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Vertigo is a common neurological complaint, which can result in significant morbidity and decreased quality of life. While pathology to peripheral and subtentorial brain structures is a well-established cause of vertigo, cortical lesions have also been linked to vertigo and may lend insight into relevant neuroanatomy. Here, we investigate the supratentorial lesion locations associated with vertigo and test whether they map to a common brain network. We performed a systematic literature search and identified 23 cases of supratentorial brain lesions associated with vertigo. We mapped the lesion locations to a standard brain template and computed the network of brain regions functionally connected to each lesion location, using a ‘wiring diagram’ of the human brain termed the human connectome (n = 1000). Sensitivity was assessed by identifying the most common connection to lesion locations associated with vertigo, and specificity was assessed through comparison with control lesions associated with symptoms other than vertigo (n = 68). We found that functional connectivity between lesion locations and the bilateral ventral posterior insula was both sensitive (22/23 lesions) and specific (voxel-wise family-wise error-corrected P < 0.05) for lesion-induced vertigo. We computed connectivity with this hub region to define a lesion-based vertigo network, which included regions in the bilateral insula, somatosensory cortex, higher-level visual areas, cingulate sulcus, thalamus and multiple cerebellar regions in the territory of the posterior inferior cerebellar artery. Next, we used stereo-electroencephalography (80 stimulation sites across 17 patients) to test whether stimulation sites associated with vertigo mapped to this same network. We found that 36/42 (86%) of stimulation sites eliciting vertigo fell within the lesion-based vertigo network in contrast to 16/39 (41%) of stimulation sites that did not elicit vertigo. Connectivity between stimulation sites and our lesion-based hub in the ventral posterior insula was also significantly associated with vertigo (P < 0.0001). We conclude that cortical lesions and direct electrical stimulation sites associated with vertigo map to a common brain network, offering insights into the causal neuroanatomical substrate of vertigo.

Due to the exhaustion of fossil fuels and environmental degradation, biodiesel has attracted much attention as a new energy source. Currently, microwave reactors are used extensively for producing biodiesel. However, nonuniform heating of producing biodiesel in microwave reactors is a major problem. In order to solve the problem, a microwave reactor with an interlayer which can obviously improve the uniformity of microwave heating was designed. In this work, the heating efficiency and heating uniformity of the reactor were discussed from two aspects of waveguide position and interlayer thickness by means of multi-physical coupling calculation. According to the calculation results, the optimization model of a microwave reactor with an interlayer was obtained. Then, based on the above optimization model of a microwave reactor with an interlayer, a stirrer that can improve the heat transfer of the fluid material was introduced. The Maxwell equation, heat transfer equation, and flow equation were coupled by the multi-physical field simulation method to explore the influence of different factors of the stirrer on power consumption and heating uniformity. Through response surface analysis, it was found that the primary and secondary order of stirring factors affecting microwave heating uniformity was stirring speed > impeller diameter > bottom clearance, and there was an interaction between different factors. From the two aspects of stirring power consumption and heating uniformity, the best stirring effect was obtained.

A microwave drying system with functions of automatic power and temperature control was developed to dry potato chips. The mass and moisture content of the sample are available online. The dielectr...

Fixing, shaping, and drying are three major processing procedures after green tea's harvest. Among them, fixing is the first and key step for the formation of green tea's specific appearance and fragrance. With traditional methods, only trained experts with years' experience can produce good green tea products, which is backward in the industrial age. In this study, intelligent green tea fixation is designed to automatically and continuously adjust the processing parameters. Aroma is online measured with an electronic nose and a few sensors' signals are selected to represent the fresh fragrance, enzymatic reaction, charring occurrence, respectively. Image information is captured with machine vision and G, R, B values are carefully processed to reflect the color changes. The original aroma signals and processed image information were fed into an adaptive fuzzy logic controller to automatically control the pot temperature continuously. With a controlled high temperature at the beginning, the enzymatic reaction could be suppressed and more polyphenols and chlorophyll were retained. In the later phase the temperature was decreased to minimize charring, and more aroma and contents were retained. The final product quality was hence greatly improved in terms of appearance, liquor color, fragrance, taste, and residue color.

Traditional solid-state fermentation processes can give fluctuating product quality and quantity due to difficulties in control and scale up. This paper describes an engineering study of an industrial-scale anaerobic solid-state fermentation process for Chinese liquor (Baijiu) production, aimed at better understanding of the traditional process, as an initial step for future optimization. This mixed-culture fermentation is done in 0.44-m3 vessels embedded in the soil. At this scale, the fermentation is limited by product inhibition. We developed mathematical models based on the Han-Levenspiel equation for product inhibition, with parameters derived from measured data. The models accurately predicted the concentrations of starch and dry matter. A model with radial conduction into a small soil volume around the fermenter and consecutive vertical conduction into the underlying soil accurately predicted the pit temperature in the heating and cooling phases. This model is very sensitive to the values used for the enthalpies of combustion, meaning that direct measurement of the heat production rate would be preferable. In the industry practice, the fermenter volume can be from around 0.20 to 15.00 m3. The model predicts that overheating will occur not only in larger fermenters, but also in the 0.44-m3 fermenters when the soil temperature is high in summer. Our model predictions are consistent with observed behavior in the industry. Our findings can be used to improve this traditional process, as well as similar systems.

We study particle capture on an angled cylinder at a range of Peclet numbers. This system was inspired by the plumose antennae of certain species of male moths that intercept female pheromones at low Peclet numbers of 0.9–23. We use confocal microscopy to measure the branching patterns of 49 moths, spanning 12 families and two orders of magnitude in mass. Among the three levels of hierarchy in antennae, we find the middle level has a prevalent branching angle, are optimal for collection of particles, collecting 30 % more than when perpendicular to the flow. Simulations and smoke visualization show that angled cylinders bend incoming streamlines, creating a lingering effect near the cylinder that can enhance deposition by diffusion. We surmise that the optimal angle arises from a trade-off between the lingering effect, which decreases with increasing angle of the cylinder, and the cylinder’s increasing projected area as it is turned more perpendicular to the flow. Using a mathematical model, we show that only cylinders at low Peclet number show improved collection at intermediate angles. Thus, we cannot rationalize the high collection rates in our wind tunnel experiments at high Peclet number. We hope that our study will inspire more research into bio-inspired particle collection of angled surfaces, and find applications in sensors and filters.

Celery (Apium graveolens) has extensive culinary usage given its characteristic aroma and flavor, which are due to the presence of butylphthalide and sedanolide. The aim of this work was to study the preparation of dried celery stalk slices through hot air or combined microwave and hot air drying at 50, 60, or 70°C with or without blanching pretreatment. The celery stalk slices that were dried at low temperatures retained aroma well. Although blanching reduced drying time (DT) and global color change, it also reduced the retention of the characteristic aroma of celery. Therefore, combined microwave and hot air drying without blanching was selected for celery stalk slices given that it reduced DT, minimized chromatic aberrations, and maximized the retention of the characteristic aroma of celery. PRACTICAL APPLICATIONS: Celery has extensive culinary usage given its characteristic aroma and flavor, owing to the presence of butylphthalide and sedanolide. Dried celery slices can be used as food flavorings in conventionally cooked and ready‐to‐eat products. Hot air and microwave drying with blanching pretreatment was investigated to dry celery to preserve its nutritional value, flavor and reduce postharvest losses. The obtained the process parameters are helpful for the application of combined microwave with hot air drying technology to preserve good quality, especially flavor of dried celery.

Background Chinese liquor, a very popular fermented alcoholic beverage with thousands of years’ history in China, though its flavour formation and microbial process have only been partly explored, is facing the industrial challenge of modernisation and standardisation for food quality and safety as well as sustainability. Meanwhile, the hidden knowledge behind the complicated and somehow empirical solid-state fermentation process of Chinese liquor can enrich the food sector to improve our quality of life, and benefit other industrial sectors in the modern biomass-based technology, economy and society. Scope and approach This review reveals the traditional fermentation process and characteristics of Chinese liquor, summarises the current study progress of flavour chemistry and responsible microbial process, and addresses future improvement and research needs. We provide here a detailed, systematic and critical review on Chinese liquor to improve the current industrial practice and serve the modern society with yet incompletely explored but useful principles. Key findings and conclusions The hidden knowledge behind the traditional Chinese liquor production is rich in useful principles including flavour chemistry, microbial growth, solid-state fermentation, enzyme production, biocatalysis, microbial community metabolism and process engineering. Studies in a more in-depth, systematic and practical way on this look-like empirical process to explore the scientific principles behind will definitely benefit the liquor industry in particular, and the (food) biotechnology sector in general.

Using a high-speed video-camera system, the hydrodynamics of gas–liquid two-phase slug flow in a vertical narrow rectangular channel with the cross section of 2.2 mm × 43 mm is investigated for laminar and turbulent regimes in the main flow and turbulent regime in the wake region of the Taylor bubble. The Taylor bubble velocity is the function of the liquid slug length ahead of it, and the interaction of Taylor bubbles for turbulent flow in main flow is weaker than that for laminar flow. Thus, two correlations are proposed for laminar and turbulent flows, respectively. The distributions of Taylor bubble velocity, lengths of liquid slug and Taylor bubble are all positively skewed. The lengths of Taylor bubble and the liquid slug decrease with the liquid flow rate. The Taylor bubble length increases with the gas flow rate, whereas the influence of the gas flow rate on the liquid slug length is insignificant.

The dynamic characteristics of gas-particle spout fluidized bed in a pulsed spouted microwave-vacuum drying system (PSMVD) were investigated. The spout fluidization process in a pseudo-2-D spout fluidized bed was simulated by computational fluid dynamics (CFD) using the inviscid two-fluid theory method (TFM) based on the kinetic theory of granular flow. The dynamic characteristics of the spout fluidized bed and the effect of spout elevation on the particle movement were revealed, which could be used to improve the uniformity of particle mixing and microwave heating. The mathematical model demonstrated that the spout fluidization process includes isolated, merged and transitional jets and the fluidization at a specific spout gas velocity has a start-up stage and a quasi-steady fluidization stage. The spout velocity was an important factor controlling particle status in the spout fluidized bed and a critical velocity was identified for effect transition of the flow pattern. There was an approximately linear correlation between the jet penetration depth and the spout velocity. When the spout gas velocity increased up to the critical velocity region, the pressure drop tended to convert from negative pressure to positive pressure.

The effect of food particle mass on the instantaneous fluid dynamic characteristics of a gas–particle spout fluidized bed in a pulsed spouted microwave–vacuum drying (PSMVD) system was investigated by a numerical method. The spout fluidization process in a pseudo-2D spout fluidized bed was simulated by computational fluid dynamics (CFD) using the inviscid two-fluid theory method (TFM) based on the kinetic theory of granular flow. The effect of particle mass on the particle flow pattern, jet penetration depth, and pressure drop was evaluated. Under a specific particle mass, the spout velocity was an important factor controlling particle status in the spout fluidized bed and a critical velocity was identified for effective transition of the flow pattern. With an increase in particle mass, the spout velocity tended to increase to obtain the expected gas–particle flow pattern and the correlation between the particle mass and particle flow pattern was revealed. This research on the fluid dynamic characteristic...

For a flow system in a marine vehicle, rolling motion induced by ocean environment usually imposes a periodical force on the system. Experimental investigation was conducted on frictional resistance of bubbly flow in three rectangular ducts in rolling motion. The cross-sections of the three ducts have the same width of 43 mm but different heights of 1.41 mm, 3.25 mm and 9.96 mm. Rolling motion can easily cause the fluctuation of frictional pressure in the rectangular duct with larger height, therefore, a narrow duct is beneficial to restrain the effect of rolling motion on frictional resistance of bubbly flow. The additional pressure drop in ducts with heights of 1.41 mm and 3.25 mm can be neglected. Increasing the gas flow rate and the rolling amplitude or decreasing the rolling period would result in the increase of the fluctuation amplitude of the frictional pressure. A new correlation by modifying the parameter C in the Chisholm correlation was acquired to describe the hydrodynamic performance of bubbly flow for rectangular ducts in rolling motion, showing a good agreement with the experimental data.

Four different drying methods, namely, air drying (AD), microwave-assisted vacuum drying (MWVD), coupled microwave–hot air drying (MWAD), and freeze drying (FD), were studied, in terms of drying time, color, reducing sugar content, shrinkage, microstructure, and sensory evaluation. The drying rate of MWVD and MWAD were notably faster than that of AD and FD. The highest reducing sugar content was observed in MWAD, followed by MWVD. No significant differences were observed in reducing sugar between air-dried and freeze-dried products. FD had the best color and shrinkage among the other drying methods. The color and shrinkage of MWVD drying is close to the fresh litchis and much better than hot air and MWAD. Scanning electron microscopy (SEM) images showed that the MWVD and FD litchis have a porous structure, whereas AD and MWAD litchis have a compact structure. The sensory evaluation suggests that peeled litchis dried by the four studied drying methods are of a quality that is accepted by consumers.

As a typical ocean environment, rolling motion can induce additional forces on a flow system. Experimental study of the characteristics of air–water mixture flow resistance in narrow rectangular channel(40 × 1.41 mm 2 ) in rolling motions was carried out with the rolling periods and amplitudes of 8 s, 12 s, 16 s, and 10°, 15°, 30°, respectively. Several homogeneous and separated flow models were evaluated against the experimental data to clarify their applicability in predicting the two-phase flow resistance in vertical rectangular channels. The comparison showed that McAdams correlation for calculating the viscosity in homogeneous model is suitable for the present situation to calculate the averaged two-phase flow resistance. Transient flow resistance under rolling condition changed periodically, as a result, attempt was conducted to illustrate the effect of rolling motion. Transient frictional pressure drop strongly depends on the mass quality, Reynolds number, rolling period and amplitude. The fluctuation amplitude of the frictional pressure drop increased with increasing mass quality and rolling amplitude. It also increased with reduction of the rolling period. A new correlation for predicting the transient frictional factor was given by including the influence of rolling parameters and was validated against the experimental data.

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 mm 2 ) 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.

Unsteady flow in axial fans with circumferential skewed blades were measured at off-design conditions using a hot-wire test, to investigate the effect of sweep on aerodynamic limit and aeroacoustic sound source. Two circumferential skewed fans, with the blade skew angles at 8.3° forward and backward, respectively, were investigated in this study. The instantaneous flow field in the upstream and downstream of these fans was measured at off-design operations, using a two-dimensional (2D) probe based on a Constant Temperature Anemometry (CTA) system, and a NI PXI data collecting system. From the measured results, the characteristics of time domain and frequency domain were presented. The three-dimensional (3D) structure and turbulent characteristics of inlet and outlet flow in circumferential skewed fans were analyzed according to flow rate. Unsteady flow instability and its relation with circumferential skewed blades, to expand stall-free operation range and suppress noise of axial fans, were discussed. The sweep blade is found to be effective in controlling unsteady flow to improve aerodynamic limit and reduce noise source in these rotors at off-design operations.

The rotor–stator interaction noise in axial fans is mainly caused by the periodic wake from the rotating fan impinging on the stator rows downstream. In order to accurately predict the noise, a thin-body BEM/Curle method is developed in this paper. It is a hybrid method combining computational aeroacoustic with Boundary Element Method (BEM) and can be used to predict the propagation of sound wave in the duct. The calculation includes three steps: firstly, the unsteady viscous flow around the blades is calculated using the CFD method to acquire the noise source information; secondly, the radiated sound pressure is calculated using the acoustic analogy Curle equation in the frequency domain; lastly, the scattering effect of the duct wall on the propagation of the sound wave is expressed using the thin-body BEM method. In comparison with the experimental results, the predicted sound pressure levels (SPLs) are correct in the Blade Passing Frequency (BPF) and its harmonics. The sound pressure directivities of sound source and scattering effect are shown in the paper. The conclusion is that the scattering effect of the duct wall cannot be ignored in the prediction of rotor–stator interaction noise and can increase the accuracy of the prediction in comparison with the results based on the free-field assumption.

Frictional resistance of air-water two-phase flow in a narrow rectangular duct subjected to rolling motion was investigated experimentally. Time-averaged and transient frictional pressure drop under rolling condition were compared with conventional correlation in laminar flow region (Rel 1400) respectively. The result shows that, despite no influence on time-averaged frictional resistance, rolling motion does induce periodical fluctuation of the pressure drop in laminar and transition flow regions. Transient frictional pressure drop fluctuates synchronously with the rolling motion both in laminar and in transition flow region, while it is nearly invariable in turbulent flow region. The fluctuation amplitude of the Relative frictional pressure gradient decreases with the increasing of the superficial velocities. Lee and Lee (2002) correlation and Chisholm (1967) correlation could satisfactorily predict time-averaged frictional pressure drop under rolling conditions, whereas poorly predict the transient frictional pressure drop when it fluctuates periodically. A new correlation with better accuracy for predicting the transient frictional pressure drop in rolling motion is achieved by modifying the Chisholm (1967) correlation on the basis of analyzing the present experimental results with a great number of data points.

The 3D flow characteristics in axial fans with circumferential skewed blades were investigated at off-design conditions using Hot-wire test, and the effect of sweep on controlling the aerodynamic limits was discussed. Two circumferential skewed fans, with the blade skew angles at 8.3° forward and backward, respectively, were investigated in this study. The 3D instantaneous velocity components in nearfield, downstream of the fans were measured using Hot-wire Anemometry (CTA) at off-design conditions. From the measured results, the structure of passage flow in circumferential skewed fans is analyzed according to flow rate. The boundary layer flow and its relation with circumferential skewed blades, to expand stall-free operation range of axial fans, were discussed. As flow rate decreases, the 3D flow structure in blade passage is controlled by the circumferential skewed blades, and the obvious suppression of decreasing passage flow near shroud and hub region; the main flow retains at mid blade span; the radial flow can’t be neglected; the forward-skewed blade is found to be effective in controlling low energy flow in the vicinity of shroud and hub to expand stall-free operation range; the effect of skewed blades on boundary layer is discussed by radial equilibrium equation; as the centrifugal force increases, the blade radial force Fr of the circumferential forward-skewed blade has an positive effect on pressure gradient, and seems to be efficient to control the style and velocity of boundary layer movement.

Experimental and numerical investigations of tip leakage flow of circumferential skewed axial fans were conducted under off-design conditions. Two circumferential skewed fans, with the blade skew angles of 8.3° forward and backward, respectively, and a base fan were investigated in this study. Aerodynamic and aeroacoustic performances were measured. The Navier—Stokes flow simulations were validated experimentally and the key analysis of tip leakage flow was based on computational fluid dynamics results. The simulations show that with a decrease in flowrate, the start of the tip leakage vortex moves towards the leading edge in the chordwise direction and towards the hub in the spanwise direction. These movements are less significant for the forward-skewed blade than for the backward-skewed blade. The strength of the tip leakage vortex decreases along the vortex line. The vortex strength for the forward-skew blade is significantly less than that for the backward-skewed blade. The aeroacoustic source intensity in the tip clearance region is reduced by employing circumferential skewed blades and changes with a change in flowrate in the same manner as the measured sound pressure level. The forward-skewed blade is found to be effective in eliminating noise sources in the tip clearance region and in controlling tip leakage flow to expand the stall-free operation range under off-design conditions.

Gas-liquid slug flow is widely encountered in many practical industrial applications. A detailed understanding of the hydrodynamics of the liquid slug is of great importance in modeling the slug flow. A visualized study using a high speed video camera system was conducted to study liquid slug characteristics of slug flow in a vertical narrow rectangular channel (3.25×40mm2). It is found that three regions could be distinguished in the stable liquid slug tagging along the leading gas slug in most cases. The characteristics of a gas slug are greatly influenced by its position in the liquid slug, and the leading slug has a significant effect on the trailing slug in laminar or transition flow. The wake region of leading slug is also actually a sudden enlargement region where the water jet out of the liquid flim. The minimum stable liquid slug length Lmin is obtained in the experiments ranging from 9 to 17Dh in fully developed turbulence flow.Copyright © 2013 by ASME

Experimental study of rolling effects on characteristics of bubbly flow in a rectangular duct (43 mm×3.25 mm×2000 mm) was performed under ambient temperature and pressure. The characteristics of bubbly flow in vertical, inclined and rolling channels have been obtained through visualization and photographic recording. In the experiment, the gas and liquid superficial velocities ranged from 0.07 m/s to 0.15 m/s and from 1.6 m/s to 2.39 m/s respectively. The bubble clusters contained no less than two bubbles exist in vertical, inclined and rolling channels. With the inclined and rolling angle increase, the bubble clusters tend to contain more bubbles. In vertical case, most bubbles aggregate in the intervals near the narrow wall, thus forms high number fraction peaks at the position around 2x/w = ±0.5. As the inclination and rolling angle increase, the bubble number fraction near the lower wall decreases and that near the upper wall increases. In addition, the number fraction peak close to the lower wall disappears and that near the upper wall becomes higher and sharper at the inclined and rolling angle no less than 10°. There exist no significant differences in bubble lateral distribution under inclined and rolling conditions at the same angle. To identify the influence of rolling on bubble lateral distribution, comparison between lateral buoyancy and additional buoyancy is made theoretically. The results show that the influence of additional buoyancy on lateral bubble distribution can be neglected result from the magnitude of lateral buoyancy is much larger than that of additional buoyancy.Copyright © 2013 by ASME

The additional force arising from rolling motions effects the change of two-phase flow resistance. Experimental studies of the characteristics of air-water mixture flow resistance in narrow rectangular channel(40 × 1.4mm2)in rolling motions were carried out with the rolling periods and angles of 8s, 12s, 16s, and 10°, 15°, 30°, respectively. The experimental results showed that the transient frictional factor changed periodically. The variation of rolling frictional factor with time is closely related to the mass quality, the two-phase Reynolds number, rolling period and amplitudes. The larger of mass quality and rolling amplitude and the small rolling period, the larger of fluctuation amplitude of frictional pressure drop were. A new correction for predicting the transient frictional factor of two-phase was proposed with a good accuracy.

PIV Experiment and pressure test of tip leakage flow of circumferential skewed axial fans were carried out under design and off-design conditions. Two circumferential skewed fans and a radial fan were investigated in this study. Aerodynamic and aeroacoustic performances were measured, and detailed flow field using PIV were measured in the region of tip leakage. The development of tip leakage vortex was analyzed through the PIV results. And the results showed that the tip leakage vortex for the forward-skewed blade is more stable. The pressure test on the casing and the far free field noise test gained the tip leakage noise component. And the results showed the forward skewed blade is found to be effective in eliminating noise source in the tip clearance region and in controlling tip leakage flow to expand the stall-free operation range under off-design conditions.

Tip-clearance noise induced by tip-leakage flow in axial flow fans, with the blades skewed circumferentially at angles of ±8.3°, has been investigated under off-design conditions by numerical simulation and experiments. Aerodynamic and aeroacoustic performances have been measured. Tip-leakage flow has been investigated by Navier-Stokes flow simulations at off-design conditions. The characteristics of noise sources in the tip-clearance region, obtained numerically, have been analyzed using vortex sound theory. Synergy between the tip-leakage vortex and the noise source in the tip region is discussed. Moreover, the noise source in the tip region has been measured by dynamic pressure sensors mounted in the casing wall near the blade tip and the acoustic far field has been obtained simultaneously as a function of flow rate. The frequency characteristic of the tip noise component is analyzed by measured results. The characteristics of noise source reveal that tip-clearance noise is associated with skewed blades, which are found to be effective in controlling tip-leakage flow and in eliminating the noise source in the tip-clearance region at off-design conditions. Forward-skewed blade are more effective than backward-skewed blades in reducing noise