Post-Certification Engineering Taxonomy and Task Value Optimization in the Aerospace Industry

Abstract:

This article proposes a novel taxonomy of post-certification engineering activities as a first step toward true lean product development (PD). Relying on key notions developed in a novel lean engineering performance model, the authors compare the leanness of post-certification versus pre-certification tasks for the design of aerospace parts. Discrete event simulation and integer linear programming models are developed to help ascertain the influence of factors such as multitasking, concurrency, task size, task value, and post-certification budget decision making on lean engineering PD performance. The models developed provide the foundation for enhanced PD performance and the establishment of optimal PD process parameters.     

A case for information theory-based modelling of human multitasking performance

Technological advances have led to increased prevalence of human multitasking. Traditionally, multitasking performance is measured for each individual task, utilising multiple performance metrics. Recently, the human operator informatic model (HOIM) has been developed as a quantitative model of human–machine interaction capable of measuring multitasking performance with a single metric. In this study, we investigated the performance effects of both a different number of tasks and five different task combinations while maintaining a constant level of overall difficulty. Results indicate that, at a constant difficulty level, neither number of tasks nor task combination significantly affects multitasking performance, indicating the reliability of input baud rate as a measure of system complexity. No task interaction effects were found among the different tasks. This study demonstrates the application of information theory for modelling of human multitasking performance and makes a case for the use of the HOIM in future studies of human information processing.     

Multitasking scheduling problems with a rate-modifying activity

Motivated by the behavioral phenomena that occur while human operators are carrying out tasks, we study multitasking scheduling problems with a rate-modifying activity. In the problems, the processing of a selected task suffers from interruptions by other tasks that are available but unfinished, and the human operators regularly engage rest breaks during work shifts allowing them to recover or mitigate some of the negative effects of fatigue. The objectives are to respectively minimize: makespan, total completion time, maximum lateness, and due-date assignment related cost by determining when to schedule the rate modifying activity and the optimal task sequence in the presence of multitasking. Scheduling models and algorithms are proposed to solve the problems. The numerical examples are presented to illustrate the theorems and algorithms.     

Unconstrained design: improving multitasking with in-vehicle information systems through enhanced situation awareness

ABSTRACT

In the age of information, in-vehicle multitasking is inevitable. The popularity of the automobile, in combination with the present information age, create a growing demand to do more in-vehicle than simply focus on the road. Unconstrained Design, a philosophy which supports rather than constrains multitasking, is proposed as a path toward enhancing performance in-vehicle. Situation Awareness (SA), a theory allowing designers to understand how operators interact in dynamic, complex environments, is used to frame this experimental investigation. Two SA-grounded human-machine interface concepts are proposed, designed to support drivers to multitask in-vehicle when frequent task switching is required. The first focuses upon supporting preparation for a Non-Driving Related Activity (NDRA), and the second upon supporting the Driving Related Activity (DRA) when an NDRA is active. While multitasking, Contextual Cueing, using a Head-up Display, produced significant reductions in NDRA response time, while an auditory lane keeping aid increased the amount of time a driver spent in the central region of a lane. The combined evidence suggests that using SA and Unconstrained Design to create of IVIS that support drivers’ ability to multitask in-vehicle can lead to task performance improvements.     

Risk-based analysis of manufacturing systems

A manufacturing system considered here consists of a machine that processes parts and an automatic conveyor that transports immediately a finished part to an assembly cell (i.e. a single workstation facility is examined). The system can hold a maximum number of processed parts on the conveyor, which determines its size. Modelling the system as a family of Birth–Death Processes with finite size in equilibrium, indexed by the system utilisation parameter, and depending on the concepts of system information and system entropy (i.e. mean information), we promote a risk-based analysis of manufacturing systems. The current number of processed parts on the conveyor determines the system particular states. The performance measures of a system are: risk (i.e. uncertainty) of the system (represented by system entropy), throughput of the system, utilisation of the machine, utilisation of the conveyor, and information range of the system. They are simultaneously investigated with respect to the system utilisation parameter, in order for an optimal trade-off among them to be established. This analysis is illustrated on the information linear, Erlang, Binomial and Pascal held manufacturing systems. Regarding the managerial insights, a use case of a system target output is considered, comparing the above system types. This approach can also be used for analysis of an assembly line consisting of multiple machines that have different operation times and buffers between them.     

The role of reward and effort over time in task switching

When multitasking in a demanding environment, operators strategically switch between tasks. Two influences on this multi-task management behaviour are the perceived rewards gained from performing a task, and the perceived effort a task requires in order to be completed. Proportionally, reward over effort is ‘rate of return’, expressing that either reward or effort changing over time spent performing a task, may influence multitasking behaviour. In the current experiment, two of four tasks within a multitasking paradigm provided constant or diminishing reward and required either constant or increasing effort in their performance. For on-going tasks, decreasing reward and increasing effort required both increased the probability of a task switch. The theory contributed here supports the study of multi-task management, and task switching model development. We discuss each in the context of safety-critical applications.     

Dependence of lead time on batch size studied by a system dynamics model

Most planning models treat lead time as a constant independent of workload, but the resulting order rate implies capacity utilisation that, in turn, affects the lead time. An important factor that determines production order rate is the batch size, and one therefore expects a relationship between batch size and lead time. This dependency is examined for different operational conditions using system dynamics simulation of a manufacturing model comprising a quality control unit that is also the bottleneck of the system. It is shown that there is an optimal batch size that results in a minimum lead time and that inventory level at optimum matches the desired inventory. Below optimal batch size, lead time increases sharply due to congestion at the bottleneck. The results have implications for production planning and implementation of process improvement.     

Effects of frequency and bandwidth on diagnostic information transfer in ultrasonic B-mode imaging

Transmitted pressure pulses in ultrasonic B-mode imaging systems are commonly characterized by their center frequency and bandwidth. Both parameters are associated with tradeoffs in spatial resolution and signal-to-noise in ultrasonic system design, with no general understanding of where they are optimal when applied to specific clinical exams. We use the ideal observer and simple psychophysical studies with human observers to evaluate the efficiency of information transfer in B-mode imaging as a function of the transmitted pulse center frequency and fractional bandwidth. Our approach uses a statistical model of backscatter relevant to breast imaging, and a 2-D model of pulse propagation based on Rayleigh-Sommerfeld diffraction theory. The statistics of the backscattered signal are combined in an ideal observer calculation that quantifies the task-relevant information contained in the radio-frequency (RF) signal after delay-and-sum beamforming. This is followed by a psychophysical evaluation of observer performance on B-mode envelope-detected images in three simple tasks. This experimental design allows us to track the flow of diagnostic information through RF acquisition and subsequent reading of the envelope image. In a low-contrast detection task and a high-contrast boundary discrimination task, optimal efficiency for human observers is observed at the highest center frequencies tested (15 MHz) and at moderate bandwidth (40%). For detection of scattering material in a high-contrast hypoechoic lesion, optimal efficiency was observed at lower center frequencies (5 MHz) and higher bandwidth (80%). The ideal observer analysis shows that this task dependence does not arise in the acquisition stage, where efficiency is maximized at 15 MHz with bandwidths of 60% or greater, but rather in the subsequent processing and reading of the envelope image. In addition, at higher frequencies more information is lost in the processing and reading than in the acquisition of reflected signals.     

Modelling of carbon utilisation efficiency and its application in milling parameters optimisation

At present, the evaluation index for low carbon manufacturing was mainly focused on the relationship between carbon emission and economic benefits or removal volume. But there was rarely comprehensive evaluation index to evaluate the carbon utilisation level of processing. Based on this, this paper presented the carbon utilisation efficiency as the comprehensive evaluation index in low carbon manufacturing. The carbon utilisation efficiency was defined as the ratio of the carbon emission of materials removal to the whole carbon emission in manufacturing process. A carbon utilisation efficiency model was established in milling process, based on flow characteristics and removal mechanism of carbon emission during milling. Then a multi-objective optimisation model was established based on Particle Swarm Optimisation, and the minimum processing time and high carbon utilisation efficiency were set as the optimisation objectives. And the experiment was performed to confirm the undetermined constant in the optimisation model and verify the effectiveness of the optimisation model. The optimised milling parameters were verified to reduce the processing time and improve the carbon utilisation efficiency.     

Personality trait theory and multitasking performance: implications for ergonomic design

Although system designers usually minimise the role of individual differences in operation, personality variables could explain differences in multitasking performance. A concomitant theoretical issue is whether primary or surface personality traits do a better job of predicting performance than the Five-Factor Model (FFM) or global traits. A sample of 174 undergraduates completed the Sixteen Personality Factor Questionnaire (16PF), which was followed by a performance task. A computer-based task that measured simultaneous performance on an arithmetic task and a mental rotation task was used to measure multitasking performance; scores measured the percent accuracy. Primary traits for low emotional sensitivity and high abstractedness, self-control, and general reasoning were all correlated with performance (R ² = .11), but global or traits corresponding to the FFM were not, except in one sporadic task trial. There was also a strong gender effect on performance. Implications for the study of personality traits in ergonomics are discussed.     

Algorithms for the joint multitasking scheduling and common due date assignment problem

In this paper, we investigate a joint multitasking scheduling and common due date assignment problem on a single machine, for which examples can be found in product delivery process in logistics. Multitasking allows the machine to perform multiple tasks. The multitasking phenomenon has been observed in various practical domains, including manufacturing and administration. In multitasking settings, each waiting job interrupts a currently in-processing job, causing an interruption time and a switching time. In common due date assignment problems, the objective is to determine the optimal value of this due date with the purpose of minimising a total penalty function, which is associated with service quality. For the problem with general interruption functions, analytical properties are obtained to reduce the search space of the optimal solutions. For the cases with linear interruption functions, we develop a polynomial-time algorithm. Numerical experiments have been conducted to validate the efficiency of our proposed algorithm. Computational results also demonstrate an interesting phenomenon that in some cases, the optimal solutions under multitasking are superior to the counterparts without multitasking. Besides, we also devise a mixed integer programme for the cases with linear interruption function.     

Investigating the role of business processes and knowledge management systems on performance: A multi-case study approach

In the ever-changing and competitive market place, organisations continuously need to improve their competitive advantage. One method to accomplish this is to form collaborative networks. Both knowledge management (KM) and KM systems play a pivotal role in the success of collaborative networks since information sharing and knowledge assets are so critical to the network. There has been a vast amount of research on KM systems but very little is known about how it affects individual and organisational performance. Drawing on the task–technology fit theory, in this study, we explore the fit or alignment between business process (task) and KM systems (technology) and its impact on KM systems utilisation based on multiple case studies. Subsequently, we investigate the impacts of both the task–technology fit and KM systems utilisation on individual and business performance. This paper contributes to the collaborative network/KM literature in several ways. First, it extends the task–technology fit theory to an important context of collaborative network/KM. Second, it replaces task with business process, which has the potential to help explain KM systems’ success on business performance. Third, the paper explores the positive impact of task–technology fit on KM system utilisation and business performance. Fourth and finally, the study provides insight into the future development of KM systems and how to better align them with managerial purposes.     

Multitasking parallel-machine scheduling with machine-dependent slack due-window assignment

We consider the problem of parallel-machine scheduling with machine-dependent slack (SLK) due-window assignment in the multitasking environment, which exists in various application domains such as Internet services, project management, and manufacturing. Motivated by practical observations, we extend the original model of multitasking to a more general model where each job’s interruption proportion depends on the job itself and its processing position. In the light of individualised service, we consider SLK due-window assignment. Our objective is to minimise the total cost that comprises the earliness, tardiness, and due-window-related costs. Finding that an optimal schedule exists when each machine is occupied by at least one job, we show that the problem is polynomially solvable. We provide a more efficient solution algorithm for a special case of the problem. Finally, we present numerical examples to illustrate the application of the theoretical results and working of the solution algorithms.     

Analysis of information flow in hierarchical organizations

It is commonly accepted today that competitive, service-oriented or manufacturing organizations are overloaded with information to an extent not experienced before. Moreover, technical employees as well as managers at all levels of an organization devote increasing resources to handling this flow of information. While the inundation of information may be useful in an organization, it reduces the productive time of all the members of the organization. This paper presents a model that links the productivity of hierarchical organizations with the amount of information processed and generated in the organization. This model is used to find the optimal conditions and optimal amount of information that needs to flow in three types of hierarchical organizations: homogeneous, semi-homogenous and non-homogenous organizations. The model defines the information processing parameters that lead to optimal productivity at each level and each type of organization. Dynamic programming is used to solve the model. The paper provides a pioneering effort in linking the amount of information processed in an organization to the productivity of the organization. In addition, the paper provides a new approach to linking the productivity of the individual functions to the overall productivity of the organization.     

Lot-splitting approach of a hybrid manufacturing system under CONWIP production control: a mathematical model

This paper discusses the advantages of lot splitting in hybrid manufacturing environments where cellular and functional layouts are combined under Constant Work in Process (CONWIP) production control. The proposed model fills a research gap in the related literature by applying lot splitting and pull production simultaneously. A linear CONWIP control mathematical model that minimises the average flow time is developed in case of lot splitting. The developed model has sequence-dependent set-up times. The demand level, coefficient of variation (CV) impact and set-up time reduction effect on CONWIP production control are also investigated. The model is solved using GAMS21.6 optimisation software; the optimal backlog list, the number and size of sublots are reported. The proposed model is compared with lot production under push control in different settings as well as with two different heuristics from the literature. Experimental results indicate that in all settings, the lot splitting is more advantageous than lot production in terms of average flow time. CV has a greater effect than set-up time reduction on average flow time.     

复杂系统人机交互中的多任务调度策略综述

目的 随着自动化技术的不断发展,系统的复杂性导致多任务成为人机系统交互中常见的场景,多任务呈现出信息模态的复杂化、任务类型多样化、任务中断普遍化等特点,其中多任务的调度策略对系统的运营安全和绩效起着十分重要作用.通过梳理和总结复杂系统人机交互中的多任务调度策略,旨在解决复杂人机系统在设计、建造、维护过程中的问题.方法 通过对国内外相关文献的回顾,以认知心理学的双任务转换生理机制实验研究为起点,从任务调度策略研究逐步分析延展到中断管理和多任务调度决策的发展过程,着重围绕人机交互过程中的多任务调度行为和任务突显性、优先级、参与感、难度、执行时间等不同属性对任务调度决策的影响,进行了详细梳理和总结.结论 在研究综述和相关文献的基础上指出了既有任务调度策略研究中存在的局限性,并从系统交互设计的角度对将来的人机交互多任务管理研究提出了建议.     

Blood flow imaging--A new real-time, 2-D flow imaging technique

This paper presents a new method for the visualization of two-dimensional (2-D) blood flow in ultrasound imaging systems called blood flow imaging (BFI). Conventional methods of color flow imaging (CFI) and power Doppler (PD) techniques are limited as the velocity component transversal to the ultrasound beam cannot be estimated from the received Doppler signal. The BFI relies on the preservation and display of the speckle pattern originating from the blood flow scatterer signal, and it provides qualitative information of the blood flow distribution and movement in any direction of the image. By displaying speckle pattern images acquired with a high frame rate in slow motion, the blood flow movement can be visually tracked from frame to frame. The BFI is easily combined with conventional CFI and PD methods, and the resulting display modes have been shown to have several advantages compared to CFI or PD methods alone. Two different display modes have been implemented: one combining BFI with conventional CFI, and one combining BFI with PD. Initial clinical trials have been performed to assess the clinical usefulness of BFI. The method especially has potential in vascular imaging, but it also shows potential in other clinical applications.     

Optimization of the LCD optical film cutting problem

The manufacturing of liquid crystal display (LCD) plays an important role in electronics manufacturing industries, such as televisions, smart phones, pads, laptops, monitors and electronic appliances. Due to the fact that the cost of LCD’s film materials may reach 60–70% of the production cost, appropriate cutting schemes can lead to better raw material utilisation and thus enhance manufacturers’ profitability. Accordingly, the determination of the optimal production plan for cutting different-sized LCD optimal films with the designed cutting angles to fulfil the customers’ orders is a critical issue for the LCD industry. In the past, few studies integrated the different cutting allocation strategies into a synthetic decision. This study proposes a mathematical programming model for the two-stage cutting problem for LCD optical films to determine the optimal cutting allocation strategy with consideration of the costs of raw materials, processing and disposal during the manufacturing process. For large-scale problems in which the runtime for obtaining the optimal solution may grow exponentially as the problem size increases, a heuristic algorithm is also provided to obtain the approximate solution within a reasonable time. Finally, the results of the practical case shows that, compared with the existing fixed-angle cutting method, the proposed approach reduces the total cost by 6.2% due to the better material utilisation. In addition, the processing cost is also reduced due to a decrease in the required materials.     

A proportional-integral-differential control of flow over a circular cylinder

In the present study, we apply proportional (P), proportional-integral (PI) and proportional-differential (PD) feedback controls to flow over a circular cylinder at Re=60 and 100 for suppression of vortex shedding in the wake. The transverse velocity at a centreline location in the wake is measured and used for the feedback control. The actuation (blowing/suction) is provided to the flow at the upper and lower slots on the cylinder surface near the separation point based on the P, PI or PD control. The sensing location is varied from 1d to 4d from the centre of the cylinder. Given each sensing location, the optimal proportional gain in the sense of minimizing the sensing velocity fluctuations is obtained for the P control. The addition of I and D controls to the P control certainly increases the control performance and broadens the effective sensing location. The P, PI and PD controls successfully reduce the velocity fluctuations at sensing locations and attenuate vortex shedding in the wake, resulting in reductions in the mean drag and lift fluctuations. Finally, P controls with phase shift are constructed from successful PI controls. These phase-shifted P controls also reduce the strength of vortex shedding, but their results are not as good as those from the corresponding PI controls.     

基于心流PAT模型的界面设计策略研究

目的 以PAT模型为视角,探究心流体验在事前阶段下的相关界面设计策略。方法 基于PAT模型,从用户、工具、任务三个层面对现有心流体验在事前阶段下互联网产品领域研究成果进行分类分析,并归纳总结出具体的前因要素,通过文献研究法、归纳法、案例分析法,针对不同的前因要素提出相应的界面设计策略。结论 针对用户层面的界面设计策略包括包容的多层次用户定位、有效且专注的时间区间设置、具备引导性的交互功能设定、趣味的感知信息提示;针对工具层面的界面设计策略包括清晰明确的界面布局、可感知的操作线索、个性化定制内容、简洁的操作服务流程、沉浸式社交互动元素;针对任务层面的界面策略包括可调节的难度动态平衡、分段式任务目标设定、多样化奖励激励机制、及时且有效的反馈机制。本次研究成果进一步深化了心流理论在界面设计领域的策略研究。