In this paper, we present a 120 GHz ultra-wideband (3.3 GHz) frequency-modulated continuous wave (FMCW) radar, designed using a millimeter-wave (mmWave) transceiver, and its application to the measurement of snowpack height over two full winter seasons. This system achieves 2 cm accuracy across the diverse snowpack and environmental conditions encountered during the winter season. Its main advantages over conventional measurement techniques are good performance during heavy snowfall, correct detection of fresh fallen snow, spatial averaging and low temperature dependence. Furthermore, our system is able to measure the backscattering coefficient of the snowpack, which is predominantly influenced by the liquid water content (LWC) of its surface layer. This relationship is confirmed by experimental measurements and numerical simulations, and could enable non-invasive first layer LWC estimations. Hence, we prove mmWave radar to be a reliable technology for snowpack monitoring under different environmental and snowpack conditions, with a wide range of applications in hydrological forecasting, avalanche risk assessment and environmental monitoring.

Snow makes a great contribution to the hydrological cycle in cold regions. The parameter to characterize available water from the snow cover is the snow water equivalent (SWE). This paper presents a near-surface based radar for determining SWE from the measured complex spectral reflectance of snowpack. The method is based on a stepped-frequency continuous wave radar (SFCW), implemented in a coherent software defined radio (SDR), in the range from 150MHz to 6GHz. An approximate method to calculate SWE is proposed. Results are compared with those provided by a cosmic-ray neutron (CRN) SWE gauge over the 2019–2020 winter in the experimental AEMet Formigal-Sarrios test site. The results suggest the viability of the approximate method. Finally, the feasibility of an auxiliary snow depth measurement sensor based on a 120GHz radar FMCW sensor (mmWave sensor) is shown.

In this paper, the efficiency of the induction system composed of 4 small coils with a given connection among them for cooking applications is analyzed. The 4-coil configuration has several advantages with respect to the single-coil induction system, for instance, higher flexibility and better heat distribution in the pan. Different configurations can be arranged according to series or parallel connections of the coils and the polarity of the currents. However, the selected configuration connection has a direct impact on the efficiency of the power transference into the pot. Therefore, in this work the efficiency of the different 4-coil configurations is analyzed. The analysis is carried out in terms of equivalent impedances. The experimental test based on impedance measurements is performed to verify the preceding analysis.

Domestic induction heating system employ the output power as control variable. The users select the desired power level among a set of possible values. The advantage of this strategy is related to the control of the associated power electronics. However, temperature control is preferred for cooking applications but it increases the complexity of the system due to the difficulties associated with the temperature estimation of the cookware. Temperature can be measured by means of contact or non-contact technique. This application demands non-contact temperature measurement due to the cooking surface, generally made of glass-ceramic, separates the cookware to the induction heating system placed bellow. Among others, temperature estimation based on radiation detectors, for instance, thermopiles, constitutes one of the most promising methods due to the immediate determination of the measure, but, the optimization of this method required a complex procedure. The aim of this paper is to provide the numerical model of this kind of the system suitable to be used for design purposes. The simulation results have been compared with analytical and experimental measurements in order to verify the correctness of the numerical model.

An infrared (IR) sensor for temperature measurement in domestic induction hobs and results of its applications are presented. It comprises an InGaAs PIN photodiode and a preamplifier which detects the infrared radiation emitted from the bottom of the pot. This sensor is potentially useful because it is a fast, cheap and contactless solution for measuring temperature. The proposed sensor has been tested in the cooking range from 75°C to 200°C with pots made of different materials. The proposed solution will allow controlled cooking and fire prevention.

In this paper, an analysis of the resistance of multi-track coils in printed circuit board (PCB) implementations, where the conductors have rectangular cross-section, for spiral planar coils is carried out. For this purpose, different analytical losses models for the mentioned conductors have been reviewed. From this review, we conclude that for the range of frequencies, the coil dimensions and the planar configuration typically used in domestic induction heating, the application in which we focus, these analysis are unsatisfactory. Therefore, in this work the resistance of multi-track winding has been calculated by means of finite element analysis (FEA) tool. These simulations provide us some design guidelines that allow us to optimize the design of multi-track coils for domestic induction heating. Furthermore, several prototypes are used to verify the simulated results, both single-turn coils and multi-turn coils.

The use of tags to annotate content creates an opportunity to explore alternatives to automate the process of extracting semantics from data sources. Semantic information is needed for many complex tasks like concept extraction and information integration. In order to establish the value of user-gen

Intelligence analysis can be aided and guided by models of the analysts' interests and priorities. This paper describes our approach to analyst modeling as part of the Ant CAFÉ project, in which analyst models are used to guide the searching behavior of a swarm of intelligent agents. Structural elements of our analyst model include concepts and relations, both of which help to capture the analyst's current interest and concerns. In addition, the concepts and relationships have associated scalar parameters to provide a quantitative measure of the user's level of interest. We have developed algorithms for dynamically adapting the weights and evolving the elements of the model itself. To evaluate these algorithms we have built an Analyst Modeling Environment workbench. We have tested our approach on this workbench using traces generated by human analysts, and have demonstrated improvements over current state of the art search engines.

In recent work we have developed a novel approach to the design and implementation of an online portal (ePortal) to help application engineers find replacements for electronic parts that have become obsolete (and hence will no longer be produced). Our approach makes use of machine learning techniques to improve the performance of a database search function. However, the purpose of this note is not to describe in detail the application nor our technical solution - that has been done elsewhere (see [1,2]). Rather, it is our intention to present some of the lessons learned from our project. Below, we provide a brief introduction to the technical approach, concentrate on several of the most salient lessons, and conclude with a description of the current state of the project.

One of the major hurdles in maintaining long-lived electronic systems is that electronic parts become obsolete, no longer available from the original suppliers. When this occurs, an engineer is tasked with resolving the problem by finding a replacement that is "as similar as possible" to the original part. The current approach involves a laborious manual search through several electronic portals and data books. The search is difficult because potential replacements may differ from the original and from each other by one or more parameters. Worse still, the cumbersome nature of this process may cause the engineers to miss appropriate solutions amid the many thousands of parts listed in industry catalogs.In this paper, we address this problem by introducing the notion of a parametric "distance" between electronic components. We use this distance to search a large parts data set and recommend likely replacements. Recommendations are based on an adaptive nearest-neighbor search through the parametric data set. For each user, we learn how to scale the axes of the feature space in which the nearest neighbors are sought. This allows the system to learn each user's judgment of the phrase "as similar as possible."

For the last few years mobile (or nomadic) computing has generated tremendous interest in both the research and the industrial community. Mobility is seen as an area of great potential benefits, both in terms of products and research contributions, However, at this time, mobile systems are so novel that there is little practical experience regarding their use. This has led to much speculation regarding a number of system issues such as determining what the killer apps will be, the hardware architecture of the nomadic machines, deciding whether communication or computation will be their primary feature and so on. One of the issues yet to be resolved is that of the architecture of these machines. Will mobile machines be essentially a new type of portable computer (although perhaps smaller, less powerful, friendlier, and pencentric) or will we carry around with us the equivalent of an X-window terminal (i.e., simply a display device, with all computation being carried out at a non-mobile server)? Examples of the first approach are the Apple Newton and the EO computers formerly marketed by AT&T, while the second approach is being explored by a number of other researchers (e.g., the InfoPad project at U.C. Berkeley, or the Xerox PARC tabs). This paper briefly describes the research issues involved and outlines the pros and cons of either approach. We also explore in detail one particular aspect, namely, the performance implications of the choice of architecture in a distributed information system. The results are presented as a set of simulation-based studies.

This paper proposes the use of repetitive broadcast as a way of augmenting the memory hierarchy of clients in an asymmetric communication environment. We describe a new technique called "Broadcast Disks" for structuring the broadcast in a way that provides improved performance for non-uniformly accessed data. The Broadcast Disk superimposes multiple disks spinning at different speeds on a single broadcast channel--in effect creating an arbitrarily fine-grained memory hierarchy. In addition to proposing and defining the mechanism, a main result of this work is that exploiting the potential of the broadcast structure requires a re-evaluation of basic cache management policies. We examine several "pure" cache management policies and develop and measure implementable approximations to these policies. These results and others are presented in a set of simulation studies that substantiates the basic idea and develops some of the intuitions required to design a particular broadcast program.

Mobile computers and wireless networks are emerging technologies that will soon be available to a wide variety of computer users. Unlike earlier generations of laptop computers, the new generation of mobile computers can be an integrated part of a distributed computing environment, one in which users change physical location frequently. The result is a new computing paradigm, nomadic computing. This paradigm will affect the design of much of our current systems software, including that of database systems.

A simple method for constructing dynamic heirarchies on a file-by-file basis is described. The results of a trace-driven simulation of a dynamic hierarchical file system are presented. A reduction in server traffic of a factor of more than two for shared files compared with a flat scheme is obtained, without a large increase in client access time. Low-overhead techniques for maintaining cache consistency by detecting missed cache invalidation are discussed.>

The issues involved in sharing information among a large collection of independent databases is explored. Some of the distinguishing features that characterize such large-scale environments (such as size, autonomy, and heterogeneity) are discussed. A multistep information sharing process for those systems is outlined and an architecture supporting that exchange is presented. A detailed description of a working prototype based on this architecture and some measurements of its performance are provided.>

The traditional model of virtual memory working sets does not account for programs that can adjust their working sets on demand. Examples of such programs are garbage-collected systems and databases with block cache buffers. We present a memory-use model of such systems, and propose a method that may be used by virtual memory managers to advise programs on how to adjust their working sets. Our method tries to minimize memory contention and ensure better overall system response time. We have implemented a memory “advice server” that runs as a non-privileged process under Berkeley Unix. User processes may ask this server for advice about working set sizes, so as to take maximum advantage of memory resources. Our implementation is quite simple, and has negligible overhead, and experimental results show that it results in sizable performance improvements.

The authors present an enhancement to distributed file systems that allows the users of the system to keep local copies of important files, decreasing the dependency over file servers. Using the notions of stashing and quasi-copies, the system allows users to tune up the quality of the service they want to receive when the file server is not reachable. One of the key points of this work is the focus on the tradeoff between availability and degradation of service. The other main contribution is the design of a distributed file system which is ideally suited to very large distributed systems, in that it provides users with greater tolerance of network partitions and server failures. It is emphasized that the use of stashing does not preclude the use of other performance-enhancing or fault-tolerant techniques. The file system architecture has been implemented and FACE, a prototype of a file system service based on Sun's NFS, is described. Performance figures are reported. These figures show that the overhead of providing the service is negligible. Current plans also call for porting the FACE design to a number of other processors.>

Currently, a variety of information retrieval systems are available to potential users.… While in many cases these systems are accessed from personal computers, typically no advantage is taken of the computing resources of those machines (such as local processing and storage). In this paper we explore the possibility of using the user's local storage capabilities to cache data at the user's site. This would improve the response time of user queries albeit at the cost of incurring the overhead required in maintaining multiple copies. In order to reduce this overhead it may be appropriate to allow copies to diverge in a controlled fashion.… Thus, we introduce the notion of quasi-copies , which embodies the ideas sketched above. We also define the types of deviations that seem useful, and discuss the available implementation strategies.—From the Authors' Abstract

A protocol is presented for negotiating access to data in a federated database. This protocol deals with several important aspects of data sharing in an environment where databases belonging to different organizations coexist and cooperate. It is based on the concept of quasicopies. These are cached values that are allowed to deviate from the central value in a controlled fashion. The degree of consistency of a quasicopy is established by the entity where the quasicopy is to reside. Two techniques are presented that can be used for numerical data and for copies that rely on version numbers. It is believed that these two ideas encompass many of the interesting cases in practice. However, it is also possible to fine tune the estimation of this function once the exact semantics of the data involved are known.>

In a network of independently owned processors (e.g. workstations), load-balancing schemes cannot consider the whole network as one unit and thus try to optimize the overall performance. Instead, they have to consider the needs of the resource owners. For this type of environment, load sharing is a more appropriate goal. An approach is proposed in which each machine in the network determines the amount of sharing it is willing to do. The scheme, called High-Low makes sure that the service provided to local jobs of a lightly doped node does not deteriorate by more than a predefined amount. It simultaneously helps improve the service at heavily loaded nodes. It is shown empirically that load sharing in a network of workstations can be effective even with a simple-minded allocation of jobs.>

Information retrieval (IR) systems provide individual remote access to centrally managed data. The current proliferation of personal computer systems, as well as advances in storage and communication technology, have created new possibilities for designing information systems which are easily accessible, economical, and responsive to user needs. This paper outlines methods of integrating personal computers (PCs) into large information systems, with emphasis on effective use of the storage and processing capabilities of these computers. In particular we discuss means for caching retrieved data at PC-equipped user sites, noting that caching in this environment poses unique problems. An event-driven simulation program is described which models information system operation. This simulator is being used to examine caching strategies. Some results of these studies are presented.