Specific parameters comparison of synchronous reluctance electric drives
The article presents the principles of comparison of different types of synchronous contactless electric drives. The mathematical description of the system is given for comparison. It is shown that classical unregulated synchronous electric drives are inferior to induction electric drives by 30–40%. It is caused by both a decrease in excitation and a decrease in the limiting load angle according to the conditions of static stability. The phase current of electric drives with FRRM has a rectangular shape which allows one to significantly improve the weight and dimensions. In this case, the electric drive with FRRM due to the compensation of the armature transverse response allows improving the system characteristics, so that the induction motor is 10–15% less than the FRRM.
Gearless electric drives with low-frequency asynchronous motors
Low-frequency asynchronous motors are considered. A mathematical description of them and a technique for calculation of their static and dynamic characteristics with the use of generalized parameters are presented. Distinguishing features of their design and parameters are indicated. Advantages of the use of gearless electric drives based on low-frequency asynchronous motors are shown for the general case and for a particular example. Issues of practical application of electric drives with low-frequency elevator motors are examined.
Introduction and experience with the primary mail services based on their names for students
Kyushu University provided mail service based on student IDs such as "1AB10123X" to the university students for many years. Using this model, we had problems communicating with the students who graduated from the University and enrolled in the graduate school. The students received new mail addresses based on their new student IDs such as "2AB12789Y". Faculty members were forced to change the student mail addresses in the mailing lists and in their mail client address book. Furthermore, students were forced to notify the e-mail address change to all of their existing contacts. We introduced a new mail system to provide addresses based on the student name, as well as student ID in April 2011. The new naming convention uses the following format: lastname.firstname.999 where 999 is a random number of 3 digits. Students can select some combination patterns of their first and last names for Japanese. We also consider the middle names for foreign students. In the system implementation, we did not have the formal information of alphabetical names for students. We generated alphabetical names from Japanese Katakana names. It is not easy for us to get the appropriate name in this manner. We implemented a confirmation stage of the alphabetical name at first use, and then students can select their mail addresses for their convenience. We paid much attention to the user interface in the system. Since April 2011, the number of users who use the mail address based on their own name has been increasing gradually. This paper will detail the usage status of the new system.