A robust method for heart sounds localization using lung sounds entropy

Heart sounds are the main unavoidable interference in lung sound recording and analysis. Hence, several techniques have been developed to reduce or cancel heart sounds (HS) from lung sound records. The first step in most HS cancellation techniques is to detect the segments including HS. This paper proposes a novel method for HS localization using entropy of the lung sounds. We investigated both Shannon and Renyi entropies and the results of the method using Shannon entropy were superior. Another HS localization method based on multiresolution product of lung sounds wavelet coefficients adopted from was also implemented for comparison. The methods were tested on data from 6 healthy subjects recorded at low (7.5 ml/s/kg) and medium 115 ml/s/kg) flow rates. The error of entropy-based method using Shannon entropy was found to be 0.1 +/- 0.4% and 1.0 +/- 0.7% at low and medium flow rates, respectively, which is significantly lower than that of multiresolution product method and those of other methods reported in previous studies. The proposed method is fully automated and detects HS included segments in a completely unsupervised manner.     

Ambulatory center of mass prediction using body accelerations and center of foot pressure

The center of body mass (COM), center of foot pressure (COP), and body segment acceleration signals are commonly used to indicate movement performance and stability during standing activities and walking. For balance maintenance and restoration, the human brain is capable of estimating and predicting the COM even in the absence of visual or vestibular information. Thus, we hypothesized that the COM may be acquired through the processing of proprioceptive somatosensory information, represented by body segment accelerations, and an external spatial reference, the ground support, represented by the COP. To investigate this hypothesis, we modeled the relationships that exist between the COP and accelerometer data with the 3-D COM trajectory, during walking on firm and irregular surfaces. The models accounted for 99.85 +/- 0.20% and 99.77 +/- 0.39% of the resultant COM trajectory's variability for the firm and irregular surfaces, respectively. This corresponded to a percentage error between the estimated and actual resultant COM of 16.06 +/- 11.11% for the firm surface and 21.41 +/- 12.70% for the doweling surface. In turn, this translates into an absolute error between the true and actual resultant COM of 3.62 +/- 2.69 cm and 4.74 +/- 3.01 cm for the firm and doweling surfaces, respectively. The model is novel in that it does not require any calibration and provides a reasonably accurate estimation of the COM, which can be compared to the brain's balance performance. Hence, this model could be used instead of the cumbersome method of video motion analysis for COM calculation.     

A robust method for estimating respiratory flow using tracheal sounds entropy

The relationship between respiratory sounds and flow is of great interest for researchers and physicians due to its diagnostic potentials. Due to difficulties and inaccuracy of most of the flow measurement techniques, several researchers have attempted to estimate flow from respiratory sounds. However, all of the proposed methods heavily depend on the availability of different rates of flow for calibrating the model, which makes their use limited by a large degree. In this paper, a robust and novel method for estimating flow using entropy of the band pass filtered tracheal sounds is proposed. The proposed method is novel in terms of being independent of the flow rate chosen for calibration; it requires only one breath for calibration and can estimate any flow rate even out of the range of calibration flow. After removing the effects of heart sounds (which distort the low-frequency components of tracheal sounds) on the calculated entropy of the tracheal sounds, the performance of the method at different frequency ranges were investigated. Also, the performance of the proposed method was tested using 6 different segment sizes for entropy calculation and the best segment sizes during inspiration and expiration were found. The method was tested on data of 10 healthy subjects at five different flow rates. The overall estimation error was found to be 8.3 +/- 2.8% and 9.6 +/- 2.8% for inspiration and expiration phases, respectively.     

Associative Liquid-In-Liquid 3D Printing Techniques for Freeform Fabrication of Soft Matter

Shaping soft materials into prescribed 3D complex designs has been challenging yet feasible using various 3D printing technologies. For a broader range of soft matters to be printable, liquid-in-liquid 3D printing techniques have emerged in which an ink phase is printed into 3D constructs within a bath. Most of the attention in this field has been focused on using a support bath with favorable rheology (i.e., shear-thinning behavior) which limits the selection of materials, impeding the broad application of such techniques. However, a growing body of work has begun to leverage the interaction or association of the two involved phases (specifically at the liquid–liquid interface) to fabricate complex constructs from a myriad of soft materials with practical structural, mechanical, optical, magnetic, and communicative properties. This review article has provided an overview of the studies on such associative liquid-in-liquid 3D printing techniques along with their fundamentals, underlying mechanisms, various characterization techniques used for ensuring the structural stability, and practical properties of prints. Also, the future paths with the potential applications are discussed.     

Application of modified nanoporous materials in ascorbic acid adsorption

In this study, three types of mesoporous materials Santa Barbara no. 15 (SBA-15), carbon mesostructured by KAIST (CMK-3), and modified carbon mesostructured by KAIST (modified CMK-3) were prepared and their capability as sorbents for vitamin C (ascorbic acid) adsorption from aqueous solutions was compared with each other. Cetyltrimethylammonium bromide (CTAB) was used for surface modification of CMK-3. The structures of different adsorbents were characterized by X-ray diffraction (XRD) and N₂ adsorption measurements, and the functionalization of CMK-3 was proved by XRD technique. The adsorption isotherms, sorption kinetics as well as the effects of some parameters such as pH value of the vitamin solution, adsorption time, and the initial vitamin concentration on the adsorption capacity of the analyte on CTAB/CMK-3 were investigated. It was found that the ultimate capacity of the adsorbents varied in the order CTAB/CMK-3?>?CMK-3?>?SBA-15. Langmuir and Freundlich isotherm models have been used to fit equilibrium data for CTAB/CMK-3. The equilibrium data were best represented by the Langmuir isotherm. Kinetic studies were performed and it was determined that the sorption kinetics of vitamin C was truly described by a pseudo-second-order kinetic model.     

Hill Matrix and Radix-64 Bit Algorithm to Preserve Data Confidentiality

There are many cloud data security techniques and algorithms available that can be used to detect attacks on cloud data, but these techniques and algorithms cannot be used to protect data from an attacker. Cloud cryptography is the best way to transmit data in a secure and reliable format. Various researchers have developed various mechanisms to transfer data securely, which can convert data from readable to unreadable, but these algorithms are not sufficient to provide complete data security. Each algorithm has some data security issues. If some effective data protection techniques are used, the attacker will not be able to decipher the encrypted data, and even if the attacker tries to tamper with the data, the attacker will not have access to the original data. In this paper, various data security techniques are developed, which can be used to protect the data from attackers completely. First, a customized American Standard Code for Information Interchange (ASCII) table is developed. The value of each Index is defined in a customized ASCII table. When an attacker tries to decrypt the data, the attacker always tries to apply the predefined ASCII table on the Ciphertext, which in a way, can be helpful for the attacker to decrypt the data. After that, a radix 64-bit encryption mechanism is used, with the help of which the number of cipher data is doubled from the original data. When the number of cipher values is double the original data, the attacker tries to decrypt each value. Instead of getting the original data, the attacker gets such data that has no relation to the original data. After that, a Hill Matrix algorithm is created, with the help of which a key is generated that is used in the exact plain text for which it is created, and this Key cannot be used in any other plain text. The boundaries of each Hill text work up to that text. The techniques used in this paper are compared with those used in various papers and discussed that how far the current algorithm is better than all other algorithms. Then, the Kasiski test is used to verify the validity of the proposed algorithm and found that, if the proposed algorithm is used for data encryption, so an attacker cannot break the proposed algorithm security using any technique or algorithm.     

Controlling Nanoscale Thermal Expansion of Monolayer Transition Metal Dichalcogenides by Alloy Engineering

2D materials, such as transition metal dichalcogenides (TMDs), graphene, and boron nitride, are seen as promising materials for future high power/high frequency electronics. However, the large difference in the thermal expansion coefficient (TEC) between many of these 2D materials could impose a serious challenge for the design of monolayer‐material‐based nanodevices. To address this challenge, alloy engineering of TMDs is used to tailor their TECs. Here, in situ heating experiments in a scanning transmission electron microscope are combined with electron energy‐loss spectroscopy and first‐principles modeling of monolayer Mo_1?xW_xS₂ with different alloying concentrations to determine the TEC. Significant changes in the TEC are seen as a function of chemical composition in Mo_1?xW_xS₂, with the smallest TEC being reported for a configuration with the highest entropy. This study provides key insights into understanding the nanoscale phenomena that control TEC values of 2D materials.     

A split-aperture transmit beamforming technique with phase coherence grating lobe suppression

A small element-to-element pitch (~.5λ) is conventionally required for phased array ultrasound transducers to avoid large grating lobes. This constraint can introduce many fabrication difficulties, particularly in the development of highfrequency phased arrays at operating frequencies greater than 30 MHz. In this paper, a new transmit beamforming technique along with sign coherence factor (SCF) receive beamforming is proposed to suppress grating lobes in large-pitch phased-array transducers. It is based on splitting the transmit aperture (N elements) into N/K transmit elements and receive beamforming on all N elements to reduce the temporal length of the transmit grating lobe signal. Therefore, the use of synthetic aperture beamforming, which can introduce relative phase distortions between the echoes received over many transmit events, can be avoided. After each transmit-receive event, the received signals are weighted by the calculated SCF to suppress the grating lobes. After pulsing all sub-apertures, the RF signals are added to generate one line of the image. Simulated 2-way radiation patterns for different K values show that grating lobes can be suppressed significantly at different steering angles. Grating lobes can be suppressed by approximately 20 dB with K = 2 at steering angles greater than 25° and an element pitch greater than 0.75λ. A technique for determining the optimal transmit sub-apertures has been developed.     

Effect of addition of tin on the microstructure and machinability of α-brass

This study was aimed at developing lead-free brass alloys with the goal of substituting lead element with tin. For this purpose, lead-free alloys with tin were developed and the microstructure, hardness and machining behaviour of the Cu–30%Zn alloy was compared with Cu–30%Zn–x%Sn (x?= 1.2, 3.2, 5.4, 8, 11.4, 13.9, 17.4). The results showed that the addition of Sn to single-α phase brass led to the formation of duplex (α?+?β′) brass and then the formation of (β′?+?? ) brass both with increased hardness. In addition, the addition of Sn to Cu–30%Zn alloy led to the decrement of equivalent machining forces (F_m), surface roughness and also the promotion of chip fragmentation due to the formation of the β′ phase, which is an improvement in machinability.     

Catalytic chemical vapour deposition synthesis of carbon spheres

Carbon spheres (CSs) were successfully grown in the presence of cobalt-silicon-mesoporous aluminum silicate (Co-Si-MAS) by chemical vapour deposition (CVD) using C₂H₂ as the source of carbon at 850 °C. The Co-Si-MAS catalysts with Si/Al molar ratios of 25, 50, 100 and 150 were synthesized by sol-gel preparation and followed by anchoring process. The scanning electron microscopy (SEM), transmission electron microscopy (TEM) images and Raman spectroscopy experiments showed that the obtained CSs possess nearly perfect spheres with diameters range from 650 to 1000 nm. It was found that CSs were fabricated under a thin film that was deposited during the catalytic reaction. On the basis of qualitative analysis it was revealed that the film included cobalt, silicon and aluminum elements. This thin film was applied as a catalyst for the synthesis of CSs.