Time Horizons and Emissions Trading

We study dynamic cap-and-trade schemes in which a policy of adjustable allowance supply determines the cap on emissions. Focusing on two common supply policies, price and quantity mechanisms, we investigate how the duration of a cap-and-trade scheme affects equilibrium emissions under its cap. More precisely, we consider the reduction in equilibrium emissions realized by shortening the duration of the scheme. We present four main results. First, the reduction in emissions is positive and bounded from below under a price mechanism. Second, the reduction in emissions is bounded from above under a quantity mechanism. Third, these upper and lower bounds coincide when the price and quantity mechanism are similar. Fourth, we identify sufficient conditions for which the reduction in emissions is strictly negative under a quantity mechanism. We quantify our theoretical results for the European Union, the world’s largest cap-and-trade scheme to use a quantity mechanism; effects on cumulative EU emissions range from trivial to substantial

Electron Transport across Vertical Silicon/MoS2/Graphene Heterostructures: Towards Efficient Emitter Diodes for Graphene Base Hot Electron Transistors

Heterostructures comprising silicon, molybdenum disulfide (MoS2), and graphene are investigated with respect to the vertical current conduction mechanism. The measured current-voltage (I-V) characteristics exhibit temperature-dependent asymmetric current, indicating thermally activated charge carrier transport. The data are compared and fitted to a current transport model that confirms thermionic emission as the responsible transport mechanism across devices. Theoretical calculations in combination with the experimental data suggest that the heterojunction barrier from Si to MoS2 is linearly temperature-dependent for T = 200-300 K with a positive temperature coefficient. The temperature dependence may be attributed to a change in band gap difference between Si and MoS2, strain at the Si/MoS2 interface, or different electron effective masses in Si and MoS2, leading to a possible entropy change stemming from variation in density of states as electrons move from Si to MoS2. The low barrier formed between Si and MoS2 and the resultant thermionic emission demonstrated here make the present devices potential candidates as the emitter diode of graphene base hot electron transistors for future high-speed electronics. Copyright © 2020 American Chemical Society

Electron Transport across Vertical Silicon/MoS2/Graphene Heterostructures: Towards Efficient Emitter Diodes for Graphene Base Hot Electron Transistors

Heterostructures comprising silicon, molybdenum disulfide (MoS2), and graphene are investigated with respect to the vertical current conduction mechanism. The measured current-voltage (I-V) characteristics exhibit temperature-dependent asymmetric current, indicating thermally activated charge carrier transport. The data are compared and fitted to a current transport model that confirms thermionic emission as the responsible transport mechanism across devices. Theoretical calculations in combination with the experimental data suggest that the heterojunction barrier from Si to MoS2 is linearly temperature-dependent for T = 200-300 K with a positive temperature coefficient. The temperature dependence may be attributed to a change in band gap difference between Si and MoS2, strain at the Si/MoS2 interface, or different electron effective masses in Si and MoS2, leading to a possible entropy change stemming from variation in density of states as electrons move from Si to MoS2. The low barrier formed between Si and MoS2 and the resultant thermionic emission demonstrated here make the present devices potential candidates as the emitter diode of graphene base hot electron transistors for future high-speed electronics. Copyright © 2020 American Chemical Society

High Photocurrent in Gated Graphene-Silicon Hybrid Photodiodes

Graphene/silicon (G/Si) heterojunction based devices have been demonstrated as high responsivity photodetectors that are potentially compatible with semiconductor technology. Such G/Si Schottky junction diodes are typically in parallel with gated G/silicon dioxide (SiO$_2$)/Si areas, where the graphene is contacted. Here, we utilize scanning photocurrent measurements to investigate the spatial distribution and explain the physical origin of photocurrent generation in these devices. We observe distinctly higher photocurrents underneath the isolating region of graphene on SiO$_2$ adjacent to the Schottky junction of G/Si. A certain threshold voltage (V$_T$) is required before this can be observed, and its origins are similar to that of the threshold voltage in metal oxide semiconductor field effect transistors. A physical model serves to explain the large photocurrents underneath SiO$_2$ by the formation of an inversion layer in Si. Our findings contribute to a basic understanding of graphene / semiconductor hybrid devices which, in turn, can help in designing efficient optoelectronic devices and systems based on such 2D/3D heterojunctions.Comment: 25 pages, 5 figure

Atomic Species Associated with the Portevin–Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin--Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, Ea(P718){\thinspace}={\thinspace}2.68{\thinspace}{\textpm}{\thinspace}0.05 eV, $\tau$0{\thinspace}={\thinspace}2{\textperiodcentered}10-15 {\textpm} 1 s as well as its broadening factor $\beta${\thinspace}={\thinspace}1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superallo

User experience and information security : An analysis of challenges

Företag som hanterar känslig patientdata har ett viktigt ansvar, att skydda sina informationstillgångar från diverse hot och se till att datan lagras säkert. Det är också av stor vikt att de anställda har den kunskap som krävs för att följa lagar och regler vid hantering av patientdata. Arbetet med informationssäkerhet kan vara svårt då det gäller att hålla en hög säkerhet, detta ska dock inte komplicera användarnas dagliga arbetsuppgifter. Syftet med denna studie är att öka kunskapen om hur företag som hanterar känslig patientdata kan tillhandahålla hög informationssäkerhet baserat på de anställdas agerande och medvetenhet gällande informationssäkerhet, samtidigt som utförandet av arbetsuppgifterna inte försvåras för användarna. Gällande informationssäkerhet har användarna en central roll i att skydda företags informationstillgångar. En användare är både den viktigaste men också den svagaste länken gällande informationssäkerhet. Anställda måste ha god medvetenhet och engagemang i informationssäkerhetsarbetet samt veta hur de ska agera vid hot eller risk. Det är också viktigt att användarna vet vilken typ av beteende som är acceptabelt när de arbetar i företagets informationssystem för att inte utsätta företaget för onödig risk. Med detta avser studien att besvara följande frågeställning: hur påverkas företags förmåga att skydda känslig data av de anställdas agerande och medvetenhet gällande informationssäkerhet? Studien har genomförts med en kvalitativ datainsamlingsmetod, inklusive kvalitativa semistrukturerade intervjuer med respondenter från samma företag, intervjuerna har genomförts både fysiskt och digitalt. Intervjuerna tillsammans med insamlad litteratur har använts för att uppnå studiens resultat samt besvara frågeställningen och syftet med arbetet. Studiens resultat visar att företags förmåga att skydda sin känsliga data påverkas av de anställdas agerande och medvetenhet om informationssäkerhet. En bristande medvetenhet kan leda till att säkerhetsrisker förblir oupptäckta. Att företag utbildar och informerar sina anställda om olika säkerhetspraxis är centralt för att öka medvetenheten och minska hot. Hantering av lösenord visade sig vara en utmaning, enklare processer och verktyg för lösenordshantering kan underlätta för de anställda