Sealed Bid Auctions vs. Ascending Bid Auctions: An Experimental Study

This paper considers the sealed bid and ascending auction, which both identifies the minimum Walrasian equilibrium prices and where truthful preference revelation constitutes an equilibrium. Even though these auction formats share many theortical properties, there are behavioral aspects that are not easily captured. To explore this issue in more detail, this paper experimentally investigates what role the design of the auction format has for its outcome. The results suggest that the sealed bid mechanism performs weakly better in all of investigated measures (consistent reporting, efficiency etc.). In addition, we find that the performance of the ascending auction is increasing over time, whereas the sealed bid auction shows no such tendency.Auctions; Non-manipulability; Efficiency; Experiments

Antitrust, the Gig Economy, and Labor Market Power

The purpose of the current study was to develop and validate an automatic algorithm for classification of cross-country (XC) ski-skating gears (G) using Smartphone accelerometer data. Eleven XC skiers (seven men, four women) with regional-to-international levels of performance carried out roller skiing trials on a treadmill using fixed gears (G2left, G2right, G3, G4left, G4right) and a 950-m trial using different speeds and inclines, applying gears and sides as they normally would. Gear classification by the Smartphone (on the chest) and based on video recordings were compared. Formachine-learning, a collective database was compared to individual data. The Smartphone application identified the trials with fixed gears correctly in all cases. In the 950-m trial, participants executed 140 ± 22 cycles as assessed by video analysis, with the automatic Smartphone application giving a similar value. Based on collective data, gears were identified correctly 86.0% ± 8.9% of the time, a value that rose to 90.3% ± 4.1% (P < 0.01) with machine learning from individual data. Classification was most often incorrect during transition between gears, especially to or from G3. Identification was most often correct for skiers who made relatively few transitions between gears. The accuracy of the automatic procedure for identifying G2left, G2right, G3, G4left and G4right was 96%, 90%, 81%, 88% and 94%, respectively. The algorithm identified gears correctly 100% of the time when a single gear was used and 90% of the time when different gears were employed during a variable protocol. This algorithm could be improved with respect to identification of transitions between gears or the side employed within a given gear

High Efficiency Microwave Amplifiers and SiC Varactors Optimized for Dynamic Load Modulation

The increasing use of mobile networks as the main source of internet connectivity is creating challenges in the infrastructure. Customer demand is a moving target and continuous hardware developments are necessary to supply higher data rates in an environmentally sustainable and cost effective way. This thesis reviews and advances the status of realizing wideband and high efficiency power amplifiers, which will facilitate improvements in network capacity and energy efficiency. Several demonstrator PAs are proposed, analyzed, designed, and characterized: First, resistive loading at higher harmonics in wideband power amplifier design suitable for envelope tracking (ET) is proposed. A 40 dBm decade bandwidth 0.4–4.1 GHz PA is designed, with 10–15 dB gain and 40–62% drain efficiency. Its versatility is demonstrated by digital pre-distortion (DPD) linearized measurements resulting in adjacent channel leakage ratios (ACLR) lower than −46 dBc for various downlink signals (WCDMA, LTE, WiMAX). Second, a theory for class-J microwave frequency dynamic load modulation (DLM) PAs is derived. This connects transistor technology and load network requirements to enable power-scalable and bandwidth conscious designs. A 38 dBm PA is designed at 2.08 GHz, maintaining efficiencies >45% over 8 dB of output power back-off (OPBO) dynamic range. From this pre-study a fully packaged 86-W peak power version at 2.14 GHz is designed. ACLR after DPD is −46 dBc at a drain efficiency of 34%. For DLM PAs there is a need for varactors with large effective tuning range and high breakdown voltage. For this purpose, SiC Schottky diode varactors are developed with an effective tuning range of 6:1 and supporting a 3:1 tuning ratio at 36 V of RF swing. Nonlinear characterization to enable Q-factor extraction in the presence of distortion is proposed and demonstrated by multi-harmonic active source- and load-pull, offering insights to tunable network design. Third, a method to evaluate and optimize dual-RF input PAs, while catering to higher harmonic conditions and transistor parasitics, is proposed. The method is validated by a PA design having a peak power of 44 +/- 0.9 dBm and 6 dB OPBO PAE exceeding 45% over a 1–3 GHz bandwidth. The results in this thesis contribute with a novel device and analysis of high efficiency and wideband PAs, aiding in the design of key components for future energy efficient and high capacity wireless systems

Air pollution episodes in Stockholm regional background air due to sources in Europe and their effects on human population

Using air quality measurements, we categorized air pollution according to source sectors in a rural background environment in southern Sweden based on hourly air-mass backward trajectories during 1997-2010. Concentrations of fine (PM2.5) and sum of fine and coarse particulate matter (PM10), accumulation mode particle number, black carbon and surface ozone were 4.0, 3.9, 4.5, 6.8 and 1.3 times higher, respectively, in air masses from the southeast as compared with those in air masses from the cleanest sector in the northwest, consistent with air-mass transport over areas with relatively high emissions of primary particulate matter (PM) and secondary PM precursors. The highest ultrafine particle numbers were associated with clean air from the northwest. We estimate that almost 7.8% and 0.6% higher premature human mortality is caused by PM2.5 and ozone exposure, respectively, when air originates from the southeast as compared with that when air originates from the northwest. Reductions of emissions in eastern Europe would reduce the highest air pollution concentrations and associated health risks. However, since air masses from the southwest are more frequent, emissions in the western part of Europe are more important for annual mean premature mortality

Insect olfaction and the evolution of receptor tuning

Insects detect odorants primarily using odorant receptors (OR) housed in the dendritic membrane of olfactory sensory neurons (OSN). Pioneering studies indicated that insects, like mammals, detect odorants in a combinatorial fashion with a specific odor ligand activating several broadly tuned ORs, and each OR being activated by several ligands. Several recent studies, however, challenge this view by providing examples where ecologically relevant odorants are detected by high-specificity ORs activating dedicated neuronal circuits. Here we review these contrasting findings on the ligand selectivity of insect ORs and their neuronal wiring, and outline scenarios describing how adaptive and neutral evolution might shape both narrow and broad receptor tuning. The fact that not all ORs display narrow tuning might partly be due to key ligands having been missed from screens or too high stimuli concentrations being used. However, the birth-and-death model of OR evolution, involving both adaptive and neutral events, could also explain the evolution of broad tuning in certain receptors due to positive selection or relaxed constraint. If the insect olfactory system indeed contains both narrowly and broadly tuned ORs, this suggests that it is a hybrid between dedicated channels and combinatorial coding. The relative extent of the two coding modes is then likely to differ between species, depending on requirements of perceived chemical space and the size of the OR repertoire. We address this by outlining scenarios where certain insect groups may be more likely to have evolved combinatorial coding as their dominant coding strategy. Combinatorial coding may have evolved predominantly in insects that benefit from the ability to discriminate between a larger number of odorants and odor objects, such as polyphagous or social species. Alternatively, combinatorial coding may have evolved simply as a mechanism to increase perceived odor space in species with small OR repertoires

Large Eddy Simulations of Fully-Developed Turbulent Pipe Flows At Moderate-To-High Reynolds Numbers

Despite the high relevance of wall-bounded turbulence for engineering and natural science applications, many aspects of the underlying physics are still unclear. In particular, at high Re close to many real-life scenarios, the true nature of the flow is partially masked by the inability of numerical simulations to resolve all turbulent scales adequately. To overcome this issue, we aim to numerically investigate fully-developed turbulent pipe flows at moderate-to-high Re ($361 \leq Re_\tau \leq 6,000$), employing LES. A grid convergence study, using the WALE subgrid stress model, is presented for $Re_\tau=361$. Additionally, the prediction accuracy of distinct subgrid-scale stress models, such as WALE, SMG, OEEVM, LDKM, and DSEM, is examined using a range of statistical measures. The results infer, as expected, that SMG and OEEVM are too dissipative, whereas WALE, LDKM, and, more surprisingly, DSEM perform rather well compared to experiments and results from DNS. Moreover, LES utilizing WALE are performed and investigated in detail for six different Reynolds numbers in the interval from $Re_\tau = 361$ to $6,000$ with gradually refined grids. These computations allow an insight into what turbulence information is retained when LES with a wall model is applied to such high Reynolds numbers in the limit of a relatively coarse grid. Second-order statistics for all values of $Re_\tau$ exhibited excellent agreement with the DNS data in the outer region. Surprisingly, results also revealed a dramatic deviation from the DNS data in the sub-viscous layer region irrespective of the $Re_\tau$, attributed to the considered scaling for mesh refinement. Overall, the WALE model enabled accurate numerical simulations of high-Reynolds-number wall-bounded flows at a fraction of the cost incurred if the inner layer was temporally and spatially resolved

Self-certified sybil-free pseudonyms

Accurate and trusted identifiers are a centerpiece for any security architecture. Protecting against Sybil attacks in a privacy-friendly manner is a non-trivial problem in wireless infrastructureless networks, such as mobile ad hoc networks. In this paper, we introduce self-certified Sybil-free pseudonyms as a means to provide privacy-friendly Sybil-freeness without requiring continuous online availability of a trusted third party. These pseudonyms are self-certified and computed by the users themselves from their cryptographic longterm identities. Contrary to identity certificates, we preserve location privacy and improve protection against some notorious attacks on anonymous communication systems

Loss of size-selectivity at histamine-induced exudation of plasma proteins in atopic nasal airways.

Plasma proteins occur in the airway lumen in inflammatory airway diseases. This study tests the hypothesis that airway microvascular-epithelial exudation of plasma proteins, as induced by a non-injurious inflammatory mediator, is characterized by loss of size-selectivity. Using a nasal pool-device, the nasal mucosa of 10 allergic individuals, without current disease, was sequentially exposed to saline and histamine (40 and 400 microg ml(-1)). Nasal lavage fluid and blood-levels of albumin (69 kD) and alpha2-macroglobulin (720 kD) were determined. Histamine produced concentration-dependent exudation of albumin and alpha2-macroglobulin. The albumin/alpha2-macroglobulin concentration ratio of the saline lavage fluid (baseline) was 40+/-19. However, at the histamine challenges the ratios were 25+/-3 and 22+/-2, respectively, which did not differ from that of circulating plasma (22+/-2). We conclude that there is minor and size-selective luminal entry of plasma proteins at baseline. However, at concentration-dependent exudative responses to histamine, plasma proteins enter the airway lumen without being sieved. These data indicate that inflammatory stimulus-induced extravasation, lamina propria distribution and paracellular epithelial passage of plasma occur with minimal size-selectivity. Inferentially, the full immunological capacity of plasma proteins may readily be made available at the surface of human intact airway mucosa