Assembly Retrieval Research Articles

Formation and retrieval of cell assemblies in a biologically realistic spiking neural network model of area CA3 in the mouse hippocampus

The hippocampal formation is critical for episodic memory, with area Cornu Ammonis 3 (CA3) a necessary substrate for auto-associative pattern completion. Recent theoretical and experimental evidence suggests that the formation and retrieval of cell assemblies enable these functions. Yet, how cell assemblies are formed and retrieved in a full-scale spiking neural network (SNN) of CA3 that incorporates the observed diversity of neurons and connections within this circuit is not well understood. Here, we demonstrate that a data-driven SNN model quantitatively reflecting the neuron type-specific population sizes, intrinsic electrophysiology, connectivity statistics, synaptic signaling, and long-term plasticity of the mouse CA3 is capable of robust auto-association and pattern completion via cell assemblies. Our results show that a broad range of assembly sizes could successfully and systematically retrieve patterns from heavily incomplete or corrupted cues after a limited number of presentations. Furthermore, performance was robust with respect to partial overlap of assemblies through shared cells, substantially enhancing memory capacity. These novel findings provide computational evidence that the specific biological properties of the CA3 circuit produce an effective neural substrate for associative learning in the mammalian brain.

Multiscale and Extended Retrieval of Associative Memory Structures in a Cortical Model of Local-Global Inhibition Balance.

Inhibitory neurons take on many forms and functions. How this diversity contributes to memory function is not completely known. Previous formal studies indicate inhibition differentiated by local and global connectivity in associative memory networks functions to rescale the level of retrieval of excitatory assemblies. However, such studies lack biological details such as a distinction between types of neurons (excitatory and inhibitory), unrealistic connection schemas, and nonsparse assemblies. In this study, we present a rate-based cortical model where neurons are distinguished (as excitatory, local inhibitory, or global inhibitory), connected more realistically, and where memory items correspond to sparse excitatory assemblies. We use this model to study how local-global inhibition balance can alter memory retrieval in associative memory structures, including naturalistic and artificial structures. Experimental studies have reported inhibitory neurons and their subtypes uniquely respond to specific stimuli and can form sophisticated, joint excitatory-inhibitory assemblies. Our model suggests such joint assemblies, as well as a distribution and rebalancing of overall inhibition between two inhibitory subpopulations, one connected to excitatory assemblies locally and the other connected globally, can quadruple the range of retrieval across related memories. We identify a possible functional role for local-global inhibitory balance to, in the context of choice or preference of relationships, permit and maintain a broader range of memory items when local inhibition is dominant and conversely consolidate and strengthen a smaller range of memory items when global inhibition is dominant. This model, while still theoretical, therefore highlights a potentially biologically-plausible and behaviorally-useful function of inhibitory diversity in memory.

Pose-free assembly retrieval based on spatial-contact skeleton

In complicated product industry such as aircraft manufacturing, an assembly model contains abundant engineering information for use in design, manufacture, and maintenance. Assembly retrieval can be used to find relevant models for knowledge reuse. However, an assembly with rotatable joints may have many poses, which brings difficulty to assembly retrieval, since there is no pose principle for assembly design. Therefore, focused on rotatable joints in assembly, a skeleton-based descriptor for pose-free assembly retrieval is proposed. The centroid points of part surfaces and contact faces in an assembly are extracted to construct a spatial-contact skeleton. The skeleton-based distance is proposed to measure the distance between two surface points, which is invariant to the rotatable joints. The distribution of skeleton distances between two parts is used to describe the pair. Considering a part paired with all other parts in the assembly, the set of part pairs is used to represent a part, and the modified Hausdorff distance is used to measure the dissimilarity between parts for assembly retrieval. Experiments are conducted to compare the accuracy of the proposed descriptor to holistic and structureless descriptors. The proposed method is shown to retrieve assemblies with similar parts and structures regardless of their rotatable joints.

Structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model

PurposeThree-dimensional computer-aided design (CAD) assembly model has become important resource for design reuse in enterprises, which implicates plenty of design intent, assembly intent, design experience knowledge and functional structures. To acquire quickly CAD assembly models associated with specific functions by using product function requirement information in the product conceptual design phase for model reuse, this paper aims to find an approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model before functional semantic-based assembly retrieval.Design/methodology/approachAn approach for structure-function correlations analysis and functional semantic annotation of CAD assembly model is proposed. First, the product knowledge model is constructed based on ontology including design knowledge and function knowledge. Then, CAD assembly model is represented by part attributed adjacency graph and partitioned into multiple functional regions. Assembly region and flow-activity region are defined for structure-function correlations analysis of CAD assembly model. Meanwhile, the extraction process of assembly region and flow-activity region is given in detail. Furthermore, structure-function correlations analysis and functional semantic annotation are achieved by considering comprehensively assembly structure and assembled part shape structure in CAD assembly model. After that, a structure-function relation model is established based on polychromatic sets for expressing explicitly and formally relationships between functional structures, assembled parts and functional semantics.FindingsThe correlation between structure and function is analyzed effectively, and functional semantics corresponding to structures in CAD assembly model are labeled. Additionally, the relationships between functional structures, assembled parts and functional semantics can be described explicitly and formally.Practical implicationsThe approach can be used to help designers accomplish functional semantic annotation of CAD assembly models in model repository, which provides support for functional semantic-based CAD assembly retrieval in the product conceptual design phase. These assembly models can be reused for product structure design and assembly process design.Originality/valueThe paper proposes a novel approach for structure-function correlations analysis and functional semantic annotation of mechanical CAD assembly model. Functional structures in assembly model are extracted and analyzed from the point of view of assembly structure and function part structure. Furthermore, the correlation relation between structures, assembled parts and functional semantics is expressed explicitly and formally based on polychromatic sets.

Clustering and retrieval of mechanical CAD assembly models based on multi-source attributes information

Abstract Content-based CAD assembly model retrieval focuses more on the similarity measure of geometry and topology information, which can hardly meet designers’ design requirements in the product conceptual design process. To search quickly and effectively the CAD assembly models related with product design requirements information for assembly model reuse, inspire designers’ design thought and product design innovation in the product conceptual design phase, a novel approach for CAD assembly model clustering and retrieval based on multi-source attributes information is proposed. First, the CAD assembly model is represented by attribute adjacency graph (AAG) with multiple attributes information, and the similarity between assembly models is evaluated comprehensively by considering part information and assembly relationship information. Then, a weighted graph is constructed for assembly clustering in model repository. Meanwhile, an improved spectral clustering algorithm is given to divide CAD assembly models into different assembly clusters. Subsequently, indexing model is established for each assembly cluster. After that, the process of assembly retrieval based on indexing model mechanism is given in detail. Finally, experiments on the prototype system verify effectiveness and feasibility of the proposed approach for assembly clustering and retrieval.

CAD assembly model retrieval based on multi-source semantics information and weighted bipartite graph

Content-based CAD assembly model retrieval focusing on similarity measure of bottom-level geometry and topology information can hardly meet design demand of engineering designers in the product design reuse. To search quickly and effectively the CAD assembly models with specific functions by using requirements of mechanical product design, inspire designers’ design thought and product design innovation, an assembly retrieval approach based on multi-source semantics information and weighted bipartite graph is proposed. The approach concerns the high-level semantics information rather than geometry and topology information of assembly model. First, the semantic ontology for mechanical assembly model is constructed considering multi-source semantics information including part semantics, assembly constraint semantics and functional semantics. Function region extraction algorithm is given for identifying functional structures in assembly model, and functional semantics of assembly model is annotated from the aspects of assembly structure granularity and part shape granularity. Subsequently, semantic similarity between concepts is evaluated comprehensively with WordNet and domain ontology, and a semantic matching model is built based on weighted bipartite graph (WBG) for solving the many-to-many semantics matching problem of semantic retrieval for CAD assembly models. Finally, a semantic-based assembly retrieval prototype system is developed and the experiment cases verify effectiveness and feasibility of the proposed assembly retrieval approach.

An efficient assembly retrieval method based on Hausdorff distance

Abstract An assembly provides significant knowledge in design reuse, since it can represent parts information and their relationships comprehensively. The retrieval of assembly has the practical value in accelerating design and enhancing efficiency. Our previous work addressed this issue by using a method based on earth mover's distance. However, it requires a longer, less favorable retrieval time to obtain the retrieval results. To solve this problem, we propose an efficient assembly retrieval method based on a modified Hausdorff distance (MHD). By employing shape distributions, each part is quantitatively described as a point and an assembly is turned into a set of points, then the MHD is performed to evaluate the dissimilarity between the generated point sets. The MHD could be used in overall retrieval of assembly, since it considers the contributions of similar and dissimilar parts. For the scenario of flexible retrieval, a directed Hausdorff distance is proposed, which only compares the local dissimilarity. Experiments are carried out to demonstrate the accuracy and efficiency of the MHD, compared with the earth mover's distance and the vector space model. Our study reveals that the proposed method can retrieve relevant assemblies efficiently on the premise of assuring the accuracy.

Risk Assessment Strategy for Decommissioning of Fukushima Daiichi Nuclear Power Station

Abstract Risk management of the Fukushima Daiichi Nuclear Power Station decommissioning is a great challenge. In the present study, a risk management framework has been developed for the decommissioning work. It is applied to fuel assembly retrieval from Unit 3 spent fuel pool. Whole retrieval work is divided into three phases: preparation, retrieval, and transportation and storage. First of all, the end point has been established and the success path has been developed. Then, possible threats, which are internal/external and technical/societal/management, are identified and selected. “What can go wrong?” is a question about the failure scenario. The likelihoods and consequences for each scenario are roughly estimated. The whole decommissioning project will continue for several decades, i.e., long-term perspective is important. What should be emphasized is that we do not always have enough knowledge and experience of this kind. It is expected that the decommissioning can make steady and good progress in support of the proposed risk management framework. Thus, risk assessment and management are required, and the process needs to be updated in accordance with the most recent information and knowledge on the decommissioning works.

An assembly retrieval approach based on shape distributions and Earth Mover’s Distance

Assembly retrieval is a significant technology to reuse the abundant design knowledge embedded in the products. However, the existing assembly retrieval methods are very few and the research on this topic is still needed. In this paper, an assembly retrieval approach based on shape distributions and Earth Mover’s Distance (EMD) is proposed. This approach concerns the shape information rather than the high-level information (such as kinematical information) of assembly model, which gives the user a simpler way to retrieve assemblies. First, a histogram is generated to capture the shape information of a part model based on shape distributions, and a point which represents the part model is constructed by taking the heights of the bins in the histogram as the coordinates. Through this way, an assembly model is simply and quantitatively described as a point set, and the comparison of assembly models is transformed into the comparison of point sets. Afterward, the corresponding EMD-based matching method is given to comprehensively evaluate the differences between assembly models by calculating the dissimilarities between the generated point sets. This matching method also enables the fuzzy retrieval, which allows the user to input several part models rather than the exact assembly model to query. Finally, an assembly retrieval prototype system is developed, and the experiments on the system have shown the effectiveness of the proposed assembly retrieval approach.

Ontology-Based Assembly Design Representation for Model Reuse

Assembly is an important part in production and development of complex products. Flexible assembly retrieval is one of the key issues to find the reusable model. The main objective of this paper is to extend the model of ontology-based assembly design for model reuse. Firstly, we propose a representation of assembly structural data including topological structure, assembly semantics, and geometrical information. Secondly, we enrich assembly design (AsD) ontology for knowledge captured and shared in Web Ontology Language 2 Description Logic (OWL 2 DL) and Semantic Web Rule Language (SWRL). And then, we define the matching strategies and similarity assessment for two matched models. Finally, we illustrate the validity of assembly design representation for model reuse through experiments.

Relaxed lightweight assembly retrieval using vector space model

Assembly searching technologies are important for the improvement of design reusability. However, existing methods require that assemblies possess high-level information, and thus cannot be applied in lightweight assemblies. In this paper, we propose a novel relaxed lightweight assembly retrieval approach based on a vector space model (VSM). By decomposing the assemblies represented in a watertight polygon mesh into bags of parts, and considering the queries as a vague specification of a set of parts, the resilient ranking strategy in VSM is successfully applied in the assembly retrieval. Furthermore, we take the scale-sensitive similarities between parts into the evaluation of matching values, and extend the original VSM to a relaxed matching framework. This framework allows users to input any fuzzy queries, is capable of measuring the results quantitatively, and performs well in retrieving assemblies with specified characteristics. To accelerate the online matching procedure, a typical parts based matching process, as well as a greedy strategy based matching algorithm is presented and integrated in the framework, which makes our system achieve interactive performance. We demonstrate the efficiency and effectiveness of our approach through various experiments on the prototype system.

A flexible assembly retrieval approach for model reuse

Nowadays, growing quantities of product models are created in industries. Usually, these models contain abundant design knowledge, either explicit or implicit, in various disciplines. As an approach to taking full advantage of the design knowledge embedded, model reuse plays an increasingly important part in complex product design and innovative design, in which enormous time and cost can be saved. While model retrieval is a natural and promising way to help designers find the right models for quick and accurate reuse, the retrieval technology for assemblies is yet to reach maturity since the previous text-based or low-level content-based assembly retrieval could not fully support the needs of users.In this paper, a new assembly retrieval approach is presented, based on which, users can input flexible queries, either rough or precise, to retrieve efficiently the whole or partial assemblies they want from the product library. First, a multilevel assembly descriptor supporting various searching requirements is elaborated, which collects different levels of information in assembly models. Then, the corresponding matching and similarity assessment methods with well-balanced efficiency and discriminability are given to evaluate the differences between assembly models. Moreover, an indexing mechanism for accelerating assembly retrieval, especially the partial retrieval, is presented to filter the unmatchable models quickly. Finally, an assembly retrieval prototype system is implemented, and the experimental results are analyzed to verify the advantages of the flexible assembly retrieval approach.

Toward a universal classification and coding system for assemblies

AbstractA variety of group technology‐based classification and coding systems have been developed to handle piece parts. These systems typically characterize parts by geometry or processing requirements, or some combination of the two. However, while there are a few situation specific classification and coding systems that address assemblies, there is no universal paradigm for the design and implementation of such a system.Part of the reason for the lack of such a system is probably due to the inherent difficulty in finding a common basis within the diversity of assemblies from industry to industry. This diversity has necessitated a “reinventing of the wheel” from case to case.In this project, we develop a GT‐based classification and coding system designed for assemblies, with specific application to a firm in the pulp and paper making machinery industry. At the same time we attempt to develop a general framework for the design of such specialized coding systems.The framework we propose focuses upon GT‐based classification and coding systems from the traditional management information system perspective; that is, the needs of the users, current and future, drive the system logic. We perceive two primary uses of the classification and coding systems. One use is for the direct retrieval of engineering designs and manufacturing plans, thus inducing efficiency within the design and planning functions. Thus, the system must reflect the practices. conventions, and culture of the organization. In most cases, this use of the system is the most immediate, it has the most immediate financial benefits, and in our case, it was the rationale for justifying the expense of the project.The second use of such a coding system is to make information contained within the engineering and manufacturing data bases readily available for operational analysis and management decision making. Examples of this include: analysis investigating cellular restructuring, cost and profit analysis of engineering designs, and evolutionary development of engineering standards by judicious editing of the data bases.The first use implies a strong focus on the user, with considerable time spent determining any cultural phenomena which may impact system use. The second use implies a need for extreme clarity in the categorization inherent in the coding structure. For example, considerable time was spent investigating blueprints to determine the diameter frequency distribution of a particular type of forging. Upon consultation with the firm. we discovered that our categorization roughly matched the categorization implicit in the pattern numbers used by their foundry. After a number ot iterations we determined a categorization of the diameter of this particular forging which reflected the reality of the empirical distribution of diameters and adhered closely with the traditionally used pattern numbering scheme. The result was that this portion of the code structure reflected current firm practice while accurately providing frequency of occurrence data which may in the future be useful to management.The dimensions of assemblies considered in our assembly coding system included: Function. The basic functional requirement satisfied by the assembly. Shape. The intrinsic and observable shape of the assembly. Dimensions(s). Critical dimensional ranges of the assembly. Facets(s). The inclusion of specific detailed items which support the primary intrinsic function of the assembly. Feature(s) and detail(s). The inclusion of items which complement the primary intrinsic function of the assembly. Material(s). The material specification of the assembly.The final form of our coding and retrieval system was three tiered, including a GT‐based coding system for piece parts, a custom GT‐based coding system for assemblies, integrated with an existing top‐down retrieval system for “large” final assemblies (whole paper‐making production systems). The top‐down retrieval system was based primarily on function, technology, and customer information. The coding and retrieval of final assemblies is used for all components tied to a unique assembly, while the coding and retrieval of piece parts and subassemblies is used for all components that are not specific to any particular final assembly. Such a system allows for rapid coding and retrieval of all piece parts, subassemblies, and assemblies manufactured by the firm.