摘要：在计算对流给热系数(HTCs)时,为查取流体的物性值,须先确定温度。确定这个温度的步骤是相当简单的,但对高粘度物质或无油基流体就变得复杂。对这种情况,现已通过非常简单的计算步骤,导出了相互关系。 在确定用以估算流体物理性质的温度时如果在热交换终了时流体的性质大体上不变化,通常使用进、出口状况下的算术平均温度。当涉及多变情况时,Kern推荐估算换热器进、出口两端的给热系数(U_h和U_c)。

摘要：在高压中小功率容量应用领域中,新一代功率器件的发展和推陈出新具有明显的特征,即在正向导通压降、击穿电压和开关频率之间进行平衡以获得最优化的组合。最近推向市场的ESBTTM,即发射极开关双极性晶体管(Emitter Switched Bipolar Transistor),代表了功率器件的一个新的产品系列,特别适合于高压高开关频率应用领域。在简单介绍发射极开关原理及其从离散到积分方程的推演之后,本文还介绍了和有效基极驱动方法有关的全部知识,因此本文也能为功率变换器设计工程师提供有益的帮助。

摘要：Many cellular models have been used to investigate bone substitutes including coralderived hydroxylapatite (HA). The aim of this study was to verify whether a new cellular model represented by Saos-eGFP cells can be used to test biomaterials by in vitro assays. SaoseGFP cells which express the enhanced Green Fluorescent Protein (eGFP), were derived from the osteoblast-like cell line Saos-2. To this purpose Saos-eGFP cells were employed to investigate the in-vitro bioactivity of a well characterized coral-derived HA biomaterial, in block and granule forms. This engineered cell line, by evaluating the emitted fluorescence, allowed us to assay (i) cell adhesion, (ii) cell proliferation and (iii) colony capability. Electron microscopy analysis was employed to evaluate the (iv) morphology of cells seeded on the biomaterial surface. (v) Histological analysis of the bone grown after scaffold implantation was carried out in specimens from two clinical cases. Saos-eGFP cells indicate, as established before, that the coralline-HA biomaterials has a good in vitro cytocompatibility when tested with human osteoblast-like cells. Some differences in proliferation activity was detected for the two different forms assayed. Cytocompatibility data from in vitro analyses were confirmed by in vivo behaviour of biomaterials. Our tests suggest that the engineered cell line Saos-eGFP represents a suitable in vitro mode for studying the biocompatibility, the cell adhesion, spreading and proliferation on biomaterials developed for clinical applications. The main advantages of this cellular model are (i) less time consuming and (ii) a reduced cost of the experiments.