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We surveyed the relationship between the scale of space weather events and their occurrence rate in Japan, and we discussed the social impact of these phenomena during the Project for Solar–Terrestrial Environment Prediction (PSTEP) in 2015–2019. The information was compiled for domestic users of space weather forecasts for appropriate preparedness against space weather disasters. This paper gives a comprehensive summary of the survey, focusing on the fields of electricity, satellite operations, communication and broadcasting, satellite positioning usage, aviation, human space activity, and daily life on the Earth's surface, using the cutting-edge knowledge of space weather. Quantitative estimations of the economic impact of space weather events on electricity supply and aviation are also given. Some topics requiring future research, which were identified during the survey are also described. [ABSTRACT FROM AUTHOR]

It is also crucial to investigate the details of the severe space weather phenomena that occurred in the past from the literature and records for considering countermeasures against future space weather disasters. Special issue "Solar-terrestrial environment prediction: toward the synergy of science and forecasting operation of space weather and space climate" The scale of space weather events and their occurrence rate in Japan was surveyed by Ishii et al. ([6]), in which the information for the space weather disaster defense was assembled. The space environmental variability (widely called "space weather") can influence the electromagnetic environment around the earth and human life. [Extracted from the article]

• Void distribution in a narrow rectangular channel with various non-uniform inlet conditions for beyond bubbly flow conditions. • Modeling of void diffusion due to bubble collision phenomena. • Validation of the models in an adiabatic air-water two-phase flow. Modeling and simulation study of industrial scale beyond-bubbly flows, like cap-bubbly, cap-turbulent and churn-turbulent, using the two-fluid model, has been limited due to the wide range of interfacial length scales involved and lack of physics-based models for bubble hydrodynamics and interaction mechanisms for such flow conditions. One important feature of beyond bubbly flow is the existence of a wide range of bubble sizes and shapes and thus different transport characteristics. The accuracy of two-fluid model predictions is strongly dependent on the constitutive relations used for the two-fluid model. The objectives of this proposed work are the following: select a set of physics-based constitutive relations and implement these models into CFX; evaluate these models for a wide range of test conditions in cap-turbulent and churn-turbulent flows. The interfacial structure is dynamically evaluated using bubble interaction mechanisms (coalescence and break up) from the two-group Interfacial Area Transport Equation implemented as source and sink terms into ANSYS CFX. The assessments for the validity of the models were carried out in comparison to data collected at Purdue University for two-phase flow in a narrow, rectangular duct. Non-uniform inlet conditions were applied in order to evaluate phase diffusion models in CFX. A new turbulence-induced bubble collision diffusion model for the two-group bubbles system has been implemented in ANSYS CFX. The CFD results predict the measured data to within the expected error, correctly capturing the transverse redistribution of phases due to diffusion for both uniform and non-uniform inlet phase distributions. This illustrates the importance of bubble collision phenomena in correctly predicting phase distributions in a channel. [ABSTRACT FROM AUTHOR]

An analytical study based on frequency domain analysis is presented on the flashing-induced flow instability in a natural circulation test facility, which was designed to investigate the flow instability for a BWR-type novel modular reactor (NMR). To address the flashing phenomena at low pressure conditions, such as initial startup transients or accidents, the liquid enthalpy change in the P-T diagram due to reduced hydrostatic head in the riser or chimney was treated as an axially uniform heat flux. Based on the drift flux model, the system transfer function was obtained through small perturbations about the steady state in the frequency domain. The D-partition method was used to determine the neutral stability boundary in the dimensionless stability plane, which was constituted of the subcooling number and phase change number. From the frequency domain analysis, the flashing stability boundary and the density wave oscillations boundary could be predicted. Some parametric studies had been performed on the system pressure and the inlet flow resistance coefficients in the stability analysis. The results showed that the flashing stability boundary was more sensitive to the system pressure than the density wave oscillations. In addition, the theoretical stability boundaries were benchmarked against the experimental stability boundaries from quasi-steady state tests. Although the general stability boundary agreed well with the experiments, certain discrepancies still existed due to the assumptions of thermal equilibrium in current study. In the future, the thermal non-equilibrium conditions including subcooled boiling will be taken into account in the flashing induced stability analysis. [ABSTRACT FROM AUTHOR]

The Purdue NMR (Novel Modular Reactor) represents a BWR-type small modular reactor with a significantly reduced reactor pressure vessel (RPV) height. Specifically, it has one third the height of a conventional BWR RPV with an electrical output of 50 MWe. The preliminary design of the NMR-50 including reactor, fuel cycle, and safety systems is described and discussed. The improved neutronics design of the NMR-50 extends the fuel cycle length up to 10 years. The NMR-50 is designed with double passive engineering safety system, which is intended to withstand a prolonged station black out with loss of ultimate heat sink accident such as experienced at Fukushima. In order to evaluate the safety features of the NMR-50, two representative design basis accidents, i.e. main steam line break (MSLB) and bottom drain line break (BDLB), are simulated by using the best-estimate thermal–hydraulic code RELAP5. The RPV water inventory, containment pressure, and the performance of engineering safety systems are investigated for about 33 h after the initiation of the accidents. [ABSTRACT FROM AUTHOR]

• A physics-informed reinforcement learning method for interfacial area transport was developed. • A prior knowledge-based stochastic policy was proposed for the flow state transitions. • The method was evaluated against multiple existing IATE models for transient bubbly flows. • A significant performance boost to the existing IATE model was achieved. The stochastic nature of turbulent two-phase flow determines that the deterministic modeling approaches always have limited predicting range and accuracy, which is due to the averaging and approximation made during the model developments. On the other hand, well-developed machine learning models that are suitable for complex tasks can be used as a surrogate to improve the predictions. In this paper, a physics-informed reinforcement learning-based method for interfacial area prediction is proposed. The method aims to capture the complexity of the two-phase flow using the advantage of reinforcement learning with the aid of the Interfacial Area Transport Equation. A Markov Decision Process (MDP) that describes the bubble transformation in the fluid flow is established by assuming that the development of two-phase flow is a stochastic process with Markov property. The details of the method's framework design are described, including the design of the MDP, environment setup, and the algorithms used to solve the RL problem. The performance of the newly proposed method is tested through experiments based on an experimental database for vertical upward bubbly air-water flows. The result shows that with a knowledge-based stochastic policy, good performance of the new method is achieved with the rRMSE of 0.1573, and it is a significant performance boost to the applied IATE model. The approaches to extending the capability of this new RL-based method are discussed, which is a reference for the further development of this approach. [ABSTRACT FROM AUTHOR]

• An experimental study was performed for air-water two-phase flow in small pipes with diameters from 12.7 to 50.8 mm. • A CNN-based model was developed for the flow regime identification. • The bubbly flow regime transition void fraction is smaller in a smaller diameter pipe. • A simple flow regime transition criterion is developed based on Mishima & Ishii's study. The two-phase flow regime and its transition is closely related to the flow channel geometry. In this study, the effect of pipe size on the bubbly-to-beyond-bubbly flow regime transition was experimentally investigated. Experiments focusing on air-water two-phase bubbly to slug flow regime transition using impedance meter and high-speed imaging were performed on 12.7 mm, 25.4 mm, and 50.8 mm inner-diameter vertical upward pipes. The flow conditions were finely selected and cover a range of superficial liquid and gas velocities of < j f > = 0.3–2.0 m/s and < j g > = 0.03–2.5 m/s. The flow regime identification was realized using a 1-D convolutional neural network-based learning algorithm, with the aid of 5 different data augmentation methods. Through the experimental results, the difference of the transition boundary between bubbly to cap-bubbly/slug flow among different pipes sizes was observed. The difference among the pipes is due to the pipe wall effect on the bubble distribution and relative motion. For a smaller diameter pipe, the transition happens in a smaller void fraction. A simple flow regime transition criterion is proposed regarding the wall effect based on Mishima-Ishii's approach. [ABSTRACT FROM AUTHOR]

The mammalian skull vault consists of several intricately patterned bones that grow in close coordination. The growth of these bones depends on the precise regulation of the migration and differentiation of osteogenic cells from undifferentiated precursor cells located above the eye. Here, we demonstrate a role for Foxc1 in modulating the influence of Bmp signaling on the expression of Msx2 and the specification of these cells. Inactivation of Foxc1 results in a dramatic reduction in skull vault growth and causes an expansion of Msx2 expression and Bmp signaling into the area occupied by undifferentiated precursor cells. Foxc1 interacts directly with a Bmp responsive element in an enhancer upstream of Msx2, and acts to reduce the occupancy of P-Smad1/5/8. We propose that Foxc1 sets a threshold for the Bmp-dependent activation of Msx2, thus controlling the differentiation of osteogenic precursor cells and the rate and pattern of calvarial bone development. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents experimental and modeling approaches in characterizing interfacial structures in gas–liquid two-phase flow. For the modeling of the interfacial structure characterization, the interfacial area transport equation proposed earlier has been studied to provide a dynamic and mechanistic prediction tool for two-phase flow analysis. A state-of-the-art four-sensor conductivity probe technique has been developed to obtain detailed local interfacial structure information in a wide range of flow regimes spanning from bubbly to churn-turbulent flows. Newly obtained interfacial area data in 8×8 rod-bundle test section are also presented. This paper also reviews available models of the interfacial area sink and source terms and existing databases. The interfacial area transport equation has been benchmarked using condensation bubbly flow data. [Copyright &y& Elsevier]

Abstract: Prediction of amount of entrained droplets or entrainment fraction in annular two-phase flow is essential for the estimation of dryout condition and analysis of post dryout heat transfer in light water nuclear reactors and steam boilers. In this study, air–water and organic fluid (Freon-113) annular flow entrainment experiments have been carried out in 9.4 and 10.2mm diameter test sections, respectively. Both the experiments covered three distinct pressure conditions and wide range of liquid and gas flow conditions. The organic fluid experiments simulated high pressure steam–water annular flow conditions. In each experiment, measurements of entrainment fraction, droplet entrainment rate and droplet deposition rate have been performed by using the liquid film extraction method. A simple, explicit and non-dimensional correlation developed by Sawant [Sawant, P.H., Ishii, M., Mori, M., 2008. Droplet entrainment correlation in vertical upward co-current annular two-phase flow. Nucl. Eng. Des. 238 (6), 1342–1352] for the prediction of entrainment fraction is further improved in this study in order to account for the existence of critical gas and liquid flow rates below which no entrainment is possible. Additionally, a new correlation is proposed for the estimation of minimum liquid film flow rate at the maximum entrainment fraction condition. The improved correlation successfully predicted the newly collected air–water and Freon-113 entrainment fraction data. Furthermore, the correlations satisfactorily compared with the air–water, helium–water and air–genklene experimental data measured by Willetts [Willetts, I.P., 1987. Non-aqueous annular two-phase flow. D.Phil. Thesis, University of Oxford]. However, comparison of the correlations with the steam–water data available in literature showed significant discrepancies. It is proposed that these discrepancies might have been caused due to the inadequacy of the liquid film extraction method used to measure the entrainment fraction or due to the change in mechanism of entrainment under high liquid flow conditions. [Copyright &y& Elsevier]

Abstract: Disturbance waves play an important role in interfacial transfer of mass, momentum and energy in annular two-phase flow. In spite of their importance, majority of the experimental data available in literature on disturbance wave properties such as velocity, frequency, wavelength and amplitude are limited to near atmospheric conditions (Azzopardi, B.J., 1997. Drops in annular two-phase flow. International Journal of Multiphase Flow, 23, 1–53). In view of this, air–water annular flow experiments have been conducted at three pressure conditions (1.2, 4.0 and 5.8bar) in a tubular test section having an inside diameter 9.4mm. At each pressure condition liquid and gas phase flow rates are varied over a large range so that the effects of density ratio, liquid flow rate and gas flow rate on disturbance wave properties can be studied systematically. A liquid film thickness is measured by two flush mounted ring shaped conductance probes located 38.1mm apart. Disturbance wave velocity, frequency, amplitude and wavelength are estimated from the liquid film thickness measurements by following the statistical analysis methods. Parametric trends in variations of disturbance wave properties are analyzed using the non-dimensional numbers; liquid phase Reynolds number (Re f), gas phase Reynolds number (Re g), Weber number (We) and Strouhal number (Sr). Finally, the existing correlations available for the prediction of disturbance wave velocity and frequency are analyzed and a new, improved correlation is proposed for the prediction of disturbance wave frequency. The new correlation satisfactorily predicted the current data and the data available in literature. [Copyright &y& Elsevier]

Abstract: An instantaneous and objective flow regime identification method for the two-phase flow is represented in the paper. The previous methods have been evolved to be an objective by replacing the heuristic determination using the sensor signals in terms of the statistical indexes. However, the flow pattern in the rapid transient or the inherently unstable flow such as the flow in the microgravity cannot be identified because of the observation time for the statistical meaning. The design of the neural network fed by the preprocessed impedance signals of the cross-sectional void fraction is proposed here to satisfy the requirement of both objective and an instantaneous identification. For the preprocessing, the both feed forward neural network and the self-organized neural network as an objective reasoning engine were tested using the experimental data for both upward and downward two-phase flow in the pipes with the inner diameter of 25.4mm and 50.8mm. It was found that the proposed flow regime identifier could successfully identify the flow regime using the short term observation data within 1s. Furthermore, the obtained flow regimes were in a good agreement with the Mishima–Ishii criteria for the upward two-phase flow. However, for the downward flow, it was found that the current flow regimes are in reasonable agreement with the Usui criteria for the slug flow region, only. Other flow regimes have strong dependency on the pipe diameter and some phenomena related to the kinematic wave propagation which was not considered reasonably in the previous criteria. Therefore, theoretical studies to build up the transition criteria for the co-current downward two-phase flow are recommended. [Copyright &y& Elsevier]

Abstract: Upward annular two-phase flow in a vertical tube is characterized by the presence of liquid film on the tube wall and entrained droplet laden gas phase flowing through the tube core. Entrainment fraction in annular flow is defined as a fraction of the total liquid flow flowing in the form of droplets through the central gas core. Its prediction is important for the estimation of pressure drop and dryout in annular flow. In the following study, measurements of entrainment fraction have been obtained in vertical upward co-current air–water annular flow covering wide ranges of pressure and flow conditions. Comparison of the experimental data with the existing entrainment fraction prediction correlations revealed their inadequacies in simulating the trends observed under high flow and high pressure conditions. Furthermore, several correlations available in the literature are implicit and require iterative calculations. Analysis of the experimental data showed that the non-dimensional numbers, Weber number (We = ρ g〈j g〉2 D/σ(Δρ/ρ g)1/4) and liquid phase Reynolds number (Re f = ρ f〈j f〉D/μ f), successfully collapse the data. In view of this, simple, explicit correlation was developed based on these non-dimensional numbers for the prediction of entrainment fraction. The new correlation successfully predicted the trends under the high flow and high pressure conditions observed in the current experimental data and the data available in open literature. However, in order to use the proposed correlation it is necessary to predict the maximum possible entrainment fraction (or limiting entrainment fraction). In the current analysis, an experimental data based correlation was used for this purpose. However, a better model or correlation is necessary for the maximum possible entrainment fraction. A theoretical discussion on the mechanism and modeling of the maximum possible entrainment fraction condition is presented. [Copyright &y& Elsevier]

Background: Msx1 and Msx2, which belong to the highly conserved Nk family of homeobox genes, display overlapping expression patterns and redundant functions in multiple tissues and organs during vertebrate development. Msx1 and Msx2 have well-documented roles in mediating epithelial-mesenchymal interactions during organogenesis. Given that both Msx1 and Msx2 are crucial downstream effectors of Bmp signaling, we investigated whether Msx1 and Msx2 are required for the Bmp-induced endothelial-mesenchymal transformation (EMT) during atrioventricular (AV) valve formation. Results: While both Msx1-/- and Msx2-/- single homozygous mutant mice exhibited normal valve formation, we observed hypoplastic AV cushions and malformed AV valves in Msx1-/-; Msx2-/- mutants, indicating redundant functions of Msx1 and Msx2 during AV valve morphogenesis. In Msx1/2 null mutant AV cushions, we found decreased Bmp2/4 and Notch1 signaling as well as reduced expression of Has2, NFATc1 and Notch1, demonstrating impaired endocardial activation and EMT. Moreover, perturbed expression of chamber-specific genes Anf, Tbx2, Hand1 and Hand2 reveals mispatterning of the Msx1/2 double mutant myocardium and suggests functions of Msx1 and Msx2 in regulating myocardial signals required for remodelling AV valves and maintaining an undifferentiated state of the AV myocardium. Conclusion: Our findings demonstrate redundant roles of Msx1 and Msx2 in regulating signals required for development of the AV myocardium and formation of the AV valves. [ABSTRACT FROM AUTHOR]

Abstract: From the significance of three-dimensional simulation of dispersed flow systems in many engineering fields, extensive study was conducted for lift force in a single particle system as well as a multiparticle system. In this study, the lift force in a single particle system was modeled by considering the effect of bubble deformation on the lift force. The model was finalized based on existing data obtained in the range of particle Reynolds number from 3.68 to 78.8, viscous number from 0.0435 to 0.203 and Eötvös number from 1.40 to 5.83. The viscous number is defined by where , , , and are, respectively, fluid viscosity, fluid density, surface tension, gravitational acceleration and density difference between phases. The applicability of the model to higher particle Reynolds number system such as an air–water system was qualitatively examined. The lift force model developed in a single particle system was extended to a multiparticle system. The applicability of the extended lift force model was qualitatively examined. The similarity between drag and lift forces were also discussed. [Copyright &y& Elsevier]

Abstract: The homeobox genes Msx1 and Msx2 function as transcriptional regulators that control cellular proliferation and differentiation during embryonic development. Mutations in the Msx1 and Msx2 genes in mice disrupt tissue–tissue interactions and cause multiple craniofacial malformations. Although Msx1 and Msx2 are both expressed throughout the entire development of the frontal bone, the frontal bone defect in Msx1 or Msx2 null mutants is rather mild, suggesting the possibility of functional compensation between Msx1 and Msx2 during early frontal bone development. To investigate this hypothesis, we generated Msx1−/−;Msx2−/− mice. These double mutant embryos died at E17 to E18 with no formation of the frontal bone. There was no apparent defect in CNC migration into the presumptive frontal bone primordium, but differentiation of the frontal mesenchyme and establishment of the frontal primordium was defective, indicating that Msx1 and Msx2 genes are specifically required for osteogenesis in the cranial neural crest lineage within the frontal bone primordium. Mechanistically, our data suggest that Msx genes are critical for the expression of Runx2 in the frontonasal subpopulation of cranial neural crest cells and for differentiation of the osteogenic lineage. This early function of the Msx genes is likely independent of the Bmp signaling pathway. [Copyright &y& Elsevier]

Abstract: Msx1 and Msx2 are highly conserved, Nk-related homeodomain transcription factors that are essential for a variety of tissue–tissue interactions during vertebrate organogenesis. Here we show that combined deficiencies of Msx1 and Msx2 cause conotruncal anomalies associated with malalignment of the cardiac outflow tract (OFT). Msx1 and Msx2 play dual roles in outflow tract morphogenesis by both protecting secondary heart field (SHF) precursors against apoptosis and inhibiting excessive proliferation of cardiac neural crest, endothelial and myocardial cells in the conotruncal cushions. During incorporation of SHF precursors into the OFT myocardium, ectopic apoptosis in the Msx1−/−; Msx2−/− mutant SHF is associated with reduced expression of Hand1 and Hand2, which from work on Hand1 and Hand2 mutants may be functionally important in the inhibition of apoptosis in Msx1/2 mutants. Later during aorticopulmonary septation, excessive proliferation in the OFT cushion mesenchyme and myocardium of Msx1−/−; Msx2−/− mutants is associated with premature down-regulation of p27KIP1, an inhibitor of cyclin-dependent kinases. Diminished accretion of SHF precursors to the elongating OFT myocardium and excessive accumulation of mesenchymal cells in the conotruncal cushions may work together to perturb the rotation of the truncus arteriosus, leading to OFT malalignment defects including double-outlet right ventricle, overriding aorta and pulmonary stenosis. [Copyright &y& Elsevier]

Abstract: Noncondensable gases that come from the containment and the interaction of cladding and steam during a severe accident deteriorate a passive containment cooling system''s performance by degrading the heat transfer capabilities of the condensers in passive containment cooling systems. This work contributes to the area of modeling condensation heat transfer with noncondensable gases in integral facilities. Previously existing correlations and models are for the through-flow of the mixture of steam and the noncondensable gases and this may not be applicable to passive containment cooling systems where there is no clear passage for the steam to escape. This work presents a condensation heat transfer model for the downward cocurrent flow of a steam/air mixture through a condenser tube, taking into account the atypical characteristics of the passive containment cooling system. An empirical model is developed that depends on the inlet conditions, including the mixture Reynolds number and noncondensable gas concentration. [Copyright &y& Elsevier]

The flat bones of the vertebrate skull vault develop from two migratory mesenchymal cell populations, the cranial neural crest and paraxial mesoderm. At the onset of skull vault development, these mesenchymal cells emigrate from their sites of origin to positions between the ectoderm and the developing cerebral hemispheres. There they combine, proliferate and differentiate along an osteogenic pathway. Anomalies in skull vault development are relatively common in humans. One such anomaly is familial calvarial foramina, persistent unossified areas within the skull vault. Mutations in MSX2 and TWIST are known to cause calvarial foramina in humans. Little is known of the cellular and developmental processes underlying this defect. Neither is it known whether MSX2 and TWIST function in the same or distinct pathways. We trace the origin of the calvarial foramen defect in Msx2 mutant mice to a group of skeletogenic mesenchyme cells that compose the frontal bone rudiment. We show that this cell population is reduced not because of apoptosis or deficient migration of neural crest-derived precursor cells, but because of defects in its differentiation and proliferation. We demonstrate, in addition, that heterozygous loss of Twist function causes a foramen in the skull vault similar to that caused by loss of Msx2 function. Both the quantity and proliferation of the frontal bone skeletogenic mesenchyme are reduced in Msx2-Twist double mutants compared with individual mutants. Thus Msx2 and Twist cooperate in the control of the differentiation and proliferation of skeletogenic mesenchyme. Molecular epistasis analysis suggests that Msx2 and Twist do not act in tandem to control osteoblast differentiation, but function at the same epistatic level. [ABSTRACT FROM AUTHOR]

In view of the practical importance of the drift-flux model for two-phase flow analysis in general and in the analysis of nuclear-reactor transients and accidents in particular, the kinematic constitutive equation for the drift velocity has been studied for various two-phase flow regimes. The constitutive equations that specify the relative motion between phases in the drift-flux model has been derived by taking into account the interfacial geometry, the body-force field, the shear stresses, the interfacial momentum transfer and the wall friction, since these macroscopic effects govern the relative velocity between phases. A comparison of the models with existing experimental data shows a satisfactory agreement. [Copyright &y& Elsevier]

This paper presents a modified two-fluid model that is ready to be applied in the approach of the two-group interfacial area transport equation. The two-group interfacial area transport equation was developed to provide a mechanistic constitutive relation for the interfacial area concentration in the two-fluid model. In the two-group transport equation, bubbles are categorized into two groups: spherical/distorted bubbles as Group 1 while cap/slug/churn-turbulent bubbles as Group 2. Therefore, this transport equation can be employed in the flow regimes spanning from bubbly, cap bubbly, slug to churn-turbulent flows. However, the introduction of the two groups of bubbles requires two gas velocity fields. Yet it is not practical to solve two momentum equations for the gas phase alone. In the current modified two-fluid model, a simplified approach is proposed. The momentum equation for the averaged velocity of both Group-1 and Group-2 bubbles is retained. By doing so, the velocity difference between Group-1 and Group-2 bubbles needs to be determined. This may be made either based on simplified momentum equations for both Group-1 and Group-2 bubbles or by a modified drift-flux model. [Copyright &y& Elsevier]

This paper presents the general strategy for modeling the source and sink terms in the two-group interfacial area transport equation. The two-group transport equation is applicable in bubbly, cap bubbly, slug, and churn-turbulent flow regimes to predict the change of the interfacial area concentration. This dynamic approach has an advantage of flow regime-independence over the conventional empirical correlation approach for the interfacial area concentration in the applications with the two-fluid model. In the two-group interfacial area transport equation, bubbles are categorized into two groups: spherical/distorted bubbles as Group 1 and cap/slug/churn-turbulent bubbles as Group 2. Thus, two sets of equations are used to describe the generation and destruction rates of bubble number density, void fraction, and interfacial area concentration for the two groups of bubbles due to bubble expansion and compression, coalescence and disintegration, and phase change. Based upon a detailed literature review of the research on the bubble interactions, five major bubble interaction mechanisms are identified for the gas–liquid two-phase flow of interest. A systematic integral approach, in which the significant variations of bubble volume and shape are accounted for, is suggested for the modeling of two-group bubble interactions. To obtain analytical forms for the various bubble interactions, a simplification is made for the bubble number density distribution function. [Copyright &y& Elsevier]

Realizing the significance of the active nucleation site density as an important parameter for predicting the interfacial area concentration in a two-fluid model formulation, the active nucleation site density has been modeled mechanistically by knowledge of the size and cone angle distributions of cavities that are actually present on the surface. The newly developed model has been validated by various active nucleation site density data taken in pool boiling and convective flow boiling systems. The newly developed model clearly shows that the active nucleation site density is a function of the critical cavity size and the contact angle, and the model can explain the dependence of the active nucleation site density on the wall superheat reported by various investigators. The newly developed model can give fairly good predictions over rather wide range of the flow conditions (0 kg/m2 s &les; mass velocity &les; 886 kg/m2 s; 0.101 MPa &les; pressure &les; 19.8 MPa; 5° &les; contact angle &les; 90°; 1.00×104 sites/m2 &les; active nucleation site density &les; 1.51×1010 sites/m2). [Copyright &y& Elsevier]

In view of the practical importance of the drift–flux model for two-phase-flow analysis in general and in the analysis of nuclear-reactor transients and accidents in particular, the distribution parameter and the drift velocity have been studied for vertical upward two-phase flow in a large diameter pipe. One of the important flow characteristics in a large diameter pipe is a liquid recirculation induced at low mixture volumetric flux. Since the liquid recirculation may affect the liquid velocity profile and promote the formation of cap or slug bubbles, the distribution parameter and the drift velocity in a large diameter pipe can be quite different from those in a small diameter pipe where the liquid recirculation may not be significant. A flow regime at a test section inlet may also affect the liquid recirculation pattern, resulting in the inlet-flow-regime dependent distribution parameter and drift velocity. Based on the above detailed discussions, two types of inlet-flow-regime dependent drift–flux correlations have been developed for two-phase flow in a large diameter pipe at low mixture volumetric flux. A comparison of the newly developed correlations with various data at low mixture volumetric flux shows a satisfactory agreement. As the drift–flux correlations in a large diameter pipe at high mixture volumetric flux, the drift–flux correlations developed by Kataoka–Ishii, and Ishii have been recommended for cap bubbly flow, and churn and annular flows, respectively, based on the comparisons of the correlations with existing experimental data. [Copyright &y& Elsevier]

Although gas–liquid bubbly flows are encountered in various engineering fields, there are very few established theoretical foundations on the interfacial area concentration, which have been supported by extensive experimental data. From this point of view, a simple equation for the interfacial area concentration has been derived from the interfacial area transport equation. The derived theoretical equation has been modified to obtain experimentally supported predictive correlation. The obtained interfacial area correlation was validated by 459 data sets measured in bubble columns and forced convective bubbly flows under various conditions. These data sets covered extensive loop and flow conditions such as channel geometry (circular or rectangular channel), channel hydraulic equivalent diameter (9.0–5500 mm), flow direction (vertical or horizontal flow), superficial gas velocity (0.000788–4.87 m/s), and superficial liquid velocity (0.00–6.55 m/s). The extensive database also covered wide ranges of physical properties such as liquid density (684–1594 kg/m3), liquid viscosity (0.410–21.1 mPas), and surface tension (20.0–75.0 mN/m). An excellent agreement was obtained between the developed semi-theoretical correlation and 459 data within an average relative deviation of ±22.0%. [Copyright &y& Elsevier]

Accurate measurement of local time-averaged two-phase flow parameters (void fraction, bubble velocity and interfacial area concentration) is important for the evaluation of two-phase flow models as well as for the development of closure relations used in the two-fluid model. In this study, a numerical simulation of the measurement of these parameters using a multi-sensor probe is performed for bubbly flow. The bubble velocity measurement being over-estimated, a probe design criterion is given to reduce the measurement error. The interfacial area concentration measurement is found under-estimated because of the inaccurate missing bubbles recovering method. Based on the simulations, a new correction method independent of the probe geometry and the bubbly flow conditions is suggested. [Copyright &y& Elsevier]

• Flashing Boundary, and Gas Generation due to Flashing have been derived from constitutive relationships. • flashing models have been developed and discussed. • Inlet restrictions do not affect the stability boundary. • Instability map found by the current method matches very closely to the experimental result. An analytical approach is presented to analyse flashing induced instabilities in two-phase flow systems. Averaged conservation equations of the drift flux model are used to describe the flow. For closure of these equations, Flashing Boundary , λ f l and Gas Generation due to Flashing , Γ g , f l have been derived from constitutive relationships for the working fluid. A few flashing models have been developed and discussed. The conservation equations have thus been solved for small perturbations assuming linear stability. The stability boundary is plotted on the Subcooling-Phase Change number plane. This boundary is corroborated with recent experimental studies. [ABSTRACT FROM AUTHOR]

• Comprehensive evaluation of three sets of constitutive models for two-group IATE is performed using the 25.4 mm ID pipe data. • Evaluation results call for improvement in predicting the developing flow with intensive bubble coalescence at bubbly to slug transition. • A new model incorporating physical-based transition function for intergroup wake-entrainment is developed. • The performance of the new model is verified using data covering a wide range of flow conditions and various types of flow channels. Interfacial Area Transport Equation (IATE) is developed to dynamically capture the flow structure change and predict Interfacial area concentration (IAC) for various flow regimes. Some recent experimental results show developing flows with intensive bubble coalescence at bubbly to slug transition in small pipes. The drastic IAC decreasing due to bubble coalescence under such conditions has not been well studied in previous IATE benchmark efforts, therefore it may not be captured by the current constitutive models for IATE. In this work, a comprehensive evaluation of the state-of-the-art two-group IATE models is performed using the small pipe data collected at bubbly and slug flow with a focus on transition. The evaluation result shows unsatisfactory performance in predicting the developing flow with intensive bubble coalescence at bubbly to slug transition. The reason is the underestimation of intergroup transfer from group I bubbles to group II bubbles. To improve the IATE performance, a new intergroup wake-entrainment model is developed to enhance the prediction capability for the intergroup void and IAC transfer. The new model incorporates a transition function derived based on the log-normal bubble size distribution and the lift force effect on bubble movement for group I bubbles, which allows for a smooth transition from bubbly to slug flow. The new intergroup transfer model significantly improves the IATE prediction capability in the 25.4 mm ID pipe and its applicability on other types of flow channels including 50.8 mm ID pipe and 200 × 10 mm duct is also verified. [ABSTRACT FROM AUTHOR]

Presents a study on the relation of hox genes, Hbox1 and Hbox7 with the pattern formation in sea urchin embryos. Development of oral ectoderm, endoterm and mesenchyme; Source of hox genes in all animal phyla including sea urchins; Relation of hox genes with deuterostome.

• The interfacial area transport in small diameter pipes is analyzed. • Drastic intergroup transfer phenomenon is observed in a 12.7mm ID pipe. • Models for predicting the initiation of drastic intergroup transfer are proposed. • The influence of pipe diameter on the shape of cap and slug bubbles is discussed. This study aims to experimentally investigate the two-group interfacial area transport in small diameter pipes. Experimental data focusing on the bubbly to slug transition regime, namely one-group to two-group transport region, are collected in a 12.7 mm vertical pipe under adiabatic, air-water conditions. The result shows the intergroup transfer in the small diameter pipe can be drastic, especially under low superficial liquid velocities. The cause of this phenomenon is mainly due to the large relative bubble size comparing to the pipe cross-sectional area. The wake entrainment effect could be enhanced by the small spherical bubbles that are acting like cap or slug bubbles in a medium-size pipe. Based on the experimental observation, a throughout analysis of the dependence of the drastic intergroup transfer is provided in this study. The models predicting the initiation of drastic intergroup transfer in small diameter pipes in terms of the bubble diameter and the void fraction are developed. These models are compared with the two-phase data among the different pipe sizes and the results show a good agreement. These newly developed models are applied to the IATE wake entrainment model by developing a transition function analogous to the sigmoid function. With the transition function, the revised IATE model is given the new ability on predicting the drastic intergroup transfer phenomenon. [ABSTRACT FROM AUTHOR]

• The interfacial area transport in small diameter pipes is analyzed. • Drastic intergroup transfer phenomenon is observed in a 12.7mm ID pipe. • Models for predicting the initiation of drastic intergroup transfer are proposed. • The influence of pipe diameter on the shape of cap and slug bubbles is discussed. This study aims to experimentally investigate the two-group interfacial area transport in small diameter pipes. Experimental data focusing on the bubbly to slug transition regime, namely one-group to two-group transport region, are collected in a 12.7 mm vertical pipe under adiabatic, air-water conditions. The result shows the intergroup transfer in the small diameter pipe can be drastic, especially under low superficial liquid velocities. The cause of this phenomenon is mainly due to the large relative bubble size comparing to the pipe cross-sectional area. The wake entrainment effect could be enhanced by the small spherical bubbles that are acting like cap or slug bubbles in a medium-size pipe. Based on the experimental observation, a throughout analysis of the dependence of the drastic intergroup transfer is provided in this study. The models predicting the initiation of drastic intergroup transfer in small diameter pipes in terms of the bubble diameter and the void fraction are developed. These models are compared with the two-phase data among the different pipe sizes and the results show a good agreement. These newly developed models are applied to the IATE wake entrainment model by developing a transition function analogous to the sigmoid function. With the transition function, the revised IATE model is given the new ability on predicting the drastic intergroup transfer phenomenon. [ABSTRACT FROM AUTHOR]

• A comprehensive review on the state-of-the-art in the development of the IATE is presented. • Improvements on IATE formulation and constitutive model development are reviewed. • An experimental database for model development and IATE validation is reviewed. • The application of IATE to system analysis codes and Computational Fluid Dynamics codes is reviewed. • The progress in extending the IATE to churn-annular transition and annular flows is reviewed. The interfacial area transport equation (IATE) employs a dynamic approach to predict interfacial area concentration (IAC) in two-phase flows. It eliminates the need for the static flow regime transition criteria and flow regime dependent IAC correlations used in closing the two-fluid model and therefore any potential artificial bifurcation or numerical oscillations stemming from these static correlations. The efforts to develop the IATE are reviewed in this work, focusing on studies within the past decade. The current state-of-the-art in IATE is a two-group interfacial area transport equation that is applicable to predict interfacial area concentration from bubbly to churn-turbulent flows. An extensive experimental database has been established in literature for various two-phase flow conditions. The database is used to develop constitutive models to close the IATE and to validate its performance. These include adiabatic and heated conditions, vertical and horizontal flow orientations, channels with flow restrictions, round, rectangular, annulus, and rod-bundle geometries, and normal-gravity and reduced-gravity conditions. IATE has been implemented into practical system analysis codes such as TRACE and computational fluid dynamics (CFD) codes such as CFX and Fluent to evaluate its performance. In addition, the recent efforts of extending the IATE beyond churn-turbulent flow to churn-annular transition and annular flows are also reviewed. These include the new instrumentation, experimental database, and additional constitutive models to predict annular flows. [ABSTRACT FROM AUTHOR]

• A four-sensor droplet-capable conductivity probe (DCCP-4) was manufactured and utilized to obtain measurements in annular and wispy-annular flow for vertical upwards flow in 1-inch pipe. • Distinct differences between droplet, bubble, and ligament distributions for annular and wispy-annular flow exemplify the probe's capability of differentiating between all flow fields comprising wispy-annular flow. • A cross-calibration between the facility electromagnetic flowmeter and the DCCP-4′s flow velocity calculation is presented as an assessment of the methodology's reliability to measure two-phase flow parameters. Understanding wispy-annular flow is crucial for the prediction of various industrial systems under numerous conditions, including nuclear power plants. Its complex interfacial structure comprised of ligament wisps, gas bubbles, and droplets has rendered it a challenge in terms of experimental two-phase flow research. In the current study, a droplet-capable conductivity probe (DCCP) is manufactured and utilized to obtain data within annular and wispy-annular flows. Initially, a background of the DCCP's design and previous works are summarized. The DCCP is then utilized to measure parameters related to three separate fields: dispersed gas (bubbles), dispersed liquid (droplets), and continuous liquids (ligaments) along different radial locations in vertical upwards pipe flow. Statistical distributions of two-phase flow parameters are presented to illustrate the reliability of the DCCP in wispy-annular flow experiments. The current work expands on past research and experimentally demonstrates the effectiveness of the DCCP in wispy-annular flow. [ABSTRACT FROM AUTHOR]

The social necessity of Space Weather information service is recognized to be more important than ever. The ICAO, International Civil Aviation Organization, will start to use global space weather information service on November 2018. Many of GNSS data providers are learning the importance of ionospheric information for servicing stable and precise positioning with GNSS. It is well known that the high latitude area is fragile against space weather disturbance. HF telecommunication is affected by ionospheric disturbances with polar cap absorption (PCA) and/or auroral activities. In addition, now people are realizing that the equator region is also affected by space weather disturbances, for example plasma bubbles, equatorial GIC. On the other hand, the social impact with solar flare has not been recognized in mid latitude countries including Japan.The Project on Solar-Terrestrial Environment Prediction (PSTEP) started on 2015 involved by more than 100 scientists for researching mainly two topics. One is to seek to answer some of the fundamental questions concerning the solar-terrestrial environmental system, and another on is to contribute to building a next-generation space weather forecast system to prepare for severe space weather disasters. We have been researching the solar flare impact on society in mid-latitude as one of the project on PSTEP with reviewing the existing researches and interviewing to the stakeholders on space weather information.We would like to discuss these topics in the presentation. [ABSTRACT FROM AUTHOR]

Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar–terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar–terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced. [ABSTRACT FROM AUTHOR]

Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar–terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar–terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced. [ABSTRACT FROM AUTHOR]

As a critical closure equation to the two-fluid model and an important tool to characterize the two-phase-flow interfacial transport, the interfacial area transport equation (IATE) was formulated by taking various physical mechanisms causing interfacial area change into account. To fulfill the dynamic prediction advantage of IATE and further replace the flow regime–based constitutive relations, the IATE model should be validated by transition data to ensure model reliability and robustness. Air-water experiments are performed in bubbly-to-slug transition flows in a 200 × 10-mm narrow rectangular duct. Four-sensor conductivity probes are used to measure the local void fraction, interfacial area concentration (IAC), and bubble velocity at three axial locations. The void fraction distribution changes significantly with the flow developing. Flow conditions with a similar area-averaged void fraction but different superficial mixture velocities are compared, and it is found that the superficial mixture velocity significantly affects the IAC. In addition, the two-group IATE model for narrow rectangular channel is evaluated using the collected data. The average relative error for the total IAC prediction is 11.4%, but the group II IAC is overestimated for most flow conditions. [ABSTRACT FROM AUTHOR]

It has long been known that field-aligned irregularities within equatorial plasma bubbles (EPBs) can cause long-range propagation of radio waves in the VHF frequencies such as those used for TV broadcasting through the so-called forward scattering process. However, no attempt has been made to use such anomalous propagations of VHF radio waves for wide-area monitoring of EPBs. In this study, we investigated the feasibility of monitoring of EPBs using VHF radio waves used for aeronautical navigation systems such as VHF Omnidirectional radio Range (VOR). There are 370 VOR stations in the Eastern and Southeastern Asian region that can be potentially used as Tx stations for the observations of anomalous propagation. We have examined the forward scattering conditions of VHF waves using the magnetic field model and confirmed that it is possible to observe the EPB-related anomalous propagation if we set up Rx stations in Okinawa (Japan), Taiwan, and Thailand. During test observations conducted in Okinawa since 2021, no signal has been received that was clearly caused by anomalous propagation due to EPBs. This is simply because EPBs have not developed to high latitudes during the observation period due to the low solar activity. In March 2023, however, possible indications of EPB-related scattering were detected in Okinawa which implies the feasibility of observing EPBs with the current observation system. We plan to conduct pilot observations in Taiwan and Thailand in future to further evaluate the feasibility of this monitoring technique. [ABSTRACT FROM AUTHOR]

Prediction of rod film thickness and its distribution in annular flow in rod bundle is of essential importance to nuclear power industry. This is attributed to the possible film dryout on fuel rods under certain conditions, which will result in a drastically increasing cladding temperature and possible fuel damage. Though there exist a lot of models or correlations to predict film thickness for annular flow in pipes, there are few models to predict rod film thickness inside rod bundle. The one-dimensional models or correlations for pipe flow cannot be used for rod bundle directly due to different geometry and flow dynamics. In relation to this, a new approach to predict the rod film thickness inside rod bundle has been developed. This approach first divides the rod bundle cross-section into three regions according to their characteristic length scales. Then, the gas and liquid flow distribution inside rod bundle has been given with reasonable assumptions. Based on the flow distribution profile, the sub-channel area-averaged gas and liquid volumetric fluxes have been given. Finally, the correlation developed for pipe flow is adopted for each sub-channel based on the local two-phase parameters in the rod bundle. Compared to experimental data obtained in-house and found in the literature, the newly proposed approach can predict rod film thickness with satisfactory accuracy. [ABSTRACT FROM AUTHOR]

An experimental investigation of horizontal forced vibration effect on void fraction variation of subcooled boiling flow was carried out in this study. In order to simulate the fuel assembly subchannel of a boiling water reactor (BWR), an annular test section with inner and our diameters of 19.1 and 38.1 mm was utilized for subcooled boiling tests under atmospheric pressure. The annular test section was attached to an eccentric-cam vibrator, which was driven by a low-speed motor and can produce horizontal forced vibrations with frequency up to 20 Hz and maximum displacement of 22.2 mm. The inlet liquid velocity and subcooling were set as v f , in = 0.25–1.00 m/s and Δ T Sub = 5–20 °C. Different heat fluxes of q ″ = 0.058–0.193 MW/m 2 were loaded through the center heater rod, and the void fraction and fluid temperature were measured during the tests under stationary (no vibration) and vibration conditions. Test results show that in the subcooled boiling region, the void fraction and fluid temperature can vary under horizontal forced vibrations, and the variation trends were presented in N Zu - N Sub and v f , in -〈 α 〉 plots. These variations can be explained by the potential changes of thermal boundary layers (TBL) and the heat transfer enhancement under vibrations. In addition, no significant change of void fraction and fluid temperature was found in or near the saturated boiling conditions under vibrations. [ABSTRACT FROM AUTHOR]

In order to investigate the potential seismic vibrations effect on two-phase flow in an annular channel, experimental tests with air-water two-phase flow under horizontal vibrations were carried out. A low-speed eccentric-cam vibration module capable of operating at motor speed of 45–1200 rpm ( f  = 0.75–20 Hz) was attached to an annular channel, which was scaled down from a prototypic BWR fuel sub-channel with inner and outer diameters of 19.1 mm and 38.1 mm, respectively. The two-phase flow was operated in the ranges of 〈 j f 〉 = 0.25–1.00 m/s and 〈 j g 〉 = 0.03–1.46 m/s with 27 flow conditions, and the vibration amplitudes controlled by cam eccentricity ( E ) were designed for the range of 0.8–22.2 mm. Ring-type impedance void meters were utilized to detect the area-averaged time-averaged void fraction under stationary and vibration conditions. A systematic experimental database was built and analyzed with effective maps in terms of flow conditions (〈 j g 〉-〈 j f 〉) and vibration conditions ( E - f and f - a ), and the potential effects were expressed by regions on the maps. In the 〈 j g 〉-〈 j f 〉 maps, the void fraction was found to potentially decrease under vibrations in bubbly flow regime and relatively lower liquid flow conditions, which may be explained by the increase of distribution parameter. Whereas and the void fraction may increase at the region closed to bubbly-to-slug transition boundary under vibrations, which may be explained by the changes of drift velocity due to flow regime change from bubbly to slug flows. No significant change in void fraction was found in slug flow regime under the present test conditions. [ABSTRACT FROM AUTHOR]

Several passive safety systems are included in the design of the Economic Simplified Boiling Water Reactor (ESBWR) safety system. To investigate the capability of the ESBWR passive safety system, the integral facility designed for ESBWR was applied to perform a series of experiments simulating Loss of Coolant Accidents (LOCAs) break events of the ESBWR. This paper is intended to summarize the LOCAs test results performed at the Purdue University Multi-Dimensional Integral Test Assembly for ESBWR application (PUMA-E) facility, namely, the Main Steam Line Break (MSLB), Bottom Drain Line Break (BDLB), Feed Water Line Break (FWLB) and Gravity Drain Line Break (GDLB). Furthermore, this study focuses on the comparison of important parameters in the main components such as Reactor Pressure Vessel (RPV), Containment, and Suppression Pool (SP) of the integral facility for those types of the LOCAs tests in three different phases of LOCAs, namely, the blowdown phase, Gravity Driven Coolant System (GDCS) period and long term cooling PCCS period. The various responses of passive safety function by GDCS, Isolation Coolant System (ICS), and Passive Containment Coolant System (PCCS) at the three different phases of LOCAs to the four types of the LOCAs tests are discussed and analyzed. [ABSTRACT FROM AUTHOR]

The prediction capability of the two-fluid model for gas–liquid dispersed two-phase flow depends on the accuracy of the closure relations for the interfacial forces. In previous studies of two-phase flow Computational Fluid Dynamics (CFD), interfacial force models for a single isolated bubble has been extended to disperse two-phase flow assuming the effect in a swarm of bubbles is similar. Limited studies have been performed investigating the effect of the bubble concentration on the lateral phase distribution. Bubbles, while moving through the liquid phase, may undergo turbulence-driven random collision with neighboring bubbles without significant coalescence. The rate of these collisions depends upon the bubble approach velocity and bubble spacing. The bubble collision frequency is expected to be higher in locations with higher bubble concentrations, i.e., volume fraction. This turbulence-driven random collision causes the diffusion of the bubbles from high concentration to low concentration. Based on experimental observations, a phenomenological model has been developed for a “turbulence-induced bubble collision force” for use in the two-fluid model. For testing the validity of the model, two-phase flow data measured at Purdue University are utilized. The geometry is a 10 mm × 200 mm cross section channel. Experimentally, non-uniform inlet boundary conditions are applied with different sparger combinations to vary the volume fraction distribution across the wider dimension. Examining uniform and non-uniform inlet data allows for the influence of the volume fraction to be studied as a separate effect. The turbulence-induced bubble collision force has been implemented in ANSYS CFX. The assessment results show agreement with the measured data, correctly capturing the redistribution of volume fraction downstream with uniform and non-uniform inlet profiles. In particular, for the non-uniform data, the transverse redistribution of volume fraction at downstream locations is captured. This signifies the importance of bubble–bubble collision phenomena in correctly predicting volume fraction distributions. [ABSTRACT FROM AUTHOR]

This work studies the hydrodynamics of the seven-pin wire-wrapped rod bundle in the sodium cartridge loop for the Versatile Test Reactor (VTR) through scaled water experiments and computational fluid dynamics (CFD) simulations. The scaling analysis is first performed to demonstrate the hydrodynamic similarity between water and sodium flows at the same Reynolds number R e. A separate-effects test facility is designed and constructed based on the scaling analysis. Detailed experimental data on the pressure drop covering a wide range of R e values (1165 to 27 689) are obtained, which are used to evaluate existing correlations for friction factor and to benchmark CFD simulations. The experimentally determined friction factors f E x p agree well with the Upgraded Cheng and Todreas Detailed Correlation and Pacio-Chen-Todreas Detailed Model within ± 7 % but are significantly underpredicted by Rehme's correlation by 25%. Various CFD near-wall treatment methods are tested using ANSYS Fluent and evaluated by experimental data. It is found that when the recommended wall y + values are met, most of the near-wall treatment methods can give accurate friction factor predictions. The resolved near-wall method ( y + ∼ 1) with the Shear Stress Transport k − ω turbulence model and the scalable wall functions ( y + > 12) with the realizable k − ε turbulence model can predict f E x p within ± 5 % . The standard wall functions ( y + > 30) and nonequilibrium wall functions ( y + > 30) with the realizable k − ε model can predict f E x p within ± 10%. [ABSTRACT FROM AUTHOR]

The article discusses the study "Combined Deficiencies of Msx1 and Msx2 Cause Impaired Patterning and Survival of the Cranial Neural Crest," by Mamoru Ishii, Henry M. Sucov et al. The study focused on the function of Msx1 and Msx2, homeobox genes implicated in several disorders affecting craniofacial development in humans. The change in the expression of the hindbrain markers Krox20 and Epha4 in Msx1/2 mutants suggests that defects in neural crest populations may result from defects in rhombomere identity.

Primordial germ cells (PGCs) are a highly migratory cell population that gives rise to eggs and sperm. Much is known about PGC specification, but less about the processes that control PGC migration. In this study, we document a deficiency in PGC development in embryos carrying global homozygous null mutations in Msx1 and Msx2 , both immediate downstream effectors of Bmp signaling pathway. We show that Msx1 −/− ;Msx2 −/− mutant embryos have defects in PGC migration as well as a reduced number of PGCs. These phenotypes are also evident in a Mesp1-Cre -mediated mesoderm-specific mutant line of Msx1 and Msx2 . Since PGCs are not marked in Mesp1 -lineage tracing, our results suggest that Msx1 and Msx2 function cell non-autonomously in directing PGC migration. Consistent with this hypothesis, we noted an upregulation of fibronectin, well known as a mediator of cell migration, in tissues through which PGCs migrate. We also noted a reduction in the expression of Wnt5a and an increase in the expression in Bmp4 in such tissues in Msx1 −/− ;Msx2 −/− mutants, both known effectors of PGC development. [ABSTRACT FROM AUTHOR]

In the initial event on a Loss of Coolant Accident (LOCA) of a typical Boiling Water Reactor (BWR), mostly non-condensable gas is forced through blowdown pipes submerged downwardly in the Suppression Pool (SP). The void penetration length in the SP is considered as a key parameter to design an alignment of Emergency Core Cooling System (ECCS) pump suction pipe in a pool for avoiding the problem of the gas intrusion to the pump. Therefore, it is very important to predict accurately the void penetration length in the SP during a LOCA. However, the existing models or correlations to predict the void penetration length in a water pool have been developed using test data with small diameter submerged tubes less than or equal to 3.5 cm. In this study, new correlations to predict the axial void penetration length during the initial and the quasi-steady phase air injection, respectively, have been developed particularly for a large diameter submerged pipe cases using the previous experimental results with large diameter submerged pipe of 7.6 and 10.2 cm. The developed correlations consider a bubble plume developed in a liquid medium as a lumped model and use the field equations with necessary assumptions to determine the equation of void penetration length. The predictions of the newly developed correlation are tested by comparing the computed results with available experimental data from the previous studies. The comparisons show a good agreement between them. [ABSTRACT FROM AUTHOR]