Current decomposition in asymmetrical, unbalanced three-phasesystems under nonsinusoidal conditions

The most attractive theories found in the literature for the representation of the electrical systems under nonsinusoidal conditions can be divided to a great extent into those operating in the time domain and those operating in the frequency domain. When three-phase systems are concerned, the time-domain approach is mainly due to Akagi and Nabae under the name of “instantaneous power theory” or “p-q theory” and is based on the Park transformation. The frequency-domain approach is mainly due to Czarnecki. At a first reading, these two theories seem to be quite different. This paper shows how the application of some interesting properties of the Park transformation leads to a unified approach to the harmonic and sequence components and hence allows derivation of the frequency-domain current decomposition proposed by Czarnecki in a more straightforward way. Moreover, an extension of this decomposition to the case of asymmetrical supply voltages is considered     

The thermoelastic behaviour of semicrystalline and of glassy poly(ether-ether-ketone)

A thermoelastic evaluation, based on simultaneous measurements of the mechanical work and of the concomitant heat of deformation by a stretching micro calorimeter, was performed on semicrystalline and glassy PEEK. The objective of this study was to utilize the sensitive technique to detect differences that would account for observed effects of micro structure on mechanical performance. A clear difference was detected beyond a 0.6% strain, where the behaviour of glassy PEEK began to exhibit inelastic features such as yielding and plastic deformation. This difference between the glassy and the semicrystalline polymers was considered the reason for the superior mechanical fatigue and fracture properties produced by the latter micro structure.     

Post-deposition treatment effects on hydroxyapatite vacuum plasma spray coatings

The purpose of this work is to evaluate the effects of post-deposition heat treatments on high and low crystallinity hydroxyapatite coatings on Ti6Al4V alloy. HA layers were produced by the vacuum plasma spray (VPS) technique, and the desired degrees of crystallinity were obtained by changing the deposition parameters. An analysis of the mechanical properties of the coatings and their adhesion to the substrate has been done by shear strength test. X-ray diffraction analysis was used to detect the structure and the chemical components in which HA dissociates during the deposition process and heat treatments. The data obtained indicates that heat treatments can increase the crystallinity of HA, but they also introduce a mechanical degradation of the coatings. After heat treatments, it was also observed that a large amount of tetracalcium phosphate was formed.     

Perspective channel-type reactor with enhanced safety

Following the search for new design solutions to develop within the framework of channel trends the reactor with enhanced safety the Research and Development Institute of Power Engineering has developed the design of the multiloop boiling water reactor (MKER). The MKER enhanced safety is attained when involving the inherent safety features, passive safety systems as well as the accident consequences confinement devices. The design realizes several advantages which are typical of the channel-type reactors, namely: the design desintegration simplifying the manufacture, control, equipment delivery and decreasing, versus the pressure vessel reactors, the accident effect if it proceeds in an explosive manner; small operating reactivity margin and fuel burnup increased due to continuous refuelling; fuel cycle flexibility allowing comparatively easily to adopt the reactor to the conjuncture of the country fuel balance; multiloop circuit of the main coolant which reduces the degree and effect of the accidents connected with the equipment and pipings rupture; monitoring of the channels and fuel assemblies leak-tightness.     

Crack growth measurements on components under cyclic loading: comparison of different methods

The cyclic crack growth behaviour was measured by means of d.c. potential drop, a.c. potential drop, ultrasonic and crack-opening displacement (COD) methods. The methods were applied to component tests on straight pipes with an outer diameter of approximately 800 mm and a wall thickness of approximately 50 mm. The pipes were subjected to constant internal pressure (about 15 MPa) and either an alternating (or pulsating) or a quasi-static bending moment using d.c. potential drop, a.c. potential drop, ultrasonic and flaw-opening (COD) methods. The efficiency of the particular methods has been proved by comparison with fractographical analysis of the fracture surfaces.     

The adhesive joint fracture due to crack propagation affected by heat and active agent concentration

The problem of fracture of the adhesive joint between two elastic bodies, due to crack propagation along the joint, acted upon by heat and active agent flux through the crack surfaces is considered. Temperature and concentration of the agent inside the crack are assumed to be constant, which implies comparatively low flux conductivity of adjacent materials. The effect of an additional flux resistance concentrated at the crack surfaces is considered. This resistance is due to the adhesive layer remnants, and causes the temperature and concentration in materials at the crack edge to be dependent on the crack speed. The effect of the applied loads on deforming the materials is supposed to be sufficiently large to neglect influence of temperature and concentration on deformations. The reverse influence, as well as cross-influence of heat and concentration transfer on each other, are also neglected. The only mechanical role played by temperature and concentration of the agent under such circumstances is their influence on fracture of the adhesive joint.     

EFFECT OF THE RATIO Th/U ON TL DATING ACCURACY

ＥＦＦＥＣＴＯＦＴＨＥＲＡＴＩＯＴｈ／ＵＯＮＴＬＤＡＴＩＮＧＡＣＣＵＲＡＣＹ￥Ｐ．Ｌ．Ｌｅｕｎｇ（梁宝鎏）；ＭｉｃｈａｅｌＪ．Ｓｔｏｋｅｓ（ＤｅｐａｒｔｍｅｎｔｏｆＰｈｙｓｉｃｓａｎｄＭａｔｅｒｉａｌｓＳｃｉｅｎｃｅ，ＣｉｔｙＰｏｌｙｔｅｃｈｎｉｃｏ...     

Simultaneous solution of emission transfer and thermal conductivityequations in the problems of atmosphere and subsurface radiothermometry

Expressions are derived that relate the half-space temperature profile and the heat flux with the brightness temperature evolution. Remote sensing methods are proposed to measure the temperature and heat flux in the atmosphere and subsoil layer by radiometric measurements