ABSTRACT
In bloodstain pattern analysis (BPA), a field of forensic science, there has been active discussion on the estimation of the area of origin of impact spatter. However, there is no established methodology to quantitatively analyze the area of origin of a swing cast-off pattern. To quantitatively analyze the methodology of previous research on estimation of area of origin, a device for generating uniform swing cast-off patterns was produced. Using artificial blood, 10 swing cast-off patterns were generated on porous paper; in each, 10 blood drops were selected for the calculation of the impact angle. Hemospat software was used for individual bloodstain analysis, and an open source code was used for estimation of area of origin. Under the same conditions, an additional 10 swing cast-off patterns were generated, and quantitative analysis was performed using trigonometric functions and an adjustment formula that minimized errors in calculating the impact angle. The adjustment formula was corrected to calculate the impact angle for the bloodstains on the porous surface. As uncertainty decreases, the error increases, and the point at which both uncertainty and error can be minimized is calculated as 75%. The existing formula included the trajectory in the estimated likelihood range in 75% of samples. When the adjustment formula was applied, the accuracy was improved, with the trajectory included in the area with a 90% likelihood.
ABSTRACT
Pores formed during the sintering of a glass/phosphor mixture affect the scattering and path of light within the resulting phosphor-in-glass (PIG) plate. An investigation of the interactions between blue light from an LED chip and pores within a PIG plate is therefore needed to understand the effect of light scattering on the optical properties. To this end, various glass compositions based on SiO2-B2O3-ZnO were prepared so as to better understand the effect of modifiers (i.e., Li2O, Na2O, La2O3, WO3) on the viscosity and pore properties at different sintering temperatures. This study found that PIGs sintered within a given viscosity range exhibit different optical properties depending on their pore size and overall porosity; a higher luminous efficacy observed in the case of intermediate scattering length values was due to an improved interaction between pores and light. This is a significant finding, as ensuring suitable PIG pore characteristics is an important factor in achieving a desired spectrum and high efficacy from white LEDs.
ABSTRACT
The transmittance of phosphor-in-glass (PIG) color converter material was studied as a factor affecting the luminescence properties of light emitting diode packaging; it is closely related to the residual pores of sintered glass. In this study, the correlation between porosity and optical properties of the glass and PIG plates was investigated. The transmittance, luminescence properties, and porosity were measured by UV-visible spectrometer, integrating sphere and scanning electron microscope, respectively. Transmittance of the sintered glass plate and the luminous efficacy of the PIG plate both increase with decreased porosity, while the light scattering coefficient decreases. Luminescence properties such as emission intensity and color coordinates are also influenced by transmittance of the PIG plate.
