Coupling polaritons in near-field radiative heat transfer between multilayer graphene/vacuum/α-MoO3/vacuum heterostructures.

Both materials and structures can significantly affect radiative heat transfer, which is more pronounced in the near-field regime of two-dimensional and hyperbolic materials, and has promising prospects in thermophotovoltaics, radiative cooling, and nanoscale metrology. Hence, it is important to investigate the near-field radiative heat transfer (NFRHT) in complicated heterostructures consisting of two-dimensional and hyperbolic materials. Recent studies have reported that adding vacuum layers to multilayer structures can effectively enhance the NFRHT. Take the case of multilayer graphene/α-MoO3 heterostructures: the effect of vacuum layers on these heterostructures has not been studied, and hence investigations on adding vacuum layers between graphene and α-MoO3 layers should be emphasized. In this work, we conduct an investigation of the NFRHT between multilayer graphene/vacuum/α-MoO3/vacuum heterostructures. Compared to unit graphene/α-MoO3 heterostructures without vacuum layers, it is found that NFRHT between the heterostructures with vacuum layers can be suppressed to 49.1% when the gap distance is 10 nm, and can be enhanced to 16.3% when the gap distance is 100 nm. These phenomena are thoroughly explained by the coupling of surface plasmon polaritons and hyperbolic phonon polaritons. Energy transmission coefficients and spectral heat flux are analysed during the calculations changing chemical potentials of graphene, thicknesses of vacuum layers, and α-MoO3 layers. This study is expected to provide guidance in implementing the thermal management of reasonable NFRHT devices based on graphene/α-MoO3 heterostructures.

Thermal Insulation Performance of SiC-Doped Silica Aerogels under Large Temperature and Air Pressure Differences.

Silica aerogel composite is an excellent thermal insulator for spacecraft under high-temperature and complex air environments. This study intends to evaluate SiC-doped silica aerogel's thermal insulation performance under large temperature and air pressure differences. In this paper, the hot surface's temperature response of SiC-doped silica aerogel with different content was studied at significant temperature differences (ΔT) when pressure changes instantaneously. Their thermal insulation performance was evaluated by analyzing the influence of pressure gradients on the unsteady-state heat transfer. When the cold surface's temperature of the specimen keeps constant at 15 °C and ΔT = 171~912 K, the results demonstrate that the correlative thermal conductivities of silica aerogel with 1% and 5.84% SiC are 0.02223~0.04077 W·m−1·K−1 at P ≈ 10 Pa and 0.03165~0.04665 W·m−1·K−1 at P = 1 atm, respectively. The aerogel composite with 0% SiC showed the best thermal insulation performance at ΔT < 200 K and P ≈ 10 Pa, while the aerogel with 5.84% SiC became the best at ΔT > 700 K and P = 1 atm. In addition, the transient pressure decreases will significantly impair the heat transfer of the gas inside the aerogel, thereby weakening the gaseous thermal conductivity and improving the thermal insulation performance.

Enhancing the flow field in parallel spiral-flow column photobioreactor to improve CO2 fixation with Spirulina sp.

A parallel spiral-flow column photobioreactor (PSCP) composed of eight spiral-flow columns, and two pipe headers was designed for scale-up cultivation of microalgae to capture CO2. To solve the disturbance of spiral flow fields among parallel columns, computational fluid dynamics (CFD) simulation was used to optimize the main structural parameters, such as the number and the height of microalgae solution outlet (MSO), to improve flow field structure and enhance the cells' light/dark cycle. The horizontal velocity in the direction of optical path and the turbulent kinetic energy (TKE) reached the peak values of 0.214 m/s and 5.28 m2/s2 when MSO number was four and MSO height was 1.05 m. Meanwhile, the disturbance of the spiral flow field among parallel columns are minimum, and microalgae light/dark cycle frequency was 33.3% higher than that of conventional bubble column photobioreactor. Therefore, the biomass yield and CO2 fixation rate of microalgae increased by 81.5% and 100.5%, respectively.

[ANTERIOR APPROACH DEBRIDEMENT AND BONE GRAFTING WITH SELF-LOCKED TITANIUM PLATE INTERNAL FIXATION FOR TREATING LUMBOSACRAL TUBERCULOSIS].

OBJECTIVE: To explore the effectiveness of stage I anterior approach debridement and autologous iliac crest graft with single self-locked titanium plate internal fixation for the treatment of lumbosacral tuberculosis. METHODS: Seven cases of lumbosacral tuberculosis were treated by stage I anterior approach debridement, autologous iliac crest graft, and single self-locked titanium plate internal fixation between February 2010 and October 2014. There were 5 males and 2 females, aged 18-65 years (mean, 41.6 years). The disease duration was 5-21 months (mean, 8 months). The patients had signs and symptoms of pain in lumbosacral region, radiating pain in unilateral lower limb or bilateral lower limbs, decreased muscular strength and disorders of superficial sensation. According to Frankel classification for spinal injury, 1 case was rated as grade C, 3 cases as grade D, and 3 cases as grade E. Preoperative imaging examination suggested L5, S1 lesions in line with the manifestations of tuberculosis; the lumbosacral angle was 16.4-28.5° (mean, 18.6°). The erythrocyte sedimentation rate was 28-105 mm/1 hour (mean, 61 mm/1 hour). All patients received 4-drug antituberculosis therapy. RESULTS: All patients underwent the operation successfully and all incisions healed at stage I, without relevant complication. All patients were followed up 14-70 months (mean, 25.6 months). All symptoms of tuberculosis disappeared and the erythrocyte sedimentation rate returned to normal. At last follow-up, Frankel classification was returned to E from D in 3 cases, returned to D from C in 1 case. Two cases suffered from pains in the lumbosacral region and at the donor site, 1 case suffered from upper abdominal discomfort and poor appetite,but these symptoms disappeared after symptomatic treatment. At last follow-up, X-ray examination indicated that the lumbosacral angle was 23.4-34.2° (mean, 28.6°). According to Bridwell criteria, 5 cases gained grade I bone fusion, and 2 cases gained grade II bone fusion, without migration of bone graft, or loosening or breakage of titanium plate or bolt. CONCLUSIONS: Stage I anterior approach debridement and autologous iliac crest graft with single self-locked titanium plate internal fixation is safe and effective in treating lumbosacral tuberculosis. It can achieve good bone fusion and stable lumbosacral stability, and maintain good deformity correction.