Crystal structure of Mg_3Pd from first-principles calculations

Crystal structure of Mg3Pd alloy was studied by first-principles calculations based on the density functional theory.The total energy,formation heat and cohesive energy of the two types of Mg3Pd were calculated to assess the stability and the preferentiality.The results show that Mg3Pd alloy with Cu3P structure is more stable than Na3As structure,and Mg3Pd alloy is preferential to Cu3P structure.The obtained densities of states and charge density distribution for the two types of crystal structure were analyzed and discussed in combination with experimental findings for further discussion of the Mg3Pd structure.

Hydration Heat Evolution of Cement and Its Relation With Setting Time

In order to veritably measure the first peak of hydration heat evolution that has been illustrated important in indicating cement behavior in early hydration, an improved way of water addition into cement in isothermally calorimetric experiment is put forward. The experimental results indicated that: the magnitude of first peak of heat evolution varies from sample to sample, correlation between heat evolution during first peak of heat evolution and initial (as well as final) setting time is unsatisfactory when samples are not classified; while groups of sample classified based on strength grade represent satisfactory correlations, which indicating the existence of close relation between hydration heat evolution in much earlier hydration age and setting property of cement in rather later age. Importance of first peak in hydration heat evolution for understanding cement setting property and reasons for sample classification are also discussed in this paper.

An Evaluation for the Probability Density of the First Hitting Time

Let h(t) be a smooth function, Bt a standard Brownian motion and th=inf{t;Bt=h(t)} the first hitting time. In this paper, new formulations are derived to evaluate the probability density of the first hitting time. If u(x, t) denotes the density function of x=Bt for t th, then uxx=2ut and u(h(t),t)=0. Moreover, the hitting time density dh(t) is 1/2ux(h(t),t). Applying some partial differential equation techniques, we derive a simple integral equation for dh(t). Two examples are demonstrated in this article.

Elastic constants and thermodynamic properties of Mg_2Si_xSn_(1-x) from first-principles calculations

This paper stuides the elastic constants and some thermodynamic properties of Mg2SixSn1-x （x = 0, 0.25, 0.5, 0.75, 1） compounds by first-principles total energy calculations using the pseudo-potential plane-waves approach based on density functional theory, within the generalized gradient approximation for the exchange and correlation potential. The elastic constants of Mg2SixSn1-x were calculated. It shows that, at 273 K, the elastic constants of Mg2Si and Mg2Sn are well consistent with previous experimental data. The isotropy decreases with increasing Sn content. The dependences of the elastic constants, the bulk modulus, the shear modulus and the Debye temperatures of Mg2Si and Mg2Si0.5Sn0.5 on pressure were discussed. Through the quasi-harmonic Debye model, in which phononic effects were considered, the specific heat capacities of Mg2SixSn1-x at constant volume and constant pressure were calculated. The calculated specific heat capacities are well consistent with the previous experimental data.

Quantum Heat Engines;Multiple-State 1D Box System

We evaluate quantum Otto, Diesel and Brayton cycles employing multiple-state 1D box system instead of ideal gas filled cylinder. The work and heat are extracted using the change in the expectation of Hamiltonian of the system which leads to the first law of thermodynamics to quantum system. The first law makes available to redefine the force which is in fact not well defined in a quantum mechanical system and then it is applied to define the quantum version of thermodynamic processes, i.e. isobaric, isovolume and adiabatic. As the results, the efficiency of quantum Otto engine depends only on the compression ratio and will be higher than the efficiency of quantum Diesel which can decrease by the widening of expansion under isobaric process. The efficiency of quantum Brayton engine may reach maximum on certain combination between the wide of box under isobaric expansion and compression, under certain conditions. The amount of levels participated in the quantum heat engine system will potentially reduce the performance of the quantum heat cycles consisting isobaric process, but it can be resisted using isobaric process controller.

THE ROLE OF INTRONIC HSE IN THE HEAT SHOCK INDUCED EXPRESSION OF HUMAN hsp 90β GENE

The first intron of human hsp90β gene is not only essential in maintaining high constitutive expression but also critical for heat shock inducibility of the hsp90β gene. Typical HSEs in the first intron play a vital role in the heat induced expression of human hsp90β gene. Slot blot analysis shows that hsp90β gene mRNA transcripts initiated from the 3’ of the first intron dominates over that of the first exon. The intronic HSEs of the hsp90β gene show much higher binding affinity toward the recombinant heat shock factor HSF1 than that of the recombinant heat shock factor HSF2.

Viscoelastic Effects on Unsteady Two-Dimensional and Mass Transfer of a Viscoelastic Fluid in a Porous Channel with Radiative Heat Transfer

An analysis of oscillatory flow of a viscoelastic fluid and mass transfer along a porous oscillating channel with radiative heat transfer in presence of first-order chemical reaction is considered. The problem is concerned with the flow through a channel in which the viscoelastic fluid is injected on one boundary of the channel with a constant velocity, while it is sucked off at the other boundary with the same velocity. The two boundaries are considered to be in close contact with the two plates placed parallel to each other. The effect of temperature oscillations at the plate (upper wall) where the suction takes place is taken into consideration. The plates are supposed to be oscillating with a given velocity in their own planes. Analytical expressions for velocity profile, the temperature, concentration profile, wall shear stress on the upper wall are obtained. The profiles of the velocity and skin friction have been presented graphically for different values of the viscoelastic parameters with the combination of the other flow parameters encountered in the problem under investigation. It is observed that velocity decrease with the increasing values of the viscoelastic parameter in comparison with Newtonian fluid. Also, the wall shear stress increase with the increasing values of the viscoelastic parameter.

基于遗传粒子群优化的热负荷预测方法

集中供热系统一次网热负荷预测对于换热站能源合理分配具有重大意义,针对换热站之间存在较强的耦合性,如何保证换热站实现节能减排的同时并保证热用户的舒适性是供热行业的首要任务,提出一种基于遗传粒子群的混合神经网络(GAPSO-CNN-BiLSTM)预测模型。首先,利用热负荷历史值、供水流量、供水温度以及回水压力构建模型输入;然后,利用完全噪声辅助聚合经验模态分解(complete ensemble empirical mode decomposition with adaptive noise,CEEMDAN)将供热负荷分解为不同子序列,以弱化供热负荷数据复杂程度,挖掘数据内部潜在特征;其次,为进一步减少模型计算时间,根据样本熵(sample entropy,SE)对子序列进行合并;最后,利用所提模型对不同子序列进行预测重构。实验表明所提模型相比LSTM、CNN-LSTM以及粒子群优化的混合神经网络(PSO-CNN-LSTM)在供热负荷预测中精度分别提高42%,32%,30%拥有更出色的特征提取能力和精度。

不锈钢表面Al/Cu涂层制备与第一性原理计算

为了研究Al/Cu涂层中金属间化合物的生成顺序和形成机理,在304不锈钢基体表面制备了Al/Cu涂层。对试样进行热处理使得Al/Cu涂层原位反应生成金属间化合物,随后测试了涂层的高温抗氧化性能。采用第一性原理计算Al-Cu金属间化合物的焓、熵、吉布斯自由能和热容等数据。将热力学和扩散动力学相结合,提出有效生成自由能模型来预测化合物在Al/Cu界面的生成顺序。结果表明:Al/Cu涂层中首先形成Al_(2)Cu相,在Al/Cu界面处出现了AlCu相,加热时间增加至20 h后出现了富Cu的Al_(4)Cu_(9)相。由第一性原理计算得出,Al-Cu金属间化合物的形成顺序为Al_(2)Cu→AlCu→Al_(4)Cu_(9),与实验结果一致。此外,氧化实验结果表明,涂层具有良好高温抗氧化性能。

氦冷固态包层第一壁内插扭带强化换热研究

针对氦冷固态包层第一壁换热能力不足,通过在第一壁冷却管道内插入扭带进行强化换热。基于工程流体力学理论和CFD软件进行了第一壁的热流体分析。研究了在相同工况下不同扭带参数对换热效果的影响。结果表明,扭带可以有效提高第一壁的换热能力,在结构参数为带厚3mm、带宽11mm、扭率2.5时换热效果最佳,第一壁内壁面平均换热系数提升了7.9%,结构温度升高量降低了8.6%。

一电厂消除脱硫系统白烟技术经济比较

为了消除燃煤电站烟囱的白烟现象,按照烟气直接加热和烟气先冷凝再加热两种方案针对一工程进行了烟囱消除白烟的初步工程方案设计,并进行了烟囱消除白烟的技术经济比较和分析。结果表明,烟气先冷凝再加热的消除烟囱白烟的方案具有明显的技术经济优势。

应用型本科高校金属学与热处理课程“两性一度”建设思考

高校“一流课程”建设是深化教学改革和推进创新创业的重要推手,其内涵主要包括课程的高阶性、创新性和挑战度。文章以应用型本科高校金属学与热处理“一流课程”建设为例,结合应用型本科高校专业培养方案和课程大纲,阐述了课程内涵建设的必要性,课程特色的专业性、学科交叉性和工程实用性,“两性一度”的建设措施,课程评价的内容与方式。通过全过程课程建设,提升学生的学成度和获得感,培养学生分析和解决实际工程复杂问题的能力。

聚变堆实验包层模块第一壁传热结构优化分析

可控核聚变是解决人类能源问题的理想途径。实验包层模块是国际热核聚变实验堆的关键部件之一。中国氦冷固态增殖剂包层模块(CH HCSB TBM)第一壁的设计,有3根冷却剂管道和5根冷却剂管道的方案。通过对这2种方案的简化,结合对流传热计算,得到第一壁的温度分布,并且提出了4根冷却剂通道的设计方案。5根冷却剂管道比3根冷却剂管道的设计许用温度低4℃。4根冷却剂通道具体结构是,通道径向尺寸为13 mm,极向尺寸为13.5 mm。这种设计在3种方案中拥有最低的温度分布,与前2种设计相比有较好的温度安全裕量,与3根管道的设计相比更能节省材料。

后备母猪初情日龄、发情次数和初配日龄与繁殖性能的关系

以长大二元杂后备母猪为研究对象,应用SPSS 19.0软件的单因素方差分析对8 875头后备母猪的前3胎数据进行分析,以探索初情日龄、初配前发情次数和初配日龄与繁殖性能的关系。研究结果表明,后备母猪初情日龄早于195 d的,其前3胎窝产总仔数分别为12.30头、12.13头和12.86头,为各组中的最高;初配前有3次或以上情期的,其前3胎窝产健仔数分别为10.57头、10.59头和11.10头,均极显著高于仅有1次发情期的（P〈0.01）,但与有2次发情期的差异不显著（P〉0.05）;后备母猪初配日龄分别为225~255 d、255~270 d和270~285 d的,其第1胎窝产健仔数依次为10.47头、10.48头和10.50头,均极显著高于初配日龄大于285 d的（P〈0.01）。因此,长大二元杂后备母猪初情日龄应控制在195 d前,初次配种日龄在225~285 d内,并有2次或以上情期经历为适宜。

青年奶山羊非繁殖季节诱发发情的研究

在奶山羊非繁殖季节的4～5月份,对293只青年羊进行了诱发发情试验。试验组用孕激素药管埋植6天或9天,分别注射PMSG(10,15,20IU/w·kg),母羊发情时注射HCG 1000IU/只或注射LRH—A100μg/只。试验羊在除去药管后进行1～2次配种。结果表明用孕激素预先处理并注射PMSG 15IU/kg·w组母羊的同期发情率为97.6％(P<0.01);第一情期受胎率为78.3％(P<0.05);第一情期配种受胎分娩率为53％。

供热工程中规划与现状的协调问题

对供热工程的现状面积和规划面积相差问题进行了探讨。分析了某供热工程出现的问题和解决问题的方法 。

ITER第一壁模块Be/Cu连接界面的热疲劳损伤分析

采用热等静压扩散连接技术并通过添加Ti/Cu中间过渡层实现了Be与Cu Cr Zr合金之间的可靠连接,所制作的ITER第一壁小模块已通过高热负荷疲劳试验。对试验后的小模块进行了超声波无损探伤,发现界面多处存在大尺寸缺陷。介绍了高热负荷疲劳试验后模块的破坏性检测与分析,结合对缺陷界面的金相观察、SEM观察及EDS分析方法,确定了缺陷形成的主要原因。

分布式变频供热系统均压管安装位置仿真分析

针对以均压管定零压差点运行调节的分布式变频供热系统,利用一维流体仿真软件Flowmaster,结合实际工程,对均压管安装在热源和第一热用户处2种位置的系统水压图和变流量调节水力特性进行了对比分析。结果表明:均压管安装在第一热用户处可以在一定程度上缓解后端换热站超压的问题,变流量调节中可提高分布式换热站的水力稳定性。

细磨石灰石粉对水泥性能的影响

将不同比表面积的石灰石粉按不同比例掺入水泥中,对水泥的性能进行研究。结果表明:石灰石粉的加入,能有效提高水泥的外加剂相容性、促进水泥的水化及提高水泥胶砂的体积稳定性;一定颗粒分布的石灰石粉对水泥胶砂的流动性能及强度有促进作用。

基于ANSYS的高地温支护结构温度应力研究

针对高地温引水隧洞模拟试验,利用有限元软件ANSYS模拟围岩支护模型在常温18℃和高地温60℃工况下养护1、3、7 d的温度场、应力场。研究表明:常温工况混凝土水化热主要通过岩板散失;高地温加速了喷射混凝土的水化反应,其内部热量、水分散失主要在混凝土边壁及岩板接触的边角处;试件岩板模型的最大第一主应力出现在混凝土试件底角处,而不是中心最高温度处。