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Anapole resonances in high-index dielectric nanoparticles arise from the destructive interference between electric and toroidal dipole moments. So far, this mode interference has been solely observed using normal incidence free-space radiation. Here we show that anapole resonances can also arise in silicon disks being excited by an in-plane oriented waveguide. We provide both far-field and near-field measurements at telecom wavelengths which, in good agreement with numerical simulations, show the expected signatures of an anapole resonance. This work paves the way towards the use of the anapole resonances in on-chip silicon photonics.

Digital twins are virtual models for representing, monitoring, and controlling real-world products, entities, and processes, and are fundamental for enabling digitalization and continuous engineering processes. The usage of digital twins for engineering software-intensive systems will significantly change current business models, development approaches, and technologies. In this regard, the application scenarios and starting conditions for companies to introduce digital twins are manifold depending on their experience in software and system engineering, the maturity of their development processes, and the strategic management support and motivation. This article describes (i) challenges and impacts on the system development activities and architecture design approaches that are caused by the introduction and exploitation of digital twins, and also (ii) proposals for tailoring and extending traditional architecture-centric engineering processes to consider digital twin concepts.

The breakthrough of smart ecosystems formed by open adaptive systems requires new testing methods. The need for safety and security on the roads is pushed ahead by new developments in the area of autonomous driving. Frameworks that support testing of control functions are therefore needed. We present a prototype platform for automotive smart ecosystem that enables testing of smart ecosystems with a special focus on visualization and integration with real world. An abstract and a detailed description of the platform components, together with argumentation of the chosen components and interface description is presented as well. The platform provides a meaningful visualization of scenarios that verify and validate behavior interaction between component of the real and virtual world.

The user segment of wireless communication systems takes profit of the outstanding performance of filtering devices based on acoustic resonators. With a spectrum more and more occupied the design of filters and duplexers for mobile devices is becoming a challenging task. Usually, the design of acoustic wave devices is mainly entrusted to optimization techniques due to the stringent constraints imposed by the technological feasibility of acoustic resonators, and the challenging electrical specifications. A stringent transmission response and very restrictive technological factors make the designing a complex and challenging task. The objective of this work is to describe a methodology for the direct synthesis of laddertype acoustic filters: stand-alone, duplexers or multiplexers. The procedure is time efficient, precise in the outcomes and provides a deep understanding of the particular interactions between technology constraints and device performance.

The presence of electro-magnetic feedthrough between package ports in the design of filter based on acoustic wave resonators may cause degraded isolation levels and transmission zeros vanishing. These effects come from the presence of complex singularities, but also from internal phase shift requirements for a full network synthesis. This paper proposes a filter design procedure with cross-couplings that takes a set of leakages into account, providing the exact resonator parameters that maintain the levels of attenuation for acoustic wave filters.

Factors limiting the isolation of conventional miniaturized filters and duplexers have been considered in the literature. They can be classified into two types of signal leakage: one occurs via the main signal path due to the finite impedance of the RX filter in the TX band in a duplexer; the second one is due to electromagnetic feedthrough (EMF), electromagnetic couplings or imperfect grounding. Because of the existence of these leakages, the isolation of usual duplexers is limited to about 50 to 55 dB.

Performing tasks with the help of smart mobile devices is demanded for various areas in everyday life. In business environments, for example, tasks requiring complex paper work (e.g., paper-based documentation in the context of machine maintenance) shall be digitally transformed with the use ofsmart mobile devices. However, the realization of respective mobile applications is challenging as coordination issues have to be addressed in this context. For example, mobile application A performing task A may have to be finished before mobile application B performing task B may be started, i.e., human-centric mobile services need to be coordinated. To accomplish the latter, a formal context capturing service dependencies is required, while at the same time considering the mobile context of each involved human-centric mobile service needs to be considered. The presented approach extends existing process management technology with mobile activities to enable this. More precisely, we developed a mobile context framework that allows for a robust and flexible execution of mobile activities. The feasibility of the approach is demonstrated through a prototypical implementation as well as case studies. Altogether, the support of human-centric mobile services is promising regarding work efficiency in numerous scenarios and application domains in everyday life.

We investigate electromagnetic fields spinning around an axis perpendicular to the local propagation direction of light. Such transverse components of the spin density occur naturally when light is highly confined, for example, in waveguides or tightly focused beams. On this account, we discuss different measurement schemes for the detection of transversely spinning fields and demonstrate an exemplary utilization of the transverse spin density.

For a variety of economic and practical reasons, security patches often cannot be deployed immediately after a patch’s release. To mitigate attacks against unpatched software, we present the design and evaluation of a Moving Target tech- nique that uses a form of software diversity called multi-variant execution. Our technique decomposes the software’s behavior into its low-level system calls and compares unpatched and patched execution traces to identify malicious behavior in the unpatched software. We evaluate our approach on benign and malicious document samples and our results indicate that multi-variant execution can detect real exploits with low false positives.

The experimental reconstruction of phase and amplitude distributions of highly confined light fields is of utmost importance for a multitude of scientific research areas. Here, we present a particle-based experimental approach and reconstruction algorithm for the fully vectorial field reconstruction and discuss its applications. This method allows for reconstruction with deep sub-wavelength resolution. Furthermore, we introduce the extension of this scheme for the reconstruction of purely evanescent fields.

Quality assurance activities are often still expensive or do not offer the expected quality. A recent trend aimed at overcoming this problem is tighter integration of several quality assurance techniques such as analysis and testing in order to exploit synergy effects and thus reduce costs or improve the coverage of quality assurance activities. However, one main challenge in exploiting such benefits is that knowledge about the relationships between many different factors is needed, such as the quality assurance techniques considered, the number of defects, the remaining defect-proneness, or product and budget data. Such knowledge is often not available. Based on a combined analysis and testing methodology called In QA, we developed an iterative rule-based procedure that considers several factors in order to gather knowledge and allows deriving different strategies to guide the quality assurance activities. We derived several specific and reasonable strategies to demonstrate the approach.

The continuing pervasion of our society with safety-critical cyber-physical systems not only demands for adequate (risk) analysis, testing and verification techniques, it also generates growing experience on their use, which can be considered as important as the tools themselves for their efficient use. This paper introduces workflow patterns to describe such best practices in a systematic way that efficiently represents this know¬ledge, and also provides a way to relate different patterns, making them easier to identify and use, and cover as wide a range of experiences as possible. The value of the approach is demonstrated using some pattern examples from a collection developed in the Artemis-project MBAT . Finally, the paper presents a wiki-based approach for developing and maintaining the pattern collection.

The development of safety-critical software-intensive systems requires systematic quality assurance on all stages of the development process. Executable development artifacts are validated against the system specifications. Risk-based test approaches enable the distribution of test effort in a specific way to cover critical system parts, functions, and requirements. The development process of safety-critical systems usually implies analysis activities for determining and understanding hazards and risks. Moreover, it requires a systematic design of the system structure and behavior based on the specification. For achieving a high degree of automation of test case derivation, existing formal models from the risk analysis and system design phases are combined. The approach presented here focuses on integration of fault trees into state-based behavior models. Therefore, fault trees are analyzed and their elements are assessed for their validity and significance for the test modeling. The approach systematically transforms the relevant fault tree elements like single critical basic events, system states, or sequences of events into elements of the state-based behavior model. The resulting model enables the automated generation of test cases considering risk-based test purposes such as the coverage of critical states, transitions, or sub-models. The feasibility of the approach is shown in a small case study.

High-quality software is an indispensable requirement today. Low-quality products can result in high overall costs (e.g., due to rework). Quality assurance can help to reduce the number of defects before a software product is delivered. However, quality assurance itself can be a major cost driver, especially testing activities. One solution for balancing these costs is to focus testing on defect-prone parts, which is nowadays often done by using product and process metrics. However, data from static quality assurance activities that is available early is usually not considered when focusing testing activities. Integration of static and dynamic quality assurance activities is a promising strategy for exploiting synergy effects and, consequently, one way to reduce costs and effort. For effective and efficient integration, knowledge about the relationships between the integrated techniques is necessary, which is often not available. Thus, assumptions have to be stated and evaluated. Existing approaches for this typically describe procedures only on a high level. Therefore, this paper presents procedures how to define, derive, and evaluate assumptions in a systematic and detailed manner for the integrated inspection and testing (In2Test) approach.

Laparoscopic partial nephrectomy has become more and more popular in the last decade. Video laparoscopes remain the gold standard of intraoperative imaging during laparoscopic interventions. However, providing only superficial images of the target tissue. In contrast, ultrasound (US) imaging may offer crucial information of the interior of the target tissue that could improve surgical outcome. In this paper, we propose a new concept and prototype system to manipulate an US-probe during laparoscopic partial nephrectomies. Our primary goal was to provide the surgeon with US-images during the intervention in real-time. The prototype system consists of three components: a conventional US-machine, a manipulator to guide the US-probe, and a joystick console to control the manipulator. The results of our experiments show that the concept is feasible for US-imaging during laparoscopic partial nephrectomy.

Open-access 802.11 wireless networks are commonly deployed in cafes, bookstores, and other public spaces to provide free Internet connectivity. These networks are convenient to deploy, requiring no out-of-band key exchange or prior trust relationships. However, such networks are vulnerable to a variety of threats including the evil twin attack where an adversary clones a client's previously-used access point for a variety of malicious purposes including malware injection or identity theft. We propose defenses that aim to maintain the simplicity, convenience, and usability of open-access networks while offering increased protection from evil twin attacks. First, we present an evil twin detection strategy called context-leashing that constrains access point trust by location. Second, we propose that wireless networks be identified by uncertified public keys and design an SSH-style authentication and session key establishment protocol that fits into the 802.1X standard. Lastly, to mitigate the pitfalls of SSH-style authentication, we present a crowd-sourcing-based reporting protocol that provides historical information for access point public keys while preserving the location privacy of users who contribute reports.

BitTorrent is currently the most popular peer-to-peer network for file sharing. However, experience has shown that BitTorrent is often used to distribute copyright protected movie and music files illegally. Consequently, copyright enforcement agencies currently monitor BitTorrent swarms to identify users participating in the illegal distribution of copyright-protected files. These investigations rely on passive methods that are prone to a variety of errors, particularly false positive identification. To mitigate the potential for false positive peer identification, we investigate the feasibility of using active methods to monitor extremely large BitTorrent swarms. We develop an active probing framework called BitStalker that identifies active peers and collects concrete forensic evidence that they were involved in sharing a particular file. We evaluate the effectiveness of this approach through a measurement study with real, large torrents consisting of over 186,000 peers. We find that the current investigative methods produce at least 11% false positives, while we show that false positives are rare with our active approach.

Tor is currently the most popular low latency anonymizing overlay network for TCP-based applications. However, it is well understood that Tor's path selection algorithm is vulnerable to end-to-end traffic correlation attacks since it chooses Tor routers in proportion to their perceived bandwidth capabilities. Prior work has shown that the fraction of malicious routers and the amount of adversary-controlled bandwidth are significant factors for predicting the number of paths that an adversary can compromise. We extend this prior work by identifying that the application-layer protocol being transported is also a significant factor in predicting path compromise. Through a simulation study driven by data obtained from the real Tor network, we show that ports commonly associated with peer-to-peer file sharing protocols and the simple mail transport protocol (SMTP) are significantly more vulnerable to this attack than other ports.

802.11 localization algorithms provide the ability to accurately position and track wireless clients thereby enabling location-based services and applications. However, we show that these localization techniques are vulnerable to noncryptographic attacks where an adversary uses a low-cost directional antenna to appear from the localization algorithm's perspective to be in another arbitrary location of their choosing. The attacker's ability to actively influence where they are positioned is a key distinguishing feature of the directional attack relative to prior localization attacks that use transmit power control to introduce localization errors. We implement a representative set of received signal strength-based localization algorithms and evaluate the attack in a real office building environment. To mitigate the attack's effectiveness, we develop and evaluate an attack detection scheme that offers a high detection rate with few false positives.

Usually, for a particular business process a multitude of variants exist. Each of them constitutes an adjustment of a reference process model to specific requirements building the process context. While some progress has been achieved regarding the configuration of process variants, there exists only little work on how to accomplish this in a sound and efficient manner, especially when considering the large number of process variants that exist in practice as well as the many syntactical and semantical constraints they have to obey. In this paper we discuss advanced concepts for the context- and constraint-based configuration of process variants, and show how they can be utilized to ensure soundness of the configured process variants. Enhancing process-aware information systems with the capability to easily configure sound process models, belonging to the same process family and fitting to the given application context, will enable a new quality in engineering process-aware information systems.

Due to the prevalence of insecure open 802.11 access points, it is currently easy for a malicious party to launch a variety of attacks such as eavesdropping and data injection. In this paper, we consider a particular threat called the evil twin attack, which occurs when an adversary clones an open access point and exploits common automatic access point selection techniques to trick a wireless client into associating with the malicious access point. We propose two lines of defense against this attack. First, we present an evil twin detection strategy called context-leashing based upon recording the nearby access points when first associating with an access point. Using this contextual information, the client determines if an adversary has setup an evil twin access point at a different location. Next, we propose an SSH-style authentication method called EAP-SWAT to perform one-way access point authentication that fits into the extensible authentication protocol (EAP) framework.

This paper presents the results of a research project where the combination of techniques of sequence-based requirements specification and model- based statistical testing has been applied to a real mirror control unit of a car door for reliability estimations. A complete chain from a requirements document to a statistical test report with a very high degree of automation is demonstrated. A practical solution for reliability analysis of embedded systems in a realistic industrial setup is proposed.

The monitoring and visualization of enterprise-wide and cross-organizational business processes is an important, but also very complex task. The information needed for visualizing processes may be scattered over heterogeneous, distributed information systems. These systems may only support fragments of the process and may use different process meta models. Besides an integrated view on these process data, any process visualization must be flexibly and dynamically adaptable to the needs of different applications and user groups. This paper discusses requirements of a flexible process visualization in distributed environments. This includes process data integration issues as well as issues related to adaptable process visualization.

Two-dimensional photonic crystals allow for various types of photonic topological insulators. In this paper, we present our efforts to directly image on-chip light propagation in topological edge states. We quantify the robustness of such states to scattering at sharp corners and defects.