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International students face many impediments under the COVID-19 pandemic. The objectives of this study are to assess the association between the perceptions of international students and the lockdown policy for COVID-19. In 2021, three different levels of lockdown policy were enforced, including level I from January to April, level III from May to July, and level II from August to December. We conducted three surveys for international graduate students using a validated questionnaire during the different lockdown levels. We collected 185, 119, and 83 valid questionnaires in level I, II, and III, respectively. There were linear trends in the correlations of lockdown policy with the knowledge (p = 0.052), attitudes (p = 0.002), and practices (p < 0.001) of COVID-19. In brief, the stricter the lockdown policy, the better the students adhered to sufficient knowledge, positive attitudes, and healthy practices. Furthermore, there were significant linear correlations of lockdown policy with the transportation, school study, leisure, family life, and diet behavior. In conclusion, lockdown policy had important impacts on the knowledge, attitudes, practices, and daily lives of international students. The findings indicated that the lockdown system and its corresponding measures appear to affect perceptions in a positive way.

Herein, we report a bifunctional sulfo-fluorous affinity (SOFA) tag-assisted enzymatic synthesis and purification strategy for the facile preparation of bioactive glycans using fluorous solid-phase extraction (FSPE). The incorporation of a sulfonate moiety onto the heavy fluorous tag significantly increases its water solubility, which allows the broad use of the inherently hydrophobic fluorous tag in aqueous buffers. In addition, the SOFA tag contains a photocleavable linker, enabling the easy release of amino-functionalized oligosaccharides by UV irradiation. The SOFA tag was used in the synthesis of both negatively charged and neutral glycans to demonstrate its broad utility as an acceptor toward six different glycosyltransferases, significantly improving the feasibility of the preparation of complex glycans using FSPE. All the reactions were performed in an aqueous buffer, a minimum amount of methanol was used to purify the products, and the SOFA tag was easily recovered after photo-irradiation. Thus, the entire synthetic process is environmentally benign.

In this paper, the design of a luminaire for badminton court illumination is demonstrated from concept through computer simulation, construction trials, on-site installation, comparison with simulations and, finally, evaluations of the illuminated environment before and after the installation of the luminaires. The luminaire is composed of two high-performance light-emitting diode lighting modules, volume scattering diffusers with a one-shot transmittance higher than 70% and a reflecting cavity with a reflectivity higher than 85%. The luminaire has three different exit faces forming three Lambertian-like light sources with low luminance so as to reduce glare to the players when looking at the flight of the shuttlecock. Under similar total electric power consumption, compared to the original traditional lighting, the average illuminance on the ground is enhanced by about 300% and the uniformity is obviously improved. A questionnaire was issued to players before and after the installation of the new light-emitting diode luminaires. The new installation gained much more positive responses for brightness, comfort and number of usable courts from the players than the old installation.

Herein, we report the first characteriza- tion of a novel galactokinase from Meiothermus tai- wanensis sp. nov. WR-220 (MtGalK), which is over- expressed in E. coli and exhibits a kcat/Km value of 168.47 mM � 1 s � 1 toward Gal at 758C. The thermo- philic MtGalK shows specific substrate recognition toward the Gal configuration with limited tolerance for modifications at the C-2 position to form prod- ucts such as GalN-1-P, GalN3-1-P, and GalNAc-1-P. Due to its unique thermostability toward elevated reaction temperatures, MtGalK served as an ideal biocatalyst in the synthesis of useful sugar-1-phos- phates and was further combined with glucose-1- phosphate thymidylyltransferase (RmlA) and a-1,4- galactosyltransferase (LgtC) to achieve the efficient preparative-scale synthesis of globotriose analogs (Gb3) using a one-pot three-enzyme system. In combination with a chemical synthetic strategy, a carbohydrate antigen from breast cancer stem cells, stage specific embryonic antigen-3 (SSEA-3) pentasaccharide, was synthesized from Gb3 in ten steps with a 23% overall yield. This flexible chemo- enzymatic strategy for the synthesis of SSEA-3 also allowed us to further expand the inventory of valua- ble natural and non-natural glycans.

Corrosion under insulation is one of the most important issues in the petroleum industry. Ordinarily, in order to check the corrosion, inspectors remove the insulation of pipelines to measure the level of corrosion on each section of pipelines. This procedure may take weeks for a site which distinctly affects the financial aspect of oil and gas companies due to the pause production of its high-value products; therefore, in most cases, inspectors spot-check pipeline corrosion based on their experience. However, because the environments on sites are various, experience-based inspection may not be suitable for every site. On the other hand, even though inspectors want to access more data for better understanding of the site before the site trip, historical data sometimes are lost or scattered which leads to a hard situation for preparation of corrosion inspection. This paper utilises passive RFID sensors, which are smart sensing technologies, to collect site data and then integrate them into a Building Information Modeling (BIM) system. A uniform corrosion model is also adapted from the theories of corrosion to leverage both sensor data and BIM elements' properties. They serve as inputs to calculate the corrosion rate which is the key value of corrosion prediction. Then, the corrosion prediction results are colour-coded on a BIM model which helps inspectors intuitively understand the prediction and prepare for the site inspection. In result, the proposed research could provide a novel approach for corrosion management under insulation.

Gauge Repeatability and Reproducibility (Gauge R&R , G.R.R) is of great importance for checking measurement system precision, traditional average-range G.R.R test involves equipment variation (EV) and appraiser variation (AV), which is not appropriate for current modern automatic measurement tools. In this paper, we designed different test experiments on film thickness (THK) and critical dimension (CD) metrology and statistically analyzed different variances impact on G.R.R. From THK G.R.R experiment ANOVA analysis, it can be seen that time interval and measurement process have no significant effect on G.R.R result, and the equipment repeatability variation is the major variation source. From CD G.R.R experiment ANOVA analysis, it can be checked that, G.R.R has significant time dependence of data collection due to test wafer changed. As a conclusion, not only appraiser’s variation but also time interval has less impact on metrology G.R.R of semiconductor wafer manufacturing process.

Glycoconjugates are ubiquitously present and play a critical role in various biological processes. Due to their low stability and incredibly high degree of structural diversity, the structural characterization of glycan generally requires chemical derivatization and sophisticated instrumentation. Herein, we report a method for complicated glycan characterization in a single assay by employing 2,5-dihydroxybenzoic acid functionalized mercury telluride nanoparticles (HgTe@DHB NPs) as a dual ionization–dissociation element in matrix-assisted laser desorption/ionization mass spectrometry. Using a linear glycan, HgTe@DHB NPs promote laser-induced extensive and intense dissociation of the glycan, superior to HgTe microparticles and other inorganic nanoparticles (TiO2, ZnO, and Mn2O3 NPs). Abundant generation of diagnostic glycosidic (Y-, and B-type ions) and cross-ring cleavage (A-type ions) ions permits unambiguous determination of the composition, sequence, branching, and linkage of labile sialylated glycans. The general utility of this approach was demonstrated by the characterization of labile sialylated glycans and two sets of complicated isomeric glycans. This phenomenon was delineated further by investigating the NP's physico-chemical characteristics, revealing that their nanoscale-dependent thermodynamic properties, including UV absorption, photoelectron release dynamics and thermal energy, were the key to levitate temperature synergistically, thus inducing spontaneous glycan decomposition during the nanoparticle-assisted laser desorption–ionization process. Our results show that this “pseudo-MS/MS” obtained by HgTe@DHB can be beneficial for the analysis of biologically relevant and more complicated carbohydrates, without the need for chemical pre-derivatization and conventional tandem mass spectrometry.

A new optical design of a confocal double-reflector, for white LED lighting, performing uniform illumination with a specific projection angle has been presented and demonstrated. In addition, the anti-glare design with double-reflector prevents direct view of the LED, and the measured veiling luminance is much lower than that in general LED-based projection lamps.

Magnetic nanoparticles (MNPs) are attractive materials that serve as a support for enzyme immobilization and facilitate separations by applying an external magnetic field; this could facilitate the recycling of enzymes and broaden their applications in organic synthesis. Herein, we report the methods for the immobilization of water-soluble and membrane-bound enzymes, and the activity difference between free and immobilized enzymes is discussed. Sialyltransferase (PmST1, from Pasteurella multocida ) and cytidine monophosphate (CMP)-sialic acid synthetase (CSS, from Neisseria meningitides ) were chosen as water-soluble enzymes and expressed using an intein expression system. The enzymes were site-specifically and covalently immobilized on PEGylated-N-terminal cysteine MNPs through native chemical ligation (NCL). Increasing the length of the PEG linker between the enzyme and the MNP surface increased the activity of the immobilized enzymes relative to the free parent enzymes. In addition, the use of a fluorescent acceptor tag for PmST1 affected enzyme kinetics. In contrast, sialyltransferase from Neisseria gonorrheae (NgST, a membrane-bound enzyme) was modified with a biotin-labeled cysteine at the C-terminus using NCL, and the enzyme was then assembled on streptavidin-functionalized MNPs. Using a streptavidin-biotin interaction, it was possible to immobilize NgST on a solid support under mild ligation conditions, which prevented the enzyme from high-temperature decomposition and provided an approximately 2-fold increase in activity compared to other immobilization methods on MNPs. Finally, the ganglioside GM3-derivative (sialyl-lactose derivative) was synthesized in a one-pot system by combining the use of immobilized PmST1 and CSS. The enzymes retained 50% activity after being reused ten times. Furthermore, the results obtained using the one-pot two-immobilized-enzyme system demonstrated that it can be applied to large-scale reactions with acceptable yields and purity. These features make enzyme-immobilized MNPs applicable to organic synthesis.

In this study, we describe the direct synthe- sis of uridine 5'-diphosphate galactose (UDP-Gal) by a wild-type bacterial thymidylyltransferase (RmlA), which is used to synthesize thymidine 5'-diphosphate glucose (TDP-glucose) in nature. By using magnesi- um (Mg 2+ ) as a cofactor and a reaction temperature of 558C, a one hundred milligram-scale synthesis of UDP-Gal was achieved by RmlA. In addition, RmlA was site-specifically and covalently immobilized on magnetic nanoparticles (MNPa) The resulting RmlA-MNP complex retained almost 95% of its ac- tivity after reuse in ten consecutive enzyme assays. Furthermore, b-1,4-galactosyltransferase (GalT) from Neisseria meningitides was successfully overex- pressed and purified by using an intein-mediated protein expression system. GalT was relatively stable at 258C, and its activity was enhanced in the pres- ence of DTT and BSA. Thus, it was feasible to syn- thesize N-acetyllactosamine (LacNAc) using RmlA and GalT in a sequential addition of enzyme and ad- justment of thereaction temperature. These results demonstrate the potential applications of bacterial RmlA in carbohydrate synthesis.

The accuracy of ion implantation is very important in semiconductor manufacturing and will directly affect the performance of the individual devices and even the whole chip. The deviation of IMP energy, dose and angle are often encountered because of the abnormality of implant equipment or process design limit. The ion implantation energy, dose and angle information can be qualitatively and quantitatively analyzed through SIMS [2], which provides a way to diagnose the issue of ion implanter. Based on SIMS analysis results, we can judge whether ion implant results meet the requirements and whether the process design achieves the expected goal. In this paper we report a SIMS data processing method for the analysis of the deviation of ion implantation angle. A term of deviation rate was defined and the related calculation method was introduced, which is proportional to the deviation angles of the ion implanter. And then, a statistical analysis of a large number of data on deviation rates and ion implantation angles showed that the whole sampling data followed normal distribution, and thus the corresponding 3 sigma could be obtained. Using the determined 3 sigma range of the deviation rates, we can define the acceptable range for deviation rate. Further, we can use the actual deviation rate to judge if the implant equipment needs maintenance or not, or suggest the direction for improvement. The equipment's maintenance time and cost can thus be minimized. This method can be used as an early detection to find an abnormity in an ion implant tool.

A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.

A planar-exit lighting surface is not only used in the luminaires but also useful in the display backlights and other illumination systems. Most planar-exit lighting surfaces are made by edge-lit with line light source or 1-D LED array. If it is not edge-lit type, the light source can be two-dimensional, but a cavity is required. In this paper, a high-efficiency cavity providing extremely high energy transmittance with photon recycling is reported and demonstrated. The cavity contains a diffuser and the high reflectivity surfaces. The optical efficiency of the cavity is calculated by a formula with considering photon recycling. Furthermore, various kinds of diffusers are applied to change the optical transmittance as well as the light pattern. When the reflectivity of the inner wall of the lighting cavity is about 96 %, the optical efficiency of the cavity is higher than 90 % with several diffusers. The experimental measurement as well as the calculation is demonstrated in the paper.

A straightforward method for fabricating a stable and covalent carbohydrate microarray based on boronate formation between the hydroxyl groups of carbohydrate and boronic acid (BA) on the glass surface was used to identify carbohydrate–protein interactions.

In this paper, we demonstrate a method to calculate the phosphor particle numbers and study the relationship among phosphor particle numbers, light output and correlated color temperature (CCT) of LEDs under remote package type and dispensing package type. We also discuss the influence of the thickness and concentration of phosphors on the performance of LEDs. We compare the various thicknesses and concentrations to check the resultant CCT and the output flux, where we can see that the lumen output is almost equal as the phosphor particle numbers is similar with the CCT at 6500±200 and 5000±100 K under the remote package type.

In this paper, we propose and demonstrate a novel design to make color mixing and projection of RGB LEDs. The optical elements include a high reflective light pipe, a volume scattering diffuser and a TIR lens. The system optical efficiency is around 46 % while the color is well mixing for the cases at the CCTs of 6500K, 4500K and 3000K.

A three-terminal optical sensor by using an aluminum-doped zinc oxide (AZO)-gated Al0.2Ga0.8As /In0.2Ga0.8As high electron mobility transistor (AZO-HEMT) on a GaAs substrate is demonstrated in this report. Optical responses under illumination of different wavelengths are investigated, as compared to a conventional Au-gated HEMT device. Experimental results demonstrate that the present design is promising for tunable optical sensing applications.

In this paper, based on Monte Carlo ray tracing we simulate light extraction efficiency and directionality of the light pattern of GaN LEDs implanted with micro-pyramid structure with or without lens encapsulation. We have shown that micro-pyramid structures at some specific slanted angles in the LEDs are useful to increase effective flux utilization through enhancement of both the directionality and light extraction efficiency.

The V-Ramp test is an important test for GOI (Gate Oxide Integrity) of MOS devices. The criterion for a product under GOI qualification is to meet the requirement with defect density lower than a target defect density (D 0 ). This paper studies the methods and guidelines in minimum sample size determination provided by JEDEC/FSA joint publication and points out their drawbacks, inconsistency, and misguidance. We provide an exact method and easy-to-use numerical solution by extending JEDEC's formula to any allowed failure number, target defect density, and confidence level. Important guidelines are also provided for reliability practitioners to reduce uncertainty resulted from imperfect sampling procedures and to avoid mistakes commonly happened in defect density evaluation against a target D 0 . Our proposed exact method can be applied on many other reliability tests that need determining a minimum sample size to save wafers and testing resources as long as the binomial distribution is applicable.

A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the presence of a previously unreported spatial distribution of emission spots across the phosphor layer. We introduce "weighting" factors based on position-dependent light strength across the phosphor surface in order to improve the model accuracy. Following the modeling algorithm in the mid-field region, we have built up a precise and practical optical model by using Monte Carlo ray tracing and weighting factors. We measure the LED radiation distribution at several representative distances to test the model performance. In all cases, the accuracy is higher than 99.5% in normalized cross correlation between the simulated pattern and experimental measurement.

Light extraction analysis of GaN-based light-emitting diodes (LEDs) with Monte Carlo ray tracing is presented. To obtain high light extraction efficiency, periodic structures introduced on the top surface and/or on the substrate of various types of LED are simulated, including wire bonding, flip chip and Thin GaN. Micro pyramid array with an apex angle from 20° to 70° is shown to effectively improve the light extraction efficiency. In addition, for an LED encapsulated within an epoxy lens, the patterned substrate with pyramid array is found to be a more effective way to increase light extraction efficiency than the surface texture.

In this paper, as to our best knowledge, we propose and demonstrate the first precise phosphor modeling scheme to simulate the chromatic performance of white LEDs with silicate phosphors. The phosphor model is useful to accurately simulate the power ratio of the blue and yellow lights emitted by the white LEDs and is important in white LED package.

A direct or bottom LED backlight is a key concept in large area LCD displays because it does not use a light guide, is flat, and is easy to assemble. In this paper, a method of luminance management for a bottom LED backlight is proposed and demonstrated. We analytically calculate both the power consumption and brightness uniformity in function of: screen brightness, screen size, backlight thickness, transmittance of the LCD panel, reflective cavity efficiency, gain and cone angle of enhancement films, LED array configuration, and the average luminous flux and radiation pattern of a single LED. Moreover, a 42-inch LCD television with this backlight design approach is made and demonstrated. The bottom backlight incorporates an array of RGGB 4-in-1 multi-chip LEDs within a highly reflective box behind a diffuser and a dual brightness enhancement film. We predict with an accuracy of 94% the brightness uniformity and with 96% the luminance level.

A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the presence of a previously unreported spatial distribution of emission spots across the phosphor layer. We introduce "weighting" factors based on position-dependent light strength across the phosphor surface in order to improve the model accuracy. Following the modeling algorithm in the mid-field region, we have built up a precise and practical optical model by using Monte Carlo ray tracing and weighting factors. We measure the LED radiation distribution at several representative distances to test the model performance. In all cases, the accuracy is higher than 99.5% in normalized cross correlation between the simulated pattern and experimental measurement.

Light extraction efficiency of GaN-based LEDs as functions of chip dimensions, absorption coefficients and package for both conventional one and Thin-GaN are analyzed based on Monte-Carlo ray tracing.

This paper demonstrates a novel retro-reflective dome that enhances the directionality of a light emitting diode (LED) by recycling photons reflected by a textured LED die surface. A simulation model is developed to describe both the photon recycling process within the dome and the role of specific pyramid patterns on the top surface of the LED die. Advanced simulations showed that a perfectly polished surface with 100% reflectivity potentially enhances the directionality of the dome by 340%, 250%, and 240% using reflective domes with 10°, 20°, and 30° light cones, respectively. In the experiment, the directionality of the domes exhibiting surface imperfections is enhanced by approximately 160%, 150%, and 130% using 10°, 20°, and 30° light cones, respectively. By incorporating a textured top surface on the LED die, the proposed dome effectively increases the directionality of the LED light source.

A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. Our method is simple and compact; it only uses a short light pipe, a thin diffuser, and a total internal reflection lens. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.

A lighting cavity is a reflecting box with light sources inside. Its exit side is covered with a diffuser plate to mix and distribute light, which addresses a key issue of luminaires, display backlights, and other illumination systems. We derive a simple but precise formula for the optical efficiency of diffuser plates attached to a light cavity. We overcome the complexity of the scattering theory and the difficulty of the multiple calculations involved, by carrying out the calculation with a single ray of light that statistically represents all the scattered rays. We constructed and tested several optical cavities using light-emitting diodes, bulk-scattering diffusers, white scatter sheets, and silver coatings. All measurements are in good agreement with predictions from our optical model.

Versatility in the design of optical systems is one of the key features of light-emitting diodes (LEDs) that has attracted considerable attention. In the analysis of systems using LEDs, it is useful to know if the distance is far enough from the LED to allow the radiation pattern to be simulated by the point source approach. We propose three far-zone conditions for LED light modeling: the far-field distance, and for practical purposes the quasi far-field and minimum far-field distances. Different types of LEDs have different far-field ranges. We analyze these differences by modulating key parameters like geometrical structure of encapsulating lens, chip size, chip shape, chip position, and package errors. We find that far-field region considerably depends more on the shape of both lens and chip than all other parameters.

— A method of calculating the luminance and luminance uniformity of a bottom LED backlight is proposed and demonstrated. Both the power consumption and brightness uniformity as a function of screen brightness, screen size, backlight thickness, transmittance of the LCD panel, reflective cavity efficiency, gain, cone angle of the enhancement films, LED array configuration, and the average luminous flux, radiation pattern, and input power of individual LEDs. Moreover, a 42-in. LCD TV using this backlight design approach was fabricated. The bottom backlight incorporates an array of RGGB 4-in-1 multi-chip LEDs within a highly reflective box behind a diffuser and a dual brightness-enhancement film. The brightness uniformity can be predicted within an accuracy of 94% and the luminance level within an accuracy of 96%.