双合金带锯条断齿、脱齿成因探讨

对以硬质为合金为锯齿、６５Ｍｎ钢为带体的“双合金带锯条”断齿、脱齿的成因进行了探讨,指出：新齿的主要原因是硬质合金成分设计不当造成锯齿的韧性不足,和齿形几何尺寸欠佳导致其受力条件恶化。并对此提出了改进措施。     

Observation of internal structures of teeth by ultrasonography

Preliminary experiments with high-resolution intensity-modulated ultrasonography techniques developed for ophthalmological diagnosis have demonstrated that at a frequency of 15 megacycles per second some internal structures can be seen in vital teeth. A relationship between time, tooth vitality, and ultrasonic viewing was observed.     

Elephant teeth from the atlantic continental shelf

Teeth of mastodons and mammoths have been recovered by fishermen from at least 40 sites on the continental shelf as deep as 120 meters. Also present are submerged shorelines, peat deposits, lagoonal shells, anz relict sands. Evidently elephants and other large mammals ranged this region during the glacial stage of low sea level of the last 25,000 years.     

Mecrowear of mammalian teeth as an indicator of diet

Microwear details on teeth of two sympatric species of hyrax are correlated with major dietary differences observed in the wild. Grazing (Procavia john-stoni) and browsing (Heterohyrax brucei) species can be distinguished. The results show that diets of extinct species may be deduced from tooth microwear.     

直齿圆锥齿轮的计算机辅助设计

为了减轻传统机械设计中繁琐的设计计算和重复的校合计算工作量,运用Auto CAD软件支持的Auto LISP和DCL语言,对直齿圆锥齿轮计算机辅助设计系统的开发进行初步探讨,以便对先进设计技术的发展有所贡献.     

Separate evolutionary origins of teeth from evidence in fossil jawed vertebrates

Placoderms are extinct jawed fishes of the class Placodermi and are basal among jawed vertebrates. It is generally thought that teeth are absent in placoderms and that the phylogenetic origin of teeth occurred after the evolution of jaws. However, we now report the presence of tooth rows in more derived placoderms, the arthrodires. New teeth are composed of gnathostome-type dentine and develop at specific locations. Hence, it appears that these placoderm teeth develop and are regulated as in other jawed vertebrates. Because tooth development occurs only in derived forms of placoderms, we suggest that teeth evolved at least twice, through a mechanism of convergent evolution.     

巨型抹香鲸齿质层元素分析

采用质子激发荧光分析方法(PIXE),对采自广西琼州海峡的一头29龄雄性抹香鲸(Physetermacrocephalus)遗骸的下颌齿齿质层作了元素测定。结果表明,测得的10个元素与Ca的平均相对含量中,以P、Zn、Sr等3个元素最高,与Ca的含量相差不到2个量级;Fe、Mn、K、S的含量中等,与Ca相差约3个量级;Ni、V、Cu等含量最低,比Ca要小约4个量级。在上述元素中,抹香鲸齿质对水中Zn的富集程度最大,达3个量级;P、Mn、Ni、Fe等次之,为2个量级;V、Cu等仅有不足百倍的富集程度;而Sr、S、K等则要比在水中小1~4个量级。除了V,抹香鲸齿质对海产动物(干质量)的其他9种元素都没有富集作用。文章还对抹香鲸不同年轮层内元素含量的变化状况与人类牙齿以及渤海江豚骨组织的元素含量作了比较。     

断齿链轮在轨道式螺旋速冻机上的应用

1问题的提出随着速冻行业和速冻设备制造行业的发展,螺旋速冻机因其占地面积少,冻结效率高而应用得越来越广泛,但螺旋式速冻机造价较高,制造工艺复杂,影响了其快速发展。螺旋速冻机的核心部件是转鼓,转鼓上的链轮是其主要构件之一。该链轮多采用分块式结构,铸造毛坯,用一定的工装上车加工齿部,不仅重量大,耗费大量不锈钢,而且机加工时间较长,加工费用较高。因此,改变链轮结构,降低重量,减少机加工成本,将具有较大的意义。2解决的办法2.1改变链轮结构我们首先在2LSSG2810螺旋速冻机上采用了断齿结构。断齿结构的特点就是在原来链轮齿形的基…     

Hinged teeth in snakes: an adaptation for swallowing hard-bodied prey

Six genera of snakes, representing at least three lineages, possess teeth that fold backward against the jaws rather than being firmly ankylosed. This condition, effected by a connective tissue hinge at the base of each tooth, is associated with suites of cephalic modifications that enable the snakes to grasp and to swallow hard-bodied prey.