TEC

About: TEC is a research topic. Over the lifetime, 5119 publications have been published within this topic receiving 84696 citations.

Pattern and evolution of seismo‐ionospheric disturbances following the 2011 Tohoku earthquakes from GPS observations

Abstract: Global Positioning System (GPS) has been widely used to sense crustal deformation and ionospheric anomalies, particularly seismic ionospheric disturbances. In March 2011, the earthquakes with magnitude of up to Mw = 9 occurred in Tohoku near the east coast of Honshu, Japan. The GPS Earth Observation Network (GEONET) in Japan with more than 1200 continuously operating stations provides a unique opportunity to study the detailed seismic ionospheric disturbances. In this paper, the pattern and evolution of seismic ionospheric disturbances following the Tohoku earthquakes are investigated by dense GEONET data, including amplitude, propagation pattern, direction, speed, and evolution. Maximal coseismic ionospheric disturbances are found with up to more than 4 TECU, and the disturbance period is around 10–20 min. The seismic ionospheric effects following the aftershocks are attenuated with the increase of the time and distance between the ionospheric pierce point and the epicenter of the main event, which last more than 2 h. Seismic ionospheric disturbance detected by GPS measurement is not only related to the main shock but also the giant aftershocks. Propagation velocities of the total electron content (TEC) disturbance show a decrease when it spreads 400–600 km away from the epicenter in the north-western direction, where it is just near the west coast of Japan. Furthermore, the TEC disturbance also has obvious directional features. In the first half hour, the TEC disturbance in the southeast direction has the biggest amplitude, while the dominant direction is changed to northwest tens of minutes later. In addition, signals with higher frequencies are existed in seismic TEC variation at the epicenter region but do not appear in the far field.

Comparison of a CFD Analysis and a Thermal Equivalent Circuit Model of a TEFC Induction Machine With Measurements

Abstract: For a totally enclosed fan-cooled induction machine, two methods of numerical analysis are compared with measurements. The first numerical method is based on computational fluid dynamics (CFDs) and the second one uses a thermal equivalent circuit (TEC). For the analysis based on CFD, a 3-D induction machine including housing is modeled. The numeric solution of the flow equations is determined for stationary temperature distributions. For the TEC, a discretized one-and-a-half-dimensional model of the induction machine is considered. With the TEC model, stationary and transient operating conditions can be simulated. Measurement results are determined by iron-copper-nickel sensors embedded in the stator winding and the housing, as well as by an IR sensor for measuring the rotor temperature. With these measurement signals, stationary and transient operating conditions can be analyzed. For stationary operating conditions, additionally, the housing temperatures are determined by an IR camera. The investigated simulation and measurement methods reveal different local and global temperatures, and thus, only certain aspects and characteristics of the obtained temperatures can be compared. Nevertheless, certain conclusions can be drawn from comparing these aspects considering the actual restrictions of each of the applied methods.

Superposed epoch analysis of the dayside ionospheric response to four intense geomagnetic storms

Abstract: [1] Prompt daytime ionospheric responses are presented for the following four intense geomagnetic storms: 29 October 2003, 30 October 2003, 20 November 2003, and 7 November 2004. We perform a superposed epoch analysis of the storms by defining the start time of the epoch when the Kan-Lee interplanetary electric field (proportional to the reconnection electric field) first reaches 10 mV/m during a period of continuously southward Bz. Measurements from the GPS receiver onboard the CHAMP satellite at 400 km altitude indicate significant low- to middle-latitude daytime total electron content (TEC) increases above the satellite within 1–2 h of the defined start time for three of the storms (∼1400 local solar time). The 20 November 2003 data follow a different pattern: the largest TEC increases appear several hours (∼5–7) following the interplanetary magnetic field Bz event onset. TEC data obtained from ground-based GPS receivers for the November 2003 storm tend to confirm a “late” TEC increase for this storm at ∼1400 LT. Estimates of vertical plasma uplift near the equator at Jicamarca longitudes (∼281 E) using the dual-magnetometer technique suggest that variability of the timing of the TEC response is associated with variability in the prompt penetration of electric fields to low latitudes. It is also found that for the November 2003 magnetic storm the cross-correlation function between the SYM-H index and the interplanetary electric field reached maximum correlation with a lag time of 4 h. Such a large lag time has never been noted before. The long delays of both the ionosphere and magnetosphere responses need to be better understood.

New Applications of an Automated System for High-Power LEDs

Abstract: An automatic system based on thermoelectric cooler (TEC), a microfan, and microcontroller is first applied to thermal management of high-power light-emitting diodes (LEDs). Its hardware is composed of microcontroller as a control core, K-type thermocouples as acquisition devices, and TEC and a microfan with heatsink as cooling vehicles. The experiment confirms that the LEDs substrate temperature can be controlled effectively, and indicates that the LED chips are operating reliably. Specifically, in high-temperature environments of 43 °C, the system can automatically drop to the low set temperature (30 °C) due to thermoelectric effect driven by TEC. Heat transfer analysis shows that maximum LED power cooled by the system is 106.7 W, and the total power consumption of the automatic cooling system is only 8.85 W. The automatic cooling system has a high cooling efficiency.