Preparation of hollow fiber membranes for gas separation

Today, immersion precipitation is the most often used process for the preparation of gas separation membranes from polymeric materials. In this process a polymer solution in the form of a thin liquid film or hollow fiber is immersed in a nonsolvent bath where the polymer precipitates and forms a membrane. \ud The immersion precipitation process can be performed by various means. The dual bath spinning process is one specific way which can be used, e.g., for the preparation of hollow fiber membranes for gas separation. In this process hollow fibers are spun by contacting the polymer solution with two properly chosen coagulents successively. The first coagulant is used to 'extract' solvent out of the polymer solution. The contact time is short in order to create a thin layer of high polymer concentration at the interface. The second coagulent is used to quickly precipitate the polymer solution to form the membrane. With this spinning process, hollow fibers with the intrinsic selectivity of the polymer material can be easily obtained without the necessity of coating.\ud This thesis is aimed on extending the knowledge on membrane formation and on further developing the dual bath spinning process for the preparation of gas separation hollow fibers with both high selectivity and high flux

A Multi-mode, Multi-class Dynamic Network Model With Queues For Advanced Transportation Information Systems

In this paper we propose a composite Variational Inequality formulation for modeling multimode, multi-class stochastic dynamic user equilibrium problem in recurrent congestion networks with queues. The modes typically refer to different vehicle types such as passenger cars, trucks, and buses sharing the same road space. Each vehicle type has its own characteristics, such as free flow speed, vehicle size. We extend single mode deterministic point model to multimode deterministic point model for modeling the asymmetric interactions among various modes. Meanwhile, each mode of travelers is classified into two classes. Class 1 is equipped travelers following stochastic dynamic user-equilibrium with less uncertainty of travel cost, class 2 is unequipped travelers following stochastic dynamic user-equilibrium with more uncertainty of travel cost. A solution algorithm based on stochastic dynamic network loading for logit-based simultaneous route and departure time choices is adopted. Finally a numerical example is presented in a simple network

Genetic algorithm for solving dynamic simultaneous route and departure time equilibrium problem

We present a genetic algorithm for solving dynamic simultaneous route and departure time equilibrium problem. Not only can a flow‐swapping process in the algorithm guarantee the flow conservation constraints between OD pair, but also accelerate the convergence velocity of the algorithm. Finally, a simulation example shows feasibility and validity of genetic algorithm. First published online: 27 Oct 201

Determination of optimal work start time

The question is: whether the system total travel cost and travel time are reduced by adjusting the work start time or not? This paper proposes the two‐level model for answering the question; the upper‐level minimizes the system travel cost and travel time by using the work start time as a decision variable, the lower‐level models the stochastic dynamic simultaneous route/departure time equilibrium problem. Finally, numerical results of a small network are provided to illustrate the behavior of the model. First Published Online: 27 Oct 201

A Hazard Analysis Based Approach to Improve the Landing Safety of a Blended-wing-body Remotely Piloted Vehicle

AbstractThe BUAA-BWB remotely piloted vehicle (RPV) designed by our research team encountered an unexpected landing safety problem in flight experiments. It has obviously affected further research project for Blended-wing-body (BWB) aircraft configuration characteristics. Searching for a safety improvement is an urgent requirement in the development work of the RPV. Combining with vehicle characteristics, a new systemic method called System-Theoretic Process Analysis (STPA) has been imported to apply on the RPV flight experiment hazard analysis. An uncontrolled system behavior “path sagging phenomenon” is identified by implementing a 3 degree of freedom simulation based on wind tunnel experiment data and establishing landing safety system dynamics archetype, then a derived safety improvement requirement emerges. To obtain higher safety design effectiveness and considering safety design precedence, a new longitudinal control surface “belly-flap” is used to eliminate hazards in landing. Finally, Flight experiments show that the hazardous factor has been correctly identified and the landing safety has been efficiently improved

Bis(2,4-dibromo-6-formyl­phenolato-κ2 O,O′)copper(II)

In the title compound, [Cu(C7H3Br2O2)2], the CuII atom, which lies on an inversion centre, is coordinated by four O atoms from two chelating bidentate 2,4-dibromo-6-formyl­phenolate ligands in a slightly distorted square-planar coordination geometry. In the crystal structure, short inter­molecular Br⋯Br [3.516 (4) and 3.653 (4) Å] and Cu⋯Br [3.255 (1) Å] contacts together with C—H⋯O hydrogen bonds generate a three-dimensional network