Quasi Maximum Likelihood for MESS Varying Coefficient Panel Data Models with Fixed Effects

The study of spatial econometrics has developed rapidly and has found wide applications in many different scientific fields,such as demog­raphy,epidemiology,regional economics,and psychology.With the deepening of research,some scholars find that there are some model specifications in spatial econometrics,such as spatial autoregressive(SAR)model and matrix exponential spatial specification(MESS),which cannot be nested within each other.Compared with the common SAR models,the MESS models have computational advantages because it eliminates the need for logarithmic determinant calculation in maxi­mum likelihood estimation and Bayesian estimation.Meanwhile,MESS models have theoretical advantages.However,the theoretical research and application of MESS models have not been promoted vigorously.Therefore,the study of MESS model theory has practical significance.This paper studies the quasi maximum likelihood estimation for ma­trix exponential spatial specification(MESS)varying coefficient panel data models with fixed effects.It is shown that the estimators of model parameters and function coefficients satisfy the consistency and asymp­totic normality to make a further supplement for the theoretical study of MESS model.

A comparison of the short-term effects of fixed platform versus rotating high-fiexion prosthesis for the patients with osteoarthrities of knee

Objective To compare the preliminary clinical outcome between fixed platform and rotating high-flexion prosthesis following total knee replacement(TKR).Methods Form January 2007 to December 2009,68 patients with osteoarthritis of

Fixed-effect and random-effects models in meta-analysis

A systematic review synthesizes evidence addressing a structured clinical question using systematic and explicit methods to search,identify,screen,critically appraise,and extract and analyze data from relevant studies.[1]A meta-analysis,on the other hand,is a statistical method that combines the quantitative results of available primary studies addressing the same question to generate a pooled summary estimate and confidence interval(CI).[2]Meta-analyses can increase statistical power,enhance precision,and answer questions that single trials are underpowered to address.Although there are systematic reviews where meta-analyses are not appropriate,when they are well-conducted and reported,systematic reviews combined with meta-analyses provide valuable information for clinicians,researchers,and policymakers.

Buckling-controlled two-way shape memory effect in a ring-shaped bilayer

Shape memory polymers(SMPs)usually have a one-way shape memory effect.In this paper,an easy-operating method to realize a two-way shape memory effect was demonstrated in a ring-shaped bilayer structure where the two layers are SMPs with different thermal transition temperatures.By designing specific thermomechanical processes,the mismatched deformation between the two layers leads to a morphology change of ring-shaped bilayer structures from a smooth ring to a gear-like buckling shape under cooling and a reversible recovery to the smooth shape under heating.Such a morphology change is ascribed to occurrence and recovery of thermoelastic buckling.This method was validated by finite element simulation.We experimentally investigated the influence of pre-strain on buckling,and it was found that both the buckling occurrence and recovery temperature vary with pre-strain.Furthermore,considering a ring-shaped SMP-SMP bilayer structure,finite element analysis was conducted to study the influence of film thickness and modulus ratio of two layers on buckling behavior.The results showed that the critical buckling wavelength was greatly influenced by film thickness and modulus ratio.W e made a theoretical analysis that accorded well with the numerical results.

Effect of Training on Two-way Shape Memory Effect and Its Stability in a Ti-Ni-Hf High Temperature Shape Memory Alloy

The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36l\li49Hf15 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.

Two-way Shape Memory Effect in a Ti-Ni-Nb Shape Memory Alloy with Wide Hysteresis

A two-way shape memory effect (TWSM E) in the Ti46.3Ni44.7Nb9 alloy has been systematically investigated by means of bending test and transmission electron microscopy (TEM ) observations. Based on the analysis of the microstructure after training. the mechanism of TWSME in the Ti46.3 Ni44.7Nb9 alloy has been discussed.

Bootstrap inference of the skew-normal two-way classification random effects model with interaction

In this paper,we consider the statistical inference problems for the fixed effect and variance component functions in the two-way classification random effects model with skewnormal errors.Firstly,the exact test statistic for the fixed effect is constructed.Secondly,using the Bootstrap approach and generalized approach,the one-sided hypothesis testing and interval estimation problems for the single variance component,the sum and ratio of variance components are discussed respectively.Further,the Monte Carlo simulation results indicate that the exact test statistic performs well in the one-sided hypothesis testing problem for the fixed effect.And the Bootstrap approach is better than the generalized approach in the one-sided hypothesis testing problems for variance component functions in most cases.Finally,the above approaches are applied to the real data examples of the consumer price index and value-added index of three industries to verify their rationality and effectiveness.

Removal of Lead Ions from Ginseng Ethanol Extracts by Dynamic Adsorption in a Fixed-bed Column

The removal of lead from ginseng ethanol extracts by a fixed-bed column filled with an adsorbent bearing amine and carboxyl groups was investigated. The Pb2+ content was determined by inductively coupled plasma mass spectrometry. When the flowrate increased from 0.12 to 0.34 ml·min-1 , the column exhibited a marked increase in percentage of lead removal from 54.9% to 92.3%. Further increase in the flowrate did not bring evident changes to the lead removal, whereas an increase in the temperature could reinforce adsorption further, suggesting that the adsorption process was controlled by external film diffusion below the flowrate of 0.34 ml·min-1 , and by the intraparticle pore diffusion of lead ions when the flowrate exceeded it. A low remaining lead amount in extracts such as 0.11 mg·kg-1 (extracts powder) was achieved. The adsorbents also adsorbed effective constituents to some extent. But 88% of constituents adsorbed were taken off using a 70% ethanol aqueous solution.

Effect of Thermal Cycling under Load on Martensite Transformation and Two-way Shape Memory Effect in a TiNi Alloy

The effect of thermal cycling under loading on martensitic transformation and two-way shape memory effect was investigated for Ti-49.8 at. pci Ni alloy. It is shown that Ms and Mf temperature increase with increasing the number of cycles, while As and Af temperature decrease during thermal cycling. The total strain et and permanent strain ep increase with increasing applied stress and number of cycles. The two-way shape memory effect can be improved by proper thermal cycling training under loading, while excessively high applied stress results in the deterioration of TWSME. The reason for the changes in martensitic transformation characteristics and two-way shape memory effect during thermal cycling under loading is discussed based on the analysis of microstructure by TEM observations.

数字经济发展促进产业结构转型升级的实证研究

从理论上来说,数字经济发展通过影响产业间结构转变、产业内劳动生产率提升和产业资源配置效率提高等方式来促进产业结构转型升级。文章以我国247个地级及以上城市2016—2019年的数据为例,采用固定效应模型分析数字经济发展对产业结构转型升级的影响。实证结果发现:数字经济发展对第一维度、第二维度和第三维度产业结构转型升级均具有显著的促进作用,子样本数据的实证结果和采取替代变量的实证结果均支持这一研究结论;在控制内生性问题后,研究结论依然成立。进一步的机制检验发现,数字经济发展主要通过消费升级效应和技术外溢效应两种途径促进产业结构转型升级。

数字经济对生态效率的非线性影响--基于门槛效应的检验

数字经济与生态环境是关乎中国式现代化发展的重要议题。本文从数字产业化与产业数字化两个维度,运用熵权法对中国30个省(区、市)2011—2021年数字经济发展水平进行测度,并利用双向固定效应、门槛效应等方法实证分析了数字经济对生态效率的影响。研究发现:数字经济显著促进了生态效率的提升,且这一结论通过了工具变量法、调整样本期和改变模型设定等稳健性检验;数字经济对生态效率的促进效应具有非线性关系,存在以数字经济、环境规制强度为门槛变量的单一门槛效应;进一步的异质性分析表明,数字经济对生态效率的促进效应、单一门槛效应以及“边际效应”递增的非线性特征在南方地区和不同数字经济维度下显著。最后,根据研究结论就如何发展数字经济提升生态效率的路径提出政策建议。

一株旱稻联合固氮菌株的分离鉴定及促生作用

[目的]旱稻是一种重要的种质资源,对成熟期旱稻根系内生固氮菌进行筛选与鉴定,以获得对旱稻有较好促生作用的菌株。[方法]采用联合固氮固体培养基培养方法,从成熟期旱稻根系中分离出内生固氮菌,通过扩增固氮酶nifH基因和16S rRNA基因进行分子鉴定和系统进化分析生化指标测定和形态学鉴定;采用透明圈法进行溶磷、产铁载体能力验证;以褐球固氮菌为阳性对照,利用ELISA测定试剂盒测定菌株分泌固氮酶活性、1-氨基环丙烷-1-羧酸(ACC)脱氨酶,采用Salkowski比色法测定生长素(IAA)含量,并研究其生长特征。将分离的固氮菌株以1%浓度(约8×10~7CFU/mL)浸泡旱稻谷种进行催芽,研究其促生效果。[结果]分离的菌株URR45为固氮菌,属于嗜温型微生物,最适生长温度为32~50℃,最适pH为6.0~6.5,不耐盐。其分泌的固氮酶含量为220.15 U/L,ACC含量为898.69 ng/mL,生长素含量为14.91 mg/L,固氮酶含量和ACC含量显著高于对照组褐球固氮菌。该菌株能够利用葡萄糖、麦芽糖等碳源,属于发酵型细菌,具有水解明胶、溶磷和产铁载体特性。该菌株经16S rRNA基因测序后通过NCBI BLAST比对,鉴定为Herbaspirillum seropedicae,隶属于Pseudomonadota门、Betaproteobacteria纲、Burkholderiale目、Oxalobacteraceae科、Herbaspirillum属,革兰氏染色呈阴性。促生试验结果表明,在主根长度、侧根长度以及测根数方面均显著高于对照组。[结论]该菌株对旱稻幼苗具有一定的促生作用,在农业上产上可作为功能性内生固氮菌开发利用。

中国人口流动的健康轨迹研究

人口的高流动性和流动人口快速老化已成为中国人口发展的显著特征。研究人口流动对我国城乡居民健康的影响及其变动趋势,对于理解和实现健康老龄化,改善人口健康水平具有重要意义。现有研究较多分析流动人口相比于城镇居民的健康状况,而对流动人口和农村居民的健康差异的研究相对缺乏;对于流动人口在老年阶段的健康状况与户籍人口的差异以及流动对人口健康的影响等关键问题尚没有确定结论。本文旨在探讨人口流动与个体健康的因果关系以及流动人口和城乡户籍人口之间随时间和年龄变化的健康差异。本文利用中国家庭动态追踪调查(CFPS)2010-2020年连续六次调查的面板数据,采用固定效应模型和线性回归模型分析人口流动的健康效应和年龄效应。研究发现2012-2020年流动对人口健康的总体影响为负,验证了流动具有健康损耗效应,存在“流行病学悖论”。从时期维度看,流动对人口健康的影响呈现由健康优势转为健康劣势的趋势,人口流动的健康选择效应和流动经历的内在健康损耗效应并存。初期流动人口具有健康优势,健康自评状况优于城乡户籍人口。随着时间推进,健康优势逐渐收敛,健康损耗效应逐渐显现。从年龄维度看,流动人口和城乡户籍人口的自评健康水平随着年龄增加都呈下降趋势,但流动人口的下降速度显著慢于城乡户籍人口,其健康优势在老年阶段逐渐消失。上述发现的政策含义是:在人口老龄化不断加深和流动人口规模保持高位,流动人口老化愈加明显的背景下,流动人口的健康老龄化成为重要挑战,在政策实践层面应关注流动经历对个体生命周期的持续影响,尤其是要重视城镇中的高龄流动人口返乡回流将健康风险转移到农村,从而增加农村整体的健康脆弱性和健康照护成本,应将人口流动因素作为优化城乡卫生健康资源配置的重要考量。

佛山地区固定献血屋与流动献血车献血工作成效分析

目的 分析固定献血屋与流动献血车在佛山地区无偿献血工作中的成效。方法 随机抽选佛山市街头流动献血车与献血屋各4个,对其2022年8月—2023年8月各类调查数据进行分析。结果 固定献血屋单点日均采血量为(59.63±5.54)U,固定献血者比例为(22.45±1.31)%,均高于流动献血车的(50.17±5.13)U、(18.03±1.25)%(P <0.05);献血不良反应发生率为(0.21±0.05)%,低于流动献血车的(0.95±0.12)%(P <0.05);工作人员对固定献血屋总满意度为100%,高于流动献血车的85.71%(P <0.05);献血者对固定献血屋总满意度为97.88%,高于流动献血车的89.64%(P <0.05)。结论 佛山地区无偿献血工作中固定献血屋与流动献血车相比单点日均采血量与固定献血者比例均更高,且工作人员与献血者满意度也更高,因此日后需要对献血屋和献血车进行改进,提高固定献血率。

数字普惠金融对耕地利用效率的影响——2011—2020年中部六省的实证

研究目的:探究数字普惠金融对于耕地利用效率的影响效应及机制,为数字普惠金融助力耕地利用效率提升提供参考。研究方法:超效率SBM模型,双向固定效应模型,中介效应模型。研究结果:(1)2011—2020年研究区耕地利用效率波动性提升且高值分布由点状演变为片状;(2)数字普惠金融指数和各维度指标对耕地利用效率均具有显著正向影响;(3)数字普惠金融对耕地利用效率的影响存在省份异质性、阶段异质性和规模异质性;(4)机制分析表明,数字普惠金融可以通过提高农民人均可支配收入和增加第一产业固定资产投资提升耕地利用效率。研究结论:应推动数字普惠金融向高质量发展转型,进一步激发信贷、投资和保险对耕地利用效率的正向作用,精准匹配金融服务需求,通过提高农民收入和增加第一产业固定资产投资改进耕地利用效率。

西部地区城镇居民文化消费的影响机制

基于2010—2020年西部地区数据,运用固定效应面板模型对城镇居民文化消费的内在影响机制进行实证分析。结果表明:科技创新和文化产业集聚对西部地区城镇居民文化消费影响均有促进作用;区域异质性和产业异质性方面,科技创新和文化产业集聚对西南地区城镇居民文化消费的促进效用均高于西北地区,且对文化服务业的消费市场影响最显著。为了优化西部文化消费结构,应探索文化产业的科技创新型发展路径,提升文化消费市场潜力。

三重价值链耦合协调发展对企业绿色全要素生产率的影响

省内价值链、国内价值链和全球价值链(三重价值链)的融合发展,是畅通国内国际双循环,也是中国企业经济软着陆的关键抓手。在高质量发展有序推进的背景下,绿色全要素生产率成为衡量企业发展的重要指标,因此有必要探讨三重价值链耦合协调发展对企业绿色全要素生产率的影响。该研究利用世界投入产出表、中国多区域投入产出表、上市公司数据测算了三重价值链耦合协调度,基于SBM方法测算包含非期望产出的绿色全要素生产率,整合得到770家上市公司2012年、2015年和2017年的平衡面板数据,通过多维固定效应回归考察三重价值链耦合协调度对企业绿色全要素生产率的影响,研究结果表明:①存在三重价值链耦合协调度提升→GVC嵌入度深化→企业绿色全要素生产率增长的正向传播机制,但效果随着企业的要素密集度增加呈现递减趋势。②机制研究和异质性分析表明,前向耦合协调发展为企业绿色全要素生产率带来更有效和长期的动能,而后向耦合协调发展为劳动密集型企业带来短期显著的绿色生产率提升。基于此,该研究提出了布局本土产业、协调三链关系的相关政策建议:①地方政府应发挥主观能动性,评估本地企业优势,保证在政策制定上更加微观具体,劳动密集型的省份或行业有效利用三重价值链的协调发展为企业的转型升级奠定基础,为地方行业的协同发展打通阻碍。②在要素投入端,注重对地方高新技术企业的资源分配,同时区域间合作完成生产供应端的高度集成,增强前向耦合协调发展对于企业内涵式增长能力的促进效应,兼顾供应链流程的绿色环保标准。③加强省域间的政策协调性和交易通达性,提高各地区企业省域间的市场专业化分工,而非单独地嵌入GVC市场,利用集聚效应推动产业全面升级,打破国内市场循环的技术壁垒。

数字经济何以影响山区农产品流通?——基于贵州省的实证研究

数字经济作为一种新的经济形态,在推动山区农产品物流、商流、信息流共享,改变山区农产品流通方式与流通效率,促进山区农产品流通等方面发挥了重要作用。本研究基于交易成本理论,利用2012—2021年贵州省及其各市(州)相关数据实证分析数字经济对山区农产品流通效率的影响与特征。研究发现:(1)贵州省及各市(州)数字经济发展水平和农产品流通效率均呈现上升趋势,数字经济能够显著促进农产品流通效率的提升;(2)从数字经济的细分维度看,数字产业化能够显著提升农产品流通效率,数字基础设施与数字技术应用对农产品流通效率的提升效果不显著;(3)数字经济对贵州省农产品流通效率的影响具有明显的区域异质性,对贵州地级市农产品流通效率的提升效果显著,而对自治州农产品流通效率提升效果较弱。基于上述研究结论,文章提出了相应的对策建议:完善数字基础设施建设;构建数字化网络平台;提升流通技术水平;制定合理的差异化发展战略。

减税降费规模与地方政府债务风险治理——机制与证据

减税降费是中国为积极应对经济下行压力、维护全局经济稳定的重要政策手段,但其规模的不断扩大会加剧地方政府债务风险。本文通过构建包含“借”、“用”、“还”3个环节的风险指标体系,采用熵权-TOPSIS法测算2015~2022年中国省级地方政府债务风险指数,使用双向固定效应模型、面板门槛模型实证分析减税降费规模对地方政府债务风险的影响。研究发现,减税降费规模与地方政府债务风险总体上呈正相关关系,并且存在经济发展水平的门槛效应,当经济发展水平跨过门槛值时,地方政府债务风险增长速度将显著降低。同时,减税降费规模与地方政府债务风险间存在非线性关系,随着减税降费规模不断扩大,地方政府债务风险增速也将被遏制。

数字化转型助力津门老字号企业品牌发展研究

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