Experimental and Numerical Investigations of High Strength Steel Welded H-section Columns

Feng Zhou,Le-Wei Tong,Yiyi Chen 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.2

This paper reports experimental and numerical investigations of high strength steel columns. A series of tests was performed on different geometries of welded H-sections fabricated from high strength steel sheet with a nominal yield stress of 460 MPa. A non-linear finite element model which includes geometric and material non-linearities was developed and verified against experimental results of high strength steel welded H-section columns. The calibrated model was shown to provide accurate predictions of the experimental ultimate loads and failure modes of the test specimens. Therefore, a parametric study was carried out over a range of cross-section geometries and column lengths. The test and numerical results of stub columns obtained in this study were compared with the nominal section capacities. It is shown that the design provisions specified in the European Code, American Specification and Chinese Code on yield slenderness limits are all conservative. The normalized flange and web slenderness limits for fully effective section codified in European Code are very close to those codified in the American Specification, which are more suitable. Furthermore, the test and numerical results of long columns obtained in this study were compared with the nominal member capacities predicted using the European Code, American Specification and Chinese Code for steel structures. It is shown that the European Code provides the best agreement between the test and numerical data with design strength predictions for high strength steel welded H-section long columns.

Hierarchical Colored Petri Nets Based Components for Workflow Systems

Feng Zhou,Rui-Feng Bo,Hong-Zhong Huang,Dan Ling,Qiang Miao 대한기계학회 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.10

Workflow systems have benefited the enterprise and customer in many aspects. But with the increasing complexity of the system, workflow design becomes a complicated and time-consuming process. In this paper, we model the system based on the Hierarchical Colored Petri Nets (HCPN) to avoid the complexity of the system, and the super nets of the model are abstracted as independent components to increase the flexibility, acceptability and maintainability of the system. Another important characteristic of this model is its convenience for reuse and workflow mining. The development process of the overhead traveling crane was given to demonstrate the proposed method.

Improved Accelerometer and Magnetometer-Based Solution to Solve Quaternion

Feng Zhou,Yanxuan Wu,Ningjun Fan 제어로봇시스템학회 2012 제어로봇시스템학회 국제학술대회 논문집 Vol.2012 No.10

Light overloaded small aircraft, such as ducted fan MAV, could use accelerometer and magnetometer to measure acceleration and earth magnetic field in the body coordinate frame. There is a quaternion that relates the measured accelerations and earth magnetic field in the body coordinate frame to calculated values in the earth coordinate frame. An overdetermined nonlinear equations which could get the quaternion need to be solved. So far, the Gauss-Newton iteration algorithm was being used most commonly to solve the overdetermined equations. However, when the inverse of Jacobian matrix is singular or conditioned, the iteration would be diverge. To overcome the problem, first, transferring the overdetermined problem to determined one by a premultiply transposition of Jacobian matrix, then using Correctional Newton with Parameter iteration algorithm to solve the determined equations. Compared to Gauss-Newton iteration algorithm, this method not only could converge more fast, but also could overcome the situation which Jacobian matrix is singular or conditioned.

[네트워크 프로토콜] 무선LAN 환경에서 TDMA방식을 이용한 동일채널 간섭 감소

Feng Zhou,최용훈(Yong-Hoon Choi),박수원(Suwon Park),이승형(Seung Hyong Rhee) 한국정보과학회 2012 정보과학회논문지 : 정보통신 Vol.39 No.2

동일 채널 간섭은 주파수가 같은 동일 채널에서 둘 또는 그 이상의 전파가 수신기에서 간섭하여 장애가 발생하는 현상이다. 본 논문에서는 고밀도의 무선랜 환경에서 동일 채널 간섭 문제를 연구하고 TDMA(Time Division Multiplexing Access) 알고리즘을 이용하여 개선방법을 제안한다. 먼저 무선랜 개발과정에서 핵심기술문제를 언급하고 동일채널 간섭의 연구 배경을 제시한다. 그 후 네트워크 성능에 영향을 많이 주는 MAC(Media Access Control) 프로토콜을 설명하고 분석한다. 마지막으로 간섭 현상 시나리오를 통해 제안한 메커니즘을 이용하여 기존의 CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) 메커니즘과 비교한다. 시뮬레이션을 통하여 개선된 성능을 확인한다. Co-channel interference is a phenomenon that two or more radio wave interfere each other in same geographic area transmit on the same frequency. In this paper, we discuss the problem of co-channel interference in high-density wireless LAN(Local Area Network) environment and propose a way to improve throughput and delay by using TDMA(Time Division Multiplexing Access) algorithm based on WLAN. First, the key technical problem of WLAN during its development process is pointed out and the research background of co-channel interference in WLAN is offered; then we analyze MAC layer protocol of IEEE 802.11b standard, which mainly affects system throughputs and channel quality. Based on a half-coverage area scenario, we provide the proposed mechanism with TDMA-based scheme. The simulation results show network throughput improvement and transmission delay reduction comparing with original CSMA/CA(Carrier Sense Multiple Access/Collision Avoidance) with RTS/CTS(Ready-To-Send/Clear-To-Send) mechanism. Finally, we summarize the achievement that we have made.

Fabrication of Poly(styrene-co-acrylic acid)/Polystyrene Anisotropic Nanoparticles via Seeded Emulsion Polymerization

Feng Zhou,Shaohui Lin,Garry L. Rempel,Qinmin Pan 한국고분자학회 2017 폴리머 Vol.41 No.6

Anisotropic nanoparticles have potentially various important applications, especially in 3D printing materials, binders and phase compatible agents, for which it is essential that the components and the structures are well designed and controlled. This paper investigated nanoparticles consisting of two lobes with opposite properties. As a model system, synthesis of poly(styrene-co-acrylic acid)/polystyrene anisotropic nanoparticles was studied and the effects of temperature, surfactant amount, inhibitors, and initiators for the involved polymerization procedures, and the swelling temperature, and swelling ratio for making the second lobe, on the morphology and size of the produced particles , were investigated. As a result, the anisotropic nanoparticles with uniform asymmetry, one lobe with hydrophilicity and the other with hydrophobicity, were successfully realized. The apparent size of the nanoparticles was below 200 nm, and the strategies for achieving various morphologies, such as snowman-like, potato-like and dumbbell-like, were established. The anisotropic nanoparticles achieved in this study are very useful in the 3D material development that is involved in our another research.

Combined bending and web crippling of aluminum SHS members

Feng Zhou,Ben Young 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.2

This paper presents experimental and numerical investigations of aluminum tubular members subjected to combined bending and web crippling. A series of tests was performed on square hollow sections (SHS) fabricated by extrusion using 6061-T6 heat-treated aluminum alloy. Different specimen lengths were tested to obtain the interaction relationship between moment and concentrated load. The non-linear finite element models were developed and verified against the experimental results obtained in this study and test data from existing literature for aluminum tubular sections subjected to pure bending, pure web crippling, and combined bending and web crippling. Geometric and material non-linearities were included in the finite element models. The finite element models closely predicted the strengths and failure modes of the tested specimens. Hence, the models were used for an extensive parametric study of cross-section geometries, and the web slenderness values ranged from 6.0 to 86.2. The combined bending and web crippling test results and strengths predicted from the finite element analysis were compared with the design strengths obtained using the current American Specification, Australian/New Zealand Standard and European Code for aluminum structures. The findings suggest that the current specifications are either quite conservative or unconservative for aluminum square hollow sections subjected to combined bending and web crippling. Hence, a bending and web crippling interaction equation for aluminum square hollow section specimens is proposed in this paper.

Pseudo-homogeneous kinetic modeling of dioctyl terephthalate (DOTP) production by esterification of terephthalic acid and 2-ethylhexanol over tetrabutyl titanate catalyst

Feng Zhou,Jinjin Cai,Xiaoning Mao,Zhenyu Wu,Yong Nie 한국화학공학회 2022 Korean Journal of Chemical Engineering Vol.39 No.9

As a green plasticizer, the industrial production of dioctyl terephthalate (DOTP) is still facing the problemof high energy consumption. To optimize the production process and reactor, it is essential to understand the kineticbehavior of reaction system. In this work, the two-step consecutive esterification of solid terephthalic acid (PTA) and 2-ethylhexanol (2-EH) catalyzed by tetrabutyl titanate was studied. First, the equilibrium constants and enthalpies of thetwo-step reaction were experimentally determined and validated by the group contribution methods. Then, a pseudohomogeneouskinetic model was developed, and the reaction order of PTA was corrected to reflect its solid phase characteristic. Non-isothermal kinetic experiments were carried out under different initial feed molar ratios and catalystconcentrations, and the kinetic parameters in the model were estimated by mathematical regression. The model predicteddata agreed well with the experimental data. Finally, the analyses of reaction rate showed that the first-step reactionwas the rate-controlling step of the whole esterification process.

Dwell Time Algorithm Based on Bounded Constrained Least Squares Under Dynamic Performance Constraints of Machine Tool in Deterministic Optical Finishing

Yunfei Zhang,Fengzhou Fang,Wen Huang,Wei Fan 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.8 No.5

The dwell time algorithm is one of the most important techniques within the deterministic optical surfacing technologies. The existing dwell time algorithms are generally based on non-negative least squares (NNLS) without considering the dynamic performance constraints of machine tools. This is a circumstance that leads to poor convergence accuracy. In this paper, a dwell time algorithm, based on bounded constrained least-squares (BCLS) under dynamic performance constraints of the machine tool, has been developed. The upper and lower constraints of the dwell time model could be derived through the acceleration and deceleration mechanism of the CNC (Computer Numerical Control) machine tools. A two-metric projection Newton iteration algorithm was used to solve the large-scale dwell time model, which greatly improved the computation efficiency. The results of the experiments and simulations showed that the proposed algorithm will give a very high convergence accuracy for optical finishing with machine tools with different dynamic performances. When the machine acceleration was set to a value as low as 0.1 g, the accuracies of the surface figures PV (Peak-to-Valley) and RMS (Root Mean Square) till improved by 40.8% and 55.2%, respectively, when using the BCLS algorithm. The influences of different dynamic performances of the machine tools on the dwell time solutions have also been investigated, which will provide a good guidance in the design of deterministic polishing machine tools.

State of the Art in Defect Detection Based on Machine Vision

Zhonghe Ren,Fengzhou Fang,Ning Yan,You Wu 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.9 No.2

Machine vision significantly improves the efficiency, quality, and reliability of defect detection. In visual inspection, excellent optical illumination platforms and suitable image acquisition hardware are the prerequisites for obtaining high-quality images. Image processing and analysis are key technologies in obtaining defect information, while deep learning is signifi-cantly impacting the fi eld of image analysis. In this study, a brief history and the state of the art in optical illumination, image acquisition, image processing, and image analysis in the fi eld of visual inspection are systematically discussed. The latest developments in industrial defect detection based on machine vision are introduced. In the further development of the fi eld of visual inspection, the application of deep learning will play an increasingly important role. Thus, a detailed description of the application of deep learning in defect classification, localization and segmentation follows the discussion of traditional defect detection algorithms. Finally, future prospects for the development of visual inspection technology are explored.

Three-Linear-Axis Grinding of Small Aperture Aspheric Surfaces

Guangpeng Yan,Kaiyuan You,Fengzhou Fang 한국정밀공학회 2020 International Journal of Precision Engineering and Vol.7 No.5

A novel approach of three-linear-axis ultra-precision grinding with wheel path generation, tool interference checking and profile compensation is proposed and systematically investigated for fabricating aspheric surfaces. The performance of the proposed techniques is evaluated by grinding an aspheric mould insert on bindless tungsten carbide. The experimental results demonstrate that the profile error can be reduced to 0.1 μm or a lower value in peak to valley (PV) after two compensation cycles. The on-machine measurement results show agreement with the off -machine measurement results when commercially available profilometers are employed. The study confirms the feasibility of the proposed wheel path determination method and the developed profile compensation approach. A mirror surface with roughness less than 8 nm in Sa is achieved.