Computation of Onset and Growth of Delamination in Double Cantilever beam Specimens Subjected to Fatigue Loading

In this article, the delamination onset and growth behavior of double cantilever beam (DCB) specimens has been presented. The modeling of a debonded region using master and slave surface technique for DCB specimens is done in ABAQUS CAE. The analysis of DCB specimens comprising of fatigue cyclic load has been done in ABAQUS. An onset and Paris delamination growth regimes are plotted. The growth regime being linear in log-log scale, the prediction of constants of this regime has been obtained using the polyfit command in the MATLAB environment. To obtain these constants has been explained in this article. Comparison of experimental and analytical results is shown for delamination growth. The strain energy release rate values for threshold and critical are indicated on the graphs. The number of cycles for delamination onset and growth has been tabulated for various load cases.Defence Science Journal, Vol. 64, No. 4, July 2014, pp. 400-405, DOI:http://dx.doi.org/10.14429/dsj.64.4069

Boron and Gamma ray irradiation effects on I-​V and C-​V characteristics of photo detector MRD 500

This paper describes the effect of 30- and 60-​MeV Boron ion and Gamma ray (Co-​60) irradn. effects on silicon photo detector (MRD 500 Motorola manufd.) for various fluence​/doses. The devices are systematically investigated by I-​V and C-​V measurements. The radiation induced elec. degrdn. is studied from I-​V measurements. C-​V measurements are made to est. the effect of irradn. on the doping concn. of the devices. The characteristics studied in this investigation show that Si PIN photodiodes are suitable for use in high radiation environment

Boron Ion Interaction with pnp Bipolar Power Transistor and Displacement Damage Effects on its Electrical Characteristics

AbstractBipolar junction transistors used in switching and amplification applications is examined for their electrical performance after irradiation with 60 MeV boron ions of different fluence. Unirradiated device base current is 5.97×10-5 A while it is 9.03×10-4 A after irradiation with a fluence of 1×1012 ions/cm2. For unirradiated device collector current is 1.22×10-3 A and is 7.31×10-4 A after irradiation to a fluence of 1×1012 ions/cm2. Base current increases whereas collector current decreases after irradiation with a fluence of 1×1012 ions/cm2. The magnitude of decrease in collector current is approximately same as that of the increase in base current, showing the leakage of the collector current due to irradiation. The output collector gain of the unirradiated transistor is 20.5 after irradiation to a fluence of 1×1012 ions/cm2 it has reduced to 0.81. The capacitance measurements for base-emitter junction show that for the unirradiated and irradiated samples, linearity of the curves indicate uniformity of shallow doping concentration. The built in potential (Vbi) for unirradiated device is 2.69V and after irradiation it is 2.52V. The device is also studied for activation energy, trap concentration and capture cross-section of deep levels are studied using deep-level transient spectroscopy (DLTS) technique. Majority carrier trap level is observed with energy Ev+0.784eV

Determination of 210Po concentration in commercially available infant formulae and assessment of daily ingestion dose

A study has been conducted to estimate the concentration of natural radioactive polonium in commercially available packaged infant food formulae available in Mumbai, India and the corresponding daily dose normalized based on its shelf life. Eleven most popular international brands of infant formulae were sourced from market and three aliquots from each sample were analysed for concordant results. Autodeposition method onto a silver planchet from hot dilute acid solution followed by alpha spectrometry was performed for estimation of polonium. Radiochemical recovery was ascertained by the addition of 209Po tracer. Radiochemical recovery of 209Po tracer was ranged from 14.7 to 98.1 %. The 210Po concentration in the samples was in the range of 0.08–0.23 Bq kg−1 on measured date and the corresponding daily dose, calculated on normalized date which is at mid-point of the shelf life of the sample, was ranged from 0.04 to 0.89 μSv d−1 as per the recommended daily consumption. The annual committed effective dose estimated based on the average of daily dose was found to be 150 μSv

Carbon ion irradiation damage effects on electrical characteristics of silicon PNP power BJTs

The 85 MeV 12C6+ and 35 MeV 12C3+ ion induced forward current gain degradation on 2N 6052 transistor is investigated by I-V measurements before and after irradiation. The decrease in gain for 85 MeV C-ion irradiated transistor is drastic, indicating the device is vulnerable for higher energy irradiation. An increase in the base current leading to degradation of the current gain may be due to displacement damage dose. C-V measurements estimate the effect of irradiation on the doping concentration of the devices. A plot of (1/C2) versus base-emitter voltage shows that the doping concentration increases marginally upon irradiation. DLTS measurements indicate the cluster defects are produced after irradiation to a fluence of 1 � 1012 ions/cm2. © 2014 IEEE

Editorial essay: Covid-19 and protected and conserved areas

The COVID-19 pandemic is having a dramatic impact on the global community; on people’s lives and health, livelihoods, economies, and behaviours. Most zoonotic disease pandemics, including COVID-19, arise from the unsustainable exploitation of nature. This special editorial provides a snapshot of how protected and conserved areas around the world are being impacted by COVID-19. For many protected and conserved areas, negative impacts on management capacity, budgets and effectiveness are significant, as are impacts on the livelihoods of communities living in and around these areas. We provide a commentary on how effectively and equitably managed systems of protected and conserved areas can be part of a response to the pandemic that both lessens the chance of a recurrence of similar events and builds a more sustainable future for people and nature. We conclude the editorial with a Call for Action for the rescue, recovery, rebuilding and expansion of the global network of protected and conserved areas