Reaction kinetic analysis of damage rate effects on defect structural evolution in Fe–Cu

In Fe–Cu alloys, Cu precipitates are formed during high-energy particle irradiation. If there exists energetic binding between vacancies and Cu atoms, vacancy clusters (voids) are formed in precipitates at an initial stage of irradiation, separate from voids in the matrix, because of the migration of Cu atoms with vacancies. In this paper, the damage rate dependence on the formation and annihilation of voids in the precipitates and in the matrix is simulated by reaction kinetic analysis. The initial formation of voids at precipitates, the annihilation of them with an increased dosage and new formation of voids in the matrix are simulated, and the results are compared with the experiments. In a high damage rate of 3.3 × 10^[−7] dpa/s, the formation of voids in Cu precipitates is not significant, but the formation of voids in the matrix is dominant, different from those in a low damage rate of 1.5 × 10^[−10] dpa/s

Contribution of cadmium to the total amount of positron creation in a reactor-based slow positron beamline

In the slow positron beamline at the Kyoto University Research Reactor (KUR), positron creation was enhanced by increasing the gamma-ray intensity at the positron source via the reaction of¹¹³Cd(n, γ)¹¹⁴Cd. To achieve this, a cadmium (Cd) cap was attached to the positron source, surrounding it, and thus, without intentional cooling, the temperature was able to reach near the melting point of Cd via nuclear heating. In this study, the degree to which the Cd cap contributes to the quantity of positron creation was estimated by using the Monte Carlo calculation code PHITS (Particle and Heavy Ion Transport code System), which simulates radiation transportation and interaction with matter. As a result, the number of positrons created was found to become 2.0 ± 0.1 times higher by using the Cd cap at the KUR slow positron beamline. The use of the Cd cap was confirmed to be significantly effective for enhancing positron creation

Microstructural Evolution in Austenitic Stainless Steels Irradiated by Neutrons with Improved Control

Nucleation and growth of interstitial type dislocation loops were investigated by fusion neutron irradiation and fission neutron irradiations with improved control. The density of loops formed by both irradiations increased linearly with the fluence. The average size of loops also increased. The rate equation analysis showed that the loops were nucleated directly by the defect processes in a cascade zone, not by the reaction among the freely migrating point defects in the matrix. If the rate of loop formation is assumed to be directly proportional to the energy of a primary knock-on atom (PKA) produced by a neutron, the threshold energy of 80 keV and the rate of loop formation of 0.05 were obtained

Sijoittamisen kehitys sosiaalisiksi sijoitusyhteisöiksi

Sijoittaminen muuttuu jatkuvasti aikakausien mukaan ja on kehittynyt viime vuosina sosiaaliseksi sijoittamiseksi. Käsitteellä tarkoitetaan sosiaalisen median piirteiden siirtymistä osaksi sijoituskäyttäytymistä. Sosiaaliset sijoitusyhteisöt tarjoavat käyttäjilleen tavan kommunikoida ja olla yhteydessä muihin sijoittajiin uudella tavalla. Sijoitusyhteisöjen palveluihin kuuluvat nykyisin keskustelupalstat ja mahdollisuus kerätä ja jakaa tietoa käyttäjien kesken. Opinnäytetyön tarkoitus on löytää sosiaalisen sijoittamisen keskeiset piirteet ja sosiaalisesta mediasta saadut vaikutteet. Työssä tutkitaan sijoitustavan syntyyn vaikuttaneita ominaisuuksia sekä listataan hyviä ja huonoja puolia sosiaalisesta sijoittamisesta. Työn tavoite on tarkastella menestystekijöitä ja niiden pohjalta selvittää, miksi sijoitustapa on toiminut menestyksekkäästi ja jatkaa kasvuaan markkinoilla. Tutkimuksessa on käytetty painettuina lähteinä alan kirjallisuutta, jotka käsittelevät online-sijoittamista ja sijoittamisen kehitystä internet kasvun myötä. Sosiaalinen sijoittaminen on aiheena varsin uusi ilmiö, josta ei ole toteutettu Suomessa montaa tutkimusta. Tämän vuoksi opinnäytetyössä hyödynnettiin enemmän ulkomaisia sähköisiä lähteitä. Opinnäytetyössä käsitellään lyhyesti suurimpia ulkomaisia sosiaalisia sijoitusalustoja, mutta pääpaino on Suomessa toimivassa Nordnetin Sharevillessä. Tutkimusmenetelmäksi valikoitui benchmarking, jota käytetään yrityksen vertailussa suhteessa kilpailijoihin tai toisen alan me-nestyjiin. Tässä opinnäytetyössä benchmarkingilla tutkittiin Sharevillen kilpailuetuja kotimaisilla markkinoilla ja verrataan sosiaalisen median ilmiöitä palveluun. Benchmarkingin avulla löydettiin yhtäläisyyksiä sosiaalisen median ja sosiaalisten sijoitusalustoiden väliltä. Tutkimuksessa löytyi myös ilmiöitä, jotka eivät ole vielä osa sijoitusalustojen palveluita, kuten mainonta, kilpailut ja tapahtumakutsut sekä yksityisen viestinnän työkalun puute käyttäjien välillä. Näiden ominaisuuksien oletetaan siirtyvän tulevaisuudessa sijoituspalveluihin hieman eri muodossa. Opinnäytetyön tutkimuksen pohjalta pääteltiin, että sosiaalinen sijoittaminen on vasta alkutaipaleellaan ja tulee muuttumaan tulevaisuudessa sekä monipuolisemmaksi että suositummaksi. Arvion mukaan muutaman vuoden päästä sosiaalinen sijoittaminen on käsitteenä tuttu lähes kaikille sijoittajille.In recent years social trading has emerged as a new form of investment. Social trading is communication between different traders and the concept refers to the incorporation of aspects of social media into the investment behavior. Social trading platforms offer users a new way to communicate and contact other people. Forums and the ability to collect and share information among users are part of the social trading platforms’ services nowadays. The purpose of this thesis project is to identify the key features of social trading and find in-fluences which are from social media. The thesis examines the features which have affected the creation of this new form of trading. The pros and cons of social investment are also listed. Based on the study the purpose is to find ways of communication in social media which are not yet part of the social trading. The theoretical framework of this thesis is drawn from printed literature on such topics as online investing, the development of investment and Internet growth. Social investing is a relatively new phenomenon, about which there have not been many studies made in Finland. Therefore, the report utilizes more international online sources. The thesis briefly discusses the largest foreign international social trading platforms, but the main focus is on the Scandinavian platform, Shareville, which is owned by Nordnet. Benchmarking was chosen as the research method and this is used to identify competitive advantages in the domestic market and to compare the social media phenomena to the service. The results of the research showed the similarities between social media and social trading platforms. Some surprising phenomena that are not yet part of investment platforms were found, such as advertising, competitions and event invitations. Based on the study the supposition is that these phenomena will be part of social trading later, but they will not be in same form. On the basis of the results, the report concludes that social investing is only in its early stages and will change in the future to become more versatile and popular. It is predicted that in a few years social trading as a concept will be familiar to almost all investors

The Effect of Planar Sinks on the Interstitial Loop Growth under High Temperature Neutron Irradiation

The role of planar sinks such as surfaces and grain boundaries for the defect structure developments was studied in fission neutron irradiated Ni and Ni alloys of 2 at% Si, Cu, Ge and Sn to the dose of 4x10^n/m^2 (>1MeV) at 573 K by comparison between thin foil irradiation and bulk irradiation. The number density of interstitial loops increases and then decreases with the increase of distance from planar sinks. Observed defect structure developments were interpreted in terms of the variation of point defect concentration with the change of sink efficiency. The necessity of the introduction of cascade localization induced bias effect is emphasized

Photoluminescence, morphology, and structure of hydrothermal ZnO implanted at room temperature with 60 keV Sn+ ions

Hydrothermal ZnO wafers implanted at room temperature with 60 keV Sn^+ ions are examined by means of photoluminescence (PL), atomic force spectroscopy (AFM), and X-ray diffractometry techniques. The PL intensity significantly decreases in the wafers implanted to doses of 4.1 × 10^[13] ions/cm^2 and higher. The AFM measurements indicate that surface roughness variation is not the cause of the significant decrease in PL intensity. Furthermore, the PL deep level (DL) band peak blueshifts after illuminating the implanted samples with the He-Cd laser 325 nm line; meanwhile, the DL band intensity first increases and then decreases with illumination time. These abnormal behaviors of the DL band are discussed

コウブンギ ノ ヒカク 二 モトヅイタ プログラム サブン ノ ヒョウジ ホウシキ

Void formation and structure change by heavy ion irradiation were investigated in GaSb and InSb thin films. The voids were formed after irradiation in both materials. The average diameter of the voids was about 15nm in GaSb and 20nm in InSb irradiated with 60 keV Snþ ions to a fluence of 0:25 x 1018 ions/m2 at room temperature. The void size in InSb is larger than that in GaSb. The large void size is quantitatively explained by the amount of induced vacancies obtained by the SRIM code simulation. The Debye-Scherrer rings were observed in the SAED patterns on both materials. The structure changes into a polycrystal by ion irradiation. Additionally, the 200 superlattice reflections in the [001] net pattern were almost absent, and the streak pattern along the h110i direction was observed in InSb. It is considered that the anti phase domains of different lengths are formed by ion irradiation. Ion irradiation transforms the structure of InSb from chemical ordering to chemical disordering via the formation of anti phase boundaries

Fission-Fusion Correlation in Mechanical Property Changes of Several Pure FCC Metals

Mechanical property changes were observed for pure Ni, Cu and Au irradiated with fission and fusion neutrons. Before comparing the results of fission neutron with fusion neutron irradiation, the importance of irradiation temperature history is discussed. The irradiation below a designed temperature at the start-up of the reactor brings very different results from that obtained from strictly temperature controlled irradiation experiments, and this depends on the relative situation between the irradiation temperature and the temperature range of nucleation stage. Although there was no overlapping for neutron fluence in the fission and fusion neutron irradiation experiments, fluence for equivalent amount of the yield strength change for fusion neutron irradiation could be predicted from the plots of yield strength against 1/4 power of the neutron fluence for fission neutron irradiated specimens , and vice versa