Aiming at machining deeply small holes in TC4 alloy,a series of experiments were carried out on a self-developed multi-axis micro electrical discharge machining(micro-EDM)machine tool.To improve machining efficiency a...Aiming at machining deeply small holes in TC4 alloy,a series of experiments were carried out on a self-developed multi-axis micro electrical discharge machining(micro-EDM)machine tool.To improve machining efficiency and decrease relative wear of electrode in machining deeply small hole in TC4 alloy,many factors in micro-EDM,such as polarity,electrical parameters and supplying ways of working fluid were studied.Experimental results show that positive polarity machining is far superior to negative polarity machining;it is more optimal when open-circuit voltage,pulse width and pulse interval are 130 V,5μs and 15μs respectively on the self developed multi-axis micro-EDM machine tool;when flushing method is applied in micro-EDM,the machining efficiency is higher and relative wear of electrode is smaller.展开更多
Electrochemical drilling(ECD)provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines.The value and fluctuation ...Electrochemical drilling(ECD)provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines.The value and fluctuation of electrolyte flowrate can seriously affect the machining stability and hole quality in ECD.In particular,when drilling multiple holes,the distribution and fluctuations of the electrolyte flowrate in each channel could influence the uniformity of the electrolyte flowrate among multiple tube electrodes,thereby affecting the machining stability and the maximum feed rate.Thus,an eight-channel flow control system was developed to measure and regulate in real time the electrolyte flowrate supplied into each individual tube electrode.This paper proposes ECD of small holes with real-time flowrate control to improve the uniformity of electrolyte flowrate in each tube electrode and reduce the fluctuations in the electrolyte flowrate.In single-hole drilling,when the electrolyte flowrate was regulated in real time,the hole quality and machining stability were considerably better than without regulation.This is because the electrolyte flowrate remains basically constant,which stabilizes the flow field.Moreover,by considering the hole profile,it was found that an electrolyte flowrate of 200.0 m L/min can be acceptable for ECD of small holes.When the eight-channel flow control system was used in multiple-hole drilling,the uniformity of the electrolyte flowrate in each tube electrode was obviously improved,which led to a more stable process.Additionally,the maximum feed rate can attain 2.40 mm/min in multiple-hole drilling.Based on these findings,a matrix(5×32)of multiple small holes was successfully fabricated with a satisfactory diameter consistency,as the machining stability and machining efficiency had been enhanced.展开更多
BACKGROUND Chronic subdural hematoma(CSDH)is a common disease in neurosurgery.The traditional treatment methods include burr hole drainage,bone flap craniectomy and other surgical methods,and there are certain complic...BACKGROUND Chronic subdural hematoma(CSDH)is a common disease in neurosurgery.The traditional treatment methods include burr hole drainage,bone flap craniectomy and other surgical methods,and there are certain complications such as recurrence,pneumocephalus,infection and so on.With the promotion of neuroendoscopic technology,its treatment effect and advantages need to be further evaluated.AIM To study the clinical effect of endoscopic small-bone approach in CSDH.METHODS A total of 122 patients with CSDH admitted to our hospital from August 2018 to August 2021 were randomly divided into two groups using the digital table method:the neuroendoscopy group(n=61 cases)and the burr hole drainage group(n=61 cases).The clinical treatment effect of the two groups of patients with CSDH was compared.RESULTS At the early postoperative stage(1 d and 3 d),the proportion of 1/2 re-expansion of brain tissue in the hematoma cavity and the proportion of complete reexpansion was higher in the neuroendoscopy group than in the burr hole drainage group,and the difference between the two groups was statistically significant(P<0.05).The recurrence rate of hematoma in the neuroendoscopy group was lower than that in the burr hole drainage group,and the difference between the two groups was statistically significant(P<0.05).No intracranial hematoma,low cranial pressure,tension pneumocephalus or other complications occurred in the neuroendoscopy group.CONCLUSION The neuroendoscopic approach for the treatment of CSDH can clear the hematoma under direct vision and separate the mucosal lace-up.The surgical effect is apparent with few complications and definite curative effect,which is worthy of clinical promotion and application.展开更多
Inverted organic-inorganic hybrid perovskite solar cells(i-PSC)with low temperature processed interlayers and weak hysteresis behaviors have shown great potential for commercialization[1-5].However,their relatively lo...Inverted organic-inorganic hybrid perovskite solar cells(i-PSC)with low temperature processed interlayers and weak hysteresis behaviors have shown great potential for commercialization[1-5].However,their relatively lower power conversion efficiency(PCE)and inferior reproducibility than conventional PSCs limit further developments.These problems are largely determined by the hole transporting layer(HTL)and the quality of the upper perovskite film[6-8];in particular,the latter is considerably influenced by the surface property of the underlying HTL.展开更多
In the light of superior interaction between pyridine unit and perovskite,a facile star-shaped triphenylamine-based hole transport material(HTM)incorporating pyridine core(coded as H-Pyr)is designed and synthesized.A ...In the light of superior interaction between pyridine unit and perovskite,a facile star-shaped triphenylamine-based hole transport material(HTM)incorporating pyridine core(coded as H-Pyr)is designed and synthesized.A reference HTM with benzene core,coded as H-Ben,is also prepared for a comparative study.The effects of varying core on HTMs are investigated by comparing the photophysical,electrochemical and hole mobility properties.It is found that pyridine core exhibits better conjunction and decreased dihedral angles with triphenylamine side arms than that of benzene,leading to obviously better hole mobility and well-matched work function.The perovskite film prepared on H-Pyr also shows improved crystallization than on H-Ben.Photoluminescence and electrochemical impedance studies indicate improved charge extraction and reduced recombination in the H-Pyr-based perovskite solar cells.Consequently,H-Pyr-based device exhibits higher efficiency than H-Ben-based one.After doping with a Lewis acid,tris(pentafluorophenyl)borane,H-Pyr-based device delivers a champion efficiency of 17.09%,which is much higher compared with 12.14% of the device employing conventional poly(3,4-ethy lenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)as HTM.Moreover,the H-Pyr-based device displays good long-term stability that the power conversion efficiency remains over 80% of the initial value after storage in ambient(relative humidity=50±5%)for 20 days.展开更多
Three star-shaped truxene-based small molecules（namely TXH,TXM,TXO） were synthesized,characterized and used as hole-transporting materials（HTMs） for perovskite solar cells（Pv SCs）. The device based on TXO delive...Three star-shaped truxene-based small molecules（namely TXH,TXM,TXO） were synthesized,characterized and used as hole-transporting materials（HTMs） for perovskite solar cells（Pv SCs）. The device based on TXO delivered a respectable power conversion efficiency（PCE） of 7.89% and a high open-circuit voltage（Voc） of 0.97 V,which far exceeded the values of the devices based on other two small molecules. The highest PCE for the device based on TXO is mainly contributed from its lowest series resistance（Rs） value and largest short-circuit current（Jsc） value under the same circumstances. All these results indicate that TXO is a promising HTM candidate for Pv SCs.展开更多
For plane singly-connected domains with insulating boundary and four point-sized contacts, C<sub>0</sub> …C<sub>3</sub>, van der Pauw derived a famous equation relating the two trans-...For plane singly-connected domains with insulating boundary and four point-sized contacts, C<sub>0</sub> …C<sub>3</sub>, van der Pauw derived a famous equation relating the two trans-resistances R<sub>01,23</sub>, R<sub>12,30</sub> with the sheet resistance without any other parameters. If the domain has one hole van der Pauw’s equation becomes an inequality with upper and lower bounds, the envelopes. This was conjectured by Szymański et al. in 2013, and only recently it was proven by Miyoshi et al. with elaborate mathematical tools. The present article gives new proofs closer to physical intuition and partly with simpler mathematics. It relies heavily on conformal transformation and it expresses for the first time the trans-resistances and the lower envelope in terms of Jacobi functions, elliptic integrals, and the modular lambda elliptic function. New simple formulae for the asymptotic limit of a very large hole are also given.展开更多
基金Project(2006AA04Z323)supported by High-tech Research and Development Program of China。
文摘Aiming at machining deeply small holes in TC4 alloy,a series of experiments were carried out on a self-developed multi-axis micro electrical discharge machining(micro-EDM)machine tool.To improve machining efficiency and decrease relative wear of electrode in machining deeply small hole in TC4 alloy,many factors in micro-EDM,such as polarity,electrical parameters and supplying ways of working fluid were studied.Experimental results show that positive polarity machining is far superior to negative polarity machining;it is more optimal when open-circuit voltage,pulse width and pulse interval are 130 V,5μs and 15μs respectively on the self developed multi-axis micro-EDM machine tool;when flushing method is applied in micro-EDM,the machining efficiency is higher and relative wear of electrode is smaller.
基金supported by the Joint Funds of the National Natural Science Foundation of China and Guangdong Province(No.U1601201)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)。
文摘Electrochemical drilling(ECD)provides an alternative technique for drilling multiple small holes in difficult-to-machine materials in numerous industrial applications such as for aeroengines.The value and fluctuation of electrolyte flowrate can seriously affect the machining stability and hole quality in ECD.In particular,when drilling multiple holes,the distribution and fluctuations of the electrolyte flowrate in each channel could influence the uniformity of the electrolyte flowrate among multiple tube electrodes,thereby affecting the machining stability and the maximum feed rate.Thus,an eight-channel flow control system was developed to measure and regulate in real time the electrolyte flowrate supplied into each individual tube electrode.This paper proposes ECD of small holes with real-time flowrate control to improve the uniformity of electrolyte flowrate in each tube electrode and reduce the fluctuations in the electrolyte flowrate.In single-hole drilling,when the electrolyte flowrate was regulated in real time,the hole quality and machining stability were considerably better than without regulation.This is because the electrolyte flowrate remains basically constant,which stabilizes the flow field.Moreover,by considering the hole profile,it was found that an electrolyte flowrate of 200.0 m L/min can be acceptable for ECD of small holes.When the eight-channel flow control system was used in multiple-hole drilling,the uniformity of the electrolyte flowrate in each tube electrode was obviously improved,which led to a more stable process.Additionally,the maximum feed rate can attain 2.40 mm/min in multiple-hole drilling.Based on these findings,a matrix(5×32)of multiple small holes was successfully fabricated with a satisfactory diameter consistency,as the machining stability and machining efficiency had been enhanced.
基金the Science and Technology Program of Nantong Health Committee,No.MA2019003,No.MA2021017,No.MB2021026,and No.MB2021027Science and Technology Program of Nantong City,No.Key003 and No.JCZ2022040and Kangda College of Nanjing Medical University,No.KD2021JYYJYB025。
文摘BACKGROUND Chronic subdural hematoma(CSDH)is a common disease in neurosurgery.The traditional treatment methods include burr hole drainage,bone flap craniectomy and other surgical methods,and there are certain complications such as recurrence,pneumocephalus,infection and so on.With the promotion of neuroendoscopic technology,its treatment effect and advantages need to be further evaluated.AIM To study the clinical effect of endoscopic small-bone approach in CSDH.METHODS A total of 122 patients with CSDH admitted to our hospital from August 2018 to August 2021 were randomly divided into two groups using the digital table method:the neuroendoscopy group(n=61 cases)and the burr hole drainage group(n=61 cases).The clinical treatment effect of the two groups of patients with CSDH was compared.RESULTS At the early postoperative stage(1 d and 3 d),the proportion of 1/2 re-expansion of brain tissue in the hematoma cavity and the proportion of complete reexpansion was higher in the neuroendoscopy group than in the burr hole drainage group,and the difference between the two groups was statistically significant(P<0.05).The recurrence rate of hematoma in the neuroendoscopy group was lower than that in the burr hole drainage group,and the difference between the two groups was statistically significant(P<0.05).No intracranial hematoma,low cranial pressure,tension pneumocephalus or other complications occurred in the neuroendoscopy group.CONCLUSION The neuroendoscopic approach for the treatment of CSDH can clear the hematoma under direct vision and separate the mucosal lace-up.The surgical effect is apparent with few complications and definite curative effect,which is worthy of clinical promotion and application.
基金financially supported by the Research Grants Council of Hong Kong(GRF grant 15246816 and CRF grant C5037-18G)Shenzhen Science and Technology Innovation Commission(Project No.JCYJ20170413154602102)+4 种基金LiaoNing Revitalization Talents Program(XLYC1807231)the DICP ZZBS201813the Natural Science Foundation of Liaoning Province of China(20180540124)the Hong Kong Polytechnic University internal research fundsthe support of Hong Kong Scholars Program(XJ2017046)。
文摘Inverted organic-inorganic hybrid perovskite solar cells(i-PSC)with low temperature processed interlayers and weak hysteresis behaviors have shown great potential for commercialization[1-5].However,their relatively lower power conversion efficiency(PCE)and inferior reproducibility than conventional PSCs limit further developments.These problems are largely determined by the hole transporting layer(HTL)and the quality of the upper perovskite film[6-8];in particular,the latter is considerably influenced by the surface property of the underlying HTL.
基金supported by the National Key R&D Program of China(2019YFB1503202)the 111 Project(B16016)+1 种基金the National Natural Science Foundation of China(61904053,51702096,U1705256 and 51572080)the Fundamental Research Funds for the Central Universities(2019MS026,2019MS027 and 2020MS080)。
文摘In the light of superior interaction between pyridine unit and perovskite,a facile star-shaped triphenylamine-based hole transport material(HTM)incorporating pyridine core(coded as H-Pyr)is designed and synthesized.A reference HTM with benzene core,coded as H-Ben,is also prepared for a comparative study.The effects of varying core on HTMs are investigated by comparing the photophysical,electrochemical and hole mobility properties.It is found that pyridine core exhibits better conjunction and decreased dihedral angles with triphenylamine side arms than that of benzene,leading to obviously better hole mobility and well-matched work function.The perovskite film prepared on H-Pyr also shows improved crystallization than on H-Ben.Photoluminescence and electrochemical impedance studies indicate improved charge extraction and reduced recombination in the H-Pyr-based perovskite solar cells.Consequently,H-Pyr-based device exhibits higher efficiency than H-Ben-based one.After doping with a Lewis acid,tris(pentafluorophenyl)borane,H-Pyr-based device delivers a champion efficiency of 17.09%,which is much higher compared with 12.14% of the device employing conventional poly(3,4-ethy lenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)as HTM.Moreover,the H-Pyr-based device displays good long-term stability that the power conversion efficiency remains over 80% of the initial value after storage in ambient(relative humidity=50±5%)for 20 days.
基金supported by the National Natural Science Foundation of China(Nos.61325026,51503209)the Natural Science Foundation of Fujian Province(No.2015H0050)
文摘Three star-shaped truxene-based small molecules（namely TXH,TXM,TXO） were synthesized,characterized and used as hole-transporting materials（HTMs） for perovskite solar cells（Pv SCs）. The device based on TXO delivered a respectable power conversion efficiency（PCE） of 7.89% and a high open-circuit voltage（Voc） of 0.97 V,which far exceeded the values of the devices based on other two small molecules. The highest PCE for the device based on TXO is mainly contributed from its lowest series resistance（Rs） value and largest short-circuit current（Jsc） value under the same circumstances. All these results indicate that TXO is a promising HTM candidate for Pv SCs.
文摘For plane singly-connected domains with insulating boundary and four point-sized contacts, C<sub>0</sub> …C<sub>3</sub>, van der Pauw derived a famous equation relating the two trans-resistances R<sub>01,23</sub>, R<sub>12,30</sub> with the sheet resistance without any other parameters. If the domain has one hole van der Pauw’s equation becomes an inequality with upper and lower bounds, the envelopes. This was conjectured by Szymański et al. in 2013, and only recently it was proven by Miyoshi et al. with elaborate mathematical tools. The present article gives new proofs closer to physical intuition and partly with simpler mathematics. It relies heavily on conformal transformation and it expresses for the first time the trans-resistances and the lower envelope in terms of Jacobi functions, elliptic integrals, and the modular lambda elliptic function. New simple formulae for the asymptotic limit of a very large hole are also given.
