The powered resonance tube: From Hartmann's discovery to current active flow control applications

Hartmann discovered the resonance tube phenomenon in 1918. Although researchers have conducted extensive studies on this topic during the intervening 90 years, no single resource lists, analyzes, synthesizes and interprets the vast body of findings. This review offers a consolidated resource tracing development of the Hartmann tube from discovery to recent advances in understanding, prediction and application of the resonance tube. This review (a) serves as a literature resource for researchers from diverse areas, (b) provides a critical assessment of the state of the art, and (c) provides examples of the vast possibilities for applying this device.Controlled flow-induced resonance can produce high-amplitude dynamic pressures and acoustic emission over a range of frequencies. Studies on such acoustic generators interested researchers during the last half of the 20th century. Hartmann demonstrated the possibility of obtaining high acoustic efficiencies when a jet is aimed at the open end of a tube closed at the other end. His work led to numerous other studies—some that examined the physics and others that developed geometric variants and explored industrial applications. In the last decade there has been renewed interest in powered resonance tubes (PRT) because of their potential as active flow control actuators. This article also evaluates the success of flow-control strategies using PRTs, and attempts to identify promising PRT applications.     

Geomagnetic pulsation over conjugate locations during geomagnetic storms and substorm

Geomagnetic data collected during magnetic storm over magnetically conjugate pair (according to IGRF 2000) of high latitude stations viz., Maitri (70° 45′ S, 11° 42′ E) and Tromso (69° 40′ N, 18° 56′ E) reveal that amplitudes of Pc6 pulsation characteristically differ. The amplitude obtained from horizontal magnetic field for the Pc6 pulsation frequency range between 0.6 and 1.6 mHz significantly differs in time corresponding to peak amplitude. The relative differences in its time of occurrence found to gradually increase around initial phase of storm and remain exactly out of phase at peak amplitude of storm. Thence, it is found to be in agreement in phase gradually until storm unwinds. This indicates that simultaneous amplitude of Pc6 pulsation at conjugate pair of stations and its time of occurrence could be a key factor to infer storm arrivals somewhat prior to its peak effects. The emphasize remains on prediction of storm arrivals only by utilizing ground based magnetometer observations. However, it is necessary to understand differences on the basis of weak, moderate, strong, and super strong cases and more exactly how they behave along the line of magnetic Meridian. Nevertheless, the analysis implies that geo-effective magnetic ejecta/clouds/CIRs/sheaths/CMEs/ICMEs giving rise to geomagnetic storm can be predicted ahead of its peak effects by having magnetometer data over conjugate locations.     

It is software process, stupid: next millennium software qualitykey

The economic impacts of software in our economy are discussed. The current economic state has been attributed to the Information Technology which has not only generated a large number of jobs but also contributed to the productivity and quality of the operations in our digital economy. The next millennium will be digital and obviously software has a very important role to play in our personal, national, and international scenes. Software will be essential in all our products from Space Station and airplanes to automobiles, television, pagers, and cellular telephones, For any organization, for that matter, even nations to succeed in the digital millennium software will be very essential. One who develops software better, cheaper, and faster will become the leader with enormous economic advantage. The key to success in software development will depend upon the software processes used to build them. Many national and international organizations have developed models based on processes to improve quality, productivity and cycle time of software development. Software Engineering Institute's Capability Maturity Model (CMM) is one such model. CMM helps in assessing the software processes and their capabilities and continuously improve them to higher levels of maturity. Similarly, ISO 9000 and the related ISO 9001 for software quality are based on software processes. This paper will bring out the importance of software processes particularly in managing the quality of software based on national and international initiatives