Linear Precoding with Resource Allocation for MIMO Relay Channels

Monroy, Edwin,Choi, Sunghyun,Jabbari, Bijan IEEE 2013 IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS Vol.12 No.11

<P>This paper considers a half-duplex relay channel with a single source, relay, and destination, where each node has multiple antennas and the relay operates in decode-and-forward (DF) mode. The additional degrees of freedoms introduced by the MIMO channels entail increased complexity in comparison with the single antenna case. We propose a new transmission strategy for the relay channel that is able to take advantage of the MIMO gains while employing practical techniques that help reduce complexity. In the proposed scheme, the source splits its message in two parts and sends them to the destination, one part directly and the other with help from the relay. For such a transmission strategy, we formulate the problem of obtaining the rate-maximizing linear precoding matrices with time, power, and spatial stream allocation and transform the problem into a convex form. We also propose a suboptimal algorithm that provides simplifying expressions to solve the resulting problem with far less computational complexity. The numerical results show that the achievable rate of our scheme is greater than the DF rate in certain scenarios, as well as that of other practical existing strategies. In addition, the rate obtained by the suboptimal method approximates the optimal rate extremely well in all considered scenarios.</P>

Las formas del acoso político del conservadurismo hacia la cuarta transformación en México

Guadalupe Villalobos Monroy,Lim, Sang-Rae 부산외국어대학교 중남미지역원 2020 이베로아메리카 Vol.22 No.2

Effect of Alpha-Lipoic Acid on Clinical and Neurophysiologic Recovery of Carpal Tunnel Syndrome: A Double-Blind, Randomized Clinical Trial

Elisa Alejandra Monroy Guızar,Leonel Garcıa Benavides,Ana Rosa Ambriz Plascencia,Sara Pascoe Gonzalez,Sylvia Elena Totsuka Sutto,Ernesto German Cardona Munoz,Miriam Mendez-del Villar 한국식품영양과학회 2018 Journal of medicinal food Vol.21 No.5

The objective of our study was to examine the effect of alpha-lipoic acid (ALA) on clinical and neurophysiologic outcomes after surgery for idiopathic carpal tunnel syndrome (CTS). We conducted a randomized, double-blind, placebo-controlled clinical trial in 20 adults diagnosed with idiopathic CTS after clinical and neurophysiologic assessment. Eligible participants took 600 mg ALA or placebo per day for 1 month before surgery, and for 2 months afterward. Further clinical and neurophysiologic assessments were undertaken immediately before surgical decompression, and at 12 weeks postoperatively with additional clinical assessments at the 4th and 8th week after surgery. Clinical outcome measures were taken by Boston Questionnaire score, the presence or absence of Tinel’s sign, and Phalen’s test findings. Median nerve conduction studies were also undertaken and interpreted according to Dumitru’s reference values. Nineteen patients completed the study; one member of the placebo group was lost during follow-up. There were significant improvements in clinical and neurophysiologic variables in the ALA treatment group, present even before surgery. Boston Questionnaire scores had improved significantly in both groups. In the ALA group, none of the participants had positive Phalen’s or Tinel’s signs at 12 weeks, and motor and sensory fiber latency and amplitude had significantly improved; in the placebo group, only the sensory distal latency had improved significantly. In conclusion, ALA administered 1 month before open decompression and for 2 months afterward improves the clinical and neurophysiologic outcomes after surgery.

Effects of the Selective Laser Melting Manufacturing Process on the Properties of CoCrMo Single Tracks

Karla P. Monroy,Jordi Delgado,Lídia Sereno,Joaquim Ciurana,Nicolas J. Hendrichs 대한금속·재료학회 2014 METALS AND MATERIALS International Vol.20 No.5

Selective Laser Melting (SLM) is an additive technology that produces solid parts by selectively meltingthin layers of metallic powder. SLM can produce significant differences in the final properties due to themelting-consolidation phenomena of the process, which can be controlled by the appropriate parameters. Therefore, the objective of this study was to create a link between the process conditions and the resultingproperties by experimenting in an own-developed SLM machine using CoCrMo powder as material. The fabricated samples were characterized by density, hardness and microstructural properties. The experimentalresults proved the capability of the SLM technique to build high dense samples. The hardnessresults gave evidence of a superior outcome compared to conventional processes. Finally, it was found thatgrain size was defined by scanning speed. Based on the results, a better understanding of the processingprinciples given by the parameters was achieved and improved fabrication quality was promoted.

A nonlinear controller based on saturation functions with variable parameters to stabilize an AUV

Campos, E.,Monroy, J.,Abundis, H.,Chemori, A.,Creuze, V.,Torres, J. The Society of Naval Architects of Korea 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

This paper deals with a nonlinear controller based on saturation functions with variable parameters for set-point regulation and trajectory tracking control of an Autonomous Underwater Vehicle (AUV). In many cases, saturation functions with constant parameters are used to limit the input signals generated by a classical PD (Proportional-Derivative) controller to avoid damaging the actuators; however this abrupt bounded harms the performance of the controller. We, therefore, propose to replace the conventional saturation function, with constant parameters, by a saturation function with variable parameters to limit the signals of a PD controller, which is the base of the nonlinear PD with gravitational/buoyancy compensation and the nonlinear PD + controllers that we propose in this paper. Consequently, the mathematical model is obtained, considering the featuring operation of the underwater vehicle LIRMIA 2, to do the stability analysis of the closed-loop system with the proposed nonlinear controllers using the Lyapunov arguments. The experimental results show the performance of an AUV (LIRMIA 2) for the depth control problems in the case of set-point regulation and trajectory tracking control.

Hidden Markov model-based heartbeat detector using electrocardiogram and arterial pressure signals

Miguel Altuve,Nelson F. Monroy 대한의용생체공학회 2021 Biomedical Engineering Letters (BMEL) Vol.11 No.3

The automatic detection of a heartbeat is commonly performed by detecting the QRS complex in the electrocardiogram(ECG), however, various noise sources and missing data can jeopardize the reliability of the ECG. Therefore, there is agrowing interest in combining the information from many physiological signals to accurately detect heartbeats. To this end,hidden Markov models (HMMs) are used in this work to jointly exploit the information from ECG, arterial blood pressure(ABP) and pulmonary arterial pressure (PAP) signals in order to conceive a heartbeat detector. After preprocessing the physiologicalsignals, a sliding window is used to extract an observation sequence to be passed through two HMMs (previouslytrained on a training dataset) in order to obtain the log-likelihoods of observation and signals a detection if the diff erenceof log-likelihoods exceeds an adaptive threshold. Several HMM-based heartbeat detectors were conceived to exploit theinformation from the ECG, ABP and PAP signals from the MIT-BIH Arrhythmia, PhysioNet Computing in CardiologyChallenge 2014, and MGH/MF Waveform databases. A grid search methodology was used to optimize the duration of theobservation sequence and a multiplicative factor to form the adaptive threshold. Using the optimal parameters found ona training database through 10-fold cross-validation, sensitivity and positive predictivity above 99% were obtained on theMIT-BIH Arrhythmia and PhysioNet Computing in Cardiology Challenge 2014 databases, while they are above 95% in theMGH/MF waveform database using ECG and ABP signals. Our detector approach showed detection performances comparablewith the literature in the three databases.

All-Optical Data Vortex Node Using an MZI-SOA Switch Array

Hyun-Do Jung,Monroy, I.T.,Koonen, A.M.J.,Tangdiongga, E. IEEE 2007 IEEE photonics technology letters Vol.19 No.21-24

<P>We propose and demonstrate a new structure of a Data Vortex switch node for all-optical routing of wavelength-division-multiplexing (WDM) 10-Gb/s optical packets. The proposed node consists of two Mach-Zehnder interferometers with integrated semiconductor optical amplifier: an optical and gate and a high-speed optical switch. In the experiment, WDM 10-Gb/s data packets are successfully routed with 1-dB power penalty at a bit-error rate of 10<SUP>-9</SUP>.</P>

A nonlinear controller based on saturation functions with variable parameters to stabilize an AUV

E. Campos,J. Monroy,H. Abundis,A. Chemori,V. Creuze,J. Torres 대한조선학회 2019 International Journal of Naval Architecture and Oc Vol.11 No.1

This paper deals with a nonlinear controller based on saturation functions with variable parameters for set-point regulation and trajectory tracking control of an Autonomous Underwater Vehicle (AUV). In many cases, saturation functions with constant parameters are used to limit the input signals generated by a classical PD (Proportional-Derivative) controller to avoid damaging the actuators; however this abrupt bounded harms the performance of the controller. We, therefore, propose to replace the conventional saturation function, with constant parameters, by a saturation function with variable parameters to limit the signals of a PD controller, which is the base of the nonlinear PD with gravitational/ buoyancy compensation and the nonlinear PD þ controllers that we propose in this paper. Consequently, the mathematical model is obtained, considering the featuring operation of the underwater vehicle LIRMIA 2, to do the stability analysis of the closed-loop system with the proposed nonlinear controllers using the Lyapunov arguments. The experimental results show the performance of an AUV (LIRMIA 2) for the depth control problems in the case of set-point regulation and trajectory tracking control.

A Theoretical Conversion of Torque Controllers for Handling a Position Servo-actuated Robot Manipulator Model

Gabriela Zepeda,Rafael Kelly,Carmen Monroy 제어·로봇·시스템학회 2024 International Journal of Control, Automation, and Vol.22 No.4

Traditional robot control theory assumes implicitly that robot manipulators are equipped with ideal torque actuators (i.e., torque-driven robots). However, it is important to note that both industrial robots and economical didactic ones do not typically feature such torque actuators. In contrast, many robotics laboratories engaged in academic and research activities employ robots equipped with position servo actuators, which do not support torque control input commands. This paper aims to bridge the gap between theory and practical implementation of robot control from an automatic control perspective. To achieve this goal, a new method is introduced for converting any torque requesting control system, designed for torque–driven robots, to be directly applied to robots using proportional embedded control with position servo actuators (servo–actuated robots lack direct torque input for control). The method relies on the inverse dynamics approach, considering the comprehensive nonlinear model of a position servo–actuated robot structure. This model encompasses servos dynamics, inheriting both the advantages and disadvantages associated with model–based control algorithms.

Antibiotic resistance and tolerance to simulated gastrointestinal conditions of eight hemolytic Bacillus pumilus isolated from pulque, a traditional Mexican beverage

Raquel González-Vázquez,Lino Mayorga-Reyes,Armando Monroy-López,Luis A. Reyes-Nava,Yadira Rivera-Espinoza,Alejandro Azaola-Espinosa 한국식품과학회 2017 Food Science and Biotechnology Vol.26 No.2

Traditional fermented sap beverages from two provinces of Mexico were studied for the isolation of pathogenic bacteria from these beverages. Eight strains of hemolytic Gram positive bacteria, identified as Bacillus pumilus (B. pumilus), were isolated. They showed different antibiotic resistance profiles and tolerances to the simulated gastrointestinal conditions. All the B. pumilus isolated were resistant to at least one antibiotic tested. Regarding the simulated gastrointestinal conditions, strains S1 and S3 were able to tolerate all the conditions. Hemolytic activity has been associated with a health risk and is often considered as a virulence determinant associated with pathogenicity. Therefore, the hemolytic activity along with the ability to tolerate gastrointestinal conditions and the resistance to antibiotics exhibited by B. pumilus strains S1 and S3 could be associated with a health risk for pulque consumers.