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Tapia-Hernandez, Alejandro,Ponce-Silva, Mario,Olivares-Peregrino, Victor Hugo,Valdez-Resendiz, Jesus Elias,Hernandez-Gonzalez, Leobardo The Korean Institute of Power Electronics 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.
Alejandro Tapia-Hernandez,Mario Ponce-Silva,Victor Hugo Olivares-Peregrino,Jesus Elias Valdez-Resendiz,Leobardo Hernandez-Gonzalez 전력전자학회 2017 JOURNAL OF POWER ELECTRONICS Vol.17 No.4
The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.
Effects of Ammonium and Calcium on Lisianthus Growth
Armando Hernandez-Perez,Luis A. Valdez-Aguilar,Oscar G. Villegas-Torres,Iran Alia-Tejacal,Libia I. Trejo-Tellez,Manuel de J. Sainz-Aispuro 한국원예학회 2016 Horticulture, Environment, and Biotechnology Vol.57 No.2
The objective of the present study was to determine the influence of ammonium (NH4+) (0% and 50% of total nitrogen, N) in combination with calcium (Ca) on the growth of lisianthus (Eustoma grandiflorum) in perlite cultures. Ammonium significantly improved leaf area, stem diameter, flower buds, and chlorophyll content (SPAD index) while increasing levels of Ca resulted in decreased leaf area, and chlorophyll contents. Application of NH4+ increased dry weight (DW) of stems, leaves and flowers with a reduction in root DW. In contrast, increased Ca caused a decrease in DW of all plant parts, except flowers. Decreased photosynthesis in NH4+-fed plants was associated with a decrease in magnesium (Mg) and potassium (K) uptake, and an increase in phosphorus (P) and sulfur (S) uptake. The potentially deleterious effect of this nutrient imbalance was counteracted by allocating more K and Mg to the shoot and flowers. The ability of lisianthus to shift the allocation of nutrients to sensitive plant parts may explain the tolerance of this species to high NH4+. Ammonium was associated with decreased peroxidase and catalase activities, suggesting that plants were under oxidative stress. Plants typically respond to high NH4+ nutrition by decreasing the uptake of Ca; however, in our study, increasing Ca and NH4+ resulted in increased Ca uptake, reaching toxic concentrations in shoot tissues.
Screening of Industrial Enzymes for Deproteinization of Shrimp Head for Chitin Recovery
Angel U. Valdez-Peña,Adriana Hernandez-Rivera,Iliana M. De-la-Garza-Rodriguez,Judith D. Espinoza-Perez,Georgina C. Sandoval-Fabian,Nagamani Balagurusamy,Juan Carlos Contreras-Esquivel 한국식품과학회 2010 Food Science and Biotechnology Vol.19 No.2
Food grade proteolytic enzymes were examined for deproteinization of shrimp head. Shrimp head was easily deproteinized by Alcalase® and trypsin at a pH of 8.0. Alcalase was chosen as the most efficient commercial enzyme for deproteinization of shrimp head. Alcalase treatment of shrimp head recorded 61% of weight loss on dry basis and a residual protein of 275 mg/g dried shrimp head. The enzymatically deproteinized shrimp head was later demineralized with lactic acid using microwave radiation at 400W. The combination of enzymatic and physicochemical treatments promoted the chitin recovery from dried shrimp head under eco-friendly conditions.
Taxonomic Reassessment of the Genus Padina (Dictyotales, Phaeophyta) from the Gulf of California
Riosmena-Rodriguez, Rafael,Paul-Chavez, Litzia,Hernandez-Carmona, Gustavo,Lopez-Vivas, Juan Manuel,Casas-Valdez, Margarita The Korean Society of Phycology 2009 ALGAE Vol.24 No.4
A monographic reassessment of Padina Adanson species from the Gulf of California was developed based on an exhaustive review of the character and characters states that have been used to delimit species in recent and historically valuable collections. Eight names (P. caulescens Thivy in Taylor, P. concrescens Thivy in Taylor, P. crispata Thivy in Taylor, P. durvillaei Bory Saint-Vincent, P. gymnospora [Kutzing] Sonder, P. mexicana Dawson, P. tetrastromatica Hauck and P. vickersiae Hoyt in Howe) were reported from the region. An analysis of 1,200 specimens led to the conclusion that only three species (P. durvillaei, P. concrescens and P. mexicana) can be recognized for the area based on four discriminating characters: presence of calcium carbonate in the cell wall; number of medullary cell layers in the basal area; number of medullary cell layers in the middle part and presence/absence of cortical cells. Comparative analysis of the species in the Gulf of California in relation to other recently evaluated species has shown a clear distinction among them suggesting Padina species were overestimated in our area.
Pappas, Christopher T.,Mayfield, Rachel M.,Henderson, Christine,Jamilpour, Nima,Cover, Cathleen,Hernandez, Zachary,Hutchinson, Kirk R.,Chu, Miensheng,Nam, Ki-Hwan,Valdez, Jose M.,Wong, Pak Kin,Granzie Proceedings of the National Academy of Sciences 2015 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.112 No.44
Jimenez-Regalaso, Enrique Javier,Cadenas-Pliego, Gregorio,Perez-Alvarez, Marissa,Hernandez-Valdez, Yessica The Polymer Society of Korea 2004 Macromolecular Research Vol.12 No.5
Water-soluble polyacrylamides hydrophobically modified with small amounts of N,N-dialkylacrylamides [N,N-dihexylacrylamide (DHAM) and N,N-dioctylacrylamide (DOAM)] have been prepared through free radical solution polymerizations using two hydrophobic initiators derived from 4,4' -azobis(4-cyanopentanoic acid) (ACVA) and long linear chains consisting of 12 and 16 carbon atoms (C12 and C16). This procedure resulted in polyacrylamides containing hydrophobic groups along the chain as well as at the chain ends. We compare the properties of this class of polymers, termed "combined associative polymers", with those of the multisticker (with hydrophobic groups along the polymer chain) and telechelic (with hydrophobic groups at the chain ends) associative polymers. These materials were prepared using DHAM or DOAM and a hydrophobic initiator (ACVA) modified with alkyl chains of two different lengths. Polymers having molecular weights (M$\_$w/) of ca. 175,000 and hydrophobic contents [H] of ca. 0.8 mol% were prepared using 0.07 mol% of initiator relative to the total monomer feed. We investigated the effects that the type, localization, and concentration of the hydrophobic groups have on the viscosities of the associative polymer solutions.
Castellanos-Lopez, S. Lirio,Cruz-Perez, Felipe A.,Rivero-Angeles, Mario E.,Hernandez-Valdez, Genaro The Korea Institute of Information and Commucation 2014 Journal of communications and networks Vol.16 No.2
Due to the unpredictable nature of channel availability, carrying delay-sensitive traffic in cognitive radio networks (CRNs) is very challenging. Spectrum leasing of radio resources has been proposed in the so called coordinated CRNs to improve the quality of service (QoS) experienced by secondary users (SUs). In this paper, the performance of coordinated CRNs under fixed-rate with hard-delay-constraints traffic is analyzed. For the adequate and fair performance comparison, call admission control strategies with fractional channel reservation to prioritize ongoing secondary calls over new ones are considered. Maximum Erlang capacity is obtained by optimizing the number of reserved channels. Numerical results reveal that system performance strongly depends on the value of the mean secondary service time relative to the mean primary service time. Additionally, numerical results show that, in CRNs without spectrum leasing, there exists a critical utilization factor of the primary resources from which it is not longer possible to guarantee the required QoS of SUs and, therefore, services with hard delay constraints cannot be even supported in CRNs. Thus, spectrum leasing can be essential for CRN operators to provide the QoS demanded by fixed-rate applications with hard delay constraints. Finally, the cost per capacity Erlang as function of both the utilization factor of the primary resources and the maximum allowed number of simultaneously rented channels is evaluated.