On-board and Ground Visual Pose Estimation Techniques for UAV Control

In this paper, two techniques to control UAVs (Unmanned Aerial Vehicles), based on visual information are presented. The first one is based on the detection and tracking of planar structures from an on-board camera, while the second one is based on the detection and 3D reconstruction of the position of the UAV based on an external camera system. Both strategies are tested with a VTOL (Vertical take-off and landing) UAV, and results show good behavior of the visual systems (precision in the estimation and frame rate) when estimating the helicopter¿s position and using the extracted information to control the UAV.

Medidas de la eficacia de los sistemas de intercambio electrónico de datos basados en la especificación ASD 2000M

La Especificación Aeroespacial y de Defensa 2000M, también conocida como S2000M, es un protocolo de intercambio electrónico de datos utilizado en el apoyo logístico de equipos de defensa. La S2000M, resultado de un trabajo conjunto entre Fuerzas Armadas (FFAA) y empresas de Naciones diversas desarrollado durante las últimas cuatro décadas, define tanto los procesos para la adquisición y mantenimiento de componentes militares, como los mensajes normalizados en apoyo de dichos procesos. Equipos de trabajo constituidos por representantes de las citadas FFAA e industria mantienen actualizada la S2000M, por lo que el protocolo evoluciona continuamente con objeto de adaptarse a las necesidades que puedan surgir. Como consecuencia de dicha actualización, existen diversas versiones de la S2000M actualmente en servicio, y este trabajo se basa en la versión denominada 2.1, si bien, una parte importante de las conclusiones del estudio pueden aplicarse a otras versiones del protocolo. A través de los años, la S2000M se ha convertido en un elemento esencial del comercio electrónico de piezas de repuesto y de servicios de mantenimiento y reparación de modernos sistemas aeronáuticos Europeos tales como los aviones de combate Typhoon, Tornado y Rafale, el avion de transporte A400M y los helicópteros NH90 y Tiger, por lo que la S2000M constituye un elemento esencial en el apoyo logístico necesario para asegurar la disponibilidad operativa de dichos sistemas. Así mismo, la S2000M juega un papel fundamental en el comercio electrónico entre las principales empresas aeronáuticas europeas y las organizaciones logísticas de defensa de Naciones tales como Alemania, España, Francia, Holanda, Italia, etc. En consecuencia, la importancia de la S2000M en aspectos tales como logística, nivel de operatividad de los sistemas de armas mencionados, comercio electrónico y sistemas de información es manifiesta, por lo que resulta necesario evaluar la eficacia y eficiencia del protocolo para optimizarlo al máximo. Con este propósito, el presente trabajo estudia la S2000M con objeto de encontrar una respuesta a la pregunta que ha constituido la base de la investigación: ¿Cómo medir el éxito de la Especificación Aeroespacial y de Defensa S2000M? Como la S2000M se utiliza para intercambiar información logística en formato electrónico entre organizaciones y entidades por medio de documentos estructurados y de procesos automatizados, los sistemas de información juegan un papel fundamental en este trabajo. En consecuencia, la base teoríca para tratar de responder a la pregunta anteriormente citada se sustenta en las investigaciones en curso sobre el éxito de los sistemas de información, adaptadas a la problemática específica del protocolo S2000M. Para finalizar, es importante mencionar que debido a que la investigación sobre la S2000M es prácticamente inexistente, este trabajo se centra en un área específica de conocimiento hasta ahora casi inexplorada. El resultado de la investigación se materializa en una serie de propuestas teoricas y prácticas con las que se contribuyen al desarrollo de tres áreas de conocimiento: S2000M, Sistemas de Información e Intercambio Electrónico de Datos. Asimismo, se proponen nuevas áreas de estudio en las tres áreas mencionadas. ABSTRAC The Aerospace and Defence Specification 2000M, in short S2000M, is an Electronic Data Interchange (EDI) standard used in the logistic support of defence equipment. The S2000M is the result of the joint effort undertaken by the Armed Forces and industry of several Nations over the last four decades. The protocol defines the business processes for the supply, maintenance and repair of military components, as well as the standard messages on support of the said processes. Representatives from industry and military keep the S2000M up-to-date and therefore, the protocol evolves continuously to support new requirements that may arise. Consequently, there are different versions of the standard currently available and this study is about one of them, precisely, Revision 2.1; however, many of the research outcomes are also be valid for other versions of the protocol. Through the years, the S2000M has become an essential element for the electronic trade of spare parts and repair services on support of modern European aeronautical systems such as the fighters Typhoon, Tornado and Rafale, the airlifter A400M and the helicopters NH90 and Tiger. As a result, the S2000M is at the center of the logistic support required to ensure the operational availability of these systems. Further, the protocol plays a key role in the electronic exchanges among main European aeronautical players and defence logistics organizations from Nations such as France, Germany, Italy, Netherlands, Spain, etc. Therefore, the significance of the S2000M on the operational availability of the mentioned weapon systems, and in logistics, electronic business and Information Systems (IS) terms is noticeable, and it is then worth evaluating how the S2000M is doing with respect to its effectiveness and efficiency in order to improve these two areas as much as possible. To this end, this work analyzes the S2000M with the aim to find a response to the following research question: How to measure the success of the Aerospace and Defence Specification 2000M? As in the end the S2000M is about the electronic exchange of logistics information among organizations and firms by means of standard messages and processes automation, IS are at the core of this dissertation. For that reason, the theoretical foundation to tackle the research question rests on the ongoing stream of research on IS success, which will be extended to take into consideration the S2000M standpoint as well. Last, it is worth noting that due to the practically inexistent research on the S2000M M, this investigation help filling a gap in this domain. The outcomes from this study materialize in a number of conceptual and practical proposals that contribute to the theory and practice on three main knowledge areas, that is, S2000M, IS and EDI. Further, this work opens the door for further research in the said or related fields.

A Spectral Analysis of LDA Turbulent Flow Measurements in a Ship Air Wake

Helicopters are one of the most important tactical elements in maritime operations. The necessity for an improvement in the conditions in which the landing and take-off operations are carried out leads to the study of the flow that separates from the ship?s superstructure over the flight deck. To investigate this flow a series of wind tunnel experiments have been performed by testing a sub-scale model of a generic frigate. Measurements of the flow?s velocity have been taken by means of Laser Doppler Anemometry (LDA) in five points that simulate the last path of the landing trajectory. The data obtained in these experiments is manipulated in a frequency analysis where the corresponding spectra are calculated. Onboard measurements from an actual full scale frigate are analyzed and compared with the wind tunnel results. Conclusions obtained consist of a series of illustrative values of turbulent energy frequency ranges which can be valuable for any study in this field. The comparison shows a clear similarity between both experiments, reasserting the wind tunnel measurements and its reliability.

Las Redes de Petri Interpretadas en el Diagnóstico de Fallos de Sistemas Híbridos. Aplicación a un Helicóptero no Tripulado

La seguridad y fiabilidad de los procesos industriales son la principal preocupación de los ingenieros encargados de las plantas industriales. Por lo tanto, desde un punto de vista económico, el objetivo principal es reducir el costo del mantenimiento, el tiempo de inactividad y las pérdidas causadas por los fallos. Por otra parte, la seguridad de los operadores, que afecta a los aspectos sociales y económicos, es el factor más relevante a considerar en cualquier sistema Debido a esto, el diagnóstico de fallos se ha convertido en un foco importante de interés para los investigadores de todo el mundo e ingenieros en la industria. Los principales trabajos enfocados en detección de fallos se basan en modelos de los procesos. Existen diferentes técnicas para el modelado de procesos industriales tales como máquinas de estado, árboles de decisión y Redes de Petri (RdP). Por lo tanto, esta tesis se centra en el modelado de procesos utilizando redes de petri interpretadas. Redes de Petri es una herramienta usada en el modelado gráfico y matemático con la habilidad para describir información de los sistemas de una manera concurrente, paralela, asincrona, distribuida y no determinística o estocástica. RdP son también una herramienta de comunicación visual gráfica útil como lo son las cartas de flujo o diagramas de bloques. Adicionalmente, las marcas de las RdP simulan la dinámica y concurrencia de los sistemas. Finalmente, ellas tienen la capacidad de definir ecuaciones de estado específicas, ecuaciones algebraicas y otros modelos que representan el comportamiento común de los sistemas. Entre los diferentes tipos de redes de petri (Interpretadas, Coloreadas, etc.), este trabajo de investigación trata con redes de petri interpretadas principalmente debido a características tales como sincronización, lugares temporizados, aparte de su capacidad para procesamiento de datos. Esta investigación comienza con el proceso para diseñar y construir el modelo y diagnosticador para detectar fallos definitivos, posteriormente, la dinámica temporal fue adicionada para detectar fallos intermitentes. Dos procesos industriales, concretamente un HVAC (Calefacción, Ventilación y Aire Acondicionado) y un Proceso de Envasado de Líquidos fueron usados como banco de pruebas para implementar la herramienta de diagnóstico de fallos (FD) creada. Finalmente, su capacidad de diagnóstico fue ampliada en orden a detectar fallos en sistemas híbridos. Finalmente, un pequeño helicóptero no tripulado fue elegido como ejemplo de sistema donde la seguridad es un desafío, y las técnicas de detección de fallos desarrolladas en esta tesis llevan a ser una herramienta valorada, desde que los accidentes de las aeronaves no tripuladas (UAVs) envuelven un alto costo económico y son la principal razón para introducir restricciones de volar sobre áreas pobladas. Así, este trabajo introduce un proceso sistemático para construir un Diagnosticador de Fallos del sistema mencionado basado en RdR Esta novedosa herramienta es capaz de detectar fallos definitivos e intermitentes. El trabajo realizado es discutido desde un punto de vista teórico y práctico. El procedimiento comienza con la división del sistema en subsistemas para seguido integrar en una RdP diagnosticadora global que es capaz de monitorear el sistema completo y mostrar las variables críticas al operador en orden a determinar la salud del UAV, para de esta manera prevenir accidentes. Un Sistema de Adquisición de Datos (DAQ) ha sido también diseñado para recoger datos durante los vuelos y alimentar la RdP diagnosticadora. Vuelos reales realizados bajo condiciones normales y de fallo han sido requeridos para llevar a cabo la configuración del diagnosticador y verificar su comportamiento. Vale la pena señalar que un alto riesgo fue asumido en la generación de fallos durante los vuelos, a pesar de eso esto permitió recoger datos básicos para desarrollar el diagnóstico de fallos, técnicas de aislamiento, protocolos de mantenimiento, modelos de comportamiento, etc. Finalmente, un resumen de la validación de resultados obtenidos durante las pruebas de vuelo es también incluido. Un extensivo uso de esta herramienta mejorará los protocolos de mantenimiento para UAVs (especialmente helicópteros) y permite establecer recomendaciones en regulaciones. El uso del diagnosticador usando redes de petri es considerado un novedoso enfoque. ABSTRACT Safety and reliability of industrial processes are the main concern of the engineers in charge of industrial plants. Thus, from an economic point of view, the main goal is to reduce the maintenance downtime cost and the losses caused by failures. Moreover, the safety of the operators, which affects to social and economic aspects, is the most relevant factor to consider in any system. Due to this, fault diagnosis has become a relevant focus of interest for worldwide researchers and engineers in the industry. The main works focused on failure detection are based on models of the processes. There are different techniques for modelling industrial processes such as state machines, decision trees and Petri Nets (PN). Thus, this Thesis is focused on modelling processes by using Interpreted Petri Nets. Petri Nets is a tool used in the graphic and mathematical modelling with ability to describe information of the systems in a concurrent, parallel, asynchronous, distributed and not deterministic or stochastic manner. PNs are also useful graphical visual communication tools as flow chart or block diagram. Additionally, the marks of the PN simulate the dynamics and concurrence of the systems. Finally, they are able to define specific state equations, algebraic equations and other models that represent the common behaviour of systems. Among the different types of PN (Interpreted, Coloured, etc.), this research work deals with the interpreted Petri Nets mainly due to features such as synchronization capabilities, timed places, apart from their capability for processing data. This Research begins with the process for designing and building the model and diagnoser to detect permanent faults, subsequently, the temporal dynamic was added for detecting intermittent faults. Two industrial processes, namely HVAC (Heating, Ventilation and Air Condition) and Liquids Packaging Process were used as testbed for implementing the Fault Diagnosis (FD) tool created. Finally, its diagnostic capability was enhanced in order to detect faults in hybrid systems. Finally, a small unmanned helicopter was chosen as example of system where safety is a challenge and fault detection techniques developed in this Thesis turn out to be a valuable tool since UAVs accidents involve high economic cost and are the main reason for setting restrictions to fly over populated areas. Thus, this work introduces a systematic process for building a Fault Diagnoser of the mentioned system based on Petri Nets. This novel tool is able to detect both intermittent and permanent faults. The work carried out is discussed from theoretical and practical point of view. The procedure begins with a division of the system into subsystems for further integration into a global PN diagnoser that is able to monitor the whole system and show critical variables to the operator in order to determine the UAV health, preventing accidents in this manner. A Data Acquisition System (DAQ) has been also designed for collecting data during the flights and feed PN Diagnoser. Real flights carried out under nominal and failure conditions have been required to perform the diagnoser setup and verify its performance. It is worth noting that a high risk was assumed in the generation of faults during the flights, nevertheless this allowed collecting basic data so as to develop fault diagnosis, isolations techniques, maintenance protocols, behaviour models, etc. Finally, a summary of the validation results obtained during real flight tests is also included. An extensive use of this tool will improve preventive maintenance protocols for UAVs (especially helicopters) and allow establishing recommendations in regulations. The use of the diagnoser by using Petri Nets is considered as novel approach.

Systematic Process for Building a Fault Diagnoser Based on Petri Nets Applied to a Helicopter

This work presents a systematic process for building a Fault Diagnoser (FD), based on Petri Nets (PNs) which has been applied to a small helicopter. This novel tool is able to detect both intermittent and permanent faults. The work carried out is discussed from theoretical and practical point of view. The procedure begins with a division of the whole system into subsystems, which are the devices that have to be modeled by using PN, considering both the normal and fault operations. Subsequently, the models are integrated into a global Petri Net diagnoser (PND) that is able to monitor a whole helicopter and show critical variables to the operator in order to determine the UAV health, preventing accidents in this manner. A Data Acquisition System (DAQ) has been designed for collecting data during the flights and feeding PN diagnoser with them. Several real flights (nominal or under failure) have been carried out to perform the diagnoser setup and verify its performance. A summary of the validation results obtained during real flight tests is also included. An extensive use of this tool will improve preventive maintenance protocols for UAVs (especially helicopters) and allow establishing recommendations in regulations

50 Years Ago We Marched: What began on the grounds of Lincoln University, ended on the steps of the Alabama State Capitol

LINCOLN UNIVERSITY - On March 25, 1965, a bus loaded with Lincoln University students and staff arrived in Montgomery, Ala. to join the Selma march for racial and voting equality. Although the Civil Rights Act of 1964 was in force, African-Americans continued to feel the effects of segregation. The 1960s was a decade of social unrest and change. In the Deep South, specifically Alabama, racial segregation was a cultural norm resistant to change. Governor George Wallace never concealed his personal viewpoints and political stance of the white majority, declaring “Segregation now, segregation tomorrow, segregation forever.” The march was aimed at obtaining African-Americans their constitutionally protected right to vote. However, Alabama’s deep-rooted culture of racial bias began to be challenged by a shift in American attitudes towards equality. Both black and whites wanted to end discrimination by using passive resistance, a movement utilized by Dr. Martin Luther King Jr. That passive resistance was often met with violence, sometimes at the hands of law enforcement and local citizens. The Selma to Montgomery march was a result of a protest for voting equality. The Student Nonviolent Coordinating Committee (SNCC) and the Southern Christian Leadership Counsel (SCLC) among other students marched along the streets to bring awareness to the voter registration campaign, which was organized to end discrimination in voting based on race. Violent acts of police officers and others were some of the everyday challenges protesters were facing. Forty-one participants from Lincoln University arrived in Montgomery to take part in the 1965 march for equality. Students from Lincoln University’s Journalism 383 class spent part of their 2015 spring semester researching the historical event. Here are their stories: Peter Kellogg “We’ve been watching the television, reading about it in the newspapers,” said Peter Kellogg during a February 2015 telephone interview. “Everyone knew the civil rights movement was going on, and it was important that we give him (Robert Newton) some assistance … and Newton said we needed to get involve and do something,” Kellogg, a lecturer in the 1960s at Lincoln University, discussed how the bus trip originated. “That’s why the bus happened,” Kellogg said. “Because of what he (Newton) did - that’s why Lincoln students went and participated.” “People were excited and the people along the sidewalk were supportive,” Kellogg said. However, the mood flipped from excited to scared and feeling intimidated. “It seems though every office building there was a guy in a blue uniform with binoculars standing in the crowd with troops and police. And if looks could kill me, we could have all been dead.” He says the hatred and intimidation was intense. Kellogg, being white, was an immediate target among many white people. He didn’t realize how dangerous the event in Alabama was until he and the others in the bus heard about the death of Viola Liuzzo. The married mother of five from Detroit was shot and killed by members of the Ku Klux Klan while shuttling activists to the Montgomery airport. “We found out about her death on the ride back,” Kellogg recalled. “Because it was a loss of life, and it shows the violence … we could have been exposed to that danger!” After returning to LU, Kellogg’s outlook on life took a dramatic turn. Kellogg noted King’s belief that a person should be willing to die for important causes. “The idea is that life is about something larger and more important than your own immediate gratification, and career success or personal achievements,” Kellogg said. “The civil rights movement … it made me, it made my life more significant because it was about something important.” The civil rights movement influenced Kellogg to change his career path and to become a black history lecturer. Until this day, he has no regrets and believes that his choices made him as a better individual. The bus ride to Alabama, he says, began with the actions of just one student. Robert Newton Robert Newton was the initiator, recruiter and leader of the Lincoln University movement to join Dr. Martin Luther King’s march in Selma. “In the 60s much of the civil rights activists came out of college,” said Newton during a recent phone interview. Many of the events that involved segregation compelled college students to fight for equality. “We had selected boycotts of merchants, when blacks were not allowed to try on clothes,” Newton said. “You could buy clothes at department stores, but no blacks could work at the department stores as sales people. If you bought clothes there you couldn’t try them on, you had to buy them first and take them home and try them on.” Newton said the students risked their lives to be a part of history and influence change. He not only recognized the historic event of his fellow Lincolnites, but also recognized other college students and historical black colleges and universities who played a vital role in history. “You had the S.N.C.C organization, in terms of voting rights and other things, including a lot of participation and working off the bureau,” Newton said. Other schools and places such as UNT, Greenville and Howard University and other historically black schools had groups that came out as leaders. Newton believes that much has changed from 50 years ago. “I think we’ve certainly come a long way from what I’ve seen from the standpoint of growing up outside of Birmingham, Alabama,” Newton said. He believes that college campuses today are more organized in their approach to social causes. “The campus appears to be some more integrated amongst students in terms of organizations and friendships.” Barbara Flint Dr. Barbara Flint grew up in the southern part of Arkansas and came to Lincoln University in 1961. She describes her experience at Lincoln as “being at Lincoln when the world was changing.“ She was an active member of Lincoln’s History Club, which focused on current events and issues and influenced her decision to join the Selma march. “The first idea was to raise some money and then we started talking about ‘why can’t we go?’ I very much wanted to be a living witness in history.” Reflecting on the march and journey to Montgomery, Flint describes it as being filled with tension. “We were very conscious of the fact that once we got on the road past Tennessee we didn’t know what was going to happen,” said Flint during a February 2015 phone interview. “Many of the students had not been beyond Missouri, so they didn’t have that sense of what happens in the South. Having lived there you knew the balance as well as what is likely to happen and what is not likely to happen. As my father use to say, ‘you have to know how to stay on that line of balance.’” Upon arriving in Alabama she remembers the feeling of excitement and relief from everyone on the bus. “We were tired and very happy to be there and we were trying to figure out where we were going to join and get into the march,” Flint said. “There were so many people coming in and then we were also trying to stay together; that was one of the things that really stuck out for me, not just for us but the people who were coming in. You didn’t want to lose sight of the people you came with.” Flint says she was keenly aware of her surroundings. For her, it was more than just marching forward. “I can still hear those helicopters now,” Flint recalled. “Every time the helicopters would come over the sound would make people jump and look up - I think that demonstrated the extent of the tenseness that was there at the time because the helicopters kept coming over every few minutes.” She said that the marchers sang “we are not afraid,” but that fear remained with every step. “Just having been there and being a witness and marching you realize that I’m one of those drops that’s going to make up this flood and with this flood things will move,” said Flint. As a student at Lincoln in 1965, Flint says the Selma experience undoubtedly changed her life. “You can’t expect to do exactly what you came to Lincoln to do,” Flint says. “That march - along with all the other marchers and the action that was taking place - directly changed the paths that I and many other people at Lincoln would take.” She says current students and new generations need to reflect on their personal role in society. “Decide what needs to be done and ask yourself ‘how can I best contribute to it?’” Flint said. She notes technology and social media can be used to reach audiences in ways unavailable to her generation in 1965. “So you don’t always have to wait for someone else to step out there and say ‘let’s march,’ you can express your vision and your views and you have the means to do so (so) others can follow you. Jaci Newsom Jaci Newsom came to Lincoln in 1965 from Atlanta. She came to Lincoln to major in sociology and being in Jefferson City was largely different from what she had grown up with. “To be able to come into a restaurant, sit down and be served a nice meal was eye-opening to me,” said Newsom during a recent interview. She eventually became accustomed to the relaxed attitude of Missouri and was shocked by the situation she encountered on an out-of-town trip. “I took a bus trip from Atlanta to Pensacola and I encountered the worse racism that I have ever seen. I was at bus stop, I went in to be served and they would not serve me. There was a policeman sitting there at the table and he told me that privately owned places could select not to serve you.” Newsom describes her experience of marching in Montgomery as being one with a purpose. “We felt as though we achieved something - we felt a sense of unity,” Newsom said. “We were very excited (because) we were going to hear from Martin Luther King. To actually be in the presence of him and the other civil rights workers there was just such enthusiasm and excitement yet there was also some apprehension of what we might encounter.” Many of the marchers showed their inspiration and determination while pressing forward towards the grounds of the Alabama Capitol building. Newsom recalled that the marchers were singing the lyrics “ain’t gonna let nobody turn me around” and “we shall overcome.” “ I started seeing people just like me,” Newsom said. “I don’t recall any of the scowling, the hitting, the things I would see on TV later. I just saw a sea of humanity marching towards the Capitol. I don’t remember what Martin Luther King said but it was always the same message: keep the faith; we’re going to get where we’re going and let us remember what our purpose is.” Newsom offers advice on what individuals can do to make their society a more productive and peaceful place. “We have come a long way and we have ways to change things that we did not have before,” Newsom said. “You need to work in positive ways to change.” Referencing the recent unrest in Ferguson, Mo., she believes that people become destructive as a way to show and vent anger. Her generation, she says, was raised to react in lawful ways – and believe in hope. “We have faith to do things in a way that was lawful and it makes me sad what people do when they feel without hope, and there is hope,” Newsom says. “Non-violence does work - we need to include everyone to make this world a better place.” Newsom graduated from Lincoln in 1969 and describes her experience at Lincoln as, “I grew up and did more growing at Lincoln than I think I did for the rest of my life.”

Military and government applications of human-machine communication by voice.

This paper describes a range of opportunities for military and government applications of human-machine communication by voice, based on visits and contacts with numerous user organizations in the United States. The applications include some that appear to be feasible by careful integration of current state-of-the-art technology and others that will require a varying mix of advances in speech technology and in integration of the technology into applications environments. Applications that are described include (1) speech recognition and synthesis for mobile command and control; (2) speech processing for a portable multifunction soldier's computer; (3) speech- and language-based technology for naval combat team tactical training; (4) speech technology for command and control on a carrier flight deck; (5) control of auxiliary systems, and alert and warning generation, in fighter aircraft and helicopters; and (6) voice check-in, report entry, and communication for law enforcement agents or special forces. A phased approach for transfer of the technology into applications is advocated, where integration of applications systems is pursued in parallel with advanced research to meet future needs.

Status of the CH-53E helicopter program, Department of the Navy : report to the Congress /

Publication date stamped on cover.

Program manual for MAST programs.

Mode of access: Internet.

Helicopterborne operations.

Loose-leaf for updating.

Shore party and helicopter support team operations /

"Supersession, FMFM 4-3, Shore Party and Helicopter Support Team Operations, of 11 August 1967."

The crane helicopter and its capabilities and prospects in Colombia, South America.

Mode of access: Internet.

Summary of studies of helicopter rotor icing.

"Contract No. AF 33(616)-2859."

The problem of vertical flight,

Mode of access: Internet.

The Skylounge system; analysis and design. A technical and economic feasibility study.

[1] Skylounge Project final report.--[2] Skylounge legal, technical, and financial supplementary study.