| 1. |
- Anchev, Stefan, 1986-
(författare)
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Information and financial markets
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The results in this thesis are consistent with the hypotheses that: 1) the incomplete dissemination of information across investors helps in explaining the occurrence and the persistence of cross-sectional stock return anomalies, 2) the properties of the investor base of a stock have implications for the informativeness of the stock's price and 3) a greater quantity of firm disclosure places less sophisticated investors at an information disadvantage. Overall, the thesis provides new empirical evidence about the role of information in financial markets.Investor Base and Stock Return AnomaliesAfter controlling for market capitalization, the predictability of future stock returns associated with each of the earnings-to-price ratio, the book-to-market ratio, the past return, the total volatility of returns and the return on assets is more pronounced among stocks with smaller total and/or institutional investor bases. These results appear even after controlling for several other stock characteristics and potential risk factors and they are both statistically and economically meaningful. Thus, they are consistent with the hypothesis that the incomplete dissemination of information across investors helps in explaining the occurrence and the persistence of cross-sectional stock return anomalies.Investor Base and Stock Price InformativenessThe relative idiosyncratic volatility of future stock returns is: 1) negatively associated with the absolute size of the total and the institutional investor base, 2) positively associated with the institutional ownership, 3) negatively (positively) associated with the average stock portfolio size (Herfindahl index) of the investor base and 4) positively associated with the indirect (i.e., through nominees) ownership. These results appear after controlling for several other stock characteristics and they are both statistically and economically meaningful. Thus, they are consistent with the hypothesis that the properties of the investor base of a stock have implications for the informativeness of the stock's price.Individual Investors and Quantity of Firm DisclosureWhen the amount of information disclosed by a firm is greater (or increases), the stock portfolio weights that individual investors allocate (through trading) to that firm's stock are lower (or decrease) and suboptimal. The former result is less pronounced or nonexistent for more financially competent individuals and for positions in firms with a poorer information environment. When they do allocate greater portfolio weights to the stock of a firm that discloses more, individuals, regardless of their financial competence, earn lower returns. Overall, these results are consistent with the hypothesis that a greater quantity of firm disclosure places less sophisticated investors at an information disadvantage.
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| 2. |
- Tong, Renbin
(författare)
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Efficient Solid-State Power Amplifiers for RF Power Source Applications
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Radio Frequency (RF) power sources are extensively applied in various fields. Radioisotope production, i.e., the production of short-lived radioactive isotopes, for positron emission tomography (PET) is one of the most important applications in the medical and healthcare domains. Full-time operation and substantial maintenance of such systems lead to high operating expenses. Hence, the development of more efficient and reliable RF power amplifiers, which are the main contributors to the energy consumption and maintenance costs of the RF power sources, is a high priority. Solid-state technology has emerged as a viable alternative to conventional vacuum tube based high-power RF/microwave systems, offering advanced control, reliability, and ease of use. Power amplifiers based on solid-state technology enable dynamic adjustment of power to optimize the transmitted energy. Furthermore, solid-state power amplifiers (SSPA) technology shows a longer lifetime leading to increased uptime and lower maintenance costs. Concisely, with the introduction of solid-state technology in high-power RF sources, RF energy can be generated more efficiently and more controllable in a smaller form factor, allowing for more compact systems with less downtime and less maintenance. This thesis is one step further toward demonstrating the feasibility of such systems.The thesis first introduces the RF measurement setup. It implements automation for quick measurements and supports the evaluation of the high-power RF performance of the developed SSPA modules. Moreover, a novel thru-only de-embedding approach is developed to address the calibration difficulties under multi-port excitation conditions. The second part of the thesis deals with the development and analysis of efficient kilowatt SSPA modules. A multimode SSPA with quasi-static supply control for power regulation is implemented. It achieves more than 90% efficiency over a 5 dB output power back-off range. Another compact and efficient SSPA, implemented in push-pull architecture, adopts harmonic load-pull integrated with the same quasi-static supply modulation which also achieves 90% efficiency over a 5 dB output power back-off range. The implemented SSPAs improve the state-of-the-art in these frequency bands and power ranges.This thesis broadens RF SSPA theoretical research to the kilowatt power range and provides a new understanding of high-power SSPAs from circuits, design methodologies, and analytical approaches. And it leads to new methods and tools to improve the energy efficiency of high-power RF sources. The knowledge gained and technology developed is not limited to RF power sources in radioisotope production applications, it can also be applied in the communication industry, such as radar systems, and other RF energy systems in industrial, scientific, and medical (ISM) fields, such as particle accelerators, welding, drying, heating, and many more.
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| 3. |
- Stålnacke, Oscar, 1988-
(författare)
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What do you expect? : individual investors' subjective expectations, information usage, and social interactions in financial decision-making
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis consists of an introductory part and four self-contained papers related to individual investors’ subjective expectations and their financial behavior. Paper [I] analyzes multiple measures of individual investors’ expectations of risk and return using survey data on a random sample of individual investors in Sweden. The results indicate that, even though expectations from different measures are correlated, the magnitude of especially the risk expectations varies considerably between measures. The variations in the expectations mainly relate to differences in the responses to the questions underlying the different measures, rather than to the methods used to obtain them. Evaluation of the measures using three different comparisons indicates that the expectation measure proposed by Dominitz and Manski (2011) is the only measure for which it is possible to distinguish between individuals’ expectations using all of the considered comparisons.Paper [II] addresses the relationship between sophistication and the expectations of individual investors with respect to risk and return. The findings show that sophisticated investors have lower (higher) risk (return) expectations that are closer to objective measures than less sophisticated investors. These results are important, since they enhance the understanding of the underlying mechanisms through which sophistication could influence individuals’ financial decisions.Paper [III] provides new evidence for the sources of information individual investors’ use when making financial decisions and the relationship between how frequently investors use this information and their expectations of the risk and return in a stock market index, their confidence in these expectations, and their portfolio risk and return. The findings indicate that individual investors use different sources of filtered financial information (e.g., information packaged by a professional intermediary) more frequently than unfiltered financial information (e.g., information from annual reports and financial statements). However, an increase in the frequency with which investors use filtered financial information is positively related to their confidence in their stock-market expectations and to the risk in their stock portfolios. For investors who instead use unfiltered financial information more frequently than filtered financial information, the results indicate that they have more accurate stock-market expectations, lower portfolio risk, and higher portfolio return.Paper [IV] links individual investors’ financial risk-taking to the behavior of peers within their community. By using detailed data at the individual level, it is found that the risk-taking among peers affects individuals’ choice of portfolio risk. The results hold for the full sample of individuals concerning their choice of the overall proportion of risky assets and stock market participants’ choice of total and systematic stock-portfolio risk. Overall, the results stress that interaction with peers is an important channel through which individual risk-taking is affected.
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| 4. |
- Azam, Sher, 1971-
(författare)
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Wide Bandgap Semiconductor (SiC & GaN) Power Amplifiers in Different Classes
- 2008
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- SiC MESFETs and GaN HEMTs have an enormous potential in high-power amplifiers at microwave frequencies due to their wide bandgap features of high electric breakdown field strength, high electron saturation velocity and high operating temperature. The high power density combined with the comparably high impedance attainable by these devices also offers new possibilities for wideband power microwave systems. In this thesis, Class C switching response of SiC MESFET in TCAD and two different generations of broadband power amplifiers have been designed, fabricated and characterized. Input and output matching networks and shunt feedback topology based on microstrip and lumped components have been designed, to increase the bandwidth and to improve the stability. The first amplifier is a single stage 26-watt using a SiC MESFET covering the frequency from 200-500 MHz is designed and fabricated. Typical results at 50 V drain bias for the whole band are, 22 dB power gain, 43 dBm output power, minimum power added efficiency at P 1dB is 47 % at 200 MHz and maximum 60 % at 500 MHz and the IMD3 level at 10 dB back-off from P 1dB is below ‑45 dBc. The results at 60 V drain bias at 500 MHz are, 24.9 dB power gain, 44.15 dBm output power (26 W) and 66 % PAE.In the second phase, two power amplifiers at 0.7-1.8 GHz without feed back for SiC MESFET and with feedback for GaN HEMT are designed and fabricated (both these transistors were of 10 W). The measured maximum output power for the SiC amplifier at Vd = 48 V was 41.3 dBm (~13.7 W), with a PAE of 32 % and a power gain above 10 dB. At a drain bias of Vd= 66 V at 700 MHz the Pmax was 42.2 dBm (~16.6 W) with a PAE of 34.4 %. The measured results for GaN amplifier are; maximum output power at Vd = 48 V is 40 dBm (~10 W), with a PAE of 34 % and a power gain above 10 dB. The SiC amplifier gives better results than for GaN amplifier for the same 10 W transistor.A comparison between the physical simulations and measured device characteristics has also been carried out. A novel and efficient way to extend the physical simulations to large signal high frequency domain was developed in our group, is further extended to study the class-C switching response of the devices. By the extended technique the switching losses, power density and PAE in the dynamics of the SiC MESFET transistor at four different frequencies of 500 MHz, 1, 2 and 3 GHz during large signal operation and the source of switching losses in the device structure was investigated. The results obtained at 500 MHz are, PAE of 78.3%, a power density of 2.5 W/mm with a switching loss of 0.69 W/mm. Typical results at 3 GHz are, PAE of 53.4 %, a power density of 1.7 W/mm with a switching loss of 1.52 W/mm.
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| 5. |
- Lapanan, Nicha, 1987-
(författare)
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Individual investors and socially responsible mutual funds
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines the behavior of individual investors towards socially responsible mutual funds. The results are reported in the four self-contained papers.Paper [I] profiles SR individual investors. An understanding of SR investors' characteristics is important for the development of hypotheses and for understanding the adoption of SR investing. We find evidence indicating, for example, that females, more educated, relatively older individuals, those with higher wealth and those living in municipalities with a higher proportion of SR investors are more likely to hold SR equity mutual funds.Paper [II] studies the relation between investments of adult children and their parents. The paper explores the importance of parent-child socialization in the formation of prosocial behavior. The study contributes to the understanding of when prosocial behavior is formed and how parent-child relationships influence it. We find evidence that there is a correlation between parents and children in the investment in SR mutual funds and that parental resources and parental experience are influential in the transmission of this prosocial behavior.Paper [III] documents individual investors' trading behavior in relation to SR equity mutual funds. Results indicate that SR investors are less likely to sell SR than conventional fund as past negative returns decrease. Nonetheless, fund flows of SR and conventional funds are similarly sensitive to past returns. There is, however, evidence that sticky SR investors' fund flows are more sensitive to past positive returns and are less sensitive to past negative returns on their SR than on their conventional funds. Despite sticky SR investors showing behavior in line with values-driven motives, they also appear to be less likely to reinvest in SR than in conventional funds.Paper [IV] examines whether SR investors are willing to forgo higher returns to invest responsibly. Based on administrative data on individual investors' equity mutual fund portfolios, it is found that socially responsible (SR) investors forgo return by investing in a socially responsible manner. In comparison with similar conventional investors (in terms of characteristics), SR investors have an equal performance on their non-SR part of their total portfolio, but an inferior performance on their SR part. Analysis of individuals' money flows to funds further indicate that fund flows of SR investors who invest in only SR funds are less sensitive to past returns. Given that investors who value non-financial fund attributes, e.g., ethical or social, may be presumed to care less about the financial performance, the results lend support to an investment behavior, at least partly, driven by prosocial concerns. Taken together, the findings favor the interpretation that some individuals willingly forgo higher financial returns to invest in accordance with their social preferences.
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| 6. |
- Sjöblom, Gustaf, 1975-
(författare)
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Metal Gate Technology for Advanced CMOS Devices
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The development and implementation of a metal gate technology (alloy, compound, or silicide) into metal-oxide-semiconductor field effect transistors (MOSFETs) is necessary to extend the life of planar CMOS devices and enable further downscaling. This thesis examines possible metal gate materials for improving the performance of the gate stack and discusses process integration as well as improved electrical and physical measurement methodologies, tested on capacitor structures and transistors. By using reactive PVD and gradually increasing the N2/Ar flow ratio, it was found that the work function (on SiO2) of the TiNx and ZrNx metal systems could be modulated ~0.7 eV from low near nMOS work functions to high pMOS work functions. After high-temperature anneals corresponding to junction activation, both metals systems reached mid-gap work function values. The mechanisms behind the work function changes are explained with XPS data and discussed in terms of metal gradients and Fermi level pinning due to extrinsic interface states.A modified scheme for improved Fowler-Nordheim tunnelling is also shown, using degenerately doped silicon substrates. In that case, the work functions of ALD/PVD TaN were accurately determined on both SiO2 and HfO2 and benchmarked against IPE (Internal Photoemission) results. KFM (Kelvin Force Microscopy) was also used to physically measure the work functions of PVD TiN and Mo deposited on SiO2; the results agreed well with C-V and I-V data.Finally, an appealing combination of novel materials is demonstrated with ALD TiN/Al2O3/HfAlOx/Al2O3/strained-SiGe surface channel pMOS devices. The drive current and transconductance were measured to be 30% higher than the Si reference, clearly demonstrating increased mobility and the absence of polydepletion. Finally, using similarly processed transistors with Al2O3 dielectric instead, low-temperature water vapour annealing was shown to improve the device characteristics by reducing the negative charge within the ALD Al2O3.
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