The Optimal Investment Strategy Based on the DEA Model

The Goodgrant Foundation is a charitable organization that wants to improve education performance of undergraduates attending colleges and universities in the US. So the foundation plans to contribute a total of US 50 million for a suitable team of schools per year under the condition of avoiding repeated other large grant organizations’ investment. The DEA (Data Estimate Analysis) model is developed to determine an optimal investment strategy for the Goodgrant Foundation. In this paper, two questions were solved: how to choose a suitable team of schools and how to allocate the investment. Before the establishment of the model, the EXCEL software is used to preprocess data. Then the DEA model which includes two models in the paper is developed. For the first question, the CCR model is established to rank schools which used efficiency from DEAP 2.1. For the second question, the resource allocation model is established to allocate investment amount by weights of allocation from MATLAB software. Accordingly, the optimal investment strategy is received for the Goodgrant Foundation. Through the analysis above, 23 from 293 schools are selected to invest. Then the schools are ranked and the investment of US 50 million for 23 schools is allocated.

CEPC Technical Design Report

The Circular Electron Positron Collider(CEPC)is a large scientific project initiated and hosted by China,fostered through extensive collaboration with international partners.The complex comprises four accelerators:a 30 GeV Linac,a 1.1 GeV Damping Ring,a Booster capable of achieving energies up to 180 GeV,and a Collider operating at varying energy modes(Z,W,H,and tt).The Linac and Damping Ring are situated on the surface,while the subterranean Booster and Collider are housed in a 100 km circumference underground tunnel,strategically accommodating future expansion with provisions for a potential Super Proton Proton Collider(SPPC).The CEPC primarily serves as a Higgs factory.In its baseline design with synchrotron radiation(SR)power of 30 MW per beam,it can achieve a luminosity of 5×10^(34)cm^(-2)s^(-1)per interaction point(IP),resulting in an integrated luminosity of 13 ab^(-1)for two IPs over a decade,producing 2.6 million Higgs bosons.Increasing the SR power to 50 MW per beam expands the CEPC's capability to generate 4.3 million Higgs bosons,facilitating precise measurements of Higgs coupling at sub-percent levels,exceeding the precision expected from the HL-LHC by an order of magnitude.This Technical Design Report(TDR)follows the Preliminary Conceptual Design Report(Pre-CDR,2015)and the Conceptual Design Report(CDR,2018),comprehensively detailing the machine's layout,performance metrics,physical design and analysis,technical systems design,R&D and prototyping efforts,and associated civil engineering aspects.Additionally,it includes a cost estimate and a preliminary construction timeline,establishing a framework for forthcoming engineering design phase and site selection procedures.Construction is anticipated to begin around 2027-2028,pending government approval,with an estimated duration of 8 years.The commencement of experiments and data collection could potentially be initiated in the mid-2030s.

Initial precursor reaction mechanism of CVD-HfC coating based on density functional theory

Recently,the preparation of ultra-high temperature HfC ceramic coating has gained significant attention,particularly through the application of the HfCl_(4)-CH_(4)-H_(2)-Ar system via Chemical Vapor Deposition(CVD),which has been found widely applied to C/C composites.Herein,an analysis of the reactions that occur in the initial stage of the CVD-HfC coating process is presented using Density Functional Theory(DFT)and Transition State Theory(TST)at the B3LYP/Lanl2DZ level.The results reveal that HfCl4 can only cleave to produce hypochlorite,which will further react with methyl to synthesize intermediates to form HfC.According to the analysis of the energy barrier and reaction constant,HfCl preferentially reacts with methyl groups to form complex adsorptive intermediates at 1573 K.With a C—Hf bond production energy of 212.8 kcal/mol(1 kcal=4.18 kJ),the reaction rate constant of HfCl+CH is calculated to be 2.15×10^(-18) cm^(3)/s at 1573 K.Additionally,both the simulation and experimental results exhibit that the upward trend of reaction rate constants with temperature is also consistent with the deposition rate,indicating that the growth curve of the reaction rate constants tends to flatten out.The proposed reaction model of the precursor’s decomposition and reconstruction during deposition process has significant implication for the process guidance.

Novel Hf_(x)Ta_(1−x)C solid solution nanowire toughened HfC coating:An effective strategy for synchronous enhanced mechanical and anti-ablation performance

Ultra-high-temperature ceramic nanowires have shown increasing potential for use as thermal structural components.Herein,novel single-crystal Hf_(0.5)Ta_(0.5)C solid solution nanowires were synthesized and incorporated with a HfC coating to construct a robust structure with Hf_(0.5)Ta_(0.5)C solid solution nanowires uniformly distributed and interconnected within the coating.The novel Hf_(0.5)Ta_(0.5)C solid solution nanowires could effectively hinder crack propagation through crack tip pinning and crack deflection.This mechanism substantially enhanced the elastic modulus and fracture toughness of the HfC coating by 53.29%and 59.67%,respectively.The toughened HfC coating displayed superior fracture toughness and good interfacial binding strength with the substrate to resist severe oxidation and scouring.Additionally,the high thermal conductivity of the toughened HfC coating promoted heat transmission.Thus,in comparison to the pure HfC coating,the toughened HfC coating displayed smaller mass and linear ablation rates of−0.35 mg·s^(−1)and−0.46μm·s^(−1),which decreased by 39.66%and 36.98%,respectively.Our work not only simultaneously enhances the mechanical properties and ablation resistance of HfC-coated carbon/carbon(C/C)composites but also provides novel prospects for advanced ultrahigh-temperature ceramic nanowires under extreme conditions.

Superior synergistic oxidation resistance of medium-entropy carbide ceramic powders rather than multi-phase carbide ceramic powders

To date,some questions about medium-entropy carbide ceramics and the corresponding multi-phase carbide ceramics with the same cations and proportions remain unclear.Regarding oxidation behavior,do both have synergistic oxidation abilities and what role does entropy stabilization play in medium-entropy carbides?In this work,the oxidation behaviors of HfC-ZrC-TiC multi-phase carbide(HZT-MPC)and(Hf_(1/3)Zr_(1/3)Ti_(1/3))C medium-entropy carbide(HZT-MEC)powders were investigated.After thermogravimetry(TG)oxidation,the TG curve of HZT-MPC had a bimodal distribution.The"preferential oxidation"of HfC/ZrC occurred within HZT-MPC,followed by the formation of multi-phase oxides(HfO_(2),ZrO_(2),and TiO_(2)).The uneven compositional distribution slowed their solid solution reactions to form Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4).The TG curve of HZT-MEC had a single peak.A uniform compositional distribution at the atomic scale promoted the rapid interdiffusion of oxides,forming Ti-doped(Hf,Zr)O_(2) and(Hf,Zr)TiO_(4) without ZrO_(2),HfO_(2),and TiO_(2) after TG oxidation.Additionally,HZT-MEC had a higher onset oxidation temperature(To;470℃)than did HZT-MPC(430℃),and the TG single peak of HZT-MEC was between the TG bimodal peaks of HZT-MPC.Therefore,HZT-MEC showed superior oxidation resistance compared to HZT-MPC,which was attributed to the entropy stabilization effect of HZT-MEC suppressing the"preferential oxidation"of HfC/ZrC and the"delayed oxidation"of TiC,promoting the synergistic oxidation ability of multiple principal elements.

泌尿生殖系统超声对胎儿先天性泌尿生殖系统异常的临床应用价值

目的探讨泌尿生殖系统超声在胎儿先天性泌尿生殖系统异常(CAKUT)中的临床应用价值,并分析其指导产前遗传学诊断的临床意义。方法回顾性收集2016年1月至2020年12月在南京医科大学附属淮安第一医院进行产前系统筛查发现的125例CAKUT胎儿病例。根据是否合并其他结构异常分为孤立性CAKUT组与非孤立性CAKUT组。对CAKUT胎儿进行定期随访,对遗传学结果及妊娠结局进行分析。采用χ2检验比较孤立性CAKUT组与非孤立性CAKUT组妊娠结局和遗传学结果的差异。结果胎儿泌尿生殖系统超声随访中发现17例肾盂扩张的病例分别于晚孕期及产后6个月内自愈;41例病例异常持续存在,但未出现临床症状,生长发育均良好;2例误诊;1例漏诊;4例病情加重于出生后1年内死亡,2例肾盂扩张(包括漏诊的1例)随访至出生6个月,具有手术指征,行手术治疗;48例行泌尿生殖系统超声检查再次确诊后家属选择终止妊娠,11例失访。68例样本行产前遗传学检查,染色体微阵列分析(CMA)发现11例(11/68,16.2%)遗传学结果异常,包括:4例染色体非整倍体异常,8例基因组拷贝数变异(其中1例同时存在染色体非整倍体异常和基因组拷贝数变异);其中非孤立性CAKUT组(25.0%,3/12)遗传学结果异常检出率高于孤立性CAKUT组(14.3%,8/56),但差异无统计学意义(χ2=0.837,P=0.360);另外10例CMA检查未见异常的胎儿样本行全外显子测序,检出1例表型为巨膀胱胎儿携带遗传自母亲的AQP2基因杂合变异,致病位点为c.559C>T(p.Arg187Cys),判定为致病性。结论泌尿生殖系统超声检查作为胎儿产前系统结构筛查超声的补充,有利于提高CAKUT诊断精准率,减少漏、误诊率,进一步指导产前诊断及胎儿远期预后评估。

Single-source precursor derived high-entropy metal–carbide nanowires:Microstructure and growth evolution

In recent years,high-entropy metal carbides(HECs)have attracted significant attention due to their exceptional physical and chemical properties.The combination of excellent performance exhibited by bulk HEC ceramics and distinctive geometric characteristics has paved the way for the emergence of one-dimensional(1D)HECs as novel materials with unique development potential.Herein,we successfully fabricated novel(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires derived via Fe-assisted single-sourced precursor pyrolysis.Prior to the synthesis of the nanowires,the composition and microstructure of(Ti,Zr,Hf,Nb,Ta)-containing precursor(PHECs)were analyzed,and divinylbenzene(DVB)was used to accelerate the conversion process of the precursor and contribute to the formation of HECs,which also provided a partial carbon source for the nanowire growth.Additionally,multi-branched,single-branched,and single-branched bending nanowires were synthesized by adjusting the ratio of PHECs to DVB.The obtained single-branched(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires possessed smooth surfaces with an average diameter of 130–150 nm and a length of several tens of micrometers,which were a single-crystal structure and typically grew along the[11¯1]direction.Also,the growth of the(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))C nanowires was in agreement with top-type vapor–liquid–solid mechanism.This work not only successfully achieved the fabrication of HEC nanowires by a catalyst-assisted polymer pyrolysis,but also provided a comprehensive analysis of the factors affecting their yield and morphology,highlighting the potential application of these attractive nano-materials.

Sublayer design and ablation resistance of CVD-TaC alternate coatings with different crystallite morphologies for C/C composites

Tantalum carbon(TaC)alternate coatings with sublayers comprised of different crystallite morphologies were prepared on carbon/carbon composites by chemical vapor deposition.Their ablative behaviors and defending mechanisms were both investigated.The specimen with the sublayer composed of columnar crystals exhibited a better ablation resistance due to the toughness enhancement induced by the lami-nated structure.However,the mechanical denudation of the sample only containing acicular crystals and the coating spallation caused by superfluous gaseous products of the sample with the sublayer composed of nanocrystals both indicate their inferior anti-ablation properties.It is believed that the results will be helpful for the structural design and practical application of chemical vapor deposition(CVD)alternate coatings.

Microstructure and evolution of hafnium carbide whiskers via polymer-derived ceramics:A novel formation mechanism

Polymer-derived ultra-high-temperature ceramic(UHTC)nanocomposites have attracted growing attention due to the increasing demands for advanced thermal structure components in aerospace.Herein,hafnium carbide(HfC)whiskers are successfully fabricated in carbon fiber preforms via the polymer-derived ceramic(PDC)method.A novel carbon nanotube(CNT)template growth mechanism combined with the PDC method is proposed in this work,which is different from the conventional vapor–liquid–solid(VLS)mechanism that is commonly used for polymer-derived nanostructured ceramics.The CNTs are synthesized and proved to be the templates for fabricating the HfC whiskers,which are generated by the released low-molecular-weight gas such as CO,CO_(2),and CH4 during the pyrolysis of a Hf-containing precursor.The formed products are composed of inner single crystal HfC whiskers that are measured to be several tens of micrometers in length and 100–200 nm in diameter and outer HfC/HfO_(2)particles.Our work not only proposes a new strategy to prepare the HfC whiskers,but also puts forward a new thinking of the efficient utilization of a UHTC polymer precursor.

(Hf_(0.5)Ta_(0.5))C ultra-high temperature ceramic solid solution nanowires

Ultra-high temperature ceramic(UHTC)nanowires are potential reinforcement materials due to it combines the perfect properties of bulk materials and unique geometric properties of one-dimensional(1D)nanostructures.Thus,developing 1D nanomaterials that have excellent morphology and structure retention in ultra-high temperature environments is of prime importance to bring their outstanding performance into full play.Herein,we report the novel solid solution((Hf_(0.5)Ta_(0.5))C)ceramic nanowires,which could not only maintain morphological and structural stability at 1900°C but also exhibit 1D nanostructures under oxyacetylene scouring and ablation at 2300°C.The morphology evolution of nanowires obeys the Rayleigh instability mechanism,and the internal structure and element distribution of nanowires remain unchanged even if the surface atoms are rearranged.The fascinating nanowires are demonstrated to have great potential as ideal reinforcement materials of composite materials and toughening phases of ceramics that are applied in ultra-high temperature environments,as well as excellent performance enhancement phases of functional materials.Our work may provide new insights into the development of ceramic nanowires and widen their applications.

Oxidation and Mechanical Properties of SiC/SiC-MoSi_2-ZrB_2 Coating for Carbon/Carbon Composites

To improve oxidation resistance of carbon/carbon （C/C） composites, a SiC/SiC-MoSi2-ZrB2 double-layer ceramic coating was prepared on C/C composites by two-step pack cementation. The phase compositions and microstructures of as-prepared multilayer coating were characterized by X-ray diffraction and scanning electron microscopy. The oxidation resistance at 1773 K and the effect of thermal shock between 1773 K and room temperature on mechanical performance of coated specimens were investigated. The results show that the SiC/SiC-MoSi2-ZrB2 coating exhibits dense structure and is composed of SiC, Si, MoSi2 and ZrB2. It can protect C/C composites from oxidation at 1773 K for more than 510 h with weight loss of 0.5%. The excellent anti-oxidation performance of the coating is due to the formation of SiO2-ZrSiO4 complex glassy film. The coating can also endure the thermal shocks between 1773 K and room temperature for 20 times with residual flexural strength of 86.1%.

Mullite Oxidation Resistant Coating for SiC-coated Carbon/Carbon Composites by Supersonic Plasma Spraying

To improve the oxidation resistance of carbon/carbon （C/C） composites, mullite coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. Phases and microstructures of mullite coating were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The coating primarily consists of a single phase of mullite （3AI203-2SIO2）. The SEM results show that mullite coating was continuous and well bonded with the SiC inner layer without penetrating crack. Mullite coating exhibited good oxidation resistance, After 98.5 h oxidation at 1773 K and 9 thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 2.57%.

Hole-pinned defect-dipoles induced colossal permittivity in Bi doped SrTiO3 ceramics with Sr deficiency

Bi doped SrTiO3 ceramics with Sr deficiency,i.e.Sr1-1.5xBixTiO3(x=0,0.01,0.05,0.1),were prepared via conventional solid-state reaction route.A colossal permittivity(CP)over 104 with low dielectric loss less than 0.05wasobtained in x=0.05 Sr1-1.5xBixTiO3 ceramics.In addition,the dielectric constant is maintained at a value greater than 104 in the range of 102-105 Hz and almost frequency independent.Phase structure analysis and density functional theory calculations suggest that the Bi·Sr-V"Sr-Bi·Sr defect complex with hole-pinned defect-dipoles maybe responsible for the high-performance CP properties.This work gives a new way to achieve high performance CP materials in ABO3 perovskite ceramics.

Pattern recognition of messily grown nanowire morphologies applying multi-layer connected self-organized feature maps

Multi-layer connected self-organizing feature maps(SOFMs) and the associated learning procedure were proposed to achieve efficient recognition and clustering of messily grown nanowire morphologies. The network is made up by several paratactic 2-D SOFMs with inter-layer connections. By means of Monte Carlo simulations, virtual morphologies were generated to be the training samples. With the unsupervised inner-layer and inter-layer learning, the neural network can cluster different morphologies of messily grown nanowires and build connections between the morphological microstructure and geometrical features of nanowires within. Then, the as-proposed networks were applied on recognitions and quantitative estimations of the experimental morphologies. Results show that the as-trained SOFMs are able to cluster the morphologies and recognize the average length and quantity of the messily grown nanowires within. The inter-layer connections between winning neurons on each competitive layer have significant influence on the relations between the microstructure of the morphology and physical parameters of the nanowires within.

Two birds with one stone: Simultaneous fabrication of HfC nanowires and CNTs through efficient utilization of polymer-derived ceramics

Carbon nanotubes(CNTs) are fabricated in carbon cloth by ultilizing the waste gasses when fabricating hafnium carbide nanowires(HfC_(NWS)) through thermal pyrolysis of Hf-containing polymer precursor.The formed HfC_(NWS) are distributed uniformly on the surface of the carbon fibers in carbon/carbon(C/C) composites and display perfect single crystal appearance.The pyrolysis of the Hf-containing organic precursor provides hafnium and carbon source for the growth of HfC_(NWS).The released waste gasses containing CO,CH4and CO_(2)are the main carbon source for the growth of CNTs.Specifically,the flexural strength of HfC_(NWS) reinforced carbon/carbon(HfC_(NWS)-C/C) composites is enhanced by ~105% compared with pure C/C,and the CNTs/carbon cloth also displays improved electrochemical performance with respect to capacitor applications.The present study introduces a novel sustainable and eco-friendly process related to polymer-derived ceramics to form advanced ceramic nanocomposites and proposes a deep understanding of the growth mechanism of CNTs.