359 research outputs found
Reliability of deep-UV light-emitting diodes
No full textThis paper analyzes the performance and reliability
of deep-ultraviolet light-emitting diodes (LEDs) on AlGaN emitting
at 280 and 295 nm. By means of detailed electroluminescence
characterization, we show that the optical properties of the LEDs
are strongly influenced by the presence of deep-level-related radiative
transitions, and we separately evaluate the contribution
of each of these recombination mechanisms on the overall light
emission. The reliability analysis presented in this paper shows
that stress determines the gradual decrease of the output power
of the LEDs, which is more prominent at low measuring current
levels. Degradation is attributed to the increase of the nonradiative
recombination rate. By means of C–V analysis, we give evidence
of modifications of the charge distribution in the active layer, taking
place as a consequence of stress: This mechanism is considered
to be related to the generation of new defect states near/within the
active region
Defect-related degradation of Deep-UV-LEDs
No full textWith this paper we describe an extensive analysis of the electro-optical degradation of deep ultraviolet
Light-Emitting Diodes emitting at 310 nm, submitted to accelerated stress test. The results obtained
within this study indicate that: (i) high current stress can induce a significant decrease in the optical
power emitted by the LEDs; (ii) optical power decrease is more prominent at low measuring current levels,
indicating that degradation is related to an increase in the concentration of defects, with subsequent
decrease in the radiative efficiency of the active layer; (iii) stress can induce a significant increase in the
operating voltage of the LEDs, due to the increase in the resistivity of the ohmic contacts or p-type semiconductor;
and (iv) after stress, LEDs show a significantly increased green parasitic emission. This result
suggest that stress induced an increase in the defectiveness of the active layer. Information on the location
of the degraded region is achieved by the analysis of the Apparent Charge Distribution curves
obtained by capacitance–voltage measurements
Value proposition analysis for solid state lighting: A case study of Ahmedali Ahmed Electrical Contracting; Marketing the product in the Kingdom of Bahrain
No full textThe proposition given to a product or service in terms of its worth given by a customer is researched and analysed to find the underlying factors contributing to the value. The study is undertaken to investigate the different factors that lays ground for increased ‘Customer value’ and ‘Product Value’. The research objective is to find the “Value Proposition Analysis for Solid State Lighting: a Case Study AhmedAli Ahmed Electrical Contracting; Marketing the product in the Kingdom of Bahrain” Most businesses generate profits, when the customers give a certain value(s) to the service/product provided by the business entity. This could involve many attributes to consider. The project overlooks in to this value significantly to understand the attributes that collectively contributes to ‘Valued Relation’ between the customer and the business. This is achieved by making effective use of literature suggested by various authors and by employing research strategies to validate the literature through the findings. The research also looks in to the case study organisation to fully understand the capabilities of the company to market the product. Thus, this analysis will be specifically looking in to the value proposition given to Solid State Lighting by the current UK customers and by clients of AhamedAli Ahmed Electrical Contracting, Kingdom of Bahrain. However, this analysis must viewed critically, as the product comes at a premium price and the study will be much centred in the Kingdom of Bahrain and cannot be generalised for the other GCC countries or the Middle East. This study is focused to generate strategies in marketing Solid State Lighting in Bahrain taking A.A.E as the Case Study Organisation understanding the Value Proposition for Solid State Lighting
Combined Optical And Electrical Analysis of AlGaN-Based Deep-UV LEDs Reliability
No full textThis paper describes an analysis of the reliability of AlGaN-based
deep-UV Light-Emitting Diodes (LEDs) emitting in the range 280-
340 nm. LEDs have been aged at their nominal operating current,
and during treatment their electrical and optical characteristics have
been continuously monitored.
Measurement results show that (i) constant current stress can
induce degradation of the optical power emitted by the devices; (ii)
degradation is more prominent at low measuring current level, thus
suggesting that efficiency decrease is related to the generation of
non-radiative paths; (iii) degradation does not imply a significant
variation of the operating voltage of the devices, thus indicating that
the characteristics of the ohmic contacts are stable over stress time;
(iv) optical power decrease takes place together with modifications of
the C-V apparent charge profiles, indicating that the generation of
non-radiative paths is related to charge instabilities in the QW region
X-Ray Computed Tomography Scans of a Composite Laminate with Voids
No full textThis dataset contains greyscale normalised TIF images from X-Ray Computed Tomography (XCT) scanning of a unidirectional carbon fibre epoxy laminate with at total void volume of around 2%. Combinations of scan times, from 30 seconds to 60 minutes, and voxel sizes, from 6 to 50 µm, were investigated for their effect on the porosity measurements. The data were obtained and analysed according to the methods described in the paper "The Effect of X-Ray Computed Tomography Scan Parameters on Porosity Assessment of CFRP Laminates" by P Galvez-Hernandez, R Smith, K Gaska, M Mavrogordato, I Sinclair, and J Kratz, which was published in the Journal of Composite Materials
Evaluation of the Lady Free Biotester® in Determining the Fertile Period
No full textSmall hand-held microscopes have been developed for self-observation of salivary ferning patterns to detect the fertile time of a woman’s menstrual cycle. The purpose of this study was to evaluate one such microscope, the Lady Free Biotester®, by comparing it with the self-observation of cervical-vaginal mucus and with the self-detection of luteinizing hormone (LH) in the urine. Twelve natural family planning teachers (average age 34.6 years) observed their cervical-vaginal mucus, tested their urine for LH, and observed salivary and cervical-vaginal mucus ferning patterns (with the Lady Free Biotester) for two menstrual cycles. Data indicated that there was a strong correlation between the LH in the urine and the peak in self-observed cervical-vaginal mucus ferning (r = 0.99,
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