In this paper, an improved mathematical model for flashover behavior of polluted insulators is proposed based on experimental tests. In order to determine the flashover model of polluted insulators, the relationship between conductivity and salinity of solution pollution layer of the insulator is measured. Then, the leakage of current amplitude of four common insulators versus axial, thermal conductivity and arc constants temperature was determined. The experimental tests show that top leakage distance (TLd) to bottom leakage distance (BLd) ratio of insulators has a significant effect on critical voltage and current. Therefore, critical voltage and current were modeled by TLd to BLd ratio Index (M). Also, salinity of solution pollution layer of the insulators has been applied to this model by resistance pollution parameter. On the other hand, arc constants of each insulator in new model have been identified based on experimental results. Finally, a mathematical model is intended for critical voltage against salinity of solution pollution layer of different insulators. This model depends on insulator profile. There is a good agreement between the experimental tests of pollution insulators obtained in the laboratory and values calculated from the mathematical models developed in the present study.

Helical deep hole drilling is a process frequently used in industrial applications to produce bores with a large length to diameter ratio. For better cooling and lubrication, the deep drilling oil is fed directly into the bore hole via two internal cooling channels. Due to the inaccessibility of the cutting area, experimental investigations that provide information on the actual machining and cooling behavior are difficult to carry out. In this paper, the distribution of the deep drilling oil is investigated both experimentally and simulatively and the results are evaluated. For the Computational Fluid Dynamics (CFD) simulation, two different turbulence models, i.e. the RANS k-ω-SST and hybrid SAS-SST model, are used and compared. Thereby, the actual used deep drilling oil is modelled instead of using fluid dynamic parameters of water, as is often the case. With the hybrid SAS-SST model, the flow could be analyzed much better than with the RANS k-ω-SST model and thus the processes that take place during helical deep drilling could be  simulated with realistic details. Both the experimental and the simulative results show that the deep drilling oil movement is almost exclusively generated by the tool rotation. At the tool’s cutting edges and in the flute, the flow velocity drops to zero for the most part, so that no efficient cooling and lubrication could take place there. In addition, cavitation bubbles form and implode, concluding in the assumption that the process heat is not adequately dissipated and the removal of chips is adversely affected, which in turn can affect the service life of the tool and the bore quality. The carried out investigations show that the application of CFD simulation is an important research instrument in machining technology and that there is still great potential in the area of tool and process optimization.

Proactive coping behavior has been considered an important personal job resource for employees. Organizations have paid considerable attention to the proactive coping behavior of employees to maintain their competitive advantage. The purpose of the current study is to discover the relationship between organizational job resources, work engagement, and proactive coping using structural equation modeling. The participants were 340 licensed Chinese social workers. In the rapidly growing social work sector in China, social work organizations require psychologically connected and dedicated social workers. Findings include the effect of organizational job resources and work engagement on proactive coping. Based on the results, impacts on organizational management are discussed.

The study intends to identify the existing implementation bottlenecks that hamper the effectiveness of the Ethiopian forest policy and laws in regional states by focusing on the Oromia Regional State. It attempts to address the question, "What are the challenges for the effective implementation of the federal forest policy and law in Ethiopia in general and Oromia Regional State in particular?". The study followed a qualitative research approach, and the relevant data was collected through in-depth interviews from 11 leaders and experts of the policy, who were purposively selected. Furthermore, relevant documents such as the constitutions, forest policies and laws, and government documents were carefully reviewed. Based on this, the study found that there is the dichotomy between the provision of the constitution regarding the forest policy and lawmaking and the constitutional amendment on one hand and the push for genuine decentralization in the Ethiopian federal state on the other. To elaborate, the constitution is rigid for amendment, and it has given the power of forest policy and lawmaking to the federal government. On the other hand, the quest for genuine decentralization requires these powers to be devolved to the regional states. As the constitution is rigid, this may continue to be the major future challenge of the forest policy and lawmaking of the state. This demonstrates a conflict of interests between the two layers of governments, i.e., the federal and regional (Oromia Regional State) governments. Respecting and practicing the constitution may be the immediate solution to this pressing problem.

Delay is the leading challenge in completing Engineering, Procurement, and Construction (EPC) projects. Delay can cause excess costs, which reduces company profits. The relationship between subcontractors and the main contractor is a critical factor that can support the success of an EPC project. The problematic financial condition of the main contractor can cause delay in payments to subcontractors. This research will set a model that combines the system dynamics and earned value method to describe the impact of subcontractor advance payments on project performance. The system dynamics method is used to model and analyze the impact of interactions between variables affecting project performance, while the earned value method is applied to quantitatively evaluate project performance and forecast schedule and cost outcomes. These two methods are used complementarily to achieve a holistic understanding of project dynamics and to optimize decision-making. The designed model selects the optimum scenario for project time and costs. The developed model comprises project performance, costs, cash flow, and performance forecasting sub-models. The novelty in this research is a new model for optimizing project implementation time and costs, adding payment rate variables to subcontractors and subcontractor performance rates. The designed model can provide additional information to assist project managers in making decisions.