The core technologies for the foldable display device are a flexible OLED panel, a flexible cover window and a folding hinge. Among them a hinge controls folding motion trajectory of an OLED panel. It is very important for an OLED panel not to apply any additional stress during folding motion. We developed the stress‐free folding (SFF) hinge with a virtual axis structure (VAS). Using SFF hinge we can achieved that the stress on OLED panel during folding is almost same as the free folding stress. As a result, there is no issue on an OLED panel in 200k folding reliability test with SFF hinge. Its torque reduction is less than 20% after 200k folding test.

In order to expand the mobile foldable technology to large size IT device, we have developed a folding hinge having high torque value. It has stress‐free folding characteristics by virtual axis structure and compact dimension by the parallel arrangement of a folding part and a torque part. Therefore, we can make a large size foldable device which is slim and narrow bezel. It has the torque value of 14 kgf·cm on device and free‐stop function. By the enlargement of friction area by the change of CAM concept and the structural optimization we can reduce abrasion of hinge CAM surface, and the torque reduction by 70k folding lifetime test is less than 20% of its initial value. It is very important progress in the foldable technology.

In the past 3 years, there is big progress of the foldable display device, so nowadays it has better durability, usability and appearance. As a result, it takes more attraction of customers in the market. In order to persist and expand this trend, we need to develop a water‐drop shape folding hinge to make device which has better appearance, flat and slim. But it has some technical issues such as more folding stress, space occupation, folding trace and so on. We have reviewed those and find optimized design of a water‐drop shape folding hinge. We have made device mock‐ups and evaluated its performance. It could be taken more attraction of customers in the market.

The aim of this work is to verify the self-quality assurances in medical institutions in Korea through the external audits by the group of experts and have a mutual discussion of the systematic problems. In order to validate the external audits 30 of 80 medical institutions across the nation were picked out considering the regional distribution and the final 25 institutions applied voluntarily to take part in this work. The basic rules were setup that any information of the participants be kept secrete and the measurements be performed with the dosimetry system already verified through intercomparision. The outputs for 2 or more photon beams, the accuracy of gantry rotation and collimator rotation and the poistional accuracy of MLC movement were measured. The findings for the output measurement showed the differences of −0.8%∼4.5%, −0.79%∼3.01%, and −0.7%∼0.07% with respect to that of the verified dosimetry system for the 6MV, 10MV, and 15MV, respectively. For the reference absorbed dose 8 (16%) of 50 photon beams in 25 medical institutions differed 2.0% or greater from the reference value. The coincidences of Field size with x-ray beam and radiation isocenters of Gantry roration and collimator rotation gave the results of within ±2 mm for every institute except 2 institutions. The positional accuracy of MLC movement agreed to within ±1 mm for every institute. For the beam qualities of 6 MV photon beams kQ values showed the distribution within 0.4% between maximum and minimum. For the protocols 21 institutions (84%) used absorbed dose to water based protocol while 4 insitutions (16%) used air kerma based one. 22 institutions employed the SSD technique while 3 institutions did the SAD one. External audit plays an important role in discovering the systematic problems of self-performing Quality Assurances and having in depth discussion for mutual complementation. Training experts of international level as well as national support system are required so that both the group of experts of medical physicists and government laboratory could perform together periodical and constant external audits.