vector-controlled PWM current-source-inverter-fed induction motor drive with a new stator current control method

In this paper, the control of the pulsewidth-modulated current-source-inverter-fed induction motor drive is discussed. The vector control system of the induction motor is realized in a rotor-flux-oriented reference frame, where only the measured angular rotor speed and the dc-link current are needed for motor control. A new damping method for stator current oscillations is introduced. The method operates in an open-loop manner and is very suitable for microcontroller implementation, since the calculation power demand is low. Also, the stator current phase error caused by the load filter is compensated without measurement of any electrical variable. With the proposed control methods the motor current sensors can be totally eliminated since the stator current measurements are not needed either for protection in the current-source-inverter-fed drives. The proposed control methods are realized using a single-chip Motorola MC68HC916Y1 microcontroller. The experimental tests show excellent performance in both steady-state and transient conditions.     

Characterization of Listeria monocytogenes isolates from the meat, poultry and seafood industries by automated ribotyping

A total of 564 Listeria monocytogenes isolates were characterized by automated ribotyping. The samples were taken from equipment, personnel and the environment after cleaning procedures and during food processing, as well as from raw materials and products from six meat, two poultry and five seafood processing plants located in the Faroe Islands, Finland, Iceland, Norway and Sweden. Altogether, 25 different ribotypes (RTs) were generated. Two RTs occurred in the samples from all three food sectors--meat, poultry and seafood. Four RTs occurred in meat and poultry plant samples and other four RTs occurred in meat and seafood plant samples. Five RTs occurred only in meat plant samples, five only in poultry plant samples and five only in seafood plant samples. Eight of the thirteen plants had their own in-house L. monocytogenes ribotype. There was geographical differences between the RTs, but no correlation between RTs and food sectors was detected. The discrimination power of automated ribotyping was satisfactory to trace the contamination sources in the food processing plants clearly indicating the sites at which improved cleaning procedures were necessary. In addition, it was possible to screen a large number of isolates with two instruments located at different institutes and to make a reliable combination of the results.     

A Study of Bistable Laminates of Generic Lay‐Up for Adaptive Structures

Abstract: Asymmetric laminates are known to exhibit two stable cylindrical states and one unstable saddle state. Such bistability has attracted attention in aerospace applications because of the potential low energy requirement to achieve a large deflection or change in shape. This paper presents experimental observations of a generic asymmetric [?30/60] laminate with and without piezoelectric actuation and compares against both energy‐based analytical and finite element (FE) models. It is observed that the analytical model offers a qualitative understanding of bistable behaviour, degree of curvature and overall shape but is unable to model the distinctive curvature changes near the boundaries which can be captured by the FE model. The investigation also presents the use of piezoelectric actuation to achieve snap‐through in both analytical and FE models, which is compared and validated with experimental characterisation.     

Removal of iron-containing impurities using the magnetic separation method

The methods of removal of iron-containing impurities from raw material are considered. In order to increase the efficiency of iron removal, dry refining of the raw material with self-cleaning roller-type separators with a magnetic system consisting of Nd - Fe - B permanent magnets is proposed. The installation of such separators will make it possible to remove from 50 to 90% of the iron-containing impurities present in the material. Translated from Steklo i Keramika, No. 1, pp. 28 – 29, January, 1999.     

Interpreting Stroop interference: An analysis of differences between task versions.

The present study investigated methodological differences between the clinical version of the Stroop Color and Word Test and the computerized single-trial version. Three experiments show that different presentations of the Stroop task can produce different levels of interference. The 1st experiment examined the effect of blocking; the 2nd experiment examined different control conditions. Greater interference in the blocked clinical version appears to result from lower response times (RTs) in the neutral condition, not from greater RTs in the incongruent condition. Experiment 3 examined the impact of shifting attention across locations while responding to Stroop stimuli. The present set of findings sheds light on the inconsistency in the clinical literature and demonstrates that the method and selection of neutral stimuli (that provide the baseline by which interference is measured) are critical because they clearly can change performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bioleaching of acid‐consuming low‐grade nickel ore with elemental sulfur addition and subsequent acid generation

The bioleaching of a nickel concentrate and an acid‐consuming nickel ore was studied using a co‐culture of Acidithiobacillus ferrooxidans and A. thiooxidans, as well as a thermophilic enrichment culture, VS2. The VS2 was dominated by a Sulfolobus species related to Sulfolobus metallicus. Nickel concentrate was readily solubilized with A. ferrooxidans and the VS2, resulting in nickel yields of 56% and 100%, respectively. Low‐grade nickel ore required 350 g H₂SO₄ kg^?1 ore for maintaining the pH of the leaching solution below 3. To overcome the high acid demand, biological elemental sulfur oxidation was combined with the ore leaching. Leaching of a 2% (wt/vol) nickel ore with a co‐culture of A. thiooxidans and A. ferrooxidans resulted in nickel yield of up to 86% with acid supplementation of 290 g H₂SO₄ kg^?1 ore. When coupled with biological sulfur oxidation, an 86% nickel recovery was achieved with 0.5% (wt/vol) ore concentration without further sulfuric acid addition. The VS2 oxidized sulfur at a rate of 0.063 g L^?1 d^?1 and the simultaneous nickel ore leaching resulted in 100% nickel yield. In summary, the potential of using elemental sulfur addition and subsequent biological acid generation to maintain the low pH during bioleaching of an acid‐consuming nickel ore was demonstrated. Copyright © 2005 Society of Chemical Industry     

Problems and pitfalls in evaluating studies for pacing in heart failure

The objectives of this study were to investigate clinical and patho-histological characteristics of childhood hepatoblastoma on their value as prognostic factors, and to evaluate the predictive impact of different staging systems for liver tumors on 72 patients treated in the German Pediatric Liver-Tumor Study HB89. Statistical analysis was performed by comparing patients' disease-free survival with characteristics and stages. Multivariate analysis was done by the Cox proportional-hazards model, the recursive partitioning and amalgamation model (RECPAM) and the model of clustering by response (CBR). The following characteristics were significantly related with prognosis: tumor involvement of one vs. both liver lobes, multifocal disseminated vs. unifocal growth pattern in the liver, distant metastases, vascular invasion, fetal vs. embryonal differentiation, and serum alpha-fetoprotein; patients with values of < or = 100 ng/ml or > or = 1,000,000 ng/ml had a worse outcome than those with 100 to 1,000,000 ng/ml. Multivariate analysis with the 3 models revealed that tumor-growth pattern, serum alpha-fetoprotein and, in the Cox and CBR models, vascular invasion also are independent prognostic factors, permitting the allocation of hepatoblastoma patients to 1 of 2 prognostic groups for differential therapy. Post-surgical staging and the conventional TNM system for liver carcinoma had a high predictive value, in contrast to a TNM system proposed by the UICC for testing on childhood liver tumors. We therefore propose that the TNM system for liver carcinoma be applied for comparison of treatment results in hepatoblastoma.     

Deuterium Plasma Focus as a Tool for Testing Materials of Plasma Facing Walls in Thermonuclear Fusion Reactors

This paper presents the first verification of the fast ion beam (FIB) and fast plasma stream (FPS) properties computed using the Lee code. Recent estimates of FIB and FPS properties in PF-400J from interferometric images are compared to our computed results. Reasonable agreement is found in the comparison of several quantities. Our computed power flow density (energy flux) and integral damage factor are 2.45 × 10¹² Wm^?2 (2 times of experimental value) and 1.78 × 10⁸ Wm^?2 s^0.5 (~almost the same as experimental value) respectively, for target placed at 1.5 cm from the anode top of PF-400J. This verification gives us confidence to proceed to systematic numerical calculations on the PF-400J and similar small plasma focus devices (PF50, NX2, NX3, FMPF-3, INTI PF) to obtain FIB properties (ion beam energy, ion beam flux, ion beam fluence, beam ion number, ion beam current, power flow density, and damage factor). These results confirm that the plasma focus, including small ones, could be useful to study the effects of cumulative pulses on target materials being considered for plasma facing walls in future tokamak or laser-implosion fusion reactors.     

Prospective evaluation of a cluster program for Finnish forestry and forest industries

In this paper, we report a prospective evaluation process for a major research program for the Finnish forestry and forest industries. To a significant extent, this process was based on fifteen participatory workshops where tools of operational research — most notably multi‐criteria methods embedded in a group support system — were deployed to help representatives from industry, the research community, and public administration in the assessment of socio‐economic impacts and the identification of further research topics. Drawing upon this case study, we also analyze the preconditions, advantages, and limitations of similar kinds of participatory processes in the implementation of formative and summative evaluations.