ABSTRACT. Abstract--Considering that the energy matrix of Honduras has undergone a drastic change during the last years due to the introduction of variable renewable energies, this change leads us to study the impact that is generated in the national interconnected system (SIN), this impact would be mainly influenced by the variability of renewable sources, given the sudden changes in both the increase and decrease of generation. In response to this impact a new methodology is proposed in the management of reserves in the SIN, different from those currently consider in the dispatch of energy. This methodology promotes a ramp reserve which consists in having the availability of rise or fall a quantity of generation in a given time, thus being able to absorb the falls or rises of large generation blocks that occur by any variant in the variable renewable generation (GRV). The calculation of the reserves will be obtained from the historical data of the ramps that occurred due to the GRV. The purpose of this calculation, besides improving the quality of the national interconnected system, is to make a comparison of the costs that would be generated by maintaining an available ramp reserve, with the costs of maintaining the system with the methodologies that it currently has.

ABSTRACT. In order to achieve a reduction in the use of disposable plastic packaging made from petroleum derivatives the use of organic wastes converted into biodegradable polymers is an opportunity. Therefore, the main objective of this research was to obtain a biopolymer developed through the conversion of orange peels. The use of tree structures allowed relating different variables that could have influence in the formulation of bioplastics. The variables that had more weight are the ratios of starch used in the formulation, the method to cool down the mix, and the drying method. In order to achieve the best biopolymer, the best variables were the use starch 100%, cooling at room temperature and dehydration for drying. The results can contribute to create a circular economy and will protect the environment.

ABSTRACT. In this article we study the current use and future parametric projection of bioenergy from sugar cane bagasse, eucalyptus and petroleum derivatives for power generation. A trend analysis and an econometric linear regression model were used to project the future demand for these energy sources. It was found that the use of bagasse grew by 6.8% and the energy generated with this resource grew by 3.1%, while the use of petroleum derivatives did not grow in the period between 2006 and 2018 for power generation A growth of the use of biomass in the form of sugar cane bagasse is projected of 16% and a decreasing behavior of the demand for the use of eucalyptus and derivatives for the generation of electrical energy until the year 2023.

ABSTRACT. It is known that 33% of traffic accidents worldwide are caused by drunk driving or drowsiness [1] [2], so a drowsiness level detection system that integrates image processing was developed with the use of Raspberry Pi3 with the OpenCV library; and sensors such as MQ-3 that measures the percentage of alcohol and the S9 sensor that measures the heart rate. In addition, it has an alert system and as an interface for the visualization of the data measured by the sensors a touch screen. With the image processing technique, facial expressions are analyzed, while physiological behaviors such as heart rate and alcohol percentage are measured with the sensors. In image test training you get an accuracy of x in a response time of x seconds. On the other hand, the evaluation of the operation of the sensors in 90% effective. So the method developed is effective and feasible.

ABSTRACT. Acoustic pollution has become a problem that is increasing in the different urbanized countries and in the path of development, due to the health problems caused by prolonged exposure to high noise levels. It is necessary to monitor and alert about decibel levels in both open and closed spaces. Artificial intelligence (AI) is a field that provides various inference techniques such as so-called fuzzy logic. And in that same direction, the application of expert systems facilitates decision making more accurately and in real time. This article presents the development of an expert system for noise monitoring and an alert mechanism, using fuzzy logic. Arduino and Raspberry Pi technology are used as hardware platforms for the development of the prototype.

ABSTRACT. Cloud Manufacturing (CM) offers the possibility to use and provide production services within an as-a-service concept. The CM paradigm enables more efficient resource utilization in the context of industry 4.0 through fully automated order processing. Existing architecture solutions, however, follow a central platform approach with a global neutral data model. As a consequence, the individuality of companies within the CM is not given any room for expression and symbioses between companies are not established. The result is a disadvantage particularly for SMEs, which generate their competitive advantage from innovative production technologies and symbiotic connections with customers and other SMEs. The focus of Collective Cloud Manufacturing (CCM) is the preservation of these characteristics, in which an over-approximation of costs through the integration of production-related simulations is to be reduced and the data security of the customer is to be enhanced. So in this work a data model for an existing concept for CCM is presented. The requirements for the data model and the run-time behavior are defined. Subsequently, the State-of-the-Art of existing models in the domain of CM are presented. The developed data model is presented with an application evaluation.

ABSTRACT. Global warming is considered the most important cumulative environmental impact of contemporary times. One of the strategies to reduce greenhouse gas emissions is the decarbonization of anthropogenic activities. One of the routes marked for this purpose is to decarbonize the energy sector, specifically the generation of electricity. Biomass is one of the renewable sources that, in addition to contributing to this purpose, allows stabilizing the electricity distribution network, given its firm power characteristics.

ABSTRACT. This paper presents an analysis of energy savings in typical university campus buildings due to Daylight Saving Time (DST) in Mexico. The electricity demand load profiles are analyzed in five facilities of the National Autonomous University of Mexico (UNAM) central campus. Each facility presents different demand characteristics according to its usage. Demand data have been obtained through electrical measurements using Survalent ONE SCADA system®. The last week winter period demand profile compared to the first week summer period demand profile are shown and analyzed. Results have shown DST effects on energy consumption in university facilities. With these results, it is also possible to develop decision-making programs to drive energy efficient plans in university campus. In addition, this information can be used to promote efficient and clean energy micro grids. Including ocean energy generation for isolated communities

ABSTRACT. In order to measure lightning flashes, different measuring systems have been developed and validated in the last 50 years. Between them, indirect measuring systems, based on the use of parallel-plate antennas to measure the electric field radiated by the electrical discharges, are one of the most common methods due to their simplicity and their low cost. This paper analyzes the influence of the shape and the physical dimensions of the parallel-plate antenna used for the indirect measurement of cloud-to-cloud and cloud-to-ground lightning flashes. The tests were carried out using simulations where the geometric shape of the antenna, the characteristics of the neighboring structures (including the electric permittivity and the electric conductivity) and the behavior of different materials (present in the electromagnetic environment) were examined. In addition, the correction factors that must be included for a complete characterization of the electric field measuring system were obtained.

ABSTRACT. In the energy sector, it is projected that by 2022, the generation of renewable energy in the energy matrix will show an 80% share of renewable energy sources and 20% fossil energy. On the other hand, the consumption of electricity, as of December 2010, the residential sector occupied the first place, registering 42.6%, followed by the commercial sector with 29.1% and finally the industrial sector (large and medium) with 28.3%. %. At the level of the important cities of Honduras, the Central District and San Pedro Sula consume 44% of the total energy of the country, corresponding 23% and 21% respectively [1]. In the General Electric Industry Law approved and published in La Gaceta on Tuesday, May 20, 2014, in Article # 15, subsection D, it is declared that energy distribution companies will be obligated to purchase the excess energy from sources of renewable energy generated by residential users. The largest consumer of electricity is the one that corresponds to the residential sector, with legislation stating that the electricity distributors must pay for the excess energy generated by the residences. This study determines that in San Pedro Sula the residence owners can install a photovoltaic energy system for their self-consumption interconnected to the network. With the objective of developing photovoltaic solar energy installations for self-consumption for residences in San Pedro Sula, to increase the availability of energy in the market, we analyze the investment and effect of this installations in the Honduras energy matrix. The investment in this green project requires $ 9,200, which can initially generate a minimum saving of $ 1,300 in the first year and then could increase per year according to the average inflation rate of 7%. The recovery of the investment is 10 years, an interest rate of 12%. It is important to mention that the useful lifetime of a photovoltaic generator is of approximately 25 years.

ABSTRACT. The development of proper condition monitoring routines is essential for the secure and reliable operation of industrial induction motors, either low or medium voltage motors. In an induction motor, is possible to develop a series of testing to evaluate the condition of its insulation system. The insulation system of an induction motor is subjected to various stresses, which degrades their characteristics day. Therefore, monitoring their condition is key to guide decision making by those in charge of their operation. In this work, a new methodology for evaluate the condition of the insulation system of induction motors based in a health index is proposed. This proposal uses a health index based on a classic method of construction, combining expert criteria with a validation using real data of motors repaired. Several study cases are required to adjust the parameters used to calculate the health index. Once the parameters of the health index are adjusted, the operating condition of several induction motors are established to test the effectiveness of the proposed tool. The results show a good performance evaluating induction motors repaired in an electric motor workshop that participated in this work. This also indicates that moving towards the use of a health index for evaluate induction motors might enhance the behavior (reliability) of an industrial plant (as a whole).

ABSTRACT. Microalgae are microorganism used for the industrial production of high value compounds. These can be cultivated in closed systems called photobioreactors. In PBR is possible to control the conditions of the crop, with the purpose of increasing the production of biomass or metabolites. The relation between the conditions of growth with the light intensity is essential for the increase of biomass. This paper describes the application of a Proportional-Integral and Derivative controller to control the light intensity within the broth in a batch culture of the Acutodesmus obliquus (Scenedesmus obliquus UTEX 393). The performance of the PID controller was tested with laboratory-level experiments using violet light. In the experiments, conventional lighting operation was compared with constant lighting inside the broth. The experiments showed that PID controller ensures excellent reference tracking capability. Additionally, the experimental results showed an increase in the percentage of lipid production compared to cultures where the intensity of light was not constant (conventional lighting).

ABSTRACT. This research presents the design of a solar tracker in order to make better use of solar energy that radiates in the skies of the province of Huancayo, a comprehensive biography with key contents and concepts was reviewed to make a good design Conceptually, a structure will be designed that adapts to the design of conventional photovoltaic systems. Everything is born from the need to take advantage of an inexhaustible resource, which is photovoltaic solar energy, a study in this field is proposed proposing the problems to be solved, and objectives such as analyzing the manufacturing costs of design, See the economic, technical and operational feasibility of the solar tracker, but above all you want to calculate the energy efficiency that can be gained by designing this type of mechanism and control system and compare with similar mechanisms existing in the market. For the development of the system, the German methodology VDI 2221 was used, which starts from a list of requirements and desires that the design must meet, and a function diagram of the previous concept is also made. To determine the most optimal solution, a morphological matrix is performed where all the solution alternatives are evaluated for each function and in the end a general solution concept is obtained and from this begins the economic, technical and operational evaluation of the solution.

ABSTRACT. This paper presents an economic feasibility study for the repowering of the La Venta I and La Venta II wind farms. First, an analysis of the wind resource of the site is presented, the monthly wind profile, wind rose and the wind distribution are presented, after the turbulence class and wind class according to the IEC 61400 standard is determined, then it is chosen a wind turbine suitable for the site. In section two, the wind turbines are distributed in the site according to the IEC-61400 standard, later, the annual energy production (PAE) is determined, after a comparison of the PAE is made before and after the repowering, then the PAE is estimated including losses for the new wind farms. In section three, the design of the electrical infrastructure is performed, first the selection of cables and transformers is made, then the energy losses produced by the cables are calculated and finally in section four an economic study is presented where the most important parameters to evaluate the economic viability of a wind farm.

ABSTRACT. This article describes the main challenges involved for designing and planning of an offshore wind farm in Mexico. First, a brief description of the site is made and analysis of the wind resource is made in a maritime location located in the municipality of Magallanes, Tabasco, which has high wind potential. Subsequently, based on the characterization of the wind data, the type and class of the wind turbine is determined based on the characterization of the wind data. Then, the optimal distribution of the wind turbines is determined and the annual energy production and the losses caused by the wake effect are estimated. Also, the main components of the off-shore wind farm infrastructure are described and a parametric study is carried out to estimate the Joule losses of submarine cables. Finally, an economic viability study of the off-shore wind farm is made and a comparison is made with an on-shore wind farm.

ABSTRACT. In the Laboral ambit there are numerous jobs that involve the performance of tasks in cold environments, such as storage in cold rooms. Knowing that temperature is an aspect that alters the heart rate, working in these conditions can generate risk factors that favor the appearance of pathologies, disorders and aggravate chronic diseases, such as cardiac, respiratory and rheumatic. In this project, we carry out a series of analytical stages that evaluate the cardiac activity of workers exposed continuously to very low temperatures. Through this reasoning, we provide information involved in the accurate interpretation of the electrical activity of the heart to detect abnormalities and determine risk factors that increase the chances of suffering physical or mental ills. As a result, we present the data obtained from 10 workers in 10 weeks, when performing the analysis, compare the graphs and data exposed by each one and determine the presence of anomalous signals. All this for the correct management, knowledge and evaluation, in order to avoid that the cold is another work risk faced by many workers.

ABSTRACT. We created an online platform to record clinical and genetic information of patients with epilepsy. The platform is helping a stablished community of neurologists to integrate their findings and to share information across borders. The application is designed in such way that it will allow scalability and maintainability in the future.

ABSTRACT. Electroencephalography (EEG) is a low-cost technique for registering rhythmic brain oscillations. Electroencephalographic studies of meditative states have been conducted for nearly 50 years, but no clear consensus has emerged about the neurophysiological changes underlying the practice of meditation. EEG 8-channel registration was performed on expert and novice meditators. A spectral analysis of the signals and a spectral entropy analysis was performed. Relevant neurophysiological differences were found between expert and novice meditators in the Alpha and Theta frequency bands and the entropy levels in each signal, that allow objective evaluation of the progression of meditation. These changes are especially noticeable in the prefrontal cortex. Changes in the states of the Alpha and Theta frequency bands may be associated with increased experience in meditation practice. Spectral entropy can serve as an indicator of long-term therapy progression.

ABSTRACT. Retinoblastoma is a malignant cancerous tumor that arises in the retina. This type of intraocular cancer occurs in 94.1% in children under five years of age and with an incidence of 1 in every 16,000-18,000 births. Given this problematic situation, the present research proposes the development of a system for the detection of retinoblastoma. This system is composed of an app and an algorithm of image processing. The idea is to identify the presence of leukocoria in the iris. Leukocoria is shown as a white pupil in flash photos. The system of the early detection of retinoblastoma was designed and implemented, afterward was tested with a control group (20) and a case group (15). The total sample (35) was composed of members between 6 months and 45 years old, where 25.71% are female, and the remaining 74.29% are male. 92% of the total sample indicates the correct functioning of the Retino App mobile application. Besides, the system's algorithm has correctly identified 93.33% of the cases and 95% of the controls.

ABSTRACT. Ubiquity of machine learning is a reality in the current world: machine learning is everywhere. Neurology is no exception. This paper presents an application of machine learning algorithms for the analysis of multi-national epilepsy clinical data. The initial purpose of the analysis was to find patters in the data, however the analysis resulted in the identification of two new epilepsy syndromes: Borderline Absence Syndrome and Childhood Myoclonic Epilepsy with Absence. It was confirmed that decision tree is an appropriate tool to present the results of supervised machine learning, helping the physicians make sense of the model and trace it back to the data.

ABSTRACT. Haptic technology allows producing computer- generated signals that a perceiver experiences through touch. In general, haptic devices can be classified as active and passive. In this paper, we present a performance evaluation of a group of 10 voluntary subjects in a task of shape perception when both active and passive kinesthetic haptic feedback are provided. The results of a series of psychophysical experiments show that active haptics is superior for shape recognition: active haptics enhances the perception of surfaces while passive haptics conveys the sensation of being guided along pathways. In addition, the guidance nature of passive haptics makes the pathway direction easy to recognize. This last observation can be effectively exploited in more challenging tasks such as navigation/mobility assistance.

ABSTRACT. This paper describes a general methodology for calculating the winding distribution in three phase rotating machines. This methodology is used in this paper for analyzing the impact of winding in the power quality and the overall performance of a low-power wind turbine based on a Radial-Flux Permanent Magnet Synchronous Generator. Moreover, it is presented a comparative study among different software technologies for calculating the winding distributions. With the proposed methodology, it is determined the winding distribution of several cases based on different combinations of poles and slots required for designing a 10 kW RF-PMSG’s. Finally, for validation purposes, the cases provided are also analyzed with Finite Element Analysis in order to determine the best winding distribution for applications in low-power and direct-driven wind turbines.

ABSTRACT. Deformed waveforms in the power grid result in the occurrence of many adverse phenomena that may pose a threat to the correct operation of powered devices, measurement systems and automation, and the power system itself. The analysis of electromagnetic transient phenomena carried out in the article showed the danger of significant overvoltages posing a threat to the primary and secondary equipment.

ABSTRACT. Microgrid represents a new paradigm in the power sector that offers more reliability and flexibility for electricity delivery. A microgrid consists of different types of power generation units, loads and energy storage systems that are controlled and coordinated. Smart power processing units play an important role in a microgrid. The present paper presents an application-specific instruction set processor for the study of power converters operating in isolated microgrids. The proposed processor has been developed in order to solve differential algebraic equations that describe the dynamical behavior of microgrid power processor.

ABSTRACT. Distribution transformers set represent a significant percentage of the assets of the electric power supply system; its monitoring, forecasting and study allow the system administrator to guarantee parameters of reliability, safety and continuity in its operation. The risk assessment of an asset considers two parameters: probability of failure and the consequences of equipment unavailability, the risk index is a widely used tool for locating investments in maintenance and repowering. This paper proposes a methodology to evaluate the consequence factor of the final unavailability of the distribution transformers considering technical characteristics, location in the network, calendar age, number of customers served and their chargeability. This information is processed through a statistical analysis to later use tools based on expert criteria, fuzzy logic and weighted sums in order to obtain the consequence index of each unit. This methodology was applied to the units to an Ecuadorian distribution company. The results obtained with the tools are consistent and provide information to the administrator about possible actions of maintenance or repowering of critical units

ABSTRACT. The environmental impact of the buildings is poorly monitored or null so that most of the buildings in cities suffer from sick building syndrome. Alternatives to monitor the health of buildings are few, expensive and difficult to deploy. the present work proposes a design of a complete solution not only to monitor the health of the building but also to register parameters that allow to get a LEED certification. The design of a low-cost remote terminal unit called sensor dot is proposed as base of the system, the same concept can used for deploy any kind of sensor or control unit. The communication of the sensor dot is based on a simplified message passing model that can be adapted to any transport network, which could extend the applications beyond the control of buildings. The results obtained from the proposed prototype make it comparable with existing commercial solutions

ABSTRACT. This paper presents the creation of an asynchronous bidirectional communications protocol, for industrial application in automated processes using Programmable Logic Controllers (PLC) from different manufacturers or from a single manufacturer, making it possible to communicate with each other or with a local server, in an efficient way (in data and processes) thus achieving the basis for the remote monitoring and control (via internet) of the entire automated industrial process. The usual master-slave network architectures were replaced by a point-to-point architecture in industrial protocols such as ModBus TCP / IP, thus reducing the number of packets, to send only information on status changes or control. With the aim of achieving an efficient and modern interface, the User - Machine Interface (UMI) is coined to show us the changes in the state of the industrial process. Since the control and monitoring of industrial processes (locally) uses a human-machine interface (HMI), the need to use a new interface is detected to perform efficient communication that can be used for communications with the local server or through a communications system that allows remote monitoring and control. Applying the concepts of web development such as UI (User Interface) and UX (User Experience), it is possible to establish, with a new UMI interface (User - machine interface), communications between Schneider Momentum PLCs, Siemens Simatic S7-300 and the user interface

ABSTRACT. The current energy demand forces researchers to delve deeper into the field of renewable energy, with solar energy being the most widely distributed on the planet, which is why the effectiveness of this method has been one of the most studied areas by researchers. This paper describes and shows the results of implement of system that performs by collecting enviromental and electrical parameters in three solar panels, Our system gave succesful results in San Salvador, El Salvador. Central America. However, due to the different factors that influence the optimization of this method, it is necessary to carry out a more exhaustive study focused on obtaining the highest performance of solar panels, which is why there is a need to design tools that allow data collection precisely and in the shortest possible time, so the prototype proposed seeks to solve this problem.

ABSTRACT. Currently, the creation, development and conservation of urban gardens is increased. What has given way to the development of a great diversity of systems that allow monitoring the resources used in the crops and guarantee a better maintenance and care of them. However, the global climatic changes that have occurred in recent years significantly threaten the production and quality of crops, so it is considered important to study and implement equipment and technologies that allow evaluating and controlling the quality of production. The continuous development of technologies and the accessibility of communication have given way to the creation of systems that use Internet of Things (IoT) that allow the control of urban gardens from a monitoring station or from a mobile device. In this research, it is proposed to design and implement a monitoring and irrigation system using the Internet of Things in an urban garden, which allows monitoring the climatic variables: humidity, temperature and CO2. The results show that the data obtained from manually supervised crops have a growth rate between 10 % and 20 % weekly while the crops that were controlled by the system have a faster growth between 10 % and 40 % weekly.

ABSTRACT. This paper presents the development of an energy model of the ESPOL campus main building, in order to estimate, diagnose, and evaluate the electrical energy consumption and also, to propose energy conservation measures (ECMs). This model used simulation tools, such as OpenStudio and EnergyPlus. The final model provides results as the annual energy performance of the building by end-use, the annual utility bill, and others. These results allowed to model some scenarios of ECMs of the building, mainly, aimed to improve lighting and air-conditioning systems. Finally, the greenhouse gas (GHG) emissions generated by each scenario were calculated and analyzed.

ABSTRACT. This paper presents a low-cost electronic nose (e-nose) device for detecting environmental gases that might be threatening for the human health such as combustible gas, alcohol, methane, carbon monoxide, hydrogen, among others. The prototype consists of a six-sensor array deployed in a compact structure. Sensors were characterized and a data acquisition system was implemented to visualize the sensors behavior. Preliminary experimental results show that the device is functional and that the sensors readings are suitable for a later classification stage.

ABSTRACT. Abstract—This article shows the use of a controller for the damping of inter-area modes using remote measurements provided by Phasor Measurement Units. The supplementary wide area damping controller scheme presented is hierarchical type where conventional local controllers are available, and a centralized control is designed using the particle swarm optimization tool. Finally, it is observed how this scheme can improve the damping for those cases where conventional controllers are not enough.

ABSTRACT. A common operation on strings is to calculate a value of similarity. The longest common subsequence (LCS) is a measure of similarity between two sequences. An extension of LCS measure is the constrained longest common subsequence (CLCS). The CLCS consists of calculating the LCS of two sequences, and it is a supersequence of a constrained sequence. This paper is an experimental evaluation of the most important CLCS algorithms. The implemented algorithms have a similar performance and were tested with different kinds of random strings belonging to the alphabets: generated uniformly at random (4, 10, 20, 32, 48 and 64 characters) and English text (239 characters). This study could help in selecting optimal algorithms for a given problem.

ABSTRACT. Abstract— Medical Staff at the rural medical clinic on the island of El Bluff, Nicaragua currently waste countless hours using a manual, paper-and-pen filing system to store medical and health information about the inhabitants on the island. In addition, using paper to store important records poses many threats such as destruction from unanticipated fires or floods. The hospital’s method of tracing pharmaceutical records is nearly as inefficient, with only one trained technician to hand record each individual pill which is distributed. To eliminate risks and disorganization surrounding the hospital’s current processes, the proposed design offers a multi-faceted solution: a database to more effectively store patient data and keep track of pharmaceutical inventory records and an application allowing the doctors to communicate with the database. Successful implementation of the proposed design should enable the doctors in the hospital to fetch, edit, and store the records of any patient in minimal time via an Android application they access on the tablet system. Using the app, the doctor will be able to fill out forms and other documents previously maintained physically. From a pharmaceutical standpoint, the app will keep track of gains and losses of the hospital’s inventory and record patient prescriptions. By creating one system which improves a large number of the medical center’s problems, including the reduction of mistakes in data recording and analysis, and will help the health center to be as productive as possible.

ABSTRACT. A numerical solver (applicable in GNU Octave and in Matlab) has been presented. The solver has been built in order to solve transient problems of circuit theory that feature fractional and nonlinear circuit elements (i.e. fractional coils and fractional capacitors that can even be nonlinear elements). The problems lead to a general form of fractional differential-algebraic equations. The introduced numerical solver relies on the SubIval numerical method, which is briefly recalled. The options for the solver are given and a simple circuit example containing fractional and nonlinear elements is considered. The problem is solved and the results are presented and analyzed along with the error estimation results.

ABSTRACT. We study the generation and dynamics of asymmetric vortex solitons in nonlocal media described with an additional parameter that models the degree of azimuthal asymmetry. The main properties of vortex solitons are investigated analytically and numerically, in the numerical case we use a recently introduced numerical variational method based on the Rayleigh-Ritz optimization principle, we find that nonlocality and the degree of asymmetry can stabilize the proposed vortex solitons. We corroborate the results reported by using spectral techniques.

ABSTRACT. In this document, some novel theoretical and computational techniques for constrained approximation of data-driven systems, are presented. The motivation for the development of these techniques came from structure-preserving matrix approximation problems that appear in the fields of system identification and model predictive control, for data-driven systems and processes. The research reported in this document is focused on finite-state approximation of data-driven systems.

Some numerical implementations of the aforementioned techniques in the simulation and model predictive control of some generic data-driven systems, that are related to electrical signal transmission models, are outlined.