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A highly efficient photoenergy conversion is strongly dependent on the cumulative cascade efficiency of the photogenerated carriers. Spatial heterojunctions are critical to directed charge transfer and, thus, attractive but still a challenge. Here, a spatially ternary titanium-defected TiO2@carbon quantum dots@reduced graphene oxide (denoted as VTi@CQDs@rGO) in one system is shown to demonstrate a cascade effect of charges and significant performances regarding the photocurrent, the apparent quantum yield, and photocatalysis such as H2 production from water splitting and CO2 reduction. A key aspect in the construction is the technologically irrational junction of Ti-vacancies and nanocarbons for the spatially inside-out heterojunction. The new "spatial heterojunctions" concept, characteristics, mechanism, and extension are proposed at an atomic-/nanoscale to clarify the generation of rational heterojunctions as well as the cascade electron transfer.

A highly efficient photoenergy conversion is strongly dependent on the cumulative cascade efficiency of the photogenerated carriers. Spatial heterojunctions are critical to directed charge transfer and, thus, attractive but still a challenge. Here, a spatially ternary titanium-defected TiO

The interfacial co-existence of oxygen and metal vacancies in metal oxide semiconductors and their highly efficient carrier transport have rarely been reported. This work reports on the co-existence of oxygen and titanium vacancies at the interface between TiO

TiO2 hierarchical microsphere assembled from anatase TiO2 nanosheets has been successfully prepared and exhibited excellent catalytic activities of H2 production and benzyl alcohol selective oxidized to benzaldehyde. These enhanced photoactivity can be mainly ascribed to the charge separation promoted by the surface F and nanosheet units, enhancement of substrate molecular transport profited from the hierarchical structure.

Correction for 'Synthesis of hydrophobic and hydrophilic TiO2 nanofluids for transformable surface wettability and photoactive coating' by Jie Hu et al., Chem. Commun., 2019, 55, 9275-9278.

Two modified TiO

Aiming at the “cabin” fire safety design concept in large space buildings, and combined with a real cabin with a spray system, Large Eddy Simulation was used for simulating the flow state of cabin fire smoke under sprinkler spray. The effect of sprinkler spray on overflowing smoke layer and the characteristics of overflowing smoke under sprinkler spray were analyzed and discussed. Results showed that sprinkler spray had a good cooling effect on smoke layer, but it made smoke layer unstable at the same time, leading to the smoke congestion phenomenon. As a result, smoke spillage was added, and the characteristics of overflowing smoke were significantly changed.

Two orthogonal modulation optical label switching(OLS) schemes, which are based on payload of polarization multiplexing-differential quadrature phase shift keying(POLMUX-DQPSK or PDQ) modulated with identifications of duobinary (DB) label and pulse position modulation(PPM) label, are researched in high bit-rate OLS network. The BER performance of hybrid modulation with payload and label signals are discussed and evaluated in theory and simulation. The theoretical BER expressions of PDQ, PDQ-DB and PDQ-PPM are given with analysis method of hybrid modulation encoding in different the bit-rate ratios of payload and label. Theoretical derivation results are shown that the payload of hybrid modulation has a certain gain of receiver sensitivity than payload without label. The sizes of payload BER gain obtained from hybrid modulation are related to the different types of label. The simulation results are consistent with that of theoretical conclusions. The extinction ratio (ER) conflicting between hybrid encoding of intensity and phase types can be compromised and optimized in OLS system of hybrid modulation. The BER analysis method of hybrid modulation encoding in OLS system can be applied to other n-ary hybrid modulation or combination modulation systems.

We present a sensitive optical sensor design by integrating a circular-hole defect with an etched diffraction grating (EDG) spectrometer based on amorphous-silicon photonic platforms. The circular-hole defect obtained from the outdiffusion of the hydrogen in the annealing process can induce strong resonant scattering loss at some special wavelengths. The positions of resonant peaks will linearly shift with the refractive index change of the detected sample (the sensitivity is $\sim$9200 nm/RIU). In addition, the influences of the defect on the sensing characteristics are numerically analyzed based on a scalar diffraction method and a Green tensor technology.

Planar waveguide gratings have shown great potential for the application of the wavelength division multiplexing (WDM) functionality in optical communications due to their compactness and high spectral flnesse. Planar gratings based on silicon nanowire technology have high light conflnements and consequently very high integration density, which is 1{2 orders of magnitude smaller than conventional silica based devices. In the present paper, we will simulate the silicon nanowire based planar grating multiplexer with total-internal-re∞ection facets using a boundary integral method. The polarization dependent characteristics of the device are analyzed. In addition, the planar grating multiplexer with 1nm spacing is fabricated and characterized. Compared with measured values, the numerical results show that the sidewall roughness in the grating facets can result in a large insertion loss for the device.

Four groups of small-scaled ethanol pool fire experiment with different aspect-ratio(s) is undertaken, to gauge the mass loss rate of fuel as well as the plume centerline temperature distribution. Comparison of plume centerline temperature is made between the theoretical values estimated by Heskestad plume model and experimental results, which indicates that: with the increasing of s, the difference between theoretical values and experimental values tend to grow greater; and when s≈1, theoretical values and experimental values cohere well.

The present paper is engaged in an experimental study over a rise-time of smoke layer interface and deduced the relation between dimensionless rise-time of smoke layer interface and dimensionless height of the shaft. Based on the theoretical results, the risetime of smoke layer interface is measured by using small scale shaft which are located at the PolyU/USTC Atrium. Our study shows that the rise-time of the smoke layer interface be inversely proportional to the 1/3 power of heat release rate of the fire source, and proportional to the 1.05 and the 1.50 power of the height in open and closed shafts, respectively. Furthermore, it is also proved that the smoke layer interface movement in open shaft be faster than that in a free space and closed shaft due to the stack effect. Under the same fire source and shaft dimensions, the velocity of smoke spreading in closed shaft is the least one.

Smoke control by a horizontal ceiling vent in an atrium is studied in this paper. A bi-directional airflow moving upward and downward across the vent might be observed and this would affect the efficiency of smoke extraction. Whether the flow is bi-directional or uni-directional depends on the pressure difference across the vent upon activation. Before opening the horizontal ceiling vent, the pressure difference should be higher than a critical value. Thickness of the smoke layer formed under the ceiling before opening the vent is found to be important. The required smoke layer thickness for getting such a critical pressure is discussed in this paper. Two situations of no temperature difference between the inside and outside of the atrium; and the outside temperature is higher than the inside temperature, are considered.

Experimental studies on natural smoke filling during an atrium fire were carried out in a new full-scale burning facility: the PolyU/USTC Atrium with inner length 22.4 m, width 11.9 m and height 2.7 m. Diesel pool fires were located at the floor with all the windows and vents of the atrium closed, leaving just a vertical gap for supplying fresh air. Two sets of experiments, each consisting of 20 hot smoke tests with pool diameters 0.6 m and 1.0 m, were per formed. Transient mass of the burning fuel, vertical temperature distributions and descending time of the smoke layer were measured. Results compiled from the tests were compared with those predicted by a smoke filling model developed from a plume equation that appeared in the literature.

A design and fabrication for planar grating demultiplexers based on a nano silicon platform are presented to obtain both a flat passband and a low crosstalk using the optimal size and structure for each grating facet. Measured results show a ∼−30 dB crosstalk and a ∼70 GHz 3 dB bandwidth can be obtained with acceptable additional loss.