Understanding Android Obfuscation Techniques: A Large-Scale Investigation in the Wild

In this paper, we seek to better understand Android obfuscation and depict a holistic view of the usage of obfuscation through a large-scale investigation in the wild. In particular, we focus on four popular obfuscation approaches: identifier renaming, string encryption, Java reflection, and packing. To obtain the meaningful statistical results, we designed efficient and lightweight detection models for each obfuscation technique and applied them to our massive APK datasets (collected from Google Play, multiple third-party markets, and malware databases). We have learned several interesting facts from the result. For example, malware authors use string encryption more frequently, and more apps on third-party markets than Google Play are packed. We are also interested in the explanation of each finding. Therefore we carry out in-depth code analysis on some Android apps after sampling. We believe our study will help developers select the most suitable obfuscation approach, and in the meantime help researchers improve code analysis systems in the right direction

Preparation and properties of antistatic high-strength aramid III/MWCNTs-OH fibers

Composite fibers made from aramid III and hydroxylated multiwalled carbon nanotubes (MWCNTs-OH) combine the excellent mechanical and electrical properties of both components, resulting in strong antistatic performance. However, it is of paramount importance to ensure the homogeneous dispersion of multi-walled carbon nanotubes functionalized with hydroxyl groups (MWCNTs-OH) within the aramid III spinning solution and optimize the compatibility between the two constituents to augment the overall performance of the composite fibers. To this end, this investigation successfully accomplished the dispersion of MWCNTs-OH in the spinning solution and probed the dispersion mechanism using molecular dynamics simulations. Moreover, composite fibers, comprising 2.4 weight percent MWCNTs-OH, were initially fabricated using the wet spinning method. These fibers displayed a uniform texture and a tensile strength of 1.210 GPa, signifying a noteworthy enhancement of 113.25% in comparison to the strength prior to modification. With respect to thermal behavior, the fibers exhibited a mass reduction of 21.24% within the temperature range of 0°C–538°C. In the temperature interval from 538°C to 800°C, the mass loss diminished to 10.31%, representing a substantial 71.03% reduction when compared to the unmodified state. Remarkably, even when subjected to temperatures exceeding 800°C, the composite fibers retained a residual mass of 68.45%, indicating a notable 61.17% increase from their initial condition. In terms of electrical properties, the fibers exhibited a specific resistance (ρ) of 3.330 × 109 Ω cm, demonstrating effective antistatic behavior. In summary, the antistatic composite fibers studied in this paper can effectively mitigate the hazards of static electricity in various applications, including military protection and engineering equipment in both military and civilian fields

A Systematic Analysis on DNA Methylation and the Expression of Both mRNA and microRNA in Bladder Cancer

Background: DNA methylation aberration and microRNA (miRNA) deregulation have been observed in many types of cancers. A systematic study of methylome and transcriptome in bladder urothelial carcinoma has never been reported. Methodology/Principal Findings: The DNA methylation was profiled by modified methylation-specific digital karyotyping (MMSDK) and the expression of mRNAs and miRNAs was analyzed by digital gene expression (DGE) sequencing in tumors and matched normal adjacent tissues obtained from 9 bladder urothelial carcinoma patients. We found that a set of significantly enriched pathways disrupted in bladder urothelial carcinoma primarily related to "neurogenesis" and "cell differentiation" by integrated analysis of -omics data. Furthermore, we identified an intriguing collection of cancer-related genes that were deregulated at the levels of DNA methylation and mRNA expression, and we validated several of these genes (HIC1, SLIT2, RASAL1, and KRT17) by Bisulfite Sequencing PCR and Reverse Transcription qPCR in a panel of 33 bladder cancer samples. Conclusions/Significance: We characterized the profiles between methylome and transcriptome in bladder urothelial carcinoma, identified a set of significantly enriched key pathways, and screened four aberrantly methylated and expressed genes. Conclusively, our findings shed light on a new avenue for basic bladder cancer research

Performance evaluation of a novel frost-free air-source heat pump integrated with phase change materials (PCMs) and dehumidification

Air-source heat pump (ASHP) has been widely used in domestic and commercial buildings because of its energy savings, high efficiency and environmental friendliness. However, the heating capacity of an ASHP system is greatly influenced by the frost accumulation on the surface of the outdoor exchanger. To solve this problem, a novel frost-free ASHP system, integrating with Phase Change Materials (PCMs) and dehumidification, has been developed. In this paper, the schematic design of this system is first presented. The effect of the match relationship between the desiccant materials and PCM thermal energy storage on the performance of the novel system is then studied using a dynamic mathematical model. The simulation results showed that the dehumidification efficiency was increased from 31.8 % to 34.7 % with the increase of the solid desiccant mass from 1.9 kg to 3.5 kg when the volume of the PCM was 1000 ml. The system COP was 2.87 when the desiccant was 2.2 kg and the volume of PCM was 1100 ml at a relative humidity of 80 % and ambient temperature of 0 °C. In addition, the water temperature was heated to 55 °C in one cycle which decreased the irreversible loss. Lastly, a correlation of the system COP with the amount of the solid desiccant and the PCM was obtained through a multivariate linear regression. The results obtained can facilitate optimal design and dynamic behavior investigation of this system

Performance Optimization and Economic Evaluation of CO2 Heat Pump Heating System Coupled with Thermal Energy Storage

CO2 air source heat pump (ASHP), as a kind of clean and efficient heating equipment, is a promising solution for domestic hot water and clean heating. However, the promotion of CO2 ASHP encounters a great resistance when it is used for space heating; namely, the return water temperature is too high that cased higher throttle loss, which decreases the COP of the CO2 ASHP unit. To solve this problem, a heating system of CO2 ASHP coupled with thermal energy storage (TES) is developed in this work. The simulation model of the studied system is established using TRNSYS software, and the model is verified by experimental data. Additionally, the performance of the studied system is optimized, and its economy is analyzed by life cycle cost (LCC). The results showed that, compared with the system before optimization, the cost of the optimized system increased, the annual operating cost of the system was reduced, and the COP of the system (COPsys) increased by 7.4%. This research is helpful in improving the application of the CO2 ASHP unit in cold server and cold areas.</jats:p

Performance Optimization and Economic Evaluation of CO2 Heat Pump Heating System Coupled with Thermal Energy Storage

CO2 air source heat pump (ASHP), as a kind of clean and efficient heating equipment, is a promising solution for domestic hot water and clean heating. However, the promotion of CO2 ASHP encounters a great resistance when it is used for space heating; namely, the return water temperature is too high that cased higher throttle loss, which decreases the COP of the CO2 ASHP unit. To solve this problem, a heating system of CO2 ASHP coupled with thermal energy storage (TES) is developed in this work. The simulation model of the studied system is established using TRNSYS software, and the model is verified by experimental data. Additionally, the performance of the studied system is optimized, and its economy is analyzed by life cycle cost (LCC). The results showed that, compared with the system before optimization, the cost of the optimized system increased, the annual operating cost of the system was reduced, and the COP of the system (COPsys) increased by 7.4%. This research is helpful in improving the application of the CO2 ASHP unit in cold server and cold areas