Understanding of the influence of process parameters on the heat transfer behavior at the metal/die interface in high pressure die casting process

The current paper focuses on the influence of the process parameters on the peak values of the interfacial heat transfer coefficient(IHTC)at metal/die interface during high pressure die casting(HPDC)process.A"step shape"casting and AM50 alloy were used during the experiment.The IHTC was determined by solving the inverse thermal problem based on the measured temperature inside the die.Results show that the initial die surface temperature(IDST,TDI)has a dominant influence while the casting pressure and fast shot velocity have a secondary influence on the IHTC peak values.By curve fitting,it was found that the IHTC peak value(hmax)changes as a function of the IDST in a manner of hmax=e αTγ DI .Such relationship between the IHTC peak value and the IDST can also be found when the casting alloy is ADC12,indicating that this phenomenon is a common characteristic in the HPDC process.     

三维变异函数的稳健统计学计算方法及其应用

在应用地质统计学进行矿床建模工作中，变异函数的计算和拟合占有非常重要的地位，其结果的好坏将直接影响建模效果．针对传统变异函数计算及拟合方法的缺陷，运用稳健统计学理论，讨论了三维情况下实验变异函数的计算以及拟合方法．矿床建模实践表明，采取上述技术取得了良好的效果．     

δ铁素体对12%Cr超超临界转子钢冲击性能的影响

高中压转子是超超临界火电机组的关键零部件,要求具有很高的高低温冲击性能,材料一般采用高铬(12%Cr)耐热合金钢.该文通过一系列实验,研究了12%Cr转子钢1Cr12W2NiMoVNbN钢组织中δ铁素体对室温冲击性能的影响.结果表明:δ铁素体的存在会严重损害该钢的冲击性能,而奥氏体晶粒尺寸在一定范围内对其冲击性能影响不大;对已经出现的δ铁素体,可以用在900～1 150℃温度区间长期保温的方法进行消除.研究结果对科学制定超超临界高中压转子铜热处理工艺具有参考价值.     

提高Si_3N_4结合SiC棚板坯体成型密度的研究

为了获得性能优良的Ｓｉ３Ｎ４－ＳｉＣ棚板，就棚板制造过程中的配料及成型工艺等问题进行了实验研究，探讨了提高Ｓｉ３Ｎ４－ＳｉＣ棚板坯体密度的最佳途径。实验表明：振动成型时，振动时间和振动压力要匹配适当，才能得到最佳的坯体密度。工艺调整适当后，Ｓｉ３Ｎ４－ＳｉＣ棚板实际使用寿命可达５００次以上。     

The Goldbach 3-primes property for polynomial rings over certain infinite fields

On the basis of Effinger and Hayes’ theorem about the Goldbach 3-primes property of polynomial rings F[x] over finite fieldsF, by model-theoretic method it is proved that for each characteristick (including 01, there exist infinitely many infinite fieldsF such that F[x] also satisfy Goldbach 3-primes property.     

嘧啶氧磷毒性和解毒试验研究

本文报道了嘧啶氧磷的急性经口，经皮毒性和解毒试验研究结果。嘧啶氧磷对小白鼠经口ＬＤ５０为８７ｍｇ／ｋｇ，大白鼠经口ＬＤ５０为１８３ｍｇ／ｋｇ，大白鼠经皮ＬＤ５０为１０６２ｍｇ／ｋｇ，氯磷定对嘧啶氧磷中毒有良好的解毒效果。     

中和沉淀法Fe_3O_4的生成过程研究

本文利用XRD等技术对中和沉淀法Fe3O4的生成条件进行了研究,得到了Fe3O4的生成条件图。并以此对中和沉淀法Fe3O4的生成过程进行了讨论,发现Fe3O4的生成过程和空气氧化法Fe3O4的生成过程截然不同。中和沉淀法Fe3O4的生成过程随R及反应PH的不同而不同。反应温度的提高有利于Fe3O4生成量的增加并使Fe3O4的生成条件区域扩大。     

关于信息战的一个数学模型

本文建立了以Ｃ＾３Ｉ系统为核心的信息战数学模型，讨论了模型的解以及关于模型几种情况的分析，通过特例，还研究了产收集和组织已方的信息元，以在战斗中赢得胜利。     

三维Minkowski空间中非类光曲线的球面达布像

本文主要给出了三维Mirdcow幽空间中非类光曲线的球面达布像的奇点的充要条件，并且建立了奇点和曲线几何不变量之间的联系，其中曲线几何不变量与曲线同螺线切触的阶数密切相关．     

Environmental changes reflected by n-alkanes of lake core in Nam Co on the Tibetan Plateau since 8.4 kaB.P.

The n-alkanes are extracted from NMLC-1 core that was drilled in the Nam Co, central Tibet. They are measured by using Gas Chromatography and Mass Spectrometry (GC/MS) for componential and quantitative analyses. According to the constructed depth-age model, the component and concentration of n-alkanes, together with total organic carbon (TOC), total nitrogen (TN) and carbonate are used to elu- cidate palaeoenvironmental changes of Nam Co during the past 8.4 ka. The results indicate that Holo- cene environment performs three stages in the lake area. In the stage of 8.4―6.7 kaB.P., it was warmer while precipitation slightly increased. This stage was ended by an obvious cold/dry event. During 6.7― 5.8 kaB.P., temperature increased rapidly and reached its maximum values at about 6.0 kaB.P. The environments were warm/wet optimum for the blooming of terrestrial plants and submerged aquatic plants. After that, temperature decreased continuously and showed the lowest values at about 3.0 kaB.P. From 2.9 kaB.P. to the present, temperature rose again but alternated with cold and warm. The lake area tended to be dry after 1.4 kaB.P. During 600―400 aB.P., the environmental feature was the reflection of "Little Ice Age".