Mobilities and the network of personal technologies: Refining the understanding of mobility structure

Our ambition here is to refine the various typologies that compose the mobility structure. We aim to complement the work done by Urry and investigate the role played in the structure of mobility by what we call the “network of personal technologies”. Our new model consists of four different levels: macro-mobilities, micro-mobilities, media mobility and disembodied mobilities. By “macro-mobilities,” we refer to the actions which imply consistent physical displacement, such as travels, tours and commuting. By “micro-mobilities,” we mean small-scale displacements, including bodily movements and emotions. With moving media, we refer both to the new mobility provided by the smartphone to the traditionally fixed media and to the penetration of these into public spaces. Finally, “disembodied mobility” designates the transformations that have taken place within the social order as earlier hierarchies of dimensions, values and meanings have been overturned. Hopefully, this new model will enable us to enhance the analysis of mobility structure by taking human beings and their bodies as a point of reference.     

Local anomaly detection for mobile network monitoring

Huge amounts of operation data are constantly collected from various parts of communication networks. These data include measurements from the radio connections and system logs from servers. System operators and developers need robust, easy to use decision support tools based on these data. One of their key applications is to detect anomalous phenomena of the network. In this paper we present an anomaly detection method that describes the normal states of the system with a self-organizing map (SOM) identified from the data. Large deviation in the data samples from the SOM nodes is detected as anomalous behavior. Large deviation has traditionally been detected using global thresholds. If variation of the data occurs in separate parts of the data space, the global thresholds either fail to reveal anomalies or reveal false anomalies. Instead of one global threshold, we can use local thresholds, which depend on the local variation of the data. We also present a method to find an adaptive threshold using the distribution of the deviations. Our anomaly detection method can be used both in exploration of history data or comparison of unforeseen data against a data model derived from history data. It is applicable to wide range of processes that produce multivariate data. In this paper we present examples of this method applied to server log data and radio interface data from mobile networks.     

Adoption barriers of network layer protocols: The case of host identity protocol

With increasing societal dependence on the Internet and new application areas emerging, the need for securing communications and identifying communication partners is expected to increase. However, the original Internet architecture is lacking these functionalities, and most of the protocols proposed to fix these issues have not been widely deployed. Often one of the reasons for such failure is that protocol designers have insufficient understanding of the potential adopters’ economic incentives so one may end up designing protocols based on false or inaccurate assumptions. In this paper, we analyze the Host Identity Protocol (HIP) from this viewpoint. Based on 19 expert interviews, we identify six main reasons why HIP has not been widely deployed yet. Most importantly, (1) the demand for the functionalities of HIP has been low. Where demand would have existed, substitute solutions have been favored because (2) they were earlier on the market, (3) they have relative advantage due to some design choices of HIP, (4) HIP lacks early adopter benefits necessitating costly coordination among multiple stakeholders in public deployment scenarios, and (5) people have misconceptions about the deployability of HIP. Additionally, (6) the research-mindedness of HIP developers has lead to strategic mistakes and non-optimal design choices from the perspective of deployment. We also suggest strategies that HIP developers could take to foster the adoption of HIP. Besides providing value to HIP developers, the results propose some new adoption barriers and deployment strategies that could be taken into account when designing new protocols. Finally, the article also provides a template that could be followed when studying the feasibility of other protocols.     

Quantization noise upconversion effects in mixer-first direct delta-sigma receivers

In this paper, we investigate the application of the direct ΔΣ receiver (DDSR) concept in a mixer-first architecture. Specifically, we analyze the degrading effects of quantization noise (Q_n) upconversion on DDSR sensitivity, which is a major concern in mixer-first DDSR architecture. We demonstrate that with the chosen approach, the mixer-first architecture is suitable for the DDSR despite the potential challenges arising from Q_n upconversion. A systematic modeling and understanding of Q_n upconversion effects is presented, which lead to simple design guidelines. The results demonstrate that a first-order low-pass Q_n filtering is sufficient in most cases for mixer-first DDSR implementations. Based on analytical results, we design a transistor-level mixer-first DDSR by merging the functionality of N-path capacitors both as channel select and Q_n filters. Simulations performed in a 28-nm complementary metal-oxideŰsemiconductor (CMOS) process show a mere 1.5-dB degradation from maximum signal-to-noise and distortion ratio (SNDR) for the worst-case scenarios arising from Q_n upconversion effects, validating the chosen approach.     

PEM water electrolyzer model for a power-hardware-in-loop simulator

Power-electronics-based power-hardware-in-loop (PHIL) simulator for water electrolyzer emulation with a nominal current of 405 A is developed to study the electrolyzer as part of a smart grid and to analyze the characteristics of various electrolyzer power supply electronics. A simplified model of a proton exchange membrane (PEM) electrolyzer is implemented into the PHIL simulator to describe the voltage and current characteristics of the electrolyzer stack. The model is verified comparing the current and the estimated hydrogen production of the PHIL simulator with the measured values of the commercial PEM electrolyzer following the measured solar photovoltaic (PV) system output power.     

Direct synthesis of high-quality single-walled carbon nanotubes by the physical nucleation of iron nanoparticles in an atmospheric pressure carbon monoxide flow

We demonstrate a direct and stable aerosol synthesis of single-walled carbon nanotubes (SWCNTs) using a hot wire generator (HWG) method, with iron physically evaporated in a carbon monoxide (CO) atmosphere as the catalyst source. A small amount of added carbon dioxide increased the lifetime of the Fe wire in reacting CO up to several weeks. This approach allowed us to significantly increase the yield of SWCNTs as compared to the previously employed inert hydrogen-containing flow through the wire. High quality and purity SWCNTs were produced, as demonstrated by high-resolution transmission electron microscopy and Raman and optical absorption spectroscopy.     

Effects of de-icing chemicals sodium chloride and potassium formate on cadmium solubility in a coarse mineral soil

Excessive use of sodium chloride (NaCl) as de-icing chemical causes environmental problems, such as elevated chloride concentrations in groundwater. On vulnerable sites, this can be avoided by using alternative organic de-icing chemicals, such as potassium formate (KHCOO). The environmental impacts of KCHOO are, however, not well known. This study reports the potential effects of NaCl and KCHOO on mechanisms controlling the mobility of cadmium (Cd) in roadside soils as a result of vehicular traffic. Changes in the solubility of Cd in a coarse mineral soil treated with these two de-icing chemicals were studied in a 50-day incubation experiment under four different moisture and temperature combinations and an initial soil Cd concentration of 3 mg kg(-1). After incubation, the distribution of soil Cd into different fractions was analyzed using a sequential extraction method. Soil pH and soil redox potential were recorded and the occurrence of Cd-Cl complexes in the soil was estimated using published stability constants. During incubation, KCHOO lowered the soil redox potential, but this was not accompanied by a decrease in the sorption capacity of oxides and the release of oxide-bound Cd into soil solution. On the other hand, elevated pH (from 4.3 to 6.7-8.5) in the formate treatments increased the sorption of Cd onto the oxide surfaces (up to 80% of total sorbed Cd). In the NaCl treatments, cation competition and formation of Cd-Cl complexes increased the water-soluble Cd fraction. Consequently, the amount of bioavailable Cd was 3.5 times smaller in the KCHOO than in the NaCl treatments.     

Organometallic tris(8-hydroxyquinoline)aluminum complexes as buffer layers and dopants in inverted organic solar cells

Tris(8-hydroxyquinoline)aluminum (Alq₃) is a frequently used material for organic light emitting diodes. The electronic properties and solubility can be tuned by chemical tailoring of the quinoline part, which makes it an interesting candidate for organic solar cells. Steady-state absorption and fluorescence, as well as time-resolved fluorescence properties of the parent Alq₃ and a series of complexes consisting of derivatives, such as 4-substituted pyrazol, methylpyrazol, arylvinyl, and pyridinoanthrene moieties, of the quinoline ligand, were studied in solutions and in thin films. Suitability of the complexes as anodic buffer layers or dopants in inverted organic solar cells based on the well known bulk heterojunction of poly(3-hexylthiophene) (P3HT) and phenyl-C₆₁-butyric acid methyl ester (PCBM) was tested. The devices equipped with the derivatives showed higher power conversion efficiency (η) compared to the photocells containing the parent Alq₃. Open circuit voltage (V_oc) was increased when the derivatives were utilized as the anodic buffer layer. Doping of the P3HT:PCBM with a small amount of Alq₃ or its derivative improved short circuit current density, V_oc, fill factor, and η, while the series resistance decreased. In addition, the devices were stable in air over several weeks without encapsulation. Possible mechanisms leading to the improvements in the photovoltaic performance by using the parent Alq₃ or its derivative as buffer layer or dopant are discussed.