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Vibration Isolation Characteristics Analysis of X-shaped Quasi-Zero Stiffness Vibration Isolator YAO Guo， YU Yong-heng， ZHANG Yi-min， WU Zhi-hua Journal of Northeastern University Natural Science    2020, 41 (5): 662-666.   DOI: 10.12068/j.issn.1005-3026.2020.05.009 Abstract （1732）   HTML    PDF（pc） （599KB）（2214）       Knowledge map    Save An X-shaped structure is applied to quasi-zero stiffness isolator to improve its low frequency isolation performance. The dynamic equation of the system is established by using the Newton’s motion law. The amplitude-frequency response curves of the system are obtained by using the incremental harmonic balance method. The effect of equivalent reduced stiffness γ on system transmissibility is discussed. Research results show that the reasonable numerical interval of dimensionless pre-compression length of horizontal spring is (0， 2). In the resonant region， the increase of γ can significantly reduce the force transmissibility. At higher excitation frequencies， the effect of the change of γ on the vibration isolation performance of the system is weak. With the decrease of γ， the displacement transmissibility in the resonance region decreases sharply. In addition， the decrease of γ will also reduce the resonance frequency and make the jump phenomenon disappear. Therefore， the equivalent reduced stiffness γ of the X-shaped quasi-zero stiffness isolator is an ideal parameter which can effectively reflect the effect of low-frequency vibration isolation of the system. The effect of equivalent reduced stiffness γ is discussed in detail. Reference | Related Articles | Metrics | Comments（0）

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Numerical Simulation of the Intersection Angle Influence on Atomization Process of Powders Produced by VIGA GUO Kuai-kuai， CHEN Jin， LIU Chang-sheng， CHEN Sui-yuan Journal of Northeastern University Natural Science    2020, 41 (5): 729-735.   DOI: 10.12068/j.issn.1005-3026.2020.05.020 Abstract （1221）   HTML    PDF（pc） （1970KB）（1570）       Knowledge map    Save The effect of intersection angle on the primary and secondary atomization of vacuum induction melting gas atomization (VIGA) was studied by the combination of experiments and computational fluid dynamics CFD simulations. The VOF (volume of fluid) multiphase flow model based on the Euler-Lagrange method was used to simulate the primary atomization process and the discrete phase model (DPM) was used to simulate the breakup process and predict the particle size distribution (PSD) of Taylor analogy breakup (TAB) in secondary atomization. The results show that the simulated area of recirculation zone decreases with the increase of intersection angle. The fragmentation morphology of metal melt is presented as "fountain→umbrella" and the primary droplets size is 0.3~0.9mm. The Weber number (We) of liquid droplets is 10~90. With increasing intersection angle， the average particle size of the powders decreases gradually. Moreover， these simulation results prove reasonable， which the simulated particle size of the powders is in agreement with the experimental one when the intersection angle is 36°. Reference | Related Articles | Metrics | Comments（0）

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Experimental Study on Calcification Process of Diaspore Bayer Red Mud XIE Li-qun， ZHANG Ting-an Journal of Northeastern University Natural Science    2018, 39 (11): 1614-1618.   DOI: 10.12068/j.issn.1005-3026.2018.11.019 Abstract （1547）   HTML    PDF（pc） （687KB）（1307）       Knowledge map    Save Large scale utilization of high alkalinity red mud generated in Bayer process is becoming a worldwide problem. Aiming at this problem， a novel calcification-carbonation process is proposed. Firstly， red mud was treated with lime， where the silicon phase is converted into hydrogarnet and alkali is removed. Then， calcification residue is decomposed by CO2 and alumina is recovered. The effect of calcification temperature， Ca-Si molar ratio， and liquid-solid ratio on alkali content in calcification process were investigated. The results indicate that the w(Na2O)in red mud reduces from 6.70% to 0.35% at reaction temperature of 160℃， Ca-Si molar ratio of 2.5∶1， liquid-solid ratio of 3∶1. Moreover， the XRD results show that diffraction peak of the alkali in red mud disappears after the calcification transformation， and hydrogarnet is the main phase. Reference | Related Articles | Metrics | Comments（0）

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Milling Force Coefcient Identication for Multi-axis and Ball-End Milling Cutter WANG Bo， LI Bai-chun， YANG Jian-yu， WANG Wan-shan Journal of Northeastern University Natural Science    2018, 39 (11): 1630-1635.   DOI: 10.12068/j.issn.1005-3026.2018.11.022 Abstract （1247）   HTML    PDF（pc） （1266KB）（1195）       Knowledge map    Save A new method for the identification of milling force coefficients is proposed for the prediction of the milling forces in multi-axis milling with ball-end cutter. Firstly， the shearing coefficients of milling forces are fitted with multiple order polynomial function of axial position angle， the identification model is derived based on average milling forces as well as the milling force model of multi-axis ball-end-cutter milling. Secondly， the experiment plan of multiple group slot milling for milling coefficient identification is presented， in which the groups are distinguished from each other by varying the angle between the cutter axis and the work piece surface in the slot milling. This experiment is used to ensure the identified coefficients contain the effect factor of different cutter postures. Finally， the proposed method is validated experimentally and the results show that the proposed method is better than that based on instantaneous milling forces in terms of anti-interference and identification precison. Reference | Related Articles | Metrics | Comments（0）

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Control Strategy for the Compensation of Imbalance and Harmonic in Energy Internet HUANG Bo-nan， ZHOU Jian-guo， SUN Qiu-ye， ZHANG Hua-guang Journal of Northeastern University Natural Science    2017, 38 (6): 761-766.   DOI: 10.12068/j.issn.1005-3026.2017.06.001 Abstract （799）   HTML    PDF（pc） （1403KB）（1929）       Knowledge map    Save The energy internet proposed recently provides a potential solution to address the increasingly serious world energy issues. Solving the power quality problem properly is one of the key problems of the energy internet to be developed adequately in the future. Considering the power quality issue caused by the nonlinear and imbalance loads widely existing in the energy internet， an imbalance and harmonic compensation strategy is proposed based on the energy router in this paper. The imbalance and harmonic compensation controllers are also developed in detail. Simulation results from MATLAB/SIMULINK are provided to demonstrate the validity and efficiency of the proposed method. Reference | Related Articles | Metrics | Comments（0）

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Tumor Microarray Gene Expression Data Classification Based on Weighted Extreme Learning Machine JIANG Lin-ying， YU Dong-hai， SHI Xin Journal of Northeastern University Natural Science    2017, 38 (6): 798-803.   DOI: 10.12068/j.issn.1005-3026.2017.06.008 Abstract （847）   HTML    PDF（pc） （594KB）（1084）       Knowledge map    Save With the development of gene microarray technology， gene expression profiling becomes a significant method for identifying different types of canners. Microarray gene expression data is from clinical trials in general， where the class distribution of samples is changeable， which makes the expression data have a chance to become more imbalanced. In this paper， the weighted extreme learning machine (WELM) was used to classify the imbalance microarray gene expressing data. In order to reduce classification error caused by the imbalance data， a weight was assigned to each sample in order to enhance the impact of minority class while reducing majority class’s impact， and improve the accuracy of tumor classification. The experimental results show that the minority class recognition rate can be well improved by the proposed method， so as to improve the overall performance of classifiers. Reference | Related Articles | Metrics | Comments（0）

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SH-CCT Diagram， Microstructure and Properties of Coarse Grain Heat-Affected Zone in Q1100 Ultra-high Strength Steel WEN Chang-fei， DENG Xiang-tao， WANG Zhao-dong， WANG Guo-dong Journal of Northeastern University Natural Science    2017, 38 (6): 809-813.   DOI: 10.12068/j.issn.1005-3026.2017.06.010 Abstract （1092）   HTML    PDF（pc） （5020KB）（1696）       Knowledge map    Save It is generally believed that coarse grain heat-affected zone (CGHAZ) in welded region is the weakest part in the welding joint of low alloy ultra-high strength steel. The thermomechanical simulator was employed to simulate the welding thermal cycle processes of CGHAZ in Q1100 ultra-high strength steel. By using thermal expansion measurement combined with OM，SEM observations and hardness test， the critical phase transformation points at the equilibrium state and welding conditions were determined and SH-CCT diagram at different cooling rates was plotted. TEM observation and Lepera reagent were used to reveal the morphology of M-A constituent. The results showed that the austenitizing temperature of this steel in the welding condition was significantly higher than that in equilibrium state. The microstructure of CGHAZ mainly consisted of bainite， bainite and martensite， and martensite accompany with the increase of cooling rate. The hardness increased gradually with the increase of cooling rates， the maximum hardness was HV464. The M-A constituent occurred when the cooling rate was lower than 10℃/s， and the lower cooling rate， the more M-A constituent. Reference | Related Articles | Metrics | Comments（0）

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Low Temperature Combustion Synthesis and Characterization of Nanocrystalline Magnesium Aluminum Spinel (MgAl2O4) Powders HUO Di， PI Chun-yang， SUN Xu-dong， KANG Yan Journal of Northeastern University Natural Science    2017, 38 (6): 814-818.   DOI: 10.12068/j.issn.1005-3026.2017.06.011 Abstract （1148）   HTML    PDF（pc） （2366KB）（1110）       Knowledge map    Save Nanocrystalline magnesium aluminate spinel (MgAl2O4) powders were prepared by a low temperature combustion synthesis method using nitrates and sucrose as starting materials， the characteristics of the as-synthesized powders were investigated in terms of heating temperature， environmental atmosphere and heating rate. The results show that particle sizes of MgAl2O4 spinel powder increase with the heating temperature of polymer precursors. When the precursors are heated in O2 atmosphere， the reduced formation temperature of pure MgAl2O4 phase and accelerated reactive species diffusion along with enlarged particle sizes can be achieved. Under the conditions of fast heating， 2∶1 molar ratio of sucrose to nitrates and O2 atmosphere， the formation temperature of MgAl2O4 phase is at 400℃ and further pure single phase is obtained at 700℃. The highly crystalline， soft agglomerated nano-sized MgAl2O4 powders are in favor of decreasing sintering temperature of high dense MgAl2O4 ceramics. Reference | Related Articles | Metrics | Comments（0）

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Surrounding Rock Response Pattern of Working Face with High-Intensity Mining Based on Microseismic Monitoring LI Yang,YANG Tian-hong,HOU Xian-gang,WANG Hong Journal of Northeastern University Natural Science    2017, 38 (6): 854-858.   DOI: 10.12068/j.issn.1005-3026.2017.06.019 Abstract （1592）   HTML    PDF（pc） （3521KB）（1302）       Knowledge map    Save IMS microseismic monitoring system was employed in Xiaojihan coal mine， a typical high-intensity mining mine in Western China. The spatial monitoring of the whole monitoring area was realized and more comprehensive information of surrounding rock failure was captured. The mine pressure behavior， strata movement， and the stress and deformation around the surrounding rock mass were analyzed based on microseismic monitoring. The results showed that the microseismic events evolved periodically with the continuous mining of 11203 working face， which is closely related to the mining pressure behavior in the working face， and the average periodic weighting length is 23m. The height of “three zones” and the influence range of mining disturbance in the working face could provide help for support design and disaster prevention. Reference | Related Articles | Metrics | Comments（0）

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Multivariate Correlative and Combined Thermal Error Model for the CNC Machine Tool with Experimental Validation MA Yue， WANG Hong-fu， SUN Wei， HUANG Yu-bin Journal of Northeastern University:Natural Science    2017, 38 (5): 700-705.   DOI: 10.12068/j.issn.1005-3026.2017.05.019 Abstract （759）   HTML    PDF（pc） （1269KB）（1192）       Knowledge map    Save To solve the problem that based on machine tool temperature that is comprehensively influenced by other factors， and thus the thermal error models had poor robustness， a multivariate correlative and combined thermal error model was put forward， which overall considers machine tool temperature， speed of power source， and temperature of coolant and environment. Least squares support vector (LS-SVM) method was applied to the thermal error model， and partial least squares (PLS) method was applied to extract the principal components as the input of LS-SVM， and the PLS-LSSVM thermal error combined model was then formulated. In addition， this model set the differential temperatures， relatively with initial temperatures， as the temperature variable， which is based on the process of numerical control machining and the principle of material thermal deformation， to make the thermal error compensation more accurate. It was tested on a precision machining center， whose results showed that the PLS-LSSVM thermal error model is more stable than the LS-SVM model， and more accurate than the partial least squares regression (PLSR) model. Besides， the root mean square error (RMSE) of the predictive thermal error with the PLS-LSSVM model is 5.5μm on average less than that with the PLS-LSSVM* model， which only takes into account the temperature measurements of the machine tool. Reference | Related Articles | Metrics | Comments（0）

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Hovering Control of Hex-Rotor Aircraft Based on Optical Flow SHI Tian-wei， WANG Hong Journal of Northeastern University:Natural Science    2015, 36 (10): 1378-1383.   DOI: 10.3969/j.issn.1005-3026.2015.10.003 Abstract （980）   HTML    PDF（pc） （798KB）（1784）       Knowledge map    Save A nonlinear controller was proposed to realize the hovering control for the hex-rotor aircraft by using the inertial optical flow. Meantime， an auxiliary hovering control system was presented to overcome the influence of external factors. Firstly， the spherical camera was used to get the image of target plane， and the projection from target point to camera lens was realized by dynamic mapping. Then the translational optical flow of target point was obtained by comparing the two continuous time images. Finally， the divergent translational optical flow was utilized as the feedback to implement the stable hovering control for the hex-rotor aircraft. The indoor textured floor was selected as the target plane， and this experiment was tested ten times totally. The actual flight tests showed that the errors on horizontal and vertical directions were all less than ±5cm， which verified the feasibility of the proposed nonlinear controller and auxiliary hovering control system. Reference | Related Articles | Metrics | Comments（0）

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Transition Zones in Flexible Stretch Forming for Surface Parts CHENG Yan-yan,LI Ming-zhe,XING Jian,WANG You Journal of Northeastern University:Natural Science    2015, 36 (10): 1435-1440.   DOI: 10.3969/j.issn.1005-3026.2015.10.015 Abstract （733）   HTML    PDF（pc） （928KB）（1039）       Knowledge map    Save According to the characteristics that the multi-gripper stretch forming machine can realize the flexibility of clamping and stretching， finite element models of rectangular and trapezoidal sheet metal were built for surface parts of trapezoidal projection plane， and numerical simulations of different transition zones for rectangular and trapezoidal metal sheets were conducted. The results showed that with the decrease of the maximum length of the transition zone， the conformability of the sheet metal to the forming die was increased， the forming force together with the maximum strain of the formed parts decreased while the strains and thickness of the effective forming zone distributed more uniformly and the formability was much better. Stretch forming experiments were done for the surface part of trapezoidal projection plane， and the experimental results were coincident with the numerical simulation results， which proved the validity of simulation. The multi-gripper stretch forming machine can reasonably choose the transition zone shape according to the shape of forming die， which improves forming quality and reduces the material and stretch forming costs. Reference | Related Articles | Metrics | Comments（0）

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The Discovery and Researching Significance of Quaternary Mammalian Fossils in North Twenty Town ,Liaoning Province Journal of Northeastern University    0, (): 0-0.   Abstract （586）   HTML          Knowledge map    Save Quaternary mammalian fossils unearthed near north twenty town in Jianping , Chaoyang of Liaoning Province. According to analyzing ,it was the antler`s fossil of Megaceros and developed from the warm moisture steppe ecosystem , Cenozoic in Middle Pleistocene. The fossil was strong siliconized. Contrast regional stratigraphy with fossil , it formed in the early Pleistocene. The antler`s fossil was buried in loess soil. Loess was result of dry and cold conditions.So it had been warm and moisture,and became dry and cold after a period . Presumably mammal was affected by climate change and died out . Related Articles | Metrics | Comments（0）

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Research on Vignetting Influence on Accuracy of Temperature Measurement and Correction Method for CCD-based Pyrometer Journal of Northeastern University    0, (): 0-0.   Abstract （564）   HTML          Knowledge map    Save Since the CCD-based pyrometer can obtain temperature field of objects, it has attracted more and more attention in academic studies recently. However, due to the existence of vignetting, there is serious photometric distortion in temperature field, and so the accuracy of temperature measurement is degraded badly. In order to improve the accuracy of temperature field measurement, a mathematical model for temperature distortion based on theories of radiation thermometry and geometrical optics is built in this paper, and the influence of optical system parameters on the accuracy of temperature field measurement is analyzed. Based on the sparsity of neighborhood gray gradient distribution (NGD), a method for the calibration of vignetting coefficient is also proposed in this paper. Compared with the calibration method using a integrating sphere, its maximum absolute error for vignetting estimation is only 0.052, and the experiment of temperature field correction for casting billets further validates the effectiveness of this calibration method. Related Articles | Metrics | Comments（0）

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Clinical Features and Serologic Analysis of Latent Syphilis LI Jun, WANG Lin-Na, ZHENG He-Yi, LIU Yong-Xin, LIU Xiu-Rong Journal of Northeastern University    2010, 30 (04): 336-339.   DOI: 10.3881/j.issn.1000-503X.2010.03.001 Abstract （1113）   HTML          Knowledge map    Save Objective To summarize the clinical features and analyze the serologic test results of latent syphilis. Methods The clinical data of 601 patients with latent syphilis who were treated in the sexually transmitted disease centre of Peking Union Medical College Hospital between January 2001 and November 2007 were retrospectively analyzed. Results Of the 601 cases of latent syphilis,there were 174 cases of early latent syphilis(EL),170 cases of late latent syphilis(LL),and 257 cases of unknown latent syphilis. Male to female ratio was 0.74:1（256 males and 345 females,respectively). Patients aged 20-39 years accounted for the largest proportion. Non-marital sexual intercourse was the main route of infection. Forty-six patients (7.65%) were co-infected with other sexually transmitted diseases. A total of 251 cases of latent syphilis (41.76%) were confirmed when the patients were receiving tests for other sexually transmitted diseases or suspected sexually transmitted diseases. Of the 601 patients with EL,LL and unknown latency,the proportion of serum rapid plasma reagin(RPR) titers higher than or equal to 8 were 72.99% (127/174),52.94% (90/170),and 60.31%(155/257),respectively. Compared with the early syphilis,serological negative conversion rate was significantly lower after treatment for l2 months in the early latent syphilis patients (P=0.044). Conclusion Education and awareness raising on syphilis should be strengthened to lower the prevalence of latent syphilis. Reference | Related Articles | Metrics | Comments（0）

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Chaos Opposition-based Learning Harmony Search Algorithm Journal of Northeastern University    0, (): 0-0.   Abstract （1221）   HTML          Knowledge map    Save Harmony search algorithm(HS) exists a shortcoming is that it is easy to fall into local optimal, For the purpose of improving this shortcoming, chaos opposition-based learning harmony search algorithm(COLHS) is proposed in this paper. Based on the consideration between aggregation and divergence, we preliminary judges this algorithm whether is trapped into local optimal or backwater status, then according to the judge result to integrate chaos disturbance strategy and local opposition-based learning. The ergodic of Logistic Chaos sequence and the space extensibility of opposition-based learning used to make the algorithm escaping local optimal. Beside, COLHS uses the history information of harmony memory to define updating factor and evolution factor. The two factors are applied to dynamically adjust pitch adjustment rate (PAR) and bandwidth (bw), which is aimed at making COLHS able to balance aggregation and divergence by effectively adjust parameter in different search stage. The numerical calculation results demonstrated that the proposed algorithm has better global optimal ability than HS and the other 8 improved HS algorithms were reported in recent literature. Related Articles | Metrics | Comments（0）