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A Web-based distributed virtual educational laboratory

TL;DR: In this paper, the authors describe specification and design of a geographically distributed system based on commercially standard components for workbenches in networked computer laboratories, which can be used for a preliminary familiarization and experimentation with instrumentation and measurement procedures.
Abstract: Evolution and cost of measurement equipment, continuous training, and distance learning make it difficult to provide a complete set of updated workbenches to every student. For a preliminary familiarization and experimentation with instrumentation and measurement procedures, the use of virtual equipment is often considered more than sufficient from the didactic point of view, while the hands-on approach with real instrumentation and measurement systems still remains necessary to complete and refine the student's practical expertise. Creation and distribution of workbenches in networked computer laboratories therefore becomes attractive and convenient. This paper describes specification and design of a geographically distributed system based on commercially standard components.

Summary (3 min read)

Introduction

  • AND MOTIVATIONS RECENT developments in virtual instrument technologies,remote measurement, distributed systems, and interactive educational environments [1], [2] greatly changed the traditional approach to teaching and practical experimentation at any educational level, from technical high schools and undergraduate academic courses through master’s and Ph.D. studies to continuous education and training in the industry.
  • This helps in reducing training costs by restricting the tutored activities only to substantial matters.
  • Distance learning allows one to limit the costs for continuous training both by providing in-house educational facilities that can be used with a flexible and adaptable schedule and by reducing the time spent in an educational laboratory outside of the company.

A. Educational Goals

  • 1) Initial Approach to Instruments, Measurement Procedures, and Applications:.
  • The system must take into account undergraduate, graduate, and doctoral students, as well as practitioners from industry.
  • Beginners who want to use instruments and measurement methodologies need tools to understand and operate in their specific application field.
  • When the student alone is using the simulation environment, educational supports will be appreciated.
  • Multimedia pages are attached to each object of the workbench front panel to explain meaning, theory, features, and use of the selected component.

B. User Accessibility

  • User’s activities must be performed in a way that is simple and easy to understand, even for people who are not experts in information technologies, also known as 1) User Friendliness.
  • 2) Simplicity of Accessing the Laboratory Resources: Access and operation transparency guarantees effective and efficient use.
  • For simulated or remote measurement, client computers may be located in any computer classroom, university office, institution, or company, when suited network connections and access authorization are provided to the network of the required educational servers.
  • For remote use, computers must be connected to the Internet via transport control protocol/Internet protocol (TCP/IP).

C. Cost Limitation and Hardware Resources Sharing

  • 1) Limitation of Laboratory Costs:Virtual instrument technologies, possibly with a limited number of local physical resources, must be used to minimize the costs of laboratory setup and maintenance.
  • Acquisition of licenses cannot be delegated to students for cost and political reasons, even if student licenses begin to appear on the market at highly reduced costs.
  • Moreover, the limited cost and the restricted installations allow for improving resource updating, thus maintaining the leading edge of educational sites and the adequacy for industrial applications.
  • Hands-on experimentation for simple and relatively cheap acquisition systems and application plants are obtained by using dedicated components available in specific laboratories or individual computers.
  • Resources must be easily and directly accessible by students, even remotely through the computer network as they were local in the laboratory or even in the computers on which students are working, also known as 4) Shared-Resource Networking.

D. Software Cost and Sharing

  • The software developing tools based on graphic, object-oriented programming methods make this job easier and feasible to a wider population, even with limited experience in computer programming.
  • 2) Standard Components and Technologies for Simulators: Standard virtual environments for simulation and simulator development make creating and testing new environments simpler and cheaper.
  • This approach should be preferred instead of building the whole instrumentation with programming languages and graphic tools since it reduces realization time and cost, increasing quality, correctness, portability, adaptability, and extendibility.
  • 3) Engineering the Simulator Components:High quality, accuracy, and correctness of simulation environments can be achieved by using software engineering.

E. Real-Time Operation

  • If the system to be measured or controlled is connected to the student’s computer directly through suited acquisition boards, real-time operation of the virtual measurement system is possible.
  • This is exactly correct only under some restrictive conditions.
  • Practically, analysis and control are still correct even if sampling is not performed contemporaneously on all input signals, but in a time period short enough to allow for considering the input values invariant within this period.
  • In control, improper use of remote sensing may lead to system instability and safety problems.
  • The interaction with the remote server should be limited to setting up and starting the experiment and, then, to retrieve the results.

F. Distributed System Engineering

  • It is relevant for the simulation system and the component library.
  • Modularity allows for combining individual components easily to create the workbench or new components, without any need of software development or adaptation.
  • The component library must be easily expandable.
  • The simulation environment and the component libraries should be portable on different hardware platforms and operating systems, also known as 3) System Portability.
  • All these f atures are provided transparently and homogeneously to the users.

G. Cooperative Development, Management, and Maintenance

  • 1) Sharing Resources and Experiences Among Universities, Institutions, and Companies:The global communication network and high-level languages allow for allocating simulation and remote acquisition programs on different servers.
  • The adoption of de facto standards and widely used development and simulation environments for virtual instrumentation (e.g., LabView by National Instruments) maximizes the opportunities for mutual exchanges of components and experiences.
  • Partitioning of design, implementation, and maintenance of the measurement components and plants among several partners allows for assigning tasks to the most suited experts, also known as 2) Specialization and Quality.
  • Centralizing design, implementation, and maintenance of resources and servers allows for better control and coordination of the whole system, also known as 3) Centralization for Standardization.
  • Other considerations on multiserver systems are found in [4] and [5].

H. Security

  • 1) Preservation of Intellectual Rights:The use of simulation environment licenses must be guaranteed and protected from unauthorized accesses.
  • This allows any user of the simulation environment for virtual laboratories to simply plug his client computer to the international network and obtain the simulation environment and the instrumentation components directly from the server without any preliminary acquisition of specific software, except the suited access authorization.
  • Simulation engine, sampler, and virtual components are created in LabView, a widely used virtual environment for measurement areas produced by National Instruments.
  • His research interests are in digital signal processing, estimation, automated instrumentation, and electromagnetic compatibility.
  • He received the degree in electrical engineering from Politecnico di Torino, Torino, Italy, in 1969.

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10 August 2022
POLITECNICO DI TORINO
Repository ISTITUZIONALE
A Web-Based Distributed Virtual Educational Laboratory / Benettazzo, L; Bertocco, M; Ferraris, Franco; Ferrero, A;
Offelli, C; Parvis, Marco; Piuri, V.. - In: IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT. - ISSN
0018-9456. - STAMPA. - 49:2(2000), pp. 349-356. [10.1109/19.843077]
Original
A Web-Based Distributed Virtual Educational Laboratory
Publisher:
Published
DOI:10.1109/19.843077
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openAccess
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(Article begins on next page)
This article is made available under terms and conditions as specified in the corresponding bibliographic description in
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IEEE

IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 49, NO. 2, APRIL 2000 349
A Web-Based Distributed Virtual
Educational Laboratory
Luigino Benetazzo, Matteo Bertocco, Franco Ferraris, Alessandro Ferrero, Fellow, IEEE, Carlo Offelli, Marco Parvis,
and Vincenzo Piuri, Senior Member, IEEE
Abstract—Evolution and cost of measurement equipment, con-
tinuous training, and distance learning make it difficult to provide
a complete set of updatedworkbenches toevery student. For a pre-
liminary familiarization and experimentation with instrumenta-
tion and measurement procedures, the use of virtual equipment
is often considered more than sufficient from the didactic point
of view, while the hands-on approach with real instrumentation
and measurement systems still remains necessary to complete and
refine the student’s practical expertise. Creation and distribution
of workbenches in networked computer laboratories therefore be-
comes attractiveand convenient.This paper describes specification
and design of a geographically distributed system based on com-
mercially standard components.
Index Terms—Distributed measurement systems, educational
laboratory, remote measurement, virtual systems.
I. INTRODUCTION AND MOTIVATIONS
R
ECENT developments in virtual instrument technologies,
remote measurement, distributed systems, and interactive
educational environments [1], [2] greatly changed the tradi-
tional approach to teaching and practical experimentation at
any educational level, from technical high schools and under-
graduate academic courses through master’s and Ph.D. studies
to continuous education and training in the industry. Practical
experimentation has a great and even increasing importance
in education to understand better the use of new complex
technologies through trial-and-error methods, especially when
it is difficult to capture and formalize system behavior in a
simple mathematical description.
The interest in virtual instruments is mainly due to the cost
of experimental laboratories both at educational sites with a
large number of students and in industry where instrumenta-
tion is used for development or production. Simulators are not
expected to replace the real instruments but can be a powerful
auxiliary didactic tool for the students in order to help them to
become acquainted with the instrument and its controls and op-
erations both in the class and remotely. This helps in reducing
training costs by restricting the tutored activities only to sub-
stantial matters.
Manuscript received May 26, 1999; revised December 14, 1999.
L. Benetazzo, M. Bertocco, and C. Offelli are with the Dipartimento di Elet-
tronica e Informatica, Universita' di Padova, Padova, Italy.
F. Ferraris and Marco Parvis are with the Dipartimento di Elettronica, Po-
litecnico di Torino, Torino, Italy.
A. Ferrero is with the Dipartimento di Elettrotecnica, Politecnico di Milano,
Milano 20133 Italy.
V. Piuri is with the Dipartimento di Elettronica e Informazione, Politecnico
di Milano, Milano 20133 Italy.
Publisher Item Identifier S 0018-9456(00)03059-X.
Remote access to educational resources is attracting an
increasing interest to realize distance learning. Continuous
training is in fact a key factor to maintain the leading edge and
improve the quality of production, products, and personnel in
many small and medium-size enterprises. Distance learning
allows one to limit the costs for continuous training both by
providing in-house educational facilities that can be used with a
flexible and adaptable schedule and by reducing the time spent
in an educational laboratory outside of the company.
Real measurements of physical phenomena are relevant
to more accurate training and to providing a better feeling
to students about measurement procedures and measurement
system design. The access to remote instrument-equipped sites
connected through a computer network becomes an interesting
solution to limit training costs without constraining educational
opportunities. Also in this case, further direct experimentation
on real systems can be considered after the preliminary remote
practice, but limited to a better understanding of the course
topics. This will reduce the cost and time for student mobility,
while preserving most of the learning opportunities on real
phenomena. The limitation consists in the possible restrictions
in real-time measurement and control of complex systems due
to bandwidth constraints and shared use of the measurement
system.
Last, the use of local acquisition boards allows for an even
more detailed experimentation without possible delays, time
inconsistencies, or operation constraints due to the networked
interconnections. This approach is, however, more expensive
than the previous solutions since the acquisition boards must
be acquired locally. However, since the virtual system is pro-
grammable, it can be used for several applications and, conse-
quently, will be cheaper than dedicated instrumentation.
The wide spectrum of data acquisition and treatment
solutions described above provides different degrees of perfor-
mance and accuracy, at correspondingly increasing costs, to
match better the evolving needs of students without wasting
precious resources. Capitalization and sharing of authors’
previous experiences led to creation of a unique educational
environment for training and experimenting in electrical and
electronic measurements. In particular, the authors merged
the system created for Web-based interaction to create and
download virtual benches [3] and the system created for remote
measurement [4]–[6]. This paper presents the system features
and architecture of a distributed educational environment based
on Web technologies and remote measurement. Such an envi-
ronment can be used to acquaint students to the measurement
procedures and laboratories, as a preliminary phase that does
0018-9456/00$10.00 © 2000 IEEE

350 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 49, NO. 2, APRIL 2000
not replace practical activities on real instrumentation and
systems but reduces tutored activities and related costs. The
flexibility of the environment allows for supporting different
kind of didactic activities, while the teacher will be responsible
of selecting the most suited approach to be used according to
the specific needs of the students and the desired curricula.
II. S
YSTEM SPECIFICATIONS AND FEATURES
The goals and features of a distributed virtual laboratory for
measurement technologies and applications follow.
A. Educational Goals
1) Initial Approach to Instruments, Measurement Proce-
dures, and Applications: The system must support students
in familiarizing themselves with measurement problems and
technologies through the use of simulators of real instrumen-
tation, measurement devices, and systems. Although desirable
for specialists, the large majority of students do not necessarily
need to learn creation of new instrumentation and measurement
procedures.
2) Student Typologies: Different kinds of students with dif-
ferent needs must be supported. The system must take into ac-
count undergraduate, graduate, and doctoral students, as well
as practitioners from industry. Beginners who want to use in-
struments and measurement methodologies need tools to under-
stand and operate in their specificapplication field.More oppor-
tunities are required for students working on metrology issues.
Advanced students in metrology areas will be interested in the
details of procedures, devices, components, and systems: cre-
ating their own instruments and experimenting with their own
measurement procedures is interesting but requires the access to
suited development systems. Since these last tasks are for spe-
cialists and have high costs, we do not consider this opportunity
in the present system version.
3) Adaptability to User Needs and Scalability to User
Level: The system must adapt operations and support to
specific users. Students with different backgrounds and needs
must be allowed for defining the resource view (i.e., devices,
components, instruments, generators, data acquisition sys-
tems), without being overwhelmed by too much information.
The system must scale transparently features and resource
view according to the level of competence, experience, and
confidence of the students.
4) Tutoring Aids: The educational system must support dif-
ferent types of interactions between students and educators. Tu-
tors in laboratories and computer classrooms can provide as-
sistance to students during classes. When the student alone is
using the simulation environment, educational supports will be
appreciated. On-line help for using the simulation environment
and the individual measurement resources can be introduced by
using standard programming techniques available in the user
interface. Multimedia pages are attached to each object of the
workbench front panel to explain meaning, theory, features, and
use of the selected component. Possible links can also be placed
to more extensive descriptions on Web sites. Multimedia and
hypertext technologies through web or CD-ROM distribution
allow for realizing an electronic book on measurement method-
ologies and instruments that can be used by students during
training. Thisbook refers on-line to the distributed measurement
educational environment and remote sensing resources to pro-
vide examples of theory and measurement methodologies. The
student can thus experiment immediately in the virtual simula-
tion environment.
B. User Accessibility
1) User Friendliness: User’s activities must be performed
in a way that is simple and easy to understand, even for people
who are not experts in information technologies.
2) Simplicity of Accessing the Laboratory Resources: The
system features must be accessible easily and homogeneously
withinthe university hosting the servers,from other universities,
from companies, and by students at home. Access and operation
transparency guarantees effective and efficient use.
3) Different Accessing Typologies: The educational system
can be accessed by using personal computers connected to the
international computer network in different locations and with
different kinds of connection. Instrument-equipped computers
(i.e., computers with acquisition boards) may be anywhere, pro-
vided that they are connected to the educational server through
Internet and to the system or the plant to be measured. They can
be in the same institution hosting the educational servers, or in
another institution or company, or even at a student’s home. For
simulated or remote measurement, client computers may be lo-
cated in any computer classroom, university office, institution,
or company, when suitednetwork connections and access autho-
rization are provided to the network of the required educational
servers. For remote use, computers must be connected to the In-
ternet via transport control protocol/Internet protocol (TCP/IP).
C. Cost Limitation and Hardware Resources Sharing
1) Limitation of Laboratory Costs: Virtual instrument tech-
nologies, possibly with a limited number of local physical re-
sources, must be used to minimize the costs of laboratory setup
and maintenance. In fact, run-time licenses of the simulation
software must be purchased to run simulations and not only
during development. This greatly affects system cost. Acqui-
sition of licenses cannot be delegated to students for cost and
political reasons, even if student licenses begin to appear on
the market at highly reduced costs. Conversely, the cost for all
students cannot be placed on the university budget due to fund
limits. Few licenses must be therefore bought by the universities
and provided temporarily to students as floating licenses valid
during the system use only.
2) Differentiation of the Hardware Supports:
Experimentation on purely virtual measurement systems
is useful as first experience. A better understanding of the
involved phenomena and measurement problems (e.g., delays,
sampling frequency, accuracy, and calibration) may need real
data. Students with knowledge and practical skills derived from
the virtual environment perform this advanced training phase
more quickly, thus using expensive and sophisticated physical
measurement resources for a shorter time. A smaller amount
of these resources are sufficient to satisfy the students’ needs,
leading to a reduced laboratory cost. Moreover, the limited cost

BENETAZZO et al.: WEB-BASED DISTRIBUTED VIRTUAL EDUCATIONAL LABORATORY 351
and the restricted installations allow for improving resource
updating, thus maintaining the leading edge of educational
sites and the adequacy for industrial applications. Hands-on
experimentation for simple and relatively cheap acquisition
systems and application plants are obtained by using dedicated
components available in specific laboratories or individual
computers. Remote sensing, acquisition, and actuation on
centralized sites become attractive to limit the laboratory costs
for expensive components, systems, and plants.
3) High Availability and Sharing of Complex and Expensive
Measurement Resources: Networking expensive resources for
measurement and application allows for better exploitation of
resources and for sharing costs. High-quality training environ-
mentsand up-to-datetechnologies are achievedat a cheaper cost
per student.
4) Shared-Resource Networking: Resources must be easily
and directly accessible by students, even remotely through the
computer network as they were local in the laboratory or even
in the computers on which students are working. Transparency
of resource networking is relevant to guarantee easy usage in-
dependently from the location.
D. Software Cost and Sharing
1) Limitation of Efforts and Time to Build Simulators: The
softwaredeveloping tools basedon graphic,object-oriented pro-
gramming methods make this job easier and feasible to a wider
population, even with limited experience in computer program-
ming. Development and maintenance costs are reduced.
2) Standard Components and Technologies for Simulators:
Standard virtual environments for simulation and simulator
development make creating and testing new environments
simpler and cheaper. This approach should be preferred instead
of building the whole instrumentation with programming lan-
guages and graphic tools since it reduces realization time and
cost, increasing quality, correctness, portability, adaptability,
and extendibility.
3) Engineering the Simulator Components: High quality,
accuracy, and correctness of simulation environments can be
achieved by using software engineering.
4) Reuse of Simulator’s Components: Availability of a com-
ponent library and use of standard design techniques allow for
reusing and enhancing development and costs.
E. Real-Time Operation
1) Real-Time Operation and Constraints: If the systemto be
measured or controlled is connected to the student’s computer
directly through suited acquisition boards, real-time operation
of the virtual measurement system is possible. When signal gen-
erators are simulated, the real-time behavior is related only to
the characteristics of the simulation environment.
Some researchers and companies claim that real-time op-
eration in virtual instruments and environments with remote
sensing is always feasible and correct under any operating and
environmental condition, including geographical computer
networks. This is exactly correct only under some restrictive
conditions. Sampling of all quantities used by the measurement
workbench is not guaranteed to be obtained exactly at the same
time when acquired by different systems that cannot share the
same sampling clock.
Data analysis for monitoring and control must therefore con-
sider explicitly the time at which samples were taken. Tradi-
tional control algorithms need a consistent picture of the inputs,
sampled contemporaneously. Practically, analysis and control
are still correct even if sampling is not performed contempo-
raneously on all input signals, but in a time period short enough
to allowfor considering the input valuesinvariant within this pe-
riod. This occurs when system dynamics are slow enough with
respect to the period. Conversely, when input signals varies at
very high frequencies, the above approximation is not correct
and remote sensing should not be used formonitoring or control.
In control, improper use of remote sensing may lead to system
instability and safety problems.
An alternative approach could be envisioned by running the
whole monitoring and control algorithm on the remote site. In
this case, the interaction with the remote server should be lim-
ited to setting up and starting the experiment and, then, to re-
trieve the results. However, this requires transfer of the control
algorithm from the client to the server. This is usually not ac-
ceptable for safety reasons of the plant connected to the remote
server.
F. Distributed System Engineering
1) Modularity: It is relevant for the simulation system and
the component library. Modularity allows for combining indi-
vidual components easily to create the workbench or new com-
ponents, without any need of software development or adapta-
tion.
2) Expandability: The component library must be easily
expandable. New components should be directly added and
made usable to students without any need for library rebuilding
or restructuring. Local integration of components allows for
distributed libraries with possible specific adaptation to local
needs.
3) System Portability: The simulation environment and the
component libraries should be portable on different hardware
platforms and operating systems. When the system is built by
using programming languages, portability is achieved with an
absolutely portable language (e.g., nowadays, Java). We can ac-
cept a reduction of portability in exchange of a higher simplicity
in creating components and measurement systems. In most edu-
cational and industrial laboratories, sufficient portability is pro-
vided by commercially standard virtual environments for mea-
surements and by limiting the use of object-oriented program-
ming (C
++
used in a standard and portable way).
4) Interoperability: Hardware and operating-system in-
dependence of the simulation environment also provides
interoperability, i.e., the ability of running some activities on
different computers, connecting to different servers for remote
measurement services, using different measurement servers
written on different machines with different languages, and
downloading components from different servers. All these
features are provided transparently and homogeneously to the
users.

352 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 49, NO. 2, APRIL 2000
G. Cooperative Development, Management, and Maintenance
1) Sharing Resources and Experiences Among Universities,
Institutions, and Companies: The global communication net-
work and high-level languages allow for allocating simulation
and remote acquisition programs on different servers. Universi-
ties, measurement institutions, and companies may join the re-
source developing teams so that the burden of simulator devel-
opment and maintenance can be distributed on all participating
bodies with mutual benefit. The adoption of de facto standards
and widely used development and simulation environments for
virtual instrumentation (e.g., LabViewby National Instruments)
maximizes the opportunities for mutual exchanges of compo-
nents and experiences.
2) Specialization and Quality: Partitioning of design, im-
plementation,and maintenance ofthe measurement components
and plants among several partners allows for assigning tasks to
the most suited experts. Specialization leads to a higher quality
of the individual components, measurement resources, and ser-
vices.
3) Centralization for Standardization: Centralizing design,
implementation, and maintenance of resources and servers al-
lows for better control and coordination of the whole system.
Centralization must not necessarily be complete: Some excel-
lence centers can be selected to manage specific tasks as well
as realize and maintain specific resources and components, in a
coordinate way. Centralization favors educational tool standard-
ization and adherence to commercial and formal standards.
4) Multiserver System: For system decentralization as well
as forcentralization and cooperation in creating and maintaining
the measurement resources and components, the system must be
realized on a multihost platform. Each host computer runs part
of the system features and resources, in cooperation and coor-
dination with the other servers. To enhance the system perfor-
mance and fault tolerance, mirrored sites are adopted to repli-
cate services and resources in different locations. Users access
the nearest server available on the network at that time. Suited
policies and strategies must be envisioned for automatic align-
ment and system consistency. Other considerations on multi-
server systems are found in [4] and [5].
H. Security
1) Preservation of Intellectual Rights: The use of simula-
tion environment licenses must be guaranteed and protected
from unauthorized accesses. Similarly, protection must be
assured also to the distribution of the virtual instrumentation
developed for training purposes.
2) Security: The access through the Internet must preserve
the integrity of data and systems.
3) Safety and Security of Measurement and Application Re-
sources: Access and useof remote physical resources as well as
instrument-equipped systemsand plants must be allowedonly to
authorized users, according to the agreements for training pro-
grams and cost sharing and by taking into account suited secu-
rity and safety operating conditions for the instrument-equipped
system or plant.
Fig. 1. Distributed system architecture.
III. SYSTEM ARCHITECTURE
The system design and experimentation took into account all
characteristics and features discussed in Section II. A homoge-
neous distributed framework was created for workbench con-
struction, storing, and distributing as well as for remote sensing
to support different educational activities.
The client–server distributed environment composed by a
multiserver architecture is shown in Fig. 1. The distribution
servers store the basic components of the virtual instruments
and generators that can be used by the students to build their
own workbench. The instrument-equipped servers are directly
connected to instruments in order to measure physical quanti-
ties in the field for remote sensing applications. Servers can be
located everywhere on the network, but physical connections
and access authorizations are given to every user.
Clients allow students to connect to servers for creating the
virtual workbenches, which encompass stand-alone generators,
virtual instruments fed by virtual generators, virtual instruments
connected to real acquisition boards installed in the client, vir-
tual instruments fed by remote sensors through the network, and
virtual generators providing control signals to either local or re-
mote actuators. Clients can be connected to servers on the same
local-area network (LAN) of the laboratory or the campus as
well as remotely in other LAN’s or even through ISDN or di-
alup connections through the Internet.
For all connections, international commercial standard pro-
tocols are adopted for the widest access, namely, TCP/IP, file
transfer protocol, hypertext transfer protocol, and secure hyper-
text transfer protocol (SHTTP) [3], [4]. This allows any user
of the simulation environment for virtual laboratories to simply
plug his client computer to the international network and ob-
tain the simulation environment and the instrumentation com-
ponents directly from the server without any preliminary acqui-
sition of specific software, except the suited access authoriza-
tion.

Citations
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Journal ArticleDOI
TL;DR: The proposed approach integrates a traditional Learning Management System (LMS) with the remote access to real instrumentation located in different laboratories, without requiring specific software components on the client side.
Abstract: This paper presents a comprehensive approach to distance learning for electric and electronic measurement courses. The proposed approach integrates a traditional Learning Management System (LMS) with the remote access to real instrumentation located in different laboratories, without requiring specific software components on the client side. The advantages of using LMSs in distance learning of measurement-related topics are summarized describing some LMS characteristics. Then, the remote laboratory system relying on virtual instruments (VIs) developed in LabVIEW and its integration with an off-the-shelf LMS are described in a project financed by the Italian Ministry of Education and University

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Journal ArticleDOI
TL;DR: A new model for sharing real laboratories on the Internet and creating a virtual on-line laboratory has been developed and validated in the field of electronic measurements and increases the possibility of practice in both academic and industrial education and enriches the current experience in e-learning.
Abstract: A new model for sharing real laboratories on the Internet and creating a virtual on-line laboratory has been developed and validated in the field of electronic measurements. Testing theories through practice is an important approach to scientific teaching, and appropriate solutions have not yet been found to support this activity in Web-based education. The on-line laboratory addresses this issue. It allows the execution via Web of real experiments and manages concurrency among users who remotely drive instruments and carry out experiments. The experimental setup can be distributed in different real laboratories, spread on a wide-area network, and controlled by local computers. Users can practice through the network and transparently to the actual locations of the devices under test in a multiuser concurrent way. The proposed paradigm increases the possibility of practice in both academic and industrial education and enriches the current experience in e-learning.

51 citations

References
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Journal ArticleDOI
John Makhoul1
01 Apr 1975
TL;DR: This paper gives an exposition of linear prediction in the analysis of discrete signals as a linear combination of its past values and present and past values of a hypothetical input to a system whose output is the given signal.
Abstract: This paper gives an exposition of linear prediction in the analysis of discrete signals The signal is modeled as a linear combination of its past values and present and past values of a hypothetical input to a system whose output is the given signal In the frequency domain, this is equivalent to modeling the signal spectrum by a pole-zero spectrum The major part of the paper is devoted to all-pole models The model parameters are obtained by a least squares analysis in the time domain Two methods result, depending on whether the signal is assumed to be stationary or nonstationary The same results are then derived in the frequency domain The resulting spectral matching formulation allows for the modeling of selected portions of a spectrum, for arbitrary spectral shaping in the frequency domain, and for the modeling of continuous as well as discrete spectra This also leads to a discussion of the advantages and disadvantages of the least squares error criterion A spectral interpretation is given to the normalized minimum prediction error Applications of the normalized error are given, including the determination of an "optimal" number of poles The use of linear prediction in data compression is reviewed For purposes of transmission, particular attention is given to the quantization and encoding of the reflection (or partial correlation) coefficients Finally, a brief introduction to pole-zero modeling is given

4,206 citations

Journal ArticleDOI
TL;DR: In this paper, a new computational algorithm for the partial correlation coefficients of a linear system given the covariance of its output when excited by a white input noise was proposed. But the proposed algorithm does not make use of the usual parameters in the linear prediction recursion.
Abstract: This paper introduces a new computational algorithm for the partial correlation coefficients of a linear system given the covariance of its output when excited by a white input noise. Although derived from Levinson's well-known procedure, the proposed algorithm does not make use of the usual parameters in the linear prediction recursion. It may be implemented using fixed point arithmetics. Application to speech waves is emphasized.

170 citations

Journal ArticleDOI
18 May 1998
TL;DR: This paper describes a client-server architecture for the remote control of instrumentation over the Internet network that allows multi-user, multi-instruments sessions to be obtained by means of a queueing process and provides instrument locking capability.
Abstract: This paper describes a client-server architecture for the remote control of instrumentation over the Internet network. The proposed solution allows multi-user, multi-instruments sessions to be obtained by means of a queueing process and provides instrument locking capability. Client applications can be easily developed by using conventional high-level programming languages or well-assessed virtual instrumentation frameworks. Performance tests are reported, which show the low overhead due to network operations with respect to the direct control of the instruments.

104 citations


"A Web-based distributed virtual edu..." refers background or methods in this paper

  • ...In particular, the authors merged the system created for Web-based interaction to create and download virtual benches [3] and the system created for remote measurement [4]–[6]....

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  • ...Other considerations on multiserver systems are found in [4] and [5]....

    [...]

  • ...through user validation was adopted [3], [4]....

    [...]

  • ...The remote connection manager in the client is an executable program running in parallel to the simulation engine [4], [6]....

    [...]

  • ...For all connections, international commercial standard protocols are adopted for the widest access, namely, TCP/IP, file transfer protocol, hypertext transfer protocol, and secure hypert xt transfer protocol (SHTTP) [3], [4]....

    [...]

Journal ArticleDOI
18 May 1998
TL;DR: Virtual instruments and distributed systems are of great interest to create advanced and flexible teaching and experimentation environments for measurement technologies at limited costs.
Abstract: Virtual instruments and distributed systems are of great interest to create advanced and flexible teaching and experimentation environments for measurement technologies at limited costs The availability of simple and efficient technological supports to dissemination and remote use of virtual systems becomes attractive to increase the diffusion of experimental practice disregarding the number of students and their location as well as the variety of instruments and measurement procedures directly available for experimentation

93 citations


"A Web-based distributed virtual edu..." refers background or methods in this paper

  • ...In particular, the authors merged the system created for Web-based interaction to create and download virtual benches [3] and the system created for remote measurement [4]–[6]....

    [...]

  • ...components’ definition to realize the virtual workbench [3],...

    [...]

  • ...through user validation was adopted [3], [4]....

    [...]

  • ...To distribute the engine and the components as well as to create the workbench while protecting the intellectual property, a Web-based interface was adopted [3]....

    [...]

  • ...For all connections, international commercial standard protocols are adopted for the widest access, namely, TCP/IP, file transfer protocol, hypertext transfer protocol, and secure hypert xt transfer protocol (SHTTP) [3], [4]....

    [...]

Journal ArticleDOI
TL;DR: The characteristics and the features related to issues of accuracy, precision and sensitivity are pointed out so as to achieve a better understanding of the effective usability of these technologies, avoid problems due to their superficial application, and promote the best use of these advanced, powerful methods.
Abstract: This article is directed to discuss the fundamental characteristics of measurement systems based on digital processing, with specific focus on virtual instruments and distributed measurement systems. Its goal is to point out the characteristics and the features related to issues of accuracy, precision and sensitivity, so as to achieve a better understanding of the effective usability of these technologies, avoid problems due to their superficial application, and promote the best use of these advanced, powerful methods. Finally, we consider the problem of the traceability of the measurement results coming from the instrumentation based on digital signal processing.

76 citations


"A Web-based distributed virtual edu..." refers background in this paper

  • ...RECENT developments in virtual instrument technologies, remote measurement, distributed systems, and interactive educational environments [1], [2] greatly changed the traditional approach to teaching and practical experimentation at any educational level, from technical high schools and undergraduate academic courses through master’s and Ph....

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Frequently Asked Questions (16)
Q1. What have the authors contributed in "A web-based distributed virtual educational laboratory" ?

This paper describes specification and design of a geographically distributed system based on commercially standard components. 

For all connections, international commercial standard protocols are adopted for the widest access, namely, TCP/IP, file transfer protocol, hypertext transfer protocol, and secure hypertext transfer protocol (SHTTP) [3], [4]. 

The global communication network and high-level languages allow for allocating simulation and remote acquisition programs on different servers. 

When the system is built by using programming languages, portability is achieved with an absolutely portable language (e.g., nowadays, Java). 

Since components are not able to run without the simulation engine and cannot be stored on the client separately, run-time verification of the user authorization performed by the authorization manager allows for saving their intellectual property. 

When signal generators are simulated, the real-time behavior is related only to the characteristics of the simulation environment. 

Experiments have shown that the proposed environment is effective for the two main goals: cost reduction and students’ satisfaction. 

4) Reuse of Simulator’s Components: Availability of a component library and use of standard design techniques allow for reusing and enhancing development and costs. 

A hypertext book can be created to guide and support the students with advanced self-training approaches, a complementary tool for traditional teaching. 

The educational system can be accessed by using personal computers connected to the international computer network in different locations and with different kinds of connection. 

For simulated or remote measurement, client computers may be located in any computer classroom, university office, institution, or company, when suited network connections and access authorization are provided to the network of the required educational servers. 

Students were asked to perform other experiments by using different generators and remotely monitored quantities as homework after regular classes at their convenience: they were required to report results after ten days. 

On-line help for using the simulation environment and the individual measurement resources can be introduced by using standard programming techniques available in the user interface. 

Advanced students in metrology areas will be interested in the details of procedures, devices, components, and systems: creating their own instruments and experimenting with their own measurement procedures is interesting but requires the access to suited development systems. 

When a client needs a set of samples, a request message with the suited parameters is sent by the virtual component representing the generator to the connection manager. 

Instrument-equipped computers (i.e., computers with acquisition boards) may be anywhere, provided that they are connected to the educational server through Internet and to the system or the plant to be measured.