MDPI - Publisher of Open Access Journals

24 pages, 12713 KB

Open AccessArticle

Designing Stress-Relieving Small Inner-City Park Environments for Teenagers

by Aida Nosrati, Mahdieh Pazhouhanfar, Chongxian Chen and Patrik Grahn

Land 2024, 13(10), 1633; https://doi.org/10.3390/land13101633 - 8 Oct 2024

Cited by 3 | Viewed by 3712

All over the world, teenagers suffer from stress-related mental illness, and research shows that being in natural environments can bring about recovery. However, centrally located areas in cities where teenagers like to hang out are being densified at the expense of green spaces. The health-promoting function of small, centrally located parks is thus becoming increasingly important. This study examines Iranian teenagers’ assessment of the restorative potential of small, centrally located parks. Such parks include attributes typical of city centers, such as trees, lighting, park benches and flowers. A discrete sampling method was used to collect responses from a sample of 265 Iranian teenagers. They were asked to randomly rate the perceived recovery potential of digitally designed models of green spaces. The results show that the teenagers evaluated the presence of water in waterbeds to have a strong positive effect on recovery possibilities. The entire green area should also be screened off from the rest of the city and convey a soft impression. It should have lighting from tall lampposts, contain plant beds and, not least, have distinctive cultural attributes such as crescent arches and fountains. In the discussion of the article, we address the practical and theoretical implications of the findings. Full article

(This article belongs to the Special Issue Landscape Architecture and Design in Urban and Peri-Urban Environment: 2nd Edition)

► Show Figures

Figure 1

17 pages, 4934 KB

Open AccessArticle

A Novel Equivalent Combined Control Architecture for Electro-Optical Equipment: Performance and Robustness

by Yang Liu, Yulong Zheng, Mo Chen, Jian Chen and Weiguo Wang

Appl. Sci. 2024, 14(15), 6708; https://doi.org/10.3390/app14156708 - 1 Aug 2024

Cited by 1 | Viewed by 1096

Abstract

In this paper, we propose a novel equivalent composite control architecture for electro-optical equipment. The improved tracking performance and loss of robustness caused by this structure have a clear relationship with

a_{2}

, the time coefficient of the compensation circuit. The compensation [...] Read more.

a_{2}

, the time coefficient of the compensation circuit. The compensation circuit can make the speed quality factor and the acceleration quality factor of the system infinite, and the jerk quality factor can be expanded to

1 / a_{2}

times the original acceleration quality factor, but it will cause a main zero point of the servo system to be far away from the virtual axis and the main poles to be close to the virtual axis. As the time coefficient of the compensation loop controller decreases, the tracking performance of the system increases, but the robustness decreases, the dynamic response deteriorates, the water bed effect becomes more obvious, and the system is more susceptible to noise and disturbances. Compared to the existing method, our method focuses on system performance and robustness. Experimental results show that our method can achieve target tracking with a peak accuracy of 64

″

and 22

″

(RMS), which is superior to the tracking performance without equivalent composite control. Full article

(This article belongs to the Special Issue Advanced Control Systems and Applications)

► Show Figures

Figure 1

13 pages, 3900 KB

Open AccessArticle

Uncertainty Constraint on Headphone Secondary Path Function for Designing Cascade Biquad Feedback Controller with Improved Noise Reduction Performance

by Yang Hua and Linhui Peng

Appl. Sci. 2024, 14(6), 2236; https://doi.org/10.3390/app14062236 - 7 Mar 2024

Viewed by 1617

Abstract

The uncertainty in the secondary path of active noise control (ANC) headphones affects the waterbed effect and stability of the feedback system. This study focuses on the uncertainty of the secondary path when real users wear headphones and proposes a new uncertainty constraint based on the measured results of the secondary path transfer function under different wearing conditions of a dummy head and limited subjects. This constraint and a cascaded second-order infinite impulse response filter with fixed coefficients are used to formulate a control strategic function, which is optimized using the Improved Grey Wolf Optimizer (IGWO) algorithm to obtain the optimal controller with better noise reduction performance. The proposed method and simulation model are validated based on the experimental test results. The results demonstrate that the safety factor and waterbed suppressing factor contained in the proposed uncertainty constraint ensure more stable noise reduction and effective suppression of the waterbed effect for new subjects without a priori data. Full article

(This article belongs to the Section Acoustics and Vibrations)

► Show Figures

Figure 1

23 pages, 2951 KB

Open AccessEditor’s ChoiceArticle

Comparison of the Gaussian Wind Farm Model with Historical Data of Three Offshore Wind Farms

by Bart Matthijs Doekemeijer, Eric Simley and Paul Fleming

Energies 2022, 15(6), 1964; https://doi.org/10.3390/en15061964 - 8 Mar 2022

Cited by 33 | Viewed by 6304

Abstract

A recent expert elicitation showed that model validation remains one of the largest barriers for commercial wind farm control deployment. The Gaussian-shaped wake deficit model has grown in popularity in wind farm field experiments, yet its validation for larger farms and throughout annual operation remains limited. This article addresses this scientific gap, providing a model comparison of the Gaussian wind farm model with historical data of three offshore wind farms. The energy ratio is used to quantify the model’s accuracy. We assume a fixed turbulence intensity of

I_{\infty} = 6 %

and a standard deviation on the inflow wind direction of

σ_{w d} = 3 °

in our Gaussian model. First, we demonstrate the non-uniqueness issue of

I_{\infty}

and

σ_{w d}

, which display a waterbed effect when considering the energy ratios. Second, we show excellent agreement between the Gaussian model and historical data for most wind directions in the Offshore Windpark Egmond aan Zee (OWEZ) and Westermost Rough wind farms (36 and 35 wind turbines, respectively) and wind turbines on the outer edges of the Anholt wind farm (110 turbines). Turbines centrally positioned in the Anholt wind farm show larger model discrepancies, likely due to deep-array effects that are not captured in the model. A second source of discrepancy is hypothesized to be inflow heterogeneity. In future work, the Gaussian wind farm model will be adapted to address those weaknesses. Full article

(This article belongs to the Special Issue Fast-Running Engineering Models of Wind Farm Flows)

► Show Figures

Figure 1

19 pages, 1107 KB

Open AccessArticle

The Influence of Buyer Power on Supply Chain Pricing with Downstream Competition

by Qiu Zhao

Sustainability 2019, 11(10), 2924; https://doi.org/10.3390/su11102924 - 23 May 2019

Cited by 3 | Viewed by 7419

Abstract

This paper aims to investigate the impact of buyer power on the wholesale price and retail price of, in the case, downstream competition. Based on a summary of the competitive characteristics of China’s retail market, a model of a vertical market was constructed to examine the influence of buyer power on the pricing decisions of manufacturers and retailers, and to analyze the mechanism of price decisions. The results showed that the buyer power of national retailers reduced the wholesale price, but the impact on local retailers remained uncertain. Although increasing buyer power initially increased the local retailer’s wholesale price and caused the ‘waterbed effect’, we found that this effect reverted when the buyer power reached a point at which the ‘anti-waterbed effect’ appeared. The opposite was true of the retail price. However, buyer power reduced the average retail price, and consumer welfare improved. Full article

(This article belongs to the Section Economic and Business Aspects of Sustainability)

► Show Figures

Figure 1

Search Results (5)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (5)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI