Dissipated Heat Energy Research Articles

Influence of airflow resistance on acoustic behaviour of needle-punched nonwoven structures

Textile materials and structures have gained significant attention in the field of noise reduction due to their porosity, softness, and good acoustic absorption properties. Porous materials are an excellent example of passive materials, which reduces sound energy by dissipating heat energy due to the presence of void structure. In textiles, nonwovens are highly porous and less expensive materials compared to woven and knitted structures. In this research, flax, jute, and polyester nonwovens were used to study the effect of various parameters such as fiber fineness, fiber cross section, areal density, and punch density on the airflow resistivity of the nonwovens and in turn its influence on the sound absorption coefficient. It was observed that the acoustic performance of woven and nonwoven structures is mainly dependent on the porosity or bulk density of the structure which also influences the airflow resistivity of the fabrics. Therefore, the investigation of the airflow resistance of the nonwovens and its correlation with the sound absorption coefficient became an important part of this study. An instrument based on ISO 9053 standard was fabricated to measure the airflow resistivity. It was observed that the increase in the areal density leads to increase in the airflow resistance of the nonwoven. The airflow resistance increases as the mass density increases and porosity decreases. It was observed that the sound absorption coefficient and airflow resistance were directly proportional.

Effects of the thermal history on the microstructural and the mechanical properties of stainless steel 316L parts produced by wire-based laser metal deposition

Laser metal deposition with coaxial wire feeding is a novel technology for additively manufacturing near-net-shape metal parts, as well as for repairing and modifying existing components. The microstructure and, thus, the mechanical properties of the deposited material significantly depend on the thermal history of the part, which is influenced by the process parameters and the amount of dissipated heat energy. In order to investigate these correlations, stainless steel 316L samples were produced under different thermal conditions and thoroughly characterized. Solid cuboids were built on a substrate plate at room temperature as well as on a preheated substrate plate. Subsequently, the influence of the different thermal conditions on the melt pool temperatures was evaluated, and the microstructures, the microhardness, and the tensile properties were analyzed. It was found that the mean melt pool temperatures and the primary dendrite arm spacing (PDAS) increased with the build height, while the cooling rates showed an inverse relationship with the build height. The determined PDAS values were correlated with the microhardness profile of the specimens using a Hall-Petch type relationship. An increased heat accumulation in the parts was thereby associated with a coarser microstructure and diminished mechanical properties. The presented results pave the way for tailoring the properties of additively manufactured components to specific requirements.

Acoustic behaviour of needle punched nonwoven structures produced from various natural and synthetic fibers

Porous materials are an excellent example of passive materials, which reduces sound energy by dissipating heat energy due to the presence of a void structure. In textiles, nonwovens are highly porous and less expensive materials compared to woven and knitted structures. The present research investigates the effect of fiber type, fiber fineness, fiber cross-sectional shape, and fabric areal density on the acoustic properties of needle punched nonwoven fabrics produced from flax comber noil and jute caddies and polyester staple fibers of circular, hollow, and hollow conjugated cross-sections. The study reveals that hollow conjugated cross section exhibits maximum noise absorption. Nonwoven made from biodegradable and recyclable jute caddies, and flax comber noil shows considerable noise absorption properties compared to polyester synthetic fiber, although they are inexpensive. Higher punch density results in better compactness of nonwoven fabric leading to improved sound absorption property. Layered nonwoven structures are responsible for better sound absorption properties due to the presence of an air layer.

The Single-Cell Revelation of Thermogenic Adipose Tissue.

The past two decades have witnessed an upsurge in the appreciation of adipose tissue (AT) as an immuno-metabolic hub harbouring heterogeneous cell populations that collectively fine-tune systemic metabolic homeostasis. Technological advancements, especially single-cell transcriptomics, have offered an unprecedented opportunity for dissecting the sophisticated cellular networks and compositional dynamics underpinning AT remodelling. The "re-discovery" of functional brown adipose tissue dissipating heat energy in human adults has aroused tremendous interest in exploiting the mechanisms underpinning the engagement of AT thermogenesis for combating human obesity. In this review, we aim to summarise and evaluate the use of single-cell transcriptomics that contribute to a better appreciation of the cellular plasticity and intercellular crosstalk in thermogenic AT.

A Finite Element Approach to Evaluate Thermoregulation in the Human Body due to the Effects of Sweat Evaporation during Cooking, Cleaning, and Walking

Sweat evaporation is the principal process of dissipating heat energy in a hot environment and during activities. Sweat loss is significantly affected by the level of energy expenditure, hormones, and the number of sweat glands. The thickness of the skin layer plays a vital role to maintain body temperature. The rate of sweat evaporation varies with ambient temperature and activity level. On increasing both metabolism and ambient temperature, sweat rate loss also increases and controls the body in the thermoregulatory system. The evaporative sweat release rate has a linear behavior. The appropriate physical and physiological parameters that affect thermoregulation have been incorporated into the model. The study presents the temperature distribution in three layers: epidermis, dermis, and subcutaneous tissue (SST) of the human dermal parts during cooking, cleaning, and walking. The solution is obtained by using the finite element method. The results demonstrate that the body mechanism keeps the body in thermoregulation by increasing the sweat evaporation rate exhibited by increasing the ambient temperature and metabolism during strenuous activities.

MEASUREMENT OF MICROCHANNELS PRODUCED IN AA6351/RUTILE COMPOSITE BY WIRE-EDM

The fabrication of microchannels, in order to dissipate the heat flux generated in the complex parts of an electronic industry, requires considerable attention since it is a complex process. Some advanced machining process like wire electrical discharge machining (WEDM) has been employed carefully for forming channels in material. However, the surfaces of these microchannels play an important role in dissipating heat energy. The present study focusses on the fabrication of AA6351/10[Formula: see text]wt.% Rutile MK grade mineral through powder metallurgy route, and their properties are evaluated. In addition, the forming of microchannels on the fabricated composite has also been done through WEDM process under varying machining conditions. WEDM process conditions considered are current, voltage and wire speed, and the response characteristics are kerf width, surface roughness and kerf depth. The hybrid approach of gray-based Taguchi coupled with PCA has been considered for optimizing the process parameters so as to get near net shape channels. The determined hardness of the composite is 64.5[Formula: see text]HB and the compressive strength is 220[Formula: see text]MPa. The optimized conditions are predicted and the regression model has been developed.

Stress-strain calculation and fatigue life assessment of V-shaped notches of turbine disk alloys

For local stress-strain behavior modeling at the notch root, both the Neuber's rule and equivalent strain energy density (ESED) method are commonly utilized in engineering practice, in which the former overestimates notch elasto-plastic responses while the latter gives conservative predictions. In this work, a correction coefficient related to the effective Poisson's ratio veff is proposed to quantify the weight of dissipated heat energy term with the modified ESED model. Notch-root strains predicted by the proposed model are compared with nonlinear FE calculations of GH4169 and TC4 V-shaped notched-bars, in which the proposed solution provides good agreement with FE results for both cases. Then, consulting the idea of local stress-strain approaches, a fatigue lifing model is derived assuming that the notched specimens fail once reach the critical total strain energy as same as that of smooth ones. Results indicated that prediction accuracy of local equivalent strains at notch roots is improved, and yields better life predictions than the Ellyin's model for the two alloys.

Elastic-plastic stress-strain calculation at notch root under monotonic, uniaxial and multiaxial loadings

The equivalent strain energy density (ESED) method was originally suggested and is still widely used to calculate the stresses and strains at notch root. It is well recognized, however, that the ESED method tends to underestimate the notch-tip stresses and strains. In order to obtain better predictions, in the present paper, a factor ((1+νe)/(1+νeff)) was introduced to modify the dissipated heat energy contained in the ESED method. A computational modeling technique coupling with Jiang-Sehitoglu plasticity model was also developed to calculate the multiaxial elastic-plastic notch-tip stress-strain responses of notched components. Extensive validations of the proposed method show that the calculated stresses and strains are in accord with experimental data and show reasonable accuracy.

Breast Tumor Targetable Fe3O4 Embedded Thermo-Responsive Nanoparticles for Radiofrequency Assisted Drug Delivery.

Non-invasive radiofrequency (RF) frequency may be utilized as an energy source to activate thermo-responsive nanoparticles for the controlled local delivery of drugs to cancer cells. Herein, we demonstrate that 180 ± 20 nm sized curcumin encapsulated chitosan-graft-poly(N-vinyl caprolactam) nanoparticles containing iron oxide nanoparticles (Fe3O4-CRC-TRC-NPs) were selectively internalized in cancer cells in vivo. Using an RF treatment at 80 watts for 2 min, Fe3O4-CRC-TRC-NPs, dissipated heat energy of 42 degrees C, which is the lower critical solution temperature (LCST) of the chitosan-graft-poly(N-vinyl caprolactam), causing controlled curcumin release and apoptosis to cultured 4T1 breast cancer cells. Further, the tumor localization studies on orthotopic breast cancer model revealed that Fe3O4-CRC-TRC-NPs selectively accumulated at the primary tumor as confirmed by in vivo live imaging followed by ex vivo tissue imaging and HPLC studies. These initial results strongly support the development of RF assisted drug delivery from nanoparticles for improved tumor targeting for breast cancer treatment.

Temperature-Stable, Energy-Efficient, and High-Bit Rate Oxide-Confined 980-nm VCSELs for Optical Interconnects

We report 980-nm VCSELs that achieve temperature-stable, energy-efficient, and high-bit rate data transmission concurrently. Oxide-aperture-dependent static characteristics and high-speed modulation properties are analyzed at room temperature and also at high temperature. It is demonstrated that VCSELs with oxide-aperture diameters smaller than ∼5 μm are most suitable to achieve energy-efficient, temperature-stable, and high-bit rate operation concurrently. We demonstrate error-free data transmission (defined as a bit error ratio < 1 × 10 −12) at 38 Gb/s from 25 to 85 °C without any change of working point and modulation condition by using VCSELs with oxide-aperture diameters smaller than 5 μm. For VCSELs smaller than ∼7 μm, 42 Gb/s error-free data transmission at 25 °C is achieved. Record low energy dissipation at 85 °C is achieved with our ∼3 μm oxide-aperture diameter VCSELs. At room temperature, only 145, 147, and 217 fJ of dissipated heat energy per bit is needed for 35, 38, and 42 Gb/s error-free data transmission. Each of these bit rates is a record low heat dissipation for 980-nm VCSELs. Our VCSELs are especially well suited for very short reach (<2 m) optical interconnects in high-performance computers, for board-to-board and chip-to-chip input/output interfaces and data buses, and for on-chip integrated photonics.

30 GHz bandwidth 850 nm VCSEL with sub‐100 fJ/bit energy dissipation at 25–50 Gbit/s

A high-speed and energy-efficient oxide-confined 850 nm vertical-cavity surface-emitting laser (VCSEL) for optical interconnects is presented. A record-high modulation bandwidth of 30 GHz is reached for a 3.5 mu m oxide aperture VCSEL, with 25 GHz bandwidth already at a bias current of 1.8 mA. The high bandwidth at low currents enables energy-efficient transmission with a dissipated heat energy in the VCSEL of <100 fJ/bit at 25, 40 and 50 Gbit/s.

Anti-cancer, pharmacokinetics and tumor localization studies of pH-, RF- and thermo-responsive nanoparticles

The curcumin-encapsulated chitosan-graft-poly(N-vinyl caprolactam) nanoparticles containing gold nanoparticles (Au-CRC-TRC-NPs) were developed by ionic cross-linking method. After “optimum RF exposure” at 40W for 5min, Au-CRC-TRC-NPs dissipated heat energy in the range of ∼42°C, the lower critical solution temperature (LCST) of chitosan-graft-poly(N-vinyl caprolactam), causing controlled curcumin release and apoptosis to cancer cells. Further, in vivo PK/PD studies on swiss albino mice revealed that Au-CRC-TRC-NPs could be sustained in circulation for a week with no harm to internal organs. The colon tumor localization studies revealed that Au-CRC-TRC-NPs were retained in tumor for a week. These results throw light on their feasibility as multi-responsive nanomedicine for RF-assisted cancer treatment modalities.

Improvement of Fire Retardant Property of Natural Fiber

Excessive exposure to noise is harmful for human health. Noise-induced hearing loss is one prevalent disorder resulted from above case. One root solution that converts the unnecessary sound waves to dissipated heat energy is acoustic absorption panel. Previous studies had looked upon potential sound-absorbing resources corresponding to natural fiber. However, several characteristics of these biodegradable supplies such as stiffness, anti-fungus and flammability are still yet to be improved. Hence, this research was undertaken to enhance the fire retardant performance of coir fiber for the production of high quality yet low cost acoustic absorption panel. Three types of additives, borax, Di-Ammonium Phosphate (DAP), and urea were investigated to perform chemical treatment for coir fiber. Experimental measurements were executed to validate the results by referring standard of ASTM E6902 (Standard Test Method for Combustible Properties of Treated Wood) by using the Fire-Tube Apparatus. Final results showed that DAP-treated fiber has the lowest percentage loss in mass of 6.67% compared to that of borax and urea-treated fiber with values of 7.60% and 9.48% respectively. This outcome clarified that DAP-treated fiber possesses higher self-extinguishing ability. Further evaluations in term of economic values, degree of hazards against health, flammability as well as reactivity supported that DAP is the best choice since its potency was ahead of the other two chemicals.

Energy Efficiency of Directly Modulated Oxide-Confined High Bit Rate 850-nm VCSELs for Optical Interconnects

The design, fabrication, and performance of the presently most energy-efficient oxide-confined 850 nm vertical-cavity surface-emitting lasers (VCSELs) for optical interconnects are presented. We employ a novel current spreading layer to reduce differential resistance. Compared to our previous designs, a higher indium content is used in the InGaAs quantum wells to increase the differential gain at low injected current densities. The influence of the oxide aperture diameter on the energy efficiency is determined by comparing the key performance parameters for a batch of VCSELs produced on the same epitaxial wafer, but with varying aperture diameters from 2.5 to 9.0 μm. The static light output power-current-voltage characteristics, small-signal modulation response, and large signal performance of our VCSELs are investigated in detail. The parameters important for energy-efficient operation are analyzed including threshold current, differential quantum efficiency, and differential resistance. We observe that our single-mode VCSELs are more energy efficient than our multimode VCSELs, although our multimode VCSELs typically exhibit a larger maximum static wallplug efficiency. Error-free (defined as a bit error ratio <;1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> ) data transmission at 25 Gb/s with a record-low dissipated heat energy of only 56 fJ/bit is achieved using a single-mode VCSEL with an oxide aperture diameter of 3.5 μm.

Energy-Efficient Oxide-Confined 850-nm VCSELs for Long-Distance Multimode Fiber Optical Interconnects

Highly energy-efficient oxide-confined 850-nm singlemode vertical-cavity surface-emitting lasers (VCSELs) for optical interconnects are presented. Error-free (defined as a bit error ratio <; 1 × 10-12) data transmission at 17 and 25 Gb/s across 100 m of multimode optical fiber is achieved with a low dissipated heat energy of only 69 and 99 fJ/bit, respectively. At 17 and 25 Gb/s, the transmission distance is increased to 1000 and 600 m, respectively. To date, our VCSELs are the most energy-efficient directly modulated lasers for data transmission across distances up to 1 km of multimode optical fiber.

Magnetic properties and magnetocaloric effect of rapidly quenched Gd–Co–Fe–Al alloys

Ternary Gd–Co–Fe–Al melts with different Gd/transition metal (TM) ratio Gd62(Co,Fe)28Al10 and Gd50(Co,Fe)40Al10 and varying Co/Fe ratios of 2/0, 2/1 and 1/2 were rapidly quenched by melt spinning. The magnetic properties as well as the magnetocaloric effect (MCE) of these ribbons with prevailing glassy phase were investigated regarding the influence of the Gd/TM ratio and the Co/Fe ratio, respectively. Gd62Co28Al10 and Gd50Co40Al10 exhibit narrow ΔSm–T curves with a maximum change of magnetic entropy ΔSmax of 4.8(1)Jkg−1K−1 and 3.8(1)Jkg−1K−1 at TΔSmax=135(5)K and 175(5) K, respectively, i.e. the MCE working temperature is essentially increased by decreasing the Gd/TM ratio. Taking Gd62Co28Al10 as starting composition, it is also possible to shift TΔSmax to about 173(5)K by changing the Co/Fe ratio to 2/1 in Gd62(Co2Fe1)28Al10, but this is accompanied by a remarkable increase of the full width at half maximum of the ΔSm–T curve. However, the combination of increasing the Co/Fe ratio and deceasing the Gd/TM ratio does not cause a further upshift of TΔSmax, but causes a remarkable reduction of the saturation magnetization and a broadening of the ΔSm-T curve over a very large temperature range. Furthermore, for this composition irreversible processes are found to be opposed to a potential cooling by the MCE by permanently dissipating heat energy during cycling of the magnetic field.

138 POSTER Design, synthesis, biochemical and biological evaluations of novel and potent small-molecule inhibitors of STAT3

The equivalent strain energy density (ESED) method was originally suggested and is still widely used to calculate the stresses and strains at notch root. It is well recognized, however, that the ESED method tends to underestimate the notch-tip stresses and strains. In order to obtain better predictions, in the present paper, a factor ((1 + νe)/(1 + νeff)) was introduced to modify the dissipated heat energy contained in the ESED method. A computational modeling technique coupling with Jiang-Sehitoglu plasticity model was also developed to calculate the multiaxial elastic-plastic notch-tip stress-strain responses of notched components. Extensive validations of the proposed method show that the calculated stresses and strains are in accord with experimental data and show reasonable accuracy.

Quantitative internal thermal energy mapping of semiconductor devices under short current stress using backside laser interferometry

In the backside interferometric thermal mapping technique, an infrared (IR) laser beam probes the temperature-induced changes in the semiconductor refractive index inside a semiconductor device, which results in a change in the measured optical phase shift. In this paper, a theoretical analysis of the phase shift is reported. The focus is on nanosecond-to-microsecond time-scale thermal mapping during high current stress, as occurring e.g., during an electrostatic discharge (ESD) event or in some power applications. An analytical expression for phase shift is obtained from the analysis of the thermal diffusion equation. The phase shift is directly proportional to the two-dimensional (2-D) heat energy density in the semiconductor active region of the device. The phase shift is also expressed in terms of the local dissipated heat energy and the heat transferred to the device top and lateral sides. In addition, the space integral of the phase shift is expressed in terms of a total energy dissipated in the device and the total heat transferred from the semiconductor to the top device layers. The theory shows an excellent agreement with experimental data obtained for a p-n diode ESD protection structure working in the avalanche regime.