Three feedforward (FFD) control techniques for position-servo machine axesare compared. All three FFD controllers are used with two different PID feedback (FBK) controllers.The two different FBK controllers have two d...Three feedforward (FFD) control techniques for position-servo machine axesare compared. All three FFD controllers are used with two different PID feedback (FBK) controllers.The two different FBK controllers have two different closed-loop bandwidths. They are demonstratedusing experimental data from a linear motor test system and from simulations. Laboratory resultsusing the linear motor hardware demonstrate that the velocity & acceleration (V&A) FFD controllerimproves tracking in all case considered, while the other two FFD controllers actually degradeperformance in many cases. Through simulation this degradation is attributed to extreme sensitivityto round off errors. This sensitivity is the result of a complex controller that is implementedoutside of the feedback loop.展开更多
The study of structure of few-electron heavy ions is of important interest due to the strong field effects. Helium-like ions are the simplest atomic multi-body systems. A considerable improved precision has been made ...The study of structure of few-electron heavy ions is of important interest due to the strong field effects. Helium-like ions are the simplest atomic multi-body systems. A considerable improved precision has been made in both theory and experiments recently. The experiment exploits the radiative recombination (RR) transitions into the vacant 1 s shell of bare and H-like ions. In this process, the energy carried by the emitted photon is the energy difference between the initial and final electron state, hω=Ekin+EB. For bare展开更多
Recently, there has been great interest in the linear polarization of photons produced by radiative electron capture (REC, the time reversed photoionization in ion-atom collisions). No such data are available for the ...Recently, there has been great interest in the linear polarization of photons produced by radiative electron capture (REC, the time reversed photoionization in ion-atom collisions). No such data are available for the high-Z regime till now. By using high efficiency by by a new generation of segmented germanium detectors that have energy as well as position resolution this field can be investigated experimentally. The展开更多
: To enrich differentially expressed sequence tags (ESTs) for aluminum (Al) tolerance, cDNA subtraction libraries were generated from Al-stressed roots of two wheat (Triticum aestivum L.) near-isogenic lines (NILs) co...: To enrich differentially expressed sequence tags (ESTs) for aluminum (Al) tolerance, cDNA subtraction libraries were generated from Al-stressed roots of two wheat (Triticum aestivum L.) near-isogenic lines (NILs) contrasting in Al-tolerance gene(s) from the Al-tolerant cultivar Atlas 66, using suppression subtractive hybridization (SSH). Expression patterns of the ESTs were investigated with nylon filter arrays containing 614 cDNA clones from the subtraction library. Gene expression profiles from macroarray analysis indicated that 25 ESTs were upregulated in the tolerant NIL in response to Al stress. The result from Northern analysis of selected upregulated ESTs was similar to that from macroarray analysis. These highly expressed ESTs showed high homology with genes involved in signal transduction, oxidative stress alleviation, membrane structure, Mg2+ transportation, and other functions. Under Al stress, the Al-tolerant NIL may possess altered structure or function of the cell wall, plasma membrane, and mitochondrion. The wheat response to Al stress may involve complicated defense-related signaling and metabolic pathways. The present experiment did not detect any induced or activated genes involved in the synthesis of malate and other organic acids in wheat under Al-stress.展开更多
Behavior and olfactory responses of grasshopper hatchlings, Melanoplus sanguinipes (F.), to odours from plant foliage and volatile compounds were tested using a glass Y-tube olfactometer and electroantennogram (EAG)te...Behavior and olfactory responses of grasshopper hatchlings, Melanoplus sanguinipes (F.), to odours from plant foliage and volatile compounds were tested using a glass Y-tube olfactometer and electroantennogram (EAG)techniques respectively. In single choice trials, newly hatched hoppers were much more sensitive to the odour from intact leaves and chopped foliage of ryegrass and wheat than other plants. Chopped sorghum leaves, but not stem-cut sorghum,were also significantly attractive. The orientation responses of grasshopper hatchlings to these plants were highly consistent with those of last instar hoppers and adults. When ryegrass was employed as the control, the odour from stem-cut alfalfa was more attractive. There was no significant difference in hopper orientation responses to the odours from chopped seedlings of sorghum, alfalfa, wheat or ryegrass.However, significantly more hoppers preferred the chopped ryegrass control to chopped Louisanna sage. Measurement of the EAG response of first instar hoppers to these plant odours showed that the odour of Louisanna sage elicited the greatest response amplitudes. In olfactory tests using different volatile components, Z-3-hexenol, E-3-hexenol,Z-hex-3-enyl acetate, E-2-hexenal and hexenal gave greater EAG responses than geraniol and 1-octen-3-ol. These results are also consistent with comparable data from adults. Newly hatched grasshoppers had similar EAG response profiles to plant materials and chemicals to those of adults, although the absolute EAG values of young hoppers were much lower than those of adults. Therefore, newly hatched hoppers were able to distinguish plants from an air control, and even host plants from non-host plants, and the feeding experience of hoppers probably has little influence on their subsequent ability as adults to identify and locate food plants.展开更多
The area along the eastern and southeastern margins of the Tengger Desert, NW China, which is sensitive to the summer monsoon variations, was selectedfor studying the environmental conditions surrounding the transitio...The area along the eastern and southeastern margins of the Tengger Desert, NW China, which is sensitive to the summer monsoon variations, was selectedfor studying the environmental conditions surrounding the transition between Paleolithic foragers and Neolithic farmer/pastoral- ists. Short cores were obtained from four lake basins in the southwestern Tengger using a hand-driven piston coring device. Proxies from these cores were supplemented by ra- diocarbon ages obtained from lake sediment cores, shoreline features and spring mound deposits. Together these records provide evidence of millennial-scale climate change events from the Pleistocene-Holocene transition to the present. Lake/wetland events, representing periods of more intensive summer monsoon, occur in the records at ～12.7-11.6, ～10.1, ～9.3, ～8.0, ～5.4, ～1.5, and ～0.8 ka BP. They do suggest that century- to millennial-scale climatic cycles are characteristic of the Holocene in the southeastern Tengger Desert although the chronology must be considered extremely tentative.展开更多
The characteristics of magnetorheological fin- ishing (MRF) technique such as the behavior of magnetic particles and the magnetic field distribution have been inves- tigated. Based on the established theoretical model...The characteristics of magnetorheological fin- ishing (MRF) technique such as the behavior of magnetic particles and the magnetic field distribution have been inves- tigated. Based on the established theoretical model, material removal function and removal rate experiments involving a K9 glass mirror are designed and carried out. Further experiments are carried out to improve the surface roughness of the workpiece. The final surface roughness with an initial value of 17.58 nm reached 0.4351 nm rms after 35 min of deterministic MRF, and the AFM measurements on microstructures of the polished surface are also improved by 0.445 nm rms without obvious defects.展开更多
We obtain formulae and estimates for character sums of the type $S\left( {\chi ,f,p^m } \right) = \sum\nolimits_{x = 1}^{p^m } {\chi \left( {f\left( x \right)} \right),} $ where pm is a prime power with m S 2, L is a ...We obtain formulae and estimates for character sums of the type $S\left( {\chi ,f,p^m } \right) = \sum\nolimits_{x = 1}^{p^m } {\chi \left( {f\left( x \right)} \right),} $ where pm is a prime power with m S 2, L is a multiplicative character (mod p^m), and f=f1/f2 is a rational function over ê. In particular, if p is odd, d=deg(f1)+deg(f2) and d* = max(deg(f1), deg(f2)) then we obtain $\left| {S\left( {\chi ,f,p^m } \right)} \right| \le \left( {d - 1} \right)p^{m\left( {1 - {1 \over {d*}}} \right)}$ for any non-constant f (mod p) and primitive character L. For p = 2 an extra factor of $2\sqrt 2$ is needed.展开更多
Commercial varieties of transgenic Bacillus thuringiensis (Bt) plants have been developed in many countries to control target pests. Initially, the expression of native Bt genes in plants was low due to mRNA insta...Commercial varieties of transgenic Bacillus thuringiensis (Bt) plants have been developed in many countries to control target pests. Initially, the expression of native Bt genes in plants was low due to mRNA instability, improper splicing, and post translation modifications. Subsequently, modifications of the native Bt genes greatly enhanced expression levels. This is a review of the developments that made modern high expression transgenic Bt plants possible, with an emphasis on the reasons for the low level expression of native Bt genes in plant systems, and the techniques that have been used to improve plant expression of Bt toxin genes.展开更多
基金This project is supported by United State's National Science Foundation (No.997761).
文摘Three feedforward (FFD) control techniques for position-servo machine axesare compared. All three FFD controllers are used with two different PID feedback (FBK) controllers.The two different FBK controllers have two different closed-loop bandwidths. They are demonstratedusing experimental data from a linear motor test system and from simulations. Laboratory resultsusing the linear motor hardware demonstrate that the velocity & acceleration (V&A) FFD controllerimproves tracking in all case considered, while the other two FFD controllers actually degradeperformance in many cases. Through simulation this degradation is attributed to extreme sensitivityto round off errors. This sensitivity is the result of a complex controller that is implementedoutside of the feedback loop.
文摘The study of structure of few-electron heavy ions is of important interest due to the strong field effects. Helium-like ions are the simplest atomic multi-body systems. A considerable improved precision has been made in both theory and experiments recently. The experiment exploits the radiative recombination (RR) transitions into the vacant 1 s shell of bare and H-like ions. In this process, the energy carried by the emitted photon is the energy difference between the initial and final electron state, hω=Ekin+EB. For bare
文摘Recently, there has been great interest in the linear polarization of photons produced by radiative electron capture (REC, the time reversed photoionization in ion-atom collisions). No such data are available for the high-Z regime till now. By using high efficiency by by a new generation of segmented germanium detectors that have energy as well as position resolution this field can be investigated experimentally. The
文摘: To enrich differentially expressed sequence tags (ESTs) for aluminum (Al) tolerance, cDNA subtraction libraries were generated from Al-stressed roots of two wheat (Triticum aestivum L.) near-isogenic lines (NILs) contrasting in Al-tolerance gene(s) from the Al-tolerant cultivar Atlas 66, using suppression subtractive hybridization (SSH). Expression patterns of the ESTs were investigated with nylon filter arrays containing 614 cDNA clones from the subtraction library. Gene expression profiles from macroarray analysis indicated that 25 ESTs were upregulated in the tolerant NIL in response to Al stress. The result from Northern analysis of selected upregulated ESTs was similar to that from macroarray analysis. These highly expressed ESTs showed high homology with genes involved in signal transduction, oxidative stress alleviation, membrane structure, Mg2+ transportation, and other functions. Under Al stress, the Al-tolerant NIL may possess altered structure or function of the cell wall, plasma membrane, and mitochondrion. The wheat response to Al stress may involve complicated defense-related signaling and metabolic pathways. The present experiment did not detect any induced or activated genes involved in the synthesis of malate and other organic acids in wheat under Al-stress.
文摘Behavior and olfactory responses of grasshopper hatchlings, Melanoplus sanguinipes (F.), to odours from plant foliage and volatile compounds were tested using a glass Y-tube olfactometer and electroantennogram (EAG)techniques respectively. In single choice trials, newly hatched hoppers were much more sensitive to the odour from intact leaves and chopped foliage of ryegrass and wheat than other plants. Chopped sorghum leaves, but not stem-cut sorghum,were also significantly attractive. The orientation responses of grasshopper hatchlings to these plants were highly consistent with those of last instar hoppers and adults. When ryegrass was employed as the control, the odour from stem-cut alfalfa was more attractive. There was no significant difference in hopper orientation responses to the odours from chopped seedlings of sorghum, alfalfa, wheat or ryegrass.However, significantly more hoppers preferred the chopped ryegrass control to chopped Louisanna sage. Measurement of the EAG response of first instar hoppers to these plant odours showed that the odour of Louisanna sage elicited the greatest response amplitudes. In olfactory tests using different volatile components, Z-3-hexenol, E-3-hexenol,Z-hex-3-enyl acetate, E-2-hexenal and hexenal gave greater EAG responses than geraniol and 1-octen-3-ol. These results are also consistent with comparable data from adults. Newly hatched grasshoppers had similar EAG response profiles to plant materials and chemicals to those of adults, although the absolute EAG values of young hoppers were much lower than those of adults. Therefore, newly hatched hoppers were able to distinguish plants from an air control, and even host plants from non-host plants, and the feeding experience of hoppers probably has little influence on their subsequent ability as adults to identify and locate food plants.
基金supported by US NSF(Grant Nos.9410923 and 9729929)National Natural Science Foundation of China(Grant No.40125001).
文摘The area along the eastern and southeastern margins of the Tengger Desert, NW China, which is sensitive to the summer monsoon variations, was selectedfor studying the environmental conditions surrounding the transition between Paleolithic foragers and Neolithic farmer/pastoral- ists. Short cores were obtained from four lake basins in the southwestern Tengger using a hand-driven piston coring device. Proxies from these cores were supplemented by ra- diocarbon ages obtained from lake sediment cores, shoreline features and spring mound deposits. Together these records provide evidence of millennial-scale climate change events from the Pleistocene-Holocene transition to the present. Lake/wetland events, representing periods of more intensive summer monsoon, occur in the records at ～12.7-11.6, ～10.1, ～9.3, ～8.0, ～5.4, ～1.5, and ～0.8 ka BP. They do suggest that century- to millennial-scale climatic cycles are characteristic of the Holocene in the southeastern Tengger Desert although the chronology must be considered extremely tentative.
基金This work was supported by the National Natural Science Foundation of China(Grant No.50175062).
文摘The characteristics of magnetorheological fin- ishing (MRF) technique such as the behavior of magnetic particles and the magnetic field distribution have been inves- tigated. Based on the established theoretical model, material removal function and removal rate experiments involving a K9 glass mirror are designed and carried out. Further experiments are carried out to improve the surface roughness of the workpiece. The final surface roughness with an initial value of 17.58 nm reached 0.4351 nm rms after 35 min of deterministic MRF, and the AFM measurements on microstructures of the polished surface are also improved by 0.445 nm rms without obvious defects.
文摘We obtain formulae and estimates for character sums of the type $S\left( {\chi ,f,p^m } \right) = \sum\nolimits_{x = 1}^{p^m } {\chi \left( {f\left( x \right)} \right),} $ where pm is a prime power with m S 2, L is a multiplicative character (mod p^m), and f=f1/f2 is a rational function over ê. In particular, if p is odd, d=deg(f1)+deg(f2) and d* = max(deg(f1), deg(f2)) then we obtain $\left| {S\left( {\chi ,f,p^m } \right)} \right| \le \left( {d - 1} \right)p^{m\left( {1 - {1 \over {d*}}} \right)}$ for any non-constant f (mod p) and primitive character L. For p = 2 an extra factor of $2\sqrt 2$ is needed.
文摘Commercial varieties of transgenic Bacillus thuringiensis (Bt) plants have been developed in many countries to control target pests. Initially, the expression of native Bt genes in plants was low due to mRNA instability, improper splicing, and post translation modifications. Subsequently, modifications of the native Bt genes greatly enhanced expression levels. This is a review of the developments that made modern high expression transgenic Bt plants possible, with an emphasis on the reasons for the low level expression of native Bt genes in plant systems, and the techniques that have been used to improve plant expression of Bt toxin genes.
