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根据PM2.5小流量采样器的工作点流量控制需求,采用dsPIC33单片机、12位A/D转换器MCP3208和12位D/A转换器MCP4922等设计了控制器的硬件驱动,融合BP神经网络与PID控制算法,与低压差质量流量控制器、无碳刷真空抽气泵等组成PM2.5采样流量系统,实现了环境气体采样流量±0.05 L/min精度的稳态控制,其实际应用效果远高于PM2.5小流量采样器的±0.33 L/min的控制要求. 相似文献
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以乙二胺、三羟甲基丙烷三丙烯酸酯和二乙醇胺或三羟甲基氨基甲烷为原料,合成了水溶性树枝状聚（胺-酯）.讨论了树枝状聚（胺-酯）用量、离心时间及溶液pH值对于Cr3＋去除率的影响.实验结果表明,25℃时,当pH=9.22,以3000 r/min的转速离心13 min,用20 mL PAE（NH2）8（c=0.01 mol/L）溶液处理10 mL CrCl3（c=0.1 mol/L）溶液时,Cr3＋的去除率最高,为81.72%;25℃时,当pH=8.48,以3000 r/min的转速离心10 min,用20 mL PAE（OH）16（c=0.01 mol/L）溶液处理10 mL CrCl3（c=0.1 mol/L）溶液时,Cr3＋的去除率最高,为90.85%;25℃时,当pH=7.67,以3000 r/min的转速离心7 min,用20 mL PAE（OH）24（c=0.01 mol/L）溶液处理10 mL CrCl3（c=0.1 mol/L）溶液时,Cr3＋的去除率最高,为95.17%. 相似文献
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Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality. 相似文献
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为了更好地帮助下肢功能障碍者进行居家下肢康复训练,重获行动能力,走向独立生活,设计一种基于轮椅的智能多姿态下肢康复训练设备控制系统。该系统选用STM32F103系列单片机作为主控芯片,采用模块化设计思想,对人机交互模块、运动控制模块、姿态变换与下肢康复训练模块的软硬件进行设计。实验结果表明,人机交互摇杆按键控制姿态变换成功率能达到97.5%,语音和手机平板APP的控制成功率也能分别达到92.5%和95.3%。控制系统运行稳定,为进一步完善智能多姿态下肢康复训练设备奠定了基础。 相似文献
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Zhi Huang Zhao-bo Chen Nan-qi Ren Dong-xue Hu Dong-huan Zheng Zhen-peng Zhang 《浙江大学学报(A卷英文版)》2009,10(11):1642-1650
To improve the working and living environment of submarine crews, an integrated system of CO2 removal and O2 regeneration was designed to work under experimental conditions for 50 people in a submarine cabin during prolonged voyages. The integrated system comprises a solid amine water desorption （SAWD） unit for CO2 collection and concentration, a Sabatier reactor for CO2 reduction and a solid polymer electrolyte （SPE） unit for O2 regeneration by electrolysis. The performances of the SAWD-Sabatier-SPE integrated system were investigated. The experimental results from the SAWD unit showed that the average CO2 concentration in the CO2 storage tank was more than 96% and the outlet CO2 concentration was nearly zero in the first 45 min, and less than 1/10 of inlet CO2 after 60 min when input CO2 was 0.5% （1000 L）. About 950 L of CO2 was recovered with a recovery rate of 92%-97%. The output CO2 concentration was less than 0.2%, which showed that the adsorption-desorption performance of this unit was excellent. In the CO2 reduction unit we investigated mainly the start-up and reaction performance of the Sabatier reactor. The start-up time of the Sabatier reactor was 6, 8 and 10 rain when the start-up temperature was 187.3, 179.5 and 168 ℃, respectively. The product water was colorless, transparent, and had a pH of 6.9-7.5, and an electrical conductivity of 80μs/cm. The sum of the concentration of metal ions （Ru^3＋, Al^3＋, Pb^2＋） was 0.028% and that of nonmetal ions （Cl^-, SO4^2-） was 0.05%. In the O2 regeneration unit, the O2 generation rate was 0.48 m^3/d and the quantity was 2400 L, sufficient to meet the submariners＇ basic oxygen demands. These results may be useful as a basis for establishing CO2-1evel limits and O2 regeneration systems in submarines or similar enclosed compartments during prolonged voyages. 相似文献
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Totransmitthemultimediadataovertheinternet ,pre encodedvideobitstreamsarepreferablebecauseofthelimitofthenetworkbandwidth .Inmostcases ,theencodershouldknowthechannelcharacteristicsinad vanceandencodethemasparameters .Consequently ,theflexibilityisreduced .Theratecontrolisemployedtocontroltheoutputbitrateaccordingtonetworkcondi tions.Forwirelessnetworks ,theirbandwidthsaremuchmorelimitedthanwirenetworks.Soratecontrolbecomesespeciallyimportantfortransmittingmultimediaoverthewirelessdomains[1- … 相似文献
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Asymmetric stereoscopic video coding can take advantage of binocular suppression in human vision by representing one of the two views in lower quality.This paper proposes a bit allocation strategy for asymmetric stereoscopic video coding.In order to improve the accuracy of bit allocation and rate control in the left view,a proportionalintegral-derivative controller is adopted.Meanwhile,to control the quality fluctuation between consecutive frames of the left view,a quality controller is adopted.Besides,a fuzzy controller is proposed to control the variation in quality between the left and right views by comparing the PSNR disparity of two views with a fixed threshold,which is used to quantize the binocular psycho-visual redundancy and adjust the quantization parameter (QP) of the right view correspondingly.The proposed algorithm has been implemented in H.264/AVC video codec,and the experimental results show its effectiveness in rate control while keeping a good quality for the left view,and fewer bits are allocated for the right view so that the overall bit rate is saved by 7.2% at most without the loss of subjective visual quality for stereoscopic video. 相似文献
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王贵兰 《邢台职业技术学院学报》2008,25(5):72-75
本文介绍了电动轮椅车控制器的设计和执行。控制结构包含两层,即轮椅姿势和轮椅速度的控制。在高层的控制结构中,姿势控制器是作为两个轮子参考速度发生器工作的。操纵杆界面和姿势控制器都处在8位微控制器中。在低层的控制结构中,速度控制器执行各个方位的操作。驱动系统采用的是三相转化模块和基于DSP的电动机控制器。控制系统的性能经过仿真验证是良好的。 相似文献
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Pirali-Kheirabadi K Razzaghi-Abyaneh M 《Journal of Zhejiang University. Science. B》2007,8(9):693-696
In the present work, the potential of acaricidal activity of chamomile flowers＇ extract was studied against engorged Rhipicephalus annulatus tick under laboratory condition. For this purpose, the engorged females ofRhipicephalus annulatus were exposed to two-fold serial dilutions of chamomile flowers＇ extract （0.5%, 1.0%, 2.0%, 4.0% and 8.0%） using ＂dipping method＂ in vitro. The engorged ticks were immersed in different plant dilutions （five ticks for each dilution） for l rain and they were immediately incubated in separate Petri dishes for each replicate at 26℃ and 80% relative humidity. Mortality rate for each treatment was recorded 5 d after incubation.
The mortality rate caused by different dilutions of chamomile flowers＇ extract ranged from 6.67% to 26.7%, whereas no mortality was recorded for non-treated control group. The mass of produced eggs varied from 0.23 g （in 8.0% solution） to 0.58 g （in control）, with no statistical differences between the treatments and control （/＇〉0.05）. Also the chamomile flowers＇ extract in highest concentration used （8.0%） caused 46.67% failure in egg laying in engorged females while no failure was observed for non-treated control group. Macroscopic observations indicated that in effective concentrations of plant （4.0% and 8.0%）, patchy hemorrhagic swelling appeared on the skin of treated ticks. The results presented for the first time in this study imply that chamomile may be considered as a promising plant for biocontrol of cattle fever tick disease in the field condition. 相似文献
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Teaching systematic phonics effectively to beginning readers requires specialized knowledge and training which many primary grade teachers lack. The current study examined effects of a year-long mentoring program to improve teachers’ knowledge and effectiveness in teaching phonics and the extent that it improved students’ achievement in reading and spelling. Teachers in urban, lower SES schools completed a 45 h course followed by 90 h of in-school training. Mentors (N = 29) worked with kindergarten, 1st, 2nd, and 3rd grade teachers (N = 69) twice a week for 30 weeks during the year. Each visit included a 45 min prep period plus 45 min of modeling and feedback in the classroom. Mentors taught teachers how to provide systematic phonics instruction to their students (N = 1,336). Monthly ratings by mentors revealed that teachers improved their phonics teaching skills with many reaching the highest ratings by May. Teachers who were non-native speakers of English took a bit longer to learn the English sound system for letters, mainly because they lacked sufficient knowledge of English sounds and had to learn them. Given the increasing diversity of the teacher work force, future research is needed to study this difficulty, its solution, and impact on students. Teachers’ agreement with principles of phonics instruction remained strong or increased from fall to spring. Students’ reading and spelling skills showed large gains during the year and far exceeded effect sizes from comparable data sources. Students met grade-level expectations at the end of kindergarten and first grade but fell short in second and third grades. General education students outperformed bilingual/ELL and special needs students although all subgroups made large gains. Findings reveal the effectiveness of an intensive mentoring model of professional development applied to a subject that is difficult to teach and to a student population known for lower reading achievement. Findings point to the need for better pre-service teacher preparation coupled with appropriate curricula and PD from districts in order to improve students’ reading achievement. 相似文献
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Robert Thomas Sands Robyn Sandra Wettenhall 《International Journal of Disability, Development & Education》2000,47(4):413-426
This paper examined the effect of a psychological intervention program on attitudes to body image of female wheelchair athletes. A single case, multiple-baseline study was employed to examine the presentation of a brief, six session, cognitive behavioural intervention program on six National female wheelchair basketball players over a period of six weeks. Initially the six wheelchair athletes' satisfaction levels were compared to 20 able-bodied basketball players on four measures: the Physical Self-Perception Profile, Multi-Dimensional Body Image Scale, Social Physique Anxiety Questionnaire, and the Body Parts Questionnaire. Results indicated that as a result of the cognitive behavioural intervention program, physical self-perception increased for the wheelchair athletes and for 50% of the wheelchair athletes on the multi-dimensional components of body image, using the non-parametric split-middle technique. Further analysis revealed a significant effect of self-perceived competence across time indicating post-hoc significant differences between baseline data and Week 6 of the intervention program. With reference to caution due to the nature of case study research, it is asserted that this study shows promise for improving various aspects of body image satisfaction by means of a cognitive-behavioural approach and has potential for wheelchair athletes and other special populations. 相似文献
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Nadeem Akhtar Abbasi Tariq Pervaiz Ishfaq Ahmed Hafiz Mehwish Yaseen Azhar Hussain 《Journal of Zhejiang University. Science. B》2013,14(9):774-784
In vitro cultures of loquat cultivar Mardan were established using shoot apices after treating with NaOCl (5%, 7%, 10%, 12%, 14% (v/v)) for 12 min and HgCl2 (0.01%, 0.05%, 0.10%, 0.20%, 0.25% (w/v)) for 2 min. A maximum survival rate of 70% was recorded after surface sterilization with 10% NaOCl. Caulogenic response was assessed on Murashige and Skoog (MS) medium fortified with assorted combinations of the cytokinins, benzylaminopurine (BAP), kinetin, and N6-(2-isopentyl)adenine (2iP). Treatment of BAP 1.5 mg/L combined with 2iP 9.0 mg/L and kinetin 1.5 mg/L was found to be optimum for shoot morphogenesis in terms of the number and subsequent growth of shoots, while the highest shoot length was yielded by the combination of BAP 0.5 mg/L, kinetin 0.5 mg/L, and 2iP 3 mg/L. Higher levels of cytokinins induced callogenesis, vitrification and stunted growth to some extent. For rhizogenesis, uniform sized micro-shoots were excised and transferred to half-strength MS medium containing auxins. The best rooting expression was observed with naphthaleneacetic acid (NAA) 1 mg/L combined with indole-3-butyric acid (IBA) 2 mg/L and paclobutrazol (PBZ) 1 mg/L. 相似文献
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为降低软籽石榴组培过程中外植体褐化程度,从外植体表面消毒时间、转瓶间隔时间、培养基的硬度、吸附剂的使用方面进行了综合试验。结果表明:表面消毒最适时间为7～9min,10d转瓶1次降低褐化的效果较好;使用硬度为5g/L琼脂的MS培养基,并添加0.1 mg/LNAA+0.1mg/LIBA+1.0mg/L6-BA+30g/L蔗糖+聚乙烯吡咯烷酮(PVP)2g/L可有效控制褐变并获得较高的愈伤诱导率。 相似文献
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Voltage source converter high-voltage direct current （VSC-HVDC） is a new power transmission technology pref- erable in small or medium power transmission. In this paper we discuss a new control system based on space vector modulation （SVM） without any voltage line sensors. Using direct power control （DPC） SVM and a new double synchronous reference frame phase-locked loop （DSRF-PLL） approach, the control system is resistant to the majority of line voltage disturbances. Also, the system response has accelerated by using a feed forward power decoupled loop. The operation of this control strategy was verified in a SIMULINK/MATLAB simulation environment. To validate this control system, a 5 kV.A prototype system was constructed. Compared to the original controllers, the current total harmonic distortion （THD）, the active and reactive deviations and the DC voltage overshoot were lowered by 2.5%, 6.2% and 8%, respectively. The rectifier power factor in the worst condition was 0.93 and the DC voltage settling time was 0.2 s. 相似文献
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Objective:To evaluate the accuracy of a scoring system combining zygote and embryo morphology in predicting the outcome of in vitro fertilization(IVF)treatment.Methods:In a study group,117 consecutive IVF or intracytoplasmic sperm injection(ICSI) cycles with embryo transfer were carried out and 312 embryos were scored Using a combmed scoring system(CSS)of zygote and embryo morphology before transplantation.In a control group,a total of 420 IVF or ICSI cycles were carried out and 1176 embryos were scored using a cumulative embryo score(CES).The effects of the combined scoring system on the embryo implantation rate and pregnancy rate per cycle were analyzed.Results:Using the combined scoring system,the embryo implantation rate(27.6%)and the clinical pregnancy rate(48.7%)were significantly higher than those in the control group(20.8%and 38.6%,respectively).Also,the implantation rate of embryos scoring≥70 (38.5%:82 sacs/213 embryos)was significantly higher (P＜0.001)than that of embryos scoring＜70(4%:4 sacs/99 embryos).The pregnancy rate of patients with embryos scoring≥70 using the combined scoring system(66.7%)Was significantly higher(P＜0.001)than that of patients with embryos scoring≥20 using the cumulative embryo score(59.0%).Conclusion:The results suggest that selecting embryos with a high Score(≥70)using the combined scoring system could inerease the implantation rate and pregnancy rate,and that using a scoring system combining assessments of human zygotes and pre-implantation embryos might predict IVF outcomes more accurately than using a cumulafive embryo score. 相似文献
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改性淀粉絮凝剂处理含油废水的试验效果 总被引：1，自引：0，他引：1
通过将玉米淀粉与氢氧化钠、三氯化铝和无水碳酸钠在恒温磁力搅拌器上搅拌、加热,使得玉米淀粉改性,制得改性淀粉絮凝剂,并研究了改性淀粉絮凝剂对含油废水的处理效果.试验结果显示,在搅拌速度与时间分别为快搅速度200 r/min,快搅时间0.5 min;慢搅速度100 r/min,慢搅时间3 min的情况下,使用改性淀粉絮凝剂处理含油废水时,COD去除率为77.94%、石油类去除率为61.2%、透光率为62.7%、SS去除率为79.96%;最佳反应条件为:投药量为12 mg/L、温度为5~30℃、pH值为6-8. 相似文献
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用成核-晶化隔离法制备了MgAl-CO3-LDHs,借助于TG-DSC、IR、XRD、SEM对其结构和形貌进行了表征。通过热老化箱实验研究了季戊四醇对PVC镁铝水滑石钙锌皂热稳定系统(Mg0.677Al0.323-CO3-LDHs/Ca(st)2/Zn(st)2)的增效性。结果表明,快速成核的等量盐、碱混合液,在100℃下回流晶化6h所得的水滑石Mg0.677Al0.323-CO3-LDHs为规整的层状晶体结构,层间距0.7455nm、晶轴a=0.3038nm、c=2.2365nm,在ac、方向的一次性晶粒分别是14nm和25.7nm。层间结晶水、层板羟基和层间阴离子CO32-脱除温度分别是249.5℃和422.1℃;含适量季戊四醇的热稳定剂系统较不含季戊四醇的初期着色和热稳定时间延长50min,分别达260min和290min。 相似文献
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In electroencephalogram (EEG) modeling techniques, data segment selection is the first and still an important step. The influence of a set of data-segment-related parameters on feature extraction and classification in an EEG-based brain-computer interface (BCI) was studied. An auto search algorithm was developed to study four datasegment-related parameters in each trial of 12 subjects’ EEG. The length of data segment (LDS), the start position of data (SPD) segment, AR order, and number of trials (NT) were used to build the model. The study showed that, compared with the classification ratio (CR) without parameter selection, the CR was increased by 20% to 30% with proper selection of these data-segment-related parameters, and the optimum parameter values were subject-dependent. This suggests that the data-segment-related parameters should be individualized when building models for BCI. 相似文献