• Journal of the Korean Society for Precision Engineering
• /
• v.13 no.1
• /
• pp.143-152
• /
• 1996

The vibratory bowl feeder is the most versatile of all hopper feeding devices for small engineering parts, and the typical nonlinear dynamic system experiencing repeated impacts with friction. We model and analyze the dynamic behavior of a single part on the vibrating track of the bowl feeder. While the previous studies are restricted to the sliding regime, we focus our analysis on the hopping regime where the high conveying rate is available. We present the numerical analysis results for conveying rate and frictional impact process both in periodic and chaotic regimes. We examined the dynamic effects from the variation of several physical parameters, and presented the important features for the design of the vibratory bowl feeder. This research holds much potential for leverage over design problems of wide range of mechanisms and tools with repeated collisions.

• Journal of the Korean Ceramic Society
• /
• v.40 no.9
• /
• pp.849-854
• /
• 2003

Temperature dependent thermoelectric power (TEP) of La$_{2.1}$ Sr$_{1.9}$ Mn$_3$O$_{10}$ system has been studied in the temperature range 80-373 K. In the low temperature ferromagnetic regime, TEP (S) follows an expression of formS＝S$_{0}$ ＋S$_{1.5}$ T$^{1.5}$ ＋S$_4$T$^4$ over the wide range of temperature. The broad peak below the ferromagnetic transition and complicated temperature dependence of S may be understood on the basis of electron-magnon scattering as predicted for an itinerant ferromagnet. High temperature TEP data can be well fitted with Mott's small polaron hopping model.

• Journal of the Korean Ceramic Society
• /
• v.39 no.9
• /
• pp.878-883
• /
• 2002

Electrical resistivity and thermoelectric power measurements on Mn-based $La_{2.1}Sr_{1.9}Mn_3O_{10}$ with layered perovskite structure as functions of temperature are presented. The experimental results demonstrate that the electronic transport in $La_{2.1}Sr_{1.9}Mn_3O_{10}$ is well described by the Emin-Holstein adiabatic small polaron model. The thermoelectric power data in the small polaron regime above Curie temperature is nearly equal to that predicted by nominal $Mn^{4+}$ valence arguments. This indicates that transport involves small polaron hopping.

• Journal of the Korean Ceramic Society
• /
• v.35 no.8
• /
• pp.885-889
• /
• 1998

The temperature dependence of dc conductivity and magnetic properties of cation deficient {{{{ { {(LaMn) }_{1-λ }O }_{3 } }} systems has been investigated,. Above 160K the magnetic susceptibility of all samples followed the Curie-Weiss law. The Curie temperature decreased as the cation deficiency increased. This is due to a strong Jahn-Teller effect originated from electrons of {{{{ { Mn}^{3+ } }} In the case of samples annealed in air and oxygen at-mosphere the charge carriers responsible for conduction in the ferromagnetic regime below the Curie tem-perature are believed to have both magnetic and lattice characteristics. However the conduction carriers in the paramagnetic regime above the Curie temperature are though to be formed by hopping process of small polarons which were generated by assistance of the Jahn-Teller effect.

• Journal of the Korean Ceramic Society
• /
• v.42 no.9 s.280
• /
• pp.613-617
• /
• 2005

We present the results of a combined magnetization, dc and magneto-transport study of the n = 2 Ruddlesden-Popper compound $Ca_3Mn_2O_7$ The negative thermoelectric powder is observed. The magnetic measurement data show that there is sharp magnetic transition at 134 K. However, the de and magnetoresistance of $Ca_3Mn_2O_7$ show no particular transport. Transport properties of the compound $Ca_3Mn_2O_7$ are interpreted in terms of activated hopping of small polarons in non-adiabatic regime. Polarons are most probably formed around $Mn^{3+}$ sites created by oxygen sub-stoichiometry.

• Journal of the Microelectronics and Packaging Society
• /
• v.24 no.2
• /
• pp.49-53
• /
• 2017

We study on the change of electrical properties of two-dimensional (2D) $SnSe_2$ materials with respect to Cl doping as $SnSe_{1.994}Cl_{0.006}$ under a high temperature condition. (300~450 K) By the simple solid-state reaction method, non-and Cl-doped 2D $SnSe_2$ materials are successfully synthesized with negligible impurities as confirmed by X-ray diffraction. From the temperature dependence of resistivity, it is observed that the conduction mechanism is changed from hopping to degenerate conduction with Cl doping. By Hall effect measurement, an increase on electron carrier concentration from ${\sim}7{\times}10^{16}$ to ${\sim}3{\times}10^{18}cm^{-3}$ with Cl doping verifies that Cl is an effective electron donor which results in the encouraged carrier concentration. Detailed analysis for temperature dependent Hall mobility reveals that the electrical transports in high temperature regime are governed by the grain boundary-controlled mechanism for non-doped $SnSe_2$, which is effectively suppressed by Cl-doping as entering metallic transport regime.