Multi-port dynamic compact thermal models of dual-chip package using model order reduction and metaheuristic optimization

Delphi-like boundary condition independent (BCI) compact thermal models (CTMs) are the standard for modelling single die packages. However their extraction, particularly in the transient case, will be time consuming due to complex numerical simulations for a large number of external conditions. Lately, new approaches to extract a BCI dynamical CTM (DCTM), based on model order reduction (MOR) were developed. Despite the numerous advantages of this recent method, the lack of numerical tools to integrate reduced-order models (ROM) makes it difficult to use at board level. In this study, a novel process flow for extracting Delphi-inspired BCI DCTMs is proposed. Thus a detailed three-dimensional model is replaced by a BCI-ROM model using FANTASTIC matrix reduction code to generate the data used in the creation of a Delphi-style BCI DCTM. That hybrid reduction method has been applied, at first on a single-chip package (QFN16) then on a dual-chip package (DFN12). Their derived CTM and DCTM have been compared in term of accuracy and creation time using, or not, MOR reduction technique. The results show that for a similar accuracy, the integration of MOR technique allows minimizing the time-consuming numerical simulations and consequently reduce the thermal network creation time by 80%.     

Assuring quality and reliability of complex electronic systems:hardware and software

Some of the most recent trends in expanding the scope of traditional quality-assurance techniques to include all phases of design, development, manufacture, and deployment, considering both hardware and software, are discussed. Emerging views on quality management are discussed. The life cycle of a product, beginning with the setting of requirements, and including assuring parts reliability, evaluating a fault-tolerant architecture, avoiding physical design hazards, enforcing software development methodology, measuring conformance to requirements in manufacture, and tracking performance in the field is considered. The author's goal is to review in a general way, what can be accomplished through use of the various assurance techniques with references given to examples from the literature, which gives historical background as well as teaches the technical methods in detail     

Dynamic resource allocation in OFDM systems: an overview of cross-layer optimization principles and techniques

Recently, a lot of research effort has been spent on cross-layer system design. It has been shown that cross-layer mechanisms (i.e., policies) potentially provide significant performance gains for various systems. In this article we review several aspects of cross-layer system optimization regarding wireless OFDM systems. We discuss basic optimization models and present selected heuristic approaches realizing cross-layer policies by means of dynamic resource allocation. Two specific areas are treated separately: models and dynamic approaches for single transmitter/receiver pairs (i.e., a point-to-point communication scenario) as well as models and approaches for point-to-multipoint communication scenarios (e.g., the downlink of a wireless cell). This article provides basic knowledge in order to investigate future OFDM cross-layer-optimization issues     

Imitation, copying, and the use of models: report writing in an introductory physics course

The article focuses on the use and misuse of models-both appropriate and inappropriate-in the report-writing practices of first year physics students, especially those from non-English speaking backgrounds. It analyzes the students' propensity to use any available text on a given topic as a source of model sentences. Examples of "copying" are provided and analyzed. It is argued that many forms of copying are legitimate learning strategies of novice writers, for the production of certain kinds of texts, but that this can become a problem when inappropriate models are used or when appropriate models are used inappropriately. Copying is discussed in relation to imitative learning and modeling as well as plagiarism, and some suggestions to improve teaching practice are made.     

Transition and change during the implementation of a computer-basedmanufacturing process planning system: an analysis using the equityimplementation model

Implementing changes in technologies, systems, work practices and organizational structures is vitally important for the survival of organizations in today's competitive environments. However, introducing changes in organizations is not easy. Employees often resist changes. This paper presents a case study of the implementation of a computer-based manufacturing process planning system in an automotive assembly plant. The paper employs an equity implementation model to understand resistance to the system by zone supervisors and quick acceptance by plant engineers, two major employee groups who were affected by this change. Factors affecting employee reactions to the change are identified and analyzed on the basis of the equity implementation model. The paper concludes that the equity implementation model provides a useful framework for understanding and explaining resistance and acceptance behavior of employees. The model can also be useful in assessing the job-related impacts of a system or technology implementation. The paper also discusses suggestions for implementers in developing successful change implementation strategies     

Real-time control of angioplasty balloon inflation based on feedback from intravascular optical coherence tomography: experimental validation on an excised heart and a beating heart model

We report on real-time control of balloon inflation inside porcine arteries. In the first step, experiments were done in a coronary artery of an excised heart. In the second step, experiments were done in a beating heart setup providing conditions very close to in vivo conditions without the complications. A programmable syringe pump was used to inflate a compliant balloon in arteries, while intravascular optical coherence tomography (IVOCT) monitoring was performed. In a feedback loop, IVOCT images were processed to provide the balloon diameter values in real time to control the pump action in order to achieve a target diameter. In different experiments, various flow rates and target diameters were used. In the excised heart experiment, there was good convergence to target diameters resulting in a satisfactory balloon inflation control. In the beating heart experiment, there were oscillations in the diameter values due to cyclic arterial contractions. In these experiments, the control system maintained diameter averages satisfactorily close to predetermined target values. Real-time control of balloon inflation could not only provide a safer outcome for angioplasty procedures, but could also provide additional information for diagnostics since it implicitly provides information about the artery response to the inflation process.     

Determining the temperature distribution of a model vessel wall under pulsed laser irradiation: an experimental attempt to measure fibrous cap thickness and detect temperature elevation in atherosclerotic lesions

In order to measure the temperature of atherosclerotic plaques, the authors developed a method to determine the temperature distribution of vessel walls using a three-layer phantom agar model. Under pulsed-laser irradiation, the thickness of upper layer corresponding to fibrous cap overlying the middle layer corresponding to atherosclerotic lesion could be calculated. The temperature was calculated from measured temperature changes under pulsed-laser irradiation     

Computed SAR and thermal elevation in a 0.25-mm 2-D model of the human eye and head in response to an implanted retinal stimulator - part I: models and methods

Retinitis pigmentosa and age-related macular degeneration lead to blindness through progressive loss of retinal photoreceptors. Attempts are under way to construct a visual prosthesis to recover a limited sense of vision for these patients with the aid of implantable electronic devices. The function of these microchips is to provide electrical stimulation to existing viable retinal tissues - living ganglion and bipolar cells - using an array of on-chip stimulus circuits, while the dominant mechanism for power and data communication for these implanted devices has been wireless inductive telemetry using coils. This paper describes methods and models used to estimate the heating induced in the human eye and surrounding head tissues subject to the operation of this retinal prosthesis. A two-dimensional 0.25-mm high-resolution human head model has been developed with the aid of a new semiautomatic graphical segmentation algorithm. Finite-difference-based numerical methods for both electromagnetic and thermal modeling have been used to determine the influence of the specific absorption rate (associated with 2-MHz inductive coupling to the implant) and of stimulator integrated circuit (IC) power on tissue heating under different operational conditions and different hypothesis on choroidal blood flow and properties of the complex implanted circuitry. Results, provided in Part II of this paper, show that temperature increases of approximately 0.6 and 0.4/spl deg/C are induced in the midvitreous of the human eye in the absence and presence of choroidal blood flow, respectively, for a 60-electrode retinal prosthesis chip. Correspondent temperature rises of approximately 0.19 and 0.004/spl deg/C on the retina are obtained for these cases. Comparison with in vivo experimental measurements on intraocular heating in dog eyes shows good agreement.