Improvement of radiative recombination rate in deep ultraviolet laser diodes with step-like quantum barrier and aluminum-content graded electron blocking layer

The design of the active region structures,including the modifications of structures of the quantum barrier(QB)and electron blocking layer(EBL),in the deep ultraviolet(DUV)Al Ga N laser diode(LD)is investigated numerically with the Crosslight software.The analyses focus on electron and hole injection efficiency,electron leakage,hole diffusion,and radiative recombination rate.Compared with the reference QB structure,the step-like QB structure provides high radiative recombination and maximum output power.Subsequently,a comparative study is conducted on the performance characteristics with four different EBLs.For the EBL with different Al mole fraction layers,the higher Al-content Al Ga N EBL layer is located closely to the active region,leading the electron current leakage to lower,the carrier injection efficiency to increase,and the radiative recombination rate to improve.

Strength and deformation characteristics of irregular columnar jointed rock mass: A combined experimental and theoretical study

The irregularity of jointed network poses a challenge to the determination of field mechanical param-eters of columnar jointed rock mass(CJRM),and a reasonable prediction of deformation and strength characteristics of CJRM is important for engineering construction.The Voronoi diagram and three-dimensional printing technology were used to make an irregular columnar jointed mold,and the irregular CJRM(ICJRM)specimens with different dip directions and dip angles were prepared.Uniaxial compression tests were performed,and the anisotropic strength and deformation characteristics of ICJRM were described.The failure modes and mechanisms were revealed in accordance with the final appearances of the ICJRM specimens.Based on the model test results,the empirical correlations for determining the field deformation and strength parameters of CJRM were derived using the dip angle and modified joint factor.The proposed empirical equations were used in the Baihetan Project,and the calculated mechanical parameters were compared with the field test results and those obtained from the tunneling quality index method.Results showed that the deformation parameters determined by the two proposed methods are all consistent with the field test results,and these two methods can also estimate the strength parameters effectively.

Effective Pyroelectric Coefficient and Polarization Offset of Compositionally Step-like Graded Ferroelectric Structures

In this paper, the effective pyroelectric coefficient and polarization offset of the compositionally step-like graded multilayer ferroelectric structures have been studied by use of the first-principles approach. It is exhibited that the dielectric gradient has a nontrivial influence on the effective pyroelectric coefficient, but has a little influence on the polarization offset; and the polarization gradient plays an important role in the abnormal hysteresis loop phenomenon of the co.mpositionally step-like graded ferroelectric structures. Moreover, the origin of the polarization offset is explored,which can be attributed to the polarization gradient in the compositionally step-like graded structure.

Intra-Atomic Electric Field Radial Potentials in Step-Like Presentation

Within the frames of semiclassical approach, intra-atomic electric field potentials are parameterized in form of radial step-like functions. Corresponding parameters for 80 chemical elements are tabulated by fitting of the semiclassical energy levels of atomic electrons to their first principle values. In substance binding energy and electronic structure calculations, superposition of the semiclassically parameterized constituent-atomic potentials can serve as a good initial approximation of its inner potential: the estimated errors of the determined structural and energy parameters make up a few percent.

Fracture behaviors of columnar jointed rock mass using interface mechanics theorem

For a special geological structure of columnar jointed rock mass(CJRM),its mechanical properties are strongly affected by the columnar joints.To describe the fracture behaviors of CJRM using the basic theories of interface mechanics for composite materials,the interface stresses of the vertical and horizontal joints,which are the two primary joints in the CJRM under triaxial compression,are studied,and their mathematical expressions are derived based on the superposition principle.Based on the obtained interface stresses of the vertical and horizontal joints in the CJRM,the crack initiation of the joint interface in the CJRM is studied using the maximum circumferential stress theory in fracture mechanics.Moreover,based on this investigation,the fracture behaviors of CJRM are analyzed.According to the results of similar material physical model tests for the CJRM,the theoretical study is verified.Finally,the influence of the mechanical parameters of the CJRM on the joint interface stress is discussed comprehensively.

输尿管结石病人术后发生尿源性脓毒症的风险预测模型构建及验证

目的:基于列线图模型构建输尿管结石病人术后发生尿源性脓毒症(US)的风险预测模型,并进行验证。方法:选取2017年10月—2020年10月于我院收治的600例输尿管结石病人作为模型组,2020年11月—2022年7月于我院收治的110例输尿管结石病人作为验证组。采用Logistic回归分析探究其术后发生US的危险因素,然后构建输尿管结石病人术后发生US的列线图风险预警模型,并验证其预测效能。结果:600例输尿管结石病人中,50例发生US,发生率为8.33%。Logistic回归分析结果显示,性别、糖尿病史、手术时间、术中灌注液体量、结石大小、术前中段尿培养阳性是输尿管结石病人术后发生US的危险因素(P<0.05)。模型组与验证组的受试者工作特征曲线下面积(AUC)分别为0.910[95%CI(0.847,0.973)]和0.885[95%CI(0.797,0.973)],两组校正曲线均与标准曲线拟合较好。结论:性别、糖尿病史、手术时间、术中灌注液体量、结石大小、术前中段尿培养阳性是输尿管结石病人术后发生US的影响因素,本研究基于上述因素构建的输尿管结石病人术后发生US的列线图风险预警模型具有较高的临床应用价值。

早期牙髓炎患者iRoot BP Plus活髓切断术后疗效分析及列线图预测模型构建

目的构建早期牙髓炎患者iRoot BP Plus活髓切断术后失败的个体化预测模型。方法选取2019年1月至2021年12月于秦皇岛市海港医院进行iRoot BP Plus活髓切断术治疗的278例早期牙髓炎患者为研究对象,记录性别、年龄、穿髓孔直径等资料并进行统计学分析,Logistic回归分析确定危险因素,绘制列线图预测模型,进行内部验证并评估临床预测效能及实用性。结果278例早期牙髓炎iRoot BP Plus活髓切断术后失败率为10.43%。将穿髓孔直径、腐质颜色、腐质质地提取为预测因子构建列线图预测模型,列线图预测模型的校正曲线与原始曲线及理想曲线接近,C-index为0.768(95%CI:0.722~0.833),模型拟合度高;列线图预测模型的阈值>0.16,可提供临床净收益,且临床净收益均高于独立预测因子。结论以穿髓孔直径、腐质颜色、腐质质地为预测因子构建的早期牙髓炎患者iRoot BP Plus活髓切断术后失败的列线图预测模型对iRoot BP Plus活髓切断术后失败的发生具有良好的预测价值。

In situ study on columnar-equiaxed transition and anaxial columnar dendrite growth of Al-15%Cu alloy by synchrotron radiography

Directional solidification of Al-15% （mass fraction） Cu alloy was investigated by in situ and real time radiography which was performed by Shanghai synchrotron radiation facility （SSRF）. The imaging results reveal that columnar to equiaxed transition （CET） is provoked by external thermal disturbance. The detaching and floating of fragments of dendrite arms are the prelude of the transition when the solute boundary layer in front of the solid-liquid interface is thin. And the dendrite triangular tip is the fracture sensitive zone. When the conditions are suitable, new dendrites can sprout and grow up. This kind of dendrite has no obvious stem and is named anaxial columnar dendrites.

双辊薄带连铸凝固过程中柱状晶向等轴晶转变的广义稳定性判据

为促进柱状晶向等轴晶转变(CET)获得均匀的等轴晶,大多数有效的理论聚焦于生长而忽略了形核的影响。为此,构建耦合细化剂异质形核和枝晶生长的理论框架,采用考虑双辊薄带连铸(VTC)凝固过程中热力学驱动力(?G)和动力学能垒(Q)的广义稳定性(GS)新概念,研究CET位置、晶粒半径和力学性能。细化剂的加入,尤其是Al-5Ti-1B细化剂,通过增加形核的?G和生长的GS使晶粒半径细化到19μm,柱状枝晶的厚度增大到5~6 mm,同时提高强度和塑性。遵循高?G-高GS准则,细化剂直径优化为0.3μm。

Predictive factors and model validation of post-colon polyp surgery Helicobacter pylori infection

BACKGROUND Recently,research has linked Helicobacter pylori(H.pylori)stomach infection to colonic inflammation,mediated by toxin production,potentially impacting colorectal cancer occurrence.AIM To investigate the risk factors for post-colon polyp surgery,H.pylori infection,and its correlation with pathologic type.METHODS Eighty patients who underwent colon polypectomy in our hospital between January 2019 and January 2023 were retrospectively chosen.They were then randomly split into modeling(n=56)and model validation(n=24)sets using R.The modeling cohort was divided into an H.pylori-infected group(n=37)and an H.pylori-uninfected group(n=19).Binary logistic regression analysis was used to analyze the factors influencing the occurrence of H.pylori infection after colon polyp surgery.A roadmap prediction model was established and validated.Finally,the correlation between the different pathological types of colon polyps and the occurrence of H.pylori infection was analyzed after colon polyp surgery.RESULTS Univariate results showed that age,body mass index(BMI),literacy,alcohol consumption,polyp pathology type,high-risk adenomas,and heavy diet were all influential factors in the development of H.pylori infection after intestinal polypectomy.Binary multifactorial logistic regression analysis showed that age,BMI,and type of polyp pathology were independent predictors of the occurrence of H.pylori infection after intestinal polypectomy.The area under the receiver operating characteristic curve was 0.969[95%confidence interval(95%CI):0.928–1.000]and 0.898(95%CI:0.773–1.000)in the modeling and validation sets,respectively.The slope of the calibration curve of the graph was close to 1,and the goodness-of-fit test was P>0.05 in the two sets.The decision analysis curve showed a high rate of return in both sets.The results of the correlation analysis between different pathological types and the occurrence of H.pylori infection after colon polyp surgery showed that hyperplastic polyps,inflammatory polyps,and the occurrence of H.pylori infection were not significantly correlated.In contrast,adenomatous polyps showed a significant positive correlation with the occurrence of H.pylori infection.CONCLUSION Age,BMI,and polyps of the adenomatous type were independent predictors of H.pylori infection after intestinal polypectomy.Moreover,the further constructed column-line graph prediction model of H.pylori infection after intestinal polypectomy showed good predictive ability.

Predictive value of NLR, Fib4, and APRI in the occurrence of liver failure after hepatectomy in patients with hepatocellular carcinoma

BACKGROUND Neutrophil-lymphocyte ratio(NLR),fibrosis index based on four factors(Fib4),aspartate aminotransferase-to-platelet ratio index(APRI)can be used for prognostic evaluation of hepatocellular carcinoma.However,no study has established an individualized prediction model for the prognosis of hepatocellular carcinoma based on these factors.AIM To screen the factors that affect the prognosis of hepatocellular carcinoma and establish a nomogram model that predicts postoperative liver failure after hepatic resection in patients with hepatocellular carcinoma.METHODS In total,220 patients with hepatocellular carcinoma treated in our hospital from January 2022 to January 2023 were selected.They were divided into 154 participants in the modeling cohort,and 66 in the validation cohort.Comparative analysis of the changes in NLR,Fib4,and APRI levels in 154 patients with hepatocellular carcinoma before liver resection and at 3 mo,6 mo,and 12 mo postoperatively was conducted.Binary logistic regression to analyze the influencing factors on the occurrence of liver failure in hepatocellular carcinoma patients,roadmap prediction modeling,and validation,patient work characteristic curves(ROCs)to evaluate the predictive efficacy of the model,calibration curves to assess the consistency,and decision curve analysis(DCA)to evaluate the model’s validity were also conducted.RESULTS Binary logistic regression showed that Child-Pugh grading,Surgical site,NLR,Fib4,and APRI were all risk factors for liver failure after hepatic resection in patients with hepatocellular carcinoma.The modeling cohort built a column-line graph model,and the area under the ROC curve was 0.986[95%confidence in terval(CI):0.963-1.000].The patients in the validation cohort utilized the column-line graph to predict the probability of survival in the validation cohort and plotted the ROC curve with an area under the curve of the model of 0.692(95%CI:0.548-0.837).The deviation of the actual outcome curves from the calibration curves of the column-line plots generated by the modeling and validation cohorts was small,and the DCA confirmed the validity.CONCLUSION NLR,Fib4,and APRI independently influence posthepatectomy liver failure in patients with hepatocellular carcinoma.The column-line graph prediction model exhibited strong prognostic capability,with substantial concordance between predicted and actual events.

考虑截面规则性的柱状节理岩体变形及强度特性研究

柱状节理岩体的复杂结构使其现场力学参数的确定存在困难,可靠地估计柱状节理岩体强度及变形特性对工程安全至关重要。结合Voronoi图形及3D打印技术制作不规则柱状节理岩体光敏树脂模具,并制备了具有不同倾角的规则及不规则柱状节理岩体试样。基于开展的单轴压缩试验结果,分析不同截面柱状节理岩体的变形及强度特性差异。根据试样最终破坏形态,揭示柱状节理岩体破坏模式及机制。结合已有研究结果,描述节理面材料对柱状节理岩体破坏形态及强度的影响。基于传统节理系数方法,提出了更能反映柱状节理岩体柱体结构特征的修正节理系数方法。采用修正节理系数法建立规则及不规则柱状节理岩体试验结果与现场变形及强度参数间的经验关系,将所提出计算公式应用于白鹤滩水电站工程,预测结果与现场实测值及RMR法(RMR为岩石质量评分指标)、Q法(Q为岩体质量指标)的预测值进行比较。结果表明,对于现场变形和强度参数,所提出的修正节理系数法的预测结果与现场实测结果较为吻合。

模型冰水平圆盘中心加载弯曲强度试验研究

由各种垂直施力引起的冰层破坏是极地探索和利用活动中重要的工程场景,而冰强度特性对于活动于此区域的平台的结构强度和安全操控的设计评估有直接影响。本文依托中国船舶科学研究中心小型冰水池,制作盐水柱状模型冰,开展模型冰水平圆盘中心加载试验。试验对环向外沿均布支撑下的水平圆盘冰样中心区域垂直加载,利用测力系统记录冰样从起始承载直至弯曲破坏的力值曲线,根据受力峰值求取冰样破坏时的弯曲强度,利用影像系统捕捉冰样破坏失效细节,分析冰样承载失效过程。在此基础上,改变加载速度和冰样温度,开展系列试验测量,分析两个因素对模型冰弯曲强度的影响。本文工作为测量分析模型冰强度特性补充了一种可行手段,也为深入研究冰区结构物与冰层垂直作用机理和冰载荷形成机制建立了初步基础。

用Columnar模型对电子空穴对复合逃逸产额的模拟计算

用一种比较简单的 Jaffe近似方法计算了质子在 Si O2 中的电子空穴对的逃逸率 ,讨论了辐照偏置、电场、质子入射角度、质子能量等对逃逸产额的影响 .得到了电子空穴对复合逃逸率与质子能量、电场成正比的结果 .计算结果与实验结果的比较 ,说明了 Jaffe近似方法可以比较正确地描述质子在二氧化硅中的总剂量效应 .

污水泵内颗粒通过性能及流动损失特性研究

为了研究柱状颗粒参数对污水泵内固液两相流动特性以及通过性能的影响规律,采用CFD-DEM耦合方法计算了离心泵内固液两相流动,基于熵产理论分析了不同颗粒物性条件下泵内的流动损失特性,并通过试验对其进行了验证。结果表明:柱状颗粒长径比、体积分数和密度影响了污水泵内颗粒的通过性能以及流动损失;固相浓度从1%增大至5%,泵的扬程降低1.97 m,效率降低2.2%,颗粒通过能力逐渐降低;颗粒密度从1000 kg/m^(3)增大至2500 kg/m^(3),泵的扬程降低1.63 m,效率降低3.76%,颗粒通过能力略有增强;在各工况下,总熵产变化规律与泵性能变化规律一致,高熵产区域主要集中在叶片进口边附近,说明熵产分析能够有效反映泵内的流动损失特性。研究结果可为污水泵的优化设计提供理论依据。

X波段双偏振雷达物理量时间—高度剖面的重构方法改进及应用研究

如何利用现有雷达体扫数据重构反射率或其它物理量的时间—高度剖面,提高雷达体扫垂直分辨率并使其适用于云微物理结构的分析,是近几年来雷达气象学的重点研究内容之一。本文基于分辨率更高的X波段双偏振雷达体扫数据,对目前最新的柱垂直廓线(Columnar Vertical Profile,简称CVP)重构算法从目标区范围的选取方面进行改进,使其能够应用于水平尺度较小的局地降水云以及发展演变迅速的对流云。结果显示:对于高原地区局地降水云个例,目标区选取5 km(径向范围)×10°(方位角范围)组成的较小扇形区域,与云雷达的对比显示,改进的CVP方法重构的基本反射率(ZH)垂直廓线体现了回波的垂直结构,尤其是中高层对流泡的结构特点,相应的时间—高度序列能够较好地反映回波顶高的变化以及中高层强度逐渐减弱、低层强度逐渐增加的特点;对于华北地区发展旺盛且局地水平不均匀的对流云个例,本文改进了原始的CVP重构目标区选取方法,对高、低仰角层采用变化的径向范围并调整插值参数,改进后重构的ZH垂直廓线有效避免了低层回波水平分布相对不均匀导致的重构分层结构,显示出高、低层回波特征以及不同阶段目标区云结构的转变。进一步对比改进前后CVP方法重构建立的各偏振量时间—高度序列,改进后准确显示了个例云系微物理特征及其随时间的变化,揭示了高原地区局地降水云中对流泡的形成及其播撒作用机制,华北地区对流云成熟阶段的各偏振量垂直分布特征及其演变。

柱状活性炭固体磷酸的制备及其催化性能的研究

为了降低酯化反应实验教学的安全隐患同时也为了增强学生的绿色环保意识,可采用固体酸替代强腐蚀性的浓硫酸来催化乙酸乙酯的合成。实验采用直接浸渍法和二次煅烧法制备了柱状活性炭固体磷酸,以磷酸负载量为评价指标优化了制备条件,利用二次煅烧后的柱状活性炭固体磷酸催化乙酸乙酯的合成并对其反应条件进行了优化。结果表明柱状活性炭固体磷酸的最佳制备条件为煅烧温度为260℃,活性炭的浸渍时间为25 h,煅烧时间为4 h。经SEM分析,二次煅烧后的柱状活性炭固体磷酸结构更加蓬松,更有利于酯化反应的进行。在最佳反应条件下,乙酸乙酯的产率能达到80.4%,重复使用3次后乙酸乙酯的产率依然可达41.7%。实验引导学生设计并制备了具有较高催化活性的固体磷酸催化剂,该过程不但可在学生心中牢牢树立安全第一、结果与环保并重的理念,也为酯化反应的绿色化改进提供有意义的借鉴。

陡倾柱状节理岩体洞室松弛特征与破坏机制

白鹤滩水电站柱状节理岩体具有特殊的柱体结构特征,洞室开挖后卸荷松弛破坏严重。通过对白鹤滩水电站4#导流洞柱状节理岩体现场破坏调查、位移和松弛深度监测,发现柱状节理洞室呈现典型的非对称破坏特征,不同部位松弛深度差异较大,左右侧边墙破坏模式受倾角影响,分别呈现倾倒破坏和滑移破坏。离散元数值模拟结果显示洞室表层围岩主要以柱间节理张拉破坏为主,内部围岩以剪切破坏为主,左右侧边墙不同的变形破坏特征是柱体倾角和地应力综合作用的结果。最后分析了不同柱体倾角对洞室变形破坏特征的影响,不同倾角下洞室各部位松弛深度差异显著,应根据洞室不同部位塑性区深度和柱体角度进行预应力锚杆设计。

TiAl金属间化合物定向技术研究进展

TiAl合金具有低密度和良好的高温性能,被视为航空航天领域极具应用潜力的一类新型结构材料。具有柱晶/单晶组织特征的全片层结构TiAl合金展现出极为优异的高温综合力学性能。本文首先介绍了定向TiAl合金的发展背景、定向组织、力学性能各向异性等基本概念;然后,基于工作原理、关键技术、组织特征三个层面,对传统Bridgman法、光学浮区法、电磁约束以及电磁冷坩埚等定向技术进行了论述;进一步,结合最新研究成果,对定向退火制备TiAl合金的工作进行了阐述;最后,展望了TiAl合金定向技术的研究方向,指出需要从优化成分设计、组织/相变可控、大尺度定向晶稳定制备等方面发展新原理与新技术。