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Zweiseitige Märkte
(2016)
Agricultural activities within city boundaries have a long history in both developed and developing countries. In this paper, a broad approach to Urban AgriCulture (UAC) is used, one that includes the production of crops in urban and peri-urban areas and ranges in developed countries from allotment gardens over community gardens to semi-entrepreneurial self-harvest farms and fully commercialized agriculture. With an empirical case study on UAC Initiatives in the Bonn/Rhein-Sieg region this work fills a gap since the lack of comprehensive and comparative studies on urban agriculture (UA) currently makes it difficult for researchers to identify the benefits of UA activities.
We present a new multi-pixel high resolution (R ≳ 107) spectrometer for the Stratospheric Observatory for Far-Infrared Astronomy (SOFIA). The receiver uses 2 × 7-pixel subarrays in orthogonal polarization, each in an hexagonal array around a central pixel. We present the first results for this new instrument after commissioning campaigns in May and December 2015 and after science observations performed in May 2016. The receiver is designed to ultimately cover the full 1.8−2.5 THz frequency range but in its first implementation, the observing range was limited to observations of the [CII] line at 1.9 THz in 2015 and extended to 1.83−2.07 THz in 2016. The instrument sensitivities are state-of-the-art and the first scientific observations performed shortly after the commissioning confirm that the time efficiency for large scale imaging is improved by more than an order of magnitude as compared to single pixel receivers. An example of large scale mapping around the Horsehead Nebula is presented here illustrating this improvement. The array has been added to SOFIA’s instrument suite already for ongoing observing cycle 4.
Companies often have difficulties determining which criteria to base their investment decisions in different countries on. When considering direct foreign investment several risk indices are available. The PCI (Peren-Clement-Index) in its original form was developed in 1998. Its further refinement improves the PCI in three major ways: First, it offers a dynamic adjustment of criteria and consideration of recent changes in the international environment. Second, it provides business specificities of a company or its industrial sector to be considered in addition to macroeconomic aspects by a two-dimensional presentation, which ensures a customized assessment. Third, the PCI allows for consolidating investment decisions by combining a resource-orientated with a market-oriented view. The PCI allows, unlike other indices, a customized and company-specific strategic planning process. Ultimately companies must take up both perspectives in the context of an international investment decision. The use of risk indices in corporate planning for assessing global investments decision creates a fundamentally new of risk assessment.
SpMV Runtime Improvements with Program Optimization Techniques on Different Abstraction Levels
(2016)
The multiplication of a sparse matrix with a dense vector is a performance critical computational kernel in many applications, especially in natural and engineering sciences. To speed up this operation, many optimization techniques have been developed in the past, mainly focusing on the data layout for the sparse matrix. Strongly related to the data layout is the program code for the multiplication. But even for a fixed data layout with an accommodated kernel, there are several alternatives for program optimizations. This paper discusses a spectrum of program optimization techniques on different abstraction layers for six different sparse matrix data format and kernels. At the one end of the spectrum, compiler options can be used that hide from the programmer all optimizations done by the compiler internally. On the other end of the spectrum, a multiplication kernel can be programmed that use highly sophisticated intrinsics on an assembler level that ask for a programmer with a deep understanding of processor architectures. These special instructions can be used to efficiently utilize hardware features in processors like vector units that have the potential to speed up sparse matrix computations. The paper compares the programming effort and required knowledge level for certain program optimizations in relation to the gained runtime improvements.
With the rising interest in vehicular communication systems many proposals for secure vehicle-to-vehicle commu- nication were made in recent years. Also, several standard- ization activities concerning the security and privacy measures in these communication systems were initiated in Europe and in US. Here, we discuss some limitations for secure vehicle- to-infrastructure communication in the existing standards of the European Telecommunications Standards Institute. Next, a vulnerability analysis for roadside stations on one side and security and privacy requirements for roadside stations on the other side are given. Afterwards, a proposal for a multi-domain public key architecture for intelligent transport systems, which considers the necessities of road infrastructure authorities and vehicle manufacturers, is introduced. The domains of the public key infrastructure are cryptographically linked based on local trust lists. In addition, a crypto agility concept is suggested, which takes adaptation of key length and cryptographic algorithms during PKI operation into account.