共查询到20条相似文献，搜索用时 156 毫秒
1.
ZHANG Wen-zi CHEN Yan-ping ZHAO Ting-yu YE Zi YU Fei-hong 《浙江大学学报(A卷英文版)》2007,8(2):180-185
By applying the wavefront coding technique to an optical system, the depth of focus can be greatly increased. Several complicated methods, such as Fisher Information based method, have already been taken to optimize for the best pupil phase mask in ideal condition. Here one simple point spread function （PSF） based method with only the standard deviation method used to evaluate the PSF stability over the depth of focus is taken to optimize for the best coefficients of pupil phase mask in practical optical systems. Results of imaging simulations for optical systems with and without pupil phase mask are presented, and the sharpness of image is calculated for comparison. The optimized results showed better and much more stable imaging quality over the original system without changing the position of the image plane. 相似文献
2.
A color-intensity feature extraction method is proposed aimed at supplementing conventional image hashing algorithms that only consider intensity of the image. An image is mapped to a set of blocks represented by their dominant colors and average intensities. The dominant color is defined by hue and saturation with the hue value adjusted to make the principal colors more uniformly distributed. The average intensity is extracted from the Y component in the YCbCr space. By quantizing the color and intensity components, a feature vector is formed in a cylindrical coordinate system for each image block, which may be used to generate an intermediate hash. Euclidean distance is modified and a similarity metric introduced to measure the degree of similarity between images in terms of the color-intensity features. This is used to validate effectiveness of the proposed feature vector. Experiments show that the color-intensity feature is robust to normal image processing while sensitive to malicious alteration, in particular, color modification. 相似文献
3.
A novel energy-regenerative active suspension (NEAS) system was designed to solve the problem of low energy recovery efficiency caused by frequent alternation of energy-recovery mode and active-control mode in a traditional energy-regenerative active suspension (TEAS) system. The energy recovery and active control could be implemented simultaneously in the NEAS. The transforming processes and the corresponding computational formulas of power conversion in the NEAS were provided. The simulation results show that the performances of energy recovery of the NEAS are improved, and the self-sustaining of power supply for the NEAS can be realized. 相似文献
4.
We presented a wireless endoscope system developed on the embedded Linux platform. This wireless endoscope system consists of three parts： the endoscope capsule, the portable equipment and the image workstation, which make this system wireless and portable. Hardware design of this system and software design of the portable equipment are described. In clinical use, patients swallow the endoscope capsule for gastrointestinal inspection. The portable equipment receives images of gastrointestinal tract via the radio frequency module while it sets and reads back parameters of the capsule via the low frequency module. Acquired image data can be saved as a FAT32 format file in an universal serial bus disk. Images can be processed and reviewed at an Microsoft Windows PC workstation in the next stage. The image acquired by this wireless endoscope system is quite effective with clear details of gastrointestinal tract. However, the endoscope capsule was large, making it difficult to swallow. So the printed circuit board design of endoscope capsule needs to be improved. 相似文献
5.
A system for mobile robot localization and navigation was presented.With the proposed system,the robot can be located and navigated by a single landmark in a single image.And the navigation mode may be following-track,teaching and playback,or programming.The basic idea is that the system computes the differences between the expected and the recognized position at each time and then controls the robot in a direction to reduce those differences.To minimize the robot sensor equipment,only one omnidirectional camera was used.Experiments in disturbing environments show that the presented algorithm is robust and easy to implement,without camera rectification.The rootmean-square error(RMSE) of localization is 1.4,cm,and the navigation error in teaching and playback is within 10,cm. 相似文献
6.
A simple method for calculating the 3D coordinates of points on a moro object in a multi-camera system is proposed.It simplifies the algorithms used in traditional computer vision system by eliminating the calculation of the CCD( charge coupled device) camera parameters and the relative position between cameras,and using solid geometry in the calculation procedres instead of the calculation of the complex matrixes,The algorithm was used in the research of generating a virtual magnified 3D image of a micro object to be operated in a micro operation system,and the satisfactory results were obtained.The application in a virtual tele-operation system for a dexterous mechanical gripper is under test. 相似文献
7.
《天津大学学报(英文版)》2019,(6)
Cr(Ⅵ) and phenol are toxic contaminants that need to be treated,and different methods have been researched to simultaneously remove these two contaminants from industrial wastewater.In this study,Cr(Ⅵ) was used as a novel Fenton-like catalyst in phenol degradation by H_2O_2.In the pH range of 3.0-11.0,the degradation efficiency of phenol decreased with elevated pH.At pH=3.0,100 mg/L phenol was effectively degraded by 2 mmol/L Cr(Ⅵ) and 20 mmol/L H_2O_2.At pH=7.0 and the same conditions as those of pH=3.0,79%of 100 mg/L phenol was removed within 6 h,which was an improvement in pH limitation compared with the Fe(Ⅱ)-mediated Fenton reaction.Quenching experiments indicated that'OH generated from the catalysis of H_2O_2 by Cr(Ⅴ) instead of Cr(Ⅵ) was the primary oxidant that degraded phenol.When pyrophosphate was added in the Cr(Ⅵ)/H_2O_2 system,complexes with the Cr(Ⅴ) intermediate rapidly formed and inhibited H_2O_2 decomposition,implying that the decomposition of H_2O_2 to'OH was catalyzed by Cr(Ⅴ) instead of Cr(Ⅵ).The presence of anions such as chloride and sulfate had insignificant effect on the degradation of phenol.TOC and UV analyses suggest that phenol could not be completely oxidized to CO_2 and H_2O,and the intermediates identified by high performance liquid chromatography further indicates that maleic acid and benzoquinone were intermediates which may be further degraded into short chain acids,primarily maleic,formic,acetic,and oxalic acids,and eventually into CO_2 and H_2O.Considering that more than 50%Cr(Ⅵ) can also be removed during this process,the Cr(Ⅵ)/H_2O_2 system is more appropriate for the simultaneous removal of Cr(Ⅵ) and phenol contaminants from industrial wastewater. 相似文献
8.
The combined use of dry cooling （DC） system and dedicated ventilation （DV） system to decouple cool-ing and dehumidification process for energy efficiency was proposed for subtropical climates like Hong Kong. In this study, the energy performance and condensation risk of the use of DCDV system were examined by analyzing its ap-plication in a typical office building in Hong Kong. Through hour-by-hour simulation using actual equipment per-formance data and realistic building and system characteristics, it was found that with the use of DCDV system, the annual energy consumption could be reduced by 54%in comparison with the conventional system （constant air vol-ume with reheat system）. In respect of condensation risk, it was found that the annual frequency of occurrence of con-densation on DC coil was 35 h. Additional simulations were conducted to examine the influence of different parame-ters on the condensation risk of DCDV system. Measures to ensure condensate-free on DC coil were also discussed. 相似文献
9.
Carolyn Dickie Laurie Dickie 《美中教育评论》2009,6(7):18-28
Demands by internal and external accreditation groups, whether governmental or professional, has resulted in education providers being more aware of partnership paradigms that develop institutional quality for mutual benefit. The focus of this article is to examine current research on educational partnerships in South-East Asia, identify purposes of academic alliances and report on collective goals, expectations and principles that academics have in relation to cross-institutional relationships. A three-round Delphi technique was used to examine the pros and cons of partnerships, how partnerships could be made more successful and to identify specific actions that individual academics could undertake to develop smarter partnerships. A conceptual framework of alliance performance is suggested and the management of a partnership is addressed in relation to shared values, capacity building and the role of an alliance manager. 相似文献
10.
A
We are all busy talking about and using the Internet,but how many of us know the history of the Internet?
Many people are surprised when they find that the Internet was set up in the 1960s.At that time,computers were large and expensive.Computer networks didn't work well.If one computer in the network broke down,then the whole network stopped.So a new network system (系统) had to be set up.It should be good enough to be used by many different computers.If part of the network was not working,information could be sent through another part.In this way computer network system would keep on working all the time. 相似文献
11.
Permanent Magnet Synchronous Motor model can exhibit a variety of chaotic phenomena under some choices of system parameters and external input. Based on the property of passive system, the essential conditions were studied, by which Permanent Magnet Synchronous Motor chaotic system could be equivalent to passive system. Using Lyapunov stability theory, the convergence condition deciding the system's characters was discussed. In the convergence condition area, the equivalent passive system could be globally asymptotically stabilized by smooth state feedback. 相似文献
12.
Traffic monitoring is of major importance for enforcing traffic management policies. To accomplish this task, the detection of vehicle can be achieved by exploiting image analysis techniques. In this paper, a solution is presented to obtain various traffic parameters through vehicular video detection system( VVDS). VVDS exploits the algorithm based on virtual loops to detect moving vehicle in real time. This algorithm uses the background differencing method, and vehicles can be detected through luminance difference of pixels between background image and current image. Furthermore a novel technology named as spatio-temporal image sequences analysis is applied to background differencing to improve detection accuracy. Then a hardware implementation of a digital signal processing (DSP) based board is described in detail and the board can simultaneously process fourchannel video from different cameras. The benefit of usage of DSP is that images of a roadway can be processed at frame rate due to DSP‘s high performance. In the end, VVDS is tested on realworld scenes and experiment results show that the system is both fast and robust to the surveillance of transportation. 相似文献
13.
Experimental study on a cryosurgery apparatus 总被引：1，自引：0，他引：1
Cryosurgery is an effective way of curing many diseases including tumors and cancers. It can be applied using a variety of systems and cryogens. Cheap, convenient, reliable equipment still needs to be developed so that cryotherapy may be accepted by surgeons and hospitals. This paper presents a cryosurgery apparatus that utilizes an auto-cascade refrigeration system. Refrigerant mixture R50/R23/R600a was selected as the working fluid. The mixture composition was altered to achieve lower temperatures and higher capacity. The lowest temperature at the cryoprobe could be as low as -100℃, and 8 W refrigeration capacity could be obtained at -80 ℃. An ice ball of 11.6 mm diameter could be formed when the cryoprobe was immersed in a water bath at 37 ℃. 相似文献
14.
Development of an evaporation crystallizer for desalination of alkaline organic wastewater before incineration 总被引：2，自引：0，他引：2
A wastewater evaporation-desalination pretreatment method was introduced to remove the Na^＋ and K^＋ salts in volatile organic compounds （VOCs） wastewater before it was fed into the incinerator. VOCs in the wastewater were volatilized in the evaporation system and then the vapor was combusted in an incinerator. Simulated phenol wastewater containing sodium chloride was evaporated and concentrated and sodium chloride was crystallized in different parameters. The experimental results showed that the higher initial concentration of sodium chloride increases the ratio of volatilization of VOCs, which was due to the effect of “salting out” （a decrease in the solubility of the nonelectrolyte in the solution, or more rigorously, an increase in its activity coefficient, caused by the salt addition （Furter and Cook, 1967））. When evaporation speed was increased from 1.67 ml/min to 2.73 ml/min, the total removal coefficient of sodium chloride was about 99.88%-99.99%. This pretreatment procedure eliminates the slag phenomenon caused by Na^＋ and K^＋ salts during wastewater incineration, so the incinerator could operate continuously, and the wastewater evaporation could increase the heat value of wastewater, and the operation cost would be reduced. 相似文献
15.
To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to evaluate the influence of cutting fluid properties on the machinability of glass. The sodium carbonate solution of 10.5% concentration was chosen as cutting fluid. Then the critical depths in scratching experiments with and without cutting fluid were examined. Based on this, turning experiments were carried out, and the surface quality of SF6 was assessed. Compared with the process of dry cutting, the main indexes of surface roughness decrease by over 70% totally. Experimental results indicated that the machinability of glass SF6 can be improved by using the sodium carbonate solution as cutting fluid. 相似文献
16.
Transient expression of chicken alpha interferon gene in lettuce 总被引：1，自引：0，他引：1
We investigated the possibility of producing chicken alpha interferon (ChIFN-α) in transgenic plants.The cDNA encoding ChIFN-a was introduced into lettuce (Lactuca sativa L.) plants by using an agro-infiltration transient expression system.The ChIFN-α gene was correctly transcribed and translated in the lettuce plants according to RT-PCR and ELISA assays.Re-combinant protein exhibited antiviral activity in vitro by inhibition of vesicular stomatitis virus (VSV) replication on chicken embryonic fibroblast (CEF).The results demonstrate that biologically active avian cytokine with potential pharmaceutical ap-plications could be expressed in transgenic lettuce plants and that it is possible to generate interferon protein in forage plants for preventing infectious diseases of poultry. 相似文献
17.
Raw corn starch granules were hydrolysized by glucoamylase in a chemostat. The hydrolysis of three different-sized granules shows that smaller granules undergo more hydrolyzation than larger ones. After 78 h, 97% of the granules was hydrolysized with diameter between 0.15 mm and 0.3 mm at 50℃. When corn starch concentration increased from 100 g/L to 250 g/L, the amount of reducing sugar produced was proportional to the initial substrate concentration and no substrate inhibition phenomenon appeared. In order to study the product inhibition exactly, the product from hydrolysis reaction itself was added into the hydrolysis system at the beginning of starch hydrolysis.Product inhibition with different quantities of product added were studied in the initial several hours,during which period enzyme inactivation could be neglected and product inhibition could be studied separately. The experiments indicate that product inhibition happens when the additional quantity exceeds 9.56 g/L. 相似文献
18.
Rong-yang WANG Min HAN Hong LIU Chun-ling WANG Hong-hong XIAN Lei ZHANG Shi-jie ZHANG Dong-xu LIU 《Journal of Zhejiang University. Science. B》2013,(6):525
To propose a method of establishing the reference mandibular plane(MP),which could be reestablished according to the coordinates of the reference points,and then facilitate the assessment of anterior alveolar morphology using cone beam computed tomography(CBCT),sixty patients with bimaxillary protrusion were randomly selected and CBCT scans were taken.The CBCT scans were transferred to Materialism’s interactive medical image control system 10.01(MIMICS 10.01),and three dimensional models of the entire jaws were constructed.Reference points determining the reference MP were positioned in the coronal,axial,sagittal windows,and the points were exactly located by recording their coordinates in the interfaces of software.The reference MP provided high intra-observer reliability(Pearson’s r 0.992 to 0.999),and inter-observer reliability(intra-class correlation coefficients(ICCs) 0.996 to 0.999). 相似文献
19.
The rotatory optics element in the tensor dielectric coefficient matrix is an important parameter for analyzing and calculating a rotatory optical fiber by electromagnetic theory. But the measurement of rotatory optics element is difficult for the rotatory optical fiber. A simple principle and method for measuring rotatory optics element are put forward in this paper. Firstly by using electromagnetic theory it was demonstrated that the rotatory optics element has a simple linear relation with the rotatory angle, and then the rotatory optics element has a simple linear relation with the magnetic field strength (or bias current in the helix coil) . Secondly a measurement system for the rotatory optics element in the rotatory optical fiber was designed. Using the measurement system the rotatory element can be obtained by measuring the bias current simply. 相似文献
20.
In order to clarify the equilibrium components in the hydrolysis solution of boron trifluoride(BF_3-H_2O),the BF_3-H_2O was prepared by mixing BF_3-CH_3OH with large amount of water,in which the stoichiometric concentration of BF_3 is less than 0.1 mol/L.Two ionic equilibrium models were proposed to simulate the hydrolysis equilibrium of BF_3 and tested by special acid-base titration technique.The most accurate ion equilibrium constants were determined.The model,which was assumed to have no HF,was proved to be more representative for the real system and used to simulate the hydrolysis equilibrium of BF_3.The simulation suggested that H~+,BF_4~-,BF_3OH~- and H_3BO_3 were the main species in the dilute hydrolysis solution,while BF_2(OH)_2~- and F~- were insignificant species whose concentrations were both in the order of 10~(-4) mol/L magnitude,and BF(OH)_3~- could be omitted because its concentration almost equaled zero.Meanwhile,the equilibrium constant of the overall ionic reaction at 25℃ was obtained as 161.6. 相似文献