Entropy Generation Analysis of the Flow Boiling in Microgravity Field.

Entropy generation analysis of the flow boiling in microgravity field is conducted in this paper. A new entropy generation model based on the flow pattern and the phase change process is developed in this study. The velocity ranges from 1 m/s to 4 m/s, and the heat flux ranges from 10,000 W/m2 to 50,000 W/m2, so as to investigate their influence on irreversibility during flow boiling in the tunnel. A phase-change model verified by the Stefan problem is employed in this paper to simulate the phase-change process in boiling. The numerical simulations are carried out on ANSYS-FLUENT. The entropy generation produced by the heat transfer, viscous dissipation, turbulent dissipation, and phase change are observed at different working conditions. Moreover, the Be number and a new evaluation number, EP, are introduced in this paper to investigate the performance of the boiling phenomenon. The following conclusions are obtained: (1) a high local entropy generation will be obtained when only heat conduction in vapor occurs near the hot wall, whereas a low local entropy generation will be obtained when heat conduction in water or evaporation occurs near the hot wall; (2) the entropy generation and the Be number are positively correlated with the heat flux, which indicates that the heat transfer entropy generation becomes the major contributor of the total entropy generation with the increase of the heat flux; (3) the transition of the boiling status shows different trends at different velocities, which affects the irreversibility in the tunnel; (4) the critical heat flux (CHF) is the optimal choice under the comprehensive consideration of the first law and the second law of the thermodynamics.

Oxygen vacancy-rich 2D/0D BiO1-XBr/AgBr Z-scheme photocatalysts for efficient visible light driven degradation of tetracycline.

Semiconductor-based photocatalytic technology, as a green and promising avenue in response to the abuse of antibiotic pollution and human health crisis, is restricted by the limited photo-absorption and fast recombination of photogenerated carriers. In this paper, all these challenges were settled by AgBr particles incorporated into oxygen-deficient BiOBr nanosheets, forming novel oxygen vacancy (OV)-rich 2D/0D Z-scheme heterojunctions. Z-scheme photocatalytic system has an effective separation rate of photogenerated carriers and an ability to maintain original redox capacity. Moreover, introducing OVs in the Z-scheme can not only improve the visible light absorption ability, but also serve as recombination centers, thus promoting the separation of electrons and holes. Notably, the photocatalytic activity of 2D/0D BiO1-XBr/AgBr (2:1) was significantly improved under the irradiation of visible light, removing 81% of tetracycline after 25 min, which was about 2.62 times and 2.03 times as high as those of BiO1-XBr and AgBr, respectively. In addition, the 2D/0D BiO1-XBr/AgBr (2:1) indicated high photocatalytic stability and reusability, and its tetracycline degradation efficiency remained stable after five cycles. In summary, this work suggests that the photocatalysts have a great potential to remove TC and provides a possible strategy for purifying water.

Hesitant Fuzzy Entropy-Based Opportunistic Clustering and Data Fusion Algorithm for Heterogeneous Wireless Sensor Networks.

Limited energy resources of sensor nodes in Wireless Sensor Networks (WSNs) make energy consumption the most significant problem in practice. This paper proposes a novel, dynamic, self-organizing Hesitant Fuzzy Entropy-based Opportunistic Clustering and data fusion Scheme (HFECS) in order to overcome the energy consumption and network lifetime bottlenecks. The asynchronous working-sleeping cycle of sensor nodes could be exploited to make an opportunistic connection between sensor nodes in heterogeneous clustering. HFECS incorporates two levels of hierarchy in the network and energy heterogeneity is characterized using three levels of energy in sensor nodes. HFECS gathers local sensory data from sensor nodes and utilizes multi-attribute decision modeling and the entropy weight coefficient method for cluster formation and the cluster head election procedure. After cluster formation, HFECS uses the same techniques for performing data fusion at the first hierarchical level to reduce the redundant information flow from the first-second hierarchical levels, which can lead to an improvement in energy consumption, better utilization of bandwidth and extension of network lifetime. Our simulation results reveal that HFECS outperforms the existing benchmark schemes of heterogeneous clustering for larger network sizes in terms of half-life period, stability period, average residual energy, network lifetime, and packet delivery ratio.

Environmental Response of 2D Thermal Cloak under Dynamic External Temperature Field.

As a typical representative of transformation thermodynamics, which is the counterpart of transformation optics, the thermal cloak has been explored extensively while most current research focuses on the structural design instead of adaptability and practicability in a dynamic environment. The evaluation of energy processes involved in the thermal cloak under dynamic conditions are also lacking, which is essential to the engineering application of this functional structure. In this paper, based on the dynamic environment of a sinusoidal form with ambient amplitude, distribution density, phase, and temperature difference as variables, we evaluated the cloaking performance and environmental response of a 2D thermal cloak. Considering the heat dissipation and energy loss in the whole procedure, local entropy production rate and response entropy were introduced to analyze the different influences of each environmental parameter on the cloaking system. Moreover, we constructed a series of comprehensive schemes to obtain the fitting equation as well as an appropriate scope to apply the thermal cloak. The results are beneficial to the novel use of the concept of entropy and valuable for further improving the working efficiency and potential engineering applications of the thermal cloak.

Energy-Efficient Multi-Disjoint Path Opportunistic Node Connection Routing Protocol in Wireless Sensor Networks for Smart Grids.

The gradual increase in the maturity of sensor electronics has resulted in the increasing demand for wireless sensor networks for many industrial applications. One of the industrial platforms for efficient usage and deployment of sensor networks is smart grids. The critical network traffic in smart grids includes both delay-sensitive and delay-tolerant data for real-time and non-real-time usage. To facilitate these traffic requirements, the asynchronous working-sleeping cycle of sensor nodes can be used as an opportunity to create a node connection. Efficient use of wireless sensor network in smart grids depends on various parameters like working-sleeping cycle, energy consumption, network lifetime, routing protocol, and delay constraints. In this paper, we propose an energy-efficient multi-disjoint path opportunistic node connection routing protocol (abbreviated as EMOR) for sensor nodes deployed in neighborhood area network. EMOR utilizes residual energy, availability of sensor node's buffer size, working-sleeping cycle of the sensor node and link quality factor to calculate optimum path connectivity after opportunistic connection random graph and spanning tree formation. The multi-disjoint path selection in EMOR based on service differentiation of real-time and non-real-time traffic leads to an improvement in packet delivery rate, network lifetime, end-end delay and total energy consumption.

Arbitrarily shaped thermal cloaks with non-uniform profiles in homogeneous media configurations.

We propose a novel class of "complete" arbitrary thermal cloaks through rotatory linear maps. Different from the conventionally circular and arbitrary shape cloaks, as well as the unconventionally non-continuous shape cloaks, the proposed cloaking performances are observed in non-uniformly structural devices. Four schemes are demonstrated with homogeneous media configurations, and expected cloaking behaviors are exhibited in the internal regions. Further investigations reveal that the proposed devices perform robustness on the thermal profiles. The findings may also open up a novel avenue to generally achieve novel behaviors in the fields of optics, electromagnetics, and so forth.

Control and design heat flux bending in thermal devices with transformation optics.

We propose a fundamental latent function of control heat transfer and heat flux density vectors at random positions on thermal materials by applying transformation optics. The expressions for heat flux bending are obtained, and the factors influencing them are investigated in both 2D and 3D cloaking schemes. Under certain conditions, more than one degree of freedom of heat flux bending exists corresponding to the temperature gradients of the 3D domain. The heat flux path can be controlled in random space based on the geometrical azimuths, radial positions, and thermal conductivity ratios of the selected materials.

Heat flux concentrator based on nanophononic metamaterials.

Heat flux concentrators have important potential applications in thermoelectric generators. In this study, we demonstrated the heat flux concentration characteristic in nanophononic metamaterials using molecular dynamics simulations. The ratio of heat flux (RHF) is used to evaluate the concentration performance, the RHF can reach 1.62. The performance is optimized by varying the height of the nanopillar and the atomic mass of the atoms in the nanopillar. Increasing the atomic mass of the atoms in the nanopillars yields better performance. We found that the main mechanism for concentration is phonon localization in the nanopillar region. Furthermore, when the distance from the surface increases, the low-frequency peak of phonon density of states (PDOS) decreases, the high-frequency peak increases, and the mode participation rate (MPR) transforms from localized to delocalized. This work provides a new design of heat flux concentrator based on nanophononic metamaterials for regulating thermal conduction.

Study on the Irradiation Evolution and Radiation Resistance of PdTi Alloys.

Medium-entropy alloys (MEAs) exhibit exceptional mechanical properties, thermal properties, and irradiation resistance, making them promising candidates for aerospace and nuclear applications. This study utilized molecular dynamics simulations to examine the defect behavior in PdTi alloys under various irradiation conditions. Simulations were performed using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) with the modified embedded-atom method (MEAM) potential to describe interatomic interactions. Various temperatures, primary knock-on atom (PKA) energies, and elemental ratios were tested to understand the formation and evolution of defects. The results show that compared to pure Pd, PdTi alloys with increased entropy exhibit significantly enhanced irradiation resistance at higher temperatures and PKA energies. This study explored the impact of different elemental ratios, including Pd, PdTi1.5, PdTi, and Pd1.5Ti. Findings indicate that increasing the Pd concentration enhances the alloy's irradiation resistance, improving mobility and recombination rates of defect clusters. A one-to-one Pd-to-Ti ratio demonstrated optimal performance. Temperature analysis revealed that at 300 K and 600 K, PdTi alloys exhibit excellent irradiation resistance at a PKA energy of 30 keV. However, as the temperature rises to 900 K, the irradiation resistance decreases slightly, and at 1200 K, the performance is likely to decline further. This study offers some useful insights into the irradiation evolution and radiation resistance of PdTi medium-entropy alloys, which may help inform their potential applications in the nuclear field and contribute to the further development of MEAs in this area.

Heat flux concentrators based on nanoscale phononic metastructures.

In recent years, nanoscale heat flux regulation has been at the forefront of research. Nanoscale heat flux concentration is of potential importance in various applications, but no research has been conducted on local heat flux concentration. In this paper, we designed two heat flux concentrators using patterned amorphous and nanomesh structures, respectively. Using molecular dynamics simulation, we find that the heat flux in the central regions is much higher than that in the adjacent regions, with the concentration ratio arriving at 9-fold. Thus a heat flux concentrator is realized using these nanophononic metastructures. The phonon localization theory was used to explain the underlying mechanism. This work provides a direct design strategy for thermal concentrators using practical nanofabrication technologies.

Nanoscale Thermal Cloaking in Silicon Film: A Molecular Dynamic Study.

Nanoscale thermal shielding is becoming increasingly important with the miniaturization of microelectronic devices. They have important uses in the field of thermal design to isolate electronic components. Several nanoscale thermal cloaks based on graphene and crystalline silicon films have been designed and experimentally verified. No study has been found that simultaneously treats the functional region of thermal cloak by amorphization and perforation methods. Therefore, in this paper, we construct a thermal cloak by the above methods, and the ratio of thermal cloaking and response temperature is used to explore its cloaking performance under constant and dynamic temperature boundary. We find that compared with the dynamic boundary, the cloaking effect produced under the constant boundary is more obvious. Under two temperature boundaries, the thermal cloak composed of amorphous and perforated has a better performance and has the least disturbance to the background temperature field. The phonon localization effect produced by the amorphous structure is more obvious than that of the perforated structure. The phonon localization of the functional region is the main reason for the cloaking phenomenon, and the stronger the phonon localization, the lower the thermal conductivity and the more obvious the cloaking effect. Our study extends the nanoscale thermal cloak construction method and facilitates the development of other nanoscale thermal functional devices.

Microvessel density at different levels of normal or injured bile duct in dogs and its surgical implications.

BACKGROUND: Ischemic recurrent stricture after surgical repair for iatrogenic bile duct injury (BDI) remains a challenge in clinical practice. The present study was designed to investigate whether ischemia is universal and of varied severity at different levels of the proximal bile duct after BDI. METHODS: A total of 30 beagle dogs were randomly divided into control, BDI, and BDI-repaired groups. The BDI animal model was established based on the classic pattern of laparoscopic cholecystectomy-related BDI. The animals were sacrificed on postoperative day 15, and bile duct tissue was harvested to assess microvessel density (MVD) at selected levels of the normal, post-BDI and BDI-repaired bile duct with the CD34 immunohistochemistry technique. RESULTS: In the control group, MVD at level H (high level) was remarkably higher than that at level L (low level). No significant difference was found between MVDs at levels H and M (middle level), as well as at levels M and L. However, the tendency was noted that the closer the level to the hilus, the greater the MVD at that level. In both the BDI and BDI-repaired groups, MVDs at level H were generally greater than those at level L, despite the unremarkable differences between MVDs at neighboring levels. In these two groups, a similar tendency of MVD distribution to that in the control group was found; the closer the level to the injury site, the lower was the MVD at that level. Moreover, compared with the MDVs at the levels M and L in the control group, MVDs at the corresponding levels in the BDI and BDI-repaired groups were all remarkably reduced (P<0.05). In addition, MVDs at all three levels in the BDI group significantly declined further after BDI repair. CONCLUSIONS: After BDI, universal ischemic damage in the injured proximal bile duct develops close to the injury site, while close to the hilus, ischemia is relatively slight. High hepaticojejunostomy, rather than low biloenterostomy or end-to-end duct anastomosis, should be recommended for BDI repair. Great care should be taken to protect the peribiliary plexus during repair.

Directed Thermal Diffusions through Metamaterial Source Illusion with Homogeneous Natural Media.

Owing to the utilization of transformation optics, many significant research and development achievements have expanded the applications of illusion devices into thermal fields. However, most of the current studies on relevant thermal illusions used to reshape the thermal fields are dependent of certain pre-designed geometric profiles with complicated conductivity configurations. In this paper, we propose a methodology for designing a new class of thermal source illusion devices for achieving directed thermal diffusions with natural homogeneous media. The employments of the space rotations in the linear transformation processes allow the directed thermal diffusions to be independent of the geometric profiles, and the utilization of natural homogeneous media improve the feasibility. Four schemes, with fewer types of homogeneous media filling the functional regions, are demonstrated in transient states. The expected performances are observed in each scheme. The related performance are analyzed by comparing the thermal distribution characteristics and the illusion effectiveness on the measured lines. The findings obtained in this paper see applications in the development of directed diffusions with minimal thermal loss, used in novel “multi-beam” thermal generation, thermal lenses, solar receivers, and waveguide.

Photoresponsive colorimetric immunoassay based on chitosan modified AgI/TiO2 heterojunction for highly sensitive chloramphenicol detection.

Chloramphenicol (CAP) is an antibiotic used for a variety of infections, however, it is banned for use in food-producing animals due to its hazards to humans blood. Herein, the highly sensitive photoresponsive colorimetric immunoassay was exploited based on AgI/TiO2 heterojunction nanomaterials. Firstly, chitosan modified AgI/TiO2 photocatalyst (CS-AgI/TiO2) was synthesized by deposition-precipitation method, which was characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS) and Fourier transform infrared spectroscopy (FTIR). Then, by utilizing CS-AgI/TiO2 labeled CAP antibody as tags, a novel competitive-type immunoassay was constructed for detection of CAP on the surface of CAP-BSA modified magnetic bead. The color development of 3,3',5,5'-tetramethylbenzidine (TMB) was obtained under visible light irradiation (λ≥420nm) and the assay was carried out in pH 3.0 ABS buffer solution by UV-Vis spectrophotometry. Under optimal conditions, the absorbance values decreased with the increasing of CAP levels in sample, which exhibited linear in the range of 0.03-12.53nM with a detection limit of 0.03nM. Meanwhile, the selectivity, repeatability, and stability were acceptable. Excitedly, no significant difference was observed for detection of the spiked CAP in the real food samples with the referenced values.

Pt NPs and DNAzyme functionalized polymer nanospheres as triple signal amplification strategy for highly sensitive electrochemical immunosensor of tumour marker.

Highly sensitive determination of tumour markers is the key for early diagnosis of cancer. Herein, triple signal amplification strategy resulting from polymer nanospheres, Pt NPs, and DNAzyme was proposed in the developed electrochemical immunosensor. First, electroactive polymer nanospheres were synthesized by infinite coordination polymerization of ferrocenedicarboxylic acid, which could generate strong electrochemical signals due to plentiful ferrocene molecules. Further, the polymer nanospheres were functionalized by Pt NPs and DNAzyme (hemin/G-quadruplex) with the ability of catalyzing H2O2, which contributes to enhance the electrochemical signals. The prepared conjugations were characterized by transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDX). And the process of preparation was monitored by zeta potential. Based on the sandwich-type immunoassay, the electrochemical immunosensor was constructed employing the conjugations as signal tags. Under optimal conditions, the DPV peak increased with the increasing of alpha fetal protein (AFP) concentration, and the linear range was from 0.1pgmL(-1) to 100ngmL(-1) with low detection limit of 0.086pgmL(-1). Meanwhile, the designed immunosensor exhibited excellent selectivity and anti-interference property, good reproducibility and stability. More importantly, there were no significant differences in analyzing real clinical samples between designed immunosensor and commercial ELISA.

Codon Optimization, Expression in Escherichia coli, and Immunogenicity of Recombinant Chinese Sacbrood Virus (CSBV) Structural Proteins VP1, VP2, and VP3.

Chinese sacbrood virus (CSBV) is a small RNA virus family belonging to the genus Iflavirus that causes larval death, and even the collapse of entire bee colonies. The virus particle is spherical, non-enveloped, and its viral capsid is composed of four proteins, although the functions of the structural proteins are unclear. In this study, we used codon recoding to express the recombinant proteins VP1, VP2, and VP3 in Escherichia coli. SDS-PAGE analysis and Western blotting revealed that the target genes were expressed at high levels. Mice were then immunized with the purified, recombinant proteins, and antibody levels and lymphocyte proliferation were analyzed by ELISA and the MTT assay, respectively. The results show that the recombinant proteins induced high antibody levels and promoted lymphocyte proliferation. Polyclonal antibodies directed against these proteins will aid future studies of the molecular pathogenesis of CSBV.