Design and evaluation of a high− fidelity virtual reality manufacturing planning system

Virtual Reality - Manufacturing applications of virtual reality (VR) technology are growing. The challenge is to design, integrate, and evaluate VR simulation for manufacturing Systems that...     

Applicability of flashing desalination technique for small scale needs using a novel integrated system coupled with nanofluid-based solar collector

The present study introduces an attempt for the application of flash desalination technique for small scale needs. An integrated system uses a flashing desalination technique coupled with nano-fluid-based solar collector as a heat source has been made to investigate both the effect of different operating modes and that of the variation of functioning parameters and weather conditions on the fresh water production. The flashing unit is performed by similar construction design technique of commercial multi-stage flashing (MSF) plant. The thermal properties of working fluid in the solar collector have been improved by using different concentrated nano-particles. Cu nano-particle is used in the modeling to determine the proper nano-fluid volume fraction that gives higher fresh water productivity. An economic analysis was conducted, since it affects the final cost of produced water, to determine the cost of fresh water production. Although a system may be technically very efficient, it may not be economical. The effect of different feed water and inlet cooling water temperatures on the system performance was studied. The mathematical model is developed to calculate the productivity of the system under different operating conditions. The proposed system gives a reasonable production of fresh water up to 7.7 l/m²/day under the operation conditions. Based on the cost of energy in Egypt, the estimated cost of the generated potable water was 11.68 US$/m³. The efficiency of the system is measured by the gained output ratio (GOR) with day time. The gained output ratio (GOR) of the system reaches 1.058. The current study showed that the solar water heater collecting area is considered a significant factor for reducing the water production cost. Also, the produced water costs decrease with increasing the collecting area of the solar water heater. The volume fractions of nano-particle in solar collector working fluid have a significant impact on increasing the fresh water production and decreasing cost.     

Effect of Hercynite Spinel on the Technological Properties of MCZ Products Used for Lining Cement Rotary Kilns

Refractories and Industrial Ceramics - Magnesia-calcium zirconate (MCZ) composite products have been tested in the transition zones of cement kilns. Such products are of interest because they are...     

Security enhancement for AES encrypted speech in communications

This paper introduces a secure speech communication approach, which is based on encryption and authentication. This system is based on Advanced Encryption Standard (AES) for encryption and private image database for enhancement of encryption and for authentication. The idea of this cryptosystem is based on XOR of one image from image database with the clear speech before encryption and embedding the index number of this image in the database as a least significant bit watermark into speech. A comparison study is held between the AES block cipher algorithm and the proposed algorithm. This proposed cryptosystem used to enhance the security of AES algorithm and increase its immunity to brute force attacks. It used also to provide authentication and enhance security by addition of extra key which don’t need to be exchanged between parts depending on the embedded image. The extra proposed step remove residual intelligibility from clear speech and fill the silent periods within speech conversation and help in destroy format and pitch information. Security analyses are presented for the proposed cryptosystem from a strict cryptographic viewpoint. Experimental results verify and prove that the proposed cryptosystem is highly secure from the cryptographic viewpoint.     

Trash into Treasure: δ‐FAPbI3 Polymorph Stabilized MAPbI3 Perovskite with Power Conversion Efficiency beyond 21%

Effective passivation and stabilization of both the inside and interface of a perovskite layer are crucial for perovskite solar cells (PSCs), in terms of efficiency, reproducibility, and stability. Here, the first formamidinium lead iodide (δ‐FAPbI₃) polymorph passivated and stabilized MAPbI₃ PSCs are reported. This novel MAPbI₃/δ‐FAPbI₃ structure is realized via treating a mixed organic cation MA _x FA_{1‐ x} PbI₃ perovskite film with methylamine (MA) gas. In addition to the morphology healing, MA gas can also induce the formation of δ‐FAPbI₃ phase within the perovskite film. The in situ formed 1D δ‐FAPbI₃ polymorph behaves like an organic scaffold that can passivate the trap state, tunnel contact, and restrict organic‐cation diffusion. As a result, the device efficiency is easily boosted to 21%. Furthermore, the stability of the MAPbI₃/δ‐FAPbI₃ film is also obviously improved. This δ‐FAPbI₃ phase passivation strategy opens up a new direction of perovskite structure modification for further improving stability without sacrificing efficiency.     

A Highly Efficient Algorithm for Phased-Array mmWave Massive MIMO Beamforming

With the rapid development of the mobile internet and the internet of things (IoT), the fifth generation (5G) mobile communication system is seeing explosive growth in data traffic. In addition, low-frequency spectrum resources are becoming increasingly scarce and there is now an urgent need to switch to higher frequency bands. Millimeter wave (mmWave) technology has several outstanding features—it is one of the most well-known 5G technologies and has the capacity to fulfil many of the requirements of future wireless networks. Importantly, it has an abundant resource spectrum, which can significantly increase the communication rate of a mobile communication system. As such, it is now considered a key technology for future mobile communications. MmWave communication technology also has a more open network architecture; it can deliver varied services and be applied in many scenarios. By contrast, traditional, all-digital precoding systems have the drawbacks of high computational complexity and higher power consumption. This paper examines the implementation of a new hybrid precoding system that significantly reduces both calculational complexity and energy consumption. The primary idea is to generate several sub-channels with equal gain by dividing the channel by the geometric mean decomposition (GMD). In this process, the objective function of the spectral efficiency is derived, then the basic tracking principle and least square (LS) techniques are deployed to design the proposed hybrid precoding. Simulation results show that the proposed algorithm significantly improves system performance and reduces computational complexity by more than 45% compared to traditional algorithms.     

Preparation,characterization, viscosity,and thermal conductivity of nitrogen-doped graphene aqueous nanofluids

Nanofluids perform a crucial role in the development of newer technologies ideal for industrial purposes. In this study, Nitrogen-doped graphene (NDG) nanofluids, with varying concentrations of nanoparticles (0.01, 0.02, 0.04, and 0.06 wt%) were prepared using the two-step method in a 0.025 wt% Triton X-100 (as a surfactant) aqueous solution as a base. Stability, zeta potential, thermal conductivity, viscosity, specific heat, and electrical conductivity of nanofluids containing NDG particles were studied. The stability of the nanofluids was investigated by UV–vis over a time span of 6 months and concentrations remain relatively constant while the maximum relative concentration reduction was 20 %. The thermal conductivity of nanofluids was increased with the particle concentration and temperature, while the maximum enhancement was about 36.78 % for a nanoparticle loading of 0.06 wt%. These experimental results compared with some theoretical models including Maxwell and Nan’s models and observed a good agreement between Nan’s model and the experimental results. Study of the rheological properties of NDG nanofluids reveals that it followed the Newtonian behaviors, where viscosity decreased linearly with the rise of temperature. It has been observed that the specific heat of NDG nanofluid reduced gradually with the increase of concentration of nanoparticles and temperature. The electrical conductivity of the NDG nanofluids enhanced significantly due to the dispersion of NDG in the base fluid. This novel type of fluids demonstrates an outstanding potential for use as innovative heat transfer fluids in medium-temperature systems such as solar collectors.     

A nonlinear filtered‐x prediction error method algorithm for digital predistortion in digital subscriber line systems

Digital predistortion of nonlinear systems is an important topic in many practical applications. This paper considers direct predistortion of a Volterra system by connecting in tandem an adaptive Volterra predistorter. The coefficients of the predistorter can be recursively estimated using the nonlinear filtered‐x least mean squares (NFxLMS) algorithm. In this paper, the prediction error method (PEM) is used to derive a novel nonlinear filtered‐x PEM (NFxPEM) algorithm. A simulation study on Volterra systems shows that the NFxPEM algorithm more significantly suppresses spectral regrowth and converges much faster than the NFxLMS algorithm. Also, the NFxPEM algorithm is used in this paper to design more efficient digital predistorter—as compared with the NFxLMS algorithm—for digital subscriber line systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Multiple access interference cancelation technique in optical CDMA systems

This paper presents a simple and efficient multiple access interference (MAI) cancelation technique in optical code division multiple access (OCDMA) system. The proposed technique is based on hybrid frequency shift keying (FSK) with an enhanced modified prime code as a signature sequence for coding techniques. Coherent FSK modulation along with incoherent demodulation using Arrayed-Waveguide Grating has been examined in the transceiver structure. In the proposed technique, a reference signal is constructed by using one of the addressed spreading sequences, and MAI cancelation is performed by subtracting the reference signal from the received signal of the desired user. The performance of the proposed FSK-OCDMA system is compared with the performance of the existing pulse position modulation (PPM)–OCDMA system. The simulation results reveal that the bit-error rate performance of the proposed technique is superior to the performance of the pulse position modulation (PPM) technique. Also, the results indicate that the proposed technique is very power efficient, and when the bit rate is constant, the network capacity can be expanded to accommodate a large number of simultaneous active users with low error rate. Moreover, the proposed technique simplifies the hardware of the receiver design.     

An investigation of speech enhancement using wavelet filtering method

This paper investigates the utilization of wavelet filters via multistage convolution by Reverse Biorthogonal Wavelets (RBW) in high and low pass band frequency parts of speech signal. Speech signal is decomposed into two pass bands of frequency; high and low, and then the noise is removed in each band individually in different stages via wavelet filters. This approach provides better outcomes because it does not cut the speech information, which occurs when utilizing conventional thresholding. We tested the proposed method via several noise probability distribution functions. Subjective evaluation is engaged in conjunction with objective evaluation to accomplish optimal investigation method. The method is simple but has surprise high quality results. The method shows superiority over Donoho and Johnstone thresholding method and Birge-Massart thresholding strategy method.