High Color Temperature Research Articles

Blue-light-excitable broadband yellow-emitting CaGd2HfSc(AlO4)3:Ce3+ garnet phosphors for white light-emitting diode devices with improved color rendering index

The current commercial white light-emitting diodes (LEDs) are generally based on the combination of blue LED chips and Y3Al5O12:Ce3+ yellow phosphors. However, because of the lack of red component, such white LED devices exhibit cool white-light emissions with low color rendering index (Ra < 75, R9 < 0). Therefore, it is urgent to discover new blue-light-excitable yellow-emitting phosphors with enhanced red emissions for fabricating high color-quality white LEDs. In the present work, we demonstrate a novel broadband yellow-emitting CaGd2HfScAl3O12:Ce3+ garnet phosphor for blue-light-excited white LEDs with improved color rendering index. The as-prepared CaGd2HfScAl3O12:Ce3+ garnet phosphor possesses a cubic structure with Ia3¯d space group, and the unit cell parameters of the representative CaGd2HfScAl3O12:2%Ce3+ phosphor are a = b = c = 12.450 Å, α = β = γ = 90°, and V = 1,929.59(4) Å3. Impressively, we find that the CaGd2HfScAl3O12:Ce3+ garnet phosphor shows an intense absorption band in the 300–500 nm wavelength range with a maximum at 452 nm owing to the 4f→5d transition of Ce3+ ions. On 452 nm excitation, the optimal CaGd2HfScAl3O12:2%Ce3+ sample exhibits a broad asymmetric yellow emission band in the wavelength range of 470–750 nm with peak at 564 nm and full width at half maximum of 151 nm. The Commission Internationale de l’Eclairage chromaticity coordinates and internal quantum efficiency of the CaGd2HfScAl3O12:2%Ce3+ sample are (0.4485, 0.5157) and 30.4%, respectively. Finally, a white LED device is fabricated by combing a 450 nm blue LED chip with commercial Y3Al5O12:Ce3+ yellow-emitting phosphor, which generates white light with low color rendering index (CRI; Ra = 74.7, R9 = −12.7) and high correlated color temperature (CCT = 6,554 K) under the 60 mA driving current. In sharp contrast, another white LED device, which is made by coating our as-prepared CaGd2HfScAl3O12:2%Ce3+ yellow-emitting phosphors onto the surface of a 450 nm blue LED chip, produces white-light emission with high CRI value (Ra = 84.5, R9 = 26.3) and relatively low CCT of 5,649 K. This work reveals that the newly discovered broadband yellow-emitting CaGd2HfScAl3O12:Ce3+ phosphors can serve as a potential color converter in high-color-quality phosphor-converted white LEDs.

Robust thermal performance and color purity of samarium based deep red emitting phosphor for near-UV chip-based high-color-rendering

In the progress of LED phosphors, the chemical stability, thermal stability, and color purity was not usually given due attention. However, the most critical problems of WLEDs are the deficit in the red-spectral region, stability, low color-rendering index (CRI) and high correlated color temperature (CCT) limit its efficiency for vivid application. Herein, the Ca3YGa3B4O15:xSm3+ (CYGB:xSm3+) were prepared by a solid-state route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), diffuse reflection spectroscopy (DRS), and as well as photoluminescence (PL) spectra are used to exemplify the resulting samples. The structure and the Sm3+ dopants in the cation-borate phosphors were quantified, signifying the importance at Ca and Y sites. Under ultraviolet radiation-induced bright deep-red emissions with high color-purity up to 97.5%. The energy-migration (EM) between the Sm3+ ion was investigated both empirically and theoretically in the region of Sm3+ contents. Several theoretical-models were employed to simulate the lifetime of Sm3+ at various-concentrations, and the processes were investigated as a forced-electric dipole. The chemical-stability of CY0.95GB:0.05Sm3+ has also been investigated in this work. Interestingly, the CY0.95GB:0.05Sm3+ showed exceptional thermal-quenching resistance of>91.2% intensity at 400 K. The WLED containing CY0.95GB:0.05Sm3+ blended with the BAM:Eu2+ and CYAB:Tb3+ phosphor demonstrated low CCT ≈ 3843 K and high CRI ≈ 91.9. These findings were healthier than the industrial WLED having Y3Al5O12:Ce3+ and blue-LED.

Study on the Influence of LED Spectrum on the Visual and Nonvisual Effects in the Interior Zone of Tunnels

Judicious use of lamps is of profound significance to improve the internal traffic safety of tunnels. This study evaluated the biological effects of spectrum on human visual and nonvisual under mesopic vision category. According to the difference of human eyes’ response to the visual and nonvisual biological effects of different wavelengths of light radiation, a method of applying the mesopic visual spectral luminous efficiency curve to the assessment of nonvisual biological effects and blue light hazards is proposed. The results show that, in theory, under mesopic vision category, the spectrum with high correlation color temperature (CCT) and high color rendering index (CRI) has higher blue light content Z-value and has greater impact on human nonvisual effects and blue light radiation damage, but it can also provide higher human perception luminance. The visual effect detection experiment of driving in the interior zones of the tunnel is simulated in the laboratory, and the critical flicker frequency and reaction time are taken as physiological indexes. The results show that the spectrum with high CCT and high CRI corresponds to lower critical flicker frequency drop value and faster reaction time, which has a positive effect on improving driving safety. Therefore, this paper suggests that the LED with high CCT and high CRI (CCT = 6500 K, CRI2012 = 95) should be used in the interior zones of the tunnel with relatively short lighting section, and the CCT and CRI should be appropriately reduced in other road environments with long lighting section to reduce the impact of spectrum on nonvisual photobiology, so as to improve road traffic safety.

The excellent luminous efficiency and high thermal stability of phosphor-in-glass for high-power laser

At present, fluorescent glass mainly emits a single yellow light. The characteristic of green and red luminescent materials limits its omni-directional combination with yellow light materials, resulting in high correlated color temperature and low color rendering index of laser lighting devices, which seriously reduces the quality of laser lighting. Therefore, the development of multi-color fluorescent glass to improve the color quality is a huge challenge in laser lighting technology. In this research, the glass matrix that can be compounded with multi-color phosphors is proposed to solve the problems of phosphor decomposition, oxidation, corrosion, and blackening during the vitrification process. Surprisingly, a 50 wt. % Ce:YAG&amp;1.5 wt. % CaAlSiN3-PiG (50 Y&amp;1.5 R-PiG) sample exhibits an excellent internal quantum efficiency of 94% and achieves a high luminous efficiency of 184 lm/W under laser irradiation. Moreover, an ultrahigh luminous efficiency of 331 lm/W is realized by using a laser device with a heat sink. It demonstrated that Y&amp;R-PiG can own excellent application prospects in high-quality lighting fields, such as laser displays and automobile headlights.

Effect of Eu2+ doping on photoluminescence of Al2O3:Tb3+ functional coatings formed by plasma electrolytic oxidation

Multifunctional coatings of Al2O3 co-doped Tb3+ or Tb3+/Eu2+ were synthesized by the rapid and facile plasma electrolytic oxidation method on pure aluminium substrate. SEM & EDS analysis revealed porous structure independent on the doping concentration, with uniform distribution of co-doped rare-earth elements and incorporated concentrations proportional to the rare-earth particles concentrations added to the basic electrolyte. The gamma phase of Al2O3 increases to the expense of the alpha phase of Al2O3 with rising content of Tb3+. The addition of Eu2+ caused no further phase transformations. The photoluminescence (PL) excitation spectrum of Al2O3:Tb3+ was featured by sharp peaks (due to inter-configurational 4f transitions of Tb3+) and orders of magnitude larger broad-band in the middle ultraviolet region ascribed to the 4f→4f5d transitions. The PL emission spectrum was featured by the typical 4f→4f transitions of Tb3+, with maximum green emission at 541 nm and intensity proportional to the doping concentration. As the Eu2+ emission and Tb3+ excitation overlap, the concentration dependent energy transfer Eu2+→Tb3+ (of dipole-dipole character) occurred, resulting in the 20x increase in total PL and 3.2x increased Tb3+ PL. The PL emission color of Al2O3:Tb3+ was green and concentration independent, while of Al2O3:Eu2+/Tb3+ the color was in the domain of cold white with high correlated color temperature, which slightly decreased with increasing Eu2+ concentration.

Is the use of high correlated color temperature light at night related to delay of sleep timing in university students? A cross-country study in Japan and China

BackgroundBlue-enriched white light at night has the potential to delay the circadian rhythm in daily life. This study was conducted to determine whether the use of high correlated color temperature (CCT) light at home at night is associated with delay of sleep timing in university students.MethodsThe survey was conducted in 2014–2015 in 447 university students in Japan and 327 students in China. Habitual sleep timing and type of CCT light at home were investigated by using a self-administered questionnaire. The Japanese students were significantly later than the Chinese students in bedtime, wake time, and midpoint of sleep. They were asked whether the lighting in the room where they spend most of their time at night was closer to warm color (low CCT) or daylight color (high CCT). The amount of light exposure level during daily life was measured for at least 1 week by the use of a light sensor in 60 students in each country.ResultsThe percentages of participants who used high CCT lighting at night were 61.6% for Japanese students and 80.8% for Chinese students. Bedtime and sleep onset time on school days and free days were significantly later in the high CCT group than in the low CCT group in Japan. The midpoint of sleep in the high CCT group was significantly later than that in the low CCT group on free days but not on school days. On the other hand, none of the sleep measurements on school days and free days were significantly different between the high CCT and low CCT groups in China. Illuminance level of light exposure during the night was significantly higher in Japanese than in Chinese, but that in the morning was significantly higher in China than in Japan.ConclusionsThe use of high CCT light at night is associated with delay of sleep timing in Japanese university students but not in Chinese university students. The effects of light at night on sleep timing and circadian rhythm may be complicated by other lifestyle factors depending on the country.

Perylene Based Solution Processed Single Layer WOLED with Adjustable CCT and CRI

In solution processed single layer white organic light emitting diode (WOLED) applications, the choice of host matrix and optimization of dopant levels represent two crucial parameters to consider. In this work, poly(N-vinylcarbazole) (PVK): 2-(4-Biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) and PVK:1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl] phenylene (OXD-7) matrices are used as hosts for perylene based devices. PVK:PBD presented better compatibility and lower turn-on voltages compared to PVK:OXD-7. Benefiting from the exciplex emission observed at 630 nm, a color rendering index (CRI) value of 90 is reached with the device containing PVK:PBD as the host and 0.1 wt.% of an orange emitting perylene derivative, i.e., PDI. Introduction of the perylene based green emitter, i.e., PTE, in this emitting layer not only caused a fading in the exciplex emission, but also resulted in disappearance of the electroplex peak at 535 nm, which is detected between PVK:PBD and PTE in bare PTE containing devices. Full visible range coverage is achieved by optimizing the PDI:PTE ratio. WOLED containing PVK:PBD:0.06 wt.% PDI:0.03 wt.% PTE presented high CRI (≥95) and adjustable correlated color temperatures (CCT, 3800 K-5100 K).

Subjective thermal response driving indoor comfort perception: A novel experimental analysis coupling building information modelling and virtual reality

Building sector professionals, together with building physicists and human scientists, recognize the occupants' key role in determining final buildings energy needs. Occupants’ behavior is strongly influenced by their perception and represents a major variable affecting buildings' energy performance, but its impact is difficult to predict since the early design stage. This study proposes a new analysis framework and field test method to better comprehend and monitor people environmental perception and attitudes since the design stage, while stimulated through immersive environment modeled in a parametric platform, able to change every specific aspect of the future spaces. To this aim, a physical office room was re-designed through virtual reality (VR) and sense-of-presence feeling was registered, with a 76% of satisfaction rate. The VR designed environment was therefore used to reproduce key design variables without modifying the indoor thermal-energy environment during the experiment. Three triggers were simulated, i.e. glass filter, window aspect ratio, and artificial lighting color temperature. Both these two latter variables significantly produced placebo effects on most of the interviewed people, who declared to feel relatively hotter in high aspect ratio window conditions and low color temperature. As expected, non-thermal triggers may affect indoor thermal perception and, potentially, may induce better thermal satisfaction and energy saving behaviors, if properly considered. The proposed novel method can assist building design since the early stages, leading to low-cost and human-centric energy efficiency enhancements.

The effects of light color temperatures on students' perceptual evaluations in design studios

AbstractIt was aimed in this study to determine the evaluations for “spatial quality,” “social adaptation,” and “individual productivity” of students in design studios, which used different light color temperature values. With this intention, a detailed research questionnaire was developed for measuring the effects on spatial perception of low color temperatures, daylight, and high color temperatures for a total of three different light color temperature values. A total of 113 students participated in the research questionnaire and the data obtained were analyzed with the SPSS package program. In conclusion, it was determined that the spaces lighted with the low color temperatures and daylight had more positive effects on the perceptual evaluations of the students compared to the spaces lighted with the high color temperatures according to the “spatial quality,” “social adaptation,” and “individual productivity” scales. Another result was that it was observed that the low color temperatures had somewhat more positive perceptual values compared to daylight. In addition, it was determined that males perceived more positively compared to females the interior design characteristics of the design studios.

Study on the effect of home night lighting environment on students’ eyestrain and visual efficacy

China has the highest incidence rate of myopia, and the number of teenagers with myopia accounts for more than half of the total number of myopia in the world. In recent years, With the increase of youth night home learning time, the impact of the night lighting environment in the home learning space on eye health has become increasingly obvious. This paper selects 112 home learning spaces of middle school students to carry out the actual measurement of lighting environment parameters and the satisfaction survey of the lighting environment, and through comparative experiments to explore the effects of illuminance, color temperature and lighting methods on eyestrain and visual efficacy. This Study found that under mixed lighting conditions, when the color temperature is 4500k, the illuminance in the range of 500lx-750lx is beneficial to relieve eyestrain and improve visual efficacy; When the illuminance is 500lx, a low color temperature (3500k) can help relieve eyestrain, and a high color temperature (6000k) can improve visual efficacy better. In addition, mixed lighting is better than local lighting for relieving eyestrain and improving visual efficacy. The results will help improve the night lighting environment in the home learning space of middle school students.

Monitoring supplied domestic water quality at Thu Dau Mot water supply enterprise

The current status assessment research of water use and quality of supplied domestic water in Thu Dau Mot city, Binh Duong province, as well as the clean water use situation of the local people. Sampling and assessment of the quality of supplied water at Thu Dau Mot Water supply enterprise. The water treatment process here is strictly conducted to ensure stability, constant pressure, inlet and outlet water flow. The analysis results of physical and chemical parameters of water quality at Thu Dau Mot Water supply enterprise show parameters within the allowable limits of water standards for domestic use QCVN 02: 2009/BYT and domestic water QCVN 01: 2009/BYT. However, during the water treatment process in the rainy season, it is time consuming and costly for the use of many chemicals in the treatment process, as high turbidity and high color temperature, low TDS, low pH, low chloride, high SS, Fe and Mn content changes in the wet season higher than in the dry season. After sampling for analysis and treatment, the output water meets the clean water standard to meet the needs of the people in Thu Dau Mot City and surrounding areas.

Explaining #theShoe based on the optimal color hypothesis: The role of chromaticity vs. luminance distribution in an ambiguous image

The image of #theShoe is a derivative image of #theDress which induces vastly different color experiences across individuals. The majority of people perceive that the shoe has grey leather with turquoise laces, but others report pink leather with white laces. We hypothesized #theShoe presents a problem of color constancy, where different people estimate different illuminants falling onto the shoe. The present study specifically aimed to understand what cues in the shoe image caused the ambiguity based on the optimal color hypothesis: our visual system knows the gamut of surface colors under various illuminants and applies the knowledge for illuminant estimation. The analysis showed that estimated illuminant chromaticity largely changes according to the assumed intensity of the illuminant. When the illuminant intensity was assumed to be low, a high color temperature was estimated. In contrast, assuming high illuminant intensity led to the estimation of low color temperature. A simulation based on a von Kries correction showed that the subtraction of estimated illuminants from the original image shifts the appearance of the shoe towards the reported states (i.e. gray-turquoise or pink-white). These results suggest that the optimal color hypothesis provides a theoretical interpretation to #theShoe phenomenon. Moreover, this luminance-dependent color-shift was observed in #theDress phenomenon, supporting the notion that the same trigger induces #theShoe.

Flow of Light: Balancing Directionality and CCT in the Office Environment

ABSTRACT Human perception and vision have evolved in response to dynamic daylight, a combination of radiation from direct sunlight and diffuse skylight, which has created a flow of variations in light, in terms of direct:diffuse distribution, intensities and spectrum. This study investigates the qualities of the flow of light in an office after adding ceiling-mounted spotlights (32° tilt angle) to traditional diffuse ceiling panels. The intention is to create a flow of task light – a light-zone at each work-plane – complementing the directionality of the natural daylight inflow from the windows. An experiment was carried out in an office, in two parts. Four ratios of direct:diffuse light were tested by 30 people. Then one ratio was tested in five combinations of high, neutral and low color temperatures by 15 people in two daylight situations: overcast and clear sky. The visual light quality and perceived atmosphere of the office environment was tested through questionnaires, reaction cards and semi-structured interviews. The direct flow of light is recommended to be more than 15% of the total illuminance at the work-plane to provide the distinct visual appearance of modeling and a cozier atmosphere, which is preferable for socializing, and less than 45% to avoid glare and high contrast for visual tasks. Direct warm and diffuse cool lighting were perceived as the most natural but were not always preferred. There is an indication of slight preference for cooler ambient lighting in clear sky situations and warmer ambient lighting in overcast situations. Especially the preference in relation to sky conditions needs to be further investigated. A field study will implement these findings in a double dynamic lighting concept responding to daylight level and sky character. Strong individual preferences for combinations of color temperatures was identified, this open up new research areas for personalized flows of light in future dynamic lighting designs.

Controlling the Surface Properties of TiO2 for Improvement of the Photo-performance and Color Uniformity of the Light-emitting Diode Devices

The photo-performance and color uniformity of the light-emitting diodes (LEDs) were enhanced by controlling the surface properties of the titanium dioxide (TiO2) particles as light scatting materials using a sol-gel-based surface modification method. Silane coupling agents of different carbon chain lengths (C3–C16) were introduced onto the TiO2 surface for investigating the light scattering effect depending on the TiO2 dispersibility in the encapsulant. The dispersibility of the modified TiO2 particles was greater than that of the as-prepared TiO2 particles (1.6–2.5 times). The dispersibility of TiO2 improved with the increasing carbon chain length of silane (C3–C6). However, the dispersibility did not increase but reduced when the carbon chain length was considerably long (C16) because the TiO2 surface was more hydrophobic than the encapsulant. After the fabrication of the LED devices, the TiO2-loaded LED device showed high photometric flux and low correlated color temperature despite using the same concentration of phosphor (3.0wt.% with respect to the added silicone resin). Furthermore, the photo-performance and color uniformity improved when the TiO2 dispersibility was increased. This can be attributed to the enhancement of light scattering in the LED package when the interfacial affinity of the TiO2/encapsulant was improved.

SrBaSiO4:Eu2+ phosphor: a novel application for improving the luminous flux and color quality of multi-chip white LED lamps

This paper described in detail the chromatic homogeneity and luminous flux influences in producing better quality white LED devices with various phosphor layers (MCW-LEDs). The method is to let Eu2+-activated strontium–barium silicate (SrBaSiO4:Eu2+) mixed with their phosphor compounding, which results in notable impact on lighting performance. The increase in concentration of yellow-green-emitting SrBaSiO4:Eu2+ phosphor also promotes the color performance and lumen output of WLED devices at high correlated color temperature around 8500K. This is the first time this approach is applied and it results can be utilized for better understanding of optical properties interaction with phosphor materials. Although SrBaSiO4:Eu2+ receives many positive responses, we still need to limit it concentration for high SrBaSiO4:Eu2+ concentration is detrimental to CQS. The appropriate choice of concentration and size of SrBaSiO4:Eu2+ is the principal factor to decide the performance of MCW-LEDs.

Ultra-high color rendering warm-white light-emitting diodes based on an efficient green-emitting garnet phosphor for solid-state lighting

High light-quality and low color temperature are two crucial factors for a comfortable healthy illumination. Phosphor-converted white light-emitting diodes (LEDs) could be readily realized by combining near-UV (380–420 nm) LED chips with tri-color phosphors, and thus near-UV-excitable inorganic phosphors with efficient visible luminescence are highly demanded for fabricating high-performance near-UV-pumped white LEDs. Herein, we demonstrated a novel highly efficient green-emitting phosphor based on Ce3+/Tb3+ ions co-activated Ca2GdHf2Al3O12 (abbreviated as: CGHAO) garnet compound, which enabled the realization of ultra-high color rendering warm-white LEDs. Notably, the CGHAO:Ce3+,Tb3+ phosphors could be efficiently excited by near-UV light around 408 nm and exhibited intense green emissions around 543 nm with high internal quantum efficiency of 82.7% and external quantum efficiency of 60.6%. The energy transfer from Ce3+ to Tb3+ ions was studied in detail, and the composition of CGHAO:Ce3+,Tb3+ phosphors was optimized. Utilizing the optimal CGHAO:0.04Ce3+,0.4Tb3+ green phosphor as color converter, a prototype near-UV-pumped white LED device was fabricated, and upon 120 mA driving current it demonstrated bright warm-white light with excellent CIE chromaticity coordinates of (0.391, 0.360), low correlated color temperature of 3575 K, ultra-high color rendering index (Ra = 94.4, R12 = 89.0, and R9 = 80.6) and good luminous efficacy of 27.40 lm·W−1. This work offers a new strategy for designing efficient LED phosphors for high-color-quality solid-state lighting.

Photoluminescence properties and thermal stability of Eu3+-activated La7Ta3W4O30 red-emitting phosphors for near-UV-excited w-LEDs

Novel trivalent europium (Eu3+)-activated La7Ta3W4O30:xEu3+ (x = 0.5 mol%–40 mol%) red-emitting phosphors were synthesized by means of a high-temperature solid-state reaction. The structure, morphology, photoluminescence, thermal-stability properties, lifetime, and color-rendering of the prepared phosphors were investigated in detail. The La7Ta3W4O30:Eu3+ phosphors show five emission peaks under near-ultraviolet (n-UV) at 397 nm, and these peaks are ascribed to the transitions of 5D0–7Fj (j = 0, 1, 2, 3 and 4) by Eu3+ ions. The optimal doping concentration of Eu3+ is 20 mol%, and the critical distance of the energy transfer between the Eu3+ ions was calculated to be 1.768 nm. The quenching temperature (T0.5) of La7Ta3W4O30:20 mol%Eu3+ is about 440 K. The quantum yield (QY) was measured to be 85.85%. The fabricated white-light-emitting diodes (w-LEDs) possess high color-rendering index (Ra) of 90, and high correlated color temperature (CCT) of 5810 K, respectively. The Commission Internationale de L' Eclairage (CIE) coordinates are (0.311, 0.322). Therefore, the prepared phosphor has a promising application for w-LEDs.

Self‐Quenching‐Resistant Red Emissive Carbon Dots with High Stability for Warm White Light‐Emitting Diodes with a High Color Rendering Index

AbstractDue to the excellent characteristics of energy‐saving, environmentally friendly and long‐life, the solid‐state lighting based on white light‐emitting diodes (WLEDs) is an emerging technology to replace traditional lighting solutions. However, the lack of red component of the most established method for fabricating commercial WLEDs results in high correlated color temperature (CCT) and low color rendering index (CRI). Herein, red‐emitting carbon dots (R‐CDs) with self‐quenching‐resistant property are synthesized using melamine and dithiosalicylic acid as precursors. In addition, R‐CDs exhibit high thermal and photostability under high temperature and strong blue light irradiation. On the basis of the unique features of R‐CDs, a WLED is fabricated by combining a blue‐LED chip with commercial Ce3+:Y3Al5O12 and R‐CDs phosphors, which exhibits warm white light with a color coordinate of (0.41, 0.38), a high CRI of 92.7 and a CCT of 3827 K. Besides, the WLED exhibits good optical stability upon the increase of drive current from 20 to 100 mA. The results suggest R‐CDs can be used as a color converter to fabricate high‐quality warm WLEDs.

Interaction effect of LED color temperatures and light-protective additive packaging on photo-oxidation in milk displayed in retail dairy case

Effect of varied LED color temperatures on photo-oxidation in 2% fat milk and protection efficiency of packaging with and without light-protective additives (LPA) under different color temperatures was firstly evaluated. Riboflavin (Rb) is one of the critical photo-sensitizers in 2% milk when exposed to LED light. Higher color temperature with higher relative intensity of Rb absorbance region resulted in lower Rb and vitamin A retention, lower dissolved oxygen content, and higher TBARS value in milk packaged with non-LPA packaging. Yellow pigmented packaging that completely blocked the Rb absorbance region of all three LED color temperatures successfully reduced the rate of degradation of milk nutrients and flavor. TiO2-added packaging partially block the destructive light wavelength; higher level of TiO2 provided a longer protection on milk freshness. Combination of appropriate LED color temperature and LPA-packaging provided a cost-effective solution for minimizing photo-oxidation in retail dairy case.

The Influence of Classroom Illumination Environment on the Efficiency of Foreign Language Learning

This paper investigated foreign language learning efficiency in four different illumination environments (in different illuminance and color temperatures), focusing on the influence of the illumination environment on foreign language learners’ sentimental status, by means of foreign language skills testing in mind-map, objective evaluation of physiological reaction, and subjective evaluation of psychological reaction. It was shown that in different illumination environments, the language skills of foreign language learners were different, and their psychological and physiological reactions varied, which influenced the efficiency of foreign language learning. The results indicated that the ideal learning space was in high illuminance and low color temperature, which increased the stimulation in foreign language learners; promoted the formation of optimistic sentiment; and enhanced their interest in, and the quality and efficiency of, foreign language learning.