Computation of thermal properties of CMSP shell and tube heat exchanger using different types of helical baffles

This paper investigates the flow and thermal properties of a combined multiple shell pass (CMSP)-shell and tube heat exchanger (STHE) with the provision of unilateral ladder-type helical baffle (ULHB) and continuous helical baffle (HB) in the outer shell pass of the heat exchanger. Two CMSP-STHEs with ULHB and HB, respectively, are compared with the traditional STHE having segmental baffles (SG-STHE) using the computational fluid dynamics method. The computational outcomes are validated with the empirical correlations of the Kern and Esso method. The Reynolds-averaged Navier–Stokes-based standard k–ω turbulence model accurately predicts the heat transfer (HT) rate and pressure drop. The computed results of HT rate, pressure drop, and logarithmic mean temperature difference corresponding to various mass flow rates (m) for three STHEs are presented. The results show that the overall HT rate of CMSP (ULHB)-STHE and the CMSP (HB)-STHE at the same mass flow rate are nearly 28.3% and 14.8% larger than that of traditional SG-STHE, respectively. Furthermore, the overall area-weighted average pressure drop (ΔP) of CMSP (HB)-STHE is smaller than that of SG-STHE by 26.5% at the same mass flow rate (m) and for CMSP (ULHB)-STHE it is larger by 2% than that of traditional STHE. Based on the above results, it is concluded that the CMSP (ULHB)-STHE is a suitable replacement for the conventional SG-STHEs.     

A novel Block Bi-diagonalization based pre-coding scheme for bit error reduction in mutiple input multiple output-orthogonal frequency division multiplexing

The MIMO-OFDM increases spectral efficiency without the use of channel state information (CSI). However, the bit error rate (BER) in the MIMO-OFDM model increases dramatically due to the increase in nonlinear distortion in the power amplifier (PA). In this research, a novel pre-coder integrated MIMO-OFDM technology is designed for effective BER reduction, and its performance is analyzed. The discrete wavelet-based OFDM system is one of the key ideas to present good orthogonal by emphasizing orthogonal wavelets. It helps to mitigate inter-symbol interference (ISI) and noise within the channel by extending the bandwidth (BW) compared to conventional OFDM systems. But, DWT-OFDM highly suffered due to downsampling, which degrades system efficiency. To overcome this, a redundant discrete wavelet transform (RDWT) is proposed in this article to enhance spectral efficiency. For modulation, 16-bit quadrature amplitude modulation (QAM) is introduced in this work. In addition to this, a block bi-diagonalization (BBD) pre-coder technique is proposed to mitigate unwanted noise and interference in the MIMO-OFDM system. The performance measures such as ergodic sum capacity, BER, throughput, average jitter noise power, mean square error (MSE), and power consumption are analyzed using the MATLAB platform. The proposed method obtains the ergodic sum capacity of 6.25 bps/Hz, a BER of 0.021, a throughput of 95.2%, MSE of −0.47, and a power consumption of 1.15 μW. The simulative results prove the efficacy of the proposed method.     

Annealing-Mediated Microduplex Structure and Texture Evolution in Severely Cold-Rolled Nanolamellar Pearlite: A Perspective on the Effect of Starting Inter-lamellar Spacing

Metallurgical and Materials Transactions A - The effect of inter-lamellar (IL) spacing on the microstructure and texture of severely cold-rolled and annealed pearlite was studied. For this purpose,...     

Kiln-fired clay bricks synergizing nickel–chromium plating sludge and fly ash: mechanical characteristics and cradle-to-gate life cycle assessment

Clean Technologies and Environmental Policy - Life cycle assessment (LCA) of novel fired clay bricks with synergistic co-valorization of nickel-chrome plating sludge (NCPS) and fly ash (FA) is...     

Cross-modal face recognition with illumination-invariant local discrete cosine transform binary pattern (LDCTBP)

Pattern Analysis and Applications - With the ever-increasing security threats in recent years, biometric authentication has become omnipresent. Among all biometric characteristics, face recognition...     

Parachute shape ultra-wideband wearable antenna for remote health care monitoring

Wireless body area networks (WBAN) is used to measure patients' health conditions continuously. Different kinds of sensors are required to measure health conditions. When such types of antennas are used on the human body, they are flexible with the movements. The usage of wearable devices is currently increasing in the biomedical field. The presented wearable antenna is suitable for biomedical applications. The presented ultra-wideband (UWB) flexible parachute shape wearable antenna is fabricated on a jeans textile substrate. The prototype antenna has a −10 dB measured impedance bandwidth of 5800 MHz (7 to 12.8 GHz) with average radiation efficiency of 75.28%. The prototype antenna's size is 40 × 40 mm² (1.32 × 1.32 ${\lambda }_0^2$ at centre frequency 9.9 GHz) and a peak gain of 4.5 dB at 12.33 GHz. The fabricated antenna is suitable for biomedical applications in X-band frequencies and can be implemented with a low-cost manufacturing process. The radiating element is made by conductive copper tape. Muscle-equivalent phantoms are used to analyze the body effect on antenna performance. The radiation effect emitted by the presented antenna on the human body is calculated by the specific absorption rate (SAR) value. The maximum SAR value of the proposed antenna is 1.84 W/kg at 12.33 GHz. This leads to promising results for wearable applications related to remote health care monitoring, such as biotelemetry and mobile health with a sensor-driven approach.     

Emergence of a Non-Van der Waals Magnetic Phase in a Van der Waals Ferromagnet

Manipulation of long-range order in 2D van der Waals (vdW) magnetic materials (e.g., CrI₃, CrSiTe₃ ,etc.), exfoliated in few-atomic layer, can be achieved via application of electric field, mechanical-constraint, interface engineering, or even by chemical substitution/doping. Usually, active surface oxidation due to the exposure in the ambient condition and hydrolysis in the presence of water/moisture causes degradation in magnetic nanosheets that, in turn, affects the nanoelectronic /spintronic device performance. Counterintuitively, the current study reveals that exposure to the air at ambient atmosphere results in advent of a stable nonlayered secondary ferromagnetic phase in the form of Cr₂Te₃ (T_C2 ≈160 K) in the parent vdW magnetic semiconductor Cr₂Ge₂Te₆ (T_C1 ≈69 K). The coexistence of the two ferromagnetic phases in the time elapsed bulk crystal is confirmed through systematic investigation of crystal structure along with detailed dc/ac magnetic susceptibility, specific heat, and magneto-transport measurement. To capture the concurrence of the two ferromagnetic phases in a single material, Ginzburg-Landau theory with two independent order parameters (as magnetization) with a coupling term can be introduced. In contrast to the rather common poor environmental stability of the vdW magnets, the results open possibilities of finding air-stable novel materials having multiple magnetic phases.     

Plastic Deformation in a Molecular Crystal Enables a Piezoresistive Response

Organic materials are promising candidates for the development of efficient sensors for many medicinal and materials science applications. Single crystals of a small molecule, 4-trifluoromethyl phenyl isothiocyanate (4CFNCS), exhibit plastic deformation when bent, twisted, or coiled. Synchrotron micro-focus X-ray diffraction mapping of the bent region of the crystal confirms the mechanism of deformation. The crystals are incorporated into a flexible piezoresistive sensor using a composite constituting PEDOT: PSS/4CFNCS, which shows an impressive performance at high-pressure ranges (sensitivity 0.08 kPa⁻¹ above 44 kPa).