In many real-time resource-constrained embedded systems, highly-predictable system behavior is a key design requirement. The “time-triggered co-operative” (TTC) scheduling algorithm provides a good match for a wide ...In many real-time resource-constrained embedded systems, highly-predictable system behavior is a key design requirement. The “time-triggered co-operative” (TTC) scheduling algorithm provides a good match for a wide range of low-cost embedded applications. As a consequence of the resource, timing, and power constraints, the implementation of such algorithm is often far from trivial. Thus, basic implementation of TTC algorithm can result in excessive levels of task jitter which may jeopardize the predictability of many time-critical applications using this algorithm. This paper discusses the main sources of jitter in earlier TTC implementations and develops two alternative implementations – based on the employment of “sandwich delay” (SD) mechanisms – to reduce task jitter in TTC system significantly. In addition to jitter levels at task release times, we also assess the CPU, memory and power requirements involved in practical implementations of the proposed schedulers. The paper concludes that the TTC scheduler implementation using “multiple timer interrupt” (MTI) technique achieves better performance in terms of timing behavior and resource utilization as opposed to the other implementation which is based on a simple SD mechanism. Use of MTI technique is also found to provide a simple solution to “task overrun” problem which may degrade the performance of many TTC systems.展开更多
The paper discusses the spatial and temporal distribution of seismic activity in the southwestern part of the Western Tien Shan. The study identifies four groups of strong earthquakes that occurred in Western and Cent...The paper discusses the spatial and temporal distribution of seismic activity in the southwestern part of the Western Tien Shan. The study identifies four groups of strong earthquakes that occurred in Western and Central Uzbekistan. The regularity of redistribution of the accumulated tectonic energy in the form of shuttle migration of seismicity with the recurrence rate of a group of strong earthquakes has been revealed. The synchronicity of periods of seismic activation of the Western Tien Shan (regional structure) and the Asian part of the Mediterranean-Asian seismic belt (structure of a large-regional scale) was found. At the same time, deviations from synchronicity are noted in the form of delays in the periods of seismic activation between the considered structures. The seismicity study revealed a deviation from the regularity of grouping of strong earthquakes in the seismic regime of the region. This was observed in the Gazli earthquakes. The strongest triple Gazli earthquakes of 1976 and 1984 with М = 7.0</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">7.3 were preceded by natural and technogenic triggers. Natural triggers included active fracturing (large fractures up to 100 km in length) in the north of Tamdybulak area, the absence any of tangible </span><span style="font-family:Verdana;">earthquakes in the epicentral area of Gazli for more than 40 years, and the appearance of small mud volcanoes</span></span><span style="font-family:Verdana;">—griffins before a strong earthquake. The technogenic triggers included a 40-year gas pumping at the Gazli fields and two underground nuclear explosions in 1966 (#273) and 1968 (#142) produced near the epicenter of the tectonic Gazli earthquakes of 1976 and 1984.展开更多
文摘In many real-time resource-constrained embedded systems, highly-predictable system behavior is a key design requirement. The “time-triggered co-operative” (TTC) scheduling algorithm provides a good match for a wide range of low-cost embedded applications. As a consequence of the resource, timing, and power constraints, the implementation of such algorithm is often far from trivial. Thus, basic implementation of TTC algorithm can result in excessive levels of task jitter which may jeopardize the predictability of many time-critical applications using this algorithm. This paper discusses the main sources of jitter in earlier TTC implementations and develops two alternative implementations – based on the employment of “sandwich delay” (SD) mechanisms – to reduce task jitter in TTC system significantly. In addition to jitter levels at task release times, we also assess the CPU, memory and power requirements involved in practical implementations of the proposed schedulers. The paper concludes that the TTC scheduler implementation using “multiple timer interrupt” (MTI) technique achieves better performance in terms of timing behavior and resource utilization as opposed to the other implementation which is based on a simple SD mechanism. Use of MTI technique is also found to provide a simple solution to “task overrun” problem which may degrade the performance of many TTC systems.
文摘The paper discusses the spatial and temporal distribution of seismic activity in the southwestern part of the Western Tien Shan. The study identifies four groups of strong earthquakes that occurred in Western and Central Uzbekistan. The regularity of redistribution of the accumulated tectonic energy in the form of shuttle migration of seismicity with the recurrence rate of a group of strong earthquakes has been revealed. The synchronicity of periods of seismic activation of the Western Tien Shan (regional structure) and the Asian part of the Mediterranean-Asian seismic belt (structure of a large-regional scale) was found. At the same time, deviations from synchronicity are noted in the form of delays in the periods of seismic activation between the considered structures. The seismicity study revealed a deviation from the regularity of grouping of strong earthquakes in the seismic regime of the region. This was observed in the Gazli earthquakes. The strongest triple Gazli earthquakes of 1976 and 1984 with М = 7.0</span><span style="font-family:""> </span><span style="font-family:Verdana;">-</span><span style="font-family:""> </span><span style="font-family:""><span style="font-family:Verdana;">7.3 were preceded by natural and technogenic triggers. Natural triggers included active fracturing (large fractures up to 100 km in length) in the north of Tamdybulak area, the absence any of tangible </span><span style="font-family:Verdana;">earthquakes in the epicentral area of Gazli for more than 40 years, and the appearance of small mud volcanoes</span></span><span style="font-family:Verdana;">—griffins before a strong earthquake. The technogenic triggers included a 40-year gas pumping at the Gazli fields and two underground nuclear explosions in 1966 (#273) and 1968 (#142) produced near the epicenter of the tectonic Gazli earthquakes of 1976 and 1984.
