• Environmental Engineering Research
• /
• v.21 no.2
• /
• pp.152-163
• /
• 2016

Present study investigates the potential of cassava peel and rubber tree bark for the removal of Cr (VI) from aqueous solution. Removal efficiency of more than 99% was obtained during the kinetic adsorption experiments with dosage of 3.5 g/L for cassava peel and 8 g/L for rubber tree bark. By comparing popular isotherm models and kinetic models for evaluating the kinetics of mass transfer, it was observed that Redlich-Peterson model and Langmuir model fitted well ($R^2$ > 0.99) resulting in maximum adsorption capacity as 79.37 mg/g and 43.86 mg/g for cassava peel and rubber tree bark respectively. Validation of pseudo-second order model and Elovich model indicated the possibility of chemisorption being the rate limiting step. The multi-linearity in the diffusion model was further addressed using multi-sites models (two-site series interface (TSSI) and two-site parallel interface (TSPI) models). Considering the influence of interface properties on the kinetic nature of sorption, TSSI model resulted in low mass transfer rate (5% for cassava peel and 10% for rubber tree bark) compared to TSPI model. The study highlights the employability of two-site sorption model for simultaneous representation of different stages of kinetic sorption for finding the rate-limiting process, compared to the separate equilibrium and kinetic modeling attempts.

• Environmental Engineering Research
• /
• v.15 no.2
• /
• pp.105-109
• /
• 2010

The European Union (EU) Water Framework Directive (WFD) (2000/60/EC) was transposed into Irish law by Statutory Instrument Nos. 722 of 2003, 413 of 2005 and 218 of 2009, which set out a new strategy and process to protect and enhance Ireland's water resources and water-dependent ecosystems. The Directive requires a novel, holistic, integrated, and iterative process to address Ireland's natural waters based on a series of six-year planning cycles. Key success factors in implementing the Directive include an in-depth and balanced treatment of the ecological, economic, institutional and cultural aspects of river basin management planning. Introducing this visionary discipline for the management of sustainable water resources requires a solemn commitment to a new mindset and an overarching monitoring and management regime which hitherto has never been attempted in Ireland. The WFD must be implemented in conjunction with a myriad of complimentary directives and associated legislation, addressing such key related topics as flood/drought management, biodiversity protection, land use planning, and water/wastewater and diffuse pollution engineering and regulation. The critical steps identified for river basin management planning under the WFD include: 1) characterization and classification of water bodies (i.e., how healthy are Irish waters?), 2) definition of significant water pressures (e.g., agriculture, forestry, septic tanks), 3) enhancement of measures for designated protected areas, 4) establishment of objectives for all surface and ground waters, and 5) integrating these critical steps into a comprehensive and coherent river basin management plan and associated programme of measures. A parallel WFD implementation programme critically depends on an effective environmental management system (EMS) approach with a plan-do-check-act cycle applied to each of the evolving six-year plans. The proactive involvement of stakeholders and the general public is a key element of this EMS approach.

• Journal of Advanced Navigation Technology
• /
• v.16 no.3
• /
• pp.433-439
• /
• 2012

In this paper, we proposed the triplexer using unit-cell of CRLH transmission line which has a bandpass characteristic to reduce adjacent channel interference. The input impedance of triplexer with each channel filter is operated open-circuit at the resonance frequencies of other channels. Such property is due to the combination a series and parallel resonance circuits of CRLH-TL unit-cell. The measured triplexer results are showed a measured insertion loss of each channel, less than 1.5 dB, matching at each port, less than 15dB and isolation between channel, better than 25 dB. Also, to validate the triplexer, a small signal amplifier with triple-band is designed and tested. the measured amplifier results show good agreements with prediction.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.3
• /
• pp.269-275
• /
• 2005

A flux lock-type SFCL consists of two coils which are wound in parallel each other through an iron core, and a HTSC thin film connects in series with coil 2. The operation of the flux-lock type SFCL can be divided into the subtractive polarity winding and the additive polarity winding operations according to the winding directions between coil 1, coil 2. When a fault occurs, the fault current in the HTS thin film exceeds the critical current so that resistance is generated in the HTS film, and thereby the fault current is limited by an instant rise in the impedance of the flux-lock type SFCL. We investigated he variances of initial fault current limiting instant according to the ratio of inductance of coil 1 and coil 2 in the flux-lock type SFCL. It was confirmed from experiments that the initial fault current limiting instant in the subtractive polarity and additive polarity windings were faster as the ratio of coil 2' inductance for coil 1's inductance increased. The 1st peak of fault current in case of the subtractive polarity winding was higher as the ratio of coil 2's inductance for coil 1's inductance increased. On the other hand, in case of the additive polarity winding, the 1st peak of fault current was lower.

• Tunnel and Underground Space
• /
• v.14 no.4
• /
• pp.261-268
• /
• 2004

The main objectives of this study are to investigate the anisotropic characteristics of rocks and to evaluate the relationships between physical properties. A series of experiments were performed in three mutually perpendicular directions for three rock types, which are granite, granitic gneiss and limestone. The relationships of measured physical properties were evaluated. The results of ultrasonic wave velocity measurement show that granite of three rock types gives the largest directional difference, and that the wave velocity in a plane parallel to a transversely isotropic one is dominantly faster than that in a subvertical or vertical plane. It implies that ultrasonic wave velocity for rock could be used as a useful tool for estimating the degree of anisotropy. The ratio of uniaxial compressive strength to Brazilian tensile strength ranges approximately from 13 to 16 for granite. from 8 to 9 for granite gneiss, and from 9 to 18 for limestone. The directional differences for granite and granitic gneiss are very small, and on the other hand, is relatively large for limestone. It is suggested that strength of rock makes quite difference depending on the rock types and loading directions, especially for the anisotropic rocks such as transversely isotropic or orthotropic rocks. The ratio of uniaxial compressive strength to point load strength index ranges from 18 to 20 for granite, from 17 to 19 for granitic gneiss, and from 21 to 24 for limestone. These results show that point load strength index makes also a difference depending on rock types and directions. Therefore. it should be noted that the ratio of uniaxial compressive strength to point load strength index could be applied to all rock types. Uniaxial compressive strength shows relatively good relationship with point load strength index, Schmidt hammer rebound value, and tensile strength. In particulat, point load strength index is shown to be the best comparative relationship. It is indicated that point load test is the most useful tool to estimate an uniaxial compressive strength indirectly.

• Journal of the Korean Wood Science and Technology
• /
• v.34 no.5
• /
• pp.11-18
• /
• 2006

This study was carried out to evaluate the mechano-sorptive deflection of shear creep of drift pin jointed solid wood. Specimens were the solid wood of Pinus densiflora. The joint was composed with steel plate and drift pin, 85mm in length and 10mm in diameter. The creep tests were conducted under the constant loads in an variable environment. Five different shearing loads were applied parallel to the grain of specimens. The shearing loads applied were 170, 340, 510, 680 and 850 kgf. The stress levels were 10, 20, and 30, 40 and 50% of the bearing strength obtained from the tension-type lateral strength test. The creep tests for specimens were carried out for 10300 hours. A few general conclusions could be drawn from this study: The mechano-sorptive deflection (${\delta}$ ms) is defined as ${\delta}\;ms={\delta}\;t-({\delta}\;c+{\delta}\;sh)-{\delta}\;o$, where ${\delta}$ t is the total deflection, ${\delta}$ c is the pure creep, ${\delta}$ sh is shrinkage-swelling behavior, and ${\delta}$ o is the initial deflection. Changes of relative humidity may cause more severe creep deflection than those of constant humidity, especially during the drying process. The mechano-sorptive behaviors of specimens, except the effects of shrinkage and swelling, gradually increased with increasing time. The deflection is increased in desorption process and recovered in adsorption process. The deflections of drift pin jointed solid wood under different loads showed almost same tendency in all specimens. Although the creep deflection tendencies of each series are very similar, the specimens subjected to a large shearing load exhibit large creep deflections in the desorption process than do those to the small shearing load specimens.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.12
• /
• pp.1133-1138
• /
• 2005

In this study, we have prepared, as the pluse power source, a commercially supplied Li-ion battery with a capacity of 700 mAh and AC resistivity of 60 md at 1 kHz and nonaqeous asymmetric hybrid capacitor composed of an activated carbon cathode and MCMB anode, and have examined the electrochemical characteristics of hybrid capacitor and the pulse performances of parallel connected hybrid capacitor/Li-ion battery source. The nonaqueous asymmetric hybrid capacitors constituted with each stack number of pairs composed of the cathode, the porous separator and the anode electrode were housed in Al-laminated film cell. The 10 stacked hybrid capacitor, which was charged and discharged at a constant current at 0.25 $mA/cm^2$ between 3 and 4.3 V, has exhibited the capacitance of 108F and the lowest equivalent series resistance was 32 $m{\Omega}$ at 1 kHz. On the other hand, the enhanced run time of Li-ion battery assisted by the hybrid capacitor was obtained with increasing of current density and pulse width in Pulse mode. The best improvement, $84\;\%$ for hybrid capacitor/Li-ion battery was obtained in the condition of a 7C-rate pulse (100 msec)/0.5C-rate standby/$10\;\%$ duty cycle.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.8
• /
• pp.689-693
• /
• 2009

We investigate the comparison of fault current characteristics between the separates three-phase flux-lock type superconducting fault current limiter(SFCL) and integrated three-phase flux-lock type superconducting fault current limiter(SFCL). The single-phase flux-lock type SFCL consists of two coils. The primary coil is wound in parallel to the secondary coil on an iron core and superconducting elements are connected to secondary coil in series. Superconducting elements are used by the YBCO coated conductor. The separated three-phase flux-lock type SFCL consists of single-phase flux-phase type SFCL in each phase. But the integrated three-phase flux-lock type SFCL consists of three-phase flux-reactors wound on an iron core. Flux-reactor consists of the same turn's ratio between coil 1 and coil 2 for each single phase. To compare the current limiting characteristics of the separated three-phase flux-lock type SFCL and integrated three-phase flux-lock type SFCL, the short circuit experiments are carried out fault condition such as the single line-to-ground fault. The experimental result shows that fault current limiting characteristic of the separated three-phase flux-lock type SFCL was better than integrated three-phase flux-lock type SFCL. And the integrated three-phase flux-lock type SFCL has an effect on sound phase.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.22 no.9
• /
• pp.904-911
• /
• 2011

This paper deals with transmission characteristics of a new dual resonant structure for designing waveguide band-pass filter. The structure which has a pass-band between two adjacent stop-bands in a single body consists of circular ridged aperture and four armed conducting patch. The dual resonant behavior of the structure can be represented by a combination of LC series and parallel resonant circuits. Also these resonant properties can be easily controlled by varying the geometry of the aperture and four armed conducting patch. Actually, the structure is fabricated on the microstrip substrate by use of etching technique so that it is formed an iris type resonator which can be easily put into the transverse plane of the waveguide. We use WR-90 standard waveguide, adapters, and VNA(vector network analyzer) to measure the resonant characteristics of the structure. It is very useful to design and to improve the cutoff skirts characteristics in the waveguide band-pass filter design area.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.8 no.5
• /
• pp.442-449
• /
• 1984

Turbulent jet flow has been studied in many ways; a plane jet, a rectangular jet, an annular jet, a round jet, a wall jet, a parallel jet, a valve jet, a cross jet, a slit jet and etc. In this report, a 45.deg. cross jet flow was tried by using two same dimensioned nozzels(dia..phi.20)which were set up at the exit of the subsonic wind tunnel. Each jet flows to the direction of 22.5.deg. to the axis of downstream of the mixed flow. The centerline of each jet meets at the distance of 217.3mm and their mixing flow could be imagined to develop beyond that distance, so the measurement was effectuated at X/X$_{0}$=1.2-1.5. The section of the mixed flow a elliptic circle which is formed by the 22.5.deg. inclined flows to the X direction. This experimental study aimed at the investigation of the turbulent mixing process of two jets; the mean velocities, the turbulent shear stresses, the correlation coefficients, and the momentum were respectively measured. The mean velocity distribution profiles of the down-stream component measured in the Y direction coincide well with the empirical equation of Gortler and those measured in the Z direction agree with the equation of H. Schlichting. Other mean velocities V over bar and W over bar components were randomly distributed. The higher values with same order of the intensity of turbulence were largely distributed at the central part of the flow. The momentum was decreased up to 70% by the shock losses and the development of intense turbulences, but it kept its value constantly beyond X/d=14. Two-channel hot-wire anemometer systems (model 1050 series), X-type hot-wire made of tungsten (dia. .phi.e.mu.m, long 3mm, model 0252 T5), a computer(model HP 9845B0, and a plotter (model HP 9872C) were used for the experiments and the analyses.s.