DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can a...DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can also form a variety of unusual structures like hairpins,triplexes and quadruplexes.These unusual DNAs sometimes have advantages over double helical DNAs in constructing nanomachines such as enhanced thermodynamic stability and higher sensitivity to external stimuli,which made them as promising motifs in recenttwo decades.Regardless of how complicated DNA-based nanomachines are,the fundamental concept in these nanomachines is based on a proper design and usage of DNA molecular switch.Among the reported DNA molecular switches,pH-controlled systems show great potentials in drug delivery and cellular pH sensing.Up to now,most of the reported pH-controlled molecular switches used i-motif or triplex DNAs.However,owing to the relatively long sequence requirement for the formation of i-motif and triplex DNAs,an invading DNA strand needs to be added to activate the molecular switch,and thus DNA wastes will be generated into the system and a full structural conversion will usually take a relatively long time of minutes to hours.To overcome the disadvantages of DNA waste generation and slow kinetics,molecular switches using smaller-size,thermodynamically stable and pH-sensible unusual DNA structures will have the advantages of easier manipulation and faster kinetics.Recently,we discovered a new type of unusual DNA structure called the minidumbbell(MDB)which is formed by a single-strand 8-nucleotide sequence.The MDB is composed of two type II tetraloops in which the first and fourth loop residues form loop-closing base pairs,the second loop residues fold into the minor groove to form base-base stacking or mispairing interactions,and the third loop residues stack on their nearby loop-closing base pairs.In particular,the MDB formed by a sequence containing two CCTG repeats has a relatively low melting temperature(Tm)of^22℃at pH 7.0,whereas its Tm can be significantly increased to^46℃at pH 5.0 due to the formation of a three hydrogen bond hemiprotonated C+·C mispair in the minor groove.This MDB,when combined with its complementary sequence,shows instant and complete structural conversions when the pH switches between 5.0 and 7.0 without using an invading DNA strand,serving as a simple and efficient pH-controlled molecular switch.In order to allow the incorporation of fluorophores to the two termini of the MDB,we aim to design a thermodynamically more stable MDB structure in this study.Through a rational design by introducing hydrophobic interactions to the MDB formed by the sequence containing two CCTG repeats at pH 5.0,we obtained an MDB structure with a record-high Tm of^62℃.Furthermore,this MDB was found to exist stably in the presence of 5’and 3’-overhanging residues,revealing its capability of being attached with fluorophores or other functional groups,and thus making it potentially a versatile pH-controlled molecular switch for designing nanomachines and nanomaterials.展开更多
The group of styrylactones isolated from the trees of genus Goniothalamus, has the particular features of the five or six-membered lactone skeleton bearing polyhydroxyl group. A number of novel styryl lactone were fou...The group of styrylactones isolated from the trees of genus Goniothalamus, has the particular features of the five or six-membered lactone skeleton bearing polyhydroxyl group. A number of novel styryl lactone were found to show moderate to sighficant cytotokicities against several human tumors.Among them, Goniofufurone has been reported by several synthetic studies on the synthesis of it. Herein, we report our study on the synthesis of goniofuforone from the commercially available optical tartaric acid using the addition of ethyl propialate to the intermediate aldehyde as the key step. The synthetic route is as following:展开更多
Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the additio...Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the addition of radiogenic 87Sr produced by the beta decay of 87Rb with a half-life of 4.88 ± 0.05 Ga.Thus,展开更多
An analysis of mutual interfering sources on RF systems using dual-band (Ka / X) radar is presented. The purpose of this paper is to improve operational performance of the system from the point of view of EMC design. ...An analysis of mutual interfering sources on RF systems using dual-band (Ka / X) radar is presented. The purpose of this paper is to improve operational performance of the system from the point of view of EMC design. The experimental dual-band antenna system have decreased the disturbing effects of most mutual interfering sources.展开更多
On going trend of miniaturization in electronic rel at ed parts, which is an average of two times in every 5～7 years introduce grindin g challenges. In grinding process, the surface waviness control of thin parts is ...On going trend of miniaturization in electronic rel at ed parts, which is an average of two times in every 5～7 years introduce grindin g challenges. In grinding process, the surface waviness control of thin parts is an ardent task due to its warpage, induced by the high specific grinding energy (2～10 J/mm 3). Therefore, coolant is often used to avoid thermal damage, obtai n better surface integrity and to prolong wheel life. However coolant, the incomp ressibility media introduce high forces at the grinding zone creating dimensiona l as well as shape instability. In view of these situations chilled air was ap plied in place of conventional coolant. The chilled air is produced using a two -stage vapor compression refrigeration cycle with characteristics of: temperatu re -35 ℃, pressure 0.2～0.3 MPa and flow rate 0.4 m 3/min. Also traces of eco - oil mist that encompass the chilled air are supplied to the grinding zone. B oth chilled air and eco-oil mist are applied through two independent paths of a specially designed twin compartment nozzle for maximizing the penetration. This paper investigates the grinding characteristics of mold insert which is closer to M2 tool steel (component widely used in connector industries) when using chil led air as coolant media. Grinding experiments were conducted using a vitrified bond CBN wheel (B91N100V) and a surface grinder. Initial study was focussed on establishing the most suita ble clamping method for the thin mold insert. FEM analysis and grinding experime nt studies were performed to quantitatively analyze the clamping induced deflect ion. Waviness value (W t) of (24～62) μm was achieved for resin clampi n g whereas (4～8) μm, (4～6) μm were achieved for magnetic and wax clamping res pe ctively. Wax clamping is predominantly used in all the grinding experiments that characterize the grinding process, which use chilled air as the coolant media. Between 0.15 to 0.9 mm 3/mm.s of specific material removal rate, ground sur face temperature of mold insert was increased from 0.3 ℃ to 59.7 ℃ for chi lled air. For the similar grinding conditions with the coolant fluid an increase from 0.9 ℃ to 14.4 ℃ was recorded. With increase of specific material removal rate from 0.15 to 0.65 mm 3/mm.s, F t/F n ratio was increased from (0.2 to 0.4), (0.6 to 1.67) for wet coolant and chilled air respectively. Despite of high F t/F n ratio and ground surface temperature, chilled air method has shown a surface waviness, W t from (2 to 5.6) μm. Microstructure examination of chilled air produced ground surface was comparable to those of using coolant fluids. Surface finish, R a of (0.45～0.7) μm was achieved for mold insert . This work will enable to have clear understanding about the quantitative influe nce of chilled air as well as the clamping method against the surface waviness o f thin mold insert.展开更多
Cotton occupies a pre-eminent place among cash crops as it guides the destiny of a large section of the farming community as well as that of a flourishing textile industry.As the yarn manufacturing industry has underg...Cotton occupies a pre-eminent place among cash crops as it guides the destiny of a large section of the farming community as well as that of a flourishing textile industry.As the yarn manufacturing industry has undergone a technological revolution,more emphasis is given to quality of the raw展开更多
Process planning and scheduling are two major plann in g and control activities that consume significant part of the lead-time, theref ore all attempts are being made to reduce lead-time by automating them. Compute r ...Process planning and scheduling are two major plann in g and control activities that consume significant part of the lead-time, theref ore all attempts are being made to reduce lead-time by automating them. Compute r Aided Process Planning (CAPP) is a step in this direction. Most of the existin g CAPP systems do not consider scheduling while generating a process plan. Sched uling is done separately after the process plan has been generated and therefore , it is possible that a process plan so generated is either not optimal or feasi ble from scheduling point of view. As process plans are generated without consid eration of job shop status, many problems arise within the manufacturing environ ment. Investigations have shown that 20%～30% of all process plans generated are not valid and have to be altered or suffer production delays when production sta rts. There is thus a major need for integration of scheduling with computer aide d process planning for generating more realistic process plans. In doing so, eff iciency of the manufacturing system as a whole is expected to improve. Decision support system performs many functions such as selection of machine too ls, cutting tools, sequencing of operations, determination of optimum cutting pa rameters and checking availability of machine tool before allocating any operati on to a machine tool. The process of transforming component data, process capabi lity and decision rules into computer readable format is still a major obstacle. This paper proposes architecture of a system, which integrates computer aided p rocess-planning system with scheduling using decision support system. A decisio n support system can be defined as " an interactive system that provides the use rs with easy access to decision models in order to support semi-structured or u nstructured decision making tasks".展开更多
The article describes the possibilities of application of simulation modeling for the analysis of infrastructure and technology of transport services of enterprises. The main technological and possible economic effect...The article describes the possibilities of application of simulation modeling for the analysis of infrastructure and technology of transport services of enterprises. The main technological and possible economic effects for the enterprises arising at performance of modeling of a transport component of their work are resulted.展开更多
The development of transgenic cotton varieties resistant to bollworms has been a major success of applying plant genetic engineering technology to agriculture,evidenced by phenomenal increase in
The structure, fabrication and emission characteristics of a silicon cold micro-cathode using ultra-shallow PN+ junction are presented. Implantation of As+ with a energy around 12 kev, rapid thermal annealing combined...The structure, fabrication and emission characteristics of a silicon cold micro-cathode using ultra-shallow PN+ junction are presented. Implantation of As+ with a energy around 12 kev, rapid thermal annealing combined with argon sputtering are used for forming ultra-shallow pn+ junction, whose depth is lower than 30nm. In a vacuum system Ⅰ-Ⅴcharacteristics were measured. The stability problem which was found in the devices testing is also discussed in this paper.展开更多
1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedan...1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedance attract attention, for high input impedance has the advantage that the networksmay be used in cascade without requiring impedance matching device. In the Higashimura and展开更多
Based on the research on the diffusion of suspended sediments discharged outside of Yangtze River estuary and the landuse of Shanghai using Landsat MSS images in several years, the authors analysed the characteristics...Based on the research on the diffusion of suspended sediments discharged outside of Yangtze River estuary and the landuse of Shanghai using Landsat MSS images in several years, the authors analysed the characteristics of TM CCT data of Shanghai scene, pointed out concrete range of maximum turbidity and growth of urban boundary of Shanghai through the information extraction.The feature vector combination method is used in the research process. The result is getting nice.展开更多
Tibet Plateau is Known as "the Roof of the World" with the area of 1,220,000km^2, which is about 1/8 land area of China. Because of the high elevation, cold climate and it caused difficulties in regional eco...Tibet Plateau is Known as "the Roof of the World" with the area of 1,220,000km^2, which is about 1/8 land area of China. Because of the high elevation, cold climate and it caused difficulties in regional economic planning and land resources management. Since 1985, the land use investigation in Tibet has been carried out, in which the basic data and thematic maps must be obtained and completed at county and township levels, in order to meet the needs of local administrations. In the investigation, remote sensing technology was comprehensively adopted. At present, the investigation in county level had been completed and the compilation is going to be carried out. Due to paying a great attention to studying on a series of key technical problems, the systematic methods of using remote sensing technology in the plateau land use investigation were formed and successfully put into application.展开更多
Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure....Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process展开更多
Punched steel sheets (metal sheets or foils) as thi n as 0.1mm are quite useful in the field of filters and various precision instrume nts. Thus, we have to develop more accurate and speedy techniques for punching t h...Punched steel sheets (metal sheets or foils) as thi n as 0.1mm are quite useful in the field of filters and various precision instrume nts. Thus, we have to develop more accurate and speedy techniques for punching t hin sheets. The traditional punching method uses an up-down pressing motion of a punch or a die on a strip of metal. The efficiency of this method is determine d by the speed of the motion. In the case of punching a sequence of tiny holes w ith a few millimeters’ interval, the speed of feeding a strip of metal to the p unching machine cannot exceed only a couple of meters per minute. We have de veloped a new technique for punching tiny holes with a pair of rotating bodies i n order to increase the feeding speed up to 100 meters per minute. Our proposed technique is shown in Fig.1 where the female tool has a round blade and the male tool has an M-shape boss. In addition, the setting of two tools i s alternating. The interference between them cannot occur because the clearance between the front and the back edge of the male tool and the female tool in the rotating direction becomes infinite in this configuration. An appropriate cleara nce is given for the thickness of the sheet between the side edge of the male to ol and the female tool. The punching itself is done by shearing. The side edge o f the male tool does contact with the female tool, but they cannot be interferin g. Our technique has another advantage to the traditional up-down pressing mach ine where the stamped out chips are hard to be discharged. It is quite easy in o ur proposed technique. Fig.2, 3 show a sample of punched material [TPP116A,+39mm88mm,Y,PZ#]Fig.1 The configuration of the punching parts using the sequential punching system.[TPP116B,+43mm155mm,X,BP#]Fig.2 A sample of punched material using the continuous punch ing lineFig.3 A exterior picture of a piece of punched steel foil(coi l) using the continuous punching For our developed high speed punching system, it is shown for (1) the configurat ion of punching tool and the punching mechanism, (2) the influence of male shape on punched hole quality, (3) the outline of continuous punching system, (4) the relation between punching speed and accuracy of hole pitch and hole dimensi on, (5) the mechanical property of punched metal sheet and (6) capability of hig her punching.展开更多
National Association for Hydrogen Energy (NAHE) was established in 2003 to facilitate the effective integration of the Russian Federation into the world hydrogen economy. The priority for the Association is to create ...National Association for Hydrogen Energy (NAHE) was established in 2003 to facilitate the effective integration of the Russian Federation into the world hydrogen economy. The priority for the Association is to create legislation and basic standards which necessary for the successful development of hydrogen energy, promote this sector to a large public and to support the development of those priority areas, where Russia has the best prospects to take a rightful place in the international division of labour (atomic hydrogen energy, fuel cells, hydrogen vehicles). Hydrogen Energy, National Association for Hydrogen Energy By now the Association has developed a draft technical regulation on security devices and systems展开更多
Remaining useful life(RUL) prediction is one of the most crucial elements in prognostics and health management(PHM). Aiming at the imperfect prior information, this paper proposes an RUL prediction method based on a n...Remaining useful life(RUL) prediction is one of the most crucial elements in prognostics and health management(PHM). Aiming at the imperfect prior information, this paper proposes an RUL prediction method based on a nonlinear random coefficient regression(RCR) model with fusing failure time data.Firstly, some interesting natures of parameters estimation based on the nonlinear RCR model are given. Based on these natures,the failure time data can be fused as the prior information reasonably. Specifically, the fixed parameters are calculated by the field degradation data of the evaluated equipment and the prior information of random coefficient is estimated with fusing the failure time data of congeneric equipment. Then, the prior information of the random coefficient is updated online under the Bayesian framework, the probability density function(PDF) of the RUL with considering the limitation of the failure threshold is performed. Finally, two case studies are used for experimental verification. Compared with the traditional Bayesian method, the proposed method can effectively reduce the influence of imperfect prior information and improve the accuracy of RUL prediction.展开更多
A useful life prediction method based on the integration of the stochastic hybrid automata(SHA) model and the frame of the dynamic fault tree(DFT) is proposed. The SHA model can incorporate the orbit environment, work...A useful life prediction method based on the integration of the stochastic hybrid automata(SHA) model and the frame of the dynamic fault tree(DFT) is proposed. The SHA model can incorporate the orbit environment, work modes, system configuration, dynamic probabilities and degeneration of components,as well as spacecraft dynamics and kinematics. By introducing the frame of DFT, the system is classified into several layers, and the problem of state combination explosion is artfully overcome.An improved dynamic reliability model(DRM) based on the Nelson hypothesis is investigated to improve the defect of cumulative failure probability(CFP), which is used to address the failure probability of components in the SHA model. The simulation using the Monte-Carlo method is finally conducted on two satellites, which are deployed with the same multi-gyro subsystem but run on different orbits. The results show that the predicted useful life of the attitude control system(ACS) with consideration of abrupt failure,degradation, and running environment is quite different between the two satellites.展开更多
Nitrogen(N)and phosphorus(P)are mineral nutrients essential for plant growth and development,playing a crucial role throughout the plant life cycle.Cotton,a globally significant textile crop,has a particularly high de...Nitrogen(N)and phosphorus(P)are mineral nutrients essential for plant growth and development,playing a crucial role throughout the plant life cycle.Cotton,a globally significant textile crop,has a particularly high demand for N fertilizer across its developmental stages.This review explores the effects of adequate or deficient N and P levels on cotton growth phases,focusing on their influence on physiological processes and molecular mechanisms.Key topics include the regulation of N-and P-related enzymes,hormones,and genes,as well as the complex interplay of N-and P-related signaling pathways from the aspects of N-P signaling integration to regulate root development,N-P signaling integration to regulate nutrient uptake,and regulation of N-P interactions—a frontier in current research.Strategies for improving N and P use efficiency are also discussed,including developing high-efficiency cotton cultivars and identifying functional genes to enhance productivity.Generally speaking,we take model plants as a reference in the hope of coming up with new strategies for the efficient utilization of N and P in cotton.展开更多
Implementing an efficient real-time prognostics and health management (PHM) framework improves safety and reduces maintenance costs in complex engineering systems.However, research on PHM framework development for rad...Implementing an efficient real-time prognostics and health management (PHM) framework improves safety and reduces maintenance costs in complex engineering systems.However, research on PHM framework development for radar systems is limited. Furthermore, typical PHM approaches are centralized, do not scale well, and are challenging to implement.This paper proposes an integrated PHM framework for radar systems based on system structural decomposition to enhance reliability and support maintenance actions. The complexity challenge associated with implementing PHM at the system level is addressed by dividing the radar system into subsystems. Subsequently, optimal measurement point selection and sensor placement algorithms are formulated for effective data acquisition. Local modules are developed for each subsystem health assessment, fault diagnosis, and fault prediction without a centralized controller. Maintenance decisions are based on each local module’s fault diagnosis and prediction results. To further improve the effectiveness of the prognostics stage, the feasibility of integrating deep learning (DL) models is also investigated.Several experiments with different degradation patterns are performed to evaluate the effectiveness of the framework’s DLbased prognostics model. The proposed framework facilitates transitioning from traditional reactive maintenance practices to a predictive maintenance approach, thereby reducing downtime and improving the overall availability of radar systems.展开更多
基金supported by General Research Fund ( CUHK14302915) from the Research Grants Council of the Hong Kong Special Administrative RegionDirect Grant ( 4053270) from the Faculty of Science of The Chinese University of Hong Kong
文摘DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can also form a variety of unusual structures like hairpins,triplexes and quadruplexes.These unusual DNAs sometimes have advantages over double helical DNAs in constructing nanomachines such as enhanced thermodynamic stability and higher sensitivity to external stimuli,which made them as promising motifs in recenttwo decades.Regardless of how complicated DNA-based nanomachines are,the fundamental concept in these nanomachines is based on a proper design and usage of DNA molecular switch.Among the reported DNA molecular switches,pH-controlled systems show great potentials in drug delivery and cellular pH sensing.Up to now,most of the reported pH-controlled molecular switches used i-motif or triplex DNAs.However,owing to the relatively long sequence requirement for the formation of i-motif and triplex DNAs,an invading DNA strand needs to be added to activate the molecular switch,and thus DNA wastes will be generated into the system and a full structural conversion will usually take a relatively long time of minutes to hours.To overcome the disadvantages of DNA waste generation and slow kinetics,molecular switches using smaller-size,thermodynamically stable and pH-sensible unusual DNA structures will have the advantages of easier manipulation and faster kinetics.Recently,we discovered a new type of unusual DNA structure called the minidumbbell(MDB)which is formed by a single-strand 8-nucleotide sequence.The MDB is composed of two type II tetraloops in which the first and fourth loop residues form loop-closing base pairs,the second loop residues fold into the minor groove to form base-base stacking or mispairing interactions,and the third loop residues stack on their nearby loop-closing base pairs.In particular,the MDB formed by a sequence containing two CCTG repeats has a relatively low melting temperature(Tm)of^22℃at pH 7.0,whereas its Tm can be significantly increased to^46℃at pH 5.0 due to the formation of a three hydrogen bond hemiprotonated C+·C mispair in the minor groove.This MDB,when combined with its complementary sequence,shows instant and complete structural conversions when the pH switches between 5.0 and 7.0 without using an invading DNA strand,serving as a simple and efficient pH-controlled molecular switch.In order to allow the incorporation of fluorophores to the two termini of the MDB,we aim to design a thermodynamically more stable MDB structure in this study.Through a rational design by introducing hydrophobic interactions to the MDB formed by the sequence containing two CCTG repeats at pH 5.0,we obtained an MDB structure with a record-high Tm of^62℃.Furthermore,this MDB was found to exist stably in the presence of 5’and 3’-overhanging residues,revealing its capability of being attached with fluorophores or other functional groups,and thus making it potentially a versatile pH-controlled molecular switch for designing nanomachines and nanomaterials.
文摘The group of styrylactones isolated from the trees of genus Goniothalamus, has the particular features of the five or six-membered lactone skeleton bearing polyhydroxyl group. A number of novel styryl lactone were found to show moderate to sighficant cytotokicities against several human tumors.Among them, Goniofufurone has been reported by several synthetic studies on the synthesis of it. Herein, we report our study on the synthesis of goniofuforone from the commercially available optical tartaric acid using the addition of ethyl propialate to the intermediate aldehyde as the key step. The synthetic route is as following:
文摘Strontium has four naturally occurring stable isotopes,84Sr,86Sr,87Sr,and 88Sr,with abundances of 0.56,9.87,approximately 7.04,and 82.53 atomic %,respectively.The 87Sr/86Sr isotope ratio is variable due to the addition of radiogenic 87Sr produced by the beta decay of 87Rb with a half-life of 4.88 ± 0.05 Ga.Thus,
文摘An analysis of mutual interfering sources on RF systems using dual-band (Ka / X) radar is presented. The purpose of this paper is to improve operational performance of the system from the point of view of EMC design. The experimental dual-band antenna system have decreased the disturbing effects of most mutual interfering sources.
文摘On going trend of miniaturization in electronic rel at ed parts, which is an average of two times in every 5～7 years introduce grindin g challenges. In grinding process, the surface waviness control of thin parts is an ardent task due to its warpage, induced by the high specific grinding energy (2～10 J/mm 3). Therefore, coolant is often used to avoid thermal damage, obtai n better surface integrity and to prolong wheel life. However coolant, the incomp ressibility media introduce high forces at the grinding zone creating dimensiona l as well as shape instability. In view of these situations chilled air was ap plied in place of conventional coolant. The chilled air is produced using a two -stage vapor compression refrigeration cycle with characteristics of: temperatu re -35 ℃, pressure 0.2～0.3 MPa and flow rate 0.4 m 3/min. Also traces of eco - oil mist that encompass the chilled air are supplied to the grinding zone. B oth chilled air and eco-oil mist are applied through two independent paths of a specially designed twin compartment nozzle for maximizing the penetration. This paper investigates the grinding characteristics of mold insert which is closer to M2 tool steel (component widely used in connector industries) when using chil led air as coolant media. Grinding experiments were conducted using a vitrified bond CBN wheel (B91N100V) and a surface grinder. Initial study was focussed on establishing the most suita ble clamping method for the thin mold insert. FEM analysis and grinding experime nt studies were performed to quantitatively analyze the clamping induced deflect ion. Waviness value (W t) of (24～62) μm was achieved for resin clampi n g whereas (4～8) μm, (4～6) μm were achieved for magnetic and wax clamping res pe ctively. Wax clamping is predominantly used in all the grinding experiments that characterize the grinding process, which use chilled air as the coolant media. Between 0.15 to 0.9 mm 3/mm.s of specific material removal rate, ground sur face temperature of mold insert was increased from 0.3 ℃ to 59.7 ℃ for chi lled air. For the similar grinding conditions with the coolant fluid an increase from 0.9 ℃ to 14.4 ℃ was recorded. With increase of specific material removal rate from 0.15 to 0.65 mm 3/mm.s, F t/F n ratio was increased from (0.2 to 0.4), (0.6 to 1.67) for wet coolant and chilled air respectively. Despite of high F t/F n ratio and ground surface temperature, chilled air method has shown a surface waviness, W t from (2 to 5.6) μm. Microstructure examination of chilled air produced ground surface was comparable to those of using coolant fluids. Surface finish, R a of (0.45～0.7) μm was achieved for mold insert . This work will enable to have clear understanding about the quantitative influe nce of chilled air as well as the clamping method against the surface waviness o f thin mold insert.
文摘Cotton occupies a pre-eminent place among cash crops as it guides the destiny of a large section of the farming community as well as that of a flourishing textile industry.As the yarn manufacturing industry has undergone a technological revolution,more emphasis is given to quality of the raw
文摘Process planning and scheduling are two major plann in g and control activities that consume significant part of the lead-time, theref ore all attempts are being made to reduce lead-time by automating them. Compute r Aided Process Planning (CAPP) is a step in this direction. Most of the existin g CAPP systems do not consider scheduling while generating a process plan. Sched uling is done separately after the process plan has been generated and therefore , it is possible that a process plan so generated is either not optimal or feasi ble from scheduling point of view. As process plans are generated without consid eration of job shop status, many problems arise within the manufacturing environ ment. Investigations have shown that 20%～30% of all process plans generated are not valid and have to be altered or suffer production delays when production sta rts. There is thus a major need for integration of scheduling with computer aide d process planning for generating more realistic process plans. In doing so, eff iciency of the manufacturing system as a whole is expected to improve. Decision support system performs many functions such as selection of machine too ls, cutting tools, sequencing of operations, determination of optimum cutting pa rameters and checking availability of machine tool before allocating any operati on to a machine tool. The process of transforming component data, process capabi lity and decision rules into computer readable format is still a major obstacle. This paper proposes architecture of a system, which integrates computer aided p rocess-planning system with scheduling using decision support system. A decisio n support system can be defined as " an interactive system that provides the use rs with easy access to decision models in order to support semi-structured or u nstructured decision making tasks".
文摘The article describes the possibilities of application of simulation modeling for the analysis of infrastructure and technology of transport services of enterprises. The main technological and possible economic effects for the enterprises arising at performance of modeling of a transport component of their work are resulted.
文摘The development of transgenic cotton varieties resistant to bollworms has been a major success of applying plant genetic engineering technology to agriculture,evidenced by phenomenal increase in
文摘The structure, fabrication and emission characteristics of a silicon cold micro-cathode using ultra-shallow PN+ junction are presented. Implantation of As+ with a energy around 12 kev, rapid thermal annealing combined with argon sputtering are used for forming ultra-shallow pn+ junction, whose depth is lower than 30nm. In a vacuum system Ⅰ-Ⅴcharacteristics were measured. The stability problem which was found in the devices testing is also discussed in this paper.
文摘1. IntroductionA large number of networks for realizing first and second order transfer functions using a currentconveyor have been reported in the literature. Especially, the networks that can offer highinput impedance attract attention, for high input impedance has the advantage that the networksmay be used in cascade without requiring impedance matching device. In the Higashimura and
文摘Based on the research on the diffusion of suspended sediments discharged outside of Yangtze River estuary and the landuse of Shanghai using Landsat MSS images in several years, the authors analysed the characteristics of TM CCT data of Shanghai scene, pointed out concrete range of maximum turbidity and growth of urban boundary of Shanghai through the information extraction.The feature vector combination method is used in the research process. The result is getting nice.
文摘Tibet Plateau is Known as "the Roof of the World" with the area of 1,220,000km^2, which is about 1/8 land area of China. Because of the high elevation, cold climate and it caused difficulties in regional economic planning and land resources management. Since 1985, the land use investigation in Tibet has been carried out, in which the basic data and thematic maps must be obtained and completed at county and township levels, in order to meet the needs of local administrations. In the investigation, remote sensing technology was comprehensively adopted. At present, the investigation in county level had been completed and the compilation is going to be carried out. Due to paying a great attention to studying on a series of key technical problems, the systematic methods of using remote sensing technology in the plateau land use investigation were formed and successfully put into application.
文摘Ⅰ The Indexes of Detecting Oil and Gas Resources The deeply buried reservoir which in a dynamic equilibrium state has a great pressure inside, and between it and earth surface there is a great difference of pressure. Therefore the hydrocarbon must spread and move vertically to the surface along the pressure gradient orientation. Hydrocarbons in the reservoir along some small rifts, cracks, joints and cleavages penetrate the overlying strata and seepage onto the surface. Thus the hydrocarbons become unvisble oil and gas signs. This process is called the phenomena of hydrocarbon microseepage of reservoir. Hydrocarbons microseepage in the process
文摘Punched steel sheets (metal sheets or foils) as thi n as 0.1mm are quite useful in the field of filters and various precision instrume nts. Thus, we have to develop more accurate and speedy techniques for punching t hin sheets. The traditional punching method uses an up-down pressing motion of a punch or a die on a strip of metal. The efficiency of this method is determine d by the speed of the motion. In the case of punching a sequence of tiny holes w ith a few millimeters’ interval, the speed of feeding a strip of metal to the p unching machine cannot exceed only a couple of meters per minute. We have de veloped a new technique for punching tiny holes with a pair of rotating bodies i n order to increase the feeding speed up to 100 meters per minute. Our proposed technique is shown in Fig.1 where the female tool has a round blade and the male tool has an M-shape boss. In addition, the setting of two tools i s alternating. The interference between them cannot occur because the clearance between the front and the back edge of the male tool and the female tool in the rotating direction becomes infinite in this configuration. An appropriate cleara nce is given for the thickness of the sheet between the side edge of the male to ol and the female tool. The punching itself is done by shearing. The side edge o f the male tool does contact with the female tool, but they cannot be interferin g. Our technique has another advantage to the traditional up-down pressing mach ine where the stamped out chips are hard to be discharged. It is quite easy in o ur proposed technique. Fig.2, 3 show a sample of punched material [TPP116A,+39mm88mm,Y,PZ#]Fig.1 The configuration of the punching parts using the sequential punching system.[TPP116B,+43mm155mm,X,BP#]Fig.2 A sample of punched material using the continuous punch ing lineFig.3 A exterior picture of a piece of punched steel foil(coi l) using the continuous punching For our developed high speed punching system, it is shown for (1) the configurat ion of punching tool and the punching mechanism, (2) the influence of male shape on punched hole quality, (3) the outline of continuous punching system, (4) the relation between punching speed and accuracy of hole pitch and hole dimensi on, (5) the mechanical property of punched metal sheet and (6) capability of hig her punching.
文摘National Association for Hydrogen Energy (NAHE) was established in 2003 to facilitate the effective integration of the Russian Federation into the world hydrogen economy. The priority for the Association is to create legislation and basic standards which necessary for the successful development of hydrogen energy, promote this sector to a large public and to support the development of those priority areas, where Russia has the best prospects to take a rightful place in the international division of labour (atomic hydrogen energy, fuel cells, hydrogen vehicles). Hydrogen Energy, National Association for Hydrogen Energy By now the Association has developed a draft technical regulation on security devices and systems
基金supported by National Natural Science Foundation of China (61703410,61873175,62073336,61873273,61773386,61922089)。
文摘Remaining useful life(RUL) prediction is one of the most crucial elements in prognostics and health management(PHM). Aiming at the imperfect prior information, this paper proposes an RUL prediction method based on a nonlinear random coefficient regression(RCR) model with fusing failure time data.Firstly, some interesting natures of parameters estimation based on the nonlinear RCR model are given. Based on these natures,the failure time data can be fused as the prior information reasonably. Specifically, the fixed parameters are calculated by the field degradation data of the evaluated equipment and the prior information of random coefficient is estimated with fusing the failure time data of congeneric equipment. Then, the prior information of the random coefficient is updated online under the Bayesian framework, the probability density function(PDF) of the RUL with considering the limitation of the failure threshold is performed. Finally, two case studies are used for experimental verification. Compared with the traditional Bayesian method, the proposed method can effectively reduce the influence of imperfect prior information and improve the accuracy of RUL prediction.
基金supported by the Fundamental Research Funds for the Central Universities(2016083)
文摘A useful life prediction method based on the integration of the stochastic hybrid automata(SHA) model and the frame of the dynamic fault tree(DFT) is proposed. The SHA model can incorporate the orbit environment, work modes, system configuration, dynamic probabilities and degeneration of components,as well as spacecraft dynamics and kinematics. By introducing the frame of DFT, the system is classified into several layers, and the problem of state combination explosion is artfully overcome.An improved dynamic reliability model(DRM) based on the Nelson hypothesis is investigated to improve the defect of cumulative failure probability(CFP), which is used to address the failure probability of components in the SHA model. The simulation using the Monte-Carlo method is finally conducted on two satellites, which are deployed with the same multi-gyro subsystem but run on different orbits. The results show that the predicted useful life of the attitude control system(ACS) with consideration of abrupt failure,degradation, and running environment is quite different between the two satellites.
基金supported by Supported by National Key Laboratory of Cotton Bio-breeding and Integrated Utilization(CB2023C07)Xinjiang Autonomous Region"Three Agricultural"Backbone Talent Training Program(2022SNGGNT024)Xinjiang Huyanghe City Science and Technology Program(2023C08).
文摘Nitrogen(N)and phosphorus(P)are mineral nutrients essential for plant growth and development,playing a crucial role throughout the plant life cycle.Cotton,a globally significant textile crop,has a particularly high demand for N fertilizer across its developmental stages.This review explores the effects of adequate or deficient N and P levels on cotton growth phases,focusing on their influence on physiological processes and molecular mechanisms.Key topics include the regulation of N-and P-related enzymes,hormones,and genes,as well as the complex interplay of N-and P-related signaling pathways from the aspects of N-P signaling integration to regulate root development,N-P signaling integration to regulate nutrient uptake,and regulation of N-P interactions—a frontier in current research.Strategies for improving N and P use efficiency are also discussed,including developing high-efficiency cotton cultivars and identifying functional genes to enhance productivity.Generally speaking,we take model plants as a reference in the hope of coming up with new strategies for the efficient utilization of N and P in cotton.
基金National Natural Science Foundation of China (42027805)。
文摘Implementing an efficient real-time prognostics and health management (PHM) framework improves safety and reduces maintenance costs in complex engineering systems.However, research on PHM framework development for radar systems is limited. Furthermore, typical PHM approaches are centralized, do not scale well, and are challenging to implement.This paper proposes an integrated PHM framework for radar systems based on system structural decomposition to enhance reliability and support maintenance actions. The complexity challenge associated with implementing PHM at the system level is addressed by dividing the radar system into subsystems. Subsequently, optimal measurement point selection and sensor placement algorithms are formulated for effective data acquisition. Local modules are developed for each subsystem health assessment, fault diagnosis, and fault prediction without a centralized controller. Maintenance decisions are based on each local module’s fault diagnosis and prediction results. To further improve the effectiveness of the prognostics stage, the feasibility of integrating deep learning (DL) models is also investigated.Several experiments with different degradation patterns are performed to evaluate the effectiveness of the framework’s DLbased prognostics model. The proposed framework facilitates transitioning from traditional reactive maintenance practices to a predictive maintenance approach, thereby reducing downtime and improving the overall availability of radar systems.
