Crime Scene Re-investigation: A Postmortem Analysis of Game Account Stealers' Behaviors

As item trading becomes more popular, users can change their game items or money into real money more easily. At the same time, hackers turn their eyes on stealing other users game items or money because it is much easier to earn money than traditional gold-farming by running game bots. Game companies provide various security measures to block account- theft attempts, but many security measures on the user-side are disregarded by users because of lack of usability. In this study, we propose a server-side account theft detection system base on action sequence analysis to protect game users from malicious hackers. We tested this system in the real Massively Multiplayer Online Role Playing Game (MMORPG). By analyzing users full game play log, our system can find the particular action sequences of hackers with high accuracy. Also, we can trace where the victim accounts stolen money goes.Comment: 7 pages, 8 figures, In Proceedings of the 15th Annual Workshop on Network and Systems Support for Games (NetGames 2017

A Comprehensive Technoeconomic and Environmental Evaluation of a Hybrid Renewable Energy System for a Smart Farm in South Korea

The farming sector like any other industry needs to be decarbonized. Hence, it is essential to meet the energy demands of the farms by adopting energy systems with a low-carbon footprint. Depending on the weather conditions, heating or cooling is needed. Within this context, this study presents a new hybrid renewable decentralized energy system that is designed to satisfy the requirements for heating, cooling, and electricity of a smart farm in South Korea. The under-investigation energy system comprises solar PV arrays, heat pumps, thermal energy storage tanks, and a wood pellet boiler. This study is the first to conduct an inclusive techno-enviroeconomic assessment of such a hybrid energy system by utilizing actual meteorological data on an hourly basis. This enables the model to be dynamic and facilitate accurate and reliable assessments. The modelling efforts have been performed in Aspen Plus and MATLAB to investigate the thermodynamic behaviour of the system. The investigation shows that the proposed system has achieved a daily average temperature of around 23.9°C inside the farm throughout the year with a standard deviation of 2.16°C. For the economic assessment, the levelized cost of energy has been selected as the main economic indicator, and this has been estimated at $0.218/kWh. It is found that the PV panels and the biomass boiler dominate the capital expenditures, and the biomass feedstock is the major contributor to the operating expenditures. Further, the proposed energy system reduces CO2 emissions, by up to 88.94%, when compared to conventional fossil-based energy systems. The outcomes of this study represent a holistic evaluation for such a low-carbon hybrid energy system when applied to greenhouses in Korea and in similar locations

Performance Evaluation of a Novel Thermal Power Plant Process with Low-Temperature Selective Catalytic Reduction

We present the concept of a novel thermal power plant process in conjunction with low-temperature selective catalytic reduction (SCR). This process can be employed to achieve modern standards for NOx emissions and solve problems related to post-gas cleaning processes, such as thermal fatigue, catalyst damage, and an increase in differential pressure in the boiler. Therefore, this study is aimed at evaluating the performance of a novel flue-gas cleaning process for use in a thermal power plant, where a low-temperature SCR is implemented, along with the existing SCR. We developed a process model for a large-scale power plant, in which the thermal power plant was divided into a series of heat exchanger block models. The mass and energy balances were solved by considering the heat transfer interaction between the hot and cold sides to obtain the properties of each material flow. Using the process model, we performed a simulation of the new process. New optimal operating conditions were derived, and the effects that the new facilities have on the existing process were evaluated. The results show that the new process is feasible in terms of operating stability and cost, as well as showing an increase in the boiler thermal efficiency of up to 1.3%

One-dimensional numerical simulation of CFB combustion: Improvement of hydrodynamic models for accurate prediction of pressure and particle size distributions

This study aims to improve the accuracy of one-dimensional numerical simulations of circulating fluidized bed (CFB) boilers by evaluating models related to solid properties, such as attrition, fragmentation, cyclone efficiency, and bed material discharge. The study validates models for estimating solids holdup and particle size distribution (PSD) using experimental results from a 12 MWth CFB boiler. The study found that accurate prediction of solid axial holdup and local PSD requires proper consideration of attrition and fragmentation, and the simulation results show that attrition has a more significant effect on numerical analysis performance than fragmentation. By using appropriate values for sand attrition constant (5E-7), char attrition constant (6E-6), and coal:1.5, sand:1.2, and char(ash):1.2 fragmentation constants, the pressure distribution measured from experiments was best predicted. The simulation successfully predicted the particle PSD distribution at a specific location in the CFB boiler and pressure change by height, similar to the experimental results In addition, this study investigated the accuracy of 3D computational fluid dynamics (CFD) simulations using solid properties obtained through 1D simulation as initial conditions compared to those based on experimental conditions. The results revealed that 3D CFD simulations using the solid properties from 1D numerical analysis are more accurate, implying that 1D-3D co-simulation approach is a good strategy to increase the simulation performance

Charge-Transfer-Induced p‑Type Channel in MoS₂ Flake Field Effect Transistors

The two-dimensional transition-metal dichalcogenide semiconductor MoS₂ has received extensive attention for decades because of its outstanding electrical and mechanical properties for next-generation devices. One weakness of MoS₂, however, is that it shows only n-type conduction, revealing its limitations for homogeneous PN diodes and complementary inverters. Here, we introduce a charge-transfer method to modify the conduction property of MoS₂ from n- to p-type. We initially deposited an n-type InGaZnO (IGZO) film on top of the MoS₂ flake so that electron charges might be transferred from MoS₂ to IGZO during air ambient annealing. As a result, electron charges were depleted in MoS₂. Such charge depletion lowered the MoS₂ Fermi level, which makes hole conduction favorable in MoS₂ when optimum source/drain electrodes with a high work function are selected. Our IGZO-supported MoS₂ flake field effect transistors (FETs) clearly display channel-type conversion from n- to p-channel in this way. Under short- and long-annealing conditions, n- and p-channel MoS₂ FETs are achieved, respectively, and a low-voltage complementary inverter is demonstrated using both channels in a single MoS₂ flake

Single-Crystalline Metallic Films Induced by van der Waals Epitaxy on Black Phosphorus

The properties of metal-semiconductor junctions are often unpredictable because of non-ideal interfacial structures, such as interfacial defects or chemical reactions introduced at junctions. Black phosphorus (BP), an elemental two-dimensional (2D) semiconducting crystal, possesses a puckered atomic structure with high chemical reactivity, and the establishment of a realistic atomic-scale picture of BP's interface toward the metallic contact has remained elusive. Here, we examine the interfacial structures and properties of physically deposited metals of various kinds on BP. We find that Au, Ag, and Bi form single-crystalline films with a (110) orientation through guided van der Waals epitaxy. Transmission electron microscopy and X-ray photoelectron spectroscopy confirm that atomically sharp van der Waals metal-BP interfaces are formed with an exceptional rotational alignment. Under a weak metal-BP interaction regime, BP's puckered structure plays an essential role in the adatom assembly process and can lead to the formation of a single crystal, which is supported by our theoretical analysis and calculations. The experimental survey also demonstrates that the BP-metal junctions can exhibit various types of interfacial structures depending on metals, such as the formation of a polycrystalline microstructure or metal phosphides. This study provides a guideline for obtaining a realistic view on metal-2D semiconductor interfacial structures, especially for atomically puckered 2D crystals