Study of LaSiO3Cl:Ce3+,Tb3+ and Ca5B2SiO10:Eu3+ Phosphors for Improving Hue Standard and Illuminating Beam of WLEDs

Remote phosphor arrangements usually have low color quality and superior lumen output to that of conformal phosphor arrangements and in-cup phosphor arrangements. For this reason, many researches are done so that we could enhance the chromatic quality for the remote phosphor arrangements. For this research, we are suggesting the double-layer remote phosphor arrangement to boost the CRI (short for color rendering index) as well as the CQS (short for color quality scale) in WLED devices. Three identical WLED arrangements which have dissimilar chromatic temperature which covers 5600 K, 8500 K will be used in this paper. The initial idea involves placing one sheet of blue phosphor LaSiO3Cl:Ce3+,Tb3+ or one sheet of red phosphor Ca5B2SiO10:Eu3+ over a sheet of yellow phosphor YAG:Ce3+. After that, seek an appropriate concentration of Ca5B2SiO10:Eu3+ so that we could obtain the most desirable chromatic performance. Judging the result, the element Ca5B2SiO10:Eu3+ seem to help improve the CRI and CQS levels. Particularly, the greater the concentration of La2O3:Eu3+ is, the greater level the CRI and the CQS will get, because of the boost in red illumination within the WLED devices. In addition, the blue phosphor layer LaSiO3Cl:Ce3+,Tb3+ helps increase the lumen output. But the decline of the lumen as well as the chromatic performance manifests if the concentration of LaSiO3Cl:Ce3+,Tb3+ and Ca5B2SiO10:Eu3+ is beyond required level. This is demonstrated by utilizing the theory of Mie-scattering as well as the law of Beer–Lambert. This research’s result is important for the augmentation of white light performance in the WLED devices

Higher chromatic rendition with Cr3+-doped yellow Y3Al5O12:Ce3+ for double-layer remote phosphor white-light-emitting diodes

Remote phosphor designs of white-light-emitting diodes (WLEDs) have been recognized for their high thermal stability and excellent luminous efficiency but not for the chromatic rendering. The study presents an approach for the remote phosphor structure to overcome the low-color-rendering issue by enriching its red-light spectral intensity through co-doping Cr3+ and Ce3+ ions into the yellow  Y3Al5O12 (YAG) phosphor compound. This ion co-doping process probably enhances emission spectra in the far-red range because of the energy transfer of the integrated ions: Ce3+ Cr3+. Additionally, the luminescence and color properties of the phosphor layer significantly depend on the doped concentration of the Cr3+ ion. Here, with 0.008% Cr3+ in the phosphor composite, either internal or external quantum performances of the dual-layer WLED light are enhanced, which achieved the number of 58.9% and 46.7%, respectively. The color rendering index (CRI) would also be higher if Cr3+ is added, about 77.9, compared to the CRI of 63.2 when using the original  YAG:Ce3+ phosphor layer

Application of green-emitting ZnS:Eu2+ for boosting the spectrum of white light-emitting diode packages

Through utilizing a nonlinear application to acquire the best lumen efficiency (LE) for radiation (also known as LER) when color rendering index (CRI) value, especially CRI of R9 for strong red exceeds 90 with correlated color temperature (CCT) range of 2700-6500 K, the white light emitting diodes (WLED) package with adjustable CCT value and comprised of mixed-type light-emitting diodes (LEDs) can be acquired. The WLED model here contains blue and red LEDs with direct emission and a phosphorconversion blue LED or pc/B-LED (including orange and green phosphors mixed with blue LED colorant). The peak wavelengths of each LED constituent are 465 and 628 nm for LEDs in blue and red, 452 nm for the blue LED colorant, 530 and 586 nm for the phosphors exhibiting green and orange colors. Under the CCT of 2722-6464 K, the attained actual LED package, either with conversion phosphor, in red or in blue, possibly displays both CRI and R9 values measured from 90 to 96, color quality scale (CQS) values measured from 89 to 94, with LERs and LEs of 303-358 lm/W and 105-119 lm/W, respectively

Application of CaTiO3:Pr3+ Phosphor for Enhancing the Hue Standard of WLEDs with Double-Film Distant Phosphor Structure

Due to its great thermal stability, the WLEDs (short for white-light diodes), which are made of PiG (short for phosphor-in-glass), appear to be an optical source most effective at generating potent white illumination. However, the actual applications they offer are limited by their poor color rendering and color uniformity. To improve the color rendering and uniformity, this study suggested utilizing a configuration involving a PiG-RPL (short for PiG integrated with a lens of phosphor in red). The phosphor YAGG (also known as Y3Al3.08Ga1.92O12:Ce3+) and borosilicate glass powders were printed, then sintered to generate the green PiG, and then using an inverted dispensing approach, we applied the CASN phosphor silicone in red color (also known as CaAlSiN3:Eu2+) to the said PiG. As a result, with a current of 350 mA, the WLEDs made of PiG-RPL exhibit highly remarkable chromatic performance for the CRI (also known as color rendering index) values determined as Ra = 95.6 with R9 = 95.2 and fidelity/gamut values determined as Rf = 92 with Rg = 99.2. The color quality of the PiG-RPL based WLEDs is steady over a wide range of currents, from 100 to 1000 mA. Moreover, PiG-RPL based WLEDs have better color uniformity than typical PiG based WLEDs. The PiG-RPL structure was proposed in this paper to improve the WLEDs’ chromatic generation as well as chromatic homogeneity. We made the PiGRPL via placing a lens of CASN phosphor above a PiG in green color made of YAGG phosphor. For WLEDs, the PiG-RPL provides extremely remarkable chromatic generation. Furthermore, the WLEDs that are made of PiG-RPL have better color uniformity than those made of PiG and PiG-RPP. The PiG-RPL color converters are considered to be promising for high-power WLEDs, offering great color rendering and color uniformity

Utilizing the right phosphor in near-ultraviolet and blue light-emitting diode devices to generate white illumination

In the scenario of solid-state lighting (SSL) gradually replacing old standard techniques; the pc-LEDs (or diodes based on conversion phosphor) becomes a common method for creating white illumination, based on SSL. As of now, both of the UV-LEDs and the blue LEDs have been still being considered for the task of creating white illumination through phosphor excitation as it hasn’t been known which LED type is truly superior. It is common that when it comes to phosphor, people will overlook the performance in LED devices with a wavelength range of 365 nm to 470 nm. Our research demonstrates the information concerning extrinsic quantum efficacy in the InxGa1-xN LED devices with the mentioned range as well as combines the information and the effectiveness of phosphor for the task of examining the performance of near-UV and blue LEDs and creating white illumination. In addition, the research demonstrates recreations for the task of assessing the white illumination mixtures under the correlated color temperature of 3000 K and 4000 K in the two LED structures

Physiochemical properties, antibacterial and antioxidant activities of Terminalia catappa seed oils from two extracting processes

Terminalia catappa is a widespread medium tree species in many tropical countries. While the majority of the studies up to date focuses on the aerial part of the plant such as leaf, stem bark and fruit, information about the phytochemical property as well as the biological property of the edible seed is still scarce. This study was the first to explore the fatty acid composition, antibacterial and antioxidant activities of the seed oil from T. catappa grown in Vietnam. The results showed that both the hot-pressed and cold-pressed oils contained a high level of unsaturated fatty acids such as oleic (~32%) and linoleic acids (28.38%-29.2%), as well as saturated fatty acids such as palmitic acid (~33.3%-33.61%). The presence of eicosadienoic acid in T. catappa seed oils was reported in this study for the first time. These oils displayed antibacterial activity against 5 out of 12 tested strains such as Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Vibrio parahaemolyticus. The antioxidant activity of the oils was also recorded by DPPH radical scavenging assays with IC50 values of 950 µg/ml and 2529 µg/ml for cold-pressed oil and hot-pressed oil respectively. This study has provided promising extracting methods and resulted in oils that could be good candidates for developing food sources with valuable fatty acids, antioxidant and antibacterial capacities against both Gram-positive and negative bacteria in the human diet

Financial Performance and Corporate Governance in Microfinance: Evidence from Vietnam

Good corporate governance is considered a building block of success for microfinance institutions (MFIs) as it is presumed to help them in achieving their social and financial goals. This study analyzes the corporate governance and financial performance relationship for MFIs in Vietnam. We construct a corporate governance index based on seven measures pertaining to board size and composition, CEO characteristics, and ownership type. We then estimate the two-way relationship between this index and each of five different financial performance indicators. To address the likely simultaneity between corporate governance and financial performance, we adopt a two-stage least squares estimation approach with instrumental variables. The results confirm the endogenous nature of corporate governance and financial performance. We conclude that profitability and sustainability of MFIs improve with good governance practices and conversely that more profitable and sustainable MFIs have better governance systems. Keywords: Corporate governance, financial performance, microfinance. DOI: 10.7176/EJBM/12-3-12 Publication date: January 31st 2020

Utilization of BaAl1.4Si0.6O3.4N0.6:Eu2+ Green-emitting Phosphor to Improve Luminous Intensity and Color Adequacy of White Light-emitting Diodes

BaAl1.4Si0.6O3.4N0.6:Eu2+ exhibiting broad excitation and emission bands with intense green emission centred at 510 nm is applied to produce high-performance white-light-emitting diodes (WLEDs). The preparation of the green phosphor utilizes NaNO3 molten salt to attain the purity phase and enhanced luminescence strength boosting the crystalline growth. The influences of BaAl1.4Si0.6O3.4N0.6:Eu2+ on the lighting intensity and color adequacy are investigated at three correlated color temperatures (CCTs) of 3000 K, 4000 K and 5000 K. The lighting output of the WLEDs with high CCTs (4000 – 5000 K) is deemed as enhanced with increasing green-phosphor concentration. The lower CCT shows greater lumen output when using a lower concentration of BaAl1.4Si0.6O3.4N0.6:Eu2+. This tendency also takes place in the case of color uniformity. Conversely, the high concentration of the phosphor is not favourable to the color rendition property of the WLED because of the excessive green-light proportion. It is recommended to keep the concentration of BaAl1.4Si0.6O3.4N0.6:Eu2+ staying below 10 wt% for better color fidelity

Chemical profiles and antibacterial activity of acetone extract of two Curcuma species from Vietnam

Curcuma thorelii Gagnep. and Curcuma cotuana Luu, Škorni?k. & H.?.Tr?n are the rare species only found in Southeast Asia. The present study was the first to explore the chemical compositions and antibacterial effects of the whole plant acetone extracts of these 2 species. Altogether 41 and 31 compounds have been identified in C. thorelii and C. cotuana extracts by gas chromatography/mass spectrometry. Accordingly, the C. thorelii extract contained (E)-labda-8(17),12-diene-15,16-dial (33.37%), vitamin E (12.33%), phytol (9.83%) as the major compounds while C. cotuana extract contained predominantly (E)-labda-8(17),12-diene-15,16-dial (14.58%), n-hexadecanoic acid (10.96%), 3,7,11,15-tetramethylhexadec-2-en-1-yl acetate (8.13%), ?-sitosterol (7.97%). In addition, results from disc diffusion assay have shown that C. thorelii acetone extract had inhibitory effects on 5 out of 10 pathogenic bacterial strains such as Bacillus cereus (ATCC 11778), Listeria monocytogenes (ATCC 19111), Staphylococcus aureus (ATCC 25923), S. aureus (ATCC 29213) and S. saprophyticus (BAA750) while C. cotuana acetone extract was found to be effective only against B. cereus. The obtained results showed that the acetone extracts of C. thorelii and C. cotuana possessed several valuable bioactive compounds as well as promising antibacterial activity, which place a good foundation for future pharmaceutical product development