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2022 Vol. 43, No. 1
Published: 2022-01-28
 
1 SI Base Units and Time Measurement
HAN Yu-tong
DOI: 10.3969/j.issn.1000-1158.2022.01.01
The importance of SI “second” and the role of “coordinate time” in the unification of space-time and other physical quantities are discussed. The relationship between “proper time” and “coordinate time” and the influence of the gravitational field on the “proper time” are illustrated by taking the Schwarzschild field as an example. It is believed that the uncertainty of time unit determines the ones of other physical units. Only the “coordinate time” has a global scope of application, and physical quantities related to large-scale space-time must be and only be characterized in coordinate quantities. The SI “second” is the unit of “proper time”, which is a local physical quantity. To use quantum benchmarks to unify the physical quantities in a large-scale space, it is necessary to further clarify the relationship between “coordinate time” and SI “second”.
2022 Vol. 43 (1): 1-6 [Abstract] ( 275 ) HTML (1 KB)  PDF (464 KB)  ( 345 )
7 A Method for Detecting Internal Defects of Metal Lattice Structure Based on YOLOv3 Algorithm
ZHANG Yu-yan, REN Teng-fei, WEN Yin-tang
DOI: 10.3969/j.issn.1000-1158.2022.01.02
To solve the problem that the defect in the lattice structure is difficult to accurately identify due to the small size and weak feature,an intelligent defect recognition method based on YOLOv3 algorithm is proposed.This method takes advantage of the deep learning network model in feature extraction,uses a multi-scale network to predict and treats the classification and location of defects as regression problems.The proposed algorithm realizes the identification of internal defects in a 3D printed lattice structure.And the detect recall is 96.6%,the accuracy is 93.2%,and the mean average precision value of model is 0.957.It provides a basis for further accurate characterization of defects and analysis of the effects of defects on the performance of lattice structures.
2022 Vol. 43 (1): 7-13 [Abstract] ( 273 ) HTML (1 KB)  PDF (2118 KB)  ( 422 )
14 Study on Flatness Error Evaluation Method of Discontinuous Plane
LOU Jian-qi, LI Wei, FU Yan-hua, LIN Hong-yun
DOI: 10.3969/j.issn.1000-1158.2022.01.03
A method for evaluating discontinuous planes based on inclusive lines is proposed. Firstly, the global noise of point cloud data is eliminated based on principal component analysis. Then, the least square plane fitting method, the multi-threshold point cloud extraction algorithm and the parallel line fitting method were used to obtain the qualified inclusive lines, and two parallel inclusive lines in the space were used to replace the inclusive plane to establish the minimum region. Finally, the flatness error evaluation of discontinuous plane is realized and the plane adjustment is guided. The experimental results show that the flatness error of the proposed method is 0.011mm lower than that of the genetic algorithm compared with the traditional feature point method, and the flatness error is reduced by 1.959mm after adjusting the plane according to the output deviation information. It can effectively evaluate the flatness error of discontinuous plane and guide the plane adjustment.
2022 Vol. 43 (1): 14-20 [Abstract] ( 297 ) HTML (1 KB)  PDF (1967 KB)  ( 383 )
21 Improved Image Edge Clipping and Filtering Algorithm Based on Local Structural Shape
SUN Xiao-hui, CAI Yong-hong, LIN Yan-fei
DOI: 10.3969/j.issn.1000-1158.2022.01.04
It is easy to cause the problem that the high frequency edges are suppressed, the continuity of the edges is destroyed and the structural features of the target are lost when the classical clipping and filtering algorithm(CFA) is applied to the edge denoising. Therefore, an improved CFA based on local structure shape features is proposed for image edge filtering. Based on the principle of CFA, a sliding template composed of 5 adjacent edge points and sliding along the edge is used in the algorithm. The point that overruns the threshold in the sliding template is predicted by the local structural shape model. To be specific, the model of the local structural contour is established by using the sliding template and applied to predict the overrun point. Then, it is judged that whether the difference between the overrun point and its predicted value is greater than the threshold, in the physical sense it means that whether the step, flange or sharp structural features are encountered. In order to test the ability of the new algorithm in edge preservation and noise reduction, comparative experiments with the traditional algorithmare carried out. The experimental results show that the improved CFA based on local structure features not only has efficient denoising ability, but also has significant protection effect on the high-frequency edge of the target structure.
2022 Vol. 43 (1): 21-25 [Abstract] ( 199 ) HTML (1 KB)  PDF (1235 KB)  ( 224 )
26 Uncertainty Analysis of 1 on 1 Laser Induced Damage Threshold Measurement
BA Rong-sheng, LI Jie, ZHOU Xin-da, ZHENG Yin-bo,XU Hong-lei, DING Lei, LI Ya-jun, NA Jin
DOI: 10.3969/j.issn.1000-1158.2022.01.05
According to the demand of measurement uncertainty evaluation for laser induced damage threshold tested by ISO 21254 method, the main uncertainty influencing factors are systematically studied. The energy density and the damage probability measurement uncertainty are analyzed by GUI method. The measurement uncertainty induced by linear fitting method is investigated by the Monte Carlo method. The influences on the fitting result is also compared by different residual error models in the procedure of the damage probability and energy density linear fitting. The analysis shows that the least square residual error model considering both damage probability error and energy density error has the best error resistance performance during the linear fitting process and it can effectively reduce the error influence on the damage threshold induced by the damage probability error and the energy density error. The same damage testing experiment data is treated by the ISO 21254 method and the Monte Carlo method. The result indicates that the threshold uncertainty is smaller and the threshold value is bigger deduced by the ISO 21254 method. Once using the ISO 21524 method, the laser induced damage threshold would be overestimated.
2022 Vol. 43 (1): 26-34 [Abstract] ( 272 ) HTML (1 KB)  PDF (1225 KB)  ( 201 )
35 The Development and Evaluation of the ZrC-C Peritectic Point
MENG Su, LIU Xu-dong, CAI Jing, DONG Lei
DOI: 10.3969/j.issn.1000-1158.2022.01.06
The ZrC-C peritectic fixed point has a very high nominal phase transition temperature (2882℃), which is higher than the upper limit of most high-temperature heating furnaces. By improving the self-designed HT271 heating furnace, the upper limit of its working temperature was increased to above 2900℃, which met the requirements of the ZrC-C peritectic fixed point experiments. ZrC powder and C powder were used to configure the mixed powder, and the filling and realizing experiments of the ZrC-C peritectic fixed point were carried out, two sets of realizing cycle data were obtained. The result of the first cycle is better: the inflection point temperature is 2882.298℃; the inflection point uncertainty is 26.3mK. It has been verified that at a temperature above 2900℃, the improved HT271 heating furnace can be used for about 30 minutes stably. In order to extend the stable use time of the HT271 furnace at extremely high temperature, the next improvement plan is proposed.
2022 Vol. 43 (1): 35-39 [Abstract] ( 186 ) HTML (1 KB)  PDF (1822 KB)  ( 419 )
40 Measurement of Shear Band Widths Based on the Digital Image Correlation Method Considering Splitted Subsets Surrounding the Monitored Point
ZHANG Bo-wen, WANG Xue-bin, DONG Wei
DOI: 10.3969/j.issn.1000-1158.2022.01.07
To accurately measure widths of narrow shear bands with high strain gradients, a new digital image correlation method was proposed based on the subset splitting . Through splitting the original subset of the monitored point, and making splitted subsets surround the point, a few splitted subsets were in simple deformational regions. Results of the best correlated subsets were taken as results of the point. The validity of the proposed method was verified by comparing measured fictitious shear band widths of the proposed method and the coarse-fine method, and shear band width measurement errors of two methods were analyzed in theory. It is shown that the measured fictitious shear band widths of the proposed method are not influenced by the subset size in theory. Measured shear band widths of the proposed method are less influenced by the subset size and more influenced by the monitored point spacing than of the coarse-fine method. Measured shear band widths of the proposed method are more accurate than of the coarse-fine method.
2022 Vol. 43 (1): 40-47 [Abstract] ( 201 ) HTML (1 KB)  PDF (4625 KB)  ( 124 )
48 Reasearch on OVMD-MPE Group Sparsity Total Variational Denoising Algorithm
CHEN Wei-xing, SUN Xi-xi
DOI: 10.3969/j.issn.1000-1158.2022.01.08
Bearing vibration data is susceptible to noise interference during the acquisition process and cannot effectively highlight weak local fault pulses, thereby affecting the efficiency of bearing fault diagnosis. To solve this problem, an ovmd-mpe group sparse total variational denoising algorithm (OVMD-MPE-GSTVD) is proposed. Firstly, variational model decomposition is used to decompose the signal, and then the optimal parameters of variational model decomposition are obtained by grasshopper optimization algorithm. Then, calculate the empirical model decomposition of each modal component to separate the noise dominant component and the useful component. Finally, the dominant component of the noise is filtered by group sparse total variational denoising algorithm, and the filtered component and useful component are combined to reconstruct the denoising signal. The experimental results show that compared with the traditional denoising method, the average signal-to-noise ratio of the simulated reconstructed signal is improved by about 3.3dB, the bearing data fault accuracy is increased to 98.9%.
2022 Vol. 43 (1): 48-56 [Abstract] ( 222 ) HTML (1 KB)  PDF (4429 KB)  ( 166 )
57 Study and Establishment of a Viscosity-temperature Correction Method
JIN Yuan, ZHU Xuan-hua, QIAO Jia-guang
DOI: 10.3969/j.issn.1000-1158.2022.01.09
In order to improve the calibration accuracy of viscometer in non-standard environment laboratory, the viscosity-temperature characteristics of refined petroleum products and refined methylsilicone oil standard viscosity liquids were systematically studied according to experimentally certified viscosity-temperature data. The Walther equation and Arrhenius equation were selected and optimized, and then the kinematic viscosity-temperature correction method of refined petroleum products standard viscosity liquids and the dynamic viscosity-temperature correction method of refined methylsilicone oil standard viscosity liquids were established with the certified values of 20℃ and 25℃ as the reference point. The results show that the maximum deviation between the calculated value and the certified value is 0.65%. The viscosity-temperature correction method used in the calibration of working viscometer is feasible to a certain extent, more accurate viscosity temperature correction in non-standard environment laboratory is realized.
2022 Vol. 43 (1): 57-64 [Abstract] ( 249 ) HTML (1 KB)  PDF (2221 KB)  ( 251 )
65 Many-objective Evolutionary Algorithm Based on Multi-subpopulation and Density Estimation for Load Distribution of Cold Rolling
ZHAO Zhi-wei, LIU Yue, XIONG Zhi-jian, YANG Xiu-wei
DOI: 10.3969/j.issn.1000-1158.2022.01.10
A many-objective evolutionary algorithm based on multi-subpopulation and density estimation is proposed. The sub-populations are divided by reference vectors, and the degree of approaching the Pareto front is improved by the convergence mechanism. In addition, the individual density is evaluated by calculating the euclidean distance between individual and reference vector, in order to maintaining the diversity of the solution set. The results of numerical simulation indicate that the convergence and diversity of the solution set obtained by the proposed algorithm is obviously better than the comparison algorithms. Finally, the load distribution is optimized by the proposed algorithm for many-objective optimization. The optimized load distribution scheme can reduce energy consumption by 2.2%, and improves product quality.
2022 Vol. 43 (1): 65-71 [Abstract] ( 226 ) HTML (1 KB)  PDF (1934 KB)  ( 249 )
72 Research on Algorithm of Camera Automatic Horizontal Observing Mark of Glass Gauge
CAI Yong-hong, SUN Xiao-hui
DOI: 10.3969/j.issn.1000-1158.2022.01.11
An algorithm of camera automatic horizontal observing the mark of glass gauge was introduced based on the relationship between marking opening size in image plane and camera height in motion system. The program block diagram of algorithm was given. The experimental results showed that the image processing error was the main uncertain factor affecting repeatability and the algorithm provided an efficient solution for camera automatic horizontal observing mark of glass gauge.
2022 Vol. 43 (1): 72-76 [Abstract] ( 180 ) HTML (1 KB)  PDF (1725 KB)  ( 166 )
77 Ultrasonic Defect Echoes Identification Based on EEMD and Low-Rank Sparse Decomposition
ZHOU Hang-rui, SUN Jian, XU Hong-wei, MIAO Cun-jian, SONG Xin
DOI: 10.3969/j.issn.1000-1158.2022.01.12
In order to detect the minor defect echoes of metal materials from noisy signal in ultrasonic nondestructive testing, a ultrasonic defect echoes identification method based on ensemble empirical mode decomposition (EEMD) and low-rank sparse decomposition was proposed. First, the EEMD was performed on the defect detection signal to obtain a series of intrinsic mode functions (IMF). The similarity measurement method based on probability density function was used to select irrelevant IMFs and these IMFs were discarded to achieve preliminary noise reduction. Then a denoising method based on short-time Fourier transform (STFT) and low-rank sparse decomposition algorithm was used for further noise suppression of the reconstructed signal. Finally, the inverse STFT was performed to obtain denoised defect echo signal in time domain. The simulated and measured signals are processed separately, and the results show that the method is effective in defect echo detection.
2022 Vol. 43 (1): 77-84 [Abstract] ( 164 ) HTML (1 KB)  PDF (3763 KB)  ( 225 )
85 Optimization Design of Non-uniform Air Gap Magnetic Field for Low-Frequency Electromagnetic Vibrator
ZHANG Xu-fei JIANG Wen-qi, HU Tian-en, ZHANG Feng-yang
DOI: 10.3969/j.issn.1000-1158.2022.01.13
Aiming at the vibration excitation signal distortion problem caused by nonlinearity of air gap magnetic induction intensity of large stroke low-frequency electromagnetic vibrator, a simplified large stroke magnetic circuit mathematical model is established based on the electromechanical coupling model analysis of electromagnetic vibrator and circuit equivalence principle. And the non-uniform distribution characteristics of air gap magnetic induction intensity are simulated and analyzed based on ANSYS Maxwell software. Based on the continuous mixed integer nonlinear programming algorithm, the distribution characteristics of air gap magnetic induction intensity corresponding to different nonlinear parameters of inner yoke outline and end face structure are simulated and analyzed respectively, and the optimal solutions of variable air gap and variable cross-section magnetic circuit with minimum nonuniformity are obtained. The simulation results show that the non-uniformity of 25.95% before optimization is reduced to 7.09% and 2.70% respectively. The optimized magnetic circuit structure can effectively improve the nonlinearity of air gap magnetic induction intensity of large stroke low-frequency electromagnetic vibrator, reduce the distortion of output vibration signal and improve the accuracy of low-frequency vibration calibration.
2022 Vol. 43 (1): 85-91 [Abstract] ( 252 ) HTML (1 KB)  PDF (3398 KB)  ( 304 )
92 The SOC Prediction Method of ELM Optimized by NTLBO Algorithm
HU Jian, LIU Chao
DOI: 10.3969/j.issn.1000-1158.2022.01.14
In order to improve the prediction accuracy of state of charge (SOC), a prediction method of SOC based on optimized extreme learning machine ELM by the new teaching-learning-based optimization (NTLBO) algorithm was proposed. Firstly, Logistics chaos was employed to optimize the elite individuals in the population to improve the global optimization performance of the algorithm. Secondly, the input weights and hidden layer thresholds of the ELM model were optimized and adjusted by the improved TLBO algorithm, and the NTLBO-ELM prediction model was constructed to improve the generalization ability of the model. The NTLBO-ELM model was tested and verified on a lithium battery and compared with the other three models. The simulation results show that the proposed method has a small prediction error and good generalization ability, which verifies the validity of the model.
2022 Vol. 43 (1): 92-96 [Abstract] ( 256 ) HTML (1 KB)  PDF (1612 KB)  ( 314 )
97 Research for on-Wafer LRRM Calibration Algorithm
HUO Ye, LIANG Fa-guo, WU Ai-hua, WANG Yi-bang, LUAN Peng, LIU Chen, SUN Jing
DOI: 10.3969/j.issn.1000-1158.2022.01.15
The LRRM calibration algorithm is researched, the measurement model of load standard is improved, the measured result is translated from the middle of the DUT to the probe tip by reference surface translation, and the calibration software is compiled based on MATLAB. The on-wafer scattering parameter measurement system is calibrated by the researched calibration method and commercial calibration method, and the same short calibration standard and attenuator are measured. The results show that at the frequency of 110MHz~110GHz, the maximum deviation of reflection magnitude is 0.02, and the maximum deviation of reflection phase is 0.3 degree, the maximum deviation of the transmission magnitude is 0.05dB, and the maximum deviation of transmission phase is 0.5 degree, which can meet the demand of on-wafer scattering parameter calibration and measurement.
2022 Vol. 43 (1): 97-101 [Abstract] ( 365 ) HTML (1 KB)  PDF (1312 KB)  ( 260 )
102 Research on Performance Evaluation Method of Calibration Results of Load-Pull System
LUAN Peng, DU-Jing, WANG Yi-bang, LIU Chen, WU Ai-hua, HU Hai-long
DOI: 10.3969/j.issn.1000-1158.2022.01.16
A method for evaluating the Performance of the on-wafer load-pull measurement system by measuring the measurement error ΔGT of the transducer gain of the passive mismatch attenuation network is introduced. The load-pull measurement system mainly measures the Performance of the power device under test from three aspects: output power (Pout), conversion gain (GT) and power added efficiency (PAE). By inserting a calibrated precision polarization step attenuator into the load end of the back-end module, the attenuation substitution measurement of ΔGT is carried out, and gives the calibration result ΔGT and the curve family of pout and PAE variation, which is convenient for designers to quickly obtain the system measurement Performance. Among them, the P;out error varies linearly with ΔGT (slope 45°); PAE error increases linearly with ΔGT. When PAE is 70% and ΔGT is 0.5dB, the corresponding power added efficiency PAE uncertainty is about 8.5%. After experimental verification, the deviation between the curve of Pout and PAE of measurement result is less than 1%.
2022 Vol. 43 (1): 102-106 [Abstract] ( 270 ) HTML (1 KB)  PDF (1486 KB)  ( 135 )
107 Fall Action Recognition Based on Computer Vision
CHENG Shu-hong, XIE Wen-rui, ZHANG Dian-fan, XU Nan
DOI: 10.3969/j.issn.1000-1158.2022.01.17
A fall behavior recognition algorithm based on multi algorithm fusion is proposed. Firstly, Yolov3 tiny detection algorithm is improved to effectively frame the human anchor and extract the target prospect according to the characteristics of human; then alphapose gesture recognition framework is used to identify the key points of human skeleton, and the main joint diagram of human body is obtained; Finally, taking the coordinate information of human joint diagram as input, the spatiotemporal graph convolution neural network is used to detect and identify falls and other actions, which can effectively detect falls in different scenes. The experimental results show that the fusion algorithm can improve the detection effect of fall behavior in different scenes, the detection accuracy can reach 97.4%, and effectively reduce the false detection rate.
2022 Vol. 43 (1): 107-113 [Abstract] ( 268 ) HTML (1 KB)  PDF (4472 KB)  ( 631 )
114 Measurement Method of Volume Radioactivity of Tritiated Methane for Airborne Tritium Monitors Calibration and Its Uncertainty Analysis
LIU Jia-yu, GUO Tao, ZHU Hui-chen, QIAN Nan, ZENG You-shi, ZHAO Chao
DOI: 10.3969/j.issn.1000-1158.2022.01.18
Aiming at the tritiated methane as the gas reference source for the calibration of airborne tritium monitor, a method for measuring its volume radioactivity is proposed. Tritiated methane is transformed into tritiated water by catalytic oxidation combustion furnace. Tritiated water is collected by two-stage series bubbler, and measured by liquid scintillation counter.Finally, the volume activity of tritiated methane is determined, and the uncertainty is analyzed.Implementing the above method, the volume radioactivity of the tritiated methane in lab and its expanded uncertainty are determined to be 17.4MBq/m3and 6.4% (k=2) separately, which meet the requirements for gaseous reference source according to GBT 30150-2013.The calibration experiment for a commercial airborne tritium monitor is conducted with the tritiated methane in lab, in which the calibration factor is 0.88. It indicates that the proposed method can provide a practical and credible technical basis for airborne tritium monitor calibration.
2022 Vol. 43 (1): 114-119 [Abstract] ( 227 ) HTML (1 KB)  PDF (942 KB)  ( 207 )
120 Simulation and Uncertainty Evaluation of Continuous on-line Monitoring Process of Carbon Dioxide Emission
Simulation and Uncertainty Evaluation of Continuous on-line Monitoring Process of Carbon Dioxide Emission
DOI: 10.3969/j.issn.1000-1158.2022.01.19
Through the establishment of carbon emission continuous online monitoring experimental platform, the continuous online monitoring process of carbon dioxide emission was simulated and analyzed. According to JJF 1059.1-2012 Evaluation and expression of uncertainty in measuirement and JJG 640-2016 Differential pressure flowmeters, the uncertainty evaluation mathematical model of carbon emission measurement results was established, the source of measurement uncertainty was comprehensively analyzed, and the uncertainty evaluation of measurement results was carried out. The results show that the expanded relative uncertainty of the experimental platform for continuous on-line monitoring of carbon emissions is 5.86%, the coverage factor is k=2, and the confidence level is 95%. The uncertainty of the measurement results mainly comes from the system error introduced by the ambient temperature.
2022 Vol. 43 (1): 120-126 [Abstract] ( 347 ) HTML (1 KB)  PDF (2181 KB)  ( 342 )
127 Evaluation of Measurement Uncertainty in the Determination of Benzo［a］pyrene in Fertilizer by Adaptive Monte Carlo Method
WANG Gao-jun, WU Hao, ZHANG Ming-hong
DOI: 10.3969/j.issn.1000-1158.2022.01.20
The code for evaluating the measurement uncertainty by adaptive Monte Carlo method was completed by compiling the calculation program in Python, and then the measurement uncertainty of benzo［a］pyrene content in fertilizer by gas chromatography-mass spectrometry was evaluated.The result showed that the standard uncertainty for the determination of benzo［a］pyrene in fertilizers by gas chromatography mass spectrometer is 0.0179mg/kg. The application of the adaptive MC method in the measurement uncertainty evaluation of the determination of fertilizer composition content is explored. The results show that this method has the advantages of wide applicability, intuitive calculation process and reliable calculation results.
2022 Vol. 43 (1): 127-132 [Abstract] ( 210 ) HTML (1 KB)  PDF (781 KB)  ( 214 )
133 Explore the Influence of Transcutaneous Electrical Acupoint Stimulation Neiguan Point on Anxiety Based on Electroencephalogram Nonlinear Dynamic Analysis Method
FAN Feng-jie, BAI Yang, JI Hui-fang
DOI: 10.3969/j.issn.1000-1158.2022.01.21
To explore the effect of Transcutaneous electrical acupoint stimulation (TEAS) Neiguan on anxiety and its possible mechanisms based on the nonlinear dynamic characteristics of EEG. Twelve anxiety patients are randomly divided into two groups. The acupuncture group receives TEAS on Neiguan point, the non-acupuncture group receives TEAS on non-acupuncture point. the EEG data is collected before and after the experiment. EEG characteristics, approximate entropy (ApEn) and correlation dimension (D;2), are extracted and analyzed to study the change of complexity, and use the change of SAS to assess the effect. Experimental results showed that the scale scores are significantly reduced, and the complexity assume a downward trend in the acupuncture group. The ApEn data are decline significantly in region AF3、F7、F3、P7、F8、F4、AF4 (p<0.05); the D;2 data of the AF3、F3、Fc5、T7、P7、F8 、F4、AF4 are markedly decline (p<0.05). There are no significant change in SAS、ApEn and D;2 of the non-acupuncture group. The results proved that TEAS Neiguan point can decrease anxiety, reduce the complexity of each brain region, the change mainly occur in bilateral frontal regions and bilateral temporal regions.
2022 Vol. 43 (1): 133-139 [Abstract] ( 225 ) HTML (1 KB)  PDF (2611 KB)  ( 219 )
140 Comparison of Biological Calibration Methods of Bioaerosol Monitor
TIAN Ying, ZHANG Guo-cheng, WU Dan, LIU Jia-qi, LI Jing-jing, HUO Sheng-wei, SHEN Shang-yi, PAN Yi-ting
DOI: 10.3969/j.issn.1000-1158.2022.01.22
The bioaerosol monitor detect biological substances in the air based on laser-induced fluorescence, which is of great significance for disease prevention and early warning of biological terrorism. The study found that the current domestic bioaerosol monitor cant distinguish different bacterial states when collecting biological particles in the air. The bioaerosol monitor detect the total number of bacteria. Through real-time quantitative PCR and colony counting method to detect the microorganisms in the BioSampler, it was found that the total number of bacteria and the number of cultivable bacteria were significantly different. Observation by scanning electron microscope and fluorescence microscope found that the impact and centrifugation of the sampler affected the viability of the microorganisms, so it is not suitable to calibrate the bioaerosol monitor by the colony culture method.
2022 Vol. 43 (1): 140-144 [Abstract] ( 262 ) HTML (1 KB)  PDF (1691 KB)  ( 441 )
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