大孔径螺旋钻机钻具的设计

论述了螺旋钻具的结构参数及螺旋钻机在临界状态工作时的情况,并对螺旋钻具的运动作了简要分析.     

谈三江平原洪涝治理

分析了三江平原地区造成洪水的影响因素及洪水危险程度;提出了防洪减灾措施.     

啁啾脉冲放大系统中单光栅展宽器的优化

计算了啁啾脉冲激光放大系统中单光栅展宽器在入射角大于和小于利特罗角两种入射情况 ,发现对同一飞秒脉冲在相同展宽比条件下 ,入射角小于利特罗角时所需光栅宽度要远小于入射角大于利特罗角时所需的光栅宽度 ,且在入射角小于利特罗角时存在一最佳入射角 ,此时所对应的光栅宽度达到最小值。同时理论分析及数值计算显示 ,在上述条件下入射角小于利特罗角时此单光栅展宽器的等效光栅对间距较入射角大于利特罗角时大为缩短。     

Partially Occluded Object Recognition Using Statistical Models

In this paper, we present a new Bayesian framework for partially occluded object recognition based on matching extracted local features on a one-to-one basis with object features. We introduce two different statistical models for occlusion: one model assumes that each feature in the model can be occluded independent of whether any other features are occluded, whereas the second model uses spatially correlated occlusion to represent the extent of occlusion. Using these models, the object recognition problem reduces to finding the object hypothesis with largest generalized likelihood. We develop fast algorithms for finding the optimal one-to-one correspondence between scene features and object features to compute the generalized likelihoods under both models. We conduct experiments illustrating the differences between the two occlusion models using different quantitative metrics. We also evaluate the recognition performance of our algorithms using examples extracted from object silhouettes and synthetic aperture radar imagery, and illustrate the performance advantages of our approach over alternative algorithms.     

浅谈碱性锌锰电池的技术革新

文章指出,高容量、长寿命、重负荷输出性能将成为碱性锌锰电池发展的方向,并针对不同的要求提出了可能的解决途径:减小钢壳壁厚度、适当的锰碳比和锌粉含量可提高容量;解决锌电极的腐蚀问题是改进贮存寿命的关键;降低内阻、选择好的隔膜材料是提高重负荷输出性能的有效方法.     

阀控密封蓄电池充电接受能力的探讨

通过对阀控密封铅蓄电池制造过程中的板栅合金、铅膏有机添加剂、化成、装配等分析,探讨了对充电接受能力的影响;并提出了有利于充电接受性能提高的途径.在铅钙板栅合金中添加一定量的Sn,在负极铅膏配方中有选择的使用有机添加剂,合适的化成工艺和环境,合理的装配和选择好的隔板材料,可提高充电接受能力.     

Pregnancy and medical radiation

Thousands of pregnant patients and radiation workers are exposed to ionising radiation each year. Lack of knowledge is responsible for great anxiety and probably unnecessary termination of pregnancies. For many patients, the exposure is appropriate, while for others the exposure may be inappropriate, placing the unborn child at increased risk. Prenatal doses from most properly done diagnostic procedures present no measurably increased risk of prenatal death, malformation, or impairment of mental development over the background incidence of these entities. Higher doses, such as those involved in therapeutic procedures, can result in significant fetal harm. The pregnant patient or worker has a right to know the magnitude and type of potential radiation effects that might result from in utero exposure. Almost always, if a diagnostic radiology examination is medically indicated, the risk to the mother of not doing the procedure is greater than is the risk of potential harm to the fetus. Most nuclear medicine procedures do not cause large fetal doses. However, some radiopharmaceuticals that are used in nuclear medicine can pose significant fetal risks. It is important to ascertain whether a female patient is pregnant prior to radiotherapy. In pregnant patients, cancers that are remote from the pelvis usually can be heated with radiotherapy. This however requires careful planning. Cancers in the pelvis cannot be adequately treated during pregnancy without severe or lethal consequences for the fetus. The basis for the control of the occupational exposure of women who are not pregnant is the same as that for men. However, if a woman is, or may be, pregnant, additional controls have to be considered to protect the unborn child. In many countries, radiation exposure of pregnant females in biomedical research is not specifically prohibited. However, their involvement in such research is very rare and should be discouraged. Termination of pregnancy is an individual decision affected by many factors. Fetal doses below 100 mGy should not be considered a reason for terminating a pregnancy. At fetal doses above this level, informed decisions should be made based upon individual circumstances.     

ITA study of non-destructive methods of inspecting and testing tunnel linings

The International Tunneling Association's Working Group on Maintenance and Repair of Underground Structures is preparing a report dealing with non-destructive methods of inspecting and testing tunnel linings. This request for information details the scope of the group's work and the types of information the group is seeking at this time.     

永发水库复建的必要性

就水库的消险和充分利用水资源发展农业生产服务等方面,论述复建永发水库工程的必要性.