Verteiltes, internetbasiertes Requirements-Engineering

This article describes the design, the prototypical implementation and the productization of DisIRE, a method for spatially Distributed, Internet-Based Requirement Engineering. DisIRE builds on theoretically founded and empirically validated approaches of collaborative requirements elicitation and decision supported requirements selection. Thus, this method supports a continuous process, particularly suited for spatially distributed environments, in which requirements dependencies are explicitly taken into consideration. Hereby DisIRE enables software manufacturers to conduct systematically both distributed and concurrent requirements engineering with their customers.     

Sequencing mixed-model assembly lines to minimize part inventory cost

A mixed-model assembly line enables the joint production of different models of a common base product in intermixed model sequence (lot size one). Previous approaches for the short-term planning task of model sequencing either aim at minimizing work overload (mixed-model sequencing and car sequencing) or leveling part usages (level scheduling). However, at many manufacturers parts are consolidated by a third party logistics provider, who stocks Just-in-Time delivered parts in a consignment warehouse adjacent to the line. The manufacturer issues a complete cargo carrier (e.g. a euro-pallet) whenever his own intermediate storage of parts is depleted. Thus, the manufacturer aims at a model sequence which minimizes his own inventory costs. This paper formalizes this novel model sequencing problem and describes different heuristic and exact procedures. Furthermore, the solutions yielded by these approaches are compared to the traditional level scheduling.     

Adaptive Bit Loading and Transmit Diversity for Iterative OFDM Receivers

In this paper, we consider a transmission system employing orthogonal frequency division multiplexing with bit-interleaved coded modulation and perfect channel state information at both transmitter and receiver. An adaptive bit loading scheme in combination with cyclic delay diversity and discontinuous Doppler diversity is proposed at the transmitter and iterative demapping and decoding at the receiver. The loading procedure minimizes the bit-error rate at the decoder output, and the transmit diversity schemes mitigate channel correlations. We analyze the iterative receiver with extrinsic information transfer charts and present the achievable gains.

Palladium(0) Nanoparticles on Glass‐Polymer Composite Materials as Recyclable Catalysts: A Comparison Study on their Use in Batch and Continuous Flow Processes

Palladium particles were generated by reduction of palladate anions bound to an ion exchange resin inside microreactors. The size and distribution of the palladium particles differed substantially depending on the degree of cross‐linking and the density of ion exchange sites on the polymer/glass composites, the latter parameter having a larger influence than the former. The polymer phase of the composite materials was used for the loading with clusters composed of palladium particles which are 1 to 10 nm in diameter. The reactivity and stability of six different palladium‐doped polymer/glass composite samples for transfer hydrogenations was investigated both under conventional and microwave heating in the batch mode as well as under continuous flow conditions using the cyclohexene‐promoted transfer hydrogenation of ethyl cinnamate as a model reaction. Regarding the heating method it was found that catalysts that are composed of larger metal particles perform better under microwave irradiating conditions whereas samples with smaller particle sizes perform better under conventional heating. Comparing batch experiments with flow‐through experiments the latter technique gives better conversion. Reusability was better in microwave heated experiments than in traditional heating.     

Synthesis of Chiral 2‐Hydroxy‐1‐methylpropanoates by Rhodium‐Catalyzed Stereoselective Hydrogenation of α‐(Hydroxymethyl)‐acrylate Derivatives

The synthesis of chiral 3‐hydroxy‐2‐methylpropanoic acid esters (e.g., “Roche ester” 3a ) based on the rhodium‐catalyzed stereoselective hydrogenation of Baylis–Hillman reaction products was investigated. Full conversions and enantioselectivities of up to 99% at a substrate/catalyst ratio of up to 500/1 were achieved by application of bisphospholanes of the catASium M series as ancillary ligands. An interesting kinetic resolution was observed by the diastereoselective hydroxy‐directed hydrogenation of related racemic β‐branched precursors affording mainly anti‐isomers with up to 96%ee.     

两级R744超市中央制冷系统节能特性

比较了以二氧化碳（R744）为工质的超市中央制冷系统制冷技术方案,包括普通两级制冷（CB）、旁通压缩两级制冷（PC）和多引射器-旁通压缩耦合两级制冷（EJ）,讨论了配置空调系统（AC）之后的功耗变化。根据计算得到,在环境温度20℃以上,相较于CB系统,PC系统的功耗减少了6.8%～12.3%;EJ系统功耗降低了6.3%～17.5%。在耦合了AC系统之后,相较于PC-AC系统,EJ-AC系统的功耗降低了4.9%～6.5%。与R404a系统相比,超市两级R744系统都有明显的节能效果。     

Excellent catalytic performance of 3D-mesoporous KIT-6 supported Cu and Ce nanoparticles in methanol steam reforming

In this study, cerium promoted copper-based catalysts were synthesized via conventional and surfactant-assisted impregnation methods using KIT-6 as a new support material. The catalytic activity of the prepared catalysts was investigated in the methanol steam reforming (MSR). The characterization results revealed the incorporation of cerium oxide and employing the surfactant-assisted impregnation method effectively controlled the size of copper particles and also improved the uniform distribution of the metal species. Among all catalysts, the CeCu/KIT-6 catalyst which was prepared using the surfactant-assisted impregnation method exhibited the best catalytic performance of about 92% methanol conversion, 99% H₂ selectivity and only 0.9% CO selectivity at 300 °C. The CeCu/KIT-6 samples showed no significant change in catalytic activity after 24 h, demonstrating that the use of 3D-mesoporous KIT-6 support significantly improved the stability of metal-based catalysts.     

Modeling the bending vibration of cross-laminated timber beams

Cross-laminated timber (CLT) is an economical construction material combining good structural properties and environmental advantages. Due to the layered geometry and the associated internal stress boundary conditions, modelling its dynamic behavior is complex. However, accurate vibration level estimations are necessary to estimate the sound insulation performance of CLT constructions. This paper outlines a method to determine the relevant elastic constants and the appropriate equations of motion to predict the vibration of beams cut from a three-ply CLT plate. Modal analysis performed on strips cut along the two principal directions provides insight in the material’s dynamics. The bending mode frequencies are determined experimentally by analyzing the sweep response spectrum using the linear prediction method. In a second step, analytical beam vibration models of increasing complexity are fitted to the measurements using a genetic optimization algorithm. Thin beam theory—the simplest model—does not predict the bending modes with sufficient accuracy. Depending on the strip direction, the bending vibrations can be modeled using Timoshenko’s theory for thick beams, or by a model for three layer sandwich beams respectively. The results show that taking the beam geometry into account is as important as estimating the orthotropic material constants to model the bending modes properly.     

Role of architectural space in blast-resistant buildings

The design of all spatial scales in a manufactured environment is part of the architectural skills and knowledge. Therefore, an architectural design should be drafted to reduce the vulner- ability of humans and buildings against unexpected events, such as terrorist attacks and bombardments. Human casualties and equipment destruction inside the buildings could be prevented by designing a suitable architectural space. This study addresses the absence of a codified and detailed criterion to evaluate architectural spaces and their design. Hence, all proposed indices for architectural spaces have been extracted using the ideas of experts in the field of architecture and explosives. Questionnaires were presented to 25 experts to weigh the effective indices using the analytic hierarchy process method. The human-oriented (ergonomic) characteristics of the building space is found to be the most important factor in facilitating crisis management, followed by the location of critical spaces.