A NECESSARY AND SUFFICIENT CONDITION ON HEREDITARY HELLY HYPERGRAPHS AND CONFORMAL HYPERGRAPHS AND THEIR EQUIVALENCE

We show in this paper, a necessary and sufficient condition on hereditary K-Helly hypergraphs and conformal hypergraphs and their equivalence.     

A SIMPLE AND FAST DRAWING APPROACH FOR ARROW DIAGRAM

This paper discusses the drawing approach arrow diagram. After repeated explorations and thinking,a simple and fast drawing approach for arrow diagram is formulated. The approach overcomes the drawback of existing drawing methods. Besides its fastness,it has the advantages of clear presentation of logical relations,easy access to correctness and it can be easily grasped by beginners.     

A NEW COMPENSATIVE SNUBBER FOR ELIMINATING THE SURGE AND NOISE IN PWM CONVERTERS

A new compensative snubber is presented for eliminating the surge current and high frequency parasitic oscillation in rectified circuit of the PWM DC-DC converters. The output surge and noise voltages are de-creased over 4/5. The working principle of the sunbber is analyesd in detail, the designing formulas are derived. The theoretic analysis is consistent with the experimental results.     

从美国引进的小麦抗锈品种的抗锈性测定和我国及美国小麦叶锈菌的毒性比较研究

1981年在河北农业大学温室分别用中国小麦叶锈菌4个小种360、376、377和60对从美国引进的13个抗锈品种进行了抗叶锈性测定,在河北省植保所田间进行了成株期对叶、条锈的抗性测定.1982年在美国堪萨斯州立大学温室分别用美国的小麦叶绣菌培养物PRTUS1、3、4、5、6、7、8、9、10、11、13和19对13个品种中的9个进行了抗叶锈性测定.苗期测定结果指出,其中3个品种Kans 63324,STW 646407和II-11996-4R-SM-1R对所测的中国小种都表现抵抗,但对美国的培养物大多数抵抗,而在所测的9个品种中没有对所有美国培养物都抵抗的.在对比两国之间中国小麦叶锈菌小种和美国小麦叶锈菌培养物的毒性时进一步指出,有些品种犹如LA1415,STW597725和STW597947对美国的少数培养物抵抗,而对所有的中国小种感染.田间试验用小麦条锈菌小种19和21接种指出品种NB61975、NB66523和STW597944对条锈是免疫的,NB61977和II-119966-4R-SM-1R是高抗的.