Search

The Mg–Zn–Ca–Sr alloy has good application prospects as a bone implant material; however, the as-cast alloy has both poor plasticity and formability, and there are few studies on its deformation properties. In this study, the microstructure, deformation behavior, textural evolution, and processing map of an Mg–3wt%Zn–1wt%Ca–0.5wt%Sr alloy were studied via a compression test using a Gleeble 1500D thermo-mechanical simulator. The mean apparent activation energy of the hot compression deformation of the Mg–3wt%Zn–1wt%Ca–0.5wt%Sr alloy was 250.44 kJ/mol. With an increase in temperature, both the grain size and the degree of dynamic recrystallization increased. Dynamically recrystallized grains predominantly nucleated near the grain boundary and the secondary phases. After compression, the alloy had a strong basal texture, and its textural strength decreased at first and then increased slightly as the deformation temperature rose. The optimal process parameters of the as-cast Mg–Zn–Ca–Sr alloy involved deformation temperatures of 603–633 K and strain rates of 0.03–0.005 s–1.

In this study, the effect of air supply pressure on atomization characteristics and dust-suppression efficiency of internal-mixing air-assisted atomizing nozzle was investigated. Firstly, the FLUENT software was employed to simulate the flow field inside the nozzle and near the outlet of the nozzle under different air supply pressures. The numerical simulation results showed that as the air supply pressure increased, the pressure and air flow velocity inside the mixing chamber of the nozzle increased dramatically, while the water flow velocity at the water injection hole decreased. At the same time, with the increase of air supply pressure, the fragmentation scale of the liquid jet was continuously shortened, thus the primary atomization of the liquid was more sufficient. Secondly, the custom-developed dust suppression experimental system via spraying was used to investigate the atomization characteristics of the nozzle. According to the experimental results, when the air supply pressure increased, both the droplet size and the droplet volume fraction decreased, the air flow rate increased exponentially, and the water flow rate decrease linearly. In addition, as the air supply pressure increased, the atomization angle, the droplet velocity and the droplet number density first increased and then decreased. Finally, the dust-reduction experiment via spraying was performed under different air supply pressures. The results showed that the dust-suppression efficiency of total dust and respirable dust had a trend of first increasing and then decreasing with the increase of the air supply pressure. The classification efficiency of dust suppression via spraying first increased and then decreased with the increase in the dust particle diameter. Furthermore, as the droplet size decreased, the peak particle diameter decreased accordingly.

Precipitate phases in an Mg–7Gd–3Y–2Zn–0.5Zr alloy aged isothermally at 240 °C were examined using high-resolution transmission electron microscopy (TEM) and high-angle annular dark-field scanning TEM. The two types of precipitation sequence that involve Mg–Gd and long period stacking ordered (LPSO) type were found. The LPSO type sequence consisted of the precipitation of γ′′, γ′, 14H-LPSO/18R-LPSO. The Mg–Gd type precipitation sequence involved the formation of β′(b.c.o.) and β1(f.c.c.). The sequence, morphology, distribution, and crystal structure of these precipitates formed during isothermal aging were investigated. The results indicated that the priority precipitation of Mg–Gd and LPSO type sequences during aging can be affected by Nd, which has a higher diffusion coefficient than Gd and Y. The dislocation structures and strengthening mechanism were also discussed.

A theoretical investigation on single bubble motion in inclined tube bundles was carried out. Due to the shear flow caused by the nonhomogeneous velocity distribution in an inclined tube bundle, single bubble motion was affected by the lift force in the horizontal direction. As a result, the flow direction of single bubble may deviate from the buoyancy direction. Then, both force analyses and velocity decompositions of two-phase in inclined tube bundles were conducted. Based on several hypotheses, a theoretical single-region model for Db > Dins and a two-region model for Db D b ≥ D c . However, the developed models can not present excellent predictions for several deviation angle data when D b D c , especially when S L - d D b D c . This unsatisfied agreements may be related to two factors. The one is the unsatisfied repearability of Todreas’s data. The other one is that several flow mechanisms of small bubbles in inclined tube bundles are not clear yet. It’s suggested that further experimental and theoretical investigations on mechanisms of bubble rotation, bubble entrainment and bubble bouncing at the curve surfaces of tubes could be conducted.

The single-phase thermal hydraulic characteristics of liquid metal sodium are very essential for the design and safety analysis of sodium-cooled fast reactor (SFR). In this paper, the pressure drop and heat transfer features of single-phase liquid sodium were experimentally investigated in a 7 rod bundle with the velocity range of 0–4 m/s, heat flux up to 120 kW/m2 and the absolute pressure range of 0–0.2 MPa. The corresponding Reynolds number ranges from 4000 to 40,000, and the Pe number varies from 0 to 340. It was found that the critical Re number for transition-turbulent flow of single-phase liquid sodium is 13,500 in the hexagonal 7-rod bundle. Then the effects of relative axial position, wall heat flux and Re number on the heat transfer were discussed, respectively. Some existing correlations in the literatures were assessed and compared with the experimental data. Results indicated that these correlations could not predict the current experiments well because of the different geometries and working fluids. The new correlations for the friction factor and Nu number calculations were proposed based on the current experimental data. For 98.5% of heat transfer data produced by the other researchers, the prediction error of the new correlation is less than 30%. For most of the experimental data, it is less than 20%, which sufficiently proves that the correlation developed in this paper could give a good prediction of the experimental data obtained by other researchers.

Shell-side two-phase pressure drops under cross-flow condition play an important role in the operation of heat exchangers. However, no well-verified general correlation for predicting two-phase friction multipliers in horizontal tube bundles is available in the open literatures. In the present paper, based on a combination of Kanizawa and Ribastki flow regime criteria with the modified Mao and Hibiki flow regime criteria, the flow patterns of two-phase vertically upward flow across horizontal tube bundles in the open literatures were identified. The results show that flow patterns have a significant effect on two-phase friction multipliers. For the bubbly flow, finely dispersed bubbly flow, and annular flow, the mass velocity effect on two-phase friction multipliers can be neglected. However, the two-phase friction multipliers of cap bubbly flow and churn flow decrease with an increasing mass velocity. Then, a general dimensionless correlation in terms of the Martinelli parameter and the two-phase Froude number were developed, which is able to accurately predicting gas–liquid two-phase flow resistances of churn flow in staggered horizontal tube bundle under cross-flow condition. New correlations for predicting two-phase friction multipliers of bubbly flow, finely dispersed bubbly flow and annular flow both in staggered and in-line horizontal tube bundles were also developed and can give excellent representations for the existing data in the open literatures.

An experimental research has been carried out for vertically upward two-phase flow of air-water across inverted half U-tube bundle with or without anti-vibration bars. Pressure drop characteristics in inverted half U-tube bundle and anti-vibration bars were obtained and analyzed. New correlations for total pressure drop of two-phase flow in inverted half U-tube bundle and local pressure drop of two-phase flow in anti-vibration bars were developed. The measured two-phase pressure drops in inverted half U-tube bundle of three walls in the test sections were unequal. The pressure drop in the side wall dominated the total pressure drop of two-phase flow in inverted half U-tube bundle for 57 ≤ G −2 ·s −1 , while the pressure drop in the front wall dominated for 114 G ≤ 143 kg·m −2 ·s −1 . An obvious mass velocity effect was observed for the total pressure drop of two-phase flow in inverted half U-tube bundle. For a given Martinelli parameter, the total pressure drop of two-phase flow in inverted half U-tube bundle decreased with an increasing mass velocity. The two-phase local pressure drop data of anti-vibration bars could be fitted well in terms of the Martinelli parameter and mass velocity.

Biodegradable metals hold promises for bone fracture repair. Their clinical translation requires pre-clinical evaluations including animal studies, which demonstrate the safety and performance of such materials prior to clinical trials. This evidence-based study investigates and analyzes the performance of bone fractures repair as well as degradation properties of biodegradable metals in animal models. Data were carefully collected after identification of population, interventions, comparisons, outcomes and study design, as well as inclusion criteria combining biodegradable metals and animal study. Twelve publications on pure Mg, Mg alloys and Zn alloys were finally included and reviewed after extraction from a collected database of 2122 publications. Compared to controls of traditional non-degradable metals or resorbable polymers, biodegradable metals showed mixed or contradictory outcomes of fracture repair and degradation in animal models. Although quantitative meta-analysis cannot be conducted because of the data heterogeneity, this systematic review revealed that the quality of evidence for biodegradable metals to repair bone fractures in animal models is ‘very low’. Recommendations to standardize the animal studies of biodegradable metals were proposed. Evidence-based biomaterials research could help to both identify reliable scientific evidence and ensure future clinical translation of biodegradable metals for bone fracture repair.

Background With the development of wearable health-monitoring technologies, a variety of textile electrodes have been produced and applied by researchers. However, there are no universal and effective methods even testing platforms for evaluating the skin–electrode electrochemical interface for textile electrodes because different human bodies have different skin characteristics. Methods An electrochemical modeling and evaluation for textile electrodes to skin was proposed, and two electrochemical evaluation platforms (EEP) were set up based on two simulated skin models (SSM). First, skin–electrode electrochemical interface (SEEI) models for traditional wet electrodes and textile electrodes were analyzed. Based on the SEEI models and YY/T 0196-2005 (Chinese YY/T pharmaceutical industry standard for disposable ECG electrode), three skin–electrode electrochemical characteristics (SEEC), including skin–electrode static impedance (SESI), skin–electrode alternating current impedance (SEAI), and skin–electrode polarization voltage (SEPV), were proposed. Then, three electrochemical evaluation methods for textile electrodes to skin were proposed and analyzed, which were the correlation between SEEC and skin–electrode contact pressure (SECP), skin–electrode relative movement (SERM), and conduction loss of active signals (CLAS). Finally, an electrochemical evaluation platform was set up based on an active simulated skin model (ASSM) and passive simulated skin model (PSSM). Results 9 feature parameters based on the passive electrochemical evaluation platform (PEEP) and 11 feature parameters based on the active electrochemical evaluation platform (AEEP) were obtained for evaluating textile electrodes. And four kinds of textile electrode characteristics including SEEC, SECP, SERM, and CLAS were quantitatively measured based on the electrochemical evaluation platform, and the testing accuracy and range for these characteristics were measured separately. Finally, correlation between SEEC and SECP for 10 kinds of textile electrode samples was studied, and 14 electrochemical characteristics and four skin–electrode contact pressure characteristics were extracted. Experimental results showed that significant correlations were found between six SEEC characteristics and SECP characteristics, and the correlation coefficient between ACI_3 and USECP was the highest. And the polarization voltages of most dry electrode samples showed a downward trend with the increase of contact pressure. Conclusions The electrochemical evaluation platform yielded effective experimental data and could provide strong support for the evaluation and application of textile electrodes, which was also effective in evaluating other bioelectric electrodes such as 3M electrode, stainless steel electrode, dry electrode and microneedle electrode.

Single-phase convection and steam-water two-phase flow boiling heat transfer experiments in an electrically heated 4 × 16 staggered horizontal rod bundle under cross-flow condition have been carried out for the following range: 45 kg m−2 s−1 ≤ G ≤ 383 kg m−2 s−1, 20.0 kW m−2 ≤ q ≤ 55.0 kW m−2, 0.02 ≤ xout ≤ 0.57 and 112 kPa ≤ Pin ≤ 190 kPa. The major effects on local flow boiling heat transfer coefficients in horizontal rod bundles were analyzed. Firstly, the row number has a significant effect on local flow boiling heat transfer coefficients since the vapor bubbles generated from the lower rods impinge on the surface of the upper rods and enhance the turbulence there. Secondly, an increasing heat flux contributes to an increase of the average bundle flow boiling heat transfer coefficient at all mass velocities. Thirdly, the local quality can also slightly enhance the flow boiling heat transfer. Fourthly, the flow boiling heat transfer can be enhanced with an increasing mass velocity under lower heat fluxes. In a general, a Chen-type correlation was developed to predict local flow boiling heat transfer coefficients in horizontal rod bundles with a maximum deviation of ±20%.

In order to investigate the continuous reverse-flow oxidation of ultralow heating value coalbed methane, a two-dimensional mathematical mode for the continuous reverse-flow oxidation of ultralow heating value coalbed methane was set up. The software FLUENT was used to simulate the thermal structure of the oxidation bed and the effect of operating conditional parameters. The result indicates that: the temperature field of oxidation bed presents trapezium. There exists obvious difference in temperature at the both ends of oxidation bed, and it is helpful to preheat the fresh gas and recover the flue gas heat. Comparing with the conventional porous media combustion, the continuous reverse-flow oxidation has lower peak temperature and outlet temperature, and the methane conversion rate remains high. With the increase of methane concentration, the high-temperature zone widens, the both of temperature and outlet temperature rise, and the reaction area moves to inlet continuously. As the inlet velocity increases, the peak of temperature and outlet temperature both rises significantly, and the reaction area shifts toward to outlet continuously. With the increase of wall heat loss, the peak of temperature and the whole temperature of oxidation bed both reduce, the high-temperature zone becomes narrow obviously, and the reaction area is far away from the inlet.

Hot compression tests on AZ40 magnesium alloy were conducted on a Gleeble 1500d hot simulation testing machine in a deformation temperature range of 330 °C-420 °C and a strain rate range of 0.002-2 s-1. Hot deformation behaviors were investigated on the basis of the analysis of the flow stressstrain curves, constitutive equation, and processing map. The stress exponent and apparent activation energy were calculated to be 5.821 and 173.96 kJ/mol, respectively. Deformation twins and cracks located in grain boundaries were generated at 330 °C and 0.02 s-1, which are associated with a high strain rate and a limited number of available slip systems. With increasing temperature and decreasing strain rate, the twins disappeared and the degree of dynamic recrystallization increased. The alloy was completely dynamically recrystallized at 420 °C and 0.002 s-1, with a homogenous grain size of approximately 13.7 μm. The instability domains of the deformation behavior can be recognized by processing maps. By considering the processing maps and characterizing the microstructure, the optimum hot deformation parameters in this experiment were determined to be 420 °C and 0.002 s-1.

The creep behavior of extrusion-solution treated (T4) Mg–12Gd–1MM–0.6Zr (wt.%) alloys with different grain sizes at 300 °C was evaluated. Results showed that the creep rate curves presented an abnormal decelerated–accelerated–decelerated evolution in the initial stage, which was caused by creep aging. The accelerated creep rate is caused by the transformation from thin β' phase into coarse β1 and β phases; and the transformation of the 3D distribution β phase from the initial single variant to network containing three variants is a key reason for the secondary deceleration of creep rate. On the other hand, as the average grain size increased from 44 μm to 90 μm, the steady-state creep rate gradually decreased, but fracture time continuously increased, so coarse grain is beneficial to creep resistance of the present alloy.

Single-phase convective heat transfer and steam-water two-phase flow boiling heat transfer experiments have been carried out with a vertical seven-rod bundle at low flow conditions near atmospheric pressure. With respect to single-phase experimental results, new correlations were developed to predict convective heat transfer coefficients of laminar flow and Reynolds numbers at the transition from the laminar region to the turbulent region. Two-phase experimental results show that the rod bundle geometry enhanced heat transfer compared with circular tubes. An obvious mass velocity effect on the flow boiling heat transfer coefficient was observed. This conclusion indicates that forced convection, instead of nucleate boiling heat transfer, dominated two-phase flow boiling heat transfer under the experimental conditions. In addition, two-phase flow boiling heat transfer coefficients in the vertical rod bundle increased first and then decreased with the quality increases for a given mass velocity. By taking the enhancement factor of forced convection and the suppression factor of nucleate boiling into account, a new correlation in terms of Boiling number, Reynolds number and Martinelli number was developed to be successful in predicting predict two-phase flow boiling heat transfer coefficients.

An experimental and theoretical research has been carried out for vertically upward two-phase flow of air–water across staggered rod bundles having inclination angles of 0°, 45° and 90°. New correlations for single-phase pressure drops in rod bundles for various inclination angles were developed. The single-phase frictional resistance in the vertical flow was found to have a minimal effect on the total flow resistance in the inclined flow. Based on the single-phase pressure drop data, a new superposition model was proposed and verified to be successful in predicting both the present data and the experimental data in previous experiments of other researchers. The two-phase friction multiplier in the inclined rod bundle, which decreased with increasing mass velocity at a given value of Martinelli parameter, could be fit well in terms of Martinelli parameter and the defined dimensionless mass velocity. In addition, the two-phase friction multiplier first increased and then decreased with increasing Martinelli parameter at a given value of mass velocity for G −2 s −1 . The new correlations developed for two-phase friction multipliers were successful in predicting the two-phase pressure drop data in the inclined rod bundle.

Experimental investigations on atmospheric steam-water two-phase flow regimes and transitions in two transparent narrow rectangular channels with cross-section areas of 1 mm × 20 mm and 2 mm × 20 mm were carried out under conditions of 0.007 ≤ Jf ≤ 0.27 m s−1, 0.05 ≤ Jg ≤ 65.2 m s−1, 0

Zinc (Zn), one of the promising candidates for biodegradable implant materials, has excellent biocompatibility and biodegradability. In this study, as-cast Zn1FexMg (x &le, 1.5 wt %) alloys were prepared to systematically explore the effects of magnesium (Mg) alloying on their microstructures, mechanical properties, and biodegradability. The microstructure of Zn1FexMg alloy consisted of Zn matrix, Zn + Mg2Zn11 eutectic structure, and FeZn13 phase. The addition of Mg not only promoted grain refinement of the alloy, but also improved its mechanical properties. The results of immersion tests showed that the addition of Mg accelerated microcell corrosion between different phases, and the modeling of the corrosion mechanism of alloys in simulated body fluid (SBF) solution was discussed to describe the interaction between different phases in the corrosion process. Zn1Fe1Mg possessed superior comprehensive mechanical properties and appropriate corrosion rate, and the values for hardness, tensile strength, yield strength, elongation, and corrosion rate were 105 HB, 157 MPa, 146 MPa, 2.3%, and 0.027 mm/a, respectively, thus revealing that Zn1Fe1Mg is a preferred candidate for biodegradable implant material.

Homogenization heat treatment of Mg–10 wt% Sn–1.5 wt% Al alloy is studied. The results show that a liquid phase begins to form in the alloy at the temperature (Tm) of 550.2 °C, so the homogenization is performed at 460 °C–510 °C, based on the empirical formula T= (0.9–0.95) Tm. But the surface oxidation phenomenon takes place when treating at 460 °C, which makes the progress of the process difficult to accomplish. Metallograph depicts that wetting phase transformation emerges during the process. For further researching, vacuum quartz tube experiment is conducted, which indicates that the phenomenon is contact with the wetting phase transformation of grain boundaries (GBs) and grain-boundary triple junctions (GB TJs).

Pressure drop experiments were conducted for a vertical two-phase air–water flow across a horizontal staggered rod bundle under conditions of air quality ranging from 0.001 to 0.3 and mass velocity ranging from 80 to 500 kg/(m 2 s). The experimental data were thoroughly analyzed and compared with predictions from existing correlations. New developed expressions provided the most accurate predictions. The two-phase friction multipliers for G ⩽ 200 kg/(m 2 s), which show a strong mass velocity effect, could be fit well in terms of the Martinelli parameter and the dimensionless mass velocity. The new correlation developed for the two-phase friction multiplier was successfully tested in predicting the experimental data for G ⩽ 200 kg/(m 2 s) in previous experiments of other researchers. Distributions of velocity and turbulent intensity were also obtained from the numerical simulation on single-phase flow of water using the CFD code ANSYS FLUENT 14.0. The SST k–ω model was verified to be the best turbulent model to gain flow characteristics in the horizontal rod bundle under experimental conditions.

Experiments have been conducted for single-phase water and two-phase air–water flow in a vertical seven-rod bundle with support plates. Measurements were made for two-phase pressure drops under conditions of total mass velocity from 200 to 850 kg m −2 s −1 , quality from 9 × 10 −4 to 0.27 and pressure from 110 to 230 kPa. Single-phase experimental results show that new developed correlations to obtain frictional factors in the vertical rod bundle and loss coefficients of support plates were in good agreement with experimental data. With respect to two-phase results, the homogeneous flow model dramatically overestimated two-phase friction multipliers in vertical rod bundles, while the new developed correlation presented good predictions. When calculating two-phase pressure drops in support plates, a new defined two-phase multiplier of local pressure drop in support plates was suggested. The two-phase multiplier data of support plates, in which an obvious mass velocity effect was observed, could be fit well in terms of Martinelli parameter and a dimensionless mass velocity. The new correlation developed for two-phase multipliers of support plates was successfully in predicting the experimental data.

The experiments of pressure drop and flow distribution in subchannels of a 37-pin wire-wrapped rod bundle have been performed to evaluate the reliability of existing friction factor correlations and provide available experimental data to validate the accuracy of the thermal hydraulic codes for the design of the lead-based reactor. The isokinetic sampling technique was applied to measure the flow rate of each subchannel at the rod bundle outlet. The experiments were carried out within the flow rate range of 0.6–5.0 kg/s and the inlet temperature range of 20–80 °C. The Reynolds number of these experiments covers the range of 1100–22,000. The CFD pre-analysis revealed that the number of rods has little effect on the subchannel friction factor. The pressure drop measuring section belongs to the fully developed region. The friction factors and flow split factors measured were compared with the existing friction factor correlations. The prediction results of the Chiu-Rohsenow-Todreas (CRT) model agree well with the experimental results of subchannels. The upgraded detailed Cheng and Todreas (UCTD) model is the best fit wire-wrapped rod bundle friction factor correlation and the maximum error is 15% between Reynolds numbers 1100 and 22,000. When it comes to the interior subchannel, the experimental data falls within 50% of the UCRD model between interior subchannel Reynolds numbers 900 and 13,000. The updated correlations for predicting bundle transition Reynolds numbers are presented in this paper. The subchannel friction factor and the flow split factor are coupled with each other. The derivation of the subchannel transition points proves that the pressure drop experiment and the flow distribution experiment are self-consistent.

During a core meltdown accident, the significant decay heat within the corium pool will continually impose thermal load on the vessel wall and challenge the integrity of reactor pressure vessel (RPV). External Reactor Vessel Cooling (ERVC) is considered to be an effective strategy to reduce the potential of vessel failure. After long-term cooling, the initially uniform melt pool can reach a final steady state with stable two-layer or three-layer configuration. Based on the COPRA facility, a series of tests were performed to study the natural convection heat transfer phenomenon of stratified corium pools. The test section was a full-scale 2D slice, simulating the hemispherical lower head of the HPR1000 reactor design. Direct electrical heating was applied in the lower part of vessel to simulate the homogenously heated ceramic pool, while no heat was generated in the upper part to model the metallic layer. A binary mixture of 20 mol% NaNO3–80 mol% KNO3 was selected as simulant material due to the similar phase-change characteristics with the prototypical melt. During the experiment, effects of heating power, top boundary condition, corium pool height, decay heat distribution and simulant material on corium pool heat transfer behavior were analyzed. The results implied that the top cooling and decay heat distribution slightly influenced the temperature and heat flux of ceramic pool, but strongly impacted the characteristics of metallic layer. The comparison between the dimensionless parameters of water tests and salt tests also demonstrated the key role of simulant material. Furthermore, the downward heat transfer Nudn and the upward heat transfer Nuup obtained from COPRA two-layer experiment were in accordance with the previous data or empirical correlations. Note that using the same simulant material for oxide layer and metal layer fails to repeat the boundary conditions in the reactor case, however, the current study pays more attention to the qualitative analysis of different influence on natural convection heat transfer behavior. More valuable information about the crust characteristics and stratification effect can be obtained by the following CFD simulation of these tests.

During hypothetical accidents of sodium-cooled fast reactors, such as unprotected loss of flow, transient power surge accidents, unprotected thermal trap accidents, etc., sodium boiling may occur. A series of boiling incipient phenomena for liquid sodium flow in an annular channel were investigated experimentally. The boiling incipience signal in different experimental conditions were analyzed through the Discrete Wavelet Transform (DWT). The various differential pressure signals in the process of boiling incipience were collected by a differential pressure transducer installed on the effective heating section. The experiment was performed in the heat flux range of 128–846 kW/m2, mass flow rate range of 7.2–122.0 kg/h, system pressure range of 0.85–28.79 kPa and inlet subcooling range of 63.1–287 °C. Since these correlations of predicting the boiling incipience for water in different channels are not suitable for the boiling incipience of liquid sodium, a semi-empirical correlation for the prediction of boiling incipience is obtained in the present study. The prediction error of the new semi-empirical correlation for experimental data is basically within ± 30% in this paper. This work provides a meaningful liquid sodium boiling incipience prediction method.

Two new models of liquid entrainment through a vertical tee branch are proposed based on theoretical analyses and experimental data, which can well predict the test results of the prototype facility of CAP1400 and the scaled down facility of AP1000. Moreover, in order to verify the applicability of the new entrainment models, these models are implemented to RELAP5 through the safety analyses with a 2 in. cold leg SBLOCA in AP1000 comparing with the original RELAP5. The contrastive results show that the RELAP5 with proposed entrainment models has more reasonable results. In addition, the modified RELAP5 can calculate less primary coolant inventory which is more conservative. Besides, the less coolant inventory is accord with the beyond design basis accident test of APEX facility (Advanced Plant Experiment). Therefore, the proposed entrainment models are more appropriate for the ADS-4 entrainment safety analyses in large advanced PWR.

Beam splitter,as a kind of linear optics instruments,has many applications such as in quantum optics and quantum information,including the preparation of nonclassical quantum states and entangled state representation.In Heisenberg picture,on the one hand,the relation of input-output of beam splitter can be easily obtained.Especially for the multicascaded beam-splitters,the input-output relation can also be directly obtained by the input-output relation of single beam splitter.On the other hand,we often need to calculate the probabilities of detecting photon number in many cases,thus we need to turn into Schrdinger picture for simplifying our calculation.Based on the equivalence between both pictures,the relation between transformation matrixes connecting these two pictures is derived.That is to say, the transform matrix corresponding to the Schrdinger picture can be obtained by transposing the transform matrix in Heisenberg picture.This concise relation constructs a bridge connecting two pictures and simplifies our calculation in the Schrdinger picture rather than step by step.Using the relation between transform matrixes of both pictures and combining the technique of integration within ordered product of operator,we further consider the coordination representation,normally ordering form and exponential expression of single beam-splitter.Then we further examine the coordination representation,normally ordering form and exponential expression of two-cascaded beam-splitters.As a generalization,the method is extended to the case of multi-cascaded beam-splitters.These investigations provide an effective way to prepare multi-mode entangled states and qubit states.In addition,a general method is shown of obtaining the total operator and its normally ordering form as well as Schmidt decomposition of the linear systems consisting of beam-splitters.As applications,2-cascaded beam-splitters is used to generate a new quantum mechanics representation and prepare the qubit states with the help of conditional measurement.The Schmidt decomposition of three-mode entangled state representation can be directly obtained by the coordination representation of 2-cascaded beam-splitters,which shows the property of entanglement.In addition,based on this representation we can clearly see that when the input states of first beam splitter are two coordinate states,the output states cannot be entangled.This implies that although the coordinate states are nonclassical,the entangled state can not be prepared either.The new proposed quantum mechanics representation will be further used to investigate the optical transformations,including wavelet transformation,Fourier transform,fractional Fourier transform,et al.Therelevant discussion will be our aim in the future research.

By using nonlinear Schrdinger equation including Raman gain and self-steepening but ignoring fiber loss situation, the propagation characteristics of Airy pulse are simulated and analyzed in the single-mode fiber. Simulations show that Airy pulse can be converted into soliton and its propagation direction is skewed due to the effects of Raman gain and self-steepening under a certain condition. In time domain, the number of small peaks of Airy pulse reduces rapidly. Airy pulse becomes a peak structure containing a main peak and sub-peaks where the energies can be ignored by changing the coefficient a reasonablely, which is approximated as the soliton structure. Therefore, Airy pulse is regarded as transforming into soliton. Meanwhile, in the case of small values b, there exists a significant difference in shape between Airy pulse and soliton. With the value of parameter b increasing slowly, the shape of Airy pulse is very close to soliton's, therefore Airy pulse can transform into soliton by changing value b reasonablely. Compared with by changing b value, Airy pulse convered into the soliton is stable by changing the a value reasonablely. Simultaneously, with the increases of values of coefficient a and amplitude b, the time-shift of Airy pulse increases. However, the time-shift of Airy pulse would decrease when Raman gain and Self-steepening become strong, no matter what the values of a and b are. Further, the acceleration properties of Airy pulse are investigated. It is found that Airy pulse autoacceleration is not a stable value at the beginning but it gradually stabilizes with the increase of transmission distance. The reason is that the energies of secondary peaks exert a tremendous influence on the main lobe of Airy pulse at the beginning, however, secondary peaks diffuse fast with the increase of transmission and then the influence can be ignored to a certain extent. So, the main peak gradually stabilizes with the increase of transmission distance.

Based on the split step Fourier method, the interaction between soliton and Airy pulse is studied in the anomalous dispersion region. And after that the strength, time-domain, and time-shift are simulated by the software of MATLAB, respectively. Results show that cross phase modulation (XPM) builds up when soliton and Airy pulse begin to overlap, which affects the properties of the two pulses. The soliton keeps its original shape but the direction of propagation is deflected by the influence of Airy pulse's self-acceleration. Airy pulse converts to soliton and the direction of propagation changes due to XPM. Therefore, the properties of Airy pulse and soliton are interacted with each other because of XPM. The time-domain of the two pulses is also influenced by XPM and their different shapes will change so as to contain a main and a secondary peaks whose structures are similar and the location and pulse width of the main and the secondary peaks are also roughly the same, which is the basis for Airy pulse to convert to soliton. In addition, the change of Airy pulse and soliton is simulated for different input intensity value of r. Simulation shows that the time-shifts of Airy pulse and soliton increase with increasing input intensity r and their variation trends are the same.