• Korean Journal of Ecology and Environment
• /
• v.41 no.3
• /
• pp.275-282
• /
• 2008

Water hardness is a significant parameter as related to aquatic toxicity of some heavy metals. Hardness dependent metals include cadmium, copper, chromium (III), nickel, lead, zinc and silver. Developed countries have applied the hardness correction procedure to derive the water quality criteria for protecting the aquatic organisms. In the present study, we investigated the hardness correction algorithms used in United States of America, European Union, Australia/New Zealand, and Canada, and analyzed the details associated with those algorithms. Toxicity values of heavy metals were definitely different after hardness correction for all of algorithms analyzed. We found that the hardness corrected toxicity values followed by the algorithms of USA and Australia/New Zealand were very similar or same, however they were slightly different for cadmium at the hardness less than 30 mg $CaCO_3\;L^{-1}$. Among the hardness correction algorithms studied, the algorithm used in Australia/New Zealand appears to be a good choice to apply in Korean situation due to its simplicity compared to the algorithm of USA.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.12
• /
• pp.98-106
• /
• 2016

Measurements of the elastic modulus and hardness using a nano indentation machine rely on the equation for the fitted contact area, which is valid for only sink-in materials. For most soft engineering materials that involve pile-up behavior rather than sink-in, the contact area equation underestimates the contact area and thus overestimates the elastic modulus and hardness. This study proposes a correction method to amend erroneous hardness measurements in pile-up situations. The method is a supplemental derivation to the original hardness measurement with the known value of the elastic modulus. The method was examined for soft engineering metals, Al 6061 T6 and C 12200, via tensile tests, nano indentation tests, impression observations, and finite element analysis. The proposed technique shows reasonable agreement with the analytical results accounting for strain gradient plasticity from a previous study.

• Journal of Animal Science and Technology
• /
• v.60 no.9
• /
• pp.21.1-21.2
• /
• 2018

• Journal of Biosystems Engineering
• /
• v.33 no.1
• /
• pp.63-68
• /
• 2008

This study was carried out to find a useful method to predict hardness of tomato using optical spectrum data. Optical spectrum of reflectance and transmittance data were collected processed by 9 kind of preprocessing methods-normalizations of mean, maximum and range, SNV (standard normal variate), MSC (multiplicative scatter correction), the first derivative and second derivative of Savitzky-Golay and Norris-Gap. With the preprocessed and non-processed original spectrum data, prediction models of hardness of tomato were developed using analytical tools of PLS (partial least squares) and MLR (multiple linear regression) and tested for their validation. The test of validation resulted that the analytical tools of PLS and MLR output similar performances while the transmittance spectra showed much better result than the reflectance spectra.

• Transactions of Materials Processing
• /
• v.4 no.2
• /
• pp.123-130
• /
• 1995

The present study is concerned with the hydrostatic extrusion process for the copper-clad aluminum rod through metallurgical joining. The rigid viscoplastic finite element analyses are performed for the steady state extrusion process of the bimetal rod. An algorithm for finding the interface profile of the bimetal rod by tracking a particle path in Eulerian domain is presented. The distributions of the effective strain rate, equivalent stress and hardness are examined for the several extrusion ratios. Experiments are also carried out for the copper-clad aluminum rod at room temperature. It is found out that the finite element predictions are generally in good agreement with the experimental observations. The detail comparisons of the extrusion loads predicted by the element method with those by experiments are given.

• Journal of Biosystems Engineering
• /
• v.32 no.4
• /
• pp.207-214
• /
• 2007

Based on the profiles of cone index with depth, physical properties of hardpan in selected rice fields were measured and analyzed in the study. An error correction algorithm removing a random measurement error from raw CI profile data was introduced in the study. The properties of hardpan included the shape, the thickness and the rice root growing layer. The analysis of physical properties of hardpan in the rice fields showed that the type of hardpan could be classified into 6 categories. The thickness of hardpan ranged from 6 cm up to 41 cm and the average hardness of hardpan was analyzed to be from 1.1 MPa through 3.2 MPa in Cone index.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.10
• /
• pp.901-906
• /
• 2016

The purpose of this study is to improve productivity by implementing one-pass full penetration welding using laser-arc hybrid welding for AH36. On increasing the thickness of the plate, a higher power of laser and arc was required to obtain full penetration. However, increasing the power of heat source caused undercut defects at both ends of the bead. This undercut was prevented by controlling the parameters of welding voltage and pulse correction. Hardness measurement and tensile test were conducted to apprehend the mechanical properties of weld. Also, by carrying out the microstructure observation for laser and arc regions, microstructural properties were understood.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.27 no.2
• /
• pp.183-187
• /
• 2005

The coronal approach has been used for over a century by neurosurgeons to access to the anterior cranium. Indications for the coronal approach expanded from use in the correction of congenital skeletal anomalies to applications in acute maxillofacial trauma and secondary deformity correction, oncologic surgery and reconstruction, and esthetic surgery. Complications were such as injury to frontal branch of the facial nerve, motor nerve paralysis, hematoma under flap, trismus, ptosis, epiphora, infection and anterior temporal depression. $Medpor^{(R)}$ is made up of dense polyethylene connected in porous structures. It is easily shapable without collapsing the pores due to it's hardness and tissue growth takes place at the porosities. Based on these advantages, $Medpor^{(R)}$ has been used in augmentation and restoration in craniofacial defect. A temporal depression after the coronal approach for treatment of Le Fort III fracture was successfully reconstruction with $Medpor^{(R)}$ and we report this case with review of literature.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.20 no.4
• /
• pp.111-119
• /
• 2016

Rebound hammer test, SonReb method and concrete core test are most useful testing methods for estimate the concrete compressive strength of deteriorated concrete structures. But the accuracy of the NDE results on the existing structures could be reduced by the effects of the uncertainty of nondestructive test methods, material effects by aging and carbonation, and mechanical damage by drilling of core. In this study, empirical procedure for verifying the in-situ compressive strength of concrete is suggested through the probabilistic analysis on the 268 data of rebound and ultra-pulse velocity and core strengths obtained from 106 bridges. To enhance the accuracy of predicted concrete strength, the coefficients of core strength, and surface hardness caused by ageing or carbonation was adopted. From the results, the proposed equation by KISTEC and the estimation procedures proposed by authors is reliable than previously suggested equation and correction coefficient.

• Korean Journal of Materials Research
• /
• v.32 no.3
• /
• pp.139-145
• /
• 2022

Reheat treatment process of mold is necessary when partial machining of the mold is required, such as shape correction for an existing mold. If defects such as cracks or significant deterioration of mechanical properties of the mold occur during reheat treatment, it is impossible to reuse the mold. In this study, reheat treatment was performed up to two times for STD11 tool steel, and microstructure and mechanical properties according to the reheat treatment were evaluated. Carbide fraction and grain size of prior austenite were almost unchanged after the reheat treatment. Hardness and impact toughness increased significantly after QT treatment, and these properties were maintained without significant change even after the reheat treatment. It is concluded that up to two iterations of reheat treatment does not cause deterioration of properties of STD11 tool steel. Based on these results, a mold for a face-lifted front bumper was manufactured through machining and reheat-treating of an existing mold.