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镧系膨胀——一种极为异常的现象

稀土 1991年第1期12卷 64-67页

作者： k.a.gschneidner 郭春泰美国Iowa州立大学材料科学与工程系阿姆斯实验室

本文考查了在某些含稀土ThCr_2Si_2型相中早已观察到的镧系膨胀(相对于镧系收缩而言),并与大多数这种相中所观察到的正常镧系收缩性质进行了比较。很明显镧系膨胀是由于几何因素引起的,即如果一个小的镧系原子代替一个大的镧系原子,只要... 详细信息

本文考查了在某些含稀土ThCr_2Si_2型相中早已观察到的镧系膨胀(相对于镧系收缩而言),并与大多数这种相中所观察到的正常镧系收缩性质进行了比较。很明显镧系膨胀是由于几何因素引起的,即如果一个小的镧系原子代替一个大的镧系原子,只要Si-Si和Si-M(M为非稀土过渡元素)的间距保持不变,则c轴膨胀。形成这些化合物过程中,也发生电子转移。在大多数情况下,电子转移对于镧系膨胀是更重要的。它是镧系膨胀仅发生在RM_2Si_2(M=Cu,Ag)、RCu_2Ge_2和部分RPt_2Si_2系化合物中的原因。

关键词：镧系膨胀 ThCr2Si 型镧系化合物

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稀土化学和物理冶金学

稀土 1986年第1期 67-69+52页

作者： k.a.gschneidner,邱巨峰 Jr

评论了稀土基础研究、应用研究、工艺和商业应用等方面的目前状况。简要概括了一位外国人所观察到的中国的作用及其影响。本文第三部分介绍了作者正在研究的问题的一个方面—交换增强的顺磁体中自旋涨落的猝灭。

关键词：自旋涨落电子比热稀土热容稀土市场有机金属有序化温度中华人民共和国应用研究科学研究

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稀土科学技术与工业的美好前景

稀土 1984年第4期 72-74+34页

作者： k.a.gschneidner,常好勇 Jr.

引言“一个笼罩在神秘之中的莫名其妙的谜”。这虽然是邱吉尔形容苏联的一句话,但用来描述奇妙的稀土世界,却也很为恰当。在这个宇宙内,我们

关键词：稀土材料价态不稳定性化合价磁学性质自旋涨落

热处理对Gd5Sn4合金结构与磁性能的影响

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热处理对Gd5Sn4合金结构与磁性能的影响

Aqueous-phase reforming of hydroxyacetone solution to bio-based H_(2)over supported Pt catalysts

第七届中国功能材料及其应用学术会议

作者：钟喜春张虎刘仲武曾德长余红雅邱万奇 k.a.gschneidner V.k.Pecharsky 华南理工大学材料科学与工程学院 The Ames Laboratory U.S.Department of EnergyIowa State UniversityAmesIowa 50011-3020USA 中国科学院磁学国家重点实验室北京凝聚态物理国家实验室 Department of Materials Science and Engineering Iowa State UniversityAmesIowa 50011-2300USA

在氩气气氛中用熔炼法制备了GdSn合金,采用真空感应退火炉对铸态样品进行均匀化热处理,通过X射线衍射和SQUID磁强计研究了均匀化热处理对GdSn合金结构与磁性能的影响。结果表明,经1300℃,2h均匀化退火后,主相GdSn由铸态的85.39%提高到98... 详细信息

在氩气气氛中用熔炼法制备了GdSn合金,采用真空感应退火炉对铸态样品进行均匀化热处理,通过X射线衍射和SQUID磁强计研究了均匀化热处理对GdSn合金结构与磁性能的影响。结果表明,经1300℃,2h均匀化退火后,主相GdSn由铸态的85.39%提高到98.47%(摩尔百分比),大大提高了GdSn合金的均匀性。GdSn合金的居里温度由退火前的约82k降低到约80k;均匀化热处理对样品低场下的最大磁熵变值(-ΔS)的影响较大,由退火前21.5J/(kg·k)上升到退火后的24.65J/(kg·k)(ΔH=1592kA/m)。

关键词： Gd5Sn4 热处理晶体结构磁性能

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Green Energy & Environment 2024年第4期9卷 777-788页

作者： A.k.k.Vikla k.koichumanova Songbo He k.Seshan Joint International Research Laboratory of Circular Carbon Nanjing Tech UniversityNanjing211816China Faculty of Science and Technology University of Twente7500 AE EnschedeThe Netherlands CoRe Pro 9723 BL GroningenThe Netherlands

Aqueous-phase reforming(APR)is an attractive process to produce bio-based hydrogen from waste biomass streams,during which the catalyst stability is often challenged due to the harsh reaction *** this work,three Pt-based catalysts supported on C,AlO(OH),and ZrO_(2)were investigated for the APR of hydroxyacetone solution in afixed bed reactor at 225℃and 35 *** them,the Pt/C catalyst showed the highest turnover frequency for H_(2)production(TOF of 8.9 molH_(2)molPt^(-1)min^(-1))and the longest catalyst *** the AlO(OH)and ZrO_(2)supported Pt catalysts,the side reactions consuming H_(2),formation of coke,and Pt sintering result in a low H_(2)production and the fast catalyst *** proposed reaction pathways suggest that a promising APR catalyst should reform all oxygenates in the aqueous phase,minimize the hydrogenation of the oxygenates,maximize the WGS reaction,and inhibit the condensation and coking reactions for maximizing the hydrogen yield and a stable catalytic performance.

关键词： APR Hydroxyacetone TOF Bio-based H_(2) Support effect

Rare Earths and Magnetic Refrigeration

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Journal of Rare Earths 2006年第6期24卷 641-647页

作者： karl A gschneidner Vitalij k Pecharsky Materials and Engineering Physics Program Ames Laboratory and Department of Materials Science and Engineering Iowa State University Ames Iowa USAJr. Materials and Engineering Physics Program Ames Laboratory and Department of Materials Science and Engineering Iowa State University Ames Iowa USA

Magnetic refrigeration is a revolutionary, efficient, environmentally friendly cooling technology, which is on the threshold of commercialization. The magnetic rare earth materials are utilized as the magnetic refrigerants in most cooling devices, and for many cooling application the Nd2Fe14B permanent magnets are employed as the source of the magnetic field. The status of the near room temperature magnetic cooling was reviewed.

关键词： magnetic refrigeration magnetocaloric effect gadolinium Gd5 ( Si1- x Gex ) 4 La ( Fe 13 - x Six ) Hy Nd2 Fe14 B permanent magnets active magnetic regenerator cycle rare earths

Direct scaling of residual displacements for bilinear and pinching oscillators

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Earthquake Engineering and Engineering Vibration 2024年第1期23卷 129-149页

作者： Mohammad Saifullah Vinay k.Gupta Department of Civil Engineering Indian Institute of Technology KanpurKanpur 208016India

The estimation of residual displacements in a structure due to an anticipated earthquake event has increasingly become an important component of performance-based earthquake engineering because controlling these displacements plays an important role in ensuring cost-feasible or cost-effective repairs in a damaged structure after the *** attempt is made in this study to obtain statistical estimates of constant-ductility residual displacement spectra for bilinear and pinching oscillators with 5%initial damping,directly in terms of easily available seismological,site,and model *** of the available models for the bilinear and pinching oscillators are useful when design spectra for a seismic hazard at a site are not *** statistical estimates of a residual displacement spectrum are proposed in terms of earthquake magnitude,epicentral distance,site geology parameter,and three model parameters for a given set of ductility demand and a hysteretic energy capacity coefficient in the case of bilinear and pinching models,as well as for a given set of pinching parameters for displacement and strength at the breakpoint in the case of pinching model *** proposed scaling model is applicable to horizontal ground motions in the western *** earthquake magnitudes less than 7 or epicentral distances greater than 20 km.

关键词： residual displacement spectrum bilinear hysteresis model pinching hysteresis model nonlinear analysis scaling model

Analysis of the Oscillatory Flows of Multiple Shock Waves in a Constant Area Duct

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Journal of Thermal Science 2024年第3期33卷 794-806页

作者： k JAMES Jintu kIM Heuy Dong Department of Mechanical Engineering Andong National UniversityAndong36729Republic of Korea CAD-IT korea Co. Ltd.Seoul08591Republic of Korea

The oscillatory response of multiple shock waves to downstream perturbations in a supersonic flow is studied numerically in a rectangular *** shock waves are formed inside the duct at a shock Mach number of *** duct has an exit height of H,and the effect of duct resonance on multiple shock oscillations is investigated by attaching exit ducts of lengths 0H,50H,and *** downstream disturbance frequency varied from 10 Hz to 200 Hz to explore the oscillation characteristics of the multiple shock *** oscillatory response of shock waves under self-excited and forced oscillation conditions are analyzed in terms of wall static pressure,shock train leading-edge location,shock train length,and the size of the separation *** extent of the initial shock location increases with an increase in exit duct length for the self-excited oscillation *** analysis of the shock train leading edge and the spectral analysis of wall static pressure variations are *** variation in the shock train length is analyzed using the pressure ratio method for self-excited as well as forced *** RMS amplitude of the normalized shock train length(ζ_(ST))increases with an increase in the exit duct length for the self-excited oscillation *** the downstream perturbation frequency is increased,ζ_(ST)is decreased for exit duct *** all exit duct designs and downstream forcing frequencies,the size of the separation bubble grows and shrinks during the shock oscillations,demonstrating the dependence on duct resonance and forced oscillations.

关键词： shock train downstream disturbance supersonic flow shock wave boundary layer interaction duct resonance flow separation

Impact of Fin Arrangement on Heat Transfer and Melting Characteristics of Phase Change Material

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Journal of Thermal Science 2024年第2期33卷 435-456页

作者： Arun UNIYAL Yogesh k.PRAJAPATI Department of Mechanical Engineering National Institute of Technology UttarakhandSrinagar(Garhwal)246174India Department of Mechanical Engineering BIT SindriDhanbadJharkhand828123India

Present work investigates the heat transfer and melting behaviour of phase change material(PCM) in six enclosures(enclosure-1 to 6) filled with paraffin *** enclosures are equipped with distinct arrangements of the fins while keeping the fin's surface area equal in each *** analysis has been presented to recognize the suitable fin arrangements that facilitate improved heat transfer and melting rate of the *** wall of the enclosure is maintained isothermal for the temperature values 335 k,350 k and 365 *** length of the enclosure including fins is ranging between 0 and *** have been illustrated through the estimation of important performance parameters such as energy absorbing capacity,melting rate,enhancement ratio,and Nusselt *** has been found that melting time(to melt 100% of the PCM) is 60.5%less in enclosure-2(with two fins of equal length) as compared to the enclosure-1,having no *** the fin surface area equal,if the longer fin is placed below the shorter fin(enclosure-3),melting time is further decreased by 14.1% as compared to ***,among all the configurations,enclosure-6 with wire-mesh fin structure exhibits minimum melting time which is 68.4% less as compared to the *** on the findings,it may be concluded that fins are the main driving agent in the enclosure to transfer the heat from heated wall to the *** design and positioning of the fins improve the heat transfer rate followed by melting of the PCM in the entire area of the *** of the favourable vortices and natural convection current in the enclosure accelerate the melting phenomenon and help to reduce charging time.

关键词： phase change material enclosure fin melting fraction energy storage heat transfer