Analysis of semiconductors with field-dependent mobility
Using the time domain analysis of Lagrangian approach, the small-signal behavior of a semiconductor with field-dependent mobility under various contact conditions is analyzed. A generalized closed form solution for an impulse current response is derived when the carrier velocity characteristic is expressed by a piecewise linear function. This result gives an accurate description of the transient performance of the device and can provide good insight into device operation. Numerical examples are given for a negative differential mobility GaAs crystal, considering the conditions under which negative resistances occur. A generalized small-signal impedance of the semiconductor is given, from which previous results reported for particular devices can be obtained as special cases.
Space charge limited and emitter current limited injections in space charge region of semiconductors
If, in a space charge region of a semiconductor device, a unipolar drift current is a main component of the total current, an analogy with motion of electrons in vacuum exists. In the space charge limited emission, injection of minority carriers is limited by space charges, as in a punched-through p-n-p diode. On the other hand, in a transistor, minority carriers are injected into the depletion layer between the base and the collector, after diffusion in the neutral base region. This injection is limited by emitter current, and this mode of injection corresponds to a temperature limited emission in a vacuum tube. In this paper, equations of minority carrier impedances will be calculated in both these cases, and negative resistances can be expected at some transit angles. Then a generalized equation, which includes these two modes of injections as special cases, will be obtained. This generalized equation corresponds to the Llewellyn-Peterson equation of vacuum tubes, which include the space charge limited emission and the temperature limited emission as special cases.
Research on health and oral health status of elderly living alone compared to elderly living with their families - based on the data (2014) from the 6th two-year Korea national health and nutrition examination survey -
Objectives: I examined the health and oral health status of elderly people living alone compared to elderly people living with their families by using data (2014) from the 6th Two-Year Korea National Health and Nutrition Examination Survey. Methods: Among 1,454 health survey respondents aged 65 years and over who participated in the 6th Two-Year Korea National Health and Nutrition Examination Survey conducted in 2014, 311 were elderly people living alone and 1,143 were elderly people living with their families. Results: In terms of socio-demographic characteristics, the percentage of elderly people living alone was high especially in women and when the subjects’ age, education level, and income level were low. In terms of oral health status, the percentage of elderly people living alone was high when elderly people thought that their subjectively viewed health was poor and the frequency of drinking and exercise was low. In terms of oral health status, the percentage of elderly people living alone was high among elderly people who did not have good oral health in their subjective view and did not get oral examinations for a year and had a lot of difficulty chewing. Conclusions: Family support or additional social support for elderly people who live alone should be considered to promote the healthy lives of elderly people.