Method validation of 16 types of structural amino acids using an automated amino acid analyzer

An analytical method for the simultaneous determination of 16 types of structural amino acids in infant formula using an automated amino acid analyzer was validated through tests of precision, accuracy and linearity. The automated analysis of the amino acids was performed on an ion-exchange packed column with a visible detector. The certificated reference material (CRM) 1546 from NIST was used as the test sample to determine the precision and accuracy of the analytical method. The regression analyses revealed good correlations [correlation coefficient (r ²)] that were greater than 0.99. The recovery values of the amino acids were ranged from 87.18 to 118.08%. The limits of detection and limits of quantification were less than 0.059 mg/100 g and less than 0.198 mg/100 g, respectively. The intra- and inter-day precisions were less than 14.62% in the CRM sample.     

Discharge power dependence of structural and electrical properties of Al-doped ZnO conducting film by magnetron sputtering (for PDP)

In order to investigate the possible application of ZnO films as a transparent conducting oxide (TCO) electrode for AC PDP, ZnO:Al films were prepared by DC magnetron sputtering method. The effects of discharge power and doping concentration on the structural and electrical properties of ZnO films were mainly studied experimentally. Five-inch PDP cells using either a ZnO:Al or indium tin oxide (ITO) electrode were also fabricated separately under the same manufacturing conditions. The luminous properties of both the PDP cells were measured and compared with each other.By doping the ZnO target with 2 wt% of Al₂O₃, the film deposited at a discharge power of 40 W resulted in the minimum resistivity of 8.5 × 10⁻⁴ Ω-cm and a transmittance of 91.7%. However, a high doping concentration of 3 wt% of Al₂O₃ and excessive sputtering power over 40 W may induce high defect density and limit the growth of small grains. Although the luminance and luminous efficiency of the cell using ZnO:Al are lower than those of the cell with the ITO electrode by about 10%, these values are sufficient enough to be considered for the normal operation of AC PDP.     

Cluster-Based Stable BSM Dissemination System for Safe Autonomous Platooning

Recently, the importance of vehicle safety supporting system has been highlighted as autonomous driving and platooning has attracted the researchers. To ensure driving safety, each vehicle must broadcast a basic safety message (BSM) every 100 ms. However, stable BSM exchange is difficult because of the changing environment and limited bandwidth of vehicular wireless communication. The increasing number of vehicles on the road increases the competition to access wireless networks for BSM exchange; this increases the packet collision rate. An increased packet collision rate impairs the transmission and reception of BSM information, which can easily cause a traffic accident. We propose a solution, the vehicular safety support system (V3S), which exchanges BSMs reliably even when many vehicles are on the road. The V3S uses a clustering scheme to decrease network traffic by reducing the amount of data exchanged between a vehicle and the roadside unit (RSU). In addition, the V3S reduces the collision rate of wireless network packets by broadcasting the vehicle's BSM in an allocated timeslot using the time division multiple access (TDMA) MAC protocol. The V3S also deals with insufficient bandwidth for dedicated short-range communications (DSRC) by changing DSRC channels according to traffic flow. In evaluating the packet error rate for stable BSM packet delivery, the V3S demonstrates an excellent packet error rate of less than 1%, compared to the 802.11p with its packet error rate of 82%.     

Optimization of microscale vortex generators in a microchannel using advanced response surface method

Mixing based on mass diffusion and advective flow at low Reynolds number is important on design of microscale vortex generators. We studied on the optimization of micromixer for the improvement of mass transport using an advanced response surface method to be closely approximate the real map of mixing performance. We considered four rib geometries simultaneously; rib angle, rib height, rib width, and rib spacing. The optimized microchannel was occurred at a micromixer configuration where θ, d/h, a/d, and b/d were 35.6°, 0.7, 0.127, and 1.10, respectively. The channel length to obtain the mixing uniformity over 95% was 1344 μm.     

Industrial CO2 emissions from energy use in Korea: A structural decomposition analysis

This paper attempts to quantify energy consumption and CO₂ emissions in the industrial sectors of Korea. The sources of the changes in CO₂ emissions for the years 1990–2003 are investigated, in terms of a total of eight factors, through input–output structural decomposition analysis: changes in emission coefficient (caused by shifts in energy intensity and carbon intensity); changes in economic growth; and structural changes (in terms of shifts in domestic final demand, exports, imports of final and intermediate goods, and production technology). The results show that the rate of growth of industrial CO₂ emissions has drastically decreased since the 1998 financial crisis in Korea. The effect on emission reductions due to changes in energy intensity and domestic final demand surged in the second period (1995–2000), while the impact of exports steeply rose in the third period (2000–2003). Of all the individual factors, economic growth accounted for the largest increase in CO₂ emissions. The results of this analysis can be used to infer the potential for emission-reduction in Korea.     

Low temperature milling of the LiNH2 + LiH hydrogen storage system

Ball milling of the LiNH₂ + LiH storage system was performed at 20 °C, −40 °C, and −196 °C, and the resulting powders were analyzed using X-ray diffraction, scanning electron microscopy, nuclear magnetic resonance (NMR), specific surface area analysis, and kinetics cycling measurements. Ball milling at −40 °C showed no appreciable deviations from the 20 °C sample, but the −196 °C powder exhibited a significant increase in the hydrogen desorption kinetics. NMR analysis indicates that a possible explanation for the kinetics increase is the retention of internal defects generated during the milling process that are annealed at the collision site at higher milling temperatures.     

Force modeling and machining characteristics of the intermittent grinding wheels

In the surface grinding operations, the grinding fluid cannot be supplied sufficiently in the cutting zone. Temperature generated in the cutting zone increases rapidly and causes thermal damage such as burning on the surface of a workpiece. To reduce thermal damage, the intermittent grinding wheels, which have an excellent cooling effect, have been applied. This paper describes machining characteristics by using intermittent grinding wheels. The grinding force of the intermittent wheels has been simulated by the SIMULAB, which is a program for simulating dynamic systems. Using the intermittent grinding wheels, the characteristics of grinding force, temperature, surface roughness, and geometric error have been evaluated experimently.     

Grafting of poly(vinyl chloride) and polypropylene with styrene in a supercritical CO2 solvent medium: Synthesis and characterization

Graft copolymerization of styrene onto poly(vinyl chloride) (PVC) and polypropylene (PP) was carried out in a supercritical CO₂ medium using AIBN as a free radical initiator. The supercritical CO₂ medium served as a reaction medium in addition to being a solvent for the styrene monomer and the free radical initiator. The reaction temperature and pressure were kept above the critical points of the solvent‐monomer mixture to form a homogeneous single‐phase medium. The resulting graft copolymers were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR) techniques. The weight percent of grafting was determined using IR absorbance ratio technique. TGA results showed that the thermal stabilily of grafted copolymer of PVC was better than that of PVC, while grafted copolymer of PP had poorer thermal stability than PP. DSC results showed that glass transition temperatures (T_g's) of the grafted copolymers were higher than those of the starting polymers PVC and PP. The presence of polystyrene attached to the backbone polymer was confirmed by ¹H NMR and ¹³C NMR analyses.     

The effect of carrier gas and H(hfac) on MOCVD Cu films using (hfac)Cu(1,5-COD) as a precursor

The deposition characteristics of metalorganic chemical vapor deposition (MOCVD) Cu using (hfac)Cu(1,5-COD)(1,1,1,5,5,5-hexafluro-2,4pentadinato Cu(I) 1,5-cyclooctadiene) as a precursor have been investigated in terms of carrier gas effects and adding H(hfac) to the carrier gas stream. Using hydrogen carrier gas led to a higher MOCVD Cu deposition rate and a lower film resistivity compared to an argon carrier gas system. Improvements in surface roughness of the MOCVD Cu films and a (111) preferred orientation texture were obtained by using hydrogen as a carrier gas. When a ligand such as H(hfac) was added to Ar carrier gas, the deposition rate was significantly enhanced. Moreover, H(hfac) added to both carrier gas streams led, to lower MOCVD Cu film resistivity. However, film adhesion was somewhat weak compared to that observed with the Ar or H₂ carrier gas system, probably due to the larger F content near the interface between the copper and the titanium-nitride film. In conclusion, smooth Cu films with a low resistivity can be obtained by manipulating the deposition conditions, such as carrier gas type and ligand addition. The deposition mechanism of MOCVD Cu is also discussed in the paper.     

Characterization of microgels by Brookfield viscometry with cylindrical,T‐bar,and flags impeller spindles

Neutralized 0.5% microgels of the crosslinked copolymer of methyl vinyl ether and maleic anhydride were characterized by the penetrating ball test and by Brookfield viscometry with the # 7 cylindrical, T‐E, and flag‐impeller spindles. Apparent wall slip between the microgel and the #7 cylindrical spindle is a surface phenomenon that is more pronounced for “hard” microgels than for “soft” microgels and depends strongly on the interaction between the surface of the spindle and the microgel. Apparent wall slip can be enhanced by coating the #7 spindle with hydrophobic polymers and polymers with carboxyl groups and suppressed by coating the spindle with vinylpyrrolidone‐based polymers. Similar apparent wall slip was also noticed for the cross‐linked polyacrylic acid microgel. Apparent wall slip was not noticed when the T‐E spindle and the flag‐impeller spindle were used in viscosity measurement. The viscosity of microgels measured with a #7 spindle coated with polyvinylpyrrolidone, a T‐E spindle, and a flag‐impeller spindle correlate well with each other, indicating that the apparent wall slip is suppressed equally well by these three spindles. A simple penetrating ball test was used to differentiate hard microgels from soft microgels. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 67–74, 1999