The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the s...The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the sleeve, the dynamic model of the sleeve detach and reunion drive was theoretically measured, and it was verified that the device is simple to operate and convenient to maintain, thus it has great social values.展开更多
To meet the increasing demand of wireless broadband applications in future 5G cellular networks, Device-to-Device(D2D) communications serve as a candidate paradigm to improve spectrum efficiency. Considering the chall...To meet the increasing demand of wireless broadband applications in future 5G cellular networks, Device-to-Device(D2D) communications serve as a candidate paradigm to improve spectrum efficiency. Considering the challenges after D2 D transmission is introduced for future cellular networks, this paper deals with mode selection and resource allocation issues related with D2 D communications. First, we propose a mode selection scheme which aims at guaranteeing the transmission of cellular users and also considering the potential interference. We analyze the condition under which D2 D underlay mode should be used. Second, we answer the question of "how to effectively reuse cellular resource once underlaying mode is adopted". We further present a resource allocation scheme that focuses on minimizing overall interference as well as a power control method to improve the performance of D2 D systems. Simulation results demonstrate that system parameters greatly affect the switching condition of mode selection and probability of choosing underlay mode. Furthermore, for D2 D underlaying scenario, the proposed resource allocation algorithm guarantees the transmission of cellular users with consideration of transmission requirements of D2 D users. Hence, the proposed scheme can achieve better user experience.展开更多
In order to effectively control the dust at the transshipment point with foam-sol, this paper attempted to study the characteristics of dust diffusion at transshipment point and the foam-sol foaming device with diffus...In order to effectively control the dust at the transshipment point with foam-sol, this paper attempted to study the characteristics of dust diffusion at transshipment point and the foam-sol foaming device with diffusion outlet was also designed in this paper. To study the diffusion rules of coal dust, fluent discrete phase model was utilized in the numerical simulation, as the coal dust was thrown down at a horizontal velocity of 2.5 m/s. A foam-sol foaming device was designed, through which foaming agent could be automatically sucked into the Venturi by the negative pressure. The automatic controller was also equipped,which could transform the energy of the compressed air into the constant pressure difference so that the gelling agent could be qualitatively added into the gel container. The diffusion outlet that could spray out foam-sol in a continuous, conical and 3D manner was also designed. Moreover, this paper also carried out the contrast experiments on dust removal efficiency among water, aqueous foam and foam-sol. The results clearly show that the symmetrical whirlpools appeared below the inlet where the largest whirlpool diameter was 0.52 m, and the horizontal distance from swirl range to the inlet was approximately0.69 m. By using the self-designed foaming device, the foaming was multiplied by 30 times and the volume ratio with water and foaming agent reached 95%:5%. In this context, the gas pressure was controlled at 0.3 MPa, with gas flow at 15 m3/h and water flow at 0.5 m3/h, with water pressure controlled between0.34 and 0.36 MPa. The foam-sol has the highest dust removal efficiency than other agents.展开更多
Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devic...Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devices for hurricane fighting. The decreasing of hurricane energy takes place under the reaction of directed air current against the hurricane air current mass. The air current is created by propellers, located in cylindrical frames with nozzles at a current exit. The devices function due to horizontal hurricanes air current. The essential factor lies in absence of influence on ecology. The devices are of simple constructions, it results in simplification of their production technology and lower cost,展开更多
Research and development design is involved with inflatable lifting web professional boots in architecture industry limited space installation work technology field. This web-based boot includes boot body, lifting dev...Research and development design is involved with inflatable lifting web professional boots in architecture industry limited space installation work technology field. This web-based boot includes boot body, lifting device and support to support the feet and the lifting device to fix on the boot body. The support uses the lifting device to connect to the bottom of the boot body, and through the lifting device function, it can have lifting displacement to the boot bottom. The workers put foot fixed on the support, so as to make the inflating lifting boots walk along with the workers. The adjusting lifting device can make support member move far or near the bottom direction of boot body. The workers can lift higher or lower along with the support. The workers can adjust the lifting device according to specific work height, without using or moving ladder or stool, to save time and improve the work efficiency.展开更多
AIM: To evaluate the feasibility, reproducibility and efficacy of a new tissue anchoring device in a porcine survival model. METHODS: Gastrotomies were performed using a needle-knife and balloon dilator in 10 female Y...AIM: To evaluate the feasibility, reproducibility and efficacy of a new tissue anchoring device in a porcine survival model. METHODS: Gastrotomies were performed using a needle-knife and balloon dilator in 10 female Yorkshire pigs weighing 30-35 kg. Gastric closure was attempted using a new tissue anchoring device. The tightness of the closure was confirmed by means of air insufflation and the ability to maintain gastric distension with stability in peritoneal pressure measured with a Veress needle. All animals were monitored daily for signs of peritonitis and sepsis over 14 d. During necropsy, the peritoneal cavity and the gastric access site were examined.RESULTS: Transgastric access, closure and 14 d survival was achieved in all pigs. The mean closure time was 18.1 ± 19.2 min and a mean of 2.1 ± 1 devices were used. Supplementary clips were necessary in 2 cases. The closure time was progressively reduced (24.8 ± 13.9 min in the first 5 pigs vs 11.4 ± 5.9 min in the last 5, P = NS). At necropsy, the gastric access site was correctly closed in all cases with all brace-bars present. One device was misplaced in the mesocolon. Minimal adhesions were observed in 3 pigs and signs of mild peritonitis and adhesions in one. CONCLUSIONS: The use of this new tissue anchoring device in porcine stomachs is feasible, reproducible and effective and requires a short learning curve.展开更多
This experiment was conducted in silty clay loam soil and cultivated with previous season wheat. Tillage for experiment field was applied using moldboard plow with 0.22-0.24 m depth, the rate of tractor velocity was 2...This experiment was conducted in silty clay loam soil and cultivated with previous season wheat. Tillage for experiment field was applied using moldboard plow with 0.22-0.24 m depth, the rate of tractor velocity was 2.45 km hf^-1, as a tillage velocity. Two rates of tractor velocities (first factor) were applied: 3.24 km hr^-1, for the first velocity, and 4.71 km hr^-1 for the second, Three types of tillers (second factor) were used: disk harrow, rotavator tiller, and spring spike tooth harrow. The first velocity rate was: 2.51 km hr-l(with disk harrow as a machinery unit), 2.92 km hr^-1 (with rotivator), and 3.06 km hrl(with spring spike tooth harrow), while the second velocity rate was: 3.19 km hr-1 (with disk harrow as a machinery unit), 4.05 km hrl(with rotivator), and 4.26 km hrl(with spring spike tooth harrow). Split plot design in RCBD with three replicates was used at the constant of soil moisture 11%-13%. Results were analyzed statistically and means were tested with LSD. The results showed the significant differences between both two experiment factors and their interaction for all study parameters which included: slippage percentage, practical productivity, numbers of masses 〉 5 cm m^-2, and the implement width. At the constant of pulverization equipment types, the higher percentage of slippage was 16.45%, the higher rate of practical productivity was 0.677 h hr1, and the higher rate of implement width was 2.05 m, while the rate of masses 〉 5 cm m-2 decreased to 13.8 mass m2. At the constant of velocity, disk harrow achieved higher slippage percentage 17.69%, spring spike tooth harrow tiller achieved higher practical productivity 0.858 h hr^-1 and higher rate of implement width 2.73 m, and the rotivator achieved the lower rate of masses 〉 5 cm m2 and 4.1 mass m2. The comparison among the three pulverization equipment typess was the purpose of this study to give the best studied indexes under two different velocities.展开更多
In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slop...In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slope. Modulating the argument of current output from ONLLY testing equipment can make the relay protection device operate, thus, the data used for calculation would be obtained naturally after several trails. In order to make sure how effective that method could be, some experiment data is given as well.展开更多
The potential of externally applied FRP (fiber-reinforced plastic) sheets, being employed in retrofitting schemes aimed to repair and strengthen RC (reinforced concrete) structural elements damaged by prototype st...The potential of externally applied FRP (fiber-reinforced plastic) sheets, being employed in retrofitting schemes aimed to repair and strengthen RC (reinforced concrete) structural elements damaged by prototype strong earthquakes, is presented and discussed in this study. The limitation of the debonding mode of failure of these FRP sheets is highlighted and the necessity to develop efficient anchoring devices for these FRP sheets is underlined. The behavior of such a novel HAD (hybrid anchoring device) capable of anchoring CFRP (carbon fiber reinforcing plastic) sheets to RC structural elements, is presented and discussed. The behavior of the device itself was studied through a 3D non-linear numerical simulation at the preliminary design stage in order to establish certain desired features such as the ductile behavior of the device itself as well as the satisfactory performance of the FRP sheets wrapped around this device. This HAD was next applied as part of a strengthening scheme aimed to upgrade the flexural capacity of an RC bridge-type pier specimen subjected to a cyclic seismic-type loading sequence. The obtained results demonstrated an increase in the specimen's flexural capacity by 100% as well as a similar increase in its capability of dissipating energy in a ductile manner during the cyclic load sequence. Moreover, the employed 3D non-linear numerical simulation yielded reasonably good agreement between the measured and the predicted cyclic response of this specimen strengthened by CFRP layers, which were anchored by the novel HAD. The successful behavior of this novel HAD, which has been patented with No. WO2011073696, is currently being tried with a number of other retrofitting schemes employing FRP sheets externally attached on RC structural elements.展开更多
OOS (out-of-step) condition prevention becomes an imperative task to avoid possible power system blackout and collapses. To be confident in correct OOS relaying, the OOS protection device behavior under the vast maj...OOS (out-of-step) condition prevention becomes an imperative task to avoid possible power system blackout and collapses. To be confident in correct OOS relaying, the OOS protection device behavior under the vast majority of power system abnormal regimes should be tested. Comprehensive testing procedure becomes especially important for complex power systems when power system parameters and consequently device settings are not clearly defined or may vary in time. For such complex systems the real OOS protection device testing may become a problem because of specific waveforms of signals persisting during OOS condition. The goal of the methodology, presented in the paper, is to achieve the possibility of out-of-step protection device testing under close-to-real power system operation conditions. The power system stability modelling software is used as a source of test signals. The accurate model of power system in conjunction with dynamical modelling features allows to verify the reliability of OOS protection scheme under consideration as also allows the device settings correction, if necessary. The methodology allows to test the real device with signals waveforms which are hardly obtainable using traditional testing technique.展开更多
Internal arcs cause a rapid increase in pressure in electrical installations. The type of insulation gas has influence on pressure development. Typically SF6 is used incompact metal-clad switchgear, however, it has a ...Internal arcs cause a rapid increase in pressure in electrical installations. The type of insulation gas has influence on pressure development. Typically SF6 is used incompact metal-clad switchgear, however, it has a high global warming potential. Because of this, the replacement of SF6 by alternative gases such as CO2 is under discussion. The pressure developments in a closed vessel filled with air, SF6 and CO2 are measured and compared. During internal arcing in gas-insulated switchgear, overpressure causes a rupture of a burst plate and hot gas escapes into the surrounding room mixing with air. In order to predict the pressure development in electrical installations reliably, the portion of energy causing pressure rise, arc voltage as well as reliable gas data i.e., thermodynamic and transport properties, must be known in a wide range of pressure and temperature. These data are up to now not available for CO2/air mixtures. The thermodynamic properties are directly calculated from the number densities, internal partition functions and enthalpies of formation. The transport coefficients are deduced using the Chapman-Enskog method. Comparing measured and calculated pressure developments in a test arrangement demonstrates the quality of the calculation approach.展开更多
With the development of sound and light technology, they are increasingly being applied to art exhibitions and creations, and even become an indispensable part of the work of art. Installation art prints are more orna...With the development of sound and light technology, they are increasingly being applied to art exhibitions and creations, and even become an indispensable part of the work of art. Installation art prints are more ornamental interesting, appealing and shocking when being promoted by sound and light technology, but also providing more ideas and methods for creators. The creators but also should pay attention to rational use of sound and light technology to achieve better performance results.展开更多
A cross-flow wind turbine near a structure was tested for the performance. The results showed that the performance of a cross-flow wind turbine near a structure was up to 30% higher than the one without a structure. I...A cross-flow wind turbine near a structure was tested for the performance. The results showed that the performance of a cross-flow wind turbine near a structure was up to 30% higher than the one without a structure. In addition, we tried to get higher performance of a cross-flow wind turbine by using an Inlet Guide Structure and a Flow Deflector. An Inlet Guide Structure was placed on the edge of a structure and a Flow Deflector was set near a cross-flow wind turbine and can improve ambient wind environments of the wind turbine, the maximum power coefficients were about 15 to 40% higher and the tip speed ratio range showing the high power coefficient was wide and the positive gradients were steep apparently.展开更多
Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from various problems, such...Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from various problems, such as voltage and frequency instability and power quality issues. To overcome these problems, the capacity for available power transfer of a transmission network should be enhanced. Researchers worldwide have addressed this issue by using flexible AC transmission system (FACTS) devices. We have conducted a comprehensive review of how FACTS controllers are used to enhance the avail- able transfer capability (ATC) and power transfer capability (PTC) of power system networks. This review includes a discussion of the classification of different FACTS devices according to different factors. The popularity and applications of these devices are discussed together with relevant statistics. The operating principles of six major FACTS devices and their application in increasing ATC and PTC are also presented. Finally, we evaluate the performance of FACTS devices in ATC and PTC improvement with respect to different control algorithms.展开更多
An increasing trend in use of tracking devices such as geolocators is based on the assumption that the information gathered from such devices provides reliable information about the migratory behavior of free-living b...An increasing trend in use of tracking devices such as geolocators is based on the assumption that the information gathered from such devices provides reliable information about the migratory behavior of free-living birds. This underlying as- sumption is rarely tested, as evidenced by the absence in many studies of controls, in particular treated controls, and so far never with a reasonable statistical power. Published studies have shown reduced survival prospects or delayed breeding in some species, suggesting that there may be reason to doubt that tracking devices provide unbiased information. Therefore, we conducted a meta-analysis of studies applying geolocators to wild birds to determine whether geolocators affected fitness components. Ge- olocators had an overall negative effect on fitness components, in particular survival, and ecological variables. Effect size was larger for aerial foragers than for other species. Moreover the leg band attachment method was more detrimental for birds than the leg-loop backpack harness. A meta-regression model of effect size showed independent negative effects of geolocators on ae- rial foragers, smaller species, species with smaller migration distances and in studies where geolocators were attached with a ring. These results suggest that geolocator studies should be interpreted with caution, but also raise questions whether it is ethically defensible to use geolocators on aerial foragers or small species without carrying out robust pilot studies.展开更多
This paper proposes an optical device which can continuously change the polarization state of terahertz (THz) waves. The device consists of metal gate, anU-refleetlon coatings, liquid crystal and mirror. By changing...This paper proposes an optical device which can continuously change the polarization state of terahertz (THz) waves. The device consists of metal gate, anU-refleetlon coatings, liquid crystal and mirror. By changing the refractive index of liquid crystal in the interface between the metal gate and the mirror, the phase difference between two beams with orthogonal polarization is varied and a continuous phase sliift is achieved. The phase shift of the device is calculated by using the finite difference time domain (FDTD) method, and the transmittance and reflectance are calculated by using the rigorous coupled wave analysis (RCWA) method. The results reveal that the structure can realize continuously tunable phase shift for THz wave at 1 THz.展开更多
文摘The design of sleeve detach and reunion drive device of screw melt ex- truder equipment was optimized, based on the present installation of hygraulic drive device to achieve the mechanical opening and closing of the sleeve, the dynamic model of the sleeve detach and reunion drive was theoretically measured, and it was verified that the device is simple to operate and convenient to maintain, thus it has great social values.
基金supported by the National Natural Science Foundation of China(No.61501371)National 863 High Tech R&D Program of China(project number:2014AA01A703)+1 种基金National Science and Technology Major Project of the Ministry of Science and Technology of China(project number:2014ZX03001025-006)The international Exchange and Cooperation Projects of Shaanxi Province(project number:2016KW-046)
文摘To meet the increasing demand of wireless broadband applications in future 5G cellular networks, Device-to-Device(D2D) communications serve as a candidate paradigm to improve spectrum efficiency. Considering the challenges after D2 D transmission is introduced for future cellular networks, this paper deals with mode selection and resource allocation issues related with D2 D communications. First, we propose a mode selection scheme which aims at guaranteeing the transmission of cellular users and also considering the potential interference. We analyze the condition under which D2 D underlay mode should be used. Second, we answer the question of "how to effectively reuse cellular resource once underlaying mode is adopted". We further present a resource allocation scheme that focuses on minimizing overall interference as well as a power control method to improve the performance of D2 D systems. Simulation results demonstrate that system parameters greatly affect the switching condition of mode selection and probability of choosing underlay mode. Furthermore, for D2 D underlaying scenario, the proposed resource allocation algorithm guarantees the transmission of cellular users with consideration of transmission requirements of D2 D users. Hence, the proposed scheme can achieve better user experience.
基金supported by the National Natural Science Fund of China (No. 51304146)131 Innovative Talents Cultivation Engineering for Tianjin Province of Chinathe National Innovation Training Project of Undergraduate Student of China (No. 201210060042)
文摘In order to effectively control the dust at the transshipment point with foam-sol, this paper attempted to study the characteristics of dust diffusion at transshipment point and the foam-sol foaming device with diffusion outlet was also designed in this paper. To study the diffusion rules of coal dust, fluent discrete phase model was utilized in the numerical simulation, as the coal dust was thrown down at a horizontal velocity of 2.5 m/s. A foam-sol foaming device was designed, through which foaming agent could be automatically sucked into the Venturi by the negative pressure. The automatic controller was also equipped,which could transform the energy of the compressed air into the constant pressure difference so that the gelling agent could be qualitatively added into the gel container. The diffusion outlet that could spray out foam-sol in a continuous, conical and 3D manner was also designed. Moreover, this paper also carried out the contrast experiments on dust removal efficiency among water, aqueous foam and foam-sol. The results clearly show that the symmetrical whirlpools appeared below the inlet where the largest whirlpool diameter was 0.52 m, and the horizontal distance from swirl range to the inlet was approximately0.69 m. By using the self-designed foaming device, the foaming was multiplied by 30 times and the volume ratio with water and foaming agent reached 95%:5%. In this context, the gas pressure was controlled at 0.3 MPa, with gas flow at 15 m3/h and water flow at 0.5 m3/h, with water pressure controlled between0.34 and 0.36 MPa. The foam-sol has the highest dust removal efficiency than other agents.
文摘Hurricane fighting devices are recommended. The devices belong to the sphere of artificial weather conditions changes over the Earth surface. The purpose of the paper is the development of the original design of devices for hurricane fighting. The decreasing of hurricane energy takes place under the reaction of directed air current against the hurricane air current mass. The air current is created by propellers, located in cylindrical frames with nozzles at a current exit. The devices function due to horizontal hurricanes air current. The essential factor lies in absence of influence on ecology. The devices are of simple constructions, it results in simplification of their production technology and lower cost,
文摘Research and development design is involved with inflatable lifting web professional boots in architecture industry limited space installation work technology field. This web-based boot includes boot body, lifting device and support to support the feet and the lifting device to fix on the boot body. The support uses the lifting device to connect to the bottom of the boot body, and through the lifting device function, it can have lifting displacement to the boot bottom. The workers put foot fixed on the support, so as to make the inflating lifting boots walk along with the workers. The adjusting lifting device can make support member move far or near the bottom direction of boot body. The workers can lift higher or lower along with the support. The workers can adjust the lifting device according to specific work height, without using or moving ladder or stool, to save time and improve the work efficiency.
基金Supported by A Grant from the Instituto de Salud Carlos III(PI08/90026)
文摘AIM: To evaluate the feasibility, reproducibility and efficacy of a new tissue anchoring device in a porcine survival model. METHODS: Gastrotomies were performed using a needle-knife and balloon dilator in 10 female Yorkshire pigs weighing 30-35 kg. Gastric closure was attempted using a new tissue anchoring device. The tightness of the closure was confirmed by means of air insufflation and the ability to maintain gastric distension with stability in peritoneal pressure measured with a Veress needle. All animals were monitored daily for signs of peritonitis and sepsis over 14 d. During necropsy, the peritoneal cavity and the gastric access site were examined.RESULTS: Transgastric access, closure and 14 d survival was achieved in all pigs. The mean closure time was 18.1 ± 19.2 min and a mean of 2.1 ± 1 devices were used. Supplementary clips were necessary in 2 cases. The closure time was progressively reduced (24.8 ± 13.9 min in the first 5 pigs vs 11.4 ± 5.9 min in the last 5, P = NS). At necropsy, the gastric access site was correctly closed in all cases with all brace-bars present. One device was misplaced in the mesocolon. Minimal adhesions were observed in 3 pigs and signs of mild peritonitis and adhesions in one. CONCLUSIONS: The use of this new tissue anchoring device in porcine stomachs is feasible, reproducible and effective and requires a short learning curve.
文摘This experiment was conducted in silty clay loam soil and cultivated with previous season wheat. Tillage for experiment field was applied using moldboard plow with 0.22-0.24 m depth, the rate of tractor velocity was 2.45 km hf^-1, as a tillage velocity. Two rates of tractor velocities (first factor) were applied: 3.24 km hr^-1, for the first velocity, and 4.71 km hr^-1 for the second, Three types of tillers (second factor) were used: disk harrow, rotavator tiller, and spring spike tooth harrow. The first velocity rate was: 2.51 km hr-l(with disk harrow as a machinery unit), 2.92 km hr^-1 (with rotivator), and 3.06 km hrl(with spring spike tooth harrow), while the second velocity rate was: 3.19 km hr-1 (with disk harrow as a machinery unit), 4.05 km hrl(with rotivator), and 4.26 km hrl(with spring spike tooth harrow). Split plot design in RCBD with three replicates was used at the constant of soil moisture 11%-13%. Results were analyzed statistically and means were tested with LSD. The results showed the significant differences between both two experiment factors and their interaction for all study parameters which included: slippage percentage, practical productivity, numbers of masses 〉 5 cm m^-2, and the implement width. At the constant of pulverization equipment types, the higher percentage of slippage was 16.45%, the higher rate of practical productivity was 0.677 h hr1, and the higher rate of implement width was 2.05 m, while the rate of masses 〉 5 cm m-2 decreased to 13.8 mass m2. At the constant of velocity, disk harrow achieved higher slippage percentage 17.69%, spring spike tooth harrow tiller achieved higher practical productivity 0.858 h hr^-1 and higher rate of implement width 2.73 m, and the rotivator achieved the lower rate of masses 〉 5 cm m2 and 4.1 mass m2. The comparison among the three pulverization equipment typess was the purpose of this study to give the best studied indexes under two different velocities.
文摘In this paper, a method to calculate the slope of the ratio restraint characteristic of a transformer differential relay protection is proposed. The method allows using some concise but effective means to get the slope. Modulating the argument of current output from ONLLY testing equipment can make the relay protection device operate, thus, the data used for calculation would be obtained naturally after several trails. In order to make sure how effective that method could be, some experiment data is given as well.
文摘The potential of externally applied FRP (fiber-reinforced plastic) sheets, being employed in retrofitting schemes aimed to repair and strengthen RC (reinforced concrete) structural elements damaged by prototype strong earthquakes, is presented and discussed in this study. The limitation of the debonding mode of failure of these FRP sheets is highlighted and the necessity to develop efficient anchoring devices for these FRP sheets is underlined. The behavior of such a novel HAD (hybrid anchoring device) capable of anchoring CFRP (carbon fiber reinforcing plastic) sheets to RC structural elements, is presented and discussed. The behavior of the device itself was studied through a 3D non-linear numerical simulation at the preliminary design stage in order to establish certain desired features such as the ductile behavior of the device itself as well as the satisfactory performance of the FRP sheets wrapped around this device. This HAD was next applied as part of a strengthening scheme aimed to upgrade the flexural capacity of an RC bridge-type pier specimen subjected to a cyclic seismic-type loading sequence. The obtained results demonstrated an increase in the specimen's flexural capacity by 100% as well as a similar increase in its capability of dissipating energy in a ductile manner during the cyclic load sequence. Moreover, the employed 3D non-linear numerical simulation yielded reasonably good agreement between the measured and the predicted cyclic response of this specimen strengthened by CFRP layers, which were anchored by the novel HAD. The successful behavior of this novel HAD, which has been patented with No. WO2011073696, is currently being tried with a number of other retrofitting schemes employing FRP sheets externally attached on RC structural elements.
文摘OOS (out-of-step) condition prevention becomes an imperative task to avoid possible power system blackout and collapses. To be confident in correct OOS relaying, the OOS protection device behavior under the vast majority of power system abnormal regimes should be tested. Comprehensive testing procedure becomes especially important for complex power systems when power system parameters and consequently device settings are not clearly defined or may vary in time. For such complex systems the real OOS protection device testing may become a problem because of specific waveforms of signals persisting during OOS condition. The goal of the methodology, presented in the paper, is to achieve the possibility of out-of-step protection device testing under close-to-real power system operation conditions. The power system stability modelling software is used as a source of test signals. The accurate model of power system in conjunction with dynamical modelling features allows to verify the reliability of OOS protection scheme under consideration as also allows the device settings correction, if necessary. The methodology allows to test the real device with signals waveforms which are hardly obtainable using traditional testing technique.
文摘Internal arcs cause a rapid increase in pressure in electrical installations. The type of insulation gas has influence on pressure development. Typically SF6 is used incompact metal-clad switchgear, however, it has a high global warming potential. Because of this, the replacement of SF6 by alternative gases such as CO2 is under discussion. The pressure developments in a closed vessel filled with air, SF6 and CO2 are measured and compared. During internal arcing in gas-insulated switchgear, overpressure causes a rupture of a burst plate and hot gas escapes into the surrounding room mixing with air. In order to predict the pressure development in electrical installations reliably, the portion of energy causing pressure rise, arc voltage as well as reliable gas data i.e., thermodynamic and transport properties, must be known in a wide range of pressure and temperature. These data are up to now not available for CO2/air mixtures. The thermodynamic properties are directly calculated from the number densities, internal partition functions and enthalpies of formation. The transport coefficients are deduced using the Chapman-Enskog method. Comparing measured and calculated pressure developments in a test arrangement demonstrates the quality of the calculation approach.
文摘With the development of sound and light technology, they are increasingly being applied to art exhibitions and creations, and even become an indispensable part of the work of art. Installation art prints are more ornamental interesting, appealing and shocking when being promoted by sound and light technology, but also providing more ideas and methods for creators. The creators but also should pay attention to rational use of sound and light technology to achieve better performance results.
文摘A cross-flow wind turbine near a structure was tested for the performance. The results showed that the performance of a cross-flow wind turbine near a structure was up to 30% higher than the one without a structure. In addition, we tried to get higher performance of a cross-flow wind turbine by using an Inlet Guide Structure and a Flow Deflector. An Inlet Guide Structure was placed on the edge of a structure and a Flow Deflector was set near a cross-flow wind turbine and can improve ambient wind environments of the wind turbine, the maximum power coefficients were about 15 to 40% higher and the tip speed ratio range showing the high power coefficient was wide and the positive gradients were steep apparently.
基金supported by the Ministry of Higher Education of Malaysia and University of Malaya under the E-Science Fund Research Grant(No.SF005-2013)the UMRG Project RP015D-13AET
文摘Global demand for power has significantly increased, but power generation and transmission capacities have not increased proportionally with this demand. As a result, power consumers suffer from various problems, such as voltage and frequency instability and power quality issues. To overcome these problems, the capacity for available power transfer of a transmission network should be enhanced. Researchers worldwide have addressed this issue by using flexible AC transmission system (FACTS) devices. We have conducted a comprehensive review of how FACTS controllers are used to enhance the avail- able transfer capability (ATC) and power transfer capability (PTC) of power system networks. This review includes a discussion of the classification of different FACTS devices according to different factors. The popularity and applications of these devices are discussed together with relevant statistics. The operating principles of six major FACTS devices and their application in increasing ATC and PTC are also presented. Finally, we evaluate the performance of FACTS devices in ATC and PTC improvement with respect to different control algorithms.
文摘An increasing trend in use of tracking devices such as geolocators is based on the assumption that the information gathered from such devices provides reliable information about the migratory behavior of free-living birds. This underlying as- sumption is rarely tested, as evidenced by the absence in many studies of controls, in particular treated controls, and so far never with a reasonable statistical power. Published studies have shown reduced survival prospects or delayed breeding in some species, suggesting that there may be reason to doubt that tracking devices provide unbiased information. Therefore, we conducted a meta-analysis of studies applying geolocators to wild birds to determine whether geolocators affected fitness components. Ge- olocators had an overall negative effect on fitness components, in particular survival, and ecological variables. Effect size was larger for aerial foragers than for other species. Moreover the leg band attachment method was more detrimental for birds than the leg-loop backpack harness. A meta-regression model of effect size showed independent negative effects of geolocators on ae- rial foragers, smaller species, species with smaller migration distances and in studies where geolocators were attached with a ring. These results suggest that geolocator studies should be interpreted with caution, but also raise questions whether it is ethically defensible to use geolocators on aerial foragers or small species without carrying out robust pilot studies.
基金supported by the National Key Basic Research Program of China(No.2007CB310403)
文摘This paper proposes an optical device which can continuously change the polarization state of terahertz (THz) waves. The device consists of metal gate, anU-refleetlon coatings, liquid crystal and mirror. By changing the refractive index of liquid crystal in the interface between the metal gate and the mirror, the phase difference between two beams with orthogonal polarization is varied and a continuous phase sliift is achieved. The phase shift of the device is calculated by using the finite difference time domain (FDTD) method, and the transmittance and reflectance are calculated by using the rigorous coupled wave analysis (RCWA) method. The results reveal that the structure can realize continuously tunable phase shift for THz wave at 1 THz.