Constant Discharge Rate Research Articles

An Energy Efficiency Evaluation Research Based on Heat Generation Behavior of Lithium-Ion Battery

Energy efficiency across a range of state of charge (SOC) is an important performance parameter in variable Battery Energy Storage System (BESS). A novel method was proposed to evaluate the effect of heat generation with the parameters of resistance and entropy change on the energy efficiency. The energy efficiency was evaluated through measuring the resistance and entropy change during different DOD (depth of discharge). The internal resistance was determined by constant current discharge, followed by plots of V vs I at constant SOC, and found it exhibit a reduction as SOC increasing. In addition, the entropy change was measured by the temperature change of the open-circuit voltage. Energy efficiency results were obtained at constant charge input levels and different discharge rates under the different DOD. The result show that the energy efficiency has a decreasing trend with the increase of the depth of discharge, and the energy efficiency plateaus at 60% DOD. The energy efficiency is decreased from 88.8% to 87.3% under 1C discharge from 20% to 80% DOD. Furthermore, the lower the current rate, the higher the energy efficiency under the constant DOD. We isolate the effects of undercharge and underdischarge, and find the difference of energy efficiency under different current rate increases gradually with the increase of DOD.

Synthesis of nanostructured materials by using metal-cyanide coordination polymers and their lithium storage properties

Herein, we demonstrate a novel and simple two-step process for preparing LiCoO2 nanocrystals by using a Prussian blue analogue Co3[Co(CN)6]2 as a precursor. The resultant LiCoO2 nanoparticles possess single crystalline nature and good uniformity with an average size of ca. 360 nm. The unique nanostructure of LiCoO2 provides relatively shorter Li(+) diffusion pathways, thus facilitating the fast kinetics of electrochemical reactions. As a consequence, high reversible capacity, excellent cycling stability and rate capability are achieved with these nanocrystals as cathodes for lithium storage. The LiCoO2 nanocrystals deliver specific capacities of 154.5, 135.8, 119, and 100.3 mA h g(-1) at 0.2, 0.4, 1, and 2 C rates, respectively. Even at a high current density of 4 C, a reversible capacity of 87 mA h g(-1) could be maintained. Importantly, a capacity retention of 83.4% after 100 cycles is achieved at a constant discharge rate of 1 C. Furthermore, owing to facile control of the morphology and size of Prussian blue analogues by varying process parameters, as well as the tailored design of multi-component metal-cyanide hybrid coordination polymers, with which we have successfully prepared porous Fe2O3@NixCo3-xO4 nanocubes, one of the potential anode materials for lithium-ion batteries, such a simple and scalable approach could also be applied to the synthesis of other nanomaterials for energy storage devices.

Yolk–shelled cathode materials with extremely high electrochemical performances prepared by spray pyrolysis

A facile, continuous preparation process of yolk-shell-structured lithium-metal oxide powders without a template for use as cathode materials in lithium ion batteries is introduced for the first time. Single and double-shelled LiNi0.5Mn1.5O4 yolk-shell powders as the first target materials are prepared directly by spray pyrolysis from a spray solution with sucrose, at a short residence time of 4 s. Fast combustion and contraction of a carbon-mixed oxide composite intermediate, formed from a micro-sized droplet inside a hot wall reactor maintained at 700 °C, produces the yolk-shell powders. The yolk-shell structure of the precursor powders directly prepared by spray pyrolysis is well maintained even at a high post-treatment temperature of 750 °C. The yolk-shell LiNi0.5Mn1.5O4 powders delivered a 1000(th) high discharge capacity of 108 mA h g(-1) at 10 C. The discharge capacities are as high as 103, 95, and 91 mA h g(-1) at extremely high discharge rates of 100, 200, and 300 C and the corresponding specific energy densities are 420, 370, and 328 W h kg(-1). The capacity retention at a constant discharge rate of 200 C is 90% after 500 cycles.

Vanadium oxide nanowire – Graphene binder free nanocomposite paper electrodes for supercapacitors: A facile green approach

Vanadium oxide has attracted interest for energy storage applications due to its high theoretical capacitance and stable layered structure. The low electronic conductivity, of V2O5 necessitates combining with conducting materials, typically carbon. However combining with conductive carbon materials may require binders, which compromise the active surface. In this study, V2O5 nanowire (VNWs)–graphene composite flexible paper electrodes were prepared without using binders. Graphene introduces conductivity and electric double layer capacitance (EDLC) to the composite. Graphene sheets were prepared using an alkaline deoxygenation process (hGO), which is a green alternative to traditional hydrazine reduction. Coin cell type supercapacitors were assembled using the hGO–VNW paper electrodes as the anode and spectracarb fiber cloth as the cathode in a two-electrode cell configuration. Electrochemical studies for different compositions of VNWs on hGO are reported. The composite electrode hGO–VNW120, showed balanced EDL and pseudocapacitance as well as an energy density of 38.8 Wh kg−1 at a power density of 455 W kg−1. The maximum power density of 3.0 kW kg−1 was delivered at a constant current discharge rate of 5.5 A g−1. The device prepared using hGO–VNW120 anode showed a specific capacitance of 80 F g−1.

Measuring Artificial Recharge with Fiber Optic Distributed Temperature Sensing

Heat was used as a tracer to measure infiltration rates from a recharge basin. The propagation of diurnal oscillation of surface water temperature into the basin bed was monitored along a transect using Fiber Optic Distributed Temperature Sensing (FODTS). The propagation rate was related to downward specific discharge using standard theory of heat advection and dispersion in saturated porous media. An estimate of the temporal variation of heat propagation was achieved using a wavelet transform to find the phase lag between the surface temperature diurnal oscillation and the correlated oscillation at 0.33 and 0.98 m below the bed surface. The wavelet results compared well to a constant velocity model of thermal advection and dispersion during periods of relatively constant discharge rates. The apparent dispersion of heat was found to be due primarily to hydrodynamic mechanisms rather than thermal diffusion. Specific discharge estimates using the FODTS technique also compared well to water balance estimates over a four month period, although there were occasional deviations that have yet to be adequately explained. The FODTS technique is superior to water balance in that it produces estimates of infiltration rate every meter along the cable transect, every half hour. These high resolution measurements highlighted areas of low infiltration and demonstrated the degradation of basin efficiency due to source waters of high suspended solids. FODTS monitoring promises to be a useful tool for diagnosing basin performance in an era of increasing groundwater demand.

Thermal activity within the western-slope geothermal zone of Aso volcano, Japan: Development of a new thermal area

Since June of 2006, vigorous new fumaroles, accompanied by hydrothermal eruptions, have formed at the Yoshioka hot spring of Aso volcano in Japan. Prior to this date, the hot spring was a minor thermal area, emitting only 0.2×106J/s of hot water. The steam flux increased significantly to 15–30×106J/s in October 2006. After November 2006, the new fumaroles have maintained a largely constant heat discharge rate of approximately 4.6×106J/s (170tonne/day), which is almost 20 times higher than that of the previous natural thermal activity. Mudslides, earthquakes, and human-related factors did not cause the geothermal events observed at Yoshioka. On the basis of energy estimations, we infer that the hydrothermal eruptions and increased flow have resulted from an increase in the volcanic fluid flux from a deep aquifer to the steam-dominated reservoir beneath Yoshioka.

Discussion of “Generalized Method for Storm-Water Pumping Station Design” by S. David Graber

The author develops an approximate method for calculating the constant rate of discharge and accompanying temporary runoff storage volume for small storm-water pumping stations based on an idea presented by Burton (1980) along with a variant of the modified rational method (MRM). Some background information is provided before discussing the author’s analysis, using the author’s notation as much as possible to avoid confusion. The rational formula or rational method (ASCE 1992, p. 90–96) gives the peak flow rate from a catchment as

Investigation of Groundwater Potential in Melaka District of Malaysia

The paper assesses groundwater quality and productivity in Melaka, Peninsular Malaysia. 238 data set shallow boreholes, 20 data set deep boreholes were collected and continuous pumping test data were used to determine productivity of the aquifers. 68 water samples were tested for water quality. The productivity of the wells and the characteristics of the aquifer were evaluated by pumping test using both the constant discharge rate and steps drawdown methods. The potential of shallow groundwater is low with average discharge <5 m3/hour. The potential of deep groundwater is high category with average discharge > 20 m3/hour. The results show that 32% (538 km2) from total area of Melaka district (1650 km2) is low potential categories, 56% (922 km2) is moderate and 12% (194 km2) is high. Based on the chemical data, the quality of deep aquifer is fresh. Therefore, it is available for drinking water with minimum treatment.

Outflow properties of silos: The effect of arching

Engineers working on the field of agriculture, food- or pharmaceutical industry or in the architecture frequently meet problems arising from the special properties of granular assemblies. Storing large amount of particulate raw materials is mostly made by using large containers, called silos. The design of such large silos is far not an easy problem. The outflow properties are one of the most important parameters of silo design. The constant discharge rate of silos differs from the discharge rate of containers filled with liquids. In case of fluids, the flowing velocity and discharge rate changes with fluid level. In case of granular materials, the velocity is constant (independent of the filling level of silo). There are methods used for the determination of silo discharge rate, but these are mostly experimental without physical explanation of the phenomenon. In this paper we demonstrate that the constant discharge rate is caused by the formation and collapse of arches in the bin. Based on this assumption, we derive an equation for determining the discharge rate. Using the same arching hypothesis we derive the equations describing the velocity distribution at silo outlets. The usability of our new approach is demonstrated by experimental investigations.

Novel electrosensory advertising during diurnal resting period in male snoutfish, Marcusenius altisambesi (Mormyridae, Teleostei)

During the day, weakly electric snoutfish, such as Marcusenius altisambesi from the Okavango delta, avoid visually oriented predators by hiding in sheltered, dark places where they discharge their electric organs at a low and variable rate, interspersed with occasional short bursts (mean discharge rate, 4–12 Hz). Hence, histograms of inter-discharge intervals (IDI) are broad and bimodal (IDI range, about 15–500 ms; “variable IDI pattern”). We report here that with a female neighbor in electrical communication reach, captive males of M. altisambesi (N = 4) each showed a novel type of IDI resting pattern that was characterized by a higher and more constant discharge rate (16–28 Hz). These IDI histograms were unimodal and narrow (IDI range, about 11–100 ms; “regularized IDI pattern”). In each of these males, the regularized pattern vanished when the female neighbors were replaced by males, and the common variable IDI pattern of low rate was observed instead. In an unforced choice paradigm, six M. altisambesi experimental females were allowed to choose between two electric fish decoys, one playing back the novel regularized IDI pattern and one playing back the variable IDI pattern. Five experimental females significantly preferred staying close to the decoy playing back the regularized IDI pattern, whereas one female showed the opposite preference. It appears that males advertise to females during their diurnal period of overt inactivity, with an inconspicuous signal that neither threatens conspecifics nor alerts predators by overt behavior. A secondary function of the regularized male IDI pattern could be to advance the reproductive cycle of females.

A New Performance Estimate Method for Design of Storage-Type Domestic Electrical Water-Heaters Based on the CFD Simulation

The 3D physical model of the electrical water heater was built. The water-heater performance was resolved by computer fluid dynamics simulation (CFD). The heater performance is characterized by a new method rather than that the discharge efficiency, extraction efficiency and fraction of heat recoverable. The new method is based on the constant discharge water temperature and rate for end user, 5L/min and 43°C that include the hot water from EWH and cold water from outside EWH. But the water discharge rate from EWH was variable as the water temperature discharge from EWH was variable. Compared with the traditional method, it is more close to the user using reality condition.

Groundwater in fractured granite for water supply to remote areas in Malaysia

Groundwater in fractured granite in Malaysia was found to be an economical source of water supply for various remote industries and communities. The uses include for agricultural processing, mineral water bottling, granite quarry, golf course irrigation and drinking water supply. Forty five tubewells belong to private companies operating in various places in the area were evaluated in terms of the yields and water quality. The wells were drilled using rotary air-percussion method to a maximum depth of 200 m and provided with 6 inch PVC casing and screens. The productivity of the wells and the characteristics of aquifer were evaluated by pumping tests using a constant discharge rate and step drawdown methods. The average yield of the wells at allowable drawdown of 40 m was found to be 428 m3 per day. Results from water quality analysis indicate that the water is fresh with total dissolved solids (TDS) concentration between 101 and 150 mg/L. The hardness of the water varies from as low as 9.01 mg/L to a maximum of 337 mg /L. On the average the water is moderately hard with the hardness value of 73.17 mg/L. The water facies of the groundwater was found to be of Calcium-Sodium-Bicarbonate water.

Performance Estimate for Design of Storage-Type Domestic Electrical Water-Heaters Based on the CFD Simulation

The 3D physical model of the electrical water heater was built. The water-heater performance of two kind structures was resolved by computer fluid dynamics simulation (CFD). The heater performance is characterized by a new method rather than that the discharge efficiency, extraction efficiency and fraction of heat recoverable. The new method is based on the constant discharge water temperature and rate for end user, 5L/min and 43°C that include the hot water from EWH and cold water from outside EWH. But the water discharge rate from EWH was variable as the water temperature discharge from EWH was variable. The discharge efficiency of conventional EWH was 79.312%, and the discharge efficiency of improved EWH was 84.97%. Compared with the traditional method, it is more close to the user using reality condition.

Eliminating Discharge Imbalances in Predicting Shallow Water Flows with Shocks

The shallow water equations are widely used in modelling environmental flows. Being a hyperbolic system of differential equations, they admit shocks that represent hydraulic jumps and bores. Although the water surface can be solved satisfactorily with the modern shock-capturing schemes, the predicted flow rate often suffers from imbalances where shocks occur, eg the mass conservation is violated by failing to maintain a constant discharge rate at every cross-section in a steady open channel flow. A total-variation-diminishing Lax-Wendroff scheme is developed, and used to demonstrate how to achieve an exact flux balance. The performance of the proposed methods is inspected through some test cases, which include 1- and 2-dimensional, flat and irregular bed scenarios. The proposed methods are shown to preserve the mass exactly, and can be easily extended to other shock-capturing models.

Implications of depletion of groundwater levels in three layered aquifers and its management to optimize the supply demand in the urban settlement near Kahota Industrial Triangle area, Islamabad, Pakistan

This study deals with the implications of depletion of groundwater levels in three layered aquifers and its management to optimize the supply demand in the urban settlement near Kahota Industrial Triangle area, located adjacent to the Soan River, Islamabad Pakistan. Initially, a groundwater 3-D steady-state flow model has been developed, calibrated to the known observed heads of 24 water wells, verified, and confirmed that convergence has actually arrived and hydraulic heads are no more changing. Later, the transient simulation was carried out with the constant discharge rates of groundwater by means of pumping wells, storage factor, porosity, and observed drawdown matched with the simulated drawdown that appears to fall in close agreement with a difference of 0.25 m. As such, the developed groundwater model has facilitated to understand, evaluate, and to predict regional trends of groundwater flow regimes and their ultimate utilization at a maximum rate of 4.5 million gallons/day for the growing urban settlement. The calibrated and verified model was then used to simulate the depletion of groundwater level, annual water balance, discharge versus time drawdown, and a temporal behavior of the system over an extended period of pumping. The modeling results indicate that, due to the pumping, the direction of flow has changed: first from groundwater regimes to the Soan River and then it is entirely reversed from the Soan River to the groundwater regimes as the drawdown started to deepen.

Morphodynamics of Headcut Development and Soil Erosion in Upland Concentrated Flows

In agricultural regions, gully erosion is now recognized as a dominant source of soil loss, and the development and upstream migration of headcuts is critical to the initiation, incision, and dissection of these upland areas. This study examined the effect of soil texture on headcut development and migration using four common soils from the southeastern United States, tested on bed surface slopes ranging from 1 to 5% and overland flow rates ranging from 45 to 71 L min−1 In response to this flow, actively migrating headcuts developed with migration rates ranging from 0.00001 to 0.0025 m s−1, maximum scour depths ranging from 0.042 to 0.148 m, and sediment discharge rates ranging from 0.00017 to 0.0356 kg s−1 depending on the soil and boundary conditions imposed. Nearly all experimental runs resulted in steady‐state soil erosion, wherein the headcut developed attained a constant rate of migration, shape, and sediment discharge as a function of time. These experimental observations were successfully compared with predictive equations for mass conservation, jet entry angle, maximum scour depth, and migration rate developed for actively migrating headcuts in upland concentrated flows. These results further demonstrate that systematic headcut development can occur in a range of soils, slopes, and flow rates, and that modified jet impingement theory can be used to predict the erosional characteristics of these headcuts, thus providing the necessary analytical framework for improving soil erosion prediction technology.

A three‐dimensional numerical simulation of spreading umbrella clouds

During explosive volcanic eruptions, an eruption column buoyantly rises as a turbulent plume, and an umbrella cloud spreads laterally as a gravity current at the neutral buoyancy level. The source conditions of explosive eruptions such as mass discharge rates of magma at vents have been estimated from the field observations (e.g., satellite images) on the height of the eruption columns and the spreading rate of umbrella clouds on the basis of the one‐dimensional (1‐D) plume model and the gravity current model. However, these simplified models contain empirical constants (entrainment coefficient of turbulent plume, k, and Froude number of gravity current, λ) that should be justified. We developed a time‐dependent three‐dimensional (3‐D) numerical model of eruption clouds to independently determine the values of these constants. The 3‐D model is designed to calculate quantitative features of turbulent mixing between an eruption cloud and the ambient air without any a priori empirical constants by applying a sufficiently fine grid size with a third‐order accuracy scheme. It has reproduced the fundamental features of eruption clouds including eruption columns, pyroclastic flows, coignimbrite ash clouds, and umbrella clouds. The altitudes of the spreading umbrella clouds in the 3‐D simulations are consistent with those of the neutral buoyancy level of eruption columns estimated by the 1‐D plume model with the entrainment coefficient k ∼ 0.1. The relationship between the volumetric flow rate and the spreading rate of the umbrella cloud in the 3‐D simulations is explained by the axisymmetrical gravity current model with λ ∼ 0.2 for eruption clouds in the tropical atmosphere and λ ∼ 0.1 for those in the midlatitude atmosphere. On the other hand, the total column height in the 3‐D simulations strongly oscillates even for a constant mass discharge rate, and its time average tends to be substantially greater than the column height estimated by the 1‐D plume model with k ∼ 0.1, particularly for large‐scale eruption clouds in the midlatitude atmosphere. We recommend a method to estimate the mass discharge rate from the observation of the column height or the spreading rate of umbrella cloud. The method and the accuracy of the 3‐D simulations are tested on the basis of the field data (e.g., the total height of the eruption column, the altitude and the spreading rate of the umbrella cloud, and the mass discharge rate) of the Pinatubo 1991 eruption.

Afterhyperpolarization time-course and minimal discharge rate in low threshold motor units in humans

The alpha-motoneurone afterhyperpolarization (AHP) duration correlates with a number of its muscle unit properties in animal preparations. In humans, the interval death rate (IDR) analysis has been used to estimate the time course of human motoneurone AHP based on the pattern of motor unit firing. The purpose of this experiment was first, to examine the relationship between estimated AHP time course and the minimal firing rate of the motor unit and second, to examine the relationship between the AHP and motor unit contractile properties in the tibialis anterior (TA) muscle. Motor unit data were obtained from the TA muscle during low force isometric contractions lasting 600 s. Muscle unit twitch characteristics were determined using spike-triggered averaging (STA) and the motoneurone AHP time course was estimated using the IDR analysis. Minimal discharge rate and derecruitment threshold torque were determined for 2 s preceding motor unit derecruitment. The AHP time constant and minimal discharge rate were negatively correlated, whereas the derecruitment threshold torque was not associated with the AHP time constant. The estimated AHP duration, however, is considerably shorter than the mean ISI of the minimal discharge rate suggesting that synaptic noise and AHP duration are important factors in dictating the minimal discharge rate in low force voluntary contractions in humans. The AHP time constant did not vary significantly with motor unit twitch amplitude; however, significant positive relationships were found between the AHP time constant and the temporal properties of the motor unit twitch. The calculated AHP time course using the IDR analysis, therefore, is a reasonable estimate and coupled with motor unit properties attained with STA, it provides a powerful method to describe low-threshold motor units.

小円板上での粒子崩落量制御による超音波場利用型湿式粒子微量定量供給

In order to continuously feed small particles into a container for wet particulate materials, an ultrasonic wet microfeeder equipped with a small disk under a nozzle was developed and the performance was evaluated under various operating conditions. The behavior of particles on the disk and their discharge rate from the microfeeder, Ni(s-1), were measured using small spherical and irregular particles. It was experimentally confirmed that the particle discharge rate Ni depended on such variables as nozzle/disk clearance, particle's shape and size, applied voltage and frequency, and disk surface roughness. By controlling the above variables appropriately, constant discharge rate could be obtained in the range of nearly 100-3000, 60-900, and 20-300s-1 respectively for spherical particles of 81, 127 and 180μm in average diameter dp.

The pain-induced decrease in low-threshold motor unit discharge rate is not associated with the amount of increase in spike-triggered average torque

Objective Activation of nociceptive afferents decreases motor unit discharge rates in static contractions. There is also evidence that during experimental muscle pain the motor unit twitch force increases, which has been hypothesized to compensate for the decrease in discharge rate to maintain constant force. This study examined whether there is an association between the magnitude of change in motor unit discharge rate and the amount of increase in the spike-triggered average torque during experimental muscle pain. Methods Sixteen subjects performed three constant-torque isometric ankle dorsi-flexions at 10% of the maximal force (MVC) alternated with two contractions at constant discharge rate of a target motor unit, before and following injection of 0.5 ml of hypertonic (painful) or isotonic (control) saline into the tibialis anterior muscle. Results The discharge rate of the target unit at 10% MVC decreased following injection of hypertonic saline ( P < 0.05; mean ± SD, before: 9.9 ± 1.3 pulses per second, pps; after injection: 8.9 ± 1.0 pps). The peak of the spike-triggered average torque increased with pain ( P < 0.05; before: 0.56 ± 0.55 mNm; during pain: 0.95 ± 1.02 mNm) but the increase was not correlated with the decrease in discharge rate ( R = 0.08). Propagation velocity and action potential peak-to-peak amplitude did not change with pain. Conclusions The pain-induced modifications in the estimated motor unit twitch torque (1) were not caused by changes in muscle fiber action potential, and (2) were not associated with the decrease in discharge rate. Significance Maintenance of constant force during static painful contractions is not explained by a matching between changes in contractile and control motor unit properties.