Superluminal propagation from IR physics

One may believe that front velocities of waves in a given theory coincide with the UV limit of phase velocities for any dispersion relations. This implies that IR physics is irrelevant to the discussion of propagation speed of waves. We first consider a theory that contains higher spatial derivatives in the wave equation and prove that front velocities coincide with the UV limit of phase velocities, at least, if parity is conserved. However, we also show that front velocities do not coincide with the UV limit of phase velocities in general dispersion relations. We explicitly give several examples in which front velocities are superluminal owing to an IR or intermediate energy scale property of dispersion relations even if the UV limit of phase velocities is luminal. Our finding conveys the important caution that not only UV physics but also IR physics can be significant to superluminality.Comment: 10 pages, 4 figure

Analysis of the Interaction Torque on the Arm Based on Via-Point Movement

To produce a desired movement, the human motor control system must regular the interaction torque generated owing to the multi-joint structure of the body. In this study, the trajectories of human movements were evaluated considering the interaction torque generated through the elbow and shoulder joints. Measurement experiments were conducted, in which the participants performed movements corresponding to a three-point task, and the results indicated that the interaction torque is correlated with certain characteristics of the trajectories of the arm movements. Moreover, the contribution of the interaction torque in realizing the task differs in the cases of dominant and non-dominant hands. In addition, through a simulation, the interaction torque of simulated trajectories was modulated to examine the corresponding effect on the arm movements. For a point-to-point movement, certain characteristics of the actual movements were reproduced in the simulated trajectories. However, for a three-point movement, the characteristics of the simulated trajectories were only partially similar to those of the measured trajectories. The findings indicate that the interaction torque notably influences the motor control, and the tuning of the interaction torque is more complex than the other criteria of motor control

B-code Generation for a CNC Dentistry Wire Bending Mechanism

In the present study, the generation of CNC wire bending code (B-code) is explored and an automatic converter is developed in Excel through some mathematical formulae. The B-code comprises of three parameters which have been determined from the previous work, known as feeding length (L), plane rotation angle (R) and bend-ing angle (A). These parameters control the movement of the designed wire bending machine in this way; (L) tells the feeding mechanism how long the straight wire to be fed, (R) constructs the turning mechanism to rotate in certain degrees before the bending operation starts and (A) determines the degrees of bend, performed by the bending mechanism. The input of the converter is the Cartesian XYZ coordinate of each bend point, obtained from the CAD file. This paper also describes the XYZ extraction process from an IGES file, in addition to the CNC code generation. The practicality of these procedures is demonstrated through an example, starting from the wire design, follows by the XYZ extraction and ends with the B-code generation. Moreover, the graphical simulation of the bending operation by the designed mechanism is also presented. However, the capability of these codes in controlling the wire bending machine in the real bending operation will not be discussed in the present work

A simulation-based approach to decision support for lean practitioners

In today’s global competition, having a lean production system is a must for companies to remain competitive. By identifying and eliminating waste throughout a product’s entire value stream by means of a set of LM tools, companies are able to produce and assemble any product range in any order or quantity. In order to do these, personnel needs to have the expertise in deciding which LM tool to implement at the right time and on the right place. However, this expertise is not always available. Therefore, this paper proposes a simulation-based decision support (SDS) tool to assist the decision making in LM tool implementation. The SDS tool provides five functions through an interactive use of process simulation. The functions are layout, zoom-in/zoom-out, task status, Key Performance Indicators (KPI) status and R.A.G (Red, Amber and Green) status (quantifying waste). These functions are incorporated into a process model of coolant hose manufacturing (CHM) factory which was developed in this study. Layout function provides a bird’s eye view of the whole process model and shows how the manufacturing process runs with the flow of materials and products. Zoom-in/zoom-out function provides a detail view of manufacturing processes of the factory. For KPI and RAG status functions, examples of LM tool implementations are used to show how different parameters affect the outcome of manufacturing process. Bar charts of KPIs are also available during simulation. Feasibility study showed how SDS tool enhance the visual perception and analysis capabilities of lean practitioners through availability of specific functions in the simulation model. Hence, decisions in LM implementation could be made correctly and with increased confidence by lean practitioners

Novel availability and performance ratio for internal transportation and manufacturing processes in job shop company

Purpose: Purpose of this study includes the quantification of the impact of transportation efficiency onto the workstations the transportation serves in term of throughput and total lead time elapsed by product. Besides, it aims to synchronize the capacity available among workstations throughout a production line by studying the upper limit of throughput could be afforded by each workstation as well as their connection with each other. This study is also done on the purpose of promoting fulfillment of customer demand at shorter delivery time and minimal equipment utilization. Investigation on implementation of Overall Equipment Effectiveness (OEE) in an aerospace part-manufacturing company is studied to track out the potential opportunities to be improved. Design/methodology/approach: Site observation is conducted on all the five manufacturing workstations in the aforementioned aerospace part manufacturing company. Time data of both automated processes and manual processes are collected and they are used to construct simulation model. From that, various scenarios of transportation efficiency are simulated in Experiment 1. In addition, Experiment 2 is also set to examine the maximum capacity of each workstation. All of these are to highlight the relationship between workstation and processes and to verify the condition of imbalanced capacity among workstations in the company. In short, this has necessitated the integration of workstation and transportation activities within the company. These are followed by proposal of measures to quantify the wastes identified. Findings: The paper finds that implementation of OEE alone does not consider the reasonability of customer demand fulfillment. The results show that both transportation efficiency and imbalanced capacity throughout production system are not emphasized by OEE implementation in the case company. Therefore, responsibility of all workstations and transportation process in delivering demand on time are quantified. Transportation process which serves as the connectors of manufacturing processes is quantified and monitored by proposed Transportation Measure (TM) whereas workstations are measured using novel availability and performance ratio. Research limitations/implications: Future research should be conducted to examine the impact of other station within a company such as warehouse and logistic department to the performance of equipment and materials in manufacturing workstation. Besides, the material availability as well as the skills or performance of man power could be further incorporated into the measures to consider all the entities involved in manufacturing processes. Practical implications: The proposed availability and performance ratio for both transportation and manufacturing processes, which are related to each other, help in promoting better effectiveness of production system in terms of production amount and lead time. Besides, reasonable utilization equipment and minimal consumption of material are incorporated in the measures to promote Lean way in fulfilling customer demand. The effectiveness of entire production line is examined as a unity with joint responsibility under varying transportation efficiency and cycle time of each workstation. Both measures could be implemented together to optimize the production system and quantify the hidden wastes which are neglected in the OEE implementation. Originality/value: The novel availability and performance ratio are proposed to consider customer demand, historical equipment utilization and Takt time of each workstation to examine the possibility and reasonability of demand fulfillment. This prevents both over-processing and overproduction issues which are invisible in OEE. Furthermore, delay propagation throughout production system and interrelationship between processes are quantified under transportation measure. Other novelty of the paper is that it monitors the waiting time and lead time spent in each workstation at the same time considering utilization of workstation. The proposed Transportation Measure (TM) aims to reduce the queue length and waiting time at destination workstation at minimal utilization of forklift. It also promotes less capacity investment in transportation and prioritizes its scheduling according to urgency of destination workstation.Peer Reviewe

Expectation Management in a Global Collaboration Project Using a Deterministic Design Approach

Expectation management in product engineering design aims at setting achievable goals for both customers and designers, while leaving room for creativity and passion. This is especially challenging in the global workplace. Using an example of a design project, the Dental Headrest project (DHR), this paper reviews how expectations were managed in a successful, collaborative project between the University of Tokushima (UT) and Massachusetts Institute of Technology (MIT). The goal of the project was to design an innovative mechanism for the positioning a dental chair headrest so satisfy both the needs of a patient for comfort and a clinician for flexibility and access. The design team was formed with six students from the MIT MechE’s Precision Machine Design class, while the challenge proposed by a UT team of dentists and design engineers. The team followed a deterministic design procedure inducing understating the challenge and reviewing prior art, strategy and concept generation, detailed module design and fabrication and testing, culminating in presentation and documentation. Through the process was coordinated by online communication and collaborative working spaces which ensured real-time information transfer between the continents. The conclusion was a face-to-face meeting between the two institutions. This DHR project resulted in an innovative design of headrest adjusting mechanism that was implemented in a prototype. Moreover, the students, faculty and clinicians benefitted from the experience of innovative design collaboration in a multidisciplinary, global team.CIMIT: Center for Integration of Medicine and Innovative TechnologyJ. Morita Corporatio

Examination of Overall Equipment Effectiveness (OEE) in Term of Maynard's Operation Sequence Technique (MOST)

It is a common practice to quantify any process or entire production line in manufacturing industry especially to measure three main losses named time losses, performance losses and quality defect exist in production. Overall Equipment Effectiveness (OEE) fulfils the requirement by providing the measure of equipment via single measure which is monitored from time to time by responsible personnel so that corresponding optimization or Kaizen could be done. However, there are many lean wastes which could be 'invisible' or tolerated under the conventional definition of OEE. The hidden waste includes unnecessary production which was classified as operating time and the underestimated effect of excessive transportation or setup time. These could be minimized and sometimes avoidable via work measurement, method study and study of the work, which are under the study of Maynard's Operation Sequence Technique (MOST). This paper intends to examine and quantify the hidden lean waste in OEE from the perspective of method and work of an operation with the integration of MOST study. Operations are analyzed in every single step and broken down into details of activities, which are then re-designed for minimal non-value added activity in operation based on the standard allowable. The OEE data after the study of work is computed and compared with the OEE before the MOST study. The comparison shows the improvement in term of OEE after the MOST study and this implies that the hidden waste inside OEE definition could be tracked out for a better effectiveness. Any reduction in the non-value added activities or downtime ensure larger room for more value added activities or uptime and therefore the availability of production. It is expected to provide a new insight in implementing OEE at a different way and stay beware of the assumptions in OEE to avoid any hidden waste

Overall equipment effectiveness estimation for priority improvement in the production line

The objective of this research is to propose an enhancement of the overall equipment effectiveness (OEE) by including information on OEE estimation, value added (VA) cost, and non-value added (NVA) cost through simulation and the Taguchi experimental method. This additional information can enhance the original OEE as a key performance indicator (KPI) and act as a guide for a company in deciding on the priority improvement required. If a company relies solely on the ordinary OEE calculation, it can only arrive at a decision for priority improvement through the lowest score measured and will be in the dark as to the level of improvement required in the production line. Decision-makers in the company need to consider information other than the OEE score if their intention is to see a profound improvement in the performance of the production line. This research proposes a procedure which employs simulation and the Taguchi experimental method