A new engineering medium, called nanofluid attracted a wide range of researches on many cooling processes in engineering applications, which are prepared by dispersing nanoparticles or nanotubes in a ...host fluid. In this paper, the stability of nanofluids is discussed as it has a major role in heat transfer enhancement for further possible applications. It also represents general stabilization methods as well as various types of instruments for stability inspection. Characterization, analytical models and measurement techniques of nanofluids after preparation by a single step or two-step method are studied.
Elastic strain engineering for ultralow mechanical dissipation Ghadimi, A H; Fedorov, S A; Engelsen, N J ...
Science (American Association for the Advancement of Science),
2018-May-18, 2018-05-18, 20180518, Letnik:
360, Številka:
6390
Journal Article
Recenzirano
Extreme stresses can be produced in nanoscale structures; this feature has been used to realize enhanced materials properties, such as the high mobility of silicon in modern transistors. We show how ...nanoscale stress can be used to realize exceptionally low mechanical dissipation when combined with "soft-clamping"-a form of phononic engineering. Specifically, using a nonuniform phononic crystal pattern, we colocalize the strain and flexural motion of a free-standing silicon nitride nanobeam. Ringdown measurements at room temperature reveal string-like vibrational modes with quality (
) factors as high as 800 million and
× frequency exceeding 10
hertz. These results illustrate a promising route for engineering ultracoherent nanomechanical devices.
In real-time quantum feedback protocols, the record of a continuous measurement is used to stabilize a desired quantum state. Recent years have seen successful applications of these protocols in a ...variety of well-isolated micro-systems, including microwave photons and superconducting qubits. However, stabilizing the quantum state of a tangibly massive object, such as a mechanical oscillator, remains very challenging: the main obstacle is environmental decoherence, which places stringent requirements on the timescale in which the state must be measured. Here we describe a position sensor that is capable of resolving the zero-point motion of a solid-state, 4.3-megahertz nanomechanical oscillator in the timescale of its thermal decoherence, a basic requirement for real-time (Markovian) quantum feedback control tasks, such as ground-state preparation. The sensor is based on evanescent optomechanical coupling to a high-Q microcavity, and achieves an imprecision four orders of magnitude below that at the standard quantum limit for a weak continuous position measurement--a 100-fold improvement over previous reports--while maintaining an imprecision-back-action product that is within a factor of five of the Heisenberg uncertainty limit. As a demonstration of its utility, we use the measurement as an error signal with which to feedback cool the oscillator. Using radiation pressure as an actuator, the oscillator is cold damped with high efficiency: from a cryogenic-bath temperature of 4.4 kelvin to an effective value of 1.1 ± 0.1 millikelvin, corresponding to a mean phonon number of 5.3 ± 0.6 (that is, a ground-state probability of 16 per cent). Our results set a new benchmark for the performance of a linear position sensor, and signal the emergence of mechanical oscillators as practical subjects for measurement-based quantum control.
Quantum correlations between imprecision and backaction are a hallmark of continuous linear measurements. Here, we study how measurement-based feedback can be used to improve the visibility of ...quantum correlations due to the interaction of a laser field with a nanomechanical oscillator. Backaction imparted by the meter laser, due to radiation-pressure quantum fluctuations, gives rise to correlations between its phase and amplitude quadratures. These quantum correlations are observed in the experiment both as squeezing of the meter field fluctuations below the vacuum level in a homodyne measurement and as sideband asymmetry in a heterodyne measurement, demonstrating the common origin of both phenomena. We show that quantum feedback, i.e., feedback that suppresses measurement backaction, can be used to increase the visibility of the sideband asymmetry ratio. In contrast, by operating the feedback loop in the regime of noise squashing, where the in-loop photocurrent variance is reduced below the vacuum level, the visibility of the sideband asymmetry is reduced. This is due to backaction arising from vacuum noise in the homodyne detector. These experiments demonstrate the possibility, as well as the fundamental limits, of measurement-based feedback as a tool to manipulate quantum correlations.
The superior features of Matrimid®5218 polymer and 1-ethyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (EmimTf2N) as an ionic liquid (IL) were combined to prepare efficient membranes for ...CO2/CH4 separation. The blended membranes, which were prepared with direct physical mixing of the polymer and the IL, were characterized by structural analyses such as SEM, DSC, FTIR-ATR, and tensile tests. During the membrane preparation procedure, heterogeneous structures with fixed and well-distributed IL ponds were created. Transport properties i.e. permeability, diffusivity, and solubility of the blended membranes with different IL contents (10, 20, 30, and 40 wt% based on the polymer weight) were evaluated at different operating conditions. With encapsulating IL into the ponds within the polymeric matrix, the membranes were able to operate appropriately for gas separation. For instance, at the transmembrane pressure of 8 bar and 35 °C for the membrane with 40 wt% EmimTf2N, the CO2 permeability coefficient was increased from 6.5 to 38 Barrer, about 484%, and the CO2/CH4 permselectivity value was increased from 32 to 63, about 96%. The prepared polymer/IL blended membranes are realized to be superior candidates for CO2/CH4 separation.
•Blended membranes of Matrimid®5218 and (EmimTf2N) were fabricated.•The membranes were characterized by SEM, DSC, and FTIR-ATR analyses.•Heterogeneous structures with distributed IL ponds were detected for membranes.•With encapsulated IL into polymeric matrix, the membranes operated properly in CO2/CH4 gas separation.
Global health authorities are trying to work out the current status of the novel coronavirus (COVID-19) outbreak and explore methods to reduce the rate of its transmission to healthy individuals. In ...this viewpoint we provide insights concerning how health care professionals can unintentionally shift the novel coronavirus type to more drug-resistant forms. It is worth noting that viruses usually have different sensitivities to physical and chemical damaging agents such antiviral drugs, UV and heat ranging from extremely sensitive (ES) to extremely resistant (ER) based on a bell-shaped curve. Given this consideration, the widespread infection of people with such ER viruses would be a real disaster. Here, we introduce a modified treatment method for COVID-19-associated pneumonia. In this proposed method, COVID-19 patients will receive a single dose of 100, 180 or 250 mSv X-ray radiation that is less than the maximum annual radiation dose of the residents of high background radiation areas of Ramsar that is up to 260 mSv. In contrast with antiviral drugs, a single dose of either 100, 180 or 250 mSv of low LET X-rays cannot exert a significant selective pressure on the novel coronavirus (SARS-CoV-2) and hence does not lead to directed accelerated evolution of these viruses. Moreover, Low Dose Radiation (LDR) has the capacity of modulating excessive inflammatory responses, regulating lymphocyte counts, and controling bacterial co-infections in patients with COVID-19.
Conventional energy resource problems made power system planners apply more renewable energy sources (RESs) in the power system. RESs have a significant impact on fulfilling the world's energy ...demand, protecting the environment at least in the exploration phase, and providing energy reliability as well as security for the new generation of power grids. In this regard, wind power generation is considered a promising solution. However, by increasing the share of wind power generation units in the power sector, some challenges, such as voltage problems, transient stability, increasing system losses, and line congestions can occur. Consequently, an alternative solution is required to accelerate wind power units' connections to the grid by preventing the problems caused by the penetration of wind power. In this regard, Flexible Alternating Current Transmission Systems (FACTS) devices can play an important role while they can improve power grid dynamic performance. This paper presents a review of the optimization techniques applied to accelerate the penetration of wind energy by exploiting FACTS devices. The topic identifies the objectives and optimization formulations, as well as schemes and models available in the published literature. This survey gives noteworthy insights to the researchers to cover available solutions in these regards. The literature in the field is summarized in different aspects, such as FACTS technology, objective functions, constraints, optimization methods, planning or operation purposes, and load flow types. At each aspect, a comparison is derived to recognize the most important issues. The result of the review is the finding of future work and contributions which can be done in the field of wind energy integration acceleration using FACTS devices and the output of the paper can be used as a guide for researchers to find a new path for research in this area.
This paper presents a review of the optimization techniques applied to accelerate the penetration of wind energy by exploiting flexible alternating current transmission systems devices. The topic identifies the objectives and optimization formulations, as well as schemes and models available in the published literature. This survey gives noteworthy insights to the researchers to cover available solutions in these regards.
In the current study, two different vessels with single and two steps were experimentally and numerically studied. The experimental tests were conducted at 7.5, 8.025, 8.5, and 9.5 m/s, i.e., at beam ...Froude numbers from 3.22 to 4.09. The measured parameters include bow rise-up, trim angle, and resistance. Followed by validating the numerical setup against the experimental measurements, simulations of the fluid flow around the vessel at 10 m/s and 12 m/s speeds were conducted using STAR-CCM+ software. Two-phase flow was analyzed using the finite volume method as well as volume of fluid technique considering the overset meshing scheme. Based on the experimental results, addition of the transverse step enhanced the stability of the vessel and reduced its trim. It was also concluded that the resistance of the single-step high-speed vessel was considerably reduced compared to that with no step. Of note, both single-step and two-step models were stable at speeds up to 12 m/s. Finally, based on Taguchi test design method, a number of numerical models were extracted and the interaction of the three parameters of the first and second step length and the speed at two levels was investigated. Based on these findings, as the length of the second step increased, the resistance increased as well.
Mechanical resonators with high quality factors are widely used in precision experiments, ranging from gravitational wave detection and force sensing to quantum optomechanics. Beams and membranes are ...well known to exhibit flexural modes with enhanced quality factors when subjected to tensile stress. The mechanism for this enhancement has been a subject of debate, but is typically attributed to elastic energy being “diluted” by a lossless potential. Here we clarify the origin of the lossless potential to be the combination of tension and geometric nonlinearity of strain. We present a general theory of dissipation dilution that is applicable to arbitrary resonator geometries and discuss why this effect is particularly strong for flexural modes of nanomechanical structures with high aspect ratios. Applying the theory to a nonuniform doubly clamped beam, we show analytically how dissipation dilution can be enhanced by modifying the beam shape to implement “soft clamping,” thin clamping, and geometric strain engineering, and derive the ultimate limit for dissipation dilution.
Chest tube is a flexible plastic tube used to discharge secretion in the cavity between the lungs and chest named pleural cavity. Normally, there is a small amount of fluid in the cavity between the ...lungs and chest; This fluid helps the movement of lungs during breathing without abrasion. Entrance of bit of air, blood or pus because injury in the pleural cavity can prevent the lungs from fully opening. Full or partial collapse of the lungs makes breathing difficult and can lead to respiratory arrest; putting chest tube in the pleural cavity causes the discharge of secretion and helps patients comfort. Chest Electro-Drainage mobile system is designed to drain air, blood, water and pus accumulated in the space between the visceral and parietal pleural cavity. Based on low volume and weight, this system can be used to treat Pneumothorax, Hemothorax and Hydrothorax and so forth, both in the emergency state and treatment centers. Obviously, this system will be an action to reduce deaths especially in the case of Pneumothorax.
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