11 research outputs found
Lower bounds for the first eigenvalue of the magnetic Laplacian
We consider a Riemannian cylinder endowed with a closed potential 1-form A
and study the magnetic Laplacian with magnetic Neumann boundary conditions
associated with those data. We establish a sharp lower bound for the first
eigenvalue and show that the equality characterizes the situation where the
metric is a product. We then look at the case of a planar domain bounded by two
closed curves and obtain an explicit lower bound in terms of the geometry of
the domain. We finally discuss sharpness of this last estimate.Comment: Replaces in part arXiv:1611.0193
Teams between Neo-Taylorism and Anti-Taylorism
The concept of teamworking is the product of two distinct
developments. One: a neo-
Tayloristic form of organization of work, of which Toyota has shown
that it can be very profitable, was
packaged and reframed to make it acceptable to the Western public.
Two: anti-Tayloristic ways of
organizing work, inspired by ideals of organizational democracy,
were relabeled to make these
acceptable to profit-oriented managers.
Drawing on empirical research in Scandinavia, Germany, The
Netherlands and the UK, as
well as on published case studies of Japanese companies, the paper
develops a neo-Tayloristic and an
anti-Tayloristic model of teamworking.
Key concerns in the teamworking literature are intensification of
work and the use of shop
floor autonomy as a cosmetic or manipulative device. Indeed, all the
features of neo-Tayloristic
teamworking are geared towards the intensification of work. However,
one of the intensification
mechanisms, the removal of Tayloristic rigidities in the division of
labor, applies to anti-Tayloristic
teamworking as well. This poses a dilemma for employee
representatives. In terms of autonomy, on the
other hand, the difference between neo-Tayloristic and
anti-Tayloristic teamworking is real.
In anti-Tayloristic teamworking, there is no supervisor inside the
team. The function of
spokesperson rotates. All team members can participate in
decision-making. Standardization is not
relentlessly pursued; management accepts some measure of worker
control. There is a tendency to
alleviate technical discipline, e.g. to find alternatives for the
assembly line. Buffers are used.
Remuneration is based on proven skill level; there are no group
bonuses.
In contrast, in neo-Tayloristic teamworking, a permanent supervisor
is present in the team as
team leader. At most, only the team leader can participate in
decision-making. Standardization is
relentlessly pursued. Management prerogatives are nearly unlimited.
Job designers treat technical
discipline, e.g. short-cycled work on the assembly line, as
unproblematic. There are no buffers. A
substantial part of wages consists of individual bonuses based on
assessments by supervisors on how
deeply workers cooperate in the system. Group bonuses are also
given.
The instability and vulnerability of anti-Tayloristic teamworking
imply that it can only
develop and flourish when managers and employee representatives put
determined effort into it. The
opportunity structure for this contains both economic and political
elements. In mass production, the
economic success of Toyota, through skillful mediation by management
gurus, makes the opportunity
structure for anti-Tayloristic teamworking relatively unfavorable
A New Approach to Solve Permutation Scheduling Problems with Ant Colony Optimization
A new approach for solving permutation scheduling problems with Ant Colony Optimization is proposed in this paper. The approach assumes that no precedence constraints between the jobs have to be fulfilled. It is tested with an ant algorithm for the Single Machine Total Weighted Deviation Problem. The new approach uses ants that allocate the places in the schedule not sequentially, as the standard approach, but in random order. This leads to a better utilization of the pheromone information
Probing the Conformational Dynamics of Affinity-Enhanced T Cell Receptor Variants upon Binding the Peptide-Bound Major Histocompatibility Complex by Hydrogen/Deuterium Exchange Mass Spectrometry.
Binding of the T cell receptor (TCR) to its cognate, peptide antigen-loaded major histocompatibility complex (pMHC) is a key interaction for triggering T cell activation and ultimately elimination of the target cell. Despite the importance of this interaction for cellular immunity, a comprehensive molecular understanding of TCR specificity and affinity is lacking. We conducted hydrogen/deuterium exchange mass spectrometry (HDX-MS) analyses of individual affinity-enhanced TCR variants and clinically relevant pMHC class I molecules (HLA-A*0201/NY-ESO-1 <sub>157-165</sub> ) to investigate the causality between increased binding affinity and conformational dynamics in TCR-pMHC complexes. Differential HDX-MS analyses of TCR variants revealed that mutations for affinity enhancement in TCR CDRs altered the conformational response of TCR to pMHC ligation. Improved pMHC binding affinity was in general observed to correlate with greater differences in HDX upon pMHC binding in modified TCR CDR loops, thereby providing new insights into the TCR-pMHC interaction. Furthermore, a specific point mutation in the β-CDR3 loop of the NY-ESO-1 TCR associated with a substantial increase in binding affinity resulted in a substantial change in pMHC binding kinetics (i.e., very slow k <sub>on</sub> , revealed by the detection of EX1 HDX kinetics), thus providing experimental evidence for a slow induced-fit binding mode. We also examined the conformational impact of pMHC binding on an unrelated TRAV12-2 gene-encoded TCR directed against the immunodominant MART-1 <sub>26-35</sub> cancer antigen restricted by HLA-A*0201. Our findings provide a molecular basis for the observed TRAV12-2 gene bias in natural CD8 <sup>+</sup> T cell-based immune responses against the MART-1 antigen, with potential implications for general ligand discrimination and TCR cross-reactivity processes
Beam-ACO Applied to Assembly Line Balancing
Assembly line balancing concerns the design of assembly lines for the manufacturing of products. In this paper we consider the time and space constrained simple assembly line balancing problem with the objective of minimizing the number of necessary work stations. This problem is denoted by TSALBP-1 in the literature. For tackling this problem we propose a Beam-ACO approach, which is an algorithm that results from hybridizing ant colony optimization with beam search. The experimental results show that our algorithm is a state-of-the-art metaheuristic for this problem
New generic algorithms for hard knapsacks
Abstract. In this paper, we study the complexity of solving hard knapsack problems, i.e., knapsacks with a density close to 1 where latticebased low density attacks are not an option. For such knapsacks, the current state-of-the-art is a 31-year old algorithm by Schroeppel and Shamir which is based on birthday paradox techniques and yields a running time of Õ(2n/2) for knapsacks of n elements and uses Õ(2n/4) storage. We propose here two new algorithms which improve on this bound, finall
Reviews on drag reducing polymers
Polymers are effective drag reducers owing to their ability to suppress the formation of turbulent eddies at low concentrations. Existing drag reduction methods can be generally classified into additive and non-additive techniques. The polymer additive based method is categorized under additive techniques. Other drag reducing additives are fibers and surfactants. Non-additive techniques are associated with the applications of different types of surfaces: riblets, dimples, oscillating walls, compliant surfaces and microbubbles. This review focuses on experimental and computational fluid dynamics (CFD) modeling studies on polymer-induced drag reduction in turbulent regimes. Other drag reduction methods are briefly addressed and compared to polymer-induced drag reduction. This paper also reports on the effects of polymer additives on the heat transfer performances in laminar regime. Knowledge gaps and potential research areas are identified. It is envisaged that polymer additives may be a promising solution in addressing the current limitations of nanofluid heat transfer applications