JSC "Krastsvetmet" has launched the production of glass melting units(GU) and glass feeders(GF),with the number of bushings being from 200 to 4000,made from platinum-rhodium alloys doped with oxide forming a...JSC "Krastsvetmet" has launched the production of glass melting units(GU) and glass feeders(GF),with the number of bushings being from 200 to 4000,made from platinum-rhodium alloys doped with oxide forming and reinforcing elements.The proprietary technology for dispersion-stabilized material of PtRh10DS composition having high strength and performance properties has been developed and applied.Combined products production was launched where bushings made of PtRh-20 alloy are welded to the plate of the dispersion-stabilized PtRh10DS material.The manufacture of seamless spinning assemblies has been organized.展开更多
The descriptions of fossil Triassic marine pla- codonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are...The descriptions of fossil Triassic marine pla- codonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are conver- gent with those of Halitherium/Dugong or Mo- eritherium in their general function. Whereas Halitherium possessed a horny oral pad and counterpart and a special rasp-like tongue to grind seagrass, as does the modern Dugong, placodonts had large teeth that covered their jaws to form a similar grinding pad. The sirenia also lost their anterior teeth during many Millions of years and built a horny pad instead and specialized tongue to fed mainly on seagrass, whereas placodonts had only macroalgae availa- ble. Indirect evidence for Triassic macroalgae is provided by benthic palaeocommunities from different layers and extended European regions in the Germanic Basin. Studies of tooth wear stages for Placodus indicate that anterior teeth may have been used in a similar manner to the procumbent front teeth of modern Dugong. Paraplacodus and Placodus seem to have used these teeth as spatulas to dig out seaplants. Cyamodus and other placodonts such as Placochelys had smaller or reduced anterior teeth. The scarcity of highly worn palatine or maxillary and lower jaw dentary Placodus or Cyamodus teeth (less then 0.5%) suggests that they had a relatively soft diet. The seaplants would only have been squeezed in a similar feeding strategy to that of modern Dugong feeding on seagrass without jaw rotation and grinding. The phylogenetic trend in tooth reduction within the placodonts Paraplacodus, Placodus, especially in Cyamodus but also Placochelys, and Henodus within 11 My appears to have been a result of this plant-feeding adaptation and may even explain the origin or at least close relationship of the earliest Upper Triassic turtles as toothless algae and jellyfish feeders, in terms of the long-term convergent development with the sirens.展开更多
The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the...The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.展开更多
In this research, the performance of the solar thermal powered systems (STPS) is analyzed with different models (without inserts, with inserts and with Nano fluids with different concentrations) and its impact on the ...In this research, the performance of the solar thermal powered systems (STPS) is analyzed with different models (without inserts, with inserts and with Nano fluids with different concentrations) and its impact on the Electric load in a residential/Institutional Electrical Distribution system. For this purpose, the electrical and solar thermal water heater is tested and validated. Solar thermal powered systems and its impact on the Institutional electrical distribution feeders are tested and compared with the energy efficiency (EE) and cost optimization. The goal of this paper is to analyze the impact of solar thermal energy on electrical energy consumption in the electrical distribution feeder level. The electrical system cost and energy consumptions are tabulated and observed that there is a considerable savings.展开更多
Secondary metabolites and synthetic iminosugars that structurally resemble monosaccharides are potent inhibitors of a-glucosidase activity. The enzyme is core in cleaving sucrose in phloem feeding insects and it also ...Secondary metabolites and synthetic iminosugars that structurally resemble monosaccharides are potent inhibitors of a-glucosidase activity. The enzyme is core in cleaving sucrose in phloem feeding insects and it also plays a crucial role of reducing osmotic stress via the formation of oligosaccharides. Inhibition of hydrolysis by iminosug- ars should result in nutritional deficiencies and/or disruption of normal osmoregulation. Deoxynojirimycin （DNJ） and 2 N-alkylated analogs [N-butyl DNJ （NB-DNJ） and N-nonyl DNJ （NN-DNJ）] were the major iminosugars used throughout the study. The extensive experiments conducted with a-glucosidase of the whitefly Bemisia tabaci indicated the competitive nature of inhibition and that the hydrophilic DNJ is a potent inhibitor in com- parison to the more hydrophobic NB-DNJ and NN-DNJ compounds. The same inhibitory pattern was observed with the psyllid Cacopsylla bidens a-glucosidase. In contrast to the above pattern, enzymes of the aphids, Myzus persicae and Aphis gossypii were more sen- sitive to the hydrophobic iminosugars as compared to DNJ. In vivo experiments in which adult B. tabaci were fed dietary iminosugars, show that the hydrophilic DNJ was far less toxic than the lipophilic NB-DNJ and NN-DNJ. It is proposed that this pattern is attributed to the better accessibility of the hydrophobic NN-DNJ to the a-glucosidase membrane- bound compartment in the midgut. Based on the inhibitory effects of certain polyhydroxy N-alkylated iminosugars, a-glucosidase of phloem feeding hemipterans could serve as an attractive target site for developing novel pest control agents.展开更多
The purpose of this study is to analyze the galloping characteristics of the catenary positive feeder in fluctuating wind areas considering dynamic-wind angle of attack and aerodynamic damping.Firstly,the flow field m...The purpose of this study is to analyze the galloping characteristics of the catenary positive feeder in fluctuating wind areas considering dynamic-wind angle of attack and aerodynamic damping.Firstly,the flow field model of the catenary positive feeder was established,the fluctuating wind field was simulated by Davenport wind power spectrum and linear filtering method,and the wind speed at inlet in calculation domain was controlled by editing the profile file to simulate and calculate the aerodynamic characteristics of the positive feeder in the fluctuating wind area.Then,taking the positive feeder as the research object,the mathematical model of actual structure and the corresponding finite element model were established.By applying the wind load to the finite element model,the influence of aerodynamic damping caused by the self-movement of the positive feeder on the galloping response was analyzed,and the frequency domain characteristics of galloping displacement of the positive feeder considering aerodynamic damping were studied.Finally,the calculation method of aerodynamic damping by the Guidelines for Electrical Transmission Line Structural Loading(ASCE No.74)was used for the galloping response of the positive feeder and compared with the proposed method.The results show that when considering aerodynamic damping,the galloping amplitude of the positive feeder decreases significantly,and the first-order resonance effect on the vertical displacement and horizontal displacement decreases significantly.The galloping trajectories calculated by the two methods are consistent.Therefore,this study is of great significance to further clarify the ice-free galloping mechanism of the catenary positive feeder in violent wind areas.展开更多
Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were s...Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.展开更多
In our previous study, five homologous feeder cell lines, Monkey ear skin fibroblasts （MESFs）, clonally derived fibroblasts from the MESFs （CMESFs）, monkey oviductal fibroblasts （MOFs）, monkey follicular granulo...In our previous study, five homologous feeder cell lines, Monkey ear skin fibroblasts （MESFs）, clonally derived fibroblasts from the MESFs （CMESFs）, monkey oviductal fibroblasts （MOFs）, monkey follicular granulosa fibroblast-like （MFGs） cells, monkey follicular granulosa epithelium-like （MFGEs） cells, were developed for the maintenance of rhesus embryonic stem cells （rESCs）. We found that MESFs, CMESFs, MOFs and MFGs, but not MFGEs, support the growth of rhesus embryonic stem cells. Moreover, we detected some genes that are upregulated in supportive feeder cell lines by semi-quantitative PCR. In the present study, we applied the GeneChip Rhesus Macaque Genome Array of Affymetrix Corporation to study the expression profiles of these five feeder cell lines, in purpose to find out which cytokines and signaling pathways were important in maintaining the rESCs, mRNAs of eight genes, including GREM2, bFGF, KITLG, DKK3, GREM1, AREG, SERPINF1 and LTBP1, were found to be upregulated in supportive feeder cell lines, but not in MFGE. The results indicate that many signaling pathways may play redundant roles in supporting the undifferentiated growth and maintenance of pluripotency in rESCs.展开更多
Background: Eurasian Sparrowhawks(Accipiter nisus) increasingly represent successful city-dwellers. Thereby, a rich food supply indicated by high numbers of small birds is believed to be the key driver for this bird-e...Background: Eurasian Sparrowhawks(Accipiter nisus) increasingly represent successful city-dwellers. Thereby, a rich food supply indicated by high numbers of small birds is believed to be the key driver for this bird-eating raptor species to settle in urban environments. However, as small passerine birds show particularly strong antipredator responses, sparrowhawks may not simply focus on patches of highest prey densities, but rather respond strategically to prey behavior, raising the importance of other parameters in determining the occurrence within urban landscapes.Methods: To deepen our knowledge on habitat requirements of urban sparrowhawks, bird surveys were carried out during winter between December 2005 and January 2017 in 36 city parks in Vienna, Austria. Besides food supply also park size, canopy heterogeneity and the connectivity with other green spaces were considered.Results: Occurrence of sparrowhawks was positively affected by increasing park size, prey density and the interaction between both. Bird feeder density and park connectivity with other green spaces were of minor importance in explaining the presence of this species. Canopy heterogeneity didn't affect city park occupancy by Eurasian Sparrowhawks.Conclusions: Our results suggest that large city parks, particularly when characterized by high prey densities, substantially contribute to protect and preserve ecologically important bird species such as raptors within the urban environment—a landscape already struggling with biodiversity losses and functional homogenization.展开更多
Fault location for distribution feeders short circuit especially single-phase grounding fault is an important task in distribution system with non-effectively grounded neutral.Fault location mode for distribution feed...Fault location for distribution feeders short circuit especially single-phase grounding fault is an important task in distribution system with non-effectively grounded neutral.Fault location mode for distribution feeders using fault generated current and voltage transient traveling waves was investigated.The characteristics of transient traveling waves resulted from each short circuit fault and their transmission disciplinarian in distribution feeders are analyzed.This paper proposed that double end travelling waves theory which measures arriving time of fault initiated surge at both ends of the monitored line is fit for distribution feeders but single end traveling waves theory not.According to different distribution feeders,on the basis of analyzing original traveling waves reflection rule in line terminal, Current-voltage mode,voltage-voltage mode and current-current mode for fault location based on traveling waves are proposed and aerial mode component of original traveling waves is used to realize fault location.Experimental test verify the feasibility and correctness of the proposed method.展开更多
An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for poss...An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for possible variation in loads and distributed generation between different feeders fed from a given transformer, allowing the line voltages to be kept within limits on all feeders. A combination of computer simulation and practical experiments was used. A model constructed in Excel gave preliminary results, which was used to specify a more detailed model in Matlab? Simulink. A small-scale 220/380 V distribution network was constructed, with currents limited to 5 A per phase. Finally, a rotary switch was constructed, suitable for currents up to 500 A, which would be required for a full-scale low voltage distribution network. The results showed that the voltage could be kept within limits, even with a large difference in load and distributed generation from one feeder to another.展开更多
An extensive suite of igneous sills was intruded into the Tertiary sedimentary section of the Jiaojiang sag, East China Sea. This suite has been well imaged offshore through 2D and 3D seismic surveys, showing a close ...An extensive suite of igneous sills was intruded into the Tertiary sedimentary section of the Jiaojiang sag, East China Sea. This suite has been well imaged offshore through 2D and 3D seismic surveys, showing a close relationship with CO2 content in nearby gas discoveries. A new observational model, which incorporates simple upward propagation, simple horizontal propagation, and transgressive propagation, was proposed to interpret these sill intrusions. In this model, the source magma of the saucer-shaped sills was injected from their lowest points near the center. The transgressive propagation can be interpreted as a combination of the vertical and horizontal propagation. Most shallow sub-volcanic intrusions in the Jiaojiang sag exhibit fingered characteristics, both vertically and horizontally. The vertical fingered propagation produced saucer-shaped sills arranged in the flower style. Along the brims of lower sills could usually be found the upper sills, which are interpreted to have formed simultaneously with or later than the lower feeder sills. In the second type, the chilled paths of the older sills were reutilized by subsequent intrusions. The horizontal fingered propagation formed sheet intrusions that exhibit groove, lobate, tubular, and crevasse splay- like geometry in plan view. In 3D view, the sheet intrusions have still preserved the lower center and higher rim that similar with the sub-rounded saucer-shaped sills. Although fracture propagation may be important, flow inflation was the key mechanism of magma intrusion. Further consideration of the mechanisms underlying sill formation may help explain the fingered characteristics of sill propagation.展开更多
In vitro growth and maintenance of embryonic stem (ES) cell lines derived from ICM cells of various blastocysts of 129 strain mice, the sustenance of their pluripotency and normal karyotype depend on the feeder layer ...In vitro growth and maintenance of embryonic stem (ES) cell lines derived from ICM cells of various blastocysts of 129 strain mice, the sustenance of their pluripotency and normal karyotype depend on the feeder layer of mouse embryonic fibroblasts (MEF). Compared with the feeder layer of MEF cells, medium conditioned by Buffalo rat liver cells (BRL-CM) is able to maintain pluripotency and karyo-typic normality of ES cells only in short term cell propagation. Besides, ES cells grown in BRL-CM are also capable of aggregation with 8-cell embryos of Swiss strain and develop into germ line chimaeras. Modification to the method of aggregating ES cells with early embryos by making a hole in agar layer on the top of MEF feeder cells was shown to be more convenient and efficient than the conventional microdrop method.展开更多
Induced pluripotent stem （iPS） cells can be derived from human somatic cells by cellular reprograrnming. This technology provides a potential source of non-controversial therapeutic ceils for tissue repair, drug dis...Induced pluripotent stem （iPS） cells can be derived from human somatic cells by cellular reprograrnming. This technology provides a potential source of non-controversial therapeutic ceils for tissue repair, drug discovery, and opportunities for studying the molecular basis of human disease. Normally, mouse embryonic fibroblasts （MEFs） are used as feeder layers in the initial derivation of iPS lines. The pur- pose of this study was to determine whether SNL fibrohlasts can be used to support the growth of human iPS cells reprogrammed from somatic cells using lentiviral expressed reprogramming factors. In our study, iPS cells expressed common pluripotency markers, dis- played human embryonic stem cells （hESCs） morphology and unmethylated promoters of NANOG and OCT4. These data demonstrate that SNL feeder cells can support the derivation and maintenance of human iPS cells.展开更多
For a surface mounting machine (SMM) in printed circuit board (PCB) assembly line, there are four problems, e.g. CAD data conversion, nozzle selection, feeder assignment and placement sequence determination. A hierarc...For a surface mounting machine (SMM) in printed circuit board (PCB) assembly line, there are four problems, e.g. CAD data conversion, nozzle selection, feeder assignment and placement sequence determination. A hierarchical planning for them to maximize the throughput rate of an SMM is presented here. To minimize set-up time, a CAD data conversion system was first applied that could automatically generate the data for machine placement from CAD design data files. Then an effective nozzle selection approach was implemented to minimize the time of nozzle changing. And then, to minimize picking time, an algorithm for feeder assignment was used to make picking multiple components simultaneously as much as possible. Finally, in order to shorten pick-and-place time, a heuristic algorithm was used to determine optimal component placement sequence according to the decided feeder positions. Experiments were conducted on a four head SMM. The experimental results were used to analyse the assembly line performance.展开更多
Because of the increasingly prominent problem of alumina content inhomogeneity in large or super-scale aluminum reduction cells,a transient numerical model for the alumina mixing process was developed for a400kA cell,...Because of the increasingly prominent problem of alumina content inhomogeneity in large or super-scale aluminum reduction cells,a transient numerical model for the alumina mixing process was developed for a400kA cell,and the relationship between the alumina content distribution and electrolyte flow field was analyzed.In the ANSYS software platform,several numerical simulation cases were presented to display the influence of the feeder configuration on the alumina mixing characteristics.The results showed that a large vortex flow of the molten electrolyte is beneficial for alumina mixing and uniform distribution in the inner areas of the vortexes.The alumina particles reach the inter-electrode zone in10?15s from the beginning of the feeding action,and the risk of early precipitation occurs in10?25s after the feeding.It was also found that a suitable grouping of feeders could reduce the content fluctuation and gradient.Therefore,a feeding on demand strategy was proposed,and the simulation results showed that although the spatial characteristics are not changed,the uniformity of the alumina content was markedly improved.展开更多
To satisfy the demand for good quality underwater welding and maintenance of nuclear power stations,a set of local dry automatic welding systems has been developed.These systems were based on an underwater robot that ...To satisfy the demand for good quality underwater welding and maintenance of nuclear power stations,a set of local dry automatic welding systems has been developed.These systems were based on an underwater robot that consisted of a special high-power underwater welding power supply,diving wire feeder,mini drain cap,welding robot,and special underwater welding torch.With a digital signal controller microprocessor as its core and combined with a dual inverter topology,the welding power supply was characterized by full-digital construction and multi-waveform flexible output.A compact diving wire feeding device was designed,based on the armature voltage negative feedback and high-frequency chopping pulse width modulation.This device yielded a high-efficiency seal of the driving motor with the help of dynamic and static sealing technology.To overcome the difficulty of local protection and deslagging in the welding area,a mini drain cap(with a duplexgas structure)based on the principle of the convergent nozzle was designed.The practical tests and the underwater welding experiments revealed that the underwater robotic local dry welding system is quite feasible.That is,the system could strike the arc stably and reliably in the shallow water environment,and formed beautiful welding seams.展开更多
文摘JSC "Krastsvetmet" has launched the production of glass melting units(GU) and glass feeders(GF),with the number of bushings being from 200 to 4000,made from platinum-rhodium alloys doped with oxide forming and reinforcing elements.The proprietary technology for dispersion-stabilized material of PtRh10DS composition having high strength and performance properties has been developed and applied.Combined products production was launched where bushings made of PtRh-20 alloy are welded to the plate of the dispersion-stabilized PtRh10DS material.The manufacture of seamless spinning assemblies has been organized.
文摘The descriptions of fossil Triassic marine pla- codonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are conver- gent with those of Halitherium/Dugong or Mo- eritherium in their general function. Whereas Halitherium possessed a horny oral pad and counterpart and a special rasp-like tongue to grind seagrass, as does the modern Dugong, placodonts had large teeth that covered their jaws to form a similar grinding pad. The sirenia also lost their anterior teeth during many Millions of years and built a horny pad instead and specialized tongue to fed mainly on seagrass, whereas placodonts had only macroalgae availa- ble. Indirect evidence for Triassic macroalgae is provided by benthic palaeocommunities from different layers and extended European regions in the Germanic Basin. Studies of tooth wear stages for Placodus indicate that anterior teeth may have been used in a similar manner to the procumbent front teeth of modern Dugong. Paraplacodus and Placodus seem to have used these teeth as spatulas to dig out seaplants. Cyamodus and other placodonts such as Placochelys had smaller or reduced anterior teeth. The scarcity of highly worn palatine or maxillary and lower jaw dentary Placodus or Cyamodus teeth (less then 0.5%) suggests that they had a relatively soft diet. The seaplants would only have been squeezed in a similar feeding strategy to that of modern Dugong feeding on seagrass without jaw rotation and grinding. The phylogenetic trend in tooth reduction within the placodonts Paraplacodus, Placodus, especially in Cyamodus but also Placochelys, and Henodus within 11 My appears to have been a result of this plant-feeding adaptation and may even explain the origin or at least close relationship of the earliest Upper Triassic turtles as toothless algae and jellyfish feeders, in terms of the long-term convergent development with the sirens.
文摘The performance of complementary feeders, running in parallel, can be significantly improved by installing static transfer switches （STSs） at critical locations. We develop the STS control logic, which transfers the critical load from the preferred feeder to the alternate feeder when a voltage sag or a fault occurs on the preferred feeder. A forced commutation technique is proposed and implemented to turn off the preferred feeders＇ thyristor, thus avoiding cross current to flow and minimizing the transfer time. Simulation results show that the forced commutation technique is more effective as compared to the recently proposed time delay technique for STS operation. Two different feeders, namely New Exchange, the preferred feeder, and Sector 1-10/2, the alternate feeder of Islamabad Electric Supply COmpany （IESCO）, Pakistan, have been selected for case studies. The software PSCAD/EMTDC professional package has been used for simulation.
文摘In this research, the performance of the solar thermal powered systems (STPS) is analyzed with different models (without inserts, with inserts and with Nano fluids with different concentrations) and its impact on the Electric load in a residential/Institutional Electrical Distribution system. For this purpose, the electrical and solar thermal water heater is tested and validated. Solar thermal powered systems and its impact on the Institutional electrical distribution feeders are tested and compared with the energy efficiency (EE) and cost optimization. The goal of this paper is to analyze the impact of solar thermal energy on electrical energy consumption in the electrical distribution feeder level. The electrical system cost and energy consumptions are tabulated and observed that there is a considerable savings.
文摘Secondary metabolites and synthetic iminosugars that structurally resemble monosaccharides are potent inhibitors of a-glucosidase activity. The enzyme is core in cleaving sucrose in phloem feeding insects and it also plays a crucial role of reducing osmotic stress via the formation of oligosaccharides. Inhibition of hydrolysis by iminosug- ars should result in nutritional deficiencies and/or disruption of normal osmoregulation. Deoxynojirimycin （DNJ） and 2 N-alkylated analogs [N-butyl DNJ （NB-DNJ） and N-nonyl DNJ （NN-DNJ）] were the major iminosugars used throughout the study. The extensive experiments conducted with a-glucosidase of the whitefly Bemisia tabaci indicated the competitive nature of inhibition and that the hydrophilic DNJ is a potent inhibitor in com- parison to the more hydrophobic NB-DNJ and NN-DNJ compounds. The same inhibitory pattern was observed with the psyllid Cacopsylla bidens a-glucosidase. In contrast to the above pattern, enzymes of the aphids, Myzus persicae and Aphis gossypii were more sen- sitive to the hydrophobic iminosugars as compared to DNJ. In vivo experiments in which adult B. tabaci were fed dietary iminosugars, show that the hydrophilic DNJ was far less toxic than the lipophilic NB-DNJ and NN-DNJ. It is proposed that this pattern is attributed to the better accessibility of the hydrophobic NN-DNJ to the a-glucosidase membrane- bound compartment in the midgut. Based on the inhibitory effects of certain polyhydroxy N-alkylated iminosugars, a-glucosidase of phloem feeding hemipterans could serve as an attractive target site for developing novel pest control agents.
基金supported by National Natural Science Foundation of China (No.51867013)Natural Science Foundation of Gansu Province (No.20JR5RA414)。
文摘The purpose of this study is to analyze the galloping characteristics of the catenary positive feeder in fluctuating wind areas considering dynamic-wind angle of attack and aerodynamic damping.Firstly,the flow field model of the catenary positive feeder was established,the fluctuating wind field was simulated by Davenport wind power spectrum and linear filtering method,and the wind speed at inlet in calculation domain was controlled by editing the profile file to simulate and calculate the aerodynamic characteristics of the positive feeder in the fluctuating wind area.Then,taking the positive feeder as the research object,the mathematical model of actual structure and the corresponding finite element model were established.By applying the wind load to the finite element model,the influence of aerodynamic damping caused by the self-movement of the positive feeder on the galloping response was analyzed,and the frequency domain characteristics of galloping displacement of the positive feeder considering aerodynamic damping were studied.Finally,the calculation method of aerodynamic damping by the Guidelines for Electrical Transmission Line Structural Loading(ASCE No.74)was used for the galloping response of the positive feeder and compared with the proposed method.The results show that when considering aerodynamic damping,the galloping amplitude of the positive feeder decreases significantly,and the first-order resonance effect on the vertical displacement and horizontal displacement decreases significantly.The galloping trajectories calculated by the two methods are consistent.Therefore,this study is of great significance to further clarify the ice-free galloping mechanism of the catenary positive feeder in violent wind areas.
基金supported by the National Natural Science Foundation of China (Grant No.52274290)the Basic Science Center Project for the National Natural Science Foundation of China (No.72088101).
文摘Horizontal segregation has been a constraint to the development and application of super-high bed sintering.To eliminate the horizontal segregation of super-high bed sintering,several typical sintering machines were sampled and analyzed,and theoretical calculation was made to compare the bed depth and their differences in different areas within the mixture bin.Then,solutions were proposed and applied to a 265 m^(2) sintering machine.The results showed that the horizontal seg-regation of the 265 m^(2) sintering machine was dominated by particles larger than 8 mm with horizontal segregation degree of 0.48,while 360 and 550 m^(2) sintering machines were affected by 5-8 mm and 1-3 mm particles with horizontal segregation degree of 0.27 and 0.31,respectively.Causes analysis indicated the different segregation distribution results from the matching of the bed depth of each area within the mixture bin.Finally,the horizontal segregation degree not larger than 0.06 was achieved by optimizing the time parameters and the division of three zones on the 265 m^(2) sintering machine.
文摘In our previous study, five homologous feeder cell lines, Monkey ear skin fibroblasts （MESFs）, clonally derived fibroblasts from the MESFs （CMESFs）, monkey oviductal fibroblasts （MOFs）, monkey follicular granulosa fibroblast-like （MFGs） cells, monkey follicular granulosa epithelium-like （MFGEs） cells, were developed for the maintenance of rhesus embryonic stem cells （rESCs）. We found that MESFs, CMESFs, MOFs and MFGs, but not MFGEs, support the growth of rhesus embryonic stem cells. Moreover, we detected some genes that are upregulated in supportive feeder cell lines by semi-quantitative PCR. In the present study, we applied the GeneChip Rhesus Macaque Genome Array of Affymetrix Corporation to study the expression profiles of these five feeder cell lines, in purpose to find out which cytokines and signaling pathways were important in maintaining the rESCs, mRNAs of eight genes, including GREM2, bFGF, KITLG, DKK3, GREM1, AREG, SERPINF1 and LTBP1, were found to be upregulated in supportive feeder cell lines, but not in MFGE. The results indicate that many signaling pathways may play redundant roles in supporting the undifferentiated growth and maintenance of pluripotency in rESCs.
文摘Background: Eurasian Sparrowhawks(Accipiter nisus) increasingly represent successful city-dwellers. Thereby, a rich food supply indicated by high numbers of small birds is believed to be the key driver for this bird-eating raptor species to settle in urban environments. However, as small passerine birds show particularly strong antipredator responses, sparrowhawks may not simply focus on patches of highest prey densities, but rather respond strategically to prey behavior, raising the importance of other parameters in determining the occurrence within urban landscapes.Methods: To deepen our knowledge on habitat requirements of urban sparrowhawks, bird surveys were carried out during winter between December 2005 and January 2017 in 36 city parks in Vienna, Austria. Besides food supply also park size, canopy heterogeneity and the connectivity with other green spaces were considered.Results: Occurrence of sparrowhawks was positively affected by increasing park size, prey density and the interaction between both. Bird feeder density and park connectivity with other green spaces were of minor importance in explaining the presence of this species. Canopy heterogeneity didn't affect city park occupancy by Eurasian Sparrowhawks.Conclusions: Our results suggest that large city parks, particularly when characterized by high prey densities, substantially contribute to protect and preserve ecologically important bird species such as raptors within the urban environment—a landscape already struggling with biodiversity losses and functional homogenization.
基金supported by Natural Science Foundation of Shandong Province(ZR2009FM054)
文摘Fault location for distribution feeders short circuit especially single-phase grounding fault is an important task in distribution system with non-effectively grounded neutral.Fault location mode for distribution feeders using fault generated current and voltage transient traveling waves was investigated.The characteristics of transient traveling waves resulted from each short circuit fault and their transmission disciplinarian in distribution feeders are analyzed.This paper proposed that double end travelling waves theory which measures arriving time of fault initiated surge at both ends of the monitored line is fit for distribution feeders but single end traveling waves theory not.According to different distribution feeders,on the basis of analyzing original traveling waves reflection rule in line terminal, Current-voltage mode,voltage-voltage mode and current-current mode for fault location based on traveling waves are proposed and aerial mode component of original traveling waves is used to realize fault location.Experimental test verify the feasibility and correctness of the proposed method.
文摘An on-line tap-changing circuit was developed for use with low voltage transformers (10 kV/380 V, or equivalent), in which the tap positions could be set independently for each low voltage feeder. This allows for possible variation in loads and distributed generation between different feeders fed from a given transformer, allowing the line voltages to be kept within limits on all feeders. A combination of computer simulation and practical experiments was used. A model constructed in Excel gave preliminary results, which was used to specify a more detailed model in Matlab? Simulink. A small-scale 220/380 V distribution network was constructed, with currents limited to 5 A per phase. Finally, a rotary switch was constructed, suitable for currents up to 500 A, which would be required for a full-scale low voltage distribution network. The results showed that the voltage could be kept within limits, even with a large difference in load and distributed generation from one feeder to another.
基金supported by National Basic Research Program of China (973) under grant No.2009CB219400
文摘An extensive suite of igneous sills was intruded into the Tertiary sedimentary section of the Jiaojiang sag, East China Sea. This suite has been well imaged offshore through 2D and 3D seismic surveys, showing a close relationship with CO2 content in nearby gas discoveries. A new observational model, which incorporates simple upward propagation, simple horizontal propagation, and transgressive propagation, was proposed to interpret these sill intrusions. In this model, the source magma of the saucer-shaped sills was injected from their lowest points near the center. The transgressive propagation can be interpreted as a combination of the vertical and horizontal propagation. Most shallow sub-volcanic intrusions in the Jiaojiang sag exhibit fingered characteristics, both vertically and horizontally. The vertical fingered propagation produced saucer-shaped sills arranged in the flower style. Along the brims of lower sills could usually be found the upper sills, which are interpreted to have formed simultaneously with or later than the lower feeder sills. In the second type, the chilled paths of the older sills were reutilized by subsequent intrusions. The horizontal fingered propagation formed sheet intrusions that exhibit groove, lobate, tubular, and crevasse splay- like geometry in plan view. In 3D view, the sheet intrusions have still preserved the lower center and higher rim that similar with the sub-rounded saucer-shaped sills. Although fracture propagation may be important, flow inflation was the key mechanism of magma intrusion. Further consideration of the mechanisms underlying sill formation may help explain the fingered characteristics of sill propagation.
文摘In vitro growth and maintenance of embryonic stem (ES) cell lines derived from ICM cells of various blastocysts of 129 strain mice, the sustenance of their pluripotency and normal karyotype depend on the feeder layer of mouse embryonic fibroblasts (MEF). Compared with the feeder layer of MEF cells, medium conditioned by Buffalo rat liver cells (BRL-CM) is able to maintain pluripotency and karyo-typic normality of ES cells only in short term cell propagation. Besides, ES cells grown in BRL-CM are also capable of aggregation with 8-cell embryos of Swiss strain and develop into germ line chimaeras. Modification to the method of aggregating ES cells with early embryos by making a hole in agar layer on the top of MEF feeder cells was shown to be more convenient and efficient than the conventional microdrop method.
基金supported by the National Institute of Health,USA (No.R21 RR025408)
文摘Induced pluripotent stem （iPS） cells can be derived from human somatic cells by cellular reprograrnming. This technology provides a potential source of non-controversial therapeutic ceils for tissue repair, drug discovery, and opportunities for studying the molecular basis of human disease. Normally, mouse embryonic fibroblasts （MEFs） are used as feeder layers in the initial derivation of iPS lines. The pur- pose of this study was to determine whether SNL fibrohlasts can be used to support the growth of human iPS cells reprogrammed from somatic cells using lentiviral expressed reprogramming factors. In our study, iPS cells expressed common pluripotency markers, dis- played human embryonic stem cells （hESCs） morphology and unmethylated promoters of NANOG and OCT4. These data demonstrate that SNL feeder cells can support the derivation and maintenance of human iPS cells.
文摘For a surface mounting machine (SMM) in printed circuit board (PCB) assembly line, there are four problems, e.g. CAD data conversion, nozzle selection, feeder assignment and placement sequence determination. A hierarchical planning for them to maximize the throughput rate of an SMM is presented here. To minimize set-up time, a CAD data conversion system was first applied that could automatically generate the data for machine placement from CAD design data files. Then an effective nozzle selection approach was implemented to minimize the time of nozzle changing. And then, to minimize picking time, an algorithm for feeder assignment was used to make picking multiple components simultaneously as much as possible. Finally, in order to shorten pick-and-place time, a heuristic algorithm was used to determine optimal component placement sequence according to the decided feeder positions. Experiments were conducted on a four head SMM. The experimental results were used to analyse the assembly line performance.
基金Projects(51574289,61533020,51674300)supported by the National Natural Science Foundation of ChinaProject(2015CXS017)supported by Innovation-driven Plan in Central South University,China
文摘Because of the increasingly prominent problem of alumina content inhomogeneity in large or super-scale aluminum reduction cells,a transient numerical model for the alumina mixing process was developed for a400kA cell,and the relationship between the alumina content distribution and electrolyte flow field was analyzed.In the ANSYS software platform,several numerical simulation cases were presented to display the influence of the feeder configuration on the alumina mixing characteristics.The results showed that a large vortex flow of the molten electrolyte is beneficial for alumina mixing and uniform distribution in the inner areas of the vortexes.The alumina particles reach the inter-electrode zone in10?15s from the beginning of the feeding action,and the risk of early precipitation occurs in10?25s after the feeding.It was also found that a suitable grouping of feeders could reduce the content fluctuation and gradient.Therefore,a feeding on demand strategy was proposed,and the simulation results showed that although the spatial characteristics are not changed,the uniformity of the alumina content was markedly improved.
基金This work was supported by the National Natural Science Foundation of China(Grant Numbers 51375173).
文摘To satisfy the demand for good quality underwater welding and maintenance of nuclear power stations,a set of local dry automatic welding systems has been developed.These systems were based on an underwater robot that consisted of a special high-power underwater welding power supply,diving wire feeder,mini drain cap,welding robot,and special underwater welding torch.With a digital signal controller microprocessor as its core and combined with a dual inverter topology,the welding power supply was characterized by full-digital construction and multi-waveform flexible output.A compact diving wire feeding device was designed,based on the armature voltage negative feedback and high-frequency chopping pulse width modulation.This device yielded a high-efficiency seal of the driving motor with the help of dynamic and static sealing technology.To overcome the difficulty of local protection and deslagging in the welding area,a mini drain cap(with a duplexgas structure)based on the principle of the convergent nozzle was designed.The practical tests and the underwater welding experiments revealed that the underwater robotic local dry welding system is quite feasible.That is,the system could strike the arc stably and reliably in the shallow water environment,and formed beautiful welding seams.
