Experimental and simulative analysis of relationship between ultraviolet irradiations and concentration of negative air ions in small chambers

In the past five decades, it has not been publicly reported that there may be a certain relationship between fluctuation of air ions concentration (AIC) and intensity of ultraviolet (UV) irradiations in small chambers. However, our experiments with UV irradiations in small chambers indicate that 254 nm UV-C irradiation conduces to high negative AIC (NAIC) and low positive AIC (PAIC) in small chambers, and that NAIC is approximately proportional to average UV-C light intensity in small chambers. These phenomena cannot be covered by the traditional model. To address these, we developed a new model to simulate and analyze these phenomena. With this model, not only do the simulation results well agree with the experimental results, but also the linear relationship between the NAIC and the average UV-C light intensity is well interpreted.     

Reproducibility comparison among multiangle spectrophotometers

New color‐measuring instruments known as multiangle spectrophotometers have been recently created to measure and characterize the goniochromism of special‐effect pigments in many materials with a particular visual appearance (metallic, interference, pearlescent, sparkle, or glitter). These devices measure the gonioapparent color from the spectral relative reflectance factor and the L*a*b* values of the sample with different illumination and observation angles. These angles usually coincide with requirements marked in American Society for Testing and Materials (ASTM) and Deutsches Institut Für Normung standards relating to the gonioapparent color, but the results of comparisons between these instruments are still inconclusive. Therefore, the main purpose of this study is to compare several multiangle spectrophotometers at a reproducibility level according to ASTM E2214‐08 guidelines. In particular, we compared two X‐Rite multi‐gonio spectrophotometers (MA98 and MA68II), a Datacolor multi‐gonio spectrophotometer (FX10), and a BYK multi‐gonio spectrophotometer (BYK‐mac). These instruments share only five common measurement geometries: 45° × ?30° (as 15°), 45° × ?20° (as 25°), 45° × 0° (as 45°), 45° × 30° (as 75°), 45° × 65° (as 110°). Specific statistical studies were used for the reproducibility comparison, including a Hotelling test and a statistical intercomparison test to determine the confidence interval of the partial color differences ΔL*, Δa*, Δb*, and the total color difference ΔE*_ab. This was conducted using a database collection of 88 metallic and pearlescent samples that were measured 20 times without the replacement of all the instruments. The final findings show that in most measurement geometries, the reproducibility differences between pairs of instruments are statistically significant, although in general, there is a better reproducibility level at certain common geometries for newer instruments (MA98 and BYK‐mac). This means that these differences are due to systematic or bias errors (angle tolerances for each geometry, photometric scales, white standards, etc.), but not exclusively to random errors. However, neither of the statistical tests used is valid to discriminate and quantify the detected bias errors in this comparison between instruments. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 160–167, 2013.     

Radiometric methods for UV process design and process monitoring

A wide variety of radiometric instruments are now available for measuring the radiant characteristics of industrial and laboratory UV lamps. Relating these characteristics to the performance of a UV-cured product depends on how well the selected parameters match the critical factors of the cure process. Further, the distinction between process design and process monitoring is significant, especially in the UV exposure characteristics to be measured. The differences in instruments and the reasons for these differences are followed by suggestions of how to avoid some common errors and how to report data more completely. Optical terminology, specifications, methods, and how radiometric measures are used in system design and in production monitoring are presented. Presented at the 80th Annual Meeting of the Federation of Societies for Coatings Technology, October 30–November 1, 2002, in New Orleans, LA. 910 Clopper Rd., Gaithersburg, MD 20878. Photo courtesy of Electronic Instrumentation & Technology (EIT), Inc., Sterling, VA.     

多模腔注塑模具的流道平衡控制

分析了多模腔注塑模具分流道的平衡性,探讨了浇注系统的影响因素以及浇注系统平衡的控制与调节,结果表明:同模多腔模具流道非平衡排布时,可通过调节浇口的长度及截面尺寸来补充流道长度的差异而引起的不平衡;而对于异模多腔模具,应将模腔容积作为调整系数,依此来设计流道的长度和浇口的长度及截面尺寸。     

对圆柱齿轮设计方法设计步骤的改进

在圆柱齿轮设计中，传统设计方法与设计步骤存在着许多不妥之处，设计步骤只是追求一次性设计成功，设计结果单一且仅仅可行。本文力求设计的齿轮机构传动性能最好、齿轮啮合重合度大，同时追求齿轮结构紧凑、体积小、重量轻，加工制造方便。本文对传统设计方法与设计步骤进行了改良，并以直齿圆柱齿轮设计为例，列举了国内教科书中相同的设计例题，通过新旧设计方法、设计步骤、设计结果的对比比较，充分体现了新方法的优越性。     

Paper based self-powered UV photodiode: Enhancing photo-response with AZO back-field layer

The development of self-powered UV photodiode on green substrate is still a challenge. In this study, highly conductive Al doped ZnO (AZO) film was sputter-deposited on paper substrate at room temperature; subsequently, paper-based Schottky photodiodes were successfully fabricated by following Au-ZnO-Al and Au-ZnO-AZO-Al structure designs, respectively. These UV light-based devices operate successfully without external power. Au-ZnO-AZO-Al photodiode shows improved response and faster speed compared to Au-ZnO-Al photodiode. The one-dimensional Poisson simulation results demonstrate that the improvement is attributed to the strong electric field in the ZnO-AZO n-n⁺ high-low junction, thus, enhancing the collection rate and drifting speed of the photogenerated carriers. In addition, AZO can form favorable ohmic contact with the Al electrodes, further improving the device performance. The photo-response of the paper-based photodiode device shows high reproducibility and stability. Based on these outstanding results, we conclude that these paper-based electronic devices have great potential to replace conventional petroleum-based flexible electronic devices, thus, contributing to the green/sustainable development.     

Combustion of Environmentally Altered Molybdenum Trioxide Nanocomposites

Nanocomposite thermite mixtures are currently under development for many primer applications due to their high energy densities, high ignition sensitivity, and low release of toxins into the environment. However, variability and inconsistencies in combustion performance have not been sufficiently investigated. Environmental interactions with the reactants are thought to be a contributing factor to these variabilities. Combustion velocity experiments were conducted on aluminum (Al) and molybdenum trioxide (MoO₃) mixtures to investigate the role of environmental interactions such as light exposure and humidity. While the Al particles were maintained in an ambient, constant environment, the MoO₃ particles were exposed to UV or fluorescent light, and highly humid environments. Results show that UV and fluorescent lighting over a period of days does not significantly contribute to performance deterioration. However, a humid environment severely decreases combustion performance if the oxidizer particles are not heat‐treated. Heat treatment of the MoO₃ greatly increases the material's ability to resist water absorption, yielding more repeatable combustion performance. This work further quantifies the role of the environment in the decrease of combustion performance of nanocomposites over time.     

A study of the effect of optimization function on calculated parameters of wilson equation

Estimated values of Wilson parameters depend upon the objective function which is used in the optimization procedure. The relationships between these estimated parameters seem to be more important than the values themselves, and the desirable paired parameters are confined to a region near ridge lines. This region represents a high level of joint confidence. In this study four different objective functions were used in the investigation of binary and ternary systems. Also, comparisons were made on calculated V/L equilibrium values predicted for ternary systems by using parameters estimated from binary and from the sole use of ternary data. Using the parameters estimated from binary data with a chosen objective function did not produce the best sum of squares of errors in a ternary system for the same objective function. Based on the overall performance, the best objective function to fit parameters in three ternaries is the one to fit the pressure.     

A NUMERICAL STUDY OF THE AIRFLOW PATTERNS IN A SAUSAGE DRYER

ABSTRACT

This paper describes the use of a computational fluid dynamics code (Star-CD)in the food industry. We assessed the capability of CFD to predict airflow patterns in a modern sausage dryer by comparing numerical results with experimental air velocity data. Qualitative and quantitative comparisons showed that simulated values agreed closely with measurements although some discrepancies appeared for specific flow conditions. Using CFD, it was established that these differences couid be attributed to slow time-variations in the blower airflow rate. These comparisons also revealed errors in measurement.     

Photostabilization of polystyrene/montmorillonite nanocomposite. A factorial experimental design 24

The weathering behavior of polystyrene (PS) and PS/montmorillonite nanocomposite with and without addition of ultraviolet (UV) absorber and/or antioxidant was investigated. Samples were exposed to UV radiation in the laboratory for periods of up to approximately 12 weeks. The samples were exposed for various irradiation intervals, and their tensile and impact strength was monitored through a factorial experimental design 2⁴. The molecular weight, yellowness, and fracture surface were also monitored. The results generated by analysis of variance (ANOVA) Table showed that UV absorber and exposure time had the most important effects positive and negative, respectively. These results could be seen for neat PS and PS/MMT nanocomposite. The presence of antioxidant alone did not have any significant effect but when mixed with UV absorber presented a small synergism. These results corroborate with molecular weight, yellowing and fracture surface of tensile and impact samples. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effects of ultraviolet absorbers on the ultraviolet degradation of rice‐hull/high‐density polyethylene composites

In China, rice‐hull powder is widely used as a fiber component to reinforce polymers because of its ready availability and lower cost compared to wood fibers. However, an issue concerning these composites is their weathering durability. In this study, the effects of two ultraviolet absorbers (UVAs), UV‐326 and UV‐531, on the durability of rice‐hull/high‐density polyethylene (HDPE) composites were evaluated after the samples were exposed to UV‐accelerated weathering tests for up to 2000 h. All of the samples showed significant fading and color changes in exposed areas. X‐ray photoelectron spectroscopy and Fourier transform infrared spectroscopy were used to detect surface chemical changes. The results indicate that surface oxidation commenced immediately within the first 500 h of exposure for all of the samples. However, the control rice‐hull/HDPE composites underwent a greater degree of oxidation than those with the UVAs. Scanning electron microscopy revealed that the rice‐hull/HDPE composites degraded significantly upon accelerated UV aging, with dense cracking on the exposed surface. The UVAs provided effective protection for the rice‐hull/HDPE composites, and UV‐326 had a more positive effect on the color stability than UV‐531. The results reported herein serve to enhance our understanding of the efficiency of UV stabilizers in the protection of rice‐hull/HDPE composites against UV radiation, with a view toward improving their formulation. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Investigation of design parameter effects on high current performance of lithium-ion cells with LiFePO<Subscript>4</Subscript>/graphite electrodes

Electrode design is an essential task for successful development of lithium-ion batteries. Provided that the same materials are given, proper dimensioning of the electrodes and balanced composition of the materials in them can maximize the cell performance, such as the discharge capacity. However, many electrode design parameters have conflicting effects on the performance, and thus careful optimization of these parameters is required. This study experimentally investigated the effects of several electrode design parameters on the performance of lithium ion cells with a LiFePO₄ cathode and a natural graphite anode, focusing on their high current operations. The conflicting effects of the conductor ratio (the weight fraction of electronic particle additives), electrode thickness, and electrode density (porosity) on the cell capacity were studied. In addition, a detailed one-dimensional electrochemical model was also used to simulate the observed performance characteristics and to identify their underlying mechanisms limiting the performance. Based on the experimental and numerical results, the optimal ranges for the electrode design parameters were discussed to achieve better performance of the LiFePO₄/graphite batteries.     

The NETmix reactor: Pressure drop measurements and 3D CFD modeling

NETmix is a new static mixing technology based on a network of mixing chambers interconnected by channels. Three NETmix reactors with different geometries were used to obtain experimental data for pressure drop and a generalized model for pressure drop in NETmix reactors has been developed. This model features a single adjustable parameter and it is only dependent on the geometric configuration of the NETmix design. The Z factor and the power number were also determined to compare the performance of different NETmix configurations with other existing mixers. The dynamic measurement of pressure drop was used to evaluate the mixing dynamics in the NETmix chambers and, above the critical Reynolds number, the natural oscillation frequency was quantified. Furthermore, a three-dimensional computational fluid dynamic transport model was also developed and validated. The energy performance of the three NETmix prototypes was quantified and shown to be very competitive with the compared existing static mixers. The developed 3D CFD transport model, validated by the reported experimental data, enables the computation of transport properties for any geometrical design and fluid properties, and avoids the need for experimental data each time a new NETmix configuration is designed.     

A NUMERICAL STUDY OF THE AIRFLOW PATTERNS IN A SAUSAGE DRYER

This paper describes the use of a computational fluid dynamics code (Star-CD)in the food industry. We assessed the capability of CFD to predict airflow patterns in a modern sausage dryer by comparing numerical results with experimental air velocity data. Qualitative and quantitative comparisons showed that simulated values agreed closely with measurements although some discrepancies appeared for specific flow conditions. Using CFD, it was established that these differences couid be attributed to slow time-variations in the blower airflow rate. These comparisons also revealed errors in measurement.     

Effects of UV degradation on surface hydrophobicity, crack, and thickness of MWCNT-based nanocomposite coatings

Surface degradation is a common problem in polymeric coatings when they are exposed to sunlight, moisture, and oxygen. In order to reduce their surface degradation, thus keeping the coatings’ original properties, multi-wall carbon nanotubes (MWCNTs) were added, and the coatings were exposed to UV light and salt fog for various lengths of time. At 0 days of UV exposure, contact angle values of 0%, 0.25%, 0.5%, 1%, and 2% MWCNT-based nanocomposite coatings of 75 μm (∼3 mil) thickness were between 85° and 89°. However, after 16 days of UV exposure, contact angle values of the same samples were reduced to 11°, 13°, 34°, 50°, and 54°, respectively. Longer UV exposures resulted in several microcracks on the surface of the coated samples in the absence of nanoscale inclusions, while very minimal cracks or degradation appeared on the MWCNT-loaded samples. Test results also showed that UV exposure along with salt fogging reduced the coating thickness up to 24% at 0% CNTs; in contrast, this reduction was only 7% with a 2% MWCNT coating. These results clearly indicate that MWCNTs added to polymeric coatings reduce UV degradation, lessen surface cracks, protect the film thickness, and hence increase the lifetime of the polymeric coatings.     

A fibre-optic UV system for H2SO4 production in aerosol chambers causing minimal thermal effects

A novel fibre-optic UV illumination system for sulphuric acid (H₂SO₄) production has been developed. The illumination system described in this paper provides sufficient ultraviolet light (UV) power while causing practically no thermal effect on the aerosol chamber (temperature variation <0.005 °C at full UV illumination). A similar thermal stability has not been achieved in other comparable experimental set-ups so far. The spectrum provided by the fibre-optic UV system corresponds to the UVB region, illuminates the chamber in a reasonably uniform way and is comparable to the ground level actinic flux. The UV system has been installed for the Cosmics Leaving OUtdoor Droplets (CLOUD) chamber experiments at CERN. Precise, easily-adjustable and reproducible concentrations of H₂SO₄ were generated by adjusting the UV light intensity. This paper gives an overview on the design of this new system as well as insights on its performance and application.     

UV degradation of clay‐reinforced polypropylene nanocomposites

The aim of this work is to experimentally characterize the UV‐degradation process at both the surface and at different layers across the thickness of injection‐molded polypropylene (PP) matrix containing different amounts of nanosized montmorillonite (MMT) clay particles. These nanocomposite materials have been exposed to UV irradiations (λ = 320 nm) at different preset temperatures (25, 45, and 65°C) in the presence of oxygen and during different exposure times. The extent of such process at these layers was determined using both the FTIR spectroscopy and the wide‐angle X‐ray diffraction analyses. The micromechanical properties across the thickness have been characterized using the nanoindentation technique. The obtained results have indicated that the UV‐degradation process for the nanocomposite materials is much more intense than the one observed for the neat PP. Moreover, it has been noted that such degradation process is not uniform across the thickness of the exposed materials. Results obtained from the X‐ray analysis have shown an increase of the crystallinity of the polymer molecules at only the external surface of the exposed materials. This was confirmed using the nanoindentation test as an increase of the Young's modulus at this layer was noted. POLYM. ENG. SCI., 56:469–478, 2016. © 2016 Society of Plastics Engineers     

Deterioration of polyaramid and polybenzimidazole woven fabrics after ultraviolet irradiation

In this study the degradation of woven fabrics of meta‐aramid and the blend of para‐aramid and polybenzimidazole fibers when exposed to environmental conditions has been investigated under accelerated ageing conditions. Generally, these polymeric materials have been used for the outer layer of protective clothing, particularly for fire‐fighting. The performance of these fabrics plays an important role in preventing burn‐injuries to fire fighters. Frequent exposure of these materials to various environmental conditions (especially sunlight) can degrade the polymeric chain and affect their performance properties. Hence, the degradation of the fabrics has been studied in terms of loss of tensile and tear strength; reduction in abrasion resistance; and extension at break. It was observed that ultraviolet (UV) irradiation negatively impacted on the mechanical properties of both the polymeric materials significantly. This can be attributed to chemical changes in the polymeric chains due to the photo‐oxidation of the polymer. Scanning electron microscopy images revealed surface decomposition of the filaments due to UV irradiation. Exposure of polybenzimidazole resulted in rapid loss of mechanical and chemical properties in comparison with meta‐aramid. However, decomposition and degradation of polybenzidimazole was not statistically significant. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43073.     

Investigation and optimization of photocurrent transient measurements on nano-TiO2

Chronoamperometry with chopped light has been applied to commercial and homemade TiO₂ nanopowders, both doped and undoped, to gain information on the charge recombination processes which take place in the oxide and affect its photocatalytic performance. The photocurrent transients can be attributed to photoinduced electron–hole separation, trapping, recombination, and scavenging. In order to evaluate what mainly affects the shape of the transients and the transient time constants (τ) which can be derived, the type and concentration of the electrolyte, the irradiation source (UV or visible light), and the presence of a hole acceptor (oxalate) were varied. The reproducibility of quantitative measurements was best when an inert electrolyte (NaClO₄) has been employed under an N₂-saturated atmosphere. Under these conditions, both Pr-TiO₂ and N-TiO₂ samples show a definitely higher τ than the undoped oxide, which indicates a slower recombination kinetics, both under UV and visible irradiation. Therefore, these are promising as photocatalysts.     

Evaluation of methods for verifying the performance of color‐measuring instruments. Part II: Inter‐instrument reproducibility

Part I described an experiment in which the repeatability of a number of common, commercially available spectrocolorimeters was compared using ASTM procedures. ASTM E2214‐02 Standard Practice for Specifying and Verifying the Performance of Color‐Measuring Instruments is intended to standardize the terminology and procedures used to evaluate color measuring instruments. In this article, we develop reproducibility results from a medium‐term study of 10 commercial spectrocolorimeters. The comparisons are presented so as to contrast between the traditional color difference based specifications found in the historical literature and in manufacturer's literature and the more complex multidimensional methods specified in E2214. Instrument to instrument contrasts are reported as well as tests of agreement across a set of instruments as a whole. The results confirm common understandings. Hemispherical diffuse instruments exhibit a higher level of inter‐instrument agreement than do bidirectional (45:0) instruments. The results also provide support for a surprising conclusion about the statistical significance of the minor differences in both inter‐instrument agreement and inter‐model agreement for a single manufacturer. Some speculations on the impact of these conclusions to the development of future comparisons of spectrocolorimeters are given. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 176–294, 2007