Drop In Number Research Articles

Thermal boundary layer depletion in minichannels by electrohydrodynamic conduction pumping

The article presents a numerical analysis of two-dimensional laminar flow and heat transfer in a minichannel with flat plate electrode pairs periodically flushed to the bottom wall. The two-way coupled governing equations of flow, heat transfer, electric potential and charge conservation are solved using the opensource finite-volume framework of OpenFOAM. Two cases of the minichannel at completely horizontal (case A) and 90° bent (case B) configurations are considered. The inlet laminar flow with Reynolds number varying from 10 to 1000 has been taken into account. The applied electric potential is varied in three steps 0, 0.5 and 1 kV. Electrohydrodynamic (EHD) conduction pumping due to the residual conductivity of the working fluid and the electric-field enhanced dissociation of free charges generate vortices in the proximity of electrodes. The flow and thermal performance of the minichannel in the presence of EHD conduction induced vortices are quantified in terms of pressure drop, Nusselt number and a performance factor (which is a combined function of pressure drop and Nusselt number). The vortices generated by EHD conduction pumping phenomenon deplete the thermal boundary layer, aid mixing and enhance the heat transfer. The mean and local Nusselt numbers are notably increased with only a minimal raise in pressure drop. In both the configurations of the minichannel, the performance factor is greater than 1 for the entire parameter space considered in this study. However, the thermal boundary layer depletion and heat transfer enhancement is prominent at low Reynolds number flows. The maximum drop in performance factor from case A to case B is only 18.5%. Results of this study indicate that EHD conduction pumping is a potential technique to enhance heat transfer in minichannels with minimum additional power consumption.

Aerosol indirect effects on orographic clouds and precipitation

The sensitivity of warm orographic cloud development to aerosol indirect effects was investigated through aerosol-aware Weather Research and Forecast model simulations contrasting aerosol-cloud-precipitation interactions using the default (generic) aerosol and regional aerosol measurements from the Integrated Precipitation and Hydrology Experiment in the Southern Appalachian Mountains for three rainfall events: 1) enhanced local convection; 2) a frontal system, and 3) a tropical system. Using the regional aerosol activation spectrum yields higher number of drops than using the default, smaller cloud droplets and delayed rainfall onset under weak synoptic forcing conditions. Evaluation against aircraft measurements in isolated convective clouds reveals that while the model microphysics falls short of reproducing the vertical structure of nonprecipitating clouds, the liquid water content, and the concentration of cloud droplets near cloud base are in keeping with observations. The simulated cloud vertical structure shows the regional signature of orographic enhancement over the mountains vis-a-vis the adjacent plains. In the inner region, valley-ridge circulations organize the spatial patterns of cloudiness under weak synoptic forcing. The formation of early afternoon low-level clouds over the ridges in the summertime reflects the aerosol indirect effect. By contrast, for large-scale systems with strong and sustained moisture convergence at low levels (frontal and tropical systems), mechanically forced rainfall efficiency is enhanced, there is no delay in the onset of precipitation, and the aerosol indirect effect is negligible. This study shows that the impact of aerosol-cloud-precipitation interactions on the spatial variability of orographic rainfall is conditional on weather regime.

Proposal of intense pulsed light soldering process for improving the drop impact reliability of Sn–3.0Ag–0.5Cu ball grid array package

Until now, electronic packages have been manufactured using the conventional convection reflow process. However, it is becoming challenging to apply the reflow process because it is time-consuming and produces thick intermetallic compounds (IMCs) at the joint interface. In addition, the reflow process consumes a lot of power because of the preheating required and the generation of waste heat, thereby interfering with carbon neutrality. To overcome these issues, the feasibility of intense pulsed light (IPL) radiation soldering for the ball grid array package assembly process was investigated in this study. A very thin IMC was formed at the IPL-soldered joint (IMC thickness = 1.2 μm) because of the short IPL process time. However, the IMC formed during the reflow process was 6.1 μm-thick. Thus, the drop impact reliability of the IPL-soldered joint (number of drops to failure = 277) substantially improved compared with that of the reflow-soldered joint (number of drops to failure = 103). In addition, the power consumption of the IPL radiation soldering process was 17.95 kWh, considerably lower than that of the conventional convection reflow process (29.50 kWh). Therefore, we suggest that IPL soldering has a high potential to reduce process time, IMC thickness (enhancing the drop impact reliability), and power consumption.

Microstructural Characterization of Sn57Bi1Ag Solder Alloy Joints

Sn57Bi1Ag alloy system meets the basic solderability requirements while reliability of solder is less known. The presence of intermetallics that form at the solder-joint interface and in the bulk solder is the primary reason to cause joint failure on simple loading. Furthermore, dissolution of soldered surface (copper, gold, silver, nickel, etc.) into the solder during reflow alters the composition of the interface leading to the formation of intermetallic phases. The present paper addresses the characterization of low temperature Sn57Bi1Ag solder alloy, its joint interface metallurgy and integrity. Generally, formation of intermetallic phases (Cu3Sn, Cu6Sn5, Ag3Sn, AuSn2, Ni3Sn4, etc.) at the solder-pad interface is in the range of 0.3 to 1.0µm. On thermal ageing at 75°C (0.55Tm), the intermetallic phases grow further up to 2.3µm, particularly CuSn and AuSn phases. In addition, to distributed eutectic tin (Sn) and bismuth (Bi) phases, fine eutectic tin and bismuth phases and primary tin (β-Sn) are also observed. Coarsening of Bi and Sn phases is noticed on thermal ageing (75°C and 100°C). The rate of coarsening increases with the supply of thermal energy promoting Sn/Bi atomic diffusion and movement of eutectic boundaries (grain boundaries). However, the Sn-Bi interface is stable without any significant changes in eutectic structures and its morphologies. The mechanical drop test of the Sn57Bi1Ag solder joint passed 120 drops, characteristic life corresponds to the number of drops for a failure of 63.2%. Evaluated as per JESD22-B111 specification to a maximum peak acceleration of 1500G and half-sine shock pulse duration of 0.5 milliseconds, soldered the alloy to copper OSP surface. The solder joint also passed 1200cycles evaluated at -40 to +125°C. Electrical connectivity of the solder joints soldered to ENIG plated test boards is recorded continuously. Crystallographic orientation of Sn and Bi second phases is observed using electron back scattered diffraction (EBSD) of thermal aged solder joints and are also presented in this paper.

Seizure-free days as a novel outcome in patients with Lennox-Gastaut syndrome: Post hoc analysis of patients receiving cannabidiol in two randomized controlled trials.

In this post hoc analysis, we aimed to assess seizure-free days as a potential new outcome measure to use in randomized placebo-controlled trials (RCTs) of patients with Lennox-Gastaut syndrome (LGS). In two phase 3 RCTs (GWPCARE3, GWPCARE4), eligible patients were randomized to receive plant-derived highly purified cannabidiol (CBD; Epidiolex® in the USA; 100 mg/mL oral solution) at 10 mg/kg/day (CBD10; GWPCARE3 only), at 20 mg/kg/day (CBD20), or matched placebo. The treatment period comprised a 2-week dose titration and a 12-week maintenance period. This post hoc analysis evaluated the least-squares (LS) mean changes from baseline and difference versus placebo in the number of drop or total seizure-free days per 28 days during the treatment period or maintenance period alone. LS mean changes were estimated using an analysis of covariance model, with categorical age and baseline number of drop or total seizure-free days as covariates, and treatment group as a fixed factor. A total of 396 patients were included in this post hoc analysis. During the 14-week treatment period, LS mean changes from baseline in number of drop seizure-free days per 28 days for patients receiving placebo (n = 161), CBD10 (n = 73), and CBD20 (n = 162) were 2.81 (95% confidence interval [CI] = 1.75-3.88), 5.64 (95% CI = 4.08-7.20), and 6.45 (95% CI = 5.39-7.52), respectively. The LS mean differences in number of drop seizure-free days versus placebo were 2.83 (95% CI = .98-4.68) for CBD10 and 3.64 (95% CI = 2.18-5.10) for CBD20. For total seizure-free days, LS mean differences versus placebo were 2.63 (95% CI = .92-4.34) for CBD10 and 3.50 (95% CI = 2.16-4.85) for CBD20. The improvements from baseline in seizure-free days during the maintenance period alone were similar to the entire treatment period. Drop and total seizure-free days represent potential new and clinically meaningful endpoints for future RCTs in patients with LGS.

Tracing the Rain Formation Pathways in Numerical Simulations of Deep Convection

AbstractQuantifying the microphysical process contributions to surface precipitation in numerical simulations can be challenging. This is due to the fact that many microphysical processes contribute to the formation and depletion of rain drops and there is almost always a spatial/temporal mismatch between where/when rain is formed and where/when it strikes the surface. In this work, we develop a tracing method that tracks the sources and sinks of raindrop mass and number as they are advected by the Weather Research and Forecasting model. Applying the method to an idealized squall line confirms that convective precipitation is dominated by warm rain processes (autoconversion and accretion) while stratiform precipitation is dominated by the melting of rimed and unrimed ice crystals. Sensitivity experiments in which the prescribed cloud drop number concentration is increased confirm the conventional wisdom that weakened autoconversion increases the fraction of raindrops originating from cold rain processes. The method also reveals that when applied to deep convection the Khairoutdinov and Kogan autoconversion scheme produces an excessive number of raindrops which are subsequently clipped in P3 microphysics to keep the rain size distribution within prescribed limits. This problem can mostly be mitigated by increasing the assumed radius for raindrops created by autoconversion.

Cooling of a solar panel using nanofluid turbulent flow to improve energy and exergy efficiencies: Optimizing and simulating the effect of rectangular pin-fin height

BackgroundDue to increasing progress of the industry, enhancing rate of heat transfer with passive procedures has been the focus of researchers. One of these procedures is employing of pin-fins with varied shapes to disturb flow and enhance heat transfer rate. This study examines impact of rectangular pin-fins by varied heights and two-phase MgO-SiO2/water hybrid nanofluid (NF) on efficiency of the solar collector employing finite volume method (FVM). MethodsSolidwork software is employed for geometry modeling of the solar collector with rectangular pin-fins. Also, ANSYS FLUENT 2022 software is employed for numerical simulations. To ensure the obtained results, the grids with different elements are utilized to estimate average Nusselt number (Nuave) considering steady nanofluid flow. The MgO-SiO2/water hybrid NF is simulated employing the two-phase mixture model. The RNG k-ε turbulence model is employed to model turbulent flow. The inlet Reynolds number (Re) alters from 7000 to 31,000 and volume fraction (φ) varies from 1 to 3% when height of the pin-fins is 8, 10, 12, and 14 mm. ResultsThe pressure drop and mean Nusselt number are strongly influenced by velocity and volume fraction of nanoparticles (NPs) at inlet of solar collector. When φ = 3% and Re = 31,000, adding rectangular pin-fins with a height of 14 mm causes the Nuave to enhance by 133.81% compared to collector without pin-fins. For solar collector with rectangular pin-fins with a height of 8 mm, the energy efficiency is increased by 26.91% by enlarging Re from 7000 to 31,000 when φ = 3%. For solar collector with rectangular pin-fins with a height of 14 mm, the exergy efficiency is enlarged by 36.60% by enlarging Re from 7000 to 31,000 when φ = 3%.

Thermal Performance Evaluation of Plate-Type Heat Exchanger with Alumina–Titania Hybrid Suspensions

This paper aims to develop models for the thermal conductivity and viscosity of hybrid nanofluids of aluminium oxide and titanium dioxide (Al2O3-TiO2). The study investigates the impact of fluid temperature (283 K–298 K) on the performance of a plate heat exchanger using Al2O3-TiO2 hybrid nanofluids with different particle volume ratios (0:5, 1:4, 2:3, 3:2, 4:1, and 5:0) prepared with a 0.1% concentration in deionised water. Experimental evaluations were conducted to assess the heat transfer rate, Nusselt number, heat transfer coefficient, Prandtl number, pressure drop, and performance index. Due to the lower thermal conductivity of TiO2 nanoparticles compared to Al2O3, a rise in the TiO2 ratio decreased the heat transfer coefficient, Nusselt number, and heat transfer rate. Inlet temperature was found to decrease pressure drop and performance index. The Al2O3 (5:0) nanofluid demonstrated the maximum enhancement of around 16.9%, 16.9%, 3.44%, and 3.41% for the heat transfer coefficient, Nusselt number, heat transfer rate, and performance index, respectively. Additionally, the TiO2 (0:5) hybrid nanofluid exhibited enhancements of 0.61% and 2.3% for pressure drop and Prandtl number, respectively. The developed hybrid nanofluids enhanced the performance of the heat exchanger when used as a cold fluid.

Correcting Deviations of Emulated Spatial Correlation for Prefaded Signal Synthesis Method With Limited Number of Random Drops in MIMO OTA Testing

The prefaded signals synthesis (PFS) is a well-established over-the-air (OTA) testing solution, which can reconstruct the desired spatial profiles of the target channel by adjusting the power weights of the multiple probes. However, practical channel emulation campaigns tend to use a limited number of random drops due to limited time budget and hardware capacity constraint, which may cause the emulated spatial correlation to be deviated from the expected one due to the loss of ergodicity. In this article, the properties of the emulated channel under the PFS method are reexamined for a given set of initial subpath phases that are randomly configured at different probes. The analytical expressions of the spatial–temporal correlation function (STCF) are thus derived by averaging over time, compared with the general manipulations of ensemble averaging in the literature. Our derivations indicate that the spatial correlation function (SCF) of the emulated channel may deviate from the expected form for a given set of initial subpath phases in the classic PFS method. An improved configuration method for initial subpath phases is proposed. Simulation results show that the proposed method can reproduce the exact SCF in any random drop while unaffecting other important channel properties, for example, the temporal correlation function (TCF).

Reduction of Eyedrop Volume for Topical Ophthalmic Medications with the Nanodropper Bottle Adaptor.

To determine the drop volume and total number of dispensed drops using the Nanodropper eyedrop bottle adaptor (Nanodropper, Inc.) compared to drops dispensed from stock bottles to potentially limit ocular toxicity of these eyedrops and prolong bottle use. Six topical ocular hypotensive medications (5 solutions, 1 suspension), one steroid (suspension) and two artificial tears emulsions were selected for this study. An analytical balance was used to determine the mass per 10 drops with and without the volume-reducing adaptor and repeated until the bottles were completely emptied. The density of each product was determined using the calculated density. The average drop volume and number of drops per bottle for the nine medications were compared with and without the adaptor with paired t-testing. When all medications were assessed, the drops delivered with the adaptor were 62.1% smaller than eyedrops administered from standard bottles. Compared to stock bottle eyedrops, which had a mean volume of 39.8 ± 2.1 μL, the adaptor resulted in drops with a mean volume of 15.1 ± 1.0 μL, p<0.0001. The adaptor delivered 2.6x the number of drops dispensed from a standard 2.5 mL bottle (184.1 ± 15.1 drops with adaptor and 69.8 ± 4.9 drops from stock bottle, p<0.0001). The Nanodropper eyedrop bottle adaptor can significantly reduce drop volume and increase the overall number of drops dispensed compared with stock eyedrop bottles. Further studies are needed to elucidate the clinical impact of utilizing decreased drop volume with direct comparison to current standards of care.

Statistical self-organization of an assembly of interacting walking drops in a confining potential.

A drop bouncing on a vertically vibrated surface may self-propel forward by standing waves and travels along a fluid interface. This system called walking drop forms a non-quantum wave-particle association at the macroscopic scale. The dynamics of one particle has triggered many investigations and has resulted in spectacular experimental results in the last decade. We investigate numerically the dynamics of an assembly of walkers, i.e., a large number of walking drops evolving on a unbounded fluid interface in the presence of a confining potential acting on the particles. We show that even if the individual trajectories are erratic, the system presents a well-defined ordered internal structure that remains invariant to parameter variations such as the number of drops, the memory time and the bath radius. We rationalize such non-stationary self-organization in terms of the symmetry of the waves and show that oscillatory pair potentials form a wavy collective state of active matter.

Factors Affecting the Incidence of Ptosis after Trabeculectomy.

The aim of this study was to investigate the incidence of postoperative ptosis after primary trabeculectomy and the possible factors contributing to ptosis. A total of 312 patients (339 eyes) who underwent trabeculectomy with mitomycin-C between 2015 and 2020 were retrospectively evaluated. Patients who had regular follow-up for at least 6 months and no history of ptosis or ptosis surgery were included. Age, sex, glaucoma type, preoperative and postoperative intraocular pressure, preoperative and postoperative antiglaucoma medications, number of antiglaucoma drops, duration of antiglaucoma medication use, history of eye itching due to antiglaucoma medication-associated allergy, duration of follow-up, postoperative needling, needling time, and ocular massage were recorded. Ptosis was defined as ≥2 mm reduction in margin-reflex distance 1 from preoperative levels. Ptosis that had not improved for at least 6 months was considered persistent ptosis. Multivariate logistic regression was used to determine potential predictors of ptosis development. Ptosis after trabeculectomy was observed in 35 of 339 eyes (10.3%). Thirty eyes of 30 patients (8.8%) had transient ptosis and 5 eyes of 4 patients (1.5%) had persistent ptosis. Preoperative duration of antiglaucoma medication use, drug(s) used (prostaglandin analogs, beta-blockers, alpha-2 agonists, carbonic anhydrase inhibitors, or combinations of these), needling time, and ocular massage after trabeculectomy did not differ significantly between groups (p>0.05). Needling and eye itching due to antiglaucoma medication-associated allergy were significantly higher in patients with ptosis (p<0.05). Ptosis after trabeculectomy is an important problem for glaucoma patients. It has been observed that needling and a history of eye itching due to antiglaucoma drug-associated allergy may increase the risk of ptosis.

Controlling the impact dynamic behavior of a water-in-oil compound drop using the dielectrowetting effect

Controlling the impact dynamic behavior of a water-in-oil compound drop is vital for applications such as the enhancement of printing resolution and the preparation of innovative liquid-separation materials and devices. A phase diagram is constructed between the impact behavior, Weber number, and equilibrium contact angle of the water drop. The dynamic impact behavior of water-in-oil compound drops can be effectively controlled by changing the surface wettability using the dielectrowetting effect. The maximum spreading factor βm at different wettabilities shares a similar scale law βm∝We0.17 for 45.75 < We < 299.62 and βm∝We0.23 for 385.38 < We < 1183.19. Finally, the relationship between the velocity and radius of the rebounded drops was consistent with the results for pure water drops. Our findings indicate that the impact behavior of water-in-oil compound drops can be controlled at the right time scales using a dielectrowetting substrate; this is applicable in industries such as printing and liquid separation.

Adult norms for the Corbett Targeted Coin Test

Study DesignClinical measurement IntroductionDexterity is important for daily activities. The Corbett Targeted Coin Test (CTCT) measures dexterity with palm-to-finger translation and proprioceptive target placement, but lacks established norms. Purpose of the StudyTo establish norms for the CTCT with healthy adult subjects. MethodsThe inclusion criteria consisted of participants that were community dwelling, non-institutionalized, able to make a fist with both hands, perform finger-to-palm translation of twenty coins, and be at least 18 years of age. CTCT standardized testing procedures were followed. Quality of performance (QoP) scores were determined by speed in seconds and number of coin drops (each a 5-second penalty). QoP was summarized within each age, gender and hand dominance subgroup using the mean, median, minimum, and maximum. Correlation coefficients were computed for relationships between age and QoP, and between handspan and QoP. ResultsOf the 207 individuals who participated, 131 were females and 76 males with an age range of 18-86 and mean age of 37.16. Individual QoP scores ranged from 13.8 to 105.3 seconds, with median scores ranging from 28.7 to 53.3 seconds. The mean for males was 37.5 seconds for the dominant hand (range 15.7-105.3) and 42.3 seconds (range 17.9.-86.8) for the non-dominant hand. The mean for females was 34.7 seconds for the dominant hand (range 14.8-67.0) and 38.6 seconds (range 13.8.-82.7) for the non-dominant hand. Lower QoP scores indicate a faster and/or more accurate dexterity performance. Females showed better median QoP for most age groups. The best median QoP scores were seen in the 30-39 and 40-49 age ranges. DiscussionOur study agrees to some extent with other research that reported dexterity decreases with age, and increases with smaller hand spans. ConclusionNormative data for the CTCT can be a guide for clinicians evaluating and monitoring patient dexterity with palm-to-finger translation and proprioceptive target placement.

Studies on characterization of properties of low-grade hematite iron ores and their fired pellets

ABSTRACT In this study, pellets were made from iron ores of Ramallakota and Veldurthi mines, Andhra Pradesh, by the addition of 1.5 to 4.5 wt.% of bentonite and molasses binders. Dried iron ore pellets were fired at 1173, 1373 and 1573K for 1, 2 and 3h. The aim has been to determine the effects of type of iron ore and binder, and firing conditions on the properties of resulting fired pellets. Chemical compositions and XRD patterns of studied iron ores revealed them to be of low- grade hematite iron ores having 27–46% Fe. Drop number of dried pellets got increased with an increase in their binder contents. Both the types of fired iron ore pellets exhibited an increase in their crushing strengths and decrease in apparent porosity with rise of firing temperature and time due to an increase in the extent of sintering of particles, as revealed by SEM micrographs.

Experimental and numerical investigation of thermal-hydraulic performance of bi-metallic (Al-Cu) plate fin heat sink

In this research, an experimental study of thermal-hydraulic performance of bi-metallic (Al-Cu) plate fin heat sink (PFHS) under forced convection in wind tunnel is investigated. The key parameters such as pressure drop, Reynolds and Nusselt numbers, heat transfer coefficient, thermal resistance, power pumping and profit factor have studied. Then the PFHS has simulated and the results have validated with test. A good agreement is seen in the results of pressure drop between test and simulation. The results show an increase of performance of the applied bi-metal sink compared with similar single aluminum one in available literature. Finally, in order to improve the thermal behavior of PFHS, porous materials have been used in numerical simulation. Because of using a porous layer in the fin spaces, the pressure drop has been increased in comparison with the normal state. Thus, pumping power has increased which means the more energy consumption is needed for the cooling process so the profit factor is decreased. On the other hand, the amount of thermal resistance is decreased by 12% compared with bi-metallic PFHS without porous materials. The results of this study could be used as the fundamental of the future researches.

Использование в качестве удобрений азотосодержащих производственных отходов животноводческого происхождения

Currently, along with the intensive development of livestock production, there is a question of recycling waste generated as a result of its production. The aim of the study was to study the impact of industrial waste of animal origin on the quality and yield of spring wheat. The research was carried out in 2021-2022 in the conditions of the experimental field of I.A. Bunin YSU. The object of the study was the spring wheat variety Aquilon. It was found that the studied plant variants were distinguished by high rates of photosynthetic activity. The maximum values for chlorophyll a were characterized by plants in the variant where blood flour was used as fertilizer (20.68 mg/g of raw mass). Chlorophyll b was observed more in plants on variants using blood meal (18.05 mg/g) and corn meal (18.69 mg/g). The height of the plants in the variant using blood flour was the maximum, so in the phase of milk ripeness it was 70.6 cm. In the control variant , the height of plants in this phase of development was 58 cm. The highest protein values were recorded in the grain obtained in the variant where sheep wool was used as fertilizer - 16.5%, exceeding the control by 1.8%. Also, the grain obtained in this variant was characterized by high gluten levels - 31.3%. It should be noted that such indicators as gluten quality, vitreousness and the number of drops increased sharply compared to the control variant. The laboratory baking of bread from the obtained flour showed that the obtained samples of products according to organoleptic and physico-chemical parameters met the requirements of GOST. Keywords: SPRING WHEAT, PROTEIN, FERTILIZER, SHEEP WOOL, BLOOD MEAL, CORN MEAL, GLUTEN, GRAIN QUALITY

Intense Pulsed Light Soldering of Sn–3.0Ag–0.5Cu Ball Grid Array Component on Au/Pd(P)/Ni(P) Surface‐Finished Printed Circuit Board and Its Drop Impact Reliability

Intense pulsed light (IPL) soldering is investigated as an alternative soldering process to conventional reflow soldering. IPL soldering is suitable for achieving a carbon‐neutral society due to its low power consumption. In addition, it has several advantages in electronic device manufacturing, including low thermal damage, short processing time, and applicability to large‐area processes. Herein, an electroless‐nickel/electroless‐palladium/immersion‐gold surface finish and Sn–3.0Ag–0.5Cu solder are used. Three IPL parameters, pulse width, pulse number, and frequency, are considered in the soldering process. The microstructures of the interface and solder matrix are observed using a field‐emission scanning electron microscope equipped with an electron probe microanalyzer. Furthermore, board‐level drop impact tests are conducted to investigate the mechanical reliability of the joints. The results show that the compositions and morphologies of intermetallic compounds (IMCs) vary with the IPL parameters, which significantly affect the reliability. Specifically, the number of drops to failure increases ≈6.7 times under optimum IPL condition compared to reflow soldering. This is because cracks propagate through the solder matrix and discontinuous IMCs. Based on the obtained results, IPL‐based soldering is a promising alternative to reflow soldering.

Fractal image analysis and bruise damage evaluation of impact damage in guava

Impact bruise damage and quality of ‘Gim Ju’ guava were investigated for different drop heights and number of drops using fractal image analysis. For the impact test, a stainless-steel metal ball (250 g) was dropped on fruit from three drop heights (0, 0.3, 0.6 m) either once or five times. Fruit quality was evaluated for impact energy, bruise area (BA), bruise volume (BV), bruise susceptibility, bruise score and pulp color (L*, a*, b* and C values). The fractal dimension (FD) value using fractal image analysis was analyzed at the bruise region. Results showed that five drops (0.3 m) with a high impact energy (3 678.75 J) and a single drop (0.6 m) with a low impact energy (1 471.50 J) exhibited no significant in BA, BV, bruise score as well as all color values (L*, a*, b* and C). While the FD value of a single drop from 0.6 m had a higher FD value than that of five drops from 0.3 m. It is indicated that FD exhibited a better performance to classify impact bruising level of guava than BA, BV and color parameters. The FD value gradually decreased with increase of storage time and bruise severity. The correlation coefficient (r) values of FD (r = − 0.794 and − 0.745) between BA and BV were more significant than those L* (r = − 0.660 and − 0.615) and a* (r = 0.579 and 0.473). The coefficient of determination (R2) of the polynomial equation in bruised fruit (R2 = 0.85 to 0.99) was greater than the control (no bruise) (R2 = 0.80). A higher R2val (0.88 and 0.92) was exhibited at five drops. Interestingly, FD analysis showed greater potential than color measurement to assess bruise impact damage in guava.

Drop-on-Demand Electrohydrodynamic Jet Printing of Microlens Array on Flexible Substrates

The inkjet-printing technique is regarded as an efficient method to fabricate microlens arrays used in digital cameras, medical endoscopes, displays, optical communication, and light source devices. The diameter, height, and aspect ratio of the microlens are the major contributors to these optical properties. Hence, the optical characteristics of the microlens array can vary with the type of inkjet-printing method. In this study, by employing electrohydrodynamic (EHD) jet printing with the drop-on-demand strategy, we fabricated microlenses and microlens arrays using a UV-curable photopolymer liquid on flexible poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-coated poly(ethylene terephthalate). By controlling the number of printing drops, which is regarded as an efficient approach to control the dimension of the microlens, lenses with diameters of 11.9 ± 0.2 and 24.4 ± 0.5 μm and aspect ratio ranging from 0.22 to 0.33 were constructed. It was found that the focal length (15.44–26.79 μm), numerical aperture (0.39–0.46), and f-number (1.3–1.1) varied with the number of printing drops. The results demonstrate that the EHD-printed microlenses have a much shorter focal length, higher numerical aperture, and smaller f-number than the previously reported printed lenses. Hence, the EHD-printed microlens can be utilized to produce wide-angle-of-view applications and capture accurate images with insufficient light intensity. In addition, the proposed EHD-printing method may provide a cost-effective and simple route for manufacturing microlens arrays.