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In the world of financial management, constructing an effective investment portfolio is a key task for investors. An optimal portfolio allows investors to achieve their financial goals while managing potential risks in a dynamic and uncertain market environment. It is acknowledged that one foundational principle in portfolio construction is risk diversification. In portfolio construction, two popular methods for optimizing investment decisions are the minimal volatility portfolio and the maximum Sharpe ratio portfolio. This research collects historical stock data from Nasdaq to evaluate the effectiveness of these two portfolio strategies. By applying the Mean-Variance Model to six representative stocks across different sectors, this study aims to determine which strategy performs superior cumulative returns. Results show that the minimal volatility portfolio achieved a relatively higher cumulative return, outperforming the maximum Sharpe ratio strategy and the market index. This study provides important insights for risk-averse investors looking for steady returns by highlighting the benefit of a lower-risk portfolio in producing better cumulative returns.

The drainage and sewage interception project hi Zhaoyang District involved the installation of a DN1000 municipal sewer pipeline with a total length of 1541 m. Considering factors such as geological conditions, pipe diameter, buried depth, groundwater level, as well as the impact of nearby underground and aboveground structures and traffic, the trenchless construction method of pipe jacking was selected for implementation. The pipeline followed the route of Weiba Road, crossed Jinying Avenue, and then proceeded along the Second Ring East Road until it reached the bank of Yaowan River. The project design took into account practical considerations, including the sewer pipe diameter, material selection, pipeline routing, construction of pipe jacking starting shafts, and the design and modification of arriving shafts, in line with the specific engineering requirements.

Based on the interpretation of GB 18352.6-2016 and combined with the author's actual development experience, the key design points and solutions of the three key problems of fuel system that meet China 6 emission regulations are described, Technical route selection of evaporative emission, definition of technical route of fuel tank and control strategy of tank pressure, evaporative emission control, etc..

With the further tightening of light vehicle emission regulations, the emission limit of evaporative pollutants is reduced from 2.0g/test to 0.7g/test from the fifth stage to the sixth stage in China. The definition of evaporative pollutants in the regulation refers to the hydrocarbon loss from the fuel system of the vehicle. Through the actual evaporation test, it is found that the tested emissions include not only the hydrocarbon emissions from the fuel system, but also the hydrocarbon emissions from the non fuel system. In this study, an experimental study on evaporative pollutants was carried out for a vehicle and its components developed by Dongfeng Motor Company. The results show that the hydrocarbon emission from fuel system accounts for 21% of the total hydrocarbon emission. In order to reduce the emission of evaporative pollutants, we can start from two aspects: one is to improve the design of fuel system; the other is to carry out specific pretreatment for non fuel system.

In the development process of a certain CHINA VI proprietary brand car model, there exists the problem of intermittent “dada” sound in the cockpit during idling. After investigation, it’s determined that the air pulse noise generated when the canister purge solenoid valve is working, it is transmitted to the car panels through the pipeline, and then to the cockpit, which would cause a “dada” sound. By adding expansion chamber in the desorption pipe and designing part of the pipeline which fixed in the clamp as rubber pipe, the intensity of air pulse can be effectively reduced and the transmission path of air pulse vibration can be blocked. Through objective testing and subjective evaluation, the scheme can greatly reduce the idle noise of the cockpit, thus improving the NVH performance of the vehicle and bringing comfortable riding environment to the passengers.

The property right of small water conservancy projects (hereinafter referred to as SWCP) currently can be defined as three different forms: public property rights, private property rights, and a combination of public and private property rights. The main participants are the government, farmers, and other organizations. The interests and demands of different subjects are different, so the property rights structure of the SWCPs are also different. In order to explore the evolutionary law of the property right structure of SWCPs in the case of conflicting demands of multiple stakeholders, a game model for the evolutionary law of each main body of SWCPs was proposed in this paper. By analyzing the feasibility of the game of multi-stakeholder appeal conflicts, a multi-stakeholder game model was established. The game and evolution of each stakeholder were analyzed, and the evolution of the property rights of SWCPs under the game of each subject was simulated and analyzed. The research results show that if the incentives and constraints of cooperation between farmers and cooperatives, associations and other organizations are greater than the cost of cooperation, farmers will participate in the cooperation and invest in elements actively, thus promoting the integration of elements, thereby contributing resource complementarity among participants and leaving more cooperation surplus. If the benefits of cooperation between the government and farmer organizations plus the total benefits of the incentive and restraint mechanism are greater than the total cost of active cooperation, furthermore, the incremental benefits of the incentive and restraint mechanism are not lower than the incremental costs of participating in the cooperative, then, farmer organizations are easier to get succeed. The research results have certain reference significance for the option of the property rights and management modes of SWCPs.