Metakaolin-based geopolymers have shown promise as suitable candidates for 14C immobilization and final disposal. It has been shown that the physicochemical properties of metakaolin wasteforms meet, and often far exceeding, the strict compression strength and leaching acceptance criteria of the South Korea radioactive waste disposal site. However, it is not possible to analyze and characterize the internal structure of the geopolymer wasteform by conventional characterization techniques such as microscopy without destruction of the wasteform; an impractical solution for inspecting wasteforms destined for final disposal. Internal inspection is important for ensuring wastes are homogenously mixed throughout the wasteform and that the wasteform itself does not pose any significant defects that may have formed either during formulation and curing or as a result of testing prior to final disposal. X-ray Computed Tomography (XCT) enables Non-Destructive Evaluation (NDE) of objects, such as final wasteforms, allowing for both their internal and external, characterization without destruction. However, for accurate quantification of an objects dimensions the spatial resolution (length and volume measures) must be know to a high degree of precision and accuracy. This often requires extensive knowledge of the equipment being used, its precise set-up, maintenance and calibration, as well as expert operation to yield the best results. A spatial resolution target consists of manufactured defects of uniformed dimensions and geometries which can be measured to a high degree of accuracy. Implementing the use of a spatial resolution target, the dimensions of which are known and certified independently, would allow for rapid dimensional calibration of XCT systems for the purpose of object metrology. However, for a spatial resolution target to be practical it should be made of the same material as the intended specimen, or at least exhibit comparable X-ray attenuation. In this study, attempts have been made to manufacture spatial resolution targets using geopolymer, silica glass, and alumina rods, as well as 3D printed materials with varying degrees of success. The metakaolin was activated by an alkaline activator KOH to from a geopolymer paste that was moulded into a cylinder (Diameter approx. 25 mm). The solidified geopolymer cylinder as well as both the silica glass rod and alumina rod (Diameter approx. 25 mm) we cut to approximately 4 mm ± 0.5 mm height with additional end caps cut measuring 17.5 mm ± 2.5 mm height. All parts were then polished to a high finish and visually inspected for their suitability as spatial resolution targets.

본 논문은 위치기반 게임(LBG, location-based game)에서 플레이어(player)와 주변 사물의 위치를 신속하게 탐색할 수 있는 공간객체 압축기법인 SBR(Shrinking of Bounding Rectangle based on grid)을 제안한다. 이 기법은 공간 객체의 좌표를 압축하여 위치기반 서버가 플레이어들의 변경된 위치나 주변 장애물에 대한 정보를 신속하게 탐색하고 플레이어에게 빠르게 전송할 수 있도록 한다. 제안 기법은 기존 기법의 단점을 극복하기 위해 게임영역을 일정한 크기의 그리드(grid)로 분할한 후 공간 객체의 좌표를 그리드 크기로 축소함으로써 객체 사이의 중첩이 발생되지 않도록 하였다. 제안기법으로 공간 데이터를 압축하여 시뮬레이션 한 결과 노드접근 횟수가 기존의 압축기법보다 단축되었다.

The purpose of the present study was to examine gaze effects on spatial and kinematic characteristics during a pointing task. Subjects were asked to watch and point to an aimed target (2 mm in diameter) displayed on a vertically mounted board. Four gaze conditions were developed as combinations of "seeing-aiming" in terms of the eye movements: Focal-Focal (F-F), Focal-Fixing (F-X), Fixing-Focal (X-F), and Fixing-Fixing (X-X). Both the home target and an aimed target were presented for 1 second and then were disappeared in F-F and X-F. In X-F and X-X, only an aimed target disappeared after 1 second. Subjects were asked to point (with index finger tip) to an aimed target accurately as soon as the aimed target was removed. A significant main effect of gaze was found (p<.01) for normalized movement time. Peripheral retina targets had significantly larger absolute error compared to central retina targets on the x (medio-lateral) and z (superior-inferior) axes (p<.01). A significant undershooting to peripheral retina targets on the x axis was found (p<.01). F-F and X-F had larger peak velocities compared to F-X and X-X (p<.01). F-F and X-F were characterized by more time spent in the deceleration phase compared to F-X and X-X (p<.01). The present study demonstrates that central vision utilizes a form of on-line visual processing to reach to an object, and thus increases spatial accuracy. However, peripheral vision utilizes a relatively off-line visual processing with a dependency on proprioceptive information.

목적: 본 연구의 목적은 조준운동의 개시 후에 목표위치가 변화되는 상황에서 초기 목표지점에 대한 주시점 고정과 변화된 목표지점으로의 주시점 이동이 안구운동패턴과 조준의 정확성에 미치는 영향을 분석함으로써 목표에 대한 주시점 고정의 역할을 연구하는 것이다. 방법: 10명의 오른손잡이 여자 대학생이 피험자로서 실험에 참여하였다. 피험자는 세 가지 과제조건(목표고정, 주시점 고정, 주시점 이동)에서 다섯 지점에 위치한 목표를 향해 무작위로 각각 10회씩 총 150회의 조준운동을 수행하였다. 피험자가 과제를 수행하는 동안 눈과 손의 운동패턴을 측정하였으며, 측정된 자료로부터 조준운동과 안구운동의 정확성과 일관성, 그리고 조준운동과 안구운동의 관계를 계산하였다. 결과: 주시점 고정 조건에서, 손과 주시점의 반경오차는 초기 목표지점과 새로운 목표지점 사이의 거리가 증가함에 따라 증가하였다. 새로운 목표에 대한 단속성안구운동의 잠복기는 주시점 고정 조건보다 주시점 이동 조건에서 더 지연되었다. 반면 목표에 접촉하기 전에 주시점이 고정된 기간은 주시점 이동 조건 보다 주시점 고정 조건에서 더 긴 것으로 나타났다. 목표 고정 조건과 주시점 이동 조건에서는 동작 종료 시점에서의 철필과 주시점 간격이 목표지점 사이의 차이를 보이지 않았으나, 주시점 고정 조건에서는 초기 목표지점과 새로운 목표지점 사이의 거리가 증가할수록 커지는 것으로 나타났다. 결론: 이러한 결과는 조준운동시의 주시점 고정이 사지가 도달해야 할 공간적 좌표를 명시함으로써 손의 운동을 위한 공간적 참조기준으로 작용할 수 있음을 시사한다.