A Bifurcation Analysis and Sensitivity Study of Brake Creep Groan

Creep groan is the undesirable vibration observed in the brake pad and disc as brakes are applied during low-speed driving. The presence of friction leads to nonlinear behavior even in simple models of this phenomenon. This paper uses tools from bifurcation theory to investigate creep groan behavior in a nonlinear 3-degrees-of-freedom mathematical model. Three areas of operational interest are identified, replicating results from previous studies: region 1 contains repelling equilibria and attracting periodic orbits (creep groan); region 2 contains both attracting equilibria and periodic orbits (creep groan and no creep groan, depending on initial conditions); region 3 contains attracting equilibria (no creep groan). The influence of several friction model parameters on these regions is presented, which identify that the transition between static and dynamic friction regimes has a large influence on the existence of creep groan. Additional investigations discover the presence of several bifurcations previously unknown to exist in this model, including Hopf, torus and period-doubling bifurcations. This insight provides valuable novel information about the nature of creep groan and indicates that complex behavior can be discovered and explored in relatively simple models.

Prediction of COVID-19 pandemic dynamics in Russia based on simple mathematical models of epidemics

Introduction: The COVID-19 pandemic which began in 2020 and has taken more than five million lives has become a threat to the very existence of mankind. Therefore, predicting the spread of COVID-19 in each individual country is a very urgent task. The complexity of its solution is due to the requirement for fast processing of large amounts of data and the fact that the data are mostly inaccurate and do not have the statistical properties necessary for the successful application of statistical methods. Therefore, it seems important to develop simple forecasting methods based on classical simple models of epidemiology which are only weakly sensitive to data inaccuracies. It is also important to demonstrate the feasibility of the approach in relation to the incidence data in Russia. Purpose: Obtaining forecast data based on classical simple models of epidemics, namely SIR and SEIR. Methods: For discrete versions of SIR and SEIR models, it is proposed to estimate the parameters of the models using a reduced version of the least squares method, and apply a scenario approach to the forecasting. The simplicity and a small number of parameters are the advantages of SIR and SEIR models, which is very important in the context of a lack of numerical input data and structural incompleteness of the models. Results: A forecast of the spread of COVID-19 in Russia has been built based on published data on the incidence from March 10 to April 20, 2020, and then, selectively, according to October 2020 data and October 2021 data. The results of the comparison between SIR and SEIR forecasts are presented. The same method was used to construct and present forecasts based on morbidity data in the fall of 2020 and in the fall of 2021 for Russia and for St. Petersburg. To set the parameters of the models which are difficult to determine from the official data, a scenario approach is used: the dynamics of the epidemic is analyzed for several possible values of the parameters. Practical relevance: The results obtained show that the proposed method predicts well the time of the onset of the peak incidence, despite the inaccuracy of the initial data.

Elementary tutorial for multilevel analysis using visualizations

The tutorial aims to explain the basics of multilevel level models using visualizations. It is meant for students and researchers who are relatively new to multilevel analysis. By avoiding formula's as much as possible, the tutorial may in particular be useful for persons with statistical anxiety. Various simple models are explained by visualizing the predicted values from these models.

Noise-induced coherence in molecular processes

Excitation of molecules by incident incoherent electromagnetic radiation, such as sunlight, is described in detail and contrasted with the effect of coherent (e.g. laser) light. The nature of the quantum coherences induced by the former, relevant to transport processes in nature and in technology, is emphasized. Both equilibrium and steady state scenarios are discussed, Three examples: simple models, calcium excitation in polarized light, and the isomerization of retinal in rhodopsin are used to expose the underlying qualitative nature of the established coherences.

Hybrid Models for Weather Parameter Forecasting

The objective of the paper is to compare hybrid conjunction models with conventional models for the reduction of errors in weather forecasting. Besides the simple models like RBF model, SMO model, and LibSVM model, different hybrid conjunction models have been used for forecasting under different schemes. The forecasts from these models are further compared on the basis of errors calculated and time taken by the hybrid models and simple models in order to forecast weather parameters. In this paper, conjunction models over the convectional models are designed for forecasting the weather parameters for the reduction of error. India is a tropical country with variations in weather conditions. The objective is to build a conjunction model with less error to forecast weather parameters. A hybrid conjunction model is developed and analysed for different weather parameters for different metropolitan cities of India. Performance measurement is analysed for weather parameters. It is observed that, on the basis of error comparison and time taken by the models, the hybrid wavelet-neuro-RBF model gives better results as compared to the other models due to lower values of determined errors, better performance, and lesser time taken. The study becomes significant as weather forecasting with accuracy is a complex task along with the reduction of prediction error by the application of different models and schemes. It is concluded that the proposed hybrid model is helpful for forecasting and making policies in advance for the betterment of the human being, farmers, tourists, and so on as in all these activities, weather forecast plays an important role.

A retrospective on hydrological modelling based on half a century with the HBV model

Hydrological models are important tools that are commonly used as the basis for water resource management planning. In the 1970s the development of several relatively simple models started and a number of so-called conceptual (or bucket-type) models were suggested. In these models, the complex and heterogeneous hydrological processes in a catchment are represented by a limited number of storage elements and fluxes between these. While a major motivation for such relatively simple models in the early days were computational limitations, today some of these models are still used frequently despite vastly increased computational opportunities. The HBV model, which was first applied about 50 years ago in Sweden, is a typical example of a conceptual catchment model and has gained large popularity over the past 50 years. During several model intercomparisons, the HBV model performed well despite (or because of) its relatively simple model structure. Here, the history of model development from thoughtful considerations of different model structures to modelling studies using hundreds of catchments and cloud computing facilities, is described. Furthermore, the wide range of model applications is discussed. The aim is to provide an understanding of the background of model development and a basis for addressing the balance between model complexity and data availability, which will face hydrologists also in the coming decades.

UPAYA PENGEMBANGAN KURIKULUM KEWIRAUSAHAAN DARI UNIVERSITAS TARUMANAGARA KEPADA PESERTA DIDIK SMA DON BOSCO PADANG, SUMATERA BARAT

It is important to maintain or increase company profits as a goal that the company must continuously achieve. Businesses are usually activated in increasing company profits obtain and guide consumers and always dominate the existing market. In the concept of sales, the emphasis is on the seller's needs, which means that the focus of activities is to sell goods and services only. This old concept is implemented for products that are not favorites. In this case, the seller's goal is to sell what they can produce rather than make the products and services that customers want because it takes extra hard effort to obtain sales results intended to achieve the goal. The form chosen during the implementation of Inquiry Learning and Problem Based Learning where students were trained in almost 2 hours to understand business problems in mathematical calculations and there was training in answering calculation and theory questions. Management ability is also based on mathematical analysis of the simple models of the problems. From data collection and data processing, conclusions can be drawn to understand the pattern of consumer demand. This action helps startups understand the pattern of consumer demand in fulfilling customer satisfaction.Penting untuk bisa mempertahankan atau meningkatkan laba perusahaan sebagai tujuan yang harus terus dicapai oleh perusahaan. Usaha yang biasanya digiatkan dalam peningkatan keuntungan perusahaan yaitu memperoleh dan membimbing konsumen serta kemampuan untuk selalu menguasai pasar yang ada. Dalam konsep penjualan lebih ditekankan untuk kebutuhan penjual yang berarti fokus kegiatas adalah untuk menjual barang dan jasa semata. Konsep lama ini dilaksanakan untuk produk-produk yang tidak favorit. Dalam kasus ini, tujuan penjual hanya untuk menjual apa yang mampu mereka produksi daripada mampu membuat produk dan jasa yang benar benar diinginkan oleh pelanggan. Karena itu dibutuhkan usaha extra keras untuk memperoleh hasil penjualan yang dimaksudkan untuk mencapai tujuan. Bentuk yang dipilih pada saat pelaksanaan Inquiry Learning dan Problem Based Learning dimana para siswa peserta didik dilatih dalam kurun waktu hampir 2 jam untuk mengerti problematika bisnis dalam perhitungan matematika dan ada pelatihan mejawab soal-soal perhitungan dan teori. Kemampuan manajemen sebenarnya juga dilandasi oleh analisa matematis dari model atau problematika yang sederhana. Dari pengumpulan data dan pengolahan data dapat diambil kesimpulan untuk mengerti pola atau pattern dari permintaan konsumen yang terjadi. Hal ini membantu para startup mengerti pola dari permintaan konsumen dalam pemenuhan kepuasan konsumen tersebut.