• Steel and Composite Structures
• /
• v.47 no.6
• /
• pp.743-757
• /
• 2023

In this paper, the dynamic response of a simply-supported composite sandwich plate with a viscoelastic core based on the Golla-Hughes-McTavish (GHM) viscoelastic model is investigated analytically. The formulation is developed using the three-layered sandwich panel theory. Hamilton's principle has been employed to derive the equations of motion. Since classical models, like kelvin-voigt and Maxwell models, cannot express a comprehensive description of the dynamic behavior of viscoelastic material, the GHM method is used to model the viscoelastic core of the plate in this research. The main advantage of the GHM model in comparison with classical models is the consideration of the frequency-dependent characteristic of viscoelastic material. Identification of the material parameters of GHM mini-oscillator terms is an essential procedure in applying the GHM model. In this study, the focus of viscoelastic modeling is on the development of GHM parameters identification. For this purpose, a new method is proposed to find these constants which express frequency-dependent behavior characterization of viscoelastic material. Natural frequencies and loss factors of the sandwich panel based on ESL and three-layered theories in different geometrics are described at 30℃ and 90℃; also, the comparisons show that obtained natural frequencies are grossly overestimated by ESL theory. The argumentations of differences in natural frequencies are also illustrated in detail. The obtained results show that the GHM model presents a more accurate description of the plate's dynamic response by considering the frequency dependency behavior of the viscoelastic core.

• ETRI Journal
• /
• v.46 no.2
• /
• pp.347-359
• /
• 2024

A simultaneous transfer and bonding (SITRAB) process using areal laser irradiation is introduced for high-yield and cost-effective production of mini- or micro-light-emitting diode (LED) display panels. SITRAB materials are special epoxy-based solvent-free pastes. Three types of pot life are studied to obtain a convenient SITRAB process: Room temperature pot life (RPL), stage pot life (SPL), and laser pot life (LPL). In this study, the RPL was found to be 1.2 times the starting viscosity at 25℃, and the SPL was defined as the time the solder can be wetted by the SITRAB paste at given stage temperatures of 80℃, 90℃, and 100℃. The LPL, on the other hand, was referred to as the number of areal laser irradiations for the tiling process for red, green, and blue LEDs at the given stage temperatures. The process windows of SPL and LPL were identified based on their critical time and conversion requirements for good solder wetting. The measured RPL and SPL at the stage temperature of 80℃ were 6 days and 8 h, respectively, and the LPL was more than six at these stage temperatures.

• Horticultural Science & Technology
• /
• v.28 no.6
• /
• pp.980-984
• /
• 2010

Research regarding respiration rate, off-flavor related material and freshness maintenance effect of active MA mini-packaging on perilla leaves has been carried in this study. Respiration rate was highly maintained at high oxygen treatments ($CO_2:O_2:N_2$=0:30:70 and 0:50:50), higher than non-treatment and low oxygen treatments (6:2:92, 0:10:90) during the storage period, and ethylene production was relatively higher. However, off-flavor related materials, acetaldehyde and ethanol production was noticeably low. Weight losses of non-treatment and low-oxygen treatment were about 1.8 and 1.4%, respectively. At the fifth day of storage there was no weight loss. Ascorbic acid content was 13.3 mg/100 g F.W. at the first day of storage. At the third day of storage non-treatment showed the lowest value of ascorbic acid, 8.8 mg/100 g F.W. Ascorbic acid content of active MA treatment gradually decreased without a striking difference as the storage day extended. Chlorophyll content was the lowest at the fifth day of storage with non-treatment, 47.5 (SPAD-502 unit) while the active MA treatment maintained high level of chlorophyll content, 53.0. Sensory evaluation (vision) showed that marketability gradually decreased but was maintained in high oxygen treatments (0:30:70 and 0:50:50), even at the fifth day of storage. Occurrence of off-flavor in non-treatment at the fifth day of storage was extremely low, 2.6; whereas high in high oxygen treatment, 3.4. Active MA packaging maintained freshness two more days at room temperature (about $27^{\circ}C$).

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.20 no.2
• /
• pp.29-33
• /
• 2014

Active air flushing mini-pumps were installed in a rigid polypropylene container ($32cm{\time}23cm{\time}18cm$) containing 900 g of fresh green peppers for effectively controlling its $O_2$ concentration on real time basis to preserve the product quality. The performance of the constructed system was compared to that of the modified atmosphere (MA) container system with gas diffusion tube controlled in close/open cycles responding to real time $O_2$ concentration at 10 and $20^{\circ}C$. In the control logic, the $O_2$ concentration was programmed to be located exactly at 13% or stay in the range of 13-15%. The active air flushing system could control the $O_2$ concentration in the desired level or range at both temperatures, while the passive diffusion system could work only under the low temperature condition of $10^{\circ}C$. At higher temperature of $20^{\circ}C$, the passive diffusion system could not manage the produce respiration increased more highly than the gas transfer through the diffusion tube, resulting in too low $O_2$ concentration and too high $CO_2$ concentration which would be injurious to the green pepper. When tested at $20^{\circ}C$, the MA container system could preserve the green pepper better than the perforated air package in terms of weight loss, ascorbic acid and chlorophyll contents and firmness.

• Journal of the Microelectronics and Packaging Society
• /
• v.27 no.4
• /
• pp.55-60
• /
• 2020

The PERC photovoltaic (PV) modules installed in PV power plant are still reports potential-induced degradation (PID) degradation due to high voltage potential differences. This is because Na+ ions in the cover glass of PV modules go through the encapsulant (EVA) and transferred to the surface of solar cells. As positive charges are accumulated at the ARC (SiOx/SiNx) interface where many defects are distributed, shunt-resistance (Rsh) is reduced. As a result, the leakage current is increased, and decrease in solar cell's power output. In this study, to prevent of this phenomenon, a Moth-eye nanostructure was deposited on the rear surface of an optical film using Nano-Imprint Lithography method, and a solar mini-module was constructed by inserting it between the cover glass and the EVA. To analyze the PID phenomenon, a cell-level PID acceleration test based on IEC 62804-1 standard was conducted. Also analyzed power output (Pmax), efficiency, and shunt resistance through Light I-V and Dark I-V. As a result, conventional solar cells were decreased by 6.3% from the initial efficiency of 19.76%, but the improved solar cells with the Moth-eye nanostructured optical film only decreased 0.6%, thereby preventing the PID phenomenon. As of Moth-eye nanostructured optical film, the transmittance was improved by 4%, and the solar module output was improved by 2.5%.

• Asian-Australasian Journal of Animal Sciences
• /
• v.14 no.11
• /
• pp.1527-1533
• /
• 2001

Garole is a prolific, rare, less known and small size Indian sheep breed found in low and humid Sunderban region of West Bengal. Although information on stored Garole ram liquid semen upto 24 h is available, but there is a need to further investigate the short-term and long-term preservability of Garole ram semen for extensive utilization of this valuable germplasm by artificial insemination. The aim of the present study was to apply computer-assisted sperm analysis technique for assessing the motion characteristics of Garole ram semen stored (i) in liquid state at refrigeration temperature for short-term preservation upto 48 h and (ii) in frozen state at $-196^{\circ}C$ for long-term preservation after packaging in mini straws. Short-term preservation had a significant effect on motility (p<0.01) as the motility progressively decreased from 90.1% at 0 h to 85.5% and 73.2% after 24 and 48 h of storage, respectively. Although the decline in rapid moving sperms was also significant (p<0.01) on storage but the decrease was more pronounced at 48 h as compared to 24 h of storage period. Storage of chilled semen had also a significant effect on % linearity (p<0.05), % straightness (p<0.01), sperm velocities (p<0.01), amplitude of lateral head displacement (p<0.01) and beat frequency (pO.Ol) of spermatozoa. The replication had a significant effect for all the variables except average path and straight line velocity. However, the interactions of short-term storage and replication were non-significant for most of the variables except % of medium moving sperms, sperm velocities and beat frequency. On long-term preservation of Garole ram spermatozoa under controlled conditions the mean post-thaw recovery of 70.4 and 71.4% motile spermatozoa was achieved having 48.8 and 48.9% of rapidly motile spermatozoa, respectively in both the replicates. The effect of replication on cryopreservation was significant (p<0.05) on amplitude of lateral head displacement and beat frequency, but there was no significant effect on motility, rapidly motile spermatozoa, linearity, straightness and sperm velocities of frozen-thawed spermatozoa. It can be concluded from these results that an average 70% motility can be achieved on storage of Garole ram semen in chilled liquid state upto 48 h or in liquid nitrogen after freezing under controlled conditions in straws. However, further studies are required to evaluate the fertility of short-term and long-term preserved Garole ram semen for extensive use of this prolific sheep breed.