Junyong Lee

Measurement of spray characteristics using the background-oriented schlieren technique

The background-oriented schlieren (BOS) technique has not yet been used in the visualization of fuel spray in automotive research despite its great promise. To investigate the potential of this technique, the density distribution of a cross section of the spray was obtained by applying a filtered back projection (FBP) to the BOS results. Using the density distribution, the penetration lengths of the liquid and vapor phases of the fuel were measured and compared with the results of Mie scattering and shadowgraph images. The results show that the BOS technique is applicable for measuring the liquid and vapor penetration lengths simultaneously. Furthermore, the analysis of the back-projected density distribution revealed that the BOS technique is capable of visualizing the difference in the transient change in the density distribution due to changes in the injection pressure and the fuel volatility.

Analysis of the STR myelin basic protein locus in Koreans.

Abstract Allele und genotype frequencies and the mutation rate of a short tandem repeat locus, the myelin basic protein (MBP) gene, were studied in 973 unrelated Koreans. The alleles were distributed in two discrete regions, one in a high molecular weight region (A) above 190 bp and the other in a low molecular weight region (B) below 150 bp. In a heterozygote, two alleles were found in each region. In region A 13 alleles were found and in region B 7 alleles. Most alleles showed a difference of 4 bp, but three interalleles were found in region A. Allele frequencies in Koreans differed from those reported for Germans and Portuguese. Sets of alleles, one from each region, were linked and transmitted to the offspring. A total of 36 haplotypes and 148 genotypes was identified. In 763 gametes of 550 families, whose parent-child relationship was confirmed using other serological and DNA systems, all alleles were transmitted in a Mendelian fashion, and no mutations were observed. The polymorphism information content (PIC) in Koreans was calculated as 0.833 for region A and 0.718 for region B. The power of discrimination (PD) was 0.959 for region A and 0.901 for region B. No significant deviation from Hardy-Weinberg equilibrium could be observed for this system.

Magnetostatic Coupling Between two Nanowires of Different Width

The magnetostatic interaction between the two magnetic nanowires was studied by using the longitudinal magneto-optical Kerr effect (MOKE). For this purpose two magnetic nanowires having different widths (400 ㎚, 800 ㎚) were fabricated on an Si substrate with electron beam lithography and the lift-off method. Magnetic hysteresis loops measured by MOKE showed double switching behavior, corresponding to the separated switching fields of each wire. The switching field of the narrow wire was greatly affected by the separation between the two wires. Based on how the switching field changes with decreasing separation, it is concluded that the magnetostatic field of the 800-㎚ wire strongly affects the switching of the 400-㎚ wire when the separation is less than 0.5 ㎛.

Variation of the Switching Field of Composite Nanowires with Different Widths

The switching field of a 300 ㎚ wide nanowire has been controlled by attaching a wide wire to it. The width of the wide wires varies from 700 ㎚ to 2000 ㎚. While the connection of the two wires does not affect the switching field of the wide wires, it strongly affects the 300 ㎚-wire, resulting in a decrease of the switching field of the isolated wire from 175 Oe to 54 Oe when the 2000 ㎚-wire is connected to it. This result clearly shows that the switching field of the nanowire can be engineered by attaching a nucleation pad that has a different magnetic anisotropy.