Composition and the thermoelectric performance of β-Zn_4Sb_3

β-Zn_4Sb_3 is a promising thermoelectric material due to the abundance of zinc and antimony and reports of high efficiency in bulk samples. This work establishes the high temperature properties of β-Zn_4Sb_3 across the phase stability window. By controlling the stoichiometry, the Hall carrier concentration can be tuned from 6–9 × 10^(19) cm^(−3) without requiring extrinsic dopants. The trend in Seebeck coefficient on carrier concentration is rationalized with a single, parabolic band model. Extremely low lattice thermal conductivity (0.4–0.6 W m^(−1) K^(−1)) coupled with a moderate effective mass (1.2 m_e) and mobility leads to a large figure of merit (zT of 0.8 by 550 K). The single parabolic band model is used to obtain the carrier concentration dependence of the figure of merit and an optimum carrier concentration near 5 × 10^(19) cm^(−3) is predicted

Transition metal d-band occupancy in skutterudites studied by electron energy-loss spectroscopy

The transition-metal 3d occupancy of a series of thermoelectric skutterudites is investigated using electron energy-loss spectroscopy. We find that bonding causes an emptying of the 3d states in the binary skutterudites CoP3, CoAs3, CoSb3, and NiP3, while compared to the pure Fe the 3d occupancy in LaFe4P12 is significantly increased, consistent with the idea that each interstitial La atom (rattler) donates three electrons to compensate for missing valence electron of Fe as compared to Co. These experimental results are in agreement with previous models suggesting a predominantly covalent bonding between transition metal and pnictogen atoms in skutterudites, and provide evidence of charge transfer from La to the Fe-P complex in LaFe4P12

Accurate determination of domain boundary orientation in LaNbO4

The orientation relationship between ferroelastic domains in LaNbO4 (with 0.5 at.% Sr) is studied by selected area electron diffraction and high-resolution electron microscopy. At room temperature the domains are related through a simple rotation of approximately 95 degrees about the monoclinic [0 1 0] axis, and the interface between two adjacent domains is highly ordered. The domain boundary is found to be the (2 0 5.10)/(5.10 0 2) planes of the two domains, in excellent agreement with our theoretical predictions. This orientation differs considerably from that predicted by more elaborate ferroelastic theory

Reduction of lattice thermal conductivity from planar faults in the layered Zintl compound SrZnSb_2

The layered Zintl compound SrZnSb_2 is investigated using transmission electron microscopy (TEM) to understand the low lattice thermal conductivity. The material displays out-of-phase boundaries with a spacing from 100 down to 2 nm. Density functional theory calculations confirm that the TEM-derived defect structure is energetically reasonable. The impact of these defects on phonon scattering is analyzed within the Debye–Callaway model, which reveals a significant reduction in the acoustic phonon mean free path. This enhancement in phonon scattering leads to an ~30% reduction in lattice thermal conductivity at 300 K

En svartmalt petroleumsindustri i det grønne skiftet

Utgangspunktet for denne bacheloroppgaven er oljeselskaper og internasjonale klimaavtaler. Temaet er organisasjonenes arbeid med diverse klimaavtaler, og hvordan de implementerer avtalene i organisasjonen og utad. Gjennom en spørreundersøkelse og flere dybdeintervju har vi ønsket å avdekke følgende problemstilling: Hvordan arbeider oljeselskaper i Stavanger med Parisavtalen og andre internasjonale klimaavtaler? Med oppgavens problemstilling er ikke fokuset å vurdere i hvilken grad oljeselskapene er bærekraftige, men heller hvilke strategier de tar i bruk i henhold til avtalene. I tråd med dette er det også blitt undersøkt i intervjuer om det er noe bedriftene savner eller føler seg uhørte når det kommer til den grønne omstillingen?  Resultatene i undersøkelsen viser at selv om selskapene har kjennskap til mange av avtalene, klarer de ikke å se relevansen i bedriftens arbeid i forhold til avtalene. Det varierer også litt fra ulike avtaler, i hvor stor grad oljeselskapene har kjennskap til innholdet i avtalene og deres påvirkning på Norge. The starting point for this bachelor thesis is oil companies and international climate agreements. The topic is the organisations' work with various climate agreements, and how they implement the agreements within the organization and externally. Through a survey and several in-depth interviews, we wanted to uncover the following problem: How do oil companies in Stavanger work with the Paris Agreement and other international climate agreements? The focus fot this thesis is not to assess the extent to which the oil companies are sustainable, but rather which strategies they adopt in accordance with the agreements. In line with this, it has also been investigated in interviews whether there is something the companies miss or feel unheard when it comes to the green transition? The results of the survey show that although the companies are aware of many of the agreements, they are unable to see the relevance of the company's work in relation to the agreements. It also varies slightly from different agreements, to what extent the oil companies are aware of the content of the agreements and their impact on Norway

Comparison of open source network intrusion detection systems

Many companies and organizations offer IT-services (news papers, social sites, web developers and etc.) to the public, and those services needs to be protected. The amount of computer threats are increasing drastically, and many attacks are directed to those services companies offer. Larger companies have the economy to buy expensive security tools to protect their services, while smaller companies may have the same economy. Open source is an interesting field for those who do not have the need or the economy to buy expensive security solutions. Intrusion detection system is a well known security tool, and it could either be bought as a payment solution, or be downloaded from the web as an open source solution. Snort, Bro and Suricata are three different open source network intrusion detection systems. By comparing installation, configuration, alarms and information one can find out which solution that fits your network best. The process of setting up the test environment, installation and configuration of Snort, Bro and Suricata, and installation of Metasploit have been a time consuming process. Snort, Bro and Suricata have been tested in a network, and against a Metasploit framework with known exploits. Running Snort, Bro and Suricata in a network, have shown huge differences regarding the number of alarms produced, and also differences in the logs produced. The results after running Metasploit showed some unexpected but clarifying results in the logs created. The whole process has been evaluated, and there has been given a summary of Snort, Bro and Suricata regarding installation, configuration and alarms

En svartmalt petroleumsindustri i det grønne skiftet

Utgangspunktet for denne bacheloroppgaven er oljeselskaper og internasjonale klimaavtaler. Temaet er organisasjonenes arbeid med diverse klimaavtaler, og hvordan de implementerer avtalene i organisasjonen og utad. Gjennom en spørreundersøkelse og flere dybdeintervju har vi ønsket å avdekke følgende problemstilling: Hvordan arbeider oljeselskaper i Stavanger med Parisavtalen og andre internasjonale klimaavtaler? Med oppgavens problemstilling er ikke fokuset å vurdere i hvilken grad oljeselskapene er bærekraftige, men heller hvilke strategier de tar i bruk i henhold til avtalene. I tråd med dette er det også blitt undersøkt i intervjuer om det er noe bedriftene savner eller føler seg uhørte når det kommer til den grønne omstillingen?  Resultatene i undersøkelsen viser at selv om selskapene har kjennskap til mange av avtalene, klarer de ikke å se relevansen i bedriftens arbeid i forhold til avtalene. Det varierer også litt fra ulike avtaler, i hvor stor grad oljeselskapene har kjennskap til innholdet i avtalene og deres påvirkning på Norge. The starting point for this bachelor thesis is oil companies and international climate agreements. The topic is the organizations' work with various climate agreements, and how they implement the agreements within the organization and externally. Through a survey and several in-depth interviews, we wanted to uncover the following problem: How do oil companies in Stavanger work with the Paris Agreement and other international climate agreements? The focus of this thesis is not to assess the extent to which the oil companies are sustainable, but rather which strategies they adopt in accordance with the agreements. In line with this, it has also been investigated in interviews whether there is something the companies miss or feel unheard when it comes to the green transition? The results of the survey show that although the companies are aware of many of the agreements, they are unable to see the relevance of the company's work in relation to the agreements. It also varies slightly from different agreements, to what extent the oil companies are aware of the content of the agreements and their impact on Norway

Determination of the local concentrations of Mn interstitials and antisite defects in GaMnAs

We present a method for the determination of the local concentrations of interstitial and substitutional Mn atoms and As antisite defects in GaMnAs. The method relies on the sensitivity of the structure factors of weak reflections to the concentrations and locations of these minority constituents. High spatial resolution is obtained by combining structure factor measurement and X-ray analysis in a transmission electron microscope. We demonstrate the prevalence of interstitials with As nearest neighbors in as-grown layers.Comment: 10 pages, 4 figure

Nanoscale inclusions in the phonon glass thermoelectric material

We have investigated the thermoelectric material Zn 4 Sb 3 using transmission electron microscopy (TEM). Nanoscale inclusions with a diameter of about 10 nm were observed, constituting on the order of 1% by volume of the material. Studies using energy filtered imaging, electron diffraction, and high-angle annular dark-field STEM indicate that the inclusions consist of Zn. These inclusions are expected to scatter the medium and long-wavelength phonons effectively, thus contributing to phonon glass behavior which results in the exceptionally low thermal conductivity for this thermoelectric material