Green-emitting Gd2O2S:Tb3+ and red-emitting Y3Al5O12:Cr3+ phosphors: a suitable selection for enhancing color quality of remote phosphor structure

This article demonstrates green-emitting phosphor Gd2O2S:Tb3+ and red-emitting phosphor Y3Al5O12:Cr3+ application in the triple-layer phosphor WLED to enhance optical performance. The arrangement of phosphor layers in the WLED is red phosphor Y3Al5O12:Cr3+ on top, green phosphor Gd2O2S:Tb3+ in the middle, and yellow phosphor YAG:Ce3+ at the bottom. The principal to utilize these phosphor materials is the exploitation of additional red light component and green light component from the green and red phosphor to enrich the color rendering index (CRI) and luminous efficacy. The influences of green phosphor and red phosphor are also estimated with a new quality indicator, the color quality index (CQS). The results show red phosphor Y3Al5O12:Cr3+ enable CRI when its concentration increases while green phosphor exhibits a contrast reaction. Regarding the CQS, the optimal red phosphor concentration for CQS is from 10% to 14%, disregard the concentration in green phosphor. The improvement that applying these two phosphor materials brought comes from limiting the light loss from back-scattering and strengthen chromatic performance through addition red and green light components. These findings can support manufacturers in adapting to modern lighting requirements by improving CRI, CQS and particularly luminous efficiency to more than 40%

Design of freeform lens for WLEDs on the fishing boat

In this article, a free secondary lens is designed for an LED fishing/working lamp (LFWL), which is recommended for the purpose of taking the place of a traditional high-intensity discharge (HID) fishing lamp. To serve the lighting needs of fishing and the on-board activities on fishing boats, the innovative LED lamp is proposed. To make the freeform lens in our optics design process, we depended on Gaussian decomposition. In this way, it is easy to approach the targeted light intensity distribution curve (LIDC) of the LFWL lens. The simulated results show that the performance of the LED fishing/working lamps is much better than that of HID fishing lamps for illumination onboard, on the sea-surface, and underwater. Meanwhile, a lighting efficiency of 91% with the power consumption reduction of more than 50% can be achieved when the proposed LED fishing/working lamps are used instead of the HID fishing lamps

An implementation of rotor speed observer for sensorless induction motor drive in case of machine parameter uncertainty

The paper describes observers using model reference adaptive system for sensorless induction motor drive with the pulse width modulator and the direct torque control under the circumstances of incorrect information of induction motor parameters. An approximation based on the definition of the Laplace transformation is used to obtain initial values of the parameters. These values are utilized to simulate sensorless control structures of the induction motor drive in Matlab-Simulink environment. Performance comparison of two typical observers is carried out at different speed areas and in presence of parameter uncertainty. A laboratory stand with the induction motor drive and load unit is set up to verify the properties of observers. Experimental results confirm the expected dynamic properties of selected observer

Cooperative Group In Current Vietnamese Commercial Environment

Purpose: The article researches the compatibility between the cooperative group and the current commercial environment in Vietnam to propose for improvement to the laws and for promotion of development of the cooperative group.   Theoretical framework: Recent literature points out that the cooperative group model is quite suitable for the production and business psychology of citizens in Vietnam. In the current stage of development, however, from the influence and impact of international integration and the increasingly fierce competitive pressure of various types of enterprises, the cooperative group have encountered many difficulties to survive. On the other hand, in the context of judicial reform in Vietnam, the issue of complete law system and expanding the freedom to business has always been paid special attention by the Party and Vietnam State.   Design/methodology/approach: The authors have combined traditional research methods of legal science such as legal analysis method, legal efficiency assessment method and legal comparison method.   Findings: According to research, the cooperative group is well adapted to Vietnam's commercial environment because it is compatible with investor psychology and meets the conditions and circumstances of nature, economy and society. However, since Vietnam's deep integration with the rest of the world, the cooperative group model has faced numerous difficulties and challenges, and if suitable solutions are not found, it is very likely that this collective economy will become increasingly difficult. As a result, the article suggests some important solutions, such as offering cooperative group legal status and requiring more preferential lending policies with long loan terms, simple and quick loan procedures, and easy team cooperation.   Research, Practical & Social implications: This research may support many develop future research in Vietnam.   Originality/value: The study of the freedom to business become more and more urgent and very important in Vietnam

Comparison of calcium carbonate and titania particles on improving color homogeneity and luminous flux of WLEDs

In this paper, the experiments on phosphor-converted LEDs (pc-LEDs) with a correlated color temperature (CCT) of 8500K has been conducted with the scattering enhancement particles (SEPs) to achieve the higher color uniformity and emitted luminous flux of pc-LEDs. Moreover, this paper also introduced about choosing scattering enhancement particles (SEPs), including calcium carbonate (CaCO3) and titania (TiO2), and compared these particles’ properties by adding them into the yellow Y3Al5O12:Ce3+ phosphor compounding. Afterward, the LightTools program was applied to illustrate the optical simulation, and obtained results was analyzed and verified by applying the Mie-scattering theory. The scattering coefficients, the anisotropic scattering, the reduced scattering, and the scattering amplitudes at 455 nm and 595 nm are included in the scattering computation of SEPs. According to researched results, among the SEPs, TiO2 particles result in the highest value of color uniformity. However, a rise in their concentration is the cause of a sharp decline in luminous flux. Meanwhile, CaCO3 particles show the ability of reducing the deviated level in correlated color temperature by 620K if there is employed 30% of CaCO3 concentration. Hence, CaCO3 particles are the recommendation for achieving higher chromatic homogeneity and lumen output

Excellent color quality of phosphor converted white light emitting diodes with remote phosphor geometry

The remote phosphor structure is disadvantageous in color quality but more convenient in luminous flux when compared to conformal phosphor or in-cup phosphor structure. From this disadvantage, there are many studies to improve the color quality of the remote phosphor structure. This research will propose a dual-layer remote phosphor structure to improve color rendering index (CRI) and color quality scale (CQS) of WLEDs. The WLED package with color temperature of 8500 K is utilized in this study. The idea of the study is to locate a layer of phosphor green Y2O2S:Tb3+ or red ZnS:Sn2+ on the yellow phosphor YAG:Ce3+ film, and then finding the suitable added concentration of ZnS:Sn2+ to match the highest color quality. The results showed that ZnS:Sn2+ brings great benefits to increase CRI and CQS. The greater the ZnS:Sn2+ concentration is, the higher the CRI and CQS become owing to the rise in red light components in WLEDs. Meanwhile, the green Y2O2S:Tb3+ phosphor brings benefits to luminous flux. However, the decrease in luminous flux and color quality occurs when the concentration of ZnS:Sn2+ and Y2O2S:Tb3+ exceeds the corresponding level. This is proved by applying Mie-scattering theory and Lambert-Beer's law. The results of articles are important for WLEDs’ fabrication having higher white light quality

Speed estimators using stator resistance adaptation for sensorless induction motor drive

The paper describes speed estimators for a speed sensorless induction motor drive with the direct torque and flux control. However, the accuracy of the direct torque control depends on the correct information of the stator resistance, because its value varies with working conditions of the induction motor. Hence, a stator resistance adaptation is necessary. Two techniques were developed for solving this problem: model reference adaptive system based scheme and artificial neural network based scheme. At first, the sensorless control structures of the induction motor drive were implemented in Matlab-Simulink environment. Then, a comparison is done by evaluating the rotor speed difference. The simulation results confirm that speed estimators and adaptation techniques are simple to simulate and experiment. By comparison of both speed estimators and both adaptation techniques, the current based model reference adaptive system estimator with the artificial neural network based adaptation technique gives higher accuracy of the speed estimation

A new record of congrid eel, Bathycongrus bleekeri (Congridae) from Vietnam

Three specimens of Bathycongrus bleekeri were collected during the survey in 2015 and 2017. The newly recorded species is described herein, a small, moderately elongate species of Bathycongrus with head and body compressed; vertical fins without black mark; tail slender, attenuated, but not filiform; trunk length 1.2 times greater than head length; teeth small, conical, in about three-four rows on jaws, in a small triangular patch on vomer; 28–29 preanal vertebrae, total of 111–113 vertebrae; 26–28 preanal lateral-line pores. Additional data on the morphology and distribution of the species increases the total number of known species in the family Congridae in Vietnamese waters to twelve

Microfluidic Chip for Trapping Magnetic Nanoparticles and Heating in Terms of Biological Analysis

In this study, we reported the results of the design and the fabrication a planar coil in copper (square, a = 10 mm, 15mm high, 90 turns), these planar coils were integrated in a microfluidic chip for trapping magnetic nanoparticles and local heating applications. A small thermocouple (type K, 1 mm tip size) was put directly on top of the micro-channel in poly(dimethyl-siloxane) in order to measure the temperature inside the channel during applying current. The design of planar coils was based on optimizing the results of the magnetic calculation. The most suitable value of the magnetic field generated by the coil was calculated by ANSYS® software corresponded to the different distances from the coil surface to the micro-channel bottom (magnetic field strength Hmax = 825 A/m). The magnetic filed and heating relationship was balanced in order to manipulating the trapping magnetic nanoparticles and heating process. This design of the microfluidic chip can be used to develop a complex microfluidic chip using magnetic nanoparticles

Pulse-width modulation direct torque control induction motor drive with Kalman filter

The paper deals with application of Kalman filter in induction motor drive using pulse-width modulation direct torque control (PWM-DTC). In the first part, the conventional PWM-DTC drive is described and Kalman filter is utilized to filter components of stator current vector those are assumed to be disturbed by white noise. The second part contains simulation results that are obtained in different cases of load torque, process and measurement noise covariances. The integral time absolute error (ITAE) performance index, undershoot, ripple of important quantities are used to compare the conventional drive structure and proposed drive structure with Kalman filter. The simulation results confirm the expected dynamic response of the proposed structure