Expanded models of the project portfolio selection problem with learning effect

This research develops two new models for project portfolio selection, in which the candidate projects are composed of multiple repetitive units. To reflect some real situations, the learning effect is considered in the project portfolio selection problem for the first time. The mathematical representations of the relationship between learning experience and investment cost are provided. One numerical example under different scenarios is demonstrated and the impact of considering learning effect is then discussed.

Effect of Expanded Polytetrafluoroethylene Combined with Autologous Ear Cartilage in Nasal Plastic Surgery

Objective:To explore the effect of combined application of expanded polytetrafluoroethylene and autologous ear cartilage in nasal plastic surgery.Methods:76 cases of nasal plastic surgery patients in our hospital from September 2019 to September 2020 were selected as the research objects and divided into experimental group(38 cases,treated with expanded polytetrafluoroethylene+autologous ear cartilage surgery)and control group(38 cases,treated with autologous ear cartilage surgery).The treatment effect,appearance score and complications were compared.Results:The total effective rate of the experimental group(97.37%,37/38)was higher than that of the control group(78.95%,30/38),P<0.05;After treatment,the appearance score of the experimental group was(8.97±0.37),which was significantly higher than that of the control group(P<0.05);The total incidence of complications in the experimental group(5.26%,2/38)was significantly lower than that in the control group(21.05%,8/38),P<0.05.Conclusion:In the process of nasal plastic surgery,the combined application of autologous ear cartilage surgery and expanded polytetrafluoroethylene has obvious effect,improves the appearance of patients,and has less postoperative complications,which is worthy of promotion.

Influence of expanded polystyrene size on deformation characteristics of light weight soil

Deformation characteristics of light weight soil with different EPS (expanded polystyrene) sizes were investigated by consolidation tests.The results show that the confined stress-strain relation curve is in S shape,which has a good homologous relation with e-p curve and e-lgp curve,and three types of curves reflect obvious structural characteristics of light weight soil.When cement mixed ratio and EPS volume ratio are the same for different specimens,structural strength decreases with the increase of EPS size,but compressibility indexes basically keep unchanged within the structural strength.The settlement of light weight soil can be divided into instantaneous settlement and primary consolidation settlement.It has no obvious rheology property,and 90% of total consolidation deformation can be finished in 1 min.Settlement-time relation of light weight soil can be predicted by the hyperbolic model.S-lgt curve of light weight soil is not in anti-S shape.It is proved that there is no secondary consolidation section,so consolidation coefficient cannot be obtained by time logarithm method.Structural strength and unit price decrease with the increase of EPS size,but the reducing rate of the structural strength is lower than that of the unit price,so the cost of mixed soil can be reduced by increasing the EPS size.The EPS beads with 3-5 mm in diameter are suggested to be used in the construction process,and the prescription of mixed soil can be optimized.

Research on Complex Refraction Indices of Expanded Graphite

The expanded graphite (EG) with a low density and better extinction performance can be used in military as passive jamming material in IR and MMW bands. Its complex refractive index is a significant parameter for the extinction property. This paper presents a method to calculate the complex refractive index of EG. The reflection spectra of EG pellets were measured in the 0.24-2.6μm and 2.5-25μm bands, respectively. Based on the measurement results, the complex refractive index of EG in 5-10μm band was calculated by using Kramers-Kronig(K-K) relation and Bruggeman effective medium theory, and then the errors were analyzed. The results indicate that it is feasible to calculate the complex refractive index of EG based on its IR reflection spectra data.

Preparation and Properties of 1-octadecanol/1,3:2,4-di-(3,4-dimethyl) Benzylidene Sorbitol/Expanded Graphite Form-stable Composite Phase Change Material

A 1-octadecanol（OD）/1,3:2,4-di-（3,4-dimethyl） benzylidene sorbitol（DMDBS）/expander graphite（EG） composite was prepared as a form-stable phase change material（PCM） by vacuum melting method. The results of field emission-scanning electron microscopy（FE-SEM） showed that 1-octadecanol was restricted in the three-dimensional network formed by DMDBS and the honeycomb network formed by EG. X-ray diffraction（XRD） and Fourier transform infrared spectroscopy（FT-IR） results showed that no chemical reaction occurred among the components of composite PCM in the preparation process. The gel-to-sol transition temperature of the composite PCMs containing DMDBS was much higher than the melting point of pure 1-octadecanol. The improvements in preventing leakage and thermal stability limits were mainly attributed to the synergistic effect of the three-dimensional network formed by DMDBS and the honeycomb network formed by EG. Differential scanning calorimeter（DSC） was used to determine the latent heat and phase change temperature of the composite PCMs. During melting and freezing process the latent heat values of the PCM with the composition of 91% OD/3% DMDBS/6% EG were 214.9 and 185.9 kJ·kg-1, respectively. Its degree of supercooling was only 0.1 ℃. Thermal constant analyzer results showed that its thermal conductivity（κ） changed up to roughly 10 times over that of OD/DMDBS matrix.

Large-Eddy Simulation of Underexpanded Supersonic Swirling Jets

A large-eddy simulation of underexpanded supersonic swirling jets issuing into a quiescent environment was carried out for two typical swirl numbers.The corresponding nonswirling jet was also calculated for comparison and validation against the experimental data.The swirling effect on the various fundamental mechanisms that dictate the intricate flow phenomena,including flow features,shock cell structures.jet spreading characteristics and turbulence behaviors,was carefully analyzed,and it is found that the first shock cell length is reduced in the swirling jet in comparison with the nonswirling jet.A recirculation zone is formed in the high swirl number case,and the jet spreads quickly in the radial direction due to the swirling effect.Moreover,intensive turbulent fluctuations are generated along the jet shear layer and at the end of the jet potential core,which will be helpful in the mixing process.The obtained results provide a physical insight into understanding the mechanisms relevant to underexpanded supersonic swirling jets.

扩大内需的潜力展望与实施路径

有效需求不足是影响我国经济高质量发展的一个关键性问题。当前,导致我国有效需求不足的主要结构性因素包括:我国居民可支配收入在国民收入中的占比较低导致居民整体消费水平偏低;个别行业产能过剩约束制造业投资增长;制造业下滑、基建投资瓶颈等多重约束下的民间投资负重前行。从更为宏观的视角看,扩大国内需求激发经济增长潜力仍然具有广阔空间,主要体现在我国居民消费结构升级空间广阔;城镇化的增量空间和存量改进空间仍然存在;高储蓄率是持续发挥有效投资关键作用的基础;推进金融高水平对外开放,可引导外资为国内资本存量提供新支撑;第二次人口红利有望接替第一次人口红利,推动经济的可持续增长。为进一步扩大内需、激发我国经济增长潜力,可从以下三个方面优化宏观调控思路,一是通过扩大中央财政赤字和改革基础货币发行机制,助力畅通国内大循环;二是向居民部门让渡部分收入,推动居民消费可持续增长;三是通过稳预期、降成本、促创新,稳定民间投资。

推动经济实现质的有效提升和量的合理增长的逻辑与路径

推动经济高质量发展,既需要实现质的有效提升,又需要实现量的合理增长。经济发展数量和质量是“一枚硬币的两面”,两者相互表征、相互反馈、相互转换,最终实现量质协同演化的高质量发展。从量质协同关系的角度观察中国经济发展实践,笔者发现:在经济加速阶段,中国经济发展数量和质量均有效提升,但是并未形成量质协同的正反馈机制;在经济减速阶段,中国经济发展数量和质量均面临下行压力,同时量质协同的负反馈机制逐渐显现;在转型发展阶段,面临经济转型与外生冲击的双重压力,宏观经济政策面临目标多元化难题,加剧了经济发展量质转型难度。推动经济实现质的有效提升和量的合理增长需要:优化宏观政策,推动实现质量效益型发展;深化供给侧结构性改革,提高供给质量;完善分配方式,提高消费需求质量;坚持“两个毫不动摇”,激发各类经营主体的内生动力和创新活力;增强国家能力,加快构建高水平社会主义市场经济体制。

扩底桩竖向承载特性及群桩效应研究

为探明扩底群桩竖向承载特性,采用扩底桩筏结构,开展单桩(扩径比分别为1.5、2.0、2.5、3.0)和桩筏(扩径比为2)基础静载模型试验,分析其荷载传递规律,并建立桩间距为3.75、4.00、4.50、5.00倍桩直径时扩底桩筏基础有限元模型,研究桩间距对群桩效应影响。结果表明:扩底单桩和扩底桩筏结构荷载沉降曲线均为缓变型;扩底桩极限承载力随扩径比增大而逐渐增大,扩径比2.5~3.0时极限承载力增幅变缓,建议扩底桩扩径比取2.5~3.0;由于桩土共同沉降,桩间土压缩,桩土作用更充分,扩底桩筏基础中心桩侧摩阻力荷载分担比比扩底单桩增大了17.71%;群桩效应系数随桩间距增大而逐渐增大,桩间距为4.5~5.0倍桩直径时群桩效应系数增幅较小,群桩效应较弱,建议扩底桩筏基础桩间距取值不小于4.5倍桩直径。

全国高职学校访企拓岗工作成效、问题分析及改进建议

以2022年度高职状态数据平台企业表、走访表、校企合作表、学生就业表等9张数据表为依据,从国家、省及学校三个层面用数据展示了1441所高职学校访企拓岗工作开展情况,从走访企业覆盖行业广、拓展优质就业岗位多,深度了解企业人才需求、提高人才供给精准性,推动校企优势互补、扩大校企合作增长极三个方面分析了高职学校访企拓岗取得的显著成效,并进一步总结了高职学校访企拓岗工作存在主观认识不足、推进合作落实不力、合作目标有差异等问题。据此,提出提高访企拓岗工作认识、加强数据调度管理、提升学校服务企业能力、健全访企拓岗工作制度、完善访企拓岗工作评价机制等改进建议。

政府治理对农户宅基地扩张意愿的影响机制研究

治理农村在县域城镇化过程中出现的宅基地扩张现象,对于促进城乡融合发展、提高农村土地资源配置效率和实现共同富裕等具有重要意义。基于湖南省1316户农户样本数据,结合OLS模型和中介模型研究地方政府治理能力对农户宅基地扩张意愿的影响及机制。结果表明:地方政府治理能力对农户宅基地扩张意愿有显著的负向影响,城镇化水平在地方政府治理能力影响农户宅基地扩张意愿过程中发挥了完全中介作用;农户信息获取能力负向调节地方政府治理能力与农户宅基地扩张意愿之间的关系。因此,地方政府应提升治理能力、协调好农户住房与经济发展之间的关系、引导集中居住等,改善农户宅基地不断扩张的现象。

扩大进口、消费需求与产业结构升级

进口是国内国际双循环的交汇点,扩大进口有助于夯实新发展格局的产业基础。基于2013—2021年省级面板数据,在理论分析的基础上,实证检验了扩大进口、消费需求与产业结构升级的内在关系。结果表明:整体而言,扩大进口战略能够显著促进产业结构升级,研究结论较为稳健;从经济发展和科技创新等角度看,扩大进口只对经济发展水平较高地区和科技发展水平较强地区的产业结构升级产生显著影响;优化消费结构和扩大消费规模是推动产业结构升级的重要途径;进一步进行调节效应检验后发现,金融发展在扩大进口助推产业结构升级的过程中具有正向调节作用,且对经济发展水平较高地区和科技发展水平较低地区的调节作用更强。根据研究结论,提出了相关对策建议。

自膨式瓣膜行导管主动脉瓣膜置换术治疗单纯主动脉瓣反流患者35例

目的评价主动脉瓣膜反流(AR)患者应用自膨式瓣膜行经导管主动脉瓣膜置换术(TAVR)的安全性及可行性。方法回顾性分析2019年8月—2022年8月于河北医科大学第二医院心脏外科应用自膨式瓣膜行TAVR的重度AR患者35例,其中男25例,女10例,年龄59~83(70.03±1.07)岁。分析手术成功率、病死率、手术并发症发生率及术后患者左心功能变化。结果35例患者均采用自膨式介入瓣膜经股动脉行TAVR手术成功,成功率100%,无死亡病例。采用体外循环辅助完成手术的患者17例(48.6%),平均体外循环辅助时间(32.5±14.6)min。同期行经皮冠状动脉介入术(PCI)治疗的患者5例(14.3%)。采用瓣中瓣技术的患者14例(40.0%)。术前LVEF(48.01±12.20)%,术后1周LVEF(50.22±15.11)%,差异无统计学意义(t=0.552,P>0.05);术前左心室舒张末期内径(65.04±10.10)mm,术后1周左心室舒张末期内径(63.44±11.03)mm,差异无统计学意义(t=0.710,P>0.05)。术前5例患者存在二尖瓣中量及以上反流,术后二尖瓣反流均较术前减轻,其中2例转为少中量反流,3例转为少量反流。术后即刻出现完全性左束支传导阻滞14例(40.0%),三度传导阻滞1例(2.9%),转入心内科植入永久起搏器。术中出现心包积液1例(2.9%),胸骨正中剑突下切口植入心包引流管后痊愈。少中量瓣周漏3例(8.6%),其余为少量及微量瓣周反流32例(91.4%)。结论应用自膨式瓣膜经股动脉行TAVR治疗重度主动脉瓣关闭不全患者手术安全性高,具有创伤小、并发症少、恢复快等优点。

硼酸锌/三氧化二锑/可膨胀石墨协同体系阻燃氯丁橡胶及作用机理

为了提高氯丁橡胶(CR)的阻燃及抑烟性能,以硼酸锌(ZnB)、三氧化二锑(Sb_(2)O_(3))和膨胀石墨(EG)为复合阻燃体系,制备了阻燃CR复合材料。通过极限氧指数测定仪、垂直燃烧测定仪、热失重分析、锥形量热测试仪等进行性能表征。结果表明,当引入17 phr ZnB、3 phr Sb_(2)O_(3)与7 phr EG到阻燃CR体系,CR/ZnB/Sb_(2)O_(3)-7EG氧指数可达到39.7%,并通过UL94 V0级,热释放峰值及总热释放量降低了约84.0%和44.3%,CO和CO_(2)产量也分别降低了52.0%和80.3%,明显抑制毒性气体的释放。此外,对残炭和气相产物的分析表明,该复合体系以气-固相机理为主,在CR复合材料中表现出良好的协同阻燃效应。

Effective Supply,Consumption Upgrade,and Expanding Domestic Demand

Addressing the prolonged stagnation in household consumption growth in China is crucial for the successful implementation of the strategy to expand domestic demand.By constructing the upgrading index of consumption structure from 2002 to 2018,it is found that the overall upgrading trend of household consumption structure in China is accelerated after 2014.Theoretical analysis and empirical results indicate that,as household consumption structures rapidly upgrade with rising incomes in China,the primary factor limiting reasonable growth in household consumption is the insufficient effective supply resulting from a mismatch between the supply structure and the demand structure.As the adjustment of the supply structure depends on the continuous optimization of investment flow,expanding effective investment is the key driving force to improve effective supply,and it is also the existing component of expanding domestic demand.Further research shows that weakening investment convergence can significantly alleviate the insufficient effective supply caused by consumption upgrading.Enhancing the scientific anticipation of policy regulations and increasing the effectiveness of investments will be beneficial for realizing the strategy of expanding domestic demand.

Creation of a Non-Expanding, Non-Singular Universe

A theory of gravitation in flat space-time is applied to homogeneous, isotropic cosmological models. There are non-singular cosmological models. A natural interpretation is a non-expanding universe. The redshift is an intrinsic effect and not a Doppler effect. The universe contains only energy in the beginning, i.e. no matter exists. In the course of time matter and radiation are created from energy where the whole energy is conserved. Matter increases with time but a certain time after the beginning of the universe the creation of matter is finished and the universe appears like a static one. A modified Hubble law is considered which may explain the high redshifts of objects in the universe without the assumption of dark energy.

可发性聚苯乙烯板减载条件下高填方箱涵长期受力特征与减载效果

在高填方箱涵顶部铺设可发性聚苯乙烯(expandable polystyrene,简称EPS)板降低其荷载已经在工程中得以应用,而EPS板的蠕变会使箱涵受到的土压力随时间发生变化。现有的箱涵设计理论未能明确的反应EPS板的长期减载效果以及箱涵长期受力特性。开展了EPS板减载条件下箱涵短期受力特性模型试验,并利用模型试验结果验证数值模型。之后利用验证后的数值模拟方法分析涵-土体系应力重分布规律以及高填方箱涵长期受力特征;在此基础上提出涵-土体系力学模型,推得涵顶长期土压力计算方法,并与数值模拟结果进行对比验证。研究表明:涵顶土压力先随时间逐渐减小,然后会出现小幅增大,最终趋于稳定,对比填土完成时土压力减小了52.12%;涵侧竖向土压力和水平土压力总体上均随着时间逐渐增大并趋于稳定,涵侧上部范围内最终水平土压力比填土完毕时增长了28.32%;基底土压力也是先增大后趋于稳定。实际工程中侧墙的设计应考虑EPS板蠕变引起水平土压力的增加,避免箱涵侧墙在长期使用中产生受弯破坏。

In situ formed ultrafine metallic Ni from nickel(Ⅱ) acetylacetonate precursor to realize an exceptional hydrogen storage performance of MgH_(2)-Ni-EG nanocomposite

It has been well known that doping nano-scale catalysts can significantly improve both the kinetics and reversible hydrogen storage capacity of MgH_(2) . However, so far it is still a challenge to directly synthesize ultrafine catalysts(e.g., < 5 nm), mainly because of the complicated chemical reaction processes. Here, a facile one-step high-energy ball milling process is developed to in situ form ultrafine Ni nanoparticles from the nickel acetylacetonate precursor in the MgH_(2) matrix. With the combined action of ultrafine metallic Ni and expanded graphite(EG), the formed MgH_(2)-Ni-EG nanocomposite with the optimized doping amounts of Ni and EG can still release 7.03 wt.% H_(2) within 8.5 min at 300 ℃ after 10 cycles. At a temperature close to room temperature(50 ℃), it can also absorb 2.42 wt.% H_(2) within 1 h. It can be confirmed from the microstructural characterization analysis that the in situ formed ultrafine metallic Ni is transformed into Mg_(2)Ni/Mg_(2)NiH_4 in the subsequent hydrogen absorption and desorption cycles. It is calculated that the dehydrogenation activation energy of the MgH_(2)-Ni-EG nanocomposite is also reduced obviously in comparison with the pure MgH_(2) . Our work provides a methodology to significantly improve the hydrogen storage performance of MgH_(2) by combining the in situ formed and uniformly dispersed ultrafine metallic catalyst from the precursor and EG.

大直径扩底灌注桩单桩竖向承载力优化设计

深基础是以下部坚实土层或岩层作为持力层的基础,其埋深较大。必须在确保建筑物安全的情况下,节约用料,方便施工,且可提升经济效益。为了探究大直径灌注桩作为深基础的构件在承担上部荷载的条件下,其单桩竖向承载力的发挥情况,研究在同种地层沉积条件下,将大直径灌注桩分为同直径不同桩长、扩底式不同桩长两种情况,并按JGJ/T 225—2010《大直径扩底灌注桩技术规程》进行了计算、对比与优化,确认了定型原则,提出了合理的建议与结论。结果表明:桩身几何尺寸较短时不必进行扩底,桩身几何尺寸超过一定长度后可以进行扩底,扩底后的单桩竖向承载力会有相应的提升。扩底会出现几何长度不变但能够发挥桩侧阻力的有效长度缩短的现象。同时,桩扩底施工是否能够成功不同程度地受到地层条件与水文地质条件的制约。

消费、投资与全国统一大市场——关于进一步扩大内需,构建强大国内市场的调研报告

面对近年来复杂的国际国内经济形势,一些地区在进一步扩大内需、构建强大国内市场方面,针对各自发展实际,不断优化营商环境,切实提高居民收入,多措并举,取得了积极成效。然而,促消费政策有待优化,消费者权益保护面临挑战,市场主体活力仍显不足,基本公共服务体系建设需进一步完善,营商环境有待进一步优化等问题仍然较为突出。综合实地调研和问卷调查情况,该文建议:顺应居民消费升级趋势,着力满足居民消费需求;加强消费者权益保护,让消费者放心消费;激发市场主体活力增加有效投资;完善基本公共服务体系,助力消费投资增长;优化企业营商环境,建设全国统一大市场等。