Mode-pairing quantum key distribution with advantage distillation

Mode-pairing quantum key distribution (MP-QKD) is an easy-to-implement scheme that transcends the Pirandola--Laurenza--Ottaviani--Banchi bound without using quantum repeaters. In this paper, we present an improvement of the performance of MP-QKD using an advantage distillation method. The simulation results demonstrate that the proposed scheme extends the transmission distance significantly with a channel loss exceeding 7.6 dB. Moreover, the scheme tolerates a maximum quantum bit error rate of 8.9%, which is nearly twice that of the original MP-QKD. In particular, as the system misalignment error increases, the expandable distance of the proposed scheme also increases. The proposed system is expected to promote the practical implementation of MP-QKD in a wide range of applications, particularly in scenarios involving high channel losses and system errors

Combustion Characteristics of Hydrogen-methane Hybrid Fuels

ABSTRACT As the development and increasingly widespread use of IGCC and zero emission energy system, the development of advanced combustion capabilities for gaseous hydrogen and hydrogen rich fuels in gas turbine applications is becoming an area of much great concern. The combustion characteristics of hydrogen rich fuel is very different from nature gas in aspects such as flame stability, flame temperature, combustor acoustics, pollutant emissions, combustor efficiency, and some other important quantities. However, few of these issues are clearly understood by far. The purpose of this paper is to compare in detail the combustion performance of hydrogen-methane hybrid fuels with various volumetric H 2 fractions ranging from 0% to 100%. Meanwhile, the comparison of pure H 2 , pure CH 4 , and 80%H 2 +20%CH 4 was the emphasis. 80%H 2 +20%CH 4 hybrid gas is selected expressly because its component is approximately equal to the outcome of a hydrogen production test bed of our laboratory, and it is considered by the team to be a potential transition fuel of gas turbines between nature gas and pure hydrogen. Detailed experimental measurements and numerical simulations were conducted using a coflow jet diffusion burner. It was found that in the extent of experiments, when under equal general power, the flame length of hydrogen contained fuels wasn't much shorter than methane, and didn't get shorter with the increase of H 2 fraction as expected. That was because the shortening tendency caused by the increase of H 2 fraction was counteracted partially by the increase of fuel velocity, results of which was the extending of flame length. Maximum temperature of H 2 flame was 1733K, which was 30K higher than 80%H 2 +20%CH 4 and 120K higher than CH 4. All of the highest temperatures of the three fuels were presented at the recirculation zone of the flame. Although it seemed that the flame of CH 4 had the longest dimension compared with H 2 contained fuels when observed through photos, the high temperature region of flames was getting longer when increasing H 2 fractions. Curves of temperature distribution predicted by all the four combustion models in FLUENT investigated here had a departure away from the experimental data. Among the models, Flamelet model was the one whose prediction was comparatively close to the experimental results. Flame of H 2 and 80%H 2 +20%CH 4 had a much better stability than flame of CH 4 , they could reach a so called recirculating flame phase and never been blew out in the extent of experiments. On the contrary, CH 4 flames were blew out easily soon after they were lifted up. Distribution of OH concentration at the root of flames showed that the flame boundary of H 2 and 80%H 2 +20%CH 4 was more clearly than CH 4. That is to say, at the root of the flame, combustion of H 2 was the most intensive one, 80%H 2 +20%CH 4 took the second place, while CH 4 was the least. NOx emissions didn't show a linear relationship with the volumetric fraction of H 2 , but showed an exponential uptrend instead. It presented a fairly consistent tendency with flame

High-speed measurement-device-independent quantum key distribution with integrated silicon photonics

Measurement-device-independent quantum key distribution (MDI-QKD) removes all detector side channels and enables secure QKD with an untrusted relay. It is suitable for building a star-type quantum access network, where the complicated and expensive measurement devices are placed in the central untrusted relay and each user requires only a low-cost transmitter, such as an integrated photonic chip. Here, we experimentally demonstrate a 1.25 GHz silicon photonic chip-based MDI-QKD system using polarization encoding. The photonic chip transmitters integrate the necessary encoding components for a standard QKD source. We implement random modulations of polarization states and decoy intensities, and demonstrate a finite-key secret rate of 31 bps over 36 dB channel loss (or 180 km standard fiber). This key rate is higher than state-of-the-art MDI-QKD experiments. The results show that silicon photonic chip-based MDI-QKD, benefiting from miniaturization, low-cost manufacture and compatibility with CMOS microelectronics, is a promising solution for future quantum secure networks.Comment: 30 pages, 12 figure

Precise let-7 expression levels balance organ regeneration against tumor suppression

The in vivo roles for even the most intensely studied microRNAs remain poorly defined. Here, analysis of mouse models revealed that let-7, a large and ancient microRNA family, performs tumor suppressive roles at the expense of regeneration. Too little or too much let-7 resulted in compromised protection against cancer or tissue damage, respectively. Modest let-7 overexpression abrogated MYC-driven liver cancer by antagonizing multiple let-7 sensitive oncogenes. However, the same level of overexpression blocked liver regeneration, while let-7 deletion enhanced it, demonstrating that distinct let-7 levels can mediate desirable phenotypes. let-7 dependent regeneration phenotypes resulted from influences on the insulin-PI3K-mTOR pathway. We found that chronic high-dose let-7 overexpression caused liver damage and degeneration, paradoxically leading to tumorigenesis. These dose-dependent roles for let-7 in tissue repair and tumorigenesis rationalize the tight regulation of this microRNA in development, and have important implications for let-7 based therapeutics. DOI: http://dx.doi.org/10.7554/eLife.09431.00

Investigation into the Effects of Materials and Mixing Procedures on Air Void Characteristics of Fresh Concrete Using Air Void Analyzer (AVA)

The air void analyzer (AVA) was used to investigate the effects of concrete materials and mixing procedures on air void characteristics of fresh concrete. Twenty-seven batches of concrete were made with three mix proportions (with and without Class C fly ash or water reducer), and they were mixed with five mixing procedures (one-step mixing for 1, 2, or 4 min, two-step mixing for 4 min and ASTM C 192 lab mixing procedures) and two sizes of pan mixers (0.014 and 0.042 m3 or 0.5 and 1.5 ft3). The air content, size distribution, specific surface, and spacing factor of all the batch mixtures were examined. The results indicated that incorporating 15 % Class C fly ash replacement or recommended dosage of a lignin-based water reducer into concrete generally reduced the spacing factor of air voids. The two-step mixing method (mixing mortar for 2 min first, and then mixing the mortar with coarse aggregate for another 2 min) produced a lower air void spacing factor than the one-step, 4-min mixing method (mixing all concrete materials together at once). For concrete mixed with the one-step mixing method, the air void spacing factor reduced with mixing time. For a given concrete mixture and mixing procedure, use of different sizes of mixers provided the mixtures with different air content and different spacing factor. The air void characteristics of the corresponding fresh and hardened concrete were also examined using the Type B pressure meter and RapidAir test methods, respectively. The correlations between the results from AVA, Type B pressure meter, and RapidAir tests were studied.This article is published as Zhang, Shihai, and Kejin Wang. "Investigation into the Effects of Materials and Mixing Procedures on Air Void Characteristics of Fresh Concrete Using Air Void Analyzer (AVA)." Journal of ASTM International 3, no. 10 (2006): 1-15. Paper ID JAI100435. DOI: 10.1520/JAI100435. Copyright 2006 ASTM International. Posted with permission

Exploration of Mechanisms of Joint Deterioration in Concrete Pavements regarding Interfacial Transition Zone

As a common issue for cold weather regions, premature deterioration of concrete at joints has been reported in many states. In this paper, the mechanisms of joint deterioration were investigated, and then, experimental investigations were conducted to further verify some of the mechanisms. It was found that freeze-thaw (F-T) damage and salt crystallization are not enough to cause the observed deterioration, but the deterioration near the interfacial transition zone (ITZ) may be the cause of some of the observed phenomena. In the experimental work, samples were tested at 40°F in salt solutions to observe the deterioration in the ITZ using the scanning electron microscope (SEM). Concrete tested in MgCl2 solution indicated distress in ITZ under SEM. It was found that ITZ may act as a shortcut for ion transfer to surrounding concrete near the joints and may also be the weak point for cracking due to expansion of the paste.This article is published as Wang, Xin, Jiake Zhang, Xuhao Wang, Peter Taylor, Kejin Wang, and Xinjian Sun. "Exploration of mechanisms of joint deterioration in concrete pavements regarding interfacial transition zone." Advances in Civil Engineering 2018 (2018): 3295954. DOI: 10.1155/2018/3295954. Copyright 2018 Xin Wang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Posted with permission

Degradation of Axial Ultimate Load-bearing Capacity of Circular Thin-walled Concrete-filled Steel Tubular Stub Columns after Corrosion

This work aimed to investigate the effects of steel tube corrosion on the axial ultimate load-bearing capacity (AULC) of circular thin-walled concrete-filled steel tubular (CFST) members. Circular thin-walled CFST stub column specimens were made of steel tubes with various wall-thicknesses. These CFST column specimens were subjected to an accelerated corrosion test, where the steel tubes were corroded to different degrees of corrosion. Then, these CFST specimens with corroded steel tubes experienced an axial static loading test. Results show that the failure patterns of circular thin-walled CFST stub columns with corroded steel tubes are different from those of the counterpart CFST columns with ordinary wall-thickness steel tubes, which is a typical failure mode of shear bulging with slight local outward buckling. The ultimate strength and plastic deformation capacity of the CFST specimens decreased with the increasing degree of steel corrosion. The failure modes of the specimens still belonged to ductile failure because of the confinement of outer steel tube. The degree of steel tube corrosion, diameter-to-thickness ratio, and confinement coefficient had substantial influences on the AULC and the ultimate compressive strength of circular thin-walled CFST stub columns. A simple AULC prediction model for corroded circular thin-walled CFST stub columns was presented through the regression of the experimental data and parameter analysisThis article is published as Zhang, Fengjie, Junwu Xia, Guo Li, Zhen Guo, Hongfei Chang, and Kejin Wang. "Degradation of axial ultimate load-bearing capacity of circular thin-walled concrete-filled steel tubular stub columns after corrosion." Materials 13, no. 3 (2020): 795. DOI: 10.3390/ma13030795. Copyright 2020 by the authors. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license. Posted with permission