327,870 research outputs found
Optimal Storage Rack Design for a 3D Compact AS/RS with Full Turnover-Based Storage
No full textCompact, multi-deep (3D) automated storage and retrieval systems (AS/RS) are becoming increasingly popular for storing products with relatively low turnover on a compact area. An automated storage/retrieval crane takes care of movements in the horizontal and vertical direction in the rack, and a gravity conveying mechanism takes care of the depth movement. An important question is how to layout such systems to minimize the product storage and retrieval times. Although much attention has been paid to 2D AS/RS, multi-deep systems have hardly been studied. This paper studies the impact of system layout on crane travel time. We calculate the rack dimensions that minimize single-command cycle time under the full-turnover-based storage policy. We prove the expected travel time is minimized when the rack is square-in-time in horizontal and vertical directions and the conveyor’s dimension is the longest. We compare the model’s results with the performance of the random storage policy and show a significant crane travel time reduction can be obtained. We illustrate the findings of the study by applying them in a practical example.AS/RS;Warehousing;Order Picking;Storage Rack Design;Travel Time Model;Turnover-Based Storage
Optimal Storage Rack Design for a 3-dimensional Compact AS/RS
No full textIn this paper, we consider a newly-designed compact three-dimensional automated storage and retrieval system (AS/RS). The system consists of an automated crane taking care of movements in the horizontal and vertical direction. A gravity conveying mechanism takes care of the depth movement. Our research objective is to analyze the system performance and optimally dimension of the system. We estimate the crane’s expected travel time for single-command cycles. From the expected travel time, we calculate the optimal ratio between three dimensions that minimizes the travel time for a random storage strategy. In addition, we derive an approximate closed-form travel time expression for dual command cycles. Finally, we illustrate the findings of the study by a practical example.AS/RS;Warehousing;Order Picking;Travel Time Model;Compact Storage Rack Design
Receptor for activated C kinase-1 facilitates protein kinase C-dependent phosphorylation and functional modulation of GABA(A) receptors with the activation of G-protein-coupled receptors
No full textGABA(A) receptors are the principal sites of fast synaptic inhibition in the brain. These receptors are hetero-pentamers that can be assembled from a number of subunit classes: alpha(1-6), beta(1-3), gamma(1-3), delta(1), epsilon, theta, and pi, but the majority of receptor subtypes is believed, however, to be composed of alpha, beta, and gamma2 subunits. A major mechanism for modulating GABA(A) receptor function occurs via the phosphorylation of residues within the intracellular domains of receptor subunits by a range of serine/ threonine and tyrosine kinases. However, how protein kinases are targeted to these receptors to facilitate functional modulation remains unknown. Here we demonstrate that the receptor for activated C kinase (RACK-1) and protein kinase C (PKC) bind to distinct sites on GABA(A) receptor beta subunits. Although RACK-1 is not essential for PKC binding to GABAA receptor beta subunits, it enhances the phosphorylation of serine 409, a residue critical for the phospho-dependent modulation of GABA(A) receptor function in the beta1 subunit by anchored PKC. Furthermore, RACK-1 also enhances GABA(A) receptor functional modulation in neurons by a PKC-dependent signaling pathway with the activation of muscarinic acetylcholine receptors (mAChRs). This PKC-dependent modulation of neuronal GABAA receptors was mirrored by an increase in the phosphorylation of GABA(A) receptor beta subunits with the activation of mAChRs.Our results suggest a central role for RACK-1 in potentiating PKC-dependent phosphorylation and functional modulation of GABA(A) receptors. Therefore, RACK-1 will enhance functional cross talk between GABA(A) receptors and G-protein-coupled receptors and therefore may have profound effects on neuronal excitability
Optimal Zone Boundaries for Two-class-based Compact 3D AS/RS
No full textCompact, multi-deep (3D), Automated Storage and Retrieval Systems (AS/RS) are becoming more common, due to new technologies, lower investment costs, time efficiency and compact size. Decision-making research on these systems is still in its infancy. We study a particular compact system with rotating conveyors for the depth movement and a Storage/Retrieval (S/R) machine for the horizontal and vertical movement of unit loads. We determine the optimal storage zone boundaries for such systems with two product classes: high and low turnover, by minimizing the expected Storage/Retrieval (S/R) machine travel time. We propose a mixed-integer nonlinear programming model to determine the zone boundaries. A decomposition algorithm and a one dimensional search scheme are developed to solve the model. The algorithm is complex, but the results are appealing since most of them are in closed-form and easy to apply to optimally layout the 3D AS/RS rack. The results are compared with those under random storage, and show that a significant reduction of the machine travel time can be obtained. Finally, a practical example is studied to demonstrate the use and validate our findings.AS/RS;Class-based storage;Order picking;Storage rack design;Travel time model
In Their Element(s) - Rack Card
No full textBi-lingual rack card for the exhibition In Their Element(s): Women Artists Across Mediahttps://digitalcommons.fairfield.edu/in-their-elements-ephemera/1007/thumbnail.jp
Storage Rack.
No full textPatent for a mounted storage rack for automobiles that can be folded onto the running board. The rack may be shortened or lengthened for running boards of different lengths, or to provide a storage space of a given length
Weld toe stress concentrations in multi-planar stiffened tubular KK joints
No full textThis paper reports a parametric stress analysis of various configurations of
rack plate stiffened multi-planar welded KK joints using the finite element
method. The KK joint finds application in the leg structure of offshore oil and
gas jack-up platforms. The rack plate works as a stiffener which reduces the
stress concentration at the brace/chord intersection. This could be an immense
contribution to the increase in fatigue life of the joint, but other hot spot
sites are introduced into the joint. The rack is also used for raising and
lowering of the jack-up hull which gives the jack-up platform its jacking
capability. Over 120 models using a combination of shell and solid elements have
been built and analysed with ABAQUS. Non-dimensional joint geometric parameters
(beta, gamma and Omega) are employed in the study, with the new parameter Omega
being defined as the ratio of rack thickness to chord diameter. Stress
concentration factors (SCFs) are calculated under applied axial and OPB (out-of-
plane bending) loading. Three critical SCF locations are identified for each
load case, with each location becoming the most critical based on the
combination of the non-dimensional parameters selected for the joint. This is
important as careful design can shift the critical SCIF from an area
inaccessible to NDT to one that can be easily inspected. The SCF values
extracted from the models are used to derive six parametric equations through
multiple regression analysis performed using MINITAB. The equations describe the
SCF at the different locations as a function of the non-dimensional ratios. The
equations not only allow the rapid optimisation of multi-planar joints but also
can be used to quickly identify the location of maximum stress concentration and
hence the likely position of fatigue cracks. This in itself is an invaluable
tool for planning NDT procedures and schedules. (C) 2008 Elsevier Ltd. All
rights reserved
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Rack Protection Monitor - A Simple System
No full textThe Rack Protection Monitor is a simple, fail-safe device to monitor smoke, temperature and ventilation sensors. It accepts inputs from redundant sensors and has a hardwired algorithm to prevent nuisance power trips due to random sensor failures. When a sensor is triggered the Rack Protection Monitor latches and annunicates the alarm. If another sensor is triggered, the Rack Protection Monitor locally shuts down the power to the relay rack and sends alarm to central control
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