Intermittent Frequency Research Articles

Study on the Photo-Electro-Catalytic Oxidation of Methane

Emission control of methane from landfills has received considerable attentions in recent years. Photo-electro-catalytic oxidation of methane was carried out at the mode of continuous electrolysis and intermittent illumination with TiO2-coated titanium mesh plate as pholocatalyst and electrode in combination with ionic liquid as electrolyte under UV light irradiation. The result showed that the rapid conversion of methane was achieved under ambient pressure and temperature through photocatalytic oxidation combining with electrolysis. Under the mode of intermittent illumination (on:off = 10 min : 10 min) and continuous electrolysis (II-CE), the highest oxidation rate of methane (280 mg/(m3min)) was obtained. Under fixed off time and total illumination time, the oxidation quantity of methane linearly increased with the intermittent frequency. Photo-electro-catalytic oxidation of methane can be described by the first-order kinetics, and the apparent kinetic constant increased with the intermittent frequency.

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Introduction: Standardized Clinical Assessment and Management Plans (SCAMPs) have been shown to be effective in decreasing variation in clinical practice in children. However, the effects of a SCAMP on the variation of care and on clinical outcomes in children with critical asthma are unknown. Methods: An asthma severity score triggered SCAMP for CAN and Helium-Oxygen driven CAN (Heliox-CAN) was developed to guide step-wise escalation and weaning of asthma therapies. The SCAMP guided therapy until albuterol was weaned to an intermittent frequency of q2hrs. All children ≥ 2 years of age admitted to a step-up unit and an ICU requiring CAN were managed via the SCAMP. The incidence of diversion from the SCAMP algorithm, defined as any single diversion, was recorded. The time to q2hr from initiation of CAN was compared between pre-SCAMP to post-SCAMP patients using the Mann-Whitney test with p<0.05 as statistically significant, and via statistical process control (SPC) chart to assess for special cause variation and reduction in variation of outcomes. The rate for escalation of care, need to restart CAN, and adverse effects were also determined. Results: There were 150 pre-SCAMP and 125 post-SCAMP patients eligible for analysis. Compliance with the SCAMP was a 68%. Heliox-CAN was applied in 42% of the cases when the patient did not improve with CAN alone per the SCAMP algorithm. There was a significant decrease in median time to q2hr by 5.8 hours after the initiation of the SCAMP (pre-SCAMP 20.5 hours (IQ 13.7, 30.7) to post-SCAMP 14.7 hours (IQ 8.3, 23.9), p<0.0001). SPC analysis showed that after the implementation of the SCAMP, there was a significant decrease in the variation in time to q2hr meeting special cause variation at week 16. Only 12% of patients required escalation of care, 9% required restarting CAN after initial wean to intermittent nebulization, and only one patient with a history of ectopic atrial tachycardia developed an arrhythmia. Conclusions: A Critical Asthma SCAMP, guided by an asthma severity score, was a safe and effective method to improve clinical outcomes and decreased time of critical care management.

Study on intermittent hypoxia in children sleep apnea hypopnea syndrome model and insulin-like growth factor-1 and insulin-like growth factor binding protein-3 levels in serum

Using rats fed in intermittent hypoxia environment to study the relationship between sleep apnea hypopnea syndrome (SAHS) of children and growth retardation. The hypoxic chamber was designed and manufactured, the control of intermittent hypoxia was achieved. Twenty-four rats were randomly divided into three groups: mild and severe hypoxia group, and control group. In control group, the animals were normally fed, without interruption. The animals in other two groups were kept in the cabin, simulated mild and severe intermittent hypoxia conditions 8-hour a day, a total of 35 days. According to the results of preliminary experiments, the concentration of intermittent hypoxia and frequency were determined. The animals with mild hypoxia events occurred nearly six times per hour, the average minimum oxygen saturation dropped to 0.853, the animals with severe hypoxia events occurred nearly 24 times per hour, the average minimum oxygen saturation dropped to 0.776. Body mass and length were measured before and after experiment. The serum insulin-like growth factor (IGF)-1 and insulin-like growth factor binding protein (IGFBP)-3 expression were tested from venous blood by enzyme-linked immunosorbent assay (ELISA). The length and body mass of rats in three groups before and after experiment were not statistically different (P>0.05). Before the experiment the serum IGF-1 and IGFBP-3 levels were not significantly different (P>0.05). 35 d after the experiment, the serum IGF-1 (x±s, the same below) in the control group, mild hypoxia and severe hypoxia were (60.0±18.5) ng/ml, (40.6±9.9) ng/ml and (13.1±8.6) ng/ml, F=25.840, P<0.01; the serum IGFBP-3 were (1.93±0.23) µg/ml, (1.39±0.30) µg/ml and (0.90±0.21) µg/ml, F=33.929, P<0.01. The differences were statistically significant. The IGF-1 and IGFBP-3 levels decreased as the hypoxia increased (P<0.05). In simulated sleep apnea hypopnea syndrome, the intermittent hypoxia in young rats does not show physical growth retardation, but the serum IGF-1, IGFBP-3 levels decreased with the increase of hypoxia and decline of oxygen saturation.

Forgotten double J stent in the urinary bladder with calculus formation

Received: 23 March 2011 Accepted: 22 August 2011 Published: 30 Apri l 201 2 CASE REPORT A 40­year­old male patient came with complaints of frequency of micturition, dysuria and intermittency for six months. He underwent left uretero­renoscopic lithotripsy one year back for one cm calculus in the lower ureter. His general physical examination was unremarkable excepting for mild suprapubic pain. On investigation his complete urine examination showed many RBCs but rest of the urine examination was unremarkable. His urine culture was sterile. Plain radiograph of the abdomen revealed a radio­opaque shadow encasing a retained DJ stent which slipped into the bladder (Figure 1). The patient underwent open cystolithotomy and removal of the calculus along with the stent (Figure 2). He is asymptomatic and doing well on follow up. DISCUSSION Since its description by Finney et al. Double J ureteral stents are widely used in urological practice [1]. These stents are used to establish or improve drainage in cases of extrinsic or intrinsic obstruction of urinary passage. They are also placed after iatrogenic injuries to the ureter and prophlactically in complex abdominal CLINICAL IMAGES OPEN ACCESS Kusuma 45

Simulation of Islanding Detection for Photovoltaic Grid-Connected Inverters Based on Positive Feedback Intermittent Frequency Drift

Islanding detection is a absolutely necessary function for Photovoltaic Grid-Connected Inverters and it is very important to detect the islanding accurately and quickly with less adverse impact on power quality. This paper proposes a positive feedback intermittent active frequency drift method which can decrease the adverse impact of frequency disturbance effectively within the time restrict of islanding detection according to that of traditional islanding detection methods. The theoretical analysis and simulation results show that this algorithm which is simple, effective, fast and have less adverse impact on power quality and has certain application value.

Biomass char as a fuel for internal combustion engines

ABSTRACTSecond generation liquid biofuels from lignocellulosic feedstocks are part of a suite of solutions to peak oil and a safe climate economy. Biofuels have technological advantages over electrification for applications with minimal refuelling or recharging options such as air travel, shipping, agriculture and low or intermittent frequency trucking and rail. We examined a fuel production concept combining slow pyrolysis chars and superfine commutation. Char is micronised and suspended in diesel or water to create a reduced cost, quality and energy density liquid biofuel. Process yields and efficiencies were derived from a review of the slow pyrolysis char, coal commutation and combustion literature and used to develop theoretical estimates of process performance. Char structure and composition were also reviewed in the context of commutation and management of ash and alkalis in the fuel. The paper concluded that char based fuels had potential applications where cost was critical, but quality was not, such as diesel engines for agriculture, trucks, trains, shipping and backup electricity supply. Char water fuels increase safety by being non‐flammable and are environmentally benign, a valuable trait in sensitive environments such as coastal shipping. © 2011 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Density fluctuation of geodesic acoustic mode on the HL-2A tokamak

The density fluctuations of the geodesic acoustic mode (GAM) have been observed in Ohmic deuterium plasma discharges with a combination of rake-like and three-step Langmuir probe arrays on the HL-2A tokamak. The probe arrays with poloidal and toroidal separations of 36 and 1330 mm are applied to measure the spectral property and intermittency of the GAM density fluctuations. The poloidal and toroidal mode numbers of the fluctuations are simultaneously measured for the first time. The measured fluctuation amplitude is consistent with the theoretical prediction. High coherence and near zero phase shift of the GAM density fluctuations separated toroidally by 37.5° at the same magnetic flux surface was first observed, indicating the symmetric structure of the GAM in the toroidal direction. The peak time delays of the cross-correlation function of the fluctuations above and below the midplane suggest the expected sin θ dependence. The nonlinear three wave coupling between the GAM and the ambient turbulence is shown to be a plausible mechanism for the generation of the GAM density fluctuations. The significant coherence and the corresponding fixed phase shift (∼π) between the original data and the envelope of the high frequency ambient turbulence provide the experimental evidence for the envelope modulation. The GAM amplitude is out of phase with the particle flux. Most of the intermittent frequencies for particle flux are close to the GAM frequency.

Elementary diet reduces diarrhoea associated with microscopic colitis

Microscopic colitis is a common cause of chronic intermittent large volume and frequency diarrhoea. This benign inflammatory bowel disease is characterized histologically by an increase in intraepi...

Characterizing Nonstationary Wind Speed Using Empirical Mode Decomposition

This paper explores how to characterize nonstationary wind speed that can be modeled as a deterministic time-varying mean wind speed component plus a stationary random process for the fluctuating wind speed component. The time-varying mean wind speed is naturally extracted from the nonstationary wind data using the empirical mode decomposition (EMD). The proposed approach is then applied to the wind data recorded by the anemometers installed in the Tsing Ma suspension Bridge during Typhoon Victor to find its time-varying mean wind speed, probability distribution of fluctuating wind speed, wind spectrum, turbulence intensity, and gust factor. The resulting wind characteristics are compared with those obtained by the traditional approach based on a stationary wind model. It is found that most of nonstationary wind data can be decomposed into a time-varying mean wind speed plus a well-behaved fluctuating wind speed admitted as a stationary random process with a Gaussian distribution. The time-varying mean wind speed identified by EMD at a designated intermittency frequency level is more natural than the traditional time-averaged mean wind speed over the certain time interval. The proposed approach can also be applied to stationary wind speed with the same output as obtained by the traditional approach. It is concluded that the proposed approach is more appropriate than the traditional approach for characterizing wind speed.

Continuous Wavelet Transforms of Instantaneous Wall Pressure in Slug and Churn Upward Gas-Liquid Flow

Continuous wavelet transforms are employed to determine the time-localized frequency content (scalogram) of instantaneous wall pressure signals in upward gas-liquid flow. The flow conditions correspond to well-defined slug flow, well-defined churn flow, and flows near the transition from slug-to-churn flow. Scalograms demonstrate that the frequency content of the pressure signals is time-dependent, and visual observations of the flow conditions suggest that the time-dependent frequencies are related to identifiable physical behaviors of the flow. In well-defined slug flow, the scalograms are characterized by the presence of a dominant frequency throughout the duration of the signal and by frequency shifting events. Scalograms representing well-defined churn flow contain intermittent frequencies, and the energy density in churn flow is spread over a wider range of frequencies than in slug flow. The present results provide evidence that flows near transition alternately display characteristics of both well-defined slug and well-defined churn flows.

1149 再層流化する sink flow 乱流境界層の特性

Relaminarization properties of the turbulent boundary layer by a sink-flow are experimentally investigated. Fluctuating velocities and the Reynolds stress decreased with the relaminarization within the sink-flow section. The decrease in the wall-normal fluctuating velocity was more remarkable than that in the streamwise fluctuating velocity. The normalized intermittency frequency decreased and non-turbulent region came close to the wall. The intermittency of the wall-normal velocity fluctuation became more remarkable than that of the streamwise component. Contributions of the sweep process to the coherent structure decreased and the inward interaction became dominant.

Hydrodynamics of slug flow applied to cross‐flow filtration in narrow tubes

AbstractThis article focuses on the characterization of slug‐flow hydrodynamics in two sizes of tubular membrane diameters (6 and 15 mm) to quantify the main mechanical phenomena involved in the limitation of particle fouling during cross‐flow filtration of suspensions. By using a conductance probe technique, the flow structure was accurately identified for two geometries, and noticeable differences were observed in terms of void fractions, velocities and lengths of Taylor bubbles, and liquid slugs. This characterization allowed some data to be theoretically estimated (wall shear stress, “falling” film velocity, film thickness) thanks to the application of a phenomenological model initially developed for oil pipes. The results obtained in a 15‐mm tube showed that the ultrafiltration flux improvement, experimentally achieved with bentonite and yeast suspensions, was partly due to the increase in the wall shear stress, induced by continuous gas sparging inside the tubular filtration module. Other hydrodynamic phenomena linked to the quasi‐periodic succession of Taylor bubbles and liquid slugs were also involved in the control of the particle entrainment: intermittency frequency, reversal of the wall shear stress, instantaneous pressure variations in the long bubble wake with a higher level of turbulence, and an enhanced local mixing.

Mechanism of Wave Excitation on a Liquid Metal Surface Submerged in an Intermittent Alternating Magnetic Field.

In order to increase an interfacial area for the promotion of mass transfer in refining processes, a new method exciting surface wave on a molten metal has been proposed in the way introducing an intermittent alternating magnetic field with the stepwise change of amplitude. For estimating the mechanism of the wave excitation on a metal surface and the value of an excited interfacial area, the surface wave behavior on a liquid gallium was measured by use of a laser level sensor by changing intermittent frequency, f i , and duty, D. At lower intermittent frequency compared with the natural frequency of a liquid metal, the change in the magnetic amplitude excited surface motion on an equilibrium surface which could have been formed by the continuous imposition of each magnetic amplitude as a result of the balance between an electromagnetic pressure and a static liquid pressure. When the intermittent frequency is adjusted to the neighborhood of the natural frequency, descending of free surface in the wall vicinity takes place accompanying with increase in the magnetic amplitude and excites surface motion. When the intermittent frequency coincides with the natural one, a free surface area increases remarkably.

Accurate Stabilization of a 3 mW Single-Mode Output He-Ne Laser by Intermittent Frequency Offset Locking to an Iodine Stabilized He-Ne Laser

A high-power, unmodulated frequency standard laser light with low running cost is a powerful tool for industrial measurement involving laser calibration and interferometry in length and shape. To obtain such a laser light, we developed an intermittent frequency offset locked laser (IFOL laser). This laser system, composed of an iodine stabilized He-Ne laser (I2SL) and a high-powered symmetric three-mode He-Ne laser (HP-3ML, optical output=5 mW), provides two stabilization operational modes: (1) independent mode (I-mode) and (2) slave mode (S-mode). Utilizing the frequency pulling effect, HP-3ML is stabilized at the condition of symmetric three-mode oscillation, and a 3 mW single-mode light with frequency instability of 10-12 is obtained (I-mode). When the optical frequency deviates from the allowed limit during I-mode, HP-3ML is temporarily offset-locked to I2SL (S-mode) with frequency resettability of 10-10 and frequency instability of 10-12. After completion of the drift reset in S-mode, HP-3ML is stabilized in I-mode again, and then I2SL is turned off. In a typical case of allowed drift in ±1 MHz, repetitive operation of I-mode for 10 days and S-mode for 5 min was satisfactory. Such an intermittent operation reduces the working time of I2SL dramatically, resulting in low running cost that enables long-term use in industrial measurement.

Effect of Intermittent Hemodialysis Frequency on Metabolic Control in Acute Renal Failure

Effect of Intermittent Hemodialysis Frequency on Metabolic Control in Acute Renal Failure

Effect of Intermittent Hemodialysis Frequency on Metabolic Control in Acute Renal Failure.

Quantification of the prescribed and delivered doses of renal replacement therapy (RRT) in end-stage renal disease (ESRD) is now commonly performed, since recent data demonstrate a clear relationship between dialysis dose and outcome. In recent years, some of the quantification techniques developed for ESRD patients have been extended to the acute renal failure (ARF) setting. This extension has allowed the assessment of the specific effect of the frequency of intermittent hemodialysis (IHD) on delivered dialysis dose and metabolic control. In this review, after a discussion of the manner in which therapy prescription factors differ in the ARF and ESRD settings, the issue of the frequency of IHD in the ARF setting is explored.

Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser

Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser

Intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser

There is a need for an intense, unmodulated single-frequency stabilized laser light that guarantees absolute optical frequency in a rapid laser calibration or an ultra-high resolution interferometer. To obtain such a light, we developed a new laser system that uses an intermittent frequency offset lock of a symmetric three-mode stabilized He-Ne laser to an iodine stabilized He-Ne laser. The proposed laser system provides two operational modes: (1) independent and (2) slave mode. In the independent mode, frequency of the three-mode laser is stabilized via control of frequency difference between two intermode beats. The resultant output is a single longitudinal mode light of maximum intensity that locates at the top of the gain curve. Frequency instability of 8X10-12 (at a sampling time of 100 s) which is better than conventional stabilized lasers is attained in the independent mode. Slow optical frequency drift during the independent mode is periodically corrected by the offset lock to the iodine stabilized laser (slave mode), resulting in accurate reset of the frequency drift. After reset of the frequency deviation, the three-mode laser is again operated in the independent mode. Due to such intermittent offset lock, duty factor of the iodine stabilized laser was reduced to a few % of continuous operation.

An intermittent frequency offset lock of a transverse Zeeman laser to an iodine stabilized He-Ne laser

A single-mode frequency stabilized laser with modulation-free and moderate power is desired as a light source for an ultra-high resolution interferometer system and/or a rapid laser calibration system. For this purpose, we developed a new stabilized laser system that utilizes intermittent control of a 2 mW transverse Zeeman stabilized He-Ne laser (Zeeman laser) with an iodine stabilized He-Ne laser (I2 stabilized laser). Because of the intermittent control, working time of the I2 stabilized laser is reduced. The Zeeman laser has two operational modes: independent and slave mode. In the independent mode, the Zeeman laser is stabilized through control of Zeeman beat frequency. Temperature dependent drift of the oscillation frequency during the independent mode is periodically corrected by the slave operation utilizing frequency offset locking to the I2 stabilized laser. Frequency instability of the Zeeman laser in independent and slave modes is 7.7X10-11 and 2.0X10-11, respectively, at the sampling time of 100 s.

Hemorrhagic hypotension induces arteriolar vasomotion and intermittent capillary perfusion in rat pancreas.

Hemorrhage-induced intermittent capillary perfusion and its relation to arteriolar vasomotion was studied in rat pancreatic acinar tissue using intravital fluorescence microscopy. During prehemorrhage conditions, microscopic analysis of the pancreatic microcirculation displayed neither arteriolar vasomotion nor intermittency of capillary perfusion (n = 22 animals). Hemorrhage-induced hypotension of 40 mmHg provoked arteriolar vasomotion in 18 of 22 animals and 59 of 115 arterioles studied. The maximum relative amplitude of arteriolar vasomotion was 44 +/- 8% (range 12-81%), and vasomotion frequency averaged 4.73 +/- 0.11 cycles/min. Hemorrhagic hypotension was further accompanied by 1) a decrease of functional capillary density [length of red blood cell-perfused capillaries per area of tissue under investigation (cm/cm2)] from 515 +/- 3 cm-1 at baseline to 386 +/- 3 cm-1 (P < 0.05) and 2) the instantaneous occurrence of intermittency of capillary perfusion in all observation areas (N = 220) of the 22 animals studied. The frequency of intermittency of capillary perfusion (4.72 +/- 0.14 cycles/min) did not differ from the frequency of arteriolar vasomotion, which implies a causal relationship between these two hemorrhage-induced microvascular mechanisms with the probable aim to counteract the decrease of functional capillary density.