Effect of Resin Viscosity and Lubricants on Surface and Mechanical Properties of Glass Fiber Reinforced Polymer in Rapid Heat Cycle Molding

Aimin Zhang,Yang Hui,Junji Hou 한국고분자학회 2018 폴리머 Vol.42 No.6

Conventional injection molding (CIM) and rapid heat cycle molding (RHCM) methods are used to prepare ABS and (acrylonitrile-butadiene-styrene)/glass fiber copolymer (ABS/GF) plastic parts. Pentaerythritol stearate (PETS) and silicon particles are chosen as lubricants. Effect of resin viscosity and lubricants on properties of plastic parts was investigated. The results show that resin viscosity has some effect on surface quality of plastic parts in CIM process but no effect in RHCM process. ABS/GF plastic parts molded in RHCM process exhibit higher tensile, higher flexural strength and lower impact strength. Silicon is more effective in RHCM process than in CIM process.

Crystallization and Mechanical Properties of Glass Fiber Reinforced Polypropylene Composites Molded by Rapid Heat Cycle Molding

Aimin Zhang,Guoqun Zhao,Jialong Chai,Junji Hou,Chunxia Yang,Guilong Wang 한국섬유공학회 2020 Fibers and polymers Vol.21 No.12

The crystalline behavior and mechanical properties of PP/GF (glass fibers) composites molded by rapid heat cyclemolding (RHCM) and conventional injection molding (CIM) were compared. SEM, DSC and XRD were utilized to studycrystallization behavior of PP and PP/GF composites. Furthermore, universal testing machine was employed to investigatethe mechanical properties. Results proved that higher degree of crystallinity and larger crystal size can be obtained in RHCMin comparison to CIM. GF can induce more crystal nuclei and then reduce the crystal size due to shear stress which isgenerated in polymer matrix around fibers. Nucleating agent (NA) has a positive effect on refine grains. The average crystaldiameter of PP/NA/30 %GF is about 1.7 μm which is one-tenth of PP/30 %GF (14 μm) in RHCM. XRD tests illustrated thatα-form crystal is the main crystal type for PP and PP/GF composites in RHCM and CIM. However, there is a little β-formcrystal in RHCM for PP/GF composites without NA. NA accelerates the formation of α-form crystal and restrains theemergence of β-form crystal. The plastic parts obtained in RHCM exhibited higher strength and modulus compared with thatobtained in CIM for both tensile and flexural tests.

Research on flexible dynamics of a 6-DOF industrial robot and residual vibration control with a pre-adaptive input shaper

Tie Zhang,Kangyu Lin,Aimin Zhang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.4

The residual vibration caused by joint flexibility tends to be nonlinear and time-varying due to the complicated dynamics characteristics of 6-DOF industrial robot. To address the time-varying residual vibration problem, this paper proposes a pre-adaptive input shaping method. By simplifying the 6-DOF industrial robot standard flexible dynamics equation, the flexible dynamical parameters can be identified without additional joint encoders or other measuring instrument, while the natural frequency of each joint can also be calculated from the identified dynamical parameters. Then by setting the calculated natural frequency as the initial condition, an iterative learning scheme based on the secant method can be applied to obtain a better natural frequency estimate. Finally, using the iteration results, the input shaper’s parameters can be updated, which makes the shaper adapt to the variation of system parameters. The results of model validation show that the simplified dynamic model can reflect the robot dynamic characteristics accurately. The vibration experimental results demonstrate the effectiveness of the proposed pre-adaptive input shaper in suppressing the residual vibration.

Fault diagnosis method of belt conveyor idler based on sound signal

Yahui Zhang,Siyan Li,Aimin Li,Gaoxiang Zhang,Mingzhuang Wu 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.1

Damage to a belt conveyor idler will increase the downtime and maintenance cost, so it is very important to diagnose its fault. At present, the fault diagnosis of the idler of a belt conveyor is mostly based on vibration and temperature signal. However, contact fault diagnosis approaches are severely limited when sensors are inconvenient to install or when vibration and temperature signals cannot be returned. In this special case, the non-contact fault diagnosis method, represented by measuring acoustic signals, becomes a necessary means. To effectively extract mechanical state information from sound signals of belt conveyors and identify typical mechanical faults, we propose a fault detection method based on sample center distance weighted (support vector data description (SVDD)) and multi-frame fusion (Melfrequency cepstral coefficient (MFCC)) features. Aiming at the disadvantage that single frame MFCC features and traditional SVDD are susceptible to noise, multi-frame fusion MFCC optimization features are used as samples, and the weighted SVDD model based on sample center distance is used for fault detection. Finally, the overall recognition accuracy of the experiment is greatly improved. It is proved that MFCC features of multi-frame fusion sound signal and weighted SVDD fault detection based on sample center distance can effectively determine whether there is a fault in the of belt conveyor idler.

Experimental and Mechanism Investigation on Boiling Heat Transfer Characteristics of Alumina/Water Nanofluid on a Cylindrical Tube

Hao Zhang,Zeng-en Li,Shan Qing,Zhuangzhuang Jia,Jiarui Xu,Lin Ma,Sixian Wang,Aimin Zhang,Zhumei Luo 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2019 NANO Vol.14 No.10

Nucleate pool boiling heat transfer experiments have been conducted to nanofluids on a horizontal cylinder tube under atmospheric pressure. The nanofluids are prepared by dispersing Al2O3 nanoparticles into distilled water at concentrations of 0.001, 0.01, 0.1, 1 and 2 wt.% with or without sodium, 4-dodecylbenzenesulfonate (SDBS). The experimental results showed that: nanofluids at lower concentrations (0.001 wt.% to 1 wt.%) can obviously enhance the pool boiling heat transfer performance, but signs of deterioration can be observed at higher concentration (2 wt.%). The presence of SDBS can obviously enhance the pool boiling heat transfer performance, and with the presence of SDBS, a maximum enhancement ratio of BHTC of 69.88%, and a maximum decrease ratio of super heat of 41.12% can be found in Group NS5 and NS4, respectively. The tube diameter and wall thickness of heating surface are the influential factors for boiling heat transfer coefficient. Besides, we find that Rohsenow formula failed to predict the characteristics of nanofluids. The mechanism study shows that: the decrease of surface tension, which leads to the decrease of bubble departure diameter, and the presence of agglomerates in nanofluids are the reasons for the enhanced pool boiling heat transfer performance. At higher concentration, particle deposition will lead to the decrease of distribution density of the vaporization core, and as a result of that, the boiling heat transfer performance will deteriorate.

Research progress on heavy metals removal by graphene from wastewater

Ying Zhu,Aimin Zhang,Zhiqiang Lv 한국탄소학회 2024 Carbon Letters Vol.34 No.1

We selected literature from the core collection of the Web of Science (WOS) database as the research object and used visualization bibliometric software to analyse the 1313 collected studies. We found that the research on the graphene-based adsorption of heavy metals from wastewater has received widespread attention in various countries around the world, especially developing countries, since 2015, and Chinese researchers have made significant contributions. The adsorption mechanisms, adsorbent materials, and advanced adsorption techniques for the removal of heavy metals from wastewater by graphene have been the focus and hotspots in the research in this field in recent years. Heavy metal removal from wastewater with graphene has strong application potential. In the future, researchers in this area can focus on exploring issues such as “new materials,” “recyclability,” and “interdisciplinarity” to break through existing technological bottlenecks, supplement the technical research and development of graphene materials, and promote advances in this field. Similar content b

Model Predictive Control for Tram Charging and Its Semi-Physical Experimental Platform Design

Chujia Guo,Aimin Zhang,Hang Zhang 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

Modern trams with a super capacitor have gained a lot of attention in recent years due to its reliability, convenience, energy conservation and environmental friendliness. Because of its special charging characteristic, the traditional charging structure and control strategy cannot satisfy its charging requirements. This paper presents a new charging topology for fast charging modern trams with a super capacitor and it designs a controller using continuous control set model predictive control (CCS-MPC). There are three contributions in this paper. First, a new charging structure is designed and its mathematics model is derived. The cascade structure is adopted instead of the parallel structure to simplify the control process and to keep the rated power of the controllable part low. Second, a MPC control strategy is proposed to satisfy the charging characteristic. The optimal control signal can be obtained by solving the designed optimization problem. The optimal control signal is related to the discrete control action. In addition, mapping between the continuous control signal and the discrete control action is designed. Third, a semi-physical experimental platform is built to verify the proposed topology and control method. The simulation model and experiment platform are built to verify the correctness of the new structure and its control method. The results obtained show that the new topology can work effectively.

Reversible Coordinative Chain Transfer Polymerization of Butadiene Using a Neodymium Phosphonate Catalyst

Zhengwei Tang,Aimin Liang,Handong Liang,Jiangwei Zhao,Lin Xu,Jie Zhang 한국고분자학회 2019 Macromolecular Research Vol.27 No.8

This study involves an investigation of the chain transfer reaction of butadiene (Bd) polymerization, under the neodymium tris[bis(2-ethylhexyl)phosphate] (Nd)/diisobutyl aluminum hydride (Al)/ethylaluminum sesquichloride (Cl)/Bd catalytic system. The results show that the chain transfer reaction itself is reversible. Only chain propagation and chain exchange reactions occurred during the later period of polymerization, and there was a linear relationship between the molecular weight and the conversion rate. All polymer chains showed sufficient reactivity to propagate by reacting with the monomer. The degree of the chain transfer reaction can be determined by the amount of Al, and the molecular weight in the synthetic polybutadiene can be accurately designed by the formula Mn=54·Bd/Nd/(0.67Al/Nd-7.17). The catalyst-polymerized butadiene afforded products featuring a relatively narrow molecular weight distribution and a high cis-1,4 stereospecificity. One of these products, polybutadiene rubber, showed narrow distribution in the sample, and exhibited good physical and mechanical properties, low abrasion, and low rolling resistance.

Model Predictive Control for Tram Charging and Its Semi-Physical Experimental Platform Design

Guo, Chujia,Zhang, Aimin,Zhang, Hang The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.6

Modern trams with a super capacitor have gained a lot of attention in recent years due to its reliability, convenience, energy conservation and environmental friendliness. Because of its special charging characteristic, the traditional charging structure and control strategy cannot satisfy its charging requirements. This paper presents a new charging topology for fast charging modern trams with a super capacitor and it designs a controller using continuous control set model predictive control (CCS-MPC). There are three contributions in this paper. First, a new charging structure is designed and its mathematics model is derived. The cascade structure is adopted instead of the parallel structure to simplify the control process and to keep the rated power of the controllable part low. Second, a MPC control strategy is proposed to satisfy the charging characteristic. The optimal control signal can be obtained by solving the designed optimization problem. The optimal control signal is related to the discrete control action. In addition, mapping between the continuous control signal and the discrete control action is designed. Third, a semi-physical experimental platform is built to verify the proposed topology and control method. The simulation model and experiment platform are built to verify the correctness of the new structure and its control method. The results obtained show that the new topology can work effectively.

Yet another Hybrid Strategy for Auto-tuning SpMV on GPUs

Zhaohui Wang,Xiaojie Qiu,Aimin Zhang,Yichao Cheng,Yi Peng,Sun Sun 보안공학연구지원센터 2015 International Journal of Software Engineering and Vol.9 No.5

Sparse matrix-vector multiplication (SpMV) is a key linear algebra algorithm and is widely used in many application domains. Besides multi-core architecture, there is also extensive research focusing on accelerating SpMV on many-core Graphics Processing Units (GPUs). SpMV computations have many indirect and irregular memory accesses, and load imbalance could occur while mapping computations onto single-instruction, multiple-data (SIMD) GPUs. SpMV is highly memory bandwidth-bound, though GPUs have massive computational resources, the performance of SpMV on GPUs is still unsatisfying. In this paper, we present a new hybrid strategy for auto-tuning SpMV on GPUs. Our strategy combines the advantages of row-major storage and column-major storage. Like many other strategies, we reordered a given sparse matrix according to row lengths in decreasing order. In order to be more adaptive and efficient, we proposed a new hybrid Blocked CSR and JDS (BCJ) format based on original CSR and JDS. BCJ splits a sparse matrix into a denser part and a sparser part after reordering and uses different kernels to process the corresponding part. And we proposed corresponding auto-tuning framework to help transforming matrix and launching kernels according to the sparsity characteristics of the matrix. A CUDA implementation of BCJ outperforms the original formats significantly on a broad range of unstructured sparse matrices.