Compressive and tribological properties of Al2O3 fibre and hexagonal BN particle hybrid reinforced Al-Si alloys

Al₂O₃ fibre-hexagonal BN particle hybrid reinforced aluminium-silicon alloys were fabricated by centrifugal force infiltration route. Hardness test and ultimate compressive test results are reported. The wear and friction properties of hybrid MMCs was investigated by means of a block-on-ring (bearing steel) type wear rig in a dry sliding condition. It is shown that the hardness and ultimate compressive strength of hybrid MMCs was evidently decreased with the addition of hexagonal BN particles, however, the wear rate and coefficient of friction of hybrid MMCs was improved simultaneously with increase of BN particle volume fraction, especially for the higher applied loads in the test.     

Group decision support system for assessment of problem-basedlearning

Assessment is an important task in problem-based learning (PBL). It has a strong influence on students' approaches to learning and their outcomes. In order to provide an open and fair method of PBL assessment, a group decision support system (GDSS) has been developed. The system uses mathematical decision methods for collecting assessment criteria and their appropriate weights, and databases for storing students' details and data on the assessment criteria. It integrates databases with model bases in a cooperative decision-making environment and is implemented on a client-server platform using a relational database management system. The GDSS has been developed and used to improve the efficiency and quality of assessing students' PBL outcomes     

金刚石光电导探测器研制及在软X光测量中的初步应用

介绍了我们自己设计制造的天然Ⅱａ型金刚石光导探测器的结构，原理，制造工艺，实验标定及其在ＩＣＦ实验中软Ｘ光测量中的应用等。     

型钢矫直中产生缺陷的原因及改进

结合邯郸钢铁集团公司型棒材厂型材矫直后头、尾部普遍存在的问题,分析了产生问题的原因,通过采取一些技术措施产生了一定的效果,进一步提出了对矫直机结构的改进方案。     

摩擦诱发高铬铸铁相变的透射电镜研究

利用透射电子显微镜研究了高铬铸铁在摩擦过程中的显微组织变化。结果表明：奥氏体基体在摩擦应力的作用下发生相变。摩擦表面形成α‘Ｍ。次表层形成γ与α’Ｍ共存区；γ与．ε共存区；γ位错丛聚区。     

用偏微分方程构造过渡面

用偏微分方程的构造曲面是一种新兴的方法，本文借若干算例说明如何用偏微分方程构造两已知曲面之间的过渡面。论文着重讨论用四阶方程构造一阶连续的过渡面。     

双能X射线骨密度仪测定技术研究

以Ｌｕｎａｒ公司ＤＰＸ－Ｌ型双能Ｘ射线骨密度仪为例，研究引起测量误差的主要因素并提出质控措施。用自检模块、腰椎体膜评定仪器的体外测量精度好于１％。对１０位志愿者重复２次测量，体内精度对腰椎，ＭＰＤ（平均百分差）为０．４６，ＣＶ（变异系数）为０．７５；对股骨颈，ＭＰＤ为１．２６、ＣＶ为０．４７；Ｗａｒｄ’ｓ三角区ＭＰＤ为２．０１、ＣＶ为１．１４；大转子ＭＰＤ为１．６６、ＣＶ为０．７２。扫描图像由２位     

Calculation of the stress intensity factor for arbitrary finite cracked body by using the boundary weight function method

The state of thermal stresses for a periodic two-layered elastic space weakened by an interface thermally insulated Griffith crack and loaded by concentrated line heat sources is investigated. The analysis is performed within the framework of the homogenized model with microlocal parameters. The stress intensity factors at the crack tips are determined. Two examples of the application of the results obtained are detailed.     

Clinical and histopathological aspects of 113 necrotizing malignant melanomas of the choroid. 1. Clinical and histological features of necrotizing choroidal melanomas

BACKGROUND: Tumor necrosis may reflect a destructive immune reaction. Systematic and statistically significant comparative clinico-histopathologic studies have not yet been reported. PATIENTS AND METHODS: 113 necrotizing choroidal melanomas (NCM) recruited from 701 enucleated globes 1967-1988 were resectioned, stained and compared to 100 choroidal melanomas without necrosis (CM), and data of 74 patients with a follow-up of more than 10 years were evaluated. RESULTS: Statistically significant characteristics of NCM were: patient age < 60 yrs. for NCM 27.4%, CM 46%; patient age in men for NCM was 64 yrs on average (CM: 58 yrs.), in women for NCM 67 yrs. (CM: 59 yrs.). Time elapsed between first symptoms and enucleation was < 12 months in 15.9% of NCM (89% for CM), and > 12 months in 23.9% of NCM (11% in CM). Mixed or epitheloid cell tumors was seen in 54.9% of NCM and 49% of CM, spindle cell tumors in 36.3% of NCM and 51% in CM. Advanced tumor stages T3 and T4 were present in 45.1% resp. 36.3% of NCM compared to 37% resp. 16% in CM. Scleral invasion was documented in 67.3% of NCM and 37% of CM, extrascleral dissemination in 43% of NCM and 16% of CM. Secondary glaucomas were seen in 62.2% of NCM and 6% CM, a penetration through Bruch's membrane in 61.0% of NCM and 46% of CM. Intratumoral hemorrhage was noted in 68.14% of NCM and 24% of CM, extratumoral bleeding in 23.9% of NCM and 0% CM. Inflammatory reactions in tumors were observed in 96.7% of NCM harboring > 30% necrosis compared to 5% in CM, and extratumoral in 94.5% of NCM and 0% of CM. Intraocular extratumoral necrosis was seen in 23.9% of NCM and 0% of CM. There were no significant differences in the degree of pigmentation of the 90.3% pigmented NCM or of the 94% pigmented CM, neither in the tumor localization, being constantly behind the equator in 87% of cases. Survival of patients with NCM patients was 5 years and 9 months on average (5-year mortality rate 41.9%), and 74.3% were deceased from metastatic spread. CONCLUSIONS: Significant clinical and histopathological differences between necrotizing and non-necrotizing malignant melanomas of the choroid can be identified. The inflammatory reaction of NCM must be further elucidated, particularly with respect to the nature of tumor-infiltrating lymphocytes.     

直流电弧炉长弧泡沫渣技术

本文指出了直流电弧炉采用长弧泡沫渣技术的必要性及该技术的发展现状，总结了炉渣物理性质，化学成分，温度和气源等对炉渣泡沫化的影响，并介绍了电炉泡沫渣的操作工艺及实际应用效果，对宝钢三期１５０ｔＤＣ－ＵＨＰ电弧炉的泡沫渣工艺提出了看法。