Search results

In the field of planetary exploration, the legged-type lander is a common landing buffer device. There are two important performance metrics for legged-type landers: the energy absorption capacity and landing stability. In this paper, a novel method is proposed to optimize the honeycomb buffer of a legged-type lander. Optimization design variables are the dimension parameters of honeycomb and the objective functions are the evaluation parameters of the above two performance metrics.

A multi-body dynamic model of a lander and a finite-element model of the metal honeycomb are established. Based on the simulation results of the finite-element model and the quartic polynomial, the surrogate models are established to evaluate the energy absorption capacity of honeycomb. Considering both the multi-body dynamic model and the surrogate models, the study designed the optimization flow of dimension parameters of honeycomb. Besides, the non-dominated sorting genetic algorithm II is used for iterative calculation.

Images of surrogate models show the monotonous functional relationship between the honeycomb’s energy absorption characteristics and its dimension parameters. Optimization results show an apparent contradiction among the objective functions. Besides, according to the simulation results, this method can significantly improve the comprehensive performance of the lander.

The novel method can effectively reduce the cost of honeycomb compression tests and improve the lander’s design. Therefore, it can be used for optimizing buffers of other types of legged-type landers.

The present work aims in presenting the energy absorbing capability of different combination stacking of multiple materials, namely, Vero White and Tango Plus, under static and dynamic loading conditions.

Honeycomb structures with various multi-material stackings are fabricated using PolyJet 3D printing technique. From the static and dynamic test results, the structure having the better energy absorbing capability is identified.

It is found that from the various stacking combinations of multiple materials, the five-layered (5L) sandwich multi-material honeycomb structure has better energy absorbing capability.

This multi-material combination with a honeycomb structure can be used in the application of crash resistance components such as helmet, knee guard, car bumper, etc.

Through experimental work, various multi-material honeycomb structures and impact resistance of single material clearly indicated the inability to absorb impact loads which experiences a maximum force of 5,055.24 N, whereas the 5L sandwich multi-material honeycomb structure experiences a minimum force of 1,948.17 N, which is 38.5 per cent of the force experienced by the single material. Moreover, in the case of compressive resistance, 2L sandwich multi-material honeycomb structure experiences a maximum force of 5,887.5 N, whereas 5L sandwich multi-material honeycomb structure experiences a minimum force of 2,410 N, which is 40.9 per cent of the force experienced by two-layered (2L) sandwich multi-material honeycomb structure. In this study, the multi-material absorbed most of the input energy and experienced minimum force in both compressive and impact loads, thus showing its energy absorbing capability and hence its utility for structures that experience impact and compressive loads. A maximum force is required to deform the single and 2L material in terms of impact and compressive load, respectively, under maximum stiffness conditions.

The retail revolution swing from traditional distribution to e-tailing services and unprecedented increase in internet adoption insist practitioners to diversely plan warehousing strategies. More than practically required storage space has been identified as wastes, and also it does not improve performance. An organized framework integrating storage design policies, operational performance and customer value improvement for retail-distribution management is lacking. Therefore, the purpose of this paper is to develop broad guidelines to design the “just-right” amount of forward area, i.e., “lean buffer” answering the following questions: “What should be lean buffer size? How effective the forward area is? As per demand variations, which storage waste (SKU) should be allocated with how much storage space? What is the amount of storage waste (SW)? How smooth the material flow is in between reserve-forward area?” for storage allocation in cosmetics distribution centers.

After forecasting static storage allocation between two planning horizons, if a particular SKU is less or non-moving, then it will cause SW, as the occupied location can be utilized by other competing SKUs, and also it impedes material flow for an instance. A dynamically efficient and self-adaptive, knapsack instance based heuristics is developed in order to make effective storage utilization.

The existing state-of-the-art under study is supported with a distribution center case, and the study investigates the need of a model adopting lean management approach in storage allocation policies along with test results in LINGO. The sensitivity analysis describes the impact of varying demand and buffer size on performance. The results are compared with uniform and exponential distributed demands, and findings reveal that the proposed heuristics improves efficiency and reduce SWs in forward-reserve area.

The presented model demonstrates a novel thinking of lean adoption in designing storage allocation strategy and its performance measures while reducing wastes and improving customer value. Future research issues are highlighted, which may be of great help to the researchers who would like to explore the emerging field of lean adoption for sustainable retail and distribution operations.

The purpose of this paper is to assess the blast‐mitigation potential and the protection ability of an air‐vacated buffer placed in front of a target structure under realistic combat‐theatre conditions.

The blast‐mitigation efficacy of the air‐vacated buffer concept is investigated computationally using a combined Eulerian‐Lagrangian (CEL) fluid‐structure interaction (FSI) finite‐element analysis.

The two main findings resulting from the present work are: the air‐vacated buffer concept yields significant blast‐mitigation effects; and the buffer geometry and vacated‐air material‐state parameters (e.g. pressure, mass density, etc.) may significantly affect the extent of the blast‐mitigation effect.

The main contribution of the present work is a demonstration of the critical importance of timely deployment of the buffer relative to the arrival of the incident wave in order to fully exploit the air‐vacated buffer concept.

The contemporary e-tailing marketplace insists that distribution centers are playing the roles of both wholesalers and retailers which require different storage-handling load sizes due to different product variants. To fulfill piecewise retail orders, a separate small size-fast pick area is design called “forward buffer” wherein pallets are allocated from reserve area. Due to non-uniform pallets, the static allocation policy diminishes forward space utilization and also, more than practically required buffer size has been identified as wastage. Thus, dynamic storage allocation policy is required to design for reducing storage wastage and improving throughput considering non-uniform unit load sizes. The purpose of this paper is to model such policy and develop an e-decision support system assisting enterprise practitioners with real-time decision making.

The research method is developed as a dynamic storage allocation policy and mathematical modeled as knapsack-based heuristics. The execution procedure of policy is explained as an example and tested with case-specific data. The developed model is implemented as a web-based support system and tested with rational data instances, as well as overcoming prejudices against single case findings.

The provided model considers variable size storage-handling unit loads and recommends number of pallets allocations in forward area reducing storage wastes. The algorithm searches and suggests the “just-right” amount of allocations for each product balancing existing forward capacity. It also helps to determine “lean buffer” size for forward area ensuring desired throughput. Sensitivity and buffer performance analysis is carried out for Poisson distributed data sets followed by research synthesis.

Warehouse practitioners can use this model ensuring a desired throughput level with least forward storage wastages. The model driven e-decision support system (DSS) helps for effective real-time decision making under complicated business scenarios wherein products are having different physical dimensions. It assists the researchers who would like to explore the emerging field of “lean” adoption in enterprise information and retail-distribution management.

The paper provides an inventive approach endorsing lean thinking in storage allocation policy design for a forward-reserve model. Also, the developed methodology incorporating features of e-DSS along with quantitative modeling is an inimitable research contribution justifying rational data support.

The primary objective of this study is characterizing the anisotropic mechanical properties of corrugated cardboard and simultaneously simulating its drop cushioning dynamic effects under various drop conditions.

Static and dynamic tests were conducted on corrugated cardboard to obtain adequate experimental data in different directions. An effective anisotropic constitutive model is introduced by developing the honeycomb materials model in ANSYS LS-Dyna, and an effective approach is established toward effectively determining the material parameters from the test data obtained. The model is validated by comparing simulation results with experimental data from five drop conditions, including bottom drop, front drop, side drop, 30° side drop and edge drop. Additionally, simulations are conducted to study the cushioning performance of the packaging by dropping the corrugated cardboard at different heights.

The study establishes a fast and effective approach to simulating the drop cushioning performance of corrugated cardboard under various drop conditions, which demonstrates good agreement with experimental data.

This approach is of value for packaging protection and provides guidance for stacking of packaging during transportation.

The complications caused by metallic orthopaedic bone screws like stress-shielding effect, screw loosening, screw migration, higher density difference, painful reoperation and revision surgery for screw extraction can be overcome with the bioabsorbable bone screws. This study aims to use additive manufacturing (AM) technology to fabricate orthopaedic biodegradable cortical screws to reduce the bone-screw-related-complications.

The fused filament fabrication technology (FFFT)-based AM technique is used to fabricate orthopaedic cortical screws. The influence of various process parameters like infill pattern, infill percentage, layer height, wall thickness and different biological solutions were observed on the compressive strength and degradation behaviour of cortical screws.

The porous lattice structures in cortical screws using the rapid prototyping technique were found to be better as porous screws can enhance bone growth and accelerate the osseointegration process with sufficient mechanical strength. The compressive strength and degradation rate of the screw is highly dependent on process parameters used during the fabrication of the screw. The compressive strength of screw is inversely proportional to the degradation rate of the cortical screw.

The present study is focused on cortical screws. Further different orthopaedic screws can be modified with the use of different rapid prototyping techniques.

The use of rapid prototyping techniques for patient-specific bone screw designs is scantly reported. This study uses FFFT-based AM technique to fabricate various infill patterns and porosity of cortical screws to enhance the design of orthopaedic cortical screws.

The purpose of this paper is to propose a self‐immune automated signature generation (SISG) for polymorphic worms which is able to work well, even while being attacked by any types of malicious adversary and produces global‐suited signatures other than local‐suited signatures for its distributed architecture. Through experimentations, the method is thereafter evaluated.

The ideal worm signature exist in each copy of the corresponding worm, but never in other worm categories and normal network traffic. SISG compares each worm copy and extract the same components, then produces the worm signature from the components which must achieve low‐false positive and low‐false negative. SISG is immune from the most attacks by filtering the harmful noise made by malicious adversaries before signature generation.

NOP sled, worm body and descriptor are not good to be signature because they can be confused intricately by polymorphic engines. Protocol frames may not suit to be signature for the anti‐automated signature generation attacks. Exploit bytes is the essential part of an ideal worm signature and it can be extracted by SISG exactly.

The paper proposes a SISG for polymorphic worms which is able to work well even while being attacked by any types of malicious adversary and produces global‐suited signatures other than local‐suited signatures for its distributed architecture.

This paper aims to utilize purpose advanced fluid‐structure interaction, non‐linear dynamics, finite‐element analyses in order to investigate various phenomena and processes accompanying blast wave generation, propagation and interaction and to assess the blast‐wave‐mitigation potential of a piston‐cylinder assembly placed in front of the target structure.

The employed computational methods and tools are verified and validated by first demonstrating that they can quite accurately reproduce analytical solutions for a couple of well‐defined blast wave propagation and interaction problems.

The methods/tools are used to investigate the piston‐cylinder blast‐mitigation concept and the results obtained clearly reveal that significant blast‐mitigation effects can be achieved through the use of this concept. Furthermore, the results showed that the extent of the blast‐mitigation effect is a sensitive function of the piston‐cylinder geometrical parameters. Specifically, the mass of the piston and the length of the cylinder are found to be the dominant factors controlling the extent of the blast‐wave‐mitigation.

The work demonstrates that, when assessing the blast‐wave‐mitigation potential of the piston‐cylinder concept, it is critical that loading experienced by the piston be defined by explicitly modeling (fluid/structure) interactions between the blast wave(s) and the piston.

A straight through wind tunnel sited outdoors was completed in 1963. A 200 h.p. diesel engine gives 75 ft./sec. in the 18‐ft. square section. Models small enough to avoid serious wall constraint are tested statically with fully simulated lift systems to measure the performance and handling characteristics of V.T.O. aircraft at low forward speeds. Intake and jet flows are induced by ejector pumps which occupy representative positions in the engine bay. Engines and airframe are mounted separately to measure loads on tailored balances, and surfaces are extensively pressure plotted. Thus aerodynamic interferences are isolated, giving the physical back‐ground for the formulation of theoretical treatments and calculation methods, involving jet mixing regions and separated flows. Meanwhile empirical data is available for early design work to develop V.T.O. aircraft with useful payload and range. Configurations which minimize the download due to ground effect tend to develop large downloads during the transition manoeuvre. The worst configurations suffer nearly complete loss of the installed vertical thrust, due to aerodynamic interferences on the airframe. Moderate overloading of a V.T.O. aircraft with poor transition performance results in a long take‐off run.