Tolerance zones: a pragmatic approach to respond to problems related to open alcohol and drug scenes in Bremen/Germany

Purpose This study aims to describe and analyse an approach in the city of Bremen (Germany) to establish streetwork-supported tolerance zones for local open drug and alcohol scenes to reduce related disorder and nuisance in public spaces. Design/methodology/approach The qualitative methodology included systematic participant observations at public sites of drug and alcohol use, and problem-centred interviews with different groups of respondents (residents, passers-by, trades people, drug users, experts from addiction help and police). Findings In residential districts, tolerance zones were well accepted by their target group and found to reduce perceived disorder and nuisance in public space. However, their success depends on the social and spatial conditions of the chosen location, its surrounding urban infrastructure, cooperation among local actors and characteristics of drug using groups. Originality/value Usually, policing of open drug scenes focuses on repression and law enforcement. The example of Bremen suggests that streetwork-supported tolerance zones dedicated to the drug scene can substantially reduce disorder and nuisance in public space.

Design of a Flapping Wing Mechanism to Coordinate Both Wing Swing and Wing Pitch

This paper presents a design procedure to achieve a flapping wing mechanism for a micro-air vehicle that coordinates both the wing swing and wing pitch with one actuator. The mechanism combines a planar four-bar linkage with a spatial four-bar linkage attached to the input and output links forming a six-bar linkage. The planar four-bar linkage was designed to control the wing swing trajectory profile and the spatial four-bar linkage was designed to coordinate the pitch of the wing to the swing movement. Tolerance zones were specified around the accuracy points, which were then sampled to generate a number of design candidates. The result was 29 designs that achieve the desired coordination of wing swing and pitch, and a prototype was constructed.

Tolerance Design for Optimal Dimensional Quality of Machine Parts

The mechanical systems consist of assembled parts, between which diverse interactions take place. Tolerance analysis purpose is to study the effects of part geometric deviations on assembly functional requirements. In the current approaches from this field, the part geometrical deviations are toleranced without considering the evolution of the geometrical deviations during product exploitation. As consequence, between two parts identical as type but with different values of their geometrical features, inside the designed tolerance zones, any difference is made despite they might have significantly different life cycles or manufacturing costs. This paper presents a new conceptual approach concerning parts tolerance design, based on a new criterion, namely the dimensional quality, defined by two important features: life cycle and manufacturing cost. The main issue of this approach is the optimal relation between the manufacturing tolerance zones and the acceptable functional deviation domain. The new concept implementation is sampled in the case of an articulated arm.

A Design System for Eight-Bar Linkages as Constrained 4R Serial Chains

This paper presents a design system for planar eight-bar linkages that adds three RR constraints to a user-specified 4R serial chain. R denotes a revolute, or hinged, joint. There are 100 ways in which these constraints can be added to yield as many as 3951 different linkages. An analysis routine based on the Dixon determinant evaluates the performance of each linkage candidate and determines the feasible designs that reach the task positions in a single assembly. A random search within the user-specified tolerance zones around the task specifications is iterated in order to increase the number of linkage candidates and feasible designs. The methodology is demonstrated with the design of rectilinear eight-bar linkages that guide an end-effector through five parallel positions along a straight line.