Extracting LiDAR indices to characterise multilayered forest structure using mixture distribution functions

Discrete Light Detection and Ranging (LiDAR) data is used to stratify a multilayered eucalyptus forest and characterise the structure of the vertical profile. We present a methodology that may prove useful for a very broad range of forest management applications, particularly for timber inventory evaluation and forest growth modelling. In this study, we use LiDAR data to stratify a multilayered eucalyptus forest and characterise the structure of specific vegetation layers for forest hydrology research, as vegetation dynamics influence a catchment's streamflow yield. A forest stand's crown height, density, depth, and closure, influence aerodynamic properties of the forest structure and the amount of transpiring leaf area, which in turn determine evapotranspiration rates. We present a methodology that produces canopy profile indices of understorey and overstorey vegetation using mixture models with a wide range of theoretical distribution functions. Mixture models provide a mechanism to summarise complex canopy attributes into a short list of parameters that can be empirically analysed against stand characteristics.Few studies have explored theoretical distribution functions to represent the vertical profile of vegetation structure in LiDAR data. All prior studies have focused on a Weibull distribution function, which is unimodal. In a complex native forest ecosystem, the form of the distribution of LiDAR points may be highly variable between forest types and age classes. We compared 44 probability distributions within a two component mixture model to determine the most suitable bimodal distributions for representing LiDAR density estimates of Mountain Ash forests in south-eastern Australia. An elimination procedure identified eleven candidate distributions for representing the eucalyptus component of the mixture model.We demonstrate the methodology on a sample of plots to predict overstorey stand volumes and basal area, and understorey basal area of 18-, 37-, and 70-year old Mountain Ash forest with variable density classes. The 70-year old forest has been subjected to a range of treatments including: thinning of the eucalyptus layer with two distinct retention rates, removal of the understorey, and clear felling of patches that have 37 year old regenerating forest. We demonstrate that the methodology has clear potential, as observed versus predicted values of eucalyptus basal area and stand volume were highly correlated, with bootstrap based r² ranging from 0.61 to 0.89 and 0.67 to 0.88 respectively. Non-eucalyptus basal area r² ranged from 0.5 to 0.91.     

Stability analysis of milling processes with varying workpiece dynamics

An approach for the systematic choice of process parameters by observing the entire machining process in milling is presented. There is a varying workpiece dynamics due to the machining, wherefore a distinct change of stability characteristics is possible. The new contribution of this paper is an approach using parametric model order reduction in stability analysis. Both parametric model order reduction and stability analysis of time-delayed systems are topics of current research although their combination is hardly investigated. The approach is very efficient compared to full models or other ideas described in literature, like parametric model order reduction based on substructuring. Thus, the continuous representation of the varying workpiece dynamics enables stability analysis as well as time-domain simulations with reasonable computation times.     

Single-machine batch scheduling to minimize the total setup cost in the presence of deadlines

We address the single-machine batch scheduling problem with the objective of minimizing the total setup cost. This problem arises when there are n jobs that are partitioned into F families and when setup operations are required whenever the machine switches from processing a job of one family to processing a job of another family. We assume that setups do not require time but are associated with a fixed cost which is identical for all setup operations. Each job has a processing time and an associated deadline. The objective is to schedule all jobs such that they are on time with respect to their deadlines and the total setup cost is minimized. We show that the decision version of this problem is NP-complete in the strong sense. Furthermore, we present properties of optimal solutions and an \(O(n\log n+nF)\) algorithm that approximates the cost of an optimal schedule by a factor of F. The algorithm is analyzed in computational tests.     

Perfopticon: Visual Query Analysis for Distributed Databases

Distributed database performance is often unpredictable due to issues such as system complexity, network congestion, or imbalanced data distribution. These issues are difficult for users to assess in part due to the opaque mapping between declaratively specified queries and actual physical execution plans. Database developers currently must expend significant time and effort scanning log files to isolate and debug the root causes of performance issues. In response, we present Perfopticon, an interactive query profiling tool that enables rapid insight into common problems such as performance bottlenecks and data skew. Perfopticon combines interactive visualizations of (1) query plans, (2) overall query execution, (3) data flow among servers, and (4) execution traces. These views coordinate multiple levels of abstraction to enable detection, isolation, and understanding of performance issues. We evaluate our design choices through engagements with system developers, scientists, and students. We demonstrate that Perfopticon enables performance debugging for real‐world tasks.     

Employee creativity in war zones: Empirical evidence from small firms in Afghanistan

The major concern of employees during times of war and conflict is apparently physical survival. But how are top managers of small‐sized companies enhancing the generation of novel and useful ideas by their employees in such physically dangerous business environments? In Afghanistan, as a war‐torn country, this research examined for the first time how getting closer to employees—which is conceptualized as internal marketing orientation culture in our study—directly affects the generation of novel and useful ideas by employees in the workplace. Our analysis is based on survey data from 81 newly established small‐sized companies in Afghanistan. Results indicate a mediating role of employees' perceived psychological safety on the relationship between internal market orientation culture and employees' creative work involvement. Moreover, we discuss the impact of employees' creative work involvement on small‐sized firm competitiveness improvement in general. Finally, we extend our implications in the context of the componential theory model of creativity, which might also serve as a framework for future research.     

Fractional variable order discrete-time systems,their solutions and properties

In this paper, fractional variable order discrete state-space systems based on different definitions of fractional variable order difference are investigated.The general solution of these systems is derived. Moreover, necessary and sufficient conditions for reachability and observability are given and proven. The sufficient conditions for controllability are proposed too.     

Mixer slit plates fabricated by direct-LIGA

Direct-LIGA services combining X-ray based micro-fabrication and electroplating are routinely provided to customers worldwide on a “best effort” basis by several LIGA centers. In a publicly founded project in collaboration between BESSY and Ehrfeld Mikrotechnik BTS GmbH the direct-LIGA process was adapted and optimised for fabricating mixer slit plates for micro-reactors. The application of SU-8 as a resist in deep X-ray lithography opens new opportunities for a direct and cost-effective mass fabrication of LIGA metal micro-parts. This joint paper will report on efforts from BESSY, Micro Resist Technology, and Ehrfeld BTS in fabrication of mixer slit plates by direct-LIGA for use in modular micro-reaction technology. The high demands regarding precision and yield of the micro-slit plates need certain improvements in the LIGA processing chain. Our approach consists of X-ray patterned SU-8 resist molds with a layer thickness of up to 350 μm and an aspect ratio of up to 30:1. Furthermore, the pattern-transfer into the SU-8 resist was done by a low-cost X-ray mask based on a graphite membrane. Other processing steps like NiFe electroplating and SU-8 removal will be discussed in this paper.     

A new UV sensitive positive resist for X-ray masks manufacture

LIGA is a well-established process to fabricate metallic micro parts with high resolution, high precision and very low sidewall roughness by means of X-ray lithography and electroplating. The availability of a precise X-ray mask is a precondition for the final precision of the manufactured micro parts. Typical mask substrate materials, e.g. beryllium, carbon based foils, Si₃N₄ or SiC show different disadvantages such as low X-ray transparency or high toxicity or high prices or low conductivity or high thermal expansion or surface porosity causing X-ray scattering. For the fabrication of X-ray masks, PMMA with its unique features such as high aspect ratio patterns with high precision, exhibits low sensitivity and the layers preparation is not easy. SU-8, an epoxy-based UV and X-ray sensitive, chemically amplified, negative tone photoresist exhibits high aspect ratio patterns with vertical sidewalls. The difficult remove of the resist after the electroplating process significantly hinders the inspection of the fabricated X-ray mask. We present the use and suitability of an UV sensitive, chemically amplified, viscous, aqueous-alkaline developable, and easy removable positive tone photoresist, XP mr-P 15 AV, exhibiting high aspect ratio patterns with vertical sidewalls for the fabrication of X-ray masks by means of UV lithography on vitreous carbon substrates.     

Geometrische Dimensionierung von Seitenkanalmaschinen

Zusammenfassung Für die Auslegung von Str?mungsmaschinen ist in der Regel ein Vorentwurf notwendig, aus dem die wichtigsten. Hauptabmessungen für das Laufrad und die Leiteinrichtungen resultieren. Diese Hauptabmessungen sind auch für die Auslegung und Dimensionierung von Seitenkanalmaschinen notwendig. Auf der Grundlage der erreichbaren dimensionslosen Kennzahlen für den Optimalpunkt k?nnen die Hauptabmessungen wie z.B. Laufradau?en- und Innendurchmesser, Seitenkanalquerschnitt und Laufradquerschnitt sowie die Laufradbreite für vorgegebene Volumenstr?me und geforderte Druckverh?ltnisse π_n bzw, die polytropen spezifischen Nutzarbeiten und die vorgegebene Antriebsdrehzahl bestimmt werden. Beim Entwurf von Maschinenbaureihen lassen sich auch die Grenzbereiche für Seitenkanalmaschinen angeben. Die obere Drehzahlgrenze für Seitenkanalmaschinen, die oberhalb vonn=3000 min⁻¹ liegt, wird durch die Druckzahl und den erreichbaren polytropen Kupplungswirkungsgrad bestimmt.