This paper investigates a multi-resolution digital Earth model called PYXIS,which was developed by PYXIS Innovation Inc.The PYXIS hexagonal grids employ an efficient hierarchical labeling scheme for addressing pixels....This paper investigates a multi-resolution digital Earth model called PYXIS,which was developed by PYXIS Innovation Inc.The PYXIS hexagonal grids employ an efficient hierarchical labeling scheme for addressing pixels.We provide a recursive definition of the PYXIS grids,a systematic approach to the labeling,an algorithm to add PYXIS labels,and a discussion of the discrete Fourier transform on PYXIS grids.展开更多
Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc alloys.However,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many cases.He...Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc alloys.However,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many cases.Here,using atomic-scale transmission electron microscopy and atomic-resolution spectroscopy,we have revealed the microstructural differences between two age-hardened Al-0.5Mg-0.4Si(wt.%)alloys with and without Sc-addition.The first significant effect of Sc-addition on the precipitation microstructure of the Al-Mg-Si-Sc alloy is that Sc-atoms may distribute at theβ"-precipitate/Al-matrix interface and therefore accelerate aging kinetics at the initial stage of hardening.The second significant effect of Sc-addition is that in the transition from theβ"-hardened peak-age stage to theβ′-hardened late stage,Sc-atoms can greatly improve the stability of transitionalβ"/B'/β′composite precipitates by entering the B'-substructures and/or locating at the precipitate/Al interfaces.As such Sc-atoms effectively suppressβ"toβ'transformation and cross-sectional coarsening of bothβ"and composite precipitates,leading to much finer precipitate needles with smaller diameter but much larger length,as compared with those precipitate needles formed in the alloy without Sc-addition.Hence,the alloy with Sc-addition exhibits a much better thermal stability than that without Sc.展开更多
AIM：To describe a novel technique of creating a landing strip within the trabecular meshwork to guide trabecular micro-bypass stent（iStent） implantation in patients who underwent phacoemulsification.METHODS：Thirty...AIM：To describe a novel technique of creating a landing strip within the trabecular meshwork to guide trabecular micro-bypass stent（iStent） implantation in patients who underwent phacoemulsification.METHODS：Thirty-four eyes from 30 patients who underwent i Stent implantation after phacoemulsification from May 2014 to February 2015 were included in our retrospective study. All iStents were implanted via the ＂landing strip＂ technique. A 25-gauge microvitreoretinal blade was used to bisect the trabecular meshwork to less than 1 clock-hour, effectively creating a landing strip. The iStent applicator was pressed along the landing strip and then the stent was released into the trabecular meshwork. RESULTS：Of the 34 eyes with iStent implantation, 27（79.4%） eyes had primary open-angle glaucoma, 6（17.6%） eyes had pseudoexfoliation glaucoma, and 1（2.9%） eye had ocular hypertension. At 6-month follow-up（n=17）, the mean number of hypotensive medications decreased from 2.2±1.2 at baseline to 0.8±1.3（P=0.05） and mean intraocular pressure decreased from 19.7±4.1 mm Hg at baseline to 16.7±2.1 mm Hg（P=0.58）. Two eyes（5.9%） required subsequent trabeculectomy. CONCLUSION：The ＂landing strip＂ technique appears to be an effective way to assist with iS tent implantation.展开更多
Herbal and dietary supplement usage has increased steadily over the past several years in the United States.Among the non-bodybuilding herbal and dietary supplements,weight loss supplements were among the most common ...Herbal and dietary supplement usage has increased steadily over the past several years in the United States.Among the non-bodybuilding herbal and dietary supplements,weight loss supplements were among the most common type of HDS implicated in liver injury.While drug induced liver injury is rare,its consequences are significant and on the rise.The purpose of this review is to highlight case reports of weight loss products such as Hydroxycut and OxyElite Pro as one form of HDS that have hepatotoxic potential and to characterize its clinical effects as well as pattern of liver injury.We also propose future strategies in the identification and study of potentially hepatotoxic compounds in an effort to outline a diagnostic approach for identifying any drug induced liver injury.展开更多
Although Cu was studied extensively,the Hall-Petch relationship was mainly reported in the coarsegrained regime.In this work,fully recrystallized Cu specimens with a wide grain size regime of 0.51–14.93μm manifest a...Although Cu was studied extensively,the Hall-Petch relationship was mainly reported in the coarsegrained regime.In this work,fully recrystallized Cu specimens with a wide grain size regime of 0.51–14.93μm manifest a two-stage Hall-Petch relationship.There is a critical grain size of 3μm that divides stagesⅠandⅡwhere the Hall-Petch slope k value are quite different.The stageⅡis supposed to be validified down to 100 nm at least by comparing with a Cu-Ag alloy.The critical grain size varies in different materials systems,and the underline mechanisms are discussed based on the dislocation glide modes.展开更多
Chromium has been recognized for dec- ades as a nutritional factor that promotes the growth of broiler chickens, but the molecular mechanism is still not clearly understood. The present study was de- signed to investi...Chromium has been recognized for dec- ades as a nutritional factor that promotes the growth of broiler chickens, but the molecular mechanism is still not clearly understood. The present study was de- signed to investigate the physiological and molecular mechanisms of the effects of supplemental chromium picolinate on the growth of broiler chickens. A total of 144 21-day-old Arbor Acres male broiler chicks were randomly divided into a control and an experimental group. The control group was fed a basal diet, and the experimental group was fed the same basal diet sup- plemented with 200 μg/kg chromium picolinate. The experiment lasted for three weeks from day 28 to 42 of the birds.. Supplementation with 200 μg/kg chro- mium picolinate significantly increased body weight （ P 〈 0.05）. Serum insulin levels in chickens of the experimental group were increased significantly （P 〈0. 05 ）, whereas serum glucose concentrations were decreased （P 〈 0.05）. No significant changes were observed in serum lipid profiles in chickens fed the di- et supplemented with chromium picolinate. Gene ex- pression levels of the insulin receptor （IR） and insu- lin receptor substrate 1 （IRS-1）, two pivotal compo- nents of the insulin signaling pathway, were also in- vestigated using Real-time quantitative PCR. IR ex- pression was significantly （P 〈 0.05） increased fol- lowing chromium supplementation. Therefore, supple- mental chromium picolinate had a beneficial effect on the growth of broilers. In agreement with observations in mammals, chromium might exert its effect via po- tentiating insulin action, and ultimately by stimulating anabolism without altering body composition in chick- ens.展开更多
Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting cables.At the end of 2020,an international round robin test(RRT)was organized,in which five Chinese instit...Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting cables.At the end of 2020,an international round robin test(RRT)was organized,in which five Chinese institutions participated,and four accomplished the test.The electric-field versus current(E-I)curves obtained by each institution are highly repeatable.Those obtained by different institutions are nearly identical after appropriate curve averaging,indicating high reproducibility,except the last participant's inner core curves.The discrepancy was later determined to be the result of sample cable damage.After excluding highly deviated data,it is determined that the maximum relative standard uncertainty in I_(c) is 0.7%,and the maximum relative standard uncertainty in n-value is 12.8%.The I_(c)values are comparable to Japan's domestic RRT results,but the n-values are significantly different.The test results support the DC four-terminal method as a recommended test method,with a target relative uncertainty of less than 2%for the Ic value.展开更多
Recently,by intercalating organic ions into bulk FeSe superconductors,two kinds of layered FeSe-based superconductors[(TBA)xFeSe and(CTA)xFeSe]with superconducting transition temperatures(Tc)above 40 K have been disco...Recently,by intercalating organic ions into bulk FeSe superconductors,two kinds of layered FeSe-based superconductors[(TBA)xFeSe and(CTA)xFeSe]with superconducting transition temperatures(Tc)above 40 K have been discovered.Due to the large interlayer distance(~15A),these new layered superconductors have a large resistivity anisotropy analogous to bismuth-based cuprate superconductors.Moreover,remarkable pseudogap behavior well above Tcis revealed by nuclear magnetic resonance(NMR)measurements on77Se nuclei,suggesting a preformed pairing scenario similar to that of cuprates.Here,we report another new kind of organic-ion-intercalated FeSe superconductor,(PY)xFeSe,with a reduced interlayer distance(~10A)compared to(TBA)xFeSe and(CTA)xFeSe.By performing77Se NMR and transport measurements,we observe a similar pseudogap behavior well above Tcof~40 K and a large resistivity anisotropy of~10~4 in(PY)xFeSe.All these facts strongly support a universal pseudogap behavior in these layered FeSe-based superconductors with quasi-two-dimensional electronic structures.展开更多
Based on the numerical simulation of solidification of castings, a thermal stress formula and a thermal crack initiation criterion are established, which suggest that the cracks initiate at the two-thirds thickness of...Based on the numerical simulation of solidification of castings, a thermal stress formula and a thermal crack initiation criterion are established, which suggest that the cracks initiate at the two-thirds thickness of solidified layer from outside of castings. Cast steel wheels whose diameters are 800mm are employed to testify the positions of cracks through thermal ela- stic-plastic analyses and low magnifying structure observations conventionally. The results show that the numerical prediction of cracks coincides with the measured result, and the cracks do not necessarily follow where the defects such as shrinkage holes and porosities occur. It is also found that surface temperature control is an effective factor to avoid the crack formation.展开更多
Hot isostatic pressing （HIP） with a pressure of 180 MPa at a temperature of 1170 ℃ was introduced to an investment cast Ni-based superalloy （Mgl） turbocharger blade to explore the healing process of casting pores...Hot isostatic pressing （HIP） with a pressure of 180 MPa at a temperature of 1170 ℃ was introduced to an investment cast Ni-based superalloy （Mgl） turbocharger blade to explore the healing process of casting pores generated during investment casting. Optical micrograph and scanning electron naicroscopy （SEM） observations indicate that eutectic pores are the main cast defects in the as-cast blade before HIP. These pores normally locate at the solidification front of γ/γ＇ eutectic with a size of a few micrometers to a few tens of micrometers. After HIP for 4 h, most of the pores were closed. Based on phase characteristics, these pores were healed by the formation of γ matrix with finer and irregular-shaped γ＇ precipitates. Healing interface can be easily distinguished by SEM. Line scan by using energy dispersive X-ray spectroscopy （EDS） reveals a much higher Ti and Al concentration in the healing interface. It is proposed that solute diffusion toward the casting pores during HIP results in the formation of γ, and the much higher concentration of γ＇-forming elements Al and Ti near the healing interface contributes to the precipitation of γ＇ in the healed region in the succeeding cooling process after HIP.展开更多
CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly inve...CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 102-106 Hz,which is far low to clarify the intrinsic dielectric feature.So,microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature(≤1000°C).Good microwave dielectric properties of permittivityε=62.7,quality factor Qf=3062 GHz and temperature coefficient of the resonant frequencyτf=179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C,the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry(DSC).This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics,but derives from composition segregation,liquid phase and defects associated with internal barrier layer capacitor(IBLC).It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.展开更多
血栓性血小板减少性紫癜(thrombotic thrombocytopenic purpura,TTP)是一种罕见但有致命性的血栓性血液病。TTP分遗传型(hereditary)和免疫型(immune-mediated)。遗传型TTP是由于ADAMTS13(adisintegrin and metalloprotease with thromb...血栓性血小板减少性紫癜(thrombotic thrombocytopenic purpura,TTP)是一种罕见但有致命性的血栓性血液病。TTP分遗传型(hereditary)和免疫型(immune-mediated)。遗传型TTP是由于ADAMTS13(adisintegrin and metalloprotease with thrombospondin-1 repeats,13)基因缺陷所致,而免疫型TTP则由ADAMTS13的自身抗体抑制了其血浆活性所致。准确和及时地对疑诊TTP的患者进行诊断和分型,并将TTP与补体介导的溶血性尿毒症综合征(complement-mediated hemolytic uremic syndrome,cHUS)和其他原因所致的血栓性微血管病(thrombotic microangiopathy)相鉴别,是近年来靶向治疗成功的关键。血浆ADAMTS13活性和抑制物(或自身抗体)的检测对TTP可疑患者的诊断和进一步处理有着极其重要的临床指导意义。三期临床试验和临床实践均表明,血浆置换(therapeutic plasma exchange,TPE)、类固醇皮质激素(corticosteroids)、卡普拉西族单抗(caplacizumab)和利妥昔单抗(rituximab)四联疗法对急性免疫性TTP的治疗有效且安全。这种新疗法,可显著加速血小板计数恢复正常,减少治疗期间病情的反复,并缩短重症监护室和普通病房住院的时间。更重要的是,这种四联疗法可能降低TTP所致的死亡率和持续性微血栓所致的并发症。本文将如何诊断和处理TTP的一些最新进展作一简述。展开更多
In this paper,region reaching controller is designed for fully actuated ocean surface vessels to reach a desired target region instead of a point.There are not the requirements for both the pre-specified trajectory ou...In this paper,region reaching controller is designed for fully actuated ocean surface vessels to reach a desired target region instead of a point.There are not the requirements for both the pre-specified trajectory outside the desired region and the desired pinpoint position inside the desired region.The controller design is based on the potential energy function,backstepping recursive design methodology,and the Lyapnov stability analysis theory.If the target region is specified arbitrarily small,the target region reduces to a point,and hence the region reaching control can be a generalisation of the setpoint control.Simulation results are presented to illustrate the performance of the proposed controller.展开更多
The effects of growth time on the structure and morphology of cubic GaN nucleation layers on GaAs(001)substrates by metalorganic chemical vapor deposition (MOCVD) have been investigated using a synchrotron X-ray diffr...The effects of growth time on the structure and morphology of cubic GaN nucleation layers on GaAs(001)substrates by metalorganic chemical vapor deposition (MOCVD) have been investigated using a synchrotron X-ray diffraction(XRD).The XRD results show that the GaN 111 reflections at 54.75° inχ are a measurable component,however the 002 reflections parallel to GaAs(001) surface are not detected.The XRD Φ scans and pole figures give a convincing proof that the GaN nucleation latyers show exactly the cubic symmetrical structure.The coherence lengths along the close-packed<111> direction estuimated from the 111 peak are nanometer order of magnitude,The optimal photoluminescence (PL) spectrum was obtained from the cubic GaN epilayer deposited on the nucleation layer for 60sec.展开更多
Titanium (Ti) and hydroxyapatite (HA) coatings have been prepared via air (APS) and vacuum plasma spraying (VPS), and then their composition, structure, bonding strength and bioactivity were examined. The results obta...Titanium (Ti) and hydroxyapatite (HA) coatings have been prepared via air (APS) and vacuum plasma spraying (VPS), and then their composition, structure, bonding strength and bioactivity were examined. The results obtained reveal that in APS process many of Ti were oxidized, but in VPS the oxidization was avoided. VPS T i coating possesses better bonding condition than APS Ti coating. As for HA coat ing, higher crystallinity has been obtained while the coating was deposited by V PS as compared with APS. The simulated body fluid (SBF) tests show that both of APS and VPS HA coatings possess good bioactivity. As compared with APS, VPS is r ecommended as a better method to deposit Ti and HA coatings that can be applied as hard tissue replacement implants.展开更多
文摘This paper investigates a multi-resolution digital Earth model called PYXIS,which was developed by PYXIS Innovation Inc.The PYXIS hexagonal grids employ an efficient hierarchical labeling scheme for addressing pixels.We provide a recursive definition of the PYXIS grids,a systematic approach to the labeling,an algorithm to add PYXIS labels,and a discussion of the discrete Fourier transform on PYXIS grids.
基金supported by the National Natural Science Foundation of China(Nos.52061003,U20A20274,51661003)the Natural Science Foundation of Guangxi Province(2018GXNSFAA050012)+1 种基金the Science and Technology Major Project of Guangxi(No.AA17204036–1)the Guangxi Key Laboratory of Processing for Non-ferrous Metallic and Featured Materials(No.GXYSYF1803)。
文摘Sc-addition can significantly enhance the performance of the micro-alloyed Al-Mg-Si-Sc alloys.However,the mechanisms by which the Sc element modifies the microstructure of the alloys are still unknown in many cases.Here,using atomic-scale transmission electron microscopy and atomic-resolution spectroscopy,we have revealed the microstructural differences between two age-hardened Al-0.5Mg-0.4Si(wt.%)alloys with and without Sc-addition.The first significant effect of Sc-addition on the precipitation microstructure of the Al-Mg-Si-Sc alloy is that Sc-atoms may distribute at theβ"-precipitate/Al-matrix interface and therefore accelerate aging kinetics at the initial stage of hardening.The second significant effect of Sc-addition is that in the transition from theβ"-hardened peak-age stage to theβ′-hardened late stage,Sc-atoms can greatly improve the stability of transitionalβ"/B'/β′composite precipitates by entering the B'-substructures and/or locating at the precipitate/Al interfaces.As such Sc-atoms effectively suppressβ"toβ'transformation and cross-sectional coarsening of bothβ"and composite precipitates,leading to much finer precipitate needles with smaller diameter but much larger length,as compared with those precipitate needles formed in the alloy without Sc-addition.Hence,the alloy with Sc-addition exhibits a much better thermal stability than that without Sc.
文摘AIM：To describe a novel technique of creating a landing strip within the trabecular meshwork to guide trabecular micro-bypass stent（iStent） implantation in patients who underwent phacoemulsification.METHODS：Thirty-four eyes from 30 patients who underwent i Stent implantation after phacoemulsification from May 2014 to February 2015 were included in our retrospective study. All iStents were implanted via the ＂landing strip＂ technique. A 25-gauge microvitreoretinal blade was used to bisect the trabecular meshwork to less than 1 clock-hour, effectively creating a landing strip. The iStent applicator was pressed along the landing strip and then the stent was released into the trabecular meshwork. RESULTS：Of the 34 eyes with iStent implantation, 27（79.4%） eyes had primary open-angle glaucoma, 6（17.6%） eyes had pseudoexfoliation glaucoma, and 1（2.9%） eye had ocular hypertension. At 6-month follow-up（n=17）, the mean number of hypotensive medications decreased from 2.2±1.2 at baseline to 0.8±1.3（P=0.05） and mean intraocular pressure decreased from 19.7±4.1 mm Hg at baseline to 16.7±2.1 mm Hg（P=0.58）. Two eyes（5.9%） required subsequent trabeculectomy. CONCLUSION：The ＂landing strip＂ technique appears to be an effective way to assist with iS tent implantation.
文摘Herbal and dietary supplement usage has increased steadily over the past several years in the United States.Among the non-bodybuilding herbal and dietary supplements,weight loss supplements were among the most common type of HDS implicated in liver injury.While drug induced liver injury is rare,its consequences are significant and on the rise.The purpose of this review is to highlight case reports of weight loss products such as Hydroxycut and OxyElite Pro as one form of HDS that have hepatotoxic potential and to characterize its clinical effects as well as pattern of liver injury.We also propose future strategies in the identification and study of potentially hepatotoxic compounds in an effort to outline a diagnostic approach for identifying any drug induced liver injury.
基金supported financially by the Fundamental Research Funds for the Central Universities(No.N180204015)supported by Chinese Academy of Sciences(CAS)and Japan Society for the Promotion of Science(JSPS)through the Bilateral Program(No.GJHZ1774)supported by Ministry of Education,Culture,Sports,Science and Technology(MEXT),Japan,through the Elements Strategy Initiative for Structural Materials(ESISM)Project and the Grant-in-Aid for Scientific Research(S)(No.15H05767)。
文摘Although Cu was studied extensively,the Hall-Petch relationship was mainly reported in the coarsegrained regime.In this work,fully recrystallized Cu specimens with a wide grain size regime of 0.51–14.93μm manifest a two-stage Hall-Petch relationship.There is a critical grain size of 3μm that divides stagesⅠandⅡwhere the Hall-Petch slope k value are quite different.The stageⅡis supposed to be validified down to 100 nm at least by comparing with a Cu-Ag alloy.The critical grain size varies in different materials systems,and the underline mechanisms are discussed based on the dislocation glide modes.
基金supported by the National High Tech-nology Development Plan of China (2008AA101009)
文摘Chromium has been recognized for dec- ades as a nutritional factor that promotes the growth of broiler chickens, but the molecular mechanism is still not clearly understood. The present study was de- signed to investigate the physiological and molecular mechanisms of the effects of supplemental chromium picolinate on the growth of broiler chickens. A total of 144 21-day-old Arbor Acres male broiler chicks were randomly divided into a control and an experimental group. The control group was fed a basal diet, and the experimental group was fed the same basal diet sup- plemented with 200 μg/kg chromium picolinate. The experiment lasted for three weeks from day 28 to 42 of the birds.. Supplementation with 200 μg/kg chro- mium picolinate significantly increased body weight （ P 〈 0.05）. Serum insulin levels in chickens of the experimental group were increased significantly （P 〈0. 05 ）, whereas serum glucose concentrations were decreased （P 〈 0.05）. No significant changes were observed in serum lipid profiles in chickens fed the di- et supplemented with chromium picolinate. Gene ex- pression levels of the insulin receptor （IR） and insu- lin receptor substrate 1 （IRS-1）, two pivotal compo- nents of the insulin signaling pathway, were also in- vestigated using Real-time quantitative PCR. IR ex- pression was significantly （P 〈 0.05） increased fol- lowing chromium supplementation. Therefore, supple- mental chromium picolinate had a beneficial effect on the growth of broilers. In agreement with observations in mammals, chromium might exert its effect via po- tentiating insulin action, and ultimately by stimulating anabolism without altering body composition in chick- ens.
基金the Strategic Priority Research Program of Chinese Academy of Sciences,Grant No.XDB 2500.
文摘Currently,IEC/TC90 is working on standardizing the method for measuring critical current(Ic)in superconducting cables.At the end of 2020,an international round robin test(RRT)was organized,in which five Chinese institutions participated,and four accomplished the test.The electric-field versus current(E-I)curves obtained by each institution are highly repeatable.Those obtained by different institutions are nearly identical after appropriate curve averaging,indicating high reproducibility,except the last participant's inner core curves.The discrepancy was later determined to be the result of sample cable damage.After excluding highly deviated data,it is determined that the maximum relative standard uncertainty in I_(c) is 0.7%,and the maximum relative standard uncertainty in n-value is 12.8%.The I_(c)values are comparable to Japan's domestic RRT results,but the n-values are significantly different.The test results support the DC four-terminal method as a recommended test method,with a target relative uncertainty of less than 2%for the Ic value.
基金supported by the National Natural Science Foundation of China(Grant Nos.11888101 and 12034004)the National Key R&D Program of China(Grant No.2017YFA0303000)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB25000000)the Anhui Initiative in Quantum Information Technologies(Grant No.AHY160000)the Innovation Program for Quantum Science and Technology(Grant No.2021ZD0302800)。
文摘Recently,by intercalating organic ions into bulk FeSe superconductors,two kinds of layered FeSe-based superconductors[(TBA)xFeSe and(CTA)xFeSe]with superconducting transition temperatures(Tc)above 40 K have been discovered.Due to the large interlayer distance(~15A),these new layered superconductors have a large resistivity anisotropy analogous to bismuth-based cuprate superconductors.Moreover,remarkable pseudogap behavior well above Tcis revealed by nuclear magnetic resonance(NMR)measurements on77Se nuclei,suggesting a preformed pairing scenario similar to that of cuprates.Here,we report another new kind of organic-ion-intercalated FeSe superconductor,(PY)xFeSe,with a reduced interlayer distance(~10A)compared to(TBA)xFeSe and(CTA)xFeSe.By performing77Se NMR and transport measurements,we observe a similar pseudogap behavior well above Tcof~40 K and a large resistivity anisotropy of~10~4 in(PY)xFeSe.All these facts strongly support a universal pseudogap behavior in these layered FeSe-based superconductors with quasi-two-dimensional electronic structures.
基金the National Natural Science Foundation of China(No.59995442)Specialized Research Fund for the Doctoral Program of Higher Education of China(No.2000014117).
文摘Based on the numerical simulation of solidification of castings, a thermal stress formula and a thermal crack initiation criterion are established, which suggest that the cracks initiate at the two-thirds thickness of solidified layer from outside of castings. Cast steel wheels whose diameters are 800mm are employed to testify the positions of cracks through thermal ela- stic-plastic analyses and low magnifying structure observations conventionally. The results show that the numerical prediction of cracks coincides with the measured result, and the cracks do not necessarily follow where the defects such as shrinkage holes and porosities occur. It is also found that surface temperature control is an effective factor to avoid the crack formation.
基金financial support from the Ministry of Science and Technology of the People’s Republic of China(No.2012CB932201)the National Natural Science Foundation of China(No.51231006)+1 种基金the International Cooperation Program funded by National Natural Science Foundation of China(No.51261130091)the Key Research Program of Chinese Academy of Sciences(No.KGZD-EW-T06)
文摘Hot isostatic pressing （HIP） with a pressure of 180 MPa at a temperature of 1170 ℃ was introduced to an investment cast Ni-based superalloy （Mgl） turbocharger blade to explore the healing process of casting pores generated during investment casting. Optical micrograph and scanning electron naicroscopy （SEM） observations indicate that eutectic pores are the main cast defects in the as-cast blade before HIP. These pores normally locate at the solidification front of γ/γ＇ eutectic with a size of a few micrometers to a few tens of micrometers. After HIP for 4 h, most of the pores were closed. Based on phase characteristics, these pores were healed by the formation of γ matrix with finer and irregular-shaped γ＇ precipitates. Healing interface can be easily distinguished by SEM. Line scan by using energy dispersive X-ray spectroscopy （EDS） reveals a much higher Ti and Al concentration in the healing interface. It is proposed that solute diffusion toward the casting pores during HIP results in the formation of γ, and the much higher concentration of γ＇-forming elements Al and Ti near the healing interface contributes to the precipitation of γ＇ in the healed region in the succeeding cooling process after HIP.
基金supported by the National Natural Science Foundation of China(No.51602055).
文摘CaCu_(3)Ti_(4)O_(12)(CCTO)is a potential dielectric material with giant permittivity,good stability over the wide temperature and frequency range.However,the dielectric responses of CCTO-based ceramics are mainly investigated in the frequency of 102-106 Hz,which is far low to clarify the intrinsic dielectric feature.So,microwave dielectric properties have been investigated for the CCTO porous ceramics sintered at low temperature(≤1000°C).Good microwave dielectric properties of permittivityε=62.7,quality factor Qf=3062 GHz and temperature coefficient of the resonant frequencyτf=179 ppm/°C are achieved for the CCTO ceramics sintered at 1000°C,the dielectric loss significantly decreases two orders to 0.002 compared to that of CCTO ceramics sintered at critical temperature of 1020°C confirmed by differential scanning calorimetry(DSC).This clue indicates that giant permittivity and high loss is not intrinsic for CCTO ceramics,but derives from composition segregation,liquid phase and defects associated with internal barrier layer capacitor(IBLC).It suggests that CCTO-based ceramics is a promising microwave dielectric materials with high permittivity.
基金This work is supported by the Natural Science Foundation of China under Grant Number 51775329the Shanghai Natural Science Foundation of China under Grant Number 10.13039/10000721919ZR1422800the Open Project Program of the state key laboratory of engines(Tianjin University)under Grant Number K2019-14.
文摘In this paper,region reaching controller is designed for fully actuated ocean surface vessels to reach a desired target region instead of a point.There are not the requirements for both the pre-specified trajectory outside the desired region and the desired pinpoint position inside the desired region.The controller design is based on the potential energy function,backstepping recursive design methodology,and the Lyapnov stability analysis theory.If the target region is specified arbitrarily small,the target region reduces to a point,and hence the region reaching control can be a generalisation of the setpoint control.Simulation results are presented to illustrate the performance of the proposed controller.
文摘The effects of growth time on the structure and morphology of cubic GaN nucleation layers on GaAs(001)substrates by metalorganic chemical vapor deposition (MOCVD) have been investigated using a synchrotron X-ray diffraction(XRD).The XRD results show that the GaN 111 reflections at 54.75° inχ are a measurable component,however the 002 reflections parallel to GaAs(001) surface are not detected.The XRD Φ scans and pole figures give a convincing proof that the GaN nucleation latyers show exactly the cubic symmetrical structure.The coherence lengths along the close-packed<111> direction estuimated from the 111 peak are nanometer order of magnitude,The optimal photoluminescence (PL) spectrum was obtained from the cubic GaN epilayer deposited on the nucleation layer for 60sec.
基金This work was suppored by the National Natural Science Foundution of China(No.50102008)Shanghai Science and Technology R&D Fund(No.03JC14074 and No.035211081).
文摘Titanium (Ti) and hydroxyapatite (HA) coatings have been prepared via air (APS) and vacuum plasma spraying (VPS), and then their composition, structure, bonding strength and bioactivity were examined. The results obtained reveal that in APS process many of Ti were oxidized, but in VPS the oxidization was avoided. VPS T i coating possesses better bonding condition than APS Ti coating. As for HA coat ing, higher crystallinity has been obtained while the coating was deposited by V PS as compared with APS. The simulated body fluid (SBF) tests show that both of APS and VPS HA coatings possess good bioactivity. As compared with APS, VPS is r ecommended as a better method to deposit Ti and HA coatings that can be applied as hard tissue replacement implants.
