Final Assemblies Research Articles

Molecular recognition between a biotinylated polythiophene copolymer and phycoerythrin utilizing the biotin-streptavidin interaction

The interaction of photoactive proteins with an electroactive matrix is valuable in leading to potential technological applications in opto-electronic signal transduction for optical displays, color mimicking, biosensor, and protein research applications. In this study, the Langmuir-Blodgett technique is used to couple these components through the well-known biotin-streptavidin complexation. Biotinylated copolymers of 3-substituted thiophenes have been synthesized both to enhance mechanical film integrity and to provide the electroactive matrix for attachment of the antennae protein, phycoerythrin. It has been determined that biotinylation of the thiopene copolymers improves their film forming properties and results in stable monolayers. Pressure-area isotherms indicate that protein interaction with the polymer monolayer is occuring with the streptavidin and phycoerythrin proteins. Fluorescene spectroscopy of transferred films confirms the presence of phycoerythrin in the final molecular assemblies. Each stage of protein binding to the biotinylated copolymer monolayer could be monitored through fluorescence microscopy at the air-water interface. These results suggest that this copolymer system is a promising material for integrating virtually any biotinylated macromolecular system to an electroactive matrix. In addition, this copolymer system may be “fine tuned” to maximize protein integration by varying the distance between biotin functionalities and/or the length of the biotin spacer arm.

Scheduling for machining and assembly in a job-shop environment

The problem of scheduling n assembly jobs in a job-shop environment is addressed. Each job is characterized by multiple parts that must themselves be scheduled for processing through the shop. The individual parts combine at assembly stations to form sub-assemblies or final assemblies. Sub-assemblies combine with other subassemblies to form final assemblies. The objective pursued in the developed model is to maximize the machine utilization subject to satisfying job due date requirements. Essentially, one must consider machine availability, the amount of work on each machine for each operation, the precedence constraints, and the dispatching criteria to perform scheduling in this kind of environment. A heuristic algorithm is developed to solve the problem. The application of the algorithm is demonstrated with an example problem.

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.

Assembly manpower allocation under proportionality constraints

Allocation of manpower to the production of assemblies and subassemblies can be treated by models like linear programming. In general, final assemblies, subassemblies and components can be inventoried in order to get optimal manpower allocations. But there are situations in which the allocation to assembly operations may become more complex. Such a situation arises in the production of some electronic assemblies, where the quantity of each subassembly produced will have to bear a fixed proportion to the quantity of the final assembly because the subassemblies are not permitted to be inventoried for various reasons. This problem particularly arises in manpower systems with skills which are oriented to the products (assemblies) rather than to the operations, which is generally the case with engineering production systems. It appears from the literature that such a situation has not been dealt with so far. The fixed proportion is depicted as a set of proportionality constraints in the formulation of the problem as a linear program. A solution of a case is presented in detail.

Common component inventory problems with a budget constraint: Heuristics and upper bounds

This paper addresses a so-called assemble-to-order environment. There are a number of end items each of which requires an assembly of several components. Some of the components are unique to specific end items while others are common to two or more final products. Components must, due to the leadtimes, be ordered prior to knowing the end item demand levels (assumed poisson distributed), but final assemblies can be completed after knowing the demands. The objective is to maximize the expected profit contribution subject to a budget constraint on the component inventory investment. The resulting two-stage stochastic programming problems obtained are very difficult, if not impossible, to solve. Heuristics and bounding procedures that give good results have therefore been suggested. The proposed heuristics can easily be extended to problems with continuous demand distributions.

Optimal and heuristic solutions for a simple common component inventory problem

This paper addresses a so-called assemble-to-order environment. There are a number of end items each of which requires an assembly of several components. Some of the components are unique to specific end items while others are common to two or more final products. Components must be ordered prior to knowing the end item demand levels (assumed normally distributed), but final assemblies can be completed after knowing the demands. The problem addressed is the allocation of a given budget among the components so as to maximize the expected total of end items sold. For a relatively simple commonality structure the optimal allocation is developed. A much simpler heuristic allocation procedure is shown to give excellent performance over a wide range of parameter values.

Automatic assembly line for VTR mechanisms

An automatic assembly line for VTR mechanisms was developed. The line, 88% of the stations on which are automated, consists of 56 dedicated automatic assembly machine stations, 11 robot stations, and 9 manual assembly stations. Prior to development of the line, the product design was reviewed by using the Hitachi Assemblability Evaluation Method. System design was carried out effectively with the help of computer simulation. The installation of robots and modularized, standardized stations provided line flexibility. The robots are used for delicate and precise subassemblies of complicated shape. Development of this line reduced assembly labor to 1/6th, the necessary assembly shop area to 1/3rd, and the readjustment rate of the final assemblies to 1/5th upon line completion. Performance has subsequently been doubled.

Deep-etch views of clathrin assemblies

Clathrin assemblies were adsorbed to mica and freeze-dried by a new procedure that yields 3-D images with much topological detail. These permitted renewed inquiry into how clathrin trimers (i.e., “triskelions”) assemble into polygonal coats or baskets. Freeze-drying revealed unsuspected differences in the relative shapes and dimensions of individual trimer building blocks, as compared with the completed polygonal networks, which indicate that the assembly scheme first proposed by Crowther and Pearse (1) requires modification. Specifically, the freeze-etch images display the following new features: (1) Trimer arms possess terminal scroll-shaped hooks that can open or close and thus determine their lengths. (2) When extended, trimer arms are sufficiently long to pass around three sides of the final polygonal facet. Since current views hold that the arms pass around only two sides, the remaining length, including the terminal hook, must point into the basket interior. (3) Freeze-dried trimers display bends in their arms at specific loci that determine their final distribution in the completed baskets. (4) The completed struts of the final assemblies are uniform in calibre, cylindrical in profile, and travel directly between the vertices of each polygon, without any sign of the slew or width-variation that is predicted by the Crowther and Pearse model. Based on this direct comparison of protomer vs product, by a single technique that can image both, we offer a modified scheme for clathrin coat assembly, in which we predict that the individual arms in each clathrin triskelion emanate from its center in a slewed manner, but the final assembled struts of the basket need not be slewed. Attempts were made to capture assembly intermediates on mica to obtain support for the new scheme, but these unfortunately yielded ambiguous images of incomplete polygons with blunt projections, rather than the expected “halo” of uncommitted trimer arms. These we interpret to be “dead ends” that failed to polymerize further because they included proteolyzed components. Further assembly experiments, avoiding such hazards, are indicated.

The halting problem for linear turing assemblers

Turing assemblers are Turing machines which operate on n-dimensional tapes under restrictions which characterize a procedure of assembly rather than computation, and which are intended as an abstraction of certain algorithmic processes of molecular biology. It has been previously shown that Turing assemblers with n-dimensional tapes can simulate arbitrary Turing machines for all n>1. Here it is shown that for n=1 even nondeterministic Turing assemblers have a sharply restricted computational capability, being able to successfully assemble only regular sets. The halting problem for linear Turing assemblers is therefore algorithmically solvable, and a characterization of the set of achievable final assemblies will be given as a subclass of the context-free languages.

Roosting of starlings ( Sturnus vulgaris): A function of light and time

Starlings ( Sturnus vulgaris ) were observed returning to roost from 27 August to 7 October 1966. Initial departure towards the roost was closely correlated with light intensity. The time of departure from the feeding areas would probably show a better correlation with light intensity than would the time of departure for the first and final assemblies. As the roost is approached there is a weaker correlation between light intensity and time of departure from rendezvous areas. Starlings arrival at the roost is not simply a function of the light-time stimulus, because it also depends on the light intensity at the time starlings began flying. The latter influences their rate, the varying distances they must fly to the final roost, and behavioural interactions en route.