The thermal conductivity of benzene and toluene

The thermal conductivity of liquid toluene and benzene was measured in the temperature range 298 to 370 K, near the saturation line, using an absolute transient hot-wire technique. The measurements were made in a modified version of an existing instrument, equipped with a new automatic Wheatstone bridge, computer controlled. The bridge measures the time that the resistance of a 7-m-diameter platinum wire takes to reach predetermined values, programmed by the computer. The computer can generate up to 1024 analog voltages, via a 12-bit D/A converter. The accuracy of the measurements with this new arrangement was assessed by measuring the thermal conductivity of a primary standard, toluene, at several temperatures and was found to be of the order of 0.3%. Benzene was chosen because it is under study as a possible secondary standard for liquid thermal conductivity by the Subcommittee on Transport Properties of IUPAC.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Development of biodegradable PLA/PBT nanoblends

Poly(lactic acid)/poly(butylene terephthalate) (PLA/PBT) blends with 3, 5, and 10 wt % of PBT were produced in a twin‐screw extruder, with the addition of ethylene–glycidyl methacrylate copolymer as compatibilizer. An uncompatibilized PLA/PBT blend with 5 wt % of PBT was prepared for comparison studies. The epoxy reactive groups in the compatibilizer allowed modification of the interfacial tension in the blends and reduced the PBT dimensions. The crystallinity of the blends was studied, and its influence on mechanical properties was analyzed. Tensile tests showed an increase in strain at break from 3% for neat PLA to 49% for PLA with 3 wt % PBT, while the tensile modulus dropped from 3.59 GPa to 3.35 GPa for the same samples. Izod results showed a transition from a brittle behavior of PLA to a ductile one for compatibilized blends. These results indicate that the nanometer‐size dispersed phase was effective in changing the deformation behavior of the matrix without a significant loss of modulus. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45951.     

Flexible conductive poly(styrene‐butadiene‐styrene)/carbon nanotubes nanocomposites: Self‐assembly and broadband electrical behavior

Flexible conductive nanocomposites with the ability of self‐assembly into well‐ordered structures are promising multifunctional materials for energy conversion and storage devices. In this work, flexible nanocomposites based on multi‐walled carbon nanotubes (MWCNTs) and poly(styrene‐butadiene‐styrene) (SBS) were obtained by solution casting, followed by a post‐annealing treatment, during 7 days at 110 °C, to enable the self‐organization of the SBS. The impact of the MWCNTs on the self‐assembly was studied by atomic force microscopy and Small angle X‐rays scattering, and the conductivity of these nanocomposites was analyzed over the broadband frequency range, that is, 10^?1–10⁶ Hz. The results revealed that the lower MWCNTs loadings (～0.2 v %) were the most suitable to achieve a conductive network through the SBS, maintaining self‐assembled domains. These domains include hexagonally packed cylinders and alternating lamellae. Furthermore, at loadings above 1 v %, the impact of further MWCNTs addition on the conductivity was marginal over the whole frequency range and the self‐assembly tendency was progressively reduced. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46650.     

A 14-bit 250 kS/s two-step inverter-based incremental $$\varSigma \varDelta$$ ADC for CMOS image sensor in $$0.18\,\upmu \hbox {m}$$0.18μm technology

This paper presents an ultra-low-power, bulk-driven, source-degenerated fully differential transconductor (FD-OTA), operating in subthreshold region. The source-degeneration (SD) and bulk-drive ensure linearity and rail-to-rail input swing. The flipped voltage follower and SD resistor perform V–I conversion in input core with power efficient class AB mode of operation. The reduction in open loop gain and gain bandwidth (GBW) of bulk-drive is compensated by applying partial positive feedback at diode connected MOSFET pair. The current gain from input core to output load side is set (1:1) in OTA₁ and (1:4) in OTA₂. The OTA₂ offers increased transconductance and GBW whereas self-cascode load increases the output impedance and overall gain of the FD-OTAs. Both the input core and common source self-cascode load operate in class AB mode so these FD-OTAs provide enhanced slew rates. These OTAs have been employed to implement Biquadratic low-frequency G_m-C filter suitable for bio-signal applications. The proposed OTA₂ has used dual supply voltage of ± 0.3 V and dissipates around 70 nW power and provides 62 dB FD-open loop gain with GBW of 7.73 kHz while driving the FD-load of 2 × 15 pF. The Cadence VIRTUOSO environment using UMC 0.18 µm CMOS process technology has been used to simulate the proposed circuit. The Simulation results verified fully differential total harmonic distortion of ? 72 dB, for 1.2 V_p–p signal at 200 Hz frequency in unity gain configuration with resistive degeneration of 1 MΩ for OTA₁.     

Weld bonding of stainless steel

This paper presents a theoretical and experimental investigation of the weld bonding of stainless steels with the purpose of setting up the major technological parameters that are needed for its industrial implementation. Several commercial adhesives, with varying working times under different surface conditions are investigated for assembling standard test specimens.The numerical simulation of the process based on the commercial finite element program SORPAS is successfully utilized to help establish the most favourable welding parameters that allow spot-welding through the adhesives.The relative performance and quality of the resulting weld bonded joints is evaluated against alternative solutions based on adhesives or conventional spot-welding by means of macroetching observations, tension-shear tests and peel tests.     

2-D and 3-D shape optimization using mesh velocities to integrate analytical sensitivities with associative CAD

The design sensitivities generated with the mesh velocity method, used by the authors, are compared with those obtained by the boundary layer and boundary displacement methods. The effect of adaptive mesh refinement and error control on the quality of the velocity fields is discussed, as well as their ability to yield accurate first-order predictions of constraint values. Two numerical shape optimization examples of a 2D and a 3D component are presented. These examples are used to illustrate the benefits of integrating analytical methods of design sensitivity analysis with parametric capabilities supported by state-of-the-art CAD systems.     

Antireflection structures with use of multilevel subwavelength zero-order gratings

It is known that the zero-order two-phase-level gratings with a period much smaller and a thickness much larger than the wavelength may have antireflection properties the same as appropriate dielectric layers under normal incidence. On the basis of the rigorous coupled-wave analysis method formulation, it is shown that multilevel unidimensional phase gratings, for both TE and TM polarization, are functionally equivalent to antireflection structures of multilevel dielectric layers, even if the period is close to the wavelength.     

A real-time attack defense framework for 5G network slicing

Network Slicing (NS) is a key enabler to support 5G network services on-demand. However, since NS is a result of the recent advancement in Software-Defined Networking and Network Function Virtualization, it introduces new security issues which include attacks against an NS instance within an operator network and interslice security threats. In this scenario, identifying and mitigating attacks in real-time is of paramount importance to improve security aspects. However, it is far from being straightforward. Therefore, this work proposes the FrameRTP4, a P4-based framework that aims to deliver real-time attack detection and mitigation mechanisms in 5G NS scenarios. For this, it provides a P4-based switch that implements an Service Function Chaining protocol layer, an efficient and scalable Access Control List for the detection and mitigation of known attacks, and a monitoring system aiming to reduce the overhead induced on the control channel. Furthermore, it delivers an orchestrator that aims to control all switches in order to enable lifecycle management of NS instances and P4 table rules. Besides, it also performs some autonomous tasks such as the wildcard rules generation and the detection of new threats by using machine learning algorithms. Preliminary results point to the potential benefits of FrameRTP4 to be part of a 5G NS infrastructure.     

带间级联激光器性能对结构变化的耐受性研究

通过对两种结构参数与设计偏差较大的带间级联激光器(ICL)的研究,探讨了器件性能在结构变化下的耐受性。在300 K时,即使和4.6μm的设计波长相比蓝移700μm以上,激光器仍然性能良好,其阈值电流密度低至320 A/cm^2。此研究为带间级联激光器在结构变化方面的耐受性提供了坚实的实验依据。