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Las Cruces, United States

Nguyen T.-K.T.,Ho Chi Minh City University of Technology | Nguyen N.-V.,Ho Chi Minh City University of Technology | Prasad N.R.R.,NewMexico State University | Prasad N.R.R.,Office of NavalResearch
IEEE Transactions on Power Electronics

The paper presents an analysis on the output current ripple in zero common-mode voltage (ZCMV) PWM control of multilevel inverters. The modulation strategy for common-mode voltage (CMV) elimination in multilevel inverters is based on the 'three zero common-mode vectors' principle. The space vector diagram, which consists of vectors of ZCMV, is fully explored by properly depicting the base voltage vectors and their corresponding active switching vectors. The switching patterns are limited to those of three switching states each of which is symmetrically distributed. Based on the PWM process simplified to that of a two-level inverter with three allowable switching states and the degree of freedom existing in the switching states arrangement, a novel carrier-based pulsewidth-modulated (PWM) method with optimized output current ripple is proposed. Compared to the existing PWM methods which utilize the same kind of switching patterns, the proposed PWM method has reduced considerably the rms current ripple and total harmonic distortion (THD) of the output current in a wide region of the modulation index. The effectiveness of the proposed method is validated by both simulation and experimental results. © 2016 IEEE. Source

Kumar K.,NewMexico State University | Kumar K.,Qualcomm | Borah D.K.,New Mexico State University
IEEE Transactions on Vehicular Technology

A relaying scheme that uses both radio frequency (RF) and free space optical (FSO) links is investigated. In the proposed quantize and encode relaying (QER), a mobile source broadcasts the RF signal using quadrature amplitude modulation (QAM). The relay estimates and quantizes the log-likelihood ratio (LLR) of each received bit in the symbol and transmits the corresponding information to the destination through a high-speed FSO link or through a hybrid FSO/RF link. Relaying of multiple bits through high-speed FSO links improves RF spectrum utilization over systems where both the source and the relay transmit using RF signals. Exploiting the high available unlicensed bandwidth of the FSO links, the relay can even encode the LLRs using a channel code. Multiple encoded bits can then be mapped to FSO or hybrid FSO/RF symbols. The performance of the proposed system is analyzed, and it is shown that optimal symbol mapping can provide improvements of several decibels over conventional FSO transmissions that employ ON and OFF for binary ones and zeros, respectively. The system is found to achieve full diversity in fading FSO and RF channels. © 1967-2012 IEEE. Source

Krishna T.V.T.,Nvidia | Creusere C.D.,NewMexico State University | Voelz D.G.,NewMexico State University
IEEE Transactions on Image Processing

Polarization, a property of light that conveys information about the transverse electric field orientation, complements other attributes of electromagnetic radiation such as intensity and frequency. Using multiple passive polarimetric images, we develop an iterative, model-based approach to estimate the complex index of refraction and apply it to target classification. © 2010 IEEE. Source

Green S.R.,NewMexico State University | Picchioni G.A.,NewMexico State University | Murray L.W.,Kansas State University | Wall M.M.,U.S. Department of Agriculture

Field-grown cut and dried flowers could provide a high-value crop selection for New Mexico. We conducted a 1-year field study to evaluate flower yield and quality characteristics of common globe amaranth (Gomphrena globosa), 'Strawberry Fields' globe amaranth (Gomphrena haageana), cockscomb celosia (Celosia argentea var. cristata 'Chief Mix'), and wheat celosia (Celosia spicata 'Pink Candle'). Within-row spacing of 15 or 20 cm combined with two-row or three-row per bed plantings resulted in field planting densities ranging from 66,670 to 120,010 plants/ha of common globe amaranth and 'Strawberry Fields' globe amaranth, and 100,005 to 200,010 plants/ha of cockscomb and wheat celosia. All but cockscomb celosia produced four harvests that began 22 May and ended 18 Oct., depending on species. Both globe amaranth species had a 5- to 6-month harvest season, two to three midseason to late-season peak harvests, and over 1000 harvested stems totaling 1.4 to 1.8 kg dry weight per 1.5-m2 plot across the season. Both celosia species had a 4.5-month harvest season, one early summer peak harvest, and fewer than 300 harvested stems totaling 0.6 to 0.7 kg dry weight per plot for the year. Seasonally progressive increases in flowering stem length of both globe amaranth species and wheat celosia, and in flowering stem diameter of both globe amaranth species and cockscomb celosia, were observed. Flowering head size of both globe amaranth species and of wheat celosia varied little with harvest season, whereas the head diameter of cockscomb celosia increased with the season. Post- harvest flower retention after mechanical impact was about 2% higher for common globe amaranth than it was for 'Strawberry Fields' globe amaranth, decreased by about 6% from early to later harvests for both celosia species, and was inversely related to the head size of both globe amaranth species and cockscomb celosia. Despite the wide range in planting density, the density effect was largely limited to cockscomb celosia. For that species, three-row planting (high density) increased the total number of spray flower (multiple head) stems, provided longer stems later into the season and wider heads midway into the season, and prolonged the production of spray stems (15-cm spacing only). Results demonstrate that these four species are excellent candidates as new specialty crops in semiarid conditions. Source

Bosland P.W.,NewMexico State University | Coon D.,NewMexico State University | Reeves G.,NewMexico State University

This study established the heat levels for several high-heat chile pepper (Capsicum chinense) varieties (Trinidad Moruga Scorpion, Bhut Jolokia, Trinidad Scorpion, Douglah Trinidad Chocolate, and Trinidad 7-pot Jonah) to determine which variety has the highest average measured heat level and the relatedness of the chile peppers using molecular analysis. In replicated trials with appropriate controls at Las Cruces, NM, results show two 'Trinidad Moruga Scorpion' chile pepper plants reached more than two million Scoville heat units (SHU). This is the first confirmation of chile pepper fruit measuring more than two million SHU. A large range of heat levels was observed among the field plots-further supporting strong environmental effects on chile pepper pungency. 'Trinidad Moruga Scorpion' was significantly hotter than 'Bhut Jolokia', but 'Trinidad 7-pot Jonah', 'Douglah Trinidad Chocolate', and 'Trinidad Scorpion' did not differ significantly from 'Bhut Jolokia'. Molecular analysis with randomly amplified polymorphic DNA (RAPD) markers confirmed that the accessions are genetically unique. 'Trinidad Moruga Scorpion' belongs to the species C. chinense and is not the same chile pepper as 'Bhut Jolokia'. Source

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