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
The rapid expansion of offshore wind energy necessitates robust and cost-effective electrical collector system(ECS)designs that prioritize lifetime operational reliability.Traditional optimization approaches often sim...The rapid expansion of offshore wind energy necessitates robust and cost-effective electrical collector system(ECS)designs that prioritize lifetime operational reliability.Traditional optimization approaches often simplify reliability considerations or fail to holistically integrate them with economic and technical constraints.This paper introduces a novel,two-stage optimization framework for offshore wind farm(OWF)ECS planning that systematically incorporates reliability.The first stage employs Mixed-Integer Linear Programming(MILP)to determine an optimal radial network topology,considering linearized reliability approximations and geographical constraints.The second stage enhances this design by strategically placing tie-lines using a Mixed-Integer Quadratically Constrained Program(MIQCP).This stage leverages a dynamic-aware adaptation of Multi-Source Multi-Terminal Network Reliability(MSMT-NR)assessment,with its inherent nonlinear equations successfully transformed into a solvable MIQCP form for loopy networks.A benchmark case study demonstrates the framework’s efficacy,illustrating how increasing the emphasis on reliability leads to more distributed and interconnected network topologies,effectively balancing investment costs against enhanced system resilience.展开更多
In the interest of decreasing feed costs while maximizing the growth of weanling horses, this study examined the potential difference in the average daily gain （ADG）, gain to feed ratio （G/F）, and apparent dry mat...In the interest of decreasing feed costs while maximizing the growth of weanling horses, this study examined the potential difference in the average daily gain （ADG）, gain to feed ratio （G/F）, and apparent dry matter and crude protein digestibility in horses fed with the same diet provided in different feeder types. Sixteen weanling standardbred horses were used for the duration of the 9-week study. The horses were given 2.5% of their body weight in hay and grain daily, 2% hay and 0.5% grain, as fed in two equal feedings at 7：00 am and 7：00 pm. The first treatment used a combined hay and grain feeder with the hay rack positioned over a manger compartment. The second treatment provided hay in an open hay rack and grain in a separate, open-topped feed tub, not positioned under the hay rack. The two groups, with eight horses--four female and four male in each group, were fed in one manner or the other for the length of the study. The weanlings fed in the combined hay and grain feeder had a greater ADG （0.52 kg/d vs. 0.41 kg/d） and G/F （0.06 vs. 0.05） than the horses with the separate hay and grain feeders. Both ADG and G/F means between treatments were statistically different （P 〈 0.05）. There was not a significant difference （P 〉 0.05） in the apparent digestibility of dry matter or crude protein between the two groups. Therefore, it was concluded that the combined feeding system resulted in greater growth and apparent G/F most likely due to decreased feed wastage; however, apparent digestibility was not different between feeding systems.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
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
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
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
International thermonuclear experimental reactor （ITER） edge localized mode （ELM） coils are used to mitigate or suppress ELMs. The location of the coils in the vacuum vessel and behind the blankets exposes them to...International thermonuclear experimental reactor （ITER） edge localized mode （ELM） coils are used to mitigate or suppress ELMs. The location of the coils in the vacuum vessel and behind the blankets exposes them to high radiation levels and high temperatures. The feeders provide the power and cooling water for ELM coils. They are located in the chinmey ports and experience lower radiation and temperature levels. These coils and feeders work in a high magnetic field environment and are subjected to alternating electromagnetic force due to the interaction between high magnetic field and alternating current （AC） current in the coils. They are also subjected to thermal stresses due to thermal expansion. Using the ITER upper ELM coil and feeder as an example, mechanical analyses are performed to verify and optimize the updated design to enhance their structural performance. The results show that the conductor, jacket and bracket can meet the static, fatigue and crack threshold criteria. The optimization indicates that adding chamfers to the bracket can reduce the high stress of the bracket, and removing two rails can reduce the peak reaction force on the two rails arising from thermal expansion.展开更多
Two common problems for a typical Power distribution system are voltage collapse & instability. Challenge is to identify the vulnerable nodes and apply the effective corrective actions. This paper presents a proba...Two common problems for a typical Power distribution system are voltage collapse & instability. Challenge is to identify the vulnerable nodes and apply the effective corrective actions. This paper presents a probabilistic fuzzy approach to assess the node status and proposes feeder reconfiguration as a method to address the same. Feeder reconfiguration is altering the topological structures of distribution feeders by changing the open/closed states of the sectionalizing and ties switches. The solution is converge using a probabilistic fuzzy modeled solution, which defines the nodal vulnerability index (VI) as a function of node voltage and node voltage stability index and predicts nodes critical to voltage collapse. The information is further used to plan best combination of feeders from each loop in distribution system to be switched out such that the resulting configuration gives the optimal performance i.e. best voltage profile and minimal kW losses. The proposed method is tested on established radial distribution system and results are presented.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
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 Science and Technology Project of China South Power Grid Co.,Ltd.,Grant Nos.036000KK52222044,GDKJXM20222430。
文摘The rapid expansion of offshore wind energy necessitates robust and cost-effective electrical collector system(ECS)designs that prioritize lifetime operational reliability.Traditional optimization approaches often simplify reliability considerations or fail to holistically integrate them with economic and technical constraints.This paper introduces a novel,two-stage optimization framework for offshore wind farm(OWF)ECS planning that systematically incorporates reliability.The first stage employs Mixed-Integer Linear Programming(MILP)to determine an optimal radial network topology,considering linearized reliability approximations and geographical constraints.The second stage enhances this design by strategically placing tie-lines using a Mixed-Integer Quadratically Constrained Program(MIQCP).This stage leverages a dynamic-aware adaptation of Multi-Source Multi-Terminal Network Reliability(MSMT-NR)assessment,with its inherent nonlinear equations successfully transformed into a solvable MIQCP form for loopy networks.A benchmark case study demonstrates the framework’s efficacy,illustrating how increasing the emphasis on reliability leads to more distributed and interconnected network topologies,effectively balancing investment costs against enhanced system resilience.
文摘In the interest of decreasing feed costs while maximizing the growth of weanling horses, this study examined the potential difference in the average daily gain （ADG）, gain to feed ratio （G/F）, and apparent dry matter and crude protein digestibility in horses fed with the same diet provided in different feeder types. Sixteen weanling standardbred horses were used for the duration of the 9-week study. The horses were given 2.5% of their body weight in hay and grain daily, 2% hay and 0.5% grain, as fed in two equal feedings at 7：00 am and 7：00 pm. The first treatment used a combined hay and grain feeder with the hay rack positioned over a manger compartment. The second treatment provided hay in an open hay rack and grain in a separate, open-topped feed tub, not positioned under the hay rack. The two groups, with eight horses--four female and four male in each group, were fed in one manner or the other for the length of the study. The weanlings fed in the combined hay and grain feeder had a greater ADG （0.52 kg/d vs. 0.41 kg/d） and G/F （0.06 vs. 0.05） than the horses with the separate hay and grain feeders. Both ADG and G/F means between treatments were statistically different （P 〈 0.05）. There was not a significant difference （P 〉 0.05） in the apparent digestibility of dry matter or crude protein between the two groups. Therefore, it was concluded that the combined feeding system resulted in greater growth and apparent G/F most likely due to decreased feed wastage; however, apparent digestibility was not different between feeding systems.
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.
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.
文摘International thermonuclear experimental reactor （ITER） edge localized mode （ELM） coils are used to mitigate or suppress ELMs. The location of the coils in the vacuum vessel and behind the blankets exposes them to high radiation levels and high temperatures. The feeders provide the power and cooling water for ELM coils. They are located in the chinmey ports and experience lower radiation and temperature levels. These coils and feeders work in a high magnetic field environment and are subjected to alternating electromagnetic force due to the interaction between high magnetic field and alternating current （AC） current in the coils. They are also subjected to thermal stresses due to thermal expansion. Using the ITER upper ELM coil and feeder as an example, mechanical analyses are performed to verify and optimize the updated design to enhance their structural performance. The results show that the conductor, jacket and bracket can meet the static, fatigue and crack threshold criteria. The optimization indicates that adding chamfers to the bracket can reduce the high stress of the bracket, and removing two rails can reduce the peak reaction force on the two rails arising from thermal expansion.
文摘Two common problems for a typical Power distribution system are voltage collapse & instability. Challenge is to identify the vulnerable nodes and apply the effective corrective actions. This paper presents a probabilistic fuzzy approach to assess the node status and proposes feeder reconfiguration as a method to address the same. Feeder reconfiguration is altering the topological structures of distribution feeders by changing the open/closed states of the sectionalizing and ties switches. The solution is converge using a probabilistic fuzzy modeled solution, which defines the nodal vulnerability index (VI) as a function of node voltage and node voltage stability index and predicts nodes critical to voltage collapse. The information is further used to plan best combination of feeders from each loop in distribution system to be switched out such that the resulting configuration gives the optimal performance i.e. best voltage profile and minimal kW losses. The proposed method is tested on established radial distribution system and results are presented.
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.
