Poisson shock models leading to new classes of non-monotonic aging life distributions

Suppose a device is subjected to a sequence of shocks occurring randomly in time according to a homogeneous Poisson process. In this paper we introduce a class of non-monotonic aging distributions, the so-called New Worse then Better than Used in Failure Rate (NWBUFR) and New Worse then Better than Average Failure Rate (NWBAFR). It is shown under appropriate conditions on the probability of surviving a given number of shocks that the non-monotonic aging classes NWBUFR and NWBAFR arise from suitable Poisson shock models.     

Comparison of compensation methods applied to the analysis of topological changes in electrical networks

This paper focuses on compensation methods used in the analysis of topological changes in power systems. The objectives are twofold: (a) listing the main methods available in the literature and (b) comparing them. Methods based on the inverse matrix modification lemma, diakoptics and sensitivities are implemented and tested. The comparison is based on memory storage requirements, precision of results, number of operations (mult/div and sum/sub) and processing times. It is shown that there is a best compensation method to be used depending on the adopted network power flow equations. It is also shown that the compensation method based on sensitivities applied to changes in the Jacobian matrix has the best performance among all other methods. The results of simulations using those methods applied to a number of small and large power systems are presented.     

Realization, Operation and Results of the Multichannel Far-Infrared Polarimeter on RFX

This paper illustrates the realisation and testing of the multichannel far-infrared polarimeter for the RFX machine, a plasma confinement experiment with the Reversed Field Pinch configuration. The diagnostic is described and the its main sections are outlined: the laser system operating at λ = 118.8μm, the FIR optical line, the beam splitter and the beam detection units, the signal processing electronics and the motion electronics for the calibration halfwave plates. Emphasis is placed on the work performed on the polarimeter to make it operational. We illustrate the preliminary tests of the diagnostic equipment and the activity performed to bring the diagnostic into reliable operation, in particular the reduction of the noise produced by magnetically induced mechanical vibrations during machine shots. An example of the first Faraday angle measurements performed on five chords are presented and discussed. The measured Faraday angle was also compared to a theoretically calculated value, based on a simple plasma model, with satisfactory agreement between measured and predicted data.     

Aneurysm of sinus of Valsalva dissecting into interventricular septum

PURPOSE: We developed an algorithm using unenhanced computerized tomography (CT) for the management of acute flank pain and suspected ureteral obstruction. MATERIALS AND METHODS: During a 25-month interval 417 patients with acute flank pain underwent unenhanced helical CT. The final diagnosis was confirmed by additional imaging or clinical followup. For all patients who underwent additional imaging studies the official dictated radiology reports were used to determine whether the studies were recommended based on CT findings. Cases requiring intervention were evaluated to determine whether additional imaging was performed before the procedure. Medical records were reviewed and/or patients were interviewed to document the course of therapy and long-term outcome. RESULTS: Unenhanced helical CT diagnosed ureteral stone disease with 95% sensitivity, 98% specificity and 97% accuracy. Of the 38 patients requiring intervention, including nephrostomy catheters in 18, lithotripsy in 3 and ureteroscopic stone extraction in 7, additional imaging (excretory urography) was performed in only 1. Additional imaging studies generated by CT were done in 3 cases in which the dictated reports were indeterminate for ureteral stones, including negative excretory urography in 2 and retrograde urography in 1. In 1 patient in whom CT misdiagnosed a ureteral stone unnecessary retrograde urography revealed the calcification to be a gonadal vein phlebolith. Seven patients with false-negative examinations reported spontaneous stone passage with no complications. CONCLUSIONS: Unenhanced helical CT accurately determines the presence or absence of ureterolithiasis in patients with acute flank pain. CT precisely identifies stone size and location. When ureterolithiasis is absent, other causes of acute flank pain can be identified. In most cases additional imaging is not required.     

Integrating nonelectronic components into electronic microsystems

Microelectromechanical systems will soon usher in a new technological renaissance. Just as ICs brought the pocket calculator, PC, and video games, MEMS will provide a new set of products and markets. The author presents the state of the art, from inertial sensors to microfluidic devices.     

A lecture on autotransformers for power engineering students

A lecture on autotransformers intended specifically for power engineering students is proposed in this paper. An original approach to introducing the equipment is shown, and important information that does not appear in most textbooks is provided and discussed. In particular, a strong connection between the theoretical aspects and the engineer's every day practice is emphasized. Simple laboratory experiments are also proposed to validate the theoretical information.     

Reliability system with two types of repair facilities

This paper deals with two identical unit cold stand-by systems. Two types of repair facilities, having a considerable difference in their costs, are used to repair the units. Repair of type 2 facility, a costlier one, is always available, while for repair of type 1 facility one has to wait for some time. If this waiting time exceeds some given maximum time, one has to call costly repair i.e. repair of type 2 facility.The system has been analysed to determine the reliability measures viz. MTSF, steady state availability, expected number of repairs etc., by using theory of semi-Markov processes and regenerative processes. Integral equations are set up for deriving these measures. These equations are solved with the help of Laplace transform technique. A cost equation is derived. The condition for maximizing the profit is also derived. Certain particular cases are analysed.     

2-Unit standby system with proviso for rest and maximum rest

This paper analyses the reliability of a 2-unit standby system with a single repairman and a period of working as well as a period of rest. Model I discusses the case when the repair time distribution is general. In model II the concept of maximum resting period is introduced.     

Formulation of Mechanochemically Evolved Fly Ash Based Hybrid Inorganic–Organic Geopolymers with Multilevel Characterization

In this research, advanced hybrid inorganic–organic geopolymeric material is developed by environmentally and user friendlier approach. The presented novel approach for geopolymer formation certainly overcomes the existing drawbacks of geopolymerization technology. The effect of rice husk ash and Na₂O/SiO₂ ratios on geopolymer gel formation and mechanical strength has been previously identified via solution chemistry route; however, development of geopolymeric material having hybrid inorganic–organic characters via together mechanochemical grinding of raw materials and effect of mechanochemically activated Na₂SiO₃ on geopolymeric properties via solid state route has never before been explored. Together mechanochemical grinding of raw materials of varying compositions in solid state resulted in the formation of ready to use geopolymeric precursors; which on just addition of water led to development of advanced hybrid inorganic–organic geopolymeric material with considerably enhanced properties. XRD, FTIR and SEM characterization data of developed geopolymeric precursor powder and hybrid inorganic–organic geopolymeric material are reported and discussed in detail. As the results of the investigations, the relationship between geopolymer composition, grinding mechanism and material properties established. The composition which exhibited synergistic effect of both rice husk and SMS is found to be excellent in performance. The study showed that it is practical and better to adopt this greener solid state approach for preparation of geopolymer instead of user-unfriendlier hazardous alkaline solution based approach, to achieve sustainable growth in geopolymers as like Portland cement.