Experimental study on steady state heating performance of a multi-type heat pump system for finding the optimum control variable

This paper describes the steady state heating performance of a multi-type heat pump system. The operation range of such systems has extended to cover various situations, and there is a requirement for systems that provide sufficient performance in those situations. Thus, many researchers have made efforts to design a controller or develop control logic that ensures optimal operation. In a multi-type heat pump, effective control of individual indoor units is necessary for satisfying heating or cooling demands. In such systems, a successfully designed controller must consider cross-coupling effects among indoor units during alteration of control variables such as expansion valve opening and compressor speed. Thus, we investigated cross-coupling effects among indoor units under various working conditions to help determine an optimum and effective control variable. The heating performance and the relationship among the operating variables of the multi-type heat pump system with R410A indicated that the temperature of the indoor units’ secondary fluid was a suitable control variable.     

Formation of molybdenum boride cermet coating by the detonation spray process

The effects of the powder particle size and the acetylene/oxygen gas flow ratio during the detonation spray process on the amount of molybdenum phase, porosity, and hardness of the coatings using MoB powder were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), etc. The results show that the presence of metallic molybdenum in the coating results from decomposition of MoB powder during thermal spray. The compositions of the coatings are metallic Mo, MoB, and Mo₂B, which are different from the phases of the original powder. The amount of molybdenum phase increases monotonously with the oxygen/acetylene ratio, but the increasing rate for the fine powder is faster than that for the coarse powder. The porosity and hardness of the coating are related to the amount of molybdenum phase. The phase constitution of the coating is discussed.     

Information requirements analysis for holonic manufacturing systems in a virtual environment

The design and development of holonic manufacturing systems requires careful, and sometimes risky, decision making to ensure that they will successfully satisfy the demands of an ever-changing market. In this paper, the authors propose a methodology for a holonic manufacturing systems requirement analysis that is based on a virtual reality approach and aimed at assisting designers of such systems along the entire systems design and development process. Exploiting virtual reality helps the user collect valid information quickly and in a correct form by putting the user and the information support elements in direct relation with the operation of the system in a more realistic environment. A prototype software system tool is designed to realise the features outlined in each phase of the methodology. A virtual manufacturing environment for matching the physical and the information model domains is utilised to delineate the information system requirements of holonic manufacturing systems implementation. A set of rules and a knowledge base is appended to the virtual environment to remove any inconsistency that could arise between the material and the information flows during the requirement analysis.     

Performance evaluation of CBN,coated carbide,cryogenically treated uncoated/coated carbide inserts in finish-turning of hardened steel

In the present work, the performance of cubic boron nitride (CBN) inserts was compared with coated carbide and cryogenically treated coated/uncoated carbide inserts in terms of flank wear, surface roughness, white layer formation, and microhardness variation under dry cutting conditions for finish turning of hardened AISI H11 steel (48–49 HRC). The flank wear of CBN tools was observed to be lower than that of other inserts, but the accumulated machining time for all the four edges of carbide inserts were nearer to or better than the PCBN inserts. Results showed that tool life of carbide inserts decreased at higher cutting speeds. The surface roughness achieved under all cutting conditions for coated-carbide-treated/untreated inserts was comparable with that achieved with CBN inserts and was below 1.6 μm. The white layer formation and microhardness variation is less while turning with cryogenically treated carbide inserts than the CBN and untreated carbide. At low to medium cutting speed and feed, the performance of carbide inserts was comparable with CBN both in terms of tool life and surface integrity.     

Effect of leading edge boundary layer thickness on dimple flow structure and separation control

This paper concerns the effect of leading edge boundary layer thickness on dimple flow structure and separation control. A flat plate with adverse pressure gradient sufficient for separation was designed. Large eddy simulation (LES) with dynamic Smagorinsky subgrid model was validated. Dimples with R=0.378, 0.994, 1.453 (R is the ratio of leading edge boundary layer thickness to dimple depth) were investigated. The results show that the horseshoe vortex dominates the dimple flow structure. As R increases, the head of the horseshoe vortex rises further away from the wall and moves downstream. Hairpin vortices in the dimple wake are productions of the horseshoe vortex. Both the horseshoe vortex and the hairpin vortices energize the boundary layer by mixing with the free-stream fluid. As R increases, the separation control effectiveness decreases.     

Kinematics of a star-triangle planar parallel manipulator

This paper addresses kinematics of a 3 degree-of-freedom (DOF) planar parallel manipulator called Star-Triangle manipulator. The manipulator has good accuracy and a relatively large singularity-free workspace. First, position analysis of the manipulator is implemented indicating that both the inverse and forward position problems of the manipulator have only one solution. Then, velocity and singularity analyses of the manipulator are carried out and its isotropic configurations are identified using two Jacobian matrices. Based on the isotropic conditions, the workspace of manipulator is determined geometrically and it is shown that all points in the workspace are free of singularities. At last, kinematic accuracy of the manipulator is investigated on the workspace through a kinematic conditioning index (KCI).     

Investigation for dimension effect on mechanical behavior of a metallic curved micro-cantilever beam

This paper is aimed at studying the mechanical behaviors such as maximum stress, contact force, and fatigue life of a special designed metallic curved micro-cantilever beam, using analytical, numerical (FEM), and experimental methods. This micro-beam is an applicable specimen generally used in MEMS devices. The focus is at determining the dimensions which are very important in functional conditions, reliability evaluation, and durability of this specimen and at finding a guideline for optimum design. Various types of samples that have different dimensions have been simulated and some specific specimens requested to be fabricated by a manufacturing company. In our research work, the material of the specimen is assumed to be of metallic alloys, which have good mechanical and electrical properties. Also, the structure of the specimen has a special shape and includes some fingers which have effect on mechanical behavior and electrical conductivity. In experimental method, with specified boundary conditions, mechanical loading is applied to the beam by simple but accurate methods. In analytical approach, after some mathematical calculations, for a curved cantilever beam, the equations related to the mechanical behaviors are obtained. Finally, the results obtained from the foregoing methods are compared with each other and the most fundamental effective dimension parameter on mechanical behavior of this special designed metallic curved micro-cantilever beam is determined.     

The atomic age challenge to steel

Some months ago the submarine Nautilus was in dock for refueling. It had traveled 60,000 miles, but the total uranium used would make a lump smaller than a light bulb. This is only one example that the Atomic Age is here with us, now! How and where does this incredible Atomic Age challenge the first and greatest of America’s basic industries?     

Alloyed steel in the Ukraine

In the Ukraine, David Swan, as a part of the 11-man metallurgical exchange group to the USSR, recently visited a large special-steel plant and a ferro-alloy plant.     

Germanium,zinc’s important byproduct

A pioneer of germanium as well as Europe’s oldest and largest producer of zinc is Vieille-Montagne. Germanium output is centered at the zinc-lead plant of Balen, Belgium, where it is a byproduct of electrolytic zinc.