Changes In Phase Distribution Research Articles

Hybrid Checkerboard Metasurface Combining Passive and Active AMCs

In this paper, a hybrid checkerboard metasurface is proposed for controlling radar cross-sections (RCSs) using a small number of active devices. The proposed metasurface consists of passive and active artificial magnetic conductors. The passive metasurface contributes to reducing the RCS level owing to the dispersion characteristics of the checkerboard arrangement, while the active metasurface aids in controlling the RCS. The active RCS pattern of the proposed hybrid checkerboard metasurface in response to changes in phase distribution is also investigated. The results show that the RCS level at the boresight changed from -20.3 dBsm to 4.4 dBsm, and the main lobe of the RCS pattern steered up to 31°. The fabrication and measurement results of the proposed hybrid checkerboard metasurface are also described in this study.

Disparities in precipitation effects on PM2.5 mass concentrations and chemical compositions: Insights from online monitoring data in Chengdu

Precipitation plays a pivotal role in wet deposition, significantly affecting aerosol purification. The efficacy of precipitation in removing aerosols depends on its type and the characteristics of the particulates involved. However, further research is necessary to fully understand how precipitation impacts PM2.5 components. This study utilized high-temporal-resolution data on PM2.5, its components and meteorological factors to examine varying responses influenced by precipitation intensity and duration. The findings indicate that increased rainfall intensity and duration enhance PM2.5 and its constituents removal efficiency. Specifically, longer precipitation periods significantly improve PM2.5 purification, especially with drizzle and light rain. Moreover, there is a direct correlation between pre-precipitation PM2.5 levels and its scavenging rates, with drizzle potentially exacerbating PM2.5 pollution under cleaner conditions (≤ 35 µg/m3). Seasonally, the efficacy of removing PM2.5 components varies notably in response to drizzle and light rain. In spring, higher PM2.5 levels after drizzle were primarily due to increased organic carbon concentrations favored by higher relative humidity and lower pH conditions compared to other seasons, conducive to secondary organic aerosol production. Lower wind speeds and higher temperatures further contribute to water-soluble organic carbon accumulation. Daytime and nighttime precipitation exerted differing influences on PM2.5 components, particularly in spring where daytime drizzle and light rain significantly increased PM2.5 and its constituents, notably NO3-, potentially associated with phase distribution changes between gas and aerosol phases in low-temperature, high-RH conditions compared to nighttime. These results propose a dual-impact mechanism of precipitation on PM2.5 and provide scientific basis for designing effective control strategies.

Self-referencing photothermal digital holographic microscope for characterization of low-loss liquids

Measurement of absorption coefficients of transparent samples is important for their characterization and identification; however, it is challenging to measure low values, e.g., 10−3–10−4 cm−1 with high accuracy. Here, we report a compact photothermal lateral shearing digital holographic device. It is based on the thermal lens effect and a common-path, self-referencing digital holographic microscope comprising a glass plate, probe beam, and a CMOS camera. The change in phase distribution caused by the temperature change due to light absorption is measured from the recorded holograms to extract the sample's absorbance and absorption coefficient. The feasibility of the proposed configuration is validated by the experimental results obtained with different concentrations of gold nanoparticles (AuNPs) in an aqueous solution. Determination of AuNPs concentration in the nM range is performed, and the obtained limits of detection and quantitation are 0.04 nM and 0.13, respectively. The calibration curve is linear at a low concentration range of 0.06–0.95 nM with 1% reproducibility. In addition, the method's versatility is demonstrated by measuring the absorption coefficient of low-loss solvents, such as ethanol and water. The determined absorption coefficients agree with the reported values, confirming that this method provides good spectrometric capabilities, such as high sensitivity and accuracy.

Recurrence analysis of phase distribution changes during boiling flow in parallel minichannels

In the paper, flow boiling in three parallel minichannels with a common inlet and outlet area was examined. The synchronization between flow distributions in minichannels was analyzed in local area (image analysis) and as the process of the synchronization between inlet and outlet pressure fluctuations. These processes were studied using cross recurrence plot. The analysis of pixel brightness changes inside minichannels has been applied to identify the similarity of flow patterns changes inside minichannels. The results have revealed that the processes of synchronization have a negative impact on water inlet and outlet temperature and inlet and outlet pressure oscillations. During synchronization high amplitude of oscillations of temperature and pressure occur. The mentioned behaviors are caused mainly by reverse flow. In the paper it has been shown that recurrence analysis of inlet and outlet pressure oscillations can be used for assessment of boiling synchronization in minichannels.

Effectiveness of forced cooling during laser bending of duplex-2205

ABSTRACT Duplex-2205 is a dual-phase stainless steel having high mechanical strength and excellent corrosion resistance properties. Large spring back and high heat sensitivity are major problems in duplex-2205 during cold and hot working, respectively. Laser bending process is an advanced manufacturing process that is used for difficult to form materials with minimum heat-affected zone, negligible spring back, and high precision. Forced cooling (FC) has improved the efficiency during multiscan laser bending by reducing the waiting time. This study is focused on the analysis of the effectiveness of FC at the lower surface during single scan laser bending of duplex-2205 stainless steel. Worksheet geometry (thickness and width) and laser parameters (beam diameter, scanning speed and power) are varied to analyze the temperature profile, bend angle, mechanical and metallurgical properties during FC and compared with natural cooling condition. The results showed that a higher bend angle is observed in FC compared to natural cooling. Furthermore, tensile strength and hardness are improved whereas ductility is reduced due to change in phase distribution in the scanning region. Moreover, FC is found to be more effective at higher laser power, lower scanning speed, intermediate beam diameter, lower sheet thickness, and longer width of the worksheet.

Experimental investigation on the synchronization characteristics of a pitch-plunge aeroelastic system exhibiting stall flutter.

This study focuses on characterizing the bifurcation scenario and the underlying synchrony behavior in a nonlinear aeroelastic system under deterministic as well as stochastic inflow conditions. Wind tunnel experiments are carried out for a canonical pitch-plunge aeroelastic system subjected to dynamic stall conditions. The system is observed to undergo a subcritical Hopf bifurcation, giving way to large-amplitude limit cycle oscillations (LCOs) in the stall flutter regime under the deterministic flow conditions. At this condition, we observe intermittent phase synchronization between pitch and plunge modes near the fold point, whereas synchronization via phase trapping is observed near the Hopf point. Repeating the experiments under stochastic inflow conditions, we observe two different aeroelastic responses: low amplitude noise-induced random oscillations (NIROs) and high-amplitude random LCOs (RLCOs) during stall flutter. The present study shows asynchrony between pitch and plunge modes in the NIRO regime. At the onset of RLCOs, asynchrony persists even though the relative phase distribution changes. With further increase in the flow velocity, we observe intermittent phase synchronization in the flutter regime. To the best of the authors' knowledge, this is the first study reporting the experimental evidence of phase synchronization between pitch and plunge modes of an aeroelastic system, which is of great interest to the nonlinear dynamics community. Furthermore, given the ubiquitous presence of stall behavior and stochasticity in a variety of engineering systems, such as wind turbine blades, helicopter blades, and unmanned aerial vehicles, the present findings will be directly beneficial for the efficient design of futuristic aeroelastic systems.

Phase distribution changes of neat unsaturated polyester resin and their effects on both thermal stability and dynamic‐mechanical properties

AbstractA relationship between phase distribution of a commercial unsaturated polyester resin (UPR) and both thermal stability and dynamical mechanical properties, measured by thermogravimetric analysis and dynamic‐mechanical analysis respectively, is observed. Changes in phase distributions are achieved varying UPR components miscibility by means of temperature. Morphologies of the internal surfaces are analyzed by atomic force microscopy showing that more homogeneous nanostructures with smaller nodules result in the increase of the storage modulus and glass transition temperature of the thermosetting UPR. Tan δ peaks show that the phase rich in UP and the phase rich in polystyrene tend to decrease their differences at higher curing temperatures. Changes in the curing mechanism and kinetics with curing temperature are verified by differential scanning calorimetry. A theoretical explanation of archived morphology is proposed using interaction parameter between UP and styrene showing that higher temperatures increased their miscibility.

Consideration of existence of phase information of object shape in zeroth-order diffraction beam using electromagnetic simulation with aperture in front of objective

ABSTRACTIt has been reported that the shape of a measured object can be determined by detecting the change in phase distribution generated by a lateral shift of the object using speckle interferometry. In speckle interferometry technique, it was also reported that the shape of the object beyond the diffraction limit can be measured. In this study, the principle of this method is discussed through experiments and electromagnetic analysis. Accordingly, the results of the experiments and electromagnetic analysis of phase change only under zeroth-order diffraction light through the lateral shift of the object are investigated by shutting out the higher harmonic diffraction lights using an aperture in front of the lens. The results indicate that even if the image of the object cannot be focused upon, three-dimensional shape measurement can be performed by analysing only the zeroth-order diffraction light from the object.

Unlocking the impurity-induced pipeline corrosion based on phase behavior of impure CO2 streams

This study explored the phase behavior of impure CO2 streams and further unmasked its effects on pipeline corrosion by combing thermodynamic calculation and corrosion test. Thermodynamically, H2S impurity promotes water precipitation via reducing the H2O solubility in CO2. H2S-induced phase distribution changes point to the root cause of H2S-enhanced corrosion. To mitigate the above effects from impure CO2 streams on pipeline steel, we prepared an amorphous Ni–P coating on steel and found that the formation of protective film endows the coating with good corrosion resistance. Hence, more than 80 % of corrosion effects and the localized corrosion are effectively prevented.

The technology of thermal welding of the circulation piping of NPPS containing the influence of ultrasound

The authors propose a thermal welding technology with ultrasound treatment for NPP circulation pipe-lines. This technology can significantly increase the strength of welded connections by reducing residual stresses, grain size and welded joint degassing. Exposure to ultrasound increases the welding speed and reduces the current consumption, thus resulting in energy saving. The paper presents the results of theoretical and experimental studies of ultrasonic effects on the welded joints and heat-affected zone.As is known, bearing capacity of welded joints is significantly lower than that of the base metal. This is due to the emergence of internal and residual stresses in the process of welding which are added to operating stresses, thus resulting in the destruction of the weld joint metal.Currently, it is common practice to reduce residual stresses in welded connections of NPP circulating pipelines and equipment by means of the thermal tempering and deformation methods.Thermal and deformation methods may reduce residual stresses in the HAZ but do not eliminate structural instability and physical and chemical heterogeneity, resulting in internal stresses and microcracks in the weld metal.Specialists of the Obninsk Institute for nuclear power engineering have developed a technology for thermal welding with ultrasonic treatment during the welding process, as a result of which the metal structure becomes fine-grained and homogeneous. Internal stresses are excluded and residual stresses are relieved in the heat-affected zone.The role of individual factors of ultrasonic field in creating certain structural changes in the metal depends on the crystallization conditions. In different areas of the crystallizing melt, the effect of any of the ultrasonic field factors may dominate. For example, the dispersion of crystals may occur in the two-phase zone, and the acoustic streams and stirring may be only in the liquid phase. If the reduction of grain size and elimination of the columnar structure are due to the ultrasonic dispersion, the change in phase distribution and the dendritic process of elimination are mainly determined by changes in the temperature gradient in the melt and stirring. The reasons for dispersion are cavitation, viscous friction forces, oscillatory and radiation pressure. An increase in the rate of nucleation of crystallization centers is also associated with these parameters.

Photoperiod Modulates Fast Delayed Rectifier Potassium Currents in the Mammalian Circadian Clock.

One feature of the mammalian circadian clock, situated in the suprachiasmatic nucleus (SCN), is its ability to measure day length and thereby contribute to the seasonal adaptation of physiology and behavior. The timing signal from the SCN, namely the 24 hr pattern of electrical activity, is adjusted according to the photoperiod being broader in long days and narrower in short days. Vasoactive intestinal peptide and gamma-aminobutyric acid play a crucial role in intercellular communication within the SCN and contribute to the seasonal changes in phase distribution. However, little is known about the underlying ionic mechanisms of synchronization. The present study was aimed to identify cellular mechanisms involved in seasonal encoding by the SCN. Mice were adapted to long-day (light–dark 16:8) and short-day (light–dark 8:16) photoperiods and membrane properties as well as K+ currents activity of SCN neurons were measured using patch-clamp recordings in acute slices. Remarkably, we found evidence for a photoperiodic effect on the fast delayed rectifier K+ current, that is, the circadian modulation of this ion channel’s activation reversed in long days resulting in 50% higher peak values during the night compared with the unaltered day values. Consistent with fast delayed rectifier enhancement, duration of action potentials during the night was shortened and afterhyperpolarization potentials increased in amplitude and duration. The slow delayed rectifier, transient K+ currents, and membrane excitability were not affected by photoperiod. We conclude that photoperiod can change intrinsic ion channel properties of the SCN neurons, which may influence cellular communication and contribute to photoperiodic phase adjustment.

The Mechanics of Superplastic Forming - How to Incorporate and Model Superplastic and Superplastic-Like Conditions

Much work has been carried out in understanding the mechanics of superplasticity (SP). Some of the present challenges in SP forming revolve around the use of lower forming temperatures and faster strain rates, which may involve pushing the process boundaries to incorporate “superplastic-like” forming – perhaps also in materials with non-optimized microstructures. For process optimization there is a requirement to be able to model both within the SP and superplastic-like processing window in an integrated way. From a mechanics point of view the presence of high rate sensitivity is often seen as the key factor in controlling SP response. However, changes in phase distribution and grain morphology, or the accumulation of damage (cavitation) may compromise this assumption. The paper will examine the range of validity of some SP constitutive models and how they may be adapted to take into account processing routes that may incorporate superplastic-like and more conventional SP deformation modes.

Active phase distribution changes within a catalyst particle during Fischer–Tropsch synthesis as revealed by multi-scale microscopy

A new combination of three chemical imaging methods has been developed and applied to fresh and spent co-based Fischer–Tropsch catalysts.

Monitoring the Diffusion Layer During Passive Film Breakdown on Alloy 800 with Digital Holography

The effects of chloride and thiosulfate ions on localized corrosion of alloy 800 are investigated through dynamical observation of the change in phase image of the diffusion layer during passive film breakdown using digital holography. The results indicate that solution chemistry has a significant effect on film breakdown and diffusion layer. The phase distribution changes at different applied potentials show that in the process of film breakdown, dissolution of metal ions from pitting is not remarkable in chloride-only solution, whereas dissolution of metal ions is significantly high in thiosulfate and chloride solution. Thiosulfate has a combined effect with chloride ions in passive film degradation.

Void fraction of dispersed bubbly flow in a narrow rectangular channel under rolling conditions

Rolling motion, as a typical ocean condition, can induce additional force and change the states of a two-phase flow system. Visualized experiments was carried out on void fraction of air–water flow in a narrow rectangular channel (40 × 3 mm2) under ambient temperature and pressure as well as rolling conditions of 5°-8s, 10°-8s, 15°-8s, 15°-12s, 15°-16s (rolling amplitude-rolling period). The results showed that the void fraction oscillates periodically in rolling motions due to the induced changes in phase distribution and the slip of the interface. In addition, rolling motion gives rise to the reduction of the time-averaged void fraction. The fluctuation amplitude of the void fraction increased with the increase in rolling amplitude and the decrease in rolling period. The distribution parameter under rolling condition was obtained and compared with that under steady state. The influence coefficient K was defined by taking the rolling Reynolds number and gas Reynolds number into consideration. A new correlation for predicting the void fraction was given based on the experimental data.

Visualization of Phase Evolution in Model Organic Photovoltaic Structures via Energy-Filtered Transmission Electron Microscopy

The morphology of the active layer in an organic photovoltaic bulk-heterojunction device is controlled by the extent and nature of phase separation during processing. We have studied the effects of fullerene crystallinity during heat treatment in model structures consisting of a layer of poly(3-hexylthiophene) (P3HT) sandwiched between two layers of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Utilizing a combination of focused ion-beam milling and energy-filtered transmission electron microscopy, we monitored the local changes in phase distribution as a function of annealing time at 140 °C. In both cases, dissolution of PCBM within the surrounding P3HT was directly visualized and quantitatively described. In the absence of crystalline PCBM, the overall phase distribution remained stable after intermediate annealing times up to 60 s, whereas microscale PCBM aggregates were observed after annealing for 300 s. Aggregate growth proceeded vertically from the substrate interface via uptake of PCBM from the surrounding region, resulting in a large PCBM-depleted region in their vicinity. When precrystallized PCBM was present, amorphous PCBM was observed to segregate from the intermediate P3HT layer and ripen the crystalline PCBM underneath, owing to the far lower solubility of crystalline PCBM within P3HT. This process occurred rapidly, with segregation already evident after annealing for 10 s and with uptake of nearly all of the amorphous PCBM by the crystalline layer after 60 s. No microscale aggregates were observed in the precrystallized system, even after annealing for 300 s.

Gaseous phase hydrogen storage and electrochemical properties of Zr8Ni21, Zr7Ni10, Zr9Ni11, and ZrNi metal hydride alloys

A systematic study of four important non-Laves phase alloys, Zr8Ni21, Zr7Ni10, Zr9Ni11, and ZrNi, commonly seen in the Zr-based AB2 metal hydride alloys was presented. In order to investigate the synergetic effect between the major and secondary phases, an annealing treatment was used to change the abundances of various phases in the alloys. The structure, gaseous phase hydrogen storage, and electrochemical properties were obtained for each of the four alloy compositions before and after annealing, and the correlations among these properties were explored. Annealing generally suppressed secondary phases except for the case of Zr9Ni11, where its secondary ZrNi phase abundance increased. As the Zr/Ni ratio in the average composition increased, the maximum gaseous phase hydrogen storage capacity increased but maximized at Zr:Ni = 9:11. Comparing the properties before and after annealing, it was established that the change in phase distribution influenced the gaseous phase storage. Through the electrochemical measurements, it was found that the highest full discharge capacity was obtained at Zr:Ni = 7:10, which represents a compromise between the hydrogen desorption/discharge rate and the theoretical maximum gaseous phase hydrogen storage. As the Zr/Ni ratio increased, the high-rate dischargeability decreased, which followed the trend of the amount of metallic Ni in the surface oxide determined by magnetic susceptibility measurement. The synergetic effect was observed in the electrochemical environment by comparing the results before and after annealing. In general, annealing deteriorated and improved the electrochemical discharge capacity and high-rate dischargeability, respectively, due to the reduction in secondary phase abundance and consequent synergetic effect. Among all alloys investigated, the unannealed Zr7Ni10 demonstrated the best overall gaseous phase hydrogen storage and electrochemical capacity and could be considered as a candidate to replace the AB5 and AB2 metal hydride alloys in Ni/MH battery applications. Furthermore, the unannealed Zr8Ni21 showed a good balance between high-rate dischargeability and ease of formation.

Phase Mapping of Cardiac Fibrillation

Received January 25, 2009; accepted October 6, 2009. Phase is a descriptor that tracks the progression of a defined region of myocardium through the action potential and has been demonstrated to be an effective parameter in analyzing spatiotemporal changes during fibrillation. In this review, the basic principles behind phase mapping are presented mainly in the context of ventricular fibrillation (VF), atrial fibrillation (AF), and fibrillation from experimental monolayer data. During fibrillation, the phase distribution changes over time, depending on activation patterns. Analyzing these phase patterns provides us insight into the fibrillatory dynamics and helps clarify the mechanisms of cardiac fibrillation and modulation by interventions. Winfree1 introduced the phase analysis to study cardiac fibrillation in the late eighties. This time-encoding technique deals with a scenario where the activation periods are the same over the surface being mapped. To deal with the scenario of varying activation period over the mapped surface (common in animal and human fibrillation models), Gray et al2,3⇓ introduced the state-space encoding concept from nonlinear dynamics. In analyzing spatiotemporal phase maps constructed from electric or optical mapping of the surface of heart during VF, points around which the phase progresses through a complete cycle from −π to +π are of great interest. At these points, the phase becomes indeterminate and the activation wave fronts hinge to these points and rotate around them in an organized fashion. These points in the phase map are called phase singularity (PS) points. Bray et al4 developed a procedure to locate PS points in a phase map. Nash et al5 used phase mapping to study the entire ventricular epicardium of human hearts with a sock containing 256 unipolar contact electrodes. The development of this phase mapping tool has led to better understanding of fibrillation dynamics as evidenced by the …

PCDD/Fs removal efficiency by electrostatic precipitator and wetfine scrubber in an iron ore sintering plant

This study investigates the removal efficiency of polychlorinated dibenzo- p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) by the APCDs of an iron ore sintering plant, an electrostatic precipitator (ESP) and a wetfine scrubbing system (WS). The removal efficiencies of the ESP on the total PCDD/Fs concentration and the total PCDD/Fs I-TEQ concentration are 44.3% and 41.4%, respectively, while those of the WS are 66.7% and 68.4%, respectively, but the vapor/solid phase distribution changes after APCDs abatement. At ESP inlet, the PCDD/Fs account for 31.2% in vapor phase and for 68.8% in particulate phase while, at ESP outlet, the PCDD/Fs account for 63.3% in vapor phase and for 36.7% in solid phase. The ESP removes effectively solid-phase PCDD/Fs for its effectiveness to capture the particulate while it is ineffective in removing vapor-phase PCDD/Fs. It, on the contrary, increase for the vaporization within the ESP, especially for these congeners with a lower chlorination degree, and for the PCDD/Fs “stripping” from particulate to gas-phase during the sampling. At WS inlet, the PCDD/Fs account for 63.3% in vapor phase and for 36.7% in solid phase while, at WS outlet, the PCDD/Fs account for 21.4% in vapor phase and for 78.6% in solid phase. Considering that WS outlet temperature is about 40 °C, the PCDD/Fs vapor-phase condense to particles: therefore, even if the particulate is removed by WS, the final result is that PCDD/Fs percentage decreases in vapor-phase and increases in solid-phase.

Maldistribution of fluids in extrudates

Solid–liquid pastes featuring high volume fractions of particulates are frequently used in ceramic forming operations. When pastes are used it is important that the particulate distribution remains uniform throughout the body. The stresses imposed during extrusion processing can, however, promote differential flow between the solid and liquid phases giving rise to product and processing problems. Reliable models for predicting phase distribution changes in these multi-phase systems are in their infancy. This paper reports progress towards developing simulation techniques and practical systems to verify the numerical approaches. Pastes containing glass spheres suspended in a highly viscous Newtonian fluid have been extruded at various speeds and solids loadings. Load and liquid content data are presented which form the basis for model verification. Soil mechanics approaches are used here to encapsulate the inherently multi-phase nature of these systems. The modified Cam–Clay model has been implemented in a finite element analysis simulation of ram extrusion using the ABAQUS platform. The simulation requires regular and extensive remeshing and monitoring of the conservation of mass. Predictions of extrusion pressures and deformation behaviour are compared with the experimental data for a series of square-ended and conical dies.