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101.
Bahadir Uyulgan Hakan Cetinel Tevfik Aksoy 《Journal of Mechanical Science and Technology》2011,25(9):2171-2177
In this study, 17Mn4 (P295GH) pressure vessels steel and AISI304 stainless steel were welded with ER309L austenitic consumable.
In experimental part of the study, tensile tests were conducted on welded plates and variation of hardness values along specimen
was measured. J-integral fracture toughness values were investigated for different crack locations. In order to determine
the regions where plastic deformation did not take place due to constraint, uni-axial tensile test was performed on welded
tensile specimen after attaching strain gauges. In numerical part of the study, finite element (FE) analyses were conducted
by fixing 2-D models precracked on different locations by using ANSYS software. In these models, stress triaxiality and plastic
deformation characteristics around crack tip were determined for each crack locations after stress — strain analyses. The
limitation on the extension of plastic deformation at diffusion line causes extra increase in stress triaxiality at crack
tip. 相似文献
102.
Rodrigo del Pozo Didem Okutman Ta Hakan Dulkadirolu Derin Orhon Victorino Diez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2003,78(4):384-391
In this work, the biodegradability of wastewater from a slaughterhouse located in Ke?an, Turkey, was studied under aerobic and anaerobic conditions. A very high total COD content of 7230 mg dm?3 was found, due to an inefficient blood recovery system. Low BOD5/COD ratio, high organic nitrogen and soluble COD contents, were in accordance with a high blood content. A respirometry test for COD fractionation showed a very low readily biodegradable fraction (SS) of 2%, a rapidly hydrolysable fraction (SH) of 51%, a slowly hydrolysable fraction (XS) of 33% and an inert fraction of 6%. Kinetic analysis revealed that hydrolysis rates were much slower than these of domestic sewage. The results underlined the need for an anaerobic stage prior to aerobic treatment. Tests with an anaerobic batch reactor indicated efficient COD degradation, up to around 80% removal. Further anaerobic degradation of the remaining COD was much slower and resulted in the build up of inert COD compounds generated as part of the metabolic activities in the anaerobic reactor. Accordingly, it is suggested that an appropriate combination of anaerobic and aerobic reactors would have to limit anaerobic degradation to around 80% of the tCOD and an effluent concentration above 1000 mg dm?3, for the optimum operation of the following aerobic stage. © 2003 Society of Chemical Industry 相似文献
103.
Hakan Dogan Robert G. Meyer 《Solid-State Circuits, IEEE Journal of》2007,42(3):529-539
Gain control elements are widely used in communication systems both to limit the incident power to the circuitry and to control the amplitude of the transmitted signal. Attenuators are one way of controlling the signal amplitude. The distortion performance of common CMOS attenuator topologies is investigated in this work. CMOS device equations that model the device in different regions of operation and which also model short channel effects are used for calculating distortion performance. Calculated distortion is compared with simulation results and experimental data, and qualitative explanations of the distortion curves as well as the deviation between different sources of data are given. Potential improvements in linearity performance of attenuators via circuit design techniques have also been discussed 相似文献
104.
Hakan Johansson 《Circuits, Systems, and Signal Processing》2006,25(2):175-200
This paper introduces two classes of frequency-response masking
(FRM) linear-phase finite (length) impulse response (FIR)
filters for interpolation and decimation by arbitrary integer
factors M. As they are based on the FRM approach, the proposed
filters are low-complexity (efficient) sharp-transition
linear-phase FIR interpolation and decimation filters. Compared
to previously existing FRM linear-phase FIR filter classes for
interpolation and decimation, the new ones offer lower
complexity and more freedom in selecting the locations of the
passband and stopband edges. Furthermore, the proposed classes
of FRM filters can, as special cases, realize efficient
Mth-band FRM linear-phase FIR interpolation and decimation
filters for all values of M. Previously, only half-band
(M = 2) FRM linear-phase FIR filters have appeared in the
literature. The paper includes design techniques suitable for
the new filters and design examples illustrating their
efficiency. 相似文献
105.
Second law analysis of heat transfer in laminar flow for hexagonal cross‐section duct was analysed analytically. Geometrical effect of hexagonal duct was considered. The variation of total entropy generation was studied along the duct length. As a working fluid water and unused engine oil were used to compare the effect of fluid in the duct. Results were compared with circular cross‐section duct. It is found that the non‐dimensional entropy generation in a hexagonal cross‐section duct can be as high as a factor of four than that for a circular duct. Further, the unused engine oil gives up to about ten times lower non‐dimensional entropy generation values than that of water but needs about ten times more pumping power to heat transfer ratio. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
106.
In this study, an efficient finite element model for predicting the temperature field, volume fraction of phases and the evolution of internal stresses up to the residual stress states during quenching of axisymmetrical steel components is developed and implemented. The temperature distribution is determined by considering heat losses to the quenching medium as well as latent heat due to phase transformations. Phase transformations are modelled by discretizing the cooling cuves in a succession of isothermal steps and using the IT-diagrams. For diffusional transformations both Scheil's additivity method and Johnson-Mehl-Avrami equation are used, while Koistinen-Marburger equation is employed for martensitic transformation. Internal stresses are determined by a small strain elasto-plastic analysis using Prandtl-Reuss constitutive equations. Considering long cylinders, a generalized plane strain condition is assumed. The computational model is verified by several experimental measurements and by comparison with other known numerical results. Case studies are performed with St50, Ck45 and C60 type of solid and hollow steel components. The complete data and result sets provided for the verification examples establish a basis for benchmark problems in this field. 相似文献
107.
108.
Serdar Menekay Rıza Can Tarcan Hakan Kuntman 《Analog Integrated Circuits and Signal Processing》2009,60(3):237-248
In this paper, a method to reduce the second order effects on the circuit performances caused by the small sized MOS transistors
is proposed. A current mode square-root circuit, a squarer/divider circuit and a multiplier/divider circuit are designed using
this method. Proposed circuits have been simulated with SPICE simulator using 0.35 μm CMOS technology parameters. The main
advantages of the proposed circuit are reduced errors of the output current function, a smaller area on the chip, possibility
of controlling the output current with the control voltage, operation at higher frequencies and more efficient power consumption.
As a result, it can be considered as a useful building block for IC designer. 相似文献
109.
The efficiency of ozone treatment for degradation of the mycotoxin patulin in the presence of various metal ions was evaluated in model systems. An initial patulin concentration of 250 μg/L was ozonated and residual ozone concentration was about 0.17±0.01 mg/L at the end of the experiment. Patulin showed a weak resistance to ozone, because up to 98% of this toxin was oxidized in only one minute. Degradation rates in the presence of calcium, aluminum, copper and zinc were almost the same in the absence of these metals. However, degradation of patulin was reduced from 98 to 37% when the concentration of manganese increased from 0 to 3 mg/L. Patulin was almost completely degraded in the absence of iron, while the degradation was only 8.5% in the presence of 0.5 mg/L of iron. These results have revealed that manganese and iron significantly reduce the detoxification of patulin by ozone. Agents such as ethylenediaminetetraacetic acid and sodium polyphosphate effectively chelated iron and increased the degradation rate of patulin. None of the tested agents were able to chelate manganese and to enhance patulin degradation by ozone. 相似文献
110.
Aydın Özsan Hakan Başarır Serdar Yüceel Özkan Cücen 《Bulletin of Engineering Geology and the Environment》2009,68(3):397-408
The paper reports an assessment of the engineering geological characteristics of the rock mass to be encountered between Mecidiye
and Gazino stations on the new extension of the Ankara metro and the determination of appropriate support and excavation methods.
The rock mass quality was estimated using the rock mass rating (RMR), geological strength index (GSI) and rock mass quality
(Q) systems and the tunnel divided into sections. The RMR, Q and NATM systems were used to determine the support and excavation methods in these areas. The deformations and stress concentrations
around each tunnel section were investigated and the interaction of the support systems with the rock mass was analyzed using
finite element software. It is concluded that rock mass classification systems should be used in tandem with numerical tools,
although it is emphasized that the estimation of rock mass properties is not an exact science and both rock properties and
numerical models should be refined based on observations and the results of instrumentation installed during the construction
of a tunnel.
相似文献