Narrow Results

This study aims to classify sleep stages using electroencephalogram (EEG) signals to investigate the potential impact of entrepreneurial stress on the sleep quality of entrepreneurial students. Due to high stress and irregular schedules, entrepreneurial students are prone to sleep issues, making accurate detection and analysis of their sleep states highly significant in practice. This study proposes a lightweight deep learning model that combines Depthwise Separable Convolution (DSC) with a Bidirectional Long Short-Term Memory (Bi-LSTM) network to capture the spatiotemporal features of EEG signals. DSC effectively extracts spatial features from EEG data, reducing model complexity and computational cost, while Bi-LSTM enhances the model’s ability to capture temporal dependencies, thereby improving the identification of different sleep stages (W, N1, N2, N3, and REM). This approach balances efficiency and accuracy, making it suitable for environments with limited computational resources. Experiments were conducted on both the public Sleep-EDF dataset and a custom dataset collected from entrepreneurial students. The results show that the model achieved a sleep stage classification accuracy of 93.59% on the Sleep-EDF dataset and 88.98% on the custom entrepreneurial student dataset, demonstrating strong generalization and robustness. Additionally, the model maintained high F1-scores across different sleep stages, with particularly outstanding performance in the classification of N2 and REM stages. This study provides an efficient and interpretable tool for monitoring the sleep health of entrepreneurial students, contributing to further understanding of the relationship between sleep and entrepreneurial psychological states. It offers scientific support for enhancing the health management and learning efficiency of entrepreneurial students.

The modification of liquid metal by electric pulse (EP) is a novel method for grain refinement. In this work, based on the reported structural heredity of EP-modified liquid aluminum, we investigated its viscosity change by using torsional oscillation viscometer. The results validate the viscosity of EP-modified liquid aluminum also decreases with increasing temperature and meets approximately exponential correlation on the whole. Moreover, it is especially important that the EP-modified liquid aluminum has the higher viscosity and possesses the bigger viscous-flow cluster in a certain temperature range, which should be associated with the increase of the order degree of its liquid structure. Differential scanning calorimetry (DSC) measurement also confirms that viewpoint. These coupling results experimentally testify the proposed mechanism of electric pulse modification (EPM) modeled merely by postulation.

The purpose of the study was to comparatively investigate two NiTi orthodontic wires. It is valuable to determine the phase transformation temperature and corrosion characteristics of the orthodontic wires to further study the shape memory effect and corrosion resistance properties. Optical microscope and EDX analysis were used for microstructure characteristics and composition analysis. Differential scanning calorimetry (DSC) was carried out to identify the phase transformation behavior of the two wires. Electrochemical tests in artificial saliva at 37 ±1^°C including polarization and electrochemical impedance spectroscopy (EIS) were used to assess the corrosion resistance and corrosion mechanism of the wires. It was found that the transformation temperature range of A-wire (imported) is narrower while the A_s and A_f are close to the body temperature, which is more suitable in the orthodontic operation at early stage. The corrosion current density of A-wire is lower than that of B-wire (domestically made) while the corrosion potential is higher. EIS test results indicated that the corrosion mechanism was the same. However, the oxide layer formed on the surface of A-wire is more protective.

Our aim is to contribute to comprehension of the phenomena of precipitation in the Al–Zn–Mg alloys. For this, we have made a comparative study of the transformations of phases using the differential scanning calorimetric and the dilatometry. This last technique is relatively new in the case of Al–Zn–Mg alloys. It consists of two opposite effects (contraction and expansion) observed on the dilatometric curves. These effects translate two opposite metallurgical phenomena which are generally the precipitation and the dissolution.

Hydrogen-bonded liquid crystals (HBLCs) have been derived from nonmesogenic citric acid (CA) and mesogenic 4-heptyloxybenzoic acid (7OBA) yielding a highly ordered smectic C (Sm C) phase along with the new smectic X (Sm X) phase which has been identified as fingerprint-type texture. Optical (polarizing optical microscopy), thermal (differential scanning calorimetry) and structural (Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy) properties are studied. A noteworthy observation is that the intermolecular H-bond (between CA and 7OBA) influences on its melting point and clearing temperature of the HBLCs which exhibits lower value than those of the individual compounds. A typical extended mesophase region has been observed in the present complex while varying the mixture ratio (1:1 to 1:3) than those of individual compounds. The change in the ratio of the mesogenic compound in the mixture alters thermal properties such as enthalpy value and thermal span width in nematic (N) region of HBLC complex. Optical tilt angle measurement of CA+7OBA in Sm C phase has been discussed to identify the molecular position in the mesophase.

Hydrogen-bonded ferroelectric liquid crystals (HBFLC) are designed and synthesized from nonmesogenic chiral proton donor compound of (R)-($+$)-Methylsuccinic acid (MSA) and mesogenic proton acceptor compound of 4-undecyloxybenzoic acid (11OBA) in a different mole ratio. Intermolecular hydrogen bonds (H-bond) between the nonmesogenic and mesogenic compounds have been confirmed through experimental Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) computational studies. The steric hindrance and inductive effects of the present complex and its influence on the structure are discussed. A rich phase polymorphism in the liquid crystalline complex has been studied using polarizing optical microscope (POM) and differential scanning calorimetry (DSC). The chiral phases observed in the present complex are due to the presence of lone pair (n) to anti-bonding (${\sigma }^{\ast }$) transition symmetry which is validated by DFT studies. A noteworthy observation of induced smectic A${}^{\ast }$(Sm A${}^{\ast }$) by quenching of traditional phase (nematic) has been identified and the reason for the same has been discussed by DFT studies. The unusual phase order of Sm A${}^{\ast }$, smectic C${}^{\ast }$(Sm C${}^{\ast }$) and smectic G${}^{\ast }$(Sm G${}^{\ast }$) mesogenic phases are observed. The other liquid crystalline parameters are evaluated by experimental and theoretical calculations and the same has been compared. Increased tilt angle in liquid crystal (LC) molecules has been theoretically analyzed by natural bond orbital (NBO) studies. Stability of the HBFLC phases and its origination mechanism have been discussed with the help of highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) energies.

In this work, we performed differential scanning calorimetry (DSC) experiments to investigate the phase transition temperature and the molar enthalpy of the absorbed water confined in porous titanium dioxide. The porous titanium dioxide with three different pore size distribution and different filling fraction of the absorbed water were examined. We found that both the pore size of the examined samples and the filling fraction of the absorbed water affected the water’s phase transition temperature and its molar enthalpy.

In this study, compounds of B₆Si were irradiated using a ${}^{60}$Co gamma source that have an energy line of 1.25 MeV at the absorbed dose rates from 14.6 kGy to 194.4 kGy. Surface morphology images of the sample obtained by Scanning Electron Microscope (SEM) show that the crystal structure at a high absorbed doses $(D\ge 145.8\mathrm{\text{kGy}})$ starts to be destroyed. X-ray diffraction studies revealed that with increasing radiation absorption dose, the spectrum intensity of the sample was decreased 1.96 times compared with the initial value. Thermal properties were studied by Differential scanning calorimetry (DSC) method in the temperature range of 30–1000${}^{\circ }$C.

In this work, Fix 1211 addition has been used in different amount in the iron mix. The samples prepared have been used thermically in the temperature 77${}^{\circ }$C in normal atmosphere condition. The samples thermically developed have been thermically analyzed with the constant 5${}^{\circ }$C/min of 20 ml/min argon gas from 30${}^{\circ }$C up to 900${}^{\circ }$C. Thermo-physical mechanisms have been researched in the cement, sand and road metal with the thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) analysis. Mass kinetics, activation energy and special heat capacity have been researched for different temperature intervals. The decomposition mechanism of the mass in stages and the speed of decomposition is equal to the cost of the heat flow. The mass loss has been determined in 6.99 mg under the first code, 5.82 mg under the second code, 5.63 mg under the third code, 4.65 mg under the fourth code in $30\le T\le 900^{\circ }$C temperature interval. In addition, it has been researched that the activation energy has been changed between 0.56–0.80 eV and 0.23–0.36 eV under each code and phase passage.

B₄C and B₆Si samples have been irradiated by using swift heavy ions and high intense electron beam. Ion irradiation of the samples was carried at the different electron fluences $4.16\times 10^{16}$, $1.20\times 10^{17}$ and $1.03\times 10^{18}$ cm${}^{-2}$ ion/cm², and energy of ions flux 167 MeV. Also, the samples were irradiated with high energy electron beams at the linear electronic accelerator at different electron fluencies up to $1.03\times 10^{18}$ cm${}^{-2}$ and energy of electron beams 2.5 MeV and current density of electron beams $0.075\mu \mathrm{\text{A}}/{\mathrm{\text{cm}}}^2\cdot$s. The unirradiation and irradiation of the thermodynamic kinetics of samples at low-temperature change with a differential mechanism. In the DSC curves, at the low temperature for unirradiation and irradiation, boron carbide and boron silicide samples do not undergo phase transition. But at the $100\le T\le 330$ K temperature range, the thermodynamic mechanism of ions and electron beam irradiation are very difficult and measuring the temperature of conductivity, thermal conductivity, calibration factor, specific heat capacity becomes more complicated.

Thermal parameters of the ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ compound were investigated by Differential Scanning Calorimetry (DSC) method. Four different phases were identified in the temperature range of $20\le T\le 800^{\circ }$C. Thermodynamical parameters were determined for each phase transition. ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ samples were irradiated by 167 MeV energy ${}^{131}$Xe ions at the $5.0\times 10^{12}$, $5.0\times 10^{13}$ and $3.83\times 10^{14}$ ion/cm² intensities. The DSC analyses of the irradiated samples were carried out and determined that the temperature and thermodynamical parameters of the phase transition change in the ${\mathrm{\text{Bi}}}_2{\mathrm{\text{Se}}}_3$ compound under the influence of swift heavy ions. The change mechanism of the thermodynamical parameters has been determined depending on the irradiation doses.

This paper concerns the design method and implementation of main modules, dedicated to miniaturized digital ultrasonic devices, using advanced System-on-Chip technique. It is intended to diagnostic imaging applications such as echography. The proposed implementation allows the integration of all acquisition front end as well as signal and video processing on only one single chip. It will make possible to visualize the ultrasound images in real time. It requires high resolution and real-time image processing. The proposed design, which integrates the B-mode processing modules, includes digital beamforming, quadrature demodulation of RF signals, digital filtering, envelope detection, and video processing of the received signals. This system handles 128 scan lines and 6400 samples per scan line with a 90° angle of view span. The design uses a minimum size look-up memory to store the initial scan information. Rapid prototyping based on ARM/FPGA platform combination is used to validate the operation of the described system. This system offers significant advantages of portability and a rapid time to market.

Direct current electrodeposition of Co–P alloy coatings were carried out using gluconate bath and they were characterized by employing techniques like XRD, FESEM, DSC and XPS. Broad XRD lines demonstrate the amorphous nature of Co–P coatings. Spherical and rough nodules are observed on the surface of coatings as seen from FESEM images. Three exothermic peaks around 290, 342 and 390°C in DSC profiles of Co–P coatings could be attributed to the crystallization and formation of Co₂P phase in the coatings. As-deposited coatings consist of Co metal and oxidized Co species as revealed by XPS studies. Bulk alloy P(P^δ-) as well as oxidized P(P⁵⁺) are present on the surface of coatings. Concentrations of Co metal and P^δ- increase with successive sputtering of the coating. Observed microhardness value is 1005 HK when Co–P coating obtained from 10 g L^-1NaH₂PO₂ is heated at 400°C that is comparable with hard chromium coatings.

Composites of polyvinyl alcohol (PVA) containing silver nanoparticles were prepared using in situ synthesis of nanoparticles. Structure and properties of these composites were investigated using UV-Vis spectroscopy, XRD, DSC, SEM and AFM. The studies show that PVA can reduce the AgNO₃ to yield silver nanoparticles and in the process forms bonds with PVA chains. The anti-bacterial properties of these films were studied by qualitative as well as quantitative methods which gave the values of 98% for gram positive and 89% for gram negative bacteria.

Glycolic acid was polymerized under vacuum in the presence and absence of nano sized clay. The added clay catalyzed the condensation polymerization which can be confirmed by recording FTIR spectroscopy and intrinsic viscosity (IV) values. The relative intensity of C=O/CH is increased while increasing the amount of clay. DSC showed the appearance of multiple endotherms of poly(glycolic acid). TGA showed the percentage weight residue remain above 750°C for polymer-nano composite system was 21% and hence proved the flame retardancy (char forming) nature. TEM confirmed the nano size of the clay used to catalyze the condensation reaction. The intrinsic viscosity value was increased with the increase of percentage weight of Hectorite type clay.

A series of 11 low melting ionic liquids based on meso-substituted A₃B-porphyrins and A₂B₂-porphyrins containing one or two pyridyl substituents have been synthesized in high yields. Three of them are liquids at room temperature. All these porphyrinic salts were characterized by ¹H NMR, ¹⁹F NMR, MALDI-TOF mass spectrometry, elemental analysis and UV-visible spectroscopy. The thermal properties and conductivity values of these salt derivatives have been also measured. A specific conductivity value of up to 4 mS.cm^-1 could be obtained for a compound having the counter-anion B(C₆F₅)₄^-.

Ti(IV) phthalocyanines axially coordinated to 2,3- and 1,8-naphthalenediols have been prepared and characterized. The naphthalene axial ligands have been endowed with none, one or two sulfonate anchoring groups in order to study the performance of the dyes as DSC photosensitizers. All studied compounds showed the same efficiency. The unexpected results suggest displacement of the axial ligand with concomitant formation of a di-μ-oxotitanium-type anchoring moiety between the hydroxylated TiO₂surface and the Ti-phthalocyanine. This is probably the reason why the type of axial ligand does not play any role on the overall device efficiency. The titanium phthalocyanine absorbed in this way shows state selective electron injection were only those photons absorbed by the Soret band are capable to inject electrons into the TiO₂, while photons absorbed by the Q-band result in negligible photocurrent. This fact could explain the low efficiency of the Ti-phthalocyanines.

A phthalonitrile precursor 4-(3-hydroxypropylmercapto)phthalonitrile (3) was synthesized via a base-catalyzed nucleophilic aromatic nitro displacement of 4-nitrophthalonitrile with the 3-mercapto-1-propanol. A novel tetrasubstituted metal-free phthalocyanine (4) (M = 2H) and its metal complexes (5–8) (M = Zn, Ni, Cu and Co) bearing 3-hydroxypropylmercapto moieties were prepared by the cyclotetramerization reaction of (3) with the appropriate materials. The visible spectra of the zinc(II) phthalocyanine (5) was recorded with different concentrations and different ions as Ag⁺, Hg²⁺ and Pb²⁺ in DMF and also with different solvents as dimethylformamide and pyridine. Fluorescence spectrum of the compound (5) was also studied. Temperature and frequency dependence of AC conductivity for (4–8) was investigated in air and under vacuum and were found to be ~10^-8–10^-5 S.m^-1. Thermal properties of the phthalocyanines were examined by differential scanning calorimetry. All the novel compounds have been characterized by elemental analysis, UV-vis, FT-IR, NMR and MS spectral data and DSC techniques.

Nano-Mg(OH)₂ was synthesized by co-precipitation method. Peaks between 500 and 1250 cm^-1 in FTIR spectroscopy confirmed the presence of metal hydroxide stretching. TGA inferred that above 600°C, 50% of residue weight remained. HRTEM of nanocomposite gave an idea about the nonspherical morphology of particles of size 25 nm to 30 nm. SEM inferred that flower-like morphology for pristine Mg(OH)₂ and higher % weight of aniline-intercalated Mg(OH)₂ had agglomerated structure. UV visible spectrum inferred the presence of Mg²⁺ ion at 275 nm and the presence of amino-group-intercalated Mg(OH)₂, which had a sharp peak at 193 nm and the intensity of which increases with the increase in % weight of aniline. PL inferred that aniline-intercalated Mg(OH)₂ showed a lower intensity of which increased with higher wavelength value than the pristine and nanocomposite with PVA.

Ice storage is one technique for effective use of thermal energy. Application of bionucleant (a protein from the bacterium Pseudomonas syringae) as a snow inducer in ski field has shown great potential to enhance the quantity of snow and increase freezing temperature. In this study, differential scanning calorimeter (DSC) and lab-built ice formation reactor were employed to study experimentally the heterogeneous ice nucleation under super-cooled conditions at different dissolved bionucleant concentrations. It was found the degree of supercooling is reduced by addition of bionucleant. However, ice nucleation-activity of bionucleant will drop down when bionucleant solution is saturated/supersaturated. In our DSC measured heat release study, when bionucleant acts as ice nucleation agent in aqueous solution, prior to reaching its saturation/supersaturation, there is an increase in latent heat release during freezing/melting as the amount of dissolved bionucleant increases. In another test, the supercooling does not occur in 0.5% bionucleant solution, it began to freeze around 0°C. Our results suggest that, the addition of bionucleant may help induce ice nucleation and increase freezing temperature thereby reduces the energy consumption of ice formation for cold storage.