Numerical Analysis for Hydrogen Flame Acceleration during a Severe Accident Initiated by SBLOCA in the APR1400 Containment

We performed a hydrogen combustion analysis in the Advanced Power Reactor 1400 MWe (APR1400) containment during a severe accident initiated by a small break loss of coolant accident (SBLOCA) which occurred at a lower part of the cold leg using a multi-dimensional hydrogen analysis system (MHAS) to confirm the integrity of the APR1400 containment. The MHAS was developed by combining MAAP, GASFLOW, and COM3D to simulate hydrogen release, distribution and combustion in the containment of a nuclear power plant during the severe accidents in the containment of a nuclear power reactor. The calculated peak pressure due to the flame acceleration by the COM3D, using the GASFLOW results as an initial condition of the hydrogen distribution, was approximately 555 kPa, which is lower than the fracture pressure 1223 kPa of the APR1400 containment. To induce a higher peak pressure resulted from a strong flame acceleration in the containment, we intentionally assumed several things in developing an accident scenario of the SBLOCA. Therefore, we may judge that the integrity of the APR1400 containment can be maintained even though the hydrogen combustion occurs during the severe accident initiated by the SBLOCA.

The Study on the Shock Wave Propagation Rule of a Gas Explosion in a Gas Compartment

Combined with the k-ε turbulence model of general application, a refined finite element model of a utility tunnel’s gas compartment filled with the methane/air mixture is developed. A series of analyses are made by using the powerful industry-leading computational fluid dynamics (CFD) software flame acceleration simulator (FLACS) to study the shock wave propagation rule in the gas compartment. The longitudinal and transversal distribution laws of the explosion shock wave are gained taking into consideration the spatial characteristics of the gas compartment. The influences of a few parameters, such as initial conditions and section size of the gas compartment, on the shock wave propagation rule are further discussed. The basic procedure for predicting the peak pressure of the blast wave is provided by considering the initial conditions and the gas compartment, and the corresponding injury effect of the explosion wave on the living beings is assessed. The investigation demonstrates that the peak pressure by the coupled effect between the initial conditions is significantly influenced, especially at the upper and lower gas explosion limits. The peak pressure increases gradually as the width or height increases, and both basically meet the linear relation. The proposed method can forecast the peak pressure of the explosion shock wave in the gas compartment accurately. According to the peak pressure longitudinal and transversal distributions of the blast wave, the peak pressure is far greater than the killing pressure threshold in the underground and closed space; consequently, it is not safe for the living beings in the gas compartment.

Effects of Minimalist Footwear and Foot Strike Pattern on Plantar Pressure during a Prolonged Running

The use of minimalist shoes (MS) in running involves changes in running mechanics compared to conventional shoes (CS), but there is still little research analysing the effects of this footwear on plantar pressure, which could help to understand some risk injury factors. Moreover, there are no studies examining the effects of a prolonged running and foot strike patterns on baropodometric variables in MS. Therefore, the aim of this study was to analyse the changes produced using MS on plantar pressure during a prolonged running, as well as its interaction with the time and foot strike pattern. Twenty-one experienced minimalist runners (age 38 ± 10 years, MS running experience 2 ± 1 years) ran with MS and CS for 30 min at 80% of their maximal aerobic speed, and mean pressure, peak pressure, contact time, centre of pressure velocity, relative force and contact area were analysed using a pressure platform. Foot strike pattern and time were also considered as factors. The multivariable linear regression mixed models showed that the use of MS induced, at the end of a prolonged running, higher peak pressure (p = 0.008), lower contact time (p = 0.004) and lower contact area (p < 0.001) than using CS. Also, runners with forefoot strike pattern using MS, compared to midfoot and rearfoot patterns, showed higher mean and peak pressure (p < 0.001) and lower contact time and area (p < 0.05). These results should be considered when planning training for runners using MS, as higher peak pressure values when using this type of footwear could be a risk factor for the development of some foot injuries.

Immediate results of surgical treatment of high and intermediate risk pulmonary embolism in elderly and senile patients

The aim of the study: is to analyze the immediate results of surgical treatment of high-and intermediate-risk PE in a group of elderly and senile patients. Material and methods. The study included 43 patients operated on for high-and intermediate-risk pulmonary embolism between 2008 and 2019. In the general group of patients, the number of women prevailed and amounted to 67.4%. The average age was 65.4 ± 4.23 years old. The Miller index in the general group was 29.1 ± 1.42. The Geneva Index was 8.4 ± 1.12. The average pressure in the pulmonary artery at the time of operation was 54 ± 1.4 mm Hg, and the peak pressure was 68 ± 3.43 mm Hg. Results. 5 patients died at the hospital stage. Thus, the hospital survival rate of patients was 88.4%. Among nonlethal complications, cardiovascular and respiratory failure prevailed. According to the statement, the calculated pressure gradient in the pulmonary artery was 29.0 ± 3.1 mm Hg. Conclusion. Surgical treatment is a highly eff ective and reliable method of treatment in the group of older patients.

Influences of High-Speed Train Speed on Tunnel Aerodynamic Pressures

To comprehensively investigate the characteristics of aerodynamic pressures on a tunnel caused by the whole tunnel passage of a high-speed train at different speeds, we conduct a series of three-dimensional numerical simulations. Based on the field test results obtained by other researchers, the input parameters of our numerical simulation are determined. The process of a high-speed train travelling through a railway tunnel is divided into three stages according to the spatial relationship between the train and tunnel. Stage I: before train nose enters the entrance; Stage II: while the train body runs inside the tunnel; Stage III: after the train tail leaves the exit. The influences of high-speed train speed on the tunnel aerodynamic pressures of these three stages are systematically investigated. The results show that the maximum peak pressure value decreases with increasing distance from the entrance and increases with increasing train speed in Stage I. There is an approximately linear relationship between the three types of maximum peak pressure (positive peak, negative peak, and peak-to-peak pressures) and the power of the train speed in Stage II. These three types of maximum peak pressure values of the points near tunnel portals increase with increasing train speed in Stage III. Moreover, these three types of maximum peak pressure in the tunnel’s middle section at different train speeds are more complex than those near the tunnel portals, and there is one or more turning points due to the superimposed effects of different pressure waves.

Core Scale FEM Modeling of Thermochemical Fracturing on Cement Cube Samples

Brownfields and depleting conventional resources of fossil fuel energy are not enough to fulfill the tremendously increasing energy demands around the globe. Unconventional oil and gas resources are creating a huge impact on the enhancement of the global economy. Tight rocks are usually located in deep and high-strength formations. In this study, numerical simulation results on a new thermochemical fracturing approach is presented. The new fracturing approach was implemented to reduce the breakdown pressure of the unconventional tight formations. The hydraulic fracturing experiments presented in this study were carried out on ultra-tight cement block samples. The permeability of the block samples was less than 0.005mD. Thermochemical fracturing was carried out by a thermochemical fluids that caused a rapid exothermic reaction which resulted in the instantaneous generation of heat and pressure. Different salts of nitrogen such as sodium nitrite and ammonium chloride were used as a thermochemical fluid. The instantaneous generation of the heat and pressure caused the creation of micro-cracks. The fracturing results revealed that the novel thermochemical fracturing was able to reduce the breakdown pressure in ultra-tight cement from 1095 psi to 705 psi. The reference breakdown pressure was recorded from the conventional fracturing technique. A finite element (FEM) analysis was conducted using commercial software ABAQUS. In FEM, two approaches were used to model the thermochemical fractures namely, cohesive zone modeling (CZM) and concrete damage plasticity models (CDP). The sensitivity analysis of peak pressure and time to reach the peak pressure is also presented in this study. The sensitivity analysis can help in better designing thermochemical fluids that could lead to the maximum generation of micro-cracks and multiple fractures.

Enhancing the differentiation of walking and standing via the ratio of plantar pressures

Differentiation of standing and walking based on plantar pressures is helpful in developing strategies to reduce health risks in the workplace. In order to improve the differentiation ability, the paper proposes a new metric for posture differentiation, that is, the pressure ratio on the two anatomical plantar regions. The plantar pressures were collected from 30 persons during walking and standing. After verifying the normal distribution of the pressure ratio by the Monte Carlo method, two-way repeated-measures ANOVA was conducted for the pressure ratios. The advantage of the pressure ratio over two conventional pressure metrics (the average pressure and the peak pressure) is demonstrated by its much larger size effect. Furthermore, the pressure ratio permits to establish value ranges corresponding to walking and standing, which are less influenced by specific person factors, thus facilitating the design of a standardized posture recognition system. The underlying mechanism underlying the pressure ratio is discussed from the aspect of biomechanics of movement.

Swing Type and Batting Grip Affect Peak Pressures on the Hook of Hamate in Collegiate Baseball Players

Background: Bat swing and grip type may contribute to hook of hamate fractures in baseball players. Purpose: To compare the effects of swing type and batting grip on the pressure and rate of pressure development over the hook of hamate in collegiate baseball players. Study Design: Descriptive laboratory study. Level of evidence, 3. Methods: This was an experimental quasi-randomized study of bat grip and swing differences in National Collegiate Athletic Association Division I baseball players (N = 14; age, 19.6 ± 1.1 years [mean ± SD]). All participants performed swings under 6 combinations: 3 grip types (all fingers on the bat shaft [AO], one finger off the bat shaft [OF], and choked up [CU]) and 2 swing types (full swing and check swing). Peak pressure and rate of pressure generation over the area of the hamate were assessed using a pressure sensor fitted to the palm of the bare hand over the area of the hamate. Wrist angular velocities and excursions of radial ulnar deviation were obtained using 3-dimensional motion analysis. Results: The OF–check swing combination produced the highest peak pressure over the hamate (3.72 ± 2.64 kg/cm2) versus the AO–full swing (1.36 ± 0.73 kg/cm2), OF–full swing (1.68 ± 1.17 kg/cm2), and CU–full swing (1.18 ± 0.96 kg/cm2; P < .05 for all). There was a significant effect of condition on rate of pressure development across the 6 conditions ( P = .023). Maximal wrist angular velocities were 44% lower in all check swing conditions than corresponding full swing conditions ( P < .0001). The time to achieve the maximal wrist angular velocity was longest with the AO–full swing and shortest with the CU–check swing (100.1% vs 7.9% of swing cycle; P = .014). Conclusion: The OF–check swing condition produced the highest total pressure reading on the hook of hamate. Check swing conditions also had the steepest rate of pressure development as compared with the full swing conditions. Clinical Relevance: Batters who frequently check their swings and use an OF or AO grip may benefit from bat modifications or grip adjustment to reduce stresses over the hamate. Athletic trainers and team physicians should be aware of these factors to counsel players in the context of previous or ongoing hand injury.

Earthquake-induced hydrologic changes in the geoengineered schist landslides of Cromwell Gorge, Central Otago

<p>Geoengineered groundwater systems located within seven large (> 100 ha surface area), deep-seated, slow-creep schist landslides in Cromwell Gorge (Otago, New Zealand) are observed to respond systematically to 10 large (>Mw6.2), regional earthquakes at epicentral distances of 130-630 km. The permeabilities of the schist landslides have previously been reported to be c. 1 x 10⁻¹⁷ - 4 x 10⁻⁶ m2 and the permeability structure is dominated by large fracture zones. Of the 315 hydrological instruments in the gorge for which data have been analysed, 21 monitoring well piezometers record repeated metre- or centimetre-scale groundwater level changes, and 12 underground V-notch weirs record elevated flow rates induced by the same earthquakes. Groundwater level changes exhibit consistent temporal characteristics at all monitoring sites, namely a time to peak pressure change on the order of one month and a subsequent recovery period on the order of one year. Changes in weir flow rate are near-instantaneous with maximum flow rates reached within 0-6 hours, followed by recession periods on the order of one month. Hydrological responses to different earthquakes at each monitoring site are systematic in terms of polarity and amplitude. This comprehensive dataset enables consistent patterns in the amplitude, time to peak pressure change and recovery time of groundwater level changes, and elevated weir discharge volumes in response to earthquake shaking to be documented. Earthquakes inducing hydrological responses have been categorised into five categories based on shaking characteristics (duration, bandwidth and amplitude). Larger hydrological responses and proportionally shorter time to peak pressure change and recovery time are associated with long duration (25-50 s or longer), high-amplitude, broad bandwidth shaking. The larger amplitudes of hydrological response and proportionally shorter times to peak pressure change and recovery times, are interpreted to represent greater temporary enhancement of the landslides hydraulic properties, particularly permeability. Understanding how earthquakes can enhance or otherwise affect hydraulic properties such as permeability in fractured reservoirs is intrinsically important and may prove of economic utility for both the geothermal and hydrocarbon energy sectors.</p>

Earthquake-induced hydrologic changes in the geoengineered schist landslides of Cromwell Gorge, Central Otago

<p>Geoengineered groundwater systems located within seven large (> 100 ha surface area), deep-seated, slow-creep schist landslides in Cromwell Gorge (Otago, New Zealand) are observed to respond systematically to 10 large (>Mw6.2), regional earthquakes at epicentral distances of 130-630 km. The permeabilities of the schist landslides have previously been reported to be c. 1 x 10⁻¹⁷ - 4 x 10⁻⁶ m2 and the permeability structure is dominated by large fracture zones. Of the 315 hydrological instruments in the gorge for which data have been analysed, 21 monitoring well piezometers record repeated metre- or centimetre-scale groundwater level changes, and 12 underground V-notch weirs record elevated flow rates induced by the same earthquakes. Groundwater level changes exhibit consistent temporal characteristics at all monitoring sites, namely a time to peak pressure change on the order of one month and a subsequent recovery period on the order of one year. Changes in weir flow rate are near-instantaneous with maximum flow rates reached within 0-6 hours, followed by recession periods on the order of one month. Hydrological responses to different earthquakes at each monitoring site are systematic in terms of polarity and amplitude. This comprehensive dataset enables consistent patterns in the amplitude, time to peak pressure change and recovery time of groundwater level changes, and elevated weir discharge volumes in response to earthquake shaking to be documented. Earthquakes inducing hydrological responses have been categorised into five categories based on shaking characteristics (duration, bandwidth and amplitude). Larger hydrological responses and proportionally shorter time to peak pressure change and recovery time are associated with long duration (25-50 s or longer), high-amplitude, broad bandwidth shaking. The larger amplitudes of hydrological response and proportionally shorter times to peak pressure change and recovery times, are interpreted to represent greater temporary enhancement of the landslides hydraulic properties, particularly permeability. Understanding how earthquakes can enhance or otherwise affect hydraulic properties such as permeability in fractured reservoirs is intrinsically important and may prove of economic utility for both the geothermal and hydrocarbon energy sectors.</p>