Direct Flow Research Articles

Numerical simulation study of enhanced convective heat transfer in the tube based on winglet vortex generator

In order to enhance the heat transfer effect and improve the energy utilization efficiency of the circular tube under turbulent flow, rhombic and triangular winglet vortex generators are proposed on the basis of rectangular winglet vortex generator. The effects of three vortex generators on flow and heat transfer in the tube are investigated by numerical simulations. The results indicate that, the rectangular and triangular winglets generate two pairs of longitudinal vortices and the triangular winglets generate four pairs of longitudinal vortices due to additional shrinkage regions. The multiple longitudinal vortices increase the mixing between the fluids, raise the temperature in the central region of the tube, and enhance the heat transfer effect. Furthermore, the triangular winglet enhanced tube has the largest direct flow area and the least effect on resistance. The triangular winglet enhanced tube had the best comprehensive performance, followed by the rhombic winglet enhanced tube, and finally, the rectangular winglet enhanced tube. The performance evaluation criterion (PEC) reached 1.04-1.13, 1.05-1.15, and 1.08-1.21 for the three enhanced tubes in the given flow rate interval. In addition, the effect of inclination angle on the triangular winglet enhanced tube was further investigated, and the results show that the best comprehensive performance of enhanced heat transfer is achieved at an inclination angle of 45?, with a maximum PEC of 1.25.

Curie point depth from airborne magnetic data analysis for geothermal exploration in southern Thailand

Southern Thailand is a high heat flow region, which implies to high-potential area of geothermal resources. Direct heat flow measurements are only available from petroleum wells in Gulf of Thailand. Therefore, indirect method of Curie Point Depth (CPD) calculation has been used to evaluate the heat flow on land of southern Thailand. CPD is the theoretical depth at which subsurface temperature reaches the value of the Curie point of magnetite, which is 578 °C. CPD can be calculated by deriving the depth of the bottom of the magnetic body to the surface using spectral analysis from airborne magnetic data, and the calculated values can produce the CPD map of southern Thailand. The results show that CPD ranges from 7.88 to 19.75 km with an average of 13.74 km, and heat flow ranges from 61.54 to 154.25 mW/m2 with an average of 90.36 mW/m2. This study suggests that the high heat flow in southern Thailand, which is higher than the regular continental crust heat flow of 65 mW/m2, is possibly caused by a high heat anomaly from mantle upwelling and expressed through weak zones of faults and sutures in extensional tectonic regimes. The high heat from mantle has elevated by five zones: (1) Ranong faults zone, (2) Khlong Marui faults zone, (3) Coastline of Surat Thani and Nakhon Si Thammarat, (4) Trang and Satun zone, and (5) Bentong-Roab suture. These five zones are considered to be high-potential areas for future geothermal resources exploration.

Research and modeling of the ecological efficiency of drying refractory and building materials in vertical shaft furnaces

Based on the hypothesis of the dominant effect on the environmental efficiency of drying materials in shaft furnaces of the concentration, median diameter, dispersion, temperature and humidity of dust particles at the outlet of the dryer, a device for thermal aeration separation of dust is proposed. The analysis of mathematical modeling of aerothermodynamic processes in a two-phase medium asbestos dust ‒ gas flow confirmed the conclusions of industrial studies on the influence of aerothermodynamic parameters of direct flow on the temperature and humidity of asbestos dust in the pneumatic dryer. Based on the principle of additive classification, a mathematical model of aeration separation of dust particles directly in the dryer of the shaft furnace is constructed, depending on the parameters of the heat carrier and the proposed device.

The Influence of the Duration of Exposure to Direct Current on the Treatment Efficiency of Wastewater from Soilless Tomato Cultivation in a Bio-Electrochemical Reactor

The management of wastewater from soilless tomato cultivation poses a technological and economic challenge. Given the above, the aim of this study was to determine the treatment efficiency of wastewater from soilless tomato cultivation in a bio-electrochemical reactor under conditions of direct electric current flow. The treatment efficiency was tested in three time variants of wastewater exposure to the electric current: V1—24 h exposure phase; V2—12 h exposure phase/12 h no exposure phase; and V3—12 h no exposure phase/12 h exposure phase. Experiments were conducted with two organic substrates, sodium acetate and acetic acid, at the C/N ratio of 1.25, with a direct current intensity of 1.25 A·m−2 and hydraulic retention time of 24 h. The study results show the feasibility of achieving a satisfactory technological effect in a bio-electrochemical reactor without the need for electric current flow throughout the 24 h treatment cycle. From the energy consumption and technological standpoints, the most viable approach, ensuring 90.4 ± 1.6% and 94.9 ± 0.7% efficiencies of nitrogen and phosphorus removal, respectively, turned out to be feeding the reactor with sodium acetate and wastewater exposure to the electric current flow only during the first 12 h of the treatment cycle. The scope of the conducted research justifies its continuation in order to determine the optimal time for supplying electricity to the bio-electrochemical reactor and the impact of the C/N value on the nitrogen and COD effluent concentrations.

Flow Diversion for Treatment of Anterior Inferior Cerebellar Artery Aneurysms: Mechanism and Pitfalls from a Novel Management Strategy

Anterior inferior cerebellar artery (AICA) aneurysms present a challenge for neurosurgeons and neurointerventionalists alike. Cases of AICA aneurysms managed with endovascular flow diversion at our institute are reviewed with their angiographic outcomes. Both direct and indirect flow diversion provide complete aneurysm occlusion at follow-up. We propose a stratified method of approaching AICA aneurysms based on location, rupture status, and neck size. Careful evaluation of preoperative parameters is paramount in deciding between a surgical or a neuroendovascular approach. Low-profile stents in the future may assist in direct flow diversion of AICA trunk aneurysms. In addition, neurosurgeons need to be well versed in endovascular approaches.

Numerical simulation of hydrodynamic performance of pump-jet propulsor with serrated trailing-edge duct under different working conditions

Pump-Jet Propulsors (PJPs) have excellent propulsion performance, but the duct makes the internal flow and vortex distribution of PJP more complex. This work presents a serrated modification of the duct trailing-edge of the rear-stator PJP. A Suboff submarine is used to provide wake for PJP, and the propulsion performance and flow field of PJP in self-propelled state are analyzed. In addition, the hydrodynamic coefficients and vorticity fields of two PJPs in oblique flow are compared. The results indicate that the serrated structure can reduce the vorticity magnitude behind the duct, accelerate the shedding of PJP tailing vortex. In direct flow, the higher the inflow velocity, the better the effect of the serrated structure on weakening the wake vortex, which can reduce the vorticity by up to 52.4%. However, the propulsion efficiency of the modified PJP is reduced, but it is within 3%. In oblique flow, the hydrodynamic coefficient and propulsion efficiency of the two PJPs are significantly reduced, and the efficiency of the modified PJP is better than that of the original PJP. The larger the inflow angle, the more obvious the effect of the serrated structure on weakening the wake vortex, and the smaller the loss of propulsion performance.

Abstract 14833: Association of RV Hemodynamics From 4D Flow CMR With RV Restrictive Physiology From Pediatric to Adult Repaired Tetralogy of Fallot

Introduction: Right ventricular restrictive physiology (RVRP) is common after repair of Tetralogy of Fallot (rTOF), especially with residual pulmonary regurgitation. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) quantitates biventricular blood flow components and kinetic energy (KE) parameters, but their association with RVRP is unclear. We aimed to study 4D flow CMR parameters in adult and pediatric rTOF patients vs healthy controls and associations of 4D flow parameters with RVRP in rTOF. Methods: 103 rTOF patients (40 pediatric, 63 adult; age 24±17 years; 53M:50F) and 171 healthy controls (14 pediatric, 157 adult; age 40±15 years; 97M:74F) were prospectively recruited from centers in Singapore (2) and China (1) to undergo 4D flow CMR on multi-vendor scanners. LV and RV flow components—direct flow, retained inflow, delayed ejection flow and residual volume—and KE parameters (normalized to end-diastolic volume, KEi EDV )—global, peak systolic, average systolic, average diastolic, peak E-wave and peak A-wave—were analyzed. KE discordance was calculated as the ratio of RV and LV average systolic KEi EDV . Results: See Table. RVRP was identified in 70 patients (68%). rTOF with RVRP exhibited higher median RV stroke volume index, RV ejection fraction, RV direct flow, RV peak E-wave and E-wave/A-wave, and lower RV residual volume compared to rTOF without RVRP (all P<0.05). Using binary multivariable logistic regression analysis—and after adjustment for age, pulmonary regurtitation, LV and RV ejection fraction, RV direct flow was found to be independently associated with RVRP in rTOF (P<0.001). Conclusion: Patients with RVRP had higher RV direct flow, RVEF and RV peak E-wave energy, indicating the potential compensatory adaptations in patients with RVRP.

Optimizing a direct flow cooling battery thermal management with bod baffles for electric vehicles: An experimental and simulation study

The scarcity of energy and environmental pollution are increasingly becoming serious issues. Encouragement for the use of electric vehicles (EVs) has become a preferred solution. The battery thermal management system (BTMS) is one of the core modules for ensuring the safe operation of EVs. This paper proposes a direct flow cooling battery thermal management system (DFC-BTMS) with rod baffles for EVs. It uses a lipid organic liquid as the coolant and rod baffles as the flow disturbance structures in the flow channel. Based on extensive experimental and simulation results for 18,650-type battery, DFC-BTMS is empirically analyzed. The experimental results show that DFC-BTMS can control the average surface temperature of the battery within the safe range at a 4C discharge rate. This paper also optimizes the distance of the rod baffles and the length of the battery pack through simulation. The optimized system is comprehensively evaluated based on the Performance Evaluation Criterion (PEC). At a 3C discharge rate and a volume flow rate of 2 LPM, the optimized DFC-BTMS results in a maximum average surface temperature of 24.789 °C and a maximum temperature difference of 2.734 °C for the battery pack. The system PEC is 3.07. The proposed DFC-BTMS can provide an innovative thermal management solution for EVs.

Reducing Aerodynamic Drag on Flatbed Trailers for Passenger Vehicles Using Novel Appendable Devices

This article presents a study on the aerodynamic drag of a generic dual-axle flatbed trailer and explores ways to reduce the drag using appendable drag-reducing devices. The primary sources of drag originated from the van and trailer’s rear, along with the trailer’s wheels. The most-effective initial device for reducing drag was a full trailer underside cover, which offered a 7% drag reduction. Additionally, ladder racks, dropsides, and rear gates were studied, and it was found that protruding ladder racks significantly increased drag. Rear gates added large amounts of drag and should be removed and stored when not needed. The study also explored novel mid-section devices that increased the van’s base pressure and reduced drag. An axle test revealed that drag for single-, dual-, and triple-axle trailers was very similar in direct flow, but different in yawed flow. A drawbar length test showed a near-linear relationship between drawbar length and drag, manifesting as a 1.7% change in drag per 250 mm change in drawbar length. Several novel modifications were made to the trailer, including fitting six unique appendable devices, which offered a total 7.3% drag reduction. A novel rear van device known as the multi-stage converging cavity was introduced, which reduced drag by nearly 18%. When all the devices were used together, a total 25% drag reduction was observed for the van–trailer combination.

Pentadecapeptide BPC 157 as Therapy for Inferior Caval Vein Embolization: Recovery of Sodium Laurate-Post-Embolization Syndrome in Rats.

After inferior caval vein embolization therapy, post-embolization syndrome (sodium laurate 10 mg/kg, 0.1 mL into rat inferior caval vein, assessment at 15, 30, 60 min, prime lung lesions, thromboemboli occluding lung vessels), as a severe occlusion/occlusion-like syndrome, might be resolved as a whole by stable gastric pentadecapeptide BPC 157 therapy. At 5 min after laurate injection, stable gastric pentadecapeptide BPC 157 was implemented as therapy (10 µg/kg, 10 ng/kg intraperitoneally or intragastrically). As before, confronted with the occlusion of major vessel(s) or similar noxious procedures, such as rapidly acting Virchow triad circumstances, the particular effect of the therapy (i.e., collateral pathways activation, "bypassing vascular key", i.e., direct blood flow delivery via activation of azygos vein) assisted in the recovery of the vessel/s and counteracted multiorgan failure due to occlusion/occlusion-like syndrome as a whole in the laurate-injected rats. Along with prime lung lesions and thromboemboli occluding lung vessels, post-embolization syndrome rapidly occurred peripherally and centrally as a shared multiorgan and vessel failure, brain, heart, lung, liver, kidney, and gastrointestinal tract lesions, venous hypertension (intracranial (superior sagittal sinus), portal, and caval), aortal hypotension, progressing thrombosis in veins and arteries and stasis, congested and/or failed major veins, and severe ECG disturbances. Whatever the cause, these were all counteracted, eliminated, or attenuated by the application of BPC 157 therapy. As recovery with BPC 157 therapy commonly and rapidly occurred, reversing the collapsed azygos vein to the rescuing collateral pathway might initiate rapid direct blood delivery and start blood flow reorganization. In conclusion, we suggest BPC 157 therapy to resolve further vascular and embolization injuries.

Reducing the Flow Maldistribution in Heat Exchangers through a Novel Polymer Manifold: Numerical Evaluation

The maldistribution of working fluid is one of the issues in heat exchangers that causes a reduction in performance of not only the heat exchanger but also the entire HVAC system. One of the methods to reduce such maldistribution is to improve manifold design to evenly distribute the flow. In the present work, an advanced maldistribution reduction manifold, which was based on a preliminary maldistribution reduction manifold, was designed to further improve the flow distribution in the heat exchanger. In the design, spiral baffles are used to create vortices in the tubes to regulate the flow in each tube. The design also keeps the tubes away from the manifold inlet to avoid direct flow from the inlet. Due to the complexity, the design of the advanced maldistribution reduction manifold is for AM only, which cannot be fabricated by traditional manufacturing. To evaluate the design, a computational fluid dynamic model is developed to study flow distribution in heat exchanger manifolds. The simulation results reveal that the relative standard deviation of the tubes in the advanced maldistribution reduction design is half of the preliminary maldistribution reduction design and about 1/20 of the reference design.

Continuing WebAssembly with Effect Handlers

WebAssembly (Wasm) is a low-level portable code format offering near native performance. It is intended as a compilation target for a wide variety of source languages. However, Wasm provides no direct support for non-local control flow features such as async/await, generators/iterators, lightweight threads, first-class continuations, etc. This means that compilers for source languages with such features must ceremoniously transform whole source programs in order to target Wasm. We present WasmFX an extension to Wasm which provides a universal target for non-local control features via effect handlers, enabling compilers to translate such features directly into Wasm. Our extension is minimal and only adds three main instructions for creating, suspending, and resuming continuations. Moreover, our primitive instructions are type-safe providing typed continuations which are well-aligned with the design principles of Wasm whose stacks are typed. We present a formal specification of WasmFX and show that the extension is sound. We have implemented WasmFX as an extension to the Wasm reference interpreter and also built a prototype WasmFX extension for Wasmtime, a production-grade Wasm engine, piggybacking on Wasmtime's existing fibers API. The preliminary performance results for our prototype are encouraging, and we outline future plans to realise a native implementation.

Greater hemodynamic stresses initiate aneurysms on major cerebral arterial bifurcations.

To retrospectively investigate the hemodynamic stresses in initiating aneurysm formation on major cerebral arterial bifurcations with computational fluid dynamics (CFD) analysis. The cerebral 3D angiographic data of major cerebral arterial bifurcations of the internal carotid, middle cerebral, anterior cerebral, and basilar arteries in 80 patients harboring bifurcation aneurysms and 80 control subjects with no aneurysms were retrospectively collected for the CFD analysis of hemodynamic stresses associated with aneurysm formation. Bifurcation angles at major bifurcations in all patients were significantly positively (P < 0.001) correlated with the age. At the center of direct flow impingement (CDFI) on the bifurcation wall, total pressure was the highest but dropped rapidly toward the branches. Wall shear stress, dynamic pressure, strain rate, and vorticity were lowest at the CDFI but they increased quickly toward the branches. The bifurcation angle was significantly (P < 0.001) enlarged in patients with bifurcation aneurysms than those without them, for all major arterial bifurcations. Most aneurysms leaned toward the smaller arterial branch or the arterial branch that formed a smaller angle with the parent artery, where the hemodynamic stresses increased significantly (P < 0.05), compared with those on the contralateral arterial branch forming a larger angle with the parent artery. Following the aneurysm development, all the hemodynamic stresses on the aneurysm dome decreased significantly (P < 0.001) compared with those at the initiation site on the bifurcation wall after virtual aneurysm removal. With the decrease of bifurcation angles, all the hemodynamic stresses decreased. The formation of intracranial aneurysms on major intracranial arterial bifurcations is significantly associated with locally abnormally augmented hemodynamic stresses, which must be reduced.

Voltage-Mode Ferroelectric Synapse for Neuromorphic Computing.

Ferroelectric materials with a modulable polarization extent hold promise for exploring voltage-driven neuromorphic hardware, in which direct current flow can be minimized. Utilizing a single active layer of an insulating ferroelectric polymer, we developed a voltage-mode ferroelectric synapse that can continuously and reversibly update its states. The device states are straightforwardly manifested in the form of variable output voltage, enabling large-scale direct cascading of multiple ferroelectric synapses to build a deep physical neural network. Such a neural network based on potential superposition rather than current flow is analogous to the biological counterpart driven by action potentials in the brain. A high accuracy of over 97% for the simulation of handwritten digit recognition is achieved using the voltage-mode neural network. The controlled ferroelectric polarization, revealed by piezoresponse force microscopy, turns out to be responsible for the synaptic weight updates in the ferroelectric synapses. The present work demonstrates an alternative strategy for the design and construction of emerging artificial neural networks.

Hydrological Modeling and Evaluation of the Efficiency of Culverts in Drainage Basins Affecting the North Railway in Wadi Malham

The North Railway is one of the longest railway lines in the world, extending for 2750 km from the Riyadh region to Al-Jawf Province through many diverse topographies, including valleys where direct runoff is generated that cross the existing hydraulic protection installations on the railtrack. Direct runoff flows in quantities that exceed the capacity of existing drainage installations and cause several types of damage, owing to the nature of the drainage basins and the impact of changing natural factors and human errors. To ensure the safety of the design of hydraulic drainage installations, this indicates the need for hydrological studies of drainage basins, especially those that include important strategic facilities such as railway lines. In this study, the hydrological modeling of four subdrainage basins (No. 6, 7, 13, and 14) within Wadi Malham was applied and evaluated to determine if the drainage installations can accommodate the direct peak runoff flow. According to the results, the peak flows of 8.9 m3/s for basin No. 7 and 18.2 m3/s for basin No. 13 indicate that they are unable to handle the direct peak runoff flow from the designed storm for a return period of 100 years. The other two basins are able to pass through the peak flow. Based on the findings of this study, we recommend adding an opening for culvert C0400 in basin No. 7 and adding two openings for C0244 in basin No. 13 to accommodate the peak flow.

Permeability evaluation based on Nuclear Magnetic Resonance analysis for gas hydrate reservoir

Permeability (or hydraulic conductivity) is one of the most important parameters for analyzing hydraulic behavior of underground. For example, in the geotechnical engineering, permeability is necessary to calculate water inflow and draw down of water level during excavation, to predict the deformation time due to the consolidation, and to evaluate the barrier of the ground for radioactive waste disposal. In the petroleum industry, permeability is considered an essential parameter which is directly linked to the productivity of oil and natural gas. Therefore, predicting permeability using wireline logging or logging while drilling (LWD) is required during the assessment of the reservoir. Nuclear Magnetic Resonance (NMR) logging is performed at this point. Low-field NMR measurements are sensitive to the hydrogen proton, 1H, in liquid water but not to the 1 H bond in solid form, making it possible to obtain the bulk water volume. In addition, the hydrogen proton NMR- T2 (transverse or spin-spin) relaxation time distribution is used to infer pore-size information and to estimate permeability [1, 2]. The major methods used for estimating permeability, k, are the Schlumberger Doll Research (SDR) model and Timur-Coates (TC) model [3, 4]:&#x0D; Where fNMR is the NMR-estimated (effective) porosity. SDR model uses the averaged value of the T2 distribution plotted on log-scale of time and matches it to the experimental reference permeability with the fitting parameter a [mD/(ms)2]. The TC model seeks to differentiate between the fraction of free (mobile) fluid volume (FFV) and bound fluid volume (BFV) and estimates permeability with FFV/BFV ratio and the material constant c [m2/s2]. The permeability in the research and development of methane hydrate, which is expected to be a next-generation resource, has been estimated using above methods. Methane hydrate is an ice-like solid crystalline structure of water and methane molecules. Because hydrate is solid, NMR is not sensitive, the initial (effective) permeability can be estimated by NMR analyzer. On the other hand, A strong disconnect (up to 2 orders of magnitude) between NMR-based estimates of permeability with those determined from a laboratory study of pressure cores from the same reservoir has further cast uncertainty in the application of borehole NMR data in hydrate evaluation [5, 6]. Recently, authors provided comparisons between NMR-derived values and direct fluid flow estimates of permeability in naturally occurring hydrate-bearing sediment [7, 8]. On the basis of the NMR measurement for hydrate-bearing pressure core sediments, which were recovered from the Gulf of Mexico and Alaska North Slope, the following new hydraulic radius model was proposed [7].&#x0D; This equation estimates the specific surface based on the NMR signal and has been shown to successfully estimate the initial permeability of a hydrate reservoir by expressing a hydraulic radius model based on Kozeny's equation [9]. However, the proposed equation is not universal and has been found to overestimate for clayey and silty hydrate free sediment. This study summarizes the methods and parameters used to estimate permeability using NMR signals from hydrate-bearing sediment obtained from logging and laboratory tests for the Gulf of Mexico and Alaska North Slope. In addition, we reports parameters for predicting model for muddy sediments which was recovered from overburden of hydrate-reservoir in the Hyuganada sea in 2022 Japan [10, 11]. When using the hydraulic radius model to predict permeability of hydrate-bearing sediment, reasonable estimates can be obtained by setting the shape factor for grains Cs = 1/2 (for a circular grain) and the shape factor for the flow path cn = 4 (for the cylinder network), respectively. Although, for hydrate free muddy sediment, Cs = 1/3 for parallel plate grain shape and cn = 2 for the fracture network model matched its permeability. Furthermore, the conversion parameter from T2 relaxation time to the pore size for hydrate free muddy sediments r2 = 0.009 (mm/s) was confirmed based on the result of mercury injection capillary pressure analysis, which is lower than r2 = 0.0325 (mm/s) of hydrate-bearing sediments.

Comparing direct and indirect glottal flow waveform measurements in excised canine larynges and synthetic vocal fold models

Despite being considered the gold standard technique for delineating the flow glottogram during phonation, the inverse filtering technique has never been validated against actual volume flow measurements. This signal-processingtechnique uses the speech signal with vocal tract estimates to calculate the glottal flow waveform. The lack of validation stems from the difficulty of obtaining in-vivo flow measurements at the glottal exit. The current study aims to assess the accuracy of the inverse filtering technique by comparing its flow glottograms with direct, simultaneous volume flow measurement. A vocal tract with varied constrictions that mimic its shape according to specific vowels was connected to either an excised canine larynx or a synthetic vocal fold model. Direct volume flow measurements at the glottal exit were done using tomographic particle image velocimetry. Indirect measurements were obtained by fitting the known Rothenberg mask to the vocal tract and estimating the glottal flow waveform using the Glottal Enterprise system. Preliminary results indicate that the accuracy of the inverse filtering technique relies on the degree of vocal tract constriction. The flow glottogram aligns well with front, lax, and unrounded lip vowels, but its accuracy diminishes with tense and round vowels, particularly noticeable with the excised canine larynx.

Decoupled Modeling and Wide-Range Power Distribution Strategy for the Multisource Inverter in Microgrids

Multi-source inverter (MSI) provides a low-cost and high-power-density solution for microgrids (MGs) applications due to the removal of the dc/dc converter, which offers direct power flow between dc-side and ac-side. The existing modulation strategies for MSI transplanted from those of multilevel inverters experience a limited power distribution range due to the finite control freedom of degree provided by redundant vectors. Moreover, the power distribution between the dc ports is highly coupled with the vector synthesis, this is especially true when the voltages of the dc-port are unbalanced. To address the above issue, this article proposes a decoupled modeling method and a wide-range power distribution strategy for the MSI. The decoupled model is proposed to simplify the modulation implementation process and power distribution analysis. In the proposed model, the reference voltage vector of MSI is proportionally decomposed into two decoupled parts which can be generated independently. As a result, it can not only avoid complex modulation calculations but also ensure decoupled power distribution. Moreover, detailed theoretical analysis indicates that the proposed solution can offer an expanded power distribution range by increasing the switching actions in one switching cycle. Finally, the effectiveness of the proposed multiple-carrier modulation strategy is verified by islanded MGs experimental tests.

Kinetics of the Simplest Criegee Intermediate Reaction with Water Vapor: Revisit and Isotope Effect.

The kinetics of the simplest Criegee intermediate (CH2OO) reaction with water vapor was revisited. By improving the signal-to-noise ratio and the precision of water concentration, we found that the kinetics of CH2OO involves not only two water molecules but also one and three water molecules. Our experimental results suggest that the decay of CH2OO can be described as d[CH2OO]/dt = -kobs[CH2OO]; kobs = k0 + k1[water] + k2[water]2 + k3[water]3; k1 = (4.22 ± 0.48) × 10-16 cm3 s-1, k2 = (10.66 ± 0.83) × 10-33 cm6 s-1, k3 = (1.48 ± 0.17) × 10-50 cm9 s-1 at 298 K and 300 Torr with the respective Arrhenius activation energies of Ea1 = 1.8 ± 1.1 kcal mol-1, Ea2 = -11.1 ± 2.1 kcal mol-1, Ea3 = -17.4 ± 3.9 kcal mol-1. The contribution of the k3[water]3 term becomes less significant at higher temperatures around 345 K, but it is not ignorable at 298 K and lower temperatures. By quantifying the concentrations of H2O and D2O with a Coriolis-type direct mass flow sensor, the kinetic isotope effect (KIE) was investigated at 298 K and 300 Torr and KIE(k1) = k1(H2O)/k1(D2O) = 1.30 ± 0.32; similarly, KIE(k2) = 2.25 ± 0.44 and KIE(k3) = 0.99 ± 0.13. These mild KIE values are consistent with theoretical calculations based on the variational transition state theory, confirming that the title reaction has a broad and low barrier, and the reaction coordinate involves not only the motion of a hydrogen atom but also that of an oxygen atom. Comparing the results recorded under 300 Torr (N2 buffer gas) with those under 600 Torr, a weak pressure effect of k3 was found. From quantum chemistry calculations, we found that the CH2OO + 3H2O reaction is dominated by the reaction pathways involving a ring structure consisting of two water molecules, which facilitate the hydrogen atom transfer, while the third water molecule is hydrogen-bonded outside the ring. Furthermore, analysis based on dipole capture rates showed that the CH2OO(H2O) + (H2O)2 and CH2OO(H2O)2 + H2O pathways will dominate in the three water reaction.

Pre-event base flow as a useful indicator for flood forecasting

The hydrological cycle comprises several components, including precipitation, infiltration, evaporation, transpiration, and runoff, with the latter being a vital part of the cycle that connects precipitation to bodies of water. modelling is necessary due to limitations in standard hydrological measurement techniques, providing a better understanding of hydrological systems that were previously inaccessible, and making it essential for water resource management. Event-based rainfall-runoff modelling is a prevalent method due to its simplicity, but conventional models are limited in accounting for antecedent conditions. In order to tackle this problem, pre-event baseflow is proposed as an indicator for assessing catchment conditions for flood forecasting. This study employs a novel event-based rainfall-runoff equation that incorporates rainfall characteristics, improving hydrological modelling accuracy, and outperforms conventional models in predicting direct flow in most case studies. Overall, the study demonstrates the potential for the new equation to improve hydrological modelling accuracy and aid in a wide range of applications such as flood prediction, water resources management, and planning.