Effect of grain size on gas bubble evolution in nuclear fuel:Phase-field investigations

Numerous irradiation-induced gas bubbles are created in the nuclear fuel during irradiation, leading to the change of microstructure and the degradation of mechanical and thermal properties. The grain size of fuel is one of the important factors affecting bubble evolution. In current study, we first predict the thermodynamic behaviors of point defects as well as the interplay between vacancy and gas atom in both UO_(2) and U_(3)Si_(2) according to ab initio approach. Then, we establish the irradiation-induced bubble phase-field model to investigate the formation and evolution of intra-and inter-granular gas bubbles. The effects of fission rate and temperature on the evolutions of bubble morphologies in UO_(2) and U_(3)Si_(2) have been revealed. Especially, a comparison of porosities under different grain sizes is examined and analyzed. To understand the thermal conductivity as functions of grain size and porosity, the heat transfer capability of U_(3)Si_(2) is evaluated.

Grain-filling strategies of wheat of contrasting grain sizes under various planting patterns and irrigation levels

In a study comparing grain filling and yield in a large-and a small-grain-size wheat cultivar under two planting patterns and two irrigation regimes,plastic-covered ridge and furrow planting with sprinkler irrigation increased grain filling and yield in both cultivars.The largest contributors to grain yield were an extended active grain-filling period in Shuangda 1 and an increased mean grain-filling rate in XN538.

Effects of Different Seed Stem Sizes on the Changes of Available Elements in Rhizosphere Soil of Fritillaria thunbergii Miq.

[Objectives]This study was conducted to screen suitable seed stems of Fritillaria thunbergii Miq.from different provenances and to provide a theoretical basis for the high-yielding and high-efficiency cultivation of F.thunbergii Miq.introduced to different places.[Methods]F.thunbergii Miq.from four different provenances including Zhejiang,Nantong and Chongqing were introduced and cultivated in Wanzhou of Chongqing.The contents of available Zn,Fe,Mn,Cu,Mo,N,P,K,Ca and Mg in rhizosphere soil of F.thunbergii Miq.during five growing stages were determined after selecting different stem sizes for field cultivation.[Results]Small stems of Pan an and Ningbo provenances(SSG3,121-160/kg)and middle stems of Nantong and Fengjie provenances(SSG2,81-120/kg)showed higher soil availability.[Conclusions]In the process of introduction and cultivation of F.thunbergii Miq.,high yield and high efficiency can be achieved by selecting smaller seed stems of F.thunbergii Miq.

Effects of Macroparticle Sizes on Two-phase Mixture Discharge Under DC Voltage

随着放电等离子体在各个领域应用的不断扩大，两相体放电问题越来越重要，需要解决的基础问题之一即是两相体中放电发生、发展的特点和规律及影响因素。采用21种不同的介质材料研究直流电压下两相体放电的效应，由实验结果可知介质的介电常数对放电路径基本无影响，而介质颗粒的粒径大小对两相体放电路径的选择起决定作用，即粒径效应。此外，对颗粒介电常数、电场畸变、光电离作用和颗粒荷电等几个方面进行研究，可知两相体放电的粒径效应与颗粒粒径大小紧密相关。

Pharmacological intervention for chronic phase of spinal cord injury

Spinal cord injury is an intractable traumatic injury. The most common hurdles faced during spinal cord injury are failure of axonal regrowth and reconnection to target sites. These also tend to be the most challenging issues in spinal cord injury. As spinal cord injury progresses to the chronic phase, lost motor and sensory functions are not recovered. Several reasons may be attributed to the failure of recovery from chronic spinal cord injury. These include factors that inhibit axonal growth such as activated astrocytes, chondroitin sulfate proteoglycan, myelin-associated proteins, inflammatory microglia, and fibroblasts that accumulate at lesion sites. Skeletal muscle atrophy due to denervation is another chronic and detrimental spinal cord injury–specific condition. Although several intervention strategies based on multiple outlooks have been attempted for treating spinal cord injury, few approaches have been successful. To treat chronic spinal cord injury, neural cells or tissue substitutes may need to be supplied in the cavity area to enable possible axonal growth. Additionally, stimulating axonal growth activity by extrinsic factors is extremely important and essential for maintaining the remaining host neurons and transplanted neurons. This review focuses on pharmacotherapeutic approaches using small compounds and proteins to enable axonal growth in chronic spinal cord injury. This review presents some of these candidates that have shown promising outcomes in basic research(in vivo animal studies) and clinical trials: AA-NgR(310)ecto-Fc(AXER-204), fasudil, phosphatase and tensin homolog protein antagonist peptide 4, chondroitinase ABC, intracellular sigma peptide,(-)-epigallocatechin gallate, matrine, acteoside, pyrvate kinase M2, diosgenin, granulocyte-colony stimulating factor, and fampridine-sustained release. Although the current situation suggests that drug-based therapies to recover function in chronic spinal cord injury are limited, potential candidates have been identified through basic research, and these candidates may be subjects of clinical studies in the future. Moreover, cocktail therapy comprising drugs with varied underlying mechanisms may be effective in treating the refractory status of chronic spinal cord injury.

Low‑Temperature Oxidation Induced Phase Evolution with Gradient Magnetic Heterointerfaces for Superior Electromagnetic Wave Absorption

Gradient magnetic heterointerfaces have injected infinite vitality in optimizing impedance matching,adjusting dielectric/magnetic resonance and promoting electromagnetic(EM)wave absorption,but still exist a significant challenging in regulating local phase evolution.Herein,accordion-shaped Co/Co_(3)O_(4)@N-doped carbon nanosheets(Co/Co_(3)O_(4)@NC)with gradient magnetic heterointerfaces have been fabricated via the cooperative high-temperature carbonization and lowtemperature oxidation process.The results indicate that the surface epitaxial growth of crystal Co_(3)O_(4) domains on local Co nanoparticles realizes the adjustment of magnetic-heteroatomic components,which are beneficial for optimizing impedance matching and interfacial polarization.Moreover,gradient magnetic heterointerfaces simultaneously realize magnetic coupling,and long-range magnetic diffraction.Specifically,the synthesized Co/Co_(3)O_(4)@NC absorbents display the strong electromagnetic wave attenuation capability of−53.5 dB at a thickness of 3.0 mm with an effective absorption bandwidth of 5.36 GHz,both are superior to those of single magnetic domains embedded in carbon matrix.This design concept provides us an inspiration in optimizing interfacial polarization,regulating magnetic coupling and promoting electromagnetic wave absorption.

Determination of Particle Sizes and Crystalline Phases on Colloidal Silicon Nanoparticle Suspensions

Particle size and crystallinity of silicon nanoparticles were determined by analyzing the optical extinction spectra of colloidal suspensions. Experimental results from these colloids were anaiyzed using Mie theory in connection with effective medium theory, in order to determine particle sizes and their internal structure with the simple technique of optical transmission spectroscopy. By modeling an effective refractive index for the particles, the crystalline volume fraction can be extracted from extinction spectra in addition to information about the size. The crystalline volume fraction determined in this way were used to calibrate the ratio of the Raman cross sections for nanocrystalline and amorphous silicon, which was found to be σc./σa = 0.66

Arc erosion behaviors of AgSnO_2 contact materials prepared with different SnO_2 particle sizes

To clarify the effect of SnO2 particle size on the arc erosion behavior of AgSnO2 contact material, Ag?4%SnO2 (mass fraction) contact materials with different sizes of SnO2 particles were fabricated by powder metallurgy. The microstructure of Ag?4%SnO2 contact materials was characterized, and the relative density, hardness and electrical conductivity were measured. The arc erosion of Ag?4%SnO2 contact materials was tested, the arc duration and mass loss before and after arc erosion were determined, the surface morphologies and compositions of Ag?4%SnO2 contact materials after arc erosion were characterized, and the arc erosion mechanism of AgSnO2 contact materials was discussed. The results show that fine SnO2 particle is beneficial for the improvement of the relative density and hardness, but decreases the electrical conductivity. With the decrease of SnO2 particle size, Ag?4%SnO2contact material presents shorter arc duration, less mass loss, larger erosion area and shallower arc erosion pits.

Effect of grain size of primary α phase on bonding interface characteristic and mechanical property of press bonded Ti-6Al-4V alloy

The effect of grain size of primary α phase on the bonding interface characteristic and shear strength of bond was investigated in the press bonding of Ti-6Al-4V alloy. The quantitative results show that the average size of voids increases from 0.8 to 2.6 μm and the bonding ratio decreases from 90.9% to 77.8% with an increase in grain size of primary α phase from 8.2 to 16.4 μm. The shape of voids changes from the tiny round to the irregular strip. The highest shear strength of bond can be obtained in the Ti-6Al-4V alloy with a grain size of 8.2 μm. This is contributed to the higher ability of plastic flow and more short-paths for diffusion in the alloy with smaller grain size of primary α phase, which promote the void closure process and the formation of α/β grains across bonding interface.

A wideband low-phase-noise LC VCO for DRM/DAB frequency synthesizer

The wideband CMOS voltage-controlled oscillator（VCO）with low phase noise and low power consumption is presented for a DRM/DAB（digital radio mondiale and digital audio broadcasting）frequency synthesizer.In order to obtain a wide band and a large tuning range,a parallel switched capacitor bank is added in the LC tank.The proposed VCO is implemented in SMIC 0.18-μm RF CMOS technology and the chip area is 750 μm×560 μm,including the test buffer circuit and the pads.Measured results show that the tuning range is 44.6%;i.e.,the frequency turning range is from 2.27 to 3.57 GHz.The measured phase noise is-122.22 dBc/Hz at a 1 MHz offset from the carrier.The maximum power consumption of the core part is 6.16 mW at a 1.8 V power supply.

Effect of proteins,polysaccharides,and particle sizes on sludge dewaterability

Four batch experiments of hydrolysis and acidification were carried out to investigate the distributions of proteins （PN） and polysaccharides （PS） in the sludge, the PN/PS ratio, the particle sizes, and their relationship with sludge dewaterability （as determined by capillary suction time, CST）. The sludge flocs were stratified through centrifugation- and ultrasound-based method into four fractions： （1） slime, （2） loosely bound extracellular polymeric substances （LB-EPS）, （3） tightly bound EPS （TB-EPS）, and （4） pellet. The results showed that PN was mainly partitioned in the pellet （80.7%） and TB-EPS （9.6%） fractions, while PS distributed evenly in the four fractions. During hydrolysis and acidification, PN was transferred from the pellet and TB-EPS fractions to the slime fraction, but PS had no significant transfer trends. The mean particle sizes of the sludge flocs decreased with hydrolysis and acidification. The pH had a more significant influence on the dewaterability of sludge flocs than temperature. Sludge dewaterability during hydrolysis and acidification processes greatly deteriorated from 9.7 s at raw sludge to 340-450 s under alkaline conditions. However, it was just slightly increased under acidic conditions. Further investigation suggested that CST was affected by soluble PN, soluble PN/PS, and particle sizes of sludge flocs, but was affected slightly by total PN, PS, or PN/PS in the whole sludge flocs and other fractions （except slime）.

Effects of Additive AlCl_3 on Crystal Phase, Particle Size and Microstructural Parameters of Nanocrystalline TiO_2 Prepared by HF-PCVD

Nanocrystalline TiO2 was prepared by high frequency plasma chemical vapor deposition (HF-PCVD). The effects of additive AlCl3 on crystal phase, particle size and microstructurai parameters of TiO2 nanocrystallites were investigated by X-ray diffraction(XRD) and transmission electron microscopy (TEM). The nanocrystallites obtained experimentally are mixture of anatase and rutile, the uniform diameters of particles are about 30 nm. The phase transformation from anatase to rutile was accelerated by AlCl3, and rutile content is increased from 26.7 wt pct to 53.6 wt pct with increasing of addition of AlCl3 from 0.0 wt pct to 5.0 wt pct. The particle size is reduced and the size distribution becomes very narrow. The crystal lattice constants have the trend to decrease, and celi volumes appear as shrinkable.

Leaching behavior of V,Pb,Cd,Cr,and As from stone coal waste rock with different particle sizes

This paper investigates the leaching behavior of heavy metals(V,Pb,Cd,Cr,and As) from stone coal waste rocks with various particle sizes using dynamic leaching experiments.The results show that the dissolved concentrations of V and As initially increased and then slightly decreased as time progressed and that the dissolved concentrations of Pb,Cd,and Cr were high in the early stage before decreasing.The particle size of the stone coal waste rocks strongly influenced the heavy metal concentration in the leaching solutions.The effects of the particle size of the stone coal waste rocks on the dissolved concentrations of V,Pb,and As decreased in the order fine fraction > medium fraction > coarse fraction,and the effects of particle size on the dissolved concentrations of Cr and Cd decreased in the order medium fraction > coarse fraction > fine fraction and coarse fraction > medium fraction > fine fraction,respectively.The quantities of heavy metals dissolved from the stone coal waste rock with fine particle sizes were observed to decrease in the order V(17104.36 μg/kg) > As(609.41 μg/kg) > Pb(469.24 μg/kg) > Cr(56.35 μg/kg) > Cd(27.52 μg/kg),and the dissolution rates decreased in the order As(2.96%) > Pb(0.93%) > V(0.35%) > Cd(0.25%) > Cr(0.01%).The specific surface area,pore size of the stone coal waste rocks,and chemical forms of heavy metals also influenced the release of heavy metals from the stone coal waste rocks.Kinetic analysis showed that the dissolution of heavy metals fundamentally agreed with the rate equation controlled by the shrinking core model.The results of this study are expected to serve as a reference for the evaluation of heavy metals contamination from stone coal waste rocks.

Characterization of size effect of natural convection in melting process of phase change material in square cavity

The accelerating effect of natural convection on the melting of phase change material(PCM)has been extensively demonstrated.However,such an influence is directly dependent on the size and shape of domain in which phase change happens,and how to quantitatively describe such an influence is still challenging.On the other hand,the simulation of natural convection process is considerably difficult,involving complex fluid flow in a region changing with time,and is typically not operable in practice.To overcome these obstacles,the present study aims to quantitatively investigate the size effect of natural convection in the melting process of PCM paraffin filled in a square latent heat storage system through experiment and simulation,and ultimately a correlation equation to represent its contribution is proposed.Firstly,the paraffin melting experiment is conducted to validate the two-dimensional finite element model based on the enthalpy method.Subsequently,a comprehensive investigation is performed numerically for various domain sizes.The results show that the melting behavior of paraffin is dominated by the thermal convection.When the melting time exceeds 50 s,a whirlpoor flow caused by natural convection appears in the upper liquid phase region close to the heating wall,and then its influencing range gradually increases to accelerate the melting of paraffin.However,its intensity gradually decreases as the distance between the melting front and the heating wall increases.Besides,it is found that the correlation between the total melting time and the domain size approximately exhibits a power law.When the domain size is less than 2 mm,the accelerating effect of natural convection becomes very weak and can be ignored in practice.Moreover,in order to simplify the complex calculation of natural convection,the equivalent thermal conductivity concept is proposed to include the contribution of natural convection to the total melting time,and an empirical correlation is given for engineering applications.

基于CTA颅内动脉瘤形态联合PHASES评分对破裂出血预测研究

目的:分析头颈部计算机断层扫描血管成像(CTA)联合PHASES评分对颅内动脉瘤(IA)破裂出血的预测价值。方法:回顾性分析2021年10月—2023年9月东莞市长安医院诊治的IA患者临床资料,根据IA破裂出血与否分为IA破裂组(n=46)和IA未破裂组(n=44),收集两组临床资料,对比两组患者CTA影像瘤体特征参数和PHASES评分结果。采用受试者工作特征(ROC)曲线分析两者联合预测动脉瘤破裂的效能。结果:IA破裂组高血压、糖尿病发生率及PHASES评分均高于IA未破裂组,差异有统计学意义(P <0.05)。两组病灶位置以颈内动脉(ICA)和大脑中动脉(MCA)为主,但IA破裂组病灶位置在MCA的占比为41.30%,高于IA未破裂组的20.45%,瘤体>7 mm的最多(瘤体7~9.9 mm占65.22%),瘤体形态不规则占58.7%,未破裂组病灶位置在ICA最多(68.18%),瘤体<7 mm的居多(75.00%),瘤体形态规则囊状动脉瘤占93.18%,差异有统计学意义(P <0.05)。CTA瘤体特征参数比较,IA破裂组患者瘤颈宽度、瘤体高度、瘤体长度、动脉瘤最大直径、入射夹角、动脉瘤体颈比等参数均高于IA未破裂组,差异有统计学意义(P <0.05)。CTA瘤体特征参数+PHASES评分联合预测曲线下面积为0.916,高于CTA瘤体特征参数(0.901)和PHASES评分(0.731)。结论:CTA瘤体特征参数+PHASES评分联合预测IA患者破裂出血效能最佳。

Influence of processing parameters on the phase composition of ZrN-Si_3N_4 synthesized from zircon

The optimum parameters were determined for synthesizing ZrN-Si3N4 composite powder from zircon by carbothermal reduction-nitridation （CTRN） process. The samples were prepared by mixing the carbon black of an average particle size less than 30 μm and the zircon of 40 μm with C/ZrSiO4 mass ratios of 0.2, 0.3, 0.4, and 0.5. The prepared samples were subjected to the CTRN process at temperatures of 1673, 1723, 1753, and 1773 K for 6, 9, and 12 h. The CTRN process was conducted in an atmosphere-controlled tubular furnace in a nitrogen gas flow of 1.0 L/rain. All the products were examined by X-ray powder diffraction to determine the transformation. The results showed that the proper transformation of ZrN-Si3N4 occurred at 1773 K for 12 h with a C/ZrSiO4 mass ratio of 0.4.

Effect of gap size on microstructure of transient liquid phase bonded IN-738LC superalloy

In order to investigate the microstructure evolution and gain complete isothermal solidification time, transient liquid phase （TLP） bonding of IN-738LC superalloy was carried out using powdered AMS 4777 as the filler metal. The influence of gap size and bonding time on the joints was investigated. For example, complete isothermal solidification time for 40μm gap size was obtained as 45 min. In the case of lack of completion of isothermal solidification step, the remained molten interlayer cooled in the bonding zone under non-equilibrium condition andγ–γ′ eutectic phase formed in that area. The relationship between gap size and holding time was not linear. With the increase in gap size, eutectic phase width became thicker. In the diffusion affected zone, a much larger amount of alloying elements were observed reaching a peak. These peaks might be due to the formation of boride or silicide intermetallic. With the increase in gap size, the time required for bonding will increase, so the alloying elements have more time for diffusion and distribution in farther areas. As a result, concentrations of alloying elements decreased slightly with the increase in the gap size. The present bi-phasic model did not properly predict the complete isothermal solidification time for IN-738LC-AMS 4777-IN-738LC TLP bonding system.

Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards (Agamidae) with Different Body Sizes and Habitat Use

We acclimated adults of two viviparous （Phrynocephalus guinanens＆ and P. vlangalii） and one oviparous （P. versicolor） species of toad-headed lizards （Agamidae） to 28 ℃, 33 ℃ and 38 ℃ to examine whether thermal preference （preferred body temperature, Tp） and thermal tolerance （critical thermal minimum, CTMin; critical thermal maximum, CTMax） were affected by acclimation temperature, and correlate with body size and habitat use. Both Tp and CTMax were highest in P. versicolor and lowest in P. vlangalii, with P. guinanensis in between. The two viviparous species did not differ in CTMin and thermal tolerance range, and they both were more resistant to low temperatures and had a wider range of thermal tolerance than the oviparous species. Both CTMin and CTMax shifted upward as acclimation temperature increased in all the three species. Tp was higher in the lizards acclimated to 33 ℃ than in those to 28 ℃ or 38 ℃. The range of thermal tolerance was wider in the lizards acclimated to 28 ℃ than in those to 33 ℃ or 38 ℃. The data showed that： 1） thermal preference and tolerance were affected by acclimation temperature, and differed among the three species of Phrynocephalus lizards with different body sizes and habitat uses; 2） both Tp and CTMax were higher in the species exchanging heat more rapidly with the environment, and CTMin was higher in the species using warmer habitats during the active season; and 3） thermal preference and tolerance might correlat with body size and habitat use in Phrynocephalus lizards.

Microstructure, Content and in vitro Release of Brucine and Strychnine in Strychnos Nux-Vomica Powder with Different Particle Sizes

To explore the effect of particle size on the quality uniformity and in vitro release performance of Strychnos nux-vomica powder, seven samples of Strychnos nux-vomica powder with different particle sizes were prepared.Microstructures and particle sizes were analyzed, and high performance liquid chromatography(HPLC) was used to test the contents and in vitro release performances of brucine and strychnine in the samples. Results showed that the contents and the in vitro release rates of brucine(or strychnine) in different samples were different since there are different proportions of endosperms to epidermal cells in Strychnos nux-vomica powder with different particle sizes. Brucine and strychnine in each sample were promptly released in the first ten minutes and their cumulative release rates were higher than 70% after ten minutes. Eighty minutes later, the cumulative release rate tended to be a constant. Considering the quality uniformity and safety of Strychnos nux-vomica powder used as traditional Chinese medicine, it would be better to control the particle size of Strychnos nux-vomica powder between 100 and 140 mesh in which the maximum cumulative release rate in vitro of brucine and strychnine can be relatively low within this range.

Characteristics of phosphorus adsorption by sediment mineral matrices with different particle sizes

The particle size of sediment is one of the main factors that influence the phosphorus physical adsorption on sediment. In order to eliminate the effect of other components of sediment on the phosphorus physical adsorption, the sediment mineral matrices were obtained by removing inorganic matter, metal oxides, and organic matter from natural sediments, which were collected from the Nantong reach of the Yangtze River. The results show that an exponential relationship exists between the median particle size （Ds0） and specific surface area （Sg） of the sediment mineral matrices, and the fine sediment mineral matrix sample has a larger specific surface area and pore volume than the coarse sediment particles. The kinetic equations were used to describe the phosphorus adsorption process of the sediment mineral matrices, including the Elovich equation, quasi-first-order adsorption kinetic equation, and quasi-second-order adsorption kinetic equation. The results show that the quasi-second-order adsorption kinetic equation has the best fitting effect. Using the mass conservation and Langmuir adsorption kinetic equations, a formula was deduced to calculate the equilibrium adsorption capacity of the sediment mineral matrices. The results of this study show that the phosphorus adsorption capacity decreases with the increase of Ds0, indicating that the specific surface area and pore volume are the main factors in determining the phosphorus adsorption capacity of the sediment mineral matrices. This study will help understand the important role of sediment in the transformation of phosphorus in aquatic environments.