Design and performance optimization of asynchronous networks-on-chip

As digital systems continue to grow in complexity, the design of conventional synchronous systems is facing unprecedented challenges. The number of transistors on individual chips is already in the multi-billion range, and a greatly increasing number of components are being integrated onto a single chip. As a consequence, modern digital designs are under strong time-to-market pressure, and there is a critical need for composable design approaches for large complex systems. In the past two decades, networks-on-chip (NoC’s) have been a highly active research area. In a NoC-based system, functional blocks are first designed individually and may run at different clock rates. These modules are then connected through a structured network for on-chip global communication. However, due to the rigidity of centrally-clocked NoC’s, there have been bottlenecks of system scalability, energy and performance, which cannot be easily solved with synchronous approaches. As a result, there has been significant recent interest in combing the notion of asynchrony with NoC designs. Since the NoC approach inherently separates the communication infrastructure, and its timing, from computational elements, it is a natural match for an asynchronous paradigm. Asynchronous NoC’s, therefore, enable a modular and extensible system composition for an ‘object-orient’ design style. The thesis aims to significantly advance the state-of-art and viability of asynchronous and globally-asynchronous locally-synchronous (GALS) networks-on-chip, to enable high-performance and low-energy systems. The proposed asynchronous NoC’s are nearly entirely based on standard cells, which eases their integration into industrial design flows. The contributions are instantiated in three different directions. First, practical acceleration techniques are proposed for optimizing the system latency, in order to break through the latency bottleneck in the memory interfaces of many on-chip parallel processors. Novel asynchronous network protocols are proposed, along with concrete NoC designs. A new concept, called ‘monitoring network’, is introduced. Monitoring networks are lightweight shadow networks used for fast-forwarding anticipated traffic information, ahead of the actual packet traffic. The routers are therefore allowed to initiate and perform arbitration and channel allocation in advance. The technique is successfully applied to two topologies which belong to two different categories – a variant mesh-of-trees (MoT) structure and a 2D-mesh topology. Considerable and stable latency improvements are observed across a wide range of traffic patterns, along with moderate throughput gains. Second, for the first time, a high-performance and low-power asynchronous NoC router is compared directly to a leading commercial synchronous counterpart in an advanced industrial technology. The asynchronous router design shows significant performance improvements, as well as area and power savings. The proposed asynchronous router integrates several advanced techniques, including a low-latency circular FIFO for buffer design, and a novel end-to-end credit-based virtual channel (VC) flow control. In addition, a semi-automated design flow is created, which uses portions of a standard synchronous tool flow. Finally, a high-performance multi-resource asynchronous arbiter design is developed. This small but important component can be directly used in existing asynchronous NoC’s for performance optimization. In addition, this standalone design promises use in opening up new NoC directions, as well as for general use in parallel systems. In the proposed arbiter design, the allocation of a resource to a client is divided into several steps. Multiple successive client-resource pairs can be selected rapidly in pipelined sequence, and the completion of the assignments can overlap in parallel. In sum, the thesis provides a set of advanced design solutions for performance optimization of asynchronous and GALS networks-on-chip. These solutions are at different levels, from network protocols, down to router- and component-level optimizations, which can be directly applied to existing basic asynchronous NoC designs to provide a leap in performance improvement

Ownership structure and executive compensation in Canadian corporations

Agency theory, proposed by previous studies such as Guidry, Leone, and Rock (1999) and Arya and Huey-Lian (2004), suggests that bonus and other accounting-metric-based compensation can motivate managers to perform well in the short horizon while equity-based compensation, such as restricted shares and stock options, can serve the purpose of aligning the long run interests of shareholders and managers. The empirical evidence, for example Jensen and Murphy (1990), Kaplan (1994), Hall and Liebman (1998), Murphy (1999), Zhou (2000), and Chowdhury and Wang (2009), confirms that incentive compensation is popular in many countries. However, recent studies suggest that the relation between performance and incentive compensation is weak. Shaw and Zhang (2010) find that CEO bonus compensation is less sensitive to poor earnings performance than it is to good earnings performance. Fahlenbrach and Stulz (2011) study the relation between bank performance during the 2008 bank crisis and the bonus and equity-based compensation of bank CEOs. They find that banks with CEOs whose incentives were better aligned with the interests of shareholders performed worse than other banks. This study examines whether ownership structure can explain the differences among compensation structures of chief executive officers (CEOs). In particular, we examine the compensation structure of three distinct groups: family-controlled, institution-controlled, and widely-held firms. We distinguish these three kinds of firms to represent different levels of market imperfection. Compared with family-controlled and institution-controlled firms, widely held firms have dispersed ownership. The most significant weakness of a widely-held ownership structure is the lack of shareholder monitoring due to the unmatched benefit and cost of monitoring for small shareholders. In contrast, a holder of a large block of shares will have the same monitoring costs but the benefits to this shareholder from monitoring management and reducing agency costs would be substantial and larger than the costs of monitoring. Thus the presence of a large shareholder will reduce the agency costs. In addition, large shareholders may be willing to spend time and effort continuously to collect more information on management performance or to estimate the firm’s investment projects. This behaviour will reduce the problems that arise from information asymmetry and will decrease the waste of free cash flows by managers. Both family-controlled firms and institution-controlled firms have large shareholders. However, whether or not the control shareholders are playing an active monitoring role is still an important issue. From the viewpoint of aligning the interests of managers and shareholders, the family-controlled group is superior to the institution-controlled group. First, institutions are more flexible in moving their ownership from one firm to another depending on performance. If the costs of monitoring are high in comparison to the costs of rebalancing portfolios, institutions will choose to rebalance instead of monitoring. In contrast, a family that controls a firm does not have this flexibility. Second, family-controlled firms generally assign influential positions to family members whose focus is in line with that of the family group. Even though a non family member may be appointed as the manager, the level of monitoring is significant given the high ownership concentration by the family. However, the level of monitoring by a family may not necessarily translate into a reduction of agency costs for minority shareholders. Indeed, previous studies suggest that significant family ownership may lead to agency costs of its own. The family may divert company resources for its own benefit despite the presence of a manager who may or may not be a family member. Essentially, the family and the manager can collude to spend on perks and personal benefits at the expense of minority shareholders. Chourou (2010) suggests that excessive compensation of chief executive officers at some family owned Canadian corporations may be viewed as expropriation of minority rights. Overall, the main objective of this study is to examine whether block-holder monitoring is a substitute to the incentive components of compensation. We propose that as we move from widely-held to institution-controlled the level of monitoring may or may not increase. However, as we move further into higher control, as may be suggested by family ownership, the level of monitoring will increase but this monitoring may not necessarily reduce agency costs. The results show that the institution-controlled firms pay significantly less bonus compensation per dollar of assets than widely-held firms but the differences in equity based compensation are not significant. In addition, the family-controlled corporations offer the lowest performance-based compensation, bonus per dollar of assets, in comparison to the institution-controlled and the widely-held groups. These results indicate that the family-controlled Canadian corporations rely more on monitoring managers than paying them incentive payments in the form of bonus payments. In addition, our results indicate that the institutions which control corporations may be monitoring the managers of these corporations but this monitoring does not significantly reduce the need for the long-term incentive components of compensation. This result suggests that institutions may monitor the short-term performance effectively but they may prefer rebalancing their portfolio rather than monitoring long term performance

β-catenin ameliorates myocardial infarction by preventing YAP-associated apoptosis

Objective: To explore whether the effect of β-catenin on MI and MI-induced cardiomyocyte apoptosis is YAP-dependent. Methods: The authors established an MI rat model by ligating the anterior descending branch of the left coronary artery, and an MI cell model by treating cardiomyocytes with H2O2. Results: β-catenin downregulation was observed in MI cardiac tissues and in H2O2-treated cardiomyocytes. Lentiviral-CTNNB1 was administered to MI rats to upregulate β-catenin expression in MI cardiac tissue. β-catenin recovery reduced the myocardial infarct area, fibrosis, and apoptotic cell death in MI rats. H2O2 treatment attenuated cell viability and induced cell death in cardiomyocytes, whereas β-catenin overexpression partially reversed these changes. Moreover, H2O2 treatment caused the deactivation of Yes-Associated Protein (YAP), as detected by increased YAP phosphorylation and reduced the nuclear localization of YAP. Upregulation of β-catenin expression reactivated YAP in H2O2-treated cardiomyocytes. Reactivation of YAP was achieved by administration of Mitochonic Acid-5 (MA-5) to H2O2-treated cardiomyocytes, and deactivation of YAP by CIL56 treatment in β-catenin-overexpressing H2O2-treated cardiomyocytes. MA-5 administration increased cell viability and repressed apoptosis in H2O2-treated cardiomyocytes, whereas CIL56 treatment counteracted the effects of β-catenin overexpression on cell survival and apoptosis. Conclusions: The present data indicate that β-catenin and YAP are effective treatment targets for MI, blocking the apoptotic death of cardiomyocytes

An Evaluation of Machine Learning and Deep Learning Models for Drought Prediction using Weather Data

Drought is a serious natural disaster that has a long duration and a wide range of influence. To decrease the drought-caused losses, drought prediction is the basis of making the corresponding drought prevention and disaster reduction measures. While this problem has been studied in the literature, it remains unknown whether drought can be precisely predicted or not with machine learning models using weather data. To answer this question, a real-world public dataset is leveraged in this study and different drought levels are predicted using the last 90 days of 18 meteorological indicators as the predictors. In a comprehensive approach, 16 machine learning models and 16 deep learning models are evaluated and compared. The results show no single model can achieve the best performance for all evaluation metrics simultaneously, which indicates the drought prediction problem is still challenging. As benchmarks for further studies, the code and results are publicly available in a Github repository.Comment: Github link: https://github.com/jwwthu/DL4Climate/tree/main/DroughtPredictio

Big Data for Traffic Estimation and Prediction: A Survey of Data and Tools

Big data has been used widely in many areas including the transportation industry. Using various data sources, traffic states can be well estimated and further predicted for improving the overall operation efficiency. Combined with this trend, this study presents an up-to-date survey of open data and big data tools used for traffic estimation and prediction. Different data types are categorized and the off-the-shelf tools are introduced. To further promote the use of big data for traffic estimation and prediction tasks, challenges and future directions are given for future studies

The Differentiation Balance of Bone Marrow Mesenchymal Stem Cells Is Crucial to Hematopoiesis.

Bone marrow mesenchymal stem cells (BMSCs), the important component and regulator of bone marrow microenvironment, give rise to hematopoietic-supporting stromal cells and form hematopoietic niches for hematopoietic stem cells (HSCs). However, how BMSC differentiation affects hematopoiesis is poorly understood. In this review, we focus on the role of BMSC differentiation in hematopoiesis. We discussed the role of BMSCs and their progeny in hematopoiesis. We also examine the mechanisms that cause differentiation bias of BMSCs in stress conditions including aging, irradiation, and chemotherapy. Moreover, the differentiation balance of BMSCs is crucial to hematopoiesis. We highlight the negative effects of differentiation bias of BMSCs on hematopoietic recovery after bone marrow transplantation. Keeping the differentiation balance of BMSCs is critical for hematopoietic recovery. This review summarises current understanding about how BMSC differentiation affects hematopoiesis and its potential application in improving hematopoietic recovery after bone marrow transplantation