997 resultados para INTEGRATED DFB LASER


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Väestön ikääntyminen pakottaa yhteiskunnan ja julkisen terveydenhuollon muutoksiin. Jotta ikääntyvien ihmisten kotona asuminen voidaan mahdollistaa, palvelujärjestelmän pitää mukautua muuttuvaan tilanteeseen. Tämän diplomityön tarkoituksena on tunnistaa asiakaslähtöisiä lähellä asiakasta tarjottavia palvelukokonaisuuksia. Tutkimuksen teoreettinen viitekehys muodostuu asiakasarvon luomisesta ja palvelutarjoamista. Tarkasteluryhmänä on Etelä-Karjalan alueen 60–90-vuotiaat ja käytetty aineisto on kerätty vastaajilta postitse lähetetyllä kyselyllä. Tutkimus on eksploratiivinen ja tulosten tulkinnassa on hyödynnetty määrällisen tutkimuksen ja verkostoanalyysin menetelmiä. Työn keskeisimmät tulokset ovat tunnistetut asiakassegmentit ja heidän tarpeidensa pohjalta muodostetut palvelupaketit. Tulokset indikoivat asiakkaiden tarpeita ja tuloksia on analysoitu myös tuottajan näkökulmasta. Empiiristen tulosten lisäksi teoriaviitekehystä on kehitetty eteenpäin, jotta palvelukeskeiset teoriat voidaan ymmärtää yritysten näkökulman lisäksi asiakkaan näkökulmasta.

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Tässä tutkimuksessa selvitetään ilman hitsauslisäainetta tapahtuvan laser–TIG–hybridihitsausprosessin soveltuvuus 6 mm ja 8 mm paksujen päittäisliitettyjen S355 K2 ja Laser 355 MC rakenneterästen hitsaukseen. Hitsien tarkastelussa huomio kiinnitetään hitsausnopeuteen, hitsien tunkeumaan, liittämistehokkuuteen, hitsien kovuuteen ja hitsausliitoksen ulkonäköön. Muita tutkittavia asioita ovat laser-TIG-hybridihitsattujen levyjen muodonmuutokset ja suuresta hitsausnopeudesta sekä pienestä t8/5 jäähtymisajasta johtuvat mahdolliset kylmähalkeamat. Laser-TIG-hybridihitsejä verrataan robotti-MAG- ja käsin MAG-hitseihin sekä kaarihitsausstandardin SFS-EN ISO 5817 hitsiluokkien mukaisiin raja-arvoihin. Laser-TIG-hybridihitsausprosessissa TIG-valokaari mahdollistaa tasaisen ja lähes roiskeettoman hitsin ja lasersäde aikaansaa syvän tunkeuman sekä tasalaatuisen juurihitsin. Laser-TIG-hybridihitsausprosessilla 6 mm paksut S355 K2 rakenneteräslevyt on mahdollista hitsata levyn yhdeltä puolelta kerralla valmiiksi. Paksummat 8 mm levyt voidaan hitsata levyn yhdeltä tai molemmilta puolilta suoritettavalla laser-TIG-hybridihitsauksella. Laser-TIG-hybridihitsausprosessilla hitsatut hitsit ovat hyvin siistejä ja lähes roiskeettomia. Verrattaessa laser-TIG-hybridihitsausprosessia muihin hitsausprosesseihin sen voidaan todeta olevan erittäin kilpailukykyinen 6 mm paksujen päittäisliitettyjen rakenneterästen hitsaamisessa, mutta se soveltuu myös 8 mm paksujen rakenneterästen hitsaamiseen. Tutkitut hitsit täyttävät kaarihitsausstandardin SFS-EN ISO 5817 B- ja D-hitsiluokkien mukaiset raja-arvot. Vertailukokeet 6 mm paksulla S355 rakenneteräksellä osoittavat, että yhdeltä puolelta suoritettavan laser-TIG-hybridihitsauksen hitsausnopeus on robotti-MAG-hitsaukseen verrattuna yli nelinkertainen ja MAG-käsinhitsaukseen verrattuna yli viisinkertainen. Laser-TIG-hybridihitsauksessa liittämistehokkuus on noin viisinkertainen robotti-MAGhitsaukseen verrattuna. Molemmilta puolilta suoritettavalla laser-TIG-hybridihitsauksella voidaan 8 mm paksulla S355 rakenneteräksellä saavuttaa noin kolminkertainen hitsausnopeus ja liittämistehokkuus robotti-MAG-hitsaukseen verrattuna. Laser-TIG-hybridihitsauksessa TIG-kaaren tuoman lisälämmön ansiosta suurillakin hitsausnopeuksilla (1 m/min) voidaan saavuttaa edulliset kovuusarvot. Kovuusmittausten tulosten perusteella 6 mm ja 8 mm paksujen S355 K2 ja Laser 355 MC rakenneterästen hitsit eivät ylittäneet kaarihitsausstandardin määrittelemää 350 HV kovuuden enimmäisrajaa. Laser-TIG-hybridihitsauksen edullisesta lämmöntuonnista johtuen levyjen pituus- ja poikittaissuuntaiset muodonmuutokset ovat noin 80 prosenttia pienemmät kuin käsin suoritettavassa MAG-hitsauksessa. Laser-TIG-hybridihitsausprosessilla käytetään I-railoa, mutta robotti-MAG- ja käsin MAG-hitsausprosesseilla joudutaan käyttämään V-railoa, jolloin lämmöntuonti ja siitä johtuvat muodonmuutokset ovat suuremmat. Korkea liittämistehokkuus ja edullinen lämmöntuonti merkitsevät vähäisempiä muodonmuutoksia ja siten merkittäviä säästöjä työ-, materiaali- ja energiakustannuksissa. 8 mm ja sitä paksummilla S355 rakenneteräksillä levyn yhdeltä puolelta suoritettava päittäisliitoksen hitsaaminen on laser-TIG hybridihitsauksella haastavaa, koska yli 200 A:n TIG-kaarivirralla suuri metallisula aiheuttaa avaimenreiän sulkeutumisen ja avaimenreiän alaosaan muodostuu kaasukuplia. Tästä voidaan tehdä sellainen johtopäätös, että päittäisliitettävien levyjen ilmarakoa pitäisi kasvattaa niin suureksi, että avaimenreiän sulavirtaus ei pääse estymään. Yli 0,25 mm:n ilmarako edellyttää lasersäteen vaaputusta tai säteen halkaisijan kasvattamista. Ilmaraon kasvattaminen edellyttää myös lisäaineen käyttöä. Tutkimustulosten perusteella laser-TIG-hybridihitsausprosessilla voidaan saavuttaa merkittäviä etuja ja kustannussäästöjä, joten sen hyödyntämistä kannattaa harkita 8 mm ja sitä ohuempien päittäisliitettävien tuotteiden konepaja- ja tehdastuotannossa. Laser-TIGhybridihitsausprosessi soveltuu esimerkiksi seuraavien tuotteiden hitsaamiseen: päittäisliitettävät levyt, palkit, koneenosat, putket, säiliöt ja erilaiset pyörähdyskappaleet.

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Joining processes and techniques need to meet the trend of new applications and the development of new materials. The application in connection with thick and thin plates in industrial fields is wide and the joining technology is in very urgent need. The laser-TIG hybrid welding technology can play the respective advantages of both of them. One major advantage of the hybrid laser-TIG welding technology is its efficient use of laser energy. Additionally, it can develop into a high and new advanced welding technology and become a hot spot in both the application and research area. This thesis investigated laser –TIG hybrid welding with the aim of enlightening the reader on its advantages, disadvantages and future areas of improvement. The main objective is to investigate laser-TIG hybrid on the welding of various metals (steels, magnesium, aluminium etc.). In addition, it elaborates on various possible combinations on hybrid laser-TIG welding technology and their benefits. The possibility of using laser-TIG hybrid in welding of thick materials was investigated. The method applied in carrying out this research is by using literature review. The results showed that hybrid laser-TIG is applicable to almost all weldable metals. Also it proves to be effective in welding refractive metals. The possibility of welding with or without filler materials is of economic advantage especially in welding of materials with no filler material. Thick plate’s hybrid laser-TIG welding is showing great prospects although it normally finds its used in welding thin materials in the range of 0.4 to 0.8 mm. The findings show that laser-TIG hybrid welding can be a versatile welding process and therefore will be increasingly used industrially due to its numerous advantages and the development of new TIG arc that enhances its capabilities.

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This doctoral thesis was published in printed form in 1987. It was digitized from paper copy in 2013. Unfortunately on some pages the digitizaion process has not been complete, i.e there are some minor typographic erros on some pages.

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The present paper describes an integrated micro/macro mechanical study of the elastic-viscoplastic behavior of unidirectional metal matrix composites (MMC). The micromechanical analysis of the elastic moduli is based on the Composites Cylinder Assemblage model (CCA) with comparisons also draw with a Representative Unit Cell (RUC) technique. These "homogenization" techniques are later incorporated into the Vanishing Fiber Diameter (VFD) model and a new formulation is proposed. The concept of a smeared element procedure is employed in conjunction with two different versions of the Bodner and Partom elastic-viscoplastic constitutive model for the associated macroscopic analysis. The formulations developed are also compared against experimental and analytical results available in the literature.

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This research is an analysis of the value and content of local service offerings that enable longer periods of living at home for elderly people. Mobile health care and new distribution services have provided an interesting solution in this context. The research aim to shed light on the research question, ‘How do we bundle services based on different customer needs?’ A research process consisting of three main phases was applied for this purpose. During this process, elderly customers were segmented, the importance of services was rated and service offerings were defined. Value creation and service offering provides theoretical framework for the research. The target group is South Karelia’s 60 to 90-year old individuals and the data has been acquired via a postal questionnaire. Research has been conducted as exploratory research utilizing the methods of quantitative and social network analysis. The main results of the report are identified customer segments and service packages that fits to the segments’ needs. The results indicate the needs of customers and the results are additionally analysed from the producer’s point of view. In addition to the empirical results, the used theory framework has been developed further in order for the service-related theories to be seen from the customer’s point of view and not just from the producer’s point of view.

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The Arctic region becoming very active area of the industrial developments since it may contain approximately 15-25% of the hydrocarbon and other valuable natural resources which are in great demand nowadays. Harsh operation conditions make the Arctic region difficult to access due to low temperatures which can drop below -50 °C in winter and various additional loads. As a result, newer and modified metallic materials are implemented which can cause certain problems in welding them properly. Steel is still the most widely used material in the Arctic regions due to high mechanical properties, cheapness and manufacturability. Moreover, with recent steel manufacturing development it is possible to make up to 1100 MPa yield strength microalloyed high strength steel which can be operated at temperatures -60 °C possessing reasonable weldability, ductility and suitable impact toughness which is the most crucial property for the Arctic usability. For many years, the arc welding was the most dominant joining method of the metallic materials. Recently, other joining methods are successfully implemented into welding manufacturing due to growing industrial demands and one of them is the laser-arc hybrid welding. The laser-arc hybrid welding successfully combines the advantages and eliminates the disadvantages of the both joining methods therefore produce less distortions, reduce the need of edge preparation, generates narrower heat-affected zone, and increase welding speed or productivity significantly. Moreover, due to easy implementation of the filler wire, accordingly the mechanical properties of the joints can be manipulated in order to produce suitable quality. Moreover, with laser-arc hybrid welding it is possible to achieve matching weld metal compared to the base material even with the low alloying welding wires without excessive softening of the HAZ in the high strength steels. As a result, the laser-arc welding methods can be the most desired and dominating welding technology nowadays, and which is already operating in automotive and shipbuilding industries with a great success. However, in the future it can be extended to offshore, pipe-laying, and heavy equipment industries for arctic environment. CO2 and Nd:YAG laser sources in combination with gas metal arc source have been used widely in the past two decades. Recently, the fiber laser sources offered high power outputs with excellent beam quality, very high electrical efficiency, low maintenance expenses, and higher mobility due to fiber optics. As a result, fiber laser-arc hybrid process offers even more extended advantages and applications. However, the information about fiber or disk laser-arc hybrid welding is very limited. The objectives of the Master’s thesis are concentrated on the study of fiber laser-MAG hybrid welding parameters in order to understand resulting mechanical properties and quality of the welds. In this work only ferrous materials are reviewed. The qualitative methodological approach has been used to achieve the objectives. This study demonstrates that laser-arc hybrid welding is suitable for welding of many types, thicknesses and strength of steels with acceptable mechanical properties along very high productivity. New developments of the fiber laser-arc hybrid process offers extended capabilities over CO2 laser combined with the arc. This work can be used as guideline in hybrid welding technology with comprehensive study the effect of welding parameter on joint quality.

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Gas shielding plays an important role in laser welding phenomena. This is because it does not only provide shielding against oxidization but it has an effect in beam absorption and thus welds penetration. The goal of this thesis is to study and compare the effects of different shielding gas feeding methods in laser welding of steel. Research method is a literature survey. It is found that the inclination angle and the arrangement of the gas feeding nozzles affect the phenomena significantly. It is suggested that by designing shielding gas feeding case specifically better welding results can be obtained.

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Two field experiments were conducted in two successive seasons, 2005/2006 and 2006/2007, to determine whether management can improve faba bean competitiveness with weeds, thus helping to achieve its yield potential. The experiment included five treatments, composed of organic and mineral fertilizers, alone and mixed at different rates, along with a control and six weed control treatments, including oxadiargyl, prometryn, hand hoeing treatments alone or mixed with the herbicides, and a nonweeded treatment (control).The herbicide treatments were not superior to the two hand-hoeing treatments. Using compost favored growth and yield of faba bean more than of weeds. Adding fertilizer also improved most yield parameters. Application of compost alone or combined with 50 or 100% of the recommended NPK rate improved faba bean growth in terms of net assimilation rate, specific leaf area, and leaf weight ratio as components of relative growth rate. This improvement in growth resulted in increase of seed yield, yield components and protein of faba bean. Faba bean yield performance improved under interactive fertilizer effects and weed control treatments as growth improved, as a result of nutrient release from fertilizers and weed control.

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Laser additive manufacturing (LAM), known also as 3D printing, has gained a lot of interest in past recent years within various industries, such as medical and aerospace industries. LAM enables fabrication of complex 3D geometries by melting metal powder layer by layer with laser beam. Research in laser additive manufacturing has been focused in development of new materials and new applications in past 10 years. Since this technology is on cutting edge, efficiency of manufacturing process is in center role of research of this industry. Aim of this thesis is to characterize methods for process efficiency improvements in laser additive manufacturing. The aim is also to clarify the effect of process parameters to the stability of the process and in microstructure of manufactured pieces. Experimental tests of this thesis were made with various process parameters and their effect on build pieces has been studied, when additive manufacturing was performed with a modified research machine representing EOSINT M-series and with EOS EOSINT M280. Material used was stainless steel 17-4 PH. Also, some of the methods for process efficiency improvements were tested. Literature review of this thesis presents basics of laser additive manufacturing, methods for improve the process efficiency and laser beam – material- interaction. It was observed that there are only few public studies about process efficiency of laser additive manufacturing of stainless steel. According to literature, it is possible to improve process efficiency with higher power lasers and thicker layer thicknesses. The process efficiency improvement is possible if the effect of process parameter changes in manufactured pieces is known. According to experiments carried out in this thesis, it was concluded that process parameters have major role in single track formation in laser additive manufacturing. Rough estimation equations were created to describe the effect of input parameters to output parameters. The experimental results showed that the WDA (width-depth-area of cross-sections of single track) is correlating exponentially with energy density input. The energy density input is combination of the input parameters of laser power, laser beam spot diameter and scan speed. The use of skin-core technique enables improvement of process efficiency as the core of the part is manufactured with higher laser power and thicker layer thickness and the skin with lower laser power and thinner layer thickness in order to maintain high resolution. In this technique the interface between skin and core must have overlapping in order to achieve full dense parts. It was also noticed in this thesis that keyhole can be formed in LAM process. It was noticed that the threshold intensity value of 106 W/cm2 was exceeded during the tests. This means that in these tests the keyhole formation was possible.

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Scanning optics create different types of phenomena and limitation to cladding process compared to cladding with static optics. This work concentrates on identifying and explaining the special features of laser cladding with scanning optics. Scanner optics changes cladding process energy input mechanics. Laser energy is introduced into the process through a relatively small laser spot which moves rapidly back and forth, distributing the energy to a relatively large area. The moving laser spot was noticed to cause dynamic movement in the melt pool. Due to different energy input mechanism scanner optic can make cladding process unstable if parameter selection is not done carefully. Especially laser beam intensity and scanning frequency have significant role in the process stability. The laser beam scanning frequency determines how long the laser beam affects with specific place local specific energy input. It was determined that if the scanning frequency in too low, under 40 Hz, scanned beam can start to vaporize material. The intensity in turn determines on how large package this energy is brought and if the intensity of the laser beam was too high, over 191 kW/cm2, laser beam started to vaporize material. If there was vapor formation noticed in the melt pool, the process starts to resample more laser alloying due to deep penetration of laser beam in to the substrate. Scanner optics enables more flexibility to the process than static optics. The numerical adjustment of scanning amplitude enables clad bead width adjustment. In turn scanner power modulation (where laser power is adjusted according to where the scanner is pointing) enables modification of clad bead cross-section geometry when laser power can be adjusted locally and thus affect how much laser beam melts material in each sector. Power modulation is also an important factor in terms of process stability. When a linear scanner is used, oscillating the scanning mirror causes a dwell time in scanning amplitude border area, where the scanning mirror changes the direction of movement. This can cause excessive energy input to this area which in turn can cause vaporization and process instability. This process instability can be avoided by decreasing energy in this region by power modulation. Powder feeding parameters have a significant role in terms of process stability. It was determined that with certain powder feeding parameter combinations powder cloud behavior became unstable, due to the vaporizing powder material in powder cloud. Mainly this was noticed, when either or both the scanning frequency or powder feeding gas flow was low or steep powder feeding angle was used. When powder material vaporization occurred, it created vapor flow, which prevented powder material to reach the melt pool and thus dilution increased. Also powder material vaporization was noticed to produce emission of light at wavelength range of visible light. This emission intensity was noticed to be correlated with the amount of vaporization in the powder cloud.

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Tämä tutkimus käsittelee sähkömagneettista spektriä ja sen tuottamaa uhkaa lentotukikohdan hälytyspaikka-alue ympäristölle. Sähkömagneettinen spektri on käsitteenä ja uhkan tuottajana laaja käsite, joten tutkimuksessa keskitytään käsittelemään sähkömagneettista spektriä yleisesti uhkan tuottajana, sekä käsitellään sen kahta eri sovellutusta lasermaalinosoitusta ja lämpökameraa uhkan tuottajina tarkemmin. Lähtökohtana työlle on luoda lukijalle kuvasähkömagneettisen spektrin uhkien laajuudesta, tutkimalla itse spektrin ominaisuuksia ja käsittelemällä sen eri sovellutuksia, joihin kuuluu esimerkiksi elektroninen sodankäynti kokonaisuudessaan. Keskeisenä menetelmää tutkimuksessa on laadullinen kirjallisuustutkimus, hyödyntäen kirjallisuuslähteitä sekä sotilas- että siviililähteistä. Lähteet on pyritty valitsemaan siten, että niiden avulla voidaan muodostaa kokonaisvaltainen kuva itse sähkömagneettisesta spektristä, sen ominaisuuksista, laserin muodostamisen periaatteista, lämpökameran toiminnasta ja liittää nämä asiat hälytyspaikka-alueen uhkakuvaan. Yhteenvetona tutkimus on keskittynyt tuloksien valossa luomaan kuvan, kuinka laaja sähkömagneettisen spektrin tuottama uhka on, käsittäen itse spektrin laajuuden ja sovellutusten laajuuden tuottaman uhkakuvan, sekä tarkentaa miten lämpökamera toimii teknisesti tiedustelun välineenä. Lisäksi laser maalinosoitusta käsittelevä osio avaa lukijalle, miten lasersäteen muodostaminen tapahtuu, ja kuinka jopa 4-10km kantamaltaan olevalla lasersäteellä voi valaista maaleja kaukaakin. Johtopäätöksissä summataan yhteen uhkan laajuus, sekä perustellaan miten ja miksi sähkömagneettisen spektrin uhkilta voi suojautua. Spektrin tuottama uhkakuva on sen verran laaja ja kattava, että siltä täysin suojautuminen on mahdotonta, vaan uhkaa on pyrittävä minimoimaan.

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The purpose of this study is to identify opportunities to match marketing communication message strategies with the target audience characteristics in the Chinese luxury market entry context. Therefore, consumer behaviour and psychographic marketing segmentation fields are being reviewed in a holistic view in order to identify the similarities and connection points. Through the analysis of the messages in advertisements placed in a certain luxury and fine living magazine, message creation strategies are being anticipated.