Thermionic emission current in a single barrier varactor

From I-V measurements on Single Barrier Varactors (SBV) at different temperatures we concluded that thermionic emission across the barrier of the actual device is mainly due to transport through the X band. The same structure was also modeled with a one-dimensional drift-diffusion model, including a 'boundary condition' for thermionic emission across the heterojunction interface. By including thermionic field emission through the top of the triangular barrier of a biased diode and the effect of a non-abrupt interface at the heterojunction, we obtained good agreement between the modeled and measured I-V characteristics

Progress on single barrier varactors for submillimeter wave power generation

Theoretical work on Single Barrier Varactor (SBV) diodes, indicate that the efficiency for a multiplier has a maximum for a considerably smaller capacitance variation than previously thought. The theoretical calculations are performed, both with a simple theoretical model and a complete computer simulation using the method of harmonic balance. Modeling of the SBV is carried out in two steps. First, the semiconductor transport equations are solved simultaneously using a finite difference scheme in one dimension. Secondly, the calculated I-V, and C-V characteristics are input to a multiplier simulator which calculates the optimum impedances, and output powers at the frequencies of interest. Multiple barrier varactors can also be modeled in this way. Several examples on how to design the semiconductor layers to obtain certain characteristics are given. The calculated conversion efficiencies of the modeled structures, in a multiplier circuit, are also presented. Computer simulations for a case study of a 750 GHz multiplier show that InAs diodes perform favorably compared to GaAs diodes. InAs and InGaAs SBV diodes have been fabricated and their current vs. voltage characteristics are presented. In the InAs diode, was the large bandgap semiconductor AlSb used as barrier. The InGaAs diode was grown lattice matched to an InP substrate with InAlAs as a barrier material. The current density is greatly reduced for these two material combinations, compared to that of GaAs/AlGaAs SBV diodes. GaAs based diodes can be biased to higher voltages than InAs diodes

The effect of willow diversity on insect herbivory and predation

The relationship between plant diversity and ecosystems functions such as regulation of insect herbivory is complex and context-dependent. The empirical data necessary to account for these interactions are scarce. Our objective is to test the top-down effects of predation and bottom-up effects of plant traits to understand what drives patterns of herbivory in managed systems. We established single- and multiple-variety willow field plots with up to four varieties, to study herbivory and predation, and greenhouse experiments to investigate the effects on insect preference and performance. Herbivore damage in the field was higher in single- as opposed to multiple-variety plots for the two most prevalent insect types in one of the 3 years. Predation was higher in multiple-variety plots than in pure plots during 2016 but the opposite occurred in 2018. Predation on leaf beetle eggs was higher in multiple-variety plots, but the result was related to specific variety mixtures rather than increased numbers of varieties. Leaf beetle feeding choice and egg-laying were influenced to some extent by plant diversity. Our results give insights into the links between plant diversity, composition and levels of herbivore damage. They also spark questions about how temporal aspects influence these links

Insurance loss data for improved climate change adaptation. Conditions for data sharing and utilization

Climate change has led to an increased risk of damage to buildings and infrastructure. Norwegian municipalities have intensified their efforts to address climate change adaptation and the prevention of climate-related damage due to natural hazards. The Norwegian Directorate for Civil Protection (DSB) has developed a so-called ‘Knowledge Bank’, which is a Norwegian web-based data platform containing information about risk and vulnerability related to natural events. The Knowledge Bank serves to compile civil protection data and makes these available to municipalities, providing them with an improved overview and knowledge about undesirable events and natural disasters as a basis for cost-benefit analysis, risk, and vulnerability assessments. The platform also includes data related to natural and weather-related damage derived from insurance companies. Previous research related to insurance data and the Knowledge Bank carried out at the Klima 2050 Centre has addressed attitudes to data sharing among insurance companies, the value of insurance data, and the potential to use these data to predict events. It has also addressed the municipalities' initial perceptions and experiences. Expectations linked to a new system for sharing insurance loss data in the Knowledge Bank are high, but several issues still need to be resolved before the system can be fully exploited. There is need to improve the understanding of key factors related primarily to data sharing and quality, as well as the relevant regulatory frameworks. This will enable insurance data to become available via the Knowledge Bank so that they can be utilized by municipalities in a way that will benefit wider society. This report presents the results of a study that addresses the critical factors required for the establishment of a new system allowing insurance companies to share insurance loss data with municipalities, using the Knowledge Bank platform.publishedVersio

Regulation of forest defoliating insects through small mammal predation

Population densities of forest defoliating insects may be regulated by small mammal predation on the pupae. When outbreaks do occur, they often coincide with warm, dry weather and at barren forest sites. A proposed reason for this is that weather and habitat affect small mammal population density (numerical response) and hence pupal predation. We propose an alternative explanation: weather and habitat affect small mammal feeding behaviour (functional response) and hence the outbreak risks of forest pest insects. We report results from laboratory and field-enclosure experiments estimating rates of pupal predation by bank voles (Myodes glareolus) on an outbreak insect, the European pine sawfly (Neodiprion sertifer), at different temperatures (15 and 20 A degrees C), in different microhabitats (sheltered and non-sheltered), and with or without access to alternative food (sunflower seeds). We found that the probability of a single pupa being eaten at 20 A degrees C was lower than at 15 A degrees C (0.49 and 0.72, respectively). Pupal predation was higher in the sheltered microhabitat than in the open one, and the behaviour of the voles differed between microhabitats. More pupae were eaten in situ in the sheltered microhabitat whereas in the open area more pupae were removed and eaten elsewhere. Access to alternative food did not affect pupal predation. The results suggest that predation rates on pine sawfly pupae by voles are influenced by temperature- and habitat-induced variation in the physiology and behaviour of the predator, and not necessarily solely through effects on predator densities as previously proposed

Näyttelemisen ruumiillisuus ja intuitio : kaksi tapaani lähestyä opittua

Tässä teatteritaiteen maisterin opinnäytteessäni jäsennän ja artikuloin omaa näyttelemistäni ja näyttelijäntekniikkaani. Ajattelussani korostuvat erityisesti näyttelemisen ruumiillisuus ja ruumiin ajattelu. Tavoitteeni on näyttelemiseni avaamisen myötä ennen kaikkea paremmin ymmärtää näyttelemisen ytimessä olevaa vaikeasti sanallistettavaa ruumiillista elementtiä. Olen nimennyt tämän elementin ruumiinintuitioksi, korostaakseni näyttelemiseni ruumiillisuutta ja intuitiivisuutta erotuksena mielen ja tietoisen ajattelun tasosta. Kuvaan esimerkkien kautta ruumiinintuition seuraamisen roolia käyttökelpoisen näyttelemisen materiaalin tuottajana. Tarkastelen myös vaihtuvien näyttelemisen parametrien muodostamaa kehystä, jossa ruumiinintuitioni toimii. Tätä aina kulloiseenkin näyttelemisen kontekstiin liittyvää kehystä nimitän ruumiinlogiikaksi. Muita oleellisia käsittelemiäni näkökulmia näyttelemiseeni ovat leikki, subjektiviteetti, huomion ohjaaminen, Chekhov-tekniikka sekä itsetunto. Tukeudun tässä opinnäytteessäni oman kokemukseni lisäksi erityisesti Mikko Bredenbergin väitöstutkimukseen, Katariina Nummisen leikkiä käsittelevään artikkeliin, Elina Pirisen haastatteluun sekä Lenard Petitin pitämään Chehov- tekniikan kurssiin. Käytännön näyttelemisen kuvauksien pohjana toimivat erityisesti työharjoitteluproduktioni Saituri Oulun kaupunginteatterissa 2017–2018 sekä taiteellinen opinnäytteeni Jyväskylän kaupunginteatterin Sydänmaa-produktiossa 2018–2019. Opinnäytteeni lopputuloksena on näyttelemistäni itselleni relevantilla tavalla sanallistava malli, joka kuvaa tämänhetkistä käsitystäni omasta näyttelemisestäni. Pyrin näissä käytännön kuvauksissa pääsemään sen äärelle, miltä näytteleminen tuntuu ruumiissani, ja miten hahmottelemaani näyttelemisen mallia käytän. Toivon muidenkin voivan saada siitä näkökulmaa omaan näyttelijäntyölliseen ajatteluunsa. Pyrin tämän opinnäytteeni kautta osaltani osallistumaan laajempaan käynnissä olevaan näyttelemisen sanallistamisen prosessiin

Early growth development after nitrogen fertilization of SeedPADs and plants

I boreala skogar begränsas trädens tillväxt av olika ståndortsfaktorer och främst är det temperatur, tillgång till solljus, vatten och mineralnäring som utgör hinder. Makronäringsämnet kväve är det mineralnäringsämne som till stor del begränsar tillväxten i nordliga barrskogar. Etablering av den nya föryngringen är som mest känslig de tio första åren och ju större plantan blir desto bättre blir chanserna till överlevnad. Sådd som föryngringsmetod kantas av stor fröåtgång och osäkra föryngringsresultat vilket resulterat i utvecklandet av SweTree Technologies SeedPAD koncept. Konceptet består i användandet av ett förädlat plantagefrö inkapslat i en påse med ett hygroskopiskt material i syfte att öka plantbildningen och därmed minska frömängden, öka etableringsandelen och möjliggöra en förädlingsvinst. I denna studie utfördes tre försök i syfte att utröna om tillförsel av olika kväveformer påverkar den tidiga tillväxten. Två försök utfördes i fält med SeedPAD och ettåriga täckrotsplantor och ett försök i växthus med enbart SeedPAD. Totalt testades sex olika behandlingsalternativ i fält och tre i växthusförsöket. I växthuset testades även tre olika nivåer per behandlingsalternativ. Mätningar utfördes efter fyra månader med avseende på etablering, tillväxt samt kväveinnehåll. Överlevnaden var mycket god oavsett behandling i fält. Av alla behandlingsalternativ för SeedPAD var det endast ett alternativ som gav signifikanta tillväxtskillnader i både fält- och växthusförsöket. För SeedPAD i fält uppmättes en dubblering i tillväxt vid jämförelse med de ogödslade substraten och i växthuset en femfaldig ökning. För täckrotsplantorna uppmättes i genomsnitt 30 procents tillväxtökning för de gödslade plantorna. De var behandlade med ett kvävealternativ som inte gav någon tillväxtökning för SeedPAD. Procentuell rottillväxt skiljde sig inte signifikant åt mellan gödslade och ogödslade substrat. Resultaten i denna studie visar att det finns stor potential till förbättrad tillväxt under första växtsäsongen vid sådd med SeedPAD och planterade plantor. Betydelsen av tillförd kvävekälla, kombination och nivå är dock stor för att effekt skall visas under första växtsäsongen.Tree growth in boreal forests is limited by various site factors. Temperature, available sunlight, water and mineral nutrition are critical factors when establishing a new generation of seedlings. In these forest ecosystems, nitrogen is the factor most often restricting growth. The first ten years are the most sensitive ones when regenerating with sowing. About half of the established seedlings year one will have died at year ten. Bigger plants have greater chances of survival and successfully establish a new regeneration. Sowing as regeneration method is known for its doubtful establishment results, resulting in the development of SweTree Technologies SeedPAD concept. The concept consists of a refined seed in a package with a hygroscopic material promoting survival establishment and hence enabling reduction of the number of seeds per hectare. This would then enable use of high-value seed sources. Three different experiments were made in order to determine whether different nitrogen sources affect the early growth. Two field experiments was performed with SeedPAD and one-year-old seedlings. The third experiment was performed on SeedPAD in a greenhouse. Six different nitrogen combinations were tested in the field experiments and three combinations in the greenhouse experiment. Different levels of nitrogen fertilization were also tested in the greenhouse experiment. After four months’ measurements were performed regarding establishment, growth and nitrogen supply. The survival of SeedPAD seedlings was very good regardless of treatment in the field experiment. All experiments showed clear significant growing differences depending on the specific nitrogen treatment. Of all combinations for SeedPAD only one treatment showed significant difference. In the field experiments with SeedPAD a doubling of growth was measured for one nitrogen treatment in comparison with the untreated SeedPADs and in the greenhouse experiment the growth was five times as high as for untreated seedlings. For the one-year-old seedlings, an average of 30 % increase in growth for the fertilized seedlings were found. The results from this study indicates there is a great potential to improve the early growth of seedlings within the first growing season. The importance of nitrogen source, combination and level is great in order to show effect during the first season

User evaluation of a national web portal for climate change adaptation – A qualitative case study of the Knowledge Bank

This paper describes the development and first user evaluation of a web portal (The Knowledge Bank) for collecting and presenting national data relevant to climate change adaptation in Norway, including insurance loss data for damages arising from natural hazards and weather events. The paper examines the major drivers for municipal decision-makers to use the Knowledge Bank, presenting the results of a qualitative case study with group interviews with 11 users representing both smaller and larger Norwegian municipalities, and an individual interview with one of the developers. The findings show that the drivers for using the Knowledge Bank depend on the level of user expectations, user trust in the tool and the data, expectations for a contribution to efficiency, expectations for increased cooperation between municipal departments and municipalities, and the ability to interact with the portal, especially the ability to transfer data to and from their own data systems. Increased uptake and use of the Knowledge Bank could be reinforced with networks of users sharing awareness of the portal, teaching other users, and promoting improvement. The study provides insights into the challenges and opportunities encountered in the development of the Knowledge Bank and gives examples of how the size of the municipality may shape the drivers for uptake. These insights may also apply to the development of other national web portals for climate change adaptation data, especially when trying to incorporate sharing of insurance loss data.publishedVersio

A Distributed Heterostructure Barrier Varactor Frequency Tripler

We present a broadband nonlinear transmission line (NLTL) frequency multiplier at F-band. The multiplier consists of a finline section periodically loaded with 15 heterostructure barrier varactor (HBV) diodes. Tapered slot antennas are used to couple the fundamental signal from a WR-22 rectangular waveguide to the distributed multiplier as well as radiate the output power into free space. The frequency tripler exhibits 10-dBm peak radiated power at 130.5 GHz with more than 10% 3-dB bandwidth and 7% conversion efficiency. The tripler can be used as an inexpensive broad-band solid-state source for millimeter-wave applications