On Parameters Affecting the Sensitivity of Ultrasonic Testing of Tubes: Experimental and Simulation

The response (amplitude) of the reference notch during ultrasonic testing of tubes is dependent on several parameters like (1) size, shape and location of notch in the material (2) operating parameters like pitch, incidence angle, focusing, beam profile etc (3) Electronic parameters like PRF, pulse width etc. A thorough analysis of several parameters is made in this paper which affects the calibration sensitivity and its repeatability. Calibration during ultrasonic testing of tubes is carried out by using reference notches made on the tubes. The size and shape of the reference notches are defined in the specification of the tube. Different specifications like ASTM, ASME, AMS, BS etc recommend the type of notch to be used for calibration. These are varying from one standard to another and there is no comparison available for the achieved sensitivity during calibration. This paper deals with a comparison of the recommended size and shape of the notches in different codes and specifications. The sensitivity of test is dependent on the calibration notch size and shape. In the present work a comparison is made on the sensitivity (in terms of gain level) for different size and shape of notches used during calibration of a tube. Usually, these notches are made on the ID and OD surface of the tubes which are generally equal in size. During calibration equalization of the amplitude of indication from the ID and OD is recommended. However no sound basis is available for the reason for unequal amplitude indication from ID and OD notch. In the present work, response from the notches at ID and OD is experimentally determined and compared with modeling of the response from the ID and OD notches. The repeatability of the calibration is demonstrated by carrying out a series of repeated measurements of the gain of the response from the notch. Different specifications recommend different tests for demonstrating the repeatability of the calibration. A comparison is made here for the repeatability requirements in different specifications. An analysis of the operating and electronic parameters responsible for variation in gain during a repeatability test is made.     

Erbium-Doped Fluoroborate Glasses for Near Infrared Broadband Amplifiers

Erbium (Er³⁺)-doped alkali lead tellurofluoroborate (RLTB) glasses were prepared and characterized systematically through optical absorption and emission measurements. The emission spectra in the range 450–900 and 1400–1800 nm were recorded by exciting the samples with 532 nm (Nd : YVO₄ crystal) and 514.5 nm (Ar⁺ laser), respectively. Applying Judd–Ofelt analysis, the intensity parameters have been determined using experimental oscillator strengths of absorption bands. From the Judd–Ofelt intensity parameters, some important fluorescence properties such as spontaneous transition probabilities, radiative lifetimes and luminescence branching ratios for the ⁴S_3/2→⁴I_15/2 (0.55 μm), ⁴S_3/2→⁴I_13/2 (0.85 μm), and ⁴I_13/2→⁴I_15/2 (1.54 μm) emission transitions of Er³⁺ ion in RLTB glasses have been calculated. The continuous pumping of the samples results in fast nonradiative decay through ²H_11/2→⁴F_9/2 (~3500 cm⁻¹) transition, which in turn causes the population of Er³⁺ ions from ²H_11/2 state to the higher ⁴F_3/2 state. The emission cross sections determined for the ⁴I_13/2→⁴I_15/2 (1.54 μm) transition using the McCumber theory are in good agreement with the values obtained from the Judd–Ofelt analysis. From evaluated radiative parameters, it is suggested that these RLTB glasses are more suitable candidates for 0.85 and 1.54 μm broadband optical amplifiers.     

Implementation of Advanced Tunnel Field Effect Transistor (DP-TFET) for High Power Switching Applications

Silicon - As the technology advances to the nanoscale, advanced Tunnel Field-Effect Transistors are very prominent as a part of integrated circuits in the present trend. Advanced Tunnel FET devices...     

Dye-sensitized solar cells incorporating a "liquid" hole-transporting material

We present the first application of an amorphous "liquid" organic semiconductor in an optoelectronic device, demonstrating that it is highly suited for use as a hole-transporting material in nanostructured dye-sensitized solar cells. For such devices, we obtain power conversion efficiencies of up to 2.4% under simulated air mass 1.5 solar spectrum at 100 mWcm(-2), and incident photon-to-electron quantum efficiencies in excess of 50%.     

Nanocrystal Shape Control: Synthesis and Structure–Property Correlation in Shape‐Controlled ZnO Nanoparticles Prepared by Chemical Vapor Synthesis and their Application in Dye‐Sensitized Solar Cells (Adv. Funct. Mater. 6/2009)

Here, the large scale synthesis of nanocrystalline ZnO spheres and tetrapods in the size range of 8–40 nm by chemical vapor synthesis using zinc metal as precursor is described. A detailed study of the effect of experimental parameters on the morphology and yield is presented. High‐resolution transmission electron microscopy images of the tetrapods show that they are formed by the self assembly of four nanorods in the vapor phase. The tetrapods have optical absorption coefficients that are one order of magnitude greater than the spheres and show intense UV luminescence whereas the spheres show only the green emission. The observed differences in the optical properties are related to the presence of surface defects present in the nanospheres. The tetrapods have increased efficiencies for application in dye sensitized solar cells when compared to spheres.     

Surface Design in Solid‐State Dye Sensitized Solar Cells: Effects of Zwitterionic Co‐adsorbents on Photovoltaic Performance

In solid‐state dye sensitized solar cells (SSDSCs) charge recombination at the dye‐hole transporting material interface plays a critical role in the cell efficiency. For the first time we report on the influence of dipolar co‐adsorbents on the photovoltaic performance of sensitized hetero‐junction solar cells. In the present study, we investigated the effect of two zwitterionic butyric acid derivatives differing only in the polar moiety attached to their common 4 carbon‐chain acid, i.e., 4‐guanidinobutyric acid (GBA) and 4‐aminobutyric acid (ABA). These two molecules were implemented as co‐adsorbents in conjunction with Z907Na dye on the SSDSC. It was found that a Z907Na/GBA dye/co‐adsorbent combination increases both the open circuit voltage (V_oc) and short‐circuit current density (J_sc) as compared to using Z907Na dye alone. The Z907Na/ABA dye/co‐adsorbent combination increases the J_sc. Impedance and transient photovoltage investigations elucidate the cause of these remarkable observations.     

A Study of Workfunction Variation in Pocket Doped FD-SOI Technology Towards Temperature Analysis

Silicon - This paper focuses on a detailed study of workfunction variation to modulate the barrier height in fully depleted silicon on insulator (FD-SOI) technology including pocket doping. The...     

Density of Bismuth Boro Zinc Glasses Using Machine Learning Techniques

Journal of Inorganic and Organometallic Polymers and Materials - Machine learning techniques have been employed to predict the glass densities of...     

Boosting the Efficiency of Perovskite Solar Cells with CsBr‐Modified Mesoporous TiO2 Beads as Electron‐Selective Contact

Rapid extraction of photogenerated charge carriers is essential to achieve high efficiencies with perovskite solar cells (PSCs). Here, a new mesoscopic architecture as electron‐selective contact for PSCs featuring 40 nm sized TiO₂ beads endowed with mesopores of a few nanometer diameters is introduced. The bimodal pore distribution inherent to these films produces a very large contact area of 200 m² g^?1 whose access by the perovskite light absorber is facilitated by the interstitial voids between the particles. Modification of the TiO₂ surface by CsBr further strengthens its interaction with the perovskite. As a result, photogenerated electrons are extracted rapidly producing a very high fill factor of close to 80% a V_OC of 1.14 V and a PCE up to 21% with negligible hysteresis.