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Diego Hernandez-Hernandez,Tam Larkin,Nawawi Chouw 국제구조공학회 2024 Structural Engineering and Mechanics, An Int'l Jou Vol.89 No.4
This research addresses experimentally the relationship between the excitation frequency and both hoop and axial wall stresses in a water storage tank. A low-density polyethylene tank with six different aspect ratios (water level to tank radius) was tested using a shake table. A laminar box with sand represents a soil site to simulate Soil-Structure Interaction (SSI). Sine excitations with eight frequencies that cover the first free vibration frequency of the tank-water system were applied. Additionally, Ricker wavelet excitations of two different dominant frequencies were considered. The maximum stresses are compared with those using a nonlinear elastic spring-mass model. The results reveal that the coincidence between the excitation frequency and the free-vibration frequency of the soil-tank-water system increases the sloshing intensity and the rigid-like body motion of the system, amplifying the stress development considerably. The relationship between the excitation frequency and wall stresses is nonlinear and depends simultaneously on both sloshing and uplift. In most cases, the maximum stresses using the nonlinear elastic spring-mass model agree with those from the experiments.
Edgar Hernandez Sosa,Yulianis Martín Castejón,Alexander Batista Duharte,Deivys Portuondo,Vivian Tamayo,Humberto J. Morris Quevedo,Clara Esther Martínez Manrique 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.9
Trichilia hirta (Family Meliaceae) is a tree traditionally used in the folk medicine of Cuba to treat asthma, cancer, and ulcers. The objective of this study was to determine the phytochemical composition of ethanol extracts obtained from leaves, roots, and stem bark and to evaluate the leukocyte-stimulating effect of T. hirta root extracts on BALB/c mice. The chemical composition of the extracts was determined by phytochemical screening. Saponins, tannins, flavonoids, and coumarins were detected in extracts of T. hirta. The leukocyte-stimulating effect was evaluated by oral application of ethanol extracts (81.8 and 976 mg/kg) in BALB/c mice for 7 days. The application of 976 mg of extract/kg increased the total leukocyte count up to 15–33%; this effect was significant for neutrophil counts compared with control animals (P<.05). In addition, a dose of 82 mg/kg significantly increased total leukocytes at day 4 of the study (P<.05). The results indicated that T. hirta extracts contain phytochemicals reported as immunostimulants. The administration of these extracts to BALB/c mice indicated that ethanol extract could exhibit leukocyte-stimulating properties and makes it a promising alternative for the development of an immunoprotective agent.
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.
Vitamin D and its effects on cardiovascular diseases: a comprehensive review
( Nonanzit Perez-hernandez ),( Gad Aptilon-duque ),( Maria Cristina Nostroza-hernandez ),( Gilberto Vargas-alarcon ),( Jose Manuel Rodriguez-perez ),( Ruben Blachman-braun ) 대한내과학회 2016 The Korean Journal of Internal Medicine Vol.31 No.6
Vitamin D is a molecule that is actively involved in multiple metabolic pathways. It is mostly known for its implications related to calcium metabolism. It has also been determined that it actively participates in the cardiovascular system, influencing blood pressure, coronary artery disease and other vascular diseases, such as heart failure and atrial fibrillation. Furthermore, it has been established that this vitamin is extensively involved in the regulation of both the renin angiotensin aldosterone system and the immune system. In this review, we present the different vitamin D metabolic pathways associated with the cardiovascular pathophysiology, and we include studies in animal and human models, as well as some of the controversies found in the literature. This review also incorporates an overview of the implications in the molecular biology and public health fields.
Analysis of Asymmetric Price Transmission of Regional Potato Markets in Ecuador
Hernandez Cruz Themiz Eduardo,이윤숙 한국농식품정책학회 2023 농업경영정책연구 Vol.50 No.1
This study analyzed spatial price transmission of potato markets in Ecuador. Price transmission is an essential indicator to understand a market system. To evaluate asymmetric price transmission between two spatial markets, the Nonlinear Autoregressive Distributed Lag (NARDL) model was applied in the study. The four major provinces such as Quito, Latacunga, Riobamba and San Gabriel of potato production are selected and spatial market data are collected from the System of Agriculture Pubic Information in Ecuador. The study found that there exist asymmetric price transmissions between Riobamba and Latacunga, and Riobamba and San Gabriel for long and short run. Quito and Latacunga, and Riobamba and Quito showed asymmetric price transmission for long run, but not for short run. The positive and negative effects of the long-run relationship between Riobamba and Quito and between Riobamba and San Gabriel are bigger than between other spatial markets. It is the first study to provide empirical information about regional potato markets.
The buried arch structural system for underground structures
Hernandez-Montes, Enrique,Aschheim, Mark,Gil-Martin, Luisa Maria Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.1
In many cases, underground structures are built using conventional above-grade structural systems to carry gravity load. This paper proposes the use of underground arches, termed "buried arches", to support gravity loads, wherein the horizontal thrust of the arch is equilibrated by soil pressure. Because the horizontal soil pressure increases with depth, the depth of the arch may be reduced as the depth below grade increases. Critical to the success of such an approach is a proper accounting of creep and shrinkage for arches made of reinforced concrete. This paper addresses the influence of equilibrium, creep, and shrinkage as they affect the design of the arch from a theoretical perspective. Several examples illustrate the use of buried arches for the design of underground parking structures.
A Review on the RF Coil Designs and Trends for Ultra High Field Magnetic Resonance Imaging
Hernandez, Daniel,Kim, Kyoung-Nam Korean Society of Magnetic Resonance in Medicine 2020 Investigative Magnetic Resonance Imaging Vol.24 No.3
In this article, we evaluated the performance of radiofrequency (RF) coils in terms of the signal-to-noise ratio (S/N) and homogeneity of magnetic resonance images when used for ultrahigh-frequency (UHF) 7T magnetic resonance imaging (MRI). High-quality MRI can be obtained when these two basic requirements are met. However, because of the dielectric effect, 7T magnetic resonance imaging still produces essentially a non-uniform magnetic flux (|B<sub>1</sub>|) density distribution. In general, heterogeneous and homogeneous RF coils may be designed using electromagnetic (EM) modeling. Heterogeneous coils, which are surface coils, are used in consideration of scalability in the |B<sub>1</sub>| region with a high S/N as multichannel loop coils rather than selecting a single loop. Loop coils are considered state of the art for their simplicity yet effective |B<sub>1</sub>|-field distribution and intensity. In addition, combining multiple loop coils allows phase arrays (PA). PA coils have gained great interest for use in receiving signals because of parallel imaging (PI) techniques, such as sensitivity encoding (SENSE) and generalized autocalibrating partial parallel acquisition (GRAPPA), which drastically reduce the acquisition time. With the introduction of a parallel transmit coil (pTx) system, a form of transceiver loop arrays has also been proposed. In this article, we discussed the applications and proposed designs of loop coils. RF homogeneous coils for volume imaging include Alderman-Grant resonators, birdcage coils, saddle coils, traveling wave coils, transmission line arrays, composite right-/left-handed arrays, and fusion coils. In this article, we also discussed the basic operation, design, and applications of these coils.