistance of cermet tools are not only beneficial to the machined surface quality of workpieces, but also prolong the tool life. The analysis of tool wear proves the reliability and accuracy of fuzzy comprehensive evaluation method.

This paper aims at comparing the surface integrity and fatigue performance of hardened AISI D2 steel ball-end milled with different milling speeds. Results show that the milling speed has a significant effect on surface topography, surface roughness, microhardness and residual stress. The fatigue life for samples with hard milled surface was raised at least 83% compared with that of polished samples. This is ascribed to the high surface residual compressive stress and the enhanced microhardness induced by the hard milling process. The maximum difference in fatigue life is about 12.2% for samples milled with spindle speed N ranging from 3000 r/min to 8000 r/min. Samples milled with a low or high spindle speed have a longer fatigue life than those samples milled with a middle spindle speed condition (N=6000 r/min). Moreover, excessive surface strain hardening will increase surface brittleness which is detrimental to fatigue resistance. The increase of spindle speed can decrease the degree of strain hardening to some extent. Based on this, selecting a relatively high spindle speed can obtain a satisfying combination of surface residual stress and microhardness during the ball-end milling process of hardened AISI D2 steel, which is feasible and prospective from high fatigue performance of ball-end milled surface and the machining efficiency point of view.

A low-cost smart measurement system for resistive (bridge) or capacitive sensors is presented. The measurement system consists of three main parts: the sensor element, a universal transducer interface (UTI) and a microcontroller. The Universal Transducer Interface (UTI) is equipped with front-ends for many types of resistive (bridge) and capacitive sensors. It is a sensor-signal-to-time converter, based on a period-modulated oscillator, which generates a microcontroller-compatible output signal. The microcontroller performs data acquisition of the output signals from the UTI, controls the operating conditions and communicates with a personal computer. Continuous auto-calibration is applied to eliminate the influences of offset and gain errors. According to the experimental results the accuracy and resolution amounts to 13 bits and 16 bits, respectively, for a measurement time of about 100 ms.

Characteristics of mass spectra of isomeric tetradecadien-1-ols were investigated by electron impact mass spectrometry, and mass spectral fragmentation pathways were proposed based on collision-induced dissociation experiments and mass-analyzed ion kinetic energy spectrometry. Copyright © 1999 John Wiley & Sons, Ltd.

Characteristics of mass spectra of isomeric tetradecadien‐1‐ols were investigated by electron impact mass spectrometry, and mass spectral fragmentation pathways were proposed based on collision‐induced dissociation experiments and mass‐analyzed ion kinetic energy spectrometry. Copyright © 1999 John Wiley & Sons, Ltd.

Similarity of mass spectra of double‐bond positional isomers of tetradecen‐1‐ols and their acetates was evaluated, based on the intensity ratios of pairs of predominant ions, transformed by a novel equation to define a similarity index. © 1997 John Wiley & Sons, Ltd.

Similarity of mass spectra of double-bond positional isomers of tetradecen-1-ols and their acetates was evaluated, based on the intensity ratios of pairs of predominant ions, transformed by a novel equation to define a similarity index. © 1997 John Wiley & Sons, Ltd.