The paper studies the relation between topology optimization and size optimization of truss structures. The goal of the optimization is to minimize the structural weight under stress constraints and side constraints on member cross sectional areas. The limiting stress concept is defined and the computational formula of limiting stress for truss structures calculated by a finite element method is given. Based on the limiting stress concept the continuity of the stress function at zero cross sectional area is carefully examined which enables us to understand the dilemma of defining the stress function in the closed interval up to zero cross sectional area. By considering the relation between the limiting stress and allowable stress the feasibility of stress constraints is discussed and the difficulty of adding a new bar to the truss or deleting an existing one is better understood. We have also shown that for topology optimization of truss structures the feasible design domain in the design space is a connected domain with possible degenerate subregions as long as upper bounds on cross sectional areas are large enough. To overcome this difficulty we introduce a quality function and replace the stress constraint by a new constraint which has the same feasibility and is continuous in the closed interval up to zero cross sectional area. In this way the formulations of structural topology optimization and size optimization are unified and an optimization algorithm which works only for problems with continuous constraint functions can be applied to optimize the topology of the truss structures. Simple examples are presented to show the possibility of automatically and rationally removing or adding b a n and hence treating topological optimization in the same way as sizing optimization. Finally, further possible research on these topics is addressed.

Low-temperature industrial waste heat is an important heat source for industrial processes and utility services to reduce the consumption of fossil energy as well as lower the risk of global warming. In this article, a review of waste heat recovery e a critical solution of waste energy disposal is made in order to show the current status of heat recovery potentials and the possible technologies used industries. The concept of industrial waste heat is defined, potential sources of waste heat from industries are identified and conclusions are drawn. Then, the technologies available for waste heat recovery are illustrated in terms of heat pumps, heat exchangers, heat pipes, boilers, refrigeration cycles, power cycles and heat storage according to the transfer mode of waste heat within the recovery process. The waste heat opportunities both in developed and developing countries are discussed in order to determine the possible benefits of heat recovery as well as to make a general survey of the development of heat recovery technologies globally. Research of typical applications of industrial waste heat recovery in Asian countries and especially in China is overviewed to show the performance of this engineering in practice.

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Future human missions to Mars are expected to emphasize scientific exploration. While recent Mars rover missions have addressed a wide range of science objectives, human extravehicular activities (EVAs), including the Apollo missions, have had limited experience with science operations. Current EVAs are carefully choreographed and guided continuously from Earth with negligible delay in communications between crew and flight controllers. Future crews on Mars will be expected to achieve their science objectives while operating and coordinating with a science team back on Earth under communication latency and bandwidth restrictions. The BASALT (Biologic Analog Science Associated with Lava Terrains) research program conducted Mars analog science on Earth to understand the concept of operations and capabilities needed to support these new kinds of EVAs. A suite of software tools (Minerva) was used for planning and executing all BASALT EVAs, supporting text communication across communication latency, and managing the collection of operational and scientific EVA data. This paper describes the support capabilities provided by Minerva to cope with various geospatial and temporal constraints to support the planning and execution phases of the EVAs performed during the BASALT research program. The results of this work provide insights on software needs for future science-driven planetary EVAs.