Puolustuskykyinen valtio vai Ruotsin hälytyskello? : Suomen sotilasstrateginen asema kylmän sodan alkuvuosien asiantuntija-arvioissa

The doctoral thesis deals with Finnish and foreign expert s analyses of Finland s military strategic position and defence capability, dating back to the early years of the Cold War. Finland s military high command prepared assessments of the country s strategic position and of the capability of the Defence Forces as grounds for defence planning. Since Finland was located on the Cold War dividing line, the foreign powers were also monitoring the development of Finland s situation. The research carried out had access to the armed forces internal assessments, as well as to analyses prepared by the military intelligence services of Sweden, Britain and the United States. One of the working hypotheses was that after the WWII the ability military leadership to estimate the security political needs of the country and the organisation of its defence was severely weakened so that the dangers of the international development were not perceived and the gradual erosion of defence capability was partly unnoticed. This hypothesis proved to be wrong. Even if the Finnish military intelligence was much weaker than during the war, it was able to provide the military leadership with information of the international military development for the most part. The military leadership was also fully aware of the weakening of the defence capability of the country. They faced the difficult task of making the country s political leadership, i.e. President Paasikivi and the government, also understand the gravity of the situation. Only in the last years of his term in office Paasikivi started to believe the warnings of the military. According to another hypothesis, outside observers considered the Finnish armed forces to primarily act as reinforcements for the Soviet Red Army, and they believed that, in the event of a full-scale war, the Finns would not have been able or even willing to resist a Soviet invasion of Sweden and Norway through Finland. The study confirmed that this was approximately the view the Swedes, the British and the Americans had of the Finnish forces. Western and Swedish intelligence assessments did not show confidence in Finland s defence ability and the country was regarded almost as a Soviet satellite. Finland s strategic position was, however, considered slightly different from that of the Soviet-occupied Eastern European countries. Finland had been forced to become part of the Soviet sphere of interest and security system and this was sealed by the Finno-Soviet Treaty of Friendship, Cooperation, and Mutual Assistance in 1948. Finland had little importance to the military interests of the Western powers. In Sweden s defence planning, however, Finland played a significant role as an alarm bell of a possible Soviet surprise attack, as well as defensive frontline and buffer zone.

OP-Pohjola-ryhmän sidosryhmät : laadullinen tutkimus sidosryhmävalinnasta ja siihen vaikuttavista tekijöistä.

Tutkimus on kvalitatiivinen tapaustutkimus. Tutkimuksen tarkoitus on selvittää mitkä ovat OP -Pohjola-ryhmän tärkeimmät sidosryhmät, millä perusteella sidosryhmät erottuvat muista organisaation ympäristössä toimivista tahoista, sekä millaisten ominaisuuksien perusteella sidosryhmien tärkeyttä arvioidaan OPPohjola- ryhmän näkökulmasta. Sidosryhmät ovat yrityksen ympäristössä toimivia ryhmiä tai tahoja, joiden asema sidosryhmänä perustuu yleensä niiden kykyyn vaikuttaa yrityksen menestykseen (esimerkiksi asiakkaat) tai oikeutettuun asemaan yrityksessä (esimerkiksi omistajat ja henkilökunta). Viimeaikaisissa sidosryhmiin keskittyvässä tutkimuksessa on tunnustettu sidosryhmien merkitys yritysten menestymisen kannalta. Toisaalta kaikkien sidosryhmien huomioimiseen perustuvalla liikkeenjohtamisella on myös eettisiä perusteita. Yleistyneen käsityksen mukaan yrityksellä on vastuuta myös muita tahoja, kuin omistajiaan kohtaan. Sidosryhmien laaja-alainen huomiointi on siis osa vastuullista liiketoimintaa ja sitä kautta yritysten yhteiskuntavastuun lähtökohta. Sidosryhmiä on pyritty määrittelemään lukuisilla eri tavoilla eri tutkijoiden toimesta. Erilaiset määritelmät ovat hämärtäneet sidosryhmän käsitettä jopa niin, että käytännössä kaikki yrityksen ympäristössä toimivat tahot voidaan nähdä yrityksen sidosryhmiksi. Yrityksen on kuitenkin hyödyllistä tunnistaa sen tärkeimmät sidosryhmät, jotta se voi toteuttaa suunnitelmallista sidosryhmäpolitiikka näihin tahoihin päin. Tämä tutkimus pyrkii luomaan yleiskuvan siitä, mitkä ovat OP-Pohjola-ryhmälle sen keskeiset sidosryhmät ja miksi. Tutkimus perustuu OP-Pohjola-ryhmässä työskentelevien henkilöiden teemahaastatteluihin. Haastattelumateriaalia on analysoitu käyttäen apuna sisällönanalyysiä ja sisällön erittelyä. Tutkimuksen teoreettisena viitekehyksenä toimii Mitchellin, Anglen ja Woodin ns. sidosryhmien identifikaation malli, jonka mukaan sidosryhmän tärkeys yrityksen näkökulmasta perustuu siihen, onko sidosryhmällä valtaa, legitiimi asema tai kiireellisiä vaateita suhteessa yritykseen. Sidosryhmien identifikaation mallin mukainen analyysi osoitti, että OP-Pohjola- ryhmän tärkeimmät sidosryhmät ovat asiakkaat sekä lainsäätäjät ja viranomaiset. Muita OP-Pohjola- ryhmän sidosryhmiä ovat omistajat, hallinto, media, henkilökunta, kansalaisjärjestöt ja palkansaajajärjestöt. Sidosryhmän tärkeyteen OP-Pohjola- ryhmän näkökulmasta näytti vaikuttavan eniten sidosryhmän kyky vaikuttaa organisaation menestykseen. Tämä kyky saattoi perustua joko välilliseen tai välittömään valtaa tai esimerkiksi asiantuntemukseen finanssialasta. Se, kuinka ”äänekäs” sidosryhmä on, ei yksistään vaikuta sidosryhmän tärkeyteen yrityksen näkökulmasta. Tutkimuksessa käytettiin lähteinä enimmäkseen 2000- luvulla tehtyjä sidosryhmätutkimuksia sekä teoreettista kirjallisuutta sidosryhmiin ja yritysten vastuullisuuteen liittyen.

Tyttöjen kesken : Monikulttuurisuus ja sukupuolten tasa-arvo nuorisotyössä.

Among Girls Youth Work, Multiculturalism and Gender Equality Finland s increasingly multicultural society concerns younger generations in a very particular manner. Starting already in pre-school kindergartens, children from different cultural backgrounds share their everyday existence. The focus of this study is Finland s increasingly multicultural society that has challenged youth work professionals in particular and made them rethink questions related to content, basic values and goals of youth work. These reconsiderations include the following essential questions: which of these pedagogic principles are defined as Finnish, and under what kinds of circumstances would the youth workers be ready to negotiate about them. These questions, which are related to multiculturalism, are then linked to the girls position, status and gender equality. The research examines how gender equality is articulated in relation to multiculturalism and vice versa, in what contexts youth work-related questions are negoatiated in, and how these negotiations then relate to gender issues. The present study combines theoretical concepts and debates from both post-colonial and youth research, and has benefited greatly from previous research which has examined the everyday lives of young people with multicultural backgrounds and conceptualised the different meanings of age, ethnicity, culture and gender. Neither multiculturalism nor gender equality is, however, taken as a given concept in this study; rather the research focuses on how youth workers understand and define these concepts and how they are used. The emphasis has been on monitoring the varying consequences of different understandings and definitions in terms of everyday work and practices. The goal of this study has been to find typical ways of conceptualising multiculturalism, gender equality and the role of girls in the context of youth work. The focus of the research is not just the youth workers different views but also the notions of the girls themselves. These are then further analysed by examining the ways the girls negotiate their agency. Examples of how the girls agency is defined and the different forms of agency that are offered to the girls within the context of leisure time activities and youth work have been sought. The kind of agency the girls then assume is also examined. The data in this research is comprised of interviews with young people with multicultural backgrounds (n=39), youth workers (n=42) and of ethnographic fieldwork (2003 2005). The fieldwork concentrated on following different types of youth work activities that were targeted at girls with migrant backgrounds. These were organized both by selected municipalities and NGOs. The research shows that various questions related to multicultural issues have enhanced the visibility of gender equality in the field of youth work. The identification of gender-based inequality is especially closely linked to the position of girls from migrant backgrounds. These girls are a source of particular worry and the aim of the many activity groups for migrant girls is to educate them so that they can become equal Finnish citizens . The youth work itself is seen as gender-neutral and equality based. Equality in this context is defined as a purely quantitative concept, and the solution to any possible inequalities is thus the exact same treatment for everyone . The girls themselves seem mainly confused by the role that is offered to them. They would need a voice and the possibility to have an impact on the planning of youth work activities. They want to have their views heard. The role of the victim assigned to them is very confining and makes it difficult to act. At the same time the research shows how gender-sensitive youth work is seen to mean youth work with girls. Gender-sensitive work with boys is not really done or is done very little, even if many of the interviewees are of the opinion that the true materialization of gender equality would require boys to be taken into account too. The principle of gender equality should be shared by the entire youth work profession. Keywords Youth work, equality, multiculturalism, gender sensitivity, agency, girls, young people, sexuality

Dry sliding wear behavior of Al2O3 fiber reinforced aluminum composites

Dry sliding wear behavior of die-cast ADC12 aluminum alloy composites reinforced with short alumina fibers were investigated by using a pin-on-disk wear tester. The Al2O3 fibers were 4 mu m in diameter and were present in volume fractions (T-f)ranging from 0.03 to 0.26, The length of the fiber varied from 40 to 200 mu m. Disks of aluminum-alumina composites were rubbed against a pin of nitrided stainless steel SUS440B with a load of 10 N at a sliding velocity of 0.1 m/s. The unreinforced ADC 12 aluminum alloy and their composites containing low volume fractions of alumina (V-f approximate to 0.05) showed a sliding-distance-dependent transition from severe to mild wear. However, composites containing high volume fractions of alumina ( V-f > 0.05) exhibited only mild wear for all sliding distances. The duration of occurrence of the severe wear regime and the wear rate both decrease with increasing volume fraction. In MMCs the wear rate in the mild wear regime decreases with increase in volume fraction: reaching a minimum value at V-f = 0.09 Beyond V-f = 0.09 the wear rate increasesmarginally. On the other hand, the wear rate of the counterface (steel pin) was found to increase moderately with increase in V-f. From the analysis of wear data and detailed examination of (a) worn surfaces, (b) their cross-sections and (c) wear debris, two modes of wear mechanisms have been identified to be operative, in these materials and these are: (i) adhesive wear in the case of unreinforced matrix material and in MMCs with low Vf and (ii) abrasive wear in the case of MMCs with high V-f. (C) 2000 Elsevier Science Ltd. All rights reserved.

Effect of densification and TiB2 reinforcement on the wear of molybdenum disilicide

Wear tests were done in a pin-on-disc machine by sliding MoSi2 pins against hard-steel discs in a normal load range of 5-140 N and a speed of 0.5 m/s under nominally dry conditions in the ambient. The specific wear rate of the pin undergoes two transitions: severe to mild at low load and mild to severe at high load. The mild-wear domain is distinguished by the formation of a protective mechanically mixed layer of steel and its oxides, transferred from the counterface in particulate form. Increasing the hardness by densification and TiB2 reinforcement lowers the specific wear rate and expands the mild-wear load domain. However, even when the volume wear rate is normalised with respect to the real contact area (load/hardness) the non-dimensional wear factor is still seen to decrease with densification and reinforcement. This indicates that fracture toughness may also play an important role in determining the wear-resistance of these materials. The surface coverage on the pin by the mechanically mixed layer increases with densification and reinforcement.

A Simple Five-Level Inverter Topology for Induction Motor Drive Using Conventional Two-Level Inverters and Flying Capacitor Technique

This paper proposes a new five-level inverter topology for open-end winding induction motor (IM) drive. The popular existing circuit configurations for five-level inverter include the NPC inverter and flying capacitor topologies. Compared to the NPC inverter, the proposed topology eliminates eighteen clamping diodes having different voltage ratings in the present circuit. Moreover it requires only one capacitor bank per phase, whereas flying capacitor schemes for five level topologies require six capacitor banks per phase. The proposed topology is realized by feeding the phase winding of an open-end induction motor with two-level inverters in series with flying capacitors. The flying capacitor voltages are balanced using the switching state redundancy for full modulation range. The proposed inverter scheme is capable of producing two-level to five-level pulse width modulated voltage across the phase winding depending on the modulation range. Additionally, in case of any switch failure in the flying capacitor connection, the proposed inverter topology can be operated as a three-level inverter for full modulation range. The proposed scheme is experimentally verified on a four pole, 5hp induction motor drive.

Experimental estimation of friction force in lubricated cutting of steel

Friction force generated in lubricated cutting of steel is experimentally estimated by recording the tangential force experienced by the spherical face of a pin rubbing against a freshly cut surface. The pin and the cutting tool are both submerged in the lubricant and the pin is situated on the cut-track to record the force. The recording shows an instantaneous achievement of a peak in the force curve followed by a decline in time to a steady state value. The peak and not the steady state friction was found to be sensitive to the structure of the hydrocarbon and addition of additive to the oil. The configuration was designed and tested to demonstrate the influence of a reaction film which develops during cutting, on cutting tool friction. Given the strong correlation between the peak friction and the existence of a tribofilm in the cutting zone, the configuration is used to determine the lower limit of a cutting speed regime, which marks the initiation of lubricant starvation, in cutting of steel using an emulsion as a cutting fluid. (C) 2010 Elsevier B.V. All rights reserved.

Museoesineitä Itä-Karjalasta : Väinö Tuomaalan jatkosodan aikana keräämä esinekokoelma ja sen syntyhistoria

Jatkosodan aikana kerättiin Suomen valtaamalta alueelta Itä-Karjalasta tuhansittain museoesineitä Suomen museoihin. Kansallismuseon kokoelmiin kerättiin esineitä lähinnä suomenheimoisilta mutta myös isovenäläisiltä. Tämän tutkimuksen kohteena on lähes 400:n esineen kokoelma, joka toimitettiin Kansallismuseoon vuosina 1941 1944 ja merkittiin kansallisuudeltaan venäläiseksi. Näistä venäläisistä esineistä suurimman osan keräsi alikersanttina palvellut Väinö Tuomaala. Tutkimukseni tarkastelee Väinö Tuomaalan kokoelmaa ja etsii syitä siihen, miksi kokoelma on sellainen kuin se on, miksi se ja koko venäläisten esineiden kokoelma syntyi ja mitkä seikat vaikuttivat Tuomaalan esinevalintoihin. Tutkimuksen teoria rakentuu museologisen kirjallisuuden varaan. Tutkimuksessa tarkastellaan Väinö Tuomaalan kokoelman keräyskonteksteja. Keräyskonteksteihin kuuluvat kokoelman kerääjä, keräysajankohta ja -paikka sekä yhteenkuuluvat esineet, eli muut venäläiset esineet. Kerääjän tarkastelussa huomioidaan hänen henkilöhistoriansa ja etsitään mahdollisia keruuseen vaikuttaneita tekijöitä. Keräysajankohdan tarkastelussa huomio kiinnittyy keruuympäristöön, eli vallitseviin olosuhteisiin ja aatteelliseen ilmapiiriin, joiden vaikutuksen alaisena keruu suoritettiin. Primääriaineisto koostuu Kansallismuseon alaisen Kulttuurien museon yleisetnografisten esineiden kokoelmaan kuuluvista 198:sta Väinö Tuomaalan keräämästä esineestä verifikaatteineen, jotka ovat osa 393 esinettä käsittävästä venäläisestä kokoelmasta. Aineisto sisältää myös eri arkistojen materiaalia. Kansallisarkiston Sörnäisten toimipisteestä, entisestä sota-arkistota, löytyneitä sotapäiväkirjoja ja Tuomaalan kantakorttia on tutkimuksessa käytetty jatkosodan tapahtumien esittämiseen. Museoviraston hallinto-osaston arkiston kirjeet ja pöytäkirjat ovat antaneet tietoa kulttuurikeruun organisoinnista. Väinö Tuomaalan arkistokokoelma Seinäjoella sisältää Tuomaalan keräämää perinneaineistoa, hänen puheitaan, lehtikirjoituksiaan ja kirjeenvaihtoaan. Myös Evijärven kunnantalon kotiseutuarkistosta löytyneet kirjeet ovat valottaneet Tuomaalan jatkosodan aikaista keruutoimintaa. Suomalaisen Kirjallisuuden Seuran arkistot ovat tarjonneet materiaalia jatkosodan aikaisesta kulttuurikeruusta. Koko venäläisten esineiden kokoelma syntyi sattumalta ja organisoimattoman toiminnan tuloksena, jossa aktiivisia toimijoita olivat yksittäiset kerääjät. Intohimoisesta suhtautumisesta kansatieteellistä keruuta kohtaan johtuen, Tuomaala olisi todenäköisesti kerännyt museoesineitä missä päin Itä-Karjalaa tahansa. Väinö Tuomaalan Itä-Karjalassa keräämä esinekokoelma oli luonnollinen jatke hänen kotiseudullaan aloittamalleen keräystoiminnalle. Tuomaalan jatkosodan aikana keräämä kokoelma on kerääjän mieltymysten mukainen yritys kerätä vanhaa itäkarjalaista, kansallista talonpoikaiskulttuuria. Tuomaala pyrki keräämään klassista kansatieteellistä aineistoa monipuolisesti kansankulttuurin eri elämänalueilta. Tuomaalan esinekeruussa näkyi vahvasti talonpoikaiskulttuurin ihannointi ja halu pelastaa osa siitä tuleville sukupolville. Yrityksen onnistumiseen vaikuttivat sodanajan olosuhteet sekä aatteellinen ilmapiiri. Esineiden saatavuudella oli merkittävä osa kokoelman muodostumiseen, samoin Tuomaalan käsityksillä heimokansoista, Suur-Suomesta ja venäläisistä. Keruuvalintoihin ja keruun jatkumiseen vaikuttivat myös Kansallismuseon henkilökunta ja työstä saatu tunnustus.

Magnetic resonance imaging and ultrasonography in brachial plexus birth injury

Brachial plexus birth injury (BPBI) is caused by stretching, tearing or avulsion of the C5-C8 or Th1 nerve roots during delivery. Foetal-maternal disproportion is the main reason for BPBI. The goal of this study was to find out the incidence of posterior subluxation of the humeral head during first year of life in BPBI and optimal timing of the ultrasonographic screening of the glenohumeral joint. The glenohumeral congruity and posterior subluxation of the humeral head associated to muscle atrophy were assessed and surgical treatment of the shoulder girdle as well as muscle changes in elbow flexion contracture were evaluated. The prospective, population based part of the study included all neonates born in Helsinki area during years 2003-2006. Patients with BPBI sent to the Hospital for Children and Adolescents because of decreased external rotation, internal rotation contracture or deformation of the glenohumeral joint as well as patients with elbow flexion contracture were also included in this prospective study. The incidence of BPBI was calculated to be 3.1/1000 newborns in Helsinki area. About 80% of the patients with BPBI recover totally during the follow-up within the first year of life. Permanent plexus injury at the age of one year was noted in 20% of the patients (0.64/1000 newborns). Muscle imbalance resulted in sonographically detected posterior subluxation in one third of the patients with permanent BPBI. If muscle imbalance and posterior subluxation are left untreated bony deformities will develop. All patients with internal rotation contracture of the glenohumeral joint presented muscle atrophy of the rotator cuff muscles. Especially subscapular and infraspinous muscles were affected. A correlation was found particularly between greatest thickness of subscapular muscle and subluxation of the humeral head, degree of glenoid retroversion, as well as amount of internal rotation contracture. Supinator muscle atrophy was evident among all the studied patients with elbow flexion contracture. Brachial muscle pathology seemed to be an important factor for elbow flexion contracture in BPBI. Residual dysfunction of the upper extremity may require operative treatment such as tendon lengthening, tendon transfers, relocation of the humeral head or osteotomy of the humerus. Relocation of the humeral head improved the glenohumeral congruency among patients under 5 years of age. Functional improvement without remodeling of the glenohumeral joint was achieved by other reconstructive procedures. In conclusion: Shoulder screening by US should be done to all patients with permanent BPBI at the age of 3 and 6 months. Especially atrophy of the subscapular muscle correlates with glenohumeral deformity and posterior subluxation of the humeral head, which has not been reported in previous studies. Permanent muscle changes are the main reason for diminished range of motion of the elbow and forearm. Relocation of the humeral head, when needed, should be performed under the age of 5 years.

Why Don't Students Talk? Causes of Foreign Language Communication Apprehension in English Classes: A Comparison of High Apprehensive and Low Apprehensive Upper Secondary Students.

OBJECTIVES. Oral foreign language skills are an integral part of one's social, academic and professional competence. This can be problematic for those suffering from foreign language communication apprehension (CA), or a fear of speaking a foreign language. CA manifests itself, for example, through feelings of anxiety and tension, physical arousal and avoidance of foreign language communication situations. According to scholars, foreign language CA may impede the language learning process significantly and have detrimental effects on one's language learning, academic achievement and career prospects. Drawing on upper secondary students' subjective experiences of communication situations in English as a foreign language, this study seeks, first, to describe, analyze and interpret why upper secondary students experience English language communication apprehension in English as a foreign language (EFL) classes. Second, this study seeks to analyse what the most anxiety-arousing oral production tasks in EFL classes are, and which features of different oral production tasks arouse English language communication apprehension and why. The ultimate objectives of the present study are to raise teachers' awareness of foreign language CA and its features, manifestations and impacts in foreign language classes as well as to suggest possible ways to minimize the anxiety-arousing features in foreign language classes. METHODS. The data was collected in two phases by means of six-part Likert-type questionnaires and theme interviews, and analysed using both quantitative and qualitative methods. The questionnaire data was collected in spring 2008. The respondents were 122 first-year upper secondary students, 68 % of whom were girls and 31 % of whom were boys. The data was analysed by statistical methods using SPSS software. The theme interviews were conducted in spring 2009. The interviewees were 11 second-year upper secondary students aged 17 to 19, who were chosen by purposeful selection on the basis of their English language CA level measured in the questionnaires. Six interviewees were classified as high apprehensives and five as low apprehensives according to their score in the foreign language CA scale in the questionnaires. The interview data was coded and thematized using the technique of content analysis. The analysis and interpretation of the data drew on a comparison of the self-reports of the highly apprehensive and low apprehensive upper secondary students. RESULTS. The causes of English language CA in EFL classes as reported by the students were both internal and external in nature. The most notable causes were a low self-assessed English proficiency, a concern over errors, a concern over evaluation, and a concern over the impression made on others. Other causes related to a high English language CA were a lack of authentic oral practise in EFL classes, discouraging teachers and negative experiences of learning English, unrealistic internal demands for oral English performance, high external demands and expectations for oral English performance, the conversation partner's higher English proficiency, and the audience's large size and unfamiliarity. The most anxiety-arousing oral production tasks in EFL classes were presentations or speeches with or without notes in front of the class, acting in front of the class, pair debates with the class as audience, expressing thoughts and ideas to the class, presentations or speeches without notes while seated, group debates with the class as audience, and answering to the teacher's questions involuntarily. The main features affecting the anxiety-arousing potential of an oral production task were a high degree of attention, a large audience, a high degree of evaluation, little time for preparation, little linguistic support, and a long duration.

Recent studies on the behaviour of interference fit pins in composite plates

Composites are finding increasing application in many advanced engineering fields like aerospace, marine engineering, hightech sports equipment, etc., due to their high specific strength and/or specific stiffness values. The use of composite components in complex situations like airplane wing root or locations of concentrated load transfer is limited due to the lack of complete understanding of their behaviour in the region of joints. Joints are unavoidable in the design and manufacture of complex structures. Pin joints are one of the most commonly used methods of connection. In regions of high stresses like airplane wing root joints interference fit pins are used to increase its fatigue life and thereby increase the reliability of the whole structure. The present contribution is a study on the behaviour of the interference fit pin in a composite plate subjected to both pull and push type of loads. The interference fit pin exhibits partial contact/separation under the loads and the contact region is a non-linear function of the load magnitude. This non-linear behaviour is studied by adopting the inverse technique and some new results are presented in this paper.

A Hybrid Multilevel Inverter Topology for an Open-End Winding Induction-Motor Drive Using Two-Level Inverters in Series With a Capacitor-Fed H-Bridge Cell

In this paper, a new five-level inverter topology for open-end winding induction-motor (IM) drive is proposed. The open-end winding IM is fed from one end with a two-level inverter in series with a capacitor-fed H-bridge cell, while the other end is connected to a conventional two-level inverter. The combined inverter system produces voltage space-vector locations identical to that of a conventional five-level inverter. A total of 2744 space-vector combinations are distributed over 61 space-vector locations in the proposed scheme. With such a high number of switching state redundancies, it is possible to balance the H-bridge capacitor voltages under all operating conditions including overmodulation region. In addition to that, the proposed topology eliminates 18 clamping diodes having different voltage ratings compared with the neutral point clamped inverter. On the other hand, it requires only one capacitor bank per phase, whereas the flying-capacitor scheme for a five-level topology requires more than one capacitor bank per phase. The proposed inverter topology can be operated as a three-level inverter for full modulation range, in case of any switch failure in the capacitor-fed H-bridge cell. This will increase the reliability of the system. The proposed scheme is experimentally verified on a four-pole 5-hp IM drive.

Lubricated Tribology of a Eutectic Aluminium-Silicon Alloy in the Ultra-Mild Wear and Mild Wear Regimes for Long Sliding Times

Aluminium-silicon alloy, an important material used for the construction of internal combustion engines, exhibit pressure induced distinct regimes of wear and friction; ultra-mild and mild. In this work the alloy is slid lubricated against a spherical steel pin at contact pressures characteristic of the two test regimes, at a very low sliding velocity. In both cases, the friction is controlled at the initial stages of sliding by the abrasion of the steel pin by the protruding silicon particles of the disc. The generation of nascent steel chips helps to breakdown the additive in the oil by a cationic exchange that yields chemical products of benefits to the tribology. The friction is initially controlled by abrasion, but the chemical products gain increasing importance in controlling friction with sliding time. After long times, depending on contact pressure, the chemical products determine sliding friction exclusively. In this paper, a host of mechanical and spectroscopic techniques are used to identify and characterize mechanical damage and chemical changes. Although the basic dissipation mechanisms are the same in the two regimes, the matrix remains practically unworn in the low-pressure ultra-mild wear regime. In the higher pressure regime at long sliding times a small but finite wear rate prevails. Incipient plasticity in the subsurface controls the mechanism of wear.

Radio interference measurements on a ceramic disc insulator string with field reduction electrode

This paper presents a laboratory study of the discharge radio noise generated by ceramic insulator strings under normal conditions. In the course of study, a comparison on the performance of two types of insulator strings under two different conditions was studied namely (a) normal disc insulators in a string and (b) disc insulators integrated with a newly developed field reduction electrode fixed to the disc insulator at the pin junction. The results obtained during the study are discussed and presented.

Orientation dependence of the indentation impression morphology in a Mg alloy

The formation of anomalous indentations, with two opposite faces describing a pin-cushion effect and the other two faces normal, in long elongated grains of an extruded Mg-2Al-1Zn alloy is reported. Subsurface microstructural observations combined with Schmid factor calculations suggest that extension twinning accompanied by basal slip are the reasons for these. Johnson's expanding cavity model is invoked for further substantiation. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.