The Unidirectional Wettability Property of a New Warp-knitted Double-face Fabric

Tong Yang,Haifan Yu,Yuying Liu,Zhijia Dong,Pibo Ma 한국섬유공학회 2020 Fibers and polymers Vol.21 No.8

In order to knit a warp-knitted fabric with unidirectional wettability property, polyester multifilament and cottonyarn were used as raw materials, and samples were produced on an RD6 EL warp-knitting machine. The unidirectionalwettability property of the fabric was tested by measuring the length of artificial sweat absorbed in the fabric. And theunidirectional wettability of the fabric primarily depends on the structure and twist of the yarn, especially the twist. Themoisture absorption capacity of the yarn decreases with the yarn twist increasing. When the twist reaches a certain value, itwill prevent the entry of moisture. This provides us with an inspiration for controlling the moisture absorption of fabric by thetwist of the yarn when knitting the unidirectional wettability fabric.

Simulation of stationary Gaussian stochastic wind velocity field

Ledong Zhu,Haifan Xiang,Quanshun Ding 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.3

An improvement to the spectral representation algorithm for the simulation of wind velocity fields on large scale structures is proposed in this paper. The method proposed by Deodatis (1996) serves as the basis of the improved algorithm. Firstly, an interpolation approximation is introduced to simplify the computation of the lower triangular matrix with the Cholesky decomposition of the cross-spectral density (CSD) matrix, since each element of the triangular matrix varies continuously with the wind spectra frequency. Fast Fourier Transform (FFT) technique is used to further enhance the efficiency of computation. Secondly, as an alternative spectral representation, the vectors of the triangular matrix in the Deodatis formula are replaced using an appropriate number of eigenvectors with the spectral decomposition of the CSD matrix. Lastly, a turbulent wind velocity field through a vertical plane on a long-span bridge (span-wise) is simulated to illustrate the proposed schemes. It is noted that the proposed schemes require less computer memory and are more efficiently simulated than that obtained using the existing traditional method. Furthermore, the reliability of the interpolation approximation in the simulation of wind velocity field is confirmed.

Investigation on flutter mechanism of long-span bridges with 2d-3DOF method

Yaojun Ge,Haifan Xiang,Yongxin Yang 한국풍공학회 2007 Wind and Structures, An International Journal (WAS Vol.10 No.5

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

Microstructure and wear behavior of WC-30WB-10Co cemented carbide coating sprayed by HVOF

Baogang Liu,Sam Lu,Haifan Zhu 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6

Numerous studies have been made to enhance the wear resistance of WC-Co coatings deposited by HVOF during the lastfew years. Spherical WC-30WB-10Co powders were firstly fabricated by agglomeration and sintering process, which werethen employed to deposit coating by HVOF. The morphologies, phase composition, hardness, as well as sliding wear performanceof the as-deposited coatings were explored. The same experiments were carried out on traditional WC-12Co coatingswith the purpose of making the comparison. The results showed that the CoWB compound was formed through the reactionbetween Co and WB in the sintering process of the WC-30WB-10Co powders. The diffraction peaks of W2C, Co3W3C andCo6W6C were found in the XRD patterns of both coatings, implying that oxidation and decarburization happened in thespraying process of both powders. In relative to the traditional WC-12Co coating, the microhardness and wear resistance ofthe WC-30WB-10Co coating were greatly enhanced. Obviously, with the microhardness of the WC-30WB-10Co coating beingelevated by 34.1%, the wear rates were only 49.3% of that of WC-12Co coatings. This was resulted from the existence ofthe superhard CoWB phase in the WC-30WB-10Co coating. The wear mechanisms of both coatings were abrasive wear andoxidative wear.

On the mechanism of vertical stabilizer plates for improving aerodynamic stability of bridges

Airong Chen,Zhiyong Zhou,Haifan Xiang 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1

거북목 증후군 환자를 위한 경추보호대 디자인 연구

형성은 ( Sungeun Hyoung ),천해범 ( Haifan Cen ),김용구 ( Yonggu Kim ) 한국산업디자이너협회 2022 산업디자인학연구 Vol.16 No.2

연구배경 거북목 증후군(forward head posture, FHD)은 목 전면부의 근육이 늘어나고 목 위쪽 근육이 짧아져 신체에 비해 머리가 앞으로 튀어나온 자세를 일컫는다. 이것은 현대 사회의 잘못된 습관과 자세가 척추 상단부의 스트레스를 가중시키는 원인이 되고 있다. 따라서 본 연구에서는 주변에서 쉽게 볼 수 있는 거북목 증후군 환자를 위한 경추보호대(cervical collar) 디자인 연구를 진행하였다. 연구방법 본 연구는 문헌조사와 실증연구로 나누어 조사하였다. 문헌조사에서는 거북목 증후군의 특성과 일반인, 고령자, 장애인 등 누구나 사용 가능한 평가 방법(Product Performance Program, PPP)을 조사하였다. 실증 연구는 설문조사와 디자인 개발로 나누어 진행하였다. 연구결과 거북목증후군 자가진단 평가에서는 앉는 자세>스마트폰>컴퓨터 순으로 연관이 있었고 눈 피로도는 컴퓨터와 스마트폰의 사용과 관련성이 높았다. PPP 평가에서는 전체적으로 심미성, 경제성, 직관성, 사용성, 기능성 순으로 영향력이 높았다. 다중 회귀분석 결과 '제품의 형태적 요소'는 단순/복잡, 통일성, 조화가 관련이 있었으며 '창의적 디자인 요소'는 독창성(새로움), 실용성(기능성, 실현 가능성)이 관련 있었다. 결론 최근 들어 건강에 대한 관심이 높아지면서 디자인 분야에 있어서도 의료기기에 대한 디자인 연구가 늘어나고 있다. 따라서 본 연구는 현대 사회의 대중적인 질환인 거북목 증후군 환자를 위한 경추보호대를 연구하기 위해 문헌조사와 실증연구를 진행하여 디자인을 개발하였다. Background Turtle forward head posture to the posture in which the muscles in the front half of the neck are elongated and the muscles in the upper half of the neck are shortened, and the head protrudes forward compared with the body. This is the wrong habit and posture of modern people, which aggravates the pressure on the upper spine. Therefore, this study carried out the design of cervical protective belt for patients with forward head posture. Methods This study was divided into literature survey and empirical research. The literature survey investigated the patients with characteristics of forward head posture and the evaluation of product performance program that can be used by anyone. The empirical research was divided into questionnaire survey and design development. Results The results of self diagnosis and evaluation of forward head posture showed that the order of sitting posture > smartphone > computer was related, and eye fatigue was related to the use of computer and smartphone. The influence of PPP evaluation is aesthetics, economy, intuition, usability and functionality. The results of multiple regression analysis showed that product form elements are related to (simplicity / complexity, unity and coordination), and creative design elements are related to originality (novelty) and practicability (functionality and realizability). Conclusion In recent years, people pay more and more attention to medical devices design due to concerning of health . Therefore, this study carried out the research and design of cervical protective belt for patients with forward head posture, which is a popular disease in modern society.

Investigation on flutter mechanism of long-span bridges with 2d-3DOF method

Yang, Yongxin,Ge, Yaojun,Xiang, Haifan Techno-Press 2007 Wind and Structures, An International Journal (WAS Vol.10 No.5

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

On the mechanism of vertical stabilizer plates for improving aerodynamic stability of bridges

Chen, Airong,Zhou, Zhiyong,Xiang, Haifan Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.1

Vertical stabilizer plates have been found to be an effective aerodynamic measure to improve the aerodynamic stability of bridges either with an open cross section or with a streamlined box cross section in wind tunnel testings and have been adopted in some long span bridges. By taking an open deck II-shaped section and a closed box section as examples, the mechanism of vertical stabilizer plates for improving aerodynamic stability are investigated by using numerical simulation based on Random Vortex Method. It is found that vertical stabilizer plates can increase the amplitude of the heaving motion, and decrease that of the rotational motion of the bridge decks.

Coupled buffeting response analysis of long-span bridges by the CQC approach

Ding, Quanshun,Chen, Airong,Xiang, Haifan Techno-Press 2002 Structural Engineering and Mechanics, An Int'l Jou Vol.14 No.5

Based on the modal coordinates of the structure, a finite-element and CQC (complete quadratic combination) method for analyzing the coupled buffeting response of long-span bridges is presented. The formulation of nodal equivalent aerodynamic buffeting forces is derived based on a reasonable assumption. The power spectral density and variance of nodal displacements and elemental internal forces of the bridge structure are computed using the finite-element method and the random vibration theory. The method presented is very efficient and can consider the arbitrary spectrum and spatial coherence of natural winds and the multimode and intermode effects on the buffeting responses of bridge structures. A coupled buffeting analysis of the Jiangyin Yangtse River Suspension Bridge with 1385 in main span is performed as an example. The results analyzed show that the multimode and intermode effects on the buffeting response of the bridge deck are quite remarkable.

Simulation of stationary Gaussian stochastic wind velocity field

Ding, Quanshun,Zhu, Ledong,Xiang, Haifan Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.3

An improvement to the spectral representation algorithm for the simulation of wind velocity fields on large scale structures is proposed in this paper. The method proposed by Deodatis (1996) serves as the basis of the improved algorithm. Firstly, an interpolation approximation is introduced to simplify the computation of the lower triangular matrix with the Cholesky decomposition of the cross-spectral density (CSD) matrix, since each element of the triangular matrix varies continuously with the wind spectra frequency. Fast Fourier Transform (FFT) technique is used to further enhance the efficiency of computation. Secondly, as an alternative spectral representation, the vectors of the triangular matrix in the Deodatis formula are replaced using an appropriate number of eigenvectors with the spectral decomposition of the CSD matrix. Lastly, a turbulent wind velocity field through a vertical plane on a long-span bridge (span-wise) is simulated to illustrate the proposed schemes. It is noted that the proposed schemes require less computer memory and are more efficiently simulated than that obtained using the existing traditional method. Furthermore, the reliability of the interpolation approximation in the simulation of wind velocity field is confirmed.