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Chu, X.Z.,Cheng, Z.P.,Xiang, X.X.,Xu, J.M.,Zhao, Y.J.,Zhang, W.G.,Lv, J.S.,Zhou, Y.P.,Zhou, L.,Moon, D.K.,Lee, C.H. Pergamon Press ; Elsevier Science Ltd 2014 International journal of hydrogen energy Vol.39 No.9
The separation of a hydrogen isotope mixture on porous materials was studied using equilibrium and breakthrough experiments. The adsorption equilibria of H<SUB>2</SUB> and D<SUB>2</SUB> on SBA-15 with mesopores and molecular sieves 5A, Y, and 10X with micropores were measured at 77 K using the volumetric method. The breakthrough experiments of a H<SUB>2</SUB> and D<SUB>2</SUB> mixture in each adsorbent bed were carried out at various conditions of flow rate and pressure. The equilibrium ratio of D<SUB>2</SUB> to H<SUB>2</SUB> on mesoporous molecular sieves was larger than the ratio on microporous molecular sieves (SBA-15 > 10X > Y > 5A), but the difference among the adsorbents decreased with increases in pressure. On the other hand, the order of breakthrough separation factor showed the opposite result (SBA-15 < 10X < Y < 5A). The breakthrough separation factors for zeolite 10X was approximately equal to the equilibrium ratio of D<SUB>2</SUB> to H<SUB>2</SUB> at the corresponding partial pressures, whereas zeolites 5A and Y showed higher breakthrough separation factors than their equilibrium ratios. In SBA-15, the separation factors from breakthrough results were even smaller than the corresponding equilibrium ratio. In the microporous adsorbent with a limited pore size (zeolite 5A in the study), the diffusion mechanism contributed to the separation of hydrogen isotope gases as one of key factors.
Sterian, Corneliu Eugen D.,Wang, Cheng-Xiang,Johnsen, Ragnar,Patzold, Matthias The Korea Institute of Information and Commucation 2004 Journal of communications and networks Vol.6 No.3
We demonstrate rotationally invariant space-time (ST) trellis codes with a 4-D rectangular signal constellation for data transmission over fading channels using two transmit antennas. The rotational invariance is a good property to have that may alleviate the task of the carrier phase tracking circuit in the receiver. The transmitted data stream is segmented into eight bit blocks and quadrature amplitude modulated using a 256 point 4-D signal constellation whose 2-D constituent constellation is a 16 point square constellation doubly partitioned. The 4-D signal constellation is simply the Cartesian product of the 2-D signal constellation with it-self and has 32 subsets. The partition is performed on one side into four subsets A, B, C, and D with increased minimum-squared Euclidian distance, and on the other side into four rings, where each ring includes four points of equal energy. We propose both linear and nonlinear ST trellis codes and perform simulations using an appropriate multiple-input multiple-output (MIMO) channel model. The 4-D ST codes constructed here demonstrate about the same frame error rate (FER) performance as their 2-D counterparts, having however the added value of rotational invariance.
Measurement of aerodynamic coefficients of tower components of Tsing Ma Bridge under yaw winds
Zhu, L.D.,Xu, Y.L.,Zhang, F.,Xiang, H.F. Techno-Press 2003 Wind and Structures, An International Journal (WAS Vol.6 No.1
Tsing Ma Bridge in Hong Kong is the longest suspension bridge in the world carrying both highway and railway. It has two H-shape concrete towers, each of which is composed of two reinforced concrete legs and four deep transverse prestressed concrete beams. A series of wind tunnel tests have been performed to measure the aerodynamic coefficients of the tower legs and transverse beams in various arrangements. A 1:100 scaled 3D rigid model of the full bridge tower assembled from various tower components has been constructed for different test cases. The aerodynamic coefficients of the lower and upper segments of the windward and leeward tower legs and those of the transverse beams at different levels, with and without the dummy bridge deck model, were measured as a function of yaw wind angle. The effects of wind interference among the tower components and the influence of the bridge deck on the tower aerodynamic coefficients were also investigated. The results achieved can be used as the pertinent data for the comparison of the computed and field-measured fully coupled buffeting responses of the entire bridge under yaw winds.
Xiang Zhou,Zhong You,James Byrne, M.D. 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.1
Cerebral aneurysm is common lesion among adult population. Current methods for treating the disease have several limitations. Inspired by fern leaves, we have developed a new stent, called leaf stent, which can provide a tailored coverage at the neck of an aneurysm and thus prevent the blood from entering the aneurysm. It alone can be used to treat the cerebral aneurysm and therefore overcomes problems existing in current treating methods. The paper focuses on the numerical simulation of the leaf stents. The mechanical behaviour of the stent in various designs has been investigated using the finite element method. It has been found that certain designs provide adequate radial force and have excellent longitudinal flexibility. The performance of certain leaf stents is comparable and even superior to those of the commercially available cerebral stents such as the Neuroform stent and the Enterprise stent, commonly used for stent assisted coiling, while at the same time, providing sufficient coverage to isolate the aneurysm without using coils.
박재훈,D. Xiang,고인수,J. H. Hong,황정연,S. H. Kim,박성주,X. J. Wang,Y. J. Park,Y. W. Parc 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I
A Brookhaven National Laboratory (BNL) GUN-IV type photocathode rf gun has been fabricated to use in femto-second electron diffraction (FED), the femto-second far infra-red radiation (fs-FIR) facility, and the X-ray free electron laser (X-FEL) at the Pohang Accelerator Laboratory (PAL). The gun consists of a 1.6-cell cavity with a copper cathode, a solenoid magnet, beam diagnostic component and auxiliary systems. The dimensions of the cavity that provided the desired resonant frequency were determined by using the SUPERFISH code. The change in the resonant frequency due to the laser port and the wave-guide port on the cavity wall was estimated with Slater's perturbation theorem. The size of the ports was finalized by using a series of cutting and measuring processes. A method to measure the resonant frequency of the cavity during the operation was developed. Finally, the microwave and the basic beam parameters were measured carefully to confirm the successful fabrication of the photocathode RF gun system.
Fei-Xiang, F.,Lee, K.Y.,Li, Y.D. Pergamon Press ; Elsevier Science Ltd 2011 Engineering fracture mechanics Vol.78 No.9
The present work investigates the problem of multiple cracks on the arc-shaped interface of a semi-cylindrical magneto-electro-elastic layer bonded onto an orthotropic substrate. Continuously distributed dislocation is used to simulate the anti-plane interfacial cracks. The problem is formulated as a Cauchy singular integral equation by integrating the Green's function of an interfacial point dislocation. Both the theoretical derivation and numerical computation are verified in special cases. The effects of the interface end, crack space, layer thickness, stiffness ratio and material orthotropy are surveyed, among which the fracture behavior of the interface end deserves special attention in design.
Zhou, Xiang,You, Zhong,Byrne, James M.D. Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.1
Cerebral aneurysm is common lesion among adult population. Current methods for treating the disease have several limitations. Inspired by fern leaves, we have developed a new stent, called leaf stent, which can provide a tailored coverage at the neck of an aneurysm and thus prevent the blood from entering the aneurysm. It alone can be used to treat the cerebral aneurysm and therefore overcomes problems existing in current treating methods. The paper focuses on the numerical simulation of the leaf stents. The mechanical behaviour of the stent in various designs has been investigated using the finite element method. It has been found that certain designs provide adequate radial force and have excellent longitudinal flexibility. The performance of certain leaf stents is comparable and even superior to those of the commercially available cerebral stents such as the Neuroform stent and the Enterprise stent, commonly used for stent assisted coiling, while at the same time, providing sufficient coverage to isolate the aneurysm without using coils.