Measurements of the effective mass transfer areas for the gas–liquid rotating packed bed

Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.

Pollution characteristics of peroxyacetyl nitrate in karst areas in Southwest China

桂林是世界著名的地处喀斯特地区的旅游胜地,其光化学污染问题日益严重,过氧乙酰硝酸酯(PAN)被认为是光化学污染的可靠指标,也是本研究的重点.本研究于2021年10月首次观测了桂林的PAN的浓度为0.087-2.559ppb,同时探讨了PAN典型高值过程的成因.此次污染主要来源于东北方向污染气团的水平和高空输送,同时,高温,强辐射和低湿度等气象条件也促进了本地PAN的形成.本研究同时估算了桂林市的O3背景浓度为20.347ppb.这项研究为城市的光化学污染控制工作提供了理论基础。

Federated learning on non-IID and long-tailed data viadual-decoupling

Federated learning(FL),a cutting-edge distributed machine learning training paradigm,aims to generate a global model by collaborating on the training of client models without revealing local private data.The co-occurrence of non-independent and identically distributed(non-IID)and long-tailed distribution in FL is one challenge that substantially degrades aggregate performance.In this paper,we present a corresponding solution called federated dual-decoupling via model and logit calibration(FedDDC)for non-IID and long-tailed distributions.The model is characterized by three aspects.First,we decouple the global model into the feature extractor and the classifier to fine-tune the components affected by the joint problem.For the biased feature extractor,we propose a client confidence re-weighting scheme to assist calibration,which assigns optimal weights to each client.For the biased classifier,we apply the classifier re-balancing method for fine-tuning.Then,we calibrate and integrate the client confidence re-weighted logits with the re-balanced logits to obtain the unbiased logits.Finally,we use decoupled knowledge distillation for the first time in the joint problem to enhance the accuracy of the global model by extracting the knowledge of the unbiased model.Numerous experiments demonstrate that on non-IID and long-tailed data in FL,our approach outperforms state-of-the-art methods.

Donor-Acceptor Oligomers and Polymers Composed of Benzothiadiazole and 3-Hexylthiophene： Effect of Chain Length and Regioregularity

A series of donor-acceptor oligomer OBTThn （n = 1- 7） and polymer PBTThl and PBTTh2 composed of al- ternative 2,1,3-benzothiadiazole and 3-hexylthiophene have been designed and synthesized for the purpose of in- vestigation on the effect of chain length and side-chain regioregularity on their basic properties and photovoltaic performance. In the OBTThn oligomers and PBTThl polymer, all the hexyl side chains on thienyl units orient to- ward the same direction. Upon elongation of the chain length, the intramolecular charge transfer （ICT） absorption band in solution gradually redshifts from 398 nm for OBTThl to 505 nm for OBTThT, then to 512 nm for PBTThl polymer. Meanwhile, the HOMO energy level increases from -5.45 eV （OBTTh0 to -5.08 eV （OBTThT） and -5.09 eV （PBTThl）, and the LUMO energy level decreases from -3.11 eV （OBTTh0 to -3.30 eV （OBTThT） and -3.33 eV （PBTThl）, thus giving a smaller and smaller energy bandgap for higher oligomers and polymers. Theo- retical calculation suggests straight line-like backbone geometry for this series of oligomers and polymer. On the other hand, polymer PBTTh2 possesses a different side-chain regioregularity, in which every two neighbor hexyl side chains are arranged in different orienting direction. It is theoretically suggested to have curved line-like back- bone geometry. In solution, it shows similar photophysical and electrochemical properties as PBTThl. However in film state, it displays a less redshift in the ICT band as refer to that in solution than PBTThl. In combination with [6,6]-phenyl-C61-butyric acid methyl ester （PC61BM）, these oligomers and polymers were used as donor material to fabricate organic bulk heterojunction solar cells. Again, chain length-dependent device photovoltaic performance was observed. The device based on OBTTh4 showed a power conversion efficiency of 0.16%, while it increased to 0.36% and 0.49% for the devices based on OBTTh6 and PBTThb respectively. However, the side-chain regio- regularity has less influence on the device photovoltaic output since the device based on PBTTh~ displayed an effi- ciency of 0.52%, comparable to that of PBTThl.

三步接力机制助力超低过电位下硝酸根电还原到氨

氨的工业化生产养活了全球近一半的新增人口,被认为是20世纪最伟大的发明.近年来,氨作为一种无碳能源受到各国关注,被称为氢2.0.目前,全球合成氨主要采用传统的Haber-Bosch工艺(N_(2)+3H_(2)=2NH_(3))[1].然而,该工艺严重依赖传统的化石燃料,每年合成氨工艺的CO_(2)排放量超过4亿吨.

Highly time-resolved aerosol characteristics during springtime in Weizhou Island

A single particle aerosol mass spectrometer was deployed to measure the changes of single particle species and sizes during March 2015 in Weizhou Island of the Beibu Gulf, Guangxi province, South China. In this campaign, a total of 3,100,597 particles were sized, and 25.8%particles with both positive and negative mass spectrum were collected and 24.8%characterized in combination with the ART-2 a neural network algorithm. The distribution of sized particles was mainly in from 520 to 600 nm, and the diameters ranging from 340 to1000 nm accounted for above 90%. Eight types of particles were classified： Elemental Carbon containing（EC）, Organic Carbon containing（OC）, EC and OC combined containing particles,Na containing particles, K containing particles（K）, Levoglucosan containing particles,mineral containing particles, and Heavy Metal containing particles（HM）. EC, OC and K were the major containing particles, which accounted for 84.3% in the eight types particles. The relative ratio and size distribution of the three types were EC（48.1%, 620 nm）, OC（12.7%,440 nm）, and K（23.5%, 600 nm）, respectively. The three types of particles were a bit increasing ratios compared with those in clean periods during haze pollution periods.Combined with the back-trajectory results from the Hysplit-4 model and local pollution sources revealed that the ambient air quality on the Weizhou Island may be influenced by biomass burning in the Indochina Peninsula（biomass burning in the Indochina Peninsula）from the transportation on higher level atmospheric layer and by mainland of south China located northeast of Weizhou Island on the ground.

Screening the Optimal Patterned Surfaces Consisting of Cell Morphology Mimicking Micro-pillars and Nanotube Arrays for the Design of Titanium Implants#br#

Micron/nano scale topographic modification has been a significant focus of interest in current titanium(Ti)surface design.However,the influence of micron/nano structured surface on cell or bacterium behavior on the Ti implant has rarely been systematically evaluated.Moreover,except for popular microgrooves,little work has been carried out on the reaction of cells to the bionic structure.In this study,several micro-pillars mimicking cell morphology were prepared on Ti surfaces by lithography and contact printing(ICP)method,and they were further decorated with nanotube arrays by anodization technology.These surface modifications remarkablly increased the surface roughness of pristine Ti surface from 91.17 nm±5.57 nm to be more than 1000 nm,and reduced their water contact angles from 68.3°±0.7°to be 16.9°±2.4°.Then,the effects of these hierarchical micron/nano scale patterns on the behaviors of MG63 osteoblasts,L929 fibroblasts,SCC epithelial cells and P.gingivalis were studied,aiming to evaluate their performance in osseointegration,gingival epithelial sealing and antibacterial ability.Through an innovative scoring strategy,our findings showed that square micro-pillars with 6μm width and 2μm height combined with 85 nm diameter nanotubes was suitable for implant neck design,while square micro-pillars with 3μm width and 3.6μm height combined with 55 nm diameter nanotubes was the best for implant body design.Our study reveals the synergistic effect of the hierarchical micron/nano scale patterns on MG63 osteoblasts,L929 fibroblasts,SCC epithelial cells and P.gingivalis functions.It provides insight into the design of biomedical implant surfaces.