Main Discharge Research Articles

Study of the implementation of SPDA (Air Discharge Protection System in a school in Manaus city - AM

Brazil is a country with high incidences of atmospheric discharges and during the year, several people are killed by these discharges. The main known discharge protection measure is the SPDA (Atmospheric Discharge Protection System). In this sense, this work proposes to present the measurements of SPDA (System of Protection Against Atmospheric Discharges) in a school located in the city of Manaus and its role for local security, by measuring the variables of an SPDA system, demonstration of the technical conditions of the SPDA and arguments that point out the relevance of the correct procedure for the realization of this process and importance of spda. For this, bibliographic research and on-site field study of the entire spda installation process was carried out in the buildings, multi-sport court and school water box. According to the studies conducted, it was observed that as measurements of ohmic resistances measured were low, very close to 0 ohms. The stress measures were collected, which were also low. The INSTALLED SPDA went to the Cage of Faraday and Franklin. For the school under study, the implanted SPDA obeyed all the standards that regulate it. The college is an environment frequented by many people of different age groups, the installation of spda implanted and sized ensures the protection of heritage, as well as safety and protection to life, because in case of an atmospheric discharge, there is a system who will receive it and lead it there is a path designed for it. If there were no, the building would be fully exposed to this risk and so would people. Therefore, even if spda does not guarantee absolute protection, the protection range it meets is representative, thus ensuring in a certain way the safety of people and protection of building and people. It was also found that the maintenance of the SPDA should be done annually from the start date of the technical report, to ensure the effectiveness of the system.

Reversible hybrid sodium-CO2 batteries with low charging voltage and long-life

A reversible long-life hybrid Na-CO2 battery is proposed by using Na3Zr2Si2PO12 solid electrolyte as a separator, N-doped single-wall carbon nanohorns (N-SWCNH) as a catalyst and the saturated NaCl solution as an aqueous catholyte. The Na3Zr2Si2PO12 ceramic not only has high Na+ ion conductivity, but also prevents potential contamination from H2O and CO2 to sodium anode, and avoids the internal short-circuit touch of Na dendrite with cathode, improving the safety of the battery. Benefiting from N dopants, unique internal and interstitial nanoporous structures, N-SWCNH have large surface area for discharge products accumulation, offer substantial structural defect sites for CO2 adsorption and electron transfer, contributing to high catalytic activity and reversibility. Most importantly, the hybrid Na-CO2 battery with aqueous electrolyte facilitates the dissolution of the insulated discharge product, which overwhelmingly improves the discharge and charge reactions kinetics. Na-CO2 batteries exhibit a low charging voltage of 2.62 V and a small voltage gap of 0.49 V at a current density of 0.1 mA cm−2, a superior discharge capacity of 2293 mAh·g−1 at a current density of 0.2 mA cm−2, a high round trip efficiency of ~68.7% after 300 cycles. In-situ Raman and ex-suit XRD analyses convincingly show that NaHCO3 and carbon are the main discharge products.

Fast Ionization Waves in Extended Capillaries Initiated by High-Voltage Pulses With Varying Rise Rates: A Numerical Investigation

This article presents the results of numerical investigations of initial stages of a fast capillary discharge—initiation and propagation of a fast ionization wave and consequent formation of a conducting plasma channel. Simulations were performed for the case of a 10 cm-long narrow capillary filled with argon at 270 Pa. The wave was created by voltage pulses of negative polarity with an amplitude of 10 kV and rise times varying in the 5–40 ns range, which is comparable with switching times of conventional switching devices based on gas discharges. Obtained spatio-temporal distributions of main discharge parameters were used to study the wave dynamics in general and the structure of the wavefront and the plasma channel. Simulations have revealed that the total wave propagation time is comparable to the voltage rise-time and varies linearly from 10 to 30 ns for the considered rise-time range. It is further shown that for longer voltage rise-times, it is possible for the wavefront to reach the anode well before the applied voltage reaches the maximum, which can potentially result in suboptimal initiation of a fast capillary discharge with lower current rise rates and less effective energy input.

Profile formation of emission current of grid plasma cathode in a longitudinal magnetic field

The paper presents a gas discharge system for a grid plasma cathode which provides the generation and transport of an intense pulsed (20–250 µs) electron beam with an energy of up to 25 keV and current of up to 500 A (against its nominal value of 300 A) in a longitudinal magnetic field of 20–50 mT. The main feature of the plasma-cathode discharge system is its stable operation with no discharge constriction in an inhomogeneous magnetic field (5–30 mT) which penetrates in the system from the beam transport region. The system shows stable initiation and operation of its main discharge without current cutoffs at an argon pressure of (2–8)×10–2 Pa, which has been attained by optimizing the geometry of its electrodes as well as the position and orientation of its permanent magnets. When transported in a magnetic field, the beam current reaches its maximum at the beam center. For controlling the cross-sectional beam homogeneity, the initial distribution of the emission current from the plasma cathode is varied by varying the magnetic field penetrating in the discharge system and the current flow at its redistributing electrode. Such corrections of the initial current from the cathode provides a more homogeneous (±10%) energy distribution over the beam cross-section after transport to a distance of 300 mm.

Comparison of Magnetic Field Characteristics Produced by Three-Electrode Spark Gap Switch and Thyristor Switch in Power Pulsed Systems

Spark gap switches with three electrodes and thyristor switches were used in the pulsed power supply system of the electromagnetic launcher. Electromagnetic field radiation from switches could cause electromagnetic interference damage to the devices. In order to analyze the problem, electromagnetic field radiation waveforms around two typical switches were measured by the B-dot. Based on the wavelet analysis method, time–frequency characteristics of the radiation field are compared for the two types of switches. The results represent that the maximum frequency of the thyristor switches’ signal is much lower than that of the spark gap switches’ signal, according to the frequency distribution. The turn-on time of the spark gap from the initial triggering time to the main discharge time is 0.024 ms'C and the variation is limited to less than 0.008 ms. The maximum frequency duration is about 0.005 ms, and the variation is limited to less than 0.003 ms. The maximum signal amplitude of thyristor switches is lower than that of spark gap switches. The comparison and results will benefit the compatibility design of the system.

A limit value of the volume discharge ignition frequency in dense gases

There is deduced analytical expression for maximum value of the volume discharge ignition frequency in dense gases. That expression indicates the way for achieve maximal values of pulse repetition rates in CO2-lasers at atmospheric and super-atmospheric pressures. The increasing of pulse repetition rates is connected with sectioning of main discharge gap and excitation of volume discharge in each section from separate pulse pumping generator. This work is devoted to describing of constructions and main characteristics of some types compact pulse generators with amplitude of voltage pulses up to 200 kV, rise-times about 10 nanoseconds and pulse energy per pulse up to 20 J. For reduction of rise-time of high-voltage pulses were used spark-discharge two electrodes commutators (sharpeners) at working pressures up to 100 atm.

Study on Crystal Growth Kinetics and Preferred Orientation for LiF Crystal in Dimethyl Sulfoxide/1,3-Dioxolane-based Electrolyte

The Li/CFx primary battery with the highest energy density has been widely applied in many fields. However, the Li/CFx battery has been suffering from some problems for large-scale applications, such as low energy density, which needs to be overcome urgently. Among the technical solutions, the modification of the discharge product layer is an effective approach to solve the problem. To adjust the pore structure of the discharge product layer, it is necessary to explore both the growth and the orientation kinetics of LiF crystals as the main discharge product of Li/CFx batteries. In this work, the growth kinetics of the LiF crystal during discharge in dimethyl sulfoxide/1,3-dioxolane (DMSO/1,3-DO)-based electrolytes is first explored by kinetic models of crystal growth. The calculated results show that the nucleation and nuclei growth mechanism is best suited for the growth kinetics of the LiF crystal in the DMSO/1,3-DO (5:5 v/v)-based electrolyte, which is different from the 2D diffusion mechanism of the LiF crystal in the PC/DME (5:5 v/v). Then, the orientation kinetics of LiF crystals is investigated by using quantum-chemical calculations. The simulation results reveal that the total chemical adsorption energies of both DMSO and 1,3-DO solvent molecules on the crystal planes of LiF could change with the ratio variation of DMSO/1,3-DO. The preferred crystal orientation growth of the LiF grain during discharge mainly depends on the total chemical adsorption energy on each crystal plane of LiF, which is caused by the selective adsorption of both DMSO and 1,3-DO on different crystal planes. The study of the growth kinetics of LiF grains and the preferred orientation growth can help our understanding of the structure control mechanism of discharge products of LiF. In general, this work may pave the way for the future development of a novel electrolyte of the large-capacity Li/CFx battery with high power density.

Catheter ablation of ventricular arrhythmias and in-hospital mortality: insights from the German-wide Helios hospital network of 5052 cases.

Catheter ablation (CA) of ventricular arrhythmias is one of the most challenging electrophysiological interventions with an increasing use over the last years. Several benefits must be weighed against the risk of potentially life-threatening complications which necessitates a steady reevaluation of safety endpoints. Therefore, the aims of this study were (i) to investigate overall in-hospital mortality in patients undergoing such procedures and (ii) to identify variables associated with in-hospital mortality in a German-wide hospital network. Between January 2010 and September 2018, administrative data provided by 85 Helios hospitals were screened for patients with main or secondary discharge diagnosis of ventricular tachycardia (VT) or premature ventricular contractions (PVCs) in combination with an arrhythmia-related CA using ICD- and OPS codes. In 5052 cases (mean age 60.9 ± 14.3 years, 30.1% female) of 30 different hospitals, in-hospital mortality was 1.27% with a higher mortality in patients ablated for VT (1.99%, n = 2, 955) compared to PVC (0.24%, n = 2, 097, P < 0.01). Mortality rates were 2.06% in patients with ischaemic heart disease (IHD, n = 2, 137), 1.47% in patients with non-ischaemic structural heart disease (NIHD, n = 1, 224), and 0.12% in patients without structural heart disease (NSHD, n = 1, 691). Considering different types of hospital admission, mortality rates were 0.35% after elective (n = 2, 825), 1.60% after emergency admission/hospital transfer <24 h (n = 1, 314) and 3.72% following delayed hospital transfer >24 h after initial admission (n = 861, P < 0.01 vs. elective admission and emergency admission/hospital transfer <24 h). In multivariable analysis, a delayed hospital transfer >24 h [odds ratio (OR) 2.28, 95% confidence interval (CI) 1.59-3.28, P < 0.01], the occurrence of procedure-related major adverse events (OR 6.81, 95% CI 2.90-16.0, P < 0.01), Charlson Comorbidity Index (CCI, OR 2.39, 95% CI 1.56-3.66, P < 0.01) and its components congestive heart failure (OR 8.04, 95% CI 1.71-37.8, P < 0.01), and diabetes mellitus (OR 1.59, 95% CI 1.13-2.22, P < 0.01) were significantly associated with in-hospital death. We reported in-hospital mortality rates after CA of ventricular arrhythmias in the largest multicentre, administrative dataset in Germany which can be implemented in quality management programs. Aside from comorbidities, a delayed hospital transfer to a CA performing centre is associated with an increased in-hospital mortality. This deserves further studies to determine the optimal management strategy.

2D axial-azimuthal particle-in-cell benchmark for low-temperature partially magnetized plasmas

The increasing need to demonstrate the correctness of computer simulations has highlighted the importance of benchmarks. We define in this paper a representative simulation case to study low-temperature partially-magnetized plasmas. Seven independently developed particle-in-cell codes have simulated this benchmark case, with the same specified conditions. The characteristics of the codes used, such as implementation details or computing times and resources, are given. First, we compare at steady-state the time-averaged axial profiles of three main discharge parameters (axial electric field, ion density and electron temperature). We show that the results obtained exhibit a very good agreement within 5% between all the codes. As discharges are known to cause instabilities propagating in the direction of electron drift, an analysis of these instabilities is then performed and a similar behaviour is retrieved between all the codes. A particular attention has been paid to the numerical convergence by varying the number of macroparticles per cell and we show that the chosen benchmark case displays a good convergence. Detailed outputs are given in the supplementary data, to be used by other similar codes in the perspective of code verification.

Laboratory assessment of alternative stream velocity measurement methods.

Understanding streamflow in montane watersheds on regional scales is often incomplete due to a lack of data for small-order streams that link precipitation and snowmelt processes to main stem discharge. This data deficiency is attributed to the prohibitive cost of conventional streamflow measurement methods and the remote location of many small streams. Expedient and low-cost streamflow measurement methods used by resource professionals or citizen scientists can provide scientifically useful solutions to this data deficiency. To this end, four current velocity measurement methods were evaluated in a laboratory flume: the surface float, rising body, velocity head rod, and rising air bubble methods. The methods were tested under a range of stream velocities, cross-sectional depths, and streambed substrates. The resulting measurements provide estimates of precision and bias of each method, as well as method-specific insight and calibration formulas. The mean values of the coefficient of variation, a measure of precision, were 10% for the surface float, 10% for the velocity head rod, 14% for the rising body, and 9% for the air bubble method. The values of scaled mean error, a measure of bias, were -8% for the surface float, -4% for the velocity head rod, -1% for the rising body, and 4% for the air bubble. The velocity head rod and surface float methods were the easiest methods to use, providing greater precision at large (> = 0.6 m/s) and small (<0.6 m/s) velocities, respectively. However, the reliance on a velocity ratio for each of these methods can generate inaccuracy in their results. The rising body method is more challenging to execute and of lower precision than the former two methods but provides low bias measurements. The rising air bubble method has a complex instrument assembly that is considered impractical for potential field user groups.

Measuring method for partial discharges in a high voltage cable system subjected to impulse and superimposed voltage under laboratory conditions

A partial discharge (PD) measuring system has been deployed in order to identify and measure PD in a high voltage (HV) cable joint under impulse and superimposed voltages under laboratory conditions. The challenge is to enable the detection of PD during the impulse conditions. The method of measurement has been investigated by introducing an artificial defect in the cable joint in a controlled way to create conditions for partial discharges to occur. Next the HV cable system is subjected to AC, impulse and superimposed voltage. Two high frequency current transformers (HFCT) installed at both ends of the cable joint were used to identify PD from the cable joint and to separate PD from disturbance. Transient voltage suppressors and spark gaps are applied to protect the measuring equipment. Band pass filters with selected characteristics are applied to suppress transient disturbances and increase the chance to detect PD during the impulse. PD signals are separated from transient disturbances during data post processing and by means of pulse polarity analysis. The developed system enables the detection of so-called main and reverse discharges respectively occurring during the rise and tail time of the superimposed impulse. The measurement results obtained show the effectiveness of the presented PD measuring system for investigating the effects of voltage transients on a HV cable system in laboratory conditions.

Velocity distribution characteristics in meandering compound channels with one-sided vegetated floodplains

To discuss the effects of asymmetrically vegetated floodplains on the velocity distribution characteristics and discharge capacity of a meandering main channel, in this paper, continuous river bend models with smooth floodplains and one-sided vegetated floodplains were designed in a generalized way. Three-dimensional instantaneous velocity data were obtained with an Acoustic Doppler Velocimeter (ADV), and the velocity distribution characteristics and discharge capacities of the generalized models were compared. Compared with the smooth floodplain conditions, the one-sided vegetated floodplain conditions are associated with lower cross-sectional average velocities, lower ratios of main channel discharge to total discharge near the bending apexes with minimal extension of vegetated floodplain, but higher ratios near the bending apex with maximal extension of vegetated floodplain. The deflection degrees of depth-averaged velocities in the meandering main channel are related to the cross-sectional position, relative depth and floodplain vegetation. The depth-averaged velocities near the bending apexes are inclined towards the main channel concave sides, those in the upstream crossover area are generally inclined towards the vegetated side, and those in the downstream crossover area are obviously inclined towards the smooth side. For a given relative depth, the deflection degrees near the bending apexes are smaller than those in the crossover areas. The deflection degrees near the bending apexes with minimal extension of vegetated floodplain are smaller than those under smooth floodplain conditions, but the deflection degrees near the bending apex with maximal extension of vegetated floodplain are obviously larger than the corresponding values under smooth floodplain conditions. Near the bending apexes, the longitudinal depth-averaged velocities are higher close to the main channel convex side and lower adjacent to the concave side. When the relative depth is small, one-sided vegetated floodplain conditions feature larger transverse gradients of the cross-sectional longitudinal depth-averaged velocities near the bending apexes with minimal extension of vegetated floodplain. When the relative depth is large, the transverse gradients near the bending apexes with minimal extension of vegetated floodplain are all much smaller than the corresponding values of the smooth floodplain conditions. However, near the bending apex with maximal extension of vegetated floodplain, there are no significant differences concerning the transverse gradients of the cross-sectional longitudinal depth-averaged velocities under the both floodplain conditions. One-sided vegetated floodplain conditions significantly influence the longitudinal velocity distributions in the meandering main channel. For a given relative depth, the longitudinal velocities at the cross-sectional positions under one-sided vegetated floodplain conditions are lower than those under smooth floodplain conditions to varying extents.

Continuous‐wave plasma‐generated electric field in 3D collagen gel during cold atmospheric plasma treatment

AbstractCold atmospheric plasma (CAP) devices based on a plasma jet with helium flow are actively used nowadays in the studies of cancer treatment. In addition to well‐known factors produced by CAP devices (reactive chemical species, UV radiation, heat) that can reduce the viability of cancer cells, the effect of alternating continuous‐wave nonthermal electromagnetic fields generated by a plasma source inside the tissue remains unclear. In this article, we measured the values and frequency composition of the continuous‐wave electric field induced inside the model of a living tissue—a three‐dimensional artificial tissue composed of bovine type I collagen gel—during its irradiation with a helium plasma jet using the set of probes immersed into the gel. It was found that the electric field in artificial tissue has strong direct current (DC) with the main discharge frequency components, and at least up to four harmonics of the discharge frequency. The e‐field absolute values in artificial tissue during plasma treatment were within 300–30,000 V/m, which is significantly lower than the estimated cell membrane field of about ~107 V/m. The absolute value of the e‐field DC component nonmonotonically depends on discharge frequency with the optimal frequency range of 14–16 kHz dependent on the thickness of the artificial tissue.

Accuracy and sensitivity of radium mass balances in assessing karstic submarine groundwater discharge in the stratified Calanque of Port-Miou (Mediterranean Sea)

Submarine Groundwater Discharge (SGD) has received increased attention in recent years since it was recognized that it may be both volumetrically and chemically important. Around the Mediterranean Sea, 60% of the coastline is composed of karstic aquifers, and to properly estimate the hydrological budget of the Mediterranean Sea it is therefore necessary to better assess the karstic submarine groundwater discharges (KSGD). However, quantifying KSGD is still challenging. Among the methods recently developed to detect and quantify SGD, the mass balance method of the radium quartet 223Ra, 224Ra, 226Ra and 228Ra has proved to be a powerful technique. This approach requires characterizing all the contributing terms and sinks in the coastal water volume affected by SGD, the residence time of coastal waters, as well as a representative concentration of the tracers for both surface water and discharging groundwater. In this study we combine several approaches (223Ra, 224Ra, salinity profiles and Acoustic Doppler Current Profiler (ADCP) measurements) to examine both the accuracy and sensitivity of the radium mass balance method in the case of the cove of Port-Miou (Mediterranean Sea, France) where the main karstic spring discharges locally at 10 m depth. This study benefits from the inland in-situ access to the main karst conduit discharging to the sea which provides a long time series to characterize the brackish submarine groundwater end-member. We show that the composition of the cove water is stratified, with two water bodies: a surface brackish layer and a deeper layer. The mean KSGD value obtained with 223Ra and 224Ra mass balances in the surface water body is precise but significantly lower (0.6 ± 0.1 m3/s) than the karstic spring discharge (4 ± 1 m3/s) estimated within the karst conduit with pressure sensors. The residence time of the cove water estimated using both 224Ra and 223Ra isotopes is very low (1 ± 1 day). Our study shows that the water residence time that we calculated using the Ra mass balance is the key parameter that may impact KSGD. In addition, based on ADCP transects, we suggest that the shape and geometry of the cove, as well as the location of the discharge point of the spring play a key role in explaining these discrepant results. We therefore recommend that in such stratified coves, estimations of KSGD based on short-lived radium isotopes require accurate and independent estimates of the water residence time as well as a good knowledge of the shallow and deep circulation patterns of the cove water.

Non-Self-Sustained Hollow-Cathode Glow Discharge at Low Burning Voltages

The results of investigations of low-voltage burning modes of a non-self-sustained glow discharge with a ~0.2 m3 hollow cathode at low (≈1 Pa) pressure, which is assisted by an external injection of electrons from the electric-arc plasma. The current-voltage characteristics recorded at low burning voltages 20–80 V demonstrate that there is a threshold glow-discharge burning voltage, at which a stepwise transition takes place from the burning conditions with high plasma inhomogeneity to the conditions of homogeneous plasma glow in the entire volume of the hollow cathode. This transition, accompanied by an enhanced hollow-cathode effect, is characterized by a 20–40% increase in the main discharge current. The glow discharge burning voltage, at which this current jump takes place lies within the range 45–60 V and depends on the value of the auxiliary discharge current and working pressure.

Numerical study on the discharge pattern evolution in an atmospheric pressure helium dielectric barrier discharge under the variation of nitrogen admixture content

We report a systematic numerical study concerning the effect of traces of nitrogen admixtures on the discharge pattern dynamics in an atmospheric helium dielectric barrier discharge. By gradually increasing the N2 concentration from 1 to 1000 ppm, the discharge mode transformed from the stationary pattern, via quasi-uniform structure, stationary pattern, into the complementary pattern. Analyses revealed that Penning ionization exerted a significant influence on the electron distribution, surface charge deposition and electric field profile over the gap and thus induced the transitions in pattern structure. With the increase of N2 content, the average rate of Penning ionization within the afterglow stage presented a non-monotonic variation trend, which conformed to previous results, and seed electron level of the main discharge varied in a similar way. When the discharge was ignited with a large amount of seed electrons, the electron distribution prior to the breakdown phase tended to homogenize and the level of radial electric field during the pre-ionization process was restrained, contributing to the homogenization of the discharge. Furthermore, the formation of complementary discharge pattern was believed to be resulted from the excessive reduction of average electron density between two adjacent main discharges at above 500 ppm N2 level. The reduced electron concentration made the volume ionization more susceptible to the surface charge distribution and led to the disruption of discharge channel succession between positive and negative half cycles.

An RF ion source model for H-production

A 1D model of an RF driven ion source based on ionisation by thermal electrons is presented. The RF source differs from traditional filament and arc ion sources because there are no primary electrons present, and is simply composed of an antenna region (driver) and a main plasma discharge region. However the model does still make use of the classical plasma transport equations for particle energy and flow, as used previously in DC source models where they have worked well. The model currently uses the geometry and other source parameters of the Small Negative Ion Facility (SNIF) ion source at CCFE and only considers the hydrogen ion species, but may be easily adapted to model other RF sources. The model provides a detailed description of the plasma parameters along the source axis, i.e. plasma temperature, density and potential, as well as current densities and species fluxes, but does not consider the RF matching unit. The inputs to the model are the source geometry, RF power, the magnetic filter field, the source gas pressure and the plasma grid insert bias. Results from the model are presented and where possible compared to existing experimental data from SNIF, with varying RF power, source pressure and insert bias.

Combining hydrodynamics, hydrochemistry, and environmental isotopes to understand the hydrogeological functioning of evaporite-karst springs. An example from southern Spain

This work adopts a multicriteria approach, combining diverse karst hydrogeology techniques, to investigate the functioning of evaporite-karst systems, which are normally less studied due to the poor quality of their water resources. The applicability of using several methods was also verified. In view of previous experience at a pilot site within southern Spain, the natural responses of the main discharge point of the system of study (Lower Anzur spring) were controlled by continuous monitoring of the discharge rate, water temperature, and electrical conductivity. Water samples were collected for chemical analysis and for the determination of intrinsic fluorescence, water stable isotopes (δ18O, δ2H) and tritium (3H) concentrations. Physico-chemical data were statistically examined applying principal component analysis (PCA) and trend analysis tests (Mann-Kendall and Sen’s slope). The system shows a clear karstic functioning, highly dependent on concentrated recharge, and influenced by a limited drainage capacity of the conduit network. The piston-flow effects at the beginning of floods indicate a contribution to the drainage of deep ascending flows through the saturated zone. Subsequent drops in temperature and mineralization values in the water drained by the spring, as well as a recent infiltration deduced from the signature of intrinsic fluorescence and stable isotopes, point to a good hydrogeological connection from the recharge areas to the spring. Later restoration of the initial values of mineralization —in a much shorter time than those of temperature— reveals a faster geochemical evolution of the recently infiltrated groundwater, which may be a distinctive trait of evaporite karst aquifers. Lastly, the high solute content of the spring water in depletion conditions, with ascending trends of mineralization and temperature observed during several dry years as a consequence of lower recharge contribution, together with the tritium activity of selected samples, suggest the existence of an old component partly responsible for the spring base flow. Thus, groundwater would be linked to gravity-driven regional flows, but also to recent conduit flows. All the results obtained led us to devise a hydrogeological conceptual model to precisely reflect the functioning of the studied system. The results presented here demonstrate the advantages of using diverse techniques when investigating evaporite karst aquifers.

Effect of Main Cut and Multiple Trim Cuts on Surface Integrity of 2379 Steel

Wire electrical discharge machine (WEDM) is commonly used in producing tool and die parts. However, it rarely achieves the optimum machining condition due to the inappropriate selection of WEDM machining parameters. In this study, 2379 steel which own properties equivalent to SKD 11 was used as die material. Four main wire electrical discharge machine (WEDM) cutting parameters, namely pulse on time, pulse off time, servo voltage, ignition pulse current has been experimentally studied and optimized at both levels, main cut and multiple trim cuts using Taguchi Method. Based on Taguchi Method optimization and analysis of variance (ANOVA), the result found that pulse on time and pulse off time give significant effect on white layer thickness for both main cut and multiple trim cuts. According to Signal to Noise (S/N) ratio response, the optimal combination of A2B3C2D1 and A1B3C3D1 gave the lowest white layer thickness for main cut and multiple trim cuts respectively. It also has been found that the hardness of machined surface with multiple trim cuts is higher compared to main cut.

Distribution of phosphorus in bed sediment at confluences responding to hydrodynamics

Knowledge of the distribution of contaminants at channel confluences is critical for understanding their transport and dwelling at river networks where flow confluences constitute the key nodes. Flume experiments were conducted to study the distribution of phosphorus adsorption in surface sediment under complex hydrodynamics at channel confluences. The influence of the discharge ratio of the tributary discharge to the main stream discharge was also investigated. The results showed that the horizontal velocity and vertical velocity of flow are the dominant factors affecting the distribution of phosphorus adsorption. Flows with a larger horizontal velocity are not beneficial to phosphorus adsorption on sediment and thus low- and high-adsorption strips of phosphorus occur in the maximum velocity zone and the flow separation zone, respectively. Downwelling flows are beneficial to phosphorus adsorption on sediment as they can enhance phosphorus exchange between overlying water and the bed sediment. A small flow penetration with a small discharge ratio causes a decrease in vertical velocity in the separation zone as well as the strong intrusion of a helical cell into the bottom of this zone, which results in an increase in horizontal velocity near the bed and consequently the phosphorus adsorption is largely restricted.