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Precise Detection and Elimination of Grid Injected DC from Single Phase Inverters
Ashraf Abdel hafeez Ahmed Mahm,Ran Li 한국정밀공학회 2012 International Journal of Precision Engineering and Vol. No.
Single-phase voltage source inverters are used for connecting small scale renewable energy sources to low voltage distribution networks. They operate to supply the network with sinusoidal current. If output transformers are not used, these inverters must prevent excessive dc current injection, which may cause detrimental effects in the network. In this study, the causes of dc current injection in a common inverter topology are analyzed. This work explains the design and test of a passive filter circuit precisely measuring the dc component in the inverter output current. The filtered dc signal is then used to control the single phase inverter for the objective to keep the dc injection low – below the standard limit. Characteristics of the proposed method are illustrated using simulation and experimental results.
Tuning New Fuzzy Control for Nonlinear Second Order System
Babak Ranjbar,Gholam Dashti,Ali Omidvar,Javad Mahmoodi,Hasan Karbasi 보안공학연구지원센터 2014 International Journal of Hybrid Information Techno Vol.7 No.6
Cognitive method is used in this research to create portfilo of movement robot manipulator. Gradient descent (GD) fuzzy controller was used and robot’s postures and trajectory were expected in MATLAB/SIMULINK environment. Fuzzy logic controller (FLC) is an influential nonlinear controller to certain and uncertain systems which it is based on artificial intelligent and computes the required torques using the nonlinear feedback control law. Practically a large amount of systems have uncertainties accordingly this method has a challenge. Linear proportional-integral-derivative (PID) controller is a significant combination nonlinear stable-robust controller under condition of partly uncertain dynamic parameters of system. This technique is used to control of highly nonlinear systems especially in nonlinear time varient nonlinear dynamic system. To compensate for the dependence on model-free parameters, PID methodology is used. The nonlinear model dynamic formulation problem in uncertain system can be solved by using PID theorem. Proportional-Derivative-Integral (PID) theory is used to estimate the system dynamic.
IMPROVING ICE FORMATION BY ADDITIVE FOR COLD ENERGY STORAGE
JIN HU,OSMANN SARI,CYRIL MAHMED 대한설비공학회 2014 International Journal Of Air-Conditioning and Refr Vol.22 No.3
Ice storage is one technique for effective use of thermal energy. Application of bionucleant (a protein from the bacterium Pseudomonas syringae) as a snow inducer in ski field has shown great potential to enhance the quantity of snow and increase freezing temperature. In this study, differential scanning calorimeter (DSC) and lab-built ice formation reactor were employed to study experimentally the heterogeneous ice nucleation under super-cooled conditions at different dissolved bionucleant concentrations. It was found the degree of supercooling is reduced by addition of bionucleant. However, ice nucleation-activity of bionucleant will drop down when bionucleant solution is saturated/supersaturated. In our DSC measured heat release study, when bionucleant acts as ice nucleation agent in aqueous solution, prior to reaching its saturation/supersaturation, there is an increase in latent heat release during freezing/melting as the amount of dissolved bionucleant increases. In another test, the supercooling does not occur in 0.5% bionucleant solution, it began to freeze around 0°C. Our results suggest that, the addition of bionucleant may help induce ice nucleation and increase freezing temperature thereby reduces the energy consumption of ice formation for cold storage.
Aldahmash, Abdullah,Atteya, Muhammad,Elsafadi, Mona,Al-Nbaheen, May,Al-Mubarak, Husain Adel,Vishnubalaji, Radhakrishnan,Al-Roalle, Ali,Al-Harbi, Suzan,Manikandan, Muthurangan,Matthaei, Klaus Ingo,Mahm Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.10
Background: Embryonic stem cells (ESCs) have the potential to form teratomas when implanted into immunodeficient mice, but data in immunocompetent mice are limited. We therefore investigated teratoma formation after implantation of three different mouse ESC (mESC) lines into immunocompetent mice. Materials and Methods: BALB/c mice were injected with three highly germline competent mESCs (129Sv, BALB/c and C57BL/6) subcutaneously or under the kidney capsule. After 4 weeks, mice were euthanized and examined histologically for teratoma development. The incidence, size and composition of teratomas were compared using Pearson Chi-square, t-test for dependent variables, one-way analysis of variance and the nonparametric Kruskal-Wallis analysis of variance and median test. Results: Teratomas developed from all three cell lines. The incidence of formation was significantly higher under the kidney capsule compared to subcutaneous site and occurred in both allogeneic and syngeneic mice. Overall, the size of teratoma was largest with the 129Sv cell line and under the kidney capsule. Diverse embryonic stem cell-derived tissues, belonging to the three embryonic germ layers, were encountered, reflecting the pluripotency of embryonic stem cells. Most commonly represented tissues were nervous tissue, keratinizing stratified squamous epithelium (ectoderm), smooth muscle, striated muscle, cartilage, bone (mesoderm), and glandular tissue in the form of gut- and respiratory-like epithelia (endoderm). Conclusions: ESCs can form teratomas in immunocompetent mice and, therefore, removal of undifferentiated ESC is a pre-requisite for a safe use of ESC in cell-based therapies. In addition the genetic relationship of the origin of the cell lines to the ability to transplant plays a major role.