In Huojitu Coal Mine of Shendong mining area, the dynamic strata pressure (DSP) accidents occurred when the working faces passed the gully terrain. Focusing on this problem, we used physical simulation experimental me...In Huojitu Coal Mine of Shendong mining area, the dynamic strata pressure (DSP) accidents occurred when the working faces passed the gully terrain. Focusing on this problem, we used physical simulation experimental method to thoroughly study the influence of eroded overlying primary key strata (PKS) in the gully terrain on DSP of shallow coal seams in this paper. The result show that when mining activities took place in the uphill section of shallow coal seams in gully terrain and the PKS were eroded, the blocks could not form stable bond-beam structures since the horizontal force of PKS blocks in adjacent sloping surfaces were relatively small. The sliding instability of blocks caused rapid increase of the load on the sub-key strata (SKS) blocks, which resulted into coal slide and roof fall as well as sharp drop of active columns. This led to DSP phenomenon. When the PKS blocks were intact, there was no DSP phenomenon to enable blocks provide certain horizontal force to maintain stable bond-beam structure. The simulation results were verified by the mining practices of working face 21306 crossing the gully terrain in the Huojitu Coal Mine.展开更多
Strainburst is one type of rockburst that generally occurs in deep tunnel.In this study,the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition,and two stress p...Strainburst is one type of rockburst that generally occurs in deep tunnel.In this study,the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition,and two stress paths were designed,a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was varied.During the tests,a high-speed camera was used to record the strainburst process,and an acoustic emission(AE)monitoring system was used to monitor the AE characteristics of failure.In these two stress paths,all the marble specimens exhibited strainbursts;however,when the intermediate principal stress was varied,the rockburst became more violent.The obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of marble.Under a higher intermediate principal stress before the unloading,more elastic strain energy was accumulated in the specimen,and the cumulative AE energy was higher in the rockburst-induced failure,i.e.,more elastic strain energy was released during the failure.Therefore,more violent failure was observed:more rock fragments with a higher mass and larger size were ejected outward.展开更多
A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by disc...A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.展开更多
Greek classics, Homer, and the Greek tragedians, supposed to be the cornerstone of Western civilization, have long suffered from a stagnant and formalistic institutional approach. On the other hand, the adaptations, t...Greek classics, Homer, and the Greek tragedians, supposed to be the cornerstone of Western civilization, have long suffered from a stagnant and formalistic institutional approach. On the other hand, the adaptations, the transcriptions, or the transubstantiations of the Greek antiquity material into new stories and formats compose an abundant cultural field. Antiquity is diffused in a variety of texts, among comics as well. In this paper, we revise the comic books adaptations dealing with ancient Greek classics and classify them according to ＂the fidelity criterion-dilemma＂, to the kind of reader they imply and to the extent of authorial mastery they impose. When classics and comics collide, they create unexpected variations of the ancient material, reflecting the receiving culture＇s practices and beliefs.展开更多
For a young, media savvy, radically globalized generation, television as a platform for news has lost momentum. Ironically, however, in a media landscape with a variety of news providers competing for audiences and tr...For a young, media savvy, radically globalized generation, television as a platform for news has lost momentum. Ironically, however, in a media landscape with a variety of news providers competing for audiences and trust, television news parodies like The Daily Show with Jon Stewart and The Colbert Report attract new audiences as they seem to fill a gap. They succeed not only in entertaining and informing （even educating） a previously ＂deactivated＂, relatively young target audience, but also in initiating activism by using old and new （social） media. How can it be that a comedy show succeeds in promoting reason and gets young people to stand up for more sanity in politics and culture？ In the sense that, in this case, critical （subversive） practice comes fxom within the mainstream, is television, as the platform that has been criticized for ＂dumbing down＂ audiences （cf. Postman 1985）, actually becoming the solution for commitment7 In this constellation, what is the role of self-determined （intrinsic） and acquired （extrinsic） practices in relation to mobilized practices and practices determined by other factors？ And how do they work differently in comparison to the subversive practices of tactical media and media activism that question the methods of biopower？ This paper examines several responses to the （more and less serious） calls for action of the two shows and discusses their delicate role as entertainers, watchdogs, and activists for reason, sanity, and what is left of truth in the media. Furthermore, implications for critical media studies are considered by questioning the claims of education towards truth （of. Mitterer, 1983）.展开更多
Mycoparasitic species of Trichoderma are commercially applied as biological control agents against various fungal pathogens. The mycoparasitic interaction is host specific and includes recognition, attack and subseque...Mycoparasitic species of Trichoderma are commercially applied as biological control agents against various fungal pathogens. The mycoparasitic interaction is host specific and includes recognition, attack and subsequent penetration and killing of the host. Investigations on the underlying events revealed that Trichoderma responds to multiple signals from the host (e.g. lectins or other ligands such as low molecular weight components released from the host’s cell wall) and host attack is accompanied by morphological changes and the secretion of hydrolytic enzymes and antibiotics. Degradation of the cell wall of the host fungus is-besides glucanases and proteases-mainly achieved by chitinases. In vivo studies showed that the ech42 gene (encoding endochitinase 42) is expressed before physical contact of Trichoderma with its host, probably representing one of the earliest events in mycoparasitism, whereas Nag1 (N-acetylglucosaminidase) plays a key role in the general induction of the chitinolytic enzyme system of T. atroviride . Investigations on the responsible signal transduction pathways of T. atroviride led to the isolation of several genes encoding key components of the cAMP and MAP kinase signaling pathways, as alpha and β subunits of heterotrimeric G proteins, the regulatory subunit of cAMP-dependent protein kinase, adenylate cyclase, and three MAP kinases. Analysis of knockout mutants, generated by Agrobacterium-mediated transformation, revealed that at least two alpha-subunits of heterotrimeric G proteins are participating in mycoparasitism-related signal transduction. The Tga1 G alpha subunit was shown to be involved in mycoparasitism-related processes such as chitinase expression and overproduction of toxic secondary metabolites, whereas Tga3 was found to be completely avirulent showing defects in chitinase formation and host recognition.展开更多
With the help of engineering technologies, there are varieties of medical supports such as surgical simulations, preoperative plans, intraoperative supports, and diagnostic explanations. In order to perform preoperati...With the help of engineering technologies, there are varieties of medical supports such as surgical simulations, preoperative plans, intraoperative supports, and diagnostic explanations. In order to perform preoperative plans, the simulation model of the target organ is necessary, and is usually generated from some fine images obtained by imaging devices such as CT （computed tomography） or MRI （magnetic resonance imaging）. These devices, however, are very large and it is difficult to use them during the surgery although there is a kind of MRI that can be used during operations. On the other hand, there is a device called Ultrasonography （US Echo）. It is so handy and can be easily used during operations without radiation or magnetic effect. US images, however, are not usually used for the construction of 3D model for preoperative plans since there are so many noises in the image, and the quality of the image is not so good compared to the images obtained by CT or MRI. Therefore, the authors have tried to construct 3D volumetric shape model from just two 2D US （ultrasound） images, which are the horizontal and vertical cross-section images of the target organ. Their concrete target organ and surgery are the aorta and AAE （annuloaortic ectasia）, respectively. With some technologies of image processing, the boundary of the aorta is extracted for both cross-section images, and the thickness of the aorta is estimated. These processes are applied to not only the aorta wall but also the aorta valve. Finally, the aorta shape model can be constructed by inserting the estimated horizontal aorta images into the estimated vertical one. The constructed model has three dimensions so that it can be viewed from any point of view.展开更多
The image elements of earth-center and moon-center are obtained by processing the images of earthand moon, these image elements in combination with the inertial attitude information and the moon ephemerisare utilized ...The image elements of earth-center and moon-center are obtained by processing the images of earthand moon, these image elements in combination with the inertial attitude information and the moon ephemerisare utilized to obtain the probe initial position relative to earth, and the Levenberg-Marquardt algorithm is usedto determine the accurate probe position relative to earth, and the probe orbit relative to earth is estimated by u-sing the extended Kalman filter. The autonomous optical navigation algorithm is validated using the digital simu-lation.展开更多
To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster an...To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.展开更多
On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piez...On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.展开更多
Arbuscular mycorrhizal （AM） fungi are obligate symbionts that colonize the roots of more than 80% of land plants. Experi- ments on the relationship between the host plant and AM in soil or in sterile root-organ cult...Arbuscular mycorrhizal （AM） fungi are obligate symbionts that colonize the roots of more than 80% of land plants. Experi- ments on the relationship between the host plant and AM in soil or in sterile root-organ culture have provided clear evidence that the extraradical mycelia of AM fungi uptake various forms of nitrogen （N） and transport the assimilated N to the roots of the host plant. However, the uptake mechanisms of various forms of N and its translocation and transfer from the fungus to the host are virtually unknown. Therefore, there is a dearth of integrated models describing the movement of N through the AM fungal hyphae. Recent studies examined Ri T-DNA-transformed carrot roots colonized with AM fungi in ~SN tracer experi- ments. In these experiments, the activities of key enzymes were determined, and expressions of genes related to N assimilation and translocation pathways were quantified. This review summarizes and discusses the results of recent research on the forms of N uptake, transport, degradation, and transfer to the roots of the host plant and the underlying mechanisms, as well as re- search on the forms of N and carbon used by germinating spores and their effects on amino acid metabolism. Finally, a path- way model summarizing the entire mechanism of N metabolism in AM fungi is outlined.展开更多
China is now in an era of multiple values. While there is some virtue in previous theories on the history of literature based on the theory of evolution, class struggle and the enlightenment, when it comes to the twen...China is now in an era of multiple values. While there is some virtue in previous theories on the history of literature based on the theory of evolution, class struggle and the enlightenment, when it comes to the twenty-first century, the histories of modem Chinese literature used in teaching are farfrom adequate for meeting the developmental needs of the times, society and literature. This is especially so in view of the putting forward of the goals of ＂putting people first＂ and ＂the harmonious society,＂ and the great changes taking place in time and space, the function of literature and aesthetic taste. Hence there is an urgent need to restructure this history and establish a more fair, equal and reasonable system of evaluation. Such a system would have humanism as its highest principle, and truth, goodness and beauty as its three virtues. Its great superiority would be its functional characteristics of universality, transcendence, fairness, and human-centeredness.展开更多
Pseudo-random number generators have always been important in experimental design, computer simulation, cryptography and statistical analysis. This paper presents a method of comparing the degree of independence exhib...Pseudo-random number generators have always been important in experimental design, computer simulation, cryptography and statistical analysis. This paper presents a method of comparing the degree of independence exhibited by various random number generators, a procedure, based on consideration of the largest (in modulus) non-unit eigenvalue of the observed Markov transition matrix, is used to assess the 'randomness' of a random number generator.展开更多
For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is ...For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is discussed,and an exact analytical solution is derived with the method of expanding Bessel series and Graf addition theory.According to the analytical expression,the nonlinearity characteristics of the modulator can be precisely predicted,and the system performance can be optimized.The correctness of the analytical solution is approved by simulation results.Analytical results indicate that the nonlinearity distortion is suppressed as the decrease of modulation index,the increase of direct current bias phase shift and phase difference between two input RF signals.When the phase difference equals zero orπand the direct current bias phase shift isπ/2,there are only odd-order distortion terms.When the phase difference equals zero orπand the direct current bias phase shift isπ,there are only even-order distortion terms.展开更多
Toxin, one of the most important factors of plant fungal disease, has attracted much attention of many academicians who have been studying pathogen mycotoxin in deep research. The paper summarized chemical structures ...Toxin, one of the most important factors of plant fungal disease, has attracted much attention of many academicians who have been studying pathogen mycotoxin in deep research. The paper summarized chemical structures of some host-selective plant pathogen mycotoxins discovered in recent years and the correlation between biological activity and chemical structure of toxin.展开更多
Mycophagists can influence fungal diversity within their home ranges by ensuring the continued and effective dispersal of spores from one site to another. However, the passage of spores through the digestive tract of ...Mycophagists can influence fungal diversity within their home ranges by ensuring the continued and effective dispersal of spores from one site to another. However, the passage of spores through the digestive tract of vertebrates can affect the activity and viability of the spores ingested. This phenomenon has been rarely documented in opportunistic mycophagists consuming epigeous fungi. Using laboratory experiments, we investigated the activity and viability of spores of two epigeous ectomycorrhizal fungal species （Laccaria trichodermophora and SuiUus tomentosus） after passage through the digestive tract of two opportunistic mycophagous small rodents, the volcano mouse Peromyscus alstoni and the deer mouse P maniculatus. We found that passage through the gut of either species of rodent had a significant effect on spore activity and viability for both fungal species. The proportion of active spores （0.37-0.40） of L. trichodermophora in the feces of both species of rodents was less than that recorded for the control （0.82）. However, the proportion of active spores （0.644）.73） of S. tomentosus in the feces of each species of rodent was higher than in the control （0.40）. On the other hand, the viability of spores was lower （0.26-0.30 in L. trichodermophora and 0.604）.69 in S. tomentosus） for both fungi when consumed by either rodent relative to the controls （0.90 in L. trichodermophora and 0.82 in S. tomentosus）. These findings suggest that these rodent species may be effective dispersers of both epigeous fungi [Current Zoology 57 （3）： 293-299, 2011].展开更多
基金The support from both the National Natural Science Foundation of China (No. 50974116)the Open Research Foundation from State Key Laboratory of Coal Resources and Mine Safety at China University of Mining and Technology (No. 08KF04) are gratefully acknowledged
文摘In Huojitu Coal Mine of Shendong mining area, the dynamic strata pressure (DSP) accidents occurred when the working faces passed the gully terrain. Focusing on this problem, we used physical simulation experimental method to thoroughly study the influence of eroded overlying primary key strata (PKS) in the gully terrain on DSP of shallow coal seams in this paper. The result show that when mining activities took place in the uphill section of shallow coal seams in gully terrain and the PKS were eroded, the blocks could not form stable bond-beam structures since the horizontal force of PKS blocks in adjacent sloping surfaces were relatively small. The sliding instability of blocks caused rapid increase of the load on the sub-key strata (SKS) blocks, which resulted into coal slide and roof fall as well as sharp drop of active columns. This led to DSP phenomenon. When the PKS blocks were intact, there was no DSP phenomenon to enable blocks provide certain horizontal force to maintain stable bond-beam structure. The simulation results were verified by the mining practices of working face 21306 crossing the gully terrain in the Huojitu Coal Mine.
基金Project(2016YFC0801403) supported by the National Key Research and Development Program of ChinaProject(2017RCJJ012) supported by the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents,China+1 种基金Project(ZR2018MEE009) supported by the Shandong Provincial Natural Science Foundation,ChinaProject(MDPC2017ZR04) supported by the Open Project Fund for State Key Laboratory of Mining Disaster Prevention and Control Co-founded by Shandong Province and the Ministry of Science and Technology of China
文摘Strainburst is one type of rockburst that generally occurs in deep tunnel.In this study,the strainburst behaviors of marble specimens were investigated under tunnel-excavation-induced stress condition,and two stress paths were designed,a commonly used stress path in true triaxial unloading rockburst tests and a new test path in which the intermediate principal stress was varied.During the tests,a high-speed camera was used to record the strainburst process,and an acoustic emission(AE)monitoring system was used to monitor the AE characteristics of failure.In these two stress paths,all the marble specimens exhibited strainbursts;however,when the intermediate principal stress was varied,the rockburst became more violent.The obtained results indicate that the intermediate principal stress has a significant effect on rockburst behavior of marble.Under a higher intermediate principal stress before the unloading,more elastic strain energy was accumulated in the specimen,and the cumulative AE energy was higher in the rockburst-induced failure,i.e.,more elastic strain energy was released during the failure.Therefore,more violent failure was observed:more rock fragments with a higher mass and larger size were ejected outward.
基金Projects(51205335,50975242,51375411) supported by the National Natural Science Foundation of ChinaProject(2013J01209) supported by the Natural Science Foundation of Fujian Province,China
文摘A slotting method for cosine gears was proposed by using the involute cutter based on the conjugate theories of digital surface and gear meshing. The slotting model between the cosine tooth surface represented by discrete points and the cutter figuration determined by analytic function was built for their geometrical relationship and conjugate motion during the machining process. Conjugate points in the cutter section corresponding to the discrete points on the cosine gear tooth surface and the conjugate movements were solved. By using the flexible control of the CNC procedure, the active control of the cutting trace of the slotting cutter was accomplished and the envelop forming of the cosine gear was obtained. Based on the software C++ and Matlab, the computer aided manufacturing(CAM) system of the cosine gear was developed, and the simulation of the slotting process was accomplished. Several examples were provided to illustrate the approach. The result of the simulation demonstrates that the proposed slotting method is feasible.
文摘Greek classics, Homer, and the Greek tragedians, supposed to be the cornerstone of Western civilization, have long suffered from a stagnant and formalistic institutional approach. On the other hand, the adaptations, the transcriptions, or the transubstantiations of the Greek antiquity material into new stories and formats compose an abundant cultural field. Antiquity is diffused in a variety of texts, among comics as well. In this paper, we revise the comic books adaptations dealing with ancient Greek classics and classify them according to ＂the fidelity criterion-dilemma＂, to the kind of reader they imply and to the extent of authorial mastery they impose. When classics and comics collide, they create unexpected variations of the ancient material, reflecting the receiving culture＇s practices and beliefs.
文摘For a young, media savvy, radically globalized generation, television as a platform for news has lost momentum. Ironically, however, in a media landscape with a variety of news providers competing for audiences and trust, television news parodies like The Daily Show with Jon Stewart and The Colbert Report attract new audiences as they seem to fill a gap. They succeed not only in entertaining and informing （even educating） a previously ＂deactivated＂, relatively young target audience, but also in initiating activism by using old and new （social） media. How can it be that a comedy show succeeds in promoting reason and gets young people to stand up for more sanity in politics and culture？ In the sense that, in this case, critical （subversive） practice comes fxom within the mainstream, is television, as the platform that has been criticized for ＂dumbing down＂ audiences （cf. Postman 1985）, actually becoming the solution for commitment7 In this constellation, what is the role of self-determined （intrinsic） and acquired （extrinsic） practices in relation to mobilized practices and practices determined by other factors？ And how do they work differently in comparison to the subversive practices of tactical media and media activism that question the methods of biopower？ This paper examines several responses to the （more and less serious） calls for action of the two shows and discusses their delicate role as entertainers, watchdogs, and activists for reason, sanity, and what is left of truth in the media. Furthermore, implications for critical media studies are considered by questioning the claims of education towards truth （of. Mitterer, 1983）.
文摘Mycoparasitic species of Trichoderma are commercially applied as biological control agents against various fungal pathogens. The mycoparasitic interaction is host specific and includes recognition, attack and subsequent penetration and killing of the host. Investigations on the underlying events revealed that Trichoderma responds to multiple signals from the host (e.g. lectins or other ligands such as low molecular weight components released from the host’s cell wall) and host attack is accompanied by morphological changes and the secretion of hydrolytic enzymes and antibiotics. Degradation of the cell wall of the host fungus is-besides glucanases and proteases-mainly achieved by chitinases. In vivo studies showed that the ech42 gene (encoding endochitinase 42) is expressed before physical contact of Trichoderma with its host, probably representing one of the earliest events in mycoparasitism, whereas Nag1 (N-acetylglucosaminidase) plays a key role in the general induction of the chitinolytic enzyme system of T. atroviride . Investigations on the responsible signal transduction pathways of T. atroviride led to the isolation of several genes encoding key components of the cAMP and MAP kinase signaling pathways, as alpha and β subunits of heterotrimeric G proteins, the regulatory subunit of cAMP-dependent protein kinase, adenylate cyclase, and three MAP kinases. Analysis of knockout mutants, generated by Agrobacterium-mediated transformation, revealed that at least two alpha-subunits of heterotrimeric G proteins are participating in mycoparasitism-related signal transduction. The Tga1 G alpha subunit was shown to be involved in mycoparasitism-related processes such as chitinase expression and overproduction of toxic secondary metabolites, whereas Tga3 was found to be completely avirulent showing defects in chitinase formation and host recognition.
文摘With the help of engineering technologies, there are varieties of medical supports such as surgical simulations, preoperative plans, intraoperative supports, and diagnostic explanations. In order to perform preoperative plans, the simulation model of the target organ is necessary, and is usually generated from some fine images obtained by imaging devices such as CT （computed tomography） or MRI （magnetic resonance imaging）. These devices, however, are very large and it is difficult to use them during the surgery although there is a kind of MRI that can be used during operations. On the other hand, there is a device called Ultrasonography （US Echo）. It is so handy and can be easily used during operations without radiation or magnetic effect. US images, however, are not usually used for the construction of 3D model for preoperative plans since there are so many noises in the image, and the quality of the image is not so good compared to the images obtained by CT or MRI. Therefore, the authors have tried to construct 3D volumetric shape model from just two 2D US （ultrasound） images, which are the horizontal and vertical cross-section images of the target organ. Their concrete target organ and surgery are the aorta and AAE （annuloaortic ectasia）, respectively. With some technologies of image processing, the boundary of the aorta is extracted for both cross-section images, and the thickness of the aorta is estimated. These processes are applied to not only the aorta wall but also the aorta valve. Finally, the aorta shape model can be constructed by inserting the estimated horizontal aorta images into the estimated vertical one. The constructed model has three dimensions so that it can be viewed from any point of view.
文摘The image elements of earth-center and moon-center are obtained by processing the images of earthand moon, these image elements in combination with the inertial attitude information and the moon ephemerisare utilized to obtain the probe initial position relative to earth, and the Levenberg-Marquardt algorithm is usedto determine the accurate probe position relative to earth, and the probe orbit relative to earth is estimated by u-sing the extended Kalman filter. The autonomous optical navigation algorithm is validated using the digital simu-lation.
基金Supported by the National Natural Science Foundation of China under Grant No.50909025
文摘To provide a simulation system platform for designing and debugging a small autonomous underwater vehicle＇s （AUV） motion controller, a six-degree of freedom （6-DOF） dynamic model for AUV controlled by thruster and fins with appendages is examined. Based on the dynamic model, a simulation system for the AUV＇s motion is established. The different kinds of typical motions are simulated to analyze the motion performance and the maneuverability of the AUV. In order to evaluate the influences of appendages on the motion performance of the AUV, simulations of the AUV with and without appendages are performed and compared. The results demonstrate the AUV has good maneuverability with and without appendages.
文摘On the basic of passive damping control, we do modeling and simulating in another approach to improve the vibration alleviating effect, the piezoelectric layer damping （PLD）, which is called active control. The piezoelectric damping patches are under control of PID controller （matlab simulating） in voltage defference. Here, we use the software PRO/ENGINEER to design and model a wind turbine blade before using COMSOL to simulate the dynamic motion of the wind turbine blade and its interaction with aerodynamic force of wind in finite element method. Some different models are built-- the original turbine blade and the turbine blade with damping patches on different location and quantity. Then, according to the simulation results, we compare the effects of passive and active damping control, also the effect of patches locations and quantities under different wind speed. This research can provide a direction for future study about ways to decrease vibration of turbine blades.
基金supported by the National Natural Science Foundation of China (Grant No. 30970101)
文摘Arbuscular mycorrhizal （AM） fungi are obligate symbionts that colonize the roots of more than 80% of land plants. Experi- ments on the relationship between the host plant and AM in soil or in sterile root-organ culture have provided clear evidence that the extraradical mycelia of AM fungi uptake various forms of nitrogen （N） and transport the assimilated N to the roots of the host plant. However, the uptake mechanisms of various forms of N and its translocation and transfer from the fungus to the host are virtually unknown. Therefore, there is a dearth of integrated models describing the movement of N through the AM fungal hyphae. Recent studies examined Ri T-DNA-transformed carrot roots colonized with AM fungi in ~SN tracer experi- ments. In these experiments, the activities of key enzymes were determined, and expressions of genes related to N assimilation and translocation pathways were quantified. This review summarizes and discusses the results of recent research on the forms of N uptake, transport, degradation, and transfer to the roots of the host plant and the underlying mechanisms, as well as re- search on the forms of N and carbon used by germinating spores and their effects on amino acid metabolism. Finally, a path- way model summarizing the entire mechanism of N metabolism in AM fungi is outlined.
文摘China is now in an era of multiple values. While there is some virtue in previous theories on the history of literature based on the theory of evolution, class struggle and the enlightenment, when it comes to the twenty-first century, the histories of modem Chinese literature used in teaching are farfrom adequate for meeting the developmental needs of the times, society and literature. This is especially so in view of the putting forward of the goals of ＂putting people first＂ and ＂the harmonious society,＂ and the great changes taking place in time and space, the function of literature and aesthetic taste. Hence there is an urgent need to restructure this history and establish a more fair, equal and reasonable system of evaluation. Such a system would have humanism as its highest principle, and truth, goodness and beauty as its three virtues. Its great superiority would be its functional characteristics of universality, transcendence, fairness, and human-centeredness.
文摘Pseudo-random number generators have always been important in experimental design, computer simulation, cryptography and statistical analysis. This paper presents a method of comparing the degree of independence exhibited by various random number generators, a procedure, based on consideration of the largest (in modulus) non-unit eigenvalue of the observed Markov transition matrix, is used to assess the 'randomness' of a random number generator.
文摘For the nonlinearity distortion problem of Mach-Zehnder modulator(MZM)applied in the on-board microwave photonics system,the situation for two input radio frequency(RF)signals with different frequencies and phases is discussed,and an exact analytical solution is derived with the method of expanding Bessel series and Graf addition theory.According to the analytical expression,the nonlinearity characteristics of the modulator can be precisely predicted,and the system performance can be optimized.The correctness of the analytical solution is approved by simulation results.Analytical results indicate that the nonlinearity distortion is suppressed as the decrease of modulation index,the increase of direct current bias phase shift and phase difference between two input RF signals.When the phase difference equals zero orπand the direct current bias phase shift isπ/2,there are only odd-order distortion terms.When the phase difference equals zero orπand the direct current bias phase shift isπ,there are only even-order distortion terms.
基金Supported by the National Science Foundation Program (30271084).
文摘Toxin, one of the most important factors of plant fungal disease, has attracted much attention of many academicians who have been studying pathogen mycotoxin in deep research. The paper summarized chemical structures of some host-selective plant pathogen mycotoxins discovered in recent years and the correlation between biological activity and chemical structure of toxin.
文摘Mycophagists can influence fungal diversity within their home ranges by ensuring the continued and effective dispersal of spores from one site to another. However, the passage of spores through the digestive tract of vertebrates can affect the activity and viability of the spores ingested. This phenomenon has been rarely documented in opportunistic mycophagists consuming epigeous fungi. Using laboratory experiments, we investigated the activity and viability of spores of two epigeous ectomycorrhizal fungal species （Laccaria trichodermophora and SuiUus tomentosus） after passage through the digestive tract of two opportunistic mycophagous small rodents, the volcano mouse Peromyscus alstoni and the deer mouse P maniculatus. We found that passage through the gut of either species of rodent had a significant effect on spore activity and viability for both fungal species. The proportion of active spores （0.37-0.40） of L. trichodermophora in the feces of both species of rodents was less than that recorded for the control （0.82）. However, the proportion of active spores （0.644）.73） of S. tomentosus in the feces of each species of rodent was higher than in the control （0.40）. On the other hand, the viability of spores was lower （0.26-0.30 in L. trichodermophora and 0.604）.69 in S. tomentosus） for both fungi when consumed by either rodent relative to the controls （0.90 in L. trichodermophora and 0.82 in S. tomentosus）. These findings suggest that these rodent species may be effective dispersers of both epigeous fungi [Current Zoology 57 （3）： 293-299, 2011].
