Consumers visiting platforms that host user-generated content (UGC) not only consume content but also generate content by investing time and effort. This paper seeks to examine a UGC platform's content provision strategy: how a UGC platform can motivate consumers to generate UGC and how it can manage the balance between UGC and platform's own content. As UGC and the platform's own content perform the same function, one may be inclined to think that the two types of content are substitutes. Our analysis shows that they could function as strategic complements. This is because increasing the platform's own content provision raises the quality of content on the platform, motivates more consumers to join the platform, and increases the total UGC provision on the platform. The fact that consumers dislike advertising could lead us to believe that consumers will be less motivated to generate UGC if ad space increases. On the contrary, we find that consumers may be motivated to increase UGC provision to make up for the loss in enjoyment and increase the overall quality of contents on the platform. The public good characteristics of UGC could prompt us to think that UGC provision on the platform will be less than the socially optimal level. Our analysis identifies conditions when the total provision of UGC can be more than the social optimum. One may wonder whether it is profitable for a UGC platform to completely dispense with its own content. We find that it is always profitable for the UGC platform to offer some of its own content. This is because when consumers spend more time consuming the content, the platform can monetize their attention and earn higher ad revenue.

Non-fungible tokens (NFTs) exploded onto the global digital landscape in 2020, spurred by pandemic-related lockdowns and government stimulus (Ossinger, 2021). An NFT is a unit of data stored on a blockchain that represents or authenticates digital or physical items (Nadini, 2021). Since it resides on a blockchain, NFTs carry the benefits of decentralization, anti-tampering, and traceability (Joy et al., 2022). Fashion brands quickly capitalized on these features, launching fashion NFT collections and garnering significant profits from the sale of fashion NFTs in 2021 (Zhao, 2021). For example, Nike’s December 2021 acquisition of RTFKT (pronounced “artifact”) resulted in USD 185 million in sales less than a year after their acquisition (Marr, 2022).

Today, the metaverse is everywhere; it has become a major buzzword. The term was first coined in an American writer’s 1992 science fiction novel, Snow Crash, as a portmanteau of meta (Greek prefix meaning beyond) and universe. Nearly three decades later today, it is no longer the setting of a science fiction epic. Rather, it is becoming as real as the physical world. In the current time, the metaverse is used as a concept to describe a seamless convergence of the physical and digital worlds, or a virtual community where people can work, play-to-earn, transact and socialize (J.P. Morgan, 2022).

This paper investigates the number of scatterings a photon undergoes in random walks before escaping from a medium. The number of scatterings in random walk processes is commonly approximated as τ + τ 2 in the literature, where τ is the optical thickness measured from the center of the medium. However, it is found that this formula is not accurate. In this study, analytical solutions in sphere and slab geometries are derived for both optically thin and optically thick limits, assuming isotropic scattering. These solutions are verified using Monte Carlo simulations. In the optically thick limit, the number of scatterings is found to be 0.5 τ 2 and 1.5 τ 2 in a sphere and slab, respectively. In the optically thin limit, the number of scatterings is ≈ τ in a sphere and ≈ τ (1 − γ − ln τ + τ ) in a slab, where γ ≃ 0.57722 is the Euler-Mascheroni constant. Additionally, we present approximate formulas that reasonably reproduce the simulation results well in intermediate optical depths. These results are applicable to scattering processes that exhibit forward and backward symmetry, including both isotropic and Thomson scattering.

Mesophase pitch is a unique graphitizable material that has been used as an important precursor for highly graphitic carbon materials. In the current study, we propose to consider a spinnable mesophase pitch as a lyotropic liquid crystalline solution composed of solvent components and liquid crystalline components, so-called mesogen or mesogenic components. Among mesophase pitches, the supermesophase pitch is defined as a mesohpase pitch with 100% anisotropy, and can only be observed in pitches with a proportion of mesogenic components exceeding the threshold concentration (TC). We also examined the critical limit of AR synthetic pitch and 5 experimental spinnable mesophase pitches (SMPs). Then, we examined the effect of the solvent component on the minimum required amount of mesogenic component using a selected solvent component instead of their own solvent components. AR pitch showed 100% anisotropy with the least amount of its mesogenic component, THF insoluble components, of 60 wt.%. The solvent component, THF soluble components, extracted from AR-pitch, which has a molecular weight pattern similar to that of the original material but more amount of naphthenic alkyl chains, showed better solvent functionality than those of other THF solubles (THFSs) from other as-prepared spinnable mesophase pitches. This is why a lower amount of AR THFS can produce a supermesophase pitch when combined with the THFI (mesogenic components) of other experimental mesophase pitches. As a result of the current analysis, we define the mesogens as molecules that not only readily stack, but also maintain stacking structures in a fused state in the solution. The solvent component, on the other hand, is defined as molecules with a structure that readily decomposes in a fused state in the solution.

Gamma imaging devices that can accurately localize the radioactive contamination could be effectively used during nuclear decommissioning or radioactive waste management. While several hand-held devices have been proposed, their low efficiency due to small sensors have severely limited their application. To overcome this limitation, a high-speed gamma imaging system is under development which comprises two quad-type detectors and a tungsten coded aperture mask. Each quad-type detector consists of four rectangular NaI(Tl) crystals with dimensions of 146×146 mm2 and 72 square-type photomultiplier tubes (PMTs). The detectors are placed in front and back to serve as scatter and absorber, respectively, for Compton imaging. In addition, a coded aperture mask was fabricated in rank 19 modified uniformly redundant array pattern and placed in front of the scatter for coded aperture imaging. The system offers several advanced features including 1) high efficiency achieved by employing large-area NaI(Tl) crystals and 2) broad energy range of imaging by employing a hybrid imaging combining Compton and coded aperture imaging. The imaging performance of the system was evaluated through experiments in various conditions with different gamma energies and source positions. The imaging system provides clear images of the source locations for gamma energies ranging from as low as 59.5 keV (241Am) to as high as 1,330 keV (60Co). The imaging resolution was within the range of 7.5–9.4°, depending on gamma energies, when a hybrid maximum likelihood estimation maximization (MLEM) algorithm was used. The developed system showed high sensitivity, as the 137Cs source at distance, incurring dose rate lower than background level (0.03 μSv/h above background dose rate), could be imaged in approximately 2 seconds. Even under lower dose rate condition (i.e., 0.003 μSv/h above background dose rate), the system was able to image the source within 30 seconds. The system developed in the present study broadens the applicable conditions of the gamma ray imaging in terms of gamma ray energy, dose rate, and imaging speed. The performance demonstrated here suggests a new perspective on radiation imaging in the nuclear decontamination and radioactive waste management field.

For the export of nuclear materials (NM), the NSG guidelines require governmental assurance from the importing State that the NM will be used for peaceful purposes, safeguards and physical protection will be applied, and prior consent will be obtained for retransfer. By providing this assurance, the importing State (recipient) is responsible for fulfilling the obligations required by the exporting States (supplier). If the Nuclear Cooperation Agreement (NCA) has been concluded between the supplier and recipient, it may be replaced by implementing the procedures under the NCA. In the case of NM subject to this obligation, continuous management at the national level is required because prior consent from the supplier may be required for retransfer to a third party under the assurance or may be subject to annual reporting. The obligation swaps are the exchange of obligations of NM without the physical movement of it. Since the physical movement of NM is costly and risky, its obligations are often exchanged for commercial reasons. The basis for obligation swaps is the fungibility and equivalence of NM. The fungibility allows that the inventories of NM need not physically identify the particular NM originally obligated but identify an equivalent quantity of the same isotopic composition. In addition, under the principle of equivalence, even if NM loses its unique physical properties, it can be exchanged by another obligated or nonobligated NM. That is, the principles of equivalence and proportionality allow the comparison of quantities of uranium in different forms. Therefore, it is theoretically possible not only to exchange obligations between NM in same physical form, but also different physical forms of same composition (with the same enrichment), e.g., UO2 powder and its pellets. In U.S., it appears that there are obligation swaps of NM between different enrichment levels, but according to the NCA and its Administrative Arrangement between ROK and U.S., Canada and Australia, the principle of fungibility and equivalence shall not be used to reduce the quality of a quantity of NM. In other words, swaps between NM of different enrichment levels are not allowed under the NCA and AA. However, according to the Supplementary Arrangement between ROK and Canada, the replacement of NM by lower quality NM may only occur where the two States so decide following consultation. The U.S., Canada, and Australia, which are major suppliers of NMs, allow internal obligation swaps within the U.S. and the EU through NCA. The NCA between ROK and these countries does not address whether internal swaps are possible. Since governmental assurance does not impose restrictions on swaps, it can be considered if necessary. Although there is no actual practice of obligation swaps in ROK, research will be necessary regarding the extent to which swaps in ROK should be allowed and the need for government approval or permission.

A bilateral Nuclear Cooperation Agreement (NCA) should define what is subject to the agreement and when. Nuclear Materials (NM) are the subject of NCA with almost all countries, and the definition used in these agreements is borrowed from Article 20 of the IAEA Charter. The IAEA’s definition of NM as consisting of special fissionable material and source material and describes the types of material each contains. In order to control the export of NM under national laws and implement NCA, not only the types of NM but also quantitative criteria are required. This is because controlling small quantities of NM is impossible, unnecessary, and would create excessive administrative burdens. For this reason, the NSG guidelines establish a quantitative threshold of NM requiring control. Nevertheless, no quantitative thresholds have been agreed upon for NM subject to a NCA. Whether NM transferred is subject to the NCA is primarily a matter for the supplier states to determine. The supplier states make the decision based on quantitative criteria defined in their own export control laws. ROK identifies NM that require export licenses by reflecting the same criteria as the NSG guidelines in Foreign Trade Laws and its Notifications. Less than 500 kg of Natural Uranium, 1,000 kg of Depleted Uranium, 1,000 kg of Thorium, and 50 effective grams of special fissionable materials do not require an export license and is therefore not subject to NCA. In the US, the quantitative threshold for requiring an export license is different from that of ROK. For example, special fissionable materials that are not Pu are required if the individual shipment exceed 1 effective gram or 100 effective grams per year. The difference in the quantitative thresholds for NM between the two countries mean that the same item may be subject to NCA under US standards, but not under ROK’s. For example, the export of 8 grams of highly enriched uranium (93%) contained in a neutron detector would not be subject to the NCA in ROK, but would be considered NM subject to a NCA and required a special license in the US. Of course, in order to ensure the application of safeguards and physical protection to all NM transferred between the two countries, the agreement may not include a quantitative threshold for NM. However, the absence of such a threshold can lead to different conclusions by the two countries on the same item and make it challenging to control retransfers. The definition of quantitative standards will be necessary in the supplementary administrative arrangement for the practical control and management of NM subject to the NCA.

Under the Foreign Trade Act, an export license from the Nuclear Safety Commission is required to export items specified in Part 10 of Schedule 2 of the Public Notice of Exportation and Importation of Strategic Items (Trigger List Items). In the case of nuclear materials, deuterium, and heavy water, its cumulative amount determines whether it is trigger list item. An export license is required only if the cumulative amount exported to a single end-user country from January 1st to December 31st exceeds the regulation criteria. The reason for this cumulative control is to exclude small amounts of materials from the scope of control as they are considered less important in view of nuclear proliferation, but to prevent the possibility of acquiring large quantities of materials by importing small amounts several times. As a result, export control of nuclear material, deuterium, and heavy water requires different considerations than other Trigger List Items. First, materials exported by different companies must be consolidated to manage the cumulative amount. Second, it is necessary to continuously follow up the actual export status. If the material is not exported after it was classified as ‘non-Trigger List Items’, it should not be included in the cumulative amount. Third, there may be a difference between the accumulated quantities aggregated at the time of the classification and the time of the actual export. The classification should be changed if an export of the classified material is postponed or another export of same materials occurs before the export of the classified material. Fourth, the classification result of these materials should not be reused. Generally, the classification result could be reused within the expiration date (2 years) but in the case of substances. However, the reuse of classification result for materials should be limited as the classification results could be change depending on the cumulative amount. In addition, the sharing of classification results between different entities should also be restricted. The government approval procedures are required even for export of small amounts of nuclear materials which are less than the regulation criteria. The cumulative quantities of nuclear materials are systematically managed in the Nuclear Export & imPort control System (NEPS) through these procedures. NEPS is also linked to the custom clearance system of Korea Customs Service, which enables to track actual exports and the time of exports. However, cumulative quantities for the heavy water and deuterium are managed individually by classification reviewers. The annual export plans are received in advance from major entities which deal with the materials for nuclear uses, and the cumulative quantities for each application are managed manually. The systematic management has not been required as there were a few cases of exporting small quantities. However, systematic management may be required in the future as overseas expansion attempts from various companies in the nuclear field has been increasing. In addition, further study is needed on the criteria and system for calculating the cumulative amount. The time of aggregate the cumulative amount should be clarified by considering the difference between the time of classification and actual export. It is required to devise an efficient way to follow up the actual export.

An administrative agreement (AA) was signed between NSSC and UAE FANR in January 2023 under Article 5 of the ROK-UAE Nuclear Cooperation Agreement. The AA aims to enhance regulatory efficiency in safeguards and export control. This study reviewed the export control measures for the items subject to the agreement (ISA) and implementation procedures under ROK-UAE AA by comparing them with other countries cases. First of all, the ROK-UAE AA distinguishes between ISA and the inventory management target items. Technology is divided into two categories, one requiring consent for retransfer and the other, considering the characteristics of technology that is free to be copied and deleted, and thus less useful for inventory management. Only the former is included in the annual report, which differs from the ROK-Canada or ROK-Japan NCA, which includes all technologies subject to the agreements in the annual report. When ROK notifies export information, it is mandatory to specify whether the technology requires consent for retransfer. Furthermore, some technologies should be controlled as strategic information, even if excluded from the annual report, so efforts to prevent confusion are required. Secondly, the ROK-UAE AA covers all items in INFCIRC/254/rev.9/part1, unlike the ROK-U.S. and ROK-Canada NCA, which listed equipment subject to them. This is significant because it clarifies the criteria for regulation by increasing the consistency between the trigger list items in the domestic law and the ISA. However, the expanded ISA scope could result in some changes in export control procedures. For example, when importing nuclear material (NM) from the US, only uranium was controlled as ISA, and the packages were not considered. In contrast, when exporting fuel assemblies (FA) for UAE, both uranium and zirconium cladding should be treated as ISA. To this end, NEPS was improved to implement the features of the ROK-UAE AA. Consideration of the criteria and methods for imposing obligations under the agreement is essential because this is the first case of Korea concluded AA under exporting NPP and as a supplier of FA. Generally, the obligations for NM are imposed by the country of origin, conversion, and enrichment countries. Canada and EU recognize the fuel fabrication process as a substantial transformation and impose customs origin where the process takes place. Hence, NM fabricated from Canadian equipment is also subject to the same obligations as NM of Canadian origin. From this perspective, it would be appropriate to ensure ROK acts as a supplier and controls when exporting domestically manufactured FA. Moreover, a proper national obligation code system will be required to specify Korea’s control rights.