Dislocation network in additive manufactured steel breaks strength–ductility trade-off

Most mechanisms used for strengthening crystalline materials, e.g. introducing crystalline interfaces, lead to the reduction of ductility. An additive manufacturing process – selective laser melting breaks this trade-off by introducing dislocation network, which produces a stainless steel with both significantly enhanced strength and ductility. Systematic electron microscopy characterization reveals that the pre-existing dislocation network, which maintains its configuration during the entire plastic deformation, is an ideal “modulator” that is able to slow down but not entirely block the dislocation motion. It also promotes the formation of a high density of nano-twins during plastic deformation. This finding paves the way for developing high performance metals by tailoring the microstructure through additive manufacturing processes.     

A fast-lock and low-power DLL-based clock generator applied for DDR4

Microsystem Technologies - This paper presents a fast-lock and low-power delay-locked loop (DLL) circuit applied for DDR4. The proposed modified phase detector and modified charge pump can reduce...     

Simultaneous absolute measurements of principal angle and phase retardation with a new common-path heterodyne interferometer

This study demonstrates a new method for simultaneously measuring both the angle of the principal axis and the phase retardation of the linear birefringence in optical materials. We used a circular common-path interferometer (polariscope) as the basic structure modulated by an electro-optic (EO) modulator. An algorithm was developed to simultaneously measure the principal axis and the phase retardation of a lambda/4 or lambda/8 plate as a sample. In the case of a lambda/4 plate, the average absolute error of the principal axis is approximately 3.77 degrees, and that of the phase retardation is approximately 1.03 degrees (1.09%). The retardation error is within the 5% uncertainty range of a commercial wave plate. Fortunately, the nonlinear error caused by the reflection phase retardation of the beam splitter dose not appear in the new system. Therefore the error could be attributed to misalignment and defects in the EO modulator or the other optical components. As for the repeatability of this new common-path heterodyne interferometer, the average deviation for the principal axis is 0.186 degrees and the phase retardation is 0.356 degrees. For the stability, the average deviation for the principal axis is 0.405 degrees and the phase retardation is 0.635 degrees. The resolution of this new system is estimated to be approximately 0.5 degrees, and the principal axis and phase retardation could be measured up to pi and 2pi, respectively, without ambiguity.     

Topology and shape optimizations of substrates for chirp fiber Bragg grating spectrum tuning

A systematic method based on topology and shape optimization techniques has been developed to determine the geometry of a substrate for chirp fiber Bragg grating (FBG) spectrum tuning. The strain distribution on the FBG associated with a given wavelength spectrum is synthesized first by the application of a genetic algorithm. Then the substrate profiles determined either from topology or shape optimizations can generate the required strain distribution on FBG that responds to the required wavelength spectrum of a chirp FBG. The profile obtained from shape optimization, compared with that from topology optimization, has clear advantages in easier manufacturing and better liability. Although the strain distribution of a chirp FBG demonstrated here is simple in this study, it should be emphasized that this methodology also can be easily applied to determine other substrate profile whose strain distribution is regarding to a more complex wavelength spectrum of an FBG.     

The coating of TiC layer on the surface of nickel by electric discharge coating (EDC) with a multi-layer electrode

Multi-layer electrodes (MLEs) are proposed in this study to coat a titanium carbide (TiC) layer on the surface of a nickel workpiece by electric discharge coating (EDC). The MLE is composed of titanium (Ti) and graphite (Gr) layers with the same dimensions stacking alternately. Both of this new type of electrode and the conventional electrode, the bulk type, are compared in this study. The experimental results indicate that the Gr layer of the MLE may enhance the concentration of carbon element locally. Also, carbon element with high concentration could increase the combination of Ti and carbon (C) to become TiC, enhance surface hardness of the coated layer, decrease surface roughness of the coated layer, reduce formation of microcracks, and enhance the stability of electric discharge and coating speed.     

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

Conductive and porous nitrogen-rich materials have great potential as supercapacitor electrode materials. The exceptional efficiency of such compounds, however, is dependent on their larger surface area and the level of nitrogen doping. To address these issues, we synthesized a porous covalent triazine framework (An-CTFs) based on 9,10-dicyanoanthracene (An-CN) units through an ionothermal reaction in the presence of different molar ratios of molten zinc chloride (ZnCl₂) at 400 and 500 °C, yielding An-CTF-10-400, An-CTF-20-400, An-CTF-10-500, and An-CTF-20-500 microporous materials. According to N₂ adsorption–desorption analyses (BET), these An-CTFs produced exceptionally high specific surface areas ranging from 406–751 m²·g⁻¹. Furthermore, An-CTF-10-500 had a capacitance of 589 F·g⁻¹, remarkable cycle stability up to 5000 cycles, up to 95% capacity retention, and strong CO₂ adsorption capacity up to 5.65 mmol·g⁻¹ at 273 K. As a result, our An-CTFs are a good alternative for both electrochemical energy storage and CO₂ uptake.     

Triple-push oscillator approach: theory and experiments

This paper presents the theory and experiments of the triple-push oscillator approach. This oscillator architecture is combined with three identical oscillator subcircuits. An analytical mode analysis is used to describe the behavior of all modes. As will be shown, odd-mode currents in each oscillator subcircuit have a 120° phase shift to one another and thus produce in-phase combining for the third harmonic. The time domain analysis was performed to simulate a triple-push oscillator, showing that the phenomenon of 120° phase shift exists among each oscillator subcircuit. To prove this concept, a 4.9-GHz hybrid bipolar junction transistor (BJT) circuit and a 28.4-GHz heterojunction bipolar transistor (BJT) MMIC chip were demonstrated. The measured results showed that the 4.9-GHz BJT triple-push oscillator delivered an output power of 1.0 dBm at 4.9 GHz with 12.0-dB fundamental rejection, and the 28.4-GHz HBT MMIC chip exhibited a measured center frequency at 28.4 GHz with an output power of -15.4 dBm, while the output powers of the fundamental and the second harmonic signals were suppressed to -21 and -34 dBm     

Effects of learning support in simulation-based physics learning

This paper describes the effects of learning support on simulation-based learning in three learning models: experiment prompting, a hypothesis menu, and step guidance. A simulation learning system was implemented based on these three models, and the differences between simulation-based learning and traditional laboratory learning were explored in the context of physics studies. The effects of the support type on learning performance were also quantified. In second-year junior high school students it was found that the outcome for learning about the basic characteristics of an optical lens was significantly better for simulation-based learning than for laboratory learning. We also investigated the influences of different learning models on the students’ abstract reasoning abilities, which showed that the different learning models do not have different effects on individuals with different abstract reasoning abilities. However, we found that students who are better at higher abstract reasoning benefit more from simulation-based learning, and also that the learning results are better for experiment prompting and a hypothesis menu than for step guidance.     

A low-jitter all-digital PLL with high-linearity DCO

Microsystem Technologies - This paper describes a low-jitter all-digital phase-locked loop (ADPLL) with a high-linearity digitally controlled oscillator (DCO). The proposed DCO consists of a...     

The synthesis of multiple parameters of arbitrary FBGs via a genetic algorithm and two thermally modulated intensity spectra

This paper describes the use of a genetic algorithm and two thermally modulated fiber Bragg grating (FBG) reflection intensity spectra to perform the inverse extraction of multiple physical parameters of arbitrary FBGs, including the grating period, grating position, grating length, chirped direction, and refractive-index modulation. The developed numerical approach is applied to synthesize the parameters of uniform and chirped FBGs. The experimental results confirm the ability of the proposed method to recover the grating period, grating length, grating position, refractive-index modulation depth, and apodize factor of a 10-mm-length uniform FBG. The proposed method is suitable for fiber communication applications and smart structure-monitoring systems.