Simulation and Application of a Piezo-Driven System Enabling Vibration-Assisted Micro Milling

The ongoing miniaturization of components and the functionalization of surfaces necessitates the improvement of micro machining processes and to increase their efficiency. One method to increase the machining efficiency is reducing the process forces and tool wear, which is achieved by the implementation of vibration-assisted cutting in conventional machining processes. In vibration-assisted cutting, the conventional cutting movement is superimposed by a vibration with defined frequency. By using vibration-assisted cutting technologies, besides increased efficiency, a wider range of materials can be machined. In this paper, vibration-assisted cutting is transferred to micro machining. For this purpose, the design, simulation and application of an easy to integrate system that enables vibration-assisted cutting for micro machining processes is described. The setup was tested using a micro milling process. Two orientations between feed direction and vibration direction were investigated. Frequencies up to 15 kHz were examined, the machined material was brass (CuZn39Pb2). The effect of the superimposed vibration was analysed on the basis of process force, surface roughness, burr formation and slot bottom and was compared with the process results of micro milling without vibration-assistance. A decrease in process forces of up to 63 % was observed during vibration-assisted micro milling

Analysis of dimensional accuracy for micro-milled areal material measures with kinematic simulation

The calibration of areal surface topography measuring instruments is of high relevance to estimate the measurement uncertainty and to guarantee the traceability of the measurement results. Calibration structures for optical measuring instruments must be sufficiently small to determine the limits of the instruments. Besides other methods, micro-milling is a suitable process for manufacturing areal material measures. For the manufacturing by micro-milling with ball end mills, the tool radius (effective cutter radius) is the corresponding limiting factor: if the tool radius is too large to penetrate the concave profile details without removing the surrounding material, deviations from the target geometry will occur. These deviations can be detected and excluded before experimental manufacturing with the aid of a kinematic simulation. In this study, a kinematic simulation model for the prediction of the dimensional accuracy of micro-milled areal material measures is developed and validated. Subsequently, a radius study is conducted to determine how the tool radius r of the tool influences the dimensional accuracy of an areal crossed sinusoidal (ACS) geometry according to ISO 25178-70 [1] with a defined amplitude d and period length p. The resulting theoretical surface texture parameters are evaluated and compared to the target values. It was shown that the surface texture parameters deviate from the nominal values depending on the effective cutter radius used. Based on the results of the study, it can be determined with which effective tool radius the measurands Sa and Sq of the material measures are best met. The ideal effective radius for the application considered is between 50 and 75 μm

Kinematic simulation to investigate the influence of the cutting edge topography when ball end micro milling

During the ball end micro milling of material measures, the cutting edge topography is imaged on the machined workpiece. The influence of the chipping on the resulting surface quality is much more dominant than other kinematic effects. In this simulative study, a model is built that is able to predict the correlation between the cutting edge topography and the resulting workpiece topography. Thus, the mentioned correlation can be investigated without overlaying effects of material separation or measurement uncertainties, which are unavoidable in an experimental study. The model has been validated based on four artificial chippings

Absolute and relative stability of loss aversion across contexts

Individuals’ decisions under risk tend to be in line with the notion that “losses loom larger than gains”. This loss aversion in decision making is commonly understood as a stable in- dividual preference that is manifested across different contexts. The presumed stability and generality, which underlies the prominence of loss aversion in the literature at large, has been recently questioned by studies reporting how loss aversion can disappear, and even reverse, as a function of the choice context. The present study investigated whether loss aversion reflects a trait-like attitude of avoiding losses or rather individuals’ adaptability to different contexts. We report three experiments investigating the within-subject context sensitivity of loss aversion in a two-alternative forced-choice task. Our results show that the choice context can shift people’s loss aversion, though somewhat inconsistently. Moreover, individual estimates of loss aversion are shown to have a considerable degree of stability. Altogether, these results indicate that even though the absolute value of loss aversion can be affected by external factors such as the choice context, estimates of people’s loss aversion still capture the relative dispositions towards gains and losses across individuals

Spatial processes in linear ordering

Memory performance in linear order reasoning tasks (A > B, B > C, C > D, etc.) shows quicker, and more accurate responses to queries on wider (AD) than narrower (AB) pairs on a hypothetical linear mental model (A – B – C – D). While indicative of an analogue representation, research so far did not provide positive evidence for spatial processes in the construction of such models. In a series of 7 experiments we report such evidence. Participants respond quicker when the dominant element in a pair is presented on the left (or top) rather than on the right (or bottom). The left-anchoring tendency reverses in a sample with Farsi background (reading/writing from right to left). Alternative explanations and confounds are tested. A theoretical model is proposed that integrates basic assumptions about acquired reading/writing habits as a scaffold for spatial simulation, and primacy/dominance representation within such spatial simulations

Assessing framing of uncertainties in water management practice

Dealing with uncertainties in water management is an important issue and is one which will only increase in light of global changes, particularly climate change. So far, uncertainties in water management have mostly been assessed from a scientific point of view, and in quantitative terms. In this paper, we focus on the perspectives from water management practice, adopting a qualitative approach. We consider it important to know how uncertainties are framed in water management practice in order to develop practice relevant strategies for dealing with uncertainties. Framing refers to how people make sense of the world. With the aim of identifying what are important parameters for the framing of uncertainties in water management practice, in this paper we analyze uncertainty situations described by decision-makers in water management. The analysis builds on a series of ¿Uncertainty Dialogues¿ carried out within the NeWater project with water managers in the Rhine, Elbe and Guadiana basins in 2006. During these dialogues, representatives of these river basins were asked what uncertainties they encountered in their professional work life and how they confronted them. Analysing these dialogues we identified several important parameters of how uncertainties get framed. Our assumption is that making framing of uncertainty explicit for water managers will allow for better dealing with the respective uncertainty situations. Keywords Framing - Uncertainty - Water management practic

Imaging in Suspected Renal Colic: Systematic Review of the Literature and Multispecialty Consensus

Background Renal colic is common, and CT is frequently utilized when the diagnosis of kidney stones is suspected. CT is accurate but exposes patients to ionizing radiation and has not been shown to alter either interventional approaches or hospital admission rates. This multi-organizational transdisciplinary collaboration sought evidence-based, multispecialty consensus on optimal imaging across different clinical scenarios in patients with suspected renal colic in the acute setting. Methods In conjunction with the American College of Emergency Physicians (ACEP) eQual network, we formed a nine-member panel with three physician representatives each from ACEP, the ACR, and the American Urology Association. A systematic literature review was used as the basis for a three-step modified Delphi process to seek consensus on optimal imaging in 29 specific clinical scenarios. Results From an initial search yielding 6,337 records, there were 232 relevant articles of acceptable evidence quality to guide the literature summary. At the completion of the Delphi process consensus, agreement was rated as perfect in 15 (52%), excellent in 8 (28%), good in 3 (10%), and moderate in 3 (10%) of the 29 scenarios. There were no scenarios where at least moderate consensus was not reached. CT was recommended in 7 scenarios (24%), with ultrasound in 9 (31%) and no further imaging needed in 12 (45%). Summary Evidence and multispecialty consensus support ultrasound or no further imaging in specific clinical scenarios, with reduced-radiation dose CT to be employed when CT is needed in patients with suspected renal colic

Feedback control of arm movements using Neuro-Muscular Electrical Stimulation (NMES) combined with a lockable, passive exoskeleton for gravity compensation.

Within the European project MUNDUS, an assistive framework was developed for the support of arm and hand functions during daily life activities in severely impaired people. This contribution aims at designing a feedback control system for Neuro-Muscular Electrical Stimulation (NMES) to enable reaching functions in people with no residual voluntary control of the arm and shoulder due to high level spinal cord injury. NMES is applied to the deltoids and the biceps muscles and integrated with a three degrees of freedom (DoFs) passive exoskeleton, which partially compensates gravitational forces and allows to lock each DOE The user is able to choose the target hand position and to trigger actions using an eyetracker system. The target position is selected by using the eyetracker and determined by a marker-based tracking system using Microsoft Kinect. A central controller, i.e., a finite state machine, issues a sequence of basic movement commands to the real-time arm controller. The NMES control algorithm sequentially controls each joint angle while locking the other DoFs. Daily activities, such as drinking, brushing hair, pushing an alarm button, etc., can be supported by the system. The robust and easily tunable control approach was evaluated with five healthy subjects during a drinking task. Subjects were asked to remain passive and to allow NMES to induce the movements. In all of them, the controller was able to perform the task, and a mean hand positioning error of less than five centimeters was achieved. The average total time duration for moving the hand from a rest position to a drinking cup, for moving the cup to the mouth and back, and for finally returning the arm to the rest position was 71 s