Uncompressed Samples Research Articles

Structure refinement and performance balance of high-strength aluminum alloys using an improved thermomechanical treatment process

The microstructure of 7A85 aluminum alloy forgings often contains coarse second-phase particles and grains. To improve the microstructures and balance the properties, we used an enhanced thermomechanical treatment process that included multiaxial hot forging, multiaxial cryoforging (MACF), and three-step aging treatment. We thoroughly investigated the effects of MACF with 1–3 passes on the evolution of microstructure, three-dimensional (3D) mechanical properties at the center and edge, fracture toughness, and corrosion resistance of the alloy. Our findings revealed that multiaxial hot forging had a limited ability to crush the coarse second-phase particles. However, the higher flow stress and compound brittleness of MACF resulted in a significant increase in particle fragmentation and driving force for precipitation. Additionally, under MACF, massive dislocations proliferated due to the inhibition of dynamic recovery, forming large orientation gradient regions, which promote static recrystallization and grain refinement during solution treatment. As the number of MACF passes increased from one to three, the effect of particle crushing initially increased and then plateaued, the 3D grain sizes first decreased and then slightly increased, and the spacing of grain boundary precipitates (GBPs) increased. The dense and uniform precipitates, finest equiaxed grains, a low fraction of coarse particles, and large GBP spacing in MACF2 resulted in the higher strength, highest elongation with minimal anisotropy, superior fracture toughness, and enhanced corrosion resistance. Ultimately, MACF2 demonstrated the best overall performance and good homogeneity, with an average 3D ultimate tensile strength, average 3D yield strength, average 3D elongation, and fracture toughness at the center of 548 MPa, 476 MPa, 13.4%, and 42.5 MPa m1/2, respectively. These values were respectively 4.2%, 1.9%, 50.6%, and 13.9% higher than those of the uncompressed sample.

Impact of Audio Data Compression on Feature Extraction for Vocal Biomarker Detection: Validation Study.

Vocal biomarkers, derived from acoustic analysis of vocal characteristics, offer noninvasive avenues for medical screening, diagnostics, and monitoring. Previous research demonstrated the feasibility of predicting type 2 diabetes mellitus through acoustic analysis of smartphone-recorded speech. Building upon this work, this study explores the impact of audio data compression on acoustic vocal biomarker development, which is critical for broader applicability in health care. The objective of this research is to analyze how common audio compression algorithms (MP3, M4A, and WMA) applied by 3 different conversion tools at 2 bitrates affect features crucial for vocal biomarker detection. The impact of audio data compression on acoustic vocal biomarker development was investigated using uncompressed voice samples converted into MP3, M4A, and WMA formats at 2 bitrates (320 and 128 kbps) with MediaHuman (MH) Audio Converter, WonderShare (WS) UniConverter, and Fast Forward Moving Picture Experts Group (FFmpeg). The data set comprised recordings from 505 participants, totaling 17,298 audio files, collected using a smartphone. Participants recorded a fixed English sentence up to 6 times daily for up to 14 days. Feature extraction, including pitch, jitter, intensity, and Mel-frequency cepstral coefficients (MFCCs), was conducted using Python and Parselmouth. The Wilcoxon signed rank test and the Bonferroni correction for multiple comparisons were used for statistical analysis. In this study, 36,970 audio files were initially recorded from 505 participants, with 17,298 recordings meeting the fixed sentence criteria after screening. Differences between the audio conversion software, MH, WS, and FFmpeg, were notable, impacting compression outcomes such as constant or variable bitrates. Analysis encompassed diverse data compression formats and a wide array of voice features and MFCCs. Wilcoxon signed rank tests yielded P values, with those below the Bonferroni-corrected significance level indicating significant alterations due to compression. The results indicated feature-specific impacts of compression across formats and bitrates. MH-converted files exhibited greater resilience compared to WS-converted files. Bitrate also influenced feature stability, with 38 cases affected uniquely by a single bitrate. Notably, voice features showed greater stability than MFCCs across conversion methods. Compression effects were found to be feature specific, with MH and FFmpeg showing greater resilience. Some features were consistently affected, emphasizing the importance of understanding feature resilience for diagnostic applications. Considering the implementation of vocal biomarkers in health care, finding features that remain consistent through compression for data storage or transmission purposes is valuable. Focused on specific features and formats, future research could broaden the scope to include diverse features, real-time compression algorithms, and various recording methods. This study enhances our understanding of audio compression's influence on voice features and MFCCs, providing insights for developing applications across fields. The research underscores the significance of feature stability in working with compressed audio data, laying a foundation for informed voice data use in evolving technological landscapes.

Manufacturing supported loose-nanofiltration polymeric membranes with eco-friendly solvents on an R2R System

In this study, loose nanofiltration membranes made of polysulfone dissolved in co-solvents PolarClean and gamma-Valerolactone were prepared via slot die coating (SDC) on a roll-to-roll (R2R) system by directly coating them onto a support layer or free standing. A solution flow rate of 20 mL/min, substrate speed of 17.1 mm/s, and coating gap of 0.1 mm resulted in the formation of membranes without structural defects. Pre-wetting the support layer with dope solution minimized shrinkage of membrane layer thickness and improved interfacial adhesion. Membrane samples produced using SDC exhibited properties and performance consistent with bench-scale doctor blade extruded samples; pre-wetted and uncompressed samples (SDC-3) exhibited the highest rejection of bovine serum albumin (99.20% ± 1.31%) and along with adequate mean permeability during filtration (70.5 ± 8.33 LMH/bar). This study shows that combining sustainable materials development with SDC provides a holistic approach to membrane separations to bridge materials discovery and membrane formation.

Improvement of vanadium redox flow battery performance obtained by compression and laser perforation of electrospun electrodes

Flow battery electrodes made of electrospun carbon fibers were synthesized with substantially lower porosity than typical electrospun mats by applying compression during the stabilization stage. The objective was to create flow battery electrodes with higher volumetric surface area to support the electrochemical reaction. The physical, structural, and transport properties of these novel mats were characterized extensively. A porosity reduction of 12% was attained by this method, yielding a 50% increase volumetric surface area, while the in-plane permeability and tortuosity were found to remain relatively consistent. On the other hand, the fibers near the surfaces were somewhat compacted, which hurt the through-plane permeability, so holes were created using a CO2 laser to perforate the structure. The loss of specific surface area caused by laser perforation was quite negligible and still showed improvement compared to the uncompressed control sample. Flow battery performance tests were conducted on all samples. All electrospun samples outperformed commercial carbon mats, with the compressed samples without and without laser perforations showing markedly better performance in the activation region. The non-perforated compressed sample showed mass transfer limitations at higher current density, while the laser perforations largely eliminated this effect, yield the best performance over the entire range of current density.

Electric Conductivity Study of Porous Polyvinyl Alcohol/Graphene/Clay Aerogels: Effect of Compression.

In this work, poly(vinyl alcohol) (PVOH)/graphene (GN) oxide/clay aerogels were prepared using montmorillonite (MMT) and kaolinite (KLT) as fillers. This work paves the way for the development of aerogels filled with MMT or KLT with high conductivity. The mechanical properties of the polymer/clay aerogels are enhanced by incorporating GN into these systems. These composite materials have an enhanced thermal stability, and the combination of PVOH and GN leads to interconnected channels which favored the conductivity when a clay (MMT or KLT) is added to the mixed PVOH/GN matrix. However, after compressing the samples, the conductivities drastically decreased. These results show that the design of solid MMT/GN and KLT/GN composites as aerogels allows maximizing the space utilization of the electrode volume to achieve unhindered ion transport, which seems contrary to the general design principle of electrode materials where a suitable porous structure is desired, such as in our uncompressed samples. These findings also demonstrate the potential of these materials in electrodes, sensors, batteries, pressure-sensing applications, and supercapacitors.

Modelling of creep behaviour of timber dowelled beams

Extensive researches have been dedicated to study creep in wooden structures where good insight was gained on the phenomenological behaviour. However, long-term creep laws and practical methods to investigate the creep’s influence on safety and serviceability of wood structures during their life-cycle are still very few or don’t exist. This paper investigates the creep of wooden structures using a combined numerical and experimental study. Uni-axial tests (i.e. compression/tensile tests in different directions) were used to calibrate the constitutive law of spruce species and to identify the elastic parameters of the constitutive law. For creep parameters identification, three point bending tests were performed for compressed and uncompressed spruce wood. Subsequently, the results of the three point bending tests were used in conjunction with the numerical model in an inverse problem to obtain the viscous parameters. This technique was adopted for both compressed and uncompressed wood samples. Furthermore, a parametric study was conducted on laminated beams of uncompressed spruce boards assembled by compressed spruce dowels. The behaviour of the whole hybrid structure was studied and several interesting findings were highlighted.

Comparative analysis of the quality of recorded sound in the function of different recording formats

In article, the quality of the following encoders was analyzed: mp3, AAC, wma and OGG Vorbis. An original graphic method was used to carry out the quantitative research. It consists in comparing the number of pixels (representing data) between the spectrogram of a wav file and the spectrograms of files compressed with different codecs and bit rates. It has been shown that the Ogg Vorbis encoder retains the most data from the uncompressed wav sample in all tested bit rates (128KBit / s, 160KBit / s, 320KBit / s).

Microstructure evolution and accelerated magnetocaloric phase formation of LaFe13.1Co0.7Si1.4 alloy by forging deformation at room temperature

In order to improve the preparation process and practical process of magnetic refrigerant, a method of accelerating phase formation by cold compression plastic deformation at room temperature is proposed. To determine the significance of this method, the grain structure, phase composition and magneto-thermal effects of LaFe13.1Co0.7Si1.4 alloy were systematically studied. The results show that with the increase of compression ratio, the number of grains per unit volume increases and the grain size tends to be uniform. Compared with the uncompressed sample, the proportion of magnetothermal phase in the pre-compressed samples increases after annealing under the same conditions. When the deformation is 40%, the ratio of 1:13 phase in pre-deformed sample after 1 day annealing is 72 vol%, which is significantly better than that of the undeformed sample. After annealing for 3 days, the Curie temperature (TC) of 40% pre-deformed LaFe13.1Co0.7Si1.4 samples is 330 K, and the magnetic entropy changes to − 4.70 J/kg K and − 5.42 J/kg K under 2 T and 3 T magnetic fields, respectively. The appropriate Curie temperature and value of ∆SM make it an attractive potential candidate for magnetic refrigeration application at room or even high temperature.

Sound absorption and transmission loss properties of open-celled aluminum foams with stepwise relative density gradients

We investigate the acoustical properties of uncompressed and compressed open-celled aluminum metal foams fabricated using a directional solidification foaming process. We compressed the fabricated foams using a hydraulic press to different compression ratios and characterized the effect of compression on the cellular microstructure using microtomography and scanning electron microscopy. The static airflow resistances of the samples are measured and related to the observed microstructural changes. We measured the normal incidence acoustical properties using two- and four-microphone impedance tube methods and show that the compression substantially improves their sound absorption and transmission loss performance. We then stack individual disks with different compression ratios to create various stepwise relative density gradient configurations and show that stepwise gradients provide a significant improvement in properties as compared to the uncompressed sample. The effect of increasing and decreasing relative density gradients on the overall absorption and transmission loss behavior is characterized. Finally, we use an experimentally informed and validated transfer matrix method to predict the effect of various layer thicknesses and stacking sequences on the global acoustical properties. Our results show that open-celled metal foams with stepwise relative density gradients can be designed to provide tailored acoustic absorption performance while reducing the overall weight of the noise reduction package.

In-situ X-ray computed tomography characterization of compaction-creep-recovery response and statistical void analysis of carbon/epoxy prepregs

Vacuum bag only (VBO) prepreg processing requires several time-consuming experimental trials in order to achieve a void volume fraction (Vv) of less than 2%. Alternatively, a limited number of in-situ X-ray computed tomography (XCT) compaction-creep experiments on prepregs under pressures that are equivalent to the VBO process can potentially reduce both time and cost whilst assisting in identifying and understanding the mechanisms associated with void formation during processing. In this study, compaction-creep tests at the first dwell temperature during the cure cycle were conducted at 0.1 MPa for different dwell periods (1, 2, and 4 h) using a specially-designed compression stage installed inside an XCT machine. Based on the thickness values measured at different stages of the test, the percentage of compaction-creep and permanent deformations were determined. Three-dimensional (3D) XCT-aided geometrical models were developed both before and after the compaction-creep tests, followed by Vv calculations at each stage. The results showed that higher levels of permanent deformation were recorded in samples tested using a dwell time of 4 h, due to a lower level of recovery compared to other dwell periods. Furthermore, the most suitable condition, in terms of the lowest Vv, was found in samples manufactured with a dwell time of 2 h, where relatively small voids, with a diameter less than 100 μm and a Vv of 0.57% were observed. These values are significantly lower than those observed in uncompressed samples which have many larger voids with a diameter greater than 200 μm and a Vv of approximately 15%.

Fire structural performance of thermo-mechanically compressed spruce timber by means experiments and a three-step multi-reactions pyrolysis 3D-finite element modelling

This paper presents experimental and numerical investigations to access the relative fire structural resistance of thermo-mechanically compressed (or densified) spruce wood. First of all, thermal characterization, including thermal conductivity and specific heat, has been undertaken on both compressed and uncompressed spruce wood. The thermal degradation of both compressed and uncompressed wood has been analysed by means thermogravimetric tests using different heating rates. Both compressed and uncompressed spruce samples of dimensions of 100 mm × 100 mm × 19 mm have been subjected to fire in a cone calorimeter under 20 kW/m2 and 75 kW/m2. Finally, a predictive finite element model based on three-step multi-reactions of pyrolysis is proposed for the thermal transfer and degradation analyses of timber material. The simulated thermal profiles, the mass loss as well as the charring depths were compared to the experimentally recorded results showing a fairly good agreement.

Influence of Ramped Compression on the Dielectric Behavior of the High-Voltage Epoxy Composites.

The emergence of micro and nano-based inorganic oxide fillers with optimal filler-loadings further enhances the required insulation characteristics of neat epoxy. During manufacturing and service application, insulators and dielectrics face mechanical stresses which may alter their basic characteristics. Keeping this in mind, the facts’ influence of mechanical stresses and fillers on dielectric properties of polymeric insulators of two epoxy/silica composites were fabricated and thoroughly analyzed for dielectric characteristics under ramped mechanical compressions relative to the unfilled sample. Before compression, epoxy nanocomposites exhibited responses having an average dielectric constant of 7.68 with an average dissipation factor of 0.18. After each compression, dielectric properties of all samples were analyzed. The dissipation factor and the dielectric constant trends of each sample are plotted against a suitable frequency range. It was observed that after the successive compressions up to 25 MPa, the dielectric properties of epoxy micro-silica composites were highly affected, having an average final dielectric constant of 9.65 times that of the uncompressed sample and a dissipation factor of 2.2 times that of the uncompressed sample, and these were recorded.

Combined Effect of the Preparation Method and Compression on the Physical Stability and Dissolution Behavior of Melt-Quenched Amorphous Celecoxib.

In an earlier investigation, amorphous celecoxib was shown to be sensitive to compression-induced destabilization. This was established by evaluating the physical stability of uncompressed/compressed phases in the supercooled state (Be̅rziņš . Mol. Pharmaceutics, 2019, 16(8), 3678-3686). In this study, we investigated the ramifications of compression-induced destabilization in the glassy state as well as the impact of compression on the dissolution behavior. Slow and fast melt-quenched celecoxib disks were compressed with a range of compression pressures (125-500 MPa) and dwell times (0-60 s). These were then monitored for crystallization using low-frequency Raman spectroscopy when kept under dry (∼20 °C; <5% RH) and humid (∼20 °C; 97% RH) storage conditions. Faster crystallization was observed from the samples, which were compressed using more severe compression parameters. Furthermore, crystallization was also affected by the cooling rate used to form the amorphous phases; slow melt-quenched samples exhibited higher sensitivity to compression-induced destabilization. The behavior of the melt-quench disks, subjected to different compression conditions, was continuously monitored during dissolution using low-frequency Raman and UV/vis for the solid-state form and dissolution properties, respectively. Surprisingly the compressed samples exhibited higher apparent dissolution (i.e., higher area under the dissolution curve and initial celecoxib concentration in solution) than the uncompressed samples; however, this is attributed to biaxial fracturing throughout the compressed compacts yielding a greater effective surface area. Differences between the slow and fast melt quenched samples showed some trends similar to those observed for their storage stability.

Pyrolytic carbon from Novolac Epoxy resin compressed before photocrosslinking and pyrolysis

The so-called SU-8 formulation, originally designed as a negative photoresist, has become the gold standard for the fabrication of microelectromechanical systems (MEMS) due to its relatively versatile processability and to the unique set of properties of the carbon obtained from pyrolysis of the patternable Bis-Phenol A Novolac Epoxy (BPNE) oligomer contained therein. Here, we investigate the possibility of increasing the degree of graphitization and electrical conductivity of BPNE-derived carbon by mechanically compressing the uncured oligomer pre-pyrolysis. BPNE sheets were casted, compressed and photocrosslinked to “freeze” the material in a strained configuration before carbonization. The electrical sheet resistance was determined using the four-point probe technique. The relative sp2/sp3 content and the degree of crystallinity were compared by Raman and XRD spectroscopy. It was hypothesized that applying compressive loads of up to 2000 kg at 90°C would suffice to increase the crystallite size and the mesoscale order of the percolated graphenic carbon network by promoting the alignment of the aromatic segments from the phenolic groups before pyrolysis. However, negligible variations in the resistivity and sp2-carbon microstructural features were observed when compressing millimetric sheets of BPNE as compared to uncompressed samples, suggesting that higher forces and temperatures may be required to synthesize BPNE-derived glass-like carbon materials with a slightly more graphitic character.

Parkinson’s Diagnosis through Compressed Speech Signals at remote Locations

&#x0D; &#x0D; &#x0D; Rapid increase in Parkinson’s disease all over the world before the age of 60’s is alarming. Parkinson’s affects the neurological controls of human body. In this paper we intend to adopt machine based learning to automate the diagnosis of Parkinson’s disease with help of compressed speech signals sent via network. An advanced Solution is proposed to automate the diagnosis process more rapid than that of ordinary process. In this study Speech samples from 55 subjects have been collected, 43 with Parkinson Disease and 12 Healthy subjects. Speech signals from clients captured from various sensors and devices transmitted to the cloud for processing. In the cloud Speech samples are compressed using compression codecs MP3, MP4, G.722, G.226, GSM-EFR, AMR-WB, SVOPC/SILK, and OPUS, and then same are diagnosed without compression impact and deliver accurate results. Three classifiers SVM (Support Vector Machine), NN (Neural Network), and GA (Genetic Algorithm) are applied and calculated accurate results as compared with compressed and un-compressed voice samples. Successful experiments enabled us to achieve 90.7% accuracy. Same process can be used for online and social media applications which are available in portable devices as well.&#x0D; &#x0D; &#x0D;

Influence of cryogenic deformation on second-phase particles, grain structure, and mechanical properties of Al–Cu–Mn alloy

To refine the coarse second-phase particles (Al2Cu) and grains of Al–Cu–Mn alloy, 10% and 20% compression deformation at cryogenic and room temperatures was applied, followed by a T8 heat treatment process consisting of solution treatment, 3% cold deformation, and artificial aging. The microstructures of the compressed and heat-treated samples were investigated using a combination of scanning electron microscopy, X-ray diffractometry, electron backscattering diffractometry, and transmission electron microscopy, with the results showing that coarse Al2Cu particles are fragmented during cryogenic compression. Further, the higher dislocation densities in the cryogenically deformed samples, which lower the activation energies for atomic diffusion, promote the dissolution of particles during subsequent heat treatment. After heat treatment, the volume fraction of coarse particles decreased from 2.5% for a sample processed without deformation, to 0.5% for the sample cryogenically compressed at a ratio of 20%. Meanwhile, the higher dislocation density provides more nucleation sites for recrystallization during heat treatment. Consequently, at 33 μm, the average size of the grains in the 20% cryogenically compressed sample was much smaller than the size of the grains in the uncompressed sample (500 μm). This microstructural refinement increased the ultimate tensile strength, yield strength, and elongation from 445 MPa, 363 MPa, and 7.1% in the undeformed sample, to 471 MPa, 377 MPa, and 13.4%, respectively, in the cryogenically compressed sample.

Effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled TRIP steel

The scanning electron microscope, transmission electron microscope, optical microscope, X-ray diffraction and hardness tests were used to investigate the effect of deformation parameters in unrecrystallization range on microstructural characteristics in Al-bearing hot-rolled transformation-induced plasticity steel. The thermomechanical-controlled processing was carried out with thermomechanical simulation machine, and the samples were compressed to compression strains of 0, 0.15, 0.25 and 0.35 at compression temperatures of 850, 900 and 950 °C. The results showed that the volume fraction of polygonal ferrite increased with the increasing compression strain, while the volume fraction of retained austenite reached the maximum value at compression strain of 0.25. The volume fraction of polygonal ferrite decreased with the increasing compression temperature, whereas the volume fraction of retained austenite possessed the maximum value at compression temperature of 850 °C. Some granular retained austenite was present in uncompressed samples, and some pearlite appeared at large compression strain, while the hardness of the samples exhibited the similar variation tendency to the volume fraction of retained austenite.

Large number tracking of depth and mechanics dependent calcium signaling in chondrocytes of articular cartilage

Purpose: Moderate loading of cartilage stimulates chondrocytes to synthetize matrix proteins, but excessive loading can lead to apoptosis. It is well known that macroscale strains affect cell health, but the mechanism behind how tissue level strain causes cellular and subcellular biological response is poorly understood. Previous work done by our group showed impact-induced tissue strain resulting in mitochondrial depolarization in chondrocytes, with correlation between strain and chondrocyte death, demonstrating the importance of microscale mechanics driving chondrocyte fate after impact. The correlation between strain and mitochondrial dysfunction indicates the mitochondria’s role in mechanosensing. However, the mechanotransduction and cell signaling pathway driving this process has not been fully characterized. In traumatic brain injury, Ca2+ signaling is known to produce mitochondrial swelling, while in other tissues Ca2+ is buffered by mitochondria. However, if too much Ca2+ is taken up, the mitochondrial permeability transition pore will open, leading to depolarization and cell death. In brain injury, this process can be averted if the mitochondrial swelling is addressed immediately. This indicates an opportunity to introduce mitoprotective therapies in a similar vein in articular cartilage. To better understand chondrocyte fate and investigate the process of mitochondrial depolarization after strain, an understanding of the Ca2+ signaling during mechanical stimulation is required. We predict that chondrocytes in different regions of cartilage will show different Ca2+ signal responses, in relation to the depth dependent compressive and shear properties of the tissue. In order to test this prediction, we compare changes in Ca2+ signaling under various magnitudes of compressive and shear strain, and compare the signaling response with previous work that determined impact-induced strain thresholds for mitochondrial dysfunction and chondrocyte death. Methods: Explants of articular cartilage were sterilely dissected from the femoral condyles of neonatal calves. The explants were cultured in a solution of DMEM and Antibiotic-Antimycotic for 24 hours. After removal from culture, the explants were vertically bisected into hemicylinders. They were stained for Ca2+ ions in 5μM Fluo-8 AM for one hour at 37° C, and rinsed in pure DMEM three times for ten minutes each to remove excess stain. The bisected samples were affixed to a custom-built Tissue Deformation Imaging Stage (TDIS) that can apply compressive and shear strain while directly imaging the tissue on a Zeiss LSM 510 inverted confocal microscope [Fig. 1]. Each sample was subjected to compression and shear. Recordings were made for 1000s while uncompressed, immediately following compression, post-relaxation, and immediately following shear. From these videos we were able to extract cell locations as a function of time through a centroid tracking algorithm [Fig. 2]. We extracted location and intensity information for all cells framed within a 636× 636μm frame (∼1000 cells per video), and identified cells showing Ca2+ transients. Local strain was calculated using a 2D digital image correlation program and the intensity curve of each cell was matched with the corresponding local strain. Results: Cell tracking showed different families of curves in Ca2+ signal intensity for cells located in the superficial (0 to 200μm depth) and middle (> 200μm depth) regions [Fig. 3], as well as multiple different families of cell signals present for uncompressed, compressed, and sheared samples [Fig. 4]. Increased proportion of cells showing Ca2+signaling was observed at greater compressive strain and in comparison with unstrained samples, indicating a threshold at which abnormal Ca2+ signaling occurs. Conclusions: The development of a technique to track a large number of cells in a non-equilibrium state is an improvement upon previous methods. This method allows for the study of transient signals despite changes in location and brightness, allows for large-scale tracking of cells for population statistics and provides the basis to directly study the relationship between Ca2+ signaling and mitochondrial response. The observation of differences in cell Ca2+ signaling between the surface and middle zones before any tissue strain was applied reinforces the idea that the superficial layer has a protective role for articular cartilage. This is in agreement with previous work showing that removal of the superficial layer allowed strain to penetrate deeper into the tissue. The identification of strain thresholds for increased Ca2+ signaling aligns with previous work showing strain thresholds for mitochondrial depolarization and cell death, further promoting the role that Ca2+ has in the cellular response pathway to strain.View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Air flow through confined metal foam passage: Experimental investigation and mathematical modelling

This paper deals with flow behaviour through a confined passage filled with metal foams (MFs). Two sets (four samples) of aluminium foams of 20 and 40 ppi pore densities with 9–11% and 12–16% relative densities (RD) individually (as per supplier’s specification) were used for the study. Former RD belonged to uncompressed metal foams whereas the later was achieved by unidirectional compression of metal foam of 6–8% RD. Measured porosities of the uncompressed 20 and 40 ppi MF samples were equal, which was 0.88. However, measured porosities were 0.83 and 0.86 for compressed 20 and 40 ppi MF samples. Flow characteristics of both compressed and uncompressed samples were experimentally measured. Fourie-Plessis’s representative unit cell (RUC) model was used as an analytical tool for estimating pressure drop gradient through MFs because of its simplistic approach and independency from flow characteristics. Possible encasing wall effect on pressure drop was theoretically conducted. Due to a significant difference in estimated and experimentally obtained pressure drop gradient, authors have proposed a modification in the RUC model. The modified version of the RUC model was able to estimate pressure drop gradient of the uncompressed samples with a considerably higher accuracy.

D-DSC: Decoding Delay-based Distributed Source Coding for Internet of Sensing Things.

Spatial correlation between densely deployed sensor nodes in a wireless sensor network (WSN) can be exploited to reduce the power consumption through a proper source coding mechanism such as distributed source coding (DSC). In this paper, we propose the Decoding Delay-based Distributed Source Coding (D-DSC) to improve the energy efficiency of the classical DSC by employing the decoding delay concept which enables the use of the maximum correlated portion of sensor samples during the event estimation. In D-DSC, network is partitioned into clusters, where the clusterheads communicate their uncompressed samples carrying the side information, and the cluster members send their compressed samples. Sink performs joint decoding of the compressed and uncompressed samples and then reconstructs the event signal using the decoded sensor readings. Based on the observed degree of the correlation among sensor samples, the sink dynamically updates and broadcasts the varying compression rates back to the sensor nodes. Simulation results for the performance evaluation reveal that D-DSC can achieve reliable and energy-efficient event communication and estimation for practical signal detection/estimation applications having massive number of sensors towards the realization of Internet of Sensing Things (IoST).