Combining joint and semi-join operations for distributed queryprocessing

The application of a combination of join and semi-join operations to minimize the amount of data transmission required for distributed query processing is discussed. Specifically, two important concepts that occur with the use of join operations as reducers in query processing, namely, gainful semi-joins and pure joint attributes, are used. Some semi-joint, though not profitable themselves, may benefit the execution of subsequent join operations as reducers. Such a semi-join is termed a gainful semi-join. In addition, join attributes that are not part of the output attributes are referred to as pure join attributes. They exploit the usefulness of gainful semi-joins and use the removability of pure join attributes to reduce the amount of data transmission required for query processing. Heuristic searches are developed to determine a sequence of join and semi-join reducers for query processing. Results indicate the importance of the approach to combining joins and semi-joins for distributed query processing     

Influence of segregation in quantum well structures

The potential associated with quantum well (QW) structures is usually assumed to be a step function; this implies a compositional abruptness at each interface. But abrupt interfaces do not occur in practice, especially if one of the atoms segregates during growth. This leads to asymmetries in the QW potentials which could radically affect device performance.     

Metrology-cybernetics-control: A new approach

As a science and as a special activity concerned with measurements, the science of metrology pursues a classical, orthodox purpose, mainly involving the measurement of physical quantities. The term “measurement” is now applied also to social, economic, medical, and other disciplines, including cybernetics and problems of management and control. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 17–20, July, 1996.     

氯丁橡胶的溶液接枝反应研究

本文研究了引发剂过氧化苯甲酰的用量对ＣＲ接技ＭＭＡ－ＡＡ反应的单体转化率、接枝率及接枝胶的粘度、剥离强度等的影响，并用红外光谱和元素和元素分析对反应产物进行了表征．结果表明，体系中存在接枝、降解、交联三种反应，在不同的配方和工艺条件下，三种反应的反应程度不同．     

Repairs of the lining of a rotary cement kiln

An object of this study is the development of a composition of monolithic refractory concrete and a method of ongoing repairs of the lining of cement kilns with its use. The operation of clinker-firing kilns and the processes occurring in firing the concrete are investigated and the process operations of hot repairs of the kiln lining with the monolithic refractory concrete are described. The physicotechnical properties of the concrete and the results of experimental industrial tests are also given. Translated from Ogneupory, No. 4, pp. 25 – 26, April, 1994.     

Torque sensorless control in multidegree-of-freedom manipulator

A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller     

Prognostic factors of primary liver cancer

To investigate the prognostic factors of primary liver cancer (PLC) and improve the long-term results, 1,248 cases of PLC were analysed. Univariate analysis demonstrated that discovery approach, staging of PLC, original gamma-GPT, resection, radical resection, original AFP, tumor size, tumor number, and tumor capsule have very significant effects on prognosis of PLC (all P < 0.001); cirrhosis, HBsAg, local resection, and tumor embolus in portal vein were also significant difference (all P < 0.05); age, sex, original AFP, hepatitis, and differentiation of PLC cells were no significant difference (all P > 0.05). Multivariate analysis demonstrated that original gamma-GPT, radical resection, tumor size, and tumor number were the most significant prognostic factors (all P < 0.001). Some aspects improving long-term survival were discussed.     

连续运转的掺钛蓝宝石激光器

本文报导一种连续波氩离子激光泵浦的掺钛蓝宝石激光器。在氩离子激光功率(全谱线)为10.45瓦且仅用一组腔镜时,获得最大平均功率超过1000mW、调谐范围750～850nm的掺钛蓝宝石激光输出。     

邻异丙基酚的生产及应用

介绍了邻异丙基酚国内外研制、生产和应用情况，以及２，６－二异丙基酚的用途。