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Single imidazolate framework-67 (ZIF-67) is commonly used as a template to prepare layered double hydroxides (LDHs) with specific morphology to improve the performance of materials. Herein, the Co2+ ion in ZIF-67 is partially substituted by Ni2+ to obtain the dodecahedron bimetallic imidazolate framework (CoNi-ZIF). Subsequently, using bimetallic CoNi-ZIF as the sacrificial template, CoNi-LDH hierarchical hollow cage structures with wrinkled nanosheet arrays are synthesized at room temperature and in aqueous solution by an inexpensive and environment friendly surfactant-free approach. The optimized etched CoNi-LDH4 has a maximum specific capacitance of 1877 F g−1 at a current density of 1 A g−1, and cycling stability of 99.89% after 5000 cycles, which is significantly better than that of ZIF-67 derived CoNi-LDH67 (1357 F g−1 at 1 A g−1, cycling stability of 73.35%). The asymmetric supercapacitor with CoNi-LDH4 as a cathode and activated carbon (AC) as anode has an energy density of 49.3 Wh kg−1 at 750 W kg−1 power output and stable cycling performance (capacity retention of 92.13% after 5000 cycles). This study shows the prospect of bimetallic CoNi-ZIF derived LDHs nanostructures prepared at room temperature and in aqueous solution to improve the performance and stability of supercapacitors.

Some drawbacks of the hydraulic fracturing technology included the water pollution and reservoir destruction, hindered its development and application in shale reservoirs. CO2 fracturing fluid is c...

With increasing interest in renewable and sustainable forms of energy, the energy production from solar is growing rapidly. Pakistan is one of the nations in the world which has enormous energy resources available in all areas. Pakistan is very rich in coal resources in all provinces and has combined sources of coal reserves near about 183000 million tons. As we know that when coal is burnt in coal-fired units, it leads to the production of Greenhouse Gas (GHG) emissions. It is a matter of serious concern leading to global warming. If the quantity of feed up coal as a fuel is controlled, then by using efficient energy conservation techniques emissions of Greenhouse Gas could be controlled effectively. In this research work, integration of solar with feed water pump as a renewable energy resource in Sahiwal coal-fired power plant is proposed and maximum utilization of exhaust flue gas as an energy source in HRSG is being evaluated. With the addition and integration of solar in the feed water pump of coal fired plants, the consumption of coal is reduced which leads to a reduction in the production of greenhouse gases.

Millimeter-wave (mm-wave) spectrum unravels the humongous and accelerating demand for wireless data rates and, therefore, it will be a fundamental ingredient of the fifthgeneration (5G) wireless technology. In case of mm-wave access links, humans are the most noticeable blockers of electromagnetic waves from access points to mobile stations and hence cause temporal variation in the radio channel. This paper presents human blockage measurements in the anechoic chamber at 15, 28 and 60GHz frequencies employing 15 human subjects of different sizes and weights. An effective three-dimensional human blockage model as a double-truncated and absorbing multiple knife-edge (DTMKE) scheme is also proposed. By calculating diffraction from the DTMKE, the frequency, body orientation and antenna height dependency of the blockage are most accurately reproduced compared to the existing models, such as absorbing double knife-edge model and third generation partnership project (3GPP) human blockage model. The results demonstrate that the losses are proportional to the cross-section of the human body with respect to the radio link. Furthermore, the blockage loss decreases as the height of the transmitting antenna increases.

In the petroleum industry, the researchers have developed a new technique called enhanced oil recovery to recover the remaining oil in reservoirs. Some reservoirs are very complex and require advanced enhanced oil recovery (EOR) techniques containing new materials and additives in order to produce maximum oil in economic and environmental friendly manners. In this work, the effects of nanosuspensions (KY-200) and polymer gel HPAM (854) on oil recovery and water cut were studied in the view of EOR techniques and their results were compared. The mechanism of nanosuspensions transportation through the sand pack was also discussed. The adopted methodology involved the preparation of gel, viscosity test, and core flooding experiments. The optimum concentration of nanosuspensions after viscosity tests was used for displacement experiments and 3 wt % concentration of nanosuspensions amplified the oil recovery. In addition, high concentration leads to more agglomeration; thus, high core plugging takes place and diverts the fluid flow towards unswept zones to push more oil to produce and decrease the water cut. Experimental results indicate that nanosuspensions have the ability to plug the thief zones of water channeling and can divert the fluid flow towards unswept zones to recover the remaining oil from the reservoir excessively rather than the normal polymer gel flooding. The injection pressure was observed higher during nanosuspension injection than polymer gel injection. The oil recovery was achieved by about 41.04% from nanosuspensions, that is, 14.09% higher than polymer gel. Further investigations are required in the field of nanoparticles applications in enhanced oil recovery to meet the world's energy demands.

Line-of-sight (LOS) probability is an integral part of radio channel models for cellular network design and evaluation. The probability along with the pathloss models in LOS and non-LOS scenarios gives us an estimate of the cellular coverage. In this letter, we present a novel method to evaluate the LOS probability by using point cloud data obtained with laser scanning. The LOS probability is derived for two new scenarios, an urban open square and a shopping mall, along with an office environment, and a generic exponential LOS probability model, which shows excellent performance in the tested environments is proposed. Also the frequency dependency of LOS probability is investigated.

The recovery of heavy metals from electroplating sludge is an important technology, which can not only reduce environmental pollution, but also serve as a secondary source of metals. However, the current techniques are either non-selective or difficult to operate, which limits its applications in recovery technologies. Herein, based on the existence of multiple metal ions in electroplating sludge, Fe and Al co-doped ultrathin α-Ni(OH)2 nanosheets embedded in Ni(HCO3)2 nanowire assembly spheres were prepared by adjusting the ratio of urea under hydrothermal condition. Under the optimum conditions, the recovery of Ni, Fe, and Al are 92.58%, 81.52%, and 61.19% respectively. In addition, at the current density of 1 A g−1, the specific capacitance of the spherical composite electrode is as high as 495.6 C g−1, and the retention rate of the initial capacity is 55.58% after 3500 cycles in 6 M KOH electrolyte, showing good cycling stability. Furthermore, the ASC device (NN-4//AC) achieved a high energy density of 30.27 Wh kg−1 at a power density of 0.37 kW kg−1. A new method for converting electroplating sludge into nickel-based energy storage materials was developed, which provided a new strategy and idea for the harmless and resourceful treatment of electroplating sludge.

Accurate site-specific radio propagation simulations provide an important basis for cellular coverage analysis. The quality of these simulations relies on the accuracy of environmental description and electrical properties of constituent materials. This paper presents a novel method of on-site permittivity estimation. The method utilizes an accurate geometrical database of the environment for identifying flat and smooth surfaces producing reflections. The method exploits a limited number of on-site channel sounding to extract reflected multipaths and compare them with ray tracing based on the environmental database. The permittivity of the identified reflecting surfaces is estimated by solving an inverse reflection problem. The method was experimentally tested with limited radio channel measurements at 60 GHz in a large empty office room. The identified reflecting surfaces are classified according to their mean permittivity estimates, showing their consistency with physical material evidence and the permittivity database in the International Telecommunication Union Radiocommunication Recommendation (ITU-R P.2040-1). The estimated permittivity values are visualized as a 3-D map, giving an intuitive understanding of materials constituting the environment. This paper demonstrates on-site permittivity estimation and material classification without the need for isolated measurements of composite materials in an anechoic chamber or in situ measurements of built environments.

This paper presents the comparison of power angular spectra at frequencies below and above 6 GHz, i.e., 2, 15, 28, 60 GHz. With the increased focus on millimeter wave frequencies for ultra-high data rates, a detailed understanding of channel frequency dependence has become crucial. The analysis in this paper is based on multi-frequency radio channel measurements in an indoor coffee room environment for both line-of-sight (LOS) and non-LOS (NLOS) scenarios. For multipath extraction, two different methodologies are used at below and above 6 GHz frequency bands, respectively. The results indicate that LOS channels demonstrate a similar spatial spread at all the frequencies considered, and hence can be spatially modeled in a similar fashion. The NLOS channels exhibit larger spatial spread overall. The paths at above 6 GHz channels appear to be spatially more consistent compared to those that are below 6 GHz, where penetrated and diffracted paths also exist.

Four quaternary quinolinium inhibitors were synthesized and characterized to investigate the synergistic effect of bromide or chloride anion for protecting the steel in acid corrosive medium. The inhibition was studied through gravimetric method in 4.410 M HCl and 4.410 M HBr and the results were confirmed by molecular dynamics stimulation. It is confirmed that Br− exhibits a better synergistic effect than Cl− and therefore the cationic inhibitor is much easier to get saturate adsorbed to show a better inhibition in HBr. Inhibitors with the same cation moiety can be fastened tightly and thus be able to experience chemisorption in HBr, while physisorption is the dominating mechanism in HCl.

This paper introduces a real-time multiple input and multiple output (MIMO) channel sounder to measure the vehicle-to-vehicle (V2V) propagation channel at 5.9 GHz. Compared to the existing V2V channel sounders, our design emphasizes on improving the stability of the setup and increasing the MIMO snapshot rate. The system stability allows us to develop a high resolution parameter extraction algorithm for the data analysis, which jointly estimates parameters of multipath components such as time-of-arrival, direction of departure, direction of arrival and Doppler shift. The second emphasis increases the maximal absolute Doppler shift to 806 Hz, which the system can estimate without ambiguity. The increased snapshot rate also provides a more fluent representation of the channel dynamics. We verify the design of the channel sounder with actual V2V channel measurements. Results suggest that 80 percent of the sample snapshots have a diffuse power ratio less than 20 percent and the extracted dominant specular paths match well with the environment and dynamics of the measurement.

Describing the environment using a point cloud is a promising method for both propagation predictions and channel simulations. Recently, a specular reflection model has been proposed and verified through measurements to account for reflections from large reflecting surfaces. Here, the formulation for the specular reflections for point cloud (SRPC) is improved based on a few canonical measurements in an anechoic chamber. The specular reflection image theory for large surfaces, the Radar Cross Section equation for small surfaces, the Fresnel-Kirchhoff integral formula, and measurements are investigated. Unexpectedly to the authors, the results show that, when neglecting the diffraction effects, the contributions to the specular reflected field occur mainly from the illumination of about a third of the first Fresnel zone. A prediction of the SRPC formula is the appearance of “radio flares” due to electrically small reflecting surfaces.