Energy-Efficient Wireless Interconnect Design for Non-Destructive Testing (NDT) Applications

A method for non-destructive, wireless testing of integrated circuits(ICs) is presented in this thesis. This system is suitable for applications which require testing after the manufacturing of ICs. According to Moore\u27s Law the number of transistors in an IC doubles every two years, the current probing equipment will also have to reduce its size accordingly which will be difficult after a certain point. The proposed system relies on near field communication in order to transfer data between probe and device under test. The probe and IC will include small antenna and a transceiver circuit. The antenna and the transceiver circuit can be integrated into the device without affecting the real estate and performance. Major advantages of non-destructive probing include no damage to the pads of test chip, higher test frequencies and less maintenance which will lead to higher pin densities. The antenna and transceiver circuit to be incorporated on the test chip are completely CMOS compliant.;The presented system here is a prototype which consists of a transceiver circuit along with an ultra-wideband antenna. The system was implemented in IBM 180nm CMOS process. The transceiver circuit communicates at a high frequency of 21.5GHz which in turn reduces the area consumed by the antenna and the transceiver circuit. The results obtained for our system show that an energy efficient wireless interconnect has been successfully implemented for future non-destructive testing applications

Overcoming the Challenges for Multichip Integration: A Wireless Interconnect Approach

The physical limitations in the area, power density, and yield restrict the scalability of the single-chip multicore system to a relatively small number of cores. Instead of having a large chip, aggregating multiple smaller chips can overcome these physical limitations. Combining multiple dies can be done either by stacking vertically or by placing side-by-side on the same substrate within a single package. However, in order to be widely accepted, both multichip integration techniques need to overcome significant challenges. In the horizontally integrated multichip system, traditional inter-chip I/O does not scale well with technology scaling due to limitations of the pitch. Moreover, to transfer data between cores or memory components from one chip to another, state-of-the-art inter-chip communication over wireline channels require data signals to travel from internal nets to the peripheral I/O ports and then get routed over the inter-chip channels to the I/O port of the destination chip. Following this, the data is finally routed from the I/O to internal nets of the target chip over a wireline interconnect fabric. This multi-hop communication increases energy consumption while decreasing data bandwidth in a multichip system. On the other hand, in vertically integrated multichip system, the high power density resulting from the placement of computational components on top of each other aggravates the thermal issues of the chip leading to degraded performance and reduced reliability. Liquid cooling through microfluidic channels can provide cooling capabilities required for effective management of chip temperatures in vertical integration. However, to reduce the mechanical stresses and at the same time, to ensure temperature uniformity and adequate cooling competencies, the height and width of the microchannels need to be increased. This limits the area available to route Through-Silicon-Vias (TSVs) across the cooling layers and make the co-existence and co-design of TSVs and microchannels extreamly challenging. Research in recent years has demonstrated that on-chip and off-chip wireless interconnects are capable of establishing radio communications within as well as between multiple chips. The primary goal of this dissertation is to propose design principals targeting both horizontally and vertically integrated multichip system to provide high bandwidth, low latency, and energy efficient data communication by utilizing mm-wave wireless interconnects. The proposed solution has two parts: the first part proposes design methodology of a seamless hybrid wired and wireless interconnection network for the horizontally integrated multichip system to enable direct chip-to-chip communication between internal cores. Whereas the second part proposes a Wireless Network-on-Chip (WiNoC) architecture for the vertically integrated multichip system to realize data communication across interlayer microfluidic coolers eliminating the need to place and route signal TSVs through the cooling layers. The integration of wireless interconnect will significantly reduce the complexity of the co-design of TSV based interconnects and microchannel based interlayer cooling. Finally, this dissertation presents a combined trade-off evaluation of such wireless integration system in both horizontal and vertical sense and provides future directions for the design of the multichip system

Modeling and Design Techniques for 3-D ICs under Process, Voltage, and Temperature Variations

Three-dimensional (3-D) integration is a promising solution to further enhance the density and performance of modern integrated circuits (ICs). In 3-D ICs, multiple dies (tiers or planes) are vertically stacked. These dies can be designed and fabricated separately. In addition, these dies can be fabricated in different technologies. The effect of different sources of variations on 3-D circuits, consequently, differ from 2-D ICs. As technology scales, these variations significantly affect the performance of circuits. Therefore, it is increasingly important to accurately and efficiently model different sources of variations in 3-D ICs. The process, voltage, and temperature variations in 3-D ICs are investigated in this dissertation. Related modeling and design techniques are proposed to design a robust 3-D IC. Process variations in 3-D ICs are first analyzed. The effect of process variations on synchronization and 3-D clock distribution networks, is carefully studied. A novel statistical model is proposed to describe the timing variation in 3-D clock distribution networks caused by process variations. Based on this model, different topologies of 3-D clock distribution networks are compared in terms of skew variation. A set of guidelines is proposed to design 3-D clock distribution networks with low clock uncertainty. Voltage variations are described by power supply noise. Power supply noise in 3-D ICs is investigated considering different characteristics of potential 3-D power grids in this thesis. A new algorithm is developed to fast analyze the steady-state IR-drop in 3-D power grids. The first droop of power supply noise, also called resonant supply noise, is usually the deepest voltage drop in power distribution networks. The effect of resonant supply noise on 3-D clock distribution networks is investigated. The combined effect of process variations and power supply noise is modeled by skitter consisting of both skew and jitter. A novel statistical model of skitter is proposed. Based on this proposed model and simulation results, a set of guidelines has been proposed to mitigate the negative effect of process and voltage variations on 3-D clock distribution networks. Thermal issues in 3-D ICs are considered by carefully modeling thermal through silicon vias (TTSVs) in this dissertation. TTSVs are vertical vias which do not carry signals, dedicated to facilitate the propagation of heat to reduce the temperature of 3-D ICs. Two analytic models are proposed to describe the heat transfer in 3-D circuits related to TTSVs herein, providing proper closed-form expressions for the thermal resistance of the TTSVs. The effect of different physical and geometric parameters of TTSVs on the temperature of 3-D ICs is analyzed. The proposed models can be used to fast and accurately estimate the temperature to avoid the overuse of TTSVs occupying a large portion of area. A set of models and design techniques is proposed in this dissertation to describe and mitigate the deleterious effects of process, voltage, and temperature variations in 3-D ICs. Due to the continuous shrink in the feature size of transistors, the large number of devices within one circuit, and the high operating frequency, the effect of these variations on the performance of 3-D ICs becomes increasingly significant. Accurately and efficiently estimating and controlling these variations are, consequently, critical tasks for the design of 3-D ICs

Wireless Testing of Integrated Circuits.

Integrated circuits (ICs) are usually tested during manufacture by means of automatic testing equipment (ATE) employing probe cards and needles that make repeated physical contact with the ICs under test. Such direct-contact probing is very costly and imposes limitations on the use of ATE. For example, the probe needles must be frequently cleaned or replaced, and some emerging technologies such as three-dimensional ICs cannot be probed at all. As an alternative to conventional probe-card testing, wireless testing has been proposed. It mitigates many of the foregoing problems by replacing probe needles and contact points with wireless communication circuits. However, wireless testing also raises new problems which are poorly understood such as: What is the most suitable wireless communication technique to employ, and how well does it work in practice? This dissertation addresses the design and implementation of circuits to support wireless testing of ICs. Various wireless testing methods are investigated and evaluated with respect to their practicality. The research focuses on near-field capacitive communication because of its efficiency over the very short ranges needed during IC manufacture. A new capacitive channel model including chip separation, cross-talk, and misalignment effects is proposed and validated using electro-magnetic simulation studies to provide the intuitions for efficient antenna and circuit design. We propose a compact clock and data recovery architecture to avoid a dedicated clock channel. An analytical model which predicts the DC-level fluctuation due to the capacitive channel is presented. Based on this model, feed-forward clock selection is designed to enhance performance. A method to select proper channel termination is discussed to maximize the channel efficiency for return-to-zero signaling. Two prototype ICs incorporating wireless testing systems were fabricated and tested with the proposed methods of testing digital circuits. Both successfully demonstrated gigahertz communication speeds with a bit-error rate less than 10^−11. A third prototype IC containing analog voltage measurement circuits was implemented to determine the feasibility of wirelessly testing analog circuits. The fabricated prototype achieved satisfactory voltage measurement with 1 mV resolution. Our work demonstrates the validity of the proposed models and the feasibility of near-field capacitive communication for wireless testing of ICs.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/93993/1/duelee_1.pd

Atmospheric, Magnetospheric, and Plasmas in Space (AMPS) spacelab payload definition study, technical summary document

Some 60 instrument candidates and 80 possible science investigations were evaluated. The early analysis emphasized the science aspect in terms of the functional requirements for each of the potential experiments identified by the AMPS science working group. These requirements were then used for the grouping of instruments into practical payloads which would fit the capabilities of the Shuttle/Spacelab. This analysis resulted in the definition of eleven different AMPS configurations. The data were then used to define a typical set of requirements for a flexible AMPS laboratory. The data gathered to this point showed that a planned sequential buildup of the laboratory would be necessary to meet both physical and funding limitations. This led to the definition of five strawman payloads by the science working group, which were used to establish a conceptual laboratory and to define preliminary design of a configuration which could satisfy AMPS needs during the early program period

The assessment and rehabilitation of post stroke dysphagia

Comprehensive Screening Tests Post stroke dysphagia is common and requires accurate screening to identify patients that need further assessment and management. Nurses and other non-specialists in dysphagia are often trained to screen swallowing post-stroke. In addition to screening for dysphagia more comprehensive screening tests allow non-specialists to recommend modified oral intake. Little is known about the accuracy, clinical utility and cost effectiveness of these tests. A systematic review and meta-analysis were conducted to describe the comprehensive swallow screening tests that are available for use in acute stroke by nurses or other non-specialists. The review also evaluated the accuracy, clinical utility and cost effectiveness of these tools. In a prospective study, one of these comprehensive screening tests, the Dysphagia Trained Nurse Assessment (DTNAx) was validated against usual SLT assessment and videofluoroscopy with 47 acute stroke patients. This thesis also aimed to find out the experiences of Dysphagia Trained Nurses (DTNs) by carrying out semi-structured interviews with nine nurses. Five comprehensive screening tests for dysphagia were identified, but validation studies were mostly low or very low quality. Three studies validating the Gugging Swallow Screen provided sufficient data for meta-analysis, demonstrating high sensitivity; 96% (95%CI 0.90-0.99) but lower specificity, 65% (95%CI 0.47-0.79). The DTNAx was superior to the other tests in its safety and content validity. In its subsequent validation, compared to the SLTAx in the identification of dysphagia, the DTNAx had a sensitivity of 96.9% (95% confidence intervals CIs 83.8%-99.9%) and specificity 89.5% (95% CIs 75.2%-97.1%). Compared to the VFS in the identification of aspiration, the DTNAx had a sensitivity of 77.8% (CIs 40.0%-97.2%) and specificity 81.6% (CIs 65.7% to 92.3%). Over 81% of the diet and fluid recommendations made by the DTNs were in absolute agreement with the SLTAx. Dysphagia Trained Nurses reported high regard for the role and gave useful insights into the challenges that arise in the busy acute stroke unit. Biofeedback in dysphagia rehabilitation Ongoing dysphagia can have detrimental effects on physical and mental health post stroke. SLTs conduct more detailed assessments and provide rehabilitation to patients with persistent dysphagia. The use of biofeedback is beneficial in stroke rehabilitation and is gaining ground as an adjunct in the field of dysphagia rehabilitation but there are no robust studies of its effectiveness or feasibility in the acute stroke setting. A second systematic review and meta-analysis investigated the evidence on the effects of swallow therapy augmented by biofeedback in adults with dysphagia. Finally, a randomised controlled feasibility study into swallow strength and skill training with surface electromyography (sEMG) biofeedback in 27 acute stroke patients with dysphagia was performed. Only 23 studies were identified that investigated biofeedback as a dysphagia intervention, of which three main types were reported: surface electromyography, accelerometry and tongue manometry. Five controlled studies were included in the meta-analyses. Compared to the control, biofeedback augmented dysphagia therapy enhanced hyoid displacement significantly (three studies, MD=0.22cm; 95% CI [0.04, 0.40], p=0.02) but there was no significant difference in functional oral intake. Risk of bias was high and there was significant statistical heterogeneity. The RCT demonstrated feasibility and acceptability in participants recruited; 11 out of the 13 participants in the intervention group completed the treatment (>80% of sessions). The planned recruitment target was not met and would need to be mitigated for in future studies. Most participants found the intervention challenging but comfortable and the right duration, frequency and time post stroke. There were no related serious adverse events. There were no significant differences between groups in Functional Oral Intake Scale (FOIS), Dysphagia Severity Rating Scale (DSRS) and Penetration Aspiration Scale (PAS) at 2-weeks or at 90 days. Conclusions Using the DTNAx, trained nurses can screen acute stroke patients for dysphagia accurately and make early swallowing recommendations in line with SLTs. Further research is needed to investigate the clinical utility and cost effectiveness of this versus other swallow assessment pathways in acute stroke. Swallow strength and skill training with sEMG biofeedback is feasible and acceptable to acute stroke patients with dysphagia. It is safe and it may improve post stroke dysphagia. Further research investigating approaches to intervention delivery, treatment dose and effectiveness is indicated

The assessment and rehabilitation of post stroke dysphagia

Comprehensive Screening Tests Post stroke dysphagia is common and requires accurate screening to identify patients that need further assessment and management. Nurses and other non-specialists in dysphagia are often trained to screen swallowing post-stroke. In addition to screening for dysphagia more comprehensive screening tests allow non-specialists to recommend modified oral intake. Little is known about the accuracy, clinical utility and cost effectiveness of these tests. A systematic review and meta-analysis were conducted to describe the comprehensive swallow screening tests that are available for use in acute stroke by nurses or other non-specialists. The review also evaluated the accuracy, clinical utility and cost effectiveness of these tools. In a prospective study, one of these comprehensive screening tests, the Dysphagia Trained Nurse Assessment (DTNAx) was validated against usual SLT assessment and videofluoroscopy with 47 acute stroke patients. This thesis also aimed to find out the experiences of Dysphagia Trained Nurses (DTNs) by carrying out semi-structured interviews with nine nurses. Five comprehensive screening tests for dysphagia were identified, but validation studies were mostly low or very low quality. Three studies validating the Gugging Swallow Screen provided sufficient data for meta-analysis, demonstrating high sensitivity; 96% (95%CI 0.90-0.99) but lower specificity, 65% (95%CI 0.47-0.79). The DTNAx was superior to the other tests in its safety and content validity. In its subsequent validation, compared to the SLTAx in the identification of dysphagia, the DTNAx had a sensitivity of 96.9% (95% confidence intervals CIs 83.8%-99.9%) and specificity 89.5% (95% CIs 75.2%-97.1%). Compared to the VFS in the identification of aspiration, the DTNAx had a sensitivity of 77.8% (CIs 40.0%-97.2%) and specificity 81.6% (CIs 65.7% to 92.3%). Over 81% of the diet and fluid recommendations made by the DTNs were in absolute agreement with the SLTAx. Dysphagia Trained Nurses reported high regard for the role and gave useful insights into the challenges that arise in the busy acute stroke unit. Biofeedback in dysphagia rehabilitation Ongoing dysphagia can have detrimental effects on physical and mental health post stroke. SLTs conduct more detailed assessments and provide rehabilitation to patients with persistent dysphagia. The use of biofeedback is beneficial in stroke rehabilitation and is gaining ground as an adjunct in the field of dysphagia rehabilitation but there are no robust studies of its effectiveness or feasibility in the acute stroke setting. A second systematic review and meta-analysis investigated the evidence on the effects of swallow therapy augmented by biofeedback in adults with dysphagia. Finally, a randomised controlled feasibility study into swallow strength and skill training with surface electromyography (sEMG) biofeedback in 27 acute stroke patients with dysphagia was performed. Only 23 studies were identified that investigated biofeedback as a dysphagia intervention, of which three main types were reported: surface electromyography, accelerometry and tongue manometry. Five controlled studies were included in the meta-analyses. Compared to the control, biofeedback augmented dysphagia therapy enhanced hyoid displacement significantly (three studies, MD=0.22cm; 95% CI [0.04, 0.40], p=0.02) but there was no significant difference in functional oral intake. Risk of bias was high and there was significant statistical heterogeneity. The RCT demonstrated feasibility and acceptability in participants recruited; 11 out of the 13 participants in the intervention group completed the treatment (>80% of sessions). The planned recruitment target was not met and would need to be mitigated for in future studies. Most participants found the intervention challenging but comfortable and the right duration, frequency and time post stroke. There were no related serious adverse events. There were no significant differences between groups in Functional Oral Intake Scale (FOIS), Dysphagia Severity Rating Scale (DSRS) and Penetration Aspiration Scale (PAS) at 2-weeks or at 90 days. Conclusions Using the DTNAx, trained nurses can screen acute stroke patients for dysphagia accurately and make early swallowing recommendations in line with SLTs. Further research is needed to investigate the clinical utility and cost effectiveness of this versus other swallow assessment pathways in acute stroke. Swallow strength and skill training with sEMG biofeedback is feasible and acceptable to acute stroke patients with dysphagia. It is safe and it may improve post stroke dysphagia. Further research investigating approaches to intervention delivery, treatment dose and effectiveness is indicated

Stirling engine design manual

This manual is intended to serve both as an introduction to Stirling engine analysis methods and as a key to the open literature on Stirling engines. Over 800 references are listed and these are cross referenced by date of publication, author and subject. Engine analysis is treated starting from elementary principles and working through cycles analysis. Analysis methodologies are classified as first, second or third order depending upon degree of complexity and probable application; first order for preliminary engine studies, second order for performance prediction and engine optimization, and third order for detailed hardware evaluation and engine research. A few comparisons between theory and experiment are made. A second order design procedure is documented step by step with calculation sheets and a worked out example to follow. Current high power engines are briefly described and a directory of companies and individuals who are active in Stirling engine development is included. Much remains to be done. Some of the more complicated and potentially very useful design procedures are now only referred to. Future support will enable a more thorough job of comparing all available design procedures against experimental data which should soon be available