Double Flash Research Articles

The cross-modal double flash illusion depends on featural similarity between cross-modal inducers

Despite extensive evidence of the possible interactions between multisensory signals, it remains unclear at what level of sensory processing these interactions take place. When two identical auditory beeps (inducers) are presented in quick succession accompanied by a single visual flash, observers often report seeing two visual flashes, rather than the physical one — the double flash illusion. This compelling illusion has often been considered to reflect direct interactions between neural activations in different primary sensory cortices. Against this simple account, here we show that by simply changing the inducer signals between featurally distinct signals (e.g. high- and low-pitch beeps) the illusory double flash is abolished. This result suggests that a critical component underlying the illusion is perceptual grouping of the inducer signals, consistent with the notion that multisensory combination is preceded by determination of whether the relevant signals share a common source of origin.

Thermodynamic and economic analysis and optimization of power cycles for a medium temperature geothermal resource

Geothermal power generation technologies are well established and there are numerous power plants operating worldwide. Turkey is rich in geothermal resources while most resources are not exploited for power production. In this study, we consider geothermal resources in Kutahya–Simav region having geothermal water at a temperature suitable for power generation. The study is aimed to yield the method of the most effective use of the geothermal resource and a rational thermodynamic and economic comparison of various cycles for a given resource. The cycles considered include double-flash, binary, combined flash/binary, and Kalina cycle. The selected cycles are optimized for the turbine inlet pressure that would generate maximum power output and energy and exergy efficiencies. The distribution of exergy in plant components and processes are shown using tables. Maximum first law efficiencies vary between 6.9% and 10.6% while the second law efficiencies vary between 38.5% and 59.3% depending on the cycle considered. The maximum power output, the first law, and the second law efficiencies are obtained for Kalina cycle followed by combined cycle and binary cycle. An economic analysis of four cycles considered indicates that the cost of producing a unit amount of electricity is 0.0116$/kWh for double flash and Kalina cycles, 0.0165$/kWh for combined cycle and 0.0202$/kWh for binary cycle. Consequently, the payback period is 5.8years for double flash and Kalina cycles while it is 8.3years for combined cycle and 9years for binary cycle.

Audition influences color processing in the sound-induced visual flash illusion

Multisensory interactions can lead to illusory percepts, as exemplified by the sound-induced extra flash illusion (SIFI: Shams, Kamitani, & Shimojo, 2000, 2002). In this illusion, an audio-visual stimulus sequence consisting of two pulsed sounds and a light flash presented within a 100 ms time window generates the visual percept of two flashes. Here, we used colored visual stimuli to investigate whether concurrent auditory stimuli can affect the perceived features of the illusory flash. Zero, one or two pulsed sounds were presented concurrently with either a red or green flash or with two flashes of different colors (red followed by green) in rapid sequence. By querying both the number and color of the participants' visual percepts, we found that the double flash illusion is stimulus specific: i.e., two sounds paired with one red or one green flash generated the percept of two red or two green flashes, respectively. This implies that the illusory second flash is induced at a level of visual processing after perceived color has been encoded. In addition, we found that the presence of two sounds influenced the integration of color information from two successive flashes. In the absence of any sounds, a red and a green flash presented in rapid succession fused to form a single orange percept, but when accompanied by two sounds, this integrated orange percept was perceived to flash twice on a significant proportion of trials. In addition, the number of concurrent auditory stimuli modified the degree to which the successive flashes were integrated to an orange percept vs. maintained as separate red-green percepts. Overall, these findings show that concurrent auditory input can affect both the temporal and featural properties of visual percepts.

GW24-e0662 Computed tomography coronary angiography with a consistent dose below 2 mSv using double prospectively ECG-triggered high-pitch spiral acquisition in patients with atrial fibrillation: initial experience

ObjectivesTo evaluate the feasibility and imaging quality of double prospectively ECG-triggered high-pitch spiral acquisition mode (double flash mode) for coronary computed tomography angiography (CTCA) in patients with atrial fibrillation (AF).Methods47...

From conventional ac flash-sintering of YSZ to hyper-flash and double flash

Abstract Flash-sintering experiments were performed on conventional 8 mol% Y 2 O 3 -doped ZrO 2 . By varying the initial power spike, the steady state limited current density, the flash duration and furnace temperature, various microstructures corresponding to different sintering stages were observed. It is shown that operating the flash-sintering under the power dissipation regime may lead to microstructure heterogeneity. Under a quasi-adiabatic regime a better homogeneity is obtained. The major part of the shrinkage strain occurs within a short time interval of about 1 s, after the incubatory period. The remaining part appears to be a conventional shrinkage process induced by Joule heating. Hyper-flashes were performed over this short time interval, yielding relative densities up to 90%. Additional flashes can be subsequently applied up to full density. It is stressed that densification is not an absolute quality parameter in the optimization of the experimental conditions; inappropriate conditions may lead to fairly dense but brittle materials.

Flash illusions induced by visual, auditory, and audiovisual stimuli

When two objects are flashed at one location in close temporal proximity in the visual periphery, an intriguing illusion occurs whereby a single flash presented concurrently at another location appears to flash twice (the visual double-flash illusion: Chatterjee et al., 2011, Wilson & Singer, 1981). Here, for the first time, we investigate the time course of the effect, and directly compare it to the time course of the auditory (sound-induced flash illusion) effect, for both fission (single test flash, double inducer) and fusion (double test flash, single inducer) conditions, across stimulus onset asynchronies (SOAs) of 30 to 250 ms. In addition, using a novel audiovisual stimulus, we directly compare the cue strength of the two modalities, and whether they are additive in effect. The results show that the time course of fission and fusion is different for visual inducers, but not for auditory inducers. In audiovisual conditions, in situations of uncertainty, observers tended to follow the more reliable (auditory) cue. There was little evidence for a superadditive effect of auditory and visual cues; rather, observers tended to follow one or the other modality. The results suggest that the visually induced flash illusion and the auditory-induced effect may both stem from perceptual uncertainty, with the difference in time courses attributable to the lower temporal resolution of vision compared to audition.

Computed tomography coronary angiography with a consistent dose below 2 mSv using double prospectively ECG-triggered high-pitch spiral acquisition in patients with atrial fibrillation: initial experience

To evaluate the feasibility and imaging quality of double prospectively ECG-triggered high-pitch spiral acquisition mode (double flash mode) for coronary computed tomography angiography (CTCA) in patients with atrial fibrillation (AF). 47 patients (11 women, 36 men; mean age 64.5 ± 12.1 years) were enrolled for CTCA examinations using a dual-source CT with 2 × 128 × 0.6 mm collimation, 0.28 s rotation time and a pitch of 3.4. Double flash mode was prospectively triggered first at 60 % and later at 30 % of the R-R interval within two cardiac cycles. Image quality was evaluated using a four-point scale (1 = excellent, 4 = non-assessable). From 672 coronary artery segments, 77.5 % (521/672) was rated as score of 1, 20.8 % (140/672) as score of 2, 1.2 % (8/672) as score of 3 and 0.4 % (3/672) was rated as 'non-assessable'. The average image quality score was 1.25 ± 0.38 on a per segment basis. Mean dose-length product for CTCA was 92.6 ± 28.2 mGy cm, the effective dose was 1.30 ± 0.39 mSv (0.64-1.97 mSv). In patients with AF, double prospectively ECG-triggered high-pitch spiral acquisition mode could be a feasible and valuable scan mode for CTCA with a consistent dose below 2 mSv as well as diagnostic imaging quality.

P3-14: The Cross-Modal Double Flash Illusion Cannot be Explained by Interactions between Primary Sensory Representations

The cross-modal double flash illusion (DFI) refers to an interaction of multisensory signals wherein the presentation of a single visual flash accompanied by two cross-modal inducers, auditory or tactile pulses, results in observers reporting the presentation of two flashes. This phenomenon has become an exemplary case of the strong modulatory effect possible between cross-modal signals. However, it remains unclear precisely what about the different signals is interacting. The prevailing interpretation typically invokes interactions between different singular sensory representations—an explanation consistent with what would be expected in detection tasks. Here we investigated whether such a simple interaction could in fact account for the DFI. Using a paradigm similar to the original, we manipulated the apparent similarity of the cross-modal inducers such that they differed in attribute (1000 Hz pure tone or Gaussian noise) or modality (audio or tactile). When the inducer pair was the same, a DFI was foun...

Prospectively ECG-triggered High-pitch Spiral Acquisition for Cardiac CT Angiography in Routine Clinical Practice

This study was conducted to evaluate the mode of application, image quality (IQ), and radiation exposure resulting from introduction of a prospectively electrocardiogram-triggered high-pitch cardiac computed tomography angiography (CTA) acquisition mode into routine clinical practice. A total of 42 prospectively triggered cardiac CTAs were conducted on 34 patients (11 female, 23 male; mean age 56 ± 15 y) using a high-pitch mode (pitch 3.4) on a dual-source CT. In 8 of these patients with higher heart rates or occasional premature ventricular contractions, 2 immediately subsequent CTAs were performed ("double flash protocol"). Subjective IQ was assessed for coronary arteries using a 4-point scale (1=unevaluable to 4=excellent). Contrast-to-noise ratio (CNR) was measured in 9 locations. CT Dose Index and dose-length product were obtained, and the patients' effective dose was calculated. Mean effective doses were 2.6 ± 1.4 mSv (range: 1.1 to 6.4) for the entire cardiac examination and 1.4 ± 0.7 mSv (0.4 to 3.1) for individual high-pitch cardiac CTA. z-coverage ranged from 9.9 cm in a native coronary CTA to 31.4 cm in a bypass graft case. The overall subjective IQ was good to excellent (mean score: 3.5), with 1.5% unevaluable coronary segments. The "double flash protocol" resulted in a fully diagnostic CT study in all cases just after taking both scans into consideration. The mean CNR of all locations was 19.7 ± 2.6. Prospectively electrocardiograph-triggered high-pitch-mode cardiac CTA is a feasible and promising technique in clinical routine, allowing for evaluation of coronaries at good-to-excellent IQ and providing high CNR and minimal radiation doses. The "double flash protocol" might become a more robust tool in patients with elevated heart rates or premature ventricular contractions.

Flash cycle optimization of Sabalan geothermal power plant employing exergy concept

The Sabalan geothermal field in northwest Iran is currently under development. A single flash cycle has been selected for power generation. The analysis of the proposed design shows the maximum net power output of the plant can reach 31MW if the pressures of the separator and condenser are 5.5 and 0.3bar, respectively. To achieve optimum energy utilization, a double flash cycle was also evaluated for power generation. The results indicate the maximum net power output of the plant reaches 49.7MW if the pressures for the high- and low-pressure steps and condenser are 7.5, 1.1, and 0.1bar, respectively. Mathematical models for energy and exergy flows were developed and implemented in Engineering Equation Solver (EES) software. In the single flash cycle, the energy and exergy of the waste water were calculated as 54.8% and 41.4% of the total available energy and exergy, respectively. The energy and exergy of waste water were respectively calculated as 19.88% and 15.3% of the total available energy and exergy, in the double flash cycle. The parts of the system with largest exergy destruction in both cycles were compared and the overall exergy and energy efficiencies for the power plant were calculated. The total exergy available from production wells at Sabalan was calculated to be 111MW for the single flash system, and 114MW for the double flash system. The results of the analysis suggest a double flash cycle system for the Sabalan power plant.

Performance analysis of a novel integrated geothermal-based system for multi-generation applications

Abstract In this paper, we propose a novel integrated, geothermal-based double flash power generating, ammonia-water quadruple effect absorption, and electrolyzer system for cooling, heating, power, hot water and hydrogen production. Detailed energy and exergy analyses are carried out, and the effects of geothermal source temperature, geothermal source mass flow rate, geothermal source pressure, effect of ambient temperature are then studied parametrically. It is found that increasing geothermal source temperature, pressure and mass flow rate results in increasing power and rate of hydrogen produced. The amount of hydrogen produced is found to be increasing from 1.85 kg/day to 11.67 kg/day with rise in geothermal source temperature from 440 K to 500 K respectively, and from 7.9 kg/day to 9.6 kg/day with increase in geothermal source pressure from 3000 kPa to 5000 kPa, respectively. However, increase in geothermal source temperature, pressure, and mass flow rate has negative effects on cooling production. Moreover, a rise in ambient temperature results in better exergetic efficiency of the system.

Illusory double flashes can speed up responses like physical ones: evidence from the sound-induced flash illusion

When a single brief flash is accompanied by two auditory beeps, participants often report perceiving two flashes. The present experiment examined whether the perception of illusory redundant flashes can result in faster responses as compared to the perception of a single flash, because previous research has shown such a redundancy gain for physical stimuli. To this end, participants were asked to respond as rapidly as possible to the onset of any flash. Following their response, they additionally indicated whether they perceived a single flash or a double flash. Most importantly, we observed significant shorter reaction times in response to redundant flashes, irrespective of whether they were physically presented or illusorily perceived. Taken together, our results suggest that an illusory percept can affect simple reaction time in much the same manner as the corresponding physical stimulation.

World geothermal power production status: Energy, environmental and economic study of high enthalpy technologies

The current world status of geothermal electricity production, including installed capacities, number of units and energy produced by exploitation technology, is presented in this paper. Four geothermal model plants based on different modes of high enthalpy technologies are analyzed from energy, environmental and economic points of view for specific reservoir characteristics. Once process parameters are optimized for the best plant operation, a cost and financial analysis is performed within a given economic frame. This analysis shows that Dry Steam power plants are the most efficient. Flash steam power plants increase their exergy efficiency with increasing reservoir temperature. Double Flash technology raises the energy produced with respect to Single Flash between 17 and 25%, and economic parameters become better. An additional third flash process increases power production by 10%, but economic parameters are not improved unless a reservoir of very high temperatures is considered. The energy and economic study conclude that the choice of the best flash technology depends on the resource characteristics, the financial frame and the technology costs.

Clinical applications of time-dependent perimetry (10) receptive field properties of glaucoma patients

The receptive field center of double flash resolution (DFR) and of critical flicker fusion frequency (CFF) in a 3 degrees temporal visual field were examined in 11 normal subjects and 19 glaucoma and ocular hypertension patients. In normal subjects, the mean receptive field center of DFR was 2.17 log min of arc2 and that of CFF was 2.55 log min of arc2. In many glaucoma and ocular hypertension cases, the receptive field center of DFR (mean:2.48 log min of arc2) was significantly enlarged and came close to that of CFF (mean:2.53 log min of arc2)(p < 0.01). Although these findings were mostly seen in patients with some visual field changes, they were also encountered in 9 (70%) of the 13 cases with ocular hypertension without any visual field changes and are probably related to poor intraocular pressure control. We considered that the result was due to the dysfunction of the surrounding area of DFR that consists of interaction between sustained and transient functions of the visual pathway. This dysfunction could be closely related to the disorder of alpha-cells that occurs in the early stage of glaucoma.

Visual cortex as a site of cross-modal integration

It has been shown that visual perception can be strongly affected by auditory stimuli. It is unclear, however, what brain circuitry subserves these interactions. We used the sound-induced illusory flash effect (a single flash accompanied by two auditory beeps is perceived as two flashes (Nature 2000)) as a tool to investigate this question. This illusion is much stronger in the periphery than fovea. In a previous ERP study (NeuroReport 2001), the temporal onsets and patterns of modulation suggested that the modulation of activity by sound occurs within the visual cortex. In the present study we tried to localize the brain regions involved in the perception of the illusory flash more directly and accurately using event-related fMRI. We collected functional images of 3 participants in the following conditions. Unimodal conditions Vp and Vf consisted of visual stimulation: a small disk flashed once in the periphery or fovea, respectively. Bimodal conditions AVp and AVf consisted of auditory-visual stimulation: combination of 2 beeps with visual stimuli Vp and Vf, respectively. In another unimodal condition, Vp2, a physical double flash was presented in the periphery. Trials were randomized. Contrasting (the illusion) condition AVp against Vp resulted in activity in Brodmann's areas 17, 18, and 19. However, contrasting (no-illusion) condition AVf vs. Vf, revealed no differential activity in visual cortex. Thus, the auditory stimulation, per se, or attentional effects, could not account for the visual cortex activity associated with the illusory flash percept. Considering that the visual stimulus was identical in AVp and Vp, the enhanced activity of early visual areas in AVp can only be attributed to the perception of the illusory flash caused by sound. Similar brain areas were indicated when contrasting Vp2 against Vp, corresponding to a physical second flash. These results altogether suggest that the activity in the early visual cortical areas is modulated by sound.

Basic Quantitative Assessment of Visual Performance in Patients with Very Low Vision

A variety of approaches to developing visual prostheses are being pursued: subretinal, epiretinal, via the optic nerve, or via the visual cortex. This report presents a method of comparing their efficacy at genuinely improving visual function, starting at no light perception (NLP). A test battery (a computer program, Basic Assessment of Light and Motion [BaLM]) was developed in four basic visual dimensions: (1) light perception (light/no light), with an unstructured large-field stimulus; (2) temporal resolution, with single versus double flash discrimination; (3) localization of light, where a wedge extends from the center into four possible directions; and (4) motion, with a coarse pattern moving in one of four directions. Two- or four-alternative, forced-choice paradigms were used. The participants' responses were self-paced and delivered with a keypad. The feasibility of the BaLM was tested in 73 eyes of 51 patients with low vision. The light and time test modules discriminated between NLP and light perception (LP). The localization and motion modules showed no significant response for NLP but discriminated between LP and hand movement (HM). All four modules reached their ceilings in the acuity categories higher than HM. BaLM results systematically differed between the very-low-acuity categories NLP, LP, and HM. Light and time yielded similar results, as did localization and motion; still, for assessing the visual prostheses with differing temporal characteristics, they are not redundant. The results suggest that this simple test battery provides a quantitative assessment of visual function in the very-low-vision range from NLP to HM.

Perceptions of implied hazard for visual and auditory alerting signals

Visual and auditory alerts are increasingly important and have many applications, particularly in the presentation of hazard information in transportation and many industrial systems. This paper is concerned with the factors that govern the relative effectiveness of alerting signals involving various combinations of visual and auditory signals. The visual variables were colour, flash rate, and flash mode, combined with or without an auditory alarm. It was found that the subjects associated different levels of hazard with different alerting light colours, flash rates, flashing modes, and with combinations of auditory and visual alerts. A red flashing light was perceived as the most effective hazard warning colour, with yellow and blue warning lights indicative of less hazardous situations. The faster the flash rate, the greater is the hazard perceived. A flash rate of 60 fpm (flashes per minute) was not as effective as the rates of 180 and 240 fpm, and 240 fpm was the most effective. This implies that hazard warning signal should flash at well above 60 fpm. Having a breakup in the flashing pattern so as to provide a double or triple flash mode also increases the effectiveness of the signal. There were significant interactions between the alert variables used. The difference in perceived hazard levels for the colours blue and yellow were statistically non significant, but blue was more effective in conveying hazard message than yellow at the high flash rates. When accompanied with auditory alarms, blue and yellow were perceived to convey the same perception level of hazard as red without auditory alarms. The effect of colour on perceived hazard was also found to vary with flash mode. As compared to either visual signal alone or a visual signal with other types of acoustic alarms, a siren type of auditory alarm was found more effective for eliciting perception of hazards. There was evidence that presenting alerting signal in triple-flash mode and at high flash rate could be annoying and might not help improving hazard awareness.

Activity in human V1 follows multisensory perception

When a single brief visual flash is accompanied by two auditory bleeps, it is frequently perceived incorrectly as two flashes. Such illusory multisensory perception is associated with increased activation of retinotopic human primary visual cortex (V1) suggesting that such activity reflects subjective perception [Watkins, S., Shams, L., Tanaka, S., Haynes, J.D., Rees, G., 2006. Sound alters activity in human V1 in association with illusory visual perception. Neuroimage. 31, 1247–1256]. However, an alternate possibility is that increased V1 activity reflects either fluctuating attention or auditory–visual perceptual matching on illusion trials. Here, we rule out these possibilities by studying the complementary illusion, where a double flash is accompanied by a single bleep and perceived incorrectly as a single flash. We replicate findings of increased activity in retinotopic V1 when a single flash is perceived incorrectly as two flashes, and now show that activity is decreased in retinotopic V1 when a double flash is perceived incorrectly as a single flash. Our findings provide strong support for the notion that human V1 activity reflects subjective perception in these multisensory illusions.

Novel Structures for a 2-Bit per Cell of Nonvolatile Memory Using an Asymmetric Double Gate

A 2-bit operational metal/silicon-oxide-nitride-oxide-silicon (MONOS/SONOS) nonvolatile memory using an asymmetric double-gate (ASDG) MOSFET was studied to double flash memory density. The 2-bit programming and erasing was performed by Fowler-Nordheim (FN) tunneling in a NAND array architecture using individually controlled gates. A threshold voltage shift of programmed states for the 2-bit operation was investigated with the aid of a SILVACO® simulator in both sides of the gate by changing gate workfunctions and tunneling oxide thicknesses. In this paper, the scalability of the device down to 30 nm was demonstrated by numerical simulation. Additionally, guidelines of the 2-bit ASDG nonvolatile memory (NVM) structure and operational conditions were proposed for program, read, and erase.

DOUBLE FLASH METHODS

DOUBLE FLASH METHODS