Multiple Magnetic Phases in Van Der Waals Mn-Doped SnS2 Semiconductor

2D van der Waals magnetic semiconductors have emerged along with the possibilities of achieving an efficient gate tunability and a proximity effect with a high magnetic anisotropy compared with 3D counterparts. Little explored are multiple magnetic phases with a single crystallographic phase. Herein, the multiple magnetic phases in a Mn-doped SnS₂ single crystal with different doping concentrations using a one-step self-flux method are reported. Two ferromagnetic phases with a canted spin direction exist regardless of the Mn-doping concentration at up to 5 at%. Antiferromagnetism coexists with the ferromagnetic order and strengthens at high Mn-doping concentrations. A magnetoresistance measurement conducted on a 2 at% Mn-SnS₂ flake exhibits a positive-to-negative crossover with a value of as high as 50% and clear anisotropy, confirming the presence of ferromagnetic order in the material. By revealing multiple magnetic phases in Mn-doped SnS₂, the study broadens the scope of state-of-the-art research on layered magnetic semiconductors.     

Forensic Investigation of Ultrathin Whitetopping Pavements in Florida

Developed in the early 1990s, ultrathin whitetopping (UTW) is a relatively new technique for asphalt pavement rehabilitation. To evaluate the applicability of UTW pavement in Florida, in 1997, the Florida Department of Transportation (FDOT) constructed an experimental UTW pavement in a weigh station along I-10, located in north Florida. The performance of these test sections, however, was less than ideal, with the observation of some early cracking on the concrete surface, which developed into severe cracking with time. Therefore, a forensic investigation was conducted to determine the causes of the problems in these UTW sections, so that lessons could be learned from this experimental project, the use of UTW under Florida’s conditions could be adequately assessed, and UTW technology could be properly applied in the future. The scope of work consisted of field evaluation, laboratory testing, and pavement design evaluation. Field evaluation included a pavement condition survey, pavement temperature measurement, nondestructive load testing using a falling weight deflectometer, and slab thickness determination. Laboratory tests were performed to determine concrete and asphalt material properties. Other design and traffic data were also acquired from FDOT. Data collected from the field evaluation and laboratory testing were used in conjunction with a mechanistic UTW pavement design/evaluation procedure to determine the possible causes for premature failure. From this comprehensive evaluation, the primary cause for the failure was found to be inadequate UTW pavement design. The inadequacy of the combination of thickness and slab dimensions contributed to the early cracking of the UTW pavement.     

An 863-870 MHz spread-spectrum FSK transceiver design for wireless sensor

Simulation results of a 863-870 MHz frequency-hopped spread-spectrum (FHSS) transceiver with binary frequency shift keying (BFSK) modulation at 20 kb/s for wireless sensor applications is presented.The transmit/receive RF front end contains a BFSK modulator, an upconversion mixer, a power amplifier (PA), and an 863-870 MHz band pass filter (BPF) at the transmitter side and a low-noise amplifier with down conversion mixer to zero-IF, a low-pass channel-select filter, a limiter and a BFSK demodulator at the receiver side. The various block parameters of the transmit/receive RF front end like noise figure (NF), gain, 1 dB compression point (P-1 dB), and IIP3 are simulated and optimized to meet low power and low cost transceiver specifications.The transmitter simulations show an output ACPR (adjacent channel power ratio) of −22 dBc, 3.3 dBm P-1 dB of PA, and transmitted power of 0 dBm. The receiver simulations show 51.1 dB conversion gain, −7 dBm IIP3, −15 dB return loss (S11), and 10 dB NF. Low power arctangent-differentiated BFSK demodulator has been chosen and the BER performance has been co simulated with the analog receiver. The complete receiver achieves a BER of 10⁻³ at 10.5 dB of EbtoNo. The transceiver simulations show an RMS frequency error of 1.45 kHz.     

Effect of thermal ratcheting on the mechanical properties of Teflon and fiber based gasket materials

This paper discusses the effect of thermal ratcheting on the material properties of expand polytetrafluoroethylene (ePTFE), virgin polytetrafluoroethylene (vPTFE), and compressed nonasbestos fiber (CNA) gasket materials. Comparison between the creep strain at constant temperature and when subjected to thermal ratcheting show a 7.7 and 28% increase in the creep strain of ePTFE and vPTFE, respectively. In addition, thermal ratcheting produces a substantial reduction of creep modulus of these materials. The CNA material does not exhibit significant change in creep strain or in creep modulus with thermal ratcheting. However, all three gasket materials show a momentous raise in the creep strain when the material temperature is reduced. On declining the gasket temperature from 212 to 100 °F at the end of 20th thermal cycle, the materials—ePTFE, vPTFE, and CNA exhibit 27, 48, and 15% increase in creep strain value, respectively. The percentage of thickness reduction raises with the increase of cyclic temperature and with increase of creep pre-exposure time, except for CNA where only a small variation is observed. The coefficient of thermal expansion of both PTFE materials shows a significant change due to cyclic temperature and initial creep exposure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47265.     

Cost and time calculation in rough NC turning

The aim of this work is to present the calculation procedure for the optimum cutting conditions (cutting speed and used feed) in high speed turning through an NC rough turning cycle with complex profile. The considered optimization criteria are minimum production time and cost. A simple method for determining the variable machined length, the average workpiece diameter and the optimum number of passes is mentioned. Developed models of cutting time and cost were validated based on experimetal tests. Different models have been programmed in a Visual–Basic interface, allowing the operator to find rapidly optimum values of cutting parameters and an estimation of cutting operation cost.     

Highly selective colorimetric detection and preconcentration of Bi(III) ions by dithizone complexes anchored onto mesoporous TiO2

We successfully developed a single-step detection and removal unit for Bi(III) ions based on dithizone (DZ) anchored on mesoporous TiO₂ with rapid colorometric response and high selectivity for the first time. [(DZ)₃-Bi] complex is easily separated and collected by mesoporous TiO₂ as adsorbent and preconcentrator without any color change of the produced complex onto the surface of mesoporous TiO₂ (TiO₂-[(DZ)₃-Bi]) at different Bi(III) concentrations. This is because highly potent mesoporous TiO₂ architecture provides proficient channeling or movement of Bi(III) ions for efficient binding of metal ion, and the simultaneous excellent adsorbing nature of mesoporous TiO₂ provides an extra plane for the removal of metal ions.     

Simulation analysis of a high efficiency GaInP/Si multijunction solar cell

The solar power conversion efficiency of a gallium indium phosphide(GaInP)/silicon(Si)tandem solar cell has been investigated by means of a physical device simulator considering both mechanically stacked and monolithic structures.In particular,to interconnect the bottom and top sub-cells of the monolithic tandem,a gallium arsenide(GaAs)-based tunnel-junction,i.e.GaAs(n+)/GaAs(p+),which assures a low electrical resistance and an optically low-loss connection,has been considered.The J–V characteristics of the single junction cells,monolithic tandem,and mechanically stacked structure have been calculated extracting the main photovoltaic parameters.An analysis of the tunnel-junction behaviour has been also developed.The mechanically stacked cell achieves an efficiency of 24.27%whereas the monolithic tandem reaches an efficiency of 31.11%under AM1.5 spectral conditions.External quantum efficiency simulations have evaluated the useful wavelength range.The results and discussion could be helpful in designing high efficiency monolithic multijunction GaInP/Si solar cells involving a thin GaAs(n+)/GaAs(p+)tunnel junction.     

An investigation of surface roughness of burnished AISI 1042 steel

The aim of this study is to analyse the evolution of surface roughness finished by burnishing. Burnishing is done on a surface that was initially turned or turned and then ground.It has been noted that burnishing an AISI 1042 steel offers the best surface quality when using a small feed value. This finishing process improves roughness and introduces compressive residual stresses in the machined surface. So, it can replace grinding in the machining range of the piece.Also, an analytical model has been defined to determine the R_t factor in relation to the feed. Good correlations have been found between the experimental and analytical results.     

Roughness modeling in up-face milling

In this study, we aimed to optimize cutting parameters to minimize surface roughness in up-face milling. An experimental system method has been used to analyze the evolution of surface roughness in connection with cutting parameters, and to develop mathematical models for roughness and optimal cutting parameter calculation. Roughness results show that lower cutting speeds give poor surface quality. This is due to the formation of a built-up edge. On the other hand, higher cutting speeds result in more roughness due to vibrations. So, an optimal value of cutting speed must be used to minimize roughness. We found good correlation in experimental values of roughness .