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Nedestruktivna procjena koncentracije fotosintetskih pigmenata u li??u hrasta lu?njaka ( <i>Quercus robur</i> L.); Nondestructive estimation of photosynthetic pigment concentrations in pedunculate oak ( <i>Quercus robur</i> L.) leaves;
摘要： U radu je predstavljena nedestruktivna procjena koncentracije fotosintetskih pigmenata (ukupnih klorofila i karotenoida) u li??u hrasta lu?njaka pomo?u prijenosnog opti?kog klorofilmetra CCM-200. Istra?ivanje je provedeno 2015. godine na biljnom materijalu izlo?enom razli?itim tretmanima vla?nosti tla. U kontrolnom tertmanu sadr?aj vlage u tlu odr?avan je iznad poljskog vodnog kapaciteta, dok je u su?nom tretmanu biljkama voda bila uskra?ena 112 dana (1. 4. – 21. 7.). U drugom dijelu vegetacijskog razdoblja (22. 7. – 22. 10.) u oba tretmana vlaga tla odr?avana je iznad poljskog vodnog kapaciteta. Na temelju li??a uzorkovanoga istovremeno u oba tretmana i to sredinom jeseni (27. 10.) izra?ene su kalibracijske jednad?be koje opisuju odnos indeksa relativnog sadr?aja klorofila izmjerenoga pomo?u klorofilmetra i stvarne koncentracije fotosintetskih pigmenata (utvr?ene laboratorijski) pred sam kraj vegetacijskog razdoblja. Jednad?be su konstruirane posebno za kontrolni, a posebno za su?ni tretman. S obzirom na takav dizajn pokusa i vrijeme uzorkovanja, primarni cilj rada bio je ispitati utjecaj dugotrajnog su?nog razdoblja na homogenost parametara kalibracijskih jednad?bi (Y-odsje?aka i nagiba pravaca). Na temelju dobivenih rezultata zaklju?eno je da parametri kalibracijskih jednad?bi nisu bili utjecani su?nim tretmanom. Prema tome, rezultati istra?ivanja ukazuju na to da klorofilmetar CCM-200, uz primjenu odgovarju?ih kalibracijskih jednad?bi, predstavlja pouzdan alat za nedestruktivnu procjenu koncentracije ukupnih klorofila i karotenoida u li??u hrasta lu?njaka, bez obzira na razli?ite re?ime vla?nosti tla kojima je biljni materijal bio izlo?en tijekom vegetacijskog razdoblja. Uz to, u radu je utvr?eno da bi preciznost procjene stvarne koncentracije fotosintetskih pigmenata bilo mogu?e i dodatno pobolj?ati korekcijom klorofilnog indeksa sa specifi?nom lisnom masom.
关键词： specifi?na lisna masa,Klorofilmetar CCM-200,karotenoidi,indeks relativnoga sadr?aja klorofila u li??u,ukupni klorofili
更新于2025-09-23 15:22:29
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Three-Legs Interleaved Boost Power Factor Corrector for High-Power LED Lighting Application
摘要： In this article, a three-leg interleaved boost Power Factor Corrector (IBPFC) converter for energy-efficient LED lighting systems connected to the main grid was discussed. This IBPFC circuit presented features 60 kHz of commutation frequency and up to 3 kW of power rating. The controlled rectifier front-end boost PFC supplied a DC/DC converter to drive power LEDs suitable for street lighting or a lighting system for a stadium, etc. The IBPFC operated in continuous current mode (CCM). The ripple impact of the IBPFC converter was analyzed and a novel methodology of inductance design was presented. In the proposed design approach, the derivative calculation of the current ripple peak compared with the derivative of the input current was used to define a critical inductance value to ensure the CCM condition. Experimental validation was provided on a 3kW prototype.
关键词： IGBT,continuous current mode (CCM),interleaved converters,three-phase boost converter,ripple analysis,high-power LED lighting,power factor correction (PFC)
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 15th Brazilian Power Electronics Conference and 5th IEEE Southern Power Electronics Conference (COBEP/SPEC) - Santos, Brazil (2019.12.1-2019.12.4)] 2019 IEEE 15th Brazilian Power Electronics Conference and 5th IEEE Southern Power Electronics Conference (COBEP/SPEC) - A Resonant-Switched-Capacitor Step-Down DCa??DC Converter in CCM Operation as an LED Driver
摘要： This paper proposes a analysis of a LED driver. The driver consists of a resonant switched capacitor converter designed to operate in CCM and fed from nanogrid. This mode of operation allows the reduction of current peaks and, consequently, reduction of conduction losses. There is ZVS in the turn-off of the switches due to the full charge and discharge of the switched capacitor. Therefore, switching losses are also reduced. The inductor operates at twice the switching frequency, contributing to the reduction of the magnetic elements. In addition, this converter has the advantage of stabilizing the power of the LED by adjusting the switching frequency, without the needing sensors and control circuit, which reduces the cost of the circuit. In order to validate the comparative analysis, a 10W prototype was designed in a laboratory, operating with a switching frequency of approximately 58 KHz, and presenting an overall ef?ciency of 92.8% in nominal conditions.
关键词： CCM,LED Driver,Resonant Switched Capacitor (RSC) Converter,ZVS
更新于2025-09-23 15:19:57
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Single Stage High Brightness LED Driver with Improved Power Quality
摘要： A single switch single stage 24watt power supply is presented to run a light emitting diode (LED) load. In this power supply, the Zeta converter is used to operate in continuous conduction mode (CCM) for maintaining desired output voltage. A proportional integral (PI) controller is also proposed in the feedback to make system stable. The need of proposed controller is justified from stability analysis of the system with the help of small signal average modeling. A simulation model of the proposed LED driver is also carried out in MATLAB/SIMLINK using sim-power toolbox environment for a universal ac input mains. The results confirm a constant current of 0.4amp at output with improved power quality parameters such as total harmonic distortion (THD) and power factor (PF). All outcomes lie under the limit of IEC 61000-3-2 standards that verifies the theoretical analysis.
关键词： Small Signal Average (SSA) Modeling,Continuous Conduction Mode (CCM),THD,LED Driver,Power Factor (PF),Stability,Zeta dc-dc Converter
更新于2025-09-11 14:15:04