Achieving balance between proximity and diversity in multi-objective evolutionary algorithm

Currently, an alternative framework using the hypervolume indicator to guide the search for elite solutions of a multi-objective problem is studied in the evolutionary multi-objective optimization community very actively, comparing to the traditional Pareto dominance based approach. In this paper, we present a dynamic neighborhood multi-objective evolutionary algorithm based on hypervolume indicator (DNMOEA/HI), which benefits from both Pareto dominance and hypervolume indicator based frameworks. DNMOEA/HI is featured by the employment of hypervolume indicator as a truncation operator to prune the exceeded population, while a well-designed density estimator (i.e., tree neighborhood density) is combined with the Pareto strength value to perform fitness assignment. Moreover, a novel algorithm is proposed to directly evaluate the hypervolume contribution of a single individual. The performance of DNMOEA/HI is verified on a comprehensive benchmark suite, in comparison with six other multi-objective evolutionary algorithms. Experimental results demonstrate the efficiency of our proposed algorithm. Solutions obtained by DNMOEA/HI well approach the Pareto optimal front and are evenly distributed over the front, simultaneously.     

Profiling hospitals based on emergency readmission: a multilevel transition modelling approach

Emergency readmission is seen as an important part of the United Kingdom government policy to improve the quality of care that patients receive. In this context, patients and the public have the right to know how well different health organizations are performing. Most methods for profiling estimate the expected numbers of adverse outcomes (e.g. readmission, mortality) for each organization. A number of statistical concerns have been raised, such as the differences in hospital sizes and the unavailability of relevant data for risk adjustment. Having recognized these statistical concerns, a new framework known as the multilevel transition model is developed. Hospital specific propensities of the first, second and further readmissions are considered to be measures of performance, where these measures are used to define a new performance index. During the period 1997 and 2004, the national (English) hospital episodes statistics dataset comprise more than 5 million patient readmissions. Implementing a multilevel model using the complete population dataset could possibly take weeks to estimate the parameters. To resolve the problem, we extract 1000 random samples from the original data, where each random sample is likely to lead to differing hospital performance measures. For computational efficiency a Grid implementation of the model is developed. Analysing the output from the full 1000 sample, we noticed that 4 out of the 5 worst performing hospitals treating cancer patients were in London. These hospitals are known to be the leading NHS Trusts in England, providing diverse range of services to complex patients, and therefore it is inevitable to expect higher numbers of emergency readmissions.     

Operation, system architectures, and physical Layer design considerations of distributed MAC protocols for UWB

Impulse-based ultra wideband (I-UWB) is an attractive radio technology for large ad hoc and sensor networks due to its robustness to harmful multipath effects, sub-centimeter ranging ability, simple hardware, and low radiated power. To scale to large sizes, networks often implement distributed medium access control (MAC) protocols. However, most MAC protocols for I-UWB are centralized, and they target small wireless personal area networks and cellular networks. We propose three distributed MAC protocols suitable for I-UWB. Two multichannel protocols, called multichannel pulse sense multiple access (M-PSMA) and multichannel ALOHA achieve high aggregate throughput. A busy-signal protocol, called busy-signal multiple access (BSMA), reduces the energy wasted from re-transmitted packets. This paper describes the three protocols in terms of the protocol's operation, the supporting system architecture, and the I-UWB physical layer. Physical layer simulations confirm the feasibility of implementing the proposed systems and also provide parameters for network simulations. Network simulations show that the throughput of M-PSMA exceeds that of a centralized time-division multiple-access protocol and that the energy efficiency of BSMA far surpasses that of other distributed protocols.     

MLS‐based variable‐node elements compatible with quadratic interpolation. Part I: formulation and application for non‐matching meshes

Two‐dimensional variable‐node elements compatible with quadratic interpolation are developed using the moving least‐square (MLS) approximation. The mapping from the parental domain to the physical element domain is implicitly obtained from MLS approximation, with the shape functions and their derivatives calculated and saved only at the numerical integration points. It is shown that the present MLS‐based variable‐node elements meet the patch test if a sufficiently large number of integration points are employed for numerical integration. The cantilever problem with non‐matching meshes is chosen to check the feasibility of the present MLS‐based variable‐node elements, and the result is compared with that from the lower‐order case compatible with linear interpolation. Copyright © 2005 John Wiley & Sons, Ltd.     

A simple receding horizon control for state delayed systems and its stability criterion

In this paper, a simple receding horizon (or model predictive) control for state delayed systems is presented and its solution is given in a closed form by a reduction method. While the control for a time-delay system is usually complex, the proposed controller is simple to construct and therefore can be simply implemented in real applications. To check the closed-loop stability of the proposed controller, a sufficient condition is provided by linear matrix inequalities. In addition, a numerical algorithm is presented for computing the eigenvalues of systems with distributed time delays, which can be used as a necessary and sufficient condition to check closed-loop stability. It is shown by simulation that this simple control can be a stabilizing control for time-delay systems.     

Modular Reconfigurable Robots in Space Applications

Robots used for tasks in space have strict requirements. Modular reconfigurable robots have a variety of attributes that are well suited to these conditions, including: serving as many different tools at once (saving weight), packing into compressed forms (saving space) and having high levels of redundancy (increasing robustness). In addition, self-reconfigurable systems can self-repair and adapt to changing or unanticipated conditions. This paper will describe such a self-reconfigurable modular robot: PolyBot. PolyBot has significant potential in the space manipulation and surface mobility class of applications for space.     

一种互联网资源标志与寻址技术:Handle System

互联网最基础的资源标志与寻址技术是域名和IP地址，随着互联网资源种类的增加，以及应用的发展，出现了对新一代互联网资源标志与寻址技术的需求。介绍了一种新的互联网资源标志与寻址技术，并将这种技术应用到域名系统中。     

One-Dimensional Numerical Model for Nonuniform Sediment Transport under Unsteady Flows in Channel Networks

In this study, the proposed one-dimensional model simulates the nonequilibrium transport of nonuniform total load under unsteady flow conditions in dendritic channel networks with hydraulic structures. The equations of sediment transport, bed changes, and bed-material sorting are solved in a coupling procedure with a direct solution technique, while still decoupled from the flow model. This coupled model for sediment calculation is more stable and less likely to produce negative values for bed-material gradation than the traditional fully decoupled model. The sediment transport capacity is calculated by one of four formulas, which have taken into consideration the hiding and exposure mechanism of nonuniform sediment transport. The fluvial erosion at bank toes and the mass failure of banks are simulated to complement the modeling of bed morphological changes in channels. The tests in several cases show that the present model is capable of predicting sediment transport, bed changes, and bed-material sorting in various situations, with reasonable accuracy and reliability.     

A study on the thermal behavior in microaccelerometer manufacturing processes

Single crystal silicon (SCS) is used in a variety of microsensor applications in which stresses and other mechanical effects may dominate device performance. One of major problems associated with the manufacturing processes of the microaccelerometer based on the tunneling current concept is temperature gradient and thermal stressess. This paper deals with finite element analyses of residual stresses causing popping up, which are induced in micromachining processes of a microaccelerometer. The authors model temperature-dependent mechanical properties during focused ion beam (FIB) cutting and Pt deposition processes. The maximum thermal strain of 0.0012 occurred at the readout gap of the microaccelerometer during the Pt deposition process. The stress produced during the heating process of FIB cut was also found to be about 33–36 MPa and cooling process the maximum equivalent stress of about 34MPa still at the right corner of readout gap. The calculated maximum displacement occurred at the readout gap was 0.14 μm. This is still smaller than the popping up of about 2 μm observed in the experiment. The reason for this popping up phenomenon in munufacturing processes of microaccelerometer may be the bending of the whole wafer or it may come from the way the underetch occurs. Different SOI material and a new geometry of the accelerometer are under investigation. We want to seek after the real cause of this pop up phenomenon and diminish this by changing munufacturing processes of microaccelerometer.     

Detecting pattern-based outliers

Outlier detection targets those exceptional data that deviate from the general pattern. Besides high density clustering, there is another pattern called low density regularity. Thus, there are two types of outliers w.r.t. them. We propose two techniques: one to identify the two patterns and the other to detect the corresponding outliers.