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This paper presents a digital implementation of a DSP-based digital IEC 61000-4-15 flickermeter. According to the functions and design criteria suggested by IEC, a digital model of the flickermeter is developed and simulated by using Matlab and Code Composer Studio. Then, the developed flickermeter function is applied to perform a series of tests based on IEC Standard 61000-4-15 test procedures to...
This paper focuses on developing a mathematical model for solving the Economic Lot Scheduling Problem (ELSP) under an imperfect (shifting) process that includes joint material replenishment, in-production screening process, imperfect rework process, scraps and shortage. The Common Cycle (CC) approach is applied for the problem formulation. Although this paper only demonstrates the first step, further...
In this work, an algorithm for coupling external circuit elements to electromagnetic (EM) particle-in-cell (PIC) simulations is developed. The circuit equation including an external voltage or current source, resistance, inductance, capacitance, and a dynamic load is solved simultaneously with the EM PIC updaters through an instant measured voltage across the system to obtain the supplied current...
This work introduces a conformal finite difference time domain (CFDTD) particle-in-cell (PIC) method with an improved field emission algorithm to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the Vorpal code. For the field emission algorithm, we employ the elliptic function v(y) found by Forbes...
This paper presents a load impedance estimation and iterative-learning control for a three-phase four-wire inverter. The topology of a three-phase four wire inverter is adopted to uninterruptible power supply (UPS) applications, which can supply unbalanced load, linear load and rectified load. The proposed load impedance estimation scheme employs an RLC equivalent circuit concept to determine the...
This work introduces a conformal finite difference time domain (CFDTD) particle-in-cell (PIC) method with an improved field emission algorithm to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the Vorpal code. For the field emission algorithm, we employ the elliptic function v(y) found by Forbes...
In this work, an algorithm for coupling external circuit elements to EM PIC simulations is developed. The circuit equation including an external voltage or current source, resistance, inductance, capacitance, and a dynamic load is solved simultaneously with the EM PIC updaters through an instant measured voltage V across the system to obtain the supplied current I for feeding into the system. This...
In this work, a self-consistent general thermal field (GTF) emission model is formulated and the space charge effect on the original GTF equation developed by Jensen at NRL is studied analytically. We have also implemented the GTF algorithm in VORPAL, a conformal finite-difference timedomain (CFDTD) particle-in-cell (PIC) code. This analytic model could serve as a benchmark standard for the GTF CFDTD...
In general, the operating characteristics of RF vacuum electronic or plasma devices are affected by the power supply, e.g., a pushing effect on the oscillating frequency of a magnetron by a supplied anode current. The external impedance connected to the system under study should be included in the electromagnetic (EM) particle-in-cell (PIC) simulations especially when the system is in a transient...
In this work, a self-consistent general thermal field (GTF) emission model is formulated and the space charge effect on the original GTF equation developed by Jensen is studied analytically. We have also implemented the GTF algorithm in VORPAL, a conformal finite-difference time-domain (CFDTD) particle-in-cell (PIC) code. This analytic model could serve as a benchmark standard for the GTF CFDTD PIC...
Influence of ion effects on a space charge limited field emission flow has been studied systematically, by employing both analytical and numerical approaches. The analytic calculations are carried out self-consistently to yield the steady states of the bipolar flow. It is found that the field emission currents in the presence of saturated ion currents can be enhanced to be nearly 1.8, 1.5, and 1.4...
To ensure that the radio-frequency (RF) energy absorbed by human subjects during MRI does not produce any harmful health effects to the patient - including local thermal damage or whole-body thermoregulatory challenges - regulatory entities have set limits on the maximum local, partial-body, and whole-body specific absorption rates (SAR) of RF energy. This paper discusses numerical calculations of...
Virtual coupling is commonly used to maintain stability of penalty-based haptic rendering. However, due to dozens of design parameters involved in the dynamics and force model, to increase transparency while maintaining stability using virtual coupling remains a challenge for 6-Degree-of-Freedom (DOF) haptic rendering. Using an equivalent-angle analysis, we transform 3-DOF rotation into 1-DOF rotation,...
We propose a new fitting model for better characterizing field emitters such as a field emission array (FEA) that may be operated at high current density. In this improved model, we employ both effective work function and effective enhancement factor approximations. The experimental data can be fitted perfectly and therefore the discrepancy between the experimental results of FEA at high current density...
In this study, a two-level supply chain with linear demand and seasonal swings is simulated under varying operating situations in order to explore the relationships among bullwhip effect, lead time, forecast accuracy, seasonality, service levels and retailer's performance. Next, a series of univariate tests are undertaken to identify the relationships among the simulation outputs. Based on a structural...
Summary form only given. This work introduces a conformal finite-difference time domain (CFDTD) particle-in-cell (PIC) method with improved field emission algorithms to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the VORPAL code. Locally distorted cells with edges tangential to the metallic...
Unmanned underwater vehicles have various missions within civilian, military and academic sectors. They have the ability to explore areas unavailable to manned assets and to perform duties that are risky to humans. In particular, UUVs have the ability to perform bearings-only tracking in shallow areas near shorelines. This article compares a Logarithmic Polar Coordinates EKF (LPC-EKF) and Logarithmic...
The feasibility of designing a multistage depressed collector using conformal finite-difference time-domain particle-in-cell simulations has been studied. A feedback mechanism is implemented to provide stable time-dependent voltages for each stage of the depressed collector. An arbitrary space-time dependent spent beam distribution can be given in our time-domain simulations. We demonstrate the design...
Since TCP congestion control is ill-suited for high speed networks, designing a replacement for TCP has become a challenge. To address this problem, we extend the population ecology theory to design a novel congestion control algorithm. We treat the network flows as the species in nature, the throughput of the flows as the population number, and the bottleneck bandwidth as the food resources. Then...
This paper describes a comprehensive approach for using the memory controller to improve DRAM energy efficiency and manage DRAM power. We make three contributions: (1) we describe a simple power-down policy for exploiting low power modes of modern DRAMs; (2) we show how the idea of adaptive history-based memory schedulers can be naturally extended to manage power and energy; and (3) for situations...
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